Nystatin is known to deplete lipid rafts from mammalian cell membranes. Lipid rafts have been reported to be necessary for lipopolysaccharide signaling. In this study, it was unexpectedly found that lipopolysaccharide-induced nitric oxide production was not inhibited, but rather increased in the presence of a non-cytotoxic concentration of nystatin. Surprisingly, treatment with nystatin induced only NO production and iNOS expression in RAW264.7 cells. At the concentration used, no changes in the expression of GM1 ganglioside, a lipid raft marker on RAW264.7 cells, was seen. From studies using several kinds of inhibitors for signaling molecules, nystatin-induced NO production seems to occur via the iκB/NF-κB and the PI3 K/Akt pathway. Furthermore, because nystatin is known to activate the Na-K pump, we examined whether the Na-K pump inhibitor amiloride suppresses nystatin-induced NO production. It was found that amiloride significantly inhibited nystatin-induced NO production. The results suggest that amoderate concentration of nystatin induces NO production by Na-pump activation through the PI3 kinase/Akt/NF-κB pathway without affecting the condition of lipid rafts.
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