Metalloproteinases 2 and 9 are increased in plasma of patients with heart failure

Plasma Levels of Matrix Metalloproteinases 2 and 9 in Patients with Chronic Chagas Heart Disease and Systemic Arterial Hypertension: Correlation with TGF-Beta Plasma Levels

Background

Chronic Chagas heart disease (CCHD) and systemic arterial hypertension (SAH) frequently coexists in areas where Chagas disease is endemic. The effects of the association of both conditions (CCHD-SAH) on the extracellular matrix (ECM) remodeling are unknown. Matrix metalloproteinases (MMP) 2 and 9 are involved in ECM remodeling. The aim of this study was to evaluate MMP 2 and MMP9 in CCHD-SAH patients and to correlate their levels with those of the profibrogenic cytokine TGF-beta.

Methods

We included 19 patients with CCHD-SAH, 14 patients with CCHD alone, and 19 controls matched by sex and age. MMP-2 and MMP-9 plasma levels were studied by gel zymography and showed as optical densities (OD). TGF-beta plasma levels were measured by double-ligand ELISA and expressed as pg/mL.

Results

Median (5^th, 95^th) MMP-2 plasma levels were 1224.7 OD (1160, 1433.5) in patients with CCHD alone, 1424.1 OD (1267.5, 1561) in patients with CCHD-SAH, and 940 OD (898.1, 1000.8) in controls (p=0.001). MMP-9 plasma levels were 1870 OD (1740, 1904.1) in patients with CCHD alone, 1754.6 OD (1650, 2049) in those with CCHD-SAH and 89.7 OD (80, 96) in controls (p=0.0003). MMP-9 plasma levels were higher than those of MMP 2 in patients with CCHD-SAH (p=0.01). No correlation was found between TGF-beta plasma levels with MMP-2 serum levels (r = 0.12; p=0.7), but a moderate negative correlation (r = -0.46; p=0.048) was observed between TGF-beta and MMP-9 plasma levels.

Conclusions

MMP-2 and especially MMP-9 may play a role in the ECM remodeling process in patients with CCHD-SAH. TGF-Beta may counteract the MMP effect on the ECM remodeling process in patients with CCHD-SAH.

Fibrosis, the Bad Actor in Cardiorenal Syndromes: Mechanisms Involved

Cardiorenal syndrome is a term that defines the complex bidirectional nature of the interaction between cardiac and renal disease. It is well established that patients with kidney disease have higher incidence of cardiovascular comorbidities and that renal dysfunction is a significant threat to the prognosis of patients with cardiac disease. Fibrosis is a common characteristic of organ injury progression that has been proposed not only as a marker but also as an important driver of the pathophysiology of cardiorenal syndromes. Due to the relevance of fibrosis, its study might give insight into the mechanisms and targets that could potentially be modulated to prevent fibrosis development. The aim of this review was to summarize some of the pathophysiological pathways involved in the fibrotic damage seen in cardiorenal syndromes, such as inflammation, oxidative stress and endoplasmic reticulum stress, which are known to be triggers and mediators of fibrosis.

Thrombin induces protease-activated receptor 1 signaling and activation of human atrial fibroblasts and dabigatran prevents these effects

BACKGROUND

Data with animal cells and models suggest that thrombin activates cardiac fibroblasts (Fib) to myofibroblasts (myoFib) via protease-activated receptor 1 (PAR1) cleavage, and in this way promotes adverse atrial remodeling and, thereby, atrial fibrillation (AF).

OBJECTIVE

Here, we explored the effects of thrombin on human atrial Fib and whether they are antagonized by the clinically available direct thrombin inhibitor, dabigatran.

METHODS

Fib isolated from atrial appendages of patients without AF undergoing elective cardiac surgery were evaluated for PAR expression and treated with thrombin with or without dabigatran. PAR1 cleavage, downstream signaling and myoFib markers were investigated by immunofluorescence and Western blot. Collagen synthesis, activity of matrix metalloprotease (MMP)-2 and proliferation were assessed by Picro-Sirius red staining, gelatinolytic zymography and BrdU incorporation, respectively. Fib function was studied as capability to contract a collagen gel and stimulate the chemotaxis of peripheral blood monocytes from healthy volunteers.

RESULTS

Primary human atrial Fib expressed PAR1, while levels of the other PARs were very low. Thrombin triggered PAR1 cleavage and phosphorylation of ERK1/2, p38 and Akt, elicited a switch to myoFib enriched for αSMA, fibronectin and type I collagen, and induced paracrine/autocrine transforming growth factor beta-1, cyclooxygenase-2, endothelin-1 and chemokine (C-C motif) ligand 2 (CCL2); conversely, MMP-2 activity decreased. Thrombin-primed cells displayed enhanced proliferation, formed discrete collagen-containing cellular nodules, and stimulated the contraction of a collagen gel. Furthermore, their conditioned medium caused monocytes to migrate. All these effects were prevented by dabigatran.

CONCLUSION

These results with human cells complete the knowledge about thrombin actions on cardiac Fib and strengthen the translational potential of the emerging paradigm that pharmacological blockade of thrombin may counteract molecular and cellular events underlying AF.

Magnetic Resonance Imaging-Detected Myocardial Inflammation and Fibrosis in Rheumatoid Arthritis: Associations With Disease Characteristics and N-Terminal Pro-Brain Natriuretic Peptide Levels

OBJECTIVE

Myocardial dysfunction and heart failure (HF) are increased in rheumatoid arthritis (RA), yet there are few studies of the myocardium in RA.

METHODS

RA patients with no known heart disease or risk factors underwent gadolinium-enhanced cardiac magnetic resonance imaging (MRI). Images were assessed for left-ventricular (LV) structural and functional parameters and for myocardial late gadolinium enhancement (LGE; an indicator of myocardial fibrosis) and T2-weighted imaging (an indicator of active inflammation). We modeled the associations between RA characteristics and N-terminal pro-brain natriuretic protein (NT-proBNP) levels with LGE and T2-weighted imaging. We also assessed whether LGE and/or T2-weighted imaging were associated with abnormal LV structure or dysfunction.

RESULTS

A total of 60 RA patients were studied. LGE was present in 19 (32%) and T2-weighted imaging in 7 (12%), 5 of whom also had LGE. After adjustment for relevant confounders, higher odds of LGE with each swollen joint (odds ratio [OR] 1.87, P = 0.008), each log unit higher C-reactive protein level (OR 3.36, P = 0.047), and each log unit higher NT-proBNP (OR 20.61, P = 0.009) were found. NT-proBNP was also significantly higher (135%) among those with T2-weighted imaging than in those without T2-weighted imaging or LGE. Higher LV mass index and LV mass:end diastolic volume ratio were observed in those with T2-weighted imaging than in those with no myocardial abnormalities and in those with LGE without T2-weighted imaging; however, ejection fraction was not reduced in those with either LGE or T2-weighted imaging.

CONCLUSION

These data suggest that cardiac MRI findings indicating myocardial inflammation/fibrosis are correlated with RA disease activity and alterations in myocardial structure known to precede clinical HF.

Extracellular matrix-mediated cellular communication in the heart

The extracellular matrix (ECM) is a complex and dynamic scaffold that maintains tissue structure and dynamics. However, the view of the ECM as an inert architectural support has been increasingly challenged. The ECM is a vibrant meshwork, a crucial organizer of cellular microenvironments. It plays a direct role in cellular interactions regulating cell growth, survival, spreading, proliferation, differentiation and migration through the intricate relationship among cellular and acellular tissue components. This complex interrelationship preserves cardiac function during homeostasis; however it is also responsible for pathologic remodeling following myocardial injury. Therefore, enhancing our understanding of this cross-talk may provide mechanistic insights into the pathogenesis of heart failure and suggest new approaches to novel, targeted pharmacologic therapies. This review explores the implications of ECM-cell interactions in myocardial cell behavior and cardiac function at baseline and following myocardial injury.

Membrane Cholesterol Modulates LOX-1 Shedding in Endothelial Cells

The lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a scavenger receptor responsible for ox-LDL recognition, binding and internalization, which is up-regulated during atherogenesis. Its activation triggers endothelium dysfunction and induces inflammation. A soluble form of LOX-1 has been identified in the human blood and its presence considered a biomarker of cardiovascular diseases. We recently showed that cholesterol-lowering drugs inhibit ox-LDL binding and internalization, rescuing the ox-LDL induced apoptotic phenotype in primary endothelial cells. Here we have investigated the molecular bases of human LOX-1 shedding by metalloproteinases and the role of cell membrane cholesterol on the regulation of this event by modulating its level with MβCD and statins. We report that membrane cholesterol affects the release of different forms of LOX-1 in cells transiently and stably expressing human LOX-1 and in a human endothelial cell line (EA.hy926). In particular, our data show that i) cholesterol depletion triggers the release of LOX-1 in exosomes as a full-length transmembrane isoform and as a truncated ectodomain soluble fragment (sLOX-1); ii) endothelial cells secrete a soluble metalloproteinase which induces LOX-1 ectodomain shedding and iii) long term statins treatment enhances sLOX-1 proteolytic shedding.

Influence of spironolactone on matrix metalloproteinase-2 in acute decompensated heart failure

BACKGROUND

Matrix metalloproteinases (MMPs) are a family of enzymes important for the resorption of extracellular matrices, control of vascular remodeling and repair. Increased activity of MMP2 has been demonstrated in heart failure, and in acutely decompensated heart failure (ADHF) a decrease in circulating MMPs has been demonstrated along with successful treatment.

OBJECTIVE

Our aim was to test the influence of spironolactone in MMP2 levels.

METHODS

Secondary analysis of a prospective, interventional study including 100 patients with ADHF. Fifty patients were non-randomly assigned to spironolactone (100 mg/day) plus standard ADHF therapy (spironolactone group) or standard ADHF therapy alone (control group).

RESULTS

Spironolactone group patients were younger and had lower creatinine and urea levels (all p < 0.05). Baseline MMP2, NT-pro BNP and weight did not differ between spironolactone and control groups. A trend towards a more pronounced decrease in MMP2 from baseline to day 3 was observed in the spironolactone group (-21 [-50 to 19] vs 1.5 [-26 to 38] ng/mL, p = 0.06). NT-pro BNP and weight also had a greater decrease in the spironolactone group. The proportion of patients with a decrease in MMP2 levels from baseline to day 3 was also likely to be greater in the spironolactone group (50% vs 66.7%), but without statistical significance. Correlations between MMP2, NT-pro BNP and weight variation were not statistically significant.

CONCLUSION

MMP2 levels are increased in ADHF. Patients treated with spironolactone may have a greater reduction in MMP2 levels.

Helicobacter pylori vs coronary heart disease - searching for connections

In this review, we discussed the findings and concepts underlying the potential role of Helicobacter pylori (H. pylori) infections in the initiation, development or persistence of atherosclerosis and coronary heart disease (CHD). This Gram-negative bacterium was described by Marshall and Warren in 1984. The majority of infected subjects carries and transmits H. pylori with no symptoms; however, in some individuals these bacteria may cause peptic ulcers, and even gastric cancers. The widespread prevalence of H. pylori infections and the fact that frequently they remain asymptomatic may suggest that, similarly to intestinal microflora, H. pylori may deliver antigens that stimulate not only local, but also systemic inflammatory response. Recently, possible association between H. pylori infection and extragastric disorders has been suggested. Knowledge on the etiology of atherosclerosis together with current findings in the area of H. pylori infections constitute the background for the newly proposed hypothesis that those two processes may be related. Many research studies confirm the indirect association between the prevalence of H. pylori and the occurrence of CHD. According to majority of findings the involvement of H. pylori in this process is based on the chronic inflammation which might facilitate the CHD-related pathologies. It needs to be elucidated, if the infection initiates or just accelerates the formation of atheromatous plaque.

Circulating serum markers and QRS scar score in Chagas cardiomyopathy

Approximately 8 million people have Trypanosoma cruzi infection, and nearly 30% will manifest Chagas cardiomyopathy (CC). Identification of reliable early indicators of CC risk would enable prioritization of treatment to those with the highest probability of future disease. Serum markers and electrocardiogram (EKG) changes were measured in 68 T. cruzi-infected individuals in various stages of cardiac disease and 17 individuals without T. cruzi infection or cardiac disease. T. cruzi-infected individuals were assigned to stage A (normal EKG/chest x-ray [CXR]), B (abnormal EKG/normal CXR), or C (abnormal EKG/cardiac structural changes). Ten serum markers were measured using enzyme-linked immunosorbent assay (ELISA)/Luminex, and QRS scores were calculated. Higher concentrations of transforming growth factor-β1 (TGFβ1), and TGFβ2 were associated with stage B compared with stage A. Matrix Metalloproteinase 2 (MMP2), Tissue Inhibitors of MMP 1, QRS score, and Brain Natriuretic Protein rose progressively with increasing CC severity. Elevated levels of several markers of cardiac damage and inflammation are seen in early CC and warrant additional evaluation in longitudinal studies.

Reappraisal of quantitative gel zymography for matrix metalloproteinases

BACKGROUND

The determination of matrix metalloproteases (MMPs) is relevant in many pathophysiological conditions, especially if associated with extracellular matrix remodeling; however, the results obtained are closely linked to the method used and are not directly comparable. The aim of this study was to perform a reappraisal of quantitative gel zymography technique for MMPs in human plasma, to use for comparison with commercially available ELISA and in those experimental conditions where the MMP active form needs to be revealed.

METHODS

The critical methodological parameters of zymography were checked and a comparison with a routinely used ELISA was performed.

RESULTS

Sensitivity and reproducibility levels of zymography are suitable for detection of MMP-9 in human plasma, providing results closely related to those obtained by ELISA.

CONCLUSIONS

Analytical parameters of zymography were suitable for detection of MMPs in human plasma. Quantitative zymography for MMPs is an alternative method for comparing the results of ELISA widely employed for MMP determination, thus reducing the discrepancies between laboratories regarding gelatinase assay.

Granulocyte colony-stimulating factor partially repairs the damage provoked by Trypanosoma cruzi in murine myocardium

BACKGROUND

The hallmark of Trypanosoma cruzi infection is cardiomyopathy that leads to end-stage heart failure. We investigated whether G-CSF, known to induce heart tissue repair by bone marrow stem cell mobilization, ameliorates T. cruzi-induced myocarditis.

METHODS AND RESULTS

T. cruzi-infected C3H/He mice were treated with G-CSF and monitored for parasite burden, BMSC mobilization, cytokine profile and cardiac remodeling. G-CSF increased the expression of CXCR4, CD34, and c-Kit, indicating mobilization and migration of BMSC, some of which differentiated to cardiomyocytes as evidenced by increased levels of GATA4(+)/MEF2C(+) cells and desmin expression in chagasic hearts. G-CSF enhanced a mixed cytokine response (IL-10+TGF-β>IFN-γ+TNF-α>IL-4) associated with increased heart inflammation and no beneficial effect on parasite control. Further, G-CSF controlled T. cruzi-induced extracellular-matrix alterations of collagens (Col I and Col llI), hydroxyproline, and glycosaminoglycan contents and promoted compensatory cardiac remodeling; however, these responses were not sufficient to control T. cruzi-induced cardiomyocyte atrophy. Benznidazole treatment prior to G-CSF resulted in the control of parasitism and parasite-induced inflammation, and subsequently, G-CSF was effective in executing the tissue repair, as evidenced by extracellular-matrix homeostasis and normalization of cardiomyocyte size in chagasic hearts.

CONCLUSIONS

G-CSF treatment after T. cruzi infection enhanced migration and homing of BMSC, some of which differentiated to cardiomyocytes. Yet, G-CSF promoted a mixed (Treg>Th1>Th2) immune response that contributed to persistent inflammation and limited improvement in cardiac homeostasis. Combinatorial therapy (BZ → G-CSF) was beneficial in arresting inflammatory processes and tissue damage in chagasic hearts.

Recombinant human matrix metalloproteinase-2 impairs cardiovascular β-adrenergic responses

Growing evidence supports the involvement of matrix metalloproteinases (MMPs) in the pathogenesis of many cardiovascular diseases. Particularly, imbalanced MMP-2 activity apparently plays a critical role in cardiovascular remodelling. While some studies have suggested that MMP-2 may affect the vascular tone and impair β-adrenoreceptor function, no previous study has examined the acute haemodynamic effects of MMP-2. We examined the effects of recombinant human MMP-2 (rhMMP-2) administered intravenously to anaesthetized lambs at baseline conditions and during β(1) -adrenergic cardiac stimulation with dobutamine. We used 26 anaesthetized male lambs in two study protocols. First, rhMMP-2 (220 ng/kg/min. over 60 min.) or vehicle was infused in the lambs, and no significant haemodynamic changes were found. Therefore, we infused dobutamine at 5 μg/kg/min. i.v. (or saline) over 180 min. in lambs that had received the same rhMMP-2 infusion preceded by doxycycline i.v. at 10 mg/kg (or saline). Plasma and cardiac MMP-2 levels were assessed by gelatin zymography, and gelatinolytic activity was assessed by spectrofluorimetry. Dobutamine decreased systemic vascular resistance index, and this effect was attenuated by rhMMP-2 infusion. Moreover, dobutamine increased the cardiac index and left ventricular dP/dt(max) , and these effects were attenuated by rhMMP-2. The previous administration of doxycycline blunted rhMMP-2-induced changes in dobutamine responses. While the infusion of rhMMP-2 did not increase plasma and cardiac MMP-2 levels, it increased cardiac gelatinolytic activity, and doxycycline blunted this effect. Our findings show that rhMMP-2 exerts no major haemodynamic effects in lambs. However, rhMMP-2 impairs the responses elicited by activation of β-adrenoreceptors.

Expression of MMP-2, TIMP-2, TGF-β1, and decorin in Dupuytren's contracture

To investigate the mechanisms underlying matrix deposition in Dupuytren's disease, the expression of gelatinase A (MMP-2), the tissue inhibitor of metalloproteinase-2 (TIMP-2), transforming growth factor beta 1 (TGF-β1), decorin (DCN), and periostin was studied. The level of relative MMP-2 activation was investigated using zymography. The mRNA expression of MMP-2, TIMP-2, TGF-β1, and DCN was detected using reverse transcription polymerase chain reaction (RT-PCR), while the presence of protein was detected using immunohistochemical (IHC) and Western blot techniques. The level of MMP-2 activation was significantly elevated in tissues with Dupuytren's contracture. RT-PCR demonstrated significantly higher expression of MMP-2, TIMP-2, TGF-β1, and DCN mRNA in the pathological tissues; and the IHC and immunoblotting studies revealed elevated expression of TGF-β1, DCN, and periostin. The balance between MMP-2 and TIMP-2 was disrupted in patients with Dupuytren's disease. TGF-β1, DCN, and periostin are involved in extracellular matrix (ECM) homeostasis in Dupuytren's contracture.

Oral contraceptive containing chlormadinone acetate and ethinylestradiol reduces plasma concentrations of matrix metalloproteinase-2 in women with polycystic ovary syndrome

Biochemical markers of cardiovascular disease, including matrix metalloproteinases (MMPs), are altered in women with polycystic ovary syndrome (PCOS), with many of these alterations thought to be due to excess androgen concentrations. Despite oral contraceptives (OCs) being the first-line pharmacological treatment in women with PCOS and the importance of MMPs in many physiological conditions and pathological states, including cardiovascular diseases, no study has yet evaluated whether OCs alter plasma concentrations of MMPs. We therefore assessed whether treatment with an OC containing the anti-androgenic progestogen alters MMP profiles in women with PCOS. We analysed 20 women with PCOS who wanted hormonal contraception (OC-PCOS group), 20 ovulatory women who required hormonal contraception (OC-control group) and 20 ovulatory women who wanted non-hormonal contraception (non-OC-control group). OC consisted of cyclic use of 2 mg chlormadinone acetate/30 μg ethinylestradiol for 6 months. Plasma concentrations of MMP-2, MMP-9, TIMP-1 and TIMP-2 were measured by gelatin zymography or enzyme-linked immunoassays. OC treatment for 6 months significantly reduced plasma MMP-2 concentrations in the OC-control and OC-PCOS groups and TIMP-2 and TIMP-1 concentrations levels in the OC-control group (all p < 0.05), but had no effects on MMP-9 concentrations or on MMP-2/TIMP-2 and MMP-9/TIMP-1 ratios in any group (all p > 0.05). These findings indicated that long-term treatment with an OC containing chlormadinone acetate plus ethinylestradiol reduced plasma MMP-2 concentrations in both healthy and PCOS women. As the latter have imbalances in circulating matrix MMPs, treatment of these women with an OC may be beneficial.

Chronic cardiotoxicity of doxorubicin involves activation of myocardial and circulating matrix metalloproteinases in rats

AIM

To investigate the role of matrix metalloproteinases (MMPs) in the responses of rats to a prolonged doxorubicin (DOX) treatment.

METHODS

Male Wistar rats were used. DOX was administered by intraperitoneal injections of seven doses (cumulative dose was 15 mg/kg). Control animals were treated with saline. Tissue or plasma samples were collected at four and eight weeks after the application of the last dose. Protein levels were determined by immunoblot assay, and MMP activities were measured by gelatin zymography. Superoxide content was analyzed using a lucigenin chemiluminescence assay and superoxide dismutase (SOD) activities with a SOD assay kit. Qualitative structural alterations of the heart were characterized by transmission electron microscopy.

RESULTS

Systolic blood pressure was higher in DOX-treated rats as compared with the control rats at 8 weeks after treatment. In contrast, there were no differences in the heart rate between the control and DOX-treated rats. DOX treatment caused marked heterogeneous subcellular alterations of cardiomyocytes and structural disorganizations of the cardiac extracellular space. The effects of DOX were linked to a stimulation of plasma MMP-2 and MMP-9 activities that had already increased by 4 weeks after the end of the treatment. In the left ventricle, however, DOX only led to increased MMP-2 activation at 8 weeks after the end of treatment. These changes in tissue MMP-2 were connected with stimulation of Akt kinase activation, inhibition of SOD, an increase in superoxide levels, induction of iNOS protein expression and caspase-3 activation.

CONCLUSION

Our results show that MMPs are involved in the chronic cardiotoxicity of DOX in rats. The data also suggest that reactive oxygen species (superoxide), NO production (iNOS) and the Akt kinase pathway can modulate MMP-2 activities in rat hearts influenced by DOX.

Proteomic profiling of acute coronary thrombosis reveals a local decrease in pigment epithelium-derived factor in acute myocardial infarction

Thrombotic occlusion of an epicardial coronary artery on the grounds of atherosclerotic plaque is considered the ultimate step in AMI (acute myocardial infarction). However, the precise pathophysiological mechanisms underlying acute coronary occlusion are not fully understood. We have analysed proteomic profiles of systemic plasma and plasma derived from the site of coronary plaque rupture of non-diabetic patients with STEMI (ST-segment elevation myocardial infarction). Label-free quantification of MS/MS (tandem MS) data revealed differential regulation of complement cascade components and a decrease in anti-thrombotic PEDF (pigment epithelium-derived factor) between CS (culprit site)-derived plasma and systemic plasma. PEDF, which is known to have a protective role in atherothrombosis, was relatively decreased at the CS, with a level of expression inverse to local MMP-9 (matrix metalloproteinase-9) activity. CS plasma displayed enhanced proteolytic activity towards PEDF. Proteomics of coronary thrombus aspirates indicate that PEDF processing is associated with coronary plaque rupture.

The effect of indapamide on development of myocardial hypertrophy and fibrosis in L-NAME-induced hypertension in rat

The aim of this study was to analyze the effect of indapamide and its combination with ACE inhibitor (captopril) and antioxidant (Provinols™) on both myocardial hypertrophy and fibrosis. Wistar rats were treated with L-NAME (40 mg/kg/day, L); L-NAME plus indapamide (1 mg/kg/day), or captopril (10 mg/kg/day), or Provinols™ (40 mg/kg/day), or combination of indapamide with captopril, and indapamide with Provinols™ for 7 weeks. Blood pressure (BP), LV hypertrophy and fibrosis were determined. The content of collagens type I and III was evaluated morphometrically after picrosirius red staining. L-NAME treatment led to increased BP, LV hypertrophy, total fibrosis and relative content of collagens without the change in collagen type I/III ratio. Indapamide and captopril decreased BP, LV hypertrophy and the collagen ratio without affecting total fibrosis, while Provinols™ reduced BP, the collagen ratio and fibrosis without affecting LV hypertrophy. The combinations decreased all the parameters. Decrease of LV hypertrophy was achieved by drugs with the best reducing effect on BP, fibrosis reduction was reached by the antioxidant treatment with only partial effect on BP. Thus, the combination of antihypertensive and antioxidant treatment may represent a powerful tool in preventing myocardial remodeling induced by hypertension.

NADPH oxidase inhibition ameliorates Trypanosoma cruzi-induced myocarditis during Chagas disease

Trypanosoma cruzi, the aetiological agent of Chagas disease, invades nucleated mammalian cells including macrophages. In this study, we investigated the crosstalk between T. cruzi-induced immune activation of reactive oxygen species (ROS) and pro-inflammatory responses, and their role in myocardial pathology. Splenocytes of infected mice (C3H/HeN) responded to Tc-antigenic stimulus by more than a two-fold increase in NADPH oxidase (NOX) activity, ROS generation, cytokine production (IFN-γ > IL-4 > TNFα > IL1-β≈ IL6), and predominant expansion of CD4(+) and CD8(+) T cells. Inhibition of NOX, but not of myeloperoxidase and xanthine oxidase, controlled the ROS (>98%) and cytokine (70-89%) release by Tc-stimulated splenocytes of infected mice. Treatment of infected mice with apocynin (NOX inhibitor) in drinking water resulted in a 50-90% decline in endogenous NOX/ROS and cytokine levels, and splenic phagocytes' proliferation. The splenic percentage of T cells was maintained, though more than a 40% decline in splenic index (spleen weight/body weight) indicated decreased T-cell proliferation in apocynin-treated/infected mice. The blood and tissue parasite burden were significantly increased in apocynin-treated/infected mice, yet acute myocarditis, ie inflammatory infiltrate consisting of macrophages, neutrophils, and CD8(+) T cells, and tissue oxidative adducts (eg 8-isoprostanes, 3-nitrotyrosine, and 4-hydroxynonenal) were diminished in apocynin-treated/infected mice. Consequently, hypertrophy (increased cardiomyocytes' size and β-MHC, BNP, and ANP mRNA levels) and fibrosis (increased collagen, glycosaminoglycans, and lipid contents) of the heart during the chronic phase were controlled in apocynin-treated mice. We conclude that NOX/ROS is a critical regulator of the splenic response (phagocytes, T cells, and cytokines) to T. cruzi infection, and bystander effects of heart-infiltrating phagocytes and CD8(+) T cells resulting in cardiac remodelling in chagasic mice.

Defining characteristics of decreased cardiac output: a literature review

OBJECTIVE

The study aims to proceed a literature review of defining characteristics (DCs) of decreased cardiac output (DCO).

METHODS

  Medline database was used to perform this study. The descriptors used were "low cardiac output" and "nursing diagnosis."

RESULTS

Seventy-nine DCs were identified. Among them, 28 have already been approved by NANDA-I. Some data from microcirculation assessment such as high levels of serum lactate and decreased oxygen venous saturation were identified as indicators of this nursing diagnosis.

CONCLUSIONS

Some of the approved DCs were identified through literature review but others seem to be new as they have not been cited in the NANDA-I classification.

PRACTICAL IMPLICATIONS

Further content and clinical validations are needed to confirm if data from microcirculation might be considered as DCs of DCO.

The Athlete's Heart vs. the Failing Heart: Can Signaling Explain the Two Distinct Outcomes?

Cardiac remodeling is typically associated with disease and can lead to heart failure. In contrast, remodeling that occurs in the athlete's heart is considered an adaptive physiological response. This review provides an overview of signaling mechanisms responsible for inducing left ventricular hypertrophy in the athlete's heart and in settings of pathological hypertrophy and heart failure.

Clinical significance of matrix metalloproteinase (MMP)-2 in patients with acute heart failure

The serum levels of matrix metalloproteinases (MMPs) increase during chronic heart failure (HF) and the MMP-2 are related to a poor prognosis. However, the roles of MMP-2 in acute HF (AHF) remain unclear. We investigated the change and clinical significance of MMP-2 in these conditions. The serum levels of MMP-2 were measured in 83 AHF patients before starting treatment (day 1), 3 (day 3) and 7 (day 7) days after admission, and before discharge (predischarge). MMP-2 decreased rapidly and significantly from day 3 to day 1 (902.9 ± 304.2 versus 1220.4 ± 330.5 ng/mL; P < 0.0001), whereas that of MMP-2 was not significantly different on day 7 and at predischarge (894.7 ± 278.9 and 920.0 ± 269.6 ng/mL, respectively) compared to day 3. We evaluated the relationships between ΔMMPs, defined as the changes in MMPs from day 1 to day 3 and HF events including cardiac death, readmission to hospital for HF, and uncontrollable HF. The MMP-2 value was significantly (P = 0.004) more decreased in the event-free group (381.4 ± 256.5 ng/mL) than in the event group (211.9 ± 225.5 ng/mL) between day 1 and day 3. The results of the multivariate logistic regression model for predicting HF events found that the specific factor for HF events was ΔMMP-2. Cutoff values of ΔMMP-2 were determined and event-free curves were constructed. Kaplan-Meier curves showed that the prognosis was significantly better among the patients with reductions in ΔMMP-2 values of more than 342 ng/mL. The serum levels of MMP-2 decreased with improvements in AHF. Rapid decreases in MMP-2 may be important for a better clinical outcome in patients with AHF.

Anti-apolipoprotein A-1 IgG predicts major cardiovascular events in patients with rheumatoid arthritis

OBJECTIVE

To determine whether anti-apolipoprotein A-1 (anti-Apo A-1) IgG are associated with major cardiovascular events in patients with rheumatoid arthritis (RA).

METHODS

We determined anti-Apo A-1 IgG levels and the concentrations of cytokines, oxidized low-density lipoprotein (LDL), and matrix metalloproteinase 1 (MMP-1) MMP-2, MMP-3, and MMP-9 in sera from 133 patients with RA who did not have cardiovascular disease at baseline, all of whom were longitudinally followed up over a median period of 9 years. A major cardiovascular event was defined as a fatal or nonfatal stroke or acute coronary syndrome. The proinflammatory effects of anti-Apo A-1 IgG were assessed on human macrophages in vitro.

RESULTS

During followup, the overall incidence of major cardiovascular events was 15% (20 of 133 patients). At baseline, anti-Apo A-1 IgG positivity was 17% and was associated with a higher incidence of major cardiovascular events (adjusted hazard ratio 4.2, 95% confidence interval 1.5-12.1). Patients who experienced a subsequent major cardiovascular event had higher circulating levels of anti-Apo A-1 IgG at baseline compared with those who did not have a major cardiovascular event. Receiver operating curve analysis showed that anti-Apo A-1 IgG was the strongest of all tested biomarkers for the prediction of a subsequent major cardiovascular event, with an area under the curve value of 0.73 (P = 0.0008). At the predefined and previously validated cutoff levels, the specificity and sensitivity of anti-Apo A-1 IgG to predict major cardiovascular events were 50% and 90%, respectively. Anti-Apo A-1 IgG positivity was associated with higher median circulating levels of interleukin-8 (IL-8), oxidized LDL, and MMP-9 and higher proMMP-9 activity as assessed by zymography. On human macrophages, anti-Apo A-1 IgG induced a significant dose-dependent increase in IL-8 and MMP-9 levels and proMMP-9 activity.

CONCLUSION

Anti-Apo A-1 IgG is an independent predictor of major cardiovascular events in RA, possibly by affecting vulnerability to atherosclerotic plaque.

A functional matrix metalloproteinase (MMP)-9 polymorphism modifies plasma MMP-9 levels in subjects environmentally exposed to mercury

Mercury (Hg) exposure causes health problems including cardiovascular diseases. Although precise mechanisms have not been precisely defined yet, matrix metalloproteinases (MMPs) may be involved. The gene encoding MMP-9 presents genetic polymorphisms which affect the expression and activity level of this enzyme. Two polymorphisms in the promoter region [C(-1562)T and (CA)(n)] are functionally relevant, and are implicated in several diseases. This study aimed at examining how these polymorphisms affect the circulating MMP-9 levels and its endogenous inhibitor, the tissue inhibitor of metalloproteinase-1 (TIMP-1) in 266 subjects environmentally exposed to Hg. Blood and plasma Hg concentrations were determined by inductively coupled plasma-mass spectrometry (ICP-MS). MMP-9 and TIMP-1 concentrations were measured in plasma samples by gelatin zymography and ELISA, respectively. Genotypes for the C(-1562)T and the microsatellite (CA)(n) polymorphisms were determined. We found a positive association (P<0.05) between plasma Hg concentrations and MMP-9/TIMP-1 ratio (an index of net MMP-9 activity). When the subjects were divided into tertiles with basis on their plasma Hg concentrations, we found that the (CA)(n) polymorphism modified MMP-9 concentrations and MMP-9/TIMP-1 ratio in subjects with the lowest Hg concentrations (first tertile), with the highest MMP-9 levels being found in subjects with genotypes including alleles with 21 or more CA repeats (H alleles) (P<0.05). Conversely, this polymorphism had no effects on subjects with intermediate or high plasma Hg levels (second and third tertiles, respectively). The C(-1562)T polymorphism had no effects on MMP-9 levels. These findings suggest a significant interaction between the (CA)(n) polymorphism and low levels of Hg exposure, possibly increasing the risk of developing diseases in subjects with H alleles.

Long-term outcome after thrombectomy in acute myocardial infarction

BACKGROUND

Current data appear in favour of thrombectomy for ST-elevation myocardial infarction (STEMI). However, information on long-term outcome after thrombectomy is limited. We performed a retrospective long-term study to assess the risk of cardiac re-hospitalizations and survival after discharge from the index hospitalization for STEMI.

METHODS

Patients originally randomized to percutaneous coronary intervention (PCI) with thrombectomy vs. standard PCI were included in a retrospective long-term observational study. The primary study endpoint was the combined risk for all-cause death or cardiac re-hospitalization after index discharge under optimal medical therapy. The cumulative number of cardiac hospitalization days and ventricular remodelling assessed by echocardiography and plasma biomarkers were secondary endpoints.

RESULTS

Of 94 STEMI patients who had been randomized between 11/2000 and 03/2003, 89 patients consented to long-term follow-up. A total of 43 patients had been allocated to thrombectomy and 46 to standard primary PCI. The minimum follow-up time was 1115 days. There was a significantly lower risk for death or cardiac re-hospitalization for patients of the thrombectomy group (hazard ratio = 0.69, 95% CI: 0.49-0.98, P = 0.036). The incidence of recurrent myocardial infarction was not different (P = 0.343). No differences in cardiac remodelling were detected by echocardiography, with the exception that heart-type fatty acid binding protein at 53.2 +/- 17 months was lower in the thrombectomy group (P = 0.045).

CONCLUSION

Thrombectomy in STEMI may decrease the long-term risk for death or cardiac re-hospitalization.

Association of circulating matrix metalloproteinases with carotid artery characteristics: the Atherosclerosis Risk in Communities Carotid MRI Study

OBJECTIVE

To examine the relationship of plasma levels of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinase 1 (TIMP-1) with carotid artery characteristics measured by MRI in a cross-sectional investigation among Atherosclerosis Risk in Communities Carotid MRI Study participants.

METHODS AND RESULTS

A stratified random sample was recruited based on intima-media thickness from a previous ultrasonographic examination. A high-resolution gadolinium-enhanced MRI examination of the carotid artery was performed from 2004 to 2005 on 1901 Atherosclerosis Risk in Communities cohort participants. Multiple carotid wall characteristics, including wall thickness, lumen area, calcium area, lipid core, and fibrous cap measures, were evaluated for associations with plasma MMPs 1, 2, 3, 7, 8, and 9 and TIMP-1. Plasma MMPs 1, 3, and 7 were significantly higher among participants in the high intima-media thickness group compared with those in the low intima-media thickness group. The normalized wall index was independently associated with MMPs 3 and 7 and TIMP-1. MMP-7 was positively associated with carotid calcification. The mean fibrous cap thickness was significantly higher in individuals with elevated TIMP-1 levels. In addition, TIMP-1 was positively associated with measures of lipid core.

CONCLUSION

Circulating levels of specific MMPs and TIMP-1 were associated with carotid wall remodeling and structural changes related to plaque burden in elderly participants.

Cytokines and matrix metalloproteinases as potential biomarkers in chronic heart failure

Heart failure (HF) is accompanied by the upregulation of bioactive signaling molecules, known as cytokines, and a family of downstream proteases, matrix metalloproteinases (MMPs). It is now apparent that these molecules contribute to adverse myocardial remodeling during HF. Elevated levels of cytokines and MMPs exist in the myocardium and can subsequently spill over into the systemic circulation. The purpose of this article is to examine clinical studies of HF that have quantified levels of different types of cytokines, MMPs and endogenous tissue inhibitors of MMPs in relation to this disease process. HF is a complex syndrome that can develop from various etiologies and can be characterized into two distinct phenotypes: systolic and diastolic. This article will present recent clinical studies that have identified significant differences between the cytokine and MMP circulating profile of systolic and diastolic HF patients. In general, elevated levels of cytokines and MMPs exist in systolic HF patients when compared with diastolic HF patients, whereas diastolic HF patients have elevated levels of cytokines and MMPs when compared with controls. Therefore, future studies distinguishing between HF phenotypes may provide more consistent results in determining possible analytes to be used as biomarkers. Furthermore, this article will emphasize why standardization of analytical techniques and establishment of referent cytokine and MMP levels are necessary if these analytes are to be used as biomarkers for the diagnosis, prognosis and evaluation of treatment in the context of HF.

Role of matrix metalloproteinases and their tissue inhibitors as potential biomarkers of left ventricular remodelling in the athlete's heart

The aim of the present study was to verify whether plasma MMPs (matrix metalloproteinases) and TIMPs (tissue inhibitors of MMPs) could be used as potential markers of paraphysiological remodelling in the athlete's heart, and to correlate these matrix parameters with echocardiographic signs of LV (left ventricular) remodelling. Plasma MMP-2 and MMP-9 were measured by zymography, and TIMP-1 and TIMP-2 were measured by ELISA in 42 veteran marathoners with AH (athlete's heart), and in 25 sedentary healthy subjects (CTL). All subjects were submitted to a clinical examination and two-dimensional colour Doppler echocardiography together with the measurement of circulating NT-proBNP (N-terminal pro-B-type natriuretic peptide); GGT (gamma-glutamyl transpeptidase) was evaluated as a marker of cardiovascular disease. Veteran athletes had a significant elevation in LV dimensions and calculated LV mass index. Diastolic and systolic functions were normal for both groups. MMP-9 levels were significantly lower in AH than in CTL subjects (56.9+/-4.3 compared with 119.4+/-21.5 m-units/l, P<0.01). There were significant differences in MMP-2 between the two groups, with a down-regulation in the AH subjects (182.5+/-16.8 units/ml in CTL compared with 117.1+/-9.1 units/ml in AH, P<0.01). MMP-2 and MMP-2/TIMP-2 were inversely correlated with myocardial indices of hypertrophy in AH and CTL subjects. AH and CTL subjects showed similar TIMP values. The results of the present study indicate that MMPs and TIMPs could represent potential biomarkers of adaptive heart remodelling in the athletes. In addition, the inverse correlation of the MMP-2/TIMP-2 system with echocardiographic signs of myocardial hypertrophy could represent a new diagnostic and prognostic indicator useful in the evaluation of cardiovascular risk in athletes.

Matrix metalloproteinase-1 and -2 levels are differently regulated in acute exacerbation of heart failure in patients with and without left ventricular systolic dysfunction

Matrix metalloproteinases (MMPs) play important roles in progression of chronic heart failure (HF) by regulating cardiac extracellular matrix metabolism. However, there is no report to investigate the difference of circulating MMP-1 and MMP-2 levels between systolic HF (SHF) and diastolic HF (DHF), particularly in light of acute exacerbation of HF. We assessed 110 HF patients who were admitted because of an acute exacerbation. They were divided into two groups: SHF [n = 68, left ventricular ejection fraction (LVEF) <45%] or DHF (n = 42, LVEF > or =45%). Ten patients without HF served as controls. Serum MMP-1 and MMP-2, and plasma brain natriuretic peptide (BNP) levels were examined on admission and at discharge. Serum MMP-1 level was higher on admission in both SHF and DHF than in controls. It was higher in SHF than in DHF and did not change at discharge in both groups. Serum MMP-2 level was equally higher on admission in SHF and DHF than in controls. It decreased in both groups at discharge. Treatment-induced changes in LVEF and BNP level correlated with those in MMP-2 level in SHF but not in DHF. Circulating MMP-1 and MMP-2 levels showed different dynamics between SHF and DHF in acute exacerbation and after treatment. These differences in circulating MMP-1 and MMP-2 levels may be related to the phenotype of HF.

Inhibition of progenitor dendritic cell maturation by plasma from patients with peripartum cardiomyopathy: role in pregnancy-associated heart disease

Dendritic cells (DCs) play dual roles in innate and adaptive immunity based on their functional maturity, and both innate and adaptive immune responses have been implicated in myocardial tissue remodeling associated with cardiomyopathies. Peripartum cardiomyopathy (PPCM) is a rare disorder which affects women within one month antepartum to five months postpartum. A high occurrence of PPCM in central Haiti (1 in 300 live births) provided the unique opportunity to study the relationship of immune activation and DC maturation to the etiology of this disorder. Plasma samples from two groups (n = 12) of age- and parity-matched Haitian women with or without evidence of PPCM were tested for levels of biomarkers of cardiac tissue remodeling and immune activation. Significantly elevated levels of GM-CSF, endothelin-1, proBNP and CRP and decreased levels of TGF-beta were measured in PPCM subjects relative to controls. Yet despite these findings, in vitro maturation of normal human cord blood derived progenitor dendritic cells (CBDCs) was significantly reduced (p < 0.001) in the presence of plasma from PPCM patients relative to plasma from post-partum control subjects as determined by expression of CD80, CD86, CD83, CCR7, MHC class II and the ability of these matured CBDCs to induce allo-responses in PBMCs. These results represent the first findings linking inhibition of DC maturation to the dysregulation of normal physiologic cardiac tissue remodeling during pregnancy and the pathogenesis of PPCM.

Regulation and possible role of endocannabinoids and related mediators in hypercholesterolemic mice with atherosclerosis

In this study we analysed the possible modulation of endocannabinoids and related molecules during atherosclerosis development in mice. Wild-type and apolipoprotein E knockout (ApoE(-/-)) mice were fed either normal chow or high-cholesterol diet for 8-12 weeks, and tissue endocannabinoid levels were measured by liquid chromatography-mass spectrometry. We found increased levels of 2-AG in aortas and visceral adipose tissue (VAT) of ApoE(-/-) mice fed on high-cholesterol diet for 12 weeks as compared to ApoE(-/-) mice fed on normal chow or wild-type mice fed on cholesterol. No significant difference in 2-AG levels was observed after 8 weeks of diet, and no changes in anandamide levels were found in any group. The levels of the anandamide-related mediators with anti-inflammatory or anti-lipogenic properties, palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), decreased or increased only in VAT or in both tissues, respectively. Endocannabinoid- and OEA/PEA-degrading enzymes were expressed by macrophages within atherosclerotic lesions. In vitro, 2-AG and OEA-induced monocyte migration at 0.3-1microM, which corresponds to the levels observed in aortas. PEA 1microM also induced monocyte migration but counteracted the effect of 2-AG, whereas OEA enhanced it. Enhanced 2-AG levels in advanced atherosclerotic lesions may trigger the inflammatory process by recruiting more inflammatory cells and inducing extracellular matrix degradation via CB(2) receptors, and this possibility was supported in vitro but not in vivo by experiments with the CB(2) antagonist, SR144528.

Transgenic expression of matrix metalloproteinase-1 inhibits myocardial fibrosis and prevents the transition to heart failure in a pressure overload mouse model

Hypertension induces dysfunctional matrix remodeling that results in the development of myocardial fibrosis. Myocardial fibrosis adversely affects compliance, electrical activity and cardiac function in patients with hypertensive heart disease. Matrix metalloproteinases (MMPs) are a class of enzymes that regulate the remodeling of the matrix in response to pressure overload. Several studies have shown that the MMP-1/TIMP (tissue inhibitor of matrix metalloproteinase) ratio is decreased in hypertensive heart disease. However, the exact role that MMP-1 has in modulating the fibrotic response to hypertension is largely unknown. We hypothesized that cardiac expression of MMP-1 in mice would protect against the development of dysfunctional matrix remodeling during pressure overload. To investigate this, a suprarenal aortic banding model was utilized. Banded and unbanded MMP-1 transgenic mice were compared with appropriately matched wild-type mice. The banded mice were examined at 2 and 5 weeks after banding. MMP-1 attenuated the development of cardiac fibrosis, prevented left ventricular dilation and preserved cardiac function in mice that were exposed to pressure overload. Thus, MMP-1 protected the heart from the dysfunctional remodeling that occurs in response to chronic hypertension. In conclusion, these results suggest that strategies aimed at improving the MMP-1/TIMP balance in the myocardium may help to prevent the onset and progression of hypertensive heart disease.

Comparative assessment of matrix metalloproteinase (MMP)-2 and MMP-9, and their inhibitors, tissue inhibitors of metalloproteinase (TIMP)-1 and TIMP-2 in preeclampsia and gestational hypertension

OBJECTIVES

To compare the circulating levels of matrix metalloproteinase (MMP)-2, MMP-9, tissue inhibitors of metalloproteinase (TIMP)-1, TIMP-2, and the MMP-9/TIMP-1 and MMP-2/TIMP-2 ratios in preeclampsia and gestational hypertension with those found in normotensive pregnancies.

DESIGN AND METHODS

We studied 83 pregnant women (30 healthy pregnant women with uncomplicated pregnancies, 26 with gestational hypertension, and 27 with preeclampsia) and 30 healthy nonpregnant women in a cross-sectional study. MMP and TIMP concentrations were measured in plasma samples by gelatin zymography and ELISA, respectively.

RESULTS

We found higher plasma pro-MMP-9 levels, and higher pro-MMP-9/TIMP-1 ratios in women with gestational hypertension (95%-CI: 1.031 to 2.357, and 0.012 to 0.031, respectively), but not with preeclampsia, compared with those found in normotensive pregnant women (95%-CI: 0.810 to 1.350, and 0.006 to 0.013, respectively; both P<0.05). We found no significant differences in pro-MMP-2 levels (P>0.05).

CONCLUSIONS

The higher net MMP-9 (but not MMP-2) activity in gestational hypertension compared with normotensive pregnancy suggests that MMP-9 plays a role in the pathophysiology of gestational hypertension. Conversely, the lack of such alterations in preeclampsia is consistent with the notion that different pathophysiological mechanisms are involved in these hypertensive disorders.

Activation of signaling molecules and matrix metalloproteinases in right ventricular myocardium of rats with pulmonary hypertension

Pulmonary hypertension induces right ventricular (RV) overload, which is transmitted to cardiomyocytes via integrins that activate intracellular messengers, including focal adhesion kinase (FAK) and neuronal nitric oxide synthase (NOS1). We investigated whether RV hypertrophy (RVH) and RV failure (RVF) were associated with activation of FAK, NOS1, and matrix metalloproteinases (MMPs). Rats were treated without (RVC) or with a low dose of monocrotaline (30mg/kg) to induce RVH, and with a high dose (80mg/kg) to induce RVF. After approximately 30 days, RV function was determined using a combined pressure-conductance catheter. After sacrifice, FAK, NOS1, their phosphorylated forms (FAK-P and NOS1-P), MMP-2, and MMP-9 were quantified in RV myocardium by immunohistochemistry. In RVH and RVF, RV weight/ body weight increased by 36% and 109%, whereas RV ejection fraction decreased by 23% and 57% compared to RVC, respectively. FAK-P and FAK-P/FAK were highest in RVH (2.87+/-0.12 and 2.52+/-0.23 fold compared to RVC, respectively) and slightly elevated in RVF (1.76+/-0.17 and 1.15+/-0.13 fold compared to RVC, respectively). NOS1-P and NOS1-P/NOS1 were increased in RVH (1.63+/-0.12 and 3.06+/-0.80 fold compared to RVC, respectively) and RVF (2.16+/-0.03 and 3.30+/-0.38 fold compared to RVC, respectively). MMP-2 was highest in RVH and intermediate in RVF (3.50+/-0.12 and 1.84+/-0.22 fold compared to RVC, respectively). MMP-9 was elevated in RVH and RVF (2.39+/-0.35 and 2.92+/-0.68 fold compared to RVC, respectively). Activation of FAK in RVH points to an integrin-dependent hypertrophic response of the myocardium. Activation of NOS1 in failing RV suggests a role of excessive NO in the development of failure and activation of MMPs leading to ventricular remodeling.

Expression of a Gi-coupled receptor in the heart causes impaired Ca2+ handling, myofilament injury, and dilated cardiomyopathy

Increased signaling by G(i)-coupled receptors has been implicated in dilated cardiomyopathy. To investigate the mechanisms, we used transgenic mice that develop dilated cardiomyopathy after conditional expression of a cardiac-targeted G(i)-coupled receptor (Ro1). Activation of G(i) signaling by the Ro1 agonist spiradoline caused decreased cellular cAMP levels and bradycardia in Langendorff-perfused hearts. However, acute termination of Ro1 signaling with the antagonist nor-binaltorphimine did not reverse the Ro1-induced contractile dysfunction, indicating that Ro1 cardiomyopathy was not due to acute effects of receptor signaling. Early after initiation of Ro1 expression, there was a 40% reduction in the abundance of the sarcoplasmic reticulum Ca(2+)-ATPase (P < 0.05); thereafter, there was progressive impairment of both Ca(2+) handling and force development assessed with ventricular trabeculae. Six weeks after initiation of Ro1 expression, systolic Ca(2+) concentration was reduced to 0.61 +/- 0.08 vs. 0.91 +/- 0.07 microM for control (n = 6-8; P < 0.05), diastolic Ca(2+) concentration was elevated to 0.41 +/- 0.07 vs. 0.23 +/- 0.06 microM for control (n = 6-8; P < 0.01), and the decline phase of the Ca(2+) transient (time from peak to 50% decline) was slowed to 0.25 +/- 0.02 s vs. 0.13 +/- 0.02 s for control (n = 6-8; P < 0.01). Early after initiation of Ro1 expression, there was a ninefold elevation of matrix metalloproteinase-2 (P < 0.01), which is known to cause myofilament injury. Consistent with this, 6 wk after initiation of Ro1 expression, Ca(2+)-saturated myofilament force in skinned trabeculae was reduced to 21 +/- 2 vs. 38 +/- 0.1 mN/mm(2) for controls (n = 3; P < 0.01). Furthermore, electron micrographs revealed extensive myofilament damage. These findings may have implications for some forms of human heart failure in which increased activity of G(i)-coupled receptors leads to impaired Ca(2+) handling and myofilament injury, contributing to impaired ventricular pump function and heart failure.

Cardiac matrix metalloproteinase-2 expression independently induces marked ventricular remodeling and systolic dysfunction

Although enhanced cardiac matrix metalloproteinase (MMP)-2 synthesis has been associated with ventricular remodeling and failure, whether MMP-2 expression is a direct mediator of this process is unknown. We generated transgenic mice expressing active MMP-2 driven by the α-myosin heavy chain promoter. At 4 mo MMP-2 transgenic hearts demonstrated expression of the MMP-2 transgene, myocyte hypertrophy, breakdown of Z-band registration, lysis of myofilaments, disruption of sarcomere and mitochondrial architecture, and cardiac fibroblast proliferation. Hearts from 8-mo-old transgenic mice displayed extensive myocyte disorganization and dropout with replacement fibrosis and perivascular fibrosis. Older transgenic mice also exhibited a massive increase in cardiac MMP-2 expression, representing recruitment of endogenous MMP-2 synthesis, with associated expression of MMP-9 and membrane type 1 MMP. Increases in diastolic [control (C) 33 ± 3 vs. MMP 51 ± 12 μl; P = 0.003] and systolic (C 7 ± 2 vs. MMP 28 ± 14 μl; P = 0.003) left ventricular (LV) volumes and relatively preserved stroke volume (C 26 ± 4 vs. MMP 23 ± 3 μl; P = 0.16) resulted in markedly decreased LV ejection fraction (C 78 ± 7% vs. MMP 48 ± 16%; P = 0.0006). Markedly impaired systolic function in the MMP transgenic mice was demonstrated in the reduced preload-adjusted maximal power (C 240 ± 84 vs. MMP 78 ± 49 mW/μl2; P = 0.0003) and decreased end-systolic pressure-volume relation (C 7.5 ± 1.5 vs. MMP 4.7 ± 2.0; P = 0.016). Expression of active MMP-2 is sufficient to induce severe ventricular remodeling and systolic dysfunction in the absence of superimposed injury.