Curcumin reduces inflammation in knee osteoarthritis rats through blocking TLR4/MyD88/NF-κB signal pathway

Curcumin has been shown to possess a series of beneficial effects, such as antiinflammatory, antioxidant, analgesic, and promoting healing. However, the effect and relative mechanism of curcumin on knee osteoarthritis (OA) have not been elucidated. The aim of this study is to explore the protective effect of curcumin on monosodium iodoacetate (MIA)-induced OA. Forty-eight rats were randomized into four experimental groups: control group, OA group, OA + PBS group, and OA + curcumin group, respectively. A single intraarticular injection of MIA was applied to establish the rat model of knee OA. Hematoxylin-eosin staining was used to evaluate histological changes of knee joint. The paw withdrawal threshold was collected and the expression of synovial fluid cytokine levels was measured by ELISA. The protein expression of TRL-4, MyD88, p-I kappa B alpha, NF-kappa B, TNF-alpha, IL-1 beta, and IL6 was measured by western blot. Treating with curcumin can significantly reduce joint diameter and Mankin's score, and increase the paw withdrawal threshold. The expression of synovial fluid inflammatory biomarkers, IL-6, IL-1 beta, and TNF-alpha in the OA + curcumin group were lower than that in OA and OA + PBS group. The protein expression of the TLR4 receptor was increased in the OA, OA + PBS, and OA + curcumin group compared to the control group. However, curcumin treatment can significantly decrease the expression of MyD88, p-I kappa B alpha, NF-kappa B, TNF-alpha, IL-1 beta, and IL6 in OA + curcumin group. These findings may indicate that curcumin could block TLR4/NF-kappa B signal pathway, and reduce inflammation level to prevent knee wound in OA rats. Curcumin may be a feasible kind of medicament in the treatment of knee OA.