G6PD, OXIDATIVE STRESS AND NITRIC OXIDE INSUFFICIENCY

黑种人的血管素质伴随着氧化应激的增加和生物可利用硝酸的减少。由此产生的一氧化氮不足状态主要是由于活性氧增强了一氧化氮的氧化失活。血管细胞防御氧化应激的主要决定因素是细胞通过合成还原性烟酰胺腺嘌呤二核苷酸磷酸（NADPH）来维持还原性谷胱甘肽（GSH）储存的能力。维持NADPH浓度的主要酶是葡萄糖-6-磷酸脱氢酶（G6PD），它是戊糖磷酸途径的限速酶，将葡萄糖-6-磷酸转化为6-磷酸葡萄糖内酯，在此过程中将NADP+还原为NADPH。反过来，NADPH是谷胱甘肽还原酶将谷胱甘肽二硫（GSSG）还原为谷胱甘肽的关键辅助因子。由于谷胱甘肽过氧化物酶的活性需要谷胱甘肽过氧化物酶的活性，而谷胱甘肽合成需要NADPH，因此缺乏G6PD可能会限制细胞消除过氧化物形式的活性氧中间体的能力，过氧化物的过氧衍生物可以使一氧化氮失活。G6PD缺乏症是世界上最常见的酶病，在非裔美国人中非常普遍。该研究的核心假设是G6PD缺乏会增强正常血管的氧化应激，导致一氧化氮的氧化失活和异常的功能和适应性血管反应。为了验证这一假设，我们建议研究抑制G6PD活性或表达对内皮细胞或血管平滑肌细胞对氧化应激的敏感性的影响；通过增加G6PD的表达或可用性来评估G6PD在内皮细胞或血管平滑肌细胞中的抗氧化作用；研究G6PD对NO合成及氧化代谢的作用；并通过细胞系统和动物模型评估G6PD对血管细胞和血小板NO生物活性的作用。这些研究应该为黑人血管素质的分子机制提供新的见解，并可能导致一氧化氮不足状态的独特治疗方法。

The vascular diathesis of blacks is accompanied by increased oxidant stress and reduced bioavailable nitric acid. The resulting nitric oxide insufficiency state is largely a consequence of enhanced oxidative inactivation of nitric oxide by reactive oxygen species. A principal determinant of vascular cell defense against oxidative stress if the cell's ability to maintain reduced glutathione (GSH) stores through the synthesis of reduced nicotinamide adenine dinucleotide phosphate (NADPH). The primary enzyme responsible for maintaining NADPH concentrations is glucose-6-phosphate dehydrogenase (G6PD), which is the rate-limiting enzyme for the pentose phosphate pathway and coverts glucose-6-phosphate into 6-phosphoglucolactone, reducing NADP+ into NADPH in the process. NADPH, in turn, is a critical co-factor for the reduction of glutathione disulfide (GSSG) into GSH by glutathione reductase. Since GSH is required for the activity of glutathione peroxidase and NADPH is required for GSH synthesis, a deficiency of G6PD would be expected to limit a cell's ability to eliminate reactive oxygen intermediates in the form of peroxides, whose peroxyl derivatives can inactivate nitric oxide. Deficiency of G6PD is the most common enzymopathy worldwide, and highly prevalent among African Americans. The central hypothesis of this proposal is that G6PD deficiency enhances oxidant stress in the normal vasculature, leading to oxidative inactivation of nitric oxide and abnormal functional and adaptive vascular responses. To test this hypothesis, we propose to examine the effect of inhibiting G6PD activity or expression the susceptibility of endothelial or vascular smooth muscle cells to oxidant stress; to assess the antioxidant role of G6PD in endothelial or vascular smooth muscle cells by increasing its expression or availability; to study the role of G6PD on NO synthesis and oxidative metabolism; and to evaluate the role of G6PD on NO bioactivity in vascular cells and platelets using cell systems and animal models. These studies should provide new insights into the molecular mechanism(s) underlying the vascular diathesis of blacks, and may lead to unique therapeutic approaches for nitric oxide insufficiency states.