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In order to investigate the subcellular mechanisms underlying the beneficial effects of sarpogrelate-a 5-HT2A receptor antagonist-on diabetic cardiomyopathy, diabetes was induced in rats by injecting streptozotocin (65 mg/kg). Diabetic animals were treated with or without sarpogrelate (5 mg/kg daily) for 6 weeks; diabetic animals were also treated with insulin (10 units/kg daily) for comparison. Elevated plasma levels of glucose and lipids, depressed insulin levels, hemodynamic alterations and cardiac dysfunction in diabetic animals were partially or fully attenuated by sarpogrelate or insulin treatment. Diabetes-induced changes in myocardial high-energy phosphate stores, as well as depressed mitochondrial oxidative phosphorylation and Ca2+-uptake activities, were significantly prevented by these treatments. Reductions in sarcolemma Na+-K+ ATPase, Na+-Ca2+ exchange, Ca2+-channel density and Ca2+-uptake activities were also attenuated by treatments with sarpogrelate and insulin. In addition, decreases in diabetes-induced sarcoplasmic reticulum Ca2+-uptake, Ca2+-release and Ca2+-stimulated ATPase activities, myofibrillar Mg2+-ATPase and Ca2+-stimulated ATPase activities, and myosin Mg2+-ATPase and Ca2+-ATPase activities were fully or partially prevented by sarpogrelate and insulin treatments. Marked alterations in different biomarkers of oxidative stress, such as malondialdehyde, superoxide dismutase and glutathione peroxidase, in diabetic hearts were also attenuated by treating the animals with sarpogrelate or insulin. These observations suggest that therapy with sarpogrelate, like that with insulin, may improve cardiac function by preventing subcellular and metabolic defects as a consequence of a reduction in oxidative stress.
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Heart failure is the common concluding pathway for a majority of cardiovascular diseases and is associated with cardiac dysfunction. Since heart failure is invariably preceded by adaptive or maladaptive cardiac hypertrophy, several biochemical mechanisms have been proposed to explain the development of cardiac hypertrophy and progression to heart failure. One of these includes the activation of different neuroendocrine systems for elevating the circulating levels of different vasoactive hormones such as catecholamines, angiotensin II, vasopressin, serotonin and endothelins. All these hormones are released in the circulation and stimulate different signal transduction systems by acting on their respective receptors on the cell membrane to promote protein synthesis in cardiomyocytes and induce cardiac hypertrophy. The elevated levels of these vasoactive hormones induce hemodynamic overload, increase ventricular wall tension, increase protein synthesis and the occurrence of cardiac remodeling. In addition, there occurs an increase in proinflammatory cytokines and collagen synthesis for the induction of myocardial fibrosis and the transition of adaptive to maladaptive hypertrophy. The prolonged exposure of the hypertrophied heart to these vasoactive hormones has been reported to result in the oxidation of catecholamines and serotonin via monoamine oxidase as well as the activation of NADPH oxidase via angiotensin II and endothelins to promote oxidative stress. The development of oxidative stress produces subcellular defects, Ca2+-handling abnormalities, mitochondrial Ca2+-overload and cardiac dysfunction by activating different proteases and depressing cardiac gene expression, in addition to destabilizing the extracellular matrix upon activating some metalloproteinases. These observations support the view that elevated levels of various vasoactive hormones, by producing hemodynamic overload and activating their respective receptor-mediated signal transduction mechanisms, induce cardiac hypertrophy. Furthermore, the occurrence of oxidative stress due to the prolonged exposure of the hypertrophied heart to these hormones plays a critical role in the progression of heart failure.
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Cardiomegalia , Insuficiência Cardíaca , Transdução de Sinais , Insuficiência Cardíaca/metabolismo , Insuficiência Cardíaca/fisiopatologia , Insuficiência Cardíaca/patologia , Humanos , Cardiomegalia/metabolismo , Cardiomegalia/fisiopatologia , Cardiomegalia/patologia , Animais , Angiotensina II/metabolismo , Estresse OxidativoRESUMO
In order to determine the behavior of the right ventricle, we have reviewed the existing literature in the area of cardiac remodeling, signal transduction pathways, subcellular mechanisms, ß-adrenoreceptor-adenylyl cyclase system and myocardial catecholamine content during the development of left ventricular failure due to myocardial infarction. The right ventricle exhibited adaptive cardiac hypertrophy due to increases in different signal transduction pathways involving the activation of protein kinase C, phospholipase C and protein kinase A systems by elevated levels of vasoactive hormones such as catecholamines and angiotensin II in the circulation at early and moderate stages of heart failure. An increase in the sarcoplasmic reticulum Ca2+ transport without any changes in myofibrillar Ca2+-stimulated ATPase was observed in the right ventricle at early and moderate stages of heart failure. On the other hand, the right ventricle showed maladaptive cardiac hypertrophy at the severe stages of heart failure due to myocardial infarction. The upregulation and downregulation of ß-adrenoreceptor-mediated signal transduction pathways were observed in the right ventricle at moderate and late stages of heart failure, respectively. The catalytic activity of adenylate cyclase, as well as the regulation of this enzyme by Gs proteins, were seen to be augmented in the hypertrophied right ventricle at early, moderate and severe stages of heart failure. Furthermore, catecholamine stores and catecholamine uptake in the right ventricle were also affected as a consequence of changes in the sympathetic nervous system at different stages of heart failure. It is suggested that the hypertrophied right ventricle may serve as a compensatory mechanism to the left ventricle during the development of early and moderate stages of heart failure.
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Insuficiência Cardíaca , Infarto do Miocárdio , Humanos , Ventrículos do Coração/metabolismo , Insuficiência Cardíaca/metabolismo , Infarto do Miocárdio/metabolismo , Cardiomegalia/metabolismo , Miocárdio/metabolismo , Receptores Adrenérgicos beta/metabolismo , Catecolaminas/metabolismo , Proteínas de Ligação ao GTP/metabolismo , Adenilil Ciclases/metabolismoRESUMO
With cardiovascular disease (CVD) being a primary source of global morbidity and mortality, it is crucial that we understand the molecular pathophysiological mechanisms at play. Recently, numerous pro-inflammatory cytokines have been linked to several different CVDs, which are now often considered an adversely pro-inflammatory state. These cytokines most notably include interleukin-6 (IL-6),tumor necrosis factor (TNF)α, and the interleukin-1 (IL-1) family, amongst others. Not only does inflammation have intricate and complex interactions with pathophysiological processes such as oxidative stress and calcium mishandling, but it also plays a role in the balance between tissue repair and destruction. In this regard, pre-clinical and clinical evidence has clearly demonstrated the involvement and dynamic nature of pro-inflammatory cytokines in many heart conditions; however, the clinical utility of the findings so far remains unclear. Whether these cytokines can serve as markers or risk predictors of disease states or act as potential therapeutic targets, further extensive research is needed to fully understand the complex network of interactions that these molecules encompass in the context of heart disease. This review will highlight the significant advances in our understanding of the contributions of pro-inflammatory cytokines in CVDs, including ischemic heart disease (atherosclerosis, thrombosis, acute myocardial infarction, and ischemia-reperfusion injury), cardiac remodeling (hypertension, cardiac hypertrophy, cardiac fibrosis, cardiac apoptosis, and heart failure), different cardiomyopathies as well as ventricular arrhythmias and atrial fibrillation. In addition, this article is focused on discussing the shortcomings in both pathological and therapeutic aspects of pro-inflammatory cytokines in CVD that still need to be addressed by future studies.
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Doenças Cardiovasculares , Cardiopatias , Insuficiência Cardíaca , Humanos , Doenças Cardiovasculares/etiologia , Citocinas , Interleucina-1 , Fator de Necrose Tumoral alfaRESUMO
Angiotensin II (Ang II) is formed by the action of angiotensin-converting enzyme (ACE) in the renin-angiotensin system. This hormone is known to induce cardiac hypertrophy and heart failure and its actions are mediated by the interaction of both pro- and antihypertrophic Ang II receptors (AT1R and AT2R). Ang II is also metabolized by ACE 2 to Ang-(1-7), which elicits the activation of Mas receptors (MasR) for inducing antihypertrophic actions. Since heart failure under different pathophysiological situations is preceded by adaptive and maladaptive cardiac hypertrophy, we have reviewed the existing literature to gain some information regarding the roles of AT1R, AT2R, and MasR in both acute and chronic conditions of cardiac hypertrophy. It appears that the activation of AT1R may be involved in the development of adaptive and maladaptive cardiac hypertrophy as well as subsequent heart failure because both ACE inhibitors and AT1R antagonists exert beneficial effects. On the other hand, the activation of both AT2R and MasR may prevent the occurrence of maladaptive cardiac hypertrophy and delay the progression of heart failure, and thus therapy with different activators of these antihypertrophic receptors under chronic pathological stages may prove beneficial. Accordingly, it is suggested that a great deal of effort should be made to develop appropriate activators of both AT2R and MasR for the treatment of heart failure subjects.
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Insuficiência Cardíaca , Receptores de Angiotensina , Humanos , Receptores de Angiotensina/metabolismo , Sistema Renina-Angiotensina , Cardiomegalia , Angiotensina II/farmacologia , Receptor Tipo 1 de Angiotensina/metabolismoRESUMO
Previously, it was shown that both blood flow and angiogenesis in the ischemic hind limb of diabetic rats were increased upon CO2 treatment for 4 weeks. In the present study, we have compared the effects of 6 weeks CO2 therapy in diabetic rats with or without peripheral ischemia. Diabetes was induced in rats by a tail vein injection of streptozotocin (65 mg/kg body weight), whereas peripheral ischemia was produced by occluding the femoral artery at 2 weeks of inducing diabetes. Both diabetic and diabetic-ischemic animals were treated with or without CO2 water-bath at 37 °C for 6 weeks (30 min/day; 5 days/week) starting at 2 weeks, after the induction of ischemia. CO2 treatment did not affect heart rate and R-R interval as well as plasma levels of creatine kinase, glucose, cholesterol, triglycerides and high density lipoproteins. Unlike the levels of plasma Ox-LDL, MDA and TNF-α, the levels of NO in diabetic group were increased by CO2 water-bath treatment. On the other hand, the levels of plasma Ox-LDL and MDA were decreased whereas that of NO was increased without any changes in TNF-α level in diabetic-ischemic animals upon CO2 therapy. Treatment of diabetic animals with CO2 increased peak, mean and minimal blood flow by 20, 49 and 43% whereas these values were increased by 53, 26 and 80% in the diabetic-ischemic group by CO2 therapy, respectively. Blood vessel count in diabetic and diabetic-ischemic skeletal muscles was increased by 73 and 136% by CO2 therapy, respectively. These data indicate that peripheral ischemia augmented the increase in blood flow and development of angiogenesis in diabetic skeletal muscle upon CO2 therapy. It is suggested that greater beneficial effects of CO2 therapy in diabetic-ischemic animals in comparison to diabetic group may be a consequence of difference of changes in the redox-sensitive signal transduction mechanisms.
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Mitochondria are specialized organelles, which serve as the "Power House" to generate energy for maintaining heart function. These organelles contain various enzymes for the oxidation of different substrates as well as the electron transport chain in the form of Complexes I to V for producing ATP through the process of oxidative phosphorylation (OXPHOS). Several studies have shown depressed OXPHOS activity due to defects in one or more components of the substrate oxidation and electron transport systems which leads to the depletion of myocardial high-energy phosphates (both creatine phosphate and ATP). Such changes in the mitochondria appear to be due to the development of oxidative stress, inflammation, and Ca2+-handling abnormalities in the failing heart. Although some investigations have failed to detect any changes in the OXPHOS activity in the failing heart, such results appear to be due to a loss of Ca2+ during the mitochondrial isolation procedure. There is ample evidence to suggest that mitochondrial Ca2+-overload occurs, which is associated with impaired mitochondrial OXPHOS activity in the failing heart. The depression in mitochondrial OXPHOS activity may also be due to the increased level of reactive oxygen species, which are formed as a consequence of defects in the electron transport complexes in the failing heart. Various metabolic interventions which promote the generation of ATP have been reported to be beneficial for the therapy of heart failure. Accordingly, it is suggested that depression in mitochondrial OXPHOS activity plays an important role in the development of heart failure.
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Cardiovascular diseases, especially ischemic heart disease, as a leading cause of heart failure (HF) and mortality, will not reduce over the coming decades despite the progress in pharmacotherapy, interventional cardiology, and surgery. Although patients surviving acute myocardial infarction live longer, alteration of heart function will later lead to HF. Its rising incidence represents a danger, especially among the elderly, with data showing more unfavorable results among females than among males. Experiments revealed an infarct-sparing effect of ischemic "preconditioning" (IPC) as the most robust form of innate cardioprotection based on the heart's adaptation to moderate stress, increasing its resistance to severe insults. However, translation to clinical practice is limited by technical requirements and limited time. Novel forms of adaptive interventions, such as "remote" IPC, have already been applied in patients, albeit with different effectiveness. Cardiac ischemic tolerance can also be increased by other noninvasive approaches, such as adaptation to hypoxia- or exercise-induced preconditioning. Although their molecular mechanisms are not yet fully understood, some noninvasive modalities appear to be promising novel strategies for fighting HF through targeting its numerous mechanisms. In this review, we will discuss the molecular mechanisms of heart injury and repair, as well as interventions that have potential to be used in the treatment of patients.
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Insuficiência Cardíaca , Precondicionamento Isquêmico Miocárdico , Infarto do Miocárdio , Isquemia Miocárdica , Masculino , Humanos , Idoso , Precondicionamento Isquêmico Miocárdico/métodos , Coração , Isquemia , Insuficiência Cardíaca/terapiaRESUMO
Although ß 1-adrenoceptor ( ß 1-AR) signal transduction, which maintains cardiac function, is downregulated in failing hearts, the mechanisms for such a defect in heart failure are not fully understood. Since cardiac hypertrophy is invariably associated with heart failure, it is possible that the loss of ß 1-AR mechanisms in failing heart occurs due to hypertrophic process. In this regard, we have reviewed the information from a rat model of adaptive cardiac hypertrophy and maladaptive hypertrophy at 4 and 24 weeks after inducing pressure overload as well as adaptive cardiac hypertrophy and heart failure at 4 and 24 weeks after inducing volume overload, respectively. Varying degrees of alterations in ß 1-AR density as well as isoproterenol-induced increases in cardiac function, intracellular Ca 2 + -concentration in cardiomyocytes and adenylyl cyclase activity in crude membranes have been reported under these hypertrophic conditions. Adaptive hypertrophy at 4 weeks of pressure or volume overload showed unaltered or augmented increases in the activities of different components of ß 1-AR signaling. On the other hand, maladaptive hypertrophy due to pressure overload and heart failure due to volume overload at 24 weeks revealed depressions in the activities of ß 1-AR signal transduction pathway. These observations provide evidence that ß 1-AR signal system is either unaltered or upregulated in adaptive cardiac hypertrophy and downregulated in maladaptive cardiac hypertrophy or heart failure. Furthermore, the information presented in this article supports the concept that downregulation of ß 1-AR mechanisms in heart failure or maladaptive cardiac hypertrophy is not due to hypertrophic process per se. It is suggested that a complex mechanism involving the autonomic imbalance may be of a critical importance in determining differential alterations in non-failing and failing hearts.
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Although acute exposure of the heart to angiotensin (Ang II) produces physiological cardiac hypertrophy and chronic exposure results in pathological hypertrophy, the signal transduction mechanisms for these effects are of complex nature. It is now evident that the hypertrophic response is mediated by the activation of Ang type 1 receptors (AT1R), whereas the activation of Ang type 2 receptors (AT2R) by Ang II and Mas receptors by Ang-(1-7) exerts antihypertrophic effects. Furthermore, AT1R-induced activation of phospholipase C for stimulating protein kinase C, influx of Ca2+ through sarcolemmal Ca2+- channels, release of Ca2+ from the sarcoplasmic reticulum, and activation of sarcolemmal NADPH oxidase 2 for altering cardiomyocytes redox status may be involved in physiological hypertrophy. On the other hand, reduction in the expression of AT2R and Mas receptors, the release of growth factors from fibroblasts for the occurrence of fibrosis, and the development of oxidative stress due to activation of mitochondria NADPH oxidase 4 as well as the depression of nuclear factor erythroid-2 activity for the occurrence of Ca2+-overload and activation of calcineurin may be involved in inducing pathological cardiac hypertrophy. These observations support the view that inhibition of AT1R or activation of AT2R and Mas receptors as well as depression of oxidative stress may prevent or reverse the Ang II-induced cardiac hypertrophy.
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Angiotensina II , Cardiomegalia , Humanos , Angiotensina II/metabolismo , Cardiomegalia/metabolismo , Transdução de Sinais , Miócitos Cardíacos/metabolismo , Fibroblastos/metabolismoRESUMO
The activation of phospholipase C (PLC) is thought to have a key role in the cardiomyocyte response to several different hypertrophic agents such as norepinephrine, angiotensin II and endothelin-1. PLC activity results in the generation of diacylglycerol and inositol trisphosphate, which are downstream signal transducers for the expression of fetal genes, increased protein synthesis, and subsequent cardiomyocyte growth. In this article, we describe the signal transduction elements that regulate PLC gene expression. The discussion is focused on the norepinephrine- α1-adrenoceptor signaling pathway and downstream signaling processes that mediate an upregulation of PLC isozyme gene expression. Evidence is also indicated to demonstrate that PLC activities self-regulate the expression of PLC isozymes with the suggestion that PLC activities may be part of a coordinated signaling process for the perpetuation of cardiac hypertrophy. Accordingly, from the information provided, it is plausible that specific PLC isozymes could be targeted for the mitigation of cardiac hypertrophy.
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Isoenzimas , Fosfolipases Tipo C , Animais , Cardiomegalia/genética , Cardiomegalia/metabolismo , Expressão Gênica , Isoenzimas/metabolismo , Norepinefrina/farmacologia , Ratos , Ratos Sprague-Dawley , Fosfolipases Tipo C/metabolismo , Regulação para Cima/genéticaRESUMO
Ischemia-reperfusion (I/R) injury is well-known to be associated with impaired cardiac function, massive arrhythmias, marked alterations in cardiac metabolism and irreversible ultrastructural changes in the heart. Two major mechanisms namely oxidative stress and intracellular Ca2+-overload are considered to explain I/R-induced injury to the heart. However, it is becoming apparent that oxidative stress is the most critical pathogenic factor because it produces myocardial abnormalities directly or indirectly for the occurrence of cardiac damage. Furthermore, I/R injury has been shown to generate oxidative stress by promoting the formation of different reactive oxygen species due to defects in mitochondrial function and depressions in both endogenous antioxidant levels as well as regulatory antioxidative defense systems. It has also been demonstrated to adversely affect a wide variety of metabolic pathways and targets in cardiomyocytes, various resident structures in myocardial interstitium, as well as circulating neutrophils and leukocytes. These I/R-induced alterations in addition to myocardial inflammation may cause cell death, fibrosis, inflammation, Ca2+-handling abnormalities, activation of proteases and phospholipases, as well as subcellular remodeling and depletion of energy stores in the heart. Analysis of results from isolated hearts perfused with or without some antioxidant treatments before subjecting to I/R injury has indicated that cardiac dysfunction is associated with the development of oxidative stress, intracellular Ca2+-overload and protease activation. In addition, changes in the sarcolemma and sarcoplasmic reticulum Ca2+-handling, mitochondrial oxidative phosphorylation as well as myofibrillar Ca2+-ATPase activities in I/R hearts were attenuated by pretreatment with antioxidants. The I/R-induced alterations in cardiac function were simulated upon perfusing the hearts with oxyradical generating system or oxidant. These observations support the view that oxidative stress may be intimately involved in inducing intracellular Ca2+-overload, protease activation, subcellular remodeling, and cardiac dysfunction as a consequence of I/R injury to the heart.
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Heart failure is invariably associated with cardiac hypertrophy and impaired cardiac performance. Although several drugs have been developed to delay the progression of heart failure, none of the existing interventions have shown beneficial effects in reducing morbidity and mortality. To determine specific targets for future drug development, we have discussed different mechanisms involving both cardiomyocytes and nonmyocyte extracellular matrix (ECM)) alterations for the transition of cardiac hypertrophy to heart failure as well as for the progression of heart failure. We have emphasized the role of oxidative stress, inflammatory cytokines, metabolic alterations, and Ca2+-handling defects in adverse cardiac remodeling and heart dysfunction in hypertrophied myocardium. Alterations in the regulatory process due to several protein kinases, as well as the participation of mitochondrial Ca2+ overload, activation of proteases and phospholipases, and changes in gene expression for subcellular remodeling have also been described for the occurrence of cardiac dysfunction. Association of cardiac arrhythmia with heart failure has been explained as a consequence of catecholamine oxidation products. Since these multifactorial defects in ECM and cardiomyocytes are evident in the failing heart, it is a challenge for experimental cardiologists to develop appropriate combination drug therapy for improving cardiac function in heart failure.
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Insuficiência Cardíaca , Cardiomegalia , Humanos , Miocárdio/metabolismo , Miócitos Cardíacos/metabolismo , Estresse Oxidativo , Remodelação Ventricular/fisiologiaRESUMO
The activation of the α1-adrenoceptor-(α1-AR) by norepinephrine results in the G-protein (Gqα) mediated increase in the phosphoinositide-specific phospholipase C (PLC) activity. The byproducts of PLC hydrolytic activity, namely, 1,2-diacylglycerol and inositol-1,4,5-trisphosphate, are important downstream signal transducers for increased protein synthesis in the cardiomyocyte and the subsequent hypertrophic response. In this article, evidence was outlined to demonstrate the role of cardiomyocyte PLC isozymes in the catecholamine-induced increase in protein synthesis by using a blocker of α1-AR and an inhibitor of PLC. The discussion was focused on the α1-AR-Gqα-PLC-mediated hypertrophic signalling pathway from the viewpoint that it may compliment the other ß1-AR-Gs protein-adenylyl cyclase signal transduction mechanisms in the early stages of cardiac hypertrophy development, but may become more relevant at the late stage of cardiac hypertrophy. From the information provided here, it is suggested that some specific PLC isozymes may potentially serve as important targets for the attenuation of cardiac hypertrophy in the vulnerable patient population at-risk for heart failure.
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Isoenzimas , Fosfolipases Tipo C , Adenilil Ciclases/metabolismo , Cardiomegalia/induzido quimicamente , Catecolaminas/efeitos adversos , Proteínas de Ligação ao GTP/efeitos adversos , Proteínas de Ligação ao GTP/metabolismo , Humanos , Inositol/efeitos adversos , Isoenzimas/metabolismo , Norepinefrina/farmacologia , Fosfatidilinositóis , Receptores Adrenérgicos/metabolismo , Fosfolipases Tipo C/metabolismoRESUMO
It is now well established that ischemia/reperfusion (I/R) injury is associated with the compromised recovery of cardiac contractile function. Such an adverse effect of I/R injury in the heart is attributed to the development of oxidative stress and intracellular Ca2+-overload, which are known to induce remodeling of subcellular organelles such as sarcolemma, sarcoplasmic reticulum, mitochondria and myofibrils. However, repeated episodes of brief periods of ischemia followed by reperfusion or ischemic preconditioning (IP) have been shown to improve cardiac function and exert cardioprotective actions against the adverse effects of prolonged I/R injury. This protective action of IP in attenuating myocardial damage and subcellular remodeling is likely to be due to marked reductions in the occurrence of oxidative stress and intracellular Ca2+-overload in cardiomyocytes. In addition, the beneficial actions of IP have been attributed to the depression of proteolytic activities and inflammatory levels of cytokines as well as the activation of the nuclear factor erythroid factor 2-mediated signal transduction pathway. Accordingly, this review is intended to describe some of the changes in subcellular organelles, which are induced in cardiomyocytes by I/R for the occurrence of oxidative stress and intracellular Ca2+-overload and highlight some of the mechanisms for explaining the cardioprotective effects of IP.
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Precondicionamento Isquêmico Miocárdico , Precondicionamento Isquêmico , Traumatismo por Reperfusão , Humanos , Isquemia/metabolismo , Miocárdio/metabolismo , Miócitos Cardíacos/metabolismo , Organelas , Reperfusão , Traumatismo por Reperfusão/metabolismo , Traumatismo por Reperfusão/prevenção & controleRESUMO
It is now well known that oxidative stress promotes lipid peroxidation, protein oxidation, activation of proteases, fragmentation of DNA and alteration in gene expression for producing myocardial cell damage, whereas its actions for the induction of fibrosis, necrosis and apoptosis are considered to result in the loss of cardiomyocytes in different types of heart disease. The present article is focused on the discussion concerning the generation and implications of oxidative stress from various sources such as defective mitochondrial electron transport and enzymatic reactions mainly due to the activation of NADPH oxidase, nitric oxide synthase and monoamine oxidase in diseased myocardium. Oxidative stress has been reported to promote excessive entry of Ca2+ due to increased permeability of the sarcolemmal membrane as well as depressions of Na+-K+ ATPase and Na+-Ca2+ exchange systems, which are considered to increase the intracellular of Ca2+. In addition, marked changes in the ryanodine receptors and Ca2+-pump ATPase have been shown to cause Ca2+-release and depress Ca2+ accumulation in the sarcoplasmic reticulum as a consequence of oxidative stress. Such alterations in sarcolemma and sarcoplasmic reticulum are considered to cause Ca2+-handling abnormalities, which are associated with mitochondrial Ca2+-overload and loss of myofibrillar Ca2+-sensitivity due to oxidative stress. Information regarding the direct effects of different oxyradicals and oxidants on subcellular organelles has also been outlined to show the mechanisms by which oxidative stress may induce Ca2+-handling abnormalities. These observations support the view that oxidative stress plays an important role in the genesis of subcellular defects and cardiac dysfunction in heart disease.
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Extensive research work has been carried out to define the exact significance and contribution of regulated necrosis-like cell death program, such as necroptosis to cardiac ischemic injury. This cell damaging process plays a critical role in the pathomechanisms of myocardial infarction (MI) and post-infarction heart failure (HF). Accordingly, it has been documented that the modulation of key molecules of the canonical signaling pathway of necroptosis, involving receptor-interacting protein kinases (RIP1 and RIP3) as well as mixed lineage kinase domain-like pseudokinase (MLKL), elicit cardioprotective effects. This is evidenced by the reduction of the MI-induced infarct size, alleviation of myocardial dysfunction, and adverse cardiac remodeling. In addition to this molecular signaling of necroptosis, the non-canonical pathway, involving Ca2+/calmodulin-dependent protein kinase II (CaMKII)-mediated regulation of mitochondrial permeability transition pore (mPTP) opening, and phosphoglycerate mutase 5 (PGAM5)-dynamin-related protein 1 (Drp-1)-induced mitochondrial fission, has recently been linked to ischemic heart injury. Since MI and HF are characterized by an imbalance between reactive oxygen species production and degradation as well as the occurrence of necroptosis in the heart, it is likely that oxidative stress (OS) may be involved in the mechanisms of this cell death program for inducing cardiac damage. In this review, therefore, several observations from different studies are presented to support this paradigm linking cardiac OS, the canonical and non-canonical pathways of necroptosis, and ischemia-induced injury. It is concluded that a multiple therapeutic approach targeting some specific changes in OS and necroptosis may be beneficial in improving the treatment of ischemic heart disease.
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By virtue of their regulatory role in various metabolic and biosynthetic pathways for energy status and cellular integrity, both hydro-soluble and lipo-soluble vitamins are considered to be involved in maintaining cardiovascular function in health and disease. Deficiency of some vitamins such as vitamin A, B6, folic acid, C, D, and E has been shown to be associated with cardiovascular abnormalities whereas supplementation with these vitamins has been claimed to reduce cardiovascular risk for hypertension, atherosclerosis, myocardial ischemia, arrhythmias, and heart failure. However, the data from several experimental and clinical studies for the pathogenesis of cardiovascular disease due to vitamin deficiency as well as therapy due to different vitamins are conflicting. In this article, we have attempted to review the existing literature on the role of different vitamins in cardiovascular disease with respect to their deficiency and supplementation in addition to examining some issues regarding their involvement in heart disease. Although both epidemiological and observational studies have shown some merit in the use of different antioxidant vitamins for the treatment of cardiovascular disorders, the results are not conclusive. Furthermore, in view of the complexities in the mechanisms of different cardiovascular disorders, no apparent involvement of any particular vitamin was seen in any specific cardiovascular disease. On the other hand, we have reviewed the evidence that deficiency of vitamin B6 promoted KCl-induced Ca2+ entry and reduced ATP-induced Ca2+-entry in cardiomyocytes in addition to decreasing sarcolemmal (SL) ATP binding. The active metabolite of vitamin B6, pyridoxal 5'-phosphate, attenuated arrhythmias due to myocardial infarction (MI) as well as cardiac dysfunction and defects in the sarcoplasmic reticulum (SR) Ca2+-transport in the ischemic-reperfused hearts. These observations indicate that both deficiency of some vitamins as well as pretreatments with different vitamins showing antioxidant activity affect cardiac function, metabolism and cation transport, and support the view that antioxidant vitamins or their metabolites may be involved in the prevention rather than the therapy of cardiovascular disease.
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Although heart failure due to a wide variety of pathological stimuli including myocardial infarction, pressure overload and volume overload is associated with cardiac hypertrophy, the exact reasons for the transition of cardiac hypertrophy to heart failure are not well defined. Since circulating levels of several vasoactive hormones including catecholamines, angiotensin II, and endothelins are elevated under pathological conditions, it has been suggested that these vasoactive hormones may be involved in the development of both cardiac hypertrophy and heart failure. At initial stages of pathological stimuli, these hormones induce an increase in ventricular wall tension by acting through their respective receptor-mediated signal transduction systems and result in the development of cardiac hypertrophy. Some oxyradicals formed at initial stages are also involved in the redox-dependent activation of the hypertrophic process but these are rapidly removed by increased content of antioxidants in hypertrophied heart. In fact, cardiac hypertrophy is considered to be an adaptive process as it exhibits either normal or augmented cardiac function for maintaining cardiovascular homeostasis. However, exposure of a hypertrophied heart to elevated levels of circulating hormones due to pathological stimuli over a prolonged period results in cardiac dysfunction and development of heart failure involving a complex set of mechanisms. It has been demonstrated that different cardiovascular abnormalities such as functional hypoxia, metabolic derangements, uncoupling of mitochondrial electron transport, and inflammation produce oxidative stress in the hypertrophied failing hearts. In addition, oxidation of catecholamines by monoamine oxidase as well as NADPH oxidase activation by angiotensin II and endothelin promote the generation of oxidative stress during the prolonged period by these pathological stimuli. It is noteworthy that oxidative stress is known to activate metallomatrix proteases and degrade the extracellular matrix proteins for the induction of cardiac remodeling and heart dysfunction. Furthermore, oxidative stress has been shown to induce subcellular remodeling and Ca2+-handling abnormalities as well as loss of cardiomyocytes due to the development of apoptosis, necrosis, and fibrosis. These observations support the view that a low amount of oxyradical formation for a brief period may activate redox-sensitive mechanisms, which are associated with the development of cardiac hypertrophy. On the other hand, high levels of oxyradicals over a prolonged period may induce oxidative stress and cause Ca2+-handling defects as well as protease activation and thus play a critical role in the development of adverse cardiac remodeling and cardiac dysfunction as well as progression of heart failure.