Different Development Stages Exposure To Bisphenol A Affects Anxiety And Depression Behaviors In Mice And Its Molecular Mechanism

Bisphenol A (BPA) is one of the typical environmental endocrine disruptors which has both estrogenic and anti-estrogenic action. The effects of BPA on the brain and behavioral development have attracted attention. A growing body of evidence suggests that the central nervous system (CNS) to BPA is very sensitive.We previously found that low dose of BPA can not affect reproductive system, but interferes with the processes of sexual differentiation of brain and behaviors in the offspring; perinatal exposure to BPA affected anxiety and sexual differentiation of anxiety of offspring on childhood and adolescent. The effect of estrogen(E2)’s on brain development and sexual differentiation in the’critical period’, which extends from the late embryogenesis to early postnatal period in the rodent, and one of which period BPA exposure interference effects of estrogen on brain development most sensitive is not clear? A large body of evidence showed that E2’s antianxiety and antidepressant-like effects may depend upon many factors, including the regimen of E2utilized and interactions with the hypothalamic-pituitary-adrenal (HPA) axis. Both the amygdala and hippocampus have long been considered important components of the limbic system and regulators of the HPA response. Thus, brain targets for E2’s effects on anxiety and depression include the hippocampus and amygdala. As a kind of weak estrogenic activity of endocrine disruptors, BPA can interfere with estrogen synthesis and secretion to influence of estrogen levels in vivo, which further affects the anxiety and depression behavior has been studies for many, but the specific molecular mechanisms are still not clear. Several neurotransmitters have been implicated in the genesis of anxiety and depression with earlier data highlighting the y-aminobutyric acid (GABA) system and glutamatergic NMDA and AMPA receptors. We previously found that perinatal exposure to BPA down-regulated NMDAR expression and changed the component of NMDAR subunits. Therefore, this study was to investigate the anxiety and depression behaviors of mice which were exposed to BPA from gestation day7(GD7) to GD20or postnatal day0(PND0) to PND14. To detect the relationship between the expressions of NMDA receptor、AMPA receptor or GABA receptor in hippocampus and amygdala and the anxiety and depression-like behaviors. To further explore its possible molecular mechanism.Mehods:Male (30-35g) and female (25-30g) ICR mice were maintained on a12h light:12h dark cycle with free access to food and water. After acclimatization for1week, female mice were housed with males (female:male=1:1) and vaginal plugs and vaginal smears were checked daily. A sperm-positive smear and a plug determined gestational day (GD)0. After detection, the pregnant dams were placed individually. From GD7to GD20and PND0to PND14exposure to BPA (0.4,4mg/kg/d) respectively. The anxiety behaviors of BPA-treated mice on PND56were tested using open field, dark-light transition, mirror maze, and elevated plus maze; and depression was measured in the forced swim task. Choose the mice which not to behavioral tests on PND56, according to the requirements of separation of the hippocampus and amygdala tissue samples. Western blot to detect the expression of NMDA receptor subunit NR1、AMPA receptor subunit G1uR1and GABA receptor subunit GABAAβ1-3in hippocampus and amygdala. At the same time, body weight and the weight of reproductive organs were measured. Radiommunoassay to detect the serum levels of estrogen in female mice and the serum levels of testosterone in male mice.Meta Morph was used to measure the protein bands, and SPSS15.0software was used to analyse experimental data. Two-way ANOVAs compared group×exposure period for the reproductive organs weight and the serum levels of hormone. Mult-way ANOVAs compared gender×group×exposure period for the probe trial in open field, dark/light transition task, mirror chamber, elevated plus maze, and forced swim task. Tukey’s test was used for comparisons between groups. The statistical significance was accepted at P<0.05Results:1) Gestational exposure to BPA decreased the body weight of female offspring mice (p<0.01); lactational exposure to BPA increased the body weight of female offspring mice (p<0.05); both gestational and lactational exposure to BPA increased the body weight of male offspring mice (p<0.05, p<0.01); There were no significant differences in the reproductive organs (uterus weight or bilateral testis)/body weight.2) Gestational exposure to BPA exhibited anxiogenic effects on female offspring mice in all four models, increased the frequencies of grooming(p<0.01), reduced the time spent in light(p<0.05) and the total entries(p<0.05) in dark-light transition, reduced the time spent in mirror(p<0.05) area in mirror maze, reduced the time spent in open arms and open arm entries(p<0.01) and the number of unprotected head dips(p<0.05) in the elevated plus maze. Lactational exposure to BPA in female mice, gestational or lactational in male mice exhibited anxiogenic behaviors in two models; lactational exposure to BPA reduced the time spent in light(p<0.05) in dark-light transition, reduced the time in open arms and the open arm entries(p<0.01,p<0.01) of female offspring mice in elevated plus maze; gestational exposure to BPA reduced the time spent in light(p<0.05) in dark-light transition, reduced the open arm entries(p<0.01) of male offspring mice in elevated plus maze; lactational exposure to BPA increased the total entries(p<0.05) in mirror maze, reduced the open arm entries(p<0.01) of male offspring mice in elevated plus maze. Showed that gestational or lactational exposure to BPA have different levels of anxiety on adults, in which the gestational exposure to BPA on females of anxiety in the most significant.3) Gestational exposure to BPA increased the immobile time(p<0.01, p<0.01) of offspring mice in the forced swim task. Showed that gestational exposure to BPA significantly increased depression of female and male mice, and lactational only high doses of BPA (4mg/kg) exposure increased depression(p<0.01) of offspring mice. Showed that the gestational or lactational exposure to BPA were both increased the depression of adults.4) Western blot analysis showed that gestational exposure to BPA down-regulated the expressions of GluRland GABAAβ1-3in hippocampus and amygdala of offspring female mice(p<0.05, p<0.01), down-regulated the expression of NR1in hippocampus(0.4mg/kg, p<0.05) while up-regulated the expressions in amygdala(4mg/kg, p<0.05); Lactational exposure to BPA significantly down-regulated the expressions of GluRl and GABAA(31-3in hippocampus and amygdala and NR1in hippocampus of offspring female mice(bothp<0.05), and has not effect on NR1in amygdala. Gestational exposure to BPA(4mg/kg) down-regulated the expressions of G1uR1and GABAAβ1-3in hippocampus(p<0.01, p<0.01), and BPA(0.4mg/kg) down-regulated the expressions of GluRl and GABAAβ1-3in amydala(p<0.01, p<0.01) of offspring male mice; Lactational exposure to BPA down-regulated the expression of G1uR1in amygdala of offspring male mice(p<0.01).Conclusion:These results indicated that gestational and lactational exposure to BPA have anxiogenic and depression-like effects on offspring of adult mice, in which gestational BPA exposure on offspring mice of anxiety is more significant. The inhibiting of expression of AMPAR and GABAR in hippocampus and amygdala may be related anxiety and depression-like behaviors of BPA exposure.