Department of Orthopedics, The 309th Hospital of People's Liberation Army, Beijing 100091, P.R. China.
Mol Med Rep. 2018 Jun;17(6):8475-8483. doi: 10.3892/mmr.2018.8897. Epub 2018 Apr 19.
Osteoarthritis is a type of joint disease that may lead to other joint diseases. Previous research has demonstrated that tumor necrosis factor (TNF)‑α is associated with osteoarthritis activity and pathology. The possible mechanisms of the TNF‑α‑mediated signaling pathway have not been clearly elaborated in synovial fibroblasts. The present study aimed to investigate the potential mechanisms of TNF‑α in a mouse model of iodoacetate‑induced osteoarthritis. Reverse transcription‑quantitative polymerase chain reaction, ELISA, western blotting and immunohistochemistry were performed to evaluate the role of TNF‑α in the progression of osteoarthritis. The results revealed that the serum levels of TNF‑α, interleukin (IL)‑1β, IL‑4 and IL‑6 were significantly upregulated in a mouse model of iodoacetate‑induced osteoarthritis compared with healthy mice (P<0.01). TNF‑α, IL‑1β, IL‑4 and IL‑6 mRNA and protein levels were also significantly upregulated in synovial fibroblasts in the experimental mice (P<0.01). It was demonstrated that TNF‑α increased pro‑inflammation factors matrix metalloproteinase (MMP)‑3, MMP‑9, nuclear factor (NF)‑κB and receptor activator of NF‑κB ligand (RANKL) in synovial fibroblasts. It was also observed that the toll‑like receptor (TLR)‑3 was significantly upregulated and extracellular signal‑regulated kinase (ERK) and protein kinase B (AKT) were significantly downregulated in synovial fibroblasts in osteoarthritis mice (P<0.01). An in vitro assay demonstrated that TNF‑α inhibitor decreased mRNA and protein levels of IL‑1β, IL‑4 and IL‑6 in synovial fibroblasts. The knockdown of TLR‑3 abolished the TNF‑α upregulated mRNA and protein levels of IL‑1β, IL‑4 and IL‑6 in synovial fibroblasts. In addition, the knockdown of TLR‑3 also reversed TNF‑α‑upregulated ERK and AKT expression in synovial fibroblasts. In vivo assays demonstrated that TNF‑α inhibitor significantly decreased the deposition of IL‑1β, IL‑4 and IL‑6 as well as bone destruction and significantly increased the body weight and osteoarthritis score for osteoarthritic mice (P<0.01). TNF‑α inhibitor decreased TLR‑3 and significantly increased the expression and phosphorylation of ERK and AKT in articular cartilage (P<0.01). In conclusion the results of the present study indicate that TNF‑α serves an essential role in synovial fibroblasts in osteoarthritis, suggesting that inhibition of TNF‑α may decrease inflammation via the TLR‑3‑mediated ERK/AKT signaling pathway in a mouse model of monosodium iodoacetate‑induced osteoarthritis.
骨关节炎是一种可能导致其他关节疾病的关节疾病。先前的研究表明，肿瘤坏死因子 (TNF)-α 与骨关节炎的活动和病理学有关。TNF-α 介导的信号通路的可能机制在滑膜成纤维细胞中尚未得到明确阐述。本研究旨在探讨 TNF-α 在碘乙酸诱导的骨关节炎小鼠模型中的潜在机制。采用逆转录定量聚合酶链反应、酶联免疫吸附试验、Western blot 印迹法和免疫组织化学法评估 TNF-α 在骨关节炎进展中的作用。结果显示，与健康小鼠相比，碘乙酸诱导的骨关节炎小鼠模型中 TNF-α、白细胞介素 (IL)-1β、IL-4 和 IL-6 的血清水平显著升高(P<0.01)。实验小鼠滑膜成纤维细胞中 TNF-α、IL-1β、IL-4 和 IL-6 的 mRNA 和蛋白水平也显著上调(P<0.01)。结果表明，TNF-α 增加了滑膜成纤维细胞中的促炎因子基质金属蛋白酶 (MMP)-3、MMP-9、核因子 (NF)-κB 和核因子-κB 配体 (RANKL)。还观察到，骨关节炎小鼠滑膜成纤维细胞中 Toll 样受体 (TLR)-3 显著上调，细胞外信号调节激酶 (ERK) 和蛋白激酶 B (AKT) 显著下调(P<0.01)。体外实验表明，TNF-α 抑制剂降低了滑膜成纤维细胞中 IL-1β、IL-4 和 IL-6 的 mRNA 和蛋白水平。TLR-3 的敲低消除了 TNF-α 上调的滑膜成纤维细胞中 IL-1β、IL-4 和 IL-6 的 mRNA 和蛋白水平。此外，TLR-3 的敲低还逆转了 TNF-α 上调的滑膜成纤维细胞中 ERK 和 AKT 的表达。体内实验表明，TNF-α 抑制剂显著减少了骨关节炎小鼠中 IL-1β、IL-4 和 IL-6 的沉积、骨破坏，并显著增加了体重和骨关节炎评分(P<0.01)。TNF-α 抑制剂降低了 TLR-3 的表达，并显著增加了关节软骨中 ERK 和 AKT 的表达和磷酸化(P<0.01)。综上所述，本研究结果表明，TNF-α 在骨关节炎滑膜成纤维细胞中发挥重要作用，提示抑制 TNF-α 可能通过 TLR-3 介导的 ERK/AKT 信号通路减少炎症反应，在碘乙酸诱导的小鼠骨关节炎模型中。
