Quantitation by Liquid Chromatography-Nanoelectrospray Ionization-High-Resolution Tandem Mass Spectrometry of Multiple DNA Adducts Related to Cigarette Smoking in Oral Cells in the Shanghai Cohort Study

Development of an Optimized Two-Step Solid-Phase Extraction Method for Urinary Nucleic Acid Adductomics

The exposome represents the totality of endogenous and exogenous exposures across the lifespan. These exposures may result in DNA and RNA damage, in the form of adducts, which is a key factor in the etiology of a variety of human diseases, including cancer. It is understood that, following their repair, nucleic acid adducts are excreted into the urine, making urine an ideal, non-invasive matrix in which to study the whole-body nucleic acid adductome (the totality of nucleic acid adducts). However, the measurement of these adducts in urine presents challenges due to matrix interference and the variety of the chemical nature across the spectrum of nucleic adducts making their "one-size-fits-all" extraction by solid-phase extraction (SPE) challenging. Here, different types of SPE sorbents, and their combination, were evaluated for maximal recovery of nucleic acid adducts from urine. The SPE column combination of ENV+ coupled with PHE provided the best retention of a cocktail of 20 nucleic acid adduct standards. An untargeted high resolution mass spectrometry approach incorporating FeatureHunter 1.3 software was used to demonstrate the ability of this SPE method to successfully recover endogenous urinary nucleic acid adducts in addition to those represented by the cocktail of isotopically labeled standards. Using our approach, FeatureHunter 1.3 recognized approximately 500 adducts in both mouse and human urine samples. Isotopically labeled standards were used to identify a selection of the endogenous adducts and begin the characterization of the urinary nucleic acid adductome of mice and humans.

Reactions of [13C]-labelled tobacco smoke with DNA to generate selected adducts formed without metabolic activation

DNA adducts are central in the carcinogenic process because they can cause miscoding leading to permanent mutations in important genes involved in carcinogenesis. While it is known that tobacco smoking leads to increased levels of multiple DNA adducts, most DNA adducts detected to date in humans cannot be explicitly attributed to smoking but instead have various possible exogenous and endogenous sources. We plan to probe the tobacco source of DNA adducts by providing carbon-13 labelled ([13C]-labelled) cigarettes to smokers and analyzing [13C]-labelled DNA adducts in their oral cells to determine which adducts arise from smoking. Prior to conducting studies in humans, we first report here proof-of-principle machine smoking experiments to evaluate carbon isotopologues of (a) selected carbonyls and (b) DNA adducts resulting from direct exposure of cigarette smoke vapour-phase to calf-thymus DNA. The smoke of the study cigarettes, made from a 50:50 mixture of [13C]-labelled tobacco and a popular commercial tobacco, yielded similar concentrations of carbonyl compounds and their respective DNA adducts compared with the smoke of 1R6F reference cigarettes and the popular brand of cigarettes. We detected [13C]-isotopologues of DNA adducts such as 1,N6-etheno-dA, (8R/S)-3-(2'-deoxyribos-1-yl)-5,6,7,8-tetrahydro-8-hydroxypyrimido[1,2-a]purine-10(3H)-one (γ-OH-Acr-dG), and (6S,8S and 6R,8R)-3-(2'-deoxyribos-1-yl)-5,6,7,8-tetrahydro-8-hydroxy-6-methylpyrimido[1,2-a]purine-10(3H)-one [(6S,8S)-γ-OH-Cro-dG and (6R,8R)-γ-OH-Cro-dG], proving that they have a direct source from tobacco smoke and providing important new insights regarding their mechanisms of formation. These unique results form the basis for further studies in cell culture and in cigarette smokers to establish how carcinogens in tobacco smoke cause DNA adduct formation.

Elimination of Acrolein by Disodium 5'-Guanylate or Disodium 5'-Inosinate at High Temperature and Its Application in Roasted Pork Patty

Acrolein (ACR) is a highly active, simple unsaturated aldehyde found in various high-temperature processed foods. Its long-term accumulation in the human body increases the risk of chronic diseases. Animal and plant foodstuffs are rich in disodium 5'-guanylate (GMP) and disodium 5'-inosinate (IMP), which are authorized flavor enhancers. Herein, we used liquid chromatography with tandem mass spectrometry to explore the reaction-active kinetics and pathway of the interaction between GMP/IMP and ACR and validated it in roasted pork patties. Our results suggested that GMP and IMP could efficiently eliminate ACR by forming ACR adducts (GMP-ACR, IMP-ACR). In addition, IMP exhibited a higher reaction rate, whereas GMP had a good trapping capacity at a later stage. As carriers of GMP and IMP, dried mushrooms and shrimp exhibited an effective ACR-trapping ability in the ACR model and roasted pork patty individually and in combination. Adding 10% of dried mushroom or shrimp alone or 5% of dried mushroom and shrimp in combination eliminated up to 53.9%, 55.8%, and 55.2% ACR in a roasted pork patty, respectively. This study proposed a novel strategy to eliminate the generation of ACR in roasted pork patties by adding foodstuffs rich in GMP and IMP.