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Bungay2003_Thrombin_Generation

ABSTRACT: This model is from the article: A mathematical model of lipid-mediated thrombin generation Bungay Sharene D., Gentry Patricia A., Gentry Rodney D. Mathematical Medicine and BiologyVolume 20, Issue 1, 1 March 2003, Pages 105-29 12974500, Abstract: Thrombin is an enzyme that is generated in both vascular and non-vascular systems. In blood coagulation, a fundamental process in all species, thrombin induces the formation of a fibrin clot. A dynamical model of thrombin generation in the presence of lipid surfaces is presented. This model also includes the self-regulating thrombin feedback reactions, the thrombomodulin-protein C-protein S inhibitory system, tissue factor pathway inhibitor (TFPI), and the inhibitor, antithrombin (AT). The dynamics of this complex system were found to be highly lipid dependent, as would be expected from experimental studies. Simulations of this model indicate that a threshold lipid level is required to generate physiologically relevant amounts of thrombin. The dependence of the onset, the peak levels, and the duration of thrombin generation on lipid was saturable. The lipid concentration affects the way in which the inhibitors modulate thrombin production. A novel feature of this model is the inclusion of the dynamical protein C pathway, initiated by thrombin feedback. This inhibitory system exerts its effects on the lipid surface, where its substrates are formed. The maximum impact of TFPI occurs at intermediate vesicle concentrations. Inhibition by AT is only indirectly affected by the lipid since AT irreversibly binds only to solution phase proteins. In a system with normal plasma concentrations of the proteins involved in thrombin formation, the combination of these three inhibitors is sufficient both to effectively stop thrombin generation prior to the exhaustion of its precursor, prothrombin, and to inhibit all thrombin formed. This model can be used to predict thrombin generation under extreme lipid conditions that are difficult to implement experimentally and to examine thrombin generation in non-vascular systems. This model originates from BioModels Database: A Database of Annotated Published Models (http://www.ebi.ac.uk/biomodels/). It is copyright (c) 2005-2011 The BioModels.net Team. For more information see the terms of use. To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.

SUBMITTER: Harish Dharuri

PROVIDER: BIOMD0000000334 | BioModels | 2024-09-02

REPOSITORIES: BioModels

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A mathematical model of lipid-mediated thrombin generation.

Bungay Sharene D SD Gentry Patricia A PA Gentry Rodney D RD

Mathematical medicine and biology : a journal of the IMA 20030301 1

Thrombin is an enzyme that is generated in both vascular and non-vascular systems. In blood coagulation, a fundamental process in all species, thrombin induces the formation of a fibrin clot. A dynamical model of thrombin generation in the presence of lipid surfaces is presented. This model also includes the self-regulating thrombin feedback reactions, the thrombomodulin-protein C-protein S inhibitory system, tissue factor pathway inhibitor (TFPI), and the inhibitor, antithrombin (AT). The dynam ...[more]

PMID: 12974500

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Project description:This model is from the article: A model for the stoichiometric regulation of blood coagulation. Hockin MF, Jones KC, Everse SJ, Mann KG. Journal of Biological ChemistryVolume 277, Issue 21, 24 May 2002, Pages 18322 -18333 11893748, Abstract: We have developed a model of the extrinsic blood coagulation system that includes the stoichiometric anticoagulants. The model accounts for the formation, expression, and propagation of the vitamin K-dependent procoagulant complexes and extends our previous model by including: (a) the tissue factor pathway inhibitor (TFPI)-mediated inactivation of tissue factor (TF).VIIa and its product complexes; (b) the antithrombin-III (AT-III)-mediated inactivation of IIa, mIIa, factor VIIa, factor IXa, and factor Xa; (c) the initial activation of factor V and factor VIII by thrombin generated by factor Xa-membrane; (d) factor VIIIa dissociation/activity loss; (e) the binding competition and kinetic activation steps that exist between TF and factors VII and VIIa; and (f) the activation of factor VII by IIa, factor Xa, and factor IXa. These additions to our earlier model generate a model consisting of 34 differential equations with 42 rate constants that together describe the 27 independent equilibrium expressions, which describe the fates of 34 species. Simulations are initiated by "exposing" picomolar concentrations of TF to an electronic milieu consisting of factors II, IX, X, VII, VIIa, V, and VIIII, and the anticoagulants TFPI and AT-III at concentrations found in normal plasma or associated with coagulation pathology. The reaction followed in terms of thrombin generation, proceeds through phases that can be operationally defined as initiation, propagation, and termination. The generation of thrombin displays a nonlinear dependence upon TF, AT-III, and TFPI and the combination of these latter inhibitors displays kinetic thresholds. At subthreshold TF, thrombin production/expression is suppressed by the combination of TFPI and AT-III; for concentrations above the TF threshold, the bolus of thrombin produced is quantitatively equivalent. A comparison of the model with empirical laboratory data illustrates that most experimentally observable parameters are captured, and the pathology that results in enhanced or deficient thrombin generation is accurately described.

Project description:Tissue Factor Pathway Inhibitor-2 is Induced by Fluid Shear Stress in Vascular Smooth Muscle Cells and Affects Cell Proliferation and Survival Introduction: Vascular smooth muscle cells (SMCs) are exposed to fluid shear stress (FSS) after interventional procedures such as balloon-angioplasty. Whereas the effects of hemodynamic forces on endothelial cells are explored in detail, the influence of FSS on smooth muscle cell function is poorly characterized. Here, we investigated the effect of FSS on SMC gene expression and function. Methods: Laminar FSS of arterial level (14 dynes/cm2) was applied to SMC cultures for 24 h in a parallel-plate flow chamber. The effect of FSS on gene expression was first screened with microarray technology and the results further verified by real time (RT) PCR and immunoblotting. Protein expression was also studied in the rat carotid artery after balloon-injury and DNA synthesis and apoptosis was examined in SMCs in vitro. Results: Microarrays identified tissue-pathway inhibitor-2 (TFPI-2) as the most differentially expressed gene by FSS in cultured SMCs. The regulatory effect of FSS on the expression of TFPI-2 was confirmed by RT-PCR and immunobloting demonstrating a more than 400-fold increase in TFPI-2 expression in SMCs exposed to FSS compared to static controls and a consistent upregulation at the protein level. Functionally, SMC proliferation was decreased by FSS and recombinant TFPI-2 was found to inhibit SMC proliferation and induce SMC apoptosis as indicated by activation of caspase-3. In vivo, TFPI-2 expression was found to be up-regulated 5, 10 and 20 h after rat carotid balloon-injury and immunohistochemistry demonstrated TFPI-2 protein in luminal SMCs exposed to FSS in rat carotid intimal hyperplasia 10 days after balloon-injury. Conclusion: FSS strongly influence gene expression in cultured SMCs and induce TFPI-2 expression, which is also expressed after rat carotid balloon injury in luminal SMCs exposed to FSS. Functionally, TFPI-2 may play an important role in vessel wall repair by regulating SMC proliferation and survival. Further studies are needed to elucidate the mechanisms by which TFPI-2 control SMC function. 3 x 2 samples from a paired fluid shear stress experiment on smooth muscle cells.

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Project description:Cysteinyl leukotrienes (cysLT), i.e. LTC4, LTD4, and LTE4, are lipid mediators derived from the 5-lipoxygenase pathway. The cysLT receptors cysLT1-R and cysLT2-R are expressed on different target cells and mediate inflammatory reactions in tissue- and LT-R-specific ways. Though endothelial cells (ECs) predominantly express cysLT2-Rs, their role in vascular biology remains to be defined. To delineate cysLT2-RÂ´s action, we stimulated human umbilical vein EC with 100 nM LTD4 for 60 min, determined gene signatures by microarrays, and characterized the resulting EC phenotypes. As controls, we compared LTD4-induced genes with those induced by 10 nM thrombin, a prototype vasoactive activator of EC that binds to protease-activated receptor 1 (PAR-1). Following application of stringent filters 37 LTD4-upregulated genes were identified (> 2.5fold stimulation). Surprisingly, most of the LTD4-regulated genes were also induced by thrombin and expression of cysLT2-R- and PAR-1-regulated genes strongly correlated (Pearson correlation coefficient: r = 0.90). Moreover, LTD4 + thrombin, when added together, augmented expression of LTD4- or thrombin-stimulated genes (Wilcoxon signed rank test: p < 0.01). Prominently induced genes that may play roles in vascular injury were studied in detail: Early growth response (EGR) and nuclear receptor subfamily 4 group A; E-selectin; CXC ligand 2; interleukin 8 (IL-8); a disintegrin-like and metalloprotease (reprolysin type) with thrombospondin type 1 motif 1 (ADAMTS-1); and tissue factor (TF). Transcripts of these genes peaked at approximately 60 min, were unaffected by the cysLT1-R antagonist montelukast, and were superinduced by cycloheximide. The EC phenotype was markedly altered: LTD4 induced de novo synthesis of EGR1 protein and EGR1 localized in the nucleus in LTD4-stimulated cells; LTD4 upregulated IL-8 formation and secretion; and LTD4 raised TF protein and TF-dependent EC pro-coagulant activity. These data show that cysLT2-R activation results in a pro-inflammatory EC phenotype through activation of immediate-early genes that resemble those induced by PAR-1. As LTD4 and thrombin are formed concomitantly during vascular injury and pro-thrombotic states, cysLT2-R and PAR-1 may collaborate in vivo to mediate vascular injury and repair. Experiment Overall Design: HUVEC in passage 1 were cultured in serum-free EC medium until cells reached confluency. HUVEC were stimulated by 100 nM LTD4 (n = 4) or 10 nM thrombin (n = 4) or both agonists concomitantly (n = 3). The immediate-early gene programs of these experimental groups were identified at 60 minutes. In addition, one HUVEC preparation was stimulated with 100 nM LTD4 for 6 h and 24 h.

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