Epigenomic Medicine, Baker IDI Heart and Diabetes Institute, The Alfred Medical Research and Education Precinct, 75 Commercial Road, Melbourne, VIC, Australia.
Genes Nutr. 2012 Apr;7(2):343-55. doi: 10.1007/s12263-011-0249-3. Epub 2011 Sep 28.
The medicinal properties of the leaves and fruit of Olea Europaea (olive tree) have been known since antiquity. Numerous contemporary studies have linked the Mediterranean diet with increased health. In particular, consumption of olive oil has been associated with a decreased risk of cardiovascular disease and certain cancers. Increasingly, there has been an interest in the biological properties of polyphenols, which are minor constituents of olive oil. For example, hydroxytyrosol has been shown to be a potent antioxidant and has anti-atherogenic and anti-cancer properties. The overall aim of this study was to provide insights into the molecular mechanisms of action of hydroxytyrosol using genome-wide mRNA-Seq. Initial experiments were aimed at assessing cytotoxicity, apoptosis and cell cycle effects of hydroxytyrosol in various cell lines. The findings indicated a dose-dependent reduction in cell viability in human erythroleukemic K562 and human keratinocytes. When comparing the viability in parental CEM-CCRF and R100 cells (which overexpress the P-glycoprotein pump), it was determined that the R100 cells were more resistant to effects of hydroxytyrosol suggesting efflux by the multi-drug resistance pump. By comparing the uptake of Hoechst 33342 in the two cell lines that had been pretreated with hydroxytyrosol, it was determined that the polyphenol may have P-glycoprotein-modulating activity. Further, initial studies indicated modest radioprotective effects of relatively low doses of hydroxytyrosol in human keratinocytes. Analysis of mRNA sequencing data identified that treatment of keratinocytes with 20 μM hydroxytyrosol results in the upregulation of numerous antioxidant proteins and enzymes, including heme oxygenase-1 (15.46-fold upregulation), glutaredoxin (1.65) and glutathione peroxidase (1.53). This may account for the radioprotective activity of the compound, and reduction in oxidative stress suggests a mechanism for chemoprevention of cancer by hydroxytyrosol. Alteration in the expression of transcription factors may also contribute to the anti-cancer effects described in numerous studies. These include changes in the expression of STAT3, STAT6, SMAD7 and ETS-1. The telomerase subunit TERT was also found to be downregulated in K562 cells. Overall, our findings provide insights into the mechanisms of action of hydroxytyrosol, and more generally, we identify potential gene candidates for further exploration.
自古以来，人们就知道油橄榄（油橄榄树）的叶子和果实具有药用特性。许多当代研究将地中海饮食与健康益处联系起来。特别是，橄榄油的消费与降低心血管疾病和某些癌症的风险有关。人们对橄榄油中少量成分多酚的生物特性越来越感兴趣。例如，羟基酪醇已被证明是一种有效的抗氧化剂，具有抗动脉粥样硬化和抗癌作用。本研究的总体目标是利用全基因组 mRNA-Seq 提供对羟基酪醇作用机制的深入了解。最初的实验旨在评估羟基酪醇在各种细胞系中的细胞毒性、细胞凋亡和细胞周期作用。研究结果表明，羟基酪醇在人红白血病 K562 和人角质形成细胞中的细胞活力呈剂量依赖性降低。当比较亲本 CEM-CCRF 和 R100 细胞（过度表达 P-糖蛋白泵）中的活力时，发现 R100 细胞对羟基酪醇的作用更具抗性，表明多药耐药泵的外排。通过比较用羟基酪醇预处理过的两种细胞系中 Hoechst 33342 的摄取，确定该多酚可能具有 P-糖蛋白调节活性。此外，初步研究表明，相对较低剂量的羟基酪醇对人角质形成细胞具有适度的放射保护作用。对 mRNA 测序数据的分析表明，用 20 μM 羟基酪醇处理角质形成细胞会导致许多抗氧化蛋白和酶的上调，包括血红素加氧酶-1（上调 15.46 倍）、谷胱甘肽过氧化物酶（上调 1.53 倍）和谷胱甘肽还原酶（上调 1.65 倍）。这可能解释了该化合物的放射保护活性，并且氧化应激的减少表明羟基酪醇通过化学预防癌症的机制。转录因子表达的改变也可能导致许多研究中描述的抗癌作用。这包括 STAT3、STAT6、SMAD7 和 ETS-1 表达的改变。端粒酶亚基 TERT 也被发现下调在 K562 细胞中。总的来说，我们的研究结果提供了对羟基酪醇作用机制的深入了解，更普遍地说，我们确定了进一步探索的潜在候选基因。
