Cellular glutathione content modulates the effect of andrographolide on β-naphthoflavone-induced CYP1A1 mRNA...

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 24h after the start of treatment with Andro and β-naphthoflavone (βNF), a CYP1A inducer, the expression was profoundly suppressed at an earlier phase, namely at 6-12h, when the βNF-induced expression peaked. Although oxidized glutathione (GSSG) levels were higher in co-treated cells at 6 and 24h, 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 βNF-induced expression, and partly reversed the suppressive effect of Andro in the early phase. At 24h, the addition of GSH or NAC had no effect on βNF-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, H(2)O(2) and ascorbic acid further modified the profile of synergism of Andro on βNF-inducible CYP1A1 mRNA expression. These results suggest that GSH status might be involved in βNF-induced CYP1A1 mRNA expression, and the interaction of Andro with GSH might modulate the expression.