Abivertinib inhibits megakaryocyte differentiation and platelet biogenesis / 医学前沿

Abivertinib, a third-generation tyrosine kinase inhibitor, is originally designed to target epidermal growth factor receptor (EGFR)-activating mutations. Previous studies have shown that abivertinib has promising antitumor activity and a well-tolerated safety profile in patients with non-small-cell lung cancer. However, abivertinib also exhibited high inhibitory activity against Bruton's tyrosine kinase and Janus kinase 3. Given that these kinases play some roles in the progression of megakaryopoiesis, we speculate that abivertinib can affect megakaryocyte (MK) differentiation and platelet biogenesis. We treated cord blood CD34+ hematopoietic stem cells, Meg-01 cells, and C57BL/6 mice with abivertinib and observed megakaryopoiesis to determine the biological effect of abivertinib on MK differentiation and platelet biogenesis. Our in vitro results showed that abivertinib impaired the CFU-MK formation, proliferation of CD34+ HSC-derived MK progenitor cells, and differentiation and functions of MKs and inhibited Meg-01-derived MK differentiation. These results suggested that megakaryopoiesis was inhibited by abivertinib. We also demonstrated in vivo that abivertinib decreased the number of MKs in bone marrow and platelet counts in mice, which suggested that thrombopoiesis was also inhibited. Thus, these preclinical data collectively suggested that abivertinib could inhibit MK differentiation and platelet biogenesis and might be an agent for thrombocythemia.

High Residual Platelet Reactivity during Aspirin Therapy in Patients with Non-St Segment Elevation Acute Coronary Syndrome: Comparison Between Initial and Late Phases / Alta Atividade Plaquetária Residual em Resposta ao Ácido Acetilsalicílico na Síndrome Coronariana Aguda Sem Supra de ST: Comparação entre as Fases Aguda e Tardia

Abstract Background: High platelet reactivity (HPR) during therapy with acetylsalicylic acid (ASA) is a poor prognostic factor in acute coronary syndromes (ACS). The prevalence of HPR during ACS is greater than that reported in stable diseases. However, it is unclear whether this prevalence of HPR is a transient phenomenon or a characteristic of this high-risk population. Objective: The main objective is to compare the effects of ASA on platelet function in the initial and late phases of ACS in a single population. Secondary objectives are: correlation between the tests between themselves and the relationship between the tests and the variation of the inflammatory markers (C-reactive protein and interleukin-6). Methods: Seventy patients with non-ST segment elevation (NSTE) ACS in use of 100-200 mg of ASA per day for at least 7 days were prospectively studied. Platelet function was assessed in the first 48 hours and subsequently after 3 months using four methods: VerifyNow™ (VFN), whole blood platelet aggregation (WBPA) with arachidonic acid (AA) and collagen as agonists, and platelet function analyzer (PFA). The level of statistical significance considered was < 0.05. Results: According to the more specific methods (WBPA with AA and VFN), the incidence of HPR was significantly higher in the early phase than in the late phase: WBPA with AA: 31% versus 13%, p = 0.015; VFN: 32% versus 16%, p = 0.049. The other methods tested, which were less specific for ASA, did not show significant differences between phases. The correlation between the methods was weak or moderate (r ranging from 0.3 to 0.5, p < 0.05), and there were no significant associations between HPR and inflammatory markers. Conclusion: The prevalence of HPR during AAS therapy, assessed by specific methods for cyclooxygenase 1 (COX-1), is higher during the acute phase than in the late phase of NSTE ACS.

Resumo Fundamento: A alta atividade plaquetária (AAP) durante a terapia com ácido acetilsalicílico (AAS) é fator de mau prognóstico nas síndromes coronarianas agudas (SCA). A prevalência de AAP durante a SCA é maior do que a relatada na doença estável. No entanto, não está claro se esta prevalência de AAP é um fenômeno transitório ou característica dessa população de alto risco. Objetivo: O objetivo principal é comparar, em uma mesma população, os efeitos do AAS sobre a função plaquetária nas fases inicial e tardia da SCA. Os objetivos secundários são: correlação entre os testes entre si e a relação entre os testes e a variação dos marcadores inflamatórios (proteína C reativa e interleucina-6). Métodos: Foram estudados prospectivamente 70 pacientes com SCA sem elevação de ST (SCSST) em uso de 100 a 200 mg de AAS por dia por pelo menos 7 dias. A função plaquetária foi avaliada nas primeiras 48 horas e 3 meses após por quatro métodos: VerifyNow™ (VFN), agregometria de sangue total (AST) com ácido araquidônico (AA) e colágeno como agonistas, e analisador de função plaquetária (PFA). O nível de significância estatístico considerado foi < 0,05. Resultados: A média de idade foi de 65 ±9,7 anos e 54% da população eram do sexo feminino. De acordo com os métodos mais específicos (AST com AA e VFN), a incidência de AAP foi significativamente maior na fase inicial, em relação à tardia: AST com AA 31% versus 13%, p = 0,015; VFN 32% versus 16%, p = 0,049. Os outros métodos testados, menos específicos para o AAS, não mostraram diferenças significativas entre as fases. A correlação entre os métodos foi fraca ou moderada (r variando de 0,3 a 0,5, p < 0,05), e não houve associações significativas entre AAP e marcadores inflamatórios. Conclusão: A prevalência de AAP durante a terapia com AAS, avaliada por métodos específicos para cicloxigenase 1 (COX-1), é maior durante a fase aguda do que na tardia da SCASST.

Decreased platelet responsiveness to clopidogrel correlates with CYP2C19 and PON1 polymorphisms in atherosclerotic patients

Clopidogrel and aspirin are the most commonly used medications worldwide for dual antiplatelet therapy after percutaneous coronary intervention. However, clopidogrel hyporesponsiveness related to gene polymorphisms is a concern. Populations with higher degrees of genetic admixture may have increased prevalence of clopidogrel hyporesponsiveness. To assess this, we genotyped CYP2C19, ABCB1, and PON1 in 187 patients who underwent percutaneous coronary intervention. Race was self-defined by patients. We also performed light transmission aggregometry with adenosine diphosphate (ADP) and arachidonic acid during dual antiplatelet therapy. We found a significant difference for presence of the CYP2C19*2 polymorphism between white and non-white patients. Although 7% of patients had platelet resistance to clopidogrel, this did not correlate with any of the tested genetic polymorphisms. We did not find platelet resistance to aspirin in this cohort. Multivariate analysis showed that patients with PON1 and CYP2C19 polymorphisms had higher light transmission after ADP aggregometry than patients with native alleles. There was no preponderance of any race in patients with higher light transmission aggregometry. In brief, PON1 and CYP2C19 polymorphisms were associated with lower clopidogrel responsiveness in this sample. Despite differences in CYP2C19 polymorphisms across white and non-white patients, genetic admixture by itself was not able to identify clopidogrel hyporesponsiveness.

Efecto del 27- hidroxicolesterol en la acción antiplaquetaria de estradiol en mujeres postmenopáusicas / 27- Hydroxycholesterol reverses estradiol induced inhibition of platelet aggregation in postmenopausal women

Background: The decline of estrogen levels increases cardiovascular risk in women. Platelets express estrogen receptors and 17β-estradiol- (E2) can produce a protective effect on thrombus formation. The hydroxylation of cholesterol generates several sterols and 27-hydroxycholesterol (27HC) predominates in circulation. Aim: To evaluate the effect of 27HC as an endogenous antagonist of the anti-aggregating properties of E2 in platelets of postmenopausal women. Material and Methods: Platelet function of postmenopausal women was evaluated ex-vivo. Platelets pre-incubated with 27HC in the presence or absence of E2, were stimulated with collagen. Aggregation was evaluated using turbidimetry using a Chrono-log aggregometer. Results: Collagen-stimulated platelet aggregation was significantly inhibited by E2. The inhibitory effect of E2 on collagen-stimulated platelet aggregation was significantly reversed in the presence of 27HC. Conclusions: The suppressive effect of E2 on platelet aggregation is inhibited by 27HC, which could contribute to increase cardiovascular risk in postmenopausal women.

A pharmacodynamic study of the optimal P2Y12 inhibitor regimen for East Asian patients with acute coronary syndrome

BACKGROUND/AIMS: Newer P2Y12 inhibitors, such as prasugrel and ticagrelor, have greater antiplatelet efficacy but may increase the risk of bleeding. In this study, we compared the pharmacodynamic efficacy of prasugrel and ticagrelor in East Asian patients with acute coronary syndrome (ACS). METHODS: We selected 83 ACS patients undergoing percutaneous coronary intervention who were discharged with 90 mg ticagrelor twice daily (n = 24), 10 mg prasugrel daily (n = 39) or 5 mg prasugrel daily (n = 20). After 2 to 4 weeks, on-treatment platelet reactivity (OPR) was assessed in terms of P2Y12 reaction units (PRUs) using the VerifyNow P2Y12 assay (Accumetrics). We compared East Asian (85 < PRU < or = 275) and Caucasian (85 < PRU < or = 208) criteria for assessing the therapeutic window of OPR. RESULTS: OPR was lowest in the ticagrelor group, followed by the 10 mg prasugrel and 5 mg prasugrel groups (49.1 ± 29.9 vs. 83.7 ± 57.1 vs. 168.5 ± 60.8, respectively; p < 0.001). The 5 mg prasugrel group had the highest proportion of patients with OPR values within the therapeutic window, followed by the 10 mg prasugrel and ticagrelor groups (90.0% vs. 46.2% vs. 12.5%, respectively; p < 0.001 for East Asian criteria; 60.0% vs. 43.6% vs. 12.5%, respectively; p < 0.001 for Caucasian criteria). CONCLUSIONS: Short-term administration of 5 mg prasugrel facilitated maintenance within the therapeutic window of OPR compared with the 10 mg prasugrel and ticagrelor groups. Thus, 5 mg prasugrel daily may be the optimal antiplatelet regimen for stabilized East Asian ACS patients.

Antiplatelet Effect of Clopidogrel Can Be Reduced by Calcium-Channel Blockers

PURPOSE: Clopidogrel is metabolized by the hepatic cytochrome P450 (CYP) system into its active thiol metabolite. CYP3A4 is involved in the metabolism of both clopidogrel and dihydropyridine calcium channel blockers (CCBs). A few reports have suggested an inhibitory interaction between CCBs and clopidogrel. Accordingly, the aim of this study was to determine the effect of CCBs on the antiplatelet activity of clopidogrel by serial P2Y12 reaction unit (PRU) measurements. MATERIALS AND METHODS: We assessed changes in antiplatelet activity in patients receiving both clopidogrel and CCBs for at least 2 months prior to enrollment in the study. The antiplatelet activity of clopidogrel was measured by VerifyNow P2Y12 assay in the same patient while medicated with CCBs and at 8 weeks after discontinuation of CCBs. After discontinuation of the CCBs, angiotensin receptor blockers were newly administered to the patients or dosed up for control of blood pressure. RESULTS: Thirty patients finished this study. PRU significantly decreased after discontinuation of CCBs (238.1+/-74.1 vs. 215.0+/-69.3; p=0.001). Of the 11 patients with high post-treatment platelet reactivity to clopidogrel (PRU> or =275), PRU decreased in nine patients, decreasing below the cut-off value in seven of these nine patients after 8 weeks. Decrease in PRU was not related to CYP2C19 genotype. CONCLUSION: CCBs inhibit the antiplatelet activity of clopidogrel.

Adjunctive Cilostazol versus High Maintenance Dose of Clopidogrel in Patients with Hyporesponsiveness to Chronic Clopidogrel Therapy

PURPOSE: Whether addition of cilostazol is superior to increasing dose of clopidogrel in patients with hyporesponsiveness to chronic clopidogrel therapy is unknown. MATERIALS AND METHODS: We studied 73 patients with hyporesponsiveness to clopidogrel on standard dual antiplatelet therapy for more than 2 weeks. Clopidogrel hyporesponsiveness was defined as percent inhibition of P2Y12 reaction units (PRU) <30% on VerifyNow P2Y12 assay. Patients were randomly assigned to increased dose of clopidogrel (aspirin 100 mg+clopidogrel 150 mg daily: group A, n=38) or to receiving additional cilostazol (aspirin 100 mg+clopidogrel 75 mg+cilostazol 100 mg bid daily: group B, n=35). RESULTS: Baseline percent inhibition of PRU and PRU was similar between 2 groups (13.0+/-10.2% versus 11.8+/-9.7%, p=0.61, and 286.3+/-54.7 versus 295.7+/-53.7, p=0.44, respectively). At follow-up, percent inhibition of PRU was higher and PRU was lower significantly in group B than in group A (38.5+/-17.9% versus 28.3+/-16.6%, p=0.02, and 207.3+/-68.2 versus 241.3+/-76.7, p=0.050, respectively). Among those still showing hyporesponsiveness to clopidogrel at follow-up (21 patients in group A, 10 patients in group B), 12 patients completed further crossover study. Compared to the baseline, magnitude of change in percent inhibition of PRU and PRU showed an improved tendency after the crossover (from 2.7+/-8.7% to 15.8+/-18.4%, p=0.08, and from -18.6+/-58.0 to -61.9+/-84.3, p=0.08). CONCLUSION: Adjunctive cilostazol improved clopidogrel responsiveness better than the higher maintenance dose of clopidogrel in hyporesponsive patients with chronic clopidogrel therapy.

[Effects of L-asparginase administration on anticoagulant proteins and platelet function in patients with acute lymphoblastic leukemia]

Acute lymphoblastic leukemia is one the most common malignancies in children and adolescents. L-asparginase [L-ASP] is one of the leading medications in treatment of ALL. L.ASP interferes with the synthesis of some coagulation proteins and therefore causing disturbance in normal coagulation. In this study, the effects of L-ASP on anticoagulant proteins [protein C, protein S, and antithrombin III] and platelet function were assessed. This was a before-after study on 41 patients with ALL who refered to Mahak hospital [Tehran, Iran]. Before and after the injection of L.ASP, a bleeding time test was performed based on Ivy method. Protein C and protein S performance was assessed by turbidometry and antithrombin III performance was evaluated by chromogenic method. 48.8% of patients were female. Mean [ +/- SD] of age was 4.0 +/- 7.2. A significant reduction in the mean amount of protein C, antithrombin III and bleeding time was recorded. However, the reduction in protein S was not significant. No patient showed the symptoms of thrombosis. The results of this study showed that L. ASP drug reduced coagulation proteins [except the protein S]. This decrease along with other concomitant genetic factors can lead to thrombosis in some patients with ALL during induction therapy

Aprotinina preserva plaquetas em crianças com cardiopatia congênita acianogênica operadas com circulação extracorpórea? / Does aprotinin preserve platelets in children with acyanogenic congenital heart disease undergone surgery with cardiopulmonary bypass?

OBJETIVO: Avaliação dos efeitos hemostáticos e plaquetários em crianças submetidas a correção de cardiopatias congênitas acianogênicas com circulação extracorpórea que receberam aprotinina. MÉTODOS: Estudo prospectivo randomizado em crianças de 30 dias a 4 anos de idade, submetidas a correção de cardiopatia congênita acianogênica, com circulação extracorpórea (CEC) e divididas em dois grupos, um denominado Controle (n=9) e o outro, Aprotinina (n=10). Neste, a droga foi administrada antes e durante a CEC. A disfunção hemostática foi analisada por marcadores clínicos e bioquímicos. Foram consideradas significantes as diferenças com P<0,05. RESULTADOS: Os grupos foram semelhantes quanto às variáveis demográficas e intra-operatórias, exceto por maior hemodiluição no Grupo Aprotinina. Não houve benefício quanto aos tempos de ventilação pulmonar mecânica, permanência no centro de terapia intensiva pediátrica e hospitalar, nem quanto ao uso de inotrópicos e função renal. Ocorreu preservação da concentração plaquetária com a Aprotinina, enquanto no grupo Controle houve plaquetopenia desde o início da CEC. As perdas sanguíneas foram semelhantes nos dois grupos. Não houve complicações com o uso da Aprotinina. CONCLUSÃO: A Aprotinina preservou quantitativamente as plaquetas em crianças com cardiopatia congênita acianogênica

OBJECTIVE: Evaluation of the hemostatic and platelets effects in children with acyanogenic congenital heart disease undergone on-pump surgery who received aprotinin. METHODS: A prospective randomized study was performed on children aged 30 days to 4 years who had undergone correction of acyanogenic congenital heart disease using cardiopulmonary bypass (CPB) and were divided into two groups: Control (n=9) and Aprotinin (n=10). In the Aprotinin Group the drug was administered before and during CPB and the hemostatic dysfunction was analyzed by clinical and biochemical markers. Differences were considered to be significant when P<0.05. RESULTS: The groups were similar regarding demographic and intraoperative variables, except for a greater hemodilution in the Aprotinin Group. The drug presented no benefit regarding time of mechanical pulmonary ventilation, stay in the postoperative intensive care unit and hospital, or regarding the use of inotropic drugs and renal function. Platelet concentration was preserved with the use of Aprotinin, whereas thrombocytopenia occurred in the Control Group since the initiation of CPB. Blood loss was similar for both groups. There were no complications with the use of Aprotinin. CONCLUSION: Aprotinin quantitatively preserved the blood platelets in children with acyanogenic congenital heart disease

Aspirin non-responders in Thai ischemic stroke/TIA patients.

BACKGROUND: Aspirin resistance has been defined as inability of aspirin to protect individuals from thrombotic complications or to produce an anticipated effect from laboratory tests of platelet function. Most reported information comes from Western patients with coronary artery disease and aspirin resistance is defined by laboratory criteria. The purpose of the present study was to look for aspirin non-responders in Thai patients who presented with acute/subacute ischemic stroke and transient ischemic attack (TIA). MATERIAL AND METHOD: The authors prospectively included acute ischemic stroke/TIA patients who were treated at Thammasat Hospital from August, 2006 to July, 2007 and had already been on aspirin. Information about compliance of medication, reasons for taking aspirin, doses of aspirin, baseline characteristics, and stroke subtypes of the patients were collected. RESULTS: There were 194 acute/subacute ischemic stroke/TIA patients during the study period Forty-six patients (23.7%), who had already been on aspirin (aspirin non-responder), while having new stroke/TIA, were studied Eighteen patients were on aspirin 300-325 mg and 28 patients were on 81 mg per day. Most patients had taken aspirin 300-325mg/day as secondary prevention, while half of the patients taking aspirin 81 mg/d had diabetes mellitus and took aspirin as primary prevention. CONCLUSION: Aspirin non-responders in ischemic stroke patients are common. Future study is required to clarify mechanisms of aspirin non-responders in Thai patients.

Effect of Nitric Oxide on the Cryopreservation of Platelets / 대한진단검사의학회지

BACKGROUND: To determine whether nitric oxide (NO) could inhibit activation of platelets stored in a cold or frozen state, we measured platelet P-selectin expression and platelet-bound fibrinogen in platelet-rich plasma (PRP) with S-nitrosoglutathione (GSNO) (Sigma, USA) by flow cytometry. METHODS: PRP was prepared by centrifuging venous blood collected in a 3.2% sodium citrate tube from 10 healthy donors. It was aliquotted into 4 groups (no cryoprotectant, GSNO, GSNO/dimethyl sulfoxide [DMSO] [Sigma], and DMSO), and stored at room, cold and freezing temperatures for 24 hrs. We performed a flow cytometric analysis of all specimens stained with FITC-fibrinogen and PE-CD62P monoclonal antibodies (Becton Dickinson, USA). The results were compared according to the storage temperature and agonist among 4 groups. RESULTS: GSNO inhibited significantly the activation of frozen platelets, but not in the presence of DMSO. GSNO was also shown to preserve the aggregability of frozen platelets because in the presence of GSNO the delta percent change of P-selectin expression and fibrinogen binding of frozen platelets increased significantly irrelevant to DMSO. CONCLUSIONS: GSNO inhibited the activation of frozen platelets and preserved the platelet aggregability; therefore, it may be used as a protectant for platelet cryopreservation.

Effect of pretreatment with chromium picolinate on haematological parameters during dengue virus infection in mice.

BACKGROUND & OBJECTIVE: Dengue virus (DV) has caused severe epidemics of dengue fever (DF) and dengue haemorrhagic fever (DHF) and is endemic all over India. We have earlier reported that exposure of mice to hexavalent chromium [Cr(VI)] compounds increased the severity of dengue virus infection. Trivalent chromium picolinate (CrP) is used worldwide as micronutrient and nutritional supplement. The present study was therefore, carried out to investigate the effects of CrP on various haematological parameters during DV infection of mice. METHODS: The Swiss Albino smice were inoculated with dengue virus (1000 LD50, intracerebrally) and fed with chromium picolinate (CrP) in drinking water (100 and 250 mg/l) for 24 wk. Peripheral blood leucocytes and other haematological parameters, and spleens were studied on days 4 and 8 after virus inoculations and the findings were compared with those given only CrP and the normal control age matched mice. RESULTS: CrP in drinking water for 24 wk had no significant effects on peripheral blood cells of mice. On the other hand, there was significant decrease in different haematological parameters following inoculation of normal mice with DV. In CrP fed mice the effects of DV infection were abolished on most of the haematological parameters. INTERPRETATION & CONCLUSION: The findings of present study showed that the adverse effects of DV infection, specially on platelets and leucocytes, were abrogated by pretreatment of mice with CrP. The therapeutic utility of CrP in viral infections including dengue needs to be studied in depth.

Aspirin resistance.

Aspirin reduces the odds of serious atherothrombotic vascular events and death in a broad category of high risk patients by about one quarter. The term 'aspirin resistance' has been used to describe not only an absence of the expected pharmacologic effects of aspirin on platelets but also poor clinical outcomes, such as recurrent vascular events, in patients treated with aspirin. Various factors such as genetic, nonadherence, variable response to different doses, co-morbid conditions and drug interactions are responsible for aspirin resistance. Many methods, with their limitations, are available to measure the effects on platelets. Despite treatment failures, aspirin remains the single most cost-effective drug for the secondary prevention of atherothrombotic disease. To optimize its clinical effectiveness, clinicians should be aware of the potential causes of aspirin treatment failure, prescribe aspirin in appropriate doses, and encourage patients to take aspirin, stop smoking, and avoid regular use of NSAIDs.

[Histomorphometerical effects of retinoic acid on red cells in rat's embryo]

All-trans retinoic acid [ATRA] has beneficial and teratogenicity effects when used in a variety conditions. The objectives of this study were to determine the effects of ATRA on the red blood cells [RBC] and platelets in rat's embryo. In this study Wistar rats were used. They were maintained on laboratory chow and tap water provided ad libitum. Adult virgin females [n = 10] were mated overnight with males of the same stock. A vaginal plug and smear observed, indicated day 0 of pregnancy. Single dose of 100 mg/kg of ATRA suspended in alcohol; corn oil [1:9] mixture and was given by oral intubations on the morning of gestation day [GD] 10 to experimental group. The control group was vehicle treated. The fetuses blood [controls and ATRA treated each, n= 23] were obtained directly from heart, as placental and mother circulation was continued and subsequently processed for staining [Gimsa] and followed by counting. The fetuses' blood cells were studied by light microscope and eyepiece [x40 for count, 100 for diameter. The number of RBC and also and platelets were significantly lower than those of control group [P<0.0001, P<0.04, respectively]. There was no significant relationship between diameter of RBC in treated and control groups. The present data showed that ATRA may has negative effects on proliferation and maturation of erythroid cell and platelet progenitors, without having any deleterious effects on the dime nation of cells, probably via events involving activation or suppression of specific genes

The anti-thrombotic activity of surfactins

Platelet aggregation was inhibited and the density of platelet-rich plasma (PRP) clots was decreased by the preincubation of PRP with surfactins, an acidic lipopeptide of Bacillus subtilis complex BC1212 isolated from soybean paste, in dose-dependent manner. Our findings suggest that surfactins are able to prevent a platelet aggregation leading to an inhibition of additional fibrin clot formation, and to enhance fibrinolysis with facilitated diffusion of fibrinolytic agents.

Involvement of throm box aneA2 and tyrosine kinase in the synergistic interaction of platelet activating factor and calcium ionophore A23187 in human platelet aggregation

The present study was carried out to examine the mechanisms of the synergistic interaction of PAF and A23187 mediated platelet aggregation. We found that platelet aggregation mediated by subthreshold concentrations of PAF (5 nM) and A23187 (1 micrometer) was inhibited by PAF receptor blocker (WEB 2086, IC50=0.65 micrometer) and calcium channel blockers, diltiazem (IC50=13 micrometer) and verapamil (IC50=18 micrometer). Pretreatment of platelets with PAF and A23187 induced rise in intracellular calcium and this effect was also blocked by verapamil. While examining the role of the down stream signaling pathways, we found that platelet aggregation induced by the co-addition of PAF and A23187 was also inhibited by low concentrations of phospholipase C (PLC) inhibitor (U73122; IC50 = 10 micrometer), a cyclooxygenase inhibitor (indomethacin; IC50=0.2 micrometer) and inhibitor of TLCK, herbimycin A with IC50 value of 5 micrometer. The effect was also inhibited by a specific TXA2 receptor antagonist, SQ 29548 with very low IC50 value of 0.05 micrometer. However, the inhibitors of MAP kinase, PD98059 and protein kinase C, chelerythrine had no effect on PAF and A23187-induced platelet aggregation. These data suggest that the synergism between PAF and A23187 in platelet aggregation involves activation of thromboxane and tyrosine kinase pathways.

Reducing the risk: heart disease, stroke and aspirin.

Aspirin used in cardiovascular disease is probably the best evaluated and the most highly cost effective prophylactic available in clinical practice today. It has been evaluated in over 150 randomised controlled trials and a small daily dose of around 100 mg has been shown to reduce the risk of myocardial infarction and stroke by about 30 per cent. The saving of lives and prevention of vascular events in patients judged to be at increased risk of a vascular event for any reason is large. In healthy subjects, however, the risk of a vascular event is so low that prophylaxis by any drug is inappropriate. The earlier aspirin is given in the acute phase of a myocardial infarction the greater the saving of lives. Patients judged to be at increased risk of a vascular event, for any reason, should therefore be advised to carry aspirin and to chew and swallow one or two tablets immediately, if they experience sudden severe chest pain. Aspirin is derived from a salicylate, and salicylates are widely distributed in nature, with many functions in plants. Its use in cardiovascular disease derives from an effect on blood platelets, but other possible effects have led to suggestions that it may be of benefit in conditions other than heart disease and stroke. Current research is now focussing on the possible reduction by aspirin in the risk of dementia, certain cancers, retarded foetal growth and cataract.

Accion del Clonoxinato de lisina sobre la funcion plaquetaria comparacion con otras drogas antiinflamatorias no esteroideas / Effects of lysine clonixinate on platelet function. Comparison with other non-steroidal anti-inflammatory agents

El grupo de los antiinflamatorios no esteroideos (AINEs) posee como uno de sus mecanismos de acción la inhibición de la síntesis de prostaglandinas. Este efecto explica muchas de las acciones farmacológicas y de los eventos adversos observados en el uso clínico. La administración de AINEs a pacientes con trastornos de la hemostasia o en estados perioperatorios incrementan el riesgo de hemorragias por inhibición de las funciones plaquetarias. En este trabajo se estudian las modificaciones plaquetarias inducidas por el clonixinato de lisina comparadas con las del diclofenac, ibuprofeno y aspirina, mediante pruebas clásicas (recuento de plaquetas, producción de factor 3 plaquetario, agregación con diversos inductores) y procedimientos más recientes (medición de P-selectina por citometría de flujo). El clonixinato de lisina no produjo modificaciones en el número ni en la función plaquetaria cuando fue administrado a voluntarios sanos en las dosis terapéuticas usuales, cosa que sí ocurrió con las drogas control.