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

OBJECTIVE: Carbonyl reductase 1 (Cbr1), a recently discovered contributor to tissue glucocorticoid metabolism converting corticosterone to 20ß-dihydrocorticosterone (20ß-DHB), is upregulated in adipose tissue of obese humans and mice and may contribute to cardiometabolic complications of obesity. This study tested the hypothesis that Cbr1-mediated glucocorticoid metabolism influences glucocorticoid and mineralocorticoid receptor activation in adipose tissue and impacts glucose homeostasis in lean and obese states. METHODS: The actions of 20ß-DHB on corticosteroid receptors in adipose tissue were investigated first using a combination of in silico, in vitro, and transcriptomic techniques and then in vivo administration in combination with receptor antagonists. Mice lacking one Cbr1 allele and mice overexpressing Cbr1 in their adipose tissue underwent metabolic phenotyping before and after induction of obesity with high-fat feeding. RESULTS: 20ß-DHB activated both the glucocorticoid and mineralocorticoid receptor in adipose tissue and systemic administration to wild-type mice induced glucose intolerance, an effect that was ameliorated by both glucocorticoid and mineralocorticoid receptor antagonism. Cbr1 haploinsufficient lean male mice had lower fasting glucose and improved glucose tolerance compared with littermate controls, a difference that was abolished by administration of 20ß-DHB and absent in female mice with higher baseline adipose 20ß-DHB concentrations than male mice. Conversely, overexpression of Cbr1 in adipose tissue resulted in worsened glucose tolerance and higher fasting glucose in lean male and female mice. However, neither Cbr1 haploinsfficiency nor adipose overexpression affected glucose dyshomeostasis induced by high-fat feeding. CONCLUSIONS: Carbonyl reductase 1 is a novel regulator of glucocorticoid and mineralocorticoid receptor activation in adipose tissue that influences glucose homeostasis in lean mice.

Antifungal therapy with azoles and the syndrome of acquired mineralocorticoid excess.

The syndromes of mineralocorticoid excess describe a heterogeneous group of clinical manifestations leading to endocrine hypertension, typically either through direct activation of mineralocorticoid receptors or indirectly by impaired pre-receptor enzymatic regulation or through disturbed renal sodium homeostasis. The phenotypes of these disorders can be caused by inherited gene variants and somatic mutations or may be acquired upon exposures to exogenous substances. Regarding the latter, the symptoms of an acquired mineralocorticoid excess have been reported during treatment with azole antifungal drugs. The current review describes the occurrence of mineralocorticoid excess particularly during the therapy with posaconazole and itraconazole, addresses the underlying mechanisms as well as inter- and intra-individual differences, and proposes a therapeutic drug monitoring strategy for these two azole antifungals. Moreover, other therapeutically used azole antifungals and ongoing efforts to avoid adverse mineralocorticoid effects of azole compounds are shortly discussed.

Molecular mechanisms of posaconazole- and itraconazole-induced pseudohyperaldosteronism and assessment of other systemically used azole antifungals.

Recent reports described cases of severe hypertension and hypokalemia accompanied by low renin and aldosterone levels during antifungal therapy with posaconazole and itraconazole. These conditions represent characteristics of secondary endocrine hypertension caused by mineralocorticoid excess. Different mechanisms can cause mineralocorticoid excess, including inhibition of the adrenal steroidogenic enzymes CYP17A1 and CYP11B1, inhibition of the peripheral cortisol oxidizing enzyme 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2) or direct activation of the mineralocorticoid receptor (MR). Compared to previous experiments revealing a threefold more potent inhibition of 11ß-HSD2 by itraconazole than with posaconazole, the current study found sevenfold stronger CYP11B1 inhibition by posaconazole over itraconazole. Both compounds most potently inhibited CYP11B2. The major pharmacologically active itraconazole metabolite hydroxyitraconazole (OHI) resembled the effects of itraconazole but was considerably less active. Molecular modeling calculations assessed the binding of posaconazole, itraconazole and OHI to 11ß-HSD2 and the relevant CYP enzymes, and predicted important interactions not formed by the other systemically used azole antifungals, thus providing an initial explanation for the observed inhibitory activities. Together with available clinical observations, the presented data suggest that itraconazole primarily causes pseudohyperaldosteronism through cortisol-induced MR activation due to 11ß-HSD2 inhibition, and posaconazole by CYP11B1 inhibition and accumulation of the mineralocorticoids 11-deoxycorticosterone and 11-deoxycortisol because of hypothalamus-pituitary-adrenal axis (HPA) feedback activation. Therapeutic drug monitoring and introduction of upper plasma target levels may help preventing the occurrence of drug-induced hypertension and hypokalemia. Furthermore, the systemically used azole antifungals voriconazole, isavuconazole and fluconazole did not affect any of the mineralocorticoid excess targets, offering alternative therapeutic options.

Drug-induced endocrine blood pressure elevation.

Patients with uncontrolled hypertension are at risk for cardiovascular complications. The majority of them suffers from unidentified forms of hypertension and a fraction has so-called secondary hypertension with an identifiable cause. The patient's medications, its use of certain herbal supplements and over-the-counter agents represent potential causal factors for secondary hypertension that are often overlooked. The current review focuses on drugs that are likely to elevate blood pressure by affecting the human endocrine system at the level of steroid synthesis or metabolism, mineralocorticoid receptor activity, or by affecting the catecholaminergic system. Drugs with known adverse effects but where benefits outweigh their risks, drug candidates and market withdrawals are reviewed. Finally, potential therapeutic strategies are discussed.

Profiling of anabolic androgenic steroids and selective androgen receptor modulators for interference with adrenal steroidogenesis.

Anabolic-androgenic steroids (AAS) are testosterone derivatives developed for steroid-replacement and treatment of debilitating conditions. They are widely used by athletes in elite sports and bodybuilding due to their muscle-building and performance-enhancing properties. Excessive AAS use is associated with cardiovascular diseases, mood changes, endocrine and metabolic disorders; however, the underlying mechanisms remain unknown. Selective androgen receptor modulators (SARMs) aim to reduce adverse androgenic effects, while maximizing anabolic effects. This study assessed potential steroidogenic disturbances of 19 AAS and 3 SARMs in human adrenocortical carcinoma H295R cells, comparing basal and forskolin-activated states by mass spectrometry-based quantification of nine major adrenal steroids. Mesterolone, mestanolone and methenolone increased mineralocorticoid but decreased adrenal androgen production, indicating CYP17A1 dysfunction. Cell-free activity assays failed to detect direct CYP17A1 inhibition, supported by molecular modeling. The mRNA expression levels of 3ß-HSD2, CYP17A1, CYP21A2, CYP11B1 and CYP11B2 were unaffected, suggesting indirect inhibition involving post-translational modification and/or impaired protein stability. Clostebol and oxymetholone decreased corticosteroid but increased dehydroepiandrosterone biosynthesis in H295R cells, suggesting CYP21A2 inhibition, sustained by molecular modeling. These AAS did not affect the expression of key steroidogenic genes. None of the SARMs tested interfered with steroidogenesis. The chosen approach allowed the grouping of AAS according to their steroidogenic-disrupting effects and provided initial mechanistic information. Mesterolone, mestanolone and methenolone potentially promote hypertension and cardiovascular diseases via excessive mineralocorticoid biosynthesis. Clostebol and oxymetholone might cause metabolic disturbances by suppressing corticosteroid production, resulting in adrenal hyperplasia. The non-steroidal SARMs exhibit an improved safety profile and represent a preferred therapeutic option.

11ß-Hydroxysteroid dehydrogenases control access of 7ß,27-dihydroxycholesterol to retinoid-related orphan receptor γ.

Oxysterols previously were considered intermediates of bile acid and steroid hormone biosynthetic pathways. However, recent research has emphasized the roles of oxysterols in essential physiologic processes and in various diseases. Despite these discoveries, the metabolic pathways leading to the different oxysterols are still largely unknown and the biosynthetic origin of several oxysterols remains unidentified. Earlier studies demonstrated that the glucocorticoid metabolizing enzymes, 11ß-hydroxysteroid dehydrogenase (11ß-HSD) types 1 and 2, interconvert 7-ketocholesterol (7kC) and 7ß-hydroxycholesterol (7ßOHC). We examined the role of 11ß-HSDs in the enzymatic control of the intracellular availability of 7ß,27-dihydroxycholesterol (7ß27OHC), a retinoid-related orphan receptor γ (RORγ) ligand. We used microsomal preparations of cells expressing recombinant 11ß-HSD1 and 11ß-HSD2 to assess whether 7ß27OHC and 7-keto,27-hydroxycholesterol (7k27OHC) are substrates of these enzymes. Binding of 7ß27OHC and 7k27OHC to 11ß-HSDs was studied by molecular modeling. To our knowledge, the stereospecific oxoreduction of 7k27OHC to 7ß27OHC by human 11ß-HSD1 and the reverse oxidation reaction of 7ß27OHC to 7k27OHC by human 11ß-HSD2 were demonstrated for the first time. Apparent enzyme affinities of 11ß-HSDs for these novel substrates were equal to or higher than those of the glucocorticoids. This is supported by the fact that 7k27OHC and 7ß27OHC are potent inhibitors of the 11ß-HSD1-dependent oxoreduction of cortisone and the 11ß-HSD2-dependent oxidation of cortisol, respectively. Furthermore, molecular docking calculations explained stereospecific enzyme activities. Finally, using an inducible RORγ reporter system, we showed that 11ß-HSD1 and 11ß-HSD2 controlled RORγ activity. These findings revealed a novel glucocorticoid-independent prereceptor regulation mechanism by 11ß-HSDs that warrants further investigation.

Posaconazole-Induced Hypertension Due to Inhibition of 11ß-Hydroxylase and 11ß-Hydroxysteroid Dehydrogenase 2.

We describe two cases of hypertension and hypokalemia due to mineralocorticoid excess caused by posaconazole treatment of coccidioidomycosis and rhinocerebral mucormycosis infections, respectively. Clinical laboratory evaluations, including a comprehensive analysis of blood and urine steroid profiles, revealed low renin and aldosterone and indicated as the underlying mechanism primarily a block of 11ß-hydroxylase activity in patient 1, whereas patient 2 displayed weaker 11ß-hydroxylase but more pronounced 11ß-hydroxysteroid dehydrogenase 2 inhibition. The results show that both previously suggested mechanisms must be considered and emphasize significant interindividual differences in the contribution of each enzyme to the observed mineralocorticoid excess phenotype. The mineralocorticoid symptoms of patient 1 resolved after replacement of posaconazole therapy by isavoconazole, and posaconazole dosage de-escalation ameliorated the effects in patient 2. By providing a thorough analysis of the patients' blood and urine steroid metabolites, this report adds further evidence for two individually pronounced mechanisms of posaconazole-induced hypertension and hypokalemia. The elucidation of the factors responsible for the individual phenotype warrants further research.

Profiling withanolide A for therapeutic targets in neurodegenerative diseases.

To identify new potential therapeutic targets for neurodegenerative diseases, we initiated activity-based protein profiling studies with withanolide A (WitA), a known neuritogenic constituent of Withania somnifera root with unknown mechanism of action. Molecular probes were designed and synthesized, and led to the discovery of the glucocorticoid receptor (GR) as potential target. Molecular modeling calculations using the VirtualToxLab predicted a weak binding affinity of WitA for GR. Neurite outgrowth experiments in human neuroblastoma SH-SY5Y cells further supported a glucocorticoid-dependent mechanism, finding that WitA was able to reverse the outgrowth inhibition mediated by dexamethasone (Dex). However, further GR binding and transactivation assays found no direct interference of WitA. Further molecular modeling analysis suggested that WitA, although forming several contacts with residues in the GR binding pocket, is lacking key stabilizing interactions as observed for Dex. Taken together, the data suggest that WitA-dependent induction of neurite outgrowth is not through a direct effect on GR, but might be mediated through a closely related pathway. Further experiments should evaluate a possible role of GR modulators and/or related signaling pathways such as ERK, Akt, NF-κB, TRα, or Hsp90 as potential targets in the WitA-mediated neuromodulatory effects.

Enzymatic interconversion of the oxysterols 7ß,25-dihydroxycholesterol and 7-keto,25-hydroxycholesterol by 11ß-hydroxysteroid dehydrogenase type 1 and 2.

Oxysterols are cholesterol metabolites derived through either autoxidation or enzymatic processes. They consist of a large family of bioactive lipids that have been associated with the progression of multiple pathologies. In order to unravel (patho-)physiological mechanisms involving oxysterols, it is crucial to elucidate the underlying formation and degradation of oxysterols. A role of 11ß-hydroxysteroid dehydrogenases (11ß-HSDs) in oxysterol metabolism by catalyzing the interconversion of 7-ketocholesterol (7kC) and 7ß-hydroxycholesterol (7ßOHC) has already been reported. The present study addresses a function of 11ß-HSD1 in the enzymatic generation of 7ß,25-dihydroxycholesterol (7ß25OHC) from 7-keto,25-hydroxycholesterol (7k25OHC) and tested whether 11ß-HSD2 is able to catalyze the reverse reaction. For the first time, using recombinant enzymes, the formation of 7k25OHC from 7kC by cholesterol 25-hydroxylase (CH25H) and further stereospecific oxoreduction to 7ß25OHC by human and mouse 11ß-HSD1 could be demonstrated. Additionally, experiments using human 11ß-HSD2 showed the oxidation of 7ß25OHC to 7k25OHC. Molecular modeling provided an explanation for the stereospecific interconversion of 7ß25OHC and 7k25OHC. Production of the Epstein-Barr virus-induced gene 2 (EBI2) ligand 7ß25OHC from 7k25OHC in challenged tissue by 11ß-HSD1 may be important in inflammation. In conclusion, these results demonstrate a novel glucocorticoid-independent pre-receptor regulation mediated by 11ß-HSDs.

Carbonyl reductase 1 catalyzes 20ß-reduction of glucocorticoids, modulating receptor activation and metabolic complications of obesity.

Carbonyl Reductase 1 (CBR1) is a ubiquitously expressed cytosolic enzyme important in exogenous drug metabolism but the physiological function of which is unknown. Here, we describe a role for CBR1 in metabolism of glucocorticoids. CBR1 catalyzes the NADPH- dependent production of 20ß-dihydrocortisol (20ß-DHF) from cortisol. CBR1 provides the major route of cortisol metabolism in horses and is up-regulated in adipose tissue in obesity in horses, humans and mice. We demonstrate that 20ß-DHF is a weak endogenous agonist of the human glucocorticoid receptor (GR). Pharmacological inhibition of CBR1 in diet-induced obesity in mice results in more marked glucose intolerance with evidence for enhanced hepatic GR signaling. These findings suggest that CBR1 generating 20ß-dihydrocortisol is a novel pathway modulating GR activation and providing enzymatic protection against excessive GR activation in obesity.

DHRS7 (SDR34C1) - A new player in the regulation of androgen receptor function by inactivation of 5α-dihydrotestosterone?

DHRS7 (SDR34C1) has been associated with potential tumor suppressor effects in prostate cancer; however, its function remains largely unknown. Recent experiments using purified recombinant human DHRS7 suggested several potential substrates, including the steroids cortisone and Δ4-androstene-3,17-dione (androstenedione). However, the substrate and cofactor concentrations used in these experiments were very high and the physiological relevance of these observations needed to be further investigated. In the present study, recombinant human DHRS7 was expressed in intact HEK-293 cells in order to investigate whether glucocorticoids and androgens serve as substrates at sub-micromolar concentrations and at physiological cofactor concentrations. Furthermore, the membrane topology of DHRS7 was revisited using redox-sensitive green-fluorescent protein fusions in living cells. The results revealed that (1) cortisone is a substrate of DHRS7; however, it is not reduced to cortisol but to 20ß-dihydrocortisone, (2) androstenedione is not a relevant substrate of DHRS7, (3) DHRS7 catalyzes the oxoreduction of 5α-dihydrotestosterone (5αDHT) to 3α-androstanediol (3αAdiol), with a suppressive effect on androgen receptor (AR) transcriptional activity, and (4) DHRS7 is anchored in the endoplasmic reticulum membrane with a cytoplasmic orientation. Together, the results show that DHRS7 is a cytoplasmic oriented enzyme exhibiting 3α/20ß-hydroxysteroid dehydrogenase activity, with a possible role in the modulation of AR function. Further research needs to address the physiological relevance of DHRS7 in the inactivation of 5αDHT and AR regulation.

Virtual screening applications in short-chain dehydrogenase/reductase research.

Several members of the short-chain dehydrogenase/reductase (SDR) enzyme family play fundamental roles in adrenal and gonadal steroidogenesis as well as in the metabolism of steroids, oxysterols, bile acids, and retinoids in peripheral tissues, thereby controlling the local activation of their cognate receptors. Some of these SDRs are considered as promising therapeutic targets, for example to treat estrogen-/androgen-dependent and corticosteroid-related diseases, whereas others are considered as anti-targets as their inhibition may lead to disturbances of endocrine functions, thereby contributing to the development and progression of diseases. Nevertheless, the physiological functions of about half of all SDR members are still unknown. In this respect, in silico tools are highly valuable in drug discovery for lead molecule identification, in toxicology screenings to facilitate the identification of hazardous chemicals, and in fundamental research for substrate identification and enzyme characterization. Regarding SDRs, computational methods have been employed for a variety of applications including drug discovery, enzyme characterization and substrate identification, as well as identification of potential endocrine disrupting chemicals (EDC). This review provides an overview of the efforts undertaken in the field of virtual screening supported identification of bioactive molecules in SDR research. In addition, it presents an outlook and addresses the opportunities and limitations of computational modeling and in vitro validation methods.

Inhibition of 11ß-hydroxysteroid dehydrogenase 2 by the fungicides itraconazole and posaconazole.

Impaired 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2)-dependent cortisol inactivation can lead to electrolyte dysbalance, hypertension and cardiometabolic disease. Furthermore, placental 11ß-HSD2 essentially protects the fetus from high maternal glucocorticoid levels, and its impaired function has been associated with altered fetal growth and a higher risk for cardio-metabolic diseases in later life. Despite its important role, 11ß-HSD2 is not included in current off-target screening approaches. To identify potential 11ß-HSD inhibitors among approved drugs, a pharmacophore model was used for virtual screening, followed by biological assessment of selected hits. This led to the identification of several azole fungicides as 11ß-HSD inhibitors, showing a significant structure-activity relationship between azole scaffold size, 11ß-HSD enzyme selectivity and inhibitory potency. A hydrophobic linker connecting the azole ring to the other, more polar end of the molecule was observed to be favorable for 11ß-HSD2 inhibition and selectivity over 11ß-HSD1. The most potent 11ß-HSD2 inhibition, using cell lysates expressing recombinant human 11ß-HSD2, was obtained for itraconazole (IC50 139±14nM), its active metabolite hydroxyitraconazole (IC50 223±31nM) and posaconazole (IC50 460±98nM). Interestingly, experiments with mouse and rat kidney homogenates showed considerably lower inhibitory activity of these compounds towards 11ß-HSD2, indicating important species-specific differences. Thus, 11ß-HSD2 inhibition by these compounds is likely to be overlooked in preclinical rodent studies. Inhibition of placental 11ß-HSD2 by these compounds, in addition to the known inhibition of cytochrome P450 enzymes and P-glycoprotein efflux transport, might contribute to elevated local cortisol levels, thereby affecting fetal programming.

Evaluation of tetrabromobisphenol A effects on human glucocorticoid and androgen receptors: A comparison of results from human- with yeast-based in vitro assays.

The incidence of immune-related diseases increased over the last years in industrialized countries, suggesting a contribution of environmental factors. Impaired glucocorticoid action has been associated with immune disorders. Thus, there is an increasing interest to identify chemicals disrupting glucocorticoid action. The widely used flame retardant tetrabromobisphenol A (TBBPA) was reported earlier to potently inhibit glucocorticoid receptor (GR) and moderately androgen receptor (AR) activity in yeast-based reporter gene assays. To further characterize possible GR disrupting effects of TBBPA, transactivation experiments using a human HEK-293 cell-based reporter gene assay and cell-free receptor binding experiments were performed in the present study. Both, transactivation and GR binding experiments failed to detect any activity of TBBPA on GR function. Molecular docking calculations supported this observation. Additionally, the current study could confirm the antiandrogenic activity of TBBPA seen in the yeast assay, although the effect was an order of magnitude less pronounced in the HEK-293 cell-based system. In conclusion, TBBPA does not directly affect GR function and, considering its rapid metabolism and low concentrations found in humans, it is unlikely to cause adverse effects by acting through AR. This study emphasizes the use of cell-free assays in combination with cell-based assays for the in vitro evaluation of endocrine disrupting chemicals.

Pharmacophore Models and Pharmacophore-Based Virtual Screening: Concepts and Applications Exemplified on Hydroxysteroid Dehydrogenases.

Computational methods are well-established tools in the drug discovery process and can be employed for a variety of tasks. Common applications include lead identification and scaffold hopping, as well as lead optimization by structure-activity relationship analysis and selectivity profiling. In addition, compound-target interactions associated with potentially harmful effects can be identified and investigated. This review focuses on pharmacophore-based virtual screening campaigns specifically addressing the target class of hydroxysteroid dehydrogenases. Many members of this enzyme family are associated with specific pathological conditions, and pharmacological modulation of their activity may represent promising therapeutic strategies. On the other hand, unintended interference with their biological functions, e.g., upon inhibition by xenobiotics, can disrupt steroid hormone-mediated effects, thereby contributing to the development and progression of major diseases. Besides a general introduction to pharmacophore modeling and pharmacophore-based virtual screening, exemplary case studies from the field of short-chain dehydrogenase/reductase (SDR) research are presented. These success stories highlight the suitability of pharmacophore modeling for the various application fields and suggest its application also in futures studies.