ACEMANNAN, A BETA-(1,4)-ACETYLATED MANNAN, INDUCES NITRIC-OXIDE PRODUCTION IN MACROPHAGE CELL-LINE RAW-264.7

Acemannan is a polydispersed beta-(1,4)-linked acetylated mannan with antiviral properties. It is an immunomodulator, and studies in our lab oratory have shown that it causes activation of macrophages. Inducible NO synthase is generally expressed after transcriptional induction an d is known to mediate some of the cytotoxic action of activated macrop hages. Acemannan, in the presence of interferon-gamma, greatly increas ed the synthesis of NO in RAW 264.7 cells. This increase was preceded by increased expression of mRNA for the inducible form of macrophage N O synthase. Preincubation with pyrrolidine dithiocarbamate inhibited t he induction, indicating the involvement of nuclear factor-kappa B. Th ese results suggest that acemannan causes the activation of macrophage s by increasing the level of NO synthase at the level of transcription .