Analysis of reactive oxygen species and antioxidant defenses in complex I deficient patients revealed a specific increase in superoxide dismutase activity

The mechanism of free radical production by complex I deficiency is ill-defined, although it is of significant contemporary interest. This study studied the ROS production and antioxidant defenses in children with mitochondrial NADH dehydrogenase deficiency. ROS production has remained significantly elevated in patients compared to controls. The expression of all antioxidant enzymes significantly increased at mRNA level. However, the enzyme activities did not correlate with high mRNA or protein expression. Only the activity of superoxide dismutase (SOD) was found to correlate with higher mRNA expression in patient derived cell lines. The activities of the enzymes such as glutathione peroxidase (GPx), Catalase (CAT) and glutathione-S-transferase (GST) were significantly reduced in patients (p<0.05 or p<0.01). Glutathione reductase (GR) activity and intracellular glutathione (GSH) levels were not changed. Decreased enzyme activities could be due to post-translational or oxidative modification of ROS scavenging enzymes. The information on the status of ROS and marking the alteration of ROS scavenging enzymes in peripheral lymphocytes or lymphoblast cell lines will provide a better way to design antioxidant therapies for such disorders.     

Drought Influences the Activity of Enzymes of the Chloroplast Hydrogen Peroxide Scavenging System

Smirnoff, N. and Colomb?, S. V. 1988. Drought influences theactivity of enzymes of the chloroplast hydrogen peroxide scavengingsystem.—J. exp. Bot. 39: 1097–1108. The effect of drought on the activity of ascorbate peroxidase(AP), glutathione reductase (GR) and monodehydroascorbate reductase(MDAR) in leaves of barley (Hordeum vulgare) and tef {Eragrostistef) was studied. These enzymes are components of the chloroplasthydrogen peroxide scavenging system. Severe leaf water deficit(<–30 M Pa) resulted in increased activity (leaf dryweight basis) of GR and MDAR in barley and of AP and MDAR intef. The specific activity of all the scavenging enzymes wasgreater in droughted plants. The activities (dry weight basis)of two ‘control’ enzymes, malate dehydrogenase (barley)and phosphoenolpyruvate carboxylase (tef), not directly involvedin the scavenging system, were not affected by drought. These data suggest that drought may cause an increase in thecapacity of the hydrogen peroxide scavenging system and thatit may, therefore, increase the rate of hydrogen peroxide formationin chloroplasts. Key words: Water stress, hydrogen peroxide, enzyme activity     

Ce^3+和La^3+对人工老化沙葱种子活力及生理特性的影响

以未老化和人工老化后的沙葱(Allium mongolicum Regel.)种子为材料,采用氯化铈(Ce3+)和氯化镧(La3+)浸种,测定种子萌发和生理指标,探讨Ce3+和La3+浸种对种子萌发、老化种子活力和生理特性的影响。结果显示:(1)在老化0~5 h时,Ce3+和La3+处理可显著促进沙葱种子萌发,提高种子活力;在老化5 h后,Ce3+和La3+处理对种子萌发无明显促进作用。(2)在老化0~15 h时,Ce3+和La3+处理的沙葱种子中抗氧化酶活性和抗坏血酸(AsA)含量提高,其超氧阴离子自由基(O2-·)产生速率、过氧化氢(H2O2)含量和丙二醛(MDA)含量显著降低;在老化15 h后,Ce3+和La3+处理的种子抗氧化酶活性提高、AsA含量降低,O2-·产生速率和MDA含量提高。(3)在老化5 h时,沙葱种子呼吸速率发生跃变达到最大,Ce3+和La3+处理显著降低了种子呼吸速率。(4)Ce3+和La3+处理在老化0~5 h时提高了沙葱种子超弱发光(UWL)强度,但在老化5 h后沙葱种子的UWL强度降低。研究认为,在沙葱种子人工老化初期,Ce3+和La3+浸种处理可以诱导增强种子抗氧化酶活性和提高AsA含量,有效清除因老化产生积累的过量活性氧(ROS),减轻过氧化伤害,提高种子活力;种子老化中后期,其内部ROS产生与清除系统发生紊乱,加剧了ROS对种子结构的损伤,Ce3+和La3+浸种处理的缓解效应丧失。     

沙芥属植物活性氧清除系统对干旱胁迫的响应

以沙芥属植物沙芥和斧形沙芥幼苗为试材,采用盆栽控水干旱方法,分析其在不同干旱胁迫强度下根和叶的活性氧水平、抗氧化酶活性和抗氧化剂含量的变化,并利用隶属函数法和抗旱系数法综合评价沙芥和斧形沙芥的抗旱性。结果表明: （1）随着干旱胁迫程度的加剧,沙芥和斧形沙芥的根和叶中O^-·₂产生速率及·OH、H₂O₂、MDA含量总体呈逐渐升高的趋势,且干旱胁迫下沙芥比斧形沙芥产生了更多的ROS和MDA。（2）随着干旱胁迫程度的加剧,沙芥和斧形沙芥的根和叶中POD、APX、GST活性及叶中GR活性均先升高后降低,叶中的SOD活性以及根中GR、GPX活性均先降低后升高,根和叶中的CAT活性、叶中的GPX活性和根中SOD活性均逐渐升高;但根和叶中的SOD、POD、CAT活性在各干旱处理下均表现为斧形沙芥高于沙芥。（3）沙芥和斧形沙芥的根和叶中AsA含量随着干旱胁迫程度的加剧而先升高后降低,GSH含量逐渐升高,CAR含量逐渐降低,而VE含量在叶中逐渐升高,在根中却逐渐降低;但斧形沙芥比沙芥合成更多的AsA和GSH,其植物体内AsA GSH循环系统能清除更多的ROS。（4）沙芥和斧形沙芥的根和叶中总抗氧化能力（T AOC）均随着干旱加剧逐渐增强,且斧形沙芥的总抗氧化能力强于沙芥;活性氧清除系统的平均隶属度和综合抗旱系数显示,轻度干旱胁迫下沙芥抗旱性强于斧形沙芥,中度和重度干旱胁迫下斧形沙芥的抗旱性强于沙芥。研究认为,在干旱胁迫条件下,斧形沙芥根叶中ROS和MDA含量明显低于沙芥,而其大部分抗氧化酶活性和抗氧化剂含量高于沙芥,斧形沙芥植株体内抗氧化系统表现出更强的活性氧清除能力,从而表现出更强的抗旱性。     

Importance of ROS and antioxidant system during the beneficial interactions of mitochondrial metabolism with photosynthetic carbon assimilation

The present study suggests the importance of reactive oxygen species (ROS) and antioxidant metabolites as biochemical signals during the beneficial interactions of mitochondrial metabolism with photosynthetic carbon assimilation at saturating light and optimal CO₂. Changes in steady-state photosynthesis of pea mesophyll protoplasts monitored in the presence of antimycin A [AA, inhibitor of cytochrome oxidase (COX) pathway] and salicylhydroxamic acid [SHAM, inhibitor of alternative oxidase (AOX) pathway] were correlated with total cellular ROS and its scavenging system. Along with superoxide dismutase (SOD) and catalase (CAT), responses of enzymatic components—ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), glutathione reductase (GR) and non-enzymatic redox components of ascorbate–glutathione (Asc–GSH) cycle, which play a significant role in scavenging cellular ROS, were examined in the presence of mitochondrial inhibitors. Both AA and SHAM caused marked reduction in photosynthetic carbon assimilation with concomitant rise in total cellular ROS. Restriction of electron transport through COX or AOX pathway had differential effect on ROS generating (SOD), ROS scavenging (CAT and APX) and antioxidant (Asc and GSH) regenerating (MDAR and GR) enzymes. Further, restriction of mitochondrial electron transport decreased redox ratios of both Asc and GSH. However, while decrease in redox ratio of Asc was more prominent in the presence of SHAM in light compared with dark, decrease in redox ratio of GSH was similar in both dark and light. These results suggest that the maintenance of cellular ROS at optimal levels is a prerequisite to sustain high photosynthetic rates which in turn is regulated by respiratory capacities of COX and AOX pathways.     

Reduction of hyperhydricity in the culture of <Emphasis Type="Italic">Lepidium meyenii</Emphasis> shoots by the addition of rare earth elements

Adventitious shoots induced from maca calli on induction media without rare earth elements (REE) had higher water content and lower soluble protein concentration when compared with shoots sprouted from maca seeds. Due to lower activities of antioxidative enzymes, there were higher concentrations of H₂O₂ and malonyldialdehyde (MDA) in adventitious shoots than those in seed shoots. When La³⁺, Ce³⁺ and Nd³⁺ (0.04 mM to 0.1 mM) were added to induction media, induction rates of the adventitious shoots were only affected slightly, but hyperhydricity rates were significantly reduced. La³⁺, Ce³⁺ or Nd³⁺ enhanced the activities of antioxidative enzymes in adventitious shoots, e.g. peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR). When the concentrations of La³⁺, Ce³⁺ and Nd³⁺ were 0.1 mM, the oxygen stress in adventitious shoots was decreased to levels similar to seed shoots, where most adventitious shoots grew normally.     

Reactive Oxygen Species Scavenging Enzymes and Down-Adjustment of Metabolism Level in Mitochondria Associated with Desiccation-Tolerance Acquisition of Maize Embryo

It is a well-known fact that a mature seed can survive losing most of its water, yet how seeds acquire desiccation-tolerance is not well understood. Through sampling maize embryos of different developmental stages and comparatively studying the integrity, oxygen consumption rate and activities of antioxidant enzymes in the mitochondria, the main origin site of reactive oxygen species (ROS) production in seed cells, we found that before an embryo achieves desiccation-tolerance, its mitochondria shows a more active metabolism, and might produce more ROS and therefore need a more effective ROS scavenging system. However, embryo dehydration in this developmental stage declined the activities of most main antioxidant enzymes and accumulated thiobarbituric acid-reactive products in mitochondria, and then destroyed the structure and functional integrity of mitochondria. In physiologically-matured embryos (dehydration-tolerant), mitochondria showed lower metabolism levels, and no decline in ROS scavenging enzyme activities and less accumulation of thiobarbituric acid-reactive products after embryo dehydration. These data indicate that seed desiccation-tolerance acquisition might be associated with down-adjustment of the metabolism level in the late development stage, resulting in less ROS production, and ROS scavenging enzymes becoming desiccation-tolerant and then ensuring the structure and functional integrity of mitochondria.     

ANTIOXIDANT ENZYME RESPONSE AND REACTIVE OXYGEN SPECIES PRODUCTION IN MARINE RAPHIDOPHYTES1

Raphidophytes (class Raphidophyceae) produce high levels of reactive oxygen species (ROS), yet little is known regarding cellular scavenging mechanisms needed for protection against these radicals. Enzymatic activities of the antioxidants superoxide dismutase (SOD) and catalase (CAT) were measured in conjunction with the production of superoxide (O₂^??) and hydrogen peroxide (H₂O₂) in batch cultures of five different raphidophytes species during early exponential, late‐exponential, and stationary growth phases. The greatest concentrations of O₂^?? per cell were detected during exponential growth with reduced levels in stationary phases in raphidophytes Heterosigma akashiwo (Hada) Hada ex Y. Hara et Chihara, Chattonella marina (Subrahman.) Y. Hara et Chihara, and Chattonella antiqua (Hada) Ono (strain 18). Decreasing trends from exponential to stationary phases for SOD activity and H₂O₂ per cell were observed in all species tested. Significant correlations between O₂^?? per cell and SOD activity per cell over growth phase were only observed in three raphidophytes (Heterosigma akashiwo, Chattonella marina, and Chattonella antiqua strain 18), likely due to different cellular locations of externally released O₂^?? radicals and intracellular SOD enzymes measured in this study. CAT activity was greatest at early exponential phase for several raphidophytes, but correlations between H₂O₂ per cell and CAT activity per cell were only observed for Fibrocapsa japonica Toriumi et Takano, Chattonella antiqua (strain 18), and Chattonella subsalsa Biecheler. Our results suggest that SOD and CAT play important protective roles against ROS during exponential growth of several raphidophytes, while other antioxidant pathways may play a larger role for scavenging ROS during later growth.     

Reactive oxygen species contribute to the release of volatile organic compounds from Chlamydomonas reinhardtii during programmed cell death

Acetic acid at pH 5.0 can induce programmed cell death (PCD) in Chlamydomonas reinhardtii cells, and abundant volatile organic compounds (VOCs) were released during the process. In this study, the caspase‐3‐like activity was determined during the PCD, and it was increased significantly after 1 h. During the PCD, the dynamic release of VOCs from the cells was analyzed, and the emissions of total VOCs were raised markedly and reached the highest level at 2 h. Among the seven types of VOCs, such as alkanes, alkenes, terpenoids, alcohols, aldehydes, ketones and esters, three oxygenated compounds (aldehydes, ketones and esters) showed the most significant increase. O₂^‐· and H₂O₂ were rapidly accumulated to high levels in the cells at the beginning of the PCD, but their content was reduced during the process. The activities of antioxidant enzymes were reduced gradually and even disappeared completely, demonstrating that the reduction of reactive oxygen species (ROS) may not be scavenged by the antioxidant enzyme system. ROS have an intense oxidation and scavenging ability to volatile compounds, and the oxidation results in the production of oxygenated compounds. Therefore, the abundant production of oxygenated compounds indicated that ROS may play an important role in the dynamic release of VOCs from C. reinhardtii cells during PCD.     

The Activity of the Antioxidative System in Cadmium-Treated Arabidopsis thaliana

Changes in the content of reactive oxygen species (ROS) and activity of the antioxidant system were measured in leaves of Arabidopsis thaliana (L.) Heynh exposed to Cd²⁺. Mature plants growing in the nutrient solution were treated with Cd²⁺ at different concentrations (0, 5, 25, 50, 100 μM). An increase of content in leaves was observed at 5, 25 and 50 μM Cd²⁺. A strong accumulation of H₂O₂ was found only at the lowest Cd²⁺ concentration. The content of OH^*. was high at 50 and 100 μM Cd²⁺. Superoxide dismutase (SOD) activity was always higher in Cd²⁺-treated plants than in control. Catalase (CAT) activity decreased with increasing Cd²⁺ concentration in the nutrient solution. Guaiacol peroxidase (POX) activity was particularly high at the lowest and highest Cd²⁺ concentrations and ascorbate peroxidase (APX) activity additionally at 50 μM Cd²⁺. Enhanced activity of monodehydroascorbate reductase (MDHAR) and strong reduction in ascorbate (AA) content were observed at 25 μM Cd²⁺. Glutathione reductase (GR) activity was always higher than in control but decreased as Cd²⁺ concentration increased. However, it was accompanied by gradual content increase of SH-groups. This revised version was published online in July 2006 with corrections to the Cover Date.     

海藻酸铈配合物对毒死蜱胁迫下菠菜叶片抗坏血酸-谷胱甘肽循环的影响

以菠菜(Spinacia oleracea L.)为材料,研究了毒死蜱胁迫下海藻酸铈配合物对菠菜叶片抗坏血酸-谷胱甘肽循环的影响。结果表明,在毒死蜱胁迫下,菠菜叶片中H2O2积累量比对照明显增加,非酶促抗氧化物质-抗坏血酸(AsA)和还原型谷胱甘肽(GSH)含量明显降低,抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)、脱氢抗坏血酸还原酶(DHAR)和单脱氢抗坏血酸还原酶(MDAR)的活性明显升高。在毒死蜱胁迫下,喷施不同浓度的海藻酸铈配合物使菠菜叶片中的H2O2积累量减少,AsA和GSH含量升高,APX、GR、DHAR和MDAR等抗氧化酶活性也有所提高,缓解了毒死蜱胁迫。试验表明,适宜浓度的海藻酸铈配合物处理可使菠菜叶片对毒死蜱胁迫有一定的缓解作用。     

Antioxidant Systems in Ripening Tomato Fruits

Two cultivars of tomato (Lycopersicon esculentum Mill.), Selection-7 (shelf life 7–8 d) and ARTH-3 (shelf life 14–15 d) were analyzed for oxidative stress and the antioxidant enzyme system at different stages of fruit ripening. The results presented here suggest that during the early stages of fruit ripening, efficient antioxidant system protects the tomato fruits against the damaging effect of progressive oxidative stress. At later stages, however, oxidative damage occurs due to decreased activities of the ROS scavenging enzymes.     

Flooding-induced membrane damage, lipid oxidation and activated oxygen generation in corn leaves

Flooding effects on membrane permeability, lipid peroxidation and activated oxygen metabolism in corn (Zea mays L.) leaves were investigated to determine if activated oxygens are involved in corn flooding-injury. Potted corn plants were flooded at the 4-leaf stage in a controlled environment. A 7-day flooding treatment resulted in a significant increase in chlorophyll breakdown, lipid peroxidation (malondialdehye content), membrane permeability, and the production of superoxide (O ₂ ^- ) and hydrogen peroxide (H₂O₂) in corn leaves. The effects were much greater in older leaves than in younger ones. Spraying leaves with 8-hydroxyquinoline (an O ₂ ^- scavenger) and sodium benzoate (an .OH scavenger) reduced the oxidative damage and enhanced superoxide dismutase (SOD) activity. A short duration flooding treatment elevated the activities of SOD, catalase, ascorbate peroxidase (AP), and glutathione reductase (GR), while further flooding significantly reduced the enzyme activities but enhanced the concentrations of ascorbic acid and reduced form glutathione (GSH). It was noted that the decline in SOD activity was greater than that in H₂O₂ scavengers (AP and GR). The results suggested that O ₂ ^- induced lipid peroxidation and membrane damage, and that excessive accumulation of O ₂ ^- is due to the reduced activity of SOD under flooding stress.     

亚洲玉米螟幼虫应对大肠杆菌注射的血淋巴免疫应激反应

为研究大肠杆菌Escherichia coli侵染引发亚洲玉米螟Ostrinia furnacalis Guenée幼虫免疫应激反应的机理,本实验测定了分别注射生理盐水以及3×10³,3×10⁴,3×10⁵和3×10⁶个细胞/mL大肠杆菌后亚洲玉米螟5龄幼虫血淋巴中血细胞总数（THC）、颗粒细胞和浆血细胞数量,血清中酚氧化酶（PO）、谷胱甘肽过氧化物酶（GSH-px）、谷胱甘肽还原酶(GR)和谷胱甘肽-S-转移酶(GST)的活性,通过流式细胞仪分析了血细胞活性氧自由基(ROS)水平的动态变化。结果表明：与对照组相比,注射3×10⁵和3×10⁶个细胞/mL大肠杆菌细胞后12 h,可引起亚洲玉米螟5龄幼虫THC及浆血细胞、颗粒细胞数量明显上升(P<0.01),同时应激产生大量ROS。3×10⁴,3×10⁵和3×10⁶个细胞/mL大肠杆菌3个不同浓度处理组均引起幼虫体内PO活性显著升高(P<0.01),诱导幼虫血清中GSH-px,GST及GR的活性上升(P<0.01)。这些结果表明, 亚洲玉米螟幼虫受到大肠杆菌侵染后,其血淋巴细胞免疫和体液免疫能力受到显著影响, 可诱导血清中GSH-px,GST和GR活性升高以清除过多的ROS, 防止其毒害。     

1Alpha,25-dihydroxyvitamin D3 modulation of adipocyte reactive oxygen species production

Objective: We have previously shown 1α,25‐dihydroxyvitamin D₃ [1α,25‐(OH)₂D₃] to inhibit mitochondrial uncoupling protein 2 (UCP2) expression in adipocytes and that in vivo suppression of calcitriol levels with calcium‐rich diets increases UCP2 expression. Because UCP2 plays a significant role in the clearance of reactive oxygen species (ROS), we studied the effect of calcitriol on ROS production and ROS‐induced adipocyte proliferation. Research Methods and Procedures: ROS production in human and murine adipocytes was stimulated by high glucose (30 mM) or H₂O₂ (100 nM). Results: Both approaches resulted in increased ROS production by 27% to 100% (p < 0.05) and increased cell proliferation by 15% to 39% (p < 0.03). These effects were augmented by the addition of mitochondrial uncoupling inhibitor guanosine 5′‐diphosphate (GDP; 100 μM) or 1α,25‐(OH)₂D₃ (10 nM) and attenuated by UCP2 overexpression, suggesting that inhibition of mitochondrial uncoupling suppresses clearance of ROS and increases adipocyte proliferation. The addition of α ± tocopherol (1 μM) inhibited cell proliferation in adipocytes treated with either H₂O₂ or high glucose, indicating that ROS plays a major role in the regulation of cell proliferation in adipocytes. Moreover, stimulation of ROS with high glucose and H₂O₂ resulted in a 2‐ to 5‐fold increase in adipocyte intracellular calcium ([Ca²⁺]i; p < 0.001), and calcium channel antagonism (nifedipine, 10 μM) suppressed ROS induced calcium influx and cell proliferation, indicating that [Ca²⁺]i may also regulate ROS production and exert a mitogenic effect in adipocytes. Discussion: These data support a role of 1α,25‐(OH)₂D₃, UCP2, and [Ca²⁺]i in the regulation of adipocyte ROS production.     

Studies on the protective role of vitamin C and E against polychlorinated biphenyl (Aroclor 1254)—induced oxidative damage in Leydig cells

Free radical production and lipid peroxidation are potentially important mediators in testicular physiology and toxicology. Polychlorinated biphenyls (PCBs) are global environmental contaminants that cause disruption of the endocrine system in human and animals. The present study was conducted to elucidate the protective role of vitamin C and E against Aroclor 1254-induced changes in Leydig cell steroidogenesis and antioxidant system. Adult male rats were dosed for 30 days with daily intraperitoneal (ip) injection of 2 mg/kg Aroclor or vehicle (corn oil). One group of rats was treated with vitamin C (100 mg/kg bw/day) while the other group was treated with vitamin E (50 mg/kg bw/day) orally, simultaneously with Aroclor 1254 for 30 days. One day after the last treatment, animals were euthanized and blood was collected for the assay of serum hormones such as luteinizing hormone (LH), thyroid stimulating hormone (TSH), prolactin (PRL), triiodothyronine (T₃), thyroxine (T₄), testosterone and estradiol. Testes were quickly removed and Leydig cells were isolated in aseptic condition. Purity of Leydig cells was determined by 3β-hydroxysteroid dehydrogenase (3β-HSD) staining method. Purified Leydig cells were used for quantification of cell surface LH receptors and steroidogenic enzymes such as cytochrome P₄₅₀ side chain cleavage enzyme (P₄₅₀scc), 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17β-hydroxysteroid dehydrogenase (17β- HSD). Leydig cellular enzymatic antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), γ-glutamyl transpeptidase (γ-GT), glutathione-S-transferase (GST) and non-enzymatic antioxidants such as vitamin C and E were assayed. Lipid peroxidation (LPO) and reactive oxygen species (ROS) were also estimated in Leydig cells. Aroclor 1254 treatment significantly reduced the serum LH, TSH, PRL, T₃, T₄, testosterone and estradiol. In addition to this, Leydig cell surface LH receptors, activities of the steroidogenic enzymes such as cytochrome P₄₅₀scc, 3β-HSD, 17β-HSD, antioxidant enzymes SOD, CAT, GPX, GR, γ-GT, GST and non-enzymatic antioxidants such as vitamin C and E were significantly diminished whereas, LPO and ROS were markedly elevated. However, the simultaneous administration of vitamin C and E in Aroclor 1254 exposed rats resulted a significant restoration of all the above-mentioned parameters to the control level. These observations suggest that vitamin C and E have ameliorative role against adverse effects of PCB on Leydig cell steroidogenesis.     

Cell death and reactive oxygen species metabolism during accelerated ageing of soybean axes

In this paper, Glycine max L. seeds under accelerated ageing condition (40°C and 100% relative humidity) were used as experimental material to study the relationships between seed viability and cell death, production and scavenging of reactive oxygen species (ROS) during accelerated ageing. Water content of seeds gradually increased, while the final germination percentage, germination rate of seeds and fresh weight of seedlings produced decreased with increasing accelerated ageing time. The accelerated ageing time (T ₅₀) when final seed germination decreased to 50% was about 10.5 days. During the period of accelerated ageing, the viability of root cells was lost gradually as manifested by the increase in staining with Evans blue. The respiration rate of seeds, ^·O₂ production rate, and H₂O₂ content of axes increased, peaked at the 10 days of accelerated ageing, and then decreased. Activities of superoxide dismutase, ascorbate peroxidase, catalase, and glutathione reductase of axes decreased; and malondialdehyde contents of axes markedly increased. A sceme to explain relationships between seed vigor, cell death, and production and scavenging of ROS during accelerated ageing was suggested. This text was submitted by the authors in English.     

2-Benzoxazolinone (BOA) induced oxidative stress, lipid peroxidation and changes in some antioxidant enzyme activities in mung bean (Phaseolus aureus)

2-Benzoxazolinone (BOA), a well-known allelochemical with strong phytotoxicity, is a potential herbicidal candidate. The aim of the present study was to determine whether phytotoxicity of BOA is due to induction of oxidative stress caused by generation of reactive oxygen species (ROS) and the changes in levels of antioxidant enzymes induced in response to BOA. Effect of BOA was studied on electrolyte leakage, lipid peroxidation (LP), hydrogen peroxide (H(2)O(2)) generation, proline (PRO) accumulation, and activities of antioxidant enzymes-superoxide dismutase (SOD, 1.15.1.1), ascorbate peroxidase (APX, 1.11.1.11), guaiacol peroxidase (GPX, 1.11.1.7), catalase (CAT, 1.11.1.6) and glutathione reductase (GR, 1.6.4.2) in Phaseolus aureus (mung bean). BOA significantly enhanced malondialdehyde (MDA) content, a product of LP, in both leaves and roots of mung bean. The amount of H(2)O(2), a product of oxidative stress, and endogenous PRO increased many-fold in response to BOA. Accumulation of PRO, MDA and H(2)O(2) indicates the cellular damage in the target tissue caused by ROS generated by BOA. In response to BOA, there was a significant increase in the activities of scavenging enzymes SOD, APX, GPX, CAT, and GR in root and leaf tissue of mung bean. At 5 mM BOA, GR activity in roots showed a nearly 22-fold increase over that in control. The present study concludes that BOA induces oxidative stress in mung bean through generation of ROS and upregulation of activities of various scavenging enzymes.     

Oxidative pathways in response to polyunsaturated aldehydes in the marine diatom Skeletonema marinoi (Bacillariophyceae)

Polyunsaturated aldehydes (PUA) have recently been shown to induce reactive oxygen species (ROS) and possibly reactive nitrogen species (RNS, e.g., peroxynitrite) in the diatom Skeletonema marinoi (S. marinoi), which produces high amounts of PUA. We now are attempting to acquire better understanding of which reactive molecular species are involved in the oxidative response of S. marinoi to PUA. We used flow cytometry, the dye dihydrorhodamine 123 (DHR) as the main indicator of ROS (but which is also known to partially detect RNS), and different scavengers and inhibitors of both nitric oxide (NO) synthesis and superoxide dismutase activity (SOD). Both the scavengers Tempol (for ROS) and uric acid (UA, for peroxynitrite) induced a lower DHR‐derived green fluorescence in S. marinoi cells exposed to the PUA, suggesting that both reactive species were produced. When PUA‐exposed S. marinoi cells were treated with the NO scavenger 2‐4‐carboxyphenyl‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide (cPTIO), an opposite response was observed, with an increase in DHR‐derived green fluorescence. A higher DHR‐derived green fluorescence was also observed in the presence of sodium tungstate (ST), an inhibitor of NO production via nitrate reductase. In addition, two different SOD inhibitors, 2‐methoxyestradiol (2ME) and sodium diethyldithiocarbamate trihydrate (DETC), had an effect, with DETC inducing the strongest inhibition after 20 min. These results indicate the involvement of O₂^? generation and SOD activity in H₂O₂ formation (with downstream ROS generation dependent from H₂O₂) in response to PUA exposure. This is relevant as it refines the biological impact of PUA and identifies the specific molecules involved in the response. It is speculated that in PUA‐exposed S. marinoi cells, beyond a certain threshold of PUA, the intracellular antioxidant system is no longer able to cope with the excess of ROS, thus resulting in the observed accumulation of both O₂^?? and H₂O₂. This might be particularly relevant for population dynamics at sea, during blooms, when cell lysis increases and PUA are released. It can be envisioned that in the final stages of blooms, higher local PUA concentrations accumulate, which in turn induces intracellular ROS generation that ultimately leads to cell death and bloom decay.