Moreover, recent studies revealed that SARS-CoV-2 downregulated the expression of ACE2 in the host cell, and the disturbing ratio of ACE1/ACE2 might be crucial in the pathophysiological process of COVID-19 (Pagliaro and Penna, 2020; Sriram and Insel, 2020; Bank et al., 2021; Beyerstedt et al., 2021). Here, ACE2 is linked to COVID-19.