Effects of glutathione on antioxidant response element-mediated gene expression and apoptosis elicited by sulforaphane

• Published in: Cancer research (Chicago, Ill.) Vol. 63; no. 21; pp. 7520 - 7525
• Main Authors: KIM, Bok-Ryang, HU, Rong, KEUM, Young-Sam, HEBBAR, Vidya, SHEN, Guoxiang, NAIR, Sujit S, KONG, A.-N. Tony
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 01-11-2003
• Subjects: Acetylcysteine - analogs & derivatives; Acetylcysteine - pharmacology; Antineoplastic agents; Antioxidants - metabolism; Apoptosis - drug effects; Apoptosis - physiology; Biological and medical sciences; Buthionine Sulfoximine - pharmacology; Caspase 3; Caspases - metabolism; Cell Line, Tumor; Enzyme Activation - drug effects; Gene Expression Regulation, Neoplastic - drug effects; Glutathione - metabolism; Glutathione - pharmacology; Glutathione - physiology; Humans; Isothiocyanates; JNK Mitogen-Activated Protein Kinases; Medical sciences; Mitogen-Activated Protein Kinases - metabolism; Pharmacology. Drug treatments; Response Elements - drug effects; Thiocyanates - chemistry; Thiocyanates - pharmacology; Tumors; Antioxidant; Gene expression; Cell death; Response element; Apoptosis; Glutathione
• ISSN: 0008-5472; 1538-7445

Sulforaphane (SFN) and its N-acetyl-L-cysteine (NAC) conjugate are effective inhibitors of tumorigenesis in animal models. These compounds induce the expression of the antioxidant response element (ARE)-related genes and cause apoptosis. We studied the role of reduced glutathione (GSH) in the activations of ARE-mediated gene expression, apoptosis, and the activation of c-Jun NH(2)-terminal kinase (JNK) in HepG2-C8 cells. The cellular level of GSH decreased transiently when cells were exposed to SFN and then increased from 4 h, reaching 2.2-fold over control at 24 h. In contrast, SFN-NAC did not change the GSH level substantially during the time of incubation. ARE expression was increased in a dose-dependent manner up to 35 micro M SFN and 75 micro M SFN-NAC, respectively. The induction of ARE by SFN was 8.6-fold higher than that by SFN-NAC. Pretreatment with L-buthionine sulfoximine increased SFN-induced ARE expression significantly. The decrease in ARE expression at higher concentrations of SFN and SFN-NAC was correlated with accelerated apoptotic cell death, with a dose-dependent activation of caspase 3 activity by SFN. On addition of extracellular GSH within 6 h of treatment with SFN, the effect on ARE expression was blocked almost completely. SFN was able to activate JNK1/2, and that activation was blocked by treatment with exogenous GSH. Taken together, these results suggest that the biological effects of SFN and SFN-NAC on the induction of ARE-related gene expression and apoptosis could be different from each other; however, the different effects on ARE-related gene expression and apoptosis elicited by SFN can be blocked by the addition of GSH.