Factor In Neuronal Cell Death Research Articles

Remifentanil Suppresses Oxidative Stress and Inflammation Induced by Glutamate via Activation of PPARγ/HO-1 Signaling Pathway in Hippocampal Neuronal Cells

Excitotoxicity caused by glutamate severely damages the central nervous system, contributing to the progress of neurodegenerative diseases. Remifentanil is an ultra-short acting synthetic α-opioid receptor agonist and it protects the body against oxidative stress. Oxidative stress is a causative factor for neuronal cell death, contributing to the pathogenesis of neurological diseases. More importantly, remifentanil has been confirmed to have neuroprotective effects on cerebral ischemia. Hence, the aim of the present study was to investigate the molecular mechanism underlying the effect of remifentanil on glutamate (Glu)-induced oxidative stress and inflammation in hippocampal cells. In present study, the cell viability was detected via CCk-8 assay. The cell apoptosis was evaluated by tunel assay. Western blot was performed for measurement of protein expression level. Generation of ROS level was detected by the ROS Activity Assay Kit (KA3842, Abnova) and DCF-DA staining method. MDA and SOD levels were detected by corresponding kits. The results from the present study suggested that remifentanil enhanced cell viability, reduced cell apoptosis rate and prevented oxidative stress in glutamate-induced HT22 cells. The PPARγ/HO-1 pathway was activated by remifentanil. After inhibition of PPARγ/HO-1 pathway, the anti-apoptosis and anti-oxidative stress effects of remifentanil were abolished. In conclusion, remifentanil has anti-apoptosis and anti-oxidative stress effects on glutamate-induced HT22 Cells via PPARγ/HO-1 pathway. Hence, remifentanil is a promising agent for attenuation of cytotoxicity induced by glutamate, providing a new strategy for treatment of excitotoxicity caused by glutamate in the central nervous system.

The Library Derived 4554W Peptide Inhibits Primary Nucleation of α-Synuclein

Aggregation of α-Synuclein (αS) is widely regarded as a key factor in neuronal cell death, leading to a wide range of synucleinopathies, including Parkinson’s Disease. Development of therapeutics has therefore focused on inhibiting aggregation of αS into toxic forms. One such inhibitor, based on the preNAC region αS45-54 (4554W), was identified using an intracellular peptide library screen, and subsequently shown to both inhibit formation of αS aggregates while simultaneously lowering toxicity. Subsequent efforts have sought to determine the mode of 4554W action. In particular, and consistent with the fact that both target and peptide are co-produced during library screening, we find that the peptide inhibits primary nucleation of αS, but does not modulate downstream elongation or secondary nucleation events. These findings hold significant promise towards mechanistic understanding and development of molecules that can module the first steps in αS aggregation towards novel treatments for Parkinson’s disease and related synucleinopathies.

Hypoglycemia in High-Risk Infants Within the Immediate Postnatal Period.

The incidence of hypoglycemia in the immediate postnatal period is rising because of the increasing rate of preterm births, maternal diabetes, and maternal obesity. Severe hypoglycemia has been considered a risk factor for neuronal cell death and adverse neurodevelopmental outcomes. The American Academy of Pediatrics (AAP) suggests a goal of ≥45 mg/dL (≥2.5 mmol/L) for infants who are asymptomatic within the first 48 hours. The Pediatric Endocrine Society (PES) suggests that infants who are unable to maintain their blood glucose >50 mg/dL (>2.77 mmol/L) within the first 48 hours or >60 mg/dL (>3.33 mmol/L) after the first 48 hours are at risk for persistent hypoglycemia. While there is disagreement for target glucose levels within the first 48 hours, both the AAP and the PES suggest further investigation for persistent hypoglycemia beyond 48-72 hours, which is beyond the scope of this article. However, in the immediate postnatal period, much can be gained with familiarization of the two guidelines, as well as current management techniques. This article presents current definitions and treatment modalities for management of hypoglycemia in infants considered at high risk in the immediate postnatal period.

Chebulinic acid attenuates glutamate-induced HT22 cell death by inhibiting oxidative stress, calcium influx and MAPKs phosphorylation

Glutamate-induced excitotoxicity and oxidative stress is a major causative factor in neuronal cell death in acute brain injuries and chronic neurodegenerative diseases. The prevention of oxidative stress is a potential therapeutic strategy. Therefore, in the present study, we aimed to examine a potential therapeutic agent and its protective mechanism against glutamate-mediated cell death. We first found that chebulinic acid isolated from extracts of the fruit of Terminalia chebula prevented glutamate-induced HT22 cell death. Chebulinic acid significantly reduced intracellular reactive oxygen species (ROS) production and Ca2+ influx induced by glutamate. We further demonstrated that chebulinic acid significantly decreased the phosphorylation of mitogen-activated protein kinases (MAPKs), including ERK1/2, JNK, and p38, as well as inhibiting pro-apoptotic Bax and increasing anti-apoptotic Bcl-2 protein expression. Moreover, we demonstrated that chebulinic acid significantly reduced the apoptosis induced by glutamate in HT22 cells. In conclusion, our results in this study suggest that chebulinic acid is a potent protectant against glutamate-induced neuronal cell death via inhibiting ROS production, Ca2+ influx, and phosphorylation of MAPKs, as well as reducing the ratio of Bax to Bcl-2, which contribute to oxidative stress-mediated neuronal cell death.

Role of Ageing and Oxidative Stress in Regulation of Amyloid-Degrading Enzymes and Development of Neurodegeneration

The accumulation of cerebral amyloid βpeptide (Aβ) is a key precipitating factor for neuronal cell death in Alzheimer's Disease (AD). However, brain Aβ levels are modifiable since there is a balance between its formation from the Amyloid Precursor Protein (APP) and its removal by clearance mechanisms, which can be either through proteolysis or by protein binding and subsequent transport). Among the major enzymes degrading brain Aβ are several zinc-proteases: neprilysin (NEP), its homologues NEP2 and the Endothelin Converting Enzymes (ECE-1 and -2) and also the Insulin-Degrading Enzyme (IDE). During the ageing process, and under certain pathological conditions (e.g. ischemia and stroke), the expression and activity of these enzymes decline, which leads to a deficit of Aβ clearance and its accumulation in the brain. Some of these changes in the enzyme properties are due to their reduced expression and/or structural modification by reactive oxygen species. In this review paper we shall discuss some mechanisms of regulation of Amyloid-Degrading Enzymes (ADEs) and possible therapeutic approaches which might prevent their decline with age and after pathology.

Mixed Lineage Kinase-3 Stabilizes and Functionally Cooperates with TRIBBLES-3 to Compromise Mitochondrial Integrity in Cytokine-induced Death of Pancreatic Beta Cells

Mixed lineage kinases (MLKs) have been implicated in cytokine signaling as well as in cell death pathways. Our studies show that MLK3 is activated in leukocyte-infiltrated islets of non-obese diabetic mice and that MLK3 activation compromises mitochondrial integrity and induces apoptosis of beta cells. Using an ex vivo model of islet-splenocyte co-culture, we show that MLK3 mediates its effects via the pseudokinase TRB3, a mammalian homolog of Drosophila Tribbles. TRB3 expression strongly coincided with conformational change and mitochondrial translocation of BAX. Mechanistically, MLK3 directly interacted with and stabilized TRB3, resulting in inhibition of Akt, a strong suppressor of BAX translocation and mitochondrial membrane permeabilization. Accordingly, attenuation of MLK3 or TRB3 expression each prevented cytokine-induced BAX conformational change and attenuated the progression to apoptosis. We conclude that MLKs compromise mitochondrial integrity and suppress cellular survival mechanisms via TRB3-dependent inhibition of Akt.

Potential neuroprotective effects of acupuncture stimulation on diabetes mellitus in a global ischemic rat model

Acupuncture (ACU) is known to be effective in ischemia treatment, and glutamate (GLU) excitotoxicity is an important factor in neuronal cell death. We observed the effect of ACU on cerebral blood flow (%CBF) and ΔGLU (the changes in GLU release) in the ischemic stroke rat model of diabetic mellitus (DM). A global ischemia was induced using the eleven-vessel occlusion (11-VO) method in 14 Sprague-Dawley rats (DM), which were randomly divided into two groups: the control group and the ACU-treatment group. Extracellular ΔGLU was assessed using an intra-cerebral biosensor system measuring 256 samples per second, simultaneously with %CBF and electroencephalogram. ACU stimulation was applied to ACU points GB34 and GB39 during the ischemic period. Twenty-three diagnostic parameters were proposed first for a detailed analysis of changes in %CBF and GLU release during ischemia/reperfusion. ACU rats showed a significant decrease in ischemic (p < 0.05) and reperfusion %CBF (p < 0.0001) than control rats, and a significantly larger decrease in ischemic ΔGLU (p < 0.05) and peak level of reperfusion ΔGLU (p < 0.005) than control rats. From these results, we suggest that ACU stimulation is responsible for the potential protection of neurons through suppression of %CBF response in the increased plasma osmolality and extracellular ΔGLU in diabetic rats under ischemic conditions.

Anesthetic-Induced Oxidative Stress and Potential Protection

Prolonged exposure of developing mammals to general anesthetics affects the N-methyl-D-aspartate (NMDA)–type glutamate or γ-aminobutyric acid (GABA) receptor systems and enhances neuronal toxicity. Stimulation of immature neurons by NMDA antagonists or GABA agonists is thought to increase overall nervous system excitability and may contribute to abnormal neuronal cell death during development. Although the precise mechanisms by which NMDA antagonists or GABA agonists cause neuronal cell death are still not completely understood, up-regulation of the NMDA receptor subunit NR1 may be an initiative factor in neuronal cell death. It is increasingly apparent that mitochondria lie at the center of the cell death regulation process. Evidence for the role of oxidative stress in anesthetic-induced neurotoxicity has been generated in studies that apply oxidative stress blockers. Prevention of neuronal death by catalase and superoxide dismutase in vitro, or by M40403 (superoxide dismutase mimetic) in vivo, supports the contention that the involvement of reactive oxygen species (ROS) and the nature of neuronal cell death in rodents is mainly apoptotic. However, more evidence is necessary to in order verify the role of the NMDA receptor subunit NR1 and ROS in anesthetic-induced neurodegeneration.

Causal Role of Apoptosis-Inducing Factor for Neuronal Cell Death Following Traumatic Brain Injury

Traumatic brain injury (TBI) consists of two phases: an immediate phase in which damage is caused as a direct result of the mechanical impact; and a late phase of altered biochemical events that results in delayed tissue damage and is therefore amenable to therapeutic treatment. Because the molecular mechanisms of delayed post-traumatic neuronal cell death are still poorly understood, we investigated whether apoptosis-inducing factor (AIF), a pro-apoptotic mitochondrial molecule and the key factor in the caspase-independent, cell death signaling pathway, plays a causal role in neuronal death following TBI. Using an in vitro model of neuronal stretch injury, we demonstrated that AIF translocated from mitochondria to the nucleus of neurons displaying axonal disruption, chromatin condensation, and nuclear pyknosis in a caspase-independent manner, whereas astrocytes remained unaffected. Similar findings were observed following experimental TBI in mice, where AIF translocation to the nucleus coincided with delayed neuronal cell death in both cortical and hippocampal neurons. Down-regulation of AIF in vitro by siRNA significantly reduced stretch-induced neuronal cell death by 67%, a finding corroborated in vivo using AIF-deficient harlequin mutant mice, where secondary contusion expansion was significantly reduced by 44%. Hence, our current findings demonstrate that caspase-independent, AIF-mediated signaling pathways significantly contribute to post-traumatic neuronal cell death and may therefore represent novel therapeutic targets for the treatment of TBI.

Neuroprotection against ischemic CA1 neurodegeneration by pituitary adenylate cyclase activating polypeptide via cAMP-response-element-binding protein-mediated enhancement of endogenous DNA repair

Emerging evidence suggests that accumulation of oxidative DNA damage in nuclear genome is an important contributing factor in neuronal cell death after cerebral ischemia. It has been shown in various models of cerebral ischemia/reperfusion that there is accumulation of oxidative DNA base damage and apurinic/apyridinic abasic site (AP site) in injured neurons, which could mediate neuronal degeneration by triggering various pro-apoptotic molecules. In the brain most types of oxidative DNA damage are repaired via the base-excision repair (BER) pathway that is highly inducible in response to various sublethal stimuli. Thus, interventions that enhance the activity of the BER pathway may be a potential therapeutic strategy against ischemic cell death. In the present study, we have examined the neuroprotective effect of the neuropeptide pituitary adenylate cyclase activating polypeptide (PACAP) in the rat model of transient global cerebral ischemia. Further, we have investigated the role of BER regulation as a potential mechanism underlying the effect of PACAP. PACAP, when infused intracerebroventricularly in the rat, potently protected against CA1 neuronal cell death after global cerebral ischemia produced by 12 minutes of 4-vessel occlusion. Associated with this neuroprotection, PACAP treatment reduced the accumulation of oxidative DNA lesions, especially AP site, and subsequently attenuated the activation of pro-apoptotic molecules p53 and PUMA in the CA1 sector, suggesting that the effect of PACAP may involve the acceleration of the repair process of endogenous oxidative DNA damage. To investigate the underlying mechanism, cellular BER activity and the expression of BER enzymes were measured in the hippocampal extracts. The results revealed that PACAP markedly enhanced the hippocampal expression (at both mRNA and protein levels) and activities of the essential BER enzymes AP endonuclase (APE) and DNA polymerase-beta. Furthermore, based on the results of inhibition studies, the inducible effect of PACAP on the BER pathway was found to be dependent on the phosphorylation and nuclear translocation of cAMP-response-element-binding protein (CREB), which mediated the enhanced transcription of both APE and DNA polymerase-beta. Finally, the effect of PACAP on BER and neuroprotection was mimicked by the administration of a cAMP/protein kinase A (PKA) agonist. The results of the present study demonstrate the neuroprotective effect of PACAP in hippocampal CA1 neurons after transient global cerebral ischemia. The effect of PACAP is dependent on the activation and nuclear translocation of CREB, and involves CREB-mediated activation of BER pathway for endogenous DNA repair. The results suggest that enhancement of neuronal DNA repair capacity by PACAP or other means may be a novel potential therapeutic approach to limit ischemic neuronal loss. (This project was supported by NIH grants NS36736, NS38560, NS 43802, and NS45048).

Apoptosis-Inducing Factor Is a Key Factor in Neuronal Cell Death Propagated by BAX-Dependent and BAX-Independent Mechanisms

Mitochondria release proteins that propagate both caspase-dependent and caspase-independent cell death pathways. AIF (apoptosis-inducing factor) is an important caspase-independent death regulator in multiple neuronal injury pathways. Presently, there is considerable controversy as to whether AIF is neuroprotective or proapoptotic in neuronal injury, such as oxidative stress or excitotoxicity. To evaluate the role of AIF in BAX-dependent (DNA damage induced) and BAX-independent (excitotoxic) neuronal death, we used Harlequin (Hq) mice, which are hypomorphic for AIF. Neurons carrying double mutations for Hq/Apaf1-/- (apoptosis proteases-activating factor) are impaired in both caspase-dependent and AIF-mediated mitochondrial cell death pathways. These mutant cells exhibit extended neuroprotection against DNA damage, as well as glutamate-induced excitotoxicity. Specifically, AIF is involved in NMDA- and kainic acid- but not AMPA-induced excitotoxicity. In vivo excitotoxic studies using kainic acid-induced seizure showed that Hq mice had significantly less hippocampal damage than wild-type littermates. Our results demonstrate an important role for AIF in both BAX-dependent and BAX-independent mechanisms of neuronal injury.

Ca 2+-induced oxidative stress in brain mitochondria treated with the respiratory chain inhibitor rotenone

In this study we show that micromolar Ca 2+ concentrations (>10 μM) strongly stimulate the release of reactive oxygen species (ROS) in rotenone-treated isolated rat forebrain mitochondria. Ca 2+-stimulated mitochondrial ROS release was associated with membrane lipid peroxidation and was directly correlated with the degree of complex I inhibition by rotenone. On the other hand, Ca 2+ did not increase mitochondrial ROS release in the presence of the complex I inhibitor 1-methyl-4-phenylpyridinium. Cyclosporin A had no effect on Ca 2+-stimulated mitochondrial ROS release in the presence of rotenone, indicating that mitochondrial permeability transition is not involved in this process. We hypothesized that Ca 2+-induced mitochondrial oxidative stress associated with partial inhibition of complex I may be an important factor in neuronal cell death observed in the neurodegenerative disorder Parkinson’s disease.

Role of NAD(P)H:quinone oxidoreductase in the progression of neuronal cell death in vitro and following cerebral ischaemia in vivo.

A direct involvement of the antioxidant enzyme NAD(P)H:quinone oxidoreductase (NQO1) in neuroprotection has not yet been shown. The aim of this study was to examine changes, localization and role of NQO1 after different neuronal injury paradigms. In primary cultures of rat cortex the activity of NQO1 was measured after treatment with ethylcholine aziridinium (AF64A; 40 micro m), inducing mainly apoptotic cell death, or oxygen-glucose deprivation (OGD; 120 min), which combines features of apoptotic and necrotic cell death. After treatment with AF64A a significant NQO1 activation started after 24 h. Sixty minutes after OGD a significant early induction of the enzyme was observed, followed by a second increase 24 h later. Enzyme activity was preferentially localized in glial cells in control and injured cultures, however, expression also occurred in injured neuronal cells. Inhibition of the NQO1 activity by dicoumarol, cibacron blue or chrysin (1-100 nM) protected the cells both after exposure to AF64A or OGD as assessed by the decreased release of lactate dehydrogenase. Comparable results were obtained in vivo using a mouse model of focal cerebral ischaemia. Dicoumarol treatment (30 nmol intracerebroventricular) reduced the infarct volume by 29% (p = 0.005) 48 h after the insult. After chemical induction of NQO1 activity by t-butylhydroquinone in vitro neuronal damage was exaggerated. Our data suggest that the activity of NQO1 is a deteriorating rather than a protective factor in neuronal cell death.