Heme oxygenase-1 mediates the anti-inflammatory effect of isoflurane preconditioning in LPS-stimulated macrophages.

Abstract

The aim of this study was to investigate the anti-inflammatory action of isoflurane preconditioning in a model of lipopolysaccharide (LPS)-induced inflammation in RAW 264.7 macrophages and examine the role of heme oxygenase (HO)-1 in this process. Murine 264.7 macrophages were pretreated with or without 1%-3% isoflurane for 1 h. Thirty minutes later, the cells were incubated with or without LPS for 24 h. Cell viability was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and cell injury was assessed by measuring the release of lactate dehydrogenase (LDH). HO-1 and inducible nitric oxide synthase (iNOS) protein expression was analyzed by Western blotting. Tumor necrosis factor (TNF)-alpha levels, nitrite production and HO activity were also determined. Pretreatment with the nontoxic and clinically approved anesthetic isoflurane potently attenuated the cell injury and the decrease in cell viability that was induced by LPS. Treatment or pretreatment with 2% isoflurane induced HO-1 protein expression and caused an induction of HO activity. This result correlated with a decrease in iNOS expression, a decrease in the production of nitric oxide (NO) and impaired release of TNF-alpha in LPS-stimulated macrophages. Blockade of HO activity with tin protoporphyrin (SnPP) reversed these effects. Isoflurane preconditioning exerts its anti-inflammatory activity through the HO-1 pathway in an in vitro inflammation model.