Comparison of DNA and RNA Adduct Formation: Significantly Higher Levels of RNA than DNA Modifications in the Internal Organs of Aristolochic Acid-Dosed Rats

Prolonged exposure to aristolochic acid (AA) contaminated slimming drugs and food is believed to be associated with the development of endemic nephropathy in Belgian women and in farmers living alongside the Danube River. Decades of research has revealed the pathophysiology of carcinogenesis of AA, and the molecular mechanisms underlying renal interstitial fibrosis remain unclear. We hypothesized that RNA modification may have contributed to the observed toxicity of AA. Thus, a highly sensitive and selective ultra-high performance liquid chromatography-coupled tandem mass spectrometric method was developed to quantify RNA-AA adducts in target and nontarget organs of AA-dosed rats. The results revealed, for the first time, that AA forms RNA adducts in vitro and in vivo. Comparative studies on DNA revealed that RNA is modified by AA at frequencies approximately 6-fold higher than that of DNA in both kidney and liver tissue in AA-dosed rats. Results also demonstrated that guanosine is modified by AA at frequencies significantly higher than that of adenosine, 2-deoxyadenosine, and 2-deoxyguanosine in both organs of the AA-dosed. This finding suggests that guanosine is a major target for AA and that guanosine adducts of AA might be critical lesions in the pathophysiology of AA-induced toxicity. It is anticipated that the results of our study may open up a new area of investigating the nephrotoxicity and/or carcinogenicity by quantifying RNA adducts using the UPLC-MS/MS technique of high sensitivity and selectivity.