Increased NADPH oxidase-derived superoxide is involved in the neuronal cell death induced by hypoxia-ischemia in neonatal hippocampal slice cultures

Cannabidiol effectively prevents oxidative stress and stabilizes hypoxia-inducible factor-1 alpha (HIF-1α) in an animal model of global hypoxia

Cannabidiol (CBD) is a non-psychotomimetic phytocannabinoid derived from Cannabis sativa. It has therapeutic effects in different paradigms of brain injury, acting as a neuroprotectant. As oxidative stress is a primary risk factor for brain damage after neonatal hypoxia, we tested the effect of CBD on oxidative status and non-protein-bound iron accumulation in the immature brain after hypoxia. Moreover, we tested whether cannabidiol affects the accumulation of hypoxia-inducible factor-1 alpha (HIF-1α) which plays a key role in the regulation of cellular adaptation to hypoxia and oxidative stress. We used 7-day-old mice randomly assigned to hypoxic or control groups. Immediately after hypoxia or control exposure, pups were randomly assigned to a vehicle or CBD treatment. 24 h later, they were decapitated and the brains were immediately removed and stored for further biochemical analyses. We found that CBD reduced lipid peroxidation and prevented antioxidant depletion. For the first time, we also demonstrated that CBD upregulated HIF-1α protein level. This study indicates that CBD may effective agent in attenuating the detrimental consequences of perinatal asphyxia.

Ferrostatin-1 attenuates hypoxic-ischemic brain damage in neonatal rats by inhibiting ferroptosis

Background

Hypoxic-ischemic brain damage (HIBD) is a type of brain damage that is caused by perinatal asphyxia and serious damages the central nervous system. At present, there is no effective drug for the treatment of this disease. Besides, the pathogenesis of HIBD remains elusive. While studies have shown that ferroptosis plays an important role in HIBD, its role and mechanism in HIBD are yet to be fully understood.

Methods

The HIBD model of neonatal rats was established using the Rice-Vannucci method. A complete medium of PC12 cells was adjusted to a low-sugar medium, and the oxygen-glucose deprivation model was established after continuous hypoxia for 12 h. Laser Doppler blood flow imaging was used to detect the blood flow intensity after modeling. 2,3,5-triphenyl tetrazolium chloride staining was employed to detect ischemic cerebral infarction in rat brain tissue, and hematoxylin and eosin staining and transmission electron microscopy were used to observe brain injury and mitochondrial damage. Immunofluorescence was applied to monitor the expression of GFAP. Real-time quantitative polymerase chain reaction, western blot, and immunofluorescence were utilized to detect the expression of messenger RNA and protein. The level of reactive oxygen species (ROS) in cells was detected using the ROS detection kit.

Results

The results showed that ferrostatin-1 (Fer-1) significantly alleviated the brain injury caused by hypoxia and ischemia. Fer-1 significantly increased the expression of SLC3A2, SLC7A11, ACSL3, GSS, and GPX4 (P<0.05) and dramatically decreased the expressions of GFAP, ACSL4, TFRC, FHC, FLC, 4-HNE, HIF-1α, and ROS (P<0.05).

Conclusions

Fer-1 inhibits ferroptosis and alleviates HIBD by potentially targeting the GPX4/ACSL3/ACSL4 axis; however, its specific mechanism warrants further exploration.

Resveratrol and Some of Its Derivatives as Promising Prophylactic Treatments for Neonatal Hypoxia-Ischemia

Due to the rate of occurrence of neonatal hypoxia-ischemia, its neuronal sequelae, and the lack of effective therapies, the development of new neuroprotective strategies is required. Polyphenols (including resveratrol) are molecules whose anti-apoptotic, anti-inflammatory, and anti-oxidative properties could be effective against the damage induced by neonatal hypoxia-ischemia. In this review article, very recent data concerning the neuroprotective role of polyphenols and the mechanisms at play are detailed, including a boost in brain energy metabolism. The results obtained with innovative approaches, such as maternal supplementation at nutritional doses, suggest that polyphenols could be a promising prophylactic treatment for neonatal hypoxia-ischemia.

Chlorpromazine and Promethazine (C+P) Reduce Brain Injury after Ischemic Stroke through the PKC-δ/NOX/MnSOD Pathway

Cerebral ischemia-reperfusion (I/R) incites neurologic damage through a myriad of complex pathophysiological mechanisms, most notably, inflammation and oxidative stress. In I/R injury, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) produces reactive oxygen species (ROS), which promote inflammatory and apoptotic pathways, augmenting ROS production and promoting cell death. Inhibiting ischemia-induced oxidative stress would be beneficial for reducing neuroinflammation and promoting neuronal cell survival. Studies have demonstrated that chlorpromazine and promethazine (C+P) induce neuroprotection. This study investigated how C+P minimizes oxidative stress triggered by ischemic injury. Adult male Sprague-Dawley rats were subject to middle cerebral artery occlusion (MCAO) and subsequent reperfusion. 8 mg/kg of C+P was injected into the rats when reperfusion was initiated. Neurologic damage was evaluated using infarct volumes, neurological deficit scoring, and TUNEL assays. NOX enzymatic activity, ROS production, protein expression of NOX subunits, manganese superoxide dismutase (MnSOD), and phosphorylation of PKC-δ were assessed. Neural SHSY5Y cells underwent oxygen-glucose deprivation (OGD) and subsequent reoxygenation and C+P treatment. We also evaluated ROS levels and NOX protein subunit expression, MnSOD, and p-PKC-δ/PKC-δ. Additionally, we measured PKC-δ membrane translocation and the level of interaction between NOX subunit (p47^phox) and PKC-δ via coimmunoprecipitation. As hypothesized, treatment with C+P therapy decreased levels of neurologic damage. ROS production, NOX subunit expression, NOX activity, and p-PKC-δ/PKC-δ were all significantly decreased in subjects treated with C+P. C+P decreased membrane translocation of PKC-δ and lowered the level of interaction between p47^phox and PKC-δ. This study suggests that C+P induces neuroprotective effects in ischemic stroke through inhibiting oxidative stress. Our findings also indicate that PKC-δ, NOX, and MnSOD are vital regulators of oxidative processes, suggesting that C+P may serve as an antioxidant.

Genistein mitigates oxidative stress and inflammation by regulating Nrf2/HO-1 and NF-κB signaling pathways in hypoxic-ischemic brain damage in neonatal mice

Background

Oxidative stress and neuroinflammation play crucial roles in the progression of neonatal hypoxic-ischemic brain damage (HIBD). Genistein, a natural phytoestrogen, has been found to protect against ischemic brain injury. However, its effects and potential mechanisms in HIBD have not yet been explored.

Methods

A neonatal mouse model of hypoxia-ischemia (HI) and a cell model of oxygen-glucose deprivation/reperfusion (OGD/R) were employed. In the in vivo study, genistein (10 mg/kg; ip) was administered in mice once daily for 3 consecutive days before the operation and once immediately after HI. The effects of genistein treatment on acute brain damage and long-term responses were evaluated. Neuronal injury and apoptosis were estimated using hematoxylin and eosin (H&E) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, respectively. The expression of apoptosis-related proteins were also measured by Western blot analysis. Dihydroethidium (DHE) staining and glutathione (GSH) and malondialdehyde (MDA) production were determined to assess the extent of oxidative stress. The messenger RNA (mRNA) levels of proinflammatory cytokines were detected using real-time quantitative polymerase chain reaction (RT-qPCR) to evaluate the extent of neuroinflammation. In the in vitro study, cell counting kit-8 (CCK-8) and lactate dehydrogenase (LDH) assays, as well as propidium iodide (PI) staining, were performed to analyse the neuroprotective effects of genistein on primary cortical neurons. Western blot assays were used to detect the levels of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), phosphorylated inhibitor kappa B-α (p-IκB-α) and phosphorylated nuclear factor-kappa B (p-NF-κB) both in vivo and in vitro.

Results

Our results showed that genistein treatment effectively reduced cerebral infarction, attenuated neuronal injury and apoptosis, and contributed to the long-term recovery of neurological outcomes and brain atrophy in neonatal HIBD mice. Moreover, genistein ameliorated HIBD-induced oxidative stress and neuroinflammation. Meanwhile, genistein significantly increased cell viability, reversed neuronal injury and decreased cell apoptosis after OGD/R injury. Finally, the activation of the Nrf2/HO-1 pathway and inhibition of the NF-κB pathway by genistein were verified in the brain tissues of neonatal mice subjected to HIBD and in primary cortical neurons exposed to OGD/R.

Conclusions

Genistein exerted neuroprotective effects on HIBD by attenuating oxidative stress and neuroinflammation through the Nrf2/HO-1 and NF-κB signalling pathways.

Sustained Energy Deficit Following Perinatal Asphyxia: A Shift towards the Fructose-2,6-bisphosphatase (TIGAR)-Dependent Pentose Phosphate Pathway and Postnatal Development

Labor and delivery entail a complex and sequential metabolic and physiologic cascade, culminating in most circumstances in successful childbirth, although delivery can be a risky episode if oxygen supply is interrupted, resulting in perinatal asphyxia (PA). PA causes an energy failure, leading to cell dysfunction and death if re-oxygenation is not promptly restored. PA is associated with long-term effects, challenging the ability of the brain to cope with stressors occurring along with life. We review here relevant targets responsible for metabolic cascades linked to neurodevelopmental impairments, that we have identified with a model of global PA in rats. Severe PA induces a sustained effect on redox homeostasis, increasing oxidative stress, decreasing metabolic and tissue antioxidant capacity in vulnerable brain regions, which remains weeks after the insult. Catalase activity is decreased in mesencephalon and hippocampus from PA-exposed (AS), compared to control neonates (CS), in parallel with increased cleaved caspase-3 levels, associated with decreased glutathione reductase and glutathione peroxidase activity, a shift towards the TIGAR-dependent pentose phosphate pathway, and delayed calpain-dependent cell death. The brain damage continues long after the re-oxygenation period, extending for weeks after PA, affecting neurons and glial cells, including myelination in grey and white matter. The resulting vulnerability was investigated with organotypic cultures built from AS and CS rat newborns, showing that substantia nigra TH-dopamine-positive cells from AS were more vulnerable to 1 mM of H2O2 than those from CS animals. Several therapeutic strategies are discussed, including hypothermia; N-acetylcysteine; memantine; nicotinamide, and intranasally administered mesenchymal stem cell secretomes, promising clinical translation.

Role of Na+/K+-ATPase in ischemic stroke: in-depth perspectives from physiology to pharmacology

Na⁺/K⁺-ATPase (NKA) is a large transmembrane protein expressed in all cells. It is well studied for its ion exchanging function, which is indispensable for the maintenance of electrochemical gradients across the plasma membrane and herein neuronal excitability. The widely recognized pump function of NKA closely depends on its unique structure features and conformational changes upon binding of specific ions. Various Na⁺-dependent secondary transport systems are rigorously controlled by the ionic gradients generated by NKA and are essential for multiple physiological processes. In addition, roles of NKA as a signal transducer have also been unveiled nowadays. Plethora of signaling cascades are defined including Src-Ras-MAPK signaling, IP3R-mediated calcium oscillation, inflammation, and autophagy though most underlying mechanisms remain elusive. Ischemic stroke occurs when the blood flow carrying nutrients and oxygen into the brain is disrupted by blood clots, which is manifested by excitotoxicity, oxidative stress, inflammation, etc. The protective effect of NKA against ischemic stress is emerging gradually with the application of specific NKA inhibitor. However, NKA-related research is limited due to the opposite effects caused by NKA inhibitor at lower doses. The present review focuses on the recent progression involving different aspects about NKA in cellular homeostasis to present an in-depth understanding of this unique protein. Moreover, essential roles of NKA in ischemic pathology are discussed to provide a platform and bright future for the improvement in clinical research on ischemic stroke.

Vitamin D Attenuates Hypoxia-Induced Injury in Rat Primary Neuron Cells through Downregulation of the Dual Oxidase 1 (DUOX1) Gene

BACKGROUND This study aimed to investigate the mechanisms underlying the neuroprotective effects of vitamin D. MATERIAL AND METHODS Rat primary neuron cells were incubated under a hypoxia condition [a hypoxic chamber mixed with anaerobic gas (90% N₂, 5% CO₂) and 5% O₂] to induce cell injury. Cell transfection was performed to overexpress or suppress the expression of dual oxidase 1 (DUOX1). The malondialdehyde (MDA) and superoxide dismutase (SOD) levels were detected using a MDA (A003-2) or SOD (A001-1) kit. DUOX1 mRNA levels were detected using RT-PCR. Hypoxia-inducible factor-1alpha (HIF-1alpha), DUOX1, vitamin D receptor (VDR), NF-kappaB protein expressions were determined by western blotting. Cell apoptosis and reactive oxygen species (ROS) were evaluated by flow cytometry. RESULTS ROS increased significantly after hypoxic treatment. The expressions of HIF-1alpha and DUOX1 were significantly increased after hypoxic treatment. Vitamin D could decrease ROS level, apoptotic neuron cells and DUOX1 expression, and increase VDR expression. Downregulation of DUOX1 significantly decreased MDA level and apoptotic percentages of neuron cells, increased SOD level, and counteracted the hypoxia-induced increase of NF-kappaB signal. Further study showed that overexpression of DUOX1 significantly increased MDA level, ROS level, apoptotic percentages of neuron cells, and NF-kappaB nuclear signaling, while decreased SOD level. Vitamin D significantly counteracted the effects of DUOX1 overexpression induced injury in rat primary neuron cells. CONCLUSIONS Our study indicated that vitamin D may protect neuron cells from hypoxia-induced injury by regulating DUOX1 via the NF-kappaB signaling pathway.

TGF-β1 attenuates mitochondrial bioenergetics in pulmonary arterial endothelial cells via the disruption of carnitine homeostasis

Transforming growth factor beta-1 (TGF-β1) signaling is increased and mitochondrial function is decreased in multiple models of pulmonary hypertension (PH) including lambs with increased pulmonary blood flow (PBF) and pressure (Shunt). However, the potential link between TGF-β1 and the loss of mitochondrial function has not been investigated and was the focus of our investigations. Our data indicate that exposure of pulmonary arterial endothelial cells (PAEC) to TGF-β1 disrupted mitochondrial function as determined by enhanced mitochondrial ROS generation, decreased mitochondrial membrane potential, and disrupted mitochondrial bioenergetics. These events resulted in a decrease in cellular ATP levels, decreased hsp90/eNOS interactions and attenuated shear-mediated NO release. TGF-β1 induced mitochondrial dysfunction was linked to a nitration-mediated activation of Akt1 and the subsequent mitochondrial translocation of endothelial NO synthase (eNOS) resulting in the nitration of carnitine acetyl transferase (CrAT) and the disruption of carnitine homeostasis. The increase in Akt1 nitration correlated with increased NADPH oxidase activity associated with increased levels of p47^phox, p67^phox, and Rac1. The increase in NADPH oxidase was associated with a decrease in peroxisome proliferator-activated receptor type gamma (PPARγ) and the PPARγ antagonist, GW9662, was able to mimic the disruptive effect of TGF-β1 on mitochondrial bioenergetics. Together, our studies reveal for the first time, that TGF-β1 can disrupt mitochondrial function through the disruption of cellular carnitine homeostasis and suggest that stimulating carinitine homeostasis may be an avenue to treat pulmonary vascular disease.

Brain oxidative damage in murine models of neonatal hypoxia/ischemia and reoxygenation

The brain is one of the main organs affected by hypoxia and reoxygenation in the neonatal period and one of the most vulnerable to oxidative stress. Hypoxia/ischemia and reoxygenation leads to impairment of neurogenesis, disruption of cortical migration, mitochondrial damage and neuroinflammation. The extent of the injury depends on the clinical manifestation in the affected regions. Preterm newborns are highly vulnerable, and they exhibit severe clinical manifestations such as intraventricular hemorrhage (IVH), retinopathy of prematurity (ROP) and diffuse white matter injury (DWMI) among others. In the neonatal period, the accumulation of high levels of reactive oxygen species exacerbated by the immature antioxidant defense systems in represents cellular threats that, if they exceed or bypass physiological counteracting mechanisms, are responsible of significant neuronal damage. Several experimental models in mice mimic the consequences of perinatal asphyxia and the use of oxygen in the reanimation process that produce brain injury. The aim of this review is to highlight brain damage associated with oxidative stress in different murine models of hypoxia/ischemia and reoxygenation.

The Long-Term Impairment in Redox Homeostasis Observed in the Hippocampus of Rats Subjected to Global Perinatal Asphyxia (PA) Implies Changes in Glutathione-Dependent Antioxidant Enzymes and TIGAR-Dependent Shift Towards the Pentose Phosphate Pathways: Effect of Nicotinamide

We have recently reported that global perinatal asphyxia (PA) induces a regionally sustained increase in oxidized glutathione (GSSG) levels and GSSG/GSH ratio, a decrease in tissue-reducing capacity, a decrease in catalase activity, and an increase in apoptotic caspase-3-dependent cell death in rat neonatal brain up to 14 postnatal days, indicating a long-term impairment in redox homeostasis. In the present study, we evaluated whether the increase in GSSG/GSH ratio observed in hippocampus involves changes in glutathione reductase (GR) and glutathione peroxidase (GPx) activity, the enzymes reducing glutathione disulfide (GSSG) and hydroperoxides, respectively, as well as catalase, the enzyme protecting against peroxidation. The study also evaluated whether there is a shift in the metabolism towards the penthose phosphate pathway (PPP), by measuring TIGAR, the TP53-inducible glycolysis and apoptosis regulator, associated with delayed cell death, further monitoring calpain activity, involved in bax-dependent cell death, and XRCC1, a scaffolding protein interacting with genome sentinel proteins. Global PA was induced by immersing fetus-containing uterine horns removed by a cesarean section from on term rat dams into a water bath at 37 °C for 21 min. Asphyxia-exposed and sibling cesarean-delivered fetuses were manually resuscitated and nurtured by surrogate dams. Animals were euthanized at postnatal (P) days 1 or 14, dissecting samples from hippocampus to be assayed for glutathione, GR, GPx (all by spectrophotometry), catalase (Western blots and ELISA), TIGAR (Western blots), calpain (fluorescence), and XRCC1 (Western blots). One hour after delivery, asphyxia-exposed and control neonates were injected with either 100 μl saline or 0.8 mmol/kg nicotinamide, i.p., shown to protect from the short- and long-term consequences of PA. It was found that global PA produced (i) a sustained increase of GSSG levels and GSSG/GSH ratio at P1 and P14; (ii) a decrease of GR, GPx, and catalase activity at P1 and P14; (iii) a decrease at P1, followed by an increase at P14 of TIGAR levels; (iv) an increase of calpain activity at P14; and (v) an increase of XRCC1 levels, but only at P1. (vi) Nicotinamide prevented the effect of PA on GSSG levels and GSSG/GSH ratio, and on GR, GPx, and catalase activity, also on increased TIGAR levels and calpain activity observed at P14. The present study demonstrates that the long-term impaired redox homeostasis observed in the hippocampus of rats subjected to global PA implies changes in GR, GPx, and catalase, and a shift towards PPP, as indicated by an increase of TIGAR levels at P14.

Resveratrol mitigates the oxidative stress mediated by hypoxic-ischemic brain injury in neonatal rats via Nrf2/HO-1 pathway

CONTEXT

Hypoxic-ischemic encephalopathy (HIE) has a high morbidity and mortality rate. Resveratrol possesses numerous biological properties including antioxidant, anti-inflammatory and neuroprotective activities.

OBJECTIVE

The current experiment investigates the neuroprotective efficacy of resveratrol (RESV) against HIE by modulating Nrf2/HO-1 pathway in neonatal rats.

MATERIALS AND METHODS

Seven-day-old pups (n = 48) were divided into four groups. Group-I rats receiving 2% DMSO saline (sham), group-II rats underwent unilateral carotid artery ligation and hypoxia (92% N₂ and 8% O₂) for 2.5 h (hypoxia-ischemia; HI), group-III and IV rats received 20 (RESV 20 + HI) or 40 mg/kg (RESV 40 + HI; group-IV) of RESV via intraperitoneal injection (ip), respectively, for 7 days prior to HI induction.

RESULTS

Pre-treatment with RESV (20 or 40) markedly reduced (p < 0.01) the cerebral oedema (86.23-71.26 or 65.24%), infarct area (33.85-19.81 or 14.30%), lipid peroxidation products, inflammatory markers [IL-1β 186-110 or 82; IL-6 255-146 or 103; TNF-α 310-204 or 137; NF-κB 205-115 or 91) p65 subunit] and significantly restored (p < 0.01) the antioxidative status by enhancing the activities of glutathione peroxidase (GPx) 5.22-6.49 or 7.78; catalase (CAT) 51-55 or 59, superoxide dismutase (SOD) 2.5-3.05 or 3.25; through marked upregulation (p < 0.01) of heme oxygenase 1 (HO-1) 0.65-0.69 or 0.73; and nuclear factor erythroid 2 related factor 2 (Nrf2) 0.73-0.86 or 0.91.

DISCUSSION AND CONCLUSIONS

RESV displays its neurotherapeutic potential via upregulating the protein expression of Nrf2 and HO-1 signalling pathway and thereby attenuates oxidative stress and inflammatory response in HI-induced neonatal rats.

Excitotoxic superoxide production and neuronal death require both ionotropic and non-ionotropic NMDA receptor signaling

NMDA-type glutamate receptors (NMDAR) trigger superoxide production by neuronal NADPH oxidase-2 (NOX2), which if sustained leads to cell death. This process involves Ca²⁺ influx through NMDAR channels. By contrast, comparable Ca²⁺ influx by other routes does not induce NOX2 activation or cell death. This contrast has been attributed to site-specific effects of Ca²⁺ flux through NMDAR. Here we show instead that it stems from non-ionotropic signaling by NMDAR GluN2B subunits. To evaluate non-ionotropic effects, mouse cortical neurons were treated with NMDA together with 7-chlorokynurenate, L-689,560, or MK-801, which block Ca²⁺ influx through NMDAR channels but not NMDA binding. NMDA-induced superoxide formation was prevented by the channel blockers, restored by concurrent Ca²⁺ influx through ionomycin or voltage-gated calcium channels, and not induced by the Ca²⁺ influx in the absence of NMDAR ligand binding. Neurons expressing either GluN2B subunits or chimeric GluN2A/GluN2B C-terminus subunits exhibited NMDA-induced superoxide production, whereas neurons expressing chimeric GluN2B/GluN2A C-terminus subunits did not. Neuronal NOX2 activation requires phosphoinositide 3-kinase (PI3K), and NMDA binding to NMDAR increased PI3K association with NMDA GluN2B subunits independent of Ca²⁺ influx. These findings identify a non-ionotropic signaling pathway that links NMDAR to NOX2 activation through the C-terminus domain of GluN2B.

Dexmedetomidine Protects Against Chemical Hypoxia-Induced Neurotoxicity in Differentiated PC12 Cells Via Inhibition of NADPH Oxidase 2-Mediated Oxidative Stress

Dexmedetomidine (Dex) is a widely used sedative in anesthesia and critical care units, and it exhibits neuroprotective activity. However, the precise mechanism of Dex-exerted neuroprotection is not clear. Increased neuronal NADPH oxidase 2 (NOX2) contributes to oxidative stress and neuronal damage in various hypoxia-related neurodegenerative disorders. The present study investigated whether Dex regulated neuronal NOX2 to exert its protective effects under hypoxic conditions. Well-differentiated PC12 cells were exposed to cobalt chloride (CoCl₂) to mimic a neuronal model of chemical hypoxia-mediated neurotoxicity. The data showed that Dex pretreatment of PC12 cells significantly suppressed CoCl₂-induced neurotoxicity, as evidenced by the enhanced cell viability, restoration of cellular morphology, and reduction in apoptotic cells. Dex improved mitochondrial function and inhibited CoCl₂-induced mitochondrial apoptotic pathways. We further demonstrated that Dex attenuated oxidative stress, downregulated NOX2 protein expression and activity, and inhibited intracellular calcium ([Ca²⁺]i) overload in CoCl₂-treated PC12 cells. Moreover, knockdown of the NOX2 gene markedly improved mitochondrial function and attenuated apoptosis under hypoxic conditions. These results demonstrated that the protective effects of Dex against hypoxia-induced neurotoxicity in neural cells were mediated, at least partially, via inhibition of NOX2-mediated oxidative stress.

Astrocytic gap junction inhibition by carbenoxolone enhances the protective effects of ischemic preconditioning following cerebral ischemia

BACKGROUND

Stroke is the second leading cause of death worldwide and the most common cause of adult-acquired disability in many nations. Thus, attenuating the damage after ischemic injury and improving patient prognosis are of great importance. We have indicated that ischemic preconditioning (IP) can effectively reduce the damage of ischemia reperfusion and that inhibition of gap junctions may further reduce this damage. Although we confirmed that the function of gap junctions is closely associated with glutamate, we did not investigate the mechanism. In the present study, we aimed to clarify whether the blockade of cellular communication at gap junctions leads to significant reductions in the levels of glutamate released by astrocytes following cerebral ischemia.

METHODS

To explore this hypothesis, we utilized the specific blocking agent carbenoxolone (CBX) to inhibit the opening and internalization of connexin 43 channels in an in vitro model of oxygen-glucose deprivation/re-oxygenation (OGD/R), following IP.

RESULTS

OGD/R resulted in extensive astrocytic glutamate release following upregulation of hemichannel activity, thus increasing reactive oxygen species (ROS) generation and subsequent cell death. However, we observed significant increases in neuronal survival in neuron-astrocyte co-cultures that were subjected to IP prior to OGD/R. Moreover, the addition of CBX enhanced the protective effects of IP during the re-oxygenation period following OGD, by means of blocking the release of glutamate, increasing the level of the excitatory amino acid transporter 1, and downregulating glutamine expression.

CONCLUSIONS

Our results suggest that combined use of IP and CBX represents a novel therapeutic strategy to attenuate damage from cerebral ischemia with minimal adverse side effects.

Linalyl acetate prevents hypertension-related ischemic injury

Ischemic stroke remains an important cause of disability and mortality. Hypertension is a critical risk factor for the development of ischemic stroke. Control of risk factors, including hypertension, is therefore important for the prevention of ischemic stroke. Linalyl acetate (LA) has been reported to have therapeutic effects in ischemic stroke by modulating intracellular Ca2+ concentration and having anti-oxidative properties. The preventive efficacy of LA has not yet been determined. This study therefore investigated the preventive efficacy of LA in rat aortas exposed to hypertension related-ischemic injury, and the mechanism of action of LA.Hypertension was induced in vivo following ischemic injury to the aorta induced by oxygen-glucose deprivation and reoxygenation in vitro. Effects of LA were assayed by western blotting, by determining concentrations of lactate dehydrogenase (LDH) and reactive oxygen species (ROS) and by vascular contractility assays. LA significantly reduced systolic blood pressure in vivo. In vitro, LA suppressed ischemic injury-induced expression of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit p47phox, as well as ROS production, LDH release, and ROS-induced endothelial nitric oxide synthase suppression. These findings indicate that LA has anti-hypertensive properties that can prevent hypertension-related ischemic injury and can prevent NADPH oxidase-induced production of ROS.

Arctic ground squirrel resist peroxynitrite-mediated cell death in response to oxygen glucose deprivation

Cerebral ischemia-reperfusion (I/R) injury initiates a cascade of events, generating nitric oxide (NO) and superoxide(O₂^•-) to form peroxynitrite (ONOO^-), a potent oxidant. Arctic ground squirrels (AGS; Urocitellus parryii) show high tolerance to I/R injury. However, the underlying mechanism remains elusive. We hypothesize that tolerance to I/R modeled in an acute hippocampal slice preparation in AGS is modulated by reduced oxidative and nitrative stress. Hippocampal slices (400µm) from rat and AGS were subjected to oxygen glucose deprivation (OGD) using a novel microperfusion technique. Slices were exposed to NO, O₂^.- donors with and without OGD; pretreatment with inhibitors of NO, O₂^.- and ONOO^- followed by OGD. Perfusates collected every 15min were analyzed for LDH release, a marker of cell death. 3-nitrotyrosine (3NT) and 4-hydroxynonenal (4HNE) were measured to assess oxidative and nitrative stress. Results show that NO/O₂^.- alone is not sufficient to cause ischemic-like cell death, but with OGD enhances cell death more in rat than in AGS. A NOS inhibitor, SOD mimetic and ONOO^- inhibitor attenuates OGD injury in rat but has no effect in AGS. Rats also show a higher level of 3NT and 4HNE with OGD than AGS suggesting the greater level of injury in rat is via formation of ONOO^-.

Taking up the cudgels for the traditional reactive oxygen and nitrogen species detection assays and their use in the cardiovascular system

Reactive oxygen and nitrogen species (RONS such as H2O2, nitric oxide) confer redox regulation of essential cellular functions (e.g. differentiation, proliferation, migration, apoptosis), initiate and catalyze adaptive stress responses. In contrast, excessive formation of RONS caused by impaired break-down by cellular antioxidant systems and/or insufficient repair of the resulting oxidative damage of biomolecules may lead to appreciable impairment of cellular function and in the worst case to cell death, organ dysfunction and severe disease phenotypes of the entire organism. Therefore, the knowledge of the severity of oxidative stress and tissue specific localization is of great biological and clinical importance. However, at this level of investigation quantitative information may be enough. For the development of specific drugs, the cellular and subcellular localization of the sources of RONS or even the nature of the reactive species may be of great importance, and accordingly, more qualitative information is required. These two different philosophies currently compete with each other and their different needs (also reflected by different detection assays) often lead to controversial discussions within the redox research community. With the present review we want to shed some light on these different philosophies and needs (based on our personal views), but also to defend some of the traditional assays for the detection of RONS that work very well in our hands and to provide some guidelines how to use and interpret the results of these assays. We will also provide an overview on the "new assays" with a brief discussion on their strengths but also weaknesses and limitations.

Oxidative Stress in Hypoxic-Ischemic Encephalopathy: Molecular Mechanisms and Therapeutic Strategies

Hypoxic-ischemic encephalopathy (HIE) is one of the leading causes of morbidity and mortality in neonates. Because of high concentrations of sensitive immature cells, metal-catalyzed free radicals, non-saturated fatty acids, and low concentrations of antioxidant enzymes, the brain requires high levels of oxygen supply and is, thus, extremely sensitive to hypoxia. Strong evidence indicates that oxidative stress plays an important role in pathogenesis and progression. Following hypoxia and ischemia, reactive oxygen species (ROS) production rapidly increases and overwhelms antioxidant defenses. A large excess of ROS will directly modify or degenerate cellular macromolecules, such as membranes, proteins, lipids, and DNA, and lead to a cascading inflammatory response, and protease secretion. These derivatives are involved in a complex interplay of multiple pathways (e.g., inflammation, apoptosis, autophagy, and necrosis) which finally lead to brain injury. In this review, we highlight the molecular mechanism for oxidative stress in HIE, summarize current research on therapeutic strategies utilized in combating oxidative stress, and try to explore novel potential clinical approaches.

Pulmonary artery smooth muscle cell hyperproliferation and metabolic shift triggered by pulmonary overcirculation

Vascular cell hyperproliferation and metabolic reprogramming contribute to the pathophysiology of pulmonary arterial hypertension (PAH). An important cause of PAH in children with congenital heart disease (CHD) is increased pulmonary blood flow (PBF). To better characterize this disease course we studied early changes in pulmonary artery smooth muscle cell (PASMC) proliferation and metabolism using a unique ovine model of pulmonary overcirculation. Consistent with PAH in adults, PASMCs derived from 4-wk-old lambs exposed to increased PBF (shunt) exhibited increased rates of proliferation. While shunt PASMCs also exhibited significant decreases in mitochondrial oxygen consumption, membrane potential, and tricarboxylic acid (TCA) cycle function, suggesting a switch to Warburg metabolism as observed in advanced PAH in adults, they unexpectedly demonstrated decreased glycolytic lactate production, likely due to enhanced flux through the pentose phosphate pathway (PPP). This may be a response to the marked increase in NADPH oxidase (Nox) activity and decreased NADPH/NADP+ ratios observed in shunt PASMCs. Consistent with these findings, pharmacological inhibition of Nox activity preferentially slowed the growth of shunt PASMCs in vitro. Our results therefore indicate that PASMC hyperproliferation is observed early in the setting of pulmonary overcirculation and is accompanied by a unique metabolic profile that is independent of HIF-1α, PDHK1, or increased glycolytic flux. Our results also suggest that Nox inhibition may help prevent pulmonary overcirculation-induced PAH in children born with CHD.

NADPH oxidases promote apoptosis by activating ZNRF1 ubiquitin ligase in neurons treated with an exogenously applied oxidant

Reactive oxygen species (ROS) play an important role in causing neuronal death in a number of neurological disorders. We recently reported that ROS serve as a signal to activate neuronal apoptosis and axonal degeneration by activating ZNRF1 (zinc- and RING-finger 1), a ubiquitin ligase that targets AKT for proteasomal degradation in neurons. In the present study, we showed that the NADPH oxidase family of molecules is required for ZNRF1 activation by epidermal growth factor receptor (EGFR)-dependent phosphorylation in response to axonal injury. We herein demonstrate that NADPH oxidases promote apoptosis by activating ZNRF1, even in neurons treated with an exogenously applied oxidant. These results suggest an important role for NADPH oxidase in the initiation/promotion of neuronal degeneration by increasing ROS in close proximity to protein machineries, including those for ZNRF1 and EGFR, thereby promoting neuronal degeneration.

Neuroprotective and Functional Improvement Effects of Methylene Blue in Global Cerebral Ischemia

Transient global cerebral ischemia (GCI) causes delayed neuronal cell death in the vulnerable hippocampus CA1 subfield, as well as behavioral deficits. Ischemia reperfusion (I/R) produces excessive reactive oxygen species and plays a key role in brain injury. The mitochondrial electron respiratory chain is the main cellular source of free radical generation, and dysfunction of mitochondria has a significant impact on the neuronal cell death in ischemic brain. The aim of the present study is to investigate the potential beneficial effects of methylene blue (MB) in a four-vessel occlusion (4VO) GCI model on adult male rats. MB was delivered at a dose of 0.5 mg/kg/day for 7 days, through a mini-pump implanted subcutaneously after GCI. We first found that MB significantly improved ischemic neuronal survival in the hippocampal CA1 region as measured by cresyl violet staining as well as NeuN staining. We also found that MB has the ability to rescue ischemia-induced decreases of cytochrome c oxidase activity and ATP generation in the CA1 region following I/R. Further analysis with labeling of MitoTracker® Red revealed that the depolarization of mitochondrial membrane potential (MMP) was markedly attenuated following MB treatment. In addition, the induction of caspase-3, caspase-8, and caspase-9 activities and the increased numbers of TUNEL-positive cells of the CA1 region were significantly reduced by MB application. Correspondingly, Barnes maze tests showed that the deterioration of spatial learning and memory performance following GCI was significantly improved in the MB-treatment group compared to the ischemic control group. In summary, our study suggests that MB may be a promising therapeutic agent targeting neuronal cell death and cognitive deficits following transient global cerebral ischemia.

Autophagy in neonatal hypoxia ischemic brain is associated with oxidative stress

Autophagy is activated when the neonatal brain exposed to hypoxia ischemia (HI), but the mechanisms underlying its activation and its role in the neuronal cell death associated with HI is unclear. We have previously shown that reactive oxygen species (ROS) derived from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase play an important role in HI-mediated neuronal cell death. Thus, the aim of this study was to determine if ROS is involved in the activation of autophagy in HI-mediated neonatal brain injury and to determine if this is a protective or deleterious pathway. Initial electron microscopy data demonstrated that autophagosome formation is elevated in P7 hippocampal slice cultures exposed to oxygen-glucose deprivation (OGD). This corresponded with increased levels of LC3II mRNA and protein. The autophagy inhibitor, 3-methyladenine (3-MA) effectively reduced LC3II levels and autophagosome formation in hippocampal slice cultures exposed to OGD. Neuronal cell death was significantly attenuated. Finally, we found that the pharmacologic inhibition of NADPH oxidase using apocynin or gp91ds-tat decreased autophagy in hippocampal slice cultures and the rat brain respectively. Thus, our results suggest that an activation of autophagy contributes to neonatal HI brain injury this is oxidative stress dependent.

Nitric oxide induces hypoxia ischemic injury in the neonatal brain via the disruption of neuronal iron metabolism

We have recently shown that increased hydrogen peroxide (H₂O₂) generation is involved in hypoxia–ischemia (HI)-mediated neonatal brain injury. H₂O₂ can react with free iron to form the hydroxyl radical, through Fenton Chemistry. Thus, the objective of this study was to determine if there was a role for the hydroxyl radical in neonatal HI brain injury and to elucidate the underlying mechanisms. Our data demonstrate that HI increases the deposition of free iron and hydroxyl radical formation, in both P7 hippocampal slice cultures exposed to oxygen–glucose deprivation (OGD), and the neonatal rat exposed to HI. Both these processes were found to be nitric oxide (NO) dependent. Further analysis demonstrated that the NO-dependent increase in iron deposition was mediated through increased transferrin receptor expression and a decrease in ferritin expression. This was correlated with a reduction in aconitase activity. Both NO inhibition and iron scavenging, using deferoxamine administration, reduced hydroxyl radical levels and neuronal cell death. In conclusion, our results suggest that increased NO generation leads to neuronal cell death during neonatal HI, at least in part, by altering iron homeostasis and hydroxyl radical generation.

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HI increases the deposition of free iron and hydroxyl radical formation in the neonatal brain.

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Both these processes are NO dependent.

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Increased iron deposition is mediated via increased TfR and decreased ferritin expression.

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These processes are involved in the neuronal cell death associated with neonatal HI.

ROS produced by NOX2 control in vitro development of cerebellar granule neurons development

Reactive oxygen species (ROS) act as signaling molecules that regulate nervous system physiology. ROS have been related to neural differentiation, neuritogenesis, and programmed cell death. Nevertheless, little is known about the mechanisms involved in the regulation of ROS during neuronal development. In this study, we evaluated the mechanisms by which ROS are regulated during neuronal development and the implications of these molecules in this process. Primary cultures of cerebellar granule neurons (CGN) were used to address these issues. Our results show that during the first 3 days of CGN development in vitro (days in vitro; DIV), the levels of ROS increased, reaching a peak at 2 and 3 DIV under depolarizing (25 mM KCl) and nondepolarizing (5 mM KCl) conditions. Subsequently, under depolarizing conditions, the ROS levels markedly decreased, but in nondepolarizing conditions, the ROS levels increased gradually. This correlated with the extent of CGN maturation. Also, antioxidants and NADPH-oxidases (NOX) inhibitors reduced the expression of Tau and MAP2. On the other hand, the levels of glutathione markedly increased at 1 DIV. We inferred that the ROS increase at this time is critical for cell survival because glutathione depletion leads to axonal degeneration and CGN death only at 2 DIV. During the first 3 DIV, NOX2 was upregulated and expressed in filopodia and growth cones, which correlated with the hydrogen peroxide (H2O2) distribution in the cell. Finally, NOX2 KO CGN showed shorter neurites than wild-type CGN. Taken together, these results suggest that the regulation of ROS is critical during the early stages of CGN development.

Oxidative stress, unfolded protein response, and apoptosis in developmental toxicity

Physiological development requires precise spatiotemporal regulation of cellular and molecular processes. Disruption of these key events can generate developmental toxicity in the form of teratogenesis or mortality. The mechanism behind many developmental toxicants remains unknown. While recent work has focused on the unfolded protein response (UPR), oxidative stress, and apoptosis in the pathogenesis of disease, few studies have addressed their relationship in developmental toxicity. Redox regulation, UPR, and apoptosis are essential for physiological development and can be disturbed by a variety of endogenous and exogenous toxicants to generate lethality and diverse malformations. This review examines the current knowledge of the role of oxidative stress, UPR, and apoptosis in physiological development as well as in developmental toxicity, focusing on studies and advances in vertebrates model systems.

NADPH oxidase-2: linking glucose, acidosis, and excitotoxicity in stroke

SIGNIFICANCE

Neuronal superoxide production contributes to cell death in both glutamate excitotoxicity and brain ischemia (stroke). NADPH oxidase-2 (NOX2) is the major source of neuronal superoxide production in these settings, and regulation of NOX2 activity can thereby influence outcome in stroke.

RECENT ADVANCES

Reduced NOX2 activity can rescue cells from oxidative stress and cell death that otherwise occur in excitotoxicity and ischemia. NOX2 activity is regulated by several factors previously shown to affect outcome in stroke, including glucose availability, intracellular pH, protein kinase ζ/δ, casein kinase 2, phosphoinositide-3-kinase, Rac1/2, and phospholipase A2. The newly identified functions of these factors as regulators of NOX2 activity suggest alternative mechanisms for their effects on ischemic brain injury.

CRITICAL ISSUES

Key aspects of these regulatory influences remain unresolved, including the mechanisms by which rac1 and phospholipase activities are coupled to N-methyl-D-aspartate (NMDA) receptors, and whether superoxide production by NOX2 triggers subsequent superoxide production by mitochondria.

FUTURE DIRECTIONS

It will be important to establish whether interventions targeting the signaling pathways linking NMDA receptors to NOX2 in brain ischemia can provide a greater neuroprotective efficacy or a longer time window to treatment than provided by NMDA receptor blockade alone. It will likewise be important to determine whether dissociating superoxide production from the other signaling events initiated by NMDA receptors can mitigate the deleterious effects of NMDA receptor blockade.

Overexpression of extracellular superoxide dismutase protects against brain injury induced by chronic hypoxia

Extracellular superoxide dismutase (EC-SOD) is an isoform of SOD normally found both intra- and extra-cellularly and accounting for most SOD activity in blood vessels. Here we explored the role of EC-SOD in protecting against brain damage induced by chronic hypoxia. EC-SOD Transgenic mice, were exposed to hypoxia (FiO2.1%) for 10 days (H-KI) and compared to transgenic animals housed in room air (RA-KI), wild type animals exposed to hypoxia (H-WT or wild type mice housed in room air (RA-WT). Overall brain metabolism evaluated by positron emission tomography (PET) showed that H-WT mice had significantly higher uptake of 18FDG in the brain particularly the hippocampus, hypothalamus, and cerebellum. H-KI mice had comparable uptake to the RA-KI and RA-WT groups. To investigate the functional state of the hippocampus, electrophysiological techniques in ex vivo hippocampal slices were performed and showed that H-KI had normal synaptic plasticity, whereas H-WT were severely affected. Markers of oxidative stress, GFAP, IBA1, MIF, and pAMPK showed similar values in the H-KI and RA-WT groups, but were significantly increased in the H-WT group. Caspase-3 assay and histopathological studies showed significant apoptosis/cell damage in the H-WT group, but no significant difference in the H-KI group compared to the RA groups. The data suggest that EC-SOD has potential prophylactic and therapeutic roles in diseases with compromised brain oxygenation.

NR2B phosphorylation at tyrosine 1472 contributes to brain injury in a rodent model of neonatal hypoxia-ischemia

BACKGROUND AND PURPOSE

The NR2B subunit of the N-methyl-d-aspartate (NMDA) receptor is phosphorylated by the Src family kinase Fyn in brain, with tyrosine (Y) 1472 as the major phosphorylation site. Although Y1472 phosphorylation is important for synaptic plasticity, it is unknown whether it is involved in NMDA receptor-mediated excitotoxicity in neonatal brain hypoxia-ischemia (HI). This study was designed to elucidate the specific role of Y1472 phosphorylation of NR2B in neonatal HI in vivo and in NMDA-mediated neuronal death in vitro.

METHODS

Neonatal mice with a knockin mutation of Y1472 to phenylalanine (YF-KI) and their wild-type littermates were subjected to HI using the Vannucci model. Brains were scored 5 days later for damage using cresyl violet and iron staining. Western blotting and immunoprecipitation were performed to determine NR2B tyrosine phosphorylation. Expression of NADPH oxidase subunits and superoxide production were measured in vivo. NMDA-induced calcium response, superoxide formation, and cell death were evaluated in primary cortical neurons.

RESULTS

After neonatal HI, YF-KI mice have reduced expression of NADPH oxidase subunit gp91phox and p47phox and superoxide production, lower activity of proteases implicated in necrotic and apoptotic cell death, and less brain damage when compared with the wild-type mice. In vitro, YF-KI mutation diminishes superoxide generation in response to NMDA without effect on calcium accumulation and inhibits NMDA and glutamate-induced cell death.

CONCLUSIONS

Upregulation of NR2B phosphorylation at Y1472 after neonatal HI is involved in superoxide-mediated oxidative stress and contributes to brain injury.

Antioxidant gene therapy against neuronal cell death

Oxidative stress is a common hallmark of neuronal cell death associated with neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, as well as brain stroke/ischemia and traumatic brain injury. Increased accumulation of reactive species of both oxygen (ROS) and nitrogen (RNS) has been implicated in mitochondrial dysfunction, energy impairment, alterations in metal homeostasis and accumulation of aggregated proteins observed in neurodegenerative disorders, which lead to the activation/modulation of cell death mechanisms that include apoptotic, necrotic and autophagic pathways. Thus, the design of novel antioxidant strategies to selectively target oxidative stress and redox imbalance might represent important therapeutic approaches against neurological disorders. This work reviews the evidence demonstrating the ability of genetically encoded antioxidant systems to selectively counteract neuronal cell loss in neurodegenerative diseases and ischemic brain damage. Because gene therapy approaches to treat inherited and acquired disorders offer many unique advantages over conventional therapeutic approaches, we discussed basic research/clinical evidence and the potential of virus-mediated gene delivery techniques for antioxidant gene therapy.

Intracellular pH reduction prevents excitotoxic and ischemic neuronal death by inhibiting NADPH oxidase

Sustained activation of N-methyl-d-aspartate (NMDA) -type glutamate receptors leads to excitotoxic neuronal death in stroke, brain trauma, and neurodegenerative disorders. Superoxide production by NADPH oxidase is a requisite event in the process leading from NMDA receptor activation to excitotoxic death. NADPH oxidase generates intracellular H(+) along with extracellular superoxide, and the intracellular H(+) must be released or neutralized to permit continued NADPH oxidase function. In cultured neurons, NMDA-induced superoxide production and neuronal death were prevented by intracellular acidification by as little as 0.2 pH units, induced by either lowered medium pH or by inhibiting Na(+)/H(+) exchange. In mouse brain, superoxide production induced by NMDA injections or ischemia-reperfusion was likewise prevented by inhibiting Na(+)/H(+) exchange and by reduced expression of the Na(+)/H(+) exchanger-1 (NHE1). Neuronal intracellular pH and neuronal Na(+)/H(+) exchange are thus potent regulators of excitotoxic superoxide production. These findings identify a mechanism by which cell metabolism can influence coupling between NMDA receptor activation and superoxide production.

Hesperidin pretreatment protects hypoxia-ischemic brain injury in neonatal rat

Neonatal hypoxia-ischemic encephalopathy (HIE) remains a major cause of brain damage, leading to high disability and mortality rates in neonates. In vitro studies have shown that hesperidin, a flavanone glycoside found abundantly in citrus fruits, acts as an antioxidant. Although hesperidin has been considered as a potential treatment for HIE, its effects have not been fully evaluated. In this study, the protective effect of hesperidin pretreatment against hypoxia-ischemic (HI) brain injury and possible signal pathways were investigated using in vivo and in vitro models. In vivo HI model employed unilateral carotid ligation in postnatal day 7 rat with exposure to 8% hypoxia for 2.5h, whereas in vitro model employed primary cortical neurons of neonatal rats subjected to oxygen and glucose deprivation for 2.5h. Hesperidin pretreatment significantly reduced HI-induced brain tissue loss and improved neurological outcomes as shown in 2,3,5-triphenyltetrazolium chloride monohydrate staining and foot-fault results. The neuroprotective effects of hesperidin are likely the results of preventing an increase in intracellular reactive oxygen species and lipid peroxide levels. Hesperidin treatment also activated a key survival signaling kinase, Akt, and suppressed the P-FoxO3 level. Hesperidin pretreatment protected neonatal HIE by reducing free radicals and activating phosphorylated Akt.

Characterization of oxygen radical formation mechanism at early cardiac ischemia

Myocardial ischemia–reperfusion (I/R) causes severe cardiac damage. Although the primary function of oxymyoglobin (Mb) has been considered to be cellular O₂ storage and supply, previous research has suggested that Mb is a potentially protective element against I/R injury. However, the mechanism of its protective action is still largely unknown. With a real-time fluorescent technique, we observed that at the onset of ischemia, there was a small burst of superoxide (O₂^•–) release, as visualized in an isolated rat heart. Thus, we hypothesize that the formation of O₂^•– correlates to Mb due to a decrease in oxygen tension in the myocardium. Measurement of O₂^•– production in a Langendorff apparatus was performed using surface fluorometry. An increase in fluorescence was observed during the onset of ischemia in hearts perfused with a solution of hydroethidine, a fluorescent dye sensitive to intracellular O₂^•–. The increase of fluorescence in the ischemic heart was abolished by a superoxide dismutase mimic, carbon monoxide, or by Mb-knockout gene technology. Furthermore, we identified that O₂^•– was not generated from the intracellular endothelium but from the myocytes, which are a rich source of Mb. These results suggest that during the onset of ischemia, Mb is responsible for generating O₂^•–. This novel mechanism may shed light on the protective role of Mb in I/R injury.

Ca²⁺/calmodulin-dependent protein kinase II contributes to hypoxic ischemic cell death in neonatal hippocampal slice cultures

We have recently shown that p38MAP kinase (p38MAPK) stimulates ROS generation via the activation of NADPH oxidase during neonatal hypoxia-ischemia (HI) brain injury. However, how p38MAPK is activated during HI remains unresolved and was the focus of this study. Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) plays a key role in brain synapse development, neural transduction and synaptic plasticity. Here we show that CaMKII activity is stimulated in rat hippocampal slice culture exposed to oxygen glucose deprivation (OGD) to mimic the condition of HI. Further, the elevation of CaMKII activity, correlated with enhanced p38MAPK activity, increased superoxide generation from NADPH oxidase as well as necrotic and apoptotic cell death. All of these events were prevented when CaMKII activity was inhibited with KN93. In a neonatal rat model of HI, KN93 also reduced brain injury. Our results suggest that CaMKII activation contributes to the oxidative stress associated with neural cell death after HI.

M9, a novel region of amino-Nogo-A, attenuates cerebral ischemic injury by inhibiting NADPH oxidase-derived superoxide production in mice

AIMS

In acute stroke, neurological damage is due to oxidative stress and neuronal apoptotic death. This study investigated whether Nogo-A 290-562 residues region (M9), fused to the transduction domain of the HIV trans-activator (TAT) protein, is neuroprotective against cerebral ischemia and the mechanisms.

METHODS

Transient focal cerebral ischemia was induced by middle cerebral artery occlusion in male C57BL/6J mice. TAT-M9, its mutation or vehicle was applied via intraperitoneal injection at the onset of reperfusion. The neurobehavioral scores, infarction volumes, neuronal apoptosis, and the ratio of Bax/Bcl-2 were evaluated. Malondialdehyde (MDA), reactive oxygen species (ROS) levels, and NADPH oxidase activation were measured in the presence or absence of the NADPH oxidase inhibitor apocynin or activator tetrabromocinnamic acid (TBCA).

RESULTS

Immunofluorescence results confirmed that TAT-M9 was transduced into brain parenchyma, and it significantly improved neurological behavior, reduced infarct volumes, protected neuronal cells from apoptosis, inhibited activation of NADPH oxidase, and decreased MDA and ROS contents. Furthermore, apocynin imitated the beneficial effects of TAT-M9, while TBCA abolished them.

CONCLUSIONS

Our results demonstrate that TAT-M9 administration attenuates cerebral ischemia by inhibiting NADPH oxidase-mediated oxidative damage and neuronal apoptosis in mice. TAT-M9 may be a potential treatment for cerebrovascular disease.

Hypoxia-ischemia alters nucleotide and nucleoside catabolism and Na+,K+-ATPase activity in the cerebral cortex of newborn rats

It is well known that the levels of adenosine in the brain increase dramatically during cerebral hypoxic-ischemic (HI) insults. Its levels are tightly regulated by physiological and pathophysiological changes that occur during the injury acute phase. The aim of the present study was to examine the effects of the neonatal HI event on cytosolic and ecto-enzymes of purinergic system--NTPDase, 5'-nucleotidase (5'-NT) and adenosine deaminase (ADA)--in cerebral cortex of rats immediately post insult. Furthermore, the Na(+)/K(+)-ATPase activity, adenosine kinase (ADK) expression and thiobarbituric acid reactive species (TBARS) levels were assessed. Immediately after the HI event the cytosolic NTPDase and 5'-NT activities were increased in the cerebral cortex. In synaptosomes there was an increase in the ecto-ADA activity while the Na(+)/K(+) ATPase activity presented a decrease. The difference between ATP, ADP, AMP and adenosine degradation in synaptosomal and cytosolic fractions could indicate that NTPDase, 5'-NT and ADA were differently affected after insult. Interestingly, no alterations in the ADK expression were observed. Furthermore, the Na(+)/K(+)-ATPase activity was correlated negatively with the cytosolic NTPDase activity and TBARS content. The increased hydrolysis of nucleotides ATP, ADP and AMP in the cytosol could contribute to increased adenosine levels, which could be related to a possible innate neuroprotective mechanism aiming at potentiating the ambient levels of adenosine. Together, these results may help the understanding of the mechanism by which adenosine is produced following neonatal HI injury, therefore highlighting putative therapeutical targets to minimize ischemic injury and enhance recovery.

A novel domain of amino-Nogo-A protects HT22 cells exposed to oxygen glucose deprivation by inhibiting NADPH oxidase activity

This study aimed to investigate the protective effect of the M9 region (residues 290-562) of amino-Nogo-A fused to the human immunodeficiency virus trans-activator TAT in an in vitro model of ischemia-reperfusion induced by oxygen-glucose deprivation (OGD) in HT22 hippocampal neurons, and to investigate the role of NADPH oxidase in this protection. Transduction of TAT-M9 was analyzed by immunofluorescence staining and western blot. The biologic activity of TAT-M9 was assessed by its effects against OGD-induced HT22 cell damage, compared with a mutant M9 fusion protein or vehicle. Cellular viability and lactate dehydrogenase (LDH) release were assessed. Neuronal apoptosis was evaluated by flow cytometry. The Bax/Bcl-2 ratio was determined by western blotting. Reactive oxygen species (ROS) levels and NADPH oxidase activity were also measured in the presence or absence of an inhibitor or activator of NADPH oxidase. Our results confirmed the delivery of the protein into HT22 cells by immunofluorescence and western blot. Addition of 0.4 μmol/L TAT-M9 to the culture medium effectively improved neuronal cell viability and reduced LDH release induced by OGD. The fusion protein also protected HT22 cells from apoptosis, suppressed overexpression of Bax, and inhibited the reduction in Bcl-2 expression. Furthermore, TAT-M9, as well as apocynin, decreased NADPH oxidase activity and ROS content. The protective effects of the TAT-M9 were reversed by TBCA, an agonist of NADPH oxidase. In conclusion, TAT-M9 could be successfully transduced into HT22 cells, and protected HT22 cells against OGD damage by inhibiting NADPH oxidase-mediated oxidative stress. These findings suggest that the TAT-M9 protein may be an efficient therapeutic agent for neuroprotection.