Increase In Aldosterone Concentration Research Articles

Multiple corticosteroid abnormalities in cats with hyperaldosteronism.

BackgroundThe frequency with which multiple corticosteroid abnormalities occur in cats with aldosterone secreting adrenocortical tumors is unknown.ObjectivesTo evaluate adrenal‐derived corticosteroids in cats in which blood samples were submitted for measure of aldosterone.AnimalsTwo hundred ninety‐seven cats.MethodsRetrospective study. Analysis of a convenience sample of previously submitted serum or plasma. Progesterone, corticosterone, and cortisol were measured in feline serum or plasma samples submitted to an endocrinology laboratory for aldosterone measurements. Demographics and clinical history were retrieved from submittal forms when provided. Statistical testing was performed to investigate associations among the adrenal corticosteroids.ResultsProgesterone and corticosterone concentrations were strongly correlated (ρ = 0.74; P < .001). Progesterone (median, 5 nmol/L; interquartile range, 3‐10 nmol/L) and corticosterone (113 nmol/L, 38‐250 nmol/L) in cats with markedly increased aldosterone concentrations (≥3000 pmol/L) were higher than progesterone (1 nmol/L, 1‐2 nmol/L) and corticosterone (12 nmol/L, 3‐25 nmol/L) in cats with normal aldosterone concentrations (P < .001 for both comparisons). Progesterone concentrations ≥10 nmol/L (normal, ≤2 nmol//L) occurred in 24 of 76 (32%) cats with aldosterone concentrations ≥3000 pmol/L. Cortisol was lower in cats with aldosterone concentrations ≥3000 pmol/L as compared to those with aldosterone concentrations <500 pmol/L (59 nmol/L, 27‐103 nmol/L vs 103 nmol/L, 49‐182 nmol/L; P = .002).Conclusions and Clinical ImportanceMultiple corticosteroid abnormalities occur in a subset of cats with hyperaldosteronism. The magnitude of increases in progesterone and corticosterone in some cats with hyperaldosteronism is likely to be clinically relevant.

P3561Detection and functional characterization of angiotensin receptor type 1 autoantibodies: establishment and clinical translation

Abstract Circulating AT1R autoantibodies (AT1R-aabs) directed against the ECL2 of the AT1R with agonist-like activity are supposed to play a pathophysiological role in diseases associated with vascular and renal damage, such as preeclampsia and severehypertension (HT), but they are also thought to be involved in heart failure and primary hyperaldosteronism (PHA). Methods High-throughput screening assays aiming at a reliable detection of AT1R-aabs in sera from patients with HT and PHA were established. The agonist-like activity of AT1R-aabs was assessed by changes in intracellular calcium-levels using Fura2-QBT dye; the AlphaLISA Assay was used to assess induction of ERK1/2-phosphorylation in stably transfected AT1R-HEK-cells or in adrenocortical NCI-H295R cells. Results IgG isolated from sera of n=60 patients with PHA and n=164 with HT were screened for their capacity to increase [Ca2+]i or to activate ERK1/2. Sixteen out of 60 PHA-patients increased [Ca2+]i compared to none of the HT-patients, whereas in both disease-entities we detected AT1R-aabs inducing ERK1/2-activation with a similar prevalence (PHA: 41%, HT: 42%), indicating the existence of differentially acting AT1R-aabs. PHA-patients positive for ERK1/2-activating AT1R-aabs have significantly lower serum potassium- (3,8±0,1 vs. 4,1±0,1 mmol/l, p&lt;0,05) and renin-levels (2,7±0,5 vs. 4,5±0,7 ng/l, p&lt;0,05) together with an increased aldosterone concentration (341±37 vs. 236±20 ng/l, p&lt;0,01) concordant with the disease phenotype. Similarly, higher BP values are observed in AT1R-aab positive HT-patients (syst/diast: 148/85 vs. 167/93 mmHg, p&lt;0,0001) accompanied byhigher aldosteroneserum-levels (93±7 vs. 74±3 ng/l, p&lt;0,05). In addition, ERK1/2-activation induced by either angiotensin II or by IgG isolated from patients with PHA or HT could be differentially blocked by the use of various signaling inhibitors. In order to elucidate if stimulating AT1R-aabs could be involved in an over-secretion of aldosterone due to sustained receptor-activation, we investigatedtheir effects on NCI-H295R-cells. At the transcriptional level, AT1R-aabs were able to induce a time-dependent upregulation of the key steroidogenic enzymes involved in aldosterone biosynthesis CYP21A1-, HSD3B2-, CYP11B1-, and in particular CYP11B2-mRNA (2fold over basal), with the maximum level achieved after 8 to 12 hours. Concordant withan agonist-stimulated internalization of AT1R,AT1R-mRNA was downregulated by AT1R-aabs (up to 25% of basal) providing direct evidence of a chronic receptor-stimulation by AT1R-aabs. Conclusion Functional assays based on AT1R-activation (Ca2+ measurements &amp; ERK1/2-phosphorylation) are able to detect AT1R-aabs in 41% or 42% of patients with HT or PHA, respectively. Moreover, our data provide evidence that AT1R-aabs stabilize a specific AT1R-conformation distinct from that induced by angiotensin II thereby triggering a different intracellular signaling pattern resulting in chronic aldosterone production. Acknowledgement/Funding BMBF grant

Resistant Hypertension: Diagnosis and Management.

Resistant hypertension is defined as high blood pressure requiring 3 or more medications for adequate control or controlled blood pressure requiring 4 or more medications. Considering the growing prevalence of hypertension and the strong link with cardiovascular disease, it is vital to understand the causes and treatment of resistant hypertension. This review article starts with an overview of the prevalence and little-known pathophysiology of resistant hypertension. Afterward, we discuss the evaluation and management of suspected secondary resistant hypertension in 2 broad categories: pseudoresistant hypertension and true resistant hypertension. Strategies for the identification and management of pseudoresistant hypertension are addressed. In addition, causes of true resistant hypertension, such as obstructive sleep apnea, primary aldosteronism, and renal artery stenosis, are examined along with their respective treatments. Finally, treatment of resistant hypertension is reviewed including pharmacologic treatments and novel procedural interventions for resistant hypertension. Overall, the review hopes to provide practitioners with a cohesive approach for the diagnosis and treatment of resistant hypertension.

Effect of Melatonin on the Renin-Angiotensin-Aldosterone System in l-NAME-Induced Hypertension.

The renin-angiotensin-aldosterone system (RAAS) is a dominant player in several cardiovascular pathologies. This study investigated whether alterations induced by l-NAME, (NLG)-nitro-l-arginine methyl ester, a nitric oxide synthase inhibitor, and the protective effect of melatonin are associated with changes in the RAAS. Four groups of 3-month-old male Wistar rats (n = 10) were treated as follows for four weeks: untreated controls, rats treated with melatonin (10 mg/kg/day), rats treated with l-NAME (40 mg/kg/day), and rats treated with l-NAME + melatonin. l-NAME administration led to hypertension and left ventricular (LV) fibrosis in terms of enhancement of soluble, insoluble and total collagen concentration and content. Melatonin reduced systolic blood pressure enhancement and lowered the concentration and content of insoluble and total collagen in the LV. The serum concentration of angiotensin (Ang) 1–8 (Ang II) and its downstream metabolites were reduced in the l-NAME group and remained unaltered by melatonin. The serum aldosterone level and its ratio to Ang II (AA2-ratio) were increased in the l-NAME group without being modified by melatonin. We conclude that l-NAME-hypertension is associated with reduced level of Ang II and its downstream metabolites and increased aldosterone concentration and AA2-ratio. Melatonin exerts its protective effect in l-NAME-induced hypertension without affecting RAAS.

Evaluation of the effects of occupational noise exposure on serum aldosterone and potassium among industrial workers

The existing literature indicates that occupational exposure to noise may have adverse effects on workers’ health. The aim of this study was to evaluate the possible effects of exposure to different sound pressure levels (SPLs) on serum aldosterone and potassium concentration among Iranian blue collar workers in Golgohar Mining and Industrial Company in Sirjan, Kerman Province, Iran. This case-control study was performed on 45 workers of Golgohar Mining and Industrial Company. The subjects consisted of 30 workers from manufacturing departments and 15 office employees of the mining company. The controls, mainly with administrative jobs were exposed to 72 dBA SPL. Cases, in two separate groups, were exposed to noise levels of 88 dBA and 103 dBA, respectively. Noise intensity was measured at the desired locations. Noise measurements were performed according to the International Organization for Standardization (ISO) 9612. To measure the serum aldosterone and potassium concentrations, a 5 mL blood sample was taken from each worker at the specified time intervals and aldosterone concentration was determined using enzyme-linked immunosorbent assay (ELISA) test in the laboratory. Repeated measurement and Spearman's correlation coefficient analysis were used with α = 0.05. Exposure to the different levels of sound pressure resulted in different aldosterone concentrations and meanwhile an increase in the SPL did not affect the concentration of potassium. From 10:00 AM to 10:30 AM, as SPL increased, aldosterone concentrations did not increase significantly but from 13:30 PM to 14:00 PM, raised SPL led to a significant increase in aldosterone concentration. However, there was no correlation between the concentration of potassium and different factors. This study indicated that increases in SPLs affect aldosterone concentration but at the same time do not have significant effects on serum potassium level.

Aldosterone-to-Renin Ratio and the Relationship Between Urinary Salt Excretion and Blood Pressure in a Community of African Ancestry

Although aldosterone influences the effect of salt intake on blood pressure (BP), the extent to which this occurs at a population level is uncertain. We therefore aimed to determine, at a community level in a group of African descent, whether in the absence of primary aldosteronism, the relationship between salt intake and BP is modified by circulating aldosterone, and the extent to which this occurs. In 575 participants of African ancestry (age >16 years), we assessed whether aldosterone-to-renin ratio (ARR) is associated with the relationship between urinary sodium (Na(+))-to-potassium (K(+)) ratio (urinary Na(+)/K(+)) (from 24-h urine samples), an index of salt intake, and BP. With adjustments for confounders, interactions between ARR and urinary Na(+)/K(+) were independently associated with systolic BP (SBP) (P < 0.0001), an effect that was accounted for by interactions between serum aldosterone concentrations and urinary Na(+)/K(+) (P < 0.0001), but not between plasma renin concentrations and urinary Na(+)/K(+) (P = 0.52). The interaction between ARR and urinary Na(+)/K(+) translated into a marked difference in the relationship between urinary Na(+)/K(+) and SBP in participants above compared to below the median for ARR (effect of 1 s.d. increase in urinary Na(+)/K(+) on SBP: ARR > median = 4.2 ± 0.6 mm Hg; ARR < median = 1.2 ± 0.4 mm Hg, P < 0.0001). In addition, participants with urinary Na(+)/K(+) above the median had higher multivariate-adjusted SBP (P < 0.001) only if ARR was also above the median. In groups of African descent, in the absence of primary aldosteronism, an increased aldosterone concentration relative to renin modifies a substantial proportion of the relationship between urinary Na(+)/K(+) and BP at a community level.

Aldosterone receptor inhibition alters the viscoelastic biomechanical behavior of the aortic wall

Dynamic mechanical disturbances in the aortic wall may lead to progressive aortic dilation and possibly aneurysmal formation. Here, we investigated the previously unexplored effects of aldosterone inhibition on aortic wall viscoelastic properties in hyperlipidemic rabbits. Thirty-six New Zealand male rabbits, fed a standard diet for four weeks, were separated into three groups: control (C; n = 10), standard diet; eplerenone (A; n = 12), hyperlipidemic diet plus 100 mg/kg/d eplerenone (last 4 weeks); and vehicle (V; n = 14), hyperlipidemic diet (no eplerenone). After eight weeks, animals were sacrificed and rectangular strips from the aortic wall, cut in radial and axial orientations, were prepared. Fresh, saline-wetted strips at 37 degrees C were subjected to cyclic sinusoidal elongation from zero to 20% of the resting length at a frequency of 1 Hz. The dynamic biomechanical viscoelastic characteristics, 'elastin phase' low modulus (E(L)), 'collagen phase' high modulus (E(H)) and dissipated-energy index, were determined. Aortic tissue preparations were also examined histologically. Eplerenone increased aldosterone concentrations but did not affect blood pressure, cholesterol or potassium concentrations. There was a significant reduction of E(H) (from 3.40 to 1.80 MPa; P < 0.01) and E(L) (from 0.46 to 0.27 MPa; P < 0.05) in group A in the radial direction compared with group C. In the axial direction E(L) significantly increased in group A compared with group V (from 0.42 to 1.11 MPa; P < 0.01). Energy dissipation was not significantly different among groups, although there was a trend toward higher values in group A for both directions. Histological assessments revealed no significant differences in collagen or elastic fibers among groups. In conclusion, aldosterone receptor inhibition altered the viscoelastic properties of the aortic wall in hyperlipidemic rabbits without detectable microscopic changes in elastic or collagen fibers, an effect that progressively might predispose to dilation and/or aneurysmal formation.

Endocrine Response After Severe Subarachnoid Hemorrhage Related to Sodium and Blood Volume Regulation

Hyponatremia is often associated with, and worsens, the prognosis of severe aneurysmal subarachnoid hemorrhage (SAH). Several possible endocrine perturbations of variable severity and variable sodium and water intake have been described in SAH. However, a comprehensive study of the different hormonal systems involved in sodium and water homeostasis and circulating blood volume modifications is still needed. Our aim was to assess water and sodium regulation after severe SAH by investigating blood volume and several hormonal regulatory systems in the context of hyponatremia prevention by controlled sodium intake. Nineteen mechanically ventilated patients with severe SAH, were prospectively studied. Replacement of sodium was at least 4.5 mmol x kg(-1) x d(-1) and adjusted on natriuresis. Hormones involved in electrolyte and water homeostasis: vasopressin, renin, angiotensin, aldosterone, and natriuretic peptides were assessed every 3 days for 12 days. Red blood cell volume was measured by the isotopic method (technetium-labeled red blood cells), in the first 48 h after admission and at day 7. Cardiac function was assessed using electrocardiogram, transthoracic echocardiography, and troponin Ic (cTnI). Outcome was assessed at 3 mo. After SAH onset, hyponatremia, but not decreased circulating blood volume, was prevented by high sodium and water infusion adapted to renal excretion. The hormonal profiles were characterized by an increase in renin, angiotensin II, natriuretic peptide concentrations associated with increased troponin Ic, stable low levels of vasopressin, and the absence of increased aldosterone concentrations. There were no correlations between hormone concentrations and natriuresis. After severe SAH, in the context of multiple clinical interventions, increased natriuresis and low blood volume are consistent with cerebral salt wasting syndrome, probably related to the sequence of severe SAH, highly increased sympathetic tone, hyperreninemic hypoaldosteronism syndrome, and increased natriuretic peptides release.

High aldosterone-to-renin variants of CYP11B2 and pregnancy outcome

Increased aldosterone concentrations and volume expansion of normal pregnancies are hallmarks of normal pregnancies and blunted in pre-eclampsia. Accordingly, we hypothesized an active mineralocorticoid system to protect from pre-eclampsia. In pregnant women (normotensive n = 44; pre-eclamptic n = 48), blood pressure, urinary tetrahydro-aldosterone excretion and activating polymorphisms (SF-1 site and intron 2) of the aldosterone synthase gene (CYP11B2) were determined; 185 non-pregnant normotensive individuals served as control. Amino acid-changing polymorphisms of the DNA- and agonist-binding regions of the mineralocorticoid receptor were evaluated by RT-PCR, SSCP and sequencing. Urinary tetrahydro-aldosterone excretion was reduced in pre-eclampsia as compared to normal pregnancy (P < 0.05). It inversely correlated with blood pressure (r = 0.99, P < 0.04). Homozygosity for activating CYP11B2 polymorphisms was preferably present in normotensive as compared to pre-eclamptic pregnancies, identified (intron 2, P = 0.005; SF-1 site, P = 0.016). Two mutant haplotypes decreased the risk of developing pre-eclampsia (RR 0.16; CI 0.05-0.54; P < 0.001). In contrast, intron 2 wild type predisposed to pre-eclampsia (P < 0.0015). No functional mineralocorticoid receptor mutant has been observed. High aldosterone availability is associated with lower maternal blood pressure. In line with this observation, gain-of-function variants of the CYP11B2 reduce the risk of developing pre-eclampsia. Mutants of the mineralocorticoid receptor cannot explain the frequent syndrome of pre-eclampsia.

Aldosterone: From biosynthesis to non-genomic action onto the proteome

An increased aldosterone concentration can lead to a progression of heart diseases and to myocardial fibrosis. These fatal processes can be prevented by e.g. inhibiting the mineralocorticoid receptor (MR), which is nowadays part of a commonly applied standard therapy. Moreover, selective inhibition of aldosterone synthase (CYP11B2) is a straightforward goal whereby CYP11B1, a key enzyme in glucocorticoid biosynthesis exhibiting a high structure identity with CYP11B2 should not be inhibited. Therefore, effective test systems have been developed and rather potent and selective CYP11B2 compounds like SIAS-1 have been identified by our group. In addition to finding new inhibitors, we investigated which proteins are directly influenced by aldosterone focussing on non-genomic effects. Schizosaccharomyces pombe was chosen 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. Besides creating a reference map for this organism, protein spots affected by aldosterone as well as deoxycorticosterone (DOC) and corticosterone have been identified. In case of aldosterone, a regulatory effect of proteins that are connected with structural proteins, signal cascades, osmoregulation and calcium pathway as well as to general metabolism have been discovered. DOC causes overlapping but also different effects compared with aldosterone. As shown exemplarily for GAPDH, the aldosterone-mediated effects in S. pombe can also be verified in mammalian cells. These and further investigations contribute to a deeper understanding of so-called non-genomic aldosterone effects.

Invalidation of TASK1 potassium channels disrupts adrenal gland zonation and mineralocorticoid homeostasis

TASK1 (KCNK3) and TASK3 (KCNK9) are two-pore domain potassium channels highly expressed in adrenal glands. TASK1/TASK3 heterodimers are believed to contribute to the background conductance whose inhibition by angiotensin II stimulates aldosterone secretion. We used task1-/- mice to analyze the role of this channel in adrenal gland function. Task1-/- exhibited severe hyperaldosteronism independent of salt intake, hypokalemia, and arterial 'low-renin' hypertension. The hyperaldosteronism was fully remediable by glucocorticoids. The aldosterone phenotype was caused by an adrenocortical zonation defect. Aldosterone synthase was absent in the outer cortex normally corresponding to the zona glomerulosa, but abundant in the reticulo-fasciculata zone. The impaired mineralocorticoid homeostasis and zonation were independent of the sex in young mice, but were restricted to females in adults. Patch-clamp experiments on adrenal cells suggest that task3 and other K+ channels compensate for the task1 absence. Adrenal zonation appears as a dynamic process that even can take place in adulthood. The striking changes in the adrenocortical architecture in task1-/- mice are the first demonstration of the causative role of a potassium channel in development/differentiation.

Thyroid cysts: a new extra‐adrenal site of aldosterone synthase expression and increased aldosterone content

The rapid re-accumulation of fluid following aspiration of thyroid cystic lesions suggests that active transport of sodium and water may be involved in volume regulation of these lesions. In this study we address the possibility that aldosterone may take part in this process. Thirty-one patients (29 women and two men), with a mean age of 52.7 +/- 13.2 years (range: 27-77 years) underwent evaluation for thyroid nodules that had a sonographic cystic component. Cystic fluid obtained by FNA biopsy was sent for cytological examination and biochemical measurements. In 10 patients, material was collected for RNA extraction and determination of aldosterone synthase expression by RT-PCR amplification. All lesions were benign, cystic, colloid nodules. Cyst fluid aldosterone levels as measured by routine radioimmunoassay (RIA) were elevated above the normal plasma levels in all but five patients. Mean aldosterone levels were 27.1 +/- 22.9 ng/dl (SD) (range: 5.9-117.5 ng/dl). In contrast, cyst cortisol values were in the low, low normal serum range (6.2 +/- 2.9 microg/dl, range: 0.2-10.2 microg/dl). Sodium, chloride and potassium levels were 137 +/- 4.7 mEq/l, 98 +/- 5 mEq/l and 4.9 +/- 1.4 mEq/l, respectively. Plasma aldosterone levels were normal in all patients tested. To confirm these results, 12 samples were assayed after extraction and chromatography using a highly specific antibody. Cyst aldosterone levels in this group were elevated above the normal serum range in all but one patient (mean concentration: 24.5 +/- 14.6 ng/dl, range: 8.72-40.1 ng/dl). In this group, 18(OH)B levels were within the normal plasma range (12-55 ng/dl) in all but one patient (34.9 +/- 17 ng/dl). Furthermore, aldosterone synthase mRNA expression was found in aspirates of four of 10 patients. The increased aldosterone concentration and the presence of aldosterone synthase expression suggest that aldosterone may be locally produced and secreted in thyroid tissue. The pathophysiological implications of this finding remain to be established.

Nonselective nonsteroidal anti‐inflammatory drugs and increased cardiovascular events: stress could be the explanation

I am concerned that an injustice is being done to the NSAID analgesics by the paper from Hawkey et al. due to inadequate controls [1]. Moreover, if it causes patients to stop taking these analgesics it could even have the perverse effect of increasing the incidence of myocardial infarction (MI). The reason is their control patients did not have the same risk factors for MI because they were not in pain and chronic pain is known to increase mood-related stress factors such as anger. For example, in placebo controlled conditions we have found significantly increased anger, anxiety, fatigue and sadness within a week of stopping NSAIDs that were given for chronic pain due to osteoarthritis of the knees [2]. Anger alone has repeatedly been linked to an increased incidence of MI. When I was seeking references to confirm this I found myself agreeing emphatically with another paper in this edition of the Journal [3] when a Google search on: ‘anger, myocardial infarction, stress’, produced over 91 000 pages in 0.55 s. To quote but one of these: The relative risk of myocardial infarction in the 2 h after an episode of anger was 2.3 (95% confidence interval 1.7, 3.2) [4]. Our work also showed that during a second week of active treatment these mood changes reverted towards the norm, suggesting that it is important to maintain good pain relief rather than risk patients reducing their medication to levels that cause frequent breakthrough episodes and possibly even adding to their troubles by worries about how much of the analgesic they should take. I also noticed that a third paper in the same issue [5] made no mention of stress as a possible cause of increases in aldosterone during NSAID treatment. A Google search on ‘aldosterone, stress and mood’ produced ‘52 000 English or French pages’ in 0.33 s. They included a report of studies showing a clear link between experimental stress in volunteers and increased aldosterone concentrations in plasma [6]. Hence the cause of the rise in aldosterone that this paper seeks could well be the same one that seems to be undermining the reputation of the NSAIDs.

885 The bradycardia-hypotension reaction during head-up tilt test: clinical and hemodynamic characteristics related to blood pressure and heart rate behavior during the early stage of the test

There was no correlation between delayed increase of aldosterone and NTG provocation during HUT. The delayed increase of aldosterone observed in 22% of all patients was related to syncope recurrence during follow-up, but not to the phase of tilt in which syncope occurred. Conclusions: 1. The delayed increase of aldosterone concentration during HUT-induced syncope is a risk factor of syncope recurrence during follow-up. 2. The delayed increase of aldosterone could be the marker of disturbed activation of RAA system predisposing the patients to vasovagal syncope.

Effects of the aldosterone receptor antagonist potassium canrenoate on renal blood flow and urinary output during prolonged increased intraabdominal pressure (IAP) in pigs

Increased intraabdominal pressure can be found after major abdominal trauma and necrotizing pancreatitis and is used during laparoscopic surgery. The purpose of this study was to investigate the effect of the aldosterone receptor antagonist (potassium canrenoate) on renal hemodynamics and urinary output in pigs during increased intraabdominal pressure (IAP). The IAP was kept at 30 mmHg for 3 h by instillation of Ringer's solution into the peritoneal cavity. Eight animals were treated with potassium canrenoate and eight animals served as controls. Renal blood flow, hormones in femoral artery blood, and the urinary output were measured. The administration of potassium canrenoate was followed by increased aldosterone concentrations in arterial blood, increased blood concentration of potassium, and increased concentration of sodium in the urine, indicating satisfactory inhibition of aldosterone. Potassium canrenoate did not cause changes in cardiac output and arterial pressure. It did not affect the renal vascular resistance that increased at an IAP of 30 mmHg, or the renal blood flow that remained constant during the experiments. The group treated with potassium canrenoate had higher mean urinary output than the controls, but the difference was not significant. Increased IAP in pigs is associated with markedly reduced urinary output and increased serum concentrations of aldosterone. Although the urinary output did not increase significantly, the increased sodium concentration in the urine of canrenoate-treated animals suggests that the high blood level of aldosterone contributes to the oliguria under increased IAP.

Discovery of selective CYP11B2 (aldosterone synthase) inhibitors for the therapy of congestive heart failure and myocardial fibrosis

An increased aldosterone concentration due to congestive heart failure leads to a further progression of the disease as well as to myocardial fibrosis. To interfere with these fatal processes selective inhibition of aldosterone synthase (CYP11B2) is required. CYP11B1, a key enzyme in glucocorticoid biosynthesis showing a high homology to the target enzyme (>93%), must not be inhibited. Screening of our P450 inhibitor library for inhibition of bovine aldosterone synthase resulted in a high number of compounds showing reasonable inhibition. In the next step substances were tested for oral absorption using two artificial membrane assays. The inhibition of human CYP11B2 was evaluated using assays in fission yeast and V79MZ cells stably expressing the active human target enzyme. For selectivity, inhibition of CYP11B1, CYP11A1, CYP17, CYP19 and CYP5 was determined. Rather potent and selective compounds obtained in this way were structurally further optimised, finally leading to inhibitors showing IC 50 values within the low nanomolar range.

Reduced activity of 11 beta-hydroxysteroid dehydrogenase in patients with cholestasis.

Enhanced renal sodium retention and potassium loss in patients with cirrhosis is due to activation of mineralocorticoid receptors (MRs). Increased aldosterone concentrations, however, do not entirely explain the activation of MR in cirrhosis. Here, we hypothesize that cortisol activates MRs in patients with cholestasis. We present evidence that access of cortisol to MRs is a result of bile acid-mediated inhibition of 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2), an MR-protecting enzyme that converts cortisol to cortisone. Twelve patients with biliary obstruction and high plasma bile acid levels were studied before and after removal of the obstruction. The urinary ratio of (tetrahydrocortisol + 5 alpha-tetrahydrocortisol)/tetrahydrocortisone, a measure of 11 beta-HSD2 activity, decreased from a median of 1.91 during biliary obstruction to 0.78 at 4 and 8 weeks after removal of the obstruction and normalization of plasma bile acid concentrations. In order to demonstrate that bile acids facilitate access of cortisol to the MR by inhibiting 11 beta-HSD2, an MR translocation assay was performed in HEK-293 cells transfected with human 11 beta-HSD2 and tagged MR. Increasing concentrations of chenodeoxycholic acid led to cortisol-induced nuclear translocation of MR. In conclusion, 11 beta-HSD2 activity is reduced in cholestasis, which results in MR activation by cortisol.

Reduced activity of 11β-hydroxysteroid dehydrogenase in patients with cholestasis

Enhanced renal sodium retention and potassium loss in patients with cirrhosis is due to activation of mineralocorticoid receptors (MRs). Increased aldosterone concentrations, however, do not entirely explain the activation of MR in cirrhosis. Here, we hypothesize that cortisol activates MRs in patients with cholestasis. We present evidence that access of cortisol to MRs is a result of bile acid−mediated inhibition of 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), an MR-protecting enzyme that converts cortisol to cortisone. Twelve patients with biliary obstruction and high plasma bile acid levels were studied before and after removal of the obstruction. The urinary ratio of (tetrahydrocortisol + 5α-tetrahydrocortisol)/tetrahydrocortisone, a measure of 11β-HSD2 activity, decreased from a median of 1.91 during biliary obstruction to 0.78 at 4 and 8 weeks after removal of the obstruction and normalization of plasma bile acid concentrations. In order to demonstrate that bile acids facilitate access of cortisol to the MR by inhibiting 11β-HSD2, an MR translocation assay was performed in HEK-293 cells transfected with human 11β-HSD2 and tagged MR. Increasing concentrations of chenodeoxycholic acid led to cortisol-induced nuclear translocation of MR. In conclusion, 11β-HSD2 activity is reduced in cholestasis, which results in MR activation by cortisol.

Changes in gluco- and mineralocorticoid adrenal functions in spontaneously hypertensive rats during experimental myocardial infarction

The dynamics of corticosterone and aldosterone contents during the acute and restoration periods of experimental myocardial infarction was studied in Wistar and spontaneously hypertensive rats. In spontaneously hypertensive rats, the increase in aldosterone concentration during the acute period was followed by elevation of corticosterone content, which attested the disadaptive course of experimental myocardial infarction against the background of hereditary arterial hypertension.

Inhibition of 11beta-hydroxysteroid dehydrogenase by bile acids in rats with cirrhosis.

Renal sodium retention and potassium loss occur early, in many instances in the preascitic state of cirrhosis, an observation that cannot be fully explained by increased aldosterone concentrations. We therefore hypothesize that 11beta-hydroxysteroid dehydrogenase 2 (11beta-HSD2), which protects mineralocorticoid receptors (MR) from glucocorticosteroids, is down-regulated in cirrhosis. Cirrhosis was induced by bile duct ligation in rats. The urinary ratio of (tetrahydrocorticosterone + 5alpha-tetrahydrocorticosterone)/ 11-dehydro-tetrahydrocorticosterone [(THB+5alpha-THB)/THA] was measured by gas chromatography. Cortical collecting tubules (CCT) were isolated by microdissection and used for measurements of the activity of 11beta-HSD2 by assessing the conversion of corticosterone to dehydrocorticosterone. The mRNA content of 11beta-HSD2 was determined by reverse-transcription polymerase chain reaction (RT-PCR) in CCTs. The urinary ratio of (THB+5alpha-THB)/THA increased concomitantly with the urinary excretion of bile acids following bile duct ligation. Chenodeoxycholic acid (CDCA) dose-dependently inhibited 11beta-HSD2 in CCT with a Ki of 19.9 micromol/L. Four weeks after bile duct ligation, 11beta-HSD2 activity was decreased in CCT, an observation preceded by a reduced mRNA content at weeks 2 and 3. In cirrhosis, the MR-protecting effect by 11beta-HSD2 is diminished, and therefore, endogenous glucocorticoids can induce MR-mediated sodium retention and potassium loss.