sephin1 and Multiple-Sclerosis

central nervous system (CNS) inflammation triggers activation of the integrated stress response (ISR). We previously reported that prolonging the ISR protects remyelinating oligodendrocytes and promotes remyelination in the presence of inflammation. However, the exact mechanisms through which this occurs remain unknown. Here, we investigated whether the ISR modulator Sephin1 in combination with the oligodendrocyte differentiation enhancing reagent bazedoxifene (BZA) is able to accelerate remyelination under inflammation, and the underlying mechanisms mediating this pathway. We find that the combined treatment of Sephin1 and BZA is sufficient to accelerate early-stage remyelination in mice with ectopic IFN-γ expression in the CNS. IFN-γ, which is a critical inflammatory cytokine in multiple sclerosis (MS), inhibits oligodendrocyte precursor cell (OPC) differentiation in culture and triggers a mild ISR. Mechanistically, we further show that BZA promotes OPC differentiation in the presence of IFN-γ, while Sephin1 enhances the IFN-γ-induced ISR by reducing protein synthesis and increasing RNA stress granule formation in differentiating oligodendrocytes. Finally, pharmacological suppression of the ISR blocks stress granule formation in vitro and partially lessens the beneficial effect of Sephin1 on disease progression in a mouse model of MS, experimental autoimmune encephalitis (EAE). Overall, our findings uncover distinct mechanisms of action of BZA and Sephin1 on oligodendrocyte lineage cells under inflammatory stress, suggesting that a combination therapy may effectively promote restoring neuronal function in MS patients.

Topics: Animals; Cell Differentiation; Inflammation; Mice; Mice, Inbred C57BL; Multiple Sclerosis; Oligodendroglia; Remyelination

Multiple sclerosis is a chronic autoimmune demyelinating disorder of the CNS. Immune-mediated oligodendrocyte cell loss contributes to multiple sclerosis pathogenesis, such that oligodendrocyte-protective strategies represent a promising therapeutic approach. The integrated stress response, which is an innate cellular protective signalling pathway, reduces the cytotoxic impact of inflammation on oligodendrocytes. This response is initiated by phosphorylation of eIF2α to diminish global protein translation and selectively allow for the synthesis of protective proteins. The integrated stress response is terminated by dephosphorylation of eIF2α. The small molecule Sephin1 inhibits eIF2α dephosphorylation, thereby prolonging the protective response. Herein, we tested the effectiveness of Sephin1 in shielding oligodendrocytes against inflammatory stress. We confirmed that Sephin1 prolonged eIF2α phosphorylation in stressed primary oligodendrocyte cultures. Moreover, by using a mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis, we demonstrated that Sephin1 delayed the onset of clinical symptoms, which correlated with a prolonged integrated stress response, reduced oligodendrocyte and axon loss, as well as diminished T cell presence in the CNS. Sephin1 is reportedly a selective inhibitor of GADD34 (PPP1R15A), which is a stress-induced regulatory subunit of protein phosphatase 1 complex that dephosphorylates eIF2α. Consistent with this possibility, GADD34 mutant mice presented with a similar ameliorated experimental autoimmune encephalomyelitis phenotype as Sephin1-treated mice, and Sephin1 did not provide additional therapeutic benefit to the GADD34 mutant animals. Results presented from the adoptive transfer of encephalitogenic T cells between wild-type and GADD34 mutant mice further indicate that the beneficial effects of Sephin1 are mediated through a direct protective effect on the CNS. Of particular therapeutic relevance, Sephin1 provided additive therapeutic benefit when combined with the first line multiple sclerosis drug, interferon β. Together, our results suggest that a neuroprotective treatment based on the enhancement of the integrated stress response would likely have significant therapeutic value for multiple sclerosis patients.

Topics: Animals; Cells, Cultured; Encephalomyelitis, Autoimmune, Experimental; Female; Guanabenz; Humans; Immunity, Innate; Mice; Mice, Inbred C57BL; Multiple Sclerosis; Oligodendroglia; Rats