Li Zihao, Huang Ziyu, Zhang He, Lu Jinghan, Tian Yicheng, Piao Shang, Lin Zhiming, Bai Lunhao
Department of Orthopedics, Shengjing Hospital of China Medical University, Shenyang, 110024, China.
Foreign Languages College, Shanghai Normal University, Shanghai, 200234, China.
Cell Death Discov. 2021 Nov 10;7(1):346. doi: 10.1038/s41420-021-00746-z.
Instability and excessive use of the knee joint can cause osteoarthritis (OA). Reasonable exercise can enhance the stability of the knee joint and prevent and relieve the occurrence and development of OA. As a key switch for inflammation, P2X purinoceptor 7 (P2X7) has attracted much attention in studies of OA. Exercise can regulate P2X7 expression and activation. However, the role of P2X7 in exercise-based prevention and treatment of OA is unknown. We previously showed that moderate-intensity exercise can significantly alleviate OA symptoms. Accordingly, in this study, we evaluated the effects of exercise on P2X7 expression and activation in chondrocytes. Micro-computed tomography, hematoxylin, and eosin staining, Toluidine Blue O staining, immunohistochemistry, and terminal deoxynucleotidyl transferase dUTP nick-end labeling experiments showed that P2X7 expression was lower in the moderate-intensity exercise group than in the inflammation and low- and high-intensity exercise groups. Additionally, chondrocyte death, cartilage destruction, and the degree and severity of pyroptosis were significantly reduced, whereas autophagy levels were significantly increased in the moderate-intensity exercise group. Cell Counting Kit-8 assay, lactate dehydrogenase release, flow cytometry, enzyme-linked immunosorbent assay, cell fluorescence, western blot, reverse transcription-quantitative polymerase chain reaction, and transmission electron microscopy experiments showed that moderate activation of P2X7 promoted autophagy through the AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway and promoted autolysosome targeting for degradation of the inflammasome component NLRP3, thereby inhibiting pyroptosis. Additionally, the use of AMPK and mTOR activators and inhibitors indicated that the AMPK-mTOR signaling pathway, as the downstream of P2X7, played a key role in delaying the occurrence and development of OA. We propose that moderate-intensity exercise promoted chondrocyte autophagy through the P2X7/AMPK/mTOR signal axis to alleviate pyroptosis. Our findings provide novel insights into the positive and preventative effects of exercise on OA.
膝关节不稳定和过度使用会导致骨关节炎（OA）。合理运动可增强膝关节稳定性，预防和缓解OA的发生与发展。作为炎症的关键开关，P2X嘌呤受体7（P2X7）在OA研究中备受关注。运动可调节P2X7的表达和激活。然而，P2X7在基于运动的OA防治中的作用尚不清楚。我们之前表明，中等强度运动可显著减轻OA症状。因此，在本研究中，我们评估了运动对软骨细胞中P2X7表达和激活的影响。显微计算机断层扫描、苏木精和伊红染色、甲苯胺蓝O染色、免疫组织化学以及末端脱氧核苷酸转移酶dUTP缺口末端标记实验表明，中等强度运动组中P2X7的表达低于炎症组以及低强度和高强度运动组。此外，中等强度运动组软骨细胞死亡、软骨破坏以及细胞焦亡的程度和严重性显著降低，而自噬水平显著升高。细胞计数试剂盒8检测、乳酸脱氢酶释放、流式细胞术、酶联免疫吸附测定、细胞荧光、蛋白质印迹、逆转录-定量聚合酶链反应以及透射电子显微镜实验表明，适度激活P2X7可通过AMP激活的蛋白激酶（AMPK）/雷帕霉素哺乳动物靶蛋白（mTOR）信号通路促进自噬，并促进自溶酶体靶向降解炎性小体成分NLRP3，从而抑制细胞焦亡。此外，使用AMPK和mTOR激活剂和抑制剂表明，作为P2X7下游的AMPK-mTOR信号通路在延缓OA的发生和发展中起关键作用。我们提出，中等强度运动通过P2X7/AMPK/mTOR信号轴促进软骨细胞自噬以减轻细胞焦亡。我们的研究结果为运动对OA的积极预防作用提供了新的见解。
