Actions Of H2O2 Research Articles

The Improvement of Boron-Doped Diamond Anode System in Electrochemical Oxidation and Fenton Coupling System Degradation of p-Nitrophenol By Sensing Electrode of Iron

Boron-doped diamond (BDD) electrodes are promising anode materials in electrochemical oxidation system in degradation of wastewater containing toxic and bio-refractory organic pollutants due to their corrosion resistant ability and strong oxidation ability. In order to further improve the performance of BDD anode system, electrochemical oxidation of p-nitrophenol(PNP) was initially investigated in BDD anode system with the presence of sensing electrode. The results showed that the performance of the synthetic system was improved under neutral conditions with the joint actions of anode oxidation (64.6%) and H2O2 which was produced by oxygen reduction at carbon fiber cathode (11.9%). Under acid conditions, the degradation efficiency of PNP was further improved from 41.8% of the traditional system to 84.5% of the synthetic system. The strong oxidation ability was due to the anode oxidation (24.5%) and Fenton reaction by H2O2 and Fe2+ releasing from sensing electrode (66.7%). Moreover, under alkaline conditions, the results showed that the combined system was also improved by the coagulation of iron flocs formed from sensing electrode besides anode oxidation. Furthermore, hydroxyl radicals and H2O2 which were dominated oxidants were detected and quantified for the oxidation mechanism explanation.

A nanocomposite-based electrochemical sensor for non-enzymatic detection of hydrogen peroxide.

Hydrogen peroxide (H2O2) plays important signaling roles in normal physiology and disease. However, analyzing the actions of H2O2 is often impeded by the difficulty in detecting this molecule. Herein, we report a novel nanocomposite-based electrochemical sensor for non-enzymatic detection of H2O2. Graphene oxide (GO) was selected as the dopant for the synthesis of polyaniline (PANI), leading to the successful fabrication of a water-soluble and stable GO-PANI composite. GO-PANI was subsequently subject to cyclic voltammetry to generate reduced GO-PANI (rGO-PANI), enhancing the conductivity of the material. Platinum nanoparticles (PtNPs) were then electrodeposited on the surface of the rGO-PANI-modified glassy carbon electrode (GCE) to form an electrochemical H2O2 sensor. Compared to previously reported sensors, the rGO-PANI-PtNP/GCE exhibited an expanded linear range, higher sensitivity, and lower detection limit in the quantification of H2O2. In addition, the sensor displayed outstanding reproducibility and selectivity in real-sample examination. Our study suggests that the rGO-PANI-PtNP/GCE may have broad utility in H2O2 detection under physiological and pathological conditions.

Hydrogen peroxide activates store-operated Ca(2+) entry in coronary arteries.

Abnormal Ca(2+) metabolism has been involved in the pathogenesis of vascular dysfunction associated with oxidative stress. Here, we have investigated the actions of H2 O2 on store-operated Ca(2+) (SOC) entry in coronary arteries and assessed whether it is impaired in arteries from a rat model of metabolic syndrome. Simultaneous measurements of intracellular Ca(2+) concentration and contractile responses were made in coronary arteries from Wistar and obese Zucker rats, mounted in microvascular myographs, and the effects of H2 O2 were assessed. H2 O2 raised intracellular Ca(2+) concentrations, accompanied by simultaneous vasoconstriction that was markedly reduced in a Ca(2+) -free medium. Upon Ca(2+) re-addition, a nifedipine-resistant sustained Ca(2+) entry, not coupled to contraction, was obtained in endothelium-denuded coronary arteries. The effect of H2 O2 on this voltage-independent Ca(2+) influx was concentration-dependent, and high micromolar H2 O2 concentrations were inhibitory and reduced SOC entry evoked by inhibition of the sarcoplasmic reticulum ATPase (SERCA). H2 O2 -induced increases in Fura signals were mimicked by Ba(2+) and reduced by heparin, Gd(3+) ions and by Pyr6, a selective inhibitor of the Orai1-mediated Ca(2+) entry,. In coronary arteries from obese Zucker rats, intracellular Ca(2+) mobilization and SOC entry activated by acute exposure to H2 O2 were augmented and associated with local oxidative stress. H2 O2 exerted dual concentration-dependent stimulatory/inhibitory effects on store-operated, IP3 receptor-mediated and Orai1-mediated Ca(2+) entry, not coupled to vasoconstriction in coronary vascular smooth muscle. SOC entry activated by H2 O2 was enhanced and associated with vascular oxidative stress in coronary arteries in metabolic syndrome.

Investigation of the photo-oxidation of cassava starch granules

In this study, the combined and simultaneous actions of H2O2 and UV radiation on cassava starch granules were applied and the thermal, rheological, structural and colour properties were investigated. Samples of native cassava starch were oxidised with standard H2O2 solutions (0.1, 0.2 and 0.5 mol L−1) and exposed for 1 h under UV light (UVC radiation with λ = 256 nm), with constant stirring. The solutions were subsequently filtered, washed, dried and analysed. The thermogravimetric curves showed similar behaviour, with three main mass losses and an increase in the thermal stability of each sample. The oxidative modification performed caused a strong decrease in the setback and final viscosity parameters (RVA), a gradual decrease in the gelatinisation enthalpy (DSC) and relative crystallinity (XRD) and significant differences in the average roughness of the granules (NC-AFM). The X-ray diffraction powder patterns displayed the “A” type for all the starch granules. The colour parameters showed a decrease in the −a* value (trend to green) for all the treated samples.

A role for the sodium pump in H2O2-induced vasorelaxation in porcine isolated coronary arteries

Hydrogen peroxide (H2O2) has been proposed to act as a factor for endothelium-derived hyperpolarization (EDH) and EDH may act as a ‘back up’ system to compensate the loss of the NO pathway. Here, the mechanism of action of H2O2 in porcine isolated coronary arteries (PCAs) was investigated. Distal PCAs were mounted in a wire myograph and pre-contracted with U46619 (1nM–50μM), a thromboxane A2-mimetic or KCl (60mM). Concentration–response curves to H2O2(1μM–1mM), bradykinin (0.01nM–1μM), sodium nitroprusside (SNP) (10nM–10μM), verapamil (1nM–10μM), KCl (0–20mM) or Ca2+-reintroduction (1μM–10mM) were constructed in the presence of various inhibitors. Activity of the Na+/K+-pump was measured through rubidium-uptake using atomic absorption spectrophotometry. H2O2 caused concentration-dependent vasorelaxations with a maximum relaxation (Rmax) of 100±16% (mean±SEM), pEC50=4.18±0.20 (n=4) which were significantly inhibited by PEG-catalase at 0.1–1.0mM H2O2 (P<0.05). 10mM TEA significantly inhibited the relaxation up to 100μM H2O2 (P<0.05). 60mM K+ and 500nM ouabain significantly inhibited H2O2-induced vasorelaxation producing a relaxation of 40.8±8.5% (n=5) and 47.5±8.6% (n=6) respectively at 1mM H2O2 (P<0.0001). H2O2-induced vasorelaxation was unaffected by the removal of endothelium, inhibition of NO, cyclo-oxygenase, gap junctions, SKCa, IKCa, BKCa Kir, KV, KATP or cGMP. 100μM H2O2 had no effects on the KCl-induced vasorelaxation or Ca2+-reintroduction contraction. 1mM H2O2 inhibited both KCl-induced vasorelaxation and rubidium-uptake consistent with inhibition of the Na+/K+-pump activity. We have shown that the vascular actions of H2O2 are sensitive to ouabain and high concentrations of H2O2 are able to modulate the Na+/K+-pump. This may contribute towards its vascular actions.

A dissection of the effects of ethylene, H2O2 and high irradiance on antioxidants and several genes associated with stress and senescence in tobacco leaves

Ethylene and hydrogen peroxide are involved in the modulation of stress responses in plants, but their interrelation is not well understood. This work was designed to find differences between the actions of ethylene and H2O2 on antioxidants and senescence markers. Leaves of Nicotiana tabacum were sprayed with H2O2 or with ethephon (precursor of ethylene). To find the possible modulation of responses to acute abiotic stress, ethephon- and H2O2-sprayed leaves were further subjected to high irradiance (HL). The application of H2O2 strongly stimulated ethylene synthesis (ACC). Ethylene and H2O2, as single factors, stimulated the trolox equivalent antioxidant capacity (TEAC) and the activity of catalase (CAT), in contrast to HL alone (stimulation of nonspecific peroxidases and the total glutathione pool). However, after combined treatments (ethylene+HL and H2O2+HL), the stimulatory action of H2O2 was related to TEAC and CAT activity, while the application of ethylene stimulated the total glutathione pool. Hydrogen peroxide enhanced the expression of the three CAT genes (Cat1, Cat2 and Cat3), in contrast to ethylene (Cat2 and Cat3) and HL (Cat1). In regard to the markers of senescence and pathogenesis the most pronounced difference between the actions of ethylene and H2O2, as single factors, was related to NPR1, whereas when leaf spraying was combined with HL, differences were found at WRKY53 and PR1a. HL reversed the stimulatory effects of H2O2/ethylene-driven enhancements of the expression of several genes (Cat1, Cat2, NPR1, WRKY53). These results show that multiple stressors, as usually encountered by plants in nature, may largely change those expression patterns of genes determined in a single factor analysis. Moreover, the actions of HL (often considered the internal H2O2 trigger) and of exogenous H2O2 on gene expression are clearly different.

The effects of nitroxyl (HNO) on H2O2 metabolism and possible mechanisms of HNO signaling

Nitroxyl (HNO) possesses unique and potentially important biological/physiological activity that is currently mechanistically ill-defined. Previous work has shown that the likely biological targets for HNO are thiol proteins, oxidized metalloproteins (i.e. ferric heme proteins) and, most likely, selenoproteins. Interestingly, these are the same classes of proteins that interact with H2O2. In fact, these classes of proteins not only react with H2O2, and thus potentially responsible for the signaling actions of H2O2, but are also responsible for the degradation of H2O2. Therefore, it is not unreasonable to speculate that HNO can affect H2O2 degradation by interacting with H2O2-degrading proteins possibly leading to an increase in H2O2-mediated signaling. Moreover, considering the commonality between HNO and H2O2 biological targets, it also seems likely that HNO-mediated signaling can also be due to reactivity at otherwise H2O2-reactive sites. Herein, it is found that HNO does indeed inhibit H2O2 degradation via inhibition of H2O2-metaboilizing proteins. Also, it is found that in a system known to be regulated by H2O2 (T cell activation), HNO behaves similarly to H2O2, indicating that HNO- and H2O2-signaling may be similar and/or intimately related.

Abstract 1609: Oxidation products of green tea polyphenols induce inactivation of PKC isoenzymes and induce cell death via modulation of selenoprotein thioredoxin reductase and quinone reductase

Abstract Autooxidation of green tea polyphenols generates H2O2 and quinones which have been implicated in cell death induced by these polyphenols. While autooxidation of epigallocatechin-3-gallate (EGCG), the major green tea polyphenol, has been shown in vitro where oxygen tension is high, the role of reactive oxygen species in the action of EGCG in vivo is currently gaining attention. When DU145 prostate cancer cells were treated in vitro with EGCG, PKC isoenzymes were inactivated. This inactivation was strongly correlated with EGCG-induced cell death. Cell-permeable catalase partially blocked EGCG-induced inactivation of PKC and cell death suggesting the involvement of H2O2 in these processes. EGCG-induced cell death was enhanced by 3-amino-1,2,4-triazole, a catalase inhibitor, suggesting an inhibitory role for intracellular catalase in this process. Furthermore, the inactivated PKC isoenzymes were regenerated to their active form by thiol agents in the test tube or by the thioredoxin reductase (TR) system in cells. This suggests sulfhydryl oxidation of PKC is induced by EGCG-mediated ROS generation. Previously, others have demonstrated inactivation of TR by a quinone generated by autooxidation of EGCG. We found that EGCG treatment of intact DU145 cells inactivated TR, presumably by generation of quinone. Such inactivation of TR enhanced the net increase in inactivation of PKC due to a decrease in reversal of PKC oxidative modification. Thus, the combined actions of H2O2 and quinones induce more inactivation of PKC and cell death than either agent alone. Cotreatment of cells with auranofin, a specific inhibitor of TR, enhanced EGCG-induced inactivation of PKC and cell death. Conversely, a three-fold increase in the induction of TR, by pretreatment of DU145 cells with selenite for 48 h, completely abolished both EGCG-induced inactivation of PKC and induction of cell death. This suggests a possible antagonistic interaction between selenium and EGCG. Dicumarol, an inhibitor of phase II enzyme quinone reductase, enhanced inactivation of TR, presumably by accumulation of quinones. Conversely, an induction of quinone reductase by tertiary butylhydroquinone, decreased EGCG-induced inactivation of TR, presumably due to less accumulation of EGCG-derived quinones. This decreased inactivation of TR subsequently led to a net decrease in inactivation of PKC isoenzymes and cell death. This suggests that QR is a negative regulator of EGCG-induced inactivation of PKC and cell death. Thus, EGCG oxidation products H2O2 and quinone appear to mediate EGCG-induced cell death via inactivation of PKC isoenzymes and TR respectively. Furthermore, the data suggests that both EGCG-induced PKC inactivation and cell death are antagonized by an increase in TR and QR. This study was supported by the National Cancer Institute grant CA099216. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1609. doi:1538-7445.AM2012-1609

L‐type Ca2+ channel current from on‐cell patch is augmented by H2O2 in rat aortic smooth muscle–derived A7r5 cells

L‐type Ca2+ channels are exposed to H2O2 generated within the cells and adjacent cells such as immune cells. Although the effect of H2O2 on ICa,L has long been studied, whether it augments or inhibits ICa,L has not yet been settled. We hypothesized that extracellular and intracellular H2O2 differently modulates ICa,L. Here, we adopted two configurations of patch clamp technique to separately study these modulations in A7r5 cells, a smooth muscle cell line derived from embryonic rat aorta. Whole cell ICa,L recorded with 10 mM Ba2+ as a charge carrier was slightly inhibited with an acceleration of its decay time course by 0.1‐mM H2O2. On‐cell recording enabled us to study the effect of H2O2 without possible complication of direct oxidation of CaV1.2 by external H2O2. Single and multichannel ICa,L were recorded in the presence of 90 mM Ba2+ and Bay K 8644 repetitively applying 500 ms depolarization steps to ‐10 and 0 mV. The mean currents from these currents were significantly increased by 0.1‐mM H2O2 from 0.85 pA to 1.05 pA associated with slow inactivation: ICa,L at 500 ms, 0.56 pA in control and 0.74 pA in the presence of H2O2. Since extracellular H2O2 was not accessible to the patch membrane, these changes reflect intracellular actions of H2O2. In conclusion, ICa,L is augmented by H2O2 via intracellular signaling mechanism in A7r5 cells. Supported by National Heart, Lung, and Blood Institute Grant RO1‐HL‐085352.

Decolorization of Reactive Red 2 in Fenton and Fenton-like systems: effects of ultrasound and ultraviolet irradiation

Abstract This study utilized Fenton, Fenton-like, photo-Fenton, photo-Fenton-like, sono-Fenton, and sono-Fenton-like systems for the decolorization of Reactive Red 2 (RR2) dye. Fe2+ and Fe3+ were used to catalyze the actions of oxidants H2O2 and Na2S2O8. Pseudo-first order rate constants (k) were obtained by fitting the decolorization kinetics of RR2. With added oxidant at 0.3 mM and iron ion at 0.03 mM, the k values of H2O2/Fe2+, H2O2/Fe3+, Na2S2O8/Fe2+, and Na2S2O8/Fe3+ were 13, 0.67, 6.2, and 0.080 r−1, in order. Higher oxidant and iron concentrations resulted in faster decolorization in Fenton and Fenton-like systems. Additionally, decolorization was accelerated by ultraviolet (UV) and ultrasound (US) irradiation. When ethanol was used as a scavenger for the generated hydroxyl and sulfate radicals, it significantly inhibited the decolorization process in photo-Fenton and photo-Fenton-like systems. The k values obtained for the UV/H2O2/Fe2+, UV/Na2S2O8/Fe2+, UV/H2O2/Fe2+/C2H5OH, and UV/Na2S2O8/Fe2+/C2H...

Pharmacologic ascorbate synergizes with gemcitabine in preclinical models of pancreatic cancer

Conventional treatment approaches have had little impact on the course of pancreatic cancer, which has the highest fatality rate among cancers. Gemcitabine, the primary therapeutic agent for pancreatic carcinoma, produces minimal survival benefit as a single agent. Therefore, numerous efforts have focused on gemcitabine combination treatments. Using a ratio design, this study established that combining pharmacologically achievable concentrations of ascorbate with gemcitabine resulted in a synergistic cytotoxic response in eight pancreatic tumor cell lines. Sensitization was evident regardless of inherent gemcitabine resistance and epithelial–mesenchymal phenotype. Our analysis suggested that the promiscuous oxidative actions of H2O2 derived from pharmacologic ascorbate can culminate in synergism independent of the cancer cell's underlying phenotype and resistance to gemcitabine monotherapy. Gemcitabine–ascorbate combinations administered to mice bearing pancreatic tumor xenografts consistently enhanced inhibition of growth compared to gemcitabine alone, produced 50% growth inhibition in a tumor type not responsive to gemcitabine, and demonstrated a gemcitabine dose-sparing effect. These data support the testing of pharmacologic ascorbate in adjunctive treatments for cancers prone to high failure rates with conventional therapeutic regimens, such as pancreatic cancer.

Modulation of Hydrogen Peroxide and Acrolein-Induced Oxidative Stress, Mitochondrial Dysfunctions and Redox Regulated Pathways by the Bacopa Monniera Extract: Potential Implication in Alzheimer's Disease

Acrolein is one of the by-products of lipid peroxidation. Due to its high reactivity, it is not only a marker of lipid peroxidation but could also be an initiator of oxidative stress by adducting cellular nucleophilic groups. In brains of Alzheimer's disease (AD) patients, levels of acrolein are significantly higher in vulnerable brain region and, on primary hippocampal culture, it is more toxic than 4-hydroxyl-nonenal. The toxicity of the amyloid-beta peptide is mediated through the generation of hydrogen peroxide (H2O2). The actions of H2O2 include oxidative modifications of proteins, lipids, and DNA as observed in AD. Bacopa monniera (BM) has a long history of use in India as a memory-enhancing therapy. The objective of our study was to investigate the neuroprotective effects of the standardized extracts of BM against acrolein and H2O2 and to elucidate the mechanisms underlying this protection. Our results show that a pre-treatment with the BM extract protected the human neuroblastoma cell line SK-N-SH against H2O2 and acrolein. We demonstrated that BM pre-treatment significantly inhibited the generation of intracellular reactive oxygen species in addition to preserving the mitochondrial membrane potential. BM pre-treatment also prevented the modifications of the activity of several redox regulated proteins, i.e., NF-kappaB, Sirt1, ERK1/2, and p66Shc, so as to favor cell survival in response to oxidative stress. Thus, our findings demonstrate that BM can protect human neuroblastoma cells against H2O2 and acrolein through different mechanisms involved in the pathophysiology of AD and could have a therapeutic application in the prevention of AD.

Reactive oxygen species alters the electrophysiological properties and raises [Ca2+]iin intracardiac ganglion neurons

We have investigated the effects of the reactive oxygen species (ROS) donors hydrogen peroxide (H2O2) and tert-butyl hydroperoxide (t-BHP) on the intrinsic electrophysiological characteristics: ganglionic transmission and resting [Ca2+]i in neonate and adult rat intracardiac ganglion (ICG) neurons. Intracellular recordings were made using sharp microelectrodes filled with either 0.5 M KCl or Oregon Green 488 BAPTA-1, allowing recording of electrical properties and measurement of [Ca2+]i. H2O2 and t-BHP both hyperpolarized the resting membrane potential and reduced membrane resistance. In adult ICG neurons, the hyperpolarizing action of H2O2 was reversed fully by Ba2+ and partially by tetraethylammonium, muscarine, and linopirdine. H2O2 and t-BHP reduced the action potential afterhyperpolarization (AHP) amplitude but had no impact on either overshoot or AHP duration. ROS donors evoked an increase in discharge adaptation to long depolarizing current pulses. H2O2 blocked ganglionic transmission in most ICG neurons but did not alter nicotine-evoked depolarizations. By contrast, t-BHP had no significant action on ganglionic transmission. H2O2 and t-BHP increased resting intracellular Ca2+ levels to 1.6 ( ± 0.6, n = 11, P < 0.01) and 1.6 ( ± 0.3, n = 8, P < 0.001), respectively, of control value (1.0, ∼60 nM). The ROS scavenger catalase prevented the actions of H2O2, and this protection extended beyond the period of application. Superoxide dismutase partially shielded against the action of H2O2, but this was limited to the period of application. These data demonstrate that ROS decreases the excitability and ganglionic transmission of ICG neurons, attenuating parasympathetic control of the heart.

Modulation of SCFβ-TrCP-dependent IκBα Ubiquitination by Hydrogen Peroxide

Reactive oxygen species are known to participate in the regulation of intracellular signaling pathways, including activation of NF-kappaB. Recent studies have indicated that increases in intracellular concentrations of hydrogen peroxide (H(2)O(2)) have anti-inflammatory effects in neutrophils, including inhibition of the degradation of I kappaB alpha after TLR4 engagement. In the present experiments, we found that culture of lipopolysaccharide-stimulated neutrophils and HEK 293 cells with H(2)O(2) resulted in diminished ubiquitination of I kappaB alpha and decreased SCF(beta-TrCP) ubiquitin ligase activity. Exposure of neutrophils or HEK 293 cells to H(2)O(2) was associated with reduced binding between phosphorylated I kappaB alpha and SCF(beta-TrCP) but no change in the composition of the SCF(beta-TrCP) complex. Lipopolysaccharide-induced SCF(beta-TrCP) ubiquitin ligase activity as well as binding of beta-TrCP to phosphorylated I kappaB alpha was decreased in the lungs of acatalasemic mice and mice treated with the catalase inhibitor aminotriazole, situations in which intracellular concentrations of H(2)O(2) are increased. Exposure to H(2)O(2) resulted in oxidative modification of cysteine residues in beta-TrCP. Cysteine 308 in Blade 1 of the beta-TrCP beta-propeller region was found to be required for maximal binding between beta-TrCP and phosphorylated I kappaB alpha. These findings suggest that the anti-inflammatory effects of H(2)O(2) may result from its ability to decrease ubiquitination as well as subsequent degradation of I kappaB alpha through inhibiting the association between I kappaB alpha and SCF(beta-TrCP).

Hydrogen peroxide increases cerebral arterial KCa channel opening through activation of Akt signaling pathway

The oxidant hydrogen peroxide (H2O2) is not only an inducer of cellular damage, but can also play a role as a modulator of vascular function. Exogenous application of H2O2 (3‐300 µM) resulted in a concentration‐dependent increase in NPo of KCa single‐channel currents recorded from cell attached patches at a patch potential of +40 mV, whereas this oxidant did not change the NPo of KCa single‐channel current when recorded from excised inside‐out membrane patches of cerebral arterial muscle cells (CAMCs). The membrane permeant organic peroxide tert‐butyl hydroperoxide (t‐BOOH) (30 µM) also induced similar increase in NPo of KCa single‐channel currents in the cell‐attached patches but had no effect on NPo of the single‐channel KCa currents recorded from excised inside‐out patches at a the same patch potential. In an attempt to elucidate possible signaling mechanism mediating the effects of these oxidants on KCa channel currents in CAMCs, we examined the impact of inhibition of the phospoinositide 3‐kinase‐Akt (PI3K‐Akt) pathway on the stimulatory actions of both H2O2 and t‐BOOH on KCa channel current. Pretreatment of CAMCs with two structurally different PI3K‐Akt pathway inhibitors wortmannin (10 nM) and LY294002 (5 µM) significantly attenuated the H2O2‐ or t‐BOOH‐induced increase in NPo of single‐channel KCa currents in CAMCs. On the other hand, stimulation of cerebral arterial muscle with either H2O2 or t‐BOOH for 10 minutes induced activation of Akt as determined by western blot analysis. These findings suggest that activation of the Akt signaling pathway contributes to the H2O2‐or t‐BOOH‐induced enhancement of KCa channel currents in cerebral arterial muscle cells.

Possible role of a hydrogen peroxide-mediated mechanism in glucocorticoid receptor functional alterations associated with moderate asthma

It is well known that pathogenesis and maintenance of chronic asthma is associated with alterations of glucocorticoid receptor (GR) function, and also with persistent pulmonary inflammation, the important mediators of which are reactive oxygen and nitrogen species. In this paper, we tested a hypothesis that GR functional alterations in asthma result from the action of oxidants. To that end, we conducted a series of ex vivo treatments of peripheral blood mononuclear cells (PBMCs) of healthy donors with oxidizing agents (3 morpholinosydnonimine, SIN1; S-nitroso-N-acetyl-penicillamine, SNAP; and hydrogen peroxide, H2O2) and compared the resulting GR modifications with those previously noticed in asthmatic patients. The results show that treatment of PBMCs by H2O2 provoked an increase in the level of GR protein, accompanied by a rise in the number of hormone-binding sites and a decline in the receptor's affinity for the hormone. The H2O2 induced changes, including a characteristic GR isoprotein expression pattern, were found to be very similar to the GR changes previously observed in PBMCs of moderate asthmatic patients, but not in mild asthmatics and healthy subjects. Treatment with the other oxidants applied herein produced different effects or exerted no influence on GR. Thus, this study provides preliminary data suggesting that functional alterations of the GR associated with moderate asthma may be mediated by redox mechanisms that are based on oxidative and regulatory actions of H2O2.

Selection and identification of anaerobic lactobacilli producing inhibitory compounds against vaginal pathogens

Two strains of Lactobacillus crispatus (15L08 and 21L07) and one strain of Lactobacillus jensenii (5L08) were selected from amongst 100 isolates from the vaginas of healthy premenopausal women for properties relevant to mucosal colonization and the production of H2O2 and/or bacteriocin-like compound. All three strains self-aggregated and adhered to vaginal epithelial cells, displacing well-known vaginal pathogens, such as Gardnerella vaginalis and Candida albicans. Lactobacillus crispatus 15L08 was characterized as a potential H2O2 producer. A high level of bacteriocin-like compound was synthesized by L. jensenii 5L08, with a bactericidal mode of action for G. vaginalis, C. albicans and Escherichia coli. However, H2O2-dependent activity alone was not sufficient to inhibit the growth of C. albicans. Simultaneous actions of H2O2 and bacteriocin-like compound produced by lactobacilli may be important for antagonizing pathogenic bacteria. These strains of lactobacilli may be excellent candidates for eventual use as probiotics to restore the normal microbial communities in the vaginal ecosystem.

Role of Hydrogen Peroxide in Symptom Expression of Barley Susceptible and Resistant to Powdery Mildew

Three genotypes of barley (cultivar Ingrid) expressing the genes Mlo (susceptible), Mla12 (resistant with HR symptoms) and mlo5 (resistant without HR) in relation to infection by race A6 of Blumeria graminis f. sp. hordei have been sprayed with a solution of H2O2 after establishment of infection (2-3 days after inoculation). Under the influence of H2O2, leaves of the susceptible Mlo and mlo5-resistant plants exhibited HR-type symptoms with tissue necroses. The Mla12-resistant genotype produced HR earlier and the number of necrotic lesions increased, as compared to untreated control leaves. Treatment with H2O2 before establishment of infection (one day after inoculation), resulted in all the three genotypes in inhibition of the pathogen and symptomless response. It was possible to reverse the inhibitory as well as the HR-producing actions of H2O2 with injection of leaves with a combination of superoxide dismutase (SOD) and catalase (CAT) before treatment with H2O2. It is suggested that the hypothetical ne...

Dual action of hydrogen peroxide on synaptic transmission at the frog neuromuscular junction.

There is evidence that reactive oxygen species (ROS) are produced and released during neuromuscular activity, but their role in synaptic transmission is not known. Using a two-electrode voltage-clamp technique, at frog neuromuscular junctions, the action H2O2 on end-plate currents (EPC) was studied to determine the targets for this membrane-permeable ROS. In curarized or cut muscles, micromolar concentrations of H2O2 increased the amplitude of EPCs. Higher (> 30 microM) doses inhibited EPCs and prolonged current decay. These effects were presynaptic since H2O2 did not change the amplitude or duration of miniature EPCs (although it reduced the rate of spontaneous release at high concentrations). Quantal analysis and deconvolution methods showed that facilitation of EPCs was due to increased quantal release, while depression was accompanied by temporal dispersion of evoked release. Extracellular recordings revealed prolonged presynaptic Ca2+ entry in the presence of high H2O2. Both low and high H2O2 increased presynaptic potentiation during high-frequency stimulation. Pro-oxidant Fe2+ did not affect facilitation by low doses of H2O2 but augmented the inhibition of EPCs by high H2O2, indicating involvement of hydroxyl radicals. High Mg2+ and the ROS scavenger N-acetylcysteine eliminated both the facilitatory and depressant effects of H2O2. The facilitatory effect of H2O2 was prevented by protein kinase C (PKC) inhibitors and 4beta-phorbol 12-myristate, 13-acetate (PMA), an activator of PKC. PKC inhibitors but not PMA also abolished the depressant effect of H2O2. Our data suggest complex presynaptic actions of H2O2, which could serve as a fast feedback modulator of intense neuromuscular transmission.

The effects of pneumolysin and hydrogen peroxide, alone and in combination, on human ciliated epithelium in vitro

We have investigated the effects of pneumolysin and H2O2, putative virulence factors of Streptococcus pneumoniae, on the ciliary beat frequency and structural integrity of human ciliated epitheliumin vitro . Human ciliated epithelium was obtained by brushing the inferior nasal turbinate of healthy human volunteers. Ciliary slowing (CS) was measured using a photo-transistor technique and epithelial damage (ED) was documented using a visual scoring index. Effects of recombinant pneumolysin (100 ng/ml), a mutant pneumolysin preparation with markedly reduced haemolytic activity (100 ng/ml) and reagent H2O2 (100 μM) were measured alone and in combination, in the absence and presence of catalase (1000 units/ml). When used individually, both recombinant pneumolysin and H2O2 caused significant (P<0.05) CS and ED. The effects of H2O2 but not those of pneumolysin were almost completely attenuated by catalase, while the mutant pneumolysin preparation did not cause significant CS or ED. When used in combination, the effects of pneumolysin and H2O2 on CS and ED were additive as opposed to synergistic. These actions of pneumolysin and H2O2 may contribute to the pathogenesis of respiratory tract infections caused by the pneumococcus.