The Role of Nitric Oxide in HSV-1 Infection: The Use of an Inducible Nitric Synthase Inhibitor Aminoguanidine to Treat Neuroinflammation.

Herpes simplex virus-1 (HSV-1) is a neurotropic virus that can infect the brain, and an uncontrolled infection can lead to severe encephalitis. NO can exert both antiviral as well as cytotoxic effects in the central nervous system (CNS) depending on its concentration and site of infection. In this study, we report that treatment of an intranasal murine HSV-1 infection with aminoguanidine (AMG) decreases both neuroinflammation and neurodegeneration markers, but its positive effect depends on the time of treatment. Specifically, early treatment with AMG impaired the activation of microglia/monocytes, leading to decreased virus-specific antiviral response and higher viral titers in the brain. However, AMG treatment during the peak of brain infection significantly improved antiviral response, reduced inflammation and improved general clinical score. We also found that treatment with AMG decreased beta amyloid levels during both primary and latent infections and protected from the accumulation of phosphorylated Tau protein during early infection. Our findings position inducible nitric oxide synthetase (iNOS) as a potential therapeutic target for mitigating virus-induced neuroinflammation and neurodegeneration.