Reduction of NO synthase expression and tumor necrosis factor alpha production in macrophages by amphotericin B lipid carriers

The present study compared the abilities of different lipid carriers of amp hotericin B (AMB) to activate murine peritoneal macrophages, as assessed by their capacities to produce nitric oxide (NO) and tumor necrosis factor al pha (TNF-alpha). Although AMB alone did not induce NO production, synergy w as observed with gamma interferon but not with lipopolysaccharide. This syn ergy could not be explained by the mobilization of the nuclear activation f actor NF-kappaB by AMB. On the other hand, AMB induced TNF-alpha production without a costimulator and no synergy was observed. Anti-TNF-alpha antibod ies did not influence NO production, and an inhibitor of NO synthase did no t affect TNF-alpha production, indicating that the production of one of the se effector molecules was independent of that of the other. The incorporati on of AMB into lipid carriers reduced NO and TNF-alpha production with all formulations but more so with liposomes than with lipid complexes. NO produ ction was correlated with the induction of NO synthase II, revealed by West ern blotting. The extent of association of AMB with macrophages depended on the formulation, especially on the AMB/lipids ratio: the higher the ratio was, the greater the AMB association with macrophages. However, there was n o clear correlation between AMB association with macrophages, whether inter nalized or bound to the membrane, and immunostimulating effects, These resu lts may explain the reduced toxicities of lipid-based formulations of AMB.