Electroacupuncture serum inhibits TNF-α-mediated chondrocyte inflammation via the Ras-Raf-MEK1/2-ERK1/2 signaling pathway

The Ras-Raf-mitogen-activated protein kinase kinase (MEK)1/2-extracellular signal-regulated kinase (ERK)1/2 signaling pathway contributes to the release of chondral matrix-degrading enzymes and accelerates the degradation of articular cartilage. Electroacupuncture (EA) treatment has been widely used for the treatment of osteoarthritis (OA); however, the mechanism underlying the effects of EA on OA remains unclear. Therefore, the present study evaluated the anti-inflammatory effects and potential underlying mechanisms of EA serum (EAS) on tumor necrosis factor (TNF)-α-mediated chondrocyte inflammation. A total of 30 Sprague Dawley rats were randomly divided into three groups: The blank group; experimental group I, which received 15 min of EA treatment; and experimental group II, which received 30 min of EA treatment. Subsequently, serum samples were obtained. Chondrocytes were isolated from the knee cartilage of Sprague Dawley rats, and were identified using collagen type II immunohistochemistry. TNF-α-treated chondrocytes were used as a cell model, and subsequently the cells were treated with EAS from each group for various durations. The results demonstrated that EAS treatment significantly promoted the viability and inhibited the apoptosis of TNF-α-treated chondrocytes. In addition, interleukin (IL)-1β concentration was significantly increased in the model group compared with in the control group, whereas EAS significantly reduced IL-1β concentration in TNF-α-treated chondrocytes. Furthermore, the protein expression levels of Ras, Raf and MEK1/2 were reduced in the EAS groups compared with in the model group. EAS also significantly inhibited the phosphorylation of ERK1/2, and the expression of downstream regulators matrix metalloproteinase (MMP)-3 and MMP-13. In conclusion, these results indicated that EAS may inhibit TNF-α-mediated chondrocyte inflammation via the Ras-Raf-MEK1/2-ERK1/2 signaling pathway in vitro, thus suggesting that EAS may be considered a potential therapeutic strategy for the treatment of OA.