Published online before print May 8, 2008, doi: 10.1161/CIRCRESAHA.108.174235
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© 2008 American Heart Association, Inc.
Molecular Medicine |
Functional Mineralocorticoid Receptors in Human Vascular Endothelial Cells Regulate Intercellular Adhesion Molecule-1 Expression and Promote Leukocyte Adhesion
From the Molecular Cardiology Research Institute (B.G.N., W.B., M.E.M., I.Z.J.), Department of Medicine-Division of Cardiology, Tufts Medical Center and Tufts University School of Medicine, Boston, Mass; Istituto di Ricovero e Cura a Carattere Scientifico San Raffaele Pisana (M.C., A.l.S., G.R.), Rome, Italy; and Unit of Endocrinology (M.C., A.F.), Ospedale Sant’Eugenio, University Tor Vergata, Rome, Italy.
Correspondence to Iris Z. Jaffe, MD, PhD, Tufts Medical Center, Molecular Cardiology Research Institute, 800 Washington St, Box 80, Boston, MA 02111. E-mail ijaffe{at}tuftsmedicalcenter.org
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Abstract |
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In clinical trials, aldosterone antagonists decrease cardiovascular mortality and ischemia by unknown mechanisms. The steroid hormone aldosterone acts by binding to the mineralocorticoid receptor (MR), a ligand-activated transcription factor. In humans, aldosterone causes MR-dependent endothelial cell (EC) dysfunction and in animal models, aldosterone increases vascular macrophage infiltration and atherosclerosis. MR antagonists inhibit these effects without changing blood pressure, suggesting a direct role for vascular MR in EC function and atherosclerosis. Whether human vascular ECs express functional MR is not known. Here, we show that human coronary artery and aortic ECs express MR mRNA and protein and that EC MR mediates aldosterone-dependent gene transcription. Human ECs also express the enzyme 11-β-hydroxysteroid dehydrogenase-2 (11βHSD2), and inhibition of 11βHSD2 in aortic ECs enhances gene transactivation by cortisol, supporting that EC 11βHSD2 is functional. Furthermore, aldosterone stimulates transcription of the proatherogenic leukocyte–EC adhesion molecule intercellular adhesion molecule (ICAM)1 gene and protein expression on human coronary artery ECs, an effect inhibited by the MR antagonist spironolactone and by MR knock down with small interfering RNA. Cell adhesion assays demonstrate that aldosterone promotes leukocyte–EC adhesion, an effect that is inhibited by spironolactone and ICAM1 blocking antibody, supporting that aldosterone induction of EC ICAM1 surface expression via MR mediates leukocyte–EC adhesion. These data show that aldosterone activates endogenous EC MR and proatherogenic gene expression in clinically important human ECs. These studies describe a novel mechanism by which aldosterone may influence ischemic cardiovascular events and support a new explanation for the decrease in ischemic events in patients treated with aldosterone antagonists.
Key Words: mineralocorticoid receptor • endothelial cell • aldosterone • spironolactone • ICAM1
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Introduction |
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Ischemic cardiovascular disease is the leading cause of morbidity and mortality in the developed world. In clinical trials, aldosterone antagonists improve mortality and prevent ischemic events in cardiovascular patients1,2 by unknown mechanisms. The improvement in outcomes in these trials is greater than expected from the modest decreases in blood pressure observed, suggesting the potential for a direct beneficial effect of aldosterone antagonists on the vasculature. In humans, aldosterone infusion causes endothelial vasodilator dysfunction,3 and in patients with chronic heart failure, the aldosterone antagonist spironolactone improves endothelial function,4,5 supporting that aldosterone has negative effects on the vascular endothelium in humans.
Aldosterone is a steroid hormone that functions by binding to the intracellular mineralocorticoid receptor (MR), a ligand-activated transcription factor and member of the nuclear hormone receptor family.6 Aldosterone antagonists inhibit binding of the hormone to MR. Nuclear hormone receptors bind to specific DNA sequences in promoters of hormone-responsive genes and recruit cofactors in a ligand-dependent manner, thereby modulating gene expression (reviewed elsewhere7). In vivo, MR ligands include aldosterone and cortisol, which bind to human MR with equal affinity.8 Aldosterone-responsive tissues express the cortisol-inactivating enzyme 11-β-hydroxysteroid dehydrogenase type-2 (11βHSD2), which locally converts cortisol to derivatives that have a low affinity for MR.9 Deficiency or mutations in 11βHSD2 in humans results in the syndrome of apparent mineralocorticoid excess with hypertension and hypokalemia (reviewed elsewhere10). MR and 11βHSD2 are expressed in the kidney, where they regulate renal sodium and potassium handling, thereby maintaining and, in some situations, contributing to elevated systemic blood pressure.6 However, evidence has been accumulating for a direct role for aldosterone and MR in the cardiovascular system, independent of renal MR actions on blood pressure. We and others have demonstrated that MR and 11βHSD2 are expressed in the heart, large vessels, and vascular smooth muscle cells (VSMCs) (reviewed elsewhere11). We recently demonstrated the presence of functional MR in human VSMCs capable of modulating endogenous gene expression12 and that aldosterone-stimulated MR in VSMCs promotes vascular calcification in vitro,13 a process that is associated with increased risk of cardiovascular events in humans.
Less is known about the function of MR in vascular endothelial cells (ECs). In animal studies, immunohistochemistry with anti-MR antibody has demonstrated staining of the endothelial lining of rabbit atria, aorta, and pulmonary arteries,14 and MR and 11βHSD2 mRNA, respectively, have been identified in bovine and rat aortic ECs in culture.15,16 In human samples, low levels of MR mRNA have been identified in pulmonary artery ECs in culture.17 ECs treated with aldosterone demonstrate increased oxidative stress and cell volume.15,18 These data suggest that vascular ECs may respond directly to aldosterone. However, whether human vascular ECs express transcriptionally functional MR and whether these receptors could participate in the vascular pathophysiology of atherosclerosis are not known.
Animal models suggest that aldosterone can promote vascular inflammation. In rat models of aldosterone-induced hypertension, aldosterone caused perivascular inflammation of the coronary arteries characterized by monocyte/macrophage infiltration, increased oxidative stress, and upregulation of inflammatory genes and adhesion molecules.19–21 In mouse models of atherosclerosis, aldosterone increases atherosclerotic lesion size, macrophage infiltration, and inflammatory gene expression, effects that are inhibited by aldosterone antagonists.22 However, these animal models have significant systemic hypertension as well, making unclear which tissue(s) contribute to the observed atherosclerotic effects of aldosterone.
In this study, we test the hypothesis that proatherosclerotic effects of aldosterone are mediated in part by induction of inflammatory gene expression via MR in human vascular ECs. We demonstrate that primary human ECs express functional MR and 11βHSD2 enzyme and show that MR activation by aldosterone promotes ICAM1 gene transcription, ICAM1 surface protein expression, and leukocyte–EC adhesion.
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Materials and Methods |
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Reagents and Cell Lines
Aldosterone, spironolactone, cortisol, tumor necrosis factor (TNF)
, actinomycin D, and glycyrrhetinic acid (GA) were used as described,12 with appropriate vehicle controls. For cell line and culture conditions, see the expanded Materials and Methods section available in the online data supplement at http://circres.ahajournals.org.
Quantitative RT-PCR, Immunoblotting, Immunofluorescence, Adenovirus Infection, Transfection, Luciferase Assay, Flow Cytometry, and RNA Interference for MR Knockdown
See the expanded Materials and Methods section for a detailed description of the culture conditions, hormone treatments, assay protocols, controls, and normalization. For flow cytometry, the cells were labeled with phycoerythrin-conjugated mouse antihuman ICAM1 monoclonal antibody or IgG1 isotype control. Mean fluorescence index was calculated by subtracting the isotype Ig control mean fluorescence from the ICAM1-stained mean fluorescence. Data are expressed as percentage of mean fluorescence index of vehicle-treated cells at each treatment time.
Leukocyte Adhesion Assay
Monolayers of human coronary artery ECs (HCAECs) were treated as for flow cytometry and incubated with fluorescent U937 human monocytic cells, and adherent fluorescent cells were counted by a blinded investigator. For Figure 6C, after treatment with hormone for 18 hours, the HCAECs were incubated for 10 minutes with antihuman ICAM1 monoclonal antibody or control IgG before addition of the fluorescent leukocytes. Detailed methods are provided in the expanded Materials and Methods section.
Statistical Analysis
Quantitative RT-PCR, reporter assays, flow cytometry, and leukocyte adhesion assays were performed a minimum of three times. Values are reported as mean fold or percentage change compared with vehicle control±SEM. Within-group differences were assessed with 1-factor ANOVA. Post hoc comparisons were tested with the Student–Newman–Keuls test. For Figure 4D, data were analyzed by 1-factor ANOVA on ranks, and comparisons versus control were assessed with Dunn’s method. P<0.05 was considered significant.
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Results |
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Human Vascular ECs Express MR
The expression of MR in human vascular ECs was studied first by quantitative (Q)RT-PCR using RNA isolated from human ECs (black bars) and compared with SMCs (gray bars) derived for each cell type from the same individual or from the same vascular bed (Figure 1A). MR mRNA was detected in all human vascular ECs examined, and ECs contained, on average, substantially more MR mRNA than VSMCs (Figure 1). Coronary arterial ECs also contained significantly less MR message than iliac and saphenous vein ECs.
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The characteristic 107-kDa MR protein8 also was detected in human coronary artery, aortic, saphenous vein, and umbilical vein ECs (Figure 1B). MR protein was present predominantly in supernatant fractions from high salt lysates, as is characteristic for steroid hormone receptors.7,12 The expression and cellular localization of MR protein in ECs was also studied by immunofluorescence microscopy. In the absence of ligand, MR protein expression was detected in both the nucleus and, to a lesser extent, in the cytoplasm of HCAECs (Figure 1C). Following exposure to aldosterone for 18 hours, MR was found almost exclusively in the nucleus (Figure 1C), as is characteristic of liganded steroid hormone receptors.12,23 Preimmune serum controls in these studies were consistently negative (data not shown). These data support that human vascular ECs express MR mRNA and protein and that aldosterone-activated MR protein localizes to the nucleus of human coronary ECs.
Human Vascular ECs Express Functional MR
To determine whether the endogenous EC MR is functionally capable of aldosterone-induced transcriptional transactivation, a sensitive adenoviral reporter of MR-mediated gene expression12 was infected into human aortic and coronary artery ECs, and MR-dependent gene expression was examined. Gene expression was activated in a dose-dependent manner beginning at 1 nmol/L aldosterone in human aortic EC and 0.1 nmol/L in HCAECs (Figure 2), consistent with both the Kd for aldosterone-MR binding8 and the physiological concentration of aldosterone in vivo.24 Aldosterone did not activate an estrogen response element–containing adenoviral reporter (data not shown), supporting that aldosterone-mediated transactivation in these studies was specific for the MR binding site. Spironolactone, the competitive inhibitor of MR hormone binding, inhibited aldosterone-mediated mineralocorticoid response element (MRE) activation in human ECs but had no effect on basal expression of the MR reporter (Figure 2). These data are consistent with studies in VSMCs and in nonvascular cells showing spironolactone inhibition of MR activation at these concentrations8,12 and further support that the endogenous human aortic and coronary EC MR is a functional ligand-activated transcription factor.
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Human Vascular ECs Express Functional 11βHSD2
Aldosterone-responsive tissues express the enzyme 11βHSD2 to convert cortisol to cortisone, which is inactive on MR. Using overexpressed 11βHSD2 and human kidney 11βHSD2 as controls, immunoblotting studies confirmed that 11βHSD2 protein is expressed in human coronary artery, aorta, umbilical vein, and saphenous vein ECs (Figure 3A). 11βHSD2 protein was concentrated in the pellet fractions (Figure 3A), consistent with studies in VSMCs and nonvascular cells, in which 11βHSD2 enzyme is found localized to the membranous endoplasmic reticulum.9,12,25 11βHSD2 function in human aortic ECs was next tested using the 11βHSD2 inhibitor GA in the MRE reporter assay. Doses of GA exceeding the Ki of GA for 11βHSD2 resulted in increased cortisol-stimulated MRE activation (Figure 3B) without affecting basal reporter activity, consistent with functional enzyme inactivation of cortisol in the absence of the inhibitor. Taken together, the data of Figures 1 through 3
demonstrate for the first time that human vascular ECs contain both functional MR and 11βHSD2 and, hence, have the capacity to modulate gene expression in response to circulating aldosterone.
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Endogenous MR-Regulated Genes in HCAECs
EC genes regulated by MR in HCAECs were explored next using a candidate gene approach. Animal studies support that aldosterone infusion stimulates expression of a set of specific genes involved in vascular oxidative stress and inflammation.19–21,26–28 Based on these studies, we tested 4 candidate genes in ECs for MR regulation: 3 NADPH oxidase (Nox) subunits (Nox1,26 Nox2,26,27 and Nox421) and the cell adhesion molecule ICAM1.19–21 Using QRT-PCR, we tested RNA from HCAECs treated with 10 nmol/L aldosterone in the presence or absence of the MR antagonist spironolactone (1 µmol/L). ICAM1 and Nox4 gene expression were MR-regulated (Nox4: 120% increase after 3 hours [P<0.0001], inhibited by spironolactone [P<0.05]; data not shown), whereas neither Nox1 nor Nox2 was regulated by MR. Aldosterone treatment for 3 hours increased ICAM1 mRNA (30%) compared with vehicle-treated HCAECs (P=0.056 versus vehicle) and significantly increased ICAM1 mRNA (70% to 150%) after 24 hours (Figure 4A and 4C). ICAM1 has a known role in early atherosclerosis, where its expression on the surface of activated EC mediates leukocyte–EC adhesion. Next, HCAECs were treated with 10 nmol/L aldosterone for 18 to 36 hours, and surface ICAM1 protein was quantified by flow cytometry (Figure 4B). Aldosterone treatment increased surface ICAM1 protein 20% at 18 to 24 hours and 30% at 36 hours (Figure 4B). Stimulation for 12 hours with TNF (5 ng/mL), a known potent stimulator of EC inflammation, increased ICAM1 surface protein expression 405% (data not shown). The increase in ICAM1 mRNA and protein with aldosterone treatment was inhibited by the MR antagonist spironolactone, and spironolactone alone had no effect on ICAM1 expression in these cells (Figure 4A and 4B). These data demonstrate that MR regulates endogenous ICAM1 message abundance and surface protein expression in HCAECs. Pretreatment of HCAECs with the transcriptional inhibitor actinomycin D completely inhibited aldosterone-stimulated ICAM1 mRNA induction (Figure 4C), demonstrating that the aldosterone effect is mediated by increasing ICAM1 gene transcription. In Figure 4D, HCAECs were transfected with a luciferase reporter driven by the 3 kb upstream ICAM1 promoter region that we confirm to be activated by TNF. Aldosterone stimulated transcription from this element in an MR-dependent manner, as demonstrated by inhibition by spironolactone. These data demonstrate that aldosterone binds to endogenous MR in human coronary ECs, thereby activating the ICAM1 upstream promoter and increasing ICAM1 gene transcription and surface protein expression.
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MR Knockdown in ECs Inhibits Basal and Aldosterone-Activated ICAM1 Expression
Next, we used small interfering RNA to knock down MR message in HCAECs and examined the effect on ICAM1 gene expression. QRT-PCR with receptor-specific primers confirmed that transfection of three unrelated MR-targeted small interfering RNA oligos resulted in 90% knockdown of MR message 48 hours after transfection (Figure 5A), with no significant effect on expression of the highly homologous glucocorticoid receptor (data not shown). MR knockdown abolished aldosterone-stimulated ICAM1 expression in HCAECs (Figure 5B), clearly implicating endogenous EC MR in the mechanism. In addition, MR knockdown resulted in 80% reduction in basal ICAM1 expression in these cells. These data are consistent with ligand-independent activation of MR by factors contained in charcoal stripped serum that tonically activate ICAM1 expression in human coronary ECs.
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Effect of Aldosterone on Leukocyte Adhesion to HCAECs
We next investigated whether aldosterone promotes leukocyte adhesion to ECs. Fluorescently labeled human monocytic cells (U937 cells) were incubated with monolayers of primary HCAECs pretreated for 24 hours with vehicle or increasing doses of aldosterone, and adherent cells were quantified. Figure 6A demonstrates that at physiologically relevant concentrations, aldosterone significantly increases leukocyte–EC adhesion 2- to 3-fold compared with vehicle-treated cells. TNF, as a positive control, increased leukocyte adhesion 20-fold. 17β-Estradiol (estrogen), a nonmineralocorticoid steroid hormone, had no effect on leukocyte adhesion, suggesting that the effect is specific for aldosterone. To address the mechanism of aldosterone-stimulated leukocyte adhesion, we repeated the leukocyte adhesion assay in the presence of the MR antagonist spironolactone. Aldosterone-stimulated leukocyte adhesion to HCAECs was completely inhibited by spironolactone, whereas spironolactone alone had no effect (Figure 6B).
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The leukocyte adhesion assay was repeated in the presence of antihuman ICAM1 antibodies capable of blocking ICAM1-mediated EC–leukocyte interactions. ICAM1 blocking antibody completely inhibited aldosterone-stimulated EC–leukocyte adhesion (Figure 6C). The same concentration of mouse IgG did not significantly alter aldosterone-mediated leukocyte adhesion, supporting that this effect is specific to the ICAM1 antibody. The data in Figure 6 support that MR-mediated stimulation of ICAM1 surface protein expression in human coronary ECs promotes EC–leukocyte adhesion.
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Discussion |
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The data presented here support a new mechanism for aldosterone-mediated vascular pathology. They show that human vascular ECs express MR capable of sequence-specific, aldosterone-activated gene transcription at physiological hormone levels. These ECs also express the enzyme 11βHSD2, capable of inhibiting cortisol-dependent, MR-mediated gene transcription, supporting further that human vascular ECs respond directly to aldosterone. Endothelial MR localizes to the nucleus following activation by aldosterone and can activate promoters containing MREs. EC MR promotes basal and aldosterone-activated ICAM1 transcription, and aldosterone-activated MR enhances surface expression of ICAM1 protein and promotes leukocyte adhesion to human coronary ECs. Based on these data, we propose a model in which functional MRs in human vascular ECs regulate ICAM1 expression and promote leukocyte adhesion (Figure 7), which provides a new mechanism for the vascular protective effects of MR antagonists.
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Although previous studies have demonstrated MR and 11βHSD2 expression in cardiovascular tissues in animals14,16 and in cultured human pulmonary artery ECs,17 our data demonstrate that functional MR also is expressed in human vascular ECs from atherosclerosis-prone vascular beds and that EC MR is capable of directly modulating gene expression programs in response to aldosterone exposure. MR-mediated transcriptional changes may contribute to the long term effects of aldosterone on endothelial function that are especially relevant in patients with chronic vascular diseases like atherosclerosis and in the growing population of patients with chronically elevated aldosterone levels, including those with systolic and diastolic heart failure and low-renin hypertension.
Our data also revealed variation in the level of MR message in human coronary ECs compared with the saphenous vein and iliac artery ECs in the paired samples tested. Because the transcriptome of ECs has been shown to vary depending on the vascular bed from which the cells originate (reviewed elsewhere29), this may be explained by the different flow characteristics or circulating factors to which the ECs in these vascular beds are exposed. Differences in MR expression may regulate variation in EC gene expression and physiology of the coronary vasculature. Alternatively, these differences may reflect biological variability in the samples studied resulting from factors like sex, age, race, or medical comorbidities in the patients from which these cells were cultured. Further interpretation of differences in EC MR expression in different vascular beds will require validation in patient samples from larger cohorts.
Using a candidate gene approach, we identified Nox4 and ICAM1 as MR-regulated genes in HCAECs. In animal models, aldosterone infusion increases cardiovascular ICAM1 expression19–21; however, the cause of increased ICAM expression in these in vivo models is not clear, because they also have significant systemic hypertension caused by activated kidney MR, which can result in secondary changes in vascular gene expression. In addition, the specific role of MR in the cardiomyocyte, VSMCs, and ECs, among others in mediating ICAM1 gene regulation in these animal models is not clear. Our data demonstrate that MR in human ECs directly regulates ICAM1 transcription independent of MR activation in the kidney or other vascular tissues, which provides a potentially important mechanism for human disease that merits further investigation. We also showed that human vascular ECs express functional 11βHSD2, which may play an additional role in promoting EC ICAM1 activation, because glucocorticoids, acting via the glucocorticoid receptor, have been shown to inhibit lipopolysaccharide-induced ICAM1 expression and leukocyte adhesion to human umbilical vein ECs.30
Although MR activation by aldosterone stimulates ICAM1 promoter activity in human ECs in our studies, in silico examination of the 3kb ICAM1 upstream promoter does not reveal an obvious MRE. There are few endogenous MR-regulated genes for which the MR DNA-binding site has been carefully studied and none in vascular ECs. In the kidney, MR regulates the NaK-ATPase gene via an MRE that differs significantly from the canonical sequence.31 Hence, the presence of a novel MRE in the ICAM1 promoter cannot be ruled out and remains to be tested. Alternatively, MR activation by aldosterone may regulate the expression or activity (by posttranslational modification) of other transcription factors in ECs that may subsequently regulate ICAM1 transcription. ICAM1 expression is tightly regulated, primarily at the level of transcription, by cell type–specific ICAM1 promoter activation mediated by multiple transcription factors binding sites including nuclear factor (NF)-
B, Ets, activator protein 1, SP1, and interferon-
–responsive sites.32,33 NF-B activity is increased in rats transgenic for human renin and angiotensin II, an effect that is inhibited by treatment with MR antagonists, supporting that MR may activate NFB in vivo.34 In addition, aldosterone is known to increase vascular oxidative stress by a variety of mechanisms (reviewed elsewhere35), including increased NADPH oxidase activity36 and decreased G6PD.15 Reactive oxygen species have been implicated in regulating ICAM1 expression by many extracellular stimuli (reviewed elsewhere37), and we demonstrate that EC MR regulates expression of the NADPH oxidase Nox4. Thus, the detailed molecular mechanisms of MR regulation of ICAM1 promoter activity are likely complex and merit further investigation.
In addition to inhibiting aldosterone-stimulated ICAM1 expression, knockdown of MR in human ECs significantly decreased basal ICAM1 expression, consistent with tonic MR-mediated activation of ICAM1 expression in HCAECs. These experiments were performed in steroid-depleted serum and, thus, suggest that there may be some degree of basal, ligand-independent activation of MR by growth factors (a mechanism of activation of other steroid hormone receptors38) (Figure 7) or angiotensin II (which we have shown can activate MR-mediated gene transcription in human VSMCs12), although this hypothesis needs to be tested further. Ligand-independent activation may be mediated by posttranslational modifications such as phosphorylation, which occurs for several steroid hormone receptors, including MR, in other tissues.38,39
ICAM1 is a cell surface receptor that mediates the firm adhesion of leukocytes to ECs required for transendothelial migration, an early step in atherogenesis (reviewed elsewhere40–42). In animal models of aldosterone-induced hypertension and genetic predisposition to atherosclerosis, aldosterone promotes monocyte/macrophage accumulation in the vessel wall through unknown mechanisms.20,22,43 Our data support the hypothesis that MR activation of ICAM1 expression in ECs may mediate, in part, this effect (Figure 7), but ICAM1 activation by MR likely explains only part of the proinflammatory and atherogenic effects of aldosterone. Other cell adhesion molecules are important in leukocyte recruitment to atherosclerotic lesions,40–42 particularly vascular cell adhesion molecule (VCAM1).44 The possibility that VCAM1 expression is also regulated by aldosterone (and that the ICAM1 blocking antibody used in Figure 6C can also inhibit VCAM1-mediated EC–leukocyte adhesion) remains to be investigated.
Animal models and clinical data support that vascular ICAM1 expression promotes atherosclerotic disease and ischemia and that aldosterone may play a role in ICAM1 regulation in humans. Genetic deficiency of ICAM1 decreases native artery and vein graft atherosclerosis in mouse atherosclerosis models.45,46 In human endarterectomy specimens, EC ICAM1 expression is greater in plaques from symptomatic versus asymptomatic patients, suggesting a role for EC ICAM1 expression in plaque instability.47 Serum levels of soluble ICAM1 (sICAM1) are elevated in patients at high risk for cardiovascular events and predict cardiovascular outcomes in apparently healthy subjects.41 In patients with chronic, stable, congestive heart failure, serum aldosterone levels correlate with sICAM1 levels.48 Treatment of cardiovascular patients with angiotensin converting enzyme inhibitors and angiotensin receptor blockers, drugs that decrease both aldosterone production and MR activation by angiotensin II,12 also decrease serum sICAM1 levels.41 Thus, there are clinical data implicating ICAM1 in promoting atherosclerotic vascular disease, lending support to the possibility suggested by our data that MR regulation of ICAM1 expression in the coronary endothelium is worth exploring as a potential therapeutic target.
In summary, we have demonstrated that aldosterone activates endogenous MR and modulates gene expression of ICAM1 in human ECs and promotes leukocyte adhesion to human coronary ECs. This pathway may play a role in the proatherosclerotic effects of aldosterone and support a new explanation for the decrease in ischemic events in patients treated with aldosterone antagonists.
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Acknowledgments |
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Sources of Funding
This work was supported by NIH grant HL074892 (to I.Z.J.) and Italian governmental research grants from the Progetti Ricerca Interesse Nazionale Ministero dell’Università e della Ricerca, 2005 (to A.F.) and from the Italian Ministry of Health (Ricerca Finalizzata, 2005 (to G.R.).
Disclosures
None.
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Footnotes |
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Original received August 9, 2007; resubmission received February 19, 2008; revised resubmission received April 22, 2008; accepted April 24, 2008.
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