Matrix metalloproteinases: from biology to therapeutic strategies in cardiovascular disease

Epithelial to mesenchymal transition in mammary gland tissue fibrosis and insights into drug therapeutics

Background

The epithelial-mesenchymal transition (EMT) is a multi-step morphogenetic process in which epithelial cells lose their epithelial properties and gain mesenchymal characteristics. The process of EMT has been shown to mediate mammary gland fibrosis. Understanding how mesenchymal cells emerge from an epithelial default state will aid in unravelling the mechanisms that control fibrosis and, ultimately, in identifying therapeutic targets to alleviate fibrosis.

Methods

The effects of EGF and high glucose (HG) on EMT in mammary epithelial cells, MCF10A and GMECs, as well as their pathogenic role, were studied. In-silico analysis was used to find interacting partners and protein-chemical/drug molecule interactions.

Results

On treatment with EGF and/or HG, qPCR analysis showed a significant increase in the gene expression of EMT markers and downstream signalling genes. The expression of these genes was reduced on treatment with EGF+HG combination in both cell lines. The protein expression of COL1A1 increased as compared to the control in cells treated with EGF or HG alone, but when the cells were treated with EGF and HG together, the protein expression of COL1A1 decreased. ROS levels and cell death increased in cells treated with EGF and HG alone, whereas cells treated with EGF and HG together showed a decrease in ROS production and apoptosis. In-silico analysis of protein-protein interactions suggest the possible role of MAPK1, actin alpha 2 (ACTA2), COL1A1, and NFκB1 in regulating TGFβ1, ubiquitin C (UBC), specificity protein 1 (SP1) and E1A binding protein P300 (EP300). Kyoto Encyclopaedia of Genes and Genomes (KEGG) enrichment suggests advanced glycation end products-receptor for advanced glycation end products (AGE-RAGE) signalling pathway, relaxin signalling pathway and extra cellular matrix (ECM) receptor interactions underlying fibrosis mechanism.

Conclusion

This study demonstrates that EGF and HG induce EMT in mammary epithelial cells and may also have a role in fibrosis.

Coronary Artery Disease: From Mechanism to Clinical Practice

In most developed countries, coronary artery disease (CAD), mostly caused by atherosclerosis of coronary arteries, is one of the primary causes of death. From 1990s to 2000s, mortality caused by acute MI declined up to 50%. The incidence of CAD is related with age, gender, economic, etc. Atherosclerosis contains some highly correlative processes such as lipid disturbances, thrombosis, inflammation, vascular smooth cell activation, remodeling, platelet activation, endothelial dysfunction, oxidative stress, altered matrix metabolism, and genetic factors. Risk factors of CAD exist among many individuals of the general population, which includes hypertension, lipids and lipoproteins metabolism disturbances, diabetes mellitus, chronic kidney disease, age, genders, lifestyle, cigarette smoking, diet, obesity, and family history. Angina pectoris is caused by myocardial ischemia in the main expression of pain in the chest or adjoining area, which is usually a result of exertion and related to myocardial function disorder. Typical angina pectoris would last for minutes with gradual exacerbation. Rest, sit, or stop walking are the usual preference for patients with angina, and reaching the maximum intensity in seconds is uncommon. Rest or nitroglycerin usage can relieve typical angina pectoris within minutes. So far, a widely accepted angina pectoris severity grading system included CCS (Canadian Cardiovascular Society) classification, Califf score, and Goldman scale. Patients with ST-segment elevated myocardial infarction (STEMI) may have different symptoms and signs of both severe angina pectoris and various complications. The combination of rising usage of sensitive MI biomarkers and precise imaging techniques, including electrocardiograph (ECG), computed tomography, and cardiac magnetic resonance imaging, made the new MI criteria necessary. Complications of acute myocardial infarction include left ventricular dysfunction, cardiogenic shock, structural complications, arrhythmia, recurrent chest discomfort, recurrent ischemia and infarction, pericardial effusion, pericarditis, post-myocardial infarction syndrome, venous thrombosis pulmonary embolism, left ventricular aneurysm, left ventricular thrombus, and arterial embolism.

Long-term miR-29b suppression reduces aneurysm formation in a Marfan mouse model

Aortic root aneurysm formation and subsequent dissection and/or rupture remain the leading cause of death in patients with Marfan syndrome. Our laboratory has reported that miR‐29b participates in aortic root/ascending aorta extracellular matrix remodeling during early aneurysm formation in Fbn1^C1039G/+ Marfan mice. Herein, we sought to determine whether miR‐29b suppression can reduce aneurysm formation long‐term. Fbn1^C1039G/+ Marfan mice were treated with retro‐orbital LNA‐anti‐miR‐29b inhibitor or scrambled‐control‐miR before aneurysms develop either (1) a single dose prenatally (pregnant Fbn1^C1039G/+ mice at 14.5 days post‐coitum) (n = 8–10, each group) or (2) postnatally every other week, from 2 to 22 weeks of age, and sacrificed at 24 weeks (n = 8–10, each group). To determine if miR‐29b blockade was beneficial even after aneurysms develop, a third group of animals were treated every other week, starting at 8 weeks of age, until sacrificed (n = 4–6, each group). miR‐29b inhibition resulted in aneurysm reduction, increased elastogenesis, decreased matrix metalloproteinase activity and decreased elastin breakdown. Prenatal LNA‐anti‐miR‐29b inhibitor treatment decreased aneurysm formation up to age 32 weeks, whereas postnatal treatment was effective up to 16 weeks. miR‐29b blockade did not slow aortic growth once aneurysms already developed. Systemic miR‐29b inhibition significantly reduces aneurysm development long‐term in a Marfan mouse model. Drug administration during aortic wall embryologic development appears fundamental. miR‐29b suppression could be a potential therapeutic target for reducing aneurysm formation in Marfan syndrome patients.

[Assessment of the role of matrix metalloproteinase-3 gene polymorphism in the development of chronic heart failure]

AIM

To study the impact of a polymorphic variant of the matrix metalloproteinase-3 (MMP-3) gene on the development and course of chronic heart failure (CHF) in patients with coronary heart disease.

SUBJECTS AND METHODS

A total of 277 patients with New York Heart Association (NYHA) Functional Class (FC) II-IV CHF were examined. MMP-3 -1171 5A/6A genetic polymorphism was studied by polymerase chain reaction. A control group included 136 patients (mean age 53.6 ± 4.8 years) with no signs of cardiovascular diseases, as evidenced by the examination.

RESULTS

The frequency of the 5A allele and the 5A/5A genotype of the 1171 5A/6A polymorphic locus in the MMP-3 gene proved to be higher in the patients with CHF than that in the control group. Thus, the variability of the 5A allele (odds ratio (OR), 1.39; 95% confidence interval (CI): 1.033 to 1.869; p = 0.03) and the 5A/5A genotype (OR, 2.15; 95% CI: 1.131 to 4.070; p = 0.02) was associated with increased risk for CHF. There were significant differences in the frequency of MMP-3 alleles and genotypes in relation to FC of CHF. The frequency of the 5A/5A genotype was substantially higher in the patients with NYHA FC IV CHF than that in those with NYHA FC II CHF (32.8% versus 15.2%; p = 0.039). The frequency of the 5A allele was significantly higher in the patients with NYHA FC IV CHF than that in those with NYHA FC II CHF (55.5% and 39.3%; respectively; p = 0.019). Thus, the carriage of the 5A allele and the 5A/5A genotype of the 1171 5A/6A polymorphic locus in the MMP-3 gene is a risk factor of severe CHF.

CONCLUSION

The determination of MMP-3 -1171 5A/6A polymorphism may be recommended for the early prediction of a risk for the development and severe course of CHF.

Cysteine cathepsins in human carious dentin

Matrix metalloproteinases (MMPs) are important in dentinal caries, and analysis of recent data demonstrates the presence of other collagen-degrading enzymes, cysteine cathepsins, in human dentin. This study aimed to examine the presence, source, and activity of cysteine cathepsins in human caries. Cathepsin B was detected with immunostaining. Saliva and dentin cysteine cathepsin and MMP activities on caries lesions were analyzed spectrofluorometrically. Immunostaining demonstrated stronger cathepsins B in carious than in healthy dentin. In carious dentin, cysteine cathepsin activity increased with increasing depth and age in chronic lesions, but decreased with age in active lesions. MMP activity decreased with age in both active and chronic lesions. Salivary MMP activities were higher in patients with active than chronic lesions and with increasing lesion depth, while cysteine cathepsin activities showed no differences. The results indicate that, along with MMPs, cysteine cathepsins are important, especially in active and deep caries.

Myocardial fibrosis is unaltered by long-term administration of L-arginine in dystrophin deficient mdx mice: a histomorphometric analysis

Cardiac failure secondary to myocardial fibrosis (MF) significantly contributes to death in Duchenne muscular dystrophy (DMD), a fatal form of muscle disease. In aging, the mdx mice, an animal model of DMD, MF is similar to that observed in humans. Nitric oxide-based therapy has been proposed to retard MF in DMD and a candidate is L-arginine (L-arg). In this study we evaluated the effects of long-term therapy with L-arg in the MF of mdx mice. mdx mice (6 months old) were treated with L-arg in drinking water. Control mdx mice received water only. After 15 months of treatment, hearts were stained with Masson's trichrome for analysis of MF and with hematoxilyn and eosin for analysis of inflammation and cardiomyocyte damage. We observed that MF was not affected (29.5 +/- 2.5% of MF area for control vs 31.4 +/- 2% for L-arginine-treated animals; P > 0.05). The density of inflammatory cells was reduced (169 +/- 12 cells/mm 2 in control vs 102 +/- 9 cells/mm 2 in L-arg-treated; P < 0.05). The present study shows that long-term administration of L-arg is not effective in retarding MF in mdx dystrophinopathy.

Flavonoid glycosides isolated from Salicornia herbacea inhibit matrix metalloproteinase in HT1080 cells

Flavonoid glycosides, isorhamnetin 3-capital O, Cyrillic-beta-d-glucoside, and quercetin 3-O-beta-d-glucoside were isolated from Salicornia herbacea and their inhibitory effects on matrix metalloproteinase-9 and -2 (MMP-9 and -2) were evaluated in human fibrosarcoma cell line (HT1080). In zymography experiments, these flavonoid glycosides led to the reduction of the expression levels and activities of MMP-9 and -2 without any significant difference between these flavonoid glycosides. Protein expression levels of both MMP-9 and MMP-2 were inhibited and TIMP-1 (tissue inhibitor of metalloproteinase-1) protein level was enhanced by these flavonoid glycosides. Moreover, a transfection study carried out with AP-1 reporter construct revealed that the reporter activity was suppressed by treatment with isorhamnetin 3-capital O, Cyrillic-beta-d-glucoside. Therefore, these results suggested that these flavonoid glycosides have a potential as valuable natural chemopreventive agents for cancer.

Imidaprilat inhibits matrix metalloproteinase-2 activity in human cardiac fibroblasts induced by interleukin-1beta via NO-dependent pathway

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors are widely used in treatment of heart failure, but little is known regarding whether ACE inhibitors regulate the activity of matrix metalloproteinases (MMPs) and the tissue inhibitor of MMPs (TIMPs) in cardiac cells. The purpose of this study was to determine the ability and possible signal pathway involved of imidaprilat, an ACE inhibitor, to modulate MMP-2 and TIMP-2 in human cardiac fibroblasts in the presence of interleukin (IL)-1beta.

METHODS AND RESULTS

Using gelatin zymography and RT-PCR and Griess analysis,we found that IL-1beta increased the MMP-2 activity and transcription and nitric oxide(NO) production from supernatant of culture medium. These effects of IL-1beta were inhibited by imidaprilat or the NO synthase inhibitor, L-NMMA. Sodium nitroprusside (SNP), an exogenous NO donor, prevented significantly the effects of imidaprilat on MMP-2 inhibition. Imidaprilat alone didn't affect MMP-2 activity and expression. Neither IL-1beta nor imidaprilat has no effect on TIMP-2 transcription in cardiac fibroblasts.

CONCLUSIONS

The current study demonstrates imidaprilat inhibits MMP-2 activity and expression in human cardiac fibroblasts induced by IL-1beta via NO-dependent pathway. These data suggest that the beneficial effect of ACE inhibitors against left cardiac remodeling and heart failure may be due at least in part to regulating MMPs activity and expression by modulation of NO pathway.

Anti-tumor effects of Rubratoxin B on cell toxicity, inhibition of cell proliferation, cytotoxic activity and matrix metalloproteinase-2,9

Terrestrial fungi are a prolific source of metabolites with significant biological activities. Many important anticancer, antifungal and antibacterial chemotherapeutics are either microbial metabolites or semisynthetic derivatives. Investigating the metabolites of fungi may increase the chance of finding novel compounds. A bioassay-guided fractionation of soil fungus Penicillium purpurogenum fermentation, yielded the metabolite Rubratoxin B using morphological deformation of Pyricularia oryzae mycelia. Analysis by flow cytometry showed that Rubratoxin B inhibited the cell cycle progression of tsFT210 cells in the G2/M phase at the concentration of 24 microM. Cytotoxic activity analysis showed that Rubratoxin B has a cytotoxic activity and IC50 was 67.3 +/- 1.4 microM on human fibrosarcoma cell (HT1080), and Rubratoxin B exhibited inhibitory activities against matrix metalloproteinase (MMP)-2 and 9 on HT 1080 cells with an inhibitory rate of 61.5% and 74.7% at 30 microM, respectively.

Increased Alveolar and Plasma Gelatinases Activity during Postpump Syndrome: Inhibition by Inhaled Nitric Oxide

Postpump syndrome is associated with systemic inflammation. Matrix metalloproteinases (MMP)-2 and -9 contribute to proinflammatory and platelet-activator reactions. Nitric oxide (NO) is involved in the regulation of MMPs. The objectives of our study were to investigate the intensity of inflammation induced by 3 different surgical procedures, the effects of inflammation on the activity of MMPs, and the regulation of inflammation by inhaled NO (20 ppm). Inhaled NO was initiated immediately after tracheal intubation and maintained for the total duration of the experiments. Thirty pigs were equally randomized into 6 groups [sham; sham + NO; cardiopulmonary bypass; bypass + NO; bypass + lipopolysaccharide (1 microg/kg for 50 min); bypass + lipopolysaccharide + NO] and animals were subjected to anesthesia and mechanical ventilation up to 24 h. The levels of MMP-2 and MMP-9 in plasma and bronchoalveolar lavage were measured using zymography. Bypass resulted in a time-dependent rise in MMP activity, an effect potentiated by lipopolysaccharide. Inhaled NO attenuated the effects of bypass + lipopolysaccharide. These results confirm that MMP-2 and MMP-9 are associated with the inflammatory process causing the postpump syndrome. Preemptive and continuous administration of inhaled NO helps to prevent increased MMP-2 and MMP-9 activity.

Marfan syndrome: what internists and pediatric or adult cardiologists need to know

Marfan syndrome (MFS) is one of the most frequent connective tissue disorders, showing striking pleiotropism and clinical variability. There is autosomal dominant inheritance with complete penetrance but variable expression. Approximately 25% of MFS patients have no family history of the syndrome and represent sporadic cases due to new mutations. This hazardous condition is often associated with premature cardiovascular death unless surveillance and management are optimized. The fibrillin gene (FBN1) encodes the structure of the connective tissue protein fibrillin. MFS is caused by mutations in the fibrillin gene, located on chromosome 15 at locus 15q21. Fibrillin abnormalities reduce the structural integrity of different body systems, primarily involving the heart valves, blood vessels, lungs, bones, tendons, ligaments, cartilages, eyes, skin, spinal dura and the CNS. Patients with MFS are likely to have too little fibrillin within these structures, resulting in clinically relevant problems. For example, in the aortic wall, deficient fibrillin may trigger progressive aortic ectasia and may result in aortic dissection.

Relaxin: antifibrotic properties and effects in models of disease

Fibrosis (progressive scarring) is a leading cause of organ failure worldwide and causes loss of organ function when normal tissue is replaced with excess connective tissue. Several organs are prone to this process regardless of etiology. The pleiotropic hormone, relaxin, is emerging as a novel antifibrotic therapy. Relaxin has been shown to limit collagen production and reorganization, while stimulating increased collagen degradation. It not only prevents fibrogenesis, but also reduces established scarring. This review summarizes (1) the levels at which relaxin inhibits collagen production and existing collagen overexpression in induced models of fibrosis, and (2) the collagen-related phenotypes of relaxin- and LGR7-deficient mice. Recent studies on relaxin-deficient mice have established relaxin as an important, naturally occurring regulator of collagen turnover and provide new insights into the therapeutic potential of relaxin.

Prognostic value of tissue inhibitor of metalloproteinase-1 for cardiovascular death among patients with cardiovascular disease: results from the AtheroGene study

AIMS

Metalloproteinases are proteolytic enzymes, which decompose the extracellular matrix, influence cardiac remodelling, and are inhibited by tissue inhibitor of metalloproteinases (TIMPs). Little is known about the prognostic impact of the TIMP-1/matrix metalloproteinase complex in patients with future cardiovascular death.

METHODS AND RESULTS

In 1979 patients with suspected coronary artery disease (CAD), TIMP-1 has been determined at baseline. Among 1945 (98.4%) patients with a mean follow-up period of 2.6+/-1.2 years, 75 patients died because of cardiovascular causes. Mean concentrations of TIMP-1 were higher among patients who experienced a fatal cardiovascular event than among those who did not (820 vs. 692 ng/mL; P<0.001). Age and sex adjusted hazard ratio of future cardiovascular death associated with one standard deviation of TIMP-1 level, was 1.37 (95% CI: 1.17-1.61; P<0.001). The hazard ratio remained nearly identical after adjustment for clinical and therapeutic confounders. B-type natriuretic peptide (2.75, 95% CI: 1.94-3.89; P<0.001), C-reactive protein (1.79, 95% CI: 1.43-2.24; P<0.001), and TIMP-1 (1.30, 95% CI: 1.07-1.58; P=0.008) were independently associated with future cardiovascular death.

CONCLUSION

In patients with CAD, TIMP-1 proves as an independent predictor for future cardiovascular death.

Metalloproteinase-2 and -9 in giant cell arteritis: involvement in vascular remodeling

BACKGROUND

Both matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9) have been postulated to play roles in the pathophysiology of giant cell arteritis (GCA) because of their ability to degrade elastin. Understanding the specific mediators of arterial damage in GCA could lead to new therapeutic targets in this disease.

METHODS AND RESULTS

Temporal artery biopsy specimens were obtained from 147 consecutive patients suspected of GCA. Clinical and histopathological data were collected according to protocol. Using immunohistochemistry, we compared the expression of MMP-2 and MMP-9 in the temporal artery biopsies of both GCA cases (n=50) and controls (n=97). MMP-9 was found more frequently in positive than in negative temporal artery biopsies (adjusted odds ratio [OR], 3.20; P=0.01). In contrast, the frequency of MMP-2 was not significantly different between positive and negative biopsies (adjusted OR, 2.18; P=0.22). Both MMP-2 and MMP-9 were found in macrophages and giant cells near the internal elastic lamina and in smooth muscle cells and myofibroblasts of the media and intima. MMP-9 was also found in the vasa vasorum. MMP-9 but not MMP-2 was associated with internal elastic lamina degeneration, intimal hyperplasia, and luminal narrowing, even after adjustment for possible confounding variables.

CONCLUSIONS

MMP-9 appears more likely than MMP-2 to be involved in the pathophysiology of GCA. MMP-9 not only participates in the degradation of elastic tissue but also is associated with intimal hyperplasia, subsequent luminal narrowing, and neoangiogenesis. The expression of MMP by smooth muscle cells implicates these cells as potential secretory cells in GCA.

A mechanical model for collagen fibril load sharing in peripheral nerve of diabetic and nondiabetic rats

Peripheral neuropathy affects approximately 50% of the 15 million Americans with diabetes. It has been suggested that mechanical effects related to collagen glycation are related to the permanence of neuropathy. In the present paper, we develop a model for load transfer in a whole nerve, using a simple pressure vessel approximation, in order to assess the significant of stiffening of the collagenous nerve sheath on endoneurial fluid pressure. We also develop a fibril-scale mechanics model for the nerve, to model the straightening of wavy fibrils, producing the toe region observed in nerve tissue, and also to interrogate the effects of interfibrillar crosslinks on the overall properties of the tissue. Such collagen crosslinking has been implicated in complications in diabetic tissues. Our fibril-scale model uses a two-parameter Weibull model for fibril strength, in combination with statistical parameters describing fibril modulus, angle, wave-amplitude, and volume fraction to capture both toe region and failure region behavior of whole rat sciatic nerve. The extrema of equal and local load-sharing assumptions are used to map potential differences in diabetic and nondiabetic tissues. This work may ultimately be useful in differentiating between the responses of normal and heavily crosslinked tissue.

Sultam Hydroxamates as Novel Matrix Metalloproteinase Inhibitors

In this communication we describe the design, synthesis, and evaluation of novel sultam hydroxamates 4 as MMP-2, -9, and -13 inhibitors. Compound 26 was found to be an active inhibitor (MMP-2 IC(50) = 1 nM) with 1000-fold selectivity over MMP-1 and good oral bioavailability (F = 43%) in mouse. An X-ray crystal structure of 26 in MMP-13 confirms the key hydrogen bonds and prime side binding in the active site.

Serum profiles of matrix metalloproteinases and their tissue inhibitor in patients with acute coronary syndromes. The effects of short-term atorvastatin administration

There is increasing evidence that abnormal cytokine expression and increased metalloproteinase activity are implicated in the pathophysiology of acute coronary syndromes. This study investigates the serum profiles of representative metalloproteinases (MMP-1, -2, -9) and their tissue inhibitor (TIMP-1) in patients with myocardial infarction (MI) and unstable angina (UA) in relation to circulating proinflammatory cytokine (TNF-alpha and IL-6) activity. Furthermore, we examined the effects of a 30-day treatment with atorvastatin on serum levels of these inflammatory factors. Serum concentrations of MMP-1, -2, -9, TIMP-1, IL-6 and TNF-alpha were measured (enzyme-linked immunosorbent assay (ELISA) method) in 23 acute myocardial infarction patients and 20 unstable angina patients on 0 day, 1st, 3rd, 7th and 30th day after admission. Sixteen normal volunteers were used as healthy controls. Additionally, 12 patients of myocardial infarction group and 11 patients of unstable angina group were treated with atorvastatin (20 mg/day) for 30 days in a randomized design. In patients with myocardial infarction and unstable angina, serum levels of MMP-2, -9, TIMP-1, TNF-alpha and IL-6 were significantly higher than those of healthy controls in all time frames (p<0.05). In the group of unstable angina patients, we observed a statistically significant reduction in the levels of MMP-9, TIMP-1 and IL-6 after the 30-day atorvastatin administration. Our results suggest that serum MMPs, TIMP-1 and proinflammatory cytokines play an important role in the pathophysiology of the acute coronary syndromes. The reduction of these factors by short-term atorvastatin administration may provide a new insight into the pleiotropic effects of statins on unstable coronary artery disease.

Regulation of Collagenase Activities of Human Cathepsins by Glycosaminoglycans

Cathepsin K, a lysosomal papain-like cysteine protease, forms collagenolytically highly active complexes with chondroitin sulfate and represents the most potent mammalian collagenase. Here we demonstrate that complex formation with glycosaminoglycans (GAGs) is unique for cathepsin K among human papain-like cysteine proteases and that different GAGs compete for the binding to cathepsin K. GAGs predominantly expressed in bone and cartilage, such as chondroitin and keratan sulfates, enhance the collagenolytic activity of cathepsin K, whereas dermatan, heparan sulfate, and heparin selectively inhibit this activity. Moreover, GAGs potently inhibit the collagenase activity of other cysteine proteases such as cathepsins L and S at 37 degrees C. Along this line MMP1-generated collagen fragments in the presence of GAGs are stable against further degradation at 28 degrees C by all cathepsins but cathepsin K, whereas thermal destabilization at 37 degrees C renders the fragments accessible to all cathepsins. These results suggest a novel mechanism for the regulation of matrix protein degradation by GAGs. It further implies that cathepsin K represents the only lysosomal collagenolytic activity under physiologically relevant conditions.

Cardioprotective effects of phosphoramidon on myocardial structure and function in murine Chagas' disease

Chagas' disease is an important cause of cardiomyopathy. Endothelin-1, a vasoactive peptide has been implicated in the pathogenesis of chagasic cardiomyopathy. C57BL/6 x 129sv and CD1 mice were thus, infected with trypomastigotes of Trypanosoma cruzi (Brazil strain) and these infected mice were compared with infected mice treated with phosphoramidon. This compound inhibits endothelin-converting enzyme and neutral endopeptidases and does not affect the growth of the parasite in culture. Phosphoramidon was given in a dose of 10mg/kg for the initial 15 days post-infection None of the C57Bl/6 x 129sv mice died as a result of infection. However, there was marked myocardial inflammation and fibrosis in infected, untreated mice. The hearts of the infected, phosphoramidon-treated mice showed significantly less pathology. Cardiac magnetic resonance imaging of infected mice revealed right ventricular dilation that was less severe in those treated with phosphoramidon. Phosphoramidon-treated CD1 mice survived the acute infection. Transthoracic echocardiography demonstrated left ventricular dilation and reduced percent fractional shortening and relative wall thickness. These alterations were also attenuated as a result of phosphoramidon treatment. These data suggest that endothelin-1 contributes to the pathogenesis of chagasic cardiomyopathy and interventions that inhibit the synthesis of endothelin-1 and/or neutral endopeptidase might have a protective effect on myocardial structure and function in murine Chagas' disease.