Zhou Xinfeng, Zhang Yijian, Hou Mingzhuang, Liu Hao, Yang Huilin, Chen Xi, Liu Tao, He Fan, Zhu Xuesong
Department of Orthopaedics, The First Affiliated Hospital of Soochow University, Suzhou, China.
Orthopaedic Institute, Medical College, Soochow University, Suzhou, China.
J Bone Miner Res. 2022 May;37(5):1056-1072. doi: 10.1002/jbmr.4527. Epub 2022 Mar 3.
Reactive oxygen species (ROS) are implicated in induction of inflammatory response and cartilage degradation in osteoarthritis (OA). Melatonin has been shown to improve the chondrogenic differentiation and promote cartilage matrix synthesis in mesenchymal stem cells. However, the underlying mechanisms of melatonin-regulated antioxidant activity in OA cartilage are not known. The aim of this study was to explore the effect of melatonin on nuclear factor-erythroid 2-related factor 2 (NRF2), a key antioxidant transcription factor, and its target antioxidant genes in early-stage OA cartilage. Primary chondrocytes were isolated from rats with surgically induced OA. In vitro treatment of melatonin significantly increased cartilage matrix synthesis and upregulated antioxidant enzymes, mainly heme oxygenase 1 (HO-1), while decreasing matrix degradation enzymes and intracellular ROS. In vivo intraarticular injection of melatonin effectively ameliorated cartilage degeneration in an experimental rat OA model. Inhibition of melatonin membrane receptors by Luzindole or 4-P-PDOT reversed the beneficial effects of melatonin on cartilage matrix synthesis, implying that melatonin receptor-mediated pathway is involved in its anti-arthritic effects. Interestingly, melatonin showed no significant effect on the mRNA level of Nrf2 but significantly increased its protein level. Silencing of Nrf2 or HO-1 expression abolished the protective effects of melatonin, as shown by increased ROS levels and matrix degradation enzyme expression. Microarray assays revealed that miR-146a, a predicted target for Nrf2, was significantly upregulated in OA chondrocytes but was markedly reduced by melatonin treatment. Overexpression of miR-146a diminished the protective effects of melatonin by inhibiting NRF2 expression and aggravating OA-induced cartilage degradation. These findings demonstrate that melatonin supports the anabolic metabolism of cartilage matrix in OA chondrocytes by enhancing the protein levels of NRF2 via suppressing miR-146a. Melatonin-mediated activation of the NRF2/HO-1 axis prevents cartilage degeneration and represents a promising therapeutic target for treatment of early-stage OA. © 2022 American Society for Bone and Mineral Research (ASBMR).
活性氧（ROS）与骨关节炎（OA）中炎症反应的诱导和软骨降解有关。褪黑素已被证明可改善间充质干细胞的软骨生成分化并促进软骨基质合成。然而，褪黑素调节OA软骨中抗氧化活性的潜在机制尚不清楚。本研究的目的是探讨褪黑素对早期OA软骨中关键抗氧化转录因子核因子-红系2相关因子2（NRF2）及其靶标抗氧化基因的影响。从手术诱导的OA大鼠中分离出原代软骨细胞。褪黑素的体外处理显著增加了软骨基质合成并上调了抗氧化酶，主要是血红素加氧酶1（HO-1），同时降低了基质降解酶和细胞内ROS。在实验性大鼠OA模型中，褪黑素的体内关节内注射有效改善了软骨退变。用鲁辛朵或4-P-PDOT抑制褪黑素膜受体可逆转褪黑素对软骨基质合成的有益作用，这意味着褪黑素受体介导的途径参与了其抗关节炎作用。有趣的是，褪黑素对Nrf2的mRNA水平没有显著影响，但显著增加了其蛋白水平。Nrf2或HO-1表达的沉默消除了褪黑素的保护作用，表现为ROS水平和基质降解酶表达增加。微阵列分析显示，miR-146a是Nrf2的预测靶标，在OA软骨细胞中显著上调，但经褪黑素处理后明显降低。miR-146a的过表达通过抑制NRF2表达和加重OA诱导的软骨降解而减弱了褪黑素的保护作用。这些发现表明，褪黑素通过抑制miR-146a来提高NRF2的蛋白水平，从而支持OA软骨细胞中软骨基质的合成代谢。褪黑素介导的NRF2/HO-1轴激活可防止软骨退变，是治疗早期OA的一个有前景的治疗靶点。©2022美国骨与矿物质研究学会（ASBMR）
