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

The influence of biological sex in human skeletal muscle transcriptome during ageing

Sex is a crucial biological variable, and influence of biological sex on the change of gene expression in ageing skeletal muscle has not yet been fully revealed. In this study, the mRNA expression profiles were obtained from the Gene Expression Omnibus database. Key genes were identified by differential expression analysis and weighted gene co-expression network analysis. The gene set enrichment analysis software and Molecular Signatures Database were used for functional and enrichment analysis. A protein-protein interaction network was constructed using STRING and visualized in Cytoscape. The results were compared between female and male subgroups. Differentially expressed genes and enriched pathways in different sex subgroups shared only limited similarities. The pathways enriched in the female subgroup were more similar to the pathways enriched in the older groups without taking sex difference into consideration. The pathways enriched in the female subgroup were more similar to the pathways enriched in the older groups without taking sex difference into consideration. The muscle myosin filament pathways were downregulated in the both aged female and male samples whereas transforming growth factor beta pathway and extracellular matrix-related pathways were upregulated. With muscle ageing, the metabolism-related pathways, protein synthesis and degradation pathways, results of predicted immune cell infiltration, and gene cluster associated with slow-type myofibers drastically different between the female and male subgroups. This finding may indicate that changes in muscle type with ageing may differ between the sexes in vastus lateralis muscle.

Sibjotang Protects against Cardiac Hypertrophy In Vitro and In Vivo

Cardiac hypertrophy is developed by various diseases such as myocardial infarction, valve diseases, hypertension, and aortic stenosis. Sibjotang (, Shizaotang, SJT), a classic formula in Korean traditional medicine, has been shown to modulate the equilibrium of body fluids and blood pressure. This research study sought to explore the impact and underlying process of Sibjotang on cardiotoxicity induced by DOX in H9c2 cells. In vitro, H9c2 cells were induced by DOX (1 μM) in the presence or absence of SJT (1-5 μg/mL) and incubated for 24 h. In vivo, SJT was administrated to isoproterenol (ISO)-induced cardiac hypertrophy mice (n = 8) at 100 mg/kg/day concentrations. Immunofluorescence staining revealed that SJT mitigated the enlargement of H9c2 cells caused by DOX in a dose-dependent way. Using SJT as a pretreatment notably suppressed the rise in cardiac hypertrophic marker levels induced by DOX. SJT inhibited the DOX-induced ERK1/2 and p38 MAPK signaling pathways. In addition, SJT significantly decreased the expression of the hypertrophy-associated transcription factor GATA binding factor 4 (GATA 4) induced by DOX. SJT also decreased hypertrophy-associated calcineurin and NFAT protein levels. Pretreatment with SJT significantly attenuated DOX-induced apoptosis-associated proteins such as Bax, caspase-3, and caspase-9 without affecting cell viability. In addition, the results of the in vivo study indicated that SJT significantly reduced the left ventricle/body weight ratio level. Administration of SJT reduced the expression of hypertrophy markers, such as ANP and BNP. These results suggest that SJT attenuates cardiac hypertrophy and heart failure induced by DOX or ISO through the inhibition of the calcineurin/NFAT/GATA4 pathway. Therefore, SJT may be a potential treatment for the prevention and treatment of cardiac hypertrophy that leads to heart failure.

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.

Alendronate promotes the gene expression of extracellular matrix mediated by SP-1/SOX-9

BACKGROUND AND PURPOSE

Osteoarthritis (OA) is a disease with significant degenerative changes of articular cartilage, which is reported to be closely related to the integrity of chondrocytes extracellular matrix (ECM). Alendronate belongs to the family of bisphosphonates with promising cartilage repair function. In the present study, the effects of Alendronate on the gene expression of chondrocytes ECM and the potential mechanism will be investigated to explore the potential therapeutic property of Alendronate on OA.

METHODS

Human SW1353 chondrocytes were stimulated with 1 and 2 μM Alendronate for 12 h. The gene expression of Col2α1, COL9α2, and Acan in the treated chondrocytes was determined by qRT-PCR. QRT-PCR and western blot analysis were used to evaluate the expression level of SOX-9 in the treated chondrocytes. The expression level of SP-1 was checked by qRT-PCR and immunostaining. SiRNA against SP-1 was transfected into chondrocytes to knockdown the expression of SP-1. The levels of p-ERK1/2 and total ERK1/2 were examined using western blot analysis. TNF-α was used to induce an OA-like in vitro model in the chondrocytes for therapeutic evaluations.

RESULTS

Treatment with Alendronate increased the levels of ECM related genes (Col2α1, COL9α2, and Acan) in a dose-dependent manner through increasing the expression of SOX-9, a central regulator of ECM genes. Additionally, our findings demonstrate that the effects of Alendronate in the expression of SOX-9 are mediated by SP-1 as silencing of SP-1 abolished these effects. Notably, Alendronate increased the phosphorylation of ERK1/2 and inhibition of ERK1/2 using its specific inhibitor U0126 blocked the expression of SP-1. Finally, we found that treatment with Alendronate could rescue TNF-α-induced reduction of Col2α1, COL9α2, Acan and SOX-9.

CONCLUSION

Our data indicated that Alendronate might promote the gene expression of extracellular matrix through SOX-9 mediated by the ERK1/2/SP1 signaling pathway.

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.

Redox Regulation of the Microcirculation

The microcirculation maintains tissue homeostasis through local regulation of blood flow and oxygen delivery. Perturbations in microvascular function are characteristic of several diseases and may be early indicators of pathological changes in the cardiovascular system and in parenchymal tissue function. These changes are often mediated by various reactive oxygen species and linked to disruptions in pathways such as vasodilation or angiogenesis. This overview compiles recent advances relating to redox regulation of the microcirculation by adopting both cellular and functional perspectives. Findings from a variety of vascular beds and models are integrated to describe common effects of different reactive species on microvascular function. Gaps in understanding and areas for further research are outlined. © 2020 American Physiological Society. Compr Physiol 10:229-260, 2020.

Knockdown of SP1/Syncytin1 axis inhibits the proliferation and metastasis through the AKT and ERK1/2 signaling pathways in non-small cell lung cancer

Syncytin 1 is considered as an oncogene in various malignant tumors, but its effect on non-small cell lung cancer (NSCLC) has not been reported. We investigated the specific role of Syncytin 1 on NSCLC through the transfection of Syncytin 1 knockdown or overexpression plamids in A549 cells. Our results proved that knockdown of Syncytin 1 inhibited the proliferation, and blocked the cell cycle on G1 phase by inhibiting the expression of Nusap1, Cyclin D1, CDK6, and CDK4. Cell cycle arrest also leaded to increased apoptosis in Syncytin 1 knockdown cells. Suppression of Syncytin 1 inhibited the migration and invasion, as well as the expressions of epithelial-mesenchymal transition (EMT) makers, N-cadherin, β-catenin, and Vimentin, indicating that Syncytin 1 knockdown inhibited the metastasis via reversing the EMT process in A549 cells. The phosphorylation levels of Akt, mTOR, and Erk1/2 were all decreased in Syncytin 1 knockdown cells, suggesting the signaling pathways by which Syncytin 1 operated as an oncogene in NSCLC. Moreover, the underexpression of transcription factor SP1 downregulated the Syncytin 1 expression in A549 cells. The rescue experiment of Syncytin 1 in SP1 knockdown cells further proved that Syncytin 1 could block the inhibition of cell growth induced by SP1 knockdown. In conclusion, knockdown of SP1/Syncytin1 axis inhibited the progression of NSCLC by the reversion of tumor epithelial-mesenchymal transition process and suppression of Akt and Erk signaling pathways, suggesting that they are potential targets for targeted therapy of NSCLC.

Ameliorative Effect of Epigallocatechin Gallate on Cardiac Hypertrophy and Fibrosis in Aged Rats

The objective of the present study is to evaluate the effect of epigallocatechin gallate (EGCG) on aging-mediated cardiac hypertrophy, fibrosis, and apoptosis. The Wistar albino rats were divided into 4 groups (n = 18). Group I: young (3 months), group II: aged (24-26 months), group III: aged + EGCG (200 mg/kg for 30 days), and group IV: young + EGCG. At the end of 30 days, EGCG administration to the aged animals showed significant (P < 0.001) reduction of low-density lipoprotein, very low-density lipoprotein, triglyceride, total cholesterol with concomitant increase of high-density lipoprotein (P < 0.001) when compared with aged rats. Increased (P < 0.001) heart volume, weight with concomitant increase of left ventricular wall thickness, and reduced ventricular cavity were observed in aged rats supplemented with EGCG compared with aged animals. Histology and histomorphometry study of aged animals treated with EGCG showed marked increases in the diameter and volume of cardiomyocytes with concomitant reduction of numerical density when compared with aged animals. Reduced reactive oxygen species (P < 0.001) production with association of increased antioxidant defense system (P < 0.001) in aged hearts supplemented with EGCG when compared with aged animals. TUNEL staining and fibrosis showed a marked increase in apoptotic cell death (P < 0.001) and collagen deposition (P < 0.001) in aged animals treated with EGCG when compared with aged animals. Aged animals treated with EGCG showed a marked increase in protein expression of TGFβ, TNFα, and nuclear factor kappa B (NF-κB) and significant (P < 0.001) alteration in the gene expression of TGFβ, TNFα, NF-κB, α-SMA, and Nrf2 when compared with aged animals. Taken together, it is evident that EGCG may potentially inhibit aging-induced cardiac hypertrophy, fibrosis, and apoptosis, thereby preserving cardiac function. The proposed mechanism would be inhibition of reactive oxygen species-dependent activation of TGFβ1, TNFα, and NF-κB signaling pathway. Hence, the present study suggests that EGCG can be useful to fight against aging-induced cardiac hypertrophy, fibrosis, and apoptosis.

Role of Endothelium in Doxorubicin-Induced Cardiomyopathy

The clinical use of doxorubicin in cancer is limited by cardiotoxic effects that can lead to heart failure. Whereas earlier work focused on the direct impact of doxorubicin on cardiomyocytes, recent studies have turned to the endothelium, because doxorubicin-damaged endothelial cells can trigger the development and progression of cardiomyopathy by decreasing the release and activity of key endothelial factors and inducing endothelial cell death. Thus, the endothelium represents a novel target for improving the detection, management, and prevention of doxorubicin-induced cardiomyopathy.

Successful knock-in of Hypertrophic Cardiomyopathy-mutation R723G into the MYH7 gene mimics HCM pathology in pigs

Familial Hypertrophic Cardiomyopathy (HCM) is the most common inherited cardiac disease. About 30% of the patients are heterozygous for mutations in the MYH7 gene encoding the ß-myosin heavy chain (MyHC). Hallmarks of HCM are cardiomyocyte disarray and hypertrophy of the left ventricle, the symptoms range from slight arrhythmias to sudden cardiac death or heart failure. To gain insight into the underlying mechanisms of the diseases' etiology we aimed to generate genome edited pigs with an HCM-mutation. We used TALEN-mediated genome editing and successfully introduced the HCM-point mutation R723G into the MYH7 gene of porcine fibroblasts and subsequently cloned pigs that were heterozygous for the HCM-mutation R723G. No off-target effects were determined in the R723G-pigs. Surprisingly, the animals died within 24 h post partem, probably due to heart failure as indicated by a shift in the a/ß-MyHC ratio in the left ventricle. Most interestingly, the neonatal pigs displayed features of HCM, including mild myocyte disarray, malformed nuclei, and MYH7-overexpression. The finding of HCM-specific pathology in neonatal R723G-piglets suggests a very early onset of the disease and highlights the importance of novel large animal models for studying causative mechanisms and long-term progression of human cardiac diseases.

Mechanisms of 2,3,7,8-tetrachlorodibenzo-p-dioxin- induced cardiovascular toxicity: An overview

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant and its toxicity is mediated by the aryl hydrocarbon receptor (AHR). Mechanisms of TCDD cardiovascular toxicity consist of oxidative stress, growth factor modulation, and ionic current alteration. It is indicated that the rodent cardiovascular system is a target for TCDD cardiomyopathy. Here, our understanding of TCDD cardiovascular toxicity is reviewed.

Estimation of Some Oxidative Stress Parameters and Blood Pressure After Administration of Endothelin-1 (ET-1) in Rats

The aim of the study was to investigate changes in the plasma antioxidative activity and in lipid peroxidation after administration of endothelin-1 (ET-1) and endothelin receptor blockers and additionally, to estimate blood pressure. The study was performed on male Wistar rats (n = 6 per group) divided into 4 groups which received: (1) saline, (2) endothelin-1 (ET-1) (3 μg/kg b.w.) + saline, (3) BQ123 (1 mg/kg) + ET-1 (3 μg/kg), and (4) BQ788 (3 mg/kg) + ET-1 (3 μg/kg b.w.). The endothelin receptor antagonist was injected intravenously 30 min before ET-1 administration. Blood pressure was monitored, and the blood was collected before the saline or ET-1 administration as well as 60 and 300 min after their administration. The antioxidative properties were examined by FRAP method (ferric reducing ability of plasma), and the concentration of lipid peroxidation products was examined by the reaction with thiobarbituric acid (TBARS). It was estimated that intravenous administration of endothelin receptor blocker ETA increases plasma antioxidative properties (p < 0.01) and parallelly decreases the process of lipid peroxidation (p < 0.05 vs. ET-1) and blood pressure (p < 0.05).

Overexpression of protein kinase C ɛ improves retention and survival of transplanted mesenchymal stem cells in rat acute myocardial infarction

We assessed the effects of protein kinase C ɛ (PKCɛ) for improving stem cell therapy for acute myocardial infarction (AMI). Primary mesenchymal stem cells (MSCs) were harvested from rat bone marrow. PKCɛ-overexpressed MSCs and control MSCs were transplanted into infarct border zones in a rat AMI model. MSCs and PKCɛ distribution and expression of principal proteins involved in PKCɛ signaling through the stromal cell-derived factor 1 (SDF-1)/CXC chemokine receptor type 4 (CXCR4) axis and the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT) pathway were analyzed by immunofluorescence and western blot 1 day after transplantation. Echocardiographic measurements and histologic studies were performed at 4 weeks after transplantation, and MSC survival, expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), transforming growth factor β (TGFβ), cardiac troponin I (cTnI), von Willebrand factor (vWF), smooth muscle actin (SMA) and factor VIII and apoptosis in infarct border zones were assessed. Rat heart muscles retained more MSCs and SDF-1, CXCR4, PI3K and phosphorylated AKT increased with PKCɛ overexpression 1 day after transplantation. MSC survival and VEGF, bFGF, TGFβ, cTnI, vWF, SMA and factor VIII expression increased in animals with PKCɛ-overexpressed MSCs at 4 weeks after transplantation and cardiac dysfunction and remodeling improved. Infarct size and apoptosis decreased as well. Inhibitory actions of CXCR4 or PI3K partly attenuated the effects of PKCɛ. Activation of PKCɛ may improve retention, survival and differentiation of transplanted MSCs in myocardia. Augmentation of PKCɛ expression may enhance the therapeutic effects of stem cell therapy for AMI.

Medicinal effect and its JP2/RyR2-based mechanism of Smilax glabra flavonoids on angiotensin II-induced hypertrophy model of cardiomyocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Rhizome and root of Smilax glabra Roxb (Liliaceae family) is a widely used traditional Chinese medicine (TCM) named Tu-fu-ling (TFL) for cardiac disease therapy. The TFL flavonoids (TFLF) has been extracted and proven to possess the anti-cardiac hypertrophy effect in our previous reports. Such effect could be mediated by the modulation of intracellular Ca(2+) flux in myocardial cells, in which junctophilin-2 (JP2) and ryanodine receptor 2 (RyR2) play an important role. However, its mechanism of the anti-cardiac hypertrophy effect remains unclarified.

MATERIALS AND METHODS

2μmol/L Ang II was applied to induce hypertrophy model of rat primary cardiomyocytes. After treatment of TFLF at 0.25, 0.5 and 1.0mg/ml, the cell size was microscopic measured, and the protein and mRNA expressions of JP2 and RyR2 in cardiomyocytes were estimated by immunofluorescence imaging, ELISA and real-time PCR assay.

RESULTS

Obvious hypertrophy of cardiomyocytes was induced by Ang II but reversed by TFLF from 0.5 to 1.0mg/ml. The protein and mRNA expressions of JP2 and RyR2 in cardiomyocytes were also inhibited by Ang II but restored by TFLF at its dose range. Such effect of TFLF was exerted at a dose dependent manner, which was even better than that of verapamil.

CONCLUSIONS

Our findings may evidence the correlation between JP2/RyR2 and myocardiac hypertrophy, and indicate the JP2/RyR2-mediated anti-hypertrophy mechanism of TFLF for the first time. It deserves to be developed as a promising TCM candidate of new drug for myocardial hypertrophy treatment.

Protective effects of grape seed proanthocyanidins on cardiovascular remodeling in DOCA-salt hypertension rats

Cardiovascular remodeling, as a hallmark of hypertension-induced pathophysiology, causes substantial cardiovascular morbidity and mortality. There is increasing evidence that has demonstrated a broad spectrum of pharmacological and therapeutic benefits of grape seed proanthocyanidins (GSP) against oxidative stress and cardiovascular diseases. In this study, 180- to 200-g SD rats treated with DOCA (120 mg/week sc with 1% NaCl and 0.2% KCl in drinking water) and GSP (150, 240, 384 mg/kg) or amlodipine (ALM) (5 mg/kg) for 4 weeks were recruited. The protective effects of GSP on blood pressure and cardiovascular remodeling in rats with DOCA-salt-induced hypertension were investigated. Our results indicated that DOCA-salt could induce hypertension, cardiovascular remodeling and dysfunction, oxidative stress and the release of endothelin-1 (ET-1) and could increase JNK1/2 and p38MAPK phosphorylation. GSP or ALM treatments significantly improved hypertension, cardiovascular remodeling and dysfunction and oxidative stress, restrained the release of ET-1 and down-regulated the JNK1/2 and p38MAPK phosphorylation. These findings demonstrate that GSP has protective effects against increase of blood pressure induced by DOCA-salt hypertension and cardiovascular remodeling by inhibiting the reactive oxygen species/mitogen-activated protein kinase pathway via restraining the release of ET-1.

Protective effect of Et-1 receptor antagonist bosentan on paracetamol induced acute liver toxicity in rats

Paracetamol is one of the first rank drugs which cause hepatic damage during drug intoxications. Endothelin (ET) which is known as one of the most potent vasoactive agent has been shown to contribute in the pathophysiology of various diseases. We hypothesized that bosentan, which is a non-selective ET-1 receptor antagonist, can prevent liver damage. This study included 49 female rats. Groups; I: Healthy group, II: Paracetamol (2 g/kg orally). Groups 3, 4 and 5 received NAC 140 mg/kg (2 doses), BOS 45 mg/kg and BOS 90 mg/kg orally, respectively. 1 h after administration of pretreatment drugs, Groups 3, 4, 5 were given paracetamol. VI: received BOS 90 mg/kg. VII: received 140 mg/kg NAC (2 doses). According to biochemical results, TNF-α, ALT and AST levels were statistically increased in the paracetamol group, these parameters were improved in the bosentan groups. Paracetamol administration decreased SOD activity, GSH level and increased level of MDA in the liver, while bosentan administration significantly improved these parameters. In immunohistochemical staining ET-1 receptor expression was excessively increased in paracetamol group, but not in bosentan groups when compared to healthy control. All these results suggest that bosentan exerted protective effects against experimentally induced paracetamol toxicity in liver.

Lycopene Inhibits Urotensin-II-Induced Cardiomyocyte Hypertrophy in Neonatal Rat Cardiomyocytes

This study investigated how lycopene affected urotensin-II- (U-II-) induced cardiomyocyte hypertrophy and the possible implicated mechanisms. Neonatal rat cardiomyocytes were exposed to U-II (1 nM) either exclusively or following 6 h of lycopene pretreatment (1-10  μ M). The lycopene (3-10  μ M) pretreatment significantly inhibited the U-II-induced cardiomyocyte hypertrophy, decreased the production of U-II-induced reactive oxygen species (ROS), and reduced the level of NAD(P)H oxidase-4 expression. Lycopene further inhibited the U-II-induced phosphorylation of the redox-sensitive extracellular signal-regulated kinases. Moreover, lycopene treatment prevented the increase in the phosphorylation of serine-threonine kinase Akt and glycogen synthase kinase-3beta (GSK-3 β ) caused by U-II without affecting the protein levels of the phosphatase and tensin homolog deleted on chromosome 10 (PTEN). However, lycopene increased the PTEN activity level, suggesting that lycopene prevents ROS-induced PTEN inactivation. These findings imply that lycopene yields antihypertrophic effects that can prevent the activation of the Akt/GSK-3 β hypertrophic pathway by modulating PTEN inactivation through U-II treatment. Thus, the data indicate that lycopene prevented U-II-induced cardiomyocyte hypertrophy through a mechanism involving the inhibition of redox signaling. These findings provide novel data regarding the molecular mechanisms by which lycopene regulates cardiomyocyte hypertrophy.

Interplay between endothelin and erythropoietin in astroglia: the role in protection against hypoxia

We show that, under in vitro conditions, the vulnerability of astroglia to hypoxia is reflected by alterations in endothelin (ET)-1 release and capacity of erythropoietin (EPO) to regulate ET-1 levels. Exposure of cells to 24 h hypoxia did not induce changes in ET-1 release, while 48–72 h hypoxia resulted in increase of ET-1 release from astrocytes that could be abolished by EPO. The endothelin receptor type A (ETA) antagonist BQ123 increased extracellular levels of ET-1 in human fetal astroglial cell line (SV-FHAS). The survival and proliferation of rat primary astrocytes, neural precursors, and neurons upon hypoxic conditions were increased upon administration of BQ123. Hypoxic injury and aging affected the interaction between the EPO and ET systems. Under hypoxia EPO decreased ET-1 release from astrocytes, while ETA receptor blockade enhanced the expression of EPO mRNA and EPO receptor in culture-aged rat astroglia. The blockade of ETA receptor can increase the availability of ET-1 to the ETB receptor and can potentiate the neuroprotective effects of EPO. Thus, the new therapeutic use of combined administration of EPO and ETA receptor antagonists during hypoxia-associated neurodegenerative disorders of the central nervous system (CNS) can be suggested.

Compensation of the AKT signaling by ERK signaling in transgenic mice hearts overexpressing TRIM72

The AKT and ERK signaling pathways are known to be involved in cell hypertrophy, proliferation, survival and differentiation. Although there is evidence for crosstalk between these two signaling pathways in cellulo, there is less evidence for cross talk in vivo. Here, we show that crosstalk between AKT and ERK signaling in the hearts of TRIM72-overexpressing transgenic mice (TRIM72-Tg) with alpha-MHC promoter regulates and maintains their heart size. TRIM72, a heart- and skeletal muscle-specific protein, downregulates AKT-mTOR signaling via IRS-1 degradation and reduces the size of rat cardiomyocytes and the size of postnatal TRIM72-Tg hearts. TRIM72 expression was upregulated by hypertrophic inducers in cardiomyocytes, while IRS-1 was downregulated by IGF-1. TRIM72 specifically regulated IGF-1-dependent AKT-mTOR signaling, resulting in a reduction of the size of cardiomyocytes. Postnatal TRIM72-Tg hearts were smaller than control-treated hearts with inhibition of AKT-mTOR signaling. However, adult TRIM72-Tg hearts were larger than of control despite the suppression of AKT-mTOR signaling. Activation of ERK, PKC-α, and JNK were observed to be elevated in adult TRIM72-Tg, and these signals were mediated by ET-1 via the ET receptors A and B. Altogether, these results suggest that AKT signaling regulates cardiac hypertrophy in physiological conditions, and ERK signaling compensates for the absence of AKT signaling during TRIM72 overexpression, leading to pathological hypertrophy.

Trypanosoma cruzi infection and endothelin-1 cooperatively activate pathogenic inflammatory pathways in cardiomyocytes

Trypanosoma cruzi, the causative agent of Chagas' disease, induces multiple responses in the heart, a critical organ of infection and pathology in the host. Among diverse factors, eicosanoids and the vasoactive peptide endothelin-1 (ET-1) have been implicated in the pathogenesis of chronic chagasic cardiomyopathy. In the present study, we found that T. cruzi infection in mice induces myocardial gene expression of cyclooxygenase-2 (Cox2) and thromboxane synthase (Tbxas1) as well as endothelin-1 (Edn1) and atrial natriuretic peptide (Nppa). T. cruzi infection and ET-1 cooperatively activated the Ca²⁺/calcineurin (Cn)/nuclear factor of activated T cells (NFAT) signaling pathway in atrial myocytes, leading to COX-2 protein expression and increased eicosanoid (prostaglandins E₂ and F_2α, thromboxane A₂) release. Moreover, T. cruzi infection of ET-1-stimulated cardiomyocytes resulted in significantly enhanced production of atrial natriuretic peptide (ANP), a prognostic marker for impairment in cardiac function of chagasic patients. Our findings support an important role for the Ca²⁺/Cn/NFAT cascade in T. cruzi-mediated myocardial production of inflammatory mediators and may help define novel therapeutic targets.

Chronic cardiomyopathy is the most common and severe manifestation of human Chagas' disease, caused by the protozoan parasite Trypanosoma cruzi. Among diverse inflammation-promoting moieties, eicosanoids and the vasoactive peptide endothelin-1 (ET-1) have been implicated in its pathogenesis. Nevertheless, the link between these two factors has not yet been identified. In the present study, we found that T. cruzi infection induces gene expression of ET-1 and eicosanoid-forming enzymes in the heart of infected mice. We also demonstrated that HL-1 atrial myocytes respond to ET-1 stimulus and T. cruzi infection by induction of cyclooxygenase-2 through activation of the Ca²⁺/calcineurin/NFAT intracellular signaling pathway. Moreover, the cooperation between T. cruzi and ET-1 leads to overproduction of eicosanoids (prostaglandins E₂ and F_2α, thromboxane A₂) and the pro-hypertrophic atrial natriuretic peptide. Our results support an important role for NFAT in T. cruzi plus ET-1-dependent induction of key agents of pathogenesis in chronic chagasic cardiomyopathy. Identification of the Ca²⁺/calcineurin/NFAT cascade as mediator of cardiovascular pathology in Chagas' disease advances our understanding of host-parasite interrelationship and may help define novel potential targets for therapeutic interventions to ameliorate or prevent cardiomyopathy during chronic T. cruzi infection.

Cytochrome P450 1B1 gene disruption minimizes deoxycorticosterone acetate-salt-induced hypertension and associated cardiac dysfunction and renal damage in mice

Previously, we showed that the cytochrome P450 1B1 inhibitor 2,3',4,5'-tetramethoxystilbene reversed deoxycorticosterone acetate (DOCA)-salt-induced hypertension and minimized endothelial and renal dysfunction in the rat. This study was conducted to test the hypothesis that cytochrome P450 1B1 contributes to cardiac dysfunction, and renal damage and inflammation associated with DOCA-salt-induced hypertension, via increased production of reactive oxygen species and modulation of neurohumoral factors and signaling molecules. DOCA-salt increased systolic blood pressure, cardiac and renal cytochrome P450 1B1 activity, and plasma levels of catecholamines, vasopressin, and endothelin-1 in wild-type (Cyp1b1(+/+)) mice that were minimized in Cyp1b1(-/-) mice. Cardiac function, assessed by echocardiography, showed that DOCA-salt increased the thickness of the left ventricular posterior and anterior walls during diastole, the left ventricular internal diameter, and end-diastolic and end-systolic volume in Cyp1b1(+/+) but not in Cyp1b1(-/-) mice; stroke volume was not altered in either genotype. DOCA-salt increased renal vascular resistance and caused vascular hypertrophy and renal fibrosis, increased renal infiltration of macrophages and T lymphocytes, caused proteinuria, increased cardiac and renal nicotinamide adenine dinucleotide phosphate-oxidase activity, caused production of reactive oxygen species, and increased activities of extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase, and cellular-Src; these were all reduced in DOCA-salt-treated Cyp1b1(-/-) mice. Renal and cardiac levels of eicosanoids were not altered in either genotype of mice. These data suggest that, in DOCA-salt hypertension in mice, cytochrome P450 1B1 plays a pivotal role in cardiovascular dysfunction, renal damage, and inflammation, and increased levels of catecholamines, vasopressin, and endothelin-1, consequent to generation of reactive oxygen species and activation of extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase, and cellular-Src independent of eicosanoids.

Endothelin-1 overexpression restores diastolic function in eNOS knockout mice

BACKGROUND

The cardiac nitric oxide and endothelin-1 (ET-1) systems are closely linked and play a critical role in cardiac physiology. The balance between both systems is often disturbed in cardiovascular diseases. To define the cardiac effect of excessive ET-1 in a status of nitric oxide deficiency, we compared left ventricular function and morphology in wild-type mice, ET-1 transgenic (ET(+/+)) mice, endothelial nitric oxide synthase knockout (eNOS(-/-)) mice, and ET(+/+)eNOS(-/-) mice.

METHODS AND RESULTS

eNOS(-/-) and ET(+/+)eNOS(-/-) mice developed high blood pressure compared with wild-type and ET(+/+) mice. Left ventricular catheterization showed that eNOS(-/-) mice, but not ET(+/+)eNOS(-/-) , developed diastolic dysfunction characterized by increased end-diastolic pressure and relaxation constant tau. To elucidate the causal molecular mechanisms driving the rescue of diastolic function in ET(+/+)eNOS(-/-) mice, the cardiac proteome was analyzed. Two-dimensional gel electrophoresis coupled to mass spectrometry offers an appropriate hypothesis-free approach. ET-1 overexpression on an eNOS(-/-) background led to an elevated abundance and change in posttranslational state of antioxidant enzymes (e.g., peroxiredoxin-6, glutathione S-transferase mu 2, and heat shock protein beta 7). In contrast to ET(+/+)eNOS(-/-) mice, eNOS(-/-) mice showed an elevated abundance of proteins responsible for sarcomere disassembly (e.g., cofilin-1 and cofilin-2). In ET(+/+)eNOS(-/-) mice, glycolysis was favored at the expense of fatty acid oxidation.

CONCLUSION

eNOS(-/-) mice developed diastolic dysfunction; this was rescued by ET-1 transgenic overexpression. This study furthermore suggests that cardiac ET-1 overexpression in case of eNOS deficiency causes specifically the regulation of proteins playing a role in oxidative stress, myocytes contractility, and energy metabolism.

2,3',4,5'-Tetramethoxystilbene prevents deoxycorticosterone-salt-induced hypertension: contribution of cytochrome P-450 1B1

Reactive oxygen species (ROS) contribute to various models of hypertension, including deoxycorticosterone acetate (DOCA)-salt-induced hypertension. Recently, we have shown that ROS, generated by cytochrome P-450 1B1 (CYP1B1) from arachidonic acid, mediate vascular smooth muscle cell growth caused by angiotensin II. This study was conducted to determine the contribution of CYP1B1 to hypertension and associated pathophysiological changes produced by DOCA (30 mg/kg) given subcutaneously per week with 1% NaCl + 0.1% KCl in drinking water to uninephrectomized rats for 6 wk. DOCA-salt treatment increased systolic blood pressure (SBP). Injections of the selective inhibitor of CYP1B1, 2,3',4,5'-tetramethoxystilbene (TMS; 300 μg/kg ip every 3rd day) initiated at the 4th week of DOCA-salt treatment normalized SBP and decreased CYP1B1 activity but not its expression in the aorta, heart, and kidney. TMS also inhibited cardiovascular and kidney hypertrophy, prevented the increase in vascular reactivity and endothelial dysfunction, and minimized the increase in urinary protein and K(+) output and the decrease in urine osmolality, Na(+) output, and creatinine clearance associated with DOCA-salt treatment. These pathophysiological changes caused by DOCA-salt treatment and associated increase in vascular superoxide production, NADPH oxidase activity, and expression of NOX-1, and ERK1/2 and p38 MAPK activities in the aorta, heart, and kidney were inhibited by TMS. These data suggest that CYP1B1 contributes to DOCA-salt-induced hypertension and associated pathophysiological changes, most likely as a result of increased ROS production and ERK1/2 and p38 MAPK activity, and could serve as a novel target for the development of agents like TMS to treat hypertension.

Role of endothelin-1 receptor blockers on hemodynamic parameters and oxidative stress

Endothelin (ET) was first isolated and described by Yanagisawa et al. and has since been described as one of the most potent known vasoconstrictor compounds. ET-1 mediates its effects via two types of receptors, ETA and ETB, which are expressed in the vascular smooth muscle cells, endothelial cells, intestines and brain. Secretion of ET-1 results in long-lasting vasoconstriction, increased blood pressure and, in turn, overproduction of free radicals. As dysregulation of the endothelin system is an important factor in the pathogenesis of several diseases including atherosclerosis, hypertension and endotoxic shock, the ETA and ETB receptors are attractive therapeutic targets for treatment of these disorders. The biosynthesis and release of ET-1 are regulated at the transcriptional level. Studies have shown that p38MAP kinase, nuclear factor kappaB (NF-kappaB), PKC/ERK and JNK/c-Jun all take part in the ROS-activated production of ET-1. Furthermore, administration of ET(A) significantly reduces the generation of free radicals. However, treatment with ETB receptor blockers does not elicit the same effect. Therefore, the effects of endothelin receptor blockers on blood pressure and the generation of free radicals remain debatable. This review summarizes recent investigations into the role of endothelin receptor blockers with respect to the modulation of hemodynamic parameters and the generation of free radicals.

Tafazzin knockdown causes hypertrophy of neonatal ventricular myocytes

Mutation of the mitochondrial protein tafazzin causes dilated cardiomyopathy in Barth syndrome. We employed an adenovirus as a vector to transfer tafazzin small hairpin RNA (shRNA) into neonatal ventricular myocytes (NVMs) to investigate the effects of tafazzin knockdown. The tafazzin shRNA adenovirus consistently knocked down tafazzin mRNA and lowered cardiolipin while significantly decreasing the production of ATP by the mitochondria. The phosphorylation of AMP-activated protein kinase and mitochondrial density were both increased in tafazzin knockdown NVMs compared with scrambled shRNA controls. When we tested whether tafazzin knockdown causes hypertrophy in vitro, we found that the surface area of NVMs infected with tafazzin shRNA adenovirus was significantly increased, as were the protein synthesis and expression of the hypertrophic marker gene, brain natriuretic peptide. Taken together, our data support the concept that a decreased tafazzin expression causes cardiomyocyte hypertrophy in vitro.

Isoproterenol disperses distribution of NADPH oxidase, MMP-9, and pPKCepsilon in the heart, which are mitigated by endothelin receptor antagonist CPU0213

AIM

Spatial dispersion of bioactive substances in the myocardium could serve as pathological basis for arrhythmogenesis and cardiac impairment by beta-adrenoceptor stimulation. We hypothesized that dispersed NADPH oxidase, protein kinase Cepsilon (PKCepsilon), early response gene (ERG), and matrix metalloproteinase 9(MMP-9) across the heart by isoproterenol (ISO) medication might be mediated by the endothelin (ET) - ROS pathway. We aimed to verify if ISO induced spatially heterogeneous distribution of pPKCepsilon, NAPDH oxidase, MMP-9 and ERG could be mitigated by either an ET receptor antagonist CPU0213 or iNOS inhibitor aminoguanidine.

METHODS

Rats were treated with ISO (1 mg/kg sc) for 10 days, and drug interventions (mg/kg) either CPU0213 (30 sc) or aminoguanidine (100 ip) were administered on days 8-10. Expression of NADPH oxidase, MMP-9, ERG, and PKCepsilon in the left and right ventricle (LV, RV) and septum (S) were measured separately.

RESULTS

Ventricular hypertrophy was found in the LV, S, and RV, in association with dispersed QTc and oxidative stress in ISO-treated rats. mRNA and protein expression of MMP-9, PKCepsilon, NADPH oxidase and ERG in the LV, S, and RV were obviously dispersed, with augmented expression mainly in the LV and S. Dispersed parameters were re-harmonized by either CPU0213, or aminoguanidine.

CONCLUSION

We found at the first time that ISO-induced dispersed distribution of pPKCepsilon, NADPH oxidase, MMP-9, and ERG in the LV, S, and RV of the heart, which were suppressed by either CPU0213 or aminoguanidine. It indicates that the ET-ROS pathway plays a role in the dispersed distribution of bioactive substances following sustained beta-receptor stimulation.

Molecular biology of the myocardial Na+/H+ exchanger

The mammalian Na(+)/H(+) exchanger is a pH regulatory membrane protein that uses the sodium gradient to translocate one intracellular proton in exchange for one extracellular sodium. There are nine isoforms of the protein with varying tissue and cellular distribution, some isoforms are predominantly intracellular. In the myocardium, the Na(+)/H(+) exchanger type 1 isoform (NHE1) is the only plasma membrane isoform present in significant quantities. It plays an important role during ischemia/reperfusion damage to the myocardium and has recently been implicated in myocardial hypertrophy. The NHE1 gene is made from 12 exons and a differentially spliced version mediates Na(+)/Li(+) exchange. The NHE1 promoter is regulated by several transcription factors. In the myocardium, transcription factors both proximal and distal to the start site affect expression, including AP-2 and a thyroid responsive element. Recently, reactive oxygen species have also been shown to be important regulators of the NHE1 promoter. Structural and functional analysis of the NHE1 protein has shown that transmembrane segments IV, VII and IX are important in ion transport and susceptibility to pharmacological inhibition. NHE1 protein and mRNA levels are elevated by cardiac ischemia/reperfusion, hypertrophy and acidosis. Understanding the mechanism by which NHE1 mediates transport and its regulation of expression will give novel insights into its contributions in cardiovascular disease.

Contrasting actions of endothelin ET(A) and ET(B) receptors in cardiovascular disease

First identified as a powerful vasoconstrictor, endothelin has an extremely diverse set of actions that influence homeostatic mechanisms throughout the body. Two receptor subtypes, ET(A) and ET(B), which usually have opposing actions, mediate the actions of endothelin. ET(A) receptors function to promote vasoconstriction, growth, and inflammation, whereas ET(B) receptors produce vasodilation, increases in sodium excretion, and inhibit growth and inflammation. Potent and selective receptor antagonists have been developed and have shown promising results in the treatment of cardiovascular diseases such as pulmonary arterial hypertension, acute and chronic heart failure, hypertension, renal failure, and atherosclerosis. However, results are often contradictory and complicated because of the tissue-specific vasoconstrictor actions of ET(B) receptors and the fact that endothelin is an autocrine and paracrine factor whose activity is difficult to measure in vivo. Considerable questions remain regarding whether ET(A)-selective or nonselective ET(A)/ET(B) receptor antagonists would be useful in a range of clinical settings.

Contrasting actions of endothelin ET(A) and ET(B) receptors in cardiovascular disease

First identified as a powerful vasoconstrictor, endothelin has an extremely diverse set of actions that influence homeostatic mechanisms throughout the body. Two receptor subtypes, ET(A) and ET(B), which usually have opposing actions, mediate the actions of endothelin. ET(A) receptors function to promote vasoconstriction, growth, and inflammation, whereas ET(B) receptors produce vasodilation, increases in sodium excretion, and inhibit growth and inflammation. Potent and selective receptor antagonists have been developed and have shown promising results in the treatment of cardiovascular diseases such as pulmonary arterial hypertension, acute and chronic heart failure, hypertension, renal failure, and atherosclerosis. However, results are often contradictory and complicated because of the tissue-specific vasoconstrictor actions of ET(B) receptors and the fact that endothelin is an autocrine and paracrine factor whose activity is difficult to measure in vivo. Considerable questions remain regarding whether ET(A)-selective or nonselective ET(A)/ET(B) receptor antagonists would be useful in a range of clinical settings.

Cardiac myocyte gene expression profiling during H2O2-induced apoptosis

High levels of oxidative stress promote cardiac myocyte death, though lower levels are potentially cytoprotective/anabolic. We examined the changes in gene expression in rat neonatal cardiac myocytes exposed to apoptotic (0.2 mM) or nontoxic (0.04 mM) concentrations of H2O2(2, 4, or 24 h) using Affymetrix microarrays. Using U34B arrays, we identified a ubiquitously expressed, novel H2O2-responsive gene [putative peroxide-inducible transcript 1 (Perit1)], which generates two alternatively spliced transcripts. Using 230 2.0 arrays, H2O2(0.04 mM) promoted significant changes in expression of only 32 genes, all of which were seen with 0.2 mM H2O2. We failed to detect any increase in the rate of protein synthesis in cardiac myocytes exposed to <0.1 mM H2O2, further suggesting that global, low concentrations of H2O2are not anabolic in this system. H2O2(0.2 mM) promoted significant ( P < 0.05, >1.75-fold) changes in expression of 649 mRNAs and 187 RNAs corresponding to no established gene. Of the mRNAs, 114 encoded transcriptional regulators including Krüppel-like factors (Klfs). Quantitative PCR independently verified the changes in Klf expression. Thus, H2O2-induced cardiac myocyte apoptosis is associated with dynamic changes in gene expression. The expression of these genes and their protein products potentially influences the progression of the apoptotic response.

An autocrine role for leptin in mediating the cardiomyocyte hypertrophic effects of angiotensin II and endothelin-1

Leptin is a 16 kDa product of the obesity gene secreted primarily by adipocytes. We recently identified cardiomyocytes as a target for the direct hypertrophic effects of leptin and suggested that leptin may be a biological link between obesity and cardiovascular pathologies. Activation of the renin-angiotensin and endothelin systems is associated with development of cardiovascular diseases and plasma renin levels are elevated in obese individuals. We therefore determined possible interaction between these factors in mediating hypertrophy in cultured neonatal rat ventricular myocytes. Treatment for 24 h with leptin (3.1 nM), angiotensin II (100 nM) or endothelin-1 (ET-1, 10 nM) significantly increased cell area by 37%, 36% and 35%, respectively and significantly increased gene expression of myosin light chain-2 and alpha-skeletal actin as well as leucine incorporation. The hypertrophic effects of all three agents were prevented by leptin and a leptin triple mutant receptor antagonist whereas the AT(1) receptor blocker (Sar1-lle(8))-Ang II or the ET(A) receptor blocker BQ123 was ineffective against leptin-induced hypertrophy. Both angiotensin II and ET-1 significantly increased leptin levels in the culture medium by fivefold. Moreover, both angiotensin II and ET-1 increased the gene expression of the short form (OBRa) by 180% and long form (OBRb) of leptin receptors by 200%, and this increase was abolished by both leptin receptor and leptin antibodies and leptin triple mutant. Although both angiotensin II and ET-1 increased phosphorylation of MAPK (p38, ERK1/2 and JNK) and NF-kappaB, the ability of leptin blockade to attenuate the hypertrophic responses was generally dissociated from these effects suggesting an alternate, yet to be identified cellular pathway mediating this role of leptin. Our studies therefore suggest a novel autocrine function for leptin in mediating the hypertrophic effects of both angiotensin II and ET-1 in cardiac myocytes.

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.

Endothelin-1-mediated increase in reactive oxygen species and NADPH Oxidase activity in hearts of aryl hydrocarbon receptor (AhR) null mice

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor characterized to play a role in detection and adaptation to environmental stimuli. Genetic deletion of the AhR results in cardiac hypertrophy that is mediated primarily by endothelin-1 (ET-1); ET-1 has been implicated in the elevation of reactive oxygen species (ROS) in the heart, which are thought to contribute to several cardiovascular disorders, including cardiac hypertrophy. Thus, we tested the novel hypothesis that ET-1 induces ROS in AhR null mice via ET(A) receptor activation. We first confirmed the presence of ROS in the hearts of AhR null mice by measuring superoxide (O2*-)-dependent oxidation of dihydroethidium. Ethidium fluorescence was increased 10-fold in the hearts of AhR null mice, compared to the wild type. Then, to elucidate whether ET-1 mediated the increase in ROS, mice were chronically treated with 100 ng/kg/day of the ET(A) receptor antagonist BQ-123. In AhR null mice, BQ-123 significantly reduced elevated plasma 8-isoprostane, a systemic end product of phospholipid oxidation by ROS, and cardiac thiobarbituric acid reactive substances (TBARS), a nonspecific assessment of ROS production. Furthermore, BQ-123 reduced both cardiac lucigenin chemiluminescence and cardiac mRNA expression of NAD(P)H oxidase subunits gp91phox, p47phox, and p67phox in AhR null mice below the levels observed in wild-type mice. These findings demonstrate that ET-1 activation of ET(A) receptors mediates an increase in ROS that is associated with cardiac hypertrophy in AhR null mice. In addition, the ET-1-mediated increase in ROS appears to be initiated via increased NAD(P)H oxidase activity.

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.