Apoptosis and necrosis occur in separate neuronal populations in hippocampus and cerebellum after ischemia and are associated with differential alterations in metabotropic glutamate receptor signaling pathways

Argon gas poisoning leading to persistent memory impairment: A 2-year case report

RATIONALE

Argon gas poisoning is an often overlooked yet critical public health concern with the potential for severe and persistent neurological consequences. Current treatment protocols primarily focus on acute-phase management, but a comprehensive understanding of the long-term neurological effects remains incomplete.

PATIENT CONCERNS

A 22-year-old male worker was found unconscious in the furnace room of an argon production facility. After regaining consciousness, he presented with symptoms of dizziness, headache, fatigue, and irritability. Neurological examination revealed impairments in both recent and remote memory, notably pronounced short-term memory deficits and reduced arithmetic skills.

DIAGNOSIS

Argon gas poisoning, hypoxic encephalopathy, and mild hepatic and renal dysfunction.

INTERVENTIONS

Upon admission, symptomatic supportive measures included oxygen therapy via nasal cannula (3 L/min), daily hyperbaric oxygen therapy (1.5 ATA, 60 minutes), oral neurotrophic methylcobalamin (0.5 mg, 3 times daily), and intravenous vitamin C infusion (2 g daily) to scavenge oxygen free radicals.

OUTCOME

A 2-year telephone follow-up indicated persistent short-term memory impairment, particularly with memorizing numbers. In a memory test, he achieved a digit span forward of 5 but a digit span backward of 2, indicating impairment. Despite these challenges, his daily life and work performance remained largely unaffected.

LESSON

This case offers valuable insights into the biological mechanisms underlying prolonged neurological sequelae following asphyxiating gas exposure, specifically the persistent impairment of hippocampal function.

AIF Overexpression Aggravates Oxidative Stress in Neonatal Male Mice After Hypoxia-Ischemia Injury

There are sex differences in the severity, mechanisms, and outcomes of neonatal hypoxia-ischemia (HI) brain injury, and apoptosis-inducing factor (AIF) may play a critical role in this discrepancy. Based on previous findings that AIF overexpression aggravates neonatal HI brain injury, we further investigated potential sex differences in the severity and molecular mechanisms underlying the injury using mice that overexpress AIF from homozygous transgenes. We found that the male sex significantly aggravated AIF-driven brain damage, as indicated by the injury volume in the gray matter (2.25 times greater in males) and by the lost volume of subcortical white matter (1.71 greater in males) after HI. As compared to females, male mice exhibited more severe brain injury, correlating with reduced antioxidant capacities, more pronounced protein carbonylation and nitration, and increased neuronal cell death. Under physiological conditions (without HI), the doublecortin-positive area in the dentate gyrus of females was 1.15 times larger than in males, indicating that AIF upregulation effectively promoted neurogenesis in females in the long term. We also found that AIF stimulated carbohydrate metabolism in young males. Altogether, these findings corroborate earlier studies and further demonstrate that AIF is involved in oxidative stress, which contributes to the sex-specific differences observed in neonatal HI brain injury.

A Pilot Study of Radiomic Based on Routine CT Reflecting Difference of Cerebral Hemispheric Perfusion

Background

To explore the effectiveness of radiomics features based on routine CT to reflect the difference of cerebral hemispheric perfusion.

Methods

We retrospectively recruited 52 patients with severe stenosis or occlusion in the unilateral middle cerebral artery (MCA), and brain CT perfusion showed an MCA area with deficit perfusion. Radiomics features were extracted from the stenosis side and contralateral of the MCA area based on precontrast CT. Two different region of interest drawing methods were applied. Then the patients were randomly grouped into training and testing sets by the ratio of 8:2. In the training set, ANOVA and the Elastic Net Regression with fivefold cross-validation were conducted to filter and choose the optimized features. Moreover, different machine learning models were built. In the testing set, the area under the receiver operating characteristic (AUC) curve, calibration, and clinical utility were applied to evaluate the predictive performance of the models.

Results

The logistic regression (LR) for the triangle-contour method and artificial neural network (ANN) for the semiautomatic-contour method were chosen as radiomics models for their good prediction efficacy in the training phase (AUC = 0.869, 0.873) and the validation phase (AUC = 0.793, 0.799). The radiomics algorithms of the triangle-contour and semiautomatic-contour method were implemented in the whole training set (AUC = 0.870, 0.867) and were evaluated in the testing set (AUC = 0.760, 0.802). According to the optimal cutoff value, these two methods can classify the vascular stenosis side class and normal side class.

Conclusion

Radiomic predictive feature based on precontrast CT image could reflect the difference of cerebral hemispheric perfusion to some extent.

N-Acetylcysteine and Safranal prevented the brain damage induced by hyperthyroidism in adult male rats

Background: Hyperthyroidism is associated with impairment in the neurotransmission and severe tissue damage in the brain. The present study explored the potential deleterious effects of experimentally-induced hyperthyroidism on the neurotransmitters, oxidative homeostasis, apoptosis and DNA fragmentation in cerebral cortex, thalamus & hypothalamus, and hippocampus in rats.Methods and Results: The ameliorative effects of N-acetylcysteine (NAC; 50 mg/kg, oral) and safranal (50 mg/kg, intraperitoneal) against hyperthyroidism (L-T4 500 µg/kg, subcutaneous) were investigated. All treatments continued daily over three weeks. Hyperthyroidism was manifested by significant elevations in serum fT3 and fT4 levels and a decline in serum TSH level and body weight. It was also characterized by significant elevations in the levels of dopamine, serotonin, and 5-hydroxyindole acetic acid, and monoamine oxidase activity to varying degrees in the brain regions examined and a significant reduction in norepinephrine in hippocampus only. Hyperthyroidism resulted in a significant oxidative stress in brain typified by elevations in malondialdehyde and nitric oxide content and reductions in glutathione level and SOD and catalase activities. This led to elevations in Caspases 9 and 3 and a reduction in Bcl2 resulting in DNA damage and confirmed by the histopathology of brain tissue. The administration of NAC or safranal with L-T4 prevented these deleterious effects by reducing the oxidative load and improving the brain antioxidant status.Conclusions: Hyperthyroidism disrupted the neurotransmitters in the brain which aggravated the oxidative stress and resulted in apoptosis. N-Acetylcysteine and safranal prevented these deleterious effects by enhancing the poor antioxidant milieu of the brain.

Overexpression of apoptosis inducing factor aggravates hypoxic-ischemic brain injury in neonatal mice

Apoptosis inducing factor (AIF) has been shown to be a major contributor to neuron loss in the immature brain after hypoxia-ischemia (HI). Indeed, mice bearing a hypomorphic mutation causing reduced AIF expression are protected against neonatal HI. To further investigate the possible molecular mechanisms of this neuroprotection, we generated an AIF knock-in mouse by introduction of a latent transgene coding for flagged AIF protein into the Rosa26 locus, followed by its conditional activation by a ubiquitously expressed Cre recombinase. Such AIF transgenic mice overexpress the pro-apoptotic splice variant of AIF (AIF1) at both the mRNA (5.9 times higher) and protein level (2.4 times higher), but not the brain-specific AIF splice-isoform (AIF2). Excessive AIF did not have any apparent effects on the phenotype or physiological functions of the mice. However, brain injury (both gray and white matter) after neonatal HI was exacerbated in mice overexpressing AIF, coupled to enhanced translocation of mitochondrial AIF to the nucleus as well as enhanced caspase-3 activation in some brain regions, as indicated by immunohistochemistry. Altogether, these findings corroborate earlier studies demonstrating that AIF plays a causal role in neonatal HI brain injury.

Calcium/Calmodulin-Dependent Kinase (CaMKII) Inhibition Protects Against Purkinje Cell Damage Following CA/CPR in Mice

Ischemic brain damage is triggered by glutamate excitotoxicity resulting in neuronal cell death. Previous research has demonstrated that N-methly-D-aspartate (NMDA) receptor activation triggers downstream calcium-dependent signaling pathways, specifically Ca2+/calmodulin-dependent protein kinase II (CaMKII). Inhibiting CaMKII is protective against hippocampal ischemic injury, but there is little known about its role in the cerebellum. To examine the neuroprotective potential of CaMKII inhibition in Purkinje cells, we subjected C57BL/6 or CaMKIIα KO male mice (8-12 weeks old) to cardiac arrest followed by cardiopulmonary resuscitation (CA/CPR). We performed a dose-response study for tat-CN19o and cerebellar injury was analyzed at 7 days after CA/CPR. Acute signaling was assessed at 6 h after CA/CPR using Western blot analysis. We observed increased phosphorylation of the T286 residue of CaMKII, suggesting increased autonomous activation. Analysis of Purkinje cell density revealed a decrease in cell density at 7 days after CA/CPR that was prevented with tat-CN19o at doses of 0.1 and 1 mg/kg. However, neuroprotection in the cerebellum required doses that were 10-fold higher than what was needed in the hippocampus. CaMKIIα KO mice subjected to sham surgery or CA/CPR had similar Purkinje cell densities, suggesting CaMKIIα is required for CA/CPR-induced injury in the cerebellum. We also observed a CA/CPR-induced activation of death-associated protein kinase (DAPK1) that tat-CN19o did not block. In summary, our findings indicate that inhibition of autonomous CaMKII activity is a promising therapeutic approach that is effective across multiple brain regions.

Pre- and Post-Treatment with Novel Antiepileptic Drug Oxcarbazepine Exerts Neuroprotective Effect in the Hippocampus in a Gerbil Model of Transient Global Cerebral Ischemia

Oxcarbazepine, an antiepileptic drug, has been reported to modulate voltage-dependent sodium channels, and it is commonly used in epilepsy treatment. In this study, we investigated the neuroprotective effect of oxcarbazepine in the hippocampus after transient ischemia in gerbils. Gerbils randomly received oxcarbazepine 100 or 200 mg/kg before and after transient ischemia. We examined its neuroprotective effect in the cornu ammonis 1 subfield of the gerbil hippocampus at 5 days after transient ischemia by using cresyl violet staining, neuronal nuclei immunohistochemistry and Fluoro-Jade B histofluorescence staining for neuroprotection, and by using glial fibrillary protein and ionized calcium-binding adapter molecule 1 immunohistochemistry for reaction of astrocytes and microglia, respectively. Pre- and post-treatment with 200 mg/kg of oxcarbazepine, but not 100 mg/kg of oxcarbazepine, protected pyramidal neurons of the cornu ammonis 1 subfield from transient ischemic damage. In addition, pre- and post-treatment with oxcarbazepine (200 mg/kg) significantly ameliorated astrocytes and microglia activation in the ischemic cornu ammonis 1 subfield. In brief, our current results indicate that post-treatment as well as pre-treatment with 200 mg/kg of oxcarbazepine can protect neurons from ischemic insults via attenuation of the glia reaction.

Focal Ischaemic Infarcts Expand Faster in Cerebellar Cortex than Cerebral Cortex in a Mouse Photothrombotic Stroke Model

It is generally accepted that the cerebellum is particularly vulnerable to ischaemic injury, and this may contribute to the high mortality arising from posterior circulation strokes. However, this has not been systematically examined in an animal model. This study compared the development and resolution of matched photothrombotic microvascular infarcts in the cerebellar and cerebral cortices in adult 129/SvEv mice of both sexes. The photothrombotic lesions were made using tail vein injection of Rose Bengal with a 532 nm laser projected onto a 2 mm diameter aperture over the target region of the brain (with skull thinning). Infarct size was then imaged histologically following 2 h to 30-day survival using serial reconstruction of haematoxylin and eosin stained cryosections. This was complemented with immunohistochemistry for neuron and glial markers. At 2 h post-injury, the cerebellar infarct volume averaged ~ 2.7 times that of the cerebral cortex infarcts. Infarct volume reached maximum in the cerebellum in a quarter of the time (24 h) taken in the cerebral cortex (4 days). Remodelling resolved the infarcts within a month, leaving significantly larger residual injury volume in the cerebellum. The death of neurons in the core lesion at 2 h was confirmed by NeuN and Calbindin immunofluorescence, alongside activation of astrocytes and microglia. The latter persisted in the region within and surrounding the residual infarct at 30 days. This comparison of acute focal ischaemic injuries in cerebellar and cerebral cortices provides direct confirmation of exacerbation of neuropathology and faster kinetics in the cerebellum.

Cerebral hypoperfusion and glucose hypometabolism: Key pathophysiological modulators promote neurodegeneration, cognitive impairment, and Alzheimer's disease

Aging, hypertension, diabetes, hypoxia/obstructive sleep apnea (OSA), obesity, vitamin B12/folate deficiency, depression, and traumatic brain injury synergistically promote diverse pathological mechanisms including cerebral hypoperfusion and glucose hypometabolism. These risk factors trigger neuroinflammation and oxidative-nitrosative stress that in turn decrease nitric oxide and enhance endothelin, Amyloid-β deposition, cerebral amyloid angiopathy, and blood-brain barrier disruption. Proinflammatory cytokines, endothelin-1, and oxidative-nitrosative stress trigger several pathological feedforward and feedback loops. These upstream factors persist in the brain for decades, upregulating amyloid and tau, before the cognitive decline. These cascades lead to neuronal Ca²⁺ increase, neurodegeneration, cognitive/memory decline, and Alzheimer's disease (AD). However, strategies are available to attenuate cerebral hypoperfusion and glucose hypometabolism and ameliorate cognitive decline. AD is the leading cause of dementia among the elderly. There is significant evidence that pathways involving inflammation and oxidative-nitrosative stress (ONS) play a key pathophysiological role in promoting cognitive dysfunction. Aging and several comorbid conditions mentioned above promote diverse pathologies. These include inflammation, ONS, hypoperfusion, and hypometabolism in the brain. In AD, chronic cerebral hypoperfusion and glucose hypometabolism precede decades before the cognitive decline. These comorbid disease conditions may share and synergistically activate these pathophysiological pathways. Inflammation upregulates cerebrovascular pathology through proinflammatory cytokines, endothelin-1, and nitric oxide (NO). Inflammation-triggered ONS promotes long-term damage involving fatty acids, proteins, DNA, and mitochondria; these amplify and perpetuate several feedforward and feedback pathological loops. The latter includes dysfunctional energy metabolism (compromised mitochondrial ATP production), amyloid-β generation, endothelial dysfunction, and blood-brain-barrier disruption. These lead to decreased cerebral blood flow and chronic cerebral hypoperfusion- that would modulate metabolic dysfunction and neurodegeneration. In essence, hypoperfusion deprives the brain from its two paramount trophic substances, viz., oxygen and nutrients. Consequently, the brain suffers from synaptic dysfunction and neuronal degeneration/loss, leading to both gray and white matter atrophy, cognitive dysfunction, and AD. This Review underscores the importance of treating the above-mentioned comorbid disease conditions to attenuate inflammation and ONS and ameliorate decreased cerebral blood flow and hypometabolism. Additionally, several strategies are described here to control chronic hypoperfusion of the brain and enhance cognition. © 2016 Wiley Periodicals, Inc.

Heat shock proteins in the retina: Focus on HSP70 and alpha crystallins in ganglion cell survival

Heat shock proteins (HSPs) belong to a superfamily of stress proteins that are critical constituents of a complex defense mechanism that enhances cell survival under adverse environmental conditions. Cell protective roles of HSPs are related to their chaperone functions, antiapoptotic and antinecrotic effects. HSPs' anti-apoptotic and cytoprotective characteristics, their ability to protect cells from a variety of stressful stimuli, and the possibility of their pharmacological induction in cells under pathological stress make these proteins an attractive therapeutic target for various neurodegenerative diseases; these include Alzheimer's, Parkinson's, Huntington's, prion disease, and others. This review discusses the possible roles of HSPs, particularly HSP70 and small HSPs (alpha A and alpha B crystallins) in enhancing the survival of retinal ganglion cells (RGCs) in optic neuropathies such as glaucoma, which is characterized by progressive loss of vision caused by degeneration of RGCs and their axons in the optic nerve. Studies in animal models of RGC degeneration induced by ocular hypertension, optic nerve crush and axotomy show that upregulation of HSP70 expression by hyperthermia, zinc, geranyl-geranyl acetone, 17-AAG (a HSP90 inhibitor), or through transfection of retinal cells with AAV2-HSP70 effectively supports the survival of injured RGCs. RGCs survival was also stimulated by overexpression of alpha A and alpha B crystallins. These findings provide support for translating the HSP70- and alpha crystallin-based cell survival strategy into therapy to protect and rescue injured RGCs from degeneration associated with glaucomatous and other optic neuropathies.

Cell death and neurodegeneration in the postnatal development of cerebellar vermis in normal and Reeler mice

Programmed cell death (PCD) was demonstrated in neurons and glia in normal brain development, plasticity, and aging, but also in neurodegeneration. (Macro)autophagy, characterized by cytoplasmic vacuolization and activation of lysosomal hydrolases, and apoptosis, typically entailing cell shrinkage, chromatin and nuclear condensation, are the two more common forms of PCD. Their underlying intracellular pathways are partly shared and neurons can die following both modalities, according to the type of death-triggering stimulus. Reelin is an extracellular protein necessary for proper neuronal migration and brain lamination. In the mutant Reeler mouse, its absence causes neuronal mispositioning, with a notable degree of cerebellar hypoplasia that was tentatively related to an increase in PCD. We have carried out an ultrastructural analysis on the occurrence and type of postnatal PCD affecting the cerebellar neurons in normal and Reeler mice. In the forming cerebellar cortex, PCD took the form of apoptosis or autophagy and mainly affected the cerebellar granule cells (CGCs). Densities of apoptotic CGCs were comparable in both mouse strains at P0-P10, while, in mutants, they increased to become significantly higher at P15. In WT mice the density of autophagic neurons did not display statistically significant differences in the time interval examined in this study, whereas it was reduced in Reeler in the P0-P10 interval, but increased at P15. Besides CGCs, the Purkinje neurons also displayed autophagic features in both WT and Reeler mice. Therefore, cerebellar neurons undergo different types of PCD and a Reelin deficiency affects the type and degree of neuronal death during postnatal development of the cerebellum.

Curcumin reverses neurochemical, histological and immuno-histochemical alterations in the model of global brain ischemia

Curcumin, a curcuminoid from Curcuma longa, presents antioxidant and anti-inflammatory actions and, among pathological changes of cerebral ischemic injury, inflammation is an important one. The objectives were to study the neuroprotective action of curcumin, in a model of global ischemia. Male Wistar rats (sham-operated, ischemic untreated and ischemic treated with curcumin, 25 or 50 mg/kg, p.o.) were anesthesized and their carotid arteries occluded, for 30 min. The SO group had the same procedure, except for carotid occlusion. In the 1^st protocol, animals were treated 1 h before ischemia and 24 h later; and in the 2^nd protocol, treatments began 1 h before ischemia, continuing for 7 days. Twenty four hours after the last administration, animals were euthanized and measurements for striatal monoamines were performed, at the 1^st and 7^th days after ischemia, as well as histological and immunohistochemical assays in hippocampi. We showed in both protocols, depletions of DA and its metabolites (DOPAC and HVA), in the ischemic group, but these effects were reversed by curcumin. Additionally, a decrease seen in 5-HT contents, 1 day after ischemia, was also reversed by curcumin. This reversion was not seen 7 days later. On the other hand, a decrease observed in NE levels, at the 7^th day, was totally reversed by curcumin. Furthermore, curcumin treatments increased neuronal viability and attenuated the immunoreactivity for COX-2 and TNF-alpha, in the hippocampus in both protocols. We showed that curcumin exerts neuroprotective actions, in a model of brain ischemia that are probably related to its anti-inflammatory activity.

Brain injury in canine models of cardiac surgery

Neuropathology and neurologic impairment were characterized in a clinically relevant canine model of hypothermic (18°C) circulatory arrest (HCA) and cardiopulmonary bypass (CPB). Adult dogs underwent 2 hours of HCA (n = 39), 1 hour of HCA (n = 20), or standard CPB (n = 22) and survived 2, 8, 24, or 72 hours. Neurologic impairment and neuropathology were much more severe after 2-hour HCA than after 1-hour HCA or CPB; histopathology and neurologic deficit scores were significantly correlated. Apoptosis developed as early as 2 hours after injury and was most severe in the granule cells of the hippocampal dentate gyrus. Necrosis evolved more slowly and was most severe in amygdala and pyramidal neurons in the cornu ammonis hippocampus. Neuronal injury was minimal up to 24 hours after 1-hour HCA, but 1 dog that survived to 72 hours showed substantial necrosis in the hippocampus, suggesting that, with longer survival time, the injury was worse. Although neuronal injury was minimal after CPB, we observed rare apoptotic and necrotic neurons in hippocampi and caudate nuclei. These results have important implications for CPB in humans and may help explain the subtle cognitive changes experienced by patients after CPB.

Central axons preparing to myelinate are highly sensitive [corrected] to ischemic injury

OBJECTIVE

Developing central white matter is subject to ischemic-type injury during the period that precedes myelination. At this stage in maturation, central axons initiate a program of radial expansion and ion channel redistribution. Here we test the hypothesis that during radial expansion axons display heightened ischemic sensitivity, when clusters of Ca(2+) channels decorate future node of Ranvier sites.

METHODS

Functionality and morphology of central axons and glia were examined during and after a period of modeled ischemia. Pathological changes in axons undergoing radial expansion were probed using electrophysiological, quantitative ultrastructural, and morphometric analysis in neonatal rodent optic nerve and periventricular white matter axons studied under modeled ischemia in vitro or after hypoxia-ischemia in vivo.

RESULTS

Acute ischemic injury of central axons undergoing initial radial expansion was mediated by Ca(2+) influx through Ca(2+) channels expressed in axolemma clusters. This form of injury operated only in this axon population, which was more sensitive to injury than neighboring myelinated axons, smaller axons yet to initiate radial expansion, astrocytes, or oligodendroglia. A pharmacological strategy designed to protect both small and large diameter premyelinated axons proved 100% protective against acute ischemia studied under modeled ischemia in vitro or after hypoxia-ischemia in vivo.

INTERPRETATION

Recent clinical data highlight the importance of axon pathology in developing white matter injury. The elevated susceptibility of early maturing axons to ischemic injury described here may significantly contribute to selective white matter pathology and places these axons alongside preoligodendrocytes as a potential primary target of both injury and therapeutics.

Epigenetic regulation of motor neuron cell death through DNA methylation

DNA methylation is an epigenetic mechanism for gene silencing engaged by DNA methyltransferase (Dnmt)-catalyzed methyl group transfer to cytosine residues in gene-regulatory regions. It is unknown whether aberrant DNA methylation can cause neurodegeneration. We tested the hypothesis that Dnmts can mediate neuronal cell death. Enforced expression of Dnmt3a induced degeneration of cultured NSC34 cells. During apoptosis of NSC34 cells induced by camptothecin, levels of Dnmt1 and Dnmt3a increased fivefold and twofold, respectively, and 5-methylcytosine accumulated in nuclei. Truncation mutation of the Dnmt3a catalytic domain and Dnmt3a RNAi blocked apoptosis of cultured neurons. Inhibition of Dnmt catalytic activity with RG108 and procainamide protected cultured neurons from excessive DNA methylation and apoptosis. In vivo, Dnmt1 and Dnmt3a are expressed differentially during mouse brain and spinal cord maturation and in adulthood when Dnmt3a is abundant in synapses and mitochondria. Dnmt1 and Dnmt3a are expressed in motor neurons of adult mouse spinal cord, and, during their apoptosis induced by sciatic nerve avulsion, nuclear and cytoplasmic 5-methylcytosine immunoreactivity, Dnmt3a protein levels and Dnmt enzyme activity increased preapoptotically. Inhibition of Dnmts with RG108 blocked completely the increase in 5-methycytosine and the apoptosis of motor neurons in mice. In human amyotrophic lateral sclerosis (ALS), motor neurons showed changes in Dnmt1, Dnmt3a, and 5-methylcytosine similar to experimental models. Thus, motor neurons can engage epigenetic mechanisms to drive apoptosis, involving Dnmt upregulation and increased DNA methylation. These cellular mechanisms could be relevant to human ALS pathobiology and disease treatment.

The mitochondrial permeability transition pore regulates nitric oxide-mediated apoptosis of neurons induced by target deprivation

Ablation of mouse occipital cortex induces precisely timed and uniform p53-modulated and Bax-dependent apoptosis of thalamocortical projection neurons in the dorsal lateral geniculate nucleus (LGN) by 7 d after lesion. We tested the hypothesis that this neuronal apoptosis is initiated by oxidative stress and the mitochondrial permeability transition pore (mPTP). Preapoptotic LGN neurons accumulate mitochondria, Zn(2+) and Ca(2+), and generate higher levels of reactive oxygen species (ROS), including superoxide, nitric oxide (NO), and peroxynitrite, than LGN neurons with an intact cortical target. Preapoptosis of LGN neurons is associated with increased formation of protein carbonyls, protein nitration, and protein S-nitrosylation. Genetic deletion of nitric oxide synthase 1 (nos1) and inhibition of NOS1 with nitroindazole protected LGN neurons from apoptosis, revealing NO as a mediator. Putative components of the mPTP are expressed in mouse LGN, including the voltage-dependent anion channel (VDAC), adenine nucleotide translocator (ANT), and cyclophilin D (CyPD). Nitration of CyPD and ANT in LGN mitochondria occurs by 2 d after cortical injury. Chemical cross-linking showed that LGN neuron preapoptosis is associated with formation of CyPD and VDAC oligomers, consistent with mPTP formation. Mice without CyPD are rescued from neuron apoptosis as are mice treated with the mPTP inhibitors TRO-19622 (cholest-4-en-3-one oxime) and TAT-Bcl-X(L)-BH4. Manipulation of the mPTP markedly attenuated the early preapoptotic production of reactive oxygen/nitrogen species in target-deprived neurons. Our results demonstrate in adult mouse brain neurons that the mPTP functions to enhance ROS production and the mPTP and NO trigger apoptosis; thus, the mPTP is a target for neuroprotection in vivo.

An approach to experimental synaptic pathology using green fluorescent protein-transgenic mice and gene knockout mice to show mitochondrial permeability transition pore-driven excitotoxicity in interneurons and motoneurons

Researchers used transgenic mice expressing enhanced-green fluorescent protein (eGFP) driven by either the glycine transporter-2 gene promoter to specifically visualize glycinergic interneurons or the homeobox-9 (Hb9) gene promoter to visualize motoneurons for assessing their vulnerabilities to excitotoxins in vivo. Stereotaxic excitotoxic lesions were made in adult male and female mouse lumbar spinal cord with the specific N-methyl-D-aspartate (NMDA) receptor agonist quinolinic acid (QA) and the non-NMDA ion channel glutamate receptor agonist kainic acid (KA). QA and KA induced large-scale degeneration of glycinergic interneurons in spinal cord. Glycinergic interneurons were more sensitive than motoneurons to NMDA receptor-mediated and non-NMDA glutamate receptor-mediated excitotoxicity. Outcome after spinal cord excitotoxicity was gender-dependent, with males showing greater sensitivity than females. Excitotoxic degeneration of spinal interneurons resembled apoptosis, while motoneuron degeneration appeared non-apoptotic. Perikaryal mitochondrial accumulation was antecedent to both NMDA and non-NMDA receptor-mediated excitotoxic stimulation of interneurons and motoneurons. Genetic ablation of cyclophilin D, a regulator of the mitochondrial permeability transition pore (mPTP), protected both interneurons and motoneurons from excitotoxicity. The results demonstrate in adult mouse spinal cord that glycinergic interneurons are more sensitive than motoneurons to excitotoxicity that stimulates mitochondrial accumulation, and that the mPTP has pro-death functions mediating apoptotic and non-apoptotic neuronal degeneration in vivo.

Alterations in discrete glutamate receptor subunits in adult mouse dentate gyrus granule cells following perforant path transection

Custom-designed microarray analysis was utilized to evaluate expression levels of glutamate receptors (GluRs) and GluR-interacting protein genes within isolated dentate gyrus granule cells following axotomy of the principal input, the perforant path (PP). Dentate gyrus granule cells were evaluated by microdissection via laser capture microdissection, terminal continuation RNA amplification, and microarray analysis following unilateral PP transections at seven time points. Expression profiles garnered from granule cells on the side ipsilateral to PP transections were compared and contrasted with naive subjects and mice subjected to unilateral occipital cortex lesions. Selected microarray observations were validated by real-time quantitative PCR analysis. Postlesion time-dependent alterations in specific alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors, kainate receptors, N-methyl-D-aspartate (NMDA) receptors, and GluR-interacting protein genes were found across the time course of the study, suggesting a neuroplasticity response associated with the transsynaptic granule cell alterations following axotomy of incoming PP terminals.

Treadmill pre-training suppresses the release of glutamate resulting from cerebral ischemia in rats

This study was designed to investigate the neuroprotective effect of treadmill pre-training against the over-release of glutamate resulting from cerebral ischemia. Sprague-Dawley rats underwent 2 weeks of treadmill run-training before cerebral ischemia was performed by middle cerebral artery occlusion. The level of glutamate in brain extracellular fluid was detected before, during and after ischemia/reperfusion. The expression of metabotropic glutamate receptor-1 (mGluR1) mRNA in striatum was examined after ischemia for 80 min and reperfusion for 240 min. Neurological defect score and brain infarction volumes were measured. The treadmill pre-training significantly suppressed the release of glutamate, and reduced the expression of mGluR1 mRNA at 59% (P < 0.01) and 62% (P < 0.05), respectively, as compared with the ischemia group. The neurological defect score and infarction volume were significantly improved by 75% (P < 0.01) and 74% (P < 0.01), respectively, in the pre-training group, as compared to the ischemia group. Treadmill pre-training has a significant neuroprotective function against ischemia/reperfusion injury, by suppressing glutamate release resulting from cerebral ischemia, and this effect may be mediated by downregulation of mGluR1.

Mitochondrial and Cell Death Mechanisms in Neurodegenerative Diseases

Alzheimer’s disease (AD), Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS) are the most common human adult-onset neurodegenerative diseases. They are characterized by prominent age-related neurodegeneration in selectively vulnerable neural systems. Some forms of AD, PD, and ALS are inherited, and genes causing these diseases have been identified. Nevertheless, the mechanisms of the neuronal cell death are unresolved. Morphological, biochemical, genetic, as well as cell and animal model studies reveal that mitochondria could have roles in this neurodegeneration. The functions and properties of mitochondria might render subsets of selectively vulnerable neurons intrinsically susceptible to cellular aging and stress and overlying genetic variations, triggering neurodegeneration according to a cell death matrix theory. In AD, alterations in enzymes involved in oxidative phosphorylation, oxidative damage, and mitochondrial binding of Aβ and amyloid precursor protein have been reported. In PD, mutations in putative mitochondrial proteins have been identified and mitochondrial DNA mutations have been found in neurons in the substantia nigra. In ALS, changes occur in mitochondrial respiratory chain enzymes and mitochondrial cell death proteins. Transgenic mouse models of human neurodegenerative disease are beginning to reveal possible principles governing the biology of selective neuronal vulnerability that implicate mitochondria and the mitochondrial permeability transition pore. This review summarizes how mitochondrial pathobiology might contribute to neuronal death in AD, PD, and ALS and could serve as a target for drug therapy.

Skeletal muscle-restricted expression of human SOD1 causes motor neuron degeneration in transgenic mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of motor neurons (MNs) that causes skeletal muscle paralysis. Familial forms of ALS are linked to mutations in the superoxide dismutase-1 (SOD1) gene. The mechanisms of human SOD1 (hSOD1) toxicity to MNs are unknown. We hypothesized that skeletal muscle is a primary site of pathogenesis in ALS that triggers MN degeneration. We created transgenic (tg) mice expressing wild-type-, G37R- and G93A-hSOD1 gene variants only in skeletal muscle. These tg mice developed age-related neurologic and pathologic phenotypes consistent with ALS. Affected mice showed limb weakness and paresis with motor deficits. Skeletal muscles developed severe pathology involving oxidative damage, protein nitration, myofiber cell death and marked neuromuscular junction (NMJ) abnormalities. Spinal MNs developed distal axonopathy and formed ubiquitinated inclusions and degenerated through an apoptotic-like pathway involving capsase-3. Mice expressing wild-type and mutant forms of hSOD1 developed MN pathology. These results demonstrate that human SOD1 in skeletal muscle has a causal role in ALS and identify a new non-autonomous mechanism for MN degeneration explaining their selective vulnerability. The discovery of instigating molecular toxicities or disease progression determinants within skeletal muscle could be very valuable for the development of new effective therapies for the treatment and cure of ALS.

Cystic degeneration of the cerebellar tonsils in pediatric patients with Chiari Type I malformation

OBJECT

The operative indications and treatment algorithms for pediatric patients with Chiari Type I malformation (CM-I) vary widely. When an intradural approach and duraplasty are thought necessary at the time of surgery, neurosurgeons may elect to fulgurate or resect a portion of the cerebellar tonsils. Histological analyses of cerebellar tonsils resected during decompression in pediatric patients with CM-I have revealed multiple abnormal findings including extensive ischemic and degenerative changes. The authors describe an interesting phenomenon of cystic degeneration in the distal ends of the cerebellar tonsils in children undergoing operative treatment of CM-I.

METHODS

The authors reviewed the clinical database of 440 pediatric patients who underwent surgical decompression for CM-I performed by a single surgeon. The clinical course, preoperative MR imaging and intraoperative ultrasound characteristics, and histological findings in 3 children found to have tonsillar cystic degeneration were analyzed and detailed.

RESULTS

Cystic changes were subtle but uniformly evident on preoperative MR imaging and were more readily apparent on intraoperative ultrasonography. In each patient, the tonsillar cyst was resected. Histological examination revealed areas of cystic degenerative change characterized by distortion of the normal cerebellar architecture with absent Purkinje and internal granular cell layers. All children experienced improvement in their symptoms, without complication, postoperatively.

CONCLUSIONS

Cystic degeneration of the tonsils in pediatric patients with CM-I is an uncommon pathological process most likely resulting from long-standing and excessive compression. Based on their experience, the authors advocate expeditious surgical treatment, including intradural exploration and capacious duraplasty, for patients in whom there is evidence of this phenomenon on preoperative imaging.

Lipopolysaccharide preconditioning induces robust protection against brain injury resulting from deep hypothermic circulatory arrest

OBJECTIVE

Delayed preconditioning genetically reprograms the response to ischemic injury. Subclinical bacterial lipopolysaccharide acts through preconditioning, powerfully protecting against experimental stroke. We investigated the potential for lipopolysaccharide to protect against brain injury related to cardiopulmonary bypass.

METHODS

Neonatal piglets were blindly and randomly preconditioned with lipopolysaccharide (n = 6) or saline (n = 6). Three days later, they experienced 2 hours of deep hypothermic circulatory arrest before being weaned and supported anesthetized for 20 hours in an intensive care setting. Controls included cardiopulmonary bypass without deep hypothermic circulatory arrest (n = 3) and no cardiopulmonary bypass (n = 3). Brain injury was quantified by light and fluorescent microscopy (Fluoro-Jade; Histo-Chem, Inc, Jefferson, Ark).

RESULTS

All animals were clinically indistinguishable before surgery. Perioperative and postoperative parameters between experimental groups were similar. No control animal scored falsely positive. Histologic scores were 0.33 +/- 0.21, 0.66 +/- 0.42, and 0.5 +/- 0.24 in the cortex, basal ganglia, and hippocampus, respectively, in the lipopolysaccharide-treated animals but significantly worse in all saline control animals (1.33 +/- 0.21, P < .01; 1.66 +/- 0.33, P = .09; and 6.0 +/- 1.5, P < .01). One lipopolysaccharide-treated brain was histologically indistinguishable from controls.

CONCLUSION

This is the first evidence that lipopolysaccharide can precondition against cardiopulmonary bypass-related injury. Because lipopolysaccharide preconditioning is a systemic phenomenon offering proven protection against myocardial, hepatic, and pulmonary injury, this technique offers enormous potential for protecting against systemic neonatal injury related to cardiopulmonary bypass.

Effect of monosodium glutamate on oxidative stress and apoptosis in rat thymus

It has been demonstrated that administration of high concentrations of monosodium glutamate (MSG), induce oxidative stress in different organs, but not in thymus. In the present study we examined the role of oxidative stress in MSG-induced thymocyte apoptosis. MSG was administrated intraperitoneally (4 mg/g of body weight) for six consecutive days. Animals were sacrificed at 1st, 7th, and 15th day after last MSG dose. MSG administration to animals significantly increased apoptotic rate of thymocytes (P < 0.01), together with significant increase of malondialdehyde (MDA) level (P < 0.001) and xanthine oxidase (XO) activity (P < 0.01), in time dependent manner. Catalase activity, during examination period, was significantly decreased (0 < 0.01). Obtained results showed that MSG treatment induced oxidative stress in thymus, which may have an important role in thymocyte apoptosis induced by MSG.

Histological findings in cerebellar tonsils of patients with Chiari type I malformation

OBJECTIVES

Cerebellar tonsillectomy is often performed for relief of symptoms associated with Chiari type I malformation (CMI). Nonetheless, the idea of removing supposedly healthy central nervous tissue has been a source of concern for neurosurgeons. The aim of this paper is to determine the histological changes in the cerebellar tonsils of patients with a wide range of symptoms and conditions related to CMI.

MATERIALS AND METHODS

The cerebellar tonsils of 43 pediatric patients with CMI were sent to pathology for histological examination.

CONCLUSION

The cerebellar tonsils in a great majority of CMI patients can be abnormal. We suggest that the reported histological findings are secondary to injury and ischemia.

Structural and functional alterations of cerebellum following fluid percussion injury in rats

Cerebellum was shown to be vulnerable to traumatic brain injury (TBI) in experimental animals. However, the detailed pathological and functional changes within the cerebellum following TBI are not known. Using our established cerebellum fluid percussion injury (FPI) model, we characterized the temporal pattern and the nature of structural damage following FPI, as well as the functional changes of Purkinje cells in response to climbing fiber activation. Our results showed that 60% of Purkinje cells died within the first 24 h following moderate FPI. In contrast, clusters of densely stained shrunken granule cells were stained positive for terminal deoxynucleotidyl transferase-mediated UTP nick end labeling (TUNEL) in 1, 3 or 7 days following FPI animals. We also observed an accompanying structural damage to the cerebellar white matter tract. Disconnected axonal fibers appeared 1 day post-FPI, and loss of white matter fibers were visible 3 and 7 days post-FPI. Massive accumulation of beta-amyloid precursor protein (betaAPP) was found in the white matter tracts and molecular layer in the cerebellum of 1, 3 or 7 days FPI animals. Our functional study showed that the majority of Purkinje cells from 1 day and all cells from 3 to 7 days post-FPI had distorted membrane potential and synaptic responses to climbing fiber activation. These results suggested that there is a co-related structural and functional deterioration with a specific temporal pattern in the cerebellum following FPI. These observations provide a basis for future mechanistic investigations aiming to realize neuroprotection from cerebellar neuronal death and loss of cerebellar functionality.

Normoxic resuscitation after cardiac arrest protects against hippocampal oxidative stress, metabolic dysfunction, and neuronal death

Resuscitation and prolonged ventilation using 100% oxygen after cardiac arrest is standard clinical practice despite evidence from animal models indicating that neurologic outcome is improved using normoxic compared with hyperoxic resuscitation. This study tested the hypothesis that normoxic ventilation during the first hour after cardiac arrest in dogs protects against prelethal oxidative stress to proteins, loss of the critical metabolic enzyme pyruvate dehydrogenase complex (PDHC), and minimizes subsequent neuronal death in the hippocampus. Anesthetized beagles underwent 10 mins ventricular fibrillation cardiac arrest, followed by defibrillation and ventilation with either 21% or 100% O2. At 1 h after resuscitation, the ventilator was adjusted to maintain normal blood gas levels in both groups. Brains were perfusion-fixed at 2 h reperfusion and used for immunohistochemical measurements of hippocampal nitrotyrosine, a product of protein oxidation, and the E1alpha subunit of PDHC. In hyperoxic dogs, PDHC immunostaining diminished by approximately 90% compared with sham-operated dogs, while staining in normoxic animals was not significantly different from nonischemic dogs. Protein nitration in the hippocampal neurons of hyperoxic animals was 2-3 times greater than either sham-operated or normoxic resuscitated animals at 2 h reperfusion. Stereologic quantification of neuronal death at 24 h reperfusion showed a 40% reduction using normoxic compared with hyperoxic resuscitation. These results indicate that postischemic hyperoxic ventilation promotes oxidative stress that exacerbates prelethal loss of pyruvate dehydrogenase and delayed hippocampal neuronal cell death. Moreover, these findings indicate the need for clinical trials comparing the effects of different ventilatory oxygen levels on neurologic outcome after cardiac arrest.

Expression of cell death-associated proteins in neuronal apoptosis associated with pontosubicular neuron necrosis

Expression of apoptosis-associated proteins p53, bcl-2, bax, and caspase-3/CPP32, activation of caspase-3, and modification of proteins via poly(ADP-ribosyl)ation was studied in pontosubicular neuron necrosis (PSN), a form of perinatal brain damage revealing the morphological hallmarks of neuronal apoptosis. Immunoreactivity for p53 was completely absent. The majority of cells stained with the bax and procaspase-3 antibodies did not show morphological signs of apoptosis. In contrast, an antibody against activated caspase-3 almost exclusively stained cells with apoptotic morphology. Poly(ADP-ribosyl)ated proteins were only rarely detected in cells with apoptotic morphology. The expression patterns of bax, procaspase-3, bcl-2, and p53 in PSN were similar to that found in age-matched control brains. However, activated caspase-3 and poly-ADP-ribosylated proteins were exclusively found in apoptotic cells. These data indicate that detection of active caspase-3 is a reliable marker for apoptosis in formalin-fixed human tissue, and that neuronal apoptosis in pontosubicular neuron necrosis is accompanied by a pronounced activation of caspase-3.

Evaluation of neuronal damage following hypoxic–ischaemic brain injury in acute and early chronic periods in neonatal rats

This study was undertaken to investigate the effects of neonatal cerebral hypoxic-ischaemic brain injury (HIBI) in acute and early chronic phases in the rat. HIBI was induced in 7-day-old rat pups by ligation of the right common carotid and then the pups were exposed to 1 h of hypoxia in 8% oxygen. They were divided into two groups: 1-day (acute phase, in the first 24 h) and 5-day (early chronic phase, 120 h). Neuropathological evaluation was performed using the hippocampus, cerebral cortex and basal ganglia on the coronal plane. The following values were obtained: (i) the ratio of the infarcted area; (ii) hemispheric atrophy/asymmetry; (iii) patchy lesions confined to the thalamus, caudate and putamen; (iv) the ratio of damaged neurons to all neurons; and (v) the percentage of apoptotic neurons relative to the total neurons in all brain areas. HIBI-induced global cerebral damage and cellular damage findings did not significantly differ between the two groups. However, they showed a tendency to recover/deteriorate in both acute and early chronic phases. The ratio of ipsi- and contra-lateral hemisphere infarct areas (20.7 and 15.7% vs. 40.1 and 26.7%, respectively), basal ganglia patchy lesion ratio (27.5 vs. 36.7%) and hemispheric atrophy/asymmetry (92.4 vs. 84.7%) were found to be lower in the rat pups in the chronic phase than those in the acute phase. In contrast, increases in the ratio of damaged neurons (16.7 vs. 13.3% in the cerebral and dorsal hippocampus, respectively) and in the ratio of apoptotic neurons (ipsi-lateral: 18 vs. 6%; contra lateral hemispheres: 3.5 vs. 1.7%, respectively) were recorded. It is concluded that cellular damage tends to deteriorate (damaged and apoptotic neurons) while global damage (cerebral infarct and patchy damage) improves with the progression of HIBI. However, further studies are needed in order to elucidate this process.

The electrical response of cerebellar Purkinje neurons to simulated ischaemia

Despite lacking N-methyl-D-aspartate receptors, cerebellar Purkinje cells are highly vulnerable to ischaemic insults, which lead them to die necrotically in an -amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) receptor-dependent manner. To investigate the electrical events leading to this cell death, we whole-cell clamped Purkinje cells in cerebellar slices. Simulated ischaemia evoked an initial hyperpolarization of Purkinje cells by 8.5 mV, followed by a regenerative 'anoxic depolarization' (AD) to -14 mV. The AD was prevented by glutamate receptor blockers. In voltage-clamp mode, we used the cells' glutamate receptors to sense the rise of extracellular glutamate concentration induced by ischaemia, with GABA(A) and GABA(B) receptors blocked and Cs+ as the main pipette cation. Ischaemia induced a small (<500 pA) slowly developing inward current in Purkinje cells, followed by a sudden large inward 'AD current' (approximately 6 nA) which was largely prevented by blocking AMPA receptors. Removing extracellular calcium reduced the large glutamate-mediated current by approximately 70% at early times (after 10 min ischaemia), but had no effect at later times (15 min). Blocking the operation of glutamate transporters, by preloading cells with the slowly transported glutamate analogue PDC (L-trans-pyrrolidine-2,4-dicarboxylate), reduced the current by approximately 88% at early and 83% at later times. In Purkinje cells in slices from mice lacking the glial glutamate transporters GLAST or GLT-1, the ischaemia-evoked AD current was indistinguishable from that in wild-type slices. These data suggest that, in cerebellar ischaemia, the dominant cause of the electrophysiological dysfunction of Purkinje cells is an activation of Purkinje cell AMPA receptors. The glutamate activating these receptors is released both by exocytosis (at early times) and by reversal of a glutamate transporter, apparently in neurons.

Dose-dependent neuroprotection by 17β-estradiol after cardiac arrest and cardiopulmonary resuscitation

OBJECTIVE

Despite recent advances in the treatment of cardiac arrest, neurologic outcome remains poor. 17beta-Estradiol (E2) has been widely shown to reduce damage after experimental brain injury. The present study determined whether E2 also improves neuronal survival after experimental cardiac arrest and cardiopulmonary resuscitation and if any protection is dose-dependent.

DESIGN

A randomized trial.

SETTING

A research laboratory.

SUBJECTS

Male C57Bl/6 mice weighing 20-25 g.

INTERVENTIONS

Mice were randomized into one of six groups, receiving treatment with 0.5, 2.5, 12.5, 25, or 50 mug of E2 or vehicle 1.5 mins after return of spontaneous circulation. Ten minutes after induction of cardiac arrest (by KCl injection), cardiopulmonary resuscitation was initiated (with chest compressions, intravenous epinephrine, and ventilation with 100% O2). Additional animals of each E2-treated group were used for plasma estradiol-level analysis. Brains were removed for quantification of injury in the hippocampus and caudoputamen on day 3.

MEASUREMENTS AND MAIN RESULTS

The E2 0.5 group had physiologic estrogen levels 60 min after injection (mean +/- se, 28 +/- 5 pg/mL), whereas the E2 50 group still showed supraphysiologic levels 360 min after administration (245 +/- 32 pg/mL). Hippocampal damage was not altered with E2 treatment. Only posttreatment with the lowest E2 dose (E2 0.5) resulted in attenuated neuronal injury in the rostral and caudal caudoputamen (34 +/- 11% and 27 +/- 11%), in comparison with vehicle (68 +/- 5, p < .05; 63 +/- 4%, p < .001). Higher E2 doses did not affect brain injury.

CONCLUSIONS

We conclude that E2 has a critical dosing effect on neuronal survival, physiologic levels of E2 are neuroprotective after cardiac arrest/cardiopulmonary resuscitation, and acute exposure is sufficient for brain resuscitation.

Apoptosis and necrosis in developing cerebellum and brainstem induced after focal cerebral hypoxic-ischemic injury

Focal cerebral hypoxia-ischemia due to isolated vascular insufficiency is well known to cause ipsilateral, but not contralateral, cerebral apoptosis. Hypoxic-ischemic damage to the cerebellum and brainstem in such a model has not been established. This experimental rodent study demonstrates, through deoxyribonucleic acid fragmentation and terminal deoxynucleotidyl transferase-mediated deoxyuridine 5'-triphosphate-digoxigenin nick end labeling analysis, that neuronal cells in these infratentorial regions also suffer mild apoptosis and necrosis after focal cerebral hypoxic-ischemic injury in the newborn rat. These data provide additional insight into the mechanisms of neurological injury in the cerebellum and brainstem areas resulting from a focal cerebral hypoxic-ischemic insult and demonstrate that future therapeutic interventions for hypoxic-ischemic encephalopathy system should deal with the entire central nervous system.

In situ immunoradiographic method for quantification of specific proteins in normal and ischemic brain regions

This study tested the application of an immunoisotopic assay for immunohistochemical localization and quantification of proteins in brain sections from rats without or with transient focal ischemia. We assessed the hypothesis that measurements of protein levels in injured brain determined by an isotopic assay using [(125)I]-protein A have greater reliability than those made by conventional immunoperoxidase labeling using diaminobenzidine. Quantification of immunoreactivities for glial fibrillary acidic protein (GFAP), glutamate transporter-1 (GLT-1) and heat shock protein-70 (HSP-70) was determined by optical density signal in the immunoisotopic and immunoperoxidase assays. In ischemic brain, the immunoisotopic assay detected protein increases (cortical penumbra HSP-70, 151+/-6%), protein decreases (cortical ischemic core GLT-1, 61+/-6%) and no changes in GFAP levels compared to controls animals. These results differed from the protein levels found by the immunoperoxidase assay, which showed elevated HSP-70, GLT-1 and GFAP in all ischemic regions. We conclude that nonspecific immunosignal confounds assessments of protein expression in injured brain and that the immunoisotopic method is a valid approach to regionally localize and quantify proteins after brain injury. The disadvantage of the falsely positive overestimation of protein immunoreactivity after stroke with the immunoperoxidase method has to be weighted with the advantage of the cellular resolution.

Mitochondrial calcium and oxidative stress as mediators of ischemic brain injury

Acute ischemic and brain injury is triggered by excitotoxic elevation of intraneuronal Ca2+ followed by reoxygenation-dependent oxidative stress, metabolic failure, and cell death. Studies performed in vitro with neurons exposed to excitotoxic concentrations of glutamate demonstrate an initial rise in cytosolic [Ca2+], followed by a reduction to a normal, albeit slightly elevated concentration. This reduction in cytosolic [Ca2+] is due partially to active, respiration-dependent mitochondrial Ca2+ sequestration. Within minutes to an hour following the initial Ca2+ transient, most neurons undergo delayed Ca2+ deregulation characterized by a dramatic rise in cytosolic Ca2+. This prelethal secondary rise in Ca2+ is due to influx across the plasma membrane but is dependent on the initial mitochondrial Ca2+ uptake and associated oxidative stress. Mitochondrial Ca2+ uptake can stimulate the net production of reactive oxygen species (ROS) through activation of the membrane permeability transition, release of cytochrome c, respiratory inhibition, release of pyridine nucleotides, and loss of intramitochondrial glutathione necessary for detoxification of peroxides. Targets of mitochondrially derived ROS may include plasma membrane Ca2+ channels that mediate excitotoxic delayed Ca2+ deregulation.

Delayed neuronal death and damage of GDNF family receptors in CA1 following focal cerebral ischemia

Delayed neuronal death (DND) of pyramidal neurons in the CA1 and CA3 regions of the hippocampus has been extensively studied following global brain ischemia, whereas only little is known about DND in this highly vulnerable brain region after focal brain ischemia. In the present study, the distribution and time course of hippocampal neuronal apoptosis were studied following transient middle cerebral artery occlusion (MCAO) in rats 1, 3, 7, 14, and 30 days after the insult. In 60% of the animals, more than 90% of CA1 pyramidal neurons showed strong nick-end labeling (TUNEL) staining at day 3 with fragmentation and marginalization of the nuclei in approximately 40% of these cells. The number of TUNEL-positive cells decreased within the next days, but 30 days after MCAO, some apoptotic neurons were still present. Analysis of the expression of the glial cell line-derived neurotrophic factor (GDNF) and its receptors GFRalpha1, GFRalpha2, and GFRalpha3 using triple immunofluorescence and confocal laser scanning microscopy revealed that in all animals showing marked hippocampal DND, the neuronal staining for GFRalpha1, GFRalpha3, and GDNF decreased prior to the onset of TUNEL staining in CA1. After 7 days, some apoptotic neurons still expressed GFRalpha3, whereas only few showed GFRalpha1 immunoreactivity, indicating that GFRalpha1 may be beneficial for the survival of hippocampal neurons. The data suggest that reduced expression of GDNF and impairment of GFRalpha1/3 may contribute to hippocampal DND after focal brain ischemia.

Effects of NF-kappaB oligonucleotide "decoys" on gene expression in P7 rat hippocampus after hypoxia/ischemia

"Decoy" oligonucleotides can be used as gene-specific nuclear factor (NF-kappaB) inhibitors to regulate gene expression. We applied two different decoy oligonucleotides that contained the NF-kappaB binding consensus sequences present in the immunoglobulin G (IgG)-kappaB and Bcl-x promoter into 7-day-old (P7) rat lateral ventricles before hypoxia/ischemia (HI) and compared their effects on gene expression in hippocampi to saline-treated, scrambled decoy-treated, or untreated hippocampi exposed to HI. Left hippocampi were collected at 12 hr after HI. Electrophoretic mobility shift assays (EMSAs) showed that the two decoy treatments had different effects on NF-kappaB binding to the IgG-kappaB and Bcl-x promoter-specific consensus sequences, respectively. We assessed the decoys' effects on gene expression 12 hr after HI using ribonuclease protection assays (RPAs) and Affymetrix DNA microarrays. RPAs showed that both decoys significantly decreased interleukin (IL)-1alpha mRNA levels but had no impact on IL-1beta, IL-6, and IL-10 mRNA levels. IgG-kappaB decoys significantly decreased tumor necrosis factor (TNF)-alpha and TNF-beta mRNA levels compared to minimal changes after treatment with Bcl-x decoys. DNA microarray analyses showed that Bcl-x decoy treatment significantly decreased Bcl-x(L) mRNA levels. The decreased Bcl-x(L) mRNA levels after Bcl-x decoy treatment was confirmed by RPA analysis. DNA microarray data also indicated that several other genes were affected by both decoys. Our results suggest that different NF-kappaB decoy treatments could differentially regulate transcriptional responses to central nervous system trauma. Careful design of decoy sequences, however, is essential to acquire selective effects on cell death outcome.

Fragmented DNA transport in dendrites of retinal neurons during apoptotic cell death

Movement of fragmented DNA in dendrites of retinal neurons during the apoptotic cell death was investigated. The time-course of the movement of fragmented DNA in dendrites of retinal neurons undergoing apoptotic cell death induced by intravitreal N-methyl-d-aspartate (NMDA) injection were examined by in situ terminal dUTP-biotin nick end labeling of DNA fragments (TUNEL) method and fluorescence DNA detection technique by 4',6-diamidino-2-phenylindole (DAPI). The inhibitory effect of axoplasmic transport inhibitor, vincristine was also tested on the NMDA-induced fragmented DNA transport. The movement of fragmented DNA from apoptotic nuclei toward peripheral ends of the dendrites of the retinal neurons was clearly demonstrated. The transport of fragmented DNA, but not fragmentation per se, was completely inhibited by the co-administration of vincristine.

Pathophysiology of cerebral ischemia and brain trauma: similarities and differences

Current knowledge regarding the pathophysiology of cerebral ischemia and brain trauma indicates that similar mechanisms contribute to loss of cellular integrity and tissue destruction. Mechanisms of cell damage include excitotoxicity, oxidative stress, free radical production, apoptosis and inflammation. Genetic and gender factors have also been shown to be important mediators of pathomechanisms present in both injury settings. However, the fact that these injuries arise from different types of primary insults leads to diverse cellular vulnerability patterns as well as a spectrum of injury processes. Blunt head trauma produces shear forces that result in primary membrane damage to neuronal cell bodies, white matter structures and vascular beds as well as secondary injury mechanisms. Severe cerebral ischemic insults lead to metabolic stress, ionic perturbations, and a complex cascade of biochemical and molecular events ultimately causing neuronal death. Similarities in the pathogenesis of these cerebral injuries may indicate that therapeutic strategies protective following ischemia may also be beneficial after trauma. This review summarizes and contrasts injury mechanisms after ischemia and trauma and discusses neuroprotective strategies that target both types of injuries.

Many Mechanisms for Hsp70 Protection From Cerebral Ischemia

Overexpression of inducible Hsp70 has been shown to provide protection from cerebral ischemia both in animal models of stroke and in cell culture models. New work suggests that there are multiple routes of cell death, including apoptotic and necrotic cell death. Hsp70 is known to protect from both necrotic and apoptotic cell death. In addition to the well-studied role of Hsp70 as a molecular chaperone assisting in correct protein folding, several new mechanisms by which Hsp70 can prevent cell death have been described. Hsp70 is now known to regulate apoptotic cell death both directly by interfering with the function of several proteins that induce apoptotic cell death as well as indirectly by increasing levels of the anti-death protein bcl-2. Despite these new insights into the ways in which Hsp70 functions as an anti-death protein, further surprises are likely as we continue to gain insight into the functioning of this multifaceted protein.

MR image-guided investigation of regional signal transducers and activators of transcription-1 activation in a rat model of focal cerebral ischemia

BACKGROUND AND PURPOSE

STAT-1 is a member of a family of proteins called signal transducers and activators of transcription (STATs), and recent studies have shown its involvement in the induction of apoptosis. There is limited information on the role of STAT-1 following stroke. In this study we use MRI measurements of cerebral perfusion and bioenergetic status to target measurements of regional STAT-1 activity.

METHODS

Rats were subjected to 60 or 90 min of middle cerebral artery occlusion with and without reperfusion. MRI maps of the apparent diffusion coefficient of water and cerebral blood flow were acquired throughout the study. After the ischemia or reperfusion period, the brain was excised and samples were analyzed by Western blots using anti-phospho-STAT1 and anti-Fas antibodies. Regions were selected for analysis according to their MRI characteristics.

RESULTS

Transcriptional factor STAT-1 was enhanced in the lesion core and, to a lesser extent, in the lesion periphery, following ischemia and reperfusion. This level of activity was greater than for ischemia alone. Western blots demonstrated STAT-1 phosphorylation on tyrosine 701 and not serine 727 after ischemia and 3 h of reperfusion. Enhanced expression of the apoptotic death receptor Fas was confirmed after ischemia followed by reperfusion.

CONCLUSIONS

This study demonstrates that focal ischemia of the rat brain can induce STAT-1 activation, particularly following a period of reperfusion. The activation occurs not only in the lesion core, but also in the lesion periphery, as identified using MRI. STAT-1 may play an important role in the induction of cell death following stroke.

Histopathological alterations and functional brain deficits after transient hypoxia in the newborn rat pup: a long term follow-up

To assess temporal brain deficits consecutive to severe birth hypoxia, newborn rats were exposed for 20 min to 100% N2. This treatment induced a long-term growth retardation and a delayed, but only transient, neuronal loss (approximately 25%) in the CA1 hippocampus and parietal cortex, starting from 3 days and peaking at 6 days post-hypoxia. The expression profiles of various apoptosis-regulating proteins (including Bcl-2, Bax, p53 and caspase-3) were well correlated to the alterations of nuclear morphology depicted by 4,6-diamidino-2-phenylindole (DAPI). Whereas they confirmed a gradual histological recovery, specific DNA fragmentation patterns suggested that birth hypoxia may transiently reactivate the developmental programme of neuronal elimination. Although they successfully achieved various behavioral tests such as the righting reflex, negative geotaxis, locomotor coordination, and the eight-arm maze tasks, both developing and adult hypoxic rats were repeatedly slower than controls, suggesting that birth hypoxia is associated to moderate but persistent impairments of functional capacities.

Bcl‐2 family members make different contributions to cell death in hypoxia and/or hyperoxia in rat cerebral cortex

Hypoxic brain injury during fetal or neonatal development leads to damaged immature neurons and can result in cognitive or behavioral dysfunction. Hyperoxia therapy (treatment with oxygen) is commonly applied to infants with signs of perinatal hypoxia-anoxia. Both hypoxia and hyperoxia have been shown to result in apoptosis in the brains of rats in several animal models. One determinant of cellular commitment to cell death is the differential expression of the Bcl-2 family of proteins in response to trauma. Here, we characterize cell death and the expression of Bcl-2 homologous proteins in 7-day-old neonatal rat cerebral cortex after hypoxia (5% O(2) for 40 min) and/or hyperoxia (>95% O(2) for 2 h after hypoxia). The expression of Bcl-2 and Bcl-X(L), two anti-apoptotic proteins, decreased at 24 h after hypoxia. Bcl-X(L) increased after either hyperoxia or hypoxia+hyperoxia. We did not detect significant changes in the cytoplasmic levels of pro-apoptotic protein Bax after any of these three treatments. Using cell death ELISA and DNA FragEL assays, we observed increased cell death at 24h after hypoxia, hyperoxia or hypoxia+hyperoxia treatments. At 24 h after either hypoxia, hyperoxia or hypoxia+hyperoxia, caspase 3 activity also increased significantly. Our results suggest that both hypoxia and hyperoxia alone can induce cell death. The Bcl-2 --> cytochrome c --> caspase 3 pathway played a role in hypoxia-induced cell death, while other pathways may be involved in hyperoxia-induced cell death.

Features of cell death in brain and liver, the target tissues of progressive neuronal degeneration of childhood with liver disease (Alpers-Huttenlocher disease)

Alpers-Huttenlocher disease (AHD) is a rare encephalopathy of infancy and childhood characterized by myoclonic seizures and progressive neurological deterioration, usually associated with signs and symptoms of liver dysfunction. There is no biological marker of the disease, and ultimate diagnosis still relies on pathological examination. Features of clinical progression and pathological findings suggest AHD to be secondary to a genetically determined disorder of mitochondrial function. We report on four AHD patients and focus on their pathological features in brain, liver and muscle. Liver and muscle biopsy specimens were examined using histochemical markers of the oxidative pathways, probes to immunodetect molecules of the apoptotic cascades and electron microscopy. In liver (but not in muscle) biopsy samples, activated caspases were detected by immunohistochemistry: foci of caspase-9-positive cells were seen in a child affected with chronic, progressive fibrosis. In an 18-year-old boy, who suffered from valproic acid-associated acute hepatitis, caspase-3 cells were clustered among the necrotic foci and the foamy cells. In both patients electron microscopy revealed apoptotic nuclei. Normal muscle biopsy specimens were observed in two children, 2 and 8 years-old respectively; in the 18-year-old patient cytochrome oxidase-negative fibers as well as ultrastructural findings of mitochondrial abnormalities were observed. In no patient was there biochemical evidence of impaired oxidative metabolism. Neuropathological examination of the brains of two patients (13 months and 19 years old, respectively) showed focal distribution of the lesions affecting the telencephalic cortex and, to a lesser extent, subcortical gray nuclei. Along with the necrotizing lesions, characterized by neuronal loss, neuropil microcysts and newly formed vessels, we also observed acutely shrunken neurons and features of apoptotic cell death in the cerebral cortex only. Severe neuronal loss without necrotizing features was observed in the cerebellar cortex. The presence of both anoxic and apoptotic nuclei in brain and liver, the target tissues of the disease, is consistent with the hypothesis that abnormal activation of mitochondrion-related cell death pathways might be involved in the pathogenesis of AHD.

A computerized image analysis system for quantitative analysis of cells in histological brain sections

We propose a reliable method for automatic counting of cells in brain sections labeled with different antibodies (against NeuN, parvalbumin, GABA and c-Fos) and in Nissl-staining. Images of stained sections are converted to binary images by thresholding. Clusters of 'ON pixels' (value of 1) corresponding to cell bodies are selected based on size. The parameters of the algorithm (intensity range and cluster-size) are adjusted for different methods of staining according to expert knowledge. The automatic cell counting method (ACCM) provides correct counting results, as demonstrated by a comparison of computational results with counts gained by human experimenters and with a commercially available image analysis system. On the basis of ACCM counts, small and perhaps physiologically relevant differences in the number of labeled cells can be revealed, as demonstrated here for the GABAergic system following electrical stimulation.

Necrosis: a specific form of programmed cell death?

For a long time necrosis was considered as an alternative to programmed cell death, apoptosis. Indeed, necrosis has distinct morphological features and it is accompanied by rapid permeabilization of plasma membrane. However, recent data indicate that, in contrast to necrosis caused by very extreme conditions, there are many examples when this form of cell death may be a normal physiological and regulated (programmed) event. Various stimuli (e.g., cytokines, ischemia, heat, irradiation, pathogens) can cause both apoptosis and necrosis in the same cell population. Furthermore, signaling pathways, such as death receptors, kinase cascades, and mitochondria, participate in both processes, and by modulating these pathways, it is possible to switch between apoptosis and necrosis. Moreover, antiapoptotic mechanisms (e.g., Bcl-2/Bcl-x proteins, heat shock proteins) are equally effective in protection against apoptosis and necrosis. Therefore, necrosis, along with apoptosis, appears to be a specific form of execution phase of programmed cell death, and there are several examples of necrosis during embryogenesis, a normal tissue renewal, and immune response. However, the consequences of necrotic and apoptotic cell death for a whole organism are quite different. In the case of necrosis, cytosolic constituents that spill into extracellular space through damaged plasma membrane may provoke inflammatory response; during apoptosis these products are safely isolated by membranes and then are consumed by macrophages. The inflammatory response caused by necrosis, however, may have obvious adaptive significance (i.e., emergence of a strong immune response) under some pathological conditions (such as cancer and infection). On the other hand, disturbance of a fine balance between necrosis and apoptosis may be a key element in development of some diseases.

Comparison of calpain and caspase activities in the adult rat brain after transient forebrain ischemia

The role of calpain and caspase family proteases in postischemic neuronal death remains controversial. This study compared the timing, location, and relative activity of calpains and caspases in the adult rat brain following 10 min of transient forebrain ischemia. Western blots of cortical, striatal, and hippocampal homogenates demonstrated a alpha-spectrin cleavage pattern indicative of predominant calpain activity, which peaked between 24 and 48 h after reperfusion. However, immunohistochemical evidence of both caspase 3 activation and caspase-mediated substrate cleavage was detected as early as 1 h and as late as 7 days after reperfusion in circumscribed neuronal populations. Simultaneous or sequential caspase and calpain activation was also observed suggesting the potential for interaction of these protease systems. The complex spatiotemporal pattern of calpain and caspase activity observed in this study provides important insights for the development and evaluation of therapeutic strategies to reduce protease-mediated injury following global brain ischemia.