Upregulation of CD40 ligand and enhanced monocyte-platelet aggregate formation are associated with worse clinical outcome after ischaemic stroke

Association of elevated circulating monocyte-platelet aggregates with hypercoagulability in patients with nephrotic syndrome

BACKGROUND

Hypercoagulability emerges as a central pathological feature and clinical complication in nephrotic syndrome. Increased platelet activation and aggregability are closely related to hypercoagulability in nephrotic syndrome. Monocyte-platelet aggregates (MPAs) have been proposed to represent a robust biomarker of platelet activation. The aim of this study was to investigate levels of the circulating MPAs and MPAs with the different monocyte subsets to evaluate the association of MPAs with hypercoagulability in nephrotic syndrome.

METHODS

Thirty-two patients with nephrotic syndrome were enrolled. In addition, thirty-two healthy age and sex matched adult volunteers served as healthy controls. MPAs were identified by CD14 monocytes positive for CD41a platelets. The classical (CD14 + + CD16-, CM), the intermediate (CD14 + + CD16+, IM) and the non-classical (CD14 + CD16++, NCM) monocytes, as well as subset specific MPAs, were measured by flow cytometry.

RESULTS

Patients with nephrotic syndrome showed a higher percentage of circulating MPAs as compared with healthy controls (p < 0.001). The percentages of MPAs with CM, IM, and NCM were higher than those of healthy controls (p = 0.012, p < 0.001 and p < 0.001, respectively). Circulating MPAs showed correlations with hypoalbuminemia (r=-0.85; p < 0.001), hypercholesterolemia (r = 0.54; p < 0.001), fibrinogen (r = 0.70; p < 0.001) and D-dimer (r = 0.37; p = 0.003), but not with hypertriglyceridemia in nephrotic syndrome. The AUC for the prediction of hypercoagulability in nephrotic syndrome using MPAs was 0.79 (95% CI 0.68-0.90, p < 0.001). The sensitivity of MPAs in predicting hypercoagulability was 0.71, and the specificity was 0.78.

CONCLUSION

Increased MPAs were correlated with hypercoagulability in nephrotic syndrome. MPAs may serve as a potential biomarker for thrombophilic or hypercoagulable state and provide novel insight into the mechanisms of anticoagulation in nephrotic syndrome.

Platelet function suggests cardioembolic aetiology in cryptogenic stroke

Platelet-monocyte (PMA) and platelet-neutrophil aggregations (PNA) play critical roles in the evolution of acute ischemic stroke (AIS). The present study investigates the mechanistic basis of platelet responsiveness in cryptogenic stroke compared with cardioembolic stroke. Platelet from 16 subjects, each from cryptogenic and cardioembolic stroke groups and 18 age-matched healthy controls were subjected to different investigations. Compared to healthy controls, platelet-monocyte and platelet-neutrophil interactions were significantly elevated in cryptogenic (2.7 and 2.1 times) and cardioembolic stroke (3.9 and 2.4 times). P-selectin expression on platelet surface was 1.89 and 2.59 times higher in cryptogenic and cardioembolic strokes, respectively, compared to healthy control. Cell population with [Ca²⁺_i] in either stroke group was significantly outnumbered (by 83% and 72%, respectively, in cryptogenic and cardioembolic stroke) in comparison to healthy controls. Noteworthy, TEG experiment revealed that the cryptogenic stroke exhibited significant decline in Reaction Time (R) and amplitude of 20 mm (K) (by 32% and 33%, respectively) while thrombin burst (α-angle) was augmented by 12%, which reflected substantial boost in thrombus formation in cryptogenic stroke. Although TEG analysis reveals a state of hypercoagulability in patients with cryptogenic stroke. However, platelets from both stroke subtypes switch to a 'hyperactive' phenotype.

Baseline platelet count may predict short-term functional outcome of cerebral infarction

Background and aims

Platelets play an important role in homeostasis however, they have also been associated with increased mortality after myocardial infarction. In the present study, we investigated whether platelet count is associated with differences in the short-term prognosis at the time of hospital discharge and early neurological deterioration in ischemic stroke patients.

Methods

Patients with ischemic stroke were enrolled from among 661 cerebrovascular disease patients admitted between January 2018 and December 2020. Patients who received hyperacute treatment, had a pre-onset modified Rankin scale (mRS) ≥ 3, transient ischemic attack, or active malignant disease were excluded. The platelet count was divided into quartiles (Q1-4) according to the number of patients, and the relationship between platelet count and prognosis was assessed using multivariable analysis.

Results

In total, 385 patients were included in the study. Regarding the functional outcome by platelet count, there was a significant increase in mRS ≥ 3 at discharge in the Q4 (range: 243–1327 × 10⁹/L, p = 0.013, ORs: 1.674, 95%CI: 1.253–6.681) group compared to the Q3 (range: 205–242 × 10⁹/L) group even after adjusting for factors with P < 0.2 in univariate analysis. Furthermore, the frequency of neurological deterioration (NIHSS ≥ 4) within 1 week was significantly lower in the Q3 group than in the Q1 (range; 19–173 × 10⁹/L) and Q4 groups even after adjustment (Q1; p = 0.020 ORs: 6.634, 95%CI: 1.352–32.557, Q4; p = 0.007 ORs: 8.765, 95%CI: 1.827–42.035).

Conclusion

Platelet count at onset may affect the prognosis of cerebral infarction and early neurological deterioration. This study may help clarify the pathogenesis of cerebral infarction to improve prognosis.

Platelet-Leucocyte Aggregates as Novel Biomarkers in Cardiovascular Diseases

Simple Summary

Cardiovascular diseases are the most common cause of death worldwide. Hence, novel biomarkers are urgently needed to improve diagnosis and treatment. Platelet–leucocyte aggregates are conglomerates of platelets and leucocytes and are widely investigated as biomarkers in cardiovascular diseases. Platelet–leucocytes aggregates are present in health, but increase in patients with cardiovascular risk factors and acute or stable coronary syndromes, making them a potential diagnostic marker. Moreover, platelet–leucocyte aggregates predict outcomes after surgery or percutaneous treatment and could be used to monitor antiplatelet therapy. Emerging data about the participation of platelet–leucocyte aggregates in cardiovascular diseases pathogenesis make them an attractive target for novel therapies. Furthermore, simple detection with conventional flow cytometry provides accurate and reproducible results, although requires specific sample handling. The main task for the future is to determine the standardized protocol to measure blood concentrations of platelet–leucocyte aggregates and subsequently establish their normal range in health and disease.

Abstract

Platelet–leucocyte aggregates (PLA) are a formation of leucocytes and platelets bound by specific receptors. They arise in the condition of sheer stress, thrombosis, immune reaction, vessel injury, and the activation of leukocytes or platelets. PLA participate in cardiovascular diseases (CVD). Increased levels of PLA were revealed in acute and chronic coronary syndromes, carotid stenosis cardiovascular risk factors. Due to accessible, available, replicable, quick, and low-cost quantifying using flow cytometry, PLA constitute an ideal biomarker for clinical practice. PLA are promising in early diagnosing and estimating prognosis in patients with acute or chronic coronary syndromes treated by percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG). PLA were also a reliable marker of platelet activity for monitoring antiplatelet therapy. PLA consist also targets potential therapies in CVD. All of the above potential clinical applications require further studies to validate methods of assay and proof clinical benefits.

Soluble CD40 Levels in Plasma Are Associated with Cardiovascular Disease and in Carotid Plaques with a Vulnerable Phenotype

BACKGROUND AND PURPOSE

CD40 and CD40 ligand (CD40L) are costimulatory molecules of the tumor necrosis factor receptor superfamily and well known for their involvement in inflammatory diseases: atherosclerotic mouse models with disrupted CD40 signalling develop lesions of reduced size with a more stable plaque profile. This study investigated the potential of plasma and intraplaque levels of CD40 and CD40L as markers for cardiovascular disease (CVD) in humans and their association with plaque stability.

METHODS

Soluble CD40 and CD40L (sCD40L) were measured in plasma in 1,437 subjects from The SUrrogate markers for Micro- and Macro-vascular hard endpoints for Innovative diabetes Tools (SUMMIT) cohort. Intra-plaque levels of sCD40 and sCD40L were measured in atherosclerotic plaque homogenates from 199 subjects of the Carotid Plaque Imaging Project (CPIP) cohort.

RESULTS

Both plasma sCD40 and sCD40L levels were elevated in individuals with prevalent stroke, while sCD40 levels also were higher in individuals with a prior acute myocardial infarction. Plasma levels of sCD40 correlated with carotid intima-media thickness and total carotid plaque area and were associated with risk of cardiovascular events over a 3-year follow-up period. Intra-plaque levels of sCD40 and sCD40L were associated with plaque components characteristic for plaque vulnerability and extracellular matrix remodelling.

CONCLUSIONS

Higher plasma sCD40 and sCD40L levels are associated with prevalent CVD. Plasma sCD40 levels also correlate with the severity of carotid atherosclerosis and predict future cardiovascular events, while intra-plaque levels correlate with a vulnerable plaque phenotype. Our findings thus demonstrate that elevated levels of sCD40 and sCD40L are markers of CVD.

Targeting Platelet in Atherosclerosis Plaque Formation: Current Knowledge and Future Perspectives

Besides their role in hemostasis and thrombosis, it has become increasingly clear that platelets are also involved in many other pathological processes of the vascular system, such as atherosclerotic plaque formation. Atherosclerosis is a chronic vascular inflammatory disease, which preferentially develops at sites under disturbed blood flow with low speeds and chaotic directions. Hyperglycemia, hyperlipidemia, and hypertension are all risk factors for atherosclerosis. When the vascular microenvironment changes, platelets can respond quickly to interact with endothelial cells and leukocytes, participating in atherosclerosis. This review discusses the important roles of platelets in the plaque formation under pro-atherogenic factors. Specifically, we discussed the platelet behaviors under disturbed flow, hyperglycemia, and hyperlipidemia conditions. We also summarized the molecular mechanisms involved in vascular inflammation during atherogenesis based on platelet receptors and secretion of inflammatory factors. Finally, we highlighted the studies of platelet migration in atherogenesis. In general, we elaborated an atherogenic role of platelets and the aspects that should be further studied in the future.

Effect of platelet count on long-term prognosis of cerebral infarction

OBJECTIVE

This study aimed to analyze the correlation between platelet (PLT) count and the modified Rankin scale (mRS) in patients with cerebral infarction (CI) at the later stage of rehabilitation, which can be used to guide the secondary prevention strategy of CI.

METHODS

A total of 180 CI patients were divided into three groups according to PLT count: low PLT group (<125×109/L), medium PLT group (126- 225×109/L) and high PLT group (>226×109/L). The mRS was evaluated after three months and one year, respectively, and the difference in long-term prognosis between groups was analyzed. The mRS is an ordered scale coded from 0 (no symptoms at all) through 5 (severe disability) 6 (death).

RESULTS

Finally, a total of 99 patients had complete data. The results of the multiple comparisons among the three groups were as follows: the analysis of variance of the mRS at three months after onset yielded F = 6.714 and P = 0.002, and the difference was statistically significant. The mRS was lowest in the medium PLT group (2.09±1.465), and neurological function recovery was the best. After one year, the mRS for the medium PLT group was the lowest (1.49±1.523), with F = 6.860 and P = 0.002. The repeated measures analysis of variance revealed that the effect of continuous rehabilitation was significant in the interval from three months to one year after onset (F = 35.528, P < 0.001). This was very significant, especially for patients taking aspirin (F = 50.908, P < 0.001). However, for patients who did not take aspirin, the effect of continuous rehabilitation was not obvious during the nine months, and the difference between the results of two mRS measurements was not statistically significant (F = 1.089, P = 0.308).

CONCLUSIONS

Patients with a PLT count of 126- 225×109/L had the lowest mRS between three months and one year after onset, but had the best recovery of nerve function. Patients who persisted in taking aspirin continued to significantly recover during the 9-month period, from three months to one year after onset. Aspirin is not only a secondary preventive drug, but also an important drug to promote the rehabilitation of CI patients.

Modulators of platelet function in aging

Platelets are small, anucleated effector cells that play an important role in linking the hemostatic and inflammatory processes in the body. Platelet function is known to be altered under various inflammatory conditions including aging. A gain in platelet function during aging can increase the risk of thrombotic events, such as stroke and acute myocardial infarction. Anti-platelet therapy is designed to reduce risk of serious cerebrovascular and cardiovascular events, but the adverse consequences of therapy, such as risk for bleeding increases with aging as well. Age-associated comorbidities such as obesity, diabetes, and hyperlipidemia also contribute to increased platelet activity and thus can enhance the risk of thrombosis. Therefore, identification of unique mechanisms of platelet dysfunction in aging and in age-associated comorbidities is warranted to design novel antiplatelet drugs. This review outlines some of the current areas of research on aging-related mechanisms of platelet hyperactivity and addresses the clinical urgency for designing anti-platelet therapies toward novel molecular targets in the aging population.

Nonsurviving Patients with Severe Traumatic Brain Injury Have Maintained High Serum sCD40L Levels

BACKGROUND

Soluble cluster of differentiation 40 ligand (sCD40L) is a member of the tumor necrosis factor family with proinflamatory and procoagulant effects. A previous study found higher serum sCD40L levels at day 1 of traumatic brain injury (TBI) in nonsurviving than surviving patients. Thus the objective of this study was to compare serum sCD40L levels during the first week of a severe TBI between surviving and nonsurviving patients and to determine whether it could be used as a mortality predictor biomarker.

METHODS

In this multicenter study severe TBI patients (with Glasgow Coma Scale score <9) with an Injury Severity Score in noncranial item <9 were included. Serum sCD40L concentrations at days 1, 4, and 8 of TBI were determined. We performed receiver operating characteristic analyses to determine the capacity of 30-day TBI mortality prediction by serum sCD40L levels at days 1, 4, and 8 of TBI.

RESULTS

We found that nonsurviving (n = 34) patients in comparison with surviving (n = 90) patients had higher sCD40L levels on days 1 (P < 0.001), 4 (P = 0.004), and 8 (P < 0.001) of TBI. We also found that the areas under curve of serum sCD40L concentrations at days 1, 4, and 8 of TBI to 30-day mortality prediction were 82% (P < 0.001), 72% (P = 0.01) and 83% (P < 0.001), respectively.

CONCLUSIONS

The existence of higher serum sCD40L levels in nonsurviving than surviving patients during the first week of TBI and fact that serum sCD40L levels during the first week of TBI can be used as a mortality predictor biomarker are the new findings of our study.

Reactive leptin resistance and the profile of platelet activation in acute ischaemic stroke patients

Summary

Leptin is an adipokine that in vitro enhances agonist-induced platelet aggregation and adipokine expression. Hyperleptinaemia represents a risk factor for cardiovascular disease. We conducted a prospective evaluation of the potential link between blood platelet activation and plasma leptin levels in post-stroke patients. Using five-colour flow cyto-metry, the platelet surface expression of CD40L, CD62P, the subpopulations of monocyte-platelet aggregates and platelet-derived microparticles (PMPs) as well as the plasma leptin, soluble leptin receptor (sOb-R), leptin/sOb-R ratio, the plasma adiponectin, and leptin/adiponectin ratio were assessed in 98 stroke patients on the first (V0), 10th (V1) and 90th (V2) day after stroke and once in 78 age-, gender- and vascular risk factor-matched disease controls. We demonstrated that at V0 leptin resistance, defined as leptin/sOb-R ratio, was higher than in the controls [1.1 (0.5–1.8 vs. 0.5 (0.2–1.1); p=0.02]. After adjustment according to the factors which influence platelet activation, we confirmed the relationship between percentage of circulating PMPs and plasma leptin level (B=0.18; p=0.02) or the leptin/sOb-R ratio (B=0.23; p=0.02) in normal-weight subjects in the acute phase of stroke. No correlation could be demonstrated between the adipokine parameters and the percentage of monocyte-platelet aggregates or expression of platelet pro-inflammatory glycoproteins. In conclusion, formation of PMPs on the first day following an ischaemic stroke shows a positive correlation with leptin levels and with resistance to leptin. Leptin level does not seem to affect the expression of platelet surface proinflammatory glycoproteins.

Short-term intensive training attenuates the exercise-induced interaction of mono-1/2 cells and platelets after coronary bypass in cardiac patients

The interaction between platelets and monocytes plays a critical role in the pathogenesis and progression of cardiovascular diseases. This study investigated how short-term intensive training (SIT) influences monocyte subset characteristics and exercise-induced monocyte and platelet aggregates (MPAs) following elective coronary bypass (CABG) in cardiac patients. Forty-nine patients hospitalised for CABG were randomised into SIT (N=26) and conventional training (CT, N=23) groups. The SIT subjects underwent supervised aerobic training at 80~120 % of the ventilatory anaerobic threshold based on sub-maximal exercise tests performed 7 days post-CABG for 20 sessions with two sessions/day and 30 min/session, which were completed within four weeks after surgery. The CT subjects performed light-intensity conditioning exercise for ≤4 sessions. Resting and maximal exercise-mediated monocyte characteristics and MPA were determined before and following intervention. The SIT group had a larger improvement in ventilation efficiency and anaerobic threshold than the CT group; the SIT group exhibited larger reductions in blood monocyte subtypes 1 and 2 (Mono1 and 2) counts at rest than the CT group; the SIT group but not the CT group exhibited attenuated formation of Mono1/platelet hetero-aggregation (MPA1) and CD42b expression on Mono1/2 caused by strenuous exercise; and plasma levels of macrophage inflammatory protein-1β and soluble P-selectin showed similar trends as Mono1/2 and MPA1, respectively. In conclusion, SIT modestly improved aerobic capacity in patients following CABG. Moreover, SIT simultaneously ameliorated the CD42b expression of Mono1/2 cells and maximal exercise-induced MPA1, which may reduce the risk of inflammatory thrombosis.

Comparison of diverse platelet activation markers as indicators for left atrial thrombus in atrial fibrillation

Atrial fibrillation (AF) is well known for being a major risk factor of thromboembolic stroke. We could recently demonstrate an association of monocyte-platelet aggregates (MPAs) with the degree of thrombogenicity in patients with AF. This study investigated platelet activation markers, as potential biomarkers for the presence of left atrial (LA) thrombus in patients with AF. One hundred and eight patients with symptomatic AF underwent transesophageal echocardiography (TEE) before scheduled cardioversion or pulmonary vein isolation. In order to determine the content of MPAs by flow-cytometric quantification analyses, blood was drawn on the day of TEE. The soluble CD40 Ligand (sCD40L) and soluble P-selectin (sP-selectin) were obtained by Cytometric Bead Arrays (CBA). D-dimer levels were detected by quantitative immunological determination of fibrin degradation products. Clinical, laboratory, and echocardiographic standard parameters were obtained from all patients, including the determination of the flow in the left atrial appendage (LAA). Patients with detected LA thrombus (n = 28) compared with patients without thrombus (n = 80) showed an increased number of common risk factors, such as age, diabetes, heart failure, and coronary artery disease (CAD). The presence of LA thrombus was associated with significantly increased levels of MPAs (147 ± 12 vs. 304 ± 29 per µl; p < 0.00), sCD40L (106.3 ± 31.0 vs. 33.5 ± 2.1 pg/ml, p = 0.027), and D-dimer (0.13 ± 0.02 vs. 0.69 ± 0.21 mg FEU/l, p = 0.015). In contrast, sP-selectin showed no association with LA thrombus. A multivariate regression analysis showed that MPAs, sCD40L as well as D-dimers were independent indicators for the existence of LA thrombus. MPAs above 170 cells/µl indicated LA thrombus with a high sensitivity of 93% and a specificity of 73% (OR 62, 95% CI. 6.9-557.2, p < 0.001) in patients with AF, whereas the D-dimer lost their quality as independent indicator by using the conventional cut-off of 0.5 mg/l within the regression analysis. MPAs, as well as the D-dimer, correlated significantly negatively with the flow in the LAA measured during TEE. The content of MPAs, sCD40L, and D-dimer, but not sP-selectin showed an increased dependence on LA thrombus in patients with AF. In our study group, MPAs showed the best diagnostic test accuracy of the compared platelet markers. The different results of the examined platelet activation markers could be an indication of diverse mechanisms of LA thrombus in AF. Further studies should evaluate whether determination of MPAs in clinical routine may suffice to indicate the presence of LA thrombus in patients with AF.

Association of platelet activation markers with recurrence of atrial fibrillation after pulmonary vein isolation

Atrial fibrillation (AF) is known to cause platelet activation. AF and its degree of thrombogenesis could be associated with monocyte-platelet aggregates (MPAs). We investigated on whether the content of MPAs or other platelet activation markers is associated with the recurrence of AF after pulmonary vein isolation (PVI). A total of 73 patients with symptomatic AF underwent PVI. After 6 months, all patients were evaluated for episodes of AF recurrence. At the same time, flow-cytometric quantification analyses were performed to determine the content of MPAs. Further platelet activation parameters were detected by using either cytometric bead arrays or quantitative immunological determination. Patients with recurrent AF (n = 20) compared to individuals without AF relapse (n = 53) were associated with an increased content of MPAs (43 ± 3% vs. 33 ± 2%, p = 0.004), as well as an increased CD41 expression on monocytes (191 ± 20 vs. 113 ± 6, p = 0.001). The level of the soluble platelet activation markers such as D-dimer, sCD40L, and sP-selectin did not differ between these groups. The content of MPAs correlated weakly with the level of sCD40L (r = 0.26, p = 0.03), but not with sP-selectin and D-dimer, whereas sP-selectin and sCD40L correlated with each other (r = 0.38, p = 0.001). Only the cellular marker of platelet activation, the content of MPAs, was increased in patients with recurrent AF after PVI. In contrast, soluble markers remained unaltered. These data indicate a distinct mechanism and level of platelet activation in AF. The clinical relevance of MPAs in identifying AF recurrence or in guiding the therapy with anticoagulants remains to be elucidated.

The Antiplatelet Effect of Clopidogrel Decreases With Patient Age

Recent data suggest that clopidogrel-mediated platelet inhibition is age dependent. However, so far the effect of age on adenosine diphosphate (ADP)-inducible platelet reactivity has only been investigated by test systems measuring surrogate markers of platelet aggregation. We therefore sought to study the impact of age on platelet inhibition by clopidogrel by whole-blood flow cytometry. Platelet surface P-selectin expression, activated glycoprotein (GP) IIb/IIIa, and monocyte-platelet aggregate (MPA) formation were determined by flow cytometry in 302 patients with dual antiplatelet therapy after successful angioplasty and stenting. Patient age was independently associated with ADP-inducible P-selectin expression, GPIIb/IIIa, and MPA formation (all P < .05). Moreover, platelet surface expressions of P-selectin and activated GPIIb/IIIa were significantly higher in patients ≥75 years compared with younger patients (both P ≤ .004). Likewise, MPA formation was significantly more pronounced in patients ≥75 years ( P = .02). Finally, high P-selectin and high GPIIb/IIIa were significantly more frequent in patients ≥75 years compared with younger patients (both P < .001). Further, high MPA ADP occurred more frequently in patients ≥75 years compared to younger patients ( P < .05). In conclusion, the antiplatelet effect of clopidogrel decreases with patient age.

Platelet CD40 Exacerbates Atherosclerosis by Transcellular Activation of Endothelial Cells and Leukocytes

OBJECTIVE

Beyond their eminent role in hemostasis and thrombosis, platelets are recognized as mediators of inflammation. Platelet cluster of differentiation 40 (CD40) ligand (CD40L and CD154) plays a key role in mediating platelet-induced inflammation in atherosclerosis. CD40, the receptor for CD40L, is present on platelets; however, the role of CD40 on this cell type is until now undefined.

APPROACH AND RESULTS

We found that in both mice and humans, platelet CD40 mediates the formation of platelet-leukocyte aggregates and the release of chemokine (C-X-C motif) ligand 4. Leukocytes were also less prone to adhere to CD40-deficient thrombi. However, platelet CD40 was not involved in platelet aggregation. Activated platelets isolated from Cd40(-/-)Apoe(-/-) mice adhered less to the endothelium upon injection into Apoe(-/-) mice when compared with CD40-sufficient platelets. Furthermore, lack of CD40 on injected platelets led to reduced leukocyte recruitment to the carotid artery as assayed by intravital microscopy. This was accompanied by a decrease in endothelial vascular cell adhesion molecule-1, platelet endothelial cell adhesion molecule, VE-cadherin, and P-selectin expression. To investigate the effect of platelet CD40 in atherosclerosis, Apoe(-/-) mice received thrombin-activated Apoe(-/-) or Cd40(-/-)Apoe(-/-) platelets every 5 days for 12 weeks, starting at the age of 17 weeks, when atherosclerotic plaques had already formed. When compared with mice that received Apoe(-/-) platelets, those receiving Cd40(-/-)Apoe(-/-) platelets exhibited a >2-fold reduction in atherosclerosis. Plaques of mice receiving CD40-deficient platelets were less advanced, contained less macrophages, neutrophils, and collagen, and displayed smaller lipid cores.

CONCLUSIONS

Platelet CD40 plays a crucial role in inflammation by stimulating leukocyte activation and recruitment and activation of endothelial cells, thereby promoting atherosclerosis.

Atrial fibrillation is associated with high levels of monocyte-platelet-aggregates and increased CD11b expression in patients with aortic stenosis

A growing body of evidence suggests a pivotal role of inflammatory processes in AF in a bidirectional manner. Infiltrating leukocytes seem to promote both structural and electrical remodelling processes in patients with AF. Monocyte-platelets-aggregates (MPAs) are sensitive markers of both platelets and monocyte activation. So far it is not clear whether the content of MPAs is affected by AF. The present study examined the content of MPAs and the activation of monocytes in elderly patients with an aortic stenosis in dependence of AF. These patients are known to have a high prevalence of AF. Flow-cytometric quantification analysis demonstrated that patients with AF have an increased content of MPAs (207 ± 13 cells/µl vs 307 ± 21 cells/µl, p< 0.001), and enhanced expression of CD11b on monocytes (p< 0.001), compared to patients in stable sinus rhythm (SR). The number of CD14+/CD16+ monocytes were only slightly elevated in patients with AF. These findings were seen in patients with permanent AF. But also patients with paroxysmal AF, even when presenting in SR, the MPAs were increased by 50 % (p< 0.05) as well as the CD11b expression, which was twice as high (p< 0.05) compared to stable SR. These results demonstrate for the first time a dependency of MPAs and CD11b expression on monocytes in the presence of AF and support the notion of a close relationship between AF, thrombogenesis and inflammation. The content of MPAs and the extent of activation on monocytes appear promising as biomarkers for paroxysmal AF and as possible future targets for developing novel pharmacological therapeutic strategies.

Monocyte-platelet aggregates and CD11b expression as markers for thrombogenicity in atrial fibrillation

BACKGROUND

A strong interdependence is known between atrial fibrillation (AF), inflammation and thrombogenesis. Monocyte-platelet aggregates (MPAs) are sensitive markers of platelets and monocyte activation. It is not known whether MPAs are associated with thrombogenicity in AF. Therefore, we examined differences in the content of MPAs and CD11b expression in patients with AF in dependence of the presence of atrial thrombus formation.

METHODS

107 patients with symptomatic AF underwent transesophageal echocardiography (TEE) before planned cardioversion or pulmonary vein isolation. Flow-cytometric quantification analysis was done on the day of performed TEE to determine the content of MPAs and the expression of CD11b on monocytes and granulocytes.

RESULTS

Compared to patients without thrombus (n = 80) those with an echocardiographic proven left atrium (LA) thrombus (n = 27) showed an increased extent of the risk factors age, diabetes and heart failure. The content of MPAs (147 ± 12 vs. 311 ± 29 cells/µl, p < 0.001) as well as the CD11b expression on monocytes (p < 0.05) and granulocytes (p < 0.05) were strongly associated with the existence of a LA thrombus. The content of MPAs and the CD11b expression remained independent predictors for LA thrombus after adjustment in logistic regression analysis and negatively correlated with left atrial appendage flow velocity. MPAs above 170 cells/µl (OR 34.2, p = 0.01) had a sensitivity of 96 % and a specificity of 73 % for predicting LA-thrombus.

CONCLUSIONS

The content of MPAs and the CD11b expression on monocytes and granulocytes are increased in AF-patients with proven thrombus formation. They seem to be appropriate biomarkers for stratification of thromboembolic risk in patients with AF.

Monocyte subsets and monocyte-platelet aggregates in patients with unstable angina

Monocyte subsets and monocyte-platelet aggregates (MPAs) play important role in atherosclerosis and thrombosis. We aimed to determine their changes in patients with unstable angina (UA). In this cross-sectional case-control study, Global Registry of Acute Coronary Events (GRACE) score was determined in 95 UA patients without elevated troponin level. Thirty age-and-sex matched stable coronary heart disease (CHD) subjects served as control group. The classical (CD14++CD16-, Mon1), the intermediate (CD14++CD16+, Mon2) and the non-classical (CD14+CD16++, Mon3) monocytes, as well as subset-specific MPAs, were measured by flow cytometry. Compared with stable CHD patients, UA patients had increased Mon2 and Mon3 counts (all P < 0.001). For UA subjects, compared with GRACE score-determined low risk patients (GRACE score ≤108, n = 70), intermediate-to-high risk patients (GRACE score >108, n = 25) had higher counts of Mon2 and total MPAs, as well as Mon1- and Mon2-associated MPAs (all P < 0.001). Adjusted binary logistic regression analysis revealed that increased counts of Mon2 subset (for per 5 cells/μL increase, OR 1.186, 95% CI 1.044-1.347, P = 0.009), Mon2 MPAs (for per 5 cells/μL increase, OR 1.228, 95% CI 1.062-1.421, P = 0.006) and total MPAs (for per 5 cells/μL increase, OR 1.072, 95 % CI 1.010-1.137, P = 0.022) independently associated with GRACE score-determined intermediate-to-high risk UA patients. In UA patients with intermediate-to-high risk (determined by GRACE score), counts of Mon2 subset, Mon2-associated MPAs and total MPAs are increased, which are independent of traditional risk factors.

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.

Association between Serum Soluble CD154 Levels and Mortality in Patients with Malignant Middle Cerebral Artery Infarction

Background: CD154 and its soluble counterpart (sCD154) are proteins of the tumor necrosis factor (TNF) family and exhibit proinflamatory and procoagulant properties. Higher circulating sCD154 levels have been found in ischemic stroke patients than in controls. However, the association between circulating sCD154 levels and mortality in ischemic stroke patients has not been reported, and was the focus of this study. Methods: This was a multicenter, observational and prospective study carried out in six Spanish Intensive Care Units. We measured serum sCD154 from 50 patients with severe malignant middle cerebral artery infarction (MMCAI), defined as Glasgow Coma Scale (GCS) lower than 9, at the moment of the severe MMCAI diagnosis and from 50 healthy controls. The end-point of the study was 30-day mortality. Results: We found higher serum sCD154 levels in patients with severe MMCAI than in healthy controls (p < 0.001). We found higher serum sCD154 levels (p < 0.001) in non-surviving (n = 26) than in surviving MMCAI patients (n = 24). Multiple binomial logistic regression analysis showed that serum sCD154 levels >1.41 ng/mmL were associated with 30-day mortality (OR = 10.25; 95% CI = 2.34–44.95; p = 0.002). Conclusions: The new more important finding of our study was that serum sCD154 levels in MMCAI patients were associated with mortality.

Platelet-monocyte aggregate formation and mortality risk in older patients with severe sepsis and septic shock

BACKGROUND

Aging-related changes in platelet and monocyte interactions may contribute to adverse outcomes in sepsis but remain relatively unexamined. We hypothesized that differential platelet-monocyte aggregate (PMA) formation in older septic patients alters inflammatory responses and mortality.

METHODS

We prospectively studied 113 septic adults admitted to the intensive care unit with severe sepsis or septic shock. Patients were dichotomized a priori into one of two groups: older (age ≥ 65 years, n = 28) and younger (age < 65 years, n = 85). PMA levels were measured in whole blood via flow cytometry within 24 hours of admission. Plasma levels of IL-6 and IL-8, proinflammatory cytokines produced by monocytes upon PMA formation, were determined by commercial assays. Patients were followed for the primary outcome of 28-day, all-cause mortality.

RESULTS

Elevated PMA levels were associated with an increased risk of mortality in older septic patients (hazard ratio for mortality 5.64, 95% confidence interval 0.64-49.61). This association remained after adjusting for potential confounding variables in multivariate regression. Receiver operating curve analyses demonstrated that PMA levels greater than or equal to 8.43% best predicted 28-day mortality in older septic patients (area under the receiver operating curve 0.82). Plasma IL-6 and IL-8 levels were also significantly higher in older nonsurvivors. In younger patients, neither PMA levels nor plasma monokines were significantly associated with mortality.

CONCLUSIONS

Increased PMA formation, and associated proinflammatory monokine synthesis, predicts mortality in older septic patients. Although larger studies are needed, our findings suggest that heightened PMA formation in older septic patients may contribute to injurious inflammatory responses and an increased risk of mortality.

Alterations in platelet function during aging: clinical correlations with thromboinflammatory disease in older adults

Platelets have a dynamic functional repertoire that mediates hemostatic and inflammatory responses. Many of these functions are altered in older adults, promoting a prothrombotic, proinflammatory milieu and contributing to risk of adverse clinical events. Drawing primarily from human studies, this review summarizes important aspects of aging-related changes in platelets. The relationship between altered platelet functions and thrombotic and inflammatory disorders in older adults is highlighted. Established and developing antiplatelet therapies for the treatment of thrombotic and inflammatory disorders are also discussed in light of these data.

Female sex as an independent risk factor for stroke in atrial fibrillation: possible mechanisms

Atrial fibrillation (AF) is an independent risk factor for thromboembolism and stroke. Women with AF are at a higher overall risk for thromboembolic stroke when compared to men with AF. Recent evidence suggests that female sex, after adjusting for stroke risk profile and sex differences in utilisation of anticoagulation, is an independent stroke risk factor in AF. The inclusion of female sex has improved the accuracy of the CHADS2 stroke risk stratification schema (Congestive heart failure, Hypertension, Age 75 years or greater, Diabetes mellitus, and prior Stroke or TIA). The newly revised and validated schema, CHA2DS2-VASc, dichotomises age and incorporates female sex and vascular disease history. The pathophysiological mechanisms to explain this increased risk in women are not well understood. According to Virchow's triad, thrombosis that leads to stroke in AF should arise from three co-existing phenomena: structural abnormalities, blood stasis, and a hypercoagulable state. Herein, we explore the sex differences in the biological processes that lead to thrombus formation as applied to Virchow's Triad. The objective of this review is to describe the potential mechanisms behind the increased risk of stroke in AF associated with female sex.

Newly diagnosed depression is associated with increased beta-thromboglobulin levels and increased expression of platelet activation markers and platelet derived CD40-CD40L

BACKGROUND

Inflammation plays a key role in atherosclerotic disease. Up until now only limited evidence exists on the mechanism of cardiovascular complications in patients with depression. In addition depression was also linked to an increase in cardiovascular mortality. The present study was designed to evaluate the extent of platelet activation and platelet-derived markers of atherosclerotic disease in patients with newly diagnosed depression.

METHODS

This study used whole blood aggregometry, flow cytometry and ELISA to investigate platelet CD62P (P-selectin) expression and atherosclerotic markers (CD40, CD40L) as well as serum platelet factor 4 (PF-4) and beta-thromboglobulin (β-TG) levels in 46 participants. Patients with newly diagnosed, but not yet medically treated depression (n = 21) were compared to healthy control patients.

RESULTS

The platelet activation marker CD62P was significantly higher in patients with depression (2.62% depression versus 1.27% controls; p = 0.006). Further we found basal CD40 (6.7% vs. 4.8%; p = 0.002) and basal CD40L (31.0% vs. 22.0%; p = 0.025) to be elevated in patients with depression as compared to control persons. In addition sCD40L (52.7 vs. 44.4 ng/ml; p = 0.023) and β-TG differed significantly in depressed patients (206.9 vs. 182.8 ng/ml; p = 0.001). However, basal CD41 (97.0% vs. 96.3%; p = 0.57), CD42b (96.7% vs. 94.7%; p = 0.28) and PF-4 (89.61 vs. 81.75 IU/ml; p = 0.10) and the aggregometry results did not differ significantly between the study groups.

CONCLUSIONS

Our findings with elevated CD40 and CD40L as well as CD62P and β-TG in newly diagnosed patients emphasize that depression is linked to a prothrombotic and proinflammatory state and this possibly contributes to accelerated atherosclerosis.

Variation in dietary salt intake induces coordinated dynamics of monocyte subsets and monocyte-platelet aggregates in humans: implications in end organ inflammation

BACKGROUND

Monocyte activation and tissue infiltration are quantitatively associated with high-salt intake induced target organ inflammation. We hypothesized that high-salt challenge would induce the expansion of CD14++CD16+ monocytes, one of the three monocyte subsets with a pro-inflammatory phenotype, that is associated with target organ inflammation in humans.

METHODOLOGY/PRINCIPAL FINDINGS

A dietary intervention study was performed in 20 healthy volunteers, starting with a 3-day usual diet and followed with a 7-day high-salt diet (≥15 g NaCl/day), and a 7-day low-salt diet (≤5 g NaCl/day). The amounts of three monocyte subsets ("classical" CD14++CD16-, "intermediate" CD14++CD16+ and "non-classical" CD14+CD16++) and their associations with monocyte-platelet aggregates (MPAs) were measured by flow cytometry. Blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) was used to evaluate renal hypoxia. Switching to a high-salt diet resulted in CD14++ monocyte activation and a rapid expansion of CD14++CD16+ subset and MPAs, with a reciprocal decrease in the percentages of CD14++CD16- and CD14+CD16++ subsets. In vitro study using purified CD14++ monocytes revealed that elevation in extracellular [Na(+)] could lead to CD14++CD16+ expansion via a ROS dependent manner. In addition, high-salt intake was associated with progressive hypoxia in the renal medulla (increased R2* signal) and enhanced urinary monocyte chemoattractant protein-1 (MCP-1) excretion, indicating a temporal and spatial correlation between CD14++CD16+ subset and renal inflammation. The above changes could be completely reversed by a low-salt diet, whereas blood pressure levels remained unchanged during dietary intervention.

CONCLUSIONS/SIGNIFICANCE

The present work demonstrates that short-term increases in dietary salt intake could induce the expansion of CD14++CD16+ monocytes, as well as an elevation of MPAs, which might be the underlying cellular basis of high-salt induced end organ inflammation and potential thromboembolic risk. In addition, this process seems largely unrelated to changes in blood pressure levels. This finding provides novel links between dietary salt intake, innate immunity and end organ inflammation.

Increased Formation of Monocyte-Platelet Aggregates in Ischemic Heart Failure

Background—

Cross-talk between monocytes and platelets is reflected by the formation of monocyte-platelet aggregates (MPAs). It is not known whether MPAs are affected in heart failure (HF), and we examined differences in patients with acute HF (AHF), stable HF (SHF), stable coronary artery disease (CAD) without HF, and healthy controls (HCs).

Methods and Results—

MPAs were analyzed by flow cytometry for the 3 monocyte subsets (CD14++CD16-CCR2+ [Mon1], CD14++CD16+CCR2+ [Mon2] and CD14+CD16++CCR2– [Mon3]) in patients with AHF (n=51), SHF (n=42), stable CAD (n=44), and HCs (n=40). Counts of total MPA and MPAs associated with Mon1 and Mon2 were significantly higher in AHF compared with SHF, CAD, and HCs ( P <0.001 for all). The proportion of Mon1 aggregated with platelets was increased in AHF compared with SHF ( P =0.033), CAD ( P <0.001), and HCs ( P <0.001). A higher percentage of Mon3 aggregated with platelets was also seen in AHF compared with SHF ( P =0.012) and HCs ( P <0.001) but not compared with CAD ( P =0.647). MPAs associated with Mon2 were significantly lower in patients who experienced adverse clinical outcomes of death or rehospitalization compared with those who remained free of events ( P =0.03). Mon2 count remained an independent negative predictor of combined death and rehospitalization after adjustment for age, left ventricular ejection fraction, creatinine, and brain natriuretic peptide (hazard ratio, 0.58 [95% CI, 0.34–0.98]; P =0.043).

Conclusions—

MPA formation in patients with both acute and stable HF is increased and seems to be confined to monocytes from Mon1 and Mon2 subsets. MPAs associated with Mon2 seem to be negatively predictive of a worse prognosis in AHF.