Chloromethyl ketones inhibit interleukin-12 production in mouse macrophages stimulated with lipopolysaccharide

Abstract

Interleukin-12 (IL-12) plays a pivotal role in the development of T-helper type 1 (Th1) immune response, which may be involved in the pathogenesis of chronic inflammatory autoimmune disorders. In this study, we investigated the effects of N-α-tosyl- l-phenylalanine chloromethyl ketone (TPCK) and N-α-tosyl- l-lysine chloromethyl ketone (TLCK), serine protease inhibitors, on the production of IL-12 from macrophages stimulated with lipopolysaccharide (LPS). TPCK and TLCK potently inhibited this LPS-induced IL-12 production in a dose-dependent manner. The effect of TPCK and TLCK on the IL-12 p40 promoter activation was analyzed by transfecting monocytic RAW264.7 cells with p40 promoter–reporter constructs. The repressive effect maps to a region in the p40 promoter containing a binding site for NFκB (p40-κB). A linker scan mutant of the p40-κB site abrogates the inhibitory effect on the p40 promoter, confirming the functional relevance of the NFκB site. Our results show that TPCK and TLCK inhibit NFκB-mediated IL-12 production in macrophages.