Ketamine inhibits nitric oxide synthase in lipopolysaccharide-treated rat alveolar macrophages

Abstract

Purpose: To evaluate the effects of ketamine on the activity and protein expression of inducible nitric oxide synthase (iNOS) induced by lipopolysaccharide (LPS) in rat alveolar macrophages. Methods: Pulmonary alveolar macrophages isolated from Wistar-Kyoto rats were used. After incubation of macrophages with ketamine (1, 10, or 100 μM) and LPS (1 μg·ml-1)for 24 hr, the cell-free medium was removed for measuring the nitrite and tumour necrosis factor-a (TNF-α) levels by Griess reaction and ELISA kit, respectively, The harvested macrophages were also used to determine the activity of iNOS by using the conversion of [3H]-L-arginine to [3H]-L-citrulline method. In addition, the protein expression of iNOS was detected by Western blot analysis. Results: In rat alveolar macrophages, (i) ketamine (1 to 100 μM) caused a dose-dependent suppression of the production of nitrite and TNF-α induced by LPS and (ii) ketamine (1 00 μM) inhibited the activity (46.5 ± 4.8%, P < 0.05) and protein expression (35 ± 11%, P < 0.05) of iNOS in response to LPS. Conclusion: These results show that ketamine inhibits the activity and expression of iNOS in LPS-activated alveolar macrophages, which may be associated with the reduction of the release of TNF-α following LPS treatment.