title: Endotoxin-macrophage interaction: post-translational regulation of tumor necrosis factor expression.
abstract: Thioglycollate-elicited murine peritoneal macrophages produce significant quantities of TNF 2 to 4 h after induction with bacterial endotoxin, LPS. However, macrophages exposed to a second LPS stimulus are refractory and the amount of TNF detected in these supernatants is reduced 10- to 50-fold. The acquisition of the refractory state in vitro or in vivo requires the continued presence of LPS for a minimum of 6 to 8 h, is optimal by 20 h, and is reversible. Refractory macrophages incubated for an additional 48 h in the absence of LPS produce significant quantities of TNF after reexposure to endotoxin. Although LPS refractory macrophages do not release TNF in response to a secondary endotoxin challenge, riboprobe ribonuclease protection assays demonstrated amplification of TNF message, suggesting that post-transcriptional events are involved in the regulation of TNF production in endotoxin refractory macrophages. Immunoprecipitation studies revealed the accumulation of the 26-kDa TNF precursor in lysates of refractory macrophages, thus demonstrating a post-translational regulatory process. Although LPS refractory macrophages do not release TNF in response to a second LPS stimulus, ingestion of zymosan by these cells results in the release of significant quantities of TNF. Furthermore, LPS-refractory macrophages do not demonstrate a reduction in other effector functions including Fc-mediated erythrophagocytosis. Therefore, the LPS refractory state is a metabolically dependent post-translational regulatory process, which requires continuous LPS exposure, is specific in which macrophage effector functions are inhibited, and is reversible with further incubation or by non-LPS-related stimuli.
authors.affiliation: Department of Immunology, Lilly Research Laboratories, Indianapolis, IN 46250.
authors.forename: S H
authors.initials: SH
authors.lastname: Zuckerman
authors.forename: G F
authors.initials: GF
authors.lastname: Evans
authors.forename: Y M
authors.initials: YM
authors.lastname: Snyder
authors.forename: W D
authors.initials: WD
authors.lastname: Roeder
mesh_terms: D000818:Animals; D002474:Cell-Free System; D003888:Desensitization, Immunologic; D004731:Endotoxins / Q000276:immunology*; D004912:Erythrocytes / Q000276:immunology; D004926:Escherichia coli / Q000276:immunology; D007274:Injections, Intraperitoneal; D008070:Lipopolysaccharides / Q000008:administration & dosage; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009344:Neisseria gonorrhoeae / Q000276:immunology; D010587:Phagocytosis; D011233:Precipitin Tests; D011499:Protein Processing, Post-Translational; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D004731:Endotoxins; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha