807 C/T Polymorphism of the glycoprotein Ia gene and pharmacogenetic modulation of platelet response to dual antiplatelet treatment.

Glycoprotein (GP) Ia/IIa is a major platelet-collagen receptor playing a key role in thrombosis following collagen exposure. The 807 C/T polymorphism of the GP Ia gene (ITGA2) has been associated with platelet GP Ia/IIa receptor expression, having T-allele carriers, increased receptor density and thrombotic risk. The aim of the study was to assess the role of the 807 C/T polymorphism on modulating platelet function in patients undergoing coronary stenting receiving a 300 mg clopidogrel loading dose. Platelet aggregation was assessed in 44 patients by light transmittance aggregometry following adenosine diphosphate and collagen stimuli at baseline, and 10 min, 4 h and 24 h after clopidogrel front loading. The T allele was found in 73% of patients. Clopidogrel reduced adenosine diphosphate-induced platelet aggregation (P < 0.01), which was similar in carriers and non-carriers of the T allele throughout the study (P = 0.73). Clopidogrel reduced collagen-induced platelet aggregation only in non-carriers of the T allele (P = 0.03), which resulted in an increase in T allele carriers during the overall study (P = 0.04). In conclusion, the T allele of the GP Ia gene modulates platelet aggregation and clopidogrel antiplatelet effects, suggesting an enhanced reactivity to fibrillar collagens (exposed during coronary stenting) in T allele carriers and might contribute to an increased thrombotic risk in these patients.     

Role of glycoprotein Ia gene polymorphisms in determining platelet function in myocardial infarction patients undergoing percutaneous coronary intervention on dual antiplatelet treatment

Response variability to antiplatelet treatment has been described and the widespread use of acetylsalicylic acid (ASA) and clopidogrel requires clarification of the residual platelet reactivity (RPR). Various glycoprotein Ia (GpIa) polymorphisms have been investigated, but their influence on platelet reactivity in myocardial infarction (MI) patients undergoing percutaneous coronary intervention (PCI) on dual antiplatelet treatment is not still elucidated. Aim of this study was to evaluate the effect of C807T, G873A and T837C polymorphisms of GpIa on modulating platelet function in MI patients on dual antiplatelet treatment undergoing PCI. We measured platelet function by both a point-of-care assay (PFA100) and platelet-rich-plasma aggregation in 289 MI patients undergoing PCI and receiving dual antiplatelet treatment. Our data show that C807T/G873A polymorphisms, but not T837C, are associated with higher platelet reactivity. Carriers of the 807T/873A allele had significantly higher platelet aggregation values after arachidonic acid (AA) and collagen stimuli and, even if they did not reach the statistical significance, after 2 and 10 microM ADP stimuli; 807T/873A allele carriers had also significantly shorter closure times on PFA100/epinephrine membranes. At the multiple analyses, C807T/G873A polymorphisms resulted an independent risk factor for RPR defined by both AA induced platelet aggregation (OR=3.0, 95%CI 1.17-7.89, p=0.022) or by PFA100/epinephrine (OR=4.1, 95%CI 1.53-10.89, p=0.005). In conclusion, this study shows the 807T/873A allele of the GpIa gene is an independent risk factor for the RPR on dual antiplatelet treatment, and extends, in a larger acute coronary syndrome population, the observation that the 807T/873A allele is associated with higher platelet reactivity.     

Influence of aspirin resistance on platelet function profiles in patients on long-term aspirin and clopidogrel after percutaneous coronary intervention

Increased platelet inhibition is achieved when clopidogrel is added to aspirin (acetylsalicylic acid [ASA]). A broad variability in platelet inhibition profiles during the early phases of treatment has been demonstrated and may be attributed to ASA resistance. However, the influence of ASA sensitivity on platelet function profiles of patients on long-term dual antiplatelet therapy has yet to be explored. A total of 135 patients who had previously undergone percutaneous coronary intervention on long-term (>1 month) ASA and clopidogrel therapy was included. The PFA-100 system was used to define ASA resistance. Platelet aggregation, after adenosine diphosphate (6 and 20 micromol/L) and collagen (6 microg/ml) stimuli, and platelet activation (glycoprotein IIb/IIIa activation and P-selectin expression), after adenosine diphosphate (2 micromol/L) and thrombin receptor-activating peptide (50 micromol/L) stimuli, were assessed by light transmittance aggregometry and flow cytometry, respectively. Patient variability in response to treatment was defined by the coefficient of variability. ASA resistance was found in 60 of 135 patients (44%). Patients with diabetes were more frequently ASA resistant. Collagen/epinephrine- and collagen/adenosine diphosphate-coated cartridges on the PFA-100 had shorter closure times in the ASA-resistant population compared with ASA-sensitive patients. Platelet aggregation and activation were significantly higher in ASA-resistant patients. A broad variability (coefficient of variation >0.25) in patient response to treatment was observed in ASA-resistant and -sensitive patients. In conclusion, ASA resistance is associated with increased platelet reactivity in patients on long-term dual antiplatelet treatment.     

Glycoprotein Ia gene C807T polymorphism and risk for major adverse cardiac events within the first 30 days after coronary artery stenting

The glycoprotein complex Ia/IIa (GP Ia/IIa) is a major collagen receptor on platelets and other cell types. Recently, linked polymorphisms within the coding region of the GP Ia gene (C807T and G873A) were identified that are related to GP Ia/IIa surface expression. The T807/A873 allele is associated with high expression, whereas the C807/G873 allele is associated with low surface expression of GP Ia/IIa. Subsequently, the T807 allele was found to be associated with coronary and cerebral infarction in younger patients. Platelet adhesion to the vessel wall plays a pivotal role in thrombosis after coronary artery stent placement. The goal of this study was to test whether C807T polymorphism is associated with a higher incidence of thrombotic events following coronary stenting. Consecutive patients treated with coronary stent placement (n = 1797) were genotyped for C807T polymorphism with polymerase chain reaction and allele-specific fluorogenic probes. The composite end point was defined as death, myocardial infarction, or urgent target vessel revascularization within 30 days of stent implantation. The genotype distribution of the study population was CC in 36.5%, CT in 46.7%, and TT in 16.8% of the patients. The incidence of the composite end point was 6.5% in T allele carriers and 5.3% in noncarriers (odds ratio for T allele carriage 1.23 [95% confidence interval, 0.81-1.86], P =.33). After adjusting for other baseline characteristics, the odds ratio for the composite end point was 1.15 (0.76-1.75). Therefore, C807T genotype has no significant influence on the major adverse events occurring after coronary artery stenting.     

The C807T/G873A polymorphism in the platelet glycoprotein Ia gene and the risk of acute coronary syndrome in the Italian population

Membrane glycoprotein (GP) Ia/IIa mediates platelet adhesion to collagen. The linked C807T/G873A polymorphisms in the GP Ia gene are correlated with a variable expression of the platelet surface receptor, the 807 TT/873 AA genotype being associated with a higher receptor density. Our study aimed to evaluate the possible role of the GP Ia C807T/G873A polymorphism as a risk factor for acute coronary syndrome in the Italian population. We investigated 157 patients with acute coronary syndrome (117 with myocardial infarction and 40 with severe unstable angina) as the first manifestation of coronary disease occurring before 65 years of age, compared with 312 healthy controls. All individuals were of Italian ancestry and were genotyped for the GP Ia C807T/G873A polymorphism. Complete linkage between the 807 and 873 sites was found in all samples. The 807 TT genotype was present in 12.7% of cases and in 4.8% of controls; the odds ratio for acute coronary syndrome was 2.9 (95% CI 1.4--5.8) for the 807 TT genotype compared with C-allele carriers and 0.6 (95% CI 0.4--0.9) for the 807 CC genotype compared with T-allele carriers. For the TT genotype, compared with CC homozygotes, the increase in risk was 3.4-fold in patients with at least one risk factor (smoking, hypercholesterolaemia, diabetes, systemic hypertension) and 4.1-fold in patients with angiographically diagnosed two- or three-vessel disease. We conclude that the GP Ia 807 TT (873 AA) genotype is associated with an increased risk of acute coronary syndrome in the Italian population; conversely, the GP Ia 807 CC (873 GG) genotype seems to represent a protective factor.     

Platelet glycoprotein Ia 807C/T (Phe224) and 873G/A (Thr246) dimorphisms in Turkey

At sites of vascular injury, the platelet collagen receptor Glycoprotein Ia/IIa (GPIa/IIa) acts as an important mediator of platelet adhesion to fibrillar collagens. Two silent polymorphisms (807C/T and 873G/A) within the glycoprotein Ia gene have been implicated in increased risk of developing thrombosis and myocardial infarction in affected individuals. To provide basis for future studies, we examined the frequency of these GPIa polymorphisms for people in Turkey. We analyzed 118 unrelated individuals for their genotypes of the GPIa gene using a multiplexed allele specific-PCR based method. The allelic frequencies were found to be 34% for 807T/873A and 66% for 807C/873G; the genotypic frequencies were 13% for 807TT/873AA, 44% for 807CT/873GA, and 43% for 807CC/873GG.     

Disaggregation Following Agonist-Induced Platelet Activation in Patients on Dual Antiplatelet Therapy

Disaggregation as the difference between maximal and final platelet aggregation by light transmission aggregometry indicates the stability of platelet aggregates. We evaluated the extent of disaggregation after platelet stimulation with adenosine diphosphate (ADP), arachidonic acid (AA), collagen, epinephrine, and thrombin receptor-activating peptide (TRAP)-6 in 323 patients on dual antiplatelet therapy with daily aspirin and clopidogrel (group 1), prasugrel (group 2), or ticagrelor (group 3) therapy. All patients in group 1 underwent elective angioplasty and stenting, whereas all patients included in groups 2 and 3 suffered from acute coronary syndromes (STEMI or NSTEMI) and underwent urgent PCI. Significant differences between maximal and final platelet aggregation were observed with all agonists throughout the groups (all p<0.001). Disaggregation was highest using AA (clopidogrel 36.5%; prasugrel/ticagrelor 100%) and ADP (clopidogrel 21.7%; prasugrel/ticagrelor 100%). In contrast, low disaggregation was observed after platelet stimulation with collagen and TRAP-6 in clopidogrel-treated patients, and after platelet stimulation with collagen and epinephrine in prasugrel- and ticagrelor-treated patients. In conclusion, pathways of platelet activation that are not inhibited by standard antiplatelet therapy allow persisting platelet aggregation and may at least in part be responsible for adverse ischemic events.     

Deficiency of intact thrombospondin and membrane glycoprotein Ia in platelets with defective collagen-induced aggregation and spontaneous loss of disorder

Platelets from a patient with a severe lifelong bleeding tendency, which later spontaneously disappeared, lacked intact thrombospondin and glycoprotein (GP) Ia. Before disappearance of the bleeding disorder, results of coagulation studies and platelet aggregation in response to adenosine diphosphate (ADP), arachidonic acid, thrombin, A23187, epinephrine, and ristocetin were normal. In contrast, aggregation only occurred in the presence of collagen or wheat germ agglutinin at unusually high doses of these agonists. The platelets adhered normally to purified bovine and human type I collagen, and they did not spread in the presence of methylated type I collagen. No collagen-induced clot retraction was observed. Two-dimensional gel electrophoretic analyses of platelet proteins and immunologic studies showed that intact thrombospondin and GP Ia were absent. Aggregation in response to collagen could be restored by adding thrombospondin. Disappearance of the bleeding tendency occurred at the onset of menopause; subsequent analyses revealed that thrombospondin and GP Ia were present in platelets and that collagen-induced platelet aggregation was normal. These results suggest that both thrombospondin and GP Ia are essential in collagen-induced platelet aggregation. The spontaneous disappearance of the bleeding tendency may have been related to hormonal influences.     

Ischaemic strokes and homozygosity for the alpha2 807T allele of the platelet collagen receptor in young monozygotic twins.

A nucleotide 807T variant of the glycoprotein Ia gene that correlates with increased platelet surface levels of the platelet collagen receptor alpha2beta1 was recently found to be associated with an increased risk of ischaemic stroke in younger patients. We report the history of twins who developed ischaemic strokes and were shown to be homozygous for the alpha2 807T allele. The twins developed ischaemic strokes at the ages of 23 and 33 years, one of them with recurrent events. They had no conventional risk factors. Cardiac and vascular investigations were normal and no aetiology could be found. There was a family history of cerebrovascular disease. Genotyping of glycoprotein alpha2 C807 T was performed and both twins were found to be homozygous for the 807T allele. This allele probably contributed to the occurrence of strokes in these young men. Further prospective studies are needed to evaluate whether screening for this polymorphism should be considered in young patients with unexplained stroke, particularly when a positive family history was found.     

Comparison of increased aspirin dose versus combined aspirin plus clopidogrel therapy in patients with diabetes mellitus and coronary heart disease and impaired antiplatelet response to low-dose aspirin

The effects of therapy with aspirin 300 mg/day and with combined aspirin 100 mg/day plus clopidogrel 75 mg/day on platelet function were compared in patients with diabetes mellitus and coronary artery disease and impaired antiplatelet responses to aspirin 100 mg/day. The study population consisted of 151 outpatients with type II diabetes mellitus and coronary artery disease who were taking aspirin 100 mg/day. Of the 151 patients, a subgroup of subjects with impaired aspirin response were selected on the basis of the results of platelet aggregometry. Nonresponsiveness to aspirin was defined as mean aggregation > or =69% with 3 micromol/L adenosine diphosphate and mean aggregation > or =70% with 2 micromol/L collagen. Aspirin semiresponders were defined as meeting 1 but not both of these criteria. Nonresponders and semiresponders were randomized equally to aspirin 300 mg/day and aspirin 100 mg/day plus clopidogrel 75 mg/day, and aggregation tests were repeated after 2 weeks. Sixty of the 151 patients with diabetes (40%) were found to respond to aspirin inadequately. Platelet aggregation induced by adenosine diphosphate and collagen decreased significantly after aspirin 300 mg/day or combined therapy. Combined treatment was found to have a stronger inhibitory effect on platelet aggregation induced by adenosine diphosphate than aspirin 300 mg/day (p = 0.002). Impaired aspirin response was resolved by increasing the aspirin dose or adding clopidogrel to aspirin (p <0.0001 for each). However, desired platelet inhibition was achieved in significantly more patients by combined treatment than by aspirin 300 mg/day (p <0.05). In conclusion, aspirin 100 mg/day does not inhibit platelet function adequately in a significant number of patients with diabetes mellitus and coronary artery disease. Increasing the aspirin dose to 300 mg/day or adding clopidogrel to aspirin can provide adequate platelet inhibition in a significant number of those patients with impaired responses to low-dose aspirin.     

Glycoprotein Ia C807T polymorphism and risk of restenosis following coronary stenting

Platelets are thought to contribute to development of restenosis following percutaneous coronary interventions. The glycoprotein Ia/IIa complex is a major platelet collagen receptor, its surface expression being influenced by two, linked single nucleotide polymorphisms (C807T and G873A) in the glycoprotein Ia gene. T807 is associated with increased expression of this integrin receptor. We assessed whether T807 is associated with an increased risk of restenosis in 1769 consecutive patients treated with coronary stenting. 6-month follow-up angiograms were available in 82.4% of the patients. C807T genotype distribution was CC in 35.8%, CT in 47.6% and TT in 16.6% of the patients. Restenosis (diameter stenosis > or =50% at follow-up angiography) occurred in 32.9% of CC, 31.5% of CT and 32.1% of TT patients (P=0.87). The rate of major adverse cardiac events (death, myocardial infarction or need of reintervention) within 1 yr was 21.6% for CC, 21.7% for CT and 21.2% for TT patients (P=0.98). Thus, carriage of the GP Ia T807 allele is not associated with an increased risk of restenosis or unfavorable late outcome following coronary artery stenting.     

Human platelet alphaIIbeta3 integrin binding affinity and specificity of SJ874: antiplatelet efficacy versus aspirin

OBJECTIVE: To define the affinity and specificity of SJ874, a nonpeptide antiplatelet agent for platelet glycoprotein Ilb/IIIa integrin, and to determine the antiplatelet efficacy of SJ874 relative to those of glycoprotein IIbIIIa antagonists and aspirin. METHODS: Binding affinity and specificity of SJ874 for platelet glycoprotein IIb/IIIa integrin were determined using integrin-mediated binding and adhesion assays with human cells. Additionally, the antiplatelet efficacy of SJ874 was determined and compared with those of other glycoprotein IIb/IIIa antagonists and aspirin using light-transmittance and laser-scattering aggregometry. RESULTS: SJ874 inhibited aggregation of human platelets induced by 10 micromol/l adenosine diphosphate (ADP) with a concentration for half-maximal effect of 0.046 +/- 0.005 micromol/l using light-transmittance aggregometry. Using laser-scattering aggregometry, SJ874 was found to totally inhibit formation both of micro-aggregates and of macro-aggregates induced either by ADP or by epinephrine. In contrast, administration of 325 mg aspirin to normal healthy volunteers attenuated formation of macro-aggregates but not micro-aggregates. SJ874 inhibited binding of [125I]-fibrinogen to activated (by ADP, epinephrine, and arachidonic acid at concentrations of 100 micromol/l each) gel-filtered human platelets with a concentration for half-maximal effect of 0.0012 +/- 0.0005 micromol/l. SJ874 was demonstrated to associate more tightly with resting human platelets than did DMP754 [1] and slightly less tightly than did DMP802 [2]. SJ874 was demonstrated to exhibit a high degree of specificity for platelet glycoprotein IIb/IIIa (alphaIIb/beta3) integrin compared with other known integrins, including alphavbeta3, alphavbeta5, and alpha5beta1 (concentration for half-maximal effect > 100 micromol/l). CONCLUSION: SJ874 is a potent and specific platelet glycoprotein IIb/IIIa antagonist with high affinity for and tight association with human platelets. These data suggest that SJ874 might have good antiplatelet utility for inhibiting formation both of platelet micro-aggregates and of macro-aggregates of platelets and a long duration of action in humans due to its slow dissociation from human platelets.     

Insulin therapy is associated with platelet dysfunction in patients with type 2 diabetes mellitus on dual oral antiplatelet treatment.

OBJECTIVES: This study sought to assess the influence of type 2 diabetes mellitus (T2DM) and the impact of hypoglycemic treatment (insulin vs. noninsulin) on platelet function profiles in patients treated with dual oral antiplatelet therapy. BACKGROUND: Insulin inhibits platelet aggregation by suppressing the P2Y12 pathway. However, T2DM patients have a loss of responsiveness to insulin that leads to upregulation of the P2Y12 pathway, increased platelet reactivity, and reduced responsiveness to antiplatelet agents. Patients with insulin-treated diabetes mellitus (ITDM) have a more advanced disease status and higher atherothrombotic risk compared with non-ITDM (NITDM). However, the impact of insulin therapy on platelet dysfunction in patients treated with P2Y12 antagonists is unknown. METHODS: A total of 201 T2DM and 65 nondiabetic patients with coronary artery disease in a steady phase of aspirin and clopidogrel treatment were studied. Platelet aggregation was assessed using agonists specific (6 and 20 microM adenosine diphosphate [ADP]) and nonspecific (6 microg/ml collagen and 20 microM epinephrine) for the P2Y12 pathway. High shear-induced platelet reactivity was assessed by means of the PFA-100 system (Dade-Behring International, Miami, Florida). RESULTS: The T2DM patients had platelet aggregation and shear-induced platelet function significantly increased compared with nondiabetic patients using all assays. Platelet aggregation was increased in ITDM (n = 68) compared with NITDM (n = 133) patients after P2Y12-specific stimuli. Insulin treatment was the strongest predictor of ADP-induced aggregation. Platelet function profiles were similar between ITDM and NITDM using assays nonspecific to the P2Y12 pathway. Platelet dysfunction was independent of glycemic control and inflammatory status. CONCLUSIONS: The P2Y12-dependent and -independent pathways of platelet reactivity are altered in T2DM compared with nondiabetic patients, and ITDM have greater ADP-induced platelet aggregation compared with NITDM.     

Platelet aggregation through prothrombinase activation induced by non-aggregant doses of platelet agonists.

Activation of the prothrombinase complex, which catalyzes the formation of thrombin from prothrombin, is crucial for the (patho)physiological processes of hemostasis and thrombosis. We here report that washed platelets supplemented with prothrombin can be irreversibly aggregated with otherwise non-aggregant doses of adenosine diphosphate (10 micromol/l), thrombin (0.06 U/ml), or collagen (1 microg/ml). Prothrombinase-catalyzed prothrombin to thrombin conversion most probably supports this aggregation response, since inhibitors of thrombin (hirudin or heparin) and an inhibitor of activated factor X (DX-9065a) impair the response. A certain degree of agonist-induced platelet activation seems to be required for this prothrombin-supported aggregation response, since prothrombin alone does not induce aggregation, and blockade of glycoprotein Ia/IIa with a specific antibody inhibits the platelet aggregation response to collagen and prothrombin. These results may suggest that activation of the prothrombinase complex could be a common step of the platelet response to distinct agonists, which may be achieved at low levels of platelet stimulation.     

Clopidogrel and risk for acute coronary events

Clopidogrel bisulfate is a potent adenosine diphosphate receptor blocker that irreversibly inhibits platelet aggregation by preventing the activation of the glycoprotein IIb/IIIa pathway. This helps to prevent thrombus formation and resultant ischemic or thrombotic complications. Clopidogrel was proven to be superior to aspirin in the treatment of atherothrombotic diseases. Clopidogrel plus aspirin, known as dual antiplatelet therapy, is highly effective in patients with acute coronary syndromes or undergoing percutaneous coronary intervention. There is no apparent benefit of dual antiplatelet therapy in primary prevention. In this article, we review the benefits of clopidogrel as an antiplatelet agent and its role in the management of acute coronary syndromes and following percutaneous coronary intervention.     

Resistance in vitro to low-dose aspirin is associated with platelet PlA1 (GP IIIa) polymorphism but not with C807T(GP Ia/IIa) and C-5T Kozak (GP Ibalpha) polymorphisms

OBJECTIVES: We investigated whether three platelet gene polymorphisms, Pl(A1/A2), C807T, and C-5T Kozak (encoding, respectively, for platelet membrane glycoproteins (GP) IIIa, GP Ia/IIa, GP Ibalpha), could contribute to the resistance to a low dose of aspirin (160 mg/day). BACKGROUND: Aspirin antiplatelet effect is not uniform in all patients, and the mechanism by which some patients are in vitro resistant to aspirin remains to be determined. However, it has been suggested that polymorphisms of platelet membrane glycoproteins might contribute to aspirin resistance. METHODS: Ninety-eight patients on aspirin (160 mg/day) for at least one month were enrolled. Aspirin resistance was measured by the platelet function analyzer (PFA)-100 analyzer; genotyping of the three polymorphisms was performed using a polymerase chain reaction-based restriction fragment-length polymorphism analysis. RESULTS: Using a collagen/epinephrine-coated cartridge on the PFA-100, the prevalence of aspirin resistance was 29.6% (n = 29). Aspirin-resistant patients were significantly more often Pl(A1/A1) (86.2%; n = 25) than sensitive patients (59.4%; n = 41; p = 0.01). Of the 29 patients, 25 were reevaluated after having taken 300 mg/day aspirin for at least one month. Only 11 patients still have nonprolonged collagen epinephrine closure time, and these were all Pl(A1/A1). No relation was found between resistance status and C-5T Kozak or C807T genotypes. CONCLUSIONS: Platelets homozygous for the Pl(A1) allele appear to be less sensitive to inhibitory action of low-dose aspirin. This differential sensitivity to aspirin may have potential clinical implications whereby specific antiplatelet therapy may be best tailored according to the patient's Pl(A) genotype.     

Association of the platelet glycoprotein Ia C807T gene polymorphism with nonfatal myocardial infarction in younger patients

Recently, we have shown that two alleles of the glycoprotein (GP) Ia gene, designated C807 and T807, are associated with low or high platelet GPIa-IIa density and consequently with slower or faster rate of platelet adhesion to type I collagen, respectively. This polymorphism could therefore present a genetic predisposition for the development of thrombotic disease and hemostasis. We investigated the relationship of the GPIa C807T dimorphism to the risk of coronary artery disease (CAD) and myocardial infarction (MI). An allele-specific polymerase chain reaction (PCR) was developed for genotyping of C807T polymorphism. DNA samples from 2237 male patients who underwent coronary angiography on account of coronary heart disease as verified illness or presumptive diagnosis were genotyped. The odds ratio was calculated as an estimate of the relative risk by multiple logistic regression. We found a strong association between the T allele and nonfatal MI among individuals younger than the mean age of 62 years (n = 1,057; odds ratio, 1.57; P =.004). The odds ratio of MI increased for T807 carriers with decreasing age. The highest odds ratio was detected within the youngest 10% of the study sample (<49 years; n = 223; odds ratio, 2. 61; P =.009). In contrast, no evidence of an association between C807T dimorphism with CAD was found. Our findings suggest that inherited platelet GP variations might have an important impact on acute thrombotic disease.     

Association of the GPIa C807T and GPIIIa PlA1/A2 polymorphisms with premature myocardial infarction in men.

Aims Recent studies have reported an association between the platelet glycoprotein (GP) Ia C807T polymorphism and myocardial infarction, whereas other studies have reported contradictory results concerning the platelet GPIIIa PlA1/A2 polymorphism. In most of these studies the patients were older than 45 years. Thus we decided to examine both genotypes in 287 men who had their first myocardial infarction before age 45, and a group of 138 healthy controls.Methods and Results The frequency of T807 allele carriers was similar among myocardial infarction patients and among controls (54.6% vs 62.3%; odds ratio (OR) 0.73; 95% confidence interval (CI), 0.47-1.12). The frequency of PlA2 carriers was higher in cases than in controls (26.5% vs 15.2%; OR 1.65; CI, 1.09-2.54). After performing a logistic regression analysis, taking into account other cardiovascular risk factors, this difference did not remain significant. The combination of the risk alleles of both genotypes had no major effect on the myocardial infarction risk.Conclusions The GPIIIa PlA2 allele is not independently associated with the risk of premature myocardial infarction. The T807 allele of the GPIa gene alone or in combination with the PlA2 allele had no major effect on premature myocardial infarction risk.     

Effects of triple antiplatelet therapy (aspirin, clopidogrel, and cilostazol) on platelet aggregation and P-selectin expression in patients undergoing coronary artery stent implantation

The purpose of this study was to determine the effect of the addition of cilostazol to aspirin plus clopidogrel on platelet aggregation after intracoronary stent implantation. Twenty patients who underwent coronary stent placement were randomly assigned to therapy with aspirin plus clopidogrel (dual-therapy group, n = 10) or aspirin plus clopidogrel plus cilostazol (triple-therapy group, n = 10). A loading dose of clopidogrel (300 mg) and cilostazol (200 mg) was administered immediately after stent placement, and clopidogrel (75 mg/day) and cilostazol (100 mg twice daily) were given for 1 month. Platelet aggregation in response to adenosine diphosphate (ADP; 5 and 20 micromol/L) or collagen and P-selectin (CD-62P) expression was assayed at baseline, 2 hours, 24 hours, 1 week, and 1 month after stent placement. Inhibition of ADP-induced platelet aggregation was significantly higher in patients receiving triple therapy than those receiving dual therapy from 24 hours after stent placement, and inhibition of collagen-induced platelet aggregation was significantly higher in the triple-therapy group beginning 1 week after stent placement. P-Selectin expression was significantly lower in the triple-therapy than dual-therapy group at 1 week and 30 days. In conclusion, compared with dual antiplatelet therapy, triple therapy after coronary stent placement resulted in more potent inhibition of platelet aggregation induced by ADP and collagen. These findings suggest that triple therapy may be used clinically to prevent thrombotic complications after coronary stent placement.     

The prevalence of C807T mutation of glycoprotein Ia gene among young male survivors of myocardial infarction: a relation with coronary angiography results

INTRODUCTION: The glycoprotein complex Ia/IIa (GP Ia/IIa) is a major collagen receptor on platelets and other cell types. Recently, linked polymorphisms within the coding region of the GP Ia gene (C807T and G873A) related to GP Ia/IIa surface expression have been identified. The 807T/873A allele is associated with high expression, whereas the 807C/873G allele is associated with low surface expression of GP Ia/IIa. Subsequently, the 807T allele was found to be associated with coronary artery disease (CAD) and cerebral infarction in younger patients. Moreover, platelet thrombus formation is significantly influenced by genetic variations of the GPIb alpha and GPIa receptors and is dependent on the blood flow rate. AIM: 1. To determine the frequency of C807T polymorphism of the GPIa gene in young survivors of myocardial infarction (MI) and 2. to evaluate the relationship between the intensity of CAD in the coronary angiography examination and the 807C/T genetic status of the patients. METHODS: 102 young male survivors of MI (YSMI) -- mean age 43, range 29-49 years, mean age at the time of the first episode 37+/-3 years -- were studied. Obesity was found in 15%, diabetes in 14%, hyperlipidemia in 87%, hypertension in 22% and smoking history in 90% of cases. Familial CAD and/or MI were confirmed in 50% of patients. The control group consisted of 106 healthy volunteers with a negative family history of CAD, both medical staff members and blood donors (mean age 40, range 18-42 years). The genetic study was performed using genomic DNA obtained from peripheral blood leukocytes. The C807T polymorphism of platelet glycoprotein Ia (GPIa) was investigated using the PCR method introduced by Santoso et al. RESULTS: Coronary angiography (Siemens Bicor system) revealed single-artery disease in 34%, two-artery disease in 36% and three-artery disease in 26% of patients. In two patients there were no signs of CAD. The C807T polymorphism of GPIa was found in 73.5% of investigated patients (heterozygotes CT 59.8%, homozygotes TT 13.7%). The CC genotype was confirmed in 26.5% of patients. A similar analysis performed in the group of healthy men showed C807T polymorphism of the GPIa gene in 73.6% (CT in 58.5% and TT in 15.1% of persons, ns). CC genotype was found in 26.4% of persons. Interestingly, the T genotype frequency was similar in patients with three- or two-artery disease in comparison with patients with single-vessel or without CAD (49.3% vs. 50.7%, respectively, ns). In 75 YSMI carrying C807T polymorphism of the GPIa gene additional genetic abnormalities were confirmed in 21 patients - BclI polymorphism of b-chain fibrinogen gene, G4070A and G1691A (FV Leiden) mutation of factor V gene and C677T polymorphism of methylenetetrahydrofolate reductase gene. Partial occurrence of combined polymorphisms was found. This was confirmed independently of the number of coronary arteries involved.CONCLUSIONS: Our results may question the potential role of C807T the GPIa anomaly as a single genetic abnormality predisposing young men to coronary artery disease.