Vol. 53, Issue 3, 415-421, March 1998

Induction of Apoptosis in a Macrophage Cell Line RAW 264.7 By Acemannan, a -(1,4)-Acetylated Mannan

Lalitha Ramamoorthy and Ian R. Tizard

Department of Veterinary Pathobiology, Texas A & M University, College Station, Texas 77843

Acemannan is a polydispersed -(1,4)-linked acetylated mannan with antiviral properties. It is an immunomodulator, and studies in our laboratory have shown that it causes activation of macrophages. In the presence of IFN, acemannan induced apoptosis in RAW 264.7 cells. These cells exhibited chromatin condensation, DNA fragmentation, and laddering characteristic of apoptosis. The induction of apoptosis by acemannan and IFN does not seem to be mediated by nitric oxide, since N-nitro-L-arginine methyl ester, the nitric oxide inhibitor, had no effect. Acemannan in the presence of IFN also inhibited the expression of bcl-2. These results suggest that acemannan in the presence of IFN induces apoptosis in RAW 264.7 cells through a mechanism involving the inhibition of bcl-2 expression.