A hallmark of the immunopathology associated with Alzheimer's disease (AD) is the presence of activated microglia surrounding senile plaque deposits of beta-amyloid (A beta) peptides. A beta peptides have been shown to be potent activators of microglia and macrophages, but little is known about endogenous factors that may modulate their responses to amyloid. We investigated whether the 'anti-inflammatory' cytokines IL-4, IL-10 and IL-13 could regulate A beta-induced production of the inflammatory cytokines IL-1 alpha, IL-1 beta, TNF-alpha, IL-6 and the chemokine MCP-1. A beta(1-42) time- and dose-dependently induced the production and secretion of these inflammatory proteins in the human THP-1 monocyte cell line and in primary murine microglia, similar to what was observed for lipopolysaccharide (LPS) stimulated cells. IL-10 was found to suppress all A beta and LPS-induced inflammatory proteins measured (IL-1 alpha, IL-1 beta, IL-6, TNF-alpha and MCP-1) in both cell types with the exception of LPS-induced MCP-1 in THP-1 cells where no change was observed. In contrast to the inhibition observed for IL-10, both IL-4 and IL-13 enhanced MCP-1 secretion. IL-4 and IL-13 reduced IL-6 secretion, but effects on IL-1 alpha, IL-1 beta or TNF-alpha were dependent on cell type and stimulus conditions. Additional experiments using RT-PCR showed that IL-4, IL-10 and IL-13 mRNA is found to be present in human brain tissue. These results show that IL-4, IL-10, and IL-13 differentially regulate microglial responses to A beta and may play a role in the inflammation pathology observed surrounding senile plaques.
Alzheimer Disease Amyloid beta-Peptides