Increased expression of chondroitin sulfotransferases and proteoglycans follows AngII and may help explain pathophysiology underlying Covid‐19 respiratory failure

Abstract

The precise mechanisms by which Covid‐19 infection leads to hypoxia and respiratory failure have not yet been elucidated. Interactions between sulfated glycosaminoglycans (GAGs) and the SARS‐CoV‐2 spike glycoprotein have been identified as participating in viral adherence and infectivity. The spike glycoprotein binds to respiratory epithelium through the angiotensin converting enzyme 2 (ACE2) receptor, which endogenously interacts with Angiotensin (Ang) II to yield Angiotensin 1‐7. Stimulation of human vascular smooth muscle cells by Ang II leads to increased mRNA expression of two chondroitin sulfotransferases (CHST11 and CHST15), which are required for synthesis of chondroitin 4‐sulfate (C4S) and chondroitin 4,6‐disulfate (CSE), respectively. Total sulfated GAGs, increased sulfotransferase activity, and increased expression of the proteoglycans biglycan, syndecan‐1, perlecan, and versican followed treatment by Ang II. Candesartan, an Angiotensin II receptor blocker (Arb), largely, but incompletely, inhibited these increases, and the differences from baseline remained significant. These results suggest that another effect of Ang II also contributes to the increased expression of chondroitin sulfotransferases, total sulfated GAGs, and proteoglycans. We hypothesize that activation of ACE2 may contribute to these increases and suggest that the SARS‐CoV‐2 spike glycoprotein interaction with ACE2 may also increase chondroitin sulfotransferases, sulfated GAGs, and proteoglycans and thereby contribute to viral adherence to bronchioalveolar cells and to respiratory compromise in SARS‐CoV‐2 infection.