Localization and glucocorticoid regulation of 11β-hydroxysteroid dehydrogenase type 1 mRNA in the male mouse forebrain

11β-Hydroxysteroid dehydrogenase and the brain: Not (yet) lost in translation

11-beta-hydroxysteroid dehydrogenases (11β-HSDs) catalyse the conversion of active 11-hydroxy glucocorticoids (cortisol, corticosterone) and their inert 11-keto forms (cortisone, 11-dehydrocorticosterone). They were first reported in the body and brain 70 years ago, but only recently have they become of interest. 11β-HSD2 is a dehydrogenase, potently inactivating glucocorticoids. In the kidney, 11β-HSD2 generates the aldosterone-specificity of intrinsically non-selective mineralocorticoid receptors. 11β-HSD2 also protects the developing foetal brain and body from premature glucocorticoid exposure, which otherwise engenders the programming of neuropsychiatric and cardio-metabolic disease risks. In the adult CNS, 11β-HSD2 is confined to a part of the brain stem where it generates aldosterone-specific central control of salt appetite and perhaps blood pressure. 11β-HSD1 is a reductase, amplifying active glucocorticoid levels within brain cells, notably in the cortex, hippocampus and amygdala, paralleling its metabolic functions in peripheral tissues. 11β-HSD1 is elevated in the ageing rodent and, less certainly, human forebrain. Transgenic models show this rise contributes to age-related cognitive decline, at least in mice. 11β-HSD1 inhibition robustly improves memory in healthy and pathological ageing rodent models and is showing initial promising results in phase II studies of healthy elderly people. Larger trials are needed to confirm and clarify the magnitude of effect and define target populations. The next decade will be crucial in determining how this tale ends - in new treatments or disappointment.

11β-Hydroxysteroid dehydrogenase 1 deficiency prevents PTSD-like memory in young adult mice

Post-traumatic stress disorder (PTSD) is characterized by the co-existence of a persistent strong memory of the traumatic experience and amnesia for the peritraumatic context. Most animal models, however, fail to account for the contextual amnesia which is considered to play a critical role in the etiology of PTSD intrusive memories. It is also unclear how aging affects PTSD-like memory. Glucocorticoids alter the formation and retention of fear-associated memory. Here, we investigated whether a deficiency of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) (an intracellular glucocorticoid generating enzyme) and aging modulates fear conditioning and PTSD-like memory in mice. We first measured memory in 6 months and 24 months old 11β-HSD1 deficient (HSD1 KO) and wildtype (WT) mice following paired tone-shock fear conditioning. Then, separate groups of mice were exposed to restraint stress immediately after unpaired tone-shock contextual fear conditioning. Compared with young controls, aged WT mice exhibited enhanced auditory cued fear memory, but contextual fear memory was not different. Contextual fear memory retention was attenuated in both young and aged HSD1 KO mice. In contrast, auditory cued fear memory was reduced 24 h after training only in aged HSD1 KO mice. When fear conditioned with stress, WT mice displayed PTSD-like memory (i.e., increased fear to tone not predictive of shock and reduced fear to 'aversive' conditioning context); this was unchanged with aging. In contrast, young HSD1 KO mice fear conditioned with stress showed normal fear memory (i.e., increased fear response to conditioning context), as observed in WT mice fear conditioned alone. While aged HSD1 KO mice fear conditioned with stress also displayed normal contextual fear memory, the fear response to the 'safe' tone remained. Thus, a deficiency of 11β-HSD1 protects against both amnesia for the conditioning context and hypermnesia for a salient tone in young adult mice but only contextual amnesia is prevented in aged mice. These results suggest that brain 11β-HSD1 generated glucocorticoids make a significant contribution to fear conditioning and PTSD-like memory. 11β-HSD1 inhibition may be useful in prevention and/or treatment of PTSD.

Neuroprotective effects of food restriction in a rat model of traumatic brain injury - the role of glucocorticoid signaling

OBJECTIVE

Traumatic brain injury (TBI) is one of the most common causes of neurological damage in young and middle aged people. Food restriction (FR) has been shown to act neuroprotectively in animal models of stroke and TBI. Indeed, our previous studies showed that FR attenuates inflammation, through suppression of microglial activation and TNF-α production, suppresses caspase-3-induced neuronal cell death and enhances neuroplasticity in the rat model of TBI. Glucocorticoids (GCs) play a central role in mediating both molecular and behavioral responses to food restriction. However, the exact mechanisms of FR neuroprotection in TBI are still unclear. The goal of the present study was to examine whether FR exerts its beneficial effects by altering the glucocorticoid receptor (GR) signaling alone and/or together with other protective factors.

METHODS

To this end, we examined the effects of FR (50% of regular daily food intake for 3 months prior to TBI) on the protein levels of total GR, GR phosphoisoform Ser232 (p-GR) and its transcriptional activity, as well as 11β-HSD1, NFκB (p65) and HSP70 as factors related to the GR signaling.

RESULTS

Our results demonstrate that FR applied prior to TBI significantly changes p-GR levels, and it's transcriptional activity during the recovery period after TBI. Moreover, as a pretreatment, FR modulates other protective factors in response to TBI, such as 11β-HSD1, NF-κB (p65) and HSP70 that act in parallel with GR in it's anti-inflammatory and neuroprotective effects in the rat model of brain injury.

CONCLUSION

Our results suggest that prophylactic FR represents a potent non-invasive approach capable of changing GR signalling, together with other factors related to the GR signaling in the model of TBI.

Effects of corticosterone within the hypothalamic arcuate nucleus on food intake and body weight in male rats

OBJECTIVE

Obesity is a major cause of morbidity and mortality. Few weight-reducing medications are available, and these have limited efficacy. Cushing's Syndrome (caused by elevated glucocorticoid levels) and obesity have similar metabolic features. Though circulating glucocorticoid levels are not elevated in obesity, tissue-specific glucocorticoid levels have been implicated in the development of the metabolic phenotype of obesity. Tissue glucocorticoid levels are regulated by 11β-hydroxysteroid dehydrogenase type1 (11βHSD1), which increases the local concentration of active glucocorticoids by the production of corticosterone from 11-dehydrocorticosterone. 11βHSD1 is expressed in the hypothalamic arcuate nucleus (ARC), a major weight and appetite-regulating centre, and therefore represents a target for novel anti-obesity therapeutic agents. Thus, we sought to investigate the effect of chronic alterations of ARC corticosterone levels (mediated by 11βHSD1) on food intake and body weight in adult male rats.

METHODS

Recombinant adeno-associated virus particles bearing sense 11βHSD1 (rAAV-S11βHSD1) and small interfering 11βHSD1 (rAAV-si11βHSD1), respectively, were stereotactically injected into the ARC (bilaterally) of adult male Wistar rats. rAAV-GFP was injected into control groups of male Wistar rats. Food intake and body weight were measured three times a week for 70 days. Terminal brain, plasma and intrascapular brown adipose tissue (iBAT) samples were taken for measurement of mRNA expression and hormone levels.

RESULTS

Compared to controls, rAAV-S11βHSD1 injection resulted in higher ARC corticosterone levels, hyperphagia and increased weight gain. Conversely, rAAV-si11βHSD1 injection (compared to controls) resulted in lower ARC corticosterone levels, higher iBAT uncoupling protein-1 mRNA expression and less weight gain despite similar food intake.

CONCLUSIONS

Therefore ARC corticosterone, regulated by 11βHSD1, may play a role in food intake and body weight regulation. These data have important implications for the development of centrally-acting 11βHSD1 inhibitors, which are currently being developed for the treatment of obesity, metabolic disorders, and other conditions.

Probenecid Reduces Alcohol Drinking in Rodents. Is Pannexin1 a Novel Therapeutic Target for Alcohol Use Disorder?

AIMS

The development of novel and more effective medications for alcohol use disorder (AUD) is an important unmet medical need. Drug repositioning or repurposing is an appealing strategy to bring new therapies to the clinic because it greatly reduces the overall costs of drug development and expedites the availability of treatments to those who need them. Probenecid, p-(di-n-propylsulfamyl)-benzoic acid, is a drug used clinically to treat hyperuricemia and gout due to its activity as an inhibitor of the kidneys' organic anion transporter that reclaims uric acid from urine. Probenecid also inhibits pannexin1 channels that are involved in purinergic neurotransmission and inflammation, which have been implicated in alcohol's effects and motivation for alcohol. Therefore, we tested the effects of probenecid on alcohol intake in rodents.

METHODS

We tested the effects of probenecid on operant oral alcohol self-administration in alcohol-dependent rats during acute withdrawal as well as in nondependent rats and in the drinking-in-the-dark (DID) paradigm of binge-like drinking in mice.

RESULTS

Probenecid reduced alcohol intake in both dependent and nondependent rats and in the DID paradigm in mice without affecting water or saccharin intake, indicating that probenecid's effect was selective for alcohol and not the result of a general reduction in reward.

CONCLUSIONS

These results raise the possibility that pannexin1 is a novel therapeutic target for the treatment of AUD. The clinical use of probenecid has been found to be generally safe, suggesting that it can be a candidate for drug repositioning for the treatment of AUD.

Saturated high-fat feeding independent of obesity alters hypothalamus-pituitary-adrenal axis function but not anxiety-like behaviour

Overconsumption of dietary fat can elicit impairments in emotional processes and the response to stress. While excess dietary lipids have been shown to alter hypothalamus-pituitary-adrenal (HPA) axis function and promote anxiety-like behaviour, it is not known if such changes rely on elevated body weight and if these effects are specific to the type of dietary fat. The objective of this study was to investigate the effect of a saturated and a monounsaturated high-fat diet (HFD) on HPA axis function and anxiety-like behaviour in rats. Biochemical, metabolic and behavioural responses were evaluated following eight weeks on one of three diets: (1) a monounsaturated HFD (50%kcal olive oil), (2) a saturated HFD (50%kcal palm oil), or (3) a control low-fat diet. Weight gain was similar across the three diets while visceral fat mass was elevated by the two HFDs. The saturated HFD had specific actions to increase peak plasma levels of corticosterone and tumour-necrosis-factor-alpha and suppress mRNA expression of glucocorticoid and mineralocorticoid receptors, corticotropin-releasing hormone and 11β-hydroxysteroid dehydrogenase-1 in the paraventricular nucleus of the hypothalamus. Both HFDs enhanced the corticosterone-suppressing response to dexamethasone administration without affecting the physiological response to a restraint stress and failed to increase anxiety-like behaviour as measured in the elevated-plus maze and open field tests. These findings demonstrate that prolonged intake of saturated fat, without added weight gain, increases CORT and modulates central HPA feedback processes. That saturated HFD failed to affect anxiety-like behaviour can suggest that the anxiogenic effects of prolonged high-fat feeding may rely on more pronounced metabolic dysfunction.

Design, synthesis and in vivo study of novel pyrrolidine-based 11β-HSD1 inhibitors for age-related cognitive dysfunction

Recent findings suggest that treatment with 11β-HSD1 inhibitors provides a novel approach to deal with age-related cognitive dysfunctions, including Alzheimer's disease. In this work we report potent 11β-HSD1 inhibitors featuring unexplored pyrrolidine-based polycyclic substituents. A selected candidate administered to 12-month-old SAMP8 mice for four weeks prevented memory deficits and displayed a neuroprotective action. This is the first time that 11β-HSD1 inhibitors have been studied in this broadly-used mouse model of accelerated senescence and late-onset Alzheimer's disease.

11β-hydroxysteroid dehydrogenase inhibition as a new potential therapeutic target for alcohol abuse

The identification of new and more effective treatments for alcohol abuse remains a priority. Alcohol intake activates glucocorticoids, which have a key role in alcohol's reinforcing properties. Glucocorticoid effects are modulated in part by the activity of 11β-hydroxysteroid dehydrogenases (11β-HSD) acting as pre-receptors. Here, we tested the effects on alcohol intake of the 11β-HSD inhibitor carbenoxolone (CBX, 18β-glycyrrhetinic acid 3β-O-hemisuccinate), which has been extensively used in the clinic for the treatment of gastritis and peptic ulcer and is active on both 11β-HSD1 and 11β-HSD2 isoforms. We observed that CBX reduces both baseline and excessive drinking in rats and mice. The CBX diastereomer 18α-glycyrrhetinic acid 3β-O-hemisuccinate (αCBX), which we found to be selective for 11β-HSD2, was also effective in reducing alcohol drinking in mice. Thus, 11β-HSD inhibitors may be a promising new class of candidate alcohol abuse medications, and existing 11β-HSD inhibitor drugs may be potentially re-purposed for alcohol abuse treatment.

DHEA effects on brain and behavior: insights from comparative studies of aggression

Historically, research on the neuroendocrinology of aggression has been dominated by the paradigm that the brain receives sex steroid hormones, such as testosterone (T), from the gonads, and then these gonadal hormones modulate behaviorally relevant neural circuits. While this paradigm has been extremely useful for advancing the field, recent studies reveal important alternatives. For example, most vertebrate species are seasonal breeders, and many species show aggression outside of the breeding season, when the gonads are regressed and circulating levels of gonadal steroids are relatively low. Studies in diverse avian and mammalian species suggest that adrenal dehydroepiandrosterone (DHEA), an androgen precursor and prohormone, is important for the expression of aggression when gonadal T synthesis is low. Circulating DHEA can be converted into active sex steroids within the brain. In addition, the brain can synthesize sex steroids de novo from cholesterol, thereby uncoupling brain steroid levels from circulating steroid levels. These alternative mechanisms to provide sex steroids to specific neural circuits may have evolved to avoid the costs of high circulating T levels during the non-breeding season. Physiological indicators of season (e.g., melatonin) may allow animals to switch from one neuroendocrine mechanism to another across the year. DHEA and neurosteroids are likely to be important for the control of multiple behaviors in many species, including humans. These studies yield fundamental insights into the regulation of DHEA secretion, the mechanisms by which DHEA affects behavior, and the brain regions and neural processes that are modulated by DHEA. It is clear that the brain is an important site of DHEA synthesis and action. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Short-term inhibition of 11β-hydroxysteroid dehydrogenase type 1 reversibly improves spatial memory but persistently impairs contextual fear memory in aged mice

High glucocorticoid levels induced by stress enhance the memory of fearful events and may contribute to the development of anxiety and posttraumatic stress disorder. In contrast, elevated glucocorticoids associated with ageing impair spatial memory. We have previously shown that pharmacological inhibition of the intracellular glucocorticoid-amplifying enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) improves spatial memory in aged mice. However, it is not known whether inhibition of 11β-HSD1 will have any beneficial effects on contextual fear memories in aged mice. Here, we examined the effects of UE2316, a selective 11β-HSD1 inhibitor which accesses the brain, on both spatial and contextual fear memories in aged mice using a vehicle-controlled crossover study design.

Short-term UE2316 treatment improved spatial memory in aged mice, an effect which was reversed when UE2316 was substituted with vehicle. In contrast, contextual fear memory induced by foot-shock conditioning was significantly reduced by UE2316 in a non-reversible manner. When the order of treatment was reversed following extinction of the original fear memory, and a second foot-shock conditioning was given in a novel context, UE2316 treated aged mice (previously on vehicle) now showed increased fear memory compared to vehicle-treated aged mice (previously on UE2316). Renewal of the original extinguished fear memory triggered by exposure to a new environmental context may explain these effects. Thus 11β-HSD1 inhibition reverses spatial memory impairments with ageing while reducing the strength and persistence of new contextual fear memories. Potentially this could help prevent anxiety-related disorders in vulnerable elderly individuals.

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Aged mice were treated with UE2316 using a vehicle-controlled crossover design.

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Short-term UE2316 treatment improves spatial memory in a reversible manner.

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Contextual fear memory retention was impaired with UE2316.

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Contextual fear memory effects persisted following reversal of treatment.

Regulation of 11β-hydroxysteroid dehydrogenase type 1 and 7α-hydroxylase CYP7B1 during social stress

11β-hydroxysteroid dehydrogenase type 1 (11HSD1) is an enzyme that amplifies intracellular glucocorticoid concentration by the conversion of inert glucocorticoids to active forms and is involved in the interconversion of 7-oxo- and 7-hydroxy-steroids, which can interfere with the activation of glucocorticoids. The presence of 11HSD1 in the structures of the hypothalamic-pituitary-adrenal (HPA) axis suggests that this enzyme might play a role in the regulation of HPA output. Here we show that the exposure of Fisher 344 rats to mild social stress based on the resident-intruder paradigm increased the expression of 11HSD1 and CYP7B1, an enzyme that catalyzes 7-hydroxylation of steroids. We found that social behavioral profile of intruders was significantly decreased whereas their plasma levels of corticosterone were increased more than in residents. The stress did not modulate 11HSD1 in the HPA axis (paraventricular nucleus, pituitary, adrenal cortex) but selectively upregulated 11HSD1 in some regions of the hippocampus, amygdala and prelimbic cortex. In contrast, CYP7B1 was upregulated not only in the hippocampus and amygdala but also in paraventricular nucleus and pituitary. Furthermore, the stress downregulated 11HSD1 in the thymus and upregulated it in the spleen and mesenteric lymphatic nodes whereas CYP7B1 was upregulated in all of these lymphoid organs. The response of 11HSD1 to stress was more obvious in intruders than in residents and the response of CYP7B1 to stress predominated in residents. We conclude that social stress induces changes in enzymes of local metabolism of glucocorticoids in lymphoid organs and in brain structures associated with the regulation of the HPA axis. In addition, the presented data clearly suggest a role of 11HSD1 in modulation of glucocorticoid feedback of the HPA axis during stress.

Hyperglycemia induces the variations of 11β-hydroxysteroid dehydrogenase type 1 and peroxisome proliferator-activated receptor-γ expression in hippocampus and hypothalamus of diabetic rats

In this paper, we first observed that there were differences in expressions of 11β-HSD1 and PPAR-γ, in hippocampi and hypothalami, among constant hyperglycemia group, control group and the fluctuant glycemia group, using Immunohistochemical analysis. However, whether in expression o f 11β-HSD1 or PPAR-γ, there were no statistic differences between the control group or the fluctuant glycemia group. So, we removed the fluctuant glycemia group, retaining only constant hyperglycemia group and control group, being fed for 8 weeks. After 8 weeks of induction, 11β-HSD1 expression increased and PPAR-γ expression decreased in the constant hyperglycemia group compared with control group, both in hippocampi and hypothalami, by Western Blot. The constant hyperglycemia group also showed impaired cognition in MORRIS watermaze, lower serum corticosterone level, and higher Serum ACTH concentration after 8 weeks. We inferred that the cognition impairment may be related to the abnormal expression of 11β-HSD1 and PPAR-γ in central nerves system. As for 11β-HSD1 is a regulating enzyme, converting the inactive 11-dehydrocorticosterone into the active glucocorticoid corticosterone, thus amplifying GC action in local tissues. It is also well known that high local GC levels can affect the cognitive function. In addition, PPAR-a protective receptor, which is related to cognition.

Tissue-specific modulation of mineralocorticoid receptor function by 11β-hydroxysteroid dehydrogenases: an overview

In the last decade significant progress has been made in the understanding of mineralocorticoid receptor (MR) function and its implications for physiology and disease. The knowledge on the essential role of MR in the regulation of electrolyte concentrations and blood pressure has been significantly extended, and the relevance of excessive MR activation in promoting inflammation, fibrosis and heart disease as well as its role in modulating neuronal cell viability and brain function is now widely recognized. Despite considerable progress, the mechanisms of MR function in various cell-types are still poorly understood. Key modulators of MR function include the glucocorticoid receptor (GR), which may affect MR function by formation of heterodimers and by differential genomic and non-genomic responses on gene expression, and 11β-hydroxysteroid dehydrogenases (11β-HSDs), which determine the availability of intracellular concentrations of active glucocorticoids. In this review we attempted to provide an overview of the knowledge on MR expression with regard to the presence or absence of GR, 11β-HSD2 and 11β-HSD1/hexose-6-phosphate dehydrogenase (H6PDH) in various tissues and cell types. The consequences of cell-specific differences in the coexpression of MR with these proteins need to be further investigated in order to understand the role of this receptor in a given tissue as well as its systemic impact.

Peroxisome proliferator-activated receptor-γ activation induces 11β-hydroxysteroid dehydrogenase type 1 activity in human alternative macrophages

OBJECTIVE

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyzes the intracellular reduction of inactive cortisone to active cortisol, the natural ligand activating the glucocorticoid receptor (GR). Peroxisome proliferator- activated receptor-γ (PPARγ) is a nuclear receptor controlling inflammation, lipid metabolism, and the macrophage polarization state. In this study, we investigated the impact of macrophage polarization on the expression and activity of 11β-HSD1 and the role of PPARγ therein.

METHODS AND RESULTS

11β-HSD1 gene expression is higher in proinflammatory M1 and anti-inflammatory M2 macrophages than in resting macrophages, whereas its activity is highest in M2 macrophages. Interestingly, PPARγ activation induces 11β-HSD1 enzyme activity in M2 macrophages but not in resting macrophages or M1 macrophages. Consequently, human M2 macrophages displayed enhanced responsiveness to the 11β-HSD1 substrate cortisone, an effect amplified by PPARγ induction of 11β-HSD1 activity, as illustrated by an increased expression of GR target genes.

CONCLUSION

Our data identify a positive cross-talk between PPARγ and GR in human M2 macrophages via the induction of 11β-HSD1 expression and activity.

Intrahippocampal corticosterone response in mice selectively bred for extremes in stress reactivity: a microdialysis study

The hypothalamic-pituitary-adrenocortical (HPA) axis is one of the major stress hormone systems, and glucocorticoids (GCs) play a pivotal role in homeostatic processes throughout the body and brain. A dysregulation of the HPA axis, leading to an aberrant secretion of GCs, is associated with affective disorders such as major depression. In the present study, three mouse lines selectively bred for high (HR), intermediate (IR) or low (LR) stress reactivity were used to elucidate the temporal dynamics of intrahippocampal corticosterone (CORT) in response to a standardised stressor. In particular, we addressed the question of whether the distinct differences in HPA axis reactivity between the three mouse lines, as determined by plasma CORT measurements, are present in the central nervous system as well, and if the respective endophenotype is brought about by alterations in blood-brain barrier (BBB) functionality. We applied in vivo microdialysis in the hippocampus, demonstrating that the concentrations of CORT released from the adrenals in response to restraint stress are not only distinctly different in the plasma, but can also be found in the central nervous system, although the differences between the three mouse lines were attenuated, particularly between IR and LR animals. Additionally, a time lag of approximately 60 min was observed in all three lines regarding intrahippocampal peak concentrations of CORT after the onset of the stressor. Furthermore, we showed that the penetration and clearance of CORT in the hippocampal tissue was not affected by differences in BBB functionality because the multidrug resistance 1 P-glycoprotein (Mdr1 Pgp) was equally expressed in HR, IR and LR mice. Furthermore, we could exclude surgical damage of the BBB because peripherally-injected dexamethasone, which is a high affinity substrate for the Mdr1 Pgp and therefore restricted from entering the brain, could only be detected in the plasma and was virtually absent in the brain.

11β-hydroxysteroid dehydrogenase type 1, brain atrophy and cognitive decline

Excess cortisol levels are linked with brain atrophy and cognitive decline in older people. 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) potently amplifies intracellular glucocorticoid action by converting inert cortisone to active cortisol, but any causal importance in brain aging is unexplored. We tested the hypotheses that higher systemic 11β-HSD1 activity predicts brain atrophy and cognitive decline in older men. In a longitudinal study of 41 men (65-70 years old at baseline) we measured baseline systemic 11β-HSD1 activity, the urinary 5alpha- and 5beta-tetrahydrocortisol to tetrahydrocortisone ratio (ratio of tetrahydrometabolites of cortisol (THFs)/ratio of tetrahydrometabolites of cortisol (THE)), and assessed change in brain atrophy, white matter lesions and cognitive function over 6 years. Baseline THFs/THE correlated negatively with baseline hippocampal volumes (left: r = -0.37; right: r = -0.34; p < 0.05) and positively with ventricular volumes (r = 0.43, p = 0.006) and periventricular white matter lesions (rho = 0.31, p = 0.047). Importantly, baseline THFs/THE but not cortisol predicted increase in ventricular volumes (r = 0.33, p = 0.037) and decline in processing speed (r = -0.55, p = 0.0002) over 6 years. The predictive link between systemic 11β-HSD1 activity and progressive brain atrophy and cognitive decline suggests 11β-HSD1 inhibition as a plausible therapy for brain aging.

Reduced cortisol levels in cerebrospinal fluid and differential distribution of 11beta-hydroxysteroid dehydrogenases in multiple sclerosis: implications for lesion pathogenesis

Relapses during multiple sclerosis (MS) are treated by administration of exogenous corticosteroids. However, little is known about the bioavailability of endogenous steroids in the central nervous system (CNS) of MS patients. We thus determined cortisol and dehydroepiandrosterone (DHEA) levels in serum and cerebrospinal fluid (CSF) samples from 34 MS patients, 28 patients with non-inflammatory neurological diseases (NIND) and 16 patients with other inflammatory neurological diseases (OIND). This revealed that MS patients - in sharp contrast to patients with OIND - show normal cortisol concentrations in serum and lowered cortisol levels in the CSF during acute relapses. This local cortisol deficit may relate to poor local activation of cortisone via 11beta-hydroxysteroid dehydrogenase type 1 (11bHSD1) or to inactivation via 11bHSD2. Accordingly, 11bHSD2 was found to be expressed within active plaques, whereas 11bHSD1 was predominantly detected in surrounding "foamy" macrophages. Our study thus provides new insights into the impaired endogenous CNS cortisol regulation in MS patients and its possible relation to MS lesion pathogenesis. Moreover, an observed upregulation of 11bHSD1 in myelin-loaded macrophages in vitro suggests an intriguing hypothesis for the self-limiting nature of MS lesion development. Finally, our findings provide an attractive explanation for the effectivity of high- vs. low-dose exogenous corticosteroids in the therapy of acute relapses.

Corticosterone and dehydroepiandrosterone in songbird plasma and brain: effects of season and acute stress

Prolonged increases in plasma glucocorticoids can exacerbate neurodegeneration. In rats, these neurodegenerative effects can be reduced by dehydroepiandrosterone (DHEA), an androgen precursor with anti-glucocorticoid actions. In song sparrows, season and acute restraint stress affect circulating levels of corticosterone and DHEA, and the effects of stress differ in plasma collected from the brachial and jugular veins. Jugular plasma is an indirect index of the neural steroidal milieu. Here, we directly measured corticosterone and DHEA in several brain regions and jugular plasma, and examined the effects of season and acute restraint stress (30 min) (n = 571 samples). Corticosterone levels were up to 10x lower in brain than in jugular plasma. In contrast, DHEA levels were up to 5x higher in brain than in jugular plasma and were highest in the hippocampus. Corticosterone and DHEA concentrations were strongly seasonally regulated in plasma but, surprisingly, not seasonally regulated in brain. Acute stress increased corticosterone levels in plasma and brain, except during the molt, when stress unexpectedly decreased corticosterone levels in the hippocampus. Acute stress increased DHEA levels in plasma during the molt but had no effects on DHEA levels in brain. This is the first study to measure (i) corticosterone or DHEA levels in the brain of adult songbirds and (ii) seasonal changes in corticosterone or DHEA levels in the brain of any species. These results highlight several critical differences between systemic and local steroid concentrations and the difficulty of using circulating steroid levels to infer local steroid levels within the brain.

Glucocorticoid receptor plays an indispensable role in mineralocorticoid receptor-dependent transcription in GR-deficient BE(2)C and T84 cells in vitro

The mineralocorticoid receptor (MR) plays an important functional role in the central nervous system; however, the molecular mechanism of MR-dependent gene expression is not entirely clear. In this study, we examined the MR-dependent transcriptional regulation using a human neuronal cell line BE(2)C and an MR/GR-dependent reporter gene (HRE-luciferase) in vitro. Western blot analysis revealed that the cell line expresses MR but not glucocorticoid receptor (GR). In this experimental condition, unexpectedly, the MR-specific ligand aldosterone did not induce HRE-dependent transcription in a native or MR-overexpressed condition, whereas significant transcriptional induction by aldosterone was observed when the GR was co-expressed. The effect of aldosterone was completely inhibited by the MR antagonist spironolactone, indicating an MR-dependent effect. We found similar results in T84 colonic cells expressing neither MR nor GR, such that the aldosterone effect was obtained only when both receptors were co-expressed. The co-operative effect of GR was not obvious with the dimer-deficient mutant GR. Finally, the above findings were reproducible with different promoters containing HRE such as ENaC and MMTV. These results suggest that GR plays an indispensable role in MR-dependent transcription, possibly by forming a MR/GR heterodimer or by acting as a co-activator of MR/MR homodimer.

The biological roles of extracellular and intracytoplasmic glucocorticoids in skeletal cells

Osteoporosis is the most common metabolic disease characterized by loss of the normal density of bone, resulting in fragile bone and a higher risk of fractures. Patients under glucocorticoids treatment are susceptible to glucocorticoid-induced osteoporosis (GIO). The normal bone turnover depends on a balance between osteoblasts and osteoclasts. The skeletal cells including osteoblasts, osteoclasts, osteocytes and their precursors demonstrate altered features while they are cocultured with different extracellular glucocorticoids, or their intracytoplasmic glucocorticoids modified by genetic manipulation of 11beta-HSD isozyme. However, recent studies have also demonstrated different or even contradictive outcomes on whether the glucocorticoids inhibit or increase biological activity of these skeletal cells. Focusing on the roles of extracellular glucorticoids, intracytoplasmic glucocorticoids and the mechanism of transmembrane passage of the glucocorticoids, this review reveals that glucocorticoids may exert either inhibitive or enhancing influence on these skeletal cells, but relying on the difference in cell origins, methodology, and types of glucocorticoids. In addition, the effects of glucocorticoids may be dose- and time-dependent.

Hippocampal 11beta-hydroxysteroid dehydrogenase type 1 messenger ribonucleic acid expression has a diurnal variability that is lost in the obese Zucker rat

Circulating levels of glucocorticoids show a circadian rhythm. Obesity is associated with a flattening of the diurnal rhythm; plasma cortisol levels are slightly increased during the trough, although they are normal or low in the morning. Studies in humans and in leptin-resistant Zucker rats suggest that tissue-specific alterations in glucocorticoid exposure might play a key role for development of obesity and obesity-associated dysregulation of the hypothalamic-pituitary-adrenal axis. We hypothesized that there is a circadian rhythm in prereceptor metabolism of glucocorticoids exerted by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) in brain and/or peripheral tissues (liver, fat, and muscle) that might be abrogated in obesity. The present study demonstrates a circadian rhythm in 11beta-HSD1 mRNA expression (35-45% increase at morning vs. evening, P < 0.05) in dentate gyrus granular layer and CA1 subregions of the hippocampus in lean Zucker rats that was lost in the obese rats. Sprague Dawley rats also revealed a diurnal rhythm in hippocampal 11beta-HSD1 mRNA expression. There was no circadian variation in 11beta-HSD enzyme activity in peripheral tissues, although obese Zucker rats had a decreased enzyme activity in liver and epididymal fat (by approximately 40%, P < 0.05) compared with lean rats. In Sprague Dawley rats, 11beta-HSD activity in adipose tissue was higher in retroperitoneal and epididymal vs. sc fat (P < 0.001). In summary, obese Zucker rats lack a circadian rhythm of 11beta-HSD1 gene expression in the hippocampus, which may contribute to increased activity of the hypothalamic-pituitary-adrenal axis and altered diurnal variation of circulating corticosterone levels.