In vivo gene transfer of nitric oxide synthase enhances vasomotor function in carotid arteries from normal and cholesterol-fed rabbits

Background-The vascular endothelium is anatomically intact but functionally abnormal in preatherosclerotic states, and an early deficit in the bioavailability of nitric oxide (NO) or related molecules has been described in both humans and animal models. We hypothesized that the targeted gene transfer of NO synthase (NOS) isoforms might ameliorate or reverse the deficit. Methods and Results-We constructed a recombinant adenovirus, Ad.nNOS, that expresses the neuronal isoform of NOS (nNOS) and used it for in vivo endovascular gene transfer to carotid arteries (CA) from normal and cholesterol-fed rabbits. Vessels were harvested 3 days after gene transfer. In CA from normal rabbits, Ad.nNOS generated high levels of functional nNOS protein predominantly in endothelial cells and increased Vascular NOS activity by 3.4-fold relative to sham-infected control CA, Ad.nNOS gene transfer also significantly enhanced endothelium-dependent vascular relaxation to acetylcholine; at 3 mu mol/L acetylcholine, Ad.nNOS-treated arteries showed an 86+/-4% reduction in precontracted tension, whereas control CA showed a 47+/-6% reduction in tension. Contraction in response to phenylephrine and relaxation in response to nitroprusside were unaffected in both control and Ad.nNOS-treated CA. To determine the effect of Ad.nNOS in atherosclerotic arteries, 10 male New Zealand White rabbits maintained on a 1% cholesterol diet for 10 to 12 weeks underwent gene transfer according to the same protocol used in normal rabbits. Ad.nNOS-treated arteries showed a 2-fold increase in NADPH-diaphorase staining intensity relative to sham-infected and Ad.beta Gal-treated arteries. The CA from cholesterol-fed rabbits showed impaired acetylcholine-induced relaxation, but this abnormality was almost entirely corrected by Ad.nNOS gene transfer. Conclusions-In vivo adenovirus-mediated endovascular delivery of nNOS markedly enhances vascular NOS activity and can favorably influence endothelial physiology in the intact and atherosclerotic vessel wall.