Abstract
BACKGROUND The relationship between endoplasmic reticulum and mitochondria during acute myocardial ischemic injury is still unclear. Our study aimed to define the dynamics of endoplasmic reticulum stress and mitochondrial dysfunction during acute ischemic injury. MATERIAL AND METHODS A rat model of acute myocardial infarction and hypoxic cardiomyocytes were used in this study. Groups were set at 0 hours, 1 hour, 2 hours, 4 hours, and 6 hours after ischemic injury for both in vivo and in vitro studies. ATF6 and GRP-78 were examined to indicate endoplasmic reticulum stress. Cellular ATP and cytosolic levels of mitochondrial DNA and cytochrome c were detected to evaluate mitochondrial dysfunction. Caspase-3 was used for apoptosis analysis. RESULTS Our results showed that both mRNA and protein levels of ATF6 and GRP-78 were elevated from 1 hour after ischemic injury in vivo and in vitro (P<0.05). However, ATP levels were increased at 2 hours after ischemic injury and significantly decreased from 4 hours after ischemic injury in vivo, while ATP level of cultured cardiomyocytes decreased remarkably from 2 hours after ischemic injury (P<0.05). Cytosolic mitochondrial DNA levels began to increase from 2 hours after ischemic injury (P<0.05). Cytosolic levels of cytochrome c increased from 4 hours after ischemic injury. Additionally, both mRNA and protein expressions of caspase-3 started to significantly elevate at 6 hours after ischemic injury (P<0.05). CONCLUSIONS The present study suggested that mitochondrial dysfunction was secondary to endoplasmic reticulum stress, which provides a novel experimental foundation for further exploration of the detailed mechanism after ischemic injury, especially the interaction between endoplasmic reticulum and mitochondria.