Dataset Information

Soluble glycoprotein VI, a specific marker of platelet activation is increased in the plasma of subjects with seropositive rheumatoid arthritis.

ABSTRACT:

Objectives

Anti-citrullinated protein antibodies (ACPA) have been shown to cause platelet activation in vitro, through the low-affinity immunoglobulin G (IgG) receptor (Fc?RIIa) on platelets. Platelet activation via engagement of Fc?RIIa results in proteolytic cleavage and shedding of platelet specific glycoprotein VI (GPVI) which can be detected in the plasma as soluble GPVI (sGPVI). We hypothesized that plasma levels of sGPVI would be increased among patients with seropositive RA as a consequence of antibody-induced platelet activation and GPVI shedding.

Methods

Samples from 84 patients with RA (65 seropositive and 19 seronegative) and 67 healthy controls were collected prospectively and analysed for sGPVI using a standardised ELISA.

Results

Patients with seropositive RA had significantly higher levels of sGPVI compared to seronegative RA and controls. Median (IQR) sGPVI levels were 4.2 ng/ml (3.2, 8.0) in seropositve RA, 2.2 ng/ml (1.5, 3.5) in seronegative RA and 2.2 ng/ml (1.6, 3.4) in controls (p<0.0001). sGPVI levels correlated with ACPA titres (r = 0.32, p = 0.0026) and with RF titres (r = 0.48, p<0.0001).

Conclusion

Plasma sGPVI, a specific marker of platelet activation is increased among patients with seropositive RA.

SUBMITTER: Stack JR

PROVIDER: S-EPMC5687752 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Publications

Soluble glycoprotein VI, a specific marker of platelet activation is increased in the plasma of subjects with seropositive rheumatoid arthritis.

Stack John R JR Madigan Anne A Helbert Laura L Dunne Eimear E Gardiner Elizabeth E EE Andrews Robert K RK Finan Roisin R Smyth Elizabeth E Kenny Dermot D McCarthy Geraldine M GM

PloS one 20171115 11

<h4>Objectives</h4>Anti-citrullinated protein antibodies (ACPA) have been shown to cause platelet activation in vitro, through the low-affinity immunoglobulin G (IgG) receptor (FcγRIIa) on platelets. Platelet activation via engagement of FcγRIIa results in proteolytic cleavage and shedding of platelet specific glycoprotein VI (GPVI) which can be detected in the plasma as soluble GPVI (sGPVI). We hypothesized that plasma levels of sGPVI would be increased among patients with seropositive RA as a ...[more]

PMID: 29141000

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Project description:Essentials Collagen and thrombin when used simultaneously generate highly activated platelets. The effect of thrombin stimulation on subsequent glycoprotein VI (GPVI) function was observed. Soluble fibrin, but not protease activated receptor (PAR) activation, prevented GPVI activation. Circulating soluble fibrin in coagulopathic blood may cause an acquired GPVI signaling defect. SUMMARY:Background In coagulopathic blood, circulating thrombin may drive platelet dysfunction. Methods/Results Using calcium dye-loaded platelets, the effect of thrombin exposure and soluble fibrin generation on subsequent platelet GPVI function was investigated. Exposure of apixaban-treated platelet-rich plasma (12% PRP) to thrombin (1-10 nm), but not ADP or thromboxane mimetic U46619 exposure, dramatically blocked subsequent GPVI activation by convulxin, collagen-related peptide or fibrillar collagen. Consistent with soluble fibrin multimerizing and binding GPVI, the onset of convulxin insensitivity required 200-500 s of thrombin exposure, was not mimicked by exposure to PAR-1/4 activating peptides, was not observed with washed platelets, and was blocked by fibrin polymerization inhibitor (GPRP) or factor XIIIa inhibitor (T101). PAR-1 signaling through G?q was not required because vorapaxar blocked thrombin-induced calcium mobilization but had no effect on the ability of thrombin to impair GPVI-signaling. Convulxin insensitivity was unaffected by the metalloprotease inhibitor GM6001 or the ?IIb ?3 antagonist GR144053, indicating negligible roles for GPVI shedding or ?IIb ?3 binding of fibrin. Thrombin treatment of washed platelets resuspended in purified fibrinogen also produced convulxin insensitivity that was prevented by GPRP. Exposure of apixaban/PPACK-treated whole blood to thrombin-treated fibrinogen resulted in > 50% decrease in platelet deposition in a collagen microfluidic assay that required soluble fibrin assembly. Conclusions Conversion of only 1% plasma fibrinogen in coagulopathic blood would generate 90 nm soluble fibrin, far exceeding ~1 nmGPVI in blood. Soluble fibrin, rather than thrombin-induced platelet activation throuh PAR-1 and PAR-4, downregulated GPVI-signaling in response to stimuli, and may lead to subsequent hypofunction of endogenous or transfused platelets.

Project description:OBJECTIVE:The pathogenetic mechanisms by which HLA-DRB1 alleles are associated with anticitrullinated peptide antibody (ACPA)-positive rheumatoid arthritis (RA) are incompletely understood. RA high-risk HLA-DRB1 alleles are known to share a common motif, the 'shared susceptibility epitope (SE)'. Here, the electropositive P4 pocket of HLA-DRB1 accommodates self-peptide residues containing citrulline but not arginine. HLA-DRB1 His/Phe13? stratifies with ACPA-positive RA, while His13?Ser polymorphisms stratify with ACPA-negative RA and RA protection. Indigenous North American (INA) populations have high risk of early-onset ACPA-positive RA, whereby HLA-DRB1*04:04 and HLA-DRB1*14:02 are implicated as risk factors for RA in INA. However, HLA-DRB1*14:02 has a His13?Ser polymorphism. Therefore, we aimed to verify this association and determine its molecular mechanism. METHODS:HLA genotype was compared in 344 INA patients with RA and 352 controls. Structures of HLA-DRB1*1402-class II loaded with vimentin-64Arg59-71, vimentin-64Cit59-71 and fibrinogen ?-74Cit69-81 were solved using X-ray crystallography. Vimentin-64Cit59-71-specific and vimentin59-71-specific CD4+ T cells were characterised by flow cytometry using peptide-histocompatibility leukocyte antigen (pHLA) tetramers. After sorting of antigen-specific T cells, TCR? and ?-chains were analysed using multiplex, nested PCR and sequencing. RESULTS:ACPA+ RA in INA was independently associated with HLA-DRB1*14:02. Consequent to the His13?Ser polymorphism and altered P4 pocket of HLA-DRB1*14:02, both citrulline and arginine were accommodated in opposite orientations. Oligoclonal autoreactive CD4+ effector T cells reactive with both citrulline and arginine forms of vimentin59-71 were observed in patients with HLA-DRB1*14:02+ RA and at-risk ACPA- first-degree relatives. HLA-DRB1*14:02-vimentin59-71-specific and HLA-DRB1*14:02-vimentin-64Cit59-71-specific CD4+ memory T cells were phenotypically distinct populations. CONCLUSION:HLA-DRB1*14:02 broadens the capacity for citrullinated and native self-peptide presentation and T cell expansion, increasing risk of ACPA+ RA.

Dataset Information

Soluble glycoprotein VI, a specific marker of platelet activation is increased in the plasma of subjects with seropositive rheumatoid arthritis.

Objectives

Methods

Results

Conclusion

Publications

Soluble glycoprotein VI, a specific marker of platelet activation is increased in the plasma of subjects with seropositive rheumatoid arthritis.

Similar Datasets

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