Comparative effectiveness analysis of anticoagulant strategies in a large observational database of percutaneous coronary interventions.

BACKGROUND: Percutaneous coronary intervention (PCI) is the most commonly used procedure for coronary revascularization. There are multiple adjuvant anticoagulation strategies available. In this era of cost containment, we performed a comparative effectiveness analysis of clinical outcomes and cost of the major anticoagulant strategies across all types of PCI procedures in a large observational database. METHODS: A retrospective, comparative effectiveness analysis of the Premier observational database was conducted to determine the impact of anticoagulant treatment on outcomes. Multiple linear regression and logistic regression models were used to assess the association of initial antithrombotic treatment with outcomes while controlling for other factors. RESULTS: A total of 458,448 inpatient PCI procedures with known antithrombotic regimen from 299 hospitals between January 1, 2004 and March 31, 2008 were identified. Compared to patients treated with heparin plus glycoprotein IIb/IIIa inhibitor (GPI), bivalirudin was associated with a 41% relative risk reduction (RRR) for inpatient mortality, a 44% RRR for clinically apparent bleeding, and a 37% RRR for any transfusion. Furthermore, treatment with bivalirudin alone resulted in a cost savings of $976 per case. Similar results were seen between bivalirudin and heparin in all end-points. Combined use of both bivalirudin and GPI substantially attenuated the cost benefits demonstrated with bivalirudin alone. CONCLUSION: Bivalirudin use was associated with both improved clinical outcomes and decreased hospital costs in this large "real-world" database. To our knowledge, this study is the first to demonstrate the ideal comparative effectiveness end-point of both improved clinical outcomes with decreased costs in PCI.

Beta 1-adrenergic receptor polymorphisms confer differential function and predisposition to heart failure.

Catecholamines stimulate cardiac contractility through beta(1)-adrenergic receptors (beta(1)-ARs), which in humans are polymorphic at amino acid residue 389 (Arg/Gly). We used cardiac-targeted transgenesis in a mouse model to delineate mechanisms accounting for the association of Arg389 with human heart failure phenotypes. Hearts from young Arg389 mice had enhanced receptor function and contractility compared with Gly389 hearts. Older Arg389 mice displayed a phenotypic switch, with decreased beta-agonist signaling to adenylyl cyclase and decreased cardiac contractility compared with Gly 389 hearts. Arg389 hearts had abnormal expression of fetal and hypertrophy genes and calcium-cycling proteins, decreased adenylyl cyclase and G alpha(s) expression, and fibrosis with heart failure This phenotype was recapitulated in homozygous, end-stage, failing human hearts. In addition, hemodynamic responses to beta-receptor blockade were greater in Arg389 mice, and homozygosity for Arg389 was associated with improvement in ventricular function during carvedilol treatment in heart failure patients. Thus the human Arg389 variant predisposes to heart failure by instigating hyperactive signaling programs leading to depressed receptor coupling and ventricular dysfunction, and influences the therapeutic response to beta-receptor blockade.

Prevalence and self-reported medical history of overweight in a cardiac stress testing population.

OBJECTIVES: To determine the prevalence of overweight in a cardiac stress testing population, and the percentage of subjects who indicate a history of overweight. METHODS: A total of 251 consecutive subjects presenting for cardiac stress testing in a 450-bed community hospital from June to September 2010 were asked to complete a survey booklet. The survey included all patients presenting for stress testing, regardless of indication. Participants were subjects, ages 18 or older, and male or female. Exclusion criteria were medical (eg, pain), psychiatric (eg, psychosis), or intellectual disturbances that would preclude the successful completion of a survey booklet. RESULTS: Of the 251 participants 76.5% were overweight (BMI ≥ 25). Among the overweight participants, only 16.1% indicated a history of overweight. CONCLUSIONS: A high prevalence of overweight/obese individuals exists in a cardiac stress test population. A majority of overweight and obese patients did not indicate a history of overweight. These results indicate poor patient recognition and/or ineffective physician-to-patient education concerning unhealthy body weight. Greater and more effective efforts are needed to effectively educate patients about this modifiable risk factor for a myriad of health problems.

The relationship between childhood trauma and borderline personality symptomatology in a consecutive sample of cardiac stress test patients.

OBJECTIVE: In this study, we examined relationships between five types of childhood trauma and two measures of borderline personality symptomatology in a non-psychiatric clinical population in order to assess a potential association between these variables in a non-psychiatric-treatment-seeking population. METHOD: Using a cross-sectional sample and a survey approach in 250 consecutive patients presenting for cardiac stress testing, we explored self-reported histories of five types of childhood trauma (i.e. witnessing violence, physical neglect, emotional abuse, physical abuse, sexual abuse), several aspects of past mental healthcare, and borderline personality symptomatology using two self-report measures (the borderline personality disorder scale of the Personality Diagnostic Questionnaire-4 and the Self-Harm Inventory). RESULTS: All relationships between the individual forms of trauma and total number of childhood traumas, and measures of borderline personality symptomatology, attained statistical significance. Using multiple regression analysis, sexual abuse in childhood was an independent predictor for borderline personality symptomatology in addition to past psychiatric/counseling care, with the latter finding suggesting some inter-drift of psychiatric patients into this cardiac stress test sample. CONCLUSIONS: In this non-psychiatric-treatment-seeking population, there appear to be relationships between various forms of trauma (especially sexual abuse) and borderline personality symptomatology, reinforcing the role of childhood trauma in borderline personality disorder.

Mediating ERK 1/2 signaling rescues congenital heart defects in a mouse model of Noonan syndrome.

Noonan syndrome (NS) is an autosomal dominant disorder characterized by a wide spectrum of defects, which most frequently include proportionate short stature, craniofacial anomalies, and congenital heart disease (CHD). NS is the most common nonchromosomal cause of CHD, and 80%-90% of NS patients have cardiac involvement. Mutations within the protein tyrosine phosphatase Src homology region 2, phosphatase 2 (SHP2) are responsible for approximately 50% of the cases of NS with cardiac involvement. To understand the developmental stage- and cell type-specific consequences of the NS SHP2 gain-of-function mutation, Q79R, we generated transgenic mice in which the mutated protein was expressed during gestation or following birth in cardiomyocytes. Q79R SHP2 embryonic hearts showed altered cardiomyocyte cell cycling, ventricular noncompaction, and ventricular septal defects, while, in the postnatal cardiomyocyte, Q79R SHP2 expression was completely benign. Fetal expression of Q79R led to the specific activation of the ERK1/2 pathway, and breeding of the Q79R transgenics into ERK1/2-null backgrounds confirmed the pathway's necessity and sufficiency in mediating mutant SHP2's effects. Our data establish the developmental stage-specific effects of Q79R cardiac expression in NS; show that ablation of subsequent ERK1/2 activation prevents the development of cardiac abnormalities; and suggest that ERK1/2 modulation could have important implications for developing therapeutic strategies in CHD.

Inhibition of ischemic cardiomyocyte apoptosis through targeted ablation of Bnip3 restrains postinfarction remodeling in mice.

Following myocardial infarction, nonischemic myocyte death results in infarct expansion, myocardial loss, and ventricular dysfunction. Here, we demonstrate that a specific proapoptotic gene, Bnip3, minimizes ventricular remodeling in the mouse, despite having no effect on early or late infarct size. We evaluated the effects of ablating Bnip3 on cardiomyocyte death, infarct size, and ventricular remodeling after surgical ischemia/reperfusion (IR) injury in mice. Immediately following IR, no significant differences were observed between Bnip3(-/-) and WT mice. However, at 2 days after IR, apoptosis was diminished in Bnip3(-/-) periinfarct and remote myocardium, and at 3 weeks after IR, Bnip3(-/-) mice exhibited preserved LV systolic performance, diminished LV dilation, and decreased ventricular sphericalization. These results suggest myocardial salvage by inhibition of apoptosis. Forced cardiac expression of Bnip3 increased cardiomyocyte apoptosis in unstressed mice, causing progressive LV dilation and diminished systolic function. Conditional Bnip3 overexpression prior to coronary ligation increased apoptosis and infarct size. These studies identify postischemic apoptosis by myocardial Bnip3 as a major determinant of ventricular remodeling in the infarcted heart, suggesting that Bnip3 may be an attractive therapeutic target.

Cardiomyocyte degeneration with calpain deficiency reveals a critical role in protein homeostasis.

Regulating the balance between synthesis and proteasomal degradation of cellular proteins is essential for tissue growth and maintenance, but the critical pathways regulating protein ubiquitination and degradation are incompletely defined. Although participation of calpain calcium-activated proteases in post-necrotic myocardial autolysis is well characterized, their importance in homeostatic turnover of normal cardiac tissue is controversial. Hence, we evaluated the consequences of physiologic calpain (calcium-activated protease) activity in cultured cardiomyocytes and unstressed mouse hearts. Comparison of in vitro proteolytic activities of cardiac-expressed calpains 1 and 2 revealed calpain 1, but not calpain 2, activity at physiological calcium concentrations. Physiological calpain 1 activation was evident in adenoviral transfected cultured cardiomyocytes as proteolysis of specific substrates, generally increased protein ubiquitination, and accelerated protein turnover, that were each inhibited by coexpression of the inhibitor protein calpastatin. Conditional forced expression of calpain 1, but not calpain 2, in mouse hearts demonstrated substrate-specific proteolytic activity under basal conditions, with hyperubiquitination of cardiac proteins and increased 26S proteasome activity. Loss of myocardial calpain activity by forced expression of calpastatin diminished ubiquitination of 1 or more specific myocardial proteins, without affecting overall ubiquitination or proteasome activity, and resulted in a progressive dilated cardiomyopathy characterized by accumulation of intracellular protein aggregates, formation of autophagosomes, and degeneration of sarcomeres. Thus, calpain 1 is upstream of, and necessary for, ubiquitination and proteasomal degradation of a subset of myocardial proteins whose abnormal accumulation produces autophagosomes and degeneration of cardiomyocytes with functional decompensation.

Multiple interactions between the alpha 2C- and beta1-adrenergic receptors influence heart failure survival.

BACKGROUND: Persistent stimulation of cardiac beta1-adrenergic receptors by endogenous norepinephrine promotes heart failure progression. Polymorphisms of this gene are known to alter receptor function or expression, as are polymorphisms of the alpha 2C-adrenergic receptor, which regulates norepinephrine release from cardiac presynaptic nerves. The purpose of this study was to investigate possible synergistic effects of polymorphisms of these two intronless genes (ADRB1 and ADRA2C, respectively) on the risk of death/transplant in heart failure patients. METHODS: Sixteen sequence variations in ADRA2C and 17 sequence variations in ADRB1 were genotyped in a longitudinal study of 655 white heart failure patients. Eleven sequence variations in each gene were polymorphic in the heart failure cohort. Cox proportional hazards modeling was used to identify polymorphisms and potential intra- or intergenic interactions that influenced risk of death or cardiac transplant. A leave-one-out cross-validation method was utilized for internal validation. RESULTS: Three polymorphisms in ADRA2C and five polymorphisms in ADRB1 were involved in eight cross-validated epistatic interactions identifying several two-locus genotype classes with significant relative risks ranging from 3.02 to 9.23. There was no evidence of intragenic epistasis. Combining high risk genotype classes across epistatic pairs to take into account linkage disequilibrium, the relative risk of death or transplant was 3.35 (1.82, 6.18) relative to all other genotype classes. CONCLUSION: Multiple polymorphisms act synergistically between the ADRA2C and ADRB1 genes to increase risk of death or cardiac transplant in heart failure patients.

Obstructive Sleep Apnea in Heart Failure: Review of Prevalence, Treatment with Continuous Positive Airway Pressure, and Prognosis.

Obstructive sleep apnea is a sleep-related breathing disorder that has a major impact on cardiovascular function. It has been associated with hypertension, coronary artery disease, cardiac arrhythmias, sudden cardiac death, and heart failure. This review focuses on the relationship between obstructive sleep apnea and heart failure with either reduced or preserved ejection fraction. We discuss the pathophysiology of obstructive sleep apnea, as well as its prevalence, treatment outcomes with continuous positive airway pressure, and prognosis in these 2 distinct types of heart failure. We also identify areas in which further work is needed to improve our understanding of this association in heart failure patients.

The presence of Lys27 instead of Asn27 in human phospholamban promotes sarcoplasmic reticulum Ca2+-ATPase superinhibition and cardiac remodeling.

BACKGROUND: Phospholamban (PLN) is an inhibitor of the Ca2+ affinity of sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA2). The amino acid sequence of PLN is highly conserved, and although all species contain asparagine (Asn), human PLN is unique in containing lysine (Lys) at amino acid 27. METHODS AND RESULTS: Human PLN was introduced in the null background. Expression of human PLN, at similar levels to mouse wild-type PLN, resulted in significant decreases in the affinity of SERCA2 for Ca2+, attributed to unique spatial conformation of this PLN form and increases in its monomeric active unit compared with mouse PLN. The increased inhibition by human PLN was associated with attenuated cardiac contractility in the intact-animal, organ, and cardiomyocyte levels and with depressed calcium kinetics. These inhibitory effects could not be fully reversed even on maximal isoproterenol stimulation. There were no alterations in the expression levels of SERCA2, calsequestrin, ryanodine receptor, and FKBP12, although the sodium/calcium exchanger and the L-type Ca2+ channel expression levels were upregulated. The depressed function resulted in increased heart/body weight ratios and phosphorylation levels of Akt, p38, and Erk1/2. CONCLUSIONS: Human PLN may play a more inhibitory role than that of other species in Ca2+ cycling. Expression of human PLN in the mouse is compensated by alterations in Ca2+-handling proteins and cardiac remodeling in an effort to normalize cardiac contractility. Thus, the unique amino acid sequence of human PLN may be critical in maintaining a high cardiac reserve, which is of paramount importance in the regulation of human cardiac function.

Rescue of cardiomyocyte dysfunction by phospholamban ablation does not prevent ventricular failure in genetic hypertrophy.

Cardiac hypertrophy, either compensated or decompensated, is associated with cardiomyocyte contractile dysfunction from depressed sarcoplasmic reticulum (SR) Ca(2+) cycling. Normalization of Ca(2+) cycling by ablation or inhibition of the SR inhibitor phospholamban (PLN) has prevented cardiac failure in experimental dilated cardiomyopathy and is a promising therapeutic approach for human heart failure. However, the potential benefits of restoring SR function on primary cardiac hypertrophy, a common antecedent of human heart failure, are unknown. We therefore tested the efficacy of PLN ablation to correct hypertrophy and contractile dysfunction in two well-characterized and highly relevant genetic mouse models of hypertrophy and cardiac failure, Galphaq overexpression and human familial hypertrophic cardiomyopathy mutant myosin binding protein C (MyBP-C(MUT)) expression. In both models, PLN ablation normalized the characteristically prolonged cardiomyocyte Ca(2+) transients and enhanced unloaded fractional shortening with no change in SR Ca(2+) pump content. However, there was no parallel improvement in in vivo cardiac function or hypertrophy in either model. Likewise, the activation of JNK and calcineurin associated with Galphaq overexpression was not affected. Thus, PLN ablation normalized contractility in isolated myocytes, but failed to rescue the cardiomyopathic phenotype elicited by activation of the Galphaq pathway or MyBP-C mutations.

Human phospholamban null results in lethal dilated cardiomyopathy revealing a critical difference between mouse and human.

In human disease and experimental animal models, depressed Ca(2+) handling in failing cardiomyocytes is widely attributed to impaired sarcoplasmic reticulum (SR) function. In mice, disruption of the PLN gene encoding phospholamban (PLN) or expression of dominant-negative PLN mutants enhances SR and cardiac function, but effects of PLN mutations in humans are unknown. Here, a T116G point mutation, substituting a termination codon for Leu-39 (L39stop), was identified in two families with hereditary heart failure. The heterozygous individuals exhibited hypertrophy without diminished contractile performance. Strikingly, both individuals homozygous for L39stop developed dilated cardiomyopathy and heart failure, requiring cardiac transplantation at ages 16 and 27. An over 50% reduction in PLN mRNA and no detectable PLN protein were noted in one explanted heart. The expression of recombinant PLN-L39stop in human embryonic kidney (HEK) 293 cells and adult rat cardiomyocytes showed no PLN inhibition of SR Ca(2+)-ATPase and the virtual absence of stable PLN expression; where PLN was expressed, it was misrouted to the cytosol or plasma membrane. These findings describe a naturally-occurring loss-of-function human PLN mutation (PLN null). In contrast to reported benefits of PLN ablation in mouse heart failure, humans lacking PLN develop lethal dilated cardiomyopathy.

Proapoptotic effects of caspase-1/interleukin-converting enzyme dominate in myocardial ischemia.

Caspase-1/interleukin-converting enzyme (ICE) is a cysteine protease traditionally considered to have importance as an inflammatory mediator, but not as an apoptotic effector. Because of the dual functions of this caspase, the pathophysiological impact of its reported upregulation in hypertrophy and heart failure is not known. Here, the consequences of increased myocardial expression of procaspase-1 were examined on the normal and ischemically injured heart. In unstressed mouse hearts with a 30-fold increase in procaspase-1 content, unprocessed procaspase-1 was well tolerated, without detectable pathology. Cardiomyocyte processing and activation of caspase-1 and caspase-3 occurred after administration of endotoxin or with transient myocardial ischemia. In post-ischemic hearts, procaspase-1 overexpression was associated with strikingly increased cardiac myocyte apoptosis in the peri- and noninfarct regions and with 50% larger myocardial infarctions. Tissue culture studies revealed that procaspase-1 processing/activation is stimulated by hypoxia, and that caspase-1 acts in synergy with hypoxia to stimulate caspase-3 mediated apoptosis without activating upstream caspases. These data demonstrate that the proapoptotic effects of caspase-1 can significantly impact the myocardial response to ischemia and suggest that conditions in which procaspase-1 in the heart is increased may predispose to apoptotic myocardial injury under conditions of physiological stress.

Cardiac myosin-binding protein-C phosphorylation and cardiac function.

The role of cardiac myosin binding protein-C (cMyBP-C) phosphorylation in cardiac physiology or pathophysiology is unclear. To investigate the status of cMyBP-C phosphorylation in vivo, we determined its phosphorylation state in stressed and unstressed mouse hearts. cMyBP-C phosphorylation is significantly decreased during the development of heart failure or pathologic hypertrophy. We then generated transgenic (TG) mice in which the phosphorylation sites of cMyBP-C were changed to nonphosphorylatable alanines (MyBP-C(AllP-)). A TG line showing &40% replacement with MyBP-C(AllP-) showed no changes in morbidity or mortality but displayed depressed cardiac contractility, altered sarcomeric structure and upregulation of transcripts associated with a hypertrophic response. To explore the effect of complete replacement of endogenous cMyBP-C with MyBP-C(AllP-), the mice were bred into the MyBP-C(t/t) background, in which less than 10% of normal levels of a truncated MyBP-C are present. Although MyBP-C(AllP-) was incorporated into the sarcomere and expressed at normal levels, the mutant protein could not rescue the MyBP-C(t/t) phenotype. The mice developed significant cardiac hypertrophy with myofibrillar disarray and fibrosis, similar to what was observed in the MyBP-C(t/t) animals. In contrast, when the MyBP-C(t/t) mice were bred to a TG line expressing normal MyBP-C (MyBP-CWT), the MyBP-C(t/t) phenotype was rescued. These data suggest that cMyBP-C phosphorylation is essential for normal cardiac function.

Protein kinase Calpha negatively regulates systolic and diastolic function in pathological hypertrophy.

The protein kinase C (PKC) family is implicated in cardiac hypertrophy, contractile failure, and beta-adrenergic receptor (betaAR) dysfunction. Herein, we describe the effects of gain- and loss-of-PKCalpha function using transgenic expression of conventional PKC isoform translocation modifiers. In contrast to previously studied PKC isoforms, activation of PKCalpha failed to induce cardiac hypertrophy, but instead caused betaAR insensitivity and ventricular dysfunction. PKCalpha inhibition had opposite effects. Because PKCalpha is upregulated in human and experimental cardiac hypertrophy and failure, its effects were also assessed in the context of the Galphaq overexpression model (in which PKCalpha is transcriptionally upregulated). Normalization (inhibition) of PKCalpha activity in Galpha(q) hearts improved systolic and diastolic function, whereas further activation of PKCalpha caused a lethal restrictive cardiomyopathy with marked interstitial fibrosis. These results define pathological roles for PKCalpha as a negative regulator of ventricular systolic and diastolic function.

Physiological growth synergizes with pathological genes in experimental cardiomyopathy.

Hundreds of signaling molecules have been assigned critical roles in the pathogenesis of myocardial hypertrophy and heart failure based on cardiac phenotypes from alpha-myosin heavy chain-directed overexpression mice. Because permanent ventricular transgene expression in this system begins during a period of rapid physiological neonatal growth, resulting phenotypes are the combined consequences of transgene effects and normal trophic influences. We used temporally-defined forced gene expression to investigate synergy between postnatal physiological cardiac growth and two functionally divergent cardiomyopathic genes. Phenotype development was compared various times after neonatal (age 2 to 3 days) and adult (age 8 weeks) expression. Proapoptotic Nix caused ventricular dilation and severe contractile depression in neonates, but not adults. Myocardial apoptosis was minimal in adults, but was widespread in neonates, until it spontaneously resolved in adulthood. Unlike normal postnatal cardiac growth, concurrent left ventricular pressure overload hypertrophy did not synergize with Nix expression to cause cardiomyopathy or myocardial apoptosis. Prohypertrophic Galphaq likewise caused eccentric hypertrophy, systolic dysfunction, and pathological gene expression in neonates, but not adults. Thus, normal postnatal cardiac growth can be an essential cofactor in development of genetic cardiomyopathies, and may confound the interpretation of conventional alpha-MHC transgenic phenotypes.

Ischemic protection and myofibrillar cardiomyopathy: dose-dependent effects of in vivo deltaPKC inhibition.

To delineate the in vivo cardiac functions requiring normal delta protein kinase C (PKC) activity, we pursued loss-of-function through transgenic expression of a deltaPKC-specific translocation inhibitor protein fragment, deltaV1, in mouse hearts. Initial results using the mouse alpha-myosin heavy chain (alphaMHC) promoter resulted in a lethal heart failure phenotype. Viable deltaV1 mice were therefore obtained using novel attenuated mutant alphaMHC promoters lacking one or the other thyroid response element (TRE-1 and -2). In transgenic mouse hearts, deltaV1 decorated cytoskeletal elements and inhibited ischemia-induced deltaPKC translocation. At high levels, deltaV1 expression was uniformly lethal, with depressed cardiac contractile function, increased expression of fetal cardiac genes, and formation of intracardiomyocyte protein aggregates. Ultrastructural and immunoconfocal analyses of these aggregates revealed focal cytoskeletal disruptions and localized concentrations of desmin and alphaB-crystallin. In individual cardiomyocytes, cytoskeletal abnormalities correlated with impaired contractile function. Whereas desmin and alphaB-crystallin protein were increased approximately 4-fold in deltaV1 hearts, combined overexpression of these proteins at these levels was not sufficient to cause any detectable cardiac pathology. At low levels, deltaV1 expression conferred striking resistance to postischemic dysfunction, with no measurable effects on basal cardiac structure, function, or gene expression. Intermediate expression of deltaV1 conferred modest basal contractile depression with less ischemic protection, associated with abnormal cardiac gene expression, and a histological picture of infrequent cardiomyocyte cytoskeletal deformities. These results validate an approach of deltaPKC inhibition to protect against myocardial ischemia, but indicate that there is a threshold level of deltaPKC activation that is necessary to maintain normal cardiomyocyte cytoskeletal integrity.

Additive protection of the ischemic heart ex vivo by combined treatment with delta-protein kinase C inhibitor and epsilon-protein kinase C activator.

BACKGROUND: Protein kinase C (PKC) plays a major role in cardioprotection from ischemia/reperfusion injury. Using an HIV-1 Tat protein-derived peptide to mediate rapid and efficient transmembrane delivery of peptide regulators of PKC translocation and function, we examined the cardioprotective effect of selective delta-PKC inhibitor (deltaV1-1) and epsilon-PKC activator (psi(epsilon)RACK) peptides for ischemia/reperfusion damage in isolated perfused rat hearts. Furthermore, we examined the protective effects of these PKC isozymes in isolated perfused hearts subjected to ischemia/reperfusion damage using transgenic mice expressing these peptides specifically in their cardiomyocytes. METHODS AND RESULTS: In isolated perfused rat hearts, administration of deltaV1-1 but not psi(epsilon)RACK during reperfusion improved cardiac function and decreased creatine phosphokinase release. In contrast, pretreatment with psi(epsilon)RACK but not deltaV1-1, followed by a 10-minute washout before ischemia/reperfusion, also improved cardiac function and decreased creatine phosphokinase release. Furthermore, administration of psi(epsilon)RACK before ischemia followed by deltaV1-1 during reperfusion only conferred greater cardioprotective effects than that obtained by each peptide treatment alone. Both the delta-PKC inhibitor and epsilon-PKC activator conferred cardioprotection against ischemia/reperfusion injury in transgenic mice expressing these peptides in the heart, and coexpression of both peptides conferred greater cardioprotective effects than that obtained by the expression of each peptide alone. CONCLUSIONS: delta-PKC inhibitor prevents reperfusion injury, and epsilon-PKC activator mimics ischemic preconditioning. Furthermore, treatment with both peptides confers additive cardioprotective effects. Therefore, these peptides mediate cardioprotection by regulating ischemia/reperfusion damage at distinct time points.

Electrical remodeling in hearts from a calcium-dependent mouse model of hypertrophy and failure: complex nature of K+ current changes and action potential duration.

OBJECTIVES: This study was designed to identify possible electrical remodeling (ER) in transgenic (Tg) mice with over-expressed L-type Ca(2+) channels. Transient outward K(+) current (I(to)) and action potential duration (APD) were studied in 2-, 4-, 8-, and 9- to 12-month-old mice to determine linkage to ventricular remodeling (VR), ER, and heart failure (HF). BACKGROUND: Prolongation of APD and reduction in current density of I(to) are thought to be hallmarks of VR and HF. Mechanisms are not understood. METHODS: Patch-clamp, perfused hearts, echocardiography, and Western blots were employed using 2-, 4-, 8-, and 9- to 12-month-old Tg mice. RESULTS: Transgenic mice developed slow VR statistically manifesting at four months and continuing through death at 12 to 14 months, despite a slight up-regulation of I(to). A slight decrease or no change in APD was observed up to eight months; however, at 9 to 12 months, a small increase in APD was detected. Early afterdepolarizations were observed after application of 4-aminopyridine in Tg mice. No change was detected in protein of Kv4.3 and Kv4.2 up to eight months. At 9 to 12 months, Tg mice showed a slight decrease (41.4 +/- 6.9%, p < 0.05) in Kv4.2, consistent with a decrease in I(to). Surprisingly, Kv1.4 (the "fetal" K(+)-channel form) was up-regulated, and restitution of I(to) was slowed. Echocardiography revealed cardiac enlargement with impaired chamber function in hearts that were taken from the older animals. CONCLUSIONS: Contrary to accepted dogma, APD and I(to) in a mouse model of hypertrophy and HF are not hallmarks of pathophysiology. We suggest that [Ca(2+)](i) (i.e., [Ca(2+)] concentration) is the primary factor in triggering cardiac enlargement and arrhythmogenesis.

Sarcoplasmic reticulum adenosine triphosphatase overexpression in the L-type Ca2+ channel mouse results in cardiomyopathy and Ca2+ -induced arrhythmogenesis.

BACKGROUND: Overexpression of the L-type voltage-dependent calcium channel alpha(1C)-subunit (L-VDCC OE) in transgenic mice results in adaptive hypertrophy followed by a maladaptive phase associated with a decrease in sarcoplasmic reticulum adenosine triphosphatase (SERCA)2a expression at 8 to 10 months of age. Overexpressing SERCA to manipulate calcium (Ca(2+)) cycling and prevent pathologic phenotypes in some models of heart failure has been proven to be a promising genetic strategy. OBJECTIVE: In this study we investigated whether genetic manipulation that increases Ca(2+) uptake into the sarcoplasmic reticulum by overexpressing SERCA1a (skeletal muscle specific) into the L-VDCC OE background could restore or further deteriorate Ca(2+) cycling, contractile dysfunction, and electrical remodeling in the heart failure phenotype. RESULTS: We found that the survival rate of L-VDCC OE/SERCA1a OE double transgenic mice decreased by 50%. L-VDCC OE/SERCA1a OE mice displayed an accelerated phenotype of severe dilation of both ventricles associated with deteriorated left ventricular function. Voltage clamp experiments revealed enhanced increased inward Ca(2+) current density and decreased the transient outward potassium current. Action potential duration in double transgenic ventricular myocytes was prolonged, and isoproterenol induced early after depolarization. These mice demonstrated a high incidence of spontaneous left ventricular arrhythmia. Expression of the proarrhythmic signaling protein Ca(2+)/calmodulin-dependent kinase II (CaMKII) was increased while connexin43 expression was decreased, defining an important putative mechanism in the electrophysiologic disturbances and mortality. CONCLUSIONS: Despite previous reports of improved cardiac function in heart failure models after SERCA intervention, our results advocate the need to elucidate the involvement of augmented Ca(2+) cycling in arrhythmogenesis.