Merchant M, Safe S
Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843-4466, USA.
Biochem Pharmacol. 1995 Aug 25;50(5):663-8. doi: 10.1016/0006-2952(95)00180-8.
Rat hepatoma H4IIE and mouse hepatoma Hepa 1c1c7 cells were transiently transfected with a plasmid construct that contained the bacterial chloramphenicol acetyltransferase (CAT) gene under the control of the mouse mammary tumor virus promoter and one copy of the dioxin responsive element. Treatment of transfected H4IIE and Hepa 1c1c7 cells with 10(-13) to 10(-6) M 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) resulted in a concentration-dependent increase in transient CAT activity. Maximum CAT activity was induced in both cell lines by exposure to 10(-9) M TCDD. The induction of CAT activity correlated well with the TCDD-induced, P4501A1-dependent ethoxyresorufin O-deethylase activity. Cotreatment of transfected cells with 10(-9) M TCDD and 10(-8) to 10(-6) M alpha-naphthoflavone (alpha NF) or 6-methyl-1,3,8-trichlorodibenzofuran (MCDF) resulted in a concentration-dependent reduction of TCDD-induced CAT activity. Treatment of cells with 10(-6) M alpha NF or MCDF alone resulted in only minimal induction of CAT activity. Both antagonists inhibited the induction of genes under the control of the CYP1A1 and mouse mammary tumor virus promoters, which indicates that the alpha NF- and MCDF-mediated antagonism of TCDD-induced, aryl hydrocarbon receptor-dependent gene transcription does not depend on promoter context.
用一种质粒构建体瞬时转染大鼠肝癌H4IIE细胞和小鼠肝癌Hepa 1c1c7细胞，该质粒构建体含有在小鼠乳腺肿瘤病毒启动子和一个二噁英反应元件控制下的细菌氯霉素乙酰转移酶（CAT）基因。用10^(-13)至10^(-6) M的2,3,7,8-四氯二苯并对二噁英（TCDD）处理转染的H4IIE和Hepa 1c1c7细胞，导致瞬时CAT活性呈浓度依赖性增加。两种细胞系在暴露于10^(-9) M TCDD时均诱导出最大CAT活性。CAT活性的诱导与TCDD诱导的、P4501A1依赖性乙氧异羟肟酸O-脱乙基酶活性密切相关。用10^(-9) M TCDD和10^(-8)至10^(-6) M α-萘黄酮（αNF）或6-甲基-1,3,8-三氯二苯并呋喃（MCDF）共同处理转染细胞，导致TCDD诱导的CAT活性呈浓度依赖性降低。单独用10^(-6) M αNF或MCDF处理细胞仅导致CAT活性的最小诱导。两种拮抗剂均抑制CYP1A1和小鼠乳腺肿瘤病毒启动子控制下的基因诱导，这表明αNF和MCDF介导的对TCDD诱导的、芳烃受体依赖性基因转录的拮抗作用不依赖于启动子背景。
