ACE2 and COVID-19: It has been speculated that H2S may play a protective role against COVID-19-mediated pathology through several mechanisms: firstly, by altering the function or expression levels of angiotensin converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) receptors to impede SARS-CoV-2 entry into host cells.