The Journal of immunology : official journal of the American Association of Immunologists
-
Activation of the resident macrophage populations of the reticuloendothelial system is a key component of the complex pathophysiology of sepsis. Macrophage activation leads to production and secretion of inflammatory mediators such as cytokines, vasoactive substances, free radicals, and chemokines, which have been associated with high morbidity and mortality in the septic patient. The goal of the present study was to determine whether antioxidants could suppress Kupffer cell activation at points beyond the initiation of activation. ⋯ Furthermore, we show that N-acetylcysteine-mediated inhibition of activation requires secondary protein synthesis, but does not modulate IkappaB-alpha mRNA expression. The inhibitory effect of these drugs occurs at the very earliest steps of the LPS signal transduction cascade as it is currently understood. The results of the present study suggest that the inflammatory response to sepsis may be controlled through appropriate antioxidant therapy.
-
Randomized Controlled Trial Clinical Trial
Attenuation of proinflammatory response by recombinant human IL-10 in human endotoxemia: effect of timing of recombinant human IL-10 administration.
To determine the effects of IL-10 on cytokine and granulocyte responses during endotoxemia, two groups of eight healthy male volunteers were challenged with endotoxin (4 ng/kg) on two occasions, once in combination with placebo injection, and once in conjunction with i.v. administered recombinant human IL-10 (rhIL-10) (25 microg/kg). In group 1, rhIL-10 was administered 2 min before endotoxin challenge; in group 2, the intervention was delayed for 1 h after endotoxin administration. rhIL-10 pretreatment reduced the LPS-induced rises in temperature and release of TNF, IL-6, IL-8, and IL-1 receptor antagonist. Endotoxin-induced granulocyte accumulation in lungs, as determined by dynamic granuloscintigrams, was prevented by rhIL-10 pretreatment, whereas granulocyte recruitment in liver and spleen was only modestly reduced. ⋯ Post-treatment with rhIL-10 did not influence LPS-induced temperature responses, cytokine release, or granulocyte degranulation. Both rhIL-10 pretreatment and post-treatment reduced LPS-induced cortisol levels. These results indicate that pretreatment with rhIL-10 reduces endotoxin-induced febrile responses, cytokine responses, and granulocyte accumulation in lungs, while in this acute model post-treatment with rhIL-10 exerts limited anti-inflammatory effects.
-
The C-X-C chemokines of the IL-8 family possess potent chemotactic activity for neutrophils, but their in vivo role in inflammatory responses is not well understood. In the IgG immune complex-induced model of acute lung inflammatory injury in the rat we have evaluated the roles of two rat chemokines, macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant (CINC). Both mRNA and protein for MIP-2 and CINC appeared in a time-dependent manner after initiation of IgG immune complex deposition in lung. ⋯ Chemotactic activity in BAL fluids collected 2 h after injury from animals undergoing immune complex deposition could be shown to be chiefly due to the combined contributions of MIP-2 (39%), CINC (28%), and C5a (21%). When either MIP-2 or CINC was blocked in vivo, up-regulation of Mac-1 expression on neutrophils obtained from BAL fluids was significantly reduced. These data suggest that, in the model studied, both MIP-2 and CINC contribute significantly to the influx of neutrophils and their activation.
-
LPS tolerance is characterized by a diminished monocytic synthesis of TNF-alpha and, interestingly, IL-10 after LPS restimulation. We wondered whether granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-12, and IFN-gamma can prevent or reverse this down-regulation of TNF-alpha and IL-10 production. The LPS-induced TNF-alpha amounts in desensitized PBMC treated with GM-CSF, IFN-gamma, or IL-12 and in naive, non-cytokine-primed cultures were similar, while much more TNF-alpha was induced in cytokine-primed naive cells. ⋯ IFN-gamma and GM-CSF prevented and reversed down-regulation of TNF-alpha and IL-10 synthesis also in the model of IL-10/TGF-beta1-induced LPS hyporesponsiveness, while IL-12 was ineffective because of its obvious inability to induce IFN-gamma. In summary, after LPS desensitization/hyporesponsiveness, IFN-gamma and GM-CSF tended to normalize pro- and anti-inflammatory monocytic behavior. Our results suggest that during LPS desensitization/hyporesponsiveness, monocytes acquire a hitherto unknown functional state with an altered reaction to biologic response modifiers.
-
The influence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and IFN-gamma on the restoration of impaired TNF-alpha release in LPS-desensitized mice or their refractory macrophages was investigated. Mice pretreated with GM-CSF or IFN-gamma (50 microg/kg i.v.) and injected with 3 mg/kg LPS i.p. displayed increased plasma TNF-alpha levels compared with LPS controls. IL-10 was marginally up-regulated by GM-CSF but abrogated by IFN-gamma pretreatment. ⋯ Cells from LPS-tolerant mice showed a diminished responsiveness to LPS. However, when exposed to GM-CSF or IFN-gamma ex vivo, their TNF-alpha response to LPS was partially restored. These findings characterize GM-CSF and IFN-gamma as potent enhancers of LPS-induced TNF-alpha production in normal as well as in experimentally immunocompromised mice and provide the rationale for further experiments to explore the pharmacologic use of these cytokines for restoration of immunocompetence in sepsis-associated immunosuppression.