Selective spatiotemporal induction of matrix metalloproteinase-2 and matrix metalloproteinase-9 transcription after myocardial infarction

Myocardial remodeling after myocardial infarction (MI) is associated with increased levels of the matrix metalloproteinases (MMPs). Levels of two MMP species, MMP-2 and MMP-9, are increased after MI, and transgenic deletion of these MMPs attenuates post-MI left ventricular (LV) remodeling. This study characterized the spatiotemporal patterns of gene promoter induction for MMP-2 and MMP-9 after MI. MI was induced in transgenic mice in which the MMP-2 or MMP-9 promoter sequence was fused to the beta-galactosidase reporter, and reporter level was assayed up to 28 days after MI. Myocardial localization with respect to cellular sources of MMP-2 and MMP-9 promoter induction was examined. After MI, LV diameter increased by 70% (P < 0.05), consistent with LV remodeling. beta-Galactosidase staining in MMP-2 reporter mice was increased by 1 day after MI and increased further to 64 +/- 6% of LV epicardial area by 7 days after MI (P < 0.05). MMP-2 promoter activation occurred in fibroblasts and myofibroblasts in the MI region. In MMP-9 reporter mice, promoter induction was detected after 3 days and peaked at 7 days after MI (53 +/- 6%, P < 0.05) and was colocalized with inflammatory cells at the peri-infarct region. Although MMP-2 promoter activation was similarly distributed in the MI and border regions, activation of the MMP-9 promoter was highest at the border between the MI and remote regions. These unique findings visually demonstrated that activation of the MMP-2 and MMP-9 gene promoters occurs in a distinct spatial relation with reference to the MI region and changes in a characteristic time-dependent manner after MI.     

Abnormal cardiac wall motion and early matrix metalloproteinase activity

Activation of matrix metalloproteinases (MMPs) in the heart is known to facilitate cardiac remodeling and progression to failure. We hypothesized that regional dyskinetic wall motion of the left ventricle would stimulate activation of MMPs. Abnormal wall motion at a target site on the anterior lateral wall of the left ventricle was induced by pacing atrial and ventricular sites of five open-chest anesthetized dogs. Changes in shortening at the left ventricular (LV) pacing site and at a remote site at the anterior base of the left ventricle were monitored with piezoelectric crystals. Simultaneous atrial and ventricular pacing resulted in abnormal motion at the LV pacing site, yielding early shortening and late systolic lengthening, whereas the shortening pattern at the remote site remained unaffected. Assessment of global myocardial MMP activity showed a sevenfold increase in substrate cleavage (P < 0.02) at the LV pacing site relative to the remote site. Gelatin zymography revealed increases in 92-kDa MMP-9 activity and 86-kDa MMP-9 activity at the LV pacing site relative to the remote site, whereas MMP-2 activity was unaffected. Abnormal wall motion was associated with increases in collagen degradation (approximately 2-fold; P < 0.03), plasmin activity (approximately 1.5-fold; P < 0.05), nitrotyrosine levels (approximately 20-fold; P = 0.05), and inflammatory infiltrate (approximately 2-fold; P < 0.02) relative to the remote site. Results indicate that regional dyskinesis induced by epicardial activation is sufficient to stimulate significant MMP activity in the heart, suggesting that abnormal wall motion is a stimulus for MMP activation.     

Cardiac-restricted overexpression of extracellular matrix metalloproteinase inducer causes myocardial remodeling and dysfunction in aging mice

The matrix metalloproteinases (MMPs) play a pivotal role in adverse left ventricular (LV) myocardial remodeling. The transmembrane protein extracellular MMP inducer (EMMPRIN) causes increased MMP expression in vitro, and elevated levels occur in patients with LV failure. However, the direct consequences of a prolonged increase in the myocardial expression of EMMPRIN in vivo remained unexplored. Cardiac-restricted EMMPRIN expression (EMMPRINexp) was constructed in mice using the full-length human EMMPRIN gene ligated to the myosin heavy chain promoter, which yielded approximately a twofold increase in EMMPRIN compared with that of the age/strain-matched wild-type (WT) mice; EMMPRINexp (n=27) and WT (n=33) mice were examined at 3.2+/-0.1 or at 13.3+/-0.5 mo of age (n=43 and 26, respectively). LV end-diastolic volume (EDV) was similar in young EMMPRINexp and WT mice (54+/-2 vs. 57+/-3 microl), but LV ejection fraction (EF) was reduced (51+/-1 vs. 57+/-1%; P<0.05). In old EMMPRINexp mice, LV EDV was increased compared with WT mice values (76+/-3 vs. 58+/-3 microl; P<0.05) and LV EF was significantly reduced (45+/-1 vs. 57+/-2%; P<0.05). In EMMPRINexp old mice, myocardial MMP-2 and membrane type-1 MMP levels were increased by >50% from WT values (P<0.05) and were accompanied by a twofold higher collagen content (P<0.05). Persistent myocardial EMMPRINexp in aging mice caused increased levels of both soluble and membrane type MMPs, fibrosis, and was associated with adverse LV remodeling. These findings suggest that EMMPRIN is an upstream signaling pathway that can play a mechanistic role in adverse remodeling within the myocardium.     

Prolonged activation of tumor necrosis factor (TNF)-alpha and its soluble receptors in chronic heart failure patients both in the compensated and decompensated state. Interplay between their levels and metalloproteinase-3

INTRODUCTION: Recent clinical and experimental studies indicate that upregulation of the TNF system can contribute to the progression of cardiac remodeling and heart failure decompensation, by promoting alterations in cardiomyocyte biology and extracellular matrix metabolism. Extracellular matrix turnover is regulated by the matrix metalloproteinases (MMPs), which are endogenous enzymes responsible for extracellular collagen degradation. The present study investigates the fluctuation of serum levels of TNF-alpha, soluble TNF receptor-1 (sTNFR1) and -2 (sTNFR2), in patients with chronic heart failure both during acute decompensation and the stable state of the syndrome. The second goal of this study was to determine if a relationship exists between serum MMPs profiles (MMP-1, MMP-2, MMP-3) and circulating TNF-alpha or its soluble receptors. METHODS: Our patient group consisted of 52 patients with chronic heart failure (NYHA III-IV; mean age: 65 +/- 4 years; hypertensive cardiomyopathy: 20, ischemic cardiomyopathy: 17, dilated cardiomyopathy: 10, valvular disease: 5), who were hospitalized for acute decompensation of the syndrome. Our control group consisted of 30 healthy subjects (mean age: 57 +/- 6 years). Serum levels of TNF-alpha, sTNFR1, sTNFR2 and MMP-1,-2,-3 were measured in heart failure patients by ELISA at admission and after one month as follow-up. Values are expressed as medians and interquartile ranges. RESULTS: In our patient group, we observed a statistically significant increase in the levels of sTNFR1 and sTNFR2 at admission (sTNFR1: 5.15 ng\mL, 4.49-8.90 ng\mL, P < 0.001, sTNFR2: 13.40 ng\mL, 6.10-21.50 ng\mL, P < 0.001), and at one-month follow-up (sTNFR1: 5.30 ng\mL, 4.61-6.90 ng\mL, P < 0.001, sTNFR2: 21.80 ng\mL, 11.50-25.20 ng\mL, P < 0.001), compared to the control group (sTNFR1: 3.83 ng\mL, 3.70-3.95 ng\mL, sTNFR2: 4.00 ng\mL, 3.40-5.40 ng\mL). There was a statistically significant difference in the levels of sTNFR2 between admission and follow-up (P < 0.05). Significant correlations between serum MMP-3 and sTNFR2 levels both at admission and follow up (r -/+ 0.460, P -/+ 0.005 and r -/+ 0.338, P -/+ 0.044, respectively) were also found. CONCLUSIONS: Soluble TNF receptors are elevated in heart failure patients both in acute decompensation and stable phase. We have detected higher levels of soluble TNFR2 during the compensated phase of heart failure, suggesting that TNFR2 receptors appear to stabilize the cytokine and thereby prolong its half-life and biological functions. Finally, TNF system-mediated cardiac remodeling may exist through the activation of MMP-3 signaling pathways.     

Isothiocyanates sensitize the effect of chemotherapeutic drugs via modulation of protein kinase C and telomerase in cervical cancer cells

We determined effects of the vasopeptidase inhibitor (VPI) omapatrilat and angiotensin II type 1 receptor (AT(1)R) blocker (ARB) candesartan in rats during healing between day-2 and day-21 after reperfused myocardial infarction (RMI) on left ventricular (LV) remodeling and function, and regional matrix metalloproteinase (MMP)-9, tissue inhibitor of MMP (TIMP)-3, inducible-nitric-oxide-synthase (iNOS), oxidant-generating myeloperoxidase (MPO), and cytokines tumor-necrosis-factor (TNF)-alpha, interleukin (IL)-6 and IL-10, and transforming-growth-factor (TGF)-beta(1), and collagens. Compared to RMI-placebo, both agents reversed adverse LV remodeling and systolic and diastolic dysfunction, improved collagen remodeling, and normalized MMP-9 (activity, protein, and mRNA), TIMP-3 (protein and mRNA), and iNOS, MPO, TNF-alpha, IL-6, and TGF-beta(1) proteins, and improved MMP-9/TIMP-3 balance and IL-10 levels in previously ischemic zones. The results suggest that modulation of matrix proteases, oxidants, cytokines, and NOSs with omapatrilat and candesartan contribute to reversal of adverse collagen and LV remodeling and attenuation of LV dysfunction during healing after RMI.     

Selective matrix metalloproteinase inhibition attenuates progression of left ventricular dysfunction and remodeling in dogs with chronic heart failure

Matrix metalloproteinases (MMPs) contribute to the progression of left ventricular (LV) dysfunction and remodeling associated with heart failure (HF). The present study examined the long-term effects of a selective MMP inhibitor PG-530742 (PG) on the progression of LV dysfunction and remodeling in dogs with HF. Chronic HF [LV ejection fraction (LVEF), 相似文献   

Serum but not myocardial TNF-alpha concentration is increased in pacing-induced heart failure in rabbits

In animals and patients with severe heart failure (HF), the serum tumor necrosis factor-alpha (TNF-alpha) concentration is increased. It is, however, still controversial whether or not such increased serum TNF-alpha originates from the heart itself or is of peripheral origin secondary to gastrointestinal congestion and increased endotoxin concentration. We therefore now examined TNF-alpha in serum, myocardium, and liver of sham-operated and HF rabbits. In nine rabbits in which HF was induced by left ventricular (LV) pacing at 400 beats/min for 3 wk, LV end-diastolic diameter was increased and systolic shortening fraction (9.4 +/- 1.0 vs. 28.5 +/- 1.3%, echocardiography, P < 0.05) was reduced. Serum TNF-alpha was higher in HF than in sham-operated rabbits (240 +/- 24 vs. 150 +/- 22 U/ml, WEHI-cell assay, P < 0.05). In the heart, TNF-alpha was located mainly in the vascular endothelium (immunohistochemistry), and TNF-alpha protein (920 +/- 160 vs. 900 +/- 95 U/g) did not differ between groups. In the liver of HF rabbits, hepatocytes expressed TNF-alpha, and TNF-alpha protein was increased compared with sham-operated rabbits (2,390 +/- 310 vs. 1,220 +/- 135 U/g, P < 0.05) and correlated to the number of hepatic leukocytes (r = 0.85) and serum TNF-alpha (r = 0.69). The intestinal endotoxin concentration was 24.5 +/- 1.2 vs. 17.0 +/- 3.1 endotoxin units/g wet wt (P < 0.05) in HF compared with sham-operated rabbits. In this HF model, serum but not myocardial TNF-alpha is increased. The increased serum TNF-alpha originates from peripheral sources.     

Accelerated LV remodeling after myocardial infarction in TIMP-1-deficient mice: effects of exogenous MMP inhibition

Alterations in matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) have been implicated in adverse left ventricular (LV) remodeling after myocardial infarction (MI). However, the direct mechanistic role of TIMPs in the post-MI remodeling process has not been completely established. The goal of this project was to define the effects of altering endogenous MMP inhibitory control through combined genetic and pharmacological approaches on post-MI remodeling in mice. This study examined the effects of MMP inhibition (MMPi) with PD-166793 (30 mg.kg(-1).day(-1)) on LV geometry and function (conductance volumetry) after MI in wild-type (WT) mice and mice deficient in the TIMP-1 gene [TIMP-1 knockout (TIMP1-KO)]. At 3 days after MI (coronary ligation), mice were randomized into four groups: WT-MI/MMPi (n = 10), TIMP1-KO-MI/MMPi (n = 10), WT-MI (n = 22), and TIMP1-KO-MI (n = 23). LV end-diastolic volume (EDV) and ejection fraction were determined 14 days after MI. Age-matched WT (n = 20) and TIMP1-KO (n = 28) mice served as reference controls. LVEDV was similar under control conditions in WT and TIMP1-KO mice (36 +/- 2 and 40 +/- 2 microl, respectively) but was greater in TIMP1-KO-MI than in WT-MI mice (48 +/- 2 vs. 61 +/- 5 microl, P < 0.05). LVEDV was reduced from MI-only values in WT-MI/MMPi and TIMP1-KO-MI/MMPi mice (42 +/- 2 and 36 +/- 2 microl, respectively, P < 0.05) but was reduced to the greatest degree in TIMP1-KO mice (P < 0.05). LV ejection fraction was reduced in both groups after MI and increased in TIMP1-KO-MI/MMPi, but not in WT-MI/MMPi, mice. These unique results demonstrated that myocardial TIMP-1 plays a regulatory role in post-MI remodeling and that the accelerated myocardial remodeling induced by TIMP-1 gene deletion can be pharmacologically "rescued" by MMP inhibition. These results define the importance of local endogenous control of MMP activity with respect to regulating LV structure and function after MI.     

Hypertrophy signaling during peripartum cardiac remodeling

Molecular signaling pathways that regulate peripartum cardiac remodeling are not well understood. Our objectives were to study the role of mitogen-activated protein kinases (MAPKs), protein kinase B (Akt), and endothelial nitric oxide synthase (eNOS) in mediating pregnancy and postpartum (PP) cardiac remodeling. Methods: Adult female Sprague-Dawley rats were divided into nonpregnant (n = 5), 18 days pregnant (n = 5), 0 days PP (n = 7), and 14 days PP (n = 8). Rats underwent echocardiography under sedation to measure left ventricle (LV) size and function, and Western blots were performed to measure myocardial protein expression of MAPKs (p38, JNK, ERK), Akt, and eNOS. Results: 1) During pregnancy, there was an increase in LV mass (0.62 +/- 0.03 to 1.1 +/- 0.04 g, P < 0.001), mass/volume ratio (0.7 +/- 0.02 to 1.28 +/- 0.02 g/ml, P < 0.0001), and ejection fraction (EF) (64 +/- 3 to 74 +/- 2%). Whereas LV mass and mass/volume ratio returned to prepregnancy values in the PP period, EF remained below normal range (53 +/- 3%, P < 0.05). 2) The expression of anti-hypertrophic factors (p38, JNK, Akt) decreased during pregnancy and normalized PP, except JNK, which increased to higher than normal levels. eNOS also increased to higher than baseline levels PP. 3) Activation of p38 and JNK was directly correlated with lower LV mass/volume ratio (r = -0.81 and -0.71, respectively; P < 0.05). Conclusion: Pregnancy is associated with physiological cardiac hypertrophy. There is rapid reversal of hypertrophy in the PP period while recovery of cardiac function is delayed, possibly related to PP upregulation of JNK. A dysregulation of MAPK signaling may be an important determinant of PP cardiac dysfunction.     

In vivo TNF-alpha inhibition ameliorates cardiac mitochondrial dysfunction, oxidative stress, and apoptosis in experimental heart failure

Heart failure is associated with increased myocardial expression of TNF-alpha. However, the role of TNF-alpha in the development of heart failure is not fully understood. In the present study, we investigated the contribution of TNF-alpha to myocardial mitochondrial dysfunction, oxidative stress, and apoptosis in a unique dog model of heart failure characterized by an activation of all of these pathological processes. Male mongrel dogs were randomly assigned (n = 10 each) to 1) normal controls; 2) chronic pacing (250 beats/min for 4 wk) with concomitant administration of etanercept, a soluble p75 TNF receptor fusion protein, 0.5 mg/kg subcutaneously twice weekly; 3) chronic pacing with administration of saline vehicle. Mitochondrial function was assessed by left ventricular (LV) tissue mitochondrial respiratory enzyme activities. Oxidative stress was assessed with aldehyde levels, and apoptosis was quantified by photometric enzyme immunoassay for cytoplasmic histone-associated DNA fragments and terminal deoxynucleotide transferase-mediated nick-end labeling (TUNEL) assays. LV activity levels of mitochondrial respiratory chain enzyme complex III and V were reduced in the saline-treated dogs and restored either partially (complex III) or completely (complex V) in the etanercept-treated dogs. Aldehyde levels, DNA fragments, and TUNEL-positive cells were increased in the saline-treated dogs and normalized in etanercept-treated dogs. These changes were accompanied by an attenuation of LV dilatation and partial restoration of ejection fraction. Our data demonstrate that TNF-alpha contributes to progressive LV dysfunction in pacing-induced heart failure, mediated in part by a local impairment in mitochondrial function and increase in oxidative stress and myocyte apoptosis.     

Targeted deletion of MMP-2 attenuates early LV rupture and late remodeling after experimental myocardial infarction

Matrix metalloproteinase-2 (MMP-2) is prominently overexpressed both after myocardial infarction (MI) and in heart failure. However, its pathophysiological significance in these conditions is still unclear. We thus examined the effects of targeted deletion of MMP-2 on post-MI left ventricular (LV) remodeling and failure. Anterior MI was produced in 10- to 12-wk-old male MMP-2 knockout (KO) and sibling wild-type (WT) mice by ligating the left coronary artery. By day 28, MI resulted in a significant increase in mortality in association with LV cavity dilatation and dysfunction. The MMP-2 KO mice had a significantly better survival rate than WT mice (56% vs. 85%, P < 0.05), despite a comparable infarct size (50 +/- 3% vs. 51 +/- 3%, P = not significant), heart rate, and arterial blood pressure. The KO mice had a significantly lower incidence of LV rupture (10% vs. 39%, P < 0.05), which occurred within 7 days of MI. The KO mice exerted less LV cavity dilatation and improved fractional shortening after MI by echocardiography. The LV zymographic MMP-2 level significantly increased in WT mice after coronary artery ligation; however, this was completely prevented in KO mice. In contrast, the increase in the LV zymographic MMP-9 level after MI was similar between KO and WT mice. MMP-2 activation is therefore considered to contribute to an early cardiac rupture as well as late LV remodeling after MI. The inhibition of MMP-2 activation may therefore be a potentially useful therapeutic strategy to manage post-MI hearts.     

Inhibition of tumor necrosis factor receptor-1-mediated pathways has beneficial effects in a murine model of postischemic remodeling

The aim of the present study was to investigate the importance of tumor necrosis factor (TNF)-alpha receptor-1 (TNFR1)-mediated pathways in a murine model of myocardial infarction and remodeling. One hundred and ninety-four wild-type (WT) and TNFR1 gene-deleted (TNFR1KO) mice underwent left coronary artery ligation to induce myocardial infarction. On days 1, 3, 7, and 42, mice underwent transesophageal echocardiography. Hearts were weighed, and the left ventricle (LV) was assayed for matrix metalloproteinase (MMP)-2 and -9 activity and for tissue inhibitor of MMP (TIMP)-1 and -2 expression. Deletion of the TNFR1 gene substantially improved survival because no deaths were observed in TNFR1KO mice versus 56.4% and 18.2% in WT males and females, respectively (P < 0.002). At 42 days, LV remodeling, assessed by LV function (fractional area change of 31.9 +/- 7.9%, 32.2 +/- 7.7%, and 21.6 +/- 7.1% in TNFR1KO males, TNFR1KO females, and WT females, respectively, P < 0.04), and hypertrophy (heart weight-to-body weight ratios of 5.435 +/- 0.986, 5.485 +/- 0.677, and 6.726 +/- 0.704 mg/g, P < 0.04) were ameliorated in TNFR1KO mice. MMP-9 activity was highest at 3 days postinfarction and was highest in WT males (1.9 +/- 0.4 4, 3.6 +/- 0.24, 1.15 +/- 0.28, and 1.3 +/- 1.2 ng/100 microg protein, respectively, in TNFR1KO males, WT males, TNFR1KO females, and WT females, respectively, P < 0.002), whereas at 3 days TIMP-1 mRNA fold upregulation compared with type- and sex-matched controls was lowest in WT males (138.32 +/- 13.05, 46.74 +/- 5.43, 186.09 +/- 28.07, and 101.76 +/- 22.48, respectively, P < 0.002). MMP-2 and TIMP-2 increased similarly in all infarcted groups. These findings suggest that the benefits of TNFR1 ablation might be attributable at least in part to the attenuation of cytokine-mediated imbalances in MMP-TIMP activity.     

Matrix metalloproteinase-9 gene deletion facilitates angiogenesis after myocardial infarction

Matrix metalloproteinases (MMPs) are postulated to be necessary for neovascularization during wound healing. MMP-9 deletion alters remodeling postmyocardial infarction (post-MI), but whether and to what degree MMP-9 affects neovascularization post-MI is unknown. Neovascularization was evaluated in wild-type (WT; n = 63) and MMP-9 null (n = 55) mice at 7-days post-MI. Despite similar infarct sizes, MMP-9 deletion improved left ventricular function as evaluated by hemodynamic analysis. Blood vessel quantity and quality were evaluated by three independent studies. First, vessel density was increased in the infarct of MMP-9 null mice compared with WT, as quantified by Griffonia (Bandeiraea) simplicifolia lectin I (GSL-I) immunohistochemistry. Second, preexisting vessels, stained in vivo with FITC-labeled GSL-I pre-MI, were present in the viable but not MI region. Third, a technetium-99m-labeled peptide (NC100692), which selectively binds to activated alpha(v)beta3-integrin in angiogenic vessels, was injected into post-MI mice. Relative NC100692 activity in myocardial segments with diminished perfusion (0-40% nonischemic) was higher in MMP-9 null than in WT mice (383 +/- 162% vs. 250 +/- 118%, respectively; P = 0.002). The unique finding of this study was that MMP-9 deletion stimulated, rather than impaired, neovascularization in remodeling myocardium. Thus targeted strategies to inhibit MMP-9 early post-MI will likely not impair the angiogenic response.     

Quantification of interventricular asynchrony during LBBB and ventricular pacing

The quantification of mechanical interventricular asynchrony (IVA) was investigated. In 12 dogs left bundle branch block (LBBB) was induced by radio frequency ablation. Left ventricular (LV) and right ventricular (RV) pressures were recorded before and after induction of LBBB and during LBBB + LV apex pacing at different atrioventricular (AV) delays. Four IVA measures were validated using computer simulations on experimentally obtained pressure signals. The most robust measure for IVA was the time delay between the upslope of the LV and RV pressure signals (DeltaT(up)), estimated by cross correlation. The induction of experimental LBBB decreased DeltaT(up) from -6.9 +/- 7.0 ms (RV before LV) to -33.9 +/- 7.6 ms (P < 0.05) in combination with a significant decrease of LV maximal first derivative of pressure development over time (dP/dt(max)). During LV apex pacing, DeltaT(up) increased with decreasing AV delay up to +20.9 +/- 14.6 ms (P < 0.05). Interventricular resynchronization (DeltaT(up) = 0 ms) significantly improved LV dP/dt(max) by 15.1 +/- 5.9%. QRS duration increased significantly after induction of LBBB but did not change during LV apex pacing. In conclusion, DeltaT(up) is a reliable measure of mechanical IVA, which adds valuable information concerning the nature of asynchronous activation of the ventricles.     

Structural and functional changes in left ventricle during normotensive and preeclamptic pregnancy

Increased cardiac output in pregnancy is associated with cardiac remodeling and possible reduction in contractility, which may worsen in preeclampsia. Left ventricular (LV) geometry and function were compared between nonpregnant controls (n = 12) and normotensive (n = 44) and preeclamptic (n = 15) pregnant women using echocardiography. Load-independent comparisons of LV systolic function compared end-systolic stress (ESS) and rate-corrected velocity of circumferential fiber shortening (V(CFC)). Mean arterial pressures were 101 +/- 14 mmHg in preeclampsia, 76 +/- 6 mmHg in normotensive pregnancy, and 78 +/- 6 mmHg in controls (P < 0.005 vs. preeclampsia). LV mass increased during normotensive pregnancy (66 +/- 13 to 76 +/- 16 g/m(2); P < 0.05; controls, 65 +/- 10 g/m(2); P < 0.05) and was greater in preeclampsia (90 +/- 18 g/m(2); P < 0.05). In normotensive pregnancy, ESS decreased (59 +/- 9 to 52 +/- 11 g/cm(2); P < 0.05; controls, 66 +/- 14 g/cm(2); P < 0.005). ESS was greater in preeclampsia (60 +/- 14 g/cm(2); P < 0.05). In controls, there was an inverse relationship between ESS and V(CFC) (r = -0.78). The ESS-V(CFC) relationships in normotensive and preeclamptic pregnancy were unchanged from controls. We conclude that LV hypertrophy in normotensive and preeclamptic pregnancy matches changes in cardiac work, and LV contractility is preserved.     

Estrogen effects on MMP-13 and MMP-14 regulation of left ventricular mass in Dahl salt-induced hypertension

Background:Female Dahl salt-sensitive (DS) rats fed a low-salt diet develop hypertension at 6 months of age. Ovariectomy at 2 months of age accelerates the development of hypertension, and estrogen replacement delays it. Although acute pressure overload induces structural changes in the left ventricle (LV) further effects of gradual hypertension on LV remodeling have not been examined in the DS rat model.Objective: The purpose of this study was to test the hypothesis that aging and estrogen loss in hypertensive DS rats are accompanied by changes in LV remodeling.Methods: Four groups of DS rats were examined: young intact, middle-aged (MA) intact, MA ovariectomized (MA-OVX), and MA-OVX with 17β-eestradiol (E₂) supplementation (MA-OVX+E²). Myocardial matrix metalloproteinases (MMPs),tissue inhibitors of metalloproteinases (TIMPs),and extracellular matrix (ECM) proteins were assessed by immunoblotting.Results: Each of the 4 groups comprised 6 animals. Mean (SEM) LV mass was significantly greater in the MA-intact and the MA-OVX groups (1257 [31] mg and 1199 [25] mg, respectively; both, P < 0.05) compared with the young-intact group (697 [6] mg). LV mass in the MA-OVX+E₂ group was significantly lower compared with the MA-intact and MA-OVX groups (both, P < 0.05), suggesting that estrogen may attenuate LV remodeling.Fibronectin and collagen III and IV concentrations increased significantly in the MA-intact and MA-OOVX groups (all, P < 0.05),indicating increased fibrosis. Multiple MMPs also increased in the MA-intact an nd MA-OVX rats, including MMP-3, -7, -99, -113, and -114, and all TIMPs. In contrast, estrogen attenuated fibrosis by increasing MMP-8 concentrations and increasing collagen III fragments. From good-fit regression modeling, MMP-13 and MMP-14 concentrations correlated positively with LV mass for the MA-intact and MA-OVX groups, respectively.Conclusions: Gradual hypertension stimulated ECM turnover by increasing both MMP/TIMP production and ECM degradation.Estrogen loss or gain resulted in a shift in MMP profiles, suggesting that MMP-13 and MMP-14 may be differentially regulated in postmenopausal hypertension.     

Morphological and biochemical characterization of remodeling in aorta and vena cava of DOCA-salt hypertensive rats

Arterial remodeling occurs in response to mechanical and neurohumoral stimuli. We hypothesized that veins, which are not exposed to higher pressures in hypertension, would demonstrate less active remodeling than arteries. We assessed remodeling with two standard measures of arterial remodeling: vessel morphometry and the expression/function of matrix metalloproteinases (MMPs). Thoracic aorta and vena cava from sham normotensive and DOCA-salt hypertensive rats (110 +/- 4 and 188 +/- 8 mmHg systolic blood pressure, respectively) were used. Wall thickness was increased in DOCA-salt vs. sham aorta (301 +/- 23 vs. 218 +/- 14 mum, P < 0.05), as was medial area, but neither measure was altered in the vena cava. The aorta and vena cava expressed the gelatinases MMP-2, MMP-9, transmembrane proteinase MT1-MMP, and tissue inhibitor of metalloproteinase-2 (TIMP-2). Immunohistochemically, MMP-2 localized to smooth muscle in the aorta and densely in endothelium/smooth muscle of the vena cava. Western and zymographic analyses verified that MMP-2 was active in all vessels and less active in the vena cava than aorta. In hypertension, MMP-2 expression and activity in the aorta were increased (59.1 +/- 3.7 and 74.5 +/- 6.1 units in sham and DOCA, respectively, P < 0.05); similar elevations were not observed in the vena cava. MMP-9 was weakly expressed in all vessels. MT1-MMP was expressed by the aorta and vena cava and elevated in the vena cava from DOCA-salt rats. TIMP-2 expression was significantly increased in the aorta of DOCA rats compared with sham but was barely detectable in the vena cava of sham or DOCA-salt hypertensive rats. These findings suggest that large veins may not undergo vascular remodeling in DOCA-salt hypertension.     

Serum MMP-8: A Novel Indicator of Left Ventricular Remodeling and Cardiac Outcome in Patients after Acute Myocardial Infarction

Objective

Left ventricular (LV) remodeling following myocardial infarction (MI) is characterized by progressive alterations of structure and function, named LV remodeling. Although several risk factors such as infarct size have been identified, LV remodeling remains difficult to predict in clinical practice. Changes within the extracellular matrix, involving matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs), are an integral part of left ventricular (LV) remodeling after myocardial infarction (MI). We investigated the temporal profile of circulating MMPs and TIMPs and their relations with LV remodeling at 1 year and clinical outcome at 3 years in post-MI patients.

Methods

This prospective multicentre study included 246 patients with a first anterior MI. Serial echocardiographic studies were performed at hospital discharge, 3 months, and 1 year after MI, and analysed at a core laboratory. LV remodeling was defined as the percent change in LV end-diastolic volume (EDV) from baseline to 1 year. Serum samples were obtained at hospital discharge, 1, 3, and 12 months. Multiplex technology was used for analysis of MMP-1, -2, -3, -8, -9, -13, and TIMP-1, -2, -3, -4 serum levels.

Results

Baseline levels of MMP-8 and MMP-9 were positively associated with changes in LVEDV (P = 0.01 and 0.02, respectively). When adjusted for major baseline characteristics, MMP-8 levels remained an independent predictor LV remodeling (P = 0.025). By univariate analysis, there were positive relations between cardiovascular death or hospitalization for heart failure during the 3-year follow-up and the baseline levels of MMP-2 (P = 0.03), MMP-8 (P = 0.002), and MMP-9 (P = 0.03). By multivariate analysis, MMP-8 was the only MMP remaining significantly associated with clinical outcome (P = 0.02).

Conclusion

Baseline serum MMP-8 is a significant predictor of LV remodeling and cardiovascular outcome after MI and may help to improve risk stratification.     

ET(A)-receptor blockade prevents matrix metalloproteinase activation late postmyocardial infarction in the rat

Endothelin (ET) A (ET(A)) receptors activate matrix metalloproteinases (MMP). Since endothelin-1 (ET) is increased in myocardium late postmyocardial infarction (MI), we hypothesized that stimulation of ET(A) receptors contributes to activation of myocardial MMPs late post-MI. Three days post-MI, rats were randomized to treatment with the ET(A)-selective receptor antagonist sitaxsentan (n = 12) or a control group (n = 12). Six weeks later, there were rightward shifts of the left ventricular (LV) end-diastolic and end-systolic pressure-volume relationships, as measured ex vivo by the isovolumic Langendorff technique. Both shifts were markedly attenuated by sitaxsentan. In LV myocardium remote from the infarct, the activities of MMP-1, MMP-2, and MMP-9 were increased in the post-MI group, and the increases were prevented by sitaxsentan treatment. Expression of tissue inhibitor of MMP-1 was decreased post-MI, and the decrease was prevented by sitaxsentan treatment. Chronic post-MI remodeling is associated with activation of MMPs in myocardium remote from the infarct. Inhibition of ET(A) receptors prevents MMP activation and LV dilation, suggesting that ET, acting via the ET(A) receptor, contributes to chronic post-MI remodeling by its effects on MMP activity.     

Differential effects of left ventricular pacing sites in an acute canine model of contraction dyssynchrony

The goal of the present study was to assess the effects of left ventricular (LV) pacing sites (apex vs. free wall) on radial synchrony and global LV performance in a canine model of contraction dyssynchrony. Ultrasound tissue Doppler imaging and hemodynamic (LV pressure-volume) data were collected in seven anesthetized, opened-chest dogs. Right atrial (RA) pacing served as the control, and contraction dyssynchrony was created by simultaneous RA and right ventricular (RV) pacing to induce a left bundle-branch block-like contraction pattern. Cardiac resynchronization therapy (CRT) was implemented by adding simultaneous LV pacing to the RV pacing mode at either the LV apex (CRTa) or free wall (CRTf). A new index of synchrony was developed via pair-wise cross-correlation analysis of tissue Doppler radial strain from six midmyocardial cross-sectional regions, with a value of 15 indicating perfect synchrony. Compared with RA pacing, RV pacing significantly decreased radial synchrony (11.1 +/- 0.8 vs. 4.8 +/- 1.2, P < 0.01) and global LV performance (cardiac output: 2.0 +/- 0.3 vs. 1.4 +/- 0.1 l/min and stroke work: 137 +/- 22 vs. 60 +/- 14 mJ, P < 0.05). Although both CRTa and CRTf significantly improved radial synchrony, only CRTa markedly improved global function (cardiac output: 2.1 +/- 0.2 l/min and stroke work: 113 +/- 13 mJ, P < 0.01 vs. RV pacing). Furthermore, CRTa decreased LV end-systolic volume compared with RV pacing without any change in LV end-systolic pressure, indicating an augmented global LV contractile state. Thus, LV apical pacing appears to be a superior pacing site in the context of CRT. The dissociation between changes in synchrony and global LV performance with CRTf suggests that regional analysis from a single plane may not be sufficient to adequately characterize contraction synchrony.