Newly constructed stable reporter cell lines for mechanistic studies on electrophile-responsive element-mediated gene expression reveal a role for flavonoid planarity.
The electrophile-responsive element (EpRE) is a transcriptional enhancer involved in cancer-chemoprotective gene expression modulation by certain food components. Two stably transfected luciferase reporter cell lines were developed, EpRE(hNQO1)-LUX and EpRE(mGST-Ya)-LUX, based on EpRE sequences from the human NAD(P)H:quinone oxidoreductase (hNQO1) and the mouse glutathione-S-transferase Ya (mGST-Ya) gene, containing one and two tandem EpRE core sequences, respectively. The standard inducer tert-butylhydroquinone (tBHQ), the electrophile benzyl isothiocyanate (BITC), and the antioxidant flavonoid quercetin were found to induce luciferase expression, thereby validating these newly developed reporter cell lines. For tBHQ and BITC, but not for quercetin, higher maximum luciferase induction was found under control of the mGST-Ya EpRE as compared to the hNQO1 EpRE, pointing at different induction mechanisms. Furthermore, we investigated the structure-activity relationship for induction of luciferase expression by flavonoids in EpRE(mGST-Ya)-LUX cells, and also the relation between luciferase induction and flavonoid antioxidant potency. Five different flavonoids with a planar molecular structure were found to induce various levels of luciferase activity, whereas taxifolin, a non-planar flavonoid, did not induce luciferase activity. This suggests that a stereospecific molecular interaction may be important for EpRE-mediated gene activation, possibly with Keap1, a regulator of EpRE-controlled transcription, or with another effector or receptor protein. No consistent relation between luciferase induction level and flavonoid antioxidant potential was observed. Altogether, these results point to differences in induction mechanism between the various chemoprotective compounds tested. The newly developed stably transfected reporter cell lines provide a validated tool for future screening and mechanistic studies of EpRE-mediated gene transcription.
Boerboom
Anne-Marie J F
AM
Division of Toxicology, Wageningen University, P.O. Box 8000, 6700 EA Wageningen, The Netherlands.
Vermeulen
Martijn
M
van der Woude
Hester
H
Bremer
Birgit I
BI
Lee-Hilz
Yee Y
YY
Kampman
Ellen
E
van Bladeren
Peter J
PJ
Rietjens
Ivonne M C M
IM
Aarts
Jac M M J G
JM
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D004790:Enzyme Induction; D005419:Flavonoids / Q000737:chemistry* / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects*; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D010957:Plasmids; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic / Q000187:drug effects
D017931:DNA Primers; D005419:Flavonoids; D008156:Luciferases