Coordinate regulation of NAD(P)H:Quinone oxidoreductase and glutathione-S-transferases in primary cultures of rat neurons and glia: Role of the antioxidant/electrophile responsive element

Abstract

NAD(P)H:quinone oxidoreductase (QR) and glutathione‐S‐transferases (GSTs) are among the enzymes believed to protect an organism against oxidative stress. To test if redox‐cycling compounds regulate the expression of these enzymes in cells of neural origin, primary cultures of rat cerebellar neurons and glia were treated with tert‐butylhydroquinone (tBHQ) and hydroquinone (HQ). Basal levels of endogenous QR and GST activity were significantly greater in glia than neurons; and QR, GSTP1, and A3 were increased in glial but not neuronal cultures by treatment with tBHQ and HQ. A possible role for protein kinase C (PKC) in the tBHQ‐mediated increase in QR and GST was evaluated by activating PKC with phorbol 12‐myristate 13‐acetate or inhibiting PKC with bisindolylmaleimide I. PKC was not involved in maintaining basal expression or mediating the increased expression of GST or QR by tBHQ. Transcriptional activation of QR and rGSTP1 by tBHQ could be mediated through a common responsive element present in the 5′‐flanking region of both genes, the antioxidant/electrophile responsive element (ARE/EpRE). Transient transfection of the glial cultures with rGSTP1‐ or rQR1‐ARE/EpRE‐luciferase reporter constructs demonstrated that tBHQ transcriptionally activates the ARE/EpRE. Thus, the increased expression of genes regulated by the ARE/EpRE in cells of the central nervous system may provide protection against oxidative stress. GLIA 25:131–142, 1999. © 1999 Wiley‐Liss, Inc.

Coordinate Regulation of Glutathione Biosynthesis and Release by Nrf2-Expressing Glia Potently Protects Neurons from Oxidative Stress

“…However, the basal signal for NF-B also was highly enriched in glial cultures (ϳ15-fold). As expected from previous work, examination of basal mRNA levels indicated preferential glial expression of antioxidant factors such as NQO1, GST A3, GST P2, HO-1, catalase, thioredoxin reductase, metallothionein 1 or 2, and peroxiredoxin 1 and 5 (Dwyer et al, 1995;Murphy et al, 1998Murphy et al, , 2001Ahlgren-Beckendorf et al, 1999;Eftekharpour et al, 2000). Analysis of three separate comparisons between mRNA from GFP and Nrf2-overexpressing cultures consistently indicated the selective upregulation of a number of known and previously unknown phase II detoxification genes in response to acute Nrf2 overexpression (48 hr; Tables 3, 4).…”

“…The increased expression of various GST isoforms NQO1, HO-1, ␥-glutamylcysteine synthetase (␥-GCS; only modifier light chain upregulation was observed), thioredoxin reductase, and malic enzyme by Nrf2 overexpression in both cultures types corresponds to the gene induction profile previously observed when electrophilic agents such as tert-butylhydroquinone (tBHQ) and sulforaphane were used (Ahlgren-Beckendorf et al, 1999;Eftekharpour et al, 2000;Thimmulappa et al, 2002). Induction of these well characterized Nrf2 gene targets is, in part, supported by our own immunoblot data for HO-1, histochemical stains for NQO1, and measurements of GSH production (Fig.…”

“…One potential defense against the toxicity of reactive oxygen species (ROS) is the induction of a family of phase II detoxification enzymes (Fahey et al, 1997;Kensler, 1997). Data from our lab and others suggest that this response is expressed preferentially in astrocytes, with considerably lower levels in neurons (Ahlgren-Beckendorf et al, 1999;Eftekharpour et al, 2000;Murphy et al, 2001;. Originally thought to be restricted to promoting xenobiotic conjugation with endogenous ligands, such as glutathione (GSH) (Hayes and Pulford, 1995;Primiano et al, 1997), the observed functions of phase II enzymes have broadened recently.…”

Regulation of NAD(P)H quinone oxoreductase 1 (NQO1) in SHSY-5Y neuroblastoma cells by chemopreventive agents

“…The induction by these chemical agents is mediated via antioxidant electrophile response element. 8 The synergistic effects of expansive set of antioxidant/detoxification genes regulated by Cap 'n' Collar (CNC) transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) provide a powerful means of removing ROS/RNS species by binding to ARE/EpRE consensus sequence.…”

Pretreatment With Black Tea Polyphenols Modulates Xenobiotic-Metabolizing Enzymes in an Experimental Oral Carcinogenesis Model

“…PAHs such as DMBA are bifunctional inducers that induce both phase I and phase II detoxifying enzymes via the arylhydrocarbon receptor that binds to xenobiotic response elements of phase I and phase II enzyme genes, transactivating these genes (2,27,28). DMBA, a procarcinogen is metabolized by the consecutive actions of cytochrome P450 and epoxide hydrolase to the ultimate carcinogen 7,12-DMBA 3,4-diol 1,2-epoxide (29).…”