Di Francesco Andrea, Falconi Anastasia, Di Germanio Clara, Micioni Di Bonaventura Maria Vittoria, Costa Antonio, Caramuta Stefano, Del Carlo Michele, Compagnone Dario, Dainese Enrico, Cifani Carlo, Maccarrone Mauro, D'Addario Claudio
Faculty of Biosciences, University of Teramo, Teramo, Italy.
Faculty of Veterinary Medicine, University of Teramo, Teramo, Italy.
J Nutr Biochem. 2015 Mar;26(3):250-8. doi: 10.1016/j.jnutbio.2014.10.013. Epub 2014 Dec 3.
Extravirgin olive oil (EVOO) represents the typical lipid source of the Mediterranean diet, an eating habit pattern that has been associated with a significant reduction of cancer risk. Diet is the more studied environmental factor in epigenetics, and many evidences suggest dysregulation of epigenetic pathways in cancer. The aim of our study was to investigate the effects of EVOO and its phenolic compounds on endocannabinoid system (ECS) gene expression via epigenetic regulation in both human colon cancer cells (Caco-2) and rats exposed to short- and long-term dietary EVOO. We observed a selective and transient up-regulation of CNR1 gene - encoding for type 1 cannabinoid receptor (CB₁) - that was evoked by exposure of Caco-2 cells to EVOO (100 ppm), its phenolic extracts (OPE, 50 μM) or authentic hydroxytyrosol (HT, 50 μM) for 24 h. None of the other major elements of the ECS (i.e., CB₂; GPR55 and TRPV1 receptors; and NAPE-PLD, DAGL, FAAH and MAGL enzymes) was affected at any time point. The stimulatory effect of OPE and HT on CB₁ expression was inversely correlated to DNA methylation at CNR1 promoter and was associated with reduced proliferation of Caco-2 cells. Interestingly, CNR1 gene was less expressed in Caco-2 cells when compared to normal colon mucosa cells, and again this effect was associated with higher level of DNA methylation at CNR1. Moreover, in agreement with the in vitro studies, we also observed a remarkable (~4-fold) and selective increase in CB₁ expression in the colon of rats receiving dietary EVOO supplementation for 10 days. Consistently, CpG methylation of rat Cnr1 promoter, miR23a and miR-301a, previously shown to be involved in the pathogenesis of colorectal cancer and predicted to target CB₁ mRNA, was reduced after EVOO administration down to ~50% of controls. Taken together, our findings demonstrating CB₁ gene expression modulation by EVOO or its phenolic compounds via epigenetic mechanism, both in vitro and in vivo, may provide a new therapeutic avenue for treatment and/or prevention of colon cancer.
特级初榨橄榄油（EVOO）是地中海饮食的典型脂质来源，这种饮食习惯模式与癌症风险的显著降低有关。饮食是表观遗传学中研究较多的环境因素，许多证据表明癌症中表观遗传途径失调。我们研究的目的是通过表观遗传调控，研究EVOO及其酚类化合物对人结肠癌细胞（Caco-2）以及短期和长期摄入饮食EVOO的大鼠的内源性大麻素系统（ECS）基因表达的影响。我们观察到，将Caco-2细胞暴露于EVOO（100 ppm）、其酚类提取物（OPE，50 μM）或纯羟基酪醇（HT，50 μM）24小时后，编码1型大麻素受体（CB₁）的CNR1基因出现选择性和短暂的上调。在任何时间点，ECS的其他主要成分（即CB₂；GPR55和TRPV1受体；以及NAPE-PLD、DAGL、FAAH和MAGL酶）均未受到影响。OPE和HT对CB₁表达的刺激作用与CNR1启动子处的DNA甲基化呈负相关，并与Caco-2细胞增殖减少有关。有趣的是，与正常结肠黏膜细胞相比，CNR1基因在Caco-2细胞中的表达较低，而且这种效应同样与CNR1处较高水平的DNA甲基化有关。此外，与体外研究一致，我们还观察到，在接受饮食EVOO补充10天的大鼠结肠中，CB₁表达显著（约4倍）且选择性增加。一致的是，大鼠Cnr1启动子、miR23a和miR-301a的CpG甲基化在给予EVOO后降低至对照组的约50%，之前已证明这些甲基化参与结直肠癌的发病机制，并预测可靶向CB₁ mRNA。综上所述，我们的研究结果表明，EVOO或其酚类化合物在体外和体内均可通过表观遗传机制调节CB₁基因表达，这可能为结肠癌的治疗和/或预防提供新的治疗途径。
