Question: Neutrophil extracellular traps (NETs) are released by ANCA-stimulated neutrophils.

Title: Netting neutrophils in autoimmune small-vessel vasculitis Content: Small-vessel vasculitis (SVV) is a chronic autoinflammatory condition linked to antineutrophil cytoplasm autoantibodies (ANCAs). Here we show that chromatin fibers, so-called neutrophil extracellular traps (NETs), are released by ANCA-stimulated neutrophils and contain the targeted autoantigens proteinase-3 (PR3) and myeloperoxidase (MPO). Deposition of NETs in inflamed kidneys and circulating MPO-DNA complexes suggest that NET formation triggers vasculitis and promotes the autoimmune response against neutrophil components in individuals with SVV.

Title: Viable neutrophils release mitochondrial DNA to form neutrophil extracellular traps Content: Neutrophil extracellular traps (NETs) represent extracellular structures able to bind and kill microorganisms. It is believed that they are generated by neutrophils undergoing cell death, allowing these dying or dead cells to kill microbes. We show that, following priming with granulocyte/macrophage colony-stimulating factor (GM-CSF) and subsequent short-term toll-like receptor 4 (TLR4) or complement factor 5a (C5a) receptor stimulation, viable neutrophils are able to generate NETs. Strikingly, NETs formed by living cells contain mitochondrial, but no nuclear, DNA. Pharmacological or genetic approaches to block reactive oxygen species (ROS) production suggested that NET formation is ROS dependent. Moreover, neutrophil populations stimulated with GM-CSF and C5a showed increased survival compared with resting neutrophils, which did not generate NETs. In conclusion, mitochondrial DNA release by neutrophils and NET formation do not require neutrophil death and do also not limit the lifespan of these cells.

Title: Neutrophil extracellular traps: Is immunity the second function of chromatin? Content: Neutrophil extracellular traps (NETs) are made of processed chromatin bound to granular and selected cytoplasmic proteins. NETs are released by white blood cells called neutrophils, maybe as a last resort, to control microbial infections. This release of chromatin is the result of a unique form of cell death, dubbed "NETosis. " Here we review our understanding of how NETs are made, their function in infections and as danger signals, and their emerging importance in autoimmunity and coagulation.

Title: Neutrophil extracellular traps enriched in oxidized mitochondrial DNA are interferogenic and contribute to lupus-like disease Content: Neutrophil extracellular traps (NETs) are implicated in autoimmunity, but how they are generated and their roles in sterile inflammation remain unclear. Ribonucleoprotein immune complexes (RNP ICs), inducers of NETosis, require mitochondrial reactive oxygen species (ROS) for maximal NET stimulation. After RNP IC stimulation of neutrophils, mitochondria become hypopolarized and translocate to the cell surface. Extracellular release of oxidized mitochondrial DNA is proinflammatory in vitro, and when this DNA is injected into mice, it stimulates type I interferon (IFN) signaling through a pathway dependent on the DNA sensor STING. Mitochondrial ROS are also necessary for spontaneous NETosis of low-density granulocytes from individuals with systemic lupus erythematosus. This was also observed in individuals with chronic granulomatous disease, who lack NADPH oxidase activity but still develop autoimmunity and type I IFN signatures. Mitochondrial ROS inhibition in vivo reduces disease severity and type I IFN responses in a mouse model of lupus. Together, these findings highlight a role for mitochondria in the generation not only of NETs but also of pro-inflammatory oxidized mitochondrial DNA in autoimmune diseases.

Title: A novel mechanism of rapid nuclear neutrophil extracellular trap formation in response to Staphylococcus aureus. Content: Neutrophil extracellular traps (NETs) are webs of DNA covered with antimicrobial molecules that constitute a newly described killing mechanism in innate immune defense. Previous publications reported that NETs take up to 3-4 h to form via an oxidant-dependent event that requires lytic death of neutrophils. In this study, we describe neutrophils responding uniquely to Staphylococcus aureus via a novel process of NET formation that did not require neutrophil lysis or even breach of the plasma membrane. The multilobular nucleus rapidly became rounded and condensed. During this process, we observed the separation of the inner and outer nuclear membranes and budding of vesicles, and the separated membranes and vesicles were filled with nuclear DNA. The vesicles were extruded intact into the extracellular space where they ruptured, and the chromatin was released. This entire process occurred via a unique, very rapid (5-60 min), oxidant-independent mechanism. Mitochondrial DNA constituted very little if any of these NETs. They did have a limited amount of proteolytic activity and were able to kill S. aureus. With time, the nuclear envelope ruptured, and DNA filled the cytoplasm presumably for later lytic NET production, but this was distinct from the vesicular release mechanism. Panton-Valentine leukocidin, autolysin, and a lipase were identified in supernatants with NET-inducing activity, but Panton-Valentine leukocidin was the dominant NET inducer. We describe a new mechanism of NET release that is very rapid and contributes to trapping and killing of S. aureus.

Title: Infection-induced NETosis is a dynamic process involving neutrophil multitasking in vivo Content: Neutrophil extracellular traps (NETs) are released as neutrophils die in vitro in a process requiring hours, leaving a temporal gap that invasive microbes may exploit. Neutrophils capable of migration and phagocytosis while undergoing NETosis have not been documented. During Gram-positive skin infections, we directly visualized live polymorphonuclear cells (PMNs) in vivo rapidly releasing NETs, which prevented systemic bacterial dissemination. NETosis occurred during crawling, thereby casting large areas of NETs. NET-releasing PMNs developed diffuse decondensed nuclei, ultimately becoming devoid of DNA. Cells with abnormal nuclei showed unusual crawling behavior highlighted by erratic pseudopods and hyperpolarization consistent with the nucleus being a fulcrum for crawling. A requirement for both Toll-like receptor 2 and complement-mediated opsonization tightly regulated NET release. Additionally, live human PMNs injected into mouse skin developed decondensed nuclei and formed NETS in vivo, and intact anuclear neutrophils were abundant in Gram-positive human abscesses. Therefore early in infection NETosis involves neutrophils that do not undergo lysis and retain the ability to multitask.

Title: CXCR2 mediates NADPH oxidase–independent neutrophil extracellular trap formation in cystic fibrosis airway inflammation Content: Upon activation, neutrophils release DNA fibers decorated with antimicrobial proteins, forming neutrophil extracellular traps (NETs). Although NETs are bactericidal and contribute to innate host defense, excessive NET formation has been linked to the pathogenesis of autoinflammatory diseases. However, the mechanisms regulating NET formation, particularly during chronic inflammation, are poorly understood. Here we show that the G protein–coupled receptor (GPCR) CXCR2 mediates NET formation. Downstream analyses showed that CXCR2-mediated NET formation was independent of NADPH oxidase and involved Src family kinases. We show the pathophysiological relevance of this mechanism in cystic fibrosis lung disease, characterized by chronic neutrophilic inflammation. We found abundant NETs in airway fluids of individuals with cystic fibrosis and mouse cystic fibrosis lung disease, and NET amounts correlated with impaired obstructive lung function. Pulmonary blockade of CXCR2 by intra-airway delivery of small-molecule antagonists inhibited NET formation and improved lung function in vivo without affecting neutrophil recruitment, proteolytic activity or antibacterial host defense. These studies establish CXCR2 as a receptor mediating NADPH oxidase–independent NET formation and provide evidence that this GPCR pathway is operative and druggable in cystic fibrosis lung disease.

Title: NETs are a source of citrullinated autoantigens and stimulate inflammatory responses in rheumatoid arthritis. Content: The early events leading to the development of rheumatoid arthritis (RA) remain unclear, but formation of autoantibodies to citrullinated protein antigens (ACPAs) is considered a key pathogenic event. Neutrophils isolated from patients with various autoimmune diseases display enhanced neutrophil extracellular trap (NET) formation, a phenomenon that exposes autoantigens in the context of immunostimulatory molecules. We investigated whether aberrant NETosis occurs in RA, determined its triggers, and examined its deleterious inflammatory consequences. Enhanced NETosis was observed in circulating and RA synovial fluid neutrophils compared to neutrophils from healthy controls and from patients with osteoarthritis (OA). Further, netting neutrophils infiltrated RA synovial tissue, rheumatoid nodules, and skin. NETosis correlated with ACPA presence and levels and with systemic inflammatory markers. RA sera and immunoglobulin fractions from RA patients with high levels of ACPA and/or rheumatoid factor significantly enhanced NETosis, and the NETs induced by these autoantibodies displayed distinct protein content. Indeed, during NETosis, neutrophils externalized the citrullinated autoantigens implicated in RA pathogenesis, and anti-citrullinated vimentin antibodies potently induced NET formation. Moreover, the inflammatory cytokines interleukin-17A (IL-17A) and tumor necrosis factor-α (TNF-α) induced NETosis in RA neutrophils. In turn, NETs significantly augmented inflammatory responses in RA and OA synovial fibroblasts, including induction of IL-6, IL-8, chemokines, and adhesion molecules. These observations implicate accelerated NETosis in RA pathogenesis, through externalization of citrullinated autoantigens and immunostimulatory molecules that may promote aberrant adaptive and innate immune responses in the joint and in the periphery, and perpetuate pathogenic mechanisms in this disease.

Title: Neutrophil extracellular traps capture and kill Candida albicans yeast and hyphal forms. Content: Neutrophils phagocytose and kill microbes upon phagolysosomal fusion. Recently we found that activated neutrophils form extracellular fibres that consist of granule proteins and chromatin. These neutrophil extracellular traps (NETs) degrade virulence factors and kill Gram positive and negative bacteria. Here we show for the first time that Candida albicans, a eukaryotic pathogen, induces NET-formation and is susceptible to NET-mediated killing. C. albicans is the predominant aetiologic agent of fungal infections in humans, particularly in immunocompromised hosts. One major virulence trait of C. albicans is its ability to reversibly switch from singular budding cells to filamentous hyphae. We demonstrate that NETs kill both yeast-form and hyphal cells, and that granule components mediate fungal killing. Taken together our data indicate that neutrophils trap and kill ascomycetous yeasts by forming NETs.

Title: Neutrophil extracellular chromatin traps connect innate immune response to autoimmunity Content: Autoantibodies to DNA and histones (chromatin) are the defining antigen specificity in systemic lupus erythematosus (SLE) and related musculoskeletal disorders but the mechanisms responsible for their induction remain mysterious. That situation rapidly changed once neutrophil extracellular chromatin traps (NETs) were discovered and observed to play a conserved role in innate immune responses to a broad variety of microbial pathogens. At the center of an infectious process, neutrophils exert various antimicrobial defenses, including the release of nuclear chromatin into the extracellular space. The externalized NETs, a complex meshwork of nuclear chromatin and antimicrobial proteins, serve to immobilize and degrade microbial pathogens. Here, we critically evaluate the evidence supporting NETs versus apoptotic bodies as a source for nuclear antigens in autoimmunity. We also discuss the possibility that NET chromatin forms an essential component of immune deposits in the pathogenesis of glomerulonephritis in SLE and other autoimmune immune complex diseases.

Title: Netting neutrophils are major inducers of type I IFN production in pediatric systemic lupus erythematosus. Content: Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by a breakdown of tolerance to nuclear antigens and the development of immune complexes. Genomic approaches have shown that human SLE leukocytes homogeneously express type I interferon (IFN)-induced and neutrophil-related transcripts. Increased production and/or bioavailability of IFN-α and associated alterations in dendritic cell (DC) homeostasis have been linked to lupus pathogenesis. Although neutrophils have long been shown to be associated with lupus, their potential role in disease pathogenesis remains elusive. Here, we show that mature SLE neutrophils are primed in vivo by type I IFN and die upon exposure to SLE-derived anti-ribonucleoprotein antibodies, releasing neutrophil extracellular traps (NETs). SLE NETs contain DNA as well as large amounts of LL37 and HMGB1, neutrophil proteins that facilitate the uptake and recognition of mammalian DNA by plasmacytoid DCs (pDCs). Indeed, SLE NETs activate pDCs to produce high levels of IFN-α in a DNA- and TLR9 (Toll-like receptor 9)-dependent manner. Our results reveal an unsuspected role for neutrophils in SLE pathogenesis and identify a novel link between nucleic acid-recognizing antibodies and type I IFN production in this disease.

Title: Antibodies from patients with rheumatoid arthritis target citrullinated histone 4 contained in neutrophils extracellular traps. Content: BACKGROUND Histone deimination regulates gene function and contributes to antimicrobial response, allowing the formation of neutrophil extracellular traps (NETs). Deiminated proteins are target of anti-citrullinated peptides antibodies (ACPA) in rheumatoid arthritis (RA). OBJECTIVE The objective of this paper is to test the hypothesis that RA sera react with deiminated histones contained in NETs. METHODS Neutrophils from peripheral blood were stimulated with A23187 and acid treated; NETosis was induced by phorbol myristate acetate, and NET proteins were isolated. Sera were tested by immunoblot on acid extracted proteins from neutrophils and from NETs, and by ELISA on deiminated histone H4 or H4-derived peptides. Bands reactive with RA sera were excised from gels, digested with trypsin and subjected to matrix-assisted laser desorption/ionisation time of flight (MALDI-TOF) analysis, before and after derivatisation to detect citrullinated peptides. RESULTS RA sera reacted with a deiminated antigen of 11 KDa from activated neutrophils, recognised also by anti-H4 and antideiminated H4 antibodies. A similar reactivity was observed with NET proteins. The antigen from neutrophils or NETs was identified as citrullinated H4 by MALDI-TOF analysis. By ELISA, RA sera bound in vitro citrullinated H4. Citrullinated H4 14-34 and 31-50 peptides detected antibodies in 67% and 63% of RA sera and in less than 5% of controls; antibody titre was correlated with anti-CCP2. CONCLUSIONS Citrullinated H4 from activated neutrophils and NETs is a target of antibodies in RA, and synthetic citrullinated H4-derived peptides are a new substrate for ACPA detection. As NETosis can generate antigens for ACPA, these data suggest a novel connection between innate and adaptive immunity in RA.

Title: The role of neutrophils in the pathogenesis of systemic lupus erythematosus. Content: PURPOSE OF REVIEW Recent discoveries implicate neutrophils as important regulators of innate and adaptive immunity and in the development of organ damage in systemic autoimmune diseases, including systemic lupus erythematosus (SLE). RECENT FINDINGS Various putative SLE biomarkers are neutrophil-related, including neutrophil granular proteins and histones undergoing post-translational modifications during neutrophil extracellular trap (NET) formation. In the bone marrow, lupus neutrophils can drive B and T cell abnormalities, at least in part, by their enhanced production of type-I interferons, tumor necrosis factor-alpha (TNFα) and the B-cell stimulating factors B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL). Lupus neutrophils and, in particular, lupus low-density granulocytes (a distinct pathogenic subset) display epigenetic modifications and genomic alterations that may be relevant to their deleterious roles in SLE. Proteins and enzymes externalized by lupus NETs can affect vascular health by inducing endothelial apoptosis and oxidizing lipoproteins. Hampering NET formation through peptidylarginine deiminase inhibitors abrogates lupus phenotype and atherosclerosis in murine studies. SUMMARY Recent discoveries support the notion that neutrophils, low-density granulocytes and aberrant NET formation and clearance play important roles in lupus pathogenesis. Future studies should focus on how to selectively target these immunostimulatory pathways in this disease.

Title: PAD4 is essential for antibacterial innate immunity mediated by neutrophil extracellular traps Content: Neutrophils trap and kill bacteria by forming highly decondensed chromatin structures, termed neutrophil extracellular traps (NETs). We previously reported that histone hypercitrullination catalyzed by peptidylarginine deiminase 4 (PAD4) correlates with chromatin decondensation during NET formation. However, the role of PAD4 in NET-mediated bacterial trapping and killing has not been tested. Here, we use PAD4 knockout mice to show that PAD4 is essential for NET-mediated antibacterial function. Unlike PAD4(+/+) neutrophils, PAD4(-/-) neutrophils cannot form NETs after stimulation with chemokines or incubation with bacteria, and are deficient in bacterial killing by NETs. In a mouse infectious disease model of necrotizing fasciitis, PAD4(-/-) mice are more susceptible to bacterial infection than PAD4(+/+) mice due to a lack of NET formation. Moreover, we found that citrullination decreased the bacterial killing activity of histones and nucleosomes, which suggests that PAD4 mainly plays a role in chromatin decondensation to form NETs instead of increasing histone-mediated bacterial killing. Our results define a role for histone hypercitrullination in innate immunity during bacterial infection.

Title: Influence of DNA on the activities and inhibition of neutrophil serine proteases in cystic fibrosis sputum. Content: Uncontrolled proteolysis by neutrophil serine proteases (NSPs) in lung secretions is a hallmark of cystic fibrosis (CF). We have shown that the active neutrophil elastase, protease 3, and cathepsin G in CF sputum resist inhibition in part by exogenous protease inhibitors. This resistance may be due to their binding to neutrophil extracellular traps (NETs) secreted by the activated neutrophils in CF sputum and to genomic DNA released from senescent and dead neutrophils. Treating CF sputum with DNase dramatically increases its elastase activity, which can then be stoichiometrically inhibited by exogenous elastase inhibitors. However, DNase treatment does not increase the activities of protease 3 and cathepsin G, indicating their different distribution and/or binding in CF sputum. Purified blood neutrophils secrete NETs when stimulated by the opportunistic CF bacteria Pseudomonas aeruginosa and Staphylococcus aureus. The activities of the three proteases were unchanged in these conditions, but subsequent DNase treatment produced a dramatic increase in all three proteolytic activities. Neutrophils activated with a calcium ionophore did not secrete NETs but released huge amounts of active proteases whose activities were not modified by DNase. We conclude that NETs are reservoirs of active proteases that protect them from inhibition and maintain them in a rapidly mobilizable status. Combining the effects of protease inhibitors with that of DNA-degrading agents could counter the deleterious proteolytic effects of NSPs in CF lung secretions.

Title: Circulating mitochondrial DNA in serum of patients with granulomatosis with polyangiitis. Content: Neutrophil is a key cell in pathophysiology of granulomatosis with polyangiitis. Recently, neutrophil extracellular traps were described in this disease. Mitochondrial DNA is also released during traps formation. We measured circulating cell-free mitochondrial and genomic DNA in serum of patients with granulomatosis with polyangiitis. Subjects with the disease (14 active and 11 in remission stage) and 10 healthy controls were enrolled. Quantitative real-time polymerase chain reaction (PCR) was used to measure 79 base pairs (bp) and 230 bp mtDNA fragments. Alu repeats were quantified to evaluate abundance of nuclear DNA in serum at the presence of plasmid control. Both fragments of mtDNA (79 bp and 230 bp) and genomic DNA were elevated significantly in granulomatosis with polyangiitis compared to controls. Only the shorter 79 bp mtDNA correlated with active stage of granulomatosis with polyangiitis and clinical symptoms. A mechanism of extracellular release of mitochondrial DNA accompanies the active stage of the disease. Circulating mtDNA is extremely high in untreated patients. This suggests that biomarker properties of mtDNA are useful for monitoring of treatment.

Title: Neutrophils in the activation and regulation of innate and adaptive immunity Content: Neutrophils have long been viewed as the final effector cells of an acute inflammatory response, with a primary role in the clearance of extracellular pathogens. However, more recent evidence has extended the functions of these cells. The newly discovered repertoire of effector molecules in the neutrophil armamentarium includes a broad array of cytokines, extracellular traps and effector molecules of the humoral arm of the innate immune system. In addition, neutrophils are involved in the activation, regulation and effector functions of innate and adaptive immune cells. Accordingly, neutrophils have a crucial role in the pathogenesis of a broad range of diseases, including infections caused by intracellular pathogens, autoimmunity, chronic inflammation and cancer.

Title: Myeloperoxidase: friend and foe. Content: Neutrophilic polymorphonuclear leukocytes (neutrophils) are highly specialized for their primary function, the phagocytosis and destruction of microorganisms. When coated with opsonins (generally complement and/or antibody), microorganisms bind to specific receptors on the surface of the phagocyte and invagination of the cell membrane occurs with the incorporation of the microorganism into an intracellular phagosome. There follows a burst of oxygen consumption, and much, if not all, of the extra oxygen consumed is converted to highly reactive oxygen species. In addition, the cytoplasmic granules discharge their contents into the phagosome, and death of the ingested microorganism soon follows. Among the antimicrobial systems formed in the phagosome is one consisting of myeloperoxidase (MPO), released into the phagosome during the degranulation process, hydrogen peroxide (H2O2), formed by the respiratory burst and a halide, particularly chloride. The initial product of the MPO-H2O2-chloride system is hypochlorous acid, and subsequent formation of chlorine, chloramines, hydroxyl radicals, singlet oxygen, and ozone has been proposed. These same toxic agents can be released to the outside of the cell, where they may attack normal tissue and thus contribute to the pathogenesis of disease. This review will consider the potential sources of H2O2 for the MPO-H2O2-halide system; the toxic products of the MPO system; the evidence for MPO involvement in the microbicidal activity of neutrophils; the involvement of MPO-independent antimicrobial systems; and the role of the MPO system in tissue injury. It is concluded that the MPO system plays an important role in the microbicidal activity of phagocytes.

Title: Pathogenesis of diseases associated with antineutrophil cytoplasm autoantibodies. Content: Little is known about the etiologies of diseases associated with circulating antineutrophil cytoplasm autoantibodies (ANCA), such as primary vasculitides and inflammatory bowel diseases. However, the understanding of immune mechanisms supposedly involved in the pathogenesis of these diseases is still growing. In the present review, we first focus on the mechanisms triggering the development of ANCA, including the potential role of microbial superantigens and the possible defect(s) in the progression of apoptosis or in the removal of apoptotic cells. We next concentrate on the contribution of ANCA to the clinical symptoms and on the pathogenic role of ANCA, including the accessibility of ANCA antigens as targets for circulating antibodies and the mode of action of ANCA. Mechanisms of neutrophil activation by ANCA include the engagement of Fcgamma receptors, the possible mechanisms of neutrophil-mediated tissue damage, and the neutrophil-endothelial interaction.

Title: Neutrophils Suppress Intraluminal NK Cell-Mediated Tumor Cell Clearance and Enhance Extravasation of Disseminated Carcinoma Cells. Content: UNLABELLED Immune cells promote the initial metastatic dissemination of carcinoma cells from primary tumors. In contrast to their well-studied functions in the initial stages of metastasis, the specific roles of immunocytes in facilitating progression through the critical later steps of the invasion-metastasis cascade remain poorly understood. Here, we define novel functions of neutrophils in promoting intraluminal survival and extravasation at sites of metastatic dissemination. We show that CD11b(+)/Ly6G(+) neutrophils enhance metastasis formation via two distinct mechanisms. First, neutrophils inhibit natural killer cell function, which leads to a significant increase in the intraluminal survival time of tumor cells. Thereafter, neutrophils operate to facilitate extravasation of tumor cells through the secretion of IL1β and matrix metalloproteinases. These results identify neutrophils as key regulators of intraluminal survival and extravasation through their cross-talk with host cells and disseminating carcinoma cells. SIGNIFICANCE This study provides important insights into the systemic contributions of neutrophils to cancer metastasis by identifying how neutrophils facilitate intermediate steps of the invasion-metastasis cascade. We demonstrate that neutrophils suppress natural killer cell activity and increase extravasation of tumor cells. Cancer Discov; 6(6); 630-49. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 561.

Title: Antineutrophil cytoplasmic antibodies (ANCA). Content: Antineutrophil cytoplasmic antibodies (ANCA) are a sensitive and specific marker for ANCA-associated systemic vasculitis. Using indirect immunofluorescence on ethanol-fixed neutrophils, two major fluoroscopic patterns can be recognised: a diffuse cytoplasmic staining (C-ANCA), and a perinuclear/nuclear staining (P-ANCA). In patients with vasculitis, more of 90% of C-ANCA are directed against proteinase 3 (PR3-ANCA) whereas approximately 80-90% of P-ANCA recognise myelperoxidase (MPO-ANCA). Although C-ANCA (PR3-ANCA) is preferentially associated with Wegener's granulomatosis (WG), and P-ANCA (MPO-ANCA) with microscopic polyangiitis (MPA), idiopathic necrotising crescentic glomerulonephritis (iNCGN) and Churg-Strauss syndrome (CSS), there is not absolute specificity. Between 10-20% of patients with classical WG show P-ANCA (MPO-ANCA), and even a larger percentage of patients with MPA or CSS have C-ANCA (PR3-ANCA). Furthermore, it should be stressed that approximately 10-20% of patients with WG or MPA (and 40-50% of cases of CSS) have negative assay for ANCA. The best diagnostic performance is obtained when indirect immunofluorescence is combined with PR3 and MPO-specific ELISAs. ANCA with different and unknown antigen specificity are found in a variety of conditions other than AASV, including inflammatory bowel diseases, other autoimmune diseases, and infections where their clinical significance is unclear. ANCA levels are useful to monitor disease activity but should not be used by themselves to guide treatment. A significant increase in ANCA titres, or the reappearance of ANCA, should alert the clinicians and lead to a stricter patient control.

Title: Oxidative damage of DNA confers resistance to cytosolic nuclease TREX1 degradation and potentiates STING-dependent immune sensing. Content: Immune sensing of DNA is critical for antiviral immunity but can also trigger autoimmune diseases such as lupus erythematosus (LE). Here we have provided evidence for the involvement of a damage-associated DNA modification in the detection of cytosolic DNA. The oxidized base 8-hydroxyguanosine (8-OHG), a marker of oxidative damage in DNA, potentiated cytosolic immune recognition by decreasing its susceptibility to 3' repair exonuclease 1 (TREX1)-mediated degradation. Oxidizative modifications arose physiologically in pathogen DNA during lysosomal reactive oxygen species (ROS) exposure, as well as in neutrophil extracellular trap (NET) DNA during the oxidative burst. 8-OHG was also abundant in UV-exposed skin lesions of LE patients and colocalized with type I interferon (IFN). Injection of oxidized DNA in the skin of lupus-prone mice induced lesions that closely matched respective lesions in patients. Thus, oxidized DNA represents a prototypic damage-associated molecular pattern (DAMP) with important implications for infection, sterile inflammation, and autoimmunity.

Title: Tumor-derived exosomes induce N2 polarization of neutrophils to promote gastric cancer cell migration Content: BACKGROUND Exosomes are extracellular vesicles that mediate cellular communication in health and diseases. Neutrophils could be polarized to a pro-tumor phenotype by tumor. The function of tumor-derived exosomes in neutrophil regulation remains unclear. METHODS We investigated the effects of gastric cancer cell-derived exosomes (GC-Ex) on the pro-tumor activation of neutrophils and elucidated the underlying mechanisms. RESULTS GC-Ex prolonged neutrophil survival and induced expression of inflammatory factors in neutrophils. GC-Ex-activated neutrophils, in turn, promoted gastric cancer cell migration. GC-Ex transported high mobility group box-1 (HMGB1) that activated NF-κB pathway through interaction with TLR4, resulting in an increased autophagic response in neutrophils. Blocking HMGB1/TLR4 interaction, NF-κB pathway, and autophagy reversed GC-Ex-induced neutrophil activation. Silencing HMGB1 in gastric cancer cells confirmed HMGB1 as a key factor for GC-Ex-mediated neutrophil activation. Furthermore, HMGB1 expression was upregulated in gastric cancer tissues. Increased HMGB1 expression was associated with poor prognosis in patients with gastric cancer. Finally, gastric cancer tissue-derived exosomes acted similarly as exosomes derived from gastric cancer cell lines in neutrophil activation. CONCLUSION We demonstrate that gastric cancer cell-derived exosomes induce autophagy and pro-tumor activation of neutrophils via HMGB1/TLR4/NF-κB signaling, which provides new insights into mechanisms for neutrophil regulation in cancer and sheds lights on the multifaceted role of exosomes in reshaping tumor microenvironment.

Title: Requirement of endogenous stem cell factor and granulocyte-colony-stimulating factor for IL-17-mediated granulopoiesis. Content: IL-17 is a novel, CD4+ T cell-restricted cytokine. In vivo, it stimulates hematopoiesis and causes neutrophilia consisting of mature granulocytes. In this study, we show that IL-17-mediated granulopoiesis requires G-CSF release and the presence or induction of the transmembrane form of stem cell factor (SCF) for optimal granulopoiesis. However, IL-17 also protects mice from G-CSF neutralization-induced neutropenia. G-CSF neutralization completely reversed IL-17-induced BM progenitor expansion, whereas splenic CFU-GM/CFU-granulocyte-erythrocyte-megakaryocyte-monocyte was only reduced by 50% in both Sl/Sld and littermate control mice. Thus, there remained a significant SCF/G-CSF-independent effect of IL-17 on splenic granulopoiesis, resulting in a preservation of mature circulating granulocytes. IL-17 is a cytokine that potentially interconnects lymphocytic and myeloid host defense and may have potential for therapeutic development.

Title: Differential Requirement of the Extracellular Domain in Activation of Class B G Protein-coupled Receptors. Content: G protein-coupled receptors (GPCRs) from the secretin-like (class B) family are key players in hormonal homeostasis and are important drug targets for the treatment of metabolic disorders and neuronal diseases. They consist of a large N-terminal extracellular domain (ECD) and a transmembrane domain (TMD) with the GPCR signature of seven transmembrane helices. Class B GPCRs are activated by peptide hormones with their C termini bound to the receptor ECD and their N termini bound to the TMD. It is thought that the ECD functions as an affinity trap to bind and localize the hormone to the receptor. This in turn would allow the hormone N terminus to insert into the TMD and induce conformational changes of the TMD to activate downstream signaling. In contrast to this prevailing model, we demonstrate that human class B GPCRs vary widely in their requirement of the ECD for activation. In one group, represented by corticotrophin-releasing factor receptor 1 (CRF1R), parathyroid hormone receptor (PTH1R), and pituitary adenylate cyclase activating polypeptide type 1 receptor (PAC1R), the ECD requirement for high affinity hormone binding can be bypassed by induced proximity and mass action effects, whereas in the other group, represented by glucagon receptor (GCGR) and glucagon-like peptide-1 receptor (GLP-1R), the ECD is required for signaling even when the hormone is covalently linked to the TMD. Furthermore, the activation of GLP-1R by small molecules that interact with the intracellular side of the receptor is dependent on the presence of its ECD, suggesting a direct role of the ECD in GLP-1R activation.

Title: Non-canonical PI3K-Cdc42-Pak-Mek-Erk Signaling Promotes Immune-Complex-Induced Apoptosis in Human Neutrophils Content: Neutrophils are peripheral blood leukocytes that represent the first line of immune cell defense against bacterial and fungal infections but are also crucial players in the generation of the inflammatory response. Many neutrophil cell surface receptors regulate important cellular processes via activation of agonist-activated PI3Ks. We show here that activation of human neutrophils with insoluble immune complexes drives a previously uncharacterized, PI3K-dependent, non-canonical, pro-apoptotic signaling pathway, FcγR-PI3Kβ/δ-Cdc42-Pak-Mek-Erk. This is a rare demonstration of Ras/Raf-independent activation of Erk and of PI3K-mediated activation of Cdc42. In addition, comparative analysis of immune-complex- and fMLF-induced signaling uncovers key differences in pathways used by human and murine neutrophils. The non-canonical pathway we identify in this study may be important for the resolution of inflammation in chronic inflammatory diseases that rely on immune-complex-driven neutrophil activation.

Title: Role of the CXCR4/SDF-1 chemokine axis in circulating neutrophil homeostasis. Content: The bone marrow is the primary site for neutrophil production and release into the circulation. Because the CXC chemokine receptor-4/stromal derived factor-1 (CXCR4/SDF-1) axis plays a central role in the interactions of hematopoietic stem cells, lymphocytes, and developing neutrophils in the marrow, we investigated whether reciprocal CXCR4-dependent mechanisms might be involved in neutrophil release and subsequent return to the marrow following circulation. Neutralizing antibody to CXCR4 reduced marrow retention of infused neutrophils (45.7% +/- 0.5% to 6.9% +/- 0.5%) and was found to mobilize neutrophils from marrow (34.4% +/- 4.4%). Neutrophil CXCR4 expression and SDF-1-induced calcium flux decreased with maturation and activation of the cells, corresponding to the decreased marrow homing associated with these characteristics in vivo. Infusion of the inflammatory mediator and CXCR2 ligand KC led to mobilization of neutrophils from marrow by itself and was augmented 3-fold by low doses of CXCR4-blocking antibody that otherwise had no mobilizing effect. Examination of KC and SDF-1 calcium signaling demonstrated that the effect of KC may, in part, be due to heterologous desensitization to SDF-1. These results suggest that the CXCR4/SDF-1 axis is critical in circulating neutrophil homeostasis and that it may participate in the rapid release of neutrophils from the marrow during inflammation through a novel interaction with inflammatory CXC chemokines.

Title: Proliferating cell nuclear antigen acts as a cytoplasmic platform controlling human neutrophil survival Content: Neutrophil apoptosis is a highly regulated process essential for inflammation resolution, the molecular mechanisms of which are only partially elucidated. In this study, we describe a survival pathway controlled by proliferating cell nuclear antigen (PCNA), a nuclear factor involved in DNA replication and repairing of proliferating cells. We show that mature neutrophils, despite their inability to proliferate, express high levels of PCNA exclusively in their cytosol and constitutively associated with procaspases, presumably to prevent their activation. Notably, cytosolic PCNA abundance decreased during apoptosis, and increased during in vitro and in vivo exposure to the survival factor granulocyte colony-stimulating factor (G-CSF). Peptides derived from the cyclin-dependent kinase inhibitor p21, which compete with procaspases to bind PCNA, triggered neutrophil apoptosis thus demonstrating that specific modification of PCNA protein interactions affects neutrophil survival. Furthermore, PCNA overexpression rendered neutrophil-differentiated PLB985 myeloid cells significantly more resistant to TNF-related apoptosis-inducing ligand- or gliotoxin-induced apoptosis. Conversely, a decrease in PCNA expression after PCNA small interfering RNA transfection sensitized these cells to apoptosis. Finally, a mutation in the PCNA interdomain-connecting loop, the binding site for many partners, significantly decreased the PCNA-mediated antiapoptotic effect. These results identify PCNA as a regulator of neutrophil lifespan, thereby highlighting a novel target to potentially modulate pathological inflammation.

Title: Calicum microdomains form within neutrophils at the neutrophil–tumor cell synapse: role in antibody-dependent target cell apoptosis Content: Ca2+ messages are broadly important in cellular signal transduction. In immune cells, Ca2+ signaling is an essential step in many forms of activation. Neutrophil-mediated antibody-dependent cell-mediated cytotoxicity (ADCC) is one form of leukocyte activation that plays an important role in tumor cell killing in vitro and in patient care. Using fluorescence methodologies, we found that neutrophils exhibit Ca2+ signals during ADCC directed against breast fibrosarcoma cells. Importantly, these signals were localized to Ca2+ microdomains at the neutrophil-to-tumor cell interface where they display dynamic features such as movement, fusion, and fission. These signals were blocked by the intracellular Ca2+ buffer BAPTA. At the neutrophil–tumor cell synapse, the neutrophil’s cytoplasm was enriched in STIM1, a crucial mediator of Ca2+ signaling, whereas the Ca2+-binding proteins calbindin and parvalbumin were not affected. Our findings suggest that Ca2+ microdomains are due to an active signaling process. As Ca2+ signals within neutrophils were necessary for specific tumor cell apoptosis, a central role of microdomains in leukocyte-mediated tumor cell destruction is indicated.

Title: Invariant NKT cells modulate the suppressive activity of IL-10-secreting neutrophils differentiated with serum amyloid A. Content: Neutrophils are the main effector cells during inflammation, but they can also control excessive inflammatory responses by secreting anti-inflammatory cytokines. However, the mechanisms that modulate their plasticity remain unclear. We now show that systemic serum amyloid A 1 (SAA-1) controls the plasticity of neutrophil differentiation. SAA-1 not only induced anti-inflammatory interleukin 10 (IL-10)-secreting neutrophils but also promoted the interaction of invariant natural killer T cells (iNKT cells) with those neutrophils, a process that limited their suppressive activity by diminishing the production of IL-10 and enhancing the production of IL-12. Because SAA-1-producing melanomas promoted differentiation of IL-10-secreting neutrophils, harnessing iNKT cells could be useful therapeutically by decreasing the frequency of immunosuppressive neutrophils and restoring tumor-specific immune responses.

Title: Gout-associated uric acid crystals activate the NALP3 inflammasome Content: Development of the acute and chronic inflammatory responses known as gout and pseudogout are associated with the deposition of monosodium urate (MSU) or calcium pyrophosphate dihydrate (CPPD) crystals, respectively, in joints and periarticular tissues. Although MSU crystals were first identified as the aetiological agent of gout in the eighteenth century and more recently as a ‘danger signal’ released from dying cells, little is known about the molecular mechanisms underlying MSU- or CPPD-induced inflammation. Here we show that MSU and CPPD engage the caspase-1-activating NALP3 (also called cryopyrin) inflammasome, resulting in the production of active interleukin (IL)-1β and IL-18. Macrophages from mice deficient in various components of the inflammasome such as caspase-1, ASC and NALP3 are defective in crystal-induced IL-1β activation. Moreover, an impaired neutrophil influx is found in an in vivo model of crystal-induced peritonitis in inflammasome-deficient mice or mice deficient in the IL-1β receptor (IL-1R). These findings provide insight into the molecular processes underlying the inflammatory conditions of gout and pseudogout, and further support a pivotal role of the inflammasome in several autoinflammatory diseases.

Title: The origin and neuronal function of in vivo nonsynaptic glutamate. Content: Basal extracellular glutamate sampled in vivo is present in micromolar concentrations in the extracellular space outside the synaptic cleft, and neither the origin nor the function of this glutamate is known. This report reveals that blockade of glutamate release from the cystine-glutamate antiporter produced a significant decrease (60%) in extrasynaptic glutamate levels in the rat striatum, whereas blockade of voltage-dependent Na+ and Ca2+ channels produced relatively minimal changes (0-30%). This indicates that the primary origin of in vivo extrasynaptic glutamate in the striatum arises from nonvesicular glutamate release by the cystine-glutamate antiporter. By measuring [35S]cystine uptake, it was shown that similar to vesicular release, the activity of the cystine-glutamate antiporter is negatively regulated by group II metabotropic glutamate receptors (mGluR2/3) via a cAMP-dependent protein kinase mechanism. Extracellular glutamate derived from the antiporter was shown to regulate extracellular levels of glutamate and dopamine. Infusion of the mGluR2/3 antagonist (RS)-1-amino-5-phosphonoindan-1-carboxylic acid (APICA) increased extracellular glutamate levels, and previous blockade of the antiporter prevented the APICA-induced rise in extracellular glutamate. This suggests that glutamate released from the antiporter is a source of endogenous tone on mGluR2/3. Blockade of the antiporter also produced an increase in extracellular dopamine that was reversed by infusing the mGluR2/3 agonist (2R,4R)-4-aminopyrrolidine-2,4-dicarboxlylate, indicating that antiporter-derived glutamate can modulate dopamine transmission via mGluR2/3 heteroreceptors. These results suggest that nonvesicular release from the cystine-glutamate antiporter is the primary source of in vivo extracellular glutamate and that this glutamate can modulate both glutamate and dopamine transmission.

Title: Reactive Oxygen Species Localization Programs Inflammation to Clear Microbes of Different Size Content: How the number of immune cells recruited to sites of infection is determined and adjusted to differences in the cellular stoichiometry between host and pathogen is unknown. Here, we have uncovered a role for reactive oxygen species (ROS) as sensors of microbe size. By sensing the differential localization of ROS generated in response to microbes of different size, neutrophils tuned their interleukin (IL)-1β expression via the selective oxidation of NF-κB, in order to implement distinct inflammatory programs. Small microbes triggered ROS intracellularly, suppressing IL-1β expression to limit neutrophil recruitment as each phagocyte eliminated numerous pathogens. In contrast, large microbes triggered ROS extracellularly, amplifying IL-1β expression to recruit numerous neutrophils forming cooperative clusters. Defects in ROS-mediated microbe size sensing resulted in large neutrophil infiltrates and clusters in response to small microbes that contribute to inflammatory disease. These findings highlight the impact of ROS localization on signal transduction.

Title: Differential expression of bcl-2 and susceptibility to anti-Fas-mediated cell death in peripheral blood lymphocytes, monocytes, and neutrophils. Content: The recently identified Fas antigen (Ag) is a cell surface molecule that can mediate apoptosis. The cytoplasmic product of proto-oncogene bcl-2 has been shown to prolong the cellular survival by inhibiting apoptosis. To elucidate the physiologic significance of expression of both molecules, we examined the expression of Fas Ag and bcl-2 on blood leukocyte populations and evaluated their sensitivity to the cytolytic action of anti-Fas antibody. Although Fas Ag was expressed on a fraction of lymphocytes, both neutrophils and monocytes expressed Fas Ag constitutively. In contrast, there was marked difference among these leukocytes regarding bcl-2 expression. Lymphocytes expressed bcl-2 intensely, but monocytes showed weaker bcl-2 expression, and neutrophils were essentially absent for bcl-2 expression. Seemingly reflecting this lack of bcl-2-expression, neutrophils more easily underwent apoptotic cell death in vitro as compared with monocytes and lymphocytes. We showed that anti-Fas antibody affectively accelerated apoptotic cell death in neutrophils. However, the apoptosis-inducing effect of anti-Fas antibody was minimal on monocytes, and lymphocytes were resistant to this antibody. These results suggest that anti-Fas-mediated cell death may, in part, be determined by bcl-2 expression status in Fas+ lymphoid and hematopoietic cells.

Title: Neutrophils support lung colonization of metastasis-initiating breast cancer cells Content: Despite progress in the development of drugs that efficiently target cancer cells, treatments for metastatic tumours are often ineffective. The now well-established dependency of cancer cells on their microenvironment suggests that targeting the non-cancer-cell component of the tumour might form a basis for the development of novel therapeutic approaches. However, the as-yet poorly characterized contribution of host responses during tumour growth and metastatic progression represents a limitation to exploiting this approach. Here we identify neutrophils as the main component and driver of metastatic establishment within the (pre-)metastatic lung microenvironment in mouse breast cancer models. Neutrophils have a fundamental role in inflammatory responses and their contribution to tumorigenesis is still controversial. Using various strategies to block neutrophil recruitment to the pre-metastatic site, we demonstrate that neutrophils specifically support metastatic initiation. Importantly, we find that neutrophil-derived leukotrienes aid the colonization of distant tissues by selectively expanding the sub-pool of cancer cells that retain high tumorigenic potential. Genetic or pharmacological inhibition of the leukotriene-generating enzyme arachidonate 5-lipoxygenase (Alox5) abrogates neutrophil pro-metastatic activity and consequently reduces metastasis. Our results reveal the efficacy of using targeted therapy against a specific tumour microenvironment component and indicate that neutrophil Alox5 inhibition may limit metastatic progression.

Title: Recent developments and complexities in neutrophil transmigration. Content: PURPOSE OF REVIEW As the migration of neutrophils from blood to inflamed tissues is an essential component of innate immunity and a key contributing factor to the pathogenesis of inflammatory disorders, this aspect of leukocyte biology continues to be a highly dynamic field of research. This review summarizes recent findings in this area, focusing on the mechanisms that mediate neutrophil transmigration, an area where significant progress has been made. RECENT FINDINGS The topics to be covered will include responses that are prerequisite to neutrophil migration through venular walls, such as leukocyte luminal crawling and cellular and molecular changes in leukocytes and endothelial cells (e.g. formation of protrusions) that collectively support leukocyte transendothelial cell migration. Advances in both paracellular and transcellular neutrophil migration through endothelial cells will be discussed, addressing the associated roles and regulation of expression of endothelial cell luminal and junctional adhesion molecules. Beyond the endothelium, migration through the vascular pericyte coverage and basement membrane will be reviewed. SUMMARY The unquestionable role of neutrophils in the development and progression of inflammatory conditions suggests that a better understanding of the tissue-specific and stimulus-specific mechanisms that mediate this response may identify novel pathways that could be exploited for the development of more specific anti-inflammatory interventions.

Title: The Ly49Q receptor plays a crucial role in neutrophil polarization and migration by regulating raft trafficking. Content: Neutrophils rapidly undergo polarization and directional movement to infiltrate the sites of infection and inflammation. Here, we show that an inhibitory MHC I receptor, Ly49Q, was crucial for the swift polarization of and tissue infiltration by neutrophils. During the steady state, Ly49Q inhibited neutrophil adhesion by preventing focal-complex formation, likely by inhibiting Src and PI3 kinases. However, in the presence of inflammatory stimuli, Ly49Q mediated rapid neutrophil polarization and tissue infiltration in an ITIM-domain-dependent manner. These opposite functions appeared to be mediated by distinct use of effector phosphatase SHP-1 and SHP-2. Ly49Q-dependent polarization and migration were affected by Ly49Q regulation of membrane raft functions. We propose that Ly49Q is pivotal in switching neutrophils to their polarized morphology and rapid migration upon inflammation, through its spatiotemporal regulation of membrane rafts and raft-associated signaling molecules.

Title: Developmental Analysis of Bone Marrow Neutrophils Reveals Populations Specialized in Expansion, Trafficking, and Effector Functions Content: Summary Neutrophils are specialized innate cells that require constant replenishment from proliferative bone marrow (BM) precursors as a result of their short half‐life. Although it is established that neutrophils are derived from the granulocyte‐macrophage progenitor (GMP), the differentiation pathways from GMP to functional mature neutrophils are poorly defined. Using mass cytometry (CyTOF) and cell‐cycle‐based analysis, we identified three neutrophil subsets within the BM: a committed proliferative neutrophil precursor (preNeu) which differentiates into non‐proliferating immature neutrophils and mature neutrophils. Transcriptomic profiling and functional analysis revealed that preNeu require the C/EBP&egr; transcription factor for their generation from the GMP, and their proliferative program is substituted by a gain of migratory and effector function as they mature. preNeus expand under microbial and tumoral stress, and immature neutrophils are recruited to the periphery of tumor‐bearing mice. In summary, our study identifies specialized BM granulocytic populations that ensure supply under homeostasis and stress responses. Graphical Abstract Figure. No Caption available. HighlightsProliferation activity identifies committed neutrophil precursor in mice and humansNeutrophil subsets possess distinct transcriptomic and functional signaturesDefect in neutrophil development leads to impaired neutrophil‐mediated responsesIncreased circulating immature neutrophils are associated with cancer progression &NA; The neutrophil differentiation pathway is poorly defined. Evrard et. al. demonstrate a workflow of characterizing bone marrow neutrophil subsets on the basis of their proliferative capacity and molecular signatures and thereby define the developmental trajectory and functional properties of neutrophils.

Title: R93W mutation in Orai1 causes impaired calcium influx in platelets. Content: The intracellular Ca(2+) concentration of many nonexcitable cells is regulated by calcium store release and store-operated calcium entry (SOCE). In platelets, STIM1 was recently identified as the main calcium sensor expressed in the endoplasmic reticulum. To evaluate the role of the SOC channel moiety, Orai1, in platelet SOCE, we generated mice expressing a mutated, inactive form of Orai1 in blood cells only (Orai1(R93W)). Platelets expressing Orai1(R93W) were characterized by markedly reduced SOCE and impaired agonist-induced increases in [Ca(2+)](i). Orai1(R93W) platelets showed reduced integrin activation and impaired degranulation when stimulated with low agonist concentrations under static conditions. This defect, however, did not significantly affect the ability of Orai1(R93W) platelets to aggregate or to adhere to collagen under arterial flow conditions ex vivo. In contrast, these adherent Orai1(R93W) platelets were defective in surface phosphatidylserine exposure, suggesting that Orai1 is crucial for the platelets' procoagulant response rather than for other Ca(2+)-dependent cellular responses.

Title: Extracellular Acidic pH Activates the Sterol Regulatory Element-Binding Protein 2 to Promote Tumor Progression. Content: Conditions of the tumor microenvironment, such as hypoxia and nutrient starvation, play critical roles in cancer progression. However, the role of acidic extracellular pH in cancer progression is not studied as extensively as that of hypoxia. Here, we show that extracellular acidic pH (pH 6.8) triggered activation of sterol regulatory element-binding protein 2 (SREBP2) by stimulating nuclear translocation and promoter binding to its targets, along with intracellular acidification. Interestingly, inhibition of SREBP2, but not SREBP1, suppressed the upregulation of low pH-induced cholesterol biosynthesis-related genes. Moreover, acyl-CoA synthetase short-chain family member 2 (ACSS2), a direct SREBP2 target, provided a growth advantage to cancer cells under acidic pH. Furthermore, acidic pH-responsive SREBP2 target genes were associated with reduced overall survival of cancer patients. Thus, our findings show that SREBP2 is a key transcriptional regulator of metabolic genes and progression of cancer cells, partly in response to extracellular acidification.

Title: Visualizing the function and fate of neutrophils in sterile injury and repair Content: Neutrophils have been implicated as harmful cells in a variety of inappropriate inflammatory conditions where they injure the host, leading to the death of the neutrophils and their subsequent phagocytosis by monocytes and macrophages. Here we show that in a fully repairing sterile thermal hepatic injury, neutrophils also penetrate the injury site and perform the critical tasks of dismantling injured vessels and creating channels for new vascular regrowth. Upon completion of these tasks, they neither die at the injury site nor are phagocytosed. Instead, many of these neutrophils reenter the vasculature and have a preprogrammed journey that entails a sojourn in the lungs to up-regulate CXCR4 (C-X-C motif chemokine receptor 4) before entering the bone marrow, where they undergo apoptosis.

Title: Control of glutamate clearance and synaptic efficacy by glial coverage of neurons. Content: Analysis of excitatory synaptic transmission in the rat hypothalamic supraoptic nucleus revealed that glutamate clearance and, as a consequence, glutamate concentration and diffusion in the extracellular space, is associated with the degree of astrocytic coverage of its neurons. Reduction in glutamate clearance, whether induced pharmacologically or associated with a relative decrease of glial coverage in the vicinity of synapses, affected transmitter release through modulation of presynaptic metabotropic glutamate receptors. Astrocytic wrapping of neurons, therefore, contributes to the regulation of synaptic efficacy in the central nervous system.

Title: Differential role of CbpA and PspA in modulation of in vitro CXC chemokine responses of respiratory epithelial cells to infection with Streptococcus pneumoniae. Content: Respiratory epithelial cells play an active part in the host response to respiratory pathogens, such as Streptococcus pneumoniae, by releasing chemokines responsible for neutrophil recruitment. In order to investigate the role of specific pneumococcal virulence factors in eliciting CXC chemokine responses, type II pneumocytes (A549) and nasopharyngeal cells (Detroit-562) were infected with S. pneumoniae D39 or mutants lacking choline-binding protein A (CbpA), pneumococcal surface protein A (PspA), or specific domains thereof. In response to wild-type D39, both A549 and Detroit-562 cells showed a significant increase in CXC chemokine mRNA and interleukin-8 protein. This response was increased twofold when a cbpA deletion mutant (DeltaCbpA) was used, suggesting that CbpA inhibits CXC chemokine induction. All three N-terminal domains of CbpA are required for this effect, as in-frame deletion of the respective region of cbpA had the same effect on the CXC chemokine response as deletion of cbpA altogether. Infection with a pspA deletion mutant (DeltaPspA) led to a twofold decrease in the CXC chemokine response of A549 but not Detroit-562 cells, compared to infection with D39 at 2 h. Thus, PspA appears to have the ability to stimulate early CXC chemokine release from A549 cells. Deletion of the region of pspA encoding the first N-terminal alpha-helical domain reduced the ability of S. pneumoniae to elicit a chemokine response to the same degree as deletion of pspA altogether. Thus, the N termini of CbpA and PspA exert differential effects on CXC chemokine induction in epithelial cells infected with S. pneumoniae.

Title: Nef is physically recruited into the immunological synapse and potentiates T cell activation early after TCR engagement. Content: The HIV-1 protein Nef enhances viral pathogenicity and accelerates disease progression in vivo. Nef potentiates T cell activation by an unknown mechanism, probably by optimizing the intracellular environment for HIV replication. Using a new T cell reporter system, we have found that Nef more than doubles the number of cells expressing the transcription factors NF-kappaB and NFAT after TCR stimulation. This Nef-induced priming of TCR signaling pathways occurred independently of calcium signaling and involved a very proximal step before protein kinase C activation. Engagement of the TCR by MHC-bound Ag triggers the formation of the immunological synapse by recruiting detergent-resistant membrane microdomains, termed lipid rafts. Approximately 5-10% of the total cellular pool of Nef is localized within lipid rafts. Using confocal and real-time microscopy, we found that Nef in lipid rafts was recruited into the immunological synapse within minutes after Ab engagement of the TCR/CD3 and CD28 receptors. This recruitment was dependent on the N-terminal domain of Nef encompassing its myristoylation. Nef did not increase the number of cell surface lipid rafts or immunological synapses. Recently, studies have shown a specific interaction of Nef with an active subpopulation of p21-activated kinase-2 found only in the lipid rafts. Thus, the corecruitment of Nef and key cellular partners (e.g., activated p21-activated kinase-2) into the immunological synapse may underlie the increased frequency of cells expressing transcriptionally active forms of NF-kappaB and NFAT and the resultant changes in T cell activation.

Title: Local Ca2+ influx through Ca2+ release-activated Ca2+ (CRAC) channels stimulates production of an intracellular messenger and an intercellular pro-inflammatory signal. Content: Ca2+ entry through store-operated Ca2+ channels drives the production of the pro-inflammatory molecule leukotriene C4 (LTC4) from mast cells through a pathway involving Ca2+-dependent protein kinase C, mitogen-activated protein kinases ERK1/2, phospholipase A2, and 5-lipoxygenase. Here we examine whether local Ca2+ influx through store-operated Ca2+ release-activated Ca2+ (CRAC) channels in the plasma membrane stimulates this signaling pathway. Manipulating the amplitude and spatial extent of Ca2+ entry by altering chemical and electrical gradients for Ca2+ influx or changing the Ca2+ buffering of the cytoplasm all impacted on protein kinase C and ERK activation, generation of arachidonic acid and LTC4 secretion, with little change in the bulk cytoplasmic Ca2+ rise. Similar bulk cytoplasmic Ca2+ concentrations were achieved when CRAC channels were activated in 0.25 mm external Ca2+ versus 2 mm Ca2+ and 100 nm La3+, an inhibitor of CRAC channels. However, despite similar bulk cytoplasmic Ca2+, protein kinase C activation and LTC4 secretion were larger in 2 mm Ca2+ and La3+ than in 0.25 mm Ca2+, consistent with the central involvement of a subplasmalemmal Ca2+ rise. The nonreceptor tyrosine kinase Syk coupled CRAC channel opening to protein kinase C and ERK activation. Recombinant TRPC3 channels also activated protein kinase C, suggesting that subplasmalemmal Ca2+ rather than a microdomain exclusive to CRAC channels is the trigger. Hence a subplasmalemmal Ca2+ increase in mast cells is highly versatile in that it triggers cytoplasmic responses through generation of intracellular messengers as well as long distance changes through increased secretion of paracrine signals.

Title: in Content: Transglutaminase 2 (TGase 2) is a Ca+2-dependent enzyme that catalyzes both intracellular and extracellular cross-linking reactions by transamidation of specific glutamine residues. TGase 2 is known to be involved in the membrane-mediated events required for glucose-stimulated insulin release from the pancreatic beta cells. Here we show that targeted disruption of TGase 2 impairs glucose-stimulated insulin secretion. TGase 2-/- mice show glucose intolerance after intraperitoneal glucose loading. TGase 2-/- mice manifest a tendency to develop hypoglycemia after administration of exogenous insulin as a consequence of enhanced insulin receptor substrate 2 (IRS-2) phosphorylation. We suggest that the increased peripheral sensitivity to insulin partially compensates for the defective secretion in this animal model. TGase 2-/- mouse phenotype resembles that of the maturity-onset diabetes of young (MODY) patients. In the course of screening for human TGase 2 gene in Italian subjects with the clinical features of MODY, we detected a missense mutation (N333S) in the active site of the enzyme. Collectively, these results identify TGase 2 as a potential candidate gene in type 2 diabetes.

Title: Synaptic glutamate release by ventromedial hypothalamic neurons is part of the neurocircuitry that prevents hypoglycemia. Content: The importance of neuropeptides in the hypothalamus has been experimentally established. Due to difficulties in assessing function in vivo, the roles of the fast-acting neurotransmitters glutamate and GABA are largely unknown. Synaptic vesicular transporters (VGLUTs for glutamate and VGAT for GABA) are required for vesicular uptake and, consequently, synaptic release of neurotransmitters. Ventromedial hypothalamic (VMH) neurons are predominantly glutamatergic and express VGLUT2. To evaluate the role of glutamate release from VMH neurons, we generated mice lacking VGLUT2 selectively in SF1 neurons (a major subset of VMH neurons). These mice have hypoglycemia during fasting secondary to impaired fasting-induced increases in the glucose-raising pancreatic hormone glucagon and impaired induction in liver of mRNAs encoding PGC-1alpha and the gluconeogenic enzymes PEPCK and G6Pase. Similarly, these mice have defective counterregulatory responses to insulin-induced hypoglycemia and 2-deoxyglucose (an antimetabolite). Thus, glutamate release from VMH neurons is an important component of the neurocircuitry that functions to prevent hypoglycemia.

Title: Endothelin-1 is induced by cytokines in human vascular smooth muscle cells: evidence for intracellular endothelin-converting enzyme. Content: Endothelin-1 (ET-1) is the predominant endothelin isopeptide generated by the vascular wall and therefore appears to be the most important peptide involved in regulation of cardiovascular events. Many pathologic conditions are associated with elevations of ET-1 in the blood vessel wall. Because these conditions are often cytokine driven, we examined the effects of a mixture of cytokines on ET-1 production in human vascular smooth muscle cells (VSMCs) derived from internal mammary artery and saphenous vein (SV). Incubation of IMA and SV VSMCs with tumor necrosis factor-alpha (10 ng/ml) and interferon-gamma (1000 U/ml) in combination for up to 48 h markedly elevated the expression of mRNA for prepro-ET-1 and the release of ET-1 into the culture medium. This cytokine-stimulated release of ET-1 was inhibited by a series of dual endothelin-converting enzyme (ECE)/neutral endopeptidase inhibitors, phosphoramidon, CGS 26303, and CGS 26393, with an accompanying increase in big ET-1 release but with no effect on expression of mRNA for prepro-ET-1. These same compounds were 10 times more potent at inhibiting the conversion of exogenously applied big ET-1 to ET-1. ECE-1b/c mRNA is present in SV VSMCs, however no ECE-1a is present in these cells. Thus VSMCs most probably contain, like endothelial cells, an intracellular ECE responsible for the endogenous synthesis of ET-1. Under the influence of pro-inflammatory mediators the vascular smooth muscle can therefore become an important site of ET-1 production, as has already been established for the dilator mediators nitric oxide, prostaglandin I2, and prostaglandin E2.

Title: Getting to the site of inflammation: the leukocyte adhesion cascade updated Content: Neutrophil recruitment, lymphocyte recirculation and monocyte trafficking all require adhesion and transmigration through blood-vessel walls. The traditional three steps of rolling, activation and firm adhesion have recently been augmented and refined. Slow rolling, adhesion strengthening, intraluminal crawling and paracellular and transcellular migration are now recognized as separate, additional steps. In neutrophils, a second activation pathway has been discovered that does not require signalling through G-protein-coupled receptors and the signalling steps leading to integrin activation are beginning to emerge. This Review focuses on new aspects of one of the central paradigms of inflammation and immunity — the leukocyte adhesion cascade.

Title: PSGL-1 function in immunity and steady state homeostasis. Content: The substantial importance of P-selectin glycoprotein ligand 1 (PSGL-1) in leukocyte trafficking has continued to emerge beyond its initial identification as a selectin ligand. PSGL-1 seemed to be a relatively simple molecule with an extracellular mucin domain extended as a flexible rod, teleologically consistent with its primary role in tethering leukocytes to endothelial selectins. The rolling interaction between leukocyte and endothelium mediated by this selectin-PSGL-1 interaction requires branched O-glycan extensions on specific PSGL-1 amino acid residues. In some cells, such as neutrophils, the glycosyltransferases involved in formation of the O-glycans are constitutively expressed, while in other cells, such as T cells, they are expressed only after appropriate activation. Thus, PSGL-1 supports leukocyte recruitment in both innate and adaptive arms of the immune response. A complex array of amino acids within the selectins engage multiple sugar residues of the branched O-glycans on PSGL-1 and provide the molecular interactions responsible for the velcro-like catch bonds that support leukocyte rolling. Such binding of PSGL-1 can also induce signaling events that influence cell phenotype and function. Scrutiny of PSGL-1 has revealed a better understanding of how it performs as a selectin ligand and yielded unexpected insights that extend its scope from supporting leukocyte rolling in inflammatory settings to homeostasis including stem cell homing to the thymus and mature T-cell homing to secondary lymphoid organs. PSGL-1 has been found to bind homeostatic chemokines CCL19 and CCL21 and to support the chemotactic response to these chemokines. Surprisingly, the O-glycan modifications of PSGL-1 that support rolling mediated by selectins in inflammatory conditions interfere with PSGL-1 binding to homeostatic chemokines and thereby limit responsiveness to the chemotactic cues used in steady state T-cell traffic. The multi-level influence of PSGL-1 on cell traffic in both inflammatory and steady state settings is therefore substantially determined by the orchestrated addition of O-glycans. However, central as specific O-glycosylation is to PSGL-1 function, in vivo regulation of PSGL-1 glycosylation in T cells remains poorly understood. It is our purpose herein to review what is known, and not known, of PSGL-1 glycosylation and to update understanding of PSGL-1 functional scope.

Title: Chronic obstructive pulmonary disease and neutrophil infiltration: role of cigarette smoke and cyclooxygenase products. Content: Cigarette smoke is the main cause of chronic obstructive pulmonary disease (COPD), where it can contribute to the observed airway inflammation. PGE(2) is produced within human airways, and both pro- and anti-inflammatory activities have been reported. We quantitated PGE(2) concentrations in induced sputum supernatants from different groups of subjects and correlated the obtained values to neutrophil infiltration as well as to the expression of cyclooxygenase-2 (COX-2). Cigarette smoke extract (CSE) was used to evaluate the effect of smoking on COX-2 and PGE(2) receptor expression as well as on PGE(2) release in neutrophils and alveolar macrophages (AM) obtained from normal donors. The effects of PGE(2) and of PGE receptor agonists and antagonists were evaluated on the adhesion of neutrophil to a human bronchial epithelial cell line (16HBE). PGE(2) levels, COX-2 expression, and neutrophil infiltration were significantly higher in normal smokers and COPD smokers (P < 0.0001) compared with controls and COPD former smokers. Induced sputum supernatant caused neutrophil adhesion to 16HBE that was significantly reduced, in COPD smokers only, by PGE(2) immunoprecipitation. In vitro experiments confirmed that CSE increased PGE(2) release and COX-2 and PGE(2) receptor expression in neutrophils and AM; PGE(2) enhanced the adhesion of neutrophils to 16HBE, and a specific E-prostanoid 4 (EP(4)) receptor antagonist blunted its effect. These results suggest that CSE promote the induction of COX-2 and contributes to the proinflammatory effects of PGE(2) in the airways of COPD subjects.

Title: Tyrosine-Phosphorylated Caveolin-1 Blocks Bacterial Uptake by Inducing Vav2-RhoA-Mediated Cytoskeletal Rearrangements Content: Certain bacterial adhesins appear to promote a pathogen's extracellular lifestyle rather than its entry into host cells. However, little is known about the stimuli elicited upon such pathogen host-cell interactions. Here, we report that type IV pili (Tfp)-producing Neisseria gonorrhoeae (P(+)GC) induces an immediate recruitment of caveolin-1 (Cav1) in the host cell, which subsequently prevents bacterial internalization by triggering cytoskeletal rearrangements via downstream phosphotyrosine signaling. A broad and unbiased analysis of potential interaction partners for tyrosine-phosphorylated Cav1 revealed a direct interaction with the Rho-family guanine nucleotide exchange factor Vav2. Both Vav2 and its substrate, the small GTPase RhoA, were found to play a direct role in the Cav1-mediated prevention of bacterial uptake. Our findings, which have been extended to enteropathogenic Escherichia coli, highlight how Tfp-producing bacteria avoid host cell uptake. Further, our data establish a mechanistic link between Cav1 phosphorylation and pathogen-induced cytoskeleton reorganization and advance our understanding of caveolin function.

Title: Crucial Role of Interferon Consensus Sequence Binding Protein, but neither of Interferon Regulatory Factor 1 nor of Nitric Oxide Synthesis for Protection Against Murine Listeriosis Content: Listeria monocytogenes is widely used as a model to study immune responses against intracellular bacteria. It has been shown that neutrophils and macrophages play an important role to restrict bacterial replication in the early phase of primary infection in mice, and that the cytokines interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) are essential for protection. However, the involved signaling pathways and effector mechanisms are still poorly understood. This study investigated mouse strains deficient for the IFN-dependent transcription factors interferon consensus sequence binding protein (ICSBP), interferon regulatory factor (IRF)1 or 2 for their capacity to eliminate Listeria in vivo and in vitro and for production of inducible reactive nitrogen intermediates (RNI) or reactive oxygen intermediates (ROI) in macrophages. ICSBP−/− and to a lesser degree also IRF2−/− mice were highly susceptible to Listeria infection. This correlated with impaired elimination of Listeria from infected peritoneal macrophage (PEM) cultures stimulated with IFN-γ in vitro; in addition these cultures showed reduced and delayed oxidative burst upon IFN-γ stimulation, whereas nitric oxide production was normal. In contrast, mice deficient for IRF1 were not able to produce nitric oxide, but they efficiently controlled Listeria in vivo and in vitro. These results indicate that (a) the ICSBP/IRF2 complex is essential for IFN-γ–mediated protection against Listeria and that (b) ROI together with additional still unknown effector mechanisms may be responsible for the anti-Listeria activity of macrophages, whereas IRF1-induced RNI are not limiting.

Title: Chronic variable stress activates hematopoietic stem cells Content: Exposure to psychosocial stress is a risk factor for many diseases, including atherosclerosis. Although incompletely understood, interaction between the psyche and the immune system provides one potential mechanism linking stress and disease inception and progression. Known cross-talk between the brain and immune system includes the hypothalamic-pituitary-adrenal axis, which centrally drives glucocorticoid production in the adrenal cortex, and the sympathetic-adrenal-medullary axis, which controls stress-induced catecholamine release in support of the fight-or-flight reflex. It remains unknown, however, whether chronic stress changes hematopoietic stem cell activity. Here we show that stress increases proliferation of these most primitive hematopoietic progenitors, giving rise to higher levels of disease-promoting inflammatory leukocytes. We found that chronic stress induced monocytosis and neutrophilia in humans. While investigating the source of leukocytosis in mice, we discovered that stress activates upstream hematopoietic stem cells. Under conditions of chronic variable stress in mice, sympathetic nerve fibers released surplus noradrenaline, which signaled bone marrow niche cells to decrease CXCL12 levels through the β3-adrenergic receptor. Consequently, hematopoietic stem cell proliferation was elevated, leading to an increased output of neutrophils and inflammatory monocytes. When atherosclerosis-prone Apoe(-/-) mice were subjected to chronic stress, accelerated hematopoiesis promoted plaque features associated with vulnerable lesions that cause myocardial infarction and stroke in humans.

Title: Regulation of immune responses by extracellular vesicles Content: Extracellular vesicles, including exosomes, are small membrane vesicles derived from multivesicular bodies or from the plasma membrane. Most, if not all, cell types release extracellular vesicles, which then enter the bodily fluids. These vesicles contain a subset of proteins, lipids and nucleic acids that are derived from the parent cell. It is thought that extracellular vesicles have important roles in intercellular communication, both locally and systemically, as they transfer their contents, including proteins, lipids and RNAs, between cells. Extracellular vesicles are involved in numerous physiological processes, and vesicles from both non-immune and immune cells have important roles in immune regulation. Moreover, extracellular vesicle-based therapeutics are being developed and clinically tested for the treatment of inflammatory diseases, autoimmune disorders and cancer. Given the tremendous therapeutic potential of extracellular vesicles, this Review focuses on their role in modulating immune responses, as well as their potential therapeutic applications.

Title: Increased release of ferritin and iron by iron-loaded alveolar macrophages in cigarette smokers. Content: The lower respiratory tract of cigarette smokers contains an increased amount of iron that is predominantly sequestered within alveolar macrophages (AM), but is also present in alveolar epithelial fluid. Extracellular ferritin-bound iron could potentially be released by reductants present in cigarette smoke and catalyze generation of highly reactive hydroxyl radicals capable of causing oxidant injury. To determine whether AM are a source of alveolar extracellular ferritin and iron, we assessed in vitro release of iron, ferritin, and transferrin by AM recovered by bronchoalveolar lavage (BAL) of 27 healthy subjects including nine nonsmokers (NS), nine light smokers (LS), and nine heavy smokers (HS). Release of iron in vitro over 20 h was increased in AM recovered from LS (2.24 +/- 0.21 nmol/10(6) AM/20 h, p < 0.001) and HS (3.11 +/- 0.32 nmol/10(6) AM, p < 0.001) compared with NS (1.28 +/- 0.08 nmol/10(6) AM). Release of ferritin in vitro over 20 h was also increased in AM recovered from LS (71 +/- 24 ng/10(6) AM, p < 0.05) and HS (176 +/- 35 ng/10(6), p < 0.001) compared with NS (18 +/- 3 ng/10(6) AM). AM recovered from 12 smokers (8 HS, 4 LS) contained greater than 10 nmol of iron per 10(6) cells. These iron-loaded AM released a greater percentage of cell ferritin stores in vitro over 4 h (8.4% +/- 1.1, p < 0.01) than did AM from NS (3.2% +/- 0.6). Release of lactate dehydrogenase (LDH) over 4 h was substantially less (2.9% +/- 0.3, p < 0.001) than ferritin release.(ABSTRACT TRUNCATED AT 250 WORDS)

Title: MicroRNA-192 in diabetic kidney glomeruli and its function in TGF-beta-induced collagen expression via inhibition of E-box repressors. Content: Key features of diabetic nephropathy (DN) include the accumulation of extracellular matrix proteins such as collagen 1-alpha 1 and -2 (Col1a1 and -2). Transforming growth factor beta1 (TGF-beta), a key regulator of these extracellular matrix genes, is increased in mesangial cells (MC) in DN. By microarray profiling, we noted that TGF-beta increased Col1a2 mRNA in mouse MC (MMC) but also decreased mRNA levels of an E-box repressor, deltaEF1. TGF-beta treatment or short hairpin RNAs targeting deltaEF1 increased enhancer activity of upstream E-box elements in the Col1a2 gene. TGF-beta also decreased the expression of Smad-interacting protein 1 (SIP1), another E-box repressor similar to deltaEF1. Interestingly, we noted that SIP1 is a target of microRNA-192 (miR-192), a key miR highly expressed in the kidney. miR-192 levels also were increased by TGF-beta in MMC. TGF-beta treatment or transfection with miR-192 decreased endogenous SIP1 expression as well as reporter activity of a SIP1 3' UTR-containing luciferase construct in MMC. Conversely, a miR-192 inhibitor enhanced the luciferase activity, confirming SIP1 to be a miR-192 target. Furthermore, miR-192 synergized with deltaEF1 short hairpin RNAs to increase Col1a2 E-box-luc activity. Importantly, the in vivo relevance was noted by the observation that miR-192 levels were enhanced significantly in glomeruli isolated from streptozotocin-injected diabetic mice as well as diabetic db/db mice relative to corresponding nondiabetic controls, in parallel with increased TGF-beta and Col1a2 levels. These results uncover a role for miRs in the kidney and DN in controlling TGF-beta-induced Col1a2 expression by down-regulating E-box repressors.

Title: Actin and serum response factor transduce physical cues from the microenvironment to regulate epidermal stem cell fate decisions Content: Epidermal homeostasis depends on a balance between stem cell renewal and differentiation and is regulated by extrinsic signals from the extracellular matrix (ECM). A powerful approach to analysing the pathways involved is to engineer single-cell microenvironments in which individual variables are precisely and quantitatively controlled. Here, we employ micropatterned surfaces to identify the signalling pathways by which restricted ECM contact triggers human epidermal stem cells to initiate terminal differentiation. On small (20 μm diameter) circular islands, keratinocytes remained rounded, and differentiated at higher frequency than cells that could spread on large (50 μm diameter) islands. Differentiation did not depend on ECM composition or density. Rather, the actin cytoskeleton mediated shape-induced differentiation by regulating serum response factor (SRF) transcriptional activity. Knockdown of SRF or its co-factor MAL inhibited differentiation, whereas overexpression of MAL stimulated SRF activity and involucrin expression. SRF target genes FOS and JUNB were also required for differentiation: c-Fos mediated serum responsiveness, whereas JunB was regulated by actin and MAL. Our findings demonstrate how biophysical cues are transduced into transcriptional responses that determine epidermal cell fate.

Title: Heparan sulfate proteoglycans mediate internalization and propagation of specific proteopathic seeds. Content: Recent experimental evidence suggests that transcellular propagation of fibrillar protein aggregates drives the progression of neurodegenerative diseases in a prion-like manner. This phenomenon is now well described in cell and animal models and involves the release of protein aggregates into the extracellular space. Free aggregates then enter neighboring cells to seed further fibrillization. The mechanism by which aggregated extracellular proteins such as tau and α-synuclein bind and enter cells to trigger intracellular fibril formation is unknown. Prior work indicates that prion protein aggregates bind heparan sulfate proteoglycans (HSPGs) on the cell surface to transmit pathologic processes. Here, we find that tau fibril uptake also occurs via HSPG binding. This is blocked in cultured cells and primary neurons by heparin, chlorate, heparinase, and genetic knockdown of a key HSPG synthetic enzyme, Ext1. Interference with tau binding to HSPGs prevents recombinant tau fibrils from inducing intracellular aggregation and blocks transcellular aggregate propagation. In vivo, a heparin mimetic, F6, blocks neuronal uptake of stereotactically injected tau fibrils. Finally, uptake and seeding by α-synuclein fibrils, but not huntingtin fibrils, occurs by the same mechanism as tau. This work suggests a unifying mechanism of cell uptake and propagation for tauopathy and synucleinopathy.

Title: Distribution of dystrophin- and utrophin-associated protein complexes during activation of human neutrophils. Content: OBJECTIVE Dystrophins, utrophins, and their associated proteins are involved in structural and signaling roles in nonmuscle tissues; however, description of these proteins in neutrophils remained unexplored. Therefore we characterize the pattern expression, and the cellular distribution of dystrophin and utrophin gene products and dystrophin-associated proteins (i.e., beta-dystroglycan, alpha-syntrophin, and alpha-dystrobrevins) in relation to actin filaments in resting and activated with formyl-methionyl-leucyl-phenylalanine human neutrophils. MATERIALS AND METHODS Resting and fMLP-activated human neutrophils were analyzed by immunoblot and by confocal microscopy analysis. Immunoprecipitation assays were performed to corroborate the presence of protein complexes. RESULTS Immunoprecipitation assays and confocal analysis demonstrated the presence of two dystrophin-associated protein complexes in resting and activated neutrophils: the former formed by Dp71d/Dp71Delta(110)(m) and dystrophin-associated proteins (beta-dystroglycan, alpha-syntrophin, alpha-dystrobrevin-1, and -2), while the latter contains Up400, instead of Dp71d/Dp71Delta(110)(m), as a central component of the dystrophin-associated protein complexes (DAPC). Confocal analysis also showed the subcellular redistribution of Dp71d/Dp71Delta(110)(m) approximately DAPC and Up400 approximately DAPC in F-actin-based structures displayed during activation process with fMLP. CONCLUSIONS Our study showed the existence of two protein complexes formed by Dp71d/Dp71Delta(110)(m) or Up400 associated with DAPs in resting and fMLP-treated human polymorphonuclears. The interaction of these complexes with the actin cytoskeleton is indicative of their dynamic participation in the chemotaxis process.

Title: Ciliary Extracellular Vesicles: Txt Msg Organelles Content: Cilia are sensory organelles that protrude from cell surfaces to monitor the surrounding environment. In addition to its role as sensory receiver, the cilium also releases extracellular vesicles (EVs). The release of sub-micron sized EVs is a conserved form of intercellular communication used by all three kingdoms of life. These extracellular organelles play important roles in both short and long range signaling between donor and target cells and may coordinate systemic responses within an organism in normal and diseased states. EV shedding from ciliated cells and EV–cilia interactions are evolutionarily conserved phenomena, yet remarkably little is known about the relationship between the cilia and EVs and the fundamental biology of EVs. Studies in the model organisms Chlamydomonas and Caenorhabditis elegans have begun to shed light on ciliary EVs. Chlamydomonas EVs are shed from tips of flagella and are bioactive. Caenorhabditis elegans EVs are shed and released by ciliated sensory neurons in an intraflagellar transport-dependent manner. Caenorhabditis elegans EVs play a role in modulating animal-to-animal communication, and this EV bioactivity is dependent on EV cargo content. Some ciliary pathologies, or ciliopathies, are associated with abnormal EV shedding or with abnormal cilia–EV interactions. Until the 21st century, both cilia and EVs were ignored as vestigial or cellular junk. As research interest in these two organelles continues to gain momentum, we envision a new field of cell biology emerging. Here, we propose that the cilium is a dedicated organelle for EV biogenesis and EV reception. We will also discuss possible mechanisms by which EVs exert bioactivity and explain how what is learned in model organisms regarding EV biogenesis and function may provide insight to human ciliopathies.

Title: The Utilization of Extracellular Proteins as Nutrients Is Suppressed by mTORC1 Content: Despite being surrounded by diverse nutrients, mammalian cells preferentially metabolize glucose and free amino acids. Recently, Ras-induced macropinocytosis of extracellular proteins was shown to reduce a transformed cell's dependence on extracellular glutamine. Here, we demonstrate that protein macropinocytosis can also serve as an essential amino acid source. Lysosomal degradation of extracellular proteins can sustain cell survival and induce activation of mTORC1 but fails to elicit significant cell accumulation. Unlike its growth-promoting activity under amino-acid-replete conditions, we discovered that mTORC1 activation suppresses proliferation when cells rely on extracellular proteins as an amino acid source. Inhibiting mTORC1 results in increased catabolism of endocytosed proteins and enhances cell proliferation during nutrient-depleted conditions in vitro and within vascularly compromised tumors in vivo. Thus, by preventing nutritional consumption of extracellular proteins, mTORC1 couples growth to availability of free amino acids. These results may have important implications for the use of mTOR inhibitors as therapeutics.

Title: Role of tumor associated macrophages in tumor angiogenesis and lymphangiogenesis Content: Tumor angiogenesis is an essential process for supplying rapidly growing malignant tissues with essential nutrients and oxygen. An angiogenic switch allows tumor cells to survive and grow, and provides them access to vasculature resulting in metastatic disease. Monocyte-derived macrophages recruited and reprogrammed by tumor cells serve as a major source of angiogenic factors boosting the angiogenic switch. Tumor endothelium releases angiopoietin-2 and further facilitates recruitment of TIE2 receptor expressing monocytes (TEM) into tumor sites. Tumor-associated macrophages (TAM) sense hypoxia in avascular areas of tumors, and react by production of angiogenic factors such as VEGFA. VEGFA stimulates chemotaxis of endothelial cells (EC) and macrophages. In some tumors, TAM appeared to be a major source of MMP9. Elevated expression of MMP9 by TAM mediates extracellular matrix (ECM) degradation and the release of bioactive VEGFA. Other angiogenic factors released by TAM include basic fibroblast growth factor (bFGF), thymidine phosphorylase (TP), urokinase-type plasminogen activator (uPA), and adrenomedullin (ADM). The same factors used by macrophages for the induction of angiogenesis [like vascular endothelial growth factor A (VEGF-A) and MMP9] support lymphangiogenesis. TAM can express LYVE-1, one of the established markers of lymphatic endothelium. TAM support tumor lymphangiogenesis not only by secretion of pro-lymphangiogenic factors but also by trans-differentiation into lymphatic EC. New pro-angiogenic factor YKL-40 belongs to a family of mammalian chitinase-like proteins (CLP) that act as cytokines or growth factors. Human CLP family comprises YKL-40, YKL-39, and SI-CLP. Production of all three CLP in macrophages is antagonistically regulated by cytokines. It was recently established that YKL-40 induces angiogenesis in vitro and in animal tumor models. YKL-40-neutralizing monoclonal antibody blocks tumor angiogenesis and progression. The role of YKL-39 and SI-CLP in tumor angiogenesis and lymphangiogenesis remains to be investigated.

Title: Classification, functions, and clinical relevance of extracellular vesicles. Content: Both eukaryotic and prokaryotic cells release small, phospholipid-enclosed vesicles into their environment. Why do cells release vesicles? Initial studies showed that eukaryotic vesicles are used to remove obsolete cellular molecules. Although this release of vesicles is beneficial to the cell, the vesicles can also be a danger to their environment, for instance in blood, where vesicles can provide a surface supporting coagulation. Evidence is accumulating that vesicles are cargo containers used by eukaryotic cells to exchange biomolecules as transmembrane receptors and genetic information. Because also bacteria communicate to each other via extracellular vesicles, the intercellular communication via extracellular cargo carriers seems to be conserved throughout evolution, and therefore vesicles are likely to be a highly efficient, robust, and economic manner of exchanging information between cells. Furthermore, vesicles protect cells from accumulation of waste or drugs, they contribute to physiology and pathology, and they have a myriad of potential clinical applications, ranging from biomarkers to anticancer therapy. Because vesicles may pass the blood-brain barrier, they can perhaps even be considered naturally occurring liposomes. Unfortunately, pathways of vesicle release and vesicles themselves are also being used by tumors and infectious diseases to facilitate spreading, and to escape from immune surveillance. In this review, the different types, nomenclature, functions, and clinical relevance of vesicles will be discussed.

Title: Extracellular vesicles from human cardiac progenitor cells inhibit cardiomyocyte apoptosis and improve cardiac function after myocardial infarction. Content: AIMS Recent evidence suggests that cardiac progenitor cells (CPCs) may improve cardiac function after injury. The underlying mechanisms are indirect, but their mediators remain unidentified. Exosomes and other secreted membrane vesicles, hereafter collectively referred to as extracellular vesicles (EVs), act as paracrine signalling mediators. Here, we report that EVs secreted by human CPCs are crucial cardioprotective agents. METHODS AND RESULTS CPCs were derived from atrial appendage explants from patients who underwent heart valve surgery. CPC-conditioned medium (CM) inhibited apoptosis in mouse HL-1 cardiomyocytic cells, while enhancing tube formation in human umbilical vein endothelial cells. These effects were abrogated by depleting CM of EVs. They were reproduced by EVs secreted by CPCs, but not by those secreted by human dermal fibroblasts. Transmission electron microscopy and nanoparticle tracking analysis showed most EVs to be 30-90 nm in diameter, the size of exosomes, although smaller and larger vesicles were also present. MicroRNAs most highly enriched in EVs secreted by CPCs compared with fibroblasts included miR-210, miR-132, and miR-146a-3p. miR-210 down-regulated its known targets, ephrin A3 and PTP1b, inhibiting apoptosis in cardiomyocytic cells. miR-132 down-regulated its target, RasGAP-p120, enhancing tube formation in endothelial cells. Infarcted hearts injected with EVs from CPCs, but not from fibroblasts, exhibited less cardiomyocyte apoptosis, enhanced angiogenesis, and improved LV ejection fraction (0.8 ± 6.8 vs. -21.3 ± 4.5%; P < 0.05) compared with those injected with control medium. CONCLUSION EVs are the active component of the paracrine secretion by human CPCs. As a cell-free approach, EVs could circumvent many of the limitations of cell transplantation.

Title: Production of tyrosol by Candida albicans biofilms and its role in quorum sensing and biofilm development. Content: Tyrosol and farnesol are quorum-sensing molecules produced by Candida albicans which accelerate and block, respectively, the morphological transition from yeasts to hyphae. In this study, we have investigated the secretion of tyrosol by C. albicans and explored its likely role in biofilm development. Both planktonic (suspended) cells and biofilms of four C. albicans strains, including three mutants with defined defects in the Efg 1 and Cph 1 morphogenetic signaling pathways, synthesized extracellular tyrosol during growth at 37 degrees C. There was a correlation between tyrosol production and biomass for both cell types. However, biofilm cells secreted at least 50% more tyrosol than did planktonic cells when tyrosol production was related to cell dry weight. The addition of exogenous farnesol to a wild-type strain inhibited biofilm formation by up to 33% after 48 h. Exogenous tyrosol appeared to have no effect, but scanning electron microscopy revealed that tyrosol stimulated hypha production during the early stages (1 to 6 h) of biofilm development. Experiments involving the simultaneous addition of tyrosol and farnesol at different concentrations suggested that the action of farnesol was dominant, and 48-h biofilms formed in the presence of both compounds consisted almost entirely of yeast cells. When biofilm supernatants were tested for their abilities to inhibit or enhance germ tube formation by planktonic cells, the results indicated that tyrosol activity exceeds that of farnesol after 14 h, but not after 24 h, and that farnesol activity increases significantly during the later stages (48 to 72 h) of biofilm development. Overall, our results support the conclusion that tyrosol acts as a quorum-sensing molecule for biofilms as well as for planktonic cells and that its action is most significant during the early and intermediate stages of biofilm formation.

Title: Junctophilin-4, a component of the endoplasmic reticulum-plasma membrane junctions, regulates Ca2+ dynamics in T cells. Content: Orai1 and stromal interaction molecule 1 (STIM1) mediate store-operated Ca(2+) entry (SOCE) in immune cells. STIM1, an endoplasmic reticulum (ER) Ca(2+) sensor, detects store depletion and interacts with plasma membrane (PM)-resident Orai1 channels at the ER-PM junctions. However, the molecular composition of these junctions in T cells remains poorly understood. Here, we show that junctophilin-4 (JP4), a member of junctional proteins in excitable cells, is expressed in T cells and localized at the ER-PM junctions to regulate Ca(2+) signaling. Silencing or genetic manipulation of JP4 decreased ER Ca(2+) content and SOCE in T cells, impaired activation of the nuclear factor of activated T cells (NFAT) and extracellular signaling-related kinase (ERK) signaling pathways, and diminished expression of activation markers and cytokines. Mechanistically, JP4 directly interacted with STIM1 via its cytoplasmic domain and facilitated its recruitment into the junctions. Accordingly, expression of this cytoplasmic fragment of JP4 inhibited SOCE. Furthermore, JP4 also formed a complex with junctate, a Ca(2+)-sensing ER-resident protein, previously shown to mediate STIM1 recruitment into the junctions. We propose that the junctate-JP4 complex located at the junctions cooperatively interacts with STIM1 to maintain ER Ca(2+) homeostasis and mediate SOCE in T cells.

Title: D3 phosphoinositides and outside-in integrin signaling by glycoprotein IIb-IIIa mediate platelet actin assembly and filopodial extension induced by phorbol 12-myristate 13-acetate. Content: Phorbol 12-myristate 13-acetate (PMA) uncaps a small number of the fast-growing (barbed) ends of actin filaments, thereby eliciting slow actin assembly and extension of filopodia in human blood platelets. These reactions, which also occur in response to immunologic perturbation of the integrin glycoprotein (GP) IIb-IIIa, are sensitive to the phosphoinositide 3-kinase inhibitor wortmannin. Platelets deficient in GPIIb-IIIa integrins or with GPIIb-IIIa function inhibited by calcium chelation or the peptide RGDS have diminished PMA responsiveness. The effects of PMA contrast with thrombin receptor stimulation by >/=5 microM thrombin receptor-activating peptide (TRAP), which causes rapid and massive wortmannin-insensitive actin assembly and lamellar and filopodial extension. However, we show here that wortmannin can inhibit filopod formation if the thrombin receptor is ligated using suboptimal doses (<1 microM) of TRAP. Phosphatidylinositol 3,4-bisphosphate inhibits actin filament severing and capping by human gelsolin in vitro. The findings implicate D3 polyphosphoinositides and integrin signaling in PMA-mediated platelet stimulation and implicate D3 containing phosphoinositides generated in response to protein kinase C activation and GPIIb-IIIa signaling as late-acting intermediates leading to filopodial actin assembly.

Title: [Neutrophils and macrophages related to the pathogenesis and disease development of chronic obstructive pulmonary disease by the inflammatory reaction]. Content: Chronic obstructive pulmonary disease (COPD) is a chronic airway disorder characterized by obstructive airflow limitation which is not completely reversible with treatment. Inflammatory changes in the peripheral airways, especially those with the diameter less than 2mm (so-called small airway disease) have been speculated to be initial steps of COPD. And so it must be quite clear that neutrophils and macrophages play an essential role in the pathogenesis of these lesions. Studies with bronchoalveolar lavage demonstrated an increase in neutrophil numbers and the neutrophil chemoattractant interleukin-8. Recent studies demonstrated that neutrophils and macrophages are increased and contain a variety of proteases, which are involved in cell infiltration and activation. Studies with gene-engineered animals and anti-cytokine treatment will facilitate better understanding the role of neutrophils and macrophages, and eventual novel therapy.

Title: Effects of Hypoxia and Oxidative Stress on Expression of Neprilysin in Human Neuroblastoma Cells and Rat Cortical Neurones and Astrocytes Content: Pathogenesis of Alzheimer’s disease (AD), which is characterised by accumulation of extracellular deposits of β-amyloid peptide (Aβ) in the brain, has recently been linked to vascular disorders such as ischemia and stroke. Aβ is constantly produced in the brain from amyloid precursor protein (APP) through its cleavage by β- and γ-secretases and certain Aβ species are toxic for neurones. The brain has an endogenous mechanism of Aβ removal via proteolytic degradation and the zinc metalloproteinase neprilysin (NEP) is a critical regulator of Aβ concentration. Down-regulation of NEP could predispose to AD. By comparing the effects of hypoxia and oxidative stress on expression and activity of the Aβ-degrading enzyme NEP in human neuroblastoma NB7 cells and rat primary cortical neurones we have demonstrated that hypoxia reduced NEP expression at the protein and mRNA levels as well as its activity. On contrary in astrocytes hypoxia increased NEP mRNA expression.

Title: cDNA and genomic cloning of lacritin, a novel secretion enhancing factor from the human lacrimal gland. Content: Multiple extracellular factors are hypothesized to promote the differentiation of unstimulated and/or stimulated secretory pathways in exocrine secretory cells, but the identity of differentiation factors, particularly those organ-specific, remain largely unknown. Here, we report on the identification of a novel secreted glycoprotein, lacritin, that enhances exocrine secretion in overnight cultures of lacrimal acinar cells which otherwise display loss of secretory function. Lacritin mRNA and protein are highly expressed in human lacrimal gland, moderately in major and minor salivary glands and slightly in thyroid. No lacritin message or protein is detected elsewhere among more than 50 human tissues examined. Lacritin displays partial similarity to the glycosaminoglycan-binding region of brain-specific neuroglycan C (32 % identity over 102 amino acid residues) and to the possibly mucin-like amino globular region of fibulin-2 (30 % identity over 81 amino acid residues), and localizes primarily to secretory granules and secretory fluid. The lacritin gene consists of five exons, displays no alternative splicing and maps to 12q13. Recombinant lacritin augments unstimulated but not stimulated acinar cell secretion, promotes ductal cell proliferation, and stimulates signaling through tyrosine phosphorylation and release of calcium. It binds collagen IV, laminin-1, entactin/nidogen-1, fibronectin and vitronectin, but not collagen I, heparin or EGF. As an autocrine/paracrine enhancer of the lacrimal constitutive secretory pathway, ductal cell mitogen and stimulator of corneal epithelial cells, lacritin may play a key role in the function of the lacrimal gland-corneal axis.

Title: Control of cellular cholesterol efflux by the nuclear oxysterol receptor LXR alpha. Content: LXR alpha is a nuclear receptor that has previously been shown to regulate the metabolic conversion of cholesterol to bile acids. Here we define a role for this transcription factor in the control of cellular cholesterol efflux. We demonstrate that retroviral expression of LXR alpha in NIH 3T3 fibroblasts or RAW264.7 macrophages and/or treatment of these cells with oxysterol ligands of LXR results in 7- to 30-fold induction of the mRNA encoding the putative cholesterol/phospholipid transporter ATP-binding cassette (ABC)A1. In contrast, induction of ABCA1 mRNA in response to oxysterols is attenuated in cells that constitutively express dominant-negative forms of LXR alpha or LXR beta that lack the AF2 transcriptional activation domain. We further demonstrate that expression of LXR alpha in NIH 3T3 fibroblasts and/or treatment of these cells with oxysterols is sufficient to stimulate cholesterol efflux to extracellular apolipoprotein AI. The ability of oxysterol ligands of LXR to stimulate efflux is dramatically reduced in Tangier fibroblasts, which carry a loss of function mutation in the ABCA1 gene. Taken together, these results indicate that cellular cholesterol efflux is controlled, at least in part, at the level of transcription by a nuclear receptor-signaling pathway. They suggest a model in which activation of LXRs by oxysterols in response to cellular sterol loading leads to induction of the ABCA1 transporter and the stimulation of lipid efflux to extracellular acceptors. These findings have important implications for our understanding of mammalian cholesterol homeostasis and suggest new opportunities for pharmacological regulation of cellular lipid metabolism.

Title: Neutrophilic infiltration within the airway smooth muscle in patients with COPD. Content: BACKGROUND COPD is an inflammatory disorder characterised by chronic airflow limitation, but the extent to which airway inflammation is related to functional abnormalities is still uncertain. The interaction between inflammatory cells and airway smooth muscle may have a crucial role. METHODS To investigate the microlocalisation of inflammatory cells within the airway smooth muscle in COPD, surgical specimens obtained from 26 subjects undergoing thoracotomy (eight smokers with COPD, 10 smokers with normal lung function, and eight non-smoking controls) were examined. Immunohistochemical analysis was used to quantify the number of neutrophils, macrophages, mast cells, CD4+ and CD8+ cells localised within the smooth muscle of peripheral airways. RESULTS Smokers with COPD had an increased number of neutrophils and CD8+ cells in the airway smooth muscle compared with non-smokers. Smokers with normal lung function also had a neutrophilic infiltration in the airway smooth muscle, but to a lesser extent. When all the subjects were analysed as one group, neutrophilic infiltration was inversely related to forced expiratory volume in 1 second (% predicted). CONCLUSIONS Microlocalisation of neutrophils and CD8+ cells in the airway smooth muscle in smokers with COPD suggests a possible role for these cells in the pathogenesis of smoking induced airflow limitation.

Title: How reliable are light traps in estimating biting rates of adult Anopheles gambiae s.l. (Diptera: Culicidae) in the presence of treated bed nets? Content: The sampling efficiency of light trap catches relative to human bait catches in estimating biting rates of the mosquito Anopheles gambiae Giles was investigated in two types of community in southern Sierra Leone: (i) where most of the inhabitants slept under treated bed nets; and (ii) where most of the inhabitants slept without bed nets. The number of female A. gambiae mosquitoes caught in these communities by light trap was strongly correlated (r > or = 0.72) with those from corresponding human biting catches performed either on the same or adjacent nights. It was found that the relative sampling efficiency of light traps varied slightly but significantly with mosquito abundance in villages with treated bed nets, but not in those without them. Nevertheless, the relationship between relative sampling efficiency and mosquito abundance did not differ significantly between the two types of village. Overall, there was insufficient evidence to show that the presence of treated nets altered the relative efficiency of light traps and any bias was only slight, and unlikely to be of any practical importance. Hence, it was concluded that light traps can be used as a surrogate for human bait catches in estimating biting rates of A. gambiae mosquitoes in the two communities.

Title: Canonical transient receptor potential 5 channel in conjunction with Orai1 and STIM1 allows Sr2+ entry, optimal influx of Ca2+, and degranulation in a rat mast cell line. Content: Degranulation of mast cells in response to Ag or the calcium mobilizing agent, thapsigargin, is dependent on emptying of intracellular stores of Ca(2+) and the ensuing influx of external Ca(2+), also referred to as store-operated calcium entry. However, it is unlikely that the calcium release-activated calcium channel is the sole mechanism for the entry of Ca(2+) because Sr(2+) and other divalent cations also permeate and support degranulation in stimulated mast cells. In this study we show that influx of Ca(2+) and Sr(2+) as well as degranulation are dependent on the presence of the canonical transient receptor potential (TRPC) channel protein TRPC5, in addition to STIM1 and Orai1, as demonstrated by knock down of each of these proteins by inhibitory RNAs in a rat mast cell (RBL-2H3) line. Overexpression of STIM1 and Orai1, which are known to be essential components of calcium release-activated calcium channel, allows entry of Ca(2+) but not Sr(2+), whereas overexpression of STIM1 and TRPC5 allows entry of both Ca(2+) and Sr(2+). These and other observations suggest that the Sr(2+)-permeable TRPC5 associates with STIM1 and Orai1 in a stoichiometric manner to enhance entry of Ca(2+) to generate a signal for degranulation.

Title: Control of assembly and function of glutamate receptors by the amino-terminal domain. Content: The extracellular amino-terminal domains (ATDs) of the ionotropic glutamate receptor subunits form a semiautonomous component of all glutamate receptors that resides distal to the membrane and controls a surprisingly diverse set of receptor functions. These functions include subunit assembly, receptor trafficking, channel gating, agonist potency, and allosteric modulation. The many divergent features of the different ionotropic glutamate receptor classes and different subunits within a class may stem from differential regulation by the amino-terminal domains. The emerging knowledge of the structure and function of the amino-terminal domains reviewed here may enable targeting of this region for the therapeutic modulation of glutamatergic signaling. Toward this end, NMDA receptor antagonists that interact with the GluN2B ATD show promise in animal models of ischemia, neuropathic pain, and Parkinson's disease.

Title: H2S and HS− donor NaHS releases nitric oxide from nitrosothiols, metal nitrosyl complex, brain homogenate and murine L1210 leukaemia cells Content: Nitrosoglutathione [(GSNO), 500 nmol/l] relaxed the norepinephrine precontracted rat aortic rings. The relaxation effect was pronouncedly enhanced by H2S- and HS−-donor NaHS (30 μmol/l) at 7.5 pH but not at 6.3 pH. To study molecular mechanism of this effect, we investigated whether NaHS can release NO from NO donors. Using an electron paramagnetic resonance spectroscopy method of spin trap and by measuring the NO oxidation product, which is nitrite, by the Griess reaction, we report that NaHS released NO from nitrosothiols, namely from GSNO, S-nitroso-N-acetyl-dl-penicillamine (SNAP), from metal nitrosyl complex nitroprusside (SNP) and from rat brain homogenate and murine L1210 leukaemia cells. From the observation that the releasing effect was more pronounced at 8.0 pH than 6.0 pH, we suppose that HS−, rather than H2S, is responsible for the NO-releasing effect. Since in mammals, H2S and HS− are produced endogenously, we assume that their effect to release NO from nitrosothiols and from metal nitrosyl complexes are responsible for some of their biological activities and that this mechanism may be involved in S-nitrosothiol-signalling reactions.

Title: Signal transduction proteins that associate with the platelet-derived growth factor (PDGF) receptor mediate the PDGF-induced release of glucose-6-phosphate dehydrogenase from permeabilized cells. Content: Permeabilized rat kidney cells rapidly released glucose 6-phosphate dehydrogenase (G6PD) following stimulation with peptide growth factors (Stanton, R.C., Seifter, J.L., Boxer, D.C., Zimmerman, E., and Cantley, L. C. (1991) J. Biol. Chem. 266, 12442-12448). To evaluate the signal transduction pathways mediating release of G6PD, two cell lines transfected with wild type or mutant platelet-derived growth factor (PDGF) receptors (PDGFR) were studied using two permeabilization protocols. G6PD release was evaluated by enzyme activity and Western blot analysis. PDGF caused a significant increase in G6PD release in 1 min in cells transfected with wild type PDGFR. PDGF did not stimulate G6PD release in cells transfected with tyrosine kinase-deficient PDGFR. PDGF did not stimulate G6PD release in cells transfected with partially autophosphorylation-deficient PDGFR in which four known signaling proteins do not associate with the PDGFR. The PDGF-stimulated release of G6PD was partially restored in PDGFR mutants in which either phosphatidylinositol-3-kinase or phospholipase C gamma 1 could associate with the PDGFR. Lastly, there was no basal or PDGF-stimulated phosphorylation of G6PD. We conclude that release of G6PD: 1) requires intrinsic PDGFR tyrosine kinase activity; 2) requires PDGFR autophosphorylation; 3) is mediated by signaling proteins that associate with the PDGFR; 4) is not mediated by direct phosphorylation of G6PD.

Title: Extracellular vesicles derived from renal cancer stem cells induce a pro-tumorigenic phenotype in mesenchymal stromal cells Content: Renal carcinomas have been shown to contain a population of cancer stem cells (CSCs) that present self-renewing capacity and support tumor growth and metastasis. CSCs were shown to secrete large amount of extracellular vesicles (EVs) that can transfer several molecules (proteins, lipids and nucleic acids) and induce epigenetic changes in target cells. Mesenchymal Stromal Cells (MSCs) are susceptible to tumor signalling and can be recruited to tumor regions. The precise role of MSCs in tumor development is still under debate since both pro- and anti-tumorigenic effects have been reported. In this study we analysed the participation of renal CSC-derived EVs in the interaction between tumor and MSCs. We found that CSC-derived EVs promoted persistent phenotypical changes in MSCs characterized by an increased expression of genes associated with cell migration (CXCR4, CXCR7), matrix remodeling (COL4A3), angiogenesis and tumor growth (IL-8, Osteopontin and Myeloperoxidase). EV-stimulated MSCs exhibited in vitro an enhancement of migration toward the tumor conditioned medium. Moreover, EV-stimulated MSCs enhanced migration of renal tumor cells and induced vessel-like formation. In vivo, EV-stimulated MSCs supported tumor development and vascularization, when co-injected with renal tumor cells. In conclusion, CSC-derived EVs induced phenotypical changes in MSCs that are associated with tumor growth.

Title: E-cadherin engagement stimulates proliferation via Rac1 Content: E-cadherin has been linked to the suppression of tumor growth and the inhibition of cell proliferation in culture. We observed that progressively decreasing the seeding density of normal rat kidney-52E (NRK-52E) or MCF-10A epithelial cells from confluence, indeed, released cells from growth arrest. Unexpectedly, a further decrease in seeding density so that cells were isolated from neighboring cells decreased proliferation. Experiments using microengineered substrates showed that E-cadherin engagement stimulated the peak in proliferation at intermediate seeding densities, and that the proliferation arrest at high densities did not involve E-cadherin, but rather resulted from a crowding-dependent decrease in cell spreading against the underlying substrate. Rac1 activity, which was induced by E-cadherin engagement specifically at intermediate seeding densities, was required for the cadherin-stimulated proliferation, and the control of Rac1 activation by E-cadherin was mediated by p120-catenin. Together, these findings demonstrate a stimulatory role for E-cadherin in proliferative regulation, and identify a simple mechanism by which cell–cell contact may trigger or inhibit epithelial cell proliferation in different settings.

Title: Mobilization of intracellular copper stores by the ctr2 vacuolar copper transporter. Content: Copper plays an essential role in processes including signaling to the transcription and protein trafficking machinery, oxidative phosphorylation, iron mobilization, neuropeptide maturation, and normal development. Whereas much is known about intracellular mobilization of ions such as calcium, little information is available on how eukaryotic cells mobilize intracellular copper stores. We describe a mechanism by which the Saccharomyces cerevisiae Ctr2 protein provides bioavailable copper via mobilization of intracellular copper stores. Whereas Ctr2 exhibits structural similarity to the Ctr1 plasma membrane copper importer, microscopic and biochemical fractionation studies localize Ctr2 to the vacuole membrane. We demonstrate that Ctr2 mobilizes vacuolar copper stores in a manner dependent on amino acid residues conserved between the Ctr1 and Ctr2 copper transport family and that ctr2 Delta mutants hyper-accumulate vacuolar copper. Furthermore, a Ctr2 mutant that is mislocalized to the plasma membrane stimulates extracellular copper uptake, supporting a direct role for Ctr2 in copper transport across membranes. These studies identify a novel mechanism for copper mobilization and suggest that organisms cope with copper deprivation via the use of intracellular vesicular stores.

Title: Regulation of the small GTP-binding protein Rho by cell adhesion and the cytoskeleton. Content: Soluble factors from serum such as lysophosphatidic acid (LPA) are thought to activate the small GTP-binding protein Rho based on their ability to induce actin stress fibers and focal adhesions in a Rho-dependent manner. Cell adhesion to extracellular matrices (ECM) has also been proposed to activate Rho, but this point has been controversial due to the difficulty of distinguishing changes in Rho activity from the structural contributions of ECM to the formation of focal adhesions. To address these questions, we established an assay for GTP-bound cellular Rho. Plating Swiss 3T3 cells on fibronectin-coated dishes elicited a transient inhibition of Rho, followed by a phase of Rho activation. The activation phase was greatly enhanced by serum. In serum-starved adherent cells, LPA induced transient Rho activation, whereas in suspended cells Rho activation was sustained. Furthermore, suspended cells showed higher Rho activity than adherent cells in the presence of serum. These data indicate the existence of an adhesion-dependent negative-feedback loop. We also observed that both cytochalasin D and colchicine trigger Rho activation despite their opposite effects on stress fibers and focal adhesions. Our results show that ECM, cytoskeletal structures and soluble factors all contribute to regulation of Rho activity.

Title: Bacteria activate sensory neurons that modulate pain and inflammation Content: Nociceptor sensory neurons are specialized to detect potentially damaging stimuli, protecting the organism by initiating the sensation of pain and eliciting defensive behaviours. Bacterial infections produce pain by unknown molecular mechanisms, although they are presumed to be secondary to immune activation. Here we demonstrate that bacteria directly activate nociceptors, and that the immune response mediated through TLR2, MyD88, T cells, B cells, and neutrophils and monocytes is not necessary for Staphylococcus aureus-induced pain in mice. Mechanical and thermal hyperalgesia in mice is correlated with live bacterial load rather than tissue swelling or immune activation. Bacteria induce calcium flux and action potentials in nociceptor neurons, in part via bacterial N-formylated peptides and the pore-forming toxin α-haemolysin, through distinct mechanisms. Specific ablation of Nav1.8-lineage neurons, which include nociceptors, abrogated pain during bacterial infection, but concurrently increased local immune infiltration and lymphadenopathy of the draining lymph node. Thus, bacterial pathogens produce pain by directly activating sensory neurons that modulate inflammation, an unsuspected role for the nervous system in host-pathogen interactions.

Title: Myeloid-specific Krüppel-like factor 2 inactivation increases macrophage and neutrophil adhesion and promotes atherosclerosis. Content: RATIONALE Hemizygous deficiency of the transcription factor Krüppel-like factor 2 (KLF2) has been shown previously to augment atherosclerosis in hypercholesterolemic mice. However, the cell type responsible for the increased atherosclerosis due to KLF2 deficiency has not been identified. This study examined the consequence of myeloid cell-specific KLF2 inactivation in atherosclerosis. METHODS AND RESULTS Cell-specific knockout mice were generated by Cre/loxP recombination. Macrophages isolated from myeloid-specific Klf2 knockout (myeKlf2(-/-)) mice were similar to myeKlf2(+/+) macrophages in response to activation, polarization, and lipid accumulation. However, in comparison to myeKlf2(+/+) macrophages, myeKlf2(-/-) macrophages adhered more robustly to endothelial cells. Neutrophils from myeKlf2(-/-) mice also adhered more robustly to endothelial cells, and fewer myeKlf2(-/-) neutrophils survived in culture over a 24-hour period in comparison with myeKlf2(+/+) neutrophils. When myeKlf2(-/-) mice were mated to Ldlr(-/-) mice and then fed a high fat and high cholesterol diet, significant increase in atherosclerosis was observed in the myeKlf2(-/-)Ldlr(-/-) mice compared with myeKlf2(+/+)Ldlr(-/-) littermates. The increased atherosclerosis in myeKlf2(-/-)Ldlr(-/-) mice was associated with elevated presence of neutrophils and macrophages, with corresponding increase of myeloperoxidase as well as chlorinated and nitrosylated tyrosine epitopes in their lesion areas compared with myeKlf2(+/+)Ldlr(-/-) mice. CONCLUSIONS This study documents a role for myeloid KLF2 expression in modulating atherosclerosis. The increased neutrophil accumulation and atherosclerosis progression with myeloid-specific KLF2 deficiency also underscores the importance of neutrophils in promoting vascular oxidative stress and atherosclerosis. Collectively, these results suggest that elevating KLF2 expression may be a novel strategy for prevention and treatment of atherosclerosis.

Title: Functional hemichannels in astrocytes: a novel mechanism of glutamate release. Content: Little is known about the expression and possible functions of unopposed gap junction hemichannels in the brain. Emerging evidence suggests that gap junction hemichannels can act as stand-alone functional channels in astrocytes. With immunocytochemistry, dye uptake, and HPLC measurements, we show that astrocytes in vitro express functional hemichannels that can mediate robust efflux of glutamate and aspartate. Functional hemichannels were confirmed by passage of extracellular lucifer yellow (LY) into astrocytes in nominal divalent cation-free solution (DCFS) and the ability to block this passage with gap junction blocking agents. Glutamate/aspartate release (or LY loading) in DCFS was blocked by multivalent cations (Ca2+, Ba2+, Sr2+, Mg2+, and La3+) and by gap junction blocking agents (carbenoxolone, octanol, heptanol, flufenamic acid, and 18alpha-glycyrrhetinic acid) with affinities close to those reported for blockade of gap junction intercellular communication. Glutamate efflux via hemichannels was also accompanied by greatly reduced glutamate uptake. Glutamate release in DCFS, however, was not significantly mediated by reversal of the glutamate transporter: release did not saturate and was not blocked by glutamate transporter blockers. Control experiments in DCFS precluded glutamate release by volume-sensitive anion channels, P2X7 purinergic receptor pores, or general purinergic receptor activation. Blocking intracellular Ca2+ mobilization by BAPTA-AM or thapsigargin did not inhibit glutamate release in DCFS. Divalent cation removal also induced glutamate release from intact CNS white matter (acutely isolated optic nerve) that was blocked by carbenoxolone, suggesting the existence of functional hemichannels in situ. Our results indicated that astrocyte hemichannels could influence CNS levels of extracellular glutamate with implications for normal and pathological brain function.

Title: Matrix Remodeling Promotes Pulmonary Hypertension through Feedback Mechanoactivation of the YAP/TAZ-miR-130/301 Circuit. Content: Pulmonary hypertension (PH) is a deadly vascular disease with enigmatic molecular origins. We found that vascular extracellular matrix (ECM) remodeling and stiffening are early and pervasive processes that promote PH. In multiple pulmonary vascular cell types, such ECM stiffening induced the microRNA-130/301 family via activation of the co-transcription factors YAP and TAZ. MicroRNA-130/301 controlled a PPAR?-APOE-LRP8 axis, promoting collagen deposition and LOX-dependent remodeling and further upregulating YAP/TAZ via a mechanoactive feedback loop. In turn, ECM remodeling controlled pulmonary vascular cell crosstalk via such mechanotransduction, modulation of secreted vasoactive effectors, and regulation of associated microRNA pathways. In vivo, pharmacologic inhibition of microRNA-130/301, APOE, or LOX activity ameliorated ECM remodeling and PH. Thus, ECM remodeling, as controlled by the YAP/TAZ-miR-130/301 feedback circuit, is an early PH trigger and offers combinatorial therapeutic targets for this devastating disease.

Title: Inhibition of receptor-mediated calcium influx in T cells by unsaturated non-esterified fatty acids. Content: The effect of omega-3, omega-6 and omega-9 unsaturated fatty acids (UFAs) on receptor-mediated Ca2+ entry was investigated in a T-cell line (JURKAT) by using anti-CD3 antibodies (OKT3) to induce intracellular Ca2+ [( Ca2+]i) increase and Ca2+ influx. All the UFAs, as well as Ni2+ ions and 12-O-tetradecanoylphorbol 13-acetate, decreased the OKT3-induced sustained [Ca2+]i increase to basal levels. Although non-esterified fatty acids activate protein kinase C (PKC) [McPhail, Clayton & Snyderman (1984) Science 224, 622-624; Murakami, Chan & Routtenberg (1986) J. Biol. Chem. 261, 15424-15429], studies using H-7 and analysis of the PKC-dependent phosphorylation of 19 and 80 kDa marker substrates ruled out the involvement of PKC in UFA-induced inhibition of Ca2+ entry. Flow-cytometry analysis showed that UFAs do not interfere with antibody-receptor binding. BSA (0.2%, w/v) reversed the effect of UFAs after these fatty acids have decreased the OKT3-induced [Ca2+]i increase to basal levels. The relevance of these findings and possible mechanisms for inhibition by UFAs of receptor-mediated Ca2+ influx were discussed.

Title: Human milk proresolving mediators stimulate resolution of acute inflammation Content: Human milk contains nutrients and bioactive products relevant to infant development and immunological protection. Here, we investigated the proresolving properties of milk using human milk lipid mediator isolates (HLMIs) and determined their impact on resolution programs in vivo and with human macrophages. HLMIs reduced the maximum neutrophil numbers (14.6±1.2 × 106–11.0±1.0 × 106 cells per exudate) and shortened the resolution interval (Ri; 50% neutrophil reduction) by 54% compared with peritonitis. Using rigorous liquid-chromatography tandem-mass spectrometry (LC-MS-MS)-based lipid mediator (LM) metabololipidomics, we demonstrated that human milk possesses a proresolving LM-specialized proresolving mediator (LM-SPM) signature profile, containing SPMs (e.g. resolvins (Rv), protectins (PDs), maresins (MaRs), and lipoxins (LXs)) at bioactive levels (pico-nanomolar concentrations) that enhanced human macrophage efferocytosis and bacterial containment. SPMs identified in human milk included D-series Rvs (e.g., RvD1, RvD2, RvD3, AT-RvD3, and RvD4), PD1, MaR1, E-series Rvs (e.g. RvE1, RvE2, and RvE3), and LXs (LXA4 and LXB4). Of the SPMs identified in human milk, RvD2 and MaR1 (50 ng per mouse) individually shortened Ri by ∼75%. Milk from mastitis gave higher leukotriene B4 and prostanoids and lower SPM levels. Taken together, these findings provide evidence that human milk has proresolving actions via comprehensive LM-SPM profiling, describing a potentially novel mechanism in maternal–infant biochemical imprinting.

Title: Roles of exosomes in cardioprotection. Content: Exosomes are extracellular vesicles of endosomal origin which have emerged as key mediators of intercellular communication. All major cardiac cell types-including cardiomyocytes, endothelial cells, and fibroblasts-release exosomes that modulate cellular functions. Exosomes released from human cardiac progenitor cells (CPCs) are cardioprotective and improve cardiac function after myocardial infarction to an extent comparable with that achieved by their parent cells. Cardiac progenitor cell-derived exosomes are enriched in cardioprotective microRNAs, particularly miR-146a-3p. Circulating exosomes mediate remote ischaemic preconditioning. Moreover, they currently are being investigated as diagnostic markers. The discovery that cell-derived extracellular signalling organelles mediate the paracrine effects of stem cells suggests that cell-free strategies could supplant cell transplantation. This review discusses emerging roles of exosomes in cardiovascular physiology, with a focus on cardioprotective activities of CPC-derived exosomes.

Title: Neutrophil elastase-mediated lung disease. Content: Elastases of both the neutrophil and macrophage have been implicated in lung disease initiation and progression. Although it is unlikely that these proteases evolved for the purpose of injuring lung tissue, the elastin-rich connective tissue framework of the lungs appears to be particularly susceptible to the action of elastolytic proteases. Assuming that neutrophil elastase most likely plays a role in the migration of neutrophils toward a site of inflammation and degradation of proteins from invading organisms or other products of the inflammatory response, it is the role of inhibitors of this protease to protect normal tissues from its effects. In alpha-1 antitrypsin deficiency we find an experiment of nature that disrupts this protease-anti-protease balance, resulting in an increased risk of destructive lung disease.

Title: Coordination of p300-mediated chromatin remodeling and TRAP/mediator function through coactivator PGC-1alpha. Content: Transcriptional coactivators showing physical and functional interactions with PPARgamma include the protein acetyl transferase p300, the TRAP/Mediator complex that interacts with the general transcription machinery, and the highly regulated PGC-1alpha. We show that PGC-1alpha directly interacts with TRAP/Mediator, through the PPARgamma-interacting subunit TRAP220, and stimulates TRAP/Mediator-dependent function on DNA templates. Further, while ineffective by itself, PGC-1alpha stimulates p300-dependent histone acetylation and transcription on chromatin templates in response to PPARgamma. These functions are mediated by largely independent PPARgamma, p300, and TRAP220 interaction domains in PGC-1alpha, whereas p300 and TRAP220 show ligand-dependent interactions with a common region of PPARgamma. Apart from showing PGC-1alpha functions both in chromatin remodeling and in preinitiation complex formation or function (transcription), these results suggest a key role for PGC-1alpha, through concerted but dynamic interactions, in coordinating these steps.

Title: Inhibition of cell proliferation and induction of apoptosis by ExFABP gene targeting. Content: Ex-FABP, an extracellular fatty acid binding lipocalin, is physiologically expressed by differentiating chicken chondrocytes and myoblasts. Its expression is enhanced after cell treatment with inflammatory stimuli and repressed by anti-inflammatory agents, behaving as an acute phase protein. Chicken liver fragments in culture show enhanced protein expression after bacterial endotoxin treatment. To investigate the biological role of Ex-FABP, we stably transfected proliferating chondrocytes with an expression vector carrying antisense oriented Ex-FABP cDNA. We observed a dramatic loss of cell viability and a strong inhibition of cell proliferation and differentiation. When chondrocytes were transfected with the antisense oriented Ex-FABP cDNA we observed that Ex-FABP down-modulation increased apoptotic cell number. Myoblasts transfected with the same expression vector showed extensive cell death and impaired myotube formation. We suggest that Ex-FABP acts as a constitutive survival protein and that its expression and activation are fundamental to protect chondrocytes from cell death.

Title: Physiological astrocytic calcium levels stimulate glutamate release to modulate adjacent neurons. Content: Astrocytes can release glutamate in a calcium-dependent manner and consequently signal to adjacent neurons. Whether this glutamate release pathway is used during physiological signaling or is recruited only under pathophysiological conditions is not well defined. One reason for this lack of understanding is the limited knowledge about the levels of calcium necessary to stimulate glutamate release from astrocytes and about how they compare with the range of physiological calcium levels in these cells. We used flash photolysis to raise internal calcium in astrocytes, while monitoring astrocytic calcium levels and glutamate, which evoked slow inward currents that were recorded electrophysiologically from single neurons grown on microislands of astrocytes. With this approach, we demonstrate that modest changes of astrocytic calcium, from 84 to 140 nM, evoke substantial glutamatergic currents in neighboring neurons (-391 pA), with a Hill coefficient of 2.1 to 2.7. Because the agonists glutamate, norepinephrine, and dopamine all raise calcium in astrocytes to levels exceeding 1.8 microM, these quantitative studies demonstrate that the astrocytic glutamate release pathway is engaged at physiological levels of internal calcium. Consequently, the calcium-dependent release of glutamate from astrocytes functions within an appropriate range of astrocytic calcium levels to be used as a signaling pathway within the functional nervous system.

Title: Effects of repeated social stress on leukocyte distribution in bone marrow, peripheral blood and spleen Content: Leukocyte trafficking between the various body compartments has an important surveillance function that ensures the detection of antigen and enables the immune system to initiate a rapid and effective response. Repeated social defeat of group-housed male mice induced by daily, acute encounters with an aggressive conspecific substantially altered leukocyte trafficking and led to a gradual redistribution of immune cells in bone marrow, peripheral blood and spleen. Recurrent exposure to the stressor over a period of 2, 4 or 6 consecutive days was associated with cell mobilization and increased myelopoiesis in the bone marrow that was paralleled by an accumulation of neutrophils and monocytes in circulation and spleen. Substantial depletion of B cells in bone marrow and blood was associated with an increase in splenic B cells indicating a redirection of this cell type to the spleen. In contrast, T cells were markedly reduced in these immune compartments. The recruitment of CD11b+ leukocytes (i.e., monocytes/macrophages and neutrophils) from the bone marrow to the spleen might play a critical role in the development of functional glucocorticoid resistance in the murine spleen that was reported in context with repeated social defeat.

Title: Lipoxin a4 analogs attenuate induction of intestinal epithelial proinflammatory gene expression and reduce the severity of dextran sodium sulfate-induced colitis. Content: The anti-inflammatory eicosanoid lipoxin A(4) (LXA(4)), aspirin-triggered 15-epi-LXA(4), and their stable analogs down-regulate IL-8 secretion and subsequent recruitment of neutrophils by intestinal epithelia. In an effort to elucidate the mechanism by which these lipid mediators modulate cellular proinflammatory programs, we surveyed global epithelial gene expression using cDNA microarrays. LXA(4) analog alone did not significantly affect expression of any of the >7000 genes analyzed. However, LXA(4) analog pretreatment attenuated induction of approximately 50% of the 125 genes up-regulated in response to the gastroenteritis-causing pathogen Salmonella typhimurium. A major subset of genes whose induction was reduced by LXA(4) analog pretreatment is regulated by NF-kappaB, suggesting that LXA(4) analog was influencing the activity of this transcription factor. Nanomolar concentrations of LXA(4) analog reduced NF-kappaB-mediated transcriptional activation in a LXA(4) receptor-dependent manner and inhibited induced degradation of IkappaBalpha. LXA(4) analog did not affect earlier stimulus-induced signaling events that lead to IkappaBalpha degradation, such as S. typhimurium-induced epithelial Ca(2+) mobilization or TNF-alpha-induced phosphorylation of IkappaBalpha. To establish the in vivo relevance of these findings, we examined whether LXA(4) analogs could affect intestinal inflammation in vivo using the mouse model of DSS-induced inflammatory colitis. Oral administration of LXA(4) analog (15-epi-16-para-fluoro-phenoxy-LXA(4), 10 microg/day) significantly reduced the weight loss, hematochezia, and mortality that characterize DSS colitis. Thus, LXA(4) analog-mediated down-regulation of proinflammatory gene expression via inhibition of the NF-kappaB pathway can be therapeutic for diseases characterized by mucosal inflammation.

Title: Extracellular vesicles for drug delivery. Content: Extracellular vesicles (EVs) are cell-derived membrane vesicles, and represent an endogenous mechanism for intercellular communication. Since the discovery that EVs are capable of functionally transferring biological information, the potential use of EVs as drug delivery vehicles has gained considerable scientific interest. EVs may have multiple advantages over currently available drug delivery vehicles, such as their ability to overcome natural barriers, their intrinsic cell targeting properties, and stability in the circulation. However, therapeutic applications of EVs as drug delivery systems have been limited due to a lack of methods for scalable EV isolation and efficient drug loading. Furthermore, in order to achieve targeted drug delivery, their intrinsic cell targeting properties should be tuned through EV engineering. Here, we review and discuss recent progress and remaining challenges in the development of EVs as drug delivery vehicles.

Title: Pancreatic tumor cells with mutant K-ras suppress ERK activity by MEK-dependent induction of MAP kinase phosphatase-2. Content: Activating mutations within the K-ras gene occur in a high percentage of human pancreatic carcinomas. We reported previously that the presence of oncogenic, activated K-ras in human pancreatic carcinoma cell lines did not result in constitutive activation of the extracellular signal-regulated kinases (ERK1 and ERK2). In the present study, we further characterized the ERK signaling pathway in pancreatic tumor cell lines in order to determine whether the ERK pathway is subject to a compensatory downregulation. We found that the attenuation of serum-induced ERK activation was not due to a delay in the kinetics of ERK phosphorylation. Treatment with the tyrosine phosphatase inhibitor orthovanadate increased the level of ERK phosphorylation, implicating a vanadate-sensitive tyrosine phosphatase in the negative regulation of ERK. Furthermore, expression of a dual specificity phosphatase capable of inactivating ERK known as mitogen-activated protein (MAP) kinase phosphatase-2 (MKP-2) was elevated in most of the pancreatic tumor cell lines and correlated with the presence of active MAP kinase kinase (MEK). Taken together, these results suggest that pancreatic tumor cells expressing oncogenic K-ras compensate, in part, by upregulating the expression of MKP-2 to repress the ERK signaling pathway.

Title: Cystine/glutamate exchange regulates metabotropic glutamate receptor presynaptic inhibition of excitatory transmission and vulnerability to cocaine seeking. Content: Withdrawal from chronic cocaine reduces extracellular glutamate levels in the nucleus accumbens by decreasing cystine/glutamate exchange (xc-). Activating xc- with N-acetylcysteine restores extracellular glutamate and prevents cocaine-induced drug seeking. It was hypothesized that the activation of xc- prevents drug seeking by increasing glutamatergic tone on presynaptic group II metabotropic glutamate receptors (mGluR2/3) and thereby inhibiting excitatory transmission. In the first experiment, the capacity of glutamate derived from xc- to regulate excitatory transmission via mGluR2/3 was determined. Physiological levels of cystine (100-300 nm) were restored to acute tissue slices from the nucleus accumbens or prefrontal cortex. Cystine increased glutamate efflux and decreased miniature EPSC (mEPSC) and spontaneous EPSC (sEPSC) frequency as well as evoked EPSC amplitude. These effects of cystine were presynaptic, because there was no change in mEPSC or sEPSC amplitude, and an increase in the evoked EPSC paired-pulse facilitation ratio. The cystine-induced reduction in EPSCs was reversed by blocking either xc- or mGluR2/3. In the second experiment, blocking mGluR2/3 prevented the ability of N-acetylcystine to inhibit the reinstatement of drug seeking in rats trained to self-administer cocaine. These data demonstrate that nonsynaptic glutamate derived from xc- modulates synaptic glutamate release and thereby regulates cocaine-induced drug seeking.

Title: Balancing co-stimulation and inhibition with BTLA and HVEM Content: The interaction between B- and T-lymphocyte attenuator (BTLA), an inhibitory receptor whose extracellular domain belongs to the immunoglobulin superfamily, and herpesvirus-entry mediator (HVEM), a co-stimulatory tumour-necrosis factor receptor, is unique in that it is the only receptor–ligand interaction that directly bridges these two families of receptors. This interaction has raised many questions about how receptors from two different families could interact and what downstream signalling events might occur as a result of receptor ligation. As we discuss, recent studies show that engagement of HVEM with its endogenous ligand (LIGHT) from the tumour-necrosis factor family induces a powerful immune response, whereas HVEM interactions with BTLA negatively regulate T-cell responses.

Title: Ghrelin secretion stimulated by {beta}1-adrenergic receptors in cultured ghrelinoma cells and in fasted mice. Content: Ghrelin, an octanoylated peptide hormone produced in the stomach, rises dramatically in mouse plasma during chronic severe calorie deprivation, an event that is essential to maintain life. The mechanism for this increase is not understood. Here, we study the control of ghrelin secretion in tissue culture cells derived from mice bearing ghrelinomas induced by a tissue-specific SV40 T-antigen transgene. We found that the ghrelin-secreting cells express high levels of mRNA encoding beta(1)-adrenergic receptors. Addition of norepinephrine or epinephrine to the culture medium stimulated ghrelin secretion, and this effect was blocked by atenolol, a selective beta(1)-adrenergic antagonist. When WT mice were treated with reserpine to deplete adrenergic neurotransmitters from sympathetic neurons, the fasting-induced increase in plasma ghrelin was blocked. Inhibition was also seen following atenolol administration. We conclude that ghrelin secretion during fasting is induced by adrenergic agents released by sympathetic neurons and acting directly on beta(1) receptors on the ghrelin-secreting cells of the stomach.