DIFFERENT EFFECTS OF 3 BISPHOSPHONATES ON NITRIC-OXIDE PRODUCTION BY RAW-264 MACROPHAGE-LIKE CELLS IN-VITRO

The macrophage-suppressive properties of three bisphosphonates were ev aluated by studying their effect on nitric oxide (NO) production by ac tivated RAW 264 macrophage-like cells. The cells were activated with 1 0 mu g/ml of lipopolysaccharide, and NO was determined as nitrite in t he cell culture supernatant. The effect of the drugs on inducible NO s ynthase was determined by Western blot analysis. As free drugs, clodro nate and pamidronate inhibited NO secretion in a dose-dependent manner , whereas alendronate had no effect. Liposome encapsulation enhanced t he effect of clodronate by a factor of 7, but the potency of pamidrona te weakened slightly when encapsulated in liposomes. The inducible NO synthase expression inside the cells was also decreased by liposomal c lodronate. In contrast to pamidronate, clodronate could affect the NO secretion when given to the cells simultaneously with lipopolysacchari de, and the inhibitory action was still seen when the drug was added 2 h after lipopolysaccharide induction. The viability of the cells was not affected by free or liposomal clodronate, whereas pamidronate show ed considerable cytotoxicity. This study shows the different actions o f these three bisphosphonates on NO production by macrophages and sugg ests that liposomal clodronate is the most promising bisphosphonate as an anti-inflammatory agent, whereas aminobisphosphonates do not posse ss anti-inflammatory properties.