High excretion of etheno adducts in liver fluke-infected patients: Protection by Praziquantel against DNA damage

Chronic infection by Opisthorchis viverrini (OV) is a strong risk factor for developing cholangiocarcinoma (CCA). To clarify the involvement of oxidative stress and lipid peroxidation (LPO)-derived DNA damage, the excretion of LPO-derived etheno DNA adducts was measured in urine samples collected from healthy volunteers and OV-infected Thai subjects. 1,N-6-etheno-2'-deoxyadenosine (epsilon dA) and 3,N-4-etheno-2'-deoxycytidine (epsilon dC) levels were quantified by immunoprecipitation/high-performance liquid chromatography/fluorescence detection and P-32-postlabeling TLC. Excreted etheno adduct levels were related to indicators of inflammatory conditions [malondialdehyde (MDA) and nitrate/nitrite levels in urine and plasma alkaline phosphatase (ALP) activity]. Mean epsilon dA and epsilon dC levels were 3 to 4 times higher in urine of OV-infected patients; MDA, nitrate/nitrite, and ALP were also increased up to 2-fold. MDA and ALP were positively related to epsilon dA excretion. Two months after a single dose of the antiparasitic drug Praziquantel, epsilon dA and epsilon dC concentrations in urine of OV-infected subjects were decreased; MDA, nitrate/nitrite, and ALP were concomitantly lowered. We conclude that chronic OV infection through oxidative/nitrative stress leads to increased urinary excretion of the etheno-bridged deoxyribonucleosides, reflecting high LPO-derived DNA damage in vivo. These promutagenic DNA etheno adducts in bile duct epithelial cells may increase the risk of OV-infected patients to later develop CCA. Urinary epsilon dA and edC levels should be explored (a) as noninvasive risk markers for developing opisthorchiasis-related CCA and (b) as promising biomarkers to assess the efficacy of preventive and therapeutic interventions.