title: Role of LPS and receptor subtypes in the uptake of TNF by the murine lung.
abstract: Tumor necrosis factor alpha (TNF) is an important mediator in lung injury. The kinetics of TNF uptake by the lung are not completely understood. In this study, we evaluated the role that lipopolysaccharide (LPS) and the two types of TNF receptor (p55 and p75) play in the uptake of circulating murine TNF by the murine lung. TNF radioactively labeled with 125I (I-mTNF) was administered intravenously (2 x 10(6) cpm/mouse) to mice with both receptors (wild-type) or to mice missing one (p55-/- or p75-/-) or both (p55-/- and p75-/-) TNF receptors. Blood to lung non-reversible sequestration (Ki) and reversible uptake (Vi) were measured with multiple-time regression analysis. Uptake by lung of I-mTNF in wild-type mice had reversible and non-reversible components. This uptake was decreased by intratracheal, but not by intravenous, LPS, suggesting modulation by local, rather than systemic, inflammation. The p75-/- deficient mice retained the Ki (saturable, non-reversible) component of TNF uptake, whereas p55-/- deficient mice retained the Vi (saturable, reversible) component of TNF uptake. Both Ki and Vi components of TNF uptake were absent in the lungs of p55-/- p75-/- deficient mice. These studies show that local inflammation inhibits the uptake of circulating I-mTNF by lung and that uptake consists of two distinguishable compartments: reversible uptake mediated by the p75 receptor and non-reversible sequestration mediated by the p55 receptor.
authors.affiliation: Section of Pulmonary Diseases, Critical Care and Environmental Medicine, Tulane University Medical Center, New Orleans, LA 70112, USA. lortiz@mailhost.tcs.tulane.edu
authors.forename: L A
authors.initials: LA
authors.lastname: Ortiz
authors.forename: M
authors.initials: M
authors.lastname: Friedman
authors.forename: W A
authors.initials: WA
authors.lastname: Banks
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D004333:Drug Administration Routes; D005260:Female; D007275:Injections, Intravenous; D007442:Intubation, Intratracheal; D007457:Iodine Radioisotopes; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics / Q000378:metabolism*; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D011994:Recombinant Proteins; D013047:Specific Pathogen-Free Organisms; D013154:Spleen / Q000187:drug effects / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D015703:Antigens, CD; D007457:Iodine Radioisotopes; D008070:Lipopolysaccharides; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha