To investigate the modifying effect of enzymatically modified isoquercitrin (EMIQ) on hepatocellular tumor promotion induced by beta-naphthoflavone (BNF) treatment, male rats were administered a single intraperitoneal injection of N-diethylnitrosamine (DEN) and were fed a diet containing BNF (0.5%) for 6 weeks with or without EMIQ (0.2%) in the drinking water after DEN initiation. One week after the commencement of the administration of BNF, rats were subjected to a two-thirds partial hepatectomy. The number and area of GST-P positive foci, the number of COX2-positive cells and the area of elastica-van Gieson (EVG)-positive connective tissue fibers promoted by BNF were significantly suppressed by the administration of the antioxidant EMIQ. Real-time RT-PCR analysis revealed that EMIQ treatment decreased mRNA expression levels of Gstm1, Serpine1, Cox2 and Nfkbia and increased mRNA expression levels of Yc2 compared with those in the DEN-BNF group. These results suggest that co-administration of EMIQ suppresses the hepatocellular tumor-promoting activity of BNF in rats through the anti-inflammatory effects of EMIQ and restores the cellular redox balance altered by BNF.
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