Detection of bulky DNA lesions in the liver of patients with Wilson's disease and primary haemochromatosis

Abstract

In the human metal storage disorders of Wilson's disease and primary haemochromatosis, ion transport and excretion dysfunctions result in the intracellular deposition of copper and iron, respectively. These aberrant accumulations of transition metal ions lead to extensive tissue damage, especially in the liver. In order to investigate the possible role of metal ion-mediated oxygen free radical-generated DNA damage in these processes, DNA was isolated from liver of eight Wilson's disease patients and six haemochromatosis patients. Significant levels of bulky DNA damage were detected in these samples by 32P-postlabelling analysis, but were not found in liver DNA from age-matched controls. This form of novel DNA damage was detected in six out of eight Wilson's patients, varying between approximately 1 and 100 base modifications per 10(8) nucleotides, and in all of the haemochromatosis samples examined; the levels of modified species per 10(8) nucleotides varying from approximately 2 to 50. HPLC analysis of these bulky DNA lesions demonstrated that the species formed in Wilson's disease and in haemochromatosis were chromatographically identical but were not the same as putative purine dimers that can be generated in DNA by in vitro incubation with Cu+/Fe2+ and H2O2 (although the possibility that the adducts detected are closely related has not been ruled out). Analysis of the oxidative base lesion 8-hydroxydeoxyguanosine showed that levels were not elevated in liver DNA from either Wilson's disease or haemochromatosis sufferers. In fact, a statistically significantly lower level of this lesion was found in Wilson's disease patients than in controls. These data suggest that bulky DNA damage present in the liver of both wilson's disease and primary haemochromatosis patients may play a more important role in the induction of tissue damage than 8-hydroxydeoxyguanosine. The novel DNA damage detected by 32P-poslabelling may also be a significant factor in the initiation of neoplasia leading to malignant hepatoma in haemochromatosis patients.