RESUMO
BACKGROUND: Immobilized fibrinogen and fibrin facilitate leukocyte adhesion, as they are potent ligands for leukocyte MAC-1 (CD11b/CD18). However, fibrinogen in its soluble form also binds to MAC-1, albeit with low affinity. The level of soluble fibrinogen is increased during chronic and acute inflammation, but the function of this increase is unknown. OBJECTIVES: To study the effect of soluble fibrinogen in concentrations found in severe acute inflammation on leukocyte adhesion. METHODS: Isolated leukocytes and soluble fibrinogen were studied in various in vitro settings under static and under flow conditions. RESULTS: Soluble fibrinogen functioned as a natural antagonist of neutrophil functions that are dependent on MAC-1, such as the respiratory burst induced by unopsonized zymosan and adhesion to ICAM-1 and heparin. In addition, soluble fibrinogen inhibited lymphocyte function-associated antigen 1-dependent lymphocyte binding to ICAM-1 through a direct interaction with ICAM-1. Soluble fibrinogen reduced MAC-1-dependent binding of interleukin-8-activated neutrophils to ICAM-1-expressing cells under flow conditions. Importantly soluble fibrinogen in acute-phase concentrations (4-10 mg mL(-1) ) dose-dependently reduced neutrophil firm adhesion to tumor necrosis factor-α-activated endothelium to 40% under flow conditions. CONCLUSIONS: We propose a model in which the increased circulating concentrations of soluble fibrinogen found during the acute-phase response can act as a natural antagonist of leukocyte recruitment, and therefore might contribute to the resolution of inflammation.
Assuntos
Reação de Fase Aguda/metabolismo , Antígenos CD18/química , Fibrinogênio/química , Molécula 1 de Adesão Intercelular/química , Neutrófilos/citologia , Animais , Cálcio/química , Adesão Celular , Movimento Celular , Citosol/metabolismo , Endotélio/patologia , Citometria de Fluxo , Células Endoteliais da Veia Umbilical Humana , Humanos , Inflamação , Ativação Linfocitária , Camundongos , Neutrófilos/imunologia , Ligação Proteica , Explosão Respiratória , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Chronic obstructive pulmonary disease (COPD) is characterised by neutrophilic inflammation in the airways and these neutrophils contribute to the production of inflammatory mediators. Dampening the production of proinflammatory mediators might be an important strategy to treat COPD and glucocorticosteroids are known to do so via inhibition of nuclear factor-κB. However, this pathway is important for the control of pro- and anti-inflammatory genes. We studied the effects of dexamethasone on production and secretion of pro-inflammatory interleukin (IL)-1ß and anti-inflammatory secreted IL-1 receptor antagonist (sIL-1Ra) by human neutrophils activated with tumor necrosis factor (TNF)-α. In vitro, TNF-α-stimulated neutrophils produced significant amounts of IL-1ß and sIL-1Ra; this production was inhibited by dexamethasone. However, synthesis and secretion of sIL-1Ra was inhibited at lower concentrations dexamethasone compared to IL-1ß, which changed the IL-1ß:sIL-1Ra ratio significantly. This altered ratio resulted in a more pro-inflammatory condition, as visualised by increased intercellular adhesion molecule-1 expression on human endothelial cells. In vivo, moderate-to-severe COPD patients using inhaled glucocorticosteroids have decreased plasma sIL-Ra levels compared with mild-to-moderate patients not on glucocorticosteroid treatment. In conclusion, dexamethasone induces a pro-inflammatory shift in the IL-1ß:sIL-1Ra cytokine balance in neutrophils in vitro, which might contribute to a lack of endogenous anti-inflammatory signals to dampen inflammation in vivo.
Assuntos
Anti-Inflamatórios/uso terapêutico , Dexametasona/uso terapêutico , Fatores Imunológicos/uso terapêutico , Proteína Antagonista do Receptor de Interleucina 1/metabolismo , Interleucina-1beta/biossíntese , Neutrófilos/metabolismo , Doença Pulmonar Obstrutiva Crônica/tratamento farmacológico , Idoso , Células Cultivadas , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/metabolismo , Humanos , Molécula 1 de Adesão Intercelular/biossíntese , Proteína Antagonista do Receptor de Interleucina 1/biossíntese , Proteína Antagonista do Receptor de Interleucina 1/sangue , Interleucina-1beta/sangue , Pessoa de Meia-Idade , Neutrófilos/efeitos dos fármacos , Doença Pulmonar Obstrutiva Crônica/fisiopatologia , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
BACKGROUND: The inflammatory process in chronic obstructive pulmonary disease (COPD) is characterised by the presence of neutrophils in the lung that are able to synthesise de novo several inflammatory mediators. The local chronic persistent inflammatory response is accompanied by systemic effects such as cytokine induced priming of peripheral leucocytes and muscle wasting. The preactivation or priming of peripheral blood neutrophils was used to gain more insight into the mechanisms of this systemic inflammatory response. METHODS: Gene arrays were performed on peripheral blood neutrophils obtained from healthy donors after stimulation in vitro with tumour necrosis factor (TNF)-alpha, granulocyte-macrophage colony stimulating factor (GM-CSF), or both. The expression of many inflammatory genes was regulated in these cells following stimulation. The expression of inflammatory genes in peripheral blood neutrophils in healthy subjects and those with COPD was measured by real time RT-PCR after stimulation with TNFalpha, GM-CSF, interleukin (IL)-8, fMLP, TNFalpha + GM-CSF, and lipopolysaccharide (LPS). RESULTS: The genes regulated in the gene array with TNFalpha/GM-CSF stimulated neutrophils included cytokines (such as IL-1beta), chemokines (such as IL-8), and adhesion molecules (such as ICAM-1). Disease severity as measured by forced expiratory volume in 1 second (FEV(1)) in COPD patients correlated with expression of several of these genes including IL-1beta (r = -0.540; p = 0.008), MIP-1beta (r = -0.583; p = 0.003), CD83 (r = -0.514; p = 0.012), IL-1 receptor 2 (r = -0.546; p = 0.007), and IL-1 receptor antagonist (r = -0.612; p = 0.002). CONCLUSIONS: These data are consistent with the hypothesis that progression of COPD is associated with the activation of neutrophils in the systemic compartment. De novo expression of inflammatory mediators by peripheral blood neutrophils suggests a pro-inflammatory role for these cells in the pathogenesis of COPD.
Assuntos
Fator Estimulador de Colônias de Granulócitos e Macrófagos/genética , Neutrófilos/metabolismo , Doença Pulmonar Obstrutiva Crônica/patologia , Fator de Necrose Tumoral alfa/genética , Citocinas/metabolismo , Feminino , Volume Expiratório Forçado/fisiologia , Expressão Gênica , Fator Estimulador de Colônias de Granulócitos e Macrófagos/metabolismo , Humanos , Inflamação/genética , Inflamação/metabolismo , Masculino , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase/métodos , Doença Pulmonar Obstrutiva Crônica/genética , Doença Pulmonar Obstrutiva Crônica/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Capacidade Vital/fisiologiaRESUMO
Chronic obstructive pulmonary disease (COPD) is characterised by a chronic inflammation in the pulmonary tissue. The disease is associated with a switch from a self-limiting inflammatory response, mainly initiated by smoke inhalation, to a chronic persistent inflammatory response after prolonged interaction with cigarette smoke. The extent of the inflammatory reaction is correlated with the severity of the disease. Chronic inflammation in the pulmonary tissue is also associated with systemic effects. These effects range from cytokine-induced priming of peripheral leukocytes, to muscle wasting induced by cytokines such as tumour necrosis factor-alpha. Despite a general consensus that chronic inflammation is a characteristic phenomenon of the disease, surprisingly little is known regarding the underlying pathogenetic mechanisms. A clear communication is present between the disease mechanisms in the pulmonary compartment and peripheral tissues, leading to the concept of COPD as a systemic inflammatory disease. This communication can be mediated by: 1) leakage of reactive oxygen species and stress-induced cytokines directly into the peripheral blood, 2) (pre)activation of peripheral blood leukocytes that can result in aberrant homing and activation of inflammatory cells in distant tissues, and 3) the liberation of proinflammatory mediators by leukocytes and/or stromal cells present in the pulmonary tissues during progression of the disease. The current authors hypothesise that the occurrence of a chronic inflammatory response after prolonged interaction of the pulmonary tissue with cigarette smoke causes aberrant homing of leukocytes to the tissue and delayed apoptosis. This leads to the autonomous characteristic of the inflammatory response in patients with chronic obstructive pulmonary disease.
Assuntos
Doença Pulmonar Obstrutiva Crônica/fisiopatologia , Humanos , Inflamação , Mediadores da Inflamação/fisiologia , Leucócitos/fisiologia , Músculo Esquelético/fisiopatologia , Neutrófilos/fisiologia , Doença Pulmonar Obstrutiva Crônica/patologia , Sistema Respiratório/patologia , Sistema Respiratório/fisiopatologia , Fumar/efeitos adversos , Redução de PesoRESUMO
The bleeding syndrome of acute promyelocytic leukemia (APL) is complex and consists of disseminated intravascular coagulation (DIC) and hyperfibrinolysis. Elastase, derived from malignant promyelocytes, is believed to mediate the fibrinogeno- and fibrinolysis by aspecific proteolysis. In this study we measured the role of elastase in fifteen patients with APL by using an assay for elastase degraded fibrin(ogen) and the results were compared with those obtained in patients with sepsis induced DIC. High levels of elastase were observed in sepsis and APL. The levels of fibrinogen and fibrin degradation products were significantly higher in APL patients compared to patients with sepsis induced DIC. Nevertheless, the level of elastase degraded fibrin(ogen) was higher in the sepsis group (635.3 ng/ml, compared to 144.3 ng/ml in APL; p <0.0001). So, the enormous increase in fibrin and fibrinogen degradation products in APL cannot be explained by elastase activity. This study suggests a minor role for elastase mediated proteolysis in the hemorrhagic diathesis in APL patients.
Assuntos
Fibrinólise/efeitos dos fármacos , Leucemia Promielocítica Aguda/complicações , Elastase Pancreática/farmacologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticorpos Monoclonais/metabolismo , Testes de Coagulação Sanguínea , Suscetibilidade a Doenças/sangue , Suscetibilidade a Doenças/etiologia , Coagulação Intravascular Disseminada/sangue , Coagulação Intravascular Disseminada/enzimologia , Coagulação Intravascular Disseminada/microbiologia , Feminino , Fibrina/metabolismo , Produtos de Degradação da Fibrina e do Fibrinogênio/imunologia , Produtos de Degradação da Fibrina e do Fibrinogênio/metabolismo , Fibrinogênio/metabolismo , Hemorragia/sangue , Hemorragia/enzimologia , Hemorragia/etiologia , Humanos , Leucemia Promielocítica Aguda/sangue , Leucemia Promielocítica Aguda/enzimologia , Masculino , Pessoa de Meia-Idade , Proteínas de Neoplasias/farmacologia , Elastase Pancreática/sangue , Sepse/sangue , Sepse/complicações , Sepse/enzimologiaRESUMO
Acute promyelocytic leukaemia (APL) is a disease that is distinguished from other leukaemias by the high potential for early haemorrhagic death. Several processes are involved, such as disseminated intravascular coagulation and hyperfibrinolysis. Recently, TAFI (thrombin-activatable fibrinolysis inhibitor) was identified as a link between coagulation and fibrinolysis. TAFI can be activated by thrombin, and in its activated form potently attenuates fibrinolysis by removing C-terminal lysine and arginine residues that are important for the binding and activation of plasminogen. Activation of TAFI by the coagulation system results in a down-regulation of fibrinolytic activity and, thereby, prevents a rapid dissolution of the fibrin clot. To establish whether TAFI was involved in the severity of the bleeding complications in APL, the TAFI antigen and activity levels were determined in a group of 15 patients. The TAFI antigen concentration was normal, but the activity of TAFI was severely reduced in APL by approximately 60%. The reduction of TAFI activity was most probably caused by the action of plasmin on TAFI because in vitro experiments revealed that plasmin slightly reduced antigen levels but severely reduced TAFI activity. The acquired functional TAFI deficiency in APL may contribute to the severity of the haemorrhagic diathesis because of the impaired capacity of the coagulation system to protect the fibrin clot from fibrinolysis.