| ObjectivesThe aim of this study was to clarify the toxicity of reproductive system induced by BPs through animal experiments and investigation of occupational workers, and to explore the role of apoptosis in the underlying mechanism. And it will provide useful baseline information on exploring the underlying toxicity mechanism of human exposed to bromopropanes and developing occupational health standards.Methods1. The baseline date was collected using questionnaires. The general situation of 85 workers exposed to 1-BP and 86 workers which had no contact with toxic chemicals were surveyed. 1-BP exposure level was accessed by using the date collected by individual passive samplers, and routine analysis of workers'semen was conducted.2. 21 SD male rats were randomly divided into 3 groups. The groups were exposed to olive oil, 1-BP (1g/kg) and 2-BP (1g/kg) for 14 days by intraperitoneally injection. After two weeks injection, rats were deeply anesthetized with diethyl ether and then decapitated, the left epididymis was used for evaluating the sperm parameters. The left testis was immersed in 4% formaldehyde-phosphate buffer solution for histological examination, TUNEL analysis and immunohistochemistry for active Caspase-3. GSH and MDA were assayed by biochemical methods. In addition, real-time quantitative PCR and Western blotting were used to analyze the mRNA and protein levels of Bax, Bcl-2, P53, Fas and FasL. ResultsThere were no significant changes in sperm quality between low level exposure group and control (P>0.05). While the count and the activity rate of sperm in middle level and high level exposure group were significantly decreased when compared with the control group (P<0.05).Animal experiment showed that BPs significantly decreased the body weight when compared with the control group (P<0.05). Significant (P<0.01) decrease in epididymal sperm count was found in the BP-treated rats, and the sperm count in 1-BP group were less than that in 2- BP group. In addition, 1-BP conspicuously increased the proportion of tailless sperm (P<0.01), while there was no difference in abnormal sperms between 1-BP-treated rats and the control. However, the proportion of abnormal sperm in 2-BP group was elevated significantly (P<0.01).Morphological examination revealed no marked changes in testes of rats injected with 1-BP compared with the control, while atrophy of the seminiferous tubules and degenerated spermatogonia with pyknotic nuclei at the periphery of the tubules were noted in 2-BP-treated ratsBoth in 1-BP and 2-BP groups, TUNEL-positive cells were found in semniferous epithelium. Exposed to 1-BP significantly increased the TUNEL-positive cells per tubule (P<0.01), while the percentages of TUNEL-positive tubules, TUNEL-positive cells per tubule, and apoptotic cell index significantly increased in 2-BP-treated group (P<0.01, P<0.01, P<0.01). As expected, the 2-BP group showed a conspicuous increase in the activity of caspase-3 than in the 1-BP group.There were no significant changes in the expression of the apoptosis-related mRNAs and proteins in 1-BP group compared with control group, although a small decrease was noted (P>0.05). In 2-BP-treated rats, the expression of p53, Bax and Bcl-2 were significantly lower than that in control group (P<0.01, P<0.01, P<0.01), while the expression of Fas and FasL were the same to the control (P>0.05, P>0.05).ConclusionThe study of male workers showed that the count and the activity rate of sperm in middle level and high level exposure group were significantly decreased when compared with the control group. The animal study revealed that 1-BP, similar to 2-BP, has toxic effects on reproductive system, while the adverse effects on testis and the underlying mechanism of these two isomers of BPs may be different. In addition, the data of the apoptosis-related genes and proteins and caspase-3 activity may provide insights into the role of apoptosis in the toxic mechanisms by which 2-BP affects reproduction in male rats. The mitochondria-associated molecule Bcl-2/Bax system and p53 are involved in the induction of apoptosis in rat germ cells following 2-BP treatment. However, further efforts are required for a more complete understanding of the BPs underlying molecular mechanisms. |
