Affiliations: 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 | Mayekawa Mfg. Co. Ltd., 2000 Tatsuzawa Moriya, Ibaraki
302-0118, Japan
Note: [] To whom correspondence should be addressed. Tel.: +81 3 5841
5127; Fax: +81 3 5841 8026; E-mail: ams316@mail.ecc.u-tokyo.ac.jp
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.
