INHIBITION OF INTERLEUKIN-1 (IL-1) AND TUMOR-NECROSIS-FACTOR (TNF) PRODUCTION BY PYRIDINYL IMIDAZOLE COMPOUNDS IS INDEPENDENT OF CAMP ELEVATING MECHANISMS

Exposure of human monocytes (HM) to E. coli lipopolysacharide (LPS) results in measurable production of both IL-1beta and TNFalpha in culture supernatants. It has previously been reported that the elevation of cAMP levels in HM selectively suppresses the LPS-induced TNFalpha but not IL-1beta production. In this study we investigated whether the novel anti-inflammatory drug, SK&F 86002 [5-4(-pyridyl)-6(4-fluorophenyl)-2,3-dihydroimidazole(2,1-b)thiazol] and related analogs of the pyridinyl imidazole class, inhibit IL-1 and TNF production via a cAMP-dependent mechanism. These compounds, when added together with LPS result in inhibition of IL-1 and TNF production with equal-rank-order potency. Although the pyridinyl imidazole compounds were found to be generally weak phosphodiesterase inhibitors, they did not affect cAMP levels in HM, alone or in the presence of LPS. In contrast, PGE2, which significantly elevated intracellular cAMP levels, inhibited TNF but not IL-1 production at the transcriptional level. Taken together, these results suggest that the pyridinyl imidazoles inhibit the production of IL-1beta and TNFalpha through pathways independent of cAMP elevating mechanisms.