Inhibition of CYP450scc expression in dioxin-exposed rat Leydig cells

Protective effect of didymin against 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin-induced reproductive toxicity in male rats

PURPOSE

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin (TCDD) is one of the most potent environmental toxicants, which causes oxidative stress and adversely affects the male reproductive system. The current study aimed to evaluate the ameliorative role of didymin (DDM) against TCDD-induced testicular toxicity.

METHODS

Forty-eight male Sprague-Dawley rats were divided into four equal groups (n=12). (i) Control group, (ii) TCDD-induced group was provided with 10 μg/kg/day of TCDD, (iii) TCDD + DDM group received 10 μg/kg/day of TCDD and 2 mg/kg/day of DDM, and (iv) DDM-treated group was administered with 2 mg/kg/day of DDM. After 56 days of treatment, biochemical, steroidogenic, hormonal, spermatogenic, apoptotic, and histopathological parameters were estimated.

RESULTS

TCDD affected the biochemical profile by reducing the activities of antioxidant enzymes, while increasing the levels of malondialdehyde (MDA) and reactive oxygen species (ROS). Furthermore, it decreased the expressions of steroidogenic enzymes, 3β-hydroxysteroid dehydrogenase (HSD), 17β-HSD, steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme (CYP11A1), and 17α-hydroxylase/17, 20-lyase (CYP17A1), as well as reduced the levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and plasma testosterone. Besides, epididymal sperm count, viability, and motility were decreased, while sperm morphological anomalies were increased. Moreover, TCDD altered the apoptotic profile by up-regulating the expressions of Bax and caspase-3, while downregulated the Bcl-2 expression. Additionally, histopathological damages were prompted due to TCDD administration. However, DDM restored all the TCDD-induced damages owing to its antioxidant, anti-apoptotic, and androgenic potential.

CONCLUSION

Our data suggested that DDM might play its role as a therapeutic agent against TCDD-prompted testicular toxicity.

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

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

Maternal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin suppresses male reproductive functions in their adulthood

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a ubiquitous environmental contaminant in the environment. The developmental period is more sensitive to TCDD and there is a possibility that maternal exposure to TCDD may affect in adulthood. Adult female Wistar rats were exposed to 0.5, 1.0, and 2.0 µg/kg TCDD during the critical stage of organogenesis, that is, on GD15. The results revealed a significant decrease in indices of reproductive organ weight in adult male rats exposed to prenatal TCDD, and dose-dependent reduction in epididymal sperm reserves, percent motile, and viable sperm with an increase in percent morphological abnormal sperm. Polymerase chain reaction analysis revealed downregulated expression levels of steroidogenic markers such as steroidogenic acute regulatory, cholesterol side-chain cleavage, and 3β- and 17β-hydroxysteroid dehydrogenase (HSDs) in experimental rats. Immunofluorescence sections portrayed reduced distribution of 3β- and 17β-HSD proteins in testes of experimental rats. Furthermore, spermatogenic markers (acid phosphatase, alkaline phosphatase, lactate dehydrogenase, and sorbitol dehydrogenase) were significantly altered in the testes. Serum levels of testosterone, follicle stimulating hormones, and luteinizing hormone were significantly decreased. Testicular levels of hydrogen peroxide and lipid peroxidation were significantly elevated with a decline in superoxide dismutase, catalase, glutathione peroxidase activities, and total thiol levels. Moreover, histological and morphometric examination of testicular cross-sections depicted degenerative changes. Male fertility assessment in adult rats revealed a significant decrease in mating index, fertility index, and mean number of pre- and postimplantations with an increase in pre- and postimplantation losses in rats cohabited with in utero TCDD-exposed adult males. In conclusion, the findings of this study provided clear evidence that maternal exposure to TCDD during the critical stage of development results in suppressed reproductive health in adulthood.

Association of dioxin exposure and reproductive hormone levels in men living near the Bien Hoa airbase, Vietnam

Dioxins are endocrine-disrupting chemicals, and their effects on reproductive functions are well-documented. The aim of the present study was to measure the levels of reproductive hormones in 42 men residing near a dioxin-contaminated area in Vietnam. We measured levels of 17 2,3,7,8-substituted congeners of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) and four non-ortho polychlorinated biphenyls (PCBs) in blood. Levels of follicle-stimulating hormone, luteinizing hormone, progesterone, prolactin, estradiol, and total testosterone were measured in serum. Blood dioxin levels were elevated; the levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin was 7.3pg/g fat. Seven of the men had testosterone levels below 250ng/dL, and nine men had prolactin levels above 9.7ng/mL. Four PCDD congeners, two PCDF congeners, one PCB congener, and the sum TEQ of PCDDs, PCDDs/Fs, and PCDDs/Fs/PCBs were positively and significantly correlated with prolactin levels. Two PCDD congeners, six PCDF congeners, two PCB congeners, and the TEQs of PCDFs and PCBs were negatively and significantly correlated with testosterone levels. There were no significant correlations between dioxin congeners and follicle-stimulating hormone, luteinizing hormone, or progesterone levels.

Lipophagy Contributes to Testosterone Biosynthesis in Male Rat Leydig Cells

In recent years, autophagy was found to regulate lipid metabolism through a process termed lipophagy. Lipophagy modulates the degradation of cholesteryl esters to free cholesterol (FC), which is the substrate of testosterone biosynthesis. However, the role of lipophagy in testosterone production is unknown. To investigate this, primary rat Leydig cells and varicocele rat models were administered to inhibit or promote autophagy, and testosterone, lipid droplets (LDs), total cholesterol (TC), and FC were evaluated. The results demonstrated that inhibiting autophagy in primary rat Leydig cells reduced testosterone production. Further studies demonstrated that inhibiting autophagy increased the number and size of LDs and the level of TC, but decreased the level of FC. Furthermore, hypoxia promoted autophagy in Leydig cells. We found that short-term hypoxia stimulated testosterone secretion; however, the inhibition of autophagy abolished stimulated testosterone release. Hypoxia decreased the number and size of LDs in Leydig cells, but the changes could be largely rescued by blocking autophagy. In experimental varicocele rat models, the administration of autophagy inhibitors substantially reduced serum testosterone. These data demonstrate that autophagy contributes to testosterone biosynthesis at least partially through degrading intracellular LDs/TC. Our observations might reveal an autophagic regulatory mode regarding testosterone biosynthesis.

The association of peripubertal serum concentrations of organochlorine chemicals and blood lead with growth and pubertal development in a longitudinal cohort of boys: a review of published results from the Russian Children's Study

Organochlorine chemicals and lead are environmental exposures that have endocrine disrupting properties (EDCs) which interfere with many aspects of hormone action. Childhood and adolescence are windows of susceptibility for adverse health effects of EDCs. Our ongoing study, the Russian Children's Study (RCS), is one of the few longitudinal studies investigating the impact of EDCs on growth and puberty in boys. It is conducted in the historically contaminated city of Chapaevsk, in the Samara region. The study focuses on evaluating the associations of persistent organochlorine chemicals and lead with growth and pubertal timing. At enrollment in 2003-2005, we collected blood from 516 boys at ages 8-9 years to measure dioxins, furans, polychlorinated biphenyls (PCBs), chlorinated pesticides and lead. At enrollment and at annual visits through the ages of 18-19 years, a physician performed physical examinations that included pubertal staging and testicular volume measurements. We review the history of Chapaevsk as a research site and summarize published RCS data on the association of peripubertal serum concentrations of organochlorines and blood lead levels with growth, pubertal onset and sexual maturity. Overall, we found that persistent organochlorines and lead negatively affected growth during puberty. Our results also suggest that total toxic equivalents (TEQs), dioxin-like compounds, organochlorine pesticides and lead may delay, while nondioxin-like-PCBs may advance, the timing of male puberty. These findings promoted remediation programs in Chapaevsk, with improvement in health indicators, resulting in Chapaevsk being designated a member of the World Health Organization (WHO) network "Healthy Cities" in 2015.

Review on crosstalk and common mechanisms of endocrine disruptors: Scaffolding to improve PBPK/PD model of EDC mixture

Endocrine disruptor compounds (EDCs) are environment chemicals that cause harmful effects through multiple mechanisms, interfering with hormone system resulting in alteration of homeostasis, reproduction and developmental effect. Many of these EDCs have concurrent exposure with crosstalk and common mechanisms which may lead to dynamic interactions. To carry out risk assessment of EDCs' mixture, it is important to know the detailed toxic pathway, crosstalk of receptor and other factors like critical window of exposure. In this review, we summarize the major mechanism of actions of EDCs with the different/same target organs interfering with the same/different class of hormone by altering their synthesis, metabolism, binding and cellular action. To show the impact of EDCs on life stage development, a case study on female fertility affecting germ cell is illustrated. Based on this summarized discussion, major groups of EDCs are classified based on their target organ, mode of action and potential risk. Finally, a conceptual model of pharmacodynamic interaction is proposed to integrate the crosstalk and common mechanisms that modulate estrogen into the predictive mixture dosimetry model with dynamic interaction of mixture. This review will provide new insight for EDCs' risk assessment and can be used to develop next generation PBPK/PD models for EDCs' mixture analysis.

Origin and Differentiation of Androgen-Producing Cells in the Gonads

Sexual reproduction is dependent on the activity of androgenic steroid hormones to promote gonadal development and gametogenesis. Leydig cells of the testis and theca cells of the ovary are critical cell types in the gonadal interstitium that carry out steroidogenesis and provide key androgens for reproductive organ function. In this chapter, we will discuss important aspects of interstitial androgenic cell development in the gonad, including: the potential cellular origins of interstitial steroidogenic cells and their progenitors; the molecular mechanisms involved in Leydig cell specification and differentiation (including Sertoli-cell-derived signaling pathways and Leydig-cell-related transcription factors and nuclear receptors); the interactions of Leydig cells with other cell types in the adult testis, such as Sertoli cells, germ cells, peritubular myoid cells, macrophages, and vascular endothelial cells; the process of steroidogenesis and its systemic regulation; and a brief discussion of the development of theca cells in the ovary relative to Leydig cells in the testis. Finally, we will describe the dynamics of steroidogenic cells in seasonal breeders and highlight unique aspects of steroidogenesis in diverse vertebrate species. Understanding the cellular origins of interstitial steroidogenic cells and the pathways directing their specification and differentiation has implications for the study of multiple aspects of development and will help us gain insights into the etiology of reproductive system birth defects and infertility.

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.

The effects on steroidogenesis and histopathology of adult male Japanese quails (Coturnix coturnix japonica) testis following pre-pubertal exposure to di(n-butyl) phthalate (DBP)

In the present study, we have investigated the effects of 30-day dietary (pre-pubertal) exposure to different doses (0 (control), 1, 10, 50, 200 and 400 mg/kg bodyweight/day) of di(n-butyl) phthalate (DBP) on Leydig cells of adult male Japanese quails by quantifying the transcript levels for P450 side-chain cleavage (p450scc), P450c17 (CYP17), and 3β- and 17β-hydroxysteroid dehydrogenase (hsd) using quantitative (real-time) polymerase chain reaction (qRT-PCR). In addition, the plasma testosterone levels were analysed using radioimmunoassay (RIA) and testis was examined for evidence of gross pathology and histopathology. Our data showed that pre-pubertal exposure to DBP produced alterations in testicular architecture as evident by poorly developed or mis-shaped testis, and altered spermatogenesis due to tubular degeneration and atrophy of seminiferous tubules especially in the high DBP dose (200 and 400 mg/kg) treated groups. In addition, DBP altered several key enzymes involved in testicular steroidogenesis pathways in an apparent dose-dependent manner. For example, biphasic effects of DBP were observed for P450scc and 3β-hsd mRNA, that were generally increasing at low dose 10 mg/kg, and thereafter, an apparent dose-dependent decrease between 50 and 400mg/kg. The steroidogenic acute regulatory (StAR) protein was at the lowest detectable limits and therefore not quantifiable. These effects did not parallel the non-significant changes observed for plasma testosterone levels. The present data is consistent with previous reports showing that DBP modulates Leydig cell steroidogenesis in several species, with a potential negative effect on reproduction in those avian species that are vulnerable to endocrine disrupting chemicals.

Ameliorative effect of lycopene against 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced rat liver microsomal toxicity

The objective of the current study was to investigate the potential oxidative damage of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) in hepatic microsomal fractions in vitro and to further elucidate the potential modulatory effect of lycopene. Rat liver microsomes were divided into four groups. Group I served as a control and is incubated with vehicle (toluene). Groups II and IV were incubated with 20 µM lycopene for 1 h before further incubating; groups III and IV with 15 nM of TCDD for further 1 h. Hydrogen peroxide (H2O2) production, lipid peroxidation (LPO), protein carbonyl content and activities of uridine 5′-diphospho-glucuronyltransferase (UDPGT) and P450 were significantly increased. Moreover, the activity of antioxidant enzymes superoxide dismutase, glutathione peroxidase, catalse, glutathione- S-transferase and glutathione reductase as well as the microsomal thiol content were significantly decreased. Incubation with lycopene (group IV) maintained near normal activities of the enzymes, normalized thiol and carbonyl content and significantly reduced LPO and H2O2 production. In conclusion, the findings of the study indicate that TCDD induces a significant oxidative stress in liver microsomes as manifested by increased LPO, H2O2 production, protein carbonyl content and activities of UDPGT and P450 and decreased antioxidant enzymes activities and thiol content. By the reversal of biochemical and oxidative markers toward normalcy, the protective role of lycopene is illuminated in rat liver microsomal toxicity.

BLTK1 murine Leydig cells: a novel steroidogenic model for evaluating the effects of reproductive and developmental toxicants

Leydig cells are the primary site of androgen biosynthesis in males. Several environmental toxicants target steroidogenesis resulting in both developmental and reproductive effects including testicular dysgenesis syndrome. The aim of this study was to evaluate the effect of several structurally diverse endocrine disrupting compounds (EDCs) on steroidogenesis in a novel BLTK1 murine Leydig cell model. We demonstrate that BLTK1 cells possess a fully functional steroidogenic pathway that produces low basal levels of testosterone (T) and express all the necessary steroidogenic enzymes including Star, Cyp11a1, Cyp17a1, Hsd3b1, Hsd17b3, and Srd5a1. Recombinant human chorionic gonadotropin (rhCG) and forskolin (FSK) elicited concentration- and time-dependent induction of 3',5'-cyclic adenosine monophosphate, progesterone (P), and T, as well as the differential expression of Star, Hsd3b6, Hsd17b3, and Srd5a1 messenger RNA levels. The evaluation of several structurally diverse male reproductive toxicants including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), atrazine, prochloraz, triclosan, monoethylhexyl phthalate (MEHP), glyphosate, and RDX in BLTK1 cells suggests different modes of action perturb steroidogenesis. For example, prochloraz and triclosan antifungals reduced rhCG induction of T, consistent with published in vivo data but did not alter basal T levels. In contrast, atrazine and MEHP elicited modest induction of basal T but antagonized rhCG-mediated induction of T levels, whereas TCDD, glyphosate, and RDX had no effect on basal or rhCG induction of T in BLTK1 cells. These results suggest that BLTK1 cells maintain rhCG-inducible steroidogenesis and are a viable in vitro Leydig cell model to evaluate the effects of EDCs on steroidogenesis. This model can also be used to elucidate the different mechanisms underlying toxicant-mediated disruption of steroidogenesis.

Epigenetic: a molecular link between testicular cancer and environmental exposures

In the last decades, studies in rodents have highlighted links between in utero and/or neonatal exposures to molecules that alter endocrine functions and the development of genital tract abnormalities, such as cryptorchidism, hypospadias, and impaired spermatogenesis. Most of these molecules, called endocrine disrupters exert estrogenic and/or antiandrogenic activities. These data led to the hypothesis of the testicular dysgenesis syndrome which postulates that these disorders are one clinical entity and are linked by epidemiological and pathophysiological relations. Furthermore, infertility has been stated as a risk factor for testicular cancer (TC). The incidence of TC has been increasing over the past decade. Most of testicular germ cell cancers develop through a pre-invasive carcinoma in situ from fetal germ cells (primordial germ cell or gonocyte). During their development, fetal germ cells undergo epigenetic modifications. Interestingly, several lines of evidence have shown that gene regulation through epigenetic mechanisms (DNA and histone modifications) plays an important role in normal development as well as in various diseases, including TC. Here we will review chromatin modifications which can affect testicular physiology leading to the development of TC; and highlight potential molecular pathways involved in these alterations in the context of environmental exposures.

Polybrominated diphenyl ethers and polychlorinated dibenzo-p-dioxins and dibenzofurans in surface dust at an E-waste processing site in Southeast China

Surface dust collected from printed circuit board recycling workshop floors, roads, a schoolyard, and an outdoor food market in Guiyu, China, a village intensely involved in e-waste processing, were investigated for levels of polybrominated diphenyl ethers (PBDEs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). PBDE concentrations in dust from workshop-floors (14,800 ± 5130 ng/g) and on adjacent roads to the workshops (24,900 ± 31,600 ng/g) were highest among the study sites whereas PCDD/F concentrations were highest at the schoolyard (1316 pg/g) and in a workshop (1264 pg/g). Analyses of <2 mm and <53 μm dust particle sizes did not show any significant differences in PBDE concentrations. The cytotoxicity was investigated using two bioassays: 7-ethoxyresorufin O-deethylase (EROD-TEQ) and MTT. EROD-TEQ values ranged from 260 to 432 pg/g, with the highest in dust collected from a street lined with workshops. Using the MTT assay, cytoxicity of dust from the plastic chips drying district in Guiyu was higher than dust from the other sites investigated. This study showed that the primitive recycling of e-waste introduced toxic pollutants into the environment which are potentially harmful to the health of e-waste workers and local residents, especially children, and warrants an urgent investigation into POPs related health impacts.

Endocrine disrupting chemicals: Multiple effects on testicular signaling and spermatogenesis

In the past 200 years, an enormous number of synthetic chemicals with diverse structural features have been produced for industrial, medical and domestic purposes. These chemicals, originally thought to have little or no biological toxicity, are widely used in our daily lives as well as are commonly present in foods. It was not until the first World Wildlife Federation Wingspread Conference held in 1994 were concerns about the endocrine disrupting (ED) effects of these chemicals articulated. The potential hazardous effects of endocrine disrupting chemicals (EDCs) on human health and ecological well-being are one of the global concerns that affect the health and propagation of human beings. Considerable numbers of studies indicated that endocrine disruption is linked to "the developmental basis of adult disease," highlighting the significant effects of EDC exposure on a developing organism, leading to the propensity of an individual to develop a disease or dysfunction in later life. In this review, we intend to provide environmental, epidemiological and experimental data to associate pollutant exposure with reproductive disorders, in particular on the development and function of the male reproductive system. Possible effects of pollutant exposure on the processes of embryonic development, like sex determination and masculinization are described. In addition, the effects of pollutant exposure on hypothalamus-pituitary-gonadal axis, testicular signaling, steroidogenesis and spermatogenesis are also discussed.

The effect of environmental contaminants on testicular function

Male reproductive health has deteriorated considerably in the last few decades. Nutritional, socioeconomic, lifestyle and environmental factors (among others) have been attributed to compromising male reproductive health. In recent years, a large volume of evidence has accumulated that suggests that the trend of decreasing male fertility (in terms of sperm count, quality and other changes in male reproductive health) might be due to exposure to environmental toxicants. These environmental contaminants can mimic natural oestrogens and target testicular spermatogenesis, steroidogenesis, and the function of both Sertoli and Leydig cells. Most environmental toxicants have been shown to induce reactive oxygen species, thereby causing a state of oxidative stress in various compartments of the testes. However, the molecular mechanism(s) of action of the environmental toxicants on the testis have yet to be elucidated. This review discusses the effects of some of the more commonly used environmental contaminants on testicular function through the induction of oxidative stress and apoptosis.

Assessment of risk of PCDD/Fs and dioxin-like PCBs in marine and freshwater fish in Pearl River Delta, China

Fish consumption is known to be beneficial to human health. However since the age of industrialization, the released/disposed chemical pollutants into water systems make fish a source of various environmental toxicants to humans. In oceanic cities with heavy industrial activities, fish products contribute the greatest proportion of exposure to pollutants. In this study, risks and potential effects of dioxins to health of coastal populations in the Pearl River Delta were assessed. Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (PCBs) were measured in common fish species purchased at local markets. Concentrations of total dioxins in fish ranged from 0.481 to 9.05 pg TEQ/g wet weight were similar to the lesser concentrations reported for fish from other countries. The greatest concentrations of dioxins were measured in mandarin fish, a carnivorous freshwater fish. Exposure of murine primary leydig and ovarian cells to 2,3,7,8-tetrachlorinated dibenzo-p-dioxins (2,3,7,8-TCDD) reduced the synthesis of progesterone, testosterone and/or estrogen. The reductions were probably via inhibitory effects on the expression of the steroidogenic enzymes, steroidogenic acute regulatory protein (StAR) and cytochrome P450 side-chain cleavage enzyme (P450scc). Based on these reproductive parameters, the concentrations of dioxins and dioxin-like residues represent a moderate health risk due to consumption of fish.

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced cytotoxicity accompanied by oxidative stress in rat Sertoli cells: Possible role of mitochondrial fractions of Sertoli cells

TCDD, as an endocrine disruptor, is known to impair testicular functions and fertility. To elucidate the mechanism(s) underlying the testicular effects of TCDD, the potential toxicity of TCDD on Sertoli cells was investigated. Furthermore, the study aims to delineate whether mitochondrial fractions of Sertoli cells are involved in mediating the testicular effects of TCDD. Adult rat Sertoli cells were incubated with (5, 10 or 15nM) of TCDD for 6, 12 or 24h. Cell viability, lactate and LDH leakage into media along with lipid peroxidation, ROS generation, SOD, CAT, GPx, GR, γ-GT and β-glucuronidase activities, GSH content and Δψ(m) were measured. Superoxide anion production, COX and cardiolipin content were measured in mitochondrial fractions. Cell viability was significantly decreased while lactate and LDH leakage into media were increased. ROS generation along with lipid peroxidation was also increased. SOD, CAT, GPx, GR activities and GSH content were significantly decreased. γ-GT and β-glucuronidase activities were also decreased. Superoxide anion production was increased while COX activity and cardiolipin content were decreased in mitochondrial fractions. Moreover, the Δψ(m) was significantly decreased as measured in Sertoli cells. In conclusion, TCDD impairs Sertoli cell functions and this effect is, at least in part, attributed to oxidative stress. We have also found that TCDD increases mitochondrial superoxide anion production and decreases Δψ(m), COX activity and mitochondrial cardiolipin content. Our findings suggest that mitochondria may play an important role in ROS production, leading to the TCDD-induced oxidative stress response and resulting toxicological consequences in rat Sertoli cells.

Endocrine disruptors and Leydig cell function

During the past decades, a large body of information concerning the effects of endocrine disrupting compounds (EDCs) on animals and humans has been accumulated. EDCs are of synthetic or natural origin and certain groups are known to disrupt the action of androgens and to impair the development of the male reproductive tract and external genitalia. The present overview describes the effects of the different classes of EDCs, such as pesticides, phthalates, dioxins, and phytoestrogens, including newly synthesized resveratrol analogs on steroidogenesis in Leydig cells. The potential impact of these compounds on androgen production by Leydig cells during fetal development and in the adult age is discussed. In addition, the possible role of EDCs in connection with the increasing frequency of abnormalities in reproductive development in animals and humans is discussed.

Evaluation of 4-nonylphenol in vivo exposure in Dreissena polymorpha: Bioaccumulation, steroid levels and oxidative stress

Nonylphenol (NP) represents the most critical metabolite of alkylphenols (APs) and alkylphenol ethoxylates (APEs), non-ionic surfactants widely used in the formulation of domestic and industrial products. On the basis of in vitro and in vivo animal studies 4-nonylphenol (4-NP) is considered an endocrine disrupting chemical (EDC). The evidence to date indicates that mollusks are able to synthesize sex steroids from the precursor cholesterol and their endocrine pathways are theoretically susceptible to disruption. The aim of this study was to investigate the endocrine modulating potency of 4-NP in the freshwater mussel Dreissena polymorpha by looking at endogenous steroid levels in control and exposed individuals. 4-NP bioaccumulation in mussels tissues and alterations in the activity of enzymes related both to oxidative stress (catalase - CAT- and glutathione peroxidase - GPX-) and phase II metabolism (glutathione-S-transferase - GST-) were also assessed. The results highlighted a build-up of 4-NP in exposed mussels and an overall decrease of 17-beta-estradiol and testosterone levels. On the other hand this chemical at the tested concentrations does not interfere with the antioxidant defense mechanisms in D. polymorpha. The mechanisms by which 4-NP alter steroids levels are unknown and require more in-depth investigations.

Leydig cell transplantation restores androgen production in surgically castrated prepubertal rats

Prepubertal testicular dysfunction and the subsequent development of hypogonadism affects an estimated one in 200 children worldwide. As the testosterone levels are dynamic during development and puberty, traditional hormone treatment regimens are often inadequate, thereby leaving associated physiological conditions unresolved. Therefore, we have investigated the potential therapeutic effect of mature Leydig cell transplantation for the treatment of prepubertal primary hypogonadism through the use of a surgically induced hypogonadistic rat model system. In the experiment, Leydig cells were surgically isolated from mature Sprague-Dawley rats and transplanted into prepubertal recipients. Serum testosterone levels and microscopic analysis of the stained testicular interstitium were compared with sham-treated controls, as well as with castrated and intact rats during sexual development. At 4 weeks post-implantation, serum testosterone was detectable in Leydig cell recipients, but not in surgical controls, and progressively increased as a function of time until reaching levels comparable with sexually mature males at 12 weeks post-implantation. Histological analysis revealed a high rate of Leydig cell survival as well as steroidogenic secretory activity. Therefore, we conclude that mature Leydig cell transplantation in prepubertal hypogonadism recipients has therapeutic potential in rats and merits further investigation for clinical application.

Permethrin may disrupt testosterone biosynthesis via mitochondrial membrane damage of Leydig cells in adult male mouse

Permethrin, a popular synthetic pyrethroid insecticide used to control noxious insects in agriculture, forestry, households, horticulture, and public health throughout the world, poses risks of environmental exposure. Here we evaluate the reproductive toxicity of cis-permethrin in adult male ICR mice that were orally administered cis-permethrin (0, 35, or 70 mg/kg d) for 6 wk. Caudal epididymal sperm count and sperm motility in the treated groups were statistically reduced in a dose-dependent manner. Testicular testosterone production and plasma testosterone concentration were significantly and dose-dependently decreased with an increase in LH, and a significant regression was observed between testosterone levels and cis-permethrin residues in individual mice testes after exposure. However, no significant changes were observed in body weight, reproductive organ absolute and relative weights, sperm morphology, and plasma FSH concentration after cis-permethrin treatment. Moreover, cis-permethrin exposure significantly diminished the testicular mitochondrial mRNA expression levels of peripheral benzodiazepine receptor (PBR), steroidogenic acute regulatory protein (StAR), and cytochrome P450 side-chain cleavage (P450scc) and enzyme and protein expression levels of StAR and P450scc. At the electron microscopic level, mitochondrial membrane damage was found in Leydig cells of the exposed mouse testis. Our results suggest that the insecticide permethrin may cause mitochondrial membrane impairment in Leydig cells and disrupt testosterone biosynthesis by diminishing the delivery of cholesterol into the mitochondria and decreasing the conversion of cholesterol to pregnenolone in the cells, thus reducing subsequent testosterone production.

Bifunctional modulating effects of an indigo dimer (bisindigotin) to CYP1A1 induction in H4IIE cells

In this study, we measured and characterized the bifunctional effects of a newly identified natural compound-bisindigotin (SLY-1), isolated from leaf extracts of Isatis indigotica, to CYP1A1/EROD activities in H4IIE cells. The compound, SLY-1 (1muM) elicited a transitory and significant induction of CYP1A1 RNA/protein levels and EROD activities in the cells. Maximum levels of CYP1A1 expression and EROD induction were attained at 8 and 12h of post-treatment, respectively. Thereafter the induction decreased significantly. Similar profile of CYP1A2 and CYP1B1 mRNA induction was observed. In contrast TCDD elicited CYP1A1/EROD induction was persistent. The transitory effect by SLY-1 is most likely due to the clearance of SLY-1 by cellular metabolism. Taken together the observation indicated that SLY-1 is an Ah receptor agonist for CYP1A1/CYP1A2/CYP1B1/EROD induction. Interestingly in the TCDD/SLY-1 cotreatment study, although synergistic effects on CYP1A1 expression and EROD induction were observed at 4-8h, significant inhibitory effects to TCDD induced CYP1A1 protein and EROD activity were detected at 12-24h of post-treatment. Because there was no significant reduction of CYP1A1, CYP1A2 or CYP1B1 transcript levels between TCDD- and TCDD/SLY-1 treated cells, the data pointed to the translational and/or post-translational inhibitory effect. The cellular signal transduction system may be modulated following exposure to SLY-1. To investigate the possible mechanisms involved, various specific kinase inhibitors or activators (chelerythrin, PD98059, U0126, ZM336372, SB202190, PKA inhibitor PKI (6-22) amide, and dbcAMP) were used for the assessment. Chelerythrine, PD98059 or dbcAMP treatment in TCDD induced cells showed significant inhibitory effects on CYP1A1 mRNA/protein expressions and EROD activities. U0126 had no observable EROD inhibitory effect. ZM336372 or SB202190 showed inhibition only at EROD activities. The results indicated that the SLY-1 inhibitory effect was possibly not mediated by the cAMP/PKA, PKC or MEK pathways. Nevertheless our results indicate that SLY-1 is not only an inducer of the CYP1A1 system, but also a potent inhibitor of CYP1A1 enzyme.

Effect of a PCB-based transformer oil on testicular steroidogenesis and xenobiotic-metabolizing enzymes

Pyralene is a PCB-based transformer oil with a unique PCB congener profile when compared to other mixtures. We studied the influence of Pyralene on testicular steroidogenesis and the status of xenobiotic-metabolizing enzymes in the testis and liver of rats during oral exposure (10 and 50 mg/kg body weight, p.o. daily for 1 week) and a 3-week post-treatment recovery period. As expected, Pyralene induced a rapid and sustained increase in mRNA transcripts for CYP1A1 and CYP2B1 in hepatocytes that was associated with a dramatic increase in ethoxyresorufin-O-deethylase (EROD) and pentoxyresorufin-O-deethylase (PROD) activities. Testicular androgenesis and the conversion of progesterone to testosterone in testicular microsomes were bidirectionally affected. An increase in these parameters was observed 24h after the initial administration of Pyralene, followed by inhibition that lasted until the fourth post-treatment day. Expression PCR analysis revealed a significant decrease in 17beta-hydroxysteroid dehydrogenase (17betaHSD) transcript abundance at 48 h after Pyralene administration. In contrast, transcripts for several other steroidogenic enzymes and for testicular CYP1A1, CYP1B1, and CYP2B1 were unaffected under the same conditions. These results in the rat indicate that a sub-chronic exposure to Pyralene disrupted testicular steroidogenesis and suggest the mechanism may involve direct action on the regulation of specific steroidogenic enzymes such as 17betaHSD.