Abstract 17: SARS-CoV-2 Spike Protein Exacerbates Thromboembolic Cerebrovascular Complications in Humanized ACE2 Mouse Model

Abstract

COVID-19 doubles the risk for acute ischemic stroke in patients with cardiovascular disorders, yet, the molecular mechanisms are unclear and remain unresolved medical challenges. We hypothesize that SARS-CoV-2 spike protein exacerbates stroke and neurovascular complications via increasing coagulation and decreasing fibrinolysis by disrupting the renin-angiotensin-aldosterone system (RAAS) balance. Methods: MCA/FeCl 3 thromboembolic model was induced in humanized ACE2 knock-in mice. hACE2 mice were treated with Losartan, an angiotensin receptor blocker, after one day of SARS-CoV-2 spike protein injection. Cerebral blood flow was measured using a Laser speckle imager. Infarct size was compared using TTC stain. Vascular-induced cognitive function and dementia (VCID) were assessed using a Novel object recognition test. D-dimmer, Tissue factor -3 (TF-3), and Plasminogen activator inhibitor-1 (PAI-1) were measured using ELISA and Western blot to assess coagulation and fibrinolysis. Human brain microvascular endothelial cells (HBMEC) were exposed to hypoxia with/without SARS-Co-V2 spike protein and were assessed for coagulation factors, inflammation, and RAAS balance. Results: SARS-CoV-2 spike protein increased neuronal death and decreased cognitive function after MCA/FeCl 3 thromboembolic occlusion. hACE2 mice subjected to SARS-CoV-2 spike protein showed diminished cerebral blood flow compared to control groups. SARS-CoV-2 spike protein increased coagulation factors (increased TF-3, P<0.05) and decreased fibrinolysis (increased PAI-1, P<0.05) in hACE2 and HBMVEC. Losartan reduced spike protein-induced infarction and improved cognitive function in hACE2 mice. SARS-CoV-2 spike protein caused RAAS system imbalances in hACE2 mice by increasing AT 1 R and downstream inflammatory signal. Moreover, spike protein decreased the protective RAAS arm by decreasing AT 2 R and Mas receptors in hACE2 mice and HBMVEC. Conclusion: SARS-CoV-2 spike protein exacerbates hypercoagulation and inflammation leading to increased cerebrovascular damage and cognitive dysfunction. However, the AT 1 R blocker, Losartan, restored the RAAS balance and reduced COVID-19-induced thromboembolic cerebrovascular complications.