Upregulation of miR-199 attenuates TNF-α-induced Human nucleus pulposus cell apoptosis by downregulating MAP3K5.

MicroRNA-199 has been reported to play a potential role in the apoptosis of Human nucleus pulposus cells. However, the effect of miR-199 in regulating Human nucleus pulposus cell injury induced by TNF-α has not been previously illustrated. This study searched to probe the effect and the molecular mechanism of miR-199 on Human nucleus pulposus cell injury induced by TNF-α. Using the TNF-α model of Human nucleus pulposus cell in vitro, we found that miR-199 was extremely decreased in Human nucleus pulposus cells after TNF-α treatment. Knockdown the expression of miR-199 by recombinant adeno-associated viral vector infection markedly promoted the apoptosis of Human nucleus pulposus cells induced by TNF-α treatment, whereas miR-199 overexpression significantly decreased Human nucleus pulposus cell apoptosis. Both Dual-luciferase reporter and western blot assay proved that MAP3K5 was a direct target gene of miR-199, and miR-199 inhibited the expression of MAP3K5 via binding to its 3'-UTR. Furthermore, we proved that overexpression of miR-199 could inhibit the expression of MAP3K5 at the transcription and translation levels, whereas the inhibition of miR-199 could upregulate the expression of MAP3K5. Moreover, MAP3K5 was highly expressed in TNF-α treated Human nucleus pulposus cells and the apoptosis rate induced by TNF-α was associated with the increase in MAP3K5 expression. Importantly, knockdown the expression of MAP3K5 apparently abrogated the inhibitory effect of miR-199 mimics on TNF-α induced Human nucleus pulposus cell apoptosis. In conclusion, these results indicate that upregulation of miR-199 could inhibit Human nucleus pulposus cells injury through downregulation of MAP3K5 expression, providing an important molecular target mechanism for Human nucleus pulposus cells injury.