Michelle Bellingham

Exposure to a complex cocktail of environmental endocrine-disrupting compounds disturbs the kisspeptin/GPR54 system in ovine hypothalamus and pituitary gland.

Background Ubiquitous environmental chemicals, including endocrine-disrupting chemicals (EDCs), are associated with declining human reproductive health, as well as an increasing incidence of cancers of the reproductive system. Verifying such links requires animal models exposed to “real-life,” environmentally relevant concentrations/mixtures of EDC, particularly in utero, when sensitivity to EDC exposure is maximal. Objectives We evaluated the effects of maternal exposure to a pollutant cocktail (sewage sludge) on the ovine fetal reproductive neuroendocrine axes, particularly the kisspeptin (KiSS-1)/GPR54 (G-protein–coupled receptor 54) system. Methods KiSS-1, GPR54, and ERα (estrogen receptor α) mRNA expression was quantified in control (C) and treated (T) maternal and fetal (110-day) hypothalami and pituitary glands using semiquantitative reverse transcription polymerase chain reaction, and colocalization of kisspeptin with LHβ (luteinizing hormone β) and ERα in C and T fetal pituitary glands quantified using dual-labeling immunohistochemistry. Results Fetuses exposed in utero to the EDC mixture showed reduced KiSS-1 mRNA expression across three hypothalamic regions examined (rostral, mid, and caudal) and had fewer kisspetin immunopositive cells colocalized with both LHβ and ERα in the pituitary gland. In contrast, treatment had no effect on parameters measured in the adult ewe hypothalamus or pituitary. Conclusions This study demonstrates that the developing fetus is sensitive to real-world mixtures of environmental chemicals, which cause significant neuroendocrine alterations. The important role of kisspeptin/GPR54 in regulating puberty and adult reproduction means that in utero disruption of this system is likely to have long-term consequences in adulthood and represents a novel, additional pathway through which environmental chemicals perturb human reproduction.

Foetal Hypothalamic and Pituitary Expression of Gonadotrophin-Releasing Hormone and Galanin Systems is Disturbed by Exposure to Sewage Sludge Chemicals via Maternal Ingestion

Animals and humans are chronically exposed to endocrine disrupting chemicals (EDCs) that are ubiquitous in the environment. There are strong circumstantial links between environmental EDC exposure and both declining human/wildlife reproductive health and the increasing incidence of reproductive system abnormalities. The verification of such links, however, is difficult and requires animal models exposed to ‘real life’, environmentally relevant concentrations/mixtures of environmental contaminants (ECs), particularly in utero, when sensitivity to EC exposure is high. The present study aimed to determine whether the foetal sheep reproductive neuroendocrine axis, particularly gondotrophin‐releasing hormone (GnRH) and galaninergic systems, were affected by maternal exposure to a complex mixture of chemicals, applied to pasture, in the form of sewage sludge. Sewage sludge contains high concentrations of a spectrum of EDCs and other pollutants, relative to environmental concentrations, but is frequently recycled to land as a fertiliser. We found that foetuses exposed to the EDC mixture in utero through their mothers had lower GnRH mRNA expression in the hypothalamus and lower GnRH receptor (GnRHR) and galanin receptor (GALR) mRNA expression in the hypothalamus and pituitary gland. Strikingly, this, treatment had no significant effect on maternal GnRH or GnRHR mRNA expression, although GALR mRNA expression within the maternal hypothalamus and pituitary gland was reduced. The present study clearly demonstrates that the developing foetal neuroendocrine axis is sensitive to real‐world mixtures of environmental chemicals. Given the important role of GnRH and GnRHR in the regulation of reproductive function, its known role programming role in utero, and the role of galanin in the regulation of many physiological/neuroendocrine systems, in utero changes in the activity of these systems are likely to have long‐term consequences in adulthood and represent a novel pathway through which EC mixtures could perturb normal reproductive function.

Foetal and post-natal exposure of sheep to sewage sludge chemicals disrupts sperm production in adulthood in a subset of animals

Exposure to ubiquitous, environmental chemicals (ECs) has been hypothesized as a cause for declining male reproductive health. Understanding the long-term effects of EC exposure on reproductive health in humans requires animal models and exposure to ‘real life’, environmentally relevant, mixtures during development, a life stage of particular sensitivity to ECs. The aim of this study was to evaluate the effects of in utero and post-natal exposure to environmentally relevant levels of ECs, via sewage sludge application to pasture, on the adult male sheep testis. Hormones, liver concentrations of candidate ECs and Sertoli and germ cell numbers in testes of adult rams that were exposed to ECs in sewage sludge in utero, and until weaning via maternal exposure, and post-weaning via grazing pastures fertilized with sewage sludge, were quantified. Evaluated as a single group, exposure to sludge ECs was without significant effect on most parameters. However, a more detailed study revealed that 5 of 12 sludge-exposed rams exhibited major spermatogenic abnormalities. These consisted of major reductions in germ cell numbers per testis or per Sertoli cell and more Sertoli cell-only tubules, when compared with controls, which did not show any such changes. The sludge-related spermatogenic changes in the five affected animals were significantly different from controls (p < 0.001); Sertoli cell number was unaffected. Hormone profiles and liver candidate EC concentrations were not measurably affected by exposure. We conclude that developmental exposure of male sheep to real-world mixtures of ECs can result in major reduction in germ cell numbers, indicative of impaired sperm production, in a proportion of exposed males. The individual-specific effects are presumed to reflect EC effects on a heterogeneous population in which some individuals may be more susceptible to adverse EC effects. Such effects of EC exposure in humans could have adverse consequences for sperm counts and fertility in some exposed males.

Maternal and fetal tissue accumulation of selected endocrine disrupting compounds (EDCs) following exposure to sewage sludge-treated pastures before or after conception

This paper reports patterns of accumulation of selected EDCs in adult and fetal livers of sheep exposed to sewage sludge-treated pastures, at different times and at two stages of development.

Effects of environmental pollutants on the reproduction and welfare of ruminants

Anthropogenic pollutants comprise a wide range of synthetic organic compounds and heavy metals, which are dispersed throughout the environment, usually at low concentrations. Exposure of ruminants, as for all other animals, is unavoidable and while the levels of exposure to most chemicals are usually too low to induce any physiological effects, combinations of pollutants can act additively or synergistically to perturb multiple physiological systems at all ages but particularly in the developing foetus. In sheep, organs affected by pollutant exposure include the ovary, testis, hypothalamus and pituitary gland and bone. Reported effects of exposure include changes in organ weight and gross structure, histology and gene and protein expression but these changes are not reflected in changes in reproductive performance under the conditions tested. These results illustrate the complexity of the effects of endocrine disrupting compounds on the reproductive axis, which make it difficult to extrapolate between, or even within, species. Effects of pollutant exposure on the thyroid gland, immune, cardiovascular and obesogenic systems have not been shown explicitly, in ruminants, but work on other species suggests that these systems can also be perturbed. It is concluded that exposure to a mixture of anthropogenic pollutants has significant effects on a wide variety of physiological systems, including the reproductive system. Although this physiological insult has not yet been shown to lead to a reduction in ruminant gross performance, there are already reports indicating that anthropogenic pollutant exposure can compromise several physiological systems and may pose a significant threat to both reproductive performance and welfare in the longer term. At present, many potential mechanisms of action for individual chemicals have been identified but knowledge of factors affecting the rate of tissue exposure and of the effects of combinations of chemicals on physiological systems is poor. Nevertheless, both are vital for the identification of risks to animal productivity and welfare.

Exposure to chemical cocktails before or after conception – The effect of timing on ovarian development

Highlights • In-utero exposure to environmental chemicals disturbs ovary development.• We investigated differential effects of exposure before or after conception.• The fetal ovary is most affected by exposure after conception.• Unexpectedly, response to continuous exposure was less severe than previously.• Alterations in profiles of in utero exposure to chemicals may be most damaging.

Placental transporter localization and expression in the Human: the importance of species, sex, and gestational age differences

Abstract The placenta is a critical organ during pregnancy, essential for the provision of an optimal intrauterine environment, with fetal survival, growth, and development relying on correct placental function. It must allow nutritional compounds and relevant hormones to pass into the fetal bloodstream and metabolic waste products to be cleared. It also acts as a semipermeable barrier to potentially harmful chemicals, both endogenous and exogenous. Transporter proteins allow for bidirectional transport and are found in the syncytiotrophoblast of the placenta and endothelium of fetal capillaries. The major transporter families in the human placenta are ATP-binding cassette (ABC) and solute carrier (SLC), and insufficiency of these transporters may lead to deleterious effects on the fetus. Transporter expression levels are gestation-dependent and this is of considerable clinical interest as levels of drug resistance may be altered from one trimester to the next. This highlights the importance of these transporters in mediating correct and timely transplacental passage of essential compounds but also for efflux of potentially toxic drugs and xenobiotics. We review the current literature on placental molecular transporters with respect to their localization and ontogeny, the influence of fetal sex, and the relevance of animal models. We conclude that a paucity of information exists, and further studies are required to unlock the enigma of this dynamic organ. Summary Sentence This review summarises the existing knowledge of human placental molecular transporters (SLC and ABC superfamilies). We highlight areas where greater andmore accurate knowledge is required and discuss weaknesses of animal models for the human.

The human placental proteome is affected by maternal smoking

Highlights • The effects of maternal smoking on the term placental proteome was studied.• Maternal smoking significantly affected 18% of protein spots.• Maternal smoking affects systems controlling the development and function of placenta.• The observed placental changes may contribute to the lowered birth weights.

Peri-conceptional changes in maternal exposure to sewage sludge chemicals disturbs fetal thyroid gland development in sheep

Highlights ► We used an ovine prenatal exposure model to a mixture of environmental chemicals. ► Male fetal thyroids of mixed exposure groups have reduced follicle counts. ► Fetal thyroids of animals in mixed exposure groups show increased proliferation. ► Thyroid glands of exposed fetuses showed regions with impaired differentiation. ► Fetal plasma levels of free thyroid hormones were normal.

Effects of Exposure to Environmental Chemicals During Pregnancy on the Development of the Male and Female Reproductive Axes

There is a large body of literature describing effects of environmental chemicals (ECs), many of them anthropogenic with endocrine-disrupting properties, on development in rodent laboratory species, some of which lead to impaired reproduction and adverse health. This literature joins extensive human epidemiological data and opportunistic wildlife findings on health effects of ECs. In contrast, the effect of endocrine disruption on foetal development and reproductive performance in domestic species is less extensively documented. This applies both to domestic farm and to companion species even though the former is critical to food production and the latter share our homes and many aspects of the modern developed human lifestyle. In domestic species, the nature of chemicals exposure in utero and their consequences for animal health and production are poorly understood. A complication in our understanding is that the pace of development, ontogeny and efficiency of foetal and maternal hepatic and placental activity differs between domestic species. In many ways, this reflects the difficulties in understanding human exposure and consequences of that exposure for the foetus and subsequent adult from epidemiological and largely rodent-based data. It is important that domestic species are included in research into endocrine disruption because of their (i) wide variety of exposure to such chemicals, (ii) greater similarity of many developmental processes to the human, (iii) economic importance and (iv) close similarities to developed world human lifestyle in companion species.