Effects of bile acids on base hydroxylation in a model of human colonic mucosal DNA

被引:10
作者
Allgayer, H
Kolb, M
Stuber, V
Kruis, W
机构
[1] Heidelberg Univ, LVA Baden Wurttemberg, Rehaklin OB Tauber, Dept Oncol, D-97980 Bad Margentheim, Germany
[2] Univ Technol & Business, Dept Chem, D-73428 Aalen, Germany
[3] Univ Cologne, Protestant Hosp Koln Kalk, Dept Internal Med, D-51102 Cologne, Germany
来源
CANCER DETECTION AND PREVENTION | 2002年 / 26卷 / 01期
关键词
bile acids; oxidative DNA damage; DNA base hydroxylation; 8-OH adenine; 8-OH guanine; DNA model of colonic mucosal DNA;
D O I
10.1016/S0361-090X(02)00008-9
中图分类号
R73 [肿瘤学];
学科分类号
100214 ;
摘要
Background and aims: Increased intestinal bile acids as a possible consequence of a high fat/meat, low fiber diet are believed to play an important role in the formation of colon cancer. Interactions of bile salts particularly secondary bile acids with different cell components including DNA may contribute to carcinogenesis. To further investigate DNA damage by bile salts, we assessed the effects of a bile salt mixture containing deoxycholate and chenodeoxycholate on base hydroxylation in Chelex-treated DNA from calf thymus as a model of human colonic mucosal DNA in the presence and absence of reactive oxygen metabolites (ROM). Methods: Chelex-treated DNA from calf thymus (to remove residual iron impurities) was incubated with different bile salt concentrations (4 muM, 4.0 mM) (20.0% deoxycholate, 21.0% chenodeoxycholate) in the presence and absence of an OH generating system (25 muM FeCl3, 50 muM H2O2, 100 muM nitrilotriacetic acid) for 18 h (37 degreesC). After hydrolyzation, lyophilization and derivatization hydroxylated DNA bases were characterised and quantitated with gas chromatography-mass spectrometry (GS-MS) and SIM analysis. Two concentration ranges of bile salts were used, micromolar concentrations being present in plasma, millimolar in the gut lumen. Results: In the absence of ROM Chelex-treated DNA preparations contain only small amounts of hydroxylated base products. Bile salts at 4.0 mM significantly increased the amounts of 5-OH uracil and cis-thymine glycol. In the presence of ROM bile salts at 4.0 muM increased the production of 8-OH adenine and 8-OH guanine whereas bile salts at 4.0 mM inhibited ROM-induced base hydroxylation. Discussion: In the absence of ROM millimolar concentrations of a bile salt mixture with deoxycholate and chenodeoxycholate increase basal (spontaneous) DNA hydroxylation, whereas, they are without effects at micromolar concentrations. In the presence of ROM micromolar concentrations enhance oxidative DNA damage and millimolar concentrations were inhibitory. These results support the view that bile acids may cause oxidative DNA damage depending on their concentrations and the surrounding conditions both directly (enhancement of basal hydroxylation) and indirectly (enhancement of ROM-induced hydroxylation). (C) 2002 International Society for Preventive Oncology. Published by Elsevier Science Ltd. All rights reserved.
引用
收藏
页码:85 / 89
页数:5
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