Cellular glutathione content modulates the effect of andrographolide on β-naphthoflavone-induced CYP1A1 mRNA expression in mouse hepatocytes

We previously reported that andrographolide (Andro), a major bioactive constituent of Andrographis paniculata, synergistically enhanced the inducible expression of CYP1A1 mRNA. In this study, although the synergism was confirmed at 24 h after the start of treatment with Andro and beta-naphthoflavone (beta NF), a CYP1A inducer, the expression was profoundly suppressed at an earlier phase, namely at 6-12 h, when the beta NF-induced expression peaked. Although oxidized glutathione (GSSG) levels were higher in co-treated cells at 6 and 24 h, levels of reactive oxygen species varied depending on the treatment period and species, indicating no relation to the synergistic expression of CYP1A1 mRNA. Glutathione (GSH) and N-acetyl-L-cysteine (NAC) significantly enhanced the beta NF-induced expression, and partly reversed the suppressive effect of Andro in the early phase. At 24 h, the addition of GSH or NAC had no effect on beta NF-induced CYP1A1 mRNA expression, but significantly reduced the synergistic effect of Andro. The synergistic effect was enhanced by L-buthionine-(S,R)-sulfoximine, a GSH depleter. Furthermore, H2O2 and ascorbic acid further modified the profile of synergism of Andro on beta NF-inducible CYP1A1 mRNA expression. These results suggest that GSH status might be involved in beta NF-induced CYP1A1 mRNA expression, and the interaction of Andro with GSH might modulate the expression. (C) 2010 Elsevier Ireland Ltd. All rights reserved.