Diverse animal models to examine potential role(s) and mechanism of endocrine disrupting chemicals on the tumor progression and prevention: Do they have tumorigenic or anti-tumorigenic property?

Acting as hormone mimics or antagonists in the interaction with hormone receptors, endocrine disrupting chemicals (EDCs) have the potentials of disturbing the endocrine system in sex steroid hormone-controlled organs and tissues. These effects may lead to the disruption of major regulatory mechanisms, the onset of developmental disorders, and carcinogenesis. Especially, among diverse EDCs, xenoestrogens such as bisphenol A, dioxins, and di(2-ethylhexyl)phthalate, have been shown to activate estrogen receptors (ERs) and to modulate cellular functions induced by ERs. Furthermore, they appear to be closely related with carcinogenicity in estrogen-dependant cancers, including breast, ovary, and prostate cancers. In in vivo animal models, prenatal exposure to xenoestrogens changed the development of the mouse reproductive organs and increased the susceptibility to further carcinogenic exposure and tumor occurence in adults. Unlike EDCs, which are chemically synthesized, several phytoestrogens such as genistein and resveratrol showed chemopreventive effects on specific cancers by contending with ER binding and regulating normal ER action in target tissues of mice. These results support the notion that a diet containing high levels of phytoestrogens can have protective effects on estrogen-related diseases. In spite of the diverse evidences of EDCs and phytoestrogens on causation and prevention of estrogen-dependant cancers provided in this article, there are still disputable questions about the dose-response effect of EDCs or chemopreventive potentials of phytoestrogens. As a wide range of EDCs including phytoestrogens have been remarkably increasing in the environment with the rapid growth in our industrial society and more closely affecting human and wildlife, the potential risks of EDCs in endocrine disruption and carcinogenesis are important issues and needed to be verified in detail

Effects of some Endocrine Disruptors on Human and Grey Seal Uterine Cells

The effects of environmental contaminants in humans and animals are of great concern. Some contaminants are endocrine disruptors that may interfere with the endogenous hormonal signalling and disturb, for example, reproductive organs and functions. Primary uterine myometrial cells originating from women and Baltic grey seals were exposed to some polychlorinated biphenyls (PCBs) and their metabolites. Even though human and Baltic grey seal myometrial cells responded differently to the tested PCBs, the results indicate that PCBs can influence myometrial cell proliferation in vitro. The prevalence of uterine leiomyomas was investigated among 257 Baltic grey seals. Leiomyomas were only present in females older than 22 years, at a prevalence of 65%. Proliferation in leiomyoma cells was detected in individuals lacking ovarian proliferation support, suggesting the presence of an exogenous stimulant. By taking into account temporal alterations in the contaminant burden of the seals, PCB exposure was found to be associated with leiomyoma prevalence. In conclusion, PCB exposure may be related to uterine leiomyoma development and proliferation in Baltic grey seals in vivo. Human endometrial endothelial cells (HEECs) were exposed to some endocrine disruptors, and the effects of the endocrine disruptors on cell proliferation and viability were studied. All evaluated endocrine disruptors decreased HEEC proliferation and most also decreased HEEC viability. Further studies revealed that the reduction in HEEC proliferation after exposure to o,p’-DDT was associated with differential expression of mRNA involved in proliferation, defence response, and lipid and cholesterol metabolism compared to untreated HEEC. In conclusion, these studies suggest that endocrine disruptors affect cultured cells from the female reproductive tract of humans and grey seals, and may have deleterious effects on proliferation, viability, and genes involved in defence response, and lipid or cholesterol metabolism

Effects of some Endocrine Disruptors on Human and Grey Seal Uterine Cells

The effects of environmental contaminants in humans and animals are of great concern. Some contaminants are endocrine disruptors that may interfere with the endogenous hormonal signalling and disturb, for example, reproductive organs and functions. Primary uterine myometrial cells originating from women and Baltic grey seals were exposed to some polychlorinated biphenyls (PCBs) and their metabolites. Even though human and Baltic grey seal myometrial cells responded differently to the tested PCBs, the results indicate that PCBs can influence myometrial cell proliferation in vitro. The prevalence of uterine leiomyomas was investigated among 257 Baltic grey seals. Leiomyomas were only present in females older than 22 years, at a prevalence of 65%. Proliferation in leiomyoma cells was detected in individuals lacking ovarian proliferation support, suggesting the presence of an exogenous stimulant. By taking into account temporal alterations in the contaminant burden of the seals, PCB exposure was found to be associated with leiomyoma prevalence. In conclusion, PCB exposure may be related to uterine leiomyoma development and proliferation in Baltic grey seals in vivo. Human endometrial endothelial cells (HEECs) were exposed to some endocrine disruptors, and the effects of the endocrine disruptors on cell proliferation and viability were studied. All evaluated endocrine disruptors decreased HEEC proliferation and most also decreased HEEC viability. Further studies revealed that the reduction in HEEC proliferation after exposure to o,p’-DDT was associated with differential expression of mRNA involved in proliferation, defence response, and lipid and cholesterol metabolism compared to untreated HEEC. In conclusion, these studies suggest that endocrine disruptors affect cultured cells from the female reproductive tract of humans and grey seals, and may have deleterious effects on proliferation, viability, and genes involved in defence response, and lipid or cholesterol metabolism

Effect of bisphenol A on human endometrial stromal fibroblasts in vitro.

This study evaluated the effects of bisphenol A (BPA) on human endometrial stromal fibroblast (ESF) differentiation and expression of genes involved in oestrogen metabolism. Human ESF from eight hysterectomy specimens were cultured and treated with 5-100 μmol/l of BPA ± oestradiol or 8-br-cAMP for 48 h. mRNA expression was analysed by real-time reverse-transcription PCR. 8-br-cAMP-induced human ESF decidualization was confirmed by expression of insulin-like growth factor binding protein-1 (IGFBP1) and prolactin secretion. Short-term exposure (48 h) decreased human ESF proliferation (P<0.04) not due to apoptosis. High doses of BPA significantly induced IGFBP1 mRNA and protein, decreased P450scc mRNA, reversed the 8-br-cAMP-induced increase in HSD17B2 (oestradiol to oestrone conversion) in a dose-dependent manner and down-regulated HSD17B1 expression (oestrone to oestradiol conversion; P ≤ 0.03). 8-br-cAMP significantly potentiated this effect (P=0.028). BPA had no significant effect on aromatase and PPAR γ expression. The oestrogen-receptor antagonist ICI had no effect on gene expression in BPA-treated cells, and oestrogen receptor α, but not oestrogen receptor β, was significantly down-regulated by high doses of BPA (P=0.028). BPA has an endocrine-disrupting effect on human ESF function and gene expression but the underlying mechanisms appear not to involve oestrogen-mediated pathways

Exposure to DDT and hypertensive disorders of pregnancy among South African women from an indoor residual spraying region: The VHEMBE study

Indoor Residual Spraying (IRS), the use of insecticides inside residences for malaria control, may cause elevated exposure to insecticides such as dichlorodiphenyl trichloroethane (DDT). Evidence suggests that DDT exposure may increase blood pressure but no study has investigated associations with hypertensive disorders of pregnancy (HDP) in an IRS area. We measured the serum concentration of DDT and its breakdown product dichlorodiphenyl trichloroethylene (DDE) at the time of delivery among 733 rural South African women participating in the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE). We also collected data on HDP diagnosis through questionnaires administered to participants and medical record abstraction. We used multiple logistic regression models to examine the relation between DDT/E and HDP. p,p'-DDT and p,p'-DDE serum concentrations were associated with HDP based on self-report (OR = 1.50; 95%CI = 1.10, 2.03 for p,p'-DDT and OR = 1.58; 95%CI = 1.09, 2.28 for p,p'-DDE) and medical records (OR = 1.32; 95%CI = 0.99, 1.75 for p,p'-DDT and OR = 1.47; 95%CI = 1.03, 2.09 for p,p'-DDE). p,p'-DDE was also associated with gestational hypertension (OR = 1.44; 95% CI = 1.00, 2.07). Exposure to DDT and DDE may be associated with elevated risks of HDP in South African women residing in an area sprayed for malaria control