Platelet glycoprotein Ia C807T, Ib C3550T, and IIIa Pl(A1/A2) polymorphisms and ischemic stroke in young Taiwanese

Platelet plays a pivotal role in the pathogenesis of thrombotic cardiovascular diseases. Recently, the polymorphism of platelet glycoprotein (GP) genes has been reported to be associated with an increased risk for ischemic stroke. The purpose of this study is to evaluate the association between platelet GP genetic variants and ischemic stroke in young Taiwanese. We conducted a case-control study in 157 young ischemic stroke patients recruited between September 2001 and March 2003 and 157 age- and sex-matched controls. The genotypes of platelet GP Ia C807T, GP Ib C3550T, and GP IIIa Pl(A1/A2) polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism. Student's t-test, chi-square test, and logistic regression modeling were used for data analyses. The GP Ia C807T CC, CT and TT genotype frequencies were similar between patients (50.3%, 43.9%, 5.7%) and controls (53.5%, 38.9%, 7.6%; p=0.58). There were no significant differences in GP Ib C3550T CC and CT genotype distributions between patients (91.1%, 8.9%) and controls (91.7%, 8.3%; p=0.84). Of all subjects, none carries GP IIIa Pl(A2) mutation. In conclusion, platelet GP Ia C807T and GP Ib C3550T polymorphisms in our population are less common compared with Caucasians, and GP IIIa Pl(A1/A2) genetic mutation is not found, and all of them are not associated with ischemic stroke in young Taiwanese.     

血小板膜糖蛋白Ibα基因启动子上游"Kozak"多态性与脑梗死的相关性研究

目的研究中国雷州半岛地区汉族人群血小板膜糖蛋白(GP)Ibα基因ATG启动子上游25bp处"Koza"多态性位点与脑梗死的关系.方法采用病例-对照研究,选择中国雷州半岛地区汉族人群130例健康体检者(对照组)和148例经CT或MRI证实的脑梗死患者(CI组)为对象,用聚合酶链反应-限制性酶切片段长度多态性分析方法(PCR-RFLP)检测血小板膜糖蛋白(GP)Ib Kozak-5T/C序列基因多态性,分析其在正常人群及脑梗死患者中的频率分布特点及与缺血性脑卒中的关系.结果CI组GPIb Kozak序列C等位基因频率为0.487,对照组为0.396,两组比较差异有显著性(P＜0.05);-5C基因纯合子携带者发生脑梗死的风险是T/T或T/C基因携带者的2.0倍,经Logistic回归分析校正了年龄、血压、血脂等危险因素后,-5C纯合子与脑梗死仍密切相关(P＜0.05,OR=2.885,95%CI1.135-8.307).结论中国雷州半岛地区汉族人群GPIb Kozak序列-5T/C基因多态是脑梗死的遗传易感因素.     

The impact of CYP3A5*1/*3, PIA1/A2 and T744C polymorphisms on clopidogrel and acetylsalicylic acid response variability in Mexican population

Introduction

Clopidogrel is recommended in addition to aspirin to prevent atherothrombotic events in patients with acute coronary syndromes (ACS) and in those undergoing percutaneous coronary intervention (PCI). However, an interindividual variability in platelet inhibition response to clopidogrel has been demonstrated, and is associated with recurrent cardiovascular events. Multiple mechanisms have been associated with no response including genetics factors.

Materials and methods

The present study enrolled 60 patients with ACS undergoing emergent PCI. Platelet aggregation to adenosine diphosphate and arachidonic acid was assessed by turbidimetric method at 24 hours after dual administration of 300 mg of clopidogrel and 300 mg of acetylsalicylic acid loading dose. Clopidogrel or acetylsalicylic acid resistance was defined by persistence of Platelet Reactivity (PR = ADP-Ag > 70% or PR = Arachidonic Acid-Ag > 20%) respectively. The CYP3A51*/5*, PIA1/A2, and T744C polymorphisms were determined in all participants by PCR-RFLP.

Results

The allelic frequencies were: CYP3A5*3 (71.65%), PIA2 (10.8%), and 744 C (15.0%). We founded high percent of clopidogrel resistance (60.0%), compared with 8.3% of acetylsalicylic acid in those patients. The genotype frequencies of those polymorphisms were similar between responders and non responders defined by PR. There was a high percent of coronary adverse events.

Conclusions

We identified a high percent of clopidogrel resistance in Mexican patients with ACS undergoing PCI. However, a normal platelet response to acetylsalicylic acid was observed in most of them. There was no association between CYP3A5*1/*3, PIA1/A2, and T744C polymorphisms and clopidogrel resistance. More studies are needed to determine the possible interaction between genetics factors, platelet response to clopidogrel and cardiovascular adverse events.     

807C/T polymorphism of platelet glycoprotein Ia gene is associated with cerebral hemorrhage in a Chinese population

Platelet glycoprotein (GP) mediated the role of platelet in coagulation. Platelet GP Ia 807C/T is the only GP polymorphism associated with the expression levels of GP Ia/IIa (the platelet collagen receptor). Recently, the GP Ia 807C/T polymorphism has been reported to have no association with cerebral hemorrhage (CH) in two studies pertained to Caucasian populations. The purpose of this study is to evaluate the association between platelet GP Ia 807C/T polymorphism and CH in a Han Chinese population. We performed genotype analysis for platelet GP Ia 807C/T polymorphism in a case-control study involving 195 patients with CH and 116 age- and sex-matched controls. In contrast to previous reports, we found that the frequencies of GP Ia 807C/T T allele, CT and TT genotype were much higher in CH patients than in controls (33.9% vs. 22.8%, p = 0.004; 45.5% and 11.1% vs. 40.4% and 2.6%, p = 0.022). Logistic regression analysis revealed that the presence of GP Ia 807C/T C allele and CC genotype were both associated with a decreased risk of CH compared with T allele, CT and TT genotypes, respectively (adjusted odds ratio [OR] = 0.565, 95% CI: 0.384–0.887, p = 0.005; adjusted OR = 0.172, 95% CI: 0.043–0.639, p = 0.009; adjusted OR = 0.254, 95% CI: 0.085–0.961, p = 0.041, respectively). These findings indicated that platelet GP Ia 807C/T polymorphism could be a protective factor of CH in the Chinese population.     

Effects of glycoprotein IIb/IIIa antagonists on platelet activation: development of a transfer method to mimic peak to trough receptor occupancy

Several oral glycoprotein (GP) IIb/IIIa antagonists, Sibrafiban, Orbofiban and Lotrafiban, have been studied in large phase III trials; each has failed to provide efficacy and has been associated with increased mortality. Roxifiban has pharmacokinetic and pharmacodynamic properties believed to be more favorable than the earlier oral agents. Here, we revisit the controversial hypothesis of platelet activation liabilities of GP IIb/IIIa antagonists. The effects of site occupancy by four fibans (Roxifiban, Sibrafiban, Orbofiban and Lotrafiban) on platelet activation was assessed using P-selectin expression, fibrinogen binding and microaggregate formation. All four fibans inhibited ADP and TRAP-stimulated fibrinogen binding and microaggregate formation in a concentration-dependent manner, whereas P-selectin expression was relatively unaltered. To more vigorously test for activation liabilities, the effects of transition from peak to trough receptor occupancy upon platelet stimulation was analyzed. The high affinity of Roxifiban for resting platelets precluded reduction of site occupancy by dialysis or gel filtration. A method was developed that takes advantage of the rapid equilibrium of Roxifiban between platelets and soluble GPIIb/IIIa. The platelet occupancy is controlled by the ratio of platelet GPIIb/IIIa to soluble GPIIb/IIIa. This method allows in vitro investigation of peak/trough transitions on platelet activation. A decrease in site occupancy from peak to trough of Roxifiban or Sibrafiban did not result in increased activation of platelets. The loss of platelet-bound antagonist upon incubation with purified soluble GPIIb/IIIa returned fibrinogen binding/microaggregate formation to no drug levels. In conclusion, these studies do not provide evidence for an activation liability of GPIIb/IIIa antagonists in vitro.     

Antithrombotic effects of aspirin based on PLA1/A2 glycoprotein IIIa polymorphism in patients with coronary artery disease

OBJECTIVE: The diallelic glycoprotein IIIa polymorphism P1A1/A2 was attributed to be an inherited risk factor for coronary events. Whether this polymorphism affects response to aspirin in patients with coronary artery disease is not known. METHODS: We assessed thrombin generation (prothrombin fragment F1+2) in consecutive blood samples collected from bleeding-time wounds in 28 men with coronary artery disease; P1A2 carriers, n=9; P1A1/A1, n=19. Thrombin generation and bleeding time were measured before and after 2 weeks of aspirin 300 mg/day. RESULTS: Aspirin-depressed thrombin generation in A1 homozygotes (p=0.04), but not in A2 carriers. Bleeding time after aspirin was also prolonged in A1 subjects only (p=0.02). CONCLUSION: Genotyping for glycoprotein IIIa polymorphism might be helpful in predicting antithrombotic action of aspirin in secondary prevention of coronary artery disease.     

GABRA5基因启动子-754C／T多态性与耐药性癫痫的相关性分析

目的探讨GABRA5基因启动子-754C／T突变和癫痫耐药的相关性。方法收集125例诊断明确、治疗合理的汉族癫痫患者。根据是否符合DRE（耐药性癫痫）诊断标准将其分为耐药组（63例）和非耐药组（62例）。采用聚合酶链反应限制性片段长度多态性方法检测患者外周血GABRA5基因启动子-754c／T多态性。结果耐药组CC、CT、TT基因型分别占23．8％、41．2％、35．0％,非耐药组分别占16．1％、50．0％、33．9％,总体差异无统计学意义（x^2=1．454,P=0．483）。耐药组等位基因C、T频率分别为44．4％、55．6％,非耐药组患者分别为41．1％、58．9％,差异也无统计学意义（x^2=0．281,P=0．596）。结论本研究未发现GABRA5基因启动子-754C／T多态性与汉族DRE有关。     

Lack of association between the 807 C/T polymorphism of glycoprotein Ia gene and post-treatment platelet reactivity after aspirin and clopidogrel in patients with acute coronary syndrome

Variability in platelet response to antiplatelet therapy and its clinical relevance have been well described. However, the underlying mechanisms remain unclear. It was the aim of the present study to assess whether the response to aspirin and clopidogrel may be influenced by the 807 C/T polymorphism of the glycoprotein Ia (GpIa) gene in patients with non-ST elevation acute coronary syndrome (NSTE ACS). Six hundred one NSTE ACS patients were included in our study and were divided into three groups: CC homozygotes, CT heterozygotes ad TT homozygotes. All patients received loading doses of 600 mg clopidogrel and 250 mg aspirin at least 12 hours before blood samples were drawn. Post-treatment platelet reactivity was assessed by post treatment ADP 10 microM-induced platelet aggregation (ADP-Ag), VASP phosphorylation (PRI VASP) and P-selectin expression. Non-response to dual antiplatelet therapy was defined by high post-treatment platelet reactivity (HPPR=ADP-Ag > 70%). Significant variability in the distribution of platelet parameters was observed in the overall study population. No significant difference in platelet parameters profiles was observed within patients having the same genotype, for ADP-Ag (p=0.33), PRIVASP (p=0.72) and P-selectin expression (p=0.37). The genotype frequencies of the 807 C/T polymorphism of the GpIa gene were similar in responders and non-responders defined by persistent HPPR (p=0.104). In conclusion, our study did not show any influence of 807 C/T polymorphism of GpIa gene on post-treatment platelet reactivity assessed by ADP-Ag, PRI VASP or P-selectin expression in 601 NSTE ACS patients.     

Association study of -1727 A/T, -50 C/T and (CAA)n repeat GSK-3beta gene polymorphisms with schizophrenia

Glycogen synthase kinase-3 (GSK-3) is a downstream component of the Wnt pathway and recent studies have reported abnormal levels of GSK-3beta in schizophrenia. In a sample of 147 schizophrenic patients and 212 healthy individuals, we analyzed two common SNPs at position -1727 A/T and -50 C/T and a (CAA)(n) repeat polymorphism localized in intron 1 of the gene. The results showed that the allele, genotype and haplotype distributions for the three polymorphisms investigated do not differ between schizophrenic patients in general and control subjects. However, in the subtype of paranoid schizophrenic patients, we found that the (CAA)(3)/(CAA)(5) heterozygotes were more often represented. Although taken from a small sample, our results support the reports that GSK-3beta appears to be involved in a subtype of schizophrenic patients, but not in schizophrenia in general. In conclusion, we would speculate that this gene may be linked to some features of psychotic disorders rather than to schizophrenia itself.     

The prevalence of the platelet glycoprotein IIIa Pl(A1/A2) polymorphism in three South African ethnic groups and its effect on platelet function

Introduction

In South Africa coronary artery disease (CAD) is less common in African than Indian or white subjects. Although the association between CAD and metabolic factors have been well documented, the role of genetic factors is as yet poorly understood. Specific polymorphisms in the platelet membrane glycoprotein (GP) IIIa gene Pl^A1/A2, have been implicated in the development of CAD.

Methods

The prevalence of platelet GPIIIa (Pl^A1/A2) polymorphisms and their effect on platelet function was determined in 313 Indian, 267 white and 227 African subjects with and without a history of CAD.

Results

In subjects without a history of CAD the frequency of the unfavourable Pl^A2 allele was 8.0%, 14.8% and 8.7% in the Indian, white and African populations respectively, with the frequency being significantly higher (p < 0.05) in the white than both other groups. The frequency of the Pl^A2 allele was higher in subjects with (23.0%) than without (10.0%; p < 0.0001) a history of CAD. Aggregation studies showed that platelets carrying the Pl^A2 allele were hypersensitive to the platelet aggregating agonists ADP and collagen and produced a higher amount of TXA₂ when stimulated with low concentrations of both these agonists.

Conclusions

The positive association observed between the platelet GPIIIa Pl^A1/A2 polymorphism and platelet function suggests that the GPIIIa Pl^A2 allele may be a genetic factor that contributes to the risk of sudden death from myocardial infarction in the absence of known risk factors but it does not explain ethnic differences in the prevalence of CAD.     

Relationship of the platelet glycoprotein PlA and fibrinogen T/G+1689 polymorphisms with peripheral arterial disease and ischaemic heart disease

INTRODUCTION: Genetic variation in plasma fibrinogen and the platelet receptor GP IIIa locus has been independently associated with increased risks of ischaemic heart disease, but there have been few reports on the relationship with peripheral arterial disease. This study determined the risk of peripheral arterial disease and ischaemic heart disease associated with polymorphisms of fibrinogen T/G(+1689) and platelet glycoprotein Pl(A) genes and the effects of cigarette smoking and fibrinogen. MATERIALS AND METHODS: In the 5-year follow-up phase of the Edinburgh Artery Study, 939 subjects (60-79 years) had DNA extracted from a venous blood sample. One hundred sixteen subjects were identified as having angina, 87 a myocardial infarction, 104 had intermittent claudication and 663 subjects comprised a healthy group. RESULTS: Distribution of the fibrinogen genotype was similar across the disease and healthy groups. Logistic regression analyses found no significant association between fibrinogen genotype and ischaemic heart disease and peripheral arterial disease. A lower percentage of claudicants had the Pl(A2) allele (8.3% vs. 15.2%, p=0.025). After adjustment for age and sex, the risk of IC associated with the Pl(A2) was half that of the homozygous Pl(A1) genotype (OR 0.49, 95% CI 0.25, 0.88; p<==0.05). Adjustment for lifetime smoking and fibrinogen levels increased the odds slightly to nonsignificance. CONCLUSIONS: The Pl(A2) genotype was associated with a decreased risk of developing IC. There was no significant relationship between fibrinogen T/G(+1689) genotype and ischaemic and peripheral heart disease in this older population.     

广西人群Nogo基因rs2919126C/T和rs7575107G/T遗传多态性研究

目的研究广西正常人群中轴索生长抑制因子(Neurite growth inhibitor,Nogo)基因rs2919126C/T位点和rs7575107G/T位点多态性分布特点,并分析其在不同人群中的分布差异。方法采取多重单碱基延伸法(SNa Pshot)与DNA测序法对323例广西人群的Nogo基因rs2919126C/T位点和rs7575107G/T位点进行基因分型检测,并用统计学方法比较其基因型和等位基因频率在不同性别及组间分布差异。结果 rs2919126C/T存在CC、CT、TT 3种基因型,分布频率为6.5%、33.4%、60.1%,此位点基因型及等位基因频率在广西人群的男女之间差异无统计学意义(P>0.05)。其基因型和等位基因与国际人类基因组单体型图计划(HapMap)公布的欧洲和非洲人群的比较差异有统计学意义(P<0.01);rs7575107G/T存在GG、GT、TT 3种基因型,分布频率为2.5%、24.8%、72.7%,此位点基因型及等位基因频率在广西人群的男女之间无统计学意义(P>0.05)。基因型和等位基因频率与非洲人群之间差异均有统计学意义(P<0.01)。结论 Nogo基因rs2919126C/T位点和rs7575107G/T位点基因多态性在不同种族和地区间存在着不同程度差异。这种差异可能对研究在不同人群间Nogo基因多态性和疾病的相关性起到指导作用。     

Association between IL-1beta -511C/T and IL-1RA (86bp)n repeats polymorphisms and schizophrenia

It has been established that cytokines play a critical role in the regulation of the CNS and recent studies have suggested that dysfunctions of both pro-inflammatory (IL-1β, IL-6, and TNF-) and anti-inflammatory (IL-1RA and IL-10) cytokines could be involved in the pathophysiology of schizophrenia. Previous studies have reported that functional polymorphisms in some cytokines genes may have important regulatory effects on such system. Therefore, the aim of the present study was to explore the possible role of the IL-1β -511C/T and IL-1RA (86bp)_n repeats polymorphisms in schizophrenia. A case control association study comparing genotype and allele frequencies in 346 northen Italian subjects (169 schizophrenic patients and 177 unrelated healthy volunteers) was performed. The frequencies of IL-1β -511C and IL-1RA allele 1 (86bp)₄ are significantly higher in schizophrenic patients compared to controls (IL-1β -511 P=0.047; IL-1RA (86bp)_n P=0.002). Moreover our data show a protective effect of the IL-1RA allele 2 (86bp)₂ against schizophrenia (OR=0.59 95%CI:0.388–0.910; P=0.016) and this effect is enhanced by the concomitant presence of IL-1β -511T (OR=0.48 95%CI:0.30-0.76; P=0.002). Our findings support the hypothesis that genetically determined changes in IL-1 metabolism regulation may contribute to the pathogenesis of schizophrenia confirming a role of IL-1 gene cluster in disease susceptibility.     

Antithrombotic activity of Z4A5, a new platelet glycoprotein IIb/IIIa receptor antagonist evaluated in a rabbit arteriovenous shunt thrombosis model

Introduction

The antithrombotic effect of the glycopreotein IIb/IIIa (GP IIb/IIIa) receptor antagonist Z4A5, exert alone or combination with heparin, and/or aspirin, was examined in a rabbit arteriovenous shunt thrombosis model.

Materials and Methods

Thrombosis was induced by the insertion of a silk thread (thrombogenic substrate) into an extracorporeal shunt. Before and after drug administration (0, 5, and 15 min), ex vivo adenosine diphosphate (ADP)-induced platelet aggregation and coagulation parameters (prothrombin time (PT) and activated partial thromboplastin time (APTT)) were determined in platelet-rich plasma (PRP) and platelet poor-plasma (PPP), respectively.

Results

Our data demonstrated that, compared to the control, Z4A5 decreased the thrombus weight (31-65%) in a dose-dependent manner and inhibited ADP-induced platelet aggregation (47-98%) 5 min after Z4A5 administration (25-100 mg/kg). However, PT and APTT remained stable, even at the highest dose (100 mg/kg). Heparin (100 U/kg) and aspirin (15 mg/kg) also significantly reduced thrombus mass, but this effect was accompanied by an increase of APTT by heparin. Furthermore, the combination of heparin (100 U/kg) and a low dose of Z4A5 (25 mg/kg) failed to produce an additional benefit beyond that provided by heparin or Z4A5 alone, whereas Z4A5 (25 mg/kg) plus aspirin (15 mg/kg) potentiated the antithrombotic effects of both compounds without further increasing the values of coagulation.

Conclusions

Our results indicate that Z4A5 is an effective antithrombotic agent with no significant effects on values of coagulation. Furthermore, Z4A5 can potentiate these antithrombotic effects when prescribed with aspirin.     

Association Study between 5-HT1A Receptor Gene C(-1019)G Polymorphism and Panic Disorder in a Korean Population

Objective

Serotonergic dysfunction is quite evident in panic disorder. We investigated whether the C(-1019)G polymorphism of 5-HT1A receptor gene may play a role in the pathogenesis of panic disorder in a Korean population.

Methods

The 5-HT1A receptor genotype for the single nucleotide polymorphism (SNP) C(-1019)G was analyzed in 94 patients and 111 healthy controls. The severity of the patients'' symptoms was examined using the Spielberger State-Trait Anxiety Inventory (STAI), Panic Disorder Severity Scale (PDSS), Anxiety sensitivity index (ASI), Acute Panic Inventory (API) and Hamilton''s Rating Scale for Anxiety (HAM-A).

Results

The distribution of the genotypes of the C/G polymorphism did not differ significantly from those predicted by Hardy-Weinberg equilibrium in patients as well as the controls. No association between the C(-1019)G polymorphism and panic disorder was detected in either the allele frequency or genotype distribution. There was no significant association with genotype distribution in the panic disorder with agoraphobia. However, there was a significant difference of symptom severity between C/C, C/G, and G/G genotype or between C and G allele in panic disorder patients without agoraphobia. PDSS scores were significantly higher in subjects with the G/G genotype or with G allele in patients without agoraphobia, not in total patients or patients with agoraphobia.

Conclusion

Although there were no significant differences in the genotype and allele distributions, we found a significant association between panic symptom severity and the serotonin 1A receptor gene. This result suggests that the serotonin 1A receptor and serotonin may play a role in the pathogenesis of panic disorder.     

ALOX5AP基因T(-1340)G多态性与中国北方汉族人群冠状动脉粥样硬化性心脏病发病的关联

目的：探讨编码5-脂氧合酶激活蛋白FLAP的基因ALOX5AP T(-1340)G多态性与中国北方汉族人群冠心病发病的相关关系。 方法：选自2006-01/2007-09在解放军沈阳军区总医院行选择性冠状动脉造影者共680例。根据造影结果分为冠心病组336例均为选择性冠状动脉造影阳性,对照组344例为造影阴性或动脉管腔狭窄< 50%且临床上无相关心肌缺血证据者。在随机选择的无亲缘关系的48名中国北方汉族个体中,采用聚合酶链反应-重测序法对ALOX5AP基因进行单核苷酸多态的筛查,共发现7个多态。冠心病组和对照组受试者采用聚合酶链反应-限制性片段长度多态性方法检测ALOX5AP基因T(-1340)G多态性位点在两组间的基因型和等位基因分布。 结果：ALOX5AP基因T(-1340)G 3种基因型(TT型,TG型和GG型)在冠心病组分布频率分别为26.79%,51.79%和21.43%,在对照组分别为33.72%,47.38%和18.90%,两组间的基因型分布皆符合Hardy-Weinberg平衡定律,3种基因型在两组间的分布差异无显著性意义(χ2=3.90,P > 0.05)。G等位基因在两组间的分布频率为47.32 % 和 42.59 %,差异无显著性意义(χ2=3.08,P > 0.05)。按性别分层进行亚组分析,发现ALOX5AP T(-1340)G 多态的基因型和等位基因频率在冠心病组和对照组间的比较差异无显著性意义。 结论：5-脂氧合酶激活蛋白基因 ALOX5AP T(-1340)G 多态性与中国北方汉族人群冠心病发病可能无相关关系。     

Association of the 5-HT2A receptor gene polymorphism 102 T/C with ischemic stroke

Serotonin (5-HT) has been implicated in a number of cardiovascular disorders due to its ability to induce vascular contraction and platelet aggregation through activation of the 5-HT2 receptor family. In this study, we investigated the association of stroke in a Scandinavian population with two common polymorphisms in the 5-HT2A receptor gene. The two polymorphisms under investigation, namely the 102T/C and the −1438A/G variations of the 5-HT2A receptor gene, were examined in a case control association study involving 99 stroke patients and a comparable number of controls. Among patients, the prevalence of the homozygous 102T/T genotype was significantly higher than in controls (28.3% vs 13.5%; p<0.01). The allelic frequency of 102T carriers was also significantly higher in stroke patients than in controls (p=0.002, OR=1.88, 95%CI, 1.27–2.80). The association between the 102T allele and stroke was significant in both males and females. There was no association between stroke and the −1438A/G polymorphism. Taken together, this study indicates that the 102T/C polymorphism in the 5-HT2A receptor gene could be an independent risk factor for developing stroke.     

Lack of association between the platelet glycoprotein Ia C807T gene polymorphism and myocardial infarction in Japanese. An approach entailing melting curve analysis with specific fluorescent hybridization probes

The platelet-collagen receptor, glycoprotein Ia/IIa (integrin alpha2beta1) plays a fundamental role in the adhesion of platelets to fibrillar collagen, an event leading to platelet activation and thrombus formation and contributing to the pathogenesis of thrombotic disease. Further, glycoprotein Ia/IIa receptor density and function may be associated with two linked and silent polymorphisms (807C/T and 873G/A) within the glycoprotein Ia gene. We tested the extent to which these polymorphisms serve as genetic markers of myocardial infarction in a Japanese population. A case-control study was carried out using 210 Japanese myocardial infarction patients and 420 age- and sex-matched controls. Genotyping was accomplished using PCR followed by melting curve analysis with specific fluorescent hybridization probes. The 807CC, CT, TT genotypes linked perfectly to the 873GG, GA, AA genotypes, respectively. Allele frequencies of the 807T (873A) variant were similar in the control and patient groups (0.373 vs. 0.352). The 807T and 873A variants of platelet glycoprotein Ia gene are common and in a perfect linkage in the Japanese population, but it appears unlikely that the 807T (873A) variant represents a useful marker of increased risk for myocardial infarction.     

Effect of physiologic shear stresses and calcium on agonist-induced platelet aggregation, secretion, and thromboxane A2 formation

INTRODUCTION: Platelets in vivo react under low-shear venous-flow as well as high-shear arterial-flow conditions. Because most studies were carried out at low shear stresses, platelet granule secretion at high shear has not been examined thoroughly. We investigated the secretion of all three types of platelet granules and thromboxane A(2) formation at high shear after stimulation with ADP or thrombin. MATERIALS AND METHODS: Washed human platelets were reacted rapidly (<5 s) in a quenched-flow system simulating high-shear arterial-flow conditions (30 dyn/cm(2)). For comparison, we employed a low-shear stirring system (1-5 dyn/cm(2)). Serotonin release and membrane exposure of P-selectin (alpha), CD63 (dense), and CD107a (lysosomes) were used to assess granule secretion. Aggregation was evaluated by resistive-particle counting of the remaining platelet singlets. RESULTS AND CONCLUSIONS: ADP and thrombin induced similar strong levels of aggregation ( approximately 70%) at high shear by 5 s. Thrombin also caused release of about 40% of all alpha and dense granules within 5 s. However, by 5 s at high shear, ADP failed to induce significant granule secretion or thromboxane A(2) formation (<5%, p>0.05). By 10 min at low shear, ADP caused secretion and thromboxane A(2) formation only at non-physiological, micromolar extracellular Ca(2+) concentrations. These results emphasize the ability of thrombin to initiate multiple aspects of platelet function within seconds, while ADP was only able to induce rapid aggregation.