miR-486-5p Inhibits Inflammatory Response, Matrix Degradation and Apoptosis of Nucleus Pulposus Cells through Directly Targeting FOXO1 in Intervertebral Disc Degeneration.

Objective: microRNA-486-5p (miR-486-5p) and forkhead box protein O1 (FOXO1) play an important role in the development of intervertebral disc degeneration (IDD). However, their molecular mechanisms in IDD remain unknown.

Methods: qRT-PCR assay was used to identify miR-486-5p expression in nucleus pulposus (NP) cells. In-vitro transfection, CCK-8, flow cytometry and luciferase reporter assay were used to validate the role and relationship of miR-486-5p and FOXO1 in lipopolysaccharides (LPS)-stimulated NP cells. qRT-PCR and Western blot were used to measure the expression levels of inflammatory cytokines, matrix degrading enzymes, and extracellular matrix (ECM)-related genes.

Results: miR-486-5p expression was significantly down-regulated, while FOXO1 expression was up-regulated in LPS-treated NP cells (P<0.001). miR-486-5p over-expression repressed LPS-induced expressions of inflammatory cytokines (IL-1β, IL-6 and TNF-α) and matrix degrading enzymes (MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5), and promoted the expressions of LPS-inhibited ECM-related genes (Aggrecan and Collagen II) (all P<0.001). In addition, miR-486-5p over-expression protected NP cells against LPS-induced apoptosis. However, inhibition of miR-486-5p led to the opposite effects. Mechanically, FOXO1 was a direct target gene of miR-486-5p. Over-expressed FOXO1 aggravated LPS-induced injury, and antagonized protection effects of miR-486-5p.

Conclusions: miR-486-5p can inhibit inflammatory response, ECM degradation and apoptosis in NP cells by directly targeting FOXO1, which may contribute to the biological therapy of IDD.