Xanthohumol (XN) and its related compounds were evaluated for their effects on modulating the production of interleukin (IL)-12, the most important factor driving T helper 1 immune responses. XN showed the strongest inhibitory effect on IL-12 production in macrophages stimulated by lipopolysaccharide (LPS) or LPS/interferon-gamma. Xanthohumol 4'-O-beta-D-glucopyranoside (XNG) inhibited IL-12 production less effectively than XN. Isoxanthohumol and 8-prenylnaringenin showed comparatively lower inhibitory effects on IL-12 production than XNG. (2S)-5-methoxy-8-prenylnaringenin 7-O-beta-D-glucopyranoside did not exert any effect on IL-12 production. We then tested how these compounds affected NF-kappaB binding activity to the kappaB site in the nucleus. The compounds inhibited kappaB binding in macrophages with the same potency order as IL-12 inhibition. Furthermore, we investigated whether XN, which showed the most effective reduction of IL-12 production, attenuated skin inflammation. Chronic allergic contact dermatitis, an experimental model for psoriasis, was used to determine the anti-inflammatory effects of XN in vivo. XN treatment reduced the degree of ear thickening induced by oxazolone. Taken together, XN might be effective as an anti-inflammatory agent to reduce skin inflammation by inhibiting IL-12 production.
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