O'Brien N M, Woods J A, Aherne S A, O'Callaghan Y C
Nutritional Sciences, Department of Food Science and Technology, University College, Cork, Ireland.
Biochem Soc Trans. 2000 Feb;28(2):22-6. doi: 10.1042/bst0280022.
Much research effort has focused on the identification of phytochemicals in fruit and vegetables which exert beneficial effects. Our research examines modulatory effects of phytochemicals on cytotoxicity, genotoxicity and oxidative reactions in cell systems. Two examples of our studies are discussed. First, the potential beneficial effects of flavonoids are demonstrated. Flavonoids are reported to exhibit a wide variety of biological effects, including antioxidant and free-radical-scavenging activities. The aim of the study was to determine if flavonoids could protect against H2O2-induced DNA damage, as measured by the comet assay, in Caco-2 and HepG2 cells. Both cell lines were supplemented with increasing concentrations of myricetin, quercetin and rutin for 24 h followed by exposure to H2O2 (50 microM) for 30 min. Exposure to H2O2 for 30 min at 37 degrees C resulted in significant DNA damage and pre-incubation with the flavonoids before H2O2 exposure significantly (P <0.05) protected Caco-2 and HepG2 cells against H2O2-induced DNA damage. Secondly, we illustrate the use of cellular models to study oxysterol-induced toxicity. Oxysterols are generated during the cooking and processing of foods and may be produced endogenously by the oxidation of membrane lipids. Recent findings suggest that oxysterols may modulate cytotoxicity by exerting effects on the induction of apoptosis. 7beta-Hydroxycholesterol (7beta-OHC) and 25-hydroxycholesterol, both of which are commonly found in foods, were investigated for their abilities to induce apoptosis in a human monocytic blood cell line, U937, and in the human hepatoma cell line, HepG2 cells. U937 and HepG2 cells were incubated for up to 48 h with 30 microM oxysterol. 7beta-OHC induced apoptosis in U937 cells as measured by non-random DNA fragmentation, condensed and fragmented nuclei, and the generation of hypodiploid cells. In contrast, oxysterols may induce cell death by a different mechanism in the hepatoma cells, possibly by necrosis.
许多研究工作都集中在鉴定水果和蔬菜中具有有益作用的植物化学物质上。我们的研究考察了植物化学物质对细胞系统中细胞毒性、基因毒性和氧化反应的调节作用。文中讨论了我们的两项研究实例。首先，证明了类黄酮的潜在有益作用。据报道，类黄酮具有多种生物学效应，包括抗氧化和清除自由基的活性。该研究的目的是确定类黄酮是否能通过彗星试验检测，保护Caco-2和HepG2细胞免受过氧化氢诱导的DNA损伤。两种细胞系均用浓度递增的杨梅素、槲皮素和芦丁处理24小时，随后暴露于过氧化氢（50微摩尔）30分钟。在37摄氏度下暴露于过氧化氢30分钟会导致显著的DNA损伤，而过氧化氢暴露前用类黄酮预孵育能显著（P<0.05）保护Caco-2和HepG2细胞免受过氧化氢诱导的DNA损伤。其次，我们阐述了利用细胞模型研究氧化甾醇诱导的毒性。氧化甾醇在食品烹饪和加工过程中产生，也可能由膜脂氧化内源性产生。最近的研究结果表明，氧化甾醇可能通过对细胞凋亡诱导的作用来调节细胞毒性。研究了食品中常见的7β-羟基胆固醇（7β-OHC）和25-羟基胆固醇在人单核血细胞系U937和人肝癌细胞系HepG2细胞中诱导凋亡的能力。U937和HepG2细胞用30微摩尔氧化甾醇孵育长达48小时。通过非随机DNA片段化、细胞核浓缩和碎片化以及亚二倍体细胞的产生来检测，7β-OHC诱导U937细胞凋亡。相比之下，氧化甾醇可能通过不同机制在肝癌细胞中诱导细胞死亡，可能是通过坏死。
