Oligodendroglial connexin 47 regulates neuroinflammation upon autoimmune demyelination in a novel mouse model of multiple sclerosis

Significance In multiple sclerosis plaques, oligodendroglial connexin (Cx) 47 constituting main gap junction channels with astroglia is persistently lost. The roles of Cx47 remain undefined. Here, we show that oligodendroglia-specific conditional ablation of Cx47 exacerbated acute and chronic relapsing experimental autoimmune encephalomyelitis induced by myelin oligodendrocyte glycoprotein peptide (MOG35-55) immunization, with florid infiltration of CD3+ T cells, especially helper T (Th) 17 cells, and pronounced demyelination without influencing MOG-specific T cell induction. Microarray and immunohistochemistry analyses revealed stronger activation of proinflammatory and injury-response microglia with increased expressions of chemokines that can attract Th17 cells, and A1 astroglia at the acute phase. These findings suggest that oligodendroglia-specific Cx47 loss can augment inflammation upon autoimmune demyelination, underscoring a role for Cx47 in neuroinflammation. In multiple sclerosis plaques, oligodendroglial connexin (Cx) 47 constituting main gap junction channels with astroglial Cx43 is persistently lost. As mice with Cx47 single knockout exhibit no demyelination, the roles of Cx47 remain undefined. We aimed to clarify the effects of oligodendroglia-specific Cx47 inducible conditional knockout (icKO) on experimental autoimmune encephalomyelitis (EAE) induced by myelin oligodendrocyte glycoprotein peptide (MOG35-55) in PLP/CreERT;Cx47fl/fl mice at 14 d after tamoxifen injection. Cx47 icKO mice demonstrated exacerbation of acute and chronic relapsing EAE with more pronounced demyelination than Cx47 flox (fl)/fl littermates. CD3+ T cells more abundantly infiltrated the spinal cord in Cx47 icKO than in Cx47 fl/fl mice throughout the acute to chronic phases. CXCR3-CCR6+CD4+ and IL17+IFNγ-CD4+ helper T (Th) 17 cells isolated from spinal cord and brain tissues were significantly increased in Cx47 icKO mice compared with Cx47 fl/fl mice, while MOG35-55-specific proliferation and proinflammatory cytokine production of splenocytes were unaltered. Microarray analysis of isolated microglia revealed stronger microglial activation toward proinflammatory and injury-response phenotypes with increased expressions of chemokines that can attract Th17 cells, including Ccl2, Ccl3, Ccl4, Ccl7, and Ccl8, in Cx47 icKO mice compared with Cx47 fl/fl mice. In Cx47 icKO mice, NOS2+ and MHC class II+ microglia were more enriched immunohistochemically, and A1-specific astroglial gene expressions and astroglia immunostained for C3, a representative A1 astrocyte marker, were significantly increased at the acute phase, compared with Cx47 fl/fl mice. These findings suggest that oligodendroglia-specific Cx47 ablation induces severe inflammation upon autoimmune demyelination, underscoring a critical role for Cx47 in regulating neuroinflammation.

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