Linoleoyl ethanolamide reduces lipopolysaccharide-induced inflammation in macrophages and ameliorates 2,4-dinitrofluorobenzene-induced contact dermatitis in mice.

In our previous study, it was found that linoleoyl ethanolamide (LE) is present in sake lees, which are produced as a byproduct during the making of Japanese sake. LE is a fatty acid ethanolamide, which have been demonstrated to exert a variety of biological functions, and in this study, the anti-inflammatory effects of LE were examined using in vitro cell culture and in vivo animal experiments. In mouse RAW264.7 macrophages, LE suppressed the lipopolysaccharide (LPS)-induced expression of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6. In addition, LE inhibited LPS-induced increases in the levels of cyclooxygenase enzyme-2 and prostaglandin E(2), which are indicators of inflammation. The inhibitory effect of LE on the release of TNF-α was stronger than that of dipotassium glycyrrhizinate, which is widely used in external human skin care treatments. LE also suppressed the LPS-induced activation of Toll-like receptor 4 signaling and nuclear translocation of nuclear factor-κB (NF-κB) p65. In a contact dermatitis animal model, applying LE to affected ear skin ameliorated 2,4-dinitrofluorobenzene-induced contact dermatitis and pro-inflammatory cytokine expression at inflamed sites. These results indicate that LE exerts anti-inflammatory effects by inhibiting NF-κB signaling, and LE is proposed to be a useful therapeutic agent against contact dermatitis.