Myeloid Mineralocorticoid Receptor Transcriptionally Regulates P-Selectin Glycoprotein Ligand-1 and Promotes Monocyte Trafficking and Atherosclerosis

Objective

MR (mineralocorticoid receptor) activation associates with increased risk of cardiovascular ischemia while MR inhibition reduces cardiovascular-related mortality and plaque inflammation in mouse atherosclerosis. MR in myeloid cells (My-MR) promotes inflammatory cell infiltration into injured tissues and atherosclerotic plaque inflammation by unclear mechanisms. Here, we examined the role of My-MR in leukocyte trafficking and the impact of sex.

Approach and Results

We confirm in vivo that My-MR deletion (My-MR-KO) in ApoE-KO mice decreased plaque size. Flow cytometry revealed fewer plaque macrophages with My-MR-KO. By intravital microscopy, My-MR-KO significantly attenuated monocyte slow-rolling and adhesion to mesenteric vessels and decreased peritoneal infiltration of myeloid cells in response to inflammatory stimuli in male but not female mice. My-MR-KO mice had significantly less PSGL1 (P-selectin glycoprotein ligand 1) mRNA in peritoneal macrophages and surface PSGL1 protein on circulating monocytes in males. In vitro, MR activation with aldosterone significantly increased PSGL1 mRNA only in monocytes from MR-intact males. Similarly, aldosterone induced, and MR antagonist spironolactone inhibited, PSGL1 expression in human U937 monocytes. Mechanistically, aldosterone stimulated MR binding to a predicted MR response element in intron-1 of the PSGL1 gene by ChIP-qPCR. Reporter assays demonstrated that this PSGL1 MR response element is necessary and sufficient for aldosterone-activated, MR-dependent transcriptional activity.

Conclusions

These data identify PSGL1 as a My-MR target gene that drives leukocyte trafficking to enhance atherosclerotic plaque inflammation. These novel and sexually dimorphic findings provide insight into increased ischemia risk with MR activation, cardiovascular protection in women, and the role of MR in atherosclerosis and tissue inflammation.

Glucocorticoid and mineralocorticoid receptors and corticosteroid homeostasis are potential targets for endocrine-disrupting chemicals

Endocrine-disrupting chemicals (EDCs) have received significant concern, since they ubiquitously exist in the environment and are able to induce adverse health effects on human and wildlife. Increasing evidence shows that the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR), members of the steroid receptor subfamily, are potential targets for EDCs. GR and MR mediate the actions of glucocorticoids and mineralocorticoids, respectively, which are two main classes of corticosteroids involved in many physiological processes. The effects of EDCs on the homeostasis of these two classes of corticosteroids have also gained more attention recently. This review summarized the effects of environmental GR/MR ligands on receptor activity, and disruption of corticosteroid homeostasis. More than 130 chemicals classified into 7 main categories were reviewed, including metals, metalloids, pesticides, bisphenol analogues, flame retardants, other industrial chemicals and pharmaceuticals. The mechanisms by which EDCs interfere with GR/MR activity are primarily involved in ligand-receptor binding, nuclear translocation of the receptor complex, DNA-receptor binding, and changes in the expression of endogenous GR/MR genes. Besides directly interfering with receptors, enzyme-catalyzed synthesis and prereceptor regulation pathways of corticosteroids are also important targets for EDCs. The collected evidence suggests that corticosteroids and their receptors should be considered as potential targets for safety assessment of EDCs. The recognition of relevant xenobiotics and their underlying mechanisms of action is still a challenge in this emerging field of research.

PKCδ Mediates Mineralocorticoid Receptor Activation by Angiotensin II to Modulate Smooth Muscle Cell Function

Angiotensin II (AngII) and the mineralocorticoid receptor (MR) ligand aldosterone both contribute to cardiovascular disorders, including hypertension and adverse vascular remodeling. We previously demonstrated that AngII activates MR-mediated gene transcription in human vascular smooth muscle cells (SMCs), yet the mechanism and the impact on SMC function are unknown. Using an MR-responsive element-driven transcriptional reporter assay, we confirm that AngII induces MR transcriptional activity in vascular SMCs and endothelial cells, but not in Cos1 or human embryonic kidney-293 cells. AngII activation of MR was blocked by the MR antagonist spironolactone or eplerenone and the protein kinase C-δ (PKCδ) inhibitor rottlerin, implicating both in the mechanism. Similarly, small interfering RNA knockdown of PKCδ in SMCs prevented AngII-mediated MR activation, whereas knocking down of MR blocked both aldosterone- and AngII-induced MR function. Coimmunoprecipitation studies reveal that endogenous MR and PKCδ form a complex in SMCs that is enhanced by AngII treatment in association with increased serine phosphorylation of the MR N terminus. AngII increased mRNA expression of the SMC-MR target gene, FKBP51, via an MR-responsive element in intron 5 of the FKBP51 gene. The impact of AngII on FKBP51 reporter activity and gene expression in SMCs was inhibited by spironolactone and rottlerin. Finally, the AngII-induced increase in SMC number was also blocked by the MR antagonist spironolactone and the PKCδ inhibitor rottlerin. These data demonstrate that AngII activates MR transcriptional regulatory activity, target gene regulation, and SMC proliferation in a PKCδ-dependent manner. This new mechanism may contribute to synergy between MR and AngII in driving SMC dysfunction and to the cardiovascular benefits of MR and AngII receptor blockade in humans.

Effects of combined glucocorticoid/mineralocorticoid receptor modulation (CORT118335) on energy balance, adiposity, and lipid metabolism in male rats

Psychological stress and excess glucocorticoids are associated with metabolic and cardiovascular diseases. Glucocorticoids act primarily through mineralocorticoid (MR) and glucocorticoid receptors (GR), and compounds modulating these receptors show promise in mitigating metabolic and cardiovascular-related phenotypes. CORT118335 (GR/MR modulator) prevents high-fat diet-induced weight gain and adiposity in mice, but the ability of this compound to reverse obesity-related symptoms is unknown. Adult male rats were subcutaneously administered CORT118335 (3, 10, or 30 mg/kg) or vehicle once daily. A 5-day treatment with CORT118335 at 30 mg/kg induced weight loss in rats fed a chow diet by decreasing food intake. However, lower doses of the compound attenuated body weight gain primarily because of decreased calorific efficiency, as there were no significant differences in food intake compared with vehicle. Notably, the body weight effects of CORT118335 persisted during a 2-wk treatment hiatus, suggesting prolonged effects of the compound. To our knowledge, we are the first to demonstrate a sustained effect of combined GR/MR modulation on body weight gain. These findings suggest that CORT118335 may have long-lasting effects, likely due to GR/MR-induced transcriptional changes. Prolonged (18 days) treatment of CORT118335 (10 mg/kg) reversed body weight gain and adiposity in animals fed a high-fat diet for 13 wk. Surprisingly, this occurred despite a worsening of the lipid profile and glucose homeostasis as well as a disrupted diurnal corticosterone rhythm, suggesting GR agonistic effects in the periphery. We conclude that species and tissue-specific targeting may result in promising leads for exploiting the metabolically beneficial aspects of GR/MR modulation.

Enantioselectivity in endocrine disrupting effects of four cypermethrin enantiomers based on in vitro models

Cypermethrin (CP) is a kind of chiral pesticides that has been defined as endocrine disrupting chemical. The diversity in bioactivity, toxicity, metabolism, bioaccumulation, and degradation behaviors of CP enantiomers as well as the research deficiency had made the risk assessment of CP enantiomers very complicated. Herein, four CP enantiomers were separated as target chemicals to investigate their enantioselective endocrine disrupting effects. Firstly, dual-luciferase reporter gene assays were adopted to investigate their potential endocrine disrupting effects via various receptors. The expression levels of steroid hormones related genes and hormone secretion levels in H295R cell were measured to verify the results. Results from the reporter gene assay showed that 1R-cis-αS-CP (CP11) exhibited glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and thyroid receptor (TR) antagonistic activity with the RIC₂₀ values of 9.22 × 10^-7, 3.33 × 10^-7, and 4.47 × 10^-7 M, respectively; 1R-trans-αS-CP (CP21) also showed androgen receptor (AR) agonist activity and estrogen receptor (ER) antagonistic activity with the REC₂₀ and RIC₂₀ values were 1.07 × 10^-4 M and 4.78 × 10^-6 M, respectively. Results of qRT-PCR and hormone measurement also showed that CP11 and CP21 could disturb the expression of steroid hormones related genes and hormone secretion accordingly. Results provided here can help to understand the enantioselective ecological and health risks of CP enantiomers comprehensively and provide constructive guidance for the safe use of chiral pesticides and the invention of green pesticides.

Mineralocorticoid Receptor Antagonists-A New Sprinkle of Salt and Youth

Skin atrophy and impaired cutaneous wound healing are the recognized side effects of topical glucocorticoid (GC) therapy. Although GCs have high affinity for the glucocorticoid receptor, they also bind and activate the mineralocorticoid receptor. In light of this, one can speculate that some of the GC-mediated side effects can be remedied by blocking activation of the mineralocorticoid receptor. Indeed, according to Nguyen et al., local inhibition of the mineralocorticoid receptor via antagonists (spironolactone, canrenoate, and eplerenone) rescues GC-induced delayed epithelialization and accelerates wound closure in diabetic animals by targeting epithelial sodium channels and stimulating keratinocyte proliferation. These findings suggest that the use of mineralocorticoid receptor antagonists coupled with GC therapy may be beneficial in overcoming at least some of the GC-mediated side effects.

CD14 as a Mediator of the Mineralocorticoid Receptor-Dependent Anti-apolipoprotein A-1 IgG Chronotropic Effect on Cardiomyocytes

In vitro and animal studies point to autoantibodies against apolipoprotein A-1 (anti-apoA-1 IgG) as possible mediators of cardiovascular (CV) disease involving several mechanisms such as basal heart rate interference mediated by a mineralocorticoid receptor-dependent L-type calcium channel activation, and a direct pro-inflammatory effect through the engagement of the toll-like receptor (TLR) 2/CD14 complex. Nevertheless, the possible implication of these receptors in the pro-arrhythmogenic effect of anti-apoA-1 antibodies remains elusive. We aimed at determining whether CD14 and TLRs could mediate the anti-apoA-1 IgG chronotropic response in neonatal rat ventricular cardiomyocytes (NRVC). Blocking CD14 suppressed anti-apoA-1 IgG binding to NRVC and the related positive chronotropic response. Anti-apoA-1 IgG alone induced the formation of a TLR2/TLR4/CD14 complex, followed by the phosphorylation of Src, whereas aldosterone alone promoted the phosphorylation of Akt by phosphatidylinositol 3-kinase (PI3K), without affecting the chronotropic response. In the presence of both aldosterone and anti-apoA-1 IgG, the localization of TLR2/TLR4/CD14 was increased in membrane lipid rafts, followed by PI3K and Src activation, leading to an L-type calcium channel-dependent positive chronotropic response. Pharmacological inhibition of the Src pathway led to the decrease of L-type calcium channel activity and abrogated the NRVC chronotropic response. Activation of CD14 seems to be a key regulator of the mineralocorticoid receptor-dependent anti-apoA-1 IgG positive chronotropic effect on NRVCs, involving relocation of the CD14/TLR2/TLR4 complex into lipid rafts followed by PI3K and Src-dependent L-type calcium channel activation.

Aldosterone Impairs Vascular Smooth Muscle Function: From Clinical to Bench Research

CONTEXT

The effect of aldosterone on vascular smooth muscle cell function is still unclear. One method to measure vascular smooth muscle cell function is endothelial-independent vascular dilation, for which the key factor is sarcoplasmic reticulum calcium adenosine triphosphatase (SERCA).

OBJECTIVE

Our objective was to investigate the effect of aldosterone on vascular smooth muscle cell function and SERCA regulation.

DESIGN

We prospectively analyzed 35 patients with primary aldosteronism (PA; 32 patients with aldosterone-producing adenoma and three patients with idiopathic hyperaldosteronism) and 30 patients with essential hypertension (EH) who were enrolled as the control group. Flow and nitrate-mediated dilation were performed in both groups and 1 year after adrenalectomy in the patients with aldosterone-producing adenoma. In addition, we investigated the effect of aldosterone on SERCA regulation in human aortic smooth muscle cells.

SETTING

This study took place in an academic clinical research center.

PARTICIPANTS

Participants included 35 patients with PA and 30 patients with EH.

INTERVENTIONS

Adrenalectomy was undertaken in patients with aldosterone-producing adenoma.

RESULTS

The PA patients had significantly lower flow-mediated dilation (FMD) and nitrate-mediated dilation (NMD) values than the patients with EH (FMD: 13 ± 6 vs 16 ± 4; NMD: 16 ± 6 vs 19 ± 5; both P < .05). FMD/NMD were significantly correlated with log 24 hour-urine aldosterone (FMD: r = -0.287, P = .048; NMD: r = -0.402, P = .005) but not blood pressure. The impaired FMD and NMD values were significantly restored 1 year after adrenalectomy (FMD: 11 ± 4 to 19 ± 7; NMD: 15 ± 6 to 21 ± 6; both P < .01). Under confocal microscopy, aldosterone was shown to suppress the expression of SERCA2a of human aortic smooth muscle cells. Aldosterone significantly suppressed the expression of SERCA2a from 10(-8) M in mRNA and protein levels. This suppression was through down-regulation of mineralocorticoid receptor dependent mitochondrial transcription factors A and B2.

CONCLUSIONS

Aldosterone impairs vascular smooth muscle cell function and suppresses SERCA 2a expression.

The effect of early-life stress and chronic high-sucrose diet on metabolic outcomes in female rats

Early-life stress affects metabolic outcomes and choice of diet influences the development of metabolic disease. Here we tested the hypothesis that chronic sugar intake exacerbates metabolic deficits induced by early-life stress. Early-life stress was induced in Sprague-Dawley rats using limited nesting material in early lactation (LN, postnatal days 2-9), and siblings were given chow alone or with additional sucrose post weaning (n = 9-17 per group). Female control and LN siblings had unlimited access to either chow plus water, or chow and water plus 25% sucrose solution (Sucrose), from 3-15 weeks of age. Weekly body weight and food intake were measured. Glucose and insulin tolerance were tested at 13 and 14 weeks of age, respectively. Rats were killed at 15 weeks. Hepatic triglyceride and markers of lipid synthesis - fatty acid synthase, acetyl-CoA carboxylase alpha and oxidation - and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Pgc-1α) were examined. Mediators of hepatic glucocorticoid metabolism, specifically 11-beta hydroxysteroid dehydrogenase-1 (11βHSD-1), 5-α reductase, and glucocorticoid and mineralocorticoid receptor mRNAs were also measured. Sucrose increased caloric intake in both groups, but overall energy intake was not altered by LN exposure. LN exposure had no further impact on sucrose-induced glucose intolerance and increased plasma and liver triglycerides. Hepatic markers of fat synthesis and oxidation were concomitantly activated and 11βHSD-1 mRNA expression was increased by 53% in LN-Sucrose versus Con-Sucrose rats. Adiposity was increased by 26% in LN-Sucrose versus Con-Sucrose rats. Thus, LN exposure had minimal adverse metabolic effects despite high-sugar diet postweaning.

A double-hit model of stress dysregulation in rats: implications for limbic corticosteroid receptors and anxious behavior under amitriptyline treatment

Adversity during early life can lead to diverging endocrine and behavioral responses to stress in adulthood. In our laboratory, we evaluated the long-term effects of early life adversity and its interaction with chronic stress during adulthood. We propose this as a model of vulnerability to dysregulation of the stress response. We hypothesized that rats subjected to both protocols would show differential expression of corticosteroid receptors measured as number of neurons immunoreactive for glucocorticoid receptors (GR) or mineralocorticoid receptors (MR), in limbic areas related to the control of anxiety-like behavior. We also evaluated the effect of amitriptyline expecting to prevent the outcomes of the model. Male Wistar rats were separated from the mother (MS) for 4.5 h every day for the first 3 weeks of life. From postnatal day 50, rats were subjected to chronic variable stress (CVS) during 24 d (five types of stressor at different times of day). During the stress protocol, the rats were administered amitriptyline (10 mg/kg i.p.) daily. MS evoked lower MR expression in the central amygdaloid nucleus and this was reversed by amitriptyline. Furthermore, CVS increased MR immunoreactivity in the hippocampal area CA2 and increased anxious behavior; both effects were prevented by the antidepressant. When MS was combined with CVS during adulthood, there was a reduction of locomotor activity, with no corrective effect of amitriptyline. The differential effects among groups could mean that MS would promote an alternative phenotype that is expressed when facing CVS (a double hit) later in life.

The role of mineralocorticoid receptor function in treatment-resistant depression

BACKGROUND

Treatment-resistant depression patients show both reduced glucocorticoid receptor function and a hyperactive hypothalamic-pituitary-adrenal axis. However, few studies have examined the role of the mineralocorticoid receptor. This study aimed to evaluate the functional activity of the mineralocorticoid receptor system in regulating the hypothalamic-pituitary-adrenal axis in well-defined treatment-resistant depression patients.

MATERIAL AND METHOD

We recruited 24 subjects divided into: (a) treatment-resistant depression; (b) healthy controls. We evaluated: (a) the effect of combined glucocorticoid receptor/mineralocorticoid receptor stimulation with prednisolone; (b) the effect of prednisolone with the mineralocorticoid receptor antagonist spironolactone; and (c) the effect of spironolactone alone. The response of the hypothalamic-pituitary-adrenal axis was measured using salivary cortisol and plasma levels of drugs were also measured.

RESULTS

Treatment-resistant depression patients had higher cortisol compared with controls after all challenges. In controls, spironolactone increased cortisol compared to placebo. The co-administration of spironolactone with prednisolone in controls decreases the suppressive effects of prednisolone. In contrast, in treatment-resistant depression, spironolactone did not increase cortisol compared to placebo and spironolactone with prednisolone had no effect on the suppressive effects of prednisolone. Patients with treatment-resistant depression had a reduction in the conversation of spironolactone to the active metabolite canrenone.

CONCLUSION

Our data confirmed that treatment-resistant depression is associated with hypercortisolism and these patients no longer show an hypothalamic-pituitary-adrenal response to the administration of a mineralocorticoid receptor antagonist, suggesting that there is a mineralocorticoid receptor malfunctioning, such as a down regulation, however, pharmacokinetics and pharmacodynamics in these subjects could also have had an effect on the lack of mineralocorticoid receptor response.

Chronic effects of corticosterone on GIRK1-3 subunits and 5-HT1A receptor expression in rat brain and their reversal by concurrent fluoxetine treatment

Dysregulation of the serotonergic system and abnormalities of the hypothalamic-pituitary-adrenal axis have been demonstrated in major depression. Animal studies indicate that 5-HT1A receptor expression may be reduced by long-term administration of corticosterone. However, similar studies on the regulation of GIRK channels, one of the most important effectors of the neuronal 5-HT1A receptor, are limited. In order to address these issues, slow-release corticosterone pellets were implanted subcutaneously to adrenal intact male rats (200mg pellets, 35 days release). Starting on day 15, animals were treated for 21 days with fluoxetine (5mg/kg/day, i.p.), or vehicle. Using in situ hybridization histochemistry and receptor autoradiography, we found that chronic corticosterone treatment was accompanied by a significant decrease on the mRNAs coding for mineralocorticoid receptors in hippocampal areas. Under these conditions, 5-HT1A receptor mRNA expression decreased in dorsal raphe nucleus and dentate gyrus. However, 5-HT1A receptor levels, as measured by [(3)H]-8-OH-DPAT binding, diminished significantly only in dentate gyrus. It is noteworthy that chronic treatment with fluoxetine reversed the alterations on 5-HT1A receptor mRNA levels only in dorsal raphe. Finally, chronic corticosterone treatment produced an increase on the mRNA coding for the GIRK2 subunit in several hypothalamic and thalamic areas, which was reversed by fluoxetine. Measurements of cell density and volume of the granular layer of the dentate gyrus did not reveal significant changes after corticosterone or corticosterone plus fluoxetine treatments. These data are relevant for a better understanding of the differential regulation of pre- and postsynaptic 5-HT1A receptors by corticosterone flattened rhythm.

Dietary sodium intake regulates angiotensin II type 1, mineralocorticoid receptor, and associated signaling proteins in heart

Liberal or high-sodium (HS) intake, in conjunction with an activated renin-angiotensin-aldosterone system, increases cardiovascular (CV) damage. We tested the hypothesis that sodium intake regulates the type 1 angiotensin II receptor (AT(1)R), mineralocorticoid receptor (MR), and associated signaling pathways in heart tissue from healthy rodents. HS (1.6% Na(+)) and low-sodium (LS; 0.02% Na(+)) rat chow was fed to male healthy Wistar rats (n=7 animals per group). Protein levels were assessed by western blot and immunoprecipitation analysis. Fractionation studies showed that MR, AT(1)R, caveolin-3 (CAV-3), and CAV-1 were located in both cytoplasmic and membrane fractions. In healthy rats, consumption of an LS versus a HS diet led to decreased cardiac levels of AT(1)R and MR. Decreased sodium intake was also associated with decreased cardiac levels of CAV-1 and CAV-3, decreased immunoprecipitation of AT(1)R-CAV-3 and MR-CAV-3 complexes, but increased immunoprecipitation of AT(1)R/MR complexes. Furthermore, decreased sodium intake was associated with decreased cardiac extracellular signal-regulated kinase (ERK), phosphorylated ERK (pERK), and pERK/ERK ratio; increased cardiac striatin; decreased endothelial nitric oxide synthase (eNOS) and phosphorylated eNOS (peNOS), but increased peNOS/eNOS ratio; and decreased cardiac plasminogen activator inhibitor-1. Dietary sodium restriction has beneficial effects on the cardiac expression of factors associated with CV injury. These changes may play a role in the cardioprotective effects of dietary sodium restriction.

A bioactive compound from Polygala tenuifolia regulates efficiency of chronic stress on hypothalamic-pituitary-adrenal axis

3,6'-Disinapoyl sucrose (DISS) is the active oligosaccharide ester component from roots of Polygala tenuifolia, and its antidepressant effects was found in the forced swimming test (FST) and tail suspension test (TST). We aimed to study the antidepressant effects of DISS in the chronic unpredictable mild stress (CMS) model in rats and explore the underlying mechanisms in the hypothalamic-pituitary-adrenal (HPA) axis. We found that when subjected to the chronic stress protocol for 28 days, animals showed reduced sensitivity to reward and abnormality in the HPA axis. DISS (10 or 20 mg/kg, i.g.) improved the reward reaction as measured by increasing sucrose consumption, remarkably reduced serum CORT, ACTH and CRH levels in the CMS-treated rats. In addition, DISS enhanced the expression of glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) mRNA. These results indicated that the antidepressant effects of DISS in chronically stressed animals might relate to the modulating effects on the HPA axis, which might be an important mechanism for its antidepressant effect.

Combined receptor antagonist stimulation of the hypothalamic-pituitary-adrenal axis test identifies impaired negative feedback sensitivity to cortisol in obese men

CONTEXT

Hypothalamic-pituitary-adrenal (HPA) axis dysregulation may underlie disorders including obesity, depression, cognitive decline, and the metabolic syndrome. Conventional tests of HPA axis negative feedback rely on glucocorticoid receptor (GR) agonists such as dexamethasone but do not test feedback by endogenous cortisol, potentially mediated by both GR and mineralocorticoid receptors (MR).

OBJECTIVE

The objective of the study was to use a combination of GR (RU38486, mifepristone) and MR (spironolactone) antagonists to explore the poorly understood activation of the HPA axis that occurs in obesity.

DESIGN

This was a double-blind, placebo-controlled, randomized, crossover study.

SETTING

The study was conducted at a clinical research facility.

PARTICIPANTS

Participants included 15 lean (body mass index 22.0 +/- 1.6 kg/m(2)) and 16 overweight/obese (body mass index 30.1 +/- 3.5 kg/m(2)) men.

INTERVENTION

Subjects attended on four occasions for blood and saliva sampling every 30 min between 1800 and 2200 h. At 1100 and 1600 h before visits, subjects took 200 mg spironolactone, 400 mg RU38486, 200 mg spironolactone + 400 mg RU38486, or placebo orally.

MAIN OUTCOME MEASURES

Serum cortisol levels after drug or placebo were measured.

RESULTS

Cortisol levels did not differ between lean and obese after placebo. Spironolactone and RU38486 alone had modest effects, increasing cortisol by less than 50% in both groups. However, combined spironolactone plus RU38486 elevated cortisol concentrations substantially, more so in lean than obese men [2.9- (0.3) vs. 2.2 (0.3)-fold elevation, P = 0.002].

CONCLUSIONS

Combined receptor antagonist stimulation of the HPA axis reveals redundancy of MR and GR in negative feedback in humans. Obese men have impaired responses to combined receptor antagonist stimulation, suggesting impaired negative feedback by endogenous cortisol. Such an approach may be useful to dissect abnormal HPA axis control in neuropsychiatric and other disorders.

Synergistic induction of osteopontin by aldosterone and inflammatory cytokines in mesangial cells

Hypertensive nephrosclerosis is characterized by activation of the renin-angiotensin-aldosterone system in combination with an inflammatory response characterized by an infiltration of T-cells and mononuclear cells, which release proinflammatory cytokines like IL-1beta/TNFalpha. In various models of experimental hypertensive disease the chemokine osteopontin (OPN) enhances further leukocyte infiltration. Therefore, we investigated the induction of OPN expression in renal mesangial cells (MCs) by aldosterone and the inflammatory cytokines IL-1beta/TNFalpha. Incubation with aldosterone resulted in a time- and concentration-dependent increase in OPN mRNA and protein. OPN mRNA expression followed a biphasic time course with an early increase between 4 and 8 h and the second phase starting at 14 h. The early phase was independent of protein synthesis, indicating a direct effect of aldosterone. Aldosterone-mediated induction of OPN was prevented by spironolactone, indicative of a receptor-mediated aldosterone effect. The mineralocorticoid receptor (MR) was identified in MCs by RT-PCR and immunoprecipitation, and shown to interact with a putative aldosterone-response element of the OPN promoter. The proinflammatory cytokines IL-1beta and TNFalpha only marginally affected OPN expression in MCs. However, coincubation of aldosterone and the cytokines synergistically increased OPN mRNA and protein levels. Since the synergistic effect on OPN mRNA was inhibited by diphenyleneiodonium, we assume an involvement of reactive oxygen species (ROS). We conclude that the chemokine OPN is a target gene of aldosterone in renal MCs, which is activated via the MR, and that proinflammatory cytokines enhance aldosterone-dependent OPN expression. In vivo, this may result in further leukocyte infiltration aggravating hypertensive nephrosclerosis.

Increased production of 11beta-hydroxysteroid dehydrogenase type 2 in the kidney microsomes of squirrel monkeys (Saimiri spp.)

In squirrel monkeys (Saimiri spp.), cortisol circulates at levels much higher than those seen in man and other Old World primates, but squirrel monkeys exhibit no physiologic signs of the mineralocorticoid effects of cortisol. These observations suggest that squirrel monkeys have mechanisms for protection of the mineralocorticoid receptor (MR) from these high levels of cortisol. We previously showed that the serum cortisol to cortisone ratio in these animals is low relative to that in human serum, suggesting that production of the MR protective enzyme, 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), is increased in squirrel monkeys. Here, we directly evaluate whether increased production of 11beta-HSD2, which inactivates cortisol to cortisone, is a mechanism for protection of MR. In vitro assays showed that 11beta-HSD2 activity in squirrel monkey kidney microsomes was 3 to 7 times higher than that seen in kidney microsomes from pig or rabbit. 11beta-HSD2 protein detected by Western blot analysis was 4 to 9 times greater in squirrel monkey microsomes than in pig or rabbit microsomes. Comparison of the effect of expression of either human or squirrel monkey 11beta-HSD2 on MR transactivation activity showed similar inhibition of MR response to cortisol by both enzymes, indicating that the intrinsic activities of the human and squirrel monkey enzymes are similar. These findings suggest that one mechanism by which squirrel monkeys protect the MR from activation by high cortisol levels in the kidney is by upregulation of 11beta-HSD2 activity through increased production of the enzyme.

Stimulation of both type I and type II corticosteroid receptors blunts counterregulatory responses to subsequent hypoglycemia in healthy man

Antecedent increases of corticosteroids can blunt counterregulatory responses to subsequent stress. Our aim was to determine whether prior activation of type I corticosteroid (mineralocorticoid) or type II corticosteroid (glucocorticoid) receptors blunts counterregulatory responses to subsequent hypoglycemia. Healthy volunteers participated in five randomized 2-day protocols. Day 1 involved morning and afternoon 2-h hyperinsulinemic (9 pmol.kg(-1).min(-1)) euglycemic clamps (PE; n = 14), hypoglycemic clamps (PH; n = 14), or euglycemic clamps with oral fludrocortisone (PE + F; type I agonist, 0.2 mg, n = 14), oral dexamethasone (PE + D; type II agonist, 0.75 mg, n = 13), or both (PE + F + D; n = 14). Day 2 was identical in all protocols and consisted of a 2-h hyperinsulinemic hypoglycemic clamp. Day 2 insulin (625 +/- 40 pmol/l) and glucose (2.9 +/- 0.1 mmol/l) levels were similar among groups. Levels of epinephrine, norepinephrine, glucagon, growth hormone, and MSNA were significantly blunted by prior activation of both type I and type II corticosteroid receptors to PE. Prior activation of both corticosteroid receptors also significantly blunted NEFA during subsequent hypoglycemia. Thus, levels of a wide spectrum of key counterregulatory mechanisms (neuroendocrine, ANS, and metabolic) were blunted by antecedent pharmacological stimulation of either type I or type II corticosteroid receptors in healthy man. These data suggest that activation of type I corticosteroid receptors in man can have acute and profound regulating effects on physiological stress in man. Both type I and type II corticosteroid receptors may be involved in the multiple mechanisms controlling counterregulatory responses to hypoglycemia in healthy man.

Mineralocorticoid effects due to cortisol inactivation overload explain the beneficial use of hydrocortisone in septic shock

The role of corticosteroids in septic shock remains controversial despite their use for over 50 years. Large prospective trials of their use continue with the aim of resolving the controversy. These may well remain indecisive if basic endocrine principles are ignored. Review of the available evidence suggests that use of synthetic glucocorticoids is harmful but hydrocortisone beneficial. Consideration of the basic properties of the corticosteroids used and their receptors suggest an explanation for their differing therapeutic effects. The harmful synthetic glucocorticoids have no or reduced mineralocorticoid effects in contrast with the significant mineralocorticoid effects of hydrocortisone at the doses which have been found to be beneficial. The potent synthetic mineralocorticoid fludrocortisone is well recognised to raise peripheral resistance by sensitising the resistance vessels to endogenous or exogenous catecholamines and also causes metabolic alkalosis. We provide evidence to support our hypothesis that at the doses of hydrocortisone used, cortisol inactivation overload is the basis of the beneficial effect. The consequent mineralocorticoid effects result in increased sensitivity of the resistance vessels to endogenous and exogenous catecholamines with an increase in peripheral resistance correcting shock. In addition the metabolic alkalotic component of mineralocorticoid effect would tend to correct the prevailing metabolic acidosis. Hydrocortisone also has an attenuating, as opposed to the suppressing effect of synthetic glucocorticoids on the immune response which is also regarded as beneficial.

[Synthetic mineralocorticoid]

Fludrocortisone acetate (Florinef) is a synthetic steroid with a potent mineralocorticoid action, and used for treatment of Addison's disease and salt losing form of congenital adrenal hyperplasia. It is also used for severe hypotension to restore adequate plasma volume. Caution is necessary for possible side effects of hypernatremia, hypokalemia, hyperglycemia and congestive heart failure when used chronically. A synthetic steroid which selectively binds and activates renal MR-LBD but not GR, or non-epithelial MR, although not found at present, may be a promising mineralocorticoids to be used in the above disorders.

Hypophyseal corticosteroids stimulate somatotrope differentiation in the embryonic chicken pituitary gland

Although it is known that glucocorticoids induce differentiation of growth hormone (GH)-producing cells in rodents and birds, the effect of mineralocorticoids on GH mRNA expression and the origin of corticosteroids affecting somatotrope differentiation have not been elucidated. In this study, we therefore carried out experiments to determine the effect of mineralocorticoids on GH mRNA expression in the chicken anterior pituitary gland in vitro and to determine whether corticosteroids are synthesized in the chicken embryonic pituitary gland. In a pituitary culture experiment with E11 embryos, both corticosterone and aldosterone stimulated GH mRNA expression and increased the number of GH cells in both lobes of the pituitary gland in a dose-dependent manner. These effects of the corticosteroids were significantly reversed by pretreatment with mifepristone, a glucocorticoid receptor (GR) antagonist, or spironolactone, a mineralocorticoid receptor (MR) antagonist. Interestingly, an in vitro serum-free culture experiment with an E11 pituitary gland showed that the GH mRNA level spontaneously increased during cultivation for 2 days without any extra stimulation, and this increase in GH mRNA level was completely suppressed by metyrapone, a corticosterone-producing enzyme P450C11 inhibitor. Moreover, progesterone, the corticosterone precursor, also stimulated GH mRNA expression in the cultured chicken pituitary gland, and this effect was blocked by pretreatment with metyrapone. We also detected mRNA expression of enzymes of cytochrome P450 cholesterol side chain cleavage (P450scc) and 3beta-hydroxysteroid dehydrogenase1 (3beta-HSD1) in the developmental chicken pituitary gland from E14 and E18, respectively. These results suggest that mineralocorticoids as well as glucocorticoids can stimulate GH mRNA expression and that corticosteroids generated in the embryonic pituitary gland by intrinsic steroidogenic enzymes stimulate somatotrope differentiation.

Superior nuclear receptor selectivity and therapeutic index of methylprednisolone aceponate versus mometasone furoate

Although introduced more than 50 years ago, topical glucocorticoids are still the first line therapy for many inflammatory skin disorders such as atopic eczema, contact dermatitis and many others. Recently, significant improvements have been made to optimize the ratio of desired to unwanted effects. While with early compounds such as triamcinolone, topical side effects such as skin atrophy and telangiectasias can be observed rather frequently, newer drugs such as methylprednisolone aceponate or mometasone furoate have a significantly improved therapeutic index. The present study compared these two modern topical glucocorticoids, which possess the highest therapeutic index currently found, in terms of nuclear receptor selectivity in vitro and induction of the most important local side effects (skin atrophy and telangiectasias) in a relevant rodent model in vivo. We demonstrate that methylprednisolone aceponate displays higher specificity in nuclear receptor binding compared with mometasone furoate. Methylprednisolone aceponate was also markedly superior in terms of minimizing induction of skin atrophy or telangiectasias when compared with mometasone furoate. Based on these observations, methylprednisolone aceponate is expected to have a greater therapeutic index as compared with mometasone furoate, at least in the test systems used here. The degree to which this observation may translate into a clinical setting requires confirmation.

The acceleration of amygdala kindling epileptogenesis by chronic low-dose corticosterone involves both mineralocorticoid and glucocorticoid receptors

We have previously demonstrated that low-dose corticosterone (CS) administration, used as a model of the effect of chronic stress, accelerates epileptogenesis in the electrical amygdala kindling rat model of temporal lobe epilepsy (TLE). This current study examined the relative contributions to this effect of mineralocorticoid (MR) and glucocorticoid (GR) subtypes of glucocorticoid receptors. Female non-epileptic wistar rats 10-13 weeks of age were implanted with a bipolar electrode into the left amygdala. Five treatment groups were subjected to rapid amygdala kindling: water-control (n=9), CS treated (6 mg/100 ml added to drinking water; n=9), CS+spironolactone (MR antagonist, 50 mg/kg sc; n=9), CS+mifepristone (GR antagonist, 25 mg/kg sc; n=9), and CS+both antagonists (n=7). Rats were injected with vehicle or the relevant antagonist twice daily for the entire kindling period. Experimental groups differed significantly in the number of stimulations required to reach the 'fully kindled state' (Racine, 1972) ANOVA, F(4,38)=2.73, p=0.04). Amygdala kindling was accelerated in the CS-treated group compared with water controls (mean stimulations for full kindling: 45.2 vs. 86.5, p<0.01). This acceleration was inhibited by both the MR and GR antagonist treatments (mean stimulations: 69.6 and 70.4, p=0.04 and 0.04 vs. CS group, respectively), with the kindling rates in these groups not significantly different from water-treated subjects (p=0.26 and 0.29, respectively). The kindling rates in the MR and GR antagonist treatment groups did not significantly differ from each other (p=0.93), nor from the combined treatment group (mean stimulations: 62.8, p=0.59 and 0.54, respectively). This study demonstrates that activation of both high-affinity (MR) and low-affinity (GR) glucocorticoid receptors are involved in mediating CS-induced acceleration of amygdala kindling epileptogenesis.

Aldosterone induces circadian gene expression of clock genes in H9c2 cardiomyoblasts

We examined mRNA expression of the clock genes (Per1, Per2, and Bmal1) and PAI-1 (plasminogen activator inhibitor-1) after aldosterone treatment every 4 h up to 48 h in H9c2 cardiomyoblasts by reverse transcription-polymerase chain reaction. To block the MR (mineralocorticoid receptor), the MR antagonist, spironolactone, was added to the medium 1 h before aldosterone treatment. Aldosterone induced an initial increase and rhythmic expression of Per1, while spironolactone attenuated the acute increase in Per1 mRNA induced by aldosterone. On the other hand, aldosterone did not increase the Per2 mRNA in the acute phase, but thereafter induced a rhythmic expression of Per2. Aldosterone also induced rhythmic expression of Bmal1, a positive element of the clock genes. The rhythm of Bmal1 mRNA was anti-phase of that of Per2 mRNA. Aldosterone induced an acute increase in PAI-1 mRNA, but did not induce rhythmic expression of PAI-1. The present study demonstrated first that aldosterone regulates expression of the clock genes Per1, Per2, and Bmal1, and increases PAI-1 expression in H9c2 cardiomyoblasts. Second, an acute increase in Per1 mRNA after aldosterone treatment is mediated through MR. Third, clock genes are not related to PAI-1 expression in H9c2 cardiomyoblasts.

Aldosterone upregulates vascular endothelial growth factor expression in mouse cortical collecting duct epithelial cells through classic mineralocorticoid receptor

Accumulating evidence shows that aldosterone plays an important role in the pathogenesis of renal fibrosis but its mechanism has not been completely defined. Recently, exogenous administration of aldosterone significantly alleviated ischemic states in a model of femoral artery ligated rats, accompanied by an obvious enhancement of VEGF upregulation. We hypothesized that aldosterone may also regulate the expression of VEGF in the kidney. To confirm this, cultured cortical collecting duct epithelial cells (M-1 cell line) were incubated with aldosterone and control media, respectively. The pathway by which aldosterone regulates VEGF expression was tested by the administration of spironolactone, a specific mineralocorticoid receptor (MR) antagonist. VEGF expression was detected by immunofluorescence staining, ELISA, Western blot and RT-PCR. Aldosterone induced an elevation of VEGF excretion in a time- and dose-dependent manner. Western blotting showed a 1.4-fold elevation in cytosolic VEGF expression following aldosterone (10(-8) M) incubation for 48 h (p<0.01). After aldosterone (10(-7) M) incubation for 48 h, the mRNA level of VEGF164 and VEGF120 showed 1.8- and 1.7-fold increases, respectively (p<0.01). This upregulation was almost completely blocked by spironolactone as shown both by mRNA levels and cytosolic protein levels. In addition, the mRNA of aldosterone receptor was detected in M-1 cells. We demonstrated for the first time that aldosterone induced VEGF expression in M-1 cells, an effect mediated by classic mineralocorticoid receptor. This finding provides experimental evidence for the local non-hemodynamic action of aldosterone.

Drospirenone increases endothelial nitric oxide synthesis via a combined action on progesterone and mineralocorticoid receptors

BACKGROUND

Progestins have actions on the cardiovascular system, which depend on the structure as well as on receptor binding characteristics. Drospirenone (DRSP) is a progestin that uniquely interferes with the signaling of the mineralocorticoid receptor (MR). Hormone therapy containing DRSP results in blood pressure reduction in hypertensive post-menopausal women.

METHODS

We describe the effects of DRSP on endothelial nitric oxide (NO) synthesis and compare them with those of progesterone (P) and of medroxyprogesterone acetate (MPA). In addition, we herein tested the relevance of the anti-mineralocorticoid activity of DRSP for NO synthesis.

RESULTS

DRSP results in rapid activation of the endothelial NO synthase (eNOS) through mitogen-activated protein kinases and phosphatidylinositol 3-kinase as well as in enhanced eNOS expression. These actions depend on P receptor. When the cells are exposed to aldosterone, a reduction of eNOS expression is found that is antagonized by DRSP. This action is not shared by P or MPA. In addition, DRSP does not interfere with the induction or activation of eNOS induced by estradiol, as opposed to MPA.

CONCLUSIONS

DRSP acts on endothelial cells via a combined action through the P and MRs. These results help to interpret the anti-hypertensive effects of hormonal therapies containing DRSP.

Corticosteroid receptor-mediated mechanisms in the amygdala regulate anxiety and colonic sensitivity

Our previous studies have shown that stereotaxic implantation of corticosterone (Cort) onto the central amygdaloid nucleus increases both anxiety and colonic sensitivity. The goal of this study was to examine the relative importance of amygdaloid glucocorticoid (GR) and mineralocorticoid receptor (MR)-mediated mechanisms in the induction of anxiety and colonic hypersensitivity. In male Fischer 344 rats, Cort or cholesterol micropellets were stereotaxically implanted bilaterally at the dorsal boundary of the central amygdaloid nucleus either alone or in combination with a GR antagonist, mifepristone, or a MR antagonist, spironolactone. Anxiety was assessed on the elevated plus maze and quantified as the percentage of time spent in open arm exploration. Colonic sensitivity was measured by recording a visceromotor response, the number of abdominal muscle contractions in response to colorectal distension. In Cort-implanted rats there was a significant reduction in the percentage of time spent in the open arms of the elevated plus maze compared with cholesterol controls, indicating increased anxiety. Furthermore, colonic hypersensitivity was observed in response to colorectal distension compared with rats with cholesterol implants. In rats with Cort implants combined with either a GR or MR antagonist, there was a significant inhibition of anxiety and colonic hypersensitivity. Our data suggest that both GR and MR play a critical role in Cort-induced anxiety and colonic hypersensitivity.

Effects of repeated prenatal glucocorticoid exposure on long-term potentiation in the juvenile guinea-pig hippocampus

Synthetic glucocorticoids (sGCs) are routinely used to treat women at risk of preterm labour to promote fetal lung maturation. There is now strong evidence that exposure to excess glucocorticoid during periods of rapid brain development has permanent consequences for endocrine function and behaviour in the offspring. Prenatal exposure to sGC alters the expression of N-methyl-D-aspartate receptor (NMDA-R) subunits in the fetal and neonatal hippocampus. Given the integral role of the NMDA-R in synaptic plasticity, we hypothesized that prenatal sGC exposure will have effects on hippocampal long-term potentiation (LTP) after birth. Further, this may occur in either the presence or absence of elevated cortisol concentrations, in vitro. Pregnant guinea-pigs were injected with betamethasone (Beta, 1 mg kg(-1)) or vehicle on gestational days (gd) 40, 41, 50, 51, 60 and 61 (term approximately 70 days), a regimen comparable to that given to pregnant women. On postnatal day 21, LTP was examined at Schaffer collateral synapses in the CA1 region of hippocampal slices prepared from juvenile animals exposed to betamethasone or vehicle, in utero. Subsequently, the acute glucocorticoid receptor (GR)- and mineralocorticoid receptor (MR)-dependent effects of cortisol (0.1-10 microM; bath applied 30 min before LTP induction) were examined. There was no effect of prenatal sGC treatment on LTP under basal conditions. The application of 10 microM cortisol depressed excitatory synaptic transmission in all treatment groups regardless of sex. Similarly, LTP was depressed by 10 microM cortisol in all groups, with the exception of Beta-exposed females, in which LTP was unaltered. Hippocampal MR and GR protein levels were increased in Beta-exposed females, but not in any other prenatal treatment group. This study reveals sex-specific effects of prenatal exposure to sGC on LTP in the presence of elevated cortisol, a situation that would occur in vivo during stress.

Mineralocorticoid Receptor Activation Promotes Vascular Cell Calcification

OBJECTIVE

Clinical studies demonstrate that mineralocorticoid receptor (MR) antagonism improves outcomes in cardiovascular patients and that vascular calcification correlates with adverse cardiac events. We have recently demonstrated that human vascular smooth muscle cells (VSMCs) express functional MRs that, in response to aldosterone, modulate expression of osteogenic genes including alkaline phosphatase (ALP) and bone morphogenetic protein-2 (BMP2). This study examines the effects of MR activation by aldosterone on the process of in vitro vascular calcification.

METHODS AND RESULTS

Using immunoblotting and adenoviral promoter-reporter assays, we demonstrated that calcifying vascular cells (CVCs), an in vitro model of vascular calcification, express MRs that mediate both aldosterone- and cortisol-stimulated gene transcription. In this model, aldosterone stimulated ALP activity, an early marker of osteoblastic differentiation, as well as mineralization. Aldosterone antagonism with spironolactone abolished both effects implicating CVC MRs in the mechanism of aldosterone-stimulated vascular calcification. Inhibition of BMP2 signaling by overexpression of dominant negative BMP2 receptor did not attenuate aldosterone-induced osteoblastic differentiation.

CONCLUSIONS

Aldosterone activation of MR promotes osteoblastic differentiation and mineralization of VSMCs independent of BMP2 signaling. These data provide a mechanistic link between hormone-mediated VSMC MR activation and vascular calcification, two processes associated with increased risk of cardiovascular ischemic events in humans.

Long-term imipramine treatment affects rat brain and pituitary corticosteroid receptors and heat shock proteins levels in a gender-specific manner

Gender-related differences in the effects of imipramine, on the protein levels of glucocorticoid receptor (GR), and heat shock proteins Hsp90 and Hsp70, as well as on dexamethasone binding to corticosteroid receptors (CRs) in the pituitary, hypothalamus, hippocampus and brain cortex of non-depressed rats were studied. Differences between female and male animals in the GR protein level in the tissues of untreated animals were not noticed. However, imipramine led to opposite changes in the cellular level of GR protein in the brain of female and male rats, as well as to gender- and tissue-specific changes in in vitro dexamethasone binding to GR and mineralocorticoid receptor (MR) in the hippocampus and brain cortex. Gender-related differences in the expression of Hsp90 and Hsp70 were noticed mainly in the hippocampus, only after imipramine treatment. The observed changes in the response of GR to imipramine suggest that this antidepressant may affect both the level of the receptor protein and the mechanisms regulating its binding ability in a gender-related manner.

Effects of aldosterone receptor blockade in patients with mild-moderate heart failure taking a beta-blocker

AIMS

Spironolactone improves prognosis in severe heart failure (HF). We investigated its effects in patients with mild-moderate HF treated with an ACE inhibitor and beta-blocker.

METHODS AND RESULTS

Randomised, double-blind, parallel-group, 3-month comparison of placebo and spironolactone (25 mg daily) in 40 patients in New York Heart Association (NYHA) class I (20%), II (70%) or III (10%), with a left ventricular ejection fraction of <40%. The mean (standard error) changes from baseline in the spironolactone and placebo groups were, respectively: i) B-type natriuretic peptide (BNP) -53.4(22.2) pg/mL and +3.3(12.1) pg/mL, P=0.04, ii) pro-collagen type III N-terminal amino peptide (PIIINP) -0.6(0.2) micromol/L and +0.02(0.2) micromol/L, P=0.02 and iii) creatinine +10.7(3.2) micromol/L and -0.3(2.6) micromol/L, P=0.01. Compared with placebo, spironolactone therapy was associated with a reduction in self-reported health-related quality of life: change in visual analog score: -6 (3) vs. +6 (4); P=0.01. No differences were observed on other biochemical, neurohumoral, exercise and autonomic function assessments.

CONCLUSION

In patients with mild-moderate HF, spironolactone reduced neurohumoral activation (BNP) and a marker of collagen turnover (PIIINP) but impaired renal function and quality of life. The benefit-risk ratio of aldosterone blockade in mild HF is uncertain and requires clarification in a large randomised trial.

The effects of antidepressants on the hypothalamic-pituitary-adrenal axis

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis has been found in some psychiatric disorders, especially in older patients with severe depression. Altered feedback inhibition, as demonstrated by increased circulating cortisol and nonsuppresssion of cortisol following administration of dexamethasone, may be to blame. Two glucocorticoid receptors control the HPA axis, the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). MR regulates normal HPA fluctuations and the GR regulates in times of stress. Long-term antidepressant treatment in humans has been shown to upregulate both GR and MR in the brain, whereas short-term treatment has been shown to downregulate GR and MR. After 6-9 weeks of treatment GR function returns to normal, and the MR stays upregulated. Chronic antidepressant treatment in rodents has been shown to reduce HPA activity, even in the absence of GR or MR upregulation. These effects of antidepressants on HPA regulation may be attributed in part to regulation of the multidrug resistance protein transporter, P-glycoprotein. Finding relationships between antidepressant action and HPA regulation leads to the conclusion that the disruption of the HPA may be more a contributing factor to depression than other biological abnormalities.

α-Methyltryptamine sulfonamide derivatives as novel glucocorticoid receptor ligands

Alpha-methyltryptamine sulfonamides were identified as human glucocorticoid receptor (hGR) ligands in an ultra high throughput screening (UHTS) campaign. Described will be the hit-to-lead activities, including parallel and single point analog synthesis to map the scaffold. Ligands were identified that exhibited 30 nM binding to hGR. The SAR and selectivity of these compounds will be discussed.

Specific configuration of dendritic degeneration in pyramidal neurons of the medial prefrontal cortex induced by differing corticosteroid regimens

We previously demonstrated that hypercorticalism induces pronounced volumetric reductions in the rat medial prefrontal cortex (mPFC) and that these structural changes correlate with deficits in executive function. By applying 3-dimensional analysis of Golgi-Cox-stained material, we now demonstrate that corticosteroids can exert differential effects on dendritic arborizations of pyramidal neurons in lamina II/III of the mPFC. Treatment with the glucocorticoid receptor-selective agonist dexamethasone and with the natural adrenosteroid, corticosterone (CORT), results in significant reductions in the total length of apical dendrites in the pyramidal neurons in lamina II/III of the anterior cingulate/prelimbic and infralimbic cortices. Interestingly, although these treatments do not affect the number of dendritic branches, they are associated with impoverished arborizations in their distal portions and, in CORT-treated animals, with increased branching in the middle portions of the apical dendritic tree. Deprivation of corticosteroids by adrenalectomy leads to decreases in total apical dendritic length and spine number, but in this case, dendritic impoverishment was restricted to the middle/proximal segments of the dendritic trees. None of the treatments influenced the architecture of the basal dendrites. These results add to our knowledge of the morphological substrates through which corticosteroids may disrupt mPFC-dependent behaviors.

Chronic prenatal ethanol exposure increases glucocorticoid-induced glutamate release in the hippocampus of the near-term foetal guinea pig

Exposure to high cortisol concentration can injure the developing brain, possibly via an excitotoxic mechanism involving glutamate (Glu). The present study tested the hypothesis that chronic prenatal ethanol exposure (CPEE) activates the foetal hypothalamic-pituitary-adrenal axis to produce high cortisol exposure in the foetal compartment and alters sensitivity to glucocorticoid-induced Glu release in the foetal hippocampus. Pregnant guinea pigs received daily oral administration of ethanol (4 g/kg maternal body weight/day) or isocaloric-sucrose/pair-feeding from gestational day (GD) 2 until GD 63 (term, approximately GD 68) at which time they were euthanised, 1 h after their final treatment. Adrenocorticotrophic hormone (ACTH) and cortisol concentrations were determined in foetal plasma. Basal and electrically stimulated Glu and gamma-aminobutyric acid (GABA) efflux in the presence or absence of dexamethasone (DEX), a selective glucocorticoid-receptor agonist, were determined ex vivo in foetal hippocampal slices. Glucocorticoid receptor (GR), mineralocorticoid receptor (MR) and N-methyl-D-aspartate (NMDA) receptor NR1 subunit mRNA expression were determined in situ in the hippocampus and dentate gyrus. In the near-term foetus, CPEE increased foetal plasma ACTH and cortisol concentrations. Electrically stimulated glutamate, but not GABA, release was increased in CPEE foetal hippocampal slices. Low DEX concentration (0.3 microM) decreased stimulated glutamate, but not GABA, release in both CPEE and control foetal hippocampal slices. High DEX concentration (3.0 microM) increased basal release of Glu, but not GABA, in CPEE foetal hippocampal slices. GR, but not MR, mRNA expression was elevated in the hippocampus and dentate gyrus, whereas NR1 mRNA expression was increased in the CA1 and CA3 fields of the foetal hippocampus. These data demonstrate that CPEE increases high glucocorticoid concentration-induced Glu release in the foetal hippocampus, presumably as a consequence of increased GR expression. These effects of CPEE, coupled with increased glutamate release and increased NMDA receptor expression, may predispose the near-term foetal hippocampus to GR and Glu-NMDA receptor-mediated neurodevelopmental toxicity.

Role of glucocorticoid receptor in acclimation of killifish (Fundulus heteroclitus) to seawater and effects of arsenic

Killifish are euryhaline teleosts that adapt to rapid changes in the salinity of the seawater. It is generally accepted that acclimation to seawater is mediated by cortisol activation of the glucocorticoid receptor (GR), which stimulates CFTR mRNA expression and CFTR-mediated Cl- secretion by the gill. Because there is no direct evidence in killifish that the GR stimulates CFTR gene expression, quantitative PCR studies were conducted to test the hypothesis that cortisol activation of GR upregulates CFTR mRNA expression and that this response is required for acclimation to seawater. Inhibition of the GR by RU-486 prevented killifish from acclimating to increased salinity and blocked the increase in CFTR mRNA. In contrast, inhibition of the mineralocorticoid receptor by spironolactone had no effect on acclimation to seawater. Thus acclimation to increased salinity in killifish requires signaling via the GR and includes an increase in CFTR gene expression. Because arsenic, a toxic metalloid that naturally occurs in the aquatic environment, has been shown to disrupt GR transcriptional regulation in avian and mammalian systems, studies were also conducted to determine whether arsenic disrupts cortisol-mediated activation of CFTR gene expression in this in vivo fish model and thereby blocks the ability of killifish to acclimate to increased salinity. Arsenic prevented acclimation to seawater and decreased CFTR protein abundance. However, arsenic did not disrupt the GR-induced increase in CFTR mRNA. Thus arsenic blocks acclimation to seawater in killifish by a mechanism that does not disrupt GR-mediated induction of CFTR gene expression.

Analysis of aldosterone-induced differential receptor-independent protein patterns using 2D-electrophoresis and mass spectrometry

In the human body the mineralocorticoid aldosterone is responsible for maintaining water and electrolyte homeostasis and therefore controlling blood pressure. In addition, aldosterone has recently been associated with severe heart failure. Besides receptor-dependent action, the damaging effects of aldosterone may also be partly mediated through non-genomic mechanisms. The present study focuses on the mineralocorticoid receptor-independent action of aldosterone at the protein level. We chose the fission yeast Schizosaccharomyces pombe as a model organism, since this yeast does not contain nuclear steroid receptors, but many genes and regulatory mechanisms that are close to those of mammals. Using 2D-electrophoresis we identified for the first time protein spots affected by aldosterone in a nuclear receptor-free system. Mass spectrometry analysis using MALDI-TOF MS and nanoLC-MS/MS approaches allowed the unambiguous identification of 11 proteins that showed increased or decreased levels, which may represent newly identified players and pathways of aldosterone-induced action. Two proteins with a connection to osmotic regulation (NAD-dependent malic enzyme and glycerol-3-phosphate-dehydrogenase), as well as two proteins involved in the overall organization of the cytoskeleton, vip1 and glyceraldehyde-3-phosphate dehydrogenase, which was also found to be specifically affected by aldosterone in human HCT116 cells, are discussed.

Corticosterone can act at the posterior paraventricular thalamus to inhibit hypothalamic-pituitary-adrenal activity in animals that habituate to repeated stress

Glucocorticoids released by stress bind to glucocorticoid (GR) and/or mineralocorticoid receptors (MR) to exert negative feedback of subsequent hypothalamic-pituitary-adrenal (HPA) responses to stress. Feedback inhibition is implicated in habituation of HPA activity to repeated exposure to the same (homotypic) stressor. We hypothesized that the posterior paraventricular thalamus (pPVTh) is a site where corticosterone acts to exert negative feedback during repeated stress and that is important for habituation. As previously reported, the pPVTh inhibits HPA responses to homotypic and heterotypic stressors in repeatedly, but not acutely, stressed rats. We conducted a series of experiments involving intra-pPVTh administration of MR and/or GR agonists or antagonists during different time frames over 8 d of restraint. MR exist in the pPVTh, as do GR as shown by our immunocytochemical results. Acute intra-pPVTh injection of MR and/or GR antagonist before the eighth restraint did not alter expression of habituation. Because habituation may develop before d 8, we manipulated GR and MR in the pPVTh throughout 8 d of stress using intra-pPVTh corticosterone implants, which enhanced habituation on d 8 without affecting acute stress responses. Conversely, daily intra-pPVTh injections of GR and MR antagonists on d 1-7 of restraint prevented habituation on d 8. These data suggest that corticosterone released during repeated stress can act at GR and MR in the pPVTh to inhibit HPA responses to homotypic stress. We also found that some GR-containing cells in the pPVTh project to the medial prefrontal cortex and basolateral amygdala, suggesting that pPVTh-induced inhibition of HPA activity is potentially mediated by its projections to these select limbic structures.

Mineralocorticoid receptor function in posttraumatic stress disorder after pretreatment with metyrapone

BACKGROUND

Alterations of mineralocorticoid receptor (MR) mediated negative feedback inhibition of cortisol might contribute to abnormalities of hypothalamic-pituitary adrenal (HPA) activity in posttraumatic stress disorder (PTSD).

METHODS

In a placebo-controlled study, we examined 11 subjects with PTSD and 11 healthy controls between 14:00 and 21:00. After pretreatment with 3 g metyrapone to inhibit basal endogenous cortisol secretion, subjects orally received in randomized order .5 mg of the MR agonist fludrocortisone or placebo. Adrenocorticotropic hormone (ACTH), cortisol, and 11-deoxycortisol were measured every 30 min until 21:00.

RESULTS

Compared to placebo, fludrocortisone led to a significant decrease of ACTH and cortisol that was similar in both groups. Subjects with PTSD had higher raw cortisol and higher normed (baseline-related) ACTH and 11-deoxycortisol values after metyrapone independent of treatment with fludrocortisone or placebo.

CONCLUSIONS

While HPA responses after metyrapone seem to be stronger in PTSD compared to controls, no alterations of mineralocorticoid receptor function in PTSD were found in this study.

Mineralocorticoid receptor antagonist spironolactone prevents pig serum-induced hepatic fibrosis in rats

Mineralocorticoid receptor (MR) antagonist spironolactone (SPL) is an effective agent for prevention of cardiovascular injury. However, whether and how SPL ameliorates hepatic fibrosis in rats is unknown. Pig serum (PS) (0.5 mL, twice a week, ip) or vehicle-administered rats for 12 weeks were used as rats with hepatic fibrosis or control rats, respectively. Rats given PS were treated with SPL (50 mg/kg/day, sc) for 12 weeks. Hepatic fibrosis, using picro-sirius red staining and determination of hydroxyproline content, immunohistochemistries of alpha-smooth muscle actin (alpha-SMA)-positive hepatic stellate cells (HSCs), Na/H exchange isoform-1 (NHE-1) protein, CYP11B2 aldosterone synthase protein for liver tissues, and plasma aldosterone concentrations were compared among the 3 groups of rats. Rats given PS alone exhibited hepatic fibrosis as well as increases in the number of the alpha-SMA-positive HSCs and NHE-1 protein expression in HSCs and hepatocytes, all of which were suppressed by SPL. Rats given PS alone revealed increased CYP11B2 protein expression in HSCs and hepatocytes, which was not inhibited by SPL. Plasma aldosterone concentrations were significantly greater in rats given PS and SPL than in control rats and rats given PS alone, although they were not different between control rats and rats given PS alone. PS-induced hepatic fibrosis together with HSC activation and NHE-1 protein expression occurs via MRs, and SPL ameliorates hepatic fibrosis presumably via the inhibition of HSC activation and NHE-1 protein expression in PS-induced liver injuries. The aldosterone produced in the injured liver contributes to the PS-induced hepatic fibrosis.

Non-steroidal steroid receptor modulators

The discovery and launch of non-steroidal ligands for estrogen receptors (ERs) and for androgen receptors (ARs) demonstrated the potential of these ligands as therapeutic agents. Based on these successes, substantial attention in the past ten years has been focused on identifying non-steroidal ligands for all of the classic steroid receptors. Non-steroidal ligands are currently in the discovery phase or in early clinical development for glucocorticoid, mineralocorticoid and progesterone receptors, and therefore must still provide evidence of their beneficial features over their steroidal counterparts. Although many new compounds for ERs and ARs are also undergoing discovery phase investigation or (early) development, none have been launched in the past ten years. The complexity of steering functional selectivity remains an ongoing challenge in the development on non-steroidal ligands.

Cortisol metabolism in the Bolivian squirrel monkey (Saimiri boliviensis boliviensis)

New World squirrel monkeys (Saimiri spp.) have high circulating cortisol levels but normal electrolytes and blood pressures. The goal of the present study was to gain insight into adaptive mechanisms used by Bolivian squirrel monkeys to minimize the effects of high cortisol on mineralocorticoid receptor (MR) activity and electrolyte and water balance. Aldosterone levels in serum from 10 squirrel monkeys were 17.7 +/- 3.4 ng/dl (normal range in humans, 4 to 31 ng/dl), suggesting that squirrel monkeys do not exhibit a compensatory increase in aldosterone. The squirrel monkey MR was cloned and expressed in COS-7 cells and found to have similar responsiveness to cortisol and aldosterone as human MR, suggesting that squirrel monkey MR is not inherently less responsive to cortisol. To determine whether altered metabolism of cortisol might contribute to MR protection in squirrel monkeys, serum and urinary cortisol and cortisone were measured, and a comprehensive urinary corticosteroid metabolite profile was performed in samples from anesthetized and awake squirrel monkeys. The levels of cortisone exceeded those of cortisol in serum and urine, suggesting increased peripheral 11beta-hydroxysteroid dehydrogenase 2 activity in squirrel monkeys. In addition, a significant fraction (approximately 20%) of total corticosteroids excreted in the urine of squirrel monkeys appeared as 6beta-hydroxycortisol, compared with that in man (1%). Therefore, changes in cortisol metabolism likely contribute to adaptive mechanisms used by Bolivian squirrel monkeys to minimize effects of high cortisol.

Discovery and SAR study of novel dihydroquinoline containing glucocorticoid receptor ligands

We report the discovery of a novel class of glucocorticoid receptor (GR) ligands based on 1,2-dihydroquinoline molecular scaffold. The compounds exhibit good GR binding affinity and selectivity profile against other nuclear hormone receptors.

Mineralocorticoid Receptor Activation Causes Cerebral Vessel Remodeling and Exacerbates the Damage Caused by Cerebral Ischemia

Mineralocorticoid receptor antagonists protect against ischemic cerebrovascular disease; this appears to be caused by changes in cerebral vessel structure that would promote blood flow. Therefore, we hypothesized that mineralocorticoid receptor activation with deoxycorticosterone acetate would cause deleterious remodeling of the cerebral vasculature and exacerbate the damage caused by cerebral ischemia. Six-week-old male Wistar rats were treated with deoxycorticosterone acetate (200 mg/kg) for 6 weeks. At 12 weeks of age, the deoxycorticosterone acetate-treated rats had elevated systolic blood pressure compared with age-matched controls (157+/-5.9 versus 124+/-3.1 mm Hg deoxycorticosterone acetate versus control; P<0.05). The area of ischemic damage resulting from middle cerebral artery occlusion was greater in the deoxycorticosterone acetate-treated rats than control (63.5+/-3.72 versus 46.6+/-5.52% of the hemisphere infarcted, deoxycorticosterone acetate versus control; P<0.05). Middle cerebral artery structure was assessed using a pressurized arteriograph under calcium-free conditions. Over a range of intralumenal pressures, the lumen and ODs of the middle cerebral arteries were smaller in the deoxycorticosterone acetate-treated rats than the control rats (P<0.05). There was also an increase in the wall thickness and wall:lumen ratio in the vessels from deoxycorticosterone acetate-treated rats (P<0.05). The vessels from the deoxycorticosterone acetate-treated rats were stiffer than those from control rats as evidenced by a leftward shift in the stress/strain curve. These novel data suggest that mineralocorticoid receptor activation without salt loading and nephrectomy is sufficient to elicit deleterious effects on the cerebral vasculature that lead to inward hypertrophic remodeling and an increase in the ischemic damage in the event of a stroke.

The acute anticonvulsant effects of deoxycorticosterone in developing rats: role of metabolites and mineralocorticoid-receptor responses

PURPOSE

The mechanisms that mediate the acute anticonvulsant effects of deoxycorticosterone (DOC) were investigated in young rats.

METHODS

Fifteen-day-old rats were pretreated with a variety of compounds, including (a) agonists of the receptors that bind DOC (mineralocorticoid receptors); (b) the DOC 5alpha- and 5alpha-3alpha-reduced metabolites, plus agonists that bind the receptors of the 5alpha-reduced metabolite of DOC (progesterone receptors); and (c) DOC itself in the presence and absence of metabolism and receptor blockers. Fifteen minutes later, pentylenetetrazol (PTZ) was administered, and maximal pentylenetetrazol (MMT) seizure responses were scored.

RESULTS

Agonists of mineralocorticoid receptors increased the latency to forelimb flexion in PTZ seizures and sometimes suppressed the seizures completely. At low, nonconvulsant doses, spironolactone (a mineralocorticoid-receptor antagonist) blocked the anticonvulsant effects of a nonsedating, but not a sedating, dose of DOC. These data suggest the possible direct involvement of mineralocorticoid receptors in the anticonvulsant effects of DOC. At low, nonconvulsant doses, finasteride (which blocks the metabolism of DOC) partially blocked the protective effects of DOC, suggesting the contribution of metabolites to the anticonvulsant actions of DOC. Dihydrodeoxycorticosterone (DHDOC)-the first metabolite of DOC, an agonist at progesterone receptors, and an allosteric modulator of the gamma-aminobutyric acid (GABA)(A) receptor-and tetrahydrodeoxycorticosterone, a secondary metabolite of DOC and an allosteric modulator of the GABA(A) receptor, both blocked MMT seizures.

CONCLUSIONS

These findings suggest that both DOC and its metabolites may contribute to the anticonvulsant effects seen in young rats, perhaps acting via interactions with several different receptors.

Genomic and nongenomic effects of aldosterone in the rat heart: why is spironolactone cardioprotective?

1. Mineralocorticoid receptor (MR) antagonism with spironolactone reduces mortality in heart failure on top of ACE inhibition. To investigate the underlying mechanism, we compared the actions of both aldosterone and spironolactone to those of angiotensin (Ang) II in the rat heart. 2. Hearts of male Wistar rats were perfused according to Langendorff. Ang II and aldosterone increased left ventricular pressure (LVP) by maximally 11+/-4 and 9+/-2%, and decreased coronary flow (CF) by maximally 36+/-7 and 20+/-4%, respectively. Spironolactone did not significantly affect LVP or CF. 3. In hearts that were exposed to a 45-min coronary artery occlusion and 3 h of reperfusion, a 15-min exposure to spironolactone prior to occlusion reduced infarct size (% of risk area) from 68+/-2 to 45+/-3%, similar to the reduction (34+/-2%) observed following 'preconditioning' (15 min occlusion followed by 10 min reperfusion) prior to the 45-min occlusion. Aldosterone exposure did not affect infarct size (71+/-5%). 4. In cardiomyocytes, aldosterone decreased [(3)H]thymidine incorporation maximally by 73+/-3%, whereas in cardiac fibroblasts it decreased [(3)H]proline incorporation by 33+/-7%. Spironolactone inhibited both effects. Ang II increased DNA and collagen synthesis, and these effects were reversed by aldosterone. 5. In conclusion, aldosterone induces positive inotropic and vasoconstrictor effects in a nongenomic manner, and these effects are comparable to those of Ang II. Aldosterone reduces DNA and collagen synthesis via MR activation, and counteracts the Ang II-induced increases in these parameters. MR blockade reduces infarct size and increases LVP recovery following coronary artery occlusion. The MR-related phenomena may underlie, at least in part, the beneficial actions of spironolactone in heart failure.

Chronic prenatal ethanol exposure alters glucocorticoid signalling in the hippocampus of the postnatal Guinea pig

The present study tested the hypothesis that chronic prenatal ethanol exposure causes long-lasting changes in glucocorticoid signalling in postnatal offspring. Pregnant guinea pigs were treated with ethanol (4 g/kg maternal body weight/day), isocaloric-sucrose/pair-feeding or water throughout gestation, and maternal saliva cortisol concentration was determined 2 h after treatment at different stages of gestation. Electrically-stimulated release of glutamate and GABA, in the presence or absence of dexamethasone, as well as glucocorticoid and mineralocorticoid receptor mRNA expression, was determined in the hippocampus and prefrontal cortex of adult offspring of treated pregnant guinea pigs. Maternal saliva cortisol concentration increased throughout pregnancy, which was associated with increased foetal plasma and amniotic fluid cortisol concentration. Ethanol administration to pregnant guinea pigs increased maternal saliva cortisol concentration during early and mid-gestation. In late gestation, ethanol administration did not increase saliva cortisol concentration above that induced by pregnancy. Chronic prenatal ethanol exposure had no effect on stimulated glutamate or GABA release, but selectively prevented dexamethasone-mediated suppression of stimulated glutamate release, and decreased expression of mineralocorticoid, but not glucocorticoid, receptor mRNA in the hippocampus of adult offspring. These data indicate that maternal ethanol administration leads to excessively increased maternal cortisol concentration that can impact negatively the developing foetal brain, leading to persistent postnatal deficits in glucocorticoid regulation of glutamate signalling in the adult hippocampus.