Semen Quality and Exposure to Persistent Organochlorine Pollutants

The Association between Long-Term DDT or DDE Exposures and an Altered Sperm Epigenome-a Cross-Sectional Study of Greenlandic Inuit and South African VhaVenda Men

BACKGROUND

The organochlorine dichlorodiphenyltrichloroethane (DDT) is banned worldwide owing to its negative health effects. It is exceptionally used as an insecticide for malaria control. Exposure occurs in regions where DDT is applied, as well as in the Arctic, where its endocrine disrupting metabolite, p , p ' -dichlorodiphenyldichloroethylene (p , p ' -DDE) accumulates in marine mammals and fish. DDT and p , p ' -DDE exposures are linked to birth defects, infertility, cancer, and neurodevelopmental delays. Of particular concern is the potential of DDT use to impact the health of generations to come via the heritable sperm epigenome.

OBJECTIVES

The objective of this study was to assess the sperm epigenome in relation to p , p ' -DDE serum levels between geographically diverse populations.

METHODS

In the Limpopo Province of South Africa, we recruited 247 VhaVenda South African men and selected 50 paired blood serum and semen samples, and 47 Greenlandic Inuit blood and semen paired samples were selected from a total of 193 samples from the biobank of the INUENDO cohort, an EU Fifth Framework Programme Research and Development project. Sample selection was based on obtaining a range of p , p ' -DDE serum levels (mean = 870.734 ± 134.030  ng / mL ). We assessed the sperm epigenome in relation to serum p , p ' -DDE levels using MethylC-Capture-sequencing (MCC-seq) and chromatin immunoprecipitation followed by sequencing (ChIP-seq). We identified genomic regions with altered DNA methylation (DNAme) and differential enrichment of histone H3 lysine 4 trimethylation (H3K4me3) in sperm.

RESULTS

Differences in DNAme and H3K4me3 enrichment were identified at transposable elements and regulatory regions involved in fertility, disease, development, and neurofunction. A subset of regions with sperm DNAme and H3K4me3 that differed between exposure groups was predicted to persist in the preimplantation embryo and to be associated with embryonic gene expression.

DISCUSSION

These findings suggest that DDT and p , p ' -DDE exposure impacts the sperm epigenome in a dose-response-like manner and may negatively impact the health of future generations through epigenetic mechanisms. Confounding factors, such as other environmental exposures, genetic diversity, and selection bias, cannot be ruled out. https://doi.org/10.1289/EHP12013.

Systematic review of associations of polychlorinated biphenyl (PCB) exposure with declining semen quality in support of the derivation of reference doses for mixture risk assessments

BACKGROUND

Mixture risk assessments require reference doses for common health endpoints of all the chemicals to be considered together. In support of a mixture risk assessment for male reproductive health, we conducted a systematic review of the literature on associations between exposures to Polychlorinated Biphenyls (PCBs) and declines in semen quality. PCBs can act as Aryl-hydrocarbon Receptor (AhR)-agonists and Androgen Receptor (AR)-antagonists, both mechanisms which can affect sperm parameters. PCBs and other AR-antagonists can produce additive combination effects. Based on these observations our objective was to systematically gather data from animal and human studies to derive a reference dose for declines in semen quality for individual PCB.

METHODS

We systematically reviewed and evaluated the evidence in human epidemiological and experimental animal studies on associations between PCBs and deteriorations in semen quality. Human data and findings from animal studies with PCB mixtures were considered as supporting evidence. Information for individual congeners from animal studies was required for inclusion in mixture risk assessment. Using a robust confidence rating approach, we identified suitable studies to derive reference doses for individual PCB congeners.

RESULTS

Evaluation of human epidemiological studies revealed several reports of adverse effects on sperm parameters linked to PCB exposures, although some studies reported improved semen quality. Our review of experimental animal studies found that treatments with PCBs affected semen quality, in most cases adversely. We found robust evidence that PCB-118 and -169 were linked to declines in semen quality. Evidence for adverse effects of PCB-126, -132, -149, and -153 was moderate, whereas for PCB-77 it was slight and for PCB-180 indeterminate. Using widely accepted risk assessment procedures, we estimated reference dose values of 0.0029 µg/kg/day for PCB-118 and 0.00533 µg/kg/day for PCB-169. In addition, we derived values for PCB-126: 0.000073 µg/kg/day, PCB-132: 0.0228 µg/kg/day, PCB-149: 0.656 µg/kg/day, and PCB-153: 0.0058 µg/kg/day.

CONCLUSIONS

We found robust evidence for links between PCB exposure and deteriorations in semen quality, and derived reference doses for a set of congeners. We intend to use these values in combination with congener-specific exposure data in a mixture risk assessment for declines in semen quality, involving several other antiandrogenic chemicals.

The environmental and occupational influence of pesticides on male fertility: a systematic review of human studies

BACKGROUND

Environment plays a key role in male infertility, changing the incidence in various populations, and pesticides are one of the most studied hazards. The use of the latter has never decreased, jeopardizing the safety of workers and the general population.

OBJECTIVE

Our purpose was to summarize the results of studies discussing the association between pesticides and male fertility.

METHODS

A comprehensive literature search was performed through MEDLINE via PubMed, Scopus, and Web of Science. Only human studies were considered. Semen parameters, and DNA integrity were considered to evaluate the effect of pesticides on men.

RESULTS

A total of 64 studies that investigated their impact in terms of semen parameters (51 studies), chromatin and DNA integrity (25 studies), were included. The most frequently affected parameters were total sperm count sperm motility and morphology, although a reduction in ejaculate volume and concentration occur in several cases. A tangible worsening of semen quality was associated with organochlorines and organophosphates. Furthermore, pesticide exposure, especially pyrethroids, was related to a higher DNA fragmentation index and chromosome aneuploidy in most articles.

CONCLUSION

The epidemiological evidence supports the association between pesticides and male fertility for workers and the exposed population in terms of semen quality, DNA fragmentation and chromosome aneuploidy. This article is protected by copyright. All rights reserved.

The Role of Environmental Toxicant-Induced Oxidative Stress in Male Infertility

Infertility is a serious public health issue affecting around 15% of couples globally. Of the 60-80 million people of reproductive age affected by infertility, 40-50% are due to male factor while 30-40% of cases are still idiopathic. The recent global deterioration in sperm quality raises apprehensions regarding the toxic effects of environmental pollutants on reproductive health of males. Environmental toxicants have shown strong evidences for inducing oxidative stress affecting spermatogenesis severely, thereby leading to reduced sperm motility, count, and DNA damage. Reactive oxygen species (ROS) influences the spermatozoa development and transit process both internally and externally. Low level of ROS is indispensable for critical physiological sperm processes like sperm capacitation, motility, acrosome reaction, hyper-activation, sperm-oocyte interaction, etc., while excessive ROS disrupt antioxidant molecules which is detrimental to normal functioning of the sperm. Hence, identification of potential environmental toxicant may have clinical relevance for early screening and diagnosis of male infertility.

The Impact of Endocrine-Disrupting Chemicals in Male Fertility: Focus on the Action of Obesogens

The current scenario of male infertility is not yet fully elucidated; however, there is increasing evidence that it is associated with the widespread exposure to endocrine-disrupting chemicals (EDCs), and in particular to obesogens. These compounds interfere with hormones involved in the regulation of metabolism and are associated with weight gain, being also able to change the functioning of the male reproductive axis and, consequently, the testicular physiology and metabolism that are pivotal for spermatogenesis. The disruption of these tightly regulated metabolic pathways leads to adverse reproductive outcomes. The permanent exposure to obesogens has raised serious health concerns. Evidence suggests that obesogens are one of the leading causes of the marked decline of male fertility and key players in shaping the future health outcomes not only for those who are directly exposed but also for upcoming generations. In addition to the changes that lead to inefficient functioning of the male gametes, obesogens induce alterations that are “imprinted” on the genes of the male gametes, establishing a link between generations and contributing to the transmission of defects. Unveiling the molecular mechanisms by which obesogens induce toxicity that may end-up in epigenetic modifications is imperative. This review describes and discusses the suggested molecular targets and potential mechanisms for obesogenic–disrupting chemicals and the subsequent effects on male reproductive health.

Study of Semen Quality, Reproductive Hormone Levels, and Lipid Levels in Men From Arkhangelsk, a City in North of European Russia

Male populations in the European North of Russia have not previously been investigated for semen quality. The aim of this study was to evaluate semen parameters, reproductive hormone levels, and lipid levels in volunteers from the general urban population of the European North of Russia, to compare the data published for men from the neighboring Northern or Eastern European countries, and to evaluate associations between sperm quality and serum hormonal and lipid levels. Ninety-nine volunteers aged 23-63 years residing in the city of Archangelsk were enrolled in the study. All men had blood samples drawn and completed a questionnaire concerning their health status and lifestyle; 90 men delivered semen samples. The medians for semen volume, sperm concentration, progressive motility, and normal morphology were 3.0 ml, 42.12 million/ml, 43.8%, and 6.5%, respectively. Sperm parameters below normal threshold values were found in 38.9% of participants. It seems that the sperm quality in our study group was slightly worse than in men from Finland, Norway, Sweden, or Estonia, but very similar to that in men from Denmark or Poland. The significant negative correlations of luteinizing hormone levels and positive correlations of inhibin B levels with sperm concentration and progressive motility were revealed. Higher levels of luteinizing hormone and lower levels of inhibin B were found in participants with impaired compared to normal sperm quality. No reliable links were found between serum total cholesterol, triglyceride, high and low-density lipoprotein cholesterol, and semen parameters.

Reproductive Health Risks Associated with Occupational and Environmental Exposure to Pesticides

A marked reduction in fertility and an increase in adverse reproductive outcomes during the last few decades have been associated with occupational and environmental chemical exposures. Exposure to different types of pesticides may increase the risks of chronic diseases, such as diabetes, cancer, and neurodegenerative disease, but also of reduced fertility and birth defects. Both occupational and environmental exposures to pesticides are important, as many are endocrine disruptors, which means that even very low-dose exposure levels may have measurable biological effects. The aim of this review was to summarize the knowledge collected between 2000 and 2020, to highlight new findings, and to further interpret the mechanisms that may associate pesticides with infertility, abnormal sexual maturation, and pregnancy complications associated with occupational, environmental and transplacental exposures. A summary of current pesticide production and usage legislation is also included in order to elucidate the potential impact on exposure profile differences between countries, which may inform prevention measures. Recommendations for the medical surveillance of occupationally exposed populations, which should be facilitated by the biomonitoring of reduced fertility, is also discussed.

Endocrine disrupting chemicals: Impacts on human fertility and fecundity during the peri-conception period

It is becoming increasingly difficult to avoid exposure to man-made endocrine disrupting chemicals (EDCs) and environmental toxicants. This escalating yet constant exposure is postulated to partially explain the concurrent decline in human fertility that has occurred over the last 50 years. Controversy however remains as to whether associations exist, with conflicting findings commonly reported for all major EDC classes. The primary aim of this extensive work was to identify and review strong peer-reviewed evidence regarding the effects of environmentally-relevant EDC concentrations on adult male and female fertility during the critical periconception period on reproductive hormone concentrations, gamete and embryo characteristics, as well as the time to pregnancy in the general population. Secondly, to ascertain whether individuals or couples diagnosed as sub-fertile exhibit higher EDC or toxicant concentrations. Lastly, to highlight where little or no data exists that prevents strong associations being identified. From the greater than 1480 known EDCs, substantial evidence supports a negative association between exposure to phthalates, PCBs, PBDEs, pyrethroids, organochloride pesticides and male fertility and fecundity. Only moderate evidence exists for a negative association between BPA, PCBs, organochloride pesticides and female fertility and fecundity. Overall fewer studies were reported in women than men, with knowledge gaps generally evident for both sexes for all the major EDC classes, as well as a paucity of female fertility studies following exposure to parabens, triclosans, dioxins, PFAS, organophosphates and pyrethroids. Generally, sub-fertile individuals or couples exhibit higher EDC concentrations, endorsing a positive association between EDC exposure and sub-fertility. This review also discusses confounding and limiting factors that hamper our understanding of EDC exposures on fertility and fecundity. Finally, it highlights future research areas, as well as government, industry and social awareness strategies required to mitigate the negative effects of EDC and environmental toxicant exposure on human fertility and fecundity.

Endocrine Disrupting Chemicals and Reproductive Health in Boys and Men

Male reproductive health has declined as indicated by increasing rates of cryptorchidism, i.e., undescended testis, poor semen quality, low serum testosterone level, and testicular cancer. Exposure to endocrine disrupting chemicals (EDCs) has been proposed to have a role in this finding. In utero exposure to antiandrogenic EDCs, particularly at a sensitive period of fetal testicular development, the so-called 'masculinization programming window (MPW)', can disturb testicular development and function. Low androgen effect during the MPW can cause both short- and long-term reproductive disorders. A concurrent exposure to EDCs may also affect testicular function or damage testicular cells. Evidence from animal studies supports the role of endocrine disrupting chemicals in development of male reproductive disorders. However, evidence from epidemiological studies is relatively mixed. In this article, we review the current literature that evaluated relationship between prenatal EDC exposures and anogenital distance, cryptorchidism, and congenital penile abnormality called hypospadias. We review also studies on the association between early life and postnatal EDC exposure and semen quality, hypothalamic-pituitary-gonadal axis hormone levels and testicular cancer.

Peripubertal serum concentrations of organochlorine pesticides and semen parameters in Russian young men

BACKGROUND

Epidemiologic literature on the relation of organochlorine pesticides (OCPs) with semen quality among adult men has been inconclusive, and no studies have prospectively explored the association between peripubertal serum OCPs and semen parameters in young men.

OBJECTIVE

To evaluate prospective associations of peripubertal serum concentrations of hexachlorobenzene (HCB), β-hexachlorocylohexane (β-HCH), and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) with semen parameters among young Russian men.

METHODS

This prospective cohort study included 152 young men who enrolled in the Russian Children's Study (2003-2005) at age 8-9 years and were followed annually until young adulthood. HCB, β-HCH, and p,p'-DDE concentrations were measured at the CDC by mass spectrometry in serum collected at enrollment. Between 18 and 23 years, semen samples (n = 298) were provided for analysis of volume, concentration, and progressive motility; we also calculated total sperm count and total progressive motile count. Linear mixed models were used to examine the longitudinal associations of quartiles of serum HCB, β-HCH and p,p'-DDE with semen parameters, adjusting for total serum lipids, body mass index, smoking, abstinence time and baseline dietary macronutrient intake.

RESULTS

Lipid-adjusted medians (IQR) for serum HCB, βHCH and p,ṕ-DDE, respectively, were 150 ng/g lipid (102-243), 172 ng/g lipid (120-257) and 275 ng/g lipid (190-465). In adjusted models, we observed lower ejaculated volume with higher serum concentrations of HCB and βHCH, along with reduced progressive motility with higher concentrations of βHCH andp,ṕ-DDE. Men in the highest quartile of serum HCB had a mean (95% Confidence Interval, CI) ejaculated volume of 2.25 mL (1.89, 2.60), as compared to those in the lowest quartile with a mean (95% CI) of 2.97 mL (2.46, 3.49) (p = 0.03). Also, men in the highest quartile of serum p,ṕ-DDE had a mean (95% CI) progressive motility of 51.1% (48.6, 53.7), as compared to those in the lowest quartile with a mean (95% CI) of 55.1% (51.7, 58.5) (p = 0.07).

CONCLUSION

In this longitudinal Russian cohort study, peripubertal serum concentrations of selected OCPs were associated with lower ejaculated volume and progressive motility highlighting the importance of the peripubertal window when evaluating chemical exposures in relation to semen quality.

Are concentrations of pollutants in sharks, rays and skates (Elasmobranchii) a cause for concern? A systematic review

This review represents a comprehensive analysis on pollutants in elasmobranchs including meta-analysis on the most studied pollutants: mercury, cadmium, PCBs and DDTs, in muscle and liver tissue. Elasmobranchs are particularly vulnerable to pollutant exposure which may pose a risk to the organism as well as humans that consume elasmobranch products. The highest concentrations of pollutants were found in sharks occupying top trophic levels (Carcharhiniformes and Lamniformes). A human health risk assessment identified that children and adults consuming shark once a week are exposed to over three times more mercury than is recommended by the US EPA. This poses a risk to local fishing communities and international consumers of shark-based products, as well as those subject to the widespread mislabelling of elasmobranch products. Wider screening studies are recommended to determine the risk to elasmobranchs from emerging pollutants and more robust studies are recommended to assess the risks to human health.

Association between semen quality among men with different occupational exposures and risk of recurrent spontaneous abortion in island residents

Objective: This study aimed to evaluate the semen quality of male adults whose spouses suffer from recurrent spontaneous abortion (RSA) in the island area, and to explore the association between RSA and occupational exposures.

Methods: A total of 131 male patients were recruited and divided into two groups: spouse with recurrent spontaneous abortion group (RSA group, [Formula: see text]) and the normal fertility group (control group, [Formula: see text]). Information such as height, weight and occupational exposure history of 131 men were obtained. Semen samples were collected and analyzed. Differences in semen parameters and DNA fragmentation index (DFI) between the two groups were compared. Odds ratios (ORs) and their corresponding 95% confidence intervals were calculated to evaluate the association between occupational exposures and RSA status.

Results: Overall, no significant difference was found in sperm concentration, progressive motility and normal morphology rate between RSA and control groups. Only DFI was observed to be significantly higher in the RSA group. Evaluation of the receiver operating characteristic (ROC) curve showed DFI (AUC: 0.623, [Formula: see text]) could discriminate between males from the couples with RSA and without RSA.

Conclusion: The analysis of conventional semen parameters could not directly reflect their influence on embryonic development, and test of integrity of the sperm DNA is of paramount importance to fully understand male fertility. It is crucial to conduct studies regarding occupational exposures and pregnancy loss and/or RSA risk, since it will provide population-level data to aid in the identification of important risk factors that warrant further mechanistic investigation, and eventually lead to effective prevention and treatment strategies.

Independent and combined effects of diethylhexyl phthalate and polychlorinated biphenyl 153 on sperm quality in the human and dog

A temporal decline in human and dog sperm quality is thought to reflect a common environmental aetiology. This may reflect direct effects of seminal chemicals on sperm function and quality. Here we report the effects of diethylhexyl phthalate (DEHP) and polychlorinated biphenyl 153 (PCB153) on DNA fragmentation and motility in human and dog sperm. Human and dog semen was collected from registered donors (n = 9) and from stud dogs (n = 11) and incubated with PCB153 and DEHP, independently and combined, at 0x, 2x, 10x and 100x dog testis concentrations. A total of 16 treatments reflected a 4 × 4 factorial experimental design. Although exposure to DEHP and/or PCB153 alone increased DNA fragmentation and decreased motility, the scale of dose-related effects varied with the presence and relative concentrations of each chemical (DEHP.PCB interaction for: DNA fragmentation; human p < 0.001, dog p < 0.001; Motility; human p < 0.001, dog p < 0.05). In both human and dog sperm, progressive motility negatively correlated with DNA fragmentation regardless of chemical presence (Human: P < 0.0001, r = −0.36; dog P < 0.0001, r = −0.29). We conclude that DEHP and PCB153, at known tissue concentrations, induce similar effects on human and dog sperm supporting the contention of the dog as a sentinel species for human exposure.

Endocrine disruptors and testicular function

Despite concerns of the scientific community regarding the adverse effects of human exposure to exogenous man-made chemical substances or mixtures that interfere with normal hormonal balance, the so called "endocrine disruptors (EDs)", their production has been increased during the last few decades. EDs' extensive use has been implicated in the increasing incidence of male reproductive disorders including poor semen quality, testicular malignancies and congenital developmental defects such as hypospadias and cryptorchidism. Several animal studies have demonstrated that exposure to EDs during fetal, neonatal and adult life has deleterious consequences on male reproductive system; however, the evidence on humans remains ambiguous. The complexity of their mode of action, the differential effect according to the developmental stage that exposure occurs, the latency from exposure and the influence of the genetic background in the manifestation of their toxic effects are all responsible factors for the contradictory outcomes. Furthermore, the heterogeneity in the published human studies has hampered agreement in the field. Interventional studies to establish causality would be desirable, but unfortunately the nature of the field excludes this possibility. Therefore, future studies based on standardized guidelines are necessary, in order to estimate human health risks and implement policies to limit public exposure.

Maternal exposure to a mixture of persistent organic pollutants (POPs) affects testis histology, epididymal sperm count and induces sperm DNA fragmentation in mice

Persistent organic pollutants (POPs) are widespread throughout the environment and some are suspected to induce reproductive toxicity. As animals and humans are exposed to complex mixtures of POPs, it is reasonable to assess how such mixtures could interact with the reproductive system. Our aim is to investigate how maternal exposure to a mixture of 29 different persistent organic pollutants, formulated to mimic the relative POP levels in the food basket of the Scandinavian population, could alter reproductive endpoints. Female mice were exposed via feed from weaning, during pregnancy and lactation in 3 exposure groups (control (C), low (L) and high (H)). Testicular morphometric endpoints, epididymal sperm concentration and sperm DNA integrity were assessed in adult male offspring. We found that the number of tubules, proportion of tubule compartments and epididymal sperm concentration significantly decreased in both POP exposed groups. Epididymal sperm from both POP exposed groups showed increased DNA fragmentation. It is concluded that maternal exposure to a defined POP mixture relevant to human exposure can affect testicular development, sperm production and sperm chromatin integrity.

Cell cycle arrest and gene expression profiling of testis in mice exposed to fluoride

Exposure to fluoride results in low reproductive capacity; however, the mechanism underlying the impact of fluoride on male productive system still remains obscure. To assess the potential toxicity in testis of mice administrated with fluoride, global genome microarray and real-time PCR were performed to detect and identify the altered transcriptions. The results revealed that 763 differentially expressed genes were identified, including 330 up-regulated and 433 down-regulated genes, which were involved in spermatogenesis, apoptosis, DNA damage, DNA replication, and cell differentiation. Twelve differential expressed genes were selected to confirm the microarray results using real-time PCR, and the result kept the same tendency with that of microarray. Furthermore, compared with the control group, more apoptotic spermatogenic cells were observed in the fluoride group, and the spermatogonium were markedly increased in S phase and decreased in G2/M phase by fluoride. Our findings suggested global genome microarray provides an insight into the reproductive toxicity induced by fluoride, and several important biological clues for further investigations. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1558-1565, 2017.

A Longitudinal Study of Peripubertal Serum Organochlorine Concentrations and Semen Parameters in Young Men: The Russian Children's Study

BACKGROUND

Exposures to endocrine-disrupting chemicals during critical phases of testicular development may be related to poorer semen parameters. However, few studies have assessed the association between childhood organochlorine (OC) exposure and adult semen parameters.

OBJECTIVE

We examined whether peripubertal serum OC concentrations are associated with semen parameters among young Russian men.

METHODS

From 2003 through 2005, 516 boys were enrolled at age 8-9 years and followed for up to 10 years. Serum OCs were measured in the enrollment samples using high-resolution mass spectrometry. At 18-19 years, 133 young men provided 1 or 2 semen samples (256 samples) collected approximately 1 week apart, which were analyzed for volume, sperm concentration, and motility. Unadjusted and adjusted linear mixed models were used to examine the associations of quartiles of lipid-standardized concentrations of dioxins [2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), polychlorinated dibenzo-p-dioxins (PCDDs)], furans, polychlorinated biphenyls (PCBs), and corresponding toxic equivalents (TEQs) with semen parameters.

RESULTS

The median (range) for TCDD was 2.9 (0.4-12.1) pg/g lipid and PCDD TEQ was 8.7 (1.0-36.0) pg TEQ/g lipid. Higher quartiles of TCDD and PCDD TEQs were associated with lower sperm concentration, total sperm count, and total motile sperm count (p-trends ≤ 0.05). The highest quartile of peripubertal serum TCDD concentrations was associated with a decrease (95% CI) of 40% (18, 66%), 29% (3, 64%), and 30% (2, 70%) in sperm concentration, total sperm count, and total motile sperm count, respectively, compared with the lowest quartile. Similar associations were observed for serum PCDD TEQs with semen parameters. Serum PCBs, furans, and total TEQs were not associated with semen parameters.

CONCLUSION

Higher peripubertal serum TCDD concentrations and PCDD TEQs were associated with poorer semen parameters. Citation: Mínguez-Alarcón L, Sergeyev O, Burns JS, Williams PL, Lee MM, Korrick SA, Smigulina L, Revich B, Hauser R. 2017. A longitudinal study of peripubertal serum organochlorine concentrations and semen parameters in young men: the Russian Children's Study. Environ Health Perspect 125:460-466; http://dx.doi.org/10.1289/EHP25.

Factors associated with aberrant imprint methylation and oligozoospermia

Disturbingly, the number of patients with oligozoospermia (low sperm count) has been gradually increasing in industrialized countries. Epigenetic alterations are believed to be involved in this condition. Recent studies have clarified that intrinsic and extrinsic factors can induce epigenetic transgenerational phenotypes through apparent reprogramming of the male germ line. Here we examined DNA methylation levels of 22 human imprinted loci in a total of 221 purified sperm samples from infertile couples and found methylation alterations in 24.8% of the patients. Structural equation model suggested that the cause of imprint methylation errors in sperm might have been environmental factors. More specifically, aberrant methylation and a particular lifestyle (current smoking, excess consumption of carbonated drinks) were associated with severe oligozoospermia, while aging probably affected this pathology indirectly through the accumulation of PCB in the patients. Next we examined the pregnancy outcomes for patients when the sperm had abnormal imprint methylation. The live-birth rate decreased and the miscarriage rate increased with the methylation errors. Our research will be useful for the prevention of methylation errors in sperm from infertile men, and sperm with normal imprint methylation might increase the safety of assisted reproduction technology (ART) by reducing methylation-induced diseases of children conceived via ART.

Environmental chemicals impact dog semen quality in vitro and may be associated with a temporal decline in sperm motility and increased cryptorchidism

Adverse temporal trends in human semen quality and cryptorchidism in infants have been associated with exposure to environmental chemicals (ECs) during development. Here we report that a population of breeding dogs exhibit a 26 year (1988-2014) decline in sperm quality and a concurrent increased incidence of cryptorchidism in male offspring (1995-2014). A decline in the number of males born relative to the number of females was also observed. ECs, including diethylhexyl phthalate (DEHP) and polychlorinated biphenyl 153 (PCB153), were detected in adult dog testes and commercial dog foods at concentrations reported to perturb reproductive function in other species. Testicular concentrations of DEHP and PCB153 perturbed sperm viability, motility and DNA integrity in vitro but did not affect LH stimulated testosterone secretion from adult testis explants. The direct effects of chemicals on sperm may therefore contribute to the decline in canine semen quality that parallels that reported in the human.

Zebrafish as a possible bioindicator of organic pollutants in drinking waters with effects on reproduction: are effects cumulative or reversible?

Organic pollutants are present in drinking waters due to inefficient detection and removal treatments. For this reason, zebrafish is proposed as a complementary indicator in conventional potabilization treatments. Based on the most sensitive parameters detected in our previous work, in this study we attempted to examine the possible cumulative effect between generations of environmental pollutants likely present in drinking waters, when specimens were cultured in the same water and/or the possible reversibility of these effects when cultured in control water. To this end, embryos with the chorion intact were cultured in three drinking waters from different sources and in one control water for up to 5 months in 20 l glass tanks. Four replicates were performed in all water groups. Results in water group C (tap water from a city also located in a region with intensive agricultural activity, but from the hydrological basin of the river Xúquer) revealed a non-reversible effect on fertility rate. Also in water C there was an alteration of sex ratio towards females, although in this case the alteration was reversible. A transgenerational alteration in the germ-line via an epigenetic mechanism from the previous generation is proposed as the most plausible explanation of this effect.

Exposure to persistent organic pollutants and sperm DNA methylation changes in Arctic and European populations

Persistent organic pollutants (POPs), such as PCBs (polychlorinated biphenyls) and DDT [1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane], are environmental contaminants with potential endocrine disrupting activity. DNA methylation levels in peripheral blood lymphocytes have been associated with serum concentrations of POPs in Greenland Inuit and Korean populations. Greenland Inuits are characterized by the highest worldwide POP levels. In this cross-sectional study we evaluated the relationship between serum POP concentrations and DNA methylation levels in sperm of non-occupationally exposed fertile men from Greenland, Warsaw (Poland), and Kharkiv (Ukraine). Serum levels of PCB-153 [1,2,4-trichloro-5-(2,4,5-trichlorophenyl)benzene], as a proxy of the total PCBs body burden, and of p,p'-DDE [1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene], the main metabolite of DDT were measured. Sperm DNA methylation level was assessed globally by flow cytometric (FCM) immunodetection of 5-methyl-cytosines and at specific repetitive DNA sequences (Alu, LINE-1, Satα) by PCR-pyrosequencing after bisulfite conversion. Multivariate linear regression analysis was applied to investigate correlations between serum POP concentrations and DNA methylation. No consistent associations between exposure to POPs and sperm DNA methylation at repetitive DNA sequences were detected. A statistically significant global decrease in methylation was associated with exposure to either POP by FCM analysis. This is the first study to investigate environmental exposure to POPs and DNA methylation levels considering sperm as the target cells. Although POP exposure appears to have a limited negative impact on sperm DNA methylation levels in adult males, the global hypomethylation detected by one of the methods applied suggests that further investigation is warranted.

EDC-2: The Endocrine Society's Second Scientific Statement on Endocrine-Disrupting Chemicals

The Endocrine Society's first Scientific Statement in 2009 provided a wake-up call to the scientific community about how environmental endocrine-disrupting chemicals (EDCs) affect health and disease. Five years later, a substantially larger body of literature has solidified our understanding of plausible mechanisms underlying EDC actions and how exposures in animals and humans-especially during development-may lay the foundations for disease later in life. At this point in history, we have much stronger knowledge about how EDCs alter gene-environment interactions via physiological, cellular, molecular, and epigenetic changes, thereby producing effects in exposed individuals as well as their descendants. Causal links between exposure and manifestation of disease are substantiated by experimental animal models and are consistent with correlative epidemiological data in humans. There are several caveats because differences in how experimental animal work is conducted can lead to difficulties in drawing broad conclusions, and we must continue to be cautious about inferring causality in humans. In this second Scientific Statement, we reviewed the literature on a subset of topics for which the translational evidence is strongest: 1) obesity and diabetes; 2) female reproduction; 3) male reproduction; 4) hormone-sensitive cancers in females; 5) prostate; 6) thyroid; and 7) neurodevelopment and neuroendocrine systems. Our inclusion criteria for studies were those conducted predominantly in the past 5 years deemed to be of high quality based on appropriate negative and positive control groups or populations, adequate sample size and experimental design, and mammalian animal studies with exposure levels in a range that was relevant to humans. We also focused on studies using the developmental origins of health and disease model. No report was excluded based on a positive or negative effect of the EDC exposure. The bulk of the results across the board strengthen the evidence for endocrine health-related actions of EDCs. Based on this much more complete understanding of the endocrine principles by which EDCs act, including nonmonotonic dose-responses, low-dose effects, and developmental vulnerability, these findings can be much better translated to human health. Armed with this information, researchers, physicians, and other healthcare providers can guide regulators and policymakers as they make responsible decisions.

ECOLOGICAL AND EVOLUTIONARY APPLICATIONS FOR ENVIRONMENTAL SEX REVERSAL OF FISH

Environmental sex reversal (ESR), which results in a mismatch between genotypic and phenotypic sex, is well documented in numerous fish species and may be induced by chemical exposure. Historically, research involving piscine ESR has been carried out with a view to improving profitability in aquaculture or to elucidate the processes governing sex determination and sexual differentiation. However, recent studies in evolution and ecology suggest research on ESR now has much wider applications and ramifications. We begin with an overview of ESR in fish and a brief review of the traditional applications thereof. We then discuss ESR and its potential demographic consequences in wild populations. Theory even suggests sex-reversed fish may be purposefully released to manipulate population dynamics. We suggest new research directions that may prove fruitful in understanding how ESR at the individual level translates to population-level processes. In the latter portion of the review we focus on evolutionary applications of ESR. Sex-reversal studies from the aquaculture literature provide insight in to the evolvability of determinants of sexual phenotype. Additionally, induced sex reversal can provide information about the evolution of sex chromosomes and sex-linked traits. Recently, naturally occurring ESR has been implicated as a mechanism contributing to the evolution of sex chromosomes.

Discrimination of the effects on zebrafish reproduction from pollutants in drinking water via female, via male and/or via fecundation water

The lack of preventive policy legislation and the low removal rate of organic pollutants in conventional potabilization treatments lead to some of them being present in drinking water. The problem arises because some of these substances have detrimental effects on human reproduction health, via females, via males or even both. In this work, we established the zebrafish as a bioindicator of these types of substances with the goal of discriminating the effects through three different pathways: male, female or water where the fertilization took place.

For this purpose, four parameters were analysed: fertility rate, hatching rate and survival and abnormalities rates. So, for each parameter two groups were formed, according to whether adult males or females were reared in bottled spring water (Z) or tap water (B) and if the in vitro fertilization took place in water Z or B.

Results revealed a decline in the fertility and hatching rate in water B, due to a water effect. The most plausible explanation could be the presence of substances which affect the micropyle and chorion. Moreover, a decrease in the fertility rate due to an effect over the female was also observed, but in this case by an alteration of the oocyte quality.

Persistent organic pollutants and semen quality: The LIFE Study

Growing evidence suggests that persistent environmental chemicals such as polychlorinated biphenyls may adversely affect human fecundity. The purpose of this study was to evaluate associations between persistent environmental chemicals and semen quality among 501 male partners of couples discontinuing contraception for purposes of becoming pregnant. Men provided a blood specimen and two fresh semen samples collected approximately a month apart that underwent next day analysis for 35 semen quality endpoints. Serum samples were analyzed for 36 polychlorinated biphenyls (congeners #18, 28, 44, 49, 52, 66, 74, 87, 99, 101, 114, 118, 128, 138, 146, 149, 151, 153, 156, 157, 167, 170, 172, 177, 178, 180, 183, 187, 189, 194, 195, 196, 201, 206, 209); 1 polybrominated biphenyl (#153); 9 organochlorine pesticides; and 10 polybrominated diphenyl ethers (congeners #17, 28, 47, 66, 85, 99, 100, 153, 154183) using high resolution mass spectrometry. To estimate the effect of chemicals on semen quality, we regressed each semen marker on each chemical while adjusting for research site, age, body mass index, serum lipids, and cotinine levels. Males with chemical concentrations in the fourth quartile, as compared to the first quartile, showed significant associations for several individual chemicals in each chemical class and type of semen quality parameter indicating negative and positive associations with semen quality. Polybrominated diphenyl ethers in particular were associated with several measures of increased abnormal morphology. These exploratory results highlight the role of environmental influences on male fecundity, and are of particular interest given the ubiquitous exposures to these compounds.

Epigenetic alterations in sperm associated with male infertility

The most common form of male infertility is a low sperm count, known as oligozoospermia. Studies suggest that oligozoospermia is associated with epigenetic alterations. Epigenetic alterations in sperm, which may arise due to the exposure of gametes to environmental factors or those that pre-exist in the sperm of infertile individuals, may contribute to the increased incidence of normally rare imprinting disorders in babies conceived after assisted reproductive technology using the sperm of infertile men. Genomic imprinting is an important developmental process whereby the allelic activity of certain genes is regulated by DNA methylation established during gametogenesis. The aberrant expression of several imprinted genes has been linked to various diseases, malignant tumors, lifestyle and mental disorders in humans. Understanding how infertility and environmental factors such as reproductive toxicants, certain foods, and drug exposures during gametogenesis contribute to the origins of these disorders via defects in sperm is of paramount importance. In this review, we discuss the association of epigenetic alterations with abnormal spermatogenesis and the evidence that epigenetic processes, including those required for genomic imprinting, may be sensitive to environmental exposures during gametogenesis, fertilization and early embryonic development. In addition, we review imprinting diseases and their relationships with environmental factors. While the plasticity of epigenetic marks may make these more susceptible to modification by the environment, this also suggests that aberrant epigenetic marks may be reversible. A greater understanding of this process and the function of epidrugs may lead to the development of new treatment methods for many adult diseases in the future.

Effect of sodium fluoride on male mouse fertility

Sodium fluoride (NaF), an environmental pollutant, has been tested for its impact on fertility in several species of laboratory animals. A literature demonstrated that NaF adversely affects sperm motility, morphology, capacitation, and the acrosome reaction. However, the molecular mechanisms underlying these alterations have not yet been elucidated. Therefore, present study was designed to evaluate the regulatory pathways involved in the effect of NaF on sperm function and fertilization. In this in vitro study, mouse spermatozoa were incubated with a range of concentrations (2.5, 5, and 10 mm) of NaF for 90 min in media that support in vitro fertilization. Our results showed that NaF was associated with reduced intracellular ATP generation, motility, and motion kinematics. Likewise, short-term exposure of spermatozoa to NaF significantly reduced the intracellular calcium concentration, protein kinase-A activity, and tyrosine phosphorylation of sperm proteins, which were associated with a significant decrease in the rate of capacitation and the acrosome reaction. Finally, NaF significantly reduced the fertilization and blastocyst formation during early embryonic development. On the basis of these results, we propose that NaF reduces sperm motility, capacitation, and the acrosome reaction leading to poor fertilization and suppressed embryonic development.

Cadmium may impair prostate function as measured by prostate specific antigen in semen: A cross-sectional study among European and Inuit men

We investigated the association between cadmium in blood and the concentration of the prostate specific antigen (PSA) in semen, including the modifying effects of zinc or the CAG polymorphism in the androgen receptor (AR). Blood and semen samples were collected from 504 partners of pregnant women in Greenland, Poland and Ukraine. We found an inverse trend between cadmium and PSA (log(β) = -0.121, 95% confidence interval (CI): -0.213; -0.029, P = 0.0103) in Greenlandic men. Similar results were observed in men with a high number of CAG repeats (CAG 24) (log(β) = -0.231, 95% CI: -0.363; -0.098, P = 0.0009). Inverse trends between cadmium and PSA were found when semen zinc concentrations were below the median value for men from Ukraine and Greenland. These outcomes suggest that cadmium may impair prostate function, as measured by PSA in semen, while high zinc levels and a low number of CAG repeats protects against this action.

In vitro exposure to the organochlorine p,p'-DDE affects functional human sperm parameters

Although no information exists regarding the levels of p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) on reproductive fluids of heavily exposed populations, they are possibly quite high given the serum levels reported so far. In these populations altered semen quality has been reported, although the direct effects of this DDT metabolite on crucial sperm parameters remain largely unexplored. With this in mind, a long-term in vitro incubation that better mimics the putative continuous exposure of spermatozoa to p,p'-DDE in the female reproductive tract in vivo was used. Before compromising sperm viability, continuous p,p'-DDE exposure remarkably decreased sperm motility, possibly due to the combined reduction in the proportion of sperm with high mitochondrial membrane potential and cellular ATP levels, all of which were clearly more affected at 50 and 100 μM p,p'-DDE. Moreover, 25 μM p,p'-DDE was also able to promote a decline in sperm with high MMP, however without significantly affecting motility. On the other hand, p,p'-DDE at the highest concentration strongly inhibited the process of capacitation following 24h of incubation. In conclusion, human sperm function is affected by continuous high p,p'-DDE exposure which may ultimately compromise male fertility. Given our previously findings that showed a non-regulated Ca(2+) entry in the presence of p,p'-DDE, we suggest that this organochlorine may promote mitochondrial Ca(2+) overload which may culminate in a general mitochondrial dysfunction and cellular ATP depletion, thus affecting sperm fertilizing potential. Our findings suggest a broader understanding of the non-genomic mechanism of p,p'-DDE action in human sperm.

In utero exposure to persistent organochlorine pollutants and reproductive health in the human male

Persistent organochlorine pollutants (POPs) are ubiquitous, bioaccumulative compounds with potential endocrine-disrupting effects. They cross the placental barrier thereby resulting in in utero exposure of the developing fetus. The objective of this study was to investigate whether maternal serum concentrations of polychlorinated biphenyls (PCBs) and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) during pregnancy are associated with son's semen quality and reproductive hormone levels. During 2008-2009, we recruited 176 male offspring from a Danish cohort of pregnant women who participated in a study in 1988-1989. Each provided semen and blood samples that were analyzed for sperm concentration, total sperm count, motility, and morphology, and reproductive hormone levels, respectively. The maternal blood samples were collected in pregnancy week 30 and were analyzed for the concentrations of six PCBs (PCB-118, -138, -153, -156, -170, and -180) and p,p'-DDE. The potential associations between in utero exposure to ΣPCBs (pmol/ml), Σdioxin like-(DL) PCBs (PCB-118 and -156) (pmol/ml), and p,p'-DDE and semen quality and reproductive hormone levels were investigated using multiple regression. Maternal median (range) exposure levels of ΣPCB, ΣDL-PCB, and p,p'-DDE were 10.0 (2.1-35.0) pmol/ml, 0.8 (0.2-2.7) pmol/ml, and 8.0 (0.7-55.3) pmol/ml, respectively, reflecting typical background exposure levels in the late 1980s in Denmark. Results suggested that in utero exposure to ΣPCB, ΣDL-PCB, and p,p'-DDE was not statistically significantly associated with semen quality measures or reproductive hormone levels. Thus, results based on maternal PCB and p,p'-DDE concentrations alone are not indicative of long-term consequences for male reproductive health; however, we cannot exclude that these POPs in concert with other endocrine-modulating compounds may have adverse effects.

Persistent organic pollutants and male reproductive health

Environmental contaminants such as persistent organic pollutants (POPs) are man-made bioaccumulative compounds with long half-lives that are found throughout the world as a result of heavy use in a variety of consumer products during the twentieth century. Wildlife and animal studies have long suggested adverse effects of exposure to these compounds on human reproductive health, which, according to the endocrine disrupter hypothesis, are ascribed to the compounds’ potential to interfere with endocrine signaling, especially when exposure occurs during certain phases of fetal and childhood development. An extensive number of epidemiological studies have addressed the possible effects of exposure to POPs on male reproductive health, but the results are conflicting. Thus far, most studies have focused on investigating exposure and the different reproductive health outcomes during adulthood. Some studies have addressed the potential harmful effects of fetal exposure with respect to malformations at birth and/or reproductive development, whereas only a few studies have been able to evaluate whether intrauterine exposure to POPs has long-term consequences for male reproductive health with measurable effects on semen quality markers and reproductive hormone levels in adulthood. Humans are not exposed to a single compound at a time, but rather, to a variety of different substances with potential divergent hormonal effects. Hence, how to best analyze epidemiological data on combined exposures remains a significant challenge. This review on POPs will focus on current knowledge regarding the potential effects of exposure to POPs during fetal and childhood life and during adulthood on male reproductive health, including a critical revision of the endocrine disruption hypothesis, a comment on pubertal development as part of reproductive development and a comment on how to account for combined exposures in epidemiological research.

Association between environmental exposure to p, p'-DDE and lindane and semen quality

Scientific concern exists about the toxic effect of dichlorodiphenyldichloroethylene (p, p'-DDE) and lindane on male infertility, and the mechanism underlying male reproductive toxicity of this pesticide remains unanswered. We investigated not only the possible association between the chlorinated pesticide levels and semen quality in nonoccupationally exposed men, but also the probable mode of action using mitochondrial membrane potential (MMP), reactive oxygen species (ROS), lipid peroxidation (LPO), and sperm chromatin structure assay (SCSA). A study in 278 men (21-40 years old) who visited Obstetrics and Gynecology Department, KGMU, Lucknow, for semen analysis was conducted. We performed semen analysis according to the WHO guidelines, while p, p'-DDE and lindane analysis was done by the GLC and LPO by the spectrophotometer, and the sperm mitochondrial status, ROS, and SCSA with the flow cytometer. The questionnaire data showed no significant difference in the demographic characteristics between the two groups, i.e., trying to conceive >1 year and proven fertility. However, a significant difference in the concentration of p, p'-DDE and lindane was observed between the groups. When the subjects were divided among four categories by quartile of exposure, the subjects in the highest quartile showed low sperm motility as compared to the subjects in the lowest quartile. Pearson's correlation showed a significant negative correlation between semen p, p'-DDE, lindane level, and sperm quality and positive association with the number of cells with depolarized mitochondria, elevation in ROS production and LPO, and DNA fragmentation index (DFI). The findings are suggestive that these toxicants might cause a decline in semen quality, and these effects might be ROS, LPO, and mitochondrial dysfunction mediated.

Exposure to perfluoroalkyl substances and sperm DNA global methylation in Arctic and European populations

Perfluoroalkyl substances (PFASs) are widely used in a variety of industrial processes and products, and have been detected globally in humans and wildlife. PFASs are suspected to interfere with endocrine signaling and to adversely affect human reproductive health. The aim of the present study was to investigate the associations between exposure to PFASs and sperm global methylation levels in a population of non-occupationally exposed fertile men. Measurements of PFASs in serum from 262 partners of pregnant women from Greenland, Poland and Ukraine, were also carried out by liquid chromatography tandem mass spectrometry. Perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) were detected in 97% of the blood samples. Two surrogate markers were used to assess DNA global methylation levels in semen samples from the same men: (a) average DNA methylation level in repetitive DNA sequences (Alu, LINE-1, Satα) quantified by PCR-pyrosequencing after bisulfite conversion; (b) flow cytometric immunodetection of 5-methyl-cytosines. After multivariate linear regression analysis, no major consistent associations between PFASs exposure and sperm DNA global methylation endpoints could be detected. However, since weak but statistically significant associations of different PFASs with DNA hypo- and hyper-methylation were found in some of the studied populations, effects of PFASs on sperm epigenetic processes cannot be completely excluded, and this issue warrants further investigation.

Exposure to endocrine disrupting chemicals and male reproductive health

Endocrine disrupting chemicals (EDCs) can interfere with normal hormonal balance and may exert adverse consequences on humans. The male reproductive system may be susceptible to the effects of such environmental toxicants. This review discusses the recent progress in scientific data mainly from epidemiology studies on the associations between EDCs and male reproductive health and our understanding of possible mechanisms associated with the effects of EDCs on male reproductive health. Finally, the review provides recommendations on future research to enhance our understanding of EDCs and male reproductive health. The review highlights the need for (1) well-defined longitudinal epidemiology studies, with appropriately designed exposure assessment to determine potential causal relationships; (2) chemical and biochemical approaches aimed at a better understanding of the mechanism of action of xenoestrogens with regard to low-dose effects, and assessment of identify genetic susceptibility factors associated with the risk of adverse effects following exposure to EDCs.

In vitro exposure of Leydig cells to an environmentally relevant mixture of organochlorines represses early steps of steroidogenesis

Leydig cell steroidogenesis is mainly regulated by LH via increased cAMP production leading to STAR protein activation. STAR is essential for cholesterol shuttling inside mitochondria where steroidogenesis is initiated. Accumulating evidence suggest that persistent organochlorine compounds disrupt testicular function, but the mechanism of action remains poorly characterized. Here we report that in vitro exposure of MA-10 and MLTC-1 Leydig cells to an environmentally relevant mixture of 15 organochlorines impairs steroidogenesis. While having no effect on cell viability and basal steroid production, the organochlorine mixture caused a 50% decrease in cAMP-induced progesterone production. The mixture also reduced cAMP-induced 30 kDa STAR protein by 50% while having no effect on basal STAR protein. Basal or cAMP-induced Star mRNA levels and promoter activity were unaffected by the mixture, indicating that the organochlorine mixture acted at the translational/posttranslational level. Further supporting this is the fact that in COS-7 cells overexpressing STAR, the organochlorine mixture caused a decrease in the 30 kDa form of STAR and an accumulation of the 37 kDa forms. In addition to STAR, we found that the organochlorine mixture also decreases the levels of CYP11A1 and ADXR, two proteins essential for the conversion of cholesterol into pregnenolone. In conclusion, our data show that organochlorine exposure disrupts Leydig cell function by targeting different components of the steroidogenic pathway.

Relationships of polychlorinated biphenyls and dichlorodiphenyldichloroethylene (p,p'-DDE) with testosterone levels in adolescent males

BACKGROUND

Concern persists over endocrine-disrupting effects of persistent organic pollutants (POPs) on human growth and sexual maturation. Potential effects of toxicant exposures on testosterone levels during puberty are not well characterized.

OBJECTIVES

In this study we evaluated the relationship between toxicants [polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p´-DDE), hexachlorobenzene (HCB), and lead] and testosterone levels among 127 Akwesasne Mohawk males 10 to < 17 years of age with documented toxicant exposures.

METHODS

Data were collected between February 1996 and January 2000. Fasting blood specimens were collected before breakfast by trained Akwesasne Mohawk staff. Multivariable regression models were used to estimates associations between toxicants and serum testosterone, adjusted for other toxicants, Tanner stage, and potential confounders.

RESULTS

The sum of 16 PCB congeners (Σ16PCBs) that were detected in ≥ 50% of the population was significantly and negatively associated with serum testosterone levels, such that a 10% change in exposure was associated with a 5.6% decrease in testosterone (95% CI: -10.8, -0.5%). Of the 16 congeners, the more persistent ones (Σ8PerPCBs) were related to testosterone, whereas the less persistent ones, possibly reflecting more recent exposure, were not. When PCB congeners were subgrouped, the association was significant for the sum of eight more persistent PCBs (5.7% decrease; 95% CI: -11, -0.4%), and stronger than the sum of six less persistent congeners (3.1% decrease; 95% CI: -7.2, 0.9%). p,p´-DDE was positively but not significantly associated with serum testosterone (5.2% increase with a 10% increase in exposure; 95% CI: -0.5, 10.9%). Neither lead nor HCB was significantly associated with testosterone levels.

CONCLUSIONS

Exposure to PCBs, particularly the more highly persistent congeners, may negatively influence testosterone levels among adolescent males. The positive relationship between p,p´-DDE and testosterone indicates that not all POPs act similarly.

CITATION

Schell LM, Gallo MV, Deane GD, Nelder KR, DeCaprio AP, Jacobs A; Akwesasne Task Force on the Environment. 2014. Relationships of polychlorinated biphenyls and dichlorodiphenyldichloroethylene (p,p´-DDE) with testosterone levels in adolescent males. Environ Health Perspect 122:304-309; http://dx.doi.org/10.1289/ehp.1205984.

Evaluating the effectiveness of fish consumption advisories: modeling prenatal, postnatal, and childhood exposures to persistent organic pollutants

BACKGROUND

Because human exposure to persistent organic pollutants (POPs) occurs mainly through ingestion of contaminated food, regulatory bodies issue dietary consumption advisories to describe safe intake levels for food items of concern, particularly fish.

OBJECTIVES

Our study goal was to estimate the effectiveness of fish consumption advisories in reducing exposure of infants and children to POPs.

METHODS

We used the time-variant mechanistic model CoZMoMAN to estimate and compare prenatal, postnatal, and childhood exposure to polychlorinated biphenyl congener PCB-153 under different scenarios of maternal guideline adherence for both hypothetical constant and realistic time-variant chemical emissions. The scenarios differed in terms of length of compliance (1 vs. 5 years), extent of fish substitution (all vs. half), and replacement diet (uncontaminated produce vs. beef). We also estimated potential exposure reductions for a range of theoretical chemicals to explore how guideline effectiveness varies with a chemical's partitioning and degradation properties.

RESULTS

When assuming realistic time periods of advisory compliance, our findings suggest that temporarily eliminating or reducing maternal fish consumption is largely ineffective in reducing pre- and postnatal exposure to substances with long elimination half-lives in humans, especially during periods of decreasing environmental emissions. Substituting fish with beef may actually result in higher exposure to certain groups of environmental contaminants. On the other hand, advisories may be highly effective in reducing exposure to substances with elimination half-lives in humans shorter than the length of compliance.

CONCLUSIONS

Our model estimates suggest that fish consumption advisories are unlikely to be effective in reducing prenatal, postnatal, and childhood exposures to compounds with long elimination half-lives in humans.

Semen quality of environmentally exposed human population: the toxicological consequence

Human data on the relationship of semen quality with pesticide and metals are mostly inconsistent. The purpose of the study is to confirm the toxicity of organochlorine pesticide β- and γ-hexachlorocyclohexane (HCH), DDE and DDD, and metals lead or cadmium on sperm motility in epidemiological study among fertile and infertile men and to determine whether in vivo and in vitro results are in the same direction. Semen analysis and estimation of the toxicants were done in 60 fertile and 150 infertile men. In the in vitro studies, sperm were exposed to the highest levels of these toxicants found in vivo, as well as five and ten times higher, and to the mixture of all compounds. The study assesses sperm viability and motility for a period ranging between 30 min and 96 h. Epidemiological data showed an inverse correlation of toxicant with sperm motility. In vitro study showed that γ-HCH and lead after 12 h, cadmium after 8 h, and coexposure to toxicants after 6 h of exposure caused significant concentration- and duration-dependent decline in sperm motility. Data of in vitro study were concurrent with epidemiological finding that might be useful in establishing the possible association between exposure and effect of these selected pollutants on sperm motility.

p,p'-DDE activates CatSper and compromises human sperm function at environmentally relevant concentrations

STUDY QUESTION

Is the environmental endocrine disruptor p,p′-dichlorodiphenyldichloroethylene (p,p′-DDE) able to induce non-genomic changes in human sperm and consequently affect functional sperm parameters?

SUMMARY ANSWER

p,p′-DDE promoted Ca²⁺ flux into human sperm by activating CatSper channels even at doses found in human reproductive fluids, ultimately compromising sperm parameters important for fertilization.

WHAT IS KNOWN ALREADY

p,p′-DDE may promote non-genomic actions and interact directly with pre-existing signaling pathways, as already observed in other cell types. However, although often found in both male and female reproductive fluids, its effects on human spermatozoa function are not known.

STUDY DESIGN, SIZE, DURATION

Normozoospermic sperm samples from healthy individuals were included in this study. Samples were exposed to several p,p′-DDE concentrations for 3 days at 37°C and 5% CO₂in vitro to mimic the putative continuous exposure to this toxicant in the female reproductive tract in vivo. Shorter p,p′-DDE incubation periods were also performed in order to monitor sperm rapid Ca²⁺ responses. All experiments were repeated on a minimum of five sperm samples from different individuals.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All healthy individuals were recruited at the Biosciences School, University of Birmingham, the Medical Research Institute, University of Dundee and in the Human Reproduction Service at University Hospitals of Coimbra. Intracellular Ca²⁺ concentration ([Ca²⁺]_i) was monitored by imaging single spermatozoa loaded with Oregon Green BAPTA-1AM and further whole-cell patch-clamp recordings were performed to validate our results. Sperm viability and acrosomal integrity were assessed using the LIVE/DEAD sperm vitality kit and the acrosomal content marker PSA-FITC, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE

p,p′-DDE rapidly increased [Ca²⁺]_i (P < 0.05) even at extremely low doses (1 pM and 1 nM), with magnitudes of response up to 200%, without affecting sperm viability, except after 3 days of continuous exposure to the highest concentration tested (P < 0.05). Furthermore, experiments performed in a low Ca²⁺ medium demonstrated that extracellular Ca²⁺ influx was responsible for this Ca²⁺ increase (P < 0.01). Mibefradil and NNC 55-0396, both inhibitors of the sperm-specific CatSper channel, reversed the p,p′-DDE-induced [Ca²⁺]_i rise, suggesting the participation of CatSper in this process (P < 0.05). In fact, whole-cell patch-clamp recordings confirmed CatSper as a target of p,p′-DDE action by monitoring an increase in CatSper currents of >100% (P < 0.01). Finally, acrosomal integrity was adversely affected after 2 days of exposure to p,p′-DDE concentrations, suggesting that [Ca²⁺]_i rise may cause premature acrosome reaction (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

This is an in vitro study, and caution must be taken when extrapolating the results.

WIDER IMPLICATIONS OF THE FINDINGS

A novel non-genomic p,p′-DDE mechanism specific to sperm is shown in this study. p,p′-DDE was able to induce [Ca²⁺]_i rise in human sperm through the opening of CatSper consequently compromising male fertility. The promiscuous nature of CatSper activation may predispose human sperm to the action of some persistent endocrine disruptors.

STUDY FUNDING/COMPETING INTEREST(S)

The study was supported by both the Portuguese National Science Foundation (FCT; PEst-C/SAU/LA0001/2011) and the UK Wellcome Trust (Grant #86470). SM was supported by the Infertility Research Trust. RST is a recipient of a PhD fellowship from FCT (SFRH/BD/46002/2008). None of the authors has any conflict of interest to declare.

Environmental mercury exposure, semen quality and reproductive hormones in Greenlandic Inuit and European men: a cross-sectional study

Several animal studies indicate that mercury is a male reproductive toxicant, but human studies are few and contradictory. We examined semen characteristics and serum levels of reproductive hormones in relation to environmental exposure to mercury. Blood and semen samples were collected from 529 male partners of pregnant women living in Greenland, Poland and Ukraine between May 2002 and February 2004. The median concentration of the total content of mercury in whole blood was 9.2 ng ml(-1) in Greenland (0.2-385.8 ng ml(-1)), 1.0 ng ml(-1) in Poland (0.2-6.4 ng ml(-1)) and 1.0 ng ml(-1) in Ukraine (0.2-4.9 ng ml(-1)). We found a significantly positive association between the blood levels of mercury and serum concentration of inhibin B in men from Greenland (β=0.074, 95% confidence interval (CI)=0.021 to 0.126) and in an analysis including men from all three regions (β=0.067, 95% CI=0.024 to 0.110). The association may be due to beneficial effects of polyunsaturated fatty acids (PUFAs), which are contained in seafood and fish. No significant association (P>0.05) was found between blood concentrations of mercury and any of the other measured semen characteristics (semen volume, total sperm count, sperm concentration, morphology and motility) and reproductive hormones (free androgen index (FAI), follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone and LH × testosterone) in any region. In conclusion, the findings do not provide evidence that environmental mercury exposure in Greenlandic and European men with median whole blood concentration up to 10 ng ml(-1) has adverse effects on biomarkers of male reproductive health.

Phthalates exposure of Chinese reproductive age couples and its effect on male semen quality, a primary study

Phthalates are suspected of having adverse effects on androgen-regulated reproductive development in animals and may be toxic for human sperm. The purposes of our study were to investigate the general exposure of a Chinese reproductive age cohort to these ubiquitous pollutants and to assess their potential effect on semen quality. Six phthalate metabolites, monomethyl phthalate (MMP), monoethyl phthalate (MEP), monobutyl phthalate (MBP), monobenzyl phthalate (MBzP), mono-2-ethylhexyl phthalate (MEHP), and mono-2-ethyl-5-oxohexyl phthalate (MEOHP) were measured in spot urines of 150 individuals recruited from a Chongqing, China, reproductive institute. The questionnaire and clinical data were evaluated, and the correlations of phthalate exposure and semen qualities like semen volume, sperm concentration, motility and sperm motion parameters, were determined by multiple logistic regression analysis. The creatinine adjusted average concentrations for MMP, MEP, MBP, MBzP, MEHP and MEOHP were 41.3, 300, 41.0, 0.78, 2.99 and 3.90 μg/g, respectively. After adjustment for age, body mass index (BMI), abstinence, smoking, drinking, and education, there was a borderline-significant dose-response relationship between MBP and sperm concentration, with odd ratios (ORs) 1.0, 6.8 and 12.0 for increasing exposure tertiles (p=0.05). Although the dose-response relationships for MMP and MEP versus sperm concentration were not significant, a significant positive correlation between MEP and straight-line velocity of sperm motion was observed. The present data may imply some effects of phthalate exposure on semen. However, due to the small sample size, our finding needs to be confirmed on a larger population.