Inhibition of rat liver cytochrome P450 isozymes by isothiocyanates and their conjugates: A structure-activity relationship study
Inhibition of rat liver cytochrome P450 isozymes by isothiocyanates and their conjugates: A structure-activity relationship study
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DOI：
10.1093/carcin/17.11.2423
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发表时间：
1996-11-01
期刊：
影响因子：
4.7
通讯作者：
Chung, FL
中科院分区：
文献类型：
--
作者：
Conaway, CC;Jiao, D;Chung, FL
一系列芳烷基和烷基异硫氰酸酯，以及它们的谷胱甘肽、半胱氨酸和N-乙酰半胱氨酸缀合物被用于研究它们对从3-甲基胆蒽或苯巴比妥处理的大鼠获得的肝微粒体中的乙氧基试卤灵（EROD）、戊氧基试卤灵（PROD）和甲氧基试卤灵（MROD）的脱烷基化的抑制活性，这些反应主要由细胞色素P450（P450）同工酶1A 1和1A 2、2B 1和1A 2介导。所有异硫氰酸酯对PROD的抑制作用均强于EROD。在这些试验中，将芳烷基异硫氰酸酯的烷基链长度增加至C-6导致抑制效力增加;在较长的烷基链长度（C-8-C（1）0）下，抑制效力下降。异硫氰酸苯乙酯（PEITC）对EROD、MROD和PROD的IC（50）分别为47、46和1.8 μ M。在PEITC上取代额外的苯基也增加了抑制效力;异硫氰酸二苯基乙酯IC（50）（1，2-DPEITC）和2，2-二苯基乙基异硫氰酸酯（2，2-DPEITC）对于EROD分别为0.9和0.26 μ M，对于PROD分别为0.045和0.13 μ M，PEITC及其偶联物的相对抑制效力为N-乙酰半胱氨酸-PEITC（PEITC-NAC）<谷胱甘肽-PEITC（PEITC-GSH）<半胱氨酸-PEITC（PEITC-CYS）< PEITC，母体异硫氰酸酯是比缀合物更有效的抑制剂的观察结果表明，缀合物的解离是活性所必需的。天然存在的烷基异硫氰酸酯，萝卜硫素（SFO）和烯丙基异硫氰酸酯（AITC）在测定中是非常弱的抑制剂，这些结果表明异硫氰酸酯作为研究P450同工酶的结构探针的潜力。异硫氰酸酯对PROD的抑制活性与先前证实的肿瘤抑制效力相关，（4-甲基亚硝胺基）-1-（3-吡啶基）-1-丁酮（NNK）诱导的A/J小鼠肺肿瘤生物测定支持早期发现，即P450 2B 1是参与NNK激活的主要同工酶之一，抑制该同工酶是异硫氰酸酯化学预防活性的重要机制。
A series of arylalkyl and alkyl isothiocyanates, and their glutathione, cysteine, and N-acetylcysteine conjugates were used to study their inhibitory activity toward the dealkylation of ethoxyresorufin (EROD), pentoxyresorufin (PROD), and methoxyresorufin (MROD) in liver microsomes obtained from the 3-methylcholanthrene or phenobarbital-treated rats, These reactions are predominantly mediated by cytochrome P450 (P450) isozymes 1A1 and 1A2, 2B1 and 1A2, respectively, All isothiocyanates inhibited PROD more readily than EROD. Increases in the alkyl chain length of arylalkyl isothiocyanates to C-6 resulted in an increased inhibitory potency in these assays; at longer alkyl chain lengths (C-8-C(1)0) the inhibitory potency declined. The IC(50)s for phenethyl isothiocyanate (PEITC) were 47, 46 and 1.8 mu M for EROD, MROD and PROD, respectively. Substitution of an additional phenyl group on PEITC also increased the inhibitory potency; the IC(50)s for 1,2-diphenylethyl isothiocyanate (1,2-DPEITC) and 2,2-diphenylethyl isothiocyanate (2,2-DPEITC) were 0.9 and 0.26 mu M for EROD, and 0.045 and 0.13 mu M for PROD, respectively, The relative inhibitory potency of PEITC and its conjugates was N-acetylcysteine-PEITC (PEITC-NAC) < glutathione-PEITC (PEITC-GSH) < cysteine-PEITC (PEITC-CYS) < PEITC, The observations that the parent isothiocyanates were more potent inhibitors than the conjugates suggest that dissociation of the conjugate is required for activity. Naturally occurring alkyl isothiocyanates, sulforaphane (SFO) and allyl isothiocyanate (AITC), were very weak inhibitors in the assays, These results suggest the potential of isothiocyanates as structural probes for studying P450 isozymes, In addition, the inhibitory activity of isothiocyanates for PROD correlated with the previously demonstrated tumor inhibitory potency in (4-methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induced A/J mouse lung tumor bioassays, which supports earlier findings that P450 2B1 is one of the major isozymes involved in NNK activation and that inhibition of this isozyme is an important mechanism for the chemopreventive activity of isothiocyanates.