Influence of GSH synthesis inhibition on temporal distribution of NAD+/NADH during vascular endothelial cells proliferation

Pathological conditions states such as stroke, diabetes mellitus, hypertension, dyslipidemia are associated with increased levels of free radicals that alter normal function of the vascular endothelium and perturb vascular homeostasis. The redox couples reduced glutathione (GSH)/oxidized glutathione (GSSG), NADH/NAD+, and NADPH/NADP+ play major functions in the intracellular redox balance. Any decrease in tissue or systemic GSH levels under the aforementioned pathologies would enhance oxidative damage to the vascular endothelium. Beside their role as coenzyme that participate in cellular metabolism, pyridine nucleotides serve also as substrate for enzymes involved in DNA repair and longevity. There is scant data on NAD+/NADH kinetics and distribution during human cells proliferation. Here, we determined the influence of cellular GSH status on the early dynamics of nuclear-to-cytosol (N-to-C) NAD+ and nuclear NADH kinetics (6h interval) over 72h of endothelial cell proliferation. The IHEC cell line was used as a surrogate for human brain micro vascular endothelial cells. Inhibition of GSH synthesis by buthionine sulfoximine (BSO) and sustained low cellular GSH significantly increased nuclear NADH levels (p<0.01), which correlated with lower nuclear GSH and prolonged cell cycle S-phase. When BSO was removed the pattern of nuclear NAD+ resembled that of control group, but nuclear NADH concentrations remained elevated, as in GSH deficient cells (p<0.01). The coincidence of high nuclear NADH and lower nuclear NAD+ with S-phase prolongation are suggestive of CtBP and NAD+-dependent DNA repair enzyme activation under conditions of decreased cellular GSH. These results provide important insights into GSH control of vascular endothelial growth and restitution, key processes in the restoration of the endothelium adjacent to the post-injury lesion site.