Published online before print March 12, 2007, doi: 10.1161/HYPERTENSIONAHA.107.086926
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(Hypertension. 2007;49:1084.)
© 2007 American Heart Association, Inc.
Original Articles |
Peroxisome Proliferator-Activated Receptor 
–Independent Actions of Fenofibrate Exacerbates Left Ventricular Dilation and Fibrosis in Chronic Pressure Overload
From the Whitaker Cardiovascular Institute (T-A.S.D., L.C., M.K.R., S.N., D.S.D.S., D.A.S., R.L., F.S.) and Muscle and Aging Research Unit (N.K.L.), Boston University School of Medicine, Mass.
Correspondence to Flora Sam, Whitaker Cardiovascular Institute, Boston University School of Medicine, 650 Albany St, Room X704, Boston, MA 02118. E-mail flora.sam{at}bmc.org
 |
Abstract |
|---|
 Top Abstract IntroductionMethodsResultsDiscussionReferences |
|---|
Progressive cardiac remodeling is characterized by subsequent chamber hypertrophy, enlargement, and pump dysfunction. It is also associated with increased cardiac fibrosis and matrix turnover. Interestingly, peroxisome proliferator-activated receptor (PPAR)
activators reduce cardiac hypertrophy, inflammation, and fibrosis. Little is known about the role of fenofibrates in mediating PPAR-independent effects in response to chronic pressure overload (PO). Wild-type and PPAR-deficient mice were subjected to chronic PO caused by ascending aortic constriction to test the role of fenofibrates in chronic, progressive cardiac remodeling by a PPAR-independent mechanism. Mice were randomized to regular chow or chow-containing fenofibrate (100 mg/kg of body weight per day) for 1 week before and 8 weeks after ascending aortic constriction. In the presence of PPAR, wild-type chronic PO mice, treated with fenofibrate, had improved cardiac remodeling. However, PO PPAR-deficient mice treated with fenofibrate had increased mortality, significantly adverse left ventricular end diastolic (3.4±0.1 versus 4.2±0.1 mm) and end systolic (1.5±0.2 versus 2.5±0.2 mm) dimensions, and fractional shortening (57±3% versus 40±3%). Fenofibrate also increased myocardial hypertrophy, cardiac fibrosis, and the ratio of matrix metalloproteinase-2/tissue inhibitor of matrix metalloproteinase-2 in PO PPAR-deficient mice. Fenofibrate inhibited matrix metalloproteinase activity in vitro and aldosterone-induced increases in extracellular signal-regulated kinase phosphorylation. Thus, fenofibrate improved cardiac remodeling in chronic PO mice. However, in PPAR-deficient mice, this chronic PO was exacerbated and associated with increased myocardial fibrosis and altered matrix remodeling. In the absence of PPAR, fenofibrates exerts deleterious, pleiotropic myocardial actions. This is an important observation, because PPAR agonists are considered possible inhibitory regulators of cardiac remodeling in the remodeled heart.
Key Words: fibrosis • pressure overload • ventricular remodeling • peroxisome proliferator-activated receptor • matrix metalloproteinases
|
Introduction |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Myocardial remodeling caused by chronic hemodynamic overload is characterized by increased myocardial hypertrophy, which, although initially compensatory, is an unfavorable component of cardiac remodeling when it becomes progressive. Progressive left ventricular (LV) remodeling is characterized by subsequent chamber enlargement and pump dysfunction. These alterations occur together with increased expression of inflammatory cytokines,1 a shift from myocardial fatty acid oxidation to glucose use,2 constant myocardial extracellular matrix turnover,3 and matrix metalloproteinase (MMP) activation.4 Aldosterone plays a key role in mediating adverse LV remodeling with pressure overload (PO).5 It increases myocardial fibrosis that is independent of tissue hypertrophy and arterial pressure.6,7 Some of these effects are mediated directly by aldosterone, inducing MMP-2 and MMP-9 activities in cardiac myocytes. The mechanism partially involves activation of the MAP kinase kinase/extracellular signal-regulated kinase (ERK)1/2 pathway.8
The benefits of targeted therapies to ameliorate progressive cardiac remodeling remain to be determined. In particular, the peroxisome proliferator-activated receptor (PPAR) family and their target genes appear to contribute in regulating lipid and glucose homeostasis and are implicated as regulators of inflammation and atherosclerosis.9 Three ligand-activated transcription factors have been identified: PPAR
, PPARß/
and PPAR. PPAR is predominantly expressed in adipose tissue and regulates metabolism. PPARß/ is ubiquitously expressed9 and regulates fatty acid oxidation genes.9 In addition, PPARß/ activators exert anti-inflammatory and antihypertrophic effects in cardiomyocytes.10 In contrast, PPAR is abundant in tissues with high rates of mitochondrial fatty acid oxidation, (ie, heart, liver, and kidney) and regulates genes involved in cellular lipid catabolism. PPAR, the main isoform in the adult heart,11 is downregulated in PO hypertrophy,12 and its dysregulation is associated with cardiac dysfunction.13 Conversely, PPAR ligands reduce cardiac hypertrophy and inflammation14,15 and, in acute PO, attenuate cardiac fibrosis.9 Finally, mice lacking PPAR are reportedly resistant to pleiotropic actions of PPAR ligands.16
Fibrates are predominantly PPAR but are also PPARß/ activators.17 Fenofibrates are used clinically for dyslipidemia and hypertriglyceridemia, and it is through the activation of PPAR that lipids are lowered. Likewise, fibrates have been considered as possible therapeutic agents for the treatment of cardiac hypertrophy18 and failure. Independent of their lipid-lowering actions, fenofibrates, as PPAR agonists, may act as negative regulators of proinflammatory genes by antagonizing the activity of inflammatory transcription factors (eg, nuclear factor 
B19,20 and activator protein–121), thus decreasing myocardial inflammation.22 Likewise, inhibiting chronic inflammation in the remodeled myocardium is associated with a reduction in fibrosis.9,15,23
In the present study, we tested the hypothesis that fenofibrate exerts beneficial effects on chronic, progressive cardiac remodeling and hypertrophy by PPAR-independent actions. The present studies were aimed at determining the role of fenofibrate in the pathogenesis of cardiac remodeling using both in vivo (wild-type and PPAR-deficient mice) and in vitro studies (cultured adult rat cardiomyocytes).
|
Methods |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Animals
There were 2 groups of mice. Group A wild-type (WT) FVB mice were purchased from Charles River Laboratories (Wilmington, Mass) and group B PPAR
-deficient mice (129S4/SvJae- Pparatm1Gonz/J) were purchased from Jackson Laboratories (Bar Harbor, Maine). Study protocols were approved by the institutional animal care and use committee at Boston University.
Surgery
Both groups of mice underwent ascending aortic constriction (AAC) surgery as described previously.5 Briefly, 12- to 14-week–old mice were anesthetized with pentobarbital (15 mg/kg IP injection) and then ventilated on a Harvard rodent respirator (model 683). Aortic constriction was performed by AAC with a 7–0 silk suture around a 27-gauge needle via an anterolateral thoracotomy. This technique provided a minimal variability of the trans-constriction pressure gradients in mice.24 Sham-operated mice underwent a similar procedure without AAC.
Treatment
In group A, 32 mice (10 sham-operated and 22 banded) and, in group, B 50 mice (10 sham and 40 banded) were studied. Mice were randomly assigned to regular chow or chow-containing fenofibrate (100 mg/kg of body weight per day) for 1 week before and 8 weeks after surgery. A similar dose of fenofibrate was used by others25–27 and shown to be nontoxic. Echocardiogram, blood pressure (BP), histology, and cardiac protein analyses were performed 8 weeks after surgeries.
Echocardiography and BP Measurement
Transthoracic echocardiography was performed in conscious mice before surgery (baseline) and 2, 4, and 8 weeks after surgery. Echocardiography was performed as described previously5,24 using an Acuson Sequoia C-256 echocardiograph machine and a 15-MHz probe. Tail cuff systolic BP and heart rate (HR) were measured at 8 weeks post-AAC, in group B, using a noninvasive tail cuff system (BP-2000, VisiTech) as described previously.5,28,29
Organ Weight
Mice were euthanized 8 weeks postoperatively. The body weight, LV heart weight, and wet and dry lung weights were determined. The wet/dry ratio was taken as an indicator of pulmonary congestion and clinical heart failure.30
Fibrosis
To measure fibrosis, trichrome-stained sections (5 µm) were visualized by light microscopy, and the entire section was quantified using Bioquant Image analysis software.
Western Blot Analysis
Hearts from PPAR-deficient mice were removed and snap frozen in liquid nitrogen. The tissue was homogenized in cold lysis buffer (10x cell lysis buffer, Cell Signaling) with the addition of 1 mmol/L of phenylmethylsulfonyl fluoride, 1 mmol/L of sodium orthovanadate, and 1 µg/mL of aprotinin. The Bradford method (Bio-Rad) was used to measure protein concentration. SDS-PAGE was performed under reducing conditions on both 10% and 12% separation gels with a 4% stacking gel (Cambrex). Proteins were transferred to Immun-Blot polyvinylidene fluoride membrane (Bio-Rad). Blots were incubated with primary antibodies to the PPAR (Santa Cruz Biotechnology Inc), PPARß/, MMP-9, tissue inhibitor of MMP (TIMP)-1, MMP-2, and TIMP-2 (Chemicon) for 18 to 20 hours at 4°C. Blots were then incubated in horseradish peroxidase–conjugated secondary antibody, and the signal was detected by SuperSignal West chemiluminescence (Pierce). All of the blots were normalized with Coomassie Brilliant Blue staining of the gels (Sigma Aldrich).
Isolation of Adult Rat Ventricular Myocytes
As described previously,8 adult rat ventricular myocytes (ARVMs; 90% to 95% purity) were isolated from the hearts of adult Sprague–Dawley rats, plated at a nonconfluent density of 30 to 50 cells/mm2 on plastic culture dishes (Fisher) precoated with laminin (1 µg/cm2, Invitrogen), and maintained in ACCT medium (DMEM; BSA, 2 mg/mL; L-carnitine, 2 mmol/L; creatinine, 5 mmol/L; taurine, 5 mmol/L; penicillin, 100 IU/mL; and streptomycin, 10 g/mL) for 16 hours before drug treatment.
Drug Treatments
Myocytes were treated with aldosterone (50 nM, Sigma) for 30 minutes for signaling and 24 hours for zymography. Fenofibrate (10 µM and 100 µM, Sigma) was added 30 minutes before aldosterone.
ERK Phosphorylation
As described previously,8 ARVMs were collected in lysis buffer. Protein concentration was determined using Bradford assay (Bio-Rad). Protein was probed with anti–phospho-ERK1/2 (1:1000, Cell Signaling) or anti–total-ERK1 (1:1000, Cell Signaling) antibodies. Chemiluminescence was quantified by densitometry (Molecular Analyst, Bio-Rad).
Assessment of MMP Activity
Using in-gel zymography as described previously,31 briefly ARVMs were treated for 24 hours in 100-mm dishes in medium without albumin. Conditioned medium was concentrated, and protein was determined by the Bradford assay.32,33 MMP activity was measured by in-gel zymography with gelatin (type A from porcine skin, Sigma) as the substrate. Unstained, digested regions representing MMP activity were quantified using an imaging densitometer (GS700, Bio-Rad).
Statistical Analysis
All of the data are presented as mean±SEM. Differences between mice were tested for statistical significance by the 2-tailed Student t test or a 2-fold ANOVA with Bonferroni correction. Survival data were calculated using the Kaplan–Meier survival analysis. Similarly, in in vitro studies, differences among conditions were determined by ANOVA followed by a paired t test with the Bonferroni correction for multiple comparisons. P<0.05 was considered statistically significant.
|
Results |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
In Vivo Studies
Fenofibrate Effects on LV Structure and Function in WT Mice
Total wall thickness was increased by 2 weeks (1.22±0.09 mm versus sham: 0.99±0.02 mm; P<0.01), persisted at 4 weeks post-AAC, and slightly increased further by 8 weeks (Figure 1A). In addition, AAC caused progressive dilation with increases in LV end diastolic dimension and LV end systolic dimension that were evident at 2 weeks (3.37±0.09 and 1.97±0.01 mm, respectively), present at 4 weeks, and increased further at 8 weeks (Figure 1B and 1C). Thus, post-AAC, LV dilation was associated with a progressive decline in fractional shortening (FS), which was evident by 2 weeks (42±2% versus sham: 60±2%; P<0.0001) and continued to decline significantly at 4 and 8 weeks (Figure 1D).
|
, n=6), untreated AAC (
, n=8) and AAC+fenofibrate (
, n=6) mice. 
P<0.001 vs AAC; 
P<0.001 vs sham; *P<0.05 vs sham; #P<0.01 vs sham, 
P<0.01 vs AAC.Fenofibrate treatment significantly inhibited the increase in total wall thickness. This was evident at 2 weeks post-AAC (0.83±0.01 mm versus untreated AAC; P<0.001) and persisted at 4 and 8 weeks post-AAC (Figure 1A). In concert, by 2 weeks post-AAC, fenofibrate significantly reduced the increases in LV end diastolic dimension and LV end systolic dimension (3.85±0.07 mm and 2.2±0.07 mm versus untreated AAC, respectively; P<0.001; Figure 1B and 1C). In doing so, fenofibrate prevented the decrease in the percentage of FS seen at 2 (data not shown), 4, and 8 weeks with AAC (Figure 1D).
Survival in PPAR-Deficient Mice
Mice that survived the perioperative period were included in the Kaplan–Meier analysis as illustrated (Figure 2). Fenofibrate decreased survival in the AAC mice in comparison with the untreated AAC group (65% versus 30%; P<0.05). During the 8 weeks after surgery, there were no deaths in either sham-operated group.
|
BP and Cardiac Morphology in PPAR-Deficient Mice 8 Weeks Post-AAC
Systolic BP was not affected by fenofibrate. There was a trend to decrease BP in AAC mice (P not significant). In addition, fenofibrate treatment did not affect BP in either sham or AAC mice (Table). AAC decreased HR 8 weeks post-AAC but was no different between untreated AAC and AAC+ fenofibrate mice. Hypertrophy is seen in AAC as is evident by the increased LV heart weight/body weight ratio (Table). However, hypertrophy was increased in AAC+ fenofibrate (P<0.05 versus untreated AAC). In addition, fenofibrate also increased pulmonary congestion in AAC mice as shown by the increased wet/dry lung ratio (Table).
|
Fenofibrate Effects on LV Structure and Function in PPAR-Deficient Mice
Similar to the increased LV heart weight/body weight ratio (Table), fenofibrate increased total wall thickness in AAC (P<0.05) by echocardiography (Figure 3A). Regardless of the treatment in PPAR-deficient mice, AAC increased both LV end diastolic dimension and LV end systolic dimension. These were significant at 4 weeks and were further increased at 8 weeks (Figure 3B and 3C). AAC+ fenofibrate hearts were more dilated (Figure 3B and 3C). In concert, LV FS was progressively decreased in all of the AAC PPAR-deficient mice that were significant at 4 weeks and further decreased at 8 weeks. However, fenofibrate exacerbated the decline in LV percentage of FS in AAC at both 4 and 8 weeks (Figure 3D).
|
, n=6), untreated AAC (
, n=8 to 10) mice. *P<0.05 vs untreated Sham;
Myocardial PPAR and PPARß/ Expression in PPAR-Deficient Mice
In sham and AAC hearts, PPAR protein expression was not detectable by Western blot analysis regardless of treatment (data not shown). Similarly, PPARß/ protein expression was determined by Western blot analysis. Fenofibrate-treated AAC hearts exhibited a >9-fold increase in PPARß/ expression compared with untreated AAC hearts and sham hearts (14.7±4.6 versus 1.6±0.7 versus 1.7±0.6 arbitrary units (AU), respectively; Figure 4A and 4B).
|
Myocardial MMP and TIMP Expression in PPAR-Deficient Mice
The balance between MMP and TIMP expression is partially responsible for changes in the extracellular matrix. At 8 weeks post-AAC, MMP-2 protein expression was increased 39±26% (P<0.01 versus sham mice). Fenofibrate increased MMP-2 expression by 51±20% post-AAC (P<0.01 versus sham+fenofibrate). But, there was no difference between the untreated AAC and AAC+ fenofibrate groups. Similarly, TIMP-2 expression was increased post-AAC untreated (50±11%; P<0.01 versus sham) but not in AAC+ fenofibrate (22±16%; P not significant versus sham+fenofibrate; Figure 5A through 5C). Thus, the resulting MMP-2/TIMP-2 ratio, an index of net MMP activation, in PPAR-deficient mice was increased in AAC+ fenofibrate and unchanged in untreated-AAC hearts (6.9±1.0 versus 5.0±0.4; P<0.05; Figure 5G).
|
), untreated AAC (
MMP-9 expression was not affected by AAC and fenofibrate treatment. TIMP-1 expression, its inhibitor, was increased post-AAC compared with untreated sham (11.4±4.3 versus 4.7±0.5 AU) and further increased in AAC+ fenofibrate hearts (22.8±1.9 AU). Thus, the ensuing MMP-9/TIMP-1 ratio was significantly decreased (
2.5 fold) in AAC+ fenofibrate versus untreated AAC (1.0±0.1 versus 2.7±0.8; P<0.05; Figure 5D through 5G).
Myocardial Fibrosis in PPAR-Deficient Mice
Examination of cross-sections taken from the LV showed positive trichrome staining indicative of fibrosis. Fibrosis was increased 69% in AAC+ fenofibrate hearts compared with untreated AAC hearts (Figure 6A and 6B).
|
In Vitro Studies
Fenofibrates Induces ERK Phosphorylation in Culture in Aldosterone-Treated ARVMs
We showed previously in ARVMs that aldosterone directly induces MMP-2 and MMP-9 activities. The mechanism partially involves activation of the MEK/ERK1/2 pathway.8 We, thus, sought to explore the role of fenofibrate in aldosterone-mediated MMP expression in ARVMs. By Western blotting, treatment with aldosterone (50 nM) and fenofibrate (10 µmol/L) for 30 minutes increased phospho-ERK1/2 by 55±11% and 32±6%, respectively. ERK1/2 phosphorylation tended to increase further when aldosterone was pretreated with fenofibrate (10 µmol/L; P not significant versus aldosterone alone). Fenofibrate (100 µmol/L) for 30 minutes also increased phospho-ERK1/2, but the addition of aldosterone inhibited the increase in phospho-ERK1/2 by 44% (Figure 7A and 7B).
|
Fenofibrate Inhibits Aldosterone-Induced Increases in MMP Activity in ARVMs
In-gel zymography of conditioned medium from ARVM, treated with aldosterone (50 nM) for 24 hours, significantly increased MMP-2 (81±36%) and MMP-9 (32±5%) activities versus control (Figure 7C through 7E). Pretreatment with fenofibrate at 10 µmol/L and 100 µmol/L significantly abolished the increase in MMP-2 activity (Figure 7D) seen with aldosterone-treatment. Similarly, the aldosterone-induced increase in MMP-9 gelatinase activity was also significantly inhibited by both doses of fenofibrate (10 µmol/L and 100 µmol/L; Figure 7E).
|
Discussion |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
In this study, fenofibrate ameliorated progressive LV dilation and systolic failure seen with AAC in chronic PO WT mice. These improved effects seen with fenofibrate are because of activation of the PPAR
ligand. In contrast, in a PPAR-independent manner, fenofibrate exacerbated LV dilation, systolic failure, fibrosis, and decreased survival in chronic PO PPAR-deficient mice. These PPAR-independent effects were associated with impaired matrix turnover as shown by the increased MMP-2/TIMP-2 ratio. There was also increased myocardial PPARß/ expression in fenofibrate-treated PO PPAR-deficient mice. The beneficial effects of fenofibrate, via activation of the PPAR ligand, inhibited aldosterone-induced phospho-ERK1/2 and MMP activity in cultured ARVM.
PPAR-deficient mice are reportedly refractory to pleiotropic responses induced by PPAR ligands.16 Moreover, cardioprotective effects of PPAR activation during ischemia/reperfusion are abolished in PPAR-deficient mice.34 Similarly, myocardial fibrosis appears in an age-dependent manner in PPAR-deficient mice.35 We did not see evidence of cardiac fibrosis in sham PPAR-deficient mice, and this may be because of the younger age of our mice by the end of the study. Similarly, unlike the findings of Loichot et al,36 we do not see decreased cardiac function or HR at baseline compared with WT mice (Figures 1 and 3
). Loichot et al36 sedated their mice for echocardiography,37,38 and, because anesthesia decreases HR, which correlates with depressed cardiac function and contractility,39 this may explain their adverse findings.
Nonetheless, our study aims to address the role of fenofibrates in pathological remodeling. Our data suggest that PPAR-independent actions of fenofibrate increase fibrosis and matrix turnover and are partly responsible for the adverse effects seen in the chronic PO myocardium. In the absence of PPAR, fenofibrate exerted deleterious effects, which were associated with increased MMP-2 expression and a reduction in TIMP-2 expression. The myocardial MMP-2/TIMP-2 ratio, an index of net MMP activation, was increased in fenofibrate-treated PO PPAR-deficient mice, as was the fibrosis indicating increased matrix turnover, which may contribute to the LV hypertrophy seen. The increased LV hypertrophy seen with fenofibrate treatment in PPAR-deficient mice was not associated with elevated BP. Additionally, there was increased ANP expression (data not shown), a molecular marker of hypertrophy, in fenofibrate-treated PO PPAR-deficient mice. Fenofibrate had no affect on sham PPAR-deficient mice, suggesting that these negative effects may be apparent only during conditions of "stress," for example, such as during renin–angiotensin– aldosterone system activation with increased aldosterone or PO.5,8 The adverse effects (cardiac remodeling and fibrosis) of fenofibrate were not because of a lowering of tail-cuff BP (because there is no difference between treated or untreated PO PPAR-deficient mice). There was evidence of "clinical" heart failure in the mice, as demonstrated by a trend to decreased systolic BP in both of the AAC (PO) groups, the slight decrease in HR, and the increased pulmonary congestion (ie, wet/dry lung ratio).
Studies have demonstrated that MMP-2 and MMP-9 are augmented in dilated failing hearts3–5 and involved in the development and progression of myocardial remodeling.3 Similarly, MMP-2 and MMP-9 are increased during ischemia/reperfusion and are attenuated by PPAR agonists.34 Selective disruption of the MMP-2 gene ameliorated myocyte hypertrophy and interstitial fibrosis in PO mice.40 Thus, our data support the evidence that MMP-2 is involved in mediating PO-induced ventricular hypertrophy. Although MMP-2 was increased in untreated PO PPAR-deficient mice, it was further increased with fenofibrate treatment. TIMP-2 was increased in untreated AAC, but the expression of this inhibitor of MMP-2, in fenofibrate-treated AAC, was not as distinct. Although MMP-9 expression was not increased in fenofibrate-treated AAC,21 its inhibitor TIMP-1 possibly compensated for the lack of TIMP-2 expression by increased TIMP-1 expression. Similarly, fenofibrate may increase TIMP-1 expression to increase MMP-2 expression (because TIMPs participate in the process of MMP activation).41 Although we could not test for a cause or an effect in this in vivo model, the lack of an increase in the MMP-9/TIMP-1 ratio in AAC+ fenofibrate mice may contribute to the adverse effects of fenofibrate on cardiac function and survival. Thus, PPAR may have a protective role in preventing fenofibrate-induced exacerbation of hypertrophy in this model by its effect on MMP and TIMP interactions. Fenofibrate is a weak activator of PPARß/ and in other cell systems activates other pathways that are not PPAR dependent, such as non–receptor-mediated (nongenomic) effects.42 There are other possible hypothesizes for an unfavorable outcome in fenofibrate-treated PO PPAR-deficient mice in addition to increasing fibrosis, mortality, and activating MMPs. These non-PPAR-mediated effects include proapoptosis by inhibiting Akt phosphorylation43 and proapoptotic gene activation resulting in the progression to heart failure.44 In addition, there may be a precedent for significant species variation in PPAR-mediated responses,45 but they may also be related to the experimental model used to induce cardiac remodeling, for example, rats with myocardial infarction,46 pigs with ischemia/reperfusion,47 and humans with diabetes.48,49
We also measured other isoforms of PPAR ligands in this whole body deletion of PPAR. There was negligible myocardial expression of PPAR. Interestingly, myocardial expression of PPARß/ was significantly increased in fenofibrate-treated PO PPAR-deficient mice. The role of PPARß/ is unclear in cardiac remodeling. It has been suggested that PPARß/ agonists inhibit cardiac hypertrophy.20 Our data do not demonstrate a cause and an effect; increased PPARß/ expression in fenofibrate-treated PO PPAR-deficient mice is associated with adverse cardiac remodeling and requires further investigation. It is more likely that the adverse effects of fenofibrates would be even more marked in the absence of PPARß/ upregulation. Thus, PPARß/ expression may merely be a marker of comparatively worse LV function and adverse remodeling. PPARß/ expression was measured in fenofibrate-treated WT PO mice with chronic remodeling, that is, in the presence of PPAR ligands; there was no upregulation in PPARß/ expression (data not shown).
Similar to Dahl salt-sensitive rats50 and deoxycorticosterone acetate-salt hypertensive rats,9,15,23 fenofibrate, in our study, exerts beneficial effects on cardiac remodeling via PPAR activation in WT mice. The beneficial effect seen in our study is a decrease in wall thickness, a reduction in ventricular dilation, and an improvement in FS. We have shown that inflammatory cytokines and reactive oxygen species regulate myocardial MMP,8,51 and we now demonstrate that fenofibrate regulates the extracellular matrix in cardiac remodeling. The benefits of fenofibrates (by inhibiting aldosterone-induced increases in MMP activity) in vitro are partly because of PPAR-dependent activation by fenofibrate, and there was no increased PPARß/ or PPAR expression in ARVMs treated with fenofibrate (data not shown). The mechanisms of the improved chronic cardiac remodeling with fenofibrate (unrelated to their lipid-lowering actions) have been associated with effects on the vasculature,22 inhibition of proinflammatory19 and redox-sensitive50 transcription factors, and on cell infiltration52 and MMP-921 inhibition.
Perspectives
Fenofibrates are beneficial in progressive PO-induced cardiac remodeling, likely because of the presence of PPAR. Our study demonstrates, in cardiac remodeling, that the benefits of fenofibrate are partly because of aldosterone-stimulated inhibition of phospho-ERK and MMP. The adverse effects of fenofibrate (present only when PPAR is absent) are because of activation of MMP, increased fibrosis, left ventricular hypertrophy, and increased mortality. These findings indicate that, with PPAR deficiency, fenofibrates exert deleterious pleiotropic actions in the failing myocardium.
Interestingly, in human studies, several polymorphisms of the PPAR locus have been described.53 The V162 allele is associated with alterations in lipids and decreased cardiovascular events in diabetics.49 The effect of PPAR agonists with this allele is variable53,54 and requires further investigation.49 Because current heart failure therapies are directed at the inhibition of neurohormonal pathways, these results may provide a basis for future strategies to prevent or reverse cardiac remodeling in PO hypertrophy. However, despite their positive effects on cardiac physiology in vivo, the therapeutic benefit for fibrates in human heart failure requires longer-term studies to monitor their effects on cardiac function. Moreover, closer observation may be necessary in humans undergoing chronic fibrate therapy.48
|
Acknowledgments |
|---|
Sources of Funding
This work was supported in part by National Institutes of Health grants HL004423 (F.S.) and HL079099 (F.S.).
Disclosures
None.
Received January 3, 2007; first decision January 22, 2007; accepted February 12, 2007.
|
References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
1. Mann DL. Inflammatory mediators and the failing heart: past, present, and the foreseeable future. Circ Res. 2002; 91: 988–998.
2. Finck BN, Kelly DP. Peroxisome proliferator-activated receptor alpha (PPARalpha) signaling in the gene regulatory control of energy metabolism in the normal and diseased heart. J Mol Cell Cardiol. 2002; 34: 1249–1257.[Medline] [Order article via Infotrieve]
3. Deschamps AM, Spinale FG. Pathways of matrix metalloproteinase induction in heart failure: Bioactive molecules and transcriptional regulation. Cardiovasc Res. 2006; 69: 666–676.
4. Spinale FG. Matrix metalloproteinases: regulation and dysregulation in the failing heart. Circ Res. 2002; 90: 520–530.
5. Kuster GM, Kotlyar E, Rude MK, Siwik DA, Liao R, Colucci WS, Sam F. Mineralocorticoid receptor inhibition ameliorates the transition to myocardial failure and decreases oxidative stress and inflammation in mice with chronic pressure overload. Circulation. 2005; 111: 420–427.
6. Brilla CG, Zhou G, Matsubara L, Weber KT. Collagen metabolism in cultured adult rat cardiac fibroblasts: response to angiotensin II and aldosterone. J Mol Cell Cardiol. 1994; 26: 809–820.[CrossRef][Medline] [Order article via Infotrieve]
7. Zhou G, Kandala JC, Tyagi SC, Katwa LC, Weber KT. Effects of angiotensin II and aldosterone on collagen gene expression and protein turnover in cardiac fibroblasts. Mol Cell Biochem. 1996; 154: 171–178.[CrossRef][Medline] [Order article via Infotrieve]
8. Rude MK, Duhaney TA, Kuster GM, Judge S, Heo J, Colucci WS, Siwik DA, Sam F. Aldosterone stimulates matrix metalloproteinases and reactive oxygen species in adult rat ventricular cardiomyocytes. Hypertension. 2005; 46: 555–561.
9. Ogata T, Miyauchi T, Sakai S, Irukayama-Tomobe Y, Goto K, Yamaguchi I. Stimulation of peroxisome-proliferator-activated receptor alpha (PPAR alpha) attenuates cardiac fibrosis and endothelin-1 production in pressure-overloaded rat hearts. Clin Sci (Lond). 2002; 103 (suppl 48): 284S–288S.[Medline] [Order article via Infotrieve]
10. Gilde AJ, van der Lee KA, Willemsen PH, Chinetti G, van der Leij FR, van der Vusse GJ, Staels B, van Bilsen M. Peroxisome proliferator-activated receptor (PPAR) alpha and PPARbeta/delta, but not PPARgamma, modulate the expression of genes involved in cardiac lipid metabolism. Circ Res. 2003; 92: 518–524.
11. Frey N, Olson EN. Modulating cardiac hypertrophy by manipulating myocardial lipid metabolism? Circulation. 2002; 105: 1152–1154.
12. Barger PM, Brandt JM, Leone TC, Weinheimer CJ, Kelly DP. Deactivation of peroxisome proliferator-activated receptor-alpha during cardiac hypertrophic growth. J Clin Invest. 2000; 105: 1723–1730.[Medline] [Order article via Infotrieve]
13. Young ME, Laws FA, Goodwin GW, Taegtmeyer H. Reactivation of peroxisome proliferator-activated receptor alpha is associated with contractile dysfunction in hypertrophied rat heart. J Biol Chem. 2001; 276: 44390–44395.
14. Francis GA, Annicotte JS, Auwerx J. PPAR-alpha effects on the heart and other vascular tissues. Am J Physiol Heart Circ Physiol. 2003; 285: H1–H9.
15. Diep QN, Benkirane K, Amiri F, Cohn JS, Endemann D, Schiffrin EL. PPAR alpha activator fenofibrate inhibits myocardial inflammation and fibrosis in angiotensin II-infused rats. J Mol Cell Cardiol. 2004; 36: 295–304.[CrossRef][Medline] [Order article via Infotrieve]
16. Lee SS, Pineau T, Drago J, Lee EJ, Owens JW, Kroetz DL, Fernandez-Salguero PM, Westphal H, Gonzalez FJ. Targeted disruption of the alpha isoform of the peroxisome proliferator-activated receptor gene in mice results in abolishment of the pleiotropic effects of peroxisome proliferators. Mol Cell Biol. 1995; 15: 3012–3022.[Abstract]
17. Peters JM, Aoyama T, Burns AM, Gonzalez FJ. Bezafibrate is a dual ligand for PPARalpha and PPARbeta: studies using null mice. Biochim Biophys Acta. 2003; 1632: 80–89.[Medline] [Order article via Infotrieve]
18. Erol A. PPARalpha activators may play role for the regression of ventricular hypertrophy in hypertensive and hyperlipidemic patients. Med Hypotheses. 2006; 66: 1044–1045.[CrossRef][Medline] [Order article via Infotrieve]
19. Delerive P, Fruchart JC, Staels B. Peroxisome proliferator-activated receptors in inflammation control. J Endocrinol. 2001; 169: 453–459.[Abstract]
20. Planavila A, Rodriguez-Calvo R, Jove M, Michalik L, Wahli W, Laguna JC, Vazquez-Carrera M. Peroxisome proliferator-activated receptor beta/delta activation inhibits hypertrophy in neonatal rat cardiomyocytes. Cardiovasc Res. 2005; 65: 832–841.
21. Marx N, Sukhova GK, Collins T, Libby P, Plutzky J. PPARalpha activators inhibit cytokine-induced vascular cell adhesion molecule-1 expression in human endothelial cells. Circulation. 1999; 99: 3125–3131.
22. Diep QN, Amiri F, Touyz RM, Cohn JS, Endemann D, Neves MF, Schiffrin EL. PPARalpha activator effects on Ang II-induced vascular oxidative stress and inflammation. Hypertension. 2002; 40: 866–871.
23. Ogata T, Miyauchi T, Sakai S, Takanashi M, Irukayama-Tomobe Y, Yamaguchi I. Myocardial fibrosis and diastolic dysfunction in deoxycorticosterone acetate-salt hypertensive rats is ameliorated by the peroxisome proliferator-activated receptor-alpha activator fenofibrate, partly by suppressing inflammatory responses associated with the nuclear factor-kappa-B pathway. J Am Coll Cardiol. 2004; 43: 1481–1488.
24. Liao R, Jain M, Cui L, D’Agostino J, Aiello F, Luptak I, Ngoy S, Mortensen RM, Tian R. Cardiac-specific overexpression of GLUT1 prevents the development of heart failure attributable to pressure overload in mice. Circulation. 2002; 106: 2125–2131.
25. Duez H, Chao YS, Hernandez M, Torpier G, Poulain P, Mundt S, Mallat Z, Teissier E, Burton CA, Tedgui A, Fruchart JC, Fievet C, Wright SD, Staels B. Reduction of atherosclerosis by the peroxisome proliferator- activated receptor alpha agonist fenofibrate in mice. J Biol Chem. 2002; 277: 48051–48057.
26. Vikramadithyan RK, Hirata K, Yagyu H, Hu Y, Augustus A, Homma S, Goldberg IJ. Peroxisome proliferator-activated receptor agonists modulate heart function in transgenic mice with lipotoxic cardiomyopathy. J Pharmacol Exp Ther. 2005; 313: 586–593.
27. Carmona MC, Louche K, Nibbelink M, Prunet B, Bross A, Desbazeille M, Dacquet C, Renard P, Casteilla L, Penicaud L. Fenofibrate prevents Rosiglitazone-induced body weight gain in ob//ob mice. Int J Obes (Lond). 2005; 29: 864–871.[CrossRef][Medline] [Order article via Infotrieve]
28. Krege JH, Hodgin JB, Hagaman JR, Smithies O. A noninvasive computerized tail-cuff system for measuring blood pressure in mice. Hypertension. 1995; 25: 1111–1115.
29. Johns C, Gavras I, Handy DE, Salomao A, Gavras H. Models of experimental hypertension in mice. Hypertension. 1996; 28: 1064–1069.
30. Sam F, Sawyer DB, Xie Z, Chang DL, Ngoy S, Brenner DA, Siwik DA, Singh K, Apstein CS, Colucci WS. Mice lacking inducible nitric oxide synthase have improved left ventricular contractile function and reduced apoptotic cell death late after myocardial infarction. Circ Res. 2001; 89: 351–356.
31. Siwik DA, Pagano PJ, Colucci WS. Oxidative stress regulates collagen synthesis and matrix metalloproteinase activity in cardiac fibroblasts. Am J Physiol Cell Physiol. 2001; 280: C53–C60.
32. Coker ML, Doscher MA, Thomas CV, Galis ZS, Spinale FG. Matrix metalloproteinase synthesis and expression in isolated LV myocyte preparations. Am J Physiol Heart Circ Physiol. 1999; 277: H777–H787.
33. Coker ML, Jolly JR, Joffs C, Etoh T, Holder JR, Bond BR, Spinale FG. Matrix metalloproteinase expression and activity in isolated myocytes after neurohormonal stimulation. Am J Physiol Heart Circ Physiol. 2001; 281: H543–H551.
34. Yue TL, Bao W, Jucker BM, Gu JL, Romanic AM, Brown PJ, Cui J, Thudium DT, Boyce R, Burns-Kurtis CL, Mirabile RC, Aravindhan K, Ohlstein EH. Activation of peroxisome proliferator-activated receptor-alpha protects the heart from ischemia/reperfusion injury. Circulation. 2003; 108: 2393–2399.
35. Watanabe K, Fujii H, Takahashi T, Kodama M, Aizawa Y, Ohta Y, Ono T, Hasegawa G, Naito M, Nakajima T, Kamijo Y, Gonzalez FJ, Aoyama T. Constitutive regulation of cardiac fatty acid metabolism through peroxisome proliferator-activated receptor alpha associated with age-dependent cardiac toxicity. J Biol Chem. 2000; 275: 22293–22299.
36. Loichot C, Jesel L, Tesse A, Tabernero A, Schoonjans K, Roul G, Carpusca I, Auwerx J, Andriantsitohaina R. Deletion of peroxisome proliferator-activated receptor-alpha induces an alteration of cardiac functions. Am J Physiol Heart Circ Physiol. 2006; 291: H161–H166.
37. Yang XP, Liu YH, Rhaleb NE, Kurihara N, Kim HE, Carretero OA. Echocardiographic assessment of cardiac function in conscious and anesthetized mice. Am J Physiol Heart Circ Physiol. 1999; 277: H1967–H1974.
38. Roth DM, Swaney JS, Dalton ND, Gilpin EA, Ross J Jr. Impact of anesthesia on cardiac function during echocardiography in mice. Am J Physiol Heart Circ Physiol. 2002; 282: H2134–H2140.
39. Palakodeti V, Oh S, Oh BH, Mao L, Hongo M, Peterson KL, Ross J Jr. Force-frequency effect is a powerful determinant of myocardial contractility in the mouse. Am J Physiol Heart Circ Physiol. 1997; 273: H1283–H1290.
40. Matsusaka H, Ide T, Matsushima S, Ikeuchi M, Kubota T, Sunagawa K, Kinugawa S, Tsutsui H. Targeted deletion of matrix metalloproteinase 2 ameliorates myocardial remodeling in mice with chronic pressure overload. Hypertension. 2006; 47: 711–717.
41. Mann DL, Spinale FG. Activation of matrix metalloproteinases in the failing human heart: breaking the tie that binds. Circulation. 1998; 98: 1699–1702.
42. Pauley CJ, Ledwith BJ, Kaplanski C. Peroxisome proliferators activate growth regulatory pathways largely via peroxisome proliferator-activated receptor alpha-independent mechanisms. Cell Signal. 2002; 14: 351–358.[CrossRef][Medline] [Order article via Infotrieve]
43. Kubota T, Yano T, Fujisaki K, Itoh Y, Oishi R. Fenofibrate induces apoptotic injury in cultured human hepatocytes by inhibiting phosphorylation of Akt. Apoptosis. 2005; 10: 349–358.[CrossRef][Medline] [Order article via Infotrieve]
44. Buermans HP, Redout EM, Schiel AE, Musters RJ, Zuidwijk M, Eijk PP, van Hardeveld C, Kasanmoentalib S, Visser FC, Ylstra B, Simonides WS. Microarray analysis reveals pivotal divergent mRNA expression profiles early in the development of either compensated ventricular hypertrophy or heart failure. Physiol Genomics. 2005; 21: 314–323.
45. Choudhury AI, Chahal S, Bell AR, Tomlinson SR, Roberts RA, Salter AM, Bell DR. Species differences in peroxisome proliferation; mechanisms and relevance. Mutat Res. 2000; 448: 201–212.[Medline] [Order article via Infotrieve]
46. Morgan EE, Rennison JH, Young ME, McElfresh TA, Kung TA, Tserng KY, Hoit BD, Stanley WC, Chandler MP. Effects of chronic activation of peroxisome proliferator-activated receptor-alpha or high-fat feeding in a rat infarct model of heart failure. Am J Physiol Heart Circ Physiol. 2006; 290: H1899–H1904.
47. Xu Y, Lu L, Greyson C, Rizeq M, Nunley K, Wyatt B, Bristow MR, Long CS, Schwartz GG. The PPAR-{alpha} activator, fenofibrate, fails to provide myocardial protection in ischemia and reperfusion in pigs. Am J Physiol Heart Circ Physiol. 2006; 290: H1798–H1807.
48. Keech A, Simes RJ, Barter P, Best J, Scott R, Taskinen MR, Forder P, Pillai A, Davis T, Glasziou P, Drury P, Kesaniemi YA, Sullivan D, Hunt D, Colman P, d’Emden M, Whiting M, Ehnholm C, Laakso M. Effects of long-term fenofibrate therapy on cardiovascular events in 9795 people with type 2 diabetes mellitus (the FIELD study): randomised controlled trial. Lancet. 2005; 366: 1849–1861.[CrossRef][Medline] [Order article via Infotrieve]
49. Tai ES, Demissie S, Cupples LA, Corella D, Wilson PW, Schaefer EJ, Ordovas JM. Association between the PPARA L162V polymorphism and plasma lipid levels: the Framingham Offspring Study. Arterioscler Thromb Vasc Biol. 2002; 22: 805–810.
50. Ichihara S, Yamada Y, Ichihara G, Kanazawa H, Hashimoto K, Kato Y, Matsushita A, Oikawa S, Yokota M, Iwase M. Attenuation of oxidative stress and cardiac dysfunction by bisoprolol in an animal model of dilated cardiomyopathy. Biochem Biophys Res Commun. 2006; 10: 350:105–113.
51. Siwik DA, Colucci WS. Regulation of matrix metalloproteinases by cytokines and reactive oxygen/nitrogen species in the myocardium. Heart Fail Rev. 2004; 9: 43–51.[CrossRef][Medline] [Order article via Infotrieve]
52. Deplanque D, Gele P, Petrault O, Six I, Furman C, Bouly M, Nion S, Dupuis B, Leys D, Fruchart JC, Cecchelli R, Staels B, Duriez P, Bordet R. Peroxisome proliferator-activated receptor-alpha activation as a mechanism of preventive neuroprotection induced by chronic fenofibrate treatment. J Neurosci. 2003; 23: 6264–6271.
53. Flavell DM, Pineda T, I, Jamshidi Y, Evans D, Diamond JR, Elkeles RS, Bujac SR, Miller G, Talmud PJ, Staels B, Humphries SE. Variation in the PPARalpha gene is associated with altered function in vitro and plasma lipid concentrations in Type II diabetic subjects. Diabetologia. 2000; 43: 673–680.[CrossRef][Medline] [Order article via Infotrieve]
54. Sapone A, Peters JM, Sakai S, Tomita S, Papiha SS, Dai R, Friedman FK, Gonzalez FJ. The human peroxisome proliferator-activated receptor alpha gene: identification and functional characterization of two natural allelic variants. Pharmacogenetics. 2000; 10: 321–333.[CrossRef][Medline] [Order article via Infotrieve]
This article has been cited by other articles:
 |
|
 |
|
  D. S. De Silva, R. M. Wilson, C. Hutchinson, P. C. Ip, A. G. Garcia, S. Lancel, M. Ito, D. R. Pimentel, and F. Sam Fenofibrate inhibits aldosterone-induced apoptosis in adult rat ventricular myocytes via stress-activated kinase-dependent mechanisms Am J Physiol Heart Circ Physiol, June 1, 2009; 296(6): H1983 - H1993. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. S. A. Patel, R. di Paola, E. Mazzon, D. Britti, C. Thiemermann, and S. Cuzzocrea Peroxisome Proliferator-Activated Receptor-{alpha} Contributes to the Resolution of Inflammation after Renal Ischemia/Reperfusion Injury J. Pharmacol. Exp. Ther., February 1, 2009; 328(2): 635 - 643. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. J. H. Smeets, H. M. de Vogel-van den Bosch, P. H. M. Willemsen, A. P. Stassen, T. Ayoubi, G. J. van der Vusse, and M. van Bilsen Transcriptomic analysis of PPAR{alpha}-dependent alterations during cardiac hypertrophy Physiol Genomics, December 12, 2008; 36(1): 15 - 23. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Doi, T. Sakoda, T. Akagami, T. Naka, Y. Mori, T. Tsujino, T. Masuyama, and M. Ohyanagi Aldosterone induces interleukin-18 through endothelin-1, angiotensin II, Rho/Rho-kinase, and PPARs in cardiomyocytes Am J Physiol Heart Circ Physiol, September 1, 2008; 295(3): H1279 - H1287. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. J.H. Smeets, B. E.J. Teunissen, P. H.M. Willemsen, F. A. van Nieuwenhoven, A. E. Brouns, B. J.A. Janssen, J. P.M. Cleutjens, B. Staels, G. J. van der Vusse, and M. van Bilsen Cardiac hypertrophy is enhanced in PPAR{alpha}-/- mice in response to chronic pressure overload Cardiovasc Res, April 1, 2008; 78(1): 79 - 89. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. K. LeBrasseur, T.-A. S. Duhaney, D. S. De Silva, L. Cui, P. C. Ip, L. Joseph, and F. Sam Effects of Fenofibrate on Cardiac Remodeling in Aldosterone-Induced Hypertension Hypertension, September 1, 2007; 50(3): 489 - 496. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||