Current Cardiology Reviews - Volume 6, Issue 4, 2010

Overwhelming evidence exists in the literature to support the role of reactive oxygen species (ROS) as intracellular signaling molecules. Several degenerative diseases including coronary heart disease, have been linked with the overproduction of ROS. Many coronary heart diseases including ischemic heart disease cause cardiomyocytes to face conditions that shift their redox status to undergo a drastic change subjecting them to oxidative stress. Cardiomyocytes contain enzymes that constantly generate ROS and intracellular redox buffer in response to a specific stress developed from the dsease process. Depending on the amount of antioxidant reserve, ROS is either destroyed or persist. If ROS is overwhelming, they destroy cells, but on the other hand, if ROS activity if minimal, they may function as signaling molecules and function as savior rather than destroyer. The intention of this minireview series is to provide evidence that ROS indeed function as signaling molecules and serve to protect the cardiac cells against the disease. The review by Madhu Anand Srivastava, Professor of Physiology at the University of Montreal, Canada, entitled Modulation of Gi proteins in Hypertension: Role of Angiotensin II and Oxidative stress is an excellent example how hypertension is controlled by ROS and redox signalling. The enhanced or unaltered levels of inhibitory guanine nucleotide regulatory troteins (G-proteins - Giα-2 and Giα-3) and mRNA have been reported in different models of hypertension, whereas Gsα levels were shown to be unaltered. These changes in G-protein expression were associated with Gi functions. The enhanced levels of Giα proteins precede the development of blood pressure and suggest that overexpression of Gi proteins may be one of the contributing factors for the pathogenesis of hypertension. Enhanced oxidative stress in hypertension due to Angiotensin II is responsible for the enhanced expression of Giα proteins observed in hypertension. The review discusses the mechanism by which oxidative stress enhances the expression of Gi proteins through the activation of mitogen activated protein (MAP) kinase activity. The next article by Professor Lindsay Brown from the University of Queensland, Brisbane, Australia describes how a redox sensitive polyphenolic compound resveratrol improves cardiova-scular function in DOCA-salt hypertensive rats. This study has determined whether treatment with resveratrol prevented cardiac fibrosis and the decreased cardiovascular function in the DOCA-salt hypertensive rat as a model of human hypertension. In these DOCA-salt rats, resveratrol decreased inflammatory cell infiltration, decreased cardiac fibrosis (left ventricular interstitial and perivascular collagen content) and improved cardiac and vascular function. Resveratrol attenuated other features of cardiovascular remodelling such as increases in systolic blood pressure, left ventricular wet weight, left ventricular wall thickness, diastolic stiffness constant, as well as decreased cardiac contractility and prolonged action potential duration characteristic of DOCA-salt rats. In summary, the redox-sensitive compound resveratrol, at a nutritionally relevant dose, prevents or attenuates the adverse changes in the cardiovascular system. We propose that the anti-inflammatory and anti-fibrotic effects of resveratrol are responsible, at least in part, for its amelioration in cardiovascular remodelling in DOCA-salt rats. Next, Professor Shyamal Goswami and Dipak K Das from the University of Connecticut School of Medicine, Farmington, Connecticut, USA describes the role of HIF-1a and oxygen sensing in cardiac ischemia. Although our knowledge of the biochemistry and physiology of oxygen transport is century old, recent development of sophisticated tools of biophysical chemistry revealed that tissue oxygenation and oxygen sensing is a highly evolved process, especially in mammals. Perturbation of normal oxygen supply is associated with diseases like tumorigenesis, myocardial infarction and stroke. Available information suggests that when tissue oxygen supply is limited, mitochondria emanate signals involving reactive oxygen species generation which in turn stabilizes oxygen sensing transcription factor HIF-1. Upon stabilization, HIF-1 elicits necessary genetic response to cope with the diminished oxygen level. In view of such critical role of HIF-1 in cellular oxygen sensing, recently there has been a heightened interest in understanding the biology of HIF-1 in the context of cardiovascular system. Naranjan S. Dhalla, distinguished professor of the university of Manitoba, Winnipeg, Canada described how state-of-the-art technique of cardioprotection leads to subcellular remodelling through redox signaling. Cardiac function is compromised by oxidative stress which occurs upon exposing the heart to ischemia reperfusion (I/R) for a prolonged period. The reactive oxygen species (ROS) that are generated during I/R incur extensive damage to the myocardium and result in subcellular organelle remodeling. The cardiac nucleus, glycocalyx, myofilaments, sarcoplasmic reticulum, sarcolemma, and mitochondria are affected by ROS during I/R injury. On the other hand, brief periods of ischemia followed by reperfusion, or ischemic preconditioning (IPC), has been shown to be cardioprotective against oxidative stress by attenuating the cellular damage and alterations of subcellular organelles caused by subsequent I/R injury also occur in IPC. Endogenous defense mechanisms, such as antioxidant enzymes and heat shock proteins, are activated by IPC and thus prevent damage caused by oxidative stress. Although these cardioprotective effects of IPC against I/R injury are considered to be a consequence of changes in the redox state of cardiomyocytes, IPC is considered to promote the production of NO which may protect subcellular organelles from the deleterious actions of oxidative stress. The actions of various endogenous cardioprotective interventions are discussed to illustrate that changes in the redox state due to IPC are cardioprotective against I/R injury to the heart. In a highly original paper, Professor Hannah Vasanthi and Rajamanickam from the Advanced Research in Indian System of Medicine, SASTRA University, and Sri Ramachandra Medical College and Research Institute, Sri Ramachandra University, Tamilnadu, India, describe how a flavonoid rich fraction (FRF) of Dioscorea bulbifera Linn. (Yam) enhances mitochondrial enzymes and antioxidant status and thereby protects heart from isoproterenol induced myocardial infarction. FRF when intervened for a period of 35 days prior to isoproterenol (ISO) challenge to rats, alterations in the antioxidant status in the mitochondria were recognized in the heart tissue of ISO induced rats. ISO induced rats pretreated with FRF ameliorated the lipid peroxidation and thereby enhanced the antioxidant status as evidenced by the increase in the reduced glutathione (GSH) content and the activity of antioxidant enzymes. Moreover, the tricarboxylic acid cycle enzymes such isocitrate dehydrogenase (ICDH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH) and α-ketoglutarate dehydrogenase (α-KGDH), which were found decreased in the ISO induced rats showed an enhanced activity in FRF pretreated rats. The activity of NADH dehydrogenase and cytochrome-C-oxidase the enzymes, which transfer the electron in the electron transport chain (ETC) was also increased significantly (p<0.05) in FRF (150 mg/kg) pretreated rats, when compared with ISO induced rats. These results suggest the cardioprotective effect of FRF of Dioscorea bulbifera Linn. in ISO induced MI by attenuating the lipid peroxidation by scavenging free radicals and modulating the energy producing mitochondrial enzymes. Professor Nesrin Kartal Ozer from the Marmara University,Haydarpasa, Turkey, describes role of lipid rafts and redox signaling in cholesterol induced atherosclerosis. Kenichi Watanabe, M.D., Ph.D. professor of Clinical Pharmacology at the Nigata University, Nigata, Japan, described the role of different signaling pathways and oxidative stress in diabetic cardiomyopathy. Finally, Professor Asok Srivastava from the Department of Medicine, University of Montreal, Qubec, Canada, in a highly original paper, describes how a potent vasoconstrictor, endothelin-1, induces redox signaling through nitric oxide/cGMP system in vascular smooth muscle cells. These reviews and original papers demonstrate that low physiologically relevant concentration of ROS can regulate a variety of key molecular mechanisms. Cardiovascular diseases cause redox changes in various heart cells. The molecular implications of such change are not fully characterized. The eight component articles of this minireview series discuss various aspects of cardiac diseases regulated by redox signaling.

Nitric oxide (NO) is an important vasoprotective molecule that serves not only as a vasodilator but also exerts antihypertrophic and antiproliferative effects in vascular smooth muscle cells (VSMC). The precise mechanism by which the antihypertrophic and antiproliferative responses of NO are mediated remains obscure. However, recent studies have suggested that one of the mechanisms by which this may be achieved includes the attenuation of signal transduction pathways responsible for inducing the hypertrophic and proliferative program in VSMC. Endothelin-1 is a powerful vasoconstrictor peptide with mitogenic and growth stimulatory properties and exerts its effects by activating multiple signaling pathways which include ERK 1/2, PKB and Rho-ROCK. Both cGMP-dependent and independent events have been reported to mediate the effect of NO on these pathways leading to its vasoprotective response. This review briefly summarizes some key studies on the modulatory effect of NO on these signaling pathways and discusses the possible role of cGMP system in this process.

Cardiac function is compromised by oxidative stress which occurs upon exposing the heart to ischemia reperfusion (I/R) for a prolonged period. The reactive oxygen species (ROS) that are generated during I/R incur extensive damage to the myocardium and result in subcellular organelle remodeling. The cardiac nucleus, glycocalyx, myofilaments, sarcoplasmic reticulum, sarcolemma, and mitochondria are affected by ROS during I/R injury. On the other hand, brief periods of ischemia followed by reperfusion, or ischemic preconditioning (IPC), have been shown to be cardioprotective against oxidative stress by attenuating the cellular damage and alterations of subcellular organelles caused by subsequent I/R injury. Endogenous defense mechanisms, such as antioxidant enzymes and heat shock proteins, are activated by IPC and thus prevent damage caused by oxidative stress. Although these cardioprotective effects of IPC against I/R injury are considered to be a consequence of changes in the redox state of cardiomyocytes, IPC is considered to promote the production of NO which may protect subcellular organelles from the deleterious actions of oxidative stress. The article is intended to focus on the I/R-induced oxidative damage to subcellular organelles and to highlight the cardioprotective effects of IPC. In addition, the actions of various endogenous cardioprotective interventions are discussed to illustrate that changes in the redox state due to IPC are cardioprotective against I/R injury to the heart.

Oxygen plays a critical role in the perpetuation and propagation of almost all forms of life. The primary site of cellular oxygen consumption is the mitochondrial electron transport chain and in addition, oxygen is also used as a substrate for various enzymes involved in cellular homeostasis. Although our knowledge of the biochemistry and physiology of oxygen transport is century old, recent development of sophisticated tools of biophysical chemistry revealed that tissue oxygenation and oxygen sensing is a highly evolved process, especially in mammals. Perturbation of normal oxygen supply is associated with diseases like tumorigenesis, myocardial infarction and stroke. Available information suggests that when tissue oxygen supply is limited, mitochondria emanate signals involving reactive oxygen species generation which in turn stabilizes oxygen sensing transcription factor HIF-1. Upon stabilization, HIF-1 elicits necessary genetic response to cope with the diminished oxygen level. In view of such critical role of HIF-1 in cellular oxygen sensing, recently there has been a heightened interest in understanding the biology of HIF-1 in the context of cardiovascular system. The following review describes some of the recent advances in this regard.

Spices were some of the most valuable items of trade in the ancient and medieval world. Herbalist and folk practitioners have used plant remedies for centuries, but only recently have scientist begun to study the powers of common herbs and spices. In the current set-up, the anti-proliferative, anti-hypercholesterolemic, anti-diabetic, antiinflammatory effects of spices have overriding importance, as the key health concern of mankind nowadays is diabetes, cardio-vascular diseases, arthritis and cancer. Spices or their active compounds could be used as possible ameliorative or preventive agents for these health disorders. Spices are rich in antioxidants, and scientific studies suggest that they are also potent inhibitors of tissue damage and inflammation caused by high levels of blood sugar and circulating lipids. Because spices have very low calorie content and are relatively inexpensive, they are reliable sources of antioxidants and other potential bioactive compounds in diet. This review outlines the role of some spices used in the Indian kitchen for its flavour and taste which are potential to maintain a healthy heart.

Diabetes mellitus increases the risk of heart failure independently of underlying coronary artery disease, and many believe that diabetes leads to cardiomyopathy. The underlying pathogenesis is partially understood. Several factors may contribute to the development of cardiac dysfunction in the absence of coronary artery disease in diabetes mellitus. There is growing evidence that excess generation of highly reactive free radicals, largely due to hyperglycemia, causes oxidative stress, which further exacerbates the development and progression of diabetes and its complications. Hyperglycemia- induced oxidative stress is a major risk factor for the development of micro-vascular pathogenesis in the diabetic myocardium, which results in myocardial cell death, hypertrophy, fibrosis, abnormalities of calcium homeostasis and endothelial dysfunction. Diabetes-mediated biochemical changes show cross-interaction and complex interplay culminating in the activation of several intracellular signaling molecules. Diabetic cardiomyopathy is characterized by morphologic and structural changes in the myocardium and coronary vasculature mediated by the activation of various signaling pathways. This review focuses on the oxidative stress and signaling pathways in the pathogenesis of the cardiovascular complications of diabetes, which underlie the development and progression of diabetic cardiomyopathy.

Oxidative stress and inflammation are two sides of the same coin that are intricately combined to elicit a chronic pathophysiological stress state, especially as seen in cardiovascular remodelling. In this review, we argue that administration of deoxycorticosterone acetate (DOCA) and sodium chloride to uninephrectomised rats, defined as DOCA-salt hypertensive rats, provides a reliable animal model of oxidative and inflammatory stress in the cardiovascular system. The supporting evidence includes pathophysiological and biochemical changes together with pharmacological responses to synthetic and natural compounds that lower the concentrations of reactive free radical species and that curtail inflammatory responses in the cardiovascular system.

Guanine nucleotide regulatory proteins (G-proteins) play a key role in the regulation of various signal transduction systems including adenylyl cyclase/cAMP and phospholipase C (PLC)/phosphatidyl inositol turnover (PI). These are implicated in the modulation of a variety of physiological functions such as platelet functions, cardiovascular functions, including arterial tone and reactivity. Several abnormalities in adenylyl cyclase activity, cAMP levels and G proteins have shown to be responsible for the altered cardiac performance and vascular functions observed in cardiovascular disease states. The enhanced or unaltered levels of inhibitory G-proteins (Giα-2 and Giα-3) and mRNA have been reported in different models of hypertension, whereas Gsα levels were shown to be unaltered. These changes in G-protein expression were associated with Gi functions. The enhanced levels of Giα proteins precede the development of blood pressure and suggest that overexpression of Gi proteins may be one of the contributing factors for the pathogenesis of hypertension. The augmented levels of vasoactive peptides, including angiotensin II (AngII), were shown to contribute to enhanced expression of Giα proteins and associated adenylyl cyclase signaling and thereby increased blood pressure. In addition, enhanced oxidative stress in hypertension due to Ang II may also be responsible for the enhanced expression of Giα proteins observed in hypertension. The mechanism by which oxidative stress enhances the expression of Gi proteins appears to be through the activation of mitogen activated protein (MAP) kinase activity.

Redox mediated signaling mechanisms play crucial roles in the pathogenesis of several cardiovascular diseases. Atherosclerosis is one of the most important disorders induced mainly by hypercholesterolemia. Oxidation products and related signaling mechanisms are found within the characteristic biomarkers of atherosclerosis. Several studies have shown that redox signaling via lipid rafts play a significant role in the regulation of pathogenesis of many diseases including atherosclerosis. This review attempts to summarize redox signaling and lipid rafts in hypercholesterolemia induced atherosclerosis.

Blood coagulation is a complex biological mechanism aimed to avoid bleeding in which a highly regulated and coordinated interplay of specific proteins and cellular components respond quickly to a vascular injury. However, when this mechanisms occurs in the coronary circulation, it has not a “protective” effect, but rather, it plays a pivotal role in determining acute coronary syndromes. Coagulation recognizes Tissue Factor (TF), the main physiological initiator of the extrinsic coagulation pathway, as its starter. Since TF:VIIa complex is the critical point of the blood coagulation cascade, it is a pharmacological attractive issue for the development of agents with anti thrombotic properties that can exert their activity by inhibiting complex formation and/or its catalytic activity. In fact, it is intuitive that an antithrombotic agent able to inhibit this initial step of the coagulation pathway has several theoretical, extremely important, advantages if compared with drugs active downstream the coagulation pathway, such as FXa or thrombin. The present report gives a brief overview of TF pathophysiology, highlighting the most recent advances in the field of inhibitors of the complex TF/VIIa potentially useful in cardiovascular disease.

Diabetes mellitus is associated with well-known increases in cardiovascular morbidity and mortality. In diabetics with stable coronary artery disease, the best therapeutic option is widely discussed. Current studies comparing surgical to percutaneous revascularization have been unable to definitely demonstrate any significant advantage of one strategy over the other regarding the prevention of cardiac death or acute myocardial infarction. Therefore, even taking into account clinical and angiographic information as well as the risks determined by each type of treatment, the decision regarding the best therapeutic strategy in diabetics with stable coronary artery disease is still complex.

Adenosine monophosphate - activated kinase (AMPK) plays a key role in the coordination of the heart's anabolic and catabolic pathways. It induces a cellular cascade at the center of maintaining energy homeostasis in the cardiomyocytes.. The activated AMPK is a heterotrimeric protein, separated into a catalytic α- subunit (63kDa), a regulating β - subunit (38kDa) and a γ- subunit (38kDa), which is allosterically adjusted by adenosine triphosphate (ATP) and adenosine monophosphate (AMP). The actual binding of AMP to the γ- subunit is the step which activates AMPK. AMPK serves also as a protein kinase in several metabolic pathways of the heart, including cellular energy sensoring or cardiovascular protection. The AMPK cascade represents a sensitive system, activated by cellular stresses that deplete ATP and acts as an indicator of intracellular ATP/AMP. In the context of cellular stressors (i.e. hypoxia, pressure overload, hypertrophy or ATP deficiency) the increasing levels of AMP promote allosteric activation and phosphorylation of AMPK. As the concentration of AMP begins to increase, ATP competitively inhibits further phosphorylation of AMPK. The increase of AMP may also be induced either from an iatrogenic emboli, percutaneous coronary intervention, or from atherosclerotic plaque rupture leading to an ischemia in the microcirculation. To modulate energy metabolism by phosphorylation and dephosphorylation is vital in terms of ATP usage, maintaining transmembrane transporters and preserving membrane potential. In this article, we review AMPK and its role as an important regulatory enzyme during periods of myocardial stress, regulating energy metabolism, protein synthesis and cardiovascular protection.

Eisenmenger syndrome is the most severe form of pulmonary arterial hypertension and arises on the basis of congenital heart disease with a systemic-to-pulmonary shunt. Due to the chronic slow progressive hypoxemia with central cyanosis, adult patients with the Eisenmenger syndrome suffer from a complex and multisystemic disorder including coagulation disorders (bleeding complications and paradoxical embolisms), renal dysfunction, hypertrophic osteoarthropathy, heart failure, reduced quality of life and premature death. For a long time, therapy has been limited to symptomatic options or lung or combined heart-lung transplantation. As new selective pulmonary vasodilators have become available and proven to be beneficial in various forms of pulmonary arterial hypertension, this targeted medical treatment has been expected to show promising effects with a delay of deterioration also in Eisenmenger patients. Unfortunately, data in Eisenmenger patients suffer from small patient numbers and a lack of randomized controlled studies. To optimize the quality of life and the outcome, referral of Eisenmenger patients to spezialized centers is required. In such centers, specific interdisciplinary management strategies of physicians specialized on congenital heart diseases and PAH should be warranted. This medical update emphasizes the current diagnostic and therapeutic options for Eisenmenger patients with particularly focussing on epidemiology, clinical aspects and specific diagnostic options.

Eisenmenger syndrome is the most severe form of pulmonary arterial hypertension and arises on the basis of congenital heart disease with a systemic-to-pulmonary shunt. Due to the chronic slow progressive hypoxemia with central cyanosis, adult patients with the Eisenmenger syndrome suffer from a complex and multisystemic disorder including coagulation disorders (bleeding complications and paradoxical embolisms), renal dysfunction, hypertrophic osteoarthropathy, heart failure, reduced quality of life and premature death. For a long time, therapy has been limited to symptomatic options or lung or combined heart-lung transplantation. As new selective pulmonary vasodilators have become available and proven to be beneficial in various forms of pulmonary arterial hypertension, this targeted medical treatment has been expected to show promising effects with a delay of deterioration also in Eisenmenger patients. Unfortunately, data in Eisenmenger patients suffer from small patient numbers and a lack of randomized controlled studies. To optimize the quality of life and the outcome, referral of Eisenmenger patients to spezialized centers is required. In such centers, specific interdisciplinary management strategies of physicians specialized on congenital heart diseases and PAH should be warranted. This medical update emphasizes the current diagnostic and therapeutic options for Eisenmenger patients with particularly focussing on the medical treatment and corresponding study results.

Eisenmenger syndrome is the most severe form of pulmonary arterial hypertension and arises on the basis of congenital heart disease with a systemic-to-pulmonary shunt. Due to the chronic slow progressive hypoxemia with central cyanosis, adult patients with the Eisenmenger syndrome suffer from a complex and multisystemic disorder including coagulation disorders (bleeding complications and paradoxical embolisms), renal dysfunction, hypertrophic osteoarthropathy, heart failure, reduced quality of life and premature death. For a long time, therapy has been limited to symptomatic options or lung or combined heart-lung transplantation. As new selective pulmonary vasodilators have become available and proven to be beneficial in various forms of pulmonary arterial hypertension, this targeted medical treatment has been expected to show promising effects with a delay of deterioration also in Eisenmenger patients. Unfortunately, data in Eisenmenger patients suffer from small patient numbers and a lack of randomized controlled studies. To optimize the quality of life and the outcome, referral of Eisenmenger patients to spezialized centers is required. In such centers, specific interdisciplinary management strategies of physicians specialized on congenital heart diseases and PAH should be warranted. This medical update emphasizes the current diagnostic and therapeutic options for Eisenmenger patients with particularly focussing on specific management and surgical aspects.

This is with reference to the article entitled, “ Assessment of the Spatial QRS-T Angle by Vectorcardiography: Current Data and Perspectives” , by Christina Voulgari and Nicholas Tentolouris published in Current Cardiology Reviews Journal, November 2009, Vol. 5, No. 4, pp. 251-62. The authors have overlooked to cite the paper entitled, “ Elucidation of the spatial ventricular gradient and its link with dispersion of repolarization” , by Draisma HH, Schalij MJ, van der Wall EE, Swenne CA published in Heart Rhythm Journal, 2006, Vol. 3, No. 9, pp. 1092-9 in the above mentioned article.