Chromium-mediated oxidative stress and ultrastructural changes in root cells of developing rice seedlings

Oxidative stress and ultrastructural changes under hexavalent chromium stress were investigated in developing rice seedlings. Chromium treatment for 24 or 48h resulted in inhibition of root length and dry biomass. Atomic absorption spectrometry analysis of roots showed that chromium accumulation increased with increase in concentration and duration of metal treatment. Chromium resulted in increased production of hydrogen peroxide and superoxide radical in root cells, which was a significant change after 48h of treatment. Time-course analysis of malondialdehyde content showed no substantial variation during early treatment periods (2, 6 or 12h). Increase in malondialdehyde content was observed only after 18h and it continued to increase until 48h after treatment. Loss of membrane integrity, analyzed in terms of Evans blue uptake in root cells, showed an increase in uptake of the reagent, indicating loss of membrane integrity. The antioxidant enzyme, viz., guaiacol peroxidase, was least affected, while glutathione reductase showed significant decline after 24 or 48h of metal treatment, followed by increased activity of superoxide dismutase. The level of ascorbate was not affected by chromium, while an increase in the level of glutathione was observed. At the ultrastructural level, potential damage to the root cell was noted after 48h at 100microM of chromium compared with controls.     

缺铁水稻根转录本微点阵分析

水稻不仅是非常重要的粮食作物 ,也是用于研究的模式植物之一 .由于水稻基因组测序的完成 ,用功能基因组学的现代方法来研究缺铁相关基因的表达调控是最高效的方法之一。在前期工作的基础上 ,精心设计了缺铁和EDTA鳌合二价铁诱导5天的水稻根实验 ,并进行了转录水平的微点阵 (microarray)分析。但只获得了第 5天的结果。在 10 5 31个水稻cDNA芯片图谱中 ,缺铁和加铁比较发现了 4 5 1个差异点。对缺铁诱导的 4 5 1个差异cDNA逐一地进行NCBI (美国国家生物技术信息中心 )的BLAST(局部定位排列搜索工具 )数据库检索、分析和归类。发现其中缺铁与加铁 ( -Fe/Fe -EDTAratio)之间的相对表达水平(REL)在 2 - 9.175之间的缺铁诱导上调基因为 2 0 3个 ,缺铁诱导的下调基因为 2 4 8个。对每一类上调基因都逐一地进行了NCBI-PubMed的文献检索。利用国际网络数据库进行了功能鉴定。     

Triggering and modulation of apoptosis by oxidative stress

Cell survival requires multiple factors, including appropriate proportions of molecular oxygen and various antioxidants. Although most oxidative insults can be overcome by the cell's natural defenses, sustained perturbation of this balance may result in either apoptotic or necrotic cell death. Numerous, recent studies have shown that the mode of cell death that occurs depends on the severity of the insult. Oxidants and antioxidants can not only determine cell fate, but can also modulate the mode of cell death. Effects of oxidative stress on components of the apoptotic machinery may mediate this modulation. This review will address some of the current paradigms for oxidative stress and apoptosis, and discuss the potential mechanisms by which oxidants can modulate the apoptotic pathway.     

Heavy metals do not induce ROS production by mitochondrial respirasome

Since the discovery of the respirasome constituted by complexes I, III₂, and IV, its precise participation in mitochondrial bioenergetics is poorly understood. We previously determined a higher NADH:DBQ oxidoreductase activity coupled to a lower ROS production by the respirasome than the free complex I. Toxicological studies suggest that respiratory complexes are heavy metals target during mitochondrial intoxication increasing ROS production, reducing ATP synthesis and cell viability; however, the inhibition of respiratory complexes activities by heavy metals is still unknown. Here we showed a putative deactivation of the respirasomal-complex I by seven of the most toxicologically relevant heavy metals, without increasing the ROS production. Contrastingly, the free complex I was more resistant to heavy metals but was 30 times more ROS-producing. These results underlie the preventive role of the respirasome in mitochondrial electron leak and ROS production and recall its disassembled in some pathologies which involve mitochondrial damage and oxidative stress.     

Quantitative genome-wide analysis of yeast deletion strain sensitivities to oxidative and chemical stress

Understanding the actions of drugs and toxins in a cell is of critical importance to medicine, yet many of the molecular events involved in chemical resistance are relatively uncharacterized. In order to identify the cellular processes and pathways targeted by chemicals, we took advantage of the haploid Saccharomyces cerevisiae deletion strains (Winzeler et al., 1999). Although ~4800 of the strains are viable, the loss of a gene in a pathway affected by a drug can lead to a synthetic lethal effect in which the combination of a deletion and a normally sublethal dose of a chemical results in loss of viability. WE carried out genome-wide screens to determine quantitative sensitivities of the deletion set to four chemicals: hydrogen peroxide, menadione, ibuprofen and mefloquine. Hydrogen peroxide and menadione induce oxidative stress in the cell, whereas ibuprofen and mefloquine are toxic to yeast by unknown mechanisms. Here we report the sensitivities of 659 deletion strains that are sensitive to one or more of these four compounds, including 163 multichemicalsensitive strains, 394 strains specific to hydrogen peroxide and/or menadione, 47 specific to ibuprofen and 55 specific to mefloquine.We correlate these results with data from other large-scale studies to yield novel insights into cellular function.     

Piperine modulation of carcinogen induced oxidative stress in intestinal mucosa

The plasma-borne long-chain free fatty acids (FFA) enter skeletal muscle cells. Upon entering they are oxidized or esterified and a fraction remains free (non-esterified). The data on free fatty acids in skeletal muscles remain highly controversial. Furthermore, the composition of individual fatty acids in various lipid fractions including free fatty acids, monoglyceride and diglyceride in muscles has not been characterized. Also data on the composition of fatty acids esterified into muscle triglycerides and phospholipids are incomplete. The present study was undertaken to examine a composition of fatty acids in lipid fractions of different skeletal muscle types. For this purpose, samples of the rat soleus, red and white portions of gastrocnemius were excised, trimmed of visible fat and fascias and immediately frozen in liquid nitrogen. Samples were then pulverized and, lipids were extracted and fractionated by thin-layer chromatography. Individual long-chain fatty acids in different fractions were identified, characterized and quantitated by gas-liquid chromatography. FFA composition in the plasma was also determined. The total FFA content in the soleus, red and white gastrocnemius was 69.1 ± 10.8, 49.0 ± 13.6 and 22.7 ± 8.6 nmol/g, respectively. Palmitic and oleic acids were the major fatty acids in the muscles FFA fraction. Monoglyceride fraction of each muscle contained palmitic, stearic and linoleic acid as the major fatty acids, Diglyceride fraction contained mostly palmitic and oleic acid whereas triglyceride fraction mostly palmitic and linoleic acid.. The fraction of phospholipids was composed mostly of palmitic and linoleic acid but contained also considerable percentage of archidonic acid. Total plasma FFA/muscle FFA ratio depended on a muscle type and was: 2.4 in the soleus, 3.5 in the red and 7.4 in the white gastrocnemius. This assured transport of FFA to the myocytes. However, there were great differences in the ratio between particular FFA within the same muscle as well between the muscles. It indicates that individual FFA are either selectively transported from the plasma to the muscles or selectively used within the myocytes or both.     

Assembly defects induce oxidative stress in inherited mitochondrial complex I deficiency

Complex I (CI) deficiency is the most common respiratory chain defect representing more than 30% of mitochondrial diseases. CI is an L-shaped multi-subunit complex with a peripheral arm protruding into the mitochondrial matrix and a membrane arm. CI sequentially assembled into main assembly intermediates: the P (pumping), Q (Quinone) and N (NADH dehydrogenase) modules. In this study, we analyzed 11 fibroblast cell lines derived from patients with inherited CI deficiency resulting from mutations in the nuclear or mitochondrial DNA and impacting these different modules. In patient cells carrying a mutation located in the matrix arm of CI, blue native-polyacrylamide gel electrophoresis (BN-PAGE) revealed a significant reduction of fully assembled CI enzyme and an accumulation of intermediates of the N module. In these cell lines with an assembly defect, NADH dehydrogenase activity was partly functional, even though CI was not fully assembled. We further demonstrated that this functional N module was responsible for ROS production through the reduced flavin mononucleotide. Due to the assembly defect, the FMN site was not re-oxidized leading to a significant oxidative stress in cell lines with an assembly defect. These findings not only highlight the relationship between CI assembly and oxidative stress, but also show the suitability of BN-PAGE analysis in evaluating the consequences of CI dysfunction. Moreover, these data suggest that the use of antioxidants may be particularly relevant for patients displaying a CI assembly defect.     

Dietary modulation of oxidative stress in chronic obstructive pulmonary disease patients

Abstract

A total of 267 clinically stable chronic obstructive pulmonary disease (COPD) patients provided complete data about diet and oxidative stress markers in order to assess the relationship between antioxidant rich food groups and nutrients, and serum markers of oxidative stress in COPD. Dietary data of the last 2 years was assessed using a validated food frequency questionnaire (122 items). Levels of carbonyls, nitrotyrosine, malondialdehyde and reduced glutathione (GSH) were measured in serum. Vitamin E intake was inversely associated with levels of carbonyls (p = 0.05) and olive oil was positively associated with GSH levels (p = 0.01), in active smokers. Intake of vegetables was related to a decrease of malondialdehyde levels (p = 0.04) in former smokers. No statistically significant associations were found between remaining dietary antioxidants and serum oxidative stress markers. These results provide new data for a potential dietary modulation of systemic oxidative stress in COPD patients, particularly in those that continue smoking.     

Chilling, oxidative stress and antioxidant responses in shoot cultures of rice

Chilling of shoot cultures from Oryza sativa L. cv. Taipei 309, to 4 °C leads to conditions of oxidative stress. Tissue H₂O₂ was observed to increase more than fourfold by 8 d of chilling, and levels of reduced glutathione, which normally rise in growing shoot cultures at 25 °C, were considerably repressed in chilled cultures. Whilst the activity of ascorbate peroxidase in chilled shoots remained similar to the activities in control cultures at 25 °C, the most notable effects of chilling to 4 °C were the very significant loss of catalase and glutathione reductase activity. Although prior exposure of shoot cultures to abscisic acid (ABA) at 25 °C increased levels of catalase activity, such increased levels were not sustained when the pre-treated cultures were placed at 4 °C. Moreover such pre-treatment with ABA did not increase the subsequent ability of shoot cultures to grow at 4 °C.Abbreviations GSH reduced glutathione - GSSG oxidised glutathione - ABA cis-abscisic acid This work is supported by a grant from the Biotechnology and Biological Sciences Research Council.