Abstract-A number of polymorphisms of the platelet glycoprotein (GP) Ib-V-IX and IIb/IIIa complexes have been described, and the Pl A polymorphism of GP IIIa has been associated with coronary thrombosis. We determined the levels of ␤-thromboglobulin (␤-TG) and platelet factor 4 (PF4) and the genotype distributions of Pl A and a variable number tandem repeat (VNTR) polymorphism of GP 1b in subjects with acute stroke (nϭ609) and healthy control subjects (nϭ435). Levels of ␤-TG were higher in patients both initially (47.4 [44.7 In a logistic regression model, ␤-TG remained an independent predictor of poststroke mortality, with an odds ratio for an increase in 10 ng/mL of 1.12 (1.03 to 1.21, Pϭ0.006). In subjects who had never smoked, there was a significant difference in the genotype distributions of patients with atherothrombotic stroke (A1/A1ϭ147, A1/A2ϭ70, and A2/A2ϭ2) compared with controls (A1/A1ϭ165, A1/A2ϭ47, and A2/A2ϭ5, Pϭ0.03). The Pl A distribution of subjects with atherothrombotic stroke before the age of 50 years (A1/A1ϭ19 and A1/A2ϩA2/A2ϭ18) was also significantly different from age-and sex-matched controls (A1/A1ϭ54 and A1/A2ϩA2/ A2ϭ20, Pϭ0.02). We found no association of VNTR with stroke or poststroke mortality. These data indicate that there is a persistent state of enhanced platelet activation in subjects with acute stroke, which is associated with poststroke mortality. The increased frequency of the Pl A2 allele in young subjects with atherothrombotic stroke lends further support for a role of the Pl A polymorphism in acute thrombosis. 1,2 Under conditions of high shear stress associated with atherosclerotic narrowing of vessels, GP Ib-V-IX (GP 1b) complex binds vWF exposed at sites of endothelial cell disruption.3 This interaction results in platelet adhesion and activation and the expression of functional GP IIb/IIIa complexes (␣ IIb ␤ 3 integrin) on the platelet surface.2 GP IIb/IIIa exists in an inactive state on resting platelets, but GP Ib/vWF interaction results in a conformational change within GP IIb/IIIa, which then binds fibrinogen and vWF, resulting in platelet aggregation.

Aims/hypothesis Impaired fibrin clot lysis is a key abnormality in diabetes and complement C3 is one protein identified in blood clots. This work investigates the mechanistic pathways linking C3 and hypofibrinolysis in diabetes using ex vivo/in vitro studies. Methods Fibrinolysis and C3 plasma levels were determined in type 1 diabetic patients and healthy controls, and the effects of glycaemia investigated. C3 incorporation into fibrin clots and modulation of fibrinolysis were analysed by ELISA, immunoblotting, turbidimetric assays and electron and confocal microscopy. Results Clot lysis time was longer in diabetic children than in controls (599±18 and 516±12 s respectively; p<0.01), C3 levels were higher in diabetic children (0.55±0.02 and 0.43± 0.02 g/l respectively; p<0.01) and both were affected by improving glycaemia. An interaction between C3 and fibrin was confirmed by the presence of lower protein levels in sera compared with corresponding plasma and C3 detection in plasma clots by immunoblot. In a purified system, C3 was associated with thinner fibrin fibres and more prolongation of lysis time of clots made from fibrinogen from diabetic participants compared with controls (244±64 and 92±23 s respectively; p<0.05). Confocal microscopy showed higher C3 incorporation into diabetic clots compared with controls, and fully formed clot lysis was prolonged by 764±76 and 428±105 s respectively (p<0.05). Differences in lysis, comparing diabetes and controls, were not related to altered plasmin generation or C3-fibrinogen binding assessed by plasmon resonance. Conclusions/interpretation C3 incorporation into clots from diabetic fibrinogen is enhanced and adversely affects fibrinolysis. This may be one novel mechanism for compromised clot lysis in diabetes, potentially offering a new therapeutic target.

Summary.  P‐selectin is a member of the selectin family of cell adhesion molecules which are important in the transient attachment of leukocytes to endothelial cells and platelets. A number of polymorphisms in the gene encoding P‐selectin have been identified. Objectives were to investigate the relationship of soluble P (sP)‐selectin with P‐selectin gene polymorphisms and coronary artery disease (CAD). Two hundred and forty‐nine patients, with extent of CAD characterized by ≥50% stenosis in one or more coronary arteries, and 252 healthy controls were studied. Soluble P‐selectin was significantly higher in the patients than controls after adjustment for age, sex and smoking [patients 49.8 (47.5–52.1) ng mL−1; controls 46.7 (44.5–49.1) ng mL−1, P = 0.03). There was no association of sP‐selectin with myocardial infarction (MI) or presence of ≥50% stenosis. The −1817 T/C, −1969 G/A and −2123 C/G (but not the Thr715Pro) polymorphisms were in strong linkage disequilibrium. The Thr715Pro polymorphism was significantly associated with sP‐selectin even after adjustment for covariates [TT 48.9 (46.9–50.0) ng mL−1; TP + PP 40.7 (38.1–43.6) ng mL−1, P < 0.0001]. A significant interaction of Thr715Pro and smoking status was identified in the determination of sP‐selectin levels. There was no significant association of genotype at any of the polymorphism in relation to MI or stenosis. The Thr715Pro polymorphisms is associated with plasma sP‐selectin. This association is modulated by smoking, although the underlying mechanism remains unclear.