Discussion
ARDS, ill
LUNG, MINOR, VIRAL INFECTION, CRITICAL ILLNESS, ARDS
Both type I IFN and cortisol responses are needed in viral induced critical illness, but at different times, IFNs first and steroids later. In most people, both endogenous and exogenous steroids block the organ protective effects of IFN β on the endothelium, if there is no preceding type I IFN response. We have discovered a genetic polymorphism rs9984273 that prevents GR affecting IFNAR expression, but allows glucocorticoids to shut down STAT1-STAT2 type I IFN signaling. A schematic picture (Fig. A schematic presentation regarding the mechanisms of action of glucocorticoids. In normal conditions, IFN β binding to its receptor triggers the formation of the ISG3 complex consisting of Stat1, Stat2, and IRF9. This complex then trans-locates from the cytoplasm to the nucleus where it binds to the interferon-stimulated response element (ISRE) in hundreds of interferon-stimulated genes (ISG) leading to the production of interferon-stimulated proteins. Glucocorticoids have at least two different forms of action in this setting. (1) Glucocorticoids prevent the formation of the ISG3 complex and thus prevent activation of the IFN-beta responsive genes. (2) Glucocorticoids bind to its receptor (GR) and this complex moves from the cytoplasm to the nucleus and binds to the glucocorticoid binding site of the IFNAR2 gene, if the individual has TT at SNP rs9984273. This seems to lead to repression seen as low expression of IFNAR2. In contrast, if the individual has CC or CT this binding does not efficiently take place resulting in higher expression of IFNAR2 than in TT individuals. The size and intensity of the glucocorticoid/GR complex and the IFNAR2 gene illustrate the relative magnitude of the phenomenon in CT vs TT patientsWe found TT patients to have a trend for lower total STAT1 expression and statistically significantly less pSTAT1 than the CT patients. In contrast, TT patients had significantly more STAT2 than the CT patients, while no statistically significant differences in pSTAT2 were observed suggesting that interferon signaling differ between these genotypes. However, detailed picture regarding the dynamics is impossible to draw based on the level of STAT1/STAT2 expression, because in addition to STAT1/STAT2/IRF9 complex JAK can phosphorylate and initiate complexes of STAT1 homodimers [We detected faster decrease in IFN γ and IL-6 levels in patients with the minor allele (CT or CC) compared to those homozygous with the major allele (TT) in rs9984273 when glucocorticoids were administered. Lung specimens of TT patients had also significantly more STAT2 than the CT patients and glucocorticoids did not decrease its nuclear expression like in CT patients. It has been shown that unphosphorylated STAT2 upregulates IL-6 via co-operation of the NF-κB pathway and can do it perfectly well without STAT1 [SNP rs9984273 is a relatively common polymorphism according to available data. Approximately 45% of people with African origin, 34% of Caucasians and 10% of Asians carry the polymorphism (C allele instead of T) Our findings regarding the IFNAR2 expression are also in line with the public data. The Genotype-Tissue Expression (GTEx) portal V8 release for significant variant-gene pairs showed that rs9984273 acts as an expression quantitative trait locus (eQTL) for IFNAR2 expression in lung tissue (One may argue that patients receiving glucocorticoid treatment were more severely ill than those without glucocorticoids and that explains our findings. To exclude that possibility, we earlier performed propensity matching for a matched dataset (The role of IFNAR in COVID-19 outcome is obvious as contribution of a third SNP in IFNAR to COVID-19 severity is reported by Ma et al. [Is there a problem, if IFNAR expression is too high? In this context, the recent findings of Malle et al. [One limitation in our study is that we do not have data regarding which patients have viral induced ARDS vs bacterial, or both, or fungal in the INTEREST trial, and therefore, the results of INTEREST do not perfectly represent the situation in COVID-19. Exact microbial origin should be registered in future ARDS trials as interferon responses, specifically type 1 responses are somewhat differentially required between bacterial and viral infections. Moreover, the exact molecular mechanisms of the GR binding site in IFNAR2 and its possible additional effects to other reported SNPs in IFNAR2 require future investigations.We envision that the genetic polymorphism SNP rs9984273 reported in this paper has evolved and become enriched during previous viral outbreaks and pandemics in humans. Furthermore, we conclude that this polymorphism may, at least in part, explain the continuous controversy in studies investigating the use of glucocorticoids for ARDS, especially those of viral origin where type I IFN activity is needed. In summary, we have discovered a novel polymorphism in IFNAR2 containing a GR binding motif that is associated with the IFNAR2 expression level, IFN β response, and outcome of ARDS/COVID-19. Our study strongly indicates that simultaneous administration of IFN β and glucocorticoids should be avoided especially for those patients with TT allele in SNP rs9984273.