You Yunhui, Liu Shiqing, Peng Lijuan, Long Mei, Deng Hongxiang, Zhao Hongjun
Department of Rheumatology and Immunology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, P.R. China.
Mol Med Rep. 2015 Jul;12(1):255-60. doi: 10.3892/mmr.2015.3457. Epub 2015 Mar 9.
The presence of Arg972 insulin receptor substrate-1 (IRS-1) is associated with impaired insulin/IRS-1 signaling to activate phosphatidylinositol-3 kinase (PI3K). Tumor necrosis factor-α (TNF-α), an inflammatory cytokine with a central role in the pathogenesis of rheumatoid arthritis (RA), induces apoptosis in osteoblasts, which are the principal cell type responsible for bone loss in RA. In our previous study, an association between Arg972 IRS-1 and a high risk and severity of RA was identified. In the present study, the effects of Arg972 IRS-1 and IRS-1 on TNF-α-induced apoptosis in human osteoblasts were examined. Normal and RA osteoblasts were stably transfected with Arg972 IRS-1 and IRS-1. In addition, cells were stably transduced with IRS-1-shRNA to knock down IRS1. Following stimulation with 10 nM insulin for 30 min, the stable overexpression of Arg972 IRS-1 and knock down of IRS-1 significantly decreased IRS-1-associated PI3K activity and Akt activation/phosphorylation at serine 473 (ser473) and enhanced TNF-α-induced apoptosis in normal and in RA osteoblasts. By contrast, the stable overexpression of IRS-1 significantly increased the levels of IRS-1-associated PI3K activity and Akt phosphorylation (ser473) and inhibited TNF-α-induced apoptosis, which was eliminated by pretreatment with 50 µn BJM120, a selective PI3K inhibitor, for 30 min. In conclusion, the present study provided the first evidence, to the best of our knowledge, that insulin stimulation of Arg972 IRS-1 and IRS-1 enhanced and inhibited TNF-α-induced apoptosis, respectively in normal and RA osteoblasts by a PI3K‑dependent mechanism. These findings suggest that insulin/IRS-1 signaling is important in the pathogenesis of RA.
精氨酸972胰岛素受体底物-1（IRS-1）的存在与胰岛素/IRS-1信号传导受损有关，该信号传导可激活磷脂酰肌醇-3激酶（PI3K）。肿瘤坏死因子-α（TNF-α）是一种在类风湿关节炎（RA）发病机制中起核心作用的炎性细胞因子，可诱导成骨细胞凋亡，而成骨细胞是RA中导致骨质流失的主要细胞类型。在我们之前的研究中，已确定精氨酸972 IRS-1与RA的高风险和严重程度之间存在关联。在本研究中，检测了精氨酸972 IRS-1和IRS-1对TNF-α诱导的人成骨细胞凋亡的影响。用精氨酸972 IRS-1和IRS-1稳定转染正常和成骨细胞系来源的成骨细胞。此外，用IRS-1-shRNA稳定转导细胞以敲低IRS1。在用10 nM胰岛素刺激30分钟后，精氨酸972 IRS-1的稳定过表达和IRS-1的敲低显著降低了与IRS-1相关的PI3K活性以及丝氨酸473（ser473）处的Akt激活/磷酸化，并增强了TNF-α诱导的正常和成骨细胞系来源的成骨细胞凋亡。相比之下，IRS-1的稳定过表达显著增加了与IRS-1相关的PI3K活性和Akt磷酸化（ser473）水平，并抑制了TNF-α诱导的凋亡，而用选择性PI3K抑制剂50 µn BJM120预处理30分钟可消除这种抑制作用。总之，据我们所知，本研究首次提供了证据，即胰岛素刺激精氨酸972 IRS-1和IRS-1分别通过PI3K依赖性机制增强和抑制正常和成骨细胞系来源的成骨细胞中TNF-α诱导的凋亡。这些发现表明胰岛素/IRS-1信号传导在RA发病机制中很重要。
