Nitric oxide synthase gene transfer corrects deficient endothelial vasmotor function in hypercholesterolaemic rabbits

Background: The vascular endothelium is anatomically intact but functionally abnormal in preatherosclerotic states. In particular, nitric oxide (NO) bioavailability is reduced and may play a role in disease progression. We investigated whether targeted vascular gene transfer of nitric oxide synthase (NOS) could augment NO production and restore endothelial function. Methods: We constructed a recombinant adenovirus, Ad.nNOS, expressing the neuronal isoform of NOS (nNOS), and carried out in vivo endovascular gene transfer to carotid arteries from normal and cholesterol-fed rabbits (1% cholesterol diet for 12 weeks). Vessels were harvested 3 days after gene transfer. Results: In arteries from normal rabbits, Ad.nNOS generated high levels of functional nNOS protein in endothelial cells, and increased vascular NO production by 3.4-fold relative to sham-infected or Ad.βGal-treated control arteries (n=6, p<0.001). Ad.nNOS gene transfer significantly enhanced endothelium-dependent vascular relaxation to acetylcholine (ACh), whereas responses to phenylephrine and nitroprusside were unaffected. In atherosclerotic arteries, Ad.nNOS increased NADPH diaphorase staining intensity two-fold relative to control arteries. Relaxation to ACh was markedly reduced in atherosclerotic arteries (31 ± 5 % vs. 74 ± 6 % at 10-5 M ACh; n=6, p<0.01), but this deficit was substantially restored by Ad.nNOS gene transfer, to 57 ± 5 % (n=6, p<0.01). Conclusions: In vivo adenovirus-mediated gene transfer of nNOS markedly enhances vascular NO production, and augments endothelial vasomotor physiology in normal and atherosclerotic vessels. These results suggest that deficient NO bioavailability in atherosclerosis is not due solely to reduced NOS cofactor availability or NOS-agonist decoupling.