HSPA12B通过SSeCKS-CaM-CSE途径调控内源性H2S在糖尿病动脉粥样硬化中的作用研究

Atherosclerosis (AS) is the major cause of cardiovascular diseases in patients with diabetes. Endothelial dysfunction plays crucial roles in the development of diabetic AS. Endothelial cells produce hydrogen sulfide (H2S),which has protective effects on endothelial dysfunction, via cystathionine-γ-lyase (CSE). Our previous studies showed that overexpression of HSPA12B, an endothelial specific factor, alleviated high-glucose plus ox-LDL induced endothelial dysfunction and decrease of CSE in endothelial cells. Moreover, HSPA12B could bind to SSeCKS and regulate its expression. SSeCKS is a scaffold protein for calmodulin（CaM）which is crucial for the activity of CSE, indicating that HSPA12B may play protective roles in diabetic AS through promoting the production of H2S via SSeCKS-CaM-CSE pathway. In this project, we will firstly construct diabetic AS model in HSPA12B transgenic and knockout mice to investigate the role of HSPA12B in diabetic AS. And then we will use high glucose plus ox-LDL treated endothelial cells to test the hypothesis that HSPA12B could attenuate endothelial dysfunction via binding with SSeCKS and CaM to form a ternary complex in endothelial cells, which in turn activates CSE and promotes the production of endogenous H2S. This project will provide a new insight into the prevention and treatment for diabetic AS.

动脉粥样硬化（AS）是糖尿病患者并发心血管疾病的重要原因，内皮功能损伤是导致糖尿病AS的核心机制。内皮细胞通过胱硫醚-γ-裂解酶（CSE）催化产生具有内皮保护作用的H2S。HSPA12B是内皮细胞特异因子，我们前期预实验发现过表达HSPA12B可减轻高糖高脂诱导的内皮细胞损伤和CSE表达降低。还发现HSPA12B能与细胞骨架蛋白SSeCKS结合并调控其表达，而后者能与调节CSE活性的关键分子钙调蛋白（CaM）结合，提示HSPA12B可能通过SSeCKS-CaM-CSE途径调控内源性H2S，减轻糖尿病AS的进程。本项目将利用HSPA12B转基因及敲除小鼠糖尿病AS模型研究HSPA12B对糖尿病AS的影响；并结合高糖高脂诱导的内皮细胞损伤模型证明HSPA12B能与SSeCKS及CaM形成三元复合物，激活下游CSE，促进H2S生成，减轻内皮细胞损伤。本研究将为糖尿病AS的防治提供新思路和新靶点。

该项目前期研究观察到HSPA12B（Heat shock protein A12B）在糖尿病动脉粥样硬化中发挥作用，可以通过诱导胱硫醚-γ-裂解酶（CSE）表达参与内皮细胞保护。在该项目实施过程中，课题组还观察到HSPA12B可通过调控焦亡反应参与高糖高脂诱导的内皮细胞损伤，以及HSPA12B可缓解LPS诱导的内皮功能受损。除了在内皮细胞中发挥作用，课题组研究发现HSPA12B参与脂肪代谢及肝脏糖异生的过程。因HSPA12B在内皮细胞中发挥保护已有相关文献报道，而HSPA12B在脂肪细胞及肝脏细胞中的研究缺乏，因此本项目后续深入开展了HSPA12B在脂肪细胞脂肪酸合成及肝脏糖异生中的作用及机制研究。..项目主要研究结果：一、HSPA12B在内皮细胞中表达丰富，在糖尿病动脉粥样硬化小鼠主动脉和高糖高脂诱导的内皮细胞中HSPA12B表达下降，且HSPA12B下降与内皮细胞损伤程度呈正相关。二、HSPA12B通过焦亡反应参与调控内皮细胞损伤过程，敲除HSPA12B可加重高糖高脂诱导以及LPS诱导的焦亡，过表达HSPA12B可减轻焦亡反应。三、HSPA12B在脂肪细胞中参与脂肪酸的合成。四、在肝脏细胞中，HSPA12B通过促进FOXO1乙酰化加强肝脏糖异生作用，HSPA12B对FOXO1的调控是通过抑制miR671-5p促进HDAC3表达实现的，提示HSPA12B可能通过调控糖异生参与2型糖尿病的病理过程，为2型糖尿病的防治提供新靶点。