Platelet GP IIIa Polymorphism HPA-1 (PlA) Protects Against Subarachnoid Hemorrhage

Association of Glycoprotein IIIa PlA1/A2 Polymorphism with Risk of Stroke: Updated Meta-Analysis

Cardiovascular diseases are the main cause of death in the world, with ischemic heart disease (i.e., myocardial infarction) and cerebrovascular disease (i.e., stroke) taking the highest toll. Advances in diagnosis and treatment have led to a significant alleviation of ischemic complications, specifically in the realm of pharmacotherapy and interventional devices, while pharmacogenomics has yet to be fully leveraged to improve the burden of disease. Atherothrombotic events might occur earlier or respond worse to treatment in patients with genetic variants of GP IIb/IIIa. Therefore, we aimed to quantitate the involvement of the PlA2 variant in the risk of cerebral stroke events. A systematic search and meta-analysis were performed by pooling the risks of individual studies. A total of 31 studies comprising 5985 stroke patients and 7886 controls were analyzed. A meta-analysis of four studies on hemorrhagic stroke patients showed no association with the PIA2 rs5918(C) polymorphism in both fixed-effect (OR = 0.90 95%CI [0.71; 1.14]; p = 0.398) and random-effect models (OR = 0.86 95%CI [0.62; 1.20]; p-value = 0.386). The power of this analysis was below <30%, indicating a limited ability to detect a true effect. An analysis of the 28 studies on ischemic stroke revealed a significant association with the PIA2 rs5918(C) allele in both fixed-effect (OR = 1.16 95%CI [1.06; 1.27]; p = 0.001) and random-effect models (OR = 1.20 95%CI [1.04; 1.38]; p-value = 0.012), with a power of >80%. The PIA2 allele was associated with an increased risk of ischemic stroke. No association was found with hemorrhagic stroke, most likely due to the small number of available studies, which resulted in a lack of power.

The PlA1/A2 polymorphism of glycoprotein IIIa as a risk factor for stroke: a systematic review and meta-analysis

BACKGROUND

The PlA1/A2 polymorphism of glycoprotein IIIa (GPIIIa) has been reported to be associated with risk of stroke in some studies, although other studies suggest no such association. This meta-analysis and systematic review was conducted to investigate the hypothesis that carriage of the PlA2 allele is a risk factor for stroke.

METHODS

Electronic databases (MEDLINE and EMBASE) were searched for all articles evaluating carriage of the PlA2 allele and the incidence of stroke. Pooled odds ratios (ORs) were calculated using fixed-effect and random-effect models.

FINDINGS

A total of 35 articles were eligible for inclusion, of which 25 studies were suitable for statistical analysis. For carriage of the PlA2 allele, OR 1.12 (n = 11,873; 95% CI = 1.03-1.22; p = 0.011) was observed for the incidence of stroke in adults, with subgroup analyses identifying the association driven by stroke of an ischaemic (n = 10,494; OR = 1.15, 95% CI = 1.05-1.27; p = 0.003) but not haemorrhagic aetiology (n = 2,470; OR = 0.90, 95% CI = 0.71-1.14; p = 0.398). This association with ischaemic stroke was strongest in individuals homozygous for the PlA2 allele compared to those homozygous for wild-type PlA1 (n = 5,906; OR = 1.74, 95% CI = 1.34-2.26; p<0.001). Subgroup analysis of ischaemic stroke subtypes revealed an increased association with stroke of cardioembolic (n = 1,271; OR 1.56, 95% CI 1.14-2.12; p = 0.005) and large vessel (n = 1,394; OR = 1.76, 95% CI 1.34-2.31; p<0.001) aetiology, but not those of small vessel origin (n = 1,356; OR = 0.99, 95% CI 0.74-1.33; p = 0.950). Egger's regression test suggested a low probability of publication bias for all analyses (p>0.05).

CONCLUSIONS

The totality of published data supports the hypothesis that carriage of the PlA2 polymorphism of GPIIIa is a risk factor for ischaemic strokes, and specifically those of cardioembolic and large vessel origin.

Genetic regulation of platelet receptor expression and function: application in clinical practice and drug development

Understanding genetic contributions to platelet function could have profound clinical ramifications for personalizing platelet-directed pharmacotherapy, by providing insight into the risks and possible benefits associated with specific genotypes. This article represents an integrated summary of presentations related to genetic regulation of platelet receptor expression and function given at the Fifth Annual Platelet Colloquium in January 2010. It is supplemented with additional highlights from the literature covering (1) approaches to determining and evidence for the associations of genetic variants with platelet hypo- and hyperresponsive phenotypes, (2) the ramifications of these polymorphisms with regard to clinical responses to antiplatelet therapies, and (3) the role of platelet function/genetic testing in guiding antiplatelet therapy.

Platelet gene polymorphisms and risk of bleeding in patients undergoing elective coronary angiography: a genetic substudy of the PRAGUE-8 trial

AIM

Utilization of cardiac catheterization has increased dramatically over time. Bleeding is a major prognostic predictor after percutaneous coronary catheterization procedures. This study aimed to assess the impact of eight polymorphisms of genes encoding platelet receptors and enzymes on the risk of bleeding in patients undergoing elective coronary angiography (CAG).

METHODS

Polymorphisms of platelet receptors, GP Ia (807C>T, rs1126643), GP VI (13254T>C, rs1613662), GP IIIa (HPA-1, rs5918), PAR-1 (IVS-14A>T, rs168753), P2Y(12) (34C>T, rs6785930 and H1/H2 haplotype, rs2046934), and genetic variations of the gene coding for cyclooxygenase-1 (COX-1) (-842A>G, rs10306114 and 50C>T, rs3842787) were studied. The frequencies of gene polymorphisms carriers were investigated in 696 patients undergoing elective CAG because of suspected or proven stable coronary artery disease. Genotyping was done using PCR, followed by melting curve analysis with specific fluorescent hybridization probes.

RESULTS

In patients undergoing elective CAG (without ad hoc percutaneous coronary intervention (PCI) and without clopidogrel pretreatment) a significant association was found between bleeding risk and variations in the gene coding for COX-1 (-842A>G and 50C>T) (both p=0.013). Six other investigated polymorphisms did not show any influence on bleeding complications. After controlling for potential bleeding confounders, the association between COX-1 gene polymorphisms (-842A>G and 50C>T) and bleeding risk remained statistically significant (both odds ratios 12.1, p=0.012).

CONCLUSION

Cyclooxygenase-1 -842G and 50T alleles significantly contribute to the risk of bleeding complications in patients undergoing elective CAG. Genetic testing is able to influence the safety of diagnostic cardiac catheterization in large numbers of low risk patients with borderline indications.

Human platelet alloantigens (HPA) 1, HPA2, HPA3, HPA4, and HPA5 polymorphisms in sickle cell anemia patients with vaso-occlusive crisis

OBJECTIVES

Vaso-occlusive crisis (VOC) is a significant cause of morbidity and mortality in sickle cell anemia (SCA) patients. Insofar as polymorphism in human platelet alloantigen (HPA) exhibit a prothrombotic nature, we hypothesized that specific HPA polymorphic variants are associated with VOC. We investigated the distribution of HPA1, HPA2, HPA3, HPA4, and HPA5 alleles genotypes among VOC and non-VOC control SCA patients.

PATIENTS/METHODS

This was a case-control study. Study subjects comprised SCA patients with (VOC group; n = 127) or without (Steady-state group; n = 130) VOC events. HPA genotyping was done by PCR-SSP.

RESULTS

Significantly higher frequencies of HPA-2b, HPA-3b, and HPA-5b alleles, and marked enrichment of HPA-3b/3b, HPA-5a/5b, and HPA-5b/5b genotypes, were seen in VOC than in control SCA patients. Taking homozygous wild-type genotypes as reference, univariate analysis identified HPA-3a/3b, HPA-3b/3b, and HPA-5b/5b to be associated with VOC. Multivariate analysis confirmed the independent association of only HPA-3a/3b and HPA-3b/3b genotypes with VOC. HPA-3 genotypes were significantly correlated with VOC frequency, type, and medication, and requirement for hospitalization. While both HPA 3a/3b (P = 0.002; OR = 2.94; 95% CI = 1.49-5.77) and 3b/3b (P = 0.006; OR = 3.16; 95% CI = 1.40-7.17) genotypes were associated with need for hospitalization, only HPA-3b/3b was associated with VOC frequency, type (localized vs. generalized), and medication (narcotics vs. NSAIDs).

CONCLUSION

This confirms the association of HPA polymorphisms with SCA VOC, of which HPA-3 appears to be independent genetic risk factors for SCA VOC.

Polymorphisms of human platelet alloantigens HPA-1 and HPA-2 associated with severe coronary artery disease

OBJECTIVES

Insofar as platelet membrane glycoprotein (GP) polymorphisms were identified as potential risk factors for coronary artery disease (CAD), we investigated the contribution of human platelet antigen (HPA)-1 (GPIIb/IIIa) and HPA-2 (GPIb/IX) alleles and haplotypes to CAD pathogenesis.

METHODS

Study subjects comprised 247 middle-age CAD patients and 316 age-, gender-, and race-matched controls; HPA genotyping was performed by polymerase chain reaction with sequence specific primers.

RESULTS

The frequencies of HPA-1b (P<.001) and HPA-2b (P<.001) alleles and HPA-1a/1b (P<.001), HPA-1b/1b (P<.001), and HPA-2a/2b (P<.001) genotypes were higher in patients than control subjects. Select HPA haplotypes comprising the HPA-1b/2a (Pc=2.2 × 10(-4)) and HPA-1b/2b (Pc=.001) haplotypes which were positively associated, and the HPA-1a/2a (Pc=3.2 × 10(-5)) which was negatively associated with CAD, confer a disease susceptibility and protective nature to these haplotypes. Multivariate analysis confirmed the positive association of HPA-1b/2a [adjusted odds ratio (aOR)=3.63; 95% CI=2.42-5.43] and HPA-1b/2b (aOR=2.92; 95% CI=1.43-5.94) haplotypes with CAD, after adjustment for a number of covariates.

CONCLUSIONS

Our results suggest that HPA-1/HPA-2 haplotypes may be considered to be a major risk factor for CAD in middle-aged Tunisians.

Genotype-phenotype relationship for six common polymorphisms in genes affecting platelet function from 286 healthy subjects and 160 patients with mucocutaneous bleeding of unknown cause

Polymorphisms affecting platelet receptors and intracellular proteins have been extensively studied in relation to their potential influence in thrombosis and haemorrhages. However, few reports have addressed their impact on platelet function, with contradictory results. Limitations of these studies include, among others, small number of patients, the platelet functional parameters analyzed and their known variability in the healthy population. We studied the effect of six polymorphisms [ITGB3 1565T > C (HPA-1), GPIBA variable number tandem repeat and 524C > T (HPA-2), ITGA2 807C > T, ADRA2A 1780A > G, and TUBB1 Q43P] on platelet function in 286 healthy subjects and their potential pathogenetic role in 160 patients with hereditary mucocutaneous bleeding of unknown cause. We found no effect of any of these polymorphisms on platelet aggregation, secretion, PFA-100, and thrombin generation in platelet rich plasma. Furthermore, patients and controls showed no significant differences in the frequency of any of these polymorphisms. Thus, our study demonstrated that polymorphisms in genes affecting platelet function do not influence significantly major platelet functions and appear irrelevant in the pathogenesis of bleeding disorders.

Inherited prothrombotic risk factors in children with stroke, transient ischemic attack, or migraine

OBJECTIVE

The aim of this study was to investigate the prevalence and possible association of inherited prothrombotic risk factors in children with stroke, transient ischemic attack, or migraine.

METHODS

We performed genotypic analysis for factor V G1691A, factor II G20210A, methylenetetrahydrofolate reductase C677T, and 4 common platelet glycoprotein polymorphisms (human platelet alloantigen-1, -2, -3, and -5) in 150 children <18 years of age with established diagnoses of stroke, transient ischemic attack, or migraine. Children were classified into 5 groups, namely, childhood arterial ischemic stroke (N = 33), perinatal arterial ischemic stroke (N = 26), hemorrhagic stroke (N = 20), transient ischemic attack (N = 36), and migraine (N = 35). The control group consisted of 112 children < or =18 years of age from the same geographical region who had no history of neurologic or thromboembolic diseases.

RESULTS

Heterozygosity for factor V G1691A was associated with approximately sevenfold increased risk for arterial ischemic stroke, perinatal arterial ischemic stroke, and transient ischemic attack. Increased risk for transient ischemic attack was found in carriers of the human platelet alloantigen-2b allele, human platelet alloantigen-5a/b genotype, and combined human platelet alloantigen-2b and human platelet alloantigen-5b genotype. The presence of the human platelet alloantigen-2b allele was associated with a 2.23-fold increased risk for migraine, whereas carriers of the human platelet alloantigen-3b allele had a lower risk for arterial ischemic stroke than did carriers of the human platelet alloantigen-3a allele.

CONCLUSIONS

Factor V G1691A has an important role in susceptibility to arterial ischemic stroke, both in the perinatal/neonatal period and in childhood, as well as transient ischemic attacks. A minor impact of human platelet alloantigen polymorphisms suggests that platelet glycoprotein polymorphisms may increase the risk of transient ischemic attacks and migraine, but this should be confirmed in larger studies.

The genetics of primary haemorrhagic stroke, subarachnoid haemorrhage and ruptured intracranial aneurysms in adults

Background

The genetic basis of haemorrhagic stroke has proved difficult to unravel, partly hampered by the small numbers of subjects in any single study. A meta-analysis of all candidate gene association studies of haemorrhagic stroke (including ruptured subarachnoid haemorrhage and amyloid angiopathy-related haemorrhage) was performed, allowing more reliable estimates of risk.

Methods

A systematic review and meta-analysis of all genetic studies in haemorrhagic stroke was conducted. Electronic databases were searched until and including March 2007 for any candidate gene in haemorrhagic stroke. Odds ratio (OR) and 95% confidence intervals (CI) were determined for each gene disease association using fixed and random effect models.

Results

Our meta-analyses included 6,359 cases and 13,805 controls derived from 55 case-control studies, which included 12 genes (13 polymorphisms). Statistically significant associations with haemorrhagic stroke were identified for those homozygous for the ACE/I allele (OR, 1.48; 95% CI, 1.20–1.83; p = 0.0003) and for the 5G allele in the SERPINE1 4G/5G polymorphism (OR, 1.42; 95% CI, 1.03–1.96; p = 0.03). In addition, both &b.epsi;2 and &b.epsi;4 alleles of APOE were significantly associated with lobar haemorrhage (OR, 1.81; 95% CI, 1.26–2.62; p = 0.002 and OR, 1.49; 95% 1.08–2.05; p = 0.01 respectively). Furthermore, a significant protective association against haemorrhagic stroke was found for the factor V Leiden mutation (OR, 0.30; 95% CI, 0.10–0.87; p = 0.03).

Conclusion

Our data suggests a genetic contribution to some types of haemorrhagic stroke, with no overall responsible single gene but rather supporting a polygenic aetiology . However, the evidence base is smaller compared to ischaemic stroke. Importantly, for several alleles previously found to be associated with protection from ischaemic stroke, there was a trend towards an increased risk of haemorrhagic stroke.

Molecular Genetics of Human Intracranial Aneurysms

Intracranial aneurysms (IAs) are the dilatations of blood vessels in the brain and pose potential risk of rupture leading to subarachnoid hemorrhage. Although the genetic basis of IAs is poorly understood, it is well-known that genetic factors play an important part in the pathogenesis of IAs. Therefore, the identifying susceptible genetic variants might lead to the understanding of the mechanism of formation and rupture of IAs and might also lead to the development of a pharmacological therapy. To elucidate the molecular pathogenesis of diseases has become a crucial step in the development of new treatment strategies. Although extensive genetic research and its potential implications for future prevention of this often fatal condition are urgently needed, efforts to elucidate the susceptibility loci of IAs are hindered by the issues bewildering the most common and complex genetic disorders, such as low penetrance, late onset, and uncertain modes of inheritance. These efforts are further complicated by the fact that many IA lesions remain asymptomatic or go undiagnosed. In this review, we present and discuss the current status of genetic studies of IAs and we recommend comprehensive genome-wide association studies to identify genetic loci that underlie this complex disease.

Polymorphisms of the human platelet alloantigens HPA-1, HPA-2, HPA-3, and HPA-4 in ischemic stroke

Polymorphism in human platelet antigen (HPA)-1 and HPA-3 (GPIIb/IIIa), HPA-2 (GPIb/IX), HPA-4 (GPIIIa), and HPA-5 (GPIa/IIa) was investigated in 329 stroke patients and 444 matched control subjects. HPA genotyping was done by PCR-SSP method. Lower HPA-1a (P < 0.001) and higher HPA-1b (P < 0.001) allele frequencies were seen in patients than control subjects, and homozygosity for HPA-1b (P < 0.001) alleles was more prevalent in stroke cases than in controls. The allele and genotype distributions of the other HPA polymorphic variants were similar between cases and controls. Select HPA combined genotypes comprising the 2121 (Pc = 0.008) and 2221 (Pc = 0.018) genotypes, which were positively associated, and the 1111 (Pc < 0.001), which was negatively associated with stroke, thereby conferred a disease susceptibility and protective nature to these genotype combinations. Multivariate analysis confirmed the negative association of the 1111 (P < 0.001) and the positive association of the 2121 (P = 0.017) combined genotypes with stroke, after adjustment for a number of covariates. This is the first evidence demonstrating differential association of the common 4 HPA gene variants and specific HPA genotype combinations with stroke.

The hemostatic balance revisited through the lessons of mankind evolution

Under physiologic conditions, a hemostatic balance is achieved through the effects of natural procoagulant and anticoagulant factors which, in equilibrium with each other, provide hemostasis at the sites of vascular injury. Abnormalities of these hemostasis factors can result in a tendency toward hemorrhagic or thrombotic events. In this review the influence of inherited prothrombotic risk factors--especially the more frequent factor V Leiden and prothrombin gene mutations--on normal and abnormal hemostasis is analyzed from an evolutionary point of view. The effect of inherited bleeding disorders on the development of thrombotic or atherosclerotic processes is also discussed.

Factor VII -323 decanucleotide D/I polymorphism in atrial fibrillation: implications for the prothrombotic state and stroke risk

There are limited data on the influence of genetic polymorphisms in atrial fibrillation (AF) stroke risk. We hypothesized that a functional haemostatic polymorphism, that is, the factor VII -323 Del/Ins polymorphism, would influence the prothrombotic state associated with AF, as well as stroke risk. Other functional polymorphisms were also tested.

METHODS

We performed a cross-sectional study of 119 AF patients, who were compared to 96 patients with stroke secondary to AF. In the first patient group, we analysed plasma prothrombin fragment 1+2 levels (F1+2, an index of thrombin generation) to reflect the prothrombotic state of AF.

RESULTS

AF patients carrying the -323 Ins allele had lower plasma F1+2 levels (P=0.015). After multivariate analysis adjusted by age, sex and clinical risk factors, advanced age and 807C/T polymorphism of glycoprotein Ia (GPIa) gene were associated with higher risk of ischaemic stroke (OR: 1.06; P=0.003 and OR: 1.91; P=0.025), whilst FVII Ins -323 allele was associated with lower stroke risk (OR: 0.41; P=0.017).

CONCLUSION

FVII -323 Ins allele may modulate the prothrombotic state associated with AF. Despite the small sample size, we found that FVII Ins -323 allele could be associated with a lower stroke risk in AF, whereas the 807C/T polymorphism may increase the risk.

The systemic implications of aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is analogous to a pathophysiological watershed, disrupting brain integrity and function and precipitating an array of systemic derangements including cardiovascular, respiratory, endocrine, hematological, and immune dysfunction. Extracerebral organ dysfunction is closely linked to the magnitude of the primary neurological insult, suggesting neurogenic, neuroendocrine and neuroimmunomodulatory mechanisms. Systemic organ involvement is associated with increased mortality and neurological impairment, even after adjustment for other outcome predictors such as the severity of the initial neurological injury. This may be a reflection of secondary brain injury precipitated by hypoxemia, circulatory failure, fever, or hyperglycemia, all of which have been linked to adverse clinical outcomes. Interventions to avert or reverse these and other perturbations need to be tested in clinical trials as they represent opportunities to improve survival and neurological recovery in patients with SAH.

A study of possible correlation between subarachnoid haemorrhage related vasospasm and the post-bleed blood platelet count chart in a Caucasian population

INTRODUCTION

There has been controversy about the aetiology and pathophysiology of subarachnoid haemorrhage (SAH) related vasospasm. Several pathogenic factors like endothelin and adhesion molecules have been discussed. A recently published study concerning an exclusively Asian population suggested a relationship between SAH related vasospasm and the blood platelet count. The aim of our study was to examine this relationship in a European population.

METHOD

We carefully reviewed 88 patients with aneurysmal SAH (54 females, 34 males; mean age 52.5 years, range from 22 to 78 years) treated in our centre with regard to the occurrence of vasospasm and the blood platelet count in a ten day interval after initial SAH. Symptomatic vasospasm was defined as a focal neurological deficit or deterioration in the level of consciousness with or without confirmation of infarction on a CT scan. Thirty-seven patients (42%) developed clinically relevant vasospasm.

RESULTS

There was no statistically significant correlation between the blood platelet count chart (maximum and minimum values) and vasospasm or clinical outcome; we also found no gender or age-related influence on the above mentioned relationships.

CONCLUSIONS

In our opinion there appears to be a difference between Caucasian and Asian populations regarding the influence of platelets in the pathophysiology of SAH and vasospasm.