DETECTION OF BULKY DNA LESIONS IN THE LIVER OF PATIENTS WITH WILSONS-DISEASE AND PRIMARY HEMOCHROMATOSIS

In the human metal storage disorders of Wilson's disease and primary h aemochromatosis, ion transport and excretion dysfunctions result in th e intracellular deposition of copper and iron, respectively. These abe rrant 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 diseas e patients and six haemochromatosis patients. Significant levels of bu lky DNA damage were detected in these samples by P-32-postlabelling an alysis, but were not found in liver DNA from age-matched controls. Thi s form of novel DNA damage was detected in six out of eight Wilson's p atients, varying between approximately 1 and 100 base modifications pe r 10(8) nucleotides, and in all of the haemochromatosis samples examin ed; the levels of modified species per 10(8) nucleotides varying from approximately 2 to 50. HPLC analysis of these bulky DNA lesions demons trated that the species formed in Wilson's disease and in haemochromat osis were chromatographically identical but were not the same as putat ive purine dimers that can be generated in DNA by in vitro incubation with Cu+/Fe2+ and H2O2 (although the possibility that the adducts dete cted are closely related has not been ruled out). Analysis of the oxid ative 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 Wilso n's disease and primary haemochromatosis patients may play a more impo rtant role in the induction of tissue damage than 8-hydroxydeoxyguanos ine. The novel DNA damage detected by P-32-postlabelling may also be a significant factor in the initiation of neoplasia leading to malignan t hepatoma in haemochromatosis patients.