RESUMO
Blood neutrophils provide the first line of defense against pathogens but have also been implicated in thrombotic processes. This dual function of neutrophils could reflect an evolutionarily conserved association between blood coagulation and antimicrobial defense, although the molecular determinants and in vivo significance of this association remain unclear. Here we show that major microbicidal effectors of neutrophils, the serine proteases neutrophil elastase and cathepsin G, together with externalized nucleosomes, promote coagulation and intravascular thrombus growth in vivo. The serine proteases and extracellular nucleosomes enhance tissue factor- and factor XII-dependent coagulation in a process involving local proteolysis of the coagulation suppressor tissue factor pathway inhibitor. During systemic infection, activation of coagulation fosters compartmentalization of bacteria in liver microvessels and reduces bacterial invasion into tissue. In the absence of a pathogen challenge, neutrophil-derived serine proteases and nucleosomes can contribute to large-vessel thrombosis, the main trigger of myocardial infarction and stroke. The ability of coagulation to suppress pathogen dissemination indicates that microvessel thrombosis represents a physiological tool of host defense.
Assuntos
Coagulação Sanguínea/genética , Imunidade Inata/genética , Neutrófilos/fisiologia , Serina Proteases/fisiologia , Animais , Coagulação Sanguínea/fisiologia , Fatores de Coagulação Sanguínea/metabolismo , Fatores de Coagulação Sanguínea/fisiologia , Catepsina G/genética , Catepsina G/metabolismo , Catepsina G/fisiologia , Fibrina/metabolismo , Imunidade Inata/fisiologia , Elastase de Leucócito/genética , Elastase de Leucócito/metabolismo , Elastase de Leucócito/fisiologia , Lipoproteínas/metabolismo , Camundongos , Camundongos Knockout , Modelos Biológicos , Infarto do Miocárdio/genética , Infarto do Miocárdio/metabolismo , Neutrófilos/metabolismo , Nucleossomos/metabolismo , Processamento de Proteína Pós-Traducional/genética , Processamento de Proteína Pós-Traducional/fisiologia , Serina Proteases/genética , Serina Proteases/metabolismo , Transdução de Sinais/genética , Transdução de Sinais/fisiologia , Acidente Vascular Cerebral/genética , Acidente Vascular Cerebral/metabolismoRESUMO
The activation of initiator protein tissue factor (TF) is likely to be a crucial step in the blood coagulation process, which leads to fibrin formation. The stimuli responsible for inducing TF activation are largely undefined. Here we show that the oxidoreductase protein disulfide isomerase (PDI) directly promotes TF-dependent fibrin production during thrombus formation in vivo. After endothelial denudation of mouse carotid arteries, PDI was released at the injury site from adherent platelets and disrupted vessel wall cells. Inhibition of PDI decreased TF-triggered fibrin formation in different in vivo murine models of thrombus formation, as determined by intravital fluorescence microscopy. PDI infusion increased - and, under conditions of decreased platelet adhesion, PDI inhibition reduced - fibrin generation at the injury site, indicating that PDI can directly initiate blood coagulation. In vitro, human platelet-secreted PDI contributed to the activation of cryptic TF on microvesicles (microparticles). Mass spectrometry analyses indicated that part of the extracellular cysteine 209 of TF was constitutively glutathionylated. Mixed disulfide formation contributed to maintaining TF in a state of low functionality. We propose that reduced PDI activates TF by isomerization of a mixed disulfide and a free thiol to an intramolecular disulfide. Our findings suggest that disulfide isomerases can act as injury response signals that trigger the activation of fibrin formation following vessel injury.
