Quantification and Analysis of Novel NNK-Induced DNA Adduct
DNA adducts are the covalent modification of DNA as a result of a genotoxic chemical exposure which if not repaired, can eventually cause mutations and tumorigenesis. One particular carcinogen, 4-(Methylnitrosamino)-1-(3-pyridyl)-1- butanone, otherwise known as NNK, is a tobacco-specific carcinogen. Previously a study found a novel DNA adduct, a DNA-RNA cross-link that formed in NNK-exposed mice. In this study, a method was developed to quantify this DNA adduct. Lung tissue samples were taken from rats in 3 groups: NNK-exposed, NNK and LPS co-exposed, and a control group at 3 timepoints: 1, 5, and 15 weeks. Methods included DNA extraction from rat lung tissue, subsequent DNA hydrolysis, and purification. Liquid Chromatography Mass Spectrometry (LCMS) was used to analyze the final purified samples. This study found that the group with the highest level of DNA adduct formation was the NNK group from the 1 week timepoint. There was also a spike in adduct levels in the LPS group at the 15 week timepoint. This study also found a significant impact of solvent combinations used in Solid Phase Extraction (SPE) on the LCMS readings. Overall, the results of this experiment highlight the need for additional research regarding DNA adduct formation related to NNK exposure.