Anti-inflammatory Effects of Orobol, an Enzyme Converted Product of Genistein, on the IL-8 Production in HT-29 Colon Cells and the Dextran Sodium Sulfate (DSS)-Induced Acute Colitis Symptoms in C57BL/6 mice

Abstract

Inflammatory bowel disease (IBD) is a pathologic conditions of the gastrointestinal tract in humans. IBD has been suggested that that inflammatory responses play major roles in the pathogenesis though the etiology of IBD still remains unclear. Soy isoflavones are attractive source of food materials with anti-inflammation and gut-healty effects. After fermentation or bioconversion, the majority of soy isoflavones are transformed to their metabolites such as genistein, daidzein and so on. Recently, metabolites have been studied in their improved bioactivity. Orobol (7,8,3,4-tetrahydrowyisoflavone) is a metabolite of genistein. It has been known to anti-cancer effect for human ovarian and breast cancer. Although genistein exerts beneficial anti-inflammatory effects on colitis, orobol has not been studied about colitis yet. Interleukin-8 (IL-8), which is a major chemokine, plays a critical role in the inflammation including colitis. IL-8, derived epithelial cell, has been demonstrated to support neutrophil infiltration in various types of mucosal inflammation including IBD. In this study, I investigated the anti-inflammatory effect of orobol, a major metabolite of genistein in soybean. I found that oral administration of orobol decreased DSS-induced colitis symptoms such as weight loss, diarrhea, bloody fecal, and damaged colon tissue in C57BL/6 mice. Also, orobol reduced the IL-8 production and IL-8 mRNA in HT-29 cells. In luciferase assay, orobol inhibited the transactivation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-B) which is a major of transcription factor of IL-8. In a 359 whole human kinases, MAPK-interacting Ser/Thr kinase 1 (MNK1), which plays critical roles in various cytokine receptors signaling, was inhibited activity by orobol (IC50 = 33.43 nM) and suggested as a direct target of orobol. Additionally, orobol decreased tumor necrosis factor alpha (TNF-)-induced phosphorylation of eukaryotic initiation factor 4E (eIF4E) which is downstream of MNK1. Overall, orobol showed the anti-inflammatory effects in DSS-induced colitis mouse model. Also, orobol suppressed TNF--induced IL-8 production by directly targeting MNK1 in HT-29 colon cells. Thus, orobol could be a beneficial agent for reducing inflammation related to IBD.