In vitro regulation of extracellular superoxide dismutase in sertoli cells

Superoxidase dismutases (SODs) in the European eel: Gene characterization, expression response to temperature combined with hormonal maturation and possible migratory implications

Superoxide dismutases (SODs) are antioxidant enzymes that protect cells from oxidation. Three SODs have been identified in mammals, but there is limited information in teleosts. This study investigates SODs in the European eel and their expression patterns during testis maturation. Phylogenetic and synteny analyses revealed SODs paralogs and their evolution in vertebrates. The eel possesses one SOD1 and two SOD2/3 (a and b), indicating SOD2 and SOD3 duplication in elopomorphs. SODs expression were then evaluated in various male and female tissues. SOD1 is more expressed in females, while SOD2a and SOD2b dominate brain-pituitary-gonad tissues in both sexes. SOD3a showed predominant expression in the ovary and the male livers, whereas SOD3b was found in the pituitary and brain of both sexes. The effects of different maturation protocols (standard hormonal treatment vs. same protocol preceded with cold seawater pre-treatment) on SODs expression during testis maturation were evaluated. Salinity increase at the onset of standard treatment at 20 °C, simulating early migration, upregulated SOD1, SOD2a, and SOD2b, coinciding with spermatogonia type A differentiated cells dominance. Thereafter, SOD2a and SOD3a decreased, while SOD2b increased during hormonal treatment-induced spermatogenesis. Pre-treatment with seawater at 10 °C, mimicking the conditions at the beginning of the seawater migration, downregulated SOD1 but increased SOD3a expression. Finally, the standard hormonal treatment, replicating spawning at higher temperatures, downregulated SOD1 in eels without any pre-treatment while SOD2a expression increased in pre-treated eels. This study revealed tissue-specific, sex-dependent, and maturation-related SOD expression patterns, predicting SODs dynamic expression profiles during their reproductive migration.

Oxidative Stress-Induced Male Infertility: Role of Antioxidants in Cellular Defense Mechanisms

Male infertility is linked to several environmental and mutagenic factors. Most of these factors, i.e., lifestyle, radiations, and chemical contaminations, work on the fundamental principles of physics, chemistry, and biology. Principally, it may induce oxidative stress (OS) and produce free radicals within the cells. The negative effect of OS may enhance the reactive oxygen species (ROS) levels in male reproductive organs and impair basic functions in a couple's fertility. Evidence suggests that infertile men have significantly increased ROS levels and a reduced antioxidant capacity compared with fertile men. Although, basic spermatic function and fertilizing capacity depend on a delicate balance between physiological activity of ROS and antioxidants to protect from cellular oxidative injury in sperm, that is essential to achieve pregnancy. The ideal oxidation-reduction (REDOX) equilibrium requires a maintenance of a range of ROS concentrations and modulation of antioxidants. For this reason, the chapter focuses on the effects of ROS in sperm functions and the current concepts regarding the benefits of medical management in men with diminished fertility and amelioration of the effect to improve sperm function. Also, this evidence-based study suggests an increasing rate of infertility that poses a global challenge for human health, urging the need of health care professionals to offer a correct diagnosis, comprehension of the process, and an individualized management of the patients.

Association between a marker of sperm DNA damage and sperm indices in infertile males in Benin City, Nigeria: A cross-sectional study

Background

Studies have shown oxidative DNA damage is associated with male infertility.

Objective

This study determines the levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and some markers of oxidative stress in seminal fluid of males investigated for infertility and men of proven fertility in Benin City, Nigeria.

Materials and Methods

Semen samples produced by self or assisted masturbation were analyzed by microscopic technique according to the World Health Organization guidelines. Thereafter, samples were centrifuged and seminal fluid plasma separated and stored at -20°C prior to assay for 8-OHdG and oxidative stress biomarkers. Based on the sperm concentration/count, the overall samples were grouped into the following categories: normospermia (n = 20), oligozoospermia (n = 30), and azoospermia (n = 20). The control group comprised of 30 age-matched males of proven fertility. The seminal fluid 8-OHdG, total antioxidant status, superoxide dismutase and malondialdehyde (MDA) were assayed through ELISA and spectrophotometric methods, respectively.

Results

Seminal plasma level of 8-OHdG and MDA were significantly higher (p = 0.01) in infertile subjects than controls. The mean levels of 8-OHdG and MDA in infertile subjects were higher in azoospermia than oligospermia than normospermia and so, was least in the normospermia. Conversely, the mean levels of total antioxidant status and superoxide dismutase were significantly lower (p = 0.01) in infertile than fertile the control male subjects with levels higher in normospermia than oligospermia and least in azoospermia. Moreover, the seminal 8-OHdG correlated negatively with sperm count (r = -0.359, p = 0.01), percent motility (r = -0.388, p = 0.04), and percent morphology (r = -0.327, p = 0.02).

Conclusion

The assessment of sperm DNA damage in addition to routine seminal fluid analysis may play an important role in specific diagnosis and management of male infertility.

Stem cell-based therapies for fertility preservation in males: Current status and future prospects

With the decline in male fertility in recent years, strategies for male fertility preservation have received increasing attention. In this study, by reviewing current treatments and recent publications, we describe research progress in and the future directions of stem cell-based therapies for male fertility preservation, focusing on the use of spermatogonial stem cells (SSCs), SSC niches, SSC-based testicular organoids, other stem cell types such as mesenchymal stem cells, and stem cell-derived extracellular vesicles. In conclusion, a more comprehensive understanding of the germ cell microenvironment, stem cell-derived extracellular vesicles, and testicular organoids will play an important role in achieving male fertility preservation.

Rebuilding the human testis in vitro

Increasing rates of male infertility have led to a greater need for relevant model systems to gain further insight into male fertility and its failings. Spermatogenesis and hormone production occur within distinct regions of the testis. Defined by specialized architecture and a diverse population of cell types, it is no surprise that disruption of this highly organized microenvironment can lead to infertility. To date, no robust in vitro system has facilitated full spermatogenesis resulting in the production of fertilization‐competent human spermatozoa. Here, we review a selection of current in vitro systems available for modelling the human testis microenvironment with focus on the progression of spermatogenesis and recapitulation of the testis microenvironment.

Evaluation of toxicity of methyl tert-butyl ether (MTBE) on mouse spermatogenic cells in vitro

As a synthetic organic chemical, methyl tert-butyl ether (MTBE) is the most common fuel oxygenate. The increasing use of MTBE has raised concern over its safety. Previous studies in vivo revealed that MTBE could alter the male reproduction system. Therefore, the current experiments were designed to evaluate whether isolated mice spermatogenic cells in vitro were sensitive to exposure to MTBE at environmental levels, and to evaluate whether spermatogenic cells had undergone changes in morphologic, activity and viability parameters after exposure to MTBE. Spermatogenic cells in vitro were incubated with medium alone (control), 100 ppb, 10 ppm, 1000 ppm, 3000 ppm MTBE, respectively, for 6, 12, 18 h. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazo liumbromide) assay, staining with fluorescein diacetate (FDA) and propidium iodide (PI), and flow cytometric analyses were used to assess MTBE toxicity on cells and DNA. The results showed that there were no significant differences between control and treatments of ≤ 1000 ppm MTBE at the same time point. Although 3000 ppm MTBE could exert toxic effects directly on spermatogenic cells, environmental levels of MTBE did not exert toxic effects on cultured spermatogenic cells.

Effects of melatonin during IVM in defined medium on oocyte meiosis, oxidative stress, and subsequent embryo development

Melatonin may have beneficial effects when used in oocyte maturation and embryo development culture. The effect of melatonin during IVM on meiosis resumption and progression in bovine oocytes and on expression of antioxidant enzymes, nuclear fragmentation and free radicals, as well as on embryo development were assessed. Cumulus-oocyte complexes were matured in vitro with melatonin (10(-9) and 10(-6) M), FSH (positive control), or without hormones (negative control) in defined medium. Maturation rates were evaluated at 6, 12, 18, and 24 hours. Transcripts for antioxidant enzymes (CuZnSOD, MnSOD, and glutathione peroxidase 4 (GPX4)) in oocytes and cumulus cells, nuclear fragmentation in cumulus cells (TUNEL) and reactive oxygen species levels in oocytes (carboxy-H2 difluorofluorescein diacetate) were determined at 24 hours IVM. Effect of treatments on embryo development was determined after in vitro fertilization and culture. At 12 hours, meiosis resumption rates in FSH and melatonin-treated groups were similar (69.6%-81.8%, P > 0.05). At 24 hours, most oocytes were in metaphase II, with FSH showing highest rates (90.0%, P < 0.05) compared with the other groups (51.6%-69.1%, P > 0.05). In cumulus cells, MnSOD expression was higher in FSH group (P < 0.05) whereas Cu,ZnSOD transcripts were more abundant in melatonin group (10(-6)M; P < 0.05). Nuclear fragmentation in cumulus cells was highest in controls (37.4%/10,000 cells; P < 0.05) and lower in FSH and 10(-6)M melatonin (29.4% and 25.6%/10,000 cells, respectively). Reactive oxygen species levels were lower in oocytes matured with 10(-6)M melatonin than in control and FSH groups (P < 0.05). Embryo development from oocytes matured only with melatonin was similar to those matured in complete medium (P > 0.05). In conclusion, although melatonin during IVM in a defined medium does not stimulate nuclear maturation progression it does stimulate meiosis resumption and such treated oocytes support subsequent embryo development. Melatonin also shows cytoprotective effects on cumulus-oocyte complexes.

Seminal superoxide dismutase activity and its relationship with semen quality and SOD gene polymorphism

PURPOSE

Superoxide dismutase (SOD) is an important component of antioxidative defense systems and plays an important role in protecting spermatozoa from oxidative damage. In this study, we assessed seminal SOD activity, its association with semen parameters, and also genetic and non-genetic factors contributing to the determination of SOD activity in infertile men.

METHODS

Semen samples were obtained from 435 male infertility patients. Sperm DNA damage levels were detected with the Tdt-mediated dUTP nick end labelling (TUNEL) assay. Four single nucleotide polymorphisms (SNPs) in SOD2 and SOD3 genes were genotyped using OpenArray platform.

RESULTS

We found that seminal SOD activity was positively associated with sperm concentration and overall motility, whereas inversely with sperm DNA fragmentation. In addition, infertile men with SOD2 rs4880 CC variants showed a low level of SOD activity when compared with TT carriers (Mean ± SD: 268.3 ± 102.3 and 342.8 ± 98.2, respectively, P = 0.005). Those who consumed vitamin C/E (≥3 times per week) had a significantly higher SOD activity level than those who did not (mean ± SD: 379.8 ± 93.3 and 332.2 ± 94.9, respectively, P = 0.001).

CONCLUSIONS

Seminal SOD activity and other factors influencing SOD activity play a role in determining sperm fertilization potential and male infertility.

Changes in the plasma testosterone level and testicular superoxide dismutase activity of 5 azoospermic beagles after GnRH analogue injections

The peripheral blood plasma testosterone (T) levels and superoxide dismutase (SOD) activity were measured in 5 azoospermic (AZ-) beagles. The mean values in the AZ-dogs were significantly lower than in 7 control beagles (P<0.001). Subcutaneous injections of 1 mug/kg GnRH analogue three times weekly in the AZ-dogs induced significant increases in mean T level and SOD activity (P<0.05) and improvement in spermatogenesis. Thus, spermatogenic function in the dog appears to be maintained by T and normal SOD activity in the testis.

Aromatization and antioxidant capacity in the testis of seasonally breeding bank voles: Effects of LH, PRL and IGF-I

Aromatization and antioxidant strategies in the male gonads are important processes, which are involved in control of normal fertility. The objective of this study was to show whether luteinizing hormone (LH), prolactin (PRL), and insulin-like growth factor-I (IGF-I) as well as the length of photoperiod are able to exert an effect on aromatase expression, steroid hormone levels, and antioxidant concentrations in testes of bank voles, seasonally breeding rodents. Mature bank voles that were kept under short light cycles or long light cycles served as the animal model. Testicular sections were used for immunohistochemical visualization of aromatase expression, whereas testicular homogenates were used for radioimmunological measurement of steroids, biochemical determination of superoxide dismutase activity, total antioxidant status (TAS) and protein content. In the testes of hormone-treated voles a stronger immunostaining for aromatase was concurrent with the increase in testosterone and estradiol levels, and total antioxidant status compared with the controls. In contrast, there was a decrease in superoxide dismutase (SOD) activity. The strongest effect on aromatase immunoexpression and steroid hormone levels was detected after combined doses of LH and IGF-I, indicating a stimulatory role of these hormones on estrogen synthesis in the bank vole. An increase in total antioxidant status in testes of hormone-treated bank voles suggests the presence of testicular defense, whereas a decrease in superoxide dismutase activity indicates a protective role of administered hormones against toxic oxygen radicals. The present study also demonstrates a significant, photoperiod-dependent relationship between aromatization and antioxidant capacity in the testis of the bank vole.

Cryopreservation of pig granulosa cells: effect of FSH addition to freezing medium

We cryopreserved swine granulosa cells by a slow cooling rate system; FSH was added to the freezing medium to test its effectiveness in protecting the cells. After thawing, proliferative activity, viability, steroidogenesis and apoptosis were tested; moreover, we determined heat shock protein (HSP70) production, to investigate the recovery from stress and superoxide dismutase (SOD) and catalase activity to evaluate a possible impairment of the antioxidant pathway. E2 production was enhanced by cryopreservation in particular with FSH; on the contrary, P4 production was inhibited by the freezing process in particular without FSH. Only the higher FSH concentration (10 ng/ml) stimulated steroid secretion in freshly collected cells; P4 production by cells cryopreserved in the presence and in absence of FSH was increased by both 5 and 10 ng/ml while the lowest concentration was effective in stimulating E2 production only when FSH was added to freezing medium. Freezing did not modify proliferative activity, while apoptosis was higher in frozen than in fresh cells. HSP70 production was lower in cells cryopreserved in presence of FSH, whose antioxidant metabolism was also conserved: SOD and catalase activities were similar to control. In conclusion, cryopreservation does not seem to markedly affect granulosa cells, in particular if they are frozen in presence of FSH; the gonadotrophin somehow improves their performances after thawing, probably stimulating E2 production and the antioxidant metabolism.

Extracellular superoxide dismutase in biology and medicine

Accumulated evidence has shown that reactive oxygen species (ROS) are important mediators of cell signaling events such as inflammatory reactions (superoxide) and the maintenance of vascular tone (nitric oxide). However, overproduction of ROS such as superoxide has been associated with the pathogenesis of a variety of diseases including cardiovascular diseases, neurological disorders, and pulmonary diseases. Antioxidant enzymes are, in part, responsible for maintaining low levels of these oxygen metabolites in tissues and may play key roles in controlling or preventing these conditions. One key antioxidant enzyme implicated in the regulation of ROS-mediated tissue damage is extracellular superoxide dismutase (EC-SOD). EC-SOD is found in the extracellular matrix of tissues and is ideally situated to prevent cell and tissue damage initiated by extracellularly produced ROS. In addition, EC-SOD is likely to play an important role in mediating nitric oxide-induced signaling events, since the reaction of superoxide and nitric oxide can interfere with nitric oxide signaling. This review will discuss the regulation of EC-SOD and its role in a variety of oxidant-mediated diseases.

Transforming growth factor beta3 regulates the dynamics of Sertoli cell tight junctions via the p38 mitogen-activated protein kinase pathway

Earlier studies have implicated the significance of transforming growth factor-beta3 (TGFbeta3) in the regulation of Sertoli cell tight junction (TJ) dynamics, possibly via its inhibitory effects on the expression of occludin, claudin-11, and zonula occludens-1 (ZO-1). Yet the mechanism by which TGFbeta3 regulates the Sertoli cell TJ-permeability barrier is not known. Using techniques of semiquantitative reverse transcription-PCR (RT-PCR), immunoblotting, immunohistochemistry, and inhibitors against different kinases coupled with physiological techniques to assess the Sertoli cell TJ barrier function, it was shown that this TGFbeta3-induced effect on Sertoli cell TJ dynamics is mediated via the p38 mitogen-activated protein (MAP) kinase pathway. First, the assembly of the Sertoli cell-TJ barrier was shown to be associated with a transient but significant decline in both the TGFbeta3 production and expression by Sertoli cells. Furthermore, addition of TGFbeta3 to Sertoli cell cultures during TJ assembly indeed perturbed the TJ barrier with an IC50 at approximately 9 pM. Second, the TGFbeta3-induced disruption of the TJ barrier was associated with a transient induction in MEKK2 but not the other upstream signaling molecules that mediate TGFbeta3 action, such as Smad2, Cdc42, Rac2, and N-Ras, suggesting this effect might be mediated via the p38 MAP kinase pathway. This postulate was confirmed by the observation that TGFbeta3 also induced the protein level of the activated and phosphorylated form of p38 MAP kinase at the time the TJ barrier was perturbed. Third, and perhaps the most important of all, this TGFbeta3-mediated inhibitory effect on the TJ barrier and the TGFbeta3-induced p-p38 MAP kinase production could be blocked by SB202190, a specific p38 MAP kinase inhibitor, but not U0126, a specific MEK1/2 kinase inhibitor. These results thus unequivocally demonstrate that TGFbeta3 utilizes the p38 MAP kinase pathway to regulate Sertoli cell TJ dynamics.

Myeloid zinc finger (MZF)-like, Kruppel-like and Ets families of transcription factors determine the cell-specific expression of mouse extracellular superoxide dismutase

Extracellular superoxide dismutase (EC-SOD or SOD3) is an important protective enzyme against the toxicity of superoxide radicals that are produced under both physiological and pathophysiological conditions. We have isolated and characterized over 11 kb of the mouse EC-SOD gene and its 5'- and 3'-flanking regions. The gene consists of two exons, with the entire coding region located within exon 2. In order to study the mechanism of cell-specific gene regulation for mouse EC-SOD, we characterized 2500 bp of its 5'-flanking region using cultured cells derived from mouse lung fibroblasts (MLg), kidney medulla (mIMCD3) and hepatocytes (Hepa 1-6). Real-time PCR showed that basal expression of EC-SOD was considerably higher in MLg cells compared with the other cell types. Reporter-gene assays revealed that the proximal promoter region was sufficient to support this high expression in MLg cells. Although no obvious TATA box was identified, our results show that a highly purine-rich region from -208 to +104 contains active binding sites for both the Kruppel-like and Ets families of transcription factors. Using electrophoretic mobility shift, DNase footprinting and reporter gene assays, we identified myeloid zinc finger 1 and gut-enriched Kruppel-like-factor-like nuclear transcription factors as repressors of EC-SOD expression, whereas nuclear transcription factors from the Ets family, such as Elf-1 and GA-binding protein alpha and beta, were potent activators of EC-SOD transcription. We propose a model that highlights competition between Ets activators and Kruppel-like repressors within the proximal promoter region that determines the level of EC-SOD expression in a particular cell type.

2-Bromopropane induces DNA damage, impairs functional antioxidant cellular defenses, and enhances the lipid peroxidation process in primary cultures of rat Leydig cells

Utilization of highly enriched preparations of steroidogenic Leydig cells has proven invaluable for studying the direct effects of various hormones and agents on Leydig cell function in vitro. It is widely reported that male reproductive organs are particularly susceptible to the deleterious effects of reactive oxygen species (ROS) and lipid peroxidation, which ultimately lead to impaired fertility. The purpose of the study was to examine the potential of 2-bromopropane (2-BP) to induce oxidative stress and antioxidant function in primary cultures of rat Leydig cells. Leydig cells were isolated from the testes of Sprague-Dawley rats. The purity of Leydig cells was determined to be 94.6% and the cells maintained their testosterone secreting capabilities for 48 h. Fresh medium containing 2-BP (1.00, 0.10, 0.01 mM, and vehicle control) and 1 U human chorionic gonadotropin (hCG) were added in the cell culture. Superoxide dismutase (SOD) activity, malondialdehyde (MDA), and glutathione peroxidase (GSH-PX) were analyzed in the medium of each well by biochemical methods. Additionally, DNA damage was examined using the Comet assay. The proportion of cells with undamaged DNA was decreased significantly and those with different grades of damaged DNA were increased significantly in the cells exposed to 2-BP. The level of MDA and GSH-PX activity increased significantly in the cell groups exposed to 0.10 and 1.00 mM 2-BP, whereas, SOD activity decreased considerably in these two groups of cells when compared to the control. The data indicate that 2-BP induces DNA damage, impairs functional antioxidant cellular defenses, and enhances the lipid peroxidation in cultured Leydig cells. These effects may be responsible for the testicular toxicity noted in laboratory animals and humans.

Antioxidant superoxide dismutase - a review: its function, regulation in the testis, and role in male fertility

Extracellular superoxide dismutase (SOD(EX)), an antioxidant enzyme, was found to be present in the testis at a relatively high concentration versus other organs. In a more detailed survey of several rat tissues and cells by reverse transcriptase-polymerase chain reaction, it was shown that germ cells expressed approximately one-third that of Sertoli cells, suggesting both cell types are equipped with the machinery needed to defend themselves from radical-induced damage. When we used an in vitro model in which germ cells were co-cultured with Sertoli cells at a Sertoli:germ cell ratio of 1:1, we failed to detect any changes in the mRNA level of SOD(EX). However, the addition of increasing concentrations of germ cell secretory proteins into Sertoli cell cultures resulted in a decrease in Sertoli cell SOD(EX) expression, illustrating that germ cells can indeed regulate Sertoli cell SOD(EX). On the other hand, Sertoli cell SOD(EX) expression was stimulated when human recombinant interleukin-1alpha (IL-1alpha), a germ cell product, was included into Sertoli cells in vitro. These results, taken collectively, suggest SOD(EX) is an important antioxidant molecule in the testis that is under germ cell regulation.

Cell Junction Dynamics in the Testis: Sertoli-Germ Cell Interactions and Male Contraceptive Development

Spermatogenesis is an intriguing but complicated biological process. However, many studies since the 1960s have focused either on the hormonal events of the hypothalamus-pituitary-testicular axis or morphological events that take place in the seminiferous epithelium. Recent advances in biochemistry, cell biology, and molecular biology have shifted attention to understanding some of the key events that regulate spermatogenesis, such as germ cell apoptosis, cell cycle regulation, Sertoli-germ cell communication, and junction dynamics. In this review, we discuss the physiology and biology of junction dynamics in the testis, in particular how these events affect interactions of Sertoli and germ cells in the seminiferous epithelium behind the blood-testis barrier. We also discuss how these events regulate the opening and closing of the blood-testis barrier to permit the timely passage of preleptotene and leptotene spermatocytes across the blood-testis barrier. This is physiologically important since developing germ cells must translocate across the blood-testis barrier as well as traverse the seminiferous epithelium during their development. We also discuss several available in vitro and in vivo models that can be used to study Sertoli-germ cell anchoring junctions and Sertoli-Sertoli tight junctions. An in-depth survey in this subject has also identified several potential targets to be tackled to perturb spermatogenesis, which will likely lead to the development of novel male contraceptives.