Toxicogenomic effects of neonatal exposure to diethylstilbestrol on mouse testicular gene expression in the long term: a study using cDNA microarray analysis

Dysregulation of circadian rhythm in zebrafish (Danio rerio) by thifluzamide: Involvement of positive and negative regulators

Thifluzamide as a fungicide is toxic to brain of zebrafish embryos. Brain can regulate biological rhythms. To clarify whether thifluzamide would influence circadian rhythms, zebrafish embryos were treated with thifluzamide (0, 0.19, 1.90 and 2.85 mg/L) for 4 days. Exposure to thifluzamide induced pronounced changes in embryo brain and melatonin levels. The mRNA levels of genes related to circadian rhythms were apparently altered. Among these, the transcripts of cry1ba and clock1 were extremely correlated with exposure concentrations. Importantly, the content of cry1 showed no apparent changes, but the clock level was dramatically increased. Moreover, consistent with the inhibition of development and behavior, the levels of GH and DA were significantly inhibited. In addition, the expression levels of genes related to development, behavior and reproduction were significantly changed by thifluzamide. Therefore, we speculated that circadian disruption due to thifluzamide exposure were primarily attributed to increases in expression of clock1a and contents of clock, which might be at least in part responsible for abnormal development and behavior of zebrafish. In addition, our research will provide important insights into the grouped assessment of SDHI pesticides in future.

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.

DNA microarray-based gene expression profiling of estrogenic chemicals

We summarize updated information about DNA microarray-based gene expression profiling by focusing on its application to estrogenic chemicals. First, estrogenic chemicals, including natural/industrial estrogens and phytoestrogens, and the methods for detection and evaluation of estrogenic chemicals were overviewed along with a comprehensive list of estrogenic chemicals of natural or industrial origin. Second, gene expression profiling of chemicals using a focused microarray containing estrogen-responsive genes is summarized. Third, silent estrogens, a new type of estrogenic chemicals characterized by their estrogenic gene expression profiles without growth stimulative or inhibitory effects, have been identified so far exclusively by DNA microarray assay. Lastly, the prospect of a microarray assay is discussed, including issues such as commercialization, future directions of applications and quality control methods.

Neonatal exposure to diethylstilbestrol causes granulomatous orchitis via epididymal inflammation

Diethylstilbestrol (DES), an endocrine-disrupting chemical, is an infamous artificial estrogenic compound. Although neonatal exposure to DES has been shown to result in inflammation of the male reproductive system, it has not, to our knowledge, been reported to induce testicular inflammation. Here we report that neonatal exposure to DES caused granulomatous orchitis with spermatogenic disturbance in 4 of 17 ICR male mice at 12 weeks of age. In the animals with spermatogenic disturbance, we observed either seminiferous tubules containing only cells with Sertoli cell features (likely Sertoli cell syndrome), or tubule cells in maturation arrest that contained only spermatogonia and/or spermatocytes. Following neonatal DES exposure, 5-week-old mice exhibited inflammation in cauda epididymis; by 8 weeks, the inflammation had spread to all segments of epididymis but not the testis; by 12 weeks, inflammation of the epididymis was observed in all mice. These data indicated that cauda epididymis has increased sensitivity to neonatal DES exposure compared to other segments of epididymis and testis. The data also implied that neonatal DES exposure-induced inflammation in cauda epididymis extended gradually to the testis via corpus and caput during development.

Microarray technology offers a novel tool for the diagnosis and identification of therapeutic targets for male infertility

Male infertility is now a major reproductive health problem because of an increasing number of environmental pollutants and chemicals, which eventually result in gene mutations. Genetic alterations caused by environmental factors account for a significant percentage of male infertility. Microarray technology is a powerful tool capable of measuring simultaneously the expression of thousands of genes expressed in a single sample. Eventually, advances in genetic technology will allow for the diagnosis of patients with male infertility due to congenital reasons or environmental factors. Since its introduction in 1994, microarray technology has made significant advances in the identification and characterization of novel or known genes possibly correlated with male infertility in mice, as well as in humans. This provides a rational basis for the application of microarray to establishing molecular signatures for the diagnosis and gene therapy targets of male infertility. In this review, the differential gene expression patterns characterized by microarray in germ and somatic cells at different steps of development or in response to stimuli, as well as a number of novel or known genes identified to be associated with male infertility in mice and humans, are addressed. Moreover, issues pertaining to measurement reproducibility are highlighted for the application of microarray data to male infertility.

Neonatal administration of diethylstilbestrol has adverse effects on somatic cells rather than germ cells

Neonatal administration of diethylstilbestrol (DES) to rodents has adverse effects on spermatogenesis. However, not many studies have been conducted to determine which type of cell - germ or somatic - is the major target of DES. In order to clarify this, we tried reciprocal germ cell transplantation--transplantation of germ cells from DES-treated mice into intact mice and germ cells from normal mice into DES-treated mice. The donor germ cells were tagged with the green fluorescent protein (GFP) gene in order to distinguish the exogenous germ cells from the endogenous cells. Moreover, to obtain a large number of spermatogonia from the testes of adult mice, we performed fractionation by centrifugation with Percoll. Consequently, we found that the germ cells collected from DES-treated mice have differentiated into normal sperms in normal seminiferous tubules. However, in the case of the transplantation of normal germ cells into the seminiferous tubules of DES-treated mice, defective spermatogenesis was observed. In conclusion, DES has adverse effects on the somatic cells that are involved in spermatogenesis rather than the germ cells.

Identification and characterization of novel and unknown mouse epididymis-specific genes by complementary DNA microarray technology

To examine epididymal function, we attempted to identify highly expressed genes in mouse epididymis using a cDNA microarray containing PCR products amplified from a mouse epididymal cDNA library. We isolated one novel and four known genes-lymphocyte cytosolic protein 1 (Lcp1), complement subcomponents C1r/C1s, Uegf protein, and bone morphogenetic protein and zona pellucida-like domains 1 (Cuzd1), transmembrane epididymal protein 1 (Teddm1), and whey acidic protein 4-disulfide core domain 16 (Wfdc16)-with unknown functions in the epididymis. The novel gene, designated Serpina1f (serine peptidase inhibitor [SERPIN], clade A, member 1f), harbors an open reading frame of 1 233 bp encoding a putative protein of 411 amino acids, including a SERPIN domain. These five genes were predominantly expressed in the epididymis as compared to other organs. In situ hybridization analysis revealed their epididymal region-specific expression patterns. Real-time RT-PCR analysis revealed a significant increase in mRNA expression of these genes around puberty. Castration decreased their expression, except forLcp1. Testosterone (T) restored these reduced expressions, except forTeddm1; however, this restoration was not observed with 17 beta-estradiol (E2). Administration of T and E2 combination recovered the Serpina1f mRNA concentration; this recovery was also observed with T alone. However, the recovery of Cuzd1and Wfdc16mRNA concentrations was inadequate. Neonatal diethylstilbestrol treatment suppressed the Cuzd1, Wfdc16, and Serpina1f mRNA expression in the epididymis of 8-week-old mice; this was not observed with E2. These results suggest that our microarray system can provide a novel insight into the epididymal function on a molecular basis, and the five genes might play important roles in the epididymis.

Reproductive outcomes in men with prenatal exposure to diethylstilbestrol

OBJECTIVE

To examine prenatal diethylstilbestrol (DES) exposure in relation to male reproductive outcomes.

DESIGN

Prospective observational study.

SETTING

Participants were identified through record review, clinical trial participation, or an obstetrics clinic.

PATIENT(S)

A total of 1,085 DES-exposed and 1,047 unexposed men.

INTERVENTION(S)

Participants were exposed prenatally to DES through the mother's obstetrics care or clinical trial participation.

MAIN OUTCOME MEASURE(S)

Infertility; never fathering a pregnancy or live birth; number of pregnancies or live births fathered.

RESULT(S)

We found little evidence that prenatal DES exposure affects the likelihood of never fathering a pregnancy or live birth, or influences the mean number of fathered pregnancies or live births. Our data suggest that DES-exposed men are slightly more likely to experience infertility (relative risk [RR] = 1.3, 95% confidence interval [CI] = 1.0-1.6). The DES dose and gestational timing did not influence infertility or the number of pregnancies or live births fathered, but results were inconsistent for dose effects on the likelihood of never fathering a pregnancy or a live birth.

CONCLUSION(S)

Prenatal DES exposure may be associated with a slightly increased risk of having an infertility experience, but does not increase the likelihood of never fathering a pregnancy or a live birth, or the number of pregnancies or live births fathered.

Comprehensive analysis of the effect of phytoestrogen, daidzein, on a testicular cell line, using mRNA and protein expression profile

In this study, we examined the effects of exposure to phytoestrogen (daidzein), 17beta-estradiol (E2), diethylstilbestrol (DES) and staurosporin on the TM4 testicular cell line, using comprehensive analysis, such as cDNA microarray and two-dimension polyacrylamide gel electropholesis (2D-PAGE) analysis, and we demonstrated if these toxicogenomic analyses could classify the chemical compounds. First, RNA was extracted from TM4 cells that had been treated with daidzein (80 microM), DES, E2 (40 microM) and stauroporin (100 nM) for 30 min. We performed cDNA microarray analysis, and the expression ratio data thus obtained were then analyzed using hierarchical clustering. This hierarchical clustering showed that daidzein exposure induced a different effect on gene expression change from that of E2, DES and staurosporin. Next, protein extracted from TM4 cells also underwent cDNA microarray analysis for 3 h. We performed 2D-PAGE analysis, and the spot intensity ratio data thus obtained were analyzed using hierarchical clustering. As with cDNA microarray, the hierarchical clustering of protein spot ratios showed that daidzein exposure induced a different effect on gene expression change from that of the other substances. In conclusion, we have demonstrated for the first time that classification of these chemicals can be performed by clustering analysis, using data from cDNA microarray and 2D-PAGE analyses, and that exposure to daidzein induces effects different from those of E2, DES and staurosporin.

EFFECTS OF MALE REPRODUCTIVE TOXICANTS ON GENE EXPRESSION IN RAT TESTES

Predictive biomarkers of testicular toxicity are needed for an efficient development of drugs. The purpose of the present study was to obtain further insight into the toxicity mechanisms of various male reproductive toxicants and to detect genomic biomarkers for rapid screening of testicular toxicity. Four reproductive toxicants, 2,5-hexanedione (Sertoli cells toxicant), ethylene glycol monomethyl ether (EGME; spermatocytes toxicant), cyclophosphamide (spermatogonia toxicant) and sulfasalazine, were orally administered to male rats once. Six hours after the single dosing, gene expression in the testes was monitored by cDNA microarray and real-time RT-PCR and the testes were histopathologically examined. No histopathological abnormality was detected except for slight degeneration of spermatocytes in the EGME-treated testes. cDNA microarray analysis revealed differential gene expression profiles, and it was possible based on the profiles to characterize the action of the compounds in the testes. Interestingly, 3 spermatogenesis-related genes -- heat shock protein 70-2, insulin growth factor binding protein 3 and glutathione S transferase pi -- were affected by all the compounds. The above changes of gene expression were detectable within a short period after the dosing prior to the appearance of obvious pathological changes. These data suggest that cDNA microarray is a useful technique for evaluation of primary testicular toxicity. Furthermore, we propose the above 3 spermatogenesis-related genes as potential biomarkers of testicular toxicity.

Gene expression analysis of the rat testis after treatment with di(2-ethylhexyl) phthalate using cDNA microarray and real-time RT-PCR

To investigate the effects of di(2-ethylhexyl) phthalate (DEHP) on gene expression in rat testis, 6-week-old male Sprague-Dawley rats were given a single oral dose of 20 or 2000 mg/kg and euthanized 3, 6, 24, or 72 h thereafter. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells were significantly increased in the testis at 24 and 72 h after the exposure to 2000 mg/kg of DEHP. On cDNA microarray analysis, in addition to apoptosis-related genes, genes associated with atrophy, APEX nuclease, MutS homologue (E. coli), testosterone-repressed-prostatic-message-2 (TRPM-2), connective tissue growth factor, collagen alpha 2 type V, and cell adhesion kinase were differentially expressed. To investigate the relationship between histopathological alteration and gene expression, we selected genes associated with apoptosis and analyzed their expression by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). With 20 mg/kg of DEHP treatment, bcl-2, key gene related to apoptosis, was increased. Up-regulation of bcl-2, inhibitor of Apaf-1/caspase-9/caspase-2 cascade of apoptosis, may be related to the fact that no morphological apoptotic change was induced after dosing of 20 mg/kg DEHP. With 2000 mg/kg of DEHP treatment, the apoptotic activator cascade, Fas/FasL, FADD/caspase-8/caspase-3 cascade, and Apaf-1/caspase-9/caspase-2 cascade were increased and bcl-2 was decreased. Thus, these gene regulations might lead the cells into apoptosis in the case of high exposure to DEHP. In contrast, FADD/caspase-10/caspase-6 cascade and caspase-11/caspase-3 cascade were not increased. These results indicate that the cascades of FADD/caspase-10/caspase-6 and caspase-11/caspase-3 are not related to apoptosis with DEHP treatment.

High-risk group and high-risk life stage: Key issues in adverse effects of environmental agents on human health

Our previous studies analyzing umbilical cords show that human fetuses are exposed to multiple environmental agents. Fetuses are at a high-risk life stage in human life and our results revealed that there is a presence of potential high-risk group in Japanese babies. It suggests the necessity to develop a new method of evaluating health risk factors to human fetuses of the possible long-term effects caused by prenatal exposure to multiple environmental agents. Its main goal is to find the potential high-risk group in the next generation and to prevent the long-term effects caused by fetal exposure to multiple chemicals. Recently, we introduced our attempts to apply toxicogenomic analysis of gene expressions in umbilical cords using DNA microarray to the future health risk assessment. Our trial showed that it could be used as an effective newborn screening to detect potential high-risk groups focusing on the exposure level and the susceptibility. To improve future children's health, it is necessary to develop a risk reduction method, in addition to the establishment of the new risk assessment, to avoid multiple chemical exposures and to reduce the concentration level of persistent chemicals in the human body. Worldwide cooperation is urgently required focusing on the high-risk group and high-risk life stage. (Reprod Med Biol 2004; 3: 51-58).

Using a customized DNA microarray for expression profiling of the estrogen-responsive genes to evaluate estrogen activity among natural estrogens and industrial chemicals

We developed a DNA microarray to evaluate the estrogen activity of natural estrogens and industrial chemicals. Using MCF-7 cells, we conducted a comprehensive analysis of estrogen-responsive genes among approximately 20,000 human genes. On the basis of reproducible and reliable responses of the genes to estrogen, we selected 172 genes to be used for developing a customized DNA microarray. Using this DNA microarray, we examined estrogen activity among natural estrogens (17beta-estradiol, estriol, estrone, genistein), industrial chemicals (diethylstilbestrol, bisphenol A, nonylphenol, methoxychlor), and dioxin. We obtained results identical to those for other bioassays that are used for detecting estrogen activity. On the basis of statistical correlations analysis, these bioassays have shown more sensitivity for dioxin and methoxychlor.

Long-term alteration of gene expression without morphological change in testis after neonatal exposure to genistein in mice: toxicogenomic analysis using cDNA microarray

In this study, we carried out toxicogenomic analysis using in-house cDNA microarray to ascertain the long-term effects of neonatal exposure to genistein, also known as phytoestrogen, on testicular gene expression in mice. Male ICR mice, 1 day after birth, were exposed for 5 days to genistein (1000 microg/mouse/day) or diethylstilbestrol (DES) (50 microg/mouse/day), used as an example of a potent estrogen, and their testes were used when they were 12 weeks old. Since exposure to DES was been reported to induce morphological changes and alteration of gene expression in reproductive organs, DES was used as a positive control. Genistein-treated mice did not show any histological abnormalities or increased apoptotic cells in testes, but these abnormalities and increases were found in DES-treated mice. On the other hand, mRNA expression analysis using in-house cDNA microarray revealed that 2 down-regulated genes (GeneBank accession No. W49392 and AI430907) were detected in genistein-treated mouse testes. Moreover, real-time PCR analysis revealed that mRNAs of the W49392 gene, estrogen receptor alpha (ERalpha) and androgen receptor (AR), were down-regulated in the testes of both genistein-treated and DES-treated mice. In our present study using toxicogenomic analysis, long-term alteration in testicular mRNA expression, without morphological change in testes, was detected after neonatal treatment with genistein, indicating that the W49392 gene, in addition to ERalpha and AR, might be useful as a biological marker for predicting the effects of neonatal exposure to DES and genistein.

Effect of neonatal exposure to diethylstilbestrol on testicular gene expression in adult mouse: comprehensive analysis with cDNA subtraction method

Summary In utero or neonatal exposure to high levels of exogenous steroid hormones, such as the potent synthetic diethylstilbestrol (DES), incurs an increased risk of malfunctional male reproduction. In this study, we investigated whether neonatal exposure to DES induces the alteration of mRNA expression in adult mouse testis. Using a cDNA subtraction method, we isolated seven gene clones whose expression was changed in neonatally DES-treated mouse testis. Northern blot analysis revealed that five up-regulated genes (AF326230, AF356521, AK004975, AK006136 and BM237156) and two down-regulated genes (AK017044, AK017130) were predominantly expressed in testes of 8-week-old mice. Moreover, we confirmed that the expression of these seven genes was altered by neonatal DES-exposure using Northern blot analysis. Our results suggest that neonatal exposure to DES leads to the alteration of gene expression in the testis in the long term. These genes might be useful as biological markers of foetal or neonatal exposure to exogenous steroid hormones, such as DES.

Toxicogenomic difference between diethylstilbestrol and 17?-estradiol in mouse testicular gene expression by neonatal exposure

In this study, we investigated the effects of neonatal exposure to exogenous estrogen (diethylstilbestrol: DES, 17beta-estradiol: E2) on testicular gene expressions. Male C57BL/6J mice, 1 day after birth, were subcutaneously injected with DES or E2 (3 micrograms/mouse/day) for 5 days, and then they were raised for 8 weeks. In morphological observation of 8-week-old mice testes, spermatozoa were absent from many seminiferous tubules in DES-treated mice testes, but there was no change in E2-treated mice testes. Analysis of in-house cDNA microarray (mouse cDNA 889 genes) revealed that 17 genes were altered in DES-treated mice testes at 8 weeks of age, compared to each control. Real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) analysis of these genes revealed that some genes, which were changed in E2-treated testis, were the same as in DES-treated testis, whereas in other cases there was a difference between DES-treated and E2-treated testis. The present results suggest that each exogenous estrogenic compound has both a common gene expression change pattern and its own testicular gene expression change pattern. Mol. Reprod. Dev. 67: 19-25, 2004.

Developmental toxicity of estrogenic chemicals on rodents and other species

Antenatal sex-hormone exposure induces lesions in mouse reproductive organs, which are similar to those in humans exposed in utero to a synthetic estrogen, diethylstilbestrol. The developing organisms including rodents, fish and amphibians are particularly sensitive to exposure to estrogenic chemicals during a critical window. Exposure to estrogens during the critical period induces long-term changes in reproductive as well as non-reproductive organs, including persistent molecular alterations. The antenatal mouse model can be utilized as an indicator of possible long-term consequences of exposure to exogenous estrogenic compounds including possible environmental endocrine disruptors. Many chemicals released into the environment potentially disrupt the endocrine system in wildlife and humans, some of which exhibit estrogenic activity by binding to the estrogen receptors. Estrogen responsive genes, therefore, need to be identified to understand the molecular basis of estrogenic actions. In order to understand molecular mechanisms of estrogenic chemicals on developing organisms, we are identifying estrogen responsive genes using cDNA microarray, quantitative RT-PCR, and differential display methods, and genes related to the estrogen-independent vaginal changes in mice induced by estrogens during the critical window. In this review, discussion of our own findings related to endocrine distuptor issue will be provided.