Association of soluble endothelial protein C receptor plasma levels and PROCR rs867186 with cardiovascular risk factors and cardiovascular events in coronary artery disease patients: the Athero Gene study

LPL rs264, PROCR rs867186 and PDGF rs974819 Gene Polymorphisms in Patients with Unstable Angina

BACKGROUND

Coronary artery disease is caused by changes in the coronary arteries due to the atherosclerotic process and thrombotic changes. A very important role in the development of the atherosclerotic process in the coronary vessels is played by the inflammatory process and the immune response. Due to the important role of lipids and the coagulation process in the atherosclerotic process, research has also focused on genes affecting lipid metabolism and the coagulation system. Lipoprotein lipase (LPL) is an enzyme that metabolises lipids, hydrolysing triglycerides to produce free fatty acids and glycerol. Protein C (PC) is an essential component of coagulation and fibrinolysis. It is activated on the endothelial surface by the membrane-bound thrombin-thrombomodulin complex. Platelet-derived growth factor (PDGF) has a number of important functions in processes related to fibroblast and smooth muscle cell function. Due to their influence on lipid metabolism and coagulation processes, LPL, PROCR (endothelial cell protein C receptor) and PDGF may affect the atherosclerotic process and, thus, the risk of coronary heart disease. The aim of the study was to examine the associations between the LPL rs264, PROCR rs867186 and PDGF rs974819 gene polymorphisms and the risk of unstable angina and selected clinical parameters.

METHODS

The study included 232 patients with unstable angina and 144 healthy subjects as the control group. Genotyping was performed using real-time PCR.

RESULTS

There were no statistically significant differences in the distribution of the polymorphisms tested between the patients with unstable angina and the control subjects. The results showed associations between the PROCR rs867186 and PDGF rs974819 polymorphisms and some clinical parameters in patients with unstable angina. In patients with the PDGF rs974819 CC genotype, there were increased values for cholesterol and LDL serum levels in comparison with patients with the PDGF rs974819 CT and TT genotypes. In patients with the PROCR rs867186 AA genotype, HDL serum levels were lower than in patients with the GA genotype.

CONCLUSIONS

The results of our study did not show that the LPL rs264, PROCR rs867186 and PDGF rs974819 gene polymorphisms were significant risk factors for unstable angina in our population. The results of the study suggest that PDGF rs974819 and PROCR rs867186 may be associated with some parameters of lipid metabolism.

Genetic variant of endothelial protein C receptor genes and its serum level in B thalassemic children

BACKGROUND

Due to their chronic hypercoagulable status, thalassemic individuals are at an elevated risk of developing thromboembolic sequence consequences. The goal of the current study is to assesses the EPCR gene polymorphism and soluble EPCR in Egyptian thalassemic children and its role in hypercoagulable state.

RESEARCH DESIGN AND METHODS

Eighty children diagnosed as thalassemia major and 80 healthy youngsters as a control group. The EPCR gene was identified using a restriction fragment length polymerase chain reaction (RFLP PCR). Additionally, we assessed the soluble EPCR levels using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Frequency of 1651C-G EPCR, the GC genotype was strongly related with an increased risk of coagulation (OR = 1.83 (0.64-5.26), P = 0.0.016). In addition, soluble EPCR was considerably higher in patients with thalassemia than in controls, P value <0.001. Our study revealed significance difference between soluble EPCR and different genotypes.

CONCLUSION

Polymorphisms in the EPCR gene and an elevated soluble EPCR level in patients with β-thalassemia major may contribute to these patients' hemostatic derangement in thalassemic Egyptian children.

Elucidating mechanisms of genetic cross-disease associations at the PROCR vascular disease locus

Many individual genetic risk loci have been associated with multiple common human diseases. However, the molecular basis of this pleiotropy often remains unclear. We present an integrative approach to reveal the molecular mechanism underlying the PROCR locus, associated with lower coronary artery disease (CAD) risk but higher venous thromboembolism (VTE) risk. We identify PROCR-p.Ser219Gly as the likely causal variant at the locus and protein C as a causal factor. Using genetic analyses, human recall-by-genotype and in vitro experimentation, we demonstrate that PROCR-219Gly increases plasma levels of (activated) protein C through endothelial protein C receptor (EPCR) ectodomain shedding in endothelial cells, attenuating leukocyte-endothelial cell adhesion and vascular inflammation. We also associate PROCR-219Gly with an increased pro-thrombotic state via coagulation factor VII, a ligand of EPCR. Our study, which links PROCR-219Gly to CAD through anti-inflammatory mechanisms and to VTE through pro-thrombotic mechanisms, provides a framework to reveal the mechanisms underlying similar cross-phenotype associations.

Early protein C activation is reflective of burn injury severity and plays a critical role in inflammatory burden and patient outcomes

BACKGROUND

Navigating the complexities of a severe burn injury is a challenging endeavour where the natural course of some patients can be difficult to predict. Straddling both the coagulation and inflammatory cascades that feature strongly in the burns systemic pathophysiology, we propose the pleiotropic protein C (PC) system may produce a viable biomarker to assist traditional evaluation methods for diagnostic and prognostic purposes.

METHODS

We enrolled 86 patients in a prospective observational cohort study. Over three weeks, serial blood samples were taken and measured for PC, activated (A)PC, their receptor endothelial protein C receptor (EPCR), and a panel of inflammatory cytokines including C-reactive protein (CRP), tumour necrosis factor-α, interleukin (IL)-1β, IL-6, IL-8, and IL-17. Their temporal trends were analysed alongside clinical factors including burn size, burn depth, presence of inhalational injury, and a composite outcome of requiring increased support.

RESULTS

(i) APC increased from a nadir on Day 3 (2.3±2.1ng/mL vs 4.1±2.5ng/mL by Day 18, p<0.0005), only becoming appropriately correlated to PC from Day 6 onwards (r=0.412-0.721, p<0.05 for all Days 6-21). (ii) This early disturbance in the PC system was amplified in the more severe burns (≥30% total body surface area, predominantly full thickness, or with inhalational injury), which were characterised by a marked fall in PC activation (approximated by APC/PC ratio) and APC levels during Days 0-3 with low unchanged PC levels. Critically low levels of this cytoprotective agent was associated with greater inflammatory burden, as reflected by significantly elevated CRP, IL-6, and IL-8 levels in the more severe compared to less severe burns, and by negative correlations between both PC and APC with most inflammatory cytokines. (iii) Alongside clinical markers of severity at admission (burn size, burn depth, and presence of inhalational injury), only Day 0 APC/PC ratio (OR 1.048 (1.014-1.083), p=0.006), APC (OR 1.364 (1.032-1.803), p=0.029), PC (OR 0.899 (0.849-0.953), p<0.0005), and not any inflammatory cytokines were predictive markers of requiring increased support. Uniquely, decreased Day 0 PC was further individually associated with each increased total length of stay, ICU length of stay, intravenous fluid resuscitation, and total surgeries, as well as possibly mortality.

CONCLUSION

An early functional depletion of the cytoprotective PC system provides a physiological link between severe burns and the cytokine storm, likely contributing to worse outcomes. Our findings on the changes in APC, PC and PC activation during this pathological state support APC and PC as early diagnostic and prognostic biomarkers, and provides a basis for their therapeutic potential in severe burn injuries.

Analysis of PROC and PROS1 single nucleotide polymorphisms in a thrombophilia family

OBJECTIVE

The aim of this study was to assess the association of single nucleotide polymorphisms (SNPs) in protein C (PROC) and protein S (PROS1) genes with deep venous thrombosis (DVT) in a thrombophilia family.

METHODS

DNA were extracted from blood of participants. Five PROC SNPs and 11 PROS1 SNPs were selected from the Hapmap and 1000 Genomes databases. The minor allele frequencies (MAFs) of SNPs in the thrombophilia family (Group I) and healthy controls (Group II) were detected. SNPs were analysed by Chi-square, logistic regression and linkage disequilibrium patterns.

RESULTS

MAFs for all 16 SNPs were greater than 0.05. Chi-square analysis showed significant differences between Group I and Group II in the frequency of mutant alleles of rs1799808, rs5936, rs6123, rs12634349, rs6441600 and rs13062355 SNPs (P < .05). Logistic regression analysis found that mutant alleles of rs1799808, rs6441600 and rs13062355 SNPs may contribute to DVT in this family (OR > 1, L95 > 1). Linkage disequilibrium was found among 15 of the PROC and PROS SNPs.

CONCLUSIONS

Single nucleotide polymorphisms (SNPs) of PROC and PROS1 may be closely associated with DVT in this thrombophilia family. Mutant alleles of rs1799808, rs6441600 and rs13062355 SNPs may contribute to DVT, whereas mutant alleles of rs1799810, rs6123 and rs12634349 may protect individuals from DVT. With the exception of rs9681204, there was linkage disequilibrium between PROC and PROS1 SNPs. We found that 12 haplotypes were in linkage disequilibrium, but linkage disequilibrium was strong in only eight of these (frequency >5%).

The H1 haplotype of the endothelial protein C receptor protects against arterial thrombosis in patients with antiphospholipid syndrome

INTRODUCTION

Genetic variants in the endothelial protein C receptor gene (PROCR) may contribute to the thrombosis risk by regulating levels of the soluble form of this protein (sEPCR). We evaluated whether PROCR polymorphisms and sEPCR levels play a role in the thrombotic manifestations of antiphospholipid syndrome.

MATERIALS AND METHODS

One hundred and seventy-five patients (62 with primary antiphospholipid syndrome, 30 with antiphospholipid syndrome associated with systemic lupus erythematosus, 40 with systemic lupus erythematosus without antiphospholipid antibodies and 43 with systemic lupus erythematosus and antiphospholipid antibodies) and 66 healthy controls were included. PROCR H1 and H3 haplotypes were determined by genotyping 7014G/C and 1651C/G tag-polymorphisms, respectively. sEPCR levels were determined by enzyme-linked immunosorbent assay.

RESULTS

PROCR haplotype distribution was similar among groups of patients and controls. PROCR H1 and H3 haplotypes were less prevalent in antiphospholipid syndrome patients with arterial thrombosis than those without arterial thrombosis, but statistical significance was only reached for the H1 haplotype (58.0% vs. 85.7%, p = 0.003; odds ratio: 0.23 [95% CI 0.08-0.65]). No relationship between the PROCR H1 and H3 haplotypes and venous thrombosis was found. sEPCR levels were higher in H3 than in H1 carriers (175.5 [95% CI 60.9-290.1] ng/ml vs. 69.1 [95% CI 61.5-76.9] ng/ml, p < 0.01). No relationship of sEPCR with arterial or venous thrombosis was found.

CONCLUSION

The PROCR H1 haplotype was less frequently found in APS patients with arterial thrombosis, suggesting a protective effect of PROCR H1 against arterial thrombosis in these patients. No relationship between sEPCR and thrombosis was found.

Endothelial protein C receptor polymorphisms and risk of sepsis in a Chinese population

Objective

To examine the potential relationship of EPCR polymorphisms and the risk of sepsis in a Chinese population.

Methods

Snapshot SNP genotyping assays and DNA sequencing methods were used to detect polymorphisms of the EPCR gene, rs2069948C/T (2532C/T) and rs867186A/G (6936A/G), in 64 patients with sepsis and in 113 controls. Soluble EPCR (sEPCR) was measured by ELISA.

Results

There were significant differences in the allele and genotype frequencies of EPCR gene rs2069948C/T and allele frequencies of rs867186A/G between male and female patients and controls. Females carrying rs2069948 C/T genotype or T allele and males carrying rs867186 A allele were associated with a significantly increased risk of sepsis. Plasma sEPCR levels of sepsis patients were higher than controls and showed no correlation with EPCR gene polymorphisms.

Conclusions

EPCR polymorphisms may be associated with increased risk of sepsis, but this has no effect on the release of sEPCR in patients with sepsis.

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.

Endothelial protein C receptor gene variants not associated with severe malaria in ghanaian children

Background

Two recent reports have identified the Endothelial Protein C Receptor (EPCR) as a key molecule implicated in severe malaria pathology. First, it was shown that EPCR in the human microvasculature mediates sequestration of Plasmodium falciparum-infected erythrocytes. Second, microvascular thrombosis, one of the major processes causing cerebral malaria, was linked to a reduction in EPCR expression in cerebral endothelial layers. It was speculated that genetic variation affecting EPCR functionality could influence susceptibility to severe malaria phenotypes, rendering PROCR, the gene encoding EPCR, a promising candidate for an association study.

Methods

Here, we performed an association study including high-resolution variant discovery of rare and frequent genetic variants in the PROCR gene. The study group, which previously has proven to be a valuable tool for studying the genetics of malaria, comprised 1,905 severe malaria cases aged 1–156 months and 1,866 apparently healthy children aged 2–161 months from the Ashanti Region in Ghana, West Africa, where malaria is highly endemic. Association of genetic variation with severe malaria phenotypes was examined on the basis of single variants, reconstructed haplotypes, and rare variant analyses.

Results

A total of 41 genetic variants were detected in regulatory and coding regions of PROCR, 17 of which were previously unknown genetic variants. In association tests, none of the single variants, haplotypes or rare variants showed evidence for an association with severe malaria, cerebral malaria, or severe malaria anemia.

Conclusion

Here we present the first analysis of genetic variation in the PROCR gene in the context of severe malaria in African subjects and show that genetic variation in the PROCR gene in our study population does not influence susceptibility to major severe malaria phenotypes.

sEPCR Levels in Chronic Myeloproliferative Diseases and Their Association with Thromboembolic Events: A Case-Control Study

Objective: Venous, arterial, and microcirculatory events are frequently encountered in the clinical course of essential thrombocytosis and polycythemia vera. We aimed to investigate the levels of soluble endothelial protein C receptor (sEPCR) in myeloproliferative diseases to see whether there was a difference between the patients with and without history of thromboembolism.

Materials and Methods: The study included patients with polycythemia vera (n=12), patients with essential thrombocytosis (n=13), and controls (n=29). In all groups, we measured proteins C and S, antithrombin and sEPCR levels, and plasma concentrations of thrombin-antithrombin complex, prothrombin fragments 1+2, and D-dimer.

Results: Comparing the patients with and without history of thromboembolic attack, statistically significant differences were not observed in terms of sEPCR, D-dimer, thrombin-antithrombin complex, prothrombin fragments 1+2, and hematocrit levels (p=0.318, 0.722, 0.743, 0.324, and 0.065, respectively).

Conclusion: Significant increase in the parameters that reflect activation of coagulation, such as sEPCR, thrombin-antithrombin complex, prothrombin fragments 1+2, and D-dimer, reflects the presence of a basal condition that leads to a tendency toward thrombosis development in ET and PV when compared to healthy controls.

Association of the endothelial protein C receptor (PROCR) rs867186-G allele with protection from severe malaria

Background

Cytoadhesion of Plasmodium falciparum-infected erythrocytes to endothelial cells in microvessels is a remarkable characteristic of severe malaria. The endothelial protein C receptor (EPCR), encoded by the endothelial protein C receptor gene (PROCR), has recently been identified as an endothelial receptor for specific P. falciparum erythrocyte membrane protein 1 (PfEMP1) subtypes containing domain cassettes (DCs) 8 and 13. The PROCR rs867186-G allele (serine-to-glycine substitution at position 219 of EPCR; 219Gly) has been shown to be associated with higher levels of plasma soluble EPCR (sEPCR). In this study, the association of PROCR rs867186 with severe malaria is examined in Thai population.

Methods

A total of 707 Thai patients with P. falciparum malaria (341 with severe malaria and 336 with mild malaria) were genotyped for rs867186. To assess the association of PROCR rs867186 with severe malaria, three models (dominant, recessive and allelic) were evaluated. The rates of non-synonymous and synonymous substitutions were estimated for the coding sequence of the PROCR gene.

Results

The rs867186-GG genotype was significantly associated with protection from severe malaria (P-value = 0.026; odds ratio = 0.33; 95% confidence interval = 0.12–0.90). Evolutionary analysis provided no evidence of strong positive selection acting on the PROCR gene.

Conclusion

The rs867186-GG genotype showed significant association with protection from severe malaria. The present results suggest that PfEMP1–EPCR interaction, which can mediate cytoadhesion and/or reduce cytoprotective and anti-inflammatory effects, is crucial to the pathogenesis of severe malaria.