RESUMO
The glycoprotein (GP) IIb/IIIa receptor is found integrin present in platelet aggregations. GP IIb/IIIa antagonists interfere with platelet cross-linking and platelet-derived thrombus formation through the competition with fibrinogen and von Willebrand factor. Currently, three parenteral GP IIb/IIIa competitors (tirofiban, eptifibatide, and abciximab) are approved for clinical use in patients affected by percutaneous coronary interventions (PCI) in the location of acute coronary syndrome (ACS). GP IIb/IIIa antagonists have their mechanism of action in platelet aggregation prevention, distal thromboembolism, and thrombus formation, whereas the initial platelet binding to damage vascular areas is preserved. This work is aimed to provide a comprehensive review of the significance of GP IIb/IIIa inhibitors as a sort of antiplatelet agent. Their mechanism of action is based on factors that affect their efficacy. On the other hand, drugs that inhibit GP IIb/IIIa already approved by the FDA were reviewed in detail. Results from major clinical trials and regulatory practices and guidelines to deal with GP IIb/IIIa inhibitors were deeply investigated. The cardiovascular pathology and neuro-interventional surgical application of GP IIb/IIIa inhibitors as a class of antiplatelet agents were developed in detail. The therapeutic risk/benefit balance of currently available GP IIb/IIa receptor antagonists is not yet well elucidated in patients with ACS who are not clinically evaluated regularly for early cardiovascular revascularization. On the other hand, in patients who have benefited from PCI, the antiplatelet therapy intensification by the addition of a GP IIb/IIIa receptor antagonist (intravenously) may be an appropriate therapeutic strategy in reducing the occurrence of risks of thrombotic complications related to the intervention. Development of GP IIb/IIIa inhibitors with oral administration has the potential to include short-term antiplatelet benefits compared with intravenous GP IIb/IIIa inhibitors for long-term secondary preventive therapy in cardiovascular disease. But studies showed that long-term oral administration of GP IIb/IIIa receptor inhibitors has been ineffective in preventing ischemic events. Paradoxically, they have been linked to a high risk of side effects by producing prothrombotic and pro-inflammatory events.
Assuntos
Intervenção Coronária Percutânea , Inibidores da Agregação Plaquetária , Humanos , Inibidores da Agregação Plaquetária/uso terapêutico , Glicoproteína IIb da Membrana de Plaquetas , Complexo Glicoproteico GPIIb-IIIa de Plaquetas , AbciximabRESUMO
El estudio de la megacariopoyesis humana se ha visto obstaculizado por la relativa escasez de megacariocitos en la médula ósea (0,05-0,2 % de las células medulares), lo que ha llevado a la optimización de protocolos de expansión in vitro a partir de precursores de diversos orígenes (cordón umbilical, médula ósea y sangre periférica con o sin movilización previa). Los cultivos celulares a partir de precursores han permitido la producción y el estudio tanto de megacariocitos así como de proplaquetas y plaquetas Sin embargo, la producción in vitro óptima de megacariocitos que culminen todos los estadios de diferenciación es un reto aún no resuelto. En este trabajo reportamos los hallazgos concernientes a la determinación de las condiciones y concentraciones de trombopoyetina para lograr una óptima relación entre la cantidad de trombopoyetina empleada y el porcentaje y grado de diferenciación megacariocítica en muestras obtenidas de cinco donantes alogénicos aceptados para trasplante de médula ósea.
The study of human megakaryocytopoiesis has been hampered by the relative scarcity of megakaryocytes in bone marrow (0.05-0.2 % of medullary cells), which has led to the optimization of protocols of in vitro expansion of precursors from diverse sources (umbilical cord, bone marrow and peripheral blood with or without previous mobilization). Cell cultures from different precursors have allowed the production and study of megakaryocytes as well as proplatelets and platelets. However, the in vitro production of megakaryocytes that culminate all stages of differentiation is a challenge that has not yet been resolved. In this work we report the findings related to the determination of thrombopoietin treatment conditions and concentrations to achieve an optimal relationship between the amount of thrombopoietin and the percentage and degree of megakaryocytic differentiation in five allogeneic donors that were accepted for bone marrow transplantation.
O estudo da megacariopoiese humana tem sido dificultado pela relativa escassez de megacariócitos na medula óssea (0,05-0,2 % das células medulares), o que levou à otimização dos protocolos de expansão in vitro a partir de precursores de diversas origens (cordão umbilical, medula óssea e sangue periférico com ou sem mobilização prévia). Culturas de células a partir de precursores permitiram a produção e o estudo tanto de megacariócitos e de proplaquetas e plaquetas. No entanto, a produção ótima in vitro de megacariócitos que culminam em todas as fases de diferenciação é um desafio ainda não resolvido. Neste trabalho, relatamos as descobertas relativas à determinação das condições e concentrações de trombopoietina para obter uma relação ótima entre a quantidade de trombopoietina usada e a taxa e o grau de diferenciação megacariocítica em amostras obtidas de cinco doadores alogênicos aceitos para transplante de medula óssea.
Assuntos
Humanos , Trombopoetina/análise , Megacariócitos/citologia , Antígenos CD34/análise , Células Cultivadas/citologia , Leucaférese , Glicoproteína IIb da Membrana de Plaquetas/análise , Integrina beta3/análise , Técnicas de Cultura/métodosRESUMO
BACKGROUND Dengue virus type 4 (DENV-4) was first reported in Brazil in 1982 and since then no more cases were detected again in Brazil until 2010, when the virus was reintroduced. Over the following years, the virus spread to several Brazilian states and resulted in about 1,400,000 dengue cases, in 2013. The largest number of cases were documented in the Southeast macro-region. OBJECTIVES To determine the phylogeography of DENV-4 Genotype IIB strains isolated during the epidemics in 2012-2013 in São Paulo, Brazil, we aimed to contextualise the contribution of viruses sampled in different localities across the overall movement of DENV-4 in Brazil. METHODS Based on the envelope gene sequences retrieved from GenBank, we employed a Bayesian phylogeographic approach to assess the spatiotemporal dynamics of DENV-4 Genotype IIB in São Paulo, Brazil. FINDINGS The dispersal dynamics of DENV-4 Genotype IIB in Brazil indicated Rio de Janeiro and Mato Grosso states as the most likely routes toward São Paulo before the 2012-2013 outbreak. Likewise, Guarujá and São José do Rio Preto facilitated viral spread and transmission to other localities in the South and Southeast macro-regions in Brazil. CONCLUSIONS The spread pattern of DENV-4 Genotype IIB strains across the country supports two independent introductions of the virus in São Paulo in a short period of time. Furthermore, São Paulo appears to have played a pivotal role in the dissemination of DENV-4 to other locations in Brazil.
Assuntos
Humanos , Vírus da Dengue , Glicoproteína IIb da Membrana de Plaquetas , BrasilRESUMO
INTRODUCTION: Tumor necrosis factor-alpha (TNF-α) exerts a critical role in inflammatory events through two distinct receptors, TNFR1 and TNFR2. Platelets have been recognized as important inflammatory cells, but little is known about the effects of TNF-α on the platelet activity. OBJECTIVES: In the present study we have studied the role of TNF-α on ADP-induced platelet aggregation and its downstream signaling (c-Src and fibrinogen receptor phosphorylation, cytosolic Ca2+ mobilization, cAMP and cGMP levels and cell viability). METHODS AND RESULTS: Washed rat platelets were incubated with TNF-α (1-3000â¯pg/ml) for different time-periods (5-60â¯min) before the addition of ADP (5⯵M) to induce platelet aggregation. TNF-α concentration- and time-dependently inhibits ADP-induced aggregation, which was significantly prevented by incubation with the non-selective TNF-α receptor antagonist R7050. TNF-α (300â¯pg/ml, 30â¯min) decreases thrombin-induced elevation of cytosolic Ca++ levels by 2.2- fold compared to untreated platelets. TNF-α decreases the cAMP levels, while significantly increases the intracellular cyclic cGMP levels. However, the pre-incubation of platelets with the guanylyl cyclase inhibitor ODQ, despite decreasing the cGMP levels, does not modify the inhibitory effect of TNF-α on ADP-induced platelet aggregation. Additionally, western blotting analysis showed that TNF-α significantly reduced (Tyr 416)-c-Src and (Tyr773)-ß3 subunit of αIIbß3 integrin phosphorylation. TNF-α does not affect the platelet viability in any condition tested. CONCLUSION: Therefore, our results show that TNF-α negatively modulates ADP-induced aggregation via TNFR1/TNFR2 receptors by reducing cytosolic Ca++ levels and by inhibiting c-Src and fibrinogen receptor activation, which take place through cAMP- and cGMP-independent mechanisms.
Assuntos
Plaquetas/metabolismo , Cálcio/metabolismo , Integrina beta3/metabolismo , Agregação Plaquetária , Complexo Glicoproteico GPIIb-IIIa de Plaquetas/metabolismo , Glicoproteína IIb da Membrana de Plaquetas/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Animais , Plaquetas/citologia , GMP Cíclico/metabolismo , Citosol/metabolismo , Masculino , Fosforilação , Ratos WistarRESUMO
CONTEXTO: As doenças cardiovasculares (DCV) se caracterizam por distúrbios do coração e dos vasos sanguíneos e possuem como principais causas o consumo de tabaco, inatividade física, dieta pouco saudável e uso nocivo do álcool. São consideradas a principal causa de incapacidade e morte prematura em todo o mundo, sendo uma das principais a doença arterial coronariana (DAC). A DAC se caracteriza pela presença da aterosclerose, um complexo processo inflamatório multifatorial com acúmulo de lipoproteínas no lúmen dos vasos sanguíneos de médio e grande porte e pode ser identificada clinicamente nas suas formas crônica, como a angina estável, e aguda, nas síndromes coronarianas agudas (SCA). A SCA resulta, portanto, de um desequilíbrio entre oferta e demanda de oxigênio pelo musculo cardíaco, evoluindo para isquemia miocárdica aguda. TECNOLOGIA: Brilinta® (ticagrelor). PERGUNTA: Ticagrelor é mais eficaz do que o AAS e o Clopidogrel para a prevenção de eventos trombóticos em pacientes com SCA ou com infarto prévio? EVIDÊNCIAS: A terapia combinada de inibidores da P2Y12 (clopidogrel, prasugrel ou ticagrelor) com o AAS é superior ao uso de monoterapia com AAS. Prasugrel é provavelmente mais eficaz na prevenção de eventos isquêmicos após ICP, no entanto sem diferença estatística para alta dose (AD) de clopidogrel. Ticagrelor e clopidogrel (AD) parecem encontrar um melhor equilíbrio entre eficácia e segurança. Clopidogrel (AD) é uma alternativa ao prasugrel e ticagrelor. Ticagrelor e clopidogrel (AD) apresentaram melhor eficácia do que dose padrão (DP) de clopidogrel sem diferenças estatísticas nos desfechos de segurança. CONCLUSÕES: Não houve diferenças estatisticamente significantes entre o uso de clopidogrel (AD) e ticagrelor para os desfechos de eficácia e segurança. Clopidogrel (AD) pode ser considerada como uma alternativa ao prasugrel e ticagrelor.
Assuntos
Humanos , Síndrome Coronariana Aguda/tratamento farmacológico , Aspirina/uso terapêutico , Inibidores da Agregação Plaquetária/uso terapêutico , Glicoproteína IIb da Membrana de Plaquetas/uso terapêutico , Cloridrato de Prasugrel/uso terapêutico , Análise Custo-Benefício , Avaliação da Tecnologia Biomédica , Resultado do TratamentoRESUMO
BACKGROUND: Familial platelet disorder with a predisposition to acute myelogenous leukemia (FPD/AML) is an inherited platelet disorder caused by a germline RUNX1 mutation and characterized by thrombocytopenia, a platelet function defect, and leukemia predisposition. The mechanisms underlying FPD/AML platelet dysfunction remain incompletely clarified. We aimed to determine the contribution of platelet structural abnormalities and defective activation pathways to the platelet phenotype. In addition, by using a candidate gene approach, we sought to identify potential RUNX1-regulated genes involved in these defects. METHODS: Lumiaggregometry, α-granule and dense granule content and release, platelet ultrastructure, αIIb ß3 integrin activation and outside-in signaling were assessed in members of one FPD/AML pedigree. Expression levels of candidate genes were measured and luciferase reporter assays and chromatin immunoprecipitation were performed to study NF-E2 regulation by RUNX1. RESULTS: A severe decrease in platelet aggregation, defective αIIb ß3 integrin activation and combined αδ storage pool deficiency were found. However, whereas the number of dense granules was markedly reduced, α-granule content was heterogeneous. A trend towards decreased platelet spreading was found, and ß3 integrin phosphorylation was impaired, reflecting altered outside-in signaling. A decrease in the level of transcription factor p45 NF-E2 was shown in platelet RNA and lysates, and other deregulated genes included RAB27B and MYL9. RUNX1 was shown to bind to the NF-E2 promoter in primary megakaryocytes, and wild-type RUNX1, but not FPD/AML mutants, was able to activate NF-E2 expression. CONCLUSIONS: The FPD/AML platelet function defect represents a complex trait, and RUNX1 orchestrates platelet function by regulating diverse aspects of this process. This study highlights the RUNX1 target NF-E2 as part of the molecular network by which RUNX1 regulates platelet biogenesis and function.
Assuntos
Transtornos Plaquetários/sangue , Transtornos Plaquetários/complicações , Plaquetas/citologia , Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Leucemia Mieloide Aguda/sangue , Leucemia Mieloide Aguda/complicações , Trifosfato de Adenosina/metabolismo , Adulto , Saúde da Família , Feminino , Perfilação da Expressão Gênica , Humanos , Integrina beta3/metabolismo , Masculino , Subunidade p45 do Fator de Transcrição NF-E2/metabolismo , Linhagem , Fenótipo , Fosforilação , Agregação Plaquetária , Testes de Função Plaquetária , Glicoproteína IIb da Membrana de Plaquetas/metabolismo , Transdução de Sinais , Tirosina/metabolismo , Adulto JovemRESUMO
Loxosceles venoms can promote severe local and systemic damages. We have previously reported that Loxosceles gaucho spider venom causes a severe early thrombocytopenia in rabbits. Herein, we investigated the in vitro effects of this venom and its sphingomyelinase fraction on the main functions of platelets. Whole venom and its fraction induced aggregation of both human and rabbit platelets. Aggregation was dependent of plasma component(s) but independent of venom-induced lysophosphatidic acid generation. There was no increase in the levels of lactate dehydrogenase during platelet aggregation, ruling out the possibility of platelet lysis. The increased expression of ligand-induced binding site 1 (LIBS1) induced by L. gaucho venom and its sphingomyelinase fraction, as well as of P-selectin by the whole venom, evidenced the activation state of both human and rabbit platelets. Adhesion assays showed an irregular response when platelets were exposed to the whole venom, whereas the sphingomyelinase fraction induced a dose-dependent increase in the platelet adhesion to collagen. These findings evidence that L. gaucho venom and its sphingomyelinase fraction trigger adhesion, activation, and aggregation of both human and rabbit platelets. Thus, this work justifies the use of rabbits to investigate Loxosceles venom-induced platelet disturbances, and it also supports research on the role of platelets in the pathogenesis of loxoscelism.
Assuntos
Plaquetas/efeitos dos fármacos , Modelos Animais , Diester Fosfórico Hidrolases/farmacologia , Complexo Glicoproteico GPIIb-IIIa de Plaquetas/metabolismo , Coelhos/sangue , Esfingomielina Fosfodiesterase/farmacologia , Venenos de Aranha/farmacologia , Animais , Sítios de Ligação , Plaquetas/fisiologia , Humanos , Técnicas In Vitro , Integrina beta3/sangue , Selectina-P/sangue , Ativação Plaquetária/efeitos dos fármacos , Adesividade Plaquetária/efeitos dos fármacos , Agregação Plaquetária/efeitos dos fármacos , Glicoproteína IIb da Membrana de Plaquetas/sangueAssuntos
Linfoma de Células B/classificação , Linfoma de Células B/diagnóstico , Linfoma de Células B/genética , Linfoma de Células B/imunologia , Linfoma de Células B/patologia , Linfoma de Células B/terapia , Transtornos Linfoproliferativos/classificação , /imunologia , Células Matadoras Naturais/patologia , Glicoproteína IIb da Membrana de Plaquetas/imunologia , Linfoma Cutâneo de Células T/classificação , Linfoma Cutâneo de Células T/diagnóstico , Linfoma Cutâneo de Células T/terapia , Linfoma Difuso de Grandes Células B/diagnóstico , Linfoma Difuso de Grandes Células B/etiologia , Linfoma Difuso de Grandes Células B/terapia , Linfoma de Zona Marginal Tipo Células B/diagnóstico , Linfoma de Zona Marginal Tipo Células B/genética , Linfoma de Zona Marginal Tipo Células B/terapia , Neoplasias Cutâneas/diagnóstico , Neoplasias Cutâneas/patologia , Neoplasias Cutâneas/terapia , Plasmocitoma/diagnóstico , Plasmocitoma/imunologia , Prognóstico , Traumatismos da PernaRESUMO
Trombocitopenia é um achado frequente em unidades de terapia intensiva cardiológica; neste ambiente onde grande parte do arsenal terapêutico diminui a coagulabilidade sanguínea, a baixa contagem plaquetária representa um desafio ao médico intensivista. Este relato de caso ocorreu no Hospital Johns Hopkins, em Baltimore(EUA), em 2003, quando o autor esteve em visita a esta instituição. É apresentada uma revisão da literatura e uma breve discussão do caso