The Engineering Research Center of Feed Safety and Efficient Utilization, Education Ministry, Hunan Agriculture University, Changsha, Hunan 410128, China.
J Agric Food Chem. 2011 Nov 23;59(22):11975-82. doi: 10.1021/jf2032439. Epub 2011 Nov 1.
6-(Methylsulfinyl)hexyl isothiocyanate (6-MSITC) is a bioactive ingredient present in wasabi, a popular pungent spice in Japan. Previous studies have revealed the cytoprotective and cancer chemopreventive effects of 6-MSITC. This study aims to clarify the molecular mechanisms by investigating the action of 6-MSITC on the Nrf2/Keap1 system. 6-MSITC up-regulated the expression of NAD(P)H:quinone oxidoreductase 1 (NQO1) by increasing the Nrf2 level. Treatment with 6-MSITC extended the half-life (t(1/2)) of Nrf2 protein from 11.5 to 35.2 min, approximately three times longer. Moreover, 6-MSITC suppressed the ubiquitination of Nrf2 but not Keap1. Alternatively, a modified Keap1 was observed in 6-MSITC-treated cells accompanying reduction of normal Keap1 protein. The results from cellular fractionation and immunocytochemistry assay revealed that Nrf2 was primarily accumulated in nucleus. EMSA and the reporter gene assay further demonstrated that 6-MSITC augmented Nrf2-ARE binding and transcription activity. Silencing Nrf2 using Nrf2 siRNA markedly reduced the Nrf2 level and ARE-driven activity under both baseline and 6-MSITC-induced conditions. Our data revealed that 6-MSITC enhanced Nrf2/ARE-driven NQO1 expression by stabilizing Nrf2 that was accomplished by modifying Keap1 with consequent inhibition of the ubiquitination and proteasomal turnover of Nrf2. The findings provide an insight into the mechanisms underlying 6-MSITC in cytoprotection and cancer chemoprevention.
6-(甲基亚磺酰基)己基异硫氰酸酯（6-MSITC）是日本流行的辛辣调味料芥末中的一种生物活性成分。先前的研究揭示了 6-MSITC 的细胞保护和癌症化学预防作用。本研究旨在通过研究 6-MSITC 对 Nrf2/Keap1 系统的作用来阐明其分子机制。6-MSITC 通过增加 Nrf2 水平来上调 NAD(P)H：醌氧化还原酶 1（NQO1）的表达。用 6-MSITC 处理可将 Nrf2 蛋白的半衰期（t(1/2)）从 11.5 分钟延长至 35.2 分钟，约延长了三倍。此外，6-MSITC 抑制了 Nrf2 的泛素化，但不抑制 Keap1。相反，在 6-MSITC 处理的细胞中观察到修饰的 Keap1，同时正常的 Keap1 蛋白减少。细胞分馏和免疫细胞化学分析的结果表明，Nrf2 主要积累在细胞核中。EMSA 和报告基因分析进一步表明，6-MSITC 增强了 Nrf2-ARE 结合和转录活性。使用 Nrf2 siRNA 沉默 Nrf2，可在基线和 6-MSITC 诱导条件下显著降低 Nrf2 水平和 ARE 驱动的活性。我们的数据表明，6-MSITC 通过修饰 Keap1 使 Nrf2 稳定化，从而增强 Nrf2/ARE 驱动的 NQO1 表达，从而抑制了 Nrf2 的泛素化和蛋白酶体降解。这些发现为 6-MSITC 在细胞保护和癌症化学预防中的作用机制提供了新的见解。
