Variations of synaptic associated proteins and EphA/EphrinA5 in mice with cognition deficits following benzoapyrene treatment

Background Benzoapyrene (BaP) is a kind of widespread pollutants in the environment, and can cause cognitive impairment. Cognitive function is closely related to synaptic plasticity.

Objective This experiment investigates the changes of synaptic related proteins and erythropoietin-producing hepatocellular receptors (EphA4 and EphA5) and their ligand (EphrinA5) in mice with cognitive impairment induced by BaP, and to provide new ideas for the mechanism study on cognitive impairment induced by BaP.

Methods Forty SPF 8-week-old male ICR mice were randomly categorized into four groups, including one solvent control group (vegetable oil) and three BaP-treated groups (0.5, 2, and 10 mg·kg^-1 BaP), 10 mice per group. The treated groups were administered BaP at designed concentrations by intraperitoneal injection, once every other day, 30 times in total for 60 d. The solvent control group was injected with the same amount of vegetable oil. After 60d, open field test was used to detect the average time spent in the central area and the number of rear up of mice in a new environment, and the protein expressions of synaptophysin (SYP), postsynaptic density 95 (PSD95), EphA4, EphA5, and EphrinA5 in cerebral cortex were detected by Western blotting.

Results After the designed BaP treatment, the weight gain of mice decreased in a dose-dependent manner. Compared with the solvent control group, the average weight gain of mice in the 10 mg·kg^-1 BaP group decreased by 5.78 g (P < 0.05). The results of open field experiment showed that compared with the solvent control group, the average time spent in the central area of mice in the 10 mg·kg^-1 BaP group increased by 34.42 s, while the number of standing on hind limbs decreased by 21.57 (P < 0.05). The Western blotting results showed that the protein expressions of SYP, PSD95, and EphrinA5 in the 10 mg·kg^-1 BaP group decreased by 32.2%, 34.8%, and 14.9% respectively (P < 0.05) compared with the solvent control group, while the protein expressions of EphA4 and EphA5 in the 10mg·kg^-1 BaP group increased by 41.3% and 40.0% respectively (P < 0.05).

Conclusion Synaptic associated proteins and EphA/EphrinA5 proteins are probably correlated with the cognitive impairment in mice induced by BaP.