Overexpression of miR-140-5p inhibits lipopolysaccharide-induced human intervertebral disc inflammation and degeneration by downregulating toll-like receptor 4

Toll-like receptor 4 (TLR4) families are receptors for ligands that initiate extracellular or intracellular signaling, such as lipopolysaccharides (LPS). It has been reported that TLR4 activation resulted in the upregulation of a coordinated set of proinflammatory mediators and inhibition of matrix expression in the intervertebral disc (IVD). miR-140-5p (miR-140) is reported to participate in cellular anti-inflammatory processes and target TLR4. In the present study, we investigated the relationship between TLR4 and miR-140 in IVD degeneration. The expression of TLR4, interleukin (IL)-6, IL-I, L-1β and tumor necrosis factor (TNF)-α was higher, in high-grade IVD degeneration tissues than in low-grade tissues. In contrast, the expression of miR-140, aggrecan and collagen type II was lower in high-grade IVD degeneration tissues than in low-grade IVD degeneration tissues. LPS stimulation resulted in significant increases in TLR4 expression and decreases in miR-140 expression in nucleus pulposus (NP) cells and TLR4 was identified as a target of miR-140 by dual-luciferase reporter assay. The overexpression of miR-140 inhibited the upregulation of the expression of TLR4, TNF-α, IL-1β and IL-6 inflammation cytokines, and the activation of NF-κB and reversed the downregulation of the expression of aggrecan and collagen type II induced by LPS stimulation. In conclusion, the present study may lead to a greater understanding of IVD degeneration and provide new insights into the treatment of this disease.