Metal-Free Activation of Molecular Oxygen by 9-Fluorenone-Based Porous Organic Polymers for Selective Aerobic Oxidation

Oxygen activation is a critical step in heterogeneous oxidative processes, particularly in catalytic, electrolytic, and pharmaceutical applications. Among the various catalysts available for photocatalytic O2 activation, homogeneous aryl ketones are at the forefront. To avoid the degradation and deactivation of aryl ketones, 9-fluorenone-based porous organic polymers were designed and regulated by doping them with co-monomers. The obtained heterogeneous photocatalyst showed good performance in O2 activation, and its performance was better than that of homogeneous 9-fluorenone. The obtained heterogeneous photocatalyst showed good reusability. We believe that the presented method and findings represent an important step toward designing catalysts tailored for specific tasks.

Activation of peroxymonosulfate by Fe-Mn-modified MWCNTs for selective decontamination: Formation of high-valent metal-oxo species and superoxide anion radicals

The extensive presence of organic micropollutants in complex water matrices requires the development of selective oxidation technologies. In this study, a novel selective oxidation process was developed via the conjunction of FeMn/CNTs with peroxymonosulfate and successfully used to remove micropollutants such as sulfamethoxazole (SMX) and bisphenol A from aqueous solutions. FeMn/CNTs were prepared using a facile co-precipitation method, characterized using a series of surface characterization techniques, and then tested for pollutant removal. The results showed that the FeMn/CNTs had much greater reactivity than CNTs, manganese oxide, and iron oxide. The pseudo-first-order rate constant with FeMn/CNTs was more than 2.9-5.7 times that of the other tested materials. The FeMn/CNTs had great reactivity in a wide range of pH values from 3.0 to 9.0, with the best reactivity found at pH values of 5.0 and 7.0. High-valent metal-oxo species such as Fe(IV)O and Mn(IV)O and superoxide anion radicals were determined to be the reactive species and were responsible for the oxidation of SMX. These reactive species were selective; therefore, the overall removal performance of SMX was not obviously influenced by high levels of water components including chloride ions, bicarbonates, and natural organic matters. The results from this study may promote the design and application of selective oxidation technologies for micropollutant abatement.

Water-Soluble Nanoparticles with Twisted Double [7]Carbohelicene for Lysosome-Targeted Cancer Photodynamic Therapy

Helicene-based therapeutic agents for organelle-targeted photodynamic therapy (PDT) involving both type I and II are challenging and still underexplored. Herein, water-soluble nanoparticles containing twisted double [7]carbohelicene (D7H-NPs) are prepared through self-assembly with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] by a nanoprecipitation method. D7H-NPs display high water solubility with an average size of 46 ± 2 nm. Notably, D7H-NPs can generate efficient singlet oxygen (¹ O₂ ) and superoxide anion (O₂^· - ) upon white light irradiation, forming the basis of PDT. Moreover, the typical accumulation in lysosomes of 4T1 cancer cells paves the way to use D7H-NPs for lysosome-targeted cancer phototherapeutics. This paper reports a promising helicene-based phototherapeutic agent involving both type I and II PDT for organelle-targeted biotherapy.

Reactive Nitrogen Species Mediated Degradation of Estrogenic Disrupting Chemicals by Biochar/Monochloramine in Buffered Water and Synthetic Hydrolyzed Urine

There is increasing concern about the severe endocrine-related health problems because of the discharge of estrogenic disrupting chemicals (EDCs) into the natural environment. In this study, we investigated the activation of monochloramine (NH₂Cl) by biochar [pyrolyzed by cotton straw at 350 °C (Cot350), wheat straw at 350 and 700 °C (WS350 and WS700), and corn straw at 350 and 700 °C (CS350 and CS700)] for the degradation of estradiol (E2) and ethinylestradiol (EE2). Approximately 95% of parent E2 and EE2 was removed by Cot350/NH₂Cl in buffered solution, and 87% of E2 and 75% of EE2 were removed in urine within 24 h. Electronic paramagnetic resonance analysis and radical-quenching experiments showed that biochar activated NH₂Cl and primarily generated ^•NO radicals for the degradation of the EDCs. The nitrogen and silicon elements of Cot350 served as primary catalytic sites for NH₂Cl activation, whereas the sp²-hybridized carbon on WS700 and CS700 played a major role. The effect of major urine components (i.e., ammonia species, chloride, and bicarbonate) on the reaction pathways of biochar/NH₂Cl was also elucidated. This study provides new insights into the reaction pathways of NH₂Cl activation by biochar and suggests potential applications for other carbonaceous materials for NH₂Cl activation.

Particulate Matter 2.5 Mediates Cutaneous Cellular Injury by Inducing Mitochondria-Associated Endoplasmic Reticulum Stress: Protective Effects of Ginsenoside Rb1

The prevalence of fine particulate matter-induced harm to the human body is increasing daily. The aim of this study was to elucidate the mechanism by which particulate matter 2.5 (PM_2.5) induces damage in human HaCaT keratinocytes and normal human dermal fibroblasts, and to evaluate the preventive capacity of the ginsenoside Rb1. PM_2.5 induced oxidative stress by increasing the production of reactive oxygen species, leading to DNA damage, lipid peroxidation, and protein carbonylation; this effect was inhibited by ginsenoside Rb1. Through gene silencing of endoplasmic reticulum (ER) stress-related genes such as PERK, IRE1, ATF, and CHOP, and through the use of the ER stress inhibitor tauroursodeoxycholic acid (TUDCA), it was demonstrated that PM_2.5-induced ER stress also causes apoptosis and ultimately leads to cell death; however, this phenomenon was reversed by ginsenoside Rb1. We also found that TUDCA partially restored the production of ATP that was inhibited by PM_2.5, and its recovery ability was significantly higher than that of ginsenoside Rb1, indicating that the process of ER stress leading to cell damage may also occur via the mitochondrial pathway. We concluded that ER stress acts alone or via the mitochondrial pathway in the induction of cell damage by PM_2.5, and that ginsenoside Rb1 blocks this process. Ginsenoside Rb1 shows potential for use in skin care products to protect the skin against damage by fine particles.

Enhanced mineralization of hypersaline wastewater with Fe2+/Cu2+ catalyzed UV-Fenton process: process optimization and catalytic mechanism

The efficiency of Fenton oxidation was inhibited by the high content of salt in the industrial wastewater. However, enhanced mineralization of hypersaline industrial wastewater is necessary for advanced treatment and subsequent wastewater salt recovery process. Therefore, Fe²⁺ and Cu²⁺ catalyzed UV-Fenton oxidation were carried out to improve the total organic carbon (TOC) removal efficiency for a hypersaline wastewater from resin manufacturing. The performance of UV-Fe/Cu-Fenton oxidation was comparatively investigated and optimized using response surface methodology (RSM) to develop a practical high-efficient mineralization treatment technique for hypersaline wastewater. More than 90% of TOC was removed under optimal conditions of UV-Fe²⁺ and UV-Cu²⁺-Fenton oxidation, namely 9.6 mM Fe²⁺ and 176 mM H₂O₂, and 2.95 mM Cu²⁺ and 276 mM H₂O₂, respectively. The reactive oxygen radicals identified using electron spin resonance (ESR) spectroscopy revealed that hydroxyl radical was dominant oxidant in UV-Fe²⁺-Fenton process, while HO₂·/O₂·^- played a more important role in the UV-Cu-Fenton system. The Cl^- effect is also different for UV Fe and Cu Fenton. Moreover, no scaling and sludge problem makes UV-Cu-Fenton a promising alternative method for efficient mineralization of hypersaline industrial wastewater.

ROS scavenging Mn3O4 nanozymes for in vivo anti-inflammation

Reactive oxygen species (ROS) scavenging Mn₃O₄ nanozymes effectively protected live mice from ROS-induced ear-inflammation in vivo.

Reactive oxygen species (ROS)-induced oxidative stress is linked to various diseases, including cardiovascular disease and cancer. Though highly efficient natural ROS scavenging enzymes have been evolved, they are sensitive to environmental conditions and hard to mass-produce. Therefore, enormous efforts have been devoted to developing artificial enzymes with ROS scavenging activities. Among them, ROS scavenging nanozymes have recently attracted great interest owing to their enhanced stability, multi-functionality, and tunable activity. It has been implicated that Mn-contained nanozymes would possess efficient ROS scavenging activities, however only a few such nanozymes have been reported. To fill this gap, herein we demonstrated that Mn₃O₄ nanoparticles (NPs) possessed multiple enzyme mimicking activities (i.e., superoxide dismutase and catalase mimicking activities as well as hydroxyl radical scavenging activity). The Mn₃O₄ nanozymes therefore significantly scavenged superoxide radical as well as hydrogen peroxide and hydroxyl radical. Moreover, they were not only more stable than the corresponding natural enzymes but also superior to CeO₂ nanozymes in terms of ROS elimination. We showed that the Mn₃O₄ NPs not only exhibited excellent ROS removal efficacy in vitro but also effectively protected live mice from ROS-induced ear-inflammation in vivo. These results indicated that Mn₃O₄ nanozymes are promising therapeutic nanomedicine for treating ROS-related diseases.

Anticancer effect of linalool via cancer-specific hydroxyl radical generation in human colon cancer

AIM

To investigate the anticancer mechanisms of the monoterpenoid alcohol linalool in human colon cancer cells.

METHODS

The cytotoxic effect of linalool on the human colon cancer cell lines and a human fibroblast cell line was examined using the WST-8 assay. The apoptosis-inducing effect of linalool was measured using the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay and flow cytometry with Annexin V. Oxidative stress was investigated by staining for diphenyl-1-pyrenylphosphine, which is a cellular lipid peroxidation marker, and electron spin resonance spectroscopy. Sixteen SCID mice xenografted with human cancer cells were randomized into 3 groups for in vivo analysis: control and low-dose and high-dose linalool groups. The control group was administered tap water orally every 3 d. The linalool treatment groups were administered 100 or 200 μg/kg linalool solution orally for the same period. All mice were sacrificed under anesthesia 21 d after tumor inoculation, and tumors and organs were collected for immunohistochemistry using an anti-4-hydroxynonenal antibody. Tumor weights were measured and compared between groups.

RESULTS

Linalool induced apoptosis of cancer cells in vitro, following the cancer-specific induction of oxidative stress, which was measured based on spontaneous hydroxyl radical production and delayed lipid peroxidation. Mice in the high-dose linalool group exhibited a 55% reduction in mean xenograft tumor weight compared with mice in the control group (P < 0.05). In addition, tumor-specific lipid peroxidation was observed in the in vivo model.

CONCLUSION

Linalool exhibited an anticancer effect via cancer-specific oxidative stress, and this agent has potential for application in colon cancer therapy.

Photo-protective effect of sargachromenol against UVB radiation-induced damage through modulating cellular antioxidant systems and apoptosis in human keratinocytes

The aim of this study was to evaluate the photo-preventive effects of sargachromenol (SC) against ultraviolet B (UVB)-induced oxidative stress in human keratinocytes via assessing the antioxidant properties and underlying molecular mechanisms. SC exhibited a significant scavenging effect on UVB-induced intracellular reactive oxygen species (ROS). SC attenuated UVB-induced oxidative macromolecular damage, including the protein carbonyl content, DNA strand break, and 8-isoprostane level. Furthermore, SC decreased UVB-induced Bax, cleaved caspase-9, and cleaved caspase-3 protein levels, but increased that of Bcl-2, which are well-known key mediators of apoptosis. Moreover, SC increased superoxide dismutase, catalase, and heme oxygenase-1 protein expression. Pre-treatment with SC upregulated the main transcription factor of antioxidant enzymes, erythroid 2-related factor 2 level, which was reduced by UVB irradiation. Extracellular signal-regulated kinase (ERK) and Jun N-terminal kinases (JNK) are involved in the regulation of many cellular events, including apoptosis. SC treatment reversed ERK and JNK activation induced by UVB. Collectively, these data indicate that SC can provide remarkable cytoprotection against the adverse effects of UVB radiation by modulating cellular antioxidant systems, and suggest the potential of developing a medical agent for ROS-induced skin diseases.

Rosmarinic Acid Attenuates Cell Damage against UVB Radiation-Induced Oxidative Stress via Enhancing Antioxidant Effects in Human HaCaT Cells

This study was designed to investigate the cytoprotective effect of rosmarinic acid (RA) on ultraviolet B (UVB)-induced oxidative stress in HaCaT keratinocytes. RA exerted a significant cytoprotective effect by scavenging intracellular ROS induced by UVB. RA also attenuated UVB-induced oxidative macromolecular damage, including protein carbonyl content, DNA strand breaks, and the level of 8-isoprostane. Furthermore, RA increased the expression and activity of superoxide dismutase, catalase, heme oxygenase-1, and their transcription factor Nrf2, which are decreased by UVB radiation. Collectively, these data indicate that RA can provide substantial cytoprotection against the adverse effects of UVB radiation by modulating cellular antioxidant systems, and has potential to be developed as a medical agent for ROS-induced skin diseases.

Interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials: A review

The heterogeneous Fenton reaction can generate highly reactive hydroxyl radicals (OH) from reactions between recyclable solid catalysts and H2O2 at acidic or even circumneutral pH. Hence, it can effectively oxidize refractory organics in water or soils and has become a promising environmentally friendly treatment technology. Due to the complex reaction system, the mechanism behind heterogeneous Fenton reactions remains unresolved but fascinating, and is crucial for understanding Fenton chemistry and the development and application of efficient heterogeneous Fenton technologies. Iron-based materials usually possess high catalytic activity, low cost, negligible toxicity and easy recovery, and are a superior type of heterogeneous Fenton catalysts. Therefore, this article reviews the fundamental but important interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials. OH, hydroperoxyl radicals/superoxide anions (HO2/O2(-)) and high-valent iron are the three main types of reactive oxygen species (ROS), with different oxidation reactivity and selectivity. Based on the mechanisms of ROS generation, the interfacial mechanisms of heterogeneous Fenton systems can be classified as the homogeneous Fenton mechanism induced by surface-leached iron, the heterogeneous catalysis mechanism, and the heterogeneous reaction-induced homogeneous mechanism. Different heterogeneous Fenton systems catalyzed by characteristic iron-based materials are comprehensively reviewed. Finally, related future research directions are also suggested.

Isorhamnetin Protects Human Keratinocytes against Ultraviolet B-Induced Cell Damage

Isorhamnetin (3-methylquercetin) is a flavonoid derived from the fruits of certain medicinal plants. This study investigated the photoprotective properties of isorhamnetin against cell damage and apoptosis resulting from excessive ultraviolet (UV) B exposure in human HaCaT keratinocytes. Isorhamnetin eliminated UVB-induced intracellular reactive oxygen species (ROS) and attenuated the oxidative modification of DNA, lipids, and proteins in response to UVB radiation. Moreover, isorhamnetin repressed UVB-facilitated programmed cell death in the keratinocytes, as evidenced by a reduction in apoptotic body formation, and nuclear fragmentation. Additionally, isorhamnetin suppressed the ability of UVB light to trigger mitochondrial dysfunction. Taken together, these results indicate that isorhamnetin has the potential to protect human keratinocytes against UVB-induced cell damage and death.

6'-o-galloylpaeoniflorin protects human keratinocytes against oxidative stress-induced cell damage

6'-O-galloylpaeoniflorin (GPF) is a galloylated derivate of paeoniflorin and a key chemical constituent of the peony root, a perennial flowering plant that is widely used as an herbal medicine in East Asia. This study is the first investigation of the cytoprotective effects of GPF against hydrogen peroxide (H₂O₂)-induced cell injury and death in human HaCaT keratinocytes. GPF demonstrated a significant scavenging capacity against the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical, H₂O₂-generated intracellular reactive oxygen species (ROS), the superoxide anion radical (O₂^-), and the hydroxyl radical (•OH). GPF also safeguarded HaCaT keratinocytes against H₂O₂-provoked apoptotic cell death and attenuated oxidative macromolecular damage to DNA, lipids, and proteins. The compound exerted its cytoprotective actions in keratinocytes at least in part by decreasing the number of DNA strand breaks, the levels of 8-isoprostane (a stable end-product of lipid peroxidation), and the formation of carbonylated protein species. Taken together, these results indicate that GPF may be developed as a cytoprotector against ROS-mediated oxidative stress.

Diphlorethohydroxycarmalol attenuated cell damage against UVB radiation via enhancing antioxidant effects and absorbing UVB ray in human HaCaT keratinocytes

Exposure of human skin to excessive ultraviolet B (UVB) radiation induces pathophysiological processes via the generation of reactive oxygen species (ROS) in skin cells, such as keratinocytes. This study investigated the ability of diphlorethohydroxycarmalol (DPHC) to protect human keratinocytes (HaCaT) against UVB-induced cell damage. DPHC restored cell viability that was reduced by UVB light. DPHC had an absorption maximum close to the UVB spectrum and decreased UVB-induced intracellular ROS levels, increased levels of reduced glutathione, activated superoxide dismutase and catalase. DPHC also decreased UVB-mediated damage to cellular components, including lipids, proteins, DNA, and attenuated UVB-induced apoptosis. These results suggest that DPHC safeguards human keratinocytes against UVB-induced cell damage by absorbing UVB ray, scavenging ROS and enhancing antioxidant system.

Fisetin attenuates hydrogen peroxide-induced cell damage by scavenging reactive oxygen species and activating protective functions of cellular glutathione system

Hydrogen peroxide (H2O2) can induce cell damage by generating reactive oxygen species (ROS), resulting in DNA damage and cell death. The aim of this study is to elucidate the protective effects of fisetin (3,7,3',4',-tetrahydroxy flavone) against H2O2-induced cell damage. Fisetin reduced the level of superoxide anion, hydroxyl radical in cell free system, and intracellular ROS generated by H2O2. Moreover, fisetin protected against H2O2-induced membrane lipid peroxidation, cellular DNA damage, and protein carbonylation, which are the primary cellular outcomes of H2O2 treatment. Furthermore, fisetin increased the level of reduced glutathione (GSH) and expression of glutamate-cysteine ligase catalytic subunit, which is decreased by H2O2. Conversely, a GSH inhibitor abolished the cytoprotective effect of fisetin against H2O2-induced cells damage. Taken together, our results suggest that fisetin protects against H2O2-induced cell damage by inhibiting ROS generation, thereby maintaining the protective role of the cellular GSH system.

Photoprotective effect of Undaria crenata against ultraviolet B-induced damage to keratinocytes

Chronic exposure of the skin to ultraviolet B (UVB) radiation induces oxidative stress, which plays a crucial role in the induction of skin cancer. The brown alga Undaria crenata is a potential source of antioxidant and anti-apoptotic compounds due to its capacity to produce protective compounds against environmental factors, including UV radiation. The aim of this study was to investigate the photoprotective properties of an U. crenata ethanol extract (UCE) against UVB-induced cell damage in human HaCaT keratinocytes. UCE exhibited absorbing effect of UVB (280-320 nm) and scavenging activity against the 1,1-diphenyl-2-picrylhydrazyl radical and intracellular reactive oxygen species induced by hydrogen peroxide and UVB rays. Furthermore, electron spin resonance spectrometry revealed the significant scavenging effect of UCE against superoxide anion and hydroxyl radical. UCE reduced UVB-induced apoptosis, as shown by a decrease in apoptotic bodies and nuclear and DNA fragmentation, resulting in the recovery of cell viability. UCE also decreased the degree of UVB-induced oxidative stress to lipids, proteins, and DNA as shown by a decrease in 8-isoprostane level, protein carbonylation and DNA tails. These results suggest that UCE protects human keratinocytes against UVB-induced oxidative stress.

In vitro bactericidal activity of photo-irradiated oxydol products via hydroxyl radical generation

The oxidative power of hydroxyl radicals has been applied to disinfection systems for the purpose of oral hygiene by utilizing blue light-induced photolysis of hydrogen peroxide (H₂O₂) in our laboratory. In the present study, the bactericidal potential of blue light-irradiated oxydol products via hydroxyl radical generation was compared with that of 3% (w/v) H₂O₂. Eleven commercially available oxydol products were used in the present study. Even though a few of the products that contained ethanol, a hydroxyl radical scavenger, as an additive showed slightly lower hydroxyl radical yield as compared with 3% (w/v) H₂O₂, the blue-light irradiation of each oxydol product for 3 min showed similar or superior bactericidal activity against Staphylococcus aureus to that of 3% (w/v) H₂O₂. The results strongly suggest that any of the oxydol products tested in the present study can be used as a source of hydroxyl radicals for the disinfection technique developed in our laboratory.

An ethanol extract derived from Bonnemaisonia hamifera scavenges ultraviolet B (UVB) radiation-induced reactive oxygen species and attenuates UVB-induced cell damage in human keratinocytes

The present study investigated the photoprotective properties of an ethanol extract derived from the red alga Bonnemaisonia hamifera against ultraviolet B (UVB)-induced cell damage in human HaCaT keratinocytes. The Bonnemaisonia hamifera ethanol extract (BHE) scavenged the superoxide anion generated by the xanthine/xanthine oxidase system and the hydroxyl radical generated by the Fenton reaction (FeSO₄ + H₂O₂), both of which were detected by using electron spin resonance spectrometry. In addition, BHE exhibited scavenging activity against the 1,1-diphenyl-2-picrylhydrazyl radical and intracellular reactive oxygen species (ROS) that were induced by either hydrogen peroxide or UVB radiation. BHE reduced UVB-induced apoptosis, as shown by decreased apoptotic body formation and DNA fragmentation. BHE also attenuated DNA damage and the elevated levels of 8-isoprostane and protein carbonyls resulting from UVB-mediated oxidative stress. Furthermore, BHE absorbed electromagnetic radiation in the UVB range (280–320 nm). These results suggest that BHE protects human HaCaT keratinocytes against UVB-induced oxidative damage by scavenging ROS and absorbing UVB photons, thereby reducing injury to cellular components.

Chondracanthus tenellus (Harvey) hommersand extract protects the human keratinocyte cell line by blocking free radicals and UVB radiation-induced cell damage

The aim of this study was to investigate the protective effects of the ethanol extract of the red algae Chondracanthus tenellus (Harvey) Hommersand (CTE) on cultured human keratinocyte cell line. The cellular protection conferred by CTE was evidenced by the ability of the extract to absorb ultraviolet B (UVB; 280-320 nm) and to scavenge the radical 1,1-diphenyl-2-picrylhydrazyl, as well as intracellular reactive oxygen species (ROS), induced by either hydrogen peroxide (H(2)O(2)) or UVB radiation. In addition, both superoxide anion generated by the xanthine/xanthine oxidase system and hydroxyl radical generated by the Fenton reaction (FeSO(4) + H(2)O(2)) were scavenged by CTE, as confirmed using electron spin resonance spectrometry. In the human keratinocyte cell line, CTE decreased the degree of injury resulting from UVB-induced oxidative stress to lipids, proteins, and DNA. CTE-treated cells also showed a reduction in UVB-induced apoptosis, as exemplified by fewer apoptotic bodies and less DNA fragmentation. Taken together, these results suggest that CTE confers protection on the human keratinocyte cell line against UVB-induced oxidative stress by absorbing UVB ray and scavenging ROS, thereby reducing injury to cellular constituents.

Photo-protection by 3-bromo-4, 5-dihydroxybenzaldehyde against ultraviolet B-induced oxidative stress in human keratinocytes

Exposure of the skin to ultraviolet B (UVB) radiation leads to epidermal damage and the generation of reactive oxygen species (ROS) in skin cells, including keratinocytes. Therefore, the photo-protective effect of 3-bromo-4, 5-dihydroxybenzaldehyde (BDB) against UVB was assessed in human HaCaT keratinocytes exposed to UVB radiation in vitro. BDB restored cell viability, which decreased upon exposure to UVB radiation. BDB exhibited scavenging activity against 1, 1-diphenyl-2-picrylhydrazyl radicals, intracellular ROS induced by hydrogen peroxide (H(2)O(2)) or UVB radiation, the superoxide anion generated by the xanthine/xanthine oxidase system, and the hydroxyl radical generated by the Fenton reaction (FeSO(4)+H(2)O(2)). Moreover, BDB absorbed UVB and decreased injury resulting from UVB-induced oxidative stress to lipids, proteins and DNA. Finally, BDB reduced UVB-induced apoptosis, as exemplified by fewer apoptotic bodies and a reduction in DNA fragmentation. Taken together, these results suggest that BDB protects human keratinocytes against UVB-induced oxidative stress by scavenging ROS and absorbing UVB rays, thereby reducing injury to cellular components.

Increased glutathione synthesis following Nrf2 activation by vanadyl sulfate in human chang liver cells

Jeju ground water, containing vanadium compounds, was shown to increase glutathione (GSH) levels as determined by a colorimetric assay and confocal microscopy. To investigate whether the effects of Jeju ground water on GSH were specifically mediated by vanadium compounds, human Chang liver cells were incubated for 10 passages in media containing deionized distilled water (DDW), Jeju ground water (S1 and S3), and vanadyl sulfate (VOSO(4)). Vanadyl sulfate scavenged superoxide anion, hydroxyl radical and intracellular reactive oxygen species. Vanadyl sulfate effectively increased cellular GSH level and up-regulated mRNA and protein expression of a catalytic subunit of glutamate cysteine ligase (GCLC), which is involved in GSH synthesis. The induction of GCLC expression by vanadyl sulfate was found to be mediated by transcription factor erythroid transcription factor NF-E2 (Nrf2), which critically regulates GCLC by binding to the antioxidant response elements (AREs). Vanadyl sulfate treatment increased the nuclear translocation of Nrf2 and the accumulation of phosphorylated Nrf2. Extracellular regulated kinase (ERK) contributed to ARE-driven GCLC expression via Nrf2 activation. Vanadyl sulfate induced the expression of the active phospho form of ERK. Taken together, these results suggest that the increase in GSH level by Jeju ground water is, at least in part, due to the effects of vanadyl sulfate via the Nrf2-mediated induction of GCLC.

Kinetic analysis of reactive oxygen species generated by the in vitro reconstituted NADPH oxidase and xanthine oxidase systems

The nicotinamide adenine dinucleotide (NADH)/nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and the xanthine oxidase (XOD) systems generate reactive oxygen species (ROS). In the present study, to characterize the difference between the two systems, the kinetics of ROS generated by both the NADH oxidase and XOD systems were analysed by an electron spin resonance (ESR) spin trapping method using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), 5-(diethoxyphosphoryl)-5-methyl-pyrroline N-oxide (DEPMPO) and 5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO). As a result, two major differences in ROS kinetics were found between the two systems: (i) the kinetics of (•)OH and (ii) the kinetics of hydrogen peroxide. In the NADH oxidase system, the interaction of hydrogen peroxide with each component of the enzyme system (NADPH, NADH oxidase and FAD) was found to generate (•)OH. In contrast, (•)OH generation was found to be independent of hydrogen peroxide in the XOD system. In addition, the hydrogen peroxide level in the NADPH-NADH oxidase system was much lower than measured in the XOD system. This lower level of free hydrogen peroxide is most likely due to the interaction between hydrogen peroxide and NADPH, because the hydrogen peroxide level was reduced by ~90% in the presence of NADPH.

Applications of electron spin resonance spectrometry for reactive oxygen species and reactive nitrogen species research

Electron spin resonance (ESR) spectroscopy has been widely applied in the research of biological free radicals for quantitative and qualitative analyses of reactive oxygen species (ROS) and reactive nitrogen species (RNS). The ESR spin-trapping method was developed in the early 1970s and enabled the analysis of short-lived free radicals. This method is now widely used as one of the most powerful tools for free radical studies. In this report, some of the studies that applied ESR for the measurement of ROS and RNS during oxidative stress are discussed.

Scavenging or quenching effect of melanin on superoxide anion and singlet oxygen

Although photoprotective properties of skin melanin have been well documented, a few studies on the effect of melanin on reactive oxygen species (ROS) generated by ultraviolet (UV) irradiation have been reported. To study the interaction of melanin with ROS, scavenging or quenching effect of melanin on O(2) (*-) and (1)O(2) was examined by electron spin resonance (ESR)-spin trapping methods and a spectrophotometric method, respectively. Melanin potently interacted with O(2) (*-) generated in a hypoxanthine (HPX)-xanthine oxidase (XOD) reaction, and with (1)O(2) generated from a peroxidase, H(2)O(2), and halide system. In the HPX-XOD reaction, it was proved that melanin doses not interfere with the enzyme reaction. It is confirmed that one of the mechanisms by which melanin protects UV-induced skin damage is likely scavenging or quenching activity against ROS such as O(2) (*-) and (1)O(2).

Myristic Acid, A Side Chain of Phorbol Myristate Acetate (PMA), Can Activate Human Polymorphonuclear Leukocytes to Produce Oxygen Radicals More Potently than PMA

Myristic acid (MyA), which is a saturated fatty acid (C14:0) and a side chain of phorbol 12-myristate 13-acetate (PMA), was examined if MyA stimulates human polymorphonuclear leukocytes (PMNs) to release oxygen radicals comparable to PMA by applying electron paramagnetic resonance (EPR)-spin-trapping method. When MyA was added to isolated human PMNs, spin adducts of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)-OH and DMPO-OOH were time-dependently observed. The amounts of these spin adducts were larger than those of PMNs stimulated by PMA. These results clearly show that MyA is more potent agent to prime human PMNs than PMA, in a point of view of not only O₂^·− but also ·OH production. This fact calls attention that too much intake of MyA that is known to be contained vegetable oils can lead to crippling effect through uncontrolled production of reactive oxygen species.

Extensive screening for edible herbal extracts with potent scavenging activity against superoxide anions

To search for edible herbal extracts with potent antioxidant activity, we conducted a large scale screening based on the superoxide scavenging activity. That is, scavenging activity against superoxide anions were extensively screened from ethanol extracts of approximately 1,000 kinds of herbs by applying an electron spin resonance (ESR)-spin trapping method. Among them we chose four edible herbal extracts with prominently potent ability to reduce the signal intensity of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)-OOH, a spin adduct formed by DMPO and superoxide anion. They are the extracts from Punica granatum (Peel), Syzygium aromaticum (Bud), Mangifera indica (Kernel), and Phyllanthus emblica (Fruit), and are allowed to be used as foodstuffs according to the Japanese legal regulation. The ESR-spin trapping method coupled with steady state kinetic analysis showed that all of the four extracts directly scavenge superoxide anions, and that the superoxide scavenging potential of any of the extracts was comparable to that of L-ascorbic acid. Furthermore, polyphenol determination indicates that the activity is at least in part attributable to polyphenols. These results with such large scale screening might give useful information when choosing a potent antioxidant as a foodstuff.

Electron spin resonance analysis of superoxide anion radical scavenging activity with spin trapping agent, diphenyl-PMPO

Recently, a novel electron spin resonance (ESR) spin-trapping agent, 2-(diphenylphosphinoyl)-2-methyl-3,4-dihydro-2H-pyrrole N-oxide (Diphenyl-PMPO), was synthesized. Because it had some advantages in stability and reactivity over conventional spin-trapping agents, we applied it to the ESR analyses of superoxide anion radical scavenging activity (SOSA) of superoxide dismutase (SOD) and of well-known natural antioxidants (green tea, oolong tea, and red wine). At the same time, the results with Diphenyl-PMPO were compared with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Our results revealed that Diphenyl-PMPO showed higher detectability than DMPO in the SOSA assays of SOD and natural antioxidants, so it could be available for the ESR analyses as an alternative to conventional spin-trapping agents.

Radical scavenging and singlet oxygen quenching activity of marine carotenoid fucoxanthin and its metabolites

Antioxidant activity of carotenoids is suggested to be one of the factors for their disease preventing effects. Marine carotenoids fucoxanthin and its two metabolites, fucoxanthinol and halocynthiaxanthin, have been shown to exhibit several biological effects. The antioxidant activities of these three carotenoids were assessed in vitro with respect to radical scavenging and singlet oxygen quenching abilities. The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity of fucoxanthin and fucoxanthinol was higher than that of halocynthiaxanthin, with the effective concentration for 50% scavenging (EC 50) being 164.60, 153.78, and 826.39 microM, respectively. 2,2'-Azinobis-3-ethylbenzo thizoline-6-sulphonate radical scavenging activity of fucoxanthinol (EC 50, 2.49 microM) was stronger than that of fucoxanthin (EC 50, 8.94 microM). Hydroxyl radical scavenging activity as measured by the chemiluminescence technique showed that the scavenging activity of fucoxanthin was 7.9 times higher than that by fucoxanthinol, 16.3 times higher than that by halocynthiaxanthin, and 13.5 times higher than that by alpha-tocopherol. A similar trend was observed when the hydroxyl radical scavenging was assessed by the electron spin resonance (ESR) technique. ESR analysis of the superoxide radical scavenging activity also showed the superiority of fucoxanthin over the other two carotenoids tested. Singlet oxygen quenching ability of the three carotenoids was lower than that of beta-carotene, with quenching rate constants ( k Q, x10 (10) M (-1) s (-1)) being 1.19, 1.81, 0.80, and 12.78 for fucoxanthin, fucoxanthinol, halocynthiaxanthin, and beta-carotene, respectively. The higher radical scavenging activity of fucoxanthin and fucoxanthinol compared with halocynthiaxanthin is assumed to be due to presence of the allenic bond.

Free radical scavenging activity of propolis

We investigated the radical scavenging activity of propolis by ESR spectroscopy using spin trapping method. In addition, we examined the influence of a diet of 2% propolis on mice under oxidative stress. At low concentrations, the methanolic extract of propolis exhibited strong scavenging activity in vitro towards both the superoxide anion radical, generated by the hypoxanthine-xanthine oxidase reaction, and the NO radical, generated from the mixture of NOC-7 (NO generator) and carboxy-PTIO (spin trapping agent). An inhibitory effect of propolis on lipid peroxidation in vivo was observed, as determined by measurement of thiobarbituric acid-reactive substances in mouse liver homogenate. The level of vitamin C in the brain of mice under oxidative stress significantly increased compared with control mice under atmosphere, which was not observed in the mice given 2% propolis. The level of alpha-tocopherol in the brain of mice given 2% propolis significantly increased compared with control mice under atmosphere, which was not observed in mice under oxidative stress. SOD activity in the brain and plasma of mice given 2% propolis significantly decreased under atmosphere and oxidative stress compared with control mice. These results suggest that propolis possesses potent antioxidant activity in vitro and in vivo.

Physicochemical modeling of the role of free radicals in photodynamic therapy

A new kinetic approach is suggested and experimentally supported for quantification of the spin-trapping procedure. Accordingly, the concentration of the spin adduct formed in the interaction between the spin-trap DMPO and various free radicals (cyanopropylperoxy, cumylperoxy, phenylethylperoxy, and hydroperoxy radicals) generated by the initiated oxidation of the parent molecules is followed by kinetic ESR spectrometry. The initial sections of the corresponding kinetics are linear indicating that during this period the consumption of the adduct is negligible and thus the rate of accumulation (W(A)) approximates the rate of formation (W(f)): W(A) approximately W(f) = k(ST)[Rad(*)][DMPO], supported also by the fact that the rate of initiation of oxidation equals W(A) at high [DMPO]. In addition, the circulatory experimental apparatus enables calculation of the rate of molecular decomposition of the adduct by stopping circulation (W(f) becomes negligible) and following the decrease of the ESR signal. Corresponding rate constants are summarized.

Characterization of reactive oxygen species generated from the mixture of NaClO and H2O2 used as root canal irrigants

Characterization of a mixed solution of sodium hypochlorite (NaClO) and hydrogen peroxide (H2O2), which have been used as root canal irrigants, was investigated using electron spin resonance spectroscopy combined with a spin-trapping technique. In the solution, two kinds of reactive oxygen species, the superoxide anion radical (O2-.) and the hydroxyl radical (.OH), were detected. The pH changes and dissolved oxygen values in the NaClO-H2O2 reaction mixture were investigated. The pH influenced the generation of O2-. and .OH, and O2 was generated from H2O2. It is suggested that root canal irrigation with NaClO and H2O2 induces biological effects, such as tissue irritation (from the chemical reactions of O2-. and .OH) and physical effects, such as O2 bubbling.

Evaluation of free radical scavenging activities of antioxidants with an H(2)O(2)/NaOH/DMSO system by electron spin resonance

An H(2)O(2)/NaOH/DMSO system has been developed for the formation of three free radicals, and the application of the system was examined with the antioxidants ascorbic acid and tocopherol. Superoxide anion, hydroxyl radical,and methyl radical are simultaneously generated in this system. The scavenging activity of ascorbic acid and tocopherol for these radicals was estimated by 5, 5'-dimethyl-1-pyrroline-N-oxide spin trapping electron spin resonance. Both water-soluble and oil-soluble antioxidants could be evaluated by using this system. Ascorbic acid specifically inhibited the superoxide anion and hydroxyl radical, whereas tocopherol suppressed the methyl radical.

Quantification of singlet oxygen from hematoporphyrin derivative by electron spin resonance

The mechanism of the generation and the quantitative analysis of singlet oxygen (1O2) formed by the exposure of a hematoporphyrin derivative (HpD) to light was re-evaluated by electron spin resonance (ESR) combined with 2,2,6,6,-tetramethyl-4-piperidine (TMPD). The change from TMPD to 2,2,6,6,-tetramethyl-4-piperidine-N-oxide (TAN) has been reported to depend on singlet oxygen. However, we confirmed that this reagent also react with superoxide anion (O2-) and hydroxyl radicals (OH). Therefore, the reactions between TMPD and 1O2, O2- and OH were re-examined using a kinetic approach. We found that the generation of TAN was proportional to the concentration of TMPD and HpD, as well as to the duration and strength of the illumination. The generation of TAN was not inhibited by dimethyl-sulfoxide (DMSO) or superoxide dismutase (SOD). The reaction rate between TMPD and 1O2 was determined to be 5.0 x 10(-7) M min-1. The generation of 1O2 from HpD was 2.7 x 10(-7) M min-1 under our conditions. The competitive reaction observed between 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and TMPD for O2- or OH shows that TMPD reacts with both forms of active oxygen, but gave no ESR signal. The second-order reaction rate constant of TMPD between O2- and OH was calculated as 73 M-1 s-1 and 1.5 x 10(9) M-1 s-1, respectively. The photochemical generation of 1O2 from methylene blue, another sensitizer, was also demonstrated by this method. These results show that ESR signal of TAN can be used for the highly selective monitoring of 1O2.

Mechanisms of active oxygen species reduction by non-steroidal anti-inflammatory drugs

Many forms of active oxygen have been suggested to participate in the course of inflammation. Anti-inflammatory drugs have been considered to function as active oxygen inhibitors. However, detailed mechanisms for such inhibitory activity remain unclear because of little well established methods to study inhibitory effect of anti-inflammatory drugs on active oxygen species. In this report, the author investigated four non-steroidal anti-inflammatory drugs, including acetaminophen, sodium salicylate, naproxen and flurbiprofen, their elimination and inhibition ability of active oxygen, using of the electron spin resonance spin-trapping method and the horseradish peroxidase method. In this experiment as active oxygen models, superoxide was evolved from a hypoxanthine-xanthine oxidase reaction system, and hydrogen peroxide by the spontaneous dismutation reaction. The data here show that the amount of superoxide was reduced in the manner of concentration of non-steroidal anti-inflammatory drugs in the reaction. Kinetic studies for these reaction showed that acetaminophen and sodium salicylate reacted with superoxide competitively, whereas naproxen and flurbiprofen did not. Analysis of generation of hydrogen peroxide formed by the spontaneous dismutation of superoxide derived from the reaction system revealed that hydrogen peroxide was increased by acetaminophen and decreased by sodium salicylate, naproxen and flurbiprofen.