2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces hepatic cytochrome P450-dependent arachidonic acid epoxygenation in diverse avian orders: regioisomer selectivity and immunochemical comparison of the TCDD-induced P450s to CYP1A4 and 1A5.
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces hepatic cytochrome P450-dependent arachidonic acid epoxygenation in diverse avian orders: regioisomer selectivity and immunochemical comparison of the TCDD-induced P450s to CYP1A4 and 1A5.
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2,3,7,8-四氯二苯并-对二恶英 (TCDD) 在不同鸟类中诱导肝细胞色素 P450 依赖性花生四烯酸环氧化：TCDD 诱导的 P450 与 CYP1A4 和 1A5 的区域异构体选择性和免疫化学比较。
DOI：
10.1006/taap.1997.8360
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发表时间：
1998
影响因子：
3.8
通讯作者：
Rifkind,AB
中科院分区：
文献类型：
--
作者：
Gilday,D;Bellward,GD;Sanderson,JT;Janz,DM;Rifkind,AB
2，3，7，8-四氯二苯并-对-二恶英（TCDD）显著诱导了四种鸟类孵化后肝微粒体中细胞色素P450（CYP）依赖的花生四烯酸代谢，这四种鸟类属于四个不同的目的：鸡、鸽子、鸬鹚和大蓝鹭，增加花生四烯酸环氧化物（EDEs）、单羟基二十碳四烯酸（HETE）、ω−1，和ω−2 OH花生四烯酸产物增加5倍或更多。TCDD诱导的雏鸡微粒体具有最高的活性和最少的限制EET区域选择性。ω-OH花生四烯酸是鸡和鸽肝微粒体中的主要组成代谢物，也是鸬鹚和大蓝鹭的主要代谢产物，TCDD对ω-OH花生四烯酸没有诱导作用。在禽类肝微粒体中组成型EET形成非常低，除了在鸬鹚微粒体中几乎完全产生8，9-EET。使用鸡胚衍生的CYP 1A 4和1A 5的多克隆抗血清进行肝微粒体的Western印迹，在每个物种中识别两个TCDD诱导的条带。鸡的条带与CYP 1A 4和1A 5的分子量相同（分别为55和55.5 kDa），但其他种属的条带不同。免疫纯化的抗血清单特异性的CYP 1A 5识别带的微粒体从所有的鸟类物种，和单特异性的抗血清CYP 1A 4识别带的微粒体从鸡，鸽子，和大蓝鹭。抗CYP 1A 4和1A 5 IgG免疫抑制TCDD诱导的混合功能氧化酶活性完全在鸡和鸡胚微粒体和其他鸟类微粒体中，只有部分。结果表明：（1）TCDD对CYP依赖的花生四烯酸代谢的诱导作用，尤其是对鸟类花生四烯酸环氧化作用的诱导作用比对哺乳动物的大得多;（2）TCDD对鸟类和哺乳动物都有两种CYP 1A相关酶的诱导作用;（三）除鸡以外的鸟类中的CYP 1A酶与CYP 1A 4和1A 5不完全相同，但具有某些酶和免疫化学特征;（4）所有鸟类中的ω-OH花生四烯酸和鸬鹚中的8，9-EET都是由与CYP 1A无关的β-内酰胺酶形成的;（5）鸟类CYP 1A酶的两个不同特征是鸟类CYP 1A 4相关的P450获得独特的表位和CYP 1A 5相关的P450获得花生四烯酸环氧化的不寻常的催化效力。
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) markedly induced cytochrome P450 (CYP)-dependent arachidonic acid metabolism in liver microsomes from hatchlings of four avian species belonging to four different orders: chick, pigeon, cormorant, and great blue heron, increasing formation of arachidonic acid epoxides (EETs), monohydroxyeicosatetraenoic acids (HETEs), ω−1, and ω−2 OH arachidonic acid products by fivefold or more. Microsomes from TCDD-induced hatchling chicks had the highest activity and the least restricted EET regioselectivity. ω-OH arachidonic acid, the principal constitutive metabolite in chick and pigeon liver microsomes and a major product for cormorant and great blue heron was not induced by TCDD. Constitutive EET formation in avian liver microsomes was very low except in cormorant microsomes where 8,9-EET was generated almost exclusively. Western blots of liver microsomes using polyclonal antisera to chick embryo-derived CYP1A4 and 1A5 recognized two TCDD-induced bands in each of the species. The chick bands had the same molecular weights as CYP1A4 and 1A5 (55 and 55.5 kDa, respectively) but those of the other species differed. Immunopurified antiserum monospecific for CYP1A5 recognized a band in microsomes from all of the avian species, and monospecific antiserum for CYP1A4 recognized a band in microsomes from chick, pigeon, and great blue heron. AntiCYP1A4 and 1A5 IgG immunoinhibited TCDD-induced mixed function oxidase activity completely in chick and chick embryo microsomes and only partially in the other avian microsomes. The results demonstrate that (1) TCDD causes much greater induction of CYP-dependent arachidonic acid metabolism, and of arachidonic acid epoxygenation in particular, in avian than in mammalian species; (2) TCDD induces two CYP1A-related enzymes in birds as in mammals; (3) CYP1A enzymes in the birds other than chicks are not identical to CYP1A4 and 1A5 but share some enzymatic and immunochemical characteristics with them; (4) constitutive ω-OH arachidonic acid in all of the avian species and 8,9-EET in cormorant are formed by CYP enzymes unrelated to CYP1A; and (5) two distinct characteristics of avian CYP1A enzymes are the acquisition by avian CYP1A4-related P450 of unique epitope(s) and by CYP1A5-related P450 of unusual catalytic effectiveness for arachidonic acid epoxygenation.