Isotope Dilution nanoLC/ESI-HRMSQuantitation of Urinary N7-(1-Hydroxy-3-buten-2-yl) Guanine Adducts in Humans and Their Use as Biomarkers of Exposure to 1,3-Butadiene.

in Chemical research in toxicology by Dewakar Sangaraju, Emily J Boldry, Yesha M Patel, Vernon Walker, Irina Stepanov, Daniel Stram, Dorothy Hatsukami, Natalia Tretyakova

TLDR

  • The study looked at a chemical called 1,3-butadiene (BD) that is used in many industries and can be found in things like car exhaust and cigarette smoke. The study wanted to see if people who work in these industries or smoke cigarettes have higher levels of a chemical called N7-(1-hydroxy-3-buten-2-yl) guanine (EB-GII) in their urine. They found that people who work in these industries or smoke cigarettes do have higher levels of EB-GII in their urine, which could be a sign of exposure to BD. The study also found that small amounts of EB-GII can be made in the body without any exposure to BD, which means it might be possible to use EB-GII as a way to test for exposure to BD in the future.

Abstract

1,3-Butadiene (BD) is an important industrial and environmental chemical classified as a known human carcinogen. Occupational exposure to BD in the polymer and monomer industries is associated with an increased incidence of lymphoma. BD is present in automobile exhaust, cigarette smoke, and forest fires, raising concern about potential exposure of the general population to this carcinogen. Following inhalation exposure, BD is bioactivated to 3,4-epoxy-1-butene (EB). If not detoxified, EB is capable of modifying guanine and adenine bases of DNA to form nucleobase adducts, which interfere with accurate DNA replication and cause cancer-initiating mutations. We have developed a nanoLC/ESI-HRMSmethodology for N7-(1-hydroxy-3-buten-2-yl) guanine (EB-GII) adducts in human urine (limit of detection: 0.25 fmol/mL urine; limit of quantitation: 1.0 fmol/mL urine). This new method was successfully used to quantify EB-GII in urine of F344 rats treated with 0-200 ppm of BD, occupationally exposed workers, and smokers belonging to two different ethnic groups. EB-GII amounts increased in a dose-dependent manner in urine of laboratory rats exposed to 0, 62.5, or 200 ppm of BD. Urinary EB-GII levels were significantly increased in workers occupationally exposed to 0.1-2.2 ppm of BD (1.25 ± 0.51 pg/mg of creatinine) as compared to administrative controls exposed to <0.01 ppm of BD (0.22 ± 0.08 and pg/mg of creatinine) (p = 0.0024), validating the use of EB-GII as a biomarker of human exposure to BD. EB-GII was also detected in smokers' urine with European American smokers excreting significantly higher amounts of EB-GII than African American smokers (0.48 ± 0.09 vs 0.12 ± 0.02 pg/mg of creatinine, p = 3.1 × 10). Interestingly, small amounts of EB-GII were observed in animals and humans with no known exposure to BD, providing preliminary evidence for its endogenous formation. Urinary EB-GII adduct levels and urinary mercapturic acids of BD (MHBMA, DHBMA) were compared in a genotyped multiethnic smoker cohort.

Overview

  • The study focuses on the development of a nanoLC/ESI-HRMS methodology for detecting N7-(1-hydroxy-3-buten-2-yl) guanine (EB-GII) adducts in human urine as a biomarker of human exposure to 1,3-butadiene (BD).
  • The methodology used for the experiment includes the administration of BD to F344 rats and occupationally exposed workers, as well as the analysis of EB-GII adducts in urine samples from smokers belonging to two different ethnic groups. The study aims to validate the use of EB-GII as a biomarker of human exposure to BD and explore its potential for use in clinical practice.

Comparative Analysis & Findings

  • The study found that urinary EB-GII levels were significantly increased in workers occupationally exposed to 0.1-2.2 ppm of BD as compared to administrative controls exposed to <0.01 ppm of BD, validating the use of EB-GII as a biomarker of human exposure to BD. EB-GII was also detected in smokers' urine, with European American smokers excreting significantly higher amounts of EB-GII than African American smokers. Small amounts of EB-GII were observed in animals and humans with no known exposure to BD, providing preliminary evidence for its endogenous formation.

Implications and Future Directions

  • The study's findings suggest that EB-GII could be used as a biomarker of human exposure to BD and have potential implications for clinical practice. However, the study also identifies limitations, such as the need for further validation in larger populations and the potential for confounding factors. Future research could explore the use of EB-GII as a diagnostic tool for BD exposure and its potential for predicting cancer risk.
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