糖基化终产物通过TXNIP-NLRP3炎症小体-SCAP途径诱导糖尿病脂肪肾形成的机制研究

Our previous work demonstrated that Nε-(carboxymethyl) lysine (CML), known as one of advanced glycation end products (AGEs), was able to cause fatty kidney in type 2 diabetes (T2DM) via disrupting the function of sterol regulatory element binding protein cleavage activating protein (SCAP). Recent studies showed the activated NLRP3 inflammasome was involved in intracellular cholesterol metabolism, and it may facilitate the escape of SACP from endoplasmic reticulum to Golgi. In addition, other studies reported thioredoxin interacting protein (TXNIP) was a key link between the activators and NLRP3 inflammasome. Therefore, we proposed that CML may enhance the transfer of SCAP though TXNIP induced activation of NLRP3 inflammasome. To verify this hypothesis, we will build T2DM rat model for the in vivo study, and use the human renal tubular epithelial cell (HK-2) for the in vitro study. Furthermore, confocal laser scanning and co-immunoprecipitation will be used to investigate the crosstalk among TXNIP, NLRP3 inflammasome and SCAP, and identify molecular mechanism of CML induced abnormal transfer of SCAP. Our study may improve the understanding for the molecular basis of SCAP escape and provide a novel therapeutic target in the management of fatty kidney.

课题组前期研究证明作为糖毒性效应分子糖基化终产物的主要组分，羧甲基赖氨酸(CML)可促进胆固醇敏感器SCAP从内质网异常逃逸至高尔基体，引起肾小管胆固醇代谢紊乱，最终导致2型糖尿病脂肪肾的形成，但具体机制尚不清楚。近有研究发现激活的NLRP3炎症小体可能参与SACP的转运，而TXNIP是连接激动剂与该炎症小体的桥梁。为此，我们提出假说：2型糖尿病时，CML通过TXNIP激活NLRP3炎症小体，从而促进SCAP的异常逃逸，最终导致脂肪肾的形成。为了验证该假说，我们使用2型糖尿病大鼠模型及体外干预人肾小管上皮细胞，应用沉默TXNIP和NLRP3基因，观察肾小管脂质代谢及肾脏形态和功能；并利用激光共聚焦、免疫共沉淀等技术研究NLRP3炎症小体的状态及其与TXNIP、SCAP之间的相互作用，旨在揭示SCAP异常逃逸的机制及其与脂肪肾形成的关系，为脂肪肾的防治提供新的思路和证据。

课题组前期研究证明作为糖毒性效应分子糖基化终产物(AGEs)可促进胆固醇敏感器 SCAP从内质网异常逃逸至高尔基体，引起肾小管胆固醇代谢紊乱，最终导致2型糖尿病(T2DM)脂肪肾的形成，但具体机制尚不清楚。近有研究发现激活的NLRP3炎症小体可能参与SACP的转运，而TXNIP是连接激动剂与该炎症小体的桥梁。因此，本实验的研究目的：诣在证明T2DM时，AGEs能够通过TXNIP激活NLRP3炎症小体，从而促进SCAP的异常逃逸，最终导致脂肪肾的形成。实验方法：本实验使用T2DM小鼠模型及体外干预人肾小管上皮细胞，应用沉默TXNIP基因，观察肾小管脂质代谢及肾脏形态和功能；并利用激光共聚焦、免疫共沉淀等技术研究NLRP3炎症小体的状态及其与TXNIP及SCAP之间的相互作用。本研究结果提示：AGEs能激活NLRP3炎症小体，从而促进SCAP的异常逃逸，引起肾小管细胞脂质沉积，肾脏形态和功能改变。而TXNIP是AGEs激活NLRP3炎症小体的中间介质，沉默TXNIP可以抑制NLRP3炎症小体的激活，抑制SCAP的异常逃逸，从而减少肾小管脂质沉积，改善T2DM时肾脏形态及功能。结论：TXNIP-NLRP3炎症小体在AGEs致脂肪肾的形成中起着重要作用，可能成为T2DM时脂肪肾的治疗靶点。