key: cord-1019766-nkdnfij1
authors: Mokuda, Sho; Tokunaga, Tadahiro; Masumoto, Junya; Sugiyama, Eiji
title: Angiotensin-converting enzyme 2, a SARS-CoV-2 receptor, is upregulated by interleukin-6 via STAT3 signaling in rheumatoid synovium
date: 2020-05-27
journal: bioRxiv
DOI: 10.1101/2020.05.26.115261
sha: 1e158ba3ddb2631b5fe64399c5ea9333a51f3ef8
doc_id: 1019766
cord_uid: nkdnfij1

Detected in December 2019, the coronavirus disease 2019 (COVID-19) has since spread all over the world, resulting in a global pandemic. The disease is caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), and its symptoms usually include cough, fever, and gastrointestinal problems. Although the prevalence of rheumatoid arthritis (RA) is about 1 % of the global population and RA patients naturally have a chance of acquiring COVID-19 in this pandemic, no studies have considered the expression of angiotensin-converting enzyme 2 (ACE2) (a receptor for SARS-CoV-2) in synovial tissues. Our presenting data revealed that ACE2 expression was elevated in active rheumatoid synovium, and siRNA against STAT3 was able to downregulate ACE2 expression, which was in turn induced by IL-6 signaling.

Detected in December 2019, the coronavirus disease 2019 (COVID-19) has since spread all over the world, resulting in a global pandemic. The disease is caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), and its symptoms usually include cough, fever, and gastrointestinal problems. Although the prevalence of rheumatoid arthritis (RA) is about 1 % of the global population and RA patients naturally have a chance of acquiring COVID-19 in this pandemic, no studies have considered the expression of angiotensin-converting enzyme 2 (ACE2) (a receptor for SARS-CoV-2) in synovial tissues. Our presenting data revealed that ACE2 expression was elevated in active rheumatoid synovium, and siRNA against STAT3 was able to downregulate ACE2 expression, which was in turn induced by IL-6 signaling.

Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) has spread explosively worldwide and resulted in a pandemic of a new respiratory disease called coronavirus disease 2019 (COVID-19) in March 2020. Symptoms of COVID-19 include fever, malaise, cough, and in severe cases, pneumonia and acute respiratory distress syndrome (1, 2) . Coronavirus possesses envelope-anchored spike proteins that bind host cell surface receptors and allow viral entry into target cells. In the case of SARS-CoV-2, its spike protein mediates binding of the angiotensin-converting enzyme 2 (ACE2) receptor (3) . While ACE2 expression levels are relatively low in the airway mucosa and lungs, this protein is predominant in the stomach, intestines, gallbladder, kidney, and heart (4). Therefore, in COVID-19 patients, SARS-CoV-2 can be detected not only in nasal and oral swabs but also in rectal samples; viral RNA has also been detected in patient blood (5) .

Rheumatoid arthritis (RA) is an autoimmune disease that is characterized by systemic synovitis and affects about 1% of the world population. The expression pattern of ACE2 in synovial tissues has not yet been reported, although RA patients naturally have a chance of getting COVID-19 in this pandemic (6) (7) (8) . In this study, we investigated ACE2 expression in the synovium and its regulatory expression mechanism.

Immunohistochemistry analysis revealed that the active rheumatoid synovium, where remarkable thickening of the synovial lining and mesenchymoid transformation of the synovial stroma were observed, displayed a higher expression of ACE2 as compared to inactive samples ( Figure 1A ). Reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) for ACE2 mRNA extracted from the synovium supported these data ( Figure 1B ). ACE2 expression was found to be increased in the synovial lining and sublining regions, suggesting that its expression was elevated in fibroblast-like synoviocytes (FLS). Primary cultures of these RA-derived FLS revealed that interleukin-6 (IL-6) stimulation increased ACE2 expression ( Figure 1C ). IL-6 is known to regulate downstream target genes via signal transducer and activator of transcription 3 (STAT3) signaling activation (9) . IL-6 stimulation led to tyrosine phosphorylation of STAT3 (data not shown). Indeed, the use of small interfering RNA (siRNA) against STAT3 reduced the IL-6-dependent ACE2 expression in RA-FLS ( Figure 1D ).

We propose that ACE2 is upregulated in the synovium of active RA patients and is likely maintained by STAT3-mediated activation through the IL-6 pathway ( Figure 1E ). Therefore, RA activity may be able to alter SARS-CoV-2 entry into synovial cells. Further analyses of IL-6-induced ACE2 transcription in cells other than FLS may help elucidate the mechanisms of viral entry into target cells, as in vivo IL-6 levels are high in COVID-19 patients (2) . These data also implies that unplanned preventive withdrawal of diseasemodified antirheumatic drugs (DMARDs) could lead to increase the risk of COVID-19. staining.

Total RNA was extracted and purified from synovial tissue (a total of 7 samples from 

A novel coronavirus outbreak of global health concern

COVID-19: consider cytokine storm syndromes and immunosuppression

SARS-CoV-2 cell entry depends on ACE2 and TMPRSS2 and is blocked by a clinically proven protease inhibitor

High expression of ACE2 receptor of 2019-nCoV on the epithelial cells of oral mucosa

Molecular and serological investigation of 2019-nCoV infected patients: implication of multiple shedding routes

Clinical course of COVID-19 in a series of patients with chronic arthritis treated with immunosuppressive targeted therapies

Incidence and clinical course of COVID-19 in patients with connective tissue diseases: a descriptive observational analysis

pii: jrheum

Absence of severe complications from SARS-CoV-2 infection in children with rheumatic diseases treated with biologic drugs

Acute-phase response factor, a nuclear factor binding to acute-phase response elements, is rapidly activated by interleukin-6 at the posttranslational level

We thank the staffs of the Department of Clinical Immunology and Rheumatology at Hiroshima University Hospital, Japan, and the staffs of Dohgo Spa Hospital, Matsuyama, Ehime, Japan, for the preparation of patients' specimens.