Bacterial endotoxin lipopolysaccharide and reactive oxygen species inhibit Leydig cell steroidogenesis via perturbation of mitochondria

Gut Endotoxin Leading to a Decline IN Gonadal function (GELDING) - a novel theory for the development of late onset hypogonadism in obese men

Obesity is an increasing public health problem, with two-thirds of the adult population in many Western countries now being either overweight or obese. Male obesity is associated with late onset hypogonadism, a condition characterised by decreased serum testosterone, sperm quality plus diminished fertility and quality of life. In this paper we propose a novel theory underlying the development of obesity related hypogonadism- the GELDING theory (Gut Endotoxin Leading to a Decline IN Gonadal function). Several observational studies have previously reported an association between obesity related hypogonadism (low testosterone) and systemic inflammation. However, for the first time we postulate that the trans-mucosal passage of bacterial lipopolysaccharide (LPS) from the gut lumen into the circulation is a key inflammatory trigger underlying male hypogonadism. Obesity and a high fat/high calorie diet are both reported to result in changes to gut bacteria and intestinal wall permeability, leading to the passage of bacterial endotoxin (lipopolysaccharide- LPS) from within the gut lumen into the circulation (metabolic endotoxaemia), where it initiates systemic inflammation. Endotoxin is known to reduce testosterone production by the testis, both by direct inhibition of Leydig cell steroidogenic pathways and indirectly by reducing pituitary LH drive, thereby also leading to a decline in sperm production. In this paper we also highlight the novel evolutionary benefits of the GELDING theory. Testosterone is known to be a powerful immune-suppressive, decreasing a man's ability to fight infection. Therefore we postulate that the male reproductive axis has evolved the capacity to lower testosterone production during times of infection and resulting endotoxin exposure, decreasing the immunosuppressive influence of testosterone, in turn enhancing the ability to fight infection. While this response is adaptive in times of sepsis, it becomes maladaptive in the setting of "non-infectious" obesity related metabolic endotoxaemia.

Sirtuin 4 Regulates Lipopolysaccharide Mediated Leydig Cell Dysfunction

Bacterial lipopolysaccharide (LPS) is the most important contributing factor in pathogenesis of bacterial infection in male accessory glands; and it has shown to inhibit testicular steroidogenesis and induce apoptosis. The present study demonstrates that LPS causes mitochondrial dysfunction via suppression of sirtuin 4 (SIRT4); which in turn affects Leydig cell function by modulating steroidogenesis and apoptosis. LC-540 Leydig cells treated with LPS (10 µg/ml) showed impaired steroidogenesis and increased cellular apoptosis. The mRNA and protein expression of SIRT4 were decreased in LPS treated cells when compared to controls. The obtained data suggest that the c-Jun N-terminal kinase (JNK) activation suppresses SIRT4 expression in LPS treated Leydig cells. Furthermore, the overexpression of SIRT4 prevented LPS induced impaired steroidogenesis and cellular apoptosis by improving mitochondrial function. These findings provide valuable information that SIRT4 regulates LPS mediated Leydig cell dysfunction.

Obesity-induced down-regulation of the mitochondrial translocator protein (TSPO) impairs placental steroid production

CONTEXT

Low concentrations of estradiol and progesterone are hallmarks of adverse pregnancy outcomes as is maternal obesity. During pregnancy, placental cholesterol is the sole source of sex steroids. Cholesterol trafficking is the limiting step in sex steroid biosynthesis and is mainly mediated by the translocator protein (TSPO), present in the mitochondrial outer membrane.

OBJECTIVE

The objective of the study was to investigate the effects of maternal obesity in placental sex steroid biosynthesis and TSPO regulation.

DESIGN/PARTICIPANTS

One hundred forty-four obese (body mass index 30-35 kg/m(2)) and 90 lean (body mass index 19-25 kg/m(2)) pregnant women (OP and LP, respectively) recruited at scheduled term cesarean delivery. Placenta and maternal blood were collected.

SETTING

This study was conducted at MetroHealth Medical Center (Cleveland, Ohio).

MAIN OUTCOME MEASURES

Maternal metabolic components (fasting glucose, insulin, leptin, estradiol, progesterone, and total cholesterol) and placental weight were measured. Placenta (mitochondria and membranes separated) and cord blood cholesterol values were verified. The expression and regulation of TSPO and mitochondrial function were analyzed.

RESULTS

Plasma estradiol and progesterone concentrations were significantly lower (P < .04) in OP as compared with LP women. Maternal and cord plasma cholesterol were not different between groups. Placental citrate synthase activity and mitochondrial DNA, markers of mitochondrial density, were unchanged, but the mitochondrial cholesterol concentrations were 40% lower in the placenta of OP. TSPO gene and protein expressions were decreased 2-fold in the placenta of OP. In vitro trophoblast activation of the innate immune pathways with lipopolysaccharide and long-chain saturated fatty acids reduced TSPO expression by 2- to 3-fold (P < .05).

CONCLUSION

These data indicate that obesity in pregnancy impairs mitochondrial steroidogenic function through the negative regulation of mitochondrial TSPO.

The Role of the Immune Response in Chlamydia trachomatis Infection of the Male Genital Tract: A Double-Edged Sword

Chlamydia trachomatis (CT) is the most prevalent bacterial sexually transmitted infection in the world, with more than 100 million cases reported annually. While there have been extensive studies into the adverse effects that CT infection has on the female genital tract, and on the subsequent ability of these women to conceive, studies into the consequences on male fertility have been limited and controversial. This is in part due to the asymptomatic nature of the infection, where it is estimated that 50% of men with Chlamydia fail to show any symptoms. It is accepted, however, that acute and/or persistent CT infection is the causative agent for conditions such as urethritis, epididymitis, epididymo-orchitis, and potentially prostatitis. As with most infections, the immune system plays a fundamental role in the body’s attempts to eradicate the infection. The first and most important immune response to Chlamydia infection is a local one, whereby immune cells such as leukocytes are recruited to the site of infections, and subsequently secrete pro-inflammatory cytokines and chemokines such as interferon gamma. Immune cells also work to initiate and potentiate chronic inflammation through the production of reactive oxygen species (ROS), and the release of molecules with degradative properties including defensins, elastase, collagenase, cathespins, and lysozyme. This long-term inflammation can lead to cell proliferation (a possible precursor to cancer), tissue remodeling, and scarring, as well as being linked to the onset of autoimmune responses in genetically disposed individuals. This review will focus on the ability of the immune system to recognize and clear acute and persistent chlamydial infections in the male genital tract, and on the paradoxical damage that chronic inflammation resulting from the infection can cause on the reproductive health of the individual.

Role of poly(ADP-ribose) polymerases in male reproduction

Poly(ADP-ribose) polymerases (PARPs) are a family of enzymes involved in a wide variety of biological processes, including DNA repair and maintenance of genomic stability following genotoxic stress, and regulates the expression of various proteins at the transcriptional level as well as replication and differentiation. However, excessive activation of PARP has been shown to contribute to the pathogenesis of several diseases associated with oxidative stress (OS), which has been known to play a fundamental role in the etiology of male infertility. Based on the degree and type of the stress stimulus, PARP directs cells to specific fates (such as, DNA repair vs. cell death). A large volume of accumulated evidence indicates the presence of PARP and its homologs in testicular germ line cells and its activity may offer a key mechanism for keeping DNA integrity in spermatogenesis. On the other hand, a possible role of PARP overactivation in OS-induced male reproductive disorders and in human sperm is gaining significance in recent years. In this review, we focus on the findings about the importance of PARP-1 and PARP-2 in male reproduction and possible involvement of PARP overactivation in various clinical conditions associated with male infertility.

The Effects of Hydroalcoholic Extract of Apium graveolens Leaf on the Number of Sexual Cells and Testicular Structure in Rat

Background:

Use of medicinal plants with high antioxidant properties could be effective to increase fertility and improvement of disorders such as hormonal imbalance, impotency, oligospermia and immotile sperm. Celery (Apium graveolens) is rich in antioxidant agents. The leaf and stems of celery contain phenols, furanocoumarin and luteolin. Apigenin is one of the main flavonoids of celery leaf.

Objectives:

This study aimed to investigate the effects of hydroalcoholic extract of celery on histological properties of testis and number of sexual cells in male rats.

Materials and Methods:

Thirty-two male Wistar rats were divided into four groups of eight rats each. Control, did not receive any medication; sham, received normal saline; and two groups received celery extract orally in dosages of 100 and 200 mg/kg/BW once every two days for 60 days. At the end, animals were anesthetized, and caudal part of the right epididymis was used for sperm counting. After fixation of testis, tissue sections were prepared and studied microscopically to evaluate morphometric (lumen diameter, number of primary spermatocyte and sertoli cell) and histological changes. Data was analyzed by one-way ANOVA test using SPSS15 software. P < 0.05 was considered as statistically significant.

Results:

There was a significant increase in the number of sperms, sertoli cells, and primary spermatocyte (P < 0.05) in groups receiving extract; however, structural changes were not observed in the groups.

Conclusions:

It seems that celery increases spermatogenesis in male rats, but has no destructive effects on testicular tissue.

Chronic alcohol administration causes expression of calprotectin and RAGE altering the distribution of zinc ions in mouse testis

Several studies reported that chronic alcohol consumption alters the intestinal mucosa barrier, and subsequent entrance of endotoxins into the bloodstream. In many tissues endotoxin exposure causes the expression of calprotectin (CP) and the receptor for advanced glycation -end products (RAGE). In this study we investigated whether chronic alcohol administration causes expression of CP and RAGE in mouse testis. The distribution of free and loosely bound Zn(2+) (FLB-Zn(2+)) in the testicular tissues was also evaluated. Alcohol-induced testicular damage was documented by measuring testosterone blood levels and by light and electron microscope studies. Twenty mice were treated daily for three weeks with 3.0 g/kg of a 25% solution of alcohol. Ten mice were treated in the same period of time with a solution of maltose dextrins, isocaloric to alcohol. Twenty untreated mice were used as controls. Alcohol treated mice showed diffuse expression of CP and RAGE in the interstitial cells. RAGE was found also in the basal compartment of the seminiferous tubules. Depletion of FLB-Zn(2+) was observed in the adluminal compartment of the seminiferous tubules. Expression of CP and RAGE was not found in control mice and maltose dextrin treated mice. Our results indicated novel mechanisms by which alcohol acts in testis. Indeed, CP and RAGE may cause the generation of oxidants and inflammatory mediators, with negative impact on testicular functions. Depletion of FLB-Zn(2+) may contribute to the dysregulation of spermatogenesis.

Effect of chocolate and Propolfenol on rabbit spermatogenesis and sperm quality following bacterial lipopolysaccharide treatment

The aims of the study were to evaluate the effects of chocolate and propolis-enriched diets on rabbit spermatogenesis, sperm motility, and ultrastructure following bacterial lipopolysaccharide (LPS) treatment. Thirty-two New Zealand White rabbits were divided into four groups. The LPS-Propolfenol(®) group received propolis (500 mg/kg/day) in their diet for 15 days, while the LPS-chocolate group was fed 70% cacao chocolate (1 g/1 kg/day) for the same period. Following the diet treatments, rabbits in the LPS-Propolfenol(®) and LPS-chocolate groups, and an LPS group received a single intraperitoneal dose of 50 μg/kg LPS, and the control group received only saline. Kinematic sperm traits were evaluated with a computer assisted sperm analyzer (CASA) system, and ultrastructural characteristics were examined by transmission electron microscopy (TEM). Testicular and epididymal tissues were observed by light microscopy and TEM and multiplex real time reverse transcriptase-polymerase chain reaction (RT-PCR) assay was used to detect and quantify toll-like receptor-4 (TLR-4) gene expression. The values of the analyzed semen parameters of rabbits treated with LPS-Propolfenol(®) and LPS-chocolate did not show any variations compared with the control group, but they were lower in rabbits treated only with LPS. Alterations observed in the testicular tissue of LPS treated-rabbits were not detected in specimens from the LPS-chocolate and LPS-Propolfenol(®) groups, which showed normal spermatogenesis. The TLR-4 mRNA expression was similar in controls, in LPS treated, and in LPS-chocolate groups, but it was significantly (p < 0.01) decreased in LPS-Propolfenol(®) rabbits. In conclusion, a chocolate and propolis-enriched diet showed a protective effect on the spermatogenetic process of buck rabbits following LPS treatment.

Raloxifene activates G protein-coupled estrogen receptor 1/Akt signaling to protect dopamine neurons in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mice

Raloxifene, used in the clinic, is reported to protect brain dopaminergic neurons in mice. Raloxifene was shown to mediate an effect through the G protein-coupled estrogen receptor 1 (GPER1). We investigated if raloxifene neuroprotective effect in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated male mice is mediated through GPER1 by using its antagonist G15. Striatal concentrations of dopamine, 3,4-dihydroxyphenylacetic acid, homovanillic acid to dopamine ratio as well as dopamine transporter and vesicular monoamine transporter 2 showed that raloxifene neuroprotection of dopaminergic neurons was blocked by G15. Protection by raloxifene was accompanied by activation of striatal Akt signaling (but not ERK1/2 signaling) and increased Bcl-2 and brain-derived neurotrophic factor levels; these effects were abolished by coadministration with G15. The effect of raloxifene was not mediated through increased levels of 17β-estradiol. MPTP mice had decreased plasma testosterone, dihydrotestosterone, and 3β-diol levels; this was prevented in raloxifene-treated MPTP mice. Our results suggest that raloxifene acted through GPER1 to mediate Akt activation, increase Bcl-2 and brain-derived neurotrophic factor levels, and protection of dopaminergic neurons and plasma androgens.

Bacterial lipopolysaccharide differently modulates steroidogenic enzymes gene expressions in the brain and testis in rats

Bacterial lipopolysaccharide (LPS) is a major component of the cell wall of gram negative bacteria contributing to the pathogenesis of bacterial infection, in particular in those diseases affecting central nervous system and reproductive tissues. The present work is an attempt to study the regulation of steroidogenic enzymes gene expression in the brain and testis in LPS induced rats. Adult male albino rats were administered LPS (5mg/kg BW) to induce acute inflammation. LPS administration induced severe oxidative damage in the brain and testicular tissue which was evident from decreased activities of enzymic antioxidants and increased lipid peroxidation levels. The mRNA expression of 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD) and androgen receptor corepressor-19kDa (ARR19) in the brain and testis were determined. The mRNA expression of 3β-HSD and 17β-HSD was increased in the brain with significant decrease in the testis at 24h and 48h in LPS treated animals. The results also demonstrated an interesting finding that LPS treatment completely represses ARR19 in the brain, while not in the testis. These findings show ARR19 might play a crucial role in regulation of neuronal and testicular steroidogenesis in inflammatory diseases.

Accelerated aging of reproductive capacity in male rat offspring of protein-restricted mothers is associated with increased testicular and sperm oxidative stress

Maternal protein restriction (MPR) in pregnancy causes life course organ dysfunction, but few studies link the developmental origins of disease hypothesis to early aging. Suboptimal developmental nutrition increases oxidative stress (OS) and male infertility, damaging sperm function. We hypothesized that MPR in pregnancy accelerates age-related changes in testicular and sperm function related to both maternal diet and increased testicular OS in rat offspring. We studied male rats whose pregnant mothers ate either control (C, 20 % casein) or restricted (R, 10 % casein) isocaloric diet. After birth, mothers and offspring ate C diet. Testes were retrieved at 19 days gestation and across the life course (postnatal day (PND) 21, 36, 110, and 850) to measure OS markers, antioxidant enzymes, serum FSH, LH, and testosterone, and PND 110 sperm OS and quality. Fertility rate was evaluated at PND 110, 450, and 850. Offspring showed age- and MPR-related changes in testosterone, testicular OS markers and antioxidant enzymes and fertility, and maternal diet-related OS and sperm antioxidant enzyme changes. Developmental programming is considered a key factor in predisposing to chronic disease. Our data show that programming also plays an important role in aging trajectory. This interaction is a little studied area in aging biology that merits more investigation.

Structural and functional integrity of spermatozoa is compromised as a consequence of acute uropathogenic E. coli-associated epididymitis

Uropathogenic Escherichia coli (UPEC)-associated epididymitis is commonly diagnosed in outpatient settings. Although the infection can be successfully cleared using antimicrobial medications, 40% of patients unexplainably show persistent impaired semen parameters even after treatment. Our aim was to investigate whether pathogenic UPEC and its associated virulence factor hemolysin (hlyA) perturb the structural and functional integrity of both the epididymis and sperm, actions that may be responsible for the observed impairment and possibly a reduction of fertilization capabilities. Semen collected from patients diagnosed with E. coli-only related epididymitis showed that sperm counts were low 14 days postantimicrobial treatment regardless of hlyA status. At Day 84 following treatment, hlyA production correlated with approximately 4-fold lower sperm concentrations than in men with hlyA-negative strains. In vivo experiments with the hlyA-producing UPEC CFT073 strain in a murine epididymitis model showed that just 3 days postinfection, structural damage to the epididymis (epithelial damage, leukocyte infiltration, and edema formation) was present. This was more severe in UPEC CFT073 compared to nonpathogenic E. coli (NPEC 470) infection. Moreover, pathogenic UPEC strains prematurely activated the acrosome in vivo and in vitro. Raman microspectroscopy revealed that UPEC CFT073 undermined sperm integrity by inducing nuclear DNA damage. Consistent with these observations, the in vitro fertilization capability of hlyA-treated mouse sperm was completely abolished, although sperm were motile. These findings provide new insights into understanding the possible processes underlying clinical manifestations of acute epididymitis.

Intermedin attenuates LPS-induced inflammation in the rat testis

First reported as a vasoactive peptide in the cardiovascular system, intermedin (IMD), also known as adrenomedullin 2 (ADM2), is a hormone with multiple potent roles, including its antioxidant action on the pulmonary, central nervous, cardiovascular and renal systems. Though IMD may play certain roles in trophoblast cell invasion, early embryonic development and cumulus cell-oocyte interaction, the role of IMD in the male reproductive system has yet to be investigated. This paper reports our findings on the gene expression of IMD, its receptor components and its protein localization in the testes. In a rat model, bacterial lippolysaccharide (LPS) induced atypical orchitis, and LPS treatment upregulated the expression of IMD and one of its receptor component proteins, i.e. receptor activity modifying protein 2 (RAMP2). IMD decreased both plasma and testicular levels of reactive oxygen species (ROS) production, attenuated the increase in the gene expression of the proinflammatory cytokines tumor necrosis factor alpha (TNFα), interleukin 6 (IL6) and interleukin 1 beta (IL1β), rescued spermatogenesis, and prevented the decrease in plasma testosterone levels caused by LPS. The restorative effect of IMD on steroidogenesis was also observed in hydrogen peroxide-treated rat primary Leydig cells culture. Our results indicate IMD plays an important protective role in spermatogenesis and steroidogenesis, suggesting therapeutic potential for IMD in pathological conditions such as orchitis.

Diagnosis and management for urosepsis

Urosepsis is defined as sepsis caused by a urogenital tract infection. Urosepsis in adults comprises approximately 25% of all sepsis cases, and is in most cases due to complicated urinary tract infections. The urinary tract is the infection site of severe sepsis or septic shock in approximately 10-30% of cases. Severe sepsis and septic shock is a critical situation, with a reported mortality rate nowadays still ranging from 30% to 40%. Urosepsis is mainly a result of obstructed uropathy of the upper urinary tract, with ureterolithiasis being the most common cause. The complex pathogenesis of sepsis is initiated when pathogen or damage-associated molecular patterns recognized by pattern recognition receptors of the host innate immune system generate pro-inflammatory cytokines. A transition from the innate to the adaptive immune system follows until a T(H2) anti-inflammatory response takes over, leading to immunosuppression. Treatment of urosepsis comprises four major aspects: (i) early diagnosis; (ii) early goal-directed therapy including optimal pharmacodynamic exposure to antimicrobials both in the plasma and in the urinary tract; (iii) identification and control of the complicating factor in the urinary tract; and (iv) specific sepsis therapy. Early adequate tissue oxygenation, adequate initial antibiotic therapy, and rapid identification and control of the septic focus in the urinary tract are critical steps in the successful management of a patient with urosepsis, which includes early imaging, and an optimal interdisciplinary approach encompassing emergency unit, urological and intensive-care medicine specialists.

hCG-induced endoplasmic reticulum stress triggers apoptosis and reduces steroidogenic enzyme expression through activating transcription factor 6 in Leydig cells of the testis

Endoplasmic reticulum (ER) stress generally occurs in secretory cell types. It has been reported that Leydig cells, which produce testosterone in response to human chorionic gonadotropin (hCG), express key steroidogenic enzymes for the regulation of testosterone synthesis. In this study, we analyzed whether hCG induces ER stress via three unfolded protein response (UPR) pathways in mouse Leydig tumor (mLTC-1) cells and the testis. Treatment with hCG induced ER stress in mLTC-1 cells via the ATF6, IRE1a/XBP1, and eIF2α/GADD34/ATF4 UPR pathways, and transient expression of 50 kDa protein activating transcription factor 6 (p50ATF6) reduced the expression level of steroidogenic 3β-hydroxysteroid dehydrogenase Δ5-Δ4-isomerase (3β-HSD) enzyme. In an in vivo model, high-level hCG treatment induced expression of p50ATF6 while that of steroidogenic enzymes, especially 3β-HSD, 17α-hydroxylase/C17-20 lyase (CYP17), and 17β-hydrozysteroid dehydrogenase (17β-HSD), was reduced. Expression levels of steroidogenic enzymes were restored by the ER stress inhibitor tauroursodeoxycholic acid (TUDCA). Furthermore, lentivirus-mediated transient expression of p50ATF6 reduced the expression level of 3β-HSD in the testis. Protein expression levels of phospho-JNK, CHOP, and cleaved caspases-12 and -3 as markers of ER stress-mediated apoptosis markedly increased in response to high-level hCG treatment in mLTC-1 cells and the testis. Based on transmission electron microscopy and H&E staining of the testis, it was shown that abnormal ER morphology and destruction of testicular histology induced by high-level hCG treatment were reversed by the addition of TUDCA. These findings suggest that hCG-induced ER stress plays important roles in steroidogenic enzyme expression via modulation of the ATF6 pathway as well as ER stress-mediated apoptosis in Leydig cells.

Mitochondrial (dys)function and regulation of macrophage cholesterol efflux

Cholesterol trafficking from the outer to the cholesterol-poor inner mitochondrial membrane requires energized, polarized and actively respiring mitochondria, mediated by a highly regulated multimeric (140-200 kDa) protein complex comprising StAR (steroidogenic acute regulatory protein), mitochondrial TSPO (translocator protein), VDAC (voltage-dependent anion channel), ANT (adenine nucleotide transporter) and associated regulatory proteins. Mitochondrial cholesterol transport is rate-limiting in the CYP27A1 (sterol 27-hydroxylase)-dependent generation of oxysterol ligands for LXR (liver X receptor) transcription factors that regulate the expression of genes encoding proteins in the cholesterol efflux pathway, such as ABC transporters (ATP-binding cassette transporters) ABCA1 and ABCG1. These transporters transfer cholesterol and/or phospholipids across the plasma membrane to (apo)lipoprotein acceptors, generating nascent HDLs (high-density lipoproteins), which can safely transport excess cholesterol through the bloodstream to the liver for excretion in bile. Utilizing information from steroidogenic tissues, we propose that perturbations in mitochondrial function may reduce the efficiency of the cholesterol efflux pathway, favouring accumulation of cholesteryl ester 'foam cells' and allowing the toxic accumulation of free cholesterol at the interface between the endoplasmic reticulum and the mitochondrial membrane. In turn, this will trigger opening of the permeability transition pore, allowing unregulated production of oxysterols via CYP27A1, allowing the accumulation of esterified forms of this oxysterol within human atherosclerotic lesions. Defective cholesterol efflux also induces endoplasmic reticulum stress, proteasomal degradation of ABCA1 and Fas-dependent apoptosis, replicating findings in macrophages in advanced atherosclerotic lesions. Small molecules targeted to mitochondria, capable of sustaining mitochondrial function or improving cholesterol trafficking may aid cholesterol efflux from macrophage 'foam' cells, regressing and stabilizing the atherosclerotic plaque.

Anabolic-androgenic steroids induce apoptosis and NOS2 (nitric-oxide synthase 2) in adult rat Leydig cells following in vivo exposure

Anabolic-androgenic steroids (AAS) are synthetic derivatives of testosterone (T) predominantly taken as drugs of abuse. Using in vivo treatment of adult male rats we investigated the effects of testosterone enanthate (TE) a widely abused AAS, on apoptosis of Leydig cells. Increased T and decreased luteinizing hormone levels in serum and decreased intra-testicular T values were found in 2 and 10 weeks treated groups. Two weeks of TE-treatment stimulated the expression of inducible nitric oxide synthase (NOS2) followed by increased NO production, decreased mitochondrial membrane potential and increased prevalence of Leydig cell apoptosis. This was prevented by in vivo administration of androgen receptor blocker. The induced NOS2 level and apoptosis returned to control levels after 10 weeks of TE-treatment but testes contained fewer Leydig cells. Overall, AAS in addition to reduced steroidogenesis induce transient increase of Leydig cells apoptotic rate through mechanism associated with androgen receptor, most likely involving NOS2 induction.

Toona sinensis Leaf Aqueous Extract Improves the Functions of Sperm and Testes via Regulating Testicular Proteins in Rats under Oxidative Stress

Toona sinensis leaf (TSL) is commonly used as a vegetable and in spice in Asia. In this study, feeding with aqueous extract of TSL (TSL-A) alleviated oxidative stress and recovered the motility and functions of sperm in rats under oxidative stress. Protein expressions in testes identified by proteomic analysis and verified by Western blot demonstrated that TSL-A not only downregulated the level of glutathione transferase mu6 (antioxidant system), heat shock protein 90 kDa-β (protein misfolding repairing system), cofilin 2 (spermatogenesis), and cyclophilin A (apoptosis) but also upregulated crease3-hydroxy-3-methylglutaryl-coenzyme A synthase 2 (steroidogenesis), heat shock glycoprotein 96, and pancreatic trypsin 1 (sperm-oocyte interaction). These results indicate that TSL-A promotes the functions of sperm and testes via regulating multiple testicular proteins in rats under oxidative stress, suggesting that TSL-A is a valuable functional food supplement to improve functions of sperm and testes for males under oxidative stress.

Cytoprotective effects of fruit pulp of Eugenia jambolana on H 2 O 2 -induced oxidative stress and apoptosis in rat Leydig cells in vitro

This study was undertaken to investigate the cytoprotective effect of the fruit pulp of Eugenia jambolana (50-250 μg ml(-1) ) against the damage induced by H 2 O 2 (100 μm) exposure to Leydig cells in vitro. Cell survival with extract was found comparable to similar effects by N-acetyl-l-cysteine. H 2 O 2 -induced rise in thiobarbituric acid reactive substance formation and decline in the activity and expression of antioxidant enzymes like superoxide dismutase, catalase and glutathione-s-transferase were effectively checked. Cellular glutathione and total antioxidant capacity demonstrated significant improvement. The increase in expression of inducible nitric oxide (NO) synthase leading to NO production was successfully countered. Co-treatment of the extract helped in the down-regulation of caspase-3 and poly-ADP-ribose polymerase resulting in a significant reduction in Leydig cell apoptosis induced by H 2 O 2 . Upstream marker proteins of extrinsic (caspase-8, Fas, FasL) and intrinsic (caspase-9) pathway of metazoan apoptosis were identically down-regulated. The Bcl-2 family of proteins, though, remained unaffected. The extract also positively modulated the other marker proteins like c-Jun NH 2 -terminal kinase, p38, Akt, nuclear factor-κB, c-Fos, cellular FLICE-inhibitory protein, cyclooxygenase-2 and p53. Taken together, the above-mentioned findings establish the anti-oxidative and anti-apoptotic potency of the extract that ameliorates the H 2 O 2 -induced adverse effects on rat Leydig cells in vitro.

Effects of di-(2-ethylhexyl) phthalate and four of its metabolites on steroidogenesis in MA-10 cells

Phthalate plasticizers are used in the plastics industry to aid in processing and impart flexibility to plastics. Due to the broad use of plastics, and the tendency of plasticizers to leach out of polymers, plasticizers have become ubiquitous in the environment. Concerns about the testicular toxicity of phthalate plasticizers, in particular di-(2-ethylhexyl) phthalate (DEHP), have arisen due to their ability to cause male reproductive tract abnormalities in animal models. It has been assumed that the DEHP metabolite, mono-(2-ethylhexyl) phthalate (MEHP), is the active compound, however, metabolites such as 2-ethylhexanol, 2-ethylhexanal and 2-ethylhexanoic acid, have not been thoroughly investigated. The aim of this study was to evaluate the anti-androgenic potential of these metabolites in vitro with a mouse Leydig tumor cell line, MA-10 cells. DEHP, MEHP and 2-ethylhexanal were found to decrease cell viability, as well as steroidogenic potential. The latter was assessed using an enzyme-linked immunosorbent assay (ELISA) to quantify steroid production and quantitative real-time polymerase chain reaction (qRT-PCR) to assess gene expression analysis of key steroidogenic enzymes. 2-Ethylhexanal proved to be the most potent steroidogenic disruptor, offering intriguing implications in the search for the mechanism of phthalate testicular toxicity. Overall, the study suggests the involvement of multiple active metabolites in the testicular toxicity of DEHP.

The female menstrual cycle does not influence testosterone concentrations in male partners

BACKGROUND

The time of ovulation has since long been believed to be concealed to male heterosexual partners. Recent studies have, however, called for revision of this notion. For example, male testosterone concentrations have been shown to increase in response to olfactory ovulation cues, which could be biologically relevant by increasing sexual drive and aggressiveness. However, this phenomenon has not previously been investigated in real-life human settings. We therefore thought it of interest to test the hypothesis that males' salivary testosterone concentrations are influenced by phases of their female partners' menstrual cycle; expecting a testosterone peak at ovulation.

METHODS

Thirty young, healthy, heterosexual couples were recruited. During the course of 30-40 days, the women registered menses and ovulation, while the men registered sexual activity, physical exercise, alcohol intake and illness (confounders), and obtained daily saliva samples for testosterone measurements. All data, including the registered confounders, were subjected to multiple regression analysis.

RESULTS

In contrast to the hypothesis, the ovulation did not affect the testosterone levels, and the resulting testosterone profile during the menstrual cycle was on the average flat. The specific main hypothesis, that male testosterone levels on the day of ovulation would be higher than day 4 of the cycle, was clearly contradicted by a type II error(β)-analysis (< 14.3% difference in normalized testosterone concentration; β = 0.05).

CONCLUSIONS

Even though an ovulation-related salivary testosterone peak was observed in individual cases, no significant effect was found on a group level.

Low-dose testosterone treatment decreases oxidative damage in TM3 Leydig cells

Testosterone replacement therapy has benefits for aging men and those with hypogonadism. However, the effects of exogenous testosterone on Leydig cells are still unclear and need to be clarified. In this report, we demonstrate that testosterone supplementation can reduce oxidative damage in Leydig cells. The TM3 Leydig cell line was used as an in vitro cell model in this study. Cytoprotective effects were identified with 100-nmol l⁻¹ testosterone treatment, but cytotoxic effects were found with ≥ 500-nmol l⁻¹ testosterone supplementation. Significantly reduced reactive oxygen species (ROS) generation, lipid peroxide contents and hypoxia induction factor (HIF)-1α stabilization and activation were found with 100-nmol l⁻¹ testosterone treatment. There was a 1.72-fold increase in ROS generation in the 500-nmol l⁻¹ compared to the 100-nmol l⁻¹ testosterone treatment. A 1.58-fold increase in steroidogenic acute regulatory protein (StAR) expression was found in 50-nmol l⁻¹ testosterone-treated cells (P < 0.01). Chemically induced hypoxia was attenuated by testosterone supplementation. Leydig cells treated with low-dose testosterone supplementation showed cytoprotection by decreasing ROS and lipid peroxides, increasing StAR expression and relieving hypoxia stress as demonstrated by HIF-1α stabilization. Increased oxidative damage was found with ≥ 500-nmol l⁻¹ testosterone manipulation. The mechanism governing the differential dose effects of testosterone on Leydig cells needs further investigation in order to shed light on testosterone replacement therapy.

Toxic effects of lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on development of male reproductive system: involvement of antioxidants, oxidants, and p53 protein

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent endocrine disruptor compound and induces multiple organ dysfunctions. The effect of TCDD exposure both in adults and in utero has been well established. However, little is known about the effects of TCDD acquired through mother's milk on the development of the male reproductive system. The aim of this study was to investigate the effects and mechanisms of TCDD from lactational exposure. TCDD (1 microg/kg) was administered to C57BL/6 mouse mothers for 4 days from the day of delivery. On postnatal day 30 (PND 30) and postnatal day 60 (PND 60), body weight, body length, and anogenital distance (AGD) of male offspring were measured. The weights of the testes and epididymides were also measured. Epididymides were used for sperm counts, and testes were used to measure the activity of antioxidant enzymes (SOD, CAT, GPX, GR), the parameters of oxidative stress (hydrogen peroxide, MDA), and testosterone. In addition, expression of p53 and the proapoptotic protein, Bax, were analyzed by Western blot. TCDD exposure decreased body weight, body length, and AGD in both PND 30 and PND 60 groups compared with the control group. The activity of all antioxidant enzymes at PND 60 was decreased after TCDD treatment. TCDD treatment decreased testicular testosterone levels in both the PND 30 and PND 60 groups. The expression of p53 and Bax were also upregulated by TCDD and did not return to normal levels by PND 60. These data suggest that TCDD affects development of male offspring when the mother is exposed to TCDD during lactation. In addition, oxidative stress is a major mediator of TCDD-induced adverse effects, and p53 may play an important role in this mechanism.

Leydig cells: From stem cells to aging

Leydig cells are the testosterone-producing cells of the testis. The adult Leydig cell population ultimately develops from undifferentiated mesenchymal-like stem cells present in the interstitial compartment of the neonatal testis. Four distinct stages of adult Leydig cell development have been identified and characterized: stem Leydig cells, progenitor Leydig cells, immature Leydig cells and adult Leydig cells. The stem Leydig cells are undifferentiated cells that are capable of indefinite self-renewal, differentiation, and replenishment of the Leydig cell niche. Progenitor Leydig cells are derived from the stem Leydig cells. These spindle-shaped cells are luteinizing hormone (LH) receptor positive, have high mitotic activity, and produce little testosterone but rather testosterone metabolites. The progenitor Leydig cells give rise to immature Leydig cells which are round, contain large amounts of smooth endoplasmic reticulum, and produce some testosterone but also very high levels of testosterone metabolites. A single division of these cells produces adult Leydig cells, which are terminally differentiated cells that produce high levels of testosterone. As men age, serum testosterone levels decline, and this is associated with alterations in body composition, energy level, muscle strength, physical, sexual and cognitive functions, and mood. In the Brown Norway rat, used extensively as a model for male reproductive aging, age-related reductions in serum testosterone result from significant decline in the ability of aged Leydig cells to produce testosterone in response to LH stimulation. This review describes Leydig cell development and aging. Additionally, the molecular mechanisms by which testosterone synthesis declines with aging are discussed.

Neonatal lipopolysaccharide exposure attenuates the homotypic stress-induced suppression of LH secretion in adulthood in male rat

Neonatal immune challenges have a long-lasting influence on immune response. Using male Sprague-Dawley rats, we examined whether neonatal lipopolysaccharide (LPS) challenge alters the sensitivity of male reproductive function to adult LPS challenge and at which level (central or testes) the alteration occurs. We also examined the mRNA expression of proinflammatory cytokines in the hypothalamus and testes because they have a pivotal role in immune stress-induced suppression of gonadotropin secretion and testosterone synthesis. On day 10 after birth, all the pups were injected with LPS (100 microg/kg, i.p.) or saline. Thereafter, LPS (100 microg/kg, i.p.) or saline was injected in adulthood at 8 weeks of age. The serum LH concentration was decreased by LPS injection during adulthood in the neonatal saline-injected rats. This suppressive effect was not seen in the neonatal LPS-injected rats. The serum testosterone concentration was decreased by adult LPS injection in both the neonatal LPS-injected and neonatal saline-injected rats. The expression levels of KiSS-1, which encodes kisspeptin, known to have a crucial role in the regulation of gonadotropin secretion, and GnRH mRNA in the hypothalamus and LHbeta mRNA in the pituitary were not influenced by neonatal or adult LPS injection. On the other hand, the expression levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) mRNA in the hypothalamus and testes were increased by adult LPS injection in both the neonatal LPS-injected and neonatal saline-injected rats. Furthermore, the expression levels of these factors in the hypothalamus after adult LPS injection were significantly lower in the neonatal LPS-injected rats than in the neonatal saline-injected rats. These findings indicate that neonatal LPS challenge reduces the sensitivity of male reproductive function to the suppressive effects of LPS, mainly at the central level. Attenuation of proinflammatory cytokine synthesis in the hypothalamus might be involved in this alteration.

Lipopolysaccharide modulation of thyrotropin-releasing hormone (TRH) and TRH-like peptide levels in rat brain and endocrine organs

Lipopolysaccharide (LPS) is a proinflammatory and depressogenic agent whereas thyrotropin-releasing hormone (TRH; pGlu-His-Pro-NH2) is an endogenous antidepressant and neuroprotective peptide. LPS and TRH also have opposing effects on K+ channel conductivity. We hypothesized that LPS can modulate the expression and release of not only TRH but also TRH-like peptides with the general structure pGlu-X-Pro-NH2, where "X" can be any amino acid residue. The response might be "homeostatic," that is, LPS might increase TRH and TRH-like peptide release, thereby moderating the cell damaging effects of this bacterial cell wall constituent. On the other hand, LPS might impair the synthesis and release of these neuropeptides, thus facilitating the induction of early response genes, cytokines, and other downstream biochemical changes that contribute to the "sickness syndrome." Sprague-Dawley rats (300 g) received a single intraperitoneal injection of 100 microg/kg LPS. Animals were then decapitated 0, 2, 4, 8, and 24 h later. Serum cytokines and corticosterone peaked 2 h after intraperitoneal LPS along with a transient decrease in serum T3. TRH and TRH-like peptides were measured by a combination of high-performance liquid chromatography and radioimmunoassay. TRH declined in the nucleus accumbens and amygdala in a manner consistent with LPS-accelerated release and degradation. Various TRH-like peptide levels increased at 2 h in the anterior cingulate, hippocampus, striatum, entorhinal cortex, posterior cingulate, and cerebellum, indicating decreased release and clearance of these peptides. These brain regions are part of a neuroimmunomodulatory system that coordinates the behavioral, endocrine, and immune responses to the stresses of sickness, injury, and danger. A sustained rise in TRH levels in pancreatic beta-cells accompanied LPS-impaired insulin secretion. TRH and Leu-TRH in prostate and TRH in epididymis remained elevated 2-24 h after intraperitoneal LPS. We conclude that these endogenous neuroprotective and antidepressant-like peptides both mediate and moderate some of the behavioral and toxic effects of LPS.

The steroidogenic acute regulatory protein as a target of endocrine disruption in male reproduction

Development of the adult male reproductive tract requires proper spatial-temporal expression of the sex hormones testosterone and estrogen during fetal developmental stages and at puberty. Exogenous agents that disrupt the production and/or actions of the testosterone and estrogen and cause aberrant reproductive tract development can be thought of as endocrine disruptors (ED). This review will focus on the impact of ED on testosterone production by Leydig cells during fetal development and in the adult. In particular, the genes encoding the steroidogenic acute regulatory protein (StAR) and cytochrome P450 17 alpha hydroxylase/17,20 lyase (CYP17A1) within the steroid hormone biosynthetic pathway are highlighted as ED targets. We begin with an overview of steroidogenesis and regulation of StAR then summarize the published literature on the effects of diethylstibesterol, phthalate esters, and arsenite on male reproduction with a focus on the expression and function of StAR.

Steroidogenic acute regulatory protein (StAR), a novel mitochondrial cholesterol transporter

Cholesterol is a vital component of cellular membranes, and is the substrate for biosynthesis of steroids, oxysterols and bile acids. The mechanisms directing the intracellular trafficking of this nearly insoluble molecule have received increased attention through the discovery of the steroidogenic acute regulatory protein (StAR) and similar proteins containing StAR-related lipid transfer (START) domains. StAR can transfer cholesterol between synthetic liposomes in vitro, an activity which appears to correspond to the trans-cytoplasmic transport of cholesterol to mitochondria. However, trans-cytoplasmic cholesterol transport in vivo appears to involve the recently-described protein StarD4, which is expressed in most cells. Steroidogenic cells must also move large amounts of cholesterol from the outer mitochondrial membrane to the first steroidogenic enzyme, which lies on the matrix side of the inner membrane; this action requires StAR. Congenital lipoid adrenal hyperplasia, a rare and severe disorder of human steroidogenesis, results from mutations in StAR, providing a StAR knockout of nature that has provided key insights into its activity. Cell biology experiments show that StAR moves large amounts of cholesterol from the outer to inner mitochondrial membrane, but acts exclusively on the outer membrane. Biophysical data show that only the carboxyl-terminal alpha-helix of StAR interacts with the outer membrane. Spectroscopic data and molecular dynamics simulations show that StAR's interactions with protonated phospholipid head groups on the outer mitochondrial membrane induce a conformational change (molten globule transition) needed for StAR's activity. StAR appears to act in concert with the peripheral benzodiazepine receptor, but the precise itinerary of a cholesterol molecule entering the mitochondrion remains unclear.

StAR Search—What We Know about How the Steroidogenic Acute Regulatory Protein Mediates Mitochondrial Cholesterol Import

Cholesterol is the starting point for biosynthesis of steroids, oxysterols and bile acids, and is also an essential component of cellular membranes. The mechanisms directing the intracellular trafficking of this insoluble molecule have received attention through the discovery of the steroidogenic acute regulatory protein (StAR) and related proteins containing StAR-related lipid transfer domains. Much of our understanding of the physiology of StAR derives from studies of congenital lipoid adrenal hyperplasia, which is caused by StAR mutations. Multiple lines of evidence show that StAR moves cholesterol from the outer to inner mitochondrial membrane, but acts exclusively on the outer membrane. The precise mechanism by which StAR's action on the outer mitochondrial membrane stimulates the flow of cholesterol to the inner membrane remains unclear. When StAR interacts with protonated phospholipid head groups on the outer mitochondrial membrane, it undergoes a conformational change (molten globule transition) that opens and closes StAR's cholesterol-binding pocket; this conformational change is required for cholesterol binding, which is required for StAR activity. The action of StAR probably requires interaction with the peripheral benzodiazepine receptor.

Members of the Toll-like receptor family of innate immunity pattern-recognition receptors are abundant in the male rat reproductive tract

Protecting developing and maturing spermatozoa and reproductive tissues from microbial damage is an emerging aspect of research in reproductive physiology. Bacterial, viral, and yeast infections of the testis and epididymis can hinder maturation and movement of spermatozoa, resulting in impaired fertility. Toll-like receptors (TLRs) are a broad family of innate immunity receptors that play critical roles in detecting and responding to invading pathogens. Objectives of this study were to determine if organs of the rat male reproductive tract express mRNAs for members of the TLR family, to characterize expression patterns for TLRs in different regions of the epididymis, and to determine if TLR adaptor and target proteins are present in the male reproductive tract. Messenger RNA for Tlr1-Tlr9 was abundantly expressed in testis, epididymis, and vas deferens, as determined by RT-PCR, while Tlr10 and Tlr11 were less abundantly expressed. Tlr mRNA expression showed no region-specific patterns in the epididymis. Immunoblot analysis revealed relatively equal levels of protein for TLRs 1, 2, 4, and 6 in testis, all regions of the epididymis and vas deferens, and lower levels of TLRs 3, 5, and 9-11. TLR7 was primarily detected in the testis. The TLR adapter proteins, myeloid differentiation primary response gene 88 and TLR adaptor molecule 1, as well as v-rel reticuloendotheliosis viral oncogene homolog and NFKBIA, were prominent in testis, epididymis, and vas deferens. The abundant expression of a majority of TLR family members together with expression of TLR adaptors and activation targets provides strong evidence that TLRs play important roles in innate immunity of the male reproductive tract.

Mechanism of StAR's regulation of mitochondrial cholesterol import

The steroidogenic acute regulatory protein (StAR) mediates the acute steroidogenic response by moving cholesterol from the outer to inner mitochondrial membrane, but the mechanism of StAR's action has remained mysterious. We showed that StAR acts on the outer membrane, requires cholesterol binding, and requires the structural change previously described as a pH-dependent molten globule. The current model is that StAR's interaction with protonated phospholipid head groups on the outer mitochondrial membrane induces a molten globule transition needed for StAR to take up cholesterol. Recent data suggest a functional interaction between StAR and the peripheral benzodiazepine receptor (PBR). Whereas many models have suggested that StAR delivers cholesterol to PBR, we suggest that StAR removes cholesterol from the cholesterol-binding domain of PBR and delivers it to the inner mitochondrial membrane.

Oxidant/antioxidant interactions of nicotine, Coenzyme Q10, Pycnogenol and phytoestrogens in oral periosteal fibroblasts and MG63 osteoblasts

BACKGROUND

There is a growing awareness that oxidative stress may play a role in periodontal disease. The aim of this investigation was to evaluate potential oxidant/antioxidant interactions of nicotine with antioxidants (Coenzyme Q10 (CoQ), Pycnogenol and phytoestrogens in a cell culture model.

METHODS

Duplicate incubations of human periosteal fibroblasts and osteoblasts were performed with 14C-testosterone as substrate, in the presence or absence of CoQ (20 microg/ml), Pycnogenol (150 microg/ml), and phytoestrogens (10 and 40 microg/ml), alone and in combination with nicotine (250 microg/ml). At the end of a 24-h incubation period, the medium was solvent extracted and testosterone metabolites were separated by thin-layer chromatography and quantified using a radioisotope scanner.

RESULTS

The incubations of osteoblasts and periosteal fibroblasts with CoQ, Pycnogenol or phytoestrogens stimulated the synthesis of the physiologically active androgen DHT, while the yields of DHT were significantly reduced in response to nicotine compared to control values (p<0.001 for phytoestrogens). The combination of nicotine with CoQ, Pycnogenol or phytoestrogens increased the yields of DHT compared with incubation with nicotine alone in both cell types.

CONCLUSION

This investigation suggests that the catabolic effects of nicotine could be reversed by the addition of antioxidants such as CoQ or Pycnogenol and phytoestrogens.

Diazepam administration prevents testosterone decrease and lipofuscin accumulation in testis of mouse exposed to chronic noise stress

Lipofuscin is an autofluorescent and undegradable material, which accumulates in tissues during ageing and under different types of stress. Among these, oxidative stress represents a major trigger for lipofuscin formation. However, prolonged noise exposure is also an effective stressful stimuli. Diazepam may inhibit lipofuscinogenesis in liver and prevent the noise-induced reduction of the steroidogenesis in the adrenal gland. The aim of the study was to ascertain whether chronic noise exposure causes lipofuscin accumulation in mouse testis, and to evaluate the effects of diazepam administration. Eight-week old mice were either exposed for 6 weeks (6 h day(-1)) to white-noise (group A), or received diazepam (3 mg kg(-1), i.p.) before noise exposures (group B), while a further group was used as control (group C). Light fluorescence and transmission electron microscopy revealed lipofuscin in large amounts in the Leydig cells in mice of group A, which concomitantly had low serum testosterone levels; pre-treatment with diazepam occluded both effects. The present study indicates that: (i) chronic noise exposure causes lipofuscin accumulation at the level of the Leydig cells and a decrease in testosterone; (ii) all these effects are suppressed by pre-treatment with diazepam. As the Leydig cells represent the only cellular type of the interstitial testicular tissue having peripheral benzodiazepine receptors, these results could be explained by the capacity of the peripheral benzodiazepine receptors to prevent reactive oxygen species damage and to increase the resistance of these cells to oxidative stress.

Energized, polarized, and actively respiring mitochondria are required for acute Leydig cell steroidogenesis

The first and rate-limiting step in the biosynthesis of steroid hormones is the transfer of cholesterol into mitochondria, which is facilitated by the steroidogenic acute regulatory (StAR) protein. Recent study of Leydig cell function has focused on the mechanisms regulating steroidogenesis; however, few investigations have examined the importance of mitochondria in this process. The purpose of this investigation was to determine which aspects of mitochondrial function are necessary for acute cAMP-stimulated Leydig cell steroidogenesis. MA-10 cells were treated with 8-bromoadenosine 3',5'-cyclic monophosphate (cAMP) and different site-specific agents that disrupt mitochondrial function, and the effects on acute cAMP-stimulated progesterone synthesis, StAR mRNA and protein, mitochondrial membrane potential (Deltapsim), and ATP synthesis were determined. cAMP treatment of MA-10 cells resulted in significant increases in both cellular respiration and Deltapsim. Dissipating Deltapsim with carbonyl cyanide m-chlorophenyl hydrazone resulted in a profound reduction in progesterone synthesis, even in the presence of newly synthesized StAR protein. Preventing electron transport in mitochondria with antimycin A significantly reduced cellular ATP, potently inhibited steroidogenesis, and reduced StAR protein levels. Inhibiting mitochondrial ATP synthesis with oligomycin reduced cellular ATP, inhibited progesterone synthesis and StAR protein, but had no effect on Deltapsim. Disruption of intramitochondrial pH with nigericin significantly reduced progesterone production and StAR protein but had minimal effects on Deltapsim. 22(R)-hydroxycholesterol-stimulated progesterone synthesis was not inhibited by any of the mitochondrial reagents, indicating that neither P450 side-chain cleavage nor 3beta-hydroxysteroid dehydrogenase activity was inhibited. These results indicate that Deltapsim, mitochondrial ATP synthesis, and mitochondrial pH are all required for acute steroid biosynthesis. These results suggest that mitochondria must be energized, polarized, and actively respiring to support Leydig cell steroidogenesis, and alterations in the state of mitochondria may be involved in regulating steroid biosynthesis.

Mitochondrial function in Leydig cell steroidogenesis

The first and rate-limiting step in the biosynthesis of steroid hormones is the transfer of cholesterol into mitochondria, which is facilitated by the steroidogenic acute regulatory (StAR) protein. Recent studies of Leydig cell function have focused on the molecular events controlling steroidogenesis; however, few studies have examined the importance of the mitochondria. The purpose of this investigation was to determine which aspects of mitochondrial function are necessary for Leydig cell steroidogenesis. MA-10 tumor Leydig cells were treated with 8-bromo-cAMP (cAMP) and site-specific mitochondrial disrupters, pro-oxidants, and their effects on progesterone synthesis, StAR expression, mitochondrial membrane potential (delta psi(m)) and ATP synthesis were determined. Dissipating delta psi(m) with CCCP inhibited progesterone synthesis, even in the presence of newly synthesized StAR protein. The electron transport inhibitor antimycin A significantly reduced cellular ATP, inhibited steroidogenesis, and reduced StAR protein expression. The F0/F1 ATPase inhibitor oligomycin reduced cellular ATP and inhibited progesterone synthesis and StAR protein expression, but had no effect on delta psi(m). Disruption of pH with nigericin significantly reduced progesterone production and StAR protein, but had minimal effects on delta psi(m). Sodium arsenite at low concentrations inhibited StAR protein but not mRNA expression and inhibited progesterone without disrupting delta psi(m). The mitochondrial Ca2+ inhibitor Ru360 also inhibited StAR protein expression. These results demonstrate that delta psi(m), ATP synthesis, delta pH and [Ca2+]mt are all required for steroid biosynthesis, and that mitochondria are sensitive to oxidative stress. These results suggest that mitochondria must be energized, polarized, and actively respiring to support Leydig cell steroidogenesis and alterations in the state of mitochondria may be involved in regulating steroid biosynthesis.

Bacterial lipopolysaccharide-induced oxidative stress in the impairment of steroidogenesis and spermatogenesis in rats

Microbial infections, localized as well as systemic, are known to cause transitive or permanent male infertility. However, the mechanisms of infection-induced infertility are largely unknown. Earlier reports showed that steroidogenesis and spermatogenesis are affected during bacterial lipopolysaccharide (LPS)-induced acute inflammation. The present study used an LPS rat model to investigate the role of oxidative stress in spermatogenesis. Intraperitoneal administration of bacterial LPS (5mg/kg body weight) to adult male albino rats elevated testicular malondialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE), and decreased the activities of testicular antioxidant enzymes such as catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. The GSH/GSSG ratio also decreased significantly. Time series analysis revealed transitory oxidative stress and expression of inflammatory mediators such as interleukin-1beta (IL-1beta), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) from 3h to 12h after LPS. Testicular expression of steroidogenic acute regulatory (StAR) protein decreased to 24h, in correlation with damage to spermatogenesis. These data are consistent with oxidative stress as a major causal factor in altered steroidogenesis, spermatogenesis, and perhaps male infertility during endotoxin-induced acute inflammation.

A pH-dependent Molten Globule Transition Is Required for Activity of the Steroidogenic Acute Regulatory Protein, StAR

The steroidogenic acute regulatory protein (StAR) simulates steroid biosynthesis by increasing the flow of cholesterol from the outer mitochondrial membrane (OMM) to the inner membrane. StAR acts exclusively on the OMM, and only StAR's carboxyl-terminal alpha-helix (C-helix) interacts with membranes. Biophysical studies have shown that StAR becomes a molten globule at acidic pH, but a physiologic role for this structural transition has been controversial. Molecular modeling shows that the C-helix, which forms the floor of the sterol-binding pocket, is stabilized by hydrogen bonding to adjacent loops. Molecular dynamics simulations show that protonation of the C-helix and adjacent loops facilitates opening and closing the sterol-binding pocket. Two disulfide mutants, S100C/S261C (SS) and D106C/A268C (DA), designed to limit the mobility of the C-helix but not disrupt overall conformation, were prepared in bacteria, and their correct folding and positioning of the disulfide bonds was confirmed. The SS mutant lost half, and the DA mutant lost all cholesterol binding capacity and steroidogenic activity with isolated mitochondria in vitro, but full binding and activity was restored to each mutant by disrupting the disulfide bonds with dithiothreitol. These data strongly support the model that StAR activity requires a pH-dependent molten globule transition on the OMM.