RESUMO
beta-blockers, as class, improve cardiac function and survival in heart failure (HF). However, the molecular mechanisms underlying these beneficial effects remain elusive. In the present study, metoprolol and carvedilol were used in doses that display comparable heart rate reduction to assess their beneficial effects in a genetic model of sympathetic hyperactivity-induced HF (alpha(2A)/alpha(2C)-ARKO mice). Five month-old HF mice were randomly assigned to receive either saline, metoprolol or carvedilol for 8 weeks and age-matched wild-type mice (WT) were used as controls. HF mice displayed baseline tachycardia, systolic dysfunction evaluated by echocardiography, 50% mortality rate, increased cardiac myocyte width (50%) and ventricular fibrosis (3-fold) compared with WT. All these responses were significantly improved by both treatments. Cardiomyocytes from HF mice showed reduced peak [Ca(2+)](i) transient (13%) using confocal microscopy imaging. Interestingly, while metoprolol improved [Ca(2+)](i) transient, carvedilol had no effect on peak [Ca(2+)](i) transient but also increased [Ca(2+)] transient decay dynamics. We then examined the influence of carvedilol in cardiac oxidative stress as an alternative target to explain its beneficial effects. Indeed, HF mice showed 10-fold decrease in cardiac reduced/oxidized glutathione ratio compared with WT, which was significantly improved only by carvedilol treatment. Taken together, we provide direct evidence that the beneficial effects of metoprolol were mainly associated with improved cardiac Ca(2+) transients and the net balance of cardiac Ca(2+) handling proteins while carvedilol preferentially improved cardiac redox state.
Assuntos
Antagonistas Adrenérgicos beta/farmacologia , Insuficiência Cardíaca/tratamento farmacológico , Insuficiência Cardíaca/fisiopatologia , Líquido Intracelular/fisiologia , Receptores Adrenérgicos beta/metabolismo , Animais , Carbazóis/uso terapêutico , Carvedilol , Modelos Animais de Doenças , Insuficiência Cardíaca/genética , Insuficiência Cardíaca/mortalidade , Testes de Função Cardíaca , Hemodinâmica/efeitos dos fármacos , Hemodinâmica/genética , Líquido Intracelular/efeitos dos fármacos , Líquido Intracelular/metabolismo , Masculino , Metoprolol/uso terapêutico , Camundongos , Camundongos Congênicos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Contração Miocárdica/efeitos dos fármacos , Contração Miocárdica/genética , Propanolaminas/uso terapêutico , Distribuição AleatóriaRESUMO
Exercise training (ET) is a coadjuvant therapy in preventive cardiology. It delays cardiac dysfunction and exercise intolerance in heart failure (HF); however, the molecular mechanisms underlying its cardioprotection are poorly understood. We tested the hypothesis that ET would prevent Ca(2+) handling abnormalities and ventricular dysfunction in sympathetic hyperactivity-induced HF mice. A cohort of male wild-type (WT) and congenic alpha(2A)/alpha(2C)-adrenoceptor knockout (alpha(2A)/alpha(2C)ARKO) mice with C57BL6/J genetic background (3-5 mo of age) were randomly assigned into untrained and exercise-trained groups. ET consisted of 8-wk swimming session, 60 min, 5 days/wk. Fractional shortening (FS) was assessed by two-dimensional guided M-mode echocardiography. The protein expression of ryanodine receptor (RyR), phospho-Ser(2809)-RyR, sarcoplasmic reticulum Ca(2+) ATPase (SERCA2), Na(+)/Ca(2+) exchanger (NCX), phospholamban (PLN), phospho-Ser(16)-PLN, and phospho-Thr(17)-PLN were analyzed by Western blotting. At 3 mo of age, no significant difference in FS and exercise tolerance was observed between WT and alpha(2A)/alpha(2C)ARKO mice. At 5 mo, when cardiac dysfunction is associated with lung edema and increased plasma norepinephrine levels, alpha(2A)/alpha(2C)ARKO mice presented reduced FS paralleled by decreased SERCA2 (26%) and NCX (34%). Conversely, alpha(2A)/alpha(2C)ARKO mice displayed increased phospho-Ser(16)-PLN (76%) and phospho-Ser(2809)-RyR (49%). ET in alpha(2A)/alpha(2C)ARKO mice prevented exercise intolerance, ventricular dysfunction, and decreased plasma norepinephrine. ET significantly increased the expression of SERCA2 (58%) and phospho-Ser(16)-PLN (30%) while it restored the expression of phospho-Ser(2809)-RyR to WT levels. Collectively, we provide evidence that improved net balance of Ca(2+) handling proteins paralleled by a decreased sympathetic activity on ET are, at least in part, compensatory mechanisms against deteriorating ventricular function in HF.
Assuntos
Cálcio/metabolismo , Terapia por Exercício , Insuficiência Cardíaca/terapia , Miocárdio/metabolismo , Receptores Adrenérgicos alfa 2/metabolismo , Sistema Nervoso Simpático/fisiopatologia , Disfunção Ventricular/prevenção & controle , Animais , Proteínas de Ligação ao Cálcio/metabolismo , Modelos Animais de Doenças , Ecocardiografia , Tolerância ao Exercício , Insuficiência Cardíaca/complicações , Insuficiência Cardíaca/metabolismo , Insuficiência Cardíaca/patologia , Insuficiência Cardíaca/fisiopatologia , Masculino , Camundongos , Camundongos Congênicos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Contração Miocárdica , Miocárdio/enzimologia , Miocárdio/patologia , Norepinefrina/sangue , Esforço Físico , Receptores Adrenérgicos alfa 2/deficiência , Receptores Adrenérgicos alfa 2/genética , Projetos de Pesquisa , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , Retículo Sarcoplasmático/metabolismo , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Trocador de Sódio e Cálcio/metabolismo , Sistema Nervoso Simpático/metabolismo , Fatores de Tempo , Disfunção Ventricular/etiologia , Disfunção Ventricular/metabolismo , Disfunção Ventricular/patologia , Disfunção Ventricular/fisiopatologiaRESUMO
1. Maximal lactate steady state (MLSS) corresponds to the highest blood lactate concentration (MLSSc) and workload (MLSSw) that can be maintained over time without continual blood lactate accumulation and is considered an important marker of endurance exercise capacity. The present study was undertaken to determine MLSSw and MLSSc in running mice. In addition, we provide an exercise training protocol for mice based on MLSSw. 2. Maximal lactate steady state was determined by blood sampling during multiple sessions of constant-load exercise varying from 9 to 21 m/min in adult male C57BL/6J mice. The constant-load test lasted at least 21 min. The blood lactate concentration was analysed at rest and then at 7 min intervals during exercise. 3. The MLSSw was found to be 15.1 +/- 0.7 m/min and corresponded to 60 +/- 2% of maximal speed achieved during the incremental exercise testing. Intra- and interobserver variability of MLSSc showed reproducible findings. Exercise training was performed at MLSSw over a period of 8 weeks for 1 h/day and 5 days/week. Exercise training led to resting bradycardia (21%) and increased running performance (28%). Of interest, the MLSSw of trained mice was significantly higher than that in sedentary littermates (19.0 +/- 0.5 vs 14.2 +/- 0.5 m/min; P = 0.05), whereas MLSSc remained unchanged (3.0 mmol/L). 4. Altogether, we provide a valid and reliable protocol to improve endurance exercise capacity in mice performed at highest workload with predominant aerobic metabolism based on MLSS assessment.
Assuntos
Ácido Láctico/sangue , Condicionamento Físico Animal/fisiologia , Resistência Física/fisiologia , Corrida , Animais , Peso Corporal , Frequência Cardíaca , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Variações Dependentes do Observador , Reprodutibilidade dos TestesRESUMO
The molecular basis of the beneficial effects associated with exercise training (ET) on overall ventricular function (VF) in heart failure (HF) remains unclear. We investigated potential Ca(2+) handling abnormalities and whether ET would improve VF of mice lacking alpha(2A)- and alpha(2C)-adrenoceptors (alpha(2A)/alpha(2C)ARKO) that have sympathetic hyperactivity-induced HF. A cohort of male wild-type (WT) and congenic alpha(2A)/alpha(2C)ARKO mice in a C57BL/J genetic background (5-7 mo of age) was randomly assigned into untrained and trained groups. VF was assessed by two-dimensional guided M-mode echocardiography. Cardiac myocyte width and ventricular fibrosis were evaluated with a computer-assisted morphometric system. Sarcoplasmic reticulum Ca(2+) ATPase (SERCA2), phospholamban (PLN), phospho-Ser(16)-PLN, phospho-Thr(17)-PLN, phosphatase 1 (PP1), and Na(+)-Ca(2+) exchanger (NCX) were analyzed by Western blotting. ET consisted of 8-wk running sessions of 60 min, 5 days/wk. alpha(2A)/alpha(2C)ARKO mice displayed exercise intolerance, systolic dysfunction, increased cardiac myocyte width, and ventricular fibrosis paralleled by decreased SERCA2 and increased NCX expression levels. ET in alpha(2A)/alpha(2C)ARKO mice improved exercise tolerance and systolic function. ET slightly reduced cardiac myocyte width, but unchanged ventricular fibrosis in alpha(2A)/alpha(2C)ARKO mice. ET significantly increased the expression of SERCA2 (20%) and phospho-Ser(16)-PLN (63%), phospho-Thr(17)-PLN (211%) in alpha(2A)/alpha(2C)ARKO mice. Furthermore, ET restored NCX and PP1 expression in alpha(2A)/alpha(2C)ARKO to untrained WT mice levels. Thus, we provide evidence that Ca(2+) handling is impaired in this HF model and that overall VF improved upon ET, which was associated to changes in the net balance of cardiac Ca(2+) handling proteins.
Assuntos
Proteínas de Ligação ao Cálcio/genética , Regulação da Expressão Gênica , Insuficiência Cardíaca/genética , Miocárdio/metabolismo , Condicionamento Físico Animal/fisiologia , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/genética , Animais , Cálcio/metabolismo , Proteínas de Ligação ao Cálcio/metabolismo , Tolerância ao Exercício/fisiologia , Insuficiência Cardíaca/metabolismo , Insuficiência Cardíaca/fisiopatologia , Frequência Cardíaca/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Contração Miocárdica , Miócitos Cardíacos/citologia , Miócitos Cardíacos/metabolismo , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismoRESUMO
A insuficiência cardíaca (IC) é a via final comum da maioria das doenças cardiovasculares e uma das maiores causas de morbi-mortalidade. O desenvolvimento do estágio final da IC freqüentemente envolve um insulto inicial do miocárdio, reduzindo o débito cardíaco e levando ao aumento compensatório da atividade do sistema nervoso simpático (SNS). Existem evidências de que apesar da exposição aguda ser benéfica, exposições crônicas a elevadas concentrações de catecolaminas, liberadas pelo terminal nervoso simpático e pela glândula adrenal, são tóxicas ao tecido cardíaco e levam a deterioração da função cardíaca. Em nível molecular observa-se que a hiperatividade do SNS está associada a alterações na sinalização intracelular mediada pelos receptores beta-adrenérgicos. Sabe-se que tanto a densidade como a função dos receptores beta-adrenérgicos estão diminuídas na IC, assim como outros mecanismos intracelulares subjacentes à estimulação da via receptores beta-adrenérgicos. Nesta revisão, apresentaremos uma breve descrição da via de sinalização dos receptores beta-adrenérgicos no coração normal e as conseqüências da hiperatividade do SNS na IC. Daremos ênfase ao potencial miopático de diversos componentes da cascata de sinalização dos receptores beta-adrenérgicos discutindo estudos realizados com animais geneticamente modificados. Finalmente, discorreremos sobre o impacto clínico do conhecimento dos polimorfismos para o gene do receptor beta-adrenérgico para um melhor entendimento da progressão da IC.
Assuntos
Animais , Humanos , Camundongos , Baixo Débito Cardíaco/fisiopatologia , /fisiologia , Transdução de Sinais/fisiologia , Modelos Animais de Doenças , Progressão da Doença , Polimorfismo Genético , Receptores Adrenérgicos beta 1/genética , Receptores Adrenérgicos beta 1/fisiologia , /genéticaRESUMO
Heart failure (HF) is a common endpoint for many forms of cardiovascular disease and a significant cause of morbidity and mortality. The development of end-stage HF often involves an initial insult to the myocardium that reduces cardiac output and leads to a compensatory increase in sympathetic nervous system activity. Acutely, the sympathetic hyperactivity through the activation of beta-adrenergic receptors increases heart rate and cardiac contractility, which compensate for decreased cardiac output. However, chronic exposure of the heart to elevated levels of catecholamines released from sympathetic nerve terminals and the adrenal gland may lead to further pathologic changes in the heart, resulting in continued elevation of sympathetic tone and a progressive deterioration in cardiac function. On a molecular level, altered beta-adrenergic receptor signaling plays a pivotal role in the genesis and progression of HF. beta-adrenergic receptor number and function are decreased, and downstream mechanisms are altered. In this review we will present an overview of the normal beta-adrenergic receptor pathway in the heart and the consequences of sustained adrenergic activation in HF. The myopathic potential of individual components of the adrenergic signaling will be discussed through the results of research performed in genetic modified animals. Finally, we will discuss the potential clinical impact of beta-adrenergic receptor gene polymorphisms for better understanding the progression of HF.