SARS-COV-2 SPIKE PROTEIN EXACERBATES CEREBRAL THROMBOEMBOLIC COMPLICATIONS IN HACE2 MICE

Abstract

Purpose: 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/FeCl3 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 contribution to cognitive impairment and dementia (VCID) were assessed using a Novel object recognition test. D-dimmer, Tissue factor -3 (TF-III), 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-CoV-2 spike protein to mimic stroke. HBMEC was analyzed for coagulation factors, inflammation, and RAAS balance.

Results: SARS-CoV-2 spike protein increased neuronal death and decreased cognitive function after MCA/FeCl3 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-III) and decreased fibrinolysis (increased PAI-1) in hACE2 and HBMEC. 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 AT1R and downstream inflammatory signal. Moreover, spike protein decreased the protective RAAS arm by decreasing AT2R and Mas receptors in hACE2 brains.

Conclusion: In hACE2 mice, SARS-CoV-2 spike protein exacerbates hypercoagulation and inflammation, leading to increased cerebrovascular damage and cognitive dysfunction. However, the AT1R blocker, Losartan, restored the RAAS balance and reduced COVID-19-induced thromboembolic cerebrovascular complications.