Shi Xinge, Ye Hui, Yao Xuedong, Gao Yanzheng
Department of Orthopedics, Henan Provincial People's Hospital Zhengzhou 450003, Henan, China.
Department of Orthopedics, The Third Affiliated Hospital of Southern Medical University, Academy of OrthopedicsGuangzhou 510665, Guangdong Province, China; Department of Orthopedics, The Second Affiliated Hospital of Fujian Medical UniversityQuanzhou 362000, Fujian, China.
Am J Transl Res. 2017 Feb 15;9(2):746-754. eCollection 2017.
Osteoarthritis (OA) is a joint disease caused by the breakdown of joint cartilage and underlying bone, and places great burdens to daily life of patients. Nuclear orphan receptor nuclear receptor subfamily 4, group A, member 1 (NR4A1) is vital for cell apoptosis, but little is known about its role in OA. This study aims to reveal the expression and function of NR4A1 during OA chondrocyte apoptosis. NR4A1 expression by qRT-PCR and western blot, and chondrocyte apoptosis by TUNEL assay were detected in normal and OA joint cartilage. NR4A1 was located in cartilage sections by immunohistofluorescence. Chondrocytes from normal joint cartilage were cultured for interleukin 6 (IL6) or tumor necrosis factor (TNF) treatment and si-NR4A1 transfection, after which the possible mechanism involving NR4A1 was analyzed. Results showed that NR4A1 expression and chondrocyte apoptosis were significantly elevated in OA cartilage ( < 0.05 and < 0.01). NR4A1 was located in nuclei of normal cartilage chondrocytes, but was translocated to mitochondria and co-located with B-cell lymphoma 2 in OA chondrocytes. NR4A1 expression in cultured chondrocytes could be promoted by both IL6 and TNF treatment. si-NR4A1 partly reduced TNF-induced cell apoptosis. Inhibiting p38 by SB203580 could decrease TNF-induced NR4A1 to some extent, while inhibiting JNK could not. So NR4A1 is likely to facilitate OA chondrocyte apoptosis, which is associated with p38 MAPK and mitochondrial apoptosis pathway. This study provides a potential therapeutic target for OA treatment and offers information for regulatory mechanisms in OA.
骨关节炎（OA）是一种由关节软骨和下方骨骼破坏引起的关节疾病，给患者的日常生活带来了沉重负担。核孤儿受体核受体亚家族4、A组、成员1（NR4A1）对细胞凋亡至关重要，但对其在OA中的作用知之甚少。本研究旨在揭示NR4A1在OA软骨细胞凋亡过程中的表达和功能。在正常和OA关节软骨中，通过qRT-PCR和蛋白质印迹法检测NR4A1表达，并通过TUNEL法检测软骨细胞凋亡。通过免疫荧光法在软骨切片中定位NR4A1。对来自正常关节软骨的软骨细胞进行白细胞介素6（IL6）或肿瘤坏死因子（TNF）处理以及si-NR4A1转染，然后分析涉及NR4A1的可能机制。结果显示，OA软骨中NR4A1表达和软骨细胞凋亡显著升高（<0.05和<0.01）。NR4A1位于正常软骨细胞的细胞核中，但在OA软骨细胞中易位至线粒体并与B细胞淋巴瘤2共定位。IL6和TNF处理均可促进培养的软骨细胞中NR4A1表达。si-NR4A1部分降低了TNF诱导的细胞凋亡。用SB203580抑制p38可在一定程度上降低TNF诱导的NR4A1，而抑制JNK则不能。因此，NR4A1可能促进OA软骨细胞凋亡，这与p38丝裂原活化蛋白激酶和线粒体凋亡途径有关。本研究为OA治疗提供了一个潜在的治疗靶点，并为OA的调控机制提供了信息。
