INDUCTION OF GENE-EXPRESSION FOR NITRIC-OXIDE SYNTHASE BY IMMUNOMODULATING DRUGS IN THE RAW264.7 MURINE MACROPHAGE CELL-LINE

We have elucidated the direct effects of PSK (a protein-bound polysacc haride) and OK-432 (a streptococcal preparation), both immunomodulatin g drugs, on the gene expression for an inducible nitric oxide synthase and on the production of nitric oxide (NO) in the RAW264.7 murine mac rophage cell line. As determined by northern blot analysis, both immun omodulating drugs were potent inducers of gene expression for inducibl e NO synthase when cells were costimulated with interferon-gamma (IFN gamma). Expression of mRNA for the enzyme occurred in a dose-dependent manner after 3 h, when 10-50 mu g/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 synthe sis was thought to be mediated, in part, through tumor necrosis factor alpha (TNF alpha) induction by these agents, since a neutralizing ant ibody to TNF alpha significantly suppressed NO production in RAW264.7 cells stimulated with PSK or OK432 in combination with IFN gamma. We s peculate that NO production may play a role in tumoricidal and microbi cidal activities of PSK or OK-432 in vivo.