Endocrine toxicants including 2,3,7,8-terachlorodibenzo-p-dioxin (TCDD) and dioxin-like chemicals and endometriosis: is there a link?

Cost-effectiveness Analysis of Dienogest Compared With Gonadotropin-Releasing Hormone Agonist After Conservative Surgery for Endometriosis in China

PURPOSE

Although the clinical effect of dienogest for endometriosis after conservative surgery has been proven, the cost-effectiveness of this new pharmacotherapy remains to be determined. We aimed to assess the health economic implications of dienogest versus a gonadotropin-releasing hormone agonist (GnRH-a; goserelin in the Chinese setting.

METHODS

A decision tree model was developed to evaluate the cost-effectiveness of dienogest compared with a GnRH-a (goserelin) after conservative surgery for endometriosis during a 2-year time horizon from the perspective of a health care system in China. The cost of drugs, use of outpatient care facilities, administration of medications, routine laboratory work and imaging studies, and treatment of drug-related adverse events were considered. We obtained clinical efficacy data from the peer-reviewed literature. Base case findings were further tested with 1-way and probabilistic sensitivity analyses.

FINDINGS

The model projects that treatment with dienogest would result in a modest incremental 0.02 quality-adjusted life-year gains compared with a GnRH-a (goserelin) (1.48 vs 1.46) at a cost saving of ¥7274 (¥22,809 vs ¥30,164). Probabilistic sensitivity analysis found that dienogest has a 100% probability of % being considered cost-effective compared with a GnRH-a (goserelin) at the willingness-to-pay threshold of 3 times the gross domestic product per capita (¥64,644 × 3) of China in 2018 (¥1 = US$0.1454 and €0.1248).

IMPLICATIONS

Dienogest is more effective and cost-saving compared with a GnRH-a (goserelin) in the treatment of patients with endometriosis after conservative surgery in China.

The impact of endocrine disruptor chemicals on oocyte/embryo and clinical outcomes in IVF

The negative impact of endocrine-disrupting pesticides on human fertility is now a key issue in reproductive health. There are much fewer literature data about the impact of pesticide exposure on women than on men and very few studies of women participating in an in vitro fertilization (IVF) programme. In the present review, we found that (1) various pesticides with an endocrine-disrupting action are associated with poor oocyte maturation and competency, embryonic defects and poor IVF outcomes, and (2) some pesticide compounds are linked to specific causes of female infertility, such as premature ovarian insufficiency, polycystic ovarian syndrome, and endometriosis. IVF participants living in agricultural regions should be informed about the fertility decline, low ongoing pregnancy rates, and elevated risk of miscarriage associated with exposure to high doses of pesticides.

Dioxin and endometriosis: a new possible relation based on epigenetic theory

Endometriosis is a chronic disease characterized by the growth of endometrial-like glands and stroma outside the uterine cavity. Nowadays, the exact etiology of endometriosis is unclear and the interaction between a variety of environmental physical and chemical compounds may potentially promote the disease in women with an individual susceptibility. The first demonstration of a relation between an environmental factor and endometriosis was obtained with the chronic dietary exposure of a primate colony to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Besides the well-known dioxin's pathway of action, several papers are focusing on the role of epigenetic mechanisms, a way through which the genome responds to the environment and can lead to permanent changes in gene expression until affecting the phenotypes or cause disease. In this review, we focus on the possible role of dioxin epigenetics modification in endometriosis.

Proposed Key Characteristics of Female Reproductive Toxicants as an Approach for Organizing and Evaluating Mechanistic Data in Hazard Assessment

BACKGROUND

Identification of female reproductive toxicants is currently based largely on integrated epidemiological and in vivo toxicology data and, to a lesser degree, on mechanistic data. A uniform approach to systematically search, organize, integrate, and evaluate mechanistic evidence of female reproductive toxicity from various data types is lacking.

OBJECTIVE

We sought to apply a key characteristics approach similar to that pioneered for carcinogen hazard identification to female reproductive toxicant hazard identification.

METHODS

A working group of international experts was convened to discuss mechanisms associated with chemical-induced female reproductive toxicity and identified 10 key characteristics of chemicals that cause female reproductive toxicity: 1) alters hormone receptor signaling; alters reproductive hormone production, secretion, or metabolism; 2) chemical or metabolite is genotoxic; 3) induces epigenetic alterations; 4) causes mitochondrial dysfunction; 5) induces oxidative stress; 6) alters immune function; 7) alters cell signal transduction; 8) alters direct cell–cell interactions; 9) alters survival, proliferation, cell death, or metabolic pathways; and 10) alters microtubules and associated structures. As proof of principle, cyclophosphamide and diethylstilbestrol (DES), for which both human and animal studies have demonstrated female reproductive toxicity, display at least 5 and 3 key characteristics, respectively. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), for which the epidemiological evidence is mixed, exhibits 5 key characteristics.

DISCUSSION

Future efforts should focus on evaluating the proposed key characteristics against additional known and suspected female reproductive toxicants. Chemicals that exhibit one or more of the key characteristics could be prioritized for additional evaluation and testing. A key characteristics approach has the potential to integrate with pathway-based toxicity testing to improve prediction of female reproductive toxicity in chemicals and potentially prevent some toxicants from entering common use. https://doi.org/10.1289/EHP4971.

Polychlorinated biphenyls and its potential role in endometriosis

With the progress of global industrialization and environmental deterioration, the relationship between human health and the living environment has become an increasing focus of attention. Polychlorinated biphenyls (PCBs, including dioxin-like polychlorinated biphenyls and non-dioxin-like polychlorinated biphenyls), as part of the organic chlorine contaminants, have been suspected as playing a role in the etiopathogenesis of endometriosis. Several population-based studies have proposed that exposure to PCBs may increase the risk of developing endometriosis, while some epidemiological studies have failed to find any association between PCBs and endometriosis. The purpose of this review is to discuss the potential pathophysiological relationship between endometriosis and PCBs with a focus on both dioxin-like polychlorinated biphenyls and non-dioxin-like polychlorinated biphenyls.

Exposure to endocrine disruptors during adulthood: consequences for female fertility

Endocrine disrupting chemicals are ubiquitous chemicals that exhibit endocrine disrupting properties in both humans and animals. Female reproduction is an important process, which is regulated by hormones and is susceptible to the effects of exposure to endocrine disrupting chemicals. Disruptions in female reproductive functions by endocrine disrupting chemicals may result in subfertility, infertility, improper hormone production, estrous and menstrual cycle abnormalities, anovulation, and early reproductive senescence. This review summarizes the effects of a variety of synthetic endocrine disrupting chemicals on fertility during adult life. The chemicals covered in this review are pesticides (organochlorines, organophosphates, carbamates, pyrethroids, and triazines), heavy metals (arsenic, lead, and mercury), diethylstilbesterol, plasticizer alternatives (di-(2-ethylhexyl) phthalate and bisphenol A alternatives), 2,3,7,8-tetrachlorodibenzo-p-dioxin, nonylphenol, polychlorinated biphenyls, triclosan, and parabens. This review focuses on the hypothalamus, pituitary, ovary, and uterus because together they regulate normal female fertility and the onset of reproductive senescence. The literature shows that several endocrine disrupting chemicals have endocrine disrupting abilities in females during adult life, causing fertility abnormalities in both humans and animals.

Paternal exposures to environmental chemicals and time-to-pregnancy: overview of results from the LIFE study

Published findings from the Longitudinal Investigation of Fertility and the Environment (LIFE) Study regarding the relation between environmental chemicals and couple fecundity, as measured by time-to-pregnancy (TTP), are reviewed with a particular focus on role of the male partner. The LIFE Study recruited 501 couples from 16 counties in two U.S. states upon discontinuing contraception for purposes of becoming pregnant. Upon enrollment, couples provided a blood and urine sample for the quantification of persistent and non-persistent environmental chemicals, respectively, and then completed daily journals until pregnant or up to one year of trying. Female partners used fertility monitors to aid the timing of intercourse relative to ovulation, and digital home pregnancy test kits on the day of expected menses. Chemical classes included: metals, persistent organic pollutants, environmental phenols, and phthalates that were quantified using inductively coupled plasma mass spectrometry or isotope dilution high-resolution or tandem mass spectrometry. Time-to-pregnancy (TTP) was defined as the number of prospectively observed menstrual cycles required for pregnancy. Fecundability odds ratios (FORs) and 95% confidence intervals (CIs) were estimated for each chemical and partner after adjusting for potential confounders and accounting for right censoring and time off contraception. FORs < 1 are suggestive of diminished fecundity or a longer TTP. Significant reductions (ranging from 17-31%) in couple fecundity were observed for male partners' concentration of lead (0.83; 0.70, 0.98), 2,2',4,4'-tetrahydroxybenzophenone (0.69; 0.49, 0.97), monobenzyl (0.80; 0.67, 0.97), and monomethyl (0.81; 0.70, 0.94) phthalates after adjusting for the female partners' concentrations. Seven PCB congeners quantified in men's serum were associated with a 17-29% reduction in couple fecundity. Our findings underscore the importance of a couple-based exposure design, inclusive of the male partner, when assessing couple-dependent outcomes such as TTP to avoid misinterpretation of results based only upon the female partner.

Polymorphism p.Val231Ile alters substrate selectivity of drug-metabolizing arylamine N-acetyltransferase 2 (NAT2) isoenzyme of rhesus macaque and human

Arylamine N-acetyltransferases (NATs) are polymorphic enzymes mediating the biotransformation of arylamine/arylhydrazine xenobiotics, including pharmaceuticals and environmental carcinogens. The NAT1 and NAT2 genes, and their many polymorphic variants, have been thoroughly studied in humans by pharmacogeneticists and cancer epidemiologists. However, little is known about the function of NAT homologues in other primate species, including disease models. Here, we perform a comparative functional investigation of the NAT2 homologues of the rhesus macaque and human. We further dissect the functional impact of a previously described rhesus NAT2 gene polymorphism, causing substitution of valine by isoleucine at amino acid position 231. Gene constructs of rhesus and human NAT2, bearing or lacking non-synonymous polymorphism c.691G>A (p.Val231Ile), were expressed in Escherichia coli for comparative enzymatic analysis against various NAT1- and NAT2-selective substrates. The results suggest that the p.Val231Ile polymorphism does not compromise the stability or overall enzymatic activity of NAT2. However, substitution of Val231 by the bulkier isoleucine appears to alter enzyme substrate selectivity by decreasing the affinity towards NAT2 substrates and increasing the affinity towards NAT1 substrates. The experimental observations are supported by in silico modelling localizing polymorphic residue 231 close to amino acid loop 125-129, which forms part of the substrate binding pocket wall and determines the substrate binding preferences of the NAT isoenzymes. The p.Val231Ile polymorphism is the first natural polymorphism demonstrated to affect NAT substrate selectivity via this particular mechanism. The study is also the first to thoroughly characterize the properties of a polymorphic NAT isoenzyme in a non-human primate model.

A single gestational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin disrupts the adult uterine response to estradiol in mice

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) given as a cotreatment with estrogen exhibits antiestrogenic properties on the rodent adult uterus, but less is understood regarding hormonal responsiveness of the adult uterus from animals having been exposed to TCDD during critical periods of development. We characterized the inhibitory effects of TCDD (T) exposure at gestational day 15 (GD15), 4 weeks, and 9 weeks of age (TTT) on the adult uterus following hormone treatment. TTT-exposed mice in response to hormone treatment exhibited a blunted weight increase, had fewer uterine glands, displayed morphological anomalies, and had marked decreases in the hormonal regulation of genes involved in fluid transport (Aqp3 and Aqp5), cytoarchitectural (Dsc2 and Sprr2A), and immune (Lcn2 and Ltf) regulation. To determine if the 9-week exposure was responsible for the blunted uterine response, due to the 7- to 11-day half-life of TCDD in mice, a second set of experiments was performed to examine exposure to TCDD given at GD15, GD15 only (cross-fostered at birth), only during lactation (cross-fostered at birth), or at GD15 and 4 weeks of age. Our studies demonstrate that a single developmental TCDD exposure at GD15 is sufficient to elicit a blunted adult uterine response to estradiol and is due in part to fewer gland numbers and the reduced expression of forkhead box A2 (FoxA2), a gene involved in gland development. Together, these results provide insight regarding the critical nature of in utero exposure and the potential impact on ensuing uterine biology and reproductive health later in life.

Effects of some endocrine disruptors on cell cycle progression and murine dendritic cell differentiation

Endocrine disruptor chemicals (EDCs), which are predominantly present in the environment, are able to mimic or antagonise the biological activity of hormones primarily through the interaction with specific receptors. The main consequences are adverse effects on the growth and development of reproductive organs, the induction of cancer and effects on neuronal differentiation. In this study, we investigated the ability of certain EDCs, Bisphenol A (BPA), Bisphenol B (BPB), Bisphenol F (BPF), 4-n Nonylphenol (NP) and Octylphenol (OP), belonging to a homogeneous group of phenol origin, to interfere with specific cellular processes, namely, proliferation, by using MCF-7 breast carcinoma cells, and differentiation, by using murine bone marrow dendritic cells. We correlated the data on cell growth with the stimulation of cell cycle progression, which could become a step in the development of cancer, and we established a proliferation ranking between the tested EDCs: NP>BPA>OP>BPB>BPF. In addition, we investigated the ability of NP, BPA and OP to induce the differentiation of dendritic cells, the powerful antigen-presenting cells of the immune system. The differentiation and activation of these cells could affect a well-regulated immune response and determine an allergic sensitisation. We found that BPA and NP were active in determining differentiation.

[Hypothetical link between endometriosis and xenobiotics-associated genetically modified food]

Endometriosis is an oestrogen-dependent inflammatory disease affecting 10 % of reproductive-aged women. Often accompanied by chronic pelvic pain and infertility, endometriosis rigorously interferes with women's quality of life. Although the pathophysiology of endometriosis remains unclear, a growing body of evidence points to the implication of environmental toxicants. Over the last decade, an increase in the incidence of endometriosis has been reported and coincides with the introduction of genetically modified foods in our diet. Even though assessments of genetically modified food risk have not indicated any hazard on human health, xenobiotics-associated genetically modified food, such as pesticides residues and xenoproteins, could be harmful in the long-term. The "low-dose hypothesis", accumulation and biotransformation of pesticides-associated genetically modified food and the multiplied toxicity of pesticides-formulation adjuvants support this hypothesis. This review summarizes toxic effects (in vitro and on animal models) of some xenobiotics-associated genetically modified food, such as glyphosate and Cry1Ab protein, and extrapolates on their potential role in the pathophysiology of endometriosis. Their roles as immune toxicants, pro-oxidants, endocrine disruptors and epigenetic modulators are discussed.

Dioxins in ascites and serum of women with endometriosis: a pilot study

BACKGROUND

Animal studies and laboratory experiments have demonstrated that exposure to dioxins may be involved in the pathophysiology of endometriosis. However, recent epidemiological investigations have shown conflicting results. Although peritoneal fluid is a specific microenvironment playing a pivotal role in the development of endometriosis, to our knowledge, there is no published study evaluating the concentrations of dioxins in serum and peritoneal fluid simultaneously. The present study explores the possible correlation between the local peritoneal fluid levels of dioxins and concurrent endometriosis.

METHODS

There were 17 infertile women enrolled in the present study. After the diagnostic laparoscopic examination, the women were divided into two groups: endometriosis (n = 10) and controls (n = 7). We measured 29 dioxins simultaneously in serum and peritoneal fluid samples: 7 polychlorinated dibenzo-p-dioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs), and 12 polychlorinated biphenyls (dioxin-like PCBs). A dioxin toxic equivalency (TEQ) system was utilized to calculate the dioxin concentration in each sample.

RESULTS

Serum concentrations of itemized components of 29 dioxins were similar in the endometriosis patients compared with the controls. Higher concentrations of PCDFs and dioxin-like PCBs were observed in peritoneal fluid than in serum, whereas the reverse was shown for PCDDs. Statistical analysis showed that higher levels of dioxin TEQ (PCDDs and PCDFs) in peritoneal fluid were significantly associated with an increased risk of endometriosis (OR: 2.5; 95% CI: 1.17-5.34; P = 0.035).

CONCLUSIONS

This is the first report suggesting that higher concentrations of dioxins (PCDDs and PCDFs) in peritoneal fluid are linked to endometriosis. More detail and epidemiological research is warranted to further explore this link.

Pre-natal exposure of mice to bisphenol A elicits an endometriosis-like phenotype in female offspring

Endometriosis is a chronic gynecological disease characterized by the growth of endometrial tissue outside the uterine cavity. Exposure to endocrine disruptors during critical period of development causes long-lasting effects, being the genital system one of the targets. This study describes the effects on female genital system caused by developmental exposure to the endocrine-disrupting chemical bisphenol A (BPA) during pre- and peri-natal development in mice. To this end, timed pregnant Balb-C mice were treated from day 1 of gestation to 7 days after delivery with BPA (100, or 1000 microg/kg/day). After delivery, pups were held for 3 months; then, pelvic organs were analyzed in their entirety and livers of both pups and moms were studied for the presence of BPA. We found in the adipose tissue surrounding the genital tracts of a consistent number of treated animals, endometriosis-like structure with the presence of both glands and stroma and expressing both estrogen receptor and HOXA-10. Moreover, cystic ovaries, adenomatous hyperplasia with cystic endometrial hyperplasia and atypical hyperplasia were significantly more frequent in treated animals respect to the controls. Finally, BPA was found in the livers of exposed moms and female offspring. In conclusion, we describe for the first time an endometriosis-like phenotype in mice, elicited by pre-natal exposition to BPA. This observation may induce to thoroughly reconsider the pathogenesis and treatment of endometriosis, considering the high incidence of endometriosis and the problems caused by associated infertility.

Increased exposure to dioxin-like compounds is associated with endometriosis in a case-control study in women

Although endometriosis is thought to be an environmental disorder initiated by dioxin exposure, this association is controversial. This study was performed to test the hypothesis that endometriosis occurs more often in women exposed to higher concentrations of dioxin-like compounds (DLC) than in those women exposed to lower concentrations. Plasma samples collected prior to laparoscopic surgery from 96 women with endometriosis and 106 control patients with a normal pelvis were measured for DLC concentrations using the dioxin-responsive chemical-activated luciferase expression bioassay. The results showed that concentration (mean+/-SD) of DLC was marginally higher in patients with endometriosis (22.3+/-9.3pg CALUX-TEQ/g lipid) than in controls (20.5+/-10.8pg). After categorization of patients in a group with 'low' plasma concentrations (<25th centile) and a group with 'high' plasma concentrations (>75th centile) of DLC, the age-adjusted odds ratio to have endometriosis was 2.44 (95% CI 1.04-5.70; P=0.04) for women with high concentrations of DLC and it increased to 3.01 (95% CI 1.06-9.04; P=0.03) when only women with moderate severe endometriosis were considered. In conclusion, women exposed to higher plasma concentrations of DLC were at higher risk of having endometriosis than women exposed to lower concentrations of DLC within normal environmental concentrations.

No association between the GSTP1 exon 5 polymorphism and susceptibility to advanced stage endometriosis in the Korean population

PROBLEM

To investigate whether the glutathione-S-transferase P1 (GSTP1) exon 5 polymorphism is associated with susceptibility to advanced stage endometriosis in Korean women.

METHOD OF STUDY

Case-control study in a collective of 260 patients and 164 controls. Genotyping of the GSTP1 exon 5 polymorphism was performed by using real-time TaqMan PCR assay.

RESULTS

The genotype distribution of the GSTP1 exon 5 polymorphism in the endometriosis group was not significantly different from that of the control group (AA/AG/GG rates were 64.2%/32.7%/3.1% and 65.2%/31.7%/3.0% for the endometriosis and control groups, respectively, P = 0.977). Further subgroup analysis according to either stage or bilaterality of ovarian endometrioma also found no significant difference in the genotype distribution between any of the endometriosis subgroups and the control group.

CONCLUSION

These findings suggest that the GSTP1 exon 5 polymorphism is not a major determinant of the development of advanced stage endometriosis in the Korean population.

Serum dioxins, polychlorinated biphenyls, and endometriosis: a case-control study in Atlanta

Endometriosis among women of reproductive age can result in pain and infertility. The objectives of this study were to test if there is a relation between endometriosis and serum dioxin concentrations as expressed by total toxic equivalence and serum total polychlorinated biphenyl concentrations among women patients at one Atlanta reproductive medicine clinic during 1998-1999; a secondary objective was to provide exposure data for individual congeners of these chemicals and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane (p,p'-DDE) in women in Atlanta. Laparoscopy including biopsy and visualization of the peritoneal cavity, ovaries, outside of the fallopian tubes and uterus confirmed all endometriosis cases (n=60) and confirmed 30 controls without endometriosis. Other controls had an infertile partner (n=27) or ovulation problems (n=7) with no signs or symptoms of endometriosis. All serum samples were analyzed at the U.S. Centers for Disease Control and Prevention in 2003. Statistical analyses included Fisher's exact chi-square tests and logistic regression. Models were presented for the full study sample and for the subset that included all cases (n=60) and only controls (n=30) with surgical confirmation of disease-free status. Serum concentrations (lipid-adjusted and non lipid-adjusted) of analyzed exposure measures were low and similar for cases and controls and did not explain endometriosis in the study population.