Developmental expression and endocrine regulation of CYP1B1 in rat testis

Constitutive expression of cytochrome P450 1B1 endows testicular Leydig cells with susceptibility to 7,12-dimethylbenzanthracene-induced cell death

Testicular Leydig cells produce testosterone through the participation of steroidogenic proteins. The CYP1B1 enzyme has been shown to catalyze 7,12-dimethylbenzanthracene (DMBA), a representative polycyclic aromatic hydrocarbon. We hypothesized that exposure to DMBA causes Leydig cell cytotoxicity through activation of CYP1B1. Leydig cells were exposed to various concentrations of DMBA for the induction of CYP1B1 expression and activity. The status of CYP1B1 function was monitored by evaluation of cytotoxicity-mediated cell death. Our data show that exposure to DMBA causes cytotoxicity in Leydig cells by CYP1B1 activation. DMBA evoked a significant increase in the generation of reactive oxygen species (ROS) by which the depolarization of mitochondrial membrane potential (MMP) is initiated and caspase-3 activation is augmented. The knockdown of CYP1B1 expression resulted in the suppression of DMBA-induced apoptosis via reduced p53 activation and caspase-3 activation, suggesting that a final metabolite of DMBA (i.e., DMBA-DE) bioactivated by CYP1B1 induces p53 activation by binding to DNA and subsequently causing apoptosis via caspase-3 activation. This finding provides evidence for constitutive expression of CYP1B1 in Leydig cells, which is a trait that only requires an initiating signal for its activity. Further research on CYP1B1 activation-provoked steroid metabolism in Leydig cells may provide decisive clues for elucidating its innate function.

Vitamin E can promote spermatogenesis by regulating the expression of proteins associated with the plasma membranes and protamine biosynthesis

Vitamin E is generally believed to promote the production of ovine sperm mainly through its antioxidant effect. Our previous studies have shown that some non-antioxidant genes may also be key in mediating this process. The objective of this study was to identify key candidate proteins that were differentially expressed in response to a treatment with Vitamin E. Prepubertal ovine testicular cells were isolated and divided into two groups. They were either treated with 800 μM Vitamin E (based on our previous results) or used as a non-treated control. After 24 h, all the cells were harvested for proteomic analysis. We found 115 differentially expressed proteins, 4 of which were up-regulated and 111 were down-regulated. A GO term enrichment analysis identified 127 Biological Process, 63 Cell Component and 26 Molecular Function terms that were enriched. Within those terms, 13, 11 and 26 terms were significantly enriched, respectively. Terms related to membrane and enzyme activity including the inner acrosomal membrane, signal peptidase complex, cysteine-type endopeptidase activity, etc., were also markedly enriched, while none of the KEGG pathways were enriched. We found that many of the differentially expressed proteins, such as CD46 (membrane cofactor protein), FLNA (Filamin A), DYSF (Dysferlin), IFT20 (Intraflagellar transport 20), SPCS1 (Signal peptidase complex subunit 1) and SPCS3 (Signal peptidase complex subunit 3) were related to the acrosomal and plasma membranes. A parallel reaction monitoring (PRM) analysis verified that Vitamin E improved spermatogenesis by regulating the expression of FLNA, SPCS3, YBX3 and RARS, proteins that are associated with the plasma membranes and protamine biosynthesis of the spermatozoa.

Cytochrome P4501B1 in bone marrow is co-expressed with key markers of mesenchymal stem cells. BMS2 cell line models PAH disruption of bone marrow niche development functions

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants that are metabolized to carcinogenic dihydrodiol epoxides (PAHDE) by cytochrome P450 1B1 (CYP1B1). This metabolism occurs in bone marrow (BM) mesenchymal stem cells (MSC), which sustain hematopoietic stem and progenitor cells (HSPC). In BM, CYP1B1-mediated metabolism of 7, 12-dimethylbenz[a]anthracene (DMBA) suppresses HSPC colony formation within 6 h, whereas benzo(a)pyrene (BP) generates protective cytokines. MSC, enriched from adherent BM cells, yielded the bone marrow stromal, BMS2, cell line. These cells express elevated basal CYP1B1 that scarcely responds to Ah receptor (AhR) inducers. BMS2 cells exhibit extensive transcriptome overlap with leptin receptor positive mesenchymal stem cells (Lepr+ MSC) that control the hematopoietic niche. The overlap includes CYP1B1 and the expression of HSPC regulatory factors (Ebf3, Cxcl12, Kitl, Csf1 and Gas6). MSC are large, adherent fibroblasts that sequester small HSPC and macrophage in the BM niche (Graphic abstract). High basal CYP1B1 expression in BMS2 cells derives from interactions between the Ah-receptor enhancer and proximal promoter SP1 complexes, boosted by autocrine signaling. PAH effects on BMS2 cells model Lepr+MSC niche activity. CYP1B1 metabolizes DMBA to PAHDE, producing p53-mediated mRNA increases, long after the in vivo HSPC suppression. Faster, direct p53 effects, favored by stem cells, remain possible PAHDE targets. However, HSPC regulatory factors remained unresponsive. BP is less toxic in BMS2 cells, but, in BM, CYP1A1 metabolism stimulates macrophage cytokines (Il1b > Tnfa> Ifng) within 6 h. Although absent from BMS2 and Lepr+MSC, their receptors are highly expressed. The impact of this cytokine signaling in MSC remains to be determined.

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BMS2 and Lepr+MSC cells co-express CYP1B1 and 12 functional niche activity markers.

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CYP1B1 mRNA in BMS2 cells depends on activation of SP1 coupled to an AhR enhancer unit.

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DMBA metabolism by CYP1B1 activates p53 gene targets in BMS2 cells far more than BP.

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HSPC suppression by CYP1B1 generation of PAHDE requires rapid, non-genomic targets.

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BMS2 and Lepr+MSC share receptors activated by BP stimulation of macrophage cytokines.

Cell and region specificity of Aryl hydrocarbon Receptor (AhR) system in the testis and the epididymis

Aryl hydrocarbon receptor (AhR) plays multiple important functions in adaptive responses. Exposure to AhR ligands may produce an altered metabolic activity controlled by the AhR pathways, and consequently affect drug/toxin responses, hormonal status and cellular homeostasis. This research revealed species-, cell- and region-specific pattern of the AhR system expression in the rat and human testis and epididymis, complementing the existing knowledge, especially within the epididymal segments. The study showed that AhR level in the rat and human epididymis is higher than in the testis. The downregulation of AhR expression after TCDD treatment was revealed in the spermatogenic cells at different stages and the epididymal epithelial cells, but not in the Sertoli and Leydig cells. Hence, this basic research provides information about the AhR function in the testis and epididymis, which may provide an insight into deleterious effects of drugs, hormones and environmental pollutants on male fertility.

Morphological Examination and Transcriptomic Profiling To Identify Prednisolone Treatment in Beef Cattle

In livestock production corticosteroids are licensed only for therapy; nevertheless, they are often illegally used as growth promoters. The aim of this study was to identify morphological or biomolecular alterations induced by prednisolone (PDN) in experimentally treated beef cattle, because PDN and its metabolites are no longer detectable by LC-MS/MS methods in biological fluids. Moreover, PDN does not induce any histological alterations in the thymus, different from dexamethasone treatments. Therefore, a marker of illicit treatment for this growth promoter could be useful. Eight male Italian Friesian beef cattle were administered prednisolone acetate 30 mg day^-1 per os for 35 days, and seven beef cattle represented the control group. Six days after drug withdrawal, the animals were slaughtered. Morphological and morphometric modifications were evaluated in the epididymis and testis, whereas transcriptomic changes induced by PDN administration were investigated in peripheral blood mononuclear cells (PBMCs) at different sampling times and in skeletal muscle and testis sampled at slaughtering. In the epididymis, spermatozoa number decreased in PDN-treated animals, and in some cases they were totally absent. Correspondingly, in the testis of treated animals, down-regulation for serine/threonine kinase 11 (STK11) gene expression was detected (p < 0.01). DNA microarray analysis revealed a total of 133 differentially expressed genes in skeletal muscle and testis, and 907 and 1416 in PBMCs after 33 days of treatment and at slaughtering, respectively. Histological investigations on epididymal content could represent a promising marker for PDN treatment in beef cattle and could be used as a screening method to identify animals worthy of further investigation with official methods. Moreover, the clear transcriptomic signature of PDN treatment evidenced in PBMCs supported the possibility of using this matrix to monitor the illicit treatment in vivo during ranching.

Relative effect potency estimates of dioxin-like activity for dioxins, furans, and dioxin-like PCBs in adults based on cytochrome P450 1A1 and 1B1 gene expression in blood

BACKGROUND

In the risk assessment of PCDDs, PCDFs, and dioxin-like (DL) PCBs, regulatory authorities support the use of the toxic equivalency factor (TEF)-scheme derived from a heterogeneous data set of the relative effect potency (REPs) estimates.

OBJECTIVES

We sought to determine REPs for dioxin-like compounds (DLCs) using expression of cytochrome P450 (CYP) 1A1 and 1B1 mRNA in human peripheral blood mononuclear cells representing two different pathways.

METHODS

We used a sex and age adjusted regression-based approach comparing the strength of association between each DLC and the cytochrome P450 (CYP) 1A1 and 1B1 mRNA expression in 320 adults residing in an organochlorine-polluted area of eastern Slovakia.

RESULTS

We calculated REPs based on CYP1A1 expression for 4 PCDDs, 8 PCDFs, and 1 PCB congener, and based on CYP1B1 expression for 5 PCDFs and 11 PCB congeners. REPs from CYP1A1 correlated with REPs previously derived from thyroid volume (ρ=0.85; p<0.001) and serum FT4 (ρ=0.77; p=0.009). The 13 log REPs from CYP1A1 correlated with log WHO-TEFs (r=0.63; p=0.015) and 11 log PCB REPs with PCB consensus toxicity factors (CTFs) for compounds with WHO-TEFs (r=0.80; p=0.003). The complete set of derived 56 log REPs correlated with the log CTFs (r=0.77; p=0.001) and log WHO-TEFs (r=0.81; p<0.001).

CONCLUSIONS

REPs calculated from thyroid and cytochrome P450 endpoints realistically reflect human exposure scenarios because they are based on human chronic and low-dose exposures. While the CYP 1A1 seems more suitable for toxicity evaluation of PCDD/Fs, the CYP 1B1 is more apt for PCDFs and PCBs and reflects different pathways.

2-hydroxyoestradiol and 2-methoxyoestradiol, two endogenous oestradiol metabolites, induce DNA fragmentation in Sertoli cells

Elevated intratesticular levels of hydroxyoestradiols and methoxyoestradiols, two classes of endogenous oestradiol metabolites, have been associated with male infertility. The aim of this study was to explore the effects of 2-hydroxyoestradiol (2OHE₂ ), 4-hydroxyoestradiol (4OHE₂ ), 2-methoxyoestradiol (2ME₂ ) and 4-methoxyoestradiol (4ME₂ ) on Sertoli cell viability. For this, TM4 cells were incubated with different concentrations of these metabolites for 24 h to then evaluate the viability and DNA integrity by MTS and TUNEL assay respectively. The participation of classical oestrogen receptors and the involvement of oxidative stress and apoptotic mechanisms were also evaluated co-incubating TM4 cells with these estradiol metabolites and with the drugs ICI182780, N-acetylcysteine and Z-VAD-FMK respectively. Only high concentrations of 2OHE₂ and 2ME₂ decreased cell viability inducing DNA fragmentation. In addition, ICI182780 did not block the effect of 2OHE₂ and 2ME₂ , while N-Acetylcysteine and Z-VAD-FMK only blocked the effect of 2OHE₂ . Moreover, 2OHE₂ but not 2ME₂ induced PARP and caspase-3 cleavage. Finally, lower 2OHE₂ and 2ME₂ concentrations (0.01-0.1-1.0 μmol l^-1 ) decreased Sertoli cell viability 48 h post-treatment. Our results support the hypothesis that elevated intratesticular 2OHE₂ or 2ME₂ concentrations could be related to male infertility since 2OHE₂ by apoptosis and 2ME₂ by undetermined mechanisms induce DNA fragmentation in Sertoli cells.

Effects of sexually dimorphic growth hormone secretory patterns on arachidonic acid metabolizing enzymes in rodent heart

The arachidonic acid (AA) metabolizing enzymes are the potential therapeutic targets of cardiovascular diseases (CVDs). As sex differences have been shown in the risk and outcome of CVDs, we investigated the regulation of heart AA metabolizing enzymes (COXs, LOXs, and CYPs) by sex-dependent growth hormone (GH) secretory patterns. The pulsatile (masculine) GH secretion at a physiological concentration decreased CYP1A1 and CYP2J3 mRNA levels more efficiently in the H9c2 cells compared with the constant (feminine) GH secretion; however, CYP1B1 mRNA levels were higher following the pulsatile GH secretion. Sex differences in CYP1A1, CYP1B1, and CYP2J11 mRNA levels were observed in both the wild-type and GHR deficient mice. No sex differences in the mRNA levels of COXs, LOXs, or CYP2E1 were observed in the wild-type mice. The constant GH infusion induced heart CYP1A1 and CYP2J11, and decreased CYP1B1 in the male C57/B6 mice constantly infused with GH (0.4 μg/h, 7 days). The activity of rat Cyp2j3 promoter was inhibited by the STAT5B protein, but was activated by C/EBPα (CEBPA). Compared with the constant GH administration, the levels of the nuclear phosphorylated STAT5B protein and its binding to the rat Cyp2j3 promoter were higher following the pulsatile GH administration. The constant GH infusion decreased the binding of the nuclear phosphorylated STAT5B protein to the mouse Cyp2j11 promoter. The data suggest the sexually dimorphic transcription of heart AA metabolizing enzymes, which might alter the risk and outcome of CVDs. GHR-STAT5B signal transduction pathway may be involved in the sex difference in heart CYP2J levels.

Modulation of aryl hydrocarbon receptor-regulated enzymes by trimethylarsine oxide in C57BL/6 mice: In vivo and in vitro studies

Arsenic is a worldwide environmental pollutant that is associated with skin and several types of internal cancers. Recent reports revealed that arsenic biomethylation could activate the toxic and carcinogenic potential of arsenic. Therefore, we investigated the effect of trimethylarsine oxide (TMAO) on the activation of AhR-regulated genes in vivo and in vitro. In vivo, C57BL/6 mice received TMAO (13mg/kg i.p.) with or without the prototypical AhR ligand, TCDD (15μg/kg), then the livers were harvested at 6 and 24h post-treatment. In vitro, isolated hepatocytes from C57BL/6 mice were treated with TMAO (5μM) in the absence and presence of TCDD (1nM) for 6 and 24h. Our in vivo results demonstrated that, TMAO alone increased Cyp1a1, Cyp1a2, Cyp1b1, Nqo1, Gsta1, and Ho-1 at mRNA level. Upon co-exposure to TMAO and TCDD, TMAO potentiated the TCDD-mediated induction of Cyp1a1, Cyp1b1, and Nqo1 mRNA levels. Western blotting revealed that, TMAO alone increased Cyp1a1, Cyp1a2, Nqo1, Gsta1/2, and Ho-1 protein levels, and potentiated the TCDD-mediated induction of Cyp1a1 and Cyp1b1 protein level. In addition, TMAO alone significantly increased Cyp1a1, Cyp1a2, Nqo1, Gst, and Ho-1 activities and significantly potentiated the TCDD-mediated induction of Cyp1a1 activity. At the in vitro level, TMAO induced Cyp1a1 and potentiated the TCDD-mediated induction of Cyp1a1 at mRNA, protein and activity levels. In addition, TMAO increased the nuclear localization of AhR and AhR-dependent XRE-driven luciferase activity. Our results demonstrate that the TMAO, modulates AhR-regulated genes which could potentially participate, at least in part, in arsenic induced toxicity and carcinogenicity.

Age-related testicular toxicity of mGluR5 negative allosteric modulators appears to be unrelated to testis drug transporter maturity

Testicular degeneration was observed in exploratory toxicity studies in Wistar rats treated with several mGluR5 negative allosteric modulators. To determine if these testis effects were influenced by animal age, these compounds were administered to male Wistar rats of different ages (8, 10, and 12 weeks old) for 2 weeks followed by evaluation of male reproductive organ weights, testis histopathology, and inhibin B levels. Overall, seminiferous tubule degeneration was observed in 2/15, 5/15, and 0/15 compound treated rats from the 8, 10, and 12 week old cohorts and inhibin B was decreased in 8 and 10 week old animals, but not in 12 week old rats, suggesting that there is an age-related component to this testis toxicity. The gene expression profiles of drug transporters in the testis of rats aged PND 38 through PND 91 were very similar, indicating that immaturity of these transporters is an unlikely factor contributing to the age-related toxicity.

American Thyroid Association Guide to investigating thyroid hormone economy and action in rodent and cell models

BACKGROUND

An in-depth understanding of the fundamental principles that regulate thyroid hormone homeostasis is critical for the development of new diagnostic and treatment approaches for patients with thyroid disease.

SUMMARY

Important clinical practices in use today for the treatment of patients with hypothyroidism, hyperthyroidism, or thyroid cancer are the result of laboratory discoveries made by scientists investigating the most basic aspects of thyroid structure and molecular biology. In this document, a panel of experts commissioned by the American Thyroid Association makes a series of recommendations related to the study of thyroid hormone economy and action. These recommendations are intended to promote standardization of study design, which should in turn increase the comparability and reproducibility of experimental findings.

CONCLUSIONS

It is expected that adherence to these recommendations by investigators in the field will facilitate progress towards a better understanding of the thyroid gland and thyroid hormone dependent processes.

Systemic compensatory response to neonatal estradiol exposure does not prevent depletion of the oocyte pool in the rat

The formation of ovarian follicles is a finely tuned process that takes place within a narrow time-window in rodents. Multiple factors and pathways have been proposed to contribute to the mechanisms triggering this process but the role of endocrine factors, especially estrogens, remains elusive. It is currently hypothesized that removal from the maternal hormonal environment permits follicle formation at birth. However, experimentally-induced maintenance of high 17β-estradiol (E2) levels leads to subtle, distinct, immediate effects on follicle formation and oocyte survival depending on the species and dose. In this study, we examined the immediate effects of neonatal E2 exposure from post-natal day (PND) 0 to PND2 on the whole organism and on ovarian follicle formation in rats. Measurements of plasma E2, estrone and their sulfate conjugates after E2 exposure showed that neonatal female rats rapidly acquire the capability to metabolize and clear excessive E2 levels. Concomitant modifications to the mRNA content of genes encoding selected E2 metabolism enzymes in the liver and the ovary in response to E2 exposure indicate that E2 may modify the neonatal maturation of these organs. In the liver, E2 treatment was associated with lower acquisition of the capability to metabolize E2. In the ovary, E2 depleted the oocyte pool in a dose dependent manner by PND3. In 10 µg/day E2-treated ovaries, apoptotic oocytes were observed in newly formed follicles in addition to areas of ovarian cord remodeling. At PND6, follicles without any visible oocyte were present and multi-oocyte follicles were not observed. Our study reveals a major species-difference. Indeed, neonatal exposure to E2 depletes the oocyte pool in the rat ovary, whereas in the mouse it is well known to increase oocyte survival.

Common genetic variation in CYP1B1 is associated with concentrations of T₄, FT₃ and FT₄ in the sera of polycystic ovary syndrome patients

CYP1B1 encodes an estrogen enzyme that oxidizes 17β-estradiol to 4-hydroxyestradiol. The evidence demonstrates there may be a relationship between CYP1B1 and thyroid function. To date, no study has evaluated if genetic polymorphisms that regulate concentrations of serum FT3 and FT4 contribute to Polycyctic Ovary Syndrome (PCOS). To identify polymorphisms in the CYP1B1 locus associated with PCOS, we genotyped three common polymorphisms across the CYP1B1 locus in 226 patients. A test for association of common variants with susceptibility to PCOS was conducted in a large cohort of 609 subjects. The functional polymorphism CYP1B1 L432V (rs1056836) is associated with serum T4 (P = 0.003), serum FT3 (P < 0.001) and serum FT4 concentrations (P < 0.001). Our study provides the first evidence that genetic variants in CYP1B1 can be associated with serum T4, FT4 and FT3 levels in PCOS. These findings imply novel pathophysiological links between the CYP1B1 locus and thyroid function in PCOS.

Effect of mono-(2-ethylhexyl) phthalate on human and mouse fetal testis: In vitro and in vivo approaches

The present study was conducted to determine whether exposure to the mono-(2-ethylhexyl) phthalate (MEHP) represents a genuine threat to male human reproductive function. To this aim, we investigated the effects on human male fetal germ cells of a 10⁻⁵ M exposure. This dose is slightly above the mean concentrations found in human fetal cord blood samples by biomonitoring studies. The in vitro experimental approach was further validated for phthalate toxicity assessment by comparing the effects of in vitro and in vivo exposure in mouse testes. Human fetal testes were recovered during the first trimester (7-12 weeks) of gestation and cultured in the presence or not of 10⁻⁵ M MEHP for three days. Apoptosis was quantified by measuring the percentage of Caspase-3 positive germ cells. The concentration of phthalate reaching the fetal gonads was determined by radioactivity measurements, after incubations with ¹⁴C-MEHP. A 10⁻⁵ M exposure significantly increased the rate of apoptosis in human male fetal germ cells. The intratesticular MEHP concentration measured corresponded to the concentration added in vitro to the culture medium. Furthermore, a comparable effect on germ cell apoptosis in mouse fetal testes was induced both in vitro and in vivo. This study suggests that this 10⁻⁵ M exposure is sufficient to induce changes to the in vivo development of the human fetal male germ cells.

Estradiol-mediated suppression of CYP1B1 expression in mouse MA-10 Leydig cells is independent of protein kinase A and estrogen receptor

Estrogens have multifaceted roles in mammalian testis. In the present study, we focused on estradiol as a potential regulator of testicular cytochrome P450 1B1 (CYP1B1) expression and investigated the possible mechanisms involved in the estradiol-mediated suppression. CYP1B1 protein levels were measured in the testes of rats that were treated with 17β-estradiol benzoate (1.5 mg/kg) at different stages of development. In addition, CYP1B1 mRNA levels were measured in mouse MA-10 Leydig tumor cells treated with (a) various concentrations of 17β-estradiol benzoate, (b) 17β-estradiol benzoate in the presence of exogenous luteinizing hormone (LH), or (c) 17β-estradiol benzoate in the presence of ICI 182,780, a competitive steroidal antagonist of estrogen receptors (ERs). Treatment of neonatal, pubertal, or adult rats with 17β-estradiol benzoate was associated with a reduction of approximately 90% in testicular CYP1B1 protein content compared to age-matched controls. Treatment of MA-10 cells with 17β-estradiol benzoate (10-500 nM) produced a concentration- and time-dependent decrease in CYP1B1 mRNA levels, but had no effect on LH receptor mRNA levels or on protein kinase A (PKA) activity. However, 17β-estradiol benzoate (10-500 nM), regardless of the concentration tested, failed to attenuate the LH-elicited increase in CYP1B1 mRNA or PKA activity in MA-10 cells that were co-treated with LH and estradiol. Similarly, ICI 182,780 (10-1000 µM) did not reverse the suppressive effect of estradiol on CYP1B1 mRNA expression in MA-10 cells co-treated with estradiol and ICI 182,780. The results indicate that downregulation of testicular CYP1B1 by estradiol was independent of PKA activity and was not mediated by ERs in MA-10 cells.

Regulation of cytochrome P450 1B1 expression by luteinizing hormone in mouse MA-10 and rat R2C Leydig cells: role of protein kinase A

In the present study, we investigated the signaling pathway involved in luteinizing hormone (LH)-mediated regulation of testicular CYP1B1 in mouse MA-10 and rat R2C Leydig cells. CYP1B1 mRNA and protein levels were measured in MA-10 and R2C cells treated with LH and protein kinase activators or inhibitors. Treatment with LH or 8-bromo-cAMP, a protein kinase A (PRKA) activator, increased CYP1B1 expression and PRKA activity in a concentration-dependent manner in both cell lines, albeit to different extents. Treatment with 8-(4-chlorophenylthio)adenosine-3',5'-cyclic monophosphorothioate, Rp-isomer, a PRKA inhibitor, decreased basal CYP1B1 expression and attenuated LH-elicited increases in CYP1B1 mRNA and protein levels and PRKA activity. In contrast, treatment with a protein kinase G activator or an inhibitor of protein kinase C had no effect on basal or LH-induced CYP1B1 expression in MA-10 or R2C cells. Collectively, the results identify PRKA as the major signaling pathway involved in the LH-mediated regulation of testicular CYP1B1 expression in Leydig tumor cells.

Constitutive expression of drug metabolizing enzymes and related transcription factors in cattle testis and their modulation by illicit steroids

In veterinary species, little information about extrahepatic drug metabolism is actually available. Therefore, the presence of foremost drug metabolizing enzymes (DMEs) and related transcription factors mRNAs was initially investigated in cattle testis; then, their possible modulation following the in vivo exposure to illicit growth promoters (GPs), which represent a major issue in cattle farming, was explored. All target genes were expressed in cattle testis, albeit to a lower extent compared to liver ones; furthermore, illicit protocols containing dexamethasone and 17β-oestradiol significantly up-regulated cytochrome P450 1A1, 2E1, oestrogen receptor-α and peroxisome proliferator-activated receptor-α mRNA levels. Overall, the constitutive expression of foremost DMEs and related transcription factors was demonstrated for the first time in cattle testis and illicit GPs were shown to affect pre-transcriptionally some of them, with possible consequences upon testicular xenobiotic drug metabolism.

Effect of high intratesticular estrogen on global gene expression and testicular cell number in rats

BACKGROUND

The identification of estrogen receptors alpha and beta and aromatase in the testis has highlighted the important role of estrogens in regulating spermatogenesis. There is a wealth of information on the deleterious effects of fetal and neonatal exposure of estrogens and xenoestrogens in the testis, including spermiation failure and germ cell apoptosis. However, very little is known about gene transcripts affected by exogenous estradiol exposure in the testis. The objective of the present study was to unveil global gene expression profiles and testicular cell number changes in rats after estradiol treatment.

METHODS

17beta-estradiol was administered to adult male rats at a dose of 100 micrograms/kg body weight in saline daily for 10 days; male rats receiving only saline were used as controls. Microarray analysis was performed to examine global gene expression profiles with or without estradiol treatment. Real time RT-PCR was conducted to verify the microarray data. In silico promoter and estrogen responsive elements (EREs) analysis was carried out for the differentially expressed genes in response to estradiol. Quantitation of testicular cell number based on ploidy was also performed using flow cytometry in rats with or without estradiol treatment.

RESULTS

We found that 221 genes and expressed sequence tags (ESTs) were differentially expressed in rat testes treated with estradiol compared to the control; the microarray data were confirmed by real time RT-PCR. Gene Ontology analysis revealed that a number of the differentially expressed genes are involved in androgen and xenobiotic metabolism, maintenance of cell cytoskeleton, endocytosis, and germ cell apoptosis. A total of 33 up-regulated genes and 67 down-regulated genes showed the presence of EREs. Flow cytometry showed that estradiol induced a significant decrease in 2n cells (somatic and germ cells) and 4n cells (pachytene spermatocytes) and a marked increase in the number of elongated and elongating spermatids.

CONCLUSIONS

This study provides a novel insight into the molecular basis for spermiation failure and apoptosis caused by 17beta-estradiol and it also offers new mechanisms by which adult exposure to environmental estrogens can affect spermatogenesis and fertility.