Severe Acute Respiratory Syndrome Coronavirus 2, COVID-19, and the Renin-Angiotensin System: Pressing Needs and Best Research Practices

Abstract

The coronavirus disease 2019 (COVID-19) pandemic is associated with significant morbidity and mortality throughout the world, predominantly due to lung and cardiovascular injury. The virus responsible for COVID-19-severe acute respiratory syndrome coronavirus 2-gains entry into host cells via ACE2 (angiotensin-converting enzyme 2). ACE2 is a primary enzyme within the key counter-regulatory pathway of the renin-angiotensin system (RAS), which acts to oppose the actions of Ang (angiotensin) II by generating Ang-(1-7) to reduce inflammation and fibrosis and mitigate end organ damage. As COVID-19 spans multiple organ systems linked to the cardiovascular system, it is imperative to understand clearly how severe acute respiratory syndrome coronavirus 2 may affect the multifaceted RAS. In addition, recognition of the role of ACE2 and the RAS in COVID-19 has renewed interest in its role in the pathophysiology of cardiovascular disease in general. We provide researchers with a framework of best practices in basic and clinical research to interrogate the RAS using appropriate methodology, especially those who are relatively new to the field. This is crucial, as there are many limitations inherent in investigating the RAS in experimental models and in humans. We discuss sound methodological approaches to quantifying enzyme content and activity (ACE, ACE2), peptides (Ang II, Ang-[1-7]), and receptors (types 1 and 2 Ang II receptors, Mas receptor). Our goal is to ensure appropriate research methodology for investigations of the RAS in patients with severe acute respiratory syndrome coronavirus 2 and COVID-19 to ensure optimal rigor and reproducibility and appropriate interpretation of results from these investigations.

Keywords: angiotensin II; blood pressure; cardiovascular disease; coronavirus; hypertension.

Figure 1.. Balance of angiotensin (Ang) II and Ang-(1–7) in the renin-angiotensin system (RAS).

A, In health, the RAS is in balance: blood pressure is normal, and no disease develops. B, With perturbations from various disease states (eg, hypertension or SARS-CoV-2 infection), there is a shift towards the ACE/Ang II pathway and away from the ACE2/Ang-(1–7) pathway. ACE: angiotensin-converting enzyme, ACE2: angiotensin-converting enzyme 2, AT₁R: type 1 Ang II receptor. Figure adapted from South et al.

Figure 2.. Spectrum of possible cardiovascular manifestations of COVID-19.

MIS-C: multisystem inflammatory syndrome in children, EF: ejection fraction, PT: prothrombin time, aPTT: activated partial thromboplastin time, D-dimers: dimers of fragment D.

Figure 3.. The SARS-CoV-2 replicative cycle

(from left to right). Cell entry of SARS-CoV-2 occurs through recognition of its ACE2 receptor, and after cleavage/activation of the spike (S) protein by cellular proteases, including TMPRSS2. After fusion of the viral envelope with the cellular membrane, the viral positive strand genomic RNA, (+) gRNA, is uncoated and translated into a polyprotein, which is cleaved by viral proteases. The processed non-structural proteins assemble to form the replicase-transcriptase complex (RTC, green blobs). Proteins in this complex elicit the remodeling of membranes to form organelles (double-membrane vesicles) that are dedicated to viral RNA synthesis. The proteins of the RTC then execute viral RNA replication. This process includes production of multiple negative stand (−) subgenomic RNAs (sgRNAs), from which the positive strand (+) sgRNAs are produced. These are also messenger RNAs for the four structural protein S, envelope (E), membrane (M), and nucleocapsid (N). The N protein encapsidates the (+) gRNA to form the nucleocapsid. The S, E, and M proteins, which are co-translationally inserted in the membrane of the endoplasmic reticulum (ER), assemble with the nucleocapsid in the ER-Golgi intermediate compartment (ERGIC). After budding into the ERGIC, viral particles are transported to the plasma membrane in smooth-walled vesicles and released by exocytosis. Figure adapted from Howley and Knipe.