Genetic deletion of the p66Shc adaptor protein protects from angiotensin II-induced myocardial damage

Angiotensin II (Ang II), acting through its G protein-coupled AT1 receptor (AT1), contributes to the precocious heart senescence typical of patients with hypertension, atherosclerosis, and diabetes. AT1 was suggested to transactivate an intracellular signaling controlled by growth factors and their tyrosin-kinase receptors. In cultured vascular smooth muscle cells, this downstream mechanism comprises the p66Shc adaptor protein, previously recognized to play a role in vascular cell senescence and death. The aim of the present study was 2-fold: (1) to characterize the cardiovascular phenotype of p66Shc knockout mice (p66Shc(-/-)), and (2) to test the novel hypothesis that disrupting the p66Shc might protect the heart from the damaging action of elevated Ang II levels. Compared with wild-type littermates (p66Shc(+/+)), p66Shc(-/-) showed similar blood pressure, heart rate, and left ventricular wall thickness. However, cardiomyocyte number was increased in mutant animals, indicating a condition of myocardial hyperplasia. In p66Shc(+/+), infusion of a sub-pressor dose of Ang II (300 nmol/kg body weight [BW] daily for 28 days) caused left ventricular hypertrophy and apoptotic death of cardiomyocytes and endothelial cells. In contrast, p66Shc(-/-) were resistant to the proapoptotic/hypertrophic action of Ang II. Consistently, in vitro experiments showed that Ang II causes apoptotic death of cardiomyocytes isolated from p66Shc(+/+) hearts to a greater extent as compared with p66Shc(-/-) cardiomyocytes. Our results indicate a fundamental role of p66Shc in Ang II-mediated myocardial remodeling. In perspective, p66Shc inhibition may be envisioned as a novel way to prevent the deleterious effects of Ang II on the heart.     

Cross-talk between SIRT1 and p66Shc in vascular diseases

Accumulating evidence indicates that oxidative stress can occur through overproduction of reactive oxygen species (ROS) and/or reduced anti-oxidant potentials under pathophysiological conditions and plays an important role in the development of cardiovascular diseases (CVDs). Adapter protein p66Shc has the property to directly stimulate mitochondrial ROS generation by an oxidoreductase activity. A growing body of evidence implies that p66Shc plays a critical role in the pathophysiology of age-related vascular diseases. Silent mating type information regulator 2 homolog 1 (SIRT1), a nicotinamide adenine dinucleotide (NAD+)-dependent class III histone deacetylase (HDAC), has also been implicated in protection against vascular aging and age-related vascular diseases. Recently, we demonstrated that SIRT1 protects blood vessels from hyperglycemia-induced endothelial dysfunction through a novel mechanism involving the downregulation of p66Shc expression. In this review, we discuss the cross-talk between these two longevity genes as a mechanism of preventing vascular diseases by involving anti-oxidative stress responses and inhibiting endothelial senescence.     

Genetic deletion of p66(Shc) adaptor protein prevents hyperglycemia-induced endothelial dysfunction and oxidative stress

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.     

自噬在常见心血管疾病中的作用

自噬是细胞利用细胞内溶酶体清除过量或受损的长半衰期蛋白质及细胞器的现象。自噬可通过营养剥夺适应,清除细胞内蛋白质及微细胞器等生理及病理学作用和再利用细胞废物,以维持内环境稳定、参与生长发育和疾病的发生及发展。研究发现,自噬参与了心肌肥厚、心室重构、心肌缺血/再灌注损伤等多种心血管疾病病的理生理过程。本文主要阐述自噬在正常心脏及各种常见心脏疾病中作用的研究进展,并初步探讨可能的治疗新靶点。     

Activation of the lifespan regulator p66Shc through reversible disulfide bond formation

Cell fate and organismal lifespan are controlled by a complex signaling network whose dysfunction can cause a variety of aging-related diseases. An important protection against these failures is cellular apoptosis, which can be induced by p66(Shc) in response to cellular stress. The precise mechanisms of p66(Shc) action and regulation and the function of the p66(Shc)-specific N terminus remain to be identified. Here, we show that the p66(Shc) N terminus forms a redox module responsible for apoptosis initiation, and that this module can be activated through reversible tetramerization by forming two disulfide bonds. Glutathione and thioredoxins can reduce and inactivate p66(Shc), resulting in a thiol-based redox sensor system that initiates apoptosis once cellular protection systems cannot cope anymore with cellular stress.     

结肠癌中雌激素受体和衔接蛋白p66Shc的表达和意义

背景:雌激素和雌激素受体(ER)在结肠癌的发生、发展中起重要作用,然而ER在其中的具体作用机制尚不完全清楚。在甾类激素敏感性肿瘤细胞中,甾类激素可显著上调衔接蛋白p66Shc表达并刺激细胞增殖。目的:探讨ER和p66Shc在结肠癌中的表达特点及其临床意义。方法:以免疫组化方法检测65例石蜡包埋结肠癌组织及其癌旁非癌组织中的ER和p66Shc蛋白表达,分析p66Shc蛋白表达与结肠癌临床病理特征的相关性。结果:ER和p66Shc蛋白表达分别定位于细胞核和细胞质,结肠癌组织中的ER和p66Shc蛋白表达阳性率显著高于癌旁非癌组织(ER:47.7%对0%,P<0.01;p66Shc:49.2%对0%,P<0.01),且两者呈正相关(r=0.43,P<0.05)。p66Shc蛋白表达与结肠癌患者的性别、年龄以及原发肿瘤部位、肿瘤大小、大体类型、浸润深度、淋巴结转移、AJCC分期均无相关性,而与肿瘤组织学分级相关(高分化:22.2%,中分化:47.7%,低分化:75.0%,P=0.046)。结论:结肠癌可能是一种雌激素敏感性肿瘤。雌激素及其受体可能与p66Shc共同参与了结肠癌的发生、发展。     

Developmental regulation of p66Shc is altered by bronchopulmonary dysplasia in baboons and humans

RATIONALE: The p66(Shc) adapter protein antagonizes mitogen-activated protein, or MAP, kinase, mediates oxidative stress, and is developmentally regulated in fetal mouse lungs. OBJECTIVES: To determine if p66(Shc) is similarly regulated in primates and in bronchopulmonary dysplasia (BPD), which results from oxidative injury to immature lungs. METHODS: Normal and injured lungs from humans and baboons were evaluated by Western analysis and immunohistochemistry. MEASUREMENTS AND MAIN RESULTS: In baboons, p66(Shc) decreased 80% between 125 and 175 days' gestation (p = 0.025), then doubled after term delivery at 185 days (p = 0.0013). In the hyperoxic 140-day fetal baboon BPD model, p66(Shc) expression persisted, and its localization shifted from the epithelium of gestational controls to the mesenchyme of diseased lungs, coincident with expression of proliferating cell nuclear antigen and cleaved poly(adenyl ribose) polymerase, a marker of apoptosis. Treatment with the antibombesin antibody 2A11 attenuated BPD, reduced cell proliferation, increased p66(Shc) expression 10.5-fold, and preserved epithelial p66(Shc) localization. p66(Shc) also decreased during normal human lung development, falling 87% between 18 and 24 weeks' gestation (p = 0.02). p66(Shc) was expressed throughout 18-week human lungs, became restricted to scattered epithelial cells by 24 weeks, and localized to isolated mesenchymal cells after term delivery. In contrast, p66(Shc) remained prominent in the epithelium of lungs with acute injury or mild BPD, and in the mesenchyme of lungs with severe disease. p66(Shc) localized to tissues expressing proliferating cell nuclear antigen and cleaved poly(adenyl ribose) polymerase. CONCLUSIONS: p66(Shc) expression, cell proliferation, and apoptosis are concomitantly altered during lung development and in BPD.     

The role of C-reactive protein in cardiovascular disease risk

Over the past few years, a flurry of data in the medical literature has strongly implicated C-reactive protein (CRP) as a marker of inflammation in coronary artery disease (CAD). Recognizing the likely integral role that inflammation plays in the pathogenesis of atherosclerosis, many hospital laboratories have tests to measure CRP concentration in the clinical setting. However, the clinical use of these tests still need definition. To date, of the plasma-based markers investigated, CRP provides the strongest risk prediction for cardiovascular disease in men and women. Questions remain regarding the degree to which CRP can improve risk stratification beyond that of the traditional risk factors of CAD.     

The role of C-reactive protein in cardiovascular disease risk

The genesis of an atherosclerotic plaque depends on interplay of cellular components of the immune system such as monocytes, cytokines, and cell adhesion molecules with lipids, platelets and endothelial cells. Thus, inflammation may play a pivotal role in the propagation of coronary artery disease. Several reports have linked inflammation and cardiovascular risk, particularly a novel acute inflammatory peptide, C-reactive protein (CRP), with future risk of coronary events independent of the traditional coronary artery disease risk factors. To this end, many studies suggest that CRP may be used as a marker of sub-clinical atherosclerosis and cardiovascular risk. Specifically, CRP has been positively linked to future cardiovascular events in healthy women, healthy men, elderly patients, and high-risk individuals. In addition, reports have shown associations between CRP and peripheral vascular disease and stroke. Furthermore, preliminary data suggest that the relative efficacy of secondary preventive therapies such as statin drugs and aspirin may depend on the individual patient's baseline CRP level.