Characterization of H2O2-induced acute apoptosis in cultured neural stem/progenitor cells

Neural stem cell-derived extracellular vesicles favour neuronal differentiation and plasticity under stress conditions

Extracellular vesicles (EVs) are released by all cell types and are involved in intercellular communication. We evaluated if neural stem cells-derived EVs (NSC-EVs) regulate NSCs proliferation and differentiation under control and stress conditions. We found that NSC-EVs treatment increases cell proliferation and promotes neuronal differentiation and plasticity. The fact that nervous tissue poorly recovers after cellular damage, prump us to evaluate the effect of EVs supplementation under oxidative stress and inflammation. We demonstrate that NSC-EVs restore the proliferative potential of the NSCs affected by oxidative stress. In addition, we provide evidence that oxidative stress and inflammation induce neuronal differentiation. Interestingly, the aberrant cell phenotype induced by inflammation is restored by NSC-EVs treatment, suggesting that these vesicles ameliorate the damage burden in neurons and modulate neuronal plasticity. These results contribute to understand the role of the NSCs-derived EVs as key players for brain tissue generation and regeneration and open new pathways to the development of therapies.

RalGPS2 Interacts with Akt and PDK1 Promoting Tunneling Nanotubes Formation in Bladder Cancer and Kidney Cells Microenvironment

Simple Summary

Cell-to-cell communication in the tumor microenvironment is a crucial process to orchestrate the different components of the tumoral infrastructure. Among the mechanisms of cellular interplay in cancer cells, tunneling nanotubes (TNTs) are dynamic connections that play an important role. The mechanism of the formation of TNTs among cells and the molecules involved in the process remain to be elucidated. In this study, we analyze several bladder cancer cell lines, representative of tumors at different stages and grades. We demonstrate that TNTs are formed only by mid or high-stage cell lines that show muscle-invasive properties and that they actively transport mitochondria and proteins. The formation of TNTs is triggered by stressful conditions and starts with the assembly of a specific multimolecular complex. In this study, we characterize some of the protein components of the TNTs complex, as they are potential novel molecular targets for future therapies aimed at counteracting tumor progression.

Abstract

RalGPS2 is a Ras-independent Guanine Nucleotide Exchange Factor for RalA GTPase that is involved in several cellular processes, including cytoskeletal organization. Previously, we demonstrated that RalGPS2 also plays a role in the formation of tunneling nanotubes (TNTs) in bladder cancer 5637 cells. In particular, TNTs are a novel mechanism of cell–cell communication in the tumor microenvironment, playing a central role in cancer progression and metastasis formation. However, the molecular mechanisms involved in TNTs formation still need to be fully elucidated. Here we demonstrate that mid and high-stage bladder cancer cell lines have functional TNTs, which can transfer mitochondria. Moreover, using confocal fluorescence time-lapse microscopy, we show in 5637 cells that TNTs mediate the trafficking of RalA protein and transmembrane MHC class III protein leukocyte-specific transcript 1 (LST1). Furthermore, we show that RalGPS2 is essential for nanotubes generation, and stress conditions boost its expression both in 5637 and HEK293 cell lines. Finally, we prove that RalGPS2 interacts with Akt and PDK1, in addition to LST1 and RalA, leading to the formation of a complex that promotes nanotubes formation. In conclusion, our findings suggest that in the tumor microenvironment, RalGPS2 orchestrates the assembly of multimolecular complexes that drive the formation of TNTs.

Extraction of the antioxidant phytocomplex from wine-making by-products and sustainable loading in phospholipid vesicles specifically tailored for skin protection

The present study is aimed at valorizing grape pomace, one of the most abundant winery-making by-products of the Mediterranean area, through the extraction of the main bioactive compounds from the skin of grape pomace and using them to manufacture innovative nanoformulations capable of both avoiding skin damages and promoting skincare. The phytochemicals were recovered through maceration in hydroethanolic solution. Catechin, quercetin, fisetin and gallic acid, which are known for their antioxidant power, were detected as the main compounds of the extract. Liposomes and phospholipid vesicles modified with glycerol or Montanov 82® or a combination of both, were used as carriers for the extract. The vesicles were small (~183 nm), slightly polydispersed (PI ≥ 0.28), and highly negatively charged (~-50 mV). The extract was loaded in high amounts in all vesicles (~100%) irrespective of their composition. The antioxidant activity of the extract, measured by using the DPPH (2,2-Diphenyl-1-picrylhydrazyl) test, was 84 ± 1%, and slightly increased when loaded into the vesicles (~89%, P < 0.05). The grape pomace extract loaded vesicles were highly biocompatible and able to protect fibroblasts (3T3) from the oxidative stress induced by hydrogen peroxide.

Iron depletion with deferoxamine protects bone marrow-derived mesenchymal stem cells against oxidative stress-induced apoptosis

Bone marrow mesenchymal stem cells (BM-MSCs) are multipotent cells with self-renewal properties, making them an ideal candidate for regenerative medicine. Recently, numerous studies show that about more than 99% of transplanted cells are destroyed because of the stressful microenvironment. Meanwhile, in the target organs, iron overload can produce oxidative stress introducing it as the most important stress factor. The present study was aimed at increasing BM-MSCs' viability against oxidative stress microenvironment using iron depletion by deferoxamine (DFO). Mesenchymal stem cells are isolated and characterized from rat bone marrow. Then, the sensitivity of BM-MSCs against H2O2-induced oxidative stress was evaluated through half of the inhibitory concentration (IC50) estimation by using MTT assay. The maximum non-inhibitory concentration of DFO on BM-MSCs was determined. The next step was the comparison between DFO pre-treated BM-MSCs and untreated cells against H2O2-induced apoptosis. BM-MSCs were identified with morphologic and flow cytometry analysis. IC50 of H2O2 was determined as 0.55 mM at 4 h. Also, the maximum non-inhibitory concentration of DFO was ascertained as 5 μM at 48 h. Our results demonstrated that pretreatment with DFO significantly potentiates BM-MSCs against H2O2-induced oxidative stress which was confirmed by MTT assay, AO/EB double staining, DAPI staining, and activated caspase 3 quantification as well as western blot test. Expression of cleaved caspase 3 and pAKT/AKT ratio obviously demonstrated DFO can resist the cells against cytotoxicity. These findings may help to develop better stem cell culture medium for MSC-based cell therapy. Moreover, regulation of cell stress can be used in practical subjects.

Cysteine redox state regulates human β2-adrenergic receptor binding and function

Bronchoconstrictive airway disorders such as asthma are characterized by inflammation and increases in reactive oxygen species (ROS), which produce a highly oxidative environment. β2-adrenergic receptor (β2AR) agonists are a mainstay of clinical therapy for asthma and provide bronchorelaxation upon inhalation. We have previously shown that β2AR agonism generates intracellular ROS, an effect that is required for receptor function, and which post-translationally oxidizes β2AR cysteine thiols to Cys-S-sulfenic acids (Cys-S-OH). Furthermore, highly oxidative environments can irreversibly oxidize Cys-S-OH to Cys-S-sulfinic (Cys-SO₂H) or S-sulfonic (Cys-SO₃H) acids, which are incapable of further participating in homeostatic redox reactions (i.e., redox-deficient). The aim of this study was to examine the vitality of β2AR-ROS interplay and the resultant functional consequences of β2AR Cys-redox in the receptors native, oxidized, and redox-deficient states. Here, we show for the first time that β2AR can be oxidized to Cys-S-OH in situ, moreover, using both clonal cells and a human airway epithelial cell line endogenously expressing β2AR, we show that receptor redox state profoundly influences β2AR orthosteric ligand binding and downstream function. Specifically, homeostatic β2AR redox states are vital toward agonist-induced cAMP formation and subsequent CREB and G-protein-dependent ERK1/2 phosphorylation, in addition to β-arrestin-2 recruitment and downstream arrestin-dependent ERK1/2 phosphorylation and internalization. On the contrary, redox-deficient β2AR states exhibit decreased ability to signal via either Gαs or β-arrestin. Together, our results demonstrate a β2AR-ROS redox axis, which if disturbed, interferes with proper receptor function.

Systemic Lupus Erythematosus: Pathogenesis at the Functional Limit of Redox Homeostasis

Systemic lupus erythematosus (SLE) is a disease characterized by the production of autoreactive antibodies and cytokines, which are thought to have a major role in disease activity and progression. Immune system exposure to excessive amounts of autoantigens that are not efficiently removed is reported to play a significant role in the generation of autoantibodies and the pathogenesis of SLE. While several mechanisms of cell death-based autoantigenic exposure and compromised autoantigen removal have been described in relation to disease onset, a significant association with the development of SLE can be attributed to increased apoptosis and impaired phagocytosis of apoptotic cells. Both apoptosis and impaired phagocytosis can be caused by hydrogen peroxide whose cellular production is enhanced by exposure to endogenous hormones or environmental chemicals, which have been implicated in the pathogenesis of SLE. Hydrogen peroxide can cause lymphocyte apoptosis and glutathione depletion, both of which are associated with the severity of SLE. The cellular accumulation of hydrogen peroxide is facilitated by the myriad of stimuli causing increased cellular bioenergetic activity that enhances metabolic production of this toxic oxidizing agent such as emotional stress and infection, which are recognized SLE exacerbating factors. When combined with impaired cellular hydrogen peroxide removal caused by xenobiotics and genetically compromised hydrogen peroxide elimination due to enzymatic polymorphic variation, a mechanism for cellular accumulation of hydrogen peroxide emerges, leading to hydrogen peroxide-induced apoptosis and impaired phagocytosis, enhanced autoantigen exposure, formation of autoantibodies, and development of SLE.

Epigallocatechin Gallate Is the Most Effective Catechin Against Antioxidant Stress via Hydrogen Peroxide and Radical Scavenging Activity

Background

Hydrogen peroxide-induced neuronal oxidative stress is a serious threat to the nervous system. Catechins and related compounds are effective radical scavengers that protect against nerve cell damage.

Material/Methods

Here, we investigated the antioxidant property of various catechins in protecting against hydrogen peroxide, as well as their radical-scavenging activity.

Result

We found that catechins treatment effectively protected HT22 cells against H₂O₂-induced cell viability by decreasing and attenuating reactive oxidative species production in different proportions. In addition, all tested catechins performed radical scavenging activity, and partially removed the free radicals. Among all investigated catechins, epigallocatechin gallate was the most effective against ROS production and had the strongest radical-scavenging activity. These results suggest that beneficial effects were strongly related with structure of catechins, mainly because of the hydroxyl and galloyl groups.

Conclusions

In conclusion, epigallocatechin gallate is the most effective antioxidant polyphenol against hydrogen peroxide and radical-scavenging activity.

The pathogenesis linked to coenzyme Q10 insufficiency in iPSC-derived neurons from patients with multiple-system atrophy

Multiple-system atrophy (MSA) is a neurodegenerative disease characterized by autonomic failure with various combinations of parkinsonism, cerebellar ataxia, and pyramidal dysfunction. We previously reported that functionally impaired variants of COQ2, which encodes an essential enzyme in the biosynthetic pathway of coenzyme Q10, are associated with MSA. Here, we report functional deficiencies in mitochondrial respiration and the antioxidative system in induced pluripotent stem cell (iPSC)-derived neurons from an MSA patient with compound heterozygous COQ2 mutations. The functional deficiencies were rescued by site-specific CRISPR/Cas9-mediated gene corrections. We also report an increase in apoptosis of iPSC-derived neurons from MSA patients. Coenzyme Q10 reduced apoptosis of neurons from the MSA patient with compound heterozygous COQ2 mutations. Our results reveal that cellular dysfunctions attributable to decreased coenzyme Q10 levels are related to neuronal death in MSA, particularly in patients with COQ2 variants, and may contribute to the development of therapy using coenzyme Q10 supplementation.

Increasing methamphetamine doses inhibit glycogen synthase kinase 3β activity by stimulating the insulin signaling pathway in substantia nigra

Methamphetamine (MA), a highly abused psychostimulant, exerts neurotoxic effects on the dopaminergic system via several neurotoxicity mechanisms in the long-term administration. Since the effect of MA on the signaling insulin pathway is less studied, the current study was designed to evaluate the effect of escalating an MA regimen on different insulin signaling elements in substantia nigra (SN) and striatum of a rat. Increasing MA doses (1-14 mg/kg) were administrated intraperitoneally twice a day for 14 days in rats. In the control group, normal saline was injected in the same volume. On days 1, 14, 28, and 60 after MA discontinuation, molecular assessments were performed. Insulin receptor (IR) and insulin receptor substrate (IRS) 1 and 2 gene expression were evaluated using real-time polymerase chain reaction, and protein levels of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), phospho-PI3K, Akt, phospho-Akt, glycogen synthase kinase 3β (GSK3β), and phospho-GSK3β were measured by the Western blot analysis in SN and striatum. Messenger RNA levels of IR and insulin receptor substrate 2 were increased in SN, 1 day after the last injection. Although no changes were observed in PI3K, phospho-PI3K, Akt, phospho-Akt, and GSK3β levels, increase in the level of inactive form of GSK3β (phosphorylated on serine 9) was indicated in SN on day 28. In striatum, decreases in IR and phospho-Akt were demonstrated, without any change in other elements. Repeated escalating regimen of MA activated the insulin signaling pathway and inhibited GSK3β activity in SN. This response, which did not occur in striatum, may act as an adaptive mechanism to prevent MA-induced neurotoxicity in dopaminergic cell bodies.

Activation of Type 4 Metabotropic Glutamate Receptor Attenuates Oxidative Stress-Induced Death of Neural Stem Cells with Inhibition of JNK and p38 MAPK Signaling

Promoting both endogenous and exogenous neural stem cells' (NSCs) survival in the hostile host environments is essential to cell replacement therapy for central nervous system (CNS) disorders. Type 4 metabotropic glutamate receptor (mGluR4), one of the members of mGluRs, has been shown to protect neurons from acute and chronic excitotoxic insults in various brain damages. The present study investigated the preventive effects of mGluR4 on NSC injury induced by oxidative stress. Under challenge with H2O2, loss of cell viability was observed in cultured rat NSCs, and treatment with selective mGluR4 agonist VU0155041 conferred protective effects against the loss of cellular viability in a concentration-dependent manner, as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Pretreatment of VU0155041 (30 μM) also inhibited the excessive NSC death induced by H2O2, and group III mGluRs antagonist (RS)-a-methylserine-O-phosphate (MSOP) or gene-targeted knockdown abolished the protective action of mGluR4, indicated by propidium iodide-Hoechst and terminal deoxynucleotidyl transferase-mediated UTP nick end labeling (TUNEL) staining. Western blot assay demonstrated that mGluR4 activation reversed the decreased procaspase-8/9/3and the destructed Bcl-2/Bax expressing balance, and likewise, MSOP and mGluR4 knockdown abrogated the action of mGluR4 activity. Furthermore, inhibition of JNK and p38 mitogen-activated protein kinases (MAPKs) were observed after mGluR4 activation, and as paralleling control, JNK-specific inhibitor SP600125 and p38-specific inhibitor SB203580 significantly rescued the H2O2-mediated NSC apoptosis and cleavage of procaspase-3. We suggest that activation of mGluR4 prevents oxidative stress-induced NSC death and apoptotic-associated protein activities with involvement of inhibiting the JNK and p38 pathways in cell culture. Our findings may help to develop strategies for enhancing the resided and transplanted NSC survival after oxidative stress insult of CNS.

Effect of BDNF and Other Potential Survival Factors in Models of In Vitro Oxidative Stress on Adult Spinal Cord-Derived Neural Stem/Progenitor Cells

Transplantation of neural stem/progenitor cells (NSPCs) is a promising strategy in spinal cord injury (SCI). However, poor survival of transplanted stem cells remains a major limitation of this therapy due to the hostile environment of the injured cord. Oxidative stress is a hallmark in the pathogenesis of SCI; however, its effects on NSPCs from the adult spinal cord have yet to be examined. We therefore developed in vitro models of mild and severe oxidative stress of adult spinal cord-derived NSPCs and used these models to examine potential cell survival factors. NSPCs harvested from the adult rat spinal cord were treated with hydrogen peroxide (H2O2) in vitro to induce oxidative stress. A mild 4 h exposure to H2O2 (500 μM) significantly increased the level of intracellular reactive oxygen species with minimal effect on viability. In contrast, 24 h of oxidative stress led to a marked reduction in cell survival. Pretreatment with brain-derived neurotrophic factor (BDNF) for 48 h attenuated the increase in intracellular reactive oxygen species and enhanced survival. This survival effect was associated with a significant reduction in the number of apoptotic cells and a significant increase in the activity of the antioxidant enzymes glutathione reductase and superoxide dismutase. BDNF treatment had no effect on NSPC differentiation or proliferation. In contrast, cyclosporin A and thyrotropin-releasing hormone had minimal or no effect on NSPC survival. Thus, these models of in vitro oxidative stress may be useful for screening neuroprotective factors administered prior to transplantation to enhance survival of stem cell transplants.

Omega-3 polyunsaturated fatty acids protect neural progenitor cells against oxidative injury

The omega-3 polyunsaturated fatty acids (ω-3 PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), derived mainly from fish oil, play important roles in brain development and neuroplasticity. Here, we reported that application of ω-3 PUFAs significantly protected mouse neural progenitor cells (NPCs) against H₂O₂-induced oxidative injury. We also isolated NPCs from transgenic mice expressing the Caenorhabditis elegans fat-1 gene. The fat-1 gene, which is absent in mammals, can add a double bond into an unsaturated fatty acid hydrocarbon chain and convert ω-6 to ω-3 fatty acids. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining showed that a marked decrease in apoptotic cells was found in fat-1 NPCs after oxidative injury with H₂O₂ as compared with wild-type NPCs. Quantitative RT-PCR and Western blot analysis demonstrated a much higher expression of nuclear factor erythroid 2-related factor 2 (Nrf2), a master transcriptional factor for antioxidant genes, in fat-1 NPCs. The results of the study provide evidence that ω-3 PUFAs resist oxidative injury to NPCs.

Identification of microRNAs involved in growth arrest and cell death in hydrogen peroxide-treated human dermal papilla cells

microRNAs (miRNAs) are small non‑coding RNAs that regulate various biological processes by interfering with the translation of target genes. Several studies have suggested that miRNAs are involved in cellular responses to hydrogen peroxide (H2O2). Reactive oxygen species (ROS) are involved in hair malignancies, however, the H2O2‑induced, miRNA‑dependent regulatory mechanisms of human dermal papilla (HDP) cells are not fully understood. Our previous study demonstrated that changes in miRNA expression function to regulate growth arrest and apoptosis in UVB‑irradiated HDPs. In the present study, miRNA expression was profiled in HDPs treated with H2O2. The transcriptome analysis of H2O2‑treated HDPs enabled the identification of 68 differentially expressed miRNAs (62 were upregulated and 6 were downregulated) and 14,316 putative target genes of the miRNAs. Gene ontology (GO) analysis was utilized to verify that the putative target genes of the altered miRNAs were associated with H2O2‑induced cell growth arrest and apoptosis. This bioinformatics analysis indicated that H2O2‑response pathways involved in growth arrest and apoptosis were significantly affected. The identification of miRNAs and their putative targets may offer new therapeutic strategies for H2O2‑induced hair follicle disorders.

Transplantation of neural stem cells that overexpress SOD1 enhances amelioration of intracerebral hemorrhage in mice

Previous studies have shown that intraparenchymal transplantation of neural stem cells (NSCs) ameliorates neurologic deficits in animals with intracerebral hemorrhage (ICH). However, massive grafted cell death after transplantation, possibly caused by a hostile host brain environment, lessens the effectiveness of this approach. We focused on the effect of oxidative stress against grafted NSCs and hypothesized that conferring antioxidant properties to transplanted NSCs may overcome their death and enhance neuroprotection after ICH. Copper/zinc-superoxide dismutase (SOD1) is a specific antioxidant enzyme that counteracts superoxide anions. We investigated whether genetic manipulation to overexpress SOD1 enhances survival of grafted NSCs and accelerates amelioration of ICH. Neural stem cells that overexpress SOD1 were administered intracerebrally 3 days after ICH in a mouse model. Histologic and behavioral tests were examined after ICH. Copper/zinc-superoxide dismutase overexpression protected the grafted NSCs via a decrease in production of reactive oxygen species. This resulted in an increase in paracrine factors released by the NSCs, and an increase in surviving neurons in the striatum and a reduction in striatal atrophy. In addition, SOD1 overexpression showed progressive improvement in behavioral recovery. Our results suggest that enhanced antioxidative activity in NSCs improves efficacy of stem cell therapy for ICH.

Low-level laser therapy (LLLT) reduces oxidative stress in primary cortical neurons in vitro

Low-level laser (light) therapy (LLLT) involves absorption of photons being in the mitochondria of cells leading to improvement in electron transport, increased mitochondrial membrane potential (MMP), and greater ATP production. Low levels of reactive oxygen species (ROS) are produced by LLLT in normal cells that are beneficial. We exposed primary cultured murine cortical neurons to oxidative stressors: hydrogen peroxide, cobalt chloride and rotenone in the presence or absence of LLLT (3 J/cm², CW, 810 nm wavelength laser, 20 mW/cm²). Cell viability was determined by Prestoblue™ assay. ROS in mitochondria was detected using Mito-sox, while ROS in cytoplasm was detected with CellRox™. MMP was measured with tetramethylrhodamine. In normal neurons LLLT elevated MMP and increased ROS. In oxidatively-stressed cells LLLT increased MMP but reduced high ROS levels and protected cultured cortical neurons from death. Although LLLT increases ROS in normal neurons, it reduces ROS in oxidatively-stressed neurons. In both cases MMP is increased. These data may explain how LLLT can reduce clinical oxidative stress in various lesions while increasing ROS in cells in vitro.

Phosphatidylinositol 3 kinase/protein kinase B is responsible for the protection of paeoniflorin upon H₂O₂-induced neural progenitor cell injury

Promoting neural stem/progenitor cell (NSC/NPC) survival in the pro-apoptotic environment is critical to stem cell replacement for neurodegenerative disease therapy. Paeoniflorin (PF), one of the principal bioactive components in Paeoniae Radix, has been used widely in central nervous system (CNS) diseases treatment and serves as an antioxidant to protect neurons against oxidative stress. The present study investigated the protective effects of PF on NPC injury induced by hydrogen peroxide (H₂O₂). After challenge with 200 μM H₂O₂ for 2h, loss of cell viability and excessive apoptotic cell death were observed in cultured NPC, PF treatment conferred protective effects against the loss of cellular viability in a concentration-dependent manner. PF pretreatment also inhibited NPC apoptosis induced by H₂O₂ by reversing the decreased level of Procaspase-3 and balancing Bcl-2 and Bax expression. Furthermore, PF-mediated NPC protection was associated with an increase in phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt-1) phosphorylation in a time- and concentration-dependent manner. Selective inhibition of PI3K using LY294002 abolished PF-mediated phosphorylation of Akt-1 and NPC protection upon oxidative stress. These data suggest that PF-mediated NPC protection on H₂O₂ injury is reliant on the activation of the PI3K/Akt-1 pathway, giving insight to an essential role of PF in NPC protection.

Coenzyme Q10 protects neural stem cells against hypoxia by enhancing survival signals

Recanalization and secondary prevention are the main therapeutic strategies for acute ischemic stroke. Neuroprotective therapies have also been investigated despite unsuccessful clinical results. Coenzyme Q10 (CoQ10), which is an essential cofactor for electron transport in mitochondria, is known to have an antioxidant effect. We investigated the protective effects of CoQ10 against hypoxia in neural stem cells (NSCs). We measured cell viability and levels of intracellular signaling proteins after treatment with several concentrations of CoQ10 under hypoxia-reperfusion. CoQ10 protected NSCs against hypoxia-reperfusion in a concentration-dependent manner by reducing growth inhibition and inhibiting free radical formation. It increased the expression of a number of survival-related proteins such as phosphorylated Akt (pAkt), phosphorylated glycogen synthase kinase 3-β (pGSK3-β), and B-cell lymphoma 2 (Bcl-2) in NSCs injured by hypoxia-reperfusion and reduced the expression of death-related proteins such as cleaved caspase-3. We conclude that CoQ10 has effects against hypoxia-reperfusion induced damage to NSCs by enhancing survival signals and decreasing death signals.

Characterization of superoxide dismutases in cardiac progenitor cells demonstrates a critical role for manganese superoxide dismutase

Transplantation of cardiac progenitor cells (CPCs) is currently in early clinical testing as a potential therapeutic strategy. Superoxide is increased in the ischemic myocardium and poor survival of cells is one of the major limitations of cell transplantation therapy. Superoxide dismutase (SOD) levels were analyzed in c-kit-positive CPCs isolated from rat myocardium to identify their roles in protection against oxidative stress-induced apoptosis in vitro. CPCs were subjected to oxidative stress using xanthine/xanthine oxidase (XXO) and little apoptosis was detected. CPCs contained significantly higher levels of SOD1 and SOD2 as compared with adult cardiac cell types, both at the protein and activity levels. Both SOD1 and SOD2 were increased by XXO at the mRNA and protein level, suggesting compensatory adaptation. Only knockdown of SOD2 and not SOD1 with siRNA sensitized the cells to XXO-apoptosis, despite only accounting for 10% of total SOD levels. Finally, we found XXO activated Akt within 10 min, and this regulated both SOD2 gene expression and protection against apoptosis. Rat CPCs are resistant to superoxide-induced cell death, primarily through higher levels of SOD2 compared to adult cardiac-derived cells. Exposure to superoxide increases expression of SOD2 in an Akt-dependent manner and regulates CPC survival during oxidative stress.

Insulin in central nervous system: more than just a peripheral hormone

Insulin signaling in central nervous system (CNS) has emerged as a novel field of research since decreased brain insulin levels and/or signaling were associated to impaired learning, memory, and age-related neurodegenerative diseases. Thus, besides its well-known role in longevity, insulin may constitute a promising therapy against diabetes- and age-related neurodegenerative disorders. More interestingly, insulin has been also faced as the potential missing link between diabetes and aging in CNS, with Alzheimer's disease (AD) considered as the "brain-type diabetes." In fact, brain insulin has been shown to regulate both peripheral and central glucose metabolism, neurotransmission, learning, and memory and to be neuroprotective. And a future challenge will be to unravel the complex interactions between aging and diabetes, which, we believe, will allow the development of efficient preventive and therapeutic strategies to overcome age-related diseases and to prolong human "healthy" longevity. Herewith, we aim to integrate the metabolic, neuromodulatory, and neuroprotective roles of insulin in two age-related pathologies: diabetes and AD, both in terms of intracellular signaling and potential therapeutic approach.

(-)-Epigallocatechin-3-gallate increases the number of neural stem cells around the damaged area after rat traumatic brain injury

A major component of green tea is (-)-epigallocatechin gallate (EGCG), which has strong antioxidant properties. Here, we investigated the effect of EGCG on neural stem cell (NSC) proliferation around the damaged area following traumatic brain injury (TBI). In this study, male Wistar rats that had access to normal drinking water, or water containing 0.1% (w/v) EGCG, ad libitum received TBI at 10 weeks of age. Immunohistochemistry revealed that the number of nestin-positive cells around the damaged area after TBI in the EGCG treatment group increased significantly compared with the normal water group (P < 0.05). However, the number of 8-hydroxy-2'-deoxyguanosine-, 4-hydroxy-2-nonenal-, single-stranded DNA (ssDNA)-positive cells and the level of peroxidation around the damaged area after TBI significantly decreased in the EGCG treatment group when compared with the water group (P < 0.05). Furthermore, in contrast to the EGCG group, almost all ssDNA-positive cells in the water group co-localized with NeuN and nestin-staining. Ex vivo studies revealed that spheres could only be isolated from injured brain tissue in the water group at 3 days following TBI. However, in the EGCG group, spheres could be isolated at both 3 and 7 days following TBI. A greater number of spheres could be isolated from the EGCG group, which differentiated into neurons and glia in culture without basic fibroblast growth factor. These results indicate that consumption of water containing EGCG pre- and post-TBI inhibits free radical-induced degradation of NSCs, which have the potential to differentiate into neurons and glia around the area of damage following TBI.

Stress-resistant neural stem cells positively influence regional energy metabolism after spinal cord injury in mice

The importance of stem cells to ameliorate the devastating consequences of traumatic injuries in the adult mammalian central nervous system calls for improvements in the capacity of these cells to cope, in particular, with the host response to the injury. We have previously shown, however, that in the acutely traumatized spinal cord local energy metabolism led to decreased ATP levels after neural stem cell (NSC) transplantation. As this might counteract NSC-mediated regenerative processes, we investigated if NSC selected for increased oxidative stress resistance are better suited to preserve local energy content. For this purpose, we exposed wild-type (WT) NSC to hydrogen peroxide prior to transplantation. We demonstrate here that transplantation of WT-NSC into a complete spinal cord compression injury model even lowers the ATP content beyond the level detected in spinal cord injury-control animals. Compared to WT-NSC, stress-resistant (SR) NSC did not lead to a further decrease in ATP content. These differences between WT- and SR-NSC were observed 4 h after the lesion with subsequent transplantation. At 24 h after lesioning, these differences were no more as obvious. Thus, in contrast to native NSC, transplantation of NSC selected for oxidative stress resistance can positively influence local energy metabolism in the first hours after spinal cord compression. The functional relevance of this observation has to be tested in further experiments.

Energy metabolism in adult neural stem cell fate

The adult mammalian brain contains a population of neural stem cells that can give rise to neurons, astrocytes, and oligodendrocytes and are thought to be involved in certain forms of memory, behavior, and brain injury repair. Neural stem cell properties, such as self-renewal and multipotency, are modulated by both cell-intrinsic and cell-extrinsic factors. Emerging evidence suggests that energy metabolism is an important regulator of neural stem cell function. Molecules and signaling pathways that sense and influence energy metabolism, including insulin/insulin-like growth factor I (IGF-1)-FoxO and insulin/IGF-1-mTOR signaling, AMP-activated protein kinase (AMPK), SIRT1, and hypoxia-inducible factors, are now implicated in neural stem cell biology. Furthermore, these signaling modules are likely to cooperate with other pathways involved in stem cell maintenance and differentiation. This review summarizes the current understanding of how cellular and systemic energy metabolism regulate neural stem cell fate. The known consequences of dietary restriction, exercise, aging, and pathologies with deregulated energy metabolism for neural stem cells and their differentiated progeny will also be discussed. A better understanding of how neural stem cells are influenced by changes in energy availability will help unravel the complex nature of neural stem cell biology in both the normal and diseased state.

Hepatocyte growth factor protects human embryonic stem cell derived-neural progenitors from hydrogen peroxide-induced apoptosis

Promoting human embryonic stem cell (hESC)-derived-neural progenitor survival in the pro-apoptotic niche is pivotal for stem cell replacement therapy. The present study was designed to investigate the protective effect of hepatocyte growth factor (HGF) on hESC-derived neural progenitor injured by hydrogen peroxide (H(2)O(2)) exposure. Treatment of hESC-derived neural progenitor cells with HGF prior to H(2)O(2) exposure conferred protective effect against oxidative stress-induced apoptosis. HGF treatment increased both phosphoinositide 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase1/2 (ERK1/2) phosphorylation. However, selective inhibition of each pathway supported that the activation of PI3K/AKT, but not ERK1/2, provides survival advantage to the neural progenitor cells. Further investigation indicated that HGF pretreatment could attenuate the decrease of the expression of Bcl-2 protein induced by H(2)O(2), whereas the level of Bax was not affected. Additionally, we observed that H(2)O(2)-induced decrease of mitochondrial transmembrane potential, release of cytochrome c and increase of caspase-3 activation were alleviated by HGF pretreatment. These effects of HGF could be reversed by inhibition of the PI3K/Akt and ERKs pathways, indicating PI3K/Akt and ERKs signaling might be involved in HGF-mediated regulation of mitochondrial apoptotic pathway mediated by H(2)O(2). The neuroprotective effect of HGF might potentially be useful in stem cell-based therapies for neurodegenerative disorders.

Stromal cell-secreted factors promote the survival of embryonic stem cell-derived early neural stem/progenitor cells via the activation of MAPK and PI3K-Akt pathways

Neural stem/progenitor cells (NS/PCs) have been studied extensively with the hope of using them clinically to repair the damaged central nervous system. However, little is known about the signals that regulate the proliferation, survival, and differentiation of NS/PCs in early development. To clarify the underlying mechanisms, we took advantage of an in vitro ES cell differentiation system from which we can obtain neurospheres containing NS/PCs with characteristics of the early caudal neural tube, by treating embryoid bodies (EBs) with a low concentration of retinoic acid (RA). We found that conditioned medium from the PA6 stromal cell line (PA6CM) increased the efficiency of neurosphere formation by suppressing apoptosis and promoting the survival of the NS/PCs. PA6CM also induced the phosphorylation of Erk1/2 and Akt1 in cells derived from the EBs. Furthermore, inhibitors of the MAPK and PI3K-Akt signaling pathways, U0126 and LY294002, attenuated the effects of PA6CM, significantly increasing the number of apoptotic cells and decreasing the number of viable cells among the ES cell-derived NS/PCs. Thus, PA6CM appears to contain soluble factors that promote the survival of ES cell-derived early NS/PCs through the activation of the MAPK and PI3K-Akt pathways.

Up-regulation of calcium-dependent proteolysis in human myoblasts under acute oxidative stress

The reduced regenerative potential of muscle fibres, most likely due to a decreased number and/or function of satellite cells, could play a significant role in the progression of muscle ageing. Accumulation of reactive oxygen species has been clearly correlated to sarcopenia and could contribute to the impairment of satellite cell function. In this work we have investigated the effect of oxidative stress generated by hydrogen peroxide in cultured human skeletal muscle satellite cells. We specifically focused on the activity and regulation of calpains. These calcium-dependent proteases are known to regulate many transduction pathways including apoptosis and play a critical role in satellite cell function. In our experimental conditions, which induce an increase in calcium concentration, protein oxidation and apoptotic cell death, a significant up-regulation of calpain expression and activity were observed and ATP synthase, a major component of the respiratory chain, was identified as a calpain target. Interestingly we were able to protect the cells from these H(2)O(2)-induced effects and prevent calpain up-regulation with a natural antioxidant extracted from pine bark (Oligopin). These data strongly suggest that oxidative stress could impair satellite cell functionality via calpain-dependent pathways and that an antioxidant such as Oligopin could prevent apoptosis and calpain activation.

The novel free radical scavenger, edaravone, increases neural stem cell number around the area of damage following rat traumatic brain injury

Edaravone is a novel free radical scavenger that is clinically employed in patients with acute cerebral infarction, but has not previously been used to treat traumatic brain injury (TBI). In this study, we investigated the effect of edaravone administration on rat TBI. In particular, we used immunohistochemistry to monitor neural stem cell (NSC) proliferation around the area damaged by TBI. Two separate groups of rats were administered saline or edaravone (3 mg/kg) after TBI and then killed chronologically. We also used ex vivo techniques to isolate NSCs from the damaged region and observed nestin-positive cells at 1, 3, and 7 days following TBI in both saline- and edaravone-treated groups. At 3 days following TBI in both groups, there were many large cells that morphologically resembled astrocytes. At 1 and 7 days following TBI in the saline group, there were a few small nestin-positive cells. However, in the edaravone group, there were many large nestin-positive cells at 7 days following TBI. At 3 and 7 days following TBI, the number of nestin-positive cells in the edaravone group increased significantly compared with the saline group. There were many single-stranded DNA-, 8-hydroxy-2'-deoxyguanosine-, and 4-hydroxy-2-nonenal-positive cells in the saline group following TBI, but only a few such cells in the edaravone group following TBI. Furthermore, almost all ssDNA-positive cells in the saline group co-localized with Hu, nestin, and glial fibrillary acidic protein (GFAP) staining, but not in the edaravone group. In the ex vivo study, spheres could only be isolated from injured brain tissue in the saline group at 3 days following TBI. However, in the edaravone group, spheres could be isolated from injured brain tissue at both 3 and 7 days following TBI. The number of spheres isolated from injured brain tissue in the edaravone group showed a significant increase compared with the saline group. The spheres isolated from both saline and edaravone groups were immunopositive for nestin, but not Tuj1 or vimentin. Moreover, the spheres differentiated into Tuj1-, GFAP-, and O4-positive cells after 4 days in culture without bFGF. This result indicated that the spheres were neurospheres composed of NSCs that could differentiate into neurons and glia. Edaravone administration inhibited production of free radicals known to induce neuronal degeneration and cell death after brain injury, and protected nestin-positive cells, including NSCs, with the potential to differentiate into neurons and glia around the area damaged by TBI.

Insulin neuroprotection against oxidative stress is mediated by Akt and GSK-3beta signaling pathways and changes in protein expression

Previously we demonstrated that insulin protects against neuronal oxidative stress by restoring antioxidants and energy metabolism. In this study, we analysed how insulin influences insulin-(IR) and insulin growth factor-1 receptor (IGF-1R) intracellular signaling pathways after oxidative stress caused by ascorbate/Fe2+ in rat cortical neurons. Insulin prevented oxidative stress-induced decrease in tyrosine phosphorylation of IR and IGF-1R and Akt inactivation. Insulin also decreased the active form of glycogen synthase kinase-3beta (GSK-3beta) upon oxidation. Since phosphatidylinositol 3-kinase (PI-3K)/Akt-mediated inhibition of GSK-3beta may stimulate protein synthesis and decrease apoptosis, we analysed mRNA and protein expression of "candidate" proteins involved in antioxidant defense, glucose metabolism and apoptosis. Insulin prevented oxidative stress-induced increase in glutathione peroxidase-1 and decrease in hexokinase-II expression, supporting previous findings of changes in glutathione redox cycle and glycolysis. Moreover, insulin precluded Bcl-2 decrease and caspase-3 increased expression. Concordantly, insulin abolished caspase-3 activity and DNA fragmentation caused by oxidative stress. Thus, insulin-mediated activation of IR/IGF-1R stimulates PI-3K/Akt and inhibits GSK-3beta signaling pathways, modifying neuronal antioxidant defense-, glucose metabolism- and anti-apoptotic-associated protein synthesis. These and previous data implicate insulin as a promising neuroprotective agent against oxidative stress associated with neurodegenerative diseases.

Interleukin-1beta mediates proliferation and differentiation of multipotent neural precursor cells through the activation of SAPK/JNK pathway

Neural precursor cells (NPCs) have been experimentally used to repair the damaged nervous system either by exogenous transplantation or by endogenous activation. In post-injury inflammation, an array of cytokines including interleukin-1beta (IL-1beta) are released by host as well as invading immune cells and increased markedly. In the present study, we investigated the effects of IL-1beta on the survival, proliferation, differentiation and migration of NPCs as well as underlying intracellular signaling pathways. NPCs derived from the E16 rat brain were expanded in neurospheres that were found to express IL-1beta, IL-1RI and IL-1RII, but not IL-1alpha and IL-1ra. IL-1beta inhibited the proliferation of NPCs in a dose-dependent manner, an effect that can be reversed by IL-1ra, an antagonist for IL-1 receptor. This inhibitory effect of IL-1beta on NPCs proliferation resulted in part from its effect on increased apoptosis of NPCs. Moreover, IL-1ra did not affect NPCs lineage fate but rather inhibited GFAP expression in differentiated astrocytes. We also found that IL-1ra had no effect on the transmigration of NPCs in vitro. Finally, we showed that the effect of IL-1beta on NPCs proliferation and differentiation appeared to be mediated by SAPK/JNK, but not ERK, P38MAPK nor NF-kappaB pathways. These findings collectively suggest that the inflammatory environment following CNS injuries may influence the ability of NPCs to repair the damage.

Nitric oxide regulates cell survival in purified cultures of avian retinal neurons: involvement of multiple transduction pathways

Nitric oxide (NO) is an important signaling molecule in the CNS, regulating neuronal survival, proliferation and differentiation. Here, we explored the mechanism by which NO, produced from the NO donor S-nitroso-acetyl-d-l-penicillamine (SNAP), exerts its neuroprotective effect in purified cultures of chick retinal neurons. Cultures prepared from 8-day-old chick embryo retinas and incubated for 24 h (1 day in culture, C1) were treated or not with SNAP, incubated for a further 72 h (up to 4 days in culture, C4), fixed, and the number of cells estimated, or processed for cell death estimation, by measuring the reduction of the metabolic dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Experimental cultures were run in parallel but were re-fed with fresh medium in the absence or presence of SNAP at culture day 3 (C3), incubated for a further 24 h up to C4, then fixed or processed for the MTT assay. Previous studies showed that the re-feeding procedure promotes extensive cell death. SNAP prevented this death in a concentration- and time-dependent manner through the activation of soluble guanylate cyclase; this protection was significantly reversed by the enzyme inhibitors 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ) or LY83583, and mimicked by 8-bromo cyclic guanosine 5'-phosphate (8Br-cGMP) (GMP) or 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1), guanylate cyclase activators. The effect was blocked by the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO). The effect of NO was also suppressed by LY294002, Wortmannin, PD98059, KN93 or H89, indicating the involvement, respectively, of phosphatidylinositol-3 kinase, extracellular-regulated kinases, calmodulin-dependent kinases and protein kinase A signaling pathways. NO also induced a significant increase of neurite outgrowth, indicative of neuronal differentiation, and blocked cell death induced by hydrogen peroxide. Cyclosporin A, an inhibitor of the mitochondrial permeability transition pore considered an important mediator of apoptosis and necrosis, as well as boc-aspartyl (OMe) fluoromethylketone (BAF), a caspase inhibitor, also blocked cell death induced by re-feeding the cultures. These findings demonstrate that NO inhibits apoptosis of retinal neurons in a cGMP/protein kinase G (PKG)-dependent way, and strengthens the notion that NO plays an important role during CNS development.

Mechanisms of cell death of neural progenitor cells caused by trophic support deprivation

Cell death of neural progenitor cells is the primary problem limiting the value of neural progenitor cell-based therapy for central nervous system disorders. However, little is known about the mechanism of cell death of neural progenitor cells. In this study, we investigated the mechanisms of cell death of a multipotent cell line, MEB5, caused by deprivation of epidermal growth factor (EGF). When EGF was removed from the culture medium, the total number of viable MEB5 cells reduced, and nuclear condensation and elevation of caspase-3-like enzyme activity were observed in MEB5 cells. Treatment with a broad-range caspase inhibitor reduced cell death in a concentration-dependent manner, indicating that MEB5 cells undergo caspase-mediated apoptotic cell death caused by EGF deprivation. We also investigated the effects of glutamate receptor antagonists, antioxidants and nitric oxide synthase inhibitor on EGF deprivation-induced cell death. N-methyl-D-aspartate (NMDA) glutamate receptor antagonists, alpha-amino-3-hydrozy-5-methyl-4-isoxazole propionic acid (AMPA) glutamate receptor antagonist and nitric oxide synthase inhibitor failed to reduce cell death. In contrast, two antioxidants with different chemical structures reduced cell death in a concentration-dependent manner. The production of reactive oxygen species was detected in MEB5 cells after EGF deprivation by monitoring dichlorodihydrofluorescein fluorescence as a marker of reactive oxygen species-related radicals. Our results suggest that oxidative stress triggers caspase-mediated apoptosis of neural progenitor cells by trophic support deprivation.

D609 blocks cell survival and induces apoptosis in neural stem cells

In order to investigate the effects of tricyclodecane-9-yl-xanthogenate (D609) on the survival of neural stem cells (NSCs), which were isolated from rat forebrain, we treated the NSCs with D609 in the presence of basic fibroblast growth factor (bFGF). We found that when NSCs were exposed to 18.76-56.29 microM D609, the viability of the cells remarkably declined and apoptosis occurred. At the same time, the ROS level in NSCs was depressed. The data suggested that D609 was a powerful growth inhibitor and apoptosis inducer in NSCs.

The superoxide dismutase inhibitor diethyldithiocarbamate has antagonistic effects on apoptosis by triggering both cytochrome c release and caspase inhibition

Tumor necrosis factor-alpha (TNF-alpha) and etoposide both trigger a large and rapid production of reactive oxygen species (ROS) in HeLa cells. This occurs before translocations of the proapoptotic Bax and cytochrome c proteins, the loss of mitochondrial membrane potential (DeltaPsim), and apoptosis. We have used diethyldithiocarbamate (DDC), a well-known inhibitor of Cu, Zn superoxide dismutase to study the role of ROS in this system. We report that DDC strongly inhibits caspase activation, loss of DeltaPsim, and cell death induced by TNF-alpha or etoposide. Surprisingly, DDC does not inhibit Bax and cytochrome c translocations. On the contrary, we have observed that DDC can trigger the translocations of these proteins by itself, without altering DeltaPsim. Here, we report that DDC has at least two antagonistic apoptosis regulation functions. First, DDC triggers ROS-dependent Bax and cytochrome c translocations, which are potentially proapoptotic, and second, DDC inhibits caspase activation and activity, loss of DeltaPsim, and cell death, in a ROS-independent manner. Our results suggest an interesting model in which ROS-dependent Bax and cytochrome c translocations can be studied without interference from later apoptotic events.

Association of different prediction methods for determination of the efficiency and selectivity on neuron-based sensors

A technique has been developed to determine the efficiency and the selectivity of a single neuron-based sensor in identifying the nature of the chemical agents in an unknown sample. This has been achieved by exploiting the unique electrical identifiers, also known as "signature patterns", generated by the neuronal cell membrane. These were generated based on the variations to the extracellular electrical activity, due to the effect of a broad range of chemical agents. We demonstrate the prediction capability of the sensor in identifying the nature of an unknown test sample from a combination of three chemical agents, namely, ethanol, pyrethroid, and hydrogen peroxide. This was achieved through a two-step process. The first step was experimentally achieved by in situ recording of the changes to the extracellular electrical activity from the sensing sites or the array of microelectrodes that form the platform for patterning neurons. Simultaneous optical characterization of the cell array during the sensing process was performed to identify the associated physiological changes. The second step was mathematical and was based on developing a library of signature patterns for a set of concentrations of the various combinations of the three chemical agents. Two variants of the nearest neighbor algorithm scheme - (a) partial distance search method, and (b) search tree method, were implemented for the accurate detection of all the components with varying concentrations in the test samples of unknown nature. This technique exhibits reliability in identification up to parts-per-billion (ppb) sensitivity. The capability of standardization of this technique for potential commercial applications is also discussed.

Hydrogen peroxide alters membrane and cytoskeleton properties and increases intercellular connections in astrocytes

Excess hydrogen peroxide (H2O2) is produced in the pathogenesis of brain injuries and neurodegenerative diseases. H2O2 may damage cells through direct oxidation of lipids, proteins and DNA or it can act as a signaling molecule to trigger intracellular pathways leading to cell death. In this study, H2O2 caused plasma membranes of primary astrocytes to become more gel-like, while artificial membranes of vesicles composed of rat brain lipid extract became more liquid crystalline-like. Besides the effects on membrane phase properties, H2O2 promoted actin polymerization, induced the formation of cell-to-cell tunneling nanotube (TNT)-like connections among astrocytes and increased the colocalization of myosin Va with F-actin. Myosin Va was also observed in the H2O2-induced F-actin-enriched TNT-like connections. Western blot analysis suggests that H2O2 triggered the phosphorylation of the p38 mitogen-activated protein kinase (MAPK), and that SB203580, a specific inhibitor of p38 MAPK, suppressed the changes in membrane phase properties and cytoskeleton resulting from H2O2 treatment. These results suggest that H2O2 alters astrocyte membranes and the cytoskeleton through activation of the p38 MAPK pathway.