title: Assessment system for dioxin absorption in the small intestine and prevention of its absorption by food factors.
abstract: It has been reported that 90% of the amount of dioxin in the whole body is absorbed orally with food. However, a concise and simple system to assess dioxin absorption in the small intestine has not yet been established. The present study reports a new in vitro assessment system for this purpose. A stable dioxin-responsive cell line was established by introducing a plasmid that incorporates a xenobiotic-responsive element upstream of the luciferase gene into human hepatic HepG2 genomic DNA. Dioxin was added to the apical side of differentiated human intestinal epithelial Caco-2 cell monolayers that had been cultured on a semipermeable membrane, and the basal medium was recovered after an appropriate incubation time. To the recovered medium was added dioxin-responsive HepG2, and a luciferase assay was performed. The established stable cell line clearly showed dose-and time-dependent response to dioxin. When a food factor such as chlorophyll, which has been reported to increase dioxin excretion in in vivo studies, was added with dioxin, a significant decrease in dioxin permeability to the Caco-2 monolayer was observed. This assessment system would be useful to search for those food factors that could prevent dioxin absorption in the small intestine.
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Natsume
authors.forename: Hideo
authors.initials: H
authors.lastname: Satsu
authors.forename: Kazushige
authors.initials: K
authors.lastname: Kitamura
authors.forename: Naoto
authors.initials: N
authors.lastname: Okamoto
authors.forename: Makoto
authors.initials: M
authors.lastname: Shimizu
mesh_terms: D006528:Carcinoma, Hepatocellular; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics; D004147:Dioxins / Q000493:pharmacokinetics*; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology*; D007413:Intestinal Mucosa; D007421:Intestine, Small / Q000502:physiology*; D008113:Liver Neoplasms; D010957:Plasmids; D011401:Promoter Regions, Genetic; D014162:Transfection
chemical_list: D004147:Dioxins; D019363:Cytochrome P-450 CYP1A1