Increased urinary 1,N6-ethenodeoxyadenosine and 3,N4-ethenodeoxycytidine excretion in thalassemia patients: Markers for lipid peroxidation-induced DNA damage

Abstract Thalassemic diseases including homozygous β-thalassemia and β-thalassemia/Hb E (β-Thal/Hb E) are prevalent in Southeast Asia. Iron overload is a common complication in β-thalassemia patients which induces intracellular oxidative stress and lipid peroxidation (LPO). LPO end products generate miscoding etheno adducts in DNA which after their repair are excreted in urine. We investigated whether urinary levels of 1, N 6 -ethenodeoxyadenosine (edA) and 3, N 4 -ethenodeoxycytidine (edC) can serve as putative cancer risk markers in β-Thal/Hb E patients. edA and edC levels were assayed in collected urine samples by immunoprecipitation-HPLC-fluorescence and 32 P-postlabeling TLC, respectively. Mean edA (fmol/µmol creatinine) levels in urine of β-Thal/Hb E patients ranged from 4.8 to 120.4 (33.8 ± 3.9; n  = 37) and were 8.7 times higher compared to asymptomatic controls (1.4–13.8; 3.9 ± 0.8; n  = 20). The respective edC levels ranged from 0.15 to 32.5 (5.2 ± 1.3; n  = 37) and were increased some 13 times over controls (0.04–1.2; 0.4 ± 0.7; n  = 20). edC levels were correlated positively with NTBI ( r  = 0.517; P  = 0.002), whereas edA showed only a trend ( r  = 0.257; P  = 0.124). We conclude that the strongly increased urinary excretion of etheno adducts indicates elevated LPO-induced DNA damage in internal organs such as the liver. These highly promutagenic lesions may contribute to the increased risk of thalassemia patients to develop hepatocellular carcinoma.