FABP4诱导VE-cadherin泛素化/去泛素化失衡在脓毒症肺损伤中血管内皮屏障破坏中的作用和机制

Septic lung injury is an important reason for accelerating multiple organ failure in sepsis. One of the main mechanisms is the transparent membrane and pulmonary edema resulting from the degradation of vascular endothelial barrier caused by VE-cadherin ubiquitinated degradation. Our previous study found that fatty acid binding protein 4 (FABP4) was involved in the process of lung injury induced by sepsis and induced a decrease in the expression of deubiquitinase OTUB1, whereas ubiquitination inhibitor reduced the expression and distribution of VE-cadherin induced by FABP4. Accordingly, the project proposed: FABP4 induces the abnormal expression and distribution of VE-cadherin by disrupting the ubiquitination/deubiquitination imbalance of that, and then destroying the pulmonary vascular endothelial barrier and causing lung injury in sepsis. Therefore, this topic intends to use AAV9, immunofluorescence, co-immunoprecipitation and other techniques to observe the effect of FABP4 on ubiquitination/deubiquitinationon imbalance of VE-cadherin in septic lung injury. And further illustrate the effect and mechanism of OTUB1 on FABP4 promoting ubiquitination/deubiquitinationon imbalance of VE-cadherin. These results would provide new theory basis for prevention and treatment of septic lung injury.

脓毒症肺损伤是加速脓毒症多器官衰竭的重要原因，其主要机制之一是VE-cadherin泛素化降解导致血管内皮屏障功能破坏而形成的透明膜和肺水肿。我们前期研究发现：脂肪酸结合蛋白4（FABP4）参与脓毒症肺损伤的过程，并诱导去泛素化酶卵巢肿瘤相关蛋白酶B1（OTUB1）表达减少，而泛素化抑制剂可减少FABP4诱导的VE-cadherin表达和分布异常。据此本项目提出：FABP4通过诱导VE-cadherin泛素化/去泛素化失衡，导致VE-cadherin表达和分布异常而破坏肺血管内皮屏障功能，引起脓毒症肺损伤。因此，本课题拟利用AAV9、免疫荧光、免疫共沉淀等技术，观察FABP4在脓毒症肺损伤VE-cadherin泛素化/去泛素化失衡中的作用，阐明OTUB1在FABP4促进VE-cadherin泛素化/去泛素化失衡中的作用和分子机制。为脓毒症肺损伤的防治提供新的思路。

脓毒症肺损伤发展中，肺泡II型上皮细胞（AT II）损伤释放炎症因子促进巨噬细胞M1分化是重要机制。我们通过对脂肪酸结合蛋白4（Fatty acid binding protein 4，FABP4）研究进一步发现，参与脓毒症肺损伤的FABP4可诱导fIL-33氨基酸16位点赖氨酸（K16）去乙酰化及核浆转位，敲除大鼠AT II细胞中的全长IL-33（fIL-33）能改善脓毒症大鼠生存率和肺损伤；此外还发现，抑制组织蛋白酶G后FABP4诱导fIL-33为剪切型IL-33（cIL-33）的作用减弱，fIL-33和cIL-33分别促进巨噬细胞分化为M2和M1型。本研究通过条件敲除大鼠、免疫共沉淀、LC-MS等技术，通过整体动物实验和细胞实验，观察FABP4能诱导K16去乙酰化而促进fIL-33核转位及激活组织蛋白酶G水解fIL-33，进一步阐明fIL-33和cIL-33诱导巨噬细胞分化差异的机制，为FABP4的研究提供了新的研究通路，也脓毒症肺损伤的防治提供新的思路。