Showing papers on "Catalase published in 2006"
TL;DR: Two methods are described for the catalase assay by disappearance of peroxide are: ultraviolet spectrophotometry and permanganate titration and indirect measurements of the decrease of light absorption caused by the decomposition of hydrogen peroxide byCatalase.
Abstract: Publisher Summary This chapter discusses the assay of catalases and peroxidases are: (1) catalase assay by disappearance of peroxide; (2) method for crude cell extracts; (3) direct spectrophotometric assay of catalase and peroxidase in cells and tissues; and (4) peroxidase assay by spectrophotometric measurements of the disappearance of hydrogen donor or the appearance of their colored oxidation products. Two methods are described for the catalase assay by disappearance of peroxide are: ultraviolet spectrophotometry and permanganate titration. Ultraviolet spectrophotometryis a method devised, on the basis of the absorption curves for peroxide solutions, for determining the activity of catalase by direct measurements of the decrease of light absorption in the region 230 to 250 mμ caused by the decomposition of hydrogen peroxide by catalase. In the case of method for crude cell extracts, oxygen evolution caused by the decomposition of hydrogen peroxide is measured with the conventional manometric technique. Peroxidase assay by spectrophotometric measurements of the disappearance of hydrogen donor or the appearance of their colored oxidation products includes the guaiacol test and the pyrogallol test.
3,917 citations
TL;DR: In this article, the effects of salt stress on the activity of antioxidative enzymes and lipid peroxidation were studied in leaves and roots of two maize genotypes, BR5033 (salt-tolerant) and BR5011 (Salt-sensitive), grown under control or salt stress (nutrient solution containing 100mM NaCl) conditions.
788 citations
TL;DR: The data suggests that the outcomes of JA-SA interactions could be tailored to pathogen/pest attack by the relative concentration of each hormone.
Abstract: Salicylic acid (SA) has been proposed to antagonize jasmonic acid (JA) biosynthesis and signaling. We report, however, that in salicylate hydroxylase-expressing tobacco (Nicotiana tabacum) plants, where SA levels were reduced, JA levels were not elevated during a hypersensitive response elicited by Pseudomonas syringae pv phaseolicola. The effects of cotreatment with various concentrations of SA and JA were assessed in tobacco and Arabidopsis (Arabidopsis thaliana). These suggested that there was a transient synergistic enhancement in the expression of genes associated with either JA (PDF1.2 [defensin] and Thi1.2 [thionin]) or SA (PR1 [PR1a-beta-glucuronidase in tobacco]) signaling when both signals were applied at low (typically 10-100 microm) concentrations. Antagonism was observed at more prolonged treatment times or at higher concentrations. Similar results were also observed when adding the JA precursor, alpha-linolenic acid with SA. Synergic effects on gene expression and plant stress were NPR1- and COI1-dependent, SA- and JA-signaling components, respectively. Electrolyte leakage and Evans blue staining indicated that application of higher concentrations of SA + JA induced plant stress or death and elicited the generation of apoplastic reactive oxygen species. This was indicated by enhancement of hydrogen peroxide-responsive AoPR10-beta-glucuronidase expression, suppression of plant stress/death using catalase, and direct hydrogen peroxide measurements. Our data suggests that the outcomes of JA-SA interactions could be tailored to pathogen/pest attack by the relative concentration of each hormone.
761 citations
TL;DR: Analysis of transcriptome data generated from ROS-related microarray experiments provides a framework that will assist future efforts to address the impact of ROS signals within environmental stress conditions and elucidate the molecular mechanisms of the oxidative stress response in plants.
Abstract: Reactive oxygen species (ROS) are key players in the regulation of plant development, stress responses, and programmed cell death. Previous studies indicated that depending on the type of ROS (hydrogen peroxide, superoxide, or singlet oxygen) or its subcellular production site (plastidic, cytosolic, peroxisomal, or apoplastic), a different physiological, biochemical, and molecular response is provoked. We used transcriptome data generated from ROS-related microarray experiments to assess the specificity of ROS-driven transcript expression. Data sets obtained by exogenous application of oxidative stress-causing agents (methyl viologen, Alternaria alternata toxin, 3-aminotriazole, and ozone) and from a mutant (fluorescent) and transgenic plants, in which the activity of an individual antioxidant enzyme was perturbed (catalase, cytosolic ascorbate peroxidase, and copper/ zinc superoxide dismutase), were compared. In total, the abundance of nearly 26,000 transcripts of Arabidopsis (Arabidopsis thaliana) was monitored in response to different ROS. Overall, 8,056, 5,312, and 3,925 transcripts showed at least a 3-, 4-, or 5-fold change in expression, respectively. In addition to marker transcripts that were specifically regulated by hydrogen peroxide, superoxide, or singlet oxygen, several transcripts were identified as general oxidative stress response markers because their steady-state levels were at least 5-fold elevated in most experiments. We also assessed the expression characteristics of all annotated transcription factors and inferred new candidate regulatory transcripts that could be responsible for orchestrating the specific transcriptomic signatures triggered by different ROS. Our analysis provides a framework that will assist future efforts to address the impact of ROS signals within environmental stress conditions and elucidate the molecular mechanisms of the oxidative stress response in plants.
730 citations
TL;DR: The role of PPARalpha, which is highly activated in PEX5-/- mice with the absence of functional peroxisomes severe abnormalities of mitochondria in different organs are observed which resemble closely those in respiratory chain disorders associated with oxidative stress.
701 citations
TL;DR: Aberrations in oxidant: antioxidant balance can lead to a variety of airway diseases, such as asthma, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis which is the topic of discussion in this review.
668 citations
Journal Article•
TL;DR: Alcohol is eliminated from the body by various metabolic mechanisms, and variations in the genes for these enzymes have been found to influence alcohol consumption, alcohol-related tissue damage, and alcohol dependence.
Abstract: Alcohol is eliminated from the body by various metabolic mechanisms. The primary enzymes involved are aldehyde dehydrogenase (ALDH), alcohol dehydrogenase (ADH), cytochrome P450 (CYP2E1), and catalase. Variations in the genes for these enzymes have been found to influence alcohol consumption, alcohol-related tissue damage, and alcohol dependence. The consequences of alcohol metabolism include oxygen deficits (i.e., hypoxia) in the liver; interaction between alcohol metabolism byproducts and other cell components, resulting in the formation of harmful compounds (i.e., adducts); formation of highly reactive oxygen-containing molecules (i.e., reactive oxygen species [ROS]) that can damage other cell components; changes in the ratio of NADH to NAD + (i.e., the cell’s redox state); tissue
659 citations
TL;DR: Peroxisomes can be broadly defined as subcellular organelles bounded by a single membrane that contain as basic enzymatic constituents catalase and hydrogen peroxide (H2O2)-producing flavin oxidases and occur in almost all eukaryotic cells.
Abstract: Peroxisomes can be broadly defined as subcellular organelles bounded by a single membrane that contain as basic enzymatic constituents catalase and hydrogen peroxide (H2O2)-producing flavin oxidases and occur in almost all eukaryotic cells ([Baker and Graham, 2002][1]). In recent years, it has
544 citations
TL;DR: Analysis of reactive oxygen species (ROS) and nitric oxide (NO) levels by fluorescence and confocal laser microscopy showed an over-accumulation of O2*- and H2O2, and a reduction in the NO content in lateral and principal roots, which could regulate the cellular response to cope with damages imposed by cadmium.
Abstract: Growth of pea (Pisum sativum L.) plants with 50 microM CdCl2 for 15 d produced a reduction in the number and length of lateral roots, and changes in structure of the principal roots affecting the xylem vessels. Cadmium induced a reduction in glutathione (GSH) and ascorbate (ASC) contents, and catalase (CAT), GSH reductase (GR) and guaiacol peroxidase (GPX) activities. CuZn-superoxide dismutase (SOD) activity was also diminished by the Cd treatment, although Mn-SOD was slightly increased. CAT and CuZn-SOD were down-regulated at transcriptional level, while Mn-SOD, Fe-SOD and GR were up-regulated. Analysis of reactive oxygen species (ROS) and nitric oxide (NO) levels by fluorescence and confocal laser microscopy (CLM) showed an over-accumulation of O2*- and H2O2, and a reduction in the NO content in lateral and principal roots. ROS overproduction was dependent on changes in intracellular Ca+2 content, and peroxidases and NADPH oxidases were involved. Cadmium also produced an increase in salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) contents. The rise of ET and ROS, and the NO decrease are in accordance with senescence processes induced by Cd, and the increase of JA and SA could regulate the cellular response to cope with damages imposed by cadmium.
515 citations
TL;DR: It is suggested that differential sensitivity of C3 and C4 plants to water stress appear to be partially governed by their ability to counter oxidative stress, pertinently involving ascorbic acid and glutathione.
451 citations
TL;DR: Data is presented indicating that cadmium induces cellular death in cortical neurons in culture and this death could be mediated by an apoptotic and a necrotic mechanism.
TL;DR: Results suggest that toxic concentrations of Cd caused oxidative damage as evidenced by increased lipid peroxidation and decreased chlorophyll and protein contents, however, B. monnieri is able to combat metal induced oxidative injury involving a mechanism of activation of various enzymatic and non-enzymatic antioxidants.
TL;DR: This is the first report describing the antioxidant responses of fruit trees as well as the regulation of nucleolytic enzymes under excess B conditions and suggest that excess B-induced oxidative stress and alterations in the antioxidant and nucleolytics enzymes are suggested.
TL;DR: Flow cytometry revealed that catalase, but not superoxide dismutase, was capable of attenuating ROS-induced inhibition of motility and both viable fresh and frozen-thawed boar sperm were quite susceptible to external sources of hydrogen peroxide.
Abstract: The use of frozen semen in the swine industry is limited by problems with viability and fertility compared with liquid semen. Part of the reduction in sperm motility and fertility associated with cryopreservation may be due to oxidative damage from excessive or inappropriate formation of reactive oxygen species (ROS). Chemiluminescence measurements of ROS are not possible in live cells and are problematic because of poor specificity. An alternative approach, flow cytometry, was developed to identify viable boar sperm containing ROS utilizing the dyes hydroethidine and 2', 7'-dichlorodihydrofluorescein diacetate as oxidizable substrates and impermeant DNA dyes to exclude dead sperm. The percentage of sperm with high mitochondrial transmembrane potential was determined by flow cytometry using the mitochondrial probe 5, 5', 6, 6'-tetrachloro-1, 1', 3, 3'-tetraethylbenzimidazolylcarbocyanine iodide with propidium iodide staining to exclude nonviable cells. Sperm were incubated with and without ROS generators and free radical scavengers. Basal ROS formation was low (less than 4%) and did not differ (P = 0.26) between viable fresh and frozen-thawed boar sperm. In addition, fresh and frozen-thawed viable sperm were equally susceptible (P = 0.20) to intracellular formation of ROS produced by xanthine/xanthine oxidase (94.4 and 87.9% of sperm, respectively). Menadione increased (P < 0.05) ROS formation, decreased (P < 0.05) JC-1-aggregate fluorescence intensity, and decreased (P < 0.05) motion variables by 25 to 60%. The mechanism of inhibition of motility by ROS formation may be related to a decrease in mitochondrial charge potential below a critical threshold. Catalase and superoxide dismutase treatment in the presence of xanthine/xanthine oxidase indicated that hydrogen peroxide was the primary intracellular ROS measured. Further, catalase, but not superoxide dismutase, was capable of attenuating ROS-induced inhibition of motility. Whereas basal intracellular hydrogen peroxide formation was low in viable fresh and frozen-thawed boar sperm, both were quite susceptible to external sources of hydrogen peroxide.
TL;DR: Results indicate pomegranate flowers to possess potent antioxidant and hepatoprotective property, the former being probably responsible for the latter.
TL;DR: CAT2 expression is down-regulated during leaf senescence, while CAT3 expression is induced with age and corresponds to an accumulation of H2O2 in the vascular bundles, and CAT2 down-regulation on the transcriptional level appears as the initial step in creating the H 2O2 peak during bolting time.
Abstract: Oxygen free radicals are thought to play an essential role in senescence, especially those derived from peroxisomes. Therefore, the activities of different isoforms of the peroxisomal hydrogen peroxide (H2O2)-scavenging enzyme catalase (CAT) were analysed during senescence of Arabidopsis. CAT2 activity decreased with bolting time parallel with cytosolic ascorbate peroxidase 1 (APX1) activity before loss of chlorophyll could be measured. At the same time point, the H2O2 content increased. Subsequently, the stress-inducible CAT3 isoform was activated and APX1 activity was recovered, accompanied by a decline of the H2O2 content. In very late stages, low activities of the seed-specific CAT1 became detectable in leaves, but H2O2 increased again. Further analyses of CAT expression by promoter: beta-glucuronidase (GUS) fusions in transgenic plants revealed a vasculature-specific CAT3 expression, whereas CAT2 expression turned out to be specific for photosynthetic active tissues. CAT2 expression is down-regulated during leaf senescence, while CAT3 expression is induced with age and corresponds to an accumulation of H2O2 in the vascular bundles. CAT2 down-regulation on the transcriptional level appears as the initial step in creating the H2O2 peak during bolting time, while the decrease in APX1 activity might only be a secondary and amplifying effect.
TL;DR: The study shows that Scenedesmus sp.
TL;DR: It is concluded that alpha-pinene inhibits early root growth and causes oxidative damage in root tissue through enhanced generation of ROS, as indicated by increased lipid peroxidation, disruption of membrane integrity and elevated antioxidant enzyme levels.
TL;DR: In this article, the effect of salt stress on cell membrane damage, ion content and antioxidant enzymes in wheat (Triticum aestivum) seedlings of two cultivars salt-tolerant KRL-19 and salt-sensitive WH-542 was investigated.
Abstract: The present study was carried out to study the effect of salt stress on cell membrane damage, ion content and antioxidant enzymes in wheat (Triticum aestivum) seedlings of two cultivars salt-tolerant KRL-19 and salt-sensitive WH-542. Seedlings (4-d-old) were irrigated with 0, 50 and 100 mM NaCl. Observations were recorded on the 3rd and 6th day after salt treatment and 2nd day after salt removal. The relative water content declined with induction of salt stress, more in WH-542 than in cv. KRL-19. K+/Na+ ratio in KRL-19 was higher than in WH-542. WH-542 suffered greater damage to cellular membranes due to lipid peroxidation as indicated by higher accumulation of H2O2, MDA and greater leakage of electrolytes than KRL-19. The activities of catalase, peroxidase and ascorbate peroxidase and glutathione reductase increased with increase in salt stress in both the cultivars, however, superoxide dismutase activity declined. Upon desalanization, partial recovery in the activities of these enzymes was observed in KRL-19 and very slow recovery in WH-542.
TL;DR: Findings indicate that injection of 15d-PGJ2 at the onset of ICH is associated with activation of PPARγ and elevation of catalase expression, suppression of NF-κB activity, and restricted neutrophil infiltration, which predicted reduced behavioral deficit and neuronal damage.
Abstract: Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a transcription factor that regulates the expression of various gene products that are essential in lipid and glucose metabolism, as well as that of the peroxisome-enriched antioxidant enzyme, catalase. Activation of PPARgamma is linked to anti-inflammatory activities and is beneficial for cardiovascular diseases. However, little is known about its role in intracerebral hemorrhage (ICH). 15-Deoxy-Delta(12,14)-prostaglandin J2 (15d-PGJ2) acts as a physiologic agonist for PPARgamma. In this study, we found that injection of 15d-PGJ2 into the locus of striatal hematoma increased PPARgamma-deoxyribonucleic acid (DNA) binding activity and the expression of catalase messenger ribonucleic acid (mRNA) and protein in the perihemorrhagic area. Additionally, 15d-PGJ2 significantly reduced nuclear factor-kappaB (NF-kappaB) activation and prevented neutrophil infiltration measured by myeloperoxidase (MPO) immunoassay, and also reduced cell apoptosis measured by terminal deoxynucleotide transferase dUTP nick-end labeling (TUNEL). In addition, 15d-PGJ2 reduced behavioral dysfunction produced by the ICH. Altogether, our findings indicate that injection of 15d-PGJ2 at the onset of ICH is associated with activation of PPARgamma and elevation of catalase expression, suppression of NF-kappaB activity, and restricted neutrophil infiltration. All these events predicted reduced behavioral deficit and neuronal damage.
TL;DR: Catalase is the key enzyme of ethanol oxidation in the brain of rodents: it may be responsible for about 60% of the process and alcohol dehydrogenase plays a minor role, if any, in this process.
Abstract: Background: The exact enzymatic mechanisms of ethanol oxidation in the brain are still unclear. The catalase-mediated oxidation of ethanol was demonstrated in rat brain using incubation of brain homogenates with catalase inhibitors. The role of the alcohol dehydrogenase (ADH) or cytochrome P450–dependent system in this process is possible, but has not been confirmed. The objective of the study was to determine the contribution of the different enzymatic pathways to ethanol oxidation in brain homogenates from mice and rats.
Methods: Three approaches were used to investigate the enzymatic mechanisms of ethanol oxidation in the brain of rats and mice: (1) preincubation of brain homogenates with inhibitors of the ethanol-metabolizing enzymes (catalase, CYP2E1, ADH, and ALDH); (2) utilization of mice with genetic deficiency in ethanol-metabolizing enzymes (catalase, CYP2E1, or both enzymes); and (3) determination of ethanol oxidation in brain subcellular fractions known to have differential activity of ethanol-metabolizing enzymes. The ethanol-derived acetaldehyde (AC) and acetate were determined in brain samples by gas chromatography.
Results: The catalase inhibitors sodium azide (5 mM) and aminotriazole (5 mM) as well as CYP2E1 inhibitors diallyl sulfide (2 mM) and β-phenethyl isothiocyanate (0.1 mM) lowered significantly the accumulation of the ethanol-derived AC and acetate in brain homogenates. The ADH inhibitor 4-methyl pyrazole (5 mM) significantly decreased the acetate but not the AC accumulation. Ethanol-derived AC accumulation in brain homogenates of acatalasemic mice was 47% of the control value, 91% in CYP2E1-null mice, and 24% in double mutants (with deficiency of both catalase and CYP2E1). The highest levels of ethanol oxidation were found in microsomal and peroxisomal subcellular brain fractions, where CYP2E1 and catalase are located, respectively.
Conclusions: Catalase is the key enzyme of ethanol oxidation in the brain of rodents: it may be responsible for about 60% of the process. CYP2E1 plays an important role in ethanol oxidation in the rodent brains. Alcohol dehydrogenase plays a minor role, if any, in this process. Aldehyde dehydrogenase plays the crucial role in the further oxidation of ethanol-derived AC in the brain homogenates.
TL;DR: It is hypothesized that H2S can reduce intracellular bound ferric iron to form unbound ferrous iron, which activates iron, and increase the hepatocyte formation of reactive oxygen species (ROS), which also involves a reactive sulfur species, which depletes GSH and activates oxygen to form ROS.
Abstract: Rationale. The toxicity of H2S has been attributed to its ability to inhibit cytochrome c oxidase in a similar manner to HCN. However, the successful use of methemoglobin for the treatment of HCN poisoning was not successful for H2S poisonings even though the ferric heme group of methemoglobin scavenges H2S. Thus, we speculated that other mechanisms contribute to H2S induced cytotoxicity. Experimental procedure. Hepatocyte isolation and viability and enzyme activities were measured as described by , and . Results. Incubation of isolated hepatocytes with NaHS solutions (a H2S source) resulted in glutathione (GSH) depletion. Moreover, GSH depletion was also observed in TRIS-HCl buffer (pH 6.0) treated with NaHS. Several ferric chelators (desferoxamime and DETAPAC) and antioxidant enzymes (superoxide dismutase [SOD] and catalase) prevented cell-free and hepatocyte GSH depletion. GSH-depleted hepatocytes were very susceptible to NaHS cytotoxicity, indicating that GSH detoxified NaHS or H2S in cells. Cytotoxic...
TL;DR: Results indicate that in olive plants, salinity causes reactive oxygen species (ROS)-mediated oxidative stress, and plants respond to this situation by inducing different antioxidative enzymes, especially the NADPH-producing dehydrogenases in order to recycle NADPH necessary for the protection against oxidative damages.
Abstract: NADPH is an important molecule in the redox balance of the cell. In this paper, using olive tissue cultures as a model of the function of the NADPH-generating dehydrogenases in the mechanism of oxidative stress induced by severe salinity conditions was studied. When olive (Olea europaea) plants were grown with 200 mM NaCl, a 40% reduction in leaf fresh weight was produced. The content of non-enzymatic antioxidants such as ascorbate and glutathione was diminished between 20% to 39%, whereas the H2O2 content was increased threefold. In contrast, the analysis of the activity and protein contents of the main antioxidative enzymes showed a significant increase of catalase, superoxide dismutase and glutathione reductase. Overall, these changes strongly suggests that NaCl induces oxidative stress in olive plants. On the other hand, while the content of glucose-6-phosphate was increased almost eightfold in leaves of plants grown under salt stress, the content of NAD(P)H (reduced and oxided forms) did not show significant variations. Under salt stress conditions, the activity and protein contents of the main NADPH-recycling enzymes, glucose-6-phosphate dehydrogenase (G6PDH), isocitrate dehydrogenase (ICDH), malic enzyme (ME) and ferrodoxin-NADP reductase (FNR) showed an enhancement of 30-50%. In leaves of olive plants grown with 200 mM NaCl, analysis of G6PDH by immunocytochemistry and confocal laser scanning microscopy showed a general increase of this protein in epidermis, palisade and spongy mesophyll cells. These results indicate that in olive plants, salinity causes reactive oxygen species (ROS)-mediated oxidative stress, and plants respond to this situation by inducing different antioxidative enzymes, especially the NADPH-producing dehydrogenases in order to recycle NADPH necessary for the protection against oxidative damages. These NADP-dehydrogenases appear to be key antioxidative enzymes in olive plants under salt stress conditions.
TL;DR: In this paper, a composition consisting of extracts of five widely studied medicinal plants (Protandim) was administered to healthy human subjects ranging in age from 20 to 78 years, and after 30 and 120 days of supplementation (675 mg/day) Erythrocytes were assayed for SOD and catalase, and plasma was assessed for lipid peroxidation products as thiobarbituric acid-reacting substances (TBARS), as well as uric acid, C-reactive protein, and cholesterol (total, LDL, and HDL).
TL;DR: Modulation of phase II antioxidant enzymes and oxidative status in the liver by phenolic acids may play an important role in the protection against adverse effects related to mutagenesis and oxidative damage.
Abstract: Phenolic acids are widespread in plant foods; they contain important biological and pharmacological properties, some of which were shown to be effective in preventing cancer. We investigated the modulatory effects of phenolic acids on an antioxidant system in male Sprague-Dawley rats. Rats were orally administrated gentisic acid (GEA), gallic acid (GA), ferulic acid (FA), and p-coumaric acid (p-CA) at a dosage of 100 mg/kg body weight for 14 consecutive days. At this dose, the activities of hepatic superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase were greater after administration of all 4 phenolic acids compared with the control group (P < 0.05). The activities of these enzymes in the small intestine of rats were also significantly greater after GA and p-CA treatment compared with controls. The changes in hepatic CuZnSOD, GPx, and catalase mRNA levels induced by phenolic acids were similar to those noted in the enzyme activities. Oxidized glutathione levels were lower (P < 0.05) in the liver of all phenolic acid-supplemented rats, whereas reduced glutathione was markedly higher than in control rats, especially after administration of GA and p-CA. The liver homogenates obtained from rats that had been administered phenolic acids had higher oxygen radical absorbance capacity than those obtained from control rats. Immunoblot analysis revealed an increased total level of Nrf2, a transcription factor governing the antioxidant response element in phenolic acid-supplemented rats. Phenolic acid-mediated antioxidant enzyme expression was accompanied by upregulation of multidrug resistance-associated protein Mrp3. These experiments show that modulation of phase II antioxidant enzymes and oxidative status in the liver by phenolic acids may play an important role in the protection against adverse effects related to mutagenesis and oxidative damage.
TL;DR: Catalase eliminated the bactericidal activity of Streptococcus pneumoniae toward Staphylococcus aureus and provided a possible mechanistic explanation for the interspecies interference observed in epidemiologic studies.
Abstract: The bactericidal activity of Streptococcus pneumoniae toward Staphylococcus aureus is mediated by hydrogen peroxide. Catalase eliminated this activity. Pneumococci grown anaerobically or genetically lacking pyruvate oxidase (SpxB) were not bactericidal, nor were nonpneumococcal streptococci. These results provide a possible mechanistic explanation for the interspecies interference observed in epidemiologic studies.
TL;DR: Oxidative stress biomarker analysis demonstrated significantly increased levels of protein carbonyls, lipid hydroperoxides, and 4-hydroxy-2-nonenal compared to control muscle, and antioxidant enzyme activities were altered, with a significant decrease in superoxide dismutase activity and significant increases in catalase and glutathione peroxidase.
TL;DR: It is suggested that Cr exerts a mild, although significant, antioxidant activity in living cells, via a mechanism depending on direct scavenging of reactive oxygen (in particular hydroxyl radical) and nitrogen species.
TL;DR: Findings indicate that microglial proliferation in response to IL-1β or TNF-α is mediated by hydrogen peroxide from NADPH oxidase.
Abstract: Microglia are resident brain macrophages that become activated and proliferate following brain damage or stimulation by immune mediators, such as IL-1β or TNF-α. We investigated the mechanisms by which microglial proliferation is regulated in primary cultures of rat glia. We found that basal proliferation of microglia was stimulated by proinflammatory cytokines IL-1β or TNF-α, and this proliferation was completely inhibited by catalase, implicating hydrogen peroxide as a mediator of proliferation. In addition, inhibitors of NADPH oxidase (diphenylene iodonium or apocynin) also prevented microglia proliferation, suggesting that this may be the source of hydrogen peroxide. IL-1β and TNF-α rapidly stimulated the rate of hydrogen peroxide produced by isolated microglia, and this was inhibited by diphenylene iodonium, implying that the cytokines were acting directly on microglia to stimulate the NADPH oxidase. Low concentrations of PMA or arachidonic acid (known activators of NADPH oxidase) or xanthine/xanthine oxidase or glucose oxidase (generating hydrogen peroxide) also increased microglia proliferation and this was blocked by catalase, showing that NADPH oxidase activation or hydrogen peroxide was sufficient to stimulate microglia proliferation. In contrast to microglia, the proliferation of astrocytes was unaffected by the presence of catalase. In conclusion, these findings indicate that microglial proliferation in response to IL-1β or TNF-α is mediated by hydrogen peroxide from NADPH oxidase.
TL;DR: The results are consistent with the hypothesis that increased concentrations of antioxidants form an important component of the defense of herbivorous insects against both exogenous and endogenous oxidative radicals.