INHIBITORS OF ADP-RIBOSYLATION IMPAIR INDUCIBLE NITRIC-OXIDE SYNTHASEGENE-TRANSCRIPTION THROUGH INHIBITION OF NF KAPPA-B ACTIVATION

In murine macrophages, inducible NO synthase II (iNOS or NOS-II) is in duced at the transcriptional level by IFN-gamma, alone or synergistica lly with LPS. We investigated the possible role of reactions of ADP-ri bosylation in triggering the signaling pathways involved in NOS-II gen e expression, Stimulation with IFN-gamma and or LPS of RAW 264.7 macro phages, transiently transfected with the NOS-II promoter, was inhibite d by ADP-ribosylation inhibitors, indicating that they interfered with the signal(s) responsible for NOS-II gene transcription, We therefore explored the effect of these inhibitors on the activity of IRF-1 and NF kappa B transcription factors known to be involved in NOS-II induct ion by IFN-gamma and LPS. No effect was observed on IRF-1 activation. However, NF kappa B binding to its target sequence diminished and tran sfection experiments with an NF kappa B-driven reporter plasmid demons trating that ADP-ribosylation inhibitors suppressed NF kappa B-depende nt promoter activity, These results provide evidence that a step invol ving ADP-ribosylation is required to activate NF kappa B-mediated gene transcription. (C) 1998 Academic Press.