Adventitial gene transfer of recombinant endothelial nitric oxide synthase to rabbit carotid arteries alters vascular reactivity

Background: Adventitial gene transfer may serve as a tool to study vascular biology and may have therapeutic potential. We investigated the hypothesis that adenovirus-mediated transfer of the gene for endothelial nitric oxide synthase (eNOS) to the adventitia would alter vascular reactivity. Methods and Results: Rabbit carotid arteries were surgically isolated and adenoviral vectors encoding eNOS (AdeNOS) or β-galactosidase instilled info the periarterial sheath at a concentration of 1X10¹⁰ pfu/mL. Arteries were harvested 4 days later for immunostaining, NOS enzymatic assay, measurement of cGMP, and vasomotor studies. Transgene expression in the adventitia was confirmed by histochemistry for β-galactosidase and immunostaining for eNOS with a monoclonal antibody. Calcium-dependent NOS enzymatic activity and cOMP levels were significantly greater in the AdeNOS- transduced arteries. Maximal contractions to phenylephrine (10^-5 mol/L) were diminished in the AdeNOS-transduced arteries (4.6±0.2 versus 5,6±0.2 g; P<.05), but in the presence of the eNOS inhibitor N(G)-monomethyl-L- arginine (3X10^-4 mol/L) there was no difference between the two groups (7.1±0.2 versus 7.5±0.3 g; P=NS). Relaxations to calcium ionophore obtained during submaximal contractions to phenylephrine were significantly enhanced in the AdeNOS-transduced arteries (-log EC₅₀, 7.77±0.08 versus 7.45±0.07; P<.02). Conclusions: We conclude that eNOS gene transfer to the adventitia alters vascular reactivity, as demonstrated by diminished contractile responses to phenylephrine and enhanced relaxations to calcium ionophore. This may represent a therapeutic strategy for vascular diseases characterized by decreased bioavailability of NO.