RESUMO
Several studies provide evidence that erythropoietin (EPO) could play an important role in the recovery of the heart subjected to ischemia-reperfusion. In this regard, it has been suggested that EPO could be involved in protein kinase B (Akt) activation as a cell survival protein. The aim of the present study was to investigate the effects of EPO on the Akt/glycogen synthase kinase 3 beta (GSK-3ß) pathway in the presence or absence of wortmannin (W, Akt inhibitor) and its relationship with mitochondrial morphology and function preservation in ischemic-reperfused rat hearts. EPO improved the functional recovery of the heart subjected to ischemia-reperfusion, reduced the release of CK and the infarct size, and promoted preservation of the mitochondrial structure. Moreover, it reduced tissue lactate content and preserved glycogen in order to prevent ischemia. The results showed greater Akt activation, accompanied by preservation of swelling and mitochondrial calcium retention capacity, as well as an increase in ATP synthesis capacity. These results were accompanied by an inhibition of GSK-3ß, suggesting regulation of Akt on the opening of the mitochondrial permeability transition pore. All these beneficial effects exerted by acute treatment with EPO were prevented by W. The present study provided novel evidence that EPO not only enhances intrinsic activation of Akt during myocardial ischemia-reperfusion but also promotes GSK-3ß inhibition, contributing to mitochondrial structure and function preservation.
Assuntos
Cardiotônicos , Eritropoetina , Coração , Proteínas Proto-Oncogênicas c-akt , Traumatismo por Reperfusão , Animais , Ratos , Eritropoetina/farmacologia , Glicogênio Sintase Quinase 3 beta/metabolismo , Isquemia , Fosforilação , Proteínas Proto-Oncogênicas c-akt/metabolismo , Cardiotônicos/farmacologia , Coração/efeitos dos fármacosRESUMO
Recent studies have provided evidence that triiodothyronine (T3) might play an effective role in the recovery of ischemic myocardium, through the preservation of mitochondrial function and the improvement of energy substrate metabolism. To this respect, it has been suggested that T3 could activate AMP-activated protein kinase (AMPK), the cellular 'fuel-gauge' enzyme, although its role has yet to be elucidated. The aim of the present study was to investigate the effects produced by acute treatment with T3 (60 nM) and the pharmacological inhibition of AMPK by compound C on isolated rat left atria subjected to 75 min simulated ischemia-75 min reperfusion. Results showed that T3 increased AMPK activation during simulated ischemia-reperfusion, while compound C prevented it. At the end of simulated reperfusion, acute T3 treatment increased contractile function recovery and cellular viability conservation. Mitochondrial ultrastructure was better preserved in the presence of T3 as well as mitochondrial ATP production rate and tissue ATP content. Calcium retention capacity, a parameter widely used as an indicator of the resistance of mitochondrial permeability transition pore (MPTP) to opening, and GSK-3ß phosphorylation, a master switch enzyme that limits MPTP opening, were increased by T3 administration. All these beneficial effects exerted by T3 acute treatment were prevented when compound C was co-administrated. The present study provided original evidence that T3 enhances intrinsic activation of AMPK during myocardial ischemia-reperfusion, being this enzyme involved, at least in part, in the protective effects exerted by T3, contributing to mitochondrial structure and function preservation, post-ischemic contractile recovery and conservation of cellular viability.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Cardiotônicos/uso terapêutico , Traumatismo por Reperfusão Miocárdica/tratamento farmacológico , Traumatismo por Reperfusão Miocárdica/enzimologia , Miocárdio/enzimologia , Miocárdio/patologia , Tri-Iodotironina/uso terapêutico , Trifosfato de Adenosina/metabolismo , Animais , Cálcio/metabolismo , Cardiotônicos/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Diástole/efeitos dos fármacos , Feminino , Glicogênio Sintase Quinase 3 beta/metabolismo , Átrios do Coração/ultraestrutura , Mitocôndrias Cardíacas/efeitos dos fármacos , Mitocôndrias Cardíacas/metabolismo , Mitocôndrias Cardíacas/ultraestrutura , Contração Miocárdica/efeitos dos fármacos , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Fosforilação/efeitos dos fármacos , Ratos Sprague-Dawley , Sístole/efeitos dos fármacos , Tri-Iodotironina/farmacologiaRESUMO
AMP-activated protein kinase (AMPK) is a serine-threonine kinase that functions primarily as a metabolic sensor to coordinate anabolic and catabolic processes in the cell, via phosphorylation of multiple proteins involved in metabolic pathways, aimed to re-establish energy homeostasis at a cell-autonomous level. Myocardial ischemia and reperfusion represents a metabolic stress situation for myocytes. Whether AMPK plays a critical role in the metabolic and functional responses involved in these conditions remains uncertain. In this study, in order to gain a deeper insight into the role of endogenous AMPK activation during myocardial ischemia and reperfusion, we explored the effects of the pharmacological inhibition of AMPK on contractile function rat, contractile reserve, tissue lactate production, tissue ATP content, and cellular viability. For this aim, isolated atria subjected to simulated 75 min ischemia-75 min reperfusion (Is-Rs) in the presence or absence of the pharmacological inhibitor of AMPK (compound C) were used. Since in most clinical situations of ischemia-reperfusion the heart is exposed to high levels of fatty acids, the influence of palmitate present in the incubation medium was also investigated. The present results suggest that AMPK activity significantly increases during Is, remaining activated during Rs. The results support that intrinsic activation of AMPK has functional protective effects in the reperfused atria when glucose is the only available energetic substrate whereas it is deleterious when palmitate is also available. Cellular viability was not affected by either of these conditions.