fibrin and Activated-Protein-C-Resistance

We investigated the link between the mRNA of the procoagulant prothrombin in the placental tissue with the increased placental fibrin deposition associated with activated protein C resistance (APCR). Women with APCR were not found to produce higher levels of prothrombin transcript compared to women with a normal APC ratio. This indicates that accumulated fibrin in the placenta is not the consequence of too much production of the procoagulant prothrombin transcript, but may be associated with altered function of other haemostatic factors interacting with APC in the placenta.

Topics: Activated Protein C Resistance; Adult; Female; Fibrin; Hemostasis; Humans; Placenta; Pregnancy; Prothrombin; RNA, Messenger

The process of human blood clotting involves a complex interaction of continuous-time/continuous-state processes and discrete-event/discrete-state phenomena, where the former comprise the various chemical rate equations and the latter comprise both threshold-limited behaviors and binary states (presence/absence of a chemical). Whereas previous blood-clotting models used only continuous dynamics and perforce addressed only portions of the coagulation cascade, we capture both continuous and discrete aspects by modeling it as a hybrid dynamical system. The model was implemented as a hybrid Petri net, a graphical modeling language that extends ordinary Petri nets to cover continuous quantities and continuous-time flows. The primary focus is simulation: (1) fidelity to the clinical data in terms of clotting-factor concentrations and elapsed time; (2) reproduction of known clotting pathologies; and (3) fine-grained predictions which may be used to refine clinical understanding of blood clotting. Next we examine sensitivity to rate-constant perturbation. Finally, we propose a method for titrating between reliance on the model and on prior clinical knowledge. For simplicity, we confine these last two analyses to a critical purely-continuous subsystem of the model.

Topics: Activated Protein C Resistance; Algorithms; Blood Coagulation; Blood Coagulation Factors; Computational Biology; Computer Simulation; Fibrin; Hemophilia A; Humans; Kinetics; Models, Biological; Models, Statistical; Protein Binding; Prothrombin Time; Systems Biology; Thrombin

Activated protein C resistance (APCR) results in an ineffective anticoagulant response leading to an increased risk of thrombosis, particularly during pregnancy. Adverse pregnancy outcomes including pre-eclampsia (PET), intrauterine growth restriction (IUGR), recurrent miscarriage and placental abruption have been linked with thrombotic lesions compromising the utero-placental circulation. Using histological staining including Martius Scarlet Blue (MSB) and Haematoxylin and Eosin (H&E) and microscopy, we studied placental fibrin deposition and histological abnormalities in subjects (n=23) with APCR (APCR group), based on a ratio of less than or equal to 2.1s with the Coatest classic test and subjects (n=11) with an APC ratio in the normal range, greater than 2.1s (APCN group). Fibrin deposition was significantly higher (3.3-fold) in the APCR group compared to the APCN group. An inverse correlation between APC ratio and placental fibrin deposition was determined for the study group. Histological abnormalities were more than 2-fold higher in the APCR group compared to the APCN group. Molecular screening identified common thrombophilic mutations, FVL and FII-G20210A in the APCR group but not in the APCN group.

Topics: Activated Protein C Resistance; Female; Fibrin; Humans; Placenta; Pregnancy; Thrombophilia

The prothrombin gene mutation G20210A is a common risk factor for thrombosis and has been reported to cause APC resistance. However, the inhibition of thrombin formation by APC not only limits fibrin formation but also stimulates fibrinolysis by reducing TAFI activation. We evaluated the influence of prothrombin G20210A mutation on the anticoagulant and fibrinolytic activities of APC (1 microg/ml). Thirty-two heterozygous carriers and 32 non carriers were studied. APC anticoagulant activity was assessed by aPTT prolongation whereas APC fibrinolytic activity was determined by a microplate clot lysis assay. APC-induced aPTT prolongation was markedly less pronounced in carriers than in non carriers. On the contrary, fibrinolysis time was shortened by APC to a comparable extent in both groups. Accordingly, prothrombin levels were strongly correlated with APC-induced aPTT prolongation but not with APC-induced shortening of lysis time. The addition of purified prothrombin to normal plasma (final concentration 150%) caused APC resistance in the clotting assay over the whole range of tested APC concentrations (0.125-1.5 microg/ml). In the fibrinolytic assay, instead, prothrombin supplementation made the sample resistant to low but not to high concentrations of APC (>0.5 microg/ml). Thrombin and TAFIa determination in the presence of 1 microg/ml APC revealed that hyperprothrombinemia, although capable of enhancing thrombin generation, was unable to induce detectable TAFIa formation. It is suggested that APC resistance caused by hyperprothrombinaemia does not translate in impaired fibrinolysis, at least in the presence of high APC levels, because the increase in thrombin formation is insufficient to activate the amount of TAFI required to inhibit plasminogen conversion. These data might help to better understand the relationship between thrombin formation and fibrinolysis down-regulation.

Topics: Activated Protein C Resistance; Anticoagulants; Blood Coagulation Disorders; Carboxypeptidase B2; Down-Regulation; Fibrin; Fibrinolysis; Genetic Predisposition to Disease; Heterozygote; Humans; Mutation; Prothrombin; Prothrombin Time; Thrombin

We studied 33 women during normal uneventful pregnancies and with no history of previous adverse pregnancy events for markers of activated coagulation and thrombin activity including prothrombin fragment 1.2(PF1.2), thrombin- antithrombin (TAT), and soluble fibrin polymer (SFP). In addition, we measured potential thrombin generation through the addition of thromboplastin to patient plasma in the presence of a thrombin-specific chromogenic substrate determined serially over a period of time--Endogenous Thrombin Potential assay (ETP). This assay was performed with plasma treated and untreated with activated protein C (APC). The fibrinolytic system was assessed by measurement of thrombin activatable fibrinolysis inhibitor (TAFI). These findings were correlated with the levels of pro-inflammatory cytokines, interleukine-1 beta and tumor necrosis factor-alpha. Our data supports previous reports that indicate that resistance to activated protein C and coagulation activation markers are commonly increased in the later 2/3rds of pregnancy. There are no differences in thrombin generation potential, as determined by the ETP assay without the addition of APC, in the three trimesters. However, the thrombin reserve (TR), the ETP result without APC divided by the ETP result with the addition of APC, is increased above the reference range in the 2nd and 3rd trimesters. Patients with increased TR and resistance to APC had increased levels of TNF-alpha. Increased proinflammatory cytokines are reportedly associated with changes in the APC system with a decrease in the ability to generate APC. A sub-group of pregnancies with APC resistance had increased levels of TNF-alpha and may be important in the risk for adverse pregnancy outcomes.

Topics: Activated Protein C Resistance; Adolescent; Adult; Biomarkers; Blood Coagulation; Female; Fibrin; Humans; Inflammation Mediators; Interleukin-1; Pregnancy; Pregnancy Trimesters; Thrombin; Tumor Necrosis Factor-alpha

A total of 260 consecutive patients, referred for hypercoagulable assessment, was included in this study. Four coagulation activation markers were utilized to assess these patients [enzyme-linked immunosorbent assays for soluble fibrin polymer (TpP), prothrombin fragment 1.2, thrombin-antithrombin complex, and D-dimer]. The mean levels of the activation markers directly correlated with the number of hypercoagulable abnormalities. The percentage of patients with increased TpP levels for each group was lower than the other activation markers. The findings indicate that activation markers reflect the number of underlying thrombophilic abnormalities. Our data suggest that there is a utility in performing a panel of coagulation activation markers to assess the thrombotic risk. The measurement of soluble fibrin polymer may be more reflective of an impending vascular event.

Topics: Activated Protein C Resistance; Adolescent; Adult; Aged; Aged, 80 and over; Antiphospholipid Syndrome; Antithrombin III; Antithrombin III Deficiency; Autoimmune Diseases; Biomarkers; Enzyme-Linked Immunosorbent Assay; Factor V; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Humans; Hyperhomocysteinemia; Male; Middle Aged; Peptide Fragments; Peptide Hydrolases; Protein C Deficiency; Protein S Deficiency; Prothrombin; Risk; Solubility; Thrombophilia

A polymorphism in coagulation factor V, factor V Leiden (FVL), is the major known genetic risk factor for thrombosis in humans. Approximately 10% of mutation carriers experience clinically significant thrombosis in their lifetime. In a small subset of patients, thrombosis is associated with coinheritance of other prothrombotic gene mutations. However, the potential contribution of additional genetic risk factors in the majority of patients remains unknown. To gain insight into the molecular basis for the variable expressivity of FVL, mice were generated carrying the homologous mutation (R504Q [single-letter amino acid codes]) inserted into the endogenous murine Fv gene. Adult heterozygous (FvQ/+) and homozygous (FvQ/Q) mice are viable and fertile and exhibit normal survival. Compared with wild-type mice, adult FvQ/Q mice demonstrate a marked increase in spontaneous tissue fibrin deposition. No differences in fetal development or survival are observed among FvQ/Q, FvQ/+ or control littermates on the C57BL/6J genetic background. In contrast, on a mixed 129Sv-C57BL/6J genetic background, FvQ/Q mice develop disseminated intravascular thrombosis in the perinatal period, resulting in significant mortality shortly after birth. These results may explain the high degree of conservation of the R504/R506 activated protein C cleavage site within FV among mammalian species and suggest an important contribution of other genetic factors to the thrombosis associated with FVL in humans. (Blood. 2000;96:4222-4226)

Topics: Activated Protein C Resistance; Amino Acid Substitution; Animals; Animals, Newborn; Crosses, Genetic; Disease Models, Animal; Disseminated Intravascular Coagulation; Epistasis, Genetic; Factor V; Female; Fertility; Fibrin; Gene Targeting; Genes, Lethal; Longevity; Male; Mice; Mice, Inbred C57BL; Mice, Inbred Strains; Mice, Transgenic; Mutagenesis, Site-Directed; Phenotype; Point Mutation; Risk Factors; RNA Splicing; Thrombosis