Oxidative Stress-induced Neuronal Cell Death Research Articles

Pathogenesis of DJ-1/PARK7-Mediated Parkinson's Disease.

Parkinson's disease (PD) is a common movement disorder associated with the degeneration of dopaminergic neurons in the substantia nigra pars compacta. Mutations in the PD-associated gene PARK7 alter the structure and function of the encoded protein DJ-1, and the resulting autosomal recessively inherited disease increases the risk of developing PD. DJ-1 was first discovered in 1997 as an oncogene and was associated with early-onset PD in 2003. Mutations in DJ-1 account for approximately 1% of all recessively inherited early-onset PD occurrences, and the functions of the protein have been studied extensively. In healthy subjects, DJ-1 acts as an antioxidant and oxidative stress sensor in several neuroprotective mechanisms. It is also involved in mitochondrial homeostasis, regulation of apoptosis, chaperone-mediated autophagy (CMA), and dopamine homeostasis by regulating various signaling pathways, transcription factors, and molecular chaperone functions. While DJ-1 protects neurons against damaging reactive oxygen species, neurotoxins, and mutant α-synuclein, mutations in the protein may lead to inefficient neuroprotection and the progression of PD. As current therapies treat only the symptoms of PD, the development of therapies that directly inhibit oxidative stress-induced neuronal cell death is critical. DJ-1 has been proposed as a potential therapeutic target, while oxidized DJ-1 could operate as a biomarker for PD. In this paper, we review the role of DJ-1 in the pathogenesis of PD by highlighting some of its key neuroprotective functions and the consequences of its dysfunction.

The Neuroprotective Effects of Arecae Pericarpium against Glutamate-Induced HT22 Cell Cytotoxicity.

Arecae Pericarpium has been found to exert anti-migraine, antidepressant, and antioxidative effects. However, the mechanisms involved are unclear. This study explored the possibility that Arecae Pericarpium ethanol extract (APE) exerts neuroprotective effects against oxidative stress-induced neuronal cell death. Since glutamate excitotoxicity has been implicated in the pathogenesis and development of several neurodegenerative disorders, we explored the mechanisms of action of APE on oxidative stress-induced by glutamate. Our results revealed that pretreatment with APE prevents glutamate-induced HT22 cell death. APE also reduced both the levels of intracellular reactive oxygen species and the apoptosis of cells, while maintaining glutamate-induced mitochondrial membrane potentials. Western blotting showed that pretreatment with APE facilitates the upregulation of phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) phosphorylation; the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf-2); and the production of antioxidant enzymes, including catalase, glutamate-cysteine ligase catalytic subunits, NAD(P)H quinone oxidoreductase 1, and heme oxygenase (HO)-1. The administration of LY294002, a PI3K/Akt inhibitor, attenuated the neuroprotective effects of APE on oxidative stress-induced neuronal cell damage. This allowed us to infer that the protective effects of APE on oxidative damage to cells can be attributed to the PI3K/Akt-mediated Nrf-2/HO-1 signaling pathway.

Polydatin protects neuronal cells from hydrogen peroxide damage by activating CREB/Ngb signaling.

Oxidative stress-induced neuronal cell death contributes significantly to the physiological processes of a number of neurological disorders. Polydatin (PD) has been reported to protect against Alzheimer's disease (AD), ischemic stroke and traumatic brain injury. However, the underlying neuroprotective mechanisms remain to be elucidated. The current study suggested that PD activates AKT/cAMP response element-binding protein (CREB) signaling and induces neuroglobin (Ngb) to protect neuronal cells from hydrogen peroxide (H2O2) in vitro. PD inhibited the H2O2-induced neuronal cell death of primary mouse cortical neurons and N2a cells. Functional studies showed that PD attenuated H2O2-induced mitochondrial dysfunction and mitochondrial reactive oxygen species production. Mechanistically, PD was verified to induce the phosphorylation of AKT and CREB and increase the protein level of Ngb. The luciferase assay results showed that Ngb transcriptional activity was activated by CREB, especially after PD treatment. It was further indicated that PD increased the transcription of Ngb by enhancing the binding of CREB to the promoter region of Ngb. Finally, Ngb knockdown largely attenuated the neuroprotective role of PD against H2O2. The results indicated that PD protected neuronal cells from H2O2 by activating CREB/Ngb signaling in neuronal cells, indicating that PD has a neuroprotective effect against neurodegenerative diseases.

Antioxidant Properties and Protective Effects of Aerial Parts from Cnidium officinale Makino on Oxidative Stress-Induced Neuronal Cell Death.

The rhizomes of Cnidium officinale Makino have been used as a traditional medicine for many purposes, however, use of its aerial parts is very limited. We investigated the antioxidant properties and protective effects of the aerial parts (leaves and stems) from C. officinale on H2O2-induced toxicity in SH-SY5Y neuroblastoma. C. officinale methanol extracts (70%) were sequentially fractionated using hexane (non-polar fraction, NF), ethyl acetate (intermediate polar fraction, IF), and water (polar fraction, PF). Total phenolics and flavonoids contents were highest in IF, followed by PF. IF also showed the strongest radical scavenging activities against 2,2-diphenyl-2-picrylhydrazyl and 2,2’-azinobis(3-ethylbenzo-thiazoline-6-sulfonic acid), as well as superoxide, with the half maximal inhibitory concentrations of 13.2, 23.2, and 12.8 mg/mL, respectively. Furthermore, all fractions significantly inhibited linoleic acid peroxidation induced by the Fenton reaction or by UV irradiation. Both PF and IF protected against H2O2-induced SH-SY5Y neuronal cell death by increasing the cell survival by 22.1∼47.7 and 35.9∼50.3% at concentrations of 25∼100 and 25∼400 μg/mL, respectively, whereas NF was toxic to the cells at these concentrations. IF also significantly decreased intracellular levels of reactive oxygen species by 7.72∼47.47% at a concentration of 25∼200 μg/mL. Our results indicate that compounds from the aerial parts of C. officinale have potent antioxidant activities, which may help rescue neuronal cells from oxidative stress-induced injury. Therefore, the aerial parts, as well as the rhizomes, of C. officinale may have medicinal applications.

Transduced Tat-PRAS40 prevents dopaminergic neuronal cell death through ROS inhibition and interaction with 14-3-3σ protein

Proline rich Akt substrate (PRAS40) is a component of mammalian target of rapamycin complex 1 (mTORC1) and activated mTORC1 plays important roles for cellular survival in response to oxidative stress. However, the roles of PRAS40 in dopaminergic neuronal cell death have not yet been examined. Here, we examined the roles of Tat-PRAS40 in MPP+- and MPTP-induced dopaminergic neuronal cell death. Our results showed that Tat-PRAS40 effectively transduced into SH-SY5Y cells and inhibited DNA damage, ROS generation, and apoptotic signaling in MPP+-induced SH-SY5Y cells. Further, these protective mechanisms of Tat-PRAS40 protein display through phosphorylation of Tat-PRAS40, Akt and direct interaction with 14-3-3σ protein, but not via the mTOR-dependent signaling pathway. In a Parkinson’s disease animal model, Tat-PRAS40 transduced into dopaminergic neurons in mouse brain and significantly protected against dopaminergic cell death by phosphorylation of Tat-PRAS40, Akt and interaction with 14-3-3σ protein. In this study, we demonstrated for the first time that Tat-PRAS40 directly protects against dopaminergic neuronal cell death. These results indicate that Tat-PRAS40 may provide a useful therapeutic agent against oxidative stress-induced dopaminergic neuronal cell death, which causes diseases such as PD.

Mechanisms and Neuroprotective Activities of Stigmasterol Against Oxidative Stress-Induced Neuronal Cell Death via Sirtuin Family.

Background: Accumulating studies have confirmed that oxidative stress leads to the death of neuronal cells and is associated with the progression of neurodegenerative diseases, including Alzheimer's disease (AD). Despite the compelling evidence, there is a drawback to the use of the antioxidant approach for AD treatment, partly due to limited blood-brain barrier (BBB) permeability. Phytosterol is known to exhibit BBB penetration and exerts various bioactivities such as antioxidant and anticancer effects, and displays a potential treatment for dyslipidemia, cardiovascular disease, and dementia.Objective: In this study, the protective effects of stigmasterol, a phytosterol compound, on cell death induced by hydrogen peroxide (H2O2) were examined in vitro using human neuronal cells (SH-SY5Y cells).Methods: MTT assay, reactive oxygen species measurement, mitochondrial membrane potential assay, apoptotic cell measurement, and protein expression profiles were performed to determine the neuroprotective properties of stigmasterol.Results: H2O2 exposure significantly increased the levels of reactive oxygen species (ROS) within the cells thereby inducing apoptosis. On the contrary, pretreatment with stigmasterol maintained ROS levels inside the cells and prevented oxidative stress-induced cell death. It was found that pre-incubation with stigmasterol also facilitated the upregulation of forkhead box O (FoxO) 3a, catalase, and anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) in the neurons. In addition, the expression levels of sirtuin 1 (SIRT1) were also increased while acetylated lysine levels were decreased, indicating that SIRT1 activity was stimulated by stigmasterol, and the result was comparable with the known SIRT1 activator, resveratrol.Conclusion: Taken together, these results suggest that stigmasterol could be potentially useful to alleviate neurodegeneration induced by oxidative stress.

Kisspeptin-54 attenuates oxidative stress and neuronal apoptosis in early brain injury after subarachnoid hemorrhage in rats via GPR54/ARRB2/AKT/GSK3β signaling pathway

Oxidative stress-induced neuron apoptosis plays a crucial role in the early brain injury (EBI) after subarachnoid hemorrhage (SAH). Kisspeptin has been reported as antioxidant to reduce oxidative stress-induced neuronal cell death through G protein-coupled receptor 54 (GPR54). The goal of this study was to determine the neuroprotection of the Kisspeptin/GRP54 signaling pathway against EBI after SAH. Two hundred and ninety-two Sprague Dawley male rats were used and SAH was induced by the endovascular perforation. Exogenous Kisspeptin 54 (KP54) was delivered intranasally. Small interfering ribonucleic acid (siRNA) for endogenous KISS1, a selective GPR54 antagonist kisspeptin 234, or β-arrestin 2 siRNA for ARRB2 (a functional adaptor of GPR54) were administered intracerebroventricularly. Post-SAH evaluations included neurobehavioral tests, SAH grade, Western blot, immunofluorescence, Fluoro-Jade C, TUNEL, and Nissl staining. The results showed that endogenous KISS1 knockdown aggravated but exogenous KP54 (1.0 nmol/kg) treatment attenuated neurological deficits, brain oxidative stress, and neuronal apoptosis at 24 h after SAH. The benefits of KP54 persisted to 28 days after SAH, which significantly improved cognitive function in SAH rats. The GPR54 blockade or the ARRB2 knockout offset the neuroprotective effects of KP54 in SAH rats. In conclusion, our results suggested that administration of KP54 attenuated oxidative stress, neuronal apoptosis and neurobehavioral impairments through GPR54/ARRB2/AKT/GSK3β signaling pathway after SAH in rat. Thus, KP54 may provide an effective treatment strategy for SAH patients.

Erratum: Xiao et al., "The c-Abl-MST1 Signaling Pathway Mediates Oxidative Stress-Induced Neuronal Cell Death".

Erratum: Xiao et al., "The c-Abl-MST1 Signaling Pathway Mediates Oxidative Stress-Induced Neuronal Cell Death".

Protective Role of Transduced Tat-Thioredoxin1 (Trx1) against Oxidative Stress-Induced Neuronal Cell Death via ASK1-MAPK Signal Pathway

Oxidative stress plays a crucial role in the development of neuronal disorders including brain ischemic injury. Thioredoxin 1 (Trx1), a 12 kDa oxidoreductase, has anti-oxidant and anti-apoptotic functions in various cells. It has been highly implicated in brain ischemic injury. However, the protective mechanism of Trx1 against hippocampal neuronal cell death is not identified yet. Using a cell permeable Tat-Trx1 protein, protective mechanism of Trx1 against hydrogen peroxide-induced cell death was examined using HT-22 cells and an ischemic animal model. Transduced Tat-Trx1 markedly inhibited intracellular ROS levels, DNA fragmentation, and cell death in H2O2-treatment HT-22 cells. Tat-Trx1 also significantly inhibited phosphorylation of ASK1 and MAPKs in signaling pathways of HT-22 cells. In addition, Tat-Trx1 regulated expression levels of Akt, NF-κB, and apoptosis related proteins. In an ischemia animal model, Tat-Trx1 markedly protected hippocampal neuronal cell death and reduced astrocytes and microglia activation. These findings indicate that transduced Tat-Trx1 might be a potential therapeutic agent for treating ischemic injury.

Transduced Tat-aldose Reductase Protects Hippocampal Neuronal Cells against Oxidative Stress-induced Damage.

Aldose reductase (AR) protein, a member of the NADPH-dependent aldo-keto reductase family, reduces a wide range of aldehydes and enhances cell survival by inhibition of oxidative stress. Oxidative stress is known as one of the major pathological factor in ischemia. Since the precise function of AR protein in ischemic injury is fully unclear, we examined the function of AR protein in hippocampal neuronal (HT-22) cells and in an animal model of ischemia in this study. Cell permeable Tat-AR protein was produced by fusion of protein transduction domain in Tat for delivery into the cells. Tat-AR protein transduced into HT-22 cells and significantly inhibited cell death and regulated the mitogen-activate protein kinases (MAPKs), Bcl-2, Bax, and Caspase-3 under oxidative stress condition. In an ischemic animal model, Tat-AR protein transduced into the brain tissues through the blood-brain barrier (BBB) and drastically decreased neuronal cell death in hippocampal CA1 region. These results indicate that transduced Tat-AR protein has protective effects against oxidative stress-induced neuronal cell death in vitro and in vivo, suggesting that Tat-AR protein could be used as potential therapeutic agent in ischemic injury.

Annona atemoya Leaf Extract Improves Scopolamine-Induced Memory Impairment by Preventing Hippocampal Cholinergic Dysfunction and Neuronal Cell Death.

We explored the preventative effect of Annona atemoya leaf (AAL) extract on memory impairment in a scopolamine (SCO)-induced cognitive deficit mouse model. Fifty-eight mice were randomly divided into six groups and orally treated with AAL extract at (50, 100, or 200 mg/kg) or tacrine (TAC) for 21 days. Memory deficits were induced by a single injection of 1 mg/kg SCO (i.p.) and memory improvement was evaluated by using behavioral tests such as the passive avoidance task and Y-maze test. The levels of cholinergic functions, neuronal cell death, reactive oxygen species, and protein expression related to hippocampal neurogenesis were examined by immunohistochemical staining and western blotting. The administration of AAL extract improved memory impairment according to increased spontaneous alternation in the Y-maze and step-through latency in passive avoidance test. AAL extract treatment increased the acetylcholine content, choline acetyltransferase, and acetylcholinesterase activity in the hippocampus of SCO-stimulated mice. In addition, AAL extract attenuated oxidative stress-induced neuronal cell death of hippocampal tissue. In terms of the regulatory mechanisms, AAL extract treatment reversed the SCO-induced decreases in the expression of Akt, phosphorylation of cAMP response element binding protein, and brain-derived neurotrophic factor. Our findings demonstrate that AAL extract has the ability to alleviate memory impairment through preventative effect on cholinergic system dysfunction and oxidative stress-related neuronal cell death in a SCO-induced memory deficit animal model. Overall, AAL may be a promising plant resource for the managing memory dysfunction due to neurodegenerative diseases, such as Alzheimer’s disease (AD).

Inhibition of Oxidative Neurotoxicity and Scopolamine-Induced Memory Impairment by γ-Mangostin: In Vitro and In Vivo Evidence.

Among a series of xanthones identified from mangosteen, the fruit of Garcinia mangostana L. (Guttifereae), α- and γ-mangostins are known to be major constituents exhibiting diverse biological activities. However, the effects of γ-mangostin on oxidative neurotoxicity and impaired memory are yet to be elucidated. In the present study, the protective effect of γ-mangostin on oxidative stress-induced neuronal cell death and its underlying action mechanism(s) were investigated and compared to that of α-mangostin using primary cultured rat cortical cells. In addition, the effect of orally administered γ-mangostin on scopolamine-induced memory impairment was evaluated in mice. We found that γ-mangostin exhibited prominent protection against H2O2- or xanthine/xanthine oxidase-induced oxidative neuronal death and inhibited reactive oxygen species (ROS) generation triggered by these oxidative insults. In contrast, α-mangostin had no effects on the oxidative neuronal damage or associated ROS production. We also found that γ-mangostin, not α-mangostin, significantly inhibited H2O2-induced DNA fragmentation and activation of caspases 3 and 9, demonstrating its antiapoptotic action. In addition, only γ-mangostin was found to effectively inhibit lipid peroxidation and DPPH radical formation, while both mangostins inhibited β-secretase activity. Furthermore, we observed that the oral administration of γ-mangostin at dosages of 10 and 30 mg/kg markedly improved scopolamine-induced memory impairment in mice. Collectively, these results provide both in vitro and in vivo evidences for the neuroprotective and memory enhancing effects of γ-mangostin. Multiple mechanisms underlying this neuroprotective action were suggested in this study. Based on our findings, γ-mangostin could serve as a potentially preferable candidate over α-mangostin in combatting oxidative stress-associated neurodegenerative diseases including Alzheimer's disease.

1-O-Hexyl-2,3,5-Trimethylhydroquinone Ameliorates l-DOPA-Induced Cytotoxicity in PC12 Cells.

1-O-Hexyl-2,3,5-trimethylhydroquinone (HTHQ) has previously been found to have effective anti-oxidant and anti-lipid-peroxidative activity. We aimed to elucidate whether HTHQ can prevent dopaminergic neuronal cell death by investigating the effect on l-DOPA-induced cytotoxicity in PC12 cells. HTHQ protected from both l-DOPA-induced cell death and superoxide dismutase activity reduction. When assessing the effect of HTHQ on oxidative stress-related signaling pathways, HTHQ inhibited l-DOPA-induced phosphorylation of sustained extracellular signal-regulated kinases (ERK1/2), p38 mitogen-activated protein kinase (MAPK), and c-Jun N-terminal kinase (JNK1/2). HTHQ also normalized l-DOPA-reduced Bcl-2-associated death protein (Bad) phosphorylation and Bcl-2-associated X protein (Bax) expression, promoting cell survival. Taken together, HTHQ exhibits protective effects against l-DOPA-induced cell death through modulation of the ERK1/2-p38MAPK-JNK1/2-Bad-Bax signaling pathway in PC12 cells. These results suggest that HTHQ may show ameliorative effects against oxidative stress-induced dopaminergic neuronal cell death, although further studies in animal models of Parkinson’s disease are required to confirm this.

Momordica charantia Ethanol Extract Attenuates H₂O₂-Induced Cell Death by Its Antioxidant and Anti-Apoptotic Properties in Human Neuroblastoma SK-N-MC Cells.

Oxidative stress, which is induced by reactive oxygen species (ROS), causes cellular damage which contributes to the pathogenesis of neurodegenerative diseases. Momordica charantia (MC), a traditional medicinal plant, is known to have a variety of health benefits, such as antidiabetic, anti-inflammatory, and antioxidant effects. However, it is unknown whether MC has protective effects against oxidative stress-induced neuronal cell death. The aim of this study was to investigate the potential action of MC on oxidative stress induced by H2O2. First, we tested whether the pretreatment of Momordica charantia ethanol extract (MCEE) attenuates H2O2-induced cell death in human neuroblastoma SK-N-MC cells. MCEE pretreatment significantly improved cell viability and apoptosis that deteriorated by H2O2. Further, MCEE ameliorated the imbalance between intracellular ROS production and removal through the enhancement of the intracellular antioxidant system. Intriguingly, the inhibition of apoptosis was followed by the blockage of mitochondria-dependent cell death cascades and suppression of the phosphorylation of the mitogen-activated protein kinase signaling (MAPKs) pathway by MCEE. Taken together, MCEE was shown to be effective in protecting against H2O2-induced cell death through its antioxidant and anti-apoptotic properties.

Attenuation of oxidative stress-induced neuronal cell death by Hydnophytum formicarum Jack.

Objective: To investigate protective effects of Hydnophytum formicarum Jack. (H. formicarum) extracts via regulation of SIRT1-FOXO3a-ADAM10 signaling and antioxidant activity against H2O2-induced neurotoxicity in neuroblastoma SH-SY5Y cells. Methods: Cell viability and apoptosis of neuronal cells pretreated with H. formicarum Jack. extracts under oxidative stress were determined by MTT assay and flow cytometry. The intracellular reactive oxygen species (ROS) was performed using Carboxy-DCFDA assay. Additionally, a profile of protein expressions related to neuroprotection was detected by western blot analysis. Results: The plant extracts (methanol and ethyl acetate) elicited protective effects on the neuronal cell death as performed by the MTT assay and by apoptosis analysis via the activation of BCL-2. Both ethyl acetate and methanol extracts exerted inhibitory effects against H2O2-induced ROS generation in the SH-SY5Y cells. Furthermore, the possible mechanism of neuroprotection of H. formicarum Jack. was observed through its antioxidant properties by maintaining the levels of catalase and SOD2 proteins as well as activating SIRT1-FOXO3a pathway. Importantly, pretreatment of neuronal cells with H. formicarum Jack. significantly recovered the levels of ADAM10 protein compared with the H2O2 treatment alone. Conclusions: The recent findings suggest the protective effects of H. formicarum Jack. plant extracts on attenuating H2O2-induced neurotoxicity in human SH-SY5Y cells.

Protective effects of perilla oil and alpha linolenic acid on SH-SY5Y neuronal cell death induced by hydrogen peroxide.

BACKGROUND/OBJECTIVEOxidative stress plays a key role in neuronal cell damage, which is associated with neurodegenerative disease. The aim of present study was to investigate the neuroprotective effects of perilla oil (PO) and its active component, alpha-linolenic acid (ALA), against hydrogen peroxide (H2O2)-induced oxidative stress in SH-SY5Y neuronal cells.MATERIALS/METHODSThe SH-SY5Y human neuroblastoma cells exposed to 250 µM H2O2 for 24 h were treated with different concentrations of PO (25, 125, 250 and 500 µg/mL) and its major fatty acid, ALA (1, 2.5, 5 and 25 µ/mL). We examined the effects of PO and ALA on H2O2-induced cell viability, lactate dehydrogenase (LDH) release, and nuclear condensation. Moreover, we determined whether PO and ALA regulated the apoptosis-related protein expressions, such as cleaved-poly ADP ribose polymerase (PARP), cleaved caspase-9 and -3, BCL-2 and BAX.RESULTSTreatment of H2O2 resulted in decreased cell viability, increased LDH release, and increase in the nuclei condensation as indicated by Hoechst 33342 staining. However, PO and ALA treatment significantly attenuated the neuronal cell death, indicating that PO and ALA potently blocked the H2O2-induced neuronal apoptosis. Furthermore, cleaved-PARP, cleaved caspase-9 and -3 activations were significantly decreased in the presence of PO and ALA, and the H2O2-mediated up-regulated BAX/BCL-2 ratio was blocked after treatment with PO and ALA.CONCLUSIONSPO and its main fatty acid, ALA, exerted the protective activity from neuronal oxidative stress induced by H2O2. They regulated apoptotic pathway in neuronal cell death by alleviation of BAX/BCL-2 ratio, and down-regulation of cleaved-PARP and cleaved caspase-9 and -3. Although further studies are required to verify the protective mechanisms of PO and ALA from neuronal damage, PO and ALA are the promising agent against oxidative stress-induced apoptotic neuronal cell death.

C-Abl-mediated Drp1 phosphorylation promotes oxidative stress-induced mitochondrial fragmentation and neuronal cell death

Oxidative stress-induced mitochondrial dysfunction and neuronal cell death have important roles in the development of neurodegenerative diseases. Dynamin related protein 1 (Drp1) is a critical factor in regulating mitochondrial dynamics. A variety of posttranslational modifications of Drp1 have been reported, including phosphorylation, ubiquitination, sumoylation and S-nitrosylation. In this study, we found that c-Abl phosphorylated Drp1 at tyrosine 266, 368 and 449 in vitro and in vivo, which augmented the GTPase activity of Drp1 and promoted Drp1-mediated mitochondrial fragmentation. Consistently, c-Abl-mediated phosphorylation is important for GTPase activity of Drp1 and mitochondrial fragmentation. Furthermore, we found that Drp1 phosphorylation mediated by c-Abl is required for oxidative stress-induced cell death in primary cortical neurons. Taken together, our findings reveal that c-Abl-Drp1 signaling pathway regulates oxidative stress-induced mitochondrial fragmentation and cell death, which might be a potential target for the treatment of neurodegenerative diseases.

Krebs Cycle Intermediates Protective against Oxidative Stress by Modulating the Level of Reactive Oxygen Species in Neuronal HT22 Cells

Krebs cycle intermediates (KCIs) are reported to function as energy substrates in mitochondria and to exert antioxidants effects on the brain. The present study was designed to identify which KCIs are effective neuroprotective compounds against oxidative stress in neuronal cells. Here we found that pyruvate, oxaloacetate, and α-ketoglutarate, but not lactate, citrate, iso-citrate, succinate, fumarate, or malate, protected HT22 cells against hydrogen peroxide-mediated toxicity. These three intermediates reduced the production of hydrogen peroxide-activated reactive oxygen species, measured in terms of 2′,7′-dichlorofluorescein diacetate fluorescence. In contrast, none of the KCIs—used at 1 mM—protected against cell death induced by high concentrations of glutamate—another type of oxidative stress-induced neuronal cell death. Because these protective KCIs did not have any toxic effects (at least up to 10 mM), they have potential use for therapeutic intervention against chronic neurodegenerative diseases.

Tat-HSP22 inhibits oxidative stress-induced hippocampal neuronal cell death by regulation of the mitochondrial pathway

Oxidative stress plays an important role in the progression of various neuronal diseases including ischemia. Heat shock protein 22 (HSP22) is known to protect cells against oxidative stress. However, the protective effects and mechanisms of HSP22 in hippocampal neuronal cells under oxidative stress remain unknown. In this study, we determined whether HSP22 protects against hydrogen peroxide (H2O2)-induced oxidative stress in HT-22 using Tat-HSP22 fusion protein. We found that Tat-HSP22 transduced into HT-22 cells and that H2O2-induced cell death, oxidative stress, and DNA damage were significantly reduced by Tat-HSP22. In addition, Tat-HSP22 markedly inhibited H2O2-induced mitochondrial membrane potential, cytochrome c release, cleaved caspase-3, and Bax expression levels, while Bcl-2 expression levels were increased in HT-22 cells. Further, we showed that Tat-HSP22 transduced into animal brain and inhibited cleaved-caspase-3 expression levels as well as significantly inhibited hippocampal neuronal cell death in the CA1 region of animals in the ischemic animal model. In the present study, we demonstrated that transduced Tat-HSP22 attenuates oxidative stress-induced hippocampal neuronal cell death through the mitochondrial signaling pathway and plays a crucial role in inhibiting neuronal cell death, suggesting that Tat-HSP22 protein may be used to prevent oxidative stress-related brain diseases including ischemia.

Repression of neuronal nitric oxide (nNOS) synthesis by MTA1 is involved in oxidative stress-induced neuronal damage

The Metastasis-associated protein 1 (MTA1) coregulator, an essential component of the nucleosome remodeling and deacetylase (NuRD) complex, potentiates neuroprotective effects against ischemia/reperfusion (I/R) injury. But the underlying mechanism(s) remain largely unknown. Here, we discovered that neuronal MTA1 was a target of oxidative stress, and stimulation of neurons with oxygen glucose deprivation (OGD) treatment significantly inhibited MTA1 expression. Additionally, MTA1 depletion augmented ischemic oxidative stress and thus promoted oxidative stress-induced neuronal cell death by OGD. While studying the impact of MTA1 status on global neuronal gene expression, we unexpectedly discovered that MTA1 may modulate OGD-induced neuronal damage via regulation of distinct nitric oxide synthase (NOS) (namely neuronal NOS, nNOS) signaling. We provided in vitro evidence that NOS1 is a chromatin target of MTA1 in OGD-insulted neurons. Mechanistically, neuronal ischemia-mediated repression of NOS1 expression is accompanied by the enhanced recruitment of MTA1 along with histone deacetylases (HDACs) to the NOS1 promoter, which could be effectively blocked by a pharmacological inhibitor of the HDACs. These findings collectively reveal a previously unrecognized, critical homeostatic role of MTA1, both as a target and as a component of the neuronal oxidative stress, in the regulation of acute neuronal responses against brain I/R damage. Our study also provides a molecular mechanistic explanation for the previously reported neurovascular protection by selective nNOS inhibitors.