Suppression of cytochrome P450 (Cyp1a-1) induction in mouse hepatoma Hepa-1C1C7 cells by methoxsalen.
Cultured mouse hepatoma cell line Hepa-1c1c7 cells were treated with methoxsalen to assess the role of methoxsalen in the process of Cyp1a-1 induction. Treatment of Hepa-1c1c7 cultures with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced Cyp1a-1, as indicated by analysis of 7-ethoxyresorufin O-deethylation (EROD) activity and P4501A1 protein. When methoxsalen and TCDD were both added to cultures, TCDD-inducible EROD activity was greatly suppressed by methoxsalen in a dose-dependent manner. We find that treatment of Hepa-1c1c7 cells with methoxsalen inhibited CYP1A1 mRNA induction by TCDD as well as the concomitant increase P4501A1 protein. Formation of DNA-protein complexes between the dioxin receptor and its DRE target was inhibited by methoxsalen, as determined by gel mobility shift assays using oligonucleotides corresponding to DRE 3 of the Cyp1a-1 gene. These results suggest that the inhibitory action of methoxsalen on TCDD induction of the Cyp1a-1 gene expression in Hepa-1c1c7 cells might be antagonism of the DNA binding potential of nuclear dioxin receptor.
Jeong
H G
HG
Department of Environmental Science, Chosun University, Kwangju, Korea.
Yun
C H
CH
Jeon
Y J
YJ
Lee
S S
SS
Yang
K H
KH
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D019363:Cytochrome P-450 CYP1A1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D008114:Liver Neoplasms, Experimental; D008730:Methoxsalen / Q000494:pharmacology*; D051379:Mice; D008861:Microsomes / Q000201:enzymology; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010088:Oxidoreductases / Q000096:biosynthesis / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D018336:Receptors, Aryl Hydrocarbon / Q000302:isolation & purification / Q000378:metabolism; D014407:Tumor Cells, Cultured
D009838:Oligodeoxyribonucleotides; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D019363:Cytochrome P-450 CYP1A1; D008730:Methoxsalen