Direct Evidence of Endothelial Oxidative Stress With Aging in Humans

TLDR

Aging is linked to impaired endothelial function, as evidenced by reduced endothelium‑dependent dilation, and this decline is thought to arise from oxidative stress, yet direct evidence has been lacking. The authors compared 95 healthy men, 51 young (≈23 yr) and 44 older (≈63 yr), measuring flow‑mediated dilation and endothelial oxidative markers in brachial artery and antecubital vein samples. Older men exhibited ~50 % lower flow‑mediated dilation, higher endothelial nitrotyrosine, increased NAD(P)H oxidase‑p47phox and NF‑κB p65 expression, and a strong inverse correlation between dilation and oxidative stress, providing direct evidence that endothelial oxidative stress rises with age and contributes to reduced vascular function.

Abstract

Aging is associated with impaired vascular endothelial function, as indicated in part by reduced endothelium-dependent dilation (EDD). Decreased EDD with aging is thought to be related to vascular endothelial cell oxidative stress, but direct evidence is lacking. We studied 95 healthy men: 51 young (23±1 years) and 44 older (63±1 years). EDD (brachial artery flow-mediated dilation) was ≈50% lower in older versus young men (3.9±0.3% versus 7.6±0.3%, P <0.01; n=42 older/n=51 young). Abundance of nitrotyrosine (quantitative immunofluorescence), an oxidatively modified amino acid and marker of oxidative stress, was higher in endothelial cells (ECs) obtained from the brachial artery (1.25±0.12 versus 0.61±0.11 nitrotyrosine intensity/human umbilical vein EC [HUVEC] intensity, P =0.01; n=11 older/n=11 young) and antecubital veins (0.55±0.04 versus 0.34±0.03, P <0.05; n=19 older/n=17 young) of older men. Flow-mediated dilation was inversely related to arterial EC nitrotyrosine expression ( r =−0.62, P =0.01; n=22). In venous samples, EC expression of the oxidant enzyme NAD(P)H oxidase-p47 phox was higher in older men (0.71±0.05 versus 0.57±0.05 NAD[P]H oxidase-p47 phox intensity/HUVEC intensity, P <0.05; n=19 older/n=18 young), whereas xanthine oxidase and the antioxidant enzymes cytosolic and mitochondrial superoxide dismutase and catalase were not different between groups. Nuclear factor-κB p65, a component of the redox-sensitive nuclear transcription factor nuclear factor-κB, was elevated in both arterial (0.73±0.07 versus 0.53±0.05 NF-κB p65 intensity/HUVEC intensity, P <0.05; n=9 older/n=12 young) and venous (0.65±0.07 versus 0.34±0.05, P <0.01; n=13 older/n=15 young) EC samples of older men and correlated with nitrotyrosine expression ( r =0.51, P <0.05 n=16). These results provide direct support for the hypothesis that endothelial oxidative stress develops with aging in healthy men and is related to reductions in EDD. Increased expression of NAD(P)H oxidase and nuclear factor-κB may contribute to endothelial oxidative stress with aging in humans.