Silvia Riondino

Persistent production of platelet thromboxane A2 in patients chronically treated with aspirin.

Summary.  Background: Patients treated with aspirin may have a reduced sensitivity to its antiplatelet effect. The mechanism accounting for such a reduced sensitivity might involve an impaired interaction of aspirin with cyclooxygenase‐1 (COX)‐1. Objective: We sought to investigate whether platelets from patients under chronic treatment with aspirin still produce TxA2 and whether there is any relationship between the eventual persistent TxA2 formation and platelet aggregation. Finally, whether platelet‐derived TxA2 can be inhibited by in vitro addition of aspirin. Methods: Collagen‐induced platelet aggregation and thromboxane‐A2 (TxA2) were measured in 196 patients treated with aspirin (100–330 mg day−1) because of previous vascular events or presence of risk factors of atherosclerosis. Results: Collagen‐induced TxA2 production of the entire cohort was 128.7 ± 21.6 pg 10−8 cells, and was significantly correlated with platelet aggregation (Spearmans correlation coefficient = 0.44; P < 0.0001). Patients in the highest quartile of TxA2 showed higher platelet response to collagen (P < 0.0001) when compared with those in the lowest quartile. In a subgroup of 96 patients, platelets were treated in vitro with a TxA2 receptor antagonist (13‐azaprostanoic acid) or aspirin before stimulation with collagen. 13‐APA acid significantly inhibited platelet aggregation. Aspirin reduced (−72.9%) TxA2 production in patients with TxA2 values above the median but it was ineffective in those with TxA2 values below the median. Conclusion: In some patients chronically treated with aspirin platelet production of TxA2 may persist and account for enhanced platelet aggregation. Incomplete inhibition of COX‐1 seems to be implicated in persistent TxA2 production.

Biomarkers of platelet activation in acute coronary syndromes

The most convincing evidence for the participation of platelets in arterial thrombosis in humans comes from studies of platelet activation in patients with acute coronary syndromes (ACS) and from trials of antiplatelet drugs. Both strongly support the concept that repeated episodes of platelet activation over the thrombogenic surface of a vulnerable plaque may contribute to the risk of death from coronary causes. However, the relation of in vivo platelet activation and adverse clinical events to results of platelet function tests remains largely unknown. A valuable marker of in vivo platelet activation should be specific, unaltered by pre-analytical artefacts and reproducibly measured by easily performed methods. This article describes current biomarkers of platelet activation in ACS, reviews their advantages and disadvantages, discusses their potential pitfalls, and demonstrates emerging data supporting the positive clinical implications of monitoring in vivo platelet activation in the setting of ACS.

Soluble P-selectin as a marker of in vivo platelet activation.

BACKGROUND Platelets are the major source of circulating sP-selectin. Elevated levels of this protein have been found in many atherothrombotic disorders. Thus, we investigated whether sP-selectin dosage might reflect platelet function in patients with risk factors for or with established cardiovascular diseases and whether its levels can be modulated by aspirin therapy. METHODS Plasma sP-selectin levels and light transmission platelet aggregometry (LTA) were analyzed in 152 outpatients. The effects of a 6-month aspirin therapeutic course on sP-selectin levels and LTA in 51 consecutive patients have been also investigated. RESULTS Significant correlations were observed between sP-selectin and Mx% LTA in response to epinephrine (p=0.022) and arachidonic acid (p=0.006), or between sP-selectin and collagen lag-phase (p=0.016). Multiple regression analysis showed that the only predictors of sP-selectin levels were platelet number (p<0.001) and collagen-induced lag-phase (p<0.01). Aspirin-treated patients showed a significant reduction of sP-selectin levels by 13% (p=0.021) which significantly correlated with collagen-induced lag-phase (p=0.005). CONCLUSIONS sP-selectin dosage could be proposed as a reliable marker of platelet activation in patients with major atherosclerotic risk factors either in the absence of clinically overt disease, and might represent a valid tool to asses in vivo platelet behavior.

Plasma levels of thromboxane A2 on admission are associated with no-reflow after primary percutaneous coronary intervention

AIMS Thromboxane A2 (TXA2) is a key mediator of platelet activation and aggregation, and an important mediator of platelet-induced coronary artery constriction. We sought to investigate whether baseline plasma levels of TXA2 are associated with coronary no-reflow after primary percutaneous coronary intervention (PPCI). METHODS AND RESULTS A total of 47 consecutive patients (age, 62.5 +/- 12.7; male sex, 76.6%) admitted to our hospital for a first ST-segment elevation myocardial infarction and undergoing PPCI within 12 h of onset of symptoms were enrolled. Admission TXA2 plasma levels were measured by enzyme-linked immunosorbent assay (ELISA). Angiographic no-reflow was defined as a final TIMI flow of <or=2 or final TIMI flow of 3 with a myocardial blush grade of <2, whereas ST-segment resolution from baseline value of <or=50% was used as ECG index of no-reflow. At multivariable analysis TXA2 plasma levels, endothelin-1 (ET-1) plasma levels, and left anterior descending coronary artery (LAD) as culprit vessel were significant predictors of angiographic no-reflow (P = 0.04), whereas TXA2 and ET-1 plasma levels were the only independent predictors of lack of ST-segment resolution (P = 0.013 and 0.04, respectively). Of note, TXA2 tertiles were independent predictors of both angiographic no-reflow and lack of ST-segment resolution (OR, 3.5; 95% CI, 1.1-11; P = 0.03 and OR, 3; 95% CI, 1.3-7; P = 0.01, respectively). CONCLUSION TXA2 is an independent indicator of no-reflow that occurs after PPCI. This observation may open new therapeutic opportunity in the setting of PPCI.

Platelet function in health and disease: From molecular mechanisms, redox considerations to novel therapeutic opportunities

Increased oxidative stress appears to be of fundamental importance in the pathogenesis and development of several disease processes. Indeed, it is well known that reactive oxygen species (ROS) exert critical regulatory functions within the vascular wall, and it is, therefore, plausible that platelets represent a relevant target for their action. Platelet activation cascade (including receptor-mediated tethering to the endothelium, rolling, firm adhesion, aggregation, and thrombus formation) is tightly regulated. In addition to already well-defined platelet regulatory factors, ROS may participate in the regulation of platelet activation. It is already established that enhanced ROS release from the vascular wall can indirectly affect platelet activity by scavenging nitric oxide (NO), thereby decreasing the antiplatelet properties of endothelium. On the other hand, recent data suggest that platelets themselves generate ROS, which may evoke pro-thrombotic responses, triggering many biological processes participating in atherosclerosis initiation, progression, and complication. That oxidative stress may alter platelet function is conceivable when considering that antioxidants play a role in the prevention of cardiovascular disease, although the precise mechanism accounting for changes attributable to antioxidants in atherosclerosis remains unknown. It is possible that the effects of antioxidants may be a consequence of their enhancing or promoting the antiplatelet effects of NO derived from both endothelial cells and platelets. This review focuses on current knowledge regarding ROS-dependent regulation of platelet function in health and disease, and summarizes in vitro and in vivo evidence for their physiological and potential therapeutic relevance.

Obesity-Driven Inflammation and Colorectal Cancer

Visceral obesity is characterized by increased risk of cardiovascular disease as well as higher incidence of malignancies, including colorectal cancer (CRC), although the mechanisms linking excess adiposity with cancer are only partly characterized. Visceral obesity is currently acknowledged as a chronic inflammatory disorder and a growing body of evidence demonstrates the interconnections between obesity-related secretion pattern of adipo/cytokines and CRC. Specific molecules derived from the visceral adipose tissue (VAT), including adiponectin, leptin and resistin, are able to establish a positive feedback loop, thus increasing the proinflammatory and insulin resistant state and promoting tumorigenesis. Interestingly, these molecules have emerged as novel prognostic factors and therapeutic targets. This review will focus on current molecular and clinical evidence linking VAT-related inflammation to CRC initiation and progression, and summarize the role of dietary factors and lifestyle interventions aimed at promoting weight control and physical activity on CRC prevention and prognosis.

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.

More on: aspirin resistance: position paper of the Working Group on Aspirin Resistance. Proposal for a Laboratory Test Guiding Algorithm

1 James A, Matchar DB, Myers ER. Testing for von Willebrand disease in women with menorrhagia: a systematic review.Obstet Gynecol 2004; 104: 381–8. 2 James AH, Lukes AS, Brancazio LR, Thames E, Ortel TL. Use of a new platelet function analyzer to detect von Willebrand disease in women with menorhhagia. Am J Obstet Gynecol 2004; 191: 449–55. 3 Highman JM, O’Brien PMS, Shaw RW. Assessment of menstrual blood loss using a pictorial chart. Br J Obstet Gynaecol 1990; 97: 734–9. 4 Fressinaud E, Veyradier A, Truchaud F, Martin I, Boyer-Neumann C, Trossaert M, Meyer D. Screening for von Willebrand disease with a new analyser using high shear rates. A study of 60 cases.Blood 1998; 91: 1325–31. 5 Fressinaud E, Veyradier A, Sigaud M, Boyer-Neumann C, Le Boterff C, Meyer D. Therapeutic monitoring of von Willebrand disease: interest and limits of a platelet function analyser at high shear rates.Br J Haematol 1999; 106: 777–83. 6 Lee CA, Abdul-Kadir R. von Willebrand disease and women’s health. Semin Hematol 2005; 42: 42–8. 7 Philipp CS, Faiz A, Dowling N, Dilley A, Michaels LA, Ayers C, Miller CH, Bachmann G, Evatt B, Saidi P. Age and prevalence of bleeding disorders in women with menorrhagia. Obstet Gynecol 2005; 105: 61–6.

Platelet Hyperactivity in Hypertensive Older Patients Is Controlled by Lowering Blood Pressure

Patients with hypertension tend to have a high prevalence of atherothrombotic accidents. Platelet hyperactivity is frequently associated with hypertension. Because the vascular disease associated with hypertension evolves over the years, we investigated platelet activity parameters in a population of older hypertensive patients with no other risk factors for cardiovascular disease.

Novel High-Sensitive D-Dimer Determination Predicts Chemotherapy-Associated Venous Thromboembolism in Intermediate Risk Lung Cancer Patients

INTRODUCTION We hypothesized that the use of a novel high sensitivity (HS) assay for D-dimer determination might ameliorate venous thromboembolism (VTE) risk prediction in intermediate risk lung cancer patients in whom chemotherapy could act as a trigger for VTE onset. PATIENTS AND METHODS Pretreatment HS D-dimer levels were retrospectively evaluated in 108 lung cancer outpatients using a novel automated latex enhanced turbidimetric immunoassay. All patients were at the start of a new platinum-based chemotherapy regimen and were classified as intermediate risk according to Khoranas assessment model. Patients were followed-up for a median period of 6.9 months. RESULTS Receiver operating characteristic (ROC) curves and corresponding Bayesian analysis showed that the best performance was obtained at a cutoff level of 1500 ng/mL, which resulted in a sensitivity of 81%, a specificity of 69%, a positive predictive value (PPV) of 31%, a negative predictive value (NPV) of 96%, and an accuracy of 70%. Patients with HS D-dimer levels above the cutoff had a worse VTE-free survival (60%) compared with those with levels below the cutoff (95%; P = .0001). Multivariate Cox proportional hazards survival analysis confirmed that pretreatment HS D-dimer levels were able to significantly predict VTE with a hazard ratio of 11 (95% confidence interval, 2.62-46.2; P = .001), independently of classic VTE risk factors. CONCLUSIONS The use of HS D-dimer determination prior to chemotherapy might allow for VTE risk stratification of intermediate risk cancer patients, helping in identifying those individuals who could benefit from thromboprophylaxis.