Inhibition Of O2 Research Articles

Extracellular redox state shift: A novel approach to target prostate cancer invasion.

Extracellular superoxide dismutase (ECSOD) and the cysteine/glutamate transporter (Cys)/(xCT) are tumor microenvironment (TME) redox state homeostasis regulators. Altered expression of ECSOD and xCT can lead to imbalance of the TME redox state and likely have a profound effect on cancer invasion. In the present study, we investigated whether ECSOD and xCT could be therapeutic targets for prostate cancer (PCa) invasion. Immunohistochemistry of tumor microarray PCa tissues (N = 165) with high Gleason scores indicated that xCT protein expression is significantly increased while ECSOD protein expression is significantly decreased. Metastatic PCa indicated ECSOD protein expression is significantly decreased in epithelial area whereas xCT protein expression is significantly increased in stromal area. Furthermore, inhibition of extracellular O2•- by overexpression of ECSOD or alteration of the extracellular Cys/CySS ratio by knockdown of xCT protein inhibited PCa cell invasion. Simultaneous overexpression of ECSOD and knockdown xCT inhibited PCa cell invasion more than overexpression of ECSOD or knockdown of xCT alone. In the co-culturing system, simultaneous overexpression of ECSOD and knockdown of xCT in prostate stromal WPMY-1 cells inhibited PCa cell invasiveness more than overexpression of ECSOD alone. The decrease in PCa invasion correlated with increased of extracellular H2O2 levels. Notably, overexpression of catalase in TME reversed the inhibitory effect of ECSOD on cancer cell invasion. Impaired ECSOD activity and an upregulated of xCT protein expression may be clinical features of an aggressive PCa, particularly metastatic cancers and/or those with a high Gleason score. Therefore, shifting the extracellular redox state toward an oxidizing status by targeted modulation of ECSOD and xCT, in both cancer and stromal cells, may provide a greater strategy for potential therapeutic interventions of aggressive PCa.

Cooking treatments effect on bioactive compounds and antioxidant activity of quintonil (Amaranthus hybridus) harvested in spring and fall seasons

ABSTRACTThis study investigated the effects of cooking treatments (boiling and steaming) and season of the year (spring and fall) on vitamin C content, total phenolics content (TPC), total flavonoids content (TFC), antioxidant activity and scavenging of nitric oxide (NO•), and superoxide radical (O2–). After cooking, a significant decrease in vitamin C was observed (50 and 48.8% for boiling and 21 and 27.9% for steaming in spring and fall, respectively). TPC and TFC increased during steaming from 145–1480 mg GAE/kg and 348.6–797.2 mg QE/kg, respectively. DPPH values ranged from 2806–3801 μmol TE/kg and was affected by season whereas ORAC ranged from 1231.3–36,167.2 μmol TE/kg and was affected by cooking. The ability to scavenge NO• and O2–, were not affected by neither cooking nor season. However, the inhibition of O2– was higher for quintonil steamed in spring.

Chemical analyzes and antioxidant activities of essential oils of four wild Mentha species growing in the Tokat and its districts

The current work evaluated the chemical compositions of the essential oils (EOs) extracted from Mentha longifolia subsp. typhoides (Briq.) Harley var. typhoides PH. Davis, Mentha spicate L. subsp.spicata, Mentha longifolia (L.) Hudson subsp.longifolia and Mentha villoso nervata Opiz from gowning in the different locations of Tokat. The antioxidant activities of EOs were tested using total antioxidant activity, reducing power, inhibition of lipid peroxidation, metal chelating, H2O2, DPPH˙ and O2˙- scavenging activities. The chemical compositions of EOs were determined by GC and GC-MS. Significant differences were recorded between the percentages of many constituents depending on the geographical. The most important components were identified consecutively: linalool (nd-62.80%), menthone (0.31-60.81%), pulegone (nd-21.52%), isomenthone (nd-30.15%) and piperitoneoxide (nd-68.92%). The inhibition of lipid peroxidation, O2˙- and H2O2 scavenging activities of the EOs were very effective but their reduction power values were low. The results obtained validate that EOs of four Mentha species possess a source of antioxidant potential for medicinal and foods.

Metformin accelerates wound healing in type 2 diabetic db/db mice.

Wound healing impairment is increasingly recognized to be a consequence of hyperglycemia-induced dysfunction of endothelial precursor cells (EPCs) in type 2 diabetes mellitus (T2DM). Metformin exhibits potential for the improvement of endothelial function and the wound healing process. However, the underlying mechanisms for the observed beneficial effects of metformin application remain to be completely understood. The present study assessed whether metformin, a widely used therapeutic drug for T2DM, may accelerate wound closure in T2DM db/db mice. Genetically hyperglycemic db/db mice were used as the T2DM model. Metformin (250 mg/kg/day; intragastric) was administered for two weeks prior to EPC collection and wound model creation in db/db mice. Wound healing was evaluated by alterations in the wound area and the number of platelet endothelial cell adhesion molecule-positive cells. The function of the isolated bone marrow-derived EPCs (BM-EPCs) was assessed by a tube formation assay. The number of circulating EPCs, and the levels of intracellular nitric oxide (NO) and superoxide (O2−) were detected by flow cytometry. Thrombospondin-1 (TSP-1) expression was determined by western blot analysis. It was observed that treatment with metformin accelerated wound healing, improved angiogenesis and increased the circulating EPC number in db/db mice. In vitro, treatment with metformin reversed the impaired BM-EPC function reflected by tube formation, and significantly increased NO production while decreasing O2− levels in BM-EPCs from db/db mice. In addition, TSP-1 expression was markedly attenuated by treatment with metformin in cultured BM-EPCs. Metformin contributed to wound healing and improved angiogenesis in T2DM mice, which was, in part, associated with stimulation of NO, and inhibition of O2− and TSP-1 in EPCs from db/db mice.

Apium graveolens extract influences mood and cognition in healthy mice.

Apium graveolens is a food flavoring which possesses various health promoting effects. This study investigates the effect of a sub-acute administration of A. graveolens on cognition and anti-depression behaviors via antioxidant and related neurotransmitter systems in mice brains. Cognition and depression was assessed by various models of behavior. The antioxidant system of glutathione peroxidase (GPx), % inhibition of superoxide anion (O2-), and lipid peroxidation were studied. In addition, neurochemical parameters including acetylcholinesterase (AChE) and monoamine oxidase-type A (MAO-A) were also evaluated. Nine groups of male mice were fed for 30days with different substances-a control, vehicle, A. graveolens extract (65-500mg/kg), and reference drugs (donepezil and fluoxetine). The results indicated that the effect of the intake of A. graveolens extract (125-500mg/kg) was similar to the reference drugs, as it improved both spatial and non-spatial memories. Moreover, there was a decrease in immobility time in both the forced swimming and tail suspension tests. In addition, the A. graveolens extract reduced lipid peroxidation of the brain and increased GPx activity and the % inhibition of O2-, whereas the activities of AChE and MAO-A were decreased. Thus, our data have shown that the consumption of A. graveolens extract improved cognitive function and anti-depression activities as well as modulating the endogenous antioxidant and neurotransmitter systems in the brain, resulting in increased neuronal density. This result indicated an important role for A. graveolens extract in preventing age-associated decline in cognitive function associated with depression.

Phenolic Content, Lipid Peroxidation Inhibition and Antioxidant Potential of Leaf Essential Oil of Ginkgo biloba in Various Scavenging Models

Current study was aimed to evaluate antioxidant and lipid peroxidation inhibition efficacy of Ginkgo biloba leaf essential oil (GBEO) in different radical scavenging models along with total phenolic content. The GBEO exhibited potent antioxidant effect on the inhibition of DPPH, NO, O2−, and OH− radicals by 75.47, 72.42, 72.24 and 73.67%, whereas IC50 values of GBEO were found to be 222.08, 247.23, 132.85, and 305.06 μg/ml, respectively. In addition, the GBEO evoked significant reducing power efficacy and profound inhibitory effect on lipid-peroxidation induced by ferric ions in a dose-dependent manner. Moreover, the GBEO yielded 8.60 ± 0.01 mg/g GAE phenolic contents, confirming its role as a natural antioxidant.

266 - Alteration of Tumor Microenvironmental Redox State Inhibits Prostate Cancer Metastasis

Cancer cells exhibit a plasticity of redox state so that the conversion between redox status in tumor microenvironment (TME) can be accomplished rapidly, thus, extracellular redox-related proteins may be a new potential therapeutic targets for metastasis. Cysteine(CyS)/glutamate transporter(xCT) and extracellular superoxide dismutase (ECSOD) are mainly TME-redox state hemeostasis regulator, one control redox coupling ratio CyS/Cystine(CySS), the latter control prooxidants level. Herein, we demonstrated xCT protein expression is significantly increased and correlated with high Gleason score PCa tissues. In contrast, ECSOD protein expression is significantly decreased in high Gleason score PCa tissues. A decrease in ECSOD may result in elevation of extracellular prooxidant levels due to the increase in O2●– and OONO●, while overexpression of xCT may result in imbalance of extracellular thiol couples. These changes in the extracellular redox state are likely to have a profound effect on activation of invasion-related proteins. Inhibition of extracellular O2●– by overexpression of ECSOD using adenovirus SOD3 transduction or altering extracellular Cys/CySS levels by knock-downed xCT protein expression using siRNA xCT resulted in inhibition of PCa cell invasion and decreased activity of MMP2. Simultaneously overexpressed ECSOD and knock-downed xCT inhibited PCa cell invasion greater than overexpressed ECSOD or knock-downed xCT alone (~70%, 50%, and 30%, respectively). In the co-culturing system, overexpressed ECSOD and knock-downed xCT in both PC3 and stromal cells (WPMY-1) decreased PCa cell invasion greater than overexpressed ECSOD and knock-downed xCT in only PC3 cells or stromal cells. In conclusion, our data indicated that synergic modulation of ECSOD and xCT expression would elevate the success of site- specific redox based therapies at TME. Since, paracrine signaling from stromal cells induce PCa cells to grow and metastatic, targeting ECSOD and xCT in both cancer and stromal cells would provide a greater inhibition of PCa metastasis.

Effects of C60 on the Photochemical Formation of Reactive Oxygen Species from Natural Organic Matter.

Buckminsterfullerenes (C60) are widely used nanomaterials that are present in surface water. The combination of C60 and humic acid (HA) generates reactive oxygen species (ROS) under solar irradiation, but this process is not well understood. Thus, the present study focused on the photochemical formation of singlet oxygen (1O2), hydroxyl radical (HO•)-like species, superoxide radicals (O2•-), hydrogen peroxide (H2O2), and triplet excited states (3C60*/3HA*) in solutions containing both C60 and HA. The quantum yield coefficients of excited triplet states (fTMP) and apparent quantum yields of ROS were measured and compared to the calculated values, which were based on the conservative mixing model. Although C60 proved to have only a slight impact on the 1O2 formation from HA, C60 played a key role in the inhibition of O2•-. The photochemical formation of H2O2 followed the conservative mixing model due to the reaction of C60•- with HO2•/O2•-, and the biomolecular reaction rate constant has been measured as (7.4 ± 0.6) × 106 M-1 s-1. The apparent fTMP was significantly lower than the calculated value, indicating that the steric effect of HA was significant in the reaction of 3C60* with the TMP probe. In contrast, C60 did not have an effect on the photochemical formation of HO• from HA, suggesting that HO• is elevated from the hydrophilic surface of HA. The aforementioned results may be useful for predicting the photochemical influence of C60 on aqueous environments.

Glutathione improves survival of cryopreserved embryogenic calli of Agapanthus praecox subsp. orientalis

The effect of supplementation of reduced glutathione (GSH) to cryoprotectant solution on the generation of reactive oxygen species (ROS) (e.g., H2O2, OH·, and O2·−) and antioxidants (e.g., SOD, POD, CAT, AsA, and GSH), as well as membrane lipid peroxidation (i.e., MDA content) mitigation in cryopreserving of embryogenic calli (EC) of Agapanthus praecox subsp. orientalis was investigated. The vitrification-based cryopreservation method was used in this study. The addition of GSH at a final concentration of 0.08 mM to the cryoprotectant solution has significantly improved cryotolerance of A. praecox EC. The EC post-thaw survival rate increased by 68.34 % using the cryoprotectant solution containing 0.08 mM GSH as compared to the control (GSH-free). EC treated with GSH displayed the reduction in OH· generation activity and the contents of H2O2 and MDA, as well as enhancement in the inhibition of O2·− generation and the antioxidant activity. Treatment with exogenous GSH also increased endogenous AsA and GSH contents after dehydration step. Expression of stress-responsive genes, e.g., peroxidase (POD), peroxiredoxin, ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), and glutathione peroxidase (GPX), was also increased during cryopreservation processes. The expression of DAD1 (Defender against apoptotic cell death) was elevated, while cell death-related protease SBT was suppressed. These results demonstrated that the addition of GSH to cryoprotectant solution affects the ROS level and could effectively improve survival of A. praecox EC through enhancing antioxidant enzyme activities and decreasing cell death.

Galangin competitively inhibits xanthine oxidase by a ping-pong mechanism

Galangin is a natural flavonol isolated from plants with potent biological activities. Galangin was found to significantly inhibit xanthine oxidase (XOD) activity in a competitive manner with the generation of superoxide radical (O2−) in the enzyme catalysis, but galangin showed insignificant scavenging activity on 1,1-diphenyl-2-picryhydrazyl (DPPH) and O2– radicals. These results demonstrated that inhibition of O2– radical generation by galangin may be due to the competitive inhibition of uric acid formation by a ping-pong mechanism. XOD had one high affinity binding site for galangin with a binding constant of 3.60×104Lmol−1 at 298K. Hydrogen bond and hydrophobic interaction dominated the binding process on account of the negative enthalpy and positive entropy changes. The binding of galangin to XOD induced an increase in α-helix and random coil contents and a decrease in β-sheet and β-turn contents of XOD. Further molecular docking study validated that galangin can competitively bind to the site in the molybdenum atomic (Mo) domain, occupying the catalytic center to avoid the entrance of the substrate xanthine, resulting in the inhibition of XOD activity. These findings have provided new insights into the two-substrate kinetics of galangin on XOD and useful information for functional research of galangin in the treatment of gout and oxidative damage.

Mechanisms of the Macrolide-Induced Inhibition of Superoxide Generation by Neutrophils.

The effect of macrolides on the superoxide (O2 (-)) production by neutrophils was studied. Resting neutrophils become primed by lipopolysaccharide (LPS) or N-formyl-methionyl-leucyl-phenylalanine (fMLP), and primed neutrophils generate O2 (-) in response to fMLP or adhesion, respectively. Both LPS-primed fMLP-stimulated O2 (-) generation by macrolide-treated neutrophils and adhesion-stimulated O2 (-) generation by macrolide-treated fMLP-primed neutrophils were inhibited. Macrolide inhibition of O2 (-) generation was dependent on serum or pH. Serum could be substituted by NaHCO3. The intensity of inhibition was azithromycin = roxithromycin > clarithromycin > erythromycin, in that order. Non-antimicrobial derivatives of erythromycin, that is, EM703 and EM900, inhibited O2 (-) generation at pH 7.4. NH4Cl abolished the activity of azithromycin (AZ) only when added to neutrophils with AZ but not after incubation with AZ, suggesting that NH4Cl prevented the influx of AZ. AZ did not affect the expression of alkaline phosphatase, CD11b, and cytochrome b558 in both resting and LPS-primed neutrophils. These results suggested that macrolides did not affect granule mobilization but inhibited O2 (-) generation selectively.

Redox Nanoparticle Therapeutics for Acetaminophen-Induced Hepatotoxicity in Mice.

The purpose of this study was to evaluate the hepatoprotective effect of an antioxidative nanoparticle (RNPN) recently developed against APAP-induced hepatotoxicity in mice. The effects of oral administration of RNPN to APAP-treated mice were assessed for various biochemical liver function parameters: alanine transaminase (ALT) activity, aspartate transaminase (AST) activity, alkaline phosphatase (ALP) activity, prothrombin time, and serum albumin (ALB) level. The treatment effects were assessed in terms of free radical parameters: malondialdehyde (MDA) accumulation, glutathione peroxidase (GPx) activity, % inhibition of superoxide anion (O2 −∙), and histopathological examination. The N-acetylcysteine (NAC)-treated group exhibited an enhanced prothrombin time relative to the control group, while RNPN did not prolong prothrombin time. The RNPN-treated animals exhibited lower levels of ALT, AST, and ALP, while increased ALB levels were measured in these animals compared to those in the other groups. The RNPN-treated animals furthermore exhibited improved MDA levels, GPx activity, and % inhibition of O2 −∙, which relate to oxidative damage. Histological staining of liver tissues from RNPN-treated animals did not reveal any microscopic changes relative to the other groups. The findings of this study suggest that RNPN possesses effective hepatoprotective properties and does not exhibit the notable adverse effects associated with NAC treatment.

The Impact of Hydroxylase Inhibition on TGF‐β1 Induced Fibrosis Associated with Inflammatory Bowel Disease

Fibrosis is a complication of chronic inflammatory disorders such as inflammatory bowel disease (IBD). Fibrosis is responsible for 75% of surgical interventions in IBD. Pharmacological inhibition of O2 sensing hydroxylases ameliorates inflammation in models of IBD. We hypothesized that hydroxylase inhibition may also impact fibrosis in IBD. To test this, the effect of the hydroxylase inhibitor DMOG was investigated. Mice exposed to 2.5% dextran sodium sulphate in drinking water for 5 days and allowed to recover for 14 days, developed colon fibrosis reflected by an altered pattern of submucosal collagen deposition, increased fibroblast infiltration and higher expression of Smad3. Mice treated with DMOG exhibited lower submucosal collagen accumulation, reduced fibroblast infiltration and less Smad3 positive staining. An in vitro model was then used to investigate the mechanism of the anti‐fibrotic action of DMOG. Fibroblasts were treated with TGF‐β1, key mediator of fibrosis. DMOG was given to the cells prior to TGF‐β1, and α‐smooth muscle actin (α‐SMA) and collagen‐I were analyzed as markers of fibrosis. TGF‐β1 induced phenotypic changes associated to higher expression of collagen‐I and α‐SMA. Both markers were reduced in DMOG treated cells, suggesting an inhibition of TGF‐β1 mediated fibroblast activation. We further investigated the impact of DMOG upon TGF‐β1 signalling. DMOG did not affect Smad2/3 (canonical) TGF dependent phosphorylation. In contrast, it reduced TGF‐β1 dependent ERK (non canonical) phosphorylation. In conclusion, hydroxylase inhibition reduces fibrosis in vitro and in vivo, at least in part, through the inhibition of non canonical TGF‐β signalling.

In vitro anti-inflammatory effects of diterpenoids and sesquiterpenoids from traditional Chinese medicine Siegesbeckia pubescens

Oxidative stress imposed by reactive oxygen species plays a crucial role in pathophysiology of inflammatory diseases. In the present study, sesquiterpenoids and diterpenoids isolated from Siegesbeckia pubescens, a Chinese traditional medicine used to treat arthritis, were evaluated for inhibition of NO production in activated RAW 264.7 macrophages and FMLP/CB induced O2·- generation and elastase release in human neutrophils. In the former assay, sesquiterpenoids were more potent than diterpenoids. The C-4 carbonyl group in the carabrane-type sesquiterpenoid 3 and the C-9 ether linkage in the germacrane sesquiterpene 7 were associated with the enhanced potency. Also, for the active ent-kaurane type diterpenoids, esterification of 17-OH with isobutyric acid and acetylation of 18-OH affected the inhibition of O2·- generation and elastase release. This report is the first to describe the inhibitory effects on oxidative stress of secondary metabolites from S. pubescens. Its findings suggest that active terpenoids from the herb could be used as lead anti-inflammatory agents.

Upregulation of cannabinoid receptor‐1 and fibrotic activation of mouse hepatic stellate cells during Schistosoma J. infection: role of NADPH oxidase (693.13)

The endocannabinoid system (CS) has been implicated in schistosomiasis‐associated liver fibrosis (SSLF). However, the molecular mechanisms mediating the action of the CS in SSLF are largely unknown. The present study hypothesized that Schistosoma J. infection upregulates cannabinoid receptor (CB) signaling via activation of NADPH oxidase leading to a fibrotic phenotype in hepatic stellate cells (HSCs). A SSLF model was developed by infecting mice with Schistosoma J. cercariae in the skin. HSCs from uninfected (control) or Schistosoma J.‐infected (SSLF) mice were isolated, cultured and identified by analyzing HSC markers α‐SMA and desmin. In HSCs isolated from control or SSLF mice, both CB1 and CB2 receptors were detected, however, only the CB1 significantly increased in HSCs from SSLF mice compared to that control mice. Such increase of CB1 in HSCs was accompanied by enhanced expression of fibrotic markers α‐SMA, collagen I, and TIMP‐1. Similarly, CB1 upregulation and enhanced fibrotic changes were observed in HSCs isolated from control mice when these cells were treated with soluble egg antigen (SEA) from Schistosoma J. Interestingly, HSCs from SSLF mice or SEA‐treated HSCs from control mice exhibited enhanced superoxide (O2.‐) production as analyzed by electron spin resonance. Importantly, inhibition of O2.‐ production by knocking down NADPH oxidase genes (Nox1 or Nox4) prevented SEA‐induced upregulation of CB1 and fibrotic markers in HSCs. Further, CB1 gene silencing blocked SEA‐induced fibrotic changes in HSCs but had no effect on SEA‐induced O2.‐ production in these cells indicating a triggering role of O2.‐ production in CB1‐mediated fibrotic signaling. Taken together, these data suggest that the fibrotic activation of HSCs upon Schistosoma J. infection or SEA stimulation is associated with NADPH oxidase‐mediated redox regulation of CB1 expression, which may be a triggering mechanism for SSLF.Grant Funding Source: Supported by NIH grants HL057244, HL091464 and HL075316

Upregulation of cannabinoid receptor-1 and fibrotic activation of mouse hepatic stellate cells during Schistosoma J. infection: Role of NADPH oxidase

The endocannabinoid system (CS) has been implicated in the development of hepatic fibrosis such as schistosomiasis-associated liver fibrosis (SSLF). However, the mechanisms mediating the action of the CS in hepatic fibrosis are unclear. The present study hypothesized that Schistosoma J. infection upregulates cannabinoid receptor 1 (CB1) due to activation of NADPH oxidase leading to a fibrotic phenotype in hepatic stellate cells (HSCs). The SSLF model was developed by infecting mice with Schistosoma J. cercariae in the skin, and HSCs from control and infected mice were then isolated, cultured, and confirmed by analysis of HSC markers α-SMA and desmin. CB1 significantly increased in HSCs isolated from mice with SSLF, which was accompanied by a greater expression of fibrotic markers α-SMA, collagen I, and TIMP-1. CB1 upregulation and enhanced fibrotic changes were also observed in normal HSCs treated with soluble egg antigen (SEA) from Schistosoma J. Electron spin resonance (ESR) analysis further demonstrated that superoxide (O2−) production was increased in infected HSCs or normal HSCs stimulated with SEA. Both Nox4 and Nox1 siRNA prevented SEA-induced upregulation of CB1, α-SMA, collagen I, and TIMP-1 by inhibition of O2− production, while CB1 siRNA blocked SEA-induced fibrotic changes without effect on O2− production in these HSCs. Taken together, these data suggest that the fibrotic activation of HSCs on Schistosoma J. infection or SEA stimulation is associated with NADPH oxidase-mediated redox regulation of CB1 expression, which may be a triggering mechanism for SSLF.

Feijoa sellowianaBerg Fruit Juice: Anti-Inflammatory Effect and Activity on Superoxide Anion Generation

Feijoa sellowiana Berg var. coolidge fruit juice was studied in vivo for the anti-inflammatory activity by carrageenin-induced paw edema test and in vitro for the effects on superoxide anion release from neutrophils in human whole blood. The fruit juice was analyzed by the high-performance liquid chromatography method, and quercetin, ellagic acid, catechin, rutin, eriodictyol, gallic acid, pyrocatechol, syringic acid, and eriocitrin were identified. The results showed a significant anti-inflammatory activity of F. sellowiana fruit juice, sustained also by an effective antioxidant activity observed in preliminary studies on 1,1-diphenyl-2-picrylhydrazyl (DPPH) test. In particular, the anti-inflammatory activity edema inhibition is significant since the first hour (44.11%) and persists until the fifth hour (44.12%) of the treatment. The effect on superoxide anion release was studied in human whole blood, in the presence of activators affecting neutrophils by different mechanisms. The juice showed an inhibiting response on neutrophils basal activity in all experimental conditions. In stimulated neutrophils, the higher inhibition of superoxide anion generation was observed at concentration of 10(-4) and 10(-2) mg/mL in whole blood stimulate with phorbol-myristate-13-acetate (PMA; 20% and 40%) and with N-formyl-methionyl-leucyl-phenylalanine (FMLP; 15% and 48%). The significant reduction of edema and the inhibition of O2(-) production, occurring mainly through interaction with protein-kinase C pathway, confirm the anti-inflammatory effect of F. sellowiana fruit juice.

Scavenging of reactive oxygen species induced by hyperthermia in biological fluid

The scavenging activity of rat plasma against hyperthermia-induced reactive oxygen species was tested. The glutathione-dependent reduction of a nitroxyl radical, 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl, which was restricted by adding superoxide dismutase or by deoxygenating the reaction mixture, was applied to an index of superoxide (O2•−) generation. A reaction mixture containing 0.1 mM 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl and 1 mM glutathione was prepared using 100 mM phosphate buffer containing 0.05 mM diethylenetriaminepentaacetic acid. The reaction mixture was kept in a screw-top vial and incubated in a water bath at 37 or 44°C. The time course of the electron paramagnetic resonance signal of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl in the reaction mixture was measured by an X-band EPR spectrometer (JEOL, Tokyo, Japan). When the same experiment was performed using rat plasma instead of 100 mM PB, the glutathione-dependent reduction of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl, i.e., generation of O2•−, was not obtained. Only the first-order decay reduction of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl, which indicates direct reduction of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl, was obtained in rat plasma. Adding 0.5% albumin to the phosphate buffer reaction mixture could almost completely inhibit O2•− generation at 37°C. However, addition of 0.5% albumin could not inhibit O2•− generation at 44°C, i.e., hyperthermic temperature. Ascorbic acid also showed inhibition of O2•− generation by 0.01 mM at 37°C, but 0.02 mM or more could inhibit O2•− generation at 44°C. A higher concentration of ascorbic acid showed first-order reduction, i.e., direct one-electron reduction, of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl. Hyperthermia-induced O2•− generation in rat plasma can be mostly inhibited by albumin and ascorbic acid in the plasma.

Electrogenerated chemiluminescence of magnesium chlorophyllin a aqueous solution and its sensitive response to the carcinogen aflatoxin B1

The chlorophylls, crucial participants of photosynthesis, are large conjugated molecules with special electron donor–acceptor properties. Based on this, many investigations on the electrogenerated chemiluminescence (ECL) of chlorophyll a (Chl a) were performed in organic solvents, but no efficient signals were detected. Herein, ECL research of magnesium chlorophyllins a (Chlorins a) from simple saponification of the natural Chl a was carried out, and highly efficient and stable ECL signal was obtained for the first time. The mechanism study indicated that the ECL resulted from radical ion annihilation. Under the optimal conditions, the effect of the key gas O2 on the ECL of Chlorins a aqueous solution was investigated, and the recoverable inhibition of O2 was obviously observed. What is more, owing to the strong non-covalent interaction between Chlorins a and the carcinogen aflatoxin B1 (AFB1), ECL intensity of Chlorins a aqueous solution exhibited fast, sensitive and selective response to AFB1 with a low detection limit of 0.027ppb at the signal-to-noise ratio of 3. The costless and environmentally friendly ECL method opens a new potential way of the rapid detection of AFB1 in practical application.

Efficient reduction of Cr(VI) in groundwater by a hybrid electro-Pd process

Pd-catalytic process is effective for reducing a wide range of contaminants in groundwater. However, limited attention is paid to Cr(VI) reduction presumably due to the weakly oxidizing potential of Cr(VI) under circumneutral conditions. In this study, a new concept of in situ reducing Cr(VI) in groundwater by a hybrid electro-Pd process with automatic pH adjustments is proposed and justified. In an undivided electrolytic cell, Cr(VI) at 5 mg/L is reduced by 95% within 30 min under conditions of pH 3, 1 g/L Pd/Al2O3 and 20 mA current. Reduction of Cr(VI) increases with decreasing pH and increasing current and Pd/Al2O3 dosage. Inhibition of anodic O2 is significant but decreases with drop of pH. Atomic H is assigned as the predominant reactive species contributing to Cr(VI) reduction. Although H2O2 is effective for reducing Cr(VI), its production on Pd surface is completed inhibited by the presence of Cr(VI). The concept is ultimately justified using a specially configured three-electrode column. Cr(VI) is effectively reduced to Cr3+ in the locally acidic Pd zone, and Cr3+ is then precipitated in the downstream neutral zone. This hybrid electro-Pd process could be potentially applied in the in situ remediation of Cr(VI)-contaminated groundwater.