Effects of glutathione on antioxidant response element-mediated gene expression and apoptosis elicited by sulforaphane.
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.
Kim
Bok-Ryang
BR
Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 160 Frelinghuysen Road, Piscataway, New Jersey 08854, USA.
Hu
Rong
R
Keum
Young-Sam
YS
Hebbar
Vidya
V
Shen
Guoxiang
G
Nair
Sujit S
SS
Kong
A-N Tony
AN
D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D000975:Antioxidants / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D017879:Isothiocyanates; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020218:Response Elements / Q000187:drug effects*; D013454:Sulfoxides; D013861:Thiocyanates / Q000737:chemistry / Q000494:pharmacology*
D000975:Antioxidants; D017879:Isothiocyanates; D013454:Sulfoxides; D013861:Thiocyanates; D019328:Buthionine Sulfoximine; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C016766:sulforaphane; D005978:Glutathione; D000111:Acetylcysteine