RESUMO
To examine the effects of ischemia/reperfusion on UCPs genes expression, heart function and oxygen cost of myocardial work, hearts of adult (6 mo) and old (24 mo) rats were perfused by Langendorf preparation and subjected to 20 min ischemia followed by 40 min reperfusion. Mitochondrial permeability transition due to ischemic stimuli was evaluated by release of mitochondrial factor (lambda 250 nm) which was previously shown as a marker of MPTP opening. Expression of UCPs was detected by reverse transcriptional polymerase chain reaction. Mitochondrial membrane potential (deltaphi(m)) and oxygen consumption in isolated heart mitochondria of adult and old rats were measured. It was shown that impaired function of aging rat hearts was accompanied with an increased oxygen cost of myocardial work and lower mitochondrial membrane potential compared with adult rats. Reperfusion disturbances of cardiodynamic, contractile activity of myocardium and noneffective oxygen utilization in early period of reperfusion were less intensive in aged hearts than in adult ones. Therefore, the levels of mRNA of UCP2 in aging hearts were higher and mRNA levels of UCP3 were tended to increase. At the same time ischemia/reperfusion increased the expression of UCP2 and UCP3 in adult myocardium: mRNA levels of UCPs were significantly higher that those in control, whereas there was no such effect in aging hearts. It is concluded that uncoupling proteins are implicated in the age-depended heart dysfunction and development of the pathological mechanisms during ischemia-reperfusion.
Assuntos
Envelhecimento/genética , Expressão Gênica , Canais Iônicos/genética , Proteínas Mitocondriais/genética , Traumatismo por Reperfusão Miocárdica/genética , Consumo de Oxigênio/fisiologia , Envelhecimento/metabolismo , Animais , Coração/fisiopatologia , Testes de Função Cardíaca , Técnicas In Vitro , Masculino , Traumatismo por Reperfusão Miocárdica/metabolismo , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Miocárdio/metabolismo , Ratos , Ratos Wistar , Proteína Desacopladora 2 , Proteína Desacopladora 3RESUMO
In experiments on the primary culture of isolated neonatal rat cardiomyocytes it was determined that cardiomyocytes express ALOX5 gene encoding enzyme 5-lipoxygenase. Anoxia-reoxygenation does not affect significantly the expression of 5-lipoxygenase mRNA in cardiomyocytes. Transfection of 5-lipoxygenase-specific small interfering RNA's (siRNA) into cardiomyocytes lead to a significant reduction of 5-lipoxygenase mRNA expression in cardiomyocytes 24 hours after transfection. ALOX5 gene silencing resulted in improved viability of cell population (by 13.3% P < 0.001) due to decreased number of necrotic (by 14.6%, P < 0.001), but not apoptotic, cells during anoxia-reoxygenation. Our results indicate that siRNA against ALOX5 effectively protects cardiomyocytes against anoxia-reoxygenation injury.