Augmented BH4 by gene transfer restores nitric oxide synthase function in hyperglycemic human endothelial cells

Abstract

This study demonstrates a critical role for BH4 in regulating eNOS function, suggesting that GTPCH is a rational target to augment endothelial BH4 and recover eNOS activity in hyperglycemic endothelial dysfunction states.

Endothelial Nitric Oxide Synthase Uncoupling Impairs Endothelial Progenitor Cell Mobilization and Function in Diabetes

“…Our data therefore provide evidence for eNOS uncoupling within bone marrow in diabetes. The uncoupling of eNOS has previously been linked to its monomerization upon treatment of endothelial cells with peroxynitrite or glucose (37,48). In diabetic bone marrow, eNOS dimer-tomonomer ratio was shifted to monomerization.…”

“…Diabetesassociated eNOS uncoupling has been described in the heart, vessels, and the kidney (4,34 -39), resulting in decreased NO bioavailibility, increased superoxide production, and disrupted eNOS dimer formation within the vascular wall, while eNOS mRNA and/or protein levels are maintained or even increased (36 -38). A reduction of the essential eNOS cofactor BH 4 has been described to be mechanistically involved in eNOS uncoupling (7,31,35,37,40).…”

C-reactive protein decreases endothelial nitric oxide synthase activity via uncoupling

“…One is the de novo synthetic pathway in which the precursor GTP is catalyzed by GTPCH1, the first enzyme in this biosynthetic pathway, to dihydroneopterin triphosphate, whereby BH4 is then generated by further steps involving 6-pyruvoltetrahydropterin synthase (PTPS) and sepiapterin reductase. Recently, reduced expression and activity of GTPCH1 has been shown in coronary endothelial cells of diabetic rats and aortae of insulin-resistant rats, resulting in diminished BH4 levels [40,41]. In this context, Cai et al [40] have reported that GTPCH1 gene transfer augments intracellular BH4 as well as eNOS activity in human endothelial cells.…”

“…Recently, reduced expression and activity of GTPCH1 has been shown in coronary endothelial cells of diabetic rats and aortae of insulin-resistant rats, resulting in diminished BH4 levels [40,41]. In this context, Cai et al [40] have reported that GTPCH1 gene transfer augments intracellular BH4 as well as eNOS activity in human endothelial cells. Based on these findings, GTPCH1 is reported to be a potential and rational target to augment endothelial BH4 in reversing eNOS activity in endothelial dysfunctional states.…”

“…Dimerization is an absolute requirement for eNOS catalytic activity [22,40]. Structural studies suggest a role for BH4 in NOS dimerization based on purified recombinant proteins in reconstituted cell-free systems [22].…”