Akiyama, Masahiko

Background and Purpose— In the present study, the effect of subarachnoid hemorrhage (SAH) on the phosphorylation of endothelial NO synthase (eNOS) and the ability of recombinant erythropoietin (Epo) to augment this vasodilator mechanism in the spastic arteries were studied. Methods— Recombinant adenoviral vectors (10 9 plaque-forming units per animal) encoding genes for human Epo (AdEpo), and β-galactosidase were injected immediately after injection of autologous arterial blood into the cisterna magna (day 0) of rabbits. Cerebral angiography was performed on day 0 and day 2, and basilar arteries were harvested for Western blots, measurement of cGMP levels, and analysis of vasomotor functions. Results— Injection of autologous arterial blood into cisterna magna resulted in significant vasospasm of the basilar arteries. Despite the narrowing of arterial diameter and reduced expression of eNOS, expressions of phosphorylated protein kinase B (Akt) and phosphorylated eNOS were significantly increased in spastic arteries. Gene transfer of AdEpo reversed the vasospasm. AdEpo-transduced basilar arteries demonstrated significant augmentation of the endothelium-dependent relaxations to acetylcholine, whereas the relaxations to an NO donor, 2-( N , N -diethylamino)diazenolate-2-oxide sodium salt, were not affected. Transduction with AdEpo further increased the expression of phosphorylated Akt and eNOS and elevated basal levels of cGMP in the spastic arteries. Conclusions— Phosphorylation of eNOS appears to be an adaptive mechanism activated during development of vasospasm. The vascular protective effect of Epo against cerebral vasospasm induced by SAH may be mediated in part by phosphorylation of Akt/eNOS.

Background and Purpose— Mutation of serine 1179 to aspartate on the endothelial NO synthase (eNOS) increases NO production in the absence of stimulation by agonists. The present study was designed to determine the effect of recombinant S1179DeNOS gene expression on the vasomotor function of human pial arteries. Methods— Pial arteries were isolated from 28 patients undergoing temporal lobectomy for intractable seizures. Adenoviral vectors (10 10 pfu/mL) encoding β-galactosidase (AdCMVLacZ) or S1179DeNOS (AdCMVS1179DeNOS) were used for ex vivo gene transfer, and vasomotor function was evaluated in control and transduced arteries. Results— Contractions to cumulative additions of U46619 were not affected by expression of LacZ or S1179DeNOS. Endothelium-dependent relaxations to bradykinin or endothelium-independent relaxations to Diethylaminodiazen-1-ium-1,2-dioate were significantly reduced in arteries expressing S1179DeNOS. A superoxide dismutase mimetic, manganese (III) tetrakis (4-benzoic acid) porphyrin chloride, failed to improve the reduced relaxations to bradykinin. The levels of cGMP were significantly elevated in arteries expressing S1179DeNOS. Conclusions— Our results support the concept that high local production of NO in pial arterial wall causes adaptive reduction of vasodilator reactivity to NO.

Background and Purpose — Bovine endothelial nitric oxide synthase (eNOS) is phosphorylated directly by the protein kinase Akt at serine 1179. Mutation of this residue to the negatively charged aspartate (S1179DeNOS) increases nitric oxide (NO) production constitutively in the absence of agonist stimulus. The present study was designed to determine the effect of mutant S1179DeNOS gene expression on vasomotor function of canine cerebral arteries. Methods — Isolated basilar and middle cerebral arteries were exposed ex vivo (30 minutes at 37°C) to an adenoviral vector (10 10 plaque-forming units per milliliter) encoding the S1179DeNOS gene (AdCMVS1179DeNOS), the wild-type eNOS gene (AdCMVeNOS), or the green fluorescent protein (GFP) reporter gene (AdCMVGFP). Twenty-four hours after transduction, arteries were suspended in an organ chamber for isometric force recording, and levels of cGMP were measured by radioimmunoassay. Results — Transgene protein expression was detected mainly in the vascular adventitia. In AdCMVS1179DeNOS-transduced arteries, basal levels of cGMP were significantly elevated compared with those in control (nontransduced), AdCMVGFP-, or AdCMVeNOS-transduced vessels (n=8; P <0.01). The elevation of cGMP was abolished by a NOS inhibitor, N G -nitro- l -arginine methyl ester (L-NAME), or by incubation in the calcium-free medium in the presence of calcium chelators. In AdCMVS1179DeNOS-transduced arteries, contractions to endothelin-1 (10 −10 to 10 −8 mol/L) were significantly reduced compared with those in control and AdCMVGFP-transduced arteries (n=7; P <0.05). The vasoconstrictor effect of endothelin-1 was restored in the presence of the NOS inhibitor L-NAME. Conclusions — Our results suggest that in cerebral arteries, expression of recombinant S1179DeNOS increases basal production of NO and inhibits the vasoconstrictor effect of endothelin-1. This effect may have therapeutic application in prevention and treatment of cerebrovascular diseases.