Isoflurane preconditioning reduces the rat NR8383 macrophage injury induced by lipopolysaccharide and interferon γ

Abstract

BACKGROUND: Isoflurane exposure before an insult can reduce the insult-induced injury in various organs. This phenomenon is called isoflurane preconditioning. The authors hypothesize that isoflurane can precondition macrophages, cells that travel to all tissues and are important in the host defense and inflammation responses. METHODS: Rat NR8383 macrophages were pretreated with or without 1-3% isoflurane for 1 h at 30 min before they were incubated with or without 100 ng/ml lipopolysaccharide plus 50 U/ml interferon γ for 24 h. Cell viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. Flow cytometry was performed after cells were stained with annexin V and propidium iodide. Inducible nitric oxide synthase protein expression in macrophages was quantified by Western blotting. RESULTS: Lipopolysaccharide plus interferon γ decreased cell viability by approximately 50%. This decrease was dose-dependently inhibited by aminoguanidine, an inducible nitric oxide synthase inhibitor. Lipopolysaccharide plus interferon γ caused inducible nitric oxide synthase expression. This expression was inhibited by pretreatment with 2% but not 1% or 3% isoflurane. Isoflurane at 2% inhibited lipopolysaccharide plus interferon γ-induced accumulation of nitrite, an oxidation product of nitric oxide. Pretreatment with 2% but not 1% or 3% isoflurane improved cell viability. Lipopolysaccharide plus interferon γ increased the number of propidium iodide-positive staining cells. This increase was attenuated by 2% isoflurane pretreatment. The protective effect of 2% isoflurane was abolished by chelerythrine, calphostin C, or bisindolylmaleimide IX, protein kinase C inhibitors. CONCLUSIONS: Lipopolysaccharide plus interferon γ causes an inducible nitric oxide synthase-dependent macrophage injury. Isoflurane induces preconditioning effects that may be mediated by protein kinase C in macrophages. © 2008 American Society of Anesthesiologists, Inc.