Effects of ERK1/2 signal pathway on cardiomyocyte during glucose lowering.

OBJECTIVE: This study investigated whether the extracellular signal-regulated kinase 1/2 (ERK1/2) signal pathway affects cardiomyocyte apoptosis and the expression of tumor necrosis factor (TNF-α) at different glucose-lowering rates.

METHODS: Cardiomyocytes of Wistar neonate rats were maintained in a medium supplemented with 25 mmol/L glucosamine for 72 h. Then the medium was changed to different concentrations of glucosamine, and all cells were divided into five groups. The survival rate of cardiomyocyte was measured using the Cell Counting Kit-8; cardiomyocyte apoptosis was measured using the flow cytometry instrument and laser confocal microscope; TNF-α was measured using the enzyme-linked immunosorbent assay; and ERK1/2 protein and phosphorylation were measured using the Western blot. Cardiomyocyte apoptosis and TNF-α were measured again after adding U0126.

RESULTS: As the glucose-lowering rate increased, the survival rate of cardiomyocytes increased in group B and decreased in groups C, D, and E. The TNF-α concentration increased in groups B, C, and D and decreased in group E. After 24 h, the apoptosis rate decreased in group B and increased in groups C, D, and E. The expression of p-ERK1/2 increased in groups B, D, and E, and was the lowest in group C. After adding U0126, the survival rate of cardiomyocyte in all groups increased and TNF-α concentration decreased.

CONCLUSIONS: The influence of glucose-lowering rate on cardiomyocyte apoptosis and TNF-α was caused by the p-ERK1/2 pathway. During the glucose-lowering course, the p-ERK1/2 pathway promoted cardiomyocyte apoptosis, and TNF-α secretion was related to not only osmotic pressure but also ERK1/2 signal pathway activation.