Immunodetection of 11 beta-hydroxysteroid dehydrogenase type 2 in human mineralocorticoid target tissues: evidence for nuclear localization

The Assessment of the Hypothalamic-Pituitary-Adrenal Axis After Oncological Treatment in Pediatric Patients with Acute Lymphoblastic Leukemia

OBJECTIVE

Oncologic treatment can affect the adrenal glands, which in stressful situations may lead to life threatening adrenal crisis. The aim of the study was to assess adrenal function in pediatric acute lymphoblastic leukemia (ALL) survivors and to identify the best markers for this assessment.

METHODS

Forty-three ALL survivors, mean age 8.5±3.6 years and 45 age and sex-matched healthy controls were recruited to the study. ALL patients were assessed once within five years following oncological treatment completion. Fasting blood samples were collected from all participants to measure: fasting blood glucose (FBG); cortisol; aldosterone; plasma renin activity (PRA); dehydroepiandrostendione-sulfate (DHEA-S); and adrenocorticotropic hormone (ACTH). Moreover, diurnal profile of cortisol levels and 24-hour urinary free cortisol (UFC) were assessed. ALL survivors underwent a test with 1 ug of synthetic ACTH.

RESULTS

The study revealed lower level of PRA (1.94±0.98 ng/mL/h vs 3.61±4.85 ng/mL/h, p=0.029) and higher FBG (4.6±0.38 mmol/L vs 4.41±0.39 mmol/L, p=0.018) in the ALL group compared to controls. UFC correlated with evening cortisol (p=0.015, r=0.26), midnight cortisol (p=0.002, r=0.33), and DHEA-S (p=0.004, r=0.32). UFC also correlated with systolic and diastolic blood pressure (p=0.033, r=0.23 and p=0.005, r=0.31, respectively). The ACTH test confirmed impaired adrenal function in 4/43 ALL survivors (9%). Two of the patients who needed permanent hydrocortisone replacement had low UFC, midnight cortisol and DHEA-S levels.

CONCLUSION

These results highlight the importance of reviewing adrenal gland functionality after chemo/radiotherapy in ALL survivors. DHEA-S proved to be a good marker to assess the adrenal glands after oncological therapy. Post-treatment disturbances of the adrenal axis could be associated with metabolic complications.

Identification of glucocorticoid receptors as potential modulators of parasympathetic and sympathetic neurons within rat intracardiac ganglia

Background

Emerging evidences indicate that glucocorticoid receptors (GR) play a regulatory role in cardiac function, particularly with regard to the autonomic nervous system. Therefore, this study aimed to demonstrate the expression and the precise anatomical location of GR in relation to the parasympathetic and sympathetic innervations of the heart.

Methods

The present study used tissue samples from rat heart atria to perform conventional reverse-transcriptase polymerase chain reaction (RT-PCR), Western blot, and double immunofluorescence confocal analysis of GR with the neuronal markers vesicular acetylcholine transporter (VAChT), tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP) as well as the mineralocorticoid receptor (MR).

Results

Double immunofluorescence labeling revealed that GRs were co-expressed with VAChT in parasympathetic principal neuronal somata and nerve terminals innervating atrium. Also, GR colocalized with the sympathetic neuronal marker TH in a cluster of small intensely fluorescent (SIF) cells, on intracardiac nerve terminals and in the atrial myocardium. GR immunoreactivity was scarcely identified on CGRP-immunoreactive sensory nerve terminals. Approximately 20% of GR immunoreactive neuronal somata co-localized with MR. Finally, conventional RT-PCR and Western blot confirmed the presence of GR and MR in rat heart atria.

Conclusion

This study provides evidence for the existence of GR predominantly on cardiac parasympathetic neurons and TH-immunoreactive SIF cells suggesting a functional role of cardiac GR on cardiovascular function by modulation of the cardiac autonomic nervous system.

Naltrexone-Induced Cardiac Function Improvement is Associated With an Attenuated Inflammatory Response and Lipid Perioxidation in Volume Overloaded Rats

In previous studies, upregulation of myocardial opioid receptors as well as the precursors of their endogenous ligands were detected in the failing heart due to chronic volume overload. Moreover, opioid receptor blockade by naltrexone improved left ventricular function. In parallel, inflammatory processes through cytokines have been confirmed to play an important role in the pathogenesis of different forms of heart failure. Thus, the present study examined the systemic and myocardial inflammatory response to chronic volume overload and its modulation by chronic naltrexone therapy. Chronic volume overload was induced in male Wistar rats by applying an infrarenal aortocaval fistula (ACF) for 28 days during which the selective opioid receptor antagonist naltrexone (n = 6) or vehicle (n = 6) were administered via a subcutaneously implanted Alzet minipump. The ultrastructural, morphometric and hemodynamic characterization of ACF animals were performed using an intraventricular conductance catheter in vivo and electron microscopy in vitro. Co-localization of mu-, delta- and kappa-opioid receptor subtypes (MOR, DOR, and KOR respectively) with the voltage gated L-type Ca2+ channel (Cav1.2), the ryanodine receptor (RyR), and mitochondria in cardiomyocytes as well as IL-6, IL-12, TNF-alpha, and Malondialdehyde (MDA) were determined using double immunofluorescence confocal microscopy, RT-PCR and ELISA, respectively. In rat left ventricular myocardium, three opioid receptor subtypes MOR, DOR, and KOR colocalized with Cav1.2, RyR and mitochondria suggesting a modulatory role of the excitation-contraction coupling. In rats with ACF-induced volume overload, signs of heart failure and myocardial ultrastructural damage, chronic naltrexone therapy improved cardiac function and reversed the systemic and myocardial inflammatory cytokine expression as well as lipid peroxidation. In conclusion, antagonism of the cardiodepressive effects of the myocardial opioid system does not only improve left ventricular function but also blunts the inflammatory response and lipid peroxidation.

Identification of Mineralocorticoid Receptors, Aldosterone, and Its Processing Enzyme CYP11B2 on Parasympathetic and Sympathetic Neurons in Rat Intracardiac Ganglia

Recent interest has focused on the mineralocorticoid receptor (MR) and its impact on the myocardium and the performance of the heart. However, there is a lack of evidence about MR expression and its endogenous ligand aldosterone synthesis with specific regard to the intrinsic cardiac nervous system. Therefore, we looked for evidence of MR and aldosterone in sympathetic and parasympathetic neurons of intracardiac ganglia. Tissue samples from rat heart atria were subjected to conventional reverse-transcriptase polymerase chain reaction (PCR), Western blot, and double immunofluorescence confocal analysis of MR, corticosterone-inactivating enzyme 11β-hydroxysteroid-dehydrogenase-2 (11β-HSD2), aldosterone, and its processing enzyme CYP11B2 together with the neuronal markers vesicular acetylcholine transporter (VAChT) and tyrosine hydroxylase (TH). Our results demonstrated MR, 11β-HSD2, and CYP11B2 specific mRNA and protein bands in rat heart atria. Double immunofluorescence labeling revealed coexpression of MR immunoreactivity with VAChT in large diameter parasympathetic principal neurons. In addition, MR immunoreactivity was identified in TH-immunoreactive small intensely fluorescent (SIF) cells and in nearby VAChT- and TH-immunoreactive nerve terminals. Interestingly, the aldosterone and its synthesizing enzyme CYP11B2 and 11β-HSD2 colocalized in MR– immunoreactive neurons of intracardiac ganglia. Overall, this study provides first evidence for the existence of not only local expression of MR, but also of 11β-HSD2 and aldosterone with its processing enzyme CYP11B2 in the neurons of the cardiac autonomic nervous system, suggesting a possible modulatory role of the mineralocorticoid system on the endogenous neuronal activity on heart performance.

The Effects of Physical Exercise on Saliva Composition: A Comprehensive Review

Saliva consists of organic and inorganic constituents. During exercise, analysis of the saliva can provide valuable information regarding training stress, adaptation and exercise performance. The objective of the present article was to review the effect of physical exercise on saliva composition. The shift in the composition of the saliva, during and after a workout, reflects the benefits of exercise, its potential risks and the capability of the saliva to serve as a health indicator. The type and the frequency of training, the physical condition and the athletes’ general health influence the hormones, immunoglobulins and saliva enzymes. The correlation between saliva and physical exercise has to be further investigated and the available knowledge to be applied for the benefit of the athletes during sports activities.

11βHSD2 Efficacy in Preventing Transcriptional Activation of the Mineralocorticoid Receptor by Corticosterone

Affinity of the mineralocorticoid receptor (MR) is similar for aldosterone and the glucocorticoids (GC) cortisol and corticosterone, which circulate at concentrations far exceeding those of aldosterone. 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2) inactivation of GC within the immediate vicinity of the MR is credited with prereceptor specificity for aldosterone in cells coexpressing MR and 11βHSD2. 11βHSD2 efficacy is also critical to other recently described 11βHSD2 substrates. The aim of this work was to address doubts that low levels of expression of 11βHSD2 in aldosterone target tissues suffice to prevent the initiation of gene transcription by the MR activated by physiological concentrations of corticosterone. Cell models stably expressing an MR/Gaussia luciferase reporter and various levels of constitutive or induced 11βHSD2 at concentrations lower than those in rat kidney homogenates and microsomes were produced. Aldosterone and corticosterone were equipotent transactivators of the MR reporter gene in cells without 11βHSD2. Rate of conversion of tritiated corticosterone to 11-dehydrocorticosterone increased and corticosterone-induced nuclear translocation of MR decreased, as 11βHSD2 expression increased. The 50% maximal MR activation for the reporter gene stimulation by corticosterone rose with increasing 11βHSD2 expression, shifting the steroid dose-response curve for corticosterone-induced MR transactivation to the right. Several stable cell lines expressing an easily and reproducibly measured MR reporter system and consistent incremental amounts of 11βHSD2 protein were produced and used to document that 11βHSD2 within low physiological levels inactivates relevant concentrations of GC and decreases MR transactivation by GC in a dose-dependent fashion, laying to rest doubts of the efficacy of this enzyme.

Bioidentical hormones

After the results of the Women's Health Initiative trials were published, patient and clinician interest in potential alternatives to conventional hormone therapy (HT) has grown. A commonly used alternative therapy involves custom-compounded steroid hormone preparations, formulated by compounding pharmacies. Many postmenopausal women consider the hormones as natural or bioidentical, in contrast to hormones used in conventional HT, which they consider synthetic. In actuality, the chemical structures of many of the hormones used in bioidentical HT (BHT) are the same as those used in conventional HT. To customize formulations, compounding pharmacies frequently use saliva testing to measure hormones. However, there is a misconception that salivary hormone levels are equivalent to non-protein-bound (free) hormones in blood. Because hormonal custom-compounded formulations are not approved by the Food and Drug Administration (FDA), there are concerns regarding their purity, potency, and quality. Evolving regulatory guidelines by the FDA on oversight of these products should lessen the concerns regarding their safety and efficacy. This review addresses important misconceptions and uncertainties pertaining to BHT, the relationship between salivary and serum/plasma steroid hormone concentrations, the effect of topical progesterone creams on the endometrium, the variability in custom-compounded steroid preparations, and FDA oversight of custom-compounded products.

Salivary aldosterone and cortisone respond differently to high- and low-psychologically stressful soccer competitions

Aldosterone and cortisone are released in response to physical and psychological stress. However, aldosterone and cortisone responses in children engaged in physical competition have not been described. We examined salivary aldosterone and salivary cortisone responses among Hong Kongese boys, aged 8-11 years, during (1) a soccer match against unknown competitors (N = 84, high psychological stress condition) and (2) an intrasquad soccer scrimmage against teammates (N = 81, low psychological stress condition). Aldosterone levels increased during the soccer match and intrasquad soccer scrimmage conditions, consistent with the view that aldosterone responds to physical stress. During the soccer match, winning competitors experienced larger increases in aldosterone compared to losing competitors, indicating that the degree of aldosterone increase was attenuated by match outcome. Cortisone increased during the soccer match and decreased during the intrasquad soccer scrimmage. Competitors on teams that resulted in a tie had larger cortisone increases compared to winners or losers. These findings highlight that the degree of cortisone change is related to boy's cognitive appraisal of the competitor type (i.e., teammates vs. unknown competitors) and the competitive nature of the game (e.g., tie). These results shed new light on adrenal hormone mediators of stress and competition during middle childhood.

Testosterone, androstenedione, cortisol and cortisone levels in human unstimulated, stimulated and parotid saliva

BACKGROUND

Recently, measurements of steroids like testosterone, androstenedione, cortisol and cortisone in saliva are more and more applied in diagnostics and scientific studies. This is mainly due to the simple and non-invasive collection of saliva. We aimed to evaluate the optimal way to collect saliva for steroid hormone measurement.

METHODS

We investigated in twenty volunteers whether there is a difference between steroid hormone concentrations in unstimulated and stimulated saliva collected while chewing, using cotton and synthetic Salivettes®, citric acid or chewing gum. Furthermore, total unstimulated saliva was compared to parotid gland saliva. Testosterone, androstenedione, cortisol and cortisone were measured using Liquid-Chromatography Tandem Mass Spectrometry (LC-MS/MS).

RESULTS

Salivary testosterone, androstenedione and cortisol concentrations were unaffected by stimulation upon mouth and tongue movements, cortisone levels were on average 16% lower. Concentrations of all hormones were lower in parotid gland saliva compared to total unstimulated saliva (on average 51%, 26%, 66% and 49% lower, for testosterone, androstenedione, cortisol and cortisone, respectively). Concentrations of testosterone as well as androstenedione were lower when using synthetic Salivettes® (58% and 41%, respectively) and were higher when using cotton Salivettes® (217% and 46%, respectively). Cortisol levels in saliva were unaffected by using Salivettes®. However, cortisol and testosterone levels were higher in with chewing gum stimulated saliva (16% and 55%, respectively). Cortisone concentrations were lower in all types of stimulations (on average 25%-35%).

CONCLUSION

The way saliva is collected should be considered when analysing and interpreting salivary hormone concentrations. We advocate unstimulated saliva collection in simple polypropylene tubes for all steroid measurements.

11 beta-hydroxysteroid dehydrogenase 2 promoter methylation is associated with placental protein expression in small for gestational age newborns

Small for gestational age infants have greater risk of developing metabolic diseases in adult life. It has been suggested that low birth weight may result from glucocorticoid excess in utero, a key mechanism in fetal programming. The placental enzyme 11-beta hydroxysteroid dehydrogenase type 2 (11β-HSD2, HSD11B2 gene) acts as a barrier protecting the fetus from maternal corticosteroid deleterious effects. Low placental 11β-HSD2 transcription and activity have been associated with low birth weight, yet the mechanism regulating its protein expression is not fully understood. In the present study we aimed to analyze 11β-HSD2 protein expression in placentas of adequate and small for gestational age (AGA and SGA, respectively) newborns from healthy mothers, and to explore whether 11β-HSD2 protein expression could be modulated by DNA methylation. 11β-HSD2 protein levels were measured by western blot in placental biopsies from term AGA and SGA infants (n=10 per group). DNA methylation was profiled both globally and in the HSD11B2 promoter by liquid chromatography with UV detection and methylation-specific melting curve analysis, respectively. We found lower placental 11β-HSD2 protein expression and higher HSD11B2 promoter methylation in SGA compared to AGA. Promoter methylation was inversely correlated with both protein expression and, importantly, birth weight. No changes in global placental methylation were found. In conclusion, lower 11β-HSD2 protein expression is associated with higher HSD11B2 promoter methylation, correlating with birth weight in healthy pregnancy. Our data support the role of 11β-HSD2 in determining birth weight, providing evidence of its regulation by epigenetic mechanisms, which may affect postnatal metabolic disease risk.

Steroid hormones related to 11beta-hydroxysteroid dehydrogenase type 1 in treated obesity

The local concentration of glucocorticoids is intensively regulated by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD 1). Human 11beta-HSD 1 also reversibly catalyzes the inter-conversion of 7alpha-hydroxy- and 7beta-hydroxy-dehydroepiandrosterone (DHEA) into 7-oxo-DHEA. The cohort of 282 obese adolescents, 154 girls (median age 15.31 years, range 14.17-16.68 years) and 128 boys (median age 14.95 years, range 13.87-16.16 years), BMI (Body Mass Index) >90th percentile was examined. In samples collected before and after one month of reductive diet therapy, circulating levels of steroids were analyzed by liquid chromatography-tandem mass spectrometry and radioimmunoassay methods. The model of the treatment efficacy prediction was calculated. A significant reduction in circulating levels of cortisone, E2 and increased levels of 7beta-hydroxy-DHEA after the reductive treatment was observed. Levels of cortisol, DHEA, DHT sustained without any significant change. The predictive Orthogonal Projections to Latent Structures (OPLS) model explained 20.1 % of variability of BMI, z-score change by the basal levels of 7alpha-hydroxy-DHEA, DHEA, cortisol and E2 as the strongest predictors. Reduced levels of circulating cortisone and reduced ratios of oxygenated/reduced metabolites reflect increased reductase activity of 11beta-HSD 1 with reduced BMI, z-score. We hypothesize whether these changes can be attributed to the altered activity of 11beta-HSD 1 in the liver.

Hepatic 11β-hydroxysteroid dehydrogenase type 1 activity in obesity and type 2 diabetes using a novel triple tracer cortisol technique

AIMS/HYPOTHESIS

Dysregulation of 11β-hydroxysteroid dehydrogenase (11β-HSD) enzyme activities are implicated in the pathogenesis of obesity and insulin resistance. The aim of the study was to determine whether hepatic 11β-HSD type 1 (11β-HSD-1) enzyme activity differs in people with and without obesity and type 2 diabetes.

METHODS

We measured hepatic 11β-HSD-1 activity in the overnight fasted state in 20 lean non-diabetic participants (LND), 21 overweight/obese non-diabetic participants (OND) and 20 overweight/obese participants with type 2 diabetes (ODM) using a non-invasive approach. One mg doses of [9,12,12-(2)H3]cortisol (D cortisol) and [4-(13)C]cortisone ([(13)C]cortisone) were ingested, while [1,2,6,7-(3)H]cortisol ([(3)H] cortisol) was infused intravenously to enable concurrent measurements of first-pass hepatic extraction of ingested D cortisol and hepatic conversion of ingested [(13)C]cortisone to C13 cortisol derived from the ingested cortisone (a measure of 11β-HSD-1 activity in the liver) using an isotope dilution technique. One-way ANOVA models and Kruskal-Wallis tests were used to test the hypothesis.

RESULTS

Plasma D cortisol and C13 cortisol concentrations were lower in OND than in LND (p < 0.05) over 6 h of the study. There was no difference (p = 0.15) in C13 and D cortisol concentrations between OND and ODM and between LND and ODM for the same study period. Hepatic conversion of [(13)C]cortisone to C13 cortisol was similar between groups.

CONCLUSIONS/INTERPRETATION

Hepatic conversion of [(13)C]cortisone to C13 cortisol did not differ between the groups studied. We conclude that hepatic 11β-HSD-1 activity is similar in individuals who are overweight/obese or who have type 2 diabetes.

11β-hydroxysteroid dehydrogenases: intracellular gate-keepers of tissue glucocorticoid action

Glucocorticoid action on target tissues is determined by the density of "nuclear" receptors and intracellular metabolism by the two isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD) which catalyze interconversion of active cortisol and corticosterone with inert cortisone and 11-dehydrocorticosterone. 11β-HSD type 1, a predominant reductase in most intact cells, catalyzes the regeneration of active glucocorticoids, thus amplifying cellular action. 11β-HSD1 is widely expressed in liver, adipose tissue, muscle, pancreatic islets, adult brain, inflammatory cells, and gonads. 11β-HSD1 is selectively elevated in adipose tissue in obesity where it contributes to metabolic complications. Similarly, 11β-HSD1 is elevated in the ageing brain where it exacerbates glucocorticoid-associated cognitive decline. Deficiency or selective inhibition of 11β-HSD1 improves multiple metabolic syndrome parameters in rodent models and human clinical trials and similarly improves cognitive function with ageing. The efficacy of inhibitors in human therapy remains unclear. 11β-HSD2 is a high-affinity dehydrogenase that inactivates glucocorticoids. In the distal nephron, 11β-HSD2 ensures that only aldosterone is an agonist at mineralocorticoid receptors (MR). 11β-HSD2 inhibition or genetic deficiency causes apparent mineralocorticoid excess and hypertension due to inappropriate glucocorticoid activation of renal MR. The placenta and fetus also highly express 11β-HSD2 which, by inactivating glucocorticoids, prevents premature maturation of fetal tissues and consequent developmental "programming." The role of 11β-HSD2 as a marker of programming is being explored. The 11β-HSDs thus illuminate the emerging biology of intracrine control, afford important insights into human pathogenesis, and offer new tissue-restricted therapeutic avenues.

Histone Deacetylase Inhibition Attenuates Transcriptional Activity of Mineralocorticoid Receptor Through Its Acetylation and Prevents Development of Hypertension

Rationale:

Inhibition of histone deacetylases (HDACs) results in attenuated development of hypertension in deoxycorticosterone acetate–induced hypertensive rats and spontaneously hypertensive rats. However, the molecular mechanism remains elusive.

Objective:

We hypothesized that HDAC inhibition attenuates transcriptional activity of mineralocorticoid receptor (MR) through its acetylation and prevents development of hypertension in deoxycorticosterone acetate–induced hypertensive rats.

Methods and Results:

Expression of MR target genes was measured by quantitative real-time polymerase chain reaction. Recruitment of MR and RNA polymerase II on promoters of target genes was analyzed by chromatin immunoprecipitation assay. Live cell imaging was performed for visualization of nuclear translocation of MR. MR acetylation was determined by Western blot with anti-acetyl-lysine antibody after immunoprecipitation with anti-MR antibody. Transcriptional activity of MR was determined by luciferase assay. For establishment of a hyperaldosteronism animal, Sprague-Dawley rats underwent uninephrectomy and received subcutaneous injection of 40 mg/kg per week of deoxycorticosterone acetate and drinking water containing 1% NaCl. Treatment with a HDAC class I inhibitor resulted in reduced expression of MR target genes in accordance with reduced recruitment of MR and RNA polymerase II on promoters of target genes. HDAC inhibition promoted MR acetylation, leading to decreased transcriptional activity of MR. Knockdown or inhibition of HDAC3 resulted in reduced expression of MR target genes induced by mineralocorticoids.

Conclusions:

These results indicate that HDAC inhibition attenuates transcriptional activity of MR through its acetylation and prevents development of hypertension in deoxycorticosterone acetate–induced hypertensive rats.

Zebrafish 20β-hydroxysteroid dehydrogenase type 2 is important for glucocorticoid catabolism in stress response

Stress, the physiological reaction to a stressor, is initiated in teleost fish by hormone cascades along the hypothalamus-pituitary-interrenal (HPI) axis. Cortisol is the major stress hormone and contributes to the appropriate stress response by regulating gene expression after binding to the glucocorticoid receptor. Cortisol is inactivated when 11β-hydroxysteroid dehydrogenase (HSD) type 2 catalyzes its oxidation to cortisone. In zebrafish, Danio rerio, cortisone can be further reduced to 20β-hydroxycortisone. This reaction is catalyzed by 20β-HSD type 2, recently discovered by us. Here, we substantiate the hypothesis that 20β-HSD type 2 is involved in cortisol catabolism and stress response. We found that hsd11b2 and hsd20b2 transcripts were up-regulated upon cortisol treatment. Moreover, a cortisol-independent, short-term physical stressor led to the up-regulation of hsd11b2 and hsd20b2 along with several HPI axis genes. The morpholino-induced knock down of hsd20b2 in zebrafish embryos revealed no developmental phenotype under normal culture conditions, but prominent effects were observed after a cortisol challenge. Reporter gene experiments demonstrated that 20β-hydroxycortisone was not a physiological ligand for the zebrafish glucocorticoid or mineralocorticoid receptor but was excreted into the fish holding water. Our experiments show that 20β-HSD type 2, together with 11β-HSD type 2, represents a short pathway in zebrafish to rapidly inactivate and excrete cortisol. Therefore, 20β-HSD type 2 is an important enzyme in stress response.

G6PT-H6PDH-11βHSD1 triad in the liver and its implication in the pathomechanism of the metabolic syndrome

The metabolic syndrome, one of the most common clinical conditions in recent times, represents a combination of cardiometabolic risk determinants, including central obesity, glucose intolerance, insulin resistance, dyslipidemia, non-alcoholic fatty liver disease and hypertension. Prevalence of the metabolic syndrome is rapidly increasing worldwide as a consequence of common overnutrition and consequent obesity. Although a unifying picture of the pathomechanism is still missing, the key role of the pre-receptor glucocorticoid activation has emerged recently. Local glucocorticoid activation is catalyzed by a triad composed of glucose-6-phosphate-transporter, hexose-6-phosphate dehydrogenase and 11β-hydroxysteroid dehydrogenase type 1 in the endoplasmic reticulum. The elements of this system can be found in various cell types, including adipocytes and hepatocytes. While the contribution of glucocorticoid activation in adipose tissue to the pathomechanism of the metabolic syndrome has been well established, the relative importance of the hepatic process is less understood. This review summarizes the available data on the role of the hepatic triad and its role in the metabolic syndrome, by confronting experimental findings with clinical observations.

11Beta-hydroxysteroid dehydrogenase type 1 and its role in the hypothalamus-pituitary-adrenal axis, metabolic syndrome, and inflammation

CONTEXT

11Beta-hydroxysteroid dehydrogenase (11beta-HSD) enzymes are now appreciated to be important regulators of hormone action at a tissue level. 11Beta-HSD1 is widely expressed and increases glucocorticoid action through its unique ability to convert inactive glucocorticoids (cortisone in man, 11-dehydrocorticosterone in rodents) to their active forms (cortisol and corticosterone, respectively). The enzyme has roles in the normal hypothalamus-pituitary-adrenal (HPA) axis, has been implicated in metabolic syndrome, and may modulate various aspects of the immune response.

EVIDENCE ACQUISITION

A review of published, peer-reviewed medical literature (1990 to June 2009) on the physiology and pathophysiology of 11beta-HSD1 was performed with an emphasis on HPA axis consequences, the metabolic syndrome, and the inflammatory response.

EVIDENCE SYNTHESIS

Studies of patients with genetic defects in 11beta-HSD1 action show abnormal HPA axis responses with hyperandrogenism being a major consequence. The mechanisms underlying these abnormalities have been explored in mouse models with targeted deletion of components of the 11beta-HSD1 system. A range of experimental studies emphasize the role of 11beta-HSD1 in the metabolic syndrome and the potential for treatment with chemical inhibitors. An emerging area is the role of 11beta-HSD1 in the inflammatory response.

CONCLUSIONS

11Beta-HSD1 activity is an important component of the HPA axis and contributes to the metabolic syndrome and the normal immune response. Ongoing clinical observations and the development of selective inhibitors will further clarify the role of 11beta-HSD1 in these areas.

Salivary steroid assays – research or routine?

Salivary concentrations of unconjugated steroids reflect those for free steroids in serum although concentrations may differ because of salivary gland metabolism. Samples for salivary steroid analysis are stable for up to 7 days at room temperature, one month or more at 4°C and three months or more at −20°C. When assessed against strict criteria, the evidence shows that salivary cortisol in evening samples or following dexamethasone suppression provides a reliable and effective screen for Cushing's syndrome. Sequential salivary cortisol measurements are also extremely helpful for the investigation of suspected cyclical Cushing's syndrome. There is potential for the identification of adrenal insufficiency when used with Synacthen stimulation. Salivary 17-hydroxyprogesterone and androstenedione assays are valued as non-invasive tests for the home-monitoring of hydrocortisone replacement therapy in patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency. The diagnostic value of salivary oestradiol, progesterone, testosterone, dehydroepiandrosterone and aldosterone testing is compromised by rapid fluctuations in salivary concentrations of these steroids. Multiple samples are required to obtain reliable information, and at present the introduction of these assays into routine laboratory testing is not justified.

Differential modulation of 3T3-L1 adipogenesis mediated by 11beta-hydroxysteroid dehydrogenase-1 levels

The localized activation of circulating glucocorticoids in vivo by the enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) plays a critical role in the development of the metabolic syndrome. However, the precise contribution of 11beta-HSD1 in the initiation of adipogenesis by inactive glucocorticoids is not fully understood. 3T3-L1 fibroblasts can be terminally differentiated to mature adipocytes in a glucocorticoid-dependent manner. Both inactive rodent dehydrocorticosterone and human cortisone were able to substitute for the synthetic glucocorticoid dexamethasone in 3T3-L1 adipogenesis, suggesting a potential role for 11beta-HSD1 in these effects. Differentiation of 3T3-L1 cells caused a strong increase in 11beta-HSD1 protein levels, which occurred late in the differentiation protocol. Reduction of 11beta-HSD1 activity in 3T3-L1 fibroblasts, achieved by pharmacological inhibition or adenovirally mediated delivery of short hairpin RNA constructs, specifically blocked the ability of inactive glucocorticoids to drive 3T3-L1 differentiation. However, even modest increases in exogenous 11beta-HSD1 expression in 3T3-L1 fibroblasts, to levels comparable with endogenous 11beta-HSD1 in differentiated 3T3-L1 adipocytes, were sufficient to block adipogenesis. Luciferase reporter assays indicated that overexpressed 11beta-HSD1 was catalyzing the inactivating dehydrogenase reaction, because the ability of both active and inactive glucocorticoids to activate the glucocorticoid receptor were largely suppressed. These results suggest that the temporal regulation of 11beta-HSD1 expression is tightly controlled in 3T3-L1 cells, so as to mediate the initiation of differentiation by inactive glucocorticoids and also to prevent the inhibitory activity of prematurely expressed 11beta-HSD1 during adipogenesis.

Effect of pro-inflammatory cytokines on expression and activity of 11beta-hydroxysteroid dehydrogenase type 2 in cultured human term placental trophoblast and human choriocarcinoma JEG-3 cells

OBJECTIVE

11Beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) is thought to act as a placental barrier protecting the fetus from high levels of maternal cortisol. On the other hand, intrauterine infection is one of the main causes of preterm birth and adverse fetal outcome, and pro-inflammatory cytokines may contribute to these adverse effects. However, the effect of pro-inflammatory cytokines on 11beta-HSD2 is still not clear. Therefore, we have evaluated the effect of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) on 11beta-HSD2 in cultured human placental trophoblast and in human choriocarcinoma JEG-3 cells.

METHODS

Placental trophoblast cells were isolated from human term placenta. Placental trophoblast cells and JEG-3 cells were treated with TNF-alpha (0.1-10 ng/mL) or IL-1beta (0.1-10 ng/mL). Real-time reverse transcription polymerase chain reaction and Western blot were used to study the regulation of 11beta-HSD2 expression. 11beta-HSD2 activity was determined by measuring the rate of cortisol to cortisone conversion in the culture medium using thin-layer chromatography (TLC).

RESULTS

In placental trophoblast, TNF-alpha and IL-1beta down-regulated 11beta-HSD2 mRNA expression and activity (both P <.05). The protein level was decreased only with IL-1beta (P <.05). In JEG-3 cells, 11beta-HSD2 mRNA was decreased by TNF-alpha but up-regulated by IL-1beta, with no significant change in protein expression and activity.

CONCLUSION

Our results suggest caution in interpreting data using JEG-3 cells. However, our studies with primary trophoblast suggest that TNF-alpha and IL-1beta may increase the amount of cortisol crossing to the placenta and fetal circulation by attenuating 11beta-HSD2 activity, potentially contributing to preterm labor and altered fetal outcome in uterine infection.

Interactions between dehydroepiandrosterone and glucocorticoid metabolism in pig kidney: nuclear and microsomal 11beta-hydroxysteroid dehydrogenases

The 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) activates glucocorticoids (GC) by reversibly converting 11-keto-GC to 11-hydroxy-GC, while 11betaHSD2 and 11betaHSD3 only catalyzes the reverse reaction. Recently, rat and human 11betaHSDs were shown to interconvert 7alpha- and 7beta-hydroxy-dehydroepiandrosterone (7alpha- or 7beta-OH-DHEA) with 7-oxo-DHEA. We report that pig kidney microsomes (PKMc) and nuclei (PKN) oxidize 7alpha-OH-DHEA to 7-oxo-DHEA at higher rates with NAD+, than with NADP+. Corticosterone (CS), dehydrocoticosterone (DHC), 11alpha- and 11beta-hydroxyprogesterone, and carbenoxolone completely inhibited these reactions, while 7-oxo-DHEA only inhibited the NAD+-dependent reaction. Conversely, CS oxidation was not inhibited by 7alpha-OH-DHEA or 7-oxo-DHEA. PKMc and PKN did not convert 7-oxo-DHEA to 7-OH-DHEA with either NADPH or NADH. Finally, PKN contained a high affinity, NADPH-dependent 11betaHSD that reduces DHC to CS. The GC effects on interconversion of DHEA metabolites may have clinical significance, since DHEA and its 7-oxidized derivatives have been proposed for treatment of human autoimmune and inflammatory disorders.

Renal vacuolar H+-ATPase

Vacuolar H(+)-ATPases are ubiquitous multisubunit complexes mediating the ATP-dependent transport of protons. In addition to their role in acidifying the lumen of various intracellular organelles, vacuolar H(+)-ATPases fulfill special tasks in the kidney. Vacuolar H(+)-ATPases are expressed in the plasma membrane in the kidney almost along the entire length of the nephron with apical and/or basolateral localization patterns. In the proximal tubule, a high number of vacuolar H(+)-ATPases are also found in endosomes, which are acidified by the pump. In addition, vacuolar H(+)-ATPases contribute to proximal tubular bicarbonate reabsorption. The importance in final urinary acidification along the collecting system is highlighted by monogenic defects in two subunits (ATP6V0A4, ATP6V1B1) of the vacuolar H(+)-ATPase in patients with distal renal tubular acidosis. The activity of vacuolar H(+)-ATPases is tightly regulated by a variety of factors such as the acid-base or electrolyte status. This regulation is at least in part mediated by various hormones and protein-protein interactions between regulatory proteins and multiple subunits of the pump.

Characterisation of 11β-hydroxysteroid dehydrogenases in feline kidney and liver

11 Beta-hydroxysteroid dehydrogenases type 1 and 2 (11 beta-HSD1 and 11 beta-HSD2) are microsomal enzymes responsible for the interconversion of cortisol into the inactive form cortisone and vice versa. 11 beta-HSD1 is mainly present in the liver, and has predominantly reductase activity although its function has not yet been elucidated. 11 beta-HSD2, present in mineralocorticoid target tissues such as the kidney, converts cortisol into cortisone. Reduced activity due to inhibition or mutations of 11 beta-HSD2 leads to hypertension and hypokalemia resulting in the Apparent Mineralocorticoid Excess Syndrome (AMES). Like humans, cats are highly susceptible for hypertension. As large species differences exist with respect to the kinetic parameters (K(m) and V(max)) and amino acid sequences of both enzymes, we determined these characteristics in the cat. Both enzyme types were found in the kidneys. 11 beta-HSD1 in the feline kidney showed bidirectional activity with predominantly dehydrogenase activity (dehydrogenase: K(m) 1959+/-797 nM, V(max) 766+/-88 pmol/mg*min; reductase: K(m) 778+/-136 nM, V(max) 112+/-4 pmol/mg*min). 11 beta-HSD2 represents a unidirectional dehydrogenase with a higher substrate affinity (K(m) 184+/-24 nM, V(max) 74+/-3 pmol/mg*min). In the liver, only 11 beta-HSD1 is detected exerting reductase activity (K(m) 10462 nM, V(max) 840 pmol/mg*min). Sequence analysis of conserved parts of 11 beta-HSD1 and 11 beta-HSD2 revealed the highest homology of the feline enzymes with the correspondent enzymes found in man. This suggests that the cat may serve as a suitable model species for studies directed to the pathogenesis and treatment of human diseases like AMES and hypertension.

Stimulation of 11-beta-hydroxysteroid dehydrogenase type 2 in rat colon but not in kidney by low dietary NaCl intake

Data suggest that mineralocorticoid selectivity is differentially regulated in epithelial target tissues. We investigated whether the level of dietary NaCl intake influenced the expression and tissue distribution of 11-beta-hydroxysteroid dehydrogenase type 2 (11betaHSD-2), aldosterone receptor (MR), and glucocorticoid receptor (GR) in rat colon, kidney, and cardiovascular tissue. Rats were fed a diet with 0.01 or 3% NaCl for 10 days. Messenger RNAs were analyzed with ribonuclease protection assay, 11betaHSD-2 protein by Western blot analysis, and localization of GR and 11betaHSD-2 by immunohistochemistry. NaCl restriction elevated plasma renin and aldosterone concentration, whereas corticosterone was unaltered. In distal colon, 11betaHSD-2 mRNA and protein were augmented significantly by low-NaCl intake and immunolabeling was widely distributed in crypt and surface epithelium. The MR mRNA level was decreased, whereas GR mRNA was unaltered in distal colon. MR, GR, and 11betaHSD-2 mRNAs were not changed in kidney cortex and medulla, left cardiac ventricle, and aorta. Immunofluorescence labeling showed that GR and 11betaHSD-2 localization was mutually exclusive in kidney. In colon epithelium, nuclear staining for GR subsided as perinuclear 11betaHSD-2 immunoreactivity increased with NaCl restriction. As a functional correlate of increased 11betaHSD-2 expression in colon, the GR-stimulated sodium-hydrogen exchanger NHE-3 was lowered by NaCl restriction. Inhibition of 11betaHSD-2 activity by carbenoxolone during NaCl restriction stimulated NHE-3 expression in colon. Dexamethasone stimulated NHE-3 both in colon and kidney. These data indicate that mineralocorticoid selectivity is physiologically regulated by NaCl intake at the level of 11betaHSD-2 expression and tissue distribution in the distal colon, but not in the kidney.

Dietary phosphorus transcriptionally regulates 25-hydroxyvitamin D-1alpha-hydroxylase gene expression in the proximal renal tubule

Synthesis of the hormone 1,25-dihydroxyvitamin D, the biologically active form of vitamin D, occurs in the kidney and is catalyzed by the mitochondrial cytochrome P450 enzyme, 25-hydroxyvitamin D-1alpha-hydroxylase (1alpha-hydroxylase). We sought to characterize the effects of changes in dietary phosphorus on the kinetics of renal mitochondrial 1alpha-hydroxylase activity and the renal expression of P450c1alpha and P450c24 mRNA, to localize the nephron segments involved in such regulation, and to determine whether transcriptional mechanisms are involved. In intact mice, restriction of dietary phosphorus induced rapid, sustained, approximately 6- to 8-fold increases in renal mitochondrial 1alpha-hydroxylase activity and renal P450c1alpha mRNA abundance. Immunohistochemical analysis of renal sections from mice fed the control diet revealed the expression of 1alpha-hydroxylase protein in the proximal convoluted and straight tubules, epithelial cells of Bowman's capsule, thick ascending limb of Henle's loop, distal tubule, and collecting duct. In mice fed a phosphorus-restricted diet, immunoreactivity was significantly increased in the proximal convoluted and proximal straight tubules and epithelial cells of Bowman's capsule, but not in the distal nephron. Dietary phosphorus restriction induced a 2-fold increase in P450c1alpha gene transcription, as shown by nuclear run-on assays. Thus, the increase in renal synthesis of 1,25-dihydroxyvitamin D induced in normal mice by restricting dietary phosphorus can be attributed to an increase in the renal abundance of P450c1alpha mRNA and protein. The increase in P450c1alpha gene expression, which occurs exclusively in the proximal renal tubule, is due at least in part to increased transcription of the P450c1alpha gene.

Effect of cellular differentiation on 11beta-hydroxysteroid dehydrogenase activity in the intestine

11beta-Hydroxysteroid dehydrogenase (11betaHSD) converts endogenous glucocorticoids to their biologically inactive 11-dehydro derivatives and is therefore able to determine, at least in part, the biological action of glucocorticoids. Type 1 11betaHSD has both oxidase and reductase activities interconverting corticosterone and 11-dehydrocorticosterone, whereas type 2 11betaHSD has only oxidase activity converting corticosterone to 11-dehydrocorticosterone. Since 11betaHSD expression is regulated during development and by hormones in a tissue-specific manner and since glucocorticoids play an important role in postnatal intestinal maturation, we investigated the role of corticosteroids and cytodifferentiation in the regulation of intestinal 11betaHSD. Using rat intestinal organ cultures and epithelial cell lines derived from rat small intestine (IEC-6, IEC-18) and from human colon adenocarcinoma (Caco-2, HT-29), we analyzed the effect of corticosteroids and cytodifferentiation on 11betaHSD. Screening of the clonal cell lines showed that Caco-2 cells expressed by far the greatest 11betaHSD2 oxidase activity, lower activity was observed in HT-29 cells, and lowest activity was seen in IEC cells. Treatment with dexamethasone (50 nM) increased the activity of 11betaHSD2 in IEC-6 cells (+59%) and HT-29 cells (+31%), whereas aldosterone (50 nM) stimulated 11betaHSD2 in IEC-6 cells only (+31%). Caco-2 cells and IEC-18 cells did not respond to corticosteroids. Growth of IEC-6 cells on Matrigel, treatment of HT-29 cells with butyrate, and postconfluency of Caco-2 cells increased not only the markers of cytodifferentiation, such as alkaline phosphatase and sucrase, but also the activity of 11betaHSD2 in all of these cell lines (IEC-6, +96%; HT-29, +139%; Caco-2, +95%). Addition of corticosteroids to these more differentiated cell cultures did not enhance 11betaHSD2 activity. In intestinal organ cultures of suckling rat small intestine, dexamethasone and aldosterone stimulated 11betaHSD by more than 300%. We conclude that corticosteroids markedly and differentially regulate intestinal 11betaHSD2 and that cytodifferentiation of intestinal epithelial cells is associated with upregulation of 11betaHSD2 activity that is independent of corticosteroids.

Expression of 11 beta-hydroxysteroid dehydrogenase isoenzymes in the human pituitary: induction of the type 2 enzyme in corticotropinomas and other pituitary tumors

One of the defining biochemical features of Cushing's disease is a relative insensitivity to glucocorticoid (GC) feedback, but an analysis of the GC receptor has failed to detect any major abnormalities. However, two isoenzymes of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD), either by converting cortisone (E) to cortisol (F) (type 1) or conversely by converting F to E (type 2), play an important prereceptor role in regulating corticosteroid hormone action at several sites. 11 beta HSD1 and -2 expression within the anterior pituitary gland itself may modulate GC feedback at an autocrine level, and we have speculated that this may be deranged in Cushing's disease. Detection of 11 beta HSD type 1 and 2 immunoreactive protein was performed using fluorescence immunohistochemistry. Double immunofluorescent studies were undertaken on normal pituitary to define the cellular localization of 11 beta HSD isoenzymes using antisera against GH, ACTH, LH, FSH, PRL, and S100, a nonhormonal marker of folliculo-stellate cells. In normal pituitary, positive staining for 11 beta HSD1-immunoreactive protein was observed in GH- and PRL-secreting cells and in folliculo-stellate cells; gonadotrophs, thyrotrophs, and ACTH-positive cells were negative. 11 beta HSD2 immunoreactivity was absent in all cell types. RT-PCR detected 11 beta HSD1 messenger ribonucleic acid (mRNA) expression in the normal pituitary; 11 beta HSD2 mRNA expression was also seen in most normal tissue. By contrast, in ACTH-secreting adenomas 11 beta HSD2 immunostaining was strongly positive in every case of corticotroph adenoma. 11 beta HSD1 immunoreactivity was also observed occasionally, but to a much lesser extent. In other pituitary tumors, both functional and nonfunctional, 11 beta HSD expression was variable in terms of isoenzyme mRNA and intensity of protein staining. The expression of 11 beta HSD1 (which generates F from E) in somatotrophs and lactotrophs suggests an autocrine role for this isoenzyme in the glucocorticoid regulation of pituitary GH and PRL secretion. 11 beta HSD2 expression is markedly induced in ACTH-secreting pituitary tumors and, by converting F to E, may explain the resetting of glucocorticoid feedback control in Cushing's disease.

Cortisol-secreting adrenal adenomas express 11beta-hydroxysteroid dehydrogenase type-2 gene yet possess low 11beta-HSD2 activity

BACKGROUND

11beta-hydroxysteroid dehydrogenase Type-2 (11beta-HSD2) is an unidirectional enzyme that catalyzes the conversion of glucocorticoid hormones cortisol and corticosterone (B) into their corresponding inactive forms, cortisone, and 11-dehydrocorticosterone (DH-B). We have provided evidence that 11beta-HSD2 is expressed as messenger RNA (mRNA) and protein in human adrenocortical cells, where its activity is inhibited in vitro by the main glucocorticoid agonists, adrenocorticotropic hormone (ACTH) and angiotensin-II. It seemed worthwhile, therefore, to study the gene expression and activity of 11beta-HSD2 in cortisol-secreting adrenocortical adenomas.

METHODS

Three adrenal adenomas that produced Cushing syndrome were recruited. Three normal adrenal glands were obtained from patients who underwent unilateral nephrectomy with ipsilateral adrenalectomy for renal cancer. 11beta-HSD2 gene expression was studied by reverse transcriptionpolymerase chain reaction (RT-PCR) in adenoma and normal adrenocortical tissue. Cortisol, B, cortisone, and DH-B production by adenoma and adrenal slices in vitro was assayed by quantitative high-performance liquid chromatography (HPLC), and the activity of 11beta-HSD2 was evaluated by measuring the conversion of [3H]-cortisol to [3H]-cortisone.

RESULTS

RT-PCR allowed the detection of the 11beta-HSD2 mRNA in the three adrenal adenomas and normal adrenal cortices examined. Under basal conditions, adenoma slices secreted higher amounts of cortisol and B, but markedly lower amounts of cortisone and DH-B than adrenal slices. ACTH raised cortisol and B production from both specimens, and it lowered cortisone and DH-B yield. The level basal conversion of [3H]-cortisol to [3H]-cortisone was notably less in adenomas than in adrenals, and ACTH decreased it in both tissues.

CONCLUSIONS

Collectively, our findings indicate that cortisol-secreting adrenal adenomas express the 11beta-HSD2 gene, but the activity of the enzyme is suppressed in adenomas when compared with the normal adrenal cortex. We advance the hypothesis that the elevated local concentration of steroid hormones that occur in adenomas down-regulates 11beta-HSD2 activity, thereby contributing to their abnormal steroidogenic function.

Cortisol metabolism and the role of 11beta-hydroxysteroid dehydrogenase

Two isoforms of the enzyme 11beta-hydroxysteroid dehydrogenase (11beta-HSD) interconvert the active glucocorticoid, cortisol, and inactive cortisone. 11beta-HSD1 is believed to act in vivo predominantly as an oxo-reductase using NADP(H) as a cofactor to generate cortisol. In contrast, 11beta-HSD2 acts exclusively as an NAD-dependent dehydrogenase inactivating cortisol to cortisone, thereby protecting the mineralocorticoid receptor from occupation by cortisol. In peripheral tissues, both enzymes serve to control the availability of cortisol to bind to the corticosteroid receptors. Defective expression of 11beta-HSD2 is implicated in patients with hypertension and intra-uterine growth retardation, while 11beta-HSD1 appears to be intricately involved in the conditions of apparent cortisone reductase deficiency, insulin resistance and visceral obesity. The ability of peripheral tissues to regulate corticosteroid concentrations through 11beta-HSD isozymes is established as an important mechanism in the pathogenesis of diverse human diseases. Modulation of enzyme activity may offer a novel therapeutic approach to treating human disease while circumventing the consequences of systemic glucocorticoid excess or deficiency.

11Beta-hydroxysteroid-dehydrogenase isoforms: tissue distribution and implications for clinical medicine

11Beta-hydroxylation is essential for glucocorticoid and mineralocorticoid activity of a steroid. The enzyme catalyzing this reaction is termed 11beta-hydroxysteroid-dehydrogenase (11beta-HSD). Two isoenzymes of 11beta-HSD have been characterized in human tissues. Whereas 11beta-HSD-I works mainly as a reductase, 11beta-HSD-II only functions as an oxidizing (inactivating) enzyme for physiological glucocorticoids. Thus, the tissue distribution of both enzymes plays a crucial role for the specific glucocorticoid status of an organ. This review summarizes our knowledge of tissue distribution of both 11beta-HSD isoenzymes, their physiological function and pathophysiological role in certain clinical abnormalities, and their relevance to the metabolism of synthetic glucocorticoid and mineralocorticoid compounds.

The role of 11 beta-hydroxysteroid dehydrogenase in central obesity and osteoporosis

Both central obesity and osteoporosis are common findings in states of glucocorticoid excess. In many tissues, including adipose tissue, hydroxysteroid dehydrogenase type 1 (11beta-HSD1) catalyses the inter-conversion of active glucocorticoid, cortisol (F) and inactive cortisone (E) and regulates exposure to the glucocorticoid receptor. As such, factors which regulate 11beta-HSD1 are likely to have an important role in adipose tissue and bone physiology. Using primary cultures of human adipose stromal cells we have investigated the effect of various factors present within the adipocyte microenvironment for their effects on 11beta-HSD1 expression. IGF-1 caused a dose dependant inhibition of 11beta-HSD1 activity in both subcutaneous and omental stromal cells. Additionally, TNFalpha treatment increased 11beta-HSD1 reductase activity and mRNA expression. In adult human bone, 11beta-HSD1, but not 11beta-HSD2, expression was demonstrated using enzyme activity studies, RT-PCR and immunohistochemistry. In contrast to liver and adipose tissues, where reductase activity predominates, both reductase and dehydrogenase activities of 11beta-HSD1 were evident in bone chips and primary cultures of human osteoblasts. The action of growth factors and cytokines on glucocorticoid sensitive tissues such as adipose tissue and bone may be mediated by modulation of local glucocorticoid metabolism at a pre-receptor level.

Mineralocorticoid selectivity: molecular and cellular aspects

Aldosterone acts in mineralocorticoid-sensitive cells by binding to the mineralocorticoid receptor (MR). Because the MR displays similar affinity for aldosterone and glucocorticoid hormones and because these latter hormones are 100- to 1000-fold more abundant than aldosterone in the plasma, mechanisms are required to avoid permanent illicit occupancy of MR by glucocorticoid hormones. The main mechanism of mineralocorticoid selectivity is enzymatic: the 11beta hydroxysteroid dehydrogenase (HSD2) metabolizes glucocorticoid hormones into derivatives with a low affinity for MR. The cell biology and regulation of HSD2 are reviewed in this article, as well as its implications in human hypertension. Other factors play a role in mineralocorticoid selectivity: the MR itself, the possibility to form homodimers (MR-MR), or heterodimers (with the glucocorticoid receptor). All of these cellular events participate to successive dynamic equilibriums, which allow fine tuning of transcriptional regulation of target genes, depending on the target tissue and the hormonal status.

The N-terminal anchor sequences of 11beta-hydroxysteroid dehydrogenases determine their orientation in the endoplasmic reticulum membrane

11beta-Hydroxysteroid dehydrogenase enzymes (11beta- HSD) regulate the ratio of active endogenous glucocorticoids to their inactive keto-metabolites, thereby controlling the access of glucocorticoids to their cognate receptors. In this study, the topology and intracellular localization of 11beta-HSD1 and 11beta-HSD2 have been analyzed by immunohistochemistry and protease protection assays of in vitro transcription/translation products. 11beta-HSD constructs, tagged with the FLAG epitope, were transiently expressed in HEK-293 cells. The enzymatic characteristics of tagged and native enzymes were indistinguishable. Fluorescence microscopy demonstrated the localization of both 11beta-HSD1 and 11beta-HSD2 exclusively to the endoplasmic reticulum (ER) membrane. To examine the orientation of tagged 11beta-HSD enzymes within the ER membrane, we stained selectively permeabilized HEK-293 cells with anti-FLAG antibody. Immunohistochemistry revealed that the N terminus of 11beta-HSD1 is cytoplasmic, and the catalytic domain containing the C terminus is protruding into the ER lumen. In contrast, the N terminus of 11beta-HSD2 is lumenal, and the catalytic domain is facing the cytoplasm. Chimeric proteins where the N-terminal anchor sequences of 11beta-HSD1 and 11beta-HSD2 were exchanged adopted inverted orientation in the ER membrane. However, both chimeric proteins were not catalytically active. Furthermore, mutation of a tyrosine motif to alanine in the transmembrane segment of 11beta-HSD1 significantly reduced V(max). The subcellular localization of 11beta-HSD1 was not affected by mutations of the tyrosine motif or of a di-lysine motif in the N terminus. However, residue Lys(5), but not Lys(6), turned out to be critical for the topology of 11beta-HSD1. Mutation of Lys(5) to Ser inverted the orientation of 11beta-HSD1 in the ER membrane without loss of catalytic activity. Our results emphasize the importance of the N-terminal transmembrane segments of 11beta-HSD enzymes for their proper function and demonstrate that they are sufficient to determine their orientation in the ER membrane.

Expression of 11beta-hydroxysteroid dehydrogenase, glucocorticoid receptor, and mineralocorticoid receptor genes in rat ovary

A new concept in reproductive endocrinology is that the status of the ovary as a glucocorticoid target organ alters with follicular development. Evidence for a physiological role of glucocorticoids in the regulation of ovarian folliculogenesis has been strengthened by the discovery that 11beta-hydroxysteroid dehydrogenase (11betaHSD) mRNA expression in human granulosa cells is developmentally regulated. In this study, we quantified the pattern of expression and investigated the cellular location of 11betaHSD type 1 (11betaHSD1), 11betaHSD type 2 (11betaHSD2), glucocorticoid receptor (GR), and mineralocorticoid receptor (MR) mRNAs during follicular maturation in rat ovary. Immature female rats received treatment with eCG to induce preovulatory follicular development or eCG followed by hCG to induce luteinization. 11betaHSD1, 11betaHSD2, GR, and MR mRNAs were all detectable by ribonuclease protection assay in ovarian total RNA. Treatment with eCG alone caused an approximately 8-fold increase in the ovarian level of 11betaHSD1 mRNA, which rose to approximately 30-fold after additional treatment with hCG. Equine CG alone did not measurably affect the ovarian 11betaHSD2 mRNA level, but additional treatment with hCG reduced it to 34% of the control level. Expression of GR mRNA was unchanged by any gonadotropin treatment, while MR mRNA was down-regulated. A similar pattern of 11betaHSD1, 11betaHSD2, GR, and MR mRNA expression was observed in isolated granulosa cells. These results provide direct experimental evidence that 11betaHSD genes are gonadotropically regulated in the rat ovary, including granulosa cells, and are consistent with a shift in glucocorticoid metabolism from inactivation (due to oxidation by 11betaHSD2) to activation (reduction by 11betaHSD1) during hCG-induced granulosa cell luteinization.

11beta-hydroxysteroid dehydrogenase expression and activity in the human adrenal cortex

Although oxidation of cortisol or corticosterone by 11beta-hydroxysteroid dehydrogenase (11beta-HSD) represents the physiological mechanism conferring specificity for aldosterone on the mineralocorticoid receptor in mineralocorticoid target tissues, little attention has been paid until now to the expression and activity of this enzyme in human adrenals. We have shown that human adrenal cortex expresses 11beta-HSD type 2 (11beta-HSD2) gene, and found a marked 11beta-HSD2 activity in microsomal preparations obtained from slices of decapsulated normal human adrenal cortices. Under basal conditions, adrenal slices secreted, in addition to cortisol and corticosterone (B), sizeable amounts of cortisone and 11-dehydrocorticosterone (DH-B), the inactive forms to which the former glucocorticoids are converted by 11beta-HSD. Addition of the 11beta-HSD inhibitor glycyrrhetinic acid elicited a moderate rise in the production of cortisol and B and suppressed that of cortisone and DH-B. ACTH and angiotensin II evoked a marked rise in the secretion of cortisol and B, but unexpectedly depressed the release of cortisone and DH-B. ACTH also lowered the capacity of adrenal slices to convert [3H]cortisol to [3H]cortisone. This last effect of ACTH was concentration-dependently abolished by both aminoglutethimide and cyanoketone, which blocks early steps of steroid synthesis, but not by metyrapone, an inhibitor of 11beta-hydroxylase. Collectively, these findings indicate that the human adrenal cortex possesses an active 11beta-HSD2 engaged in the inactivation of newly formed glucocorticoids. The activity of this enzyme is negatively modulated by the main agonists of glucocorticoid secretion through an indirect mechanism, probably involving the rise in the intra-adrenal concentration of non-11beta-hydroxylated steroid hormones.

Molecular basis for hypertension in the "type II variant" of apparent mineralocorticoid excess

The syndrome of apparent mineralocorticoid excess (AME) is a heritable form of hypertension in which cortisol acts as a potent mineralocorticoid. The type I variant results in a severe clinical and biochemical phenotype and arises because of mutations in the gene encoding the type 2 isozyme of 11beta-hydroxysteroid dehydrogenase (11beta-HSD2), an enzyme responsible for the peripheral inactivation of cortisol to cortisone. Only mild abnormalities of cortisol metabolism have been found in the type II variant of AME, suggesting that it may be a separate gene defect. In an extensive consanguineous Sardinian pedigree affected with "type II" AME, a novel homozygous point mutation (C945T) was found in the human 11beta-HSD2 gene in four affected individuals. Thirteen family members were heterozygous for the resultant R279C amino acid substitution. The LOD score of linkage of the mutation to the disease was 3.23. Expression of the 11beta-HSD2 mutant cDNA resulted in an enzyme with reduced maximum velocity, but similar substrate affinity, compared with activity of the wild-type cDNA. Affected individuals were >30 years of age and had both mineralocorticoid hypertension and evidence of impaired metabolism of cortisol to cortisone. The heterozygote state was phenotypically normal but was associated with subtle defects in cortisol metabolism. AME represents a spectrum of mineralocorticoid hypertension with severity reflecting the underlying genetic defect in the 11beta-HSD2 gene; classification into distinct subtypes is inappropriate. Hypertensive populations should be screened to identify the prevalence of milder defects in 11beta-HSD2 in patients currently labeled as having "essential" hypertension.

Steroid specificity of the putative DHB receptor: evidence that the receptor is not 11betaHSD

Recently, we identified a novel putative nuclear receptor in colonic crypt cells distinct from both mineralocorticoid receptor and glucocorticoid receptor, with high affinity for 11-dehydrocorticosterone (11-DHB) (33). In the present study, competitive nuclear binding assays demonstrated that this site has a unique steroid binding specificity that distinguishes it from other steroid receptors. Western blot analysis showed the presence of 11beta-hydroxysteroid dehydrogenase-2 (11betaHSD2) but not 11betaHSD1 in colonic crypt cells and showed that 11betaHSD2 was present in the nuclear pellet. Differences in steroid specificity between the putative DHB receptor and inhibition of 11betaHSD activity indicate that binding is not to the enzyme. Furthermore, modified Chinese hamster ovary cells transfected with the 11betaHSD2 gene express nuclear 11betaHSD2 but not a nuclear DHB binding site. In conclusion, these data support the existence of a novel nuclear DHB receptor in rat colon that is distinct from the classic steroid receptors and from both 11betaHSD1 and 11betaHSD2.

Extranuclear localization of endogenous 11beta-hydroxysteroid dehydrogenase-2 in aldosterone target cells

Type 2 11beta-hydroxysteroid dehydrogenase (11betaHSD2) plays a key role in conferring aldosterone selectivity on the mineralocorticoid receptor (MR) by inactivating intracellular glucocorticoids before they can occupy the MR. 11betaHSD2 is a microsomal enzyme expressed in aldosterone target cells, although its subcellular distribution is still unclear. The goal of this study was to determine the subcellular localization of the endogenous 11betaHSD2 in renal aldosterone target cells. We generated an antibody against rabbit 11betaHSD2 and used it in combination with a nuclear marker and confocal laser scanning microscopy. On Western blots the antibody recognized a single band of approximately 41 kDa in the renal cortical collecting duct, outer medullary collecting duct, submandibular gland and adrenal cortex, whereas the colon, liver, renal medulla, and heart were negative. Immunohistochemistry showed specific reaction in the known aldosterone target cells of the kidney (connecting tubule, cortical collecting duct, and outer medullary collecting duct) with no signals over glomeruli, proximal nephron segments, and blood vessels. Staining for 11betaHSD2 was very weak in rabbit colon, and no immunoreactivity could be detected in the heart and brain. Confocal microscopy of kidney sections costained with the 11betaHSD2 antibody and the nuclear marker propidium iodide demonstrated that 11betaHSD2 is in the cytoplasmic compartment with no evidence for nuclear localization. Subcellular localization of 11betaHSD2 to a cytoplasmic compartment seems ideal for fulfilling its biological function, i.e. the efficient inactivation of intracellular glucocorticoids before they occupy MRs, which are predominantly cytoplasmic in the absence of hormone.

The role of 11beta-hydroxysteroid dehydrogenase in steroid hormone specificity

11Beta-hydroxysteroid dehydrogenase (11beta-HSD) is thought to confer aldosterone specificity to mineralocorticoid target cells by protecting the mineralocorticoid receptor (MR) from occupancy by endogenous glucocorticoids. In aldosterone target cells the type 2 11beta-HSD is present, which, in contrast to the type 1 11beta-HSD, has very high affinity for its substrate, is unidirectional and prefers NAD as cofactor. cDNAs encoding 11beta-HSD2 have been recently cloned from different species, and the cell-specific expression of its mRNA and protein were determined. 11Beta-HSD2 is expressed in every aldosterone target tissue. Northern analysis revealed that the rabbit 11beta-HSD2 is expressed at high levels in the renal collecting duct and at much lower levels in the colon. RT-PCR experiments demonstrated that 11beta-HSD2 mRNA is present only in aldosterone target cells within the kidney. We determined the subcellular localization of the rabbit 11beta-HSD2 using a chimera encoding 11beta-HSD2 and the green fluorescent protein (GFP). This construct was stably transfected into CHO and MDCK cells. The expressed 11beta-HSD2/GFP protein retained high enzymatic activity, and its characteristics were undistinguishable from those of the native enzyme. The intracellular localization of this protein was determined by fluorescence microscopy. 11Beta-HSD2-associated fluorescence was observed as a reticular network over the cytoplasm whereas the plasma membrane and the nucleus were negative, suggesting endoplasmic reticulum (ER) localization. Co-staining with markers for ER proteins, the Golgi membrane, mitochondria and nucleus confirmed that 11beta-HSD2 is localized exclusively to the ER. To determine what structural motifs are responsible for the ER localization, we generated deletion mutants missing the C-terminal 42 and 118 amino acids, and fused them to GFP. Similarly as with the intact 11beta-HSD2, these mutants localized exclusively to the ER. Both C-terminal deletion mutants completely lost dehydrogenase activity, independently whether activity was determined in intact cells or homogenates. These results indicate that 11beta-HSD2 has a novel ER retrieval signal which is not localized to the C-terminal region. In addition, the C-terminal 118 amino acids are essential for NAD-dependent 11beta-HSD activity.

Immunohistochemical localization of type 1 11beta-hydroxysteroid dehydrogenase in human tissues

Two isozymes of 11beta-hydroxysteroid dehydrogenase (11betaHSD) catalyze the interconversion of hormonally active cortisol to inactive cortisone. Activity and messenger ribonucleic acid studies indicate that type 1 11betaHSD (11betaHSD1) is expressed in glucocorticoid target tissues such as liver, gonad, and cerebellum, where it regulates the exposure of cortisol to glucocorticoid receptors. To further understand the role of 11betaHSD1 in human tissues, we have studied the localization of this isozyme using an antibody raised in sheep against amino acids 19-33 of human 11betaHSD1. Western blot analyses indicated that the immunopurified antibody recognized a band of approximately 34 kDa in human liver and decidua. Immunoperoxidase studies on liver, adrenal, ovary, decidua, and adipose tissue indicated positive cytoplasmic staining for 11betaHSD1. 11BetaHSD1 immunoreactivity was observed more intensely around the hepatic central vein, with no staining around the portal vein, hepatic artery, or bile ducts. No staining for 11betaHSD1 was observed in the adrenal medulla, but 11betaHSD1-immunoreactive protein was observed in all three zones of the adrenal cortex, with the most intense staining in the zona reticularis > zona glomerulosa > zona fasciculata. In the human ovary, immunoreactivity was observed in the developing oocyte and the luteinized granulosa cells of the corpus luteum. No staining was observed in granulosa cells, thecal cells, or ovarian stroma, which contrasted with the marked expression of 11betaHSD2 in the granulosa cell layer. Sections of human decidua showed high expression of 11betaHSD1 in decidual cells. In omental adipose tissue, 11betaHSD1 immunoreactivity was observed in both stromal and adipocyte cells. Immunohistochemical localization of 11betaHSD1 in human liver, adrenal, ovary, decidua, and adipose tissue using this novel antiserum provides us with a tool to investigate the role of this isozyme in modulating glucocorticoid hormone action within these tissues.

Corticosteroid metabolism in human granulosa-lutein cells

OBJECTIVE

The aims of this study were to determine the type and level of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) in human granulosa-leutein cells (GLE) shortly before ovulation and to correlate activity with the outcome of treatment in patients undergoing in vitro fertilization and embryo transfer (IVF/ET).

DESIGN

GLC from 32 patients undergoing IVF/ET were tested for type and level of 11 beta HSD activity in relation to treatment outcome.

PATIENTS

Periovulatory follicles were aspirated by ultrasound guided transvaginal puncture following a standard controlled ovarian stimulation protocol, approximately 36 h after administering an ovulation-inducing dose of human chorionic gonadotrophin (HCG). GLC were separated from follicular fluid by density-gradient centrifugation and taken for measurement of 11 beta HSD activity in vitro; oocytes were used for IVF/ET.

MEASUREMENTS

Interconversion of cortisol (F) and cortisone (E), and dexamethasone (D) and 11-dehydrodexamethasone (DHD) was measured in standardized assays comprising incubation of GLC with 3H-labelled substrate, with separation of substrate and product by thin-layer radiochromatography.

RESULTS

Conversion of F to E varied from 10.5 to 30.9% while that of E to F was between 2.4 and 44.6%. In the GLC of 25 patients in whom both activities were measured, dehydrogenase (F to E) activity predominated in 13 and reductase (E to F) in 12. By contrast, D (substrate for 11 beta HSD2 but not 11 beta HSD1) showed less than 1% metabolism in this system while DHD (substrate for 11 beta HSD1 and 11 beta HSD2) was converted significantly (65.6-90.5%) to D in the four patients tested. There was no significant difference in the interconversion of F and E between patients who became pregnant and those who did not.

CONCLUSIONS

The dehydrogenase and oxoreductase reactions catalysed by 11 beta HSD both occur in granulosa-lutein cells at the time of follicular rupture, probably due to 11 beta HSD1. A lack of measurable conversion of dexamethasone to 11-dehydrodexamethasone suggests that dehydrogenation due to 11 beta HSD2 is low or absent. Neither type nor level of 11 beta HSD activity measured under the present assay conditions correlates with IVF outcome.