PlA1/A2 polymorphism of platelet glycoprotein IIIa and risk of cardiovascular disease

Association of the platelet glycoprotein IIb HPA-3 polymorphism with survival after acute ischemic stroke

BACKGROUND AND PURPOSE

The role of polymorphisms of the platelet glycoprotein (GP) IIb/IIIa receptor in the development of cardiovascular disease has been the subject of intensive research. The aim of this study was to determine the association of the HPA-3 polymorphism of platelet GPIIb with ischemic stroke and subsequent survival and to identify possible interactions of HPA-3 with classic risk factors.

METHODS

HPA-3 genotype was determined by restriction fragment length polymorphism in 515 patients with ischemic stroke and 423 healthy, age-matched control subjects.

RESULTS

There was no significant difference in the genotype distribution of patients and controls, nor was there any difference when patients were subclassified into small- and large-vessel disease. The genotype distribution of the 231 patients subsequently dying during 2.8 years of follow-up (aa=45.0%, ab=46.8%, bb=8.2%) was significantly different from that of those still alive (aa=37.0%, ab=48.2%, bb=14. 8%) (P=0.03). In a Cox regression model, the relative risks for poststroke mortality in patients of aa and ab genotype compared with those of bb genotype were 2.42 (95% CI, 1.24 to 4.71) and 2.13 (95% CI, 1.09 to 4.17), respectively, after we accounted for confounding factors. In addition, significant interactions of HPA-3 with the Pl(A) polymorphism of GPIIIa (P=0.002) and with fibrinogen (P=0.01) were identified in relation to mortality.

CONCLUSIONS

HPA-3 is related to poststroke mortality, and the significant interaction of HPA-3 with Pl(A) and fibrinogen suggests that it may in some way influence the interaction of GPIIb/IIIa with fibrinogen, particularly in the presence of high fibrinogen.

Platelet GP IIIa PlA and GP Ib variable number tandem repeat polymorphisms and markers of platelet activation in acute stroke

A number of polymorphisms of the platelet glycoprotein (GP) Ib-V-IX and IIb/IIIa complexes have been described, and the PlA polymorphism of GP IIIa has been associated with coronary thrombosis. We determined the levels of beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) and the genotype distributions of PlA and a variable number tandem repeat (VNTR) polymorphism of GP 1b in subjects with acute stroke (n=609) and healthy control subjects (n=435). Levels of beta-TG were higher in patients both initially (47.4 [44.7 to 50.2] ng/mL, P<0.0001) and after 3 months (42.9 [40.3 to 45.7] ng/mL, P=0.03) compared with control subjects (39.4 [37.7 to 41.2] ng/mL). Initial levels of beta-TG were significantly higher in those who subsequently died (58.7 [52.3 to 65.8] ng/mL) compared with those still alive (42.7 [40.1 to 45.5] ng/mL, P<0.0001). In a logistic regression model, beta-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, P=0.006). In subjects who had never smoked, there was a significant difference in the genotype distributions of patients with atherothrombotic stroke (A1/A1=147, A1/A2=70, and A2/A2=2) compared with controls (A1/A1=165, A1/A2=47, and A2/A2=5, P=0.03). The PlA distribution of subjects with atherothrombotic stroke before the age of 50 years (A1/A1=19 and A1/A2+A2/A2=18) was also significantly different from age- and sex-matched controls (A1/A1=54 and A1/A2+A2/A2=20, P=0.02). 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 PlA2 allele in young subjects with atherothrombotic stroke lends further support for a role of the PlA polymorphism in acute thrombosis.

PIa1/a2 polymorphism of glycoprotein IIIa and risk of coronary artery disease and restenosis following coronary angioplasty

Glycoprotein IIIa (GpIIIa), a platelet protein that mediates platelet aggregation and thrombus formation, has attained recent widespread interest following a report that a common genetic variant of GpIIIa, known as Pla2, is an inherited risk factor for the development of premature coronary artery disease (CAD). We determined the frequency of the Pla2 allele in 589 prospectively recruited subjects aged <50 years presenting with symptomatic CAD with or without myocardial infarction and documented by coronary angiography (group I), 207 subjects investigated prospectively for restenosis 6 months after coronary balloon angioplasty (group II), and 570 control subjects without a history of angina or myocardial infarction, randomly selected from the community. Detection of the Pla2 allele was based on MspI digestion of polymerase chain reaction (PCR) amplified deoxyribonucleic acid (DNA) spanning the Pla1/a2 locus. The accuracy of genotyping was verified with a second independent method based on BstXI digestion of DNA amplified with mutagenic PCR primers. The frequency of the Pla2 allele was similar (p >0.1) in group I (170 of 1,178, 14%), group II (49 of 414, 12%), and control subjects (160 of 1,140, 14%). Among group I subjects, there was no relation (p >0.1) between the Pla2 allele frequency and the number of coronary vessels with >50% diameter obstruction, and current or previous myocardial infarction; among group II subjects, there was no difference between those with and without restenosis after angioplasty (26 of 242 and 23 of 172, respectively, p >0.1). We conclude that the Pla2 allele is not associated with a significantly elevated risk of premature CAD, myocardial infarction, or restenosis after coronary angioplasty.