Long-Evans Cinnamon (LEC) rats, a model for human
Wilson's disease, develop
chronic hepatitis and liver
tumors owing to accumulation of
copper and induced oxidative stress. Lipid peroxidation (LPO)-induced etheno-
DNA adducts in nuclear- and
mitochondrial-DNA along with apoptosis was measured in LEC rat liver. Levels of etheno-
DNA adducts (1,N6-ethenodeoxyadenosine and 3,N4-ethenodeoxycytidine) increased with age reaching a peak at 8 and 12 weeks in nuclear and
mitochondrial DNA, respectively. This is the first demonstration that etheno-
DNA adducts are also formed in
mitochondrial DNA. Apoptosis was assessed by TUNEL+ cells in liver sections.
CD95L RNA expression was also measured by in situ hybridization in the same sections. The highest nuclear
DNA adduct levels coincided with a reduced apoptotic rate at 8 weeks.
Mitochondrial-DNA adducts peaked at 12 weeks that coincided with the highest apoptotic rate, suggesting a link of etheno-
DNA adducts in
mitochondrial DNA to apoptosis. The DNA damage in liver was further enhanced and sustained by 0.5%
curcumin in the diet. Treatment for 2 weeks elevated etheno-
DNA adducts 9- to 25-fold in nuclear
DNA and 3- to 4-fold in
mitochondrial-DNA, providing a plausible explanation as to why in our earlier study [Frank et al. (2003) Mutat. Res., 523-524, 127-135],
curcumin failed to prevent liver
tumors in LEC rats. Our results also confirm the reported in vitro
DNA damaging potential of
curcumin in the presence of
copper ions by
reactive oxygen species. LPO-induced adduct formation in nuclear and
mitochondrial DNA appear as early lesions in LEC rat liver
carcinogenesis and are discussed in relation to apoptotic events in the progression of malignant disease.