Aldosteronism and peripheral blood mononuclear cell activation: a neuroendocrine-immune interface

Causes and consequences of zinc dyshomeostasis in rats with chronic aldosteronism

Iterations in Ca2+ and Mg2+ balance accompany aldosteronism (inappropriate for dietary Na+ intake). Increased Zn excretion and Zn translocation to injured tissues, including the heart, also occurs. Several causes and consequences of Zn dyshomeostasis in rats receiving aldosterone/salt treatment (ALDOST) were examined. (1) To study the role of urinary acidification in promoting hyperzincuria, acetazolamide (75 mg/kg), a carbonic anhydrase inhibitor, was used as cotreatment to raise urinary HCO3 excretion. (2) To assess Zn levels in the heart, including cardiomyocyte cytosolic free [Zn2+]i and mitochondrial Zn, the expression of metallothionein (MT-I), a Zn binding protein, and biomarkers of oxidative stress were examined. (3) Oxidative stress and cardiac pathology in response to ZnSO4 supplement (40 mg/d) were also studied. Comparison of controls and rats receiving 4 weeks ALDOST revealed the following: (1) an acidification of urine and metabolic alkalosis associated with increased urinary Zn excretion and hypozincemia, each of which were prevented by acetazolamide; (2) a rise in cardiac Zn, including increased [Zn2+]i and mitochondrial Zn, associated with increased tissue MT-I, 8-isoprostane, malondialdehyde, and gp91(phox), coupled with oxidative stress in plasma and urine; (3) ZnSO4 prevented hypozincemia, but not ionized hypocalcemia, and attenuated oxidative stress and microscopic scarring without preventing the vasculitis and perivascular fibrosis of intramural coronary arteries. Thus, the hyperzincuria seen with ALDOST is due to urinary acidification. The oxidative stress that appears in the heart is accompanied by increased tissue Zn serving as an antioxidant. Cotreatment with ZnSO4 attenuated cardiomyocyte necrosis; however, polynutrient supplement may be required to counteract the dyshomeostasis of all 3 cations that accompanies aldosteronism and contributes to cardiac pathology.

Macro- and micronutrient dyshomeostasis in the adverse structural remodelling of myocardium

Hypertension and heart failure are worldwide health problems of ever-increasing proportions. A failure of the heart, during either systolic and/or diastolic phases of the cardiac cycle, has its origins rooted in an adverse structural, biochemical, and molecular remodelling of myocardium that involves its cellular constituents, extracellular matrix, and intramural coronary vasculature. Herein we focus on the pathogenic role of a dyshomeostasis of several macro- (i.e. Ca(2+) and Mg(2+)) and micronutrients (i.e. Zn(2+), Se(2+), and vitamin D) in contributing to adverse remodelling of the myocardium and its failure as a pulsatile muscular pump. An improved understanding of how these macro- and micronutrients account for the causes and consequences of adverse myocardial remodelling carries with it the potential of identifying new biomarkers predictive of risk, onset and progression, and response to intervention(s), which could be monitored non-invasively and serially over time. Moreover, such incremental knowledge will serve as the underpinning to the development of novel strategies aimed at preventing and/or regressing the ongoing adverse remodelling of myocardium. The time is at hand to recognize the importance of macro- and micronutrient dyshomeostasis in the evaluation and management of hypertension and heart failure.

Tissue 65Zinc translocation in a rat model of chronic aldosteronism

Zinc, an essential micronutrient, is involved in wound healing. The hypozincemia seen with chronic aldosteronism is associated with enhanced fecal and urinary excretory Zn losses, and its tissue distribution is less certain. This study monitored tissue 65Zn distribution in uninephrectomized rats at weeks 1 and 4 of aldosterone/salt treatment (ALDOST). Plasma and tissue total radionucleotide uptake was determined by calculating its mean radioactivity at 1, 4, 8, 24, and 48 hours after intravenous 65Zn administration and where respective area under the concentration-time curves (AUC) were determined by the linear trapezoidal rule and expressed as a tissue:plasma AUC ratio. Examined tissues included: (1) injured heart and kidney in response to ALDOST and incised skin; (2) noninjured liver, skeletal muscle, and spleen sites of stress-linked Zn uptake; and (3) bone, a major storage and release site when Zn homeostasis is threatened. In comparison with age-matched and gender-matched controls, the following were found with week 1 and 4 ALDOST: (1) reduced plasma 65Zn; (2) an accumulation of 65Zn in heart and kidneys, where a well-known vasculopathy involves intramural vessels, and in incised skin at week 1; (3) an organ-specific increase in tissue 65Zn in liver, in keeping with upregulated metallothionein expression, skeletal muscle, and spleen; and (4) a fall in bone and healed skin Zn at week 4. Thus a wide-ranging disturbance in Zn homeostasis appears during ALDOST to include its translocation from plasma to injured heart, kidneys, and skin and noninjured liver, skeletal muscle, and spleen together with a resorption of stored Zn in bone at week 4. Zinc dyshomeostasis is an integral feature of chronic aldosteronism.

Cinacalcet and the prevention of secondary hyperparathyroidism in rats with aldosteronism

BACKGROUND

In rats receiving aldosterone/salt treatment (ALDOST), increased Ca2+ excretion leads to a fall in plasma-ionized Ca2+ and appearance of secondary hyperparathyroidism (SHPT) with parathyroid hormone (PTH)-mediated intracellular Ca2+ overloading inducing oxidative stress in diverse tissues. Parathyroidectomy prevents this scenario. Rats with ALDOST were cotreated with cinacalcet (Cina), a calcimimetic that raises the threshold of the parathyroids' Ca(2+)-sensing receptor.

METHODS AND RESULTS

We monitored plasma-ionized [Ca2+]o, PTH, and total Ca2+ in heart and peripheral blood mononuclear cells (PBMC), and evidence of oxidative stress in heart, PBMC, and plasma. Cina-treated rats for 4 weeks were compared with 4 weeks of ALDOST alone and with untreated age-/gender-matched controls. In comparison to controls, ALDOST led to a fall (P < 0.05) in Ca2+ (1.16 +/- 0.01 vs 1.03 +/- 0.01 mmol/L), which was not prevented by Cina (1.01 +/- 0.03 mmol/L); a rise (P < 0.05) in plasma PTH (36 +/- 7 vs 134 +/- 19 pg/mL) that was attenuated by Cina (69 +/- 12 pg/mL); increased (P < 0.05) cardiac [Ca2+] (3.92 +/- 0.25 vs 6.78 +/- 0.35 nEq/mg FFDT) and PBMC [Ca2+]i (29.8 +/- 2.3 vs 50.2 +/- 2.3 nmol/L), each of which was prevented with Cina (3.65 +/- 0.10 nEq/mg FFDT and 32.5 +/- 6.0 nmol/L, respectively); increased cardiac MDA (0.56 +/- 0.03 vs 0.94+/-0.07 nmol/mg protein) and PBMC H2O2 production (63.5 +/- 7.5 vs 154.0 +/- 25.2 mcb) and reduced (P < 0.05) plasma alpha1-AP activity (39.8 +/- 0.6 vs 29.6 +/- 1.8 mM), each prevented by Cina (0.66 +/- 0.04 mmol/mg protein, 58.2 +/- 12.7 mcb and 37.0 +/- 1.2 mM, respectively).

CONCLUSIONS

PTH-mediated intracellular Ca2+ overloading accounts for the induction of oxidative stress in diverse tissues in rats with aldosteronism and which can be prevented by Cina.

Aldosterone and the vascular system

Aldosterone can act in different tissues exerting physiological and pathological effects. At the vascular level, aldosterone affects endothelial function since administration of aldosterone impaired endothelium-dependent relaxations. In addition, the administration of mineralocorticoid receptor antagonists ameliorate relaxation to acetylcholine in models of both hypertension and atherosclerosis and in patients with heart failure. A reduction in nitric oxide levels seems to be the main mechanism underlying this effect due to a reduction in its production as well as an increase in its degradation by reactive oxygen species. Aldosterone is a pro-inflammatory factor that can participate in the vascular inflammatory process associated with different pathologies including hypertension through activation of the NFkappaB system, which mediates the vascular production of different cytokines. This mineralocorticoid also participates in the vascular remodeling observed in hypertensive rats since the administration of eplerenone improved the media-to-lumen ratio in these animals. This effect seems to be due to an increase in extracellular matrix. In summary, aldosterone through mineralocorticoid receptors can participate in the vascular damage associated with different pathologies including hypertension through its prooxidant, pro-inflammatory and profibrotic effects that triggered endothelial dysfunction, an inflammatory process and vascular remodeling.

Application of leukocyte transcriptomes to assess systemic consequences of risk factors for cardiovascular disease

Prevention of cardiovascular disease (CVD) remains a major health issue in the Western world. The diagnostic and therapeutic approach is currently based on risk factor assessment and treatment, which adequately predicts CVD at population level, but not at the level of a single individual. This may arise from the fact that the stage and activity of complex disease states are not likely to be captured by a single parameter or a small set of markers and thus may need a more complex representation. The aim of this review is to explore the possibility of pursuing the use of high-throughput gene expression profiling as a way to improve diagnosis, prognosis and monitoring of the disease. Novel chip-based techniques such as oligo- and cDNA microarrays can measure the abundance of thousands of mRNA transcripts in parallel and thus provide a comprehensive picture of the cell phenotype. Circulating white blood cells (WBCs), which are exposed to the systemic environment (including the risk factors) and are directly involved in the low-grade chronic inflammation related to CVD, have the potential to be used in this context to improve phenotyping of the patient. The paper reviews conceptual limitations in the use of risk factors and biomarkers, and shows the rationale beyond the possible use of circulating WBCs or subpopulations as representative cells to monitor systemic consequences of CVD. Methodological issues in performing microarray analysis of WBCs are also addressed, including controversies related to the choice of adequate cell populations and reference samples. Reproducibility and challenges occurring in the definition of a disease-specific gene panel are also discussed. The available proofs of principle from the literature presented in the last section of the review further support exploration of the application of circulating cell transcriptomics in CVD.

Congestive heart failure is a systemic illness: a role for minerals and micronutrients

Congestive heart failure (CHF) is a clinical syndrome that features a failing heart together with signs and symptoms arising from renal retention of salt and water, mediated by attendant neurohormonal activation, and which prominently includes the renin-angiotensin-aldosterone system. More than this cardiorenal perspective, CHF is accompanied by a systemic illness whose features include an altered redox state in diverse tissues and blood, an immunostimulatory state with proinflammatory cytokines and activated lymphocytes and monocytes, and a wasting of tissues that includes muscle and bone. Based on experimental studies of aldosteronism and clinical findings in patients with CHF, there is an emerging body of evidence that secondary hyperparathyroidism is a covariant of CHF. The aldosteronism of CHF predisposes patients to secondary hyperparathyroidism because of a chronic increase in Ca(2+) and Mg(2+) losses in urine and feces, with a fall in their serum ionized levels and consequent secretion of parathyroid hormone. Secondary hyperparathyroidism accounts for bone resorption and contributes to a fall in bone strength that can lead to nontraumatic fractures. The long-term use of a loop diuretic with its attendant urinary wasting of Ca(2+) and Mg(2+) further predisposes patients to secondary hyperparathyroidism and attendant bone loss. Aberrations in minerals and micronutrient homeostasis that includes Ca(2+), Mg(2+), vitamin D, zinc and selenium appear to be an integral component of pathophysiologic expressions of CHF that contributes to its systemic and progressive nature. This broader perspective of CHF, which focuses on the importance of secondary hyperparathyroidism and minerals and micronutrients, raises the prospect that dietary supplements could prove remedial in combination with the current standard of care.

Renal disease in recipients of nonrenal solid organ transplantation

Worldwide, more than 250,000 individuals who have received a liver, heart, lung, or intestinal transplant are living longer. Twenty percent to 25% of these recipients experience perioperative acute renal failure, with 10% to 15% requiring renal replacement therapy. Chronic kidney disease (CKD) is also highly prevalent, affecting 30% to 50% of the nonrenal organ transplant population with an annual end-stage renal disease risk of 1.5% to 2.0%. Both acute renal failure and CKD contribute to increased morbidity and premature mortality. The dominant causative factor for renal disorders seen in nonrenal transplant recipients are the calcineurin inhibitors (CNI) and rapamycin analogues, which singly or in combination lead to a variety of nephrotoxic injury. However, 25% to 30% of nonrenal transplant recipients with CKD have other conditions such as hypertension, focal segmental glomerulosclerosis, diabetes mellitus, and hepatitis C infection as the principal underlying cause. Management strategies for renal disease in the nonrenal transplant recipients include the following: (1) delayed introduction of CNI after graft implantation, (2) withdrawal or minimization of long-term CNI therapy, (3) timely use of an appropriate dialysis modality, and (4) expeditious introduction of supportive measures such as anemia management, phosphate binding therapy, and dietary modification. Compared with maintenance dialysis, kidney transplantation reduces long-term mortality by 60% to 70% in nonrenal transplant recipients with end-stage renal disease.

Drug Insight: aldosterone-receptor antagonists in heart failure—the journey continues

Aldosterone is an important mediator in the pathogenesis of heart failure, and increased plasma aldosterone levels are associated with a poor prognosis. Aldosterone-receptor blocking drugs can slow the progression of left ventricular remodeling and reduce the occurrence of sudden cardiac death. Two widely publicized clinical trials provide data demonstrating survival benefits with spironolactone and eplerenone in chronic and postinfarction heart failure. The publication of these trials has generated widespread enthusiasm for spironolactone and eplerenone, leading to the more frequent and sometimes unbridled use of these drugs in the medical community. We herein describe the likely mechanisms of action of aldosterone-receptor antagonists, discuss the existing clinical evidence supporting their use, and provide practical advice on their use in the management of patients with heart failure.

Pretreatment with eplerenone reduces stroke volume in mouse middle cerebral artery occlusion model

Eplerenone, a mineralocorticoid receptor antagonist, is reported to be effective to prevent end-stage cardiovascular damage induced by aldosterone. However, the effect of eplerenone on brain damage is not fully understood. Here, we investigated whether pretreatment with eplerenone attenuates stroke size in mice subjected to middle cerebral artery occlusion. Middle cerebral artery occlusion with a microfilament technique induced focal ischemia, to approximately 25% of the total area in a coronal section of the brain. Treatment with eplerenone at a dose of 1.67 mg/g chow significantly reduced the ischemic area, ischemic volume, and neurological deficit, without a blood pressure-lowering effect. Laser-Doppler flowmetry analysis showed a decrease in surface cerebral blood flow in the peripheral region after 1 h of middle cerebral artery occlusion. This decrease was smaller in mice treated with eplerenone. Superoxide production evaluated by staining with dihydroethidium was attenuated in the ischemic area of the brain in eplerenone-treated mice. Taken together, our findings suggest that eplerenone has a protective effect on ischemic brain damage, at least partly due to improvement of cerebral blood flow in the penumbra and reduction of oxidative stress.

Aldosterone, mineralocorticoid receptors, and vascular inflammation

PURPOSE OF REVIEW

Aldosterone and its mineralocorticoid receptor represent an ancient signaling system. Indeed, the mineralocorticoid receptor is older than its agonist. Both have probably served various functions through the eons and salt preservation may be relatively recent. A large body of evidence suggests that aldosterone conducts signaling in vascular cells and contributes substantially to vascular remodeling and target organ damage. A blood pressure and salt balance-independent effect was first observed in two large heart failure trials.

RECENT FINDINGS

Mineralocorticoid receptor blockade has now been shown to reduce proteinuria even in the face of angiotensin converting enzyme inhibition and AT1 receptor blockade. Mineralocorticoid receptor blockade effectively reduces target organ damage in every hypertensive model tested, irrespective of circulating renin and aldosterone levels. Protection is also observed in nonhypertensive diabetic and hyperlipidemic models. Signaling in vascular cells involves primarily the mitogen activated protein kinase pathway with participation of the epidermal growth factor receptor. Novel signaling molecules have been shown to participate in aldosterone-mediated actions including the murine double-minute type 2 protein that participates in antiapoptotic and proliferative effects. Clinically, mutations in the mineralocorticoid receptor have shed additional light on its importance.

SUMMARY

A resurgence of interest in aldosterone reflects its importance and clinical relevance for vascular remodeling and target organ damage.

Drospirenone for Oral Contraception and Hormone Replacement Therapy

The use of combined estrogen/progesterone has been shown to result in an increased cardiovascular risk in randomised double-blinded trials. However, these studies used oral progestogen (progestin) preparations, which lack anti-mineralocorticoid activity and have suboptimal anti-androgenic activity compared with progesterone. Drospirenone is a unique progestogen that has clinically been shown to have anti-mineralocorticoid/anti-androgenic effects. Drospirenone in combination with estrogen is currently being used for oral contraception and hormone replacement therapy, and has been shown to have favourable effects on a number of cardiovascular risk factors. Our review of the literature suggests that because of its anti-mineralocorticoid effects, drospirenone in conjunction with estrogen may prevent the development of cardiovascular disease in both pre- and post-menopausal women.

Micronutrients in African-Americans with decompensated and compensated heart failure

Heart failure is thought to be more common and of greater severity in African-Americans (AAs). Potential mechanisms remain uncertain. The importance of micronutrient deficiencies in the pathophysiologic expression of congestive heart failure (CHF) in AAs remains to be explored, including hypovitaminosis D, which can promote secondary hyperparathyroidism (SHPT), together with hypozincemia and hyposelenemia, the 2 most crucial trace minerals integral to diverse biologic functions. Serum parathyroid hormone (PTH), 25-hydroxyvitamin D (25(OH)D), Zn, and Se were monitored in 30 AAs hospitalized during June through December 2005, with decompensated failure and reduced ejection fraction (EF) (<35%) of predominantly nonischemic origin treated with an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin receptor blocker (ARB), furosemide, and spironolactone. Based on their symptomatic status before hospitalization, 15 patients were stratified as having protracted (>or=4 weeks) CHF, whereas 15 patients had short-term (1-2 weeks) CHF. These hospitalized patients were compared with 10 AA outpatients with stable, similarly treated compensated failure and comparable EF, and 9 AA normal volunteers without cardiovascular disease. Serum PTH was elevated in all patients with protracted CHF and in 60% of patients with short-term CHF, but not in compensated patients or normal volunteers. However, serum 25(OH)D was reduced in all patients with >or=4 weeks and 80% with either 1-2 weeks CHF or compensated failure compared with volunteers. Serum Zn was below normal in 11 of 15 patients with protracted CHF, in 8 of 15 patients with shorter duration CHF, and in 5 of 10 patients with compensated failure. Serum Se was reduced in all patients with >or=4 weeks, 60% with short-term CHF, and 90% of compensated patients. Concomitant to hypovitaminosis D, hypozincemia, and hyposelenemia, SHPT is a covariant of CHF in housebound AAs.

Macro- and micronutrients in African-Americans with heart failure

An emerging body of evidence suggests secondary hyperparathyroidism (SHPT) may be an important covariant of congestive heart failure (CHF), especially in African-Americans (AA) where hypovitaminosis D is prevalent given that melanin, a natural sunscreen, mandates prolonged exposure of skin to sunlight and where a housebound lifestyle imposed by symptomatic CHF limits outdoor activities and hence sunlight exposure. In addition to the role of hypovitaminosis D in contributing to SHPT is the increased urinary and fecal losses of macronutrients Ca(2+) and Mg(2+) associated with the aldosteronism of CHF and their heightened urinary losses with furosemide treatment of CHF. Thus, a precarious Ca(2+) balance seen with reduced serum 25(OH)D is further compromised when AA develop CHF with circulating RAAS activation and are then treated with a loop diuretic. SHPT accounts for a paradoxical Ca(2+) overloading of diverse tissues and the induction of oxidative stress at these sites which spills over to the systemic circulation. In addition to SHPT, hypozincemia and hyposelenemia have been found in AA with compensated and decompensated heart failure and where an insufficiency of these micronutrients may have its origins in inadequate dietary intake, altered rates of absorption or excretion and/or tissue redistribution, and treatment with an ACE inhibitor or AT(1) receptor antagonist. Zn and Se deficiencies, which compromise the activity of several endogenous antioxidant defenses, could prove contributory to the severity of heart failure and its progressive nature. These findings call into question the need for nutriceutical treatment of heart failure and which is complementary to today's pharmaceuticals, especially in AA.

Systemic inflammation in heart failure--the whys and wherefores

Patients with chronic heart failure (HF) are characterized by systemic inflammation, as evident by raised circulating levels of several inflammatory cytokines with increasing levels according to the degree of disease severity. In addition to the myocardium itself, several tissues and cells can contribute to this inflammation, including leukocytes, platelets, tissue macrophages and endothelial cells. Although the mechanisms for the systemic inflammation is unknown, both infectious (e.g., endotoxins) and non-infectious (e.g., oxidative stress and hemodynamic overload) events could be operating, also including activation of Toll-like receptors as well as interaction with the neurohormone system. A growing body of evidence suggests that this systemic inflammation in chronic HF may play a role in the development and progression of this disorder, not only by promoting myocardial dysfunction, but also by inducing pathogenic consequences in other organs and tissues, thereby contributing to additional aspects of the HF syndrome such as cachexia, endothelial dysfunction and anemia. Although this inappropriate immune activation and inflammation could represent a new target for therapy in patients with chronic HF, the anti-tumor necrosis factor trials have been disappointing, and future research in this area will have to more precisely identify the most important mechanisms and actors in the immunopathogenesis of chronic HF in order to develop better immunomodulating agents for this disorder.

Aldosterone synthesis and cytokine production in human peripheral blood mononuclear cells

Previously, we reported that spironolactone reduced cytokine production in cultured human peripheral blood mononuclear cells (PBMCs) with angiotensin (Ang) II stimulation. To address the mechanisms underlying this effect, we examined the contribution of aldosterone to cytokine production in cultured human PBMCs with Ang II stimulation. PBMCs expressed the messenger RNA (mRNA) of Ang II type 1 receptor (AT1R) and mineralocorticoid receptor (MR) both spontaneously and after Ang II stimulation, but expressed Ang II type 2 receptor (AT2R) under neither condition. After 24 h of incubation, exogenous Ang II induced the expression of CYP11B2 (a key enzyme of aldosterone synthesis) mRNA and caused aldosterone synthesis. CV-11974 (an AT1R antagonist) reduced Ang II-induced aldosterone synthesis, whereas PD-123319 (an AT2R antagonist) had no effect. The concentration of aldosterone peaked earlier than those of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-alpha). After 48 h of incubation (under the influence of synthesized aldosterone), CV-11974 and spironolactone significantly reduced the Ang II-enhanced production of MCP-1 and TNF-alpha, whereas PD-123319 also had no effect. In conclusion, Ang II induces aldosterone synthesis through AT1R and enhances cytokine production through an AT1R-dependent mechanism and, at least partly, through a MR-dependent mechanism in human PBMCs.

Secondary hyperparathyroidism and hypovitaminosis D in African-Americans with decompensated heart failure

OBJECTIVE

We previously noted secondary hyperparathyroidism (SHPT) in African-American patients hospitalized during February, 2005 with either untreated or treated congestive heart failure (CHF) due to ischemic or idiopathic cardiomyopathy. Herein, we hypothesized that housebound African-American patients hospitalized during the period of June 1 through August 31, 2005, with CHF would have SHPT and hypovitaminosis D.

METHODS

Twenty-five African-American patients with an ejection fraction (EF) less than 35% due to ischemic or dilated (idiopathic) cardiomyopathy were monitored: 20 were hospitalized with CHF, stratified on historical grounds as of 4 weeks' or longer duration or of 1 to 2 weeks' duration in 11 and 9 patients, respectively, despite medical care that included furosemide; serum parathyroid hormone (PTH) and 25(OH)D at the time of admission in these patients were compared to five asymptomatic outpatients seen during the summer with stable, compensated failure.

RESULTS

Serum PTH was elevated (127 +/- 13; 82-243 pg/mL) in all patients with CHF of 4 weeks' or longer duration (normal, 12-65 pg/mL) and was elevated in three of nine patients (59 +/- 8; 18-99 pg/mL) with CHF of 1 to 2 weeks' duration. Ionized hypocalcemia (1.09 +/- 0.03 and 1.08 +/- 0.02 mmol/L; normal, 1.12-1.30) and hypomagnesemia (0.47 +/- 0.02 and 0.46 +/- 0.03 mmol/L; normal, 0.53-0.67) were respectively found in long- or short-duration CHF. No compensated patient had elevated PTH (42 +/- 5; 17-53). Hypovitaminosis D (< or =30 ng/mL) was universally present in patients with CHF of 4 weeks' or longer duration (15.1 +/- 1.4; 7.0-23.8 ng/mL) and was also prevalent in the other groups (20.3 +/- 5.1, 7.0-54.1 ng/mL in CHF of 1 to 2 weeks' duration and 23.1 +/- 4.9; 17.2-42.7 ng/mL in compensated failure).

CONCLUSIONS

In African-American patients with CHF, hypovitaminosis D, aldosteronism, and loop diuretic treatment each exaggerate Ca and Mg losses to stress a fragile Ca balance leading to ionized hypocalcemia and hypomagnesemia with SHPT.

Osteopontin and carotid atherosclerosis in patients with essential hypertension

OPN (osteopontin), a pro-inflammatory cytokine, has recently emerged as a key factor in both vascular remodelling and the development of atherosclerosis. However, the relationship between OPN and atherosclerosis in patients without symptomatic cardiovascular disease is not clear. Therefore we measured plasma OPN levels and evaluated the correlation between plasma OPN levels and atherosclerosis as target organ damage in patients with EHT (essential hypertension). Plasma OPN levels were measured in 76 patients with EHT using a solid-phase sandwich ELISA. IMT (intima-media thickness), and Vd and Vs (mean diastolic and systolic flow velocities respectively) were evaluated by carotid ultrasound. The Vd/Vs ratio, an index of peripheral arterial resistance, was also calculated. The patients were divided on the basis of median OPN levels into a high-OPN group and a low-OPN group. The mean IMT and aldosterone levels were higher (P=0.024 and 0.031 respectively) and Vd/Vs was lower (P=0.007) in the high-OPN group than in the low-OPN group. Plasma OPN levels were positively correlated with mean IMT (r=0.308, P=0.0068) and negatively with Vd/Vs (r=−0.293, P=0.010). Stepwise regression analysis revealed that OPN was an independent determinant of mean IMT (P=0.007) and Vd/Vs (P=0.009), and aldosterone was an independent determinant of OPN. These results suggest that OPN plays a role in the development of atherosclerosis and may be a potential clinical marker for the prediction of atherosclerosis in patients with EHT.

Preventing oxidative stress in rats with aldosteronism by calcitriol and dietary calcium and magnesium supplements

BACKGROUND

Prominent features of the clinical syndrome of congestive heart failure (CHF) include aldosteronism and the presence of oxidative stress. Secondary hyperparathyroidism (SHPT) accompanies aldosteronism due to increased urinary and fecal excretion of Ca. SHPT accounts for intracellular Ca overloading of diverse cells, including peripheral blood mononuclear cells (PBMC), and the appearance of oxidative stress. Parathyroidectomy or a Ca channel blocker each prevent these responses. Herein, we hypothesized calcitriol, or 1,25(OH)2D3, plus a diet supplemented with Ca and Mg (CMD) would prevent SHPT and Ca overloading of PBMC and thereby oxidative stress in these cells in rats receiving aldosterone/salt treatment (ALDOST).

METHODS AND RESULTS

In rats with ALDOST for 4 weeks, without or with CMD, we monitored plasma-ionized [Ca]o and parathyroid hormone (PTH), and PBMC cytosolic-free [Ca]i and H2O2 production. Untreated, age- and gender-matched rats served as controls. Compared to controls, ALDOST led to an expected fall in plasma [Ca]o level with accompanying rise in plasma PTH level and intracellular Ca overloading of PBMC and their increased production of H2O2. CMD prevented SHPT and abrogated intracellular Ca overloading of PBMC and their increased H2O2 production.

CONCLUSIONS

The appearance of SHPT in aldosteronism, induced by fallen plasma [Ca]o, leads to PTH-mediated Ca overloading of PBMC and their increased production of H2O2. SHPT in rats with aldosteronism can be prevented by calcitriol and a diet supplemented with Ca and Mg. These findings raise the prospect that the SHPT found in CHF could be managed with macro- and micronutrients.

EPLERENONE PREVENTS ADVERSE CARDIAC REMODELLING INDUCED BY PRESSURE OVERLOAD IN ATRIAL NATRIURETIC PEPTIDE-NULL MICE

1. Atrial natriuretic peptide (ANP)-null mice (Nppa(-/-)) exhibit cardiac hypertrophy at baseline and adverse cardiac remodelling in response to transverse aortic constriction (TAC)-induced pressure overload stress. Previous studies have suggested that natriuretic peptides could potentially oppose mineralocorticoid signalling at several levels, including suppression of adrenal aldosterone production, inhibition of mineralocorticoid receptor (MR) activation or suppression of MR-mediated production of pro-inflammatory factors. Thus, we hypothesized that the MR blocker eplerenone would prevent the exaggerated left ventricular (LV) remodelling/fibrosis and dysfunction after TAC in Nppa(-/-). 2. In the present study, Nppa(-/-) and wild-type Nppa(+/+) mice fed eplerenone- or vehicle (oatmeal)-supplemented chow since weaning were subjected to TAC or sham operation. The daily dose of eplerenone administered was approximately 200 mg/kg. At 1 week after TAC, LV size and function were evaluated by echocardiogram and LV cross-sections were stained with picrosirius red for collagen volume measurement. Total RNA was extracted from the LV for real-time polymerase chain reaction analysis of osteopontin. 3. Eplerenone had no effect on baseline hypertrophy observed in sham-operated Nppa(-/-) compared with Nppa(+/+) mice. Eplerenone attenuated the TAC-induced increase in LV weight in both genotypes and completely prevented LV dilation, systolic dysfunction and interstitial collagen deposition seen in Nppa(-/-) mice after TAC. However, serum aldosterone levels were lower in Nppa(-/-) compared with Nppa(+/+) wild types. No interaction between eplerenone and genotype in osteopontin mRNA levels was observed. 4. Eplerenone prevents adverse cardiac remodelling related to pressure overload in ANP-deficient mice, mainly due to an antifibrotic effect. The mechanism whereby ANP deficiency leads to excess hypertrophy, fibrosis and early failure following TAC is increased profibrotic signals resulting from excess or unopposed MR activation, rather than increased levels of aldosterone.

Secondary hyperparathyroidism in patients with untreated and treated congestive heart failure

BACKGROUND

The congestive heart failure syndrome includes a systemic illness with wasting of soft tissues and bone. We hypothesized secondary hyperparathyroidism (HPT) would be found in hospitalized patients with decompensated congestive heart failure (CHF), where secondary aldosteronism is expected, and who were either untreated or treated medically.

METHODS

In 9 consecutive patients (7 males, 2 females; 8 African-American, 1 Caucasian; 33-60 yrs) admitted to the Regional Medical Center during a 28-day period with chronic left ventricular systolic dysfunction (EF<35%) and decompensated CHF (5 untreated; 4 treated with an angiotensin converting enzyme inhibitor, furosemide, and small-dose spironolactone), we measured: plasma parathyroid hormone (PTH); serum calcium corrected for albumin, magnesium, and phosphorus; serum creatinine and calculated creatinine clearance.

RESULTS

Plasma PTH was elevated above the normal range (6-65 pg/mL) in both untreated and treated patients with CHF (204+/-60 and 134+/-14 pg/mL, respectively). Serum corrected calcium was normal (8.4-10.2 mg/dL) in both untreated and treated CHF (9.7+/-0.l and 9.1+/-0.2 mg/dL, respectively) as were serum magnesium and phosphorus. Calculated creatinine clearance did not differ between untreated and treated patients (74+/-15 and 83+/-21 mL/min, respectively).

CONCLUSIONS

Secondary HPT was found in 5 untreated and 4 treated patients consecutively hospitalized over a 28-day period with decompensated CHF. Corrected serum calcium was normal. Plasmaionized calcium, a determinant of PTH secretion, was not measured. Although vitamin D levels were not assessed, the presence of hypovitaminosis D in these housebound patients with symptomatic CHF cannot be discounted. HPT may contribute to the systemic illness that accompanies CHF, including bone wasting.

Systemic inflammation in heart failure--the whys and wherefores

Patients with chronic heart failure (HF) are characterized by systemic inflammation, as evident by raised circulating levels of several inflammatory cytokines with increasing levels according to the degree of disease severity. In addition to the myocardium itself, several tissues and cells can contribute to this inflammation, including leukocytes, platelets, tissue macrophages and endothelial cells. Although the mechanisms for the systemic inflammation is unknown, both infectious (e.g., endotoxins) and non-infectious (e.g., oxidative stress and hemodynamic overload) events could be operating, also including activation of Toll-like receptors as well as interaction with the neurohormone system. A growing body of evidence suggests that this systemic inflammation in chronic HF may play a role in the development and progression of this disorder, not only by promoting myocardial dysfunction, but also by inducing pathogenic consequences in other organs and tissues, thereby contributing to additional aspects of the HF syndrome such as cachexia, endothelial dysfunction and anemia. Although this inappropriate immune activation and inflammation could represent a new target for therapy in patients with chronic HF, the anti-tumor necrosis factor trials have been disappointing, and future research in this area will have to more precisely identify the most important mechanisms and actors in the immunopathogenesis of chronic HF in order to develop better immunomodulating agents for this disorder.

Metabolic and immunologic derangements in cardiac cachexia: where to from here?

The onset of cardiac cachexia is characterized by a defined severe weight loss in patients with advanced chronic heart failure and it predicts an increased mortality in these patients. Recent studies with potential therapeutics investigated the effects and efficiency of beta-blockers, ghrelin, or ghrelin-agonists in cachexia. These and other new studies, like the influence of heart transplantation on cardiac cachexia, give prospect into potential therapeutic options in the future. General aim of the treatment strategy is to prevent the onset and retard the progress of cachexia. This could be achieved by modifying the metabolic, neurohormonal and immune system abnormalities, e.g. with beta-blockers and angiotensin-converting enzyme inhibitors. However, these alterations interact in a complex pathophysiological process, which is supposed to end in a vicious circle and thereby the wasting process is further promoted. To interrupt this, an early start of therapy is important to decelerate the development of cardiac cachexia. Many further investigations are needed to find out more about the pathophysiological pathways, to confirm the previous results, and to evaluate new therapeutics.

Mechanisms of disease: pathologic structural remodeling is more than adaptive hypertrophy in hypertensive heart disease

Changes in the composition of cardiac tissue develop in arterial hypertension and lead to structural remodeling of the myocardium. Structural remodeling is the consequence of a number of pathologic processes, mediated by mechanical, neurohormonal and cytokine routes, occurring in the cardiomyocyte and the noncardiomyocyte compartments of the heart. One of these processes is related to the disruption of the equilibrium between the synthesis and degradation of collagen type I and III molecules, which results in an excessive accumulation of collagen type I and III fibers in the interstitium and the perivascular regions of the myocardium. The clinical relevance of ventricular fibrosis is that it might contribute to the increased cardiac risk of patients with hypertensive heart disease. This review focuses on the mechanisms of hypertensive ventricular fibrosis and its clinical consequences. In addition, we discuss the noninvasive methods for the diagnosis of cardiac fibrosis and the therapeutic strategies aimed to promote its reduction.

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.

Efficacy of aldosterone receptor antagonism in heart failure: potential mechanisms

Results of the Randomized Aldactone Evaluation Study and the Eplerenone Post-acute Myocardial Infarction Heart Failure Efficacy and Survival Study indicate aldosterone receptor antagonism, together with angiotensin-converting enzyme inhibition and loop diuretics, is a most effective strategy in reducing risk for all-cause and cardiovascular-related mortality and morbidity in patients with symptomatic heart failure. Responsible mechanisms are likely multifactoral. As a circulating hormone, aldosterone has well-known endocrine properties that contribute to the pathophysiology of congestive heart failure. This includes Na+ resorption at the expense of K+ excretion in such tissues as kidneys, colon, sweat, and salivary glands. Mg2+ excretion at these sites is likewise enhanced by aldosterone, whereas adrenal aldosterone secretion is regulated by extracellular Mg2+. Other endocrine actions of aldosterone receptor-ligand binding include: a reduction in biologically active cytosolic-free Mg2+, with intracellular Ca2+ loading in nonepithelial cells such as peripheral blood mononuclear cells; its influence on endothelial cell function; and its central actions, including the choroid plexus, activity of the hypothalamic paraventricular nucleus, and autonomic nervous system. De novo generation of aldosterone within the cardiovasculature is recognized and findings suggest its auto/paracrine properties contribute to tissue repair. Each of these actions is interrupted by aldosterone receptor antagonism and therefore may contribute to its salutary response in heart failure.

Bone loss in rats with aldosteronism

OBJECTIVE

We hypothesized that aldosteronism is accompanied by hypercalciuria and hypermagnesuria that lead to bone loss, which could be rescued by hydrochlorothiazide and spironolactone.

METHODS

We monitored 24-hour urinary Ca and Mg excretion; plasma ionized [Ca]o and [Mg]o and plasma K; and bone mineral density of the femur. The following groups (n=5 in each group) were studied: age- and gender-matched, untreated controls; controls + 4 weeks hydrochlorothiazide; 4 weeks aldosterone/salt treatment (ALDOST, 0.75 mug/h and dietary 1% NaCl/0.4% KCl); 4 weeks ALDOST+hydrochlorothiazide (50 mg/kg in prepared food); and 4 weeks ALDOST+hydrochlorothiazide+spironolactone (200 mg/kg day in divided doses by twice-daily gavage).

RESULTS

ALDOST increased (P<0.05) urinary Ca and Mg excretion four- and twofold, respectively; hydrochlorothiazide co-treatment attenuated (P<0.05) Ca excretion in controls and during ALDOST without affecting augmented Mg excretion whereas hydrochlorothiazide+spironolactone normalized Ca and reduced Mg excretion (P<0.05). Compared with controls, plasma [Ca]o at 4 weeks of ALDOST was reduced (0.89+/-0.02 versus 0.83+/-0.03 mmol/L; P<0.05) but remained no different from levels in controls with hydrochlorothiazide and hydrochlorothiazide+spironolactone (0.88+/-0.04 and 0.97+/-0.03 mmol/L, respectively). Plasma [Mg]o fell (P<0.05) with ALDOST+hydrochlorothiazide (0.23+/-0.01 versus 0.34+/-0.01 mmol/L) and was prevented with spironolactone co-treatment (0.33+/-0.01 mmol/ dL). Hypokalemia (2.9+/-0.2 mmol/L) occurred in rats with ALDOST+hydrochlorothiazide but not with spironolactone co-treatment. At 4 weeks of ALDOST, plasma parathyroid hormone was increased (30+/-4 versus 11+/-3 pg/mL; P<0.05) and bone mineral density was reduced (0.153+/-0.006 versus 0.170+/-0.002 g/cm; P<0.05). Co-treatments with either hydrochlorothiazide or hydrochlorothiazide+spironolactone each prevented bone loss.

CONCLUSIONS

Hypercalciuria and hypermagnesuria accompany aldosteronism and account for a decline in their plasma ionized concentrations and secondary hyperparathyroidism with bone resorption. Attenuation of bone loss in aldosteronism can be achieved with hydrochlorothiazide; however, mono- and divalent cation homeostasis, together with bone integrity, are each preserved with the combination hydrochlorothiazide+spironolactone.

Ligand-specific glucocorticoid receptor activation in human platelets

Few studies have addressed the effects of classical anti-inflammatory glucocorticoids on platelet function. Here, we report for the first time that human platelets contain the glucocorticoid receptor (GR) as identified by a combination of biochemical and functional techniques. Ligand-binding studies revealed the presence of a high- and low-affinity binding site for [3H]-dexamethasone in platelets. The 2 GR ligands prednisolone and dexamethasone competed for [3H]-dexamethasone binding, as did the mineralocorticoid aldosterone. However, while prednisolone (1-10 microM) reduced adenosine diphosphate (ADP, 4 microM) and thromboxane A2 receptor agonist U46619 induced platelet aggregation (up to 75%), dexamethasone had no effect. The inhibition produced by prednisolone was reversed by preincubation with the GR antagonist mifepristone (10 microM; RU486), suggesting the functional importance of the ligand-receptor complex. In addition, prednisolone caused a marked (approximately 50%) reduction in thromboxane B2 levels, whereas dexamethasone was without effect. The apparently anomalous binding data were clarified by the fact that washed platelets (1) contained mineralocorticoid receptor and that (2) it was associated with GR. Taken together, our data suggest that platelet GR forms a heterodimeric complex with the mineralocorticoid receptor that is susceptible to differential activation by specific receptor ligands.

Responses in extracellular and intracellular calcium and magnesium in aldosteronism

We hypothesized the hypercalciuria and hypermagnesuria that accompany aldosteronism could be pharmacologically attenuated to prevent shifts in extracellular and intracellular levels of these divalent cations and the adverse outcomes associated with them. Accordingly, rats administered aldosterone/salt treatment (ALDOST) were cotreated with either hydrochlorothiazide (Hctz), to selectively reabsorb urinary Ca2+, or with Hctz plus spironolactone (Hctz+Spi), where Spi retards the excretion of these cations in both urine and feces. We monitored urinary excretion and responses in extracellular and intracellular Ca2+ and Mg2+, together with indices of oxi/nitrosative stress in plasma and ventricular tissue. At 4 weeks ALDOST we found the following: (1) hypercalciuria was reduced by Hctz and normalized by Hctz+Spi, and this combination, unlike Hctz alone, also rescued hypermagnesuria; (2) the decrease in plasma-ionized [Ca2+]o was not seen with Hctz or Hctz+Spi, whereas Spi cotreatment protected against a decline in [Mg2+]o; (3) the Ca2+ loading of peripheral blood mononuclear cells and cardiac tissue was not seen with Hctz+Spi; and (4) the induction of oxi/nitrosative stress, expressed as reduced plasma alpha1-antiproteinase activity and activation of gp91(phox) subunit of NADPH oxidase in inflammatory cells invading intramural coronary arteries of the right and left ventricles, together with vascular fibrosis, was completely prevented by Spi cotreatment. In rats with aldosteronism, cotreatment with Hctz+Spi more effectively (vis-à-vis Hctz alone) protects against adverse iterations in extracellular and intracellular concentrations of Ca2+ and Mg2+, as well as the appearance of oxi/nitrosative stress to prevent the proinflammatory vascular phenotype.

Effect of spironolactone on K(+) homeostasis and ENaC expression in lymphocytes from chronic hemodialysis patients

BACKGROUND

Cardiac disease is the major cause of death in hemodialysis patients (HD). It is now clear that aldosterone has deleterious effects in the cardiovascular system. In the present study, we evaluated the effects of an aldosterone-antagonist, spironolactone, on the extrarenal regulation of potassium in HD patients. Furthermore, to validate the effectiveness of the spironolactone dose-design, we measured the expression of Na(+)-channel (ENaC alpha subunit) in peripheral blood mononuclear cells (PBMC), before and after a two-week course of spironolactone.

METHODS

The study design included a two-week baseline period, followed by spironolactone treatment (50 mg three times weekly for 15 days), and by a two-week washout period and then a two-week placebo period. An oral K(+) load (0.3 mEq/K(+) kg body weight plus carbohydrates) was administered at the end of each period, and time-course of plasma potassium was evaluated. ENaC expression in PBMC was assessed before and after spironolactone.

RESULTS

The maximal increase in plasma potassium after the K(+) carbohydrate load was: control 5.33 +/- 0.88 mEq K(+)/L; spironolactone 5.23 +/- 0.68 mEq K(+)/L; placebo 5.38 +/- 0.61 mEq K(+)/L (N= 9). No patients developed hyperkalemia during the spironolactone treatment period. ENaC expression was significantly higher in all six HD patients studied, compared to control subjects (P < 0.05). Treatment with spironolactone in HD patients reduced alpha subunit mRNA expression to values similar to those of normal subjects.

CONCLUSION

Spironolactone may be considered for the treatment of selected chronic HD patients. The effect of the drug on a known target of aldosterone, the ENaC, demonstrates the effectiveness of the drug to block aldosterone effects in nonepithelial tissues.

The Mineralocorticoid Receptor and Oxidative Stress

Reactive oxygen species are profoundly important for many physiologic functions and are also pivotal to numerous disease processes, particularly those involving inflammation. Much evidence has accrued demonstrating that aldosterone acts locally in many cells aside from those in the cortical collecting duct. Peripheral blood monocytes and vascular smooth muscle cells are both influenced by aldosterone to produce reactive oxygen species. This production contributes to nuclear factor kappaB (NF-kappaB) activation and the genes regulated by this transcription factor. Aldosterone thereby plays an important role in atherosclerosis and hypertension-induced vascular injury. Aldosterone interacts with angiotensin (Ang) II-induced signaling. Both aldosterone and Ang II initiate ERK1/2 and JNK signaling; the effects of the two compounds is additive and involves the epidermal growth factor receptor. Recent data suggest that reactive oxygen species, might contribute to aldosterone production in nonadrenal tissues. A novel oxidized derivative of linoleic acid is a prime candidate in this regard. Oxidative stress may impair mineralocorticoid receptor function by inhibiting aldosterone binding. The latter finding has particularly important implications for elderly persons who exhibit increased oxidative stress and who are at risk for diminished aldosterone function in the distal nephron and subsequent hyperkalemia.

Excess Aldosterone under Normal Salt Diet Induces Cardiac Hypertrophy and Infiltration via Oxidative Stress

Aldosterone is known to play a role in the pathophysiology of some cardiovascular diseases. However, previous studies on aldosterone infusion have been mostly performed in animals receiving sodium loading and uninephrectomy, and thus the cardiac action of aldosterone alone remains to be fully clarified. The present study was undertaken to investigate the direct cardiac action of aldosterone infusion alone in rats not subjected to salt loading and uninephrectomy. Aldosterone (0.75 microg/h) was subcutaneously infused into rats via an osmotic minipump for 14 days. Aldosterone infusion, under a normal salt diet, induced only a slight increase in the blood pressure of normal rats throughout the infusion. However, aldosterone significantly induced cardiac hypertrophy, as shown by echocardiography and measurement of cardiomyocyte cross-sectional area. Furthermore, aldosterone caused not only cardiac interstitial macrophage infiltration but also cardiac focal inflammatory lesions, which were associated with an increase in cardiac monocyte chemoattractant protein-1 (MCP-1) and osteopontin mRNA. The slight elevation of blood pressure by aldosterone infusion was completely prevented by tempol, the superoxide dismutase mimetic. However, tempol failed to suppress cardiac hypertrophy, the formation of inflammatory lesions, and upregulation of cardiac MCP-1 and osteopontin by aldosterone, while N-acetylcysteine could inhibit all of them. Our data provide evidence that aldosterone alone can induce cardiac hypertrophy and severe inflammatory response in the heart, independently of blood pressure, even in the absence of salt loading or nephrectomy. Aldosterone seems to induce cardiac inflammation and gene expression via oxidative stress that is inhibited by N-acetylcysteine but not by tempol.

Direct and indirect effects of aldosterone on cyclooxygenase-2 and interleukin-6 expression in rat cardiac cells in culture and after myocardial infarction

Aldosterone contributes to cardiac failure, which is associated with induction of inflammatory mediators. Moreover, aldosterone was shown to induce a vascular inflammatory phenotype in the rat heart. Using Western blotting and/or real-time RT-PCR, we examined the effect of aldosterone on the expression of the proinflammatory molecules, cyclooxygenase-2 (COX-2), and IL-6 in neonatal rat ventricular cardiac myocytes and fibroblasts as well as in adult cardiomyocytes after myocardial infarction. In cardiomyocytes, aldosterone induced COX-2 but not IL-6 expression. After 4-18 h of stimulation with 1 microm aldosterone, a significant increase in COX-2 protein expression was observed, preceded by an increase of COX-2 mRNA levels. After 18 h treatment, 100 nm and 1 microm aldosterone increased COX-2 protein amount by 2- and 4-fold, respectively. Consistently, aldosterone increased by 2.5-fold prostaglandin E(2) secretion in cardiomyocytes. In cardiac fibroblasts, aldosterone increased neither COX-2 nor IL-6 mRNA expression. Interestingly, prostaglandin E(2) (100 nm) strongly induced both proinflammatory molecules in fibroblasts and cardiomyocytes. Our results indicate that aldosterone directly induces COX-2 expression in cardiomyocytes and suggest that the subsequent increase in prostaglandin secretion may act in an autocrine and/or paracrine manner inducing in turn COX-2 and IL-6 expression. In vivo, myocardial infarction strongly increased both COX-2 and IL-6 expression in ventricular cardiomyocytes. Administration of the aldosterone antagonist RU28318 completely prevented COX-2 induction by infarction and partially inhibited the increase in IL-6 mRNA. These data suggest that after myocardial infarction, mineralocorticoid receptor activity is responsible for COX-2 induction and indirectly participates in IL-6 expression in cardiomyocytes.