MicroRNA-146a Ameliorates Inflammation via TRAF6/NF-κB Pathway in Intervertebral Disc Cells

BACKGROUND Intervertebral disc degeneration (IDD) has been widely recognized as a major contributor to low back pain. Accumulating evidence suggests that IDD is linked to various pro-inflammatory cytokines and metabolites. Recently, numerous studies have demonstrated that microRNAs (miRNAs) play a pivotal role in the development of most disorders, including degenerative disc diseases. Previous reports have revealed that miRNA-146a (miR-146a) could attenuate neuropathic pain in the spinal cord. The aim of this study was to investigate the role of miR-146a in the inflammatory response of IDD. MATERIAL AND METHODS Quantitative real-time (RT)-PCR was performed to investigate the levels of miR-146a in the PBMCs (peripheral blood mononuclear cells) of patients with IDD. Human nucleus pulposus (NP) cells were transiently transfected with miR-146a mimic; control NP cell transfections lacked miR-146a. Then all NP cells were treated with LPS (10 μM) to induce inflammation. The mRNA levels of miR-146a in NP cells were determined by RT-PCR. In addition, the mRNA and protein expression levels of tumor necrosis factor (TNF), receptor-associated factor 6 (TRAF6), and nuclear factor (NF)-κB in NP cells were evaluated by quantitative RT-PCR and Western blot analysis, respectively. RESULTS We found that miR-146a was significantly downregulated in the PBMCs of patients. Moreover, overexpression of miR-146a significantly decreased the levels of pro-inflammatory cytokines in LPS-stimulated NP cells. The mRNA and protein levels of TRAF6 and NF-κB were downregulated by miR-146a overexpression. CONCLUSIONS These results suggest that overexpression of miR-146a could promote IDD through the TRAF/NF-κB pathway. Our findings also highlight miR-146a as a novel possible therapeutic target for IDD.