thromboplastin and Cardiomyopathy--Dilated

It has long been known that Tissue Factor (TF) plays a role in blood coagulation and has a direct thrombotic action that is closely related to cardiovascular risk, but it is becoming increasingly clear that it has a much wider range of biological functions that range from inflammation to immunity. It is also involved in maintaining heart haemostasis and structure, and the observation that it is down-regulated in the myocardium of patients with dilated cardiomyopathy suggests that it influences cell-to-cell contact stability and contractility, and thus contributes to cardiac dysfunction. However, the molecular mechanisms underlying these coagulation-independent functions have not yet been fully elucidated. In order to analyse the influence of TF on the cardiomyocitic proteome, we used functional biochemical approaches incorporating label-free quantitative proteomics and gene silencing, and found that this provided a powerful means of identifying a new role for TF in regulating splicing machinery together with the expression of several proteins of the spliceosome, and mRNA metabolism with a considerable impact on cell viability.. In this study, using quantitative proteomics and functional biochemical approaches, we define for the first time that, in addition to its primary role in blood coagulation, Tissue Factor also plays a novel role in regulating cell splicing machinery, with a relevant impact on cell survival. This new function may help to explain the wide range of biological activities of TF, and thus provide fruitful clues for developing new strategies for treating human diseases in which TF is dysregulated.

Topics: Cardiomyopathy, Dilated; Cell Line, Tumor; Gene Silencing; Humans; Myocytes, Cardiac; Proteomics; RNA Splicing; Thromboplastin

Heterogeneity of vascular permeability has been suggested for the coronary system. Whereas arteriolar and capillary segments are tight, plasma proteins pass readily into the interstitial space at venular sites. Fittingly, lymphatic fluid is able to coagulate. However, heart tissue contains high concentrations of tissue factor, presumably enabling bleeding to be stopped immediately in this vital organ. The distribution of pro- and anti-coagulatively active factors in human heart tissue has now been determined in relation to the types of microvessels.. Samples of healthy explanted hearts and dilated cardiomyopathic hearts were immunohistochemically stained. Albumin was found throughout the interstitial space. Tissue factor was packed tightly around arterioles and capillaries, whereas the tissue surrounding venules and small veins was practically free of this starter of coagulation. Thrombomodulin was present at the luminal surface of all vessel segments and especially at venular endothelial cell junctions. Its product, the anticoagulant protein C, appeared only at discrete extravascular sites, mainly next to capillaries. These distribution patterns were basically identical in the healthy and diseased hearts, suggesting a general principle.. Venular extravasation of plasma proteins probably would not bring prothrombin into intimate contact with tissue factor, avoiding interstitial coagulation in the absence of injury. Generation of activated protein C via thrombomodulin is favored in the vicinity of venular gaps, should thrombin occur inside coronary vessels. This regionalization of distribution supports the proposed physiological heterogeneity of the vascular barrier and complies with the passage of plasma proteins into the lymphatic system of the heart.

Topics: Adult; Arterioles; Blood Coagulation Factors; Capillaries; Capillary Permeability; Cardiomyopathy, Dilated; Case-Control Studies; Coronary Vessels; Humans; Immunohistochemistry; Infant; Lymphatic System; Myocardium; Protein C; Serum Albumin; Thrombomodulin; Thromboplastin; Venules

Protease-activated receptor-1 (PAR-1) is the high-affinity receptor for the coagulation protease thrombin. It is expressed by a variety of cell types in the heart, including cardiomyocytes and cardiac fibroblasts. We have shown that tissue factor (TF) and thrombin contribute to infarct size after cardiac ischemia-reperfusion (I/R) injury. Moreover, in vitro studies have shown that PAR-1 signaling induces hypertrophy of cardiomyocytes and proliferation of cardiac fibroblasts. The purpose of the present study was to investigate the role of PAR-1 in infarction, cardiac remodeling, and hypertrophy after I/R injury. In addition, we analyzed the effect of overexpression of PAR-1 on cardiomyocytes.. We found that PAR-1 deficiency reduced dilation of the left ventricle and reduced impairment of left ventricular function 2 weeks after I/R injury. Activation of ERK1/2 was increased in injured PAR-1(-/-) mice compared with wild-type mice; however, PAR-1 deficiency did not affect infarct size. Cardiomyocyte-specific overexpression of PAR-1 in mice induced eccentric hypertrophy (increased left ventricular dimension and normal left ventricular wall thickness) and dilated cardiomyopathy. Deletion of the TF gene in cardiomyocytes reduced the eccentric hypertrophy in mice overexpressing PAR-1.. Our results demonstrate that PAR-1 contributes to cardiac remodeling and hypertrophy. Moreover, overexpression of PAR-1 on cardiomyocytes induced eccentric hypertrophy. Inhibition of PAR-1 after myocardial infarction may represent a novel therapy to reduce hypertrophy and heart failure in humans.

Topics: Animals; Cardiomegaly; Cardiomyopathy, Dilated; Echocardiography; Gene Expression; Male; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Myocardial Infarction; Myocytes, Cardiac; Phenotype; Receptor, PAR-1; Reperfusion Injury; Thromboplastin; Ventricular Myosins; Ventricular Remodeling

We investigated the myocardial localization and expression of tissue factor (TF) and alternatively spliced human tissue factor (asHTF) in patients with dilated cardiomyopathy (DCM).. Tissue factor is expressed in cardiac muscle and may play a role in maintaining myocardial structure.. Myocardial biopsies were obtained from patients with a normal or mildly impaired ejection fraction (EF) (> or =50%) and moderate to severely reduced EF (<50%). Explanted DCM hearts were also examined. Myocardial TF expression level was assessed by real-time polymerase chain reaction, TF protein by enzyme-linked immunosorbent assay, and localization by immunohistochemistry.. We report the identification of asHTF in the human myocardium: it was located in cardiomyocytes and endothelial cells. Quantification of myocardial TF messenger ribonucleic acid in DCM revealed a decrease in the TF/glyceraldehyde-3-phosphate dehydrogenase (GAPDH) ratio (1.76 x 10(-1) +/- 6.08 x 10(-2) for EF > or =50% [n = 19] vs. 1.06 x 10(-1) +/- 5.26 x 10(-2) for EF <50% [n = 27]; p < 0.001) and asHTF/GAPDH ratio (13.91 x 10(-5) +/- 11.20 x 10(-5) for EF > or =50% vs. 7.17 x 10(-5) +/- 3.82 x 10(-5) for EF <50%; p = 0.014). Tissue factor isoform expression level was also decreased in explanted DCM hearts (p < 0.01; n = 12). Total TF protein was reduced by 26% in DCM (p < 0.05). The TF/GAPDH ratio correlated positively with the EF (r = 0.504, p < 0.0001). Immunohistochemistry showed TF localized to the sarcolemma and Z-bands of the cardiomyocytes in patients with normal EF, whereas TF was found in the cardiomyocytic cytosol around the nucleus in DCM.. Tissue factor was down-regulated in the myocardium of DCM patients. The reduction in TF expression and change in localization may influence cell-to-cell contact stability and contractility, thereby contributing to cardiac dysfunction in DCM.

Topics: Blotting, Western; Cardiomyopathy, Dilated; Case-Control Studies; DNA Primers; Female; Gene Expression; Humans; Immunohistochemistry; Male; Middle Aged; Myocardium; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Severity of Illness Index; Thromboplastin