[Changes of mitochondria membrane potential and cytoplasmic cytochrome C in neuron apoptosis induced by benzo(a)pyrene].

Objective: To investigate the changes of mitochondria membrane potential and cytoplasma cytochrome C as the mechanism of neuron apoptosis induced by B(a)P.

Methods: Primary neurons were dissociated from cerebral cortex of 1 - 3 days old SD rats and cultured with DMEM incubator at 37 degrees C. After 5 days' cultivation, the neurons were added S9 and B(a)P, and the concentrations of treated B(a)P were 0, 10, 20 and 40 micromol/L respectively. After administering of B(a)P, the neurons were cultivated for 40 hours. Apoptosis rate was measured by flow cytometry using Annexin V-FITC and propidium iodide (PI) staining, and the changes in mitochondrial potential (DeltaPsim) were tested with Rhodamine fluorescence (R2123) technique. Preparation of cytosolic extracts by centrifugation. Western blotting analysis was used to evaluate the level of cytochrome C of cytoplasm.

Results: The apoptotic rate of neuron increased in both the middle dose group and the high dose group compared with controls, and had a dose-response tendency with the concentration of B(a)P. Moreover mitochondrial potential decreased in a dose dependent manner. There was a negative correlation between DeltaPsim and the apoptotic rate of neurons (r = -0.763, P < 0.05); Western blotting analysis showed cytoplasmic cytochrome C level increased significantly, which was positively related with neuron apoptosis (r = 0.831, P < 0.01).

Conclusion: Loss of mitochondria membrane potential and increase of cytoplasma cytochrome C may be the main cause of neuron apoptosis induced by B(a)P.