松果菊苷抗衰老作用机理研究

研究了中国传统药物肉苁蓉提取物松果菊苷(echinacoside,ECH)体外清除活性氧自由基和体内抗氧化、抗衰老作用的机理。运用电子顺磁共振(electron paramagretic resonance,EPR)自旋捕捉方法研究ECH对体外产生的羟自由基(^ OH)、超氧阴离子自由基(O2^-)和脂自由基(L^ )的清除能力;并以D-半乳糖衰老小鼠为实验模型,采用低温EPR技术直接检测小鼠心、肝、肾、脑组织活性氧物种(reactive oxygen species,ROS)水平;生化方法检测小鼠全血谷胱甘肽过氧化物酶(glutathione peroxidase,GSH-Px)和脑组织单胺氧化酶(monoaminoxidase,MAO)活性及肝组织丙二醛(malondialdehvde,MDA)含量;EPR自旋捕捉方法检测血清超氧化物歧化酶(supemxide dismutase,SOD)活力;跳台法检测小鼠记忆力。结果表明ECH能较好抑制体外^ OH,O2^-和L^ 自由基,同时能够提高GSH-Px和SOD活性,降低MDA含量,因此对D-半乳糖所致衰老引起的活性氧自由基损伤具有一定修复作用。由于抑制了MAO活性而提高小鼠的记忆力。由此可以认为ECH抗脂质过氧化及改善衰老的作用与其抗氧化活性有关。     

补阳还五汤对脑缺血再灌注损伤大鼠神经元凋亡的影响

目的:研究补阳还五汤对脑缺血再灌注损伤大鼠神经元凋亡的影响。方法:利用末端标记法,泱l定补阳还五汤干预后,脑缺血再灌注损伤大鼠脑组织中神经元的凋亡情况。结果:补阳还五汤能明显降低神经元凋亡百分率,减轻病理损害。结论:补阳还五汤可显著抑制由缺血再灌注诱导的脑神经元凋亡,从而起到一定程度的神经保护作用。     

加味温胆汤对MCAO模型大鼠神经功能缺失及血管新生的影响

目的:通过观察加味温胆汤对脑缺血再灌注大鼠神经功能缺损评分、血管新生和肝细胞生长因子HGF蛋白表达的影响,研究加味温胆汤的神经保护机制。方法:采用改良Longa法建立大鼠脑缺血再灌注模型,与补阳还五汤作对照,观察加味温胆汤对大鼠神经功能缺损程度评分的影响,并用免疫组织化学法检测缺血脑组织微血管密度及HGF蛋白表达。结果:加味温胆汤能明显改善脑缺血再灌注大鼠神经缺损症状,促进血管新生及大鼠脑组织HGF蛋白表达,与补阳还五汤比较有显著差异。结论:加味温胆汤可明显改善大鼠脑缺血再灌注后神经功能,促进缺血脑组织血管新生,其机制可能与其促进HGF表达有关。     

补阳还五汤联合强力定眩片对后循环缺血性眩晕患者眩晕症状、氧化应激及血流指标的影响

目的:探讨补阳还五汤联合强力定眩片对后循环缺血(PCI)性眩晕患者眩晕症状、氧化应激及血流指标的影响。方法:选取中国中医科学院西苑医院于2018年12月~2019年12月间接收的80例PCI性眩晕患者,采用信封法将患者随机分为对照组(n=40,常规西医治疗)和研究组(n=40,常规西医基础上增加补阳还五汤联合强力定眩片治疗),比较两组患者临床疗效、眩晕症状、氧化应激及血流指标,记录两组治疗期间不良反应发生情况。结果:治疗2个疗程后,研究组的总有效率高于对照组(P<0.05)。两组患者治疗2个疗程后眩晕障碍量表(DHI)评分、超氧化物歧化酶(SOD)、一氧化氮(NO)水平、椎动脉平均血流速度、基底动脉平均血流速度均升高,且研究组高于对照组(P<0.05);两组丙二醛(MDA)水平、全血黏度、血浆黏度、红细胞压积均降低,且研究组低于对照组(P<0.05)。两组不良反应发生率比较无差异(P>0.05)。结论:补阳还五汤联合强力定眩片治疗PCI性眩晕患者,可改善患者眩晕症状及血流状况,降低机体氧化应激程度,疗效确切,且用药安全性较好。     

补阳还五汤对脑缺血/再灌注大鼠脑组织MDA和SOD作用的研究

近年来研究发现,机体代谢过程中产生的自由基及其脂质过氧化作用在脑缺血/再灌注损伤的病理生理过程中发挥着重要作用,但在多数研究中动物模型的缺血时间或再灌注时间较短,与临床病例的实际情况及脑组织凋亡出现的高峰期(2～4d)有一定差距.补阳还五汤是治疗缺血性脑血管疾病及其后遗症的有效方剂,为探讨其作用机理本文研究了该方对脑缺血45 min再灌注3d的大鼠血清及脑组织丙二醛(MDA)含量和脑组织超氧化物歧化酶(SOD)活力的影响.     

补阳还五汤口服和药浴对损伤的大鼠坐骨神经传导速度的影响

目的探讨补阳还五汤口服加药浴对坐骨神经传导速度的影响。方法60只SD大鼠暴露左侧坐骨神经。对照组只钳夹;实验组钳夹并加用补阳还五汤口服及药浴治疗。观察钳夹前和钳夹切除后大鼠坐骨神经传导速度（SNCV）。结果于2、4、6周分别测对照组、实验组的坐骨神经传导速度（SNCV）。各时间段实验组坐骨神经传导速度恢复快于对照组,P〈0．01。结论补阳还五汤口服加药浴对坐骨神经传导速度有明显的促进作用。     

依达拉奉通过Nrf2信号分子调节氧化应激减轻脑缺血再灌注诱导的神经损伤

本研究旨在探讨依达拉奉(edaravone,ED)在脑缺血再灌注损伤中发挥神经元保护作用与Nrf2信号分子间的关系。体内实验利用脑内脑中动脉闭塞(middle cerebral artery occlusion model,MCAO)建立SD大鼠脑缺血再灌注损伤模型,体外实验采用过氧化氢(H2O2)损伤PC12细胞建立氧化应激模型。通过TTC染色、HE染色、Nissl染色来检测大脑的病理状态。测定活性氧(reactive oxygen species,ROS)、丙二醛(malondialdehyde,MDA)含量、超氧化物歧化酶(superoxide dismutase,SOD)活性,来反映氧化应激水平。此外,通过Hoechst 33342染色和线粒体膜电位(mitochondrial membrane potential,MTP)测定,探究细胞水平的损伤。采用免疫组织化学和蛋白质印记测定Nrf2的表达。构建Nrf2敲除的PC12细胞系,证实Nrf2信号分子抑制氧化应激损伤的作用。结果提示,经依达拉奉给药后,在动物体内水平,TTC染色证实,脑缺血再灌注损伤(cerebral ischemia reperfusion injury,CIRI)大鼠的脑组织梗死体积减小(P<0.001),ROS和MDA水平下降(P<0.01),SOD活性上升(P<0.01);在细胞水平,凋亡细胞减少(P<0.05),MTP上升(P<0.01),ROS和MDA水平下降,SOD活性上升(P<0.01);在分子水平,免疫组化和Western印迹结果均提示,Nrf2蛋白质含量较正常组增加。H2O2诱导Nrf2基因敲除的PC12细胞损伤加重,且依达拉奉的治疗效果明显削弱。综上所述,Nrf2在依达拉奉减轻脑缺血再灌注诱导的氧化应激损伤中发挥关键作用。     

芪蝎活血通络汤对局灶性脑缺血再灌注损伤模型大鼠神经功能、氧化应激及炎症因子的影响

目的:探讨芪蝎活血通络汤对局灶性脑缺血再灌注损伤模型大鼠神经功能、氧化应激及炎症因子的影响。方法:50只SD大鼠随机选取40只采用线栓法构建脑缺血再灌注模型,其中36只成功,4只死亡。随机数字表法将36只脑缺血再灌注模型大鼠分为模型组、低剂量组(芪蝎活血通络汤2.0 mg/kg灌胃处理)、中剂量组(芪蝎活血通络汤4.0 mg/kg灌胃处理)和高剂量组(芪蝎活血通络汤8.0 mg/kg灌胃处理),每组9只,剩余10只大鼠仅切开皮肤分离和夹闭血管(对照组)。建模后芪蝎活血通络汤各剂量组给予相应剂量灌胃,对照组和模型组给予同剂量生理盐水灌胃,持续4周。用药4周后测评各组大鼠神经功能缺损程度、双侧贴纸去除时间、平衡木过杆时间,并测定各组大鼠脑组织中含水量、脑梗死面积以及氧化应激[过氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、过氧化氢酶(CAT)、丙二醛(MDA)]和炎症因子[白细胞介素-1β(IL-1β),白细胞介素-6(IL-6),肿瘤坏死因子-α(TNF-α)]指标。结果:与对照组比较,模型组大鼠m NSS评分、脑组织含水量、MDA含量、IL-6、IL-1β、TNF-α水平升高(P<0.05),双侧贴纸去除时间、平衡木过杆时间延长(P<0.05),脑梗死面积增大(P<0.05),SOD、GSH-Px、CAT活性降低(P<0.05);与模型组比较,芪蝎活血通络汤各剂量组大鼠m NSS评分、脑组织含水量、MDA含量、IL-6、IL-1β、TNF-α水平降低(P<0.05),双侧贴纸去除时间、平衡木过杆时间缩短(P<0.05),脑梗死面积缩小(P<0.05),SOD、GSH-Px、CAT活性升高(P<0.05);与低剂量组比较,中、高剂量组大鼠m NSS评分降低(P<0.05),双侧贴纸去除时间、平衡木过杆时间缩短(P<0.05);高剂量组大鼠脑梗死面积、脑组织MDA、IL-6、IL-1β、TNF-α低于低剂量组(P<0.05),SOD、GSH-Px、CAT高于低剂量组(P<0.05)。结论:芪蝎活血通络汤可降低大鼠脑缺血再灌注损伤,改善神经功能,其治疗作用可能与抗氧化,抗炎作用有关,8.0 mg/kg剂量效果最显著。     

镉暴露对黑斑蛙精巢ROS的诱导及其蛋白质氧化损伤作用机理

重金属镉对精巢发育、呼吸及神经系统信号转导等途径均有不良影响,被认为是造成两栖动物种群数量急剧下降的重要原因之一。然而,有关镉对精巢损伤的分子机理还不清楚。通过对镉暴露后的黑斑蛙精巢活性氧自由基(ROS)、蛋白质羰基(PCO)以及DNA蛋白质交联(DPC)等指标的系统分析,探讨了镉对精巢毒害的分子作用机理。随镉浓度的增加,黑斑蛙精巢细胞线粒体ROS随镉暴露浓度的增加而升高,0.5、1.0 mg/L镉染毒组与对照组比较有显著性差异(P<0.05);精巢组织PCO和DPC也随镉暴露浓度的增加而逐渐上升,且均呈明显的浓度-效应关系。结果表明:镉诱导机体产生ROS,进而导致蛋白质氧化损伤以及DNA损伤,说明精巢组织ROS的产生是镉致雄性生殖毒效应机制的重要因素之一。     

中风胶囊对脑缺血/再灌注损伤模型鼠脑组织自噬相关蛋白表达的影响*

目的: 观察中风胶囊对脑缺血/再灌注损伤(CIRI)模型鼠脑组织自噬相关蛋白表达的影响,初步揭示其对神经元损伤保护的分子机制。方法: 采用改良线栓法构建大鼠脑缺血/再灌注损伤模型,随机将60只雄性SD大鼠分为假手术组、模型组、丁苯酞组(0.054 g/kg)、中风胶囊高剂量组(1.08 g/kg)、中风胶囊中剂量组(0.54 g/kg)、中风胶囊低剂量组(0.27 g/kg),每组10只。造模结束后灌胃给药10 d,每天1次,实验结束后处死各组大鼠,摘取脑组织。各组大鼠末次给药24 h后进行神经功能评分;HE染色法观察各组大鼠脑组织病理形态;ELISA法检测各组大鼠血清雌二醇(E2)和卵泡刺激素(FSH);RT-PCR法与Western blot法分别测定各组大鼠脑组织PI3K/Akt/Beclin1信号通路关键基因及蛋白的表达。结果: 与假手术组比较,模型组大鼠体重及脑组织中p-PI3K、p-Akt等蛋白表达均显著降低,脑指数、神经功能缺损评分及脑组织Beclin1、LC3基因和蛋白表达均显著升高(P＜0.05或P＜0.01),脑组织结构排列疏松,间质水肿,神经细胞呈三角形,核固缩深染。与模型组相比,中风胶囊高剂量组大鼠体重显著升高,神经功能缺损评分显著下降(P＜0.05),脑组织病理损伤较模型组明显改善;中风胶囊各剂量组的脑指数及脑组织Beclin1、LC3的基因和蛋白表达均显著降低,脑组织中p-PI3K、p-Akt等蛋白表达均显著升高(P＜0.05或P＜0.01)。结论: 中风胶囊通过调控PI3K/Akt/Beclin1信号通路中Beclin1和LC3的表达来抑制CIRI模型鼠的自噬反应,从而发挥保护其脑神经元损伤的作用。     

Effect of Antioxidant Diets on Mitochondrial Gene Expression in Rat Brain During Aging

Age-related increase of reactive oxygen species (ROS) is particularly detrimental in postmitotic tissues. Calorie restriction (CR) has been shown to exert beneficial effects, consistent with reduced ROS generation by mitochondria. Many antioxidant compounds also mimic such effects. N-acetyl cysteine (NAC) provides thiol groups to glutathione and to mitochondrial respiratory chain proteins; thus, it may counteract both ROS generation and effects. In the present study we investigated, in different rat brain areas during aging (6, 12, and 28 months), the effect of 1-year treatment with CR and dietary supplementation with NAC on the expression of subunit 39 kDa and ND-1 (mitochondrial respiratory complex I), subunit IV (complex IV), subunit α of F₀F₁-ATP synthase (complex V) and of adenine nucleotide translocator, isoform 1 (ANT-1). The observed age-related changes of expression were prevented by the dietary treatments. The present study provides further evidence for the critical role of mitochondria in the aging process.     

Generation of Hydroxyl Radicals and Its Relation to Cellular Oxidative Damage in Plants Subjected to Water Stress

The hydroxyl radical ('OH) is one of the roost reactive mdieales known to chemistry and is believed to be a major active free radicle responsible for modifications of macmmolecules and cellular damage. Two lines of evidence strongly indicate that 'OH radicals are generated in a Fenton-type Haber-Weiss reactions in plants subjected to water stress. Firstly, water stress causes an increase in the concentration of catalytic metals, which are critical for Fenton-like reactions to proceed in vivo. Furthermore, subrmillimolar concentrations of H2O2 and ascorbic acid(or O2－ ) in the drought-stressed plants are large enough to support the Fentontype Haber-Weiss reactions. Secondly, there is oxidation of proteins and lipids in the drought-stressed plants; a process that requires a catalytic metal and that, at least for protein oxidation, is mediated by the 'OH radicals. Protein oxidation is thought to involve binding of metal ions to the proteins and subsequent site-specific attack by the 'OH radicals arising from the roetal-catalysed decomposition of H2O2. It has been proposed that protein oxidation may be a better index than lipid peroxidation because the latter fields many different products and these only appear after a lag period. The validity of malondialdehyde (MDA), an early product of lipid peroxidation, as an index of lipid peroxidation has been argued by the non-specific method of its measurement. The 'OH radicals are not the only necessary initiator for lipid peroxidation and lipid peroxidation is not usually involved in plants exposed to water stress.     

Gender differences in free radical homeostasis during aging: shorter-lived female C57BL6 mice have increased oxidative stress

Gender is a profound determinant of aging and lifespan, but little is known about gender differences in free radical homeostasis. Free radicals are proposed as key elements in the multifactorial process of aging and it is predicted that the longer-lived gender should have lower levels of oxidative stress. While the majority of studies on aging have included a single gender, recent studies in rats compared genders and found that females, the longer-lived sex, had lower oxidative stress and mitochondrial dysfunction than males. We explored the association between oxidative stress and gender-specific aging in C57BL6 mice, in which females are the shorter-lived gender. Reactive oxygen species (ROS) were measured in young and old mice by confocal imaging of dihydroethidium (DHE) oxidation in the brain, and by electron paramagnetic resonance (EPR) spectrometry of isolated brain mitochondria. Both genders exhibited significant age-dependent increases in ROS. However, females had a greater increase with age than males in DHE oxidation but not mitochondrial EPR. Superoxide dismutase 1 (Sod1) and glutathione peroxidase 1 (GPx1) protein levels were lower in old females. To determine whether enhancing antioxidant defenses would eliminate gender differences in lifespan, mice were treated chronically with a superoxide dismutase mimetic. Treatment blocked the age-dependent increase in ROS, with a greater effect in females on DHE oxidation, but not mitochondrial EPR. Treatment also increased lifespan to a greater degree in females. Our results indicate that differences in ROS homeostasis contribute to gender divergence in survival, but also suggest that mitochondrial superoxide production may not be primarily responsible for gender differences in lifespan.     

Extracellular matrix stimulates reactive oxygen species production and increases pancreatic cancer cell survival through 5-lipoxygenase and NADPH oxidase

The extracellular matrix (ECM) facilitates pancreatic cancer cells survival, which is of central importance for pancreatic adenocarcinoma that is highly fibrotic. Here, we show that reactive oxygen species (ROS) mediate the prosurvival effect of ECM in human pancreatic cancer cells. Fibronectin and laminin stimulated ROS production and NADPH oxidase activation in pancreatic cancer cells. Both pharmacological and molecular approaches show that fibronectin stimulated ROS production through activation of NADPH oxidase and NADPH oxidase-independent pathways and that 5-lipoxygenase (5-LO) mediates both these pathways. Analyses of the mechanisms of ROS production by ECM proteins and growth factors indicate that activation of NADPH oxidase (Nox4) is a common mechanism employed both by ECM proteins and growth factors to increase ROS in pancreatic cancer cells. We also found that Nox4 is present in human pancreatic adenocarcinoma tissues and that these tissues display membrane NADPH oxidase activity. ECM proteins and growth factors activate NADPH oxidase through different mechanisms; in contrast to ECM proteins, growth factors activate NADPH oxidase through 5-LO-independent mechanisms. Inhibition of 5-LO or NADPH oxidase with pharmacological inhibitors of these enzymes and with Nox4 or 5-LO antisense oligonucleotides markedly stimulated apoptosis in cancer cells cultured on fibronectin. Our results indicate that ROS generation via 5-LO and downstream NADPH oxidase mediates the prosurvival effect of ECM in pancreatic cancer cells. These mechanisms may play an important role in pancreatic cancer resistance to treatments and thus represent novel therapeutic targets.     

Effect of Short-Term Caloric Restriction on H2O2 Production and Oxidative DNA Damage in Rat Liver Mitochondria and Location of the Free Radical Source

Oxygen free radicals (ROS) of mitochondrial origin seem to be involved in aging. Whereas in other tissues complexes I or III of the respiratory chain contain the ROS generators, in this study we find that rat liver mitochondria generate oxygen radicals at complexes I, II, and III. Short-term (6 weeks) caloric restriction significantly decreased H₂O₂ production in rat liver mitochondria. This decrease in ROS production was located at complex I because it occurred with complex I-linked substrates (pyruvate/malate), but did not reach statistical significance with the complex II-linked substrate succinate. The mechanism responsible for the lowered ROS production was not a decrease in oxygen consumption. Instead, the mitochondria of caloric-restricted animals released less ROS per unit electron flow. This was due to a decrease in the degree of reduction of the complex I generator. Furthermore, oxidative damage to mitochondrial and nuclear DNA was also decreased in the liver by short-term caloric restriction. The results agree with the idea that caloric restriction delays aging, at least in part, by decreasing the rate of mitochondrial ROS generation and thus the rate of attack to molecules, like DNA, highly relevant for the accumulation of age-dependent changes.     

Electron paramagnetic resonance study of the generation of reactive oxygen species catalysed by transition metals and quinoid redox cycling by inhalable ambient particulate matter

A range of epidemiological studies in the 1990s showed that exposure to ambient particulate matter (PM) is associated with adverse health effects in the respiratory system and increased morbidity and mortality rates. Oxidative stress has emerged as a pivotal mechanism that underlies the toxic pulmonary effects of PM. A key question from a variety of studies was whether the adverse health effects of PM are mediated by the carbonaceous particles of their reactive chemical compounds adsorbed into the particles. Experimental evidence showed that PM contains redox-active transition metals, redox cycling quinoids and polycyclic aromatic hydrocarbons (PAHs) which act synergistically to produce reactive oxygen species (ROS). Fine PM has the ability to penetrate deep into the respiratory tree where it overcomes the antioxidant defences in the fluid lining of the lungs by the oxidative action of ROS. From a previous study [Valavanidis A, Salika A, Theodoropoulou A. Generation of hydroxyl radicals by urban suspended particulate air matter. The role of iron ions. Atmospher Environ 2000; 34 : 2379-2386], we established that ferrous ions in PM play an important role in the generation of hydroxyl radicals in the presence of hydrogen peroxide (H2O2). In the present study, we investigated the synergistic effect of transition metals and persistent quinoid and semiquinone radicals for the generation of ROS without the presence of H2O2. We experimented with airborne particulate matter, such as TSPs (total suspended particulates), fresh automobile exhaust particles (diesel, DEP and gasoline, GEP) and fresh wood smoke soot. Using electron paramagnetic resonance (EPR), we examined the quantities of persistent free radicals, characteristic of a mixture of quinoid radicals with different structures and a carbonaceous core of carbon-centred radicals. We extracted, separated and analysed the quinoid compounds by EPR at alkaline solution (pH 9.5) and by TLC. Also, we studied the direct production of superoxide anion and the damaging hydroxyl radical in aqueous and in DMSO suspensions of PM without H2O2. From these results, it is suggested that the cytotoxic and carcinogenic potential of PM can be partly the result of redox cycling of persistent quinoid radicals, which generate large amounts of ROS. In the second phase, the water-soluble fraction of PM elicits DNA damage via reactive transition metal-dependent formation of hydroxyl radicals, implicating an important role for hydrogen peroxide. Together, these data indicate the importance of mechanisms involving redox cycling of quinones and Fenton-type reactions by transition metals in the generation of ROS. These results are supported by recent studies indicating cytotoxic effects, especially mitochondrial damage, by PM extracts and differential mechanisms of cell killing by redox cycling quinones.     

Sesamin attenuates behavioral,biochemical and histological alterations induced by reversible middle cerebral artery occlusion in the rats

Restoration of blood flow to an ischemic brain region is associated with generation of reactive oxygen species (ROS) with consequent reperfusion injury. ROS cause lipid peroxidation, protein oxidation, and DNA damage, all of which are deleterious to cells. So diminishing the production of free radicals and scavenging them may be a successful therapeutic strategy for the protection of brain tissue in cerebral stroke. The present study investigated the neuroprotective effect of sesamin (Sn) to reduce brain injury after middle cerebral artery occlusion (MCAO). The middle cerebral artery (MCA) of adult male Wistar rat was occluded for 2 h and reperfused for 22 h. Sesamin is the most abundant lignan in sesame seed oil is a potent antioxidant. Sesamin (30 mg/kg) was given orally twice, 30 min before the onset of ischemia and 12 h after reperfusion. The initial investigations revealed that sesamin reduced the neurological deficits in terms of behavior and reduced the level of thiobarbituric acid reactive species (TBARS), and protein carbonyl (PC) in the different areas of the brain when compared with the MCAO group. A significantly depleted level of glutathione and its dependent enzymes (glutathione peroxidase [GPx] and glutathione reductase [GR]) in MCAO group were protected significantly in MCAO group treated with sesamin. The present study suggests that sesamin may be able to attenuate the ischemic cell death and plays a crucial role as a neuroprotectant in regulating levels of reactive oxygen species in the rat brain. Thus, sesamin may be a potential compound in stroke therapy.     

Neuroprotection by tempol in a model of iron-induced oxidative stress in acute ischemic stroke

Studies suggest iron exacerbates the damage caused by ischemic stroke. Our aim was to elucidate the effect of iron overload on infarct size after middle cerebral artery occlusion (MCAO) and to evaluate the efficacy of tempol, a superoxide dismutase mimetic, as a neuroprotective agent. Rats were administered iron +/- tempol before MCAO; control rats received saline. The middle cerebral artery was occluded for 24 h, and the size of the resultant infarct was assessed and expressed as the percentage of the hemisphere infracted (%HI). Iron treatment increased infarct size compared with control (51.83 +/- 3.55 vs. 27.56 +/- 3.28%HI iron treated vs. control, P = 0.01); pretreatment with tempol reversed this (51.83 +/- 3.55 vs. 26.09 +/- 9.57%HI iron treated vs. iron + tempol treated, P = 0.02). We hypothesized that reactive oxygen species (ROS) were responsible for the iron-induced damage. We measured ROS generated by exogenous iron in brain and peripheral vasculature from rats that had not undergone MCAO. There was no increase in ROS production in the brain of iron-treated rats or in brain slices incubated with iron citrate. However, ROS generation in carotid arteries incubated with iron citrate was significantly increased. ROS generation from the brain was assessed after MCAO by dihydroethidine staining; there was a dramatic increase in the ROS generation by the brain in the iron-treated rats compared with control 30 min after MCAO. We propose that iron-induced ROS generation in the cerebral vasculature adds to oxidative stress during an ischemic episode after the disruption of the blood-brain barrier.     

Photodynamic action of C-phycocyanins obtained from marine and fresh water cyanobacterial cultures: a comparative study using EPR spin trapping technique

C-phycocyanins, major biliproteins of blue green algae (cyanobacteria), widely used as colourants in food and cosmetics are known for their antioxidant as well as therapeutic potential. Recent claims indicating phycobiliproteins exert stronger photodynamic action on tumor cells than clinically approved hematoporphyrin derivatives motivate us to investigate the photodynamic action of two newly isolated C-phycocyanins from Phormidium [PHR] and Lyngbya [LY] spp, respectively in comparison with known C-phycocyanin from Spirulina sp. [SPI]. Photolysis of air saturated solutions of PHR, LY and SPI in the presence of 2,2,6,6-Tetramethyl piperidinol (TEMPL) generated three line EPR spectrum characteristic of 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxyl (TEMPOL). The increase in intensity of the EPR spectrum with time of irradiation and decrease in intensity, in the presence of 1O2 quencher DABCO confirm the formation of 1O2. Photoirradiation in the presence of spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) generated EPR signal characteristic of O2(-) adduct. Efficiency of 1O2 generation is of the order LY > PHR> SPI. The yield of reactive oxygen species (ROS) generation is found to be 1O2>O2(-) indicating type II mechanism to be the prominent pathway for photosensitation by phycocyanins.     

Drought acclimation reduces O2*- accumulation and lipid peroxidation in wheat seedlings

Abiotic stresses cause ROS accumulation, which is detrimental to plant growth. It is well known that acclimation of plants under mild or sub-lethal stress condition leads to development of resistance in plants to severe or lethal stress condition. The generation of ROS and subsequent oxidative damage during drought stress is well documented in the crop plants. However, the effect of drought acclimation treatment on ROS accumulation and lipid peroxidation has not been examined so far. In this study, the effect of water stress acclimation treatment on superoxide radical (O(2)(-z.rad;)) accumulation and membrane lipid peroxidation was studied in leaves and roots of wheat (Triticum aestivum) cv. C306. EPR quantification of superoxide radicals revealed that drought acclimation treatment led to 2-fold increase in superoxide radical accumulation in leaf and roots with no apparent membrane damage. However under subsequent severe water stress condition, the leaf and roots of non-acclimated plants accumulated significantly higher amount of superoxide radicals and showed higher membrane damage than that of acclimated plants. Thus, acclimation-induced restriction of superoxide radical accumulation is one of the cellular processes that confers enhanced water stress tolerance to the acclimated wheat seedlings.