Induction of gene expression for nitric oxide synthase by immunomodulating drugs in the RAW264.7 murine macrophage cell line

Abstract

 We have elucidated the direct effects of PSK (a protein-bound polysaccharide) and OK-432 (a streptococcal preparation), both immunomodulating drugs, on the gene expression for an inducible nitric oxide synthase and on the production of nitric oxide (NO) in the RAW264.7 murine macrophage cell line. As determined by northern blot analysis, both immunomodulating drugs were potent inducers of gene expression for inducible NO synthase when cells were costimulated with interferon-γ (IFNγ). Expression of mRNA for the enzyme occurred in a dose-dependent manner after 3 h, when 10 – 50 μg/ml PSK or 0.001 – 1 KE/ml OK-432 was used. Furthermore, NO was also produced in response to these drugs, as detected by the Griess reagent reaction. The enhancement of NO synthesis was thought to be mediated, in part, through tumor necrosis factor α (TNFα) induction by these agents, since a neutralizing antibody to TNFα significantly suppressed NO production in RAW264.7 cells stimulated with PSK or OK432 in combination with IFNγ. We speculate that NO production may play a role in tumoricidal and microbicidal activities of PSK or OK-432 in vivo.