炎症应激调节parkin介导的CD36单泛素化修饰在肾小管上皮细胞脂肪酸异常摄取中的作用

Inflammatory stress exacerbating lipid-mediated renal injury plays important roles in the progression of chronic renal fibrosis. CD36 is a class B scavenger receptor expressed in a variety of cell types such as macrophage, adipocytes and human renal tubular cells, functioning as a wide range of ligands including oxidized low density lipoprotein （ox-LDL）and long chain fatty acids. We found inflammatory stress could increase the expression of CD36 and lipid accumulation in renal tubular cells induced by fatty acid, which shows CD36 might play a key role in the progression of renal interstitial disease. Parkin, a pathogenic gene encoding protein of hereditary Parkinson disease, is also an E3 ubiquitin ligase, which can be expressed in a variety of cells, including liver cells stimulated by high fat exposure, mediating monoubiquitination of CD36 and stabilizing CD36 on cell membrane without degradation. We have already found inflammatory stress could increase the expression of Parkin in HK-2. In this research, we further study the effects of monoubiquitination of CD36 mediated by Parkin on abnormal fatty acid intake in renal tubular cells induced by inflammatory stress, aims to clarify the mechanism of inflammatory stress aggravating lipid-mediated renal injury.

炎症应激加重脂质肾毒性是导致慢性肾纤维化的重要因素。CD36是细胞膜上摄取ox-LDL和游离脂肪酸的受体，我们前期研究已证实炎症可加重脂肪酸诱导的肾小管上皮细胞CD36表达及脂质摄入，提示其在肾间质病变中可能发挥关键作用。遗传性parkinson病的致病基因编码蛋白parkin，也是泛素化过程中的E3连接酶，可在多种细胞中表达包括介导高脂环境下肝细胞CD36的单泛素化，从而稳定细胞膜CD36而不被降解。我们前期研究发现炎症应激可增加HK-2细胞Parkin的表达，但其是否参与肾小管上皮细胞CD36的单泛素化并在脂质肾毒性中发挥关键作用？本课题以肾小管上皮细胞为研究对象, 以CD36单泛素化修饰为切入点，采用基因转染过表达、RNAi等实验技术，研究parkin介导的CD36单泛素化修饰在炎症应激下肾小管脂肪酸异常摄取中的作用，旨在进一步阐明炎症加重脂质肾毒性的重要机制这一科学问题。

肾脏疾病常常合并有脂代谢紊乱，而后者在炎症应激下可能导致原有的肾脏损害加重，但机制仍不清楚。CD36是细胞摄取ox-LDL和游离脂肪酸的受体，我们研究发现，炎症应激可增加棕榈酸诱导的肾小管上皮细胞CD36的表达及其脂质摄入，而CD36的配体抑制剂SSO预处理可明显减少细胞内脂质的集聚。我们也同时证实炎症介质和棕榈酸均可上调肾小管上皮细胞Parkin的表达，并增加与CD36共定位，过表达parkin减少细胞CD36降解，增加其蛋白的稳定性，推测其机制可能与parkin介导CD36单泛素化有关。我们进一步证实基因沉默parkin表达，可减少炎症应激加重的HK-2细胞内脂质集聚这一过程。综上结果，表明炎症通过调节parkin介导的CD36单泛素化而参与了肾小管上皮细胞脂质集聚过程。本研究进一步阐明了炎症加重脂质肾毒性的重要机制这一科学问题，并进一步丰富了炎症加重脂质肾毒性这一假说。