Hipercolesterolemia y disfunción endotelial: mecanismos implicados / Hypercholesterolemia and endothelial dysfunction: mechanisms involved

El endotelio desempeña un papel clave en la regulación de la función vascular al liberar, en respuesta a distintos estímulos, numerosos factores vasoactivos. La hiperlipidemia, así como otros factores de riesgo cardiovascular, alteran ese papel homeostático que desempeña el endotelio en la regulación de la función vascular. Uno de los mecanismos fundamentales que subyacen a la disfunción endotelial parece ser una disminución en la disponibilidad de óxido nítrico (NO), lo que permite la sobreexpresión de las acciones de factores que se oponen a los efectos beneficiosos y protectores de éste sobre la pared vascular. Diversos mecanismos podrían ser responsables de esta menor disponibilidad de NO, desde alteraciones en su síntesis a una mayor degradación como consecuencia de un aumento del estrés oxidativo. En pacientes hipercolesterolémicos la reducción de los niveles de colesterol conlleva una mejoría de la función endotelial, lo que indicaría que la elevación de dichos niveles podría activar diversos mecanismos que alteraran el normal funcionamiento del endotelio. Sin embargo, existen otros grupos de fármacos, como los antioxidantes o los que bloquean el sistema renina-angiotensina, que han demostrado un efecto beneficioso sobre la función endotelial tanto en estudios clínicos como experimentales (AU)

Alteraciones del endotelio en la hipertensión / Endothelial dysfunction in hypertension

No disponible

No disponible

Papel de la agiotensina II en el desarrollo aterosclerótico: efecto de su bloqueo / Role of angiotensin II in the development of atherosclerosis: effect of blockade

La angiotensina II, el principal efector del sistema renina-angiotensina, ejerce un papel importante en la génesis y en las complicaciones de la aterosclerosis. La angiotensina II estimula la producción de especies reactivas de oxígeno en el vaso que desempeñan un papel clave en la disfunción endotelial y en la oxidación de las lipoproteínas de baja densidad (LDL). Asimismo, este péptido participa en la inducción de la respuesta inflamatoria en la pared vascular mediante la producción de moléculas de adhesión y citoquinas quimiotácticas y proinflamatorias. La angiotensina II, además, estimula la proliferación y migración de células de músculo liso y modula el cambio fenotípico de las mismas dando lugar a un aumento de la síntesis de la matriz extracelular. Finalmente, la angiotensina II también participa en las complicaciones de la aterosclerosis al favorecer la ruptura de la placa y trombogenicidad de la misma. En consecuencia, el sistema renina-angiotensina desempeña un papel clave en la patofisiología de la aterosclerosis, por lo que su bloqueo ejercerá un efecto beneficioso sobre el desarrollo aterosclerótico previniendo las alteraciones trombóticas asociadas a él (AU)

Atorvastatin prevents glomerulosclerosis and renal endothelial dysfunction in hypercholesterolaemic rabbits.

BACKGROUND: Numerous studies have shown that elevated plasma cholesterol can exacerbate renal disease. However, the effect of lipids on renal structure and vascular function in normal kidneys is less well established. Therefore, the aim of this study was to evaluate the impact of hypercholesterolaemia on glomerular structure and vascular reactivity of segmental arteries in rabbits. In addition, we also studied whether or not atorvastatin can prevent these structural and vascular alterations in hypercholesterolaemic rabbits. METHODS: Male New Zealand rabbits were fed either a normal rabbit chow or a diet containing 1% cholesterol and treated or not with atorvastatin (1 mg/kg/day) for 12 weeks. Dose-response curves to acetylcholine (10(-9)-10(-4) mol/l) and sodium nitroprusside (10(-9)-10(-4) mol/l) were studied in segmental arteries in the presence or absence of the thromboxane A2/PGH2 receptor antagonist ifetroban (10(-5) mol/l). Glomerular size and structure were also evaluated. RESULTS: Compared with control animals, hypercholesterolaemic rabbits presented glomerular hypertrophy and several types of injuries (capillary collapse, hyalinosis and alterations of Bowman's capsule), suggesting diffuse glomerulosclerosis. Segmental arteries also showed relaxing responses to acetylcholine and sodium nitroprusside which were lower than and similar to, respectively, those of control animals. The presence of ifetroban improved the acetylcholine response only in hypercholesterolaemic rabbits. Atorvastatin treatment prevented vascular and most glomerular changes associated with hypercholesterolaemia even in the presence of very high cholesterol levels. CONCLUSIONS: Atorvastatin exerts a protective effect on renal damage associated with hypercholesterolaemia even in the presence of deleterious levels of plasma cholesterol.

Relevance of endothelium-derived hyperpolarizing factor in the effects of hypertension on rat coronary relaxations.

OBJECTIVES: To evaluate the relative participation of nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF) and prostanoids in the relaxing responses induced by acetylcholine and isoproterenol in isolated coronary arteries from adult Wistar- Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). DESIGN AND METHODS: Male adult WKY rats and SHR were used in the study. Segments from left coronary arteries (approximately 350-380 microm internal diameter and 2 mm long) were mounted in an isometric myograph and pre-contracted with serotonin. Dose-response curves to acetylcholine and isoproterenol were carried out in absence and presence of the NO synthesis inhibitor NG-nitro-L-arginine methyl ester (LNAME), the inhibitor of the cyclo-oxygenase, indomethacin and KCI. Areas under the respective dose-response curves were used to calculate the approximate relative participation of NO, EDHF and prostanoids. RESULTS: Relaxations to either acetylcholine or isoproterenol were lower in SHR than in WKY rats. In WKY rats, presence of LNAME diminished (P< 0.05) relaxation to acetylcholine from 10(-9) to 10(-6) mol/l, and induced a contracting response at 10(-5) and 10(-4) mol/l of acetylcholine. Addition of indomethacin did not significantly affect dose-related relaxation to acetylcholine 10(-9) to 10(-6) mol/l in WKY rats, and reduced (P < 0.05) the contracting response observed at 10(-5) mol/l of acetylcholine. In SHR, addition of LNAME markedly reduced (P< 0.05) acetylcholine relaxations, but did not produce any contracting effect. Addition of indomethacin on top of LNAME slightly (P< 0.05) enhanced relaxing response to acetylcholine in SHR. Presence of LNAME in the media diminished (P < 0.05) relaxation to isoproterenol in both WKY rats and SHR. Addition of indomethacin on top of LNAME increased (P< 0.05) isoproterenol-relaxing response to levels similar to and higher than control conditions in WKY rats and SHR, respectively. Addition of KCI blunted both acetylcholine- and isoproterenol-relaxations in both groups. CONCLUSIONS: NO and EDHF are the main endothelium-derived relaxing factors underlying acetylcholine and isoproterenol relaxations in rat coronary arteries, respectively. EDHF reduction, and not only NO reduction play a key role in the diminished coronary relaxations induced by acetylcholine and isoproterenol in SHR. An arachidonic acid derivative with contracting activity released by acetylcholine and isoproterenol in a differential manner, could oppose the relaxing actions of NO and EDHF.

Efectos de las estatinas sobre la presión arterial

Las estatinas han demostrado claramente su capacidad para disminuir la morbimortalidad cardiovascular debido principalmente a sus efectos sobre el colesterol sérico y las LDL, además de la estabilización de la placa y la reducción del riesgo trombótico. Sin embargo, en los últimos años diversos estudios indican que las estatinas tienen además efectos sobre la PA y la protección de órganos diana. Estos efectos pueden ser en parte dependientes de la reducción de la colesterolemia, pero otros mecanismos distintos a éste parecen intervenir en los efectos antihipertensivos de las estatinas. Entre ellos sus acciones sobre el manejo renal de sodio, la respuesta constrictora a diversos agentes, el remodelado vascular y diversas acciones sobre factores vasoactivos derivados del endotelio y el sistema renina angiotensina (AU)

Angiotensina ii e hipertensión arterial: consecuencias del antagonismo de sus receptores

No disponible

The protective role of atorvastatin on function, structure and ultrastructure in the aorta of dyslipidemic rabbits.

Responses to both an endothelium-dependent (acetylcholine 10(-9)-10(-5) mol/l) and an endothelium-independent vasodilator (sodium nitroprusside 10(-10)-10(-6) mol/l) were studied in aortic rings from rabbits fed or not with a diet containing 0.5% cholesterol plus 14% coconut oil for 14 weeks and treated or not with atorvastatin (2.5 mg/kg/day). Morphometric and ultrastructure analyses were also performed. Rabbits fed the dyslipidemic diet presented higher plasma cholesterol and triglyceride concentrations than controls (P < 0.05). This was associated with intima-media thickening and, consequently, aortic stenosis (29 +/- 3%) since vessel cross-sectional area did not change. Endothelial cells presented numerous alterations in dyslipidemic rabbits. Atorvastatin treatment only reduced plasma levels in dyslipidemic rabbits (P < 0.05), which were nevertheless higher than those of controls. In addition, it prevented the reduction in acetylcholine relaxation in hypercholesterolemic animals. Atorvastatin administration also enhanced the response to acetylcholine in rabbits fed a control diet. Likewise, atorvastatin treatment reduced lesion area and consequently increased aortic lumen in dyslipidemic rabbits but did not modify media thickening. It also prevented the majority of the ultrastructural changes observed in endothelial cells. In conclusion, chronic atorvastatin treatment exerts a protective role in vascular function, structure and ultrastructure even in the presence of high cholesterol and triglyceride plasma levels.

AT(1) receptor antagonism reduces endothelial dysfunction and intimal thickening in atherosclerotic rabbits.

The effects of angiotensin (AT)(1) receptor antagonists on functional and morphological alterations associated with atherosclerosis are not well known. The current study was performed to examine the long-term effects of valsartan (3 or 10 mg/kg per day for 10 weeks) on endothelial function and structural changes in aorta from rabbits fed with either a control diet or a cholesterol-enriched diet. Rabbits fed with the cholesterol-rich diet showed higher (P<0.05) plasma levels of cholesterol than did controls. Treatment with valsartan (3 or 10 mg/kg per day) did not alter plasma cholesterol levels or systolic arterial pressure in any group. Contractions induced by angiotensin II were comparable in both control and hypercholesterolemic rabbits and were markedly reduced by treatment with valsartan. Relaxations induced by acetylcholine were lower in hypercholesterolemic rabbits than in controls. Treatment with valsartan (3 or 10 mg/kg per day) enhanced (P<0.05) this response in hypercholesterolemic rabbits but not in controls. Lumen and media cross-sectional areas were comparable in control and hypercholesterolemic rabbits. Vessel area was higher (P<0.05) in hypercholesterolemic rabbits than in controls. Intimal lesion was 29.5+/-6% in cholesterol-fed rabbits and nonexistent in control rabbits. Treatments with 3 and 10 mg/kg per day valsartan reduced (P<0.05) intimal lesion to 2.4+/-0.7% and 2.7+/-0.9%, respectively, and increased lumen area in hypercholesterolemic rabbits. No changes in either vessel or media cross-sectional areas were observed in these animals. In summary, angiotensin II, through AT(1) receptors, appears to play a key role in the development of the vascular functional and structural changes associated with hypercholesterolemia. AT(1) receptor antagonists, besides their antihypertensive effects, could be an important therapeutic tool to reduce the development of atherosclerosis.