Platelet functional implications of glycoprotein Ibalpha polymorphisms in African Americans

Glycoprotein Ib-alpha Kozak polymorphism in ischemic stroke

BACKGROUND

Recently, a T/C polymorphism in the Kozak sequence of glycoprotein Ib-alpha (GPIb-alpha) gene at position -5 from the initiator ATG codons, has been identified. The presence of -5C allele increases the surface expression of GPIb-IX-V complex in a gene dosage-dependent manner. It has been suggested that higher receptor levels might increase the adhesiveness of the platelets and confer risk for thrombosis. In this study, we aimed to investigate the association between GPIb-alpha Kozak polymorphism and ischemic stroke.

METHODS

We prospectively and consecutively recruited 231 patients (118 women and 113 men; mean age: 65 ± 14.2 years) with first ever ischemic stroke admitted to Istanbul Faculty of Medicine Edip Aktin Stroke Unit between April 2007 and June 2009. Demographic features, risk factors, clinical, and etiological subtypes were analyzed. As the control group, 220 unrelated healthy subjects were included.

RESULTS

We found that 156 patients had TT, 70 patients had TC, and 5 patients had CC genotype. At least one copy of C allele carriers were overrepresented in the ischemic stroke group (32.5%) compared with controls (23%) [odds ratio (OR): 0.61; 95% confidence interval (CI): 0.40-0.93; P = 0.03]. Among etiologic subtypes, the distribution of C allele carriers was the highest in patients with undetermined etiology (45%) and it was significantly higher than controls (OR: 0.36; 95% CI: 0.20-0.65; P = 0.0008). In other subtypes, there was no association with Kozak -5C allele.

CONCLUSION

In conclusion, these encouraging preliminary results show that GPIb-alpha T/C polymorphism might increase the risk of ischemic stroke, especially in those with undetermined etiology.

Longitudinal platelet reactivity to acute psychological stress among older men and women

Platelet reactivity to acute stress is associated with increased cardiovascular disease risk; however, little research exists to provide systematic methodological foundations needed to generate strong longitudinal research designs. Study objectives were: 1) to evaluate whether markers of platelet function increase in response to an acute psychological stress test among older adults, 2) to establish whether reactivity remains robust upon repeated administration (i.e. three occasions approximately 1 year apart), and 3) to evaluate whether two different acute speech stress tasks elicit similar platelet responses. The 149 subjects (mean age 71 years) gave a brief impromptu speech on one of two randomly assigned topics involving interpersonal conflict. Blood samples drawn at baseline and post-speech were assayed using flow cytometry for platelet responses on three outcomes (% aggregates, % P-selectin expression, and % fibrinogen receptor expression). Three-level hierarchical linear modeling analyses revealed significant stress-induced increases in platelet activation on all outcomes (p < 0.001). No significant habituation on any measure was found. Additional reactivity differences were associated with male gender, history of myocardial infarction, and use of aspirin, statins, and antidepressants. The results demonstrate that laboratory acute stress tests continued to produce robust platelet reactivity on three activation markers among older adults over 3 years.

Relationship between platelet activation related factors and polymorphism of related genes in patients with coronary heart disease of blood-stasis syndrome

OBJECTIVE

To comparatively study the expressive conditions of platelet activation related factors (GP I b, GP II b- III a and GMP-140) in healthy subjects and patients with coronary heart disease (CHD) of blood-stasis (BS) or non-blood-stasis (non-BS) syndrome, and to analyze the relationship between the activities of various glycoproteins and the polymorphism of genes.

METHODS

With case control design adopted, patients with the CHD (40 of BS, 37 of non-BS) and 39 healthy subjects for control, all fitting to the inclusion criteria, were selected in this study. The number of affected coronary branches was recorded by the contrast examination. The mean fluorescence intensity (MFI) of GP I b, GP II b- III a, and GMP-140 (CD42b, CD61, CD62p) in patients and healthy persons was measured with flow cytometry, the polymorphism of HPA-3 gene was detected by Taqman probe technique and that of HPA-2 gene was determined by gene sequencing.

RESULTS

MFI of CD61 and CD62p was higher in the CHD patients than in the healthy control, which was also higher in patients of BS syndrome than in patients of non-BS syndrome (P<0.05); MFI of CD42b was lower in the CHD patients than in the healthy control (P<0.05), but showing insignificant difference between BS and non-BS syndrome (P>0.05); at the same time, no significant difference of all the above-mentioned three MFI could be found in patients with various numbers of affected coronary branches, neither in patients with different genotypes at GP II b HPA-3 and GP I b HPA-2 polymorphism loci (P>0.05).

CONCLUSION

(1) The activities of GP II b- III a and GMP-140 were obviously increased in the genesis and developing process of CHD and CHD of BS syndrome, and so they could be taken as one of the objective indexes for microscopic diagnosis of BS syndrome. (2) The level of GP I b was lower in CHD patients than in healthy persons, but it was not a sensitive indicator for BS syndrome of CHD. (3) Levels of GP II b- III a, GP I b and GMP-140 were not related with the number of affected coronary branches in CHD patients. (4) The changes in amino-acids expression induced by the two loci brought no significant influence on GP I b and GP II b- III a activities.

Genomics: risk and outcomes in cardiac surgery

Coronary artery bypass graft surgery is associated with several frequent postoperative adverse events. Outcome prediction is valued by patients and practitioners, because it provides some measure of balancing risks and benefits and provides expensive or higher-risk therapies to individuals at highest risk. Surgeons and anesthesiologists traditionally have relied on demographic, preoperative, and intraoperative risk factors to predict outcomes after cardiac surgery. Yet, such predictions often have poor positive and negative predictive value for the individual patient. Perioperative genetics attempts to determine the impact of an individual's genetic variation on the risk of developing adverse postoperative outcomes. In this article, the authors discuss emerging evidence that a patient's genetic makeup predisposes him or her to adverse outcomes following cardiac surgery and provide examples from perioperative bleeding, myocardial injury/infarction, and atrial fibrillation.

Impact of genetic variation on perioperative bleeding

Variation in bleeding in the perioperative period is a complex and multifactorial event associated with immediate and delayed consequences for the patient and health care resources. Little is known about the complex genetic influences on perioperative bleeding. With the discovery of multiple variations in the human genome and ever-growing databases of well-phenotyped surgical patients, better identification of patients at risk of bleeding is becoming a reality. In this review, polymorphisms in the platelet receptor genes, plasminogen activator inhibitor, and angiotensin genes among others will be discussed. We will explore the nature, effects, and implications of the genetics that influence perioperative bleeding above and beyond surgical bleeding, particularly in cardiac surgery.