The Efficacy and Safety of Short-Term Tolvaptan Usage in Patients with Acute Decompensated Heart Failure.

Background: Patients admitted with acute decompensated heart failure (ADHF) have a poor prognosis and poor quality of life due to dyspnea and edema. Tolvaptan, a vasopressin V2 receptor antagonist, is an effective water diuretic. This study aimed to evaluate the efficacy and safety of a short course of tolvaptan to treat volume overload in patients with ADHF. Methods: We conducted a phase III, multicenter, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of a short course of tolvaptan (15 mg/day for 4 days) in hospitalized ADHF patients with volume overload despite the use of conventional diuretics. The primary end-point was the change in body weight after 4 days of treatment. The secondary end-points were the change in intake/output balance, change in serum sodium/potassium concentrations, physician/patient assessed signs and symptoms of heart failure after 4 days of treatment, and all-cause mortality in 1 month. Results: A total of 110 patients were screened, and 91 were randomized to receive 15 mg/day of tolvaptan for 4 days (n = 46) or matching placebo (n = 45). Compared to the placebo-treated patients, tolvaptan significantly reduced body weight (-1.36 ± 2.13 kg in the tolvaptan group vs. -0.59 ± 1.27 kg in the placebo group, p = 0.0394). The tolvaptan group also had a negative intake/urine volume balance compared to the placebo group (-509.3 ± 2788.2 ml vs. 975.5 ± 1903.1 ml, p = 0.0059). The safety profile of tolvaptan was acceptable. Conclusions: Tolvaptan significantly reduced volume overload in hospitalized ADHF patients with volume overload despite the use of conventional diuretics.

A Double-Blind, Randomized, Placebo-Controlled Study to Evaluate the Efficacy and Safety of STA-2 (Green Tea Polyphenols) in Patients with Chronic Stable Angina.

BACKGROUND: Green tea intake has been shown to improve endurance capacity in animal studies, but whether it has a similar effect on humans remains unclear. A randomized, double-blinded, parallel-controlled study was conducted to evaluate the short-term effect of STA-2, a pharmaceutical preparation of green tea polyphenols, in patients with effort-induced angina and documented positive exercise tolerance test. METHODS: A total of 79 patients recruited from three medical centers were randomly assigned to receive 2 STA-2 250 mg capsules, each containing 100 mg green tea polyphenols, three times daily, or placebo for six weeks after two consecutive symptom-limited treadmill exercise tests to ascertain the reproducibility of exercise tolerance. RESULTS: There was no difference in total exercise tolerance time from baseline to Week 6 between two groups (p = 0.639). There were also no observed improvements in subgroup analyses stratified by age, gender, and BMI categories. However, a significant reduction in low-density lipoprotein levels was shown in patients in the STA-2 group (-8.99 ± 19.18 mg/dL) versus the placebo group (0.57 ± 19.77 mg/dL), p = 0.037, with greater benefits in patients not taking antihyperlipidemic drugs (STA-2: -9.10 ± 19.96 mg/dL vs. placebo: 4.42 ± 15.08 mg/dL, p = 0.037). CONCLUSIONS: STA-2 treatment for 6 weeks did not increase exercise time as measured on a treadmill. However, this study also indicated that STA-2 treatment could have potential beneficial effects on LDL-cholesterol concentrations.

Prasugrel versus clopidogrel for acute coronary syndromes without revascularization.

BACKGROUND: The effect of intensified platelet inhibition for patients with unstable angina or myocardial infarction without ST-segment elevation who do not undergo revascularization has not been delineated. METHODS: In this double-blind, randomized trial, in a primary analysis involving 7243 patients under the age of 75 years receiving aspirin, we evaluated up to 30 months of treatment with prasugrel (10 mg daily) versus clopidogrel (75 mg daily). In a secondary analysis involving 2083 patients 75 years of age or older, we evaluated 5 mg of prasugrel versus 75 mg of clopidogrel. RESULTS: At a median follow-up of 17 months, the primary end point of death from cardiovascular causes, myocardial infarction, or stroke among patients under the age of 75 years occurred in 13.9% of the prasugrel group and 16.0% of the clopidogrel group (hazard ratio in the prasugrel group, 0.91; 95% confidence interval [CI], 0.79 to 1.05; P=0.21). Similar results were observed in the overall population. The prespecified analysis of multiple recurrent ischemic events (all components of the primary end point) suggested a lower risk for prasugrel among patients under the age of 75 years (hazard ratio, 0.85; 95% CI, 0.72 to 1.00; P=0.04). Rates of severe and intracranial bleeding were similar in the two groups in all age groups. There was no significant between-group difference in the frequency of nonhemorrhagic serious adverse events, except for a higher frequency of heart failure in the clopidogrel group. CONCLUSIONS: Among patients with unstable angina or myocardial infarction without ST-segment elevation, prasugrel did not significantly reduce the frequency of the primary end point, as compared with clopidogrel, and similar risks of bleeding were observed. (Funded by Eli Lilly and Daiichi Sankyo; TRILOGY ACS ClinicalTrials.gov number, NCT00699998.).

Unique clinical characteristics and SCN5A mutations in patients with Brugada syndrome in Taiwan.

BACKGROUND/PURPOSE: Brugada syndrome (BrS) is a hereditable sudden cardiac death (SCD). Mutations in the SCN5A gene (the most common BrS-causing gene) are responsible for 20-25% of this disease in Caucasian populations. However, the prevalence of SCN5A mutations in patients with BrS in the Chinese Han population in Taiwan remains unknown. Therefore, in this study, we investigated the prevalence of the SCN5A mutation in the largest BrS cohort in Taiwan. METHODS: We consecutively enrolled 47 unrelated patients with BrS from medical centers and hospitals in Taiwan between 2000 and 2010. Mutations within all the 27 translated exons, and exon-intron boundaries of the SCN5A-encoded cardiac sodium channel were screened in all patients with BrS using direct sequencing. A total of 500 unrelated healthy volunteers with a normal electrocardiogram were genotyped as a control group. RESULTS: SCN5A genetic variants were identified in 14 of the 47 patients with BrS and four of the 14 patients with BrS had missense mutations (1651 G>A, 1776 C>G, 3578 G>A). The prevalence rate of SCN5A mutations was approximately 8% (4/47), which was significantly lower than that reported in Caucasian populations (20-25%; p = 0.0007). The average age of these 14 BrS patients with SCN5A variants at diagnosis (12 men and 2 women) was 40 ± 13 years. Four patients experienced SCD, and six presented with seizure or syncope. Only three patients (3/14, 21.4%) had a family history of SCD. CONCLUSION: The prevalence of SCN5A mutations in the Chinese Han population in Taiwan may be lower than that reported in the Caucasian populations. In addition, most patients with BrS did not have a family history of SCD.

Proteinuria and Reduced Estimated Glomerular Filtration Rate Independently Predict Risk for Acute Myocardial Infarction: Findings from a Population-Based Study in Keelung, Taiwan.

BACKGROUND: The aim of this study was to evaluate the independent roles of proteinuria and reduced estimated glomerular filtration rate (GFR) in the development of acute myocardial infarction in a northern Taiwanese population. METHODS: We conducted a community-based prospective cohort study in Keelung, the northernmost county of Taiwan. A total of 63,129 subjects (63% women) ≥ 20 years of age who had no history of coronary heart disease were recruited and followed-up. Univariate and multivariate proportional hazards regression analysis was performed to assess the association between proteinuria and estimated GFR and the risk of acute myocardial infarction. RESULTS: There were 305 new cases of acute myocardial infarction (114 women and 191 men) documented during a four-year follow-up period. After adjustment of potential confounding covariates, heavier proteinuria (dipstick urinalysis reading 3+) and estimated GFR of less than 60 ml/min/1.73 m(2) independently predicted increased risk of developing acute myocardial infarction. The adjusted hazard ratio (aHR) of heavier proteinuria for occurrence of acute myocardial infarction was 1.85 [95% confidence intervals (CI), 1.17-2.91, p < 0.01] (vs. the reference group: negative dipstick proteinuria). The aHR of estimated GFR of 30-59 ml/min/1.73 m(2) for occurrence of acute myocardial infarction was 2.4 (95% CI, 1.31-4.38, p < 0.01) (vs. the reference group: estimated GFR ≥ 90 ml/ min/1.73 m(2)), and that of estimated GFR of 15-29 ml/min/1.73 m(2) was 5.26 (95% CI, 2.26-12.26, p < 0.01). CONCLUSIONS: We demonstrated that both heavier proteinuria and lower estimated GFR are significant independent predictors of developing future acute myocardial infarction in a northern Taiwanese population. KEY WORDS: Acute myocardial infarction; Estimated glomerular filtration rate; Proteinuria.

Association of Small-Conductance Calcium-Activated Potassium Channels and Atrial Fibrillation - How Far Have We Gone?

UNLABELLED: Atrial fibrillation (AF) is the most common sustained and most important arrhythmia in clinical practice. The mechanisms underlying AF initiation and maintenance are known to be complex and heterogeneous. The general understanding of the detailed molecular basis of AF is still incomplete. Recently, these is increasing evidence that small conductance calcium-activated potassium (SK) channels are associated with atrial action potential repolarization and the pathogenesis of AF. Although the functional role of SK channels in the genesis of AF is not entirely clear, new insights into the basic pathophysiological mechanism of AF have been provided. Besides, genome-wide association studies also implicate that genes coding for SK channels are related to the risk of developing AF. This article reviews recent work on the association of SK channels and AF, genetic studies of SK channels, and discuss future investigation and developments regarding this field. KEY WORDS: Atrial fibrillation; Genetics; Small conductance calcium-activated potassium channels.

Genetic variation-optimized treatment benefit of angiotensin-converting enzyme inhibitors in patients with stable coronary artery disease: a 12-year follow-up study.

OBJECTIVES: The objective of this study was to examine the relationship between renin-angiotensin system genotypes and the pharmacogenetics of angiotensin-converting enzyme (ACE) inhibitors in Chinese patients with coronary artery disease (CAD). METHODS: Patients with angiographic CAD were recruited from 1995 to 2003. The baseline characteristics and genetic polymorphisms [ACE gene insertion/deletion (I/D) polymorphisms, six polymorphisms of the angiotensinogen (AGT) gene, and A-1166C polymorphisms of the angiotensin-II type I receptor gene (AGT1R)] were established. Patients were divided into two groups (ACE inhibitor or no ACE inhibitor) and followed for up to 12 years. Kaplan-Meier curves and Cox regression models were used to determine the survival and major cardiovascular events (MACE) event-free survival trends. Pharmacogenetic effects were determined by several Cox regression models. RESULTS: Of the 784 patients, 432 were treated with ACE inhibitors and 352 were not. ACE inhibitors were associated with a lower MACE rate at 4000 days. In addition, the ACE I/D gene D and AGT1R gene C alleles were associated with a higher MACE rate on the basis of a multivariate regression analysis. This effect was attenuated by the pharmacogenetic interaction of ACE inhibitors and the ACE gene (ACE inhibitors* ACE gene, hazard ratio: 0.8, 95% confidence interval: 0.62-0.94, P=0.03). CONCLUSIONS: ACE inhibitors were associated with a significant decrease in MACE in Chinese patients diagnosed with CAD. Genetic variants were also associated with event-free survival, but their effects were modified by the use of ACE inhibitors.

Contrast-Induced Encephalopathy after Percutaneous Coronary Intervention.

UNLABELLED: Contrast-induced encephalopathy (CIE) is a rare complication that presents with transient neurologic deficits and is caused by neurotoxicity of intravascular contrast media. The prognosis can be extremely favorable even in comatose patients. We reported a 76-year-old woman admitted for scheduled coronary angiography. The total amount of Optiray contrast media used was 150 mL. Immediately after the procedure, the patient developed consciousness disturbance, global aphasia, cortical blindness and right-sided weakness. CIE was diagnosed by computed tomography and subsequent magnetic resonance imaging. The patient recovered completely within 48 hours without any neurological deficits. KEY WORDS: Angioplasty; Contrast-induced encephalopathy; Percutaneous coronary intervention.

Renin-Angiotensin System Genes Polymorphisms and Long-Term Prognosis in Taiwanese Patients with Hypertension and Coronary Artery Disease.

OBJECTIVES: The objective of this study was to evaluate the renin-angiotensin system genetic effects and pharmacogenetic interactions for angiotensin-converting enzyme (ACE) inhibitors in hypertensive coronary artery disease (CAD) patients. METHODS: Subjects with hypertension and angiographic CAD were recruited from 1995 to 2003. Baseline characteristics and genetic polymorphisms [ACE gene insertion/deletion (I/D) polymorphism, six polymorphisms of the angiotensinogen (AGT) gene, and A1166C polymorphisms of the angiotensin II type I receptor gene (AGT1R)] were collected. Patients were assigned to 2 groups (ACE inhibitor or No-ACE inhibitor) and followed-for up to 12 years. Kaplan-Meier curves and Cox regression models were used to demonstrate the survival and major cardiovascular events (MACE) event-free survival trends. Pharmacogenetic effects were determined by several Cox regression models. RESULTS: Of the 518 patients in our study, 290 were treated with ACE inhibitors and 228 were not. Prescription of ACE inhibitors was associated with a lower rate of MACE at 4000 days. In addition, ACE I/D gene D was associated with a higher rate of MACE in a multivariate regression analysis [hazard ration (HR): 1.64, 95% confidence interval (CI): 1.27-1.98, p < 0.001]. This effect could be attenuated by the pharmacogenetic interaction of ACE inhibitors and the ACE gene (ACE in hibitors*ACE D gene, HR: 0.68, 95% CI: 0.52-0.84, p = 0.014). CONCLUSIONS: The use of ACE inhibitors was associated with a significant decrease in MACE in hypertensive patients diagnosed with CAD. Genetic variants were also associated with event-free survival, but their effects were modified by the use of ACE inhibitors. KEY WORDS: Angiotensin-converting enzyme inhibitors; Coronary artery disease; Hypertension; Pharmacogenetic.

Next-Generation Sequencing in the Genetics of Human Atrial Fibrillation.

UNLABELLED: The International Human Genome Sequencing Consortium published the first draft of the human genome in the journal Nature in February 2001, providing the sequence of the entire genome's three billion base pairs. The Human Genome Project involves a concerted effort to better understand the human DNA sequence through identification of all the genes. The knowledge that can be derived from the genome could result in the development of novel diagnostic assays, targeted therapies and the improved ability to predict the onset, severity and progression of diseases. This has been made possible by many parallelized, high-throughput technologies such as next-generation sequencing. In this review, we discuss the possible application of next-generation sequencing in finding the susceptibility gene(s) or disease mechanism of an important human arrhythmia called atrial fibrillation. KEY WORDS: Arrhythmia; Atrial fibrillation; Genetics, Next-generation sequencing.

Significant association of rs13376333 in KCNN3 on chromosome 1q21 with atrial fibrillation in a Taiwanese population.

BACKGROUND: A recent study in individuals of European ancestry demonstrated a significant association of the single nucleotide polymorphism (SNP) rs13376333 in potassium intermediate/small conductance calcium-activated channel, subfamily N, member 3 (KCNN3) on chromosome 1q21 with lone atrial fibrillation (AF), indicating a common genetic basis for AF. The aim of the present study was to investigate whether this association between SNP rs13376333 and AF also exists in Taiwanese subjects. METHODS AND RESULTS: The SNP rs13376333 was compared in 214 lone AF patients (58.3±11.4 years) vs. 214 controls (57.7±13.2 years), and in 322 structural AF patients (69.6±13.7 years) vs. 322 controls (68.4±14.2 years) in a Taiwanese population, in a case-control design. The associations between SNP rs13376333 in KCNN3 and structural or lone AF were significant. In the lone AF group, the frequency of the minor allele of SNP rs13376333 was 8.6% compared with 3.0% in the controls (P<0.001; odds ratio [OR], 3.02; 95% confidence interval [CI]: 1.54-6.29). The frequency of the minor allele of SNP rs13376333 was 6.5% in structural AF patients compared with 3.1% in controls (P=0.004; OR, 2.18; 95%CI: 1.23-3.96). CONCLUSIONS: There are significant associations between SNP rs13376333 and the risk of developing both lone and structural AF in the Taiwanese population. The minor allele frequency of SNP rs13376333 was much lower in the Taiwanese population compared to that in the Caucasian population.

Plasma levels of tumor necrosis factor-α and interleukin-6 are associated with diastolic heart failure through downregulation of sarcoplasmic reticulum Ca2+ ATPase.

OBJECTIVE: The inflammatory process is associated with cardiac diastolic dysfunction, which has been demonstrated to be an independent prognostic marker for the mortality of critically ill patients. We investigated the association among inflammatory cytokines (tumor necrosis factor-α and interleukin-6), diastolic heart failure, and the possible molecular mechanism. DESIGN: Prospective case-controlled cohort and molecular studies. SETTING: University hospital and research laboratory. SUBJECTS: Patients with a diagnosis of diastolic heart failure by echocardiography and matched control subjects from the general population (study group 1) and also subjects from the intensive care unit (study group 2). Sarcoplasmic reticulum Ca2+-ATPase (SERCA2) gene expression and diastolic calcium decay in HL-1 cardiomyocytes were used as molecular phenotypes of diastolic heart failure. INTERVENTIONS: Soluble plasma levels of tumor necrosis factor-α and interleukin-6 were measured in all subjects. An approximate 1.75-kb promoter of the SERCA2 gene was cloned to the pGL3 luciferase reporter. The effect of tumor necrosis factor-α and interleukin-6 on SERCA2 gene expression and diastolic calcium decay of HL-1 cardiomyocytes were investigated. MEASUREMENTS AND MAIN RESULTS: Patients with diastolic heart failure had significantly higher plasma levels of tumor necrosis factor-α and interleukin-6 than the control subjects. Significant correlations (p < .01 for each) were found for tumor necrosis factor-α and E/Em (r = .87) and E/A (r = -0.69), and for interleukin-6 and E/Em (r = .80) and E/A (r = -0.65). Cytokine levels were also correlated with diastolic function in critically ill patients (study group 2), and diastolic function improved significantly in association with decrease of cytokines. Tumor necrosis factor-α, interleukin-6, and sera from critically ill patients downregulated the expression of the SERCA2 gene. Tumor necrosis factor-α and interleukin-6 also delayed the diastolic calcium reuptake and decay in cardiomyocytes. CONCLUSIONS: Through downregulation of SERCA2 gene expression, inflammatory cytokines may cause cardiac diastolic dysfunction by decreasing diastolic calcium reuptake. Our study may suggest novel therapeutic strategies for diastolic heart failure and critically ill patients by modulating inflammatory reactions.

Brugada-type electrocardiogram in the Taiwanese population--is it a risk factor for sudden death?

BACKGROUND/PURPOSE: People receive electrocardiogram (ECG) examination for various reasons in a hospital setting. An important clinical practice issue may be that cardiologists need to be consulted for Brugada-type ECGs identified through routine screening. We investigated the prevalence and prognosis of patients with Brugada-type ECG in a hospital-based population in an attempt to improve the management of these patients. METHODS: In 20,562 patients seeking medical care for non-cardiovascular reasons, 74,955 ECGs were performed from December 1999 to February 2001. The diagnostic criteria for Brugada-like ECG from the European Society of Cardiology were used. International Statistical Classification of Diseases codes and city residents' records were documented to indicate the reasons for visiting clinics or hospitalization and mortality outcome. Medical records were reviewed and telephone interviews were conducted. RESULTS: Twenty-six (0.13%) of the 20,562 patients were confirmed to have Brugada-type ECGs. None of these patients had ever experienced syncope, near syncope or sudden cardiac death. After 57.1 ± 15.8 months of follow-up, there were four deaths out of the 26 patients with Brugada-type ECG (15.4%, 95% CI: 1.53-2.9%) compared with 2899 of those without (14.1%, 95% CI: 13.6-14.5%; p=0.89, log-rank test). Neither sudden cardiac death (p=0.61) nor hospitalized death (p=0.55) was different between patients with and without Brugada-type ECG. CONCLUSION: Patients with Brugada-type ECGs are not rare in a hospital-based population. The presence of Brugada-type ECGs in patients without syncope or sudden cardiac death was not associated with hospitalized mortality.

Effects of acetyl-L-carnitine and oxfenicine on aorta stiffness in diabetic rats.

BACKGROUND: We compared the haemodynamic and metabolic effects of acetyl-L-carnitine (one of the carnitine derivatives) and of oxfenicine (a carnitine palmitoyltransferase-1 inhibitor) in streptozotocin-induced diabetes in male Wistar rats. MATERIALS AND METHODS: Diabetes was induced by a single tail vein injection of 55mgkg(-1) streptozotocin. The diabetic animals daily treated with either acetyl-L-carnitine (150mgkg(-1) in drinking water) or oxfenicine (150mgkg(-1) by oral gavage) for 8weeks,were compared with the untreated age-matched diabetic controls. Arterial wave reflection was derived using the impulse response function of the filtered aortic input impedance spectra. Thiobarbituric acid reactive substances (TBARS) measurement was used to estimate malondialdehyde (MDA) content. RESULTS: Oxfenicine, but not acetyl-L-carnitine, increased total peripheral resistance in diabetes, which paralleled its elevation in plasma levels of free fatty acids. By contrast, acetyl-L-carnitine, but not oxfenicine, resulted in a significant increase in wave transit time and a decrease in wave reflection factor, suggesting that acetyl-L-carnitine may attenuate the diabetes-induced deterioration in systolic loading condition for the left ventricle. This was in parallel with its lowering of MDA/TBARS content in plasma and aortic walls in diabetes. Acetyl-L-carnitine therapy also prevented the diabetes-related cardiac hypertrophy, as evidenced by the reduction in ratio of the left ventricular weight to body weight. CONCLUSION: Acetyl-L-carnitine, but not oxfenicine, attenuates aortic stiffening and cardiac hypertrophy, possibly through its decrease of lipid oxidation-derived MDA/TBARS in the rats with insulin deficiency.

Transcatheter embolization of a huge renal arteriovenous fistula with Amplatzer Vascular Plug.

A large renal arteriovenous fistula (RAF) may lead to heart failure, renal insufficiency, hematuria, and progressive increase in size of renal vessels. Here we present the case of a 67-year-old man with a huge left RAF, who suffered from exertional dyspnea, nocturnal orthopnea, and impaired renal function. The left renal vein and inferior vena cava were dilated to 4 cm. An Amplatzer Vascular Plug with the largest size of 30 mm in disk diameter was deployed to block the fistula, with balloons inflated at renal artery and vein in advance, to reduce the renal flow in order to prevent plug migration. The decrease of shunt flow after embolization was suboptimal. However, dyspnea ameliorated, which was associated with decreased cardiac murmur, subsided abdominal bruit, normalization of the lowered diastolic pressure, and better renal function. In addition, more microcoils can be applied, using the lodged plug as a framework, to achieve the best clinical improvement.

Effect of physical activity on the prevalence of metabolic syndrome and left ventricular hypertrophy in apparently healthy adults.

BACKGROUND/PURPOSE: Metabolic syndrome and left ventricular hypertrophy (LVH) carry high cardiovascular risks. We performed a cross-sectional study to evaluate the effect of different amounts of physical activity (PA) on the prevalence of metabolic syndrome and LVH in our study population. METHODS: This study was a cross-sectional survey of 1494 apparently healthy subjects: 776 men with a mean age of 57.6 + 12.3 years, and 718 women with a mean age of 56.4+ 11.0 years. The metabolic syndrome was defined according to modified criteria of the National Cholesterol Education Program Adult Treatment Panel III. LVH was diagnosed by electrocardiography voltage criteria. The amount of PA was determined with a questionnaire and stratified into low, moderate or high levels. RESULTS: The prevalence of metabolic syndrome and its components was as follows: metabolic syndrome, 15.5%; obesity, 29.7%; high triglyceride level, 21.7%; low high-density lipoprotein-cholesterol level, 35.9%; high blood pressure, 56.9%; and impaired fasting glucose, 13.1%. A high amount of PA (> 14 km per week walking distance) was significantly associated with lower prevalence of metabolic syndrome [odds ratio (OR) = 0.53, p = 0.001], lower prevalence of obesity (OR = 0.56, p = 0.001), triglyceridemia (OR = 0.58, p = 0.007) and LVH (OR=0.37, p = 0.006). CONCLUSION: This study suggests that high amounts of PA are inversely correlated with the prevalence of metabolic syndrome and LVH in men and women.

Angiotensin II activates signal transducer and activators of transcription 3 via Rac1 in atrial myocytes and fibroblasts: implication for the therapeutic effect of statin in atrial structural remodeling.

BACKGROUND: Recently, activation of the local renin-angiotensin system and mitogen-activated protein kinase pathways in atrial myocardium has been found to play an important role in atrial structural remodeling related to atrial fibrillation. Another important mediator of the angiotensin II (Ang II) effect is the Janus kinase/signal transducers and activators of transcription (STAT) pathway, which has never been characterized in the atrium. METHODS AND RESULTS: In cultured atrial myocytes and fibroblasts, Ang II induced tyrosine phosphorylation of STAT3 through a Rac1-dependent mechanism, which was inhibited by dominant-negative Rac1, losartan, and simvastatin. In atrial myocytes, activation of STAT3 by Rac1 was mediated by direct association of Rac1 with STAT3; however, in atrial fibroblasts, it was mediated by an indirect paracrine effect. Constitutively active STAT3 increased protein synthesis, and dominant-negative STAT3 abrogated Ang II-induced protein synthesis in atrial myocytes and fibroblasts. Rats infused long term with Ang II exhibited higher levels of activated Rac1, phospho-STAT3, collagen synthesis, and atrial fibrosis in the atria, all of which were attenuated by oral losartan and simvastatin. In human atrial tissues from patients with atrial fibrillation, Ang II and phospho-STAT3 levels were also elevated. CONCLUSIONS: The Ang II/Rac1/STAT3 pathway is an important signaling pathway in the atrial myocardium to mediate atrial structural remodeling, and losartan and statin may be able to reverse Ang II-induced atrial structural remodeling in atrial fibrillation.

Dimethylthiourea normalizes velocity-dependent, but not force-dependent, index of ventricular performance in diabetic rats: role of myosin heavy chain isozyme.

Hydroxyl radicals and hydrogen peroxide are involved in the pathogenesis of systolic dysfunction in diabetic rats, but the precise mechanisms and the effect of antioxidant therapy in diabetic subjects have not been elucidated. We aimed to evaluate the effects of dimethylthiourea (DMTU), a potent hydroxyl radical scavenger, on both force-dependent and velocity-dependent indexes of cardiac contractility in streptozotocin (STZ)-induced early and chronic diabetic rats. Seventy-two hours and 8 wk after STZ (55 mg/kg) injection, diabetic rats were randomized to either DMTU (50 mg x kg(-1) x day(-1) ip) or vehicle treatment for 6 and 12 wk, respectively. All rats were then subjected to invasive hemodynamic studies. Maximal systolic elastance (E(max)) and maximum theoretical flow (Q(max)) were assessed by curve-fitting techniques in terms of the elastance-resistance model. Both normalized E(max) (E(maxn)) and afterload-adjusted Q(max) (Q(maxad)) were depressed in diabetic rats, concomitant with altered myosin heavy chain (MHC) isoform composition and its upstream regulators, such as myocyte enhancer factor-2 (MEF-2) and heart autonomic nervous system and neural crest derivatives (HAND). In chronic diabetic rats, DMTU markedly attenuated the impairment in Q(maxad) and normalized the expression of MEF-2 and eHAND and MHC isoform composition but exerted an insignificant benefit on E(maxn). Regarding preventive treatment, DMTU significantly ameliorated both E(maxn) and Q(maxad) in early diabetic rats. In conclusion, our study shows that DMTU has disparate effects on Q(maxad) and E(maxn) in chronic diabetic rats. The advantage of DMTU in chronic diabetic rats might involve normalization of MEF-2 and eHAND, as well as reversal of MHC isoform switch.

Angiotensin II increases expression of alpha1C subunit of L-type calcium channel through a reactive oxygen species and cAMP response element-binding protein-dependent pathway in HL-1 myocytes.

Angiotensin II (Ang II) is involved in the pathogenesis of atrial fibrillation (AF). L-type calcium channel (LCC) expression is altered in AF remodeling. We investigated whether Ang II modulates LCC current through transcriptional regulation, by using murine atrial HL-1 cells, which have a spontaneous calcium transient, and an in vivo rat model. Ang II increased LCC alpha1C subunit mRNA and protein levels and LCC current density, which resulted in an augmented calcium transient in atrial myocytes. An approximately 2-kb promoter region of LCC alpha1C subunit gene was cloned to the pGL3 luciferase vector. Ang II significantly increased promoter activity in a concentration- and time-dependent manner. Truncation and mutational analysis of the LCC alpha1C subunit gene promoter showed that cAMP response element (CRE) (-1853 to -1845) was an important cis element in Ang II-induced LCC alpha1C subunit gene expression. Transfection of dominant-negative CRE binding protein (CREB) (pCMV-CREBS133A) abolished the Ang II effect. Ang II (1 micromol/L, 2 hours) induced serine 133 phosphorylation of CREB and binding of CREB to CRE and increased LCC alpha1C subunit gene promoter activity through a protein kinase C/NADPH oxidase/reactive oxygen species pathway, which was blocked by the Ang II type 1 receptor blocker losartan and the antioxidant simvastatin. In the rat model, Ang II infusion increased LCC alpha1C subunit expression and serine 133 phosphorylation of CREB, which were attenuated by oral losartan and simvastatin. In summary, Ang II induced LCC alpha1C subunit expression via a protein kinase C-, reactive oxygen species-, and CREB-dependent pathway and was blocked by losartan and simvastatin.

Renin-angiotensin system component expression in the HL-1 atrial cell line and in a pig model of atrial fibrillation.

OBJECTIVES: Local atrial tissue angiotensin II (AngII) level is elevated in atrial fibrillation (AF), but the mechanism is unknown. We hypothesized that atrial myocytes express all components of the renin-angiotensin system (RAS) and investigated whether rapid depolarization alone is sufficient to increase paracrine AngII production by up-regulating RAS component expression. METHODS: In the HL-1 atrial cell line, rapid depolarization was induced by rapid field electrical stimulation (RES) at 1.0 V/cm and 600/min (10 Hz) in atrial HL-1 cells. In a pig model of AF, AF was induced by atrial pacing at 600/min in 10 adult pigs and 10 sham-operated pigs for comparison. RESULTS: In atrial myocytes, RES induced a sustained elevation of intracellular calcium, and up-regulation of angiotensin-converting enzyme (ACE), chymase and angiotensinogen, resulting in increased AngII production. RES-induced AngII production was attenuated by enalapril [ACE inhibitor (ACEI)] and chymostatin (chymase inhibitor). Conditioned medium from RES-stimulated atrial myocytes increased [3H]leucine uptake and atrial natriuretic peptide expression in atrial myocytes, and [3H]proline uptake and collagen type 1 alpha 1 expression in atrial fibroblasts. Both were attenuated by co-incubation with the AngII type 1 receptor blocker (ARB) losartan. In the porcine model, significant structural changes and a similar pattern of changes of RAS components were noted in AF pigs. CONCLUSIONS: Atrial cells expressed all components of RAS and rapid depolarization alone was sufficient to up-regulate RAS components, increase paracrine AngII production and induce atrial structural changes, which are attenuated by ACEI, ARB and chymase inhibitor.