Protective effect of a thrombin receptor (protease-activated receptor 1) gene polymorphism toward venous thromboembolism

Role of PAR1 -506 deletion/insertion polymorphism in primary sclerosing cholangitis

AIM

Primary sclerosing cholangitis (PSC) is a rare cholestatic liver disease characterized by inflammation of the intra- and extrahepatic bile ducts. Pathogenesis of PSC is still enigmatic but is likely to be multifactorial. Recently, we identified an interleukin-6 (IL-6)-dependent signal transducer and activator of transcription 3 (STAT3) activation in CD4+ TH1 and TH17 cells in PSC. The IL-6/STAT3 pathway was shown to be regulated by protease-activated receptor 1 (PAR1) contributing to inflammation. The role of the PAR1 -506 deletion/insertion (Del/Ins) polymorphism in PSC has not yet been investigated.

METHODS

Two hundred eighty four PSC patients (200 patients with inflammatory bowel diseases [IBD] and 84 without IBD) and 309 healthy controls were genotyped for PAR1 rs11267092 (-506 Del/Ins -13 bp). Results were correlated with clinical characteristics and transplant-free survival.

RESULTS

The frequency of PAR1 -506 Ins allele carriers (Del/Ins and Ins/Ins) was significantly higher in PSC patients (57.0%) compared to healthy controls (39.8%). Furthermore, carriers of PAR1 -506 Ins allele were more likely to have PSC than noncarriers (odds ratio 2.01; 95% confidence interval, 1.45-2.79). Patients with PSC carrying the PAR1 -506 Ins allele showed significantly higher alanine aminotransferase serum levels (p = 0.0357) and a trend toward shorter transplant-free survival time compared to noncarriers (8.9 ± 6.6 years vs. 10.5 ± 7.1 years; p = 0.076).

CONCLUSIONS

Our study shows that PAR1 -506 Ins is significantly more frequent in people with PSC. As PAR1 -506 Ins allele carriers tended to have a shorter transplant-free survival, PAR1 might play a role in the development and course of PSC.

F2R Polymorphisms and Clopidogrel Efficacy and Safety in Patients With Minor Stroke or TIA

OBJECTIVE

To investigate the association between protease-activated receptor-1 (PAR-1) gene F2R polymorphisms and efficacy of clopidogrel for minor stroke or TIA.

METHODS

Three single nucleotide polymorphisms (CYP2C19*2 [681G>A, rs4244285], CYP2C19*3 [636G>A, rs4986893], and F2R [IVSn-14 A/T, rs168753]) were genotyped among 2,924 patients randomized to clopidogrel plus aspirin (n = 1,461) or aspirin alone (n = 1,463). The primary efficacy outcome was new stroke (ischemic or hemorrhagic) and the safety outcome was any bleeding.

RESULTS

Overall, 859 (29.4%) were AA homozygotes, 1,479 (50.6%) were AT heterozygotes, and 586 (20.0%) were TT homozygotes for F2R IVSn-14 polymorphisms; 1,716 (58.7%) were carriers of at least 1 CYP2C19 loss-of-function allele (*2 or *3). Compared with aspirin alone, patients with clopidogrel-aspirin treatment had a low risk of new stroke in patients with AT genotype (7.6% vs 11.3%; hazard ratio [HR], 0.63; 95% confidence interval [CI], 0.44-0.89) and TT genotype (5.8% vs 11.6%; HR, 0.46; 95% CI, 0.25-0.82) but not in carriers of the AA genotype (10.8% vs 11.6%; HR, 0.95; 95% CI, 0.63-1.44) (p = 0.03 for interaction). The association between F2R IVSn-14 A/T polymorphism and clopidogrel response was present regardless of the carrier status of the CYP2C19 loss-of-function alleles. The F2R IVSn-14 genotypes were not associated with the risk of any bleeding for clopidogrel-aspirin treatment (p = 0.66 for interaction).

CONCLUSIONS

Among patients with minor ischemic stroke or TIA who were receiving clopidogrel and aspirin, those carrying the F2R IVSn-14 T allele had a lower rate of recurrent stroke than those who were not.

CLINICALTRIALSGOV IDENTIFIER

NCT00979589.

Challenges and Opportunities in Protease-Activated Receptor Drug Development

Protease-activated receptors (PARs) are a unique class of G protein-coupled receptors (GPCRs) that transduce cellular responses to extracellular proteases. PARs have important functions in the vasculature, inflammation, and cancer and are important drug targets. A unique feature of PARs is their irreversible proteolytic mechanism of activation that results in the generation of a tethered ligand that cannot diffuse away. Despite the fact that GPCRs have proved to be the most successful class of druggable targets, the development of agents that target PARs specifically has been challenging. As a consequence, researchers have taken a remarkable diversity of approaches to develop pharmacological entities that modulate PAR function. Here, we present an overview of the diversity of therapeutic agents that have been developed against PARs. We further discuss PAR biased signaling and the influence of receptor compartmentalization, posttranslational modifications, and dimerization, which are important considerations for drug development.

Distribution of allelic and genotypic frequencies of IL1A, IL4, NFKB1 and PAR1 variants in Native American, African, European and Brazilian populations

BACKGROUND

The inflammatory response plays a key role at different stages of cancer development. Allelic variants of the interleukin 1A (IL1A), interleukin 4 (IL4), nuclear factor kappa B1 (NFKB1) and protease-activated receptor 1 (PAR1) genes may influence not only the inflammatory response but also susceptibility to cancer development. Among major ethnic or continental groups, these polymorphic variants present different allelic frequencies. In admixed populations, such as the Brazilian population, data on distribution of these polymorphisms are limited. Here, we collected samples of cancer-free individuals from the north, northeast, midwest, south and southeast regions of Brazil and from the three main groups that gave rise to the Brazilian population: Native Americans from the Brazilian Amazon, Africans and Europeans. We describe the allelic distributions of four IL1A (rs3783553), IL4 (rs79071878), NFKB1 (rs28362491) and PAR1 (rs11267092) gene polymorphisms, which the literature describes as polymorphisms with a risk of cancer or worse prognosis for cancer.

RESULTS

The genotypic distribution of the four polymorphisms was statistically distinct between Native Americans, Africans and Europeans. For the allelic frequency of these polymorphisms, the Native American population was the most distinct among the three parental populations, and it included the greatest number of alleles with a risk of cancer or worse prognosis for cancer. The PAR1 gene polymorphism allelic distribution was similar among all Brazilian regions. For the other three markers, the northern region population was statistically distinct from other Brazilian region populations.

CONCLUSION

The IL1A, IL4, NFKB1 and PAR1 gene polymorphism allelic distributions are homogeneous among the regional Brazilian populations, except for the northern region, which significantly differs from the other four Brazilian regions. Among the parental populations, the Native American population exhibited a higher incidence of alleles with risk of cancer or worse prognosis for cancer, which can indicate greater susceptibility to this disease. These genetic data may be useful for future studies on the association between these polymorphisms and cancer in the investigated populations.

Influence of Genetic Ancestry on INDEL Markers of NFKβ1, CASP8, PAR1, IL4 and CYP19A1 Genes in Leprosy Patients

BACKGROUND

Leprosy is an insidious infectious disease caused by the obligate intracellular bacteria Mycobacterium leprae, and host genetic factors can modulate the immune response and generate distinct categories of leprosy susceptibility that are also influenced by genetic ancestry.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated the possible effects of CYP19A1 [rs11575899], NFKβ1 [rs28362491], IL1α [rs3783553], CASP8 [rs3834129], UGT1A1 [rs8175347], PAR1 [rs11267092], CYP2E1 [INDEL 96pb] and IL4 [rs79071878] genes in a group of 141 leprosy patients and 180 healthy individuals. The INDELs were typed by PCR Multiplex in ABI PRISM 3130 and analyzed with GeneMapper ID v3.2. The NFKβ1, CASP8, PAR1 and IL4 INDELs were associated with leprosy susceptibility, while NFKβ1, CASP8, PAR1 and CYP19A1 were associated with the MB (Multibacilary) clinical form of leprosy.

CONCLUSIONS/SIGNIFICANCE

NFKβ1 [rs28362491], CASP8 [rs3834129], PAR1 [rs11267092] and IL4 [rs79071878] genes are potential markers for susceptibility to leprosy development, while the INDELs in NFKβ1, CASP8, PAR1 and CYP19A1 (rs11575899) are potential markers for the severe clinical form MB. Moreover, all of these markers are influenced by genetic ancestry, and European contribution increases the risk to leprosy development, in other hand an increase in African contribution generates protection against leprosy.

Proteinase activated-receptors-associated signaling in the control of gastric cancer

Gastric cancer (GC) is the fourth most common cancer in the world and the second cause of cancer-related death. Gastric carcinogenesis is a multifactorial process, in which environmental and genetic factors interact to activate multiple intracellular signals thus leading to uncontrolled growth and survival of GC cells. One such a pathway is regulated by proteinase activated-receptors (PARs), seven transmembrane-spanning domain G protein-coupled receptors, which comprise four receptors (i.e., PAR-1, PAR-2, PAR-3, and PAR-4) activated by various proteases. Both PAR-1 and PAR-2 are over-expressed on GC cells and their activation triggers and/or amplifies intracellular pathways, which sustain gastric carcinogenesis. There is also evidence that expression of either PAR-1 or PAR-2 correlates with depth of wall invasion and metastatic dissemination and inversely with the overall survival of patients. Consistently, data emerging from experimental models of GC suggest that both these receptors can be important targets for therapeutic interventions in GC patients. In contrast, PAR-4 levels are down-regulated in GC and correlate inversely with the aggressiveness of GC, thus suggesting a negative role of this receptor in the control of GC. In this article we review the available data on the expression and role of PARs in GC and discuss whether manipulation of PAR-driven signals may be useful for interfering with GC cell behavior.

Genetic variation of platelet function and pharmacology: an update of current knowledge

Platelets are critically involved in atherosclerosis and acute thrombosis. The platelet phenotype shows a wide variability documented by the inherited difference of platelet reactivity, platelet volume and count and function of platelet surface receptors. Several candidate genes have been put into focus and investigated for their functional and prognostic role in healthy individuals and patients with cardiovascular (CV) disease treated with antiplatelet agents. In addition to genetic variation, other clinical, disease-related and demographic factors are important so-called non-genetic factors. Due to the small effect sizes of single nucleotide polymorphisms (SNP) in candidate genes and due to the low allele frequencies of functional relevant candidate SNPs, the identification of genetic risk factors with high predictive values generally depends on the sample size of study cohorts. In the post-genome era new array and bioinformatic technologies facilitate high throughput genome-wide association studies (GWAS) for the identification of novel candidate genes in large cardiovascular cohorts. One of the crucial aspects of platelet genomic studies is the precise definition of a specific clinical phenotype (e.g. stent thrombosis) as this will impact importantly the findings of genomic studies like GWAS. Here, we provide an update on genetic variation of platelet receptors and drug metabolising enzymes under specific consideration of data derived by GWAS. The potential impact of this information and the role in personalised therapeutic concepts will be discussed.

VEGFR-2, CXCR-2 and PAR-1 germline polymorphisms as predictors of survival in pancreatic carcinoma

BACKGROUND

Hypoxic environment of pancreatic cancer (PC) implicates high vascular in-growth, which may be influenced by angiogenesis-related germline polymorphisms. Our purpose was to evaluate polymorphisms of vascular endothelial growth factor receptor 2 (VEGFR-2), CXC chemokine receptor 2 (CXCR-2), proteinase-activated receptor 1 (PAR-1) and endostatin (ES) as prognostic markers for disease-free (DFS) and overall survival (OS) in PC.

PATIENTS AND METHODS

Genotyping of 173 patients, surgically treated for PC between 2004 and 2011, was carried out by TaqMan(®) genotyping assays or polymerase chain reaction. Chi-square test, Kaplan-Meier estimator and Cox regression hazard model were used to assess the prognostic value of selected polymorphisms.

RESULTS

VEGFR-2 -906 T/T and PAR-1 -506 Del/Del genotypes predicted longer DFS (P = 0.003, P = 0.014) and OS (VEGFR-2 -906, P = 0.011). CXCR-2 +1208 T/T genotype was a negative predictor for DFS (P < 0.0001). Combined analysis for DFS and OS indicated that patients with the fewest number of favorable genotypes simultaneously present (VEGFR-2 -906 T/T, CXCR-2 +1208 C/T or C/C and PAR-1 -506 Del/Del) were at the highest risk for recurrence or death (P < 0.0001).

CONCLUSION

VEGFR-2 -906 C>T, CXCR-2 +1208 C>T and PAR-1 -506 Ins/Del polymorphisms are potential predictors for survival in PC.

The protease activated receptor 1 gene variation IVSn -14 A>T is associated with distant metastasis and cancer specific survival in renal cell carcinoma

PURPOSE

PAR-1 mediates angiogenesis and impacts the process of tumor growth and disease progression. We evaluated the associations of the gene variations PAR-1 IVSn -14 A>T (rs168753), -506 Ins/Del (rs11267092) and -1426 C>T (rs32934) with renal cell carcinoma pathology and cancer specific survival.

MATERIALS AND METHODS

DNA was extracted from the peripheral blood leukocytes of 236 consecutive patients with renal cell carcinoma. Genotyping was done using restriction fragment length polymorphism analysis of polymerase chain reaction amplicons and sequencing.

RESULTS

The IVSn -14 AA genotype was associated with a 3.13-fold increased risk of distant metastases (p = 0.015). In addition, cancer specific survival of patients with IVSn -14 AA was significantly worse than in those with AT/TT (HR 2.98, p = 0.019). The 1 and 4-year cancer specific survival rate for AA vs AT/TT was 89% vs 99% and 82% vs 92%, respectively. After adjusting for the stage, size, grade and necrosis (SSIGN) score on multivariable analysis, IVSn -14 AA was identified as an independent adverse prognostic factor (HR 2.72, p = 0.044). The variations -506 Ins/Del and -1426 C>T were not significantly associated with pathological factors or cancer specific survival.

CONCLUSIONS

Results suggest that the AA genotype of the PAR-1 variation IVSn -14 A>T is associated with an increased risk of metastasis and poorer prognosis of renal cell carcinoma. Therefore, assessing the individual risk based on genotypes may be a helpful adjunct to identify subgroups at high risk for a poor clinical outcome.

The association of protease activated receptor 1 gene -506 I/D polymorphism with disease-free survival in breast cancer patients

BACKGROUND

Recent data have shown that tumor development and dissemination may be regulated by procoagulant/anticoagulant axis. The aim of the present study was to search for an association of the protease activated receptor (PAR)1 gene -506 insertion/deletion (I/D), factor V Leiden (FVL), prothrombin (PT) G20210A, and methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms with disease-free survival (DFS) in breast cancer.

METHODS

Genotyping of -506 I/D in the promoter region of PAR1 gene was performed by single-strand conformation polymorphism analysis and sequencing. FVL, PT G20210A, and MTHFR C677T were also determined by the method of polymerase chain reaction-based DNA analysis. Data regarding patient's age, menopausal status, tumor size, lymph node status, disease stage, tumor grade, estrogen and progesterone receptor, c-erb B2 expression, PAR1 -506 I/D, MTHFR C677T, FVL, and PT G20210A polymorphisms were examined by the univariate and multivariate analyses.

RESULTS

Recurrent disease occurred in 29 patients (19.6 %) within a median of 20 months. It was found that tumor size, lymph node status, tumor stage, tumor grade, c-erbB2 expression, and PAR1 -506 I/D polymorphism were associated with DFS when Kaplan-Meier method was applied (P<.05). By Cox proportional hazards model, the presence of allele D at -506 locus (P=.0249) and small tumor size (P=.0001) were significant favorable prognostic factor, but c-erbB2 expression was an adverse prognostic factor (P=.0049).

CONCLUSION

Our study suggested the protective effect of the allele D at -506 locus of PAR1 gene on the recurrence of breast cancer.

Platelet pharmacogenomics

Platelet responsiveness to conventional antiplatelet therapy underlies a high interindividual variability influenced by various factors. For instance, antiplatelet therapy does not curtail the expected effects in a relevant number of patients as demonstrated by the occurrence of repeated cardiovascular events including stent thrombosis and/or by inadequate platelet inhibition measured by in vitro platelet function assays. Besides non-genetic factors such as age, gender, liver and renal function and co-medication, considerable variation of antiplatelet drug responsiveness can be attributed to genetic factors including polymorphisms and genetic variants of platelet surface proteins and drug metabolizing enzymes. Nowadays, platelet pharmacogenomics has started a new field with the goal to link genetic information of various drug targets to interindividual variability of drug response. Evolving data from large cohort studies suggest a promising role for pharmacogenomics in the context of antiplatelet therapy. Additionally, with the revolution of low cost and high-throughput genotyping techniques, genetic testing has become affordable for clinical application and individualization of therapy. However, a key issue to define the future role of pharmacogenomics will rely on the benefit and the timeliness of implementing the genetic information into therapeutic decision. Hence, it warrants further investigations to document the prognostic effects of therapeutic alterations in distinct genotypes. Concerning the safety profile of emerging antiplatelet and antithrombotic drugs in certain risk groups it would be fatal to individualize treatment barely on behalf of an atherothrombotic genotype. In contrast, individual risk assessment combining non-genetic information and pharmacogenetic analysis represents a reasonable concept. Here, we provide a review on current data describing the role of pharmacogenomics in the field of antiplatelet drug treatment in cardiovascular patients with future directions.

Genetic variations in angiogenesis pathway genes predict tumor recurrence in localized adenocarcinoma of the esophagus

OBJECTIVE

The aim of this study was to determine whether the risk of systemic disease after esophagectomy could be predicted by angiogenesis-related gene polymorphisms.

SUMMARY BACKGROUND DATA

Systemic tumor recurrence after curative resection continues to impose a significant problem in the management of patients with localized esophageal adenocarcinoma (EA). The identification of molecular markers of prognosis will help to better define tumor stage, indicate disease progression, identify novel therapeutic targets, and monitor response to therapy. Proteinase-activated-receptor 1 (PAR-1) and epidermal growth factor (EGF) have been shown to mediate the regulation of local and early-onset angiogenesis, and in turn may impact the process of tumor growth and disease progression.

METHODS

We investigated tissue samples from 239 patients with localized EA treated with surgery alone. DNA was isolated from formalin-fixed paraffin-embedded normal esophageal tissue samples and polymorphisms were analyzed using polymerase chain reaction-restriction fragment length polymorphism and 5'-end [gamma-P] ATP-labeled polymerase chain reaction methods.

RESULTS

PAR-1 -506 ins/del (adjusted P value=0.011) and EGF +61 A>G (adjusted P value=0.035) showed to be adverse prognostic markers, in both univariate and multivariable analyses. In combined analysis, grouping alleles into favorable versus nonfavorable alleles, high expression variants of PAR-1 -506 ins/del (any insertion allele) and EGF +61 A>G (A/A) were associated with a higher likelihood of developing tumor recurrence (adjusted P value<0.001).

CONCLUSION

This study supports the role of functional PAR-1 and EGF polymorphisms as independent prognostic markers in localized EA and may therefore help to identify patient subgroups at high risk for tumor recurrence.

Common hemostasis and inflammation gene variants and venous thrombosis in older adults from the Cardiovascular Health Study

BACKGROUND/OBJECTIVES

Age-related changes in blood coagulation and fibrinolysis are associated with increased risk of thrombotic events. Inherited deficiencies of coagulation proteins, such as factor V (FV) Leiden and prothrombin G20210A, explain a small fraction of venous thromboembolic disease (VTE). Additional genetic factors are likely to underlie the etiology of VTE, some of which may become manifest at older ages.

METHODS

We tested 290 common SNPs within 51 thrombosis and inflammation genes for association with VTE in the Cardiovascular Health Study, a large, prospective cohort of older adults followed for up to 12 years.

RESULTS

There were 184 VTE events that occurred at mean age of 78 years. TagSNPs within four genes encoding FXIII subunit A (F13A), FVII activating protease (HABP2), protease activated receptor-1 (F2R) and the urokinase receptor (PLAUR) showed the strongest evidence for association with VTE, with each gene having a global P-value < 0.05 and at least one tagSNP false discovery rate (FDR) q-value < 0.05. The rs3024409 variant allele of F13A1 was associated with 1.66-fold increased risk of VTE, while the minor alleles of HABP2 rs6585234 and rs3862019, F2R rs253061 and rs153311, and PLAUR rs344782 were each associated with lower risk of VTE (hazard ratios in the range of 0.49-0.66). Consistent with the observed protective association for VTE risk, the HABP2 rs3862019 variant allele was also associated with lower activity levels of coagulation factors FVIII, FIX, FX and plasminogen. We also confirm previously reported associations between common variants of the coagulation FII, FV, FVIII, FXI, alpha-fibrinogen and protein C genes and risk of VTE.

CONCLUSIONS

These findings suggest that several novel common coagulation gene variants may be related to risk of VTE in older adults. Further studies in older adults are needed to validate these findings and assess functional molecular mechanisms.

Genetic variations in angiogenesis pathway genes associated with clinical outcome in localized gastric adenocarcinoma

BACKGROUND

Angiogenesis has been attributed to be a well-recognized aspect of human cancer biology. As such, proteinase-activated receptor (PAR)-1, endostatin (ES) and interleukin-8 (IL-8) mediate the regulation of early-onset angiogenesis and in turn impact the process of tumor-growth and disease progression.

PATIENTS AND METHODS

Formalin-fixed paraffin-embedded tissues were obtained from 137 patients with localized gastric cancer at University of Southern California and Memorial Sloan-Kettering Cancer Center medical facilities. DNA was extracted and genotyping was carried out using PCR-restriction fragment length polymorphism-based protocols.

RESULTS

In false discovery rate-adjusted univariate analysis, PAR-1 -506 ins/del (P < 0.001), ES +4349 G>A (P = 0.004), and IL-8 -251 T>A (P < 0.0001) were associated with time to tumor recurrence (TTR). Further, PAR-1 -506 ins/del and IL-8 -251 were associated with overall survival (OS). After adjusting for covariates, IL-8 remained significantly associated with TTR (adjusted P = 0.003) and OS (adjusted P = 0.049), whereas ES was significantly associated with TTR (adjusted P = 0.026).

CONCLUSIONS

Polymorphisms in PAR-1, ES, and IL-8 may serve as independent molecular prognostic markers in patients with localized gastric adenocarcinoma. The assessment of the patients' individual risk on the basis of interindividual genotypes may therefore help to identify patient subgroups at high risk for poor clinical outcome.

PAR-1 genotype influences platelet aggregation and procoagulant responses in patients with coronary artery disease prior to and during clopidogrel therapy

Genetic variations of the protease-activated receptor-1 (PAR-1) have been associated with platelet receptor density and linked to thrombin receptor-activating peptide (TRAP)-induced phenotypes of platelet aggregation and P-selectin expression. We investigated whether the PAR-1 intervening sequence-14 A>T dimorphism influences platelet procoagulant activity. We also determined whether the P2Y12 antagonist clopidogrel could offset any observed functional polymorphism of the PAR-1 receptor by inhibiting P2Y12-mediated amplification of TRAP-induced responses. We studied 54 patients listed for elective percutaneous coronary intervention assessing TRAP-induced platelet aggregation and markers of procoagulant activity. Platelet responses were measured at baseline, 4 h post clopidogrel 300 mg, and 10 and 28 days following clopidogrel 75 mg daily. Each patient was genotyped for the PAR-1 intervening sequence-14 A/T dimorphism. Increased platelet aggregation and procoagulant responses were observed with PAR-1 A allele homozygotes. Clopidogrel significantly inhibited these platelet responses regardless of PAR-1 genotype, but did not offset the hyper-reactivity associated with the A/A homozygotes. We conclude that a common sequence variation within the PAR-1 gene influences TRAP-induced platelet procoagulant activity as well as aggregation. Higher platelet reactivity associated with PAR-1 IVSn-14 A allele homozygotes persists despite clopidogrel therapy. These individuals may be at higher risk of thromboembolic events and may require additional anti-platelet medication.

Effect of a thrombin receptor (protease-activated receptor 1, PAR-1) gene polymorphism in chronic hepatitis C liver fibrosis

BACKGROUND AND AIM

Tissue injury leads to activation of coagulation and generation of thrombin. Inhibition of thrombin receptor protease-activated receptor 1 (PAR-1) has been shown to reduce liver fibrosis in animals. This study aimed to evaluate the effect of PAR-1 gene polymorphism on rate of liver fibrosis (RF) in chronic hepatitis C.

METHODS

Polymorphisms studied: C > T transition 1426 bp upstream of translation start site (-1426C/T), 13 bp repeat of preceding -506 5'-CGGCCGCGGGAAG-3' sequence (-506I/D), and A > T transversion in intervening sequence (IVS) 14 bp upstream of exon-2 start site (IVS-14A/T). A total of 287 European and 90 Brazilian patients were studied.

RESULTS

1426C/T polymorphism: There was a trend to higher RF in patients with the TT genotype (P = 0.06) and an association between genotype CC and slow fibrosis (P = 0.03) in Europeans. In males, RF was significantly higher in those with the TT genotype compared to CT (P = 0.003) and CC (P = 0.007). There was a significant association between TT and fast fibrosis (P = 0.04). This was confirmed in an independent cohort of Brazilians where RF was higher in TT than in CC (P = 0.03). Analysis of -506I/D showed no difference in RF and distribution of slow/fast fibrosis among different genotypes in both populations. Analysis of IVS-14A/T showed no difference between genotypes.

CONCLUSION

In conclusion, these findings suggest that PAR-1 receptor polymorphisms influence the progression of liver fibrosis.

Mutation-prone points in thrombin receptor

BACKGROUND

Thrombin receptor (TR) is a G-protein-coupled receptor that transmits cellular responses to coagulant proteases in a variety of cell types in the vasculature and other tissues. Mutation within TR can be seen. Presently, the prediction of protein nanostructure and function is a great challenge in the proteomics and structural genomics era.

METHODS

To identify the points vulnerable to mutation is a new trend directed at expanding the knowledge on disorders in genomic and proteomic levels of diseases. In this paper, the author performed a bioinformatics analysis to find the mutation-prone positions in the amino acid sequence of TR. To identify those points in TR, a new bioinformatics tool, namely, GlobPlot was used.

RESULTS

According to this work, no position was identified to be resistant to mutation.

CONCLUSION

This means that TR is a very highly genetically unstable molecule. Thousands of types of mutation can be expected. Of interest, only a few sense mutations are mentioned in clinical settings. Therefore, many occulted sense mutations might still be detected.

Functional polymorphisms of FGA, encoding alpha fibrinogen, are associated with susceptibility to venous thromboembolism in a Taiwanese population

To determine the genetic risk factors for venous thromboembolism (VTE), this study examined 14 genetic variants from 10 hemostatic genes in 186 Taiwanese VTE patients and the same number of matched controls, which demonstrated FGA (encoding alpha fibrinogen) Thr312Ala polymorphism was the only variant significantly associated with VTE. Nine genetic polymorphisms on the fibrinogen cluster region of chromosome 4q28 were further studied, in which four FGA polymorphisms were found in strong linkage disequilibrium and were significantly associated with VTE by genotype and allele frequency analyses. Haplotype analysis showed significantly different FGA haplotype frequencies between VTE patients and controls with the haplotype F1, containing -1051G, -3A, 312Ala and TaqI duplication alleles, significantly associated with susceptibility to VTE (P = 0.001). Haplotype-pair analysis results also indicated a strong association of the haplotype-pair F1F1 with VTE in various VTE patient subgroups. In vitro functional analysis indicated that FGA -1051G, -3A and TaqI duplication alleles enhanced significantly the transcription level of FGA; however, control subjects with FGA genotypes containing these alleles had no elevated plasma fibrinogen levels. In conclusion, our experimental data indicated that functional genetic variants in FGA are risk factors for VTE in Taiwanese populations. Determination of FGA genotypes will likely contribute to primary prevention of this condition.

Proteinase-activated receptors: transducers of proteinase-mediated signaling in inflammation and immune response

Serine proteinases such as thrombin, mast cell tryptase, trypsin, or cathepsin G, for example, are highly active mediators with diverse biological activities. So far, proteinases have been considered to act primarily as degradative enzymes in the extracellular space. However, their biological actions in tissues and cells suggest important roles as a part of the body's hormonal communication system during inflammation and immune response. These effects can be attributed to the activation of a new subfamily of G protein-coupled receptors, termed proteinase-activated receptors (PARs). Four members of the PAR family have been cloned so far. Thus, certain proteinases act as signaling molecules that specifically regulate cells by activating PARs. After stimulation, PARs couple to various G proteins and activate signal transduction pathways resulting in the rapid transcription of genes that are involved in inflammation. For example, PARs are widely expressed by cells involved in immune responses and inflammation, regulate endothelial-leukocyte interactions, and modulate the secretion of inflammatory mediators or neuropeptides. Together, the PAR family necessitates a paradigm shift in thinking about hormone action, to include proteinases as key modulators of biological function. Novel compounds that can modulate PAR function may be potent candidates for the treatment of inflammatory or immune diseases.

A haplotype of the EPCR gene is associated with increased plasma levels of sEPCR and is a candidate risk factor for thrombosis

The endothelial cell protein C (PC) receptor (EPCR) facilitates PC activation by the thrombin-thrombomodulin complex. A soluble form of this receptor (sEPCR) found in plasma inhibits both activated PC (aPC) activity and PC activation by competing for PC with membrane-associated EPCR. Elevated sEPCR levels are found in approximately 20% of healthy subjects, but the mechanisms underlying this interindividual variability are unknown. We measured sEPCR levels in 100 healthy male volunteers, and observed 2 phenotypic groups of subjects. The temporal stability of sEPCR levels suggested genetic control. Extensive analysis of the EPCR gene in these subjects revealed 13 polymorphisms in complete linkage disequilibrium; these defined 3 haplotypes, 1 of which (A3) was strongly associated with high sEPCR levels. The high constitutive sEPCR levels observed in A3 haplotype carriers might reduce the efficiency of the PC system and predispose these subjects to venous thrombosis. By studying 338 patients with venous thrombosis and 338 age- and sex-matched healthy subjects, we found that the A3 haplotype was overrepresented in the patients. In multivariate analysis, subjects carrying the A3 haplotype had an increased risk of thrombosis (odds ratio [OR] = 1.8; P =.004). Thus, the A3 haplotype, which is associated with elevated plasma sEPCR levels, is a candidate risk factor for venous thrombosis.

Antistreptokinase platelet-activating antibodies are common and heterogeneous

BACKGROUND

Platelet activation by antistreptokinase (SK) antibodies could impair the clinical effect of SK administration.

OBJECTIVE

To better describe anti-SK antibodies with particular emphasis on procoagulant activities as a result of platelet activation.

PATIENTS AND METHODS

Sera were collected from 146 patients with coronary artery disease: non-SK-treated, 95 from mainland France, 31 from French Polynesia; 20 patients from mainland in year 2 after SK treatment. Serum-induced SK-dependent platelet activation resulting in procoagulant activities was assessed with washed platelets from five donors representative of the known patterns of reactivities to IgG.

RESULTS

Concentrations (2-5252 microg mL(-1)) and fibrinolytic neutralization titres (< 10 to > 1280) were found in the expected wide range and correlated (rho = 0.66, P < 0.0001). Platelet activation was detected with 145 samples, but varied in intensity and pattern (depending on the donors), although there was no systematic hierarchy; it was presumably due to IgG (inhibited by an IgG Fc receptor-blocking antibody and recovered in the IgG fraction) and only partially affected by aspirin. Marked platelet activation could be detected in samples with concentration as low as 2 microg mL(-1), and/or no detectable neutralizing titers. The way of immunization to SK was not found to influence the functional profile of antibodies.

CONCLUSION

Anti-SK platelet-activating antibodies are widespread, heterogeneous, poorly predictable on the basis of their antifibrinolytic effect and strong enough to trigger procoagulant activities. Their clinical relevance should be formally assessed, using patients' own platelets for detection owing to the variation of platelet reactivity.

An intronic polymorphism in the PAR-1 gene is associated with platelet receptor density and the response to SFLLRN

Protease-activated receptor 1 (PAR-1), the main thrombin receptor on vascular cells, plays a key role in platelet activation. We examined the range of PAR-1 expression on platelets, obtained twice, 1 week apart, from 100 healthy subjects and found a 2-fold interindividual variation in receptor numbers (95% CI = 858-1700). Because PAR-1 density was stable with time (r(2) = 76%, P <.001), we sought a genetic explanation for the observed variability. To validate this approach, we also analyzed the alpha(2)beta(1) genotype according to receptor density and platelet mRNA expression data. We found that the number of PAR-1 receptors on the platelet surface is associated with the intervening sequence IVSn-14 A/T intronic variation. The number of receptors was also found to govern the platelet response to the SFLLRN agonist, in terms of aggregation and P-selectin expression. The T allele (allelic frequency, 0.14) can be considered as an allele with decreased expression, because it was associated with lower PAR-1 expression on the platelet surface and with a lower response to SFLLRN. The IVSn-14 A/T intronic variation may therefore be clinically relevant.

Role of protease-activated receptors in airway function: a target for therapeutic intervention?

Protease-activated receptors (PARs) are G-protein-coupled, seven transmembrane domain receptors that act as cellular enzyme sensors. These receptors are activated by the proteolytic cleavage at the amino terminus, enabling interaction between the newly formed "tethered ligand" and the second extracellular loop of the receptor to confer cellular signalling. PARs can also be activated by small peptides that mimic the tethered ligand. In the respiratory tract, PARs may be regulated by endogenous proteases, such as airway trypsin and mast cell tryptase, as well as exogenous proteases, including inhaled aeroallergens such as those from house dust mite faecal pellets. Immunoreactive PARs have been identified in multiple cell types of the respiratory tract, and PAR activation has been reported to stimulate cellular mitogenesis and to promote tissue inflammation. Activation of PARs concurrently stimulates the release of bronchorelaxant and anti-inflammatory mediators, which may serve to induce cytoprotection and to minimise tissue trauma associated with severe chronic airways inflammation. Furthermore, airway inflammatory responses are associated with increased epithelial PAR expression and elevated concentrations of PAR-activating, and PAR-inactivating, proteases in the extracellular space. On this basis, PARs are likely to play a regulatory role in airway homeostasis, and may participate in respiratory inflammatory disorders, such as asthma and chronic obstructive pulmonary disease. Further studies focussing on the effects of newly developed PAR agonists and antagonists in appropriate models of airway inflammation will permit better insight into the role of PARs in respiratory pathophysiology and their potential as therapeutic targets.

[Genetic risk factors of thrombosis]

Genetic risk factors became a frequent predisposing cause of venous thromboembolism (VTE) since the discovery of two mutations: factor V Leiden and G20210A mutation of prothrombin gene. One of these both mutations is associated with around 25% of VTE events. Interaction of genetic risk factors, such as interaction of FV Leiden or G20210A mutation of prothrombin with antithrombin, protein C or protein S deficiencies, as well as interaction with acquired risk factors, have demonstrated that venous thrombosis is a multifactorial disease. The search for thrombophilia must be done in VTE occurring before the age of 45, in case of recurrencies and in case of familial history of VTE.

Genetic polymorphisms associated with venous and arterial thrombosis: an overview

OBJECTIVE

To provide an overview of genetic polymorphisms associated with thrombotic cardiovascular disease.

DATA SOURCES

A literature search using the National Library of Medicine database.

STUDY SELECTION

The literature on genetic polymorphisms associated with venous and arterial thrombosis was reviewed.

DATA EXTRACTION

Based on the literature review, the clinical significance of polymorphisms in various coagulation proteins was assessed and a summary was developed.

CONCLUSIONS

Thrombosis is a multifactorial disorder, with both congenital and acquired risk factors. It is now clear that there are many genetic abnormalities that impart an increased risk for thrombophilia, and the presence of more than 1 abnormality results in a further increased risk of thrombosis. In hemostasis, there is a balance between procoagulant factors and natural anticoagulant proteins. The first genetic thrombotic disorders described were deficiencies of the natural anticoagulants, such as antithrombin, protein C, and protein S, but these abnormalities are rare and are caused by many different mutations. More recently, single polymorphisms that are relatively common in the general population have been described in procoagulant factors, such as factor V and prothrombin, which impart an increased risk for venous thrombosis. As more scrutiny is placed on the hemostatic system, further polymorphisms have come to light. The current challenge is to elucidate the relationship between these new polymorphisms and either venous or arterial thrombotic cardiovascular disease.

Receptor polymorphisms and diseases

The aim of our review is to summarize common genetic variations of some receptors associated with clinical consequences, which were not outlined in the previous special issue of this journal. Because of the multiple pathomechanisms of diseases, a set of genetic variation can play a role in the development of pathological conditions. From the data available three articles would merit a greater interest. In systemic lupus erythematosus the associations related to some polymorphisms of Fc-, tumor necrosis factor (TNF) alpha- and interferon receptor may explore new autoimmunological and inflammatorical pathomechanisms. In the endocrinology, the androgen receptor repeat polymorphism will exert significant aspects in the development of prostate cancer. The pleoitropic responsibility of vitamin D3 receptor polymorphism in the pathogenesis of immunological disorders (primary biliary cirrhosis, inflammatory bowel disease, type 1 diabetes mellitus) and of malignancies (malignant melanoma, breast cancer) shed light on the importance of common nuclear receptors. Nevertheless, in the future studies a more consistent approach minimizing requirement bias in the selection of patients will approve our understanding the role of genetic influence on the pathogenesis of diseases.