Long noncoding RNA MALAT1 contributes to inflammatory response of microglia following spinal cord injury via the modulation of a miR-199b/IKKβ/NF-kB signaling pathway

Long noncoding RNA (In-cRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) was widely recognized to be implicated in human cancer, vascular diseases, and neurological disorders. This study was to explore the role and underlying mechanism of MALAT1 in acute spinal cord injury (ASCI). ASCI models in adult rats were established and demonstrated by a numerical decrease in BBB scores. Expression profile of MALAT1 and miR-199b following ASCI in rats and in vilro was determined using quantitative real-time PCR. RNA pull-down assays combined with RIP assays were performed to explore the interaction between MALAT1 and miR-199b. In the present study, MALAT1 expression was significantly increased (2.4-fold that of control) in the spinal cord of the rat contusion epicenter accompanied by activation of IKK beta/NF-kB signaling pathway and an increase in the level of proinflammatory cytokines TNF-alpha and IL-beta. Upon treatment with LPS. MALAT1 expression dramatically increased in the microglia in vitro, but knockdown of MALAT1 attenuated LPS-induced activation of MGs and TNF-alpha and IL-l beta production. Next, we confirmed that LPS-induced MALAT1 activated IKK beta/NF-kB signaling pathway and promoted the production of proinflammatory cytokines TNF-alpha and IL-1 beta through downregulating miR-J 199b. More importantly. MALATI knockdown gradually improved the hindlimb locomotor activity of ASCI rats as well as inhibited TNF-alpha. IL-1 beta levels, and Iba-1 protein, the marker of activated microglia in injured spinal cords. Our study demonstrated that MALATI was dysregulated in ASCI rats and in LPS-activated MGs, and MALATI knockdown was expected to attenuate ASCI through repressing inflammatory response of MGs.