Free radical spin trap alpha-phenyl-N-tert-butyl-nitron inhibits caspase-3 activation and reduces brain damage following a severe forebrain ischemic injury

α-Phenyl-N-tert-Butylnitrone and Analogous α-Aryl-N-alkylnitrones as Neuroprotective Antioxidant Agents for Stroke

The recent advances in research on the use of the antioxidant and neuroprotective agent α-phenyl-N-tert-butylnitrone (PBN) for the therapy of stroke have been reviewed. The protective effect of PBN in the transient occlusion of the middle cerebral artery (MCAO) has been demonstrated, although there have been significant differences in the neuronal salvaging effect between PBN-treated and untreated animals, each set of data having quite large inter-experimental variation. In the transient forebrain ischemia model of gerbil, PBN reduces the mortality after ischemia and the neuronal damage in the hippocampal cornu ammonis 1 (CA1) area of the hippocumpus caused by ischemia. However, PBN fails to prevent postischemic CA1 damage in the rat. As for focal cerebral ischemia, PBN significantly reduces cerebral infarction and decreases neurological deficit after ischemia using a rat model of persistent MCAO in rats. Similarly, the antioxidant and neuroprotective capacity of a number of PBN-derived nitrones prepared in the author's laboratory have also been summarized here, showing their high potential therapeutic power to treat stroke.

Potential therapeutic agents for ischemic white matter damage

Ischemic white matter damage (WMD) is increasingly being considered as one of the major causes of neurological disorders in older adults and preterm infants. The functional consequences of WMD triggers a progressive cognitive decline and dementia particularly in patients with ischemic cerebrovascular diseases. Despite the major stride made in the pathogenesis mechanisms of ischemic WMD in the last century, effective medications are still not available. So, there is an urgent need to explore a promising approach to slow the progression or modify its pathological course. In this review, we discussed the animal models, the pathological mechanisms and the potential therapeutic agents for ischemic WMD. The development in the studies of anti-oxidants, free radical scavengers, anti-inflammatory or anti-apoptotic agents and neurotrophic factors in ischemic WMD were summarized. The agents which either alleviate oligodendrocyte damage or promote its proliferation or differentiation may have potential value for the treatment of ischemic WMD. Moreover, drugs with multifaceted protective activities or a wide therapeutic window may be optimal for clinical translation.

Valproic acid attenuates global cerebral ischemia/reperfusion injury in gerbils via anti-pyroptosis pathways

Ischemic stroke is the third most common cause of death and the leading cause of disability worldwide in adults. The antiepileptic drug valproic acid (VPA) was reported to protect cerebral ischemia/reperfusion injury. However, the action mechanism of VPA in cerebral ischemia/reperfusion injury has not been fully understood. We explored the action mechanism of VPA in vivo and in vitro. Gerbils were subjected to transient global cerebral ischemic-reperfusion injury, and hippocampal neuron injury was treated with oxygen-glucose deprivation in vitro. Morris water maze test was performed to evaluate the cognitive dysfunction. Histopathological examinations and western blot were performed to evaluate the pyroptosis of neurons. The results showed that VPA attenuated the cognitive dysfunction, pyroptosis of the gerbils suffer from ischemic-reperfusion injury and decreased hippocampal neurons pyroptosis induced by oxygen-glucose deprivation in vitro. In addition, western blot and real-time PCR analysis revealed that VPA modulated the protein expression of apoptosis repressor with caspase recruitment domain (ARC), caspase-1 and IL-1β/IL-18. Our results suggested that VPA alleviated ischemic/reperfusion injury-mediated neuronal impairment by anti-pyroptotic effects.

Tat-antioxidant 1 protects against stress-induced hippocampal HT-22 cells death and attenuate ischaemic insult in animal model

Oxidative stress-induced reactive oxygen species (ROS) are responsible for various neuronal diseases. Antioxidant 1 (Atox1) regulates copper homoeostasis and promotes cellular antioxidant defence against toxins generated by ROS. The roles of Atox1 protein in ischaemia, however, remain unclear. In this study, we generated a protein transduction domain fused Tat-Atox1 and examined the roles of Tat-Atox1 in oxidative stress-induced hippocampal HT-22 cell death and an ischaemic injury animal model. Tat-Atox1 effectively transduced into HT-22 cells and it protected cells against the effects of hydrogen peroxide (H2O2)-induced toxicity including increasing of ROS levels and DNA fragmentation. At the same time, Tat-Atox1 regulated cellular survival signalling such as p53, Bad/Bcl-2, Akt and mitogen-activate protein kinases (MAPKs). In the animal ischaemia model, transduced Tat-Atox1 protected against neuronal cell death in the hippocampal CA1 region. In addition, Tat-Atox1 significantly decreased the activation of astrocytes and microglia as well as lipid peroxidation in the CA1 region after ischaemic insult. Taken together, these results indicate that transduced Tat-Atox1 protects against oxidative stress-induced HT-22 cell death and against neuronal damage in animal ischaemia model. Therefore, we suggest that Tat-Atox1 has potential as a therapeutic agent for the treatment of oxidative stress-induced ischaemic damage.

Mitochondrial Targeted Antioxidant in Cerebral Ischemia

There has been much evidence suggesting that reactive oxygen species (ROS) generated in mitochondria during cerebral ischemia play a major role in programming the senescence of organism. Antioxidants dealing with mitochondria slow down the appearance and progression of symptoms in cerebral ischemia and increase the life span of organisms. The mechanisms of mitochondrial targeted antioxidants, such as SKQ1, Coenzyme Q10, MitoQ, and Methylene blue, include increasing adenosine triphosphate (ATP) production, decreasing production of ROS and increasing antioxidant defenses, providing benefits in neuroprotection following cerebral ischemia. A number of studies have shown the neuroprotective role of these mitochondrial targeted antioxidants in cerebral ischemia. Here in this short review we have compiled the literature supporting consequences of mitochondrial dysfunction, and the protective role of mitochondrial targeted antioxidants.

Neuroprotective effect of a formula, moschus combined with borneolum synthcticum, from traditional chinese medicine on ischemia stroke in rats

Moschus compatible with borneolum synthcticum is a well-known herb pair in Traditional Chinese Medicine and the present study aims to assess the neuroprotective effect of a formula composed of this herb pair on ischemia stroke in rats. The middle cerebral artery occlusion model of focal cerebral ischemia in rat was performed by using intraluminal suture method. The behavioral scores, infarct volume, and neuron ultrastructure of model and formula-treated rats were investigated after the 2 h of ischemia and 24 h of reperfusion. Meanwhile the expression levels of caspase-3, caspase-9, Bcl-2, and Bax were measured by western blot analysis. The formula treatment showed obvious neuroprotective effect according to significant decrease of the neurological scores (P < 0.01) and the infarct volumes (P < 0.05) when compared to the MCAO group. We also observed that this formula had antiapoptosis activity on neuron cell under electron microscope. Furthermore, our result supported the idea that pro- and postadministration of this formula had an antiapoptosis effect by decreasing remarkably the expression of caspase-3 and caspase-9 (P < 0.05) as well as increasing significantly the ratio of Bcl-2 to Bax (P < 0.01). All evidences demonstrated the neuroprotective effect of this formula on ischemia stroke due to decrease of brain infract volume and modulation of the expression of apoptosis-related proteins.

Neuroprotective effects of the antioxidant action of 2-cyclopropylimino-3-methyl-1,3-thiazoline hydrochloride against ischemic neuronal damage in the brain

Ischemia is characterized by oxidative stress and changes in the antioxidant defense system. Our recent in vitro study showed that 2-cyclopropylimino-3-methyl-1,3-thiazoline hydrochloride protects cortical astrocytes against oxidative stress. In the current study, we examined the effects of 2-cyclopropylimino-3-methyl- 1,3-thiazoline hydrochloride on ischemia-induced neuronal damage in a gerbil ischemia/reperfusion models. Extensive neuronal death in the hippocampal CA1 area was observed 4 days after ischemia/reperfusion. Intraperitoneal injection of 2-cyclopropylimino- 3-methyl-1,3-thiazoline hydrochloride (0.3 mg/kg body weight) significantly prevented neuronal death in the CA1 region of the hippocampus in response to transient forebrain ischemia. 2-Cyclopropylimino-3-methyl-1,3-thiazoline hydrochloride administration reduced ischemia-induced increases in reactive oxygen species levels and malondialdehyde content. It also attenuated the associated reductions in glutathione level and superoxide dismutase, catalase, and glutathione peroxidase activities. Taken together, our results suggest that 2-cyclopropylimino- 3-methyl-1,3-thiazoline hydrochloride protects against ischemia-induced neuronal damage by reducing oxidative stress through its antioxidant actions.

Protective effects of transduced PEP-1-Frataxin protein on oxidative stress-induced neuronal cell death

Reactive oxygen species (ROS) actively contribute to the development of a number of human diseases including ischemia. In response to oxidative stress, frataxin has a significant ability to improve cell survival though its biological function is unclear in relation to ischemia. To explore frataxin's role in protecting against ischemic cell death, we constructed PEP-1-Frataxin cell-permeable fusion protein. In a dose- and time-dependent manner PEP-1-Frataxin rapidly transduced into astrocyte cells and protected them against oxidative stress-induced cell death. Further, using an animal model, immunohistochemical analysis revealed that PEP-1-Frataxin prevented neuronal cell death in the CA1 region of the hippocampus induced by transient forebrain ischemia. These results demonstrate that transduced PEP-1-Frataxin protects against cell death in vitro and in vivo, suggesting that transduction of PEP-1-Frataxin could be useful as a therapeutic agent for various human diseases related to oxidative stress.

Interleukin-1beta-induced brain injury and neurobehavioral dysfunctions in juvenile rats can be attenuated by alpha-phenyl-n-tert-butyl-nitrone

Our previous study showed that perinatal exposure to interleukin-1beta (IL-1beta), an inflammatory cytokine, induces acute injury to developing white matter in the neonatal rat brain, and alpha-phenyl-n-tert-butyl-nitrone (PBN), a free radical scavenger and antioxidant, protects against IL-1beta-induced acute brain injury. The objective of the present study was to further examine whether perinatal exposure to IL-1beta resulted in persistent brain damage and neurological disabilities, and whether PBN offers lasting protection. Intracerebral injection of IL-1beta (1 microg/kg) was performed in postnatal day 5 (P5) Sprague-Dawley rat pups and PBN (100 mg/kg) or saline was administered intraperitoneally 5 min after IL-1beta injection. Perinatal IL-1beta exposure significantly affected neurobehavioral functions in juvenile rats. Although some neurobehavioral deficits such as performance in negative geotaxis, cliff avoidance, beam walking, and locomotion were spontaneously reversible, sustained deficits such as poor performance in the vibrissa-elicited forelimb-placing test, the pole test, the passive avoidance task, and the elevated plus-maze task were still observable at P21. Perinatal IL-1beta exposure resulted in persistent brain damage including enlargement of ventricles, loss of mature oligodendrocytes, impaired myelination as indicated by the decrease in myelin basic protein immunostaining, axonal and dendritic injury, and loss of hippocampal CA1 neurons and tyrosine hydroxylase positive neurons in the substantia nigra and ventral tegmental areas of the rat brain. Treatments with PBN provided lasting protection against the IL-1beta-induced brain injury and improved the associated neurological dysfunctions in juvenile rats, suggesting that prompt treatments for brain injury induced by perinatal infection/inflammation might have important long-term consequences.

Neuroprotection by radical avoidance: search for suitable agents

Neurodegeneration is frequently associated with damage by free radicals. However, increases in reactive oxygen and nitrogen species, which may ultimately lead to neuronal cell death, do not necessarily reflect its primary cause, but can be a consequence of otherwise induced cellular dysfunction. Detrimental processes which promote free radical formation are initiated, e.g., by disturbances in calcium homeostasis, mitochondrial malfunction, and an age-related decline in the circadian oscillator system. Free radicals generated at high rates under pathophysiological conditions are insufficiently detoxified by scavengers. Interventions at the primary causes of dysfunction, which avoid secondary rises in radical formation, may be more efficient. The aim of such approaches should be to prevent calcium overload, to reduce mitochondrial electron dissipation, to support electron transport capacity, and to avoid circadian perturbations. L-theanine and several amphiphilic nitrones are capable of counteracting excitotoxicity and/or mitochondrial radical formation. Resveratrol seems to promote mitochondrial biogenesis. Mitochondrial effects of leptin include attenuation of electron leakage. Melatonin combines all the requirements mentioned, additionally regulates anti- and pro-oxidant enzymes and is, with few exceptions, very well tolerated. In this review, the perspectives, problems and limits of drugs are compared which may be suitable for reducing the formation of free radicals.

New heteroaryl nitrones with spin trap properties: Identification of a 4-furoxanyl derivative with excellent properties to be used in biological systems

A new series of heteroaryl nitrones, 1-7, bearing furoxanyl and thiadiazolyl moieties, were evaluated for their free radical-trapping properties. The physicochemical characterization by electron paramagnetic resonance (EPR) demonstrated its capability to trap and stabilize oxygen-, carbon-, sulfur-, and nitrogen-centered free radicals. The 4-furoxanyl nitrone 3 (FxBN), alpha(Z)-(3-methylfuroxan-4-yl)-N-tert-butylnitrone, showed appropriate solubility in aqueous solution and taking into account that this physicochemical property is very important for biological applications, we studied it deeply in terms of its trapping and kinetic behaviors. For this, kinetic studies of the hydroxyl adduct decay gave rate constants k(ST) of 1.22x10(10)dm(3)mol(-1)s(-1) and half-live up to 7200s at physiological pH, without any artifactual signals. The ability of FxBN to directly traps and stabilizes superoxide free radical, with a half-life of 1620s at physiological pH, was also demonstrated. Besides, FxBN-hydroxyl and -superoxide adducts exhibited distinct and characteristic EPR spectral patterns. Finally, we confirmed the ability of FxBN to act as spin trap in a specific biological system, that is, in the free radical production of experimental anti-trypanosomatid drugs using Trypanosoma cruzi microsomes as biological system. Moreover, previous observations of low FxBN toxicity transform it in a good candidate for in vivo spin trapping.

Interleukin-1beta-induced brain injury in the neonatal rat can be ameliorated by alpha-phenyl-n-tert-butyl-nitrone

To examine the possible role of inflammatory cytokines in mediating perinatal brain injury, we investigated effects of intracerebral injection of interleukin-1beta (IL-1beta) on brain injury in the neonatal rat and the mechanisms involved. Intracerebral administration of IL-1beta (1 microg/kg) resulted in acute brain injury, as indicated by enlargement of ventricles bilaterally, apoptotic death of oligodendrocytes (OLs) and loss of OL immunoreactivity in the neonatal rat brain. IL-1beta also induced axonal and neuronal injury in the cerebral cortex as indicated by elevated expression of beta-amyloid precursor protein, short beaded axons and dendrites, and loss of tyrosine hydroxylase-positive neurons in the substantia nigra and the ventral tegmental areas. Administration of alpha-phenyl-n-tert-butyl-nitrone (PBN, 100 mg/kg i.p.) immediately after the IL-1beta injection protected the brain from IL-1beta-induced injury. Protection of PBN was linked with the attenuated oxidative stress induced by IL-1beta, as indicated by decreased elevation of 8-isoprostane content and by the reduced number of 4-hydroxynonenal or malondialdehyde or nitrotyrosine-positive cells following IL-1beta exposure. PBN also attenuated IL-1beta-stimulated inflammatory responses as indicated by the reduced activation of microglia. The finding that IL-1beta induced perinatal brain injury was very similar to that induced by lipopolysaccharide (LPS), as we previously reported and that PBN was capable to attenuate the injury induced by either LPS or IL-1beta suggests that IL-1beta may play a critical role in mediating brain injury associated with perinatal infection/inflammation.

Radical trapping properties of imidazolyl nitrones

The ability of ten imidazolyl nitrones to directly scavenge free radicals (R(*)) generated in polar ((*)OH, O(*)(2)(-), SO(*)(3)(-) cysteinyl, (*)CH(3)) or in apolar (CH(3)-(*)CH-CH(3)) media has been studied. When oxygen or sulfur-centered radicals are generated in polar media, EPR spectra are not or weakly observed with simple spectral features. Strong line intensities and more complicated spectra are observed with the isopropyl radical generated in an apolar medium. Intermediate results are obtained with (*)CH(3) generated in a polar medium. EPR demonstrates the ability of these nitrones to trap radicals to the nitrone C(alpha) atom (alpha radical adduct) and to the imidazol C(5) atom (5-radical adduct). Beside the nucleophilic addition of the radical to the C(alpha) atom, the EPR studies suggest a two-step mechanism for the overall reaction of R(*) attacking the imidazol core. The two steps seem to occur very fast with the (*)OH radical obtained in a polar medium and slower with the isopropyl radical prepared in benzene. In conclusion, imidazolyl nitrones present a high capacity to trap and stabilize carbon-centered radicals.

alpha-Phenyl-n-tert-butyl-nitrone attenuates lipopolysaccharide-induced brain injury and improves neurological reflexes and early sensorimotor behavioral performance in juvenile rats

Our previous study showed that treatment with alpha-phenyl-n-tert-butyl-nitrone (PBN) after exposure to lipopolysaccharide (LPS) reduced LPS-induced white matter injury in the neonatal rat brain. The object of the current study was to further examine whether PBN has long-lasting protective effects and ameliorates LPS-induced neurological dysfunction. Intracerebral (i.c.) injection of LPS (1 mg/kg) was performed in postnatal day (P) 5 Sprague Dawley rat pups and PBN (100 mg/kg) or saline was administered intraperitoneally 5 min after LPS injection. The control rats were injected (i.c.) with sterile saline. Neurobehavioral tests were carried out from P3 to P21, and brain injury was examined after these tests. LPS exposure resulted in severe brain damage, including enlargement of ventricles bilaterally, loss of mature oligodendrocytes, impaired myelination as indicated by the decrease in myelin basic protein immunostaining, and alterations in dendritic processes in the cortical gray matter of the parietal cortex. Electron microscopic examination showed that LPS exposure caused impaired myelination as indicated by the disintegrated myelin sheaths in the juvenile rat brain. LPS administration also significantly affected neurobehavioral functions such as performance in righting reflex, wire hanging maneuver, cliff avoidance, negative geotaxis, vibrissa-elicited forelimb-placing test, beam walking, and gait test. Treatment with PBN, a free radical scavenger and antioxidant, provided protection against LPS-induced brain injury and associated neurological dysfunction in juvenile rats, suggesting that antioxidation might be an effective approach for therapeutic treatment of neonatal brain injury induced by infection/inflammation.

MEK-inhibitor U0126 in hyperglycaemic focal ischaemic brain injury in the rat

BACKGROUND

Hyperglycaemia aggravates ischaemic brain injury, possibly due to activation of signalling pathways involving mitogen-activated protein kinases (MAPK). In this study, the activation of MAPK/ERK was inhibited using the upstream inhibitor of MAPK-ERK-kinase (MEK) U0126, and the effects on focal brain ischaemia were evaluated during normo- and hyperglycaemia.

MATERIALS AND METHODS

Temporary (90 min) middle cerebral artery occlusion (MCAO) was induced in five groups of rats. U0126 (400 microg kg(-1)) or vehicle was given as 60-min intravenous infusions starting either 30 min prior to MCAO or 30 min prior to reperfusion. The infarct size was determined by perfusion with tetrazolium red after 24 h of survival, and the neurology was tested with the 4-level scale of Bederson and performance on an inclined plane. The inhibitory effect on the targeted MEK enzyme was investigated by analysing the phosphorylation of the downstream target ERK with western immunoblotting. Two subgroups were investigated with magnetic resonance imaging (MRI), including diffusion-weighted (DWI) and perfusion-weighted imaging (PWI).

RESULTS

U0126 effectively reduced the infarct size and improved neurology in hyperglycaemic rats both when given before and after ischemic onset. This effect was not accompanied by any detectable changes in cerebral blood flow on MRI. Normoglycaemic rats had generally milder injuries compared with the hyperglycaemic and there was a nonsignificant trend for U0126 to reduce damage also in the nonhyperglycaemic groups.

CONCLUSIONS

In conclusion, U0126 appears to be neuroprotective in this model of hyperglycaemic ischaemic brain injury. The findings support the pathogenic importance of the MEK-ERK pathway in hyperglycaemic-ischaemic brain injury.

alpha-Phenyl-n-tert-butyl-nitrone reduces lipopolysaccharide-induced white matter injury in the neonatal rat brain

Lipopolysaccharide (LPS)-induced white matter injury in the neonatal rat brain is at least partially associated with oxidative stress. alpha-Phenyl-n-tert-butyl-nitrone (PBN) (100 mg/kg) significantly attenuated LPS (1 mg/kg)-induced brain injury, as indicated by the reduction in bilateral ventricular enlargement, apoptotic cell death of oligodendrocytes (OLs), and the loss of OL immunoreactivity in the neonatal rat brain. Protection of PBN was linked with the attenuated oxidative stress induced by LPS, as indicated by the decreased elevation of 8-isoprostane content and by the reduced number of 4-hydroxynonenal or malondialdehyde positive OLs following LPS exposure. Interestingly, while LPS exposure elevated, rather than depleted, levels of the reduced glutathione (GSH) and the GSH/GSSG (oxidized form) ratio, LPS exposure significantly suppressed glutathione peroxidase activity in the rat brain. PBN attenuated LPS-induced alterations in glutathione homeostasis in the rat brain. Additionally, the inflammatory responses were also reduced in the PBN-treated brain, as indicated by the decreased number of activated microglia following LPS exposure and by the consequently decreased elevation of interleukin1-beta and tumor necrosis factor-alpha contents in the rat brain. The overall results suggest that antioxidant PBN, more than a straightforward free radical scavenger, may also involve anti-inflammatory and anti-apoptotic properties in protection of the neonatal rat brain from LPS-induced injury.

Alpha-Phenyl-n-tert-butyl-nitrone attenuates lipopolysaccharide-induced neuronal injury in the neonatal rat brain

Although white matter damage is a fundamental neuropathological feature of periventricular leukomalacia (PVL), the motor and cognitive deficits observed later in infants with PVL indicate the possible involvement of cerebral neuronal dysfunction. Using a previously developed rat model of white matter injury induced by cerebral lipopolysaccharide (LPS) injection, we investigated whether LPS exposure also results in neuronal injury in the neonatal brain and whether alpha-phenyl-n-tert-butyl-nitrone (PBN), an antioxidant, offers protection against LPS-induced neuronal injury. A stereotactic intracerebral injection of LPS (1 mg/kg) was performed in Sprague-Dawley rats (postnatal day 5) and control rats were injected with sterile saline. LPS exposure resulted in axonal and neuronal injury in the cerebral cortex as indicated by elevated expression of beta-amyloid precursor protein, altered axonal length and width, and increased size of cortical neuronal nuclei. LPS exposure also caused loss of tyrosine hydroxylase positive neurons in the substantia nigra and the ventral tegmental areas of the rat brain. Treatments with PBN (100 mg/kg) significantly reduced LPS-induced neuronal and axonal damage. The protection of PBN was associated with an attenuation of oxidative stress induced by LPS as indicated by the reduced number of 4-hydroxynonenal, malondialdehyde or nitrotyrosine positive cells in the cortical area following LPS exposure, and with the reduction in microglial activation stimulated by LPS. The finding that an inflammatory environment may cause both white matter and neuronal injury in the neonatal brain supports the possible anatomical correlate for the intellectual deficits and the other cortical and deep gray neuronal dysfunctions associated with PVL. The protection of PBN may indicate the potential usefulness of antioxidants for treatment of these neuronal dysfunctions.

Reperfusion injury following cerebral ischemia: pathophysiology, MR imaging, and potential therapies

Introduction

Restoration of blood flow following ischemic stroke can be achieved by means of thrombolysis or mechanical recanalization. However, for some patients, reperfusion may exacerbate the injury initially caused by ischemia, producing a so-called “cerebral reperfusion injury”. Multiple pathological processes are involved in this injury, including leukocyte infiltration, platelet and complement activation, postischemic hyperperfusion, and breakdown of the blood–brain barrier.

Methods/results and conclusions

Magnetic resonance imaging (MRI) can provide extensive information on this process of injury, and may have a role in the future in stratifying patients’ risk for reperfusion injury following recanalization. Moreover, different MRI modalities can be used to investigate the various mechanisms of reperfusion injury. Antileukocyte antibodies, brain cooling and conditioned blood reperfusion are potential therapeutic strategies for lessening or eliminating reperfusion injury, and interventionalists may play a role in the future in using some of these therapies in combination with thrombolysis or embolectomy. The present review summarizes the mechanisms of reperfusion injury and focuses on the way each of those mechanisms can be evaluated by different MRI modalities. The potential therapeutic strategies are also discussed.

Rip immunoreactivity significantly decreases in the stratum oriens of hippocampal CA1 region after transient forebrain ischemia in gerbils

In the present study, we observed ischemia-related changes in Rip recognizing the promyelinating and myelinating oligodendrocytes in the hippocampus proper after 5 min of transient forebrain ischemia in gerbils. Rip immunoreactivity was significantly altered in the hippocampal CA1 region but not in the CA2/3 region after ischemic insult. In the sham-operated group, Rip immunoreactivity was shown in the cell bodies and processes of oligodendrocytes in all layers of the hippocampus proper. From 15 min to 2 days after ischemic insult, Rip immunoreactivity was similar to that of sham-operated group. Three days after ischemic insult, Rip-immunoreactive processes were tangled in the stratum oriens of the CA1 region, and Rip protein level decreased from this time after ischemia. Thereafter, Rip immunoreactivity was decreased time dependently in the CA1 region. Seven days after ischemic insult, Rip-immunoreactive processes were tangled and densely detected in the stratum oriens adjacent to the stratum pyramidale. In brief, these results indicate that the significant decrease of Rip immunoreactivity in processes in the stratum oriens of the hippocampal CA1 region occurs at late time after ischemia, and this decrease in Rip immunoreactivity may be associated with delayed neuronal death of CA1 pyramidal cells.

Protective Effects of Breviscapine on Ischemic Vascular Dementia in Rats

Breviscapine, a traditional Chinese medicine, is extensively used in clinic to treat cardiovascular diseases and cerebrovascular injury. In this study, we demonstrated the effects of breviscapine on vascular dementia (VD) rats, which were mimicked by permanent occlusion of bilateral common carotid arteries. Breviscapine (2 mg/kg for 14 d) improved the performance of learning and memory of VD rats in Morris water maze, decreased the level of lipid peroxidation and free radicals, and attenuated the pathological alterations, such as nuclear shrink, cellular edema and irregular arrangement of pyramidal layer in the hippocampal CA(1) area. In vitro experiment, breviscapine (50 microg/l) protected cortical neuron from injury and decreased intracellular calcium overloading induced by H2O2 (10 mM). The results suggest that breviscapine has therapeutic effect on cerebral ischemia and vascular dementia.

Comparison of Neuroprotective Effects Induced by α-Phenyl-N-tert-butyl nitrone (PBN) and N-tert-Butyl-α-(2 sulfophenyl) nitrone (S-PBN) in Lithium-Pilocarpine Status Epilepticus

The status epilepticus (SE) induced in rats by lithium-pilocarpine (Li-pilo) shares many common features with soman-induced SE including extensive limbic neuropathology. Reactive oxygen species are hypothesized to play a role in the SE induced neuropathology and we propose that the free radical scavengers alpha-phenyl-N-tert-butyl nitrone (PBN) and N-tert-butyl-alpha-(2 sulfophenyl) nitrone (S-PBN) may be neuroprotective. PBN or S-PBN were administered either immediately following pilocarpine (exposure treatment) or 5 min after the onset of SE as determined by ECoG activity. SE was allowed to continue for 3 h before termination with propofol. The rats were sacrified 24 h following pilocarpine administration. S-PBN induced minor effects to reduce SE duration and improve neurological deficit 24 h following pilocarpine administration. One hundred and fifty milligrams per kilograms PBN administered 5 min after SE onset produced significant neuroprotection in the parietal, occipital, perirhinal and piriform cortices as well as the lateral amygdala. One hundred and fifty milligrams per kilograms S-PBN was neuroprotective only in the occipital and perirhinal cortex while 300 mg/kg S-PBN exacerbated cortical neuropathology. S-PBN administered 5 min after SE onset exacerbated neuropathology in thalamic regions. In contrast, PBN and S-PBN administered as exposure treatment exacerbated neuropathology in thalamic and CA3 regions. The differential neuroprotective effects of PBN and S-PBN may be the result of the poor brain penetration by S-PBN. The results suggest that free radical scavenger activity is neuroprotective in cortical regions during cholinergic convulsions. Regional variations in drug-induced neuroprotectant activity in Li-pilo SE are common and suggest multiple mechanisms of neuropathology.

Chelation of intracellular calcium reduces cell death after hyperglycemic in vitro ischemia in murine hippocampal slice cultures

The aggravating effect of high glucose levels during cerebral ischemia has been extensively documented in clinical studies and in vivo models of global and focal ischemia. Detailed mechanistic studies of hyperglycemic ischemia have so far been hampered by the lack of in vitro models since glucose during anoxia in vitro is highly protective. We have previously reported glucose toxicity in murine hippocampal organotypic slice cultures exposed to anoxia in an acidotic medium containing high potassium and low calcium. In the present study, we compared the importance of calcium, nitric oxide and free radicals during in vitro ischemia (IVI) and hyperglycemic (40 mM) IVI. Extracellular calcium was a ubiquitous factor for cell death after IVI, but its removal from the medium had no effect on cell death after hyperglycemic IVI. When intracellular calcium was chelated by the 1,2-Bis(2-amino-5-fluorophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl) ester (BAPTA-AM) cell death appeared earlier but was mitigated in hyperglycemic IVI, while it was increased in glucose-free IVI. Addition of the nitric oxide synthase (NOS) inhibitor N(omega)-Nitro-L-arginine methyl ester hydrochloride (L-NAME) or the free radical scavengers N-tert-butyl-alpha-phenylnitrone (PBN), deferoxamine and N-acetyl-L-cysteine (NAC) did not affect cell damage in either paradigm. We conclude that the aggravating effect of hyperglycemia during in vitro ischemia is partially mediated by calcium ions released from intracellular stores.

Antioxidant-like protein 1 is altered in non-pyramidal cells and expressed in astrocytes in the gerbil hippocampal CA1 region after transient forebrain ischemia

In the present study, we observed chronological changes of antioxidant-like protein 1 (AOP-1) in the gerbil hippocampal CA1 region after 5 min of transient forebrain ischemia using immunohistochemistry and western blot. AOP-1 was significantly altered in the CA1 region after transient ischemia. In the sham-operated group, AOP-1 immunoreactivity was detected in pyramidal and non-pyramidal cells of the CA1 region. At 30 min after ischemic insult, AOP-1 immunoreactivity and protein level was decreased in the CA1 region. At 12 h after ischemic insult, AOP-1 immunoreactivity and protein level was highest in this region. At this time, after ischemia, AOP-1 immunoreactivity in non-pyramidal cells was high compared to the sham-operated group. Based on double immunofluorescence study, AOP-1-immunoreactive neurons were identified as GABAergic, which were stained with GAD or parvalbumin. Thereafter, AOP-1 immunoreactivity and protein levels were decreased time-dependently. From 4 days after ischemic insult, AOP 1 immunoreactivity was generally expressed in astrocytes. Five days after ischemic insult, AOP-1 immunoreactivity and protein level was increased again to 1.4 folds compared to that of the sham-operated group. In brief, AOP-1 immunoreactivity was increased in GABAergic non-pyramidal cells in the hippocampal CA1 region at early time after ischemic insult and was expressed in astrocytes at late time after ischemia. This result suggests that AOP-1 may be important role in homeostasis of GABAergic neurons because these neurons are resistant to ischemic damage.

Copper chaperone for Cu,Zn-SOD supplement potentiates the Cu,Zn-SOD function of neuroprotective effects against ischemic neuronal damage in the gerbil hippocampus

In the present study, we investigated the chronological alterations in SOD1 and its copper chaperone (chaperone for superoxide dismutase, CCS) immunoreactivities and their neuroprotective effects against neuronal damage in the gerbil hippocampus after 5 min of transient forebrain ischemia. SOD1 and CCS immunoreactivities were significantly increased in the stratum pyramidale of the CA1 region at 24 and 12 h after ischemic insult, respectively. At 24 h after ischemic insult, the SOD1 and CCS immunoreactivities were colocalized in the CA1 pyramidal cells of the stratum pyramidale. Thereafter, their immunoreactivities were significantly decreased in the CA1 region. To elucidate the effects of CCS or CCS/SOD1, we constructed the expression vectors PEP-1-SOD and PEP-1-CCS. In the CCS-treated group and the CCS/SOD1-treated group, 43.9 and 78.9% pyramidal cells, respectively, compared to the sham-operated group, were stained with cresyl violet 5 or 7 days after ischemic insult. The distribution pattern of active astrocytes and microglia in the PEP-CCS/SOD1-treated group 5 days after ischemic insult was similar to that of the sham-operated group. In addition, the SOD activity in the PEP-CCS- or PEP-CCS/SOD1-treated group was maintained by 10 days after ischemic insult. The SOD activity was higher in the PEP-CCS/SOD1-treated group vs the CCS-treated group. These results suggest that the enhanced expression of SOD1 and CCS may be related to compensatory mechanisms against ischemic damage and that cotreatment with CCS and SOD1 has a greater neuroprotective effect than treatment with CCS or SOD1 in isolation.

α-Phenyl-n-tert-butyl-nitrone attenuates hypoxic–ischemic white matter injury in the neonatal rat brain

White matter of the neonatal brain is highly sensitive to hypoxic-ischemic insult. The susceptibility of premature oligodendrocytes (OLs) to free radicals (FRs) produced during hypoxia-ischemia (HI) has been proposed as one of the mechanisms involved. To test this hypothesis, and to further investigate if the FR scavenger alpha-phenyl-N-tert-butyl-nitrone (PBN) attenuates hypoxic-ischemic white matter damage (WMD), postnatal day 4 (P4) SD rats were subjected to bilateral common carotid artery ligation (BCAL), followed by 8% oxygen exposure for 20 min. Pathological changes were evaluated on P6 and P9, 2 and 5 days after the HI insult. HI caused severe WMD including rarefaction, necrosis and cavity formation in the corpus callosum, external and internal capsule areas. OL injury was evidenced by degeneration of O4 positive OLs on P6. Disrupted myelination was verified by decreased immunostaining of myelin basic protein (MBP) on P9. Axonal injury was demonstrated by increased amyloid precursor protein (APP) immunostaining on both P6 and P9. Two lipid peroxidation end products, malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), showed a one-fold elevation within 1-24 h following HI. 4-HNE immunostaining was found to specifically localize in the white matter area. Furthermore, pyknotic O4+ OLs were double-labeled with 4-HNE. These findings suggest that FRs are involved in the pathogenesis of neonatal WMD. PBN (100 mg/kg, i.p.) treatment alleviated the pathological changes of WMD following HI. It improved the survival of O4 positive OLs, attenuated hypomyelination and reduced axonal damage. PBN treatment also decreased the brain concentration of MDA/4-HNE and positive 4-HNE staining in the white matter area. These findings indicate that in the current WMD model, PBN protects both OLs and axons, the two main components in the white matter, from neonatal HI insult. FR scavenging appears to be the primary mechanism underlying its neuroprotective effect.

Development of the nitrone-based spin trap agent NXY-059 to treat acute ischemic stroke

The only current FDA-approved treatment for acute ischemic stroke is thrombolysis with tissue plasminogen activator (tPA). However, there are numerous shortcomings to tPA treatment including an increased incidence of intracerebral hemorrhage (ICH) and a short therapeutic window (3-6 h). In recent years, studies have attempted to identify new therapeutics that might be neuroprotective following ischemic strokes. Free radical scavenging spin trap agents have been proposed as potential candidates for stroke therapy because of the hypothesized role of free radicals in the progression of stroke and ischemia-induced neurodegeneration. Novel spin trap agents like (disodium-[(tert-butylimino) methyl] benzene-1,3-disulfonate N-oxide (NXY-059) are of particular interest, not only because they are broad-spectrum nitrone-based free radical scavengers, but also because of their safety profile in humans. Moreover, the rationale for developing NXY-059 for the treatment of acute ischemic stroke is further supported by the drug's reported neuroprotective effects. In addition, NXY-059 may represent a useful adjunct stroke therapy to tPA, since preclinical studies have demonstrated that NXY-059 increases the therapeutic window for tPA and lowers the occurrence of tPA-induced ICH.

Nitrones as neuroprotective agents in cerebral ischemia, with particular reference to NXY-059

Stroke is a major clinical problem, and acute pharmacological intervention with neuroprotective agents has so far been unsuccessful. Recently, there has been considerable interest in the potential therapeutic benefit of nitrone-derived free radical trapping agents as neuroprotective agents. Nitrone compounds have been shown to be beneficial in animal models of various diseases, and the prototypic compound alpha-phenyl-N-tert-butylnitrone (PBN) has been extensively demonstrated to be neuroprotective in rat models of transient and permanent focal ischemia. The nitrone radical trapping agent disodium 2,4-disulfophenyl-N-tert-butylnitrone (NXY-059) has also been shown to be neuroprotective in these models. Furthermore, it has recently been shown to improve neurological function and reduce infarct volume in a primate model of permanent focal ischemia even when given 4 hr postocclusion. While radical trapping activity is demonstrable with NXY-059 and other nitrone compounds such as PBN, this activity is weak. Arguments for and against ascribing radical trapping as the therapeutic mechanism of action are discussed. This compound is well tolerated in human stroke patients and can be administered to produce plasma concentrations exceeding those effective in animal models; crucially, at the same time, it has also been shown to be effective in animal models. NXY-059 may thus be the first compound to be examined in stroke patients using drug exposure and time to treatment that have been shown to be effective in animal models of stroke.

Stilbazulenyl nitrone, a novel antioxidant, is highly neuroprotective in focal ischemia

Azulenyl nitrones are novel chain-breaking antioxidants with low oxidation potentials and high lipophilicity-properties favoring their efficacy as neuroprotectants. We tested the second-generation azulenyl nitrone, stilbazunenlyl nitrone (STAZN), in focal ischemic stroke. Physiologically monitored rats received 2 hours of middle cerebral artery occlusion by intraluminal suture, resulting in substantial cortical and striatal infarcation. Neurobehavior was quantified on a standard battery, and brains were perfusion-fixed for quantitative histopathology at 3 days. In 3 independent series, rats were treated at either 2h + 4h, or 2h + 4h + 24h + 48h, after onset of ischemia; vehicle-treated rats received dimethylsulfoxide or saline. All animals (n = 52) developed high-grade neurological deficits (score 11 of 12) during ischemia, which improved, in STAZN-treated rats, within 1-1.5 h of the initial dose and fell to a median score of 3 at 72 h, compared to 8 in vehicle rats. STAZN treatment reduced mean cortical infarct volume by 64-97%, and total infarct volume by 42-72%. In over one-half of STAZN-treated animals, cortical infarction was virtually abolished. Regression analysis predicted that STAZN would confer approximately 50% cortical neuroprotection even in the most severely affected cases. The potency of STAZN was orders-of-magnitude greater than other nitrones such as NXY-059. These results suggest that STAZN has great promise for ischemic stroke.

Postischemic hypothermia inhibits the generation of hydroxyl radical following transient forebrain ischemia in rats

A small reduction of body temperature during reperfusion following cerebral ischemia has been known to ameliorate neuronal injury. However, the mechanisms underlying postischemic hypothermia-induced neuroprotection are poorly understood. The burst of reactive oxygen species (ROS) formation that occurs during reperfusion has been documented to be involved in ischemic neuronal degeneration. In this study, we investigated the effect of postischemic hypothermia on ROS production following transient forebrain ischemia using an in vivo microdialysis technique. Forebrain ischemia was induced by bilateral carotid artery occlusion combined with hemorrhagic hypotension for 20 min in male Wistar rats. The body temperature was kept at 37 degrees C during ischemia and controlled at either 32 degrees C or 37 degrees C after reperfusion. The amount of hydroxyl radical produced in striatum was evaluated by measurement of 2,3- and 2,5-dihydroxybenzoic acid (DHBA), which is generated by salicylate hydroxylation. We also measured the extracellular concentration of xanthine, while determining striatal blood flow by the hydrogen clearance technique. In animals whose postischemic body temperature was maintained at 37 degrees C, the levels of 2,3- and 2,5-DHBA significantly increased after reperfusion. The peak levels of 2,3- and 2,5- DHBA were 2.9-fold and 2.7-fold increased above the corresponding baseline values, respectively. Postischemic hypothermia completely inhibited the hydroxyl radical formation. Likewise, xanthine formation was also inhibited by postischemic hypothermia. In contrast, striatal cerebral blood flow was not altered by temperature modulation during reperfusion. These results suggest that inhibition of ROS production accompanied with suppression of xanthine formation is implicated in the neuroprotection of postischemic hypothermia.

Combined argatroban and edaravone caused additive neuroprotection against 15 min of forebrain ischemia in gerbils

We investigated whether or not a combination of the selective thrombin inhibitor, argatroban, and the free radical scavenger, edaravone (MCI-186), ameliorates postischemic hypoperfusion and decreases mortality after 15 min of forebrain ischemia in the gerbil. Argatroban or edaravone alone significantly increased postischemic cerebral blood flow and attenuated brain edema after reperfusion. However, only the combination increased the survival ratio (P<0.05 by Mantel-Cox) and protected the damage of neuronal cells. The present study indicates that anticoagulants and free radical scavengers reciprocally function to inhibit the progression of ischemic cell damage and that a combination of these types of drugs will help to improve the outcomes after cerebral ischemia.