ABSTRACT
Protein Z-dependent protease inhibitor (ZPI) is a plasma inhibitor of factor (F)Xa and FXIa. In an earlier study, five mutations were identified within the ZPI gene of venous thrombosis patients and healthy controls. Two of these were nonsense mutations and three were missense mutations in important regions of the protein. Here we report that two of these latter three mutations, F145L and Q384R, impair the inhibitory function of ZPI in vitro. Recombinant wild-type and mutant proteins were prepared; stability in response to thermal challenge was similar. Inhibition of FXa in the presence of the cofactor protein Z was reduced 68-fold by the Q384R mutant; inhibition of FXIa by the F145L mutant was reduced two- to three-fold compared to the wild-type ZPI. An analysis of all five ZPI mutations was undertaken in a cohort of venous thrombosis patients (n=550) compared to healthy controls (n=600). Overall, there was a modest increase in incidence of these mutations in the thrombosis group (odds ratio 2.0, 1.05-3.7, p=0.044). However, in contrast to W324X (nonsense mutation), the Q384R missense mutation and R88X nonsense mutation were evenly distributed in patients and controls; F145L was rare. The final mutation (S143Y) was also rare and did not significantly alter ZPI function in laboratory studies. The F145L and particularly the Q384R mutation impaired the function of the coagulation inhibitor ZPI; however, there was no convincing association between these mutations and venous thrombosis risk. The functional role for ZPI in vivo has yet to be clarified.
Subject(s)
Blood Coagulation/genetics , Mutation, Missense , Serpins/genetics , Venous Thrombosis/genetics , Adult , Case-Control Studies , Chi-Square Distribution , Enzyme Stability , Factor XIa/metabolism , Factor Xa/metabolism , Female , Gene Frequency , Genotype , Humans , Kinetics , Male , Middle Aged , New Zealand , Odds Ratio , Phenotype , Protein Conformation , Protein Denaturation , Recombinant Proteins/metabolism , Risk Assessment , Risk Factors , Serpins/blood , Serpins/chemistry , Structure-Activity Relationship , Venous Thrombosis/blood , Venous Thrombosis/enzymologyABSTRACT
BACKGROUND: Although inherited thrombophilias are more common in patients with venous thromboembolism, their influence on the development of myocardial infarction (MI) requires clarification. METHODS AND RESULTS: To determine whether there are increased frequencies of mutations/polymorphisms in 14 genes potentially causing thrombophilia in patients with no flow-limiting stenoses after MI compared with patients with > or =1 flow-limiting stenosis of >50%, we studied 395 patients (60 with no flow-limiting stenosis) who underwent angiography at approximately 1 month. The mutations/polymorphisms studied included Factor V Leiden, prothrombin variant G20210A, beta-fibrinogen 448 (G/A), endothelial protein C receptor (23-base pair insertion), methyl tetrahydrofolate reductase 677 (C/T), platelet glycoprotein IIIa PlA1/A2, plasminogen activator inhibitor-1 4G/5G, angiotensin II type 1 receptor (A/C), hemochromatosis gene 282 (G/A), nitric oxide synthase (NOS) (3 forms: eNOS, eNOS3, eNOS4), p22 phox of NADPH oxidase C242T, and angiotensin-converting enzyme insertion/deletion polymorphism. The frequencies of Factor V Leiden and the beta-fibrinogen 448 A allele were higher in patients with no flow-limiting stenosis than in patients with > or =1 stenosis (11.7% vs 3.6%, odds ratio [OR] 3.6, 95% CI 1.3-9.4, P =.015; and 42% vs 27%, OR 2.0, 95% CI 1.1-3.5, P =.018, respectively), and there was a trend toward an increased frequency of prothrombin variant G20210A (6.7% vs 2.1%, OR 3.4, 95% CI 0.95-11.8, P =.069). However, in patients with no flow-limiting stenosis after MI the frequencies of the other gene mutations/polymorphisms were not increased. Also, there were no significant interactions between any of these 14 mutation/polymorphisms, major cardiovascular risk factors, and the absence of any flow-limiting stenosis, except for Factor V Leiden and hypertension (OR 6.34, 95% CI 2.67-100, P =.004). CONCLUSIONS: Patients with no flow-limiting stenosis after MI had increased frequencies of 2 inherited thrombophilias (Factor V Leiden and beta-fibrinogen 448 A allele), and there was a trend toward an increased frequency of prothrombin variant G20210A compared with patients with > or =1 stenosis. These data suggest that polymorphisms/mutations in some gene products influencing coagulation may influence the pathogenesis of MI.
