MicroRNA-29b modulates Japanese encephalitis virus-induced microglia activation by targeting tumor necrosis factor alpha-induced protein 3.

Japanese encephalitis virus (JEV), a single-stranded RNA (ssRNA) virus, is the leading cause of encephalitis in Asia. Microglial activation is one of the key events in JEV-induced neuroinflammation. Although the various microRNAs (miRNAs) has been shown to regulate microglia activation during pathological conditions including neuroviral infections, till date, the involvement of miRNAs in JEV infection has not been evaluated. Hence, we sought to evaluate the possible role of miRNAs in mediating JEV-induced microglia activation. Initial screening revealed significant up-regulation of miR-29b in JEV-infected mouse microglial cell line (BV-2) and primary microglial cells. Furthermore, using bioinformatics tools, we identified tumor necrosis factor alpha-induced protein 3, a negative regulator of nuclear factor-kappa B signaling as a potential target of miR-29b. Interestingly, in vitro knockdown of miR-29b resulted in significant over-expression of tumor necrosis factor alpha-induced protein 3, and subsequent decrease in nuclear translocation of pNF-κB. JEV infection in BV-2 cell line elevated inducible nitric oxide synthase, cyclooxygenase-2, and pro-inflammatory cytokine expression levels, which diminished after miR-29b knockdown. Collectively, our study demonstrates involvement of miR-29b in regulating JEV- induced microglial activation.