The preventive effect of green tea on the gap junction intercellular communication in renal epithelial cells treated with a renal carcinogen.
OBJECTIVE
Clinical studies imply that (-)-epigallocatechin-3-gallate (EGCG), a main ingredient of green tea catechins, has a chemopreventive action against cancers and suppresses the proliferation of cancer cells. However, there is no report about its chemopreventive effect for renal cancer. We previously determined that renal carcinogens suppressed the gap junction intercellular communication (GJIC) of renal epithelial cells. In this study, we investigated the effect of EGCG on the GJIC of renal epithelial cells treated with a renal carcinogen.


METHODS
Mardin-Darby canine kidney (MDCK) cells were used to determine the protective effects of EGCG on dimethylnitrosamine-induced alteration of GJIC and connexin 43 (Cx 43). The maximum concentration of EGCG was determined by the lactate dehydrogenase assay method. The scrape-loading dye transfer method was used to assess the expression and cellular localization of Cx 43. The phosphorylation status of Cx 43 was determined by Western blot analysis.


RESULTS
The optimal noncytotoxic concentration of EGCG was determined to be 10 microg/ml. The levels of GJIC and Cx 43 expression were markedly decreased in MDCK cells exposed to dimethylnitrosamine. A 12-h pretreatment with EGCG greatly ameliorated the GJIC-inhibitory effects of dimethylnitrosamine.


CONCLUSIONS
These results suggest that the preservation of GJIC may indicate the chemopreventive effect of green tea on renal epithelial cells treated with a renal carcinogen in vitro.
Takahashi
Hajime
H
Department of Urology, Nagasaki University School of Medicine, Nagasaki, Japan.
Nomata
Koichiro
K
Mori
Ken-Ichi
K
Matsuo
Manabu
M
Miyaguchi
Taishi
T
Noguchi
Mitsuru
M
Kanetake
Hiroshi
H
D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D002273:Carcinogens; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002450:Cell Communication / Q000187:drug effects*; D002471:Cell Transformation, Neoplastic / Q000187:drug effects; D018031:Connexin 43 / Q000096:biosynthesis; D004128:Dimethylnitrosamine; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D017629:Gap Junctions / Q000187:drug effects*; D007668:Kidney / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007680:Kidney Neoplasms / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*; D013662:Tea / Q000737:chemistry*
D016588:Anticarcinogenic Agents; D002273:Carcinogens; D018031:Connexin 43; D013662:Tea; D002392:Catechin; C045651:epigallocatechin gallate; D004128:Dimethylnitrosamine