Reactive oxygen species modulate angiotensin II-induced beta-myosin heavy chain gene expression via Ras/Raf/extracellular signal-regulated kinase pathway in neonatal rat cardiomyocytes

Calorie restriction anti-hypertrophic effects are associated with improved mitochondrial content, blockage of Ca2+-induced mitochondrial damage, and lower reverse electron transport-mediated oxidative stress

Calorie restriction is a nutritional intervention that reproducibly protects against the maladaptive consequences of cardiovascular diseases. Pathological cardiac hypertrophy leads to cellular growth, dysfunction (with mitochondrial dysregulation), and oxidative stress. The mechanisms behind the cardiovascular protective effects of calorie restriction are still under investigation. In this study, we show that this dietetic intervention prevents cardiac protein elevation, avoids fetal gene reprogramming (atrial natriuretic peptide), and blocks the increase in heart weight per tibia length index (HW/TL) seen in isoproterenol-induced cardiac hypertrophy. Our findings suggest that calorie restriction inhibits cardiac pathological growth while also lowering mitochondrial reverse electron transport-induced hydrogen peroxide formation and improving mitochondrial content. Calorie restriction also attenuated the opening of the Ca2+-induced mitochondrial permeability transition pore. We also found that calorie restriction blocked the negative correlation of antioxidant enzymes (superoxide dimutase and glutatione peroxidase activity) and HW/TL, leading to the maintenance of protein sulphydryls and glutathione levels. Given the nature of isoproterenol-induced cardiac hypertrophy, we investigated whether calorie restriction could alter cardiac beta-adrenergic sensitivity. Using isolated rat hearts in a Langendorff system, we found that calorie restricted hearts have preserved beta-adrenergic signaling. In contrast, hypertrophic hearts (treated for seven days with isoproterenol) were insensitive to beta-adrenergic activation using isoproterenol (50 nM). Despite protecting against cardiac hypertrophy, calorie restriction did not alter the lack of responsiveness to isoproterenol in isolated hearts harvested from isoproterenol-treated rats. These results suggest (through a series of mitochondrial, oxidative stress, and cardiac hemodynamic studies) that calorie restriction possesses beneficial effects against hypertrophic cardiomyopathy.

Doxorubicin conjugates: a practical approach for its cardiotoxicity alleviation

INTRODUCTION

Doxorubicin (DOX) emerges as a cornerstone in the arsenal of potent chemotherapeutic agents. Yet, the clinical deployment of DOX is tarnished by its proclivity to induce severe cardiotoxic effects, culminating in heart failure and other consequential morbidities. In response, a panoply of strategies has undergone rigorous exploration over recent decades, all aimed at attenuating DOX's cardiotoxic impact. The advent of encapsulating DOX within lipidic or polymeric nanocarriers has yielded a dual triumph, augmenting DOX's therapeutic efficacy while mitigating its deleterious side effects.

AREAS COVERED

Recent strides have spotlighted the emergence of DOX conjugates as particularly auspicious avenues for ameliorating DOX-induced cardiotoxicity. These conjugates entail the fusion of DOX through physical or chemical bonds with diminutive natural or synthetic moieties, polymers, biomolecules, and nanoparticles. This spectrum encompasses interventions that impinge upon DOX's cardiotoxic mechanism, modulate cellular uptake and localization, confer antioxidative properties, or refine cellular targeting.

EXPERT OPINION

The endorsement of DOX conjugates as a compelling stratagem to mitigate DOX-induced cardiotoxicity resounds from this exegesis, amplifying safety margins and the therapeutic profile of this venerated chemotherapeutic agent. Within this ambit, DOX conjugates stand as a beacon of promise in the perpetual pursuit of refining chemotherapy-induced cardiac compromise.

The Impact of Exercise on Redox Equilibrium in Cardiovascular Diseases

Cardiovascular diseases constitute the most important public health problem in the world. They are characterized by inflammation and oxidative stress in the heart and blood. Physical activity is recognized as one of the best ways to prevent these diseases, and it has already been applied in treatment. Physical exercise, both aerobic and anaerobic and single and multiple, is linked to the oxidant–antioxidant imbalance; however, this leads to positive adaptive changes in, among others, the increase in antioxidant capacity. The goal of the paper was to discuss the issue of redox equilibrium in the human organism in the course of cardiovascular diseases to systemize updated knowledge in the context of exercise impacts on the organism. Antioxidant supplementation is also an important issue since antioxidant supplements still have great potential regarding their use as drugs in these diseases.

Oxidative stress - Complex pathological issues concerning the hallmark of cardiovascular and metabolic disorders

Oxidative stress is a complex biological process characterized by the excessive production of reactive oxygen species (ROS) that act as destroyers of the REDOX balance in the body and, implicitly, inducing oxidative damage. All the metabolisms are impaired in oxidative stress and even nucleic acid balance is influenced. ROS will promote structural changes of the tissues and organs due to interaction with proteins and phospholipids. The constellation of the cardiovascular risk factors (CVRFs) will usually develop in subjects with predisposition to cardiac disorders. Oxidative stress is usually related with hypertension (HTN), diabetes mellitus (DM), obesity and cardiovascular diseases (CVDs) like coronary artery disease (CAD), cardiomyopathy or heart failure (HF), that can develop in subjects with the above-mentioned diseases. Elements describing the complex relationship between CVD and oxidative stress should be properly explored and described because prevention may be the optimal approach. Our paper aims to expose in detail the complex physiopathology of oxidative stress in CVD occurrence and novelties regarding the phenomenon. Biomarkers assessing oxidative stress or therapy targeting specific pathways represent a major progress that actually change the outcome of subjects with CVD. New antioxidants therapy specific for each CVD represents a captivating and interesting future perspective with tremendous benefits on subject's outcome.

Modulation of Reactive Oxygen Species Homeostasis as a Pleiotropic Effect of Commonly Used Drugs

Age-associated diseases represent a growing burden for global health systems in our aging society. Consequently, we urgently need innovative strategies to counteract these pathological disturbances. Overwhelming generation of reactive oxygen species (ROS) is associated with age-related damage, leading to cellular dysfunction and, ultimately, diseases. However, low-dose ROS act as crucial signaling molecules and inducers of a vaccination-like response to boost antioxidant defense mechanisms, known as mitohormesis. Consequently, modulation of ROS homeostasis by nutrition, exercise, or pharmacological interventions is critical in aging. Numerous nutrients and approved drugs exhibit pleiotropic effects on ROS homeostasis. In the current review, we provide an overview of drugs affecting ROS generation and ROS detoxification and evaluate the potential of these effects to counteract the development and progression of age-related diseases. In case of inflammation-related dysfunctions, cardiovascular- and neurodegenerative diseases, it might be essential to strengthen antioxidant defense mechanisms in advance by low ROS level rises to boost the individual ROS defense mechanisms. In contrast, induction of overwhelming ROS production might be helpful to fight pathogens and kill cancer cells. While we outline the potential of ROS manipulation to counteract age-related dysfunction and diseases, we also raise the question about the proper intervention time and dosage.

The Oxidative Balance Orchestrates the Main Keystones of the Functional Activity of Cardiomyocytes

This review is aimed at providing an overview of the key hallmarks of cardiomyocytes in physiological and pathological conditions. The main feature of cardiac tissue is the force generation through contraction. This process requires a conspicuous energy demand and therefore an active metabolism. The cardiac tissue is rich of mitochondria, the powerhouses in cells. These organelles, producing ATP, are also the main sources of ROS whose altered handling can cause their accumulation and therefore triggers detrimental effects on mitochondria themselves and other cell components thus leading to apoptosis and cardiac diseases. This review highlights the metabolic aspects of cardiomyocytes and wanders through the main systems of these cells: (a) the unique structural organization (such as different protein complexes represented by contractile, regulatory, and structural proteins); (b) the homeostasis of intracellular Ca²⁺ that represents a crucial ion for cardiac functions and E-C coupling; and (c) the balance of Zn²⁺, an ion with a crucial impact on the cardiovascular system. Although each system seems to be independent and finely controlled, the contractile proteins, intracellular Ca²⁺ homeostasis, and intracellular Zn²⁺ signals are strongly linked to each other by the intracellular ROS management in a fascinating way to form a "functional tetrad" which ensures the proper functioning of the myocardium. Nevertheless, if ROS balance is not properly handled, one or more of these components could be altered resulting in deleterious effects leading to an unbalance of this "tetrad" and promoting cardiovascular diseases. In conclusion, this "functional tetrad" is proposed as a complex network that communicates continuously in the cardiomyocytes and can drive the switch from physiological to pathological conditions in the heart.

Oxidative Stress in Human Pathology and Aging: Molecular Mechanisms and Perspectives

Reactive oxygen and nitrogen species (RONS) are generated through various endogenous and exogenous processes; however, they are neutralized by enzymatic and non-enzymatic antioxidants. An imbalance between the generation and neutralization of oxidants results in the progression to oxidative stress (OS), which in turn gives rise to various diseases, disorders and aging. The characteristics of aging include the progressive loss of function in tissues and organs. The theory of aging explains that age-related functional losses are due to accumulation of reactive oxygen species (ROS), their subsequent damages and tissue deformities. Moreover, the diseases and disorders caused by OS include cardiovascular diseases [CVDs], chronic obstructive pulmonary disease, chronic kidney disease, neurodegenerative diseases and cancer. OS, induced by ROS, is neutralized by different enzymatic and non-enzymatic antioxidants and prevents cells, tissues and organs from damage. However, prolonged OS decreases the content of antioxidant status of cells by reducing the activities of reductants and antioxidative enzymes and gives rise to different pathological conditions. Therefore, the aim of the present review is to discuss the mechanism of ROS-induced OS signaling and their age-associated complications mediated through their toxic manifestations in order to devise effective preventive and curative natural therapeutic remedies.

Diazoxide Modulates Cardiac Hypertrophy by Targeting H2O2 Generation and Mitochondrial Superoxide Dismutase Activity

BACKGROUND

Cardiac hypertrophy involves marked wall thickening or chamber enlargement. If sustained, this condition will lead to dysfunctional mitochondria and oxidative stress. Mitochondria have ATP-sensitive K+ channels (mitoKATP) in the inner membrane that modulate the redox status of the cell.

OBJECTIVE

We investigated the in vivo effects of mitoKATP opening on oxidative stress in isoproterenol- induced cardiac hypertrophy.

METHODS

Cardiac hypertrophy was induced in Swiss mice treated intraperitoneally with isoproterenol (ISO - 30 mg/kg/day) for 8 days. From day 4, diazoxide (DZX - 5 mg/kg/day) was used in order to open mitoKATP (a clinically relevant therapy scheme) and 5-hydroxydecanoate (5HD - 5 mg/kg/day) or glibenclamide (GLI - 3 mg/kg/day) were used as mitoKATP blockers.

RESULTS

Isoproterenol-treated mice had elevated heart weight/tibia length ratios (HW/TL). Additionally, hypertrophic hearts had elevated levels of carbonylated proteins and Thiobarbituric Acid Reactive Substances (TBARS), markers of protein and lipid oxidation. In contrast, mitoKATP opening with DZX avoided ISO effects on gross hypertrophic markers (HW/TL), carbonylated proteins and TBARS, in a manner reversed by 5HD and GLI. Moreover, DZX improved mitochondrial superoxide dismutase activity. This effect was also blocked by 5HD and GLI. Additionally, ex vivo treatment of isoproterenol- induced hypertrophic cardiac tissue with DZX decreased H2O2 production in a manner sensitive to 5HD, indicating that this drug also acutely avoids oxidative stress.

CONCLUSION

Our results suggest that diazoxide blocks oxidative stress and reverses cardiac hypertrophy. This pharmacological intervention could be a potential therapeutic strategy to prevent oxidative stress associated with cardiac hypertrophy.

ERK1/2: An Integrator of Signals That Alters Cardiac Homeostasis and Growth

Integration of cellular responses to extracellular cues is essential for cell survival and adaptation to stress. Extracellular signal-regulated kinase (ERK) 1 and 2 serve an evolutionarily conserved role for intracellular signal transduction that proved critical for cardiomyocyte homeostasis and cardiac stress responses. Considering the importance of ERK1/2 in the heart, understanding how these kinases operate in both normal and disease states is critical. Here, we review the complexity of upstream and downstream signals that govern ERK1/2-dependent regulation of cardiac structure and function. Particular emphasis is given to cardiomyocyte hypertrophy as an outcome of ERK1/2 activation regulation in the heart.

The endocrinological component and signaling pathways associated to cardiac hypertrophy

Although myocardial growth corresponds to an adaptive response to maintain cardiac contractile function, the cardiac hypertrophy is a condition that occurs in many cardiovascular diseases and typically precedes the onset of heart failure. Different endocrine factors such as thyroid hormones, insulin, insulin-like growth factor 1 (IGF-1), angiotensin II (Ang II), endothelin (ET-1), catecholamines, estrogen, among others represent important stimuli to cardiomyocyte hypertrophy. Thus, numerous endocrine disorders manifested as changes in the local environment or multiple organ systems are especially important in the context of progression from cardiac hypertrophy to heart failure. Based on that information, this review summarizes experimental findings regarding the influence of such hormones upon signalling pathways associated with cardiac hypertrophy. Understanding mechanisms through which hormones differentially regulate cardiac hypertrophy could open ways to obtain therapeutic approaches that contribute to prevent or delay the onset of heart failure related to endocrine diseases.

Improvement in cardiac function of ovariectomized rats by antioxidant tempol

A rise in heart disease incidence in women after menopause has led to investigations into the role of female sex hormones on cardiac function. Although various adverse changes in cardiac contractile function following loss of female sex hormones have been reported, a clear mechanism of action has never been characterized. In order to examine whether an elevation in oxidative stress is a major cause of cardiac contractile dysfunction after female sex hormone deprivation, cardiac functions of ovariectomized rats with and without supplementation of superoxide scavenger tempol were compared to those of sham-operated controls. Chronic deprivation of female sex hormones reduced total oxidative capacity and increased plasma carbonyl protein content. Tempol supplementation of ovariectomized rats significantly ameliorated plasma oxidative stress status. Echocardiography demonstrated a significant decrease in left ventricular ejection fraction in ovariectomized rats, which was completely prevented by tempol supplementation. Decreased myocardial contractility occurs with reduced maximum myofilament force of contraction and amplitude of transient intracellular Ca²⁺ concentration, both phenomena completely attenuated by tempol supplementation. However, tempol only partially prevented shift of heart myosin heavy chain from dominant α-to β-isoform of ovariectomized rats. Immunoblot analysis of protein carbonylation indicated that tempol supplementation significantly reduced the level of cardiac myofibrillar proteins oxidation increased in ovariectomized rat heart. Taken together, the results indicate changes of cardiac contractile machinery following loss of female sex hormones were, in part, due to an increase in oxidative stress, and antioxidant supplementation could be considered another potential prevention measure in postmenopausal women.

Systems Toxicology Approach for Testing Chemical Cardiotoxicity in Larval Zebrafish

Transcriptomic approaches can give insight into molecular mechanisms underlying chemical toxicity and are increasingly being used as part of toxicological assessments. To aid the interpretation of transcriptomic data, we have developed a systems toxicology method that relies on a computable biological network model. We created the first network model describing cardiotoxicity in zebrafish larvae-a valuable emerging model species in testing cardiotoxicity associated with drugs and chemicals. The network is based on scientific literature and represents hierarchical molecular pathways that lead from receptor activation to cardiac pathologies. To test the ability of our approach to detect cardiotoxic outcomes from transcriptomic data, we have selected three publicly available data sets that reported chemically induced heart pathologies in zebrafish larvae for five different chemicals. Network-based analysis detected cardiac perturbations for four out of five chemicals tested, for two of them using transcriptomic data collected up to 3 days before the onset of a visible phenotype. Additionally, we identified distinct molecular pathways that were activated by the different chemicals. The results demonstrate that the proposed integrational method can be used for evaluating the effects of chemicals on the zebrafish cardiac function and, together with observed cardiac apical end points, can provide a comprehensive method for connecting molecular events to organ toxicity. The computable network model is freely available and may be used to generate mechanistic hypotheses and quantifiable perturbation values from any zebrafish transcriptomic data.

The role of reactive oxygen species in myocardial redox signaling and regulation

Reactive oxygen species (ROS) are subcellular messengers in gene regulatory and signal transduction pathways. In pathological situations, ROS accumulate due to excessive production or insufficient degradation, leading to oxidative stress (OS). OS causes oxidation of DNA, membranes, cellular lipids, and proteins, impairing their normal function and leading ultimately to cell death. OS in the heart is increased in response to ischemia/reperfusion, hypertrophy, and heart failure. The concentration of ROS is determined by their rates of production and clearance by antioxidants. Increases in OS in heart failure are primarily a result of the functional uncoupling of the respiratory chain due to inactivation of complex I. However, increased ROS in the failing myocardium may also be caused by impaired antioxidant capacity, such as decreased activity of Cu/Zn superoxide dismutase (SOD) and catalase (CAT) or stimulation of enzymatic sources, including, cyclooxygenase, xanthine oxidase (XO), nitric oxide synthase, and nonphagocytic NAD(P)H oxidases (Noxs). Mitochondria are the main source of ROS during heart failure and aging. Increased production of ROS in the failing heart leads to mitochondrial permeability transition, which results in matrix swelling, outer membrane rupture, a release of apoptotic signaling molecules, and irreversible injury to the mitochondria. Alterations of "redox homeostasis" leads to major cellular consequences, and cellular survival requires an optimal regulation of the redox balance.

The role of reactive oxygen species in the pathophysiology of cardiovascular diseases and the clinical significance of myocardial redox

Acute and chronic excessive intracellular increase of reactive oxygen species (ROS) is involved in the development and progression of cardiovascular diseases. ROS are by-products of various oxidative physiological and biochemical processes. Sources of ROS are mitochondrial respiration, NADH/NADPH oxidase, xanthine oxidoreductase or the uncoupling of nitric oxide synthase (NOS) in vascular cells. ROS mediate various signaling pathways that underlie cardiovascular pathophysiology. The delicate equilibrium between free-radical generation and antioxidant defense is altered in favor of the former, thus leading to redox imbalance, oxidative stress, and increased cellular injury. An understanding of the pathophysiological mechanisms mediated by oxidative stress is crucial to the prevention and treatment of cardiovascular diseases.

Diazoxide prevents reactive oxygen species and mitochondrial damage, leading to anti-hypertrophic effects

Pathological cardiac hypertrophy is characterized by wall thickening or chamber enlargement of the heart in response to pressure or volume overload, respectively. This condition will, initially, improve the organ contractile function, but if sustained will render dysfunctional mitochondria and oxidative stress. Mitochondrial ATP-sensitive K⁺ channels (mitoKATP) modulate the redox status of the cell and protect against several cardiac insults. Here, we tested the hypothesis that mitoKATP opening (using diazoxide) will avoid isoproterenol-induced cardiac hypertrophy in vivo by decreasing reactive oxygen species (ROS) production and mitochondrial Ca²⁺-induced swelling. To induce cardiac hypertrophy, Swiss mice were treated intraperitoneally with isoproterenol (30 mg/kg/day) for 8 days. Diazoxide (5 mg/kg/day) was used to open mitoKATP and 5-hydroxydecanoate (5 mg/kg/day) was administrated as a mitoKATP blocker. Isoproterenol-treated mice had elevated heart weight/tibia length ratios and increased myocyte cross-sectional areas. Additionally, hypertrophic hearts produced higher levels of H₂O₂ and had lower glutathione peroxidase activity. In contrast, mitoKATP opening with diazoxide blocked all isoproterenol effects in a manner reversed by 5-hydroxydecanoate. Isolated mitochondria from Isoproterenol-induced hypertrophic hearts had increased susceptibility to Ca²⁺-induced swelling secondary to mitochondrial permeability transition pore opening. MitokATP opening was accompanied by lower Ca²⁺-induced mitochondrial swelling, an effect blocked by 5-hydroxydecanoate. Our results suggest that mitoKATP opening negatively regulates cardiac hypertrophy by avoiding oxidative impairment and mitochondrial damage.

Mitochondrial ATP-sensitive potassium channel opening inhibits isoproterenol-induced cardiac hypertrophy by preventing oxidative damage

Cardiac hypertrophy is a chronic complex disease that occurs in response to hemodynamic load and is accompanied by oxidative stress and mitochondrial dysfunction. Mitochondrial ATP-sensitive K channels (mitoKATPs) have previously been shown to prevent oxidative cardiac damage under conditions of ischemia/reperfusion. However, the effect of these channels on cardiac hypertrophy has not been tested to date. In this study, we show that treatment of Swiss mice with isoproterenol (30 mg·kg·d) induces cardiac hypertrophy while significantly decreasing the levels of reduced protein thiols, glutathione, catalase, and superoxide dismutase activity, indicative of a condition of oxidative imbalance. Treatment with diazoxide (a mitoKATP opener, 5 mg·kg·d) normalized the levels of protein thiols and reduced glutathione, rescued superoxide dismutase activity, and significantly prevented cardiac hypertrophy. The protective effects of diazoxide were mitigated by the mitoKATP blockers 5-hydroxydecanoate (5 mg·kg·d) and glibenclamide (3 mg·kg·d), demonstrating that they were related to activation of the channel. Taken together, our results establish that mitoKATP activation promotes very robust prevention of cardiac hypertrophy and associated oxidative imbalance and suggest that these channels can be important drug targets for the pharmacological control of cardiac hypertrophy.

Taxifolin protects against cardiac hypertrophy and fibrosis during biomechanical stress of pressure overload

Cardiac hypertrophy is a key pathophysiological component to biomechanical stress, which has been considered to be an independent and predictive risk factor for adverse cardiovascular events. Taxifolin (TAX) is a typical plant flavonoid, which has long been used clinically for treatment of cardiovascular and cerebrovascular diseases. However, very little is known about whether TAX can influence the development of cardiac hypertrophy. In vitro studies, we found that TAX concentration-dependently inhibited angiotensin II (Ang II) induced hypertrophy and protein synthesis in cardiac myocytes. Then we established a mouse model by transverse aortic constriction (TAC) to further confirm our findings. It was demonstrated that TAX prevented pressure overload induced cardiac hypertrophy in mice, as assessed by ventricular mass/body weight, echocardiographic parameters, myocyte cross-sectional area, and the expression of ANP, BNP and β-MHC. The excess production of reactive oxygen species (ROS) played critical role in the development of cardiac hypertrophy. TAX arrested oxidative stress and decreased the expression of 4-HNE induced by pressure overload. Moreover, TAX negatively modulated TAC-induced phosphorylation of ERK1/2 and JNK1/2. Further studies showed that TAX significantly attenuated left ventricular fibrosis and collagen synthesis through abrogating the phosphorylation of Smad2 and Smad2/3 nuclear translocation. These results demonstrated that TAX could inhibit cardiac hypertrophy and attenuate ventricular fibrosis after pressure overload. These beneficial effects were at least through the inhibition of the excess production of ROS, ERK1/2, JNK1/2 and Smad signaling pathways. Therefore, TAX might be a potential candidate for the treatment of cardiac hypertrophy and fibrosis.

Angiotensin II blockade: how its molecular targets may signal to mitochondria and slow aging. Coincidences with calorie restriction and mTOR inhibition

Caloric restriction (CR), renin angiotensin system blockade (RAS-bl), and rapamycin-mediated mechanistic target of rapamycin (mTOR) inhibition increase survival and retard aging across species. Previously, we have summarized CR and RAS-bl's converging effects, and the mitochondrial function changes associated with their physiological benefits. mTOR inhibition and enhanced sirtuin and KLOTHO signaling contribute to the benefits of CR in aging. mTORC1/mTORC2 complexes contribute to cell growth and metabolic regulation. Prolonged mTORC1 activation may lead to age-related disease progression; thus, rapamycin-mediated mTOR inhibition and CR may extend lifespan and retard aging through mTORC1 interference. Sirtuins by deacetylating histone and transcription-related proteins modulate signaling and survival pathways and mitochondrial functioning. CR regulates several mammalian sirtuins favoring their role in aging regulation. KLOTHO/fibroblast growth factor 23 (FGF23) contribute to control Ca(2+), phosphate, and vitamin D metabolism, and their dysregulation may participate in age-related disease. Here we review how mTOR inhibition extends lifespan, how KLOTHO functions as an aging suppressor, how sirtuins mediate longevity, how vitamin D loss may contribute to age-related disease, and how they relate to mitochondrial function. Also, we discuss how RAS-bl downregulates mTOR and upregulates KLOTHO, sirtuin, and vitamin D receptor expression, suggesting that at least some of RAS-bl benefits in aging are mediated through the modulation of mTOR, KLOTHO, and sirtuin expression and vitamin D signaling, paralleling CR actions in age retardation. Concluding, the available evidence endorses the idea that RAS-bl is among the interventions that may turn out to provide relief to the spreading issue of age-associated chronic disease.

Puerarin inhibits angiotensin II-induced cardiac hypertrophy via the redox-sensitive ERK1/2, p38 and NF-κB pathways

AIM

To investigate the effects of puerarin (Pue), an isoflavone derived from Kudzu roots, on angiotensin II (Ang II)-induced hypertrophy of cardiomyocytes in vivo and in vitro.

METHODS

C57BL/6J mice were infused with Ang II and treated with Pue (100 mg·kg(-1)·d(-1), po) for 15 d. After the treatment, systolic blood pressure (SBP) and left ventricular wall thickness were assessed. The ratios of heart weight to body weight (HW/BW) and left ventricular weight to body weight (LVW/BW) were determined, and heart morphometry was assessed. Expression of fetal-type genes (ANP, BNP and β-MHC) in left ventricles was measured using semi-quantitative RT-PCR. Mouse primary cardiomyocytes were treated with Pue (50, 100, 200 μmol/L), then exposed to Ang II (1 μmol/L). ROS level was examined with flow cytometry, the binding activity of NF-κB was determined using EMSA. Western blot was used to measure the levels of ERK1/2, p38 and NF-κB pathway proteins. [(3)H]leucine incorporation was used to measure the rate of protein synthesis.

RESULTS

Oral administration of Pue significantly suppressed Ang II-induced increases in the myocyte surface area, HW/BW, LVW/BW, SBP and left ventricular wall thickness. Furthermore, Pue significantly suppressed Ang II-induced increases in ANP, BNP and β-MHC expression in the left ventricles in vivo. Treatment of cardiomyocytes with Pue (50-500 μmol/L) did not affect the viability of cardiomyocytes in vitro. Pretreatment of cardiomyocytes with Pue dose-dependently inhibited Ang II-induced increases in ROS production, NF-κB binding activity, protein synthesis and cell breadth. Furthermore, pretreatment with Pue significantly suppressed Ang II-induced activation of ERK1/2, p38 and the NF-κB pathway proteins and the expression of ANP and β-MHC in cardiomyocytes. The positive drug valsartan exerted similar effects on Ang II-induced cardiac hypertrophy in vivo and in vitro.

CONCLUSION

Pue attenuates Ang II-induced cardiac hypertrophy by inhibiting activation of the redox-sensitive ERK1/2, p38 and the NF-κB pathways.

Sirtuin 6 protects cardiomyocytes from hypertrophy in vitro via inhibition of NF-κB-dependent transcriptional activity

BACKGROUND AND PURPOSE

Sirtuin 6 (SIRT6) is involved in regulation of glucose and fat metabolism. However, its possible contribution to cardiac dysfunction remains to be determined. In the present study, the effect of SIRT6 on cardiac hypertrophy induced by angiotensin II (AngII) and the underlying molecular mechanisms were investigated.

EXPERIMENTAL APPROACH

The expression and deacetylase activity of SIRT6 were measured in hypertrophic cardiomyocytes induced by AngII. After SIRT6 overexpression by transfection, or depletion by RNA interference in neonatal rat cardiomyocytes, cellular hypertrophy was monitored by measuring cell surface area and the mRNA levels of hypertrophic biomarkers. Further, the interaction between SIRT6 and the transcription factor NF-κB was investigated by co-immunoprecipitation, confocal immunofluorescence microscopy and luciferase reporter gene assay. The expression and deacetylase activity of SIRT6 were measured in vivo, using the abdominal aortic constriction (AAC) model of cardiac hypertrophy in rats.

KEY RESULTS

In AngII-induced hypertrophic cardiomyocytes and also in AAC-induced hypertrophic hearts, the expression of SIRT6 protein was upregulated, while its deacetylase activity was decreased. Overexpression of wild-type SIRT6 but not its catalytically inactive mutant, attenuated AngII-induced cardiomyocyte hypertrophy. We further demonstrated a physical interaction between SIRT6 and NF-κB catalytic subunit p65, whose transcriptional activity could be repressed by SIRT6 overexpression.

CONCLUSIONS AND IMPLICATIONS

Our findings suggest that SIRT6 suppressed cardiomyocyte hypertrophy in vitro via inhibition of NF-κB-dependent transcriptional activity and that this effect was dependent on its deacetylase activity.

Resveratrol inhibits angiotensin II-induced ERK1/2 activation by downregulating quinone reductase 2 in rat vascular smooth muscle cells

Our previous studies showed that resveratrol could inhibit the proliferation of vascular smooth muscle cells (VSMCs) and repress mRNA and protein expression of quinone reductase 2 (NQO2). This study further explored the potential mechanisms whereby resveratrol inhibits the proliferation of rat VSMCs. Lentiviral vectors that incorporated NQO2 small interfering RNA (siRNA) were constructed and transduced into rat VSMCs. The cell proliferation was detected using the bromodeoxyuridine (BrdU) assay. Cultured rat VSMCs were stimulated with angiotensin II and the level of reactive oxygen species (ROS) was measured using a ROS assay kit. A realtime quantitative PCR was used to detect NQO2 mRNA levels. Extracellular signal-regulated kinase (ERK1/2) and NQO2 protein expression were determined by Western blotting analysis. The inhibitory effect of resveratrol (10 and 50 µmol/L) on the proliferation of rat VSMCs in the NQO2 siRNA group was significantly weaker than that in the normal and scrambled siRNA group (P < 0.01). The ROS level in the NQO2 siRNA and resveratrol (50 µmol/L) treatment groups were lower than that in the normal and scrambled siRNA groups (P < 0.01 in both). Compared with the normal and scrambled siRNA group, the phosphorylation of ERK1/2 was significantly decreased in the NQO2 siRNA and resveratrol (50 µmol/L) treatment group (P < 0.01 in both). In conclusion, high concentration of resveratrol inhibits angiotensin II-induced ERK1/2 phosphorylation and subsequent proliferation by down-regulation of NQO2 in cultured rat VSMCs.

Evidence for the importance of adiponectin in the cardioprotective effects of pioglitazone

The favorable effects of the peroxisome proliferator-activated receptor-gamma ligand pioglitazone on glucose metabolism are associated with an increase in the fat-derived hormone adiponectin in the bloodstream. A recent clinical trial, Prospective Pioglitazone Clinical Trial in Macrovascular Events, demonstrated that pioglitazone improved cardiovascular outcomes in patients with type 2 diabetes mellitus. However, the functional role of adiponectin in cardioprotection by pioglitazone has not been examined experimentally. Here we investigated the effect of pioglitazone on angiotensin II (Ang II)-induced cardiac hypertrophy and assessed the potential contribution of adiponectin to the action of pioglitazone on the heart. Wild-type or adiponectin-deficient mice were treated with pioglitazone as food admixture at a concentration of 0.01% for 1 week followed by 2 weeks of infusion with Ang II at 3.2 mg/kg per day. Ang II infusion in wild-type mice resulted in exacerbated myocyte hypertrophy and increased interstitial fibrosis, which were accompanied by elevated phosphorylation of extracellular signal-regulated kinase and expression of transforming growth factor-beta1 in the heart. Treatment of wild-type mice with pioglitazone attenuated cardiac hypertrophy and fibrosis, extracellular signal-regulated kinase phosphorylation, and transforming growth factor-beta1 expression in response to Ang II. Pioglitazone also increased the plasma adiponectin level and phosphorylation of cardiac AMP-activated protein kinase in wild-type mice in the presence of Ang II. The suppressive effects of pioglitazone on Ang II-induced cardiac hypertrophy and fibrosis were diminished in adiponectin-deficient mice. Furthermore, pioglitazone had no effects on the phosphorylation of extracellular signal-regulated kinase and AMP-activated protein kinase in the Ang II-infused heart of adiponectin-deficient mice. These data provide direct evidence that pioglitazone protects against Ang II-induced pathological cardiac remodeling via an adiponectin-dependent mechanism.

Soluble epoxide hydrolase plays an essential role in angiotensin II-induced cardiac hypertrophy

Pathophysiological cardiac hypertrophy is one of the most common causes of heart failure. Epoxyeicosatrienoic acids, hydrolyzed and degraded by soluble epoxide hydrolase (sEH), can function as endothelium-derived hyperpolarizing factors to induce dilation of coronary arteries and thus are cardioprotective. In this study, we investigated the role of sEH in two rodent models of angiotensin II (Ang II)-induced cardiac hypertrophy. The protein level of sEH was elevated in the heart of both spontaneously hypertensive rats and Ang II-infused Wistar rats. Blocking the Ang II type 1 receptor with losartan could abolish this induction. Administration of a potent sEH inhibitor (sEHI) prevented the pathogenesis of the Ang II-induced hypertrophy, as demonstrated by decreased left-ventricular hypertrophy assessed by echocardiography, reduced cardiomyocyte size, and attenuated expression of hypertrophy markers, including atrial natriuretic factor and beta-myosin heavy chain. Because sEH elevation was not observed in exercise- or norepinephrine-induced hypertrophy, the sEH induction was closely associated with Ang II-induced hypertrophy. In vitro, Ang II upregulated sEH and hypertrophy markers in neonatal cardiomyocytes isolated from rat and mouse. Expression of these marker genes was elevated with adenovirus-mediated sEH overexpression but decreased with sEHI treatment. These results were supported by studies in neonatal cardiomyocytes from sEH(-/-) mice. Our results suggest that sEH is specifically upregulated by Ang II, which directly mediates Ang II-induced cardiac hypertrophy. Thus, pharmacological inhibition of sEH would be a useful approach to prevent and treat Ang II-induced cardiac hypertrophy.

Crocetin protects against cardiac hypertrophy by blocking MEK-ERK1/2 signalling pathway

Oxidative stress plays a critical role in the progression of pathological cardiac hypertrophy and heart failure. Because crocetin represses oxidative stress in vitro and in vivo, we have suggested that crocetin would repress cardiac hypertrophy by targeting oxidative stress-dependent signalling. We tested this hypothesis using primary cultured cardiac myocytes and fibroblasts and one well-established animal model of cardiac hypertrophy. The results showed that crocetin (1–10 μM) dose-dependently blocked cardiac hypertrophy induced by angiogensin II (Ang II; 1 μM) in vitro. Our data further revealed that crocetin (50 mg/kg/day) both prevented and reversed cardiac hypertrophy induced by aortic banding (AB), as assessed by heart weight/body weight and lung weight/body weight ratios, echocardio-graphic parameters and gene expression of hypertrophic markers. The inhibitory effect of crocetin on cardiac hypertrophy is mediated by blocking the reactive oxygen species (ROS)-dependent mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase-1/2 (MEK/ERK1/2) pathway and GATA binding protein 4 (GATA-4) activation. Further investigation demonstrated that crocetin inhibited inflammation by blocking nuclear factor kappa B (NF-κB) signalling and attenuated fibrosis and collagen synthesis by abrogating MEK-ERK1/2 signalling. Overall, our results indicate that crocetin, which is a potentially safe and inexpensive therapy for clinical use, has protective potential in targeting cardiac hypertrophy and fibrosis by suppression of ROS-dependent signalling pathways.

Angiotensin II: a hormone involved in and contributing to pro-hypertrophic cardiac networks and target of anti-hypertrophic cross-talks

Angiotensin II (Ang II) plays a major role in the progression of myocardial hypertrophy to heart failure. Inhibiting the angiotensin converting enzyme (ACE) or blockade of the corresponding Ang II receptors is used extensively in clinical practice, but there is scope for refinement of this mode of therapy. This review summarizes the current understanding of the direct effects of Ang II on cardiomyocytes and then focus particularly on interaction of components of the renin-angiotensin system with other hormones and cytokines. New findings described in approximately 400 papers identified in the PubMed database and published during the 2.5 years are discussed in the context of previous relevant literature. The cardiac action of Ang II is influenced by the activity of different isoforms of ACE leading to different amounts of Ang II by comparison with other angiotensinogen-derived peptides. The effect of Ang II is mediated by at least two different AT receptors that are differentially expressed in cardiomyocytes from neonatal, adult and failing hearts. The intracellular effects of Ang II are influenced by nitric oxide (NO)/cGMP-dependent cross talk and are mediated by the release of autocrine factors, such as transforming growth factor (TGF)-beta1 and interleukin (IL)-6. Besides interactions with cytokines, Ang II is involved in systemic networks including aldosterone, parathyroid hormone and adrenomedullin, which have their own effects on cardiomyocytes that modify, amplify or antagonize the primary effect of Ang II. Finally, hyperinsulemia and hyperglycaemia influence Ang II-dependent processes in diabetes and its cardiac sequelae.

Propofol depresses angiotensin II-induced cardiomyocyte hypertrophy in vitro

Cardiomyocyte hypertrophy is formed in response to pressure or volume overload, injury, or neurohormonal activation. The most important vascular hormone that contributes to the development of hypertrophy is angiotensin II (Ang II). Accumulating studies have suggested that reactive oxygen species (ROS) may play an important role in cardiac hypertrophy. Propofol is a general anesthetic that possesses antioxidant action. We therefore examined whether propofol inhibited Ang II-induced cardiomyocyte hypertrophy. Our results showed that both ROS formation and hypertrophic responses induced by Ang II in cardiomyocytes were partially blocked by propofol. Further studies showed that propofol inhibited the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and mitogen-activated protein kinase/ERK kinase 1/2 (MEK1/2) induced by Ang II via a decrease in ROS production. In addition, propofol also markedly attenuated Ang II-stimulated nuclear factor-kappaB (NF-kappaB) activation via a decrease in ROS production. In conclusion, propofol prevents cardiomyocyte hypertrophy by interfering with the generation of ROS and involves the inhibition of the MEK/ERK signaling transduction pathway and NF-kappaB activation.

All-trans retinoic acid prevents angiotensin II- and mechanical stretch-induced reactive oxygen species generation and cardiomyocyte apoptosis

Cardiomyocyte apoptosis has an important role in the transition from compensatory cardiac remodeling to heart failure. All-trans retinoic acid (RA), a bioactive vitamin A derivative, prevents stretch- and angiotensin II (Ang II)-induced cardiac hypertrophy. However, the anti-apoptotic potential of RA in the heart remains unexplored. Here, we demonstrate that stretch- and Ang II-induced apoptosis is prevented by RA in neonatal cardiomyocytes. RA improved mitochondrial function by inhibiting the stretch- and Ang II-induced reduction in mitochondrial membrane potential, cytochrome c release and by increasing the Bcl2/Bax ratio. RA inhibited stretch- and Ang II-induced intracellular reactive oxygen species (ROS) generation and upregulated the SOD2 level. Hydrogen peroxide-induced increases in the number of TUNEL-positive cells and percentage of Annexin V positive cells, were dose-dependently inhibited by RA. The thiol antioxidant, N-acetyl cysteine (NAC), completely inhibited stretch- and Ang II-induced apoptosis. Using diazoxide (mitochondrial ATP-sensitive K(+) channel opener) and SDS (NADPH oxidase activator), we confirmed that RA suppressed both mitochondrial- and NADPH oxidase-derived ROS. We also observed that both RAR and RXR were involved in preventing Ang II- and stretch-induced ROS production and apoptosis, by using selective retinoid receptor agonists and antagonists. Our data provide the first evidence that RA prevents Ang II and stretch induced apoptosis, by inhibiting ROS generation and increasing the anti-oxidant defense system, suggesting that RA-mediated signaling may provide a new therapeutic target for the prevention of the cardiac remodeling process.

Tetramethylpyrazine inhibits angiotensin II-increased NAD(P)H oxidase activity and subsequent proliferation in rat aortic smooth muscle cells

Tetramethylpyrazine (TMP) is the major component extracted from the Chinese herb, Chuanxiong, which is widely used in China for the treatment of cardiovascular problems. The aims of this study were to examine whether TMP may alter angiotenisn II (Ang II)-induced proliferation and to identify the putative underlying signaling pathways in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with TMP and then stimulated with Ang II, [3H]-thymidine incorporation and the ET-1 expression was examined. Ang II increased DNA synthesis which was inhibited by TMP (1-100 microM). TMP inhibited the Ang II-induced ET-1 mRNA levels and ET-1 secretion. TMP also inhibited Ang II-increased NAD(P)H oxidase activity, intracellular reactive oxygen species (ROS) levels, and the ERK phosphorylation. Furthermore, TMP and antioxidants such as Trolox and diphenylene iodonium decreased Ang II-induced ERK phosphorylation, and activator protein-1 reporter activity. In summary, we demonstrate for the first time that TMP inhibits Ang II-induced proliferation and ET-1, partially by interfering with the ERK pathway via attenuation of Ang II-increased NAD(P)H oxidase and ROS generation. Thus, this study delivers important new insight in the molecular pathways that may contribute to the proposed beneficial effects of TMP in cardiovascular disease.

Involvement of oxidants and AP-1 in angiotensin II-activated NFAT3 transcription factor

Cardiomyocyte hypertrophy is associated with multiple pathophysiological cardiovascular conditions. Recent studies have substantiated the finding that oxidants may contribute to the development of cardiomyocyte hypertrophy. Activation of the nuclear factor of activated T cells-3 (NFAT3) transcription factor has been shown to result from endocrine inducers of cardiomyocyte hypertrophy such as angiotensin II (ANG II) and serves as an important molecular regulator of cardiomyocyte hypertrophy. In this study, we found that antioxidant enzyme catalase and antioxidants N-acetyl-l-cysteine, alpha-phenyl-N-tert-butylnitrone, and lipoic acid prevent ANG II from activating NFAT3 promoter-luciferase. H(2)O(2) induces a time- and dose-dependent activation of NFAT3 transcription factor. A dominant negative form of NFAT3 transcription factor inhibited H(2)O(2) from activating NFAT3 promoter. An inhibitor of ERKs, but not phosphoinositide 3-kinase or p38 MAPKs, blocked NFAT3 activation by H(2)O(2). The NFAT3 binding site in the promoters of most genes contains a weak activator protein-1 (AP-1) binding site adjacent to the core consensus NFAT binding sequence. ERK inhibitor PD98059 was found previously to inhibit AP-1 activation by H(2)O(2). Inactivation of AP-1 transcription factor by cotransfection of a dominant negative c-Jun, TAM67, prevented H(2)O(2) or ANG II from activating NFAT3 promoter. NFAT3 promoter containing the core NFAT cis-element without AP-1 binding site failed to show activation by H(2)O(2) treatment. Our data suggest that hypertrophy inducers ANG II and H(2)O(2) may activate NFAT3 in cardiomyocyte through an AP-1 transcription factor-dependent mechanism.

Antihypertrophic effect of Na+/H+ exchanger isoform 1 inhibition is mediated by reduced mitogen-activated protein kinase activation secondary to improved mitochondrial integrity and decreased generation of mitochondrial-derived reactive oxygen species

Although inhibition of Na+/H+ exchanger isoform 1 (NHE-1) reduces cardiomyocyte hypertrophy, the mechanisms underlying this effect are not known. Recent evidence suggests that this may be associated with improved mitochondrial function. To understand the mechanistic bases for mitochondrial involvement in the antihypertrophic effect of NHE-1 inhibition, we examined the effect of the NHE-1-specific inhibitor N-[2-methyl-4,5-bis(methylsulphonyl)-benzoyl]-guanidine, hydrochloride (EMD, EMD87580; 5 microM) on the hypertrophic phenotype, mitogen-activated protein kinase (MAPK) activity, mitochondrial membrane potential (Deltapsim), permeability transition (MPT) pore opening, and superoxide generation in phenylephrine (PE)-treated neonatal rat cardiomyocytes. EMD significantly suppressed markers of cell hypertrophy, including cell surface area and gene expression of atrial natriuretic peptide and alpha-skeletal actin. EMD inhibited the PE-induced MPT pore opening, prevented the loss in Deltapsim, and attenuated superoxide generation induced by PE. Moreover, the activation of p38 MAPK (p38) and extracellular signal-regulated kinase (ERK) 1/2 MAPKs induced by PE was significantly attenuated in the presence of EMD as well as the antioxidant catalase. To examine the role of MPT and mitochondrial Ca2+ uniport in parallel with EMD, the effects of cyclosporin A (0.2 microM) and ruthenium red (10 microM) were evaluated. Both agents significantly attenuated PE-induced hypertrophy and inhibited both mitochondrial dysfunction and p38 and ERK1/2 MAPK activation. Our results suggest a novel mechanism for attenuation of the hypertrophic phenotype by NHE-1 inhibition that is mediated by a reduction in PE-induced MAPK activation and superoxide production secondary to improved mitochondrial integrity.

Epigallocathechin-3 gallate inhibits cardiac hypertrophy through blocking reactive oxidative species-dependent and -independent signal pathways

Cardiac hypertrophy is a major cause of morbidity and mortality worldwide. Recent in vitro and in vivo studies have suggested that reactive oxygen species (ROS) may play an important role in cardiac hypertrophy. It was therefore thought to be of particular value to examine the effects of antioxidants on cardiac hypertrophy. Epigallocatechin-3-gallate (EGCG) is a major bioactive polyphenol present in green tea and a potent antioxidant. The current study was designed to test the hypothesis that EGCG inhibits cardiac hypertrophy in vitro and in vivo. In this study, we investigated the effects of EGCG on angiotensin II- (Ang II) and pressure-overload-induced cardiac hypertrophy. Our results showed that EGCG attenuated Ang II- and pressure-overload-mediated cardiac hypertrophy. Both reactive oxygen species generation and NADPH oxidase expressions induced by Ang II and pressure overload were suppressed by EGCG. The increased hypertension by pressure overload was almost completely blocked after EGCG treatment. Further studies showed that EGCG inhibited Ang II-induced NF-kappaB and AP-1 activation. Inhibition of the activity of NF-kappaB was through blocking ROS-dependent p38 and JNK signaling pathways, whereas inhibition of AP-1 activation was via blocking EGFR transactivation and its downstream events ERKs/PI3K/Akt/mTOR/p70(S6K). The combination of these actions resulted in repressing the reactivation of ANP and BNP, and ultimately preventing the progress of cardiac hypertrophy. These findings indicated that EGCG prevents the development of cardiac hypertrophy through ROS-dependent and -independent mechanisms involving inhibition of different intracellular signaling transductional pathways.

Antiproliferative effect of isosteviol on angiotensin-II-treated rat aortic smooth muscle cells

Isosteviol is a derivative of stevioside, a constituent of Stevia rebaudiana, which is commonly used as a noncaloric sugar substitute in Japan and Brazil. The aims of this study were to examine whether isosteviol alters angiotensin-II-induced cell proliferation in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with isosteviol, then stimulated with angiotensin II, after which [(3)H]thymidine incorporation and endothelin-1 secretion were examined. Isosteviol (1-100 micromol/l) inhibits angiotensin-II-induced DNA synthesis and endothelin-1 secretion. Measurements of 2'7'-dichlorofluorescin diacetate, a redox-sensitive fluorescent dye, showed an isosteviol-mediated inhibition of intracellular reactive oxygen species generated by the effects of angiotensin II. The inductive properties of angiotensin II on extracellular signal-regulated kinase (ERK) phosphorylation were found reversed with isosteviol and antioxidants such as N-acetylcysteine. In summary, we speculate that isosteviol inhibits angiotensin-II-induced cell proliferation and endothelin-1 secretion via attenuation of reactive oxygen species generation. Thus, this study provides important insights that may contribute to the effects of isosteviol on the cardiovascular system.

Oxidative stress and atherosclerosis

Understanding of the pathophysiology of atherosclerosis can provide new strategies for the prevention and treatment of patients with this common disease. Clinical, epidemiologic, and basic molecular science studies have identified oxidative stress as a factor contributing to the development and progression of atherosclerosis. Oxidative stress also participates in the pathogenesis of endothelial dysfunction and hypertension, two important factors in many patients with atherosclerosis. Further, it contributes to mechanisms of disease progression such as lipid oxidation and vascular remodeling. This article reviews the role of reactive oxygen species and oxidative stress in atherosclerosis.

Nitric oxide inhibits endothelin-1-induced cardiomyocyte hypertrophy through cGMP-mediated suppression of extracellular-signal regulated kinase phosphorylation

Cardiac hypertrophy is a compensatory mechanism in response to a variety of cardiovascular diseases. Recently, reactive oxygen species and nitric oxide (NO) have been demonstrated to be involved in the pathogenesis of atherosclerosis; however, the role of these free radicals in the development of cardiac hypertrophy remains unclear. In this study, we investigate NO modulation of cellular signaling in endothelin-1 (ET-1)-induced cardiomyocyte hypertrophy in culture. ET-1 treatment of cardiomyocytes increased constitutive NO synthase activity and induced NO production via the stimulation of ET-receptor subtype ET(B). Using Northern blot analysis and chloramphenicol acetyltransferase assay, we found that NO suppressed the ET-1-induced increase in c-fos mRNA level and promoter activity. In contrast, ET-1 stimulation of c-fos expression was augmented by depletion of endogenous NO generation with the addition of NO scavenger PTIO into cardiomyocytes. Cells cotransfected with the dominant negative and positive mutants of signaling molecules revealed that the Ras/Raf/extracellular-signal regulated kinase (ERK) signaling pathway is involved in ET-induced c-fos gene expression. Furthermore, NO directly inhibited ET-1-induced ERK phosphorylation and activation in a cGMP-dependent manner, indicating that NO modulates ET-1-induced c-fos expression via its inhibitory effect on ERK signaling pathway. The ET-1-stimulated activator protein-1 (AP-1) DNA binding activity and AP-1-mediated reporter activity were attenuated by NO. In addition, NO also significantly inhibited ET-1-stimulated promoter activity of hypertrophic marker gene beta-myosin heavy chain and the enhanced protein synthesis. Taken together, our findings provide the molecular basis of NO as a negative regulator in ET-1-induced cardiac hypertrophy.

Tetramethylpyrazine downregulates angiotensin II-induced endothelin-1 gene expression in vascular endothelial cells

1. Tetramethylpyrazine (TMP) is one of the active ingredients of the Chinese herb Ligusticum wallichii Franchat. It is well documented that TMP exerts a cardiovascular protective effect. The aims of the present study were to examine whether TMP alters angiotenisn (Ang) II-induced endothelin (ET)-1 gene expression and to identify the putative underlying signalling pathways in vascular endothelial cells. 2. Cultured vascular endothelial cells were pre-incubated with TMP, stimulated with AngII and ET-1 gene expression was then examined. The effects of TMP pretreatment on AngII-induced extracellular signal-regulated kinase (ERK) phosphorylation were investigated to elucidate the intracellular mechanism responsible for the effects of TMP on ET-1 gene expression. 3. Tetramethylpyrazine inhibited AngII-induced ET-1 gene expression, as revealed by nothern blotting and a promoter activity assay. Tetramethylpyrazine also inhibited the AngII-induced increase in intracellular reactive oxygen species (ROS), as measured by the redox sensitive fluorescent dye 2' 7'-dichlorofluorescin diacetate and ERK phosphorylation. 4. In summary, we have demonstrated, for the first time, that TMP inhibits AngII-induced ROS generation, ERK phosphorylation and ET-1 gene expression in vascular endothelial cells. Thus, the present study delivers important new insights into the molecular pathways that may contribute to the proposed beneficial effects of TMP in the cardiovascular system.

Redox-dependent protein kinase regulation by angiotensin II: mechanistic insights and its pathophysiology

Reactive oxygen species (ROS) are proposed to induce cardiovascular diseases, such as atherosclerosis, hypertension, restenosis, and fibrosis, through several mechanisms. One such mechanism involves ROS acting as intracellular second messengers, which lead to induction of unique signal transductions. Angiotensin II (AngII), a potent cardiovascular pathogen, stimulates ROS production through the G protein-coupled AngII type 1 receptor expressed in its target organs, such as vascular tissues, heart, and kidney. Recent accumulating evidence indicates that through ROS production, AngII activates downstream ROS-sensitive kinases that are critical in mediating cardiovascular remodeling. Each of these ROS-sensitive kinases could potentially mediate its own specific function. In this review, we will focus our discussion on the current findings that suggest novel mechanisms of how AngII mediates activation of these redox-sensitive kinases in target organs, as well as the pathological significance of their activation.

Inhibitory effect of trilinolein on endothelin-1-induced c-fos gene expression in cultured neonatal rat cardiomyocytes

Trilinolein, isolated from the traditional Chinese herb Sanchi (Panax notoginseng), has been shown to have myocardial protective effects via its antioxidant ability. However, the cellular and molecular mechanisms of the protective effect of trilinolein in the heart remain to be elucidated. Oxidative mechanisms have been implicated in neonatal cardiomyocyte hypertrophy. We previously reported that ET-1 induces ROS generation via the ET(A) receptor and ROS modulates c-fos gene expression. We have therefore examined whether trilinolein attenuates ROS production and ET-1-induced c-fos gene expression in cardiomyocytes. Cultured neonatal rat cardiomyocytes were stimulated with ET-1 (10 nM), and c-fos gene expression was examined. Trilinolein (1 and 10 microM) inhibited ET-1-induced c-fos gene expression in cardiomyocytes. We also examined the effects of trilinolein on ET-1-increased NADPH oxidase activity and superoxide formation. Trilinolein inhibited ET-1-increased NADPH oxidase activity and superoxide formation in a concentration-dependent manner. This increase in superoxide production by ET-1 was significantly inhibited by trilinolein, diphenyleneiodonium, or N-acetylcysteine. Trilinolein also decreased ET-1- or H2O2-induced extracellular signal-regulated kinase (ERK) phosphorylation, c-Jun NH2-terminal kinase (JNK) phosphorylation, and activator protein-1 activation. These data indicate that trilinolein inhibits ET-1-induced ERK phosphorylation, JNK phosphorylation, and c-fos gene expression via attenuating superoxide production in cardiomyocytes.

Resveratrol inhibits angiotensin II-induced endothelin-1 gene expression and subsequent proliferation in rat aortic smooth muscle cells

Resveratrol is a phytoestrogen naturally found in grapes and is the major constituent of wine thought to have a cardioprotective effect. The aims of this study were to examine whether resveratrol alters angiotenisn II-induced cell proliferation and endothelin-1 gene expression and to identify the putative underlying signaling pathways in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with resveratrol then stimulated with angiotensin II, after which [3H]thymidine incorporation and endothelin-1 gene expression were examined. The intracellular mechanism of resveratrol in cellular proliferation and endothelin-1 gene expression was elucidated by examining the phosphorylation level of angiotensin II-induced extracellular signal-regulated kinase (ERK). The inhibitory effects of resveratrol (1-100 microM) on angiotensin II-induced DNA synthesis and endothelin-1 gene expression were demonstrated with Northern blot and promoter activity assays. Measurements of 2'7'-dichlorofluorescin diacetate, a redox-senstive fluorescent dye, showed a resveratrol-mediated inhibition of intracellular reactive oxygen species generated by the effects of angiotensin II. The inductive properties of angiotensin II and H2O2 on ERK phosphorylation and activator protein-1-mediated reporter activity were found reversed with resveratrol and antioxidants such as N-acetyl-cysteine. In summary, we speculate that resveratrol inhibits angiotensin II-induced cell proliferation and endothelin-1 gene expression, and does so in a manner which involves the disruption of the ERK pathway via attenuation of reactive oxygen species generation. Thus, this study provides important insight into the molecular pathways that may contribute to the proposed beneficial effects of resveratrol on the cardiovascular system.

Inhibition of angiotensin II induced endothelin-1 gene expression by 17-beta-oestradiol in rat cardiac fibroblasts

OBJECTIVE

To examine whether 17-beta-oestradiol (E(2)) may alter angiotensin II (Ang II) induced cell proliferation and to identify the putative underlying signalling pathways in rat cardiac fibroblasts.

DESIGN

Cultured rat cardiac fibroblasts were preincubated with E(2) then stimulated with Ang II. [(3)H]Thymidine incorporation and endothelin-1 (ET-1) gene expression were examined. The effect of E(2) on Ang II induced NADPH oxidase activity, reactive oxygen species (ROS) formation, and extracellular signal regulated kinase (ERK) phosphorylation were tested to elucidate the intracellular mechanism of E(2) in proliferation and ET-1 gene expression.

RESULTS

Ang II increased DNA synthesis, which was inhibited with E(2) (1-100 nmol/l). E(2), but not 17-alpha-oestradiol, inhibited Ang II induced ET-1 gene expression as shown by northern blotting and promoter activity assay. This effect was prevented by co-incubation with the oestrogen receptor antagonist ICI 182,780 (1 micromol/l). E(2) also inhibited Ang II increased NADPH oxidase activity, ROS formation, ERK phosphorylation, and activator protein-1 mediated reporter activity.

CONCLUSIONS

The results suggest that E(2) inhibits Ang II induced cell proliferation and ET-1 gene expression, partially by interfering with the ERK pathway through attenuation of ROS generation. Thus, this study provides important new insight regarding the molecular pathways that may contribute to the proposed beneficial effects of oestrogen on the cardiovascular system.

Role of mitogen-activated protein kinase pathway in reactive oxygen species-mediated endothelin-1-induced beta-myosin heavy chain gene expression and cardiomyocyte hypertrophy

Endothelin-1 (ET-1) has been found to increase cardiac beta-myosin heavy chain (beta-MyHC) gene expression and induce hypertrophy in cardiomyocytes. ET-1 has been demonstrated to increase intracellular reactive oxygen species (ROS) in cardiomyocytes. The exact molecular mechanism by which ROS regulate ET-1-induced beta-MyHC gene expression and hypertrophy in cardiomyocytes, however, has not yet been fully described. We aim to elucidate the molecular regulatory mechanism of ROS on ET-1-induced beta-MyHC gene expression and hypertrophic signaling in neonatal rat cardiomyocytes. Following stimulation with ET-1, cultured neonatal rat cardiomyocytes were examined for 3H-leucine incorporation and beta-MyHC promoter activities. The effects of antioxidant pretreatment on ET-1-induced cardiac hypertrophy and mitogen-activated protein kinase (MAPKs) phosphorylation were studied to elucidate the redox-sensitive pathway in cardiomyocyte hypertrophy and beta-MyHC gene expression. ET-1 increased 3H-leucine incorporation and beta-MyHC promoter activities, which were blocked by the specific ET(A) receptor antagonist BQ-485. Antioxidants significantly reduced ET-1-induced 3H-leucine incorporation, beta-MyHC gene promoter activities and MAPK (extracellular signal-regulated kinase, p38, and c-Jun NH2 -terminal kinase) phosphorylation. Both PD98059 and SB203580 inhibited ET-1-increased 3H-leucine incorporation and beta-MyHC promoter activities. Co-transfection of the dominant negative mutant of Ras, Raf, and MEK1 decreased the ET-1-induced beta-MyHC promoter activities, suggesting that the Ras-Raf-MAPK pathway is required for ET-1 action. Truncation analysis of the beta-MyHC gene promoter showed that the activator protein-2 (AP-2)/specificity protein-1 (SP-1) binding site(s) were(was) important cis-element(s) in ET-1-induced beta-MyHC gene expression. Moreover, ET-1-induced AP-2 and SP-1 binding activities were also inhibited by antioxidant. These data demonstrate the involvement of ROS in ET-1-induced hypertrophic responses and beta-MyHC expression. ROS mediate ET-1-induced activation of MAPK pathways, which culminates in hypertrophic responses and beta-MyHC expression.

17beta-estradiol downregulates angiotensin-II-induced endothelin-1 gene expression in rat aortic smooth muscle cells

It is well documented that 17beta-estradiol (E(2)) exerts a cardiovascular protective effect. A possible role of E(2) in the regulation of endothelin-1 (ET-1) production has been reported. However, the complex mechanisms by which E(2) inhibits ET-1 expression are not completely understood. The aims of this study were to examine whether E(2) may alter angiotensin II (Ang II)-induced cell proliferation and ET-1 gene expression and to identify the putative underlying signaling pathways in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with E(2), then stimulated with Ang II, and [(3)H]thymidine incorporation and ET-1 gene expression were examined. The effect of E(2) on Ang-II-induced extracellular signal-regulated kinase (ERK) phosphorylation was tested to elucidate the intracellular mechanism of E(2) in proliferation and ET-1 gene expression. Ang II increased DNA synthesis which was inhibited with E(2) (1- 100 nM). E(2), but not 17alpha-estradiol, inhibited the Ang-II-induced ET-1 gene expression as revealed by Northern blotting and promoter activity assay. This effect was prevented by coincubation with the estrogen receptor antagonist ICI 182,780 (1 microM). E(2) also inhibited Ang-II-increased intracellular reactive oxygen species (ROS) as measured by a redox-sensitive fluorescent dye, 2',7'-dichlorofluorescin diacetate, and ERK phosphorylation. Furthermore, E(2) and antioxidants, such as N-acetyl cysteine and diphenylene iodonium, decreased Ang-II-induced cell proliferation, ET-1 promoter activity, ET-1 mRNA, ERK phosphorylation, and activator protein-1-mediated reporter activity. In summary, our results suggest that E(2) inhibits Ang-II-induced cell proliferation and ET-1 gene expression, partially by interfering with the ERK pathway via attenuation of ROS generation. Thus, this study provides important new insight regarding the molecular pathways that may contribute to the proposed beneficial effects of estrogen on the cardiovascular system.

The inhibitory effect of trilinolein on norepinephrine-induced beta-myosin heavy chain promoter activity, reactive oxygen species generation, and extracellular signal-regulated kinase phosphorylation in neonatal rat cardiomyocytes

The myocardial protective effects of trilinolein, isolated from the traditional Chinese herb Sanchi (Panax notoginseng), are thought to be related to its antioxidant activity. However, the intracellular mechanism underlying the protective effect of trilinolein in the heart remains unclear. In the present study, we investigated the effect of trilinolein on norepinephrine (NE)-induced protein synthesis in cardiomyocytes. Cultured neonatal rat cardiomyocytes were stimulated with NE, then protein content, [(3)H]-leucine incorporation, and beta-myosin heavy chain (beta-MyHC) promoter activity were examined. The effect of trilinolein on NE-induced intracellular reactive oxygen species (ROS) generation was measured with a redox- sensitive fluorescent dye (2',7'-dichlorofluorescin diacetate) and extracellular signal-regulated kinase (ERK) phosphorylation by Western blotting. Trilinolein inhibited NE-increased protein synthesis, beta-MyHC promoter activity, and intracellular ROS. Both trilinolein and the antioxidant, N-acetyl-cysteine, decreased NE- and H(2)O(2)-induced protein synthesis, beta-MyHC promoter activity, and ERK phosphorylation. These data indicate that trilinolein inhibits NE-induced protein synthesis via attenuation of ROS generation in cardiomyocytes.

17beta-estradiol inhibits cyclic strain-induced endothelin-1 gene expression within vascular endothelial cells

It has been well documented previously that 17beta-estradiol (E2) exerts a protective effect on cardiovascular tissue. The possible role of E2 in the regulation of endothelin (ET)-1 production has been previously reported, although the complex mechanisms by which E2 inhibits ET-1 expression are not completely understood. The aims of this study were to examine whether E2 was able to alter strain-induced ET-1 gene expression and also to identify the putative underlying signaling pathways that exist within endothelial cells. For cultured endothelial cells, E2 (1-100 nM), but not 17alpha-estradiol, inhibited the level of strain-induced ET-1 gene expression and also peptide secretion. This inhibitory effect elicited by E2 was able to be prevented by the coincubation of endothelial cells with the estrogen receptor antagonist ICI-182,780 (1 microM). E2 also inhibited strain-enhanced NADPH oxidase activity and intracellular reactive oxygen species (ROS) generation as measured by the redox-sensitive fluorescent dye 2',7'-dichlorofluorescin diacetate and the level of extracellular signal-regulated kinase (ERK) phosphorylation. Furthermore, the presence of E2 and antioxidants such as N-acetylcysteine and diphenylene iodonium were able to elicit a decrease in the level of strain-induced ET-1 secretion, ET-1 promoter activity, ET-1 mRNA, ERK phosphorylation, and activator protein-1 binding activity. In summary, we demonstrated, for the first time, that E2 inhibits strain-induced ET-1 gene expression, partially by interfering with the ERK pathway via the attenuation of strain-induced ROS generation. Thus this study delivers important new insight regarding the molecular pathways that may contribute to the proposed beneficial effects of estrogen on the cardiovascular system.

Inhibitory effect of resveratrol on angiotensin II-induced cardiomyocyte hypertrophy

Resveratrol is proposed to account in part for the protective effect of red wine on the cardiovascular system. Angiotensin II (Ang II) is a potent hypertrophic stimulus in cardiomyocytes. In this study, we determined the effect of resveratrol on Ang II-induced cardiomyocyte hypertrophy. Cultured neonatal rat cardiomyocytes were stimulated with Ang II, and [3H]leucine incorporation and beta-myosin heavy chain (beta-MyHC) promoter activity were examined. Intracellular reactive oxygen species (ROS) were measured by a redox-sensitive fluorescent dye, 2' 7'-dichlorofluorescin diacetate, and the extracellular signal-regulated kinase (ERK) phosphorylation was examined by Western blotting. Resveratrol inhibited Ang II-increased intracellular ROS levels. Furthermore, resveratrol, as well as the antioxidant N-acetyl-cysteine, decreased Ang II- or H2O2-increased protein synthesis, beta-MyHC promoter activity, and ERK phosphorylation. In summary, we demonstrate for the first time that resveratrol inhibits Ang II-induced cardiomyocyte hypertrophy via attenuation of ROS generation.

Inhibitory effect of trilinolein on angiotensin II-induced cardiomyocyte hypertrophy

The myocardial protective effects of trilinolein, isolated from the Chinese herb Sanchi (Panax notoginseng), may be related to its antioxidant effects. In the present study, we investigated the effects of trilinolein on angiotensin II-induced cardiomyocyte hypertrophy. Cultured neonatal rat cardiomyocytes were stimulated with angiotensin II, [3H]leucine incorporation and the beta-myosin heavy chain promoter activity were examined. We also examined the effects of trilinolein on angiotensin II-induced intracellular reactive oxygen species generation. Trilinolein significantly inhibited angiotensin II-increased protein synthesis, beta-myosin heavy chain promoter activity, and intracellular reactive oxygen species generation. Antioxidant N-acetylcysteine also decreased angiotensin II-increased protein synthesis and beta-myosin heavy chain promoter activity. Furthermore, trilinolein and N-acetylcysteine decreased angiotensin II- or hydrogen peroxide (H2O2)-activated mitogen-activated protein kinases (MAPKs) phosphorylation, and activator protein-1 (AP-1)- [or nuclear factor-kappaB (NF-kappaB)]-reporter activities. These data indicate that trilinolein inhibits angiotensin II-induced cardiomyocyte hypertrophy and beta-myosin heavy chain promoter activity via attenuation of reactive oxygen species generation.