Corticosteroids reduce pathologic interferon responses by downregulating STAT1 in patients with high-risk COVID-19

Abstract

COVID-19: Corticosteroids counteract inflammation by interferonThe ability of corticosteroid drugs to alleviate extreme inflammation in severe cases of COVID-19 is linked to their reduction of the gene expression that is stimulated by interferon, an immunological cytokine protein. Interferon is crucial for a healthy immune response, but when produced in excess it can play a central role in causing damaging inflammation. Hyun-Woo Jeong at the Max Planck Institute for Molecular Biomedicine, Munster, Germany, and colleagues in South Korea compared the activity of genes involved in the inflammatory response in blood cells from COVID-19 patients and healthy donors. The results provided insights into the role of altered gene activity in both aggravation and improvement of COVID-19. Of particular interest was the ability of corticosteroids to downregulate the activity of a gene called STAT1, involved in mediating interferon signals. We do not yet understand exactly how corticosteroids attenuate hyperinflammatory responses and alleviate high-risk coronavirus disease 2019 (COVID-19). We aimed to reveal the molecular mechanisms of hyperinflammation in COVID-19 and the anti-inflammatory effects of corticosteroids in patients with high-risk COVID-19. We performed single-cell RNA sequencing of peripheral blood mononuclear cells (PBMCs) from three independent COVID-19 cohorts: cohort 1 was used for comparative analysis of high-risk and low-risk COVID-19 (47 PBMC samples from 28 patients), cohort 2 for longitudinal analysis during COVID-19 (57 PBMC samples from 15 patients), and cohort 3 for investigating the effects of corticosteroid treatment in patients with high-risk COVID-19 (55 PBMC samples from 13 patients). PBMC samples from healthy donors (12 PBMC samples from 12 donors) were also included. Cohort 1 revealed a significant increase in the proportion of monocytes expressing the long noncoding RNAs NEAT1 and MALAT1 in high-risk patients. Cohort 2 showed that genes encoding inflammatory chemokines and their receptors were upregulated during aggravation, whereas genes related to angiogenesis were upregulated during improvement. Cohort 3 demonstrated downregulation of interferon-stimulated genes (ISGs), including STAT1, in monocytes after corticosteroid treatment. In particular, unphosphorylated STAT-dependent ISGs enriched in monocytes from lupus patients were selectively downregulated by corticosteroid treatment in patients with high-risk COVID-19. Corticosteroid treatment suppresses pathologic interferon responses in monocytes by downregulating STAT1 in patients with high-risk COVID-19. Our study provides insights into the mechanisms underlying COVID-19 aggravation and improvement and the effects of corticosteroid treatment.