ABSTRACT Autophagy is a major intracellular degradation process that plays an important role in cell survival, stress responses, nutrient sensing and development. Our previous studies have shown that Rg2, a triterpenoid saponin contained in ginseng, protects cells against UVB-induced genotoxicity by increasing DNA repair, in possible association with modulation of protein levels involved in p53 pathway. In this study, we determined an upregulation of autophagy by Rg2. Rg2 treatment for 24 h in MCF-7, a breast cancer cell, did not show cytotoxicity up to 200 μM. Rg2 also upregulated the level of p-p53, p-AMPK, p-ACC, Atg-7 and LC3-II and decreased the level of p62 in concentration-dependent manners. We also determined the level of p53, AMPK, p62, Atg-7 and LC3 after UVB exposure and subsequent incubation in growth medium for 24 h. UVB increased the level of p-p53, p-AMPK, p-ACC and decreased the levels of p62, Atg-7 and LC3-II. Interestingly, Rg2 treatment for 24 h after UVB exposure increased the levels of p-p53, p-AMPK, p-ACC, Atg-7 and LC3-II and decreased the level of cyclobutane pyrimidine dimer, a UVB-induced DNA damage in concentration-dependent manners. All these results suggest that Rg2 increased autophagy and decreased UVB-induced DNA damage, in possible association with the modulation of protein levels in p53- and autophagic pathways.

中文翻译：

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人参皂苷 Rg2 在 MCF-7 细胞中上调自噬

摘要 自噬是一种主要的细胞内降解过程，在细胞存活、应激反应、营养感知和发育中起着重要作用。我们之前的研究表明，人参中含有的三萜皂苷 Rg2 通过增加 DNA 修复来保护细胞免受 UVB 诱导的基因毒性，这可能与 p53 途径中涉及的蛋白质水平的调节有关。在这项研究中，我们确定了 Rg2 对自噬的上调。Rg2 在乳腺癌细胞 MCF-7 中处理 24 小时，在高达 200 μM 时未显示细胞毒性。Rg2 还以浓度依赖性方式上调 p-p53、p-AMPK、p-ACC、Atg-7 和 LC3-II 的水平并降低 p62 的水平。我们还确定了在 UVB 暴露和随后在生长培养基中孵育 24 小时后 p53、AMPK、p62、Atg-7 和 LC3 的水平。UVB 增加了 p-p53、p-AMPK、p-ACC 的水平并降低了 p62、Atg-7 和 LC3-II 的水平。有趣的是，UVB 暴露后 24 小时的 Rg2 处理增加了 p-p53、p-AMPK、p-ACC、Atg-7 和 LC3-II 的水平，并降低了环丁烷嘧啶二聚体的水平，这是一种 UVB 诱导的 DNA 损伤浓度-依赖的方式。所有这些结果表明，Rg2 增加了自噬并减少了 UVB 诱导的 DNA 损伤，这可能与 p53 和自噬途径中蛋白质水平的调节有关。