Detection of Aldehydic DNA Lesions Using Aldehyde Reactive Probe

In living cells, reactive oxygen species (ROS) such as superoxide anion, hydrogen peroxide (H
2
O
2
), and hydroxyl radicals are constitutively produced endogenously and also induced by exogenous agents including ionizing radiation, ultraviolet (UV) light, and a various redox cycling chemicals including polycyclic aromatic hydrocarbons. Massive production of ROS that overwhelms cellular defense systems can result in serious outcomes such as cell death. H
2
O
2
is produced at a relatively high rate as a product of aerobic metabolism. In the presence of transition metals (Fe
2+
and Cu
+
), H
2
O
2
can generate hydroxyl radicals via the Fenton reaction (
1
). The highly reactive hydroxyl radical can induce protein modification, lipid peroxidation, and
DNA
damage (
2
,
3
). Although the heterocyclic bases of nucleic acids are important sites of free radical-mediated alteration, such as 8-hydroxyguanine (8-OHG) (
4
), the sugar-phosphate backbone is also highly vulnerable to attack. Abstraction of a hydrogen atom from each carbon from deoxyribose produces a carbon-based sugar radical that can rearrange, resulting in scission of the nucleic acid strand, deoxyribose fragmentation, as well as formation of base loss lesions, so-called apurinic/apyrimidinic (AP) sites (
5
,
6
). These deoxyribose lesions frequently contain aldehydic moieties; however, they have been difficult to examine, mainly owing to the large variety of products, as well as their chemical instability, even at mild temperatures and neutral pH (
7
).