miR-125 regulates PI3K/Akt/mTOR signaling pathway in rheumatoid arthritis rats via PARP2

The present study aimed to explore miR-125 effects on rheumatoid arthritis (RA) development to provide a potential target for RA. Briefly, rat RA model was established (Model group) by injection of Freund’s Complete Adjuvant into the left hind toe. Normal rats injected with saline in the same location were set as Normal group. All rats’ secondary foot swelling degree, polyarthritis index score, spleen and thymus index were measured. Synovial tissues were subjected to Hematoxylin–Eosin (HE) staining and immunohistochemistry. Synovial cells of each group were isolated and named as Normal-C group and Model-C group, respectively. Synovial cells of Model-C group further underwent cotransfection with miR-125 mimics and PARP2-siRNA (mimics+siPARP2 group) or with miR-125 negative control (NC) and PARP2-siRNA NC (NC group). Quantitative reverse transcriptase PCR (qRT-PCR), Western blot, luciferase reporter assay, ELISA, and MTT assay were performed. As a result, compared with Normal group, rats of Model group showed significantly higher secondary foot swelling degree, polyarthritis index score, spleen and thymus index (P<0.01). Down-regulated miR-125 and up-regulated PARP2 was found in synovial tissues of Model group when compared with Normal group (P<0.01). Synovial tissues of Model-C group exhibited severe hyperplasia and inflammatory cell infiltration. Luciferase reporter assay indicated that PARP2 was directly inhibited by miR-125. Compared with NC group, cells of mimics+siPARP2 group had significantly lower IL-1β, MMP-1 and TIMP-1 levels, absorbance value, and p-PI3K, p-Akt and p-mTOR relative expression (P<0.01 or P<0.05). Thus, miR-125 might attenuate RA development by regulating PI3K/Akt/mTOR signaling pathway via directly inhibiting PARP2 expression.