ADVENTITIAL EXPRESSION OF RECOMBINANT ENOS GENE RESTORES NO PRODUCTION IN ARTERIES WITHOUT ENDOTHELIUM

The current study was designed to determine the effect of recombinant endothelial nitric ic oxide synthase (eNOS) gene expression on endothe lium-dependent relaxations to bradykinin in isolated canine basilar, c oronary, or femoral arteries. Arterial rings were exposed ex vivo (30 minutes at 37 degrees C) to an adenoviral vector encoding either the e NOS gene (AdCMVeNOS) or the beta-galactosidase reporter gene (AdCMV be ta-Gal). Twenty-four hours after transduction, transgene expression wa s evident mainly in the adventitia. Expression of recombinant proteins was much higher in basilar arteries than in coronary or femoral arter ies. Rings of control, AdCMV beta-Gal, and AdCMVeNOS arteries with and without endothelium were suspended for isometric tension recording. L evels of cGMP were measured by radioimmunoassay. In AdCMVeNOS basilar arteries with endothelium, relaxations to low concentrations of bradyk inin (3x10(-11) to 10(-9) mol/L) were significantly augmented. In cont rast, in coronary and femoral arteries with endothelium, AdCMVeNOS tra nsduction did not affect relaxations to bradykinin. Removal of the end othelium abolished bradykinin-induced relaxations in control and AdCMV beta-Gal basilar arteries. However, in basilar arteries transduced wi th AdCMVeNOS even when the endothelium was removed, stimulation with b radykinin (3x10(-11) to 10(-9) mol/L) caused relaxations as well as in creases in cGMP production. The relaxations to bradykinin were complet ely blocked by an NOS inhibitor, N-G-nitro-L-arginine methyl ester. El ectron microscopic analysis revealed that recombinant eNOS protein was expressed in fibroblasts of the basilar artery adventitia. These resu lts suggest that genetically modified adventitial fibroblasts may rest ore production of NO in cerebral arteries without endothelium. Our fin dings support a novel concept in vascular biology that fibroblasts in the adventitia may play a role in the regulation of vascular tone afte r successful transfer and expression of recombinant eNOS gene.