Increased mitochondrial H2O2 production promotes endothelial NF-κB activation in aged rat arteries

Previous studies have shown that the aging vascular system undergoes pro-atherogenic phenotypic changes, including increased oxidative stress and a pro-inflammatory shift in endothelial gene expression profile. To elucidate the link between increased oxidative stress and vascular inflammation in aging, we compared the carotid arteries and aortas of young and aged (24 mo old) Fisher 344 rats. In aged vessels there was an increased NF-κB activity (assessed by luciferase reporter gene assay and NF-κB binding assay), which was attenuated by scavenging H2O2. Aging did not alter the vascular mRNA and protein expression of p65 and p50 subunits of NF-κB. In endothelial cells of aged vessels there was an increased production of H2O2 (assessed by 5,6-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate-acetyl ester fluorescence), which was attenuated by the mitochondrial uncoupler FCCP. In young arteries and cultured endothelial cells, antimycin A plus succinate significantly increased FCCP-sensitive mitochondrial H2O2 generation, which was associated with activation of NF-κB. In aged vessels inhibition of NF-κB (by pyrrolidenedithiocarbamate, resveratrol) significantly attenuated inflammatory gene expression and inhibited monocyte adhesiveness. Thus increased mitochondrial oxidative stress contributes to endothelial NF-κB activation, which contributes to the pro-inflammatory phenotypic alterations in the aged vaculature. Our model predicts that by reducing mitochondrial H2O2 production and/or directly inhibiting NF-κB novel anti-aging pharmacological treatments (e.g., calorie restriction mimetics) will exert significant anti-inflammatory and vasoprotective effects.