Differential effect of arecoline on the endogenous dioxin-responsive cytochrome P450 1A1 and on a stably transfected dioxin-responsive element-driven reporter in human hepatoma cells.
Dioxin-responsive element-mediated chemical activated luciferase expression (DRE-CALUX) is one of alternative bioassays for the determination of dioxin levels. We have previously established a DRE-CALUX cell line, Huh7-DRE-Luc, by using stable transfection of Huh-7 cells with a reporter plasmid (4xDRE-TATA-Luc) carrying a DRE-driven firefly luciferase gene. It was also shown that arecoline, a major areca nut alkaloid, inhibited the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced cytochrome P450 1A1 (CYP1A1) activation in Huh-7 cells. The TCDD-activated aryl hydrocarbon receptor (AhR) induces the DRE-CALUX activation and CYP1A1 gene expression via binding to DRE in promoter regions of these dioxin-responsive genes. In the present study, the effect of arecoline on the TCDD-induced activation of DRE-CALUX and CYP1A1 enzyme in Huh7-DRE-Luc and Huh-7 cells, respectively, was examined. It was found that arecoline inhibited TCDD-induced CYP1A1 activation and however enhanced TCDD-induced DRE-CALUX activation. This finding indicates the differential effect of arecoline on the endogenous dioxin-responsive CYP1A1 and on a stably transfected DRE-driven reporter in human hepatoma cells. The present study suggests that induction of DRE-CALUX alone does not necessarily parallel with endogenous CYP1A1 gene expression, and that the reporter assay may detect interactions that are not functional in endogenous gene.
Chao
How-Ran
HR
Department of Environmental Science and Engineering, National Pingtung University of Science and Technology, Neipu 912, Pingtung, Taiwan.
Wang
Ya-Fen
YF
Chen
Hung-Ta
HT
Ko
Ying-Chin
YC
Chang
Eddy Essen
EE
Huang
Yuh-Jeen
YJ
Tsai
Feng-Yuan
FY
Tsai
Cheng-Hsien
CH
Wu
Chia-Hsin
CH
Tsou
Tsui-Chun
TC
D001115:Arecoline / Q000494:pharmacology*; D001681:Biological Assay; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D019363:Cytochrome P-450 CYP1A1 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins; D020218:Response Elements
D000072317:Polychlorinated Dibenzodioxins; D001115:Arecoline; D008156:Luciferases; D019363:Cytochrome P-450 CYP1A1