Ellagic acid induces NAD(P)H:quinone reductase through activation of the antioxidant responsive element of the rat NAD(P)H:quinone reductase gene.

Abstract

Induction of cellular detoxification enzymes can increase detoxification of carcinogens and reduce carcinogen-induced mutagenesis and tumorigenesis. To determine if the dietary anticarcinogen ellagic acid induced enzymes which detoxify xenobiotics and carcinogens, we examined the effect of ellagic acid on the expression of the phase II detoxification enzyme NAD(P)H:quinone reductase (QR). QR is induced by xenobiotics and antioxidants interacting with the xenobiotic responsive and antioxidant responsive elements of the 5' regulatory region of the QR gene. Ellagic acid is structurally related to the antioxidants which induce QR and we proposed that ellagic acid would induce QR expression through activation of the antioxidant responsive element of the QR gene. Rats fed ellagic acid demonstrated a 9-fold increase in hepatic and a 2-fold increase in pulmonary QR activity, associated with an 8-fold increase in hepatic QR mRNA. To determine if this increase in QR mRNA was due to activation of the antioxidant responsive element, transient transfection studies were performed with plasmid constructs containing various portions of the 5' regulatory region of the rat QR gene. These transfection studies confirmed that ellagic acid induces transcription of the QR gene and demonstrated that this induction is mediated through the antioxidant responsive element of the QR gene.