Measurement of active TGF-beta generated by cultured cells.
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Animals↗
Biomedical subjects
R Mazzieri
Publications and source records attributed to R Mazzieri.
Proteolytic control of growth factor availability.
Most growth factors are released from cells in a form that does not permit immediate interaction with their high affinity receptors. An important mechanism for presentation of these released latent growth factors is activation by the plasminogen activator-plasmin system. The involvement of this system in the biology of Transforming Growth Factor-beta (TGF-beta) is reviewed.
Animals↗
[Peripartum cardiomyopathy. A critical analysis of immunosuppression].
The authors review the literature about peripartum cardiomyopathy and describe a case of a white woman, 31 years old, primipara, who developed myocardial failure six hours after caesarian operation, with good results after immunosuppressive therapy.
Adult↗
Control of type IV collagenase activity by components of the urokinase-plasmin system: a regulatory mechanism with cell-bound reactants.
The urokinase-type plasminogen activator (uPA) and the matrix-degrading metalloproteinases MMP-2 and MMP-9 (type IV collagenases/gelatinases) have been implicated in a variety of invasive processes, including tumor invasion, metastasis and angiogenesis. MMP-2 and MMP-9 are secreted in the form of inactive zymogens that are activated extracellularly, a fundamental process for the control of their activity. The physiological mechanism(s) of gelatinase activation are still poorly understood; their comprehension may provide tools to control cell invasion. The data reported in this paper show multiple roles of the uPA-plasmin system in the control of gelatinase activity: (i) both gelatinases are associated with the cell surface; binding of uPA and plasmin(ogen) to the cell surface results in gelatinase activation without the action of other metallo- or acid proteinases; (ii) inhibition of uPA or plasminogen binding to the cell surface blocks gelatinase activation; (iii) in soluble phase plasmin degrades both gelatinases; and (iv) gelatinase activation and degradation occur in a dose- and time-dependent manner in the presence of physiological plasminogen and uPA concentrations. Thus, the uPA-plasmin system may represent a physiological mechanism for the control of gelatinase activity.
Collagenases↗
Plasminogen/plasminogen activator and growth factor activation.
The plasminogen/plasminogen activator system is widely used in extracellular proteolysis. In this review the involvement of this system in tumour invasion, cell migration, growth factor presentation and inhibition of angiogenesis are discussed.
Animals↗
TGF-beta latency: biological significance and mechanisms of activation.
Transforming growth factor (TGF-) beta is secreted as a latent complex in which the mature growth factor remains associated with its propeptide. In order to elicit a biological response, the cytokine must be released from the latent complex, a process termed latent TGF-beta activation or TGF-beta formation. Although latent TGF-beta activation is a critical step in the regulation of its activity, little is known about the molecular mechanisms that lead to the production of active TGF-beta. In this article, we present an overview of the data available on this topic, and we propose a tentative model for the mechanism of TGF-beta formation based upon the observations with different cell systems and on recent findings on the structure of the latent TGF-beta complex.
Animals↗
Latent transforming growth factor-beta: structural features and mechanisms of activation.
Transforming growth factor-beta are cytokines with a wide range of biological effects. They play a pathologic role in inflammatory and fibrosing diseases such as nephrosclerosis. TGF-beta s are secreted in a latent form due to noncovalent association with latency associated peptide (LAP), which is a homodimer formed from the propeptide region of TGF-beta. LAP is disulfide linked to another protein, latent TGF-beta binding protein (LTBP). LTBP has features in common with extracellular matrix proteins, and targets latent TGF-beta to the matrix. Activation of latent TGF-beta can be accomplished in vitro by denaturing treatments, plasmin digestion, ionizing radiation and interaction with thrombospondin. The mechanisms by which latent TGF-beta is activated physiologically are not well understood. Results to date suggest an important role for proteases, particularly plasmin, although other mechanisms probably exist. A general model of activation is proposed in which latent TGF-beta is released from the extracellular matrix by proteases, localized to cell surfaces, and activated by cell-associated plasmin.
Animals↗
Identification and characterization of an eight-cysteine repeat of the latent transforming growth factor-beta binding protein-1 that mediates bonding to the latent transforming growth factor-beta1.
Most cultured cell types secrete small latent transforming growth factor-beta (TGF-beta) as a disulfide-bonded complex with a member of the latent TGF-beta binding protein (LTBP) family. Using the baculovirus expression system, we have mapped the domain of LTBP-1 mediating covalent association with small latent TGF-beta1. Coexpression in Sf9 cells of small latent TGF-beta1 with deletion mutants of LTBP-1 showed that the third eight-cysteine repeat of LTBP-1 is necessary and sufficient for covalent interaction with small latent TGF-beta1. Analysis by mass spectrometry of this eight-cysteine repeat, produced as a recombinant peptide in Sf9 cells, confirmed that it was N-glycosylated, as expected from the primary sequence. No other post-translational modifications of this domain were detected. Alkylation of the recombinant peptide with vinyl pyridine failed to reveal any free cysteines, indicating that, in the absence of small latent TGF-beta, the eight cysteines of this domain are engaged in intramolecular bonds. These data demonstrate that the third LTBP-1 eight-cysteine repeat recognizes and associates covalently with small latent TGF-beta1 through a mechanism that does not require any specific post-translational modification of this domain. They also suggest that this domain adopts different conformations depending on whether it is free or bound to small latent TGF-beta.
Animals↗
Tumor cell-conditioned medium stimulates expression of the urokinase receptor in vascular endothelial cells.
We have previously reported that culture medium conditioned by human SK-Hep1 hepatoma cells or mouse S180 sarcoma cells induces in vitro angiogenesis and stimulates production of urokinase plasminogen activator (uPA) in vascular endothelial cells. These activities are mediated by a 3.5-10 kDa, heparin-binding peptide that upregulates endothelial cell expression of basic fibroblast growth factor (bFGF; Peverali et al., 1994, J. Cell. Physiol. 161:1-14.) We now report that SK-Hep 1 or S180 cell-conditioned medium rapidly induces a 4- to 5-fold increase in cell-bound uPA activity and in the high-affinity binding of 125I-prouPA to vascular endothelial cells. Ligand blotting and purification experiments show an equivalent increase in the synthesis of a cell surface protein corresponding to the endothelial cell uPA receptor (uPAR) on the basis of M, (45-50 kDa) and sensitivity to phosphatidylinositol-specific phospholipase C (PI-PLC). The tumor cell-conditioned media also upregulate uPAR mRNA levels in endothelial cells. Thus, the increase in uPA binding capacity of endothelial cells is mediated by an increased expression of uPAR. The uPAR-inducing activity of SK-Hep 1 or S180 cell-conditioned medium is not neutralized by antibodies to bFGF, and is associated with a peptide that has a M, higher than 10 kDa and no affinity for heparin. Therefore, it appears to be distinct from the bFGF/uPA-inducing factor secreted by the same cells, and from other heparin-binding cytokines that upregulate uPAR expression in endothelial cells.
Animals↗
Vascular endothelial growth factor increases urokinase receptor expression in vascular endothelial cells.
Vascular endothelial growth factor (VEGF) is a potent angiogenic factor and endothelial cell-specific mitogen that stimulates urokinase-type plasminogen activator (uPA) activity in vascular endothelial cells. Here, we report that VEGF increases the high affinity binding of uPA to the same cells and that this binding is prevented by a peptide corresponding to the uPA receptor (uPAR) binding growth factor-like domain of uPA. Ligand cross-linking, ligand blotting, and uPA-Sepharose affinity chromatography revealed an increase in a cell surface uPA binding protein that corresponds to the uPAR on the basis of its affinity for uPA, M(r) of 50,000-55,000, and phosphatidylinositol-specific phospholipase C sensitivity. By Scatchard analysis, VEGF increased the number of uPAR molecules by 2.8-3.5-fold and concomitantly decreased their affinity for uPA. By northern blotting uPAR mRNA was increased in a dose- and time-dependent manner in response to VEGF. Taken together, these findings demonstrate that VEGF-induced angiogenesis is accompanied by increased uPAR expression and uPA activity on the endothelial cell surface. These observations are consistent with the notion that the uPA-uPAR interaction facilitates cellular invasion.
Animals↗
Assignment of the human urokinase receptor gene (PLAUR) to 19q13.
Through in situ hybridization of a cDNA probe to metaphase chromosomes, we localized the gene for the human urokinase receptor (PLAUR) on chromosome 19. RBG-banding permitted subchromosomal localization of the PLAUR gene to 19q13.
Chromosomes, Human, Pair 19↗
Expression of the urokinase receptor in vascular endothelial cells is stimulated by basic fibroblast growth factor.
Basic fibroblast growth factor, a potent angiogenesis inducer, stimulates urokinase (uPA) production by vascular endothelial cells. In both basic fibroblast growth factor-stimulated and -nonstimulated bovine capillary endothelial and human umbilical vein endothelial cells single-chain uPA binding is mediated by a membrane protein with a Mr of 42,000. Exposure of bovine capillary or endothelial human umbilical vein endothelial cells to pmolar concentrations of basic fibroblast growth factor results in a dose-dependent, protein synthesis-dependent increase in the number of membrane receptors for uPA (19,500-187,000) and in a parallel decrease in their affinity (KD = 0.144-0.790 nM). With both cells, single-chain uPA binding is competed by synthetic peptides whose sequence corresponds to the receptor-binding sequence in the NH2-terminal domain of uPA. Exposure of bovine capillary endothelial cells to transforming growth factor beta 1, which inhibits uPA production and upregulates type 1 plasminogen activator inhibitor, the major endothelial cell plasminogen activator inhibitor, has no effect on uPA receptor levels. These results show that basic fibroblast growth factor, besides stimulating uPA production by vascular endothelial cells, also increases the production of receptors, which modulates their capacity to focalize this enzyme on the cell surface. This effect may be important in the degradative processes that occur during angiogenesis.
Adrenal Cortex↗
Correlation between gallium-67 imaging and endomyocardial biopsy in children with severe dilated cardiomyopathy.
Fourty-four patients (aged 10 months to 15 years) were assessed in a double-blind study to observe the correlation between myocardial uptake of 67-gallium and endomyocardial biopsy in the detection of moderate to severe myocardial inflammation. The sensitivity and specificity of gallium-67 imaging were 87 and 81%, respectively. Based on these findings, immunosuppressive therapy can be assigned to children with dilated cardiomyopathy and positive myocardial uptake, since moderate and severe myocardial inflammation may be detected by this non-invasive method.
Adolescent↗
[Immunosuppressive drugs for the treatment of active myocarditis in children. Hemodynamic evaluation].
PURPOSE: To analyse hemodynamic parameters (left ventricles ejection fraction, cardiac index, mean pulmonary wedge pressure and left ventricle diastolic diameter, in a group of children with active myocarditis (diagnosed by endomyocardial biopsy) pre and post treatment with conventional therapy and immunosuppressive drugs (isolated prednisone or prednisone associated with azathioprine or cyclosporine). PATIENTS AND METHODS: Forty-four pediatric patients with active myocarditis were studied. Twenty males and 24 females from 10 months to 15 years old (median = 1.3 years). All patients were submitted to hemodynamic study and endomyocardial biopsy. The hemodynamic parameters mentioned above were analysed before and after the proposed therapy. The patients were distributed in group according to the admission in the protocol, group I (9 pts)--conventional therapy (CT); group II (12 pts)--CT plus prednisone; group III (16 pts)--CT plus prednisone plus azathioprine; group IV (13 pts)--CT plus prednisone plus cyclosporine. RESULTS: Forty-four patients were submitted to four different groups of therapeutic protocol. The hemodynamic parameters were analysed in each of them. Left ventricle ejection fraction were no significantly different in the pre and post therapeutic scheme in group I and II, they were significantly higher (p less than 0.05) in group III and IV. The same happened with cardiac index. The mean pulmonary wedge pressure no presented statistical differences in group I and II before and after treatment but significantly lower lends were observed in group III and IV. The same behavior were noted in the left ventricle end diastolic diameter. CONCLUSION: The association of azathioprine or cyclosporine to prednisone presented better results in the left ventricle function, when compared with conventional drugs or isolated use of prednisone, based in the analysis of same hemodynamic parameters.
Adolescent↗
[Early surgical correction of the left coronary artery with origin at the pulmonary trunk. Late development].
The report of these two cases show the accentuated and progressive increase in the ventricular contractility in the late postoperative period in patients who underwent surgical correction of left coronary artery with origin at the pulmonary trunk. Male and female infants, both developed congestive heart failure not controlled by medical treatment. The diagnosis was made by EKG and confirmed by coronary angiogram. They were surgically treated by translocation of the left coronary artery from the pulmonary artery to the aorta. Nine and seven years later, respectively both patients are free of symptoms with marked recovery of the left ventricle function without alteration in height and weight and in excellent clinical conditions. The early surgical treatment in these cases, even with unfavourable clinical status is the only way to change the natural history of this pathology, with an increase of the ventricular contractility.
Coronary Vessel Anomalies↗
[Tuberous sclerosis associated with left ventricle rhabdomyoma].
Female infant, presenting with flexion spasms, skin hypochromatic spots and systolic ejection murmur. A clinical diagnosis of tuberous sclerosis, supported by computerized brain tomography and neurosonographic data, was made. Echocardiographic and cineangiocardiographic studies disclosed an associated tumor in left ventricle outlet. After resection of the rhabdomyoma, the patient is asymptomatic with neural manifestations controlled under valproic acid.
Echocardiography↗
[Endomyocardial biopsy and myocardial imaging with 67-gallium in the diagnosis of active myocarditis in children with dilated myocardiopathy].
PURPOSE: This study was designed to compare 67Ga imaging and endomyocardial biopsy (EB) in children with severe dilated cardiomyopathy (DC), as well as to evaluate the results in a group of patients with active myocarditis submitted to immunosuppressive therapy. PATIENTS AND METHODS: Forty-four pediatric patients with severe DC were studied. Twenty males and 24 females from 10 months to 15 year old (median = 2.6 years). All patients were submitted to a protocol including 67Ga uptake and EB. In patients submitted to immunosuppressive therapy these procedures were repeated after six months. RESULTS: In 32 patients (72.7%) the EB revealed presence of inflammatory process; 21 (65.6%) of these had a positive 67Ga uptake and 11 (34.4%) negative. Twelve patients with no evidence of inflammatory process in the EB, nine (75%) presented negative 67Ga uptake. However, when the intensity of myocardial inflammatory was analysed (mild, moderate and severe) and correlated with 67Ga imaging, was observed that the majority of patients with negative 67Ga uptake (11 patients) had mild inflammatory infiltration (nine patients). In this way the 67Ga uptake demonstrated a good correlation in the diagnosis of moderate and severe inflammatory process in children with DC. This is important because the use of immunosuppressive drugs is indicated only in these group. CONCLUSION: The 67Ga imaging is a noninvasive diagnostic method with a good sensitivity to the diagnostic method with a good sensitivity to the diagnosis of AM in children with severe DC, demonstrating to be very useful in the therapeutic approach.
Adolescent↗
[Primary rhabdomyosarcoma of the heart in children. A case report].
The authors report a case of a child, 10 years old with a primary rhabdomyosarcoma of the heart that obstructed both caval veins. The clinical picture that lasted just three months before the admission was characterized by persistent fever, accentuated loss of weight and a very deteriorated general aspect. We emphasize the clinical aspects and other subsidiary elements that easily allowed to make the precise diagnosis in life as well as the therapeutic measures and follow up, besides a review of the literature, where it was confirmed the rarity of this pathological entity.
Angiocardiography↗