Adult exposure to diethylstilbestrol induces spermatogenic cell apoptosis in vivo through increased oxidative stress in male hamster

Rapid prolactin induction in adult male rats after treatment with diethylstilbestrol

Diethylstilbestrol (DES) is a synthetic oestrogen known to disrupt the endocrine system and to cause reproductive toxicity mediated via the hypothalamic-pituitary-adrenal axis; however, its molecular mechanism of action is poorly understood. In the present study, we found that, after only 1 week of exposure to DES, blood testosterone dramatically decreased and that this decrease was associated with a strong induction of prolactin (PRL). Even with the increase in PRL, the luteinising hormone and follicle-stimulating hormone mRNAs slightly decreased. Our results show that, after 48 hours of a single dose of DES, there was a six-fold increase in PRL expression. After exploring the upstream mechanisms, we determined that dopamine, which inhibits PRL secretion in male rats, did not decrease in the pituitary gland of DES-treated rats, whereas vasoactive intestinal peptide (VIP), which mediates the acute release of PRL, was elevated. Serotonin (5-HT) increased in the brain of male rats 24 hours after a single DES treatment; however, PRL, VIP or 5-HT was not induced by DES in female rats. Our results indicate that DES induces the expression of pituitary PRL in male rats by stimulating VIP in the hypothalamus and 5-HT in the central nervous system.

Diethylstilbestrol induces morphological changes in the spermatogonia, Sertoli cells and Leydig cells of adult rat

It is now established that diethylstilbestrol (DES) has damaging effects on the male reproductive system. However, to date there have been no studies morphological analysis of adult rat testes upon treatment with DES. Here, we examined whether DES has any significant morphological effect on steroidogenesis and spermatogenesis. DES was injected subcutaneously at 3 μg/day and 30 μg/day in adult male Sprague-Dawley (SD) rats for two different treatment lengths (1 or 3 weeks), after which rats were necropsied. TUNEL labeling, cell counting, and morphological analysis were used to evaluate the effects of DES. A high dose of DES and longer exposure severely affected the cellular development of the testis. Specifically, DES treatment disrupted both steroidogenesis and spermatogenesis by decreasing the number of spermatogonia, Sertoli cells, and Leydig cells in a dose- and time-dependent manner. Thus, DES may account for decreases in the number of spermatogenic cells, Sertoli cells and Leydig cells, which in turn may lead to reduced fertility in males.

Alteration in apoptotic rate of testicular cells and sperms following administration of Bisphenol A (BPA) in Wistar albino rats

The aim of the study was to evaluate the effect of Bisphenol A [BPA] widely used as a plasticizer in the formation of polycarbonate plastics and epoxy resins, exposure causing alteration in apoptosis rate, and protective effect of Vitamin E when supplemented with BPA orally. Adult male Wistar albino rats aged 3 months were randomly divided into seven groups: control (olive oil treated) BPA-treated (dose 5, 50,100 μg/100gmBW) and Vitamin E intervention group (dose 5, 50, 100 μg/100gmBW BPA+ Vitamin E dose 4 mg/100gmBW). Animals were sacrificed 3 months later, and blood and tissue samples were collected. Apoptotic changes were analyzed in epididymal spermatozoa and testis tissue by binding of annexin V apoptotic biomarker. A significant decline in the weight of testis, testosterone level, and sperm count was observed. Histopathological and apoptotic changes were observed in testis tissue. In epididymal sperms, the early apoptotic cells were observed by staining of annexin V-conjugated FITC and PI green fluorescence in spermatozoa head which indicated the damage of membrane and late apoptotic cells. These changes reduced significantly in Vitamin E-treated groups though were not found to be comparable to control animals. All these changes were attributed to disrupted spermatogenesis that would interfere with sperm formation. Thus, the study infers that BPA affects the apoptosis process in the testis and epididymal sperm that would interfere with its function and contribute to infertility, whereas Vitamin E-supplemented dose has a protective effect towards these changes, indicating its role in improving male fertility.

Diethylstilbestrol induces oxidative DNA damage, resulting in apoptosis of spermatogonial stem cells in vitro

) in SSCs was detected using p-Nitro Blue Tetrazolium (NBT) assay. The viability of cells after DES treatment was examined in the CCK8 (cell counting kit-8) cytotoxicity assay. The results showed that DES-induced DNA damage causes an increase in intracellular superoxide anions which are reduced by the flavonoid, quercetin. Investigating the molecular mechanisms and biology of SSCs provides a better understanding of spermatogonial stem cell regulation in the testis.

Obesogens and male fertility

In the last decades, several studies evidenced a decrease in male fertility in developed countries. Although the aetiology of this trend in male reproductive health remains a matter of debate, environmental compounds that predispose to weight gain, namely obesogens, are appointed as contributors because of their action as endocrine disruptors. Obesogens favour adipogenesis by an imbalance of metabolic processes and can be found virtually everywhere. These compounds easily accumulate in tissues with high lipid content. Obesogens change the functioning of male reproductive axis, and, consequently, the testicular physiology and metabolism that are pivotal for spermatogenesis. The disruption of these tightly regulated metabolic pathways leads to adverse reproductive outcomes. Notably, adverse effects of obesogens may also promote disturbances in the metabolic performance of the following generations, through epigenetic modifications passed by male gametes. Thus, unveiling the molecular pathways by which obesogens induce toxicity that may end up in epigenetic modifications is imperative. Otherwise, a transgenerational susceptibility to metabolic diseases may be favoured. We present an up-to-date overview of the impact of obesogens on testicular physiology, with a particular focus on testicular metabolism. We also address the effects of obesogens on male reproductive parameters and the subsequent consequences for male fertility.

Diethylstilbestrol activates CatSper and disturbs progesterone actions in human spermatozoa

STUDY QUESTION

Is diethylstilbestrol (DES), a prototypical endocrine-disrupting chemical (EDC), able to induce physiological changes in human spermatozoa and affect progesterone actions?

SUMMARY ANSWER

DES promoted Ca²⁺ flux into human spermatozoa by activating the cation channel of sperm (CatSper) and suppressed progesterone-induced Ca²⁺ signaling, tyrosine phosphorylation and sperm functions.

WHAT IS KNOWN ALREADY

DES significantly impairs the male reproductive system both in fetal and postnatal exposure. Although various EDCs affect human spermatozoa in a non-genomic manner, the effect of DES on human spermatozoa remains unknown.

STUDY DESIGN, SIZE, DURATION

Sperm samples from normozoospermic donors were exposed in vitro to a range of DES concentrations with or without progesterone at 37°C in a 5% CO₂ incubator to mimic the putative exposure to this toxicant in seminal plasma and the female reproductive tract fluids. The incubation time varied according to the experimental protocols. All experiments were repeated at least five times using different individual sperm samples.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human sperm intracellular calcium concentrations ([Ca²⁺]_i) were monitored with a multimode plate reader following sperm loading with Ca²⁺ indicator Fluo-4 AM, and the whole-cell patch-clamp technique was performed to record CatSper and alkalinization-activated sperm K⁺ channel (KSper) currents. Sperm viability and motility parameters were assessed by an eosin-nigrosin staining kit and a computer-assisted semen analysis system, respectively. The ability of sperm to penetrate into viscous media was examined by penetration into 1% methylcellulose. The sperm acrosome reaction was measured using chlortetracycline staining. The level of tyrosine phosphorylation was determined by western blot assay.

MAIN RESULTS AND THE ROLE OF CHANCE

DES exposure rapidly increased human sperm [Ca²⁺]_i dose dependently and even at an environmentally relevant concentration (100 pM). The elevation of [Ca²⁺]_i was derived from extracellular Ca²⁺ influx and mainly mediated by CatSper. Although DES did not affect sperm viability, motility, penetration into viscous media, tyrosine phosphorylation or the acrosome reaction, it suppressed progesterone-stimulated Ca²⁺ signaling and tyrosine phosphorylation. Consequently, DES (1-100 μM) significantly inhibited progesterone-induced human sperm penetration into viscous media and acrosome reaction.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Although DES has been shown to disturb progesterone actions on human spermatozoa, this study was performed in vitro, and caution must be taken when extrapolating the results in practical applications.

WIDER IMPLICATIONS OF THE FINDINGS

The present study revealed that DES interfered with progesterone-stimulated Ca²⁺ signaling and tyrosine phosphorylation, ultimately inhibited progesterone-induced human sperm functions and, thereby, might impair sperm fertility. The non-genomic manner in which DES disturbs progesterone actions may be a potential mechanism for some estrogenic endocrine disruptors to affect human sperm function.

STUDY FUNDING/COMPETING INTERESTS

National Natural Science Foundation of China (No. 31400996); Natural Science Foundation of Jiangxi, China (No. 20161BAB204167 and No. 20142BAB215050); open project of National Population and Family Planning Key Laboratory of Contraceptives and Devices Research (No. 2016KF07) to T. Luo; National Natural Science Foundation of China (No. 81300539) to L.P. Zheng. The authors have no conflicts of interest to declare.

Downregulation of cytochrome P450scc as an initial adverse effect of adult exposure to diethylstilbestrol on testicular steroidogenesis

Reproductive toxicities and endocrine disruptions caused by chemicals in adult males are still poorly understood. It is our objectives to understand further details of the initial adverse effects leading severe testicular toxicities of a pharmaceutical endocrine disruptor, diethylstilbestrol (DES). Downregulations of both testicular regulatory proteins, such as the steroidogenic acute regulatory protein (StAR) and the peripheral benzodiazepine receptor (PBR), which play important roles in the transport of cholesterol into the mitochondria, and cytochrome P450 mediating the cholesterol side chain cleavage reaction (P450scc), were observed in the rat orally administered DES (340 μg/kg/2 days) for 2 weeks. We found that after only 1 week treatment with DES, the blood and testicular testosterone (TS) levels were drastically decreased without abnormalities of the StAR and PBR; however, the protein and mRNA levels of P450scc were diminished. Decrease in the conversion rate of cholesterol to pregnenolone was delayed in the in vitro assay using the testicular mitochondrial fraction from the rat treated with DES for 1 week. When the precursors in TS biosynthesis containing the testis were identified and determined by liquid chromatography-mass spectrometry analysis, decreased levels of all precursors except cholesterol were observed. In conclusion, suppressed cytochrome P450scc expression in adult male rat was identified as an initial target of DES in testicular steroidogenesis disorder leading reproductive toxicities.

Quinestrol induces spermatogenic apoptosis in vivo via increasing pro-apoptotic proteins in adult male mice

The effects of quinestrol on spermatogenesis were investigated in adult male mice by daily intragastric administration of quinestrol with various doses of 5, 10, 50 and 100mg/kg body weight for 10 days. The sperm counts declined while the number of abnormal spermatozoa went up in mice treated with quinestrol. The testicular weight and seminiferous tubular area gradually declined with increasing dosages of quinestrol to 50 and 100mg/kg. Rarefied germ cells showed irregular distributions in the seminiferous tubules of mice treated with 50 and 100mg/kg quinestrol. Apoptosis was highly pronounced in spermatogonia, spermatocytes, spermatids and Leydig cells. Antioxidant enzyme activities - superoxide dismutase and glutathione peroxidase - as well as total antioxidant capacity significantly reduced, while malondialdehyde contents increased. The number of germ cells expressing caspase-3, p53, Bax and FasL significantly increased whereas cells expressing Bcl-2 significantly decreased in groups treated with 50 and 100mg/kg quinestrol compared with the control. The concentration of nitrogen monoxidum also increased significantly under these dosages. The results suggest that quinestrol stimulates oxidative stress to induce apoptosis in spermatogenic cells through the mitochondrial and death receptor pathways in adult male mice.

Maternal cypermethrin exposure during the perinatal period impairs testicular development in C57BL male offspring

Numerous studies have demonstrated that endocrine-disrupting compounds (EDC) are a possible cause of male reproductive organ malfunction and malformation. Cypermethrin (CYP) is a widely used synthetic pyrethroid and a potential EDC. This study aimed to examine the effects of perinatal exposure to low-dose CYP on the development and function of the offspring testes. Pregnant mice were intragastrically administered 0.12 to 12 mg/kg/day CYP from embryonic day 0.5 (E0.5) to weaning (PD21.5, postnatal day 21.5). Maternal exposure to 0.12, 1.2, and 12 mg/kg/day CYP affected the body and organ weight of the offspring. Exposure of CYP led to a dose-dependent decrease in the male-to-female sex ratio. A histopathological analysis revealed a thinner seminiferous epithelium layer at PD21.5, interstitial hyperplasia at PD45.5, and germ cell vacuolization at PD90.5 in the 12 mg/kg/day CYP group. The TUNEL assay results revealed increased germ cell apoptosis in the 12 mg/kg/day CYP group. The serum testosterone (T) level decreased, whereas the estradiol level increased with age in the 1.2 and 12 mg/kg/day CYP groups. The RT-PCR analysis demonstrated decreased expression of T production-related, mitosis-related, and meiosis-related genes in the 1.2 and 12 mg/kg/day CYP groups. The in vitro experimental results demonstrated reduced expression of steroidogenesis genes and decreased T levels. It is concluded that perinatal exposure to low-dose CYP affects testes development and function in adults.

Changes in expression levels of oxidative stress-related genes in mouse epididymides by neonatal exposure to low-dose decabromodiphenyl ether

Decabromodiphenyl ether (decaBDE), one of the polybrominated diphenyl ethers (PBDEs), is the most well-known flame retardant and is used worldwide. In a previous study, we identified adverse effects of neonatal decaBDE exposure on mouse epididymides, such as decreased epididymal weight. On the other hand, neonatal exposure to diethylstilbestrol (DES), an artificial estrogenic compound, also causes several adverse effects on epididymides. DES exposure results in decreased epididymal weight, morphological abnormalities, and permanent alterations in the expression levels of several genes. The molecular mechanisms underlying the harmful effects of decaBDE exposure remain unclear. Many studies have reported that PBDEs have estrogenic activity, which may contribute to the induction of the adverse effects of decaBDE exposure. We aimed to examine the effects of neonatal decaBDE exposure on epididymides. Our data showed that (1) no histological change was observed on epididymal tissues from neonatal decaBDE exposure, unlike the effect of DES, (2) decaBDE exposure did not induce the alterations in gene expression observed with DES exposure; instead alterations in gene expression of certain oxidative stress-related genes were observed, and (3) the expression of ubiquitin C increased in decaBDE-exposed mouse epididymides. Our present data suggest the possibility that increased oxidative stress plays a role in the harmful effects observed in mouse epididymides after decaBDE-exposure.

Protective Effects of Lycium barbarum Polysaccharides on Testis Spermatogenic Injury Induced by Bisphenol A in Mice

To observe the effects of Lycium barbarum polysaccharides (LBP) on testis spermatogenic injuries induced by Bisphenol A (BPA) in mice. BPA was subcutaneously injected into mice at a dose of 20 mg/kg body weight (BW) for 7 consecutive days. LBP was administered simultaneously with BPA by gavage daily at the dose of 50, 100, and 200 mg/kg BW for 7 days. After treatment, the weight and the histopathology changes of testis and epididymis were examined; the contents of T, LH, GnRH, antioxidant enzyme, and malondialdehyde (MDA) in serum were detected; proapoptotic protein Bax and antiapoptotic protein Bcl-2 were also detected by immunohistochemical method. Results showed that the weights of testis and epididymis were all increased after supplement with different dosages of LBP compared with BPA group, and the activities of SOD and GSH-Px were significantly increased in LBP groups, while MDA contents were gradually decreased. Moreover, the levels of T, LH, and GnRH were significantly elevated in serum treated with 100 mg/kg LBP. LBP also shows significant positive effects on the expression of Bcl-2/Bax in BPA treated mice. It is concluded that LBP may be one of the potential ingredients protecting the adult male animals from BPA induced reproductive damage.

Effects of Ginkgo Biloba on Testicle Injury Induced by Diethylstilbestrol in Mice

To evaluate the effect of gingko biloba (EGb) on diethylstilbestrol (DES) induced testicle injury in mice. Fifty male mice were divided into a control group (A), DES group (B), and 3 EGb groups (C, D, E). The EGb-treated groups received peritoneal EGb at 8.75 (C), 17.5 (D), 35 mg/kg (E) BW daily for 7 days. The control group was given equivalent amount of normal saline. The mice in groups B, C, D and E were injected hypodermically with DES at 40 mg/kg BW daily 4 hours after the first herbal administration, while the control was given olive oil. Compared with DES group, the testis coefficients-relative testicular weight increased in the three EGb-treated groups. No significant difference was observed in epididymis coefficients. Lipid peroxidation status and antioxidant enzyme activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were significantly elevated in testes of EGb-treated groups. Lactate dehydrogenase (LDH) activities and malonaldehyde (MDA) contents were significantly decreased in testes of the EGb groups. The results indicate that EGb protects the testis from diethylstilbestrol-induced injury.

Oxidatively damaged proteins in the early stage of testicular toxicities in male rats by orally administered with a synthetic oestrogen, diethylstilbestrol

The molecular mechanism of severe adverse effects of the endocrine disruptor diethylstilbestrol (DES) on reproductive organs is not currently understood. The effects of DES on testicular proteins were studied in adult male rats orally treated with 0.35 and 3.5mg DES/kg every two days for two weeks before the manifestation of morphological toxicities. Two up-regulated proteins (glutamine synthetase and chaperonin containing TCP1), two down-regulated proteins (thioredoxin-like 1 and testis-specific autoantigen) and two proteins with altered isoelectric points (protein disulfide isomerase [PDI a3] and enolase 1) were identified in DES groups. Carbonylation of PDI a3 was detected. A significant decrease in PDI activity and significant increases in caspase-12 and calpain activities were also found in the group. It is suggested that testicular toxicity by DES was initiated by the down-regulation of thioredoxin-like-1 leading to the cellular redox inbalances, and the resultant oxidative modification of several important proteins involved in protein foldings.

Adult exposure to sasanguasaponin induces spermatogenic cell apoptosis in vivo through increased oxidative stress in male mice

Effects of sasanguasaponin (SGS), a compound from defatted seeds of Camellia oleifera, on abnormal spermatogenesis were studied in adult male mice using daily intragastric administration of 100, 200 and 400 mg/kg body weight (BW) for 6 weeks. The sperm counts decreased and the number of abnormal spermatozoa increased in mice treated with SGS at 400 mg/kg dose level. Testicular weight and seminiferous tubular area gradually decreased as dosage increased to 400 mg/kg SGS. Germ cells were rarefied and showed irregular distribution in seminiferous tubules (STs). Apoptosis was pronounced among spermatocytes and spermatids at the 400 mg/kg dose level. Antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and total antioxide capacity (T-AOC) markedly decreased and malondialdehyde (MDA) concentration increased in the testes. These results suggest that adult exposure to SGS (400 mg/kg) induces spermatogenic apoptosis through increased oxidative stress in male mice.

Overview of developmental and reproductive toxicity research in China: history, funding mechanisms, and frontiers of the research

Reproductive and developmental toxicology (DART) is the discipline that deals with adverse effects on male and female resulting from exposures to harmful chemical and physical agents. DART research in China boasted a long history, but presently has fallen behind the western world in education and research. The funding mechanisms for DART research in China were similar to that for other toxicological disciplines, and the funding has come from research grants and fellowships provided by national, ministerial, and provincial institutions. Finally, the frontiers of DART research in China could be summarized as follows: (1) use of model animals such as the zebrafish and roundworm, and use of cutting-edge techniques such as stem cell culture, as well as transgenic, metabonomic, and virtual screening to study the mechanisms of developmental toxicity for some important toxicants in China; (2) use of model animals and other lower-level sentinel organisms to evaluate and monitor the developmental toxicogical risk of environmental chemicals or pollutants; (3) epidemiological studies of some important reproductive hazards; (4) in-depth studying of the reproductive and developmental toxicity of some important environmental chemicals; and (5) evaluation and study of the reproductive and developmental toxicity of traditional Chinese medicines.