IL-1 beta converting enzyme is a target for nitric oxide-releasing aspirin: New insights in the antiinflammatory mechanism of nitric oxide-releasing nonsteroidal antiinflammatory drugs

Caspase-1, the IL-1 beta converting enzyme (ICE), is required for intracell ular processing/maturation of IL-1 beta and IL-18, NO releasing nonsteroida l antiinflammatory drugs (NSAIDs) are a new class of NSAID derivatives that spare the gastric mucosa, Here, we tested the hypothesis that NCX-4016, a NO-aspirin derivative, inhibits proinflammatory cytokine release from endot oxin (LPS)-challenged monocytes, Our results demonstrated that exposing LPS -stimulated human monocytes to NCX-4016 resulted in a 40-80% inhibition of IL-1 beta, IL-8, IL-12, IL-18, IFN-gamma, and TNF-alpha release with an EC5 0 of 10-20 muM for IL-1 beta and IL-18, Incubating LPS-primed monocytes wit h NCX-4016 resulted in intracellular NO formation as assessed by measuring nitrite/nitrate, intracellular cGMP concentration, and intracellular NO for mation. Exposing LPS-stimulated monocytes to aspirin or celecoxib caused a 90% inhibition of prostaglandin E-2 generation but had no effect on cytokin e release. NCX-4016, similar to the NO donor S-nitroso-N-acetyl-D-L-penicil lamine, inhibited caspase-1 activity with an EC50 of approximate to 20 muM. The inhibition of caspase-1 by NCX-4016 was reversible by the addition of DTT, which is consistent with S-nitrosylation as the mechanism of caspase-1 inhibition. NCX-4016, but not aspirin, prevented ICE activation as measure d by assessing the release of ICE p20 subunit, IL-18 immunoneutralization r esulted in a 60-80% reduction of IL-1 beta, IL-8, IFN-gamma, and TNF-alpha release from LPS-stimulated monocytes, Taken together, these data indicate that incubating human monocytes with NCX-4016 causes intracellular NO forma tion and suppresses IL-1 beta and IL-18 processing by inhibiting caspase-1 activity. Caspase-1 inhibition is a new, cycloxygenase-independent antiinfl ammatory mechanism of NO-aspirin.