MALAT1 Contributes To Inflammatory Response Of Microglia Via The Modulation Of A MiR-199b/IKKβ/NF-κB Signaling Pathway

Background:The inflammatory response of microglia(MGs)following acute spinal cord injury(ASCI)is an important factor in aggravating spinal cord injury.Long noncoding RNA(Inc RNA)metastasis-associated lung adenocarcinoma transcript l(MALAT1)was widely recognized to be implicated in human cancer,vascular diseases,and neurological disorders.Recent research indicated that miR-199b associated with MALAT1 is involved in the inflammatory response following spinal cord injury.This study was to explore the role of MALAT1 in microglial inflammatory response following acute spinal cord injury(ASCI)and its related mechanisms.Methods:ASCI models in adult rats were established by Allen’s modified method,and rat behavior was measured by BBB score.LPS induced microglia to establish an inflammatory response model,constructed a lentiviral plasmid and transfected knockdown MALATA1 and miR-199b.Expression profile of MALAT1 and miR-199b following ASCI in rats and in vitro 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.The expression of downstream related signaling pathway proteins Iba-1,IKKp,p-IκBα,and p-p65 was detected by Western blot.The expression of the inflammatory factors TNF-α and IL-1β was measured by ELISA.Results:The results of the study show that MALAT1 expression was significantly increased(2.4-fold that of control)in the spinal cord of the rat contusion epicenter accompanied by activation of IKKβ/NF-κB signaling pathway and an increase in the level of proinflammatory cytokines TNF-α and IL-1β.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-α and IL-1β production.We also confirmed that LPS-induced microglia MALAT1 promotes the production of pro-inflammatory cytokines TNF-α and IL-1β by down-regulating miR-199b to activate IKKβ/NF-κB signaling pathway.Further in vivo experiments showed that MALAT1 knockdown inhibited microglia markers TNF-α,IL-1β and Iba-1 protein expression,and gradually improved the behavioral score of ASCI rats.Conclusion:MALAT1 is involved in the inflammatory response induced by microglia activation and demonstrates that MALAT1 promotes microglial inflammatory responses following spinal cord injury via the miR-199b/IKKβ/NF-κB signaling pathway.MALAT1 knockdown could attenuate ASCI through repressing inflammatory response of MGs.