Hypertension augmented COVID-19 through renin-induced internalization of platelet-ACE2 / SARS-Cov-2 complexes

Hypertension, for unknown reasons, is a primary co-morbidity risk factor for poor COVID-19 outcomes. SARS- Cov-2 breaches the lung blood-air barrier to spread among organs inducing endothelial cell dysfunction and multi-organ thromboembolism. ACE2 is the high affinity receptor for SARS-Cov-2 with TMPRSS2 cleavage then enabling fusion. However, ACE2 and TMPRSS are not co-expressed by all SARS-Cov-2 infected organs. We discovered human platelets express ACE2 and TMPRSS, bind SARS-Cov-2 spike protein, and internalize ACE2-spike protein complexes. SARS-Cov-2 RNA accumulates within platelets. Platelets are activated in essential hypertension, transgenic renin expression stimulates fibrosis and coagulation, and inhibition of coagulation blocks renin fibrosis. The direct renin inhibitor Aliskiren blocks thrombosis in hypertensive animals, so renin intercalates into coagulation to initiate thromboembolic disease. We discovered cells releasing prorenin stimulate explosive platelet activation, but in a unique way; the onset of activation was very delayed, and activation was always maximal. Mechanistically, prorenin interacted with quiescent platelets promoting escape of intracellular phosphatidylserine onto the platelet surface. Phosphatidylserine organizes tenase and prothrombinase coagulation complexes, forming factor Xa and then thrombin that explosively activated the platelet PAR1 thrombin receptor. Aliskiren abolished phosphatidylserine expression, thrombin formation, and thrombosis. This establishes renin as a novel, direct platelet agonist. Platelets displaying surface phosphatidylserine are rapidly cleared by engulfment by endothelial cells and perivascular macrophages of the reticuloendothelial system of liver, lung, and spleen. We postulate hypertension and renin expression promotes phosphatidylserine display on platelets, initiating coagulation and platelet activation, but also promoting rapid platelet clearance. This, we postulate, internalizes SARS-Cov-2 into cells that need not express ACE2 or TMPRSS2, themselves. Aim 1. Test the hypothesis that renin-activated platelets are entry vectors for SARS-Cov-2 into endothelial cells and macrophages of the reticuloendothelial system. Aim 2. Test the hypothesis renin-stimulated platelet turnover in vivo introduces SARS-Cov-2 pseudotyped lentivirus-platelet complexes into diverse organs. This project will establish a functional connection between hypertension and SARS-Cov-2 infection, identify renin activated platelets as novel SARS-Cov-2 entry vectors, and define a basis for altered platelet clearance in renin-clamped hypertensive mice. This provides a translational basis for Aliskiren use to normalize hypertension risk in COVID-19, elucidates novel approaches to suppress SARS-Cov-2 organ infection and damage, and establish circulating platelet ACE2 expression as a measure of risk for COVID-19 multi-organ damage.