Granulocyte colony-stimulating factor reduces the endoplasmic reticulum stress in a rat model of diabetic cardiomyopathy

Abstract

Prolonged endoplasmic reticulum (ER) stress contributes to the apoptosis of cardiomyocytes, which leads to the development of diabetic cardiomyopathy. Previously, we reported that the granulocyte colony-stimulating factor (G-CSF) reduces the cardiomyocyte apoptosis in diabetic cardiomyopathy; however, the precise mechanisms associated with this process are not yet fully understood. Therefore, in this study, we investigated whether the mechanism of the anti-apoptotic effect of G-CSF was associated with ER stress in a rat model of diabetic cardiomyopathy. Diabetic cardiomyopathy was induced in rats using a high-fat diet combined with the administration of a low-dose of streptozotocin. Diabetic rats were treated with G-CSF or saline for 5 days. Cardiac function was evaluated using serial echocardiography before and 4 weeks after treatment. The rate of cardiomyocyte apoptosis and the expression levels of proteins related to ER stress, including glucose-regulated protein 78 (GRP78), caspase-9, and caspase-12 were analyzed in the cardiac tissue. G-CSF treatment significantly reduced cardiomyocyte apoptosis in the diabetic myocardium and downregulated the expression levels of these proteins in diabetic rats treated with low-dose streptozotocin when compared to that in rats treated with saline. In addition, GCSF treatment significantly downregulated the expression levels of proteins related to ER stress, such as GRP78, inositolrequiring enzyme-1 alpha (IRE-1 alpha), and C/EBP homologous protein (CHOP) in H9c2 cells under high glucose (HG) conditions. Moreover, G-CSF treatment significantly improved the diastolic dysfunction in serial echocardiography assessments. In conclusion, the anti-apoptotic effect of G-CSF may be associated with the downregulation of ER stress.