Fractionation of aqueous cigarette tar extracts:: Fractions that contain the tar radical cause DNA damage

被引:236
作者
Pryor, WA
Stone, K
Zang, LY
Bermúdez, E
机构
[1] Louisiana State Univ, Inst Biodynam, Baton Rouge, LA 70803 USA
[2] Calif State Univ Stanislaus, Turlock, CA 95380 USA
关键词
D O I
10.1021/tx970159y
中图分类号
R914 [药物化学];
学科分类号
100701 ;
摘要
Previously, we have shown that aqueous cigarette tar (ACT) extracts contain a long-lived tar radical that associates with DNA in isolated rat alveolar macrophages and causes DNA damage in isolated rat thymocytes. These ACT solutions reduce oxygen to produce superoxide and, ultimately, hydrogen peroxide. In this study, we report the fractionation of ACT solutions prepared from the tar from five cigarettes using Sephadex columns. The fractions were analyzed by UV and electron paramagnetic resonance (EPR) spectroscopy and gas chromatography/mass spectrometry (GC/MS). The fractions containing polyphenolic species (principally catechol and hydroquinone, as determined by MS) caused most of the observed DNA damage in rat thymocytes. These DNA-damaging fractions produced superoxide, H2O2, and hydroxyl radicals. Stable free radicals were identified as o- and p-benzosemiquinone radicals by EPR spectroscopy. Hydroxyl radicals were detected by EPR spin-trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Catalase inhibited the EPR signal of the DMPO-OH adduct, indicating that H2O2 is the precursor of the hydroxyl radical spin adduct. The Sephadex separation resulted in a 90-fold concentration of the hydrogen peroxide-generating capacity of the fractions that contained polyphenols, relative to the unfractionated ACT solution. Another fraction, which contained nicotine, caused some DNA damage, but this damage was 28-fold less than the damage caused by the most damaging phenolic fraction. These results support our hypothesis that the tar radical system is an equilibrium mixture of semiquinones, hydroquinones, and quinones. The tar radical associates with DNA, causes DNA damage, and very likely is involved in the toxicity associated with cigarette smoking.
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页码:441 / 448
页数:8
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