Azole antifungals: weak inhibitors of inducible nitric oxide synthase in mouse and human cells

The effect of three azole antifungals on inducible nitric oxide (iNOS) activity in different mouse and human cells was evaluated. The iNOS activity was determined by L-citrulline and nitrite measurement. In the murine macrophage cell line RAW 264.7, in mouse peritoneal macrophages (MPM) and in human colorectal adenocarcinoma cells (DLD-1), iNOS activity could be induced with lipopolysaccharides and cytokines. Under similar conditions, no iNOS induction was found in human monocytes/macrophages. The concentration of itraconazole, ketoconazole or miconazole needed to inhibit iNOS activity by 50% in RAW 264.7 cells, MPM and DLD-1 cells was > or = 10 mumol l-1. This is at least 100 times more than the concentrations of these azole antifungals required to produce a 50% inhibition of yeast growth and ergosterol synthesis of, for example, Candida albicans after the same incubation period. These results show that azole antifungals are weak inhibitors of iNOS in intact cells.