The role of 25-hydroxycholesterol in the pathophysiology of brain vessel dysfunction associated with infection and cholesterol dysregulation.

The antiviral enzyme cholesterol 25-hydroxylase (CH25H) and its metabolite 25-hydroxycholesterol (25HC), which modulates cholesterol metabolism during infection, have been associated with vascular pathology. Viral infections have been linked to intracerebral haemorrhage (ICH) risk, but the molecular mechanisms leading to ICH via antiviral responses remain unknown. We hypothesised that the CH25H/25HC pathway impacts neuroendothelial integrity in the context of infection-associated ICH. Using a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein-induced zebrafish ICH model and foetal human SARS-CoV-2-associated cortical tissue containing microbleeds, we identified upregulation of CH25H in infection-associated cerebral haemorrhage. Using zebrafish models and human brain endothelial cells, we asked whether 25HC promotes neurovascular dysfunction by modulating cholesterol metabolism. We found that 25HC and pharmacological inhibition of cholesterol synthesis had an additive effect to exacerbate brain bleeding in zebrafish and in vitro neuroendothelial dysfunction. 25HC-induced dysfunction was also rescued by cholesterol supplementation in vitro. These results demonstrate that 25HC can dysregulate brain endothelial function by remodelling cholesterol metabolism. We propose that CH25H/25HC plays an important role in the pathophysiology of brain vessel dysfunction associated with infection and cholesterol dysregulation in the context of ICH.