Possible role of vascular intima for generation of coagulant activity in patients undergoing coronary thrombolysis with recombinant tissue-type plasminogen activator. A randomized, placebo-controlled study

Increase in plasma plasminogen activators inhibitor type 1 concentration after fibrinolytic treatment in patients with acute myocardial infarction is associated with 4G/5G polymorphism of PAI-1 gene

BACKGROUND

Preliminary data suggest that plasma concentration of plasminogen activators inhibitor type 1 (PAI-1) is genetically determined and may be related to differential regulation of plasma PAI-1 concentration at baseline and after stimulation.

AIM

This study aimed to evaluate whether increase in the plasma PAI-1 antigen concentration or activity after fibrinolytic therapy in patients with acute myocardial infarction is associated with the -675 4G/5G genetic polymorphism in the promoter region of PAI-1 gene.

RESULTS & CONCLUSIONS

Our study revealed that a rebound effect is observed in PAI-1 activity (ActPAI-1) and PAI-1 antigen (AgPAI-1) concentration after standard streptokinase treatment with maximal values of 3 h (t3) after the completion of streptokinase infusion. Both ActPAI-1 and AgPAI-1 were significantly higher at t3 compared to the levels before fibrinolytic treatment: 37.3 (20.0-67.7) vs. 10.0 (3.6-26.0) IU L(-1); P = 0.00001 and 29.9 (15.6-42.3) vs. 20.9 (13.0-30.2) ng mL(-1); P = 0.001, respectively. The stratification of the patients by genotype revealed that carriers of the 4G allele had higher concentrations of PAI-1 antigen 3 h after streptokinase infusion: 30.9 vs. 13.8 ng mL(-1); P = 0.019. No significant association between PAI-1 activity and genotype was found. In conclusion, the rebound effect in serum PAI-1 concentration observed after streptokinase treatment may be related to the 4G/5G polymorphism in the PAI-1 gene promoter.

Activation of coagulation factor VII by tissue-type plasminogen activator

To investigate the effect of tissue-type plasminogen activator (t-PA) on blood coagulation, we examined the effects of the addition of t-PA to normal pool plasma (NPP) on clotting times such as diluted prothrombin time (PT) and kaolin clotting time (KCT). The diluted PT but not the KCT was significantly shortened by the addition of t-PA to NPP compared with the normal controls, suggesting a t-PA-induced activation of blood coagulation through factor VII (FVII) activation. The activated factor VII (FVIIa) concentration in the NPP was significantly increased by the addition of t-PA. Although the FVIIa formation was not observed following the incubation of purified FVII with only t-PA or plasminogen, an increase in the FVIIa level was observed after the incubation of purified FVII with t-PA together with plasminogen, or only plasmin. This plasmin-mediated FVIIa formation was also confirmed by Western blotting. These findings suggest that t-PA enhances the activation of the coagulation system through FVII activation.

Plasma resistance to activated protein C regulates the activation of coagulation induced by thrombolysis in patients with ischaemic heart disease

OBJECTIVE

To determine whether there was a relation between plasma resistance to activated protein C and the coagulation activation induced during thrombolysis with 100 mg alteplase in 25 patients with acute ischaemic heart disease.

METHODS

Blood samples were collected before (t = 0 h), during (t = 2.25 h), and after (t = 4 h, t = 12 h, and t = 24 h) thrombolysis to examine the relation between baseline activated protein C resistance ratio and markers of coagulation activation-that is, thrombinantithrombin III-complexes and prothrombin fragment 1 + 2 generated during thrombolysis.

RESULTS

There was a negative correlation between activated protein C resistance ratio and area under the curve of thrombin-antithrombin III-complexes (rs = - 0.60; P < 0.003) and there was a trend to a negative correlation between activated protein C resistance ratio and area under the curve of prothrombin fragment 1 + 2 (rs = - 0.37; P = 0.07). This accorded with the negative correlation between activated protein C resistance ratio and the peak value of thrombin-antithrombin III-complexes (rs = - 0.55; P < 0.005) and between activated protein C resistance ratio and the peak value of prothrombin fragment 1 + 2 (rs = - 0.42; P < 0.04). Components of the protein C/S system or known inhibitors of activated protein C may influence the activated protein C resistance ratio. There were no associations between the activated protein C resistance ratio and protein C, protein C inhibitor, or plasminogen activator inhibitor type-1, whereas there was a trend to a negative correlation between activated protein C resistance ratio and protein S.

CONCLUSIONS

The results indicate that plasma resistance to activated protein C may be one of the main mechanisms regulating the activation of coagulation induced by thrombolysis. This study suggests that it may be possible to single out individuals with a high risk of reocclusion before the start of thrombolytic therapy.

Design of a linker for trivalent thrombin inhibitors: interaction of the main chain of the linker with thrombin

N alpha-Acetyl[D-Phe45,Arg47]hirudin45-65 (P53) is a bivalent thrombin inhibitor (Ki = 5.6 nM) that consists of an active site inhibitor segment, [N alpha-acetyl-(dF)PRP]; a fibrinogen recognition exo site inhibitor segment, hirudin55-65 (DFEEIPEEYLQ-OH); and a linker, hirudin49-54 (QSHNDG), connecting these inhibitor segments (DiMaio et al., 1990). The structure-function relationships of the linker were studied using a combination of various omega-amino acids, which modified the length of the linker as well as the number and the locations of peptide bonds. Linkers with 14-18 atoms (counting only the atoms contributing to the length of the linker) showed a competitive inhibition with Ki = 1.7-3.4 nM. The potency of the inhibitors with 12-13-atom linkers was sensitive to the chemical structure of the linker. The high-potency inhibitors showed a competitive inhibition, while the low-potency inhibitors showed a hyperbolic inhibition. Among them, an inhibitor with a 13-atom linker showed the highest potency (Ki = 0.51 nM, an 11-fold improvement from that of P53 above), indicating that this is an optimal linker length. Since linkers with 6-10 atoms failed to bridge the active site and exo site inhibitor segments, a minimum of 11 atoms was required to bridge them, even though the potency of the inhibitor with an 11-atom linker was weak (Ki = 26 nM). Molecular dynamics simulation of the inhibitors with 13-atom linkers suggested that some linkers serve as a functional domain with the amide bond of the linker interacting with thrombin through hydrogen bonds.(ABSTRACT TRUNCATED AT 250 WORDS)