前列环素在糖尿病血小板异常中的作用及应用：潜在的全新抗血小板治疗靶点

Platelet abnormalities are one of the hallmarks of diabetes, which contributes to the pathogenesis of atherosclerosis and thrombosis. Our recent studies have clearly demonstrated that hyperglycemia-induced activation of aldose reductase (AR) increases ROS production, which consequently leads to the platelet hyperreactivity via the phosphorylation of p38 MAPK. Likewise, AR-mediated ROS increase contributes to the platelet apoptosis via the phosphorylation of p53 (p-p53) under hyperglycemia. Both platelet hyperreactivity and apoptosis increase procoagulant activity, ultimately leading to increased thrombosis in diabetes. Prostacyclin (PGI2) is well recognized to inhibit platelet aggregation via the G-protein coupled receptor and cAMP signaling, and our preliminary findings have shown that PGI2 maintains the mitochondrial function and inhibit the apoptosis. However, the mechanism on how PGI2 protects diabetic platelet is still unknown. We now have evidence in diabetic platelets that PGI2 induces the expression of Beclin1 and LC3II with concomitant reduced expression of p-p53 and active Caspase 3. Based on these findings, we hypothesize that PGI2 induces the mitophagy and removes the damaged mitochondria, which protects against apoptosis in the diabetic platelet, resulting in inhibiting thrombosis. With the use of confocal microscopy and computed tomography, the present study will investigate the mechanistic role of PGI2 in apoptosis and mitophagy in diabetic platelets, and provide the rationale for development of PGI2-based therapies to combat heart attacks and strokes, particularly in the high risk diabetic patients.

血小板异常是糖尿病（DM）的特征之一，可导致动脉粥样硬化和血栓形成。我们已证明，高血糖可激活醛糖还原酶（AR）导致ROS增加，并通过p38 MAPK磷酸化引起血小板高反应性，同时AR介导的ROS增加还可通过p-p53促进血小板凋亡，导致促凝活性增高，使DM血栓形成增多。前列环素（PGI2）是公认的通过G蛋白偶联受体和cAMP信号抑制血小板聚集。我们的初步研究结果显示：PGI2可维持线粒体功能和抑制血小板凋亡，但PGI2对DM血小板异常的机制尚未明确。进一步结果显示：在DM中PGI2可增加自噬标记物（Beclin1和LC3II）的表达，同时减少p-p53和Caspase 3的表达。据此，我们提出假设：PGI2通过诱导DM线粒体自噬，清除受损的线粒体，对抗DM血小板凋亡，抑制血栓形成。本项目拟阐明PGI2在血小板凋亡及线粒体自噬的作用及其机制，为寻找预防和治疗糖尿病血栓形成的靶点提供科学依据。

血小板功能障碍是血栓形成的关键因素，也是糖尿病（DM）并发心血管疾病的重要特征。超过65％的糖尿病患者死于血栓相关心血管疾病。在糖尿病中，活性和聚集力增强的血小板更容易形成微血栓，10%～40%的糖尿病患者表现出对一线抗血小板药物阿司匹林的低敏感。因此，我们迫切需要探索针对DM患者的对抗血小板功能障碍的新疗法。前列环素（PGI2）能抑制血栓形成，预防血栓性心血管事件，但其对血小板的抗激活作用分子机制尚不清楚。本项目按既定计划顺利进行，主要结果如下：1）相较于健康组，糖尿病组外周血PGI2浓度显著降低，PGI2类似物——伊洛前列素（IP）显著减少糖尿病颈动脉结扎小鼠模型的血栓形成；2）IP可有效降低离体培养的人类血小板中p53及Bid活化，抑制其介导的DM血小板凋亡；3）IP可有效增强高糖条件下的离体培养人类血小板的线粒体自噬；4）进一步研究发现，除以上保护机制外，IP还可抑制DM对血小板GLUT3上调作用，改善由GLUT3上调所致的血小板葡萄糖代谢重编程，抑制凋亡；5）利用PGI2受体敲除小鼠（IPKO），采用STZ+高脂饮食诱导糖尿病及颈动脉结扎模型，我们发现阻断PGI2受体信号后，颈动脉血栓显著加剧。我们的研究进一步明确了PGI2及其受体通路通过抑制凋亡、促进自噬以及葡萄糖代谢重编程三条途径实现对血小板异常激活和血栓形成的保护作用，提示前列环素类似物可作为治疗糖尿病高血栓患者的有效辅助替代疗法，为心血管疾病治疗提供了新途径新思路。本项目研究成果目标也顺利完成，受本基金资助，项目负责人作为通讯作者共发表SCI论文5篇，其中3篇分别发表于业内顶级研究期刊Journal of Clinical Investigation， Circulation Research和Circulation。