miR-136-5p Regulates the Inflammatory Response by Targeting the IKK/NF-B/A20 Pathway After Spinal Cord Injury

Background/Aims: miR-136-5p participates in recovery after spinal cord injury (SCI) via an unknown mechanism. We investigated the mechanism underlying the involvement of miR-136-5p in the inflammatory response in a rat model of SCI. Methods: Sprague-Dawley rat astrocytes were cultured in vitro to construct a reporter plasmid. Luciferase assays were used to detect the ability of miR-136-5p to target the IKK and A20 genes. Next, recombinant lentiviral vectors were constructed, which either overexpressed miR-136-5p or inhibited its expression. The influence of miR-136-5p overexpression and miR-136-5p silencing on inflammation was observed in vivo in an SCI rat model. The expression of IL-1, IL-6, TNF-, IFN-, and related proteins (A20, IKK, and NF-B) was detected. Results:In vitro studies showed that luciferase activity was significantly activated in the presence of the 3' untranslated region (UTR) region of the IKK gene after stimulation of cells with miR-136-5p. However, luciferase activity was significantly inhibited in the presence of the 3'UTR region of the A20 gene. Thus, miR-136-5p may act directly on the 3'UTR regions of the IKK and A20 genes to regulate their expression. miR-136-5p overexpression promoted the production of related cytokines and NF-B in SCI rats and inhibited the expression of A20 protein. Conclusion: Overexpression of miR-136-5p promotes the generation of IL-1, IL-6, TNF-, IFN-, IKK, and NF-B in SCI rats but inhibits the expression of A20. Under these conditions, inflammatory cell infiltration into the rat spinal cord increases and injury is significantly aggravated. Silencing of miR-136-5p significantly reduces the protein expression results described after miR-136-5p overexpression and ameliorates the inflammatory cell infiltration and damage to the spinal cord. Therefore, miR-136-5p might be a new target for the treatment of SCI. (c) 2018 The Author(s) Published by S. Karger AG, Basel