Angiotensin-Converting Enzyme 2 Roles in the Pathogenesis of COVID-19

The new pandemic Coronavirus Disease 2019 (COVID-19) causes a wide range of clinical consequences, from asymptomatic infection to acute respiratory failure, and it is very heterogeneous. The renin-angiotensin system (RAS) is well recognized as a key regulating system in circulatory homeostasis that plays prominent roles in pathophysiological processes in abnormal activation, for instance, renal and cardiovascular diseases, obesity, and stroke. Angiotensin-converting enzyme 2(ACE2) is a component of the RAS system. However, unlike the ACE, its activity is not inhibited by the ACE inhibitors. The major product of ACE2 is Ang1-7, known as a vasodilator peptide and part of the depressant arm of the RAS. There are two forms of ACE2; Transmembrane ACE2 and soluble ACE2. Coronavirus is covered with some proteins in order to help viral attachment to the cell membrane ACE2 as a receptor and then fuse and enter the cells. ACE2 was expressed in the oral cavity, salivary glands of the mouth, esophagus, myocardial cells, kidney, and enterocytes, along with all the respiratory tract, intestine, and blood vessels. In this article, the renin- angiotensin system and its components have been explained. Moreover, the organs involved in COVID-19 disease, and the possible causes of damage to these organs have also been discussed. The probable mechanism of using ACE2 in viral attachment and the probable treatment processes will also be reviewed based on the surface proteins of the virus and ACE2. In addition, we briefly discuss anti-angiotensin drugs and why patients with chronic diseases are more susceptible to COVID-19 infection and show worse progression.