RESUMO
BACKGROUND: The development of a procoagulant state in sepsis, owing to aberrant expression of tissue factor (TF) and a sharp decrease in the level of its major inhibitor, TF pathway inhibitor (TFPI), could lead to microthrombotic organ failure. The mechanism for the decline in TFPI activity in the lung could involve plasmin-mediated cleavage of the inhibitor. OBJECTIVE: To investigate the effect of plasmin generation on lung-associated TFPI activity, in normal conditions and during infusion of endotoxin (lipopolysaccharide [LPS]) in mice. METHODS: Plasmin generation and TFPI activity were assayed in the lungs of mice deficient in tissue-type plasminogen (Plg) activator (t-PA) or Plg, at 2 h after LPS or saline injection. RESULTS: The sharp loss of lung-associated TFPI activity at 2 h after LPS challenge paralleled the abrupt increase in plasmin generation. TFPI activity was significantly retained in both t-PA(-/-) and Plg(-/-) mice, which are unable to generate plasmin. CONCLUSION: The increased plasmin generation during the early stages of sepsis could cleave/inactivate TFPI and thus lead to thrombotic complications.
Assuntos
Coagulação Sanguínea , Endotoxemia/sangue , Fibrinolisina/metabolismo , Lipoproteínas/metabolismo , Pulmão/metabolismo , Animais , Citocinas/metabolismo , Modelos Animais de Doenças , Regulação para Baixo , Endotoxemia/induzido quimicamente , Endotoxemia/complicações , Endotoxemia/genética , Endotoxinas , Feminino , Lipoproteínas/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Plasminogênio/deficiência , Plasminogênio/genética , Inibidor 1 de Ativador de Plasminogênio/genética , Inibidor 1 de Ativador de Plasminogênio/metabolismo , RNA Mensageiro/metabolismo , Trombose/sangue , Trombose/etiologia , Fatores de Tempo , Ativador de Plasminogênio Tecidual/deficiência , Ativador de Plasminogênio Tecidual/genética , Regulação para CimaRESUMO
The tyrosine kinase receptor, c-Met, and its substrate, the hepatocyte growth factor (HGF), are implicated in the malignant progression of glioblastomas. In vivo detection of c-Met expression may be helpful in the diagnosis of malignant tumours. The C6 rat glioma model is a widely used intracranial brain tumour model used to study gliomas experimentally. We used a magnetic resonance imaging (MRI) molecular targeting agent to specifically tag the cell surface receptor, c-Met, with an anti-c-Met antibody (Ab) linked to biotinylated Gd (gadolinium)-DTPA (diethylene triamine penta acetic acid)-albumin in rat gliomas to detect overexpression of this antigen in vivo. The anti-c-Met probe (anti-c-Met-Gd-DTPA-albumin) was administered intravenously, and as determined by an increase in MRI signal intensity and a corresponding decrease in regional T(1) relaxation values, this probe was found to detect increased expression of c-Met protein levels in C6 gliomas. In addition, specificity for the binding of the anti-c-Met contrast agent was determined by using fluorescence microscopic imaging of the biotinylated portion of the targeting agent within neoplastic and 'normal'brain tissues following in vivo administration of the anti-c-Met probe. Controls with no Ab or with a normal rat IgG attached to the contrast agent component indicated no non-specific binding to glioma tissue. This is the first successful visualization of in vivo overexpression of c-Met in gliomas.
