Aging and luteinizing hormone effects on reactive oxygen species production and DNA damage in rat Leydig cells

Black Chokeberry (Aronia melanocarpa) Juice Supplementation Improves Oxidative Stress and Aging Markers in Testis of Aged Rats

Spermatogenesis is a process that continues until the end of an individual's life, although with reduced activity with advancing age. Inflammation, oxidation, and apoptosis are events considered as predictors of pathogenesis and the development of age-related diseases observed in aged testes. The use of natural compounds with antioxidant and anti-inflammatory properties has a beneficial effect on the inflammatory and oxidative status of the aged testis. The aim of this study was to determine the effect of supplementation with antioxidant-rich black chokeberry (Aronia melanocarpa) juice on several markers of oxidative stress and aging in rat testis. In total, 24 male Wistar rats were divided into three experimental groups: young controls aged 2 months, old controls aged 27 months, and 27-month-old rats supplemented with black chokeberry juice at a dose of 10 mL/kg for 3 months. A. melanocarpa juice supplementation led to reduced oxidative stress, manifested by increased immunoexpression of nNOS, eNOS, and MAS1 in the seminiferous tubules and in the Leydig cells. The morphometrically determined tubule structure data showed no significant differences between the three groups. However, the intensity of the immunoreaction for TRK-C and NT3 in Leydig cells was demonstrably higher in the supplemented old animals compared with the old controls. There was a significantly higher number of blood vessels around the seminiferous tubules in the supplemented animals compared to the old controls. These data indicate that supplementation with A. melanocarpa juice slows down aging processes in the testis and preserves the functional activity of Leydig cells.

A Review on the Impact of Oxidative Stress and Medicinal Plants on Leydig Cells

Leydig cells are essential for steroidogenesis and spermatogenesis. An imbalance in the production of reactive oxygen species (ROS) and the cellular antioxidant level brings about oxidative stress. Oxidative stress (OS) results in the dysfunction of Leydig cells, thereby impairing steroidogenesis, spermatogenesis, and ultimately, male infertility. To prevent Leydig cells from oxidative insults, there needs to be a balance between the ROS production and the cellular protective capacity of antioxidants. Evidence indicates that medicinal plants could improve Leydig cell function at specific concentrations under basal or OS conditions. The increased usage of medicinal plants has been considered a possible alternative treatment for male infertility. This review aims to provide an overview of the impact of oxidative stress on Leydig cells as well as the effects of various medicinal plant extracts on TM3 Leydig cells. The medicinal plants of interest include Aspalathus linearis, Camellia sinensis, Moringa oleifera, Morinda officinale, Taraxacum officinale, Trichilia emetica, Terminalia sambesiaca, Peltophorum africanum, Ximenia caffra, Serenoa repens, Zingiber officinale, Eugenia jambolana, and a combination of dandelion and fermented rooibos (CRS-10). According to the findings obtained from studies conducted on the evaluated medicinal plants, it can, therefore, be concluded that the medicinal plants maintain the antioxidant profile of Leydig cells under basal conditions and have protective or restorative effects following exposure to oxidative stress. The available data suggest that the protective role exhibited by the evaluated plants may be attributed to their antioxidant content. Additionally, the use of the optimal dosage or concentration of the extracts in the management of oxidative stress is of the utmost importance, and the measurement of their oxidation reduction potential is recommended.

Anthocyanins Prevent AAPH-Induced Steroidogenesis Disorder in Leydig Cells by Counteracting Oxidative Stress and StAR Abnormal Expression in a Structure-Dependent Manner

Testosterone deficiency may increase the risk of sexual dysfunction and the failure of spermatogenesis. Oxidative stress that is derived from the destruction of homeostasis, disease, and exposure to contaminants can damage the steroidogenicity process in Leydig cells, resulting in a reduction in testosterone synthesis. Anthocyanins are a group of innoxious antioxidants widely recognized in food sources, and are an ideal candidate to relieve oxidative stress-related steroidogenesis disorder. However, there is still a major gap in our knowledge of the structure-function relationship of anthocyanin on the activity mentioned above. In the present study, four anthocyanins including cyanidin-3-glucoside (Cy-3-glu), delphinidin-3-glucoside (Dp-3-glu), pelargonidin-3-glucoside (Pg-3-glu), and cyanidin-3,5-diglucoside (Cy-3,5-diglu) were applied to reverse testosterone generation after employing 2,2'-Azobis(2-amidinopropane)-dihydrochloride (AAPH) as the inducer of oxidative stress in R2C cells. The results demonstrated that all four kinds of anthocyanins can inhibit ROS generation, alleviate mitochondrial membrane potential damage, and contribute to increased testosterone. Among them, Cy-3,5-diglu with diglycoside performed best on antioxidative ability and improved cell dysfunction and upregulated the expression of the steroidogenic acute regulatory protein (StAR). The molecular docking further revealed the direct combination between anthocyanins and StAR, suggesting that anthocyanins with monosaccharide were more likely to interact with StAR than with diglycoside. Taken together, these data indicate that recipient R2C cells under oxidative stress submitted to anthocyanins exhibited improved steroidogenesis in a structure-dependent manner. Anthocyanins could be considered the ideal ingredients against oxidative stress-induced testosterone deficiency.

Animal models of male reproductive ageing to study testosterone production and spermatogenesis

Ageing is the time-dependent gradual decline of the functional characteristics in an organism. It has been shown that it results in the loss of reproductive health and fertility. The age-dependent decline of fertility is a potential issue as the parenthood age is increasing in Western countries, mostly due to socioeconomic factors. In comparison to women, for whom the consequences of ageing are well documented and general awareness of the population is extensively raised, the effects of ageing for male fertility and the consequences of advanced paternal age for the offspring have not been widely studied. Studies with humans are welcome but it is hard to implement relevant experimental approaches to unveil the molecular mechanisms by which ageing affects male reproductive potential. Animal models have thus been extensively used. These models are advantageous due to their reduced costs, general easy maintenance in laboratory facilities, rigorous manipulation tools, short lifespan, known genetic backgrounds, and reduced ethical constraints. Herein, we discuss animal models for the study of male reproductive ageing. The most well-known and studied reproductive ageing models are rodents and non-human primates. The data collected from these models, particularly studies on testicular ageing, steroidogenesis, and genetic and epigenetic changes in spermatogenesis are detailed. Notably, some species challenge the currently accepted ageing theories and the concept of senescence itself, which renders them interesting animal models for the study of male reproductive ageing.

Leydig cell function in adult male rats is disrupted by perfluorotetradecanoic acid through increasing oxidative stress and apoptosis

Perfluorotetradecanoic acid (PFTeDA) is a long-chain perfluoroalkyl compound with increased applications. Its effect on Leydig cell function and its underlying mechanism remain unclear. Male Sprague-Dawley rats (60 days old) were gavaged with PFTeDA at doses of 0, 1, 5, and 10 mg/kg/day from 60 to 87 days after birth. PFTeDA significantly reduced serum testosterone levels at 1 mg/kg and higher doses, while markedly increasing serum luteinizing hormone level at 10 mg/kg and follicle-stimulating hormone at ≥1 mg/kg. PFTeDA significantly reduced the sperm number at the cauda of epididymis at ≥1 mg/kg. PFTeDA also reduced the number of CYP11A1-positive Leydig cells due to increased apoptosis shown by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. PFTeDA significantly repressed the expression of Cyp17a1 and Star and their proteins at 1-10 mg/kg, while it increased the expression of Srd5a1 and its protein (an immature Leydig cell biomarker) at 10 mg/kg. PFTeDA markedly increased testicular malondialdehyde level, while inhibiting antioxidants (SOD1, SOD2, and CAT), triggering oxidative stress, thereby further inducing BAX and CASP3 while inhibiting BCL2, which led to cell apoptosis. PFTeDA also reduced DHH level secreted by Sertoli cells, which indirectly affected Leydig cell function. PFTeDA inhibited testosterone secretion in primary Leydig cells in vitro by increasing reactive oxygen species and inducing apoptosis at 50 μM. In conclusion, PFTeDA inhibits the function of Leydig cells by inducing oxidative stress and subsequently stimulating cell apoptosis.

A Case Study on Integrating a New Key Event Into an Existing Adverse Outcome Pathway on Oxidative DNA Damage: Challenges and Approaches in a Data-Rich Area

Adverse outcome pathways (AOPs) synthesize toxicological information to convey and weigh evidence in an accessible format. AOPs are constructed in modules that include key events (KEs) and key event relationships (KERs). This modular structure facilitates AOP expansion and network development. AOP development requires finding relevant information to evaluate the weight of evidence supporting each KER. To do this, the use of transparent/reproducible search methods, such as systematic review (SR), have been proposed. Applying SR to AOP development in a data-rich area is difficult as SR requires screening each article returned from a search. Here we describe a case study to integrate a single new KE into an existing AOP. We explored the use of SR concepts and software to conduct a transparent and documented literature search to identify empirical data supporting the incorporation of a new KE, increase in cellular reactive oxygen species (ROS), upstream of an existing AOP: “Oxidative DNA Damage Leading to Chromosomal Aberrations and Mutations”. Connecting this KE to the AOP is supported by the development of five new KERs, the most important being the first adjacent KER (increase in ROS leading to oxidative DNA damage). We initially searched for evidence of all five KERs and screened 100 papers to develop a preliminary evidence map. After removing papers not containing relevant data based on our Population, Exposure, Comparator and Outcome statement, 39 articles supported one or more KERs; these primarily addressed temporal or dose concordance of the non-adjacent KERs with limited evidence supporting the first adjacent KER. We thus conducted a second focused set of searches using search terms for specific methodologies to measure these first two KEs. After screening, 12 articles were identified that contained quantitative evidence supporting the first adjacent KER. Given that integrating a new KE into an existing AOP requires the development of multiple KERs, this approach of building a preliminary evidence map, focusing evidence gathering on the first adjacent KER, and applying reproducible search strategies using specific methodologies for the first adjacent KER, enabled us to prioritize studies to support expansion of this data-rich AOP.

Healthy Immunity on Preventive Medicine for Combating COVID-19

Immunomodulation is influenced by the consumption of nutrients, and healthy immunity is pivotal to defending an individual from a variety of pathogens. The immune system is a network of intricately regulated biological processes that is comprised of many organs, cellular structures, and signaling molecules. A balanced diet, rich in vitamins, minerals, and antioxidants, is key to a strengthened immune system and, thus, crucial to proper functioning of various physiological activities. Conversely, deficiencies of these micronutrients, involving impaired immunity, are linked to numerous health complications, along with a host of pathologies. Coronavirus disease 2019 (COVID-19) is a dangerous infectious disease caused by a β-form of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its genomic variants, which enter host cells upon binding to the angiotensin converting enzyme 2 receptors, and is associated with substantial morbidities and mortalities globally. Patients afflicted with COVID-19 display asymptomatic to severe symptoms, occurrences of which are multifactorial and include diverse immune responses, sex and gender differences, aging, and underlying medical conditions. Geriatric populations, especially men in comparison to women, regardless of their states, are most vulnerable to severe COVID-19-associated infections and complications, with fatal outcomes. Advances in genomic and proteomic technologies help one understand molecular events, including host–pathogen interactions and pathogenesis of COVID-19 and, subsequently, have developed a variety of preventive measures urgently, ranging from mask wearing to vaccination to medication. Despite these approaches, no unique strategy is available today that can effectively prevent and/or treat this hostile disease. As a consequence, the maintenance of a boosted immune system could be considered a high priority of preventive medicine for combating COVID-19. Herein, we discuss the current level of understanding underlining the contribution of healthy immunity and its relevance to COVID-19 molecular pathogenesis, and potential therapeutic strategies, in the management of this devastating disease.

High Throughput scRNA-Seq Provides Insights Into Leydig Cell Senescence Induced by Experimental Autoimmune Orchitis: A Prominent Role of Interstitial Fibrosis and Complement Activation

Leydig cells (Lc), located in the interstitial space of the testis between seminiferous tubules, produce 95% of testosterone in male individuals, which is pivotal for male sexual differentiation, spermatogenesis, and maintenance of the male secondary sex characteristics. Lc are prone to senescence in aging testes, resulting in compromised androgen synthesis capability upon aging. However, little is known about whether Lc undergo senescence in a chronic inflammatory environment. To investigate this question, mouse models of experimental autoimmune orchitis (EAO) were used, and Lc were analyzed by high throughput scRNA-Seq. Data were screened and analyzed by correlating signaling pathways with senescence, apoptosis, androgen synthesis, and cytokine/chemokine signaling pathways. EAO did induce Lc senescence, and Lc senescence in turn antagonized androgen synthesis. Based on the correlation screening of pathways inducing Lc senescence, a plethora of pathways were found to play potential roles in triggering Lc senescence during EAO, among which the Arf6 and angiopoietin receptor pathways were highly correlated with senescence signature. Notably, complement and interstitial fibrosis activated by EAO worsened Lc senescence and strongly antagonized androgen synthesis. Furthermore, most proinflammatory cytokines enhanced both senescence and apoptosis in Lc and spermatogonia (Sg) during EAO, and proinflammatory cytokine antagonism of the glutathione metabolism pathway may be key in inducing cellular senescence during EAO.

Epimedium protects against dyszoospermia in mice with Pex3 knockout by exerting antioxidant effects and regulating the expression level of P16

Oxidative stress (OS) is one of the primary factors leading to male infertility. Oral administration of antioxidants has thus far been found to significantly improve the quality of human sperm. Therefore, antioxidant treatment has become the consensus among international experts on male infertility. In this study, peroxisomal biogenesis factor 3 (Pex3)-knockout (KO, -/-) mice were used as a model to compare the efficacy of three types of traditional Chinese medicine (TCM) granules (Epimedium [YYH], Cuscuta [TSZ], and Rhodiola [HJT]) for male reproductive function rescue. YYH was revealed to be the best and exerted a rescue effect on Pex3-/- mice with spermatogenesis defects. In addition, YYH prominently reduced ROS levels in the testes, inhibited DNA oxidative damage in spermatogenic cells, promoted the proliferation of spermatogenic cells, and inhibited apoptosis in Pex3-/- male mice. Furthermore, the mechanism by which YYH ameliorated dyszoospermia was confirmed via the establishment of cyclin-dependent kinase inhibitor 2 A (P16Ink4a)-KO mice. Specifically, Pex3-/- mice produced elevated amounts of ROS, which damaged germ cell DNA and further activated the signaling pathway of the cell senescence regulatory protein P16-CDK6, resulting in cell cycle arrest and eventually contributing to spermatogenesis dysfunction. YYH supplementation partially corrected the associated phenotype in gene KO mice by affecting P16 expression levels, thus improving the reproductive outcome to a certain extent.

Sirt1 and Nrf2: regulation of Leydig cell oxidant/antioxidant intracellular environment and steroid formation†

Previous studies reported that, with aging, Leydig cell intracellular antioxidants are reduced in concentration and intracellular ROS levels increase, suggesting that oxidant/antioxidant imbalance may contribute to the reduced testosterone production that characterizes the aging cells. As yet, little is known about how the Leydig cell oxidant/antioxidant environment is regulated. Sirt1, an enzyme that deacetylates transcription factors, and the transcription factor Nrf2, have been shown to be associated with cellular response to oxidative stress. We hypothesized that Sirt1 and/or Nrf2 might be involved in regulating the oxidant/antioxidant environment of Leydig cells, and therefore, the testosterone production. We found that Sirt1 and Nrf2 are present in the Leydig cells of Brown Norway rats, though reduced in aged cells. In MA-10 cells in which Sirt1 or Nrf2 were suppressed by nicotinamide (NAM) or ML385, respectively, or in which siRNAs were used for knockdown of Sirt1 or Nrf2, increased ROS levels and decreased progesterone production occurred. In rat Leydig cells, inhibition of Sirt1 by culturing the cells with NAM resulted in increased ROS and reduced testosterone production, and subsequent removal of NAM from the culture medium resulted in increased testosterone production. Activation of rat Leydig cells Sirt1 with honokiol or of Nrf2 with sulforaphane resulted in the maintenance of testosterone production despite the exposure of the cells to oxidizing agent. These results, taken together, suggest that Sirt1 and Nrf2 are involved in maintaining the Leydig cell oxidant/antioxidant environment, and thus in maintaining steroid production.

Oncostatin M stimulates immature Leydig cell proliferation but inhibits its maturation and function in rats through JAK1/STAT3 signaling and induction of oxidative stress in vitro

BACKGROUND

Oncostatin M (OSM) is a member of the interleukin-6 group of cytokines, which can regulate cell proliferation, growth, and function. Immature Leydig cells have the ability to proliferate and differentiate, and adult Leydig cells have the function of testosterone synthesis. However, the role and underlying mechanisms of OSM on the proliferation and function of Leydig cells remain unclear.

METHODS

The effects of OSM on the proliferation, apoptosis, and function of immature Leydig cells isolated from 35-day-old rats and the function of adult Leydig cells isolated from 63-day-old rats in vitro.

RESULTS

OSM stimulated immature Leydig cell proliferation after up-regulating the expression of Ccnd1 and Cdk4 to drive the transition of G1 phase to M2 phase in the cell cycle at 10 and 100 ng/ml. OSM did not affect the apoptosis of immature Leydig cells up to 100 ng/ml. OSM inhibited testosterone production in immature and adult Leydig cells by down-regulating the expression of Lhcgr, Star, Cyp11a1, Hsd3b1, and Cyp17a1 at 1-100 ng/ml. OSM induced reactive oxygen species and down-regulated the expression of antioxidant genes and lowered mitochondrial membrane potential at 10 and 100 ng/ml in both Leydig cells. Janus kinase 1 (JAK1) antagonist filgotinib and signal transducer and activator of transcription 3 (STAT3) antagonist S3I-201 reversed the effect of OSM, indicating that it acts on JAK1/STAT3 signaling.

CONCLUSION

Oncostatin M stimulates immature Leydig cell proliferation while inhibiting the function of immature and adult Leydig cells.

Impact of Environmental and Lifestyle Use of Chromium on Male Fertility: Focus on Antioxidant Activity and Oxidative Stress

Male reproductive tissues are strongly susceptible to several environmental and lifestyle stressors. In general, male reproductive health is highly sensitive to oxidative stress, which results in reversible and/or irreversible changes in testosterone-producing cells, spermatogenesis, and sperm quality. Chromium compounds are widely used in the +3 and +6 valence states, as food supplements, and in the industrial field, respectively. Chromium (III) compounds, i.e., Cr(III)-tris-picolinate, [Cr(pic)₃], known as chromium picolinate, are used as nutritional supplements for the control of diabetes, body weight, and muscular growth. However, previous studies showed that animal models exposed to chromium picolinate experienced degenerative changes in spermatogenesis. Contradictory results are documented in the literature and deserve discussion. Furthermore, the long-term effects of chromium picolinate on the antioxidant system of treated subjects have not been properly studied. Comprehensive studies on the role of this compound will help to establish the safe and useful use of chromium supplementation. On the other hand, chromium (VI) compounds are widely used in several industries, despite being well-known environmental pollutants (i.e., welding fumes). Chromium (VI) is known for its deleterious effects on male reproductive health as toxic, carcinogenic, and mutagenic. Previous studies have demonstrated severe lesions to mouse spermatogenesis after exposure to chromium (VI). However, workers worldwide are still exposed to hexavalent chromium, particularly in electronics and military industries. Data from the literature pinpoints mechanisms of oxidative stress induced by chromium compounds in somatic and germ cells that lead to apoptosis, thus underlining the impairment of fertility potential. In this review, we analyze the benefits and risks of chromium compounds on male fertility, as well as the mechanisms underlying (in)fertility outcomes. Although supplements with antioxidant properties may maximize male fertility, adverse effects need to be investigated and discussed.

Leydig cell aging: Molecular mechanisms and treatments

Late-onset hypogonadism, resulting from deficiency in serum testosterone (T), affects the health and quality of life of millions of aging men. T is synthesized by Leydig cells (LCs) in response to luteinizing hormone (LH). LH binds LC plasma membrane receptors, inducing the formation of a supramolecular complex of cytosolic and mitochondrial proteins, the Steroidogenic InteracTomE (SITE). SITE proteins are involved in targeting cholesterol to CYP11A1 in the mitochondria, the first enzyme of the steroidogenic cascade. Cholesterol translocation is the rate-determining step in T formation. With aging, LC defects occur that include changes in SITE, an increasingly oxidative intracellular environment, and reduced androgen formation and serum T levels. T replacement therapy (TRT) will restore T levels, but reported side effects make it desirable to develop additional strategies for increasing T. One approach is to target LC protein-protein interactions and thus increase T production by the hypofunctional Leydig cells themselves.

The role of noble bumblebee (Bombus terrestris) queen glycosaminoglycan in aged rat and gene expression profile based on DNA microarray

Glycosaminoglycans (GAGs) have been used to diminish the deleterious effects associated with aging by preventing the destruction of cartilage, bone, discs, and skin. The objective of this study was to evaluate the anti-aging effect of a newly prepared GAG derived from bumblebee (Bombus terrestris) queen (BTQG, 10 mg/kg). Gryllus bimaculatus (Gb, cricket) GAG (GbG, 10 mg/kg) or glucosamine sulfate (GS) was used as a positive control. N-glycans derived from BTQG contained hexose polymers including Hex₄HexNAc₃Pen₁, Hex₉, and Hex₅HexNAc₃dHex₂ as the primary components. The GAGs were intraperitoneally administered to 14-month-old aged rats for 1 month. BTQG reduced the serum levels of free fatty acid, alkaline phosphatase (ALP), glutamate pyruvate transaminase (GPT), creatinine, and blood urea nitrogen (BUN), showing hepato-and renal-protective effects with anti-lipidemic activities comparable to GS. The changes of gene expression profile of liver tissue by cDNA microarray showed the simultaneous upregulation of 36 genes in the BTQG-treated rat group compared to the control group, including secretogranin II (Scg2), Activator (AP)-1-regulated protein-related reactive oxygen species (ROS) DNA damage repair, metallothionein 1a, and alpha-2 macroglobulin. The BTQG-treated group also showed 417 downregulated genes, including vimentin, moesin, and mitochondrial carbonic anhydrase. Insect glycosaminoglycan from the bumblebee (B. terrestris) queen may help decelerate the aging stage by ameliorating the aging effects on circulation, and liver and kidney function.

PFAS Environmental Pollution and Antioxidant Responses: An Overview of the Impact on Human Field

Due to their unique properties, perfluorinated substances (PFAS) are widely used in multiple industrial and commercial applications, but they are toxic for animals, humans included. This review presents some available data on the PFAS environmental distribution in the world, and in particular in Europe and in the Veneto region of Italy, where it has become a serious problem for human health. The consumption of contaminated food and drinking water is considered one of the major source of exposure for humans. Worldwide epidemiological studies report the negative effects that PFAS have on human health, due to environmental pollution, including infertility, steroid hormone perturbation, thyroid, liver and kidney disorders, and metabolic disfunctions. In vitro and in vivo researches correlated PFAS exposure to oxidative stress effects (in mammals as well as in other vertebrates of human interest), produced by a PFAS-induced increase of reactive oxygen species formation. The cellular antioxidant defense system is activated by PFAS, but it is only partially able to avoid the oxidative damage to biomolecules.

Ambient sulfur dioxide could have an impact on testicular volume from a observational study on a population of infertile male

Background

The effect of ambient pollutants on the male reproductive system is controversial. This retrospective study investigated the effect of environmental pollutants on male reproductive health.

Methods

Male patients with primary infertility (n = 282) were identified from a single center between January 2016 and December 2017. Patients were physically examined for the presence of varicocele and for the volume of both testicles. Semen quality was measured in terms of the total sperm count, sperm concentration, and the percentage of sperm cells with motility and normal morphology. Data were acquired on the concentration of ambient pollutants, namely particulate matters of diameter < 2.5 μm, sulfur dioxide (SO₂), nitrogen oxides (NO_x), and ozone (O₃), measured on daily and hourly basis, from the Environmental Protection Administration Executive Yuan, Taiwan. Individual exposure to pollutants was estimated based on the reported residential address of each participant. Statistical analysis indicated the effect of each pollutant on the testicular volume, sex hormone profile, and semen parameters.

Results

The mean ± standard deviation of age was 36.7 ± 7.3 years. The average sperm count and concentration were 41.9 million/mL and 34.1 million/mL, respectively. The mean levels of serum testosterone, follicle-stimulating hormone, and luteinizing hormone were 3.57 ± 1.68 ng/mL, 7.59 ± 6.3 IU/L, and 4.68 ± 3.49 IU/L, respectively. According to the multivariate linear regression model, NO_x exposure was a risk factor for decreased sperm concentration and motility (p = 0.043 and 0.032). Furthermore, SO₂ exposure was negatively associated and testicular volume (p < 0.01).

Conclusions

NO₂ and SO₂ exposure were negatively associated with the seminal parameter and decreased testicular volume, respectively, in a population of men with infertility. However, additional prospective studies are needed to ascertain the cause–effect relation of current results.

Peptide Hormone Regulation of DNA Damage Responses

DNA damage response (DDR) and DNA repair pathways determine neoplastic cell transformation and therapeutic responses, as well as the aging process. Altered DDR functioning results in accumulation of unrepaired DNA damage, increased frequency of tumorigenic mutations, and premature aging. Recent evidence suggests that polypeptide hormones play a role in modulating DDR and DNA damage repair, while DNA damage accumulation may also affect hormonal status. We review the available reports elucidating involvement of insulin-like growth factor 1 (IGF1), growth hormone (GH), α-melanocyte stimulating hormone (αMSH), and gonadotropin-releasing hormone (GnRH)/gonadotropins in DDR and DNA repair as well as the current understanding of pathways enabling these actions. We discuss effects of DNA damage pathway mutations, including Fanconi anemia, on endocrine function and consider mechanisms underlying these phenotypes. (Endocrine Reviews 41: 1 - 19, 2020).

Bisphenols and Leydig Cell Development and Function

Bisphenol A (BPA) is a ubiquitous environmental pollutant, mainly from the production and use of plastics and the degradation of wastes related to industrial plastics. Evidence from laboratory animal and human studies supports the view that BPA has an endocrine disrupting effect on Leydig cell development and function. To better understand the adverse effects of BPA, we reviewed its role and mechanism by analyzing rodent data in vivo and in vitro and human epidemiological evidence. BPA has estrogen and anti-androgen effects, thereby destroying the development and function of Leydig cells and causing related reproductive diseases such as testicular dysgenesis syndrome, delayed puberty, and subfertility/infertility. Due to the limitation of BPA production, the increased use of BPA analogs has also attracted attention to these new chemicals. They may share actions and mechanisms similar to or different from BPA.

Propofol Inhibits Androgen Production in Rat Immature Leydig Cells

Background: Propofol is a widely used anesthetic. Whether propofol inhibits androgen production by rat Leydig cells and the underlying mechanism remains unclear. The objective of the current study was to examine the effects of propofol exposure to rat primary immature Leydig cells and to define propofol-induced inhibition of steroidogenic enzymes in both rat and human testes in vitro.

Methods: Immature Leydig cells were purified from 35-day-old male Sprague–Dawley rats and were exposed to propofol for 3 h. The androgen production by Leydig cells under basal, luteinizing hormone, 8bromo-cAMP, and steroid-substrate stimulated conditions and gene expression of Leydig cells after exposure to propofol were measured. Immature Leydig cells were treated with propofol for 3 h and switched to propofol-free medium for additional 3 and 9 h to test whether propofol-induced inhibition is reversible. ³H-Steroids were used to evaluate the direct action of propofol on cytochrome P450 cholesterol side chain cleavage (CYP11A1), 3β-hydroxysteroid dehydrogenase (HSD3B), cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17A1), and 17β-hydroxysteroid dehydrogenase 3 (HSD17B3) activities in rat and human testes in vitro.

Results: Propofol significantly lowered luteinizing hormone and 8bromo-cAMP stimulated androgen production by Leydig cells after 3-h exposure. Further investigation showed that propofol down-regulated the expression of Cyp11a1 and Cyp17a1 and their proteins at 5 and 50 µM, although it up-regulated Lhcgr expression at 50 µM. Propofol significantly suppressed phosphorylation of ERK1/2 and induced ROS production in immature Leydig cells at 5 and 50 µM. Propofol significantly induced apoptosis of immature Leydig cells at 50 µM. Propofol specifically inhibited rat and human testis HSD3B activities in vitro. The half maximal inhibitory concentrations of propofol for rat and human HSD3B enzymes were 1.011 ± 0.065 and 3.498 ± 0.067 µM, respectively. The mode of action of propofol of inhibiting HSD3B was competitive when pregnenolone was added. At 50 µM, propofol did not directly inhibit rat and human testis CYP11A1, CYP17A1, and HSD17B3 activities in vitro.

Conclusion: Propofol inhibits androgen production via both directly inhibiting HSD3B activity and down-regulating Cyp11a1 and Cyp17a1 expression in Leydig cells. Suppression of steroidogenic enzymes is presumably associated with the lower production of androgen by Leydig cells after propofol treatment. However, propofol-induced inhibition on androgen production is reversible.

Delayed Puberty by Ziram Is Associated with Down Regulation of Testicular Phosphorylated AKT1 and SIRT1/PGC-1α Signaling

Ziram is a dimethyldithiocarbamate fungicide, which may influence the male reproductive system as a potential endocrine disruptor. We interrogated the disruption of ziram on rat progenitor Leydig cell development. Prepubertal male Sprague-Dawley rats were orally treated with 0, 2, 4, or 8 mg/kg ziram for 2 weeks. We investigated the effects of ziram on serum testosterone levels, Leydig cell number, and Leydig and Sertoli cell gene and protein expression, SIRT1/PGC-1α levels, and phosphorylation of AKT1, ERK1/2, and AMPK in vivo. We also interrogated the effects of ziram on reactive oxidative species (ROS) level, apoptosis rate, and mitochondrial membrane potential of progenitor Leydig cells in vitro. Ziram decreased serum testosterone and follicle-stimulating hormone levels, the down-regulated Leydig cell-specific gene ( Lhcgr, Scarb1, Star, Cyp17a1, and Hsd17b3), and their protein expression. However, ziram stimulated anti-Müllerian hormone production. Ziram lowered SIRT1/PGC-1α and phosphorylated protein levels of AKT1. Ziram induced ROS and apoptosis and lowered the mitochondrial membrane potential of progenitor Leydig cells in vitro. In conclusion, ziram disrupts Leydig cell development during the prepubertal period potentially through the SIRT1/PGC-1α and phosphorylated AKT1 signaling.

A young testicular microenvironment protects Leydig cells against age-related dysfunction in a mouse model of premature aging

Testicular Leydig cells (LCs) are the primary source of circulating androgen in men. As men age, circulating androgen levels decline. However, whether reduced LC steroidogenesis results from specific effects of aging within LCs or reflects degenerative alterations to the wider supporting microenvironment is unclear; inability to separate intrinsic LC aging from that of the testicular microenvironment in vivo has made this question difficult to address. To resolve this, we generated novel mouse models of premature aging, driven by CDGSH iron sulfur domain 2 (Cisd2) deletion, to separate the effects of cell intrinsic aging from extrinsic effects of aging on LC function. At 6 mo of age, constitutive Cisd2-deficient mice display signs of premature aging, including testicular atrophy, reduced LC and Sertoli cell (SC) number, decreased circulating testosterone, increased luteinizing hormone/testosterone ratio, and decreased expression of steroidogenic mRNAs, appropriately modeling primary testicular dysfunction observed in aging men. However, mice with Cisd2 deletion (and thus premature aging) restricted to either LCs or SCs were protected against testicular degeneration, demonstrating that age-related LCs dysfunction cannot be explained by intrinsic aging within either the LC or SC lineages alone. We conclude that age-related LC dysfunction is largely driven by aging of the supporting testicular microenvironment.—Curley, M., Milne, L., Smith, S., Jørgensen, A., Frederiksen, H., Hadoke, P., Potter, P., Smith, L. B. A Young testicular microenvironment protects Leydig cells against age-related dysfunction in a mouse model of premature aging.

Testosterone May Hold Therapeutic Promise for the Treatment of Ischemic Stroke in Aging: A Closer Look at Laboratory Findings

Male sex is more prone to cerebrovascular disorders, yet the exact role of androgens in cerebral ischemia remains unclear. Here we reviewed current understanding of testosterone (TES) neuroprotective activity against ischemic stroke and mechanisms underlying these effects in aging. TES may exert a neuroprotective effect in aging through pathways including inhibition of oxidant molecules production, enhancing the enzymatic antioxidant capacity of the brain and modulation of apoptotic cell death. Given this, a better understanding of the neuroprotective roles of TES may propose an effective therapeutic strategy to improve the quality of life and decrease androgen-related cerebrovascular problems in the aging men.

Steroidogenesis in Leydig cells: effects of aging and environmental factors

Serum testosterone (TS) levels decrease with aging in both humans and rodents. Using the rat as a model system, it was found that age-related reductions in serum TS were not due to loss of Leydig cells, but rather to the reduced ability of the Leydig cells to produce TS in response to luteinizing hormone (LH). Detailed analyses of the steroidogenic pathway have suggested that two defects along the pathway, LH-stimulated cAMP production and cholesterol transport to and into the mitochondria, are of particular importance in age-related reductions in TS production. Although the mechanisms involved in these defects are far from certain, increasing oxidative stress appears to play a particularly important role. Interestingly, increased oxidative stress also appears to be involved in the suppressive effects of endocrine disruptors on Leydig cell TS production.

Feedback inhibition of CREB signaling by p38 MAPK contributes to the negative regulation of steroidogenesis

BACKGROUND

Steroidogenesis is a complex, multi-steps biological process in which, cholesterol precursor is converted to steroids in a tissue specific and tropic hormone dependent manner. Given that steroidogenesis is achieved by coordinated functioning of multiple tissue specific enzymes, many steroids intermediates/metabolites are generated during this process. Both the steroid products as well as major lipoprotein cholesterol donor, high-density lipoprotein 3 (hHDL₃) have the potential to negatively regulate steroidogenesis via increased oxidative stress/reactive oxygen species (ROS) generation.

METHODS

In the current study, we examined the effects of treatment of a mouse model of steroidogenesis, Y1-BS1 adrenocortical tumor cells with pregnenolone, 22(R)-Hydroxycholesterol [22(R)-diol] or hHDL₃ on ROS production, phosphorylation status of p38 MAPK and cAMP response element-binding protein (CREB), CREB transcriptional activity and mRNA expression of StAR, CPY11A1/P450scc and antioxidant enzymes, superoxide dismutases [Cu,ZnSOD (SOD1), MnSOD (SOD2)], catalase (CAT) and glutathione peroxidase 1 (GPX1). We also detected the steroid product in p38 MAPK inhibitor treated Y1 cells by HPLC-MS / MS.

RESULTS

Treatment of Y1 cells with H₂O₂ greatly enhanced the phosphorylation of both p38 MAPK and CREB protein. Likewise, treatment of cells with pregnenolone, 22(R) diol or hHDL₃ increased ROS production measured with the oxidation-sensitive fluorescent probe 2',7'-Dichlorofluorescin diacetate (DCFH-DA). Under identical experimental conditions, treatment of cells with these agents also increased the phosphorylation of p38 MAPK and CREB. This increased CREB phosphorylation however, was associated with its decreased transcriptional activity. The stimulatory effects of pregnenolone, 22(R)-diol and hHDL₃ on CREB phosphorylation was abolished by a specific p38 MAPK inhibitor, SB203580. Pregnenolone, and 22(R) diol but not hHDL₃ upregulated the mRNA expression of SOD1, SOD2 and GPX1, while down-regulated the mRNA levels of StAR and CYP11A1. The p38 inhibitor SB203580 could increase the steroid production in HDL3, 22(R)-diol or pregnenolone treated cells.

CONCLUSION

Our data demonstrate induction of a ROS/p38 MAPK -mediated feedback inhibitory pathway by oxy-cholesterol and steroid intermediates and products attenuates steroidogenesis via inhibition of CREB transcriptional activity.

Aging has the opposite effect on cAMP and cGMP circadian variations in rat Leydig cells

The Leydig cell physiology displays a circadian rhythm driven by a complex interaction of the reproductive axis hormones and circadian system. The final output of this regulatory process is circadian pattern of steroidogenic genes expression and testosterone production. Aging gradually decreases robustness of rhythmic testosterone secretion without change in pattern of LH secretion. Here, we analyzed effect of aging on circadian variation of cAMP and cGMP signaling in Leydig cells. Results showed opposite effect of aging on cAMP and cGMP daily variation. Reduced amplitude of cAMP circadian oscillation was probably associated with changed expression of genes involved in cAMP production (increased circadian pattern of Adcy7, Adcy9, Adcy10 and decreased Adcy3); cAMP degradation (increased Pde4a, decreased Pde8b, canceled rhythm of Pde4d, completely reversed circadian pattern of Pde7b and Pde8a); and circadian expression of protein kinase A subunits (Prkac/PRKAC and Prkar2a). Aging stimulates expression of genes responsible for cGMP production (Nos2, Gucy1a3 and Gucy1b3/GUCYB3) and degradation (Pde5a, Pde6a and Pde6h) but the overall net effect is elevation of cGMP circadian oscillations in Leydig cells. In addition, the expression of cGMP-dependent kinase, Prkg1/PRKG1 is up-regulated. It seems that aging potentiate cGMP- and reduce cAMP-signaling in Leydig cells. Since both signaling pathways affect testosterone production and clockwork in the cells, further insights into these signaling pathways will help to unravel disorders linked to the circadian timing system, aging and reproduction.

Role of the steroidogenic acute regulatory protein in health and disease

Steroid hormones are an important class of regulatory molecules that are synthesized in steroidogenic cells of the adrenal, ovary, testis, placenta, brain, and skin, and influence a spectrum of developmental and physiological processes. The steroidogenic acute regulatory protein (STAR) predominantly mediates the rate-limiting step in steroid biosynthesis, i.e., the transport of the substrate of all steroid hormones, cholesterol, from the outer to the inner mitochondrial membrane. At the inner membrane, cytochrome P450 cholesterol side chain cleavage enzyme cleaves the cholesterol side chain to form the first steroid, pregnenolone, which is converted by a series of enzymes to various steroid hormones in specific tissues. Both basic and clinical evidence have demonstrated the crucial involvement of the STAR protein in the regulation of steroid biosynthesis. Multiple levels of regulation impinge on STAR action. Recent findings demonstrate that hormone-sensitive lipase, through its action on the hydrolysis of cholesteryl esters, plays an important role in regulating STAR expression and steroidogenesis which involve the liver X receptor pathway. Activation of the latter influences macrophage cholesterol efflux that is a key process in the prevention of atherosclerotic cardiovascular disease. Appropriate regulation of steroid hormones is vital for proper functioning of many important biological activities, which are also paramount for geriatric populations to live longer and healthier. This review summarizes the current level of understanding on tissue-specific and hormone-induced regulation of STAR expression and steroidogenesis, and provides insights into a number of cholesterol and/or steroid coupled physiological and pathophysiological consequences.

The Transcription Factor MEF2 Is a Novel Regulator of Gsta Gene Class in Mouse MA-10 Leydig Cells

Testosterone is essential for spermatogenesis and the development of male sexual characteristics. However, steroidogenesis produces a significant amount of reactive oxygen species (ROS), which can disrupt testosterone production. The myocyte enhancer factor 2 (MEF2) is an important regulator of organogenesis and cell differentiation in various tissues. In the testis, MEF2 is present in Sertoli and Leydig cells throughout fetal and adult life. MEF2-deficient MA-10 Leydig cells exhibit a significant decrease in steroidogenesis concomitant with a reduction in glutathione S-transferase (GST) activity and in the expression of the 4 Gsta members (GST) that encode ROS inactivating enzymes. Here, we report a novel role for MEF2 in ROS detoxification by directly regulating Gsta expression in Leydig cells. Endogenous Gsta1-4 mRNA levels were decreased in MEF2-deficient MA-10 Leydig cells. Conversely, overexpression of MEF2 increased endogenous Gsta1 levels. MEF2 recruitment to the proximal Gsta1 promoter and direct binding on the -506-bp MEF2 element were confirmed by chromatin immunoprecipitation and DNA precipitation assays. In MA-10 Leydig cells, MEF2 activates the Gsta1 promoter and cooperates with Ca(2+)/calmodulin-dependent kinases I to further enhance Gsta1 promoter activity. These effects were lost when the -506-bp MEF2 element was mutated or when a MEF2-Engrailed dominant negative protein was used. Similar results were obtained on the Gsta2, Gsta3, and Gsta4 promoters, suggesting a global role for MEF2 factors in the regulation of all 4 Gsta genes. Altogether, our results identify a novel role for MEF2 in the expression of genes involved in ROS detoxification, a process essential for adequate testosterone production in Leydig cells.

Steroidogenic fate of the Leydig cells that repopulate the testes of young and aged Brown Norway rats after elimination of the preexisting Leydig cells

The capacity of Brown Norway rat Leydig cells to produce testosterone (T) decreases with aging. In a previous study, we reported that a new generation of Leydig cells can be restored in both young and old rat testes after a single injection of ethane dimethanesulfonate (EDS), and that the abilities of the new Leydig cells in young and old rats to produce T were equivalent. Our objective herein was to compare the steroidogenic fate of the new Leydig cells over time. Young (3 month-old) and old (18 month-old) rats were injected with EDS to eliminate the existing Leydig cells. Ten weeks after EDS, Leydig cells had been restored and T production by the new Leydig cells isolated from young and old rat testes was equivalent. Thirty weeks after EDS treatment of young rats, the ability of the new Leydig cells to produce T had not diminished from 10 weeks post-EDS. In contrast, at 30 weeks post-EDS, T production by new cells in old rat testes was reduced significantly from the 10-week level. Serum T levels at 10 and 30 weeks were consistent with Leydig cell T production. Serum LH levels did not differ in any group. Thus, although the Leydig cells restored to both young and old rats after EDS initially produced T at high, equivalent levels, the cells in the old testes did not maintain this ability. These results suggest that: 1) the cells from which new populations of Leydig cells are derived may differ depending upon the age of the rat; and/or 2) factors extrinsic to the new Leydig cells in young and old testes differ, and it is these differences that are responsible for reductions in T by the newly formed Leydig cells in the testes of old rats.

Knockout of the transcription factor Nrf2: Effects on testosterone production by aging mouse Leydig cells

Aging in rodents and men is associated with reduced serum levels of testosterone and Leydig cell testosterone productions. To further investigate the mechanism by which Leydig cell testosterone production declines, the effect of knocking out Nrf2, a master regulator of phase 2 antioxidant genes, was examined. In wild-type mice, testosterone production and serum testosterone levels remained unchanged through middle age (8 months), but then were reduced significantly by old age (21-24 months). In contrast, serum testosterone levels and Leydig cell testosterone production were reduced significantly in the Nrf2-/- mice as early as middle age, and were reduced further in the aged mice. Reduced steroidogenesis in the knockout mice was associated with reduced antioxidant capacity, and increased expression of protein nitrotyrosine residues, a marker of ROS. These results support the hypothesis that, over time, increases in oxidative stress contribute to or cause the reduced testosterone production that characterizes Leydig cell aging.

Morphological and functional maturation of Leydig cells: from rodent models to primates

BACKGROUND

Leydig cells (LC) are the sites of testicular androgen production. Development of LC occurs in the testes of most mammalian species as two distinct growth phases, i.e. as fetal and pubertal/adult populations. In primates there are indications of a third neonatal growth phase. LC androgen production begins in embryonic life and is crucial for the intrauterine masculinization of the male fetal genital tract and brain, and continues until birth after which it rapidly declines. A short post-natal phase of LC activity in primates (including human) termed 'mini-puberty' precedes the period of juvenile quiescence. The adult population of LC evolves, depending on species, in mid- to late-prepuberty upon reawakening of the hypothalamic-pituitary-testicular axis, and these cells are responsible for testicular androgen production in adult life, which continues with a slight gradual decline until senescence. This review is an updated comparative analysis of the functional and morphological maturation of LC in model species with special reference to rodents and primates.

METHODS

Pubmed, Scopus, Web of Science and Google Scholar databases were searched between December 2012 and October 2014. Studies published in languages other than English or German were excluded, as were data in abstract form only. Studies available on primates were primarily examined and compared with available data from specific animal models with emphasis on rodents.

RESULTS

Expression of different marker genes in rodents provides evidence that at least two distinct progenitor lineages give rise to the fetal LC (FLC) population, one arising from the coelomic epithelium and the other from specialized vascular-associated cells along the gonad-mesonephros border. There is general agreement that the formation and functioning of the FLC population in rodents is gonadotrophin-responsive but not gonadotrophin-dependent. In contrast, although there is in primates some controversy on the role of gonadotrophins in the formation of the FLC population, there is consensus about the essential role of gonadotrophins in testosterone production. Like the FLC population, adult Leydig cells (ALC) in rodents arise from stem cells, which have their origin in the fetal testis. In contrast, in primates the ALC population is thought to originate from FLC, which undergo several cycles of regression and redifferentiation before giving rise to the mature ALC population, as well as from differentiation of stem cells/precursor cells. Despite this difference in origin, both in primates and rodents the formation of the mature and functionally active ALC population is critically dependent on the pituitary gonadotrophin, LH. From studies on rodents considerable knowledge has emerged on factors that are involved besides LH in the regulation of this developmental process. Whether the same factors also play a role in the development of the mature primate LC population awaits further investigation.

CONCLUSION

Distinct populations of LC develop along the life span of males, including fetal, neonatal (primates) and ALC. Despite differences in the LC lineages of rodents and primates, the end product is a mature population of LC with the main function to provide androgens necessary for the maintenance of spermatogenesis and extra-gonadal androgen actions.

Leydig cell aging and hypogonadism

Leydig cell testosterone (T) production is reduced with age, resulting in reduced serum T levels (hypogonadism). A number of cellular changes have been identified in the steroidogenic pathway of aged Leydig cells that are associated with reduced T formation, including reductions in luteinizing hormone (LH)-stimulated cAMP production, the cholesterol transport proteins steroidogenic acute regulatory (STAR) protein and translocator protein (TSPO), and downstream steroidogenic enzymes of the mitochondria and smooth endoplasmic reticulum. Many of the changes in steroid formation that characterize aged Leydig cells can be elicited by the experimental alteration of the redox environment of young cells, suggesting that changes in the intracellular redox balance may cause reduced T production. Hypogonadism is estimated to affect about 5 million American men, including both aged and young. This condition has been linked to mood changes, worsening cognition, fatigue, depression, decreased lean body mass, reduced bone mineral density, increased visceral fat, metabolic syndrome, decreased libido, and sexual dysfunction. Exogenous T administration is now used widely to elevate serum T levels in hypogonadal men and thus to treat symptoms of hypogonadism. However, recent evidence suggests that men who take exogenous T may face increased risk of stroke, heart attack, and prostate tumorigenesis. Moreover, it is well established that administered T can have suppressive effects on LH, resulting in lower Leydig cell T production, reduced intratesticular T concentration, and reduced spermatogenesis. This makes exogenous T administration inappropriate for men who wish to father children. There are promising new approaches to increase serum T by directly stimulating Leydig cell T production rather than by exogenous T therapy, thus potentially avoiding some of its negative consequences.

Autocrine androgen action is essential for Leydig cell maturation and function, and protects against late-onset Leydig cell apoptosis in both mice and men

Leydig cell number and function decline as men age, and low testosterone is associated with all “Western” cardio-metabolic disorders. However, whether perturbed androgen action within the adult Leydig cell lineage predisposes individuals to this late-onset degeneration remains unknown. To address this, we generated a novel mouse model in which androgen receptor (AR) is ablated from ∼75% of adult Leydig stem cell/cell progenitors, from fetal life onward (Leydig cell AR knockout mice), permitting interrogation of the specific roles of autocrine Leydig cell AR signaling through comparison to adjacent AR-retaining Leydig cells, testes from littermate controls, and to human testes, including from patients with complete androgen insensitivity syndrome (CAIS). This revealed that autocrine AR signaling is dispensable for the attainment of final Leydig cell number but is essential for Leydig cell maturation and regulation of steroidogenic enzymes in adulthood. Furthermore, these studies reveal that autocrine AR signaling in Leydig cells protects against late-onset degeneration of the seminiferous epithelium in mice and inhibits Leydig cell apoptosis in both adult mice and patients with CAIS, possibly via opposing aberrant estrogen signaling. We conclude that autocrine androgen action within Leydig cells is essential for the lifelong support of spermatogenesis and the development and lifelong health of Leydig cells.—O’Hara, L., McInnes, K., Simitsidellis, I., Morgan, S., Atanassova, N., Slowikowska-Hilczer, J., Kula, K., Szarras-Czapnik, M., Milne, L., Mitchell, R. T., Smith, L. B. Autocrine androgen action is essential for Leydig cell maturation and function, and protects against late-onset Leydig cell apoptosis in both mice and men.

Steroidogenesis in MA-10 mouse Leydig cells is altered via fatty acid import into the mitochondria

Mitochondria are home to many cellular processes, including oxidative phosphorylation and fatty acid metabolism, and in steroid-synthesizing cells, they are involved in cholesterol import and metabolism, which is the initiating step in steroidogenesis. The formation of macromolecular protein complexes aids in the regulation and efficiency of these mitochondrial functions, though because of their dynamic nature, they are hard to identify. To overcome this problem, we used Blue-Native PAGE with whole-gel mass spectrometry on isolated mitochondria from control and hormone-treated MA-10 mouse tumor Leydig cells. The presence of multiple mitochondrial protein complexes was shown. Although these were qualitatively similar under control and human chorionic gonadotropin (hCG)-stimulated conditions, quantitative differences in the components of the complexes emerged after hCG treatment. A prominent decrease was observed with proteins involved in fatty acid import into the mitochondria, implying that mitochondrial beta-oxidation is not essential for steroidogenesis. To confirm this observation, we inhibited fatty acid import utilizing the CPT1a inhibitor etomoxir, resulting in increased steroid production. Conversely, stimulation of mitochondrial beta-oxidation with metformin resulted in a dose-dependent reduction in steroidogenesis. These changes were accompanied by changes in mitochondrial respiration and in the lactic acid formed during glycolysis. Taken together, these results suggest that upon hormonal stimulation, mitochondria efficiently import cholesterol for steroid production at the expense of other lipids necessary for energy production, specifically fatty acids required for beta-oxidation.

Age related changes of cAMP and MAPK signaling in Leydig cells of Wistar rats

Here, we chronologically analyzed age-associated changes of cAMP- and MAPK-signaling in Leydig cells (LCs) in relation with decreased testosterone (T) production. In Wistar rats, decreased serum T observed in 12 to 24-month-old rats was not related to decreased serum LH concentration but to reduced luteinizing hormone receptor (Lhr/LHR) and time-coordinated reduction of steroidogenic gene expression (decreased Cyp11a1, Cyp17a1 in 12-month-old rats followed by decreased Star/StAR, Hsd3b/HSD3B, Hsd17b4, and increased Cyp19a1 later in life). The predecessors of age-related changes noted in LCs from 6 to 12-month-old rats were increased level of soluble adenylate cyclase (Adcy/AC) 10, increased JNK phosphorylation but suppressed P38 MAPK. At approximately the same time changed mRNA abundance for transcription factors important for steroidogenesis was detected (increased Nur77 and decreased Sf1, Dax1). Aging caused biphasic expression pattern of ERK1/2 and Nur77: increased in 12-month but decreased in LCs from 24-month-old rats. Further, decreased basal cAMP level observed from 12 to 24th month coincidence with increased expression of cAMP-specific phosphodiesterase (Pde)4a, Pde4b and regulatory subunit of protein kinase A (Prkar/PKAR). Exposing of senescent LCs to permeable cAMP-analog improved transcription of Sf1, Nur77, Star, Cyp11a1,Cyp17a1, but without effect on aging pattern of Dax1, Pde4a/b, Prkar2a, Lhr and MAPK genes. Collectively, results indicated that age-related LC dysfunction is accompanied with changes in MAPK and cAMP signaling and coordinated reduction in the expression of many of the genes that participate in T synthesis. The predecessors of aged-related changes are increased ratio of pJNK/JNK, AC10 and decreased P38 level in LCs from 6-month-old rats.

Mitochondrial and sex steroid hormone crosstalk during aging

Decline in circulating sex steroid hormones accompanies several age-associated pathologies which may influence human healthspan. Mitochondria play important roles in biosynthesis of sex steroid hormones, and these hormones can also regulate mitochondrial function. Understanding the cross talk between mitochondria and sex steroid hormones may provide insights into the pathologies associated with aging. The aim of this review is to summarize the current knowledge regarding the interplay between mitochondria and sex steroid hormones during the aging process. The review describes the effect of mitochondria on sex steroid hormone production in the gonads, and then enumerates the contribution of sex steroid hormones on mitochondrial function in hormone responsive cells. Decline in sex steroid hormones and accumulation of mitochondrial damage may create a positive feedback loop that contributes to the progressive degeneration in tissue function during aging. The review further speculates whether regulation between mitochondrial function and sex steroid hormone action can potentially influence healthspan.

The opposing roles of nitric oxide and cGMP in the age-associated decline in rat testicular steroidogenesis

The molecular mechanism of the aging-associated dysfunction of Leydig cells (LCs) is complex and poorly understood. In this study, we analyzed the contribution of nitric oxide (NO) and cGMP signaling to the age-dependent decline in LC function. Significant (>50%) decreases in serum, intratesticular, and LC androgens in aging rats (15-24 months) were accompanied by a proportional increase in NO production, an up-regulation of cGMP levels, and the expression of soluble guanylyl cyclase-1B and protein kinase G1 in LCs. In contrast, LC cAMP levels decreased with age, most likely reflecting the up-regulation of cAMP-specific phosphodiesterase expression. Moreover, the expression of genes encoding enzymes responsible for cholesterol transport and its conversion to T were reduced. Exposing LCs from aged animals to NO further increased cGMP levels and decreased cAMP and androgen production, whereas the addition of cell-permeable 8-bromoguanosine-cGMP alone had the opposite effect. In vivo inhibition of cGMP-specific phosphodiesterase-5 for 3 and 6 months in aged rats led to a partial restoration of androgens, NO, and cyclic nucleotide levels, as well as the expression of steroidogenic and NO/cGMP signaling genes. These results indicate that a progressive increase in NO production contributes to the age-dependent decrease in steroidogenesis in a cGMP-independent manner, whereas the sustained elevation in cGMP levels significantly slows the decline in LC function.