In vivo gene transfer of inducible nitric oxide synthase to carotid arteries from hypercholesterolemic rabbits

BACKGROUND AND PURPOSE: Hypercholesterolemia is associated with endothelial dysfunction. Inducible nitric oxide synthase (iNOS) is upregulated in atherosclerotic vessels. However, its role in the regulation of vascular function is not completely understood. We examined the effect of adenovirus-mediated gene transfer of iNOS to the hypercholesterolemic rabbit carotid artery in vivo. METHODS: Rabbits were fed a high-cholesterol or chow diet for 10 weeks. Two doses (1x10(8) and 1x10(9) plaque-forming units [pfu]/mL) of adenoviral vectors encoding iNOS (AdiNOS) or beta-galactosidase (Ad(beta)gal) were luminally delivered to the carotid arteries from chow- and cholesterol-fed animals. Vascular reactivity and superoxide levels were assessed in Ad(beta)gal- and AdiNOS-transduced vessels from chow- and cholesterol-fed animals after 3 days. RESULTS: Endothelium-dependent vasorelaxation was impaired in the carotid artery from cholesterol-fed animals. In AdiNOS-transduced arteries, transgene expression was demonstrated by positive immunostaining in the endothelium. Transduction with low-dose (1x10(8) pfu/mL) AdiNOS did not affect vascular reactivity in arteries from chow- and cholesterol-fed animals. In contrast, high-dose (1x10(9) pfu/mL) AdiNOS significantly reduced endothelium-dependent relaxation in vessels from cholesterol- but not chow-fed rabbits. After both low- and high-dose iNOS gene transfer, levels of O2*(-) were significantly (P<0.05) elevated in carotid arteries from cholesterol-fed animals. Incubation with an O2*(-) scavenger did not reverse vascular dysfunction in these arteries. CONCLUSIONS: Adenoviral-mediated overexpression of iNOS results in increased production of O2*(-) in carotid arteries from cholesterol- but not chow-fed animals. High-dose AdiNOS gene transfer is associated with reduced endothelium-dependent and -independent relaxation in vessels from cholesterol-fed animals.