ENHANCEMENT OF INDUCIBLE-TYPE NO SYNTHASE GENE-TRANSCRIPTION BY PROTEIN-SYNTHESIS INHIBITORS - ACTIVATION OF AN INTRACELLULAR SIGNAL-TRANSDUCTION PATHWAY BY LOW CONCENTRATIONS OF CYCLOHEXIMIDE

Treatment of mouse macrophage-like RAW 264.7 cells with certain protein synthesis inhibitors is followed by accumulation of the mRNA for the inducible isoform of nitric oxide synthase (I-NOS). The activity of these compounds on the i-NOS gene in RAW 264.7 cells was analyzed here in detail. Results show that both cycloheximide and anisomycin can efficiently induce i-NOS mRNA, even when used at concentrations so low (0.25 mu g/ml) to have only negligible effects on protein synthesis; puromycin, on the other hand, shows only a limited effect on i-NOS mRNA expression, detectable only when cells are treated with higher concentrations of inhibitor (25 mu g/ml). In RAW 264.7 cells, low concentrations of cycloheximide trigger an immediate-early gene response, as indicated by induction of c-fos and JE mRNAs, and can efficiently activate transcription of transiently transfected recombinant reporter genes including either the i-NOS or the c-fos gene promoters.