Abstract
Hypertension and chronic kidney disease (CKD) are among the most common comorbidities associated with coronavirus disease 2019 (COVID-19) severity and mortality risk. Renin-angiotensin system (RAS) blockers are cornerstones in the treatment of both hypertension and proteinuric CKD. In the early months of the COVID-19 pandemic, a hypothesis emerged suggesting that the use of RAS blockers may increase susceptibility for COVID-19 infection and disease severity in these populations. This hypothesis was based on the fact that angiotensin-converting enzyme 2 (ACE2), a counter regulatory component of the RAS, acts as the receptor for severe acute respiratory syndrome coronavirus 2 cell entry. Extrapolations from preliminary animal studies led to speculation that upregulation of ACE2 by RAS blockers may increase the risk of COVID-19-related adverse outcomes. However, these hypotheses were not supported by emerging evidence from observational and randomized clinical trials in humans, suggesting no such association. Herein we describe the physiological role of ACE2 as part of the RAS, discuss its central role in COVID-19 infection and present original and updated evidence from human studies on the association between RAS blockade and COVID-19 infection or related outcomes, with a particular focus on hypertension and CKD.