In Kyung Lee

Silver nanoparticles induce oxidative cell damage in human liver cells through inhibition of reduced glutathione and induction of mitochondria-involved apoptosis.

Silver nanoparticles (AgNPs), which have well-known antimicrobial properties, are extensively used in various medical and general applications. Despite the widespread use of AgNPs, relatively few studies have been undertaken to determine the cytotoxic effects of AgNPs exposure. This study investigates possible molecular mechanisms underlying the cytotoxic effects of AgNPs. Here, we show that AgNPs-induced cytotoxicity was higher compared than that observed when AgNO(3) was used as a silver ion source. AgNPs induced reactive oxygen species (ROS) generation and suppression of reduced glutathione (GSH) in human Chang liver cells. ROS generated by AgNPs resulted in damage to various cellular components, DNA breaks, lipid membrane peroxidation, and protein carbonylation. Upon AgNPs exposure, cell viability decreased due to apoptosis, as demonstrated by the formation of apoptotic bodies, sub-G(1) hypodiploid cells, and DNA fragmentation. AgNPs induced a mitochondria-dependent apoptotic pathway via modulation of Bax and Bcl-2 expressions, resulting in the disruption of mitochondrial membrane potential (Δψ(m)). Loss of Δψ(m) was followed by cytochrome c release from the mitochondria, resulting in the activation of caspases 9 and 3. The apoptotic effect of AgNPs was exerted via the activation of c-Jun NH(2)-terminal kinase (JNK) and was abrogated by the JNK-specific inhibitor, SP600125 and siRNA targeting JNK. In summary, the results suggest that AgNPs cause cytotoxicity by oxidative stress-induced apoptosis and damage to cellular components.

Eckol protects V79-4 lung fibroblast cells against γ-ray radiation-induced apoptosis via the scavenging of reactive oxygen species and inhibiting of the c-Jun NH2-terminal kinase pathway

The radioprotective effect of eckol against gamma-ray radiation-induced oxidative stress and its possible protective mechanisms were investigated. Eckol was found to reduce the intracellular reactive oxygen species generated by gamma-ray radiation. Moreover, eckol also protected against radiation-induced cellular DNA damage and membrane lipid peroxidation, which are the main targets of radiation-induced damage. In addition, eckol recovered the cell viability damaged by radiation via the inhibition of apoptosis. Irradiated cells with eckol treatment reduced the expression of bax, the activation of caspase 9 and caspase 3, which were induced by radiation. However, irradiated cells with eckol recovered the expression of bcl-2 and mitochondrial cytochrome c which were decreased by radiation. The anti-apoptotic effect of eckol exerted via the inhibition of mitogen-activated protein kinase kinase-4 (MKK4/SEK1)-c-Jun NH(2)-terminal kinase (JNK)-activator protein 1 (AP-1) cascades induced by radiation. In summary, the results suggest that eckol protects cells against the oxidative stress induced by radiation via the reduction of reactive oxygen species and the attenuation of activation in SEK1-JNK-AP-1 pathway.

Mitochondria protection of baicalein against oxidative damage via induction of manganese superoxide dismutase.

This study investigated the cytoprotective effect of baicalein (5,6,7-trihydroxyflavone) against oxidative stress-induced mitochondrial dysfunction. Electron spin resonance (ESR) spectrometry revealed that baicalein showed significant scavenging effects on superoxide radicals and hydroxyl radicals. When H(2)O(2) treatment induces an increase in mitochondrial reactive oxygen species (ROS), baicalein treatment decreased high level of ROS. Baicalein significantly reduced alteration of Bcl-2 family proteins, the release of cytochrome c from mitochondria into the cytosol via inhibition of mitogen-activated protein kinase kinase-4 (MKK4/SEK1) and c-Jun NH(2)-terminal kinase (JNK) cascades induced by H(2)O(2) treatment. Manganese superoxide dismutase (MnSOD) is an important antioxidant enzyme in mitochondria against oxidative stress. Baicalein restored both MnSOD protein expression and activity, which were abolished by H(2)O(2) treatment. The transcription factor NF-E2-related factor 2 (Nrf2) is a critical regulator of MnSOD, achieved by binding to the antioxidant response element (ARE). Baicalein restored nuclear Nrf2 protein expression and its ARE binding activity, which were abolished by H(2)O(2) treatment. These studies demonstrate that baicalein attenuates mitochondrial oxidative stress by activating Nrf2-mediated MnSOD induction.

Radioprotective effect of geraniin via the inhibition of apoptosis triggered by γ-radiation-induced oxidative stress.

The radioprotective effect of geraniin, a tannin compound isolated from Nymphaea tetragona Georgi var. (Nymphaeaceae), against γ-radiation-induced damage was investigated in Chinese hamster lung fibroblast (V79-4) cells. Geraniin recovered cell viability detected by MTT test and colony formation assay, which was compromised by γ-radiation, and reduced the γ-radiation-induced apoptosis by the inhibition of loss of the mitochondrial membrane potential. Geraniin protected cellular components (lipid membrane, cellular protein, and DNA) damaged by γ-radiation, which was detected by lipid peroxidation, protein carbonyl formation, and comet assay. Geraniin significantly reduced the level of intracellular reactive oxygen species generated by γ-radiation, which was detected using spectrofluorometer, flow cytometer, and confocal microscope after 2′,7′-dichlorodihydrofluorescein diacetate staining. Geraniin normalized the superoxide dismutase and catalase activities, which were decreased by γ-radiation. These results suggest that geraniin protects cells against radiation-induced oxidative stress via enhancing of antioxidant enzyme activities and attenuating of cellular damage.

Cytoprotective Effects of Triphlorethol-A Against Formaldehyde-Induced Oxidative Damage and Apoptosis: Role of Mitochondria-Mediated Caspase-Dependent Pathway

The toxicity of formaldehyde (HCHO) has been attributed to its ability to form adducts with DNA and proteins. Triphlorethol-A, derived from Ecklonia cava, was reported to exert a cytoprotective effect against oxidative stress damage via an antioxidant mechanism. The aim of this study was to examine the mechanisms underlying the triphlorethol-A ability to protect Chinese hamster lung fibroblast (V79-4) cells against HCHO-induced damage. Triphlorethol-A significantly decreased the HCHO-induced intracellular reactive oxygen species (ROS) production. Triphlorethol-A prevented increased cell damage induced by HCHO via inhibition of mitochondria-mediated caspase-dependent apoptosis pathway. Triphlorethol-A diminished HCHO-induced mitochondrial dysfunction, including loss of mitochondrial membrane action potential (Δψ) and adenosine triphosphate (ATP) depletion. Furthermore, the anti-apoptotic effect of triphlorethol-A was exerted through inhibition of c-Jun NH2-terminal kinase (JNK), which was enhanced by HCHO. Our data indicate that triphlorethol-A exerts a cytoprotective effect in V79-4 cells against HCHO-induced oxidative stress by inhibiting the mitochondria-mediated caspase-dependent apoptotic pathway.

Butin reduces oxidative stress-induced mitochondrial dysfunction via scavenging of reactive oxygen species

This study investigated the cytoprotective effect of butin, a flavonoid, on hydrogen peroxide (H(2)O(2))-induced mitochondrial dysfunction. Electron spin resonance (ESR) spectrometry revealed butins significant scavenging effects on superoxide radicals and hydroxyl radicals. When H(2)O(2) was used to induce an increase in mitochondrial reactive oxygen species (ROS) in Chinese hamster lung fibroblast (V79-4) cells, butin treatment decreased high level of ROS. Butin also attenuated intracellular Ca(2+) levels that have been induced by H(2)O(2). Furthermore, butin recovered ATP levels and succinate dehydrogenase activity that had been decreased by H(2)O(2) treatment. We conclude these results suggest butin decreased mitochondrial ROS accumulation, balanced intracellular Ca(2+) levels, and improved mitochondrial energy production, thus recovering mitochondrial function.

7,8-Dihydroxyflavone suppresses oxidative stress-induced base modification in DNA via induction of the repair enzyme 8-oxoguanine DNA glycosylase-1.

The modified guanine base 8-oxoguanine (8-oxoG) is abundantly produced by oxidative stress, can contribute to carcinogenesis, and can be removed from DNA by 8-oxoguanine DNA glycosylase-1 (OGG1), which acts as an 8-oxoG glycosylase and endonuclease. This study investigated the mechanism by which 7,8-dihydroxyflavone (DHF) inhibits oxidative stress-induced 8-oxoG formation in hamster lung fibroblasts (V79-4). DHF significantly reduced the amount of 8-oxoG induced by hydrogen peroxide (H2O2) and elevated the levels of OGG1 mRNA and protein. DHF increased the binding of nuclear factor erythroid 2-related factor 2 (Nrf2) to antioxidant response element sequences in the upstream promoter region of OGG1. Moreover, DHF increased the nuclear levels of Nrf2, small Maf proteins, and the Nrf2/small Maf complex, all of which are decreased by H2O2 treatment. Likewise, the level of phosphorylated Akt, which activates Nrf2, was decreased by H2O2 treatment but restored by DHF treatment. The levels of OGG1 and nuclear translocation of Nrf2 protein were decreased upon treatment with PI3K inhibitor or Akt inhibitor, and DHF treatment did not restore OGG1 and nuclear Nrf2 levels in these inhibitor-treated cells. Furthermore, PI3K and Akt inhibitors abolished the protective effects of DHF in cells undergoing oxidative stress. These data indicate that DHF induces OGG1 expression via the PI3K-Akt pathway and protects cells against oxidative DNA base damage by activating DNA repair systems.

Empetrum nigrum var. japonicum Extract Suppresses γ-Ray Radiation-Induced Cell Damage via Inhibition of Oxidative Stress

The ethylacetate fraction of Empetrum nigrum var. japonicum (ENE) was shown to reduce intracellular reactive oxygen species (ROS) generated by γ-radiation and activate antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), and gluthathion peroxidase (GPx). ENE protected cells against radiation-induced cellular DNA damage, membrane lipid peroxidation, and protein modification, which are the main points of radiation-induced damage. In addition, ENE recovered cell viability by inhibiting apoptosis after cells were treated with radiation. ENE treatment also reduced γ-radiation induced Bax, and caspase 9 and 3 expression in irradiated cells. However, irradiated cells with ENE recovered Bcl-2 expression, which was reduced by radiation. This anti-apoptotic effect of ENE was due to the inhibition of mitogen-activated protein kinase kinase-4 (MKK4/SEK1)-c-Jun NH(2)-terminal kinase (JNK) cascades induced by γ-radiation. In summary, these results suggest that ENE protects cells against γ-radiation-induced oxidative stress via the reduction of ROS and attenuation of apoptosis.

Butin (7,3',4'-Trihydroxydihydroflavone) Reduces Oxidative Stress-Induced Cell Death via Inhibition of the Mitochondria-Dependent Apoptotic Pathway

Recently, we demonstrated that butin (7,3′,4′-trihydroxydihydroflavone) protected cells against hydrogen peroxide (H2O2)-induced apoptosis by: (1) scavenging reactive oxygen species (ROS), activating antioxidant enzymes such superoxide dismutase and catalase; (2) decreasing oxidative stress-induced 8-hydroxy-2′-deoxyguanosine levels via activation of oxoguanine glycosylase 1, and (3), reducing oxidative stress-induced mitochondrial dysfunction. The objective of this study was to determine the cytoprotective effects of butin on oxidative stress-induced mitochondria-dependent apoptosis, and possible mechanisms involved. Butin significantly reduced H2O2-induced loss of mitochondrial membrane potential as determined by confocal image analysis and flow cytometry, alterations in Bcl-2 family proteins such as decrease in Bcl-2 expression and increase in Bax and phospho Bcl-2 expression, release of cytochrome c from mitochondria into the cytosol and activation of caspases 9 and 3. Furthermore, the anti-apoptotic effect of butin was exerted via inhibition of mitogen-activated protein kinase kinase-4, c-Jun NH2-terminal kinase (JNK) and activator protein-1 cascades induced by H2O2 treatment. Finally, butin exhibited protective effects against H2O2-induced apoptosis, as demonstrated by decreased apoptotic bodies, sub-G1 hypodiploid cells and DNA fragmentation. Taken together, the protective effects of butin against H2O2-induced apoptosis were exerted via blockade of membrane potential depolarization, inhibition of the JNK pathway and mitochondria-involved caspase-dependent apoptotic pathway.