Effects Of Mineralocorticoid Receptor Blockade Research Articles

Effects of Mineralocorticoid Receptor Blockade and Statins on Kidney Injury Marker 1 (KIM-1) in Female Rats Receiving L-NAME and Angiotensin II.

Kidney injury molecule-1 (KIM-1) is a biomarker of renal injury and a predictor of cardiovascular disease. Aldosterone, via activation of the mineralocorticoid receptor, is linked to cardiac and renal injury. However, the impact of mineralocorticoid receptor activation and blockade on KIM-1 is uncertain. We investigated whether renal KIM-1 is increased in a cardiorenal injury model induced by L-NAME/ANG II, and whether mineralocorticoid receptor blockade prevents the increase in KIM-1. Since statin use is associated with lower aldosterone, we also investigated whether administering eiSther a lipophilic statin (simvastatin) or a hydrophilic statin (pravastatin) prevents the increase in renal KIM-1. Female Wistar rats (8-10 week old), consuming a high salt diet (1.6% Na+), were randomized to the following conditions for 14 days: control; L-NAME (0.2 mg/mL in drinking water)/ANG II (225 ug/kg/day on days 12-14); L-NAME/ANG II + eplerenone (100 mg/kg/day p.o.); L-NAME/ANG II + pravastatin (20 mg/kg/day p.o.); L-NAME/ANG II + simvastatin (20 mg/kg/day p.o.). Groups treated with L-NAME/ANG II had significantly higher blood pressure, plasma and urine aldosterone, cardiac injury/stroke composite score, and renal KIM-1 than the control group. Both eplerenone and simvastatin reduced 24-h urinary KIM-1 (p = 0.0046, p = 0.031, respectively) and renal KIM-1 immunostaining (p = 0.004, p = 0.037, respectively). Eplerenone also reduced renal KIM-1 mRNA expression (p = 0.012) and cardiac injury/stroke composite score (p = 0.04). Pravastatin did not affect these damage markers. The 24-h urinary KIM-1, renal KIM-1 immunostaining, and renal KIM-1 mRNA expression correlated with cardiac injury/stroke composite score (p < 0.0001, Spearman ranked correlation = 0.69, 0.66, 0.59, respectively). In conclusion, L-NAME/ANG II increases renal KIM-1 and both eplerenone and simvastatin blunt this increase in renal KIM-1.

Attenuation of Mineralocorticoid Receptor Signaling Promotes Vascular Recovery from Hind Limb Ischemia in a Sex Specific Manner

Peripheral arterial disease (PAD) is a growing concern affecting 8.5 million Americans annually and contributing to both fatal and non‐fatal cardiovascular ischemic events. Importantly, available evidence indicates that women experience higher rates of occlusion, reintervention, and mortality than males, however, mechanisms underlying these sex differences remain unclear. Recent evidence has revealed sex‐specific deleterious effects of mineralocorticoid receptor (MR) signaling in a variety of cardiovascular conditions including vascular inflammation and endothelial dysfunction, which have been implicated in PAD. Whether MR signaling differentially impairs microvascular adaptations in males and females following an ischemic insult, however, has not been examined. Accordingly, we evaluated the hypothesis that attenuation of MR signaling promotes microvascular compensation and perfusion recovery following hind limb ischemia (HLI) to a greater extent in females than in males involving enhanced capillary neovascularization and augmented outward remodeling of existing collaterals. Male and female C57BL/6J mice (10–12 weeks old) underwent unilateral femoral artery ligation and excision to induce HLI after implantation of pellets containing either placebo or the MR antagonist spironolactone (20mg/kg/day, sc). The contralateral leg underwent sham surgery with no ligation or excision. Hind limb perfusion was serially assessed for 28 days with laser Doppler imaging. At 28 days post occlusion, the hind limb vasculature was perfusion fixed following maximal dilation and perfused with bismuth for assessment of collateral morphology by micro‐CT imaging. These studies were complemented with immunohistochemistry and angiogenic assay experiments. Additional preliminary HLI experiments were conducted in male mice with endothelial cell‐specific MR (EC MR) deletion. Systemic inhibition of MR signaling enhanced recovery of hind limb perfusion in female, not male, mice. This effect of MR blockade was associated with greater outward collateral remodeling in females compared to males. Interestingly, spironolactone similarly increased skeletal muscle capillary density in both hind limbs of males and females consistent with impairment of VEGF‐stimulated capillary sprouting by the MR agonist aldosterone in an aortic angiogenesis assay. Finally, preliminary studies revealed enhanced recovery of hind limb perfusion in male mice with EC MR deletion and that EC MR deletion enhanced aortic capillary sprouting in vitro. Taken together, these data suggest that MR signaling limits the microvascular response to ischemia and that enhanced perfusion recovery following MR blockade in females involves greater collateral expansion compared to males. Significant vascular cell‐specificity of MR signaling underlying these responses may contribute to these sex differences and warrant further investigation.Support or Funding InformationFunded by HL136386, HL095590, and HL088105.

Effect of Spironolactone on Myocardial Fibrosis and Other Clinical Variables in Patients with Hypertrophic Cardiomyopathy

BackgroundMyocardial fibrosis has proved to be an important marker and determinant in the pathogenesis of hypertrophic cardiomyopathy. In particular, scar formation, if substantial, can promote ventricular tachyarrhythmias or progressive heart failure in the absence of left ventricular outflow obstruction. Therefore, an intervention to mitigate myocardial fibrosis would be potentially advantageous to hypertrophic cardiomyopathy patients. MethodsEligible hypertrophic cardiomyopathy patients were randomized 1:1 in a prospective double-blind fashion to spironolactone 50 mg or placebo to be taken over a 12-month period. The primary endpoint was the effect of mineralocorticoid receptor blockade on serum markers of collagen synthesis and degradation. A number of other functional and morphologic variables and biomarkers comprised secondary exploratory measures. ResultsFifty-three hypertrophic cardiomyopathypatients (41 ± 13 years old; 72% men) were randomized; demographic and clinical variable were well matched at baseline. Absolute change between baseline and 12 months did not differ between hypertrophic cardiomyopathy patients treated with spironolactone and those receiving placebo with respect to serum markers of collagen synthesis or degradation, fibrosis by late gadolinium enhancement on cardiac magnetic resonance imaging, or other clinical variables, including objective measure of functional capacity (peak VO2), New York Heart Association functional class, left ventricular wall thickness, mass and volume, and left atrial size, as well as assessment of diastolic function (P = .4-1.0). ConclusionsThese findings do not support the use of spironolactone in hypertrophic cardiomyopathy to improve left ventricular remodeling by mitigating myocardial fibrosis or altering clinical course.

Low-dose eplerenone decreases left ventricular mass in treatment-resistant hypertension.

Mineralocorticoid receptor antagonists are increasingly used in patients with treatment-resistant hypertension (TRH). There is experimental evidence for blood pressure (BP) independent effects of mineralocorticoid receptor blockade on cardiovascular target organ damage. We hypothesized that low-dose eplerenone (50 mg) will reduce left ventricular mass (LVM) beyond its BP-lowering effects. We performed a randomized, double-blind, placebo-controlled, parallel group study in 51 patients with TRH. Patients were allocated to receive either eplerenone 50 mg or placebo for 6 months, while other antihypertensive agents could be added in both groups to achieve a BP target of less than 140/90 mmHg. LVM was assessed by MRI before and after treatment. Baseline office BP was similar in the eplerenone and the placebo group (166 ± 21/91 ± 15 versus 159 ± 19/94 ± 8 mmHg, n.s.). BP was similarly reduced in the eplerenone versus the placebo group (-35 ± 20/-15 ± 11 versus -30 ± 19/-13 ± 7 mmHg, n.s.). However, LVM was reduced only in the eplerenone group (from 155 ± 33 to 136 ± 33 g, P < 0.001), but not in the placebo group (152 ± 32 versus 148 ± 38 g, P = 0.45). Despite similar BP-lowering, only patients with TRH who were allocated to eplerenone experienced a reduction of LVM. Thus, our data suggest that in patients with TRH, mineralocorticoid receptor antagonists should be used preferentially in order to achieve an effective reduction of LVM along with the improvement of BP control.

Effects of mineralocorticoid receptor blockade on empathy in patients with major depressive disorder.

The mineralocorticoid receptor (MR) is highly expressed in the hippocampus and prefrontal cortex and is involved in social cognition. We recently found that pharmacological stimulation of the MR enhances emotional empathy but does not affect cognitive empathy. In the current study, we examined whether blockade of the MR impairs empathy in patients with major depressive disorder (MDD) and healthy individuals. In a placebo-controlled study, we randomized 28 patients with MDD without psychotropic medication and 43 healthy individuals to either placebo or 300mg spironolactone, a MR antagonist. Subsequently, all participants underwent two tests of social cognition, the Multifaceted Empathy Test (MET) and the Movie for the Assessment of Social Cognition (MASC), measuring cognitive and emotional facets of empathy. In the MET, we found no significant main effect of treatment or main effect of group for cognitive empathy but a highly significant treatment by group interaction (p < 0.01). Patients had higher cognitive empathy scores compared to controls in the placebo condition but not after spironolactone. Furthermore, in the spironolactone condition reduced cognitive empathy was seen in MDD patients but not in controls. Emotional empathy was not affected by MR blockade. In the MASC, no effect of spironolactone could be revealed. Depressed patients appear to exhibit greater cognitive empathy compared to healthy individuals. Blockade of MR reduced cognitive empathy in MDD patients to the level of healthy individuals. Future studies should further clarify the impact of MR functioning on different domains of social cognition in psychiatric patients.

Effects of mineralocorticoid receptor blockade on empathy in patients with major depressive disorder

Effects of mineralocorticoid receptor blockade on empathy in patients with major depressive disorder

Effect of mineralocorticoid receptor blockade on hippocampal‐dependent memory in adults with obesity

ObjectiveThe hippocampus is crucial for paired-associate learning. Obesity is associated with increased MR activity in peripheral and possibly central tissues, decreased hippocampal size in humans and impaired hippocampal learning in rodents. The MR is expressed in hippocampal neurons and MR blockade improves hippocampal learning in obese animals. We sought to determine whether MR blockade would modulate paired-associate learning in obese men and women.Design and MethodsMen and women ages 20-61 years with BMIs between 30-45 kg/m2 were randomly assigned to placebo (n=11; 7 women) or 50 mg spironolactone daily (n=12; 7 women) for six weeks. At baseline and post treatment, subjects underwent a clinical and hormonal evaluation. They also underwent a computerized task that assesses paired-associate learning and has been shown by functional magnetic resonance imaging to activate the hippocampus.ResultsIn an ANCOVA model that adjusted for baseline paired-associate learning, age, and race, spironolactone treatment was associated with a significant (p=0.043) improvement in hippocampal memory as compared to placebo treatment.ConclusionsOur findings demonstrate, for the first time, that blocking MR with chronic, low-dose spironolactone treatment improves paired-associate learning in obese individuals, suggesting that MR activation contributes to hippocampal memory modulation in humans.

Abstract 543: Impact of Eplerenone on Vascular Function in LOX-1 Overexpressing Mice on High-Fat Diet

Experimental and clinical studies support a protective effect of aldosterone-binding mineralocorticoid receptor (MR) blockade on heart failure. The impact of MR antagonist eplerenone on endothelial function is less well understood. In this study, we analyzed the effects of high-fat diet (HFD) and MR blockade on metabolic parameters and endothelial function in mice overexpressing the endothelial oxidized LDL receptor LOX-1. Mice were fed standard diet (STD) or HFD with or without MR blocker eplerenone for 20 weeks. In agreement with clinical studies aldosterone plasma levels (LC-MS/MS) were elevated in eplerenone-treated mice. Body weight, epididymal, retroperitoneal, mesenteric and perivascular fat were increased after HFD. Diet-induced obesity elevated triglycerides, total cholesterol, and LDL plasma levels. Total cholesterol/HDL cholesterol ratio was increased in HFD fed LOX-1tg mice and decreased by eplerenone. LDLR-/- and HFD-fed LOX1tg and LOX1tg/LDLR-/- (LOLR) mice showed elevated fasting blood glucose levels compared to STD, which were partially normalized by eplerenone. LDLR-/-, LOX 1tg and LOLR mice had impaired endothelial function in thoracic aortas (Mulvany myograph) compared to C57BL/6J mice. HFD pronounced endothelial dysfunction in LOX-1tg and LOLR mice, which was improved by eplerenone. Reactive oxygen species can limit NO availability and were reduced in aorta and adipose tissues after eplerenone. Using a new method to evaluate flow-mediated dilation with a self-developed Optical Coherence Tomography (OCT) device, we could show endothelial dysfunction in saphenous artery in vivo after HFD. This was not restored by eplerenone. In epididymal white adipose tissue of LOX-1tg mice, HFD increased CD206, CD11c, F4/80, leptin, NADPH oxidase (Nox) 1, 2 and 4 and TNF-α mRNA expression (real-time PCR). Eplerenone treatment had no significant impact on CD11c, F4/80 and IL-6 expression, but elevated anti-inflammatory IL-10. CD206, Nox1, Nox2 and Nox4 expression was reduced by eplerenone in mice on HFD. In conclusion, our data support beneficial effects of MR blockade by eplerenone on endothelial function, metabolic parameters, inflammation and oxidative stress in a proatherosclerotic mouse model overexpressing LOX-1 on HFD.

Beneficial effects of mineralocorticoid receptor blockade in experimental non-alcoholic steatohepatitis.

Therapeutic options to treat Non-alcoholic steatohepatitis (NASH) are limited. Mineralocorticoid receptor (MR) activation could play a role in hepatic fibrogenesis and its modulation could be beneficial for NASH. To investigate whether eplerenone, a specific MR antagonist, ameliorates liver damage in experimental NASH. C57bl6 mice were fed a choline-deficient and amino acid-defined (CDAA) diet for 22 weeks with or without eplerenone supplementation. Serum levels of aminotransferases and aldosterone were measured and hepatic steatosis, inflammation and fibrosis scored histologically. Hepatic triglyceride content (HTC) and hepatic mRNA levels of pro-inflammatory pro-fibrotic, oxidative stress-associated genes and of MR were also assessed. CDAA diet effectively induced fibrotic NASH, and increased the hepatic expression of pro-inflammatory, pro-fibrotic and oxidative stress-associated genes. Hepatic MR mRNA levels significantly correlated with the expression of pro-inflammatory and pro-fibrotic genes and were significantly increased in hepatic stellate cells obtained from CDAA-fed animals. Eplerenone administration was associated to a reduction in histological steatosis and attenuation of liver fibrosis development, which was associated to a significant decrease in the expression of collagen-α1, collagen type III, alpha 1 and Matrix metalloproteinase-2. The expression of MR correlates with inflammation and fibrosis development in experimental NASH. Specific MR blockade with eplerenone has hepatic anti-steatotic and anti-fibrotic effects. These data identify eplerenone as a potential novel therapy for NASH. Considering its safety and FDA-approved status, human studies are warranted.

Cardiac Magnetic Resonance Assessment of Interstitial Myocardial Fibrosis and Cardiomyocyte Hypertrophy in Hypertensive Mice Treated With Spironolactone

BackgroundNearly 50% of patients with heart failure (HF) have preserved LV ejection fraction, with interstitial fibrosis and cardiomyocyte hypertrophy as early manifestations of pressure overload. However, methods to assess both tissue characteristics dynamically and noninvasively with therapy are lacking. We measured the effects of mineralocorticoid receptor blockade on tissue phenotypes in LV pressure overload using cardiac magnetic resonance (CMR).Methods and ResultsMice were randomized to l‐nitro‐ω‐methyl ester (l‐NAME, 3 mg/mL in water; n=22), or l‐NAME with spironolactone (50 mg/kg/day in subcutaneous pellets; n=21). Myocardial extracellular volume (ECV; marker of diffuse interstitial fibrosis) and the intracellular lifetime of water (τic; marker of cardiomyocyte hypertrophy) were determined by CMR T1 imaging at baseline and after 7 weeks of therapy alongside histological assessments. Administration of l‐NAME induced hypertensive heart disease in mice, with increases in mean arterial pressure, LV mass, ECV, and τic compared with placebo‐treated controls, while LV ejection fraction was preserved (>50%). In comparison, animals receiving both spironolactone and l‐NAME (“l‐NAME+S”) showed less concentric remodeling, and a lower myocardial ECV and τic, indicating decreased interstitial fibrosis and cardiomyocyte hypertrophy (ECV: 0.43±0.09 for l‐NAME versus 0.25±0.03 for l‐NAME+S, P<0.001; τic: 0.42±0.11 for l‐NAME groups versus 0.12±0.05 for l‐NAME+S group). Mice treated with a combination of l‐NAME and spironolactone were similar to placebo‐treated controls at 7 weeks.ConclusionsSpironolactone attenuates interstitial fibrosis and cardiomyocyte hypertrophy in hypertensive heart disease. CMR can phenotype myocardial tissue remodeling in pressure‐overload, furthering our understanding of HF progression.

Mineralocorticoid Receptor Blockade Reduced Oxidative Stress in Renal Transplant Recipients: A Double-Blind, Randomized Pilot Study

Background: Previous experimental studies from our laboratory have demonstrated that aldosterone plays a central role in renal ischemic processes. This study was designed to evaluate the effect of mineralocorticoid receptor blockade in renal transplant recipients from living donors. Methods: 20 adult kidney transplant recipients from living donors were included in a double-blind, randomized, placebo-controlled clinical pilot study that compared spironolactone and placebo. Placebo or spironolactone (25 mg) was administered 1 day before and 3 days posttransplantation. Renal function and urinary kidney injury molecule-1, interleukin-18, and heat shock protein 72 as well as urinary hydrogen peroxide (H₂O₂) levels were quantified. Results: No significant differences were seen between the groups studied regarding age, gender, indication for kidney transplantation, residual renal function, renal replacement therapy, or warm and cold ischemia periods. In contrast, spironolactone administration significantly reduced the oxidative stress assessed by the urinary H₂O₂ excretion, in spite of no differences in renal function or reduction in tubular injury biomarkers. Conclusions: The findings of this exploratory study strongly suggest that aldosterone promotes oxidative stress and that the administration of spironolactone reduces the production of urinary H₂O₂ as a result of lesser formation of surrogate reactive oxygen species secondary to the ischemia-reperfusion phenomenon.

Spironolactone reduces blood pressure and albuminuria of obese hypertensive patients with Metabolic Syndrome

In recent years, a role for aldosterone in pathophysiology of metabolic syndrome and hypertension in this syndrome has been suggested. However, the treatment with antagonists of mineralocorticoid receptor in these individuals has not properly addressed. To evaluate the effects of mineralocorticoid receptor blockade on blood pressure, inflammatory, metabolic and renal parameters in non-diabetic hypertensive individuals with the metabolic syndrome. Twenty nine patients with metabolic syndrome were enrolled in a prospective protocol that consisted of 2 periods: baseline (2 weeks) in which demographic data were obtained and antihypertensive medicines were withdrawn, and treatment period when the individuals were treated with spironolactone 25-50 mg once-a-day, for 16 weeks. In both periods, inflammatory, metabolic and renal parameters were assessed and the 24-hour ambulatory blood pressure monitorization was performed. After spironolactone treatment, 24 hour systolic and diastolic blood pressure decreased from 143.5 ± 15.17 mmHg to 133.2 ± 17.34 mmHg (p = 0.025) and from 85.2 ± 11.10 mmHg to 79.3 ± 11.78 mmHg (p = 0.026), respectively. HDL-cholesterol increased from 44.0 ± 8.67 mg/dl to 49.0 ± 6.75mg/dl (p = 0.000) and C-reactive protein decreased significantly from 6.3 ± 7.54 mg/l to 4.6 ± 6.3 mg/l (p = 0.009). Fasting plasma glucose, insulin, HOMA-IR and triglycerides did not change significantly after mineralocorticoid receptor blockade. Estimated glomerular filtration rate did not change whereas the logarithm of albuminuria decreased significantly from 2.5 ± 0.92 to 2.0 ± 0.9 (p = 0.028). In hypertensive subjects with MS the administration of spironolactone in monotherapy was effective for hypertension control, decreased urinary albumin excretion and increased HDL-cholester ol plasma.

Sex-specific Effects of Spironolactone on Blood Pressure in Gonadectomized Male and Female Wistar Rats

A low-salt diet is known to decrease and salt excess to increase blood pressure in humans and rodents. Sex steroids seem to play a role in salt dependent hypertension. However, little is known about sex differences in mineralocorticoid receptor blockade between male and female rats. The objective of the work was at first to investigate the effects of a low-salt vs. a high-salt diet on blood pressure without the influence of gonadal steroids in male and female rats. Second, to determine the sex-specific effects of mineralocorticoid receptor blockade by spironolactone in high-salt and low-salt fed gonadectomized male and female animals. Normotensive male and female Wistar rats were gonadectomized and put on a low (NaCl<0.03%) or high (NaCl=4%) salt diet. On each diet animals received spironolactone or placebo. Blood pressure was measured by tail-cuff-method; 24-h urine samples were collected in metabolic cages and blood was collected for hormonal measurements. High-salt diet significantly increased systolic blood pressure in both sexes. This effect could be blocked effectively by spironolactone only in male rats. Spironolactone treatment significantly increased aldosterone levels in males and females independent of the sodium content of the diet. High sodium diet significantly increased relative kidney weight, which was not altered by spironolactone treatment. Independently of gonadal steroids a high-salt diet increased blood pressure in gonadectomized male and female rats. Spironolactone lowered blood pressure only in male not in female rats on a high-salt diet clearly indicating sex-specific effects of the mineralo-corticoid antagonist spironolactone.

Protective effects of mineralocorticoid receptor blockade against neuropathy in experimental diabetic rats

Mineralocorticoid receptor (MR) blockade is an effective treatment for hypertension and diabetic nephropathy. There are no data on the effects of MR blockade on diabetic peripheral neuropathy (DPN). The aim of this study was to determine whether MRs are present in the peripheral nerves and to investigate the effectiveness of MR blockade on DPN in streptozotocin (STZ)-induced diabetic rats. Expression of MR protein and messenger RNA (mRNA) was examined in the peripheral nerves using Western blot analysis and RT-PCR. We next studied the effects of the selective MR antagonist eplerenone and the angiotensin II receptor blocker candesartan on motor and sensory nerve conduction velocity (NCV), morphometric changes and cyclooxygenase-2 (COX-2) gene and NF-κB protein expression in the peripheral nerves of STZ-induced diabetic rats. Expression of MR protein and mRNA in peripheral nerves was equal to that in the kidney. Motor NCV was significantly improved by 8 weeks of treatment with either eplerenone (39.1 ± 1.2 m/s) or candesartan (46.4 ± 6.8 m/s) compared with control diabetic rats (33.7 ± 2.0 m/s) (p < 0.05). Sensory NCV was also improved by treatment with candesartan or eplerenone in diabetic rats. Eplerenone and candesartan caused significant improvement in mean myelin fibre area and mean myelin area compared with control diabetic rats (p < 0.05). COX-2 mRNA and NF-κB protein were significantly elevated in the peripheral nerves of diabetic rats compared with control rats, and treatment with eplerenone or candesartan reduced these changes in gene expression (p < 0.05). MR blockade may have neuroprotective effects on DPN.

Aldosterone, From (Patho)Physiology to Treatment in Cardiovascular and Renal Damage

Aldosterone, a steroid hormone with mineralocorticoid activity, is far more than merely a salt-and-water hormone. Aldosterone has a number of non-classical, mineralocorticoid receptor (MR)-mediated actions, including tissue remodeling, modulation of vascular tone and stimulating inflammation and fibrosis, which may fuel progression of end organ damage. Aldosterone breakthrough during blockade of the renin-angiotensin aldosterone system (RAAS) may explain why this treatment regimen only confers partial cardiovascular and renal protection. Of major interest, aldosterone is deleterious only if inappropriately high for its sodium status i.e. high aldosterone and high sodium. The mechanism of sodium dependence of aldosterone-induced renal and cardiovascular damage continues to fascinate. Aldosterone excess increases sodium and fluid retention and consequently increases blood pressure, which, in turn, mediates target organ damage. Moreover, blood pressure independent effects play a role with dissociation of low circulating and high tissue aldosterone levels during high sodium intake and possibly enhanced MR signaling. MR blockade is a valuable strategy, which has potency to halt the progressive end organ damage as observed during current treatments. In heart failure, MR blockade on top of RAAS blockade reduces hard clinical endpoints. Despite encouraging results on the intermediate endpoint proteinuria, long-term data on the efficacy and safety of MR blockade in preventing dialysis and/or cardiovascular endpoints in chronic kidney disease are still lacking. It is obligatory that future clinical studies on the effects of MR blockade on end-organ damage take into account the sodium status.

Effects of mineralocorticoid receptor blockade on glucocorticoid-induced renal injury in adrenalectomized rats

Aldosterone is well recognized as the selective physiological ligand for mineralocorticoid receptor in epithelia. However, in-vitro studies have demonstrated that the affinity of aldosterone and glucocorticoids for mineralocorticoid receptor is similar. We hypothesized that glucocorticoids are involved in the development of renal injury through an mineralocorticoid receptor-dependent mechanism. Uninephrectomized (UNX) rats were treated with 1% NaCl and divided into three groups: vehicle, bilateral adrenalectomy (ADX) + hydrocortisone (HYDRO; 5 mg/kg/day, s.c.), ADX + HYDRO + eplerenone (0.125% in chow). HYDRO-treated UNX-ADX rats showed increased blood pressure and urinary albumin-to-creatinine ratio with an increase in the expression of the mineralocorticoid receptor target genes, serum and glucocorticoid-regulated kinases-1 and Na+/H+ exchanger isoform-1, in renal tissues. HYDRO treatment induced morphological changes in the kidney, including glomerulosclerosis and podocyte injury. Treatment with eplerenone markedly decreased the gene expression and reduced the albuminuria and renal morphological changes. In contrast, dexamethasone (0.2 mg/kg per day, s.c.) + UNX + ADX induced hypertension and albuminuria in different groups of rats. Eplerenone failed to ameliorate these changes. Our findings indicate that chronic glucocorticoid excess could activate mineralocorticoid receptor and, in turn, induce the development of renal injury.

Renoprotective effects of mineralocorticoid receptor blockade in heminephrectomized (pro)renin receptor transgenic rats

1. Nephropathy and elevated plasma aldosterone concentrations (PAC) have been observed in (pro)renin receptor transgenic (TG) rats. In the present study, we hypothesized that PAC and/or mineralocorticoid receptor contribute to the nephropathy of TG rats. To test this hypothesis, the effects of a high-sodium (8% NaCl) diet and heminephrectomy on PAC were examined. 2. Feeding of the high-sodium diet for 12 weeks similarly decreased PAC in TG and wild-type (WT) rats. Heminephrectomy further reduced PAC in TG rats fed a high-sodium diet, but had no effect on PAC in WT rats fed a high-sodium diet. 3. Next, the effects of eplerenone (125 mg/kg per day) and dietary salt restriction (0.36% NaCl diet) on proteinuria and renal morphology were examined in rats fed a high-sodium diet or subjected to heminephrectomy. Both eplerenone and dietary sodium restriction significantly reduced the arterial pressure of TG rats, but had no effect in WT rats. In TG rats, treatment with eplerenone significantly decreased urinary protein excretion, but dietary sodium restriction did not. 4. Nephrin and podocin mRNA levels, as determined by real-time quantitative reverse transcription-polymerase chain reaction, were significantly lower in TG rats than in WT rats. In TG rats, eplerenone treatment significantly increased nephrin mRNA levels, but not podocin mRNA levels. Dietary salt restriction significantly increased mRNA levels of both nephrin and podocin. Although zonula occludens (ZO)-1 mRNA levels were similar in both WT and TG rats, eplerenone treatment significantly decreased ZO-1 mRNA levels in TG rats. 5. The results of the present study suggest that the improvement in proteinuria following eplerenone treatment is independent of its effects on sodium balance and may be mediated by effects on the expression of slit diaphragm proteins.

Increased aldosterone among HIV-infected women with visceral fat accumulation

Increased aldosterone has been associated with obesity and the metabolic syndrome in non-HIV-infected individuals, but aldosterone has not been investigated among HIV-infected patients with increased visceral adipose tissue (VAT). Twenty-four-hour urine aldosterone was assessed among age and BMI-matched HIV-infected women with increased VAT, HIV-infected women without increased VAT and healthy controls. Twenty-four hour urine aldosterone was higher in HIV-infected women with increased VAT and was associated with SBP, VAT and hemoglobin A1c. Increased aldosterone may contribute to the detrimental effects of excess visceral adiposity on blood pressure and glucose homeostasis among HIV patients.

Effect of mineralocorticoid receptor blockade on the renal renin–angiotensin system in Dahl salt-sensitive hypertensive rats

The (pro)renin receptor exists in the kidney, blood vessels and the heart. (Pro)renin binds to the receptor and induces tissue injuries directly, completely independent of angiotensin II (Ang II). The renal renin-angiotensin-aldosterone system is activated in salt-sensitive hypertensive rats with in-vitro studies showing aldosterone increases angiotensin-converting enzyme (ACE) activity, renin production and angiotensin II type 1 receptor (AT1R) activity. However, the effect of blockade of mineralocorticoid receptor on the renal (pro)renin receptor, angiotensinogen, ACE and AT1R in Dahl salt-sensitive rats is unknown. The following parameters were measured in Dahl salt-sensitive rats and in Dahl salt-resistant rats fed high-salt or low-salt diets and treated for 8 weeks with or without eplerenone (100 mg/kg per day, orally): blood pressure, plasma renin activity, plasma aldosterone concentration, kidney weight and Ang II contents, urinary protein excretion, glomerular injury (assessed by semiquantitative morphometric analysis) and levels of expression in the kidney of (pro)renin receptor protein and messenger RNA (mRNA) for angiotensinogen, ACE and AT1R. Dahl salt-sensitive rats fed a high-salt diet had increased kidney/body weight (175%) and urinary protein excretion (886%) and decreased plasma renin activity and plasma aldosterone concentration. The rats developed progressive sclerotic and proliferative glomerular changes, concomitant with increased expression of renal (pro)renin receptor protein and mRNA levels of angiotensinogen, ACE and AT1R and kidney Ang II content. Treatment with eplerenone in Dahl salt-sensitive rats was associated with significant improvements in kidney to body weight ratio, urinary protein excretion and renal injury scores and decreased renal (pro)renin receptor protein expression and angiotensinogen and AT1R mRNA levels and kidney Ang II content. A high salt diet increased the renal renin-angiotensin system, whereas blockade of mineralocorticoid receptors attenuated renal injuries by decreasing the activity of tissue renin-angiotensin system in Dahl salt-sensitive rats.

Eplerenone Decreases Inflammatory Foci in Spontaneously Hypertensive Rat Hearts With Minimal Effects on Blood Pressure

The blood pressure (BP)-lowering effects of mineralocorticoid receptor (MR) antagonists in salt-sensitive rat models of hypertension are well understood. However, studies in salt-independent models have yielded mixed results, and therefore, we measured the hemodynamic effects of MR blockade in spontaneously hypertensive rats. We treated spontaneously hypertensive rats for 8 weeks with 30-300 mg.kg.d eplerenone or 20 mg.kg.d losartan and monitored BP using radiotelemetry and performed histopathological analyses of the hearts. Eplerenone, in contrast to losartan, caused only a small reduction in systolic BP at the highest dose tested. Both reduced left ventricular wall thickness, although eplerenone was less effective than losartan. Only losartan decreased heart weight. We observed foci of cardiomyopathy characterized by combinations of infiltrating monocytes, necrotic myocytes, and interstitial fibrosis in hearts of control animals. The number of foci seemed to be decreased in hearts of losartan- and eplerenone-treated animals. In a second study, using quantitative histomorphometry, the number of foci was significantly reduced by 20 mg.kg.d losartan (by 68%) or by 300 mg.kg.d eplerenone (by 50%). Our data support the hypothesis that a direct BP-independent effect on the progression of cardiomyopathy in the heart may be one basis for the cardiac protection afforded by MR antagonism.