Measurement of soluble P-selectin and soluble CD40 ligand in serum and plasma

Impact of specific preclinical variables on coagulation biomarkers in cancer-associated thrombosis

Coagulation biomarkers are being actively studied for their diagnostic and prognostic value in patients with venous thromboembolism and cancer, as well as in the study of pathogenic mechanisms between cancer and thrombosis. For the results of such studies to be accurate and reproducible, attention must be paid to minimize sources of error in all phases of testing. The pre-analytical phase of laboratory testing is known to be fraught with the majority of errors. Coagulation testing is particularly susceptible to conditions during collection, processing, transport and storage of specimens which can lead to clinically significant errors in results. In addition, changes in pre-analytical conditions can impact different biomarkers differently. Therefore, research studies investigating coagulation biomarkers must carefully standardize not just the analytical phase, but also the pre-analytical phase of testing to ensure accuracy and reliability. We briefly review the impact of pre-analytical conditions on coagulation testing in general, and on specific biomarkers in cancer and thrombosis. In addition, we provide recommendations to reduce pre-analytical errors by developing and sharing standard operating procedures that specifically target standardization of methodologies for collecting specimens and measuring current and emerging coagulation biomarkers in cancer studies.

The CD40-CD40L Dyad as Immunotherapeutic Target in Cardiovascular Disease

Chronic inflammation drives the development of atherosclerosis. Despite optimal treatment of classical cardiovascular risk factors, a substantial portion of the population has elevated inflammatory biomarkers and develops atherosclerosis-related complications, indicating that a residual inflammatory risk drives atherosclerotic cardiovascular disease in these patients. Additional anti-inflammatory therapeutic strategies are therefore required. The co-stimulatory molecule CD40 and its ligand CD40L (CD154) have a central role in the regulation of the inflammatory response during the development of atherosclerosis by modulating the interaction between immune cells and between immune cells and non-immune cells. In this review, we discuss the role of the CD40-CD40L dyad in atherosclerosis, and we discuss recent studies on the therapeutic potential of novel CD40-CD40L targeting strategies in cardiovascular medicine.

Biomarkers of vascular injury and endothelial dysfunction after recent glucose intolerance in pregnancy

OBJECTIVE

Women with gestational diabetes mellitus and milder gestational impaired glucose intolerance have elevated future risks of type 2 diabetes and cardiovascular disease. However, it is unclear whether they show postpartum evidence of vascular injury/dysfunction, an early event in the natural history of cardiovascular disease.

METHODS

In total, 337 women underwent a glucose challenge test and oral glucose tolerance test in pregnancy, yielding four gestational glucose tolerance groups: gestational diabetes mellitus, gestational impaired glucose intolerance, abnormal glucose challenge test with normal glucose tolerance on the oral glucose tolerance test and normal glucose challenge test with normal glucose tolerance. At 3 years postpartum, they underwent repeat oral glucose tolerance test (on which 69 women had pre-diabetes/diabetes) and measurement of the following serum markers of vascular injury/dysfunction: thrombomodulin, E-selectin, P-selectin, intercellular adhesion molecule-3 and vascular cell adhesion molecule-1.

RESULTS

At 3 years postpartum, mean adjusted vascular cell adhesion molecule-1 was the only vascular marker that differed across the previous gestational glucose tolerance groups. On multiple linear regression analysis, each strata of gestational dysglycaemia was an independent predictor of lower vascular cell adhesion molecule-1 at 3 years postpartum (gestational diabetes mellitus: p = 0.005; gestational impaired glucose intolerance: p = 0.003; abnormal glucose challenge test normal glucose tolerance: p = 0.0008), as was current pre-diabetes/diabetes ( p = 0.01).

CONCLUSION

Dysregulation of vascular cell adhesion molecule-1 may be an early event in the natural history of cardiovascular disease in women with recent glucose intolerance in pregnancy.

Reduced platelet hyper-reactivity and platelet-leukocyte aggregation after periodontal therapy

Background

Platelets from untreated periodontitis patients are hyper-reactive and form more platelet-leukocyte complexes compared to cells from individuals without periodontitis. It is not known whether the improvement of the periodontal condition achievable by therapy has beneficial effects on the platelet function. We aimed to assess the effects of periodontal therapy on platelet reactivity.

Methods

Patients with periodontitis (n = 25) but unaffected by any other medical condition or medication were included and donated blood before and after periodontal therapy. Reactivity to ADP or oral bacteria was assessed by flow cytometric analysis of membrane markers (binding of PAC-1, P-selectin, CD63) and platelet-leukocyte complex formation. Reactivity values were expressed as ratio between the stimulated and unstimulated sample. Plasma levels of soluble (s) P-selectin were determined by enzyme-linked immunosorbent assay (ELISA).

Results

Binding of PAC-1, the expression of P-selectin and CD63 in response to the oral bacterium P. gingivalis were lower at recall (1.4 ± 1.1, 1.5 ± 1.2, and 1.0 ± 0.1) than at baseline (2.7 ± 4.1, P = 0.026, 6.0 ± 12.5, P = 0.045, and 2.7 ± 6.7, P = 0.042, respectively). Formation of platelet-leukocyte complexes in response to P. gingivalis was also reduced at recall compared to baseline (1.2 ± 0.7 vs. 11.4 ± 50.5, P = 0.045). sP-selectin levels were significantly increased post-therapy.

Conclusions

In periodontitis patients, the improvement of the periodontal condition is paralleled by a reduction in platelet hyper-reactivity. We suggest that periodontal therapy, as an intervention for improved oral health, can facilitate the management of thrombotic risk, and on the long term can contribute to the prevention of cardiovascular events in patients at risk.

Trial registration

Current Controlled Trials identifier ISRCTN36043780. Retrospectively registered 25 September 2013.

Electronic supplementary material

The online version of this article (doi:10.1186/s12959-016-0125-x) contains supplementary material, which is available to authorized users.

Reproducibility over time and effect of low-dose aspirin on soluble P-selectin and soluble CD40 ligand

Platelet markers [soluble CD40 ligand (sCD40L) and soluble p selectin (sPselectin)] are associated with platelet activation and cardiovascular events. We sought to investigate the reproducibility of these markers over time and the effect of low-dose aspirin on sCD40L and sPselectin in plasma and serum. Following an overnight fast, 40 healthy volunteers had weekly phlebotomy and were administered aspirin 81 mg/day between weeks 3 and 4. Reproducibility over time was assessed by coefficient of variation (CV) and inter-class correlation coefficient. Correlation between markers was assessed using Pearson r statistic. Difference between levels pre- and post-aspirin was measured with Wilcoxon signed-rank test. Data are presented as median (interquartile range). sCD40L and sPselectin measurements were reproducible over time in plasma and serum (CV < 10 %). Measurement of sCD40L and sPselectin in plasma correlated with levels in serum before aspirin and after aspirin. There was no significant correlation between sCD40L and sPselectin. After 1-week of aspirin 81 mg/day, there was a reduction in sCD40L and sPselectin in serum and plasma, respectively. Soluble CD40L and sPselectin are independent markers that are reproducible over time in both plasma and sera and are reduced by 1-week of low-dose aspirin.

New frontiers for platelet CD154

The role of platelets extends beyond hemostasis. The pivotal role of platelets in inflammation has shed new light on the natural history of conditions associated with acute or chronic inflammation. Beyond the preservation of vascular integrity, platelets are essential to tissue homeostasis and platelet-derived products are already used in the clinics. Unanticipated was the role of platelets in the adaptative immune response, allowing a renewed conceptual approach of auto-immune diseases. Platelets are also important players in cancer growth and dissemination. Platelets fulfill most of their functions through the expression of still incompletely characterized membrane-bound or soluble mediators. Among them, CD154 holds a peculiar position, as platelets represent a major source of CD154 and as CD154 contributes to most of these new platelet attributes. Here, we provide an overview of some of the new frontiers that the study of platelet CD154 is opening, in inflammation, tissue homeostasis, immune response, hematopoiesis and cancer.

Is delayed pressure urticaria associated with increased systemic release of sCD40L?

BACKGROUND

Elevated levels of soluble CD40 Ligand (sCD40L) were found in serum but not in plasma of patients with chronic spontaneous urticaria (CU). What is important is that sCD40L has proinflammatory properties, and its elevated plasma level may indicate increased risk of cardiovascular events. These observations should stimulate further evaluation of sCD40L in different forms of urticaria.

AIM

In the present study, sCD40L plasma level was investigated in delayed pressure urticaria (DPU).

METHODS

As platelets are predominant and variable sources of sCD40L, we investigated sCD40L concentration in platelet-poor plasma (PPP), which seems the best way to minimize the potential contribution of these cells to the ligand level.

RESULTS

Plasma sCD40L concentration was significantly increased in the DPU group compared to the healthy controls.

CONCLUSIONS

It seems that DPU is associated with increased systemic release of sCD40L, which is believed to derive predominantly from activated platelets. The present study as well as the earlier contributions suggest that distinct cells activity, including platelets, may be identified in different types of urticaria.

CD40-CD40L: linking pancreatic, adipose tissue and vascular inflammation in type 2 diabetes and its complications

Numerous epidemiological studies have consistently demonstrated the strong association between type 2 diabetes mellitus (T2DM) and an increased risk to develop cardiovascular disease. The pathogenesis of T2DM and its complications are characterized by pancreatic, adipose tissue and vascular inflammation. CD40 and CD40L, members of the tumour necrosis factor (receptor) TNF(R) family, are well known for their role in immunity and inflammation. Here we give an overview on the role of CD40-CD40L interactions in the pathogenesis of T2DM with a special focus on pancreatic, adipose tissue and vascular inflammation. In addition, we explore the role of soluble CD40L (sCD40L) as a potential biomarker for the development of cardiovascular disease in T2DM subjects. Finally, the therapeutic potential of CD40-CD40L inhibition in T2DM is highlighted.

Reduced thrombin generation and soluble P-selectin after intravenous enoxaparin during PCI

PURPOSE

The objective of our study was to identify changes in the coagulation and serum concentration of soluble P-selectin (sP-sel) after i.v. bolus of 0.75 mg/kg enoxaparin in a group of 33 patients during PCI.

METHODS AND RESULTS

As compared to baseline, i.v. enoxaparin increased anti -Xa activity and FIIa inhibition together with APTT and thrombin time tests within 20 min, that persisted for 60 min. At 6 h, the results of all tests had returned to baseline. In contrast, the level of prothrombin fragments (F1 + 2) decreased persistingly for a period of 6 h (baseline 1.19 ± 0.42 nmol/l, after 20 min 1.03 ± 0.46 nmol/l, after 60 min 1.06 ± 0.43 nmol/l, after 6 h 0.95 ± 0.40 nmol/l, p < 0.001 vs. baseline for all values). In addition, i.v. enoxaparin decreased serum sP-sel level (baseline 111.80 ± 37.05 ng/ml, after 20 min 87.80 ± 33.17 ng/ml, after 60 min 86.45 ± 29.15 ng/ml, after 6 h 92.24 ± 31.34 ng/ml, p < 0.001 vs. baseline value for all). sP-sel level mildly correlated with both F Xa inhibition (r = -0.275, p < 0.05) and F1 + 2 level (r = 0.274, p < 0.05).

CONCLUSION

Intravenous enoxaparin induced target F Xa inhibition (>0.6 IU/ml) for 60 min in 82% of study patients. During the 6 h of monitoring, a decrease of thrombin generation (F1 + 2) and sP-selectin levels were observed.

Increased plasma levels of soluble CD40 ligand correlate with platelet activation markers and underline the need for standardized pre-analytical conditions

OBJECTIVES

To investigate whether sCD40L dosage might represent a useful tool to explore in vivo platelet function.

DESIGN AND METHODS

sCD40L and sP-selectin levels and light transmission aggregometry (LTA) were analyzed in 69 healthy donors. Immunoassays were performed on platelet-depleted citrate plasma samples. The effects of in vitro aspirin treatment on the release of sCD40L were investigated in 15 subjects following platelet stimulation. The effects of a 1-month therapeutic course of low-dose aspirin on sP-selectin and sCD40L levels were also investigated.

RESULTS

A significant correlation was observed between sCD40L and sP-selectin (p<0.01). In vitro aspirin treatment remarkably decreased sCD40L levels following platelet activation by exogenous agonists. sCD40L directly correlated with LTA (Rho=0.62, p<0.0001). In vivo aspirin treatment significantly reduced both sP-selectin and sCD40L levels (both p<0.01) in a direct correlation (Rho=0.66, p<0.05).

CONCLUSIONS

Citrated plasma samples reflect sCD40L released from platelets, thus yielding the most valid estimates of in vivo circulating levels of this platelet activation markers.

Clinical correlates, heritability, and genetic linkage of circulating CD40 ligand in the Framingham Offspring Study

BACKGROUND

The CD40 receptor and its ligand (CD40L) are known to modulate both inflammation and thrombosis-2 processes important for the development and clinical expression of atherosclerosis. Circulating soluble CD40L (sCD40L) concentration predicts cardiovascular risk in selected patient samples. The purpose of this study was to determine the predictors of sCD40L in a large, community-based sample.

METHODS

We determined both serum and plasma sCD40L concentration in 3,259 participants (54% women) from the Framingham Offspring Study.

RESULTS

In multivariable models, advancing age was the only consistent (inverse) correlate of both serum and plasma sCD40L concentration. Overall, the variability explained by clinical covariates was very low for both measurements of sCD40L; with values of only 1.4% and 2.7% for serum and plasma, respectively. We observed that genetic factors accounted for a modest (12% serum; 14% plasma) amount of the adjusted variability in sCD40L.

CONCLUSIONS

Circulating sCD40L concentration was poorly associated with known cardiovascular disease (CVD) risk factors and was modestly heritable. Determining if either serum or plasma sCD40L are predictive of CVD risk in the community will require longitudinal follow-up.

Concurrent evaluation of novel cardiac biomarkers in acute coronary syndrome: myeloperoxidase and soluble CD40 ligand and the risk of recurrent ischaemic events in TACTICS-TIMI 18

AIMS

We investigated the prognostic performance of myeloperoxidase (MPO), and soluble CD40 ligand (sCD40L) along with B-type natriuretic peptide (BNP), high-sensitivity C-reactive protein (hsCRP), and cardiac troponin I (cTnI) for non-fatal recurrent ischaemic events in non-ST elevation acute coronary syndrome (ACS).

METHODS AND RESULTS

We measured plasma MPO and sCD40L in 1524 patients with ACS treated with tirofiban and randomized to early invasive vs. conservative management in the TACTICS-TIMI 18 trial who survived to 180 days. Patients with elevated baseline MPO (>884 pM) were at higher risk of non-fatal myocardial infarction or rehospitalization for ACS at 30 days (9.3 vs. 4.6%, P < 0.001). In contrast, no difference was observed with higher sCD40L (>989 pg/mL, 7.6 vs. 6.3%, P = 0.31). MPO remained associated with recurrent ischaemic events after adjustment for age, ST-deviation, diabetes, prior coronary artery disease, heart failure, cTnI, hsCRP, and sCD40L (OR 2.10; 95% CI 1.36-3.23, P = 0.001). This association was attenuated by 180 days (OR 1.26; 0.95-1.68). Stratification using baseline MPO, BNP, and cTnI identified a >3-fold gradient of risk.

CONCLUSION

MPO adds to BNP and cTnI for short-term risk assessment for recurrent ischaemic events in non-ST elevation ACS. sCD40L was not associated with risk in this population treated with a platelet GPIIb/IIIa receptor antagonist.

Association of low-grade inflammation and platelet activation in patients with hypertension with microalbuminuria

Increased levels of sCD40L (soluble CD40 ligand) have been associated with enhanced in vivo platelet activation, and may represent a molecular link between inflammation and a prothrombotic state. The aim of the present study was to analyse the relationship between platelet activation, endothelial dysfunction, low-grade inflammation and sCD40L in patients with hypertension with or without MA (microalbuminuria). A cross-sectional comparison of sCD40L levels was performed in 25 patients with MH (essential hypertension with MA) pair-matched for gender and age with 25 patients with EH (essential hypertension) and 25 HS (healthy subjects with normotension). Circulating levels of CRP (C-reactive protein), a marker of inflammation, sP-selectin (soluble P-selectin), a marker of in vivo platelet activation, and ADMA (asymmetric dimethylarginine) and vWF (von Willebrand factor), markers of endothelial dysfunction, were analysed in each subject. sCD40L levels were increased in patients with MH compared with either patients with EH (P<0.001) or HS (P<0.0001). A highly significant correlation between plasma sCD40L and sP-selectin (P<0.0001), vWF (P<0.001) or CRP levels (P<0.05) was observed in patients with MH. Multivariate regression analysis showed that sP-selectin was the strongest independent predictor of sCD40L levels (P<0.0001) in patients with MH. Patients with hypertension with both vWF and CRP levels above the median had the highest sCD40L levels (P<0.0001). Factorial ANOVA of all of the patients with hypertension confirmed that only patients with MH with low-grade inflammation had elevated levels of sCD40L. In conclusion, sCD40L levels appear to discriminate a subset of patients characterized by MA and low-grade inflammation, suggesting that inhibition of the CD40/CD40L system may represent a potential therapeutic target in subjects with hypertension at a high risk of cardiovascular events.

CD40/CD40L system and vascular disease

Several distinct lines of investigation in the context of atherosclerosis dealing with low-grade inflammation, oxidative stress and platelet activation are now emerging, with CD40/CD40L system as the missing link. CD40 ligand is a transmembrane glycoprotein structurally related to tumour necrosis factor-alpha and more than 95% of the circulating CD40L derives from platelets. CD40L appears as a multiplayer of several cell types in the inflammatory network. The peculiarity of CD40L as an inflammatory mediator derived from platelets expands the functional repertoire of platelets from players of haemostasis and thrombosis to powerful amplifiers of inflammation by promoting the release of cytokines and chemokines, cell activation and cell-cell interactions. The multifunctional role of CD40L, as a simultaneous activator of all these systems, further blurs the intricate relationship between such events both in the physiological systems and the pathological derangement occurring in atherothrombosis.

Baseline level of platelet-leukocyte aggregates, platelet CD63 expression, and soluble P-selectin concentration in patients with posttraumatic stress disorder: a pilot study

Platelets may have an important role in the development of cardiovascular disease (CVD) as a result of chronic stress. We conducted a pilot study to evaluate the effect of posttraumatic stress disorder (PTSD) on baseline platelet activation. Platelet-leukocyte aggregates (PLA) and CD63 expression were measured by flow cytometry, and soluble (s)P-selectin concentration was determined in sera of 20 Croatian male combat veterans with PTSD and 20 healthy civilians. Groups were matched in sex, age, body mass index (BMI) and traditional CVD risk factors. Our data showed no differences in measured parameters. Other platelet activation markers should be determined and a larger sample size used in future studies.

Platelet membrane CD154 and sCD154 in progressive peripheral arterial disease: A pilot study

OBJECTIVE

The expression and potential role of platelet membrane CD154 and sCD154 in atherosclerosis was investigated in patients with peripheral arterial disease.

METHODS

This prospective observational study measured the expression of platelet-bound CD154 and soluble CD154 (sCD154) in 39 patients with critical limb ischaemia (CLI, n=15), stable intermittent claudication (SIC, n=12) and age-matched controls (AMC, n=12). Basal and agonist-stimulated CD154, P-selectin expression and fibrinogen binding was measured by whole blood flow cytometry, while sCD154 was measured in paired plasma samples by ELISA.

RESULTS

Basal expression of CD154 on the platelet surface was enhanced in both groups of patients with peripheral arterial disease. However, the critical limb ischaemics showed the highest level of basal expression 0.7+/-0.3 [median+/-IQR] and was significantly increased compared to both stable intermittent claudicants and age-matched controls (P<0.001). On agonist stimulation with either ADP or thrombin critical limb ischaemics demonstrated greater platelet reactivity and propensity to express CD154 compared to age-matched controls (P<0.05). Confirmation of the cellular expression of CD154 results was obtained by measuring sCD154 concentrations in autologous plasma samples. Here plasma levels of sCD154 in critical limb ischaemics were significantly greater than both stable intermittent claudicants and age-matched controls (P<0.005).

CONCLUSIONS

Enhanced basal platelet expression and increased propensity to express CD154 and sCD154 in critical limb ischaemics compared to both controls and patients with stable intermittent claudication support evidence for the role of CD154 in atherogenesis and suggest a novel function in progressive and acute peripheral arterial disease.

Cell-derived microparticles and exosomes in neuroinflammatory disorders

All blood cells and the vascular endothelium shed microparticles (MP) from their plasma membranes when suitably stimulated, and assay of MP in patient blood has found increasing application to the monitoring of disease states. In addition, mounting evidence suggests that MP are not mere epiphenomena but play significant roles in the pathophysiology of thromboses, inflammation, and cancers. This chapter endeavors to summarize the limited number of studies thus far done on MP in neurological disorders such as multiple sclerosis (MS), transient ischemic attacks, and the neurological manifestations of antiphospholipid syndrome (APS). In addition, the chapter offers some plausible hypotheses on possible roles of MP in the pathophsyiology of these disorders, chiefly, the hypothesis that MP are indeed important participants in some neuropathologies, especially those which are ischemic in nature, but probably also inflammatory ones. The chapter also goes over the history and general principles of MP studies (e.g., assay methods and pitfalls), comparison with alternative methods (e.g., soluble markers of disease states), subclasses of MP (such as exosomes), and other topics aimed at helping readers to consider MP studies in their own clinical fields. Tables include a listing of bioactive agents known to be carried on MP, many of which were heretofore considered strictly soluble, and some of which can be transferred from cell to cell via MP vectors, for example certain cytokine receptors.

Influence of pre-analytical and analytical factors on soluble CD40L measurements

The soluble form of CD40L (CD40 ligand), a pro-atherogenic mediator, has emerged as a diagnostic and prognostic marker for cardiovascular events. However, as platelets can shed CD40L upon activation, accurate measurement has proved challenging. The present study addresses the controversy regarding the appropriate specimen and preparation for laboratory evaluation of blood sCD40L (soluble CD40L). Serum and plasma (collected in EDTA, citrate or heparin) were collected from healthy volunteers (n=20), and sCD40L was analysed by ELISA immediately or after one to three freeze–thaw cycles and at different centrifugation speeds. Urine sCD40L levels were measured in subjects with low- and high-plasma sCD40L levels. Serum sCD40L levels (5.45±4.55 ng/ml; P<0.001) were higher than in citrate, EDTA or heparin plasma (1.03±1.07, 1.43±1.03 or 1.80±1.25 ng/ml respectively), with no significant differences between plasma preparations. Increasing g values (200–13000 g), which gradually deplete plasma of platelets, yielded lower sCD40L levels. Repeated freeze–thaw cycles significantly (P<0.05) increased sCD40L concentrations in platelet-rich, but not platelet-depleted, plasma (up to 2.4-fold). Bilirubin and haemoglobin interfered positively, and triacylglycerols (triglycerides) and cholesterol quenched CD40L signalling. No sCD40L was detected in urine samples. In conclusion, serum yields higher sCD40L concentrations than plasma; accurate measurements of sCD40L require exclusion of platelets and avoiding their post-hoc activation. Samples with high concentrations of bilirubin, haemoglobin and/or triacylglycerols should be excluded, as these substances interfere with the assay.

Measures of Thrombosis and Fibrinolysis

Our recent understanding of acute coronary syndrome as an atherothrombotic process has led to research efforts in the development of markers of thrombosis and fibrinolysis for risk prediction in cardiovascular heart disease. Although American Heart Association/American College of Cardiology guidelines recommend fibrinogen as a category I risk factor and also suggest factor VII, plasminogen activator inhibitor-1, tissue-type plasminogen activator, and von Willebrand factor as other potentially clinically useful markers, these tests have not come into routine clinical use. Their development as predictors of risk may be hampered by inconsistent laboratory methodology, which causes difficulty in comparing result interpretation with published trial studies. This article presents the history of development for these tests, proper laboratory handling, the best trial data that present evidence of their accuracy, and current guidelines for clinical use.

Serum markers of vascular inflammation in dyslipemia

Atherosclerosis is widely recognized as an inflammatory disease because systemic and local inflammatory events mediate all phases of plaque development and progression. Basic and clinical studies have focused on identifying potentially useful markers of inflammation. In this article, we review the inflammatory pathogenesis of atherosclerosis, and highlight recent results of several of the more promising markers of inflammation for cardiovascular risk assessment. Of these markers, the most reliable and accessible for clinical use is currently high-sensitivity C-reactive protein (CRP). At present, most clinical guidelines do not recommend routine measurement of these inflammatory markers. However, these serum markers of vascular inflammation may be useful as an adjunct to lipid screening, especially for patients whose lipid values may not be severely elevated, but who are at intermediate risk according to scoring systems that take into account multiple established risk factors. In addition, since the pleiotropic effects of statins include the inhibition of inflammatory response, serum inflammatory markers could also be useful for monitoring this action. Nevertheless, several issues have to be evaluated before the measurements of inflammatory markers can be used for cardiovascular risk prediction in either clinical practice or in clinical trials evaluating anti-atherosclerotic drugs.

Supplementation with mixed tocopherols increases serum and blood cell gamma-tocopherol but does not alter biomarkers of platelet activation in subjects with type 2 diabetes

BACKGROUND

Some studies have shown potential benefit of vitamin E on platelet function, but several clinical trials failed to show improved cardiovascular outcome with alpha-tocopherol supplementation. Gamma-tocopherol, a major dietary form of vitamin E, may have protective properties different from those of alpha-tocopherol.

OBJECTIVE

We compared the effects of supplementation with alpha-tocopherol (500 mg) and a gamma-tocopherol-rich compound (500 mg, containing 60% gamma-tocopherol) on serum and cellular tocopherol concentrations, urinary tocopherol metabolite excretion, and in vivo platelet activation in subjects with type 2 diabetes.

DESIGN

Fifty-eight subjects were randomly assigned to receive either 500 mg alpha-tocopherol/d, 500 mg mixed tocopherols/d, or matching placebo. Serum, erythrocyte, and platelet tocopherol and urinary metabolite concentrations were measured at baseline and after the 6-wk intervention. Soluble CD40 ligand, urinary 11-dehydro-thromboxane B2, serum thromboxane B2, soluble P-selectin, and von Willebrand factor were measured as biomarkers of in vivo platelet activation.

RESULTS

Serum alpha-tocopherol increased with both tocopherol treatments. Serum and cellular gamma-tocopherol increased 4-fold (P < 0.001) in the mixed tocopherol group, whereas red blood cell gamma-tocopherol decreased significantly after alpha-tocopherol supplementation. Excretion of alpha-carboxyethyl-hydroxychroman increased significantly after supplementation with alpha-tocopherol and mixed tocopherols. Excretion of gamma-carboxyethyl-hydroxychroman increased significantly after supplementation with mixed tocopherols and after that with alpha-tocopherol, which may reflect the displacement of gamma-tocopherol by alpha-tocopherol due to incorporation of the latter into lipoproteins in the liver. Neither treatment had any significant effect on markers of platelet activation.

CONCLUSIONS

Supplementation with alpha-tocopherol decreased red blood cell gamma-tocopherol, whereas mixed tocopherols increased both serum alpha-tocopherol and serum and cellular gamma-tocopherol. Changes in serum tocopherol closely reflect changes in cellular concentrations of tocopherols after supplementation.

Plasma, serum, and platelet expression of CD40 ligand in adults with cardiovascular disease

The application of soluble CD40 ligand (sCD40L) as a biomarker has garnered great scientific and clinical interest. However, there are many uncertainties with regard to the biology of sCD40L. Although presumed to be a marker of platelet activation, relative levels in plasma, serum, and platelet expression are unknown, as is the optimal method for its measurement. We measured CD40L from serum, platelet-poor plasma, and platelet surface in adults who had stable cardiovascular disease (CVD) and those who had unstable CVD (n = 40). Plasma sCD40L did not differ significantly between groups. Serum sCD40L was significantly lower (1.4 +/- 1.3 vs 5.2 +/- 3.7 ng/ml, p <0.001) and platelet membrane CD40L expression was higher (1.4 +/- 0.7% vs 0.9 +/- 0.6%, p = 0.03) in unstable compared with stable CVD. When the 2 groups were considered together, there was a significant correlation between plasma and serum sCD40L levels (rho = 0.4, p = 0.02) and negative correlations between plasma (rho = -0.3, p = 0.04) and serum (rho = -0.4, p = 0.01) sCD40L levels with platelet membrane CD40L expression. In unstable CVD, the correlation between sCD40L measurements was poor. Consistent with enhanced platelet activation, there was a positive correlation between platelet aggregation and surface CD40L expression (rho = 0.5, p = 0.02) and between platelet expression of CD40L and P-selectin (rho = 0.4, p = 0.05) in unstable CVD. There was no correlation between CD40L and platelet count or C-reactive protein. Only surface expression of CD40L compared with platelet-derived (plasma) or total (serum) CD40L level proved a reliable marker of platelet function in patients who had stable CVD and those who had unstable CVD. In conclusion, our data demonstrate the complex nature of CD40L and highlight the distinct processes of expression, shedding, and clearance of this ligand in patient populations.

Elevated circulating platelet-derived microparticles in patients with active inflammatory bowel disease

OBJECTIVES

Platelet-derived microparticles (PDMPs) are active molecules involved in the hemostatic and inflammatory responses. To evaluate the changes in the platelet function in patients with inflammatory bowel disease (IBD), we measured circulating PDMP levels.

METHODS

Twenty-five healthy controls, 44 patients with ulcerative colitis (UC), and 43 patients with Crohn's Disease (CD) were studied. The PDMP and soluble P-selectin (sP-selectin) levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

In the healthy controls, the PDMP levels were 17.2 +/- 6.2 U/mL. Significant differences were not observed between the healthy controls and inactive UC patients (20.8 +/- 9.5 U/mL, n = 25) or between the healthy controls and inactive CD patients (17.6 +/- 7.8 U/mL, n = 24). In contrast, the PDMP levels were significantly higher in both active UC (49.2 +/- 33.6 U/mL, n = 19) and active CD (48.6 +/- 42.8 U/mL, n = 19) patients than in the healthy controls. A significant correlation was found between the PDMP levels and the clinical activity indexes (CAI) of UC patients (r = 0.65, p < 0.01, n = 44), and between the PDMP levels and Crohn's disease activity indexes (CDAI) (r = 0.72, p < 0.01, n = 43). Elevated PDMP levels in active patients were significantly reduced after remission. A significant correlation was observed between the PDMP levels and the sP-selectin levels (r = 0.60, p < 0.01, n = 122).

CONCLUSION

Elevated circulating PDMPs in active IBD patients suggest a role for platelets in the pathogenesis of IBD.

Soluble CD40L in Plasma of Patients with Primary Biliary Cirrhosis

CD40 ligand (CD40L) is expressed by activated T cells and interacts with the CD40 molecule present on B cells and endothelial cells, promoting immunoglobulin switching in the former and cytokine upregulation in the latter. CD40L exists in both a soluble (sCD40L) and a membrane-bound form. Because primary biliary cirrhosis (PBC) is characterized by targeting of small intrahepatic bile ducts by autoreactive T cells, plasma concentrations of sCD40L were investigated using enzyme-linked immunosorbent assay (ELISA) to measure plasma concentrations of sCD40L in 12 patients with PBC and 12 healthy controls. No difference could be detected between plasma concentrations of sCD40L in patients versus controls (P = 0.977). No correlation between age and plasma levels of sCD40L could be identified (P = 0.24). We concluded that PBC patients do not exhibit higher plasma concentrations of sCD40L than age-matched controls, a finding common to several autoimmune diseases. Further investigation of the CD40-CD40L system is strongly encouraged.