Anticoagulant proteins in a population of Mexican mestizo donors.

BACKGROUND: To determine the activity of antithrombin (AT), protein C (PC), and protein S (PS), as well as the frequency of deficiencies of these proteins in a population of healthy Mexican mestizo blood donors. METHODS: AT, PC, and PS were determined from 1,502 plasma samples of healthy blood donors by using commercial kits in a coagulometer 4 STA (Diagnostica Stago, Asnières, France). RESULTS: A total of 741 women and 761 men were under study. They were divided into age range groups (18-24, 25-34, 35-44, 45-54, and 55-64 years). Activity of AT, PC, and PS was determined. For AT, activity values were specific for each age group according to gender when it had to do with PS, as well as when PC was determined. Frequencies of AT, PC, PS, and activated PC resistance activity deficiencies were obtained from reference levels (RLs) and average levels of this study. Differences were found between both frequencies for AT, PC, and PS, and the average levels obtained were used in this study. The frequencies of the activity deficiencies obtained through the values gotten in this population were: AT, 0.6%; PC, 1.06% (which is higher than the one obtained using the RLs described by commercial kits 0.33% and 0.66%, respectively); and PS, 1% (which is less than 4.5%). CONCLUSIONS: It is necessary to know the characteristics and biological behavior of the coagulation proteins in the Mexican population because the RLs used have been established for populations that are genetically different.

C5a receptor-deficient mice are protected from thrombophilia and endothelial cell activation induced by some antiphospholipid antibodies.

Recent findings indicate that complement activation--involving specifically C3 and C5--contributes to antiphospholipid (aPL)-mediated thrombosis. Two complement effector pathways are initiated by the cleavage of C5, C5a and C5b, which leads to the formation of the C5b-9 membrane attack complex. To delineate and distinguish the role of C5a from the C5b-9 membrane attack complex seeded by C5b, we examined the in vivo effects (thrombosis) of aPL on C5a receptor-deficient (C5aR-/-) mice. C5aR-/- and C5aR+/+ mice were injected with IgM or with IgG from two different patients with APS (IgM-APS or IgG-APS) or with control IgM or IgG (IgM-NHS or IgG-NHS) twice. Complement fixing activity of the Ig fractions and anticardiolipin activity in the sera of the mice were determined by enzyme-linked immunosorbent assay. Surgical procedures to study thrombus dynamics were performed. IgM-APS but not IgG-APS fixed C1q to cardiolipin-coated plates. IgM-APS significantly enhanced thrombus size in C5aR+/+ mice compared to C5aR+/+ mice treated with IgM-NHS (3198 +/- 2361 microm2 versus 585 +/- 460 microm2). C5aR-/- mice treated with IgM-APS showed a significant reduction in thrombi size as compared with C5aR+/+ mice (676 +/- 690 microm2 versus 3198 +/- 2361 microm2; P = 0.001). IgG-APS enhanced thrombus formation significantly in C5aR+/+ when compared to IgG-NHS-treated mice (3507 +/- 965 microm2 versus 1321 +/- 798 microm2), and these effects were not altered in C5aR-/- mice (3400 +/- 1681 microm2). The data indicate that C5aR-/- mice are protected from the thrombogenic effects of some aPL antibodies.

Polyamines inhibit both platelet aggregation and glycoprotein IIb/IIIa activation.

Platelet aggregation is inhibited by the polyamines putrescine, spermidine, and spermine. To date, the mechanism of action has not been clearly identified. Evidence suggests that polyamines may interact with the fibrinogen receptor (GP IIb/IIIa), interfering with platelet-platelet attachment. The effect of polyamines on human platelet aggregation and GP IIb/IIIa activation was evaluated. For the aggregation experiments, platelets were obtained from heparin- or citrate-collected blood. Our results indicate that the polyamines putrescine, spermidine, and spermine cause a dose-dependent inhibition of ADP- or collagen-mediated platelet aggregation with an order of potency spermine>spermidine>putrescine. In addition, spermine arrests or inhibits thrombin-, epinephrine-, arachidonate-, or ristocetin-induced platelet aggregation. Expression of platelet membrane glycoproteins IIb, IIIa, and IX is not reduced by polyamines. However, spermine inhibits the ADP- or thrombin-induced activation of GP IIb/IIIa. It is concluded that the final step in aggregation, common to all agonists, ie, fibrinogen binding to GP IIb/IIIa, is inhibited by spermine through inhibition of the agonist-induced activation of GP IIb/IIIa that precedes fibrinogen-ligand binding.

Venous thrombosis among patients with AIDS.

Thrombosis has been considered an uncommon complication in patients with AIDS. In a 42-month period, 28 adult male homosexuals with AIDS experienced 34 thrombotic events. All but three received HAART regimen, two a successful round of double nucleoside analog therapy, and one patient received no treatment. Median age of group was 38.5 years (range, 24 to 56 years). Median time from HIV infection to thrombosis was 40.5 months (range, 3 to 108 months). No patient had previous thrombosis, family history of thrombosis, or prothrombotic conditions. There were 31 deep vein thromboses, two pulmonary thromboembolisms, and one renal vein thrombosis. Six patients had two thrombotic events. The rate of thrombosis during the 42-month study period was 1.52% (cumulative incidence = 0.30%/year), while the rate of thrombosis in 600 patients before the era of protease inhibitor therapy was 0.33% (cumulative incidence approximately 0.055%/year) (p < 0.001). Due to high incidence of thrombotic recurrences and hemorrhagic complications while using oral anticoagulants, acetylsalicylic acid was initiated; no thrombotic episodes were recorded while using this drug. Protein C and protein S deficiency were found in nine and two patients, respectively. Two patients had lupus anticoagulant and two activated protein C resistance (APCR) without FV Leiden mutation (APCR test was negative after initial screening). Fifteen patients had no thrombophilic abnormalities. These data suggest that protease inhibitors could be a risk factor for venous thrombosis not due to thrombophilic abnormalities but likely related to abnormalities in platelets or endothelium.

[National evaluation of the diagnosis of activated protein C resistance]. / Evaluación nacional del diagnóstico de la resistencia a la proteína C activada.

Thrombophilia or prothrombotic state appears when activation of blood hemostatic mechanisms overcomes the physiological anticoagulant capacity allowing a thrombotic event. Thrombosis is the leading worldwide mortality cause and due to its high associated morbidity and mortality, it should be insisted in the opportune identification of a thrombophilic state. The study of thrombophilia identifies individuals at high risk for thrombosis. This meeting was conceived first to analyze the current status of the diagnosis of thrombophilia in Mexico and second to create the base for a national consensus for thrombophilia screening and for the establishment of a national center for laboratory reference and quality control for thrombophilia. Since searching of activated protein C resistance (APCR) and FV Leiden seem to have priority either in the clinical setting and in public health services, it was decided to start with these two abnormalities as a model to analyze the current status of thrombophilia diagnosis in the clinical laboratory. At this time, several thrombophilic abnormalities have been described however, APCR remains the most important cause of thrombophilia, accounting for as much as 20% to 60% of all venous thrombosis. APCR is a consequence of the resistance of activated FV to be inactivated by activated protein C. Procoagulant activity of activated FV increases the risk of thrombosis. Hereditary APCR is almost always due to a point mutation at the nucleotide 1691 of the FV gen inducing an Arg506Glu substitution in FV molecule. This mutation is better known as FV Leiden. Heterocygous carriers of FV Leiden have a thrombotic risk 5 to 10 times higher than general population while the risk for the homocygote state is increased 50 to 100-fold. When activated PC is added to plasma from patients with FV Leiden, this last resists the anticoagulant effect of activated PC. Therefore, thrombin production is not inhibited. This phenomenon is called APCR. The functional test evaluates the partially activated thromboplastin time (aPTT) in a plasma sample before and after adding activated PC. The result is reported as a standardized sensibility index: aPTT post-activated PC/aPTT pre-activated PC. The conclusions of this national reunion pretend to optimize the available resources in our country in order to allow a wide and less-expensive diagnosis of patients with thrombosis.