Reciprocal Regulation of HSD11B1 and HSD11B2 Predicts Glucocorticoid Sensitivity in Childhood Acute Lymphoblastic Leukemia.

There are few biomarkers to predict efficacy of glucocorticoid treatment in childhood acute lymphoblastic leukemia (ALL) at diagnosis. Here, we demonstrate reciprocal regulation of 11beta-hydroxysteroid dehydrogenase (11ß-HSD), may predict the apoptotic response of ALL to glucocorticoid treatment. Our data may be useful to refine glucocorticoid treatment, to retain benefit while minimizing side effects.

Pravastatin ameliorates placental vascular defects, fetal growth, and cardiac function in a model of glucocorticoid excess.

Fetoplacental glucocorticoid overexposure is a significant mechanism underlying fetal growth restriction and the programming of adverse health outcomes in the adult. Placental glucocorticoid inactivation by 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2) plays a key role. We previously discovered that Hsd11b2(-/-) mice, lacking 11ß-HSD2, show marked underdevelopment of the placental vasculature. We now explore the consequences for fetal cardiovascular development and whether this is reversible. We studied Hsd11b2(+/+), Hsd11b2(+/-), and Hsd11b2(-/-) littermates from heterozygous (Hsd11b(+/-)) matings at embryonic day (E)14.5 and E17.5, where all three genotypes were present to control for maternal effects. Using high-resolution ultrasound, we found that umbilical vein blood velocity in Hsd11b2(-/-) fetuses did not undergo the normal gestational increase seen in Hsd11b2(+/+) littermates. Similarly, the resistance index in the umbilical artery did not show the normal gestational decline. Surprisingly, given that 11ß-HSD2 absence is predicted to initiate early maturation, the E/A wave ratio was reduced at E17.5 in Hsd11b2(-/-) fetuses, suggesting impaired cardiac function. Pravastatin administration from E6.5, which increases placental vascular endothelial growth factor A and, thus, vascularization, increased placental fetal capillary volume, ameliorated the aberrant umbilical cord velocity, normalized fetal weight, and improved the cardiac function of Hsd11b2(-/-) fetuses. This improved cardiac function occurred despite persisting indications of increased glucocorticoid exposure in the Hsd11b2(-/-) fetal heart. Thus, the pravastatin-induced enhancement of fetal capillaries within the placenta and the resultant hemodynamic changes correspond with restored fetal cardiac function. Statins may represent a useful therapeutic approach to intrauterine growth retardation due to placental vascular hypofunction.

Conditional Deletion of Hsd11b2 in the Brain Causes Salt Appetite and Hypertension.

BACKGROUND: The hypertensive syndrome of Apparent Mineralocorticoid Excess is caused by loss-of-function mutations in the gene encoding 11ß-hydroxysteroid dehydrogenase type 2 (11ßHSD2), allowing inappropriate activation of the mineralocorticoid receptor by endogenous glucocorticoid. Hypertension is attributed to sodium retention in the distal nephron, but 11ßHSD2 is also expressed in the brain. However, the central contribution to Apparent Mineralocorticoid Excess and other hypertensive states is often overlooked and is unresolved. We therefore used a Cre-Lox strategy to generate 11ßHSD2 brain-specific knockout (Hsd11b2.BKO) mice, measuring blood pressure and salt appetite in adults. METHODS AND RESULTS: Basal blood pressure, electrolytes, and circulating corticosteroids were unaffected in Hsd11b2.BKO mice. When offered saline to drink, Hsd11b2.BKO mice consumed 3 times more sodium than controls and became hypertensive. Salt appetite was inhibited by spironolactone. Control mice fed the same daily sodium intake remained normotensive, showing the intrinsic salt resistance of the background strain. Dexamethasone suppressed endogenous glucocorticoid and abolished the salt-induced blood pressure differential between genotypes. Salt sensitivity in Hsd11b2.BKO mice was not caused by impaired renal sodium excretion or volume expansion; pressor responses to phenylephrine were enhanced and baroreflexes impaired in these animals. CONCLUSIONS: Reduced 11ßHSD2 activity in the brain does not intrinsically cause hypertension, but it promotes a hunger for salt and a transition from salt resistance to salt sensitivity. Our data suggest that 11ßHSD2-positive neurons integrate salt appetite and the blood pressure response to dietary sodium through a mineralocorticoid receptor-dependent pathway. Therefore, central mineralocorticoid receptor antagonism could increase compliance to low-sodium regimens and help blood pressure management in cardiovascular disease.

Biological Roles of Hydroxysteroid (11-Beta) Dehydrogenase 1 (HSD11B1), HSD11B2, and Glucocorticoid Receptor (NR3C1) in Sheep Conceptus Elongation.

In sheep, the elongating conceptus synthesizes and secretes interferon tau (IFNT) as well as prostaglandins (PGs) and cortisol. The enzymes, hydroxysteroid (11-beta) dehydrogenase 1 (HSD11B1) and HSD11B2 interconvert cortisone and cortisol. In sheep, HSD11B1 is expressed and active in the conceptus trophectoderm as well as in the endometrial luminal epithelia; in contrast, HSD11B2 expression is most abundant in conceptus trophectoderm. Cortisol is a biologically active glucocorticoid and ligand for the glucocorticoid receptor (NR3C1 or GR) and mineralocorticoid receptor (NR3C2 or MR). Expression of MR is not detectable in either the ovine endometrium or conceptus during early pregnancy. In tissues that do not express MR, HSD11B2 protects cells from the growth-inhibiting and/or proapoptotic effects of cortisol, particularly during embryonic development. In study one, an in utero loss-of-function analysis of HSD11B1 and HSD11B2 was conducted in the conceptus trophectoderm using morpholino antisense oligonucleotides (MAOs) that inhibit mRNA translation. Elongating, filamentous conceptuses were recovered on Day 14 from ewes infused with control morpholino or HSD11B2 MAO. In contrast, HSD11B1 MAO resulted in severely growth-retarded conceptuses or conceptus fragments with apoptotic trophectoderm. In study two, clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 genome editing was used to determine the role of GR in conceptus elongation and development. Elongating, filamentous-type conceptuses (12-14 cm in length) were recovered from ewes gestating control embryos (n = 7/7) and gestating GR-edited embryos (n = 6/7). These results support the idea that the effects of HSD11B1-derived cortisol on conceptus elongation are indirectly mediated by the endometrium and are not directly mediated through GR in the trophectoderm.

[Roles of type II 11ß-hydroxysteroid dehydrogenase and its signaling factors in pathogenesis of persistent pulmonary hypertension in neonatal rats].

OBJECTIVE: To study the roles of type II 11ß-hydroxysteroid dehydrogenase (11ß-HSD2) and it's signaling factors in the lung tissue in pathogenesis of persistent pulmonary hypertension (PPH) in neonatal rats. METHODS: Six Sprague-Dawley rats on the 19th day of pregnancy were randomly divided into PPH and control groups (n=3 each). The PPH group was intraperitoneally injected with indomethacin (0.5 mg/kg) twice daily and exposed in 12% oxygen for three days, in order to prepare a fetal rat model of PPH. The control group was intraperitoneally injected with an equal volume of normal saline and exposed to air. Neonatal rats were born by caesarean section from both groups on the 22nd day of pregnancy. In each group, 15 neonatal rats were randomly selected and sacrificed. 11ß-HSD2 expression in the lung tissue of neonatal rats were observed by Confocal laser technology, and serum cortisol levels and prostacyclin, renin, angiotensin and aldosterone in the lung tissue of both groups were measured using ELISA. RESULTS: 11ß-HSD2 protein was widely expressed in the lung tissue of the control and PPH groups. The levels of 11ß-HSD2 and prostacyclin in the lung tissue were lower in the PPH group than in the control group, while serum cortisol levels and renin, angiotensin and aldosterone in the lung tissue were higher in the PPH group than in the control group (P<0.05). CONCLUSIONS: 11ß-HSD2 and it's signaling factors play roles in pathogenesis of PPH in neonatal rats.

Modulation of 11ß-hydroxysteroid dehydrogenase as a strategy to reduce vascular inflammation.

Atherosclerosis is a chronic inflammatory disease in which initial vascular damage leads to extensive macrophage and lymphocyte infiltration. Although acutely glucocorticoids suppress inflammation, chronic glucocorticoid excess worsens atherosclerosis, possibly by exacerbating systemic cardiovascular risk factors. However, glucocorticoid action within the lesion may reduce neointimal proliferation and inflammation. Glucocorticoid levels within cells do not necessarily reflect circulating levels due to pre-receptor metabolism by 11ß-hydroxysteroid dehydrogenases (11ß-HSDs). 11ß-HSD2 converts active glucocorticoids into inert 11-keto forms. 11ß-HSD1 catalyses the reverse reaction, regenerating active glucocorticoids. 11ß-HSD2-deficiency/inhibition causes hypertension, whereas deficiency/inhibition of 11ß-HSD1 generates a cardioprotective lipid profile and improves glycemic control. Importantly, 11ß-HSD1-deficiency/inhibition is atheroprotective, whereas 11ß-HSD2-deficiency accelerates atherosclerosis. These effects are largely independent of systemic risk factors, reflecting modulation of glucocorticoid action and inflammation within the vasculature. Here, we consider whether evidence linking the 11ß-HSDs to vascular inflammation suggests these isozymes are potential therapeutic targets in vascular injury and atherosclerosis.

Programming effects of glucocorticoids.

Fetal glucocorticoid overexposure is a key potential mechanism underlying the link between low birthweight and later life diseases. The fetus is protected from high maternal glucocorticoid levels by the placental enzyme 11ß-hydroxysteroid dehydrogenase type 2. Antenatal glucocorticoid administration to women at threat of preterm labor, and high endogenous maternal glucocorticoid levels during pregnancy associate with lower birthweight. Long-term consequences for offspring include hypothalamic-pituitary-adrenal axis activation, increased metabolic and cardiovascular disorders, and neurodevelopmental sequelae. Strategies are needed to limit antenatal glucocorticoid use to those most at risk of preterm labor and to identify those most at risk of future disease.

Glucocorticoids and neonatal brain injury: the hedgehog connection.

Glucocorticoids (GCs) play a critical role in neural development; however, their prenatal or neonatal therapeutic use can have detrimental effects on the developing brain. In this issue of the JCI, Heine and Rowitch report that the molecular mechanisms underlying these detrimental effects involve the sonic hedgehog (Shh) signaling pathway, a crucial regulator of brain development and neural stem/progenitor cells (see the related study beginning on page 267). They show that GCs suppress Shh-induced proliferation of cerebellar progenitor cells in postnatal mice and that, conversely, Shh signaling is protective against GC-induced neonatal cerebellar injury by inducing the enzyme 11betaHSD2, which inactivates the GCs corticosterone and prednisolone, but not dexamethasone. The data provide a rationale for the therapeutic use of 11betaHSD2-sensitive GCs, but not dexamethasone, or for the exploitation of the neuroprotective effect of Shh agonists to prevent GC-induced pre- or neonatal brain injury.

Hedgehog signaling has a protective effect in glucocorticoid-induced mouse neonatal brain injury through an 11betaHSD2-dependent mechanism.

Glucocorticoids (GCs) are administered to human fetuses at risk of premature delivery and to infants with life-threatening respiratory and cardiac conditions. However, there are ongoing concerns about adverse effects of GC treatment on the developing human brain, although the precise molecular mechanisms underlying GC-induced brain injury are unclear. Here, we identified what we believe to be novel cross-antagonistic interactions of Sonic hedgehog (Shh) and GC signaling in proliferating mouse cerebellar granule neuron precursors (CGNPs). Chronic GC treatment (from P0 through P7) in mouse pups inhibited Shh-induced proliferation and upregulation of expression of N-myc, Gli1, and D-type cyclin protein in CGNPs. Conversely, acute GC treatment (on P7 only) caused transient apoptosis. Shh signaling antagonized these effects of GCs, in part by induction of 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2). Importantly, 11betaHSD2 antagonized the effects of the GCs corticosterone, hydrocortisone, and prednisolone, but not the synthetic GC dexamethasone. Our findings indicate that Shh signaling is protective in the setting of GC-induced mouse neonatal brain injury. Furthermore, they led us to propose that 11betaHSD2-sensitive GCs (e.g., hydrocortisone) should be used in preference to dexamethasone in neonatal human infants because of the potential for reduced neurotoxicity.

In silico structure-function analysis of pathological variation in the HSD11B2 gene sequence.

11beta-Hydroxysteroid dehydrogenase type 2 (11betaHSD2) is a short-chain dehydrogenase/reductase (SDR) responsible for inactivating cortisol and preventing its binding to the mineralocorticoid receptor (MR). Nonfunctional mutations in HSD11B2, the gene encoding 11betaHSD2, cause the hypertensive syndrome of apparent mineralocorticoid excess (AME). Like other such Mendelian disorders, AME is rare but has nevertheless helped to illuminate principles fundamental to the regulation of blood pressure. Furthermore, polymorphisms in HSD11B2 have been associated with salt sensitivity, a major risk factor for cardiovascular mortality. It is therefore highly likely that sequence variation in HSD11B2, having subtle functional ramifications, will affect blood pressure in the wider population. In this study, a three-dimensional homology model of 11betaHSD2 was created and used to hypothesize the functional consequences in terms of protein structure of published mutations in HSD11B2. This approach underscored the strong genotype-phenotype correlation of AME: severe forms of the disease, associated with little in vivo enzyme activity, arise from mutations occurring in invariant alignment positions. These were predicted to exert gross structural changes in the protein. In contrast, those mutations causing a mild clinical phenotype were in less conserved regions of the protein that were predicted to be relatively more tolerant to substitution. Finally, a number of pathogenic mutations are shown to be associated with regions predicted to participate in dimer formation, and in protein stabilization, which may therefore suggest molecular mechanisms of disease.

Glycyrrhetinic acid attenuates vascular smooth muscle vasodilatory function in healthy humans.

Abnormal glucocorticoid metabolism contributes to vascular dysfunction and cardiovascular disease. Cortisol activation of vascular mineralocorticoid and glucocorticoid receptors is regulated by two types of 11beta-HSD (11-beta hydroxysteroid dehydrogenase), namely 11beta-HSD2 and 11beta-HSD1 (type 2 and type 1 11beta-HSD respectively). We hypothesized that inhibition of 11beta-HSD would attenuate vascular function in healthy humans. A total of 15 healthy subjects were treated with the selective 11beta-HSD inhibitor GA (glycyrrhetinic acid) or matching placebo in a randomized double-blinded cross-over trial. 11beta-HSD activity was assessed by the urinary cortisol/cortisone ratio, and vascular function was measured using strain-gauge plethysmography. Endothelial function was measured through incremental brachial artery administration of methacholine (0.3-10 microg/min) and vascular smooth muscle function with incremental verapamil (10-300 microg/min). GA increased the 24-h urinary cortisol/cortisone ratio compared with placebo (P=0.008). GA tended to reduce the FBF (forearm blood flow) response to methacholine (P=0.09) and significantly reduced the FBF response to verapamil compared with placebo (P=0.04). MAP (mean arterial pressure) did not differ between the study conditions. 11beta-HSD inhibition attenuated vascular smooth muscle vasodilatory function in healthy humans. Disturbances in cortisol activity resulting from 11beta-HSD inactivation is therefore a second plausible mechanism for mineralocorticoid-mediated hypertension in humans.

Changes in 11beta-hydroxysteroid dehydrogenase type 2 expression in a low-protein rat model of intrauterine growth restriction.

BACKGROUND: Intrauterine growth restriction (IUGR) is associated with systemic hypertension of the offspring later in life. The exact mechanisms are still incompletely understood. 11ß-Hydroxysteroid dehydrogenase 2 (11ß-HSD2) in the distal renal tubule protects the mineralocorticoid receptor from cortisol. As we did not find a suppression of 11ß-HSD2 in total kidney of IUGR animals, our objective was to investigate whether a suppression of 11ß-HSD2 could be detected on a more sophisticated level such as in situ protein and gene expression of 11ß-HSD2 in mildly hypertensive IUGR offspring. METHODS: IUGR rats after maternal low-protein diet (n = 17) were compared with controls (n = 18). At 70 and 120 days of age, in situ distribution of 11ß-HSD2 gene and protein expression was investigated by RT-PCR of microdissected tubules and immunohistochemistry. For in situ localization studies, double staining for 11ß-HSD2 and calbindin was used. Serum levels of corticosterone and dehydrocorticosterone were measured by tandem mass spectrometry. RESULTS: In IUGR rats, intra-arterial blood pressure significantly increased at Day 120 of life. Serum corticosterone/dehydrocorticosterone ratios and 11ß-HSD2 mRNA in total kidney were not altered in IUGR animals. However, 11ß-HSD2 mRNA concentration was significantly lower in microdissected tubuli of IUGR animals (Day 120: 0.18 ± 0.14 vs 1.00 ± 0.32 rel. units in controls; P < 0.05). In IUGR animals, immunostaining scores for 11ß-HSD2 were significantly lower than in controls (P < 0.05). Double staining with calbindin showed lower expression of 11ß-HSD2 in distal segments of the distal tubule. CONCLUSIONS: Our data indicate lower gene and protein expression of the pre-receptor enzyme 11ß-HSD2 in IUGR animals when looking at specific renal compartments, but not in total kidney extracts. Thus, lower 11ß-HSD2 as a mechanism for hypertension later in life might be missed without methods for in situ detection.

Aldosterone in uremia - beyond blood pressure.

Aldosterone was in the past considered only as a prohypertensinogenic agent. It has recently become clear that apart from the classical endocrine action, i.e. causing blood pressure elevation as a result of salt retention, aldosterone has numerous blood-pressure-independent actions on nonepithelial tissue. Under conditions of high salt concentration, aldosterone is injurious to the kidney, heart and vasculature. Of particular interest are recent observations that aldosterone is a permissive factor for the effect of minor increases in plasma sodium concentration on endothelial cell dysfunction. Despite surprising effects of aldosterone blockade on blood pressure of anuric dialysis patients, the potential role of mineralocorticoid receptor blockade in dialysis patients is currently unclear and requires controlled investigation to define the risk of potential hazards, specifically hyperkalemia.

Mediators of mineralocorticoid receptor-induced profibrotic inflammatory responses in the heart.

Coronary, vascular and perivascular inflammation in rats following MR (mineralocorticoid receptor) activation plus salt are well-characterized precursors for the appearance of cardiac fibrosis. Endogenous corticosterone, in the presence of the 11betaHSD2 (11beta hydroxysteroid dehydrogenase type 2) inhibitor CBX (carbenoxolone) plus salt, produces similar inflammatory responses and tissue remodelling via activation of MR. MR-mediated oxidative stress has previously been suggested to account for these responses. In the present study we thus postulated that when 11betaHSD2 is inhibited, endogenous corticosterone bound to unprotected MR in the vessel wall may similarly increase early biomarkers of oxidative stress. Uninephrectomized rats received either DOC (deoxycorticosterone), CBX or CBX plus the MR antagonist EPL (eplerenone) together with 0.9% saline to drink for 4, 8 or 16 days. Uninephrectomized rats maintained on 0.9% saline for 8 days served as controls. After 4 days, both DOC and CBX increased both macrophage infiltration and mRNA expression of the p22(phox) subunit of NADPH oxidase, whereas CBX, but not DOC, increased expression of the NOX2 (gp91(phox)) subunit. eNOS [endothelial NOS (NO synthase)] mRNA expression significantly decreased from 4 days for both treatments, and iNOS (inducible NOS) mRNA levels increased after 16 days of DOC or CBX; co-administration of EPL inhibited all responses to CBX. The responses characterized over this time course occurred before measurable increases in cardiac hypertrophy or fibrosis. The findings of the present study support the hypothesis that endogenous corticosterone in the presence of CBX can activate vascular MR to produce both inflammatory and oxidative tissue responses well before the onset of fibrosis, that the two MR ligands induce differential but overlapping patterns of gene expression, and that elevation of NOX2 subunit levels does not appear necessary for full expression of MR-mediated inflammatory and fibrogenic responses.

Local and systemic glucocorticoid metabolism in inflammatory arthritis.

BACKGROUND: Isolated, primary synovial fibroblasts generate active glucocorticoids through expression of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). This enzyme produces cortisol from inactive cortisone (and prednisolone from prednisone). OBJECTIVE: To determine how intact synovial tissue metabolises glucocorticoids and to identify the local and systemic consequences of this activity by examination of glucocorticoid metabolism in patients with rheumatoid arthritis (RA). METHODS: Synovial tissue was taken from patients with RA during joint replacement surgery. Glucocorticoid metabolism in explants was assessed by thin-layer chromatography and specific enzyme inhibitors. RT-PCR and immunohistochemistry were used to determine expression and distribution of 11beta-HSD enzymes. Systemic glucocorticoid metabolism was examined in patients with RA using gas chromatography/mass spectrometry. RESULTS: Synovial tissue synthesised cortisol from cortisone, confirming functional 11beta-HSD1 expression. In patients with RA, enzyme activity correlated with donor erythrocyte sedimentation rate (ESR). Synovial tissues could also convert cortisol back to cortisone. Inhibitor studies and immunohistochemistry suggested this was owing to 11beta-HSD2 expression in synovial macrophages, whereas 11beta-HSD1 expression occurred primarily in fibroblasts. Synovial fluids exhibited lower cortisone levels than matched serum samples, indicating net local steroid activation. Urinary analyses indicated high 11beta-HSD1 activity in untreated patients with RA compared with controls and a significant correlation between total body 11beta-HSD1 activity and ESR. CONCLUSIONS: Synovial tissue metabolises glucocorticoids, the predominant effect being glucocorticoid activation, and this increases with inflammation. Endogenous glucocorticoid production in the joint is likely to have an impact on local inflammation and bone integrity.

Pre-receptorial regulation of steroid hormones in bone cells: insights on glucocorticoid-induced osteoporosis.

In the past decades, concern on glucocorticoid-induced osteoporosis has increased with the widespread use of exogenous glucocorticoids (GC). Mature bone-forming cells (osteoblasts) are considered to be the principal site of action of GC in the skeleton. More likely, it is the entire cellular and molecular network surrounding these cells that is targeted by pharmacological doses of GC. Not only osteoblast and osteocyte metabolism, but the whole differentiation of mesenchymal stem cell toward the osteoblast lineage has been proven to be sensitive to GC. The effects of GC on this process are different according to the stage of differentiation of bone cell precursors. The presence of intact GC signalling is crucial for normal bone development and physiology, as opposed to the detrimental effect of high dose exposure. Both the physiological and pharmacological effects of GC are locally modulated by the activity of the 11beta-hydroxysteroid dehydrogenase 1 (HSD1) that acts primarily as a glucocorticoid activator converting the inactive glucocorticoid (cortisone) into the active hormone (cortisol). We reviewed the metabolic and differentiation pathways controlled by GC signalling. These data have been merged with the recent evidences that 11beta-HSD1 exert an important role by regulating the vulnerability of bone cells to GC. The different kinetics of 11beta-HSD1 at various stage of differentiation and the GC-dependency of enzymatic activity have been presented.

11beta-hydroxysteroid dehydrogenase type 1 and obesity.

The metabolic syndrome consists of a constellation of co-associated metabolic abnormalities such as insulin resistance, type 2 diabetes, dyslipidaemia, hypertension and visceral obesity. For many years endocrinologists have noted the striking resemblance between this disease state and that associated with Cushing's syndrome. However, in the metabolic syndrome plasma cortisol levels tend to be normal or lower than in normal individuals. Nevertheless there is strong evidence that glucocorticoid action underlies metabolic disease, largely from rodent obesity models where removing glucocorticoids reverses obesity and its metabolic abnormalities. The apparent paradox of similar metabolic defects - despite the opposing plasma glucocorticoid profiles of Cushing's and idiopathic metabolic syndrome - remained intriguing until the discovery that intracellular glucocorticoid reactivation was elevated in adipose tissue of obese rodents and humans. The enzyme that mediates this activation, conversion of cortisone (11-dehydrocorticosterone in rodents) to cortisol (corticosterone in rodents), locally within tissues is 11beta -hydroxysteroid dehydrogenase type 1 (11beta -HSD1). In order to determine whether elevated tissue 11beta -HSD1 contributed to obesity and metabolic disease, transgenic mice overexpressing 11beta -HSD1 in adipose tissue or liver were made. Adipose-selective 11beta -HSD1 transgenic mice exhibited elevated intra-adipose and portal, but not systemic corticosterone levels, abdominal obesity, hyperglycaemia, insulin resistance, dyslipidaemia and hypertension. In contrast, transgenic overexpression of 11beta -HSD1 in liver yielded an attenuated metabolic syndrome with mild insulin resistance, dyslipidaemia, hypertension and fatty liver, but not obesity or glucose intolerance. Together with early data using non-selective 11beta -HSD1 inhibitors to insulin sensitise humans, this corroborated the notion that the enzyme may be a good therapeutic target in the treatment of the metabolic syndrome. Further, a transgenic model of therapeutic 11beta -HSD1 inhibition, 11beta -HSD1 gene knock-out (11beta -HSD1-/-) mice, exhibited improved glucose tolerance, a 'cardioprotective' lipid profile, reduced weight gain and visceral fat accumulation with chronic high-fat feeding. Recent evidence further suggests that high fat-mediated downregulation of adipose 11beta -HSD1 may be an endogenous pathway that underpins adaptive disease resistance in genetically predisposed mouse strains. This mechanism could feasibly make up a genetic component of innate obesity resistance in humans. The efficacy of 11beta -HSD1 inhibitors has recently been extended to include increased energy expenditure and reduction of arteriosclerosis, and therefore may be of significant therapeutic value in the metabolic syndrome, with complementary effects upon liver adipose tissue, muscle, pancreas and plaque-prone vessels.

Aldosterone target neurons in the nucleus tractus solitarius drive sodium appetite.

Sodium appetite can be enhanced by the adrenal steroid aldosterone via an unknown brain mechanism. A novel group of neurons in the nucleus tractus solitarius expresses the enzyme 11-beta-hydroxysteroid dehydrogenase type 2, which makes them selectively responsive to aldosterone. Their activation parallels sodium appetite in different paradigms of salt loss even in the absence of aldosterone. These unique aldosterone target neurons may represent a previously unrecognized central convergence point at which hormonal and neural signals can be integrated to drive sodium appetite.

P-glycoprotein restricts access of cortisol and dexamethasone to the glucocorticoid receptor in placental BeWo cells.

Exposure of the fetus and placenta to maternal glucocorticoids is normally limited by the placental glucocorticoid barrier, which consists primarily of placental 11beta-hydroxy-steroid dehydrogenase type 2-mediated conversion of cortisol to the biologically inactive cortisone. Studies in the rodent brain show that P-glycoprotein (P-gp) is also an important physiological regulator of glucocorticoid access to the glucocorticoid receptor (GR) in target cells because it exports cortisol back into peripheral circulation against a concentration gradient. Whether P-gp of placental origin also has this capacity is unknown. Therefore, we used the human placental choriocarcinoma cell line BeWo and its daughter cell line, BeWoMDR, virally transduced with P-gp, to assess whether placental P-gp regulates access of glucocorticoids to the GR. Quantitative PCR showed that BeWoMDR cells express approximately 10-fold higher levels of P-gp mRNA than BeWo cells, and syncytialization increased P-gp mRNA by approximately 7-fold. Elevated P-gp expression in BeWoMDR cells reduced activation of the GR by dexamethasone and cortisol (10(-9) to 10(-6) M) to around 40% of that in BeWo cells. Inhibition of P-gp-mediated glucocorticoid efflux by cyclosporin A in BeWoMDR cells returned GR activation to levels similar to those in BeWo cells. Diffusion of dexamethasone across BeWoMDR monolayers occurred at a slower rate than that across BeWo monolayers, but this difference was eliminated by cyclosporin A. These data support the hypothesis that P-gp contributes to the placental glucocorticoid barrier. Thus, 11beta-hydroxysteroid dehydrogenase type 2 and P-gp may act in unison to reduce fetal and placental exposure to maternal glucocorticoids and thereby minimize their growth inhibitory actions.

11beta-Hydroxysteroid dehydrogenase type 2 protects the neonatal cerebellum from deleterious effects of glucocorticoids.

11beta-Hydroxysteroid dehydrogenase type 2 is a glucocorticoid metabolizing enzyme that catalyzes rapid inactivation of corticosterone and cortisol to inert 11-keto derivatives. As 11beta-hydroxysteroid dehydrogenase type 2 is highly expressed in the developing brain, but not in the adult CNS, we hypothesized that it may represent a protective barrier to the deleterious actions of corticosteroids on proliferating cells. To test this hypothesis we have investigated the development and growth of the cerebellum in neonatal C57BL/6 mice and mice lacking 11beta-hydroxysteroid dehydrogenase type 2 (-/-). 11beta-Hydroxysteroid dehydrogenase type 2-/- mice had consistently lower body weight throughout the neonatal period, coupled with a smaller brain size although this was normalized when corrected for body weight. The cerebellar size was smaller in 11beta-hydroxysteroid dehydrogenase type 2-/- mice, due to decreases in size of both the molecular and internal granule layers. When exogenous corticosterone was administered to the pups between postnatal days 4 and 13, 11beta-hydroxysteroid dehydrogenase type 2(-/-) mice were more sensitive, showing further inhibition of cerebellar growth while the wildtype mice were not affected. Upon withdrawal of exogenous steroid, there was a rebound growth spurt so that at day 21 postnatally, the cerebellar size in 11beta-hydroxysteroid dehydrogenase type 2-/- mice was similar to untreated mice of the same genotype. Furthermore, 11beta-hydroxysteroid dehydrogenase type 2-/- mice had a delay in the attainment of neurodevelopmental landmarks such as negative geotaxis and eye opening. We therefore suggest that 11beta-hydroxysteroid dehydrogenase type 2 acts as to protect the developing nervous system from the deleterious consequences of glucocorticoid overexposure.