Association Between P-selectin Gene Polymorphisms And Soluble P-selectin Levels And Their Relation To Thromboembolic Events In Patients With Nonvalvular Atrial Fibrillation

BackgroundAssociation between P-selectin gene polymorphisms and soluble P-selectin levels and their relation to thromboembolic events in patients with nonvalvular atrial fibrillation.P-selectin[also known as granule membrane protein-140(GMP-140),platelet activation-dependent granule-external membrane protein(PADGEM) and CD62]is a member of the selectin family of cell adhesion molecules expressed at the surface of activated endothelial cells and platelets,that mediates the interaction of activated endothelial cells or platelets with leukocytes.The protein is localized in the alpha granules of platelets and the Weibel-Palade bodies of endothelial cells,with a soluble form present in the plasma.Levels of plasma P-selectin(soluble P-selectin, sP-selectin) are mainly platelet derived and can be regarded a marker for platelet activatio.In humans,plasma P-selectin levels have therefore been used to substantiate active participation of platelets in thrombotic disease。The P-selectin gene is situated on chromosome 1q21-q24,spans＞50kb and contains 17 exons.In the ECTIM study,thirteen polymorphisms were identified:five in in the distal P-selectin promoter and eight in the exonic sequences.Some polymorphisms of the P-selectin gene have been reported that could affect the peptide sequence of the protein and its regulatory sequences.It is report that the P-selectin gene was identified as being significantly associated with levels of plasma soluble P-selectin(sP-selectin) and thromboembolic events.Several polymorphisms of P-selectin gene has previously been reported including three missense polymorphisms:2123 C/G and 1817 T/C in the distal P-selectin promoter within putative binding sites for a number of transcription factors including AP-1 and c-Fos13,Thr715Pro in exon 13 and plasma levels of P-selectin are especially determined by the P-selectin Thr715Pro polymorphism and high concentrations of soluble P-selectin are associated with risk of venous thromboembolism and the P-selectin Thr715Pro variant.These findings suggest the polymorphisms of P-selectin gene to be involved in the development of thromboembolic events by mediated the plasma soluble P-selectin levels.It is well known that atrial fibrillation is associated with high incidence of thromboembolic events,propably due to a prothrombotic or hypercoagulable state.Some genetic alterations of haemostatic markers in haemostatic risk factors may contribute to the increased risk of thromboembolism in nonvalvular atrial fibrillation patients.Recent studies indicate,the a-fibrinogen Thr312Ala polymorphism contributes to the pathogenesis of thromboembolic complications associated with the presence of atrial fibrillation.The contribution of genetic alterations in factors of the coagulation and fibrinolytic pathways(that is hemostatic risk factors) to the development of hypercoagulation state in atrial fibrillation requires clarification.At present,these is no report that SNPs in P-selectin is associated with thromboembolic events in patients with nonvalvular atrial fibrillation. ObjectivesTo investigate the association between the polymorphism of P-selectin gene in the position of 2123C/G,1817T/C,Thr715Pro and sP-selectin levels and their relation to thromboembolic events in patients with nonvalvular atrial fibrillation(AF) in Han Nationality of Southern China,we used polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) to determine the polymorphism of P-selectin gene in the position of 2123C/G,1817T/C,Thr715Pro.Methods:1.Clinic index of body mass index,blood pressure,plasma lipids,fibrinogen, C-reactive protein were measured in 95 nonvalvular AF patients with thromboembolic events and 106 nonvalvular AF controls without thromboembolic events,who were documented ischemic stroke by MRI and/or CT or venous thromboembolism(VTE) by colour doppler ultrasound.The presence of nonvalvular atrial fibrillation was established on clinical examination at the time of ischemic stroke or venous thromboembolism(VTE) and confirmed on a diagnostic 12-lead ECG and echocardiography.2.Samples were collected when the patients were admitted to hospital.The concentrations of the soluble P-selectin(sP-selectin) was quantified by ELISA3.Genomic DNA in white blood cell from venous blood was abstracted by reagent box.By polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP),we analyzed P-selectin gene polymorphism in patients and controls and compared the distribution of genotype and allele in two group.Based on this,we compared the other result and clinic index including prevalence rate of hypertention and diabetes mellitus,BMI,level of serum cholesterol,triglyceride,high density lipoprotein cholesterol,lowdensity lipoprotein cholesterol,fibrinogenn and C-reactive protein. Results:1.Total cholesterol and C-reactive protein in patient group were significantly higher than those of controls with P value of 0.000 and 0.009 respectively while other clinic features such as age,the component of female,history of cigarette,age,BMI, the morbidity of hypertention and diabetes mellitus,triglyceride,high density lipoprotein cholesterol,low density lipoprotein cholesterol and fibrinogen show no difference between nonvalvular AF patients with thromboembolic events and nonvalvular AF controls without thromboembolic events(P＞0.05).2.The presence of G allele in 2123C/G locus was found to be a greater risk factor in nonvalvular AF subjects with thromboembolic events than in nonvalvular AF controls without thromboembolic events.The odds ratio(OR) of GG were 3.500 (1.401～8.744),when compared with CC genotype,(P＜0.05).however 1817T/C allele show no significant difference(P＞0.05).3.There were statistical differences in levels of sP-selectin between patients and controls(P=0.000).The concentration of the soluble P-selectin is significantly different between patients and controls.4.Soluble P-selectin levels have no correlation with serum cholesterol and C-reactive protein with P value of 0.095and 0.069 respectively.5.The 2123C/G polymorphisms were associated with plasma sP-selectin level and patients with GG genotype tended to present higher level of plasma sP-selectin level than those carrying GC or CC genotype(P＜0.05).Genotype and allele distributions significantly differed in 2123C/G locus with P value of 0.020 and 0.015 respectively between patients and controls.6.Soluble P-selectin levels were not related to 1817T/C allele(P＞0.05) and no significant difference was found in 1817T/C locus genotype and allele distribution frequency with P value of 0.443 and 0.207 respectively between patients and controls. 7.The Thr715Pro polymorphism was not found in Han Nationality of Southern China in this study.Conclusions1.The 2123C/G polymorphism of P-selectin gene was associated with thromboembolic events in patients with nonvalvular atrial fibrillation,the genotype of GG may be a genetic risk factor for the thromboembolic process in patients with nonvalvular AF.2.The 2123C/G polymorphism of P-selectin gene was associated with soluble P-selectin levels or thromboembolic events in patients with nonvalvular atrial fibrillation,however 1817T/C locus polymorphism was not associated.3.Thr715Pro locus SNP does not exist in Han Nationality of Southern China.4.This study revealed a relationship between P-selectin gene polymorphisms and serum sP-selectin levels or thromboembolic events.The P-selectin gene affect the development of the thromboembolic process in patients with nonvalvular AF by mediating the concentration and function of soluble P-selectin.