Kim Bok-Ryang, Hu Rong, Keum Young-Sam, Hebbar Vidya, Shen Guoxiang, Nair Sujit S, Kong A-N Tony
Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 160 Frelinghuysen Road, Piscataway, New Jersey 08854, USA.
Cancer Res. 2003 Nov 1;63(21):7520-5.
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.
萝卜硫素（SFN）及其N - 乙酰 - L - 半胱氨酸（NAC）共轭物在动物模型中是有效的肿瘤发生抑制剂。这些化合物可诱导抗氧化反应元件（ARE）相关基因的表达并引发细胞凋亡。我们研究了还原型谷胱甘肽（GSH）在HepG2 - C8细胞中ARE介导的基因表达激活、细胞凋亡以及c - Jun氨基末端激酶（JNK）激活中的作用。当细胞暴露于SFN时，GSH的细胞水平短暂下降，然后从4小时开始上升，在24小时时达到对照水平的2.2倍。相比之下，在孵育期间SFN - NAC并未显著改变GSH水平。分别在高达35 μM SFN和75 μM SFN - NAC时，ARE表达呈剂量依赖性增加。SFN对ARE的诱导作用比SFN - NAC高8.6倍。用L - 丁硫氨酸亚砜胺预处理可显著增加SFN诱导的ARE表达。在较高浓度的SFN和SFN - NAC下ARE表达的降低与加速的凋亡细胞死亡相关，SFN可剂量依赖性激活caspase 3活性。在用SFN处理6小时内添加细胞外GSH，对ARE表达的影响几乎完全被阻断。SFN能够激活JNK1/2，并且该激活作用可被外源性GSH处理所阻断。综上所述，这些结果表明SFN和SFN - NAC对ARE相关基因表达诱导和细胞凋亡的生物学效应可能彼此不同；然而，SFN对ARE相关基因表达和细胞凋亡的不同作用可通过添加GSH来阻断。
