Soluble P-selectin in the plasma of patients with connective tissue diseases

Role of Platelets in Rheumatic Chronic Autoimmune Inflammatory Diseases

Platelets are essential in maintaining blood homeostasis and regulating several inflammatory processes. They constantly interact with immune cells, have immunoregulatory functions, and can affect, through immunologically active substances, endothelium, leukocytes, and other immune response components. In reverse, inflammatory and immune processes can activate platelets, which might be significant in autoimmune disease progression and arising complications. Thus, considering this interplay, targeting platelet activity may represent a new approach to treatment of autoimmune diseases. This review aims to highlight the role of platelets in the pathogenic mechanisms of the most frequent chronic autoimmune inflammatory diseases to identify gaps in current knowledge and to provide potential new targets for medical interventions.

Soluble Platelet Release Factors as Biomarkers for Cardiovascular Disease

Platelets are the main players in thrombotic diseases, where activated platelets not only mediate thrombus formation but also are involved in multiple interactions with vascular cells, inflammatory components, and the coagulation system. Although in vitro reactivity of platelets provides information on the function of circulating platelets, it is not a full reflection of the in vivo activation state, which may be relevant for thrombotic risk assessment in various disease conditions. Therefore, studying release markers of activated platelets in plasma is of interest. While this type of study has been done for decades, there are several new discoveries that highlight the need for a critical assessment of the available tests and indications for platelet release products. First, new insights have shown that platelets are not only prominent players in arterial vascular disease, but also in venous thromboembolism and atrial fibrillation. Second, knowledge of the platelet proteome has dramatically expanded over the past years, which contributed to an increasing array of tests for proteins released and shed from platelets upon activation. Identification of changes in the level of plasma biomarkers associated with upcoming thromboembolic events allows timely and individualized adjustment of the treatment strategy to prevent disease aggravation. Therefore, biomarkers of platelet activation may become a valuable instrument for acute event prognosis. In this narrative review based on a systematic search of the literature, we summarize the process of platelet activation and release products, discuss the clinical context in which platelet release products have been measured as well as the potential clinical relevance.

Effects of xinfeng capsules on expression of platelet granule membrane protein 140 and platelet cluster of differentiation 40 ligand in peripheral blood of adjuvant arthritis rats

Platelet GMP-140 and CD40L as specific markers of platelet activation play an important role in the morbidity and development of rheumatoid arthritis. The expression of GMP-140, CD40L increases in peripheral blood of AA rats. And they have correlation with voix pedis' swelling, AI. XFC could inhibit the inflammatory response through inhibiting platelet activation of AA rats, which means decreasing the expression of GMP-140, CD40L in peripheral blood. So, the voix pedis' swelling and AI were decreased as the result.

Serum-soluble selectin levels in patients with rheumatoid arthritis and systemic sclerosis

Soluble forms of selectins may play a regulatory role in inflammatory responses that are key to the pathophysiology of rheumatic diseases such as rheumatoid arthritis (RA) and systemic sclerosis (SSc). The aim of this study was to examine whether the elevated serum-soluble (s) selectin levels are associated with RA or SSc. Serum sE-, sL- and sP-selectin levels were measured by sandwich enzyme-linked immunosorbent assay in 34 RA patients, 30 SSc patients and 16 healthy subjects. The levels of sE-selectin were significantly higher in RA and SSc patients than those in healthy subjects. The sL-selectin level was significantly lower in RA patients compared to healthy subjects. Serum sP-selectin levels were not significantly different among the study groups. The active RA patients had significantly higher serum sE- and sL-selectin levels compared to inactive RA patients. Also, some correlations were observed between the serum selectin levels and measures of disease activity such as erythrocyte sedimentation rate and C-reactive protein in RA patients. The higher levels of sE-selectin were found in SSc patients with pulmonary fibrosis, and there was also a negative correlation between diffusion capacity for carbon monoxide and serum sE-selectin. Serum levels of selectins may provide a useful additional marker for disease activity in RA patients and for disease severity in SSc patients.

Selectins-an emerging target for drug delivery

Selectins are multifunctional adhesion molecules that mediate the initial interactions between circulating leukocytes and cells of the endothelium. First identified over a decade ago, selectins have provided insight into areas as diverse as normal lymphocyte homing, leukocyte recruitment during inflammatory responses, carbohydrate ligand biosynthesis and adhesion-mediated signalling. Of late, selectins were introduced as targets for drug delivery in the development of new anti-inflammatory therapeutics and in anti-cancer therapy. This review will examine the selectins and their ligands with a focus on recent findings on their role in physiology and pathophysiology as well as the emerging role of selectins as targets in controlled drug delivery.

Modulation of plasma levels of soluble adhesion molecules and nitric oxide in healthy volunteers by exposure to swine dust

Short-time exposure to swine dust causes an intense airways inflammation and symptoms of systemic inflammation in healthy volunteers. Here, we sought to study whether this response involved signs of endothelial cell activation. Peripheral blood cell counts and plasma levels of sE-selectin, sP-selectin, sICAM-1, interleukin-8, nitrite and nitrate were measured in blood samples from 17 healthy subjects before and after a 3-hr exposure to swine dust in a swine confinement building. Dust exposure induced a 3-fold increase of blood neutrophil p = 0.0009) and 1.5-fold increase of monocyte counts (p = 0.0047). IL-8 was detected in 15 individuals after exposure (p = 0.001). Endothelial cell markers such as sICAM and nitrate increased by 10 and 34% resp. (p = 0.011 and 0.017), whereas sE-selectin remained unchanged and sP-selectin was reduced by 15% (p = 0.031). Thus, short time exposure to swine dust induced a systemic inflammatory response with evidence of endothelial and inflammatory cell activation.

Lupus anticoagulant and history of thrombosis are not associated with persistent endothelial cell activation in systemic lupus erythematosus

Antiphospholipid antibodies (aPL), especially lupus anticoagulant (LAC), characterize systemic lupus erythematosus (SLE) patients at increased risk for arterial and venous thromboembolic complications. It has been reported that purified human anti-phospholipid antibodies cause endothelial cell activation in in vitro experiments. In order to investigate whether increased endothelial cell activation is associated with thromboembolic events in SLE patients with LAC, we measured plasma levels of thrombomodulin (TM), von Willebrand factor (vWf), sP-selectin, vascular cell adhesion molecule-1 (sVCAM-1) and ED1-fibronectin in a study of 76 patients with SLE. Patients were subdivided on the basis of: no history of thrombosis and LAC-negative (n = 22) or LAC-positive (n = 17); positive history of thrombosis and LAC-negative (n = 16) or LAC-positive (n = 21). The median SLE disease activity index (SLEDAI) was 4. Although concentrations of sTM, vWf, sP-selectin and sVCAM-1 were significantly elevated in SLE compared with values in healthy controls, they did not differ between the four groups, between patients with or without history of thrombosis, and between patients with or without LAC. Presence of anticardiolipin antibodies could not explain these negative findings. Adjustment of the concentrations for significantly associated variables, such as age, hypertension, smoking, immunosuppressive treatment and concentrations of creatinine, cholesterol and homocysteine, did not change the main results of the study. Only sTM was significantly lower in patients with both LAC and thrombosis than in patients without both these features after adjustment for serum creatinine concentrations. In conclusion, we did not find an association between endothelial cell activation and presence of LAC or history of thrombosis in SLE.

Soluble P-selectin moderates complement-dependent reperfusion injury of ischemic skeletal muscle

P-selectin is an adhesion molecule expressed on activated endothelial and platelet surfaces. The function of the short consensus repeats (SCRs) of P-selectin, homologous with the SCRs of complement regulatory proteins is largely unknown. In a model of murine hindlimb ischemia where local reperfusion injury is partly mediated by IgM natural antibody and classical complement pathway activation, we hypothesized that human soluble P-selectin (sP-sel) would moderate the complement component of the inflammatory response. Infusion of sP-sel supernatant or purified (p) sP-sel prepared from activated human platelets, reduced ischemic muscle vascular permeability by 48% and 43%, respectively, following reperfusion. Hindlimb immunohistochemistry demonstrated negligible C3 staining colocalized with IgM in these groups compared with intense staining in the untreated injured mice. In vitro studies of mouse serum complement hemolytic activity showed that psP-sel inhibited the classical but not alternative complement pathway. Flow cytometry demonstrated that psP-sel inhibited C1q adherence to sensitized red blood cells. From these data we conclude that sP-sel moderates skeletal muscle reperfusion injury by inhibition of the classical complement pathway.

Soluble P-selectin in human plasma: effect of anticoagulant matrix and its levels in patients with cardiovascular disorders

P-Selectin represents a cell surface glycoprotein that is constitutively present in the Weibel-Palade bodies of endothelial cells and in the alpha-granules of platelets. In inflammation and thrombogenic conditions, plasmatic P-selectin levels are markedly elevated, indicating the leakage of this marker from these sites. In this study, a quantitative sandwich enzyme-linked immunosorbent assay (ELISA) utilizing a monoclonal soluble P-selectin (sP-selectin) antibody was employed to assess this marker in blood samples collected in various anticoagulants such as heparin, hirudin, sodium citrate (3.2% and 3.8%), and ethylenediaminetetraacetic acid (EDTA). The soluble P-selectin levels ranged from 26 ng/mL to 44 ng/mL. Sodium citrate (3.8%) was used to collect platelet-poor plasma (PPP) from patients with heparin-induced thrombocytopenia (HIT), coronary angioplasty (CA), or coronary atherectomy (CAT). In comparison with the control group (approximately 30 ng/mL), all of these patient groups showed a marked elevation of sP-selectin levels (HIT = 96 ng/mL [n = 18], CA = 46 ng/mL [n = 6] and CAT = 60 ng/mL [n = 10]). In platelet-rich plasma (PRP) preparations using various anticoagulants, the sP-selectin levels were markedly higher, ranging from 87 ng/ mL to 117 ng/mL (n = 10). In patients recruited into a clinical trial (the argatroban [ARG] 911 Study), in which argatroban was used as an alternate anticoagulant in patients with HIT, a 25% to 35% decrease in sP-selectin levels was observed after 72 hours of argatroban treatment. In addition, the relative ratio between levels in PRP and PPP in these patients differed, suggesting that the anticoagulant matrix influences the sP-selectin levels. These data clearly suggest that the anticoagulant matrix and blood collection procedures may significantly influence the plasmatic P-selectin levels. Furthermore, in different clinical conditions, elevation of this marker may reflect endogenous platelet activation; however, optimal anticoagulant for blood collection is important for proper diagnostic validation.

Increased serum levels of soluble L-selectin (CD62L) in patients with active systemic lupus erythematosus (SLE)

The adhesion molecule L-selectin (CD62L) mediates lymphocyte recirculation and leucocyte rolling on vascular endothelium at sites of inflammation. Serum levels of soluble L-selectin (sL-selectin) were measured in patients with SLE in order to relate these levels to clinical activity and immunological parameters. An ELISA was used to detect the soluble form of human L-selectin (CD62L) in 42 patients with SLE and in 33 healthy individuals. The mean +/- s.e.m. values of sL-selectin were 1285 +/- 121 ng/ml for patients with SLE and 986 +/- 180 ng/ml for healthy blood donors, but there was no significant difference. When patients with active SLE were analysed, higher levels of circulating sL-selectin were found when compared with patients without activity (1497 +/- 167 ng/ml versus 941 +/- 150 ng/ml; P = 0.028). We found a significant correlation between the levels of sL-selectin and of dsDNA antibodies (r = 0.36, P = 0. 044) and between levels of sL-selectin and SLE Disease Activity Index (SLEDAI) score (r = 0.42, P = 0.003). Patients with active SLE studied cross-sectionally showed significant elevations of sL-selectin (CD62L) compared with controls. Thus, the levels of this soluble adhesion molecule correlated with active disease and levels of anti-dsDNA antibodies.

Kinetics of platelet P-selectin mobilization: concurrent surface expression and release induced by thrombin or PMA, and inhibition by the NO donor SNAP

Activated platelets and endothelium surface express the cell adhesion molecule P-selectin (CD62P), which plays an important role in mediating interactions with leukocytes. Increased levels of a functional soluble form of P-selectin (sP-selectin) have been reported in several pathological states but it is not clear whether this circulating sP-selectin originates from platelets and/or endothelial cells. Here we describe the concurrent kinetics of intracellular storage, surface expression and release of platelet P-selectin induced by thrombin or the protein kinase C activator PMA. Platelet activation with submaximal concentrations of thrombin (0.1 U/ml) resulted in a rapid decrease of intracellular P-selectin. This decrease of intracellular P-selectin concurred with a gradual increase of surface expression and an initial increase of sP-selectin. Our results indicate that intracellular stores of P-selectin were only partly mobilized upon activation with submaximal concentrations of thrombin. A high concentration of thrombin (1.0 U/ml) induced a rapid and nearly total decrease of intracellular stores and a more pronounced, but transient, increase of surface expression. The release of P-selectin was fast and occurred during the initial activation phase. The NO donor SNAP inhibited both surface expression and release of platelet P-selectin in a similar manner. PMA (0.1-1.0 microM) mediated a more slow, gradual and sustained surface expression and release of P-selectin than thrombin. Thus, surface expression and release of platelet P-selectin show different kinetics depending on the mode of activation.

Serum concentrations of sICAM-1, sE-, sP- and sL-selectins in patients with Schistosoma mansoni infection and association with disease severity

Increased serum concentrations of soluble intercellular adhesion molecule-1 (sICAM-1, CD54) and of soluble E- (CD62E), but not soluble P- (CD62P) and L- (CD62 L) selectins, were detected in Malagasy patients living in an hyperendemic focus of Schistosoma mansoni. Levels of sICAM-1 remained elevated for several months after treatment with praziquantel. Serum levels of ICAM-1, but not of other markers, were significantly correlated with the disease severity, as indicated by ultrasonographical data, and with some circulating fibrosis markers (at least hyaluronic acid). sICAM-1 level may reflect endothelial inflammatory reactions, probably harmful, in the liver and may be useful for monitoring morbidity evolution in schistosomiasis mansoni.

Elevated plasma levels of soluble P-selectin in patients with acute myocardial infarction and unstable angina. An inverse link to lipoprotein(a)

P-selectin in platelets and endothelial cells mediates adhesive interactions between platelet, leukocyte and endothelium to form thrombi. The purpose of the present study was to investigate the plasma level of soluble P-selectin (sP-selectin) in patients with coronary heart disease and the relationship between sP-selectin and plasma concentration of lipoprotein(a) [Lp(a)]. Levels of sP-selectin and Lp(a) were determined by enzyme-linked immunoabsorbent assay on plasma taken from patients with acute myocardial infarction (AMI), old myocardial infarction (OMI), unstable angina (UA), stable angina (SA) and the controls. In patients with AMI and UA, sP-selectin levels (79.62+/-3.82 ng/ml, 43.75+/-2.97 ng/ml, respectively) were significantly higher (P<0.01) than those in patients with OMI (15.92+/-1.34 ng/ml), SA (15.31+/-1.51 ng/ml), and the controls (14.93+/-1.33 ng/ml), but there was no difference between AMI and UA groups. Among all subjects studied, there was an inverse correlation between Lp(a) and sP-selectin (r=-0.315 P<0.001). These findings indicate that plasma levels of sP-selectin are increased in patients with AMI and UA, and high levels of soluble P-selectin may play a role in the pathogenesis of acute coronary events.

In situ expression and soluble form of P-selectin in human glomerulonephritis

To clarify the early involvement of cellular adhesion molecules in human glomerulonephritis, we investigated P-selectin and high endothelial venules' (HEVs) marker MECA-79 expression in kidney specimens by immunohistochemical and in situ hybridization analyses, and measured serum and urinary soluble P-selectin levels by enzyme-linked immunosorbent assay. In normal controls, P-selectin and MECA-79 expression were negative in glomeruli (N = 4), and serum soluble P-selectin levels were 114.3 +/- 36.8 ng/ml (mean +/- SEM, N = 12). Soluble P-selectin was not detectable in urine of all cases. In proliferative glomerulonephritis involving rapidly progressive glomerulonephritis (N = 6), IgA nephropathy (N = 26), lupus nephritis (N = 7) and acute glomerulonephritis (N = 2), both glomerular and interstitial P-selectin expression were up-regulated. Glomerular P-selectin expression correlated positively with local cellular accumulation, endocapillary proliferation and CD41b (platelet) staining. Interstitial P-selectin expression showed a positive correlation with the grade of local cellular infiltrates. P-selectin mRNA signals detected by in situ hybridization were only observed on capillary or venous endothelium in the interstitium, but not in glomeruli. In addition, MECA-79 was expressed on the plump endothelial cells at the cortico-medullary junction (outer medulla). Serum soluble P-selectin levels were significantly higher in patients with proliferative glomerulonephritis, especially in glomerular and interstitial P-selectin positive staining, and correlated with glomerular endocapillary proliferation. These observations suggested that P-selectin was associated with both glomerular and interstitial leukocyte accumulation in human glomerulonephritis, and might be expressed by two distinct mechanisms that are the activated platelets in glomeruli and the de novo expression in the interstitial lesions that correlated with MECA-79 expression as HEVs like vessels, and serum soluble P-selectin may be a useful marker for predicting in situ P-selectin expression associated with glomerular endocapillary proliferation in nephritis.

Age-related augmentation of stroke tendency evaluated using plasma P-selectin levels

Plasma soluble P-selectin is thought to be a useful marker for thrombotic diseases. To evaluate the thrombotic state and risk of stroke in aged healthy subjects, we investigated plasma P-selectin levels in healthy subjects and ischemic stroke patients. Plasma P-selectin was measured in 67 healthy subjects and 35 aged (>or= 65 years of age) patients with chronic ischemic stroke using a sandwich enzyme-linked immunosorbent assay (ELISA). Plasma P-selectin was significantly higher in aged (>or= 65 years of age) healthy subjects than in young (< 65 years of age) healthy subjects. Significant difference did not exist between aged healthy subjects and aged stroke patients who were not receiving anti-platelet agents. Anti-platelet agent had no significant effect on plasma P-selectin levels in aged stroke patients. The amounts of P-selectin released from platelets into the plasma after stimulation with adenosin diphosphate in young and aged healthy subjects were not significantly different. Elevated levels of P-selectin in aged healthy subjects suggests the existence of a subclinical thrombotic state which can result in a stroke. Elevated P-selectin levels are not thought to be due to platelet hyperfunction.