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PubMed1990

Heparin promotes the binding of thrombin to fibrin polymer. Quantitative characterization of a thrombin-fibrin polymer-heparin ternary complex.

The binding of human alpha-thrombin (IIa) to fibrin polymer (FnIIp) was studied in the presence and absence of a high affinity 20,300 Mr heparin (H) at pH 7.4, I 0.15, and 23 degrees C. In the absence of heparin, thrombin interacts with a high affinity class of binding sites on fibrin polymer with a dissociation constant of 301 +/- 36 nM in a manner which is independent of the enzyme active site. Studies of thrombin binding as a function of heparin and fibrin polymer concentrations imply that a ternary thrombin-fibrin polymer-heparin complex (IIa.FnIIp.H) is formed. Assembly of the ternary complex occurs randomly through the interactions of all three possible intermediate binary complexes; IIa.H, IIa.FnIIp, and FnIIp.H. Using an independently determined value of 280 +/- 35 nM for the FnIIp.H dissociation constant, global fits of the binding data yield a dissociation constant of 15 +/- 6 nM for the IIa.H interaction and 47 +/- 9 nM for the IIa.H intermediate binary complex interaction with FnIIp. These studies indicate that heparin enhances the binding of thrombin to fibrin polymer 6.4-fold with an overall dissociation constant for ternary complex formation of 705 nM2. The effect of heparin molecular weight on ternary complex formation has also been investigated. Heparins of molecular weights 11,200-20,300 behave similarly with respect to their influence on ternary complex formation, whereas heparins of lower molecular weight are less effective in promoting thrombin binding to fibrin polymer. This effect of heparin is also independent of whether it has high or low affinity for antithrombin III. The demonstration of the formation of a ternary IIa.FnIIp.H complex complements kinetic evidence indicating the formation of an analogous ternary complex with fibrin II monomer (Hogg, P. J., and Jackson, C. M. (1989) Proc. Natl. Acad. Sci. U. S. A. 86, 3619-3623). The possible implications of these findings for the in vivo distribution and actions of thrombin and the clinical efficacy of heparin are also discussed.

Antithrombin III↗

PubMed1989

Abnormalities of pathways of fibrin turnover in lung lavage of rats with oleic acid and bleomycin-induced lung injury support alveolar fibrin deposition.

Alveolar fibrin deposition commonly accompanies acute lung injury, but the nature of the local abnormalities of coagulation and fibrinolysis that support pathologic fibrin deposition are not well understood. The trended abnormalities of procoagulant and fibrinolytic activities occurring in lung lavage fluids of Fischer 344 rats after lung injury induced by intravenous oleic acid (OA) or intratracheal bleomycin were studied. After injury by either agent, bronchoalveolar lavage (BAL) contained increased procoagulant activity and decreased fibrinolytic activity. Lavage procoagulant activity was mainly due to an activator of Factor X attributable to the extrinsic coagulation pathway, and fibrinolytic activity was almost completely plasminogen dependent. Major mechanisms of inhibition of fibrinolytic activity involved both the inhibition of the plasminogen activator (PA) and plasmin. These abnormalities were temporally associated with prominent alveolar fibrin deposition in both models. In OA-treated animals, lavage fibrinolytic activity was absent or profoundly decreased, and antiplasmin and procoagulant activities were increased within 4 hours after the induction of acute lung injury. By 24 hours after OA, lavage PA inhibitor (PAI) activity was elevated with sustained antiplasmin activity. By 3 days after OA, these abnormalities had resolved in association with almost complete resolution of alveolar fibrin deposits. Within 3 days after bleomycin-induced lung injury, lavage procoagulant activity was increased and fibrinolytic activity was depressed due to increased antiplasmin and PAI activities. These conditions persisted for 2 weeks, during which time alveolar fibrin deposition was associated with the development of pulmonary fibrosis. These data indicate that a disruption of the normal balance between procoagulant and fibrinolytic activities occurs in alveolar lining fluids of rats with alveolitis induced by either OA or bleomycin, and that concurrent abnormalities of pathways of fibrin turnover that occur in alveolar lining fluids promote the alveolar fibrin deposition associated with these lung injuries.

Animals↗

PubMed1988

The binding sites on fibrin(ogen) for guinea pig liver transglutaminase are similar to those of blood coagulation factor XIII. Characterization of the binding of liver transglutaminase to fibrin.

The present study represents detailed investigations into the nature of interactions between an intracellular "tissue" transglutaminase and a plasma protein, fibrinogen. We demonstrate a specific, saturable, and reversible binding of transglutaminase to fibrin(ogen). The binding was time- and temperature-dependent, was independent of divalent metal ions, did not require the release of either fibrinopeptide A or B, and was partially inhibited by the presence of sodium chloride or plasma proteins, properties similar to Factor XIII binding to fibrin(ogen). Both Factor XIII and liver transglutaminase also shared similar binding sites on fibrinogen, the A alpha- and the B beta-chains. The binding characteristics of liver transglutaminase were thus similar to Factor XIII binding to fibrin, but there were also important differences. Scatchard analyses of the binding data indicated that the affinity of liver transglutaminase (Kd = 4.17 x 10(-7) M) was at least 40-fold weaker compared with the affinity of Factor XIII to fibrinogen. Consequently, a 20-fold molar excess of Factor XIII a-chains specifically and completely inhibited the binding of liver transglutaminase to des-A-fibrinogen. The association between liver transglutaminase and fibrin(ogen) was also critically controlled by the conformational states of the two proteins. Substances capable of altering the conformation of either transglutaminase (such as guanosine 5'-triphosphate) or of fibrinogen (such as the tetrapeptide Gly-Pro-Arg-Pro and Fragment D) disrupted binding. Excess CaCl2 was able to counteract the effects of guanosine 5'-triphosphate on transglutaminase binding to fibrin. In contrast, Factor XIII binding to fibrin was unaffected by either guanosine 5'-triphosphate, CaCl2, or Gly-Pro-Arg-Pro, suggesting a more stable association between the two proteins. The physiologic implications of transglutaminase-fibrin(ogen) interactions are discussed.

Animals↗

PubMed1996

A monoclonal antibody that recognizes a neo-antigen exposed in the E domain of fibrin monomer complexed with fibrinogen or its derivatives: its application to the measurement of soluble fibrin in plasma.

Using urea-solubilized human fibrin monomer as an immunogen, we raised in mice a battery of monoclonal antibodies that reacted with the immunogen but not with urea-treated or native fibrinogen. Although they all failed to react with acid-solubilized fibrin monomer (acid-FM) alone, an antibody designated as IF-43 was found to recognize acid-FM, which was bound with fibrinogen or its derivatives to form a 1:2 complex of soluble fibrin. The epitope for this antibody, thus, appears to be exposed most probably by conformation changes induced in the acid-FM molecule upon formation of the complex. Because IF-43 was able to recognize fibrin-derived plasmic fragment E treated with urea but not the thrombin- and urea-treated amino-terminal disulfide knot of fibrinogen, the presence of the A alpha (52-78) residue segment seems to be prerequiste for the epitope expression. The antibody was found to react with soluble fibrin monomer spiked to normal plasma dose-dependently up to 200 micrograms/mL. By an aggregation assay using latex beads coated with IF-43, we found that concentrations of soluble fibrin monomer in plasma derived from patients with thrombotic diseases were mostly elevated, but not necessarily correlated with those of the D-dimer, reflecting another aspects of the disease. Furthermore, the soluble fibrin monomer in plasma derived from patients with thrombotic diseases was found to be depleted solely of the A peptides, but not the B peptides, based on its subunit polypeptide compositions lacking the beta-chain on immunoblotting.

Animals↗

PubMed2025

Autologous Fibrin Glue in Pterygium Surgery as an Alternative to Commercial Fibrin Glue.

PURPOSE: The aim of this study was to evaluate the efficacy and safety of autologous fibrin glue in pterygium surgery, comparing it with commercial fibrin glue in terms of postoperative complications, graft stability, and recurrence rate. METHODS: A prospective, randomized, double-blind study was conducted, involving 42 patients with primary pterygium who underwent autologous conjunctival-limbal transplantation. The graft was fixed using autologous fibrin glue (Group 1, G1) or commercial fibrin glue (Group 2, G2). All patients underwent surgery performed by the same surgeon and were reevaluated on postoperative days 7, 30, 90, and 180 by an independent observer, assessing clinical parameters in the preoperative, intraoperative, and postoperative periods. RESULTS: No cases of severe adverse events were reported. Complete graft dehiscence occurred in 1 patient from G1. The G2 group had more cases of subconjunctival hemorrhage ( P = 0.0355). Pyogenic granuloma was observed in 1 patient from G2 and 2 patients from G1. There was no significant difference in recurrence rates between the groups (15% in G1 vs. 5% in G2; P = 0.2918). In both groups, graft dimensions tended to decrease slightly in the early postoperative period, followed by stabilization. CONCLUSIONS: Autologous fibrin glue demonstrated efficacy and safety comparable to commercial fibrin glue, making it a viable alternative to conjunctival graft fixation in primary pterygium surgery.

Humans↗

PubMed1986

Plasminogen activator content of human tumor and adjacent normal tissue measured with fibrin and non-fibrin assays.

Plasminogen activators are enzymes which convert the zymogen to plasmin, the physiological enzyme for dissolving fibrin. There are two different physiological activator enzymes, urokinase (UK) and tissue plasminogen activator (t-PA, also known as vascular activator). The most striking difference in the behavior of the two activators is the ability of fibrin to augment the activity of t-PA but not of UK. Since tumor and normal tissues have been shown to contain different ratios of UK:t-PA, it can be anticipated that their comparative activator activities measured with fibrinolytic assays would yield different results from those measured with non-fibrin tests. This study was designed to test the validity of earlier conclusions that: (a) the measured activity of t-PA is augmented in fibrinolytic assays when compared with a non-fibrin assay based on azocaseinolysis; and (b) this difference could explain the failure of some laboratories using fibrinolytic assays to detect a difference in activator activity between tumor and normal tissues or to find more activity in the normal tissue. Azocaseinolytic and fibrinolytic (fibrin plate) assays were used to measure activator activity in a series of 14 normal-tumor tissue pairs. Using azocasein tests, cancer tissues were found to contain significantly higher median activities than normal tissues [Wilcoxon test, P less than 0.05; 13.8 versus 3.7 Committee on Thrombolytic Agents (CTA) units/g tissue, respectively], whereas no significant difference was found with fibrin assays (43.5 versus 69.0 CTA units/g tissue, respectively). Of total activator activity, the median percentage of UK was significantly higher in tumor (95%) than in normal tissue (58%). In addition, using azocaseinolysis it was found that the median UK activity was significantly higher in tumor (12.1 CTA units/g) relative to normal (3.51 CTA units/g) tissues, whereas no difference was found for t-PA. To explain these results in tumor and normal tissues, a mathematical model was derived to describe the difference between azocasein and fibrin assays for both purified plasminogen activator enzymes and activator enzymes in tissue extracts. The model fits the data well, confirming in a quantitative manner the hypotheses of the study. In addition, the study revealed that the azocaseinolytic assay was able to measure the full potential activator activity of purified pro-urokinase enzyme. Pro-urokinase activity could not be measured with standard fibrinolytic assays. These results show the importance of selection and interpretation of plasminogen activator assays in studies dealing with malignant transformation.

Caseins↗

PubMedDate not supplied

Fibrin glue alone and skeletal myoblasts in a fibrin scaffold preserve cardiac function after myocardial infarction.

Current efforts in cardiac tissue engineering center around the use of scaffolds that deliver cells to the epicardial surface. In this study, we examined the effects of fibrin glue as an injectable scaffold and wall support in ischemic myocardium. The left coronary artery of rats was occluded for 17 min, followed by reperfusion. Echocardiography was performed 8 days after infarction. One to 2 days later, either 0.5% bovine serum albumin (BSA) in phosphate-buffered saline, fibrin glue alone, skeletal myoblasts alone, or skeletal myoblasts in fibrin glue were injected into the ischemic left ventricle. Echocardiography was again performed 5 weeks after injection. The animals were then sacrificed and the hearts were fresh frozen and sectioned for histology and immunohistochemistry. Both the fractional shortening (FS) and infarct wall thickness of the BSA group decreased significantly after 5 weeks (p = 0.0005 and 0.02, respectively). In contrast, both measurements for the fibrin glue group, cells group, and cells in fibrin glue group did not change significantly (FS: p = 0.18, 0.89, and 0.19, respectively; wall thickness: p = 0.40, 0.44, 0.43, respectively). Fibrin glue is capable of preserving infarct wall thickness and cardiac function after a myocardial infarction in rats and may be useful as a biomaterial scaffold for myocardial cell transplantation.

Animals↗

PubMed2004

Use of soluble fibrin antigen instead of D-dimer as fibrin-related marker may enhance the prognostic power of the ISTH overt DIC score.

The overt DIC score of the DIC subcommittee of the ISTH includes a fibrin-related marker (FRM) as indicator of intravascular fibrin formation. The type of marker to be used has not been specified, but D-dimer antigen, or fibrin degradation products are used by most investigators. Soluble fibrin complexes have been suggested as more specific indicators of acute intravascular fibrin formation. The aim of the present study was to compare the predictive value of the overt DIC score concerning clinical outcome in a surgical intensive care cohort, using either D-dimer antigen, or soluble fibrin antigen as FRM. The cutoff values for 2 and 3 score points for the FRM were assigned on the basis of the 25% and 75% quartiles of 1870 plasma samples obtained from 359 ICU patients during a period of 6 months. For 331 patients with complete diagnostic workup and day 1 blood samples, the Iatro SF as FRM component of the overt DIC score displayed the highest prognostic power concerning clinical outcome. The 28-day mortality of patients with overt DIC at day 1, using Iatro SF as FRM assay was 50.0%, whereas 28-day mortality of patients without overt DIC was 14.0% (p <0.0001). Using MDA D-dimer, and TINAquant D-dimer, 28-day mortality was between 35.5% and 39.3% in patients with overt DIC, and 15.5% to 15.6% in patients without overt DIC. Selection of the FRM as component of the DIC score has a small, but relevant impact on the prognostic performance of the overt DIC score. The present data on the distribution of values may provide a basis for the selection of appropriate cutoff points for assigning 2, and 3 points in the score.

Adolescent↗

PubMed1976

Detection of soluble intermediates of the fibrinogen-fibrin conversion using erythrocytes coated with fibrin monomers.

The presence of minimal amounts of fibrinogen-fibrin intermediates in human plasma was visualized by an agglutination reaction of glutaraldehyde-treated human erythrocytes coated with purified fibrin monomers. A degree of monomer coating was established which produced erythrocytes not agglutinated by normal plasma but by plasma containing minimal amounts of soluble complexes of fibrinogen with fibrin monomers. Under standardized conditions of coating, erythrocyte concentration, temperature, pH, and incubation time, the agglutination time varied with the ratio of soluble fibrin to fibrinogen in plasma. The test was sensitive down to a soluble fibrin concentration of 0.675% of the plasma fibrinogen concentration. Early fibrinogen and fibrin degradation products (FDP) in the plasma led to a prolongation of the agglutination time at a concentration of more than 16 mg/100 ml. Late FDP in a concentration of 100 mg/100 ml did not convert a positive test to negative. The test was not affected by heparin and protamine at concentrations of up to 12.5 and 50 NIH units/ml, respectively.

Batroxobin↗

PubMed1986

Fibrinogen, fibrin and fibrin degradation products in relation to atherosclerosis.

Many human atherosclerotic lesions, showing no evidence of fissure or ulceration, contain a large amount of fibrin which may be in the form of mural thrombus on the intact surface of the plaque, in layers within the fibrous cap, in the lipid-rich centre, or diffusely distributed throughout the plaque. Small mural thrombi are invaded by SMCs and collagen is deposited in patterns closely resembling the early proliferative gelatinous lesions. In experimental animals, thrombi are converted into lesions with all the characteristics of fibrous plaques, and in saphenous-vein bypass grafts, fibrin deposition is the main cause of wall thickening and occlusion. There seems little doubt that fibrin deposition can both initiate atherogenesis and contribute to the growth of plaques. Epidemiological studies indicate that increased levels of fibrinogen and clotting activity are associated with accelerated atherosclerosis, and although blood fibrinolytic activity has given inconsistent results, in arterial intima both fibrinolytic activity and plasminogen concentration are decreased in cardiovascular disease. Fibrin may stimulate cell proliferation by providing a scaffold along which cells migrate, and by binding fibronectin, which stimulates cell migration and adhesion. Fibrin degradation products, which are present in the intima, may stimulate mitogenesis and collagen synthesis, attract leukocytes, and alter endothelial permeability and vascular tone. In the advanced plaque fibrin may be involved in the tight binding of LDL and accumulation of lipid. Thus there is extensive evidence that enhanced blood coagulation is a risk factor not only for thrombotic occlusion, but also for atherogenesis. Enhanced blood coagulation frequently coexists with hyperlipidaemia and, together, these may have a synergistic effect on atherogenesis.

Animals↗

PubMed1984

Fibrin-mediated vascular injury: demonstration of vascular endothelial cell retraction in response to soluble fibrin-associated factors.

Until recently, fibrin deposition has been generally viewed as a ubiquitous, but passive, characteristic of both acute and chronic inflammatory processes. An increasing number of studies, however, suggest that fibrin deposition and fibrin degradation products may play an active role in these reactions, especially in the development of tissue edema. As the intravascular-to-extravascular "gateway" for movement of fluids, solutes, and cells must pass, the vascular endothelial cells may play a crucial regulatory role in this process. Recent evidence suggests that the interaction of whole fibrin with endothelial cells may lead to endothelial cell injury. This work examines the role of fibrin and fibrinogen-associated factors (FAF) in the injury of cultured vascular endothelial cells (VEC). It was demonstrated that endothelial cell injury, evidenced by retraction of the cells, was induced not only by whole fibrin, but also by soluble thrombin-cleaved products of fibrinogen. This reaction was shown to be specific for endothelial cells, nontoxic, and completely reversible. The general biological importance of this reaction was further underscored in that active factors could be generated from fibrinogen obtained from a number of species. Reproducible, quantitative assays of cultured endothelial cell retraction were developed to aid in the characterization of the endothelial cell-specific FAFs.

Animals↗

PubMed1981

Cross-linking of alpha 2-plasmin inhibitor and fibronectin to fibrin by fibrin-stabilizing factor.

Two plasma proteins, alpha 2-plasmin inhibitor and plasma fibronectin, are cross-linked to fibrin by plasma transglutaminase (R-glutaminyl-peptide : amine gamma-glutamyl-yltransferase, EC 2.3.2.13, fibrin stabilizing factor) when blood coagulation takes place. The cross-linking reactions of these proteins were analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS) using these radioactively labeled proteins. Both proteins were cross-linked exclusively to the alpha-chain of fibrin, and each of these cross-linking reactions proceeded independently without being influenced by the other cross-linking reaction. The cross-linking of fibronectin to the alpha-chain proceeded steadily at a rate similar to that of the cross-linked polymerization of the alpha-chain. In contrast, the cross-linking reaction of alpha2-plasmin inhibitor to fibrin proceeded markedly faster than that of fibrin polymerization but did not proceed further after reaching a certain relatively low level of cross-linking. Most of the cross-linked alpha 2-plasmin inhibitor molecules at this stage of the fibrin cross-linking were in the form of complex with the alpha-chain monomer. The complex with the alpha-chain monomer was gradually transformed to a complex with the alpha-chain polymer as the cross-linking polymerization of the alpha chain proceeded. The rate of the transformation was the same as that for the disappearance of the alpha-chain monomer, indicating that whether the alpha-chain was cross-linked to alpha 2-plasmin inhibitor or not, the alpha-chain underwent cross-linking polymerization at the same rate.

Blood Coagulation↗

PubMed1980

Significance of tryptophan residues in the D-domain of the fibrin molecule in fibrin polymer formation.

The modification of fibrin monomer with H2O2 caused reduction of the association activity of fibrin monomer. The association activity was not reduced even by modification of approx. 16 out of the total 64 tryptophan residues in the fibrin molecule; it was then abolished by further modification of the following several residues. Fragment D obtained by proteolysis of fibrinogen with plasmin, inhibited the association activity of fibrin monomer and the modification of approx. six out of the total 21 tryptophan residues in the fragment led to the complete loss of the inhibitory effect. It was concluded from these studies that about six tryptophan residues in the D-domain of fibrin are important for the association of fibrin monomer.

Chemical Phenomena↗

PubMed1984

The enhanced activation of Glu-plasminogen by urokinase in the presence of fibrin or des A fibrin as measured by the release of B beta peptide and FDP.

Fresh plasma was incubated either with urokinase (UK) alone or the mixture of UK and human thrombin or Reptilase. In a purified system Glu-plasminogen (Glu-plg) was incubated with fibrinogen or fibrinogen plus thrombin in the presence of UK. At intervals, aprotinin was added to stop the reactions and the amounts of B beta peptide and fibrin(ogen) degradation products (FDP, FgDP) were measured by radioimmunoassay and enzyme immunoassay, respectively. Results obtained by using plasma showed that fibrin was degraded faster than fibrinogen upon the addition of UK to the plasma or plasma clotted with thrombin. B beta peptide was released faster from the clot than plasma. The clot formation caused by Reptilase (release of fibrinopeptide A) was accompanied by increase in the release of B beta 1-42 from des A fibrin (fibrin without fibrinopeptide A). In a purified system, fibrin was degraded faster than fibrinogen upon the activation of Glu-plg by UK. These results may correlate well with the observation that Glu-plg was activated better by UK in the presence of fibrin than fibrinogen.

Aprotinin↗

PubMed1994

Fibrin-bound lipoprotein(a) promotes plasminogen binding but inhibits fibrin degradation by plasmin.

Conflicting results have been obtained from studies of the effects of lipoprotein(a) [Lp(a)] on plasminogen binding to fibrin and fibrin-dependent activation by tissue plasminogen activation (t-PA). We performed binding studies of Glu-plasminogen (0-16 microM) to immobilized D-dimer +/- Lp(a) (0.20 microM). In the absence of Lp(a), Scatchard analysis revealed a binding constant of KD = 1.01 +/- 0.18 microM, with two plasminogen binding sites per D-dimer. In the presence of Lp(a), a lower affinity (KD 3.10 +/- 0.23 microM) was found, but five binding sites were present, suggesting that plasminogen bound to fibrin-bound Lp(a) rather than to D-dimer. Consistent with this explanation was the finding that when D-dimer-coated plates were first precoated with Lp(a) before plasminogen was added, similar lower affinity plasminogen binding was found. This binding to Lp(a) was fibrin-dependent since, in its absence, plasminogen failed to bind to Lp(a). Therefore, a conformational change in Lp(a) appeared to be required for plasminogen binding to occur. This finding of two types of binding sites of different affinities helps to explain why Lp(a) has been reported to inhibit plasminogen binding to fibrin in studies in which only low concentrations of plasminogen (< 0.4 microM) were used. At these concentrations, few of the low-affinity binding sites on fibrin-bound Lp(a) will be occupied by plasminogen, an effect that was found to be exaggerated by the omission of NaCl.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed2002

Interaction of fibrin(ogen) with the endothelial cell receptor VE-cadherin: mapping of the receptor-binding site in the NH2-terminal portions of the fibrin beta chains.

Interaction of fibrin with endothelial cells stimulates capillary tube formation thus promoting angiogenesis. This interaction occurs via endothelial cell receptor VE-cadherin and fibrin beta chain 15-42 regions [Bach, T. L., et al. (1998) J. Biol. Chem. 272, 30719-30728]. To clarify the mechanism of this interaction, we expressed in Escherichia coli a number of recombinant fibrin(ogen) fragments containing the beta15-42 region or the VE-cad(1-2) and VE-cad(1-4) fragments encompassing two and four extracellular NH2-terminal domains of VE-cadherin, respectively, and tested interaction between them by surface plasmon resonance and ELISA. Neither the recombinant Bbeta1-57 or Bbeta1-64 fragments, nor beta15-57 or beta15-64 prepared from the latter fragments by thrombin treatment to remove fibrinopeptides B, bound the recombinant VE-cadherin fragments. At the same time, a dimeric recombinant thrombin-treated (beta15-66)2 fragment, which had been disulfide-linked via Cys65 to mimic the dimeric arrangement of the beta chains in fibrin, bound VE-cad(1-4) well, but not VE-cad(1-2); no binding was observed with the untreated (Bbeta1-66)2 dimer. We next mutated several residues in the dimer, His16, Arg17, Pro18, and Asp20, and tested the interaction of the thrombin-treated mutants with VE-cad(1-4) by ligand blotting and surface plasmon resonance. No binding was observed with the H16A and R17Q single mutants and the H16P, P18V double mutant while the P18A and D20N single mutants bound VE-cad(1-4) with the same affinity as the thrombin-treated wild-type dimer. These results indicate that the VE-cadherin binding site in fibrin includes NH2-terminal regions of both fibrin beta-chains, that His16 and Arg17 are critical for the binding, and that the third and/or fourth extracellular domains of VE-cadherin are required for the binding to occur.

Amino Acid Sequence↗

PubMed2004

Differential effect of calcium phosphate and calcium pyrophosphate on binding of matrix metalloproteinases to fibrin: comparison to a fibrin-binding protease from inflammatory joint fluids.

The ability of calcium phosphate (CaP) and calcium pyrophosphate (CaPPi) to mediate matrix metalloproteinase-2 and -9 (MMP-2 and MMP-9) binding to fibrin was evaluated. Substrate gel electrophoresis (gelatin zymography) revealed that CaP bound MMP-2 and MMP-9, forming a high molecular weight aggregate with lowered electrophoretic mobility. Formation of the CaP : MMP aggregate was necessary for fibrin binding. In contrast, CaPPi did not aggregate MMPs and did not promote uptake of MMPs into fibrin. Scatchard analysis (Ca/P ratio) revealed that CaPPi (1.96) was chemically similar to calcium pyrophosphate dihydrate (2.00) compared to amorphous CaP (1.50) or crystalline CaP, hydroxyapatite (1.66). MMP : CaP interaction appeared to be electrostatic in nature as high salt concentration (NaCl > 150 mm) reduced binding. In contrast, two non-ionic detergents (Brij-35 and Tween-20) did not prevent MMP : CaP binding. MMP : CaP interaction did not involve the C-terminal MMP region because the specific tissue inhibitor of metalloproteinases (TIMPs) also did not block MMP : CaP interaction and fibrin binding. Although MMP : CaP binding could be decreased with albumin, this effect appeared non-specific due to the high albumin concentration required. High albumin concentration could also partially dissociate preformed MMP : CaP complexes. Interestingly, type I and type IV collagen substantially increased MMP : fibrin-binding activity, whereas denatured collagen, gelatin, did not. Inflammatory joint fluid from five patients also demonstrated similar MMP fibrin-binding activity consistent with CaP mediation. The relevance of these findings to CaP and CaPPi in the pathogenesis of crystal arthropathies such as basic calcium phosphate (BCP) and calcium pyrophosphate dihydrate crystal disease (CPPD) is discussed.

Adult↗

PubMed1977

Cross-linking of actin and fibrin by fibrin-stabilizing factor.

Fibrin-stabilizing factor is known to cross-link fibrin monomers. This study was undertaken to explore whether a similar interaction might occur between actin and fibrin. Purified actin and fibrinogen were labeled with 131I and 125I, respectively. The interaction of actin and fibrin, under different conditions, was evaluated by gel electrophoresis. The data show that actin and fibrin are cross-linked in the presence of fibrin-stabilizing factor.

Actins↗