DNA adduct formation by ochratoxin A: Review of the available evidence

Figures & data

Table I. Mutagenicity and genotoxicity of ochratoxin A in vitro.

Test system	Results (positive/negative)	References
Ames test	Negative	(Wehner et al. 1978)
S. typhimurium TA 98, 100, 1535, 1537, 1538
S. typhimurium TA 102	Negative	(Wurgler et al. 1991)
S. typhimurium TA 98, 100, 1535, 1537, 1538	Negative	(Bendele et al. 1985)
S. typhimurium TA 98, 100, 1535, 1538, 102,104	Negative	(Follmann and Lucas 2003)
S. typhimurium TA 97, 98,100, 1535	Negative	(NTP 1989)
S. typhimurium TA 100, 2638	Negative	(Zepnik et al. 2001)
S. typhimurium TA 98, 1535, 1538	Positive (in the presence of mouse, but not rat kidney microsomes)	(Obrecht-Pflumio et al. 1999)
S. typhimurium TA 100, 1535, 1538	Positive (hepatocyte culture medium)	(Hennig et al. 1991)
SOS DNA Reparatur	Negative	(Sakai et al. 1992)
SOS Chromotest	Negative	(Krivobok et al. 1987)
E. coli PQ 35, 37
E. coli PQ 35, 37	Positive (at cytotoxic concentrations)	(Malaveille et al. 1991)
Mutagenicity in mammalian cells	Negative	(Bendele et al. 1985)
L5178Y TK+/- mouse lymphoma cells
HPRT	Negative	(Umeda et al. 1977)
lacZ′-mutations (NIH/3T3 mouse fibroblasts expressing human CYP450)	Positive	(de Groene et al. 1996)
DNA repair
Rat and mouse hepatocytes	Positive (weak effects only at cytotoxic concentrations)	(Mori et al. 1984)
Rat hepatocytes	Negative	(Bendele et al. 1985)
Rat hepatocytes	Positive	(Dorrenhaus and Follmann 1997)
DNA strand breaks	Positive	(Stetina and Votava 1986)
Chinese hamster ovary cells
Rat fibroblasts
Mouse splenocytes	Positive	(Creppy et al. 1985)
MDCK kidney epithelial cells	Positive	(Lebrun and Follmann 2002)
HepG2 cells	Positive	(Ehrlich et al. 2002)
Micronuclei-Test Syrian embryo fibroblasts	Positive	(Dopp et al. 1999)
HepG2 cells	Positive	(Ehrlich et al. 2002)
Sister Chromatid Exchange Chinese hamster ovary cells	Negative	(NTP 1989)
Porcine urinary bladder epithelial cells	Positive	(Follmann et al. 1995)
Human lymphocytes	Positive (?)	(Hennig et al. 1991)
Human lymphocytes	Negative	(Cooray 1984)

Figure 1. Biotransformation of Ochratoxin A.

Table II. Results from DNA binding studies using radiolabelled ochratoxin A.

Treatment conditions	Results	Limit of detection	References
Male rat, single oral dose of 1 mg/kg b.w., 24 h	No adducts detected, ^3H	2.7/10^9 DNA bases	(Gautier et al. 2001)
Rats, single oral dose of 210 µg/kg, 24 h	No adducts detected, ^3H	1.3/10^10 DNA bases	(Schlatter et al. 1996)
Rats, single oral dose of 500 µg/kg, 48 h	No adducts detected, ^14C	<3/10^9 DNA bases	(Mally et al. 2004)
Human and rat hepatocytes	No adducts detected, ^3H	2/10^9 DNA bases	(Gross-Steinmeyer et al. 2002)

Table III. Results from a range of in vivo studies using ³²P-postlabelling to assess DNA adduct formation by ochratoxin A.

Species/strain	Dosing regimen	DNA adducts in kidney	Comments/conclusions	References
Γ Swiss mice	2.5 mg/kg b.w. by gavage sacrifice 24–72 h after single dose	24 adduct spots Maximum adduct levels after 72 h	9 adduct spots in liverMaximum adduct levels after 72 h	(Pfohl-Leszkowicz et al. 1991)
		40/10^9 nucleotides, No background	7/10^9 nucleotides
Γ Swiss mice	2.5 mg/kg b.w. by gavage sacrifice 48 h after single dose	24 adduct spots Maximum adduct levels after 48 h	15 adduct spots in liver Maximum adduct levels after 48 h	(Pfohl-Leszkowicz et al. 1993)
		103/10^9 nucleotides, No background	42/10^9 nucleotides No background
Γ Swiss mice	2.0 mg/kg b.w. by gavage sacrifice 48 h after single dose	221/10^9 nucleotides, No background	pre-treatment with indomethacin and aspirin reduced adduct formation by 95%: involvement of prostaglandin- H-synthetase suggested	(Obrecht-Pflumio et al. 1996)
E BDF1-C57B1 mice		15 adduct spots	15 adduct spots in liver	(Petkova-Bocharova et al. 1998)
	0.5 mg/kg b.w. by gavage	4.5/10^9 nucleotides	66/10^9 nucleotides
	2 mg/kg b.w. by gavage sacrifice 48 h after single dose	13/10^9 nucleotides No background	984/10^9 nucleotides
Γ Sprague Dawley rats	0.2 mg (/kg b.w.?) by gavage	22/10^9 nucleotides	OTA in plasma 5.9 µ/ml (14.6 µM)	(Miljkovic et al. 2003)
	1.0 mg (/kg b.w.?) by gavage	41/10^9 nucleotides	42.4 µg/ml (105.3 µM)
	0.2 mg(/kg b.w.?) in feed	6/10^9 nucleotides	5.7 µg/ml (14.0 µM)
	1.0 mg(/kg b.w.?) in feed for 5 days, sacrifice on day 6	11/10^9 nucleotides	31.0 µg/ml (77.0 µM) Kidney pathology and loss of body weight only after 1 mg by gavage
Γ Lewis rats	2 mg/kg b.w. by gavage sacrifice 48 h after single dose	12 adduct spots 70/10^9 nucleotides	Pretreatment with N-acetyl-cysteine, acivcin or buthionine-sulfoximine reduced addduct formation: involvement of oxidative stress and a glutathione conjugate suggested	(Pfohl-Leskowicz et al. 2002)
Γ Lewis rats	0.4 mg/kg b.w. by gavage 3 times/week for 2 years	Up to 10 adduct spots 4–25/10^9 nucleotides	Cotreatment with MESNA reduced adduct formation: involvement of a glutathione conjugate suggested	(Pfohl-Leskowicz et al. 2002)
Γ Dark Agouti rats	0.4 mg/kg b.w. by gavage 3 times/week for 2 years	Up to 12 adduct spots 2.6–114/10^9 nucleotides Background 0.5/10^9 nucleotides	Dark Agouty more susceptible than Lewis rats: CYP 2C and CYP 1A implicated in OTA genotoxicity	(Pfohl-Leskowicz et al. 2002) (Castegnaro et al. 1998)
Γ Dark Agouti or Lewis rat?	0.4 mg/kg b.w. by gavage 3 times/week for 2 years	2 distinct adduct spots		(Arlt et al. 2001)
Γ Dark Agouti rats	0.4 mg/kg b.w. by gavage 3 times/week for 2 years	Up to 19 adduct spots		(Pfohl-Leszkowicz et al. 1998)
Γ F344 rats	1 mg/kg b.w. by gavage sacrifice 24 h after single dose	31–71 /10^9 nucleotides Background 6–24/10^9nucleotides	No binding of ^3H-ochratoxin A to DNA detected, suggesting spots observed by postlabelling may be caused by oxidative stress and/or cytotoxicity	(Gautier et al. 2001)
Γ F344 rats	2 mg/kg b.w. by gavage 5 times/week for 2 weeks, sacrifice 72 h after final dose	no treatment related adducts detected		(Mally et al. 2004)
Γ F344 rats	0.5–2 mg/kg b.w. by gavage 5 times/week for 2 weeks, sacrifice 72 h after final dose	No treatment related adducts detected	High blood and organ concentrations of OTA at terminal sacrifice, prominent kidney pathology, (oxidative) DNA damage present as indicated by the Comet Assay	(Mally et al. 2005a)

Figure 2. Chemical structure of a carbon- and an oxygen-bonded C8-deoxyguanosine formed by photorirradiation of OTA in the presence of dGMP.

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