title: Burn-induced acute lung injury requires a functional Toll-like receptor 4.
abstract: The role of the Toll-like receptor 4 (TLR4), a component of the innate immune system, in the development of burn-induced acute lung injury (ALI) has not been completely defined. Recent data suggested that an intact TLR4 plays a major role in the development of organ injury in sterile inflammation. We hypothesized that burn-induced ALI is a TLR4-dependent process. Male C57BL/6J (TLR4 wild-type [WT]) and C57BL/10ScN (TLR4 knockout [KO]) mice were subjected to a 30% total body surface area steam burn. Animals were killed at 6 and 24 h after the insult. Lung specimens were harvested for histological examination after hematoxylin-eosin staining. In addition, lung myeloperoxidase (MPO) and intercellular adhesion molecule 1 immunostaining was performed. Lung MPO was measured by an enzymatic assay. Total lung keratinocyte-derived chemoattractant (IL-8) content was measured by enzyme-linked immunosorbent assay. Western blot was performed to quantify phosphorylated IκBα, phosphorylated nuclear factor κB p65 (NF-κBp65), and high mobility group box 1 expression. Acute lung injury, characterized by thickening of the alveolar-capillary membrane, hyaline membrane formation, intraalveolar hemorrhage, and neutrophil infiltration, was seen in WT but not KO animals at 24 h. Myeloperoxidase and intercellular adhesion molecule 1 immunostaining of KO animals was also similar to sham but elevated in WT animals. In addition, a reduction in MPO enzymatic activity was observed in KO mice as well as a reduction in IL-8 levels compared with their WT counterparts. Burn-induced ALI develops within 24 h after the initial thermal insult in our model. Toll-like receptor 4 KO animals were clearly protected and had a much less severe lung injury. Our data suggest that burn-induced ALI is a TLR4-dependent process.
authors.affiliation: Division of Trauma, Surgical Critical Care, and Burns, Department of Surgery, University of California, San Diego School of Medicine, San Diego, California, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Krzyzaniak
authors.forename: Gerald
authors.initials: G
authors.lastname: Cheadle
authors.forename: Carrie
authors.initials: C
authors.lastname: Peterson
authors.forename: William
authors.initials: W
authors.lastname: Loomis
authors.forename: James
authors.initials: J
authors.lastname: Putnam
authors.forename: Paul
authors.initials: P
authors.lastname: Wolf
authors.forename: Andrew
authors.initials: A
authors.lastname: Baird
authors.forename: Brian
authors.initials: B
authors.lastname: Eliceiri
authors.forename: Vishal
authors.initials: V
authors.lastname: Bansal
authors.forename: Raul
authors.initials: R
authors.lastname: Coimbra
mesh_terms: D055371:Acute Lung Injury / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002056:Burns / Q000378:metabolism* / Q000503:physiopathology*; D004797:Enzyme-Linked Immunosorbent Assay; D006609:High Mobility Group Proteins / Q000378:metabolism; D020672:I-kappa B Proteins / Q000378:metabolism; D018799:Intercellular Adhesion Molecule-1; D016209:Interleukin-8 / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D000072000:NF-KappaB Inhibitor alpha; D009195:Peroxidase / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000378:metabolism
chemical_list: D006609:High Mobility Group Proteins; D020672:I-kappa B Proteins; D016209:Interleukin-8; C000606205:Nfkbia protein, mouse; D051197:Toll-Like Receptor 4; D051996:Transcription Factor RelA; D018799:Intercellular Adhesion Molecule-1; D000072000:NF-KappaB Inhibitor alpha; D009195:Peroxidase