RESUMEN
Diabetes affects more than 150 million people worldwide, and it is estimated that this would increase to 299 million by the year 2025. The incidence of and mortality from cardiovascular disease are two- to eightfold higher in subjects with diabetes than in those without, coronary artery disease accounting for the large majority of deaths. Among the full spectrum of biochemical effects of high glucose, generation of oxygen-derived free radicals is one of the main pathophysiological mechanisms linking hyperglycemia to atherosclerosis, nephropathy, and cardiomyopathy. The adaptor protein p66(Shc) is implicated in mitochondrial reactive oxygen species (ROS) generation and translation of oxidative signals into apoptosis. Indeed, p66(Shc-/-) mice display prolonged lifespan, reduced production of intracellular oxidants, and increased resistance to oxidative stress-induced apoptosis. Accordingly, a series of studies defined the pathophysiological role of p66(Shc) in cardiovascular disease where ROS represent a substantial triggering component. As p66(Shc) modulates the production of cellular ROS, it represents a proximal node through which high glucose exerts its deleterious effects on different cell types; indeed, several studies tested the hypothesis that deletion of the p66(Shc) gene may confer protection against diabetes-related cardiovascular complications. The present review focuses on the reported evidence linking p66(Shc) signaling pathway to high glucose-associated endothelial dysfunction, atherogenesis, nephropathy, and cardiomyopathy.
Asunto(s)
Enfermedades Cardiovasculares/etiología , Angiopatías Diabéticas/etiología , Estrés Oxidativo/fisiología , Proteínas Adaptadoras de la Señalización Shc/fisiología , Animales , Enfermedades Cardiovasculares/metabolismo , Angiopatías Diabéticas/metabolismo , Humanos , Enfermedades Renales/etiología , Enfermedades Renales/metabolismo , Proteínas Adaptadoras de la Señalización Shc/genética , Proteínas Adaptadoras de la Señalización Shc/metabolismo , Transducción de Señal , Proteína Transformadora 1 que Contiene Dominios de Homología 2 de SrcRESUMEN
Increased production of reactive oxygen species (ROS) and loss of endothelial NO bioavailability are key features of vascular disease in diabetes mellitus. The p66(Shc) adaptor protein controls cellular responses to oxidative stress. Mice lacking p66(Shc) (p66(Shc-/-)) have increased resistance to ROS and prolonged life span. The present work was designed to investigate hyperglycemia-associated changes in endothelial function in a model of insulin-dependent diabetes mellitus p66(Shc-/-) mouse. p66(Shc-/-) and wild-type (WT) mice were injected with citrate buffer (control) or made diabetic by an i.p. injection of 200 mg of streptozotocin per kg of body weight. Streptozotocin-treated p66(Shc-/-) and WT mice showed a similar increase in blood glucose. However, significant differences arose with respect to endothelial dysfunction and oxidative stress. WT diabetic mice displayed marked impairment of endothelium-dependent relaxations, increased peroxynitrite (ONOO(-)) generation, nitrotyrosine expression, and lipid peroxidation as measured in the aortic tissue. In contrast, p66(Shc-/-) diabetic mice did not develop these high-glucose-mediated abnormalities. Furthermore, protein expression of the antioxidant enzyme heme oxygenase 1 and endothelial NO synthase were up-regulated in p66(Shc-/-) but not in WT mice. We report that p66(Shc-/-) mice are resistant to hyperglycemia-induced, ROS-dependent endothelial dysfunction. These data suggest that p66(Shc) adaptor protein is part of a signal transduction pathway relevant to hyperglycemia vascular damage and, hence, may represent a novel therapeutic target against diabetic vascular complications.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/deficiencia , Endotelio Vascular/fisiopatología , Eliminación de Gen , Hiperglucemia/patología , Estrés Oxidativo , Animales , Aorta/citología , Aorta/enzimología , Diabetes Mellitus Experimental , Depuradores de Radicales Libres/metabolismo , Hemo-Oxigenasa 1/metabolismo , Hiperglucemia/inducido químicamente , Técnicas In Vitro , Contracción Isométrica , Luminiscencia , Masculino , Ratones , Óxido Nítrico Sintasa de Tipo III/metabolismo , Ácido Peroxinitroso/metabolismo , Proteínas Adaptadoras de la Señalización Shc , Proteína Transformadora 1 que Contiene Dominios de Homología 2 de Src , Estreptozocina , Sustancias Reactivas al Ácido Tiobarbitúrico/metabolismo , Sistema Vasomotor/fisiopatologíaRESUMEN
BACKGROUND: Vasoconstrictive, proliferative and oxidative effects of angiotensin II (Ang II) are mediated by Ang II type 1 (AT1) receptors. The effects of Ang II via the Ang II type 2 (AT2) receptor subtype (AT2R) are less well defined. Growing evidence shows the existence of cross-talk between the Ang II receptor subtypes, which is revealed by AT1R blockade. Hence, under certain conditions, AT2R may act as an antagonistic system with respect to the AT1R. METHODS: The present study was designed to investigate the effects of long-term treatment with the AT1R antagonist losartan on the AT2R-mediated response to Ang II in thoracic aortas isolated from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Untreated animals from both groups were used as controls. The mRNA expression of AT1R and AT2R was measured by reverse transcription-polymerase chain reaction. RESULTS: During contraction in response to norepinephrine, Ang II induced concentration-dependent relaxation only in aortas isolated from SHR chronically treated with losartan (8 weeks; 30 mg/kg/day in drinking water). These relaxations were inhibited by the selective AT2R blocker PD123319, N(G)-nitro-L-arginine methyl ester (L-NAME), and B2receptor antagonist HOE-140. Accordingly, nitric oxide (NO) production was increased by Ang II only in the aortas of treated SHR. After AT1R blockade, AT2R mRNA was significantly increased. These findings demonstrate that, in hypertensive rats, chronic AT1R blockade is associated with an inverted vasomotor response to Ang II via AT2R-mediated NO production. CONCLUSIONS: The losartan-unmasked AT2R-vasorelaxation could significantly contribute to the beneficial hemodynamic effects of AT1R blockade. In view of this, our study highlights the importance of the integrated Ang II receptor network, which may help to define further the mechanisms of the well-established vascular protective effects of AT1R blockers.
Asunto(s)
Bloqueadores del Receptor Tipo 1 de Angiotensina II/farmacología , Aorta Torácica/fisiopatología , Hipertensión/fisiopatología , Losartán/farmacología , Ratas Endogámicas SHR , Receptor de Angiotensina Tipo 2/metabolismo , Acetilcolina/farmacología , Angiotensina II/farmacología , Animales , Aorta Torácica/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/metabolismo , Endotelio Vascular/fisiopatología , Frecuencia Cardíaca/efectos de los fármacos , Masculino , Óxido Nítrico/biosíntesis , Nitroprusiato/farmacología , Norepinefrina/farmacología , ARN Mensajero/metabolismo , Ratas , Ratas Endogámicas WKY , Receptor de Angiotensina Tipo 1/genética , Receptor de Angiotensina Tipo 2/genética , Vasoconstricción , VasodilataciónRESUMEN
BACKGROUND: Enhanced production of reactive oxygen species (ROS) has been recognized as the major determinant of age-related endothelial dysfunction. The p66shc protein controls cellular responses to oxidative stress. Mice lacking p66shc (p66shc-/-) have increased resistance to ROS and a 30% prolonged life span. The present study investigates age-dependent changes of endothelial function in this model. METHODS AND RESULTS: Aortic rings from young and old p66shc-/- or wild-type (WT) mice were suspended for isometric tension recording. Nitric oxide (NO) release was measured by a porphyrinic microsensor. Expression of endothelial NO synthase (eNOS), inducible NOS (iNOS), superoxide dismutase, and nitrotyrosine-containing proteins was assessed by Western blotting. Nitrotyrosine residues were also identified by immunohistochemistry. Superoxide (O2-) production was determined by coelenterazine-enhanced chemiluminescence. Endothelium-dependent relaxation in response to acetylcholine was age-dependently impaired in WT mice but not in p66shc-/- mice. Accordingly, an age-related decline of NO release was found in WT but not in p66shc-/- mice. The expression of eNOS and manganese superoxide dismutase was not affected by aging either in WT or in p66shc-/- mice, whereas iNOS was upregulated only in old WT mice. It is interesting that old WT mice displayed a significant increase of O2- production as well as of nitrotyrosine expression compared with young animals. Such age-dependent changes were not found in p66shc-/- mice. CONCLUSIONS: We report that inactivation of the p66shc gene protects against age-dependent, ROS-mediated endothelial dysfunction. These findings suggest that the p66shc is part of a signal transduction pathway also relevant to endothelial integrity and may represent a novel target to prevent vascular aging.