Assay system for simultaneous measurement of three steroidogenic enzyme activities in rat and human testis--effect of human chorionic gonadotropin

Role of endocrine disruptors in male infertility and impact of COVID-19 on male reproduction

Several epidemiological studies suggest strong association of endocrine disruptors (EDs) with impaired male reproduction. High levels of polychlorinated biphenyls in serum are associated with low sperm count and poor fertility. A high dichloro diphenyl trichloroethane (DDT) concentration results in low serum testosterone (T) and poor semen quality. DDT stimulates estrogen production by acting as estrogen receptor agonist and potent androgen receptor antagonist. Phthalates, another group of EDs, induce seminiferous tubule degeneration with impaired spermatogenesis via disruption of gene expression that regulates cholesterol and lipid homeostasis resulting in low T. Bisphenol A, a strong exogenous estrogen with antiandrogen effect, lowers serum follicle-stimulating hormone, luteinizing hormone, and T, resulting in impaired development of seminiferous tubules and spermatogenesis. Di(2-ethylhexyl) phthalates can exert their antiandrogenic action by directly inhibiting testosterone biosynthesis via cytochrome P-450 dysfunction. Since these EDs are commonly found in plastic bottles, cosmetics, pesticides, some metal food cans, etc., and accumulate in the environment, it is very important to observe caution and avoid their exposure. This updated chapter also reviews the impact of COVID-19-related infection on male reproduction.

Steroid biosynthetic enzyme activities in leachate-exposed female perch (Perca fluviatilis) as biomarkers for endocrine disruption

Studies have shown that adult female perch in a freshwater lake, Molnbyggen, Sweden, have a reproductive disorder caused by unidentified endocrine disrupting compounds (EDCs) leaching from a local refuse dump. The adverse effects include shallow open sores, low ratio of sexually mature individuals, low gonadosomatic index and low circulating levels of androgens. We hypothesised that the low androgen levels could be a result of impaired production and/or stimulated excretion of androgens by EDCs. From October 2000 to November 2001, at time-points important in the perch reproductive cycle, adult female perch were collected in Molnbyggen and in the reference lake, Djursjön. The activities of three key enzymes in androgen biosynthesis: 17alpha-hydroxylase (17OHlase), 17,20-lyase (lyase) and 17beta-hydroxysteroid dehydrogenase (17betaHSD) were determined in head kidney or ovary. The relationship between enzyme activities and plasma steroid concentrations was examined. Ovarian histopathology and the determination of brain aromatase activity were also included in the study. Similar 17OHlase, 17betaHSD and aromatase activities were found in Molnbyggen females and reference fish throughout the year. Head kidney 17OHlase showed a positive correlation to cortisol levels (r=0.754; p<0.001) but not to androgen levels. Molnbyggen females exhibited lower ovarian lyase activity during vitellogenesis than reference fish. Atretic oocytes were on most occasions more frequent in sexually immature than in sexually mature females. The results suggest that neither 17OHlase, 17betaHSD nor aromatase is the target for EDCs disrupting the androgen homeostasis of exposed female perch. Further investigation is needed to establish the role of decreased ovarian lyase activity in endocrine homeostasis, but the possibility of increased excretion of androgens should also be examined.

Marked inhibition of testosterone biosynthesis by the hepatotoxin nodularin due to apoptosis of Leydig cells

We previously observed that the serum testosterone level was greatly reduced in the course of diethylnitrosamine-nodularin-induced hepatocarcinogenesis in Fischer 344 male rats (Lim et al., Gastroenterological Carcinogenesis, 1999). As an extension of this observation, this study was undertaken to investigate the molecular mechanism of downregulation of testosterone and its effect on target organs in Fischer 344 male rats treated with the hepatotoxin nodularin. After treating the rats with nodularin, a marked reduction of the testosterone level was noted in both serum and testis, with an accompanying accumulation of cholesterol in serum. Reduction of serum testosterone was not due to increased degradation of testosterone in the liver but to impaired biosynthesis in the testes, reduced activities of the cholesterol side chain cleavage enzyme and 17alpha-hydroxylase, and decreased expression of the steroidogenic acute regulatory protein gene, all of which constitute rate-limiting steps for testosterone biosynthesis in the testes. Intraperitoneal injection of nodularin into rats induced cuboidal changes of glandular epithelium in ventral prostates and apoptotic changes of spermatogonium, for example, nuclear chromatin condensation, shrinkage, and detachment from Sertoli cells, which included many lysosomal granules. Leydig cells also showed evidence of chromatin condensation and significant induction of peroxisome proliferation. In conclusion, the potential causes of impaired testosterone biosynthesis might have been apoptosis of Leydig cells induced by direct toxicity of the hepatotoxin on testes or hypothalamopituitary dysfunction.

Absence of correlation between in situ expression of cytochrome P450 17alpha hydroxylase/lyase and 3beta-hydroxysteroid dehydrogenase/(Delta5-4) isomerase messenger ribonucleic acids and steroidogenesis during pubertal development in the rat testis

Changes in expression of Leydig cell 3beta-hydroxysteroid dehydrogenase (3betaHSD) and 17alpha-hydroxylase/C17-20 lyase (P450(17alpha)) messenger RNA (mRNA) during pubertal development have not been well characterized in the rat. In the present study, expression of 3betaHSD and P450(17alpha) were determined in frozen sections of testes of immature (days 21 and 28), pubertal (days 45 and 60) and adult (day 90) rats by in situ hybridization using digoxigenin-labeled riboprobes and quantified densitometrically. Measures of steroidogenesis in this study, 3betaHSD and P450(17alpha) enzyme activities per testis and plasma testosterone concentration, increased during pubertal development, peaking at 45-60 days of age. Expression of 3betaHSD protein, a marker for Leydig cell function, was abundantly immunolocalized to the interstitial compartment of the testis. Quantified densitometrically, the amount of 3betaHSD protein did not vary significantly during pubertal development. Transcripts of 3betaHSD and P450(17alpha) were expressed abundantly by clusters of immature Leydig cells in immature animals. However, in contrast to measures of steroidogenesis during pubertal development, mRNA of 3betaHSD and P450(17alpha) decreased to undetectable levels at the age of 45 and 60 days, respectively. The decline in mRNA of 3betaHSD and P450(17alpha) was confirmed by Northern analysis. Expression of 3betaHSD and P450(17alpha) transcripts rebounded in the adult at 90 days and were comparable to levels of expression observed in immature animals. These results show that during pubertal development the steady-state accumulation of mRNA of 3betaHSD and P450(17alpha) are not correlated with accumulation of 3betaHSD protein, enzyme activities of 3betaHSD and P450(17alpha), or testosterone secretion. Possible explanations of the depletion of transcripts during pubertal development include: specific inhibition of transcription, increased mRNA instability, or high translational activity.

Inhibition of androgen synthesis by 22-hydroximino-23,24-bisnor-4-cholen-3-one

The 22-hydroximino-23,24-bisnor-4-cholen-3-one (22-oxime) was synthesized and evaluated as an inhibitor of 17 alpha-hydroxylase/C17,20-lyase in rat testicular microsomes and the 5 alpha-reducatase of human prostatic microsomes from patients with benign prostatic hypertrophy. The 22-oxime demonstrated moderate inhibition for the 17 alpha-hydroxylase (Ki 74 nM vs. Km 29 nM) with progesterone as substrate and potent inhibition (Ki 18 nM vs. Km 76 nM) for the C17,20-lyase activity with 17 alpha-hydroxyprogesterone as substrate. Further investigation of this enzyme with progesterone as substrate demonstrated the inhibition occurred mainly at the 17 alpha-hydroxylation step of the progesterone substrate. The 22-oxime also demonstrated potent and competitive inhibition of 5 alpha-reductase in human prostatic microsomes (Ki 1.4 nM vs. Km 14 nM). When adult male rats were injected subcutaneously (sc) daily with 22-oxime (50 mg/kg/day) for 21 days, the concentrations of serum and testicular testosterone were significantly reduced by 65% and 59%, respectively, in comparison to vehicle-treated controls. Furthermore, both testosterone and DHT concentrations in rat prostatic tissue were significantly decreased by 60% and 44% compared to control tissue. Serum LH concentrations were unchanged in the 22-oxime-treated group compared to the control group. This indicates that the reduction in androgen concentrations in animals treated with this compound is not due to its influence on pituitary feedback mechanisms which result in reduced LH secretion. These results suggest that 22-oxime is effective in reducing androgen synthesis through the inhibition of 17 alpha-hydroxylase, C17,20-lyase, and 5 alpha-reductase both in vitro and in vivo.

Adenomatous leydig cell hyperplasia of the testicle remnant after subtotal orchidectomy in the rat

Subtotal orchidectomy is a suitable method to induce adenomatous Leydig cell hyperplasia in the testicular remnant without irradiation or toxic chemicals. Very expressed hyperplasia of the smooth endoplasmic reticulum was detectable electronmicroscopically in the newly formed Leydig cells. The activity of Δ⁵-3β-hydroxysteroid dehydrogenase in the homogenate of the testicular remnant was found considerably elevated. These observations suggest a steroidogenetic activity of the proliferating Leydig cells.

Changes in the expression of cytochrome P450c17 associated with ovarian cystic follicles. An immunocytochemical and enzymatic analysis of porcine ovaries

The steroidogenic activity of normal preovulatory and cystic follicles, and corpora lutea of porcine ovaries was investigated by immunocytochemical and radioenzymatic techniques. Using a specific antibody to porcine cytochrome P450c17, immunocytochemical staining was specifically localized in the theca interna layer of normal follicles and undetectable in the granulosa layer. The theca interna layers of non-luteinized cystic follicles were immunoreactive while those of luteinized follicles were not. Corpora lutea cells were essentially negative. The 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase activity was similar in luteinized cystic follicular and corpora lutea tissues, which had 8 times higher activity than found in normal preovulatory follicles. The formation of either corpora lutea or luteinized cysts led to a profound decline (12- to 15-fold) in 17 alpha-hydroxylase and 17,20 lyase activities compared to normal preovulatory follicles. In agreement with these enzyme findings, radioimmunoassays revealed very high levels of progesterone with nearly undetectable levels of androgens in the luteinized cysts. These studies demonstrate the functional similarities between cells of luteinized cysts and those of normal corpora lutea and suggest a pathology associated suppression of P450c17 expression in porcine cystic follicles.

Effect of zidovudine (AZT) on reproductive and hematopoietic systems in the male rat

The effects of Zidovudine (AZT) on parameters of the reproductive and hematopoietic systems of male rats were evaluated and compared to those of the controls. Young male Wistar rats were divided into three groups. The control rats (Group 1) received no drug. AZT was administered via drinking water to rats in Groups 2 and 3 (0.1 mg/mL Group 2, and 1.0 mg/mL Group 3) for 4 weeks. Daily water intake and weekly body weight were monitored. Serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone (T), prolactin (PRL) and intratesticular T levels were determined by specific radioimmunoassays. Serum AZT was measured by HPLC. Bone-marrow toxicity was monitored by colony-forming units of erythroid (CFU-E) and granulocyte-macrophage (CFU-GM) assays. The body weight of all rats increased 2-fold in four weeks, and no significant differences were observed between control and treated groups. Ventral prostate (VP) weight decreased significantly (P less than 0.05) by 32% in Group 2 and 27% in Group 3 rats, compared to the control group. Seminal vesicle (SV) weight decreased by 20% in Group 2 (NS) and 30% in Group 3 (P less than 0.05) rats. No significant differences were observed in testes weight or in the intratesticular sperm count between control and AZT-treated groups. Serum T levels (ng/mL) decreased significantly in Group 2 rats (2.8 +/- 0.4 in control to 1.7 +/- 0.2, P less than 0.05) but recovered (2.6 +/- 0.5) in Group 3 when compared to Group 1 (control). Serum LH and PRL levels showed a significant increase (P less than 0.05) in Group 3 compared to control or Group 2 rats. Serum FSH and intratesticular T levels showed no significant change. A significant (P less than 0.05) dose-dependent decrease in CFU-E and in CFU-GM was observed in AZT-treated rats compared to controls. These results demonstrate that the effects of AZT on the reproductive system in the male rat are more subtle and complex, compared to its significant effects on bone-marrow. This suggests that important interactions may exist between the endocrine and hematopoietic systems.

Inhibition of 17 alpha-hydroxylase/C17-C20 lyase by bifluranol and its analogues

A simple assay for the measurement of the activities of both 17 alpha-hydroxylase and C17-C20 lyase is described. No extraction procedures are required. The separation of substrate and products is achieved using HPLC which allows the collection of the components of interest and the monitoring of the recovery of various steroids. Using this assay, bifluranol (known to show anti-prostatic activity in vivo) and some analogues were tested for inhibitory activity towards these enzyme activities. Each compound was active, although less potent than ketoconazole, and this activity may contribute towards the in vivo action.