Apoptosis related gene products in differentiated and tumorigenic rat Leydig cells and following regression induced by the cytotoxin ethane dimethanesulphonate

Testosterone regulates granzyme K expression in rat testes

OBJECTIVE

Testosterone depletion induces increased germ cell apoptosis in testes. However, limited studies exist on genes that regulate the germ cell apoptosis. Granzymes (GZM) are serine proteases that induce apoptosis in various tissues. Multiple granzymes, including GZMA, GZMB and GZMN, are present in testes. Th us, we investigated which granzyme may be testosterone responsive and possibly may have a role in germ cell apoptosis aft er testosterone depletion.

METHODS

Ethylene dimethane sulfonate (EDS), a toxicant that selectively ablates the Leydig cells, was injected into rats to withdraw the testosterone. The testosterone depletion effects after 7 days post-EDS were verified by replacing the testosterone exogenously into EDS-treated rats. Serum or testicular testosterone was measured by radioimmunoassay. Using qPCR, mRNAs of granzyme variants in testes were quantified. The germ cell apoptosis was identified by TUNEL assay and the localization of GZMK was by immunohistochemistry.

RESULTS

EDS treatment eliminated the Leydig cells and depleted serum and testicular testosterone. At 7 days post-EDS, testis weights were reduced 18% with increased germ cell apoptosis plus elevation GZMK expression. GZMK was not associated with TUNEL-positive cells, but was localized to stripped cytoplasm of spermatids. In addition, apoptotic round spermatids were observed in the caput epididymis.

CONCLUSIONS

GZMK expression in testes is testosterone dependent. GZMK is located adjacent to germ cells in seminiferous tubules and the presence of apoptotic round spermatids in the epididymis suggest its role in the degradation of microtubules in ectoplasmic specializations. Thus, overexpression of GZMK may indirectly regulate germ cell apoptosis by premature release of round spermatids from seminiferous tubule lumen.

Glucocorticoid Receptor as a Potential Target to Decrease Aromatase Expression and Inhibit Leydig Tumor Growth

Leydig cell tumors are the most frequent interstitial neoplasms of the testis with increased incidence in recent years. They are hormonally active and are considered one of the steroid-secreting tumors. Although usually benign, the malignant phenotype responds poorly to conventional chemotherapy or radiation, highlighting the need to identify new therapeutic targets for treatment. Here, we identified a novel glucocorticoid-mediated mechanism that controls cell growth in Leydig cell tumors. We found that a synthetic glucocorticoid receptor agonist, dexamethasone, reduces cell proliferation in rat Leydig tumor cells by decreasing the expression and the enzymatic activity of the estrogen-producing enzyme aromatase. This inhibitory effect relies on the ability of activated glucocorticoid receptor to regulate the aromatase gene transcriptional activity through the recruitment of nuclear receptor corepressor protein and silencing mediator of retinoid and thyroid hormone receptors to a newly identified putative glucocorticoid responsive element within the aromatase promoter II. Our in vivo studies reveal a reduction of tumor growth, after dexamethasone treatment, in animal xenografts. Tumors from dexamethasone-treated mice exhibit a decrease in the expression of the proliferation marker Ki-67 and the aromatase enzyme. Our data demonstrate that activated glucocorticoid receptor, decreasing aromatase expression, induces Leydig tumor regression both in vitro and in vivo, suggesting that glucocorticoid receptor might be a potential target for the therapy of Leydig cell tumors.

Male germ cell apoptosis: regulation and biology

Cellular apoptosis appears to be a constant feature in the adult testis and during early development. This is essential because mammalian spermatogenesis is a complex process that requires precise homeostasis of different cell types. This review discusses the latest information available on male germ cell apoptosis induced by hormones, toxins and temperature in the context of the type of apoptotic pathway either the intrinsic or the extrinsic that may be used under a variety of stimuli. The review also discusses the importance of mechanisms pertaining to cellular apoptosis during testicular development, which is independent of exogenous stimuli. Since instances of germ cell carcinoma have increased over the past few decades, the current status of research on apoptotic pathways in teratocarcinoma cells is included. One other important aspect that is covered in this review is microRNA-mediated control of germ cell apoptosis, a field of research that is going to see intense activity in near future. Since knockout models of various kinds have been used to study many aspects of germ cell development, a comprehensive summary of literature on knockout mice used in reproduction studies is also provided.

CORDYCEPS SINENSISMYCELIUM INDUCES MA-10 MOUSE LEYDIG TUMOR CELL APOPTOSIS BY ACTIVATING THE CASPASE-8 PATHWAY AND SUPPRESSING THE NF-κB PATHWAY

Cordyceps sinensis has been used as nutritious food and medicine in Chinese society. CS can inhibit tumor growth and induce tumor cell apoptosis. CS induced MA-10 mouse Leydig tumor cell death, but the anti-tumor mechanisms are not fully understood. Thus, the aim of this study was to investigate the apoptotic effect of CS on MA-10 cells and determine the molecular mechanism. CS (2-10 mg/ml) was added to MA-10 cells at different time scales (0-24 h). The condensation of DNA chromatin and apoptotic nuclear fragmentation increased in CS-treated MA-10 cells. Western blot analysis showed that 3 hours of CS treatment caused an increase in caspase-3 and -8 expressions only, which provided further evidence for the involvement of caspase-3 and -8 in CS-induced MA-10-cell apoptosis. CS blocked NF-?B protein expression in a dose-dependent relationship. CS induces MA-10 cell apoptosis by activating caspase-8-dependent and caspase-9-independent pathways and downregulating NF-?B protein expression.

Clusterin overexpression in both malignant and nonmalignant prostate epithelial cells induces cell cycle arrest and apoptosis

Expression of the castration-induced clusterin protein is incompatible with the survival of human prostate cancer cells in tissues and in cell culture. To investigate the fate of human prostate epithelial cells, when engineered to maintain expression of clusterin protein, we have used an IRES-hyg vector and hygromycin selection. PC-3 prostate tumour cells were substantially more sensitive to clusterin expression than nonmalignant PNT1a cells, showing multiple phenotypic changes including cell cycle arrest and increased apoptosis. The results strengthen the hypothesis that clusterin expression is proapoptotic. Expression of exogenous clusterin in both cell types resulted in its relocation from the cytoplasm and a nuclear accumulation of the protein, as was also seen in the same cells when apoptosis was induced by etoposide treatment. To survive clusterin expression, the PC-3 tumour cells developed apoptosis-inhibitory properties. This could have significance for the resistance of prostate cancers to chemo/radiotherapy, where clusterin overexpression is observed.

Absence of Fas protein detection by flow cytometry in human spermatozoa

OBJECTIVE

To investigate the expression of Fas protein on the surface of ejaculated spermatozoa of normozoospermic and nonnormozoospermic men.

DESIGN

Prospective study.

SETTING

University infertility clinic.

PATIENT(S)

Twenty-three volunteer normozoospermic men (controls) and 43 men undergoing infertility evaluation (cases).

INTERVENTION(S)

Analysis of ejaculated spermatozoa by indirect immunofluorescence of Fas protein by flow cytometry.

MAIN OUTCOME MEASURE(S)

Comparison of flow cytometric analysis of autofluorescence, control tests (secondary antibody and isotype control), and experimental tests (anti-Fas monoclonal antibody) in the spermatozoa of ejaculated samples.

RESULT(S)

No expression of Fas protein was found on the surface of ejaculated spermatozoa of controls and cases.

CONCLUSION(S)

The Fas molecules are not present in substantial amounts in the ejaculated spermatozoa of normozoospermic and nonnormozoospermic men. Therefore, our results do not support the "abortive apoptosis" theory.

Cell biology of Leydig cells in the testis

This article reviews results on differentiation, structure, and regulation of Leydig cells in the testes of rodents and men. Two different populations-fetal and adult Leydig cells-can be recognized in rodents. The cells in these two populations are different in ultrastructure, life span, capacity for androgen synthesis, and mechanisms of regulation. A brief survey on the origin, ontogenesis, characterization of precursors, ultrastructure, and functional markers of fetal and adult Leydig cells is presented, followed by an analysis of genes in Leydig cells and the role of luteinizing hormone and its receptor, steroidogenic acute regulatory protein, hydroxysteroid dehydrogenases, androgen and its receptor, anti-Müllerian hormone, estrogens, and thyroid hormones. Various growth factors modulate Leydig cell differentiation, regeneration, and steroidogenic capacity, for example, interleukin 1alpha, transforming growth factor beta, inhibin, insulin-like growth factors I and II, vascular endothelial growth factor, and relaxin-like growth factor. Retinol and retinoic acid increase basal testosterone secretion in adult Leydig cells, but decrease it in fetal Leydig cells. Resident macrophages in the interstitial tissue of the testis are important for differentiation and function of Leydig cells. Apoptosis of Leydig cells is involved in the regulation of Leydig cell number and can be induced by cytotoxins. Characteristics of aging Leydig cells in rodents seem to be species specific. 11beta-hydroxysteroid dehydrogenase protects testosterone synthesis in the Leydig cells of stressed rats. Last, the following aspects of human Leydig cells are briefly described: origin, differentiation, triphasic development, aging changes, pathological changes, and gene mutations leading to infertility.

Epididymal epithelial cell involution following a single intraperitoneal administration of ethane dimethanesulfonate in the goat (Capra hircus)

Ethane dimethanesulfonate (EDS) selectively destroys Leydig cells in rats and a few other smaller animal species but not in mice and quail. In the teleost fish, it stimulates testicular activity instead. It also causes formation of sperm granulomas, reduction of sperm fertilizing ability, and destruction of clear cells in the epididymis. Investigations involving larger animal species are scanty. We have previously reported that EDS has no effect on goat Leydig cells but appears to have a direct cytotoxic effect on the seminiferous epithelium. This study was therefore designed to investigate the effects of EDS on goat epididymal cytoarchitecture. EDS was administered intraperitoneally at two dose levels, 75 and 25 mg/kg body wt. The former dose was rather toxic, killing three of five goats in this group within 24 h whereas the latter dose was well tolerated. Six days after treatment, the goats were hemicastrated and the epididymis was isolated and processed for light and electron microscopy. Involution associated with EDS was observed in epithelial cells of all regions of the epididymis, each having its own specific and peculiar changes. In the caput, there was increased cytoplasmic density accompanied by enlarged vacuoles and paucity of secretory vesicles in the apical cytoplasm. The Golgi cisternae were dilated and disorganized and, in the basal aspect, large dense staining bodies or inclusions, degenerative mitochondria, and lamellated bodies were observed. In the corpus, large vacuoles containing flocculent materials occurred in the entire cell cytoplasm but were particularly numerous and large in the midcytoplasm, completely obliterating the Golgi area. There was a dramatic reduction in epithelial height in the cauda epididymis accompanied by sparse distribution of markedly shortened microvilli. The epithelial cells had extensively lobulated nuclei and disorganized cytoplasm with dilated Golgi apparatus and large conglomerations of tubular structures. These structural changes suggest that EDS causes degeneration of goat epididymal epithelial cells. These effects are likely to result from the direct action of the compound on the epithelium.