Membrane-bound Angiotensin-converting Enzyme 2 Research Articles

Insights on SARS-CoV-2 Molecular Interactions With the Renin-Angiotensin System.

The emergence of SARS-CoV-2/human/Wuhan/X1/2019, a virus belonging to the species Severe acute respiratory syndrome-related coronavirus, and the recognition of Coronavirus Disease 2019 (COVID-19) as a pandemic have highly increased the scientific research regarding the pathogenesis of COVID-19. The Renin Angiotensin System (RAS) seems to be involved in COVID-19 natural course, since studies suggest the membrane-bound Angiotensin-converting enzyme 2 (ACE2) works as SARS-CoV-2 cellular receptor. Besides the efforts of the scientific community to understand the virus’ molecular interactions with human cells, few studies summarize what has been so far discovered about SARS-CoV-2 signaling mechanisms and its interactions with RAS molecules. This review aims to discuss possible SARS-CoV-2 intracellular signaling pathways, cell entry mechanism and the possible consequences of the interaction with RAS components, including Angiotensin II (Ang II), Angiotensin-(1-7) [Ang-(1-7)], Angiotensin-converting enzyme (ACE), ACE2, Angiotensin II receptor type-1 (AT1), and Mas Receptor. We also discuss ongoing clinical trials and treatment based on RAS cascade intervention. Data were obtained independently by the two authors who carried out a search in the PubMed, Embase, LILACS, Cochrane, Scopus, SciELO and the National Institute of Health databases using Medical Subject Heading terms as “SARS-CoV-2,” “COVID-19,” “Renin Angiotensin System,” “ACE2,” “Angiotensin II,” “Angiotensin-(1-7),” and “AT1 receptor.” Similarly to other members of Coronaviridae family, the molecular interactions between the pathogen and the membrane-bound ACE2 are based on the cleavage of the spike glycoprotein (S) in two subunits. Following the binding of the S1 receptor-binding domain (RBD) to ACE2, transmembrane protease/serine subfamily 2 (TMPRSS2) cleaves the S2 domain to facilitate membrane fusion. It is very likely that SARS-CoV-2 cell entry results in downregulation of membrane-bound ACE2, an enzyme that converts Ang II into Ang-(1-7). This mechanism can result in lung injury and vasoconstriction. In addition, Ang II activates pro-inflammatory cascades when binding to the AT1 Receptor. On the other hand, Ang-(1-7) promotes anti-inflammatory effects through its interactions with the Mas Receptor. These molecules might be possible therapeutic targets for treating COVID-19. Thus, the understanding of SARS-CoV-2 intracellular pathways and interactions with the RAS may clarify COVID-19 physiopathology and open perspectives for new treatments and strategies.

Pathogenesis and preventive approach of hypercoagulopathy and microvascular thrombosis induced mortality from COVID-19

Background: COVID-19 is the current pandemic infection caused by severe acute respiratory syndrome coronavirus-2 (SARS Cov-2). Pulmonary collapse in severe critical COVID-19 patients may be due to development of multiple micro thrombi within pulmonary vasculature. As COVID-19 pandemic is accelerating, it is important to understand the molecular mechanism through which SARSCov2 induces hypercoagulopathy and intravascular thrombosis to be able to design more appropriate therapy. Focus of this review is to identify mechanisms through re-analysis of publicly available data by which SARS-Cov2 infection induce mortality by augmenting intravascular thrombosis and attempt to understand therapeutic approach to it. Findings: SARS Cov-2 accesses host cells via membrane bound angiotensin converting enzyme-2 (ACE2). This leads to imbalance of renin angiotensin system (RAS) increase ratio of Ag-II: Ag-1-7. Ag-II stimulates release of IP-10 from endothelium which upregulates local renin angiotensin system in endothelial cell by positive feedback process. Therefore it is suggested that angiotensin-II of renin angiotensin systemr in endothelial cells sustained proinflammatory signal and developed microvascular thrombosis. During inflammation both extrinsic and intrinsic coagulation pathways are activated. Fibrinolysis is suppressed by imbalance activity of two system: Ang-II-PAI-1 (plasminigen activator inhibitor-1) and Bradykinin-tPA (tissue plasminogen activator) system. Therapy with low molecular weight heparin (LMWH), which have anticoagulant and anti-inflammatory property, is associated with better prognostic in patients with severe COVID-19. ACE inhibitors decrease production of Ag-II and increases availability of bradykinin and consequence reduces coagulopathy Conclusion: Thus it is concluded that SARS-Cov2 infection induces microvascular thrombosis from hyperinflammation, misbalance between Ag-II and Ag-1-7 and imbalance activity of two system: Ang-II-PAI-1 and bradykinin-tPA system. ACE inhibitor and anticoagulant mainly LMWH and UFH may serve potential role in COVID-19 therapy particularly in patients with hypercoagulopathy and microvascular thrombosis. Keywords: COVID19; angiotensin converting enzyme; renin angiotensin system; fibrinolysis; microvascular thrombosis; ACE inhibitor; heparin

Protein Kinase C-δ Mediates Shedding of Angiotensin-Converting Enzyme 2 from Proximal Tubular Cells.

Angiotensin-converting enzyme 2 (ACE2) degrades angiotensin (Ang) II to Ang-(1–7), and protects against diabetic renal injury. Soluble ACE2 fragments are shed from the proximal tubule, and appear at high levels in the urine with diabetes. High glucose-induced shedding of ACE2 from proximal tubular cells is mediated by the enzyme “a disintegrin and metalloproteinase-17″ (ADAM17). Here, we investigated the mechanism for constitutive shedding of ACE2. Mouse proximal tubular cells were cultured and ACE2 shedding into the media was assessed by enzyme activity assay and immunoblot analysis. Cells were incubated with pharmacologic inhibitors, or transfected with silencing (si) RNA. Incubation of proximal tubular cells with increasing concentrations of D-glucose stimulated ACE2 shedding, which peaked at 16 mM, while L-glucose (osmotic control) had no effect on shedding. In cells maintained in 7.8 mM D-glucose, ACE2 shedding was significantly inhibited by the pan-protein kinase C (PKC) competitive inhibitor sotrastaurin, but not by an inhibitor of ADAM17. Incubation of cells with the PKC-α and -β1-specific inhibitor Go6976, the PKC β1 and β2-specific inhibitor ruboxistaurin, inhibitors of matrix metalloproteinases-2,-8, and -9, or an inhibitor of ADAM10 (GI250423X) had no effect on basal ACE2 shedding. By contrast, the PKC-δ inhibitor rottlerin significantly inhibited both constitutive and high glucose-induced ACE2 shedding. Transfection of cells with siRNA directed against PKC-δ reduced ACE2 shedding by 20%, while knockdown of PKC-ε was without effect. These results indicate that constitutive shedding of ACE2 from proximal tubular cells is mediated by PKC-δ, which is also linked to high glucose-induced shedding. Targeting PKC-δ may preserve membrane-bound ACE2 in proximal tubule in disease states and diminish Ang II-stimulated adverse signaling.