Reduction of the soluble cyclic GMP vasorelaxing system in the vascular wall of stroke-prone spontaneously hypertensive rats: effect of the alpha1 -receptor blocker doxazosin.

OBJECTIVE: The aim of the present study was to analyse the nitric oxide (NO)/cyclic GMP (cGMP) relaxing system in spontaneously hypertensive rats of the stroke-prone substrain (SHRSP). DESIGN: The study was performed in 20-week-old SHRSP rats. A group of normotensive Wistar-Kyoto (WKY) rats was used as control. RESULTS: The endothelium-dependent relaxation to acetylcholine was reduced in SHRSP rats (n = 15). No modifications in the expression of the endothelial nitric oxide synthase were found in the vascular wall of WKY rats (n = 15) and SHRSP rats. SHRSP rats demonstrated an impaired relaxing response to the NO-donor sodium nitroprusside that was accompanied by a reduction in the level of the main second messenger of NO, cyclic GMP. The expression of the soluble guanylate cyclase (sGC) beta1-subunit was markedly reduced in the vascular wall of SHRSP rats. In the experimental model of SHRSP, an increased concentration of catecholamines has been reported. Therefore, we evaluated the effect of an alpha1-receptor blocker, doxazosin, on the NO/cGMP system. Doxazosin [10 mg/kg body weight (bw) per day for 15 days, n = 15] reduced mean arterial pressure (MAP) in SHRSP rats. Treatment with doxazosin preserved the endothelium-independent relaxation response to sodium nitroprusside in aortic segments from SHRSP rats which was associated with an increased expression of the sGC beta1-subunit. A dose of doxazosin (1 mg/kg bw per day, n = 15) that did not modify MAP partially prevented sGC protein expression in the vascular wall. CONCLUSIONS: Independently of the endothelial NO-generating system, impaired vasorelaxation could also result from vascular smooth muscle cell layer dysfunction. Doxazosin treatment improved the endothelial-independent relaxation and preserved the cGMP generating system in the vascular wall of SHRSP rats.

[Effect of HMG-CoA reductase inhibition on endothelial dysfunction-inducing protein in hypercholesterolemic rabbits]. / Efecto de la inhibición de la HMG-CoA reductasa sobre la proteína inductora de disfuncion endotelial en conejos hipercolesterolémicos.

INTRODUCTION AND OBJECTIVES: In our laboratory, we recently obtained evidence that cultured bovine endothelial cells contain cytosolic proteins that form complexes with the 3'-unstranslated region of endothelial nitric oxide synthase (eNOS) mRNA and are associated with its destabilization. The aim of this study was to determine the presence of such proteins and the level of eNOS expression in hypercholesterolemic rabbits as an in vivo model of endothelial dysfunction. METHODS AND RESULTS: Endothelium-dependent relaxation in response to acetylcholine was reduced in aortic segments from hypercholesterolemic rabbits compared with controls. Treatment of hypercholesterolemic rabbits with simvastatin (25 mg/kg body weight/day) restored endothelium-dependent relaxation. Aortic eNOS expression was reduced in hypercholesterolemic rabbits and was accompanied by enhanced binding activity of a 60-KDa cytosolic protein and reduced stability of eNOS mRNA. Simvastatin treatment upregulated eNOS expression and reduced the interaction of cytosolic protein with the 3'-untranslated region of eNOS mRNA. CONCLUSIONS: These results demonstrate the presence of a 60-KDa protein that binds to eNOS mRNA and reduces eNOS expression in the vascular wall.

Alteration of the soluble guanylate cyclase system in the vascular wall of lead-induced hypertension in rats.

Low-level lead exposure is a known cause of hypertension that has been associated with increased reactive oxygen species activity and endothelial-dependent vasorelaxation impairment. The effect of lead exposure on the vascular nitric oxide (NO)/cyclic guanocine monophosphate (cGMP) system was analyzed. Wistar rats were exposed to 5 ppm lead acetate in the drinking water during 30 d. Mean arterial BP increased significantly in the lead-treated rats. Relaxation to both acetylcholine and sodium nitroprusside (SNP) was reduced in lead-treated rats; however, the vascular wall of lead-administered rats showed an increased expression of endothelial NO synthase. The expression of both subunits (alpha(1) and beta(1)) of soluble guanylate cyclase (sGC) and the cGMP accumulated in the vascular wall were decreased in lead-treated rats. Cotreatment of lead with vitamin C (3 mmol/L) prevented the increase on mean arterial BP, improved the relaxation to both acetylcholine and sodium nitroprusside, and restored the normal expression of endothelial NO synthase and sGC proteins in the vascular wall. In conclusion, lead exposure altered both the endothelium-dependent and -independent relaxing response and induced a reduced expression of sGC in the vascular wall. These effects were abrogated with the antioxidant vitamin C, which suggests the involvement of reactive oxygen species in the regulation of the NO/cGMP relaxing system in the vascular wall of lead-treated rats.

Efecto de la inhibición de la HMG-CoA reductasa sobre la proteína inductora de disfunción endotelial en conejos hipercolesterolémicos / Effect of HMG-CoA reductase inhibition on endothelial dysfunction-inducing protein in hypercholesterolemic rRabbits

Introducción y objetivos. Recientemente se ha demostrado en nuestro laboratorio que las células endoteliales en cultivo expresan proteínas citosólicas que forman complejos con el ARNm de la óxido nítrico sintasa endotelial (NOSe) en la región 3' que no codifica para proteína (3'-UTR). Esta unión fue asociada con la desestabilización del ARNm de dicha enzima. El objetivo de este estudio fue determinar la presencia de estas proteínas citosólicas y el nivel de expresión de la proteína NOSe en la pared vascular de conejos hipercolesterolémicos como un modelo in vivo de disfunción endotelial. Métodos y resultados. La relajación dependiente del endotelio a acetilcolina estuvo reducida en segmentos aórticos de conejos hipercolesterolémicos comparados con los conejos control. El tratamiento de los conejos hipercolesterolémicos con simvastatina (25 mg/kg peso/día) restauró la relajación dependiente del endotelio.La expresión de NOSe se encontró reducida en la pared vascular de los conejos hipercolesterolémicos, lo cual se acompañó de un aumento en la capacidad de unión de la proteína citosólica de 60 kDa y de una reducción en la estabilidad del ARNm de la NOSe. El tratamiento con simvastatina aumentó la expresión de NOSe y redujo la interacción de la proteína citosólica a la región 3'-UTR del ARNm de la NOSe. Conclusiones. Estos resultados demuestran una relación entre la presencia de la proteína de 60 kDa y la abundancia de NOSe en la pared vascular y la funcionalidad endotelial (AU)