Reduction in antioxidant defenses may contribute to ochratoxin A toxicity and carcinogenicity.
Ochratoxin A (OTA) is a renal carcinogen in rodents. Its human health significance is unclear. It likely depends upon the mechanism of carcinogenesis. In a previous microarray study a reduction in nuclear factor-erythroid 2 p45-related factor 2 (Nrf2)-dependent gene expression was observed in the kidney but not in the liver of rats fed OTA up to 12 months. Nrf2 regulates detoxification and antioxidant gene expression. The present report shows that OTA decreased the protein expression of several markers of the Nrf2-regulated gene battery in kidney in vivo indicating that the effects observed at mRNA level may be of biological significance. The OTA-mediated Nrf2 response could be reproduced in an NRK renal cell line and in primary hepatocyte cultures. In in vitro systems, an OTA-mediated inhibition of Nrf2 activity was demonstrated by electrophoretic mobility shift and Antioxidant Regulatory Element-driven luciferase reporter assays. The reduction of Nrf2-regulated gene expression resulted in oxidative DNA damage as evidenced by formation of abasic sites in vitro and confirmed in kidney in vivo. All OTA-mediated effects observed were prevented by pretreatment of cell cultures with inducers of Nrf2 activity. Our data suggest that reduction of cellular defense against oxidative stress by Nrf2 inhibition may be a plausible mechanism of OTA nephrotoxicity and carcinogenicity.
Cavin
Christophe
C
Quality and Safety Department, Nestlé Research Center, CH-1000 Lausanne 26, Switzerland. christophe.cavin@rdls.nestle.com
Delatour
Thierry
T
Marin-Kuan
Maricel
M
Holzhäuser
Daisy
D
Higgins
Larry
L
Bezençon
Claudine
C
Guignard
Gabriela
G
Junod
Sylviane
S
Richoz-Payot
Janique
J
Gremaud
Eric
E
Hayes
John D
JD
Nestler
Sandra
S
Mantle
Peter
P
Schilter
Benoît
B
D000818:Animals; D002273:Carcinogens / Q000633:toxicity*; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004224:Diterpenes / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects*; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D009793:Ochratoxins / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D020218:Response Elements / Q000187:drug effects; D018570:Risk Assessment; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
D002273:Carcinogens; D004224:Diterpenes; D051267:NF-E2-Related Factor 2; C495637:Nfe2l2 protein, rat; D009793:Ochratoxins; D012333:RNA, Messenger; C025589:ochratoxin A; D004247:DNA; D005982:Glutathione Transferase; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione