Alterations of Gene Expression in Adult Male Rat Testis and Pituitary Shortly After Subacute Administration of the Antiandrogen Flutamide

Throughout in vitro first spermatogenic wave: Next-generation sequencing gene expression patterns of fresh and cryopreserved prepubertal mice testicular tissue explants

INTRODUCTION

Suitable cryopreservation procedures of pre-pubertal testicular tissue associated with efficient culture conditions are crucial in the fields of fertility preservation and restoration. In vitro spermatogenesis remains a challenging technical procedure to undergo a complete spermatogenesis.The number of haploid cells and more specifically the spermatic yield produced in vitro in mice is still extremely low compared to age-matched in vivo controls and this procedure has never yet been successfully transferred to humans.

METHODS

To evaluate the impact of in vitro culture and freezing procedure, pre-pubertal testicular mice testes were directly cultured until day 4 (D4), D16 and D30 or cryopreserved by controlled slow freezing then cultured until D30. Testes composed of a panel of 6.5 dpp (days postpartum), 10.5 dpp, 22.5 dpp, and 36.5 dpp mice were used as in vivo controls. Testicular tissues were assessed by histological (HES) and immunofluorescence (stimulated by retinoic acid gene 8, STRA8) analyses. Moreover, a detailed transcriptome evaluation study has been carried out to study the gene expression patterns throughout the first in vitro spermatogenic wave.

RESULTS

Transcriptomic analyses reveal that cultured tissues expression profiles are almost comparable between D16 and D30; highlighting an abnormal kinetic throughout the second half of the first spermatogenesis during in vitro cultures. In addition, testicular explants have shown dysregulation of their transcriptomic profile compared to controls with genes related to inflammation response, insulin-like growth factor and genes involved in steroidogenesis.

DISCUSSION

The present work first shows that cryopreservation had very little impact on gene expression in testicular tissue, either directly after thawing or after 30 days in culture. Transcriptomic analysis of testis tissue samples is highly informative due to the large number of expressed genes and identified isoforms. This study provides a very valuable basis for future studies concerning in vitro spermatogenesis in mice.

Flutamide treatment reveals a relationship between steroidogenic activity of Leydig cells and ultrastructure of their mitochondria

Our present knowledge on interrelation between morphology/ultrastructure of mitochondria of the Leydig cell and its steroidogenic function is far from satisfactory and needs additional studies. Here, we analyzed the effects of blockade of androgen receptor, triggered by exposure to flutamide, on the expression of steroidogenic proteins (1) and ultrastructure of Leydig cells' constituents (2). We demonstrated that increase in the expression level of steroidogenic (StAR, CYP11A1, 3β-HSD, and CYP19A1) proteins (and respective mRNAs) in rat testicular tissue as well as elevation of intratesticular sex steroid hormone (testosterone and estradiol) levels observed in treated animals correspond well to morphological alterations of the Leydig cell ultrastructure. Most importantly, up-regulation of steroidogenic proteins' expression apparently correlates with considerable multiplication of Leydig cell mitochondria and subsequent formation of local mitochondrial networks. Interestingly, we showed also that the above-mentioned processes were associated with elevated transcription of Drp1 and Mfn2 genes, encoding proteins implicated in mitochondrial dynamics. Collectively, our studies emphasize the importance of mitochondrial homeostasis to the steroidogenic function of Leydig cells.

Early exposure to paracetamol reduces level of testicular testosterone and changes gonadal expression of genes relevant for steroidogenesis in rats offspring

In this study, we investigated the effects of early paracetamol treatment on the testicular level of testosterone and expression of genes important for steroid biosynthesis and reproduction in male rats offspring. Rats were continuously exposed to paracetamol at doses of 5 or 15 mg/kg b.w. during pregnancy and the first two months of the postpartum development. Testosterone level was determined by ELISA. Profile of gene expression for the testicular steroidogenic factors were evaluated using the Real-Time PCR. Our results showed that paracetamol reduces testicular testosterone level and causes compensatory transactivation of genes important for steroidogenesis and reproductive capacity. We have observed significant over-expression of several genes involved in cholesterol transport and steroid biosynthesis e.g., genes for steroidogenic acute regulatory protein, hydroxysteroid dehydrogenases, luteinizing hormone subunit beta, gonadotropin and androgen receptors. Up-regulation of these genes with parallel testosterone reduction in the testicles could be the possible mechanism that maintains and prevents the loss of the steroidogenic function.

Semicarbazide disturbs the reproductive system of male zebrafish (Danio rerio) through the GABAergic system

Semicarbazide (SMC), an emerging water contaminant, exerts anti-estrogenic effects in female zebrafish. However, the exact influence of SMC on male reproduction remains unclear. In this study, adult male zebrafish were exposed to 1-1000μg/L SMC in a semi-static system for 28 d prior to examining the testicular somatic index (TSI), testis histology, plasma sex hormone levels, and the transcription of genes involved in reproduction. The results showed that testicular morphology was altered and TSI was down-regulated by high concentrations of SMC (≥100μg/L and 1000μg/L, respectively). Plasma testosterone and 17β-estradiol concentrations were significantly decreased by all of the SMC treatments, along with down-regulation of the corresponding steroidogenic gene transcripts. These changes were associated with the inhibition of gamma-aminobutyric acid synthesis and function, in addition to the decreased expression of reproductive regulators. Our results contribute to elucidating the mechanisms underlying the adverse reproductive effects of SMC in male zebrafish.

Transcripts of genes encoding reproductive neuroendocrine hormones and androgen receptor in the brain and testis of goldfish exposed to vinclozolin, flutamide, testosterone, and their combinations

Vinclozolin (VZ) is a pesticide that acts as an anti-androgen to impair reproduction in mammals. However, VZ-induced disruption of reproduction is largely unknown in fish. In the present study, we have established a combination exposure in which adult goldfish were exposed to VZ (30 and 100 μg/L), anti-androgen flutamide (Flu, 300 μg/L), and androgen testosterone (T, 1 μg/L) to better understand effects of VZ on reproductive endocrine system. mRNA levels of kisspeptin (kiss-1 and kiss-2) and its receptor (gpr54), salmon gonadotropin-releasing hormone (gnrh3) and androgen receptor (ar) in the mid-brain, and luteinizing hormone receptor (lhr) in the testis were analyzed and compared with those of control following 10 days of exposure. kiss-1 mRNA level was increased in goldfish exposed to 100 µg/L VZ and to Flu, while kiss-2 mRNA level was increased following exposure to Flu and to combinations of 30 µg/L VZ with Flu, 100 µg/L VZ with T, and Flu with T. gpr54 mRNA level was increased in goldfish exposed to Flu and to combination of 30 µg/L VZ with Flu and 100 µg/L VZ with T. gnrh3 mRNA level was increased in goldfish exposed to 100 µg/L VZ, to Flu, and to combinations of 30 µg/L VZ with Flu, 100 µg/L VZ with T, and Flu with T. The mid-brain ar mRNA level was increased in goldfish exposed to Flu and to combinations of 30 µg/L VZ with Flu, 100 µg/L VZ with T, and Flu with T. Testicular lhr mRNA level was increased in goldfish exposed to Flu and to combination of 30 µg/L VZ with Flu. These results suggest that VZ and Flu are capable of interfering with kisspeptin and GnRH systems to alter pituitary and testicular horonal functions in adult goldfish and the brain ar mediates VZ-induced disruption of androgen production.

Testosterone Mediates Seasonal Growth of the Song Control Nuclei in a Tropical Bird

In mid- to high-latitude songbirds, seasonal reproduction is stimulated by increasing day length accompanied by elevated plasma sex steroid levels, increased singing, and growth of the song control nuclei (SCN). Plasticity of the SCN and song behavior are primarily mediated by testosterone (T) and its metabolites in most species studied thus far. However, the majority of bird species are tropical and have less pronounced seasonal reproductive cycles. We have previously documented that equatorial rufous-collared sparrows (Zonotrichia capensis) exhibit seasonal neuroplasticity in the SCN. Manipulating T in these birds, however, did not alter singing behavior. In the current study, we investigated whether T mediates plasticity of the SCN in a similar manner to temperate songbirds. In the first experiment, we treated captive male birds with T or blank implants during the nonbreeding season. In a second experiment, we treated captive male birds with either blank implants, T-filled implants, T with flutamide (FLU; an androgen receptor antagonist) or T with FLU and 1,4,6-androstatriene-3,17-dione (ATD; an estrogen synthesis inhibitor) during the breeding season. In both experiments, the volumes of the brain areas high vocal center (HVC), Area X, and robust nucleus of the arcopallium (RA) were measured along with singing behavior. In summary, T stimulated growth of HVC and RA, and the combined effect of FLU and ATD reversed this effect in HVC. Area X was not affected by T treatment in either experiment. Neither T-treated birds nor controls sang in captivity during either experiment. Together, these data indicate that T mediates seasonal changes in the HVC and RA of both tropical and higher- latitude bird species even if the environmental signals differ. However, unlike most higher-latitude songbirds, we found no evidence that motivation to sing or growth of Area X are stimulated by T under captive conditions.

Effects of short-term exposure to the model anti-androgen, flutamide on reproductive function based endpoints in female Murray rainbowfish (Melanotaenia fluviatilis)

The aim of the present study was to evaluate the responses of female Murray rainbowfish (Melanotaenia fluviatilis) to the model anti-androgen, flutamide in a short-term exposure. Adult female Murray rainbowfish were exposed to nominal (measured) concentrations of 125 (104), 250 (163), 500 (378) and 1000 (769) µg/L of flutamide for seven days in a semi-static set-up. Plasma vitellogenin (VTG), 11-keto testosterone (11-KT) and 17β-estradiol (E2) concentrations, brain aromatase activity and ovarian histology were assessed following the exposure. No treatment-related mortality was found in rainbowfish and there was no effect of flutamide on the developmental stage of the ovaries. Histological investigation revealed absence of mature oocytes in flutamide-treated fish. In addition, a significant reduction in the sizes of the vitellogenic oocytes was found after treatment with 500 and 1000 µg/L flutamide. The circulating levels of VTG and the activity of aromatase in the brain were also significantly reduced in fish treated with 500 and 1000 µg/L flutamide. Treatment with higher concentrations of flutamide reduced the levels of 11-KT and E2 in plasma. The results from this study demonstrate that a short-term exposure to the model anti-androgen, flutamide can adversely affect the reproductive function based on end-points such as plasma VTG, 11-KT and E2; brain aromatase activity and sizes of the oocytes in female Murray rainbowfish. Further, a positive correlation between these experimental variables suggests hormonal imbalance.

Protective effects of Eugenia jambolana extract versus N-acetyl cysteine against cisplatin-induced damage in rat testis

To assess the protective effects of Eugenia jambolana extract (EJE) or N-acetyl cysteine (NAC) on testis, cisplatin (CIS, 5 mg kg(-1) bw, single dose) was administered either alone or along with EJE (25 mg kg(-1) bw, alternate day) or NAC (150 mg kg(-1) bw, Day 1 and 4) for 7 days. Significant alterations in serum LH, FSH and testosterone were observed in CIS group which were effectively modulated by EJE or NAC supplementation. Upregulation of 3β-HSD gene indicated the rise in functional Leydig cells. This was further confirmed from the identical improvement in hCG-stimulated testosterone production in isolated Leydig cells. Reduction in oxidative stress was associated with restoration of total antioxidant capacity and glutathione levels, and activation of antioxidant enzymes, SOD, catalase, glutathione s-transferase (GST) and glutathione reductase (GR). CIS-induced apoptosis of germ and Leydig cells was contained by both NAC and EJE intervention by effective modulation of apoptotic markers in the extrinsic, intrinsic and other pathways of metazoan apoptosis. Taken together, the study findings establish the potential of EJE as a therapeutically better antioxidant than NAC for use in curtailing the adverse effects of anticancer drugs on testicular function.

Effects of the natural endocrine disruptor equol on the pituitary function in adult male rats

Equol (EQ), a potent biologically active metabolite of the soy isoflavone daidzein, interacts with estrogen receptors (ERs), however, as suggested recently, EQ may also exert anti-androgenic actions in androgen regulated tissues like prostate and seminal vesicles in adult male rats. However, data regarding a putative anti-androgenic activity of EQ on pituitary function in male individuals are still lacking. Therefore, we investigated the effects of EQ on androgen- and estrogen-regulated gene expressions in the pituitary and circulating luteinizing hormone (LH) and prolactin (PRL) levels in adult male rats. 3-Month-old male Sprague-Dawley rats (n=12 per group) were treated by gavage for 5 days with either EQ (100 and 250 mg/kg BW/day) or vehicle olive oil (1 ml/rat/day). As reference compound, the pure anti-androgenic drug flutamide (FLUT) was employed at a dose of 100 mg/kg BW/day. At day 5, animals were sacrificed. Levels of pituitary hormones and gene expression were measured by radioimmunoassays and quantitative TaqMan(®) real-time reverse transcription polymerase chain reaction, respectively. The present findings revealed that the pituitary mechanisms involved in the effects of EQ and FLUT were different due to the opposite changes in the mRNA expression levels of estrogen receptor subtype alpha (ERα)-, truncated estrogen receptor product-1 (TERP-1)- and -2 (TERP-2)-, gonadotropin releasing hormone receptor (GnRH receptor)-, beta-subunit of LH (LHβ)-, and gonadotropin alpha subunit (α-subunit) genes. EQ displayed typical ER-agonistic actions as shown by the significant increases in ERα-, TERP-1/-2 mRNA expressions and serum PRL levels along with the significant reduction in serum LH levels, whereas FLUT exerted opposite effects on gonadotropin secretion and expression. Taken together, our findings are the first in vivo data that upon sub-acute oral exposure of EQ show an estrogenic effect on reproductive endocrine activity of the pituitary in adult male rats. However, EQ did not exert anti-androgenic effects on male rat pituitary function as observed at the levels of mRNA expression of androgen- and estrogen-regulated genes and circulating pituitary hormones.

Effect of tetrabrombisphenol A on induction of apoptosis in the testes and changes in expression of selected testicular genes in CD1 mice

Tetrabromobisphenol A (TBBPA) is a substance widely used in industry as a flame retardant. TBBPA was found in the environment and was detected even in the human body. The effect of this chemical was observed in different cell lines in vitro and it is supposed that TBBPA may affect various hormonal systems in vivo. In this study we examined the effect of TBBPA on the reproductive parameters of two generations of outbred mice in vivo. Experimental and control animals of F1 generation were bred in various conditions to enable evaluation of the possible trans-generational effect. An increased incidence of apoptosis in the testes and changes in the morphometry of seminiferous tubules was detected in the experimental animals. In addition, changes in the expression pattern of selected genes encoding proteins that play an important role during spermatogenesis were observed. In contrast, sperm quality and reproduction were not affected by TBBPA.

Endosulfan and flutamide, alone and in combination, target ovarian growth in juvenile catfish, Clarias batrachus

Juvenile Catfish(es), Clarias batrachus of 50 days post hatch (dph) were exposed to endosulfan (2.5 parts per billion [ppb]) and flutamide (33 ppb), alone and in combination for 50 days to access their impact on ovarian development. The doses used in this study were nominal considering pervious reports. Sampling was done at 100 dph to perform histology and measurement of various transcripts, estradiol-17β and aromatase activity. In general, treatments enhanced expression of ovary-specific transcription factors, steroidogenic enzymes steroidogenic acute regulatory protein and aromatases while transcripts of tryptophan hydroxylase2 (tph2) and catfish gonadotropin-releasing hormone declined in the brain of all treated groups with maximum reduction in the endosulfan group. Significant reduction of tph2 immunoreactivity in the forebrain/telencephalon-preoptic area endorsed our results. Increased number of pre-vitellogenic and less immature oocytes in the treated groups indicated hastened ovarian growth. Elevated ovarian aromatase activity and plasma estradiol-17β levels were noticed in the treated groups with maximum being in the endosulfan group. These data together demonstrate that the exposure of endosulfan causes synchronous precocious ovarian development better than flutamide, alone or in combination. Our results suggest that both endosulfan and flutamide alter ovarian growth by triggering precocious development in catfish.

Endosulfan and flutamide impair testicular development in the juvenile Asian catfish, Clarias batrachus

Endosulfan and flutamide, a widely used pesticide and a prostate cancer/infertility drug, respectively, have an increased risk of causing endocrine disruption if they reach water bodies. Though many studies are available on neurotoxicity/bioaccumulation of endosulfan and receptor antagonism of flutamide, only little is known about their impact on testicular steroidogenesis at molecular level. Sex steroids play an important role in sex differentiation of lower vertebrates including fishes. Hence, a small change in their levels caused by endocrine disruptors affects the gonadal development of aquatic vertebrates significantly. The aim of this study was to evaluate the effects of endosulfan and flutamide on testis-related transcription factor and steroidogenic enzyme genes with a comparison on the levels of androgens during critical period of catfish testicular development. We also analyzed the correlation between the above-mentioned genes and catfish gonadotropin-releasing hormone (cfGnRH)-tryptophan hydroxylase2 (tph2). The Asian catfish, Clarias batrachus males at 50 days post hatch (dph) were exposed to very low dose of endosulfan (2.5 μg/L) and flutamide (33 μg/L), alone and in combination for 50 days. The doses used in this study were far less than those used in the previous studies of flutamide and reported levels of endosulfan in surface water and sediments. Sampling was done at end of the treatments (100 dph) to perform testicular germ cell count (histology), measurements of testosterone (T) and 11-ketotestosterone (11-KT) by enzyme immunoassay and transcript quantification by quantitative real-time PCR. In general, treatments decreased the expression of several genes including testis-related transcription factors (dmrt1, sox9a and wt1), steroidogenic enzymes (11β-hsd2, 17β-hsd12 and P450c17), steroidogenic acute regulatory protein and orphan nuclear receptors (nr2c1 and Ad4BP/SF-1). In contrast, the transcripts of cfGnRH and tph2 were elevated in the brain of all treated groups with maximum elevation in the endosulfan group. However, combination of endosulfan and flutamide (E+F) treatment showed minor antagonism in a few results of transcript quantification. Levels of T and 11-KT were elevated after flutamide and E+F treatments while no change was seen in the endosulfan group signifying the effect of flutamide as an androgen receptor antagonist. All the treatments modulated testis growth by decreasing the progression of differentiation of spermatogonia to spermatocytes. Based on these results, we suggest that the exposure to endosulfan and flutamide, even at low doses, impairs testicular development either directly or indirectly at the level of brain.

Exposure of neonatal rats to anti-androgens induces penile mal-developments and infertility comparable to those induced by oestrogens

We previously reported that oestrogen exposure in neonatal rats induced permanent infertility and malformed penis characterized by fat accumulation, which replaced most of the smooth muscle cells and cavernous spaces in the body of the penis, structures essential for erection. The objective of this study was to determine if reduced androgen production/action in the neonatal period, in the absence of exogenous oestrogen exposure, induces penile deformities similar to those caused by oestrogen. Male rats were treated from postnatal days 1-6 with GnRH antagonist antide (A, 10 mg/kg) or androgen receptor (AR) antagonist flutamide (F, 50 mg/kg) or F + A, with or without AR agonist dihydrotestosterone (DHT, 20 mg/kg). For comparison, pups received diethylstilbestrol (DES, 0.1 mg/kg), with or without DHT. Tissues were collected at ages 7 and 12 days and at adulthood. Flutamide alone decreased penile length and weight significantly (p < 0.05), but it caused neither fat accumulation, nor affected fertility (80% vs. 87% in controls). Antide alone reduced penile length and weight significantly, and induced fat accumulation in 4/11 rats and infertility in 13/14 rats. Conversely, all 11 F + A-treated rats, similar to all nine DES-treated rats, had fat accumulation and loss of smooth muscle cells and cavernous spaces in the body of the penis and were infertile. In addition, reductions in penile length and weight were higher than in rats treated with F or A alone. DHT co-administration mitigated penile deformities in the DES group, but did not in the F + A group. Testicular testosterone was reduced by 70-95% at 7 or 12 days of age in all treated groups, except in the F group, which had threefold higher testosterone than controls. Collectively, data unequivocally show that reduced androgen production/action in the neonatal period, in the absence of oestrogen exposure, induces permanent infertility and malformed penis similar to that caused by oestrogen.

LDH-C can be differentially expressed during fermentation of CHO cells

Expression of CHO mRNA was measured with special microarrays from the Consortium for Chinese Hamster Ovary (CHO) Cell Genomics led by Prof. Wei-Shou Hu of the University of Minnesota and Prof. Miranda Yap of the Bioprocess Technology Institute of A*STAR, Singapore

(http://hugroup.cems.umn.edu/CHO/cho_index.html). Cultivation experiments were performed in small scale 2L stirred tank bioreactors. During fermentation a temperature shift of -3°C was performed. This was accompanied by a reduction of the cell specific lactate production rate.

The analysis of transcriptome samples before and after the temperature shift with microarrays showed several changes in the expression of available gene markers. LDH-C expression raised about 2 fold after temperature shift. LDH-A did not change. As LDH-C is known to be a specialized isoenzyme in sperm cells for consuming lactate in a lactate containing milieu, LDH-C could be proposed as a target for genetic engineering, facilitating lactate consumption in the late phase of high cell density cultures and prolonging longevity of CHO production cultures by reducing lactate and base accumulation.

Role of estrogen in the regulation of spermatogenesis in the Indian wall lizard Hemidactylus flaviviridis

The role of estrogen in the Indian wall lizard, Hemidactylus flaviviridis during PMSG induced spermatogenesis in the regression phase and during normal spermatogenesis in the active breeding phase was investigated. Blood hormone levels demonstrated a high testosterone to estrogen ratio in the breeding and vice verse during the regressed phase. PMSG treatment (30 IU in 100 μl saline/lizard/alternate day for 30 days) during the regressed phase stimulated spermatogenesis which was associated with a significant (p<0.001) rise in plasma testosterone levels. Complete spermatogenesis with sperms was resolved in many tubular sections. However, co-administration of PMSG plus estrogen in high doses (2 μg of estradiol benzoate/alternate day) for the same period not only curtailed germ cell proliferation significantly but also induced apoptosis in germ cells. There was no significant reduction in testicular weight but sperms were found completely absent in all the tubules. Decline in the plasma testosterone was more pronounced in high compared to low estrogen treated groups. Further, low estrogen administration had little effect either on raising the plasma levels of estrogen or subsequently on spermatogenesis which was identically observed in the breeding phase too. Estrogen intervention (2 μg) in the breeding phase also profoundly suppressed spermatogenesis leading to a severe depletion in germ cells. Simultaneously, there was a significant rise in germ cell apoptosis which was associated with an up-regulation of extrinsic (caspase 8, Fas, FasL) and intrinsic (caspase 9, Bax, Bcl2) markers in these cells. Taken together, the above data indicate that the estrogen plays a key role in regulating spermatogenesis in the wall lizard retarding it during testicular quiescence and eliminating germ cells through apoptosis during the active breeding phase.

A molecular and phenotypic integrative approach to identify a no-effect dose level for antiandrogen-induced testicular toxicity

The safety assessment of chemicals for humans relies on identifying no-observed adverse effect levels (NOAELs) in animal toxicity studies using standard methods. With the advent of high information content technologies, especially microarrays, it is pertinent to determine the impact of molecular data on the NOAELs. Consequently, we conducted an integrative study to identify a no-transcriptomic effect dose using microarray analyses coupled with quantitative reverse transcriptase PCR (RT-qPCR) and determined how this correlated with the NOAEL. We assessed the testicular effects of the antiandrogen, flutamide (FM), in a rat 28-day toxicity study using doses of 0.2-30 mg/kg/day. Plasma testosterone levels and testicular histopathology indicated a NOAEL of 1 mg/kg/day. A no-effect dose of 0.2 mg/kg/day was established based on molecular data relevant to the phenotypic changes. We observed differential gene expression starting from 1 mg/kg/day and a deregulation of more than 1500 genes at 30 mg/kg/day. Dose-related changes were identified for the major pathways (e.g., fatty acid metabolism) associated with the testicular lesion (Leydig cell hyperplasia) that were confirmed by RT-qPCR. These data, along with protein accumulation profiles and FM metabolite concentrations in testis, supported the no-effect dose of 0.2 mg/kg/day. Furthermore, the microarray data indicated a dose-dependent change in the fatty acid catabolism pathway, a biological process described for the first time to be affected by FM in testicular tissue. In conclusion, the present data indicate the existence of a transcriptomic threshold, which must be exceeded to progress from a normal state to an adaptative state and subsequently to adverse toxicity.

Gene expression profiling of the androgen receptor antagonists flutamide and vinclozolin in zebrafish (Danio rerio) gonads

The studies presented in this manuscript focus on characterization of transcriptomic responses to anti-androgens in zebrafish (Danio rerio). Research on the effects of anti-androgens in fish has been characterized by a heavy reliance on apical endpoints, and molecular mechanisms of action (MOA) of anti-androgens remain poorly elucidated. In the present study, we examined effects of a short term exposure (24-96h) to the androgen receptor antagonists flutamide (FLU) and vinclozolin (VZ) on gene expression in gonads of sexually mature zebrafish, using commercially available zebrafish oligonucleotide microarrays (4×44K platform). We found that VZ and FLU potentially impact reproductive processes via multiple pathways related to steroidogenesis, spermatogenesis, and fertilization. Observed changes in gene expression often were shared by VZ and FLU, as demonstrated by overlap in differentially-expressed genes and enrichment of several common key pathways including: (1) integrin and actin signaling, (2) nuclear receptor 5A1 signaling, (3) fibroblast growth factor receptor signaling, (4) polyamine synthesis, and (5) androgen synthesis. This information should prove useful to elucidating specific mechanisms of reproductive effects of anti-androgens in fish, as well as developing biomarkers for this important class of endocrine-active chemicals.

Embryonic exposure to octylphenol induces changes in testosterone levels and disrupts reproductive efficiency in rats at their adulthood

The purpose of the present study was to investigate the effects of prenatal exposure to octylphenol (OP) at the dose of 50mg/kg body weight on days 1, 7 and 14 of pregnancy on reproductive health of male rats at adulthood. F1 male rats from control and OP exposed animals were weaned and maintained up to postnatal day (PND) 100. The indices of testis, epididymis and seminal vesicles were significantly decreased in male rats exposed to OP during embryonic development when compared with controls. Significant reduction in the epididymal sperm count, viable sperms and motile sperms and number of tail coiled sperms (HOS-test) were observed in experimental rats when compared to control rats. The levels of serum testosterone and also activity levels of testicular hydroxysteroid dehydrogenases were significantly decreased with a significant increase in the serum follicle stimulating and leutinizing hormones in experimental rats. Furthermore, embryonic exposure to OP caused significant down regulation of StAR, 3ß hydroxysteroid dehydrogenase and 17ß hydroxysteroid dehydrogenase mRNAs in testis of adult rats as compared to control rats. The results of fertility studies revealed that there was an increase in the mating index in experimental rats with an increase in the pre- and post-implantation losses in rats cohabited with treated animals indicating poor male reproductive performance.

Polychlorinated biphenyls have inhibitory effect on testicular steroidogenesis by downregulation of P45017α and P450scc

Polychlorinated biphenyls (PCBs) are environmental pollutants that are quite toxic to biological systems. This study examined the inhibitory effect of PCB126 and PCB114 on testicular steroidogenesis in male rats. Male Sprague Dawley rats received weekly intraperitoneal injections of PCB126 (0.2 mg/kg) or PCB114 (20 mg/kg) or vehicle (corn oil). Animals from each group were sacrificed at 2, 5 and 8 weeks after the injections. Blood and testis tissue samples were collected for the hormone assay, Western blotting and reverse transcriptase polymerase chain reaction (RT-PCR). The testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were assayed, and the expression levels of the mRNA and proteins associated with the testosterone biosynthesis pathway were measured to determine the effect of PCB126 and PCB114 on testicular steroidogenesis. The results showed that the testis weight was significantly higher in the PCB126-treated rats given eight shots. Moreover, the serum testosterone levels were significantly lower in the PCB126 and PCB114-treated groups than the control. The transcription and translation levels of P45017α and P450scc were significantly lower in the PCB126-treated groups than the control. These results suggest that PCB126 may affect testicular steroidogenesis by downregulating P45017α, P450 scc and have inhibitory effect on the testicular functions.

Induction of spermatogenic cell apoptosis in prepubertal rat testes irrespective of testicular steroidogenesis: a possible estrogenic effect of di(n-butyl) phthalate

Although di(n-butyl) phthalate (DBP), a suspected endocrine disruptor, induces testicular atrophy in prepubertal male rats, whether it exerts estrogenic activity in vivo remains a matter of debate. In the present study, we explored the estrogenic potency of DBP using 3-week-old male rats, and then examined the relationship between estrogen-induced spermatogenic cell apoptosis and testicular steroidogenesis. Daily exposure to DBP for 7 days caused testicular atrophy due to loss of spermatogenic cells, whereas testicular steroidogenesis was almost the same with the control values. A single exposure of DBP decreased testicular steroidogenesis in addition to decreasing the level of serum LH at 3 h after DBP treatment, with an extremely high incidence of apoptotic spermatogenic cells at 6 h after administration. To elucidate the estrogenic activity of DBP, we carried out an inhibition study using pure antiestrogen ICI 182,780 (ICI) in a model of spermatogenic cell apoptosis induced by DBP or estradial-3-benzoate (EB). Although both the DBP- and EB-treated groups showed a significant increase in spermatogenic cell apoptosis, ICI pretreatment significantly decreased the number of apoptotic spermatogenic cells in these two groups. In contrast, testicular steroidogenesis and serum FSH were significantly reduced in all the treated groups, even in the DBP+ICI and EB+ICI groups. Taken together, these findings led us to conclude that estrogenic compounds such as DBP and EB induce spermatogenic cell apoptosis in prepubertal rats, probably by activating estrogen receptors in testis, and that reduction in testicular steroidogenic function induced by estrogenic compounds is not associated with spermatogenic cell apoptosis.

Adverse effects associated with persistent stimulation of Leydig cells with hCG in vitro

The detrimental effects of persistent stimulation with hCG were investigated in rat Leydig cells in vitro. Significant rise in lipid peroxidation and reactive oxygen species (ROS) with concomitant attenuation in the activities of antioxidant enzymes: superoxide dismutase, catalase, and glutathione-S-transferase was observed. Transcripts for catalase and superoxide dismutase were also depleted. Subsequent to each hCG challenge, the total antioxidant capacity in the target cells also declined significantly (P < 0.05). There was an increase in cell apoptosis (23%), which was associated with a rise in caspase-3 activity, PARP cleavage, and Fas, FasL, caspase-8 expression. While Bax and Caspase-9 expression remained unchanged, Bcl-2 demonstrated a marked decline. Taken together, the above data indicate that persistent hCG stimulation of Leydig cells induced adverse effects leading to oxidative stress and apoptosis which was channeled primarily through the extrinsic pathway.

The role of androgen receptors in regulating territorial aggression in male song sparrows

This paper examines the role that androgen receptors (ARs) play in modulating aggressive behavior in male song sparrows, Melospiza melodia morphna. Song sparrows are seasonally breeding, territorial birds that maintain year-round territories with male-female pair bonds formed during the spring breeding season. Plasma testosterone levels peak as territories are established and mates acquired. In late summer, testosterone levels fall and remain basal during the non-breeding season. We examined the role of ARs in regulating territorial aggression in captive song sparrows under short- and long-day conditions as well as just prior to, and at the start of the breading season in freely living birds using the nonsteroidal antiandrogen flutamide to block AR function. Birds were implanted with either empty or drug filled silastic implants for 18 to 42 days and then challenged with a novel male decoy to assess the individual birds level of male-male aggression. Freely living birds remained on their home territory and underwent a simulated territorial intrusion, whereas laboratory-held birds were assessed using a laboratory simulated territorial intrusion and remained in their home cage. Experimental treatment of male song sparrows decreased aggressive behavior during the pre-breeding life history substage (March-April) in freely living birds as well as in laboratory-held birds under long-day (16L:8D) conditions. During the early breeding substage (April-May) there was no measurable effect of flutamide treatment on aggressive behavior, nor was there a difference in behavior in the (8L:16D) laboratory birds. This demonstrates that ARs are an important component of the neuroendocrine control of aggressive behavior. Given that flutamide only affected aggression during the pre-breeding substage and in LD birds, the results suggest that AR dependent control of aggressive behavior changes as song sparrow life history states change.

Di-(2 ethylhexyl) phthalate and flutamide alter gene expression in the testis of immature male rats

We previously demonstrated that the androgenic and anti-androgenic effects of endocrine disruptors (EDs) alter reproductive function and exert distinct effects on developing male reproductive organs. To further investigate these effects, we used an immature rat model to examine the effects of di-(2 ethylhexyl) phthalate (DEHP) and flutamide (Flu) on the male reproductive system. Immature male SD rats were treated daily with DEHP and Flu on postnatal days (PNDs) 21 to 35, in a dose-dependent manner. As results, the weights of the testes, prostate, and seminal vesicle and anogenital distances (AGD) decreased significantly in response to high doses of DEHP or Flu. Testosterone (T) levels significantly decreased in all DEHP- treated groups, whereas luteinizing hormone (LH) plasma levels were not altered by any of the two treatments at PND 36. However, treatment with DEHP or Flu induced histopathological changes in the testes, wherein degeneration and disorders of Leydig cells, germ cells and dilatation of tubular lumen were observed in a dose-dependent manner. Conversely, hyperplasia and denseness of Leydig, Sertoli and germ cells were observed in rats given with high doses of Flu. The results by cDNA microarray analysis indicated that 1,272 genes were up-regulated by more than two-fold, and 1,969 genes were down-regulated in response to DEHP, Flu or both EDs. These genes were selected based on their markedly increased or decreased expression levels. These genes have been also classified on the basis of gene ontology (e.g., steroid hormone biosynthetic process, regulation of transcription, signal transduction, metabolic process, biosynthetic process...). Significant decreases in gene expression were observed in steroidogenic genes (i.e., Star, Cyp11a1 and Hsd3b). In addition, the expression of a common set of target genes, including CaBP1, Vav2, Plcd1, Lhx1 and Isoc1, was altered following exposure to EDs, suggesting that they may be marker genes to screen for the anti-androgenic or androgenic effects of EDs. Overall, our results demonstrated that exposure to DEHP, Flu or both EDs resulted in a alteration of gene expression in the testes of immature male rats. Furthermore, the toxicological effects of these EDs on the male reproductive system resulted from their anti-androgenic effects. Taken together, these results provide a new insight into the molecular mechanisms underlying the detrimental impacts of EDs, in regards to anti-androgenic effects in humans and wildlife.

Alteration of testicular steroidogenesis and histopathology of reproductive system in male rats treated with triclosan

Triclosan (TCS), a chlorophenol, is widely used as a preservative in different types of commercial preparations. The reports on TCS-mediated endocrine disruption are controversial and the present study aimed to elucidate the probable mode of action of TCS as an antiandrogenic compound using a robust study design. Male albino rats, Rattus norvegicus, were treated with three doses of triclosan for a period of 60 days followed by the analysis of various biochemical parameters. RT-PCR analysis demonstrated a significant decrease in mRNA levels for testicular steroidogenic acute regulatory (StAR) protein, cytochrome P450(SCC), cytochrome P450(C17), 3beta-hydroxysteroid dehydrogenase (3beta-HSD), 17beta-hydroxysteroid dehydrogenase (17beta-HSD) and androgen receptor (AR) in TCS treated rats (p<0.05). TCS also induced a perturbed translation of testicular StAR, and AR proteins as shown by Western blot analysis in treated groups of rats. A reduced level of StAR was further indicated by immunohistochemistry in testicular Leydig cells. Further, there was a significant decrease (p<0.05) in the level of serum lutenizing hormone (LH), follicle stimulating hormone (FSH), cholesterol, pregnenolone, and testosterone. In vitro assays demonstrated more than 30% decrease in testicular 3beta-HSD and 17beta-HSD enzyme activities in treated group of animals. Extensive histopathological malformations were observed in the testis and sex accessory tissues of the treated rats. Overall this study showed that TCS decreased the synthesis of androgens followed by reduced sperm production in treated male rats which could be mediated by a decreased synthesis of LH and FSH thus involving hypothalamo-pituitary-gonadal axis.

Effects of endocrine disrupting chemicals from leather industry effluents on male reproductive system

The leather tanning industry is characterized by the production of different kinds of effluents, generated in each step of leather processing. These effluents have various chemical compounds which may cause toxicity and endocrine disruption and are thus known as endocrine disrupting chemicals (EDC). This study was aimed to examine the androgenic potential of leather industry effluents collected from northern region of India. Hershberger assay data showed a significant increase (p<0.05) in the weight and structure of sex accessory tissues of castrated rats. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis demonstrated a significant change (p<0.05) in the expression patterns of the major steroidogenic enzymes in adrenal and testes namely, cytochrome P450scc, 3beta-hydroxysteroid dehydrogenase, 17beta-hydroxysteroid dehydorgenase in castrated and intact rats. This was further supported by increased enzymatic activities measured in vitro spectrophotometrically. Serum hormone profile demonstrated a dose dependent increase in testicular and adrenal testosterone productions in intact and castrated rats, respectively. This was further supported by decreased level of gonadotrophic hormones (LH and FSH) in treated groups of animals. Further, the effluent treatment resulted in the development of hyperplasia in seminiferous tubules of testes in treated rats as evident from histopathological studies and about two-fold increases in daily sperm production. On analysis of water samples using GC-MS, it was found to contain various aromatic compounds (nonylphenol, hexaclrobenzene and several azo dyes) some of which independently demonstrated similar effects as shown by water samples. Our data suggests that the effluents from leather industry have potential EDC demonstrating androgenic activities.

Disruption of LH-induced testosterone biosynthesis in testicular Leydig cells by triclosan: probable mechanism of action

Triclosan (TCS) is an antimicrobial chemical widely used in different commercial preparations. The present study demonstrated the mechanism of action of TCS-induced anti-androgenicity in rat Leydig cells. Treatment of purified cells with increasing concentrations of TCS (0.001, 0.01, 0.1, 1 and 10 microM) resulted in a significantly decreased activity of adenylyl cyclase enzyme which was followed by a decreased synthesis of cAMP. This decreased cAMP level resulted in the disruption of entire steroidogenic cascade causing a depressed synthesis of testosterone. However, TCS-induced decrease in the production of testosterone returned to normalcy when cells were treated with forskolin (an adenylyl cyclase activator). Transcription followed by translational of four prominent steroidogenic enzyme/proteins, cytochrome P450 side chain cleavage (P450scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD), 17beta-hydroxysteroid dehydrogenase (17beta-HSD) and steroidogenic acute regulatory (StAR) protein, also decreased in a dose-dependent manner in TCS-treated Leydig cells as determined by RT-PCR, enzyme assay and Western blot. These results suggested that the disruption of the activity of adenylyl cyclase enzyme by TCS in turn leads to the disruption of intermediate steroidogenic cascade causing a depressed testosterone production. The study further confirmed the anti-androgenic activity of TCS in Leydig cells with highest effective concentration at 1 microM.

Effects of endocrine disrupting chemicals on expression of phospholipid hydroperoxide glutathione peroxidase mRNA in rat testes

Phospholipid hydroperoxide glutathione peroxidase (PHGPx), an antioxidative selenoprotein, is modulated by estrogen in the testis and oviduct. To examine whether potential endocrine disrupting chemicals (EDCs) affect the microenvironment of the testes, the expression patterns of PHGPxmRNA and histological changes were analyzed in 5-week-old Sprague-Dawley male rats exposed to several EDCs such as an androgenic compound [testosterone (50, 200, and 1,000 µg/kg)], anti-androgenic compounds [flutamide (1, 5, and 25 mg/kg), ketoconazole (0.2 and 1 mg/kg), and diethylhexyl phthalate (10, 50, and 250 mg/kg)], and estrogenic compounds [nonylphenol (10, 50, 100, and 250 mg/kg), octylphenol (10, 50, and 250 mg/kg), and diethylstilbestrol (10, 20, and 40 µg/kg)] daily for 3 weeks via oral administration. Mild proliferation of germ cells and hyperplasia of interstitial cells were observed in the testes of the flutamide-treated group and deletion of the germinal epithelium and sloughing of germ cells were observed in testes of the diethylstilbestrol-treated group. Treatment with testosterone was shown to slightly decrease PHGPxmRNA levels in testes by the reverse transcriptionpolymerase chain reaction. However, anti-androgenic compounds (flutamide, ketoconazole, and diethylhexyl phthalate) and estrogenic compounds (nonylphenol, octylphenol, and diethylstilbestrol) significantly upregulated PHGPxmRNA in the testes (p < 0.05). These findings indicate that the EDCs might have a detrimental effect on spermatogenesis via abnormal enhancement of PHGPx expression in testes and that PHGPx is useful as a biomarker for toxicity screening of estrogenic or antiandrogenic EDCs in testes.

Transcription of Key Genes Regulating Gonadal Steroidogenesis in Control and Ketoconazole- or Vinclozolin-Exposed Fathead Minnows

This study evaluated changes in the expression of steroidogenesis-related genes in male fathead minnows exposed to ketoconazole (KTC) or vinclozolin (VZ) for 21 days. The aim was to evaluate links between molecular changes and higher level outcomes after exposure to endocrine-active chemicals (EACs) with different modes of action. To aid our analysis and interpretation of EAC-related effects, we first examined variation in the relative abundance of steroidogenesis-related gene transcripts in the gonads of male and female fathead minnows as a function of age, gonad development, and spawning status, independent of EAC exposure. Gonadal expression of several genes varied with age and/or gonadal somatic index in either males or females. However, with the exception of aromatase, steroidogenesis-related gene expression did not vary with spawning status. Following the baseline experiments, expression of the selected genes in male fathead minnows exposed to KTC or VZ was evaluated in the context of effects observed at higher levels of organization. Exposure to KTC elicited changes in gene transcription that were consistent with an apparent compensatory response to the chemical's anticipated direct inhibition of steroidogenic enzyme activity. Exposure to VZ, an antiandrogen expected to indirectly impact steroidogenesis, increased pituitary expression of follicle-stimulating hormone beta-subunit as well as testis expression of 20beta-hydroxysteroid dehydrogenase and luteinizing hormone receptor transcripts. Results of this study contribute to ongoing research aimed at understanding responses of the teleost hypothalamic-pituitary-gonadal axis to different types of EACs and how changes in molecular endpoints translate into apical outcomes reflective of either adverse effect or compensation.

Effects of neonatal exposure to 4-tert-octylphenol, diethylstilbestrol, and flutamide on steroidogenesis in infantile rat testis

Exposure of neonatal testis, populated by fetal-type Leydig cells, to endocrine-active compounds may have far-reaching consequences. Our aim was to resolve the sensitivity of testosterone synthesis of infant rat (Sprague-Dawley) testis to diethylstilbestrol (DES; 0.1-1.0 mg/kg), 4-tert-octylphenol (OP; 10-100 mg/kg), and Flutamide (FLU; 2.0-25 mg/kg) given by daily sc injections from birth to postnatal day 4. Testes and serum were collected on day 14 when body and testis weight, testicular histology, circulating testosterone, LH and FSH levels, and steroidogenic acute regulatory protein (StAR) and 3beta-hydroxy-steroid-dehydrogenase (3beta-HSD) protein levels were determined. DES at each dose and FLU at 25 mg/kg dose reduced testis weight and the diameter of seminiferous cords. FLU caused some Leydig cell hyperplasia. Plasma testosterone was reduced in all DES animals, LH elevated in DES 0.5 mg/kg and FLU 25 mg/kg animals, and FSH reduced in the DES 1.0 mg/kg group. Basal testicular ex vivo progesterone and human chorionic gonadotropin (hCG)-stimulated testosterone production were decreased in DES animals. Despite a decrease in hCG-induced cyclic adenosine-3',5'-monophosphate (cAMP) production, intratesticular testosterone was increased in the FLU 10 and 25 mg/kg groups. OP 100 mg/kg elevated hCG-induced progesterone production only. No changes were seen in 3beta-HSD protein levels in any treatment group. StAR levels were reduced in DES animals. The results indicate the sensitivity of postnatal fetal-type Leydig cells to endocrine-active compounds. Suppression of StAR expression level was an early sign of the DES-induced steroidogenic lesion. FLU-induced changes suggest the importance of androgen receptor-mediated regulation of testosterone synthesis in the postnatal rat testis. Octylphenol appeared less effective in bringing about acute steroidogenic changes.

Microarray analysis of androgen-regulated gene expression in testis: the use of the androgen-binding protein (ABP)-transgenic mouse as a model

BACKGROUND

Spermatogenesis is an androgen-dependent process, yet the molecular mechanisms of androgens' actions in testis are poorly understood. Transgenic mice overexpressing rat androgen-binding protein (ABP) in their testes have reduced levels of intratesticular androgens and, as a result, show a progressive impairment of spermatogenesis. We used this model to characterize changes in global gene expression in testis in response to reduced bioavailability of androgens.

METHODS

Total RNA was extracted from testes of 30-day old transgenic and wild-type control mice, converted to cRNA, labeled with biotin, and hybridized to oligonucleotide microarrays. Microarray results were confirmed by real-time reverse transcription polymerase chain reaction.

RESULTS

Three-hundred-eighty-one genes (3.05% of all transcripts represented on the chips) were up-regulated and 198 genes (1.59%) were down-regulated by at least a factor of 2 in the androgen-deficient animals compared to controls. Genes encoding membrane proteins, intracellular signaling molecules, enzymes, proteins participating in the immune response, and those involved in cytoskeleton organization were significantly overrepresented in the up-regulated group. Among the down-regulated transcripts, those coding for extracellular proteins were overrepresented most dramatically, followed by those related to proteolysis, cell adhesion, immune response, and growth factor, cytokine, and ion channel activities. Transcripts with the greatest potential impact on cellular activities included several transcription factors, intracellular signal transducers, secreted signaling molecules and enzymes, and various cell surface molecules. Major nodes in the up-regulated network were IL-6, AGT, MYC, and A2M, those in the down-regulated network were IL-2, -4, and -10, MAPK8, SOCS1, and CREB1.

CONCLUSION

Microarray analysis followed by gene ontology profiling and connectivity analysis identified several functional groups of genes and individual genes responding to sustained reduction of androgen levels in the mouse testis. These include genes whose products function as transcription factors, cell surface molecules including ion channels, extra- and intracellular signaling molecules, and secreted enzymes with the potential of regulating cell-to-cell attachment. The transcription factors CREB1 (down-regulated) and MYC (up-regulated) may mediate the most important initial phases of the testicular response to reduced levels of androgens. These results suggest specific avenues for further research that will lead to a better understanding of how androgens regulate spermatogenesis.

Estrogen provides neuroprotection against activated microglia-induced dopaminergic neuronal injury through both estrogen receptor-α and estrogen receptor-β in microglia

Estrogen provides neuroprotection against neurodegenerative diseases, including Parkinson's disease. Its effects may stem from interactions with neurons, astrocytes, and microglia. We demonstrate here in primary cultures of rat mesencephalic neurons that estrogen protects them from injury induced by conditioned medium obtained from lipopolysaccharide (LPS)-activated microglia. LPS-induced nitrite production and tumor necrosis factor-alpha up-regulation in microglia were blocked by estrogen pretreatment. Estrogen neuroprotection was related to microglial activation of estrogen receptors (ERs), insofar as the protective effect of the microglia-conditioned medium was overridden by pretreatment of microglia with the ER antagonist ICI 182,780. On the other hand, the specific ERalpha antagonist, MPP dihydrochloride, only partially blocked the effects of estrogen, suggesting that estrogen protection was mediated via both ERalpha and ERbeta. LPS treatment did not change ERalpha mRNA levels in microglia, astrocytes, and neurons, but it up-regulated ERbeta mRNA levels in microglia and astrocytes. Similarly, increased ERbeta protein levels were detected in LPS-activated microglia. More interesting was that immunocytochemical analysis revealed that ERbeta was localized in the cytoplasm of microglia and in the cell nucleus of astrocytes and neurons. In summary, our results support the notion that estrogen inhibits microglial activation and thus exhibits neuroprotective effects through both ERalpha and ERbeta activation. The cytoplasm location of microglial ERbeta suggests the possible involvement of nonclassical effects of estrogen on microglia. Changes in microglial ERbeta expression levels may modulate such effects of estrogen.

Androgen-regulated transcripts in the neonatal mouse testis as determined through microarray analysis

Androgens are required for normal spermatogenesis in mammalian testes. These hormones directly regulate testicular somatic cells that, in turn, support germ cell differentiation. However, the identity of genes under androgen regulation in the testis are not well known. In the present study, neonatal male mice (8 days postpartum) treated by testosterone propionate (TP) were used to study androgen action in the testis as evidenced by alterations in gene expression. Mice were treated with 0.5 mg of TP or dihydrotestosterone (DHT) or vehicle (oil), and testes were harvested 4, 8, and 16 h after treatment. Global gene expression was monitored by microarray analysis. Real-time reverse transcription-polymerase chain reaction was performed to confirm the microarray results. The methodology was verified by confirming the presence of previously characterized TP-regulated genes, including Pem in Sertoli cells and Cyp17a1 in Leydig cells. No significant differences in gene expression were found between TP- and DHT-treated samples. Microarray analysis identified 141, 119, and 109 up-regulated genes at 4, 8 and 16 h after TP treatment, respectively, and 83, 99, and 111 down-regulated genes at the same corresponding time points. The androgen regulation of the selected gene was verified further using testes from flutamide-treated adult mice and isolated Sertoli cells in culture. The data generated in the present study may serve as a foundation for hypothesis-driven research and provide insights regarding gene networks and pathways under androgen control in the testis.

Neonatal exposure to di(n-butyl) phthalate (DBP) alters male reproductive-tract development

The purpose of this study was to evaluate male reproductive-organ development in early postnatal male rats following neonatal exposure to di(n-butyl) phthalate (DBP) and identify a mechanism of action. Neonatal male rats were injected subcutaneously from d 5 to 14 after birth with corn oil (control) and DBP (5, 10, or 20 mg/animal). Animals were killed at postnatal day (PND) 31 and PND 42, respectively, and testes, epididymis, seminal vesicles, ventral prostate, levator ani plus bulbocavernosus muscles (LABC), and Cowper's glands were weighed. In addition, the expressions of androgen receptor (AR), estrogen receptors (ERs), and steroidogenic factor-1 (SF-1) were also examined in the testes. Total body weights gains were significantly reduced at PND 29-31, but gradually recovered on PND 42. However, DBP (20 mg/animal) significantly reduced the weights of testes and accessory sex organs (seminal vesicles, LABC, and Cowper's glands), but not of the epididymis. These adverse effects persisted through puberty at PND 42. Serum testosterone levels did not show any significant changes in the control and DBP treatment groups. Histomorphological examination showed mild diffuse Leydig-cell hyperplasia in the interstitium of severely affected tubules on PND 31. Only a few multinuclear germ cells were observed. DBP (20 mg/animal) significantly decreased the expression of AR, whereas ER expression and SF-1 expression were increased in a dose-dependent manner on PND 31 in the rat testes. On PND 42, DBP (20 mg/animal) significantly inhibited ER expression in the testes, but not AR, ER, and SF-1. These results demonstrate that neonatal exposure to DBP produces permanent changes in the endocrine system and leads to abnormal male reproductive-tract development until puberty. Thus our data suggest that DBP is likely to exert its antiandrogenic actions through disruption of AR or ER expression during the early neonatal stage.