ACE2 and COVID-19: In addition to the mechanism where the spike protein binding to ACE2 and subsequent downregulation of plasma membrane ACE2 is the major factor that increases angiotensin II (1–8) [22], the enhancement of spike protein binding to host cell receptors by angiotensin II (1–8) and shorter angiotensin peptides should play a critical role by amplifying the spike protein–angiotensin II cycle in COVID-19 pathology.