DANTROLENE INHIBITS NITRIC-OXIDE SYNTHASE IN RAT ALVEOLAR MACROPHAGESTREATED WITH LIPOPOLYSACCHARIDE AND INTERFERON-GAMMA

Purpose: To examine the effects of clantrolene on nitric oxide (NO) pr oduction and on the activity and protein expression of inducible nitri c oxide synthase (iNOS) induced by lipopolysaccharide (LPS) plus inter feron-gamma (IFN gamma) in rat alveolar macrophages. Methods: Pulmonar y alveolar macrophages isolated from Sprague Dawley rats were used. Af ter incubation of macrophages with dantrolene (1 to 100 mu M) and LPS (1 mu g.ml(-1)) and IFN-gamma (100 u.ml(-1)) for 24 hr, the cell-free medium was removed for measuring the nitrite and tumour necrosis facto r-alpha (TNF-alpha) levels by Griess reaction and ELISA kit, respectiv ely. The harvested macrophages were also used to determine the activit y of iNOS by using the conversion of [H-3]-L-arginine to [H-3]-L-citru lline method. Protein expression of iNOS was detected by Western biot analysis. Results: In rats alveolar macrophages, (I) dantrolene (1 to 100 mu M) caused a doss-dependent suppression of the production of nit rite and TNF-alpha induced by LPS (1 mu g.ml(-1)) plus IFN-gamma (100 u.ml(-1)) and (ii) dantrolene (100 mu M) inhibited the activity (by 37 +/- 5%, P < 0.01) and protein expression (by 39 +/- 12%, P < 0.01) of iNOS in response to LPS plus IFN-gamma. Conclusion: Dantrolene inhibi ts NO production as well as the activity and expression of iNOS in alv eolar macrophages treated with LPS plus IFN-gamma, which may be associ ated with the reduction of TNF-alpha production.