DNA damage occurs continuously in cells of living organisms and can disrupt genomic integrity. While most damaged nucleotides are repaired, DNA adducts have been postulated to accumulate and possibly participated in the aging process. Most evidence of DNA adducts accumulating with age have been indirect rather than direct chemical quantification. Here we characterize tissue-specific accumulation of DNA adducts both in rat tissues and human non-failing heart tissue. The characterization and identification of age-related DNA adducts was addressed using a high-throughput stepped MRM approach scanning a wide range of DNA modifications losing m/z 116, the mass of the deoxyribose (from transition m/z 225 → 109 to transition m/z 525 → 409), using high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Most DNA adducts did not accumulate with age, but in each tissue, some specific adducts did increase with age. We found that N²-CMdG, an advanced glycation end-products resulting from the reaction between glyoxal with 2’-deoxyguanosine, increased significantly with age in rat liver and heart but not in human heart. However, we identified two novel DNA adducts that are significantly and positively correlated with age in the human non-failing heart: 1, N⁶ etheno-dA, which can arise from lipid peroxidation of polyunsaturated fatty acids, and a currently unidentified adduct with a m/z of 328 (“328”). Interestingly, we also found that the “328” adduct significantly increased with age in rat heart and brain. We hypothesize that the increase of 1, N⁶ etheno-dA and the 328 molecule with age might induce alterations in gene expression in the heart, although our approach cannot determine which cell type accumulates the DNA adduct. These experiments indicate that while most DNA adducts do not accumulate with age, there are specific molecules that do increase with age. Furthermore, we identify two molecules that increase with age in the human heart.

Jacqueline Gamboa-Wilson

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