The regulation of reactive oxygen species production during programmed cell death

Allicin inhibits oxidative stress-induced mitochondrial dysfunction and apoptosis by promoting PI3K/AKT and CREB/ERK signaling in osteoblast cells

Osteoporosis is a disease of the skeleton that is characterized by the loss of bone mass and degeneration of bone microstructure, resulting in an increased risk of fracture. Oxidative stress, which is known to promote oxidative damage to mitochondrial function and also cell apoptosis, has been recently indicated to be implicated in osteoporosis. However, there are few agents that counteract oxidative stress in osteoporosis. In the present study, the protective effects of allicin against the oxidative stress-induced mitochondrial dysfunction and apoptosis were investigated in murine osteoblast-like MC3T3-E1 cells. The results demonstrated that allicin counteracted the reduction of cell viability and induction of apoptosis caused by hydrogen peroxide (H₂O₂) exposure. The inhibition of apoptosis by allicin was confirmed by the inhibition of H₂O₂-induced cytochrome c release and caspase-3 activation. Moreover, the inhibition of apoptosis by allicin was identified to be associated with the counteraction of H₂O₂-induced mitochondrial dysfunction. In addition, allicin was demonstrated to be able to significantly ameliorate the repressed phosphoinositide 3-kinase (PI3K)/AKT and cyclic adenosine monophosphate response element-binding protein (CREB)/extracellular-signal-regulated kinase (ERK) signaling pathways by H₂O₂, which may also be associated with the anti-oxidative stress effects of allicin. In conclusion, allicin protects osteoblasts from H₂O₂-induced oxidative stress and apoptosis in MC3T3-E1 cells by improving mitochondrial function and the activation of PI3K/AKT and CREB/ERK signaling. The present study implies a promising role of allicin in oxidative stress-associated osteoporosis.

Prevalence and audiological profiles of GJB2 mutations in a large collective of hearing impaired patients

Mutations in the GJB2 gene are known to represent the commonest cause of hereditary and congenital hearing loss. In this study, a complete sequencing of the GJB2 gene in a cohort of 506 patients from a single, large cochlear implant program in Europe was performed. Audiological testing for those patients who could actively participate was performed using pure tone audiometry (PTA). Those unable to undergo PTA were measured using click-auditory brainstem response (ABR). Data analysis was performed to determine genotype-phenotype correlations of the mutational status vs. audiological profiles and vs. age at the time of presentation. An overall prevalence of biallelic mutations of 13.4% was found for the total collective. When subsets of younger patients were examined, the prevalence increased to 27% of those up to age 18 and 35% of those up to age 5 at the time of testing, respectively. This increase was found to be highly significant (p < 0.001). Analysis of the mean PTA thresholds revealed a strong correlation between allele combination status and mean PTA (p = 0.021). The prevalence of simple heterozygotes was found to be approximately 10.1%, which is around 3.3 times the value expected in the general population. As GJB2 follows a recessive pattern of inheritance, the question arises as to why such a large fraction of simple heterozygotes was observed among the hearing impaired patients included in this study.

Ketamine-induced oxidative stress at different developmental stages of zebrafish (Danio rerio) embryos

The changes induced by ketamine exposure were developmental stage-dependent, and related with the gradual development of the antioxidant defense system of the embryo, which is dependent on changes in energy-sensing pathways.

Monosodium glutamate-induced oxidative kidney damage and possible mechanisms: a mini-review

Animal studies suggest that chronic monosodium glutamate (MSG) intake induces kidney damage by oxidative stress. However, the underlying mechanisms are still unclear, despite the growing evidence and consensus that α-ketoglutarate dehydrogenase, glutamate receptors and cystine-glutamate antiporter play an important role in up-regulation of oxidative stress in MSG-induced renal toxicity. This review summaries evidence from studies into MSG-induced renal oxidative damage, possible mechanisms and their importance from a toxicological viewpoint.

Neuroprotective compounds of Tilia amurensis

BACKGROUND

Tilia amurensis (Tiliacese) has been used for anti-tumor and anti-inflammatory in Korea, China, and Japan.

OBJECTIVE

In this study, we isolated five compounds from T. amurensis and determined whether protected neuronal cells against glutamate-induced oxidative stress in HT22 cells.

MATERIALS AND METHODS

Compounds were isolated using chromatographic techniques including silica gel, Sephadex LH-20 open column and high performance liquid chromatography analysis, and evaluated neuroprotective effect in HT22 cells by 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay.

RESULTS

β-D-fructofuranosyl α-D-glucopyranoside (1), (-)-epicatechin (2), nudiposide (3), lyoniside (4), and scopoletin (5) were isolated by bioactivity-guided fractionation from the ethyl acetate fraction of T. amurensis. Among them, (-)-epicatechin, nudiposide, lyoniside, and scopoletin had significant neuroprotective activities against glutamate-injured neurotoxicity in HT22 cells.

CONCLUSION

These results demonstrated that compound two, three, four, and five have a pronounced protective effect against glutamate-induced neurotoxicity in HT22 cells.

Ginsenoside Rg3 antagonizes adriamycin-induced cardiotoxicity by improving endothelial dysfunction from oxidative stress via upregulating the Nrf2-ARE pathway through the activation of akt

BACKGROUND

Adriamycin (ADM) is an antineoplastic agent that is effective against a wide range of cancers, but cardiac toxicity limits its clinical application. Ginsenoside Rg3 (Rg3), an anti-cancer active ingredient of Panax ginseng, was reported to have anti-oxidative, anti-apoptotic, and cardioprotective properties.

PURPOSE

The current study aimed to investigate the possible protective effect of Rg3 against ADM-induced cardiotoxicity.

STUDY DESIGN

The activity of Rg3 to improve endothelial dysfunction was processed both in vivo and in vitro.

METHODS

We investigated the cardioprotective effect of Rg3 on ADM treated rats by echocardiography. The endothelial dysfunction was assessed using an aortic ring assay. Cardiac microvascular endothelial cells were cultured to investigate the effects of Rg3 on ADM-treated cells.

RESULTS

Results showed that Rg3 could ameliorate the decrease in the ejection fraction and fractional shortening that was induced by ADM, and improve the left ventricular outflow. The aortic ring assay showed that Rg3 could partially recover the abnormal vascular function. In vitro studies showed that Rg3 could promote cell viability to attenuate ADM induced oxidative damage and apoptosis. This counteraction was achieved partially via activation of the Nrf2-ARE pathway through the activation of Akt.

CONCLUSION

These findings elucidated the potential of Rg3 as a promising reagent for treating ADM-induced cardiotoxicity in clinic.

Pifithrin-α provides neuroprotective effects at the level of mitochondria independently of p53 inhibition

Impaired mitochondrial integrity and function are key features of intrinsic death pathways in neuronal cells. Therefore, key regulators of intrinsic death pathways acting upstream of mitochondria are potential targets for therapeutic approaches of neuroprotection. The tumor suppressor p53 is a well-established regulator of cellular responses towards different kinds of lethal stress, including oxidative stress. Recent reports suggested that p53 may affect mitochondrial integrity and function through both, transcriptional activation of mitochondria-targeted pro-death proteins and direct effects at the mitochondrial membrane. In the present study, we compared the effects of pharmacological inhibition of p53 by pifithrin-α with those of selective p53 gene silencing by RNA interference. Using MTT assay and real-time cell impedance measurements we confirmed the protective effect of both strategies against glutamate-induced oxidative stress in immortalized mouse hippocampal HT-22 neurons. Further, we observed full restoration of mitochondrial membrane potential and inhibition of glutamate-induced mitochondrial fragmentation by pifithrin-α which was, in contrast, not achieved by p53 gene silencing. Downregulation of p53 by siRNA decreased p53 transcriptional activity and reduced expression levels of p21 mRNA, while pifithrin-α did not affect these endpoints. These results suggest a neuroprotective effect of pifithrin-α which occurred at the level of mitochondria and independently of p53 inhibition.

Bax and caspases regulate increased production of mitochondria-derived reactive species in neuronal apoptosis: LACK of A role for depletion of cytochrome c from the mitochondrial electron transport chain

A Bax-dependent increase of reactive oxygen species (ROS) and other reactive species (RS) occurs after withdrawing NGF from mouse sympathetic neurons in cell culture. Possible mechanisms underlying the increased ROS/RS are leakage of electrons from the mitochondrial electron transport chain secondary to caspase cleavage of respiratory complexes or leakage secondary to depletion of cytochrome c from the chain. We previously demonstrated that deletion of Bax or caspase 3 from these cells reduces ROS/RS production to near baseline levels indicating a central role for both Bax and caspase 3 in generating the ROS/RS. Here we depleted cytochrome c to a similar level in neurons from wild type and bax hemizygous or knockout mice by NGF withdrawal or treatment with H₂O₂. Death was prevented with a caspase inhibitor that caused a partial reduction of ROS/RS levels but did not completely prevent the ROS/RS increase. ROS/RS was highest in bax wild-type cells, lowest in bax knockout cells, and at an intermediate level in the bax hemizygous cells. These and our previous findings indicate that Bax and caspase 3 are necessary for the increased ROS/RS after withdrawing NGF from these cells and that little or none of the increased ROS/RS are secondary to a depletion of cytochrome c from the electron transport chain.

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Bax lies upstream of all increased production of ROS by mitochondria in NGF-deprived sympathetic neurons.

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The broad-spectrum caspase inhibitor BAF blocks some but not all increased ROS after NGF withdrawal.

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Caspase 3 deletion blocks almost all of the increased ROS after NGF withdrawal suggesting that BAF does not block all caspase activity or that it has non-specific pro-oxidant effects.

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Depletion of cytochrome c from the electron transport chain contributes little or nothing to increased ROS after NGF withdrawal.

Neuroprotective effects of α-iso-cubebenol on glutamate-induced neurotoxicity

α-Iso-cubebenol is a natural compound isolated from Schisandra chinensis, and is reported to have beneficial bioactivity including anti-inflammatory and anti-tumor activities. Glutamate-induced oxidative neuronal damage has been implicated in a variety of neurodegenerative disorders. Here we investigated the mechanisms of α-iso-cubebenol protection of mouse hippocampus-derived neuronal cells (HT22 cells) from apoptotic cell death induced by the major excitatory neurotransmitter, glutamate. Pretreatment with α-iso-cubebenol markedly attenuated glutamate-induced loss of cell viability and release of lactate dehydrogenase), in a dose-dependent manner. α-Iso-cubebenol significantly reduced glutamate-induced intracellular reactive oxygen species and calcium accumulation. Strikingly, α-iso-cubebenol inhibited glutamate-induced mitochondrial depolarization, which releases apoptosis-inducing factor from mitochondria. α-Iso-cubebenol also suppressed glutamate-induced phosphorylation of extracellular-signal-regulated kinases. Furthermore, α-iso-cubebenol induced CREB phosphorylation and Nrf-2 nuclear accumulation and increased the promoter activity of ARE and CREB in HT22 cells. α-Iso-cubebenol also upregulated the expression of phase-II detoxifying/antioxidant enzymes such as HO-1 and NQO1. Subsequent studies revealed that the inhibitory effects of α-iso-cubebenol on glutamate-induced apoptosis were abolished by small interfering RNA-mediated knockdown of CREB and Nrf-2. These findings suggest that α-iso-cubebenol prevents excitotoxin-induced oxidative damage to neurons by inhibiting apoptotic cell death, and might be a potential preventive or therapeutic agent for neurodegenerative disorders.

Polydatin Alleviates Small Intestine Injury during Hemorrhagic Shock as a SIRT1 Activator

Objective. To evaluate the role of SIRT1 in small intestine damage following severe hemorrhagic shock and to investigate whether polydatin (PD) can activate SIRT1 in shock treatment. Research Design and Methods. The severe hemorrhagic shock model was reproduced in Sprague Dawley rats. Main Outcome Measures. Two hours after drug administration, half of the rats were assessed for survival time evaluation and the remainder were used for small intestinal tissue sample collection. Results. Bleeding and swelling appeared in the small intestine with epithelial apoptosis and gut barrier disturbance during hemorrhagic shock. SIRT1 activity and PGC-1α protein expression of the small intestine were decreased, which led to an increase in acetylated SOD2 and decreases in the expression and activity of SOD2, resulting in severe oxidative stress. The decreased SIRT1 activity and expression were partially restored in the PD administration group, which showed reduced intestine injury and longer survival time. Notably, the effect of PD was abolished after the addition of Ex527, a selective inhibitor of SIRT1. Conclusions. The results collectively suggest a role for the SIRT1-PGC-1α-SOD2 axis in small intestine injury following severe hemorrhagic shock and that PD is an effective SIRT1 activator for the shock treatment.

Beneficial Effects of Polygonum multiflorum on Hippocampal Neuronal Cells and Mouse Focal Cerebral Ischemia

Beneficial effects of the water extract of Polygonum multiflorum (WEPM) and their mechanisms were investigated in HT22 hippocampal cells and hippocampus of middle cerebral artery occlusion (MCAO) mice. In HT22 cells against glutamate-induced oxidative stress, pretreatment with WEPM resulted in significantly reduced apoptotic neuronal death. Pretreatment with WEPM resulted in the suppression of ROS accumulation in connection with cellular Ca 2+ level after exposure to glutamate. Treatment with glutamate alone led to suppressed protein level of mature brain-derived neurotrophic factor (BDNF) and phosphorylated cAMP response element binding protein (CREB); however, pretreatment with either WEPM or anti-oxidant N-acetyl-ʟ-cysteine (NAC) resulted in the significant enhancement of levels of these proteins. In addition, levels of mature BDNF expression and CREB phosphorylation were increased by combined treatment with WEPM, NAC, and intracellular Ca 2+ inhibitor BAPTA compared to other treatment groups. In MCAO mice, we confirmed the critical role of mature BDNF expression and CREB phosphorylation by WEPM in the neurons of the hippocampus. Our results suggest that WEPM mainly exerted beneficial effects on hippocampal neurons through the suppression of ROS accumulation and up-regulation of mature BDNF expression and CREB phosphorylation.

A single fraction from Uncaria sinensis exerts neuroprotective effects against glutamate-induced neurotoxicity in primary cultured cortical neurons

We identified a neuroprotective single fraction among 62 ones of hexane extract from Uncaria sinensis (JGH43IA) and investigated its effects and mechanisms in primary cortical neurons. Pretreatment with JGH43IA showed a significantly increase cell viability in a dose-dependent manner with a decrease in the lactate dehydrogenase release. When we performed morphological assay and flow cytometry to determination of the type of cell death, pretreatment with JGH43IA showed a significant reduction of glutamate-induced apoptotic cell death. Then we explored the downstream signaling pathways of N-methyl-D-aspartate receptor (NMDAR) with calpain activation to elucidate possible pathways of neuroprotection by JGH43IA. Pretreatment with JGH43IA exhibited a significant attenuation of NMDAR GluN2B subunit activation and a decrease in active form of calpain 1 leading to subsequent cleavage of striatal-enriched protein tyrosine phosphatase (STEP). In addition, pretreatment with JGH43IA showed a marked increase of cAMP responsive element binding protein. These results suggest that JGH43IA may have neuroprotective effects through down-regulation of NMDAR GluN2B subunit and calpain 1 activation, and subsequent alleviation of STEP cleavage. This single fraction from U. sinensis might be a useful therapeutic agent for brain disorder associated with glutamate injury.

Nrf2 and HSF-1 Pathway Activation via Hydroquinone-Based Proelectrophilic Small Molecules is Regulated by Electrochemical Oxidation Potential

Activation of the Kelch-like ECH-associated protein 1/nuclear factor (erythroid-derived 2)-like 2 and heat-shock protein 90/heat-shock factor-1 signal-transduction pathways plays a central role in combatting cellular oxidative damage and related endoplasmic reticulum stress. Electrophilic compounds have been shown to be activators of these transcription-mediated responses through S-alkylation of specific regulatory proteins. Previously, we reported that a prototype compound (D1, a small molecule representing a proelectrophilic, para-hydroquinone species) exhibited neuroprotective action by activating both of these pathways. We hypothesized that the para-hydroquinone moiety was critical for this activation because it enhanced transcription of these neuroprotective pathways to a greater degree than that of the corresponding ortho-hydroquinone isomer. This notion was based on the differential oxidation potentials of the isomers for the transformation of the hydroquinone to the active, electrophilic quinone species. Here, to further test this hypothesis, we synthesized a pair of para- and ortho-hydroquinone-based proelectrophilic compounds and measured their redox potentials using analytical cyclic voltammetry. The redox potential was then compared with functional biological activity, and the para-hydroquinones demonstrated a superior neuroprotective profile.

Neuroprotection and spatial memory enhancement of four herbal mixture extract in HT22 hippocampal cells and a mouse model of focal cerebral ischemia

BACKGROUND

Four traditional Korean medicinal herbs which act in retarding the aging process, Polygonum multiflorum Thunb., Rehmannia glutinosa (Gaertn) Libosch., Polygala tenuifolia Willd., and Acorus gramineus Soland., were prepared by systematic investigation of Dongeuibogam (Treasured Mirror of Eastern Medicine), published in the early 17th century in Korea. This study was performed to evaluate beneficial effects of four herbal mixture extract (PMC-12) on hippocampal neuron and spatial memory.

METHODS

High performance liquid chromatography (HPLC) analysis was performed for standardization of PMC-12. Cell viability, lactate dehydrogenase, flow cytometry, reactive oxygen species (ROS), and Western blot assays were performed in HT22 hippocampal cells and immunohistochemistry and behavioral tests were performed in a mouse model of focal cerebral ischemia in order to observe alterations of hippocampal cell survival and subsequent memory function.

RESULTS

In the HPLC analysis, PMC-12 was standardized to contain 3.09% 2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucoside, 0.35% 3',6-disinapoyl sucrose, and 0.79% catalpol. In HT22 cells, pretreatment with PMC-12 resulted in significantly reduced glutamate-induced apoptotic cell death. Pretreatment with PMC-12 also resulted in suppression of ROS accumulation in connection with cellular Ca(2+) level after exposure to glutamate. Expression levels of phosphorylated p38 mitogen-activated protein kinases (MAPK) and dephosphorylated phosphatidylinositol-3 kinase (PI3K) by glutamate exposure were recovered by pretreatment with either PMC-12 or anti-oxidant N-acetyl-L-cysteine (NAC). Expression levels of mature brain-derived neurotrophic factor (BDNF) and phosphorylated cAMP response element binding protein (CREB) were significantly enhanced by treatment with either PMC-12 or NAC. Combination treatment with PMC-12, NAC, and intracellular Ca(2+) inhibitor BAPTA showed similar expression levels. In a mouse model of focal cerebral ischemia, we observed higher expression of mature BDNF and phosphorylation of CREB in the hippocampus and further confirmed improved spatial memory by treatment with PMC-12.

CONCLUSIONS

Our results suggest that PMC-12 mainly exerted protective effects on hippocampal neurons through suppression of Ca(2+)-related ROS accumulation and regulation of signaling pathways of p38 MAPK and PI3K associated with mature BDNF expression and CREB phosphorylation and subsequently enhanced spatial memory.

Sequential Upregulation of Superoxide Dismutase 2 and Heme Oxygenase 1 by tert-Butylhydroquinone Protects Mitochondria during Oxidative Stress

Oxidative stress is linked to mitochondrial dysfunction in aging and neurodegenerative conditions. The transcription factor nuclear factor E2-related factor 2 (Nrf2)-antioxidant response element (ARE) regulates intracellular antioxidative capacity to combat oxidative stress. We examined the effect of tert-butylhydroquinone (tBHQ), an Nrf2-ARE signaling pathway inducer, on mitochondrial function during oxidative challenge in neurons. tBHQ prevented glutamate-induced cytotoxicity in an HT-22 neuronal cell line even with an 8-hour exposure delay. tBHQ blocked glutamate-induced intracellular reactive oxygen species (ROS) and mitochondrial superoxide accumulation. It also protected mitochondrial function under glutamate toxicity, including maintaining mitochondrial membrane potential, mitochondrial Ca(2+) hemostasis, and mitochondrial respiration. Glutamate-activated, mitochondria-mediated apoptosis was inhibited by tBHQ as well. In rat primary cortical neurons, tBHQ protected cells from both glutamate and buthionine sulfoximine toxicity. We found that tBHQ scavenged ROS and induced a rapid upregulation of superoxide dismutase 2 (SOD2) expression and a delayed upregulation of heme oxygenase 1 (HO-1) expression. In HT-22 cells with a knockdown of SOD2 expression, delayed treatment with tBHQ failed to prevent glutamate-induced cell death. Briefly, tBHQ rescues mitochondrial function by sequentially increasing SOD2 and HO-1 expression during glutamate-mediated oxidative stress. This study is the first to demonstrate the role of tBHQ in preserving mitochondrial function during oxidative challenge and provides a clinically relevant argument for using tBHQ against acute neuron-compromising conditions.

Pemetrexed induces apoptosis in malignant mesothelioma and lung cancer cells through activation of reactive oxygen species and inhibition of sirtuin 1

Pemetrexed is a multitargeted antifolate used for the treatment of malignant mesothelioma and non-small cell lung cancer (NSCLC). However, the mechanism by which pemetrexed induces apoptosis remains unclear. In the present study, we investigated the involvement of reactive oxygen species (ROS) and sirtuin 1 (SIRT1) in pemetrexed-induced apoptosis in MSTO-211 malignant mesothelioma cells and A549 NSCLC cells. Pemetrexed enhanced caspase-dependent apoptosis, induced intracellular ROS generation, and downregulated SIRT1 in the MSTO-211 and A549 cells. Pemetrexed-induced apoptosis, which was prevented by pretreatment with N-acetyl-cysteine (NAC), was mediated by effects on the mitochondria, including mitochondrial membrane potential transition (MPT) and cytosolic release of cytochrome c, and also involved regulation of SIRT1 expression. Interference with SIRT1 expression using siRNA enhanced pemetrexed-induced apoptosis through mitochondrial dysfunction and ROS generation, whereas resveratrol, an activator of SIRT1, protected against pemetrexed-induced apoptosis. These results show that pemetrexed induces apoptosis in MSTO-211 mesothelioma cells and A549 NSCLC cells through mitochondrial dysfunction mediated by ROS accumulation and SIRT1 downregulation.

Effects of heavy metals (Cd, Cu, Cr, Pb, Zn) on fish glutathione metabolism

The glutathione metabolism contains crucial antioxidant molecules to defend the organisms against oxidants. Thus, the aim of this study was to investigate the response of the glutathione metabolism in the liver of freshwater fish Oreochromis niloticus exposed to metals (Cu, Cd, Cr, Pb, Zn) in different periods. Fish were exposed to metals (as 1 μg/mL) individually for 1, 7, and 14 days and subsequently antioxidant enzymes (glutathione peroxidase, GPX; glutathione reductase, GR and glutathione S-transferase, GST) and glutathione levels (total glutathione, tGSH; reduced glutathione, rGSH; oxidized glutathione, GSSG and GSH/GSSG ratios) in the liver were measured. There was no fish mortality during the experiments, except Cu exposure. The antioxidant enzymes responded differently to metal exposures depending on metal types and exposure durations. GPX activity increased only after Cd exposure, while GST activity increased following 7 days of all metal exposures. However, GR activity did not alter in most cases. Total GSH and GSH/GSSG levels generally decreased, especially after 7 days. Data showed that metal exposures significantly altered the response of antioxidant system parameters, particularly at day 7 and some recovery occurred after 14 days. This study suggests that the response of antioxidant system could help to predict metal toxicity in the aquatic environments and be useful as an "early warning tool" in natural monitoring studies.

Release of mitochondrial Opa1 following oxidative stress in HT22 cells

Cellular mechanisms involved in multiple neurodegenerative diseases converge on mitochondria to induce overproduction of reactive oxygen species, damage to mitochondria, and subsequent cytochrome c release. Little is currently known regarding the contribution mitochondrial dynamics play in cytochrome c release following oxidative stress in neurodegenerative disease. Here we induced oxidative stress in the HT22 cell line with glutamate and investigated key mediators of mitochondrial dynamics to determine the role this process may play in oxidative stress induced neuronal death. We report that glutamate treatment in HT22 cells induces increase in reactive oxygen species (ROS), release of the mitochondrial fusion protein Opa1 into the cytosol, with concomitant release of cytochrome c. Furthermore, following the glutamate treatment alterations in cell signaling coincide with mitochondrial fragmentation which culminates in significant cell death in HT22 cells. Finally, we report that treatment with the antioxidant tocopherol attenuates glutamate induced-ROS increase, release of mitochondrial Opa1 and cytochrome c, and prevents cell death.

A simple but highly efficient multi-formyl phenol–amine system for fluorescence detection of peroxide explosive vapour

A simple, highly stable, sensitive and selective fluorescent system for peroxide explosives was developedviaan aromatic aldehyde oxidation reaction.

Cognitive Enhancing and Neuroprotective Effect of the Embryo of the Nelumbo nucifera Seed

The aim of the present study was to evaluate the effect of ENS on cognitive impairment induced by scopolamine and its potential neuroprotective effect against glutamate-induced cytotoxicity in HT22 cell and to investigate the underlying mechanisms. ENS (3, 10, 30, and 100 mg/kg), scopolamine (1 mg/kg), and donepezil (1 mg/kg) were administered to mice during a test period. Scopolamine impaired memory and learning in a water maze test and a passive avoidance test. The neuroprotective effect of ENS (10 and 100 μg/mL) was investigated on glutamate-induced cell death in HT22 cells by MTT assay. We investigated acetylcholinesterase inhibition in hippocampus and antioxidant activity, ROS levels, and Ca²⁺ influx in HT22 cells to elucidate the potential mechanisms of ENS. We found that ENS significantly ameliorated scopolamine-induced memory impairment and inhibited AChE activity in hippocampus. In vitro, ENS showed potent neuroprotective effects against glutamate-induced neurotoxicity in the HT22 cell. In addition, ENS induced a decrease in ROS production and intercellular Ca²⁺ accumulation and showed DPPH radical and H₂O₂ scavenging activity. In conclusion, ENS showed both a memory improving effect and a neuroprotective effect. Our results indicate that ENS may be of use in the treatment and prevention of neurodegenerative disorders.

Mitochondrial function and energy metabolism in neuronal HT22 cells resistant to oxidative stress

BACKGROUND AND PURPOSE

The hippocampal cell line HT22 is an excellent model for studying the consequences of endogenous oxidative stress. Extracellular glutamate depletes cellular glutathione by blocking the glutamate/cystine antiporter system xc-. Glutathione depletion induces a well-defined programme of cell death characterized by an increase in reactive oxygen species and mitochondrial dysfunction.

EXPERIMENTAL APPROACH

We compared the mitochondrial shape, the abundance of mitochondrial complexes and the mitochondrial respiration of HT22 cells, selected based on their resistance to glutamate, with those of the glutamate-sensitive parental cell line.

KEY RESULTS

Glutamate-resistant mitochondria were less fragmented and displayed seemingly contradictory features: mitochondrial calcium and superoxide were increased while high-resolution respirometry suggested a reduction in mitochondrial respiration. This was interpreted as a reverse activity of the ATP synthase under oxidative stress, leading to hydrolysis of ATP to maintain or even elevate the mitochondrial membrane potential, suggesting these cells endure ineffective energy metabolism to protect their membrane potential. Glutamate-resistant cells were also resistant to oligomycin, an inhibitor of the ATP synthase, but sensitive to deoxyglucose, an inhibitor of hexokinases. Exchanging glucose with galactose rendered resistant cells 1000-fold more sensitive to oligomycin. These results, together with a strong increase in cytosolic hexokinase 1 and 2, a reduced lactate production and an increased activity of glucose-6-phosphate dehydrogenase, suggest that glutamate-resistant HT22 cells shuttle most available glucose towards the hexose monophosphate shunt to increase glutathione recovery.

CONCLUSIONS AND IMPLICATIONS

These results indicate that mitochondrial and metabolic adaptations play an important role in the resistance of cells to oxidative stress.

Andrographis paniculata leaf extract prevents thioacetamide-induced liver cirrhosis in rats

This study investigated the hepatoprotective effects of ethanolic Andrographis paniculata leaf extract (ELAP) on thioacetamide-induced hepatotoxicity in rats. An acute toxicity study proved that ELAP is not toxic in rats. To examine the effects of ELAP invivo, male Sprague Dawley rats were given intraperitoneal injections of vehicle 10% Tween-20, 5 mL/kg (normal control) or 200 mg/kg TAA thioacetamide (to induce liver cirrhosis) three times per week. Three additional groups were treated with thioacetamide plus daily oral silymarin (50 mg/kg) or ELAP (250 or 500 mg/kg). Liver injury was assessed using biochemical tests, macroscopic and microscopic tissue analysis, histopathology, and immunohistochemistry. In addition, HepG2 and WRL-68 cells were treated invitro with ELAP fractions to test cytotoxicity. Rats treated with ELAP exhibited significantly lower liver/body weight ratios and smoother, more normal liver surfaces compared with the cirrhosis group. Histopathology using Hematoxylin and Eosin along with Masson’s Trichrome stain showed minimal disruption of hepatic cellular structure, minor fibrotic septa, a low degree of lymphocyte infiltration, and minimal collagen deposition after ELAP treatment. Immunohistochemistry indicated that ELAP induced down regulation of proliferating cell nuclear antigen. Also, hepatic antioxidant enzymes and oxidative stress parameters in ELAP-treated rats were comparable to silymarin-treated rats. ELAP administration reduced levels of altered serum liver biomarkers. ELAP fractions were non-cytotoxic to WRL-68 cells, but possessed anti-proliferative activity on HepG2 cells, which was confirmed by a significant elevation of lactate dehydrogenase, reactive oxygen species, cell membrane permeability, cytochrome c, and caspase-8,-9, and, -3/7 activity in HepG2 cells. A reduction of mitochondrial membrane potential was also detected in ELAP-treated HepG2 cells. The hepatoprotective effect of 500 mg/kg of ELAP is proposed to result from the reduction of thioacetamide-induced toxicity, normalizing reactive oxygen species levels, inhibiting cellular proliferation, and inducing apoptosis in HepG2 cells.

Ferulago angulata activates intrinsic pathway of apoptosis in MCF-7 cells associated with G1 cell cycle arrest via involvement of p21/p27

Ferulago angulata is a medicinal plant that is traditionally known for its anti-inflammatory and antiulcer properties. The present study was aimed to evaluate its anticancer activity and the possible mechanism of action using MCF-7 as an in vitro model. F. angulata leaf extracts were prepared using solvents in the order of increasing polarity. As determined by MTT assay, F. angulata leaves hexane extract (FALHE) revealed the strongest cytotoxicity against MCF-7 cells with the half maximal inhibitory concentration (IC₅₀) value of 5.3±0.82 μg/mL. The acute toxicity study of FALHE provided evidence of the safety of the plant extract. Microscopic and flow cytometric analysis using annexin-V probe showed an induction of apoptosis in MCF-7 by FALHE. Treatment of MCF-7 cells with FALHE encouraged the intrinsic pathway of apoptosis, with cell death transducing signals that reduced the mitochondrial membrane potential with cytochrome c release from mitochondria to cytosol. The released cytochrome c triggered the activation of caspase-9. Meanwhile, the overexpression of caspase-8 suggested the involvement of an extrinsic pathway in the induced apoptosis at the late stage of treatment. Moreover, flow cytometric analysis showed that FALHE treatment significantly arrested MCF-7 cells in the G₁ phase, which was associated with upregulation of p21 and p27 assessed by quantitative polymerase chain reaction. Immunofluorescence and the quantitative polymerase chain reaction analysis of MCF-7 cells after treatment with FALHE revealed an upregulation of Bax and a downregulation of Bcl-2 proteins. These findings proposed that FALHE suppressed the proliferation of MCF-7 cells via cell cycle arrest and the induction of apoptosis through intrinsic pathway.

Cytoskeleton remodeling and oxidative stress description in morphologic changes of chondrocyte in Kashin-Beck disease

Kashin-Beck disease (KBD) is a kind of deformity disease involved in cytoskeleton and inner homeostasis regulation. The enrichment analysis of bioprocess, networks, and related disease set were performed. The development regulation, metabolic process, and apoptosis were important procession in KBD; it revealed the up-regulated process in removal of superoxide radicals, glycolysis and glucose catabolic process, regulation of cytoskeleton rearrangement and phagosome in antigen presentation. Morphological changes of KBD chondrocyte were investigated by transmission electronic microscopy compare with the normal one. The ultrastructure of KBD chondrocyte referred to oxidative stress and metabolic dysfunction has been found.

Neuroprotective effect of 1-methoxyoctadecan-1-ol from Uncaria sinensis on glutamate-induced hippocampal neuronal cell death

ETHNOPHARMACOLOGICAL RELEVANCE

We isolated a single compound, 1-methoxyoctadecan-1-ol (MOD), from dried hooks and stems of Uncaria sinensis, which is used in traditional Korean medicine to provide relief from various nervous related symptoms.

MATERIALS AND METHODS

Neuroprotective effects of MOD against glutamate-induced oxidative stress in HT22 cells were investigated by analyzing cell viability, lactate dehydrogenase, flow cytometry, reactive oxygen species (ROS) and Western blot assays.

RESULTS

Exposure to glutamate alone resulted in remarkable hippocampal neuronal cell death; however, pretreatment with MOD resulted in suppression of neuronal death and ROS accumulation in connection with cellular Ca2+ level after exposure to glutamate. Stimulation by glutamate also caused significant protein level of phosphorylated p38 mitogen-activated protein kinases (MAPK), and dephosphorylated phosphatidylinositol-3 kinase (PI3K), however, pretreatment with MOD resulted in inhibition of these changes in protein level. Treatment with glutamate alone led to suppressed protein level of mature brain-derived neurotrophic factor (BDNF) and phosphorylated cAMP response element binding protein (CREB); however, pretreatment with MOD resulted in significant enhancement of this level of protein. Anti-oxidant N-acetyl-L-cysteine and both Ca2+ inhibitors, BAPTA and EGTA, showed effects similar to those of MOD in all proteins examined, except mature BDNF.

CONCLUSIONS

Our results suggest that MOD mainly exerted neuroprotective effects in suppression of ROS accumulation and up-regulation of mature BDNF in association with p38 MAPK and PI3K signaling in hippocampal neuronal cells.

The Effects of Loranthus parasiticus on Scopolamine-Induced Memory Impairment in Mice

This study is undertaken to evaluate cognitive enhancing effect and neuroprotective effect of Loranthus parasiticus. Cognitive enhancing effect of Loranthus parasiticus was investigated on scopolamine-induced amnesia model in Morris water maze test and passive avoidance test. We also examined the neuroprotective effect on glutamate-induced cell death in HT22 cells by MTT assay. These results of Morris water maze test and passive avoidance test indicated that 10 and 50 mg/kg of Loranthus parasiticus reversed scopolamine-induced memory deficits. Loranthus parasiticus also protected against glutamate-induced cytotoxicity in HT22 cells. As a result of in vitro test for elucidating possible mechanism, Loranthus parasiticus inhibited AChE activity, ROS production, and Ca(2+) accumulation. Loranthus parasiticus showed memory enhancing effect and neuroprotective effect and these effects may be related to inhibition of AChE activity, ROS level, and Ca(2+) influx.

Neuroprotective Effect of Steamed and Fermented Codonopsis lanceolata

Codonopsis lanceolata has been used as an herbal medicine for several lung inflammatory diseases, such as asthma, tonsillitis, and pharyngitis. Previously, we showed the neuroprotective effect of steamed and fermented C. lanceolata (SFC) in vitro and in vivo. In the current study, the treatment of HT22 cells with SFC decreased glutamate-induced cell death, suggesting that SFC protected HT22 cells from glutamate-induced cytotoxicity. Based on these, we sought to elucidate the mechanisms of the neuro-protective effect of SFC by measuring the oxidative stress parameters and the expression of Bax and caspase-3 in HT22 cells. SFC reduced contents of ROS, Ca²⁺ and NO. Moreover, SFC restored contents of glutathione and glutathione reductase as well as inhibited Bax and caspase-3 activity in HT22 cells. These results indicate that steamed and fermented C. lanceolata (SFC) extract protected HT22 cells by anti-oxidative effect and inhibition of the expression of Bax and caspase-3.

Effect of tacrine-3-caffeic acid, a novel multifunctional anti-Alzheimer's dimer, against oxidative-stress-induced cell death in HT22 hippocampal neurons: involvement of Nrf2/HO-1 pathway

AIMS

Oxidative stress (OS) plays an important role in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD). This study was designed to uncover the cellular and biochemical mechanisms underlying the neuroprotective effects of tacrine-3-caffeic acid (T3CA), a novel promising multifunctional anti-Alzheimer's dimer, against OS-induced neuronal death.

METHODS AND RESULTS

T3CA protected HT22 cells against high-concentration-glutamate-induced cell death in time- and concentration-dependent manners and potently attenuated glutamate-induced intracellular reactive oxygen species (ROS) production as well as mitochondrial membrane-potential (ΔΨ) disruption. Besides, T3CA significantly induced nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation and increased its transcriptional activity, which were demonstrated by Western blotting, immunofluorescence, and antioxidant response element (ARE)-luciferase reporter gene assay. Further studies showed that T3CA potently up-regulated heme oxygenase-1 (HO-1), an endogenous antioxidative enzyme and a downstream effector of Nrf2, at both mRNA and protein levels. The neuroprotective effects of T3CA were partially reversed by brusatol, which reduced protein level of Nrf2, or by inhibiting HO-1 with siRNA or ZnPP-IX, a specific inhibitor of HO-1.

CONCLUSIONS

Taken together, these results clearly demonstrate that T3CA protects neurons against OS-induced cell death partially through Nrf2/ARE/HO-1 signaling pathway, which further supports that T3CA might be a promising novel therapeutic agent for OS-associated diseases.

Neuroprotective effects of 4,5-dimethoxypyrocatechol isolated from Cynanchum paniculatum on HT22 cells

BACKGROUND

Cynanchum paniculatum, belongs to the family Asclepiadaceae and is used to treat various diseases, such as invigorate blood, alleviate edema and to relieve pain and toxicity for a long time.

MATERIALS AND METHODS

4,5-Dimethoxypyrocatechol was isolated from the 80% methanol extract of C. paniculatum and its neuroprotective effect was evaluated by MTT assay.

RESULTS

4,5-Dimethoxypyrocatechol had neuroprotective effect on the glutamate-induced cellular oxidative death in HT22 cells.

CONCLUSION

Furthermore, we found that reactive oxygen species (ROS) accumulation and calcium concentration by oxidative stress were reduced by 4,5-dimethoxypyrocatechol in HT22 cells.

Diabetic peripheral neuropathy: role of reactive oxygen and nitrogen species

The prevalence of diabetes has reached epidemic proportions. There are two forms of diabetes: type 1 diabetes mellitus is due to auto-immune-mediated destruction of pancreatic β-cells resulting in absolute insulin deficiency and type 2 diabetes mellitus is due to reduced insulin secretion and or insulin resistance. Both forms of diabetes are characterized by chronic hyperglycemia, leading to the development of diabetic peripheral neuropathy (DPN) and microvascular pathology. DPN is characterized by enhanced or reduced thermal, chemical, and mechanical pain sensitivities. In the long-term, DPN results in peripheral nerve damage and accounts for a substantial number of non-traumatic lower-limb amputations. This review will address the mechanisms, especially the role of reactive oxygen and nitrogen species in the development and progression of DPN.

Common defects of mitochondria and iron in neurodegeneration and diabetes (MIND): a paradigm worth exploring

A popular, if not centric, approach to the study of an event is to first consider that of the simplest cause. When dissecting the underlying mechanisms governing idiopathic diseases, this generally takes the form of an ab initio genetic approach. To date, this genetic 'smoking gun' has remained elusive in diabetes mellitus and for many affected by neurodegenerative diseases. With no single gene, or even subset of genes, conclusively causative in all cases, other approaches to the etiology and treatment of these diseases seem reasonable, including the correlation of a systems' predisposed sensitivity to particular influence. In the cases of diabetes mellitus and neurodegenerative diseases, overlapping themes of mitochondrial influence or dysfunction and iron dyshomeostasis are apparent and relatively consistent. This mini-review discusses the influence of mitochondrial function and iron homeostasis on diabetes mellitus and neurodegenerative disease, namely Alzheimer's disease. Also discussed is the incidence of diabetes accompanied by neuropathy and neurodegeneration along with neurodegenerative disorders prone to development of diabetes. Mouse models containing multiple facets of this overlap are also described alongside current molecular trends attributed to both diseases. As a way of approaching the idiopathic and complex nature of these diseases we are proposing the consideration of a MIND (mitochondria, iron, neurodegeneration, and diabetes) paradigm in which systemic metabolic influence, iron homeostasis, and respective genetic backgrounds play a central role in the development of disease.

Oxidative stress in Alzheimer's disease

Oxidative stress plays a significant role in the pathogenesis of Alzheimer's disease (AD), a devastating disease of the elderly. The brain is more vulnerable than other organs to oxidative stress, and most of the components of neurons (lipids, proteins, and nucleic acids) can be oxidized in AD due to mitochondrial dysfunction, increased metal levels, inflammation, and β-amyloid (Aβ) peptides. Oxidative stress participates in the development of AD by promoting Aβ deposition, tau hyperphosphorylation, and the subsequent loss of synapses and neurons. The relationship between oxidative stress and AD suggests that oxidative stress is an essential part of the pathological process, and antioxidants may be useful for AD treatment.

Functionalized acridin-9-yl phenylamines protected neuronal HT22 cells from glutamate-induced cell death by reducing intracellular levels of free radical species

The in vitro neuronal cell death model based on the HT22 mouse hippocampal cell model is a convenient means of identifying compounds that protect against oxidative glutamate toxicity which plays a role in the development of certain neurodegenerative diseases. Functionalized acridin-9-yl-phenylamines were found to protect HT22 cells from glutamate challenge at submicromolar concentrations. The Aryl(1)-NH-Aryl(2) scaffold that is embedded in these compounds was the minimal pharmacophore for activity. Mechanistically, protection against the endogenous oxidative stress generated by glutamate did not involve up-regulation of glutathione levels but attenuation of the late stage increases in mitochondrial ROS and intracellular calcium levels. The NH residue in the pharmacophore played a crucial role in this regard as seen from the loss of neuroprotection when it was structurally modified or replaced. That the same NH was essential for radical scavenging in cell-free and cell-based systems pointed to an antioxidant basis for the neuroprotective activities of these compounds.

TNFα-induced apoptosis in human myeloid cell lines HL-60 and K562 is dependent of intracellular ROS generation

The present study determines the role of reactive oxygen species (ROS) production and calcium signaling evoked by the tumor necrosis factor-alpha (TNFα) on apoptosis in the human leukemia HL-60 and K562 cell lines. The results show that treatment of both cell lines cells with 10 ng/mL TNFα resulted in a rise in the percentage of apoptotic cells after 6 h of treatment. It was also observed that the administration of 10 ng/mL TNFα increased intracellular ROS production, as well as a time-dependent increase in caspase-8, -3, and -9 activities. The present results also show that the pretreatment with well-known antioxidants such as trolox and N-acetyl cysteine partially reduced the caspase activation caused by the administration of TNFα. The findings suggest that TNFα-induced apoptosis is dependent on alterations in intracellular ROS generation in human leukemia HL-60 and K562 cells.

Role of transient receptor potential channel 1 (TRPC1) in glutamate-induced cell death in the hippocampal cell line HT22

Transient receptor potential channel 1 (TRPC1; a cation channel activated by store depletion and/or through an intracellular messenger) is expressed in a variety of tissues, including the brain. To study the physiological function of TRPC1, we investigated the role of endogenously expressed TRPC1 in glutamate-induced cell death, using the murine hippocampal cell line HT22. Knocking down TRPC1 mRNA using TRPC1-shRNA or blocking of TRPC channels using 2-APB (≥200 μM) robustly attenuated glutamate-induced cell death after 24 h of incubation with 5 mM glutamate. Glutamate toxicity in HT22 cells seems to involve metabotropic glutamate receptor mGluR5 since MPEP (2-methyl-6-(phenylethynyl)-pyridine), an mGluR5 antagonist (≥100 μM), abrogated glutamate toxicity. Furthermore, a direct activation of mGluR5 by CHPG [(RS)-chloro-5-hydroxyphenylglycine; 100 μM or 300 μM] promoted HT22 cell death. TRPC1 knock-down markedly reduced CHPG-induced cell death. These observations suggest that glutamate-induced cell death in HT22 cells activates mGluR5 receptors, which significantly increases Ca(2+) influx through TRPC1 channels. TRPC1 knock-down prevented glutamate- and CHPG-induced cell death, suggesting that glutamate-induced toxicity in HT22 cells is mediated through TRPC1 channels and an mGluR5-dependent pathway. Together, this work provides evidence for a novel receptor activation pathway of TRPC1 in glutamate-induced toxicity.

Neuroprotective effects of Polygonum multiflorum extract against glutamate-induced oxidative toxicity in HT22 hippocampal cells

ETHNOPHARMACOLOGICAL RELEVANCE

Dried roots of Polygonum multiflorum have traditionally been used in the retarding of aging process in East Asian countries and its extracts exhibit anti-oxidative activities.

MATERIALS AND METHODS

Neuroprotective effects of ethyl acetate extract from Polygonum multiflorum (EEPM) were investigated against glutamate-induced oxidative cell death in HT22 hippocampal cells. Cell viability, cytotoxicity, morphological, flow cytometry, and Western blot assays were performed in order to observe alterations of neuronal cell survival or death related pathways.

RESULTS

Pretreatment with EEPM resulted in significantly decreased glutamate-induced neurotoxicity and also resulted in drastically inhibited glutamate-induced apoptotic and necrotic neuronal death. To elucidate possible pathways of neuroprotection by EEPM, we explored the activation of mitogen activated protein kinases (MAPKs), phosphatidylinositol-3-kinase, and cAMP responsive element binding protein (CREB). Treatment with glutamate alone led to activation of extracellular regulated kinase (ERK), Jun N-terminal kinase, and p38 during the late phase after glutamate exposure, but pretreatment with EEPM resulted in significantly attenuated activation of these proteins. Pretreatment with EEPM resulted in increased activation of CREB. The specific inhibitors of ERK and p38, PD98059 and SB203580, abrogated the neuroprotective effects of EEPM. When we evaluated calpain I and striatal-enriched protein tyrosine phosphatase (STEP), active form of calpain I was significantly increased after glutamate exposure, and, along with this, active form of STEP showed a decrease. Pretreatment with EEPM resulted in significant recovery of pro-calpain I and active form of STEP caused by glutamate. Co-treatment with calpain inhibitor ALLN and EEPM had a synergistic effect on neuronal death and contributed to blockade of activation of both ERK and p38 with increased activation of CREB.

CONCLUSIONS

These results suggest that Polygonum multiflorum extract may have neuroprotective effects through both alleviation of ERK and p38 activation with increased activation of CREB under oxidative stress and has potential as a therapeutic intervention for treatment of oxidative neuronal death.

Focal cerebral ischemic injury decreases calbindin expression in brain tissue and HT22 cells

Calbindin is a calcium binding protein that controls intracellular calcium levels and has a neuroprotective function against apoptotic stimuli. We investigated the expression of calbindin in ischemic brain injury. Focal cerebral ischemia was induced in male rats by middle cerebral artery occlusion (MCAO) and cerebral cortices were collected 24 h after MCAO. Cerebral ischemia significantly increased infarct volume. RT-PCR and Western blot analyses showed that MCAO injury induced a decrease of calbindin expression. Moreover, immunohistochemical staining showed that the number of calbindin-positive cells decreased in ischemic regions of MCAO-operated animals. In cultured hippocampal-derived cell lines, glutamate exposure increased intracellular Ca²⁺ concentrations and decreased calbindin expression. Taken together, both in vivo and in vitro results demonstrated decreases of calbindin after neuronal cell injury. These results suggest that decreases of calbindin in ischemic brain injury contribute to neuronal cell death.