5α-Tetrahydrocorticosterone: A topical anti-inflammatory glucocorticoid with an improved therapeutic index in a murine model of dermatitis

BACKGROUND AND PURPOSE

Glucocorticoids are powerful anti-inflammatory drugs, but are associated with many side-effects. Topical application in atopic dermatitis leads to skin thinning, metabolic changes, and adrenal suppression. 5α-Tetrahydrocorticosterone (5αTHB) is a potential selective anti-inflammatory with reduced metabolic effects. Here, the efficacy and side-effect profile of 5αTHB were compared with hydrocortisone in preclinical models of irritant dermatitis.

EXPERIMENTAL APPROACH

Acute irritant dermatitis was invoked in ear skin of male C57BL/6 mice with a single topical application of croton oil. Inflammation was assessed as oedema via ear weight following treatment with 5αTHB and hydrocortisone. Side-effects of 5αTHB and hydrocortisone were assessed following chronic topical steroid treatment (28 days) to non-irritated skin. Skin thinning was quantified longitudinally by caliper measurements and summarily by qPCR for transcripts for genes involved in extracellular matrix homeostasis; systemic effects of topical steroid administration also were assessed. Clearance of 5αTHB and hydrocortisone were measured following intravenous and oral administration.

KEY RESULTS

5αTHB suppressed ear swelling in mice, with ED50 similar to hydrocortisone (23 μg vs. 13 μg). Chronic application of 5αTHB did not cause skin thinning, adrenal atrophy, weight loss, thymic involution, or raised insulin levels, all of which were observed with topical hydrocortisone. Transcripts for genes involved in collagen synthesis and stability were adversely affected by all doses of hydrocortisone, but only by the highest dose of 5αTHB (8× ED50 ). 5αTHB was rapidly cleared from the systemic circulation.

CONCLUSIONS AND IMPLICATIONS

Topical 5αTHB has potential to treat inflammatory skin conditions, particularly in areas of delicate skin.

Comparison of mechanisms of angiostasis caused by the anti-inflammatory steroid 5α-tetrahydrocorticosterone versus conventional glucocorticoids

5α-Tetrahydrocorticosterone (5αTHB) is an effective topical anti-inflammatory agent in mouse, with less propensity to cause skin thinning and impede new blood vessel growth compared with corticosterone. Its anti-inflammatory effects were not prevented by RU38486, a glucocorticoid receptor antagonist, suggesting alternative mechanisms. The hypothesis that 5αTHB directly inhibits angiogenesis to a lesser extent than hydrocortisone was tested, focussing on glucocorticoid receptor mediated actions. New vessel growth from aortae from C57BL/6 male mice was monitored in culture, in the presence of 5αTHB, hydrocortisone (mixed glucocorticoid/mineralocorticoid receptor agonist) or the selective glucocorticoid receptor agonist dexamethasone. Transcript profiles were studied, as was the role of the glucocorticoid receptor, using the antagonist, RU38486. Ex vivo, 5αTHB suppressed vessel growth from aortic rings, but was less potent than hydrocortisone (EC50 2512 nM 5αTHB, versus 762 nM hydrocortisone). In contrast to conventional glucocorticoids, 5αTHB did not alter expression of genes related to extracellular matrix integrity or inflammatory signalling, but caused a small increase in Per1 transcript, and decreased transcript abundance of Pecam1 gene. RU38486 did not antagonise the residual effects of 5αTHB to suppress vessel growth or regulate gene expression, but modified effects of dexamethasone. 5αTHB did not alter expression of glucocorticoid-regulated genes Fkbp51 and Hsd11b1, unlike hydrocortisone and dexamethasone. In conclusion, compared with hydrocortisone, 5αTHB exhibits limited suppression of angiogenesis, at least directly in blood vessels and probably independent of the glucocorticoid receptor. Discriminating the mechanisms employed by 5αTHB may provide the basis for the development of novel safer anti-inflammatory drugs for topical use.

A Rat Model of Post-Traumatic Stress Syndrome Causes Phenotype-Associated Morphological Changes and Hypofunction of the Adrenal Gland

Background: Rats exposed to chronic predator scent stress mimic the phenotype of complex post-traumatic stress disorder (PTSD) in humans, including altered adrenal morphology and function. High- and low-anxiety phenotypes have been described in rats exposed to predator scent stress (PSS). This study aimed to determine whether these high- and low-anxiety phenotypes correlate with changes in adrenal histomorphology and corticosteroid production. Methods: Rats were exposed to PSS for ten days. Thirty days later, the rats’ anxiety index (AI) was assessed with an elevated plus-maze test. Based on differences in AI, the rats were segregated into low- (AI ≤ 0.8, n = 9) and high- (AI > 0.8, n = 10) anxiety phenotypes. Plasma corticosterone (CORT) concentrations were measured by ELISA. Adrenal CORT, desoxyCORT, and 11-dehydroCORT were measured by high-performance liquid chromatography. After staining with hematoxylin and eosin, adrenal histomorphometric changes were evaluated by measuring the thickness of the functional zones of the adrenal cortex. Results: Decreased plasma CORT concentrations, as well as decreased adrenal CORT, desoxyCORT and 11-dehydroCORT concentrations, were observed in high- but not in low-anxiety phenotypes. These decreases were associated with increases in AI. PSS led to a significant decrease in the thickness of the zona fasciculata and an increase in the thickness of the zona intermedia. The increase in the thickness of the zona intermedia was more pronounced in low-anxiety than in high-anxiety rats. A decrease in the adrenal capsule thickness was observed only in low-anxiety rats. The nucleus diameter of cells in the zona fasciculata of high-anxiety rats was significantly smaller than that of control or low-anxiety rats. Conclusion: Phenotype-associated changes in adrenal function and histomorphology were observed in a rat model of complex post-traumatic stress disorder.

Modulation of 11β-hydroxysteroid dehydrogenase functions by the cloud of endogenous metabolites in a local microenvironment: The glycyrrhetinic acid-like factor (GALF) hypothesis

11β-Hydroxysteroid dehydrogenase (11β-HSD)-dependent conversion of cortisol to cortisone and corticosterone to 11-dehydrocorticosterone are essential in regulating transcriptional activities of mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). Inhibition of 11β-HSD by glycyrrhetinic acid metabolites, bioactive components of licorice, causes sodium retention and potassium loss, with hypertension characterized by low renin and aldosterone. Essential hypertension is a major disease, mostly with unknown underlying mechanisms. Here, we discuss a putative mechanism for essential hypertension, the concept that endogenous steroidal compounds acting as glycyrrhetinic acid-like factors (GALFs) inhibit 11β-HSD dehydrogenase, and allow for glucocorticoid-induced MR and GR activation with resulting hypertension. Initially, several metabolites of adrenally produced glucocorticoids and mineralocorticoids were shown to be potent 11β-HSD inhibitors. Such GALFs include modifications in the A-ring and/or at positions 3, 7 and 21 of the steroid backbone. These metabolites may be formed in peripheral tissues or by gut microbiota. More recently, metabolites of 11β-hydroxy-Δ4androstene-3,17-dione and 7-oxygenated oxysterols have been identified as potent 11β-HSD inhibitors. In a living system, 11β-HSD isoforms are not exposed to a single substrate but to several substrates, cofactors, and various inhibitors simultaneously, all at different concentrations depending on physical state, tissue and cell type. We propose that this "cloud" of steroids and steroid-like substances in the microenvironment determines the 11β-HSD-dependent control of MR and GR activity. A dysregulated composition of this cloud of metabolites in the respective microenvironment needs to be taken into account when investigating disease mechanisms, for forms of low renin, low aldosterone hypertension.

Carbonyl reductase 1 amplifies glucocorticoid action in adipose tissue and impairs glucose tolerance in lean mice

OBJECTIVE

Carbonyl reductase 1 (Cbr1), a recently discovered contributor to tissue glucocorticoid metabolism converting corticosterone to 20β-dihydrocorticosterone (20β-DHB), is upregulated in adipose tissue of obese humans and mice and may contribute to cardiometabolic complications of obesity. This study tested the hypothesis that Cbr1-mediated glucocorticoid metabolism influences glucocorticoid and mineralocorticoid receptor activation in adipose tissue and impacts glucose homeostasis in lean and obese states.

METHODS

The actions of 20β-DHB on corticosteroid receptors in adipose tissue were investigated first using a combination of in silico, in vitro, and transcriptomic techniques and then in vivo administration in combination with receptor antagonists. Mice lacking one Cbr1 allele and mice overexpressing Cbr1 in their adipose tissue underwent metabolic phenotyping before and after induction of obesity with high-fat feeding.

RESULTS

20β-DHB activated both the glucocorticoid and mineralocorticoid receptor in adipose tissue and systemic administration to wild-type mice induced glucose intolerance, an effect that was ameliorated by both glucocorticoid and mineralocorticoid receptor antagonism. Cbr1 haploinsufficient lean male mice had lower fasting glucose and improved glucose tolerance compared with littermate controls, a difference that was abolished by administration of 20β-DHB and absent in female mice with higher baseline adipose 20β-DHB concentrations than male mice. Conversely, overexpression of Cbr1 in adipose tissue resulted in worsened glucose tolerance and higher fasting glucose in lean male and female mice. However, neither Cbr1 haploinsfficiency nor adipose overexpression affected glucose dyshomeostasis induced by high-fat feeding.

CONCLUSIONS

Carbonyl reductase 1 is a novel regulator of glucocorticoid and mineralocorticoid receptor activation in adipose tissue that influences glucose homeostasis in lean mice.

Quantitative analysis of 11-dehydrocorticosterone and corticosterone for preclinical studies by liquid chromatography/triple quadrupole mass spectrometry

RATIONALE

The activity of the glucocorticoid activating enzyme 11β-hydroxysteroid dehydrogenase type-1 (11βHSD1) is altered in diseases such as obesity, inflammation and psychiatric disorders. In rodents 11βHSD1 converts inert 11-dehydrocorticosterone (11-DHC) into the active form, corticosterone (CORT). A sensitive, specific liquid chromatography/tandem mass spectrometry method was sought to simultaneously quantify total 11-DHC and total and free CORT in murine plasma for simple assessment of 11βHSD1 activity in murine models.

METHODS

Mass spectrometry parameters were optimised and a method for the chromatographic separation of CORT and 11-DHC was developed. Murine plasma was prepared by 10:1 chloroform liquid-liquid extraction (LLE) for analysis. Limits of quantitation (LOQs), linearity and other method criteria were assessed, according to bioanalytical method validation guidelines.

RESULTS

Reliable separation of 11-DHC and CORT was achieved using an ACE Excel 2 C18-AR (2.1 × 150 mm; 2 μm) fused core column at 25°C, with an acidified water/acetonitrile gradient over 10 min. Analytes were detected by multiple reaction monitoring after positive electrospray ionisation (m/z 345.1.1 ➔ 121.2, m/z 347.1 ➔ 121.1 for 11-DHC and CORT, respectively). The LOQs were 0.25 and 0.20 ng/mL for 11-DHC and CORT, respectively.

CONCLUSIONS

This LC/MS method is suitable for the reliable analysis of 11-DHC and CORT following simple LLE of murine plasma, bringing preclinical analysis in line with recommendations for clinical endocrinology and biochemistry.

Measurement of 1α hydroxycorticosterone in the Japanese banded houndshark, Triakis scyllium, following exposure to a series of stressors

An endocrine glucocorticoid response following exposure to a stressor has been well described for many vertebrates. However, despite demonstration of secondary stress responses in a number of elasmobranchs, our understanding of the endocrine control of these responses is lacking. This is largely due to the unusual structure of the dominant corticosteroid in elasmobranch fish, 1α-hydroxycorticosterone (1α-OH-B). Here we describe plasma extraction and HPLC separation procedures that allowed for the measurement of 1α-OH-B and corticosterone from plasma samples in the cannulated, conscious free-swimming Japanese banded houndshark, Triakis scyllium. While patterns of concentration in the plasma for 1α-OH-B and corticosterone were found to be similar in all experiments conducted, circulating levels of 1α-OH-B were consistently 100-fold greater than circulating levels of corticosterone. Immediately following cannulation surgery, circulating levels of 1α-OH-B increased 7-fold compared to pre-surgery levels, while the levels were 11-fold higher than pre-stress levels 30 min post a repeated handling/air-exposure stress. A three week period of fasting resulted in a 22-fold increase in circulating levels of 1α-OH-B in the banded houndshark. This is the first report of direct measurement of changes in circulating levels of the primary corticosteroid in elasmobranch fish, 1α-OH-B, following exposure to a stressor such as handling/air-exposure. Data indicate the steroid may respond similarly to the classic glucocorticoid response, such as cortisol in teleosts.

Measurement of 11-dehydrocorticosterone in mice, rats and songbirds: Effects of age, sex and stress

Glucocorticoids (GCs) are secreted into the blood by the adrenal glands and are also locally-produced by organs such as the lymphoid organs (bone marrow, thymus, and spleen). Corticosterone is the primary circulating GC in many species, including mice, rats and birds. Within lymphoid organs, corticosterone can be locally produced from the inactive metabolite, 11-dehydrocorticosterone (DHC). However, very little is known about endogenous DHC levels, and no immunoassays are currently available to measure DHC. Here, we developed an easy-to-use and inexpensive immunoassay to measure DHC that is accurate, precise, sensitive, and specific. The DHC immunoassay was validated in multiple ways, including comparison with a mass spectrometry assay. After assay validations, we demonstrated the usefulness of this immunoassay by measuring DHC (and corticosterone) in mice, rats and song sparrows. Overall, corticosterone levels were higher than DHC levels across species. In Study 1, using mice, we measured steroids in whole blood and lymphoid organs at postnatal day (PND) 5, PND23, and PND90. Corticosterone and DHC showed distinct tissue-specific patterns across development. In Studies 2 and 3, we measured circulating corticosterone and DHC in adult rats and song sparrows, before and after restraint stress. In rats and song sparrows, restraint stress rapidly increased circulating levels of both steroids. This novel DHC immunoassay revealed major changes in DHC concentrations during development and in response to stress, which have important implications for understanding GC physiology, effects of stress on immune function, and regulation of local GC levels.

Challenges, pitfalls and surprises: development and validation of a monoclonal antibody for enzyme immunoassay of the steroid 1α-hydroxycorticosterone in elasmobranch species

Sharks and rays are popular species used in wildlife ecotourism and aquariums to educate the public on the behavior, ecology and conservation challenges of elasmobranchs. To understand long-term physiological health and welfare under varying social and husbandry conditions, we developed and validated an enzyme immunoassay (EIA) to measure stress/ionoregulatory hormones in managed and semi-free range southern rays (Hypanus americanus). Banked serum and interrenal samples from 27 female rays managed at Disney's The Seas with Nemo and Friends® and Castaway Cay were used to evaluate measurement of 1α-hydroxycorticosterone (1αOHB) relative to corticosterone (B). Although commercial EIAs are available for B, those tested exhibit only low relative cross-reactivity to 1αOHB (3-5%). To improve measurement of 1αOHB, we developed a monoclonal antibody using a synthesized 1αOHB-derivative for evaluation using high-performance liquid chromatography (HPLC) and EIA. Relative displacements of cross-reactant compounds showed that the antibody had good sensitivity for the target antigen 1αOHB, and low sensitivity to related steroids (desoxycorticosterone and B), but greater sensitivity to 11-dehydrocorticosterone. Tests of competitive vs. noncompetitive EIA formats, reagent titration, and incubation times of the antibody and conjugate were used to optimize sensitivity, repeatability and precision of measured 1αOHB in standards and samples (4 ng/ml, 90% binding). Tests of sample pre-treatment (pH adjustment) and extraction with varying solvent polarity were used to optimize measurement of 1αOHB in <1 ml (serum) or 1 g (interrenal) samples. HPLC analysis revealed the 1αOHB EIA to be superior for measurement of 1αOHB compared to use of a B EIA with or without HPLC fractioning. Results may prove useful for extrapolation to guide best practices for 1αOHB measurement in other elasmobranch species. Improved measurement of stress/ionoregulatory hormones in sharks and rays will be important for many aspects of collection, transport, medical treatment in aquaria and conservation management of these charismatic and ecologically important species.

Glucocorticoids Reprogram β-Cell Signaling to Preserve Insulin Secretion

Excessive glucocorticoid exposure has been shown to be deleterious for pancreatic β-cell function and insulin release. However, glucocorticoids at physiological levels are essential for many homeostatic processes, including glycemic control. We show that corticosterone and cortisol and their less active precursors 11-dehydrocorticosterone (11-DHC) and cortisone suppress voltage-dependent Ca²⁺ channel function and Ca²⁺ fluxes in rodent as well as in human β-cells. However, insulin secretion, maximal ATP/ADP responses to glucose, and β-cell identity were all unaffected. Further examination revealed the upregulation of parallel amplifying cAMP signals and an increase in the number of membrane-docked insulin secretory granules. Effects of 11-DHC could be prevented by lipotoxicity and were associated with paracrine regulation of glucocorticoid activity because global deletion of 11β-hydroxysteroid dehydrogenase type 1 normalized Ca²⁺ and cAMP responses. Thus, we have identified an enzymatically amplified feedback loop whereby glucocorticoids boost cAMP to maintain insulin secretion in the face of perturbed ionic signals. Failure of this protective mechanism may contribute to diabetes in states of glucocorticoid excess, such as Cushing syndrome, which are associated with frank dyslipidemia.

Biosynthesis of 1α-hydroxycorticosterone in the winter skate Leucoraja ocellata: evidence to suggest a novel steroidogenic route

The present study explores the ability of intracellular bacteria within the renal-inter-renal tissue of the winter skate Leucoraja ocellata to metabolize steroids and contribute to the synthesis of the novel elasmobranch corticosteroid, 1α-hydroxycorticosterone (1α-OH-B). Despite the rarity of C1 hydroxylation noted in the original identification of 1α-OH-B, literature provides evidence for steroid C1 hydroxylation by micro-organisms. Eight ureolytic bacterial isolates were identified in the renal-inter-renal tissue of L. ocellata, the latter being the site of 1α-OH-B synthesis. From incubations of bacterial isolates with known amounts of potential 1α-OH-B precursors, one isolate UM008 of the genus Rhodococcus was seen to metabolize corticosteroids and produce novel products via HPLC analysis. Cations Zn²⁺ and Fe³⁺ altered metabolism of certain steroid precursors, suggesting inhibition of Rhodococcus steroid catabolism. Genome sequencing of UM008 identified strong sequence and structural homology to that of Rhodococcus erythropolis PR4. A complete enzymatic pathway for steroid-ring oxidation as documented within other Actinobacteria was identified within the UM008 genome. This study highlights the potential role of Rhodococcus bacteria in steroid metabolism and proposes a novel alternative pathway for 1α-OH-B synthesis, suggesting a unique form of mutualism between intracellular bacteria and their elasmobranch host.

11β-HSD1 suppresses cardiac fibroblast CXCL2, CXCL5 and neutrophil recruitment to the heart post MI

We have previously demonstrated that neutrophil recruitment to the heart following myocardial infarction (MI) is enhanced in mice lacking 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) that regenerates active glucocorticoid within cells from intrinsically inert metabolites. The present study aimed to identify the mechanism of regulation. In a mouse model of MI, neutrophil mobilization to blood and recruitment to the heart were higher in 11β-HSD1-deficient (Hsd11b1^-/- ) relative to wild-type (WT) mice, despite similar initial injury and circulating glucocorticoid. In bone marrow chimeric mice, neutrophil mobilization was increased when 11β-HSD1 was absent from host cells, but not when absent from donor bone marrow-derived cells. Consistent with a role for 11β-HSD1 in 'host' myocardium, gene expression of a subset of neutrophil chemoattractants, including the chemokines Cxcl2 and Cxcl5, was selectively increased in the myocardium of Hsd11b1^-/- mice relative to WT. SM22α-Cre directed disruption of Hsd11b1 in smooth muscle and cardiomyocytes had no effect on neutrophil recruitment. Expression of Cxcl2 and Cxcl5 was elevated in fibroblast fractions isolated from hearts of Hsd11b1^-/- mice post MI and provision of either corticosterone or of the 11β-HSD1 substrate, 11-dehydrocorticosterone, to cultured murine cardiac fibroblasts suppressed IL-1α-induced expression of Cxcl2 and Cxcl5 These data identify suppression of CXCL2 and CXCL5 chemoattractant expression by 11β-HSD1 as a novel mechanism with potential for regulation of neutrophil recruitment to the injured myocardium, and cardiac fibroblasts as a key site for intracellular glucocorticoid regeneration during acute inflammation following myocardial injury.

Glucocorticoids and 11β-HSD1 are major regulators of intramyocellular protein metabolism

The adverse metabolic effects of prescribed and endogenous glucocorticoid excess, 'Cushing's syndrome', create a significant health burden. While skeletal muscle atrophy and resultant myopathy is a clinical feature, the molecular mechanisms underpinning these changes are not fully defined. We have characterized the impact of glucocorticoids upon key metabolic pathways and processes regulating muscle size and mass including: protein synthesis, protein degradation, and myoblast proliferation in both murine C2C12 and human primary myotube cultures. Furthermore, we have investigated the role of pre-receptor modulation of glucocorticoid availability by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in these processes. Corticosterone (CORT) decreased myotube area, decreased protein synthesis, and increased protein degradation in murine myotubes. This was supported by decreased mRNA expression of insulin-like growth factor (IGF1), decreased activating phosphorylation of mammalian target of rapamycin (mTOR), decreased phosphorylation of 4E binding protein 1 (4E-BP1), and increased mRNA expression of key atrophy markers including: atrogin-1, forkhead box O3a (FOXO3a), myostatin (MSTN), and muscle-ring finger protein-1 (MuRF1). These findings were endorsed in human primary myotubes, where cortisol also decreased protein synthesis and increased protein degradation. The effects of 11-dehydrocorticosterone (11DHC) (in murine myotubes) and cortisone (in human myotubes) on protein metabolism were indistinguishable from that of CORT/cortisol treatments. Selective 11β-HSD1 inhibition blocked the decrease in protein synthesis, increase in protein degradation, and reduction in myotube area induced by 11DHC/cortisone. Furthermore, CORT/cortisol, but not 11DHC/cortisone, decreased murine and human myoblast proliferative capacity. Glucocorticoids are potent regulators of skeletal muscle protein homeostasis and myoblast proliferation. Our data underscores the potential use of selective 11β-HSD1 inhibitors to ameliorate muscle-wasting effects associated with glucocorticoid excess.

Acute Effects of Lysergic Acid Diethylamide on Circulating Steroid Levels in Healthy Subjects

Lysergic acid diethylamide (LSD) is a serotonin 5-hydroxytryptamine-2A (5-HT2A ) receptor agonist that is used recreationally worldwide. Interest in LSD research in humans waned after the 1970s, although the use of LSD in psychiatric research and practice has recently gained increasing attention. LSD produces pronounced acute psychedelic effects, although its influence on plasma steroid levels over time has not yet been characterised in humans. The effects of LSD (200 μg) or placebo on plasma steroid levels were investigated in 16 healthy subjects using a randomised, double-blind, placebo-controlled, cross-over study design. Plasma concentration-time profiles were determined for 15 steroids using liquid-chromatography tandem mass-spectrometry. LSD increased plasma concentrations of the glucocorticoids cortisol, cortisone, corticosterone and 11-dehydrocorticosterone compared to placebo. The mean maximum concentration of LSD was reached at 1.7 h. Mean peak psychedelic effects were reached at 2.4 h, with significant alterations in mental state from 0.5 h to > 10 h. Mean maximal concentrations of cortisol and corticosterone were reached at 2.5 h and 1.9 h, and significant elevations were observed 1.5-6 h and 1-3 h after drug administration, respectively. LSD also significantly increased plasma concentrations of the androgen dehydroepiandrosterone but not other androgens, progestogens or mineralocorticoids compared to placebo. A close relationship was found between plasma LSD concentrations and changes in plasma cortisol and corticosterone and the psychotropic response to LSD, and no clockwise hysteresis was observed. In conclusion, LSD produces significant acute effects on circulating steroids, especially glucocorticoids. LSD-induced changes in circulating glucocorticoids were associated with plasma LSD concentrations over time and showed no acute pharmacological tolerance.

Pregnancy-induced adaptations of the central circadian clock and maternal glucocorticoids

Maternal physiological adaptations, such as changes to the hypothalamic-pituitary-adrenal (HPA) axis, are central to pregnancy success. Circadian variation of the HPA axis is dependent on clock gene rhythms in the hypothalamus, but it is not known whether pregnancy-induced changes in maternal glucocorticoid levels are mediated via this central clock. We hypothesized that hypothalamic expression of clock genes changes across mouse pregnancy and this is linked to altered HPA activity. The anterior hypothalamus and maternal plasma were collected from C57Bl/6J mice prior to pregnancy and on days 6, 10, 14 and 18 of gestation (term=d19), across a 24-h period (0800, 1200, 1600, 2000, 0000, 0400 h). Hypothalamic expression of clock genes and Crh was determined by qPCR, plasma ACTH concentration measured by Milliplex assay and plasma corticosterone concentration by LC-MS/MS. Expression of all clock genes varied markedly across gestation, most notably at mid-gestation when levels of each gene were elevated. The pregnancy-induced increase in maternal corticosterone levels (by up to 14-fold on day 14) was not accompanied by a parallel shift in plasma ACTH (28% lower on day 14 compared with non-pregnant levels). Moreover, while circadian rhythmicity in corticosterone was maintained up to day 14 of gestation, this was effectively lost by day 18. Overall, our data show that the central circadian clock undergoes marked adaptations throughout mouse pregnancy, changes that are likely to contribute to maternal physiological adaptations. Importantly, however, neither hypothalamic clock genes nor plasma ACTH levels appear to drive the marked increase in maternal corticosterone after mid-gestation.

Decreased 11β-Hydroxysteroid Dehydrogenase 1 Level and Activity in Murine Pancreatic Islets Caused by Insulin-Like Growth Factor I Overexpression

We have reported a high expression of IGF-I in pancreatic islet β-cells of transgenic mice under the metallothionein promoter. cDNA microarray analysis of the islets revealed that the expression of 82 genes was significantly altered compared to wild-type mice. Of these, 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1), which is responsible for the conversion of inert cortisone (11-dehydrocorticosterone, DHC in rodents) to active cortisol (corticosterone) in the liver and adipose tissues, has not been identified previously as an IGF-I target in pancreatic islets. We characterized the changes in its protein level, enzyme activity and glucose-stimulated insulin secretion. In freshly isolated islets, the level of 11β-HSD1 protein was significantly lower in MT-IGF mice. Using dual-labeled immunofluorescence, 11β-HSD1 was observed exclusively in glucagon-producing, islet α-cells but at a lower level in transgenic vs. wild-type animals. MT-IGF islets also exhibited reduced enzymatic activities. Dexamethasone (DEX) and DHC inhibited glucose-stimulated insulin secretion from freshly isolated islets of wild-type mice. In the islets of MT-IGF mice, 48-h pre-incubation of DEX caused a significant decrease in insulin release, while the effect of DHC was largely blunted consistent with diminished 11β-HSD1 activity. In order to establish the function of intracrine glucocorticoids, we overexpressed 11β-HSD1 cDNA in MIN6 insulinoma cells, which together with DHC caused apoptosis and a significant decrease in proliferation. Both effects were abolished with the treatment of an 11β-HSD1 inhibitor. Our results demonstrate an inhibitory effect of IGF-I on 11β-HSD1 expression and activity within the pancreatic islets, which may mediate part of the IGF-I effects on cell proliferation, survival and insulin secretion.

C21-steroids inactivation and glucocorticoid synthesis in the developing lung

Glucocorticoids (GCs) are important regulators of lung development. The genes normally involved in GC synthesis in adrenals are co-expressed with 20α-hydroxysteroid dehydrogenase (20α-HSD) in the developing lung. In this study, C21-steroid metabolism was investigated in fetal and postnatal mouse lungs. Incubation of [(3)H]-progesterone with lung explant cultures of different perinatal developmental time points revealed two different (antenatal vs. postnatal) complex metabolization patterns. Progesterone inactivation was predominant. 20αOH-derivatives were more abundant after birth and some metabolites were 5α-reduced. Using [(3)H]-progesterone as substrate, corticosterone synthesis was only observed in a fraction of lung explants from gestation day (GD) 15.5. Neither aldosterone synthase nor P450c17 activity was observed. With epithelial-enriched primary cell cultures, deoxycorticosterone synthesis from [(3)H]-progesterone was observed. With lung explants incubated with [(3)H]-corticosterone as substrate, [(3)H]-4-pregnen-21-ol-3,11,20-trione (11-dehydrocorticosterone), the product of 11β-HSD2, accumulated in higher proportion on GD 15.5 than at later developmental time points. The temporal correlation observed between levels of progesterone inactivation by 20α-HSD (higher after birth) and the sensitivity of lung development to GCs suggests a role for 20α-HSD in the modulation of GR occupancy through the control of 21-hydroxylase substrate and product levels. In conclusion, the developing lung is characterized by effective inactivation of c21-steroids by 20α-HSD. The formation of active GCs from the "adrenal"-like pathway was observed with some lung explants and primary epithelial cell cultures. Coexistence of this GC synthesis pathway with 20α-HSD activity strongly suggests local regulation of GC action and is compatible with intracrine/paracrine actions of GC.

11-Dehydrocorticosterone causes metabolic syndrome, which is prevented when 11β-HSD1 is knocked out in livers of male mice

Metabolic syndrome is growing in importance with the rising levels of obesity, type 2 diabetes, and insulin resistance. Metabolic syndrome shares many characteristics with Cushing's syndrome, which has led to investigation of the link between excess glucocorticoids and metabolic syndrome. Indeed, increased glucocorticoids from intracellular regeneration by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) drives insulin resistance and increases adiposity, but these metabolic changes are assumed to be due to increased circulating glucocorticoids. We hypothesized that increasing the substrate for 11β-HSD1 (11-dehydrocorticosterone, 11-DHC) would adversely affect metabolic parameters. We found that chronic administration of 11-DHC to male C57BL/6J mice resulted in increased circulating glucocorticoids, and down-regulation of the hypothalamic-pituitary-adrenal axis. This elevated 11β-HSD1-derived corticosterone led to increased body weight gain and adiposity and produced marked insulin resistance. Surprisingly liver-specific 11β-HSD1 knockout (LKO) mice given 11-DHC did not show any of the adverse metabolic effects seen in wild-type mice. This occurred despite the 11-DHC administration resulting in elevated circulating corticosterone, presumably from adipose tissue. Mice with global deletion of 11β-HSD1 (global knockout) were unaffected by treatment with 11-DHC, having no increase in circulating corticosterone and exhibiting no signs of metabolic impairment. Taken together, these data show that in the absence of 11β-HSD1 in the liver, mice are protected from the metabolic effects of 11-DHC administration, even though circulating glucocorticoids are increased. This implies that liver-derived intratissue glucocorticoids, rather than circulating glucocorticoids, contribute significantly to the development of metabolic syndrome and suggest that local action within hepatic tissue mediates these effects.

Adrenalectomy amplifies aldosterone induced injury in cardiovascular tissue: an effect attenuated by adrenally derived steroids

Aldosterone induces fibrotic changes in cardiovascular tissues but its effects have usually been demonstrated in models of pre-existing renal injury and/or hypertension. This study tests the hypothesis that aldosterone can directly induce vascular fibrotic changes in the absence of prior renal injury or hypertension. Experiments were conducted in intact or adrenalectomized (ADX) mice. Mice were divided into groups and treated for 1 week with vehicle or aldosterone (8 μg/kg/day)± inhibitor (800 μg/kg/day): CONTROLS, mice treated with aldosterone, ADX-CONTROLS, ADX+corticosterone (CORT 8 μg/kg/day), ADX with aldosterone, ADX with aldosterone plus the mineralocorticoid receptor (MR) antagonist RU-318, ADX with aldosterone+CORT (CORT inhibitor dose), and ADX with aldosterone+11-dehydro-CORT. Aortic smooth muscle to collagen ratio, aorta intimal thickness (μm), heart weight/body weight ratio (mg/gm), and left ventricular collagen (%) were measured. Prior to sacrifice, blood pressures were normal in all animals. Lower dose CORT alone had no effect on any of the variables examined. Aldosterone exposure was associated with extra-cellular matrix accumulation in cardiovascular tissues in intact mice and adrenalectomy exacerbated these effects. RU-318, CORT (inhibitor dose), and 11-deydro-CORT each attenuated the early fibrotic changes induced by aldosterone. In the heart, aldosterone exposure affected all the parameters measured and caused intimal hypercellularity with monocytes adhering to endothelial cells lining coronary vessels. Cultured endothelial cells exposed to aldosterone (10nM) released E-selectin, produced collagen, and promoted monocyte adhesion. These effects were inhibited by RU-318 and 11-deydro-CORT but not by CORT. Thus, adrenalectomy enhances aldosterone induced early fibrotic changes in heart and aorta. Aldosterone initially targets vascular endothelial cells. MR antagonists and 11-dehydro-CORT, an 11β-HSD dehydrogenase end-product, directly attenuate these effects.

11β-Hydroxysteroid dehydrogenase type 1 selective inhibitor BVT.2733 protects osteoblasts against endogenous glucocorticoid induced dysfunction

Pharmacologic glucocorticoids (GCs) inhibit osteoblast function and induce osteoporosis. 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) may play a role in osteoporosis as it regulates GC action at a pre-receptor level by converting inactive GC to its active form. Further, 11β-HSD1 was found increasingly expressed in bone with age. In spite of these observations, its function in senile osteoporosis remains uncertain. In this study we constructed a lentiviral vector overexpressing mouse 11β-HSD1 and then MC3T3-E1 preosteoblast cells were infected by the negative control lentivirus and 11β-HSD1-overexpressing lentivirus, respectively. The mRNA and protein levels of 11β-HSD1 were significantly increased in MC3T3-E1 cells that were infected by 11β-HSD1-overexpressing lentivirus compared to the cells infected by the negative control lentivirus. The osteogenic differentiation of MC3T3-E1 preosteoblast cells was dramatically suppressed by 11β-HSD1 overexpression under the reductase substrate dehydrocorticosterone (DHC). The inhibition effect was similar to the inhibition of osteogenesis by over-dose GCs, including ALP activity, the ultimate calcium nodus formation as well as the expression of the osteogenic genes such as ALP, BSP, OPN and OCN. However, with addition of BVT.2733, a selective inhibitor of 11β-HSD1, all of the above osteogenic repression effects by 11β-HSD1 overexpression were reversed. Furthermore, a GC receptor antagonist RU486 also showed the similar effect, preventing inhibition of osteogenesis by 11β-HSD1 overexpression. These results demonstrated that the specific 11β-HSD1 inhibitor BVT.2733 can reverse the suppression effect towards osteogenic differentiation in 11β-HSD1 overexpressed MC3T3-E1 cells. Inhibition of 11β-HSD1 can be a new therapeutic strategy for senile osteoporosis.

Human aldosterone synthase: recombinant expression in E. coli and purification enables a detailed biochemical analysis of the protein on the molecular level

Aldosterone, the most important human mineralocorticoid, is involved in the regulation of the blood pressure and has been reported to play a key role in the formation of arterial hypertension, heart failure and myocardial fibrosis. Aldosterone synthase (CYP11B2) catalyzes the biosynthesis of aldosterone by successive 11β- and 18-hydroxylation followed by an 18-oxidation of 11-deoxycorticosterone and thus comprises an important drug target. For more than 20 years, all attempts to purify recombinant human CYP11B2 in significant amounts for detailed analysis failed due to its hydrophobic nature as a membrane protein. Here, we present the successful expression of the protein in E. coli yielding approx. 90 nmol/l culture, its purification and detailed enzymatic characterization. Biochemical analyses have been performed using in vitro conversion assays which revelead a V(max) of 238±8 nmol products/nmol hCYP11B2/min and a K(m) of 103±8 μM 11-deoxycorticosterone. Furthermore, binding analyses indicated a very loose binding of the first intermediate of the reaction, corticosterone with a K(d) value of 115±6 μM whereas for 11-deoxycorticosterone a K(d) of 1.34±0.13 μM was estimated. Upon substrate conversion of 11-deoxycorticosterone, new intermediates have been identified as 19- and 18-hydroxylated products not described before for the human enzyme. To understand the differences in substrate conversion, we constructed a new homology model based on the 3D structure of CYP11A1, performed docking studies and calculated the activation energy for hydrogen abstraction of the different ligands. The data demonstrated that the 11β-hydroxylation requires much less abstraction energy than hydroxylation at C18 and C19. However, the C18 and C19 hydroxylated products might be of clinical importance. Finally, purified CYP11B2 represents a suitable tool for the investigation of potential inhibitors of this protein for the development of novel drugs against hypertension and heart failure as was shown using ketoconazole.

5α-Reduced glucocorticoids: a story of natural selection

5α-Reduced glucocorticoids (GCs) are formed when one of the two isozymes of 5α-reductase reduces the Δ(4-5) double bond in the A-ring of GCs. These steroids are largely viewed inert, despite the acceptance that other 5α-dihydro steroids, e.g. 5α-dihydrotestosterone, retain or have increased activity at their cognate receptors. However, recent findings suggest that 5α-reduced metabolites of corticosterone have dissociated actions on GC receptors (GRs) in vivo and in vitro and are thus potential candidates for safer anti-inflammatory steroids. 5α-Dihydro- and 5α-tetrahydro-corticosterone can bind with GRs, but interest in these compounds had been limited, since they only weakly activated metabolic gene transcription. However, a greater understanding of the signalling mechanisms has revealed that transactivation represents only one mode of signalling via the GR and recently the abilities of 5α-reduced GCs to suppress inflammation have been demonstrated in vitro and in vivo. Thus, the balance of parent GC and its 5α-reduced metabolite may critically affect the profile of GR signalling. 5α-Reduction of GCs is up-regulated in liver in metabolic disease and may represent a pathway that protects from both GC-induced fuel dyshomeostasis and concomitant inflammatory insult. Therefore, 5α-reduced steroids provide hope for drug development, but may also act as biomarkers of the inflammatory status of the liver in metabolic disease. With these proposals in mind, careful attention must be paid to the possible adverse metabolic effects of 5α-reductase inhibitors, drugs that are commonly administered long term for the treatment of benign prostatic hyperplasia.

Local metabolism of glucocorticoids in Prague hereditary hypertriglyceridemic rats--effect of hypertriglyceridemia and gender

11β-Hydroxysteroid dehydrogenase type 1 (11HSD1) is a microsomal NADPH-dependent oxidoreductase which elevates intracellular concentrations of active glucocorticoids. Data obtained from mouse strains with genetically manipulated 11HSD1 showed that local metabolism of glucocorticoids plays an important role in the development of metabolic syndrome. Tissue specific dysregulation of 11HSD1 was also found in other models of metabolic syndrome as well as in a number of clinical studies. Here, we studied local glucocorticoid action in the liver, subcutaneous adipose tissue (SAT) and skeletal muscles of male and female Prague hereditary hypertriglyceridemic rats (HHTg) and their normotriglyceridemic counterpart, the Wistar rats. 11HSD1 bioactivity was measured as a conversion of [(3)H]11-dehydrocorticosterone to [(3)H]corticosterone or vice versa. Additionally to express level of active 11HSD1 protein, enzyme activity was measured in tissue homogenates. mRNA abundance of 11HSD1, hexoso-6-phosphate dehydrogenase (H6PDH) and the glucocorticoid receptor (GR) was measured by real-time PCR. In comparison with normotriglyceridemic animals, female HHTg rats showed enhanced regeneration of glucocorticoids in the liver and the absence of any changes in SAT and skeletal muscle. In contrast to females, the glucocorticoid regeneration in males of HHTg rats was unchanged in liver, but stimulated in SAT and downregulated in muscle. Furthermore, SAT and skeletal muscle exhibited not only 11-reductase but also 11-oxidase catalyzed by 11HSD1. In females of both strains, 11-oxidase activity largely exceeded 11-reductase activity. No dramatic changes were found in the mRNA expression of H6PDH and GR. Our data provide evidence that the relationship between hypertriglyceridemia and glucocorticoid action is complex and gender specific.

Adaptation of a corticosterone ELISA to demonstrate sequence-specific effects of angiotensin II peptides and C-type natriuretic peptide on 1alpha-hydroxycorticosterone synthesis and steroidogenic mRNAs in the elasmobranch interrenal gland

It is thought that a single corticosteroid, 1alpha-hydroxycorticosterone (1alpha-B), is both a glucocorticoid and mineralocorticoid in the elasmobranch fishes. We investigated the putative mineralocorticoid role of 1alpha-B by examining regulation of interrenal 1alpha-B synthesis by osmoregulatory hormones in the euryhaline stingray Dasyatis sabina. Using synthesized steroid, a commercial enzyme-linked immunoassay was validated for the quantification of 1alpha-B. In interrenal cultures, the antinatriuretic peptide angiotensin II (ANG II) was potently steroidogenic, whereas C-type natriuretic peptide had no effect on 1alpha-B titers. However, both peptides significantly decreased abundance of rate-limiting steroidogenic mRNAs (steroidogenic acute regulatory protein, StAR; cholesterol side-chain cleavage, P450scc). We also isolated cDNAs encoding ANG II from three species of elasmobranch, verifying heterogeneity among elasmobranch peptides at the first amino acid position. Potential implications of this heterogeneity were investigated by examining the effects of homologous and heterologous ANG II on interrenal steroid production and steroidogenic mRNAs. Changes at amino acid position three, but not position one, of ANG II significantly affected steroidogenic potency. Conversely, changes at position one, but not position three, significantly affected the potency of ANG II to alter levels of steroidogenic mRNAs. This study is the first to demonstrate regulation of elasmobranch steroidogenic mRNAs by osmoregulatory peptides.

Pregnancy and lactation have anti-obesity and anti-diabetic effects in A(y)/a mice

AIM

Dominant 'yellow' mutation at the mouse agouti locus (A(y)) results in obesity. Pregnancy and lactation are characterized by large energy demand. The aim of this study was to investigate whether obesity would develop in pregnant and suckling A(y) mice.

METHODS

Body weight and food intake in pregnancy, lactation, and after weaning, plasma leptin, insulin, corticosterone and blood glucose concentrations on days 7, 13 and 18 of pregnancy, days 1, 10, 21 and 80 postpartum, glucose and insulin tolerance on pregnancy days 7 and 18 were measured in C57Bl/6J mice of a/a (normal metabolism) and A(y)/a genotypes. The same parameters were also measured in age-matched virgin females.

RESULTS

Virgin A(y)/a females exhibited hyperphagia, enhanced body weight, glucose intolerance and normal blood parameters at the mating age. With age, they developed obesity, hyperleptinaemia, hyperinsulinaemia and hyperglycaemia. Obesity did not develop in mated A(y)/a mice; during suckling, they had equal food intake and body weight as a/a mice. During pregnancy, glucose tolerance was enhanced in A(y)/a mice and became equal in both genotypes. In both genotypes, concentrations of hormones increased, and glucose decreased from pregnancy day 7 to day 18 and returned to normal values after parturition. A(y)/a mice did not differ from a/a in corticosterone, insulin and glucose levels during pregnancy and lactation, in leptin levels during suckling; however, A(y)/a mice had two times higher leptin levels than a/a during pregnancy. After weaning, A(y)/a mice began to eat and weigh more than a/a exhibiting normal metabolic parameters for 50 days.

CONCLUSION

Pregnancy and lactation retard obesity and diabetes development in A(y) mice.

Profiling of 19-norandrosterone sulfate and glucuronide in human urine: implications in athlete's drug testing

19-Norandrosterone (19-NA) as its glucuronide derivative is the target metabolite in anti-doping testing to reveal an abuse of nandrolone or nandrolone prohormone. To provide further evidence of a doping with these steroids, the sulfoconjugate form of 19-norandrosterone in human urine might be monitored as well. In the present study, the profiling of sulfate and glucuronide derivatives of 19-norandrosterone together with 19-noretiocholanolone (19-NE) were assessed in the spot urines of 8 male subjects, collected after administration of 19-nor-4-androstenedione (100mg). An LC/MS/MS assay was employed for the direct quantification of sulfoconjugates, whereas a standard GC/MS method was applied for the assessment of glucuroconjugates in urine specimens. Although the 19-NA glucuronide derivative was always the most prominent at the excretion peak, inter-individual variability of the excretion patterns was observed for both conjugate forms of 19-NA and 19-NE. The ratio between the glucuro- and sulfoconjugate derivatives of 19-NA and 19-NE could not discriminate the endogenous versus the exogenous origin of the parent compound. However, after ingestion of 100mg 19-nor-4-androstenedione, it was observed in the urine specimens that the sulfate conjugates of 19-NA was detectable over a longer period of time with respect to the other metabolites. These findings indicate that more interest shall be given to this type of conjugation to deter a potential doping with norsteroids.

11beta-hydroxysteroid dehydrogenases are regulated during the pulmonary granulomatous response to the mycobacterial glycolipid trehalose-6,6'-dimycolate

OBJECTIVE

Tuberculosis has a staggering influence on world health, resulting in nearly 2 million deaths per year. The influence of glucocorticoids during Mycobacterium tuberculosis infection has been under investigation for decades; however, the identity of mycobacterial factors and the mechanism by which glucocorticoids are tissue specifically regulated to influence immune function during acute granuloma formation are unknown.

METHODS

One factor implicated in initiating immunopathology during M. tuberculosis infection is trehalose-6,6'-dimycolate (TDM), a glycolipid component of the mycobacterial cell wall. Intravenous administration of TDM causes inflammatory responses in lungs of mice similar to M. tuberculosis infection and has been used as a successful model to examine proinflammatory regulation and early events involved in the manifestation of pathology.

RESULTS AND CONCLUSION

IL-6, IL-1alpha and TNF-alpha mRNA and protein peaked during the initiation of granuloma formation. Pulmonary corticosterone levels were elevated when the proinflammatory response was greatest, dropping to half of that upon the establishment of granuloma pathology on day 7. It is hypothesized that once corticosterone reaches the site of inflammation, the enzymes 11beta-hydroxysteroid dehydrogenases (11betaHSDs) can influence bioavailability by interconverting corticosterone and the inert metabolite 11-dehydrocorticosterone. RT-PCR demonstrated that pulmonary 11betaHSD type 1 mRNA decreased 4-fold and 11betaHSD type 2 (11betaHSD2) mRNA expression increased 2.5-fold on day 3 after injection, suggesting that corticosterone regulation in the lung, specifically the reduction of active corticosterone by 11betaHSD2, may influence the progression of granuloma formation in response to the mycobacterial glycolipid.

[Dehydroepiandrosterone sulfate effect at the conversion of corticosterone to 11-dehydrocorticosterone in stress conditions: the scheme of regulation]

It had been shown that the reaction of conversion of corticosterone (CS) to 11-dehydrocorticosterone (11-DHCS) was increased in chronic intermissions, but not in sharp stress influences in male rats, especially under dehydroepiandrosterone sulfate (DHEAS) employment. The injection of naltrexone 20 min before DHEAS in dose 0.1 mg/kg which selectively blocked the mu-opiate receptors canceled this effect that indicated the participation of in-opiate receptors in such regulation. The DHEAS effect realized through the endogenous ACTH, and such was of the central nature. On the base of ourselves and the literature dates we intraduced the scheme of DHEAS- and mu-opiate-dependent regulation of CS/11-DHCS interchangings.

Studies on neurosteroids XXIII. Analysis of tetrahydrocorticosterone isomers in the brain of rats exposed to immobilization using LC-MS

The identification and quantification of tetrahydrocorticosterone isomers (THBs; 3alpha,5alpha-, 3beta,5alpha-, 3alpha,5beta- and 3beta,5beta-THB) in rat brains using liquid chromatography (LC)-mass spectrometry (MS) are described. For the identification, the THBs were converted to the atmospheric pressure chemical ionization (APCI)-active derivatives, i.e., the dinitrobezoyl esters and 2-nitro-4-trifluoromethylphenyl hydrazones, and detected in the negative-ion mode. These derivatives showed 60- and 40-fold higher sensitivities, respectively, than intact steroids measured in the positive-APCI-MS. The derivatized THBs were satisfactorily separated from the others during the reversed-phase LC. The THBs were not detected at all in the brains of the unstressed rats. When the rats were exposed to the immobilization for 20 min, 3alpha,5alpha- and 3beta,5alpha-THB were detected as the major metabolites together with small amounts of 3alpha,5beta- and 3beta,5beta-THB in the male rat brain, while only 3alpha,5alpha-THB was detected in the female rats. Thus, the steroid variety found in the brains was different between the sexes. In the next step, 3alpha,5alpha-THB, a major metabolite found in the brains of the stressed rats, was quantified as its dinitrobezoyl ester. This method was accurate and reproducible, and the limit of quantitation was 1.0 ng/g tissue when a 50 mg tissue sample was used. There was also a sex difference in the brain 3alpha,5alpha-THB level; it was significantly higher in the female rats than in the male rats (P<0.05), although the brain corticosterone level was not higher in the stressed female rats than in the male rats (no statistical difference).

Distinct features of dehydrocorticosterone reduction into corticosterone in the liver and duodenum of the domestic fowl (Gallus gallus domesticus)

The mammalian 11-beta hydroxysteroid dehydrogenase type 1 (11 betaHSD1) reduces glucocorticoids (GC) at C11 from the 11-keto-GC nonactive form to the 11-hydroxy-GC active form, an action essential for survival. Whereas GC metabolism at C11 and the role of 11 betaHSD1 are studied extensively in mammals, information about these in birds is scattered. Herein, we report the GC bidirectional metabolism in chickens. In hens' liver and duodenal mucosa, 11 betaHSD1-like mRNA expression was detected; and 11 betaHSD1-like immunoreactivity was found linked to membranes of hepatocytes and duodenal enterocytes. With either NADH or NADPH, the membranal fraction of liver and duodenal mucosa converted dehydrocorticosterone (A) into corticosterone (B) with K(m) (1.1-8.7 microM) and V(max) (10-40 pmol/mg protein/min) values similar to those reported for mammalian 11 betaHSD1. In the presence of NADP(+) or NAD(+), these membranal fractions oxidized B into A. With either NADPH or NADH, the cytosol of chicken liver and duodenal mucosa reduced A into B (K(m) of 1.1 - 2.3 microM and V(max) of 260-960 pmol/mg protein/min). These cytosolic fractions did not convert any amount of B into A when incubated with either NADP(+) or NAD(+). This may suggest that chicken liver and duodenal mucosa express 11 betaHSD1 that is a membrane-bound oxoreductase which uses both NADPH/NADP(+) and NADH/NAD(+) as cosubstrates. The substantial reduction of A into B (but no conversion of B into A) found in the cytosol is most likely executed by a unidirectional soluble reductase, different than 11 betaHSD1.

Identification of plasma glucocorticoids in pallid sturgeon in response to stress

Compared to teleosts, little is known about the stress response in chondrosteans, and the glucocorticoid(s) most responsive to stress have never been definitively determined in sturgeon. In terms of cortisol production, pallid sturgeon (Scaphirhynchus albus) have a low physiological response to stress compared to other sturgeons (Acipenser s.p.). Because of this, our null hypothesis was that cortisol is not the predominant glucocorticoid secreted in response to stress in pallid sturgeon. Our objective was to identify the putative glucocorticoids present in the plasma of pallid sturgeon during the stress response. Pallid sturgeon were subjected to a severe confinement stress (12 h) with an additional handling stressor for the first 6 h. Control fish were not subjected to confinement but were handled only to collect blood. Blood plasma was collected at time 0, 6, and 12 h. Gas chromatography/mass spectrometry was used to screen the plasma for the spectrum of glucocorticoids and determine the putative steroid secreted during the stress response. Cortisol was the primary glucocorticoid detected in stressed pallid sturgeon. In addition, the cortisol metabolites cortisone, alloTHE (5alpha-pregnane-3alpha,17alpha,21-triol-11,20-dione), allo-alpha-cortolone (3alpha,17alpha,20alpha,21-tetrahydro-5alpha-pregnan-11-one), and allo-beta-cortolone (3alpha,17alpha,20beta,21-tetrahydro-5alpha-pregnan-11-one) were detected. Plasma cortisol increased from a resting concentration of 0.67 ng/ml to 10.66 ng/ml at 6h followed by a decrease to 6.78 ng/ml by 12 h. Plasma glucose increased significantly by time 6 and 12 h in both stressed and unstressed groups and remained elevated at time 12h, while resting lactate concentrations were low to non-detectable and did not increase significantly with the stressor over time. Cortisol was the primary glucocorticoid synthesized and secreted in response to a stressor in pallid sturgeon. Though the proportional increase in plasma cortisol in stressed pallid sturgeon was lower than many other species of sturgeon, the concentration was high enough to elicit a secondary stress response as seen by changes in plasma glucose.

Early and late effects of steroid hormones on the central nervous system

Steroids have fast and probably partly GABA-mediated central anaesthetic effects for which a strict structure-function correlation is required. They also affect short- and long-term activity in the CNS in other ways. One of these is long-term potentiation (the persistent facilitation of synaptic transmission), which occurs particularly in the hippocampus after repetitive stimulation of a fibre pathway. Two clearly distinguished components of the evoked response can be studied in the hippocampus: the excitatory postsynaptic potential (EPSP) which denotes the graded depolarization of the somadendritic region of the neuron and the population spike (PS), a manifestation of the all-or-none discharge of the cell action potential. Corticosterone had a significant depressant effect on the EPSP component of the evoked response immediately and 15 min after injection. Thereafter EPSP amplitudes were within normal values. Corticosterone significantly decreased the PS immediately after the train, the component remaining low 30 min after the train. 5 alpha-Dihydrocorticosterone (a ring A-reduced metabolite of corticosterone) significantly reduced the PS component of the response at all times after injection. 18-Hydroxydeoxycorticosterone and deoxycorticosterone significantly decreased both EPSP and PS components of the evoked response from the time of infusion. Contrary to expectation, tetrahydrodeoxycorticosterone was ineffective in decreasing, and if anything, enhanced the development of long-term potentiation. 18-Hydroxydeoxycorticosterone 21-acetate behaved like vehicle, except for the first 30 min after injection, when the EPSP was decreased. Different steroids can selectively affect different parts of a neuron and appear to show a different structure-function correlation for long-term potentiation from that required for anaesthesia.

Metabolomic Approach To Evaluate the Toxicological Effects of Nonylphenol with Rat Urine

Metabolomics has focused on toxicological applications to (1) understand the mechanisms of toxicity, (2) identify novel biomarkers of toxicity, and (3) provide in vivo assessment in animal models through simple and fast methods to date. The toxicological effects of nonylphenol (NP) were evaluated after intraperitoneal injection of rats with 0, 50, and 250 mg kg(-1) day(-1) NP for four consecutive days. In the nontargeted approach, different extraction conditions were introduced to investigate the effects of NP on rats through gas chromatography/mass spectrometry (GC/MS). The GC/MS data obtained were further analyzed with partial least-squares discriminant analysis to compare toxicological effects between control and treated groups. The targeted approach was also used in combination with GC/MS to quantify endocrine hormones and to identify possible biomarkers in rat urine under optimal extraction conditions. In addition, we considered the metabolic trajectory to examine the metabolite profiles and patterns related to steroid metabolism in rats that were treated with NP, considering both treatment amount and time. The data suggest that tetrahydrocorticosterone and 5alpha-tetrahydrocorticosterone are possible urinary biomarkers of NP-induced toxicity. This metabolomic approach is a promising tool to assist with screening in toxicological studies.

Renal interstitial corticosterone and 11-dehydrocorticosterone in conscious rats

Deficiencies in the conversion between active and inactive glucocorticoids in the kidney can lead to hypertension. However, the significance of glucocorticoid metabolism in specific kidney regions in vivo is not clear, possibly in part due to the difficulty in measuring glucocorticoid levels in kidney regions in vivo. We used microdialysis techniques to sample renal interstitial fluid from conscious rats. The levels of corticosterone (active) and 11-dehydrocorticosterone (inactive) were analyzed by liquid chromatography-tandem mass spectrometry. Direct infusion of the 11β-hydroxysteroid dehydrogenase (11β-HSD) inhibitor carbenoxolone into the renal medulla induced hypertension, and significantly increased corticosterone levels and the corticosterone/11-dehydrocorticosterone ratio, an index of 11β-HSD activity, in the renal medullary microdialysate, but not in urine or the plasma. Further characterization of conscious, untreated rats ( n = 13–16) indicated that corticosterone concentrations (ng/ml) were 0.8 ± 0.1, 1.0 ± 0.1, 66.7 ± 8.1, and 7.9 ± 1.1 in cortical microdialysate, medullary microdialysate, the plasma, and urine, respectively. The corticosterone/11-dehydrocorticosterone ratios were 0.8 ± 0.1, 0.6 ± 0.1, 10.6 ± 1.4, and 1.7 ± 0.1, respectively, in these 4 types of sample. The expression level of 11β-HSD1 was higher in the medulla than in the cortex, whereas 11β-HSD2 was most enriched in the outer medulla. Microdialysate levels of corticosterone were ∼1.6-fold higher in afternoons than in mornings, whereas plasma levels differed by 2.8-fold. These results demonstrated that corticosterone excess in the renal medulla might be sufficient to cause hypertension and provided the first characterization of renal interstitial glucocorticoids.

Corticosterone impairs the mRNA expression and activity of 3beta- and 17beta-hydroxysteroid dehydrogenases in adult rat Leydig cells

Clinical and experimental studies, including our own observations, have shown the adverse effects of excess glucocorticoids on testicular steroid hormone production. The present study was designed to gain insight into the molecular mechanisms by which excess corticosterone impairs Leydig cell steroidogenesis. To achieve this, adult rats were administered with corticosterone-21-acetate (2 mg/100 g body weight) twice daily for 15 days. After the treatment period, rats were killed by decapitation. The testes were removed, decapsulated aseptically and used for the isolation of Leydig cells. Purified Leydig cells were used for assessing the activity of 3beta- and 17beta-hydroxysteroid dehydrogenases (HSDs) and total RNA isolation. For in vitro studies, purified Leydig cells (7.5 x 10(6) cells) of control rats were plated in culture flasks and exposed to different concentrations (50, 100, 200, 400, and 800 nmol/L) of corticosterone for 24 h. At the end of incubation, total RNA was isolated from cultured Leydig cells, and the mRNA of 3beta- and 17beta-HSDs was quantified by RT-PCR. A significant reduction in the activities and levels of 3beta-HSD type-I and 17beta-HSD type-III mRNAs in Leydig cells were observed. In vitro studies demonstrated a dose-dependent significant impairment in both the activity and mRNA expression of these enzymes. These results suggest that corticosterone might have a direct effect on the transcription of the genes of 3beta- and 17beta-HSD. It is inferred from the present in vivo and in vitro studies that one of the molecular mechanisms by which excess corticosterone decreases the steroidogenic potency of Leydig cells is by suppressing the mRNA expression of 3beta-HSD type-I and 17beta-HSD type-III enzymes.

Cellular distribution of the GABAA receptor-modulating 3alpha-hydroxy, 5alpha-reduced pregnane steroids in the adult rat brain

The 3alpha-hydroxy,5alpha-reduced pregnane steroids, allopregnanolone and allotetrahydrodeoxycorticosterone, are the most potent endogenous positive modulators of GABA(A) receptor-mediated inhibition. This study presents the first immunohistochemical examination of the cellular distribution of 3alpha-hydroxy,5alpha-reduced pregnane steroids across the brain. We found a widespread distribution in the adult rat, with dense immunolabelling in the olfactory bulb, striatum and cerebral cortex, and lower density labelling in the brainstem reticular formation. In general terms, this distribution accords with the regional concentrations of 3alpha-hydroxy,5alpha-reduced steroids determined, in other laboratories, by brain region sampling and either gas chromatography-mass fragmentography or radioimmunoassay. However, immunohistochemistry allowed for a more detailed examination of regional distribution and cellular specificity. All immunoreactivity was confined to the cell bodies and thick dendrites of neurones; no identifiable glia were labelled. In most brain areas, the location and morphology of labelled cells identified them as excitatory neurones. In addition, cell populations known to be projecting GABAergic neurones (e.g. cerebellar Purkinje cells) were immunoreactive, whereas local inhibitory neurones generally were not. The cellular distribution of 3alpha-hydroxy,5alpha-reduced steroids suggests that sensory, motor, limbic and homeostatic systems can be influenced by neurosteroids at multiple stages of processing.

Development of an Enzyme-Linked Immunosorbent Assay for Serum 11-Dehydrocorticosterone in Rat and Mouse

We have developed an enzyme-linked immunosorbent assay (ELISA) for serum 11-dehydrocorticosterone (4-pregnen-21-ol-3,11,20-trione). The antiserum against 11-dehydrocorticosterone 21-hemisuccinate-conjugated bovine serum albumin was raised in rabbits. As an enzyme-labeled antigen, 11-dehydrocorticosterone 21-hemisuccinate was conjugated to horseradish peroxidase. Two ELISA systems were established: one without the extraction of steroids from serum (direct method), and another that used an HPLC purification step (HPLC method). The cross-reactivity of all steroids tested against the antibody was low except cortisone (92%); however, since cortisone levels in rats and mice are negligible, cortisone does not interfere with this direct ELISA. The measurable range of serum 11-dehydrocortiocosterone in both the direct and HPLC methods was 0.3-250 ng/ml and 0.78-400 ng/ml, respectively. Both methods displayed satisfactory parallel dilution, recovery and reproducibility; moreover, the values obtained with each method significantly correlated with the alternate method. To evaluate the two ELISA systems, the serum concentrations of 11-dehydrocorticosterone in normal rats and mice were determined by these two systems. The levels in Wistar rats fluctuated from 3 to 14 weeks of age (7.8+/-2.6 ng/ml) but at 1 week (1.7+/-1.2 ng/ml) were significantly low compared to other ages. No sex differences were found in rats and mice. Further, using the proposed direct method, chronological changes of rat serum 11-dehydrocorticosterone levels after 11-dehydrocorticosterone administration have been investigated together with corticosterone levels. These results verify that the proposed ELISA for 11-dehydrocorticosterone is useful for measuring 11beta-HSD activities in combination with the determination of serum corticosterone in rats and mice.

The anxiolytic effect of pregnancy in rats is reversed by finasteride

Several studies have shown the influence of the oestrous cycle on anxiety levels and the important role of progesterone in this effect. The metabolism of this steroid hormone yields neuroactive steroids among them allopregnanolone (alloP) and allotetrahydrodeoxycorticosterone (alloTHDOC), which bind to GABAA receptors and have anxiolytic effects. Considering that during pregnancy there is an increase in levels of both progesterone and its metabolites, the main objectives of this work were: (1) to assess changes in anxiety levels during pregnancy and (2) to verify the role of alloP and alloTHDOC in this process using finasteride, an inhibitor of 5alpha-reductase, the enzyme responsible for their synthesis. The results showed a significant reduction in anxiety levels on the 19th day of pregnancy, which was reversed by finasteride, suggesting a role for alloP and alloTHDOC in the anxiolytic process.

MDCK cells express serotonin-regulable 11beta-hydroxysteroid dehydrogenase type 2

Prior to this work, we found that adrenal as well as extra-adrenal factors activate the response of renal 11beta-hydroxysteroid dehydrogenase 2 to stressful situations. These results -showing ways through which the organism hinders the pathological occupation of mineralocorticoid receptors by glucocorticoids leading to sodium retention and hypertension- prompted the present study on the nature of the above-mentioned extra-adrenal factors. Serotonin was chosen because of its properties as a widely distributed neurohormone, known to interact with glucocorticoids at many sites, also exhibiting increased levels and effects under stressful situations. We studied serotonin effects on 11beta-hydroxysteroid dehydrogenase 2 activity in a cell line derived from distal nephron polarized-epithelium, employing 3H-corticosterone as substrate. The end-product, 3H- 11 -dehydrocorticosterone was separated from the substrate by HPLC and quantified. Serotonin stimulated 1I beta-hydroxysteroid dehydrogenase 2 activity only at 2nM and 25pM, the magnitude of the response depending also on substrate concentration. The stimulation was blocked by the specific inhibitors methiothepin and ketanserin. We postulate that the organism partially prevents renal mineralocorticoid receptor occupancy by glucocorticoids, circulating at enhanced levels under stressful situations, through serotonin-mediated catabolic regulation of the 11beta-hydroxysteroid dehydrogenase 2 activity. Given many, mostly positive, interactions between both hormones, this might eventually pave the way to studies on a new regulatory axis.

[The activity of 11beta-hydroxysteroid dehydrogenase of rat kidney and liver at inherited stress-induced arterial hypertension]

11beta-hydroxysteroid dehydrogenase (11beta-HSD) is the key enzyme of glucocorticoid metabolism, which catalyzes interconversion of corticosterone and 11-dehydrocorticosterone in rat. The activity of 11beta-HSD in kidneys of rats with inherited stress-induced arterial hypertension (ISIAH) was significantly (p < 0.05) higher than that in WAG rats. The opposite was observed in the activity of liver 11beta-HSD. Under stress condition no changes in the kidney 11beta-HSD activity of both strains were observed, but the liver 11beta-HSD activity in ISIAH rats was significantly (p < 0.05) higher as compared to basal level and stressed WAG rats. It is possible that the features of the 11beta-HSD activity in ISIAH rats may reflect the hypertensive status of ISIAH rats.

Characterization of cDNAs encoding cholesterol side chain cleavage and 3beta-hydroxysteroid dehydrogenase in the freshwater stingray Potamotrygon motoro

The interrenal gland (adrenocortical homolog) of elasmobranchs produces a unique steroid, 1alpha-hydroxycorticosterone (1alpha-B). The synthesis of this and most other steroids requires both cholesterol side chain cleavage (CYP11A) and 3beta-hydroxysteroid dehydrogenase (HSD3). To facilitate the study of elasmobranch steroidogenesis, we isolated complementary DNAs encoding CYP11A and HSD3 from the freshwater stingray Potamotrygon motoro. The P. motoro CYP11A (2182 bp total length) and HSD3 (2248 bp total length) cDNAs harbor open reading frames that encode proteins of 542 and 376 amino acids (respectively) that are similar (CYP11A: 39-61% identical; HSD3: 36-53% identical) to their homologs from other vertebrates. In molecular phylogenetic analysis, P. motoro CYP11A segregates with CYP11A proteins (and not with related CYP11B proteins) and P. motoro HSD3 segregates with steroidogenic HSD3 proteins from other fishes. CYP11A and HSD3 mRNA is found only in interrenal and gonadal tissues, indicating de novo steroidogenesis is restricted to these tissues. Because 1alpha-B is thought to act in the elasmobranch response to hydromineral disturbances, we examined the effect of adapting P. motoro to 10 ppt seawater on mRNAs encoding steroidogenic genes. The P. motoro response to this salinity challenge does not include interrenal hypertrophy or an increase in the levels of interrenal CYP11A, HSD3 or steroidogenic acute regulatory protein (StAR) mRNA. This study is the first to isolate full length cDNAs encoding elasmobranch CYP11A and HSD3 and the first to examine the regulation of steroidogenic genes in elasmobranch interrenal cells.

A neuroactive steroid inhibits guinea pig airway sensory nerves via Maxi-K channel activation

BACKGROUND

Although neurogenic inflammation via the activation of C-fibers in the airway may have an important role in the pathogenesis of asthma, their regulatory mechanism remains uncertain.

OBJECTIVE

The pharmacological profiles of a neuroactive steroid, allotetrahydrocorticosterone, on the activation of C-fibers in airway tissues were investigated, and the mechanism how a neuroactive steroid regulates airway inflammatory reactions was clarified.

METHODS

The effects of allotetrahydrocorticosterone on electrical field stimulation-induced bronchial smooth muscle contraction in guinea pig airway tissues were investigated. The influences of K+ channel blockers and intracellular protein inhibitors on the effects of allotetrahydrocorticosterone were examined.

RESULTS

Allotetrahydrocorticosterone dose-dependently inhibited electrical field stimulation-induced guinea pig bronchial smooth muscle contraction. The inhibitory effects of allotetrahydrocorticosterone on electrical field stimulation-induced bronchial contraction were reduced by the pretreatment of Maxi-K+ channel blockers, iberiotoxin and charybdotoxin, but not other K+ channel blockers, dendrotoxin or glibenclamide. Pretreatment with pertussis toxin diminished the inhibitory effect of allotetrahydrocorticosterone, but not an adenylate cyclase inhibitor, SQ 22536, nor a specific inhibitor of mitogen-activated protein kinase kinase, PD 98059.

CONCLUSIONS

These findings suggest that allotetrahydrocorticosterone negatively modulates the activation of C-fibers in guinea pig airway tissues via the opening of Maxi-K+ channels and a pertussis toxin-sensitive G-protein-coupled mechanism.

Chronic corticosterone treatment increases the endocannabinoid 2-arachidonylglycerol in the rat amygdala

This research was designed to examine the effect of three weeks of administration of corticosterone (20 mg/kg) on endocannabinoid content and cannabinoid CB1 receptor binding in the amygdala. It was found that the endocannabinoid 2-arachidonylglycerol was significantly increased in the amygdala following chronic corticosterone treatment. However, there was no change in either the maximal binding (Bmax) or binding affinity (KD) of [3H]-CP 55,940 to the CB1 receptor in the amygdala. Given the role of amygdalar endocannabinoids in the regulation of emotionality, this suggests that the ability of glucocorticoids to influence affective behavior may involve interactions with regulation of endocannabinoid content.

Stimulation of testosterone production in rat Leydig cells by aldosterone is mineralocorticoid receptor mediated

The testis is known to be a site of corticosterone action, and testosterone production in Leydig cells is directly inhibited by glucocorticoids. Glucocorticoids bind to both glucocorticoid receptors (GRs) and to mineralocorticoid receptors (MRs). In Leydig cells, selective mineralocorticoid binding could result from oxidative inactivation of glucocorticoid by type 1 and/or 2 11beta-hydroxysteroid dehydrogenase (11betaHSD), as both isoforms are expressed. However, it remains unclear whether Leydig cells express MRs and respond directly to mineralocorticoid action. Therefore, the aims of the present study were to ascertain: (1) whether MR mRNA, protein and receptor binding are present in Leydig cells; and (2) if the mineralocorticoid modulates testosterone production. The mRNA encoding MR, as well as protein, and binding activity were each observed in adult rat Leydig cells. MR-ligand binding specificity within isolated Leydig cells was evaluated further by measuring displacement of MR binding to aldosterone by corticosterone in the presence and absence of carbenoxolone, an inhibitor of 11betaHSD1 and 2 that decreases conversion to biologically inert 11-dehydrocorticosterone. Carbenoxolone inhibited 11betaHSD oxidative activity, and reduced corticosterone-binding by 50%. Mineralocorticoid effects on steroidogenesis were assessed in the presence of aldosterone (0.01-10 nM) with or without the MR antagonist, RU28318. Aldosterone induced dose-dependent increases in both basal and luteinizing hormone-stimulated testosterone production. RU28318 eliminated the increase, indicating that these effects of aldosterone were mediated by the MR. The effects of aldosterone and luteinizing hormone (0.1 ng/ml) on testosterone production were synergistic, suggesting that the two hormones increased steroidogenesis through separate pathways. We conclude that Leydig cells express MRs and that testosterone production is subject to regulation by aldosterone.

A neuroactive steroid, allotetrahydrocorticosterone inhibits sensory nerves activation in guinea-pig airways

We examined the effects of a neuroactive steroid, allotetrahydrocorticosterone on the activation of capsaicin-sensitive afferent sensory nerves (C-fibers). Allotetrahydrocorticosterone (0.0001-1.0 microg/ml) dose-dependently inhibited electrical field stimulation-induced guinea-pig bronchial smooth muscle contraction, but not the substance P-induced contraction at 1.0 microg/ml. Allotetrahydrocorticosterone (0.01-1.0 microg/ml) also reduced the capsaicin-induced release of substance P-like immunoreactivity from guinea-pig airway tissues in a dose-dependent manner. The inhibitory effect of allotetrahydrocorticosterone on electrical field stimulation-induced bronchial contraction were reduced by the pretreatment of voltage-dependent K+ channel blockers, tetraethylammonium (1 mM). This evidence suggests that allotetrahydrocorticosterone negatively modulate the activation of C-fibers and substance P release from their endings in airway tissues via the opening of voltage-dependent K+ channels.

Comparative enzymology of 11beta-hydroxysteroid dehydrogenase type 1 from six species

11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD1), catalyzing the intracellular activation of cortisone to cortisol, is currently considered a promising target to treat patients with metabolic syndrome; hence, there is considerable interest in the development of selective inhibitors. For preclinical tests of such inhibitors, the characteristics of 11beta-HSD1 from the commonly used species have to be known. Therefore, we determined differences in substrate affinity and inhibitor effects for 11beta-HSD1 from six species. The differences in catalytic activities with cortisone and 11-dehydrocorticosterone were rather modest. Human, hamster and guinea-pig 11beta-HSD1 displayed the highest catalytic efficiency in the oxoreduction of cortisone, while mouse and rat showed intermediate and dog the lowest activity. Murine 11beta-HSD1 most efficiently reduced 11-dehydrocorticosterone, while the enzyme from dog showed lower activity than those from the other species. 7-ketocholesterol (7KC) was stereospecifically converted to 7beta-hydroxycholesterol by recombinant 11beta-HSD1 from all species analyzed except hamster, which showed a slight preference for the formation of 7alpha-hydroxycholesterol. Importantly, guinea-pig and canine 11beta-HSD1 displayed very low 7-oxoreductase activities. Furthermore, we demonstrate significant species-specific variability in the potency of various 11beta-HSD1 inhibitors, including endogenous compounds, natural chemicals and pharmaceutical compounds. The results suggest significant differences in the three-dimensional organization of the hydrophobic substrate-binding pocket of 11beta-HSD1, and they emphasize that species-specific variability must be considered in the interpretation of results obtained from different animal experiments. The assessment of such differences, by cell-based test systems, may help to choose the appropriate animal for safety and efficacy studies of novel potential drug candidates.

Effect of neurosteroids on the retinal gabaergic system and electroretinographic activity in the golden hamster

It has been established that neurosteroids can either inhibit or enhance GABA(A) receptor activity. Although GABA is the main inhibitory neurotransmitter in the mammalian retina, the effects of neurosteroids on retinal GABAergic activity have not been investigated. The aim of this work was to study the neurochemical and electroretinographic effects of neurosteroids in the golden hamster. On one hand, pregnenolone sulfate inhibited and allotetrahydrodeoxycorticosterone increased GABA-induced [36Cl]- uptake in neurosynaptosomes. On the other hand, in whole retinas, pregnenolone sulfate increased, whereas allotetrahydrodeoxycorticosterone decreased high potassium-induced [3H]GABA release. The effect of both neurosteroids on GABA release was Ca2+-dependent, as in its absence release was not altered. The intravitreal injection of pregnenolone sulfate or vigabatrin (an irreversible inhibitor of GABA degradation) significantly decreased scotopic b-wave amplitude, whereas the opposite effect was evident when bicuculline or allotetrahydrodeoxycorticosterone were injected. A protein with a molecular weight close to that of hamster adrenal cytochrome P450 side-chain cleavage (P450scc) was detected in the hamster retina. P450scc-like immunoreactivity was localized in the inner nuclear and the ganglion cell layers. These results indicate that neurosteroids significantly modulate retinal GABAergic neurotransmission and electroretinographic activity. In addition, the selective localization of P450scc suggests that neurosteroid biosynthesis might occur only in some layers of the hamster retina.

Effect of high-fat diet on KKAy and ob/ob mouse liver and adipose tissue corticosterone and 11-dehydrocorticosterone concentrations

The present study was performed to compare glucocorticoid levels in obese KKA (y) and ob/ob mice with those in normal C57BL/6J mice, and the effect of high-fat diet on glucocorticoids in KKA (y) and ob/ob mice. Liver, mesenteric and epididymal adipose tissue corticosterone and 11-dehydrocorticosterone concentrations as well as circulating corticosterone concentrations were measured. The KKA (y) and ob/ob mice displayed elevated serum corticosterone levels compared to normal mice, 2.0 to 2.8-fold in KKA (y), and 11 to 16-fold in ob/ob mice. Liver corticosterone levels were 3.0 to 5.1 and 6.2 to 8.1-fold, and 11-dehydrocorticosterone levels were 3.4 to 3.6 and 6.7 to 8.2-fold higher in KKA (y) and ob/ob mice compared to normal mice. Mesenteric adipose tissue corticosterone levels were 2.7 to 4.2-fold higher, and 11-dehydrocorticosterone levels were 2 to 4-fold higher in ob/ob than in KKA (y) mice. Epididymal adipose tissue corticosterone levels were 3.0 to 6.2-fold higher, and 11-dehydrocorticosterone levels were 1.8 to 2.0-fold higher in ob/ob than in KKA (y) mice. Circulating, hepatic, and mesenteric and epididymal adipose tissue glucocorticoid concentrations were low in the normal C57BL/6J mouse, high in the ob/ob mouse, and intermediate in the KKA (y) mouse. 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) mRNA levels were doubled in ob/ ob compared to KKA (y) mice in all three tissues. Glucocorticoid concentrations correlated with 11beta-HSD1 mRNA levels. High-fat diet had no effect on the tissue glucocorticoid concentrations.

Corticosterone 21-acetate in vivo induces acute stress in chicken thymus: cell proliferation, apoptosis and cytokine responses

In vivo effects of acute stress induced by corticosterone 21-acetate in male Gallus domesticus thymus are studied and the steroid actions are evaluated in terms of cell proliferation, apoptosis and cytokine response in 10- and 21-day-old chickens. Steroid treatment induced thymocyte apoptosis and cell death decreased in the cortical-medullar direction and was more evident in younger animals. 24 h after treatment, the observed effect was reversed. The mitotic activity and thymic cells containing cytokine-like molecules were also affected. Indeed, the acute stress stimulated cytokine immunoreactivity to anti-IL-1alpha, IL-6 and TNF-alpha antibodies both in epithelial cells and interdigitating cells located in medullar and cortical-medullar regions. The increased cytokine expression observed after 12 h was maintained after 24 h. The comparison between 10- and 21-day-old chickens showed a lower number of cells containing cytokine-like molecules in younger specimens. The present findings suggest that cytokines activated by acute stress in vivo could contribute to restoring immunological homeostasis and influence thymic glucocorticoid-mediated functions.

Ratio between the Contents of 11-Dehydrocorticosterone and Corticosterone after Acute and Repeated Stress: Effect of Dehydroepiandrosterone Sulfate

Acute stress was accompanied by reduction of 11-dehydrocorticosterone to corticosterone in male rats. The reverse reaction predominated during repeated stress and increased after administration of dehydroepiandrosterone sulfate. Treatment with mu-opioid receptor antagonist naltrexone in a dose of 0.1 mg/kg 20 min before administration of dehydroepiandrosterone sulfate abolished this effect.