Eplerenone: a selective aldosterone receptor antagonist (SARA)

Cell-type specific effects of mineralocorticoid receptor gene expression suggest intercellular communication regulating fibrosis in skeletal muscle disease

Introduction: Duchenne muscular dystrophy (DMD) is a fatal striated muscle degenerative disease. DMD is caused by loss of dystrophin protein, which results in sarcolemmal instability and cycles of myofiber degeneration and regeneration. Pathology is exacerbated by overactivation of infiltrating immune cells and fibroblasts, which leads to chronic inflammation and fibrosis. Mineralocorticoid receptors (MR), a type of nuclear steroid hormone receptors, are potential therapeutic targets for DMD. MR antagonists show clinical efficacy on DMD cardiomyopathy and preclinical efficacy on skeletal muscle in DMD models. Methods: We have previously generated myofiber and myeloid MR knockout mouse models to dissect cell-specific functions of MR within dystrophic muscles. Here, we compared skeletal muscle gene expression from both knockouts to further define cell-type specific signaling downstream from MR. Results: Myeloid MR knockout increased proinflammatory and profibrotic signaling, including numerous myofibroblast signature genes. Tenascin C was the most highly upregulated fibrotic gene in myeloid MR-knockout skeletal muscle and is a component of fibrosis in dystrophic skeletal muscle. Surprisingly, lysyl oxidase (Lox), canonically a collagen crosslinker, was increased in both MR knockouts, but did not localize to fibrotic regions of skeletal muscle. Lox localized within myofibers, including only a region of quadriceps muscles. Lysyl oxidase like 1 (Loxl1), another Lox family member, was increased only in myeloid MR knockout muscle and localized specifically to fibrotic regions. Discussion: This study suggests that MR signaling in the dystrophic muscle microenvironment involves communication between contributing cell types and modulates inflammatory and fibrotic pathways in muscle disease.

Blockade of the mineralocorticoid receptor improves markers of human endothelial cell dysfunction and hematological indices in a mouse model of sickle cell disease

Increased endothelin-1 (ET-1) levels in patients with sickle cell disease (SCD) and transgenic mouse models of SCD contribute to disordered hematological, vascular, and inflammatory responses. Mineralocorticoid receptor (MR) activation by aldosterone, a critical component of the Renin-Angiotensin-Aldosterone-System, modulates inflammation and vascular reactivity, partly through increased ET-1 expression. However, the role of MR in SCD remains unclear. We hypothesized that MR blockade in transgenic SCD mice would reduce ET-1 levels, improve hematological parameters, and reduce inflammation. Berkeley SCD (BERK) mice, a model of severe SCD, were randomized to either sickle standard chow or chow containing the MR antagonist (MRA), eplerenone (156 mg/Kg), for 14 days. We found that MRA treatment reduced ET-1 plasma levels (p = .04), improved red cell density gradient profile (D50 ; p < .002), and increased mean corpuscular volume in both erythrocytes (p < .02) and reticulocytes (p < .024). MRA treatment also reduced the activity of the erythroid intermediate-conductance Ca2+ -activated K+ channel - KCa 3.1 (Gardos channel, KCNN4), reduced cardiac levels of mRNAs encoding ET-1, Tumor Necrosis Factor Receptor-1, and protein disulfide isomerase (PDI) (p < .01), and decreased plasma PDI and myeloperoxidase activity. Aldosterone (10-8  M for 24 h in vitro) also increased PDI mRNA levels (p < .01) and activity (p < .003) in EA.hy926 human endothelial cells, in a manner blocked by pre-incubation with the MRA canrenoic acid (1 μM; p < .001). Our results suggest a novel role for MR activation in SCD that may exacerbate SCD pathophysiology and clinical complications.

Development of eplerenone nano sono-crystals using factorial design: enhanced solubility and dissolution rate via anti solvent crystallization technique

OBJECTIVE

The purpose of this work was to improve EP solubility by using a sono-crystalization approach to reduce particle size and hence, increase the dissolution rate. Significance Eplerenone (EP) is an antagonist of the aldosterone receptor and is used for the treatment of hypertension and chronic heart failure. EP was classed as biopharmaceutical classification (BCS) class II because of its poor solubility and high permeability, which retards dissolution rate and drug absorption, and decreases bioavailability.

METHODS

Three-factors and two-level (2³) multifactorial design have been employed to study the effect of independent variables which are drug concentration; (X1), stabilizer type (X2), and stabilizer concentration (X3) on responses; saturated solubility of EP in distilled water (Y1), saturated solubility in acidic media pH 1.2 (Y2), particle size (Y3), and polydispersity index, PDI (Y4). Also, they were characterized by Fourier transformed infrared spectroscopy (FTIR), Powder X-ray diffraction (PXRD), Differential scanning calorimetry (DSC), and yield percentage. The optimum formula was further subjected to an in-vitro release study.

RESULTS

The optimized formulation showed a saturated solubility of EP as 1.29, and 1.86 (mg/ml) in distilled water and acidic media (pH 1.2) respectively. Also, the particle size of 133 nm, and PDI of 0.824 with a small percentage of the difference between the observed and predicted values. Ninety-one percent of EP was released within 10 min., and it was completely released within 45 min. with a significantly higher release rate compared to raw drug.

CONCLUSION

This work resulted in a satisfactory enhancement of solubility and dissolution rate which, is suitable for further in-vivo analysis.

Eplerenone repurposing in management of chorioretinopathy: Mechanism, nanomedicine-based delivery applications and future trends

Chronic central serous chorioretinopathy (CSCR) is an ocular threatening disease, a common cause of central vision loss, affecting the posterior pole of the eye. Eplerenone (EPL) is a selective mineralocorticoid receptor antagonist that used primarily to treat hypertension. Recently, it has shown many benefits in modifying the physio-pathological processes occurring upon stimulation of renin-angiotensin aldosterone system at the ocular level. In CSCR treatment, several clinical studies and case reports prove the efficacy and safety of EPL. However, some setbacks for such studies as a relatively small number of participants and short follow-up periods. This review article is intended to describe theories about the nature and classification of CSCR and recapitulate EPL therapeutic benefits as selective mineralocorticoid receptor antagonist in the treatment of CSCR. Furthermore, a literature survey on clinical studies discussing the results of use of EPL in treatment of CSCR. In addition, EPL therapeutic formulations that were developed up to date, and the future potential delivery systems will be suggested.

Differentiation between emerging non-steroidal and established steroidal mineralocorticoid receptor antagonists: head-to-head comparisons of pharmacological and clinical characteristics

INTRODUCTION

Mineralocorticoid receptor (MR) antagonists (MRAs) provide cardiorenal protection. However steroidal MRAs might induce hyperkalemia and sex hormone-related adverse effects. Several novel non-steroidal MRAs are being developed that are highly selective for the MR and may have an improved safety profile.

AREAS COVERED

This narrative review summarizes data from head-to-head comparisons of emerging non-steroidal MRAs with older steroidal MRAs, including pharmacological characteristics, pharmacokinetic properties, clinical outcomes, and safety, and highlights similarities and differences between emerging agents and established steroidal MRAs.

EXPERT OPINION

Head-to-head comparisons in phase 2 trials suggest that the new non-steroidal MRAs exhibit at least equivalent efficacy to steroidal MRAs but may have a better safety profile in patients with heart failure and/or kidney disease. When also taking into account data from recent phase 3 placebo-controlled trials, these novel non-steroidal MRAs have the potential to provide a cardiorenal benefit above that of current optimized standard-of-care treatment in a high-risk population with reduced renal function, and with a lower risk of hyperkalemia. To optimize therapy, further research is needed to clarify the molecular differences in the mode of action of non-steroidal MRAs versus steroidal MRAs, and biomarkers that are predictive of MRA response need to be identified and validated.

Aldosterone Inhibits In Vitro Myogenesis by Increasing Intracellular Oxidative Stress via Mineralocorticoid Receptor

BACKGROUND

Despite clinical evidence indicating poor muscle health in subjects with primary aldosteronism (PA), it is still unclear whether the role of aldosterone in muscle metabolism is direct or mediated indirectly via factors, such as electrolyte imbalance or impaired glucose uptake. As one approach to clarify this issue, we investigated the effect of aldosterone on in vitro myogenesis and the potential mechanism explaining it.

METHODS

Myogenesis was induced in mouse C2C12 myoblasts with 2% horse serum. Immunofluorescence, quantitative reversetranscription polymerase chain reaction, Western blot, viability, and migration analyses were performed for experimental research.

RESULTS

Recombinant aldosterone treatment suppressed muscle differentiation from mouse C2C12 myoblasts in a dose-dependent manner, and consistently reduced the expression of myogenic differentiation markers. Furthermore, aldosterone significantly increased intracellular reactive oxygen species (ROS) levels in myotubes, and treatment with N-acetyl cysteine, a potent biological thiol antioxidant, reversed the decrease of myotube area, myotube area per myotube, nucleus number per myotube, and fusion index due to aldosterone through decreasing oxidative stress. A binding enzyme-linked immunosorbent assay confirmed that mineralocorticoid receptor (MR) interacted with aldosterone in C2C12 myoblasts, while eplerenone, an MR inhibitor, blocked aldosterone-stimulated intracellular ROS generation during myogenesis and markedly attenuated the suppression of in vitro myogenesis by aldosterone.

CONCLUSION

These findings support the hypothesis that hypersecretion of aldosterone, like PA, directly contributes to muscular deterioration and suggest that antioxidants and/or MR antagonists could be effective therapeutic options to reduce the risk of sarcopenia in these patients.

Improved 11α-hydroxycanrenone production by modification of cytochrome P450 monooxygenase gene in Aspergillus ochraceus

Eplerenone is a drug that protects the cardiovascular system. 11α-Hydroxycanrenone is a key intermediate in eplerenone synthesis. We found that although the cytochrome P450 (CYP) enzyme system in Aspergillus ochraceus strain MF018 could catalyse the conversion of canrenone to 11α-hydroxycanrenone, its biocatalytic efficiency is low. To improve the efficiency of 11α-hydroxycanrenone production, the CYP monooxygenase-coding gene of MF018 was predicted and cloned based on whole-genome sequencing results. A recombinant A. ochraceus strain MF010 with the high expression of CYP monooxygenase was then obtained through homologous recombination. The biocatalytic rate of this recombinant strain reached 93 % at 60 h without the addition of organic solvents or surfactants and was 17-18 % higher than that of the MF018 strain. Moreover, the biocatalytic time of the MF010 strain was reduced by more than 30 h compared with that of the MF018 strain. These results show that the recombinant A. ochraceus strain MF010 can overcome the limitation of substrate biocatalytic efficiency and thus holds a high poten tial for application in the industrial production of eplerenone.

Eplerenone: The Multifaceted Drug in Cardiovascular Pharmacology

Conventionally, rennin-angiotensin-aldosterone system (RAAS) inhibition has focused on angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers and angiotensin receptor-neprilysin inhibitors (ARNI) are the latest addition to this armamentarium. However, mineralocorticoid receptor antagonists (MRAs) also constitute an integral part of this anti-RAAS brigade, which are perceived more often as diuretics and are often under prescribed in heart failure (HF) despite being universally advocated by all major guidelines. Apart from HF, they have also shown promise in the management of hypertension, post-myocardial infarction, and hyperaldosteronism. Eplerenone, Food and Drug Administration (FDA) approved in 2002, is an acceptable alternative to spironolactone due to its sparing androgenic effects. In two big pivotal trials in heart failure (EMPHASIS -HF) and post-myocardial infarction (EPHESUS), the drug has firmly shown a reduction in adverse cardiovascular events. It has an established place in the management of resistant hypertension too. In this article, we will discuss the role of RAAS and its pathophysiology, pitfalls of spironolactone, which led to success of its congener, eplerenone, major studies conducted on eplerenone, current role of eplerenone, and comparison of the two MRAs.

Effects of Eplerenone on Blood Pressure and Echocardiographic and Serum Biochemical Variables in Five Healthy Dogs: A Pilot Study

Eplerenone (EP), an aldosterone antagonist, is reported to produce renal and cardiac protective effects in noncanine species. However, there are no detailed reports available on cardiovascular effects of EP in dogs. This study aimed to determine effect of EP on echocardiographic parameters, blood pressures, and biochemical variables in healthy dogs. Five healthy Beagle dogs were randomly divided and repeatedly used in each of 3 dose groups, receiving 2.5, 5, or 10 mg/kg BW EP orally q24 h for 4 wks. Serum biochemical test, blood pressure, and Doppler echocardiography measurements were performed before EP administration and at 1, 2, and 4 weeks after EP administration. Treatment with EP reduced mean blood pressure in a dose-dependent manner and significantly (but in a dose-independent manner) decreased left atrium/aorta ratio, early diastolic transmitral flow, early diastolic transmitral flow/late diastolic transmitral flow, peak velocity of early diastolic transmitral flow/peak velocity of early diastolic mitral annular motion, left ventricle and right ventricle Tei indices, stroke volume, cardiac output, and mid systole myocardial velocity gradient 1 to 4 weeks after administration. Deceleration time of early diastolic transmitral flow significantly increased after EP administration. No significant changes were observed in serum biochemical variables. The results indicated that EP might reduce preload, thereby decreasing left atrial size. In addition, reduction of left ventricular stiffness may have theoretically taken place but this could not be tested using the present study design. It is suggested that EP administration within the dose range used in this study is safe for administration to healthy dogs. Further studies are needed to explore both safety and efficacy, as well as to seek a recommended dose range of EP treatment in client-owned dogs with heart disease.

The effect of eplerenone on the renin-angiotensin-aldosterone system of rats with thyroid dysfunction

OBJECTIVES

This study was conducted to evaluate the effect of eplerenone on the RAAS and kidney function in rats with thyroid hormone disorders.

METHODS

This study involved 30 male Wistar albino rats, divided into three groups. The first group (N = 6) served as a control. The second group involved 12 rats with experimentally induced hypothyroidism through receiving propylthiouracil (0.05% w/v) in drinking water for one month, which was divided into two subgroups of six rats each. The first subgroup served as a positive hypothyroid control, and the second subgroup received oral daily dose of eplerenone (100 mg/kg) for 14 days. The third group included 12 rats with induced hyperthyroidism with L-thyroxin (0.0012% w/v) in drinking water, and rats in this group were also divided into two subgroups. The first subgroup served as a positive hyperthyroid control, and the second subgroup received oral eplerenone 100 mg/kg.

RESULTS

Eplerenone indicated a significant increase in renin and angiotensin I from 184.09 pg/ml and 178.66 pg/ml to 603.31 pg/ml and 250.88 pg/ml, respectively, meanwhile, aldosterone indicated no significant changes after inducing hypothyroidism and eplerenone administration. The induction of hyperthyroidism led to a significant increase in angiotensin I from 248.84 pg/ml to 292.22 pg/ml. Oral administration of eplerenone for 14 days caused a significant increase aldosterone from 364.23 pg/ml to 497.02 pg/ml.

CONCLUSION

Eplerenone significantly increased the serum renin and angiotensin I in hypothyroid and aldosterone and angiotensin I in hyperthyroid rats. Aldosterone in hypothyroid rats was not changed by eplerenone.

Spironolactone, a Classic Potassium-Sparing Diuretic, Reduces Survivin Expression and Chemosensitizes Cancer Cells to Non-DNA-Damaging Anticancer Drugs

Spironolactone, a classical diuretic drug, is used to treat tumor-associated complications in cancer patients. Spironolactone was recently reported to exert anti-cancer effects by suppressing DNA damage repair. However, it currently remains unclear whether spironolactone exerts combinational effects with non-DNA-damaging anti-cancer drugs, such as gemcitabine and epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs). Using the cancer cells of lung cancer, pancreatic cancer, and glioblastoma, the combinational effects of spironolactone with gemcitabine and osimertinib, a third-generation EGFR-TKI, were examined in vitro with cell viability assays. To elucidate the underlying mechanisms, we investigated alterations induced in survivin, an anti-apoptotic protein, by spironolactone as well as the chemosensitization effects of the suppression of survivin by YM155, an inhibitor of survivin, and siRNA. We also examined the combinational effects in a mouse xenograft model. The results obtained revealed that spironolactone augmented cell death and the suppression of cell growth by gemcitabine and osimertinib. Spironolactone also reduced the expression of survivin in these cells, and the pharmacological and genetic suppression of survivin sensitized cells to gemcitabine and osimertinib. This combination also significantly suppressed tumor growth without apparent adverse effects in vivo. In conclusion, spironolactone is a safe candidate drug that exerts anti-cancer effects in combination with non-DNA-damaging drugs, such as gemcitabine and osimertinib, most likely through the suppression of survivin.

Efficacy and toxicity of antihypertensive pharmacotherapy relative to effective dose 50

Antihypertensive drugs have usually been approved at doses near the top of their respective dose-response curves. Efficacy plateaus but adverse drug reactions (ADRs), such as falls, cerebral or renal ischaemia, increase as dose is increased, especially in older patients with comorbidities. ADRs reduce adherence and may be difficult to ascertain reliably. Higher doses have generally not been shown to reduce total mortality, which provides a summary of efficacy and safety. Weight loss and other lifestyle measures are essential and may be sufficient treatment in many young and low risk patients. Most antihypertensive drug lower systolic blood pressure by around 10 mmHg, which reduces stroke and heart failure by about a quarter. Clinical trials have not been designed to demonstrate specific blood pressure treatment thresholds and targets, which are mostly extrapolated from epidemiology. Mean population oral effective dose 50 may be the most appropriate dose at which to commence antihypertensive drugs. The dose can then be titrated up if greater efficacy is demonstrated, or lowered if ADRs develop. Lower dose combination therapy may best balance benefit and harms with fewer ADRs and additive, potentially synergistic, efficacy.

Mineralocorticoid receptor antagonism improves parenchymal arteriole dilation via a TRPV4-dependent mechanism and prevents cognitive dysfunction in hypertension

Hypertension and mineralocorticoid receptor activation cause cerebral parenchymal arteriole remodeling; this can limit cerebral perfusion and contribute to cognitive dysfunction. We used a mouse model of angiotensin II-induced hypertension to test the hypothesis that mineralocorticoid receptor activation impairs both transient receptor potential vanilloid (TRPV)4-mediated dilation of cerebral parenchymal arterioles and cognitive function. Mice (16-18 wk old, male, C57Bl/6) were treated with angiotensin II (800 ng·kg-1·min-1) with or without the mineralocorticoid receptor antagonist eplerenone (100 mg·kg-1·day-1) for 4 wk; sham mice served as controls. Data are presented as means ± SE; n = 5-14 mice/group. Eplerenone prevented the increased parenchymal arteriole myogenic tone and impaired carbachol-induced (10-9-10-5 mol/l) dilation observed during hypertension. The carbachol-induced dilation was endothelium-derived hyperpolarization mediated because it could not be blocked by N-nitro-l-arginine methyl ester (10-5 mol/l) and indomethacin (10-4 mol/l). We used GSK2193874 (10-7 mol/l) to confirm that in all groups this dilation was dependent on TRPV4 activation. Dilation in response to the TRPV4 agonist GSK1016790A (10-9-10-5 mol/l) was also reduced in hypertensive mice, and this defect was corrected by eplerenone. In hypertensive and eplerenone-treated animals, TRPV4 inhibition reduced myogenic tone, an effect that was not observed in arterioles from control animals. Eplerenone treatment also improved cognitive function and reduced microglia density in hypertensive mice. These data suggest that the mineralocorticoid receptor is a potential therapeutic target to improve cerebrovascular function and cognition during hypertension. NEW & NOTEWORTHY Vascular dementia is a growing public health issue that lacks effective treatments. Transient receptor potential vanilloid (TRPV)4 channels are important regulators of parenchymal arteriole dilation, and they modulate myogenic tone. The data presented here suggest that TRPV4 channel expression is regulated by the mineralocorticoid receptor (MR). MR blockade also improves cognitive function during hypertension. MR blockade might be a potential therapeutic approach to improve cerebrovascular function and cognition in patients with hypertension.

Low-dose spironolactone ameliorates insulin resistance and suppresses elevated plasminogen activator inhibitor-1 during gestational testosterone exposure

CONTEXT

Elevated gestational circulating testosterone has been associated with pathological pregnancies that increase the risk of development of cardiometabolic disorder in later life.

OBJECTIVE

We hypothesised that gestational testosterone exposure, in late pregnancy, causes glucose deregulation and atherogenic dyslipidaemia that would be accompanied by high plasminogen activator inhibitor-1 (PAI-1). The study also hypothesise that low-dose spironolactone treatment would ameliorate these effects.

METHODS

Pregnant Wistar rats received vehicle, testosterone (0.5 mg/kg; sc), spironolactone (0.5 mg/kg, po) or testosterone and spironolactone daily between gestational days 15 and 19.

RESULTS

Gestational testosterone exposure led to increased HOMA-IR, circulating insulin, testosterone, 1-h post-load glucose, atherogenic dyslipidaemia, PLR, PAI-1 and MDA. However, all these effects, except that of circulating testosterone, were ameliorated by spironolactone.

CONCLUSIONS

These results demonstrate that low-dose spironolactone ameliorates glucose deregulation and atherogenic dyslipidaemia during elevated gestational testosterone exposure, at least in part, by suppressing elevated PAI-1.

Mineralocorticoid Receptor Blockade in End-Stage Renal Disease

PURPOSE OF REVIEW

The purpose of this study was to summarize recent findings about cardiovascular benefits and safety of aldosterone blockade in patients with end-stage renal disease (ESRD).

RECENT FINDINGS

It is now well recognized that aldosterone's deleterious cardiovascular impact is not limited to its pressor effect arising from an increase in sodium reabsorption in the kidneys. Aldosterone has also been shown to increase blood pressure by a direct activation of the sympathetic nervous system, to cause endothelial and vascular smooth muscle cell dysfunction, myocardial remodeling and fibrosis, and to have pro-arrhythmogenic actions in the heart. These unconventional extra-renal effects of aldosterone make its blockade feasible and potentially beneficial for patients with ESRD. Accumulating data support the idea that aldosterone antagonism leads to a better blood pressure control, reduction in left ventricular (LV) mass, improved LV function, and reduced all-cause and cardiovascular mortality in ESRD patients. Reassuringly, rates of major adverse events, especially, significant hyperkalemia-the most feared adverse consequence-were low with careful patient selection and monitoring.

Synthesis and Physicochemical Characterization of the Process-Related Impurities of Eplerenone, an Antihypertensive Drug

Two unknown impurities were observed during the process development for multigram-scale synthesis of eplerenone (Inspra^®). The new process-related impurities were identified and fully characterized as the corresponding (7β,11α,17α)-11-hydroxy- and (7α,11β,17α)-9,11-dichloroeplerenone derivatives 12a and 13. Seven other known but poorly described in the literature eplerenone impurities, including four impurities A, B, C and E listed in the European Pharmacopoeia 8.4 were also detected, identified and fully characterized. All these contaminants result from side reactions taking place on the steroid ring C of the starting 11α-hydroxy-7α-(methoxycarbonyl)-3-oxo-17α-pregn-4-ene-21,17-carbolactone (12) and the key intermediate (7α,17α)-9(11)-enester 7, including epimerization of the C-7 asymmetric center, oxidation, dehydration, chlorination and lactonization. The impurities were isolated and/or synthesized and fully characterized by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR) and high-resolution mass spectrometry/electrospray ionization (HRMS/ESI). Their ¹H- and ¹³C-NMR signals were fully assigned. The molecular structures of the eight impurities, including the new (7β,11α,17α)-11-hydroxy- and (7α,11β,17α)-9,11-dichloroeplerenone related substances 12a and 13, were solved and refined using single-crystal X-ray diffraction (SCXRD). The full identification and characterization of these impurities should be useful for the quality control and the validation of the analytical methods in the manufacture of eplerenone.

Population Pharmacokinetics of Eplerenone in Japanese Patients With Chronic Heart Failure

To characterize eplerenone pharmacokinetics (PK) in Japanese chronic heart failure (CHF) patients and to estimate the impact of factors that may affect eplerenone PK, population pharmacokinetic (PPK) analysis was conducted. In addition, PK of Japanese CHF and Western CHF patients from a previous clinical pharmacology study were compared in the analysis. Eplerenone PK was characterized by a 1-compartment PPK model with first-order absorption and lag time in Japanese CHF patients. The population mean of apparent oral clearance (CL/F) in Japanese CHF patients was estimated as 5.31 L/h, which was similar to the mean CL/F for Western CHF patients. In the full model approach, creatinine clearance (CLcr) on CL/F and body weight on apparent central volume of distribution (Vc/F) were selected as factors that may affect PK. The effect of CLcr on CL/F predicted that CL/F would be decreased by 25% when CLcr was decreased from 80 mL/min to 50 mL/min. The effect of body weight on Vc/F predicted that Vc/F would be decreased by 18% when body weight was decreased from 80 kg to 60 kg. Distribution of individual CL/F estimates for Japanese CHF patients overlapped CL/F observed values for Western CHF patients, and CL/F values for Western CHF patients were contained within the distribution of CL/F estimates for Japanese CHF patients. No obvious difference between Japanese and Western subjects was detected even in the updated model by adding the data obtained from Western CHF patients and Western healthy adults to the model constructed with data from Japanese CHF patients.

Effect of polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer on bioadhesion and release rate property of eplerenone pellets

The present study involved the design and development of oral bioadhesive pellets of eplerenone. A solid dispersion of eplerenone was developed with a hydrophilic carrier, polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus^®). Bioadhesive pellets were prepared from this solid dispersion using a combination of HPMC K4M and Carbopol 934P. Both the solid dispersion and the pellets were evaluated for various physicochemical properties such as solubility, entrapment efficiency, drug content, surface morphology, mucoadhesion and swelling behavior. Analysis carried out using FT-IR, DSC and XRD found no interaction between the eplerenone and excipients. The solid dispersion had irregular-shaped smooth-surfaced particles of diameter 265 ± 105.5 μm. In TEM analysis, eplerenone particles of size 79-120 nm were found. The solubility and dissolution of eplerenone in the Soluplus^®-based solid dispersion were 5.26 and 2.50 times greater, respectively. Investigation of the swelling behavior of the pellets showed that the thickness of the gel layer increased continuously over the duration of the study. Moreover, a correlation was observed between the thickness and strength of the gel layer and the percentage release. The mechanism of drug release was found to be non-Fickian (anomalous), with the release kinetics approaching first-order kinetics. The bioavailability of the eplerenone bioadhesive pellet formulation was studied using Wistar rats and was found to be improved. An in vivo mucoadhesion study showed that the pellets are retained for 24 h in rabbits. It was concluded that Soluplus^® had a positive effect on the solubility and dissolution of pellets without affecting the bioadhesion.

Eplerenone — A Novel Selective Aldosterone Blocker

OBJECTIVE:

To review the pharmacology, pharmacokinetics, clinical efficacy, and safety of eplerenone, a new selective aldosterone blocker.

DATA SOURCES:

Primary literature and review articles were obtained via MEDLINE search (1966–April 2002). Additional studies and abstracts were identified from the bibliographies of reviewed literature.

STUDY SELECTION AND DATA EXTRACTION:

Studies and review articles related to eplerenone, aldosterone, aldosterone antagonist, and spironolactone were reviewed. Data pertinent to this article were included.

DATA SYNTHESIS:

Eplerenone is a selective aldosterone blocker. Recent data have demonstrated the deleterious effects of aldosterone in several chronic disease states including hypertension and heart failure. Animal studies using eplerenone have shown a positive role for aldosterone antagonism in the treatment of hypertension, heart failure, myocardial infarction, renal disease, and atherosclerosis. In humans, eplerenone appears to be effective for the treatment of hypertension. An ongoing study will examine the effect of eplerenone for heart failure. To date, the incidence of adverse effects with eplerenone has been slightly lower than with spironolactone.

CONCLUSIONS:

Eplerenone appears to be a promising drug in a new class of agents called selective aldosterone blockers. The drug may be approved for treatment of hypertension in 2002. Additional studies are ongoing that may provide information on other clinical uses for this medication.

Mineralocorticoid receptor antagonists, a class beyond spironolactone--Focus on the special pharmacologic properties of eplerenone

The renin-angiotensin-aldosterone system can be blocked at specific levels by using different classes of pharmacologic agents, including angiotensin-converting-enzyme inhibitors, angiotensin II receptor blockers and mineralocorticoid receptor antagonists. Broad use of the latter, such as spironolactone, has been limited by significant incidence of gynecomastia and other sex-related adverse effects. These problems can be overcome with use of eplerenone, a selective mineralocorticoid receptor antagonist. Eplerenone has been specifically developed to bind selectively to the mineralocorticoid receptors in order to minimize binding to the progesterone and androgen receptors. In the last decade, multiple scientific evidences have been accumulated showing the efficacy and safety of the drug in multiple clinical conditions, including heart failure and arterial hypertension. Eplerenone is generally well tolerated, with the most frequent adverse event being hyperkalemia, with sexual adverse events (i.e. gynecomastia) being more uncommon, due to the selectivity of eplerenone. This review focuses on the pharmacodynamic and pharmacokinetic properties of eplerenone, thus providing the scientific basis to fully understand drug-to-drug interactions, in particular, and its efficacy and tolerability, in general. Noteworthy, the activity of eplerenone in special conditions and different patient populations is summarized.

The Angiotensin Converting Enzyme Inhibitor Lisinopril Improves Muscle Histopathology but not Contractile Function in a Mouse Model of Duchenne Muscular Dystrophy

Background: Angiotensin converting enzyme inhibitors (ACEi) are the current standard of care treatment for cardiac dysfunction in Duchenne muscular dystrophy patients. We previously showed treatment with an ACEi plus mineralocorticoid receptor (MR) antagonist improves limb and respiratory skeletal muscles, in addition to cardiac muscles, in a dystrophic mouse model at 20 weeks-of-age.

Objective: To determine whether previously observed preclinical benefits of an ACEi plus MR antagonist on dystrophic skeletal muscles can be reproduced by increasing ACEi dosage alone. We also compared functional and histological outcome measures at 10 and 20 weeks-of-age.

Methods: Dystrophin deficient utrophin haplo-insufficient (utrn ^+/- ; mdx) “het” mice were treated with 10, 20, or 50 mg/kg × day of the ACEi lisinopril from 4 to 10 weeks-of-age via water bottles and compared with C57BL/10 wild-type control mice and untreated hets. Data from 10 week-old het mice were also compared to data collected from an untreated het group at 20 weeks-old. In vivo cardiac and grip strength measurements, in vitro diaphragm and extensor digitorum longus muscle force measurements, and histopathological analyses were performed. One-way ANOVA followed by Dunnett post hoc comparison was used to determine significance.

Results: ACEi treatment reduced skeletal muscle damage but had no significant effect on muscle force. Body weight, heart rate, grip strength and blood pressure were unaffected by treatment. Limb muscle histopathology was more informative at 10 than 20 weeks-of-age.

Conclusions: These results suggest increased ACEi dosage alone cannot improve all dystrophic parameters. Further optimization of MR antagonists in 20 week-old mice is warranted.

Mineralocorticoid receptors are present in skeletal muscle and represent a potential therapeutic target

Early treatment with heart failure drugs lisinopril and spironolactone improves skeletal muscle pathology in Duchenne muscular dystrophy (DMD) mouse models. The angiotensin converting enzyme inhibitor lisinopril and mineralocorticoid receptor (MR) antagonist spironolactone indirectly and directly target MR. The presence and function of MR in skeletal muscle have not been explored. MR mRNA and protein are present in all tested skeletal muscles from both wild-type mice and DMD mouse models. MR expression is cell autonomous in both undifferentiated myoblasts and differentiated myotubes from mouse and human skeletal muscle cultures. To test for MR function in skeletal muscle, global gene expression analysis was conducted on human myotubes treated with MR agonist (aldosterone; EC50 1.3 nM) or antagonist (spironolactone; IC50 1.6 nM), and 53 gene expression differences were identified. Five differences were conserved in quadriceps muscles from dystrophic mice treated with spironolactone plus lisinopril (IC50 0.1 nM) compared with untreated controls. Genes down-regulated more than 2-fold by MR antagonism included FOS, ANKRD1, and GADD45B, with known roles in skeletal muscle, in addition to NPR3 and SERPINA3, bona fide targets of MR in other tissues. MR is a novel drug target in skeletal muscle and use of clinically safe antagonists may be beneficial for muscle diseases.

Pharmacological profile of CS-3150, a novel, highly potent and selective non-steroidal mineralocorticoid receptor antagonist

The present study was designed to characterize the pharmacological profile of CS-3150, a novel non-steroidal mineralocorticoid receptor antagonist. In the radioligand-binding assay, CS-3150 inhibited (3)H-aldosterone binding to mineralocorticoid receptor with an IC50 value of 9.4nM, and its potency was superior to that of spironolactone and eplerenone, whose IC50s were 36 and 713nM, respectively. CS-3150 also showed at least 1000-fold higher selectivity for mineralocorticoid receptor over other steroid hormone receptors, glucocorticoid receptor, androgen receptor and progesterone receptor. In the reporter gene assay, CS-3150 inhibited aldosterone-induced transcriptional activation of human mineralocorticoid receptor with an IC50 value of 3.7nM, and its potency was superior to that of spironolactone and eplerenone, whose IC50s were 66 and 970nM, respectively. CS-3150 had no agonistic effect on mineralocorticoid receptor and did not show any antagonistic or agonistic effect on glucocorticoid receptor, androgen receptor and progesterone receptor even at the high concentration of 5μM. In adrenalectomized rats, single oral administration of CS-3150 suppressed aldosterone-induced decrease in urinary Na(+)/K(+) ratio, an index of in vivo mineralocorticoid receptor activation, and this suppressive effect was more potent and longer-lasting than that of spironolactone and eplerenone. Chronic treatment with CS-3150 inhibited blood pressure elevation induced by deoxycorticosterone acetate (DOCA)/salt-loading to rats, and this antihypertensive effect was more potent than that of spironolactone and eplerenone. These findings indicate that CS-3150 is a selective and highly potent mineralocorticoid receptor antagonist with long-lasting oral activity. This agent could be useful for the treatment of hypertension, cardiovascular and renal disorders.

Effects of Add-on Therapy Consisting of a Selective Mineralocorticoid Receptor Blocker on Arterial Stiffness in Patients with Uncontrolled Hypertension

OBJECTIVE

Aldosterone plays an important role in the pathogenesis of atherosclerosis; however, the significance of mineralocorticoid receptor blockade for atherosclerosis has not been fully elucidated. In this study, the effect of add-on eplerenone on the degree of arterial stiffness was examined in patients with uncontrolled hypertension.

METHODS

Forty-seven uncontrolled hypertensive patients who had previously been treated with anti-hypertensive drugs were examined retrospectively. Thirty-two patients received add-on therapy consisting of eplerenone (Group E) and 15 patients received add-on therapy with a Calcium channel blocker (CCB) or an increased dose of CCB (Group C) in addition to their baseline medications. Both the systolic blood pressure (SBP) and diastolic blood pressure (DBP) values were significantly decreased at two and 12 months in Group C. In contrast, neither the SBP nor DBP values were significantly changed at two months and eventually decreased at 12 months in Group E. The degree of arterial stiffness, as evaluated according to the cardio-ankle vascular index (CAVI), did not improve at either two or 12 months in Group C, whereas the CAVI values improved as early as at two months and the improvement was sustained at 12 months in Group E. The extent of change in the CAVI was not associated with the level of changes in the SBP or DBP values in Group E.

CONCLUSION

Treatment with eplerenone added to the patient's baseline medications improves the degree of arterial stiffness as early as at two months after the beginning of treatment, independent of the blood pressure-lowering actions of these drugs in patients with uncontrolled hypertension.

Design, synthesis, and structure-activity relationships of dihydrofuran-2-one and dihydropyrrol-2-one derivatives as novel benzoxazin-3-one-based mineralocorticoid receptor antagonists

Dihydrofuran-2-one and dihydropyrrol-2-one derivatives were identified as novel, potent and selective mineralocorticoid receptor (MR) antagonists by the structure-based drug design approach utilizing the crystal structure of MR/compound complex. Introduction of lipophilic substituents directed toward the unfilled spaces of the MR and identification of a new scaffold, dihydropyrrol-2-one ring, led to potent in vitro activity. Among the synthesized compounds, dihydropyrrol-2-one 11i showed an excellent in vitro activity (MR binding IC50=43nM) and high selectivity over closely related steroid receptors such as the androgen receptor (AR), progesterone receptor (PR) and glucocorticoid receptor (GR) (>200-fold for AR and PR, 100-fold for GR).

Development and validation of RP-HPLC method for estimation of eplerenone in spiked human plasma

A rapid and simple high performance liquid chromatography (HPLC) method with a UV detection (241 nm) was developed and validated for estimation of eplerenone from spiked human plasma. The analyte and the internal standard (valdecoxib) were extracted with a mixture of dichloromethane and diethyl ether. The chromatographic separation was performed on a HiQSil C-18HS column (250 mm×4.6 mm, 5 μm) with a mobile phase consisting of acetonitrile:water (50:50, v/v) at flow rate of 1 mL/min. The calibration curve was linear in the range 100–3200 ng/mL and the heteroscedasticity was minimized by using weighted least squares regression with weighting factor 1/X.

Stroke, high blood pressure and the Renin-Angiotensin-aldosterone system - new developments

This review considers whether a case can be made for a protective effect of inhibitors and blockers of the renin-angiotensin-aldosterone system (RAAS) on the cerebral circulation. It first looks at whether there exists a preferential effect on the cerebral circulation during a drug-induced lowering of high arterial blood pressure and cardiovascular morbi-mortality. It then goes on to consider background studies on the relationship between inhibition of the RAAS and stroke. This is followed by exploration of possible new directions in the inhibition of the RAAS and its effect on stroke.

The importance of renin-angiotensin blockade in patients with cardio-renal disease

The existence of the renin-angiotensin-aldosterone system was first postulated over 100 years ago. Following the identification of all the major components, came the discovery of their potential pathogenicity in cardiovascular and renal disease. The introduction of drugs that inhibit the synthesis or actions of this system has prompted a number of trials that have largely shaped how cardiovascular and renal disease is managed today. The continued discovery of yet more components of this system promises to further our understanding of its influence on disease processes and herald the development of more highly selective drugs, ensuring that the renin-angiotensin-aldosterone system will continue to be a key area of interest for many years to come.

Effect of eplerenone versus spironolactone on cortisol and hemoglobin A₁(c) levels in patients with chronic heart failure

BACKGROUND

It has been reported that mineralocorticoid receptor antagonist improves the prognosis of chronic heart failure (CHF). Recently, hemoglobin A₁(c) (HbA₁(c)) levels have been reported to be an independent risk factor for mortality in CHF, suggesting the important role of insulin resistance in CHF. We compared the metabolic effect of a selective mineralocorticoid receptor blocker eplerenone with spironolactone in CHF patients.

METHODS

One hundred seven stable outpatients with mild CHF, who were already receiving standard therapy for CHF, were randomized (1:2) to spironolactone (25 mg/d) or eplerenone (50 mg/d). Plasma levels of B-type natriuretic peptide, adiponectin, HbA₁(c) and cortisol were measured before and after 4 months treatment with spironolactone or eplerenone.

RESULTS

There were no differences in baseline characteristics including hemodynamic parameters and plasma levels of biomarkers between 2 groups. In both groups, plasma B-type natriuretic peptide levels were significantly decreased and plasma aldosterone levels were significantly increased after 4 months. In patients receiving spironolactone (n = 34), plasma adiponectin levels were significantly decreased (12.6 ± 1.4-11.2 ± 1.3 μg/mL, P < .0001) and HbA₁(c) and cortisol levels were significantly increased (5.61 ± 0.1-5.8 ± 0.1%, P < .0001, 11.3 ± 0.8-14.7 ± 1.3 μg/dL, P = .003, respectively). In patients receiving spironolactone, there was a significant positive correlation between the change in cortisol and the change in HbA₁(c) (r = 0.489, P = .003). In contrast, in patients receiving eplerenone (n = 73), plasma levels of adiponectin, HbA₁(c) and cortisol did not change.

CONCLUSION

These findings indicated that the metabolic effect of eplerenone differed from that of spironolactone and that eplerenone had a superior metabolic effect especially on HbA₁(c) in CHF patients.

Mineralocorticoid receptor blockade enhances the antiproteinuric effect of an angiotensin II blocker through inhibiting podocyte injury in type 2 diabetic rats

Treatment with angiotensin II type 1 receptor blockers (ARBs) is the first-line therapy for hypertensive patients with diabetic nephropathy. However, emerging clinical evidence indicates that mineralocorticoid receptor (MR) blockers have blood pressure-independent antiproteinuric effects. We sought to determine whether treatment with an MR blocker, eplerenone, enhances the effects of an ARB, telmisartan, on podocyte injury and proteinuria in type 2 diabetic Otsuka-Long-Evans-Tokushima-Fatty (OLETF) rats. From 20 to 50 weeks old, diabetic OLETF rats showed higher systolic blood pressure (SBP) and urinary protein excretion (U(protein)V) than nondiabetic control Long-Evans-Tokushima-Otsuka rats. At 50 weeks old, OLETF rats also showed glomerular sclerosis and podocyte injury, whereas nephrin and podocin mRNA levels in isolated glomeruli were significantly decreased. Treatment with telmisartan (3 mg/kg/day p.o.) decreased SBP and U(protein)V, increased nephrin and podocin mRNA levels, and attenuated glomerular sclerosis and podocyte injury. Eplerenone (100 mg/kg/day p.o.) did not alter SBP but elicited similar changes in renal parameters. However, greater reductions in U(protein)V and podocyte injury and greater increases in nephrin and podocin mRNA levels were observed in the combination treatment group. Hydralazine (25 mg/kg/day p.o.) decreased SBP but did not alter any renal parameters. These data indicate that MR blockade enhances the SBP-independent antiproteinuric effect of an ARB through inhibiting podocyte injury in type 2 diabetic rats.

Plasma concentrations of matrix metalloproteinase-2, tissue inhibitor of metalloproteinase-1 and osteopontin reflect severity of heart failure in DOCA-salt hypertensive rat

The matrix metalloproteinases (MMPs) and their endogenous inhibitors, the tissue inhibitors of metalloproteinases (TIMPs) play a key role in extracellular matrix maintenance and are altered in the failing heart, both in experimental models and in chronic end-stage heart failure in humans. As the common diagnostic markers of heart failure, atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) primarily reflect increased pressure loading, determination of soluble, heart-derived MMPs and TIMPs in plasma, as well as the determination of the emerging fibrosis marker osteopontin (OPN) might be valuable tools for detecting heart fibrosis. In this study the effect of spironolactone treatment on plasma MMP-2, TIMP-1 and OPN levels was assessed in a heart failure animal model. Unilaterally nephrectomized Sprague Dawley rats received subcutaneous injection of 100 mg deoxycorticosterone acetate (DOCA) once a week and 1% (w/v) NaCl in drinking water. Blood pressure was monitored weekly and blood samples were collected after 1, 2 and 4 weeks. After 6 weeks, left ventricular contractility (LVC) and heart weight-to-body weight ratio (HW/BW) were assessed. DOCA treatment increased plasma MMP-2, TIMP-1 and OPN concentrations. Alterations of plasma marker levels were correlated with changes of HW/BW and paralleled impaired LVC. Furthermore, beneficial effects of spironolactone treatment were observed. In DOCA-salt hypertensive rats, plasma concentrations of MMP-2, TIMP-1 and OPN reflected heart failure associated with haemodynamic, functional and morphological changes. Based on these findings, it appears reasonable to use plasma markers of fibrosis to monitor the development of heart failure.

Aldosterone receptor antagonism alleviates proteinuria, but not malignant hypertension, in Cyp1a1-Ren2 transgenic rats

The contribution of elevated aldosterone to the pathogenesis of malignant, ANG II-dependent hypertension remains uncertain. Therefore, we examined whether chronic mineralocorticoid receptor blockade attenuates the development of malignant hypertension in transgenic rats (TGRs) with inducible expression of the Ren2 gene [TGR(Cyp1a1Ren2)]. Systolic blood pressure (SBP) was measured by radiotelemetry in male TGRs in three groups: 1) control (n = 9), 2) hypertensives (HT; n = 8), and 3) hypertensives + spironolactone (11 mg.kg(-1).day(-1) sc; HTS; n = 8). Malignant hypertension was induced with dietary indole-3-carbinol (0.3%) for 10 days. Metabolic measurements were taken at the beginning of the study and at days 2 and 9. HT exhibited elevated SBP (125 +/- 3 vs. 187 +/- 5 mmHg), plasma renin activity (5 +/- 1 vs. 29 +/- 10 ng ANG I.ml(-1).h(-1)), plasma ANG II (175 +/- 39 vs. 611 +/- 74 fmol/ml), and plasma aldosterone (0.31 +/- 0.04 vs. 5.42 +/- 1.02 nmol/l). Urinary aldosterone excretion increased 5.5-fold by day 2 and an additional 90% by day 9. HT was associated with a 1.8-fold increase in proteinuria by day 9 that was alleviated by treatment with spironolactone (25 +/- 5 vs. 13 +/- 3 mg/day), suggesting that aldosterone contributes to the renal damage observed in malignant hypertension. Urinary Na+ excretion was decreased 76% on day 2, despite a sixfold increase in urinary aldosterone excretion. Decrease in urinary Na+ excretion on day 2 in HT suggests that Na+ reabsorption was increased in response to the increase in aldosterone; however, the lack of a change in SBP between HT and HTS suggests that mechanisms independent of aldosterone stimulation make a greater contribution to the maintenance of elevated arterial pressure in malignant hypertension in Cyp1a1-Ren2 transgenic rats.

Aldosterone receptor antagonism exacerbates intrarenal angiotensin II augmentation in ANG II-dependent hypertension

Effects of aldosterone receptor (AR) blockade with eplerenone (epl) on renal Na(+) excretion, arterial blood pressure, intra-adrenal and renal ANG II, and plasma aldosterone levels during ANG II-dependent hypertension were evaluated. Rats from one cohort (n = 10/group) 1) control, 2) control + epl (25 mg/day), 3) ANG II (60 ng/min), and 4) ANG II + epl were maintained in metabolic cages for 28 days for daily urine collections. Systolic blood pressure (SBP) was measured weekly by tail-cuff. In a second cohort (n = 12/group), daily SBP was measured by telemetry (n = 6 rats/group) 1) control, 2) ANG II, and 3) ANG II + epl. A diet containing epl (0.1%) was provided after 1 wk of ANG II infusion. Direct monitoring of BP by telemetry showed that epl delayed the onset of the increase in SBP by 2 days and slightly reduced SBP (186 +/- 6 vs. 177 +/- 8 mmHg). Epl transiently increased Na(+) excretion within 24 h of treatment in both normo- and hypertensive rats; however, balance was reestablished within 5 days suggesting that alternative mechanisms for conserving Na(+) are activated. Cortical alpha-epithelial Na(+) channel content (alpha-ENaC) was not altered after 21 days of epl treatment. Epl exacerbated the ANG II-mediated increases in intrarenal ANG II (226 +/- 16 vs. 365 +/- 38 fmol/g) and further increased intra-adrenal ANG II (3.9 +/- 0.3 vs. 8.2 +/- 0.9 fmol/mg) and aldosterone (255 +/- 55 vs. 710 +/- 87 pmol/mg) content. Exacerbation of intrarenal ANG II levels likely contributes to the maintenance of alpha-ENaC protein content and thus Na(+) reabsorption, which helps explain the ineffectiveness of AR blockade in reducing SBP in ANG II-infused models of hypertension.

Effects of serum containing Xinlikang on angiotensin ii induced hypertrophy in cultured neonatal rat cardiomyocytes

OBJECTIVE

To evaluate the effects of Xinlikang (XLK) on angiotensin II (Ang II) induced hypertrophic cultured neonatal rat's cardiomyocyte (CMC).

METHODS

Primary cultured neonatal rat's CMCs with the purity certified by immunohistochemical technique, were divided into three groups. Rats in the normal control group were untreated; those in the model group were established into hypertrophic models but underwent no treatment; and those in the XLK group were established to hypertrophic models and treated with XLK containing serum obtained from rats with aorta coarctation after 8 days of feeding with XLK. MTT and phase-contrast microscope were used to evaluate the effect of XLK on cell activity, pulsating rhythm and surface area; Atrial natriuretic peptide (ANP) expression was determined by radioimmunoassay; Protein content was determined by Bradford method; and DNA synthesis was detected by flow cytometric assay.

RESULTS

Immunohistochemistry results showed that more than 90% of the cells were alpha-sarcometin actin stained positive cells. No significant effect of XLK on normal CMC was found. Ang II could significantly induce hypertrophy in CMCs, and XLK could significantly decrease the increased surface area and the accelerated pulsating rate in them. ANP expression was 780 +/- 38 microg/L in the model group, and 430 +/- 23 microg/L in the control group, and the elevated expression of ANP in model rats was significantly decreased in the XLK group; The DNA content in the G0/G1 and G2/M phases was significantly enhanced and at the same time it was accompanied with increase of total protein content in the model rats after being stimulated by Ang II for 24 h, showing that serum-containing XLK could also significantly suppress total protein synthesis (P < 0.05).

CONCLUSION

XLK could improve Ang II mediated pathological growth of CMCs without influencing the growth of normal CMCs, suggesting that XLK is probably an effective drug for treatment of myocardial hypertrophy and heart failure.

Future pharmacologic agents for treatment of heart failure in children

The addition of new agents to the armamentarium of treatment options for heart failure in pediatric patients is exciting and challenging. Administration of these therapies to pediatric patients will require careful scrutiny of the data and skilled application. Developmental changes in drug metabolism, excretion, and distribution are concerning in pediatric patients, and inappropriate evaluation of these parameters can have disastrous results. Manipulation of the neurohormonal pathways in heart failure has been the target of most recently developed pharmacologic agents. Angiotensin receptor blockers (ARBs), aldosterone antagonists, beta-blockers, and natriuretic peptides are seeing increased use in pediatrics. In particular, calcium sensitizing agents represent a new frontier in the treatment of acute decompensated heart failure and may replace traditional inotropic therapies. Endothelin receptor antagonists have shown benefit in the treatment of pulmonary hypertension, but their use in heart failure is still debatable. Vasopressin antagonists, tumor necrosis factor inhibitors, and neutral endopeptidase inhibitors are also targeting aspects of the neurohormonal cascade that are currently not completely understood. The future of pharmacologic therapies will include pharmacogenomic studies on new and preexisting therapies for pediatric heart failure. The education and skill of the practitioner when applying these agents in pediatric heart failure is of utmost importance.

[Modern pharmacological aspects of hyperaldosteronism therapy]

The prevalence of primary hyperaldosteronism is 5-10% of all hypertensive patients, and clearly above the estimated prevalence in the past. In nearly 30% of patients with therapy resistant hypertension, primary hyperaldosteronism is detected if they are investigated thoroughly. This will result in 1.5 to 2.5 million people in Germany suffering from primary hyperaldosteronism. Besides efficient diagnostic procedures, an effective treatment is of increasing importance. The aldosterone-producing adenoma (Conn's syndrome) is primarily cured by operation, in most cases performed endoscopically. Bilateral hyperplasia, which is found in two-thirds of primary hyperaldosteronism, is treated primarily by mineralocorticoid receptor antagonist: 12.5-50 mg/day spironolactone (in case of anti-androgenic side-effects alternatively by 50-100 mg/day eplerenone). If the blood pressure can not be lowered by this first-line treatment, an additional treatment with potassium-sparing diuretics, calcium-antagonists, ACE-inhibitors or angiotensin-2-antagonists is necessary. The start of medication should be closely monitored by serum electrolyte and creatinine controls.

Protective effect of spironolactone on endothelial cell apoptosis

Human umbilical vein endothelial cells (HUVECs) undergo apoptosis in response to serum deprivation. We show that the nonspecific mineralocorticoid receptor antagonist, spironolactone, protects from caspase-3 activation induced by serum deprivation in contrast to the selective mineralocorticoid receptor antagonist, eplerenone, that is nonprotective. We also demonstrate that progesterone, hydrocortisone, and dexamethasone all protect HUVECs from serum-deprivation-induced caspase-3 activation, whereas aldosterone and dihydrotestosterone have no effect. Spironolactone has been demonstrated to display agonist activity only to the progesterone receptor (PR), and we additionally show that spironolactone and progesterone, but not eplerenone, inhibit mitochondrial cytochrome c release and cleavage of nuclear poly (ADP-ribose) polymerase (PARP) and increase cell viability. Additionally, the PR antagonist mifepristone (RU486) partially blocked the inhibitory effect of both spironolactone and progesterone on caspase-3 activation, cytochrome c release, and nuclear PARP cleavage. Nitric oxide (NO) protects HUVECs from apoptosis in response to various stimuli including serum-deprivation; however, the NO synthase inhibitor N-monomethyl-l-arginine, did not abolish inhibition of caspase-3 activation or PARP cleavage by spironolactone. Thus, we demonstrate that spironolactone protects HUVECs from serum-deprivation-induced apoptosis by inhibition of caspase-3 activity, cytochrome c release and PARP cleavage by a NO-independent mechanism; further, this effect is likely mediated by the agonist properties of spironolactone toward the PR.

Effect of parathyroidectomy on cardiac fibrosis and apoptosis: possible role of aldosterone

BACKGROUND/AIM

It has been demonstrated that parathyroidectomy prevents left ventricular hypertrophy in uremic animals. Although this effect may be mediated by direct actions of parathormone (PTH), it may also be exerted through regulation of profibrotic factors such as aldosterone. In adrenal cortex cell cultures, PTH increases aldosterone release. The objective of this work is to assess the effect of parathyroidectomy on aldosterone levels and on cardiac fibrosis and apoptosis in uremic rats.

METHODS

Four groups of rats were studied: C, control; 5/6Nx, 5/6 nephrectomy; PTx, parathyroidectomy, and 5/6NxPTx, 5/6 nephrectomy plus parathyroidectomy. Thirty days after the last surgical procedure the animals were sacrificed. Serum creatinine, ionized calcium, aldosterone, PTH, cardiac weight, fibrosis and apoptosis were measured.

RESULTS

Serum creatinine levels were significantly higher in 5/6Nx and 5/6NxPTx groups (1.62 +/- 0.21 and 1.38 +/- 0.15 mg/dl) than in C and PTx groups (0.66 +/- 0.02 and 0.47 +/- 0.01 mg/dl, p < 0.001). Potassium levels were significantly higher in the 5/6Nx and 5/6NxPTx groups (5.2 +/- 0.3 and 5.4 +/- 0.3 mg/dl) than in the C group (4.3 +/- 0.06 mg/dl, p < 0.05). Values in 5/6Nx and 5/6NxPTx groups were not significantly different from each other. PTH levels were significantly higher in the 5/6Nx group (470.5 +/- 156.3 microg/ml) than in the controls (102.3 +/- 14.3 microg/ml). PTH levels in the PTx group (1.78 +/- 0.52 microg/ml) and in the 5/6NxPTx group (81.64 +/- 32.15 microg/ml) were similar to control values. Ionized calcium was lower in PTx and 5/6NxPTx groups (0.80 +/- 0.07 and 0.89 +/- 0.07 mmol/l) as compared with C and 5/6Nx groups (1.14 +/- 0.01 and 0.96 +/- 0.01 mmol/ l, p < 0.01). The heart weight as percentage of the body weight increased significantly in 5/6Nx animals (4.20 +/- 0.15%) compared to the C group (3.41 +/- 0.27%, p < 0.05); parathyroidectomy reversed the heart weight increment in the 5/6NxPTx animals (3.58 +/- 0.16%). Myocardial fibrosis was significantly higher in the 5/6Nx group (12.5 +/- 1.1%) than in the C group (7.3 +/- 1.5%, p < 0.001); in the 5/6NxPTx animals fibrosis returned towards control values (8.9 +/- 0.2%). Myocardial apoptosis rose significantly in 5/6Nx animals (24.3 +/- 1.2%) compared to the C group (6.7 +/- 0.83%, p < 0.001); parathyroidectomy reversed the apoptosis in the 5/6NxPTx animals (10.4 +/- 0.49%). Aldosterone levels increased significantly in the 5/6Nx group (2,461 +/- 257 pg/ml) compared to the C group (703 +/- 81 pg/ml, p < 0.001); in the 5/6NxPTx animals aldosterone levels were below control values (509 +/- 99 pg/ml).

CONCLUSIONS

Uremia was associated to myocardial hypertrophy, fibrosis and apoptosis. Surgically induced hypoparathyroidism prevented the development of these disorders. Our results suggest that in the remnant kidney rat model myocardial hypertrophy, fibrosis, and apoptosis are mediated by high circulating aldosterone levels. Aldosterone, in turn, may be regulated by PTH.

Aldosterone receptor antagonists in the medical management of chronic heart failure

The benefits of aldosterone receptor antagonists (spironolactone and eplerenone) for patients with heart failure were shown in 2 recent randomized controlled trials. Some of the proposed mechanisms of action of aldosterone antagonists are (1) inhibition of myocardial and vascular remodeling, (2) blood pressure reduction, (3) decreased collagen deposition, (4) decreased myocardial stiffness, (5) prevention of hypokalemia and arrhythmia, (6) modulation of nitric oxide synthesis, and (7) immunomodulation. Like many hormone receptors, the aldosterone receptor can be either nuclear or membrane bound. Most of the activities of the aldosterone receptor are subserved by the nuclear receptors and often lead to alterations in gene transcription. Although these agents are well tolerated in carefully selected patient populations that meet the inclusion criteria of large clinical trials, their use in unselected elderly patients with heart failure and multiple comorbidities has been associated with a significant risk of hyperkalemia and renal failure. Although no convincing data exist to predict which individual patients will respond to aldosterone inhibition, patients with more severe heart failure and those with acute myocardial infarction with concomitant heart failure or left ventricular dysfunction are most likely to respond. Theoretically, aldosterone receptor antagonists may also be beneficial in patients with more mild to moderate systolic heart failure or even in those with diastolic heart failure, although direct evidence is still lacking.

Pharmacokinetics of eplerenone after single and multiple dosing in subjects with and without renal impairment

The influence of renal impairment on the pharmacokinetics of eplerenone following single and multiple dosing was evaluated. Subjects (n = 64) were stratified based on creatinine clearance values as follows: renal impairment (mild, moderate, severe), hemodialysis, and normal matches. Subjects received a single dose of eplerenone 100 mg on day 1 and then received 100 mg once daily on days 3 to 8. There were no statistically significant differences between any of the renal impairment groups and their matched-normal groups for area under the curve (AUC), C(max), or CL/F or CL/F/WT following either single or multiple dosing (P > or = .093). The inactive metabolite and inactive ring-opened form displayed greater AUCs in renal impairment. Hemodialysis removed approximately 10% of the eplerenone dose. Eplerenone 100 mg once daily was well tolerated in all groups. Considering that renal function had no significant effects on eplerenone CL/F and that eplerenone metabolites are inactive, no dose adjustment appears necessary in patients with renal dysfunction.