Adjudin-mediated germ cell depletion alters the anti-oxidant status of adult rat testis

Mono-(2-ethylhexyl) phthalate (MEHP) affects intercellular junctions of Sertoli cell: A potential role of oxidative stress

We analyzed the potential role of oxidative stress induced by mono (2-ethylhexyl) phthalate (MEHP) in adherent cell junction protein expression of prepubertal rat Sertoli cells (SC) in vitro. Five-day SC cultures were treated with MEHP (200μM) for 24h and compared to cells in basal conditions. Western blot and immunofluorescent (IF) analyses showed that MEHP induced increase of N-cadherin and catenin expression, modifying its distribution. Concomitantly, Cx-43 expression decreased significantly and delocalization of the IF signal for tight junction proteins (occludin, claudin-11 and ZO-1) occurred. Indicative of oxidative stress, MEHP induced in SC an increase of lipoperoxides, a decrease in glutathione (GSH) levels and a concomitant increase in Glutathione S-Transferases (GST) activity. Antioxidant N-acetyl-cysteine (1mM) treatment prevented GSH decrease and N-cadherin and α-catenin up-regulation induced by MEHP. Our data suggest that oxidative stress signaling is a mechanism involved in adherent cell junctions disruption induced by MEHP in SC cultures.

Modulatory role of kolaviron in phenytoin-induced hepatic and testicular dysfunctions in Wistar rats

Phenytoin, an anticonvulsant agent used for the treatment of epilepsy has been reported to exhibit toxic side effects on the liver and testes. The present study investigated the protective effects of kolaviron (KV, a bioflavonoid from Garcinia kola seeds) against hepatic and testicular damage in rats exposed to phenytoin. The study consisted of four groups of six rats per group. Group I rats received 2 mL/kg of corn alone while group II received 75 mg/kg of phenytoin (PHT) alone. Groups III and IV were co-treated with kolaviron (200 mg/kg KV) and vitamin E (500 mg/kg VTE), respectively, for 14 days. The antioxidant status, hepatic and reproductive functional parameters were subsequently determined. PHT treatment significantly (p < 0.05) increased superoxide dismutase (SOD) and catalase (CAT) activities, elevated lipid peroxidation (LPO) and hydrogen peroxide (H2O2) levels along with significant reduction in the hepatic and testicular levels of glutathione (GSH). Moreover, PHT exposure elicited significant increases in alkaline phosphatase (ALP) and aspartate aminotransferase (AST) levels. The significant reduction in seminal epithelium thickness and the diameter of seminiferous tubules was accompanied with marked decrease in sperm motility, sperm count, and viability in PHT-treated rats. However, antioxidant status and the functional indices of liver and testes were restored to near control levels in rats co-treated with KV and VTE. In conclusion, KV and VTE protect the liver and testes against functional impairment due to PHT treatment.

The biology of spermatogenesis: the past, present and future

The physiological function of spermatogenesis in Caenorhabditis elegans, Drosophila melanogaster and mammals is to produce spermatozoa (1n, haploid) that contain only half of the genetic material of spermatogonia (2n, diploid). This half number of chromosomes from a spermatozoon will then be reconstituted to become a diploid cell upon fertilization with an egg, which is also haploid. Thus, genetic information from two parental individuals can be passed onto their offspring. Spermatogenesis takes place in the seminiferous epithelium of the seminiferous tubule, the functional unit of the mammalian testis. In mammals, particularly in rodents, the fascinating morphological changes that occur during spermatogenesis involving cellular differentiation and transformation, mitosis, meiosis, germ cell movement, spermiogenesis and spermiation have been well documented from the 1950s through the 1980s. During this time, however, the regulation of, as well as the biochemical and molecular mechanisms underlying these diverse cellular events occurring throughout spermatogenesis, have remained largely unexplored. In the past two decades, important advancements have been made using new biochemical, cell and molecular biology techniques to understand how different genes, proteins and signalling pathways regulate various aspects of spermatogenesis. These include studies on the differentiation of spermatogonia from gonocytes; regulation of spermatogonial stem cells; regulation of spermatogonial mitosis; regulation of meiosis, spermiogenesis and spermiation; role of hormones (e.g. oestrogens, androgens) in spermatogenesis; transcriptional regulation of spermatogenesis; regulation of apoptosis; cell-cell interactions; and the biology of junction dynamics during spermatogenesis. The impact of environmental toxicants on spermatogenesis has also become an urgent issue in the field in light of declining fertility levels in males. Many of these studies have helped investigators to understand important similarities, differences and evolutionary relationships between C. elegans, D. melanogaster and mammals relating to spermatogenesis. In this Special Issue of the Philosophical Transactions of the Royal Society B: Biological Sciences, we have covered many of these areas, and in this Introduction, we highlight the topic of spermatogenesis by examining its past, present and future.

Adjudin-mediated Sertoli-germ cell junction disassembly affects Sertoli cell barrier function in vitro and in vivo

Adjudin, an analogue of lonidamine, affects adhesion between Sertoli and most germ cells, resulting in reversible infertility in rats, rabbits and dogs. Previous studies have described the apical ectoplasmic specialization, a hybrid-type of Sertoli cell-elongating/elongated spermatid adhesive junction, as a key target of adjudin. In this study, we ask if the function of the blood-testis barrier which is constituted by co-existing tight junctions, desmosome-gap junctions and basal ectoplasmic specializations can be maintained when the seminiferous epithelium is under assault by adjudin. We report herein that administration of a single oral dose of adjudin to adult rats increased the levels of several tight junction and basal ectoplasmic specialization proteins during germ cell loss from the seminiferous epithelium. These findings were corroborated by a functional in vitro experiment when Sertoli cells were cultured on Matrigel™-coated bicameral units in the presence of adjudin and transepithelial electrical resistance was quantified across the epithelium. Indeed, the Sertoli cell permeability barrier was shown to become tighter after adjudin treatment as evidenced by an increase in transepithelial electrical resistance. Equally important, the blood-testis barrier in adjudin-treated rats was shown to be intact 2 weeks post-treatment when its integrity was monitored following vascular administration of inulin-fluorescein isothiocyanate which failed to permeate past the barrier and enter into the adluminal compartment. These results illustrate that a unique mechanism exists to maintain blood-testis barrier integrity at all costs, irrespective of the presence of germ cells in the seminiferous epithelium of the testis.

Potential biological role of poly (ADP-ribose) polymerase (PARP) in male gametes

Maintaining the integrity of sperm DNA is vital to reproduction and male fertility. Sperm contain a number of molecules and pathways for the repair of base excision, base mismatches and DNA strand breaks. The presence of Poly (ADP-ribose) polymerase (PARP), a DNA repair enzyme, and its homologues has recently been shown in male germ cells, specifically during stage VII of spermatogenesis. High PARP expression has been reported in mature spermatozoa and in proven fertile men. Whenever there are strand breaks in sperm DNA due to oxidative stress, chromatin remodeling or cell death, PARP is activated. However, the cleavage of PARP by caspase-3 inactivates it and inhibits PARP's DNA-repairing abilities. Therefore, cleaved PARP (cPARP) may be considered a marker of apoptosis. The presence of higher levels of cPARP in sperm of infertile men adds a new proof for the correlation between apoptosis and male infertility. This review describes the possible biological significance of PARP in mammalian cells with the focus on male reproduction. The review elaborates on the role played by PARP during spermatogenesis, sperm maturation in ejaculated spermatozoa and the potential role of PARP as new marker of sperm damage. PARP could provide new strategies to preserve fertility in cancer patients subjected to genotoxic stresses and may be a key to better male reproductive health.

An in vivo study on adjudin and blood-testis barrier dynamics

Adjudin is known to specifically affect Sertoli-germ cell adhesion, resulting in germ cell loss from the seminiferous epithelium and transient infertility. The apical ectoplasmic specialization (ES) was shown to be the primary target of adjudin because adhesion was unaffected in organs that lack this structure. Herein we expand previous findings by treating rat pups with adjudin, and we aimed to address two questions. First, can adjudin perturb germ cell adhesion in the seminiferous epithelium of testes in which the apical ES is not yet present? Second, can adjudin affect assembly of the blood-testis barrier (BTB) at 15-18 d of age? Interesting changes were noted when aged-matched testes from control and adjudin-treated rats were examined, including a delay in the appearance of developing germ cells as well as a delay in the formation of the tubule lumen. Immunoblotting using antibodies against BTB-constituent proteins indicated that formation of the BTB was affected in rat pups gavaged with adjudin. These results were corroborated by immunofluorescence microscopy, which showed profound changes in the cellular distribution of tight junction and basal ES proteins. Moreover, the BTB was shown to be compromised in 30-d-old rats when its integrity was assessed by a functional in vivo assay. By 45 d of age, however, the seminiferous epithelium of treated rats was indistinguishable from that of control rats. Collectively these results demonstrate that adjudin targets the apical ES as well as the basal ES and tight junction, which in turn delays assembly of the BTB.

Testicular cell junction: a novel target for male contraception

Even though various contraceptive methods are widely available, the number of unwanted pregnancies is still on the rise in developing countries, pressurizing the already resource limited nations. One of the major underlying reasons is the lack of effective, low cost, and safe contraceptives for couples. During the past decade, some studies were performed using animal models to decipher if the Sertoli-germ cell junction in the testis is a target for male fertility regulation. Some of these study models were based on the use of hormones and/or chemicals to disrupt the hypothalamic-pituitary-testicular axis (e.g., androgen-based implants or pills) and others utilized a panel of chemical entities or synthetic peptides to perturb spermatogenesis either reversibly or non-reversibly. Among them, adjudin, a potential male contraceptive, is one of the compounds exerting its action on the unique adherens junctions, known as ectoplasmic specializations, in the testis. Since the testis is equipped with inter-connected cell junctions, an initial targeting of one junction type may affect the others and these accumulative effects could lead to spermatogenic arrest. This review attempts to cover an innovative theme on how male infertility can be achieved by inducing junction instability and defects in the testis, opening a new window of research for male contraceptive development. While it will still take much time and effort of intensive investigation before a product can reach the consumable market, these findings have provided hope for better family planning involving men.