Abstract TP071: Cerebrovascular dysfunction and neurodegeneration in a combined model of MTHFR deficiency and acute SARS-CoV-2 infection

Introduction: Methylene tetrahydrofolate reductase (MTHFR) is a crucial enzyme in the folate cycle that regulates several physiological processes including nucleotide synthesis, epigenetic modifications, and neurotransmitter (including dopamine) synthesis. Interestingly, loss-of-function polymorphisms in MTHFR, with 20-40% worldwide prevalence, is associated with COVID-19 morbidity and mortality as well as increased risk of cerebrovascular disorders and neurodegenerative diseases. Mthfr-deficient ( Mthfr +/ ) mice which mimic these polymorphisms, exhibit cognitive impairment and cerebrovascular deficits. Emerging evidence suggests that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause significant acute or chronic neurological complications. However, the combined impact of Mthfr deficiency and acute SARS-CoV-2 infection on the risk of cerebrovascular dysfunction and neurodegeneration is unknown. Method: Ten-month-old Mthfr +/- and wild type (WT) mice were inoculated intranasally with mock or 10 4 PFU of the mouse-adapted (MA10) strain of SARS-CoV-2. The mice were euthanized three days post-infection (dpi), and lung and brain tissues were examined through quantitative PCR (qPCR) and immunostaining for markers of blood-brain barrier (BBB) disruption, inflammation, and the dopaminergic system. Plasma samples were also collected and processed for untargeted metabolomics. Results: Mthfr +/- and WT mice showed comparable lung viral titer but no detectable virus in the brain. qPCR and immunostaining revealed significantly reduced ZO-1 (BBB tight junction protein) and enhanced vascular leaks in brains of Mthfr +/- infected mice. MA10 infection also increased IL-1β mRNA, cortical microglia count and caspase-1 intensity in Mthfr +/- mice indicating the activation of NLRP3 inflammasome. Metabolomics data revealed dopamine (NLRP3 pathway inhibitor) as the most significantly reduced plasma metabolite in Mthfr +/- infected mice. In addition, MA10 infection induced nigrostriatal dopaminergic degeneration marked by tyrosine hydroxylase (TH), decreased TH+ dopaminergic neuron count, and increased α-synuclein levels in the substantia nigra of Mthfr +/- mice. Conclusion: SARS-CoV-2 infection can cause BBB disruption, neuroinflammation, low plasma dopamine, and nigrostriatal dopaminergic degeneration particularly in a mouse model of MTHFR deficiency, increasing the risk of cerebrovascular disorders and cognitive deficits among post-COVID neurological effects.