XBP1调控内质网应激预适应减轻脂肪细胞炎症的作用及机制研究

Nutritional excess can trigger both metabolic and adipocyte inflammatory response that lead to metabolic dysfunction and atherosclerosis. The Endoplasmic reticulum (ER) is also highly responsive to cellular nutrient and energy status which is called ER stress. Previously, we reported that enhanced ER stress contributes to inflammation in ischemia-induced retinopathy. On the other hand, the unfolded protein response (UPR) is also activated under inflammatory conditions mediated by ER stress adaptation pathways. Activation of UPR serves to induce signaling and transcriptional events that reestablish ER homeostasis. X-box binding protein 1(XBP1) is a master regulator of the adaptive UPR in response to ER stress. Activated XBP1 induces ER chaperone genes to ameliorate ER stress. Our preliminary experiments identified that overexpression of XBP1 by adenovirus infection can inhibited TNF-α induced inflammation on human umbilical vein endothelial cell (HUVEC). However, the exact role of XBP1 and the signaling pathways in adipocyte inflammation remains poorly understood. In this study, we investigate the role of XBP1 in free fatty acid (FFA) induced inflammatory response in 3T3-L1 adipocytes preconditioned with ER stress. We test whether Exposure of 3T3-L1 adipocytes to low dose ER stress inducers alone results in changes of inflammatory gene expression (TNF-α,IL-6, MCP-1, PAI-1). We investigate mRNA and protein level changes of XBP1 and TNF-α, IL-6, MCP-1 in ER stress preconditioned 3T3-L1 adipocytes inflammation. Furthermore, pharmaceutical inhibition of XBP1 activation or knockdown of XBP1 by siRNA and overexpression of spliced XBP1 by adenovirus infection are explored to identify the key role of XBP1 in the protection effect of ER stress preconditioning in 3T3-L1 adipocytes inflammation. Finally, the phosphorylation level of IKK, IKBα, and NFκB in IKK-NFκB pathway and the level of phosphorylation IRE1α, GRP78 protein level in UPR are tested to clarify the molecular mechanism of XBP1 in protective effect of ER stress preconditioning against FFA elicited 3T3-L1 adipocytes inflammation, which is likely through activation of XBP1-mediated UPR and inhibition IKK-NFκB pathway. There studies collectively indicate a new strategy for controling adipocyte inflammation related obesity.

我们前期研究证实内质网应激在缺氧诱导的人视网膜血管内皮细胞炎症中起重要作用。但内质网应激也可激活X盒结合蛋白1（XBP1）启动未折叠蛋白反应减低细胞损伤。我们预实验证明，XBP1下调TNF-α诱导的人脐静脉内皮细胞炎症，但XBP1对脂肪细胞炎症及内质网应激相关的调节及机制未明。本项目在游离脂肪酸诱导的脂肪细胞炎症模型的基础上，探讨内质网应激预适应对脂肪细胞炎症的保护作用；抑制和过表达XBP1，探讨XBP1在内质网应激预适应对脂肪细胞炎症保护作用中的关键调节；检测炎症信号通路关键因子IKK、IKBα、核转录因子NFκB及未折叠蛋白反应重要启动因子IRE1α、GRP78蛋白表达，探讨XBP1对IKK－NFκB通路及未折叠蛋白反应通路的调节作用，探寻XBP1改善脂肪细胞炎症的分子机制，为治疗肥胖及肥胖相关疾病提供新的治疗方向。