O treinamento por natação leva a uma sobrecarga de volume no coração, que induz a hipertrofia cardíaca (HC) excêntrica, com aumento da massa e do diâmetro cardíaco. Neste trabalho foram investigadas as adaptações no sistema cardiovascular e na expressão de genes relacionados à HC patológica, na gênese da HC por treinamento de natação. 42 ratas wistar foram divididas em grupos: sedentário controle (SC) treinado protocolo 1 (P1) e treinado protocolo 2 (P2). O treinamento de P1 foi de 1x60min/dia, 5x/semana, por 10 semanas. O de P2 foi igual ao P1 até a 8ª semana. Na 9ª semana 2x/dia e na 10ª semana 3x/dia. Os grupos treinados, em relação ao SC, apresentaram bradicardia de repouso, melhora no desempenho físico do teste máximo e do consumo máximo de oxigênio e HC, sem alterar a pressão arterial média e a expressão dos genes do fator natriurético atrial e da alfa actina esquelética. O grupo P2 apresentou aumento no diâmetro cardíaco e redução da expressão do gene da beta miosina de cadeia pesada. Este último resultado é contrário à literatura para a HC patológica, que mostra o aumento não só da expressão deste gene como a dos outros genes estudados. Os resultados de HC de P2 assemelham-se aos encontrados em estudos recentes com atletas de modalidades de maior componente aeróbio, sendo este um bom modelo para investigação dos mecanismos envolvidos na HC destes atleta / Swimming training leads to a cardiac volume overload that induces excentric cardiac hypertrophy (CH) with an increase in cardiac mass and diameter. Cardiovascular system adaptations and expression of genes relatated with pathological CH were investigated in swimming training CH. We studied 42 wistar females, divided in sedentary control (SC) group, protocol 1 trained group (P1) and protocol 2 trained group (P2). The P1 training program was once a day for 5 times/week for 10 weeks. P2 was the same as P1 until 8th week. In 9th week it was twice a day and in 10th week 3 times a day. Trained groups, in contrast with SC, showed rest bradycardia, improvement in physical performance, maximum oxygen uptake and CH, with no alteration in the medium arterial pressure and in the expression of atrial natriuretic factor and skeletal alpha actin genes. Moreover, P2 showed an increase in cardiac diameter and decrease in the expression of beta myosin heavy chain gene. This expression result is different of patological CH literature wich shows an increase of this gene expression and also in the others genes we had investigated. P2 CH results were similar to those recently found in endurance-type athletes, sugesting this is a good model to investigate mechanisms involved in endurance-type athletes CH

Die chronisch ischämische Herzkrankheit und der Myokardinfarkt (MI) sind die häufigsten Gründe für schwere Krankheit und vorzeitigen Tod in den entwickelten Ländern. Langfristig kommt es als Folge des Infarktes zur Kollateralgefäßbildung und zur Entwicklung einer kompensatorischen Herzhypertrophie. Eine Vielzahl von adaptativen Veränderungen in diesem Prozess konnte identifiziert werden. Wir konnten zeigen, dass in der akuten Phase nach MI Kontraktions- und Relaxationsgeschwindigkeit des Myokards erhöht waren. Die Expression der Hitzeschockproteine (HSP) 25 und 72 war verstärkt und korrelierte mit der Relaxationsgeschwindigkeit. In der chronischen Phase nach MI entwickelte sich eine signifikante Herzhypertrophie, die mit verminderter Kontraktions- und Relaxationsgeschwindigkeit einherging. Für die verlangsamte Relaxation war die verminderte Aktivität der Ca2+-ATPase des sarkoplasmatischen Retikulums (SERCA) als entscheidender Faktor anzusehen. Bei transgener Überexpression von Renin / Angiotensinogen ist die Relaxationsgeschwindigkeit des Myokards war wie auch nach MI durch geringere SERCA- Protein Expression vermindert. Die Empfindlichkeit der kontraktilen Funktion gegenüber Sauerstoffmangel und Reoxygenierung war nach MI gegenüber dem Kontrollmyokard geringer. Dafür konnten die verstärkte Expression der antioxidativ wirksamen HSPs und die erhöhte Aktivität der Glutathionperoxidase und der Superoxiddismutase, eine Verschiebung des Kreatinkinase (CK)- Isoenzymmusters und eine verminderte SERCA- Aktivität verantwortlich gemacht werden. Die Repolarisation der Aktionspotentiale der Kardiomyozyten war nach MI gegenüber den Kontrolltieren signifikant verlangsamt. Bereits eine 10-fach geringere artifizielle Dehnung des Gewebes führte nach MI im Vergleich zu Kontrolltieren zum Auftreten von Nachdepolarisationen und Extra-Aktionspotentialen. Ausschließlich in MI ließ sich durch die artifizielle Dehnung Vorhofflimmern auslösen, d.h. nach Myokardinfarkt war der mechano- elektrische Feedback Mechanismus empfindlicher. Die dehnungsinduzierten Veränderungen konnten durch Gadolinium unterdrückt werden, was auf eine Beteiligung von dehnungsaktivierten Ionenkanälen an den beobachteten Phänomenen schließen ließ. Auch kardiale Fibroblasten zeigten nach MI signifikante Änderungen ihrer elektrophysiologischen Eigenschaften, was zur Arrhythmieentstehung beitragen kann. Mittels molekularer Analysen konnten wir zeigen, dass der unter Sauerstoffmangel stabilisierte Transkriptionsfaktor Hif-1alpha in der Lage ist, den Promoter des Wilms' Tumor Suppressor Gens 1 (WT1) direkt transkriptionell zu aktivieren. Das führte zu verstärkter Expression von WT1 in den Herzen nach Myokardinfarkt, und zu verstärkter Expression von WT1 in Herz und Niere bei systemischer normobarer Hypoxie. Die WT1 Expression im Herzen nach MI ließ sich in den Koronargefäßen lokalisieren. Koexpression mit Proliferations- und Vaskulogenesemarkern ließ vermuten, dass WT1 nach MI eine wichtige Rolle für die Neovaskulogenese spielt. Die gewonnenen Ergebnisse tragen zum Verständnis der pathophysiologischen Veränderungen bei kardialer Hypertrophie nach Myokardinfarkt bei und eröffnen möglicherweise langfristig neue therapeutische Ansätze. / Chronic ischemic heart disease and myocardial infarction are the most common causes for morbidity and mortality in industrialized countries. A survived myocardial infarction (MI) results in a long run in collateral formation and the development of cardiac hypertrophy. A variety of adaptive responses in this process had been identified. We could show that in the acute phase after Mi in rats, contraction- and relaxation rates of the myocardium are increased. The higher relaxation rate correlates to an increased expression of heat shock proteins. In the chronic phase after MI, with the development of cardiac hypertrophy, contraction and relaxation rates decrease. The decrease in the relaxation rate could be attributed to a reduced activity of the Ca- ATPase of the sarcoplasmic reticulum (SERCA2). Transgenic overexpression of renin / angiotensinogen also resulted in a reduced SERCA2 expression and, consequently, lower relaxation rate. The susceptibility of contractile function to hypoxia - reoxygenation was reduced after MI compared to sham operated control animals. The lower susceptibility to hypoxia - reoxygenation could be attributed to an increased expression of heat shock proteins, higher activities of the antioxidant enzymes glutathionperoxidase and superoxiddismutase, shifts in the isoenzyme distribution of the creatine kinase, and a reduced SERCA2 activity. Repolarization of cardiomyocyte action potentials was found to be delayed after MI. A 10-fold lower artificial stretch of the tissue after MI than after sham operation caused afterdepolarizations and extra action potentials. Higher artificial stretch caused atrial fibrillation only after MI suggesting an intensified mechano-electrical feedback mechanism after MI. Stretch- induced electrical abnormalities could be suppressed by gadolinium suggesting the involvement of stretch-activated ion channels in the electrical abnormalities. Also electrophysiological properties of cardiac fibroblasts were significantly altered after MI, which may contribute to the increased risk for arrhythmia after infarction. Furthermore, we could show that the Hif-1alpha transcription factor, which is stabilized under hypoxic conditions is capable to directly activate the Wilms'' tumor suppressor 1 (WT1) transcriptionally. This leads to an increased expression of WT1 in the heart after MI and in heart and kidneys after systemic hypoxia. After MI, WT1 is expressed mainly in coronary vessels. Co-expression of WT1 with markers of proliferation and vasculogenesis suggests a role of WT1 in neovasculogenesis. These findings contribute to our understanding of pathophysiological alterations in the development of cardiac hypertrophy after MI and may contribute to the development of new therapeutic approaches.

Herzinsuffizienz mit konsekutivem Herzversagen ist ein zentrales kardiovaskuläres Problem der heutigen Bevölkerung.Ursächlich ist insbesondere eine progrediente Herzhypertrophie. Die Calcium-Calmodulin abhängige Phosphatase Calcineurin (CnR) spielt hierbei in der Pathogenese eine entscheidende Rolle. CnR wird über seine Calciumbindungsstellen an der regulatorischen Untereinheit Calcineurin B (CnB) aktiviert.Um zu untersuchen, inwieweit CnB bei der Hypertrophie verschiedener Ätiologien reguliert wird, wurde in linksventrikulären Myokardbiopsien von Patienten mit Aortenstenose (AS= 14) bzw. aus explantierten Herzen mit Dilatativer Kardiomyopathie (DCM=27) und Koronarer Herzerkrankung (KHK=7) der mRNA-und Proteingehalt von CnB bestimmt und mit der Expression von ANP und BNP korreliert. Als Kontrollgruppe dienten 15 abgelehnte Spenderherzen mit normaler systolischer Funktion und gesunder Morphologie. In den Herzen der Kontroll-, DCM-, und KHK-Gruppen wurde der linksventrikuläre Fibrosegehalt bestimmt. Hierzu wurden eine extern standardisierte Real-Time-PCR-Technik und ein etabliertes Western Blot Verfahren angewandt. Die Ergebnisse werden im Median ± 25%/75%-Perzentile angegeben und mit dem Mann-Whitney-Test bzw. Korrelationsanalysen nach Spearman berechnet. In den Herzen mit DCM zeigte sich eine signifikante Erhöhung der CnB mRNA auf ca. das Dreifache der Kontrollen (293% der Ko, p / Heart failure is a central cardiovascular problem for the current population. Cardiac hypertrophy is a central factor. The calcium-Calmodulin dependent phosphatase Calcineurin (CnR) plays a crucial role in the pathogenesis. CnR is activated via its calcium-binding site in the regulatory subunit Calcineurin B (CnB). In order to examine, to what extent CnB is regulated in different aetiologies of hypertrophy, we analysed CnB´s mRNA and protein in left ventricular samples from patients with aortic valve stenosis (AS = 14) and from explanted hearts with dilated (DCM=27) and ischemic (ICM=7) cardiomyopathy and correlated them with the expression of ANP and BNP. As a control, 15 rejected donor hearts with normal systolic function and non-pathologic changed morphology were used. Fibrosis of the left ventricle was determined in three groups: control , DCM and ICM. Therefore, we used an externally standardized real-time PCR and an established Western Blot. Data are given as median ± 25%/75%- percentiles; Mann Whitney test and Spearman´s correlation-analyses were used. CnB mRNA was significantly raised in DCM (293% of control, p

Les catécholamines induisent la synthèse d’AMPc par une stimulation des récepteurs β-adrénergiques et contrôlent ainsi la fonction cardiaque en activant une pléiade de voies de signalisation intracellulaires. Les protéines Epac sont des facteurs d’échange pour les petites protéines G et sont directement activés par l’AMPc. Devant l’importance de la voie β-adrénergique dans la physiopathologie cardiaque et dans le but de mieux comprendre la régulation des processus cellulaires dépendants de l’AMPc dans le cœur, il apparaît essentiel de caractériser le rôle des facteurs d’échange Epac dans le myocarde. Dans une première partie, cette étude démontre que les effets de Epac sur l’hypertrophie des cardiomyocytes ventriculaires de rats nouveaux nés requièrent les GTPases H-Ras et Rap2B. Epac active la voie PLC/IP3/Ca2+ qui est nécessaire pour l’activation de H-Ras. Au niveau transcriptionnel, Epac induit l’export nucléaire de HDAC4 permettant l’activation d’un programme génique d’hypertrophie. Dans une deuxième partie, cette étude révèle l’implication de Epac1 dans l’hypertrophie des cardiomyocytes in vivo, chez la souris. La délétion de Epac1 protège du remodelage cardiaque induit par l’activation prolongée des récepteurs β-adrénergiques et améliore la fonction cardiaque. La surexpression de Epac1 spécifiquement dans le myocarde entraîne une hypertrophie des cardiomyocytes. Par ailleurs, la voie β-AR/Epac1 induit l’accumulation de protéines ubiquitinylées et provoque l’activation du processus d’autophagie in vitro et in vivo. L’autophagie protège des effets délétères de la voie β-adrénergique/Epac en participant à l’élimination des agrégats protéiques et en contrant les effets hypertrophiques de Epac1. Ces résultats ouvrent de nouvelles perspectives pour le traitement de l’hypertrophie et de l’insuffisance cardiaque. / Catecholamines regulate cardiac function by stimulating β-adrenergic receptors (β-AR), leading to cAMP production and activation of a multiplicity of signaling pathways. Epac proteins are exchange factors for small G proteins which are directly activated by cAMP. Given the importance of the β-adrenergic pathway in cardiac physiopathology, it becomes essential to characterize functions of Epac protein in myocardium. In a first part, this study shows that H-Ras and Rap2B GTPases are involved in Epac-induced neonatal rat cardiac myocytes hypertrophy. Epac induces activation of the PLC/IP3/Ca2+ pathway which is necessary for H-Ras activation. At the transcriptional level, Epac causes HDAC4 nuclear export leading to activation of a hypertrophic gene program. In a second part, this study reveals implication of Epac1 in cardiac hypertrophy in vivo. Deletion of Epac1 in mice protects from cardiac remodeling induced by chronic isoproterenol infusion and enhances cardiac function. Cardiac specific overexpression of Epac1 in mice induces cardiac myocytes hypertrophy. Interestingly, β-AR/Epac1 pathway triggers ubiquitinated proteins accumulation and activation of autophagy both in vitro and in vivo. By eliminating aggregates and by counteracting hypertrophic effects of Epac, autophagy protects from deleterious effects of the β-AR/Epac pathway. These results open news insights into the treatment of cardiac hypertrophy and heart failure.

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O hipertireoidismo é uma patologia epidemiologicamente importante, que afeta o sistema cardiovascular de forma proeminente. O estado hipertireoideo pode afetar o metabolismo basal, consumo de O2 celular, sistema renina angiotensina, assim como, estimular a produção de espécies ativas de oxigênio. Estas alterações produzem consequências morfológicas, funcionais, bioquímicas e moleculares no tecido cardíaco. A hipertrofia cardíaca, decorrente do hipertireoidismo, instala-se devido a uma série de eventos que sinalizam à proliferação e sobrevivência celular, envolvendo as espécies ativas de oxigênio, a ativação do sistema renina angiotensina cardíaco e o sistema nervoso autonômico. Neste estudo, bloqueamos o receptor AT1 da angiotensina II para avaliarmos a influência do sistema renina angiotensina cardíaco sobre o desenvolvimento da hipertrofia cardíaca, a participação do balanço autonômico sobre o coração e o papel das espécies ativas de oxigênio neste processo, em modelo experimental de hipertireoidismo. Para isto, foram utilizados ratos Wistar machos, pesando cerca de 220g, divididos em 4 grupos experimentais: Controle (C), Losartan (L) (10 mg/Kg de peso corporal/dia, 28 dias, sonda intragástrica) , T4 (12mg/L água de beber, 28 dias), e T4+L. Foram avaliados a massa cardíaca, análise espectral do balanço simpato-vagal, a expressão protéica do receptor AT1 da Angiotensina II e da gp91phox, peróxido de hidrogênio (H2O2), Nrf-2 e Heme-oxigenase-1 (HO-1) no tecido cardíaco. A hipertrofia cardíaca e o desequilíbrio autonômico induzidos pelo hipertireoidismo foram atenuados no grupo T4+L. Os níveis de H2O2, Nrf-2, gp91phox e HO-1 foram elevados no grupo T4, e significativamente reduzidos no grupo T4+L, quando comparados ao grupo Controle. A expressão protéica do receptor AT1 esteve elevada nos dois grupos hipertireoideos. Os resultados obtidos sugerem que o bloqueio do receptor AT1 promove importante impacto sobre o balanço simpato-vagal e a hipertrofia cardíaca, no hipertireoidismo, sendo as espécies ativas de oxigênio e o sistema Nrf-2/HO-1 possíveis mediadores destas alterações. / Hyperthyroidism is an epidemiologic relevant pathology, which substantially affects the cardiovascular system. The hyperthyroid state may affect basal metabolism, O2 cell consumption, renin-angiotensin system, and increase reactive oxygen species production. Those alterations produce morphological, biochemical, functional and molecular consequences in cardiac tissue. Hyperthyroidism induced cardiac hypertrophy develops due to a set of events, which signals cell survival and proliferation, including reactive oxygen species, cardiac rennin-angiotensin system, and autonomic nervous system. In the present study, the role of cardiac renin-angiotensin system on development of hyperthyroidism induced cardiac hypertrophy, and the involvement of autonomic nervous system and reactive oxygen species, were assessed trough blockade of angiotensin II receptor AT1. For that, were used male Wistar rats, weighting about 220g, divided in 4 experimental groups,: Control (C), Losartan (L) (10mg/Kg body weight/day, 28 days, intragastric probe), T4 (12mg/L L-thyroxin in drinking water, 28 days), and T4+L. Cardiac mass, spectral analysis (autonomic balance), hydrogen peroxide (H2O2), and myocardial protein expression of angiotensin II receptor (AT1), NADPH oxidase, Nrf-2, and heme-oxygenase-1 (HO-1), were quantified. Cardiac hypertrophy and autonomic umbalance induced by thyroid hormones were attenuated in the T4+losartan group. The H2O2, as well as Nrf-2, gp91phox, AT1 and HO-1 immunocontent were elevated in T4 group. All these effects were attenuated by losartan, except AT1 levels. The overall results suggest that blockade of AT1 receptor lead to relevant impact on autonomic balance and cardiac hypertrophy, being ROS and Nrf-2/ HO-1 system possible mediators in this alterations in experimental hyperthyroidism.

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