New method for the quantitative assessment of axonal damage in focal cerebral ischemia

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.

Axonal damage and behavioral deficits in rats with repetitive exposure of the brain to laser-induced shock waves: Effects of inter-exposure time

Much attention has been given to effects of repeated exposure to a shock wave as a possible factor causing severe higher brain dysfunction and post-traumatic stress disorder (PTSD)-like symptoms in patients with mild to moderate blast-induced traumatic brain injury (bTBI). However, it is unclear how the repeated exposure and the inter-exposure time affect the brain. In this study, we topically applied low-impulse (∼54 Pa·s) laser-induced shock waves (LISWs; peak pressure, ∼75.7 MPa) to the rat brain once or twice with the different inter-exposure times (15 min, 1 h, 3 h, 24 h and 7 days) and examined anxiety-related behavior and motor dysfunction in the rats as well as expression of β-amyloid precursor protein (APP) as an axonal damage marker in the brains of the rats. The averaged APP expression scores for the rat brains doubly-exposed to LISWs with inter-exposure times from 15 min to 24 h were significantly higher than those for rats with a single exposure (P < 0.0001). The rats with double exposure to LISWs showed significantly more frequent anxiety-related behavior (P < 0.05) and poorer motor function (P < 0.01) than those of rats with a single exposure. When the inter-exposure time was extended to 7 days, however, the rats showed no significant differences either in axonal damage score or level of motor dysfunction. The results suggest that the cumulative effects of shock wave-related brain injury can be avoided with an appropriate inter-exposure time. However, clinical bTBI occurs in much more complex environments than those in our model. Further study considering other factors, such as the effects of acceleration, is needed to know the clinically-relevant, necessary inter-exposure time.

Post-ischemic treatment of WIB801C, standardized Cordyceps extract, reduces cerebral ischemic injury via inhibition of inflammatory cell migration

ETHNOPHARMACOLOGICAL RELEVANCE

Anti-inflammatory therapy has been intensively investigated as a potential strategy for treatment of cerebral stroke. However, despite many positive outcomes reported in animal studies, anti-inflammatory treatments have not proven successful in humans as yet. Although immunomodulatory activity and safety of Cordyceps species (Chinese caterpillar fungi) have been proven in clinical trials and traditional Asian prescriptions for inflammatory diseases, its anti-ischemic effect remains elusive.

AIM OF THE STUDY

In the present study, therefore, we investigated the potential therapeutic efficacy of WIB801C, the standardized extract of Cordyceps militaris, for treatment of cerebral ischemic stroke.

MATERIALS AND METHODS

The anti-chemotactic activity of WIB801C was assayed in cultured rat microglia/macrophages. Sprague-Dawley rats were subjected to ischemic stroke via either transient (1.5-h tMCAO and subsequent 24-h reperfusion) or permanent middle cerebral artery occlusion (pMCAO for 24-h without reperfusion). WIB801C was orally administered twice at 3- and 8-h (50mg/kg each) after the onset of MCAO. Infarct volume, edema, blood brain barrier and white matter damages, neurological deficits, and long-term survival rates were investigated. The infiltration of inflammatory cells into ischemic lesions was assayed by immunostaining.

RESULTS

WIB801C significantly decreased migration of cultured microglia/macrophages. This anti-chemotactic activity of WIB-801C was not mediated via adenosine A3 receptors, although cordycepin, the major ingredient of WIB801C, is known as an adenosine receptor agonist. Post-ischemic treatment with WIB801C significantly reduced the infiltration of ED-1-and MPO-positive inflammatory cells into ischemic lesions in tMCAO rats. WIB801C-treated rats exhibited significantly decreased infarct volume and cerebral edema, less white matter and blood-brain barrier damages, and improved neurological deficits. WIB801C also improved survival rates over 34 days after ischemia onset. A significant reduction in infarct volume and neurobehavioral deficits by WIB801C was also observed in rats subjected to pMCAO.

CONCLUSIONS

In summary, post-ischemic treatment of WIB801C reduced infiltration of inflammatory cells into ischemic lesions via inhibition of chemotaxis, which confers long-lasting histological and neurological protection in ischemic brain. WIB801C may be a promising anti-ischemic drug candidate with clinically relevant therapeutic time window and safety.

Preclinical stroke research--advantages and disadvantages of the most common rodent models of focal ischaemia

This review describes the most commonly used rodent models and outcome measures in preclinical stroke research and discusses their strengths and limitations. Most models involve permanent or transient middle cerebral artery occlusion with therapeutic agents tested for their ability to reduce stroke-induced infarcts and improve neurological deficits. Many drugs have demonstrated preclinical efficacy but, other than thrombolytics, which restore blood flow, none have demonstrated efficacy in clinical trials. This failure to translate efficacy from bench to bedside is discussed alongside achievable steps to improve the ability of preclinical research to predict clinical efficacy: (i) Improvements in study quality and reporting. Study design must include randomization, blinding and predefined inclusion/exclusion criteria, and journal editors have the power to ensure statements on these and mortality data are included in preclinical publications. (ii) Negative and neutral studies must be published to enable preclinical meta-analyses and systematic reviews to more accurately predict drug efficacy in man. (iii) Preclinical groups should work within networks and agree on standardized procedures for assessing final infarct and functional outcome. This will improve research quality, timeliness and translational capacity. (iv) Greater uptake and improvements in non-invasive diagnostic imaging to detect and study potentially salvageable penumbral tissue, the target for acute neuroprotection. Drug effects on penumbra lifespan studied serially, followed by assessment of behavioural outcome and infarct within in the same animal group, will increase the power to detect drug efficacy preclinically. Similar progress in detecting drug efficacy clinically will follow from patient recruitment into acute stroke trials based on evidence of remaining penumbra.

Combination treatment of experimental stroke with Niaspan and Simvastatin, reduces axonal damage and improves functional outcome

In this study we examined the effect of combination treatment of experimental stroke with Niaspan, a prolonged-release formulation of Niacin (vitamin B3), and Simvastatin, a cholesterol-lowering drug, on functional outcome, axonal damage, axonal density and the of Iba-1 immunoreactive microglia expression in the ischemic brain of rats. Adult male rats were subjected to 2 h middle cerebral artery occlusion (MCAo) and treated with or without Niaspan alone, Simvastatin alone and combination Niaspan and Simvastatin starting 24 h after MCAo and daily for 14 days. Neurological functional tests were performed. Axonal damage and density were evaluated by Amyloid Precursor Protein (APP) and Bielschowsky silver, respectively. Nogo66 Receptor (NgR) expression and immunoreactive microglia (Iba-1) were also measured in the ischemic brain. Niaspan and Simvastatin monotherapy and combination treatment significantly promote functional outcome after stroke (p<0.05) compared to MCAo control animals. Combination treatment with Niaspan and Simvastatin induces additive but not synergetic effects when compared to Niaspan or Simvastatin monotherapy groups. Combination treatment significantly decreased APP expression and increased Bielschowsky silver expression. NGR and Iba-1 expression were significantly decreased in the ischemic brain. These data suggest that treatment of experimental stroke with combination of Niaspan and Simvastatin significantly improves functional outcome, reduces axonal damage and increases axonal density. Decreased expression of the NGR and reduced activated microglia may contribute to functional recovery after stroke.

Nogo-A is involved in secondary axonal degeneration of thalamus in hypertensive rats with focal cortical infarction

We investigate whether Nogo-A is involved in the secondary axonal degeneration in the thalamus after distal middle cerebral artery occlusion (MCAO) in stroke-prone renovascular hypertensive rats (RHRSP). The expression of Nogo-A in ipsilateral ventroposterior nucleus (VPN) of the thalamus in RHRSP was observed at 1, 2 and 4 weeks after distal MCAO. In addition, intracerebroventricular infusion of NEP1-40, a Nogo-66 receptor (NgR) antagonist peptide, was administered starting 24 h after MCAO and continued for 1, 2 and 4 weeks, respectively. Axonal damage and regeneration were evaluated by analysis of the immunoreactivity (IR) of amyloid betaA4 precursor protein (APP), growth associated protein 43 (GAP-43) and microtubule associated protein 2 (MAP-2) in ipsilateral VPN of the thalamus at 1, 2 and 4 weeks after distal MCAO. Following ischemia, the expression of Nogo-A in oligodendrocytes increased persistently and its localization became redistributed around damaged axons and dendrites. Administration of NEP1-40 downregulated the expression of Nogo-A, reduced axonal injury and enhanced axonal regeneration. Our data suggest that Nogo-A is involved in secondary axonal degeneration and that inhibition of Nogo-A can reduce neuronal damage in the thalamus after distal MCAO.

Controlled low-pressure perfusion at the beginning of reperfusion attenuates neurologic injury after spinal cord ischemia

OBJECTIVE

Paraplegia caused by spinal cord ischemia remains a serious complication after surgical repair of thoracoabdominal aortic aneurysms. This study tests the hypothesis that controlled low-pressure perfusion at the beginning of reperfusion can attenuate neurologic injury of the spinal cord after transient ischemia.

METHODS

Spinal cord ischemia was accomplished in rabbits by occlusion of the infrarenal aorta with a balloon catheter for 25 minutes. In the normal reperfusion group, reperfusion was completely restored immediately after ischemia, whereas perfusion pressure was controlled between 45 and 55 mm Hg during the first 10 minutes followed by complete reperfusion in the low-pressure reperfusion group. Functional evaluation with the Tarlov score during a 14-day observation period, histopathologic assessment of the lumbar spinal cord, and measurements of malondialdehyde levels and amyloid precursor protein immunoreactivity were performed.

RESULTS

Neurologic impairment was remarkably attenuated in the low-pressure reperfusion group (compared with the Tarlov scores of the normal reperfusion group, P < .05 at day 2; P < .01 at days 1, 7, and 14). Compared with the normal reperfusion group, malondialdehyde levels were significantly lower in the low-pressure reperfusion group (P < .05), and the large motor neurons of the low-pressure reperfusion group were preserved to a much greater extent (P < .05). White matter injury of the low-pressure reperfusion group was also markedly attenuated as evidenced by reduction of vacuolation area of the white matter (P < .05) and decrease of the amyloid precursor protein immunoreactivity (P < .05).

CONCLUSION

Reperfusion initiated with low-pressure perfusion exerts neuroprotective effects on the spinal cord against ischemia/reperfusion injury.

Transient cognitive deficits are associated with the reversible accumulation of amyloid precursor protein after mild traumatic brain injury

Mild traumatic brain injury (MTBI) may frequently cause transient behavioral abnormalities without observable morphological findings. In this study, we investigated neuropathological mechanisms underlying transient cognitive deficits after MTBI. Mongolian gerbils were subjected to experimental MTBI. At various time points after injury, behavioral changes were evaluated by the open-field test and T-maze test, and immunohistochemistry of microtubule-associated protein (MAP2) and amyloid precursor protein (APP) was performed to examine disruptions of the neuronal cytoskeleton and axonal transport, respectively. Transient cognitive deficits were observed after MTBI. Sustained MAP2 loss was found within the cortical impact site, but not the hippocampus. Transient APP accumulation at the same time as transient cognitive deficits occurred in the ipsilateral hemisphere, particularly in the subcortical white matter. These results suggest that the axonal dysfunction indicated by the reversible APP accumulation in the white matter, but not the sustained neuronal cytoskeletal damage reflected by the cortical MAP2 loss confined to the impact site, is responsible for the transient functional deficits after MTBI.

Melatonin decreases neurovascular oxidative/nitrosative damage and protects against early increases in the blood-brain barrier permeability after transient focal cerebral ischemia in mice

We have recently shown that melatonin decreases the late (24 hr) increase in blood-brain barrier (BBB) permeability and the risk of tissue plasminogen activator-induced hemorrhagic transformation following ischemic stroke in mice. In the study, we further explored whether melatonin would reduce postischemic neurovascular oxidative/nitrosative damage and, therefore, improve preservation of the early increase in the BBB permeability at 4 hr after transient focal cerebral ischemia for 60 min in mice. Melatonin (5 mg/kg) or vehicle was given intraperitoneally at the beginning of reperfusion. Hydroethidine (HEt) in situ detection and immunohistochemistry for nitrotyrosine were used to evaluate postischemic accumulation in reactive oxygen and nitrogen species, respectively, in the ischemic neurovascular unit. BBB permeability was evaluated by spectrophotometric and microscopic quantitation of Evans Blue leakage. Relative to controls, melatonin-treated animals not only had a significantly reduced superoxide accumulation in neurovascular units in boundary zones of infarction, by reducing 35% and 54% cytosolic oxidized HEt in intensity and cell-expressing percentage, respectively (P < 0.001), but also exhibited a reduction in nitrotyrosine by 52% (P < 0.01). Additionally, melatonin-treated animals had significantly reduced early postischemic disruption in the BBB permeability by 53% (P < 0.001). Thus, melatonin reduced postischemic oxidative/nitrosative damage to the ischemic neurovascular units and improved the preservation of BBB permeability at an early phase following transient focal cerebral ischemia in mice. The findings further highlight the ability of melatonin in anatomical and functional preservation for the ischemic neurovascular units and its relevant potential in the treatment of ischemic stroke.

Ebselen induced C6 glioma cell death in oxygen and glucose deprivation

Studies have shown that ebselen is an antiinflammatory and antioxidative agent. Its protective effect has been investigated in oxidative stress related diseases such as cerebral ischemia in recent years. However, experimental evidence also shows that ebselen causes cell death in several different cell types. Whether ebselen will have a beneficial or detrimental effect on cells under ischemic condition is not known. Herein, we studied the effect of ebselen on C6 glioma cells under oxygen and glucose deprivation (OGD), an in vitro ischemic model. We found that ebselen significantly enhanced cell death after 3 h of OGD as observed by lactase dehydrogenase (LDH) release and cellular morphological changes. Further studies revealed that depletion of cellular glutathione level by the combined action of ebselen and OGD played a role in enhanced cell death as demonstrated by the following evidence: (1) cellular GSH was significantly depleted by the combined effort of ebselen and OGD, compared to that of ebselen or OGD insult alone; (2) exogenous addition of N-acetyl cysteine completely diminished the cell damage induced by ebselen and OGD; (3) supplement of glucose, which provides cellular reducing agents and thus maintains cellular GSH level, to the OGD medium diminished C6 cell damage induced by ebselen. We conclude that depleting cellular glutathione plays an important role in ebselen-induced cell death with OGD. Our results suggest that ebselen can have a beneficial or toxic effect, depending on the availability of GSH.

Temporal window of vulnerability to repetitive experimental concussive brain injury

OBJECTIVE

Repetitive concussive brain injury (CBI) is associated with cognitive alterations and increased risk of neurodegenerative disease.

METHODS

To evaluate the temporal window during which the concussed brain remains vulnerable to a second concussion, anesthetized mice were subjected to either sham injury or single or repetitive CBI (either 3, 5, or 7 days apart) using a clinically relevant model of CBI. Cognitive, vestibular, and sensorimotor function (balance and coordination) were evaluated, and postmortem histological analyses were performed to detect neuronal degeneration, cytoskeletal proteolysis, and axonal injury.

RESULTS

No cognitive deficits were observed in sham-injured animals or those concussed once. Mice subjected to a second concussion within 3 or 5 days exhibited significantly impaired cognitive function compared with either sham-injured animals (P < 0.05) or mice receiving a single concussion (P < 0.01). No cognitive deficits were observed when the interconcussion interval was extended to 7 days, suggestive of a transient vulnerability of the brain during the first 5 days after an initial concussion. Although all concussed mice showed transient motor deficits, vestibulomotor dysfunction was more pronounced in the group that sustained two concussions 3 days apart (P < 0.01 compared with all other groups). Although scattered degenerating neurons, evidence of cytoskeletal damage, and axonal injury were detected in selective brain regions between 72 hours and 1 week after injury in all animals sustaining a single concussion, the occurrence of a second concussion 3 days later resulted in significantly greater traumatic axonal injury (P < 0.05) than that resulting from a single CBI.

CONCLUSION

These data suggest that a single concussion is associated with behavioral dysfunction and subcellular alterations that may contribute to a transiently vulnerable state during which a second concussion within 3 to 5 days can lead to exacerbated and more prolonged axonal damage and greater behavioral dysfunction.

Contributors to white matter damage in the frontal lobe in Alzheimer's disease

Abnormalities of cerebral white matter are present in a majority of patients with Alzheimer's disease (AD) and probably contribute to motor dysfunction and cognitive impairment. The white matter abnormalities are usually attributed to degenerative vascular disease and cerebral amyloid angiopathy (CAA) but the evidence is scanty or inconclusive. In the present study we examined sections of frontal lobe from 125 autopsy-confirmed cases of AD and assessed the relationship of degenerative large and small vessel disease, CAA, parenchymal Abeta load and APOE genotype, to several objective measures of white matter damage: extent of immunolabelling for glial fibrillary acidic protein (GFAP), axonal accumulation of amyloid precursor protein (APP), axon density in superficial and deep white matter, and intensity of staining for myelin. We found no association between atherosclerosis, arteriolosclerosis, CAA or APOE genotype and white matter damage. However, labelling of white matter for GFAP correlated strongly with the parenchymal Abeta load (P = 0.0003) and with APP accumulation (P = 0.008). Our findings suggest that severity of frontal white matter damage in AD is closely related to parenchymal Abeta load and that in most cases the contribution of degenerative vascular disease, CAA and APOE is relatively minor.

Cilostazol Attenuates Gray and White Matter Damage in a Rodent Model of Focal Cerebral Ischemia

Background and Purpose— To evaluate whether delayed treatment with the antiplatelet agent cilostazol reduces the volume of infarction in the gray and white matter in a rodent model of permanent focal cerebral ischemia and to explore the mechanism of the neuroprotective effect in vivo.

Methods— Cilostazol (30 or 50 mg/kg) or vehicle was administered by gavage 30 minutes and 4 hours after the induction of cerebral ischemia by permanent occlusion of the left middle cerebral artery (MCA). Animals were euthanized 24 hours after MCA occlusion, and the volume of gray matter damage was evaluated by quantitative histopathology. Axonal damage was determined with amyloid precursor protein immunohistochemistry. Dynamic susceptibility contrast MRI was used to assess regional cerebral blood volume (CBV) and cerebral blood flow (CBF).

Results— Treatment with the higher dose of cilostazol (50 mg/kg) significantly reduced the volume of gray matter damage and axonal damage in the cerebral hemisphere by 45.0% ( P <0.02) and 42.4% ( P <0.002), respectively, compared with the control group. Relative CBV in the peri-infarct area after MCA occlusion was significantly increased in the cilostazol-treated group (50 mg/kg) compared with the control group ( P <0.05). Relative CBF tended to be higher in the cilostazol-treated group compared with the control group.

Conclusions— Treatment with cilostazol significantly reduced the gray and white matter damage associated with permanent focal ischemia. Cilostazol improved CBV and CBF in the peri-infarct area. The major action of cilostazol is to increase perfusion in the ischemic penumbra.

An Evaluation of White Matter Injury After Spinal Cord Ischemia in Rats: A Comparison with Gray Matter Injury

We quantitatively assessed both gray and white matter injury after spinal cord ischemia in rats, and the relationship between the magnitude of gray and white matter injury was determined. Twenty-five male rats were anesthetized with isoflurane, and spinal cord ischemia (SCI) was induced by balloon intraaortic occlusion combined with hypotension. The animals were randomly allocated to one of the following three groups: animals with SCI for 12 min (SCI-12; n = 8), 15 min (SCI-15; n = 9), or those with sham operation (n = 8). Twenty-four hours after reperfusion, hindlimb motor function was assessed using the Basso-Beattie-Bresnahan scale scoring. Gray matter damage was assessed on the basis of the number of normal neurons in the ventral horn. White matter damage was assessed on the basis of the extent of vacuolation and amyloid precursor protein immunoreactivity in the ventral and ventrolateral white matter. There were significantly less normal neurons in the SCI-15 group compared with those in the SCI-12 and sham groups (P < 0.05). There was a significant positive correlation between the Basso-Beattie-Bresnahan scores and the number of normal neurons. The percentages of vacuolation areas in the SCI-15 group were significantly larger compared with those in the SCI-12 and sham groups (30% +/- 10% versus 9% +/- 7%, 0% +/- 0%, P < 0.05). Immunohistochemical analysis revealed increased amyloid precursor protein immunoreactivity in the swollen axons, especially in the SCI-15 group. There was a significant negative correlation between the number of normal neurons and percentages of vacuolation areas. These results indicate that both gray and white matter were injured after SCI in rats and the degree of white mater injury was correlated with the severity of gray matter injury after a relatively short recovery period.

Detrimental effects of 17beta-oestradiol after permanent middle cerebral artery occlusion

Oestrogen is a complex hormone whose role as a neuroprotectant in experimental stroke has been published in numerous studies. However, although some clinical studies report a reduction in stroke incidence by oestrogen replacement therapy in postmenopausal women, others have found increased mortality and morbidity after stroke. Diathermy occlusion of the proximal middle cerebral artery (MCAO), one of the most reproducible rodent stroke models, has consequently been employed to investigate physiologic and supraphysiologic doses of 17beta-oestradiol on ischaemic brain damage. Lister Hooded rats were ovariectomised (OVX) and a 21-day release pellet (placebo, 0.025 or 0.25 mg 17beta-oestradiol) implanted in the neck. At 2 weeks after OVX, animals underwent MCAO and were perfusion fixed 24 hours later. Neuronal perikaryal damage was assessed from haematoxylin and eosin-stained sections and in adjacent sections, axonal pathology was assessed with amyloid precursor protein and Neurofilament 200 (NF-200) immunohistochemistry. 17beta-Oestradiol induced a dose-dependent increase in neuronal perikaryal damage, 0.025 and 0.25 mg 17beta-oestradiol increased damage by 20% (P<0.05) and 27.5% (P<0.01) compared with placebo. 17beta-Oestradiol did not influence axonal pathology compared with placebo. Our results suggest that 17beta-oestradiol treatment can exacerbate brain damage in experimental stroke. Thus, further investigation into the role of oestrogen and the mechanisms which mediate its effects in stroke is required.

Melatonin attenuates gray and white matter damage in a mouse model of transient focal cerebral ischemia

We have previously shown that melatonin reduces infarct volumes and enhances neurobehavioral and electrophysiological recoveries following transient middle cerebral artery (MCA) occlusion in rats. In the study, we examined whether melatonin would display neuroprotection against neuronal, axonal and oligodendrocyte pathology after 24 hr of reperfusion following 1 hr of MCA occlusion in mice. Melatonin (5 mg/kg) or vehicle was given intraperitoneally at the commencement of reperfusion. Neurological deficits were assessed 24 hr after ischemia. Gray matter damage was evaluated by quantitative histopathology. Axonal damage was determined with amyloid precursor protein and microtubule-associated protein tau-1 immunohistochemistry to identify postischemic disrupted axonal flow and oligodendrocyte pathology, respectively. Oxidative damage was assessed by 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 4-hydroxynonenal (4-HNE) immunohistochemistry. Relative to controls, melatonin-treated animals not only had a significantly reduced volume of gray matter infarction by 42% (P<0.001), but also exhibited a decreased score of axonal damage by 42% (P<0.001) and a reduction in the volume of oligodendrocyte pathology by 58% (P<0.005). Melatonin-treated animals also had significantly reduced immunopositive reactions for 8-OHdG and 4-HNE by 53% (P<0.001) and 49% (P<0.001), respectively. In addition, melatonin improved sensory and motor neurobehavioral outcomes by 47 and 30%, respectively (P<0.01). Thus, delayed (1 hr) treatment with melatonin reduced both gray and white matter damage and improved neurobehavioral outcomes following transient focal cerebral ischemia in mice. The finding of reduced oxidative damage observed with melatonin suggests that its major mechanisms of action are mediated through its antioxidant and radical scavenging activity.

Sodium 4-phenylbutyrate protects against cerebral ischemic injury

Sodium 4-phenylbutyrate (4-PBA) is a low molecular weight fatty acid that has been used for treatment of urea cycle disorders in children, sickle cell disease, and thalassemia. It has been demonstrated recently that 4-PBA can act as a chemical chaperone by reducing the load of mutant or mislocated proteins retained in the endoplasmic reticulum (ER) under conditions associated with cystic fibrosis and liver injury. In the present study, we evaluated the neuroprotective effect of 4-PBA on cerebral ischemic injury. Pre- or post-treatment with 4-PBA at therapeutic doses attenuated infarction volume, hemispheric swelling, and apoptosis and improved neurological status in a mouse model of hypoxia-ischemia. Moreover, 4-PBA suppressed ER-mediated apoptosis by inhibiting eukaryotic initiation factor 2alpha phosphorylation, CCAAT/enhancer-binding protein homologous protein induction, and caspase-12 activation. In neuroblastoma neuro2a cells, 4-PBA reduced caspase-12 activation, DNA fragmentation, and cell death induced by hypoxia/reoxygenation. It protected against ER stress-induced but not mitochondria-mediated cell death. Additionally, 4-PBA inhibited the expression of inducible nitric-oxide synthase and tumor necrosis factor-alpha in primary cultured glial cells under hypoxia/reoxygenation. These results indicate that 4-PBA could protect against cerebral ischemia through inhibition of ER stress-mediated apoptosis and inflammation. Therefore, the multiple actions of 4-PBA may provide a strong effect in treatment of cerebral ischemia, and its use as a chemical chaperone would provide a novel approach for the treatment of stroke.

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.

A peptide inhibitor of c-Jun N-terminal kinase protects against excitotoxicity and cerebral ischemia

Neuronal death in cerebral ischemia is largely due to excitotoxic mechanisms, which are known to activate the c-Jun N-terminal kinase (JNK) pathway. We have evaluated the neuroprotective power of a cell-penetrating, protease-resistant peptide that blocks the access of JNK to many of its targets. We obtained strong protection in two models of middle cerebral artery occlusion (MCAO): transient occlusion in adult mice and permanent occlusion in 14-d-old rat pups. In the first model, intraventricular administration as late as 6 h after occlusion reduced the lesion volume by more than 90% for at least 14 d and prevented behavioral consequences. In the second model, systemic delivery reduced the lesion by 78% and 49% at 6 and 12 h after ischemia, respectively. Protection correlated with prevention of an increase in c-Jun activation and c-Fos transcription. In view of its potency and long therapeutic window, this protease-resistant peptide is a promising neuroprotective agent for stroke.

Grey matter and white matter ischemic damage is reduced by the competitive AMPA receptor antagonist, SPD 502

Protection of both grey and white matter is important for improvement in stroke outcome. In the present study the ability of a competitive alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) antagonist to protect axons, oligodendrocytes, and neuronal perikarya, was examined in a rodent model of transient focal cerebral ischemia. SPD 502 (8-methyl-5-(4-( -dimethylsulfamoyl)phenyl)-6,7,8,9-tetrahydro-1H-pyrrolo[3,2h]-isoquinoline-2,3-dione-3-o(4-hydroxybutyricacid-2-yl)oxime) was administered as an intravenous bolus (16 mg/kg) 15 minutes before transient (3-hour) middle cerebral artery (MCA) occlusion, followed by an intravenous infusion (16 mg kg(-1) hr(-1)) of the drug for 4 hours. Twenty-one hours after ischemia, axonal damage was reduced by 45% (P = 0.006) in the SPD 502-treated group compared with the vehicle. The anatomic extent of ischemically damaged oligodendrocytes, determined by Tau1 immunoreactivity, was reduced in the cerebral cortex by 53% (P = 0.024) in SPD 502-treated rats compared with vehicle-treated rats, but there was minimal effect in the subcortex. The volume of neuronal perikaryal damage after MCA occlusion was significantly reduced by SPD 502 in the cerebral cortex (by 68%; P = 0.005), but there was minimal change in the subcortex with drug treatment. The AMPA receptor antagonist significantly reduced the anatomic extent of lipid peroxidation (assessed as the volume of 4-hydroxynonenol immunoreactivity), and this may have contributed to its ability to protect multiple cell types in ischemia. The data demonstrate that AMPA blockade protects both grey and white matter from damage induced by transient focal ischemia.