Polymorphisms in the P-selectin (CD62P) and P-selectin glycoprotein ligand-1 (PSGL-1) genes and coronary heart disease

The roles of P-selectin in cancer cachexia

P-selectin, a cell adhesion molecule of the selectin family, is expressed on the surface of activated endothelial cells (ECs) and platelets. Binding of P-selectin to P-selectin glycoprotein ligand-1 (PSGL-1) supports the leukocytes capture and rolling on stimulated ECs and increases the aggregation of leukocytes and activated platelets. Cancer cachexia is a systemic inflammation disorder characterized by metabolic disturbances, reduced body weight, loss of appetite, fat depletion, and progressive muscle atrophy. Cachexia status is associated with increased pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), which activates ECs to release P-selectin. Single-nucleotide polymorphisms (SNPs) loci of P-selectin encoding gene SELP are associated with higher level of plasma P-selectin and increase the susceptibility to cachexia in cancer patients. Elevated P-selectin expression has been observed in the hypothalamus, liver, and gastrocnemius muscle in animal models with cancer cachexia. Increased P-selectin may cause excessive inflammatory processes, muscle atrophy, and blood hypercoagulation, thus facilitating the development of cancer cachexia. In this review, physiological functions of P-selectin and its potential roles in cancer cachexia have been summarized. We also discuss the therapeutic potential of P-selectin inhibitors for the treatment of cancer cachexia.

Radiofrequency ablation reduces expression of SELF by upregulating the expression of microRNA-26a/b in the treatment of atrial fibrillation

BACKGROUND

In this study, we aimed to investigate the role of miR-26a and miR-26b in the management of AF.

METHODS

Real-time PCR was carried out to determine plasma microRNA expression in AF patients pre- and post-radiofrequency ablation. The correlation between the expression of SELP and miR-26a/miR-26b was also studied using luciferase assays to establish a miR-26a/miR-26b/SELP signaling pathway.

RESULTS

The relative expression of SELP reached its peak in pre-ablation AF ( +) patients, while ablation treatment reduced the expression of SELP in AF ( +) patients. Similarly, AF pigs showed dysregulation of miR-26a/b and SELP, thus verifying the involvement of miR-26a/b and SELP in AF. Meanwhile, the regulatory association between SELP and miR-26a/b was also investigated, and the results showed that the presence of pre-miR-26a/b increased the levels of miR-26a/b and inhibited the mRNA/protein expression of SELP. Finally, using bioinformatic tools and luciferase assays, SELP mRNA was confirmed as the target of miR-26a/b, which affected the effect of AF ablation treatment.

CONCLUSIONS

RFA helped to restore circulating levels of miR-26, which were reduced in atrial fibrillation. Meanwhile, miR-26 is a potential cause for the elevated plasma levels of pro-thrombogenic SELP in that disease.

Study of the Association of V640L (rs6133) Polymorphism in the Platelet P-selectin Gene with Acetylsalicylic Acid Resistance in Patients after Coronary Bypass Surgery

Aim.To study the association of V640L (rs6133) polymorphism in the P-selectin gene with acetylsalicylic acid (ASA) resistance in patients with coronary heart disease after coronary bypass surgery (CABG).Material and methods.The study included 104 patients aged 36-78 years (mean age 61.6±6.9 years) with stable angina pectoris: 61 (58.7%) patients had functional class II (according to Canadian Cardiovascular Society), 41 (39.4%) – class III and 2 (1.9%) – class IV. Atherosclerotic lesions of the coronary arteries were confirmed by coronary angiography. The antiplatelet therapy was stopped for at least 5 days before CABG. In the postoperative period, from the first day, all patients received 100 mg of ASA in enteric form, 61 patients received alone ASA therapy, 43 patients – combined antiplatelet therapy: ASA+clopidogrel (75 mg/day). The aggregation study was performed with an optical aggregometer, using 5 μM adenosinediphosphate (ADP) and 1 mM arachidonic acid inductors before CABG, on 1-3 day and on 8-10 day after surgical treatment. DNA samples were examined for the V640L (rs6133) polymorphism in the P-selectin gene by real-time polymerase chain reaction (PCR) using the allele-specific primers.

Results. The frequency of the homozygous GG genotype of the rs6133 polymorphism was 84.6%; heterozygous GT genotype – 15.4%. The amplitude of aggregation with ADP before CABG, on 1-3 day and on 8-10 day after CABG for carriers of homozygotes of allele G vs carriers of the allele T were: 47.9±19.3%, 44.5±17.8%, 30.1±13.2% vs 47.9±17.1%, 46.3±16.5%, 39.6±22.0%, respectively (p=0.497, 0.441 and 0.687, respectively). The amplitude of aggregation with arachidonic acid before CABG, on 1-3 day and on 8-10 day after CABG for carriers of homozygotesof allele G vs carriers of the allele T, were: 47.9±23.2%, 24.5±21.7%, 12.3±16.3% vs 54.3±17.8%, 29.7±23.7%,  11±10.9%, respectively (p=0.416, 0.825 and 0.872, respectively). In the first 10 days of the postoperative period, 6 thrombotic events (5.7%) were observed in the study group: 2 strokes and 4 perioperative myocardial infarctions. Five events occurred in the group of patients with the GG genotype, 1 event in the group of patients with the GT genotype.Conclusion. V640L (rs6133) polymorphism in the P-selectin gene is not associated with ASA resistance in patients with coronary artery disease after CABG. The T allele of the rs6133 polymorphism is not associated with increased platelet aggregation activity after CABG and does not increase the risk of adverse events in the first 10 days after CABG.

Expression of CD62P and CD154 in peripheral blood of patients with rheumatoid arthritis and their correlation with clinical indexes

The aim of this study is to investigate the expression of CD62P and CD154 in peripheral blood of patients with rheumatoid arthritis (RA) and their correlation with the clinical indexes of RA. A total of 60 RA patients diagnosed and treated in the Department of Rheumatism in our hospital from January to December 2016 were selected as the RA group, and 60 cases of healthy subjects were selected as the control group. CD62P and CD154 levels in peripheral blood were determined by flow cytometry using the FACS Vantage flow cytometer, and the correlation analysis with the clinical indexes of RA patients were conducted. The levels of CD62P and CD154 in the peripheral blood of RA group were 28.75% ± 1.48% and 26.84% ± 1.03%, respectively, which were significantly higher than those of the control group ( P < 0.05). The levels of white blood cell (WBC), platelet (PLT), erythrocyte sedimentation rate (ESR), rheumatoid factor (RF), C-reactive protein (CRP), and interleukin (IL)-37 in the RA group were significantly higher than those in the control group ( P < 0.05). Pearson test showed that CD62P and CD154 levels in the peripheral blood in the RA group were positively correlated with serum WBC, PLT, ESR, RF, CRP, IL-37, and disease activity score 28 (DAS28) ( P < 0.05), but not correlated with disease course ( P > 0.05). The expression of CD62P and CD154 in peripheral blood of patients with RA was upregulated, and their expression levels were correlated with the activity of RA and the degree of joint lesion.

Development and validation of a rapid method for genotyping three P-selectin gene polymorphisms based on high resolution melting analysis

BACKGROUND

High resolution melting (HRM) analysis is one of the newer, reliable, and sensitive genotyping techniques, which offers considerable time and cost savings. P-selectin is an adhesion molecule that has a role in the initial phases of leukocyte adhesion to stimulated platelets and endothelial cells in inflammation. Multiple polymorphisms in P-selectin gene (SELP) that affect the protein sequence have been described. The aim of this study was to design, optimize, and validate a simple and rapid in-house HRM-based method for genotyping the NM_003005.3:c.992G>A (c.992G>A), NM_003005.3:c.1918G>T (c.1918G>T), and NM_003005.3:c.2266A>C (c.2266A>C) SELP polymorphisms.

METHODS

Initial genotyping of three SELP polymorphisms was performed by applying polymerase chain reaction (PCR) with sequence-specific primers (SSP), which was used as a reference method for determination of analytical sensitivity. PCR-HRM was performed with primers for c.2266A>C reported in the literature. Primers for the remaining two polymorphisms were designed using Primer-BLAST. Precision testing was performed using three samples with different genotypes. For accuracy, analytical sensitivity and specificity testing, 20 wild type, 10 heterozygous, and 10 homozygous samples were chosen per polymorphism. Results were expressed as percentage of concordance with the acceptability criterion ≥95%.

RESULTS

Agreement of results was 100% for all validation parameters except for analytical sensitivity for c.1918G>T and c.2266A>C, with agreement of 90%. Repeated analysis using both methods revealed an error in initial genotyping and correct genotyping by PCR-HRM, which was confirmed by Sanger sequencing.

CONCLUSION

The validation confirmed PCR-HRM as a precise, accurate, and specific method for genotyping the c.992G>A, c.1918G>T, and c.2266A>C SELP polymorphisms.

Impact of genetic polymorphisms on platelet function and response to anti platelet drugs

Cardiovascular genomic consists in the identification of polymorphic genes responsible for the susceptibility to cardiovascular disease including coronary artery disease (CAD). Genes involved in platelet activation and aggregation play a key role in the predisposition to CAD. A considerable inter-variability of platelet response to agonists and to drugs exists and in particular the hyper-reactivity phenotype seems to be heritable. Besides glycoproteins and receptors expressed on platelets surface whose mutations significantly impact on platelet function, moreover researchers in the last decades have paid great attention to the genes involved in the response to anti-platelet drugs, considering their pivotal role in the treatment and outcomes of CAD patients especially those undergoing PCI. With the outbreak of advanced techniques developed to analyse human genetic footprints, researchers nowadays have shifted from genetic linkage analysis and a candidate gene approach toward genome-wide association (GWAS) studies and the analysis of miRNA-mRNA expression profiles.

Biomarkers for arterial and venous thrombotic disorders

The haemostatic system maintains the blood in a fluid state, but allows rapid clot formation at sites of vascular injury to prevent excessive bleeding. Unbalances within the haemostatic system can lead to thrombosis. Inspite of successful research our understanding of the disease pathogenesis is still incomplete. There is great hope that genetic, genomic, and epigenetic discoveries will enhance the diagnostic capability, and improve the treatment options. During the preceding 20 years, the identification of polymorphisms and the elucidation of their role in arterial and venous thromboses became an important area of research. Today, a large body of data is available regarding associations of single nucleotide polymorphisms (SNPs) in candidate genes with plasma concentrations and e. g. the risk of ischaemic stroke or myocardial infarction. However, the results for individual polymorphisms and genes are often controversial. It is now well established that besides acquired also hereditary risk factors influence the occurrence of thrombotic events, and environmental factors may add to this risk. Currently available statistical methods are only able to identify combined risk genotypes if very large patient collectives (>10,000 cases) are tested, and appropriate algorithms to evaluate the data have yet to be developed. Further research is needed to understand the functional effects of genetic variants in genes of blood coagulation proteins that are critical to the pathogenesis of arterial and venous thrombotic disorders. In this review genetic variants in selected genes of the haemostatic system and their relevance for arterial and venous thrombosis will be discussed.

Determinants of platelet-leukocyte aggregation and platelet activation in stroke

BACKGROUND

Platelet-leukocyte aggregation (PLA) and platelet activation are found to be on the higher side in ischemic stroke patients. The correlation of PLA with clinical features has not been intensively investigated and the influence of genetic factors on PLA is still unexplored. The interaction of platelets with leukocytes is mainly determined by the proteins encoded by six genes: P-Selectin (SELP encodes CD62P) on the thrombocyte binding to P-Selectin-Glycoprotein-Ligand-1 (PSGL1) on the leukocyte, intracellular-adhesion-molecule 2 (ICAM2) interacting with Integrin alpha M (ITGAM) and Glycoprotein 1b-alpha (GP1BA) binding to Integrin alpha L (ITGAL).

METHODS

Seventy-nine patients with acute ischemic stroke and 151 controls without vascular disease from a single German center were enrolled. A neurologist and a neuroradiologist ascertained clinical and radiological features. PLA and platelet activation were analyzed using flow cytometry with various antibodies. Coding as well as tagging SNPs in six genes determining PLA were genotyped. Three groups of parameters were correlated with each other: (i) clinical and radiological parameters, (ii) laboratory parameters, (iii) genetic parameters. For the comparisons, robust nonparametric statistical tests were applicable.

RESULTS

PLA and platelet activation were higher in ischemic stroke patients compared to controls. Both, anticoagulant and antiplatelet treatment in the patient group affected platelet activation but not PLA. PLA correlated weakly with measures of stroke severity but not with thrombus length or stroke etiology. The association of SNP rs2228315 in the P-Selectin Glycoprotein Ligand-1-gene (PSGL1) with ischemic stroke and platelet activation was significant before correction for multiple testing while a trend was observed for the association with PLA. Regression analysis revealed that (i) platelet activation was an independent determinant of stroke, (ii) that PLA correlated with stroke, sex, age and platelet activation and (iii) that platelet activation correlated only with stroke. None of the SNPs survived in the regression analysis for stroke, PLA or platelet activation as dependent variables.

CONCLUSIONS

The most important result of our study is that PLA and platelet activation are independent of other vascular risk factors correlated with stroke in our sample. In addition, we identified the missense SNP rs2228315 in the PSGL1-gene as a candidate polymorphism for ischemic stroke-related PLA. Association between this SNP and stroke as well as coronary artery disease has also been shown by two other studies.

Impact of variables of the P-selectin - P-selectin glycoprotein ligand-1 axis on leukocyte-platelet interactions in cardiovascular disease

The formation of leukocyte-platelet aggregates (LPA), through the P-selectin - P-selectin glycoprotein ligand (PSGL)-1 axis, plays a pivotal role in atherothrombosis. In order to investigate the influence of platelet (pP-selectin) and soluble P-selectin (sP-selectin), and of variations in the genes encoding for P-selectin (SELP) and PSGL-1 (SELPLG) on LPA formation, we assessed monocyte (MPA)- and neutrophil-platelet aggregates (NPA) as well as pP-selectin by flow cytometry in 263 patients undergoing angioplasty and stenting. sP-selectin was determined by ELISA, the SELP Pro715 allele and the SELPLG Ile62 allele were determined by allele specific PCR. The Pro715 allele was significantly associated with lower levels of in vivo pP-selectin and sP-selectin, while agonists´ inducible pP-selectin was not influenced by the Pro715 allele. PP-selectin was significantly associated with MPA and NPA formation. The in vivo formation of MPA and NPA depended to 19 % and 7.4 %, respectively, on in vivo pP-selectin, irrespective of the Pro715 allele and the Ile62 allele carrier status. TRAP-6 inducible MPA and NPA depended to 34 % and 27 %, respectively, on TRAP-6 inducible pP-selectin, but were independent of the Pro715 allele carrier status. Carriers of the Ile62 allele showed a stronger correlation between TRAP-6 inducible pP-selectin and TRAP-6 inducible MPA/NPA than non-carriers. Furthermore, TRAP-6 inducible NPA were higher in Ile62 allele carriers, which suggests higher thrombin sensitivity. In conclusion, our findings point to the significant role of pP-selectin for MPA and NPA formation, while other variables like sP-selectin, the SELP Pro715 allele and the SELPLG Ile62 allele have less influence.

Heterogeneous effect of two selectin gene polymorphisms on coronary artery disease risk: a meta-analysis

Background

The selectins play important roles in the inflammatory process of coronary artery disease (CAD) and myocardial infarction (MI). Previous studies have shown ambiguous findings regarding a possible association between the selectin genes and CAD. The E-selectin Ser128Arg polymorphism and the P-selectin Thr715Pro polymorphism have been investigated widely but with inconsistent results. We performed a comprehensive meta-analysis to shed light on this issue.

Methods

Data were extracted by searches of MEDLINE, Embase, CNKI, Wanfang, Google Scholar, PORTA, GeNii, CiNii, J-STAGE, Nurimedia and Koreanstudies Information Service System [Kiss] up to October 2013, in which 10 studies on the Ser128Arg polymorphism with 3369 cases and 2577 controls and 10 studies on the Thr715Pro polymorphism with 5886 cases and 18345 controls. A random-effects model was used to calculate the combined odds ratios. The between-study heterogeneity and publication bias were addressed.

Results

The 128Arg carriers had a significant increased risk of CAD (allele comparison: P = 0.02, OR = 1.33, 95%CI 1.04–1.69, P_{heterogeneity} = 0.01); The 715Pro conferred a non-significant risk reduction relative to the 715Thr (allele comparison: P = 0.40, OR = 0.94, 95%CI 0.82–1.08, P_{heterogeneity} = 0.03).Subgroup analyses demonstrated that the 128Arg carriers had a significant increased risk of CAD among Asians (allele comparison: P = 0.001, OR = 2.07, 95%CI 1.33–3.24, P_{heterogeneity} = 0.77) but not among Caucasians (allele comparison: P = 0.33, OR = 1.13, 95%CI 0.88–1.45, P_{heterogeneity} = 0.08). Carrier status for the 715Pro was significantly associated with reduced risk of MI (allele comparison: P = 0.04, OR =  0.81, 95%CI 0.67–0.99, P_{heterogeneity} = 0.14). The asymmetric funnel plot and the Egger's test (P = 0.041) suggested the presence of publication bias for the Ser128Arg polymorphism.

Conclusion

Our results suggested there is an increase in the risk of CAD conferred by the Ser128Arg polymorphism and the thr715Pro polymorphism may be a protective factor of MI.

The Thr715Pro variant impairs terminal glycosylation of P-selectin

P-selectin variant 715Pro is associated with lower concentrations of plasma P-selectin and reduced risk for thrombosis. We examined the influence of 715Pro on P-selectin synthesis, post-translational processing, surface expression and function using HEK293 cells, which do not express endogenous P-selectin. Mass spectrometry revealed that HEK293 cells produced recombinant P-selectin which has a glycosylation pattern comparable to platelet P-selectin. Compared to wild-type transfectants, 715Pro transfectants have ~50% less terminally glycosylated P-selectin and accumulate more immature P-selectin in Golgi. Following Brefeldin A treatment, the majority of 715Pro P-selectin is not modified by Golgi enzymes, while wild-type P-selectin undergoes complete modification. Flow cytometry revealed that 715Pro transfectants have ~20% less P-selectin on the cell surface compared to wild-type transfectants. Secretion of P-selectin by 715Pro transfectants was about 38% lower compared to wild-type transfectants. Binding of HL-60 cells to 715Pro transfectants was ~29% lower than to wild-type transfectants. This observation was confirmed by the presence of fewer platelet-monocyte aggregates (PMA) in the blood of healthy individuals and patients with angiographically proven atherosclerosis, carrying 715Pro P-selectin compared to individuals with wild-type P-selectin. We conclude that the 715Pro variant impairs terminal glycosylation of P-selectin in Golgi, leading to reduced amounts of mature P-selectin and subsequently less surface expression and secretion of P-selectin. The reduced surface expression of 715Pro P-selectin contributes to inefficient adhesion to HL-60 cells or monocytes.

The sex-specific association of Met62Ile gene polymorphism in P-selectin glycoprotein ligand (PSGL-1) with carotid plaque presence: preliminary study

Atherosclerosis is known as an inflammatory disease in which a recruitment of leukocytes to the endothelium wall represents a preliminary step of the initiation and the development of disease. The P-selectin glycoprotein ligand (PSGL-1) seems to be the major molecule mediating leukocyte-endothelium interactions and leukocyte rolling on stimulated endothelium. There are limited number of studies reporting on association of Met62Ile SNP in PSGL-1 gene and the risk for atherosclerosis. The aim of this study was to analyze possible association of this polymorphism with an advanced carotid atherosclerosis and biochemical markers of inflammation and haemostasis. The 275 patients consecutively admitted for carotid endarterectomy with stenosis >70% and 256 controls of the same ethnic origin were included in the study. The Met62Ile genotypes were determined by PCR RFLP. The Ile/Ile homozygotes had significantly higher CRP compared to the other genotypes in patients. Female patients had Ile allele dose-dependent association with the carotid plaque presence (Met/Met vs. Met/Ile vs. Ile/Ile; OR 1, OR 2.02, CI 1.0-4.08, OR 4.08, CI 1.0-16.81, respectively, p = 0.04). Our results suggest the impact of PSGL-1 Met62Ile polymorphism on inflammation in advanced atherosclerosis. We observed the sex-differential association of Met62Ile with advanced carotid atherosclerosis. Studies in larger and different populations should validate and further examine the suggested role of genetic variations in PSGL-1 with atherosclerosis and thrombosis.

Contribution of SELP and PSGL-1 genotypes and haplotypes to the presence of coronary heart disease in Tunisians

P-selectin (SELP) and its counter-receptor, P-selectin glycoprotein ligand-1 (PSGL-1), play key role in the transient attachment of leukocytes to endothelial cells predisposing to coronary heart disease (CHD). In the current report, 293 angiographically proven CHD patients and 327 age, gender, and race-matched controls were included. Our aim was to evaluate the contribution to CHD of the following SNPs: C-2123G, G-1969A and T715P in SELP, Met62Ile and the VNTR variants in PSGL-1 gene in a North African population from Tunisia. While there were no significant differences in the distribution of SELP or PSGL-1 alleles or genotypes between patients and controls, a trend for a significant association of the C-2123G genotypes distribution with incident CHD was observed (P=0.06). Assuming an additive model of transmission, the risk was 74% higher among subjects carrying the GG genotypes in comparison to those carrying the CC genotype (OR=1.74 [1.01-2.98], P=0.04) and 80% higher in the recessive model (OR=1.80 [1.08-3.01], P=0.02). Haplotype analysis did not identify any specific SELP or PSGL-1 haplotypes to be associated with CHD. The present study demonstrated no evidence of association between individual SELP or PSGL-1 SNPs or haplotypes with incident CHD. However, this study replicates absence of association of the mostly studied SNP, T715P, previously reported in individuals with African origin.

SELP and SELPLG genetic variation is associated with cell surface measures of SELP and SELPLG: the Atherosclerosis Risk in Communities Carotid MRI Study

BACKGROUND

P-selectin (SELP) and its ligand, P-selectin glycoprotein ligand 1 (SELPLG), play key roles in both the inflammatory response and the atherosclerotic process. Previous studies have shown genetic variation in the SELP gene [selectin P (granule membrane protein 140 kDa, antigen CD62)] to be associated with plasma SELP concentrations; however, the major biological function of SELP (and SELPLG) is at the cell surface. We therefore investigated the association of SELP polymorphisms with platelet SELP measures and polymorphisms in the SELPLG gene (selectin P ligand) with lymphocyte, granulocyte, and monocyte SELPLG measures among 1870 participants in the Atherosclerosis Risk in Communities (ARIC) Carotid MRI Study.

METHODS

Whole-blood flow cytometry was used to analyze leukocyte and platelet markers in the ARIC Carotid MRI Study. The allele frequencies for the SELP and SELPLG polymorphisms of whites and African Americans were markedly different; therefore, all analyses were race specific.

RESULTS

SELP T715P was significantly associated with lower values for platelet SELP measures in whites (P = 0.0001), whereas SELP N562D was significantly associated with higher values for SELP measures in African Americans (P = 0.02). SELPLG M62I was significantly associated with lower granulocyte and monocyte SELPLG measures in African Americans (P = 0.003 and P = 0.0002, respectively) and with lower lymphocyte SELPLG measures in whites (P = 0.01).

CONCLUSIONS

Specific SELP and SELPLG polymorphisms were associated with cell surface measures of SELP and SELPLG in both whites and African Americans in the ARIC Carotid MRI Study. To our knowledge, this study is the first to examine the association of SELP and SELPLG genetic variation with measures of cell surface SELP and SELPLG.

P-selectin glycoprotein ligand-1 decameric repeats regulate selectin-dependent rolling under flow conditions

P-selectin glycoprotein ligand-1 (PSGL-1) interacts with selectins to support leukocyte rolling along vascular wall. L- and P-selectin bind to N-terminal tyrosine sulfate residues and to core-2 O-glycans attached to Thr-57, whereas tyrosine sulfation is not required for E-selectin binding. PSGL-1 extracellular domain contains decameric repeats, which extend L- and P-selectin binding sites far above the plasma membrane. We hypothesized that decamers may play a role in regulating PSGL-1 interactions with selectins. Chinese hamster ovary cells expressing wild-type PSGL-1 or PSGL-1 molecules exhibiting deletion or substitution of decamers with the tandem repeats of platelet glycoprotein Ibalpha were compared in their ability to roll on selectins and to bind soluble L- or P-selectin. Deletion of decamers abrogated soluble L-selectin binding and cell rolling on L-selectin, whereas their substitution partially reversed these diminutions. P-selectin-dependent interactions with PSGL-1 were less affected by decamer deletion. Videomicroscopy analysis showed that decamers are required to stabilize L-selectin-dependent rolling. Importantly, adhesion assays performed on recombinant decamers demonstrated that they directly bind to E-selectin and promote slow rolling. Our results indicate that the role of decamers is to extend PSGL-1 N terminus far above the cell surface to support and stabilize leukocyte rolling on L- or P-selectin. In addition, they function as a cell adhesion receptor, which supports approximately 80% of E-selectin-dependent rolling.

P-selectin polymorphisms' influences on P-selectin serum concentrations and on their familial correlation: the STANISLAS family study

BACKGROUND

P-selectin is an adhesion molecule known to be involved in the pathogenesis of several diseases through its major role in the initial phase of leukocytes recruitment during inflammation. However, genetic characterization of soluble P-selectin remains unclear.

OBJECTIVES

In the STANISLAS cohort, we study the familial correlations of P-selectin levels and investigate the association of six P-selectin polymorphisms (C-2123G, A-1969G, S290N, N562D, V599L and T715P) and cardiovascular risk factors with P-selectin concentrations.

PATIENTS/METHODS

Full phenotypic and genotypic information was available for 136 healthy families composed of both natural parents and at least one child (boys, n = 125; and girls, n = 139) aged more than 4 years.

RESULTS

While no correlation was observed between spouses, family correlations of P-selectin concentrations were highly significant for sibling (0.50 +/- 0.12, P < 10(-3)) and child-parent pairs (0.42 +/- 0.04, P < 10(-3)). P-selectin haplotypes explained about 25% of the variability of P-selectin concentrations, this effect being mainly due to the additive effects of two polymorphisms, V599L and T715P. After adjusting for the effect of the P-selectin polymorphisms, the sibling and child-parent correlations decreased to (0.39 +/- 0.08, P < 10(-4)) and (0.32 +/- 0.06, P < 10(-4)), respectively.

CONCLUSIONS

In the present study, we showed that two P-selectin polymorphisms, V599L and T715P, explained about 25% of the variability of P-selectin concentrations and accounted for about 40% of their family resemblance. These results would suggest a genetic influence on P-selectin concentrations beyond the contribution of the P-selectin gene.

Selectin haplotypes and the risk of venous thrombosis: influence of linkage disequilibrium with the factor V Leiden mutation

BACKGROUND

Selectins (E-, L- and P-selectin) and their most important counter-receptor P-selectin glycoprotein ligand (SELPLG) facilitate the interaction of platelets, leukocytes and endothelial cells at inflammatory sites. Selectin polymorphisms/haplotypes have been associated with cardiovascular disease.

OBJECTIVES

We investigated the association between haplotypes (H) of these four genes and deep venous thrombosis (DVT) risk. We additionally explored the effect of linkage disequilibrium (LD) with the nearby Factor V Leiden mutation (FVL). Furthermore, interactions between SELPLG polymorphisms and selectin polymorphisms were investigated.

PATIENTS/METHODS

Leiden Thrombophilia Study (LETS) subjects were genotyped for 24 polymorphisms by TaqMan or PCR-RFLP, detecting all common haplotypes in four blocks. P-selectin was analyzed in two blocks, upstream (SELPup) and downstream (SELPdown) of the recombination hotspot.

RESULTS

In E- and L-selectin, none of the haplotypes was associated with DVT risk. In SELPup, H2-carriers had a 1.3-fold increased risk (95% CI, 1.0-1.7), whereas H4-carriers had a 1.4-fold decreased risk (95% CI, 0.5-1.0). In SELPdown, H2-carriers had a 1.3-fold increased risk (95% CI, 1.0-1.7). Because of LD with FVL, we subsequently excluded all FVL-carriers and all risks disappeared. Mutual adjustment within a logistic regression model resulted in disappearance of the risks for the SELP haplotypes, whereas FVL risk remained.

CONCLUSIONS

After adjustment for LD with FVL, none of the selectin haplotypes was associated with DVT risk, showing that the increased risks of the selectin haplotypes were a reflection of the effect of FVL on thrombosis risk.

Association of the single-nucleotide polymorphism and haplotype of the P-selectin gene with ischemic stroke

Inflammation has recently proven to be associated with the pathogenesis of atherosclerosis and inflammatory genes are good candidates for the risk of developing atherosclerosis. The early phase of atherosclerosis involves the recruitment of inflammatory cells from the circulation and their transendothelial migration. This process is mainly mediated by cellular adhesion molecules. The adhesion molecule P-selectin may play a role in the pathogenesis of atherosclerosis. Polymorphism of P-selectin gene, which may affect the production level of the adhesion molecule, has been associated with a number of atherosclerotic disease. To test this hypothesis, we investigated the relationship of P-selectin gene polymorphisms and ischemic stroke in a Chinese population. We analyzed single nucleotide polymorphisms of P-selectin gene -2,123 G/C, -1,969 G/A, -1,817 T/C and Thr715Pro in three hundred and five patients with ischemic stroke and 280 age and sex matched controls, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing method. There were no significant differences in the genotype, allele and haplotype frequencies of P-selectin gene polymorphisms between the group of patients with ischemic stroke and the control group. Furthermore, there was no significant association of genotype, allele and haplotype at any of the polymorphism in relation to any subtype of ischemic stroke. We did not observe an association between P-selectin gene polymorphisms and ischemic stroke or any subtype of ischemic stroke. However, further studies are needed to explore the complex interaction between environmental factors and P-selectin gene polymorphisms in the risk of ischemic stroke, particularly in ethnically different populations.

Specific P-selectin and P-selectin glycoprotein ligand-1 genotypes/haplotypes are associated with risk of incident CHD and ischemic stroke: the Atherosclerosis Risk in Communities (ARIC) study

OBJECTIVE

P-selectin (PSEL) and its ligand, P-selectin glycoprotein ligand-1 (PSGL-1), play key roles in both the inflammatory response and the atherosclerotic process, but there are conflicting results regarding the affect of PSEL and PSGL-1 gene variation on risk for cardiovascular and cerebrovascular disease. We tested the association of four PSEL and two PSGL-1 polymorphisms with incident coronary heart disease (CHD) and ischemic stroke among 13,875 participants in the prospective Atherosclerosis Risk in Communities (ARIC) study. We also tested common haplotypes in the PSEL and PSGL-1 genes to assess associations with incident CHD and ischemic stroke.

METHODS AND RESULTS

Incident ischemic stroke and CHD were identified through annual telephone calls and hospital and death certificate surveillance. Five hundred and twenty-five validated ischemic stroke and 1654 CHD events were identified. Allele frequencies for all PSEL and PSGL-1 polymorphisms were markedly different between whites and African Americans; therefore, all analyses were performed race-specific. Independent analyses showed the PSEL 290NN genotype to be a significant predictor of CHD in whites (HRR 1.30, 95%CI 1.00-1.70, P=0.05). PSGL-1 genotypes carrying the 62I allele were significantly protective for incident CHD (HRR 0.53, 95%CI 0.31-0.92, P=0.02) and ischemic stroke (HRR 0.73, 95%CI 0.55-0.97, P=0.03) in African Americans. Haplotype analyses showed the PSEL NNVP haplotype to be a significant predictor of incident CHD in whites (HRR 2.09, 95%CI 1.23-3.55, P=0.006). No significant haplotype findings were observed in African Americans.

CONCLUSIONS

PSEL S290N, in single polymorphism analysis and in the haplotypic background with T715P, was associated with increased risk of incident CHD in whites. The PSGL-1 M62I polymorphism was associated with decreased risk of both incident CHD and stroke in African Americans. These findings illustrate the complex relationship between genetic variation and disease in different racial groups.

Evolutionary conservation of P-selectin glycoprotein ligand-1 primary structure and function

BACKGROUND

P-selectin glycoprotein ligand-1 (PSGL-1) plays a critical role in recruiting leukocytes in inflammatory lesions by mediating leukocyte rolling on selectins. Core-2 O-glycosylation of a N-terminal threonine and sulfation of at least one tyrosine residue of PSGL-1 are required for L- and P-selectin binding. Little information is available on the intra- and inter-species evolution of PSGL-1 primary structure. In addition, the evolutionary conservation of selectin binding site on PSGL-1 has not been previously examined in detail. Therefore, we performed multiple sequence alignment of PSGL-1 amino acid sequences of 14 mammals (human, chimpanzee, rhesus monkey, bovine, pig, rat, tree-shrew, bushbaby, mouse, bat, horse, cat, sheep and dog) and examined mammalian PSGL-1 interactions with human selectins.

RESULTS

A signal peptide was predicted in each sequence and a propeptide cleavage site was found in 9/14 species. PSGL-1 N-terminus is poorly conserved. However, each species exhibits at least one tyrosine sulfation site and, except in horse and dog, a T [D/E]PP [D/E] motif associated to the core-2 O-glycosylation of a N-terminal threonine. A mucin-like domain of 250-280 amino acids long was disclosed in all studied species. It lies between the conserved N-terminal O-glycosylated threonine (Thr-57 in human) and the transmembrane domain, and contains a central region exhibiting a variable number of decameric repeats (DR). Interspecies and intraspecies polymorphisms were observed. Transmembrane and cytoplasmic domain sequences are well conserved. The moesin binding residues that serve as adaptor between PSGL-1 and Syk, and are involved in regulating PSGL-1-dependent rolling on P-selectin are perfectly conserved in all analyzed mammalian sequences. Despite a poor conservation of PSGL-1 N-terminal sequence, CHO cells co-expressing human glycosyltransferases and human, bovine, pig or rat PSGL-1 efficiently rolled on human L- or P-selectin. By contrast, pig or rat neutrophils were much less efficiently recruited than human or bovine neutrophils on human selectins. Horse PSGL-1, glycosylated by human or equine glycosyltransferases, did not interact with P-selectin. In all five species, tyrosine sulfation of PSGL-1 was required for selectin binding.

CONCLUSION

These observations show that PSGL-1 amino acid sequence of the transmembrane and cytoplasmic domains are well conserved and that, despite a poor conservation of PSGL-1 N-terminus, L- and P-selectin binding sites are evolutionary conserved. Functional assays reveal a critical role for post-translational modifications in regulating mammalian PSGL-1 interactions with selectins.

High concentrations of soluble P-selectin are associated with risk of venous thromboembolism and the P-selectin Thr715 variant

BACKGROUND

The cell adhesion molecule P-selectin has an important role in the pathophysiology of thrombosis. The effect on venous thromboembolism (VTE) of increased circulating concentrations of soluble P-selectin (sP-selectin) and their association with the P-selectin variant Thr715Pro is still uncertain.

METHODS

This study was a case-control study of 116 patients with confirmed recurrent VTE and at least 1 event of unprovoked deep venous thrombosis or pulmonary embolism, and 129 age- and sex-matched healthy individuals. We measured sP-selectin by ELISA and P-selectin gene (SELP) variation by genotyping and sampled blood after a mean interval of 2.55 years after the most recent VTE event.

RESULTS

The mean (SD) sP-selectin concentration was higher in patients than in controls: 47.3 (15.0) microg/L vs 36.8 (11.0) microg/L, P <0.001. The unadjusted odds ratio (OR) for sP-selectin >55.1 microg/L, representing the 95th percentile for controls, was 8.5 (95% CI, 3.7-23.3; P <0.001) and increased after adjustment for factor V Leiden, the prothrombin G20210A variant, increased factor VIII, and hyperhomocysteinemia (OR, 10.6; 95% CI, 4.1-31.2; P <0.001). Pro715 carriers were more prevalent among controls than patients (21.7% vs 14.7%). sP-selectin concentrations were lower in this subgroup than in noncarriers: 31.3 (7.9) microg/L vs 44.1 (14.1) microg/L; P <0.001).

CONCLUSIONS

Increased sP-selectin concentrations are associated with VTE and genotype status. sP-selectin concentrations are lower in individuals carrying the P-selectin Pro715 variant than in those without this variant.

SELPLG and SELP single-nucleotide polymorphisms in multiple sclerosis

P-Selectin (SELP) and P-selectin glycoprotein ligand-1 (SELPLG) constitute a receptor/ligand complex involved in the recruitment of activated lymphocytes, a critical event in the pathogenesis of multiple sclerosis (MS). In order to determine whether genetic variation in these pivotal molecules influences susceptibility to MS, we genotyped 214 Italian patients compared with 220 Italian controls for three single-nucleotide polymorphisms (SNPs): SELPLG Met62Ile, SELP C-2123G and SELP Thr715Pro. No significant differences in both SELP SNPs were found between patients and controls, whereas a decreased frequency of the Met62Ile SNP was found in patients versus controls in the Italian population (P = 0.025). To confirm these preliminary findings, the Met62Ile SNP was analysed in 938 UK trio families. This SNP did not show evidence for association with susceptibility to MS in the larger UK cohort. Therefore, none of the SNPs investigated is associated with MS, although this analysis does not conclusively exclude SELPLG and SELP as genetic risk factors for MS as much variation remains untested.