Ochratoxin A alters cell adhesion and gap junction intercellular communication in MDCK cells.
Ochratoxin A (OTA) is one of the most potent renal carcinogens studied to date, but the mechanism of tumor formation by ochratoxin A remains largely unknown. Cell adhesion and cell-cell communication participate in the regulation of signaling pathways involved in cell proliferation and growth control and it is therefore not surprising that modulation of cell-cell signaling has been implicated in cancer development. Several nephrotoxicants and renal carcinogens have been shown to alter cell-cell signaling by interference with gap junction intercell communication (GJIC) and/or cell adhesion, and the aim of this study was to determine if disruption of cell-cell interactions occurs in kidney epithelial cells in response to OTA treatment. MDCK cells were treated with OTA (0-50 microM) for up to 24h and gap junction function was analyzed using the scrape-load/dye transfer assay. In addition, expression and intracellular localization of C x 43, E-cadherin and beta-catenin were determined by immunoblot and immunofluorescence analysis. A clear decrease in the distance of dye transfer was evident following treatment with OTA at concentrations/incubation times which did not affect cell viability. Consistent with the functional inhibition of GJIC, treatment with OTA resulted in a dose-dependent decrease in C x 43 expression. In contrast to C x 43, OTA did not alter total amount of the adherens junction proteins E-cadherin and beta-catenin. Moreover, Western blot analysis of Triton X-100 soluble and insoluble protein fractions did not indicate translocation of cell adhesion molecules from the membrane to the cytoplasm. However, a approximately 78 kDa fragment of beta-catenin was detected in the detergent soluble fraction, indicating proteolytic cleavage of beta-catenin. Immunofluorescence analysis also revealed changes in the pattern of both beta-catenin and E-cadherin labeling, suggesting that OTA may alter cell-adhesion. Taken together, these data support the hypothesis that disruption of cell-cell signaling may contribute to OTA toxicity and carcinogenicity.
Mally
Angela
A
Department of Toxicology, University of Würzburg, Germany. mally@toxi.uni-wuerzburg.de
Decker
Martina
M
Bekteshi
Michaela
M
Dekant
Wolfgang
W
D000818:Animals; D015153:Blotting, Western; D015820:Cadherins / Q000096:biosynthesis; D002273:Carcinogens / Q000633:toxicity*; D002448:Cell Adhesion / Q000187:drug effects; D002450:Cell Communication / Q000187:drug effects*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D018031:Connexin 43 / Q000096:biosynthesis; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009793:Ochratoxins / Q000633:toxicity*; D051176:beta Catenin / Q000096:biosynthesis
D015820:Cadherins; D002273:Carcinogens; D018031:Connexin 43; D009793:Ochratoxins; D051176:beta Catenin; C025589:ochratoxin A