Participação do trânsito de cálcio e suas proteínas reguladoras na melhoria da função cardíaca de ratos com estenose aórtica supravalvar e disfunção ventricular submetidos a treinamento físico
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2019-03-01
Autores
Silva, Vitor Loureiro da
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Universidade Estadual Paulista (Unesp)
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Introdução: Diversos modelos experimentais têm avaliado o processo de remodelação cardíaca (RC); dentre eles, destaca-se a indução à estenose aórtica supravalvar (EAo). Os mecanismos fisiopatológicos responsáveis pela depressão da função cardíaca incluem alterações no trânsito de cálcio (Ca2+) e em suas proteínas regulatórias. O treinamento físico (TF) tem sido utilizado na terapêutica das cardiopatias. Na patologia cardíaca por sobrecarga pressórica, o TF restaura, total ou parcialmente, a atividade e/ou expressão das proteínas regulatórias do trânsito de Ca2+, otimizando o fluxo de Ca2+ intracelular e atenuando o prejuízo funcional cardíaco. Objetivo: Analisar a participação do trânsito de Ca2+ e suas proteínas reguladoras na melhoria da função cardíaca de ratos com EAo e disfunção ventricular pelo TF. Material e Métodos: Ratos Wistar machos (70-90 g), submetidos à cirurgia de EAo, foram divididos em dois grupos: controle operado (Sham) e EAo. Após 18 semanas da cirurgia, foi analisada função cardíaca para redistribuição dos grupos: não expostos ao TF (Sham, n= 36 e EAo, n= 29) e treinados (ShamTF, n= 33 e EAoTF, n= 32) durante 10 semanas. O treinamento físico aeróbio (TFa) em esteira foi realizado com velocidade equivalente ao limiar de lactato, obtida durante os testes de esforço (inicial, 4a e 7a semanas e final). A RC foi avaliada por ecocardiografia, músculo papilar e cardiomiócito isolados e macroscopia post mortem. O trânsito de cálcio miocárdico foi analisado pela elevação de cálcio extracelular, potenciação pós-pausa e bloqueios da bomba de Ca2+ do retículo sarcoplasmático (SERCA2a), pelo ácido ciclopiazônico, e dos canais de cálcio do tipo L, pelo diltiazem, no músculo papilar e pelo cardiomiócito. A expressão das proteínas envolvidas no trânsito de Ca2+ foi avaliada por Western Blot. Os resultados foram discutidos ao nível de significância de 5%. Resultados: Na 18ª semana, antes do TFa, os animais EAo apresentavam hipertrofia ventricular esquerda concêntrica, disfunção diastólica e sistólica e intolerância ao exercício físico. O TFa atenuou a disfunção diastólica e beneficiou a função sistólica dos animais com sobrecarga pressórica. Os animais EAoTF apresentaram melhor resposta à potenciação pós-pausa e ao bloqueio da SERCA2a que os EAo, o que sugere adequações positivas na recaptura de Ca2+ pelo retículo sarcoplasmático. Após inibição dos canais de cálcio tipo L houve diferença de resposta entre os grupos EAo e EAoTF, a qual também sugeriu melhor atividade da SERCA2a. Na análise do cardiomiócito, o TFa foi capaz de melhorar aspectos da função mecânica e a responsividade dos miofilamentos ao Ca2+ dos animais cardiopatas. Os animais EAo apresentaram alteração na expressão proteica do Receptor de Rianodina, da SERCA2a e do NCX, sendo que o TFa restaurou os níveis da SERCA2a e do NCX próximos aos valores normais. Conclusão: Adequações positivas no trânsito de Ca2+ e suas proteínas reguladoras pelo TFa participam da atenuação da disfunção ventricular em ratos com estenose aórtica supravalvar.
Introduction: Several experimental models have been proposed for the study of cardiac remodeling (CR); among them, the induction of supravalvular aortic stenosis (AoS). The pathophysiological mechanisms responsible for the cardiac function depression include changes in calcium (Ca2+) and its regulatory proteins. Exercise training (ET) has been used in the management of cardiopathies. In cardiac pathology due to pressure overload, ET completely or partially restores the activity and/or expression of regulatory proteins of Ca2+ handling, optimizing intracellular Ca 2+ flow and attenuating cardiac functional impairment. Objective: To analyze the participation of Ca2+ handling and its regulatory proteins in the improvement of the cardiac function of rats with aortic stenosis and ventricular dysfunction by ET. Material and Methods: Male Wistar rats (70-90 g) submitted to supravalvular aortic stenosis (AoS) were divided into two groups: operated control (Sham) and aortic stenosis (AoS). After 18 weeks of the surgical procedure, cardiac function analysis was performed for redistribution of the groups: non-exposed to exercise training (Sham, n = 36 and AoS, n = 29) and trained (ShamET, n = 33 and AoSET, n = 32) for 10 weeks. The treadmill exercise training was performed with a velocity equivalent to the lactate threshold, obtained during effort tests (initial, 4th and 7th weeks, and final). CR was evaluated by echocardiography, papillary muscle and cardiomyocyte isolated and postmortem macroscopy. The myocardial calcium handling was analyzed by the elevation of extracellular calcium, post-pause potentiation and Ca2+ pump blockade of the sarcoplasmic reticulum (SERCA2a), by cyclopiazonic acid, and L-type calcium channels by diltiazem in the papillary muscle and by the isolated cardiomyocyte. Expression of the proteins involved in Ca2+ handling was evaluated by Western Blot. The results were discussed at a significance level of 5%. Results: At the 18th week, before the ET, the AoS animals presented concentric left ventricular hypertrophy, diastolic and systolic dysfunction and intolerance to physical exercise. The ET attenuated the diastolic dysfunction 9 and benefited the systolic function of the animals with pressure overload. AoSET animals presented better response to post-pause potentiation and SERCA2a blockade than the AoS, suggesting a positive adaptation to the Ca2+ recapture by the sarcoplasmic reticulum. After inhibition of the L-type calcium channels there was a difference in response between the AoS and AoSET groups, which also suggested better SERCA2a activity. In the cardiomyocyte analysis, the ET was able to improve aspects of the mechanical function and the responsiveness of the myofilaments to the Ca2+ of the AoS animals. AoS animals presented alteration in the protein expression of the Rianodine Receptor, SERCA2a and NCX, and ET restored SERCA2a and NCX levels near normal values. Conclusion: Positive adaptations in the Ca2+ handling and its regulatory proteins by ET participate in the attenuation of ventricular dysfunction in rats with supravalvar aortic stenosis.
Introduction: Several experimental models have been proposed for the study of cardiac remodeling (CR); among them, the induction of supravalvular aortic stenosis (AoS). The pathophysiological mechanisms responsible for the cardiac function depression include changes in calcium (Ca2+) and its regulatory proteins. Exercise training (ET) has been used in the management of cardiopathies. In cardiac pathology due to pressure overload, ET completely or partially restores the activity and/or expression of regulatory proteins of Ca2+ handling, optimizing intracellular Ca 2+ flow and attenuating cardiac functional impairment. Objective: To analyze the participation of Ca2+ handling and its regulatory proteins in the improvement of the cardiac function of rats with aortic stenosis and ventricular dysfunction by ET. Material and Methods: Male Wistar rats (70-90 g) submitted to supravalvular aortic stenosis (AoS) were divided into two groups: operated control (Sham) and aortic stenosis (AoS). After 18 weeks of the surgical procedure, cardiac function analysis was performed for redistribution of the groups: non-exposed to exercise training (Sham, n = 36 and AoS, n = 29) and trained (ShamET, n = 33 and AoSET, n = 32) for 10 weeks. The treadmill exercise training was performed with a velocity equivalent to the lactate threshold, obtained during effort tests (initial, 4th and 7th weeks, and final). CR was evaluated by echocardiography, papillary muscle and cardiomyocyte isolated and postmortem macroscopy. The myocardial calcium handling was analyzed by the elevation of extracellular calcium, post-pause potentiation and Ca2+ pump blockade of the sarcoplasmic reticulum (SERCA2a), by cyclopiazonic acid, and L-type calcium channels by diltiazem in the papillary muscle and by the isolated cardiomyocyte. Expression of the proteins involved in Ca2+ handling was evaluated by Western Blot. The results were discussed at a significance level of 5%. Results: At the 18th week, before the ET, the AoS animals presented concentric left ventricular hypertrophy, diastolic and systolic dysfunction and intolerance to physical exercise. The ET attenuated the diastolic dysfunction 9 and benefited the systolic function of the animals with pressure overload. AoSET animals presented better response to post-pause potentiation and SERCA2a blockade than the AoS, suggesting a positive adaptation to the Ca2+ recapture by the sarcoplasmic reticulum. After inhibition of the L-type calcium channels there was a difference in response between the AoS and AoSET groups, which also suggested better SERCA2a activity. In the cardiomyocyte analysis, the ET was able to improve aspects of the mechanical function and the responsiveness of the myofilaments to the Ca2+ of the AoS animals. AoS animals presented alteration in the protein expression of the Rianodine Receptor, SERCA2a and NCX, and ET restored SERCA2a and NCX levels near normal values. Conclusion: Positive adaptations in the Ca2+ handling and its regulatory proteins by ET participate in the attenuation of ventricular dysfunction in rats with supravalvar aortic stenosis.
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Estenose Aórtica, Treinamento físico aeróbio, Hipertrofia fisiológica, Função cardíaca, trânsito de cálcio, aortic stenosis, aerobic exercise training, physiological hypertrophy, cardiac function, calcium handling