We investigated the involvement of NF-kappaB in the regulation of COX-2 protein expression and prostaglandin production in LPS-stimulated J774 macrophages. Incubation of J774 cells with LPS (1 microg/ml) for 24 h caused an increase of COX-2 protein expression and accumulation of both PGE2 and 6-keto-PGF1alpha in the cell culture medium. Ammonium pyrrolidinedithiocarbamate (APDC, 0.1, 1, 10 microM) and N-alpha-p-tosyl-L-lysine chloromethylketone (TLCK, 1, 10, 100 microM), two inhibitors of NF-kappaB activation, suppressed in a concentration-dependent manner both LPS-induced COX-2 protein expression and prostanoid generation. Moreover, APDC and TLCK both inhibited the LPS-induced increase of NF-kappaB DNA binding activity and prevented IkappaB-alpha degradation. Our results show for the first time that NF-kappaB is involved in COX-2 protein expression in LPS-stimulated J774 macrophages and suggest that inhibitors of NF-kappaB activation may represent a useful tool for the pharmacological control of inflammation.