Platelets and autoimmunity

The increased level of COX-dependent arachidonic acid metabolism in blood platelets from secondary progressive multiple sclerosis patients

Platelet activation is increasingly postulated as a possible component of the pathogenesis of multiple sclerosis (MS), especially due to the increased risk of cardiovascular events in MS. Arachidonic acid cascade metabolized by cyclooxygenase (COX) is a key pathway of platelet activation. The aim of our study was to investigate the COX-dependent arachidonic acid metabolic pathway in blood platelets from secondary progressive multiple sclerosis (SP MS) patients. The blood samples were obtained from 50 patients (man n = 22; female n = 28), suffering from SP MS, diagnosed according to the revised McDonald criteria. Platelet aggregation was measured in platelet-rich plasma after arachidonic acid stimulation. The level of COX activity and thromboxane B2 concentration were determined by ELISA method. Lipid peroxidation was assessed by measuring the level of malondialdehyde. The results were compared with a control group of healthy volunteers. We found that blood platelets obtained from SP MS patients were more sensitive to arachidonic acid and their response measured as platelet aggregation was stronger (about 14 %) relative to control. We also observed a significantly increased activity of COX (about 40 %) and synthesis of thromboxane B2 (about 113 %). The generation of malondialdehyde as a marker of lipid peroxidation was about 10 % higher in SP MS than in control. Cyclooxygenase-dependent arachidonic acid metabolism is significantly increased in blood platelets of patients with SP MS. Future clinical studies are required to recommend the use of low-dose aspirin, and possibly other COX inhibitors in the prevention of cardiovascular risk in MS.

Scavenging nucleic acid debris to combat autoimmunity and infectious disease

Nucleic acid-containing debris released from dead and dying cells can be recognized as damage-associated molecular patterns (DAMPs) or pattern-associated molecular patterns (PAMPs) by the innate immune system. Inappropriate activation of the innate immune response can engender pathological inflammation and autoimmune disease. To combat such diseases, major efforts have been made to therapeutically target the pattern recognition receptors (PRRs) such as the Toll-like receptors (TLRs) that recognize such DAMPs and PAMPs, or the downstream effector molecules they engender, to limit inflammation. Unfortunately, such strategies can limit the ability of the immune system to combat infection. Previously, we demonstrated that nucleic acid-binding polymers can act as molecular scavengers and limit the ability of artificial nucleic acid ligands to activate PRRs. Herein, we demonstrate that nucleic acid scavengers (NASs) can limit pathological inflammation and nucleic acid-associated autoimmunity in lupus-prone mice. Moreover, we observe that such NASs do not limit an animal's ability to combat viral infection, but rather their administration improves survival when animals are challenged with lethal doses of influenza. These results indicate that molecules that scavenge extracellular nucleic acid debris represent potentially safer agents to control pathological inflammation associated with a wide range of autoimmune and infectious diseases.

Correlation of the L-Arginine Pathway with Thrombo-Inflammation May Contribute to the Outcome of Acute Ischemic Stroke

BACKGROUND

Immune responses contribute to secondary injury after acute ischemic stroke (AIS), and metabolites of the L-arginine pathway are associated with stroke outcome. Here, we analyzed the relationship of the L-arginine pathway with thrombo-inflammatory biomarkers in AIS and their additive and independent associations to outcome.

METHODS

Serial changes in P-selectin, tPA, MCP-1, sCD40L, IL-6, IL-8, L-arginine, and asymmetric and symmetric dimethylarginine (ADMA, SDMA) were investigated in 55 patients with AIS and without infection within 6 and 72 hours after stroke onset. Outcomes were assessed as National Institutes of Health Stroke Scale (NIHSS) worsening by 24 hours, poststroke infection, and death by 1 month.

RESULTS

Serum levels of L-arginine showed negative correlation, whereas ADMA and SDMA showed positive correlation with thrombo-inflammatory biomarkers in the hyperacute phase. Most of these correlations disappeared by 72 poststroke hours. Correlation of MCP-1 with both ADMA and SDMA levels at 6 hours was associated with both NIHSS worsening and poststroke infections, respectively; sCD40L and SDMA correlation at 6 hours was also associated with NIHSS worsening. Negative correlation between P-selectin and L-arginine concentrations in the hyperacute phase was associated with NIHSS worsening. Strong negative correlation was found between IL-6 and L-arginine levels in the hyperacute phase in patients with poststroke infection. Only L-arginine and SDMA at 72 hours were independently associated with poststroke infection respectively.

CONCLUSIONS

Concentration of L-arginine and ADMA/SDMA differentially correlates with thrombo-inflammation in the hyperacute phase of ischemic stroke. Such correlations are independently associated with poststroke infection but not with other outcomes.

The Role of Platelets in Chronic Urticaria

BACKGROUND

Platelets are implicated in many pathophysiological processes, including inflammation and immunity. Ever-growing evidence suggests the active involvement of platelets in the pathogenesis of various inflammatory disorders, including cutaneous inflammatory diseases. A limited number of studies have investigated the role of platelets in chronic urticaria (CU). In this review, we summarize the current knowledge regarding the role of platelets in chronic spontaneous and inducible urticarias.

METHODS

A literature search was performed using PubMed and Google Scholar, and the references of relevant literature were reviewed.

RESULTS

Overall, in CU patients, conflicting results have been obtained from the assessment of platelet indices, such as mean platelet volume, platelet count and distribution width, as well as markers of platelet aggregation and activation. Nevertheless, a few studies showed significant changes of such parameters in CU patients compared to controls, in apparent correlation with clinical severity, autoreactivity and/or inflammatory status.

CONCLUSIONS

In the absence of definitive conclusions, the pathogenic role of platelets in CU needs to be further explored. Platelets might represent a link between inflammation, coagulation and histamine release in the pathophysiological network of CU.

Mean platelet volume is decreased in adults with active lupus disease

BACKGROUND

Only a few biomarkers are available for assessing disease activity in systemic lupus erythematosus (SLE). Mean platelet volume (MPV) has been recently studied as an inflammatory biomarker. It is currently unclear whether MPV may also play a role as a biomarker of disease activity in adult patients with SLE.

OBJECTIVE

We investigated the association between MPV and disease activity in adult patients with SLE.

METHODS

In this retrospective study, we compared two groups of adult patients divided according to disease activity (36 per group). Subjects were age- and gender-matched.

RESULTS

MPV was significantly decreased with respect to those of inactive patients (7.16±1.39 vs. 8.16±1.50, p=0.005). At a cutoff level of 8.32fL, MPV has a sensitivity of 86% and a specificity of 41% for the detection of disease activity. A modest positive correlation was found between MPV and albumin (r=0.407, p=0.001), which in turn is inversely associated with disease activity.

CONCLUSIONS

In summary, MPV is decreased in adult patients with active lupus disease, and positively correlated with albumin, another biomarker of disease activity. Prospective studies are needed to evaluate the prognostic value of this biomarker.

Mean platelet volume is decreased in adults with active lupus disease

BACKGROUND

Only a few biomarkers are available for assessing disease activity in systemic lupus erythematosus (SLE). Mean platelet volume (MPV) has been recently studied as an inflammatory biomarker. It is currently unclear whether MPV may also play a role as a biomarker of disease activity in adult patients with SLE.

OBJECTIVE

We investigated the association between MPV and disease activity in adult patients with SLE.

METHODS

In this retrospective study, we compared two groups of adult patients divided according to disease activity (36 per group). Subjects were age- and gender-matched.

RESULTS

MPV was significantly decreased with respect to those of inactive patients (7.16±1.39 vs. 8.16±1.50, p=0.005). At a cutoff level of 8.32 fL, MPV has a sensitivity of 86% and a specificity of 41% for the detection of disease activity. A modest positive correlation was found between MPV and albumin (r=0.407, p=0.001), which in turn is inversely associated with disease activity.

CONCLUSIONS

In summary, MPV is decreased in adult patients with active lupus disease, and positively correlated with albumin, another biomarker of disease activity. Prospective studies are needed to evaluate the prognostic value of this biomarker.

Comparison of the predictive value of plateletcrit with various other blood parameters in gestational diabetes development

Gestational diabetes is the most encountered metabolic disease in pregnancy and affects both the mother and fetus adversely. Low-grade subchronic inflammation is associated with gestational diabetes development. Platelets (PLT) play role in blood coagulation and inflammatory process. We aimed to compare the various platelet indices in patients with GDM and healthy pregnant controls and to determine whether PLT indices are useful in Gestational diabetes diagnosis. The present study was performed at the Zonguldak Bulent Ecevit University, School of Medicine, Department of Obstetrics and Gynecology. Statistically significant relationships with plateletcrit, mean platelet volume, and platelet distribution width and patients with GDM were found (p < 0.001). Plateletcrit had higher sensitivity and specificity than other platelet indices. Although plateletcrit is a largely unknown or an underestimated parameter in complete blood count, it gives more precise information than platelet count and mean platelet volume. Platelet-related indices and their determination are inexpensive and routinely ordered markers, the significance of which is often ignored. They may be useful in screening for gestational diabetes as an adjunct to oral glucose tolerance test.

Anti-citrullinated protein antibodies contribute to platelet activation in rheumatoid arthritis

Introduction

Although the role of platelets in rheumatoid arthritis (RA) is relatively unexplored, recent studies point towards a contribution of platelets in arthritis. We set out to determine platelet phenotype in RA and studied whether this could be influenced by the presence of anti-citrullinated protein antibodies (ACPA).

Methods

Platelets from healthy controls were incubated in the presence of plasma of patients with RA or age- and sex-matched healthy controls and plasma from ACPA^neg or ACPA^pos patients or in the presence of plate-bound ACPA. Characteristics of platelets isolated from patients with RA were correlated to disease activity.

Results

Platelets isolated from healthy controls displayed markers of platelet activation in the presence of plasma derived from RA patients, as determined by P-selectin expression, formation of aggregates and secretion of soluble CD40 ligand (sCD40L). Furthermore, levels of P-selectin expression and sCD40L release correlated with high ACPA titres. In accordance with these findings, enhanced platelet activation was observed after incubation with ACPA^pos plasma versus ACPA^neg plasma. Pre-incubation of platelets with blocking antibodies directed against low-affinity immunoglobulin G receptor (FcγRIIa) completely inhibited the ACPA-mediated activation. In addition, expression of P-selectin measured as number of platelets correlated with Disease Activity Score in 44 joints, C-reactive protein level, ACPA status and ACPA level.

Conclusions

We show for the first time that ACPA can mediate an FcγRIIa-dependent activation of platelets. As ACPA can be detected several years before RA disease onset and activated platelets contribute to vascular permeability, these data implicate a possible role for ACPA-mediated activation of platelets in arthritis onset.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0665-7) contains supplementary material, which is available to authorized users.

Platelet and red blood cell interactions and their role in rheumatoid arthritis

Cytokines, lymphocytes, platelets and several biomolecules have long been implicated in the pathology of rheumatoid arthritis (RA), and the influences of antibody production and tagging, and cytokine, chemokine and enzyme production at specific rheumatoid joints were thought to be exclusive to the advancement of disease parameters. Another role player in RA is red blood cells (RBCs) which, of late, have been found to be involved in RA pathobiology, as there is a positive correlation between RBC counts and joint pathology, as well as with inflammatory biomarkers in the disease. There is also an association between RBC distribution width and the incidence of myocardial infarction amongst RA patients, and there is a change in the lipid distribution within RBC membranes. Of late, certain RBC-associated factors with previously obscure roles and cell-derived particles thought to be inconsequential to the other constituents of plasma were found to be active biomolecular players. Several of these have been discovered to be present in or originating from RBCs. Their influences have been shown to involve in membrane dynamics that cause structural and functional changes in both platelets and RBCs. RBC-derived microparticles are emerging entities found to play direct roles in immunomodulation via interactions with other plasma cells. These correlations highlight the direct influences of RBCs on exacerbating RA pathology. This review will attempt to shed more light on how RBCs, in the true inflammatory milieu of RA, are playing an even greater role than previously assumed.

Early Dynamics of P-selectin and Interleukin 6 Predicts Outcomes in Ischemic Stroke

BACKGROUND

Thromboinflammatory molecules connect the prothrombotic state, endothelial dysfunction, and systemic/local inflammation in the acute phase of ischemic stroke.

METHODS

We prospectively investigated (1) serial changes in the levels of thromboinflammatory biomarkers in 76 patients with acute ischemic stroke (6, 24, and 72 hours after onset); (2) compared with 44 patients with asymptomatic severe (≥70%) carotid stenosis and 66 patients with Parkinson disease; and (3) we applied multiple regression methods, relating biological biomarkers combined with demographic data and comorbidities to poststroke infection, death, and functional outcome, and assessed the ability of the models to predict each outcome.

RESULTS

Interleukin 6 (IL-6) levels and change of IL-6 concentrations by 72 hours correlated with the size of tissue damage indicated by S100B titers. Levels of IL-6 and P-selectin at 72 hours were higher in patients with large-artery versus lacunar stroke. High concentration of IL-6, monocyte chemotactic protein 1, and S100B at 6 hours were associated with poststroke infections; high concentration of IL-6, S100B, and high-sensitivity C-reactive protein (hsCRP) correlated with death. Change of P-selectin from 6 to 72 hours by 1 unit increased the incidence of poststroke infections with an odds ratio of 22.7; each 100 units of IL-6 at baseline increased the odds of death by 9‰, and at 72 hours, the odds of poststroke infections by 4‰. Each unit of baseline hsCRP elevated the odds of death by 7%.

CONCLUSIONS

In regression models, in which biological, demographic, and comorbid factors were combined, those biological biomarkers predicted poor outcome with high accuracy, which were characterized by an increasing concentration by 72 hours. Two particular biomarkers emerged to predict outcomes besides hsCRP: early dynamic changes in the systemic levels of P-selectin and IL-6.

Platelets and vascular inflammation of the brain

There is emerging evidence that platelets have an important role in inflammation beyond their involvement in hemostasis. Platelets can contribute to inflammatory reactions via crosstalk both with immune cells and endothelial cells. Inflamed vessels are characterized by the presence of activated endothelial cells. These activated endothelial cells upregulate receptors necessary for leukocyte recruitment, but also for the adhesion of platelets. Subsequently, immune cells can bind to platelets through adhesion receptors presented on the platelet surface, thus supporting leukocyte recruitment to the vessel wall. There are several neurological diseases associated with vascular inflammation including multiple sclerosis (MS) and stroke. Increased markers of platelet activation could be demonstrated in patients suffering from MS compared to healthy individuals. Reports from murine models indicate that platelets may be of importance for disease progression and severity by mediating leukocyte recruitment as one potential underlying mechanism. Blocking platelet function disease severity was considerably ameliorated. Moreover, processes of tissue remodelling may be influenced by platelet derived mediators. Whether a role of platelets for vascular inflammation can be extrapolated to further neurological diseases will have to be investigated in further in depth experimental and clinical trials.

CONCLUSION

Platelets and platelet associated mechanisms may offer novel starting points to understand neurovascular diseases from a different point of view and to develop novel approaches to access the disease.

Platelets convert peripheral blood circulating monocytes to regulatory cells via immunoglobulin G and activating-type Fcγ receptors

BACKGROUND

Monocytes and macrophages produce interleukin (IL)-10, an immunoregulatory cytokine and a potent therapeutic tool for immune disorders. Augmentation of IL-10 production with a concomitant reduction of proinflammatory cytokines in macrophages in vitro is attained by doubly stimulating the cells with a toll-like receptor ligand and immunoglobulin (Ig)G immune complexes, a response known as that of regulatory (or alternatively activated/M2) macrophages. However, it has not been explored sufficiently how such a regulatory response could be exploited for anti-inflammation. Our objective is to find a potential way or condition for augmenting IL-10 by monocytes/macrophages in vivo and in vitro.

RESULTS

We show that platelets, when they are opsonized with IgG, can convert human peripheral blood circulating monocytes to IL-10-producing regulatory monocytes in vitro and also in a murine in vivo model. Co-culturing of platelets and monocytes in the presence of anti-integrin IgG and a bacterial lipopolysaccharide augmented IL-10 production via a direct interaction between platelets and monocytes. This novel way of enhancing IL-10 was mediated by activating-type Fc receptors for IgG.

CONCLUSION

These findings indicate that the IgG-bound platelet-induced conversion of monocytes to regulatory cells might provide a novel strategy for controlling inflammation.

Platelets: more than a sack of glue

Platelets are primary effector cells in hemostasis. Emerging evidence over the last decade, however, demonstrates that platelets also have critical roles in immunity and inflammation. These nontraditional functions of platelets influence the development, progression, and evolution of numerous diseases, including arthritis, cancer, cardiovascular disease, and infectious syndromes. This chapters reviews recently discovered attributes of platelets that contribute to human disease, paying particular attention to the inflammatory activities of this anucleate cytoplast.

Evaluation of the efficacy and safety of different Tripterygium preparations on collagen-induced arthritis in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Tripterygium preparations (TPs), a traditional Chinese Medicines extracted from Tripterygium wilfordii Hook f., are widely used for treatment of rheumatoid arthritis (RA). However, TPs from different Pharmaceutical factory have different efficacy and side effects for RA treatment.

AIM OF THE STUDY

The purpose of the current study is to evaluate the efficacy and safety of four TPs from different Pharmaceutical factory in china on the treatment of collagen-induced arthritis (CIA) rats and provide a theoretical and experimental basis for the individualized use of TPs.

MATERIALS AND METHODS

The model of wistar rats of CIA was made, and the rats were perfused a stomach with four TPs for 3 weeks continuously. Then arthritis severity was determined by visual examination of the paws and histopathologic changes of joint, liver, kidney and testis were determined by hematoxylin-eosin (H&E) staining. The expression of inflammatory cytokines (IL-1β, TNF-α, IL-17 and IL-6) in the joint was analyzed by real-time PCR, and the count and motion parameters (sperm motility and progressive sperm) of sperm in cauda epididymis were assessed with computer-assisted sperm analysis (CASA) system. Routine blood tests were conducted using automated hematology analyzer, and the aspartate aminotransferase (AST), alanine aminotransferase (ALT) activities, creatinine (Cr), and blood urea nitrogen (BUN) in serum of CIA rats were measured using a UniCel DxC 880i autoanalyzer.

RESULTS

All of tested TPs could reduce inflammatory score, histopathological arthritis severity and joint׳s inflammatory cytokines (IL-1β, TNF-α, IL-17 and IL-6) expression in CIA rats, however, TP-D showed stronger inhibitory effect for inflammatory score compared with other three TPs in vivo. All of tested TPs did not show hepatotoxicity and nephrotoxicity and also had little effect for the concentration of hemoglobin (Hb) and the count of white blood cell (WBC). Analysis of red blood cell (RBC) number showed that TP-C and TP-D could reverse lower RBC number in untreated CIA rats to normal level. Interestingly, the results showed TPs named TP-C and TP-D could decrease platelet (PLT) number which significantly increases in untreated CIA rats. Reproductive toxicity, the main side effect of TPs, assay showed that the sperm quality (density, viability, and motility) in four of TPs-treated CIA rats were decreased significantly, consistently with spermatogenic cell density reduced. However parallel analysis showed that in four TPs-treated rats, the number of sperm, motile sperm and progressive sperm were highest in TP-D group, in contrast, were lowest in TP-C group.

CONCLUSIONS

These findings suggested that four TPs showed significantly therapeutic effect on ameliorating inflammation of CIA rats, with no obvious hepatotoxicity and nephrotoxicity in vivo. TP-D showed advantages with its higher efficacy and less reproductive toxicity as well as increasing RBC number, decreasing PLT number in CIA treatment. Thus, in the development of individualized treatment plan for RA patients, TP-D might be considered preferentially.

Bacteria exploit platelets

In this issue of Blood, Arman et al show that bacteria use immunoglobulin G (IgG) from plasma to engage platelet surface receptors FcγRIIA and integrin αIIbβ3 to induce platelet activation, which is further facilitated by platelet factor 4 (PF4).

Can platelet indices be new biomarkers for severe endometriosis?

Objective. The aim of this study was to investigate whether platelet indices-mean platelet volume (MPV), platelet distribution width (PDW), and plateletcrit (PCT) would be useful as noninvasive biomarkers for determining the severity of endometriosis. Methods. A retrospective review of the medical charts of 164 patients diagnosed with endometriosis and who were operated on between 2001 and 2013 was performed. The stage of endometriosis was determined according to revised American Society for Reproductive Medicine criteria. Results. In patients with advanced endometriosis (Stages 3-4), PLT, PCT levels were found to be significantly higher and MPV, PDW values to be significantly lower when compared to initial endometriosis (Stages 1-2). In addition, there was a significant positive correlation between PLT (r: 0.800, P: 0.001) and PCT (r: 0.727, P: 0.002) and the inflammatory marker white blood cell count (WBC). Conclusion. Our finding may not sufficient for employing platelet indices solely in this differential diagnosis, but our finding could provide a suggestion for clinical physicians so that attention is paid to the value of platelet indices and that these may be taken into account when making decisions about the initial or advanced stages of endometriosis.

Platelets and cancer: a casual or causal relationship: revisited

Human platelets arise as subcellular fragments of megakaryocytes in bone marrow. The physiologic demand, presence of disease such as cancer, or drug effects can regulate the production circulating platelets. Platelet biology is essential to hemostasis, vascular integrity, angiogenesis, inflammation, innate immunity, wound healing, and cancer biology. The most critical biological platelet response is serving as "First Responders" during the wounding process. The exposure of extracellular matrix proteins and intracellular components occurs after wounding. Numerous platelet receptors recognize matrix proteins that trigger platelet activation, adhesion, aggregation, and stabilization. Once activated, platelets change shape and degranulate to release growth factors and bioactive lipids into the blood stream. This cyclic process recruits and aggregates platelets along with thrombogenesis. This process facilitates wound closure or can recognize circulating pathologic bodies. Cancer cell entry into the blood stream triggers platelet-mediated recognition and is amplified by cell surface receptors, cellular products, extracellular factors, and immune cells. In some cases, these interactions suppress immune recognition and elimination of cancer cells or promote arrest at the endothelium, or entrapment in the microvasculature, and survival. This supports survival and spread of cancer cells and the establishment of secondary lesions to serve as important targets for prevention and therapy.

The predictive value of mean platelet volume, plateletcrit and red cell distribution width in the differentiation of autoimmune gastritis patients with and without type I gastric carcinoid tumors

Autoimmune gastritis is an autoimmune and inflammatory condition that may predispose to gastric carcinoid tumors or adenocarcinomas. The early diagnosis of these tumors is important in order to decrease morbidity and mortality. Platelet indices such as mean platelet volume and plateletcrit levels increase in inflammatory, infectious and malign conditions. The primary aim of this study was to explore wheter platelet indices and red cell distribution width have any predictive role in the discrimination of autoimmune gastritis patients with and without gastric carcinoid tumors. Also secondary aim of this study was to investigate whether any changes exist betwenn autoimmune gastritis and functional dyspepsia patients by means of platelet indices. Plateletcrit (0.22 ± 0.06 vs. 0.20 ± 0.03%, p < 0.001) and red cell distribution width (16.11 ± 3.04 vs. 13.41 ± 0.95%, p < 0.001) were significantly higher in autoimmune gastritis patients compared to control group. Receiver operating curve analysis suggested that optimum plateletcrit cut-off point was 0.20% (AUC: 0.646), and 13.95% as the cut off value for red cell distribution width (AUC: 0.860). Although plateletcrit (0.22 ± 0.06 vs. 0.21 ± 0.04%, p = 0.220) and mean platelet volume (8.94 ± 1.44 vs. 8.68 ± 0.89 fl, p = 0.265) were higher in autoimmune gastritis patients without carcinoid tumor compared to patients with carcinoid tumors, these parameters were not statistically significant. Changes in plateletcrit and red cell distribution width values may be used as a marker in the discrimination of autoimmune gastritis and fucntional dyspepsia patients but not useful in patients with gastric carcinoid tumor type I.