title: Thrombomodulin-dependent effect of factor VLeiden mutation on factor XIII activation.
abstract: BACKGROUND
  Factor V Leiden mutation (FV(Leiden)) is associated with impaired down-regulation of activated FV procoagulant activity and loss of FV anticoagulant function that result in an increased risk of venous thromboembolism. As the downstream effects of FV(Leiden) on clot formation and fibrinolyis have only partially been revealed, we investigated its effect on the activation of factor XIII (FXIII) and the cross-linking of fibrin.
  
  
  METHODS
  In the plasma samples of fifteen healthy individuals with known FV genotypes coagulation was initiated by recombinant human tissue factor and phospholipids with or without recombinant human thrombomodulin (rhTM). FV deficient plasma supplemented with purified wild type FV or FV(Leiden) were also investigated. Clots were recovered and analyzed by SDS-PAGE and quantitative densitometric evaluation of Western blots.
  
  
  RESULTS
  rhTM considerably delayed the activation of FXIII in the plasma from FV wild type individuals. This effect of rhTM was significantly impaired in the plasma from FV(Leiden) carriers. The results were confirmed in experiments with FV deficient plasma supplemented by FV prepared from wild type individuals or FV(Leiden) homozygotes. Fibrin γ-chain dimerization was also considerably delayed by rhTM in plasma samples from individuals without Leiden mutation, but not in plasma samples from FV(Leiden) heterozygotes or homozygotes. The difference between heterozygotes and homozygotes was not statistically significant.
  
  
  CONCLUSIONS
  The highly diminished delaying effect of TM on FXIII activation and on the cross-linking of fibrin in FV(Leiden) carriers might represent a novel mechanism contributing to the increased thrombosis risk of these individuals.
authors.affiliation: Clinical Research Center University of Debrecen, Medical and Health Science Center, Debrecen, Hungary.
authors.forename: Zsuzsa
authors.initials: Z
authors.lastname: Koncz
authors.forename: Zsuzsa
authors.initials: Z
authors.lastname: Bagoly
authors.forename: Gizella
authors.initials: G
authors.lastname: Haramura
authors.forename: Zoltán A
authors.initials: ZA
authors.lastname: Mezei
authors.forename: László
authors.initials: L
authors.lastname: Muszbek
mesh_terms: D000328:Adult; D000368:Aged; D003167:Complement Activation / Q000235:genetics* / Q000276:immunology*; D015536:Down-Regulation / Q000276:immunology*; D005165:Factor V / Q000235:genetics* / Q000276:immunology*; D005176:Factor XIII / Q000276:immunology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D018180:Thrombomodulin / Q000276:immunology*; D055815:Young Adult
chemical_list: D018180:Thrombomodulin; C095381:factor V Leiden; D005165:Factor V; D005176:Factor XIII