Effects of bisphenol A on apoptosis and insulin secretion of insulinoma cells in rats

Objective This experiment investigates the effects of BPA on apoptosis and insulin secretion of insulinoma cells (INS-1 cells) in rats.

Methods INS-1 cells were routinely cultured and exposed in RPMI 1640 medium containing different concentrations of BPA (6, 30, and 150 μmol·L^-1, respectively), with DMSO as solvent (final concentration ≤ 0.1%). Methyl thiazolyl tetrazolium assay was used to detect survival rate of INS-1 cells; flow cytometry was used to detect apoptosis rate of INS-1 cells; reactive oxygen species (ROS) kit was used to detect ROS level of INS-1 cells; glucose-stimulated insulin secretion assay was used to detect insulin secretion of INS-1 cells; reverse transcription polymerase chain reaction and Western blotting were used to detect expressions of Bcl-2, Bax, caspase3 genes and their proteins in INS-1 cells, respectively.

Results Compared with the DMSO solvent control group, the survival rate of INS-1 cells was increased in the 30 μmol·L^-1 BPA group and decreased in the 150 μmol·L^-1 BPA group (P < 0.01). The results of flow cytometry showed that the total apoptosis rate of INS-1 cells was increased in the 6 and 150 μmol·L^-1 BPA groups (P < 0.05). The content of ROS in INS-1 cells was increased in the 6, 30, and 150 μmol·L^-1 BPA groups (P < 0.05). The results of glucose-stimulated insulin secretion assay showed that under the stimulation of basic concentration of glucose (5.6 mmol·L^-1), the level of insulin secretion of INS-1 cells was increased in the 6 and 30 μmol·L^-1 BPA groups, and decreased in the 150 μmol·L^-1 BPA group (P < 0.05); under the stimulation of high concentration of glucose (16.7 mmol·L^-1), the level of insulin secretion was increased in the 30 μmol·L^-1 BPA group (P < 0.05), and decreased in the 6 and 150 μmol·L^-1 BPA groups (P < 0.05). The mRNA and protein relative expression levels of anti-apoptotic gene Bcl-2 were decreased in the 6 and 150 μmol·L^-1 BPA groups and increased in the 30 μmol·L^-1 BPA group (P < 0.05); the mRNA and protein relative expression levels of pro-apoptotic gene Bax were increased in the 150 μmol·L^-1 BPA group (P < 0.05); the mRNA and protein relative expression levels of caspase3 were increased in the 150 μmol·L^-1 BPA group and decreased in the 30 μmol·L^-1 BPA group (P < 0.05), the ratios of mRNA and protein relative expression levels of Bcl-2 to Bax were decreased in the 6 and 150 μmol·L^-1 BPA groups; the ratio of protein relative expression level of cleaved-caspase3 to caspase3 was increased in the 6 and 150 μmol·L^-1 BPA groups (P < 0.05).

Conclusion BPA administration at 30μmol·L^-1 could promote proliferation and insulin secretion of INS-1 cells, while that at 6 and 150 μmol·L^-1 could reduce the viability of INS-1 cells, induce apoptosis, and decrease the level of insulin secretion, which may be related to oxidative damage.