Polymorphism of platelet glycoprotein IIb and risk of thrombosis and restenosis after coronary stent placement

Pathogenesis and Clinical Significance of In-Stent Restenosis in Patients with Diabetes

Diabetes mellitus (DM) is a strong risk factor for the development of cardiovascular diseases such as coronary heart disease, cerebrovascular disease, and peripheral arterial disease (PAD). In the population of people living with DM, PAD is characterised by multi-level atherosclerotic lesions as well as greater involvement of the arteries below the knee. DM is also a factor that significantly increases the risk of lower limb amputation. Percutaneous balloon angioplasty with or without stent implantation is an important method of the treatment for atherosclerotic cardiovascular diseases, but restenosis is a factor limiting its long-term effectiveness. The pathogenesis of atherosclerosis in the course of DM differs slightly from that in the general population. In the population of people living with DM, more attention is drawn to such factors as inflammation, endothelial dysfunction, platelet dysfunction, blood rheological properties, hypercoagulability, and additional factors stimulating vascular smooth muscle cell proliferation. DM is a risk factor for restenosis. The purpose of this paper is to provide a review of the literature and to present the most important information on the current state of knowledge on mechanisms and the clinical significance of restenosis and in-stent restenosis in patients with DM, especially in association with the endovascular treatment of PAD. The role of such processes as inflammation, neointimal hyperplasia and neoatherosclerosis, allergy, resistance to antimitotic drugs used for coating stents and balloons, genetic factors, and technical and mechanical factors are discussed. The information on restenosis collected in this publication may be helpful in planning further research in this field, which may contribute to the formulation of more and more precise recommendations for the clinical practice.

Association of platelet ITGA2B and ITGB3 polymorphisms with ex vivo antiplatelet effect of ticagrelor in healthy Chinese male subjects

Ticagrelor (TIC) is the first reversible P2Y12 receptor antagonist that exhibits rapid antiplatelet effect by indirect inhibition of the GPIIb/IIIa complex. Polymorphisms in genes coding GPIIb/IIIa, namely ITGA2B and ITGB3, are associated with aspirin resistance and risk for thrombotic diseases. We assessed whether ITGA2B and ITGB3 polymorphisms can influence the ex vivo antiplatelet activity of ticagrelor in Chinese population. A total of 196 healthy Chinese male individuals were recruited. ADP-induced platelet aggregation was determined using optical aggregometry at baseline and after incubation of the platelet-rich plasma with 15 and 50 μM ticagrelor, respectively. Single nucleotide polymorphisms in ITGA2B (rs5911 G>T) and ITGB3 (rs4642 A>G and rs4634 G>A) were genotyped by sequencing. TIC at both concentrations of 15 and 50 μM decreased ADP-induced platelet aggregation significantly (P < 0.05, respectively). As compared to ITGA2B rs5911 GG homozygotes, individuals with the rs5911 TG genotype showed significantly increased inhibition of platelet aggregation (IPA) by both 15 and 50 μM ticagrelor incubation (P < 0.05, respectively). Neither rs4642 nor rs4634 polymorphism affected ticagrelor-induced IPA. We suggest that the ITGA2B rs5911 GG genotype is associated with decreased ex vivo antiplatelet activity of ticagrelor in healthy Chinese male subjects.

Platelet glycoprotein IIb HPA-3 a/b polymorphism is associated with native arteriovenous fistula thrombosis in chronic hemodialysis patients

OBJECTIVE

The aim of this study was to investigate the association of Glycoprotein IIb (GPIIb) human platelet antigen-3 (HPA-3) a/b polymorphism with end-stage renal disease (ESRD) on hemodialysis (HD) and native Arteriovenous fistula (AVF) thrombosis.

METHODS

The polymorphism in the GPIIb subunit of the receptor HPA-3 (a and b alleles) was identified by polymerase chain reaction with sequence-specific primers (PCR-SSP) in 145 HD patients and 120 healthy controls from a Chinese Han population. The HD patients were classified into two groups: G1 and G2. G1 included 65 HD patients presented at least one AVF thrombosis episode and G2 included 80 HD patients without any episode of AVF thrombosis.

RESULTS

There were no significant differences in either HPA-3 a/b genotypes (aa, ab, and bb) frequency distribution (p = 0.396) or allele (a and b) frequency distribution (p = 0.146) between HD patients and control groups. However, there were significant differences in both HPA-3 a/b genotypes (aa, ab, and bb) distribution (χ(2) = 6.127, p = 0.047) and allele (a and b) frequency distribution (χ(2) = 5.954, p = 0.015) between G1 and G2. The relative risk of native AVF dysfunction in ab + bb patients compared with that of aa patients was 2.31 (95% confidence interval: 1.18-4.52).

CONCLUSIONS

These findings suggest an association between AVF thrombosis and the HPA-3b allele, and it is likely that HPA-3 a/b polymorphisms could be useful markers for potential risk of native AVF thrombosis in HD patients.

Platelet glycoprotein IIb HPA-3 polymorphism and acute coronary syndromes

BACKGROUND

There is considerable research interest about the platelet GPIIb/IIIa receptor polymorphisms in CAD.

METHODS

We investigated differences in the frequency of the polymorphism in the GPIIb subunit of the receptor HPA-3 (a and b allele) between patients with more extensive coronary thrombosis such as patients with ST segment elevation (STEMI) and those with less extensive coronary thrombosis such as those with non-ST elevation myocardial infarction (NSTEMI), unstable angina (UA) or chronic CAD. We studied 118 CAD patients, of which 38 suffered from STEMI, 62 from NSTEMI or UA and 18 from chronic CAD and 15 healthy individuals. Patients were followed-up for 21+/-6 months for occurrence of death, myocardial infarction and revascularization.

RESULTS

Seventeen out of 38 (45%) patients with STEMI were homozygous for the HPA-3 b allele compared to 6 out 62 (10%) with NSTEMI-UA , 4 out of 18 (22%) with chronic CAD and 2 out of 15 (13%) healthy controls (chi(2)=16,4, p=0.03.) Homozygous patients for the HPA-3b exhibited a 5-fold higher risk for STEMI compared to heterozygous patients for HPA-3b or homozygous for HPA-3a allele (OR: 5.90, 95% CI: 2.15-16.54, p=0.01) after adjustment for age, sex and risk factors. The HPA-3 genotypes were not related with cardiovascular events during follow-up.

CONCLUSIONS

Among patients with an acute coronary syndrome those being HPA-3b homozygous have a tendency to develop ST segment elevation myocardial infarction instead of non-ST segment elevation infarction or unstable angina. There is no association between the HPA-3 genotypes and future cardiovascular events.

Present status of outcome prediction of invasive coronary treatment by using genetic markers

A growing number of studies suggest that the outcome after invasive coronary treatment may be in part genetically determined. Here, we review the present status of outcome prediction of invasive coronary treatments by using genetic markers. Although some studies found an association between one or another genetic marker with one or another clinical endpoint, many other studies found no such relations; to date, none of the genetic markers that have been investigated in association studies are used in routine clinical practice to prospectively assess the prognosis following invasive coronary treatment or to decide upon therapeutic strategies. Many associations between genetic markers and certain clinical endpoints were initially reported in small studies but could not be confirmed in larger ones. Some of these discrepancies may be explained by publication bias. Some genetic variants may have true effects on clinical endpoints, which, albeit biologically interesting, do not bear much clinical relevance. On the other hand, many-if not most-studies that have been published to date are more or less grossly underpowered and very rarely report on the results of an a priori power analysis. Thus, there is still a need for further high-quality studies designed to investigate the specific contribution of genetic factors to the outcome after invasive coronary interventions.

Genetic predictive factors in restenosis

Restenosis is still the main drawback of percutaneous transluminal coronary angioplasty (PTCA). It is thought to be a multifactorial process where recoil of the vessel, neointimal proliferation and thrombus formation are thought to play a role. Until now it has proven difficult to predict restenosis on clinical and procedural grounds, however, genetic epidemiology might provide more insights. In this review several genetic variables, i.e. polymorphisms that were determined in relation to restenosis are described. The single nucleotide polymorphisms (SNPs) described in the literature so far involve; the renin-angiotensin system, platelet aggregation, the inflammatory response, matrix metalloproteinases, smooth muscle cell proliferation, lipids and oxidative stress and nitric oxide. Nowadays DNA-microarrays have been developed which make it possible to test 50 or 60 polymorphisms at once. However, the risk of error due to multiple testing should be kept in mind. The results of the studies described should be interpreted with care. Many of the published studies are of relatively small sample size, which sometimes show more positive outcomes than the larger studies, this is possibly due to publication bias towards more positive results. The small sample size studies also exhibit wide confidence intervals. On the other hand, one must take into account that the process of restenosis is a multifactorial one and it is likely that multiple genes are involved. Thus, relatively small odds ratios relating to single gene contribution to restenosis can be of paramount importance when encompassed in the overall picture. Although still much research has to be done, stratification according to genetic make-up may enable tailoring of the interventional treatment to the individual patient.

Haptoglobin genotype is predictive of major adverse cardiac events in the 1-year period after percutaneous transluminal coronary angioplasty in individuals with diabetes

OBJECTIVE

The goal of this study was to determine whether the haptoglobin (Hp) genotype was predictive of restenosis and major adverse cardiac events (MACEs) after percutaneous transluminal coronary angioplasty (PTCA) in individuals with diabetes.

RESEARCH DESIGN AND METHODS

A consecutive series of 935 diabetic patients treated with oral agents and/or insulin were followed for 1 year after PTCA. The primary study end point was angiographic restenosis, MACEs and secondary study end points were defined as target vessel revascularization, myocardial infarction, and death. Two alleles exist at the Hp gene locus, denoted 1 and 2. The Hp genotype (Hp 1-1, Hp 2-1, or Hp 2-2) was determined by PCR.

RESULTS

In multivariate analysis controlling for all known determinants of outcome after PTCA, we found that the Hp genotype was a highly significant independent predictor of MACEs in the 1-year period after PTCA in individuals with diabetes. This was predominantly due to differences in the risk of myocardial infarction during that period: Hp 1-1, 0 of 129 (0%); Hp 2-1, 20 of 424 (4.7%); and Hp 2-2, 32 of 382 (8.4%); P < 0.0001.

CONCLUSIONS

The Hp genotype seems to be highly predictive of adverse cardiac events, particularly myocardial infarction, in the 1-year period after PTCA. Determination of the Hp genotype may be useful in the evaluation of new therapies to reduce cardiovascular risk after PTCA.

The role of platelet receptors and adhesion molecules in coronary artery disease

Platelets play a significant role in coronary artery disease through interactions with each other and with other cell types. These interactions are mediated by certain receptors on the surface of platelets and other cells which can lead to intra-coronary thrombus formation and occlusion that may result in acute coronary syndromes. The important roles of the currently available anti-platelet therapies have been well established in many clinical outcome trials in cardiovascular patients. An understanding of these different interactions provides the clinician with a background that supports the clinical importance of currently available anti-platelet therapies. Moreover, knowledge of the mechanisms of cellular crosstalk will lead to important advances in the development of better antithrombotic therapies.

Platelet antigens. The role of human platelet alloantigens (HPA) in blood transfusion and transplantation

In this review, we describe the platelet surface molecules with special focus on the polymorphic glycoproteins giving rise to the human platelet alloantigen (HPA) system. We list the platelet glycoprotein complexes GPIa/IIa, GPIIb/IIIa, GPIb/V/IX and some other molecules, the corresponding genes that encode them and we describe their polymorphisms as well as their physiological function. Based on data obtained by serological and molecular methods, we explain how ancestral HPA alloepitopes have developed into the modern variants. We also describe the tissue distribution of these proteins, which seems to be wider than thought initially, and discuss the significance of the HPA encoding genes distribution in various populations. Methods for their determination are then described briefly Since HPA alloepitopes can induce antibodies with resulting clinical conditions such as: post-transfusion refractoriness to platelets (PTR); post-transfusion thrombocytopenic purpura (PTTP); and fetomaternal alloimmune thrombocytopenia (FMAIT), the mechanism of this alloimmunization and its prevention is described. Although the humoral arm is more important from the clinical viewpoint, the activation of the cytotoxic arm by HPA alloepitopes is also possible. These polymorphisms also seem to have a role in certain other clinical circumstances, therefore their impact on cardiovascular diseases and haemostatic disorders as well as their role in the transplantation of solid organs and bone marrow is addressed. We conclude that during the last decades, the research of the platelet membrane molecules contributed considerably to the diagnostics, prevention and therapy of the blood coagulation and haemostatic disorders, to the management of the neonatal thrombocytopenias, transfusion-related thrombocytopenias, refractoriness to platelet transfusions and autoimmune disorders. It also changed our view on the role of HPA alloepitopes in bone marrow and solid organ transplantation. In the future, this accumulated knowledge will be useful for the development of the cell-based therapies and immune modulation of both acquired and hereditary diseases.

Platelet glycoprotein gene polymorphisms and risk of thrombosis: facts and fancies

Over the past several years, platelet glycoprotein gene polymorphisms have received increasing attention as possible inherited determinants of prothrombotic tendency. However, their role in genetic susceptibility to thrombotic disease remains controversial. The glycoprotein IIIa Leu33Pro amino acid substitution appears to be associated with a subtle effect on platelet thrombogenicity in vitro, but is not a major risk factor for arterial thrombotic disease among the general population. Evidence suggests that the glycoprotein IIIa Pro33 allele may be associated with increased risk of thrombotic events following coronary re-vascularization and possibly among younger subjects with atherosclerosis. The nucleotide 807T variant of glycoprotein Ia is associated with increased platelet glycoprotein Ia/IIa receptor density, collagen-induced platelet adhesion and an increased risk of early onset myocardial infarction and stroke. Evaluation of the roles of the glycoprotein Ibalpha Thr145Met and variable number of tandem repeat polymorphisms has been complicated by their lack of well-defined effects on platelet adhesive function and the strong linkage disequilibrium between the two sites. Future epidemiologic studies of platelet glycoprotein gene polymorphisms will require larger sample sizes and family based approaches to further elucidate clinically important associations with thrombotic disease, including gene-environment and gene-gene interactions. Other polymorphisms of potential functional significance within genes encoding platelet membrane proteins will undoubtedly be discovered. The challenge will be to integrate advances in platelet biology with molecular and genetic epidemiology to enhance our understanding of the genetic determinants of common, but etiologically complex thrombotic diseases.

The effect of human platelet alloantigen polymorphisms on the in vitro responsiveness to adrenaline and collagen

A number of clinical studies have suggested that carriage of the low frequency allele (b) of the human platelet antigen 1 (HPA-1) system is a risk factor for coronary thrombosis. We have examined the effect of a series of HPA biallelic polymorphisms (systems -1, -2, -3 and -5) on the in vitro platelet aggregation in response to adrenaline and collagen in 30 healthy volunteers. There was a significantly higher prevalence (10 out of 18) of carriers of the HPA-1b polymorphism among subjects showing a > 50% aggregation response to adrenaline ('responders') than the prevalence (1/12) in 'non-responders' (P < 0.05). Platelets heterozygous for the HPA-1b polymorphism showed a significantly higher rate (slope) and greater extent (%) of adrenaline-induced aggregation than platelets not carrying the HPA-1b allele (P < 0.05). A greater extent of collagen-induced aggregation was also demonstrated in HPA-1ab platelets (P < 0.05). Inhibition of adrenaline-induced aggregation following incubation with aspirin was greater (P < 0.01) in HPA-1ab than in HPA-1aa platelets. Collagen-induced aggregation was slower in carriers of the HPA-5b allele than in HPA-5aa subjects (P < 0.05). Polymorphisms of the HPA-2 and HPA-3 systems were not associated with different aggregation responses to either adrenaline or collagen. These results support the clinical observation that polymorphism HPA-1b may predispose to increased platelet thrombogenicity and suggest that the presence of polymorphism HPA-5b might render the platelet less reactive to collagen.

Platelet glycoprotein IIb polymorphism, traditional risk factors and non-fatal myocardial infarction in young women

Several platelet glycoprotein polymorphisms have been associated with an increased risk of myocardial infarction (MI) in studies that included predominantly men. In a population-based sample of 68 Caucasian women < 45 years old with non-fatal MI and 346 demographically similar control subjects, we found an increased risk of MI among women who possessed at least one copy of the glycoprotein IIb Ser843 allele compared with those lacking the Ser843 allele (odds ratio 1.85; 95% confidence interval = 1.03-3.33). The increased risk was present only in subgroups of women who smoked cigarettes, had hypercholesterolaemia or who had a family history of early onset MI. The Ser843 variant of glycoprotein IIb may be associated with an increased risk of MI in young women with other cardiovascular risk factors. Additional studies involving larger numbers of subjects are needed to confirm this preliminary finding.

Platelet glycoprotein polymorphisms as risk factors for thrombosis

Both blood platelets and genetics contribute to the development of acute ischemic arterial diseases. A careful analysis of the various clinical association studies supports a modest increased risk for coronary artery disease events in carriers of the PIA2 polymorphism of GPIIIa. Investigations with both platelets and stable cells lines have shown the PIA2 polymorphism is prothrombotic. Only a handful of studies have been performed for platelet GPla (integrin alpha2) and GPIb-IX-V, but there is support for the 807 T/C polymorphism of GPIa and the met145 and VNTR B/C genotype of GPIbalpha as risk factors in younger age groups. And isolated reports suggest other platelet polymorphisms (GPIIb, FcgammaRIIa, P-selectin, alpha2 adrenergic receptor, transforming growth factor [TGF]beta) are risk factors for arterial disease or produce a prothrombotic phenotype. Platelet glycoprotein polymorphisms should be added to the list of genetic risk factors for arterial thrombosis, particularly in younger patients and women.

Genetic risk factors and restenosis after percutaneous coronary interventions

Restenosis is the major limitation of percutaneous coronary interventions. Depending on the form of intervention and patients' characteristics, 20 to 50% of the treated patients incur significant restenosis. Restenosis is caused by a complex and only partially understood cascade of events. Thrombus formation at the injury site, formation of the neointima as a result of the migration and proliferation of smooth muscle cells (SMC) and extracellular matrix production, as well as constrictive remodeling of the vessel wall contribute by a variable degree to restenosis. Restenosis is not a random event but it affects selectively a certain subset of patients. These patients have some peculiar characteristics that help to identify the presence of a higher risk for restenosis. Conventional patient-related factors account only for a relatively small portion of the predictive power, much more contribution comes from lesion and procedural characteristics. There is increasing evidence that inherited factors may explain at least part of the excessive risk for restenosis observed in certain patients. Evidence exists that gene polymorphisms may lead to quantitative or functional alterations of the respective gene products. Recent studies have also found significant associations between several polymorphic alleles encoding for proteins with a relevant role in the process of lumen renarrowing and restenosis after percutaneous coronary interventions. The best studied polymorphisms in this regard are those of the genes encoding for angiotensin-converting enzyme and platelet glycoprotein-IIIa. Completed or ongoing studies have focused on polymorphisms of genes encoding for proteins interfering with lipid metabolism, hemostasis, nitric oxide production, inflammatory mechanisms, SMC proliferation and matrix production. The results of this research will have considerable pathophysiological and therapeutical implications for the battle against restenosis.