Allyl sulfides such as diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS), typical flavor components of Allium vegetables, have been shown to inhibit benzo[a]pyrene (B[a]P)-induced carcinogenesis in animal models. As a possible mechanism of this inhibition, the effect of these volatile substances on cytochrome P450 (CYP)1 (CYP1A1, 1A2 and 1B1)-mediated bioactivation of B[a]P was investigated using a human hepatoma cell model (HepG2). DADS and DATS inhibited the B[a]P-induced ethoxyresorufin O-deethylase (EROD) activity, a marker enzyme for CYP1, by 30-90% and 70-95% at 100-1,000 μM concentration, respectively. The cell viability, an indicator of the capacity to inhibit B[a]P bioactivation, was increased by treatments of 100-1,000 μM DADS and 10-100 μM DATS. Immunoblot results indicated that the B[a]P inducible CYP1A2 protein was suppressed by 100-1,000 μM of DADS and 10-100 μM of DATS, but CYP1A1 and 1B1 were not detectable in any microsomes. Analysis of B[a]P metabolites revealed that the level of 7,8-diol formed was significantly reduced in the DADS and DATS treated microsomes as compared to the control. The level of 9,10-diol and 4,5-diol formed was also lowered by the allyl sulfide treatments. These results suggest that the protective mechanism of allyl sulfides on B[a]P-induced carcinogenesis is possibly related with the modulation of CYP1-mediated bioactivation of B[a]P.
烯丙基
硫醚,如
二烯丙基硫醚(
DAS)、
二烯丙基二硫化物(
DADS)和
二烯丙基三
硫化物(
DATS),是薤白蔬菜的典型风味成分,在动物模型中已被证明可抑制
苯并[a]芘(B[a]P)诱导的致癌作用。作为这种抑制作用的可能机制,我们使用人肝癌细胞模型(HepG2)研究了这些挥发性物质对细胞色素 P450 (CYP)1(CYP1A1、1A2 和 1B1)介导的 B[a]P
生物活化的影响。在 100-1,000 μM 浓度下,
DADS 和
DATS 对 B[a]P 诱导的乙氧基
瑞香素 O-脱乙基酶(EROD)活性(一种 CYP1 的标记酶)的抑制率分别为 30%-90% 和 70%-95%。细胞存活率是抑制 B[a]P
生物活化能力的指标,100-1,000 μM
DADS 和 10-100 μM
DATS 处理可提高细胞存活率。免疫印迹结果表明,B[a]P 诱导的 CYP1A2 蛋白受到 100-1,000 μM 的
DADS 和 10-100 μM 的
DATS 的抑制,但在任何微粒体中都检测不到 CYP1A1 和 1B1。对 B[a]P 代谢物的分析表明,与对照组相比,在
DADS 和
DATS 处理过的微粒体中形成的 7,8
-二醇水平明显降低。烯丙基
硫醚处理也降低了形成的 9,10
-二醇和 4,5
-二醇的
水平。这些结果表明,烯丙基
硫醚对 B[a]P 诱导的癌变的保护机制可能与调节 CYP1 介导的 B[a]P
生物活化有关。