SUMO化修饰FXR受体调控糖尿病心肌损伤的机制研究

Oxidative stress triggered cardiomyocyte apoptosis and fibrosis is an important pathophysiological mechanism of diabetic cardiomyopathy (DCM). And it is the main cause of heart failure and death in patients with DCM. Inhibitory effect of FXR on the expression of TNF-α and IL-1β can significantly reduce reactive oxygen/nitrogen species generated and inhibit DCM myocardial oxidative stress. However, the regulation mechanism of these inflammatory factors is still not clear. SUMOylation of transcription factor plays an important role in the trans-repressor genes expression regulation. Combined with the basis of preliminary studies, we speculate that the SUMOylation of FXR inhibiting of inflammatory factors is a key mechanism of their anti-inflammation activity. To confirm this hypothesis, we will use RNAi, Co-IP and ChIP to investigate SUMOylation regulate FXR, which in turn trans-repress the expression of TNF-α and IL-1β, inhibit oxidative stress, attenuate apoptosis and remodeling in high glucose-treated cardiomyocyte in vitro and in vivo SUMO-KO DCM mice model. Exploring this possible mechanism, we can provide new clues to clarify the role of FXR in DCM.

氧化应激及炎症触发心肌细胞凋亡和纤维化是糖尿病致心肌损伤的重要病理生理机制，是导致DCM患者心力衰竭和死亡的主要原因。配体激活FXR抑制TNF-α和IL-1β等炎症因子转录表达可以显著减少活性氧(氮)自由基生成，减轻DCM心肌纤维化及心肌细胞凋亡。然而调控这些炎症因子表达的分子机制目前尚不清楚。SUMO化修饰在调控转录因子反式阻遏基因表达中发挥重要作用。结合前期研究基础，我们推测SUMO化修饰FXR抑制炎症因子表达是其发挥抗心肌损伤作用的关键机制。为证实以上假说，本课题拟通过体外高糖培养心肌细胞和在SUMO基因敲除DCM小鼠模型中，采用RNAi、Co-IP及ChIP等技术明确SUMO化修饰调控 FXR反式阻遏TNF-α和IL-1β等炎症因子表达，从而抑制氧化应激、细胞凋亡与重构的作用并探讨其可能机制，为阐明糖尿病心肌损伤机制提供新线索。

我们前期工作在心肌细胞和心肌成纤维细胞中发现一条具有功能活性的核受体FXR-SHP级联通路，本项目通过在体和离体实验，围绕SUMO化修饰FXR受体调控糖尿病心肌损伤、心肌肥厚、缺血再灌注损伤和心肌重构进行了一系列研究。研究结果表明：1）通过改变SUMO化修饰水平，可调控核受体FXR在心肌缺血再灌注损伤过程中的促凋亡作用，由此证实FXR的心脏效应可以通过SUMO化调节，且调控FXR的SUMO化水平可能对MI/R损伤具有治疗前景；2）调控去SUMO化修饰的SENP3蛋白酶等在急性心梗及心肌重构中具有重要作用；3）FXR翻译后修饰调节相关的去泛素化酶USP4是心肌肥厚的负性调节因子；4）与FXR类似的核受体ROR对糖尿病心肌病及心肌缺血再灌注损伤具有保护性作用以及与FXR功能上存在交叉对话的核受体LXR在心梗和重构中发挥重要作用。综上，本研究阐明了FXR等核受体通路及翻译后修饰调节在糖尿病心肌损伤、心肌肥厚、心肌重构及缺血再灌注损伤中发挥关键作用。因此，筛选特异性干预FXR等核受体通路及翻译后修饰调节的药物有望成为治疗以上心血管疾病的新的干预靶点。