MiR‐409‐3p and MiR‐1896 co‐operatively participate in IL‐17‐induced inflammatory cytokine production in astrocytes and pathogenesis of EAE mice via targeting SOCS3/STAT3 signaling

: Th17 cells and interleukin-17 (IL-17) have been found to play an important role in the pathology of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Response to IL-17, reactive astrocytes accompany with immune cells infiltration and axonal damage in MS/EAE. However, the role and the regulatory mechanism of IL-17-activated astrocytes in inflammation and in the EAE process still remain largely unknown. Here, we elucidated that miR-409-3p and miR-1896, as co-upregulated microRNAs in activated astrocytes and in EAE mice, targeted suppressor of cytokine signaling proteins 3 (SOCS3). Overexpression of miR-409-3p or miR-1896 significantly reduced SOCS3 expression and increased phosphorylation of STAT3 as well as induced the inflammatory cytokines production (IL-1β, IL-6, IP-10, MCP-1, and KC), CD4+ T cells migration and demyelination, in turn aggravating EAE development. Importantly, the effects of co-overexpression of miR-409-3p and miR-1896 in vitro or in vivo are strongly co-operative. In contrast, simultaneously silenced miR-409-3p and miR-1896 co-operatively ameliorates inflammation and demyelination in the central nervous system of EAE mice. Collectively, our findings highlight that miR-409-3p and miR-1896 co-ordinately promote the production of inflammatory cytokines in reactive astrocytes through the SOCS3/STAT3 pathway and enhance reactive astrocyte-directed chemotaxis of CD4+ T cells, leading to aggravate pathogenesis in EAE mice. Co-inhibition of miR-409-3p and miR-1896 may be a therapeutic target for treating MS and neuroinflammation.