ABSTRACT
Objective To explore the effects of extracellular regulated protein kinase 1/2 (ERK1/2) signal pathway on cardiomyocyte apoptosis and tumor necrosis factor-α (TNF-α) expression at different glucose-lowing rates,and the influence of glucose-lowing rate on cardiomyocyte injury and inflammatory secretion function,as well as its mechanism.Methods Cardiomyocytes of Wistar neonate rat were maintained in medium supplemented with 25 mmol/L glucose for 72 h.Then the medium was changed to different concentrations of glucose and all cells were divided into five groups.Group A was control group whose medium supplemented with 25 mmol/L glucose.Medium of group B,C,D,E was supplemented with 20,15,10,5 mmol/L glucose (glucose-lowing rate was 5,10,15,20 mmol/L) respectively.Survival rate of cardiomyocyte was measured by CCK8 kit.Cardiomyocyte apoptosis was measured by flow cytometry instrument and laser confocal microscope after Annexin V-PI.TNF-α was measured by ELISA.ERK1/2 protein and phosphorylation were measured by Western blot.Cardiomyocyte apoptosis and TNF-α levels were measured again after U0126 was added.Results At the same time point,along with the glucose-lowing rate increased,survival rate of cardiomyocyte in group A was increased and those in group C,D,E were decreased (P＜ 0.05).TNF-α concentration was increased in group B,C,D and decreased in group E.After 24 h,apoptosis rate decreased in group B and increased in group C,D,E (P＜0.05).ERK1/2 phosphorylation level increased in group B,D,and E(P＜0.05).The ERK1/2 phosphorylation level in group B was the lowest.After U0126 was added,survival rates of cardiomyocyte in all groups were increased (P＜0.01) while TNF-α concentrations were decreased (P＜0.05).In every group,survival rate of eardiomyocyte after 48 h was lower than that after 3 h and 24 h,while TNF-α concentration was higher (P＜0.05).Conclusion Influence of glucose-lowering rate for cardiomyocyte apoptosis and TNF-o is caused by ERK1/2 pathway.In the glucose-lowering course,ERK1/2 pathway promotes cardiomyocytes apoptosis and TNF-α secretion is related with not only osmotic pressure,but also ERK1/2 signal pathway activation as well.