Multiple sclerosis (MS) is a disabling autoimmune disease affecting individuals in their most productive years and is also prevalent among US Veterans. MS is caused by abnormal activation of myelin-specific autoreactive T and B cells and their CNS infiltration. At present, there is no cure for MS and the treatments for MS involve a diverse array of disease-modifying therapies (DMTs) targeting autoimmunity but with relatively little or no effects on the CNS disease of MS as the disease progression continues. Recently, anti-CD20-based B cell-depleting therapy has been approved for the treatment of MS. B cells participate in the autoimmune process by presenting autoantigens and producing autoantibodies. B cells also regulate T cell-mediated autoimmune responses by producing effector (IL-6) or regulatory (IL-10) cytokines. B cell depletion is known to inhibit TH1 and TH17 cell immune responses in MS patients and in its animal models (experimental autoimmune encephalomyelitis; EAE), a mechanism of B cell depletion therapy. B cell depletion therapy, however, suffers from potential adverse effects, such as opportunistic infections and the generation of neutralizing antibodies as well as low efficacy. Mechanistically, anti-CD20-antibodies depleting effector B cells also deplete the regulatory B cells, thus causing loss of regulatory B cell function for inhibition and recovery of MS/EAE disease. This underscores the need for a new therapy that selectively inhibits effector/ pathogenic functions of B cells while sparing or promoting regulatory/protective B cell functions. Recently, our laboratory reported a novel immunomodulatory mechanism of S-nitrosoglutathione (GSNO; an endogenous S-nitrosothiol) in the EAE model. GSNO-mediated S-nitrosylation plays a critical role in physiological nitric oxide (NO) signaling for the regulation of multiple cellular pathways. We reported that exogenous GSNO or optimization of endogenous GSNO, by blocking its turnover using GSNO reductase (GSNOR) inhibitor (GSNORi), attenuates the effector T cell (TH17) and effector (IL-6+) B cell functions while increasing the regulatory T cells (Treg) and regulatory (IL-10+) B cell functions and thus protects against the EAE disease. Based on this, we propose to investigate the preclinical therapeutic potential of GSNO/GSNORi (S-nitrosylation)-mediated signaling mechanisms in B and T cell-mediated immunomodulation and their potential efficacy against CNS disease using the EAE model. Aim 1 is proposed to evaluate the preclinical therapeutic potentials of GSNOR inhibitors. Aim 2 is proposed to investigate the mechanisms underlying GSNOR inhibitor-mediated immunomodulation. The present study, based on our original contributions, investigates a novel mechanism of balanced regulation of regulatory vs. effector functions of B cells under autoimmune disease conditions. We expect that the proposed study will evaluate the preclinical potential of injectable (N6022) and orally active (N91115) G...