Renin-Angiotensin System Blockers and the COVID-19 Pandemic: At Present There Is No Evidence to Abandon Renin-Angiotensin System Blockers

Abstract

During the spread of the severe acute respiratory syndrome coronavirus-2, some reports of data still emerging and in need of full analysis indicate that certain groups of patients are at risk of COVID-19. This includes patients with hypertension, heart disease, diabetes mellitus, and clearly the elderly. Many of those patients are treated with renin-angiotensin system blockers. Because the ACE2 (angiotensin-converting enzyme 2) protein is the receptor that facilitates coronavirus entry into cells, the notion has been popularized that treatment with renin-angiotensin system blockers might increase the risk of developing a severe and fatal severe acute respiratory syndrome coronavirus-2 infection. The present article discusses this concept. ACE2 in its full-length form is a membrane-bound enzyme, whereas its shorter (soluble) form circulates in blood at very low levels. As a mono-carboxypeptidase, ACE2 contributes to the degradation of several substrates including angiotensins I and II. ACE (angiotensin-converting enzyme) inhibitors do not inhibit ACE2 because ACE and ACE2 are different enzymes. Although angiotensin II type 1 receptor blockers have been shown to upregulate ACE2 in experimental animals, the evidence is not always consistent and differs among the diverse angiotensin II type 1 receptor blockers and differing organs. Moreover, there are no data to support the notion that ACE inhibitor or angiotensin II type 1 receptor blocker administration facilitates coronavirus entry by increasing ACE2 expression in either animals or humans. Indeed, animal data support elevated ACE2 expression as conferring potential protective pulmonary and cardiovascular effects. In summary, based on the currently available evidence, treatment with renin-angiotensin system blockers should not be discontinued because of concerns with coronavirus infection.

Keywords: ACE inhibitor; COVID-19; angiotensin receptor blocker; coronavirus; severe acute respiratory syndrome.

Figure.

Overview of the connections between renin-angiotensin system blockers, ACE2 (angiotensin-converting enzyme 2) and the coronavirus. The carboxypeptidase ACE2 converts Ang II (angiotensin II) to Ang-(1–7) and Ang I to Ang-(1–9) (A), yet is not blocked by ACE (angiotensin-converting enzyme) inhibitors, which prevent the conversion of Ang I to Ang II. ACE2 also binds and internalizes SARS-Cov-2 (severe acute respiratory syndrome coronavirus-2; B), after priming by the serine protease TMPRSS2 (transmembrane protease, serine 2). Shedding of membrane-bound ACE2 by a disintegrin and metalloprotease 17 (ADAM17) results in the occurrence of soluble (s) ACE2, which can no longer mediate SARS-Cov-2 entry and which might even prevent such entry by keeping the virus in solution. AT₁R (Ang II, via its type 1 receptor) upregulates ADAM17, and AT₁R blockers (ARBs) would prevent this.