Update on Activities in Endocrine Disruptor Research and Policy

Occurrence and sources of hormones in water resources-environmental and health impact

Within recent years, hormones have become emergent contaminants in the water environment. They easily accumulate in living organisms which in effect leads to numerous health problems (endocrine-disrupting mechanism is one of the most known toxic effects). Microbial resistance to antibiotics also became one of the emergent issues related to hormone presence. It was shown that the most common in the environment occur estrogens (E1, E2, E3, and EE2). It has been proven that large amounts of hormones are released from aquaculture as well as from wastewater treatment plants (due to the relatively low separation efficiency of conventional wastewater treatment processes). Within the article's scope, the literature review was performed. The analysis was regarding the characterization of the hormone substances present in the environment, their influence on living organisms and the environment, as well as its potential sources classification.

In vitro impact of genistein and mono(2-ethylhexyl) phthalate (MEHP) on the eicosanoid pathway in spermatogonial stem cells

Perinatal exposures to endocrine disrupting chemicals (EDCs) alter the male reproductive system. Infants are exposed to genistein (GEN) through soy-based formula, and to Mono(2-ethylhexyl) Phthalate (MEHP), metabolite of the plasticizer DEHP. Spermatogonial stem cells (SSCs) are formed in infancy and their integrity is essential for spermatogenesis. Thus, understanding the impact of EDCs on SSCs is critical. Prostaglandins (PGs) are inflammatory mediators synthesized via the eicosanoid pathway starting with cyclooxygenases (Coxs), that regulate physiological and pathological processes. Our goal was to study the eicosanoid pathway in SSCs and examine whether it was disrupted by GEN and MEHP, potentially contributing to their adverse effects. The mouse C18-4 cell line used as SSC model expressed high levels of Cox1 and Cox2 genes and proteins, and eicosanoid pathway genes similarly to levels measured in primary rat spermatogonia. Treatments with GEN and MEHP at 10 and 100 μM decreased Cox1 gene and protein expression, whereas Cox2, phospholipase A2, prostaglandin synthases transcripts, PGE2, PGF2a and PGD2 were upregulated. Simultaneously, the transcript levels of spermatogonia progenitor markers Foxo1 and Mcam and differentiated spermatogonial markers cKit and Stra8 were increased. Foxo1 was also increased by EDCs in primary rat spermatogonia. This study shows that the eicosanoid pathway is altered during SSC differentiation and that exposure to GEN and MEHP disrupts this process, mainly driven by GEN effects on Cox2 pathway, while MEHP acts through an alternative mechanism. Thus, understanding the role of Cox enzymes in SSCs and how GEN and MEHP exposures alter their differentiation warrants further studies.

Update on the Health Effects of Bisphenol A: Overwhelming Evidence of Harm

In 1997, the first in vivo bisphenol A (BPA) study by endocrinologists reported that feeding BPA to pregnant mice induced adverse reproductive effects in male offspring at the low dose of 2 µg/kg/day. Since then, thousands of studies have reported adverse effects in animals administered low doses of BPA. Despite more than 100 epidemiological studies suggesting associations between BPA and disease/dysfunction also reported in animal studies, regulatory agencies continue to assert that BPA exposures are safe. To address this disagreement, the CLARITY-BPA study was designed to evaluate traditional endpoints of toxicity and modern hypothesis-driven, disease-relevant outcomes in the same set of animals. A wide range of adverse effects was reported in both the toxicity and the mechanistic endpoints at the lowest dose tested (2.5 µg/kg/day), leading independent experts to call for the lowest observed adverse effect level (LOAEL) to be dropped 20 000-fold from the current outdated LOAEL of 50 000 µg/kg/day. Despite criticism by members of the Endocrine Society that the Food and Drug Administration (FDA)'s assumptions violate basic principles of endocrinology, the FDA rejected all low-dose data as not biologically plausible. Their decisions rely on 4 incorrect assumptions: dose responses must be monotonic, there exists a threshold below which there are no effects, both sexes must respond similarly, and only toxicological guideline studies are valid. This review details more than 20 years of BPA studies and addresses the divide that exists between regulatory approaches and endocrine science. Ultimately, CLARITY-BPA has shed light on why traditional methods of evaluating toxicity are insufficient to evaluate endocrine disrupting chemicals.

Ambient Exposure to Agricultural Pesticides during Pregnancy and Risk of Cerebral Palsy: A Population-Based Study in California

Cerebral palsy (CP) is the most common neuro-motor disability in young children. Disruptions of maternal hormone function during pregnancy have been linked to CP risk. We investigated whether prenatal exposure to pesticide compounds with endocrine-disrupting action affect CP risk. We conducted a case-control study of 3905 CP cases and 39,377 controls born between 1998 and 2010 in California to mothers who lived in proximity (within 2 km) to any agricultural pesticide application recorded in the California Pesticide Use Reporting (PUR) system. We focused on 23 pesticides considered endocrine disruptors that are frequently used, and we found that exposure to any of the 23 pesticides in the first trimester was associated with elevated CP risks in female offspring (OR = 1.19; 95% CI: 1.05-1.35) but not males (OR = 0.99; 95% CI: 0.89-1.09) compared to the unexposed offspring. Positive associations were estimated for 15 pesticides suspected to affect the estrogen and 7 pesticides suspected to affect the thyroid hormone system. Our study suggests that first trimester exposure to pesticides that are suspected endocrine disruptors are associated with CP risk in female offspring. Pesticide exposures in early pregnancy may have sex-specific influences on the neuro-motor development of the fetus by interfering with endocrine systems.

Risk Assessment of Cosmetics Using Triclosan on Future Generation's Germ Cell Maturation via Lactating Mother Rats

Triclosan (TCS) is a widely used chemical in personal care and household products as an antimicrobial agent but some studies have reported it as being estrogenic. We investigated the influence of TCS on the male reproductive system of postnatal pups. Lactating mother rats (Rattus norvegicus) were given daily doses of 0 mg, 3 mg, and 5 mg/kg/day from the day of delivery until 28 days, equivalent to their natural breastfeeding duration. At 28 days, the male pups of all three groups were sacrificed and their biochemical parameters evaluated. TCS-treated pups had decreased mRNA levels for 3β hydro-hydroxysteroid dehydrogenases (3βHSD), OCT3/4, and androgen receptor (AR) (p < 0.05). The higher dose (5 mg/kg/day) male pups exhibited more significantly affected germ cell maturation and decreased body weight. In summary, TCS-treated lactating mothers passed the deleterious effects to their untreated male pups as exhibited by reduced androgens synthesis and subsequently decreased sperm count.

Maternal Exposure to Environmental Disruptors and Sexually Dimorphic Changes in Maternal and Neonatal Oxidative Stress

CONTEXT

Early pregnancy exposure to endocrine disrupting chemicals (EDCs) may contribute to poor birth outcomes through oxidative stress (OS)-mediated disruption of the maternal and fetal milieu. Most studies have investigated the effect of single EDC exposures on OS.

OBJECTIVE

Assess the association of uniquely weighted mixtures of early pregnancy exposures with the maternal and neonatal OS markers.

DESIGN

Prospective analysis of mother-infant dyads.

SETTING

University hospital.

PARTICIPANTS

56 mother-infant dyads.

MAIN OUTCOME MEASURES

The association of OS markers (nitrotyrosine, dityrosine, chlorotyrosine) in maternal first trimester and term, and cord blood plasma with maternal first trimester exposure levels of each of 41 toxicants (trace elements, metals, phenols, and phthalates) from 56 subjects was analyzed using Spearman correlations and linear regression. The association of OS markers with inflammatory cytokines and birth outcomes were analyzed by Spearman correlation and linear regression analysis, respectively. Weighted mixtures of early pregnancy exposures were created by principal component analysis and offspring sex-dependent and independent associations with oxidative stress markers were assessed.

RESULTS

(1) An inverse relationship between levels of maternal/cord OS markers and individual EDCs was evident. In contrast, when assessed as EDC mixtures, both direct and inverse associations were evident in a sex-specific manner; (2) the maternal term OS marker, nitrotyrosine, was inversely associated with gestational age, and (3) both direct and inverse associations were evident between the 3 OS markers and individual cytokines.

CONCLUSIONS

Provides proof of concept that effects of exposures on OS varies when assessed as EDC mixtures versus individually.