title: Role of nitric oxide in tolerance to lipopolysaccharide in mice.
abstract: The injection of repeated doses of lipopolysaccharide (LPS) results in attenuation of the febrile response, which is called endotoxin tolerance. We tested the hypothesis that nitric oxide (NO) arising from inducible NO synthase (iNOS) plays a role in endotoxin tolerance, using not only pharmacological trials but also genetically engineered mice. Body core temperature was measured by biotelemetry in mice treated with NG-monomethyl-L-arginine (L-NMMA, 40 mg/kg; a nonselective NO synthase inhibitor) or aminoguanidine (AG, 10 mg/kg; a selective iNOS inhibitor) and in mice deficient in the iNOS gene (iNOS KO) mice. Tolerance to LPS was induced by means of three consecutive LPS (100 microg/kg) intraperitoneal injections at 24-h intervals. In wild-type mice, we observed a significant reduction of the febrile response to repeated administration of LPS. Injection of L-NMMA and AG markedly enhanced the febrile response to LPS in tolerant animals. Conversely, iNOS-KO mice repeatedly injected with LPS did not become tolerant to the pyrogenic effect of LPS. These data are consistent with the notion that NO modulates LPS tolerance in mice and that iNOS isoform is involved in NO synthesis during LPS tolerance.
authors.affiliation: Departamento de Morfologia, Estomatologia e Fisiologia, Faculdade de Odontologia de Ribeirão Preto, USP, 14040-904 Ribeirão Preto, SP, Brazil. branco@forp.usp.br
authors.forename: Mirela B
authors.initials: MB
authors.lastname: Dias
authors.forename: Maria C
authors.initials: MC
authors.lastname: Almeida
authors.forename: Evelin C
authors.initials: EC
authors.lastname: Carnio
authors.forename: Luiz G S
authors.initials: LG
authors.lastname: Branco
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects; D000818:Animals; D004361:Drug Tolerance; D005334:Fever / Q000139:chemically induced* / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000008:administration & dosage* / Q000506:poisoning*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000172:deficiency* / Q000235:genetics; D052247:Nitric Oxide Synthase Type II
chemical_list: D008070:Lipopolysaccharides; C440499:lipopolysaccharide, Escherichia coli O111 B4; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse