Smith W A, Arif J M, Gupta R C
Graduate Center for Toxicology, University of Kentucky Medical Center, Lexington 40536-0305, USA.
Mutat Res. 1998 Feb 13;412(3):307-14. doi: 10.1016/s1383-5718(97)00203-9.
Due to the large and expanding number of potential cancer chemopreventive agents, there is an increasing need for short term tests to study the efficacy and mechanisms of these agents. In this study, we have employed a microsome-mediated test system to study the effect of several suspected chemopreventive agents on the DNA adduct formation capacity of the potent mammary carcinogen, dibenzo[a,l]pyrene (DBP). Bioactivation of DBP by Aroclor 1254-induced rat liver microsomes in the presence of calf thymus DNA (300 microg/ml) resulted in the formation of one major and six other prominent DNA adducts (324 adducts/10(7) nucleotides). These adducts were previously determined to be deoxyadenosine (dA) and deoxyanosine (dG)-derivatives of both anti- and syn-DBP-11,12-diol-13,14-epoxides (DBPDE). Intervention with ellagic acid, chlorophyllin, benzyl isocyanate (BIC), oltipraz or genistein (150 microM) strongly diminished DBP-DNA adduction by > or = 75%. Linoleic acid, curcumin and butylated hydroxytoluene (BHT) also significantly inhibited DBP DNA adduction (26-46%) while N-acetylcysteine (NAC) had no effect. Moreover, nonenzymatic studies with anti- and syn-DBPDE isomers revealed that chlorophyllin, ellagic acid, BIC and BHT may be inhibiting DBP-DNA adduction in an enzymatic-independent manner since these agents diminished DBPDE-DNA adduction by 30-75%. Genistein, oltipraz and curcumin did not diminish DBPDE-DNA adduction and therefore most likely require the presence of the microsomal subcellular fraction to inhibit DBP-DNA adduction.
由于潜在的癌症化学预防剂数量众多且不断增加，对用于研究这些药剂功效和作用机制的短期试验的需求也日益增长。在本研究中，我们采用了微粒体介导的试验系统，以研究几种可疑化学预防剂对强效乳腺致癌物二苯并[a,l]芘（DBP）的DNA加合物形成能力的影响。在小牛胸腺DNA（300微克/毫升）存在的情况下，用Aroclor 1254诱导的大鼠肝微粒体对DBP进行生物活化，导致形成一种主要的和其他六种突出的DNA加合物（324个加合物/10⁷个核苷酸）。这些加合物先前被确定为反式和顺式DBP - 11,12 - 二醇 - 13,14 - 环氧化物（DBPDE）的脱氧腺苷（dA）和脱氧肌苷（dG）衍生物。用鞣花酸、叶绿酸、苄基异氰酸酯（BIC）、奥替普拉或染料木黄酮（150微摩尔）进行干预，可使DBP - DNA加合作用强烈减少≥75%。亚油酸、姜黄素和丁基化羟基甲苯（BHT）也显著抑制DBP - DNA加合作用（26 - 46%），而N - 乙酰半胱氨酸（NAC）则没有作用。此外，用反式和顺式DBPDE异构体进行的非酶学研究表明，叶绿酸、鞣花酸、BIC和BHT可能以不依赖酶的方式抑制DBP - DNA加合作用，因为这些药剂可使DBPDE - DNA加合作用减少30 - 75%。染料木黄酮、奥替普拉和姜黄素并未减少DBPDE - DNA加合作用，因此很可能需要微粒体亚细胞部分的存在才能抑制DBP - DNA加合作用。
