Integrated Studies on Male Reproductive Toxicity of Bis(2-ethylhexyl)-tetrabromophthalate: in Silico, in Vitro, ex Vivo, and in Vivo

Abstract

Bis­(2-ethylhexyl)­tetrabromophthalate (TBPH) has been widely detected in the environment and organisms; thus, its toxic effects on male reproduction were systematically studied. First, we found that TBPH can stably bind to the androgen receptor (AR) based on in silico molecular docking results and observed an antagonistic activity, but not agonistic activity, on the AR signaling pathway using a constructed AR-GRIP1 yeast assay. Subsequently, we validated the adverse effects on male germ cells by observing inhibited androgen production and proliferation in Leydig cells upon in vitro exposure and affected general motility and motive tracks of zebrafish sperm upon ex vivo exposure. Finally, the in vivo reproductive toxicity was demonstrated in male zebrafish by reduced mating behavior in F0 generation when paired with unexposed females and abnormal development of their offspring. In addition, reduced sperm motility and impaired germ cells in male zebrafish were also observed, which may be related to the disturbed homeostasis of sex hormones. Notably, the specifically suppressed AR in the brain provides further evidence for the antagonistic effects as above-mentioned. These results confirmed that TBPH affected male reproduction through a classical nuclear receptor-mediated pathway, which would be helpful for assessing the ecological and health risks of TBPH.

Mechanistic Insights into 1,2-bis(2,4,6-tribromophenoxy)ethane-Induced Male Reproductive Toxicity in Zebrafish

“…Consequently, the cumulative body proximity duration (Figure D) and cumulative body contact duration (Figure E) were significantly decreased in the 0.1, 10 μg/L, and 1, 10 μg/L BTBPE treatments, respectively. In a variety of model fish such as medaka, peacock fish, and mosquito-eating fish, mating behavior has been considered as an important indicator for reproductive toxicity. − Similar with our results, exposure to TBPH also increased the average distance and decreased the average time in proximity of paired zebrafish, indicating abnormal reproductive behavior . Hence, our results suggested that BTBPE exposure to male zebrafish led to underperformance of reproductive behavior, even when paired with unexposed females.…”

“…Each sample was repeated three times to determine the average value, and the sperm motility test for each fish was completed within 2 h after collecting fresh zebrafish semen. Detailed definitions of sperm motility parameters are described previously. , …”

“…For example, decabromodiphenyl ethane (DBDPE) can cause DNA damage in rat testicular cells, resulting in the arrest of germ cell cycle and the inhibition of sperm production in rats . Our previous study also suggests that bis­(2-ethylhexyl) tetrabromophthalate (TBPH) can induce male reproductive toxicity by altering sperm motility and hormone homeostasis in zebrafish through the androgen receptor (AR) signaling pathway . Given that BTBPE is a novel brominated flame retardant (NBFR) with a structure similar to that of polybrominated diphenyl ethers (PBDEs), we hypothesize that it may also lead to male reproductive toxicity.…”

Bis(2-ethylhexyl)-tetrabromophthalate Poses a Higher Exposure Risk and Induces Gender-Specific Metabolic Disruptions in Zebrafish Liver

“…Therefore, in this study, we conducted a 28-day exposure to evaluate TBPH accumulation in female and male zebrafish tissues (brain, liver, gonad, and muscle). These tissues are relatively accessible and serve as the main target organs for traditional brominated flame retardants, causing neurotoxicity, disruption of reproductive endocrine function, metabolic interference, and motor activity (muscle contraction). ,− Overall, the TBPH content gradually increased in the first 2 weeks, with accumulation profiles diverging among tissues and genders in the subsequent days. For example, TBPH content peaked at the 14th and 21st day in the brain, muscle, and liver of female and male zebrafish, persisting in the gonad until the 28th day (Figure ).…”