Role of G6PD in Myocardial Oxidant Stress & Hypertrophy

描述(由申请人提供)：活性氧物种(ROS)在心血管疾病的病理生理学中起着重要作用。虽然ROS通常被认为是细胞有氧代谢的有害和有毒的副产物，但越来越多的证据表明，ROS也是关键的细胞内信号分子，能够调节细胞的生长和肥大。NADPH通过作为抗氧化酶的辅助因子，在调节ROS水平中发挥多种作用。NADPH也是通过依赖ROS的信号通路调节细胞生长/肥大的关键酶产生ROS的底物。在此背景下，葡萄糖-6-磷酸脱氢酶(G6PD)和磷酸戊糖途径(PPP)的作用变得极其重要。G6PD是PPP中的第一个限速酶，负责在与葡萄糖-6-磷酸氧化耦合的反应中产生NADPH。虽然G6PD普遍表达，但G6PD在调节心脏抗氧化防御和细胞信号通路中的作用仍不清楚。我们的初步数据表明，抑制G6PD会耗尽抗氧化剂储备，增加心肌细胞对急性氧化损伤的敏感性，这与G6PD作为抗氧化酶的作用是一致的。相反，我们还发现，抑制G6PD还导致α1肾上腺素能受体刺激后丝裂原活化蛋白激酶ERK1/2活性显著减弱和心肌细胞肥大，支持G6PD在调节细胞生长/肥大中的作用。这些观察结果导致了我们的中心假设，即G6PD是戊糖磷酸途径中的限速酶，调节胞浆NADPH水平，从而(1)保护心脏免受氧化损伤，(2)调节心肌生长/肥大。我们将利用体外(分离的成人心肌细胞)、体外(分离的朗宁多夫灌流心脏)和体内(小鼠模型)方法的多学科方法来确定PPP和G6PD在心脏中的重要性，并探索其作为治疗与氧化应激相关的心血管疾病的潜在靶点。

DESCRIPTION (provided by applicant): Reactive oxygen species (ROS) play a significant role in the pathophysiology of cardiovascular disease. Though ROS have been conventionally regarded as harmful and toxic by-products of cellular aerobic metabolism, emerging evidence has suggested that ROS also function as crucial intracellular signaling molecules, capable of regulating cellular growth and hypertrophy. NADPH plays multiple roles in the regulation of ROS levels through its actions as a cofactor for antioxidant enzymes. NADPH also serves as a substrate for the generation of ROS by key enzymes that modulate cell growth/hypertrophy via ROS-dependent signaling pathways. In this context, the role of glucose-6-phosphate dehydrogenase (G6PD) and the pentose phosphate pathway (PPP) becomes extremely important. G6PD functions as the first and rate-limiting enzyme in the PPP, responsible for the generation of NADPH in a reaction coupled to the oxidation of glucose-6-phosphate. Although G6PD is ubiquitously expressed, the role of G6PD in regulating antioxidant defense and cell signaling pathways in the heart remains unknown. Our preliminary data suggest that inhibition of G6PD depletes antioxidant reserves and increases susceptibility to acute oxidative injury in cardiomyocytes, consistent with the role of G6PD as an antioxidant enzyme. Conversely, we have found that inhibition of G6PD also results in marked attenuation of mitogen-activated protein kinase ERK1/2 activation and cardiomyocyte hypertrophy following alpha1-adrenergic receptor stimulation, supporting the role of G6PD in modulating cell growth/hypertrophy. These observations led to our central hypothesis that G6PD, the rate-limiting enzyme in the pentose phosphate pathway, regulates cytosolic NADPH levels, and thereby (1) protects the heart from oxidative injury and (2) modulates myocardial growth/hypertrophy. We will utilize a multidisciplinary approach of in-vitro (isolated adult cardiomyocytes), ex-vivo (isolated Langendorff perfused hearts) and in-vivo (mouse models) methods to define the importance of the PPP and G6PD in the heart as well as explore its potential as a therapeutic target for the treatment of cardiovascular diseases associated with oxidative stress.