Ethyl caffeate suppresses NF-κB activation and its downstream inflammatory mediators, iNOS, COX-2, and PGE2 in vitro or in mouse skin

1 Ethyl caffeate, a natural phenolic compound, was isolated from Bidens pilosa, a medicinal plant popularly used for treating certain inflammatory syndromes. The purpose of this study was to investigate the structural activity, and the anti- inflammatory functions and mechanism( s) of ethyl caffeate. 2 Ethyl caffeate was found to markedly suppress the lipopolysaccharide ( LPS)- induced nitric oxide ( NO) production ( IC50 5.5 mu gml (-1)), mRNA and protein expressions of inducible nitric oxide synthase ( iNOS), and prostaglandin E-2 ( PGE(2)) production in RAW 264.7 macrophages. 3 Transient gene expression assays using human cox- 2 promoter construct revealed that ethyl caffeate exerted an inhibitory effect on cox- 2 transcriptional activity in 12- O- tetradecanoylphorbol- 13-acetate ( TPA)- treated MCF- 7 cells. 4 Immunohistochemical studies of mouse skin demonstrated that TPA- induced COX- 2 expression was significantly inhibited by ethyl caffeate with a superior effect to that of celecoxib, a nonsteroidal anti- inflammatory drug. 5 The phosphorylation and degradation of inhibitor kappa B ( I kappa B) and the translocation of nuclear transcription factor- kappa B ( NF- kappa B) into the nucleus, as well as the activation of mitogen- activated protein kinases ( MAPKs) induced by LPS in macrophages, were not affected by ethy l caffeate. Ethyl caffeate, however, could inhibit NF- kB activation by impairing the binding of NF- kappa B to its cis- acting element. These results suggest that ethyl caffeate suppresses iNOS and COX- 2 expressions partly through the inhibition of the NF- kappa B center dot DNA complex formation. 6 Structure - activity relationship analyses suggested that the catechol moiety and alpha, beta- unsaturated ester group in ethyl caffeate are important and essential structural features for preventing NFkB center dot DNA complex formation. This study provides an insight into the probable mechanism( caffeate.