Functional studies of 11 beta-hydroxysteroid dehydrogenase

The multifaceted mineralocorticoid receptor

The primary adrenal cortical steroid hormones, aldosterone, and the glucocorticoids cortisol and corticosterone, act through the structurally similar mineralocorticoid (MR) and glucocorticoid receptors (GRs). Aldosterone is crucial for fluid, electrolyte, and hemodynamic homeostasis and tissue repair; the significantly more abundant glucocorticoids are indispensable for energy homeostasis, appropriate responses to stress, and limiting inflammation. Steroid receptors initiate gene transcription for proteins that effect their actions as well as rapid non-genomic effects through classical cell signaling pathways. GR and MR are expressed in many tissues types, often in the same cells, where they interact at molecular and functional levels, at times in synergy, others in opposition. Thus the appropriate balance of MR and GR activation is crucial for homeostasis. MR has the same binding affinity for aldosterone, cortisol, and corticosterone. Glucocorticoids activate MR in most tissues at basal levels and GR at stress levels. Inactivation of cortisol and corticosterone by 11β-HSD2 allows aldosterone to activate MR within aldosterone target cells and limits activation of the GR. Under most conditions, 11β-HSD1 acts as a reductase and activates cortisol/corticosterone, amplifying circulating levels. 11β-HSD1 and MR antagonists mitigate inappropriate activation of MR under conditions of oxidative stress that contributes to the pathophysiology of the cardiometabolic syndrome; however, MR antagonists decrease normal MR/GR functional interactions, a particular concern for neurons mediating cognition, memory, and affect.

Simultaneous determination of tetrahydrocortisol, allotetrahydrocortisol and tetrahydrocortisone in human urine by liquid chromatography-electrospray ionization tandem mass spectrometry

Simultaneous quantification method of three major metabolites of cortisone and cortisol, tetrahydrocortisol, allotetrahydrocortisol and tetrahydrocortisone by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) was investigated in a positive mode using a recently developed picolinyl derivatization. Conversion of each steroid into the corresponding picolinyl derivatives (1b, 2b or 3b) was performed by mixed anhydride method using picolinic acids and 2-methyl-6-nitrobenzoic anhydride. Derivatization proceeded smoothly to afford the corresponding 3, 21-dipicolinyl derivatives. Positive ion-ESI mass spectra of the picolinyl derivatives were dominated by an appearance of [M+H](+) as base peaks in all cases. The picolinyl derivatives provided 15 to 80-fold higher ESI response in the LC-ESI-MS/MS (selected reaction monitoring: SRM) when compared to those of underivatized molecules in a positive LC-ESI mode. The use of the picolinyl ester, solid-phase extraction, and deuterium labeled internal standards enabled the concentrations of these metabolites in human urine to be determined simultaneously by LC-ESI-MS/MS (SRM) with a small sample volume of less than 1microl urine.

Restructuring the neuronal stress response with anti-glucocorticoid gene delivery

Glucocorticoids, the adrenal steroids released during stress, compromise the ability of neurons to survive neurological injury. In contrast, estrogen protects neurons against such injuries. We designed three genetic interventions to manipulate the actions of glucocorticoids, which reduced their deleterious effects in both in vitro and in vivo rat models. The most effective of these interventions created a chimeric receptor combining the ligand-binding domain of the glucocorticoid receptor and the DNA-binding domain of the estrogen receptor. Expression of this chimeric receptor reduced hippocampal lesion size after neurological damage by 63% and reversed the outcome of the stress response by rendering glucocorticoids protective rather than destructive. Our findings elucidate three principal steps in the neuronal stress-response pathway, all of which are amenable to therapeutic intervention.

Urinary cortisol to cortisone metabolites in hypertensive obese children

Childhood obesity is accompanied by a variety of cardiovascular risk factors (hypertension, insulin resistance, dyslipidaemia) which tend to aggregate (syndrome X). 11beta-hydroxysteroid dehydrogenase (11beta-HSD) is supposed to play a role in the pathogenesis of hypertension and the development of syndrome X. There are two isoforms of 11beta-HSD. 11beta-HSD-2 is responsible for the inactivation of cortisol to inactive cortisone. In the case of impaired enzyme activity the ratio of urinary tetrahydrocortisol (THF)+ its isomer allotetrahydrocortisol (5alpha-THF)/tetrahydrocortisone (THE) is elevated. 11beta-HSD-1 is an oxo-reductase, which type catalyses the conversion of cortisone to cortisol. The aim of the present study was to investigate if there was any alteration in the urinary cortisol metabolites reflecting 11beta-HSD activity in hypertensive obese children (no.=15) as compared to normotensive obese (no.=11) and normotensive non-obese children (no.=15). We found an increased excretion of cortisol metabolites in hypertensive obese children compared to obese and normal - weight children having normal blood pressure. The ratio of THF+5alpha(THF/THE had a significant correlation with systolic blood pressure. On the basis of our study the ratio of THF+5alpha-THF/ THE reflecting on altered enzyme activity seems to be an independent factor influencing especially systolic blood pressure in hypertensive obese children.

Glycyrrhetinic acid-induced apoptosis in thymocytes: impact of 11beta-hydroxysteroid dehydrogenase inhibition

It has been proposed that glycyrrhetinic acid (GA) enhances endogenous glucocorticoid (GC) action by suppressing the metabolism of the steroid. We show here that marked involution of the thymus occurred within 24 h of a single intraperitoneal administration of GA in mice. Thymocytes from mice treated with GA exhibited DNA cleavage and mitochondrial transmembrane potential disruption, as demonstrated with agarose gel electrophoresis and flow cytometric analysis. Immunocytochemical staining revealed that CD4(+)CD8(+) double positive cells markedly decreased after GA treatment. In contrast to GA in vivo, GA in vitro did not induce apoptosis of cultured thymocytes. These findings suggest that the apoptosis-inducing effect of GA on thymocytes is due to its indirect action. Because GA has been known to inhibit 11beta-hydroxysteroid dehydrogenase (11beta-HSD), we measured the enzyme activity in major organs and endogenous corticosterone concentration after GA treatment. The results showed a significant decrease of 11beta-HSD activity (P < 0.0001) and an increase in serum corticosterone concentration (P < 0.005). We concluded that the inhibition of hepatic 11beta-HSD activity by GA has a serious effect on GC metabolism, which results in a significant elevation of systemic GC levels. Apoptosis of thymocytes occurred as a consequence of the elevation in the level of endogenous corticosterone.

Stable isotope methodology for kinetic studies of interconversion of cortisol and cortisone in a human subject

Oral administration of 5 mg each of deuterium-labeled cortisol ([1,1,19,19,19-2H5]cortisol, cortisol-d5) and cortisone-d5 ([1,1,19,19,19-2H5]cortisone) to a human subject on two different occasions four weeks apart provided a useful means of characterizing the kinetics of the interconversion of cortisol and cortisone. From the data on plasma concentration measurements of cortisol-d5, cortisone-d5, cortisone-5, endogenous cortisol and endogenous cortisone by gas chromatography-mass spectrometry, it was demonstrated that (1) the plasma concentration ratio of cortisone-d5 to cortisol-d5 approached a plateau 4-5 h following either the cortisol-d5 or cortisone-d5 administration and the plateau values for the cortisone-d5 and cortisol-d5 administration were almost identical (about 0.43) and (2) dosing with only 5 mg of the deuterium-labeled steroids suppressed the plasma concentrations of endogenous cortisol and cortisone.