Enhanced endothelium-dependent relaxations after gene transfer of recombinant endothelial nitric oxide synthase to rabbit carotid arteries.

We tested the effects of overexpression of the endothelial nitric oxide synthase (eNOS) gene in the normal arterial wall by adenoviral-mediated gene transfer. Rabbit carotid arteries were surgically isolated and exposed to adenoviral vectors encoding eNOS (AdeNOS) or beta-galactosidase (Ad betaGal) on the contralateral side. Vector solutions at a concentration of 1 x 10(10) plaque forming units/mL were instilled for 20 minutes before restoration of flow. Arteries were harvested 4 days later for immunostaining, measurement of cGMP, and vasomotor studies. Endothelium-specific gene transfer was confirmed by staining for beta-galactosidase in the Ad betaGal arteries. Immunostaining of en face endothelial cell imprints from AdeNOS-transduced arteries with a monoclonal antibody to eNOS showed increased immunoreactivity. Basal cGMP levels were significantly greater in the AdeNOS-transduced arteries (18.4+/-4.6 versus 4.2+/-0.5 pmol/mg protein; P<.05). Contractions to phenylephrine were significantly reduced in the AdeNOS-transduced arteries (area under curve, 106+/-5 versus 119+/-7; P<.05), but in the presence of the eNOS inhibitor, N(G)-monomethyl-L-arginine (L-NMMA, 3 x 10(-4) mol/L), there was no difference between the two (area under curve, 148+/-5 versus 153+/-6; P=NS). Relaxations to acetylcholine obtained during submaximal contractions to phenylephrine were significantly enhanced in the AdeNOS-transduced arteries (EC50, 7.45+/-0.05 versus 7.23+/-0.03; P<.05). We conclude that overexpression of eNOS in the endothelium results in diminished contractile responses, as well as enhanced endothelium-dependent relaxations. These findings imply a possible role for vascular eNOS gene transfer in the treatment of vasospasm and endothelial dysfunction.