RESUMEN
Endotoxin, a constituent of Gram-negative bacteria, stimulates macrophages to release large quantities of tumor necrosis factor (TNF) and interleukin-1 (IL-1), which can precipitate tissue injury and lethal shock (endotoxemia). Antagonists of TNF and IL-1 have shown limited efficacy in clinical trials, possibly because these cytokines are early mediators in pathogenesis. Here a potential late mediator of lethality is identified and characterized in a mouse model. High mobility group-1 (HMG-1) protein was found to be released by cultured macrophages more than 8 hours after stimulation with endotoxin, TNF, or IL-1. Mice showed increased serum levels of HMG-1 from 8 to 32 hours after endotoxin exposure. Delayed administration of antibodies to HMG-1 attenuated endotoxin lethality in mice, and administration of HMG-1 itself was lethal. Septic patients who succumbed to infection had increased serum HMG-1 levels, suggesting that this protein warrants investigation as a therapeutic target.
Asunto(s)
Bacteriemia/sangre , Proteínas Portadoras/metabolismo , Endotoxemia/sangre , Endotoxinas/toxicidad , Proteínas del Grupo de Alta Movilidad/metabolismo , Macrófagos/metabolismo , Animales , Proteínas Portadoras/genética , Proteínas Portadoras/inmunología , Proteínas Portadoras/toxicidad , Línea Celular , Células Cultivadas , Endotoxinas/sangre , Proteína HMGB1 , Proteínas del Grupo de Alta Movilidad/genética , Proteínas del Grupo de Alta Movilidad/inmunología , Proteínas del Grupo de Alta Movilidad/toxicidad , Humanos , Sueros Inmunes/inmunología , Inmunización Pasiva , Interferón gamma/farmacología , Interleucina-1/farmacología , Dosificación Letal Mediana , Leucocitos Mononucleares/metabolismo , Lipopolisacáridos/toxicidad , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C3H , ARN Mensajero/genética , ARN Mensajero/metabolismo , Factores de Tiempo , Factor de Necrosis Tumoral alfa/farmacologíaRESUMEN
BACKGROUND: Sepsis is a life-threatening disorder resulting from systemic inflammatory and coagulatory responses to infection. High-mobility group box 1 protein (HMGB1), an abundant intranuclear protein, was recently identified as a potent lethal mediator of sepsis. However, the precise mechanisms by which HMGB1 exerts its lethal effects in sepsis have yet to be confirmed. We recently reported that plasma HMGB1 levels correlated with disseminated intravascular coagulation (DIC) score, indicating that HMGB1 might play an important role in the pathogenesis of DIC. OBJECTIVES: To investigate the mechanisms responsible for the lethal effects of HMGB1, and more specifically, to explore the effects of HMGB1 on the coagulation system. METHODS: Rats were exposed to thrombin with or without HMGB1, and a survival analysis, pathologic analyses and blood tests were conducted. The effects of HMGB1 on the coagulation cascade, anticoagulant pathways and surface expression of procoagulant or anticoagulant molecules were examined in vitro. RESULTS: Compared to thrombin alone, combined administration of thrombin and HMGB1 resulted in excessive fibrin deposition in glomeruli, prolonged plasma clotting times, and increased mortality. In vitro, HMGB1 did not affect clotting times, but inhibited the anticoagulant protein C pathway mediated by the thrombin-thrombomodulin complex, and stimulated tissue factor expression on monocytes. CONCLUSIONS: These findings demonstrate the procoagulant role of HMGB1 in vivo and in vitro. During sepsis, massive accumulation of HMGB1 in the systemic circulation would promote the development of DIC.
Asunto(s)
Coagulación Sanguínea/efectos de los fármacos , Coagulantes/farmacología , Coagulación Intravascular Diseminada/sangre , Proteínas del Grupo de Alta Movilidad/metabolismo , Proteínas Represoras/metabolismo , Trombosis/sangre , Animales , Pruebas de Coagulación Sanguínea , Células Cultivadas , Coagulantes/toxicidad , Citocinas/sangre , Modelos Animales de Enfermedad , Coagulación Intravascular Diseminada/inducido químicamente , Coagulación Intravascular Diseminada/metabolismo , Coagulación Intravascular Diseminada/patología , Activación Enzimática/efectos de los fármacos , Fibrina/metabolismo , Proteína HMGB1 , Hemólisis/efectos de los fármacos , Proteínas del Grupo de Alta Movilidad/farmacología , Proteínas del Grupo de Alta Movilidad/toxicidad , Humanos , Inflamación/sangre , Riñón/efectos de los fármacos , Riñón/metabolismo , Riñón/patología , Pulmón/efectos de los fármacos , Pulmón/patología , Masculino , Monocitos/efectos de los fármacos , Monocitos/metabolismo , Proteína C/metabolismo , Ratas , Ratas Sprague-Dawley , Proteínas Represoras/farmacología , Proteínas Represoras/toxicidad , Trombina , Tromboplastina/metabolismo , Trombosis/inducido químicamente , Trombosis/metabolismo , Trombosis/patologíaRESUMEN
High-mobility group-1 (HMG-1), an abundant, highly conserved cellular protein, is widely known as a nuclear DNA-binding protein that stabilizes nucleosome formation, facilitates gene transcription, and regulates the activity of steroid hormone receptors. We discovered that HMG-1 is a late mediator of delayed endotoxin lethality. When released by activated monocytes, it participates in the development of lethality and it activates downstream cytokine release. This review covers the general features of HMG-1 and its newly appreciated role as a cytokine.
Asunto(s)
Proteínas Portadoras/fisiología , Citocinas/fisiología , Endotoxemia/metabolismo , Endotoxinas/toxicidad , Proteínas del Grupo de Alta Movilidad/fisiología , Monocitos/metabolismo , Reacción de Fase Aguda/etiología , Secuencia de Aminoácidos , Animales , Proteínas Portadoras/sangre , Proteínas Portadoras/química , Proteínas Portadoras/genética , Proteínas Portadoras/toxicidad , Drosophila melanogaster/metabolismo , Endotoxinas/farmacología , Proteína HMGB1 , Proteínas del Grupo de Alta Movilidad/sangre , Proteínas del Grupo de Alta Movilidad/química , Proteínas del Grupo de Alta Movilidad/genética , Proteínas del Grupo de Alta Movilidad/toxicidad , Humanos , Mediadores de Inflamación/metabolismo , Proteínas de Insectos/química , Proteínas de Insectos/fisiología , Interleucina-1/farmacología , Pulmón/metabolismo , Pulmón/patología , Macrófagos/efectos de los fármacos , Modelos Biológicos , Datos de Secuencia Molecular , Monocitos/efectos de los fármacos , Familia de Multigenes , Adenohipófisis/citología , Procesamiento Proteico-Postraduccional , Receptor para Productos Finales de Glicación Avanzada , Receptores Inmunológicos/metabolismo , Choque Séptico/etiología , Choque Séptico/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/fisiología , Especificidad de la Especie , Factor de Necrosis Tumoral alfa/farmacología , Vertebrados/metabolismoRESUMEN
Acute inflammatory lung injury is often a delayed complication of critical illness and is associated with increased mortality. High mobility group-1 (HMG-1) protein, in addition to its role as a transcriptional regulatory factor, has recently been identified as a late mediator of endotoxin lethality. In the present studies, HMG-1 given intratracheally produced acute inflammatory injury to the lungs, with neutrophil accumulation, the development of lung edema, and increased pulmonary production of IL-1beta, TNF-alpha, and macrophage-inflammatory protein-2. In endotoxin-induced acute lung inflammation, administration of anti-HMG-1 Abs either before or after endotoxin exposure decreased the migration of neutrophils to the lungs as well as lung edema. These protective effects of anti-HMG-1 were specific, because pulmonary levels of IL-1beta, TNF-alpha, or macrophage-inflammatory protein-2 were not decreased after therapy with anti-HMG-1. Together, these findings indicate that HMG-1 is a distal mediator of acute inflammatory lung injury.