Developmental exposure of mice to dioxin promotes transgenerational testicular inflammation and an increased risk of preterm birth in unexposed mating partners

Environmental factors affecting female fertility

INTRODUCTION

Over the recent years, scientific community has increased its interest on solving problems of female fertility pathology. Many factors acting separately or in combination affect significantly the reproductive life of a woman. This review summarizes current evidence regarding the direct and/or indirect action of environmental factors and endocrine disrupting chemicals (EDCs; i.e. heavy metals, plasticizers, parabens, industrial chemicals, pesticides, or medications, by-products, anti-bacterial agents, perfluorochemicals) upon assisted and non-assisted female fertility, extracted from in vivo and in vitro animal and human published data. Transgenerational effects which could have been caused epigenetically by the action of EDCs have been raised.

METHODS

This narrative review englobes and describes data from in vitro and in vivo animal and human studies with regard to the action of environmental factors, which include EDCs, on female fertility following the questions for narrative reviews of the SANRA (a scale for the quality assessment of narrative review articles). The identification of the studies was done: through the PubMed Central and the PubMed of the MEDLINE, the Google Scholar database and the Cochrane Library database until December 2023 combining appropriate keywords ("specific environmental factors" including "EDCs" AND "specific negative fertility outcomes"); by manual scanning of references from selected articles and reviews focusing on these subjects. It includes references to EDCs-induced transgenerational effects.

RESULTS

From the reported evidence emerge negative or positive associations between specific environmental factors or EDCs and infertility outcomes such as infertility indices, disrupted maturation of the oocytes, anovulation, deranged transportation of the embryo and failure of implantation.

CONCLUSION

The revealed adverse outcomes related to female fertility could be attributed to exposure to specific environmental factors such as temperature, climate, radiation, air pollutants, nutrition, toxic substances and EDCs. The recognition of fertility hazards related to the environment will permit the limitation of exposure to them, will improve female fertility and protect the health potential of future generations.

Dichloroacetic acid and trichloroacetic acid as disinfection by-products in drinking water are endocrine-disrupting chemicals

Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) are two typical non-volatile disinfection by-products (DBPs) found in drinking water. Increasing evidence has demonstrated that they show reproductive toxicity. However, whether they might have endocrine disrupting properties remains largely unknown. To discover this, we treated male mice or pregnant mice with 0, 1-, 102-, 103-, 104-, or 5 × 104-fold maximal concentration level (MCL) of DCAA or TCAA in drinking water. In male mice, the levels of testosterone in serum and androgen receptor (AR) in testis were declined with ≥ 103-fold MCL of DCAA (26.4 mg/kg/d) or TCAA (52.7 mg/kg/d). In pregnant mice, miscarriage rates were increased with ≥ 104-fold MCL of DCAA (264 mg/kg/d) or ≥ 103-fold MCL of TCAA. The levels of FSH in serum were increased and those of estradiol and progesterone were reduced with ≥ 103-fold MCL of DCAA or TCAA. The protein levels of estrogen receptors (ERα and ERβ) in ovary were reduced with ≥ 102-fold MCL of DCAA (2.64 mg/kg/d) or TCAA (5.27 mg/kg/d). Exposure to some certain fold MCL of DCAA or TCAA also altered the protein levels of ERα and ERβ in uterus and placenta. Exposure to 5 × 104-fold MCL of both DCAA and TCAA showed the combined effects. Therefore, both DCAA and TCAA could be considered as novel reproductive endocrine disrupting chemicals, which might be helpful for further assessment of the toxicological effects of DCAA and TCAA and the awareness of reproductive endocrine disrupting properties caused by DCAA and TCAA in drinking water.

Environmental Toxicant Exposure Paralyzes Human Placental Macrophage Responses to Microbial Threat

Exposure to environmental toxicants (such as dioxins) has been epidemiologically linked to adverse reproductive health outcomes, including placental inflammation and preterm birth. However, the molecular underpinnings that govern these outcomes in gravid reproductive tissues remain largely unclear. Placental macrophages (also known as Hofbauer cells) are crucial innate immune cells that defend the gravid reproductive tract and help promote maternal-fetal tolerance. We hypothesized that exposure to environmental toxicants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) could alter placental macrophage responses to inflammatory insults such as infection. To test this, placental macrophages were cultured in the presence or absence of TCDD and then infected with the perinatal pathogen Group B Streptococcus (GBS). Our results indicate that TCDD is lethal to placental macrophages at and above a 5 nM concentration and that sublethal dioxin exposure inhibits phagocytosis and cytokine production. Taken together, these results indicate that TCDD paralyzes placental macrophage responses to bacterial infection.

2,3,7,8-tetrachlorodibenzo-p-dioxin induces multigenerational testicular toxicity and biosynthetic disorder of testosterone in BALB/C mice: Transcriptional, histopathological and hormonal determinants

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent environmental contaminant, is an endocrine disrupter with a proven reproductive toxicity in mammals. However, its effects on male fertility across generations are still elusive. The current work evaluates the toxicity of dioxin on male reproductive system in two separate groups of BALB/C mice; a group of pubertal males directly exposed to TCDD (referred to as DEmG), and a group of indirectly exposed males (referred to as IDEmG) comprises of F1, F2 and F3 males born from TCDD-exposed pregnant females. Both groups were exposed to 25 μg TCDD/kg body weight for a week. Our data show that males of TCDD-DEmG exhibited significant alterations in the expression of certain genes involved in the detoxification of TCDD and the biosynthesis of testosterone. This was accompanied with testicular pathological symptoms, including a sloughing in the germinal epithelium and a congestion of blood vessels in interstitial tissue with the presence of multinuclear cells into seminiferous tubule, with a 4-fold decline in the level of serum testosterone and reduced sperm count. Otherwise, the male reproductive toxicity across F1, F2 and F3 generations from TCDD-IDEmG was mainly characterized by: i) a reduce in body and testis weight. ii) a decrease in gene expression of steriodogenesis enzyme, e.g., AhR, CYP1A1, CYP11A1, COX1, COX2, LOX5 and LOX12. iii) a remarked and similar testicular histopathology that found for DEmG, iv) a serious decline in serum testosterone. v) a decreased male-to-female ratio. vi) a low sperm count with increasing abnormalities. Thus, pubertal or maternal exposure to TCDD provokes multigenerational male reproductive toxicity in mice, ultimately affecting the spermatogenesis and suggesting that the hormonal alternation and sperm abnormality are the most marked effects of the indirect exposure of mammalian male to TCDD.

17α-estradiol does not adversely affect sperm parameters or fertility in male mice: implications for reproduction-longevity trade-offs

17α-estradiol (17α-E2) is referred to as a nonfeminizing estrogen that was recently found to extend healthspan and lifespan in male, but not female, mice. Despite an abundance of data indicating that 17α-E2 attenuates several hallmarks of aging in male rodents, very little is known with regard to its effects on feminization and fertility. In these studies, we evaluated the effects of 17α-E2 on several markers of male reproductive health in two independent cohorts of mice. In alignment with our previous reports, chronic 17α-E2 treatment prevented gains in body mass, but did not adversely affect testes mass or seminiferous tubule morphology. We subsequently determined that chronic 17α-E2 treatment also did not alter plasma 17β-estradiol or estrone concentrations, while mildly increasing plasma testosterone levels. We also determined that chronic 17α-E2 treatment did not alter plasma follicle-stimulating hormone or luteinizing hormone concentrations, which suggests 17α-E2 treatment does not alter gonadotropin-releasing hormone neuronal function. Sperm quantity, morphology, membrane integrity, and various motility measures were also unaffected by chronic 17α-E2 treatment in our studies. Lastly, two different approaches were used to evaluate male fertility in these studies. We found that chronic 17α-E2 treatment did not diminish the ability of male mice to impregnate female mice, or to generate successfully implanted embryos in the uterus. We conclude that chronic treatment with 17α-E2 at the dose most commonly employed in aging research does not adversely affect reproductive fitness in male mice, which suggests 17α-E2 does not extend lifespan or curtail disease parameters through tradeoff effects with reproduction.

Endocrine-Disrupting Chemicals and Disease Endpoints

Endocrine-disrupting chemicals (EDCs) have significant impacts on biological systems, and have been shown to interfere with physiological systems, especially by disrupting the hormone balance. During the last few decades, EDCs have been shown to affect reproductive, neurological, and metabolic development and function and even stimulate tumor growth. EDC exposure during development can disrupt normal development patterns and alter susceptibility to disease. Many chemicals have endocrine-disrupting properties, including bisphenol A, organochlorines, polybrominated flame retardants, alkylphenols, and phthalates. These compounds have gradually been elucidated as risk factors for many diseases, such as reproductive, neural, and metabolic diseases and cancers. Endocrine disruption has been spread to wildlife and species that are connected to the food chains. Dietary uptake represents an important source of EDC exposure. Although EDCs represent a significant public health concern, the relationship and specific mechanism between EDCs and diseases remain unclear. This review focuses on the disease-EDC relationship and the disease endpoints associated with endocrine disruption for a better understanding of the relationship between EDCs-disease and elucidates the development of new prevention/treatment opportunities and screening methods.

Environmental factors affecting pregnancy outcomes

INTRODUCTION

Pregnancy represents a fragile period in the life of a woman, vulnerable to hazardous environmental substances which might affect maternal and fetal metabolism. The possible influence of environmental factors, including endocrine disrupting chemicals (EDCs), upon the mother and the fetus before and/or during pregnancy might be associated directly and/or indirectly to deleterious pregnancy outcomes. Because the existence of such associations would be, to our view, of major importance to the scientific community, their investigation is the scope of this critical review.

METHODS

This critical review includes in vivo animal and human studies regarding the role of environmental factors, including EDCs, on pregnancy outcomes complying with the SANRA (a scale for the quality assessment of narrative review articles) questions for narrative reviews. Studies were identified by searching the MEDLINE (PubMed and PubMed Central), the Cochrane library and the Google Scholar databases till October 2022 with the combinations of the appropriate key words (detailed environmental factors including EDCs AND detailed negative pregnancy outcomes) as well as by scanning references from already included articles and relevant reviews manually. Because environmental factors and EDCs have been associated to epigenetic alterations, special care has been given to EDC-induced transgenerational effects on pregnancy outcomes.

RESULTS

The existing evidence suggests positive associations between specific environmental factors and negative pregnancy outcomes such as ectopic pregnancies, pregnancy losses, gestational diabetes, hypertensive disorders of pregnancy, preterm births, birth defects, intrauterine growth restriction, and small or large for gestational age babies.

CONCLUSION

Environmental factors and EDCs may have a catalytic effect on the course and the outcomes of pregnancy.

Paternal Nicotine/Ethanol/Caffeine Mixed Exposure Induces Offspring Rat Dysplasia and Its Potential "GC-IGF1" Programming Mechanism

Clinical and animal studies suggest that paternal exposure to adverse environments (bad living habits and chronic stress, etc.) has profound impacts on offspring development; however, the mechanism of paternal disease has not been clarified. In this study, a meta-analysis was first performed to suggest that paternal exposure to nicotine, ethanol, or caffeine is a high-risk factor for adverse pregnancy outcomes. Next, we created a rat model of paternal nicotine/ethanol/caffeine mixed exposure (PME), whereby male Wistar rats were exposed to nicotine (0.1 mg/kg/d), ethanol (0.5 g/kg/d), and caffeine (7.5 mg/kg/d) for 8 weeks continuously, then mated with normal female rats to obtain a fetus (n = 12 for control group, n = 10 for PME group). Then, we analyzed the changes in paternal hypothalamic-pituitary-adrenal (HPA) axis activity, testicular function, pregnancy outcomes, fetal serum metabolic indicators, and multiple organ functions to explore the mechanism from the perspective of chronic stress. Our results demonstrated that PME led to enhanced paternal HPA axis activity, decreased sperm quality, and adverse pregnancy outcomes (stillbirth and absorption, decreased fetal weight and body length, and intrauterine growth retardation), abnormal fetal serum metabolic indicators (corticosterone, glucolipid metabolism, and sex hormones), and fetal multi-organ dysfunction (including hippocampus, adrenal, liver, ossification, and gonads). Furthermore, correlation analysis showed that the increased paternal corticosterone level was closely related to decreased sperm quality, adverse pregnancy outcomes, and abnormal offspring multi-organ function development. Among them, the decreased activity of the glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axis may be the main mechanism of offspring development and multi-organ dysfunction caused by PME. This study explored the impact of common paternal lifestyle in daily life on offspring development, and proposed the GC-IGF1 programming mechanisms of paternal chronic stress-induced offspring dysplasia, which provides a novel insight for exploring the important role of paternal chronic stress in offspring development and guiding a healthy lifestyle for men.

Effects of dioxins on animal spermatogenesis: A state-of-the-art review

The male reproductive system is especially affected by dioxins, a group of persistent environmental pollutants, resulting in irreversible abnormalities including effects on sexual function and fertility in adult males and possibly on the development of male offspring. The reproductive toxicity caused by dioxins is mostly mediated by an aryl hydrocarbon receptor (AhR). In animals, spermatogenesis is a highly sensitive and dynamic process that includes proliferation and maturation of germ cells. Spermatogenesis is subject to multiple endogenous and exogenous regulatory factors, including a wide range of environmental toxicants such as dioxins. This review discusses the toxicological effects of dioxins on spermatogenesis and their relevance to male infertility. After a detailed categorization of the environmental contaminants affecting the spermatogenesis, the exposure pathways and bioavailability of dioxins in animals was briefly reviewed. The effects of dioxins on spermatogenesis are then outlined in detail. The endocrine-disrupting effects of dioxins in animals and humans are discussed with a particular focus on their effects on the expression of spermatogenesis-related genes. Finally, the impacts of dioxins on the ratio of X and Y chromosomes, the status of serum sex hormones, the quality and fertility of sperm, and the transgenerational effects of dioxins on male reproduction are reviewed.

Multi- and Transgenerational Effects of Environmental Toxicants on Mammalian Reproduction

Environmental toxicants (ETs) are an exogenous chemical group diffused in the environment that contaminate food, water, air and soil, and through the food chain, they bioaccumulate into the organisms. In mammals, the exposure to ETs can affect both male and female fertility and their reproductive health through complex alterations that impact both gametogeneses, among other processes. In humans, direct exposure to ETs concurs to the declining of fertility, and its transmission across generations has been recently proposed. However, multi- and transgenerational inheritances of ET reprotoxicity have only been demonstrated in animals. Here, we review recent studies performed on laboratory model animals investigating the effects of ETs, such as BPA, phthalates, pesticides and persistent contaminants, on the reproductive system transmitted through generations. This includes multigenerational effects, where exposure to the compounds cannot be excluded, and transgenerational effects in unexposed animals. Additionally, we report on epigenetic mechanisms, such as DNA methylation, histone tails and noncoding RNAs, which may play a mechanistic role in a nongenetic transmission of environmental information exposure through the germline across generations.

Parental exposure to 3-methylcholanthrene before gestation adversely affected the endocrine system and spermatogenesis in male F1 offspring

The compound 3-methylcholanthrene (3-MC) is an environmental pollutant belonging to the PAHs, which reportedly have the potential to disrupt the endocrine systems of animals. In the present study, 4-week-old male and female mice were given 3-MC through their diet at a dose of 0.5mg/kg of chow for 6 weeks before pregnancy. The first filial (F₁) generation offspring of exposed or unexposed parental mice were sacrificed at the age of 5 or 10 weeks (F₁-5W or F₁-10W), and the potential effects on the F₀ and F₁ offspring were evaluated. The results showed that the serum and testicular testosterone (T) levels and the genes involved in T synthesis in F₀ males and male F₁-5W individuals born from female mice exposed to 3-MC were significantly decreased. In addition, histological analysis suggested that exposure to 3-MC significantly disrupted testicular morphology in F₀ mice and in the offspring of female mice exposed to 3-MC. Further investigation revealed that genes involved in spermatogenesis, such as Phosphoglycerate kinase 2 (Pgk2), Glial cell derived neurotrophic factor (Gdnf), Myeloblastosis oncogene (Myb), DEAD box helicase 4 (Ddx4) and KIT proto-oncogene receptor tyrosine kinase (Kit), were suppressed in these mice. However, the adverse effects of parental 3-MC exposure on the adolescent mice were mitigated when they grew to adulthood, which was verified by studies on F₁-10W mice. Our results suggest that female exposure to 3-MC has the potential to disrupt the endocrine system and spermatogenesis in male offspring; nevertheless, the adverse effects might be mitigated with age.

Differential Expression Profiles and Potential Intergenerational Functions of tRNA-Derived Small RNAs in Mice After Cadmium Exposure

Cadmium (Cd) is a toxic heavy metal and ubiquitous environmental endocrine disruptor. Previous studies on Cd-induced damage to male fertility mainly focus on the structure and function of testis, including cytoskeleton, blood-testis barrier, and steroidogenesis. Nevertheless, to date, no studies have investigated the effects of Cd exposure on sperm epigenetic inheritance and intergenerational inheritance. In our study, we systematically revealed the changes in sperm tRNA-derived small RNAs (tsRNA) profiles and found that 14 tsRNAs (9 up-regulated and 5 down-regulated) were significantly altered after Cd exposure. Bioinformatics of tsRNA-mRNA-pathway interactions revealed that the altered biological functions mainly were related to ion transmembrane transport, lipid metabolism and cell membrane system. In addition, we focused on two stages of early embryo development and selected two organs to study the impact of these changes on cell membrane system, especially mitochondrion and lysosome, two typical membrane-enclosed organelles. Surprisingly, we found that the content of mitochondrion was significantly decreased in 2-cell stage, whereas remarkably increased in the morula stage. The contents of mitochondrion and lysosome were increased in the testes of 6-day-old offspring and livers of adult offspring, whereas remarkably decreased in the testes of adult offspring. This provides a possible basis to further explore the effects of paternal Cd exposure on offspring health.

TCDD-induced IL-24 secretion in human chorionic stromal cells inhibits placental trophoblast cell migration and invasion

Environmental pollutant dioxins are potentially harmful to pregnant women and can lead to severe adverse outcomes in pregnancy, such as spontaneous abortion and stillbirth. However, little is currently known about the underlying toxicological mechanism. Our previous study reported that the IL-24 gene is a dioxin response gene during 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) treatment. Here, we further tested the effect of TCDD on IL-24 expression in human chorionic stromal cells. We also investigated the effect of IL-24 on the behaviors of human placental trophoblast cells and predicted the potential mechanism underlying these behaviors using functional network analysis. We found that TCDD stimulates IL-24 expression in human chorionic stromal cells in an AhR (aromatic hydrocarbon receptor)-related manner. We also found that IL-24 inhibits the migration and invasion of human placental trophoblast cells, the possible mechanism of which involves thirteen key proteins and mitochondrial function. Our findings suggest that IL-24 is a potential factor induced by TCDD to regulate trophoblast cell invasion, which potentially involves in TCDD-induced abortion.

OUP accepted manuscript

Exposure to environmental toxicants during preconception has been shown to affect offspring health and epigenetic mechanisms such as DNA methylation are hypothesized to be involved in adverse outcomes. However, studies addressing the effects of exposure to environmental toxicants during preconception on epigenetic changes in gametes are limited. The objective of this study is to determine the effect of preconceptional exposure to a dioxin-like polychlorinated biphenyl (3,3',4,4',5-pentachlorobiphenyl [PCB126]) on DNA methylation and gene expression in testis. Adult zebrafish were exposed to 3 and 10 nM PCB126 for 24 h and testis tissue was sampled at 7 days postexposure for histology, DNA methylation, and gene expression profiling. Reduced representation bisulfite sequencing revealed 37 and 92 differentially methylated regions (DMRs) in response to 3 and 10 nM PCB126 exposures, respectively. Among them, 19 DMRs were found to be common between both PCB126 treatment groups. Gene ontology (GO) analysis of DMRs revealed that enrichment of terms such as RNA processing, iron-sulfur cluster assembly, and gluconeogenesis. Gene expression profiling showed differential expression of 40 and 1621 genes in response to 3 and 10 nM PCB126 exposures, respectively. GO analysis of differentially expressed genes revealed enrichment of terms related to xenobiotic metabolism, oxidative stress, and immune function. There is no overlap in the GO terms or individual genes between DNA methylation and RNA sequencing results, but functionally many of the altered pathways have been shown to cause spermatogenic defects.

Associations of paternal and maternal per- and polyfluoroalkyl substances exposure with cord serum reproductive hormones, placental steroidogenic enzyme and birth weight

BACKGROUND

Maternal per- and polyfluoroalkyl substances (PFAS) exposure has been associated with placental function and fetal growth measures. However, few studies have simultaneously investigated paternal and maternal exposure effects.

OBJECTIVES

We evaluated the associations of paternal or maternal PFAS levels with placental function and fetal growth measures.

METHODS

We studied six PFAS measured in matched parental serums collected within 3 days before delivery in a birth cohort from LaiZhouWan, China. Outcomes evaluated include cord serum estradiol (n = 351), testosterone (n = 349), placental P450aromatase (n = 125), and birth weight (n = 369). Multiple linear regression was applied to estimate the associations for these outcomes according to paternal or maternal PFAS level after adjusting for socio-demographic confounders. Co-adjustment analysis of both paternal and maternal PFAS in the same model was performed.

RESULTS

Maternal and paternal PFAS levels were correlated (Spearman's r = 0.23-0.45). Maternal PFAS were associated with increased estradiol (e.g.

, PFOA

β = 0.03, 95%CI: 0.00, 0.07), testosterone (e.g.

, PFUA

β = 0.14, 95%CI: 0.00, 0.27), and P450aromatase (e.g.

, PFOA

β = 0.13, 95%CI: 0.04, 0.22). Maternal PFAS were also associated with a lower mean of birth weight but the estimated 95% CI included the null. Paternal PFAS were not associated with any of the outcomes evaluated.

CONCLUSIONS

Several maternal PFAS were associated with fetal steroid hormones and placental enzymes. Despite a correlation of PFAS level within the couples, no association was found for paternal PFAS exposure on these outcomes. The findings suggest the intrauterine PFAS exposure effect on fetal endocrine hormones and growth is unlikely to be confounded by exposure sources or familial factors shared within the couples.

Experimental Evidence of 2,3,7,8-Tetrachlordibenzo-p-Dioxin (TCDD) Transgenerational Effects on Reproductive Health

Previous studies have demonstrated that endocrine disruptors (EDs) can promote the transgenerational inheritance of disease susceptibility. Among the many existing EDs, 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) affects reproductive health, including in humans, following direct occupational exposure or environmental disasters, for instance the Agent Orange sprayed during the Vietnam War. Conversely, few studies have focused on TCDD multigenerational and transgenerational effects on human reproductive health, despite the high amount of evidence in animal models of such effects on male and female reproductive health that mimic human reproductive system disorders. Importantly, these studies show that paternal ancestral TCDD exposure substantially contributes to pregnancy outcome and fetal health, although pregnancy outcome is considered tightly related to the woman’s health. In this work, we conducted a systematic review of the literature and a knowledge synthesis in order (i) to describe the findings obtained in rodent models concerning TCDD transgenerational effects on reproductive health and (ii) to discuss the epigenetic molecular alterations that might be involved in this process. As ancestral toxicant exposure cannot be changed in humans, identifying the crucial reproductive functions that are negatively affected by such exposure may help clinicians to preserve male and female fertility and to avoid adverse pregnancy outcomes.

Ability of Ureaplasma parvum to invade mouse sperm, fertilize eggs through infected sperm, and impair mouse sperm function and embryo development

OBJECTIVE

To examine the effect of Ureaplasma parvum (U. parvum) infection on mouse sperm motility, structure, and fertilizing ability and on embryo development.

DESIGN

In vitro model of the effects of U. parvum serovar 3 infection on mouse sperm.

SETTING

Basic research laboratory.

INTERVENTION(S)

None.

ANIMALS

Mice.

MAIN OUTCOME MEASURE(S)

Mouse sperm motility was examined using the swim-up method, and their motility parameters were analyzed using the sperm motility analysis system. Localization and invasion of U. parvum were observed with fluorescence, confocal, and scanning electron microscopy. After in vitro fertilization with U. parvum-infected sperm, the quality of the fertilized egg and embryo development were assessed.

RESULT(S)

U. parvum was attached and internalized into mouse sperms and localized mainly at the sperm head and midpiece. U. parvum-infected mouse sperms exhibited decreased motility in a dose- and duration-dependent manner. Electron micrographs revealed that U. parvum infection induced the aggregation and morphological destruction of mouse sperm. Infected mouse sperm transported U. parvum into the fertilized egg with reduced fertilization rates, and infected embryo development was impaired.

CONCLUSION(S)

U. parvum infection caused deterioration of the mouse sperm quality and its functions, which affected the fertilization rate and embryo development.

Development of a Range of Plausible Noncancer Toxicity Values for 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Based on Effects on Sperm Count: Application of Systematic Review Methods and Quantitative Integration of Dose Response Using Meta-Regression

Regulatory agencies have derived noncancer toxicity values for 2,3,7,8-tetrachlorodibenzo-p-dioxin based on reduced sperm counts relying on single studies from a large body of evidence. Techniques such as meta-regression allow for greater use of the available data while simultaneously providing important information regarding the uncertainty associated with the underlying evidence base when conducting risk assessments. The objective herein was to apply systematic review methods and meta-regression to characterize the dose-response relationship of gestational exposure and epididymal sperm count. Twenty-three publications (20 animal studies consisting of 29 separate rat experimental data sets, and 3 epidemiology studies) met inclusion criteria. Risk of bias evaluation was performed to critically appraise study validity. Low to very low confidence precluded use of available epidemiological data as candidate studies for dose-response due to inconsistencies across the evidence base, high risk of bias, and general lack of biological coherence, including lack of clinical relevance and dose-response concordance. Experimental animal studies, which were found to have higher confidence following the structured assessment of confidence (eg, controlled exposure, biological consistency), were used as the basis of a meta-regression. Multiple models were fit; points of departure were identified and converted to human equivalent doses. The resulting reference dose estimates ranged from approximately 4 to 70 pg/kg/day, depending on model, benchmark response level, and study validity integration approach. This range of reference doses can be used either qualitatively or quantitatively to enhance understanding of human health risk estimates for dioxin-like compounds.

Evaluation of testicular structure in mice after exposure to environmentally relevant doses of manganese during critical windows of development

Despite being an essential trace element with great importance for vital metabolic activities, the manganese (Mn) can also cause damage to organ systems. However, data on the effect of this metal on the male reproductive system are limited, especially using relevant doses to human exposure. The present study aimed to evaluate and compare the effects of Mn exposure on the testicular structure of mice. Three experiments were conducted: (I) direct exposure to realistic doses (0.013, 0.13, and 1.3 mg/kg/day of MnCl₂); (II) parental and direct exposure to realistic doses (as in experiment I), where the animals were exposed during intrauterine development and from lactation until reproductive maturity; (III) direct exposure to high doses (15, 30, and 60 mg/kg/day of MnCl₂). Biometric, histopathological, histomorphometric and stereological parameters of the testis were evaluated, in addition to sperm morphology. Bioinformatic analyses were performed to identify potential Mn binding sites in 3β-HSD and P450ssc, as well as their protein-protein interaction network. The results obtained were compared using the integrated biomarker response index (IBR). There was an increase of seminiferous tubules pathologies in all experimental conditions tested, with effects on tubular volume, as well as a reduction in tubular diameter. The IBR analyses showed that parental and direct exposure had a significant negative effect on the testicular structure due to the exposure of this metal to sensitive periods of animal development. This study suggests that Mn has the potential to alter the morphological parameters of the testes, affecting the spermatogenesis in mice.

Transgenerational disease specific epigenetic sperm biomarkers after ancestral exposure to dioxin

Dioxin was historically one of the most common industrial contaminants with several major industry accidents, as well as governmental actions involving military service, having exposed large numbers of the worldwide population over the past century. Previous rat studies have demonstrated the ability of dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)) exposure to promote the epigenetic transgenerational inheritance of disease susceptibility in subsequent generations. The types of disease previously observed include puberty abnormalities, testis, ovary, kidney, prostate and obesity pathologies. The current study was designed to use an epigenome-wide association study (EWAS) to identify potential sperm DNA methylation biomarkers for specific transgenerational diseases. Therefore, the transgenerational F3 generation dioxin lineage male rats with and without a specific disease were compared to identify differential DNA methylation regions (DMRs) as biomarkers for disease. The genomic features of the disease-specific DMRs were characterized. Observations demonstrate that disease-specific epimutation DMRs exist for the transgenerational dioxin lineage rats that can potentially be used as epigenetic biomarkers for testis, kidney, prostate and obesity diseases. These disease-specific DMRs were associated with genes that have previously been shown to be linked with the specific diseases. This EWAS for transgenerational disease identified potential epigenetic biomarkers and provides the proof of concept of the potential to develop similar biomarkers for humans to diagnose disease susceptibilities and facilitate preventative medicine.

Knockout of family with sequence similarity 170 member A (Fam170a) causes male subfertility, while Fam170b is dispensable in mice†

Families with sequence similarity 170 members A and B (FAM170A and FAM170B) are testis-specific, paralogous proteins that share 31% amino acid identity and are conserved throughout mammals. While previous in vitro experiments suggested that FAM170B, an acrosome-localized protein, plays a role in the mouse sperm acrosome reaction and fertilization, the role of FAM170A in the testis has not been explored. In this study, we used CRISPR/Cas9 to generate null alleles for each gene, and homozygous null (-/-) male mice were mated to wild-type females for 6 months to assess fertility. Fam170b-/- males were found to produce normal litter sizes and had normal sperm counts, motility, and sperm morphology. In contrast, mating experiments revealed significantly reduced litter sizes and a reduced pregnancy rate from Fam170a-/- males compared with controls. Fam170a-/-;Fam170b-/- double knockout males also produced markedly reduced litter sizes, although not significantly different from Fam170a-/- alone, suggesting that Fam170b does not compensate for the absence of Fam170a. Fam170a-/- males exhibited abnormal spermiation, abnormal head morphology, and reduced progressive sperm motility. Thus, FAM170A has an important role in male fertility, as the loss of the protein leads to subfertility, while FAM170B is expendable. The molecular functions of FAM170A in spermatogenesis are as yet unknown; however, the protein localizes to the nucleus of elongating spermatids and may mediate its effects on spermatid head shaping and spermiation by regulating the expression of other genes. This work provides the first described role of FAM170A in reproduction and has implications for improving human male infertility diagnoses.

Epigenetic Transgenerational Inheritance of Obesity Susceptibility

The prevalence of obesity and associated diseases has reached pandemic levels. Obesity is often associated with overnutrition and a sedentary lifestyle, but clearly other factors also increase the susceptibility of metabolic disease states. Ancestral and direct exposures to environmental toxicants and altered nutrition have been shown to increase susceptibility for obesity and metabolic dysregulation. Environmental insults can reprogram the epigenome of the germline (sperm and eggs), which transmits the susceptibility for disease to future generations through epigenetic transgenerational inheritance. In this review, we discuss current evidence and molecular mechanisms for epigenetic transgenerational inheritance of obesity susceptibility. Understanding ancestral environmental insults and epigenetic transgenerational impacts on future generations will be critical to fully understand the etiology of obesity and to develop preventative therapy options.

Developmental 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure of either parent enhances the risk of necrotizing enterocolitis in neonatal mice

BACKGROUND

Necrotizing enterocolitis (NEC) is a rare, but potentially fatal intestinal inflammatory condition most often arising in premature infants. Infants provided formula are also at greater risk of developing this disease. Although the majority of formula-fed, preterm infants do not develop NEC, up to 30% of infants with the disease do not survive. Thus, identifying additional, currently unrecognized factors, which may predispose a specific infant to NEC development would be a significant clinical advancement. In this regard, we have previously reported that offspring of female or male mice with a history of developmental exposure to the environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exhibit altered sensitivity to inflammatory challenges and are frequently born premature. Herein, we examined the possibility that, compared to unexposed mice (F1_NONE ), developmental TCDD exposure of either parent (maternal, F1M_TCDD , or paternal, F1P_TCDD ) would enhance the risk of NEC in offspring (F2_TCDD mice) in association with supplemental formula feeding.

METHODS

Beginning on postnatal day 7, all neonates were randomized to maternal milk only or maternal milk with up to 20 supplemental formula feedings. All pups remained with the Dams and were additionally allowed to nurse ad libitum.

RESULTS

Formula-fed F2_NONE pups rarely developed NEC while this disease was common in formula-fed F2M_TCDD and F2P_TCDD mice. Unexpectedly, 50% of F2M_TCDD pups that were not provided supplemental formula also developed NEC.

CONCLUSIONS

Our studies provide evidence that a history of parental TCDD exposure enhances the risk of NEC in offspring and suggest exposure to environmental immunotoxicants such as TCDD may also contribute to this inflammatory disease in humans.

The effects of CLP-induced sepsis on proliferation and apoptosis of granulosa and theca cells in rat ovary: A histochemical and ultrastructural study

Sepsis is defined as a systemic inflammatory response to infection. This study is aimed to evaluate the effects of experimental sepsis on the proliferation and apoptosis of granulosa and theca cells in the rat ovary. 28-day-old immature Wistar-Albino female rats were treated with pregnant mare serum gonadotrophin to develop the first generation of preovulatory follicles. Sepsis was induced by cecal ligation and puncture (CLP). Following in vivo 5-Bromo-2-deoxyuridine (BrdU) labeling, animals were sacrificed and ovaries were embedded in paraffin and Epon. Besides electron microscopic evaluation, BrdU, cleaved caspase-3, p27 immunostaining, and TUNEL labeling were performed. In CLP-operated animals, cleaved caspase-3 immunoreactivity was significantly increased in Graafian follicles. TUNEL and BrdU labeling in the ovarian follicles were not statistically different between CLP and sham-operated rats. In septic animals, p27 immunoreactivity was increased significantly in the nuclei of oocytes and decreased in the cytoplasm of granulosa and theca cells in multilaminar primary follicles compared to the sham group. In ultrastructural evaluation, increased apoptosis was observed in theca interna and granulosa cells in both the early and late stages of follicles in the CLP group. In conclusion, experimentally-induced sepsis leads to apoptosis in ovarian follicles at advanced stages of development. Our data suggest that although sepsis may not cause a potential threat to developing follicles at least in the short term, more severe damage may occur during advanced stages of follicle development.

Transgenerational epigenetic and transcriptomic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure in rat

In rats, direct exposure to TCDD causes myriad toxicities. Exposed rats experience hepatotoxicity, wasting syndrome and immune suppression, amongst others. "Inherited exposure", as occurs in the F3 generation of directly exposed F0 animals, has also been shown to cause toxicity: both male and female F3 rats demonstrate an increased incidence of adult onset disease, females also display reproductive abnormalities and increased incidence of ovarian diseases while males show increased incidence of kidney disease and an altered sperm epigenome. Here, we explore the hepatic transcriptomic profile of male and female F3 Sprague-Dawley rats bred through the paternal germ line from F0 dams exposed to a single dose of TCDD (0, 30, 100, 300 or 1000 ng/kg body weight) by oral gavage. We hypothesize that RNA transcripts with altered abundance in livers of unexposed F3 progeny of treated F0 Sprague-Dawley rats may result from epigenetic modifications to the genome. We further survey patterns of differential methylation within male F3 rat testis. Female F3 rats demonstrated more TCDD-mediated hepatic transcriptomic changes than males, with differences primarily in the lowest dose group. In testis from male F3 rats, multiple olfactory receptors displayed patterns of differential methylation. Hypermethylation of Egfr and Mc5r among testes from TCDD lineage rats was observed, but without corresponding changes in hepatic mRNA abundance. Further studies examining these differences in other tissue types are warranted.

Acute and sub-acute bisphenol-B exposures adversely affect sperm count and quality in adolescent male mice

Bisphenol-B (BPB), an analogue of bisphenol-A is used in the plastic industry. It has been found to leach from plastic containers leading to its contamination in canned food products. Moreover, it has also been detected in human samples such as sera and urine. BPB is recognized as a potential endocrine disrupting chemical owing to its estrogenic and anti-androgenic nature. Therefore, it was pertinent to study the effect of BPB exposure during the adolescence age (5-6 weeks old) in male mice. Weekly intraperitoneal injections of 5, 10 and 15% LD₅₀ of BPB were given for 2 weeks to acute exposure groups and for 4 weeks to sub-acute exposure groups. BPB exposure induces change in enzymatic and non-enzymatic oxidative stress markers in sperm samples. DNA damage was also observed in sperm cells on acute and sub-acute exposures. Furthermore, BPB exposure led to a marked decline in sperm count and compromised sperm morphology. Computer assisted sperm analysis (CASA) revealed a significant decrease in sperm quality and progressive motility. Thus, both the acute and sub-acute exposures of adolescent male mice to BPB adversely affect the sperms' quality, functions and morphology.

The effects of magnesium sulfate on cyclophosphamide-induced ovarian damage: Folliculogenesis

Cyclophosphamide (CYP) is one of the alkylating chemotherapeutic agents and its adverse effects on folliculogenesis in the ovary are well-known due to the previous scientific research on this topic. Magnesium has various effects in organisms, including catalytic functions on the activation and inhibition of many enzymes, and regulatory functions on cell proliferation, cell cycle, and differentiation. In this study, the effects of magnesium sulfate (MgSO₄) on CYP induced ovarian damage were investigated. Immature Wistar-Albino female rats of 28-days were treated with pregnant mare serum gonadotrophin (PMSG) to develop the first generation of preovulatory follicles. Rats of the experimental groups were then treated with either CYP (100 mg/kg, i.p) and MgSO₄ (270 mg/kg loading dose; 27 mg/kg maintenance doseX12, i.p) solely or in combination. Following in-vivo 5-bromo-2-deoxyuridine (BrdU) labeling, animals were sacrificed and ovaries were embedded in paraffin and Epon. In the ovaries, added to the evaluation of general morphology and follicle count; BrdU and TUNEL-labeling, cleaved caspase-3 and p27 (cyclin-dependent kinase inhibitor) staining was also performed immunohistochemically and an ultrastructural evaluation was performed by transmission electron microscopy (TEM). The number of primordial follicles were decreased and multilaminar primary and atretic follicles were increased in CYP group. After MgSO₄ treatment, while primordial follicle pool were elevated, the number of atretic follicles were decreased. Additionally, decreased BrdU-labeling, increased cleaved caspase 3 immunoreactivity and increased TUNEL labeling were observed in CYP group. In CYP treated animals, observations showed that while MgSO₄ administration caused no alterations in BrdU proliferation index and caspase-3 immunoreactivity, it significantly reduced the TUNEL labeling. It was also observed that, while p27 immunoreactivity significantly increased in the nuclei of granulosa and theca cells in the CYP group; MgSO₄ treatment significantly reduced these immunoreactivities. The ultrastructural observations showed frequent apoptotic profiles in granulosa and theca cells in both early and advanced stages of follicles in the CYP group and the MgSO₄ treatment before the CYP application led to ultrastructural alleviation of the apoptotic process. In conclusion, our data suggest that MgSO₄ may provide an option of pharmacologic treatment for fertility preservation owing to the beneficial effects of on chemotherapy-induced accelerated follicular apoptotic process, and the protection of the primordial follicle pool.

The Ancestral Environment Shapes Antiviral CD8+ T cell Responses across Generations

Recent studies have linked health fates of children to environmental exposures of their great grandparents. However, few studies have considered whether ancestral exposures influence immune function across generations. Here, we report transgenerational inheritance of altered T cell responses resulting from maternal (F0) exposure to the aryl hydrocarbon receptor ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Since F0 exposure to TCDD has been linked to transgenerational transmission of reproductive problems, we asked whether maternal TCDD exposure also caused transgenerational changes in immune function. F0 exposure caused transgenerational effects on the CD8+ T cell response to influenza virus infection in females but not in males. Outcrosses showed changes were passed through both parental lineages. These data demonstrate that F0 exposure to an aryl hydrocarbon receptor (AHR) agonist causes durable changes to immune responses that can affect subsequent generations. This has broad implications for understanding how the environment of prior generations shapes susceptibility to pathogens and antiviral immunity in later generations.

Paternal developmental toxicant exposure is associated with epigenetic modulation of sperm and placental Pgr and Igf2 in a mouse model

Preterm birth (PTB), parturition prior to 37 weeks' gestation, is the leading cause of neonatal mortality. The causes of spontaneous PTB are poorly understood; however, recent studies suggest that this condition may arise as a consequence of the parental fetal environment. Specifically, we previously demonstrated that developmental exposure of male mice (F1 animals) to the environmental endocrine disruptor 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was associated with reduced sperm quantity/quality in adulthood and control female partners frequently delivered preterm. Reproductive defects persisted in the F2 and F3 descendants, and spontaneous PTB was common. Reproductive changes in the F3 males, the first generation without direct TCDD exposure, suggest the occurrence of epigenetic alterations in the sperm, which have the potential to impact placental development. Herein, we conducted an epigenetic microarray analysis of control and F1 male-derived placentae, which identified 2171 differentially methylated regions, including the progesterone receptor (Pgr) and insulin-like growth factor (Igf2). To assess if Pgr and Igf2 DNA methylation changes were present in sperm and persist in future generations, we assessed methylation and expression of these genes in F1/F3 sperm and F3-derived placentae. Although alterations in methylation and gene expression were observed, in most tissues, only Pgr reached statistical significance. Despite the modest gene expression changes in Igf2, offspring of F1 and F3 males consistently exhibited IUGR. Taken together, our data indicate that paternal developmental TCDD exposure is associated with transgenerational placental dysfunction, suggesting epigenetic modifications within the sperm have occurred. An evaluation of additional genes and alternative epigenetic mechanisms is warranted.

Epigenetic transgenerational inheritance of testis pathology and Sertoli cell epimutations: generational origins of male infertility

Male reproductive health has been in decline for decades with dropping sperm counts and increasing infertility, which has created a significant societal and economic burden. Between the 1970s and now, a general decline of over 50% in sperm concentration has been observed in the population. Environmental toxicant-induced epigenetic transgenerational inheritance has been shown to affect testis pathology and sperm count. Sertoli cells have an essential role in spermatogenesis by providing physical and nutritional support for developing germ cells. The current study was designed to further investigate the transgenerational epigenetic changes in the rat Sertoli cell epigenome and transcriptome that are associated with the onset of testis disease. Gestating female F0 generation rats were transiently exposed during the period of fetal gonadal sex determination to the environmental toxicants, such as dichlorodiphenyltrichloroethane (DDT) or vinclozolin. The F1 generation offspring were bred (i.e. intercross within the lineage) to produce the F2 generation grand-offspring that were then bred to produce the transgenerational F3 generation (i.e. great-grand-offspring) with no sibling or cousin breeding used. The focus of the current study was to investigate the transgenerational testis disease etiology, so F3 generation rats were utilized. The DNA and RNA were obtained from purified Sertoli cells isolated from postnatal 20-day-old male testis of F3 generation rats. Transgenerational alterations in DNA methylation, noncoding RNA, and gene expression were observed in the Sertoli cells from vinclozolin and DDT lineages when compared to the control (vehicle exposed) lineage. Genes associated with abnormal Sertoli cell function and testis pathology were identified, and the transgenerational impacts of vinclozolin and DDT were determined. Alterations in critical gene pathways, such as the pyruvate metabolism pathway, were identified. Observations suggest that ancestral exposures to environmental toxicants promote the epigenetic transgenerational inheritance of Sertoli cell epigenetic and transcriptome alterations that associate with testis abnormalities. These epigenetic alterations appear to be critical factors in the developmental and generational origins of testis pathologies and male infertility.

Paternal Environmental Toxicant Exposure and Risk of Adverse Pregnancy Outcomes

Purpose of Review

Current clinical efforts to predict and prevent preterm birth are primarily focused on the mother and have made minimal progress in improving outcomes. However, recent data indicate that paternal factors can also influence timing of birth. Herein, we will review recent human and murine data examining the contribution of the father to pregnancy outcomes with an emphasis on environmental exposures that can negatively impact fertility and the timing of birth.

Recent Findings

Human epidemiology studies now clearly indicate that a variety of paternal factors (age, race, weight, smoking status) can influence sperm quality, birth timing and, in some studies, offspring health. Utilizing a mouse model, our data have 57demonstrated that developmental exposure to the environmental toxicant TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) is associated with a transgenerational reduction in sperm number and quality and an increased risk of preterm birth in an unexposed partner.

Summary

Toxicant exposure history can clearly influence sperm quality in men and mice. Murine data further indicate that exposures which negatively affect sperm quality also impair placental function, potentially leading to preterm birth and other adverse outcomes. Of particular concern, these changes have been linked to epigenetic alterations within the male germ cell which can then be transmitted across multiple generations. Since it is not possible to prevent an ancestral toxicant exposure in a human population, identifying lifestyle modifications that can be implemented during the preconception period to improve sperm quality should be explored for the therapeutic potential to reduce the incidence of PTB and its sequelae.

Multigenerational and Transgenerational Effects of Dioxins

Dioxins are ubiquitous and persistent environmental contaminants whose background levels are still reason for concern. There is mounting evidence from both epidemiological and experimental studies that paternal exposure to the most potent congener of dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), can lower the male/female ratio of offspring. Moreover, in laboratory rodents and zebrafish, TCDD exposure of parent animals has been reported to result in reduced reproductive performance along with other adverse effects in subsequent generations, foremost through the paternal but also via the maternal germline. These impacts have been accompanied by epigenetic alterations in placenta and/or sperm cells, including changes in methylation patterns of imprinted genes. Here, we review recent key studies in this field with an attempt to provide an up-to-date picture of the present state of knowledge to the reader. These studies provide biological plausibility for the potential of dioxin exposure at a critical time-window to induce epigenetic alterations across multiple generations and the significance of aryl hydrocarbon receptor (AHR) in mediating these effects. Currently available data do not allow to accurately estimate the human health implications of these findings, although epidemiological evidence on lowered male/female ratio suggests that this effect may take place at realistic human exposure levels.

Proposed Key Characteristics of Male Reproductive Toxicants as an Approach for Organizing and Evaluating Mechanistic Evidence in Human Health Hazard Assessments

BACKGROUND

Assessing chemicals for their potential to cause male reproductive toxicity involves the evaluation of evidence obtained from experimental, epidemiological, and mechanistic studies. Although mechanistic evidence plays an important role in hazard identification and evidence integration, the process of identifying, screening and analyzing mechanistic studies and outcomes is a challenging exercise due to the diversity of research models and methods and the variety of known and proposed pathways for chemical-induced toxicity. Ten key characteristics of carcinogens provide a valuable tool for organizing and assessing chemical-specific data by potential mechanisms for cancer-causing agents. However, such an approach has not yet been developed for noncancer adverse outcomes.

OBJECTIVES

The objective in this study was to identify a set of key characteristics that are frequently exhibited by exogenous agents that cause male reproductive toxicity and that could be applied for identifying, organizing, and summarizing mechanistic evidence related to this outcome.

DISCUSSION

The identification of eight key characteristics of male reproductive toxicants was based on a survey of known male reproductive toxicants and established mechanisms and pathways of toxicity. The eight key characteristics can provide a basis for the systematic, transparent, and objective organization of mechanistic evidence relevant to chemical-induced effects on the male reproductive system. https://doi.org/10.1289/EHP5045.

Transgenerational Effects of Endocrine-Disrupting Chemicals on Male and Female Reproduction

Endocrine-disrupting chemicals are known to interfere with normal reproductive function and hormone signaling. Phthalates, bisphenol A, pesticides, and environmental contaminants such as polychlorinated biphenyls and dioxins are known endocrine-disrupting chemicals that have been shown to negatively affect both male and female reproduction. Exposure to these chemicals occurs on a daily basis owing to these compounds being found in plastics, personal care products, and pesticides. Recently, studies have shown that these chemicals may cause transgenerational effects on reproduction in both males and females. This is of concern because exposure to these chemicals prenatally or during adult life can negatively impact the reproductive health of future generations. This mini-review summarizes the endocrine-disrupting chemicals that humans are exposed to on a daily basis and what is known about the transgenerational effects that these chemicals may have on male and female reproduction.

Assessment of Glyphosate Induced Epigenetic Transgenerational Inheritance of Pathologies and Sperm Epimutations: Generational Toxicology

Ancestral environmental exposures to a variety of factors and toxicants have been shown to promote the epigenetic transgenerational inheritance of adult onset disease. One of the most widely used agricultural pesticides worldwide is the herbicide glyphosate (N-(phosphonomethyl)glycine), commonly known as Roundup. There are an increasing number of conflicting reports regarding the direct exposure toxicity (risk) of glyphosate, but no rigorous investigations on the generational actions. The current study using a transient exposure of gestating F0 generation female rats found negligible impacts of glyphosate on the directly exposed F0 generation, or F1 generation offspring pathology. In contrast, dramatic increases in pathologies in the F2 generation grand-offspring, and F3 transgenerational great-grand-offspring were observed. The transgenerational pathologies observed include prostate disease, obesity, kidney disease, ovarian disease, and parturition (birth) abnormalities. Epigenetic analysis of the F1, F2 and F3 generation sperm identified differential DNA methylation regions (DMRs). A number of DMR associated genes were identified and previously shown to be involved in pathologies. Therefore, we propose glyphosate can induce the transgenerational inheritance of disease and germline (e.g. sperm) epimutations. Observations suggest the generational toxicology of glyphosate needs to be considered in the disease etiology of future generations.

Sperm epimutation biomarkers of obesity and pathologies following DDT induced epigenetic transgenerational inheritance of disease

Dichlorodiphenyltrichloroethane (DDT) has previously been shown to promote the epigenetic transgenerational inheritance of adult onset disease in rats. The current study investigated the potential that sperm epimutation biomarkers can be used to identify ancestral induced transgenerational obesity and associated pathologies. Gestating F0 generational female rats were transiently exposed to DDT during fetal gonadal sex determination, and the incidence of adult-onset pathologies was assessed in the subsequent F1, F2, and F3 generations. In addition, sperm differential DNA methylation regions (DMRs) that were associated with specific pathologies in the transgenerational F3 generation males were investigated. There was an increase of testis disease and early-onset puberty in the F2 generation DDT lineage males. The F3 generation males and females had significant increases in the incidence of obesity and multiple disease. The F3 generation DDT males also had significant increases in testis disease, prostate disease, and late onset puberty. The F3 generation DDT females had increases in ovarian and kidney disease. Epigenetic alterations of the germline are required for the transgenerational inheritance of pathology. Therefore, the F3 generation sperm was collected to examine DMRs for the ancestrally exposed DDT male population. Unique sets of DMRs were associated with late onset puberty, prostate disease, kidney disease, testis disease, obesity, and multiple disease pathologies. Gene associations with the DMR were also identified. The epigenetic DMR signatures identified for these pathologies provide potential biomarkers for transgenerationally inherited disease susceptibility.

Physiological and anatomical aspects of the reproduction of mice with reduced Syndecan-1 expression

BACKGROUND

Syndecan-1 is a heparan sulfate proteoglycan acting as a co-receptor for cytokines and growth factors mediating developmental, immunological and angiogenic processes. In human, the uteroplacental localization of Syndecan-1 and its reduced expression in pregnancy-associated pathologies, such as the intrauterine growth restriction, suggests an influence of Syndecan-1 in embryo-maternal interactions. The aim of the present study was to identify the effect of a reduced expression of Syndecan-1 on the reproductive phenotype of mice and their progenies.

METHODS

Reproductive characteristics have been investigated using animals with reduced Syndecan-1 and their wildtype controls after normal mating and after vice versa embryo transfers. Female mice were used to measure the estrus cycle length and the weight gain during pregnancy, as well as for histological examination of ovaries. Male mice were examined for the concentration, motility, viability and morphology of spermatozoa. Organs like heart, lung, liver, kidney, spleen, brain and ovaries or testes and epididymis of 6-month-old animals were isolated and weighed. Statistical analyses were performed using two-tailed students t-test with P < .05 and P < .02, chi square test (P < .05) and Fisher's Exact Test (P < .05). A linear and a non-linear mixed-effects model were generated to analyze the weight gain of pregnant females and of the progenies.

RESULTS

Focusing on the pregnancy outcome, the Syndecan-1 reduced females gave birth to larger litters. However, regarding the survival of the offspring, a higher percentage of pups with less Syndecan-1 died during the first postnatal days. Even though the ovaries and the testes of Syndecan-1 reduced mice showed no histological differences and the ovaries showed a similar number of primary and secondary follicles and corpora lutea, the spermatozoa of Syndecan-1 reduced males showed more tail and midpiece deficiencies. Concerning the postnatal and juvenile development the pups with reduced Syndecan-1 expression remained lighter and smaller regardless whether carried by mothers with reduced Syndecan-1 or wildtype foster mothers. With respect to anatomical differences kidneys of both genders as well as testes and epididymis of male mice with reduced syndecan-1 expression weighed less compared to controls.

CONCLUSIONS

These data reveal that the effects of Syndecan-1 reduction are rather genotype- than parental-dependent.

Evaluation of an in vitro mouse testis organ culture system for assessing male reproductive toxicity

BACKGROUND

Development of an in vitro system capable of producing mature sperm remains a challenging goal, with only few successes reported. Such a system, could be used to test agents for potential toxicity to the male reproductive system; to explore this, we exposed immature mouse testis fragments in culture to ethinylestradiol (EE), a well-known testicular toxicant in vivo.

METHODS

Testis fragments from postnatal day 5 mice were cultured in Albumax I medium. After 24 hr of culture, fragments were treated with 0.01, 0.1 or 1 nM EE, then harvested after 20 days in culture and examined for histology or gene expression measures by quantitative PCR.

RESULTS

There was substantial variability between fragments in the degree of spermatogenesis observed. The percentage of seminiferous tubules containing any dead germ cells increased as a result of EE exposure in a dose dependent fashion. This was accompanied with a decreased percentage of tubules with round spermatids. Expression of estrogen receptor 1, cytochrome P450, family 11, subfamily a, and polypeptide 1 also was reduced, depending on the dose.

CONCLUSION

These gene expression changes in the testis fragments are similar to those seen after animals have been exposed to EE. Gene expression changes in testis fragments are encouraging, but the variability across samples will need to be reduced for this in vitro system to become a generally applicable method for assessing testicular toxicants.

The Seveso accident: A look at 40 years of health research and beyond

A 1976 chemical factory explosion near Seveso, Italy exposed residents to high levels of 2,3,7,8-tetracholorodibenzo-p-dioxin (TCDD or dioxin). Dioxin is a known human carcinogen and potent endocrine disruptor. It is highly lipophilic and has a long half-life in humans. Much of what we know and can learn about the risks of dioxin exposure on human health arose from the tragic circumstances of Seveso. This review aims to describe the Seveso accident, summarize the results of 40 years of research on the health of the Seveso population since the accident, and discuss next-stage research on the health of Seveso residents, their children, and grandchildren.

Ancestral TCDD Exposure Induces Multigenerational Histologic and Transcriptomic Alterations in Gonads of Male Zebrafish

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), the classic aryl hydrocarbon receptor (AhR) agonist, is a potent environmental toxicant and endocrine-disrupting chemical (EDC) with known developmental toxicity in humans, rodents, and fish. Early life exposure to some EDCs, including TCDD, is linked to the occurrence of adult-onset and multigenerational disease. Previous work exposing juvenile F0 zebrafish (Danio rerio) to 50 ppt (parts per trillion) TCDD during reproductive development has shown male-mediated transgenerational decreases in fertility (F0-F2) and histologic and transcriptomic alterations in F0 testes. Here, we analyzed male germline alterations in F1 and F2 adult fish, looking for changes in testicular histology and gene expression inherited through the male lineage that could account for decreased reproductive capacity. Testes of TCDD-lineage F1 fish displayed an increase in spermatogonia (immature germ cells) and decrease in spermatozoa (mature germ cells). No histological changes were present in F2 fish. Transcriptomic analysis of exposed F1 and F2 testes revealed alterations in lipid and glucose metabolism, oxidation, xenobiotic response, and sperm cell development and maintenance genes, all of which are implicated in fertility outcomes. Overall, we found that differential expression of reproductive genes and reduced capacity of sperm cells to mature could account for the reproductive defects previously seen in TCDD-exposed male zebrafish and their descendants, providing insight into the distinct multigenerational effects of toxicant exposure.

Rodent Models of Experimental Endometriosis: Identifying Mechanisms of Disease and Therapeutic Targets

BACKGROUND

Although it has been more than a century since endometriosis was initially described in the literature, understanding the etiology and natural history of the disease has been challenging. However, the broad utility of murine and rat models of experimental endometriosis has enabled the elucidation of a number of potentially targetable processes which may otherwise promote this disease.

OBJECTIVE

To review a variety of studies utilizing rodent models of endometriosis to illustrate their utility in examining mechanisms associated with development and progression of this disease.

RESULTS

Use of rodent models of endometriosis has provided a much broader understanding of the risk factors for the initial development of endometriosis, the cellular pathology of the disease and the identification of potential therapeutic targets.

CONCLUSION

Although there are limitations with any animal model, the variety of experimental endometriosis models that have been developed has enabled investigation into numerous aspects of this disease. Thanks to these models, our under-standing of the early processes of disease development, the role of steroid responsiveness, inflammatory processes and the peritoneal environment has been advanced. More recent models have begun to shed light on how epigenetic alterations con-tribute to the molecular basis of this disease as well as the multiple comorbidities which plague many patients. Continued de-velopments of animal models which aid in unraveling the mechanisms of endometriosis development provide the best oppor-tunity to identify therapeutic strategies to prevent or regress this enigmatic disease.

Human and animal evidence of potential transgenerational inheritance of health effects: An evidence map and state-of-the-science evaluation

BACKGROUND

An increasing number of reports suggest early life exposures result in adverse effects in offspring who were never directly exposed; this phenomenon is termed "transgenerational inheritance." Given concern for public health implications for potential effects of exposures transmitted to subsequent generations, it is critical to determine how widespread and robust this phenomenon is and to identify the range of exposures and possible outcomes.

OBJECTIVES

This scoping report examines the evidence for transgenerational inheritance associated with exposure to a wide range of stressors in humans and animals to identify areas of consistency, uncertainty, data gaps, and to evaluate general risk of bias issues for the transgenerational study design.

METHODS

A protocol was developed to collect and categorize the literature into a systematic evidence map for transgenerational inheritance by health effects, exposures, and evidence streams following the Office of Health Assessment and Translation (OHAT) approach for conducting literature-based health assessments.

RESULTS

A PubMed search yielded 63,758 unique records from which 257 relevant studies were identified and categorized into a systematic evidence map by evidence streams (46 human and 211 animal), broad health effect categories, and exposures. Data extracted from the individual studies are available in the Health Assessment Workspace Collaborative (HAWC) program. There are relatively few bodies of evidence where multiple studies evaluated the same exposure and the same or similar outcomes. Studies evaluated for risk of bias generally had multiple issues in design or conduct.

CONCLUSIONS

The evidence mapping illustrated that risk of bias, few studies, and heterogeneity in exposures and endpoints examined present serious limitations to available bodies of evidence for assessing transgenerational effects. Targeted research is suggested to addressed inconsistencies and risk of bias issues identified, and thereby establish more robust bodies of evidence to critically assess transgenerational effects - particularly by adding data on exposure-outcome pairs where there is some evidence (i.e., reproductive, metabolic, and neurological effects).

Sex-Dependent Influence of Developmental Toxicant Exposure on Group B Streptococcus-Mediated Preterm Birth in a Murine Model

Infectious agents are a significant risk factor for preterm birth (PTB); however, the simple presence of bacteria is not sufficient to induce PTB in most women. Human and animal data suggest that environmental toxicant exposures may act in concert with other risk factors to promote PTB. Supporting this "second hit" hypothesis, we previously demonstrated exposure of fetal mice (F1 animals) to the environmental endocrine disruptor 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) leads to an increased risk of spontaneous and infection-mediated PTB in adult animals. Surprisingly, adult F1_males also confer an enhanced risk of PTB to their control partners. Herein, we used a recently established model of ascending group B Streptococcus (GBS) infection to explore the impact of a maternal versus paternal developmental TCDD exposure on infection-mediated PTB in adulthood. Group B Streptococcus is an important contributor to PTB in women and can have serious adverse effects on their infants. Our studies revealed that although gestation length was reduced in control mating pairs exposed to low-dose GBS, dams were able to clear the infection and bacterial transmission to pups was minimal. In contrast, exposure of pregnant F1_females to the same GBS inoculum resulted in 100% maternal and fetal mortality. Maternal health and gestation length were not impacted in control females mated to F1_males and exposed to GBS; however, neonatal survival was reduced compared to controls. Our data revealed a sex-dependent impact of parental TCDD exposure on placental expression of Toll-like receptor 2 and glycogen production, which may be responsible for the differential impact on fetal and maternal outcomes in response to GBS infection.

Spermatogenesis disruption by dioxins: Epigenetic reprograming and windows of susceptibility

Dioxins are a group of highly persistent chemicals that are generated as by-products of industrial and natural processes. Reduction in sperm counts is among the most sensitive endpoints of dioxin toxicity. The exact mechanism by which dioxins reduce sperm counts is not known. Recent data implicate the role of epididymal factors rather than disruption of spermatogenesis. Studies reviewed here demonstrate that dioxins induce the transfer of environmental conditions to the next generation via male germline following exposures during the window of epigenetic reprogramming of primordial germ cells. Increased incidence of birth defects in offspring of male veterans exposed to dioxin containing, Agent Orange, suggest that dioxins may induce epigenomic changes in male germ cells of adults during spermatogenesis. This is supported by recent animal data that show that environmental conditions can cause epigenetic dysregulation in sperm in the context of specific windows of epigenetic reprogramming during spermatogenesis.

Occupational, Environmental, and Lifestyle Factors and their Contribution to Preterm Birth - An Overview

Preterm birth (PTB) is a significant public health concern and a leading cause of infant mortality and morbidity worldwide and often contributes to various health complications later in life. More than 60% of PTBs occur in Africa and south Asia. This overview discusses the available information on occupational, environmental, and lifestyle factors and their contribution to PTB and proposes new etiological explanations that underlie this devastating pregnancy complication. Several factors such as emotional, stress, social, racial, maternal anxiety, multiple pregnancies, infections during pregnancy, diabetes and high blood pressure, and in-vitro fertilization pregnancy have been shown to be associated with PTB. Data are emerging that occupational, environmental exposure and lifestyle factors might also be associated in part with PTB, however, they are at best limited and inconclusive. Nevertheless, data on heavy metals such as lead, air pollutants and particulate matters, bisphenol A, phthalate compounds, and environmental tobacco smoke (ETS) are promising and point to higher incidence of PTB associated with exposure to them. Thus, these observations can be used to advise pregnant women or women of reproductive age to avoid such exposures and adopt positive lifestyle to protect pregnancy and normal fetal development. There is a need to conduct well-planned epidemiological studies that include all the pathology causing factors that may contribute to adverse pregnancy outcomes, including PTB.

Developmental Toxicant Exposure Is Associated with Transgenerational Adenomyosis in a Murine Model

The common environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or, commonly, dioxin) is a known endocrine disruptor that has been linked to the development of endometriosis in experimental models. Using a murine model, we previously demonstrated that in utero TCDD exposure promotes the transgenerational development of an “endometriosis-like” uterine phenotype consisting of reduced responsiveness to progesterone, as well as subfertility and an increased risk of preterm birth. Because adenomyosis is frequently observed as a comorbidity in women with endometriosis, herein we sought to determine the incidence of adenomyosis in nonpregnant mice with a history of direct or indirect TCDD exposure. Using histologic assessment and immunohistochemical staining, we analyzed murine uteri for adenomyosis, microvessel density, and expression of estrogen receptors alpha and beta (ESR1 and ESR2). Our studies revealed that unexposed control mice did not exhibit adenomyosis, whereas this disease was frequently observed in mice with a history of early-life TCDD exposure. A transgenerational impact of developmental TCDD exposure was demonstrated, because a subset of mice with only an indirect exposure (F3) also exhibited adenomyosis. Microvessel density within the uterus was significantly higher in all groups of TCDD-exposed mice compared with control animals, with density correlated to the severity of disease. Both ESR1 and ESR2 proteins exhibited alterations in expression in experimental mice compared with controls. Similar to women with endometriosis, we observed a significant reduction in the ratio of Esr1:Esr2 mRNA in all F1 mice compared with controls. Although this retrospective study was not designed to specifically address mechanisms associated with the development of adenomyosis, our data suggest that developmental TCDD exposure permanently alters adult steroid responses, which may contribute to the transgenerational development of adenomyosis.

Exposure to the environmental endocrine disruptor TCDD and human reproductive dysfunction: Translating lessons from murine models

Humans and other animals are exposed to a wide array of man-made toxicants, many of which act as endocrine disruptors that exhibit differential effects across the lifespan. In humans, while the impact of adult exposure is known for some compounds, the potential consequences of developmental exposure to endocrine disrupting chemicals (EDCs) is more difficult to ascertain. Animal studies have revealed that exposure to EDCs prior to puberty can lead to adult reproductive disease and dysfunction. Specifically, in adult female mice with an early life exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), we demonstrated a transgenerational occurrence of several reproductive diseases that have been linked to endometriosis in women. Herein, we review the evidence for TCDD-associated development of adult reproductive disease as well as known epigenetic alterations associated with TCDD and/or endometriosis. We will also introduce new "Organ-on-Chip" models which, combined with our established murine model, are expected to further enhance our ability to examine alterations in gene-environment interactions that lead to heritable disease.