DigitalCommons@PCOM

Anti-inflammatory effects of xanthohumol in RAW 264.7 macrophages are mediated through the activation of AMP kinase

Suwanee, GA

Xanthohumol (XN), a prenylated chalcone extracted from common hop plants, has been studied for its anti-inflammatory properties. In this study, we hypothesize that XN induces M2 polarization of macrophages and the resulting anti-inflammatory effects are mediated through the activation of adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. RAW 264.7 cells were treated with either 0.1% DMSO or XN and the culture supernatant was collected for ELISA and whole cell lysates were collected for western blotting. Our results demonstrate that XN upregulated the secretion of IL10, a signature cytokine for M2 polarization, in RAW264.7 cells. We further demonstrated that XN increased arginase expression, a marker for M2 polarization, and suppressed IFNγ-mediated upregulation of inducible nitric oxide synthase (iNOS) expression, a marker for M1 polarization. Additionally, XN decreased IFNγ – induced elevation of nitrite release, indicating the inhibitory effects of XN against M1 polarization. Furthermore, XN at 25μM increased the secretion of catecholamines from macrophages comparable to IL4, an inducer of M2 phenotype and these effects were accompanied by an increased expression of tyrosine hydroxylase, a rate-limiting enzyme of catecholamine biosynthesis. Finally, XN and AICAR, an AMPK stimulator, upregulated the expression of phospho-AMPK and arginase while dorsomorphin, an established inhibitor of the AMPK pathway failed to do so in RAW264.7 cells. These results provide evidence for the anti-inflammatory effects of XN mediated through the induction of M2 polarization and activation of AMPK signaling pathway.