Developmental toxicity of estrogenic chemicals on rodents and other species

ABSTRACT  Antenatal sex-hormone exposure induces lesions in mouse reproductive organs, which are similar to those in humans exposed in utero to a synthetic estrogen, diethylstilbestrol. The developing organisms including rodents, fish and amphibians are particularly sensitive to exposure to estrogenic chemicals during a critical window. Exposure to estrogens during the critical period induces long-term changes in reproductive as well as non-reproductive organs, including persistent molecular alterations. The antenatal mouse model can be utilized as an indicator of possible long-term consequences of exposure to exogenous estrogenic compounds including possible environmental endocrine disrupters. Many chemicals released into the environment potentially disrupt the endocrine system in wildlife and humans, some of which exhibit estrogenic activity by binding to the estrogen receptors. Estrogen responsive genes, therefore, need to be identified to understand the molecular basis of estrogenic actions. In order to understand molecular mechanisms of estrogenic chemicals on developing organisms, we are identifying estrogen responsive genes using cDNA microarray, quantitative RT-PCR, and differential display methods, and genes related to the estrogen-independent vaginal changes in mice induced by estrogens during the critical window. In this review, discussion of our own findings related to endocrine distuptor issue will be provided.     

Modulation of human α(4)β(2) nicotinic acetylcholine receptors by brominated and halogen-free flame retardants as a measure for in vitro neurotoxicity

Brominated flame retardants (BFRs) are abundant persistent organic pollutants with well-studied toxicity. The toxicological and ecological concern associated with BFRs argues for replacement by safer alternatives. However, the (neuro)toxic potential of alternative halogen-free flame retardants (HFFRs) is unknown. Previous research identified the nervous system as a sensitive target organ for BFRs, with modulation of excitatory nicotinic acetylcholine (nACh) receptors as one of the modes of action. Since it is essential to assess the (neuro)toxic potential of HFFRs before large scale use, we measured the effects of three BFRs and 13 HFFRs on the function of human α(4)β(2) nACh receptors, expressed in Xenopus oocytes, using the two-electrode voltage-clamp technique. The results demonstrate that some BFRs (TBBPA and to a lesser extent BDE-209) and HFFRs (TPP, Alpi, APP, MMT and to a lesser extent ATH, ATO, MHO, MPP, RDP and ZHS) act as nACh receptor antagonists. Contrary, BPS, BDP, DOPO and ZS were unable to modulate nACh receptors. Despite the lack of toxicological data on HFFRs and the need for additional studies to perform a full (neuro)toxic risk assessment, the current data on antagonistic effects on nACh receptors could be an important step in prioritizing viable HFFRs for substitution of BFRs.     

Prenatal Exposure to BPA and Offspring Outcomes: The Diabesogenic Behavior of BPA

Obesity and type 2 diabetes mellitus (T2DM) are the most common metabolic disorders, with prevalence rates that are reaching epidemic proportions. Both are complex conditions affecting virtually all ages and with serious health consequences. The underlying cause of the problem is still puzzling, but both genetic and environmental factors including unhealthy diet, sedentary lifestyle, or the exposure to some environmental endocrine disrupting chemicals (EDCs) are thought to have a causal influence. In addition, the impact of early environment has recently emerged as an important factor responsible for the increased propensity to develop adult-onset metabolic disease. Suboptimal maternal nutrition during critical windows in fetal development is the most commonly studied factor affecting early programming of obesity and T2DM. In recent years, increasing experimental evidence shows that exposure to EDCs could also account for this phenomenon. In the present review, we will overview the most relevant findings that confirm the critical role of bisphenol-A, one of the most widespread EDCs, in the development of metabolic disorders.     

双酚A的活性炭吸附特性

研究了活性炭吸附双酚A(BPA)的规律、吸附特性和吸附处理效果。结果表明:吸附速度快,1 h达到平衡。吸附符合弗兰德利希公式,吸附常数K=191 m g/g,1n=0.239。吸附容量大,且受被吸附质浓度的影响小。当pH>9和有其他有机物存在时,因BPA发生电离和竞争吸附使吸附容量减小,吸附规律发生变化。但活性炭吸附可使BPA浓度降低到0.08 m g/L以下,是处理含BPA废水的一种有效方法。     

双酚A的活性污泥法处理特性

研究了活性污泥法处理双酚A(BPA)废水的效果、降解动力学特性和净化机理。结果表明:污泥驯化与否对处理效果影响很大,驯化污泥对双酚A降解率可达90%以上。测得的最大比基质降解速率(qm ax)为0.35-d 1,半饱和常数(Ks)为15.5 m g/L,降解速率较慢。活性污泥法处理时BPA的去除主要是生物降解起作用,吸附作用很小,BPA不会在剩余污泥中积累。     

Effect of an endocrine disruptor on mammalian fertility. Application of monoclonal antibodies against sperm proteins as markers for testing sperm damage

PROBLEM: To determine the influence of an endocrine disruptor [bisphenol-A (BPA)] on the integrated reproductive process as well as on individual reproductive organs and gametes in order to select suitable markers for testing sperm damage. METHOD OF STUDY: The effect of BPA on fertility in vivo in multigenerational studies in an outbred stock of mice was studied. Damage of reproductive organs was assessed by histochemical methods and damage of spermatozoa by means of a panel of monoclonal antibodies (MoAbs) against intra-acrosomal sperm proteins. RESULTS: BPA had a negative influence on offspring born of mice, on reproductive organs, and on acrosome integrity of mice spermatozoa. Selected MoAbs against intra-acrosomal mammalian sperm proteins, cross-reacted with mouse spermatozoa, were used for determination of the acrosome integrity. BPA had no effect on body weight and testicle weight of males. CONCLUSIONS: The present results demonstrate that BPA has a negative effect on in vivo fertility of mice, with impact on spermatogenesis and sperm quality. Monoclonal antibodies against intra-acrosomal sperm proteins can be used for detecting sperm damage.     

Bisphenol-A induces cell cycle delay and alters centrosome and spindle microtubular organization in oocytes during meiosis

Bisphenol-A (BPA) is a widely used environmental estrogen-like chemical that has a weak estrogenic activity. This study aimed to test the potential inhibitory effects of BPA on meiotic cell cycle progression, centrosomes and spindle integrity in mouse cumulus-oocyte complexes (COCs). They were exposed to BPA (10-30 microM; 2.3-6.8 ppm) during meiosis-I and the formation of metaphase-II (M-II) spindle. Exposure to BPA during meiosis-I caused a dose-dependent retardation/inhibition of cell cycle progression; 74 and 61% of cells reached metaphase-I (M-I) in the presence of 10 and 30 microM BPA, respectively, (81% in controls, P<0.001). A more striking delay was noted when oocytes were exposed to BPA during the formation of M-II spindle, i.e. 61 and 41% of cells (94% in controls, P<0.001) reached M-II while the remaining cells remained at M-I. Depending on dose, both (i) loosening and elongation of meiotic spindles and (ii) compaction and dispersion of pericentriolar material (PCM) were noted in all samples, all of which resulted in a series of spindle abnormalities. Interestingly, no chromosome was detected in the first polar body after the 10 and 30 microM BPA treatments. When the cells were freed from BPA exposure at 10 and 30 microM, 70 and 61%, of the cells succeeded in reaching M-II (93% in controls, P<0.001), respectively. In conclusion, one mode of action of BPA is a moderately severe yet reversible delay in the meiotic cell cycle, possibly by a mechanism that degrades centrosomal proteins and thus perturbs the spindle microtubule organization and chromosome segregation.     

双酚A对成年雄性小鼠体质量、摄食和肝功能的影响

目的 探讨双酚A对成年雄性小鼠体质量、摄食和肝功能的影响.方法 100只成年雄性ICR小鼠随机分为阴性对照组、己烯雌酚对照组、双酚A 2、20、100 mg/kg组,各组动物用相应受试物连续灌胃2周,于第8周将小鼠处死.用酶化学方法检测丙氨酸氨基转移酶(ALT)、天门冬氨酸氨基转移酶(AST)、γ-谷氨酞基转移酶(GG...     

Molecular changes induced by bisphenol-A in rat Sertoli cell culture

Bisphenol-A (BPA) is an industrial chemical and is known to act as an endocrine disrupter. This study was designed to evaluate how BPA regulates Sertoli cell (SC) signal molecules. Purified rat SCs were cultured and treated with BPA (200?µmol/l) at various time points. Western blot analysis was used to determine the activation of extracellular signal-related kinases 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), p38 mitogen activated protein kinase (MAPK), nuclear factor kappa B (NF-κB), cyclooxygenase-1,2 (COX-1, 2), estrogen receptor-α (ER-α), and androgen receptor (AR). The levels of transferrin (TF), prostaglandin E₂ (PGE₂), and prostaglandin F_2α (PGF_2α) in culture medium were quantified by ELISA. Interleukin (IL)-1β and IL-6 mRNAs were measured by quantitative real-time PCR (QRT-PCR). Compared with the control, BPA activated the phosphorylation of ERK1/2 (p-ERK1/2) through 30?min to 6?h. TF was down-regulated at 6 and 24?h. Furthermore, IL-1β was up-regulated at 30?min and IL-6 was up-regulated at 1 and 24?h. ERK activity inhibitor (PD98059, 10?µmol/l) inhibited these molecular changes. These results reveal the possibility that BPA may have adverse effects on spermatogenesis via ERK1/2.     

The effects of prenatal exposure to ethinyl estradiol and bisphenol-A on the developing brain, reproductive organ and behavior of mouse

ABSTRACT This study investigated the effects of ethinyl estradiol (EE) and bisphenol‐A (BPA) on the maturation of fetuses, reproductive organ, brain development, and behavior. Twenty‐eight Jcl‐ICR pregnant mice were divided into 0.2 mg/kg of EE, 0.02 mg/kg of EE, BPA and control groups. Pregnant mice belonging to 0.2 mg/kg of EE and 0.02 mg/kg of EE group were daily injected subcutaneously either 0.2 mg/kg or 0.02 mg/kg of EE dissolved in olive oil from 11 to 19 days of gestation. The BPA group received an injection of 100 mg/kg of BPA dissolved in olive oil while the control group received an injection of olive oil alone subcutaneously on the same days of gestation. Neurological and behavioral development was examined by means of the sensorimotor reflexes until day 10 and openfield test on day 40 after birth. Myelination of the brain and maturation of testis were histologically examined. Obtained results were: 1) Pregnant mice in the 0.2 mg/kg EE group had no live births. 2) The mean litter size in the 0.02 mg/kg EE group was smaller than that in the BPA and control groups. The mean body weight at birth and that at the age of 60 days showed no significant differences among groups. 3) In the openfield test at the age of 40 days, the mean number of grooming and line‐crossing in the inner field in the 0.02 mg/kg EE group were significantly higher than those in the control group and the mean number of grooming, rearing and line‐crossing in the outer field in 0.02 mg/kg EE group were significantly higher than those in the BPA group. The mean numbers of defecation in both 0.02 mg/kg EE group and BPA group were less than those in the control group. 4) The mean diameter of seminiferous tubules and number of spermatocytes layers in the 0.02 mg/kg EE group and BPA were significantly less than those in the control group. 5) The mean diameter of tractus mamillothalamics in the 0.02mg/kg EE group and BPA group showed no significant differences compared with that in the control group. These findings suggested that prenatal exposure to EE or BPA adversely affects litter size, openfield behavior and spermatogenesis.