Neuroprotective effect of Capsicum annuum var. abbreviatum against hydrogen peroxide-induced oxidative stress in HT22 hippocampus cells

ABSTRACT

Phenolic compounds isolated from pepper (Capsicum annum) have been demonstrated to have neuroprotective effects, whereas the physiological properties of Capsicum annuum var. abbreviatum (CAA) have not been studied. Thus, we investigate the chemical composition and neuroprotective activity of CAA extract (CAAE) in HT22 hippocampus cells against H₂O₂-induced neurotoxicity. CAAE treatment resulted in a significant protection of H₂O₂-exposed HT22, this protection ultimately occurred through an inhibition of MDA and ROS levels and an induction of SOD activity. Furthermore, CAAE treatment reduced H₂0₂-induced apoptosis though decreasing the expression of pro-apoptotic factors (Bax, cytochrome c, and cleaved caspases-3) while increasing the expression of the anti-apoptotic factors (Bcl-2), as well as the accumulation of nucleus-Nrf2-mediated HO-1 signaling. Interestingly, CAAE has a high concentration of unique phenolic compositions (chlrogenic acid, tangeretin, etc.) than other capsicum annum extracts. Altogether, these findings suggest that CAAE can be a useful natural resource for alleviating neurodegenerative diseases.     

Carvedilol,a third-generation β-blocker prevents oxidative stress-induced neuronal death and activates Nrf2/ARE pathway in HT22 cells

Carvedilol, a nonselective β-adrenoreceptor blocker with pleiotropic activities has been shown to exert neuroprotective effect due to its antioxidant property. However, the neuroprotective mechanism of carvedilol is still not fully uncovered. Nuclear factor E2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway is an important cellular stress response pathway involved in neuroprotection. Here we investigated the effect of carvedilol on oxidative stress-induced cell death (glutamate 2 mM and H₂O₂ 600 μM) and the activity of Nrf2/ARE pathway in HT22 hippocampal cells. Carvedilol significantly increased cell viability and decreased ROS in HT22 cells exposed to glutamate or H₂O₂. Furthermore, carvedilol activated the Nrf2/ARE pathway in a concentration-dependent manner, and increased the protein levels of heme oxygenase-1(HO-1) and NAD(P)H quinone oxidoreductase-1(NQO-1), two downstream factors of the Nrf2/ARE pathway. Collectively, our results indicate that carvedilol protects neuronal cell against glutamate- and H₂O₂-induced neurotoxicity possibly through activating the Nrf2/ARE signaling pathway.     

Dual cell protective mechanisms activated by differing levels of oxidative stress in HT22 murine hippocampal cells

Oxidative stress is recognized as one of the pathogenic mechanisms involved in neurodegenerative disease. However, recent evidence has suggested that regulation of cellular fate in response to oxidative stress appears to be dependent on the stress levels. In this study, using HT22 cells, we attempted to understand how an alteration in the oxidative stress levels would influence neuronal cell fate. HT22 cell viability was reduced with exposure to high levels of oxidative stress, whereas, low levels of oxidative stress promoted cell survival. Erk1/2 activation induced by a low level of oxidative stress played a role in this cell protective effect. Intriguingly, subtoxic level of H₂O₂ induced expression of a growth factor, progranulin (PGRN), and exogenous PGRN pretreatment attenuated HT22 cell death induced by high concentrations of H₂O₂ in Erk1/2-dependent manner. Together, our study indicates that two different cell protection mechanisms are activated by differing levels of oxidative stress in HT22 cells.     

Neuroprotective effect of PEP-1-peroxiredoxin2 on CA1 regions in the hippocampus against ischemic insult

Background

Oxidative stress is a leading cause of various diseases, including ischemia and inflammation. Peroxiredoxin2 (PRX2) is one of six mammalian isoenzymes (PRX1–6) that can reduce hydrogen peroxide (H₂O₂) and organic hydroperoxides to water and alcohols.

Methods

We produced PEP-1-PRX2 transduction domain (PTD)-fused protein and investigated the effect of PEP-1-PRX2 on oxidative stress-induced neuronal cell death by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Western blot, immunofluorescence microscopy, and immunohistochemical analysis.

Results

Our data showed that PEP-1-PRX2, which can effectively transduce into various types of cells and brain tissues, could be implicated in suppressing generation of reactive oxygen species, preventing depolarization of the mitochondrial membrane, and inhibiting the apoptosis pathway in H₂O₂-stimulated HT22, murine hippocampal neuronal cells, likely resulting in protection of HT22 cells against H₂O₂-induced toxicity. In addition, we found that in a transient forebrain ischemia model, PEP-1-PRX2 inhibited the activation of astrocytes and microglia in the CA1 region of the hippocampus and lipid peroxidation and also prevented neuronal cell death against ischemic damage.

Conclusions

These findings suggest that the transduced PEP-1-PRX2 has neuroprotective functions against oxidative stress-induced cell death in vitro and in vivo.

General significance

PEP-1-PRX2 could be a potential therapeutic agent for oxidative stress-induced brain diseases such as ischemia.     

Blockade of SOCE protects HT22 cells from hydrogen peroxide-induced apoptosis

Oxidative stress is an established event in the pathology of neurobiological diseases. Previous studies indicated that store-operated Ca²⁺ entry (SOCE) has been involved in oxidative stress. The present study was carried out to investigate the effects of SOCE inhibition on neuronal oxidative stress injury induced by hydrogen peroxide (H₂O₂) in HT22 cells, a murine hippocampal neuronal model. H₂O₂ insult induced significant intracellular Ca²⁺ overload, mitochondrial dysfunction and cell viability decrease. Inhibition of SOCE by pharmacological inhibitor and STIM1 RNAi significantly alleviated intracellular Ca²⁺ overload, restored the mitochondrial membrane potential (MMP), decreased cytochrome C release and eventually inhibited H₂O₂-induced cell apoptosis. These findings suggest that SOCE inhibition exhibited neuroprotection against oxidative stress induced by H₂O₂ and SOCE might be a useful therapeutic target in neurobiological disorders.     

Hydroxytyrosol glucuronides protect renal tubular epithelial cells against H(2)O(2) induced oxidative damage

Hydroxytyrosol (2-(3′,4′-dihydroxyphenyl)ethanol; HT), the most active ortho-diphenolic compound, present either in free or esterified form in extravirgin olive oil, is extensively metabolized in vivo mainly to O-methylated, O-sulfated and glucuronide metabolites. We investigated the capacity of three glucuronide metabolites of HT, 3′-O-β-d-glucuronide and 4′-O-β-d-glucuronide derivatives and 2-(3′,4′-dihydroxyphenyl)ethanol-1-O-β-d-glucuronide, in comparison with the parent compound, to inhibit H₂O₂ induced oxidative damage and cell death in LLC-PK1 cells, a porcine kidney epithelial cell line. H₂O₂ treatment exerted a toxic effect inducing cell death, interacting selectively within the pro-death extracellular-signal relate kinase (ERK 1/2) and the pro-survival Akt/PKB signaling pathways. It also produced direct oxidative damage initiating the membrane lipid peroxidation process. None of the tested glucuronides exhibited any protection against the loss in renal cell viability. They also failed to prevent the changes in the phosphorylation states of ERK and Akt, probably reflecting their inability to enter the cells, while HT was highly effective. Notably, pretreatment with glucuronides exerted a protective effect at the highest concentration tested against membrane oxidative damage, comparable to that of HT: the formation of malondialdehyde, fatty acid hydroperoxides and 7-ketocholesterol was significantly inhibited.     

Oxidative stress impairs autophagic flux in prion protein-deficient hippocampal cells

We previously reported that autophagy is upregulated in Prnp-deficient (Prnp^0/0) hippocampal neuronal cells in comparison to cellular prion protein (PrP^C)-expressing (Prnp^+/+) control cells under conditions of serum deprivation. In this study, we determined whether a protective mechanism of PrP^C is associated with autophagy using Prnp^0/0 hippocampal neuronal cells under hydrogen peroxide (H₂O₂)-induced oxidative stress. We found that Prnp^0/0 cells were more susceptible to oxidative stress than Prnp^+/+ cells in a dose- and time-dependent manner. In addition, we observed enhanced autophagy by immunoblotting, which detected the conversion of microtubule-associated protein 1 light chain 3 β (LC3B)-I to LC3B-II, and we observed increased punctate LC3B immunostaining in H₂O₂-treated Prnp^0/0 cells compared with H₂O₂-treated control cells. Interestingly, this enhanced autophagy was due to impaired autophagic flux in the H₂O₂-treated Prnp^0/0 cells, while the H₂O₂-treated Prnp^+/+ cells showed enhanced autophagic flux. Furthermore, caspase-dependent and independent apoptosis was observed when both cell lines were exposed to H₂O₂. Moreover, the inhibition of autophagosome formation by Atg7 siRNA revealed that increased autophagic flux in Prnp^+/+ cells contributes to the prosurvival effect of autophagy against H₂O₂ cytotoxicity. Taken together, our results provide the first experimental evidence that the deficiency of PrP^C may impair autophagic flux via H₂O₂-induced oxidative stress.     

Tat-glyoxalase protein inhibits against ischemic neuronal cell damage and ameliorates ischemic injury

Methylglyoxal (MG), a metabolite of glucose, is the major precursor of protein glycation and induces apoptosis. MG is associated with neurodegeneration, including oxidative stress and impaired glucose metabolism, and is efficiently metabolized to S-D-lactoylglutathione by glyoxalase (GLO). Although GLO has been implicated as being crucial in various diseases including ischemia, its detailed functions remain unclear. Therefore, we investigated the protective effect of GLO (GLO1 and GLO2) in neuronal cells and an animal ischemia model using Tat-GLO proteins. Purified Tat-GLO protein efficiently transduced into HT-22 neuronal cells and protected cells against MG- and H₂O₂-induced cell death, DNA fragmentation, and activation of caspase-3 and mitogen-activated protein kinase. In addition, transduced Tat-GLO protein increased D-lactate in MG- and H₂O₂-treated cells whereas glycation end products (AGE) and MG levels were significantly reduced in the same cells. Gerbils treated with Tat-GLO proteins displayed delayed neuronal cell death in the CA1 region of the hippocampus compared with a control. Furthermore, the combined neuroprotective effects of Tat-GLO1 and Tat-GLO2 proteins against ischemic damage were significantly higher than those of each individual protein. Those results demonstrate that transduced Tat-GLO protein protects neuronal cells by inhibiting MG- and H₂O₂-mediated cytotoxicity in vitro and in vivo. Therefore, we suggest that Tat-GLO proteins could be useful as a therapeutic agent for various human diseases related to oxidative stress including brain diseases.     

Application of confocal laser scanning microscopy to detect oxidative stress in human colon cells

Introduction Excess of intracellular reactive oxygen species in relation to antioxidative systems results in an oxidative environment which may modulate gene expression or damage cellular molecules. These events are expected to greatly contribute to processes of carcinogenesis. Only few studies are available on the oxidative/reductive conditions in the colon, an important tumour target tissue. It was the objective of this work to further develop methods to assess intracellular oxidative stress within human colon cells as a tool to study such associations in nutritional toxicology.

Methods We have measured H₂O₂-induced oxidative stress in different colon cell lines, in freshly isolated human colon crypts, and, for comparative purposes, in NIH3T3 mouse embryo fibroblasts. Detection was performed by loading the cells with the fluorigenic peroxide-sensitive dye 6-carboxy-2′,7′-dichlorodihydrofluorescein diacetate (diacetoxymethyl ester), followed by in vitro treatment with H₂O₂ and fluorescence detection with confocal laser scanning microscopy (CLSM). Using the microgel electrophoresis (“Comet”) Assay, we also examined HT29 stem and clone 19A cells and freshly isolated primary colon cells for their relative sensitivity toward H₂O₂-induced DNA damage and for steady-state levels of endogenous oxidative DNA damage.

Results A dose-response relationship was found for the H₂O₂-induced dye decomposition in NIH3T3 cells (7.8–125 μM H₂O₂) whereas no effect occurred in the human colon tumour cell lines HT29 stem and HT29 clone 19A (62–1000 μM H₂O₂). Fluorescence was significantly increased at 62 μM H₂O₂ in the human colon adenocarcinoma cell line Caco-2. In isolated human colon crypts, the lower crypt cells (targets of colon cancer) were more sensitive towards H₂O₂ than the more differentiated upper crypt cells. In contrast to the CLSM results, oxidative DNA damage was detected in both cell lines using the Comet Assay. Endogenous oxidative DNA damage was highest in HT29 clone 19A, followed by the primary colon cells and HT29 stem cells.

Conclusions Oxidative stress in colon cells leads to damage of macromolecules which is sensitively detected in the Comet Assay. The lacking response of the CLSM-approach in colon tumour cells is probably due to intrinsic modes of protective activities of these cells. In general, however, the CLSM method is a sensitive technique to detect very low concentrations of H₂O₂-induced oxidative stress in NIH3T3 cells. Moreover, by using colon crypts it provides the unique possibility of assessing cell specific levels of oxidative stress in explanted human tissues. Our results demonstrate that the actual target cells of colon cancer induction are indeed susceptible to the oxidative activity of H₂O₂.     

Adiponectin and colon cancer: evidence for inhibitory effects on viability and migration of human colorectal cell lines

Exogenous hydrogen peroxide (H₂O₂) induces oxidative stress and apoptosis in cancer cells. This study evaluated the antiapoptotic effects of pan-caspase and caspase-3, -8, or -9 inhibitors on H₂O₂-treated Calu-6 and A549 lung cancer cells in relation to reactive oxygen species (ROS) and glutathione (GSH). Treatment with 50–500 μM H₂O₂ inhibited the growth of Calu-6 and A549 cells at 24 h and induced apoptosis in these cells. All the tested caspase inhibitors significantly prevented cell death in H₂O₂-treated lung cancer cells. H₂O₂ increased intracellular ROS levels, including that of O ₂ ^·? , at 1 and 24 h. It also increased the activity of catalase but decreased the activity of SOD. In addition, H₂O₂ triggered GSH deletion in Calu-6 and A549 cells at 24 h. It reduced GSH levels in Calu-6 cells at 1 h but increased them at 24 h. Caspase inhibitors decreased O ₂ ^·? levels in H₂O₂-treated Calu-6 cells at 1 h and these inhibitors decreased ROS levels, including that of O ₂ ^·? , in H₂O₂-treated A549 cells at 24 h. Caspase inhibitors partially attenuated GSH depletion in H₂O₂-treated A549 cells and increased GSH levels in these cells at 24 h. However, the inhibitors did not affect GSH deletion and levels in Calu-6 cells at 24 h. In conclusion, H₂O₂ induced caspase-dependent apoptosis in Calu-6 and A549 cells, which was accompanied by increases in ROS and GSH depletion. The antiapoptotic effects of caspase inhibitors were somewhat related to the suppression of H₂O₂-induced oxidative stress and GSH depletion.     

p38 MAPK and Ca2+ contribute to hydrogen peroxide-induced increase of permeability in vascular endothelial cells but ERK does not

To examine the involvement of p38 mitogen-activated protein kinase (p38 MAPK) and extra-cellular signal-regulated kinase (ERK) in the oxidative stress-induced increase of permeability in endothelial cells, the effects of a p38 MAPK inhibitor (SB203580) and ERK inhibitor (PD90859) on the H₂O₂-induced increase of permeability in bovine pulmonary artery endothelial cells (BPAEC) were investigated using a two-compartment system partitioned by a semi-permeable filter. H₂O₂ at 1 mM caused an increase of the permeation rate of fluorescein isothiocyanate (FITC)-labeled dextran 40 through BPAEC monolayers. SB203580 inhibited the H₂O₂-induced increase of permeability but PD98059 did not, though activation (phosphorylation) of both p38 MAPK and ERK was observed in H₂O₂-treated cells in Western blot analysis. An H₂O₂-induced increase of the intracellular Ca²⁺ concentration ([Ca²⁺]_i) was also observed and an intracellular Ca²⁺ chelator (BAPTA-AM) significantly inhibited the H₂O₂-induced increase of permeability. However, it showed no inhibitory effects on the H₂O₂-induced phosphorylation of p38 MAPK and ERK. The H₂O₂-induced increase of [Ca²⁺]_i was not influenced by SB203580 and PD98059. These results indicate that the activation of p38 MAPK and the increase of [Ca²⁺]_i are essential for the H₂O₂-induced increase of endothelial permeability and that ERK is not.     

Sensitization of H2O2-induced TRPM2 activation and subsequent interleukin-8 (CXCL8) production by intracellular Fe2+ in human monocytic U937 cells

Transient receptor potential melastatin 2 (TRPM2) is an oxidative stress-sensitive Ca²⁺-permeable channel. In monocytes/macrophages, H₂O₂-induced TRPM2 activation causes cell death and/or production of chemokines that aggravate inflammatory diseases. However, relatively high concentrations of H₂O₂ are required for activation of TRPM2 channels in vitro. Thus, in the present study, factors that sensitize TRPM2 channels to H₂O₂ were identified and subsequent physiological responses were examined in U937 human monocytes. Temperature increase from 30 °C to 37 °C enhanced H₂O₂-induced TRPM2-mediated increase in intracellular free Ca²⁺ ([Ca²⁺]_i) in TRPM2-expressing HEK 293 cells (TRPM2/HEK cells). The H₂O₂-induced TRPM2 activation enhanced by the higher temperature was dramatically sensitized by intracellular Fe²⁺-accumulation following pretreatment with FeSO₄. Thus intracellular Fe²⁺-accumulation sensitizes H₂O₂-induced TRPM2 activation at around body temperature. Moreover, intracellular Fe²⁺-accumulation increased poly(ADP-ribose) levels in nuclei by H₂O₂ treatment, and the sensitization of H₂O₂-induced TRPM2 activation were almost completely blocked by poly(ADP-ribose) polymerase inhibitors, suggesting that intracellular Fe²⁺-accumulation enhances H₂O₂-induced TRPM2 activation by increase of ADP-ribose production through poly(ADP-ribose) polymerase pathway. Similarly, pretreatment with FeSO₄ stimulated H₂O₂-induced TRPM2 activation at 37 °C in U937 cells and enhanced H₂O₂-induced ERK phosphorylation and interleukin-8 (CXCL8) production. Although the addition of H₂O₂ to cells under conditions of intracellular Fe²⁺-accumulation caused cell death, concentration of H₂O₂ required for CXCL8 production was lower than that resulting in cell death. These results indicate that intracellular Fe²⁺-accumulation sensitizes TRPM2 channels to H₂O₂ and subsequently produces CXCL8 at around body temperature. It is possible that sensitization of H₂O₂-induced TRPM2 channels by Fe²⁺ may implicated in hemorrhagic brain injury via aggravation of inflammation, since Fe²⁺ is released by heme degradation under intracerebral hemorrhage.     

Effects of Selenium and Topiramate on Cytosolic Ca2+ Influx and Oxidative Stress in Neuronal PC12 Cells

It has been widely suggested that selenium (Se) deficiency play an important role in the pathophysiology of epilepsy. It has been reported that Se provides protection against the neuronal damage in patients and animals with epilepsy by restoring the antioxidant defense mechanism. The neuroprotective effects of topiramate (TPM) have been reported in several studies but the putative mechanism of action remains elusive. We investigated effects of Se and TPM in neuronal PC12 cell by evaluating Ca²⁺ mobilization, lipid peroxidation and antioxidant levels. PC12 cells were divided into eight groups namely control, TPM, Se, H₂O₂, TPM + H₂O₂, Se + H₂O₂, Se + TPM and Se + TPM + H₂O₂. The toxic doses and times of H₂O₂, TPM and Se were determined by cell viability assay which is used to evaluate cell viability. Cells were incubated with 0.01 mM TPM for 5 h and 500 nM Se for 10 h. Then, the cells were exposed to 0.1 mM H₂O₂ for 10 h before analysis. The cells in all groups except control, TPM and Se were exposed to H₂O₂ for 15 min before analysis. Cytosolic Ca²⁺ release and lipid peroxidation levels were higher in H₂O₂ group than in control, Se and TPM combination groups although their levels were decreased by incubation of Se and TPM combination. However, there is no difference on Ca²⁺ release in TPM group. Glutathione peroxidase activity, reduced glutathione and vitamin C levels in the cells were lower in H₂O₂ group than in control, Se and TPM groups although their values were higher in the cells incubated with Se and TPM groups than in H₂O₂ groups. In conclusion, these results indicate that Se induced protective effects on oxidative stress in PC12 cells by modulating cytosolic Ca²⁺ influx and antioxidant levels. TPM modulated also lipid peroxidation and glutathione and vitamin C concentrations in the cell system.     

Effects of H2O2 on the growth, secretion, and metabolism of hybridoma cells in culture

Summary The effect of low concentrations of hydrogen peroxide (H₂O₂) (5 × 10⁻⁷−9.5 × 10⁻⁷ M) on cell growth and antibody production was investigated with murine hybridoma cells (Mark 3 and anti-hPL) in culture. Cell growth, measured by flow cytometry with morphological parameters, was significantly stimulated by H₂O₂ (8 × 10⁻⁷ M) but H₂O₂ concentration of 7 × 10⁻⁶ M and above increased cell death. H₂O₂ stimulation of antibody production was nonsignificant. The metabolism of cells treated with 8 × 10⁻⁷ or 1 × 10⁻⁵ M H₂O₂ was similar to that of the control in terms of glucose and glutamine consumption, lactate and ammonia production, and amino acid concentrations in the medium. The concentrations of lactate dehydrogenase, a marker of cell death, in test and control cells were similar. However, concentrations of intracellular free radicals measured by flow cytometry with dihydrorhodamine 123 (DHR 123) and dichlorofluorescein diacetate (DCFH-DA) as fluorochromes were different. The reactive oxygen species content of cells in 8 × 10⁻⁷ M H₂O₂ was similar to that of the controls, but there was a sudden, marked production of superoxide anions (detected with DHR 123) and H₂O₂ or peroxides (detected with DCFH-DA) by cells incubated with 1 × 10⁻⁵ M H₂O₂ which increased with increasing H₂O₂ until cell death.     

Heat stress-induced H2O2 is required for effective expression of heat shock genes in Arabidopsis

The mechanisms of sensing and signalling of heat and oxidative stresses are not well understood. The central question of this paper is whether in plant cells oxidative stress, in particular H₂O₂, is required for heat stress- and heat shock factor (HSF)-dependent expression of genes. Heat stress increases intracellular accumulation of H₂O₂ in Arabidopsis cell culture. The accumulation was greatly diminished using ascorbate as a scavenger or respectively diphenyleneiodonium chloride (DPI) as an inhibitor of reactive oxygen species production. The mRNA of heat shock protein (HSP) genes, exemplified by Hsp17.6, Hsp18.2, and the two cytosolic ascorbate peroxidase genes Apx1, Apx2, reached similar levels by moderate heat stress (37°C) or by treatment with H₂O₂, butylperoxide and diamide at room temperature. The heat-induced expression levels were significantly reduced in the presence of ascorbate or DPI indicating that H₂O₂ is an essential component in the heat stress signalling pathway. Rapid (15 min) formation of heat shock promoter element (HSE) protein-binding complex of high molecular weight in extracts of heat-stressed or H₂O₂-treated cells and the inability to form this complex after ascorbate treatment suggests that oxidative stress affects gene expression via HSF activation and conversely, that H₂O₂ is involved in HSF activation during the early phase of heat stress. The heat stress induction of a high mobility HSE-binding complex, characteristic for later phase of heat shock response, was blocked by ascorbate and DPI. H₂O₂ was unable to induce this complex suggesting that H₂O₂ is involved only in the early stages of HSF activation. Significant induction of the genes tested after diamid treatment and moderate expression of the sHSP genes in the presence of 50 mM ascorbate at 37°C occurred without activation of HSF, indicating that other mechanisms may be involved in stress signalling. Electronic Supplementary Material Supplementary material is available for this article at http//dx.doi.org/10.1007/s11103-006-0045-4 Roman A. Volkov and Irina I. Panchuk contributed equally     

Neuroprotective effects of corn silk maysin via inhibition of H2O2-induced apoptotic cell death in SK-N-MC cells

Aims

Neuroprotective effects of maysin, which is a flavone glycoside that was isolated from the corn silk (CS, Zea mays L.) of a Korean hybrid corn Kwangpyeongok, against oxidative stress (H₂O₂)-induced apoptotic cell death of human neuroblastoma SK-N-MC cells were investigated.

Main methods

Maysin cytotoxicity was determined by measuring cell viability using MTT and lactate dehydrogenase (LDH) assays. Intracellular reactive oxygen species (ROS) were measured using a 2,7-dichlorofluorescein diacetate (DCF-DA) assay. Apoptotic cell death was monitored by annexin V-FITC/PI double staining and by a TUNEL assay. Antioxidant enzyme mRNA levels were determined by real-time PCR. The cleavage of poly (ADP-ribose) polymerase (PARP) was measured by western blotting.

Key findings

Maysin pretreatment reduced the cytotoxic effect of H₂O₂ on SK-N-MC cells, as shown by the increase in cell viability and by reduced LDH release. Maysin pretreatment also dose-dependently reduced the intracellular ROS level and inhibited PARP cleavage. In addition, DNA damage and H₂O₂-induced apoptotic cell death were significantly attenuated by maysin pretreatment. Moreover, maysin pretreatment (5–50 μg/ml) for 2 h significantly and dose-dependently increased the mRNA levels of antioxidant enzymes (CAT, GPx-1, SOD-1, SOD-2 and HO-1) in H₂O₂ (200 μM)-insulted cells.

Significance

These results suggest that CS maysin has neuroprotective effects against oxidative stress (H₂O₂)-induced apoptotic death of human brain SK-N-MC cells through its antioxidative action. This report is the first regarding neuroprotective health benefits of corn silk maysin by its anti-apoptotic action and by triggering the expression of intracellular antioxidant enzyme systems in SK-N-MC cells.     

Compensatory activation of ERK1/2 in Atg5-deficient mouse embryo fibroblasts suppresses oxidative stress-induced cell death

Despite of the increasing evidence that oxidative stress may induce non-apoptotic cell death or autophagic cell death, the mechanism of this process is unclear. Here, we report a role and a down-stream molecular event of Atg5 during oxidative stress-induced cell death. Compared to wild type (WT) cells, Atg5-deficient mouse embryo fibroblasts (Atg5^-/- MEFs) and Atg5 knockdown HT22 neuronal cells were more resistant to cell death induced by H₂O₂. On the contrary, Atg5^-/- MEFs were as sensitive to tumor necrosis factor (TNF)-α and cycloheximide as WT cells, and were more sensitive to cell death triggered by amino acid-deprivation than WT MEFs. Treatment with H₂O₂ induced the recruitment of a GFP-LC3 fusion protein and conversion of LC3 I to LC3 II, correlated with the extent of autophagosome formation in WT cells, but much less in Atg5-deficient cells. Among stress kinases, ERK1/2 was markedly activated in Atg5^-/- MEFs and Atg5 knockdown HT22 and SH-SY5Y neuronal cells. The inhibition of ERK1/2 by MEK1 inhibitor (PD98059) or dominant negative ERK2 enhanced the susceptibility of Atg5^-/- MEFs to H₂O₂-induced cell death. Further, reconstitution of Atg5 sensitized Atg5^-/- MEFs to H₂O₂ and suppressed the activation of ERK1/2. These results suggest that the inhibitory effect of Atg5 deficiency on cell death is attributable by the compensatory activation of ERK1/2 in Atg5^-/- MEFs during oxidative stress-induced cell death.     

The role of intracellular zinc in H2O2-induced oxidative stress in human erythrocytes

In vitro exposure of human erythrocytes to H₂O₂ at concentrations of 30–1000 μM resulted in a dose-dependent increase of the intracellular levels of Zn²⁺ and inhibition of the cytosolic esterase activity, which is a major marker of erythrocyte viability. The observed effect depended on the concentration of H₂O₂ and the duration of exposure of the cells to this compound. An inverse relationship between the changes in the intracellular level of labile zinc ions and esterase activity in the cells exposed to hydrogen peroxide was detected; this was indicative of the role of Zn²⁺ in the programmed death of red blood cells. The combined action of hydrogen peroxide and N',N'-tetrakis-(2-pyridyl-methyl)-ethylenediamine, an intracellular zinc ion chelator, has been found to eliminate the cytotoxic effect of H₂O₂, whereas the addition of Zn²⁺ to the erythrocyte incubation medium enhanced the effects of hydrogen peroxide. The reduction of the concentration of non-protein thiol groups due to a decrease of the level of reduced glutathione was shown to contribute to the release of Zn²⁺ from the intracellular binding sites during oxidative stress induced by H₂O₂ in human erythrocytes.