Navegando por Palavras-chave "Platelet Aggregation"
Agora exibindo 1 - 4 de 4
Resultados por página
Opções de Ordenação
- ItemSomente MetadadadosAção De Calicreína Plasmática Humana Sobre A Resposta Da Agregação Plaquetária Induzida Por Doses Hipoagregantes De Adp(Universidade Federal de São Paulo (UNIFESP), 2017-09-28) Fontes, Tatiana Neves [UNIFESP]; Oliva, Maria Luiza Vilela [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Human plasma kallikreín (huPK) potentiates platelet responses to subthreshold doses of ADP, although huPK itself, does not índuce platelet aggregation. In the present investigation, we observe that huPK pretreatment of platelets , potentiates ADP-induced platelet actívation by prior proteolysis of the G-proteincoupled receptor PAR-1. The potentiation of ADP-induced platelet activation by huPK is mediated by the integrin allb~3 through interactions with the KGD/KGE sequence motif ín huPK. Integrin allbf33 is a cofactor for huPK binding to platelets to support PAR-1 hydrolysis that contributes to activation of the ADP signaling pathway. This activation pathway leads to phosphorylation of Src, AktS473, ERK1/2, and p38 MAPK, and to Ca2+ release. The effect of huPK is blocked by specific antagonists of PAR-1 (SCH 19197) and allb~3 (abciximab) and by synthetic peptides comprising the KGD and KGE sequence motifs of huPK. Further, recombinant plasma kallikrein ínhibítor, rBbKI, also blocks this entíre mechanism. These results suggest a new function for huPK. Formation of plasma kallikrein lowers the threshold for ADP~induced platelet activation. The present observatíons are consistent wíth the notion that plasma kallikrein promotes vascu!ar disease and thrombosis in the intravascular compartment.
- ItemSomente MetadadadosCaracterização de inibidores da coagulação sanguínea e da agregação plaquetária presentes na saliva do carrapato Amblyomma cajennense (Acari: Ixodidae) (Fabricius, 1787)(Universidade Federal de São Paulo (UNIFESP), 2003) Simons, Simone Michaela [UNIFESP]; Chudzinski-Tavassi, Ana Marisa [UNIFESP]Os carrapatos constituem um dos mais importantes grupos de artropode parasitas hematofagos de animais domesticos, silvestres e do homem. 0 Amblyomma cajennese constitui uma das principais especies de vetores de varios patogenos causadores de doencas como a babesiose, febre maculosa e Lyme simile. Objetivo: Avaliar a atividade da saliva do carrapato Amalyomma cajennese sobre os mecanismos de coagulacao, agregacao de plaquetas e fibrinolise, alem de isolar e caracterizar um inibidor de Fator Xa, um inibidor de trombina e um inibidor de agregacao plaquetaria. Metodos: A obtencao da saliva bruta foi realizada seguindo o metodo de Tatchell modificado. A atividade inibitoria sobre FXa e trombina, tanto da saliva bruta quanto das fracoes obtidas apos cromatografia foram avaliadas utilizando-se os substratos cromogenicos S-2765 e S-2238 respectivamente; a atividade fibrinolitica foi verificada em placas de fibrina humana, contendo plasminogenio e a inibicao da agregacao plaquetaria foi verificada tanto em PRP (induzida por ADP, colageno, ristocetina e acido araquidonico) quanto em plaquetas lavadas (induzida por colageno. Tanto o p1 quanto as massas moleculares das proteinas da saliva foram determinados por eletroforese bi-dimensional. 0 fracionamento das proteinas da saliva foi realizado atraves de cromatografia de troca ionica (Resource Q) eluida com um gradiente linear de NaCI (0-500mM), as fracoes com atividade inibitoria sobre FXa, trombina e agregacao plaquetaria foram separadas em pools, sendo que o Plli que apresentava atividade inibitoria sobre o FXa foi submetido a uma gel filtracao (TSK gel 2000 sw) e o material obtido denominado Amblyomim-X. A capacidade inibitoria do Amblyomin-X foi analisada frente diferentes condicoes (efeito de ions calcio, presenca de deferentes concentracoes do inibidor, diferentes tempos de incubacao e na presenca de componentes do complexo protrombinase). Resultados: A saliva bruta inibiu o FXa, a trombina e a agregacao plaquetaria, e um inibidor de FXa de cerca de 67kDa, denominado Amblyomin-X foi isolado. 0 Ambiyomin-X inibiu de forma eficiente e rapida o FXa isolado (IC50 de 4,7gg) e tambem inibiu a geracao de trombina no complexo protrombinase de forma dose...(au)
- ItemSomente MetadadadosExpressão heteróloga, purificação e estudo de efeitos da rSculptina na coagulação sanguínea(Universidade Federal de São Paulo (UNIFESP), 2021) Viana, Juliana Da Silva [UNIFESP]; Tavassi, Ana Marisa Chudzinski [UNIFESP]; Universidade Federal de São PauloObjective: To investigate the action of recombinant Sculptin as an anticoagulant and a inhibition of thrombin-induced platelet activation. Methods: E. coli strain BL21 (DE3) containing plasmid Sculptin-Pet28a was cultivated with IPTG induction. After expression, the culture was lysed and the supernatant subjected to affinity chromatography, another ion exchange and finally gel filtration. The purified protein profile was monitored during these steps using SDS-Page. Blood clotting time, partially activated thromboplastin time (aPTT), prothrombin time (PT) and thrombin time (TT) assays were evaluated in the presence of rSculptin using diagnostic kits. The evaluation of the effect of rSculptin on platelets was performed in a platelet aggregation assay. Furthermore, the action of the recombinant protein was evaluated ex vivo with aPTT and PT assays after animal treatment. Finally, an in vivo bleeding time test was performed. Results: The purified protein showed activity on aPTT, PT and TT evaluated in vitro, extending them in a dose response, but with greater sensitivity for TT. It also inhibited platelet aggregation when thrombin was used as an agonist. Furthermore, when rSculptin was administered to animals at a concentration of 1 mg/kg, it significantly prolonged the clotting time of the plasmas evaluated in the aPTT and PT assays, the same was not observed for the concentration of 0.1 mg/kg. Finally, in the preliminary in vivo bleeding time assay, the studied protein prolonged the clotting time of treated animals at the concentration evaluated (1 mg/kg). Conclusion: The results obtained demonstrate that rSculptin has action on the clotting times evaluated in animal plasma. Furthermore, the essays shows the maintenance of the biological activity of this protein on blood clotting after it been administered to animals. Although preliminary, the results obtained in the assessment of bleeding time suggest an anticoagulant potential of rSculptin in vivo.
- ItemAcesso aberto (Open Access)Receptores plaquetários P2Y12: importância na intervenção coronariana percutânea(Sociedade Brasileira de Cardiologia - SBC, 2013-09-01) Falcão, Felipe José de Andrade [UNIFESP]; Carvalho, Leonardo; Chan, Mark; Alves, Claudia Maria Rodrigues [UNIFESP]; Carvalho, Antonio Carlos [UNIFESP]; Caixeta, Adriano [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); National University of Singapore Yong Loo Lin School of MedicinaApart from their role in hemostasis and thrombosis, platelets are involved in many other biological processes such as wound healing and angiogenesis. Percutaneous coronary intervention is a highly thrombogenic procedure inducing platelets and monocytes activation through endothelial trauma and contact activation by intravascular devices. Platelet P2Y12 receptor activation by adenosine diphosphate facilitates non-ADP agonist-mediated platelet aggregation, dense granule secretion, procoagulant activity, and the phosphorylation of several intraplatelet proteins, making it an ideal drug target. However, not all compounds that target the P2Y12 receptor have similar efficacy and safety profiles. Despite targeting the same receptor, the unique pharmacologic properties of each of these P2Y12 receptor-directed compounds can lead to very different clinical effects.