Regional differences and temporal trends in male reproductive health disorders: semen quality may be a sensitive marker of environmental exposures

Di-(2-ethylhexyl) phthalate (DEHP)-induced testicular toxicity through Nrf2-mediated Notch1 signaling pathway in Sprague-Dawley rats

Di-(2-ethylhexyl) phthalate (DEHP) is an environmental endocrine disruptor widely used in China that is harmful to the male reproductive system. Many studies have shown that DEHP causes testicular toxicity through oxidative stress, but the specific mechanism is unknown. Because the Notch pathway is a key mechanism for regulating cell growth and proliferation, we investigated whether Notch is involved in DEHP-induced testicular toxicity and whether vitamins E and C could rescue testicular impairment in Sprague-Dawley (SD) rats. Compared with the control group, we found that DEHP exposure induced testicular toxicity through oxidative stress injury, and it decreased the testosterone level (P < .01) and upregulated nuclear factor-erythroid 2 related factor (Nrf2) expression (P < .01). Therefore, because oxidative stress might be the initiating factor of DEHP-induced testicular toxicity, treatment with the antioxidant vitamins E and C activated the Notch1 signaling pathway in the testis and in Leydig cells. Treatment with vitamins E and C normalized the oxidative stress state after DEHP exposure and restored testicular development to be similar to the control group. In summary, antioxidant vitamins E and C may be used to treat DEHP-induced testicular toxicity.

Vitamin E and vitamin C attenuate Di-(2-ethylhexyl) phthalate-induced blood-testis barrier disruption by p38 MAPK in immature SD rats

As an environmental endocrine disruptor, Di-(2-ethylhexyl) phthalate (DEHP) affects blood-testis barrier (BTB)-associated proteins expression, which compromises BTB integrity and causes infertility. Notably, DEHP-induced testicular toxicity is related to oxidative stress, but the specific mechanism remains unclear. Therefore, we sought to investigate this mechanism and determine whether vitamin C and vitamin E administration would attenuate the BTB impairment induced by DEHP in vivo and by Mono-(2-Ethylhexyl) Phthalate (MEHP) in vitro, respectively. HE staining and EM found that DEHP exposure led to spermatogenesis dysfunction and BTB disruption, respectively. The Western blot and immunofluorescence results showed that DEHP exposure caused BTB impairment through oxidative stress-mediated p38 mitogen-activated protein kinase (MAPK) signaling pathway. Furthermore, Vitamin E and vitamin C could alleviate the oxidative stress, block DEHP-induced spermatogenesis dysfunction and BTB disruption by inhibiting p38 MAPK signaling pathway. In summary, vitamin E and vitamin C are good candidates for the treatment of DEHP-induced male infertility.

Current Knowledge on Endocrine Disrupting Chemicals (EDCs) from Animal Biology to Humans, from Pregnancy to Adulthood: Highlights from a National Italian Meeting

Wildlife has often presented and suggested the effects of endocrine disrupting chemicals (EDCs). Animal studies have given us an important opportunity to understand the mechanisms of action of many chemicals on the endocrine system and on neurodevelopment and behaviour, and to evaluate the effects of doses, time and duration of exposure. Although results are sometimes conflicting because of confounding factors, epidemiological studies in humans suggest effects of EDCs on prenatal growth, thyroid function, glucose metabolism and obesity, puberty, fertility, and on carcinogenesis mainly through epigenetic mechanisms. This manuscript reviews the reports of a multidisciplinary national meeting on this topic.

Endocrine disrupting chemicals and impact on male reproductive health

Endocrine disrupting chemicals (EDCs) have been known to adversely affect the endocrine system leading to compromised functions of hormones. The presence of these compounds in everyday products such as canned food, water bottles, plastics, cosmetics, fertilizers, kid’s toys and many others goods is a greater concern for general population. The persistent and long-term use of EDCs has deleterious effects on human reproductive health by interfering with the synthesis and mechanism of action of sex hormones. Any change during the synthesis or action of the sex hormones may result in abnormal reproductive functions which includes developmental anomalies in the reproductive tract and decline in semen quality. The present paper provides an overview of the EDCs and their possible impact on male reproductive health with major focus on semen quality which leads to male infertility.

Temporal trends in sperm count: a systematic review and meta-regression analysis

BACKGROUND

Reported declines in sperm counts remain controversial today and recent trends are unknown. A definitive meta-analysis is critical given the predictive value of sperm count for fertility, morbidity and mortality.

OBJECTIVE AND RATIONALE

To provide a systematic review and meta-regression analysis of recent trends in sperm counts as measured by sperm concentration (SC) and total sperm count (TSC), and their modification by fertility and geographic group.

SEARCH METHODS

PubMed/MEDLINE and EMBASE were searched for English language studies of human SC published in 1981-2013. Following a predefined protocol 7518 abstracts were screened and 2510 full articles reporting primary data on SC were reviewed. A total of 244 estimates of SC and TSC from 185 studies of 42 935 men who provided semen samples in 1973-2011 were extracted for meta-regression analysis, as well as information on years of sample collection and covariates [fertility group ('Unselected by fertility' versus 'Fertile'), geographic group ('Western', including North America, Europe Australia and New Zealand versus 'Other', including South America, Asia and Africa), age, ejaculation abstinence time, semen collection method, method of measuring SC and semen volume, exclusion criteria and indicators of completeness of covariate data]. The slopes of SC and TSC were estimated as functions of sample collection year using both simple linear regression and weighted meta-regression models and the latter were adjusted for pre-determined covariates and modification by fertility and geographic group. Assumptions were examined using multiple sensitivity analyses and nonlinear models.

OUTCOMES

SC declined significantly between 1973 and 2011 (slope in unadjusted simple regression models -0.70 million/ml/year; 95% CI: -0.72 to -0.69; P < 0.001; slope in adjusted meta-regression models = -0.64; -1.06 to -0.22; P = 0.003). The slopes in the meta-regression model were modified by fertility (P for interaction = 0.064) and geographic group (P for interaction = 0.027). There was a significant decline in SC between 1973 and 2011 among Unselected Western (-1.38; -2.02 to -0.74; P < 0.001) and among Fertile Western (-0.68; -1.31 to -0.05; P = 0.033), while no significant trends were seen among Unselected Other and Fertile Other. Among Unselected Western studies, the mean SC declined, on average, 1.4% per year with an overall decline of 52.4% between 1973 and 2011. Trends for TSC and SC were similar, with a steep decline among Unselected Western (-5.33 million/year, -7.56 to -3.11; P < 0.001), corresponding to an average decline in mean TSC of 1.6% per year and overall decline of 59.3%. Results changed minimally in multiple sensitivity analyses, and there was no statistical support for the use of a nonlinear model. In a model restricted to data post-1995, the slope both for SC and TSC among Unselected Western was similar to that for the entire period (-2.06 million/ml, -3.38 to -0.74; P = 0.004 and -8.12 million, -13.73 to -2.51, P = 0.006, respectively).

WIDER IMPLICATIONS

This comprehensive meta-regression analysis reports a significant decline in sperm counts (as measured by SC and TSC) between 1973 and 2011, driven by a 50-60% decline among men unselected by fertility from North America, Europe, Australia and New Zealand. Because of the significant public health implications of these results, research on the causes of this continuing decline is urgently needed.

Male infertility among bakers associated with exposure to high environmental temperature at the workplace

Objective

This study aimed to evaluate the prevalence of male infertility among bakers exposed to high environmental temperature.

Methods

This cross-sectional study was conducted to obtain information using a validated questionnaire administered through an interview. The mean wet bulb globe temperature (WBGT) index in the bakeries was measured. A new statistical formula was used to estimate the prevalence of infertility among bakers.

Results

A total of 137 bakers working in 20 bakeries and 107 individuals included in the comparable control group with variations in age, race, marital status, and income and with history of cigarette smoking were recruited. Using a newly devised formula, the prevalence of infertility among the exposed group was 22.7%, compared with 3.0% in the control group (p = 0.013). All possible confounding factors associated with infertility among bakers were excluded such as cigarette smoking, age, and race. There were unfavorable hot working conditions in bakeries, with a WBGT index of 37.4 °C, while the average WBGT for offices was 25.5 °C (p < 0.0001).

Conclusion

Our study showed that the rate of infertility among bakers was high, which resulted from exposure to high environmental temperature at the workplace as evidenced by the WBGT index. This finding should alert the healthcare authorities to take necessary measures under the labor code to curtail infertility among bakers.

Smoke, alcohol and drug addiction and male fertility

In recent decades, the decline in human fertility has become increasingly more worrying: while therapeutic interventions might help, they are vexing for the couple and often burdened with high failure rates and costs. Prevention is the most successful approach to fertility disorders in males and females alike. We performed a literature review on three of the most common unhealthy habits - tobacco, alcohol and drug addiction - and their reported effects on male fertility. Tobacco smoking is remarkably common in most first-world countries; despite a progressive decline in the US, recent reports suggest a prevalence of more than 30% in subjects of reproductive age - a disturbing perspective, given the well-known ill-effects on reproductive and sexual function as well as general health. Alcohol consumption is often considered socially acceptable, but its negative effects on gonadal function have been consistently reported in the last 30 years. Several studies have reported a variety of negative effects on male fertility following drug abuse - a worrying phenomenon, as illicit drug consumption is on the rise, most notably in younger subjects. While evidence in these regards is still far from solid, mostly as a result of several confounding factors, it is safe to assume that cessation of tobacco smoking, alcohol consumption and recreational drug addiction might represent the best course of action for any couple trying to achieve pregnancy.

Diethylstilbestrol regulates mouse gubernaculum testis cell proliferation via PLC-Ca2+ -CREB pathway

Recent evidence suggested a positive correlation between environmental estrogens (EEs) and high incidence of abnormalities in male urogenital system, but the mechanism remains unclear. Diethylstilbestrol (DES) is a nonsteroidal synthetic estrogen that disrupts the morphology and proliferation of gubernaculum testis cells, but the underlying mechanism is unclear. In this study, mouse gubernaculum testis cells were pretreated with phospholipase C (PLC) inhibitor U-73122 and then treated with DES. The results demonstrated that U-73122 impaired DES-evoked intracellular Ca2+ mobilization in gubernaculum testis cells and inhibited DES-induced proliferation of gubernaculum testis cells. Mechanistically, we found that U-73122 inhibited DES-induced activation of cAMP-response element binding protein (CREB) in gubernaculum testis cells. In conclusion, these data suggest that the effects of DES on mouse gubernaculum testis cells are mediated by PLC-Ca²⁺ -CREB pathway.

SIGNIFICANCE OF THE STUDY

Environmental estrogens remain a serious threat to male reproductive health, and it is important to understand the mechanism by which EEs affect the male productive system. Here we explore potential mechanisms how the proliferation and contractility of gubernaculum testis cells are regulated by diethylstilbestrol. Our findings provide the first evidence that PLC-Ca²⁺ -CREB signalling pathway mediates the nongenomic effects of diethylstilbestrol on gubernaculum testis cells. These findings provide new insight into the role of diethylstilbestrol in the aetiology of male reproductive dysfunction and will help develop better approaches for the prevention and therapy of male reproductive malformation.

[Effect of Di-(2-ethylhcxyl) phthalate exposure on blood-testis barrier integrity in rats]

OBJECTIVE

To investigate mechanism of di-(2-ethylhcxyl)phthalate (DEHP) exposure in causing blood-testis barrier (BTB) impairment in rats.

METHODS

Two-months-old male SD rats were randomly divided into corn oil control group and DEHP (750 mg/kg) exposure group for daily intragastic treatment for 30 consecutive days. After the treatments the rats were examined for histomorphological changes of the testicle using HE staining and the expressions of the junction proteins N-cadherin β-catenin, occludin and connexin43 of the BTB using Western blot. In the in vitro study, the vitality and ROS generation level in Sertoli cells exposed to different concentrations of DEHP were examined with MTT and ROS assay kits, respectively, and Nrf2 and p-p38 expressions were detected with Western blot.

RESULTS

Compared with the control group, the rats with DEHP exposure showed structural damage of the seminiferous tubule and polarity loss of the spermatids. DEHP exposure caused significantly decreased expressions of occludin and connexin43 but increased expressions of N-cadherin and β-catenin in the testicle tissues of the rats (P<0.05). The vitality of Sertoli cells was obviously decreased and ROS level increased significantly after exposure of the cells to increasing concentrations of DEHP, which also resulted in significantly up-regulated Nrf2 and p-p38 expressions (P<0.05).

CONCLUSIONS

DEHP exposure causes increased oxidative stress in the Sertoli cells of the testis, activates p38 MAPK signaling pathway, and results eventually in impaired spermatogenesis in rats.

Aluminum exposure for 60days at human dietary levels impairs spermatogenesis and sperm quality in rats

Concerns about environmental aluminum (Al) and reproductive health have been raised. We investigated the effects of Al exposure at a human relevant dietary level and a high level exposure to Al. Experiment 1 (Lower level) rats were treated orally for 60 days: a) controls - ultrapure water; b) aluminum at 1.5mg/kg bw/day and c) aluminum at 8.3mg/kg bw/day. Experiment 2 (High level) rats were treated for 42 days: a) controls - ultrapure water; b) aluminum at 100mg/kg bw/day. Al decreased sperm count, daily sperm production, sperm motility, normal morphological sperm, impaired testis histology; increased oxidative stress in reproductive organs and inflammation in testis. Our study shows the specific presence of Al in the germinative cells and, that low concentrations of Al in testes (3.35μg/g) are sufficient to impair spermatogenesis and sperm quality. Our findings provide a better understanding of the reproductive health risk of Al.

The environment and male reproduction: The effect of cadmium exposure on reproductive function and its implication in fertility

Cadmium is an environmental pollutant known as endocrine disruptor. Testis is particularly susceptible to cadmium, and testis injury occurs at high but even low levels of exposure. Cadmium reproductive toxicity is mediated by multiple mechanisms, including structural damage to testis vasculature and blood-testis barrier, inflammation, cytotoxicity on Sertoli and Leydig cells, oxidative stress mainly by means of mimicry and interference with essential ions, apoptosis, interference with selected signaling pathways and epigenetic regulation of genes involved in the regulation of reproductive function, and disturbance of the hypothalamus-pituitary-gonadal axis. The current review outlines epidemiological observational findings from environmental and occupational exposure in humans, and reports experimental studies in humans and animals. Lastly, a focus on the pathogenetic mechanisms of cadmium toxicity and on the specific mechanisms of cadmium sensitivity and resistance, particularly assessed in animal models, is included. Despite convincing experimental findings in animals and supporting evidences in humans identifying cadmium as reproductive toxicant, observational findings are controversial, suffering from heterogeneity of study design and pattern of exposure, and from co-exposure to multiple pollutants.

Phthalates and heavy metals as endocrine disruptors in food: A study on pre-packed coffee products

Phthalate plasticizers and heavy metals are widely recognized to be pollutants that interfere with key developmental processes such as masculinization. We investigated the release of phthalates and heavy metals in coffee brewed from coffee packed in single-serve coffee containers made from different types of materials: metal, biodegradable and plastics. We detected with GC-MS small amounts phthalates, below the tolerated daily risks levels, in all the coffees prepared from the different types of capsules. Specifically, Di (2-ethyl-hexyl)-phthalate and DiBP: Diisobuthyl-pthalate were ubiquitously present despite the high variability among the samples (respective range 0.16-1.87 μg/mL and 0.01-0.36 μg/mL). Whereas, diethyl-phthalate (range 0.20-0.26 μg/mL) and di-n-buthyl-phthalate (range 0.02-0.14 μg/mL) were detected respectively in one and three out of the four types of capsule tested. In contrast, we detected by atomic mass spectrometry on mineralized samples heavy metals lead (Pb) and nickel (Ni), in all coffee tested. PB levels (respective range 0.32-211.57 μg/dose) accounted for 42-79%, whereas Ni levels (respective range 166.25-1950.26 μg/dose) accounted for >100% of the tolerable daily intake. These results add to the already present concerns related to the multiple pathways of human exposure and the ubiquitous presence of these pollutants in consumer products and their long-term effect on human health.

Endocrine-disrupting chemicals-Mechanisms of action on male reproductive system

Endocrine-disrupting chemicals (EDCs) are exogenous compounds that can cause disturbances in the endocrine system and have multiple harmful effects on health by targeting different organs and systems in the human body. Mass industrial production and widespread use of EDCs have resulted in worldwide contamination. Accumulating evidence suggest that human exposure to EDCs is related to the impairment of male reproductive function and can interrupt other hormonally regulated metabolic processes, particularly if exposure occurs during early development. Investigation of studies absent in previous reviews and meta-analysis of adverse effects of EDCs on functioning of the male reproductive system is the core of this work. Four main modes of action of EDCs on male fertility have been summarized in this review. First, studies describing estrogen- pathway disturbing chemicals are investigated. Second, androgen-signaling pathway alterations and influence on androgen sensitive tissues are examined. Third, evaluation of steroidogenesis dysfunction is discussed by focusing on the steroid hormone biosynthesis pathway, which is targeted by EDCs. Last, the reportedly destructive role of reactive oxygen species (ROS) on sperm function is discussed. Spermatogenesis is a remarkably complex process, hence multiple studies point out various dysfunctions depending on the development state at which the exposure occurred. Collected data show the need to account for critical windows of exposure such as fetal, perinatal and pubertal periods as well as effects of mixtures of several compounds in future research.

Human exposure to endocrine disrupting chemicals: effects on the male and female reproductive systems

Endocrine disrupting chemicals (EDCs) comprise a group of chemical compounds that have been examined extensively due to the potential harmful effects in the health of human populations. During the past decades, particular focus has been given to the harmful effects of EDCs to the reproductive system. The estimation of human exposure to EDCs can be broadly categorized into occupational and environmental exposure, and has been a major challenge due to the structural diversity of the chemicals that are derived by many different sources at doses below the limit of detection used by conventional methodologies. Animal and in vitro studies have supported the conclusion that endocrine disrupting chemicals affect the hormone dependent pathways responsible for male and female gonadal development, either through direct interaction with hormone receptors or via epigenetic and cell-cycle regulatory modes of action. In human populations, the majority of the studies point towards an association between exposure to EDCs and male and/or female reproduction system disorders, such as infertility, endometriosis, breast cancer, testicular cancer, poor sperm quality and/or function. Despite promising discoveries, a causal relationship between the reproductive disorders and exposure to specific toxicants is yet to be established, due to the complexity of the clinical protocols used, the degree of occupational or environmental exposure, the determination of the variables measured and the sample size of the subjects examined. Future studies should focus on a uniform system of examining human populations with regard to the exposure to specific EDCs and the direct effect on the reproductive system.

EDCs Mixtures: A Stealthy Hazard for Human Health?

Endocrine disrupting chemicals (EDCs) are exogenous chemicals that may occur naturally (e.g., phytoestrogens), while others are industrial substances and plasticizers commonly utilized worldwide to which human exposure, particularly at low-doses, is omnipresent, persistent and occurs in complex mixtures. EDCs can interfere with/or mimic estrogenic hormones and, consequently, can simultaneously trigger diverse signaling pathways which result in diverse and divergent biological responses. Additionally, EDCs can also bioaccumulate in lipid compartments of the organism forming a mixed “body burden” of contaminants. Although the independent action of chemicals has been considered the main principle in EDCs mixture toxicity, recent studies have demonstrated that numerous effects cannot be predicted when analyzing single compounds independently. Co-exposure to these agents, particularly in critical windows of exposure, may induce hazardous health effects potentially associated with a complex “body burden” of different origins. Here, we performed an exhaustive review of the available literature regarding EDCs mixtures exposure, toxicity mechanisms and effects, particularly at the most vulnerable human life stages. Although the assessment of potential risks to human health due to exposure to EDCs mixtures is a major topic for consumer safety, information regarding effective mixtures effects is still scarce.

Risk of childhood mortality in family members of men with poor semen quality

STUDY QUESTION

What is the familial childhood mortality in first-degree (FDR) and second-degree relatives (SDR) of patients undergoing semen analysis (SA)?

SUMMARY ANSWER

The relationship between infertility and congenital malformations (CM) in offspring is complex, with an increased risk of death due to CM in FDR, but not SDR, of men with lower semen parameters.

WHAT IS KNOWN ALREADY

Semen quality is an established predictor of men's somatic health. We can gain a better understanding of possible genetic or environmental determinants of the infertility phenotype by exploring familial aggregation of childhood mortality in relatives of men with poor semen quality.

STUDY DESIGN, SIZE, DURATION

Retrospective cohort study from the Subfertility, Health and Assisted Reproduction study (cohort compiled 1996-2011) linked with patient/familial information from the Utah Population Database (UPDB). Index cases included a clinic-referred sample of 12 889 men who underwent SA and had adequate familial and follow-up data in the UPDB. Parameters of semen quality included: semen concentration, sperm count, motility, total motile count, sperm head morphology, sperm tail morphology and vitality.

PARTICIPANTS/MATERIALS, SETTING, METHODS

SA data were collected from two tertiary medical center andrology laboratories that have captured ~90% of all SA performed in Utah since 2004. Age- and sex-matched fertile controls were selected to create the comparison group for determining risk of childhood death (to age 20 years) in family members. A total of 79 750 siblings and 160 016 aunts/uncles were used to investigate the familial aggregation of childhood mortality. The main outcome was childhood mortality in FDR and SDR of men with SA and their matched controls. All-cause and cause-specific Cox proportional hazard models were used to test the association between semen quality and childhood mortality in family members. Cause-specific models were considered for cancer and CM.

MAIN RESULTS AND THE ROLE OF CHANCE

In the cohort of men with SA, there were 406 (1.0%) deaths in FDR and 772 (1.1%) deaths in SDR due to any cause. There was no significant difference in the risk of all-cause childhood mortality between the relatives of men with SA and the fertile control group [hazard ratio (HR)_Female = 1.08, 95% CI = 0.88, 1.32; HR_Male = 0.88, 95% CI = 0.75, 1.04]. We found no association between semen quality and risk for childhood cancer mortality in FDR or SDR (HR_FDR = 0.98, 95% CI = 0.62, 1.54; HR_SDR = 1.12, 95% CI = 0.83, 1.50). The FDR of men with SA and fertile controls were followed on average for 19.71 and 19.73 years, respectively. During this period of follow-up, FDR of men with SA had an unadjusted 40% relative risk of increased CM-related death. After stratifying by semen parameters and adjusting for birth year, we found FDR of men with worse semen quality, and notably azoospermic men (HR = 2.69, 95% CI = 1.24,5.84), were at higher risk of CM-related death.

LIMITATIONS REASONS FOR CAUTION

A large proportion of men with SA in the study had normal semen parameters. It is important to note that these men themselves may not be subfertile, but they were subfertile at the couple level (i.e. the female partner may be infertile). In addition, care is needed when interpreting our results, as we do not have semen measures on our sample of fertile men. Second, we were unable to include potential confounders such as medical comorbidities, smoking status, or environmental exposures. Third, men with SA were seen at the University of Utah or Intermountain Health Care clinics for a fertility evaluation thereby suggesting a more select population. Fourth, we chose to categorize morphology into equally distributed quartiles as a response to the fact that the World Health Organization threshold for normal motility changed multiple times during our study period. Lastly, we do not know the proportion of female partners with diagnosed infertility. We chose not to subcategorize each infertile male by infertile diagnosis because our goal was to understand how semen parameters influenced familial childhood mortality.

WIDER IMPLICATIONS OF THE FINDINGS

We are not the first study to show a relationship between fertility and CMs. Children conceived through ART may be at higher risk of birth defects, however it is not known if the relationship is causal or if there is some underlying factor linking infertility and birth outcomes. This study provides further evidence that the increased risk of congenital birth defects may not be due to the ART, but rather genetic or environmental factors that link the two outcomes. We encourage further research in order to confirm a relationship between semen quality and increased risk for CM.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by the National Institutes of Health - National Institute of Aging [Grant numbers 1R21AG036938-01, 2R01 AG022095 and 1K12HD085852-01]. Authors have no competing interests to disclose.

TRIAL REGISTRATION NUMBER

Not applicable.

Timing of Maternal Exposure and Foetal Sex Determine the Effects of Low-level Chemical Mixture Exposure on the Foetal Neuroendocrine System in Sheep

We have shown that continuous maternal exposure to the complex mixture of environmental chemicals (ECs) found in human biosolids (sewage sludge), disrupts mRNA expression of genes crucial for development and long-term regulation of hypothalamic-pituitary gonadal (HPG) function in sheep. The present study investigated whether exposure to ECs only during preconceptional period or only during pregnancy perturbed key regulatory genes within the hypothalamus and pituitary gland and whether these effects were different from chronic (life-long) exposure to biosolid ECs. The findings demonstrate that the timing and duration of maternal EC exposure influences the subsequent effects on the foetal neuroendocrine system in a sex-specific manner. Maternal exposure prior to conception, or during pregnancy only, altered the expression of key foetal neuroendocrine regulatory systems such as gonadotrophin-releasing hormone and kisspeptin to a greater extent than when maternal exposure was 'life-long'. Furthermore, hypothalamic gene expression was affected to a greater extent in males than in females and, following EC exposure, male foetuses expressed more 'female-like' mRNA levels for some key neuroendocrine genes. This is the first study to show that 'real-life' maternal exposure to low levels of a complex cocktail of chemicals prior to conception can subsequently affect the developing foetal neuroendocrine system. These findings demonstrate that the developing neuroendocrine system is sensitive to EC mixtures in a sex-dimorphic manner likely to predispose to reproductive dysfunction in later life.

Improved Fecundity in Northern China: A Secular Trend from 1980 to 2003

Objective

This study aimed to assess the trend of human fecundity over time in China.

Methods

This retrospective study was conducted in Tongliao, China. Couples who were married during the time period between January 1, 1981 and December 31, 2003 were considered eligible for this study. A total of 27,413 individuals provided valid information via house-to-house interviews. The 12-month cumulative pregnancy rate (CPR) and annual percentage change were used as the outcome measurements.

Results

There was a significant increase in the CPR over the five successive time groups. A break point in 1988 divided the entire study period into two distinct segments: 1981–1988, during which the CPR increased from 72.2% to 84.2%, and 1988–2003, during which the CPR increased from 84.2% to 87.2%.

Conclusions

The findings were unlikely to be the result of biases, and could not be explained by increased medical treatment for infertility and changes in the prevalence of sexually transmitted diseases. Dramatic societal and behavioral changes due to the unique family planning policy and economic reform policies in China might have been the plausible reason for the results.

Steroid Androgen Exposure during Development Has No Effect on Reproductive Physiology of Biomphalaria glabrata

Gastropod mollusks have been proposed as alternative models for male reproductive toxicity testing, due to similarities in their reproductive anatomy compared to mammals, together with evidence that endocrine disrupting chemicals can cause effects in some mollusks analogous to those seen in mammals. To test this hypothesis, we used the freshwater pulmonate snail, Biomphalaria glabrata, for which various genetic tools and a draft genome have recently become available, to investigate the effects of two steroid androgens on the development of mollusk secondary sexual organs. Here we present the results of exposures to two potent androgens, the vertebrate steroid; 5α-dihydrotestosterone (DHT) and the pharmaceutical anabolic steroid; 17α-methyltestosterone (MT), under continuous flow-through conditions throughout embryonic development and up to sexual maturity. Secondary sexual gland morphology, histopathology and differential gene expression analysis were used to determine whether steroid androgens stimulated or inhibited organ development. No significant differences between tissues from control and exposed snails were identified, suggesting that these androgens elicited no biologically detectable response normally associated with exposure to androgens in vertebrate model systems. Identifying no effect of androgens in this mollusk is significant, not only in the context of the suitability of mollusks as alternative model organisms for testing vertebrate androgen receptor agonists but also, if applicable to other similar mollusks, in terms of the likely impacts of androgens and anti-androgenic pollutants present in the aquatic environment.

Intake of Fruits and Vegetables with Low-to-Moderate Pesticide Residues Is Positively Associated with Semen-Quality Parameters among Young Healthy Men

BACKGROUND

Numerous studies have shown that occupational or environmental pesticide exposure can affect male fertility. There is less evidence, however, regarding any potentially adverse effects of pesticide residues in foods on markers of male fertility potential.

OBJECTIVES

We examined the relations between fruit and vegetable intake, considering pesticide residue status, and semen quality and serum concentrations of reproductive hormones in healthy young men.

METHODS

The Rochester Young Men's Study is a cross-sectional study that recruited men aged 18-22 y (n = 189) in Rochester, New York. Participants completed a questionnaire, provided a semen sample, had a blood sample drawn, and underwent a physical examination at enrollment. Semen samples were analyzed for total sperm count, sperm concentration, morphology, motility, ejaculate volume, total motile count, and total normal count. Dietary intake during the previous year was assessed by a validated food-frequency questionnaire. Fruit and vegetables were categorized as having high [Pesticide Residue Burden Score (PRBS) ≥4] or low-to-moderate (PRBS <4) pesticide residues on the basis of data from the USDA Pesticide Data Program. Linear regression models were used to analyze the associations of fruit and vegetable intake with semen variables and reproductive hormones while adjusting for potential confounding factors.

RESULTS

The total intake of fruit and vegetables was unrelated to semen quality. However, the intake of fruit and vegetables with low-to-moderate pesticide residues was associated with a higher total sperm count and sperm concentration, whereas the intake of fruit and vegetables with high pesticide residues was unrelated to semen quality. On average, men in the highest quartile of low-to-moderate-pesticide fruit and vegetable intake (≥2.8 servings/d) had a 169% (95% CI: 45%, 400%) higher total sperm count and a 173% (95% CI: 57%, 375%) higher sperm concentration than did men in the lowest quartile (<1.1 servings/d; P-trend = 0.003 and 0.0005, respectively). The intake of fruit and vegetables, regardless of pesticide-residue status, was not associated with reproductive hormone concentrations.

CONCLUSIONS

The consumption of fruit and vegetables with low-to-moderate pesticide residues was positively related to sperm counts in young men unselected by fertility status. This suggests that pesticide residues may modify the beneficial effects of fruit and vegetable intake on semen quality.

Environmental Chemical Assessment in Clinical Practice: Unveiling the Elephant in the Room

A growing body of evidence suggests chemicals present in air, water, soil, food, building materials and household products are toxicants that contribute to the many chronic diseases typically seen in routine medical practice. Yet, despite calls from numerous organisations to provide clinicians with more training and awareness in environmental health, there are multiple barriers to the clinical assessment of toxic environmental exposures. Recent developments in the fields of systems biology, innovative breakthroughs in biomedical research encompassing the "-omics" fields, and advances in mobile sensing, peer-to-peer networks and big data, provide tools that future clinicians can use to assess environmental chemical exposures in their patients. There is also a need for concerted action at all levels, including actions by individual patients, clinicians, medical educators, regulators, government and non-government organisations, corporations and the wider civil society, to understand the "exposome" and minimise the extent of toxic exposures on current and future generations. Clinical environmental chemical risk assessment may provide a bridge between multiple disciplines that uses new technologies to herald in a new era in personalised medicine that unites clinicians, patients and civil society in the quest to understand and master the links between the environment and human health.

The reference values for semen parameters of 1213 fertile men in Guangdong Province in China

Semen samples were collected from 1213 fertile men whose partners had a time-to-pregnancy (TTP) ≤12 months in Guangdong Province in Southern China, and semen parameters including semen volume, sperm concentration, total counts, motility, and morphology were evaluated according to the World Health Organization (WHO) 2010 guideline. All semen parameters analyzed were normal in ~62.2% of the total samples, whereas ~37.8% showed at least one of the semen parameters below normal threshold values. The fifth centiles (with 95% confidence intervals) were 1.3 (1.2–1.5) ml for semen volume, 20 × 10⁶ (18×10⁶–20×10⁶) ml⁻¹ for sperm concentration, 40 × 10⁶ (38×10⁶–44×10⁶) per ejaculate for total sperm counts, 48% (47%–53%) for vitality, 39% (36%–43%) for total motility, 25% (23%–27%) for sperm progressive motility, 5.0% (4%–5%) for normal morphology. The pH values ranged from 7.2 to 8.0 with the mean ± standard deviation at 7.32 ± 0.17. No effects of age and body mass index were found on semen parameters. Occupation, smoking and alcohol abuse, varicocele appeared to decrease semen quality. Sperm concentration, but not sperm morphology, is positively correlated with TTP, whereas vitality is negatively correlated with TTP. Our study provides the latest reference values for the semen parameters of Chinese fertile men in Guangdong Province, which are close to those described in the new WHO guidelines (5^th Edition).

Environmentally Induced Epigenetic Transgenerational Inheritance of Reproductive Disease

Reproductive disease and fertility issues have dramatically increased in the human population over the last several decades, suggesting environmental impacts. Epigenetics provides a mechanistic link by which an organism can respond to environmental factors. Interestingly, environmentally induced epigenetic alterations in the germ line can promote aberrant gene expression and disease generationally. Environmentally induced epigenetic transgenerational inheritance is defined as germ-line transmission of altered epigenetic information between generations in the absence of continued environmental exposures. This form of nongenetic inheritance has been shown to directly influence fertility and reproductive disease. This review describes the studies in a variety of species that impact reproductive disease and abnormalities. Observations suggest serious attention be paid to the possibility that ancestral exposures to environmental insults promotes transgenerational inheritance of reproductive disease susceptibility. Environmentally induced epigenetic transgenerational inheritance appears to be an important contributing factor to reproductive disease in many organisms, including humans.

Toward a multi-country monitoring system of reproductive health in the context of endocrine disrupting chemical exposure

BACKGROUND

Worrying trends regarding human reproductive endpoints (e.g. semen quality, reproductive cancers) have been reported and there is growing circumstantial evidence for a possible causal link between these trends and exposure to endocrine disrupting chemicals (EDCs). However, there is a striking lack of human data to fill the current knowledge gaps. To answer the crucial questions raised on human reproductive health, there is an urgent need for a reproductive surveillance system to be shared across countries.

METHODS

A multidisciplinary network named HUman Reproductive health and Global ENvironment Network (HURGENT) was created aiming at designing a European monitoring system for reproductive health indicators. Collaborative work allowed setting up the available knowledge to design such a system. Furthermore we conducted an overview of 23 potential indicators, based upon a weight of evidence (WoE) approach according to their potential relation with EDC exposure.

RESULTS

The framework and purposes of the surveillance system are settled as well as the approach to select suitable reproductive indicators. The indicators found with the highest scores according to the WoE approach are prostate and breast cancer incidence, sex ratio, endometriosis and uterine fibroid incidence, indicators related to the testicular dysgenesis syndrome, precocious puberty incidence and reproductive hormone levels.

CONCLUSION

Not only sentinel health endpoints, but also diseases with high burdens in public health are highlighted as prior indicators in the context of EDC exposure. Our work can serve as a basis to construct, as soon as possible, the first multi-country reproductive monitoring system.

Cell-Based High-Throughput Screening for Aromatase Inhibitors in the Tox21 10K Library

Multiple mechanisms exist for endocrine disruption; one nonreceptor-mediated mechanism is via effects on aromatase, an enzyme critical for maintaining the normal in vivo balance of androgens and estrogens. We adapted the AroER tri-screen 96-well assay to 1536-well format to identify potential aromatase inhibitors (AIs) in the U.S. Tox21 10K compound library. In this assay, screening with compound alone identifies estrogen receptor alpha (ERα) agonists, screening in the presence of testosterone (T) identifies AIs and/or ERα antagonists, and screening in the presence of 17β-estradiol (E2) identifies ERα antagonists. Screening the Tox-21 library in the presence of T resulted in finding 302 potential AIs. These compounds, along with 31 known AI actives and inactives, were rescreened using all 3 assay formats. Of the 333 compounds tested, 113 (34%; 63 actives, 50 marginal actives) were considered to be potential AIs independent of cytotoxicity and ER antagonism activity. Structure-activity analysis suggested the presence of both conventional (eg, 1, 2, 4, - triazole class) and novel AI structures. Due to their novel structures, 14 of the 63 potential AI actives, including both drugs and fungicides, were selected for confirmation in the biochemical tritiated water-release aromatase assay. Ten compounds were active in the assay; the remaining 4 were only active in high-throughput screen assay, but with low efficacy. To further characterize these 10 novel AIs, we investigated their binding characteristics. The AroER tri-screen, in high-throughput format, accurately and efficiently identified chemicals in a large and diverse chemical library that selectively interact with aromatase.

Lifestyles Associated With Human Semen Quality: Results From MARHCS Cohort Study in Chongqing, China

Decline of semen quality in past decades is suggested to be potentially associated with environmental and sociopsychobehavioral factors, but data from population-based cohort studies is limited. The male reproductive health in Chongqing College students (MARHCS) study was established in June 2013 as a perspective cohort study that recruited voluntary male healthy college students from 3 universities in Chongqing. The primary objectives of the MARHCS study are to investigate the associations of male reproductive health in young adults with sociopsychobehavioral factors, as well as changes of environmental exposure due to the relocation from rural campus (in University Town) to metro-campus (in central downtown). A 93-item questionnaire was used to collect sociopsychobehavioral information in manner of interviewer-interviewing, and blood, urine and semen samples were collected at the same time. The study was initiated with 796 healthy young men screened from 872 participants, with a median age of 20. About 81.8% of this population met the WHO 2010 criteria on semen quality given to the 6 routine parameters. Decreases of 12.7%, 19.8%, and 17.0%, and decreases of 7.7%, 17.6%, and 14.7% in total sperm count and sperm concentration, respectively, were found to be associated with the tertiles of accumulated smoking amount. Fried food consumption (1-2  times/wk or ≥3  times/wk vs nonconsumers) was found to be associated with decreased total sperm count (10.2% or 24.5%) and sperm concentration (13.7% or 17.2%), respectively. Coffee consumption was found to be associated with increased progressive and nonprogressive motility of 8.9% or 15.4% for subjects consuming 1-2  cups/wk or ≥3  cups/wk of coffee, respectively. Cola consumption appeared an association with decreased semen volume at 4.1% or 12.5% for 1-2  bottles/wk or ≥3  bottles/wk. A cohort to investigate the effects of environmental/sociopsychobehavioral factors act on semen quality was successfully set up. We found smoking, coffee/cola/fried foods consumption to be significantly associated with semen quality from the baseline investigation.

Sertoli cells are the target of environmental toxicants in the testis - a mechanistic and therapeutic insight

INTRODUCTION

Sertoli cells support germ cell development in the testis via an elaborate network of cell junctions that confers structural, communicating, and signaling support. However, Sertoli cell junctions and cytoskeletons are the target of environmental toxicants. Because germ cells rely on Sertoli cells for the provision of structural/functional/nutritional support, exposure of males to toxicants leads to germ cell exfoliation due to Sertoli cell injuries. Interestingly, the molecular mechanism(s) by which toxicants induce cytoskeletal disruption that leads to germ cell exfoliation is unclear, until recent years, which are discussed herein. This information can possibly be used to therapeutically manage toxicant-induced infertility/subfertility in human males.

AREAS COVERED

In this review, we provide a brief update on the use of Sertoli cell system developed for rodents and humans in vitro, which can be deployed in any research laboratory with minimal upfront setup costs. These systems can be used to collect reliable data applicable to studies in vivo. We also discuss the latest findings on the mechanisms by which toxicants induce Sertoli cell injury, in particular cytoskeletal disruption. We also identify candidate molecules that are likely targets of toxicants.

EXPERT OPINION

We provide two hypothetical models delineating the mechanism by which toxicants induce germ cell exfoliation and blood-testis barrier disruption. We also discuss molecules that are the targets of toxicants as therapeutic candidates.

Distinct expression and localization of the type II diacylglycerol kinase isozymes δ, η and κ in the mouse reproductive organs

BACKGROUND

We have revealed that the type II diacylglycerol kinases (DGKs) δ, η and κ were expressed in the testis and ovary. However, these enzymes' functions in the reproductive organs remain unknown.

RESULTS

In this study, we first identified the expression sites of type II DGKs in the mouse reproductive organs in detail. Reverse transcription-polymerase chain reaction and Western blotting confirmed that DGKδ2 (splicing variant 2) but not DGKδ1 (splicing variant 1) and DGKκ were expressed in the testis, ovary and uterus. DGKη1 (splicing variant 1) but not DGKη2 (splicing variant 2) was strongly detected in the ovary and uterus. Interestingly, we found that a new alternative splicing product of the DGKη gene, DGKη3, which lacks exon 26 encoding 31 amino acid residues, was expressed only in the testis. Moreover, we investigated the distribution of type II DGKs in the testis, ovary and uterus through in situ hybridization. DGKδ2 was distributed in the primary spermatocytes of the testis and ovarian follicles. DGKη1 was distributed in the oviductal epithelium of the ovary and the luminal epithelium of the uterus. Intriguingly, DGKη3 was strongly expressed in the secondary spermatocytes and round spermatids of the testis. DGKκ was distributed in the primary and secondary spermatocyte of the testis.

CONCLUSION

These results indicate that the expression patterns of the type II DGK isoforms δ2, η1, η3 and κ differ from each other, suggesting that these DGK isoforms play specific roles in distinct compartments and developmental stages of the reproductive organs, especially in the processes of spermatogenesis and oocyte maturation.

Dibutyl phthalate induces oxidative stress and impairs spermatogenesis in adult rats

Phthalates are abundantly produced plasticizers, and dibutyl phthalate (DBP) is the most widely used derivative in various consumer products and medical devices. This study was conducted to further explore the potential testicular toxicity of DBP in adult rats and to elucidate the underlying mechanisms. Adult male albino rats were treated orally with DBP at doses of 0, 200, 400, or 600 mg/kg/day for 15 consecutive days. Testicular weight, sperm count, and motility were significantly decreased. Treatment with DBP decreased serum follicle-stimulating hormone and testosterone levels and testicular lactate dehydrogenase activity. DBP treatment also decreased serum total antioxidant capacity and the activities of the testicular antioxidant enzymes, such as superoxide dismutase, catalase, and glutathione reductase. Further, DBP treatment provoked degeneration with absence of spermatogenesis and sperms and necrosis in some of seminiferous tubules. These results indicated that oxidative stress and subsequent decrease in testosterone secretion were the potential underlying mechanism of DBP-induced testicular toxicity.

Globalization, climate change, and transgenerational epigenetic inheritance: will our descendants be at risk?

Transgenerational epigenetic inheritance has gained increased attention due to the possibility that exposure to environmental contaminants induce diseases that propagate across generations through epigenomic alterations in gametes. In laboratory animals, exposure to environmental toxicants such as fungicides, pesticides, or plastic compounds has been shown to produce abnormal reproductive or metabolic phenotypes that are transgenerationally transmitted. Human exposures to environmental toxicants have increased due to industrialization and globalization, as well as the incidence of diseases shown to be transgenerationally transmitted in animal models. This new knowledge poses an urgent call to study transgenerational consequences of current human exposures to environmental toxicants.

Diethylstilbestrol affects the expression of GPER in the gubernaculum testis

Recent evidence suggested a positive correlation between environmental estrogens (EEs) and high incidence of abnormalities in male urogenital system. EEs are known to cause the abnormalities of testes development and testicular descent. Diethylstilbestrol (DES) is a nonsteroidal synthetic estrogen that disrupts the morphology and proliferation of gubernacular cells, and its nongenomic effects on gubernaculum testis cells may be mediated by G protein-coupled estrogen receptor (GPER). In this study, we detected the expression of GPER in mouse gubernacular testis and investigated the effects of DES on the expression of GPER in gubernaculum testis cells. RT-PCR analysis revealed that GPER mRNA was expressed in the gubernaculum. GPER protein was detected in the parenchymal cells of the gubernaculum early in development. Furthermore, we demonstrate that GPER inhibitor G15 relieved DES-induced inhibition of GPER expression in gubernaculum testis cell, but ER inhibitor ICI 182780 had the converse effects on DES-induced inhibition of GPER expression in these cells. These data suggest that the effects of DES on mouse gubernaculum testis cells are mediated at least partially by the regulation of GPER expression.

Relationship between self-reported residential indoor remodeling and semen quality: a case-control study

The present study examined the association between residential indoor remodeling and poor semen quality. Sperm donors aged 18–45 years old were recruited in Shanghai, China. Semen specimens were collected and analyzed. An in-person interview was conducted to obtain information on the history of indoor remodeling and potential confounders. A total of 70 participants with abnormal semen quality (case group) and 68 controls were examined. A total of 20 subjects reported indoor remodeling in the recent 24 months, and among them 17 subjects reported indoor remodeling in the recent 12 months. Compared with participants with no history of indoor remodeling, participants with a history of indoor remodeling in the recent 24 months were more than three times as likely to have poor sperm quality (adjusted odds ratio = 3.8, 95% confidence interval: 1.3–12.0) after controlling for potential confounders. The association was strengthened when the analysis was restricted to those who had indoor remodeling in the recent 12 months. Our findings provide preliminary evidence that indoor remodeling has an adverse effect on semen quality.

Male fertility: Is spermiogenesis the critical step for answering biomedical issues?

Regarding male fertility, biomedical issues have opposite goals to treat infertility or develop contraceptive drugs. Recently, the identification of the molecular mechanisms involved in germ cell differentiation suggest that spermiogenesis has to be put at the crossroad to reach these goals. Concerning fertility issues, citizens in our modern world are schizophrenic. On one side, couples have the possibility to control conception; and on the other side, more and more couples suffer from the misfortune of being infertile. These two societal problems lead to intensive research and conflicting government policies. However, these opposing goals rely on a better understanding of germ cell differentiation.

Epidemiologic methods for investigating male fecundity

Fertility is a couple concept that has been measured since the beginning of demography, and male fecundity (his biological capacity to reproduce) is a component of the fertility rate. Unfortunately, we have no way of measuring the male component directly, although several indirect markers can be used. Population registers can be used to monitor the proportion of childless couples, couples who receive donor semen, trends in dizygotic twinning, and infertility diagnoses. Studies using time-to-pregnancy (TTP) may identify couple subfecundity, and TTP data will correlate with sperm quality and quantity as well as sexual activity and a number of other conditions. Having exposure data available for couples with a fecund female partner would make TTP studies of interest in identifying exposures that may affect male fecundity. Biological indicators such as sperm quality and quantity isolate the male component of fertility, and semen data therefore remain an important source of information for research. Unfortunately, often over half of those invited to provide a sperm sample will refuse, and the study is then subject to a selection that may introduce bias. Because the most important time windows for exposures that impair semen production could be early fetal life, puberty, and the time of ejaculation; longitudinal data over decades of time are required. The ongoing monitoring of semen quality and quantity should continue, and surveys monitoring fertility and waiting TTP should also be designed.

Our stolen figures: the interface of sexual differentiation, endocrine disruptors, maternal programming, and energy balance

This article is part of a Special Issue "Energy Balance". The prevalence of adult obesity has risen markedly in the last quarter of the 20th century and has not been reversed in this century. Less well known is the fact that obesity prevalence has risen in domestic, laboratory, and feral animals, suggesting that all of these species have been exposed to obesogenic factors present in the environment. This review emphasizes interactions among three biological processes known to influence energy balance: Sexual differentiation, endocrine disruption, and maternal programming. Sexual dimorphisms include differences between males and females in body weight, adiposity, adipose tissue distribution, ingestive behavior, and the underlying neural circuits. These sexual dimorphisms are controlled by sex chromosomes, hormones that masculinize or feminize adult body weight during perinatal development, and hormones that act during later periods of development, such as puberty. Endocrine disruptors are natural and synthetic molecules that attenuate or block normal hormonal action during these same developmental periods. A growing body of research documents effects of endocrine disruptors on the differentiation of adipocytes and the central nervous system circuits that control food intake, energy expenditure, and adipose tissue storage. In parallel, interest has grown in epigenetic influences, including maternal programming, the process by which the mother's experience has permanent effects on energy-balancing traits in the offspring. This review highlights the points at which maternal programming, sexual differentiation, and endocrine disruption might dovetail to influence global changes in energy balancing traits.

Environmentally induced epigenetic transgenerational inheritance of male infertility

Decreasing male fertility has been observed for the past fifty years. Examples of affected reproductive parameters include decreases in sperm count and sperm quality and increases in testicular cancer, cryptorchidism and hypospadias. Exposures to environmental toxicants during fetal development and early postnatal life have been shown to promote infertility. Environmental exposures inducing epigenetic changes related to male infertility range from life style, occupational exposures, environmental toxicants and nutrition. Exposures during fetal gonadal sex determination have been shown to alter the epigenetic programming of the germline that then can transmit this altered epigenetic information to subsequent generations in the absence of any exposures. This environmentally induced epigenetic transgenerational inheritance of disease will be a component of the etiology of male infertility.

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.

Semen quality trends in French regions are consistent with a global change in environmental exposure

A retrospective study carried out recently in a large sample of men, close to the general population, has reported a significant and strong decline in sperm concentration and morphology in the whole of France between 1989 and 2005. We studied these trends within each region of France. Data were obtained from the Fivnat database. The study sample comprised male partners of sterile women in whom both tubes were absent or blocked. They were located at the assisted reproductive technology center. A Bayesian spatio-temporal model with parametric time trends, adjusted for age, was used to model overall time trends for each region. The results show that sperm concentration decreased in almost all regions of France. Among them, Aquitaine showed the highest decrease and Midi-Pyrénées had the lowest average for the whole period. Regarding total motility, most regions showed a slight increase while Bourgogne showed a steep and significant decrease. While considering sperm morphology, there was a decrease in most of the regions. The decrease in Aquitaine and Midi-Pyrénées was stronger when compared with the overall trend. In conclusion, a decrease in sperm concentration and morphology, already shown at the French metropolitan territory level, was observed in most regions of France. This is consistent with a global change in environmental exposure, according to the endocrine disruptor hypothesis especially. Indeed, ubiquitary exposure to chemicals has been growing in the general population of France since the 1950s, and the results do not appear to support the lifestyle hypothesis. The highest decreases and lowest values are consistently observed in two proximate regions that are both highly agricultural and densely populated.

Environmental toxicants perturb human Sertoli cell adhesive function via changes in F-actin organization mediated by actin regulatory proteins

STUDY QUESTION

Can human Sertoli cells cultured in vitro and that have formed an epithelium be used as a model to monitor toxicant-induced junction disruption and to better understand the mechanism(s) by which toxicants disrupt cell adhesion at the Sertoli cell blood-testis barrier (BTB)?

SUMMARY ANSWER

Our findings illustrate that human Sertoli cells cultured in vitro serve as a reliable system to monitor the impact of environmental toxicants on the BTB function.

WHAT IS KNOWN ALREADY

Suspicions of a declining trend in semen quality and a concomitant increase in exposures to environmental toxicants over the past decades reveal the need of an in vitro system that efficiently and reliably monitors the impact of toxicants on male reproductive function. Furthermore, studies in rodents have confirmed that environmental toxicants impede Sertoli cell BTB function in vitro and in vivo.

STUDY DESIGN, SIZE AND DURATION

We examined the effects of two environmental toxicants: cadmium chloride (0.5-20 µM) and bisphenol A (0.4-200 µM) on human Sertoli cell function. Cultured Sertoli cells from three men were used in this study, which spanned an 18-month period.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human Sertoli cells from three subjects were cultured in F12/DMEM containing 5% fetal bovine serum. Changes in protein expression were monitored by immunoblotting using specific antibodies. Immunofluorescence analyses were used to assess changes in the distribution of adhesion proteins, F-actin and actin regulatory proteins following exposure to two toxicants: cadmium chloride and bisphenol A (BPA).

MAIN RESULTS AND THE ROLE OF CHANCE

Human Sertoli cells were sensitive to cadmium and BPA toxicity. Changes in the localization of cell adhesion proteins were mediated by an alteration of the actin-based cytoskeleton. This alteration of F-actin network in Sertoli cells as manifested by truncation and depolymerization of actin microfilaments at the Sertoli cell BTB was caused by mislocalization of actin filament barbed end capping and bundling protein Eps8, and branched actin polymerization protein Arp3. Besides impeding actin dynamics, endocytic vesicle-mediated trafficking and the proper localization of actin regulatory proteins c-Src and annexin II in Sertoli cells were also affected. Results of statistical analysis demonstrate that these findings were not obtained by chance.

LIMITATIONS, REASONS FOR CAUTION

(i) This study was done in vitro and might not extrapolate to the in vivo state, (ii) conclusions are based on the use of Sertoli cell samples from three men and (iii) it is uncertain if the concentrations of toxicants used in the experiments are reached in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

Human Sertoli cells cultured in vitro provide a robust model to monitor environmental toxicant-mediated disruption of Sertoli cell BTB function and to study the mechanism(s) of toxicant-induced testicular dysfunction.

Shedding light on the controversy surrounding the temporal decline in human sperm counts: a systematic review

We systematically examined the evidence of declining sperm counts and the hypothesis that an increased exposure to environmental pollutants is responsible for such decline. Search engines, including PUBMED, MEDLINE, EMBASE, BIOSIS, and Cochrane library, were used to identify epidemiologic studies published from 1985 to 2013. We concluded that there is no enough evidence to confirm a worldwide decline in sperm counts. Also, there seems to be no scientific truth of a causative role for endocrine disruptors in the temporal decline of sperm production. Such assumptions are based on few meta-analyses and retrospective studies, while other well-conducted researches could not confirm these findings. We acknowledge that difficult-to-control confounding factors in the highly variable nature of semen, selection criteria, and comparability of populations from different time periods in secular-trend studies, the quality of laboratory methods for counting sperm, and apparently geographic variations in semen quality are the main issues that complicate the interpretation of the available evidence. Owing to the importance of this subject and the uncertainties still prevailing, there is a need not only for continuing monitoring of semen quality, reproductive hormones, and xenobiotics, but also for a better definition of fecundity.