miR-140-5p regulates T cell differentiation and attenuates experimental autoimmune encephalomyelitis by affecting CD4⁺T cell metabolism and DNA methylation

We previously demonstrated that decreased expression of miR-140-5p was associated with the progression of multiple sclerosis (MS) and miR-140-5p targeted STAT1 and interfered with the expression of IFN-γ. However, the underlying mechanisms how miR-140-5p regulated the differentiation of encephalomyelitic CD4⁺T cell remained unclear. In this study, we analyzed the levels of miR-140-5p in a mouse model of experimental autoimmune encephalomyelitis (EAE). We also analyzed the outcomes in response to either over- or under-expression of miR-140-5p. We found that the expression of miR-140-5p was inversely related to the progression of EAE. With the remission of the disease, the expression of miR-140-5p was restored to levels comparable to the control. The expression of miR-140-5p was downregulated in the encephalomyelitic CD4⁺T cells whereas enhanced expression of miR-140-5p inhibited the development of T helper type 1 (Th1) cell and significantly attenuated EAE. MiR-140-5p also caused hypermethylation of STAT1 and demethylation of GATA3. Furthermore, we found that miR-140-5p enhanced mitochondrial glycolysis in CD4⁺T cells with simultaneous activation of ATP activity. By blockage of the respiratory electron transport chain with the inhibitors of complex I and III, the effect of miR-140-5p on Th1 differentiation was blocked, which suggested a role for mitochondrial respiratory pathway in miR-140-5p-mediated inhibition of Th1 differentiation. In summary, our results demonstrated that the expression of miR-140-5p was negatively correlated with the progression of EAE and that miR-140-5p regulated Th1 differentiation via DNA methylation and mitochondrial respiratory pathway.