Potency of isothiocyanates to induce luciferase reporter gene expression via the electrophile-responsive element from murine glutathione S-transferase Ya

Isothiocyanates are electrophiles that are able to induce phase II biotransformation enzyme gene expression via an electrophile-responsive element (EpRE) in the gene regulatory region. To study the potency of different isothiocyanates to induce the expression of EpRE-regulated genes, a Hepa-1c1c7 luciferase reporter cell line was exposed to structurally different isothiocyanates. The reporter cell line, EpRE(mGST-Ya)–LUX, contains the EpRE from the regulatory region of the mouse glutathione S-transferase Ya gene. Isothiocyanates containing a methyl-sulfur side chain, e.g. sulforaphane, showed a lower EC50 (0.8–3.2 μM) and a comparable induction factor (17–22.4) compared to the structurally different isothiocyanates containing an alkyl or aromatic side chain, e.g. allyl and phenylethyl isothiocyanate (EC50 3.9–6.5 μM, induction factor 17.5–23). After 24 h of exposure, on average (±SD) 23 ± 5% of the isothiocyanate was found in the cells and 77% in the cell medium. Isothiocyanates prove to be strong inducers of electrophile-responsive element-mediated gene expression at physiological concentrations. The here described luciferase reporter cell line is a suitable assay to measure the potency of compounds to induce EpRE-regulated gene expression.