Protective vasomotor effects of in vivo recombinant endothelial nitric oxide synthase gene expression in a canine model of cerebral vasospasm

Background and Purpose - Post-subarachnoid hemorrhage (SAH) cerebral vasospasm is a potentially devastating condition whose pathogenesis involves impaired nitric oxide (NO) bioavailability. We aimed to determine whether recombinant endothelial NO synthase (eNOS) gene expression may protect vasomotor function and prevent vasospasm in a canine experimental SAH model. Methods - Recombinant adenoviral vectors (5 × 10⁹ plaque-forming units/animal) encoding genes for eNOS (AdeNOS) and β-galactosidase (AdLacZ) or vehicle were injected into the cerebrospinal fluid (CSF) of dogs on day - 1 (ie, 24 hours before the first intra-CSF injection of blood on day 0). Cerebral angiography was performed at day 0 (baseline) and day 7 (immediately before death), and tissues were harvested for additional studies. Results - Western analysis and immunohistochemistry detected recombinant eNOS exclusively in cerebral arteries isolated from AdeNOS-transduced dogs, and in this group of animals CSF NO concentrations were significantly elevated by day 2. Analysis of day 7 versus day 0 cerebral angiograms for each group revealed significant spasm at the basilar artery midpoint in AdLacZ-transduced and nontransduced dogs but not in AdeNOS-transduced dogs. Isometric force recording of basilar arteries isolated from AdeNOS-transduced dogs showed significantly augmented relaxations to bradykinin and reduced contractions to endothelin-1. Conclusions - Our results suggest that expression of recombinant eNOS in the adventitia of cerebral arteries may contribute toward protection against post-SAH vasospasm.