B cell-mediated immunomodulation by S-nitrosoglutathione (GSNO) in experimental autoimmune encephalomyelitis

Abstract Background Experimental autoimmune encephalomyelitis (EAE) is the most commonly used animal model for human multiple sclerosis (MS), a demyelinating autoimmune disease mediated by T and B lymphocytes. The aim of the present study was to investigate the role of S-nitrosoglutathione (GSNO), a physiological nitric oxide carrier molecule, in regulation of effector or regulatory B cell function as IL-6 and IL-10 expressions and thus the potential role of GSNO in targeting B cell-mediated immunopathogenesis in MS using EAE model. Methods To this purpose, the in vivo EAE mouse model, generated by immunization with myelin oligodendrocyte glycoprotein (MOG) 35-55 peptide, or in vitro model of cultured B cells stimulated with lipopolysaccharide or anti-IgM antibody were treated with exogenous GSNO or N6022, an inhibitor of GSNO reductase (GSNOR; GSNO degrading enzyme) to increase endogenous GSNO, and then analyzed for B cell specific IL-6 and IL-10 expression. Results In EAE model, administration of exogenous GSNO or inhibition of endogenous GSNO catabolism by N6022 treatment ameliorated the clinical disease with decreased CNS infiltration of B cells. In addition, GSNO/N6022 treatments increased the number of IL-10+ B cells but decreased the number of IL-6+ B cells in the CNS and spleen. Accordingly, GSNO/N6022 treatments increased the expression of IL-10 while reducing the IL-6 expression in the blood. Similar observations were also made in in vitro B cell culture model where GSNO treatment increased the IL-10+ B cells but decreased the IL-6+ B cells under BCR or TLR4 stimulatory conditions and under CD40 and BAFF co-stimulatory conditions. Accordingly, GSNO treatment increased the B cell production of IL-10 but reduced the IL-6 production under both stimulatory and co-stimulatory conditions. In vitro stimulation and co-stimulation of cultured naïve B cells increased two major distinct B cell populations; CD1dlow CD5high and CD1dhigh CD5high. In both populations, GSNO treatment increased the number of IL-10+ cells but decreased the IL-6+ cells. Conclusion These data document, for the first time, that cellular GSNO homeostasis is a critical target for the regulation of IL-10+ B cells vs. IL-6+ B cells mediated immune balance under auto-immune disease conditions.