The present investigation demonstrates distinct patterns of activation for
antioxidant/electrophile-responsive elements (ARE/EpREs) in cells of neuronal versus hepatic origin suggesting the possibility of cell-/tissue-specific signaling pathways and/or
transcription factors required for ARE/EpRE activation. The ARE/EpRE is a cis-acting regulatory
element found in 5'-flanking regions of numerous genes including
NAD(P)H:
quinone oxidoreductase (QR) and
glutathione S-
transferases. Insomuch as ARE/EpRE activation has been studied primarily in
hepatoma cell lines there is little information on how these responsive elements and corresponding genes are regulated in brain. ARE/EpRE-reporter constructs were transiently transfected into IMR-32 human
neuroblastoma cells. Activation of ARE/EpRE sequences by
tert-butylhydroquinone (
tBHQ), a redox-cycling compound, in IMR-32 cells (20- to 30-fold) is dramatically different from the minimal response seen in HepG2 human
hepatoma cells (2- to 3-fold). beta-napthoflavone, an ARE/EpRE inducer in HepG2 cells, as well as the
oxidants hydrogen peroxide and
tert-butyl hydroperoxide did not induce the ARE/EpRE in IMR-32 cells. In addition, we show that the core sequence containing a complete 5' palindrome is necessary for maximal activation of the ARE/EpRE in IMR-32 cells. Mutations within this palindromic sequence decrease basal level expression and block induction by
tBHQ but not
phorbol 12-myristate 13-acetate. Furthermore, activation of the hQR-ARE/EpRE by
tBHQ correlates with induction of endogenous QR activity in IMR-32
neuroblastoma cells (15-fold). Thus, elucidating the mechanism of ARE/EpRE activation in this human
neuroblastoma cell line may identify unknown
transcription factors or signal transduction cascades regulating ARE/EpRE-driven gene expression.