Richard D. Patten

Cardiotoxicity of the cancer therapeutic agent imatinib mesylate

Imatinib mesylate (Gleevec) is a small-molecule inhibitor of the fusion protein Bcr-Abl, the causal agent in chronic myelogenous leukemia. Here we report ten individuals who developed severe congestive heart failure while on imatinib and we show that imatinib-treated mice develop left ventricular contractile dysfunction. Transmission electron micrographs from humans and mice treated with imatinib show mitochondrial abnormalities and accumulation of membrane whorls in both vacuoles and the sarco- (endo-) plasmic reticulum, findings suggestive of a toxic myopathy. With imatinib treatment, cardiomyocytes in culture show activation of the endoplasmic reticulum (ER) stress response, collapse of the mitochondrial membrane potential, release of cytochrome c into the cytosol, reduction in cellular ATP content and cell death. Retroviral gene transfer of an imatinib-resistant mutant of c-Abl, alleviation of ER stress or inhibition of Jun amino-terminal kinases, which are activated as a consequence of ER stress, largely rescues cardiomyocytes from imatinib-induced death. Thus, cardiotoxicity is an unanticipated side effect of inhibition of c-Abl by imatinib.

17β-Estradiol Reduces Cardiomyocyte Apoptosis In Vivo and In Vitro via Activation of Phospho-Inositide-3 Kinase/Akt Signaling

Female gender and estrogen-replacement therapy in postmenopausal women are associated with improved heart failure survival, and physiological replacement of 17&bgr;-estradiol (E2) reduces infarct size and cardiomyocyte apoptosis in animal models of myocardial infarction (MI). Here, we characterize the molecular mechanisms of E2 effects on cardiomyocyte survival in vivo and in vitro. Ovariectomized female mice were treated with placebo or physiological E2 replacement, followed by coronary artery ligation (placebo-MI or E2-MI) or sham operation (sham) and hearts were harvested 6, 24, and 72 hours later. After MI, E2 replacement significantly increased activation of the prosurvival kinase, Akt, and decreased cardiomyocyte apoptosis assessed by terminal deoxynucleotidyltransferase dUTP nick-end labeling (TUNEL) staining and caspase 3 activation. In vitro, E2 at 1 or 10 nmol/L caused a rapid 2.7-fold increase in Akt phosphorylation and a decrease in apoptosis as measured by TUNEL staining, caspase 3 activation, and DNA laddering in cultured neonatal rat cardiomyocytes. The E2-mediated reduction in apoptosis was reversed by an estrogen receptor (ER) antagonist, ICI 182,780, and by phospho-inositide-3 kinase inhibitors, LY294002 and Wortmannin. Overexpression of a dominant negative-Akt construct also blocked E2-mediated reduction in cardiomyocyte apoptosis. These data show that E2 reduces cardiomyocyte apoptosis in vivo and in vitro by ER- and phospho-inositide-3 kinase–Akt–dependent pathways and support the relevance of these pathways in the observed estrogen-mediated reduction in myocardial injury.

Design of a Phase 1/2 Trial of Intracoronary Administration of AAV1/SERCA2a in Patients With Heart Failure

BACKGROUND Heart failure (HF) remains a major cause of morbidity and mortality in North America. With an aging population and an unmet clinical need by current pharmacologic and device-related therapeutic strategies, novel treatment options for HF are being explored. One such promising strategy is gene therapy to target underlying molecular anomalies in the dysfunctional cardiomyocyte. Prior animal and human studies have documented decreased expression of SERCA2a, a major cardiac calcium cycling protein, as a major defect found in HF. METHODS AND RESULTS We hypothesize that increasing the activity of SERCA2a in patients with moderate to severe HF will improve their cardiac function, disease status, and quality of life. Gene transfer of SERCA2a will be performed via an adeno-associated viral (AAV) vector, derived from a nonpathogenic virus with long-term transgene expression as well as a clinically established favorable safety profile. CONCLUSIONS We describe the design of a phase 1 clinical trial of antegrade epicardial coronary artery infusion (AECAI) administration of AAVI/SERCA2a (MYDICAR) to subjects with HF divided into 2 stages: in Stage 1, subjects will be assigned open-label MYDICAR in one of up to 4 sequential dose escalation cohorts; in Stage 2, subjects will be randomized in parallel to 2 or 3 doses of MYDICAR or placebo in a double-blinded manner.

Beneficial effects of metoprolol in heart failure associated with coronary artery disease: a randomized trial.

OBJECTIVES This clinical trial was performed to determine the safety and clinical impact of titrated metoprolol therapy in patients with heart failure, documented coronary artery disease and a low ejection fraction. BACKGROUND Despite known cardiodepressant effects, long-term use of beta-adrenergic antagonists appears to be beneficial in patients with idiopathic dilated cardiomyopathy. However, this therapy has not been critically evaluated in patients with heart failure and coronary artery disease. METHODS In 50 patients with heart failure, known coronary artery disease and an ejection fraction < or = 0.40, we examined the impact of metoprolol therapy in a 6-month double-blind, placebo-controlled randomized trial, assessing the frequency of heart failure exacerbations and changes in symptoms (New York Heart Association functional class), ejection fraction and exercise duration. Placebo-treated patients who completed 6-month follow-up studies then underwent a trial with metoprolol therapy (crossover group). RESULTS Metoprolol was titrated to a mean maximal dose of 87 mg/day (range 25 to 100) without serious adverse reactions. During double-blind therapy, use of a beta-blocker was associated with a significant reduction in the number of hospital admissions (4% vs. 32%, p < 0.05), overall improved functional class (p = 0.02), increased ejection fraction (4 +/- 7% [mean +/- SD] compared with 0 +/- 6%, p < 0.05) and a greater increase in exercise duration (193 +/- 276 vs. 38 +/- 213 s with placebo, p < 0.01). Crossover outcome paralleled the favorable impact seen during randomized metoprolol therapy. CONCLUSIONS Cautious use of titrated metoprolol appears to be safe and beneficial when added to standard heart failure therapy in patients with dilated cardiomyopathy associated with coronary artery disease.

Small Animal Models of Heart Failure Development of Novel Therapies, Past and Present

Received June 23, 2008; accepted January 20, 2009. The study of heart failure requires viable animal models whereby chronic changes in myocardial structure and function can evolve and the progression of heart failure and left ventricular (LV) dysfunction can be quantified. During the past 40 years, basic and translational scientists have used small animal models to explore the pathophysiology of heart failure and to develop novel therapies that might slow the progression of this prevalent and fatal disease. The purpose of this review is to describe commonly used heart failure models in rodents and to cite examples of how these models have been used to evaluate novel therapies for the treatment of heart failure. Heart failure models were originally developed in rats because of numerous potential advantages inherent in a small animal model (see Table 1). Housing and maintenance costs for rats are much lower than for large animals, thus reducing costs and increasing the number of animals included in a given study to improve the statistical power. Moreover, more recent technological advances in echocardiography, MRI, and micromanometer conductance catheters have greatly streamlined the assessment of cardiac function in rodents, removing a significant barrier to their use in heart failure research. The development of suitable expertise to perform open-chest surgical procedures and invasive hemodynamic assessments in rats is far easier compared with that required for mice. Additionally, investigators are able to perform a greater number of postmortem histological or molecular biological analyses given the approximately 10-fold greater myocardial mass of rats compared with mice. For these reasons, the rat models detailed below have been the most widely and successfully used heart failure models in basic and translational research. View this table: Table. Commonly Used Rodent Heart Failure Models Myocardial infarctions (MIs) in rats were originally induced by the sequential administration of subcutaneous isoproterenol …

Causes of death and rehospitalization in patients hospitalized with worsening heart failure and reduced left ventricular ejection fraction: Results from efficacy of vasopressin antagonism in heart failure outcome study with tolvaptan (EVEREST) program

BACKGROUND The postdischarge rehospitalization and death rates are high in patients with acute heart failure (HF) syndromes despite optimization of standard therapy for chronic HF. To the best of our knowledge, there has been no systematic analysis of the causes of death and rehospitalization in this patient population. METHODS This was a prespecified analysis of adjudicated cause-specific all-cause mortality and cardiovascular (CV) hospitalization in the Efficacy of Vasopressin Antagonism in Heart Failure Outcome Study with Tolvaptan (EVEREST) trial, a randomized, double-blind, placebo-controlled study in patients hospitalized with worsening HF and left ventricular ejection fraction < or =40% comparing tolvaptan, an oral vasopressin receptor antagonist to placebo, in addition to standard care. RESULTS Of the 4,133 randomized, there were 5,239 rehospitalizations and 1,080 deaths during a median of 9.9 months. Of all deaths, 41.0% were due to HF, 26.0% due to sudden cardiac death (SCD), 2.6% due to acute myocardial infarction (MI), 2.2% due to stroke, and 13.2% due to non-CV causes. Of all hospitalizations, 39.2% were non-CV, whereas 46.3% were for HF, and a minority of hospitalizations was due to stroke, MI, arrhythmia, or other CV causes. CONCLUSIONS Despite close follow-up and evidence-based therapy within a clinical trial, rehospitalization and death remain high. Although most deaths were from HF, one quarter of patients had SCD. In addition, there were almost as many non-CV hospitalizations as HF hospitalizations. Knowledge of the causes of death and rehospitalization may be essential for proper management and early initiation of therapy.

Parasympathetic response in chick myocytes and mouse heart is controlled by SREBP.

Parasympathetic stimulation of the heart, which provides protection from arrhythmias and sudden death, involves activation of the G protein-coupled inward rectifying K+ channel GIRK1/4 and results in an acetylcholine-sensitive K+ current, I KACh. We describe a unique relationship between lipid homeostasis, the lipid-sensitive transcription factor SREBP-1, regulation of the cardiac parasympathetic response, and the development of ventricular arrhythmia. In embryonic chick atrial myocytes, lipid lowering by culture in lipoprotein-depleted serum increased SREBP-1 levels, GIRK1 expression, and I KACh activation. Regulation of the GIRK1 promoter by SREBP-1 and lipid lowering was dependent on interaction with 2 tandem sterol response elements and an upstream E-box motif. Expression of dominant negative SREBP-1 (DN-SREBP-1) reversed the effect of lipid lowering on I KACh and GIRK1. In SREBP-1 knockout mice, both the response of the heart to parasympathetic stimulation and the expression of GIRK1 were reduced compared with WT. I KACh, attenuated in atrial myocytes from SREBP-1 knockout mice, was stimulated by SREBP-1 expression. Following myocardial infarction, SREBP-1 knockout mice were twice as likely as WT mice to develop ventricular tachycardia in response to programmed ventricular stimulation. These results demonstrate a relationship between lipid metabolism and parasympathetic response that may play a role in arrhythmogenesis.

The β-Catenin/T-Cell Factor/Lymphocyte Enhancer Factor Signaling Pathway Is Required for Normal and Stress-Induced Cardiac Hypertrophy

ABSTRACT In cells capable of entering the cell cycle, including cancer cells, β-catenin has been termed a master switch, driving proliferation over differentiation. However, its role as a transcriptional activator in terminally differentiated cells is relatively unknown. Herein we utilize conditional, cardiac-specific deletion of the β-catenin gene and cardiac-specific expression of a dominant inhibitory mutant of Lef-1 (Lef-1Δ20), one of the members of the T-cell factor/lymphocyte enhancer factor (Tcf/Lef) family of transcription factors that functions as a coactivator with β-catenin, to demonstrate that β-catenin/Tcf/Lef-dependent gene expression regulates both physiologic and pathological growth (hypertrophy) of the heart. Indeed, the profound nature of the growth impairment of the heart in the Lef-1Δ20 mouse, which leads to very early development of heart failure and premature death, suggests β-catenin/Tcf/Lef targets are dominant regulators of cardiomyocyte growth. Thus, our studies, employing complementary models in vivo, implicate β-catenin/Tcf/Lef signaling as an essential growth-regulatory pathway in terminally differentiated cells.

The effect of ventricular assist devices on post-transplant mortality an analysis of the United network for organ sharing thoracic registry

OBJECTIVES This study sought to determine the relationship between pre-transplant ventricular assist device (VAD) support and mortality after heart transplantation. BACKGROUND Increasingly, VADs are being used to bridge patients to heart transplantation. The effect of these devices on post-transplant mortality is unclear. METHODS Patients 18 years or older who underwent first-time, single-organ heart transplantation in the U.S. between 1995 and 2004 were included in the analyses. This study compared 1,433 patients bridged with intracorporeal and 448 patients bridged with extracorporeal VADs with 9,455 United Network for Organ Sharing status 1 patients not bridged with a VAD with respect to post-transplant mortality. Because the proportional hazards assumption was not met, hazard ratios (HRs) for different time periods were estimated. RESULTS Intracorporeal VADs were associated with an HR of 1.20 (95% confidence interval [CI]: 1.02 to 1.43; p = 0.03) for mortality in the first 6 months after transplant and an HR of 1.99 (95% CI: 1.44 to 2.75; p < 0.0001) beyond 5 years. Between 6 months and 5 years, the HRs were not significantly different from 1. Extracorporeal VADs were associated with an HR of 1.91 (95% CI: 1.53 to 2.37; p < 0.0001) for mortality in the first 6 months and an HR of 2.93 (95% CI: 1.19 to 7.25; p = 0.02) beyond 5 years. The HRs were not significantly different from 1 between 6 months and 5 years, except for an HR of 0.23 (95% CI: 0.06 to 0.91; p = 0.04) between 24 and 36 months. CONCLUSIONS Extracorporeal VADs are associated with higher mortality within 6 months and again beyond 5 years after transplantation. Intracorporeal VADs are associated with a small increase in mortality in the first 6 months and a clinically significant increase in mortality beyond 5 years. These data do not provide evidence supporting VAD implantation in stable United Network for Organ Sharing status I patients awaiting heart transplantation.

Estrogen Attenuates Left Ventricular and Cardiomyocyte Hypertrophy by an Estrogen Receptor–Dependent Pathway That Increases Calcineurin Degradation

Left ventricular (LV) hypertrophy commonly develops in response to chronic hypertension and is a significant risk factor for heart failure and death. The serine-threonine phosphatase calcineurin (Cn)A plays a critical role in the development of pathological hypertrophy. Previous experimental studies in murine models show that estrogen limits pressure overload–induced hypertrophy; our purpose was to explore further the mechanisms underlying this estrogen effect. Wild-type, ovariectomized female mice were treated with placebo or 17&bgr;-estradiol (E2), followed by transverse aortic constriction (TAC), to induce pressure overload. At 2 weeks, mice underwent physiological evaluation, immediate tissue harvest, or dispersion of cardiomyocytes. E2 replacement limited TAC-induced LV and cardiomyocyte hypertrophy while attenuating deterioration in LV systolic function and contractility. These E2 effects were associated with reduced abundance of CnA. The primary downstream targets of CnA are the nuclear factor of activated T-cell (NFAT) family of transcription factors. In transgenic mice expressing a NFAT-activated promoter/luciferase reporter gene, E2 limited TAC-induced activation of NFAT. Moreover, the inhibitory effects of E2 on LV hypertrophy were absent in CnA knockout mice, supporting the notion that CnA is an important target of E2-mediated inhibition. In cultured rat cardiac myocytes, E2 inhibited agonist-induced hypertrophy while also decreasing CnA abundance and NFAT activation. Agonist stimulation also reduced CnA ubiquitination and degradation that was prevented by E2; all in vitro effects of estrogen were reversed by an estrogen receptor (ER) antagonist. These data support that E2 reduces pressure overload induced hypertrophy by an ER-dependent mechanism that increases CnA degradation, unveiling a novel mechanism by which E2 and ERs regulate pathological LV and cardiomyocyte growth.