Steroid and xenobiotic effects on the adrenal cortex: mediation by oxidative and other mechanisms

Endocrine disruptors, aryl hydrocarbon receptor and cortisol secretion

PURPOSE

Endocrine disruptors exert a plethora of effects in endocrine tissues, from altered function to carcinogenesis. Given its lipophilic nature, the adrenal cortex represents an ideal target for endocrine disruptors and thus, possibly, xenobiotic-induced adrenocortical dysfunction. However, there is no clear understanding of the effect of endocrine disruptors on adrenal steroidogenesis, in particular as regards the aryl hydrocarbon receptor (AHR) pathway, one of the key mediators.

METHODS

The present review recapitulates available evidence on the effects of AHR ligands on adrenal steroidogenesis, with focus on cortisol secretion.

RESULTS

Short-term exposure to AHR ligands most often induced a stress-like corticosteroid response followed by decreased responsiveness to stressors with long-term exposure. This was observed in several experimental models across species as well as in animals and humans in real-life settings. Prenatal exposure led to different effects according to sex of the offspring, as observed in murine models and in children from mothers in several countries. In vitro findings proved highly dependent on the experimental setting, with reduced cortisol response and steroidogenic enzyme synthesis mostly observed in fish and increased cortisol synthesis and secretion observed in murine and human adrenal cell lines. Of note, no AHR-binding element was detected in steroidogenic enzyme promoters, suggesting the involvement of additional factors.

CONCLUSION

Our review provides evidence for the impact of AHR ligands on adrenocortical function and indicates further avenues of research to better clarify its effects.

Carving the senescent phenotype by the chemical reactivity of catecholamines: An integrative review

Macromolecules damaged by covalent modifications produced by chemically reactive metabolites accumulate in the slowly renewable components of living bodies and compromise their functions. Among such metabolites, catecholamines (CA) are unique, compared with the ubiquitous oxygen, ROS, glucose and methylglyoxal, in that their high chemical reactivity is confined to a limited set of cell types, including the dopaminergic and noradrenergic neurons and their direct targets, which suffer from CA propensities for autoxidation yielding toxic quinones, and for Pictet-Spengler reactions with carbonyl-containing compounds, which yield mitochondrial toxins. The functions progressively compromised because of that include motor performance, cognition, reward-driven behaviors, emotional tuning, and the neuroendocrine control of reproduction. The phenotypic manifestations of the resulting disorders culminate in such conditions as Parkinson's and Alzheimer's diseases, hypertension, sarcopenia, and menopause. The reasons to suspect that CA play some special role in aging accumulated since early 1970-ies. Published reviews address the role of CA hazardousness in the development of specific aging-associated diseases. The present integrative review explores how the bizarre discrepancy between CA hazardousness and biological importance could have emerged in evolution, how much does the chemical reactivity of CA contribute to the senescent phenotype in mammals, and what can be done with it.

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.

Translocator protein (18 kDa): an update on its function in steroidogenesis

Translocator protein (18 kDa) (TSPO) is a ubiquitous mitochondrial protein. Studies of its responses to drug and endogenous ligands have shown TSPO to be involved either directly or indirectly in numerous biological functions, including mitochondrial cholesterol transport and steroid hormone biosynthesis, porphyrin transport and heme synthesis, apoptosis, cell proliferation, and anion transport. Localised to the outer mitochondrial membrane of steroidogenic cells, TSPO has been shown to associate with cytosolic and mitochondrial proteins as part of a large multiprotein complex involved in mitochondrial cholesterol transport, the rate-limiting step in steroidogenesis. There is general agreement as to the structure and pharmacology of TSPO. Stimulation of TSPO has been shown to have therapeutic use as anxiolytics by inducing allopregnanolone production in the brain, and also potentially for re-establishing androgen levels in hypogonadal ageing animals. Until recently, there has been general agreement regarding the role of TSPO in steroidogenesis. However, recent studies involving genetic depletion of TSPO in mice have created controversy about the role of this protein in steroid and heme synthesis. We review the data on the structure and function of TSPO, as well as the recent results obtained using various genetic animal models. Taken together, these studies suggest that TSPO is a unique mitochondrial pharmacological target for diseases that involve increased mitochondrial activity, including steroidogenesis. Although there is no known mammalian species that lacks TSPO, it is likely that, because of the importance of this ancient protein in evolution and mitochondrial function, redundant mechanisms may exist to replace it under circumstances when it is removed.

Non-enzymatic molecular damage as a prototypic driver of aging

The chemical potentialities of metabolites far exceed metabolic requirements. The required potentialities are realized mostly through enzymatic catalysis. The rest are realized spontaneously through organic reactions that (i) occur wherever appropriate reactants come together, (ii) are so typical that many have proper names (e.g. Michael addition, Amadori rearrangement, and Pictet-Spengler reaction), and (iii) often have damaging consequences. There are many more causes of non-enzymatic damage to metabolites than reactive oxygen species and free radical processes (the "usual suspects"). Endogenous damage accumulation in non-renewable macromolecules and spontaneously polymerized material is sufficient to account for aging and differentiates aging from wear-and-tear of inanimate objects by deriving it from metabolism, the essential attribute of life.

Transcriptome Pathway Analysis of Pathological and Physiological Aldosterone-Producing Human Tissues

Supplemental Digital Content is available in the text.

Primary aldosteronism is present in ≈10% of hypertensives. We previously performed a microarray assay on aldosterone-producing adenomas and their paired zona glomerulosa and fasciculata. Confirmation of top genes validated the study design and functional experiments of zona glomerulosa selective genes established the role of the encoded proteins in aldosterone regulation. In this study, we further analyzed our microarray data using AmiGO 2 for gene ontology enrichment and Ingenuity Pathway Analysis to identify potential biological processes and canonical pathways involved in pathological and physiological aldosterone regulation. Genes differentially regulated in aldosterone-producing adenoma and zona glomerulosa were associated with steroid metabolic processes gene ontology terms. Terms related to the Wnt signaling pathway were enriched in zona glomerulosa only. Ingenuity Pathway Analysis showed "NRF2-mediated oxidative stress response pathway" and "LPS (lipopolysaccharide)/IL-1 (interleukin-1)–mediated inhibition of RXR (retinoid X receptor) function" were affected in both aldosterone-producing adenoma and zona glomerulosa with associated genes having up to 21- and 8-fold differences, respectively. Comparing KCNJ5-mutant aldosterone-producing adenoma, zona glomerulosa, and zona fasciculata samples with wild-type samples, 138, 56, and 59 genes were differentially expressed, respectively (fold-change >2; P<0.05). ACSS3, encoding the enzyme that synthesizes acetyl-CoA, was the top gene upregulated in KCNJ5-mutant aldosterone-producing adenoma compared with wild-type. NEFM, a gene highly upregulated in zona glomerulosa, was upregulated in KCNJ5 wild-type aldosterone-producing adenomas. NR4A2, the transcription factor for aldosterone synthase, was highly expressed in zona fasciculata adjacent to a KCNJ5-mutant aldosterone-producing adenoma. Further interrogation of these genes and pathways could potentially provide further insights into the pathology of primary aldosteronism.

Effects of phenol on ovarian P450arom gene expression and aromatase activity in vivo and antioxidant metabolism in common carp Cyprinus carpio

Ovarian cyp19a mRNA expression and P450 aromatase activity were measured in vivo in common carp Cyprinus carpio exposed to phenol for 96 h. Production of reactive oxygen species (ROS) and parameters of antioxidant defense system in serum ovary and liver of this fish after long-term phenol exposure were also studied. In vivo exposure of fish to sublethal dose of phenol for 96 h caused marked attenuation of ovarian cyp19a1a gene expression and P450 aromatase activity. Production of ROS like hydrogen peroxide and hydroxyl radicals in serum, liver and ovary in fish exposed to phenol for 15 days elevated significantly from day 1 to day 7 with no further significant increase thereafter compared to their respective control values. Total superoxide dismutase (SOD) and catalase activities in serum and ovary decreased gradually and significantly from day 1 to day 4, which then increased significantly for the rest of the exposure days. Liver SOD activity seemed to be distinctly responsive to phenol. SOD activity in liver of phenol-exposed fish started to increase gradually from day 1 to 4 with no further increase thereafter. Catalase activities in all the tissues showed significant inhibition up to day 4 which then increased gradually and significantly up to day 15 of phenol exposure compared to their respective control values. From our results, it appears that sublethal dose of phenol has the endocrine disruptive potential and effect is mediated via inhibition of ovarian P450arom gene expression and aromatase activity in vivo. Sublethal dose of phenol also caused oxidative stress, and antioxidant systems are very much effective to prevent the damages caused by the generation of ROS.

Adrenocortical endocrine disruption

The adrenal has been neglected in endocrine disruption regulatory testing strategy. The adrenal is a vital organ, adrenocortical insufficiency is recognised in life threatening "adrenal crises" and Addison's disease, and the consequences of off-target toxicological inhibition of adrenocortical steroidogenesis is well recognised in clinical medicine, where drugs such as aminoglutethimide and etomidate killed patients via unrecognised inhibition of adrenocortical steroidogenic enzymes (e.g. CYP11B1) along the cortisol and aldosterone pathways. The consequences of adrenocortical dysfunction during early development are also recognised in the congenital salt wasting and adrenogenital syndromes presenting neonatally, yet despite a remit to focus on developmental and reproductive toxicity mechanisms of endocrine disruption by many regulatory agencies (USEPA EDSTAC; REACH) the assessment of adrenocortical function has largely been ignored. Further, every step in the adrenocortical steroidogenic pathway (ACTH receptor, StAR, CYP's 11A1, 17, 21, 11B1, 11B2, and 3-hydroxysteroid dehydrogenase Δ4,5 isomerase) is known to be a potential target with multiple examples of chemicals inhibiting these targets. Many of these chemicals have been detected in human and wildlife tissues. This raises the question of whether exposure to low level environmental chemicals may be affecting adrenocortical function. This review examines the omission of adrenocortical testing in the current regulatory frameworks; the characteristics that make the adrenal cortex particularly vulnerable to toxic insult; chemicals and their toxicological targets within the adrenocortical steroidogenic pathways; the typical manifestations of adrenocortical toxicity (e.g. human iatrogenically induced pharmacotoxicological adrenal insufficiency, manifestations in typical mammalian regulatory general toxicology studies, manifestations in wildlife) and models of adrenocortical functional assessment. The utility of the in vivo ACTH challenge test to prove adrenocortical competency, and the H295R cell line to examine molecular mechanisms of steroidogenic pathway toxicity, are discussed. Finally, because of the central role of the adrenal in the physiologically adaptive stress response, the distinguishing features of stress, compared with adrenocortical toxicity, are discussed with reference to the evidence required to claim that adrenal hypertrophy results from stress rather than adrenocortical enzyme inhibition which is a serious adverse toxicological finding. This article is part of a special issue entitled 'Endocrine disruptors and steroids'.

Practical approaches for evaluating adrenal toxicity in nonclinical safety assessment

The adrenal gland has characteristic morphological and biochemical features that render it particularly susceptible to the actions of xenobiotics. As is the case with other endocrine organs, the adrenal gland is under the control of upstream organs (hypothalamic-pituitary system) in vivo, often making it difficult to elucidate the mode of toxicity of a test article. It is very important, especially for pharmaceuticals, to determine whether a test article-related change is caused by a direct effect or other associated factors. In addition, antemortem data, including clinical signs, body weight, food consumption and clinical pathology, and postmortem data, including gross pathology, organ weight and histopathologic examination of the adrenal glands and other related organs, should be carefully monitored and evaluated. During evaluation, the following should also be taken into account: (1) species, sex and age of animals used, (2) metabolic activation by a cytochrome P450 enzyme(s) and (3) physicochemical properties and the metabolic pathway of the test article. In this review, we describe the following crucial points for toxicologic pathologists to consider when evaluating adrenal toxicity: functional anatomy, blood supply, hormone production in each compartment, steroid biosynthesis, potential medulla-cortex interaction, and species and gender differences in anatomical features and other features of the adrenal gland which could affect vulnerability to toxic effects. Finally practical approaches for evaluating adrenal toxicity in nonclinical safety studies are discussed.

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.

Antioxidant mediated ameliorative steroidogenesis by Commelina benghalensis L. and Cissus quadrangularis L. against quinalphos induced male reproductive toxicity

Quinalphos (QP) is speculated to cause endocrine disruption through the generation of reactive oxygen species (ROS) by oxidative stress (OS). Exposure of QP decreased testosterone level considerably which resulted in reduced viable sperms in mice. The QP induced toxicity is initiated by the formation of free radicals as it is evidenced from the increased Lipid peroxidation (LPO) and diminution of antioxidant enzymes in testicular tissue. Increased serum cholesterol and reduced testicular cholesterol indicated the inhibition of cholesterol transport and biosynthesis in testicular tissues. Lack of cholesterol in testicular tissue impaired the steroidogenesis by down-regulating the expression of StAR protein, Cytochrome P450, 3β-HSD and 17β-HSD leading to reduced testosterone level. Treatment of Commelina benganlensis (CBE) and Cissus quadrangularis (CQE) significantly recovered the alterations in antioxidant profiles as well as increased LPO, thereby recovering the decreased mRNA expression levels of intermediate enzymes. However, CQE effectively protected the OS and prevented the inhibition of steroidogenesis thereby preventing male infertility.

Oxidative stress in testis of animals during aging with and without reproductive activity

The free radical theory of aging postulates that an imbalance between reactive oxygen species (ROS) and reactive nitrogen species (RNS) and antioxidant defenses is important in senescence. To address this issue and gain insight into the aging process, we have evaluated the antioxidant defenses and have assessed oxidative damage in testis tissues in aging male rats. In order to relate aging and reproduction, animals with and without reproductive activity were studied. In reproductive animals the results showed a progressive increase in antioxidant enzyme activity until 12 months of age followed by an abrupt fall at 24 months. In non-reproductive animals, antioxidant activity was stable through 12 months of age, but again, fell abruptly at 24 months of age. In addition, increased aconitase activity and increased testosterone levels were found among reproductively active animals. The data demonstrate the existence of metabolic differences in testis of reproductively experienced animals and reproductively naïve animals.

Oxidative stress-related proteins in a Conn's adenoma tissue. Relevance for aldosterone's prooxidative and proinflammatory activity

BACKGROUND AND AIM

Angiotensin II (Ang II) induces oxidative stress (OxSt), which is essential for cardiovascular remodeling. Aldosterone also induces fibrosis and remodeling through direct effect on non-classical mineralocorticoid (MR) target tissues. However, studies on the role of aldosterone on OxSt and related factors in humans are lacking.

MATERIALS AND METHODS

We assessed gene and protein expression of p22phox (RT-PCR and Western blot), NAD(P)H oxidase subunit essential for superoxide production and gene expression of transforming growth fator (TGF) beta, plasminogen activator inhibitor (PAI)-1, and heme oxygenase (HO)-1, effectors of OxSt (RT-PCR), in a Conn's adenoma, removed from a patient with primary hyperaldosteronism. Ang II type 1 (AT1R) and MR receptors expression were also evaluated (RT-PCR). The normal adrenal tissue adjacent to the adenoma was used as control.

RESULTS

p22phox gene and protein expression were higher (31% and 53%, respectively) in the adrenal adenoma. TGFbeta, PAI-1, and HO-1 gene expression were also higher (25%, 129%, and 25%, respectively) in the adrenal adenoma while AT1R gene expression was similar (8%). The expression of MR in the adenoma was documented.

CONCLUSIONS

This report demonstrates in a human model that the increased aldosterone production has effects on enzyme systems related to OxSt, enhancing the systemic fibrogenic effects of aldosterone excess through TGFbeta and PAI-1 expression which was previously demonstrated only indirectly in vitro and in animal models. The presence of MR expression in the adenoma may link the hormone with the adenoma growth. Therefore, the results of this study derived from a single case might represent an important working hypothesis for further research in a larger number of cases to clarify the role of aldosterone overproduction on OxSt and its clinical relevance.

Protective effects of estrogens and caloric restriction during aging on various rat testis parameters

AIM

To investigate the effects of 17beta-estradiol (E2), Peganum harmala extract (PHE) and caloric restriction (CR) on various testis parameters during aging.

METHODS

Twelve month-old male rats were treated for 6 months with either E2 or PHE, or submitted to CR (40%).

RESULTS

Our results show that estrogens and CR are able to protect the male gonad by preventing the decrease of testosterone and E2 levels as well as the decrease of aromatase and estrogen receptor gene expressions. Indeed, E2, PHE and CR treatments induced an increase in the superoxide dismutase activities and decreased the activity of testicular enzymes: gamma-glutamyl transferase, alkaline phosphatase, lactate deshydrogenase as well as the aspartate and lactate transaminases in aged animals. In addition, the testicular catalase and gluthatione peroxidase activities were enhanced in E2, PHE and CR-treated rats compared to untreated animals at 18 months of age. Moreover, the positive effects of estradiol, PHE and CR were further supported by a lower level of lipid peroxidation. Recovery of spermatogenesis was recorded in treated rats.

CONCLUSION

Besides a low caloric diet which is beneficial for spermatogenesis, a protective antioxydant role of estrogens is suggested. Estrogens delay testicular cell damage, which leads to functional senescence and, therefore, estrogens are helpful in protecting the reproductive functions from the adverse effects exerted by reactive oxygen species (ROS) produced in large quantities in the aged testis.

Antioxidant Protective Mechanisms against Reactive Oxygen Species (ROS) Generated by Mitochondrial P450 Systems in Steroidogenic Cells

Mitochondrial P450 type enzymes catalyze central steps in steroid biosynthesis, including cholesterol conversion to pregnenolone, 11beta and 18 hydroxylation in glucocorticoid and mineralocorticoid synthesis, C-27 hydroxylation of bile acids, and 1alpha and 24 hydroxylation of 25-OH-vitamin D. These monooxygenase reactions depend on electron transfer from NADPH via FAD adrenodoxin reductase and 2Fe-2S adrenodoxin. These systems can function as a futile NADPH oxidase, oxidizing NADPH in absence of substrate, and leak electrons via adrenodoxin and P450 to O(2), producing superoxide and other reactive oxygen species (ROS). The degree of uncoupling depends on the P450 and steroid substrate. Studies with purified proteins and overexpression in cultured cells show consistently that adrenodoxin, but not reductase, is responsible for ROS production that can lead to apoptosis. In the ovary and corpus luteum, antioxidant enzyme activities superoxide dismutase, catalase, and glutathione peroxidase parallel steroidogenesis. Antioxidant beta-carotene, alpha-tocopherol, and ascorbate can protect against oxidative damages of P450 systems. In testis Leydig cells, steroidogenesis is associated with aging of the steroidogenic capacity.

Effect of glutathione depletion on Leydig cell steroidogenesis in young and old brown Norway rats

Changes in the oxidant/antioxidant environment of aging Leydig cells have been shown to be correlated with the reduced ability of these cells to produce testosterone. With this in mind, we hypothesized that the experimental depletion of glutathione (GSH), an abundant Leydig cell intracellular antioxidant, might result in reduced testosterone production. Incubation of Leydig cells isolated from the testes of adult Brown Norway rats with buthionine sulfoximine (BSO) reduced GSH content by more than 70% and testosterone production by about 40%. The antioxidants vitamin E, N-tert-butyl-alpha-phenylnitrone and Trolox countered BSO's effect on steroidogenesis but not on GSH depletion. Together, BSO and glutathione ethyl ester maintained intracellular GSH and also testosterone production, whereas 1,2-dithiole-3-thione, which increases intracellular GSH, increased testosterone production. In vivo studies also were conducted. Young (4 month old) and old (24 month old) rats were injected with BSO twice a day for 7 d, after which Leydig cells were isolated and analyzed in vitro. BSO treatment reduced Leydig cell GSH content by 70% and the ability of the Leydig cells to produce testosterone by more than 50%. As with aging, decreases were seen in LH-stimulated cAMP production, steroidogenic acute regulatory protein, cholesterol side-chain cleavage, 3beta-hydroxysteroid dehydrogenase, and 17alpha-hydroxylase/17,20-lyase. The results of these studies, taken together, are consistent with the hypothesis that alteration in the oxidant/antioxidant environment may play a significant, causative role in the age-related reduced ability of Leydig cells to produce testosterone.

Effects of Progesterone on Benzene Toxicity in Rats

Benzene is a frequently used industrial solvent. Its toxic manifestations could be modified by sex hormones, but mechanisms of their action are poorly understood. We have examined the influence of progesterone on lipid peroxidation (malondialdehyde), reduced glutathione (GSH), and cytochrome P450 2E1 (CYP2E1) in the liver and kidneys of female rats. Progesterone applied to benzene-treated rats inhibited the formation of reactive oxygen species (ROS), but in ovariectomised benzene-treated rats it significantly increased GSH in the liver. No improvement in CYP2E1 activity was observed in progesterone treated rats. Our results evidence that progesterone changes benzene toxicity (generation of ROS, oxidative stress). However, the probable antioxidative effect of progesterone needs to be confirmed by further studies.

Oxidative stress in the testis of hyperglycemic rabbits treated with repaglinide

In the present study, the induction of oxidative stress was examined in the testis of alloxan-induced diabetic rabbits. In addition, the protective effect of repaglinide, an oral anti-diabetic, at a dose of 1 mg daily was studied after four and eight weeks of the treatment. For these purposes, the levels of superoxide dismutase (Cu,Zn-SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R), glutathione (GSH), ascorbic acid (AA), lipid peroxidation products (LPO) and protein carbonyl groups (PCG) were quantified. Hyperglycemia resulted in significant increases in the antioxidative enzymes, Cu, Zn-SOD, CAT, GSH-Px, and GSSG-R after four and eight weeks, respectively. There was also an increase in GSH level, and a decrease in the level of AA. These effects were accompanied by an elevation in testicular LPO levels and PCG levels. Repaglinide was found to normalize the activity of GSSG-R and levels of GSH and AA, and blunted the increased lipid peroxidation, however no decrease in PCG levels were observed. In conclusion, some oxidative changes provoked in the testis of rabbits by hyperglycemia, were found to be reduced with repaglinide treatment at therapeutic dose.

Adrenal toxicology: a strategy for assessment of functional toxicity to the adrenal cortex and steroidogenesis

The adrenal is the most common toxicological target organ in the endocrine system in vivo and yet it is neglected in regulatory endocrine disruption screening and testing. There has been a recent marked increase in interest in adrenal toxicity, but there are no standardised approaches for assessment. Consequently, a strategy is proposed to evaluate adrenocortical toxicity. Human adrenal conditions are reviewed and adrenocortical suppression, known to have been iatrogenically induced leading to Addisonian crisis and death, is identified as the toxicological hazard of most concern. The consequences of inhibition of key steroidogenic enzymes and the possible toxicological modulation of other adrenal conditions are also highlighted. The proposed strategy involves an in vivo rodent adrenal competency test based on ACTH challenge to specifically examine adrenocortical suppression. The H295R human adrenocortical carcinoma cell line is also proposed to identify molecular targets, and is useful for measuring steroids, enzymes or gene expression. Hypothalamo-pituitary-adrenal endocrinology relevant to rodent and human toxicology is reviewed (with an emphasis on multi-endocrine axis effects on the adrenal and also how the adrenal affects a variety of other hormones) and the endocrinology of the H295R cell line is also described. Chemicals known to induce adrenocortical toxicity are reviewed and over 60 examples of compounds and their confirmed steroidogenic targets are presented, with much of this work published very recently using H295R cell systems. In proposing a strategy for adrenocortical toxicity assessment, the outlined techniques will provide hazard assessment data but it will be regulatory agencies that must consider the significance of such data in risk extrapolation models. The cases of etomindate and aminoglutethimide induced adrenal suppression are clearly documented examples of iatrogenic adrenal toxicity in humans. Environmentally, sentinel species, such as fish, have also shown evidence of adrenal endocrine disruption attributed to exposure to chemicals. The extent of human sub-clinical adrenal effects from environmental chemical exposures is unknown, and the extent to which environmental chemicals may act as a contributory factor to human adrenal conditions following chronic low-level exposures will remain unknown unless purposefully studied.

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.

Vitamin E, aging and Leydig cell steroidogenesis

Previous studies have suggested that oxidant-induced damage may play a role in the reduced ability of aged Brown Norway rat Leydig cells to produce testosterone. We reasoned that if this was the case, antioxidants such as vitamin E (VE) would be expected to have protective effects on steroidogenesis. To test this hypothesis, the effects of VE on Leydig cell steroidogenesis were examined both in vitro and in vivo. In vitro studies were conducted using Leydig cells isolated from the testes of young adult Brown Norway rats. In one experiment, isolated cells were incubated with luteinizing hormone (LH) alone or with LH plus VE (1.3-40 microg/ml). At each of 3, 5 and 7 days thereafter, the ability of the cells to produce testosterone was greater in the presence of VE than in its absence, and depended upon VE dose. Culturing the Leydig cells with the antioxidants melatonin or N-tert-butyl-alpha-phenylnitrone also protected Leydig cell steroidogenic function. Additionally, VE was found to suppress Fe2+/sodium ascorbate-induced lipid peroxidation in Leydig cells. These studies strongly supported the contention that VE has a protective effect on Leydig cell steroidogenesis. These in vitro results prompted us to ask whether, in vivo, VE also would affect steroidogenesis as Leydig cells age. To this end, rats were provided one of three diets, begun when the rats were 6 months of age and carried out through age 25 months: VE-deficient, VE-control, or VE-supplemented. The VE-deficient diet had no effect on the age-related reductions in Leydig cell testosterone production observed in VE-control rats. The VE-supplemented diet did not prevent age-related reductions in steroidogenesis, but the reductions at ages 23 and 25 months were significantly less than those seen in Leydig cells from VE-control or VE-deficient rats. Taken together, the results of the in vitro and in vivo studies reported herein are consistent with the conclusion that vitamin E exerts a protective effect on Leydig cell steroidogenesis.

Studies on the protective role of vitamin C and E against polychlorinated biphenyl (Aroclor 1254)--induced oxidative damage in Leydig cells

Free radical production and lipid peroxidation are potentially important mediators in testicular physiology and toxicology. Polychlorinated biphenyls (PCBs) are global environmental contaminants that cause disruption of the endocrine system in human and animals. The present study was conducted to elucidate the protective role of vitamin C and E against Aroclor 1254-induced changes in Leydig cell steroidogenesis and antioxidant system. Adult male rats were dosed for 30 days with daily intraperitoneal (ip) injection of 2 mg/kg Aroclor or vehicle (corn oil). One group of rats was treated with vitamin C (100 mg/kg bw/day) while the other group was treated with vitamin E (50 mg/kg bw/day) orally, simultaneously with Aroclor 1254 for 30 days. One day after the last treatment, animals were euthanized and blood was collected for the assay of serum hormones such as luteinizing hormone (LH), thyroid stimulating hormone (TSH), prolactin (PRL), triiodothyronine (T(3)), thyroxine (T(4)), testosterone and estradiol. Testes were quickly removed and Leydig cells were isolated in aseptic condition. Purity of Leydig cells was determined by 3beta-hydroxysteroid dehydrogenase (3beta-HSD) staining method. Purified Leydig cells were used for quantification of cell surface LH receptors and steroidogenic enzymes such as cytochrome P(450) side chain cleavage enzyme (P(450)scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 17beta-hydroxysteroid dehydrogenase (17beta- HSD). Leydig cellular enzymatic antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), gamma-glutamyl transpeptidase (gamma-GT), glutathione-S-transferase (GST) and non-enzymatic antioxidants such as vitamin C and E were assayed. Lipid peroxidation (LPO) and reactive oxygen species (ROS) were also estimated in Leydig cells. Aroclor 1254 treatment significantly reduced the serum LH, TSH, PRL, T(3), T(4), testosterone and estradiol. In addition to this, Leydig cell surface LH receptors, activities of the steroidogenic enzymes such as cytochrome P(450)scc, 3beta-HSD, 17beta-HSD, antioxidant enzymes SOD, CAT, GPX, GR, gamma-GT, GST and non-enzymatic antioxidants such as vitamin C and E were significantly diminished whereas, LPO and ROS were markedly elevated. However, the simultaneous administration of vitamin C and E in Aroclor 1254 exposed rats resulted a significant restoration of all the above-mentioned parameters to the control level. These observations suggest that vitamin C and E have ameliorative role against adverse effects of PCB on Leydig cell steroidogenesis.

Gene expression profiles of the rat brain both immediately and 3 months following acute sarin exposure

We have studied sarin-induced global gene expression patterns at an early time point (15 min; 0.5xLD50) and a later time point (3 months; 1xLD50) using Affymetrix: Rat Neurobiology U34 chips in male, Sprague-Dawley rats and have identified a total of 65 (early) and 38 (late) genes showing statistically significant alterations from control levels at 15 min and 3 months, respectively. At the early time point, those that are classified as ion channel, cytoskeletal and cell adhesion molecules, in addition to neuropeptides and their receptors predominated over all other groups. The other groups included: cholinergic signaling, calcium channel and binding proteins, transporters, chemokines, GABAnergic, glutamatergic, aspartate, catecholaminergic, nitric oxide synthase, purinergic, and serotonergic signaling molecules. At the late time point, genes that are classified as calcium channel and binding proteins, cytoskeletal and cell adhesion molecules and GABAnergic signaling molecules were most prominent. Seven molecules (Ania-9, Arrb-1, CX-3C, Gabab-1d, Nos-2a, Nrxn-1b, PDE2) were identified that showed altered persistent expression in both time points. Selected genes from each of these time points were further validated using semi quantitative RT-PCR approaches. Some of the genes that were identified in the present study have been shown to be involved in organophosphate-induced neurotoxicity by both other groups as well as ours. Principal component analysis (PCA) of the expression data from both time points was used for comparative analysis of the gene expression, which indicated that the changes in gene expression were a function of dose and time of euthanasia after the treatment. Our model also predicts that besides dose and duration of post-treatment period, age and possibly other factors may be playing important roles in the regulation of pathways, leading to the neurotoxicity.

Suppression of steroidogenesis and activator protein-1 transcription factor activity in rat adrenals by vitamin E deficiency-induced chronic oxidative stress

Excessive oxidative stress and associated macromolecular damage are considered to be key features of aging, and appear to contribute to the age-related decline in steroid hormone production in adrenal and testicular Leydig cells. The current studies were initiated to examine the potential mechanism by which excessive oxidative stress during aging attenuates the functional expression of the oxidant-responsive transcription factor Activator protein-1. Chronic oxidative stress was induced in vivo by maintaining groups of rats on a diet deficient in vitamin E for 6 months. Plasma, liver, and adrenal tissues from vitamin E-deficient animals had negligible levels of this vitamin and showed high susceptibility to in vitro lipid peroxidation. Synthesis and secretion of corticosterone in response to corticotropin (ACTH), dibutyryl-cAMP, or 20alpha-hydroxycholesterol in vitro was significantly reduced in adrenocortical cells prepared cells from rats deficient in vitamin E. AP-1 DNA-binding activity was diminished approximately 55 % in adrenal extracts from vitamin E-deficient rats with no corresponding change in the binding activity of SP-1. The vitamin E deficiency-mediated loss of AP-1 activity was not due to an alteration in the dimeric composition of constituent proteins, but rather to a general down-regulation of steady-state levels of members of the Fos and Jun families of proteins. Interestingly, vitamin E deficiency also reduced the expression of the redox-regulated Ref-1 protein. Collectively these data demonstrate that chronic oxidative stress specifically down-regulates essential components of the AP-1 transcription factor complex, and suggest that aberrancies in AP-1 expression may adversely affect processes crucial for intracellular cholesterol transport and steroid hormone production.

Aging alters the functional expression of enzymatic and non-enzymatic anti-oxidant defense systems in testicular rat Leydig cells

In aged rats, trophic hormone-stimulated testosterone secretion by isolated Leydig cells is greatly reduced. The current studies were initiated to establish a functional link between excess oxidative stress and the age-related decline in steroidogenesis. Highly purified Leydig cell preparations obtained from 5-month (young mature) and 24-month (old) Sprague-Dawley rats were employed to measure and compare levels of lipid peroxidation, non-enzymatic (alpha-tocopherol, ascorbic acid, and reduced/oxidized glutathione) and enzymatic (Cu, Zn-superoxide dismutase, Cu, Zn-SOD; Mn-superoxide dismutase, Mn-SOD; glutathione peroxidase-1, GPX-1, and catalase, CAT) anti-oxidants. The extent of lipid peroxidation (oxidative damage) in isolated membrane fractions was quantified by measuring the content of thiobarbituric acid-reactive substances (TBARS) under basal conditions, or in the presence of non-enzymatic or enzymatic pro-oxidants. Membrane preparations isolated from Leydig cells from old rats exhibited two- to three-fold enhancement of basal TBARS formation. However, aging had no significant effect on TBARS formation in response to either non-enzymatic or enzymatic pro-oxidants. Among the non-enzymatic anti-oxidants, the levels of reduced glutathione were drastically reduced during aging, while levels of alpha-tocopherol and ascorbic acid remained unchanged. Both steady-state mRNA levels and catalytic activities of Cu, Zn-SOD, Mn-SOD, and GPX-1 were also significantly lower in Leydig cells from 24-month-old rats as compared with 5-month-old control rats. In contrast, neither mRNA levels nor enzyme activity of catalase was sensitive to aging. From these data we conclude that aging is accompanied by reduced expression of key enzymatic and non-enzymatic anti-oxidants in Leydig cells leading to excessive oxidative stress and enhanced oxidative damage (lipid peroxidation). It is postulated that such excessive oxidative insult may contribute to the observed age-related decline in testosterone secretion by testicular Leydig cells.

The organochlorine o,p'-DDD disrupts the adrenal steroidogenic signaling pathway in rainbow trout (Oncorhynchus mykiss)

The mechanisms of action of o,p'-DDD on adrenal steroidogenesis were investigated in vitro in rainbow trout (Oncorhynchus mykiss). Acute exposures to o,p'-DDD inhibited ACTH-stimulated cortisol secretion while cell viability decreased significantly only at the highest concentration tested (200 microM o,p'-DDD). Stimulation of cortisol secretion with a cAMP analogue (dibutyryl-cAMP) was inhibited at a higher concentration than that needed to inhibit ACTH-stimulated cortisol synthesis in cells exposed to o,p'-DDD. Forskolin-stimulated cortisol secretion and cAMP production, and NaF-stimulated cAMP production were inhibited in a concentration-dependent manner by o,p'-DDD. In contrast, basal cortisol secretion was stimulated while basal cAMP production was unaffected by o,p'-DDD. Pregnenolone-stimulated cortisol secretion was enhanced by o,p'-DDD at a physiologically relevant pregnenolone concentration, while o,p'-DDD inhibited cortisol secretion when a pharmacological concentration of pregnenolone was used. Our results suggest that the cAMP generation step is a target in o,p'-DDD-mediated disruption of ACTH-stimulated adrenal steroidogenesis in rainbow trout but that other downstream targets such as steroidogenic enzymes responsible for cortisol synthesis might also be affected.

Oxidative stress and loss of cortisol secretion in adrenocortical cells of rainbow trout (Oncorhynchus mykiss) exposed in vitro to endosulfan, an organochlorine pesticide

The effects of endosulfan, a widely used organochlorine pesticide, on cortisol secretion, cell viability, antioxidants and lipid peroxidation were investigated in enzymatically dispersed head kidney cells of rainbow trout (Oncorhynchus mykiss). ACTH- and dbcAMP-stimulated cortisol secretion, and cell viability were impaired in a dose-related manner following acute in vitro exposure to endosulfan (EC(50) 19 microM, LC(50) 366 microM) and the loss of cortisol secretion was detected even at concentrations of endosulfan that did not decrease cell viability. Stimulation with dbcAMP did not restore cortisol secretion in endosulfan exposed cells while stimulation with pregnenolone maintained cortisol secretion until viability of cells was affected. Thus endosulfan may disrupt processes between the step generating cAMP and the step where pregnenolone is used. Activity of catalase increased at concentrations of endosulfan that did not impair cortisol secretion, and decreased at higher doses. Glutathione peroxidase (GPx) activity was significantly reduced at doses of endosulfan that also reduced levels of glutathione, an essential cofactor of GPx. Exposure up to 1 x 10(-7) M endosulfan increased the activity of glutathione transferase. The present in vitro study identified endosulfan as a chemical inducing a loss of secretory responses in teleost adrenocortical steroidogenic cells and alterations in the activity of enzymes known to be involved in oxidative stress pathways. Moreover, the significant increase in lipid hydroperoxides levels provided further evidence for endosulfan-induced oxidative stress.

The adrenal cortex and steroidogenesis as cellular and molecular targets for toxicity: critical omissions from regulatory endocrine disrupter screening strategies for human health?

Current testing strategies to assess the endocrine disrupting properties of chemicals have omitted examination of the adrenal gland and do not adequately cover the process of steroidogenesis. Steroidogenesis is critical for adrenocortical function as well as that of the testes and ovaries, and presents multiple molecular targets for toxicity, ranging from general effects on all steroidogenic tissues (e.g. via StAR protein or CYP11A1 cholesterol side-chain cleavage) through to specific targets affecting only adrenocortical function (e.g. CYP11beta/18 and glucocorticoid synthesis). Numerous chemicals of environmental relevance are now being shown to affect adrenocortical function both in vivo in aquatic species and in vitro in human cell lines, and given the vital role of the adrenal gland to human health and development, there is a strong case for including dedicated assessment techniques in screening batteries for endocrine-disrupting chemicals, not least to assist in general data interpretation (e.g. whether adrenal hypertrophy is due to stress or to a more sinister adrenocortical insufficiency). Cell lines such as H295R (derived from a human adrenocortical adenocarcinoma) currently exist that will allow assessment of cortisol production and most of the major enzymes and functional proteins in the steroidogenic pathway (e.g. StAR; CYP11A1/scc; CYP11beta/18; CYP17; CYP19; CYP21; 3beta-hydroxysteroid dehydrogenase). Adequate assessment of adrenocortical function, as with any component of the integrated endocrine system, probably also will require the development of specific in vivo methodology to include effects on hypothalamo-pituitary function. Finally, although there is currently no direct evidence that environmental exposure to endocrine-disrupting (oestrogenic) chemicals has actually caused adverse human health effects, lessons have been learned on their potential from the diethylstilboestrol case. Similar evidence exists from aminoglutethimide and etomidate on the lethal impact of unpredicted chemically induced adrenal insufficiency in sensitive human subgroups, and it would seem prudent to incorporate relevant tests for adrenal function and steroidogenesis into current regulatory validation programmes.

Testicular germ-cell apoptosis in stressed rats following combined exposure to pyridostigmine bromide, N,N-diethyl m-toluamide (DEET), and permethrin

This study reports and characterizes the testicular apoptosis following daily exposure of male Sprague-Dawley rats to subchronic combined doses of pyridostigmine bromide (PB, 1.3 mg/kg/d in water, oral), a drug used for treatment of myasthenia gravis and prophylactic treatment against nerve agents during the Persian Gulf War; the insect repellent N,N-diethyl m-toluamide (DEET, 40 mg/kg/d in ethanol, dermal); and the insecticide permethrin (0.13 mg/kg in ethanol, dermal), with and without stress for 28 d. Combined exposure to these chemicals was implicated in the development of illnesses including genitourinary disorders among many veterans of the Persian Gulf War. Previous studies from this laboratory have shown that exposure to combination of these chemicals produced greater toxicity compared to single components. Exposure to stress alone did not cause any significant histopathological alterations in the testes. Administration of combination of these chemicals induced apoptosis in rat testicular germ cells, Sertoli cells, and Leydig cells, as well as in the endothelial lining of the blood vessels. Testicular damage was significantly augmented when the animals were further exposed to a combination of chemicals and stress. Histopathological examination of testicular tissue sections showed that apoptosis was confined to the basal germ cells and spermatocytes, indicating suppression of spermatogenesis. Increased apoptosis of testicular cells coincided, in timing and localization, with increased expression of the apoptosis-promoting proteins Bax and p53. Furthermore, significant increase of 3-nitrotyrosine immunostaining in the testis revealed oxidative and/or nitrosation induction of cell death. In conclusion, combined exposure to real-life doses of test compounds caused germ-cell apoptosis that was significantly enhanced by stress.

Identification of two novel ACTH-responsive genes encoding manganese-dependent superoxide dismutase (SOD2) and the zinc finger protein TIS11b [tetradecanoyl phorbol acetate (TPA)-inducible sequence 11b]

ACTH is the major trophic factor regulating and maintaining adrenocortical function, affecting such diverse processes as steroidogenesis, cell proliferation, cell migration, and cell survival. We used differential display RT-PCR to identify genes that are rapidly induced by ACTH in the bovine adrenal cortex. Of 42 PCR products differentially amplified from primary cultures of bovine adrenocortical cells treated with 10 nM ACTH, six identified mRNAs that were confirmed by Northern blot analysis to be induced by ACTH. Four of these amplicons encoded noninformative repetitive sequences. Of the other two sequenced amplicons, one encoded a partial sequence for mitochondrial manganese-dependent superoxide dismutase (SOD2), an enzyme that is likely to protect adrenocortical cells from the cytotoxic effects of radical oxygen species generated during steroid biosynthesis. The second was identified as TIS11b (phorbol-12-myristate-13-acetate-inducible sequence 11b)/ERF-1/cMG, a member of the CCCH double-zinc finger protein family. SOD2 induction by ACTH was independent of extracellular steroid concentration or oxidative stress. SOD2 and TIS11b mRNA expressions were rapidly induced by ACTH, reaching a maximal level after 8 h and 3 h of treatment, respectively. These ACTH effects were mimicked by forskolin but appeared independent of cortisol secretion. Upon ACTH treatment, induction of TIS11b expression closely followed the previously characterized peak of vascular endothelial growth factor (VEGF) expression. Transfection of a TIS11b expression plasmid into 3T3 fibroblasts induced a decrease in the expression of a reporter gene placed upstream of the VEGF 3'-untranslated region, indicating that TIS11b may be an important regulator of VEGF expression through interaction with its 3'-untranslated region.

Age-related increase in mitochondrial superoxide generation in the testosterone-producing cells of Brown Norway rat testes: relationship to reduced steroidogenic function?

Aging in Brown Norway rats is accompanied by the reduced production of testosterone by the Leydig cells, the testicular cells responsible for synthesizing and secreting this essential steroid. As yet, the mechanism by which Leydig cell steroidogenesis is reduced is unknown. Herein we assess the production of mitochondrial reactive oxygen species by intact Leydig cells isolated from the testes of young and old rats. To this end, Leydig cells were incubated with lucigenin (bis-N-methylacridinium nitrate), a probe that enters cells, localizes to mitochondria, and yields a significant chemiluminescent response following its reaction with intramitochondrial superoxide. Leydig cells from old rats elicited significantly greater lucigenin-derived chemiluminescence (LDCL) than those from young rats. Electron microscopic stereological analysis revealed that the absolute volume of mitochondria in the old cells was reduced from that in the young. These results, taken together, suggest that there are age-related changes in the production of reactive oxygen species by the mitochondria of Leydig cells, with those of old Leydig cells producing significantly greater levels than those of young Leydig cells. The results are consistent with the proposal that mitochondrial-derived reactive oxygen may play a role in the irreversible decline in the ability of old Leydig cells to produce testosterone.

Phenanthrenequinone disrupts progesterone production in rat luteal cells

The ability of the environmental contaminant phenanthrene (PH) and its photooxidized product phenanthrenequinone (PHQ) to disrupt progesterone secretion was examined in a model system of in vitro suspensions of luteal cells from the rat. Treatment with PHQ dramatically inhibited luteinizing hormone (LH) stimulated progesterone secretion. PHQ also generated a significant increase in reactive oxygen species (ROS). In the absence of LH, however, PHQ stimulated a small increase in basal progesterone secretion. The parent compound, PH, did not alter progesterone or ROS release. Since there is evidence that PHQ lowers the activity of nitric oxide synthase (NOS) and that nitric oxide (NO) affects progesterone production, we examined the response to the NOS inhibitors N-monomethyl-L-arginine, Zn protoporphyrin-9, and aminoguanidine in luteal cells. However, there was no effect of these agents on LH stimulated progesterone secretion. These results indicated that PHQ is a potent disrupter of progesterone secretion and should perhaps be considered in assessing the risk of PH to humans.

Modulation of steroidogenesis by selenium in a novel adrenal cell line developed using targeted tumorigenesis

Glutathione peroxidase (GPx-1) is a selenoenzyme that metabolizes H(2)O(2), a source of potentially toxic free radicals. Steroidogenesis is markedly inhibited by H(2)O(2) in vitro.

OBJECTIVE

to study the effects of selenium deficiency on GPx activity and adrenal steroidogenesis in a novel adrenal cell line developed using targeted tumorigenesis.

METHODS

AN4Rppc7 cells were grown for 7 days in serum-free medium. 8-Br-cAMP-stimulated concentrations of steroid hormones were measured by RIA. StAR (Steroid Acute Reactive Protein) mRNA was measured by Northern blot.

RESULTS

selenium deficiency caused a 99% There was a 51%, progesterone, corticosterone and aldosterone production, respectively (p<0.05 by ANOVA). StAR mRNA was not affected by selenium.

CONCLUSIONS

selenium deficiency causes a marked decrease in GPx activity. Decreased steroid hormone production occurs for selenium concentrations equal or lower than 5 nM. The absence of changes in StAR mRNA content suggests that selenium deficiency does not affect cholesterol access to the mitochondria.

Association between serum alpha-tocopherol and serum androgens and estrogens in older men

There is evidence supporting a role for sex hormones in the etiology of prostate cancer. Supplementation with alpha-tocopherol reduced prostate cancer in the alpha-Tocopherol, beta-Carotene Prevention Study (ATBC Study). The objective of this study was to assess the relation of baseline levels of serum alpha-tocopherol and serum sex hormones in older men. A cross-sectional analysis of serum alpha-tocopherol and sex hormone concentrations was conducted within a subset of the ATBC Study. Serum was collected in the morning after an overnight fast at baseline from 204 men ages 50-69 years participating in the ATBC Study and free of prostate cancer. Hormones were measured by radioimmunoassay, and alpha-tocopherol was measured by high-performance liquid chromatography by standard procedures. Multivariate linear regression was used to evaluate the association of serum alpha-tocopherol with nine androgens and estrogens after controlling for age, body mass index, hormone assay batch, and serum cholesterol. Serum alpha-tocopherol was significantly inversely associated with serum androstenedione, testosterone, sex hormone-binding globulin, and estrone. The difference in hormone concentration per milligram of alpha-tocopherol was 1.8-2.6% for these four hormones. These results indicated that alpha-tocopherol is related to concentrations of several sex hormones in older men and may have implications for the observed protective effect of supplemental vitamin E in relation to prostate cancer in the ATBC Study.

Superoxide Dismutase in Human Adrenal and its Disorders: A Correlation with Development and Neoplastic Changes

In adrenal glands, oxidative free radicals are synthesized in the course of hormonal production, and enzyme superoxide dismutase (SOD) is considered to scavenge these harmful superoxide radicals and, subsequently, to protect the cells. We studied immunohistochemical localization of Mn (manganese)-SOD and Cu,Zn (copper-zinc)-SOD in human adrenal and its disorders from fetus to adult obtained from autopsy or surgery in order to examine the possible biological significance of these two enzymes. In fetal adrenal (n = 4), Cu,Zn-SOD and Mn-SOD were detected only in the fetal cortex. In adrenal glands from children (n = 21) to adults (n = 15), Mn-SOD immunoreactivity was exclusively detected in adrenal medulla, whereas Cu,Zn-SOD immunoreactivity was present only in adrenocortical parenchymal cells, weakly in the zona glomerulosa, and markedly in the zona reticularis. There were no differences in relative immunointensity and/or patterns of immunolocalization of these two SODs among different age groups. Both Cu,Zn-SOD and Mn-SOD immunoreactivity were detected in compact tumor cells of adrenocortical adenoma (n = 16). Marked immunoreactivity of both Cu,Zn-SOD and Mn-SOD was detected in adrenocortical carcinoma (n = 11) and pheochromocytoma (n = 5). These results indicate that Cu,Zn-SOD and Mu-SOD may play different roles as a scavenger or antioxidants in normal human adrenal glands, i.e., Cu,Zn-SOD as a scavenger of toxic superoxide radicals generated during steroidogenesis and Mn-SOD during catecholamine production. Cu,Zn-SOD and Mn-SOD immunoreactivities detected in adrenal neoplasms are also considered to represent altered expression of these enzymes associated with neoplastic transformation, as reported in other human malignancies.

Structure-activity relationship for inhibition of CYP11B1-dependent glucocorticoid synthesis in Y1 cells by aryl methyl sulfones

The effects of xenobiotics on CYP11B1-dependent corticosterone synthesis (11 beta-hydroxylase) in mouse adrenocortical Y1 cells were studied. 3-Methylsulfonyl-2,2-bis(4-chlorophenyl)-1,1-dichloroethene (MeSO2-DDE) and some methylsulfonyl polychlorinated biphenyls (MeSO2-PCB) inhibited the corticosterone synthesis, whereas PCBs or DDE did not. This indicates a crucial role of the methyl sulfone group for this inhibitory effect. Kinetic analyses of MeSO2-DDE and the two most potent MeSO2-PCBs were conducted using Lineweaver-Burk double-reciprocal plots. The data showed a competitive inhibition of CYP11B1 by the compounds, with apparent inhibitory constants (Ki) of 1.6, 4.6, and 6.7 microM for MeSO2-DDE, 4-MeSO2-2,3,6,4'-tetrachlorobiphenyl, and 4-MeSO2-2,3,6,3',4'-pentachlorobiphenyl, respectively. For comparison, the substrate K(m) was 3.5 microM in the cells, and metyrapone and ketoconazole had apparent Ki-values of 0.8 and 0.04 microM, respectively. In contrast to all previously known inhibitors of CYP11B1, the aryl methyl sulfones are the first examples of CYP11B1 inhibitors not being heterocyclic amines or steroids. The aryl methyl sulfones are widespread environmental pollutants and their inhibition of CYP11B1 constitutes another potential mechanism for endocrine disruption. Their influence on the synthesis of adrenocortical hormones thus merits further interest.

Induction of neurosteroid synthesis by NMDA receptors in isolated rat retina: a potential early event in excitotoxicity

Here we investigated the possible regulation of neurosteroidogenesis by N-methyl-D-aspartic acid (NMDA) receptor activation and addressed the hypothesis that neurosteroid synthesis may be involved in acute excitotoxicity. In the isolated retina, exposure to NMDA modified pregnenolone and pregnenolone sulphate formation. This effect was dose and time dependent, the synthesis being increased by relatively moderate NMDA doses (1-100 microM) within 30 min exposure and reduced to its control value by 60 min or by raising drug concentrations. NMDA-stimulated neurosteroid synthesis was blocked by (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclo-hepten-5,10-imine hydrogen maleate (MK-801) and 3(2-carboxypiperazine-4-yl)propyl-1-phosphonic acid (CPP), depended on extracellular calcium and reproduced by glutamate. Lactate dehydrogenase (LDH) release and morphological analysis revealed that retinal cell viability was not significantly affected after 30 min exposure to 50 microM NMDA, but severe cell damage occurred by 60 min. When the GABAA (gamma-aminobutyric acid) receptor agonist muscimol (1-1000 microM), known to activate retinal neurosteroidogenesis, was added together with NMDA, no additional increase in neurosteroid synthesis was observed, and NMDA-induced LDH release remained unchanged. However, exposure to a high concentration of muscimol alone (500 microM) provoked a similar degree of toxicity to NMDA. By contrast, bicuculline abolished the increase in neurosteroidogenesis and LDH release. Similarly, pretreatment with R (+)-p-aminoglutethimide (AMG), an inhibitor of cholesterol side-chain cleavage cytochrome P450, attenuated acute retinal cell damage. The inhibitory nature of AMG on NMDA-stimulated neurosteroidogenesis was confirmed in the observation that drug treatment reduced pregnenolone content and did not affect the bindings of [3H] MK-801 and [3H] muscimol. The results demonstrate that NMDA receptors regulate neurosteroidogenesis through a transneuronal mechanism, which implies GABAA receptor activation. The early NMDA-mediated stimulation of neurosteroid synthesis seems to play a critical role in acute excitotoxicity; consequently, its inhibition is likely to delay neuronal cell death.

Antioxidant capacity is correlated with steroidogenic status of the corpus luteum during the bovine estrous cycle

The reactions of steroid hormone biosynthesis are accompanied by formation of oxygen radicals. We determined the levels of some antioxidants and antioxidative enzymes at different developmental stages of bovine corpora lutea to examine their correlation with steroidogenic status. Plasma progesterone concentrations of estrous cycle synchronized cows increased until day 16, and then decreased rapidly during luteal regression. The levels of steroidogenic cytochrome P450scc and adrenodoxin paralleled the changes in plasma progesterone. Among the antioxidative enzymes examined, the SOD and catalase activities showed patterns most similar to plasma progesterone. Catalase and SOD activities increased 6-8 fold from day 6 to 16 of the estrous cycle and then decreased during the luteal regression. Ascorbate and beta-carotene showed low but significant correlation with P450scc and plasma progesterone levels. The profiles of two lipophilic antioxidants in corpora lutea were very different. beta-carotene concentration increased by approximately 6 fold from day 6 to 16, and decreased in regressive tissue. alpha-tocopherol showed a 3 fold increase between days 6 and 9 followed by a rapid decrease. Thus, at the peak of steroidogenesis at mid-luteal phase alpha-tocopherol levels decreased, but beta-carotene levels increased. The correlation between the levels of some antioxidant enzymes and compounds with progesterone levels indicates that antioxidative mechanisms are activated to cope with steroidogenesis dependent oxyradical formation in the bovine corpus luteum.

11 beta-Hydroxylase activity in glucocorticoid suppressible hyperaldosteronism: lessons for essential hypertension?

Corticosteroid 11 beta-hydroxylation is catalysed by 11 beta-hydroxylase and aldosterone synthase. Using plasma steroid ratios, the level of this process in patients with glucocorticoid-suppressible hyperaldosteronism (GSH) was compared with that in unaffected control subjects and in patients with Conn's syndrome. Based on both 11-deoxycortisol:cortisol (S:F) and 11-deoxycorticosterone:corticosterone (DOC:B) ratios, patients with GSH showed impaired resting 11 beta-hydroxylase activity. In GSH, but not in the other groups, the S:F ratio was significantly correlated with basal plasma aldosterone concentration. ACTH infusion increased the S:F ratio in all these patient groups, suggesting a common partial deficiency. The results also indicate that 11 beta-hydroxylation may be rate-limiting in normal subjects. In control subjects and patients with Conn's syndrome, the DOC:B ratio was not affected by ACTH. However, in GSH patients, this ratio fell markedly, indicating an increased efficiency of 11 beta-hydroxylation of DOC (but not S). This may be due to the activation by ACTH of the zona fasciculata chimaeric aldosterone synthase characteristic of this disease. Plasma aldosterone, corticosterone and DOC concentrations, appeared to be more sensitive to ACTH in GSH than the other groups. The defect in 11 beta-hydroxylation in GSH accounts for the increased levels of DOC reported in the condition, and may contribute to the phenotypic variability.

Novel involvement of a mitochondrial steroid hydroxylase (P450c11) in xenobiotic metabolism

Adrenocortical mitochondrial cytochrome P450 isozymes of the Cyp11 family normally synthesize steroids with a very strict substrate specificity. However, for the first time, P450c11 was additionally shown to metabolize and bioactivate the adrenotoxic environmental pollutant 3-methylsulfonyl-2,2-bis(4-chlorophenyl)-1,1-dichloroethene (MeSO2-DDE). This conclusion is based on a striking correlation between inductions of MeSO2-DDE and deoxycorticosterone metabolism by forskolin in the adrenocortical cell lines Y1 and Kin-8, inhibition of P450c11-dependent activities in Y1 cells by MeSO2-DDE, and metabolism of MeSO2-DDE by non-steroidogenic COS cells after transfection with a cDNA encoding P450c11. The interaction between xenobiotics and glucocorticoid synthesis should focus more attention to xenobiotic-induced hormonal disturbances.

Alteration of the adrenal antioxidant defense system during aging in rats

The goal of this study was to determine to what extent aging affects the antioxidant defense system of the rat adrenal and to evaluate the impact of any change in this system on the recognized age-related decline in steroidogenic capacity of adrenocortical cells. The studies were conducted on young (2-5 mo) and aging (12-27 mo) Sprague-Dawley rats and involved procedures measuring steroidogenesis; oxidative damage to tissue; non enzymatic antioxidants such as vitamin C, E, and glutathione; and tissue antioxidant enzyme (Mn and CuZn superoxide dismutases, catalase, and glutathione peroxidase) activity and expression (mRNA, protein mass, and location). Some measurements were made also on rats maintained on vitamin E-deficient diets. The data show that adrenals from young animals are especially well protected against oxidative events; i.e., these adrenals show the least endogenous lipid peroxidation and the highest level of resistance to prooxidant-induced damage (of various tissues measured) and show exceedingly high levels of tissue antioxidants. Aging, on the other hand, results in oxidative changes in adrenal tissue that are generally linked in time to a reduction in efficiency of the normally protective antioxidant defense system and to the decline in corticosterone production. We speculate that these events are causally related, i.e., that the age-related reduction in oxidative mechanisms in adrenal tissues leads to oxidative damage of membrane or cytosolic factors important to cholesterol transport, and, as a consequence of this damage, cholesterol cannot reach appropriate mitochondrial cholesterol side chain cleavage sites, and corticosterone production fails.

Generation of free radicals and messenger function

Free radicals are toxic agents that are produced as by-products of metabolic activity. A number of antioxidant mechanisms work to protect cells from damage. Recent evidence indicates, however, that free radicals and related oxidants such as hydrogen peroxide may also have a beneficial role, working as messengers to control cell function. These agents are generated in response to agonists, production is regulated by intracellular signal pathways, and they appear to be used to control particular cellular processes. Free radicals may perform these functions in a number of cell types. Also, they are produced in muscles and there is evidence that they may work as messengers in smooth muscle cells.