The role of S-nitrosoglutathione reductase (GSNOR) in T cell-mediated immunopathology of experimental autoimmune encephalomyelitis (EAE)

•EAE elevates GSNOR expression/activity in the spinal cord.•GSNOR-deficient mice had milder EAE disease than wild-type mice.•N91115 (GSNOR inhibitor) treated mice had milder EAE disease than untreated mice.•GSNOR inhibition or knockout suppresses Th1/Th17 but boosts Treg cells in EAE. Previously, we reported that both S-nitrosoglutathione (GSNO), a carrier of cellular nitric oxide, and N6022, an injectable form of GSNO reductase (GSNOR) inhibitor that increases endogenous GSNO levels, alleviate experimental autoimmune encephalomyelitis (EAE) in mice by suppressing Th1 and Th17 immune responses. Building on these findings, we explored the role of GSNOR in EAE pathogenesis and evaluated the efficacy of an orally active GSNOR inhibitor (N91115) in treating the EAE disease. EAE mice exhibited heightened expression/activity of GSNOR in the spinal cord, and the knockout of the GSNOR gene resulted in much milder clinical manifestations of EAE, with lower degrees of demyelination and axonal loss, reduced microglial and astrocyte activations, as well as suppressed Th1 and Th17 cell responses, alongside bolstered Treg immune responses. Next, we evaluated the efficacy of N91115 against EAE immunopathology. Consistent with our findings in GSNOR deficient EAE mice, daily N91115 administration reduced clinical EAE severity, with less spinal cord demyelination and axonal loss compared to untreated EAE mice. Furthermore, N91115 treated EAE mice showed diminished Th1 and Th17 immune responses and enhanced Treg responses. This observation underscores the potential of increased GSNOR expression and activity as a risk factor exacerbating EAE immunopathology, while simultaneously highlighting its potential as a target for modifying the disease. Furthermore, the balanced immune regulation provided by orally active N91115 (IL-6/IL-17a vs. IL-10) presents a promising alternative to immunosuppressive drugs, reducing the risk of opportunistic infections.