Cardiovascular Research, Institute of Physiology, University of Zürich, Switzerland.
Circ Res. 2012 Jul 20;111(3):278-89. doi: 10.1161/CIRCRESAHA.112.266593. Epub 2012 Jun 12.
Hyperglycemic memory may explain why intensive glucose control has failed to improve cardiovascular outcomes in patients with diabetes. Indeed, hyperglycemia promotes vascular dysfunction even after glucose normalization. However, the molecular mechanisms of this phenomenon remain to be elucidated.
The present study investigated the role of mitochondrial adaptor p66(Shc) in this setting.
In human aortic endothelial cells (HAECs) exposed to high glucose and aortas of diabetic mice, activation of p66(Shc) by protein kinase C βII (PKCβII) persisted after returning to normoglycemia. Persistent p66(Shc) upregulation and mitochondrial translocation were associated with continued reactive oxygen species (ROS) production, reduced nitric oxide bioavailability, and apoptosis. We show that p66(Shc) gene overexpression was epigenetically regulated by promoter CpG hypomethylation and general control nonderepressible 5-induced histone 3 acetylation. Furthermore, p66(Shc)-derived ROS production maintained PKCβII upregulation and PKCβII-dependent inhibitory phosphorylation of endothelial nitric oxide synthase at Thr-495, leading to a detrimental vicious cycle despite restoration of normoglycemia. Moreover, p66(Shc) activation accounted for the persistent elevation of the advanced glycated end product precursor methylglyoxal. In vitro and in vivo gene silencing of p66(Shc), performed at the time of glucose normalization, blunted ROS production, restored endothelium-dependent vasorelaxation, and attenuated apoptosis by limiting cytochrome c release, caspase 3 activity, and cleavage of poly (ADP-ribose) polymerase.
p66(Shc) is the key effector driving vascular hyperglycemic memory in diabetes. Our study provides molecular insights for the progression of diabetic vascular complications despite glycemic control and may help to define novel therapeutic targets.
高血糖记忆可能解释了为什么强化血糖控制未能改善糖尿病患者的心血管结局。事实上，即使在血糖恢复正常后，高血糖仍会促进血管功能障碍。然而，这一现象的分子机制仍有待阐明。
本研究旨在探讨线粒体衔接蛋白 p66(Shc) 在这种情况下的作用。
在高糖暴露的人主动脉内皮细胞(HAECs)和糖尿病小鼠的主动脉中，蛋白激酶 CβII (PKCβII) 使 p66(Shc) 激活，在血糖恢复正常后仍持续存在。p66(Shc) 的持续上调和线粒体易位与持续的活性氧 (ROS) 产生、一氧化氮生物利用度降低和细胞凋亡有关。我们表明，p66(Shc) 基因的过表达受启动子 CpG 低甲基化和普遍调控非抑制性 5 诱导的组蛋白 3 乙酰化的表观遗传调控。此外，p66(Shc) 衍生的 ROS 产生维持了 PKCβII 的上调和 PKCβII 依赖性内皮型一氧化氮合酶 Thr-495 的抑制性磷酸化，导致尽管恢复了正常血糖水平，但仍存在有害的恶性循环。此外，p66(Shc) 的激活导致晚期糖基化终产物前体甲基乙二醛的持续升高。在葡萄糖正常化时进行的 p66(Shc) 的体外和体内基因沉默，减弱了 ROS 的产生，恢复了内皮依赖性血管舒张，并通过限制细胞色素 c 释放、半胱天冬酶 3 活性和多聚（ADP-核糖）聚合酶的裂解，减轻了细胞凋亡。
p66(Shc) 是糖尿病中驱动血管高血糖记忆的关键效应因子。我们的研究为尽管血糖控制但仍发生糖尿病血管并发症的进展提供了分子见解，并可能有助于确定新的治疗靶点。
