Increased IL-2 production in T cells by xanthohumol through enhanced NF-AT and AP-1 activity

Xanthohumol (XN) is a major chalcone found in hop, which is used to add bitterness and flavor to beer. In this study, we investigated the effects of XN on the production of interlukin-2 (IL-2), a potent T cell growth factor. Treatment with XN significantly increased IL-2 production in mouse EL-4 T cells activated with phorbol 12-myristate 13-acetate (PMA) plus ionomycin (Io) in a dose-dependent manner. To further characterize its regulatory mechanism of XN on increased IL-2 production, the effects of XN on IL-2 promoter activity and the activity of several transcription factors modulating IL-2 expression were analyzed. XN enhanced activity of the IL-2 promoter, which contains distal and proximal regulatory elements in PMA/Io-activated EL-4 T cells. Furthermore, the activity of NF-AT and AP-1 was enhanced but NF-κB activity was not influenced by XN in PMA/Io-activated EL-4 T cells. These results suggest that XN increased IL-2 production at the transcriptional levels via the up-regulation of NF-AT and AP-1 in PMA/Io-activated EL-4 T cells.