miR-146a negatively regulates the induction of proinflammatory cytokines in response to Japanese encephalitis virus infection in microglial cells

Increasing evidence confirms the involvement of virus infection and miRNA, such as miR-146a, in neuroinflammation-associated epilepsy. In the present study, we investigated the upregulation of miR-146a with RT-qPCR and in situ hybridization methods in a mice infection model of Japanese encephalitis virus (JEV) and in vitro. Subsequently we investigated the involvement of miR-146a in modulating JEV-induced neuroinflammation. It was demonstrated that JEV infection promoted miR-146a production in BALB/c mice brain and in cultured mouse microglial C8-B4 cells, along with pro-inflammatory cytokines, such as IL-1 beta, IL-6, TNF-alpha, IFN-beta and IFN-alpha. We also found that miR-146a exerted negative regulatory effects upon IL-1 beta, IL-6, TNF-alpha, IFN-beta and IFN-alpha in C8-B4 cells. Accordingly, miR-146a downregulation with a miR-146a inhibitor promoted the upregulation of IL-1 beta, IL-6, TNF-alpha, IFN-beta and IFN-alpha, whereas miR-146a upregulation with miR-146a mimics reduced the upregulation of these cytokines. Moreover, miR-146a exerted no regulation upon JEV growth in C8-B4 cells. In conclusion, JEV infection upregulated miR-146a and pro-inflammatory cytokine production, in mice brain and in cultured C8-B4 cells. Furthermore, miR-146a negatively regulated the production of JEV-induced pro-inflammatory cytokines, in virus growth independent fashion, identifying miR-146a as a negative feedback regulator in JEV-induced neuroinflammation, and possibly in epilepsy.