Adventitial expression of recombinant endothelial nitric oxide synthase gene reverses vasoconstrictor effect of endothelin-1

The present study was designed to determine the effect of recombinant endothelial nitric oxide synthase (eNOS) gene expression on reactivity of canine basilar arteries to endothelin-1 (ET-1). The arteries were exposed (30 min at 37°C ex vivo) to adenoviral vectors encoding eNOS gene (AdCMVeNOS) or β-galactosidase reporter gene (AdCMVβ-Gal). Twenty-four hours following transduction, transgene expression was evident mainly in the vascular adventitia. During contractions to uridine 5′-triphosphate (UTP), ET-1 (10^-10 to 3 x 10^-9M) caused further increase in tension in control and AdCMVβ-Gal-transduced arteries. In contrast, ET-1 caused concentration-dependent relaxations of AdCMVeNOS-transduced arteries. The relaxations to ET-1 were endothelium-independent. They were abolished by N^G-nitro-L-arginine methyl ester or by chemical treatment of the adventitia with paraformaldehyde prior to gene transfer. ET-1 (10^-9M) significantly increased intracellular cyclic GMP levels only in arteries expressing recombinant eNOS gene. The relaxations to ET-1 in AdCMVeNOS-transduced arteries were strongly reduced by BQ-123, an ET_A receptor antagonist, but were not affected by BQ-788, an ET_B receptor antagonist. These results demonstrate that genetically modified adventitia of cerebral arteries can produce nitric oxide in response to ET-1 via activation of ET_A receptors.