Cerebrovascular Effects Of Pre/post-losartan Treatment In Humanized ACE2 Knock-in Mice After SARSCoV-2 Spike Protein Injection

SARS-CoV-2 has killed millions of people globally and has left many with devastating health problems, including neurological deficits. SARS-CoV-2 invades endothelial cells via binding its Spike-protein with angiotensin-converting enzyme 2 (ACE2) receptors. Losartan, an angiotensin receptor blocker, upregulates ACE2 expression. We hypothesize that pre-treatment with losartan could increase the cerebrovascular dysfunction associated with SARS-CoV-2 spike-protein, while post-SARS-CoV-2 losartan would provide potential protective effects. Methods: Recombinant SARS-CoV-2 spike-protein was injected intravenously in transgenic hACE2 mice, humanized ACE2 receptors knock-in mice. Treatment with losartan was started either two weeks before or right after spike-protein injection. Cognitive function was assessed using Y-Maze. Vascular density and cerebral blood flow were evaluated in the hACE2 mice with/out spike protein injection. Western blot and RT-PCR analysis were used to measure protein/gene expression. Results: Spike-protein injection decreased cerebral vascular density and cerebral blood flow in hACE2 brains compared to control (*P<0.05), which was associated with increased cognitive dysfunction in h ACE2 mice (*P<0.05). Pre-losartan treatment exacerbated spike protein-induced cognitive dysfunction, while post-losartan treatment helped restore cognitive function (*P<0.05). Spike-protein decreased ACE2 expression and increased endothelial cell inflammation and apoptosis, as shown by the increased expression of TNF- α ; and caspase-3 (*P<0.05), which were prevented by post-losartan treatment. Conclusion: Spike-protein decreased vascular density, cerebral blood flow, and cognitive function via increasing brain endothelial cell apoptosis. Pre-losartan treatment exacerbated the detrimental effects of spike-protein, while post-losartan treatment restored ACE2 expression and decreased SARS-CoV-2 spike-protein damaging effects.