Objective: To investigate the effects of monobromobiphenyl ether (4-BDE) on the expression of γH2AX in the rat testis, and the possible mechanism of 4-BDE affecting the reproductive function of the male rats.
Methods: Twenty-four SD male rats were randomly divided into 4 groups: control and low-, medium- and high-dose 4-BDE, the control rats treated intragastrically with olive oil, and the animals in the latter three groups with 4-BDE at 50, 100 and 200 mg/kg/d, respectively, all for 30 consecutive days. Then all the rats were killed and the testis tissues harvested for HE staining, examination of the apoptosis of the cells by TUNEL and determination of the expressions of H2AX mRNA and γH2AX by q-PCR and Western blot.
Results: HE staining manifested occasional reduction or absence of spermatogonial and Sertoli cells in the seminiferous tubules in the medium- and high-dose 4-BDE groups. Compared with the controls, the rats exposed to 4-BDE showed a significant dose-dependent increase in the apoptosis of the testis tissue (P < 0.05), even more significant in the medium- and high-dose 4-BDE groups than in the low-dose group (P < 0.05). There was a dose-effect relationship in the apoptosis index, but with no statistically significant difference between the medium- and high-dose 4-BDE groups (P > 0.05). The results of q-PCR exhibited no statistically significant difference in the expression level of H2AX mRNA either between the control and 4-BDE-exposed rats (P > 0.05) or among the three 4-BDE groups (P > 0.05). The expression of the γH2AX protein was remarkably higher in the 4-BDE groups than in the control (P < 0.05), but not significantly different among the 4-BDE groups (P > 0.05).
Conclusions: Exposure to 4-BDE at 100 or 200 mg/kg/d damages the structure of seminiferous tubules, increases the apoptosis of testicular cells, significantly up-regulates the expression of the γH2AX protein, and consequently increases DNA double-strand breaks (DSB) in the rat testis. The apoptosis of testicular cells may be related to DSB./.
Keywords: DNA double-strand break; apoptosis; rat; polybrominated diphenyl ether; γH2AX.