Elevated microRNA‑145‑5p increases matrix metalloproteinase‑9 by activating the nuclear factor‑κB pathway in rheumatoid arthritis

: The present study explored whether miR‑145‑5p can aggravate the development and progression of rheumatoid arthritis (RA) by regulating the expression of matrix metalloproteinases (MMPs). ELISAs, reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR), and western blotting were used to examine the expression levels of MMP‑1, MMP‑3, MMP‑9, and MMP‑13 in fibroblast‑like synoviocytes (FLS) from patients with RA. Levels of MMP‑1, MMP‑3, MMP‑9, and MMP‑13 were assessed in the right hind ankles of a murine collagen‑induced arthritis (CIA) model by RT‑qPCR and immunohistochemical (IHC) analysis. The effects of activation or inhibition of the nuclear factor‑κB (NF‑κB) pathway on MMPs were evaluated by RT‑qPCR and western blotting. Subcellular localization of NF‑κB p65 was visualized by confocal microscopy. Overexpression of miR‑145‑5p increased the expression of MMP‑3, MMP‑9, and MMP‑13 in RA‑FLS. Moreover, injection of a miR‑145‑5p agomir into mice increased MMP‑3, MMP‑9, and MMP‑13, as demonstrated by RT‑qPCR and IHC analysis. A chemical inhibitor that selectively targets NF‑κB (BAY11‑7082) significantly attenuated MMP‑9 expression, while it did not influence the levels of MMP‑3 and MMP‑13. Immunofluorescence analysis revealed that nuclear localization of p65 was significantly enhanced, indicating that miR‑145‑5p enhances activation of the NF‑κB pathway by promoting p65 nuclear translocation. miR‑145‑5p overexpression also significantly increased phosphorylated p65 levels; however, the levels of IkB‑a were reduced in response to this miRNA. Moreover, our results indicated that miR‑145‑5p aggravated RA progression by activating the NF‑κB pathway, which enhanced secretion of MMP‑9. In conclusion, modulation of miR‑145‑5p expression is potentially useful for the treatment of RA inflammation, by regulating the expression of MMPs, and MMP‑9 in particular, through inhibition of the NF‑κB pathway.