Organ-protective effect of angiotensin-converting enzyme 2 and its effect on the prognosis of COVID-19

This article reviews the correlation between angiotensin-converting enzyme 2 (ACE2) and severe risk factors for coronavirus disease 2019 (COVID-19) and the possible mechanisms. ACE2 is a crucial component of the renin-angiotensin system (RAS). The classical RAS ACE-Ang II-AT1R regulatory axis and the ACE2-Ang 1-7-MasR counter-regulatory axis play an essential role in maintaining homeostasis in humans. ACE2 is widely distributed in the heart, kidneys, lungs, and testes. ACE2 antagonizes the activation of the classical RAS system and protects against organ damage, protecting against hypertension, diabetes, and cardiovascular disease. Similar to SARS-CoV, SARS-CoV-2 also uses the ACE2 receptor to invade human alveolar epithelial cells. Acute respiratory distress syndrome (ARDS) is a clinical high-mortality disease, and ACE2 has a protective effect on this type of acute lung injury. Current research shows that the poor prognosis of patients with COVID-19 is related to factors such as sex (male), age (>60 years), underlying diseases (hypertension, diabetes, and cardiovascular disease), secondary ARDS, and other relevant factors. Because of these protective effects of ACE2 on chronic underlying diseases and ARDS, the development of spike protein-based vaccine and drugs enhancing ACE2 activity may become one of the most promising approaches for the treatment of COVID-19 in the future.