Yan Jidong, Guo Yuanxu, Fei Yao, Zhang Rui, Han Yan, Lu Shemin
Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China.
Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China.
Acta Biochim Biophys Sin (Shanghai). 2017 Feb 6;49(2):110-118. doi: 10.1093/abbs/gmw125.
Glutathione peroxidase 1 (GPx1) is a selenium (Se)-containing protein and is induced in cartilage formation. GPx1 eliminates reactive oxygen species (ROS), which are required for chondrogenic induction. The physiological properties of GPx1 in cartilage and the redox mechanisms involved are not known. The effects of GPx1 on chondrogenic differentiation of ATDC5 cells were examined through short hairpin RNA-mediated gene silencing. The results demonstrated that GPx1 knockdown impaired gene expression of sex determining region Y-box 9, collagen II (Col II), and aggrecan. GPx1 knockdown suppressed the accumulation of cartilage glycosaminoglycans (GAGs) and the proliferation of chondrocyte. GPx1 knockdown also induced cell apoptosis. However, cell sensitivity toward exogenous oxidative stress was not increased after GPx1 knockdown. Unexpectedly, GPx1 knockdown not only induced oxidative stress characterized by the increased production of ROS but also caused reductive stress indicated by an elevation of glutathione (GSH)/oxidized GSH (GSSG) ratio. Furthermore, GPx1 knockdown-mediated reductive and oxidative stress could be antagonized by a thiol-oxidizing agent diamide and a thiol-containing compound N-acetylcysteine (NAC), respectively. Moreover, NAC attenuated GPx1 knockdown-induced cell apoptosis, while diamide prevented GPx1 knockdown-suppressed chondrocyte proliferation. Finally, diamide but not NAC could rescue GPx1 knockdown-mediated impaired chondrogenic differentiation. In summary, GPx1 is essential for chondrogenic induction in ATDC5 cells mainly through modulation of intracellular GSH/GSSG ratio, rather than an antioxidant enzyme to detoxify ROS. In addition, GPx1 knockdown-induced impaired chondrogenesis may participate in the pathogenesis of the endemic osteoarthropathy due to Se deficiency. These observations offer novel insights for the development of therapeutic target during cartilage degeneration.
谷胱甘肽过氧化物酶1（GPx1）是一种含硒（Se）的蛋白质，在软骨形成过程中被诱导表达。GPx1可清除活性氧（ROS），而ROS是软骨形成诱导所必需的。GPx1在软骨中的生理特性以及所涉及的氧化还原机制尚不清楚。通过短发夹RNA介导的基因沉默研究了GPx1对ATDC5细胞软骨分化的影响。结果表明，GPx1基因敲低会损害性别决定区Y盒9、胶原蛋白II（Col II）和聚集蛋白聚糖的基因表达。GPx1基因敲低抑制了软骨糖胺聚糖（GAGs）的积累和软骨细胞的增殖。GPx1基因敲低还诱导了细胞凋亡。然而，GPx1基因敲低后细胞对外源氧化应激的敏感性并未增加。出乎意料的是，GPx1基因敲低不仅诱导了以ROS产生增加为特征的氧化应激，还导致了以谷胱甘肽（GSH）/氧化型谷胱甘肽（GSSG）比值升高为指标的还原应激。此外，GPx1基因敲低介导的还原应激和氧化应激可分别被硫醇氧化剂二酰胺和含硫醇化合物N-乙酰半胱氨酸（NAC）拮抗。此外，NAC减轻了GPx1基因敲低诱导的细胞凋亡，而二酰胺则阻止了GPx1基因敲低抑制的软骨细胞增殖。最后，二酰胺而非NAC可以挽救GPx1基因敲低介导的软骨分化受损。总之，GPx1对ATDC5细胞的软骨形成诱导至关重要，主要是通过调节细胞内GSH/GSSG比值，而不是作为一种解毒ROS的抗氧化酶。此外，GPx1基因敲低诱导的软骨形成受损可能参与了缺硒所致地方性骨关节炎的发病机制。这些观察结果为软骨退变过程中治疗靶点的开发提供了新的见解。
