PYRROLIDINE DITHIOCARBAMATE INHIBITS INDUCTION OF NITRIC-OXIDE SYNTHASE ACTIVITY IN RAT ALVEOLAR MACROPHAGES

Since nuclear factor kappa B (NF-κB) is activated during many inflammatory conditions, we assessed its role in expression of the L- arginine-nitric oxide pathway by rat alveolar macrophages. Pyrrolidine dithiocarbamate (PDTC), an inhibitor of NF-κB activation, was added to cultured macrophages stimulated with lipopolysaccharide (LPS) and interferon- γ (IFNγ). Inducible nitric oxide synthase (iNOS) activity was determined by measuring the stable nitrogen oxide end products of L-arginine oxidation: Nitrite (NO2 —) and nitrate (NO3 —). Ten, 25 and 50 μM PDTC progressively inhibited iNOS activity by macrophages. When 30 μM PDTC was added 2 h before LPS + IFNγ, L-arginine oxidation by macrophages was inhibited by >99%; L- arginine oxidation was reduced by 70% if 50 μM PDTC and the stimuli were introduced together; NO2 — and NO3 — were not decreased significantly if 50 μM PDTC was added 6 h after LPS + IFNγ. Cycloheximide added along with LPS + IFNγ really inhibits iNOS activity, while cycloheximide added 6 h after LPS + IFNγ did not reduce NO2— and NO3 — in tissue culture supernatants. These findings suggest iNOS activity in macrophages treated with LPS + IFNγ requires NF-κB activation. © 1993 Academic Press, Inc.