Removal Of Peroxide Research Articles

Evaluation of commercial zerovalent iron sources in combination with solar energy to remove microcontaminants from natural water at circumneutral pH

Solar zerovalent iron (ZVI) was studied at circumneutral pH in combination with hydrogen peroxide and persulfate for removal of imidacloprid as a model contaminant in natural water. Three commercial ZVI sources, steel wool (ZVI-SW) and two iron micro-powders (ZVI-MS and ZVI-S) were independently evaluated. First, different ZVI corrosion conditions were tested in contact with air, exposed to natural solar radiation and with addition of oxidants, such as H2O2 and S2O82−, demonstrating the importance of released iron. Then, the technical feasibilities of solar/H2O2/ZVI and solar/S2O82−/ZVI were assessed for the elimination of 1 mg/L of imidacloprid. In general, H2O2 concentrations and treatment times were high. Only ZVI-MS (1 mM) reached 80% imidacloprid degradation after 157 min and 3 mM (102 mg/L) of H2O2. Solar/S2O82−/ZVI performance was better, reaching >80% imidacloprid degradation in <60 min with 1 mM (192 mg/L) S2O82− for all ZVI sources. Efficiency was highest with ZVI-MS, which was therefore selected for feasibility testing of a microcontaminant (MC) mixture containing 100 μg/L each of atrazine, carbendazim, imidacloprid and thiamethoxam with both solar/oxidizing agents/ZVI. H2O2 took 180 min to achieve 76% degradation of the sum of MCs, while 80% total degradation was reached after 69 min by adding S2O82−, confirming its higher efficiency. Finally, this study showed that ZVI in combination with solar radiation does not enhance significantly the photocatalytic cycle.

Regulation of Dual Activity of Ascorbate Peroxidase 1 From Arabidopsis thaliana by Conformational Changes and Posttranslational Modifications.

Ascorbate peroxidase (APX) is an important reactive oxygen species (ROS)-scavenging enzyme, which catalyzes the removal of hydrogen peroxide (H2O2) to prevent oxidative damage. The peroxidase activity of APX is regulated by posttranslational modifications (PTMs), such as S-nitrosylation, tyrosine nitration, and S-sulfhydration. In addition, it has been recently reported that APX functions as a molecular chaperone, protecting rice against heat stress. In this study, we attempted to identify the various functions of APX in Arabidopsis and the effects of PTMs on these functions. Cytosol type APX1 from Arabidopsis thaliana (AtAPX1) exists in multimeric forms ranging from dimeric to high-molecular-weight (HMW) complexes. Similar to the rice APX2, AtAPX1 plays a dual role behaving both as a regular peroxidase and a chaperone molecule. The dual activity of AtAPX1 was strongly related to its structural status. The main dimeric form of the AtAPX1 protein showed the highest peroxidase activity, whereas the HMW form exhibited the highest chaperone activity. Moreover, in vivo studies indicated that the structure of AtAPX1 was regulated by heat and salt stresses, with both involved in the association and dissociation of complexes, respectively. Additionally, we investigated the effects of S-nitrosylation, S-sulfhydration, and tyrosine nitration on the protein structure and functions using gel analysis and enzymatic activity assays. S-nitrosylation and S-sulfhydration positively regulated the peroxidase activity, whereas tyrosine nitration had a negative impact. However, no effects were observed on the chaperone function and the oligomeric status of AtAPX1. Our results will facilitate the understanding of the role and regulation of APX under abiotic stress and posttranslational modifications.

Application of Advanced Oxidation Process Using Ozonation Assisted with Hydrogen Peroxide for Organic Compounds Removal from Bayer Liquor

ABSTRACT One of the alumina industry’s main problems is the organic matter in the Bayer liquor during the Bayer Process released in the bauxite digestion process and accumulating in the process. It reduces as process efficiency and results in impurities in the final product. Several studies have shown that removing organic matter by ozonation can be attractive for industrial applications since ozone can be generated in situ and achieve faster results. For this reason, the goal of the present work was to study the removal of organic matter from the Bayer liquor. The effect of ozone dosage and O3/H2O2 combination was evaluated at 40 °C and 80 °C. Results indicated that the organic matter mineralization achieved 19% at 80 °C, using 6.5 g/L of O3 and 0.05 mol/L of H2O2, where 95.4% generated carbon dioxide. At the same conditions, 45.6% of oxalate was degraded. The UV/vis analyses demonstrated the decrease in organic chain size and the color of the samples before and after the oxidation process. An advanced oxidation process (O3 and O3/H2O2 combination) effectively removed a range of organic impurities from the Bayer liquor impacting the quality of the final product.

Antimicrobial activity of bleached cattail fibers (Typha domingensis) impregnated with silver nanoparticles and benzalkonium chloride

AbstractTypha domingensis (Cattail) fiber is a significant natural resource, abundant in cellulose. The study reports the useful utilization of T. domingensis fiber for physicochemical impregnation of silver nanoparticles and benzalkonium chloride, in the development of a material with antimicrobial activity. The fibers were pre‐treated with alkaline hydrogen peroxide (bleaching) for partial removal of lignin, pectin and waxes. Subsequently treated in a solution of different concentrations of benzalkonium chloride and Tollens' reagent. The new materials obtained were carefully investigated for their structure and thermal stability, morphology and susceptibility to antimicrobials (Staphylococcus aureus, Escherichia coli, Salmonella typhimuruim, and Salmonella enteritidis). Fourier transform infrared spectra showed the presence of benzalkonium chloride. The morphology analysis showed the silver nanoparticles on the surface of the bleached fibers. The susceptibility profile to antimicrobials was confirmed by the formation of inhibition halos (≅11.26 mm). Based on the properties of the materials obtained, it can be concluded that the modified cattail fibers have the potential to be used as a functional filler, or coating, in the development of antimicrobial composites.

Chloroplast thylakoid ascorbate peroxidase PtotAPX plays a key role in chloroplast development by decreasing hydrogen peroxide in Populus tomentosa.

Chloroplast development is a complex process that is critical to the growth and development of plants. However, the detailed mechanism of chloroplast development in woody plants remains unclear. In this study, we showed that chloroplasts with elaborate thylakoids could develop from proplastids in the cells of calli derived from leaf tissues of Populus tomentosa upon exposure to light. Chloroplast development was confirmed at the molecular and cellular levels. Transcriptome analysis revealed that genes related to photoreceptors and photosynthesis were significantly up-regulated during chloroplast development in a time-dependent manner. In light-induced chloroplast development, a key process was the removal of hydrogen peroxide, in which thylakoid-localized PtotAPX played a major role; light-induced chloroplast development was enhanced in PtotAPX-overexpressing transgenic P. tomentosa callus with lower levels of hydrogen peroxide, but was suppressed in PtotAPX antisense transgenic callus with higher levels of hydrogen peroxide. Moreover, the suppression of light-induced chloroplast development in PtotAPX antisense transgenic callus was relieved by the exogenous reactive oxygen species scavenging agent N,N'-dimethylthiourea (DMTU). Based on these results, we propose that PtotAPX-mediated removal of reactive oxygen species plays a key role in chloroplast development from proplastids upon exposure to light in P. tomentosa.

The Use of Hydrogen Peroxide and Hydrazine Sulfate for Removal of Chromium from Electroplating Effluents

The use of hydrogen peroxide and hydrazine sulfate for the treatment of chrome-containing rinsing waters of galvanic production of machine-building enterprises is proposed. The process of reducing chromium (6+) to (3+) from rinsing waters with a concentration of 8.55 mg/dm3 was studied. These reagents allow reducing more than 99% of chromium (6+) to chromium (3+) and maintaining a low salt content of treated wastewater. The consumption of hydrogen peroxide is 1.5 mg/dm3, and the consumption of hydrazine sulfate is 10 mg/dm3. The current situation in the treatment of galvanic wastewater leads to pollution of the environment with dangerous substances (CN-, Cr6+, F-, Cd2+), irrational use of raw materials and significant economic losses. The possibility of extracting valuable components from wastewater, in order to recycle them and return the treated water to production, is considered. Hydrogen peroxide is effective for treating acidic wastewater, and hydrazine sulfate can be used for both acidic and alkaline wastewater. Removal of excess hydrogen peroxide from the solution after reduction of chromium (6+) before precipitation of chromium (3+) hydroxide is required. The toxicity of hydrazine compounds must be taken into account.

Structure and functional properties of the cold-adapted catalase from Acinetobacter sp. Ver3 native to the Atacama plateau in northern Argentina.

Heme catalases remove hydrogen peroxide by catalyzing its dismutation into water and molecular oxygen, thereby protecting the cell from oxidative damage. The Atacama plateau in northern Argentina, located 4000 m above sea level, is a desert area characterized by extreme UV radiation, high salinity and a large temperature variation between day and night. Here, the heme catalase KatE1 from an Atacama Acinetobacter sp. isolate was cloned, expressed and purified, with the aim of investigating its extremophilic properties. Kinetic and stability assays indicate that KatE1 is maximally active at 50°C in alkaline media, with a nearly unchanged specific activity between 0°C and 40°C in the pH range 5.5-11.0. In addition, its three-dimensional crystallographic structure was solved, revealing minimal structural differences compared with its mesophilic and thermophilic analogues, except for a conserved methionine residue on the distal heme side, which is proposed to comprise a molecular adaptation to oxidative damage.

Experimental study on lowering oleic acid value and peroxide value of camellia sinensis by scraping film molecular distillation

Camellia oil is a kind of natural product with high added value. In the process of production, processing, and transportation, acidic substances and peroxides that reduce the quality of oil are produced. In this paper, it was refined by scraping membrane molecular distillation device. The factors affecting the molecular distillation results were analyzed and studied through a single factor experiment and orthogonal experiment. On the surface of the experiment, the optimal process parameters were as follows: the temperature was 190℃, the pressure was 1 Pa, the scraping speed was 300r/min, and the feed amount was 900g/h. Under this condition, the acid value in camellia oil decreased from 2.67mgKOH/g to 0.19mgKOH/g, and the free fatty acid removal rate was 92.88%. The peroxide value decreased from 16.78mmol/kg to 1.03mmol/kg, and the peroxide removal rate was 93.86%. The experimental results showed that the surface of the scraping membrane molecular distillation equipment could meet the national standard of acid value and peroxide value under the appropriate technological parameters, and there was no solvent residue, which was a safe physical purification process.

Nox4 Facilitates TGFβ1-Induced Fibrotic Response in Human Tenon's Fibroblasts and Promotes Wound Collagen Accumulation in Murine Model of Glaucoma Filtration Surgery.

Collagen accumulation in sub-conjunctival tissue at the surgical wound is one of the major complications associated with glaucoma filtration surgery (GFS). This process often leads to unwanted fibrotic scar formation at the lesion site and dysfunction of tissues. Previously, we demonstrated that NADPH oxidase 4 (Nox4) is implicated in transforming growth factor-beta (TGFβ)-induced collagen production in ocular fibroblasts and scarring responses in a mouse model of corneal injury. Here, we propose that Nox4 is an important facilitator of TGFβ-induced responses. We tested this hypothesis in human Tenon’s fibroblasts (HTF) and also assessed a role of Nox4 in an experimental mouse model of GFS. TGFβ1 induced Nox4 mRNA expression but downregulated Nox5 in HTF. Targeting Nox4 gene expression with an adenovirus carrying a Nox4 small interfering RNA (siRNA) (Ad-Nox4i) or removal of hydrogen peroxide (H2O2) with EUK-134 (25 μM) in HTFs significantly reduced TGFβ1-induced Nox4 expression, H2O2 production, and collagen synthesis (p < 0.05, n = 3–6). SIS3 (5 μM) that prevents Smad3 phosphorylation is found to suppress TGFβ1-induced collagen production in HTFs. Furthermore, Ad-Nox4i and EUK-134 both abolished TGFβ1-stimulated proliferation of HTFs. We also compared collagen deposition at the wound arising from GFS between wildtype (WT) and Nox4 knockout (KO) mice. Both collagen deposition and fibrovascularization at the wound were significantly decreased in Nox4 KO mice at 14 days after GFS. Our results provide comprehensive evidence that Nox4 is an important mediator for TGFβ1-induced responses in HTFs and collagen deposition in surgical wound following GFS in mice. As such, pharmacological inhibition of Nox4 would be a viable therapeutic strategy for the control of scarring after glaucoma surgery.

Dairy antioxidant system

A review of dairy antioxidants was done based on local and international sources. Oxidative processes of fat are the main cause of chemical spoilage of milk and dairy products. Lipid oxidation is associated mainly with the amount of unsaturated fatty acids in the shells of fat globules and plasma phospholipids, as well as with the amount of free fat. The products of oxidative reactions at different stages of lipid oxidation with atmospheric oxygen are fatty acid hydroperoxides, peroxides, aldehydes, ketones, hydroxy acidswhich not only worsen the organoleptic characteristics of milk, but some of them are toxic substances. The antioxidant ability of milk is due to vitamins A, C, E, carotenoids, enzymes, lactoferin, sulfur-containing amino acids. One of the most powerful natural antioxidants is ascorbic acid, which is able to absorb superoxide anion radicals, alkoxyl radicals, superoxide, iron oxide, nitric oxide. Group E vitaminsare described, being the primary fat-soluble antioxidants. Among this group of substances, the most biologically active form is ?-tocopherol. The contribution of carotenoids to antioxidant protection has been determined. Beta carotene is considered as a preventive antioxidant, as it can block singlet oxygen which ishighly toxic. The mechanisms of antioxidant action of various enzymes are disclosed. Xanthioxidase has been shown to oxidize various aldigides and purine bases to the corresponding acids. Lactoperoxidase catalyzes the oxidation of thiocyanate with hydrogen peroxide to form thiociagen. Catalase oxidizes hydrogen peroxide to form water and molecular oxygen. Glutathione peroxidase is capable of rapidly removing hydrogen peroxide and other peroxides. The mechanism of the antioxidant action of lactoferrin is described which is based on iron the chelation by it. The functions of sulfur-containing amino acids due to the binding of free radicals are disclosed. Determining the total antioxidant activity can be a biomarker of its biological value, which will allow to choose the most perspective areas of milk processing..

Data on the removal of peroxides from functionalized polyethylene glycol (PEG) and effects on the stability and sensitivity of resulting PEGylated conjugates.

Cyanine-5 (Cy5) is a fluorescent dye active in the far-red region of the visible spectrum (λex = 646 nm, λem = 662 nm) [1]. While Cy5 displays fluorescence in its oxidized form, it can be readily converted to its non-fluorescent hydrocyanine equivalent (H-Cy5) when exposed to reducing agents. H-Cy5 can then be converted back to its fluorescent oxidized form when exposed to reactive oxygen species (ROS), allowing it to act as a highly sensitive, high wavelength fluorescent ROS sensor [2]. However, H-Cy5 is a small, poorly water-soluble molecule, and is rapidly taken up into cells in vivo, preventing its use for sensing extracellular ROS, which are implicated in inflammation, wound healing, and other processes [3], [4], [5], [6]. A solution to this lies in the conjugation of Cy5 to a polyethylene glycol (PEG) polymer, increasing its solubility [7]. This conjugate (Cy5-PEG) can be reduced to H-Cy5-PEG to allow the highly sensitive detection of ROS in an aqueous extracellular environment. However, after PEG conjugation, a significant decrease in stability and sensitivity is observed, likely owing to the presence of ROS contaminants in commercial samples of PEG. It has been reported that these ROS impurities can be removed from PEG through a simple freeze-drying procedure [8]. Here, we demonstrate that a simple, straightforward method for the purification of PEG can allow the synthesis of a highly functional, water-soluble ROS sensor that could be used for extracellular ROS sensing.

Removal of Polycyclic Aromatic Hydrocarbons in a Heterogeneous Fenton Like Oxidation System Using Nanoscale Zero-Valent Iron as a Catalyst

Oil and gas effluents contains highly toxic and harmful organic pollutants. Therefore, it is necessary to eliminate and/or reduced the concertation of organic pollutants to a technologically acceptable levels before their discharge into water streams. This study investigates the application of nanoscale zero-valent iron (nZVI), and hydrogen peroxide (H2O2) for removal of organic pollutants from real oily produced water. Batch studies were performed and effect of different operating parameters, including concentration of nZVI and H2O2, pH and reaction time were studied. Moreover, optimization of independent variables was performed using central composite design (CCD) in response surface methodology (RSM). The experimental set up provided maximum removal efficiencies of 89.5% and 75.3% for polycyclic aromatic hydrocarbons (PAHs) and chemical oxygen demand (COD), respectively. The optimum values of independent variables such as concentrations of nZVI, and H2O2, contact time and pH were obtained as 4.35 g/L, 1.60 g/L, 199.9 min and 2.9, respectively. Predicted PAHs and COD removal efficiencies at the optimum values of independent variables were found as 89.3% and 75.7%, respectively which are in line with the experimental values. The study indicates that application of heterogeneous Fenton like oxidation system using nZVI as a catalyst is an efficient treatment method for removal of organic pollutants from real produced water.

Txn2 haplodeficiency does not affect cochlear antioxidant defenses or accelerate the progression of cochlear cell loss or hearing loss across the lifespan

Thioredoxin 2 (TXN2) is a small redox protein found in nearly all organisms. As a mitochondrial member of the thioredoxin antioxidant defense system, TXN2 interacts with peroxiredoxin 3 (PRDX3) to remove hydrogen peroxide. Accordingly, TXN2 is thought to play an important role in maintaining the appropriate mitochondrial redox environment and protecting the mitochondrial components against oxidative stress. In the current study, we investigated the effects of Txn2 haplodeficiency on cochlear antioxidant defenses, auditory function, and cochlear cell loss across the lifespan in wild-type (WT) and Txn2 heterozygous knockout (Txn2+/-) mice backcrossed onto CBA/CaJ mice, a well-established model of age-related hearing loss. Txn2+/- mice displayed a 58% decrease in TXN2 protein levels in the mitochondria of the inner ears compared to WT mice. However, Txn2 haplodeficiency did not affect the thioredoxin or glutathione antioxidant defense in both the mitochondria and cytosol of the inner ears of young mice. There were no differences in the levels of mitochondrial biogenesis markers, mitochondrial DNA content, or oxidative DNA and protein damage markers in the inner ears between young WT and Txn2+/- mice. In a mouse inner ear cell line, knockdown of Txn2 did not affect cell viability under hydrogen peroxide treatment. Consistent with the tissue and cell line results, there were no differences in hair cell loss or spiral ganglion neuron density between WT and Txn2+/- mice at 3-5 or 23-25months of age. Furthermore, Txn2 haplodeficiency did not affect auditory brainstem response threshold, wave I latency, or wave I amplitude at 3-5, 15-16, or 23-25months of age. Therefore, Txn2 haplodeficiency does not affect cochlear antioxidant defenses, accelerate degeneration of cochlear cells, or affect auditory function in mice across the lifespan.

Inflammation/bioenergetics-associated neurodegenerative pathologies and concomitant diseases: a role of mitochondria targeted catalase and xanthophylls

Various inflammatory stimuli are able to modify or even “re-program” the mitochondrial metabolism that results in generation of reactive oxygen species. In noncommunicable chronic diseases such as atherosclerosis and other cardiovascular pathologies, type 2 diabetes and metabolic syndrome, these modifications become systemic and are characterized by chronic inflammation and, in particular, “neuroinflammation” in the central nervous system. The processes associated with chronic inflammation are frequently grouped into “vicious circles” which are able to stimulate each other constantly amplifying the pathological events. These circles are evidently observed in Alzheimer’s disease, atherosclerosis, type 2 diabetes, metabolic syndrome and, possibly, other associated pathologies. Furthermore, chronic inflammation in peripheral tissues is frequently concomitant to Alzheimer’s disease. This is supposedly associated with some common genetic polymorphisms, for example, Apolipoprotein-E ε4 allele carriers with Alzheimer’s disease can also develop atherosclerosis. Notably, in the transgenic mice expressing the recombinant mitochondria targeted catalase, that removes hydrogen peroxide from mitochondria, demonstrates the significant pathology amelioration and health improvements. In addition, the beneficial effects of some natural products from the xanthophyll family, astaxanthin and fucoxanthin, which are able to target the reactive oxygen species at cellular or mitochondrial membranes, have been demonstrated in both animal and human studies. We propose that the normalization of mitochondrial functions could play a key role in the treatment of neurodegenerative disorders and other noncommunicable diseases associated with chronic inflammation in ageing. Furthermore, some prospective drugs based on mitochondria targeted catalase or xanthophylls could be used as an effective treatment of these pathologies, especially at early stages of their development.

Enhanced electrochemical oxidation process with hydrogen peroxide pretreatment for removal of high strength ammonia from semiconductor wastewater

Electrochemical oxidation (EO) process was investigated for decomposing ammonia in wastewater from semiconductor industry. This wastewater typically contains high concentration of hydrogen peroxide as well as ammonia in nature. As results of lab test, the presence of hydrogen peroxide exhibited a significant negative effect on ammonia removal efficiency, which was described by an oxidant-scavenging reaction pathway with recurrence relationship. Hydrogen peroxide removal by activated carbon was proposed as a pretreatment of EO process not only for the enhancement of reaction rate but also for the stability of effluent quality. As results of pilot test, ammonia removal rates were enhanced 2 ∼ 3.5 times after pretreatment. In addition, economic analysis results indicated that operating expense with pretreatment was about 60 % of that without pretreatment, which was about 30 % less than that in conventional chlorination without addition of hazardous chemicals. The suggested process has great potential for alternative to conventional chlorination in treatment of high strength ammonia wastewater from semiconductor industry.

Impairment of photosynthetic capacity and hydrogen peroxide removal in castor bean affected by bacterial leaf spot

Bacterial leaf spot caused by Xanthomonas axonopodis pv. ricini (Xar) is the only important disease of bacterial etiology reported to threaten castor bean production. No cultivars expressing resistance to the pathogen are known. Hence, knowledge of the physiological and biochemical alterations caused by the bacterium to castor bean plants could shed light into alternative approaches to obtain plant resistance. Leaf gas exchange parameters were measured with a portable infrared gas analyzer; Chlorophyll a fluorescence parameters were determined with an Imaging-PAM chlorophyll fluorometer; photosynthetic pigments, malondialdehyde (MDA) and activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POX) and glutathione reductase (GR) were quantified using standard biochemical assays; and production of hydrogen peroxide (H2O2) and superoxide anion (O2•-) was detected by histochemistry. Inoculated leaves exhibited significant reduction in photosynthetic capacity, accumulation of H2O2, absence of O2•- accumulation, higher concentrations of MDA and higher activities of SOD, APX and POX compared to non-inoculated plants. Bacterial infection of castor bean triggered severe alterations, mainly related to stomatal closure that consequently compromised the CO2 influx into infected tissue. Small increases in SOD activity seemed to be sufficient to remove O2•-, but detoxification of the H2O2 generated during the O2•- dismutation process appeared to be inefficient. Higher concentrations of MDA in inoculated compared to non-inoculated plants indicated membrane damage due to lipid peroxidation. Some of the physiological and biochemical alterations in castor bean plants resulting from Xar infection have not previously been reported for other plants infected by bacteria.

Poly(ethylene glycol)-based biofunctional hydrogels mediated by peroxidase-catalyzed cross-linking reactions

Biofunctional hydrogels prepared by a peroxidase, especially horseradish peroxidase (HRP), serve as an excellent class of materials or platform for the development of cellular scaffolds because their biocompatibility and mild and tunable reaction conditions provide them with desirable properties. In this focus review, we summarize our decade of research into HRP-mediated fabrication of biofunctional hydrogels and their applications, in particular cell culture scaffolds. A brief overview of potential substrates employed in HRP and improvement of the HRP hydrogelation system from the initial step until the hydrogen peroxide removal stage in an effort to meet environmental standards is discussed. We highlight our system and describe its biocompatibility and ability to functionalize molecules to support biofabrication by increasing cellular adhesiveness, retaining growth factor affinity, and finally accelerating the formation of two- and three-dimensional multicellular architectures. In the last section, we outline the adoption of hydrogelation as a self-standing, compartmentalized reaction system, i.e., the use of hydrogel marble to conduct cell-free biosynthesis. We believe that this HRP-mediated hydrogel system offers great potential not only as a cell culture scaffold but also for various biomedical applications. Biofunctional hydrogels were formed by horseradish peroxidase (HRP)-catalyzed cross-linking reaction. Poly(ethylene glycol) (PEG) incorporated with phenol or thiol group was used as a base polymer to form irreversible or redox responsive cross-links, respectively. Thiolated PEGs showed slower hydrogelation kinetics than phenolated ones; however, in the presence of phenolic small compounds, the cross-linking reaction was promoted without the aid of exogenous hydrogen peroxide. Moreover, in situ incorporation of bioactive entities, such as proteins, realized biofunctionalization of hydrogels for potential applications for bioengineering and biomedical applications.

Modulation of (Homo)Glutathione Metabolism and H2O2 Accumulation during Soybean Cyst Nematode Infections in Susceptible and Resistant Soybean Cultivars.

In plant immune responses, reactive oxygen species (ROS) act as signaling molecules that activate defense pathways against pathogens, especially following resistance (R) gene-mediated pathogen recognition. Glutathione (GSH), an antioxidant and redox regulator, participates in the removal of hydrogen peroxide (H2O2). However, the mechanism of GSH-mediated H2O2 generation in soybeans (Glycine max (L.) Merr.) that are resistant to the soybean cyst nematode (SCN; Heterodera glycines Ichinohe) remains unclear. To elucidate this underlying relationship, the feeding of race 3 of H. glycines with resistant cultivars, Peking and PI88788, was compared with that on a susceptible soybean cultivar, Williams 82. After 5, 10, and 15 days of SCN infection, we quantified γ-glutamylcysteine (γ-EC) and (homo)glutathione ((h)GSH), and a gene expression analysis showed that GSH metabolism in resistant cultivars differed from that in susceptible soybean roots. ROS accumulation was examined both in resistant and susceptible roots upon SCN infection. The time of intense ROS generation was related to the differences of resistance mechanisms in Peking and PI88788. ROS accumulation that was caused by the (h)GSH depletion-arrested nematode development in susceptible Williams 82. These results suggest that (h)GSH metabolism in resistant soybeans plays a key role in the regulation of ROS-generated signals, leading to resistance against nematodes.

Triplaris gardneriana seeds extract exhibits in vitro anti-inflammatory properties in human neutrophils after oxidative treatment.

Triplaris gardneriana Wedd. (Polygonaceae family) is a plant species from Brazilian semiarid region which is used in local traditional medicine for the treatment of inflammatory conditions such as hemorrhoids. In this study, the in vitro anti-inflammatory activity of different concentrations of ethanolic extract from T. gardneriana seeds (EETg) was performed in order to contribute to the knowledge about etnomedicinal use of this plant species. The anti-inflammatory properties were evaluated through different approaches, such as in vitro protein anti-denaturation test, scavenging of reactive oxygen species (ROS) and myeloperoxidase (MPO) inhibition in human neutrophils activated by phorbol-12-myristate-13-acetate (PMA). Besides that, molecular docking was performed to provide new insights about the interaction between the major phenolic components in the plant extract and MPO. EETg was characterized showing a total phenol content of 153.5±6.3μg gallic acid equivalent/mg extract, ability to remove hydrogen peroxide (H2O2) in a concentration-dependent manner and had a spectroscopic profile which suggests the presence of hydroxyl groups. EETg was able to prevent protein denaturation ranging from 40.17 to 75.09%. The extract, at 10 and 20μg/mL, was able to modulate neutrophils pro-inflammatory functions, such as degranulation and burst respiratory. In both assays, the EETg had anti-inflammatory effect comparable to nonsteroidal anti-inflammatory drugs. Among the main phenolic compounds of EETg, quercitrin, quercetin and catechin showed the highest binding affinity in silico to MPO. This study demonstrated, for the first time, that the anti-inflammatory effect of T. gardneriana seeds occurs due to its modulatory effect on human neutrophil degranulation and free-radical scavenging activity.

Systemic Lupus Erythematosus: Pathogenesis at the Functional Limit of Redox Homeostasis

Systemic lupus erythematosus (SLE) is a disease characterized by the production of autoreactive antibodies and cytokines, which are thought to have a major role in disease activity and progression. Immune system exposure to excessive amounts of autoantigens that are not efficiently removed is reported to play a significant role in the generation of autoantibodies and the pathogenesis of SLE. While several mechanisms of cell death-based autoantigenic exposure and compromised autoantigen removal have been described in relation to disease onset, a significant association with the development of SLE can be attributed to increased apoptosis and impaired phagocytosis of apoptotic cells. Both apoptosis and impaired phagocytosis can be caused by hydrogen peroxide whose cellular production is enhanced by exposure to endogenous hormones or environmental chemicals, which have been implicated in the pathogenesis of SLE. Hydrogen peroxide can cause lymphocyte apoptosis and glutathione depletion, both of which are associated with the severity of SLE. The cellular accumulation of hydrogen peroxide is facilitated by the myriad of stimuli causing increased cellular bioenergetic activity that enhances metabolic production of this toxic oxidizing agent such as emotional stress and infection, which are recognized SLE exacerbating factors. When combined with impaired cellular hydrogen peroxide removal caused by xenobiotics and genetically compromised hydrogen peroxide elimination due to enzymatic polymorphic variation, a mechanism for cellular accumulation of hydrogen peroxide emerges, leading to hydrogen peroxide-induced apoptosis and impaired phagocytosis, enhanced autoantigen exposure, formation of autoantibodies, and development of SLE.