Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
Carcinogenesis. 2013 Nov;34(11):2587-92. doi: 10.1093/carcin/bgt246. Epub 2013 Jul 10.
Sulforaphane (SFN) is a potent inducer of detoxication enzymes such as NAD(P)H:quinone oxidoreductase 1 (NQO1) and glutathione-S-transferase (GST) via the Kelch-like erythroid-derived protein with CNC homology-associated protein 1 (Keap1)-NF-E2-related factor 2 (Nrf2) signaling pathway. NQO1 reduces the carcinogenic estrogen metabolite, catechol estrogen-3,4-quinone, whereas GSTs detoxify it through conjugation with glutathione. These 3,4-quinones can react with DNA to form depurinating DNA adducts. Thus, SFN may alter estrogen metabolism and thus protect against estrogen-mediated DNA damage and carcinogenesis. Human breast epithelial MCF-10A cells were treated with either vehicle or SFN and either estradiol (E2) or its metabolite 4-hydroxyestradiol (4-OHE2). 4-Hydroxy-derived estrogen metabolites and depurinating DNA adducts formed from E2 and its interconvertable metabolite estrone (E1) were analyzed by mass spectrometry. Levels of the depurinated adducts, 4-OHE1/2-1-N3Adenine and 4-OHE1/2-1-N7Guanine, were reduced by 60% in SFN-treated cells, whereas levels of 4-OCH3E1/2 and 4-OHE1/2-glutathione conjugates increased. To constitutively enhance the expression of Nrf2-regulated genes, cells were treated with either scrambled or siKEAP1 RNA. Following E2 or 4-OHE2 treatments, levels of the adenine and guanine adducts dropped 60-70% in siKEAP1-treated cells, whereas 4-OHE1/2-glutathione conjugates increased. However, 4-OCH3E1/2 decreased 50% after siKEAP1 treatment. Thus, treatment with SFN or siKEAP1 has similar effects on reduction of depurinating estrogen-DNA adduct levels following estrogen challenge. However, these pharmacologic and genetic approaches have different effects on estrogen metabolism to O-methyl and glutathione conjugates. Activation of the Nrf2 pathway, especially elevated NQO1, may account for some but not all of the protective effects of SFN against estrogen-mediated DNA damage.
萝卜硫素 (SFN) 通过 Kelch 样红细胞衍生蛋白与 CNC 同源相关蛋白 1 (Keap1)-NF-E2 相关因子 2 (Nrf2) 信号通路诱导解毒酶的表达，如 NAD(P)H：醌氧化还原酶 1 (NQO1) 和谷胱甘肽-S-转移酶 (GST)。NQO1 减少致癌雌激素代谢物儿茶酚雌激素-3,4-醌，而 GSTs 通过与谷胱甘肽结合来解毒。这些 3,4-醌可以与 DNA 反应形成脱嘌呤 DNA 加合物。因此，SFN 可能改变雌激素代谢，从而防止雌激素介导的 DNA 损伤和致癌作用。用人乳腺上皮 MCF-10A 细胞用载体或 SFN 以及雌二醇 (E2) 或其代谢物 4-羟基雌二醇 (4-OHE2) 处理。通过质谱分析 E2 及其可互变代谢物雌酮 (E1) 形成的 4-羟基衍生雌激素代谢物和脱嘌呤 DNA 加合物。SFN 处理细胞后，脱嘌呤加合物 4-OHE1/2-1-N3 腺嘌呤和 4-OHE1/2-1-N7 鸟嘌呤的水平降低了 60%，而 4-OCH3E1/2 和 4-OHE1/2-谷胱甘肽缀合物的水平增加。为了持续增强 Nrf2 调节基因的表达，用 scrambled 或 siKEAP1 RNA 处理细胞。用 E2 或 4-OHE2 处理后，siKEAP1 处理细胞中的腺嘌呤和鸟嘌呤加合物水平下降了 60-70%，而 4-OHE1/2-谷胱甘肽缀合物增加。然而，siKEAP1 处理后 4-OCH3E1/2 减少了 50%。因此，SFN 或 siKEAP1 处理对雌激素刺激后脱嘌呤雌激素-DNA 加合物水平的降低有类似的影响。然而，这些药理和遗传方法对 O-甲基和谷胱甘肽缀合物的雌激素代谢有不同的影响。Nrf2 通路的激活，特别是 NQO1 的升高，可能解释了 SFN 对雌激素介导的 DNA 损伤的部分保护作用，但不是全部。
