MicroRNA-26a-5p regulates the expression of inducible nitric oxide synthase via activation of NF-κB pathway in human osteoarthritis chondrocytes.

Inducible nitric oxide synthase (iNOS) expression is associated with the pathogenesis of osteoarthritis (OA). This study was undertaken to investigate whether interleukin-1β (IL-1β)-mediated induction of iNOS can be regulated by microRNA-26a-5p (hsa-miR-26a-5p) in OA. Bioinformatics approaches show that 3'UTR of iNOS mRNA contained the 'seed-matched-sequence' for hsa-miR-26a-5p. IL-1β-induced expression of iNOS correlated with the down-regulation of miR-26a-5p in human OA chondrocytes. hsa-miR-26a-5p directly suppressed the luciferase activity of 3'UTR-iNOS reporter clone. Transfection with pre-miR-26a-5p induced marked silencing of iNOS expression. Activation of NF-κB pathway down-regulated the expression of hsa-miR-26a-5p and induced iNOS expression. In short, this is the first report that shows hsa-miR-26a-5p is a direct regulator of iNOS expression in human chondrocytes. hsa-miR-26a-5p may be an important regulator of human cartilage homeostasis and a new target for OA therapy.