Possible mechanism responsible for allopurinol-nephrotoxicity: lipid peroxidation and systems of producing- and scavenging oxygen radicals

In order to elucidate toxic and protective mechanisms responsible for allopurinol-induced nephrotoxicity in rats, we investigated changes in plasma creatinine concentration, renal lipid peroxidation, and renal activities of xanthine oxidase, superoxide dismutase and catalase, as enzymatic factors in producing and scavenging oxygen radicals. The rats received subcutaneous injections of allopurinol in a dose of 100 mg/kg body weight, once a day for 3 days. In comparison to the control rats, the following changes were observed in the allopurinol-administered rats: an increase in plasma creatinine concentration, increases in renal contents of malonaldehyde, hypoxanthine and xanthine, and an increase of renal activity of xanthine oxidase, and decreases in renal activities of superoxide dismutase and catalase. Peaks in these changes were observed coincidentally on the third day after the administration of the drug was started. Afterwards, these parameters all returned to the control levels. These results strongly suggested that the allopurinol nephrotoxicity was attributed to the increase of lipid peroxidation which had been caused both by an increase in the ability of producing the oxygen radicals and by a decrease in the ability of scavenging the radicals.     

石榴皮鞣质对羟自由基和超氧阴离子自由基的清除作用

目的：研究石榴皮鞣质清除自由基的作用。方法：通过罗丹明B—Cu^2＋-H2O2体系产生·OH，邻苯三酚自氧化体系产生O2^-。同时比较石榴皮鞣质提取物，鞣花酸一没食子酸混合溶液，以及维生素C的作用效果，根据作用常数的大小讨论3种溶液及其各自的浓度对自由基的清除作用，并初步推断作用机制。结果：石榴皮鞣质对羟自由基和超氧阴离子自由基均具有较好的清除作用，较低浓度时即可发挥清除作用。结论：石榴皮鞣质对自由基侵害有保护作用。     

虎杖晶4号对人血PMNs呼吸暴发和氧自由基的作用

应用化学发光法测定①人血PMNs受PMA刺激产生的化学发光;②黄嘌呤—黄嘌呤氧化酶体系产生O_2;③VitC—CU~(2+)—酵母多糖产主·OH;④H_2O_2的释放。观察虎杖晶4号对上述体系产生自由基的影响。结果提示.虎杖晶4号对PMN呼吸暴发的早期(1～6 min)有明显的抑制作用,呈剂量依赖性;而在12min时发光强度均高于空白对照.表明因虎杖晶4号而使呼吸暴发滞后。其对O_2.·OH.H_2O_2均有清除作用.且呈剂量依赖性.IC_(50)分别为14.6.29.6和13.0μmol·L~(-1).     

埃必定对人血白细胞呼吸爆发和氧自由基的抑制作用

目的观察埃必定对人血白细胞呼吸爆发和氧自由基的影响，初步探讨埃必定的抗炎作用机制。方法用化学发光法测定人血白细胞受调理的酵母多糖刺激发生呼吸爆发的活性氧、碱性二甲基亚砜－鲁米诺体系产生的超氧阴离子自由基（Ｏ·２）、ＶｉｔＣ－Ｃｕ２＋酵母多糖产生的羟自由基（·ＯＨ）及过氧化氢（Ｈ２Ｏ２）的释放，观察了埃必定对上述体系产生的自由基的影响。结果埃必定对白细胞的呼吸爆发有显著的抑制作用；对Ｏ·２、·ＯＨ有清除作用，呈剂量依赖性，对Ｈ２Ｏ２无清除作用。结论埃必定对人血白细胞呼吸爆发具有抑制作用，对氧自由基具有清除作用     

卡托普利与谷胱甘肽清除氧自由基的比较研究

用化学发光方法比较研究了卡托普利（Ｃａｐ）和谷胱甘肽（ＧＳＨ）抗氧自由基的作用。结果表明，Ｃａｐ和ＧＳＨ都具有相似的基本结构一取代的Ｎ－羧甲基－β－巯基丙酰胺。两者对黄嘌呤－黄嘌呤氧化酶体系以及碱性连苯三酚自氧化体系产生的都有清除作用并具量效关系．Ｃａｐ比ＧＳＨ的清除作用大。两者对Ｈ２Ｏ２的清除作用的量效关系曲线十分相似。结果提示．Ｃａｐ具有ＧＳＨ相似的抗氧自由基作用．并且有取代的Ｎ－羧甲基－β－巯基丙酰胺这种结构特征的化合物，也可能具有ＧＳＨ样的作用。     

芦荟大黄素、芦荟素清除氧自由基作用的研究

目的:研究芦荟大黄素和芦荟素对超氧阴离子自由基(O2-.)、羟自由基(.OH)的清除作用。方法:采用邻苯三酚自氧化体系产生(O2-.),研究芦荟大黄素、芦荟素对O2-.的清除作用;利用Fenton反应产生.OH,研究芦荟大黄素、芦荟素对.OH的清除作用;计算表观清除率及IC50,并与特异性清除剂维生素C做比较。结果:芦荟大黄素、芦荟素、维生素C对O2-.的IC50分别为6.8,8.5,11mg.L-1,对.OH的IC50分别为0.24,0.25,9.1mg.L-1,其清除能力芦荟大黄素>芦荟素>维生素C。结论:芦荟大黄素、芦荟素对O2-.、.OH均有较强清除能力,且清除能力与浓度呈明显的量效关系。     

(一)表没食子儿茶素没食子酸酯对活性氧自由基的清除作用机制

本文研究了(一)表没食子儿茶素没食子 酸酯[(—)-EGCG]清除O_(?)和·OH的半数清除率SC_(50)、清除速率常数k和清除反应的化学计量因子n,用体外模型分析了药物对活性氧自由基的清除机制和(—)-EGCG自由基的启动及结构特点,推论药物的清除反应中心为B、D和A环,每分子药物可捕捉6个O_(?)或·OH,与化学计量因子n=6相符。     

Quantification of total oxidant scavenging capacity of antioxidants for peroxynitrite, peroxyl radicals, and hydroxyl radicals

We have extended the application of our previously reported total oxidant scavenging capacity (TOSC) assay (Winston et al., Free Radical Biol. Med. 24, 480-493, 1998) to permit facile quantification of the absorbance capacity of antioxidants toward three potent oxidants, i.e., hydroxyl radicals, peroxyl radicals, and peroxynitrite. Respectively, these oxidants were generated by the iron plus ascorbate-driven Fenton reaction, thermal homolysis of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (ABAP), and 3-morpholinosydnonimine N-ethylcarbamide (SIN-1). Each of these oxidants reacts with alpha-keto-gamma-methiolbutyric acid (KMBA), which is oxidized and yields ethylene. The antioxidant capacity of the compounds tested is quantified from their ability to inhibit ethylene formation relative to a control reaction. Assay conditions were established in which control reactions give comparable yields of ethylene with each of the oxidants studied. Thus, the relative efficiency of various antioxidants could be compared under conditions of quantitatively similar KMBA oxidizing capability by the three oxidants. Reduced glutathione was an efficient scavenger of peroxyl radicals, but scavenged peroxynitrite and hydroxyl radicals relatively poorly. Uric acid, Trolox, and ascorbic acid were comparable scavengers of peroxynitrite and peroxyl radicals. Uric acid and Trolox were approximately an order of magnitude less efficient as scavengers of hydroxyl radicals. The classical hydroxyl radical scavenging agents mannitol, dimethyl sulfoxide, and benzoic acid had much higher TOSC values with hydroxyl than with peroxyl radicals or peroxynitrite. The very different chemical reactivity toward KMBA by the SIN-1- and iron-ascorbate-generated oxidants indicates that hydroxyl radical is not a major oxidant produced by the SIN-1 system. The data show that the TOSC assay is useful and robust in distinguishing the reactivity of various oxidants and the relative capacities of antioxidants to scavenge these oxidants.     

Inflammatory cells and oxygen radicals

At sites of inflammation, multiple inflammatory cells including eosinophils, neutrophils, and macrophages are capable of generating reactive oxygen species (ROS), which can contribute to development of various diseases. In case of allergic inflammation, for example, the lung cells obtained by bronchoalveolar lavage (BAL) following antigen challenge generates superoxide anion at nanomolar concentrations. Eosinophils obtained from BAL following a segmental allergen challenge generate more superoxide anion than eosinophils obtained from the peripheral circulation. Such ROS may contribute not only to tissue injury but also to inflammatory reactions. For example, hydrogen peroxide can stimulate both neutrophil and eosinophil adhesion as an autocrine or paracrine mediator via the upregulation of beta2 integrin. Furthermore, ROS may alter morphological or functional properties of endothelial cells, including permeability and adhesion molecule expression. Thus, ROS can promote adhesive interaction between inflammatory and endothelial cells, which could culminate in manifestations of inflammatory diseases such as bronchial asthma.     

Reactivity of various phenothiazine derivatives with oxygen and oxygen radicals

7,8-Dihydroxychlorpromazine, 7,8-dihydroxyprochlorperazine and 7,8-dihydroxyperphenazine all reacted with O₂ to make hydrogen peroxide (H₂O₂). The rate of reaction between the ortho-dihydroxyphenothiazines and O₂ was increased by superoxide dismutase, an enzyme which catalyzes the dismutation of the superoxide radical (O₂^?) to H₂O₂ and O₂. This indicated the formation of O₂^? during the autoxidation of the ortho-dihydroxyphenothiazines. Several phenothiazines lacking the ortho-dihydroxy groups did not consume O₂ at a detectable rate (did not generate H₂O₂). All ortho-dihydroxyphenothiazines tested also reacted with O₂ in the presence of methional to form ethylene. Ethylene formation was inhibited by catalase and hydroxyl radical (·OH) trapping agents, such as sodium benzoate; this indicated ·OH formation from the ortho-dihydroxyphenothiazines. In addition, several nonhydroxylated phenothiazines and monohydroxylated phenothiazines inhibited ethylene generation from 6-aminodopamine, which also generates ·OH. This inhibition was probably mediated by a reaction between the phenothiazine and ·OH. All of the above reactions (generation of H₂O₂, O₂^? or ·OH or reaction with ·OH) may be responsible for some of the beneficial and/or adverse effects of administered phenothiazines.     

Structure-activity relationships for the inhibition of lipid peroxidation and the scavenging of free radicals by synthetic symmetrical curcumin analogues

A number of ring substituted analogues of curcumin were synthesized. Their antioxidant properties were studied using three models, inhibition of lipid peroxidation, scavenging of 1,1'-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethyl-benzthiazoline-6-sulphonate radical (ABTS+.). In all the models, the phenolic analogues were more active than the non-phenolic analogues, some of which were inactive. The highest antioxidant activity was obtained when the phenolic group was sterically hindered by the introduction of two methyl groups at the ortho position. This and several other compounds were more active than the standard antioxidants alpha-tocopherol and trolox. This study has demonstrated that the phenolic group is important for the antioxidant activity of curcumin and that the structural features that enhance the antioxidant properties of phenols are optimized in curcumin to a significant extent.     

帕金森病与氧自由基

该文对近年来在帕金森病与氧自由基关系方面的研究工作做了回顾 ,许多事实表明 ,氧自由基在帕金森病的发病过程中起着重要作用 ,帕金森病患者机体处于氧应激状态 ,帕金森病病变部位的选择性决定了其氧自由基产生的特点 ,其它有关帕金森病的致病学说均与氧自由基有着密切关系。     

Curcumin prevents streptozotocin-induced islet damage by scavenging free radicals: a prophylactic and protective role

Pancreatic islet cell death is the cause of deficient insulin production in diabetes mellitus. Approaches towards prevention of cell death are of prophylactic importance in control and management of hyperglycemia. Generation of oxidative stress is implicated in streptozotocin, a beta cell specific toxin-induced islet cell death. In this context, antioxidants raise an interest for therapeutic purposes. Curcumin, a common dietary spice is a well known antioxidant and hence we investigated its effect on streptozotocin-induced islet damage in vitro. Isolated islets from C57/BL6J mice were incubated with curcumin for 24 h and later exposed to streptozotocin for 8 h. The effect of streptozotocin exposure to islets was determined with respect to islet viability and functionality, cellular reactive oxygen species concentrations and levels of activated poly (ADP-ribose) polymerase-1. Cellular antioxidant potential (Cu/Zn superoxide dismutase) and advanced glycation end-product related damage was assessed to determine the metabolic status of treated and untreated islets. Islet viability and secreted insulin in curcumin pretreated islets were significantly higher than islets exposed to streptozotocin alone. Curcumin retarded generation of islet reactive oxygen species along with inhibition of Poly ADP-ribose polymerase-1 activation. Although curcumin did not cause overexpression of Cu/Zn superoxide dismutase, it prevented reduction in levels of cellular free radical scavenging enzymes. Our data shows that curcumin protects islets against streptozotocin-induced oxidative stress by scavenging free radicals. We show here for the first time, that prophylactic use of curcumin may effectively rescue islets from damage without affecting the normal function of these cellular structures.     

阿魏酸及其类似物的合成及其清除自由基活性研究

目的:合成阿魏酸及其类似物并研究其清除1,1-二苯基苦基苯肼自由基(DPPH·)的能力。方法:不同对羟基苯甲醛衍生物和丙二酸进行Knoevenagel缩合反应,得到阿魏酸及其类似物;用体外清除DPPH·测定法检测其清除自由基的能力。结果:合成了9个化合物,其中7个为新报道化合物;在体外清除DPPH·测定中,这些化合物对DPPH·的清除率有较大差异。结论:阿魏酸及其类似物苯环上3,5位取代基可以明显地影响此类化合物清除DPPH·的能力。甲氧基和乙氧基可明显提高活性,溴次之,硝基则降低活性。     

Antioxidant behaviour of caffeine: efficient scavenging of hydroxyl radicals.

Considerable controversy exists in the literature regarding the toxicity of coffee, including its possible carcinogenic and anticarcinogenic properties. This study reports on the reaction of 1,3,7-trimethylxanthine (caffeine) with the hydroxyl radical (.OH), as investigated by electron spin resonance (ESR) spin trapping. The .OH was generated by the Fenton reaction (Fe2+ + H2O2) as well as by the reaction of chromium(V) with H2O2. The results show that caffeine effectively scavenges .OH with a reaction rate constant of approximately 5.9 x 10(9) M-1 sec-1 that is comparable with those of other efficient .OH radical scavengers. ESR measurements provide evidence that a caffeine-derived oxygen-centred radical is formed in the reaction of caffeine with .OH and suggest a biochemical basis for the understanding of the reported anticarcinogenic properties of caffeine and related methylxanthine compounds.     

Inhibition of mouse hepatocyte intercellular communication by paraquat-generated oxygen free radicals

Intercellular communication through gap junctions functions in electrical synapsing, homeostasis, hormonal response, embryogenesis, and growth control. Many neurotoxicants, teratogens, and carcinogens are capable of inhibiting gap junctional intercellular communication and this effect may be related to their toxic activity. In addition, many of these toxic agents are capable of stimulating oxygen free radical production in cells. The purpose of this study was to determine if oxygen free radicals at noncytotoxic levels could inhibit intercellular communication in primary cultured mouse hepatocytes. Intercellular communication was evaluated in 24-hr-old cultures of male B6C3F1/Cr1BR mouse hepatocytes by microinjection of fluorescent Lucifer Yellow CH dye and visualization of dye spread to adjacent hepatocytes (dye-coupling). Dye-coupling was rapidly established in freshly plated primary cultured hepatocytes reaching a level of over 90% after 24 hr of culture. After 24 hr, dye-coupling paralleled hepatocyte survival. Treatment of hepatocyte cultures with noncytotoxic concentrations of paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride; PQ) (0.5-5 mM), hydrogen peroxide (0.5-2 mM), glucose oxidase (0.1 U/ml), or xanthine oxidase (0.2 U/ml plus 1 mM xanthine) for exposure durations of 2-8 hr resulted in concentration-dependent decreases in dye-coupling. Addition of the antioxidants DPPD (N,N-diphenyl-p-phenylenediamine; 25 microM) and vitamin E (D,L-alpha-tocopherol acetate; 100 microM) decreased the inhibitory effect of PQ on dye-coupling. In contrast, addition of the catalase inhibitor 3-amino-1,2,4-triazole or the glutathione depletor diethylmaleate to PQ-treated cultures potentiated PQ-induced inhibition of dye-coupling. PQ stimulated NADPH-dependent mouse liver microsomal superoxide radical production. Thus, one effect of prooxidant compounds appears to be the inhibition of IC. This effect may be important in the sublethal toxicity of oxygen radical generating compounds.     

黄皮酰胺抗脂质过氧化及对氧自由基清除作用

黄皮酰胺是一种生物碱,可抑制铁-半胱氨酸体系引起的大鼠脑,心,肝和睾丸微粒体脂质过氧化,电子自旋共振法研究表明,黄皮酰可清除由佛波醇豆蔻酸乙酸酸酯(PMA)刺激人多形核白细胞(PML)所产生的氧自由基,自旋探针测氧法结果表明,对PMA刺激PML时的氧消耗无影响,在Fenton反应体系中,对羟自由基的清除率为36.6％,在黄嘌呤-黄嘌呤氧化酶和光照核黄素体系中,对超氧阴离子的清除作用分别为21.2％和16.2％。结果提示黄皮酰胺对氧自由基的直接捕捉作用是其抗脂质过氧化作用的机理之一。     

Alzheimer's disease and oxygen radicals: new insights

Alzheimer's disease (AD) is the most common form of neurodegenerative disease, with dementia, in the elderly. In addition to the presence of senile plaques and neurofibrillary tangles, the AD brain exhibits evidence for oxygen radical-mediated damage, a situation commonly known as oxidative stress. However, the ability to directly implicate this mechanism in AD has been a difficult task for several reasons. First, most of the analytical approaches used to investigate oxidative stress turned out to be unreliable. Second, the majority of the published studies have been performed in post-mortem tissues with advanced disease, leaving open the question as to whether oxidative stress is an early event or a common final step secondary to the degenerative process. The discovery of the isoprostanes, recent studies performed in living patients, and the development of transgenic animal models of AD-amyloidosis are three important factors that are helping us to better understand and define the role that oxygen radicals might play in AD pathogenesis. Here we review some of the most recent works that have supported the importance of oxygen radical-mediated damage in AD. The accumulated information points toward an earlier involvement than previously thought of oxidative stress in the pathogenesis of the disease, making this a potential target for therapeutic intervention, especially in subjects at high risk for developing AD.