A detailed analysis of hydrogen peroxide-induced cell death in primary neuronal culture

Amburana cearensis seed extract protects brain mitochondria from oxidative stress and cerebellar cells from excitotoxicity induced by glutamate

ETHNOPHARMACOLOGICAL RELEVANCE

Amburana cearensis (Allemao) A.C.Sm. is a medicinal plant of the Brazilian Caatinga reported to present antioxidant and anti-inflammatory activity. This study aimed to evaluate the neuroprotective effect of the extracts obtained from the seeds of A. cearensis in primary cultures of cerebellar cells subjected to excitotoxicity induced by glutamate and brain mitochondria submitted to oxidative stress.

MATERIALS

and methods: Primary cultures of cerebellar cells were treated with the ethanol (ETAC), hexane (EHAC), dichloromethane (EDAC) and ethyl acetate (EAAC) extracts of the seeds of A.cearensis and subjected to excitotoxicity induced by glutamate (10µM). Mitochondria isolated from rat brains were submitted to oxidative stress and treated with ETAC.

RESULTS

Only the EHAC extract reduced cell viability by 30% after 72h of treatment. Morphological analyses by Immunofluorescence showed positive staining for glutamine synthetase, β-III tubulin, GFAP and IBA1 similar to control cultures, indicating a better preservation of astrocytes, neurons and microglia, after excitotoxic damage induced by glutamate in cerebellar cultures treated with the extracts. The ETAC extract also protected mitochondria isolated from rat brains from oxidative stress, reducing the swelling, dissipation of the membrane potential, ROS production and calcium influx.

CONCLUSION

Thus, this study suggests that the seed extracts from A. Cearensis exhibit neuroprotective potential against oxidative stress and excitotoxicity induced by glutamate and can be considered a potential therapeutic agent in the treatment of neurodegenerative diseases.

A Cystine-Rich Whey Supplement (Immunocal®) Provides Neuroprotection from Diverse Oxidative Stress-Inducing Agents In Vitro by Preserving Cellular Glutathione

Oxidative stress is a principal mechanism underlying the pathophysiology of neurodegeneration. Therefore, nutritional enhancement of endogenous antioxidant defenses may represent a viable treatment option. We investigated the neuroprotective properties of a unique whey protein supplement (Immunocal®) that provides an essential precursor (cystine) for synthesis of the endogenous antioxidant, glutathione (GSH). Primary cultures of rat cerebellar granule neurons (CGNs), NSC34 motor neuronal cells, or HT22 hippocampal cells were preincubated in medium containing Immunocal and then subsequently treated with agents known to induce oxidative stress. Immunocal protected CGNs against neurotoxicity induced by the Bcl-2 inhibitor, HA14-1, the nitric oxide donor, sodium nitroprusside, CuCl₂, and AlCl₃. Immunocal also significantly reduced NSC34 cell death due to either H₂O₂ or glutamate and mitigated toxicity in HT22 cells overexpressing β-amyloid_1-42. The neuroprotective effects of Immunocal were blocked by inhibition of γ-glutamyl-cysteine ligase, demonstrating dependence on de novo GSH synthesis. These findings indicate that sustaining GSH with Immunocal significantly protects neurons against diverse inducers of oxidative stress. Thus, Immunocal is a nutritional supplement worthy of testing in preclinical animal models of neurodegeneration and in future clinical trials of patients afflicted by these diseases.

Cytocompatible cell encapsulation via hydrogel photopolymerization in microfluidic emulsion droplets

Encapsulating cells within biocompatible materials is a widely pursued and promising element of tissue engineering and cell-based therapies. Recently, extensive interest in microfluidic-enabled cell encapsulation has emerged as a strategy to structure hydrogels and establish custom cellular microenvironments. In particular, it has been shown that the microfluidic-enabled photoencapsulation of cells within PEG diacrylate (PEGDA)-based microparticles can be performed cytocompatibly within gas-permeable, nitrogen-jacketed polydimethylsiloxane microfluidic devices, which mitigate the oxygen inhibition of radical chain growth photopolymerization. Compared to bulk polymerization, in which cells are suspended in a static hydrogel-forming solution during gelation, encapsulating cells via microfluidic processing exposes cells to a host of potentially deleterious stresses such as fluidic shear rate, transient oxygen depletion, elevated pressures, and UV exposure. In this work, we systematically examine the effects of these factors on the viability of cells that have been microfluidically photoencapsulated in PEGDA. It was found that the fluidic shear rate during microdroplet formation did not have a direct effect on cell viability, but the flow rate ratio of oil to aqueous solution would impart harmful effects to cells when a critical threshold was exceeded. The effects of UV exposure time and intensity on cells, however, are more complex, as they contribute unequally to the cumulative rate of peroxy radical generation, which is strongly correlated with cell viability. A reaction-diffusion model has been developed to calculate the cumulative peroxy radical concentration over a range of UV light intensity and radiation times, which was used to gain further quantitative understanding of experimental results. Conclusions drawn from this work provide a comprehensive guide to mitigate the physical and biochemical damage imparted to cells during microfluidic photoencapsulation and expands the potential for this technique.

Vulnerability to a Metabolic Challenge Following Perinatal Asphyxia Evaluated by Organotypic Cultures: Neonatal Nicotinamide Treatment

The hypothesis of enhanced vulnerability following perinatal asphyxia was investigated with a protocol combining in vivo and in vitro experiments. Asphyxia-exposed (AS) (by 21 min water immersion of foetuses containing uterine horns) and caesarean-delivered control (CS) rat neonates were used at P2-3 for preparing triple organotypic cultures (substantia nigra, neostriatum and neocortex). At DIV 18, cultures were exposed to different concentrations of H₂O₂ (0.25-45 mM), added to the culture medium for 18 h. After a 48-h recovery period, the cultures were either assessed for cell viability or for neurochemical phenotype by confocal microscopy. Energy metabolism (ADP/ATP ratio), oxidative stress (GSH/GSSG) and a modified ferric reducing/antioxidant power assay were applied to homogenates of parallel culture series. In CS cultures, the number of dying cells was similar in substantia nigra, neostriatum and neocortex, but it was several times increased in AS cultures evaluated under the same conditions. A H₂O₂ challenge led to a concentration-dependent increase in cell death (>fourfold after 0.25 mM of H₂O₂) in CS cultures. In AS cultures, a significant increase in cell death was only observed after 0.5 mM of H₂O₂. At higher than 1 mM of H₂O₂ (up to 45 mM), cell death increased several times in all cultures, but the effect was still more prominent in CS than in AS cultures. The cell phenotype of dying/alive cells was investigated in formalin-fixed cultures exposed to 0 or 1 mM of H₂O₂, co-labelling for TUNEL (apoptosis), MAP-2 (neuronal phenotype), GFAP (astroglial phenotype) and TH (tyrosine hydroxylase; for dopamine phenotype), counterstaining for DAPI (nuclear staining), also evaluating the effect of a single dose of nicotinamide (0.8 nmol/kg, i.p. injected in 100 μL, 60 min after delivery). Perinatal asphyxia produced a significant increase in the number of DAPI/TUNEL cells/mm³, in substantia nigra and neostriatum. One millimolar of H₂0₂ increased the number of DAPI/TUNEL cells/mm³ by ≈twofold in all regions of CS and AS cultures, an effect that was prevented by neonatal nicotinamide treatment. In substantia nigra, the number of MAP-2/TH-positive cells/mm³ was decreased in AS compared to CS cultures, also by 1 mM of H₂0₂, both in CS and AS cultures, prevented by nicotinamide. In agreement, the number of MAP-2/TUNEL-positive cells/mm³ was increased by 1 mM H₂O₂, both in CS (twofold) and AS (threefold) cultures, prevented by nicotinamide. The number of MAP-2/TH/TUNEL-positive cells/mm³ was only increased in CS (>threefold), but not in AS (1.3-fold) cultures. No TH labelling was observed in neostriatum, but 1 mM of H₂O₂ produced a strong increase in the number of MAP-2/TUNEL-positive cells/mm³, both in CS (>2.9-fold) and AS (>fourfold), decreased by nicotinamide. In neocortex, H₂O₂ increased the number of MAP-2/TUNEL-positive cells/mm³, both in CS and AS cultures (≈threefold), decreased by nicotinamide. The ADP/ATP ratio was increased in AS culture homogenates (>sixfold), compared to CS homogenates, increased by 1 mM of H₂0₂, both in CS and AS homogenates. The GSH/GSSG ratio was significantly decreased in AS, compared to CS cultures. One millimolar of H₂O₂ decreased that ratio in CS and AS homogenates. The present results demonstrate that perinatal asphyxia induces long-term changes in metabolic pathways related to energy and oxidative stress, priming cell vulnerability with both neuronal and glial phenotype. The observed effects were region dependent, being the substantia nigra particularly prone to cell death. Nicotinamide administration in vivo prevented the deleterious effects observed after perinatal asphyxia in vitro, a suitable pharmacological strategy against the deleterious consequences of perinatal asphyxia.

The Differential Effects of Erythropoietin Exposure to Oxidative Stress on Microglia and Astrocytes in vitro

The neonatal brain is especially susceptible to oxidative stress owing to its reduced antioxidant capacity. Following hypoxic-ischemic (HI) injury, for example, there is a prolonged elevation in levels of hydrogen peroxide (H2O2) in the immature brain compared to the adult brain, resulting in lasting injury that can lead to life-long disability or morbidity. Erythropoietin (Epo) is one of few multifaceted treatment options that have been promising enough to trial in the clinic for both term and preterm brain injury. Despite this, there is a lack of clear understanding of how Epo modulates glial cell activity following oxidative injury, specifically, whether it affects microglia (Mg) and astrocytes (Ast) differently. Using an in vitro approach using primary murine Mg and Ast subjected to H2O2 injury, we studied the oxidative and inflammatory responses of Mg and Ast to recombinant murine (rm)Epo treatment. We found that Epo protects Ast from H2O2 injury (p < 0.05) and increases secreted nitric oxide levels in these cells (p < 0.05) while suppressing intracellular reactive oxygen species (p < 0.05) and superoxide ion (p < 0.05) levels only in Mg. Using a multiplex analysis, we noted that although H2O2 induced the levels of several chemokines, rmEpo did not have any significant specific effects on their levels, either with or without the presence of conditioned medium from injured neurons (NCM). Ultimately, it appears that rmEpo has pleiotropic effects based on the cell type; it has a protective effect on Ast but an antioxidative effect only on Mg without any significant modulation of chemokine and cytokine levels in either cell type. These findings highlight the importance of considering all cell types when assessing the benefits and pitfalls of Epo use.

Protective Effects of Degraded Soybean Polysaccharides on Renal Epithelial Cells Exposed to Oxidative Damage

This study aimed to investigate the protective effects of degraded soybean polysaccharides (DSP) on oxidatively damaged African green monkey kidney epithelial (Vero) cells. Low DSP concentration (10 μg/mL) elicited an evident protective effect on H₂O₂-induced cell injury (0.3 mmol/L). The cell viabilities of the H₂O₂-treated group and the DSP-protected group were 57.3 and 93.1%, respectively. The cell viability decreased to 88.3% when the dosage was increased to 100 μg/mL. DSP protected Vero cells from H₂O₂-mediated oxidative damage by enhancing cellular superoxide dismutase activity and total antioxidant capacity and by decreasing malonaldehyde content and lactate dehydrogenase release. The H₂O₂-treated cells stimulated the aggregation of calcium oxalate monohydrate crystals. DSP could also reduce the crystal size, decrease the attached crystal content, and prevent the cell aggregation by alleviating oxidative injury and lipid peroxidation, enhancing antioxidant capacity, and decreasing hyaluronan expression on cellular surfaces. The internalization ability of the injured cells was improved after these cells were exposed to DSP solution. The regulation ability of DSP-repaired cells on calcium oxalate dihydrate formation, crystal attachment, aggregation, and internalization was lower than that of normal cells but was higher than that of the injured cells. DSP may be a potential green drug to prevent calcium oxalate (CaOx) stone formation because DSP could protect cells from oxidative damage and inhibit CaOx crystal formation.

Water-soluble fractions from defatted sesame seeds protect human neuroblast cells against peroxyl radicals and hydrogen peroxide-induced oxidative stress

Oxidative stress is involved in the development of aging-related diseases, such as neurodegenerative diseases. Dietary antioxidants that can protect neuronal cells from oxidative damage play an important role in preventing such diseases. Previously, we reported that water-soluble fractions purified from defatted sesame seed flour exhibit good antioxidant activity in vitro. In the present study, we investigated the protective effects of white and gold sesame seed water-soluble fractions (WS-wsf and GS-wsf, respectively) against 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) and hydrogen peroxide (H2O2) induced oxidative stress in human neuroblast SH-SY5Y cells. Pretreatment with WS-wsf and GS-wsf did not protect cells against AAPH-induced cytotoxicity, while simultaneous co-treatment with AAPH significantly improved cell viability and inhibited membrane lipid peroxidation. These results suggest that WS-wsf and GS-wsf protect cells from AAPH-induced extracellular oxidative damage via direct scavenging of peroxyl radicals. When oxidative stress was induced by H2O2, pretreatment WS-wsf and GS-wsf significantly enhanced cell viability. These results suggest that in addition to radical scavenging, WS-wsf and GS-wsf enhance cellular resistance to intracellular oxidative stress by activation of the Nrf-2/ARE pathway as confirmed by the increased Nrf2 protein level in the nucleus and increased heme oxygenase 1 (HO-1) mRNA expression. The roles of ferulic and vanillic acids as bioactive antioxidants in these fractions were also confirmed. In conclusion, our results indicated that WS-wsf and GS-wsf, which showed antioxidant activity in vitro, are also efficient antioxidants in a cell system protecting SH-SY5Y cells against both extracellular and intracellular oxidative stress.

Oxygen-Purged Microfluidic Device to Enhance Cell Viability in Photopolymerized PEG Hydrogel Microparticles

Encapsulating cells within biocompatible materials is a widely used strategy for cell delivery and tissue engineering. While cells are commonly suspended within bulk hydrogel-forming solutions during gelation, substantial interest in the microfluidic fabrication of miniaturized cell encapsulation vehicles has more recently emerged. Here, we utilize multiphase microfluidics to encapsulate cells within photopolymerized picoliter-volume water-in-oil droplets at high production rates. The photoinitiated polymerization of polyethylene glycol diacrylate (PEGDA) is used to continuously produce solid particles from aqueous liquid drops containing cells and hydrogel forming solution. It is well understood that this photoinitiated addition reaction is inhibited by oxygen. In contrast to bulk polymerization in which ambient oxygen is rapidly and harmlessly consumed, allowing the polymerization reaction to proceed, photopolymerization within air permeable polydimethylsiloxane (PDMS) microfluidic devices allows oxygen to be replenished by diffusion as it is depleted. This sustained presence of oxygen and the consequential accumulation of peroxy radicals produce a dramatic effect upon both droplet polymerization and post-encapsulation cell viability. In this work we employ a nitrogen microjacketed microfluidic device to purge oxygen from flowing fluids during photopolymerization. By increasing the purging nitrogen pressure, oxygen concentration was attenuated, and increased post-encapsulation cell viability was achieved. A reaction-diffusion model was used to predict the cumulative intradroplet concentration of peroxy radicals, which corresponded directly to post-encapsulation cell viability. The nitrogen-jacketed microfluidic device presented here allows the droplet oxygen concentration to be finely tuned during cell encapsulation, leading to high post-encapsulation cell viability.

Streptomyces antioxidans sp. nov., a Novel Mangrove Soil Actinobacterium with Antioxidative and Neuroprotective Potentials

A novel strain, Streptomyces antioxidans MUSC 164^T was recovered from mangrove forest soil located at Tanjung Lumpur, Malaysia. The Gram-positive bacterium forms yellowish-white aerial and brilliant greenish yellow substrate mycelium on ISP 2 agar. A polyphasic approach was used to determine the taxonomy status of strain MUSC 164^T. The strain showed a spectrum of phylogenetic and chemotaxonomic properties consistent with those of the members of the genus Streptomyces. The cell wall peptidoglycan was determined to contain LL-diaminopimelic acid. The predominant menaquinones were identified as MK-9(H₆) and MK-9(H₈), while the identified polar lipids consisted of aminolipid, diphosphatidylglycerol, glycolipid, hydroxyphosphatidylethanolamine, phospholipid, phosphatidylinositol, phosphatidylethanolamine, phosphatidylglycerol and lipid. The cell wall sugars consist of galactose, glucose and ribose. The predominant cellular fatty acids (>10.0%) were identified as iso-C_15:0 (34.8%) and anteiso-C_15:0(14.0%). Phylogenetic analysis identified that closely related strains for MUSC 164^T as Streptomyces javensis NBRC 100777^T (99.6% sequence similarity), Streptomyces yogyakartensis NBRC 100779^T (99.6%) and Streptomyces violaceusniger NBRC 13459^T (99.6%). The DNA–DNA relatedness values between MUSC 164^T and closely related type strains ranged from 23.8 ± 0.3% to 53.1 ± 4.3%. BOX-PCR fingerprints comparison showed that MUSC 164^T exhibits a unique DNA profile, with DNA G + C content determined to be 71.6 mol%. Based on the polyphasic study of MUSC 164^T, it is concluded that this strain represents a novel species, for which the name Streptomyces antioxidans sp. nov. is proposed. The type strain is MUSC 164^T (=DSM 101523^T = MCCC 1K01590^T). The extract of MUSC 164^T showed potent antioxidative and neuroprotective activities against hydrogen peroxide. The chemical analysis of the extract revealed that the strain produces pyrazines and phenolic-related compounds that could explain for the observed bioactivities.

Reinjury risk of nano-calcium oxalate monohydrate and calcium oxalate dihydrate crystals on injured renal epithelial cells: aggravation of crystal adhesion and aggregation

BACKGROUND

Renal epithelial cell injury facilitates crystal adhesion to cell surface and serves as a key step in renal stone formation. However, the effects of cell injury on the adhesion of nano-calcium oxalate crystals and the nano-crystal-induced reinjury risk of injured cells remain unclear.

METHODS

African green monkey renal epithelial (Vero) cells were injured with H2O2 to establish a cell injury model. Cell viability, superoxide dismutase (SOD) activity, malonaldehyde (MDA) content, propidium iodide staining, hematoxylin-eosin staining, reactive oxygen species production, and mitochondrial membrane potential (Δψm) were determined to examine cell injury during adhesion. Changes in the surface structure of H2O2-injured cells were assessed through atomic force microscopy. The altered expression of hyaluronan during adhesion was examined through laser scanning confocal microscopy. The adhesion of nano-calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) crystals to Vero cells was observed through scanning electron microscopy. Nano-COM and COD binding was quantitatively determined through inductively coupled plasma emission spectrometry.

RESULTS

The expression of hyaluronan on the cell surface was increased during wound healing because of Vero cell injury. The structure and function of the cell membrane were also altered by cell injury; thus, nano-crystal adhesion occurred. The ability of nano-COM to adhere to the injured Vero cells was higher than that of nano-COD crystals. The cell viability, SOD activity, and Δψm decreased when nano-crystals attached to the cell surface. By contrast, the MDA content, reactive oxygen species production, and cell death rate increased.

CONCLUSION

Cell injury contributes to crystal adhesion to Vero cell surface. The attached nano-COM and COD crystals can aggravate Vero cell injury. As a consequence, crystal adhesion and aggregation are enhanced. These findings provide further insights into kidney stone formation.

Drug-induced reactive oxygen species (ROS) rely on cell membrane properties to exert anticancer effects

Pharmacological concentrations of small molecule natural products, such as ascorbic acid, have exhibited distinct cell killing outcomes between cancer and normal cells whereby cancer cells undergo apoptosis or necrosis while normal cells are not adversely affected. Here, we develop a mathematical model for ascorbic acid that can be utilized as a tool to understand the dynamics of reactive oxygen species (ROS) induced cell death. We determine that not only do endogenous antioxidants such as catalase contribute to ROS-induced cell death, but also cell membrane properties play a critical role in the efficacy of ROS as a cytotoxic mechanism against cancer cells vs. normal cells. Using in vitro assays with breast cancer cells, we have confirmed that cell membrane properties are essential for ROS, in the form of hydrogen peroxide (H2O2), to induce cell death. Interestingly, we did not observe any correlation between intracellular H2O2 and cell survival, suggesting that cell death by H2O2 is triggered by interaction with the cell membrane and not necessarily due to intracellular levels of H2O2. These findings provide a putative mechanistic explanation for the efficacy and selectivity of therapies such as ascorbic acid that rely on ROS-induced cell death for their anti-tumor properties.

Melatonin Protects Human Adipose-Derived Stem Cells from Oxidative Stress and Cell Death

BACKGROUND

Adipose-derived stem cells (ASCs) have applications in regenerative medicine based on their therapeutic potential to repair and regenerate diseased and damaged tissue. They are commonly subject to oxidative stress during harvest and transplantation, which has detrimental effects on their subsequent viability. By functioning as an antioxidant against free radicals, melatonin may exert cytoprotective effects on ASCs.

METHODS

We cultured human ASCs in the presence of varying dosages of hydrogen peroxide and/or melatonin for a period of 3 hours. Cell viability and apoptosis were determined with propidium iodide and Hoechst 33342 staining under fluorescence microscopy.

RESULTS

Hydrogen peroxide (1-2.5 mM) treatment resulted in an incremental increase in cell death. 2 mM hydrogen peroxide was thereafter selected as the dose for co-treatment with melatonin. Melatonin alone had no adverse effects on ASCs. Co-treatment of ASCs with melatonin in the presence of hydrogen peroxide protected ASCs from cell death in a dose-dependent manner, and afforded maximal protection at 100 µM (n=4, one-way analysis of variance P<0.001). Melatonin co-treated ASCs displayed significantly fewer apoptotic cells, as demonstrated by condensed and fragmented nuclei under fluorescence microscopy.

CONCLUSIONS

Melatonin possesses cytoprotective properties against oxidative stress in human ASCs and might be a useful adjunct in fat grafting and cell-assisted lipotransfer.

MiR-15a/16 Regulates Apoptosis of Lung Epithelial Cells after Oxidative Stress

Lung epithelial cell apoptosis is an important feature of hyperoxia-induced lung injury. Death receptor-associated extrinsic pathway and mitochondria-associated intrinsic pathway both mediate the development of lung epithelial cell apoptosis. Despite decades of research, molecular mechanisms of hyperoxia-induced epithelial cell apoptosis remain incompletely understood. Here we report a novel regulatory paradigm in response to hyperoxia-associated oxidative stress. Hyperoxia markedly up-regulated miR-15a/16 levels in lung epithelial cells, broncho-alveolar lavage fluid (BALF) and lung tissue. This effect was mediated by hyperoxia-induced reactive oxygen species (ROS). Functionally, miR-15a/16 inhibitors induced caspase 3-mediated lung epithelial cell apoptosis, in the presence of hyperoxia. MiR-15a/16 inhibitors robustly enhanced FADD level and down-regulated Bcl-2 expression. Consistently, cleaved caspase 8 and 9 were highly induced in the miR-15a/16 deficient cells, after hyperoxia. Using airway epithelial cell specific, miR-15a/16^-/- mice, we found that Bcl-2 significantly reduced in lung epithelial cells in vivo after hyperoxia. In contrast, caspase 3, 8 and Bcl-2 associated death promoter (BAD) were highly elevated in the miR-15a/16^-/- epithelial cells in vivo. Interestingly, in lung epithelial malignant cells, rather than benign cells, deletion of miR-15a/16 prevented apoptosis. Furthermore, deletion of miR-15a/16 in macrophages also prohibited apoptosis, opposite to what we have found in normal lung epithelial cells. Taken together, our data suggested that miR-15a/16 may exert differential roles in different cell types. MiR-15a/16 deficiency result in lung epithelial cell apoptosis in response to hyperoxia, via modulating both intrinsic and extrinsic apoptosis pathways.

High-Throughput Phenotypic Screening of Human Astrocytes to Identify Compounds That Protect Against Oxidative Stress

Astrocytes are the predominant cell type in the nervous system and play a significant role in maintaining neuronal health and homeostasis. Recently, astrocyte dysfunction has been implicated in the pathogenesis of many neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Astrocytes are thus an attractive new target for drug discovery for neurological disorders. Using astrocytes differentiated from human embryonic stem cells, we have developed an assay to identify compounds that protect against oxidative stress, a condition associated with many neurodegenerative diseases. This phenotypic oxidative stress assay has been optimized for high-throughput screening in a 1,536-well plate format. From a screen of approximately 4,100 bioactive tool compounds and approved drugs, we identified a set of 22 that acutely protect human astrocytes from the consequences of hydrogen peroxide-induced oxidative stress. Nine of these compounds were also found to be protective of induced pluripotent stem cell-differentiated astrocytes in a related assay. These compounds are thought to confer protection through hormesis, activating stress-response pathways and preconditioning astrocytes to handle subsequent exposure to hydrogen peroxide. In fact, four of these compounds were found to activate the antioxidant response element/nuclear factor-E2-related factor 2 pathway, a protective pathway induced by toxic insults. Our results demonstrate the relevancy and utility of using astrocytes differentiated from human stem cells as a disease model for drug discovery and development.

SIGNIFICANCE

Astrocytes play a key role in neurological diseases. Drug discovery efforts that target astrocytes can identify novel therapeutics. Human astrocytes are difficult to obtain and thus are challenging to use for high-throughput screening, which requires large numbers of cells. Using human embryonic stem cell-derived astrocytes and an optimized astrocyte differentiation protocol, it was possible to screen approximately 4,100 compounds in titration to identify 22 that are cytoprotective of astrocytes. This study is the largest-scale high-throughput screen conducted using human astrocytes, with a total of 17,536 data points collected in the primary screen. The results demonstrate the relevancy and utility of using astrocytes differentiated from human stem cells as a disease model for drug discovery and development.

Secretory pathway Ca(2+)-ATPase isoform 1 knockdown promotes Golgi apparatus stress injury in a mouse model of focal cerebral ischemia-reperfusion: In vivo and in vitro study

The present study was designed to investigate the potential role of secretory pathway Ca(2+)-ATPase isoform 1(SPCA1) in experimental focal cerebral ischemia-reperfusion injury. Cerebral ischemia-reperfusion was induced by transient middle cerebral artery occlusion (MCAO) for 2h s in Sprague-Dawley rats, and then the expression levels of SPAC1 mRNA and protein were determined. Results showed that SPCA1 level was transiently increased 1 day after reperfusion in peri-infarction area, while markedly increased in infarction core on 3day and 7 day after reperfusion. Then a SPCA1 lentivirus was used to achieve knockdown of SPCA1 gene: Ca(2+) transporting type 2C, member 1 (ATP2C1) gene. It has been observed that SPCA1 knockdown by lentivirus markedly increased cerebral infarction volume in vivo. Meanwhile, SPCA1 knockdown also facilitated per-oxidative production, including nitric oxide (NO) and 3-nitrotyrosine (3-NT) and decreased the expression of total superoxide dismutase (SOD) and manganese superoxide dismutase (MnSOD). Moreover, in vitro study showed that SPCA1 knockdown increased hydrogen peroxide (H2O2)-induced lactate dehydrogenase (LDH) leakage dose-dependently, and elevated caspase3 level in neuro-2a (N2a) cells. In addition, SPCA1 knockdown increased H2O2-induced production of nitric oxide and 3-NT dose-dependently, and reversed the increased activity of total SOD and MnSOD in neuro-2a cells. In conclusion, the present study indicated that SPCA1 could suppress over active Golgi apparatus (GA) stress thus attenuate cerebral ischemia-reperfusion injury.

Mitochondrial c-Fos May Increase the Vulnerability of Neuro2a Cells to Cellular Stressors

Although c-Fos expression in mitochondria is known to increase under excitatory injury via kainic acid or N-methyl-D-aspartate injection, the authentic function of c-Fos in mitochondria remains unknown. We found that c-Fos expression in the mitochondria of neuroblastoma Neuro2a cells was augmented by oxygen and glucose deprivation (OGD), which is a common in vitro model for brain ischemia. Then we demonstrated that Neuro2a cells stably expressing c-Fos exclusively in the mitochondria were more vulnerable to stressors such as OGD, rotenone (which is known to induce mitochondrial dysfunction) and hydrogen peroxide (a reactive oxygen species). Since mitochondrial dysfunction and the generation of reactive oxygen species are known to be caused by OGD, our findings indicate that mitochondrial c-Fos increases neuronal vulnerability to brain ischemia. This suggests that mitochondrial c-Fos play a potential role in inducing neuronal death on, and can therefore act as a potential drug target for brain ischemia.

Hydrogen Peroxide-Induced Oxidative Stress Activates Proteasomal Trypsin-Like Activity in Human U373 Glioma Cells

Degradation of oxidized or oxidatively modified proteins is an essential part of the cellular antioxidant defense system. 4-Hydroxy-2-nonenal, a major reactive aldehyde formed by lipid peroxidation, causes many types of cellular damage. The major proteolytic system for modified protein degradation is the ubiquitin-proteasome pathway. However, our previous studies using U937 human leukemic cells showed that 4-hydroxy-2-nonenal-modified glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is degraded by cathepsin G. In the present study, U373 human glioma cells were cultured in the presence of hydrogen peroxide (H2O2) to investigate the relationships of proteasome and/or cathepsin G activities and H2O2-induced GAPDH degradation. Treatment of cells with H2O2 for 5 h in culture decreased GAPDH activity as well as its protein concentration in a concentration-dependent manner. Two proteasomal activities (peptidylglutamyl-peptide hydrolase and chymotrypsin-like hydrolase activities) and cathepsin G activity were decreased by H2O2 treatment in a concentration-dependent manner, but proteasomal trypsin-like hydrolase activity increased with cell exposure to high H2O2 concentrations. Among the protease inhibitors examined here, H2O2-induced activation of trypsin-like activity and GAPDH degradation were inhibited by the proteasome inhibitor lactacystin. Furthermore, H2O2-induced activation of trypsin-like activity was also inhibited by another proteasome inhibitor MG-132. These results suggested that proteasomal trypsin-like activity played an important role in eliminating oxidatively modified GAPDH formed in these cells during H2O2 exposure.

Neuroprotective effects of the Phellinus linteus ethyl acetate extract against H2O2-induced apoptotic cell death of SK-N-MC cells

Numerous studies have suggested that neuronal cells are protected against oxidative stress-induced cell damage by antioxidants, such as polyphenolic compounds. Phellinus linteus (PL) has traditionally been used to treat various symptoms in East Asian countries. In the present study, we prepared an ethyl acetate extract from the fruiting bodies of PL (PLEA) using hot water extraction, ethanol precipitation, and ethyl acetate extraction. The PLEA contained polyphenols as its major chemical component, and thus, we predicted that it may exhibit antioxidant and neuroprotective effects against oxidative stress. The results showed that the pretreatment of human brain neuroblastoma SK-N-MC cells with the PLEA (0.1-5 μg/mL) significantly and dose-dependently reduced the cytotoxicity of H2O2 and the intracellular ROS levels and enhanced the expression of HO-1 (heme oxygenase-1) and antioxidant enzymes, such as CAT (catalase), GPx-1 (glutathione peroxidase-1), and SOD-1 and -2 (superoxide dismutase-1 and -2). The PLEA also directly scavenged free radicals. PLEA pretreatment also significantly attenuated DNA fragmentation and suppressed the mRNA expression and activation of mitogen-activated protein kinases extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 kinase, which are induced by oxidative stress and lead to cell death. PLEA pretreatment inhibited the activation of the apoptosis-related proteins caspase-3 and poly (ADP-ribose) polymerase. These results demonstrate that the PLEA has neuroprotective effects against oxidative stress (H2O2)-induced neuronal cell death via its antioxidant and anti-apoptotic properties. PLEA should be investigated in an in vivo model on its potential to prevent or ameliorate neurodegenerative disease.

Aβ selectively impairs mGluR7 modulation of NMDA signaling in basal forebrain cholinergic neurons: implication in Alzheimer's disease

Degeneration of basal forebrain (BF) cholinergic neurons is one of the early pathological events in Alzheimer's disease (AD) and is thought to be responsible for the cholinergic and cognitive deficits in AD. The functions of this group of neurons are highly influenced by glutamatergic inputs from neocortex. We found that activation of metabotropic glutamate receptor 7 (mGluR7) decreased NMDAR-mediated currents and NR1 surface expression in rodent BF neurons via a mechanism involving cofilin-regulated actin dynamics. In BF cholinergic neurons, β-amyloid (Aβ) selectively impaired mGluR7 regulation of NMDARs by increasing p21-activated kinase activity and decreasing cofilin-mediated actin depolymerization through a p75(NTR)-dependent mechanism. Cell viability assays showed that activation of mGluR7 protected BF neurons from NMDA-induced excitotoxicity, which was selectively impaired by Aβ in BF cholinergic neurons. It provides a potential basis for the Aβ-induced disruption of calcium homeostasis that might contribute to the selective degeneration of BF cholinergic neurons in the early stage of AD.

Multiassay analysis of the toxic potential of hydrogen peroxide on cultured neurons

To clarify discrepancies in the literature on the adverse effects of hydrogen peroxide on neurons, this study investigated the application of this peroxide to cultured cerebellar granule neurons with six assays frequently used to test for viability. Cultured neurons efficiently cleared exogenous H2O2. Although viability was not affected by exposure to 10 µM hydrogen peroxide, an exposure to the peroxide in higher concentrations rapidly lowered, within 15 min, the cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltertrazolium bromide (MTT) reduction capacity to 53% ± 1% (100 µM) and 31% ± 1% (1,000 µM) and the 3-amino-7-dimethylamino-2-methyl-phenazine hydrochloride (neutral red; NR) uptake to 84% ± 6% (100 µM) and 33% ± 1% (1,000 µM) of control cells. The release of glycolytically generated lactate was stopped within 30 min in neurons treated with 1,000 µM peroxide. In contrast, even hours after peroxide application, the cell morphology, the number of propidium iodide-positive cells, and the extracellular activity of the cytosolic enzyme lactate dehydrogenase (LDH) were not significantly altered. The rapid loss in MTT reduction and NR uptake after exposure of neurons to H2O2 for 5 or 15 min correlated well with a strongly compromised MTT reduction and a very high extracellular LDH activity observed after further incubation in peroxide-free medium for a total incubation period of 24 hr. These data demonstrate that cultured neurons do not recover from damage that is inflicted by a short exposure to H2O2 and that the rapid losses in the capacities of neurons for MTT reduction and NR uptake are good predictors of delayed cell damage.

Electrochemically reduced water protects neural cells from oxidative damage

Aging-related neurodegenerative disorders are closely associated with mitochondrial dysfunction and oxidative stresses and their incidence tends to increase with aging. Brain is the most vulnerable to reactive species generated by a higher rate of oxygen consumption and glucose utilization compared to other organs. Electrochemically reduced water (ERW) was demonstrated to scavenge reactive oxygen species (ROS) in several cell types. In the present study, the protective effect of ERW against hydrogen peroxide (H₂O₂) and nitric oxide (NO) was investigated in several rodent neuronal cell lines and primary cells. ERW was found to significantly suppress H₂O₂ (50–200 μM) induced PC12 and SFME cell deaths. ERW scavenged intracellular ROS and exhibited a protective effect against neuronal network damage caused by 200 μM H₂O₂ in N1E-115 cells. ERW significantly suppressed NO-induced cytotoxicity in PC12 cells despite the fact that it did not have the ability to scavenge intracellular NO. ERW significantly suppressed both glutamate induced Ca²⁺ influx and the resulting cytotoxicity in primary cells. These results collectively demonstrated for the first time that ERW protects several types of neuronal cells by scavenging ROS because of the presence of hydrogen and platinum nanoparticles dissolved in ERW.

MicroRNA-23a-3p attenuates oxidative stress injury in a mouse model of focal cerebral ischemia-reperfusion

The present study was designed to investigate the potential role of miR-23a-3p in experimental brain ischemia-reperfusion injury. Cerebral ischemia reperfusion was induced by transient middle cerebral artery occlusion (MCAO) for 1h in C57/BL6 mice. And miR-23a-3p angomir was transfected to upregulate the miR-23a-3p level. Our results showed that miR-23a-3p levels were transiently increased at 4h after reperfusion in the peri-infarction area, while markedly increased in the infarction core at reperfusion 4h and 24h. Importantly, in vivo study demonstrated that miR-23a-3p angomir treatment through intracerebroventricular injection markedly decreased cerebral infarction volume after MCAO. Simultaneously, miR-23a-3p reduced peroxidative production nitric oxide (NO) and 3-nitrotyrosine (3-NT), and increased the expression of manganese superoxide dismutase (MnSOD). In vitro study demonstrated that miR-23a-3p decreased hydrogen peroxide (H2O2)-induced lactate dehydrogenase (LDH) leakage dose-dependently, and reduced protein levels of activated caspase-3 in neuro-2a cells. In addition, miR-23a-3p reduced H2O2-induced production of NO and 3-NT dose-dependently, and reversed the decreased activity of total SOD and MnSOD in neuro-2a cells. Our study indicated that miR-23a-3p suppressed oxidative stress and lessened cerebral ischemia-reperfusion injury.

Corneal dystrophy-causing SLC4A11 mutants: suitability for folding-correction therapy

SLC4A11 mutations cause some cases of the corneal endothelial dystrophies, congenital hereditary endothelial corneal dystrophy type 2 (CHED2), Harboyan syndrome (HS), and Fuchs endothelial corneal dystrophy (FECD). SLC4A11 protein was recently identified as facilitating water flux across membranes. SLC4A11 point mutations usually cause SLC4A11 misfolding and retention in the endoplasmic reticulum (ER). We set about to test the feasibility of rescuing misfolded SLC4A11 protein to the plasma membrane as a therapeutic approach. Using a transfected HEK293 cell model, we measured functional activity present in cells expressing SLC4A11 variants in combinations representing the state found in CHED2 carriers, affected CHED2, FECD individuals, and unaffected individuals. These cells manifest respectively about 60%, 5%, and 25% of the water flux activity, relative to the unaffected (WT alone). ER-retained CHED2 mutant SLC4A11 protein could be rescued to the plasma membrane, where it conferred 25%-30% of WT water flux level. Further, some ER-retained CHED2 mutants expressed at 30°C supported increased water flux compared with 37°C cultures. Caspase activation and cell vitality assays revealed that expression of SLC4A11 mutants in HEK293 cells does not induce cell death. We conclude that therapeutics able to increase cell surface localization of ER-retained SLC4A11 mutants hold promise to treat CHED2 and FECD patients.

Short time exposure to hydrogen peroxide induces sustained glutathione export from cultured neurons

Hydrogen peroxide is a normal by-product of cellular metabolism that in higher concentrations can cause oxidative stress. Cultured cerebellar granule neurons efficiently disposed of micromolar concentrations of hydrogen peroxide with half-times in the minute range in a process that predominately involved catalase. Application of up to 100 µM hydrogen peroxide did not affect the cell viability for up to 4h, but caused a time- and concentration-dependent increase in the extracellular glutathione (GSH) content that was accompanied by a matching decrease in the cellular GSH content. Hydrogen peroxide at 100 µM stimulated maximally the GSH export from viable neurons, but did not affect GSH export from cultured astrocytes. The peroxide-induced extracellular GSH accumulation from neurons was lowered by 70% in the presence of MK571, an inhibitor of multidrug resistance protein (Mrp) 1. The extracellular GSH content determined after 4h of incubation was already significantly increased after a 5-min exposure of neurons to hydrogen peroxide and became maximal after 15 min of peroxide application. These data demonstrate that just a short exposure of viable cerebellar granule neurons to micromolar concentrations of hydrogen peroxide stimulates a prolonged Mrp1-mediated export of cellular GSH. This process may compromise the antioxidative potential of neurons and increase their sensitivity toward drugs and toxins.

Neuroprotective effects of orientin on hydrogen peroxide‑induced apoptosis in SH‑SY5Y cells

Neurodegenerative diseases remain a global issue which affects the ageing population. Efforts towards determining their aetiologies to understand their pathogenic mechanisms are underway in order to identify a pathway through which therapeutic measures can be applied. One such pathogenic mechanism, oxidative stress (OS), is widely considered to be involved in neurodegenerative disease. Antioxidants, most notably flavonoids, have promising potential for therapeutic use as shown in in vitro and in vivo studies. In view of the importance of flavonoids for combating OS, this study investigated the neuroprotective effects of orientin, which has been reported to be capable of crossing the blood‑brain barrier. The maximum non‑toxic dose (MNTD) of orientin against SH‑SY5Y neuroblastoma cells was determined using a 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide (MTT) assay. The effects of the MNTD and the half MNTD (½MNTD) of orientin on cell cycle progression and intracellular reactive oxygen species (ROS) levels, as well as the activity of caspases 3/7, 8 and 9 after exposure to 150 µM of hydrogen peroxide (H2O2) were also determined using flow cytometry, a 2',7'‑dichlorodihydrofluorescein‑diacetate (DCFH‑DA) assay and caspase assay kits, respectively. The results revealed that orientin at ≤20 µM was not cytotoxic to SH‑SY5Y cells. After treatment with orientin at the MNTD, the percentage of apoptotic cells was significantly reduced compared with that in cells treated with 150 µM H2O2 alone. The results also showed that, although orientin at the MNTD and ½MNTD did not reduce intracellular ROS levels, it significantly inhibited the activity of caspases 3/7. Caspase 9 was significantly inactivated with orientin at the MNTD. Findings from this study suggest that the neuroprotection conferred by orientin was the result of the intracellular mediation of caspase activity.

Theoretical aspects and modelling of cellular decision making, cell killing and information-processing in photodynamic therapy of cancer

Background

The aim of this report is to provide a mathematical model of the mechanism for making binary fate decisions about cell death or survival, during and after Photodynamic Therapy (PDT) treatment, and to supply the logical design for this decision mechanism as an application of rate distortion theory to the biochemical processing of information by the physical system of a cell.

Methods

Based on system biology models of the molecular interactions involved in the PDT processes previously established, and regarding a cellular decision-making system as a noisy communication channel, we use rate distortion theory to design a time dependent Blahut-Arimoto algorithm where the input is a stimulus vector composed of the time dependent concentrations of three PDT related cell death signaling molecules and the output is a cell fate decision. The molecular concentrations are determined by a group of rate equations. The basic steps are: initialize the probability of the cell fate decision, compute the conditional probability distribution that minimizes the mutual information between input and output, compute the cell probability of cell fate decision that minimizes the mutual information and repeat the last two steps until the probabilities converge. Advance to the next discrete time point and repeat the process.

Results

Based on the model from communication theory described in this work, and assuming that the activation of the death signal processing occurs when any of the molecular stimulants increases higher than a predefined threshold (50% of the maximum concentrations), for 1800s of treatment, the cell undergoes necrosis within the first 30 minutes with probability range 90.0%-99.99% and in the case of repair/survival, it goes through apoptosis within 3-4 hours with probability range 90.00%-99.00%. Although, there is no experimental validation of the model at this moment, it reproduces some patterns of survival ratios of predicted experimental data.

Conclusions

Analytical modeling based on cell death signaling molecules has been shown to be an independent and useful tool for prediction of cell surviving response to PDT. The model can be adjusted to provide important insights for cellular response to other treatments such as hyperthermia, and diseases such as neurodegeneration.

Nogo/RTN4 isoforms and RTN3 expression protect SH-SY5Y cells against multiple death insults

Among the members of the reticulon (RTN) family, Nogo-A/RTN4A, a prominent myelin-associated neurite growth inhibitory protein, and RTN3 are highly expressed in neurons. However, neuronal cell-autonomous functions of Nogo-A, as well as other members of the RTN family, are unclear. We show here that SH-SY5Y neuroblastoma cells stably over-expressing either two of the three major isoforms of Nogo/RTN4 (Nogo-A and Nogo-B) or a major isoform of RTN3 were protected against cell death induced by a battery of apoptosis-inducing agents (including serum deprivation, staurosporine, etoposide, and H2O2) compared to vector-transfected control cells. Nogo-A, -B, and RTN3 are particularly effective in terms of protection against H2O2-induced increase in intracellular reactive oxygen species levels and ensuing apoptotic and autophagic cell death. Expression of these RTNs upregulated basal levels of Bax, activated Bax, and activated caspase 3, but did not exhibit an enhanced ER stress response. The protective effect of RTNs is also not dependent on classical survival-promoting signaling pathways such as Akt and Erk kinase pathways. Neuron-enriched Nogo-A/Rtn4A and RTN3 may, therefore, exert a protective effect on neuronal cells against death stimuli, and elevation of their levels during injury may have a cell-autonomous survival-promoting function.

Enhanced neuroprotective effects of resveratrol delivered by nanoparticles on hydrogen peroxide-induced oxidative stress in rat cortical cell culture

Resveratrol (RES) has recently been reported as a potential antioxidant in treatment of ischemia/reperfusion injury through attenuating oxidative stress and apoptosis. However, application of RES is limited for its insolubility and short half-time. Latest evidence raises the possibility of developing nanoparticle-based delivery systems with improved solubility, stability and cytotoxicity of lipophilic drug. Here, we reported first a simple way to produce RES-loaded nanoparticles (RES-NPs) based on poly(N-vinylpyrrolidone)-b-poly(ε-caprolactone) polymer and further evaluated the protective effect of RES-NPs on hydrogen peroxide-induced oxidative stress and apoptosis in rat cortical cell culture. The controlled release pattern of RES-loaded nanoparticles was characterized by in vitro release experiments. Cytotoxicity tests proved cytocompatibility of these nanoparticles with neurons. Shown by coumarin-6 loaded nanoparticles, the uptake of nanoparticles by neurons was considered through endocytosis, which could lead to higher uptake efficiency at lower concentration. Thereby, the hypothesis is raised that RES-NPs could demonstrate enhanced neuroprotection compared to an equivalent dose of free RES at lower concentration, especially. It was further supported by enhanced reduction of LDH release, elimination of ROS and MDA, and attenuation of apoptosis signal (ratio of Bax/Bcl-2, activation of caspase-3). RES-NPs could be a potential treatment needing intensive research for ischemia/reperfusion related disorder including stroke.

Eco-friendly synthesis of size-controllable amine-functionalized graphene quantum dots with antimycoplasma properties

Size-controllable amine-functionalized graphene quantum dots (GQDs) are prepared by an eco-friendly method with graphene oxide sheets, ammonia and hydrogen peroxide as starting materials. Using a Sephadex G-25 gel column for fine separation, for the first time we obtain GQDs with either single or double layers. By atomic force microscopy characterization, we confirm that hydrogen peroxide and ammonia play a synergistic role on graphene oxide (GO), in which the former cuts the GO into small pieces and the latter passivates the active surface to give amine-modified GQDs. Due to the low cytotoxicity and excellent biocompatibility of the obtained amine-functionalized GQDs, besides the multiwavelength imaging properties of GQDs, for the first time we find that this kind of GQD exhibits good antimycoplasma properties. Given the superior antimycoplasma effect of the GQDs and their eco-friendly mass production with low cost, these new GQDs may offer opportunities for the development of new antimycoplasma agents, thus extending their widespread application in biomedicine.

Quercetin prevents protein nitration and glycolytic block of proliferation in hydrogen peroxide insulted cultured neuronal precursor cells (NPCs): Implications on CNS regeneration

Survival along with optimal proliferation of neuronal precursors determines the outcomes of the endogenous cellular repair in CNS. Cellular-oxidation based cell death has been described in several neurodegenerative disorders. Therefore, this study was aimed at the identification of the potent targets of oxidative damage to the neuronal precursors and its effective prevention by a natural flavonoid, Quercetin. Neuronal precursor cells (NPCs), Nestin+ and GFAP (Glial fibrillary acidic protein)+ were isolated and cultured from adult rat SVZ (subventricular zone). These cells were challenged with a single dose of H2O2 (50μM) and/or pre-treated with different concentrations of Quercetin. H2O2 severely limited the cellular viability and expansion of the neurospheres. Cellular-oxidation studies revealed reduction in glutathione dependent redox buffering along with depletion of enzymatic cellular antioxidants that might potentiate the nitrite (NO2(-)) and superoxide anion (O2(-)) mediated peroxynitrite (ONOO(-)) formation and irreversible protein nitration. We identified depleted PK-M2 (M2 isoform of pyruvate kinase) activity and apoptosis of NPCs revealed by the genomic DNA fragmentation and elevated PARP (poly ADP ribose polymerase) activity along with increased Caspase activity initiated by severely depolarised mitochondrial membranes. However, the pre-treatment of Quercetin in a dose-response manner prevented these changes and restored the expansion of neurospheres preferably by neutralizing the oxidative conditions and thereby reducing peroxynitrite formation, protein nitration and PK-M2 depletion. Our results unravel the potential interactions of oxidative environment and respiration in the survival and activation of precursors and offer a promise shown by a natural flavonoid in the protective strategy for neuronal precursors of adult brain.

The pharmacology and therapeutic potential of (-)-huperzine A

(−)-Huperzine A (1) is an alkaloid isolated from a Chinese club moss. Due to its potent neuroprotective activities, it has been investigated as a candidate for the treatment of neurodegenerative diseases, including Alzheimer’s disease. In this review, we will discuss the pharmacology and therapeutic potential of (−)-huperzine A (1). Synthetic studies of (−)-huperzine A (1) aimed at enabling its development as a pharmaceutical will be described.

Orexin A decreases lipid peroxidation and apoptosis in a novel hypothalamic cell model

Current data support the idea that hypothalamic neuropeptide orexin A (OxA; hypocretin 1) mediates resistance to high fat diet-induced obesity. We previously demonstrated that OxA elevates spontaneous physical activity (SPA), that rodents with high SPA have higher endogenous orexin sensitivity, and that OxA-induced SPA contributes to obesity resistance in rodents. Recent reports show that OxA can confer neuroprotection against ischemic damage, and may decrease lipid peroxidation. This is noteworthy as independent lines of evidence indicate that diets high in saturated fats can decrease SPA, increase hypothalamic apoptosis, and lead to obesity. Together data suggest OxA may protect against obesity both by inducing SPA and by modulation of anti-apoptotic mechanisms. While OxA effects on SPA are well characterized, little is known about the short- and long-term effects of hypothalamic OxA signaling on intracellular neuronal metabolic status, or the physiological relevance of such signaling to SPA. To address this issue, we evaluated the neuroprotective effects of OxA in a novel immortalized primary embryonic rat hypothalamic cell line. We demonstrate for the first time that OxA increases cell viability during hydrogen peroxide challenge, decreases hydrogen peroxide-induced lipid peroxidative stress, and decreases caspase 3/7 induced apoptosis in an in vitro hypothalamic model. Our data support the hypothesis that OxA may promote obesity resistance both by increasing SPA, and by influencing survival of OxA-responsive hypothalamic neurons. Further identification of the individual mediators of the anti-apoptotic and peroxidative effects of OxA on target neurons could lead to therapies designed to maintain elevated SPA and increase obesity resistance.

Neuroprotective properties of Loranthus parasiticus aqueous fraction against oxidative stress-induced damage in NG108-15 cells

Loranthus parasiticus, a Chinese folk medicine, has been widely used for the treatment of brain diseases, particularly in southwest China. Hence, the present neuroprotection model was designed to investigate its neuroprotective properties against H(2)O(2)-induced oxidative stress in NG108-15 cells. L. parasiticus aqueous fraction (LPAF), which was selected in the present study, had proved to be the most active fraction among the other tested extracts and fractions in our previous screening. The restoration of depleted intracellular glutathione (GSH), a major endogenous antioxidant, by LPAF was observed after H(2)O(2) insult. Pretreatment with LPAF substantially reduced the production of intracellular reactive oxygen species generated from H(2)O(2). Apoptotic features such as externalization of phosphatidylserine and disruption of mitochondrial membrane potential were significantly attenuated by LPAF. In addition, cell cycle analysis revealed a prominent decrease in the H(2)O(2)-induced sub-G(1) population by LPAF. Moreover, apoptotic morphological analysis by DAPI nuclear staining demonstrated that NG108-15 cells treated with H(2)O(2) exhibited apoptotic features, while such changes were greatly reduced in cells pretreated with LPAF. Taken together, these findings confirmed that LPAF exerts marked neuroprotective activity, which raises the possibility of potential therapeutic application of LPAF for managing oxidative stress-related neurological disorders and supports the traditional use of L. parasiticus in treating brain-related diseases.

Trichothecene mycotoxins inhibit mitochondrial translation--implication for the mechanism of toxicity

Fusarium head blight (FHB) reduces crop yield and results in contamination of grains with trichothecene mycotoxins. We previously showed that mitochondria play a critical role in the toxicity of a type B trichothecene. Here, we investigated the direct effects of type A and type B trichothecenes on mitochondrial translation and membrane integrity in Saccharomyces cerevisiae. Sensitivity to trichothecenes increased when functional mitochondria were required for growth, and trichothecenes inhibited mitochondrial translation at concentrations, which did not inhibit total translation. In organello translation in isolated mitochondria was inhibited by type A and B trichothecenes, demonstrating that these toxins have a direct effect on mitochondrial translation. In intact yeast cells trichothecenes showed dose-dependent inhibition of mitochondrial membrane potential and reactive oxygen species, but only at doses higher than those affecting mitochondrial translation. These results demonstrate that inhibition of mitochondrial translation is a primary target of trichothecenes and is not secondary to the disruption of mitochondrial membranes.

Pathological alterations of astrocytes in stroke-prone spontaneously hypertensive rats under ischemic conditions

Stroke-prone spontaneously hypertensive rats (SHRSP/Izm) develop severe hypertension, and more than 95% of them die of cerebral stroke. We showed the vulnerability of neuronal cells of SHRSP/Izm rats. Furthermore, we analyzed the characteristics of SHRSP/Izm astrocytes during a stroke. It is known that the proliferating ability of SHRSP/Izm astrocytes is significantly enhanced compared with those in the normotensive Wistar Kyoto rats (WKY/Izm) strain. Conversely, the ability of SHRSP/Izm astrocytes to form tight junctions (TJ) was attenuated compared with astrocytes from WKY/Izm rats. During the stress of hypoxia and reoxygenation (H/R), lactate production, an energy source for neuronal cells, decreased in SHRSP/Izm astrocytes in comparison with the WKY/Izm strain. Moreover, during H/R, SHRSP/Izm astrocytes decreased their production of glial cell line-derived neurotrophic factor (GDNF) in comparison with WKY/Izm astrocytes. Furthermore, SHRSP/Izm rats decreased production of l-serine, compared with WKY/Izm rats following nitric oxide (NO) stimulation. Additionally, in H/R, astrocytes of SHRSP/Izm rats expressed adhesion molecules such as VCAM-1 at higher levels. It is possible that all of these differences between SHRSP/Izm and WKY/Izm astrocytes are not associated with the neurological disorders in SHRSP/Izm. However, attenuated production of lactate and reduced GDNF production in astrocytes may reduce required energy levels and weaken the nutritional status of SHRSP/Ism neuronal cells. We suggest that the attenuation of astrocytes' functions accelerates neuronal cell death during stroke, and may contribute to the development of strokes in SHRSP/Izm. In this review, we summarize the altered properties of SHRSP/Izm astrocytes during a stroke.

A TNF receptor 2 selective agonist rescues human neurons from oxidative stress-induced cell death

Tumor necrosis factor (TNF) plays a dual role in neurodegenerative diseases. Whereas TNF receptor (TNFR) 1 is predominantly associated with neurodegeneration, TNFR2 is involved in tissue regeneration and neuroprotection. Accordingly, the availability of TNFR2-selective agonists could allow the development of new therapeutic treatments of neurodegenerative diseases. We constructed a soluble, human TNFR2 agonist (TNC-scTNF(R2)) by genetic fusion of the trimerization domain of tenascin C to a TNFR2-selective single-chain TNF molecule, which is comprised of three TNF domains connected by short peptide linkers. TNC-scTNF(R2) specifically activated TNFR2 and possessed membrane-TNF mimetic activity, resulting in TNFR2 signaling complex formation and activation of downstream signaling pathways. Protection from neurodegeneration was assessed using the human dopaminergic neuronal cell line LUHMES. First we show that TNC-scTNF(R2) interfered with cell death pathways subsequent to H(2)O(2) exposure. Protection from cell death was dependent on TNFR2 activation of the PI3K-PKB/Akt pathway, evident from restoration of H(2)O(2) sensitivity in the presence of PI3K inhibitor LY294002. Second, in an in vitro model of Parkinson disease, TNC-scTNF(R2) rescues neurons after induction of cell death by 6-OHDA. Since TNFR2 is not only promoting anti-apoptotic responses but also plays an important role in tissue regeneration, activation of TNFR2 signaling by TNC-scTNF(R2) appears a promising strategy to ameliorate neurodegenerative processes.

Pathophysiologically relevant levels of hydrogen peroxide induce glutamate-independent neurodegeneration that involves activation of transient receptor potential melastatin 7 channels

Stroke/brain ischemia is a leading cause of death and long-term disabilities. Increased oxidative stress plays an important role in the pathology of brain ischemia. Hydrogen peroxide (H(2)O(2)) is a major oxidant known to cause neuronal injury; however, the detailed mechanism remains unclear. Previous studies have suggested that H(2)O(2)-induced injury is associated with increased intracellular Ca(2+), mediated by glutamate receptors or voltage-gated Ca(2+) channels. Here, we demonstrate that, at concentrations relevant to stroke, H(2)O(2) induces a Ca(2+)-dependent injury of mouse cortical neurons in the absence of activation of these receptors/channels. With the culture medium containing blockers of glutamate receptors and voltage-gated Ca(2+) channels, brief exposure of neurons to H(2)O(2) induced a dose-dependent injury. Reducing [Ca(2+)](e) inhibited whereas increasing [Ca(2+)](e) potentiated the H(2)O(2) injury. Fluorescent Ca(2+) imaging confirmed the increase of [Ca(2+)](i) by H(2)O(2) in the presence of the blockers of glutamate receptors and voltage-gated Ca(2+) channels. Addition of 2-aminoethoxydiphenyl borate, an inhibitor of transient receptor potential melastatin 7 (TRPM7) channels, or the use of TRPM7-small interference RNA, protected the neurons from H(2)O(2) injury. In contrast, overexpressing TRPM7 channels in human embryonic kidney 293 cells increased H(2)O(2) injury. Our findings indicate that H(2)O(2) can induce Ca(2+) toxicity independent of glutamate receptors and voltage-gated Ca(2+) channels. Activation of TRPM7 channels is involved in such toxicity.

A strong protective action of guttiferone-A, a naturally occurring prenylated benzophenone, against iron-induced neuronal cell damage

Guttiferone-A (GA) is a natural occurring polyisoprenylated benzophenone with several reported pharmacological actions. We have assessed the protective action of GA on iron-induced neuronal cell damage by employing the PC12 cell line and primary culture of rat cortical neurons (PCRCN). A strong protection by GA, assessed by the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carbox-anilide (XTT) assay, was revealed, with IC(50) values <1 µM. GA also inhibited Fe(3+)-ascorbate reduction, iron-induced oxidative degradation of 2-deoxiribose, and iron-induced lipid peroxidation in rat brain homogenate, as well as stimulated oxygen consumption by Fe(2+) autoxidation. Absorption spectra and cyclic voltammograms of GA-Fe(2+)/Fe(3+) complexes suggest the formation of a transient charge transfer complex between Fe(2+) and GA, accelerating Fe(2+) oxidation. The more stable Fe(3+) complex with GA would be unable to participate in Fenton-Haber Weiss-type reactions and the propagation phase of lipid peroxidation. The results show a potential of GA against neuronal diseases associated with iron-induced oxidative stress.

Novel morphological features of developing white matter pericytes and rapid scavenging of reactive oxygen species in the neighbouring endothelia

Capillary endothelia and pericytes form a close morphological arrangement allowing pericytes to regulate capillary blood flow, in addition to contributing to vascular development and support. Vascular changes associated with oxidative stress are implicated in important pathologies in developing whiter matter, but little is known about the vascular unit in white matter of the appropriate age or how it responds to oxidative stress. We show that the ultrastructural arrangement of post-natal day 10 (P10) capillaries involves the apposition of pericyte somata to the capillary inner basement membrane and penetration of pericyte processes onto the abluminal surface where they form close connections with endothelial cells. Some pericytes have an unusual stellate morphology, extending processes radially from the vessel. Reactive oxygen species (ROS) were monitored with the ROS-sensitive dye 2',7'-dichlorofluorescin (DCF) in the endothelial cells. Exposure to exogenous ROS (100 μm H(2) O(2) or xanthine/xanthine oxidase), evoked an elevation in intracellular ROS that declined to baseline during the ongoing challenge. A second challenge failed to evoke an intracellular ROS rise unless the nerve was rested for > 4 h or exposed to very high levels of exogenous ROS. Exposure to a first ROS challenge prior to loading with DCF also prevented the intracellular ROS rise from a second challenge, proving that dye washout during exposure to ROS is not responsible for the loss of a second response. Perfusion with 30 μm extracellular Ca(2+) or the voltage-gated Ca(2+) antagonist diltiazem partially prevented this rapid scavenging of intracellular ROS, but blocking either catalase or glutathione peroxidase did not. The phenomenon was present over a range of post-natal ages and may contribute to the high ROS-tolerance of endothelial cells and act to limit the release of harmful ROS onto neighbouring pericytes.

Redox signaling regulates transcriptional activity of the Ca2+-dependent repressor DREAM

DREAM/KChIP3 (Downstream Regulatory Element Antagonist Modulator) is a multifunctional Ca(2+)-binding protein that acts in the nucleus as a Ca(2+)-dependent transcriptional repressor. Binding to DNA and repressor activity of DREAM is regulated by Ca(2+), specific post-translational modifications as well as by protein-protein interactions with several nucleoproteins. Here, using the yeast two-hybrid assay, we characterized the interaction of DREAM with peroxiredoxin 3 (Prdx3), an antioxidant enzyme that uses the thioredoxin system as electron donor. Importantly, the DREAM/Prdx3 interaction is Ca(2+) dependent and is blocked by DTT. Coexpression of Prdx3 enhances DREAM binding to DRE sites and its repressor activity in vivo. Two cysteine residues in the N-terminal domain of DREAM are responsible for the redox modulation of its activity. Double Cys to Ser substitution results in a mutant DREAM with stronger repressor activity. Finally, we show that transient DREAM knockdown sensitizes PC12 cells to H(2)O(2)-induced oxidative stress, suggesting a protective role for DREAM against oxidative damage.