Objective: To investigate the effect of N,N-dimethylformamide (DMF) on calcium homeostasis and calpain I and II gene expression in human hepatocytes (HL-7702).
Methods: HL-7702 cells were exposed to different concentrations of DMF (10, 25, 50, 100, or 200 mmol/L); other HL-7702 cells, which were used as a control group, were exposed to the equal volume of DMEM; the intracellular Ca(2+) concentration was monitored using the calcium fluorescent probe (fluo-3/AM). After 24-h exposure to DMF (10, 25, 50, 100, 150, or 200 mmol/L), the morphology of hepatocytes was observed under an inverted phase contrast microscope, and the cell viability was measured by MTT assay. After 24-h exposure to DMF (10, 25, 50, 100, or 150 mmol/L), the mRNA expression levels of calpain I and II in hepatocytes were measured by real-time quantitative PCR.
Results: There were significant differences in cell viability among different exposure groups (P < 0.01); the 50, 100, 150, and 200 mmol/L DMF exposure groups had a significantly lower cell viability than the control group (P < 0.05). Under the inverted phase contrast microscope, HL-7702 cells gradually lost the original shape, with swelling and shrinking, as the dose of DMF increased, and those treated with 150 mmol/L DMF even became round and floated. The fluorescence density of fluo-3 in hepatocytes increased as the dose of DMF rose, demonstrating a dose-response relationship, and there were significant differences among these exposure groups (P < 0.05). There were significant differences in mRNA expression levels of calpain I and II among these exposure groups (P < 0.01), and the expression increased as the dose of DMF rose; but DMF did not promote the mRNA expression of calpain I at a concentration of 150 mmol/L.
Conclusion: DMF can cause damage to hepatocytes, which is related to intracellular calcium increase and calpain mRNA increase.