Redox properties of diphenols and their correlation to induction of enzyme synthesis

Transcription of detoxification enzymes can be enhanced by a large variety of exogenous molecules. The mechanism of this increased transcription by so many structurally unrelated compounds is not yet completely understood. The cytosolic enzyme NAD(P)H:(quinone acceptor) oxidoreductase, considered as a marker for protective enzyme induction, can be induced in murine hepatoma cells by diphenolic antioxidants, known as chemoprotectors in vivo against toxic effets of carcinogens. To better understand the mechanism by which this induction takes place, we have tried to correlate the induction of quinone reductase with a redox property of these diphenols. In absence of a reliable one-electron reduction potential for all these diphenols, we have chosen a physico-chemical parameter related to their redox potential, namely the rare constant of singlet oxygen quenching by these enzyme inducers (k(Delta)). We have observed linear correlations between the efficiency of the induction of quinone reductase activity and log k(Delta). For a number of phenols (Phi OH), the one-electron reduction potential E (Phi O ./Phi O-) has been previously determined by pulse radiolysis, and logk(Delta) is itself related to E. These correlations point to the involvement of a redox regulation in the transcription enhancements of genes encoding for quinone reductase.