大鼠肝细胞核膜脂质过氧化对核DNA影响的研究

采用大鼠肝脏细胞核为材料,研究了核膜脂质过氧化对核ＤＮＡ的影响。证实核膜脂质过氧化可以引起ＤＮＡ损伤,表现为ＤＮＡ的增色效应、熔解温度、从ＤＮＡ向ＥＢ的能量转移效率降低,圆二色谱发生显著变化。另外受损ＤＮＡ对ＤＮａｓｅⅠ产生明显抗性和琼脂糖凝胶电泳结果提示核膜脂质过氧化引起的ＤＮＡ损伤可能以交联为主,同时利用原子力显微镜（ＡＦＭ）直接观察到了交联ＤＮＡ的生成。各种自由基清除剂对ＤＮＡ损伤保护的差异说明脂类自由基可能在活性氧自由基引起的ＤＮＡ损伤中具有重要作用。     

亚油酸体系脂质过氧化引起的DNA损伤研究

用含两个双键的不饱和脂肪酸-亚油酸作为模型化合物,分析其过氧化程度,同时检测了由于脂质过氧化而引起的DNA损伤,结果表明:在脂质过氧化过程中,DNA与亚油酸过氧化产物反应生成一种荧光物质、其最大激发波长315nm最大发射波长410nm并随着氧化时间增加而增加,与此同时,双链DNA百分含量明显下降,DNA-溴乙锭复合物荧光显著降低,反映了DNA二级结构受到破坏.上述结果揭示了脂质过氧化产物在自由基引起DNA的损伤中可能起重要作用     

脂质过氧化引起的DNA损伤研究进展

脂质过氧化可以引起各种碱基损伤、DNA链断裂和各种荧光产物生成,并对DNA分子鸟嘌呤碱基具有选择性损伤.过渡金属离子可以明显加深脂质过氧化对DNA的损伤程度.多种抗氧化剂、活性氧自由基清除剂对脂质过氧化引起的DNA损伤有一定程度的保护作用.具有致突、致癌作用的8－羟基鸟嘌呤已经观察到．脂质过氧化的致突变、致癌变作用机制引起了人们的极大兴趣．     

金樱子多糖的抗氧化作用

目的：探讨金樱子多糖(PRL)体外抗氧化作用。方法：邻苯三酚自氧化法测定PRL清除超氧阴离子自由基效果;比色法测定PRL对羟自由基诱导红细胞溶血、脂质过氧化反应的影响。结果：PRL能显著清除超氧阴离子自由基、押制羟自由基对细胞膜的破坏而引起的溶血和脂质过氧化产物的形成。结论：PRL具有显著的抗氧化作用。     

铝离子对二价铁离子启动的卵磷脂脂质体脂质过氧化的影响

利用化学发光、ＴＢＡ 反应与测量共轭二烯的方法观测了Ａｌ３ ＋ 对Ｆｅ２ ＋ 启动的卵磷脂脂质体脂质过氧化的影响。实验结果显示,在生理ｐＨ 条件下,Ａｌ３ ＋ 对Ｆｅ２ ＋ 启动的脂质过氧化有增强作用,表现为缩短潜伏期和加快脂质过氧化的反应速率, Ａｌ３ ＋ 的增强作用与脂质体中原先存在的过氧化物有关。这可能是因为在脂质体存在的条件下,Ａｌ３ ＋ 加速了Ｆｅ２ ＋ 的氧化,且加速作用与脂质体中原先存在的过氧化物的含量有关;另一方面,Ａｌ３ ＋ 可以引起脂质体的聚集,表现为浊度的增加;测量脂质体上标记的脂肪酸自旋标记物５ － Ｄｏｘｙｌ ｓｔｅａｒｉｃ ａｃｉｄ 的ＥＳＲ 波谱发现： Ａｌ３ ＋ 降低了脂质体的膜脂的流动性。研究表明： Ａｌ３ ＋ 对Ｆｅ２ ＋ 启动的卵磷脂脂质体的过氧化的增强作用可能与Ａｌ３ ＋ 加速了Ｆｅ２ ＋ 的氧化和改变了脂质体的物理状态有关     

阿霉素通过改变肌质网的钙转运造成心肌损伤

蒽醌类他合物阿霉素和柔毛霉素等广泛应用于肿瘤治疗,但因长期服用可造成心肌损伤,使其临床应用受到很大限制。阿霉素致心肌损伤的原理尚未阐明。80年代初曾有人提出脂质过氧化学说,认为苯醌/半醌之间的氧化还原反应促使体内产生超氧自由基和羟自由基,引起心肌细胞膜脂质过氧化,从而造成膜对     

羟自由基对人红细胞磷脂酰乙醇胺脂质体相变性质的影响

研究了过氧化氢与亚铁离子体系产生的羟自由基对人红细胞膜磷脂酸乙醇胺(PE)脂质体相变性质的影响.结果表明,羟自由基导致脂质体不饱和脂肪酸链的含量明显降低和丙二醛(MDA)含量显著升高,同时其膜流动性随之下降.在室温下,羟自由基诱使PF脂质体冰冻断裂面出现脂质颗粒,说明羟自由基通过脂质过氧化作用可促进PE脂质体从脂双层转变为非双层结构.     

羟自由基对人红细胞磷脂酰乙醇胺脂质体相变性质的影响

研究了过氧化氢与亚铁离子体系产生的羟自由基对人红细胞膜磷脂酸乙醇胺(PE)脂质体相变性质的影响.结果表明,羟自由基导致脂质体不饱和脂肪酸链的含量明显降低和丙二醛(MDA)含量显著升高,同时其膜流动性随之下降.在室温下,羟自由基诱使PF脂质体冰冻断裂面出现脂质颗粒,说明羟自由基通过脂质过氧化作用可促进PE脂质体从脂双层转变为非双层结构.     

白藜芦醇甙及其衍生物对脂质体膜氧化稳定性研究

<正> 白藜芦醇甙(Piceid)是蓼科植物虎杖的一种有效成份,其基本结构为二苯乙烯。据文献报导,白藜芦醇甙具有抗菌消炎、抑制肝损伤等作用。本文以白藜芦醇甙及其疏水衍生物为保护剂,通过测定在外源自由基影响下的脂质过氧化程度,研究了保护剂对脂质膜氧化稳定性的作用。为解决脂质体稳定性提供了一些启示。     

天然抗氧化剂丹参酮Ⅱ—A对肝细胞脂质过氧化产物与DNA相互作用的影响

［３Ｈ］花生四烯酸标记的肝细胞,经ＦｅＣｌ２－ＤＴＰＡ启动脂质过氧化后,细胞ＤＮＡ出现放射性,并随保温时间增加而逐渐增高,表明在细胞内脂质过氧化产物与ＤＮＡ发生相互作用,生成了一种ＤＮＡ加成物,经测定它具有特征荧光光谱,显示较低的增色效应和Ｔｍ值。用高度敏度荧光图象显微镜直接观察发现丹参酮Ⅱ－Ａ经细胞摄取后主要滞留在细胞膜与胞浆中。它能有效地抑制细胞脂质过氧化,减少脂质－ＤＮＡ加成物的产生,并阻止了细胞存活率和Ｏ６甲基鸟嘌呤转移酶活性的降低,其抑制率与ＶｉｔＥ,ＢＨＴ相近,但显著高于ＮａＮ３,甘露醇和ＳＯＤ。上述结果提示丹参酮Ⅱ－Ａ是一种新的有效的细胞内脂质过氧化产物与ＤＮＡ相互作用的抑制剂。它对ＤＮＡ的保护作用可能是通过清除脂类自由基而阻断脂质过氧化的链式反应,抑制ＤＮＡ加成物的生成,从而减少了细胞毒性。     

Cold atmospheric-pressure plasma induces DNA–protein crosslinks through protein oxidation

Reactive oxygen and nitrogen species (ROS and RNS) generated by cold atmospheric-pressure plasma could damage genomic DNA, although the precise types of these DNA damage induced by plasma are poorly characterized. Understanding plasma-induced DNA damage will help to elucidate the biological effect of plasma and guide the application of plasma in ROS-based therapy. In this study, it was shown that ROS and RNS generated by physical plasma could efficiently induce DNA-protein crosslinks (DPCs) in bacteria, yeast, and human cells. An in vitro assay showed that plasma treatment resulted in the formation of covalent DPCs by activating proteins to crosslink with DNA. Mass spectrometry and hydroperoxide analysis detected oxidation products induced by plasma. DPC formation were alleviated by singlet oxygen scavenger, demonstrating the importance of singlet oxygen in this process. These results suggested the roles of DPC formation in DNA damage induced by plasma, which could improve the understanding of the biological effect of plasma and help to develop a new strategy in plasma-based therapy including infection and cancer therapy.     

Reactive oxygen species and DNA damage after ultrasound exposure

The aim of this work was to detect the formation of hydrogen peroxide and hydroxyl radicals after ultrasound (US) exposure and test the hypothesis that reactive oxygen species induced by ultrasound can contribute to DNA damage. Formation of reactive oxygen species was observed in incubated medium after sonication with 1 MHz continuous ultrasound at the intensities of 0.61-2.44 W/cm2. Free radicals and hydrogen peroxide produced by ultrasound exposure of cells can lead to DNA damage. Comet assay was used to assess the effect of ultrasound on the level of nuclear DNA damage. The nucleated erythrocytes from fish were exposed in vitro to ultrasound at the same intensities and frequency. It was noticed that ultrasound in all used intensities induced DNA damage. The effect was not eliminated by the addition of catalase, which indicates that DNA damage was not caused by hydrogen peroxide only. The results showed that the DNA damage can be repair and this mechanism was the most effective after 30 and 60 min after sonication. Furthermore, the ultrasound-induced DNA damage in the presence of sonosensitizer (Zn- and AlCl-phthalocyanine) was studied. It was noticed that phthalocyaniens (Pcs) alone or with ultrasound did not induce significant changes in the level of DNA damage.     

An approach towards understanding the genesis of sunlight-induced skin cancer

The molecular basis of the sunlight-induced skin carcinogenesis has been elucidated. Of the two ultraviolet components of sunlight that reach the earth's surface the UV-B is known to be carcinogenic but the mode of action of UV-A, the predominant component of sunlight, is ill understood. Using the liposomes as a model system, it has been shown here that UV-A causes dose-dependent lipid peroxidation as estimated by measurements of conjugated dienes, lipid hydroperoxides, malondialdehydes and the fluorescent adducts (Schiff bases) produced by the reaction of MDA with glycine. Direct exposure to sunlight has also been shown to cause dose-dependent lipid peroxidation. The UV-A induced lipid peroxidation has also been shown to be dependent on dose rate. While the sodium formate, dimethyl sulphoxide, superoxide dismutase and EDTA do not have any significant effect, sodium azide, histidine, beta-carotene and dimethylfuran were shown to inhibit significantly the UV-A induced lipid peroxidation, thereby providing significant evidence of the involvement of singlet oxygen (1O2) as the initiating agent. The use of D2O in place of H2O as the liposome dispersing medium enhanced to great extent the UV-A induced lipid peroxidation, thereby lending additional support to the finding that singlet oxygen was the initiating agent. The possible mode of formation of 1O2 on exposure to UV-A was discussed. This study also highlighted the role of environmental factors on the sunlight-induced cutaneous damage. Finally, the relation between lipid peroxidation, DNA damage and carcinogenesis has been discussed in a way to suggest the possible link between sunlight exposure and causation of skin cancer.     

Induction of a cytotoxic T lymphocyte (CTL) response to plasmid DNA delivered via Lipodine liposomes

We have previously shown that liposome-mediated plasmid DNA immunisation may be a preferred alternative to the use of naked DNA. Lipodine DNA formulations consist of liposomes containing entrapped DNA plasmid by the dehydration-rehydration (DRV) method. Such liposome formulations are distinct from liposomes with externally complexed DNA in that the majority of the DNA is "internal" to the liposome structure and hence protected from DNAase degradation. Previous studies on the immune response induced by DNA vaccines entrapped in Lipodine have focused on the humoural response. In the present study, we have expanded the analysis profile in order to include the cytotoxic T lymphocyte (CTL) component of the immune response. We have analysed the immune response induced by DNA entrapped in Lipodine compared to that induced by DNA alone when delivered subcutaneously, a route of administration not normally inducing significant plasmid DNA mediated immune activation. Our results indicate that delivery of a small dose of plasmid DNA in Lipodine results in an improved antibody response to the plasmid encoded antigen and a strong antigen specific CTL response compared to that induced by DNA delivered alone.     

DNA damage by oxygen radicals and excited state species: a comparative study using enzymatic probes in vitro

Repair enzyme-containing extracts from a variety of cell types are used to analyse and compare DNA damage induced by oxygen radicals and excited molecules. The differing potentials of these extracts for recognising DNA damage leads to characteristic DNA damage profiles after treatment with superoxide (xanthine/xanthine oxidase), gamma-rays, chemically generated singlet oxygen, photosensitizers (rose bengal, methylene blue), UV254 and a 1,2-dioxetane. Three different types of damage profiles are distinguished and assigned to the predominant action of hydroxyl radicals, singlet oxygen or to the photoexcitation of thymine residues. The method applied in this study allows the analysis of DNA damage and the identification or exclusion of the participation of different ultimate reactive species without chemical identification of the lesions.     

Hg2+胁迫对浮萍体细胞DNA一级结构和抗氧化酶系的损伤(英文)

 主要从DNA一级结构及抗氧化酶系变化两方面,研究了Hg2+胁迫下浮萍体细胞的损伤。结果表明：运用随机扩增多态性DNA法（Random amplified polymorphism DNA, RAPD）和DNA梯法（DNA Ladder）,5～10 mg·L-1　Hg2+处理组可检测到基因组DNA的明显损伤,20 mg·-1 Hg2+已导致细胞坏死;RAPD法较DNA Ladder法更灵敏。本文还发现,活性氧和抗氧化酶系很可能参与了浮萍体细胞凋亡过程。低浓度的Hg2+胁迫可刺激抗氧化酶活性升高,以清除体内活性氧,而一旦活性氧水平超出一定域值,抗氧化酶活性急速下降,导致细胞凋亡。      

Oxygen free radicals in cell senescence: are they signal transducers?

Oxygen free radicals have a major impact on senescence of primary human cells. In replicative senescence, which is induced by uncapping of telomeres, the rate of telomere shortening is largely determined by telomere-specific accumulation of DNA damage induced by reactive oxygen species (ROS). More intense ROS-generating stressors can induce premature senescence via generation of telomere-independent DNA damage. Interestingly, ROS levels were also elevated when premature senescence was triggered by pathways downstream or independent of DNA damage. This has led to the suggestion that ROS generation could be a specific component of the signalling pathways inducing senescence. However, the available data are compatible with the concept that senescence is triggered as a DNA damage response. ROS appear to be involved as inducers of DNA damage rather than as specific signalling molecules. The upregulation of ROS production often seen in premature senescence might be related to retrograde response initiated by mitochondria.     

In vitro effect of gliclazide on DNA damage and repair in patients with type 2 diabetes mellitus (T2DM)

Type 2 diabetes mellitus is associated with elevated level of oxidative stress, which is one of the most important factors responsible for the development of chronic complications of this disease. Moreover, it was shown that diabetic patients had increased level of oxidative DNA damage and decreased effectiveness of DNA repair. These changes may be associated with increased risk of cancer in T2DM patients, since DNA damage and DNA repair play a pivotal role in malignant transformation. It was found that gliclazide, an oral hypoglycemic drug with antioxidant properties, diminished DNA damage induced by free radicals. Therefore, the aim of the present study was to evaluate the in vitro impact of gliclazide on: (i) endogenous basal and oxidative DNA damage, (ii) DNA damage induced by hydrogen peroxide and (iii) the efficacy of DNA repair of such damage. DNA damage and DNA repair in peripheral blood lymphocytes of 30 T2DM patients and 30 non-diabetic individuals were evaluated by alkaline single cell electrophoresis (comet) assay. The extent of oxidative DNA damage was assessed by DNA repair enzymes: endonuclease III and formamidopyrimidine-DNA glycosylase. The endogenous basal and oxidative DNA damages were higher in lymphocytes of T2DM patients compared to non-diabetic subjects and gliclazide decreased the level of such damage. The drug significantly decreased the level of DNA damage induced by hydrogen peroxide in both groups. Gliclazide increased the effectiveness of DNA repair in lymphocytes of T2DM patients (93.4% (with gliclazide) vs 79.9% (without gliclazide); P< or =0.001) and non-diabetic subjects (95.1% (with gliclazide) vs 90.5% (without gliclazide); P< or =0.001). These results suggest that gliclazide may protect against the oxidative stress-related chronic diabetes complications, including cancer, by decreasing the level of DNA damage induced by reactive oxygen species.     

Induction of oxidative DNA damage in u937 cells by TNF or anti-Fas stimulation

TNF and Fas signaling pathways are reported to induce mitochondrial damage associated with production of oxygen radicals. We examined whether such radical production elicited detectable nuclear DNA damage in U937 cells following treatment with TNF or with anti-Fas antibodies. Using GC-mass spectroscopy for analysing base oxidation, several oxidized species increased significantly following TNF treatment, whereas anti-Fas resulted in less detectable oxidative damage using this assay. Cytogenetic analysis showed that, in the presence of aphidicolin, which blocks several types of DNA repair, TNF induced extensive chromosomal damage. Aphidicolin also synergized with TNF and anti-Fas in inducing cell death which was prevented by reducing atmospheric oxygen or addition of n -acetyl cysteine, a scavenger of oxygen radicals. Thus, several lines of evidence point to the TNF and Fas pathways inducing extensive oxidative DNA damage and repair, and suggest potential roles for these pathways in mutagenesis and aging.     

DNA strand breaks in mammalian tissues induced by methylarsenics

DNA damage induced by administration of dimethylarsinic acid (DMAA) to rats and mice was investigated. At 12 h after administration of DMAA, DNA single-strand breaks were induced markedly in lung. The majority of dimethylarsine, one of the main metabolites, in the expired air was excreted within 6–18 h after administration of DMAA to rats. In vitro experiments using nuclei isolated from lung of mice indicated that DNA strand breaks were caused by dimethylarsine. Furthermore, the strand breaks after exposure to dimethylarsine were reduced in the presence of catalase and/or superoxide dismutase. These results strongly suggest that the strand breaks are induced not by dimethylarsine itself but by active oxygen, e.g., O ₂ ^? and ·OH, produced both by dimethylarsine and molecular oxygen. When DNA was exposed to dimethylarsine, thiobarbituric acid (TBA)-reactive intermediates andcis-thymine glycol were produced. Dimethylarsine appears to induce DNA damage by the mechanism similar to the damage produced by ionizing radiation.