Quantitative NanoLC/NSI+-HRMS Method for 1,3-Butadiene Induced bis-N7-guanine DNA-DNA Cross-Links in Urine

1,3-Butadiene (BD) is a common environmental and industrial chemical widely used in plastic and rubber manufacturing and also present in cigarette smoke and automobile exhaust. BD is classified as a known human carcinogen based on evidence of carcinogenicity in laboratory animals treated with BD by inhalation and epidemiological studies revealing an increased risk of leukemia and lymphohematopoietic cancers in workers occupationally exposed to BD. Upon exposure via inhalation, BD is bioactivated to several toxic epoxides including 3,4-epoxy-1-butene (EB), 3,4-epoxy-1,2-butanediol (EBD), and 1,2,3,4-diepoxybutane (DEB); these are conjugated with glutathione and excreted as 2-(N-acetyl-L-cystein-S-yl)-1-hydroxybut-3-ene/1-(N-acetyl-L-cystein-S-yl)-2-hydroxybut-3-ene (MHBMA), 4-(N-acetyl-L-cystein-S-yl)-1,2-dihydroxybutane (DHBMA), and 1,4-bis-(N-acetyl-L-cystein-S-yl)butane-2,3-diol (bis-BDMA). Exposure to DEB generates monoalkylated DNA adducts, DNA-DNA crosslinks, and DNA-protein crosslinks, which can cause base substitutions, genomic rearrangements, and large genomic deletions. In this study, we developed a quantitative nanoLC/NSI+-HRMS methodology for 1,4-bis-(gua-7-yl)-2,3-butanediol (bis-N7G-BD) adducts in urine (LOD: 0.1 fmol/mL urine, LOQ: 1.0 fmol/mL urine). This novel method was used to quantify bis-N7G-BD in urine of mice treated with 590 +/- 150 ppm BD for 2 weeks (6 h/day, 5 days/week). Bis-N7G-BD was detected in urine of male and female BD-exposed mice (574.6 +/- 206.0 and 571.1 +/- 163.4 pg/mg of creatinine, respectively). In addition, major urinary metabolites of BD, bis-BDMA, MHBMA and DHBMA, were measured in the same samples. Urinary bis-N7G-BD adduct levels correlated with DEB-derived metabolite bis-BDMA (r = 0.80, Pearson correlation), but not with the EB-derived DNA adducts (EB-GII) or EB-derived metabolites MHBMA and DHBMA (r = 0.24, r = 0.14, r = 0.18, respectively, Pearson correlations). Urinary bis-N7G-BD could be employed as a novel non-invasive biomarker of exposure to BD and bioactivation to its most mutagenic metabolite, DEB. This method will be useful for future studies of 1,3-butadiene exposure and metabolism.

Automated summary

1,3-Butadiene (BD) is a common chemical used in plastic and rubber manufacturing, and exposure to BD has been linked to an increased risk of cancer. BD is metabolized into toxic epoxides that can cause DNA damage. A novel method for quantifying specific BD metabolites in urine has been developed, which can be used as a non-invasive biomarker for BD exposure and metabolism.