Phase 2 Enzyme Induction by the Major Metabolite of Oltipraz
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- 作者：Jacobus P. Petzer ; Mettachit Navamal ; Jesse K. Johnson ; Mi-Kyoung Kwak ; Thomas W. Kensler ; and James C. Fishbein
- 刊名：Chemical Research in Toxicology
- 出版年：2003
- 出版时间：November 2003
- 年：2003
- 卷：16
- 期：11
- 页码：1463 - 1469
- 全文大小：117K
- 年卷期：v.16,no.11(November 2003)
- ISSN：1520-5010
文摘
Treatment for 48 h of murine Hepa 1c1c7 cells in culture with the cancer chemopreventiveoltipraz (1) followed by addition of CD3I and immediate cell lysis yields, by LC/MS analysis,three isotopomers of the methylated pyrrolopyrazine (2), a known human metabolite of oltipraz.The major isotopomer (58%) is the one containing two CD3- groups attached to the pendantsulfur atoms of the pyrrolopyrazine ring, the others containing one CD3- and one CH3- groupor two CH3- groups. It is concluded from this that the unmethylated pyrrolopyrazine (4) isthe major metabolite of oltipraz. Prodrugs 5 and 6, which have been shown to rapidly generate4 in the presence of GSH at physiological pH, induce the phase 2 enzyme NQO1 in Hepa 1c1c7cells with potencies on par with oltipraz itself: CDNQO1 = 14.4 ± 1.3, 20.1 ± 4.6, and 23.6 ±1.6 
M for oltipraz, 5, and 6, respectively. Pretreatment of oltipraz, 5, and 6 in cell culturemedia with 1 mM GSH, which is shown to immediately convert 5 and 6 to 4, followed byincubation with Hepa 1c1c7 cells shows similar potencies for oltipraz and the (decomposed)produrgs, with CDNQO1 = 18.0 ± 4.4 M for 5, 17.8 ± 0.2 M for 6, and 13.5 ± 1.4 M foroltipraz. Treatment with compound 6 of murine hepatoma cells containing a luciferase geneunder the control of the antioxidant response element (ARE) from the mouse heme oxygenase(ho-1) gene elicits induction of luciferase activity, CD = 35.8 ± 2.8 M, somewhat greater thanthe potency than oltipraz itself. Western blots of nuclear proteins isolated from Hepa 1c1c7cells and probed with anti-Nrf2 indicate that as compared to vehicle DMSO, compound 6stimulates nuclear translocation of Nrf2 from the cytosol. From this study, it is concludedthat the major metabolite of the cancer chemopreventive oltipraz is a phase 2 enzyme inducerof comparable potency that activates the ARE and initiates nuclear translocation of transcription factor Nrf 2.
M for oltipraz, 5, and 6, respectively. Pretreatment of oltipraz, 5, and 6 in cell culturemedia with 1 mM GSH, which is shown to immediately convert 5 and 6 to 4, followed byincubation with Hepa 1c1c7 cells shows similar potencies for oltipraz and the (decomposed)produrgs, with CDNQO1 = 18.0 ± 4.4 M for 5, 17.8 ± 0.2 M for 6, and 13.5 ± 1.4 M foroltipraz. Treatment with compound 6 of murine hepatoma cells containing a luciferase geneunder the control of the antioxidant response element (ARE) from the mouse heme oxygenase(ho-1) gene elicits induction of luciferase activity, CD = 35.8 ± 2.8 M, somewhat greater thanthe potency than oltipraz itself. Western blots of nuclear proteins isolated from Hepa 1c1c7cells and probed with anti-Nrf2 indicate that as compared to vehicle DMSO, compound 6stimulates nuclear translocation of Nrf2 from the cytosol. From this study, it is concludedthat the major metabolite of the cancer chemopreventive oltipraz is a phase 2 enzyme inducerof comparable potency that activates the ARE and initiates nuclear translocation of transcription factor Nrf 2.