Loss of gap junctions from DDT-treated rat liver epithelial cells

The mechanism by which the liver tumor promoter 1,1-bis(p-pchlorophenyl)-2,2,2-trichloroethane (DDT) inhibits gap junctional intercellular communication (GJIC) in WB-F344 rat liver epithelial cells could involve gap junction loss and/or decreased gap junction channel permeability. We examined these...

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Bibliographic Details
Published in:Carcinogenesis (New York) 1994-02, Vol.15 (2), p.301-306
Main Authors: Ruch, Randall J., Bonney, William J., Sigler, Kristi, Guan, Xiaojun, Matesic, Diane, Schafer, Lydia D., Dupont, Emmanuel, Trosko, James E.
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Carcinogenesis, carcinogens and anticarcinogens
Cells, Cultured
Chemical agents
Connexin 43 - genetics
Connexin 43 - metabolism
DDT - toxicity
Epithelial Cells
Epithelium - drug effects
Immunohistochemistry
Intercellular Junctions - drug effects
Liver - cytology
Liver - drug effects
Medical sciences
Rats
Rats, Inbred F344
RNA, Messenger - metabolism
Tumors
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Summary:The mechanism by which the liver tumor promoter 1,1-bis(p-pchlorophenyl)-2,2,2-trichloroethane (DDT) inhibits gap junctional intercellular communication (GJIC) in WB-F344 rat liver epithelial cells could involve gap junction loss and/or decreased gap junction channel permeability. We examined these two possibilities in the present study. Immunohistochemical studies using antibodies specific to connexin43, the major gap junction protein expressed by these cells, revealed that gap junction number and size were reduced during exposure to DDT. The reductions in gap junctions (33–91%) correlated with dose-dependent (1–10 μM) and time-dependent (0.5–4 h) decreases in cell-to-cell fluorescent dyecoupling (64–85%), as well as cellular levels of phosphorylated connexin43. These effects were reversible following removal of the tumor promoter from the culture medium, although cycloheximide reduced the level of gap junction reformation. The losses in gap junctions were not due to decreased connexin43 gene expression since steady-state levels of connexin43 mRNA were not similarly affected by DDT. Fenarimol (10 μM), a structural analog of DDT, did not inhibit GJIC and had no effect on gap junction structure or connexin43 expression. These data suggest that the inhibition of GJIC by DDT resulted from the removal of gap junctions from the plasma membrane and their degradation rather than simply a decrease in their permeability.
ISSN:0143-3334
1460-2180
DOI:10.1093/carcin/15.2.301