Epigenetic: a molecular link between testicular cancer and environmental exposures

Dysbiosis of Gut Microbiome Aggravated Male Infertility in Captivity of Plateau Pika

Captivity is an important and efficient technique for rescuing endangered species. However, it induces infertility, and the underlying mechanism remains obscure. This study used the plateau pika (Ochotona curzoniae) as a model to integrate physiological, metagenomic, metabolomic, and transcriptome analyses and explore whether dysbiosis of the gut microbiota induced by artificial food exacerbates infertility in captive wild animals. Results revealed that captivity significantly decreased testosterone levels and the testicle weight/body weight ratio. RNA sequencing revealed abnormal gene expression profiles in the testicles of captive animals. The microbial α-diversity and Firmicutes/Bacteroidetes ratio were drastically decreased in the captivity group. Bacteroidetes and Muribaculaceae abundance notably increased in captive pikas. Metagenomic analysis revealed that the alteration of flora increased the capacity for carbohydrate degradation in captivity. The levels of microbe metabolites' short-chain fatty acids (SCFAs) were significantly high in the captive group. Increasing SCFAs influenced the immune response of captivity plateau pikas; pro-inflammatory cytokines were upregulated in captivity. The inflammation ultimately contributed to male infertility. In addition, a positive correlation was observed between Gastranaerophilales family abundance and testosterone concentration. Our results provide evidence for the interactions between artificial food, the gut microbiota, and male infertility in pikas and benefit the application of gut microbiota interference in threatened and endangered species.

Cadmium and lead implication in testis cancer; is there a connection?

Testis cancer (TC) is the most common malignancy of young men. Current evidence from studies, alongside genetics and hormonal status, suggests a significant role of toxic metals, cadmium (Cd) and lead (Pb), in the origin and development of TC. Besides oxidative stress and endocrine disruption, interaction with bioelements is one of the critical mechanisms of Cd and Pb toxicity and malign transformation. This study aimed to investigate metal levels in blood, healthy, and tumor testis tissue and to reveal hormone, oxidative status, and bioelements levels in patients with TC. The study enrolled 52 patients with TC and 61 healthy volunteers. Toxic metals and bioelements levels were analyzed by atomic absorption spectrophotometry (AAS) while electrochemiluminescence immunoassay (ECLIA) and spectrophotometry methods were used for hormone and oxidative parameters evaluation. Significantly higher blood Cd levels were depicted in TC cohort. Furthermore, blood Cd elevation was associated with a 1.98 higher probability of TC developing. However, a metal concentration between healthy and tumor testis tissue did not differ significantly. Lower levels of estradiol and testosterone, established in a cohort of TC patients, followed the significant role of hormones in TC development. At the same time, ischemia-modified albumin (IMA) has been recognized as a parameter with very good accuracy as a potential diagnostic marker for TC. The study revealed different distribution patterns of copper (Cu) and zinc (Zn) in the three compartments of the patients, as well significant correlation between essential metals Cu/Zn and toxic metals Cd/Pb indicating metal-metal interactions as pivotal mechanisms of metals toxicity.

H3 histone methylation landscape in male urogenital cancers: from molecular mechanisms to epigenetic biomarkers and therapeutic targets

During the last decades, male urogenital cancers (including prostate, renal, bladder and testicular cancers) have become one of the most frequently encountered malignancies affecting all ages. While their great variety has promoted the development of various diagnosis, treatment and monitoring strategies, some aspects such as the common involvement of epigenetic mechanisms are still not elucidated. Epigenetic processes have come into the spotlight in the past years as important players in the initiation and progression of tumors, leading to a plethora of studies highlighting their potential as biomarkers for diagnosis, staging, prognosis, and even as therapeutic targets. Thus, fostering research on the various epigenetic mechanisms and their roles in cancer remains a priority for the scientific community. This review focuses on one of the main epigenetic mechanisms, namely, the methylation of the histone H3 at various sites and its involvement in male urogenital cancers. This histone modification presents a great interest due to its modulatory effect on gene expression, leading either to activation (e.g., H3K4me3, H3K36me3) or repression (e.g., H3K27me3, H3K9me3). In the last few years, growing evidence has demonstrated the aberrant expression of enzymes that methylate/demethylate histone H3 in cancer and inflammatory diseases, that might contribute to the initiation and progression of such disorders. We highlight how these particular epigenetic modifications are emerging as potential diagnostic and prognostic biomarkers or targets for the treatment of urogenital cancers.

Ciprofloxacin and enrofloxacin can cause reproductive toxicity via endocrine signaling pathways

Ciprofloxacin (CIP) and enrofloxacin (ENR) are veterinary antibiotics commonly utilized to treat and prevent animal diseases. Environmental and dietary antibiotic residues can directly and indirectly affect the reproductive development of animals and humans. This article investigated the reproductive toxicity of CIP in male zebrafish, showing that it could decrease the spermatogonial weight and damage the spermatogonial tissue. The sex hormone assays showed that CIP decreased fshb and lhb gene expression and plasma testosterone (T). In addition, transcriptome analysis indicated that the effect of CIP on zebrafish might be related to the endocrine signaling pathways. ENR, which was selected for further study, inhibited mouse Leydig (TM3) and Sertoli (TM4) cell proliferation and caused cell cycle arrest. The sperm concentration, serum luteotropic hormone (LH) and follicle-stimulating hormone (FSH), and T levels decreased in adolescent mice after ENR treatment for 30d in vivo. Hematoxylin and eosin (H&E) staining showed that ENR exposure potentially induced testicular injury, while the real-time quantitative PCR (qPCR) results indicated that ENR inhibited the mRNA expression of key genes in the Leydig cells (cyp11a1, 3β-HSD, and 17β-HSD), Sertoli cells (Inhbβ and Gdnf) and spermatogenic cells (Plzf, Stra8 and Dmc1). In conclusion, these findings indicated that ENR exposure might influence the development of the testes of pubescent mice.

Endocrine-disrupting chemicals affect sertoli TM4 cell functionality through dysregulation of gap junctional intercellular communication in vitro

The frequencies of adverse outcomes associated with male reproductive health, including infertility and testicular cancer, are increasing. These adverse trends are partially attributed to increased exposure to environmental agents such as endocrine-disrupting chemicals (EDCs). This study addresses effects on EDCs on adjacent prepubertal Sertoli TM4 cells, specifically on 1) testicular gap junctional intercellular communication (GJIC), one of the hallmarks of non-genotoxic carcinogenicity, 2) GJIC building blocks connexins (Cx), and 3) mitogen-activated protein kinases MAPKs. We selected eight representatives of EDCs: bisphenol A and organochlorine chemicals such as pesticides dichlorodiphenyltrichloroethane, lindane, methoxychlor, and vinclozolin, industrial chemical 2,2',4,4',5,5'-hexachlorobiphenyl, and components of personal care products, triclocarban and triclosan. EDCs rapidly dysregulated GJIC in Sertoli TM4 cells mainly via MAPK p38 and/or Erk1/2/pathways by the intermediate hyper- or de-phosphorylation of Cx43 (Ser368, Ser282) and translocalization of Cx43 from the plasma membrane, suggesting disturbed intracellular trafficking of Cx43 protein. Surprisingly, EDCs did not rapidly activate MAPK Erk1/2 or p38; on the contrary, TCC and TCS decreased their activity (phosphorylation). Our results indicate that EDCs might disrupt testicular homeostasis and development via testicular GJIC, junctional and non-junctional functions of Cx43 and MAPK-signalling pathways in Sertoli cells.

Epigenetics and Testicular Cancer: Bridging the Gap Between Fundamental Biology and Patient Care

Testicular cancer is the most common solid tumor affecting young males. Most testicular cancers are testicular germ cell tumors (TGCTs), which are divided into seminomas (SGCTs) and non-seminomatous testicular germ cell tumors (NSGCTs). During their development, primordial germ cells (PGCs) undergo epigenetic modifications and any disturbances in their pattern might lead to cancer development. The present study provides a comprehensive review of the epigenetic mechanisms–DNA methylation, histone post-translational modifications, bivalent marks, non-coding RNA–associated with TGCT susceptibility, initiation, progression and response to chemotherapy. Another important purpose of this review is to highlight the recent investigations regarding the identification and development of epigenetic biomarkers as powerful tools for the diagnostic, prognostic and especially for epigenetic-based therapy.

Ki67 and LSD1 Expression in Testicular Germ Cell Tumors Is Not Associated with Patient Outcome: Investigation Using a Digital Pathology Algorithm

TGCTs represent a model of curable disease afflicting especially young men. Defining tumor biological characteristics is crucial to increase current knowledge and tailor the best clinical management. Ki67, a potential prognostic marker, still exhibits heterogenous associations with patient outcomes, thus bringing the need of corroboration with larger cohorts in clinical practice. LSD1, an epigenetic enzyme, represents a future target for epigenetic drugs that may lower treatment-associated morbidity. This study aimed to assess Ki67/LSD1 immunoexpression across all TGCT histological subtypes and correlate it with clinicopathological features. Results were compared with an in silico analysis of the TCGA database. Immunohistochemistry for Ki67 and LSD1 was carried out in a cohort of 157 TGCT tumor samples and assessed using a digital pathology algorithm. LSD1 protein expression was explored in TGCT cell lines, including ATRA-differentiated clones. There was a significant positive correlation between Ki67 and LSD1 H-scores (r_s = 0.182, p = 0.037). Ki67 positivity percentage and H-score were significantly higher in non-seminomas (p = 0.0316 and 0.0113, respectively). Expression was not significantly different according to clinicopathological features, including stage, IGCCCG prognosis-based system, or relapse/progression-free survival, which was corroborated by in silico analysis. Our study, making use of digital image analysis, does not confirm the utility of these biomarkers in a daily practice cohort. Although not affecting patient outcome in our cohort, LSD1 is expressed overall in TGCTs, suggesting sensitivity to LSD1 inhibitors.

Association between male infertility and male-specific malignancies: systematic review and meta-analysis of population-based retrospective cohort studies

OBJECTIVE

To investigate the current evidence that correlates impaired male fertility with the risk of developing male-related malignancies.

DESIGN

Systematic review and meta-analysis of population-based retrospective cohort studies.

SETTING

Not applicable.

PATIENT(S)

Men diagnosed with impaired fertility status and subsequently observed to determine incidence risk in developing testicular cancer (TCa) or prostate cancer (PCa).

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

Pooled risk ratio (RR) differences among male factor infertility subjects compared with a fertile control population, and meta-regression analysis according to age at baseline, mean follow-up, range of study time, and year of publication.

RESULT(S)

Six studies met the inclusion criteria and were critically examined. Four studies examined male infertility and TCa (n = 161,634; 174 TCa cases), and four examined infertility in relation to PCa (n = 183,950 men; 377 PCa cases) from 1963 to 2014. The pooled RR was 2.033 (95% confidence interval [CI], 1.66-2.48); heterogeneity: Q = 3.04 (degree of freedom [df] = 3); I² = 1.55% for TCa and 1.68 (95% CI, 1.17-2.4); Q = 23.3(df = 3); I² = 87.1% for PCa.

CONCLUSION(S)

Male infertility was associated with a subsequent risk of both TCa and PCa. Although the clinical significance of these findings remains uncertain, future studies should evaluate the underlying mechanisms to determine whether testis and prostate screening practices should be altered in men with male infertility.

CLINICAL TRIAL REGISTRATION NUMBER

PROSPERO 167277.

Is Testicular Germ Cell Cancer Estrogen Dependent? The Role of Endocrine Disrupting Chemicals

Testicular germ cell cancer (TGCC) is the most frequent cancer of the young male, with an increasing incidence worldwide. The pathogenesis and reasons for this increase remain unknown. However, epidemiological and experimental data have suggested that, similar to genital malformations and sperm impairment, it could result from the interaction of genetic and environmental factors including fetal exposure to endocrine-disrupting chemicals (EDCs) with estrogenic effects. In this review, we analyze the expression of classic and nonclassic estrogen receptors by TGCC cells, the way they may influence germ cell proliferation induced by EDCs, and discuss how this estrogen dependency supports the developmental and environmental hypothesis.

Testosterone disruptor effect and gut microbiome perturbation in mice: Early life exposure to doxycycline

Veterinary tetracyclines drugs are emerging organic pollutants detected at high concentrations in the urine of school children and a potential public health risk. However, the implications of early-life exposure to tetracyclines on testosterone production, being new endocrine disruptors, remain unknown. We investigated whether the early-life exposure to low-doxycycline, a widely used tetracycline, on mitochondria dysfunction and testosterone disruption in Leydig cells in vitro and in vivo. Next, we determined the mRNA levels of testis cells markers for early-life exposure to low-doxycycline outcomes of testis health in later-life. Finally, we compared the weight gain performance exposed to low- and therapeutic-doses through 15 weeks and examined the role of the microbiota during development. Our results showed doxycycline disturbed steroidogenesis process by mitochondrial dysfunction in mouse Leydig tumor cell line (MLTC-1) cells in vitro. Leydig cells mitochondrial function was disrupted by early-life exposure to low-doxycycline from birth to 49 days, causing testosterone deficiency and decreased quality of the sperm in mice. Early-life exposure to low-doxycycline significantly altered the mRNA levels of key genes in Leydig cells (Cyp11a1, Cyp17a1 and 17β-HSD) and spermatogenic cells (Grfal, Plzf, and Stra8) in later-life in mice. Subchronic low- and therapeutic-doses doxycycline changed gut microbiota differences in diversity reduction and compositional alteration. Moreover, the weight gain effects of doxycycline were only observed in low-dose in male mice. Overall, these results provide insight into the effects of doxycycline on both testis and gut microbiota health. The results provide insight that environmental antibiotics are needed additional research to classify as ECDs.

The Role of DNA/Histone Modifying Enzymes and Chromatin Remodeling Complexes in Testicular Germ Cell Tumors

It is well established that cancer cells exhibit alterations in chromatin structure and accessibility. Indeed, the dysregulation of many protein-coding players with enzymatic activity (DNA and histone-modifying enzymes) and chromatin remodelers have been depicted in various tumor models in recent years. Still, little attention has been directed towards testicular germ cell tumors (TGCTs)-representing the most common neoplasm among young adult Caucasian men-with most studies focusing on exploring the role of DNA methyltransferases (DNMTs) and DNA demethylases (TETs). TGCTs represent a complex tumor model, associated with developmental and embryogenesis-related phenomena, and display seldom (cyto)genetic aberrations, leaving room for Epigenetics to explain such morphological and clinical diversity. Herein, we have summarized the major findings that were reported in literature regarding the dysregulation of DNA/histone-modifying enzymes and chromatin remodelers in TGCTs. Additionally, we performed in silico analysis of The Cancer Genome Atlas database to find the most relevant of those players in TGCTs. We concluded that several DNA/histone-modifying enzymes and chromatin remodelers may serve as biomarkers for subtyping, dictating prognosis and survival, and, possibly, for serving as targets of directed, less toxic therapies.

Bile acid-FXRα pathways regulate male sexual maturation in mice

The bile acid receptor Farnesol-X-Receptor alpha (FRXα) is a member of the nuclear receptor superfamily. FRXα is expressed in the interstitial compartment of the adult testes, which contain the Leydig cells. In adult, short term treatment (12 hours) with FRXα agonist inhibits the expression of steroidogenic genes via the induction of the Small heterodimer partner (SHP). However the consequences of FRXα activation on testicular pathophysiology have never been evaluated. We demonstrate here that mice fed a diet supplemented with bile acid during pubertal age show increased incidence of infertility. This is associated with altered differentiation and increase apoptosis of germ cells due to lower testosterone levels. At the molecular level, next to the repression of basal steroidogenesis via the induction expression of Shp and Dax-1, two repressors of steroidogenesis, the main action of the BA-FRXα signaling is through lowering the Leydig cell sensitivity to the hypothalamo-pituitary axis, the main regulator of testicular endocrine function. In conclusion, BA-FRXα signaling is a critical actor during sexual maturation.

Male reproductive cancers and infertility: a mutual relationship

Reproductive dysfunction and malignancies related to the male gender represent a serious health concern, whose incidence has significantly risen over the past years. Prior to treatment, testicular or prostate cancer patients often display poor semen characteristics similar to subfertile or infertile patients. This fact is underscored by cases where the malignancy is often diagnosed in males who undergo a general fertility screening. This review aims to examine the associations between male infertility and reproductive cancers focusing on common etiologies and biological mechanisms underlining these pathologies. Furthermore, we discuss compelling epidemiological data hypothesizing that male reproductive failure may act as a precursor of future andrological malignancies, including testicular or prostate cancer, thus providing a stimulus for a more specific research in male reproductive health and emphasizing the importance of this relation for physicians taking care of male patients with a reproductive disease.

Identification of the link between the hypothalamo-pituitary axis and the testicular orphan nuclear receptor NR0B2 in adult male mice

The small heterodimer partner (SHP, nuclear receptor subfamily 0, group B, member 2; NR0B2) is an atypical nuclear receptor known mainly for its role in bile acid homeostasis in the enterohepatic tract. We previously showed that NR0B2 controls testicular functions such as testosterone synthesis. Moreover, NR0B2 mediates the deleterious testicular effects of estrogenic endocrine disruptors leading to infertility. The endocrine homeostasis is essential for health, because it controls many physiological functions. This is supported by a large number of studies demonstrating that alterations of steroid activity lead to several kinds of diseases such as obesity and infertility. Within the testis, the functions of the Leydig cells are mainly controlled by the hypothalamo-pituitary axis via LH/chorionic gonadotropin (CG). Here, we show that LH/CG represses Nr0b2 expression through the protein kinase A-AMP protein kinase pathway. Moreover, using a transgenic mouse model invalidated for Nr0b2, we point out that NR0B2 mediates the repression of testosterone synthesis and subsequent germ cell apoptosis induced by exposure to anti-GnRH compound. Together, our data demonstrate a new link between hypothalamo-pituitary axis and NR0B2 in testicular androgen metabolism, making NR0B2 a major actor of testicular physiology in case of alteration of LH/CG levels.

Hepatotoxicity induced by neonatal exposure to diethylstilbestrol is maintained throughout adulthood via the nuclear receptor SHP

BACKGROUND

Liver physiology is sensitive to estrogens, which suggests that the liver might be a target of estrogenic endocrine disrupters (EED). However, the long-term consequences of neonatal exposure to EED on liver physiology have rarely been studied. The nuclear receptor small heterodimer partner (SHP) mediates the deleterious effects of neonatal exposure to diethylstilbestrol (DES) on male fertility.

OBJECTIVES

As SHP is involved in liver homeostasis, we aimed to determine whether neonatal estrogenic exposure also affected adult liver physiology through SHP. Male mouse pups were exposed to DES in the first 5 days of life.

RESULTS

DES exposure leads to alterations in the postnatal bile acid (BA) synthesis pathway. Neonatal DES-exposure affected adult liver BA metabolism and subsequently triglyceride (TG) homeostasis. The wild-type males neonatally exposed to DES exhibited increased liver weight and altered liver histology in the adult age. The use of deficient male mice revealed that SHP mediates the deleterious effects of DES treatment. These long-term effects of DES were associated with differently timed alterations in the expression of epigenetic factors.

CONCLUSIONS

However, the molecular mechanisms by which neonatal exposure persist to affect the adult liver physiology remain to be defined. In conclusion, we demonstrate that neonatal DES exposure alters adult hepatic physiology in an SHP-dependent manner.

[Prevalence and possible causes of hypospadias]

Hypospadias is the most common congenital malformation of the male external genitalia. After the heart and circulatory system, it is the second most common developmental disorder in males. It is due to a midline fusion defect of the male urethra, which results in a misplaced urethral meatus. Hypospadias may be distal, medial and proximal. It may occur as an isolated defect or it may develop together with other genital disorders (retention of testes in one or both sides, microphallus, bifid scrotum) or with malformation of other organs. In some cases syndromic forms may also occur. Genetic factors play a crucial role in the occurrence of early developmental defect, but endocrine and environmental factors may also be important in the aetiology of hypospadias. It may be associated with various sex and autosomal chromosomal abnormalities. Monogenic and chromosomal causes of hypospadias accounts for about in 30% of all cases, while genetic factors remain unknown in 70% of cases. The authors summarize the development of the male external genitalia, the prevalence and possible causes of hypospadias. They propose that better understanding of the pathogenesis of the disease may contribute to the prevention and decreased prevalence of the disease.

Spermatogenesis and cryptorchidism

Cryptorchidism represents the most common endocrine disease in boys, with infertility more frequently observed in bilateral forms. It is also known that undescended testes, if untreated, lead to an increased risk of testicular tumors, usually seminomas, arising from mutant germ cells. In normal testes, germ cell development is an active process starting in the first months of life when the neonatal gonocytes transform into adult dark (AD) spermatogonia. These cells are now thought to be the stem cells useful to support spermatogenesis. Several researches suggest that AD spermatogonia form between 3 and 9 months of age. Not all the neonatal gonocytes transform into AD spermatogonia; indeed, the residual gonocytes undergo involution by apoptosis. In the undescended testes, these transformations are inhibited leading to a deficient pool of stem cells for post pubertal spermatogenesis. Early surgical intervention in infancy may allow the normal development of stem cells for spermatogenesis. Moreover, it is very interesting to note that intra-tubular carcinoma in situ in the second and third decades have enzymatic markers similar to neonatal gonocytes suggesting that these cells fail transformation into AD spermatogonia and likely generate testicular cancer (TC) in cryptorchid men. Orchidopexy between 6 and 12 months of age is recommended to maximize the future fertility potential and decrease the TC risk in adulthood.

Global incidence and outcome of testicular cancer

Background

Testicular cancer is a rare tumor type accounting for 1% of malignancies in men. It is, however, the most common cancer in young men in Western populations. The incidence of testicular cancer is increasing globally, although a decline in mortality rates has been reported in Western countries. It is important to identify whether the variations in trends observed between populations are linked to genetic or environmental factors.

Methods

Age-standardized incidence rates and age-standardized mortality rates for testicular cancer were obtained for men of all ages in ten countries from the Americas, Asia, Europe, and Oceania using the Cancer Incidence in Five Continents (CI5plus) and World Health Organization (WHO) mortality databases. The annual percent change was calculated using Joinpoint regression to assess temporal changes between geographical regions.

Results

Testicular cancer age-standardized incidence rates are highest in New Zealand (7.8), UK (6.3), Australia (6.1), Sweden (5.6), USA (5.2), Poland (4.9), and Spain (3.8) per 100,000 men. India, China, and Colombia had the lowest incidence (0.5, 1.3, and 2.2, respectively) per 100,000 men. The annual percent changes for overall testicular cancer incidence significantly increased in the European countries Sweden 2.4%, (2.2; 2.6); UK 2.9%, (2.2; 3.6); and Spain 5.0%, (1.7; 8.4), Australia 3.0%, (2.2; 3.7), and China 3.5%, (1.9; 5.1). India had the lowest overall testicular cancer incidence −1.7%, (−2.5; −0.8). Annual percent changes for overall testicular cancer mortality rates were decreasing in all study populations, with the greatest decline observed in Sweden −4.2%, (−4.8; −3.6) and China −4.9%, (−6.5; −3.3).

Conclusion

Testicular cancer is increasing in incidence in many countries; however, mortality rates remain low and most men are cured. An understanding of the risks and long-term side effects of treatment are important in managing men with this disease.

An alkylphenol mix promotes seminoma derived cell proliferation through an ERalpha36-mediated mechanism

Long chain alkylphenols are man-made compounds still present in industrial and agricultural processes. Their main use is domestic and they are widespread in household products, cleansers and cosmetics, leading to a global environmental and human contamination. These molecules are known to exert estrogen-like activities through binding to classical estrogen receptors. In vitro, they can also interact with the G-protein coupled estrogen receptor. Testicular germ cell tumor etiology and progression are proposed to be stimulated by lifelong estrogeno-mimetic exposure. We studied the transduction signaling pathways through which an alkyphenol mixture triggers testicular cancer cell proliferation in vitro and in vivo. Proliferation assays were monitored after exposure to a realistic mixture of 4-tert-octylphenol and 4-nonylphenol of either TCam-2 seminoma derived cells, NT2/D1 embryonal carcinoma cells or testis tumor in xenografted nude mice. Specific pharmacological inhibitors and gene-silencing strategies were used in TCam-2 cells in order to demonstrate that the alkylphenol mix triggers CREB-phosphorylation through a rapid, ERα36-PI3kinase non genomic pathway. Microarray analysis of the mixture target genes revealed that this pathway can modulate the expression of the DNA-methyltransferase-3 (Dnmt3) gene family which is involved in DNA methylation control. Our results highlight a key role for ERα36 in alkylphenol non genomic signaling in testicular germ cell tumors. Hence, ERα36-dependent control of the epigenetic status opens the way for the understanding of the link between endocrine disruptor exposure and the burden of hormone sensitive cancers.

Human infertility: are endocrine disruptors to blame?

Over recent decades, epidemiological studies have been reporting worrisome trends in the incidence of human infertility rates. Extensive detection of industrial chemicals in human serum, seminal plasma and follicular fluid has led the scientific community to hypothesise that these compounds may disrupt hormonal homoeostasis, leading to a vast array of physiological impairments. Numerous synthetic and natural substances have endocrine-disruptive effects, acting through several mechanisms. The main route of exposure to these chemicals is the ingestion of contaminated food and water. They may disturb intrauterine development, resulting in irreversible effects and may also induce transgenerational effects. This review aims to summarise the major scientific developments on the topic of human infertility associated with exposure to endocrine disruptors (EDs), integrating epidemiological and experimental evidence. Current data suggest that environmental levels of EDs may affect the development and functioning of the reproductive system in both sexes, particularly in foetuses, causing developmental and reproductive disorders, including infertility. EDs may be blamed for the rising incidence of human reproductive disorders. This constitutes a serious public health issue that should not be overlooked. The exposure of pregnant women and infants to EDs is of great concern. Therefore, precautionary avoidance of exposure to EDs is a prudent attitude in order to protect humans and wildlife from permanent harmful effects on fertility.