Ochratoxin A-mediated DNA and protein damage: roles of nitrosative and oxidative stresses.
Ochratoxin A (OTA) is a mycotoxin occurring in a variety of foods. OTA is nephrotoxic and nephrocarcinogenic in rodents. An OTA-mediated increase of the inducible nitric oxide synthase (iNOS) expression was observed in normal rat kidney renal cell line and in rat hepatocyte cultures, suggesting the induction of nitrosative stress. This was associated with an increased nuclear factor kappa-light chain enhancer of activated B cells activity. The potential consequences of iNOS induction were further investigated. A significant increase in the levels of protein nitrotyrosine residues was observed with OTA. In addition, OTA was found to increase the level of DNA abasic sites in both cell cultures system. This end point was used as an indirect measure of 8-nitroguanine formation. Treatment of the cells with L-N(6)-(1-iminoethyl) lysine, a specific inhibitor of iNOS activity, inhibited the OTA-mediated overnitration of proteins but did not reduce the level of DNA abasic sites. It was found previously that nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) activators were able to restore the cellular defense against oxidative stress and could prevent DNA abasic sites in cell cultures. In the present study, pretreatment of the cells with activators of Nrf2 prevented OTA-mediated increase in lipid peroxidation, confirming the potential of Nrf2 activators to confer protection against OTA-mediated oxidative stress. In addition, it was found that Nrf2 activators could also prevent OTA-induced protein nitration and cytotoxicity. In conclusion, the present data further confirm oxidative stress as a key source of OTA-induced DNA damage and provide additional evidence for a role of this mechanism in OTA carcinogenicity. The exact role of nitrosative stress still remains to be established.
Cavin
Christophe
C
Quality and Safety Department, Nestlé Research Center, Vers-chez-les-Blanc, CH-1000 Lausanne 26, Switzerland. christophe.cavin@rdls.nestle.com
Delatour
Thierry
T
Marin-Kuan
Maricel
M
Fenaille
François
F
Holzhäuser
Daisy
D
Guignard
Gabrièla
G
Bezençon
Claudine
C
Piguet
Dominique
D
Parisod
Véronique
V
Richoz-Payot
Janique
J
Schilter
Benoît
B
D000447:Aldehydes / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002273:Carcinogens / Q000633:toxicity*; D002851:Chromatography, High Pressure Liquid; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004249:DNA Damage / Q000187:drug effects; D024202:Electrophoretic Mobility Shift Assay; D051547:Heme Oxygenase-1 / Q000096:biosynthesis; D008297:Male; D050984:NF-E2 Transcription Factor, p45 Subunit / Q000235:genetics; D016328:NF-kappa B / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis; D009793:Ochratoxins / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D026361:Reactive Nitrogen Species / Q000633:toxicity*; D017382:Reactive Oxygen Species / Q000633:toxicity*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry
D000447:Aldehydes; D002273:Carcinogens; D015853:Cysteine Proteinase Inhibitors; D050984:NF-E2 Transcription Factor, p45 Subunit; D016328:NF-kappa B; D009793:Ochratoxins; D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; C025589:ochratoxin A; D052247:Nitric Oxide Synthase Type II; D051547:Heme Oxygenase-1; C027576:4-hydroxy-2-nonenal