5,7-Dihydroxyflavone Analogues May Regulate Lipopolysaccharide-Induced Inflammatory Responses by Suppressing IκBα-Linked Akt and ERK5 Phosphorylation in RAW 264.7 Macrophages

Abstract

We studied the anti-inflammatory activity of twelve 5,7-dihydroxyflavone analogues in lipopolysaccharide- (LPS-) stimulated RAW 264.7 macrophages. We found that chrysin (1) and 4′-methoxytricetin (9) showed relatively significant anti-inflammatory activity and low cytotoxicity. Moreover,1and9recovered the expression levels of iNOS and COX2, as well as those of the intracellular inflammatory mediators IL-1βand IL-6, which were upregulated by LPS stimulation. In addition,1and9actively regulated the phosphorylation of IκBα, leading to the activation of NFκB. Phosphorylation of Akt and ERK5 (upstream of NFκB) by LPS stimulation was significantly regulated by1and9, as well as by BIX 02189 and LY 294002, which are phosphorylation inhibitors of ERK5 and Akt, respectively. The results suggest that compounds1and9may suppress the levels of iNOS and COX2 by regulating phosphorylation of Akt, ERK5, and IκBαand thus NFκB-related signaling pathways, resulting in anti-inflammatory effects in the cells. Because1and9showed low cytotoxicity and regulated both PGE2and NO production caused by inflammatory responses, they may hold promise as natural anti-inflammatory agents.