ACE2 and COVID-19: The hypothesis would explain why angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme-1 inhibitors (ACE-Is), which downregulate the classical RAS by either blocking angiotensin II (Ang-II) signalling or Ang-II synthesis, respectively, and upregulate ACE-2, may reduce mortality in COVID-19 patients [146, 147].