Cardioprotective effect of chronic hyperglycemia: effect on hypoxia-induced apoptosis and necrosis (original) (raw)
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Antioxidant treatment attenuates hyperglycemia-induced cardiomyocyte death in rats
Journal of Molecular and Cellular Cardiology, 2004
Diabetes and oxidative stress concur to cardiac myocyte death in various experimental settings. We assessed whether N-acetyl-l-cysteine (NAC), an antioxidant and glutathione precursor, has a protective role in a rat model of streptozotocin (STZ)-induced diabetes and in isolated myocytes exposed to high glucose (HG). Diabetic rats were treated with NAC (0.5 g/kg per day) or vehicle for 3 months. At sacrifice left ventricle (LV) myocyte number and size, collagen deposition and reactive oxygen species (ROS) were measured by quantitative histological methods. Diabetes reduced LV myocyte number by 29% and increased myocyte volume by 20% compared to non-diabetic controls. NAC protected from myocyte loss (+25% vs. untreated diabetics, P < 0.05) and reduced reactive hypertrophy (–16% vs. untreated diabetics, P < 0.05). Perivascular fibrosis was high in diabetic rats (+88% vs. control, P < 0.001) but prevented by NAC. ROS production and fraction of ROS-positive cardiomyocyte nuclei were drastically raised in diabetic rats (2.4- and 5.1-fold vs. control, P < 0.001) and normalized by NAC. In separate experiments, isolated adult rat ventricular myocytes were incubated in a medium containing high concentrations of glucose (HG, 25 mM) ± 0.01 mM NAC; myocyte survival (Trypan blue exclusion and apoptosis by TUNEL) and glutathione content were evaluated. The number of dead and apoptotic myocytes increased five and 6.7-fold in HG and glutathione decreased by 48% (P < 0.05). NAC normalized cell death and apoptosis and prevented glutathione loss. NAC effectively protects from hyperglycemia-induced myocyte cell death and compensatory hypertrophy through direct scavenging of ROS and replenishment of the intracellular glutathione content.
High-glucose--triggered apoptosis in cultured endothelial cells
Diabetes, 1995
High ambient glucose concentration, linked to vascular complications in diabetes in vivo, modulates mRNA expression of fibronectin, collagen, tissue-type plasminogen activator, and plasminogen activator inhibitor and induces delayed replication and excess cell death in cultured vascular endothelial cells. To determine the role of high ambient glucose (30 mmol/1) in apoptosis, paired cultures of individual isolates of human umbilical vein endothelial cells (HUVECs) were exposed to both high (30 mmol/1) and low (5 mmol/1) concentrations of glucose for short-term (24, 48, and 72 h) and long-term (13 ± 1 days) experiments. Incubation of HUVECs with high glucose for >48 h increased DNA fragmentation (13.7 ± 6.5% of total DNA, mean ± SD) versus cultures kept in 5 mmol/1 glucose (10.9 ± 5.6%, P < 0.005), as measured by [ 3 H]thymidine assays. Data were confirmed by apoptosisspecific fluorescence-activated cell sorter analysis of confluent HUVEC cultures, which displayed after long-term exposure to 30 mmol/1 glucose a 1.5-fold higher prevalence of apoptosis than control cultures exposed to 5 mmol/1 glucose (P < 0.005). In contrast, no increase in DNA fragmentation in response to 30 mmol/1 glucose was seen for standardized cell lines (K 562, P 815, YT) and flbroblasts. Expression of clusterin mRNA, originally reported to be a molecular marker of apoptosis, was only slightly affected by short-term (24-h) high-glucose exposure but was significantly reduced after long-term incubation in 30 mmol/1 glucose (82.2 ± 13.8% of control) versus 5 mmol/1 glucose, which questions the role of clusterin gene expression as a marker of apoptosis. The results demonstrate that high ambient glucose can promote apoptosis in HUVECs in vitro and suggest potential endothelial damage by hyperglycemia in diabetic patients. Diabetes 44:1323-1327, 1995 A poptosis or programmed cell death is an active process of cell suicide (1), morphologically and biochemically different from necrosis, and is actively regulated. It requires energy as well as de novo gene transcription and protein synthesis (2,3). Apoptotic cells shrink and show membrane blebbing, condensed chromatin, and formation of apoptotic bodies, and are en-From the
European Journal of Heart Failure, 2010
Exposure to a high glucose medium or diabetes has been found to protect the heart against ischaemia. The activation of antiapoptotic and proliferative factors seems to be involved in this cardioprotection. This study was designed to evaluate the role of hyperglycaemia in cardiac function, programmed cell survival, and cell death in diabetic rats after myocardial infarction (MI). Methods and results Male Wistar rats were divided into four groups (n ¼ 8): control (C), diabetic (D), myocardial infarcted (MI), and diabetic myocardial infarcted (DI). The following measures were assessed in the left ventricle: size of MI, systolic and diastolic function by echocardiography, cytokines by ELISA (TNF-a, IL-1b, IL-6, and IL-10), gene expression by real-time PCR (Bax, Fas, p53, Bcl-2, HIF1-a, VEGF, and IL8r), caspase-3 activity by spectrofluorometric assay, glucose transporter type 1 and 4 (GLUT-1 and GLUT-4) protein expression by western blotting, and capillary density and fibrosis by histological analysis. Systolic function was improved by hyperglycaemia in the DI group, and this was accompanied by no improvement in diastolic dysfunction, a reduction of 36% in MI size, reduced proinflammatory cytokines, apoptosis activation, and an increase in cell survival factors (HIF1-a, VEGFa and IL8r) assessed 15 days post-MI. Moreover, hyperglycaemia resulted in angiogenesis (increased capillary density) before and after MI, accompanied by a reduction in fibrosis. Conclusion Together, these results suggest that greater plasticity and cellular resistance to ischaemic injury result from chronic diabetic hyperglycaemia in rat hearts.
Biochimica et Biophysica Acta (BBA) - General Subjects, 2012
Background: Cardiac cell apoptosis is the initiating factor of cardiac complications especially diabetic cardiomyopathy. Mitochondria are susceptible to the damaging effects of elevated glucose condition. Calcium overload and oxidative insult are the two mutually non-exclusive phenomena suggested to cause cardiac dysfunction. Here, we examined the effect of high-glucose induced calcium overload in calpain-1 mediated cardiac apoptosis in an in vitro setting. Methods: H9c2, rat ventricular myoblast cell line was treated with elevated glucose condition and the cellular consequences were studied. Intracellular calcium trafficking, ROS generation, calpain-1 activation and caspase-12 and caspase-9 pathway were studied using flow cytometry, confocal microscopy and Western blot analysis. Results: High-glucose treatment resulted in increased intracellular calcium ([Ca 2 + ]i) which was mobilized to the mitochondria. Concomitant intra-mitochondrial calcium ([Ca 2 + ]m) increase resulted in enhanced reactive oxygen and nitrogen species generation. These events led to mitochondrial dysfunction and apoptosis. Cardiomyocyte death exhibited several classical markers of apoptosis, including activation of caspases, appearance of annexin V on the outer plasma membrane, increased population of cells with sub-G 0 /G 1 DNA content and nuclear condensation. Key findings include elucidation of cell signaling mechanism of high-glucose induced calcium-dependent cysteine protease calpain-1 activation, which triggers non-conventional caspases as alternate mode of cell death. Conclusion: This information increases the understanding of cardiac cell death under hyperglycemic condition and can possibly be extended for designing new therapeutic strategies for diabetic cardiomyopathy. General significance: The novel findings of the study reveal that high glucose induces apoptosis by both mitochondria-dependent and independent pathways via concomitant rise in intracellular calcium.
British Journal of Pharmacology, 2001
1 Alterations of the vessel structure, which is mainly determined by smooth muscle cells through cell growth and/or cell death mechanisms, are characteristic of diabetes complications. We analysed the in¯uence of high glucose (22 mM) on cultured human aortic smooth muscle cell growth and death, as hyperglycaemia is considered one of the main factors involved in diabetic vasculopathy. 2 Growth curves were performed over 96 h in medium containing 0.5% foetal calf serum. Cell number increased by 2 ± 4 fold over the culture period in the presence of 5.5 mM (low) glucose, while a 20% reduction in ®nal cell number was observed with high glucose. Under serum-free conditions, cell number remained constant in low glucose cultures, but a 40% decrease was observed in high glucose cultures, suggesting that high glucose may induce increased cell death rather than reduced proliferation. Reduced ®nal cell number induced by high glucose was also observed after stimulation with 5 or 10% foetal calf serum. 3 The possible participation of oxidative stress was investigated by co-incubating high glucose with dierent reactive oxygen species scavengers. Only catalase reversed the eect of high glucose. Intracellular H 2 O 2 content, visualized with 2',7'-dichloro¯uorescein and quanti®ed by¯ow cytometry, was increased after high glucose treatment. 4 To investigate the cell death mechanism induced by high glucose, apoptosis and necrosis were quanti®ed. No dierences were observed regarding the apoptotic index between low and high glucose cultures, but lactate dehydrogenase activity was increased in high glucose cultures. 5 In conclusion, high glucose promotes necrotic cell death through H 2 O 2 formation, which may participate in the development of diabetic vasculopathy. British Journal of Pharmacology (2001) 133, 967 ± 974
Journal of advanced Biomedical and Pharmaceutical Sciences
Diabetes and its associated hyperglycemia represent a major health problem. One of the common complications of diabetes is endothelial dysfunction which leads to several cardiovascular diseases. Studying the effect of hyperglycemia and possible treatment strategies necessities the induction of diabetes in vivo that requires a long time for endothelial dysfunction to develop. Recently, in vitro models of hyperglycemia have been introduced in which vascular tissues are incubated in media containing a high concentration of glucose which ultimately requires much less time for endothelial dysfunction development. In this study, we examined the effect of incubation of isolated aortic rings in a high glucose medium on their relaxation and contractile responses as well as the histopathological changes of aortic tissues. We also examined the involvement of oxidative stress and apoptosis in hyperglycemia-induced endothelial dysfunction. The results of our study showed that incubation of aortic rings with high glucose media resulted in a significant reduction of relaxation response of precontracted aortic rings along with an enhanced contractile response to epinephrine. This was associated with obvious histopathological alterations of aortic tissues. Aortic rings incubated in high glucose also exhibited increased oxidative stress and a reduction of the anti-apoptotic marker, Bcl2. In conclusion, in vitro, high glucose can be used as a model for studying endothelial dysfunction and its possible mechanisms involving oxidative stress and apoptotic pathway.
Myocardial Cell Death in Human Diabetes
Circulation Research, 2000
The renin-angiotensin system is upregulated with diabetes, and this may contribute to the development of a dilated myopathy. Angiotensin II (Ang II) locally may lead to oxidative damage, activating cardiac cell death. Moreover, diabetes and hypertension could synergistically impair myocardial structure and function. Therefore, apoptosis and necrosis were measured in ventricular myocardial biopsies obtained from diabetic and diabetic-hypertensive patients. Accumulation of a marker of oxidative stress, nitrotyrosine, and Ang II labeling were evaluated quantitatively. The diabetic heart showed cardiac hypertrophy, cavitary dilation, and depressed ventricular performance. These alterations were more severe with diabetes and hypertension. Diabetes was characterized by an 85-fold, 61-fold, and 26-fold increase in apoptosis of myocytes, endothelial cells, and fibroblasts, respectively. Apoptosis in cardiac cells did not increase additionally with diabetes and hypertension. Diabetes increased necrosis by 4-fold in myocytes, 9-fold in endothelial cells, and 6-fold in fibroblasts. However, diabetes and hypertension increased necrosis by 7-fold in myocytes and 18-fold in endothelial cells. Similarly, Ang II labeling in myocytes and endothelial cells increased more with diabetes and hypertension than with diabetes alone. Nitrotyrosine localization in cardiac cells followed a comparable pattern. In spite of the difference in the number of nitrotyrosine-positive cells with diabetes and with diabetes and hypertension, apoptosis and necrosis of myocytes, endothelial cells, and fibroblasts were detected only in cells containing this modified amino acid. In conclusion, local increases in Ang II with diabetes and with diabetes and hypertension may enhance oxidative damage, activating cardiac cell apoptosis and necrosis.
Glucose modulates cell death due to normobaric hyperoxia by maintaining cellular ATP
Glucose modulates cell death due to normobaric hyperoxia by maintaining cellular ATP. Am. J. Physiol. 274 (Lung Cell. Mol. Physiol. 18): L159–L164, 1998.—To determine whether glucose depletion is a principal determinant of hyperoxic cell death in vitro, human lung epithelial-like cells (A549) were exposed to hyperoxia (95% O2) in either 10, 30, or 50 ml of medium (Ham’s F-12K). Glucose was depleted in the medium after 36, 60, or 96 h, respectively. Medium lactate dehydrogenase (LDH) activity increased only after glucose was depleted. To confirm that glucose depletion was critical to cell death, cells exposed to 95% O2 were supplemented with glucose at regular intervals to reestablish initial medium glucose concentra- tions. Other cells received no supplements. Without supple- mentation, glucose was depleted within 48 h, followed within 12 h by an almost complete loss of cell ATP and elevated medium LDH activity. Glucose-supplemented cells appeared normal microscopically and did not release LDH activity despite an extracellular pH of 6.5 due to fermentation. Additional experiments at sea-level pressure confirmed that glucose supplementation prevents extensive cell death in hyperoxia in cultured A549 cells.
Oxidative stress as a common mediator for apoptosis induced-cardiac damage in diabetic rats
The Open …, 2008
Aim:To investigate the possible role of oxidative stress as a common mediator of apoptosis and cardiac damage in diabetes.Materials and Methods:This experimental work was conducted on 5 groups of Wistar rats. Group I was the control group. Diabetes type 1 was induced in other groups (by streptozotocin) and animals received insulin or vitamin E (300 mg /kg body weight), both insulin and vitamin E, or no treatment for 4 weeks according to their group. At the end of the study, serum and cardiac tissues were examined for biochemical parameters of cardiac function, oxidative stress and apoptosis. Electron microscopy pictures of cardiac tissue were also evaluated for signs of cardiac damageResults: Markers of oxidative stress, apoptosis, inflammation as well as manifestations of cardiac damage as assessed by electron microscopy were significantly decreased in rats treated with both insulin and vitamin E when compared with untreated diabetic rats or rats treated with either insulin or vitamin E aloneConclusion:Administration of both vitamin E and insulin was effective in reducing markers of oxidative stress and apoptosis and improving parameters of cardiac function in experiments animals. Antioxidants might prove beneficial as an adjuvant treatment in addition to insulin in type 1 diabetes associated with manifestations of cardiac complications
Cardiovascular Research, 2009
Aims Ischaemic cardiac injury is significantly increased in diabetic patients, but its underlying mechanisms remain incompletely understood. The current study attempted to identify new molecular mechanisms potentially contributive to hyperglycaemic-exaggeration of myocardial ischaemic injury. Methods and results Adult mouse cardiomyocytes were cultured in normal-glucose (NG, 5.5 mM) or high-glucose (HG, 25 mM) medium. Twelve hours after NG or HG pre-culture, cardiomyocytes were subjected to 3 h of simulated ischaemia (SI), followed by 3 h of reperfusion (R) in NG medium. Prior to and after SI/R, the following were determined: cardiomyocyte death and apoptosis, sustained oxidative/ nitrative stress and thioredoxin (Trx) activity, expression, and nitration. Compared with NG-cultured cardiomyocytes, 12 h HG culture significantly increased superoxide and peroxynitrite production, increased Trx-1 nitration, and reduced Trx activity (P , 0.01). Despite being subject to identical SI/R procedures and conditions, cells pre-cultured in HG sustained greater injury, evidenced by elevated lactate dehydrogenase release and caspase-3 activation (P , 0.01). Moreover, SI/R induced greater superoxide/peroxynitrite overproduction and greater Trx-1 nitration and inactivation in HG pre-cultured cardiomyocytes than in NG pre-cultured cardiomyocytes. Finally, the supplementation of human Trx-1, superoxide scavenger, or peroxynitrite decomposition catalyst in HG pre-cultured cells reduced Trx-1 nitration, preserved Trx-1 activity, and normalized SI/R injury to levels observed in NG pre-cultured cardiomyocytes. Conclusion High glucose sensitized cardiomyocytes to ischaemia/reperfusion injury through nitrative Trx-1 inactivation. Interventions restoring Trx-1 activity in the diabetic heart may represent novel therapies attenuating cardiac injury in diabetic patients.