Department of Ophthalmology, Kresge Eye Institute, Detroit, Michigan 48201, USA.
Invest Ophthalmol Vis Sci. 2010 Mar;51(3):1765-72. doi: 10.1167/iovs.09-4171. Epub 2009 Oct 29.
Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has been hypothesized as a mediator in the activation of multiple pathways implicated in the pathogenesis of diabetic retinopathy. The objective of this study was to understand the mechanism by which high glucose inactivates GAPDH in retinal microvascular cells.
Bovine retinal endothelial cells (BRECs), transfected with GAPDH, were incubated in 20 mM glucose. The effect of the overexpression of GAPDH on its activity, apoptosis, and upstream signaling pathways, protein kinase C, and hexosamine pathways was determined. The effect of the inhibitors of nitration and ribosylation on GAPDH activity, its nuclear translocation and reversal of glucose insult was also evaluated.
High glucose decreased GAPDH activity, expression, and nuclear translocation. Overexpression of GAPDH prevented glucose-induced inhibition of its activity, nuclear translocation, apoptosis, and activation of protein kinase C and hexosamine pathways. Inhibitors of nitration and ribosylation ameliorated glucose-induced inhibition of GAPDH, and their addition during the normal glucose exposure that followed high glucose levels had a beneficial effect on GAPDH activity and the degree of nitration and ribosylation.
In hyperglycemia, GAPDH in retinal microvascular cells is inhibited by its covalent modifications, and this activates multiple pathways implicated in the pathogenesis of diabetic retinopathy. The agents that can directly target modification of GAPDH have potential in inhibiting the development and in arresting the progression of diabetic retinopathy.
甘油醛-3-磷酸脱氢酶（GAPDH）被认为是糖尿病性视网膜病变发病机制中多个途径激活的介质。本研究旨在了解高葡萄糖使视网膜微血管细胞中 GAPDH 失活的机制。
用 GAPDH 转染的牛视网膜内皮细胞（BRECs）在 20mM 葡萄糖中孵育。测定 GAPDH 过表达对其活性、细胞凋亡和上游信号通路、蛋白激酶 C 和己糖胺通路的影响。还评估了硝化和核糖基化抑制剂对 GAPDH 活性、核易位以及逆转葡萄糖损伤的影响。
高葡萄糖降低了 GAPDH 的活性、表达和核易位。GAPDH 的过表达可防止葡萄糖诱导的其活性、核易位、细胞凋亡以及蛋白激酶 C 和己糖胺通路的激活抑制。硝化和核糖基化抑制剂可改善葡萄糖诱导的 GAPDH 抑制作用，并且在高葡萄糖水平之后的正常葡萄糖暴露期间添加这些抑制剂对 GAPDH 活性以及硝化和核糖基化的程度具有有益作用。
在高血糖中，视网膜微血管细胞中的 GAPDH 被其共价修饰抑制，这激活了糖尿病性视网膜病变发病机制中多个途径。可直接靶向修饰 GAPDH 的药物具有抑制糖尿病性视网膜病变发展和阻止其进展的潜力。
