• Biomolecules & Therapeutics
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• v.26 no.6
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• pp.584-590
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• 2018

Osteoporosis development is closely associated with oxidative stress and reactive oxygen species (ROS). Taurine has potential antioxidant effects, but its role in osteoblasts is not clearly understood. The aim of this study was to determine the protective effects and mechanisms of actions of taurine on hydrogen peroxide ($H_2O_2$)-induced oxidative stress in osteoblast cells. UMR-106 cells were treated with taurine prior to $H_2O_2$ exposure. After treatment, cell viability, apoptosis, intracellular ROS production, malondialdehyde content, and alkaline phosphate (ALP) activity were measured. We also investigated the protein levels of ${\beta}-catenin$, ERK, CHOP and NF-E2-related factor 2 (Nrf2) along with the mRNA levels of Nrf2 downstream antioxidants. The results showed that pretreatment of taurine could reverse the inhibition of cell viability and suppress the induced apoptosis in a dose-dependent manner: taurine significantly reduced $H_2O_2$-induced oxidative damage and expression of CHOP, while it induced protein expression of Nrf2 and ${\beta}-catenin$ and activated ERK phosphorylation. DKK1, a Wnt/${\beta}-catenin$ signaling inhibitor, significantly suppressed the taurine-induced Nrf2 signaling pathway and increased CHOP. Activation of ERK signaling mediated by taurine in the presence of $H_2O_2$ was significantly inhibited by DKK1. These data demonstrated that taurine protects osteoblast cells against oxidative damage via Wnt/${\beta}-catenin$-mediated activation of the ERK signaling pathway.

• The Korean Journal of Physiology and Pharmacology
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• v.16 no.5
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• pp.313-320
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• 2012

In this study, we focused to identify whether eupatilin (5,7-dihydroxy-3',4',6-trimethoxyflavone), an extract from Artemisia argyi folium, prevents $H_2O_2$-induced injury of cultured feline esophageal epithelial cells. Cell viability was measured by the conventional MTT reduction assay. Western blot analysis was performed to investigate the expression of 5-lipoxygenase by $H_2O_2$ treatment in the absence and presence of inhibitors. When cells were exposed to 600 ${\mu}M$ $H_2O_2$ for 24 hours, cell viability was decreased to 40%. However, when cells were pretreated with 25~150 ${\mu}M$ eupatilin for 12 hours, viability was significantly restored in a concentration-dependent manner. $H_2O_2$-treated cells were shown to express 5-lipoxygenase, whereas the cells pretreated with eupatilin exhibited reduction in the expression of 5-lipoxygenase. The $H_2O_2$-induced increase of 5-lipoxygenase expression was prevented by SB202190, SP600125, or NAC. We further demonstrated that the level of leukotriene $B_4$ ($LTB_4$) was also reduced by eupatilin, SB202190, SP600125, NAC, or nordihydroguaiaretic acid (a lipoxygenase inhibitor) pretreatment. $H_2O_2$ induced the activation of p38MAPK and JNK, this activation was inhibited by eupatilin. These results indicate that eupatilin may reduce $H_2O_2$-induced cytotoxicity, and 5-lipoxygenase expression and $LTB_4$ production by controlling the p38 MAPK and JNK signaling pathways through antioxidative action in feline esophageal epithelial cells.

• The Korean Journal of Physiology and Pharmacology
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• v.10 no.1
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• pp.51-58
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• 2006

The promoting effect of hydrogen peroxide ($H_2O_2$) against the cytotoxicity of 1-methyl-4-phenylpyridinium ($MPP^+$) in differentiated PC12 cells was assessed by measuring the effect on the mitochondrial membrane permeability. Treatment of PC12 cells with $MPP^+$ resulted in the nuclear damage, decrease in the mitochondrial transmembrane potential, cytosolic accumulation of cytochrome c, activation of caspase-3, increase in the formation of reactive oxygen species (ROS) and depletion of GSH. Addition of $H_2O_2$ enhanced the $MPP^+-induced$ nuclear damage and cell death. Catalase, Carboxy-PTIO, Mn-TBAP, N-acetylcysteine, cyclosporin A and trifluoperazine inhibited the cytotoxic effect of $MPP^+$ in the presence of $H_2O_2$. Addition of $H_2O_2$ promoted the change in the mitochondrial membrane permeability, ROS formation and decrease in GSH contents due to $MPP^+$ in PC12 cells. The results show that the $H_2O_2$ treatment promotes the cytotoxicity of $MPP^+$ against PC12 cells. $H_2O_2$ may enhance the $MPP^+$-induced viability loss in PC12 cells by promoting the mitochondrial membrane permeability change, release of cytochrome c and subsequent activation of caspase-3, which is associated with the increased formation of ROS and depletion of GSH. The findings suggest that $H_2O_2$ as a promoting agent for the formation of mitochondrial permeability transition may enhance the neuronal cell injury caused by neurotoxins.

• Herbal Formula Science
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• v.26 no.4
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• pp.329-340
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• 2018

Objectives : In Traditional Korean medicine, Daucus carota L. has been used for treating dyspepsia, diarrhea, dysentery and cough. Recent pharmacognosic evidence showed D. carota has anti-oxidant, anti-cancer, anti-fungal, and hypotensive effects. Present study investigated hepato-protective effect of D. carota ethanol extract (DCE) against oxidative stress in HepG2 cells. Methods : After HepG2 cells were pretreated with different concentrations of DCE, the cells were exposed to tert-butyl hydroperoxide (tBHP) for inducing oxidative stress. Cell viability, hydrogen peroxide production, glutathione concentration, and mitochondrial membrane potentials were measured to explore hepato-protective effect of DCE. Phosphorylation of AMP-activated protein kinase (AMPK) and effect of compound C on cell viability were determined to investigate the role of AMPK on DCE-mediated cytoprotection. Results : DCE significantly decreased the tBHP-mediated cytotoxicity in a concentration dependent manner and reduced the changes on apoptosis-related proteins by tBHP in HepG2 cells. In addition, DCE significantly prevented hydrogen peroxide production, glutathione depletion, and mitochondrial membrane impairment induced by tBHP. Treatment with DCE increased phosphorylation of AMPK, and the DCE-mediated cytoprotection was abolished by pretreatment with compound C. Conclusions : These results demonstrate that DCE can protect hepatocytes from oxidative stress through activation of AMPK.

• Environmental Engineering Research
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• v.20 no.3
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• pp.205-211
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• 2015

Reduced forms of iron, such as zero-valent ion (ZVI) and ferrous ion (Fe[II]), can activate dissolved oxygen in water into reactive oxidants capable of oxidative water treatment. The corrosion of ZVI (or the oxidation of (Fe[II]) forms a hydrogen peroxide ($H_2O_2$) intermediate and the subsequent Fenton reaction generates reactive oxidants such as hydroxyl radical ($^{\bullet}OH$) and ferryl ion (Fe[IV]). However, the production of reactive oxidants is limited by multiple factors that restrict the electron transfer from iron to oxygen or that lead the reaction of $H_2O_2$ to undesired pathways. Several efforts have been made to enhance the production of reactive oxidants by iron-induced oxygen activation, such as the use of iron-chelating agents, electron-shuttles, and surface modification on ZVI. This article reviews the chemistry of oxygen activation by ZVI and Fe(II) and its application in oxidative degradation of organic contaminants. Also discussed are the issues which require further investigation to better understand the chemistry and develop practical environmental technologies.

• Korean Journal of Food Science and Technology
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• v.31 no.5
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• pp.1363-1370
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• 1999

This study was performed to investigate the average molecular weight range of chitosan hydrolysates showing maximum effect in macrophage activation. Nitrite production by continuous macrophage cell line J774A.1 was the highest at $10\;{\mu}g/ml$ concentration of intact chitosan. Hydrogen peroxide production by J774A.1 showed the high value of $894\;{\mu}M/mg$ macrophage protein at $1,000\;{\mu}g/ml$ concentration of chitosan hydrolysate fraction 5 and $1,044\;{\mu}M/mg$ macrophage protein at $100\;{\mu}g/ml$ concentration of the fraction 6. Chitsan hydrolysate fraction 4, fraction 6 and intact chitosan enhanced $IL-1{\alpha}$ production, while the others did not. The production of tumor necrosis factor showed the high value at $1,000\;{\mu}g/ml$ concentration of chitosan hydrolysate fraction 4, $100\;{\mu}g/ml$ concentration of the fraction 5 and fraction 6, and $10\;{\mu}g/ml$ concentration of intact chitosan. In conclusion, fractions 4, 5 and 6 of the chitosan hydrolysatets with average molecular weight of $24,000{\sim}64,000$ calculated by HPLC analysis are the most effective in macrophage activation tested in this study.

• Biomolecules & Therapeutics
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• v.28 no.1
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• pp.25-33
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• 2020

Several recent studies have reported that reactive oxygen species (ROS), superoxide anion and hydrogen peroxide (H₂O₂), play important roles in various cellular signaling networks. NADPH oxidase (Nox) isozymes have been shown to mediate receptor-mediated ROS generation for physiological signaling processes involved in cell growth, differentiation, apoptosis, and fibrosis. Detectable intracellular levels of ROS can be induced by the electron leakage from mitochondrial respiratory chain as well as by activation of cytochrome p450, glucose oxidase and xanthine oxidase, leading to oxidative stress. The up-regulation and the hyper-activation of NADPH oxidases (Nox) also likely contribute to oxidative stress in pathophysiologic stages. Elevation of the renal ROS level through hyperglycemia-mediated Nox activation results in the oxidative stress which induces a damage to kidney tissues, causing to diabetic nephropathy (DN). Nox inhibitors are currently being developed as the therapeutics of DN. In this review, we summarize Nox-mediated ROS generation and development of Nox inhibitors for therapeutics of DN treatment.

• Molecules and Cells
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• v.26 no.4
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• pp.329-337
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• 2008

Src-family kinases are critically involved in the control of cytoskeleton organization and in the generation of integrin-dependent signaling responses, inducing tyrosine phosphorylation of many signaling and cytoskeletal proteins. Activity of the Src family of tyrosine kinases is tightly controlled by inhibitory phosphorylation of a carboxy-terminal tyrosine residue, inducing an inactive conformation through binding with its SH2 domain. Dephosphorylation of C-ter tyrosine, as well as its deletion of substitution with phenylalanine in oncogenic Src kinases, leads to autophosphorylation at a tyrosine in the activation loop, thereby leading to enhanced Src activity. Beside this phophorylation/dephosphorylation circuitry, cysteine oxidation has been recently reported as a further mechanism of enzyme activation. Mounting evidence describes Src activation via its redox regulation as a key outcome in several circumstances, including growth factor and cytokines signaling, integrin-mediated cell adhesion and motility, membrane receptor cross-talk as well in cell transformation and tumor progression. Among the plethora of data involving Src kinase in physiological and pathophysiological processes, this review will give emphasis to the redox component of the regulation of this master kinase.

• Restorative Dentistry and Endodontics
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• v.36 no.4
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• pp.306-312
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• 2011

Objectives: This clinical study evaluated the effect of light activation on the whitening efficacy and safety of in-office bleaching system containing 15% hydrogen peroxide gel. Materials and Methods: Thirty-three volunteers were randomly treated with (n = 17, experimental group) or without light activation (n = 16, control group), using Zoom2 white gel (15% $H_2O_2$, Discus Dental) for a total treatment time of 45 min. Visual and instrumental color measurements were obtained using Vitapan Classical shade guide and Shadepilot (DeguDent) at screening test, after bleaching, and 1 month and 3 month after bleaching. Data were analyzed using t-test, repeated measure ANOVA, and chi-squared test. Results: Zoom2 white gel produced significant shade changes in both experimental and control group when pre-treatment shade was compared with that after bleaching. However, shade difference between two groups was not statistically significant (p > 0.05). Tooth shade relapse was not detected at 3 months after bleaching. The incidence of transient tooth sensitivity was 39.4%, with being no differences between two groups. Conclusions: The application of light activation with Zoom2 white gel system neither achieved additional whitening effects nor showed more detrimental influences.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.63-70
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• 2023

Ultrasound-assisted dissolution of U₃O₈ powder in carbonate solution was explored to determine if and how ultrasound act during the dissolution. The variation of U₃O₈ solid particles and uranyl complexes under ultrasound treatment and magnetic stirring was observed in carbonate media. The results show that the use of ultrasound can increase the solubility and dissolution rate of U₃O₈ powder than that under magnetic stirring. The crush of U₃O₈ particles and the reduction of the activation energy (Ea, kJ/mol) of U₃O₈ dissolution reaction were observed, which both play an important role in the ultrasonic-assisted dissolution of U₃O₈ in carbonate-peroxide solution. Meanwhile, there is no observation of the ultrasound effect on the distribution of uranyl species and hydrolysis of uranyl complexes during the ultrasound treatment in carbonate-peroxide solution. Although the generation of ·OH radicals under ultrasound (22 ± 2 kHz) was observed, the oxidation of ·OH had little effect on the dissolution of U₃O₈ in the carbonate-peroxide solution system.