DNA damage consistent with apoptosis in transient focal ischaemic neocortex

In vivo assessment of APPJ discharge on the earthworm: coelomic TAC and MDA levels, cell death, and tissue regeneration

The effective medical applications of cold atmospheric pressure plasma jet (APPJ) have been reported by many researchers, including sterilization of liquid and solid surfaces, treatment of chronic wounds, treatment of cancer tumors, and blood clots. Therefore, in this study, we exposed Aporrectodea trapezoides and Eisenia fetida earthworms to APPJ discharge (0-30 s) to evaluate the impacts on regeneration of missed segments, apoptosis, lipid peroxidation (LPo), catalase activity (CAT), total antioxidant capacity (TAC), total proteins, and protein profile. Results showed APPJ induced significant effects on regeneration ability of earthworms after 20 and 30 s of exposure (p < 0.05). Atmospheric pressure plasma jet did not have significant effects on MDA content and TUNEL-positive cells, but this effect was significant for TAC and CAT in both species (p < 0.05). In conclusion, the present study revealed for the first time that regeneration of missed segments in earthworms can be stimulated by plasma treatment.

Excitotoxicity: Still Hammering the Ischemic Brain in 2020

Interest in excitotoxicity expanded following its implication in the pathogenesis of ischemic brain injury in the 1980s, but waned subsequent to the failure of N-methyl-D-aspartate (NMDA) antagonists in high profile clinical stroke trials. Nonetheless there has been steady progress in elucidating underlying mechanisms. This review will outline the historical path to current understandings of excitotoxicity in the ischemic brain, and suggest that this knowledge should be leveraged now to develop neuroprotective treatments for stroke.

Phaseic Acid, an Endogenous and Reversible Inhibitor of Glutamate Receptors in Mouse Brain

Phaseic acid (PA) is a phytohormone regulating important physiological functions in higher plants. Here, we show the presence of naturally occurring (-)-PA in mouse and rat brains. (-)-PA is exclusively present in the choroid plexus and the cerebral vascular endothelial cells. Purified (-)-PA has no toxicity and protects cultured cortical neurons against glutamate toxicity through reversible inhibition of glutamate receptors. Focal occlusion of the middle cerebral artery elicited a significant induction in (-)-PA expression in the cerebrospinal fluid but not in the peripheral blood. Importantly, (-)-PA induction only occurred in the penumbra area, indicting a protective role of PA in the brain. Indeed, elevating the (-)-PA level in the brain reduced ischemic brain injury, whereas reducing the (-)-PA level using a monoclonal antibody against (-)-PA increased ischemic injury. Collectively, these studies showed for the first time that (-)-PA is an endogenous neuroprotective molecule capable of reversibly inhibiting glutamate receptors during ischemic brain injury.

Estrogen and neuroprotection: from clinical observations to molecular mechanisms

We now appreciate that estrogen is a pleiotropic gonadal steroid that exerts profound effects on the plasticity and cell survival of the adult brain. Over the past century, the life span of women has increased, but the age of the menopause remains constant. This means that women may now live over one third of their lives in a hypoestrogenic, postmenopausal state. The impact of prolonged hypoestrogenicity on the brain is now a critical health concern as we realize that these women may suffer an increased risk of cognitive dysfunction and neurodegeneration due to a variety of diseases. Accumulating evidence from both clinical and basic science studies indicates that estrogen exerts critical protective actions against neurodegenerative conditions such as Alzheimer's disease and stroke. Here, we review the discoveries that comprise our current understanding of estrogen action against neurodegeneration. These findings carry far-reaching possibilities for improving the quality of life in our aging population.

A neuroprotective polysaccharide from Hyriopsis cumingii

A water-soluble polysaccharide from Hyriopsis cumingii (HCp) was isolated by hot-water extraction and ethanol precipitation. We investigated the preliminary neuroprotective activity of HCp on cerebral ischemia/reperfusion (I/R)-induced rat brain tissue injury using the middle cerebral artery occlusion (MCAO) model. The structural analysis showed that the major component of HCp (HP-I) is an α-(1→4)-d-glucan branched with a single α-d-glucose at C-6 every five residues on average and has a weight-average molecular weight of about 2.65 × 10(5). Pharmacological studies revealed that HCp improves and restores nerve function impairment, significantly increases brain tissue total superoxide dismutase activity, lowers malondialdehyde content effectively, and reduces brain levels of caspase-3 mRNA expression in a dose-effect manner, indicating that H. cumingii polysaccharide possesses significant neuroprotective effects.

Mitochondria: joining forces to thwart cell death

Mitochondria are highly dynamic organelles that undergo constant cycles of fusion and fission. An additional level of regulation of mitochondrial function, which is particularly important in neurons, is their active transport along microtubules. Recent evidence suggests that the mitochondrial fusion/fission machinery as well as the molecular motors responsible for their movement constitute powerful regulatory control points that directly impact metabolism and regulation of cell death. This is true for not only apoptosis, but also for excitotoxicity where calcium overload is a major component of the cell death process. In this review, we will describe the molecular mechanisms regulating fusion and fission and how this impinges on cell survival in the context of acute neuronal injury.

Effect of Kangxin Capsule on the expression of nerve growth factors in parietal lobe of cortex and hippocampus CA1 area of vascular dementia model rats

OBJECTIVE

To observe the effect of Kangxin Capsule (KXC) on the expression of nerve growth factor (NGF) as well as the morphology and amount of nerve synapse in the cortical parietal lobe and hippocampus CA, area of vascular dementia ( VD) model rats.

METHODS

The model rats of VD made by photochemical reaction technique were randomly divided into five groups: the model group (MG), the high-dose, middle-dose and low-dose KXC groups (HDG, MDG and LDG), and the Western medicine hydergin control group (WMG). They were treated respectively with distilled water, high, middle and low dosage of KXC suspended liquid, and hydergin for a month. Besides, a blank group consisting of normal (non-model) rats was set up for control (CG). The ultrastructure of nerve synapse in the cortical parietal lobe and hippocampus CA1 area of the rats were observed and its density estimated. The condition of NGF positive neurons in the above-mentioned two regions were also observed by immunohistochemical stain.

RESULTS

All the KXC or hydergin treated groups demonstrated a normal amount of nerve synapse with integral structure in the cortical parietal lobe and hippocampus CA, area, which approached that in the CG and was superior to that in the MG. Also, the NGF positive neuron in all the treated groups was much more than that in MG with significant difference ( P<0.01), approaching to that in the CG.

CONCLUSION

KXC could elevate the expression of NGF in the cortical parietal lobe and hippocampus CA, area, preserve the number and morphology of synapse, thus to protect the function of nerve system from ischemic injury.

Sequential and spatial profiles of apoptosis in ischemic penumbra after two-vein occlusion in rats

Object

The two-vein occlusion model is known to be useful for ischemic penumbra studies in vivo. It was applied here to examine sequential changes in the expression of Bax and Bcl-2 proteins and in apoptotic cells to assess the relationship between penumbra and apoptosis.

Methods

Two cortical veins were occluded photochemically by using rose bengal dye in 27 Wistar rats. The animals were killed with perfusion fixation at the following intervals: 4, 12, 24, 48, 96, and 168 hours after vein occlusion (four at each interval; three additional rats were sham-treated). Immunohistochemical analysis for the Bcl-2 family of proteins was performed along with the terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling (TUNEL) assay to examine the relationship to single-cell death.

Cells positive for antiapoptotic proteins began to appear in the TUNEL assay for animals killed 24 hours after vein occlusion, with a peak at 48 hours. These cells were localized in the core of infarction. Immunohistochemical staining for Bax protein showed an increased presence around ischemic lesions at 4 hours after vein occlusion, and the amounts continued to rise until 24 hours, when the localization was diffuse around the core of infarction. Negative findings on immunohistochemical studies for Bcl-2 protein were seen at the early phase after two-vein occlusion.

Conclusions

After vein occlusion, apoptosis appeared sequentially and widely in cortical lesions considered to be the penumbra. Therefore, control of apoptosis would be expected to offer a therapeutic window for treatment of venous infarction.

Oxidative metabolism, apoptosis and perinatal brain injury

Perinatal hypoxic-ischaemic injury (HII) is a significant cause of neurodevelopmental impairment and disability. Studies employing 31P magnetic resonance spectroscopy to measure phosphorus metabolites in situ in the brains of newborn infants and animals have demonstrated that transient hypoxia-ischaemia leads to a delayed disruption in cerebral energy metabolism, the magnitude of which correlates with the subsequent neurodevelopmental impairment. Prominent among the biochemical features of HII is the loss of cellular ATP, resulting in increased intracellular Na+ and Ca2+, and decreased intracellular K+. These ionic imbalances, together with a breakdown in cellular defence systems following HII, can contribute to oxidative stress with a net increase in reactive oxygen species. Subsequent damage to lipids, proteins, and DNA and inactivation of key cellular enzymes leads ultimately to cell death. Although the precise mechanisms of neuronal loss are unclear, it is now clear both apoptosis and necrosis are the significant components of cell death following HII. A number of different factors influence whether a cell will undergo apoptosis or necrosis, including the stage of development, cell type, severity of mitochondrial injury and the availability of ATP for apoptotic execution. This review will focus on some pathological mechanisms of cell death in which there is a disruption to oxidative metabolism. The first sections will discuss the process of damage to oxidative metabolism, covering the data collected both from human infants and from animal models. Following sections will deal with the molecular mechanisms that may underlie cerebral energy failure and cell death in this form of brain injury, with a particular emphasis on the role of apoptosis and mitochondria.

Inflammation in areas of remote changes following focal brain lesion

Focal brain lesions can lead to metabolic and structural changes in areas distant from but connected to the lesion site. After focal ischemic or excitotoxic lesions of the cortex and/or striatum, secondary changes have been observed in the thalamus, substantia nigra pars reticulata, hippocampus and spinal cord. In all these regions, inflammatory changes characterized by activation of microglia and astrocytes appear. In the thalamus, substantia nigra pars reticulata and hippocampus, an expression of proinflammatory cytokine like tumor necrosis factor-alpha and interleukin-1beta is induced. However, time course of expression and cellular localisation differ between these regions. Neuronal damage has consistently been observed in the thalamus, substantia nigra and spinal cord. It can be present in the hippocampus depending on the procedure of induction of focal cerebral ischemia. This secondary neuronal damage has been linked to antero- and retrograde degeneration. Anterograde degeneration is associated with somewhat later expression of cytokines, which is localised in neurons. In case of retrograde degeneration, the expression of cytokines is earlier and is localised in astrocytes. Pharmacological intervention aiming at reducing expression of tumor necrosis factor-alpha leads to reduction of secondary neuronal damage. These first results suggest that the inflammatory changes in remote areas might be involved in the pathogenesis of secondary neuronal damage.

Neuropathological Studies on Cycloate-Induced Neuronal Cell Death in the Rat Brain

The herbicide cycloate (carbamothioic acid, ethyl(cyclohexyl)-S-ethyl ester) given as a single oral dose to rats, caused selective neuronal cell death in two regions in the rat forebrain, the pyramidal neurons of layers II-III throughout the pyriform cortex and in granule cells of the caudal ventro-lateral dentate gyrus. Male Alderley Park rats, 6-8-week-old, were given a single oral dose of either 0 or 2000 mg/kg cycloate and killed for neuropathological investigation 1, 2, 3, 7, 14 or 28 days after dosing, using a regime of perfusion fixation with modified Karnovsky's fixative, followed by routine paraffin embedding. Seven transverse levels of brain were examined from each rat. Cycloate-induced neuronal cell death was seen in the pyriform cortex 1 day after dosing and persisted through to Day 28, the lesion was more marked in the rostral compared to the caudal region of the pyriform cortex. Neuronal cell death was also observed in the ventro-lateral caudal dentate gyrus on Days 1-14, day after dosing. In the early stages, Days 1-3 and to a lesser extent Day 7, the neuronal cell death resembled apoptosis, characterized by condensation of nuclear material, cell shrinkage and strong cytoplasmic eosinophilia. By Days 14 and 28 and to a lesser extent Day 7, the cell death resembled necrosis, i.e. karyorrhectic nuclei with pale irregular cytoplasm. Microglial accumulation was associated with the neuronal cell injury. In control brains, an occasional apoptotic body was seen in both the pyriform cortex and dentate gyrus. Our results demonstrate that cycloate is a novel neurotoxicant, which following a single large oral dose induces a cell specific and highly localized forebrain lesion. The time course data analyzed temporally, suggests that cycloate may cause an up regulation of apoptosis in selected regions of the adult brain.

Molecular mechanisms of neuroprotective action of immunosuppressants--facts and hypotheses

Cyclosporin A (CsA) and FK506 (Tacrolimus) are short polypeptides which block the activation of lymphocytes and other immune system cells. Immunosuppressants exert neuroprotective and neurotrophic action in traumatic brain injury, sciatic nerve injury, focal and global ischemia in animals. Their neuroprotective actions are not understood and many hypotheses have been formed to explain such effects. We discuss a role of drug target--calcineurin in neuroprotective action of immunosuppressants. Protein dephosphorylation by calcineurin plays an important role in neuronal signal transduction due to its ability to regulate the activity of ion channels, glutamate release, and synaptic plasticity. In vitro FK506 protects cortex neurons from NMDA-induced death, augments NOS phosphorylation inhibiting its activity and NO synthesis. However, in vivo experiments demonstrated that FK506 in neuroprotective doses did not block excitotoxic cell death nor did it alter NO production during ischemia/reperfusion. Tissue damage in ischemia is the result of a complex pathophysiological cascade, which comprises a variety of distinct pathological events. Resident non-neuronal brain cells respond rapidly to neuronal cell death and may have both deleterious and useful role in neuronal damage. There is increasing evidence that reactive gliosis and post-ischemic inflammation involving microglia contribute to ischemic damage. We have demonstrated that FK506 modulates hypertrophic/proliferative responses and proinflammatory cytokine expression in astrocytes and microglia in vitro and in focal transient brain ischemia. Our findings suggest that astrocytes and microglia are direct targets of FK506 and modulation of glial response and inflammation is a possible mechanism of FK506-mediated neuroprotection in ischemia.

Kainic acid lesion-induced nigral neuronal death

Parkinson's disease (PD) is characterized by progressive death of dopamine (DA) neurons in the substantia nigra pars compacta. We report a rat model that exhibits progressive death of nigral neurons following unilateral injection of kainic acid in the striatum. In situ end-labeling revealed significant numbers of dying nigral neurons ipsilateral to the lesion during the first 3 weeks following injection. An indication of the gradual nature of death was that similar small numbers of cells were detected at each time point. These early morphological markers of neuronal death led to a significant reduction (20%) at 5 months of tyrosine hydroxylase-positive neurons and total number of neurons in the ipsilateral substantia nigra compared with the contralateral control. To examine the role of nigrostriatal DA metabolism in the observed nigral neuronal death, we manipulated DA metabolism during the initial 2 weeks following kainic acid lesion. Neurons in the ventral tier of the substantia nigra pars compacta were protected from death by treatment with 2,4-diamino-6-hydroxy-pyrimidine (DAHP), an inhibitor of GTP cyclohydrolase, the initial enzyme in the synthesis of the tyrosine hydroxylase co-substrate, tetrahydrobiopterin (BH(4)). Neurons in both the dorsal and ventral tier of substantia nigra pars compacta were protected from death by treatment with DAHP and L-DOPA. These experiments suggest that intrastriatal kainic acid lesion is an in vivo model of trophic support withdrawal. This experimental procedure is useful for studying mechanisms underlying protracted death of nigral DA neurons and may provide valuable mechanistic information relevant to understanding the etiology of PD.

Ischemia and stroke

Cell death following cerebral ischemia is mediated by a complex pathophysiologic interaction of different mechanisms. In this Chapter we will outline the basic principles as well as introduce in vitro and in vivo models of cerebral ischemia. Mechanistically, excitotoxicity, peri-infarct depolarization, inflammation and apoptosis seem to be the most relevant mediators of damage and are promising targets for neuroprotective strategies.

Apoptosis occurs in the penumbra zone during short-duration focal ischemia in the rat

To investigate the appearance of apoptosis in short-duration focal ischemia, the authors induced left middle cerebral artery (MCA) occlusion in male rats by insertion of an intraluminal suture. The total number of apoptotic cells was determined by hematoxylin-eosin staining and TUNEL labeling and confirmed by gel electrophoresis. The data indicate that the total number of apoptotic cells increased with ischemia duration (P = 0.0006), with most apoptotic cells located in the striatum of the ischemic hemisphere. As the duration of ischemia lengthened, necrosis became more prevalent and apoptosis receded to the periphery of the infarct. Using iodo[14C]-antipyrine to correlate the distribution of apoptosis to regional CBF (rCBF), the authors found that rCBF in the ischemic dorsolateral striatum was compatible with penumbra flow and significantly lower than the ventromedial striatum and frontoparietal cortex. This difference disappeared after 45 minutes of reperfusion. The authors conclude that focal ischemia of short duration results in changes compatible with apoptosis in regions of low rCBF, and this can occur without necrosis. This model is relevant to transient ischemic attack in the human and may suggest that, in addition to being a harbinger of stroke, transient ischemic attacks may cause histopathologic changes not yet clinically detectable.

Estrogens: protective or risk factors in brain function?

Over the past century, the average lifespan of women has increased from 50 to over 80 years, but the age of the menopause has remained fixed at 51 years. This "change of life" is marked by a dramatic and permanent decrease in circulating levels of ovarian estrogens. Therefore, more women will live a greater proportion of their lives in a chronic hypoestrogenic state. Ovarian steroid hormones are pleiotropic and have multiple, diverse, and possibly opposing actions in different contexts. In light of recent reports of the possible health risks of hormone replacement therapy (HRT) on several different physiological systems, the question of whether estrogens are protective or risk factors must be carefully re-evaluated.

Cellular replacement therapy for Parkinson's disease--where we are today?

The concept of replacing lost dopamine neurons in Parkinson's disease using mesencephalic brain cells from fetal cadavers has been supported by over 20 years of research in animals and over a decade of clinical studies. The ambitious goal of these studies was no less than a molecular and cellular "cure" for Parkinson's disease, other neurodegenerative diseases, and spinal cord injury. Much research has been done in rodents, and a few studies have been done in nonhuman primate models. Early uncontrolled clinical reports were enthusiastic, but the outcome of the first randomized, double blind, controlled study challenged the idea that dopamine replacement cells can cure Parkinson's disease, although there were some significant positive findings. Were the earlier animal studies and clinical reports wrong? Should we give up on the goal? Some aspects of the trial design and implantation methods may have led to lack of effects and to some side effects such as dyskinesias. But a detailed review of clinical neural transplants published to date still suggests that neural transplantation variably reverses some aspects of Parkinson's disease, although differing methods make exact comparisons difficult. While the randomized clinical studies have been in progress, new methods have shown promise for increasing transplant survival and distribution, reconstructing the circuits to provide dopamine to the appropriate targets and with normal regulation. Selected promising new strategies are reviewed that block apoptosis induced by tissue dissection, promote vascularization of grafts, reduce oxidant stress, provide key growth factors, and counteract adverse effects of increased age. New sources of replacement cells and stem cells may provide additional advantages for the future. Full recovery from parkinsonism appears not only to be possible, but a reliable cell replacement treatment may finally be near.

PKC and Raf-1 inhibition-related apoptotic signalling in N2a cells

In this study, a neuroblastoma N2a cell line was applied to investigate mechanisms of apoptosis induced either by selective inhibition of protein kinase C (PKC) by low amounts of staurosporine (STS(10) ) or by inhibition PI3-K after wortmannin (WM) treatment. We present evidence that, in the absence of serum in the medium, decreased phosphorylation of Raf-1 and BAD112, as well as Akt and BAD136, proteins and their translocation to mitochondria coincided with STS10 - or WM-induced apoptosis, respectively. Concomitantly, release of cytochrome c into the cytosol indicated a BCL-2-dependent mode of cell death after both treatments. Furthermore, in typical 'gain of function' experiments, cells with overexpression of permanently active Raf-1 or Akt transgenes displayed a significantly higher and independent resistance to either STS10 or WM. Thus, our results indicate that PKC/Raf-1/BAD112, as well as PI3-K/Akt/BAD136 signalling pathways, are both necessary for N2a cell survival and thus are unable to functionally substitute for each other as long as the cells do not receive additional signal(s) derived from serum. However, in the presence of serum, undefined trophic signal(s) can stimulate cross-talk between these two pathways at a level upstream from Raf-1 and Akt phosphorylation. In this case, only simultaneous inhibition of PKC and PI3-K is able to induce apoptosis.

Neuroprotective MK801 is associated with nitric oxide synthase during hypoxia/reoxygenation in rat cortical cell cultures

The neuroprotective effect of MK801 against hypoxia and/or reoxygenation-induced neuronal cell injury and its relationship to neuronal nitric oxide synthetase (nNOS) expression were examined in cultured rat cortical cells. Treatment of cortical neuronal cells with hypoxia (95% N(2)/5% CO(2)) for 2 h followed by reoxygenation for 24 h induced a release of lactate dehydrogenase (LDH) into the medium, and reduced the protein level of MAP-2 as well. MK801 attenuated the release of LDH and the reduction of the MAP-2 protein by hypoxia, suggesting a neuroprotective role of MK801. MK801 also diminished the number of nuclear condensation by hypoxia/reoxygenation. The NOS inhibitors 7-nitroindazole (7-NI) and N (G)-nitro-L-arginine methyl ester (L-NAME), as well as the Ca(2+) channel blocker nimodipine, reduced hypoxia-induced LDH, suggesting that nitric oxide (NO) and calcium homeostasis contribute to hypoxia and/or the reoxygenation-induced cell injury. The levels of nNOS immunoactivities and mRNA by RT-PCR were enhanced by hypoxia with time and, down regulated following 24 h reoxygenation after hypoxia, and were attenuated by MK801. In addition, the reduction of nNOS mRNA levels by hypoxia/reoxygenation was also diminished by MK801. Further delineation of the mechanisms of NO production and nNOS regulation are needed and may lead to additional strategies to protect neuronal cells against hypoxic/reoxygenation insults.

Induction of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression in rat brain after focal ischemia/reperfusion

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a glycolytic enzyme, has been recently identified to be involved in the initiation of neuronal apoptosis. To investigate the serial changes and cellular localization of GAPDH expression, and its role in ischemia/reperfusion-induced neuronal apoptosis, the authors analyzed immunohistochemically brain areas of rats subjected to middle cerebral artery occlusion (MCAO) and reperfusion. Nuclear overexpression of GAPDH was noted in the ischemic core area after 2 hours of MCAO without reperfusion. During the subsequent reperfusion, nuclear accumulation of GAPDH in this area decreased in a time-dependent manner. However, cytoplasmic and nuclear GAPDH immunoreactivity was detected in neurons of the penumbra area of the parietal cortex, in rats subjected to 2-hour MCAO followed by 3-hour reperfusion. The increase of nuclear GAPDH immunoreactivity was persistently noted up to 48 hours of reperfusion, whereas cytoplasmic immunoreactivity correlated inversely with the duration of reperfusion. Moreover, double staining revealed colocalization of nuclear GAPDH and TUNEL in the penumbra area. The authors' study demonstrated that overexpression of GAPDH and nuclear translocation occurred in both the ischemic core and penumbra area soon after focal ischemia. These processes could be viewed as an early marker of ischemia/reperfusion-induced apoptotic neuronal death. The results suggest that GAPDH may play a critical role in the progression and spread of ischemic neuronal damage.

Neuronal apoptosis inhibitory protein expression after traumatic brain injury in the mouse

Apoptosis of brain cells is triggered by traumatic brain injury (TBI) and is blocked by caspase inhibitors. The neuronal apoptosis inhibitor protein (NAIP), which has been shown to inhibit apoptosis by both caspase-dependant and caspase-independent mechanisms, is neuroprotective in rat models of cerebral ischemia and axotomy. In order to gain a better appreciation of CNS apoptosis following head injury in general and the possible involvement of NAIP specifically, we have configured a mouse model of TBI. In addition to demonstrating apoptosis, the spatiotemporal expression or levels of a number of proteins with apoptosis modulating effects have been determined. Apoptosis of neurons and oligodendrocytes following TBI was observed in brain sections which were triple-stained with in situ end labeling, bisbenzimide and immunofluorescent stain for neuron specific nuclear protein and myelin-associated glycoprotein, respectively. Further evidence for apoptosis following TBI in this model was obtained in brain samples using ligation-mediated PCR amplification of DNA fragments and gel electrophoresis. The temporal profile of apoptosis was similar to the temporal profile of microglial activation determined by CD11b staining and TNFa expression induced by TBI. NAIP staining in sections of cerebral cortex and subcortical white matter increased at 6 h and decreased towards control levels at 24 h post-TBI. Temporal changes in the expression of NAIP were also observed using Western blot analysis of brain samples removed from injured cortex and sub-cortical white matter. At the time that NAIP expression decreased markedly (24 h post-TBI), procaspase-3 levels also decreased, PARP cleavage increased, and the highest levels of apoptosis were observed. These findings have implications in our understanding of traumatically induced programmed cell death and may be useful in the configuration of therapies for this common injury state.

Cycloheximide reduces infarct volume when administered up to 6 h after mild focal ischemia in rats

We have previously described a rodent model of brief (30 min) middle cerebral artery occlusion followed by reperfusion, in which infarction develops gradually, reaching completion more than 3 days after ischemia, accompanied by morphological, biochemical, and pharmacological evidence of apoptosis. In the present study, we tested the hypotheses that delayed administration of a protein synthesis inhibitor would be effective in reducing tissue injury in this slowly evolving ischemic infarction, and that efficacy of this treatment would wane with more prolonged ischemia. Focal cerebral ischemia was induced in Long-Evans rats by occlusion of the right middle cerebral artery. Infarction volume was analyzed using triphenyl tetrazolium chloride staining, and morphology was studied using hematoxylin and eosin stained sections. Following 30 min middle cerebral artery occlusion and reperfusion, the core ischemic region exhibited vacuolization in the neuropil by 36 h after ischemia, and infarction reached full size by 7 days after ischemia. Cycloheximide reduced infarct volume when given up to 6 h after ischemia. If the duration of ischemic insult was increased to 90 min, the therapeutic window for delayed cycloheximide was only 30 min. In permanent middle cerebral artery occlusion, cycloheximide was ineffective even when given prior to ischemia onset. After mild, but not severe, ischemic insults, cerebral infarction develops slowly and may be treatable with protein synthesis inhibitors, even when treatment is delayed for up to 6 h after the onset of ischemia.

DNA fragmentation in ischemic core and penumbra in focal cerebral ischemia in rats

Although apoptotic cell death has been suggested to be involved in ischemic injury of the brain, the precise mechanisms of ischemic neuronal cell death are unknown. Here, we examined the biochemical feature of apoptosis (i.e. DNA fragmentation) in male spontaneously hypertensive rats (5-7 months old) subjected to photothrombotic distal middle cerebral artery (MCA) occlusion. After MCA occlusion, the brain was cut in a cryostat to produce a standard coronal block and samples were dissected from the regions corresponding to the ischemic core, penumbra and contralateral control areas. Changes in cerebral blood flow (CBF) were monitored at 1 mm posterior and 2-4 mm lateral to the bregma by means of a laser-Doppler flowmetry. After MCA occlusion, CBF was decreased to 72+/-18 (+/-S.D.), 50+/-14, and 35+/-11% of the control values at 2, 3, and 4 mm from the midline, respectively. DNA fragmentation characteristics of apoptosis were examined in these samples by conventional and pulse-field gel electrophoresis. On the conventional gel electrophoresis, nucleosomal DNA fragmentation was detected in the penumbral zone at 6 h after MCA occlusion. Large DNA fragments of 50 and 20 kbp were detected in the penumbral zone and also in the ischemic core region at 3 h after distal MCA occlusion. The large DNA fragments seen on the pulse-field gel elecrophoresis were further degraded to small DNA fragments at 6 h after MCA occlusion in the penumbral zone but not in the core regions. The evolving DNA fragmentation was observed between 3 and 6 h after the onset of brain ischemia in the penumbra, suggesting that apoptosis may contribute to the development of ischemic infarction.

Hyperglycemia enhances DNA fragmentation after transient cerebral ischemia

Previous histopathologic results have suggested that one mechanism whereby hyperglycemia (HG) leads to exaggerated ischemic damage involves fragmentation of DNA. DNA fragmentation in normoglycemia (NG) and HG rats subjected to 30 minutes of forebrain ischemia was studied by terminal deoxynucleotidyl transferase mediated DNA nick-labeling (TUNEL) staining, by pulse-field gel electrophoresis (PFGE), and by ligation-mediated polymerase chain reaction (LM-PCR). High molecular weight DNA fragments were detected by PFGE, whereas low molecular weight DNA fragments were detected using LM-PCR techniques. The LM-PCR procedure was performed on DNA from test samples with blunt (without Klenow polymerase) and 3'-recessed ends (with Klenow polymerase). In addition, cytochrome c release and caspase-3 activation were studied by immunocytochemistry. Results show that HG causes cytochrome c release, activates caspase-3, and exacerbates DNA fragments induced by ischemia. Thus, in HG rats, but not in control or NGs, TUNEL-stained cells were found in the cingulate cortex, neocortex, thalamus, and dorsolateral crest of the striatum, where neuronal death was observed by conventional histopathology, and where both cytosolic cytochrome c and active caspase-3 were detected by confocal microscopy. In the neocortex, both blunt-ended and stagger-ended fragments were detected in HG, but not in NG rats. Electron microscopy (EM) analysis was performed in the cingulate cortex, where numerous TUNEL-positive neurons were observed. Although DNA fragmentation was detected by TUNEL staining and electrophoresis techniques, EM analysis failed to indicate apoptotic cell death. It is concluded that HG triggers a cell death pathway and exacerbates DNA fragmentation induced by ischemia.

Caspase mRNA expression in a rat model of focal cerebral ischemia

Proteins of the caspase family are involved in the signalling pathway that ultimately leads to programmed cell death (apoptosis), which has been reported to occur in some experimental models of stroke. In a previous paper we used quantitative reverse transcription and polymerase chain reaction (RT-PCR) to characterise changes in the mRNA expression of one member of this family, caspase-3, in a rat model of permanent focal ischemia. Here we have used this technique to study the expression of a further three caspases which are involved in different aspects of caspase signalling. Caspase-8, involved in Fas-mediated apoptosis, was upregulated in the cortex of ischemic rats. Caspase-11, which leads to the synthesis of the functional form of the cytokine interleukin-1 beta, also showed increased expression, but with a different temporal profile from caspase-8. In contrast, caspase-9, which forms part of the pathway signalling through the mitochondria, showed a decrease in expression. The expression of a further four caspases (1, 2, 6 and 7) has also been characterised in a simpler experiment. These caspases all showed distinctive patterns of expression following the induction of ischemia. These data lead us to conclude that caspase expression as a whole is under very strict transcriptional control in this model. Certain elements of caspase signalling, such as the Fas-induced pathway and the events upstream of IL-1 beta processing, are upregulated, while others are not. This may be due to some form of genetic program activated in response to ischemia in the brain and may highlight which biological pathways are modulated.

Caspase 3 inhibition attenuates hydrogen peroxide-induced DNA fragmentation but not cell death in neuronal PC12 cells

Exposure of neurons to H(2)O(2) results in both necrosis and apoptosis. Caspases play a pivotal role in apoptosis, but exactly how they are involved in H(2)O(2)-mediated cell death is unknown. We examined H(2)O(2)-induced toxicity in neuronal PC12 cells and the effects of inducible overexpression of the H(2)O(2)-scavenging enzyme catalase on this process. H(2)O(2) caused cell death in a time- and concentration-dependent manner. Cell death induced by H(2)O(2) was found to be mediated in part through an apoptotic pathway as H(2)O(2)-treated cells exhibited cell shrinkage, nuclear condensation and marked DNA fragmentation. H(2)O(2) also triggered activation of caspase 3. Genetic up-regulation of catalase not only significantly reduced cell death but also suppressed caspase 3 activity and DNA fragmentation. While the caspase 3 inhibitor DEVD inhibited both caspase 3 activity and DNA fragmentation induced by H(2)O(2) it did not prevent cell death. Treatment with the general caspase inhibitor ZVAD, however, resulted in complete attenuation of H(2)O(2)-mediated cellular toxicity. These results suggest that DNA fragmentation induced by H(2)O(2) is attributable to caspase 3 activation and that H(2)O(2) may be critical for signaling leading to apoptosis. However, unlike inducibly increased catalase expression and general caspase inhibition both of which protect cells from cytotoxicity, caspase 3 inhibition alone did not improve cell survival suggesting that prevention of DNA fragmentation is insufficient to prevent H(2)O(2)-mediated cell death.

Apoptosis has a prolonged role in the neurodegeneration after hypoxic ischemia in the newborn rat

Birth asphyxia can cause moderate to severe brain injury. It is unclear to what degree apoptotic or necrotic mechanisms of cell death account for damage after neonatal hypoxia-ischemia (HI). In a 7-d-old rat HI model, we determined the contributions of apoptosis and necrosis to neuronal injury in adjacent Nissl-stained, hematoxylin and eosin-stained, and terminal deoxynucleotidyl transferase-mediated UTP nick end-labeled sections. We found an apoptotic-necrotic continuum in the morphology of injured neurons in all regions examined. Eosinophilic necrotic neurons, typical in adult models, were rarely observed in neonatal HI. Electron microscopic analysis showed "classic" apoptotic and necrotic neurons and "hybrid" cells with intermediate characteristics. The time course of apoptotic injury varied regionally. In CA3, dentate gyrus, medial habenula, and laterodorsal thalamus, the density of apoptotic cells was highest at 24-72 hr after HI and then declined. In contrast, densities remained elevated from 12 hr to 7 d after HI in most cortical areas and in the basal ganglia. Temporal and regional patterns of neuronal death were compared with expression of caspase-3, a cysteine protease involved in the execution phase of apoptosis. Immunocytochemical and Western blot analyses showed increased caspase-3 expression in damaged hemispheres 24 hr to 7 d after HI. A p17 peptide fragment, which results from the proteolytic activation of the caspase-3 precursor, was detected in hippocampus, thalamus, and striatum but not in cerebral cortex. The continued expression of activated caspase-3 and the persistence of cells with an apoptotic morphology for days after HI suggests a prolonged role for apoptosis in neonatal hypoxic ischemic brain injury.

Apoptosis after experimental stroke: fact or fashion?

This review examines the appearance of hallmarks of apoptosis following experimental stroke. The reviewed literature leaves no doubt that ischemic cell death in the brain is active, that is, requires energy; is gene directed, that is, requires new gene expression; and is capase-mediated, that is, uses apoptotic proteolytic machinery. However, sufficient differences to both classical necrosis and apoptosis exist which prevent easy mechanistic classification. It is concluded that ischemic cell death in the brain is neither necrosis nor apoptosis but is a chimera which appears on a continuum that has apoptosis and necrosis at the poles. The position on this continuum could be modulated by the intensity of the ischemic injury, the consequent availability of ATP and new protein synthesis, and both the age and context of the neuron in question. Thus the ischemic neuron may look necrotic but have actively died in an energy dependent manner with new gene expression and destruction via the apoptotic proteolytic machinery.

Induction of oxidative DNA damage in the peri-infarct region after permanent focal cerebral ischemia

To address the role of oxidative DNA damage in focal cerebral ischemia lacking reperfusion, we investigated DNA base and strand damage in a rat model of permanent middle cerebral artery occlusion (MCAO). Contents of 8-hydroxyl-2'-deoxyguanosine (8-OHdG) and apurinic/apyrimidinic abasic sites (AP sites), hallmarks of oxidative DNA damage, were quantitatively measured in nuclear DNA extracts from brains obtained 4-72 h after MCAO. DNA single- and double-strand breaks were detected on coronal brain sections using in situ DNA polymerase I-mediated biotin-dATP nick-translation (PANT) and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL), respectively. Levels of 8-OHdG and AP sites were markedly elevated 16-72 h following MCAO in the frontal cortex, representing the peri-infarct region, but levels did not significantly change within the ischemic core regions of the caudateputamen and parietal cortex. PANT- and TUNEL-positive cells began to be detectable 4-8 h following MCAO in the caudate-putamen and parietal cortex and reached maximal levels at 72 h. PANT- and TUNEL-positive cells were also detected 16-72 h after MCAO in the lateral frontal cortex within the infarct border, where many cells also showed colocalization of DNA single-strand breaks and DNA fragmentation. In contrast, levels of PANT-positive cells alone were transiently increased (16 h after MCAO) in the medial frontal cortex, an area distant from the infarct zone. These data suggest that within peri-infarct brain regions, oxidative injury to nuclear DNA in the form of base and strand damage may be a significant and contributory cause of secondary expansion of brain damage following permanent focal ischemia.

Differential changes of bax, caspase-3 and p21 mRNA expression after transient focal brain ischemia in the rat

Recent studies of transient focal ischemia have focused interest on apoptotic mechanisms of neuronal cell death involving constitutive pro-apoptotic proteins. The finding of specific patterns of novel gene expression might indicate the activation of pro-apoptotic genes in previously ischemic areas. Thus, we investigated gene expression for the pro-apoptotic regulators, Bax and caspase-3, after transient focal brain ischemia, together with the p53-regulated cell cycle inhibitor, p21/WAF1/CIP1. Reversible occlusion of the middle cerebral artery for 2 h was carried out in halothane-anesthetized rats using the poly-L-lysine coated filament method. In situ hybridization was performed at 0, 1, 3, 6 h and 1, 3 and 7 d of recirculation and in sham controls. Radioactive antisense probes served for detection of bax, p21 and caspase-3 mRNAs on brain sections, and quantitative film autoradiography was combined with image-averaging techniques. Bax mRNA tended to decline after focal brain ischemia within 1 d. p21 mRNA was upregulated with a perifocal pattern at 3 h and 1 d after ischemia whereas the ischemic regions themselves failed to show significant upregulation. Caspase-3 mRNA was elevated in the resistant dorsomedial cortex at 1 d. A pro-apoptotic pattern of novel gene expression, involving Bax and caspase-3, was not observed after transient focal brain ischemia. Rather, the perifocal expression of p21 and caspase-3 mRNAs observed at 1 d after ischemia points to reactive changes in resistant brain areas.

The pyrrolopyrimidine U101033E is a potent free radical scavenger and prevents Fe(II)-induced lipid peroxidation in synaptosomal membranes

The pyrrolopyrimidine U101033E is a therapeutic compound potentially useful in stroke, head injury and other oxidative stress conditions. Electron paramagnetic resonance (EPR) techniques of spin labeling and spin trapping in conjunction with measures of lipid and protein oxidation have been used to investigate the proposed antioxidant capacity of U101033E. We report potent antioxidant activity of this agent in aqueous cell-free solution as measured by spin trapping. U101033E significantly (P<0.005) reduces the formation of the EPR active spin trap N-t-butyl-alpha-phenylnitrone (PBN)-radical adduct by 17.1% at a concentration of 1 microM, four orders of magnitude less than the concentration of PBN. As measured by the decrease in signal intensity of lipid-resident nitroxide stearate spin probes, an EPR assay for lipid peroxidation, this pyrrolopyrimidine compound efficiently protected against hydroxyl radical-induced lipid peroxidation in cortical synaptosomal membranes deep within the membrane bilayer, but not closer to the membrane surface. In addition, U101033E partially prevents synaptosomal protein oxidation in the presence of Fe(II); however, U101033E demonstrates some protein oxidative effects itself. These results are supportive of the proposed role of U101033E as a lipid-specific antioxidant, especially for protection against lipid peroxidation that occurs deep within the membrane bilayer, but raise some potential concerns about the oxidative nature of this agent toward proteins.

Critical temporal modulation of neuronal programmed cell injury

1. As a free radical, nitric oxide (NO) may be toxic to neurons through mechanisms that directly involve DNA damage. Lubeluzole, a novel benzothiazole compound, has recently been demonstrated to be neuroprotective through the signal transduction pathways of NO. We therefore examined whether neuroprotection by lubeluzole was dependent upon the molecular pathways of programmed cell death (PCD). 2. In primary hippocampal neurons, evidence of PCD was determined by hematoxylin and eosin (H&E) stain, transmission electron microscopy, and annexin-V binding. NO administration with the NO generators sodium nitroprusside (300 microM) or SIN-1 (300 microM) directly induced PCD. 3. Neurons positive for PCD increased from 22+/-3% (untreated) to 72+/-3% (NO) over a 24-hr period. Coadministration of NO and lubeluzole (750 nM), a neuroprotective concentration, actively decreased PCD expression on H&E stain from 72+/-3% (NO only) to 25+/-3% (NO and lubeluzole). Significant reduction in DNA fragmentation by lubeluzole also was evident on electron microscopy. Application of lubeluzole in concentrations that were not neuroprotective or administration of the biologically inactive R-isomer did not significantly alter NO-induced PCD, suggesting that neuroprotection by lubeluzole was intimately linked to the modulation of PCD. Lubeluzole also was able to prevent the initial stages of cellular membrane inversion labeled with annexin-V binding, an early and sensitive indicator of PCD. Interestingly, the critical period for lubeluzole to reverse PCD induction appeared to be within the first 4 hr following NO exposure. 4. Further investigation into the neuroprotective pathways that alter PCD may provide greater insight into the molecular mechanisms that ultimately determine neuronal injury.

Why do neuroprotective drugs work in animals but not humans?

Many neuroprotective agents that seemed promising in animal studies of ischemic brain injury prove to have no effect when tested in clinical trials, suggesting that fundamental elements of translational research require better definition. A number of modifications have led to improvements in preclinical and human studies since the earliest controlled trials failed to confirm hypotheses suggested by animal data. Continued re-evaluation and sharing of information derived from the laboratory bench or the patient's bedside should eventually lead to effective neuroprotection in acute stroke. Experimental data should be carefully studied to improve the quality of agents coming to clinical trials and to design trial phasing that effectively determines drug safety and efficacy. This article will examine preclinical modeling and its translation to prospective studies of acute stroke therapy and will focus on some potential solutions directed at clinical trial design.

Distribution and kainate-mediated induction of the DNA mismatch repair protein MSH2 in rat brain

DNA repair is one of the most essential systems for maintaining the inherited nucleotide sequence of genomic DNA over time. Repair of DNA damage would be particularly important in neurons, because these cells are among the longest-living cells in the body. MSH2 is one of the proteins which are involved in the recognition and repair of a specific type of DNA damage that is characterized by pair mismatches. We studied the distribution of MSH2 in rat brain by immunohistochemical analysis. We found the level of MSH2 expression in rat brain to be clearly heterogeneous. The highest intensity of staining was found in the pyramidal neurons of the hippocampus and in the entorhinal and frontoparietal cortices. Positive cells were observed in the substantia nigra pars compacta, in cerebellar granular and Purkinje cells, and in the motor neurons of the spinal cord. We investigated the possible modulation of MSH2 expression after injection of kainate. Systemic administration of kainate induces various behavioural alterations and a typical pattern of neuropathology, with cell death in the hippocampal pyramidal neurons of the CA3/CA4 fields. Kainate injection also resulted in a marked, dose-dependent increase of MSH2 immunoreactivity in the hippocampal neurons of the CA3/CA4 fields. The effect was specific, since no changes in immunoreactivity were detected in the dentate gyrus nor in other brain areas. In summary, our data suggest that a mismatch DNA repair system, of which MSH2 protein is a representative component, is heterogeneously expressed in the rat brain and specifically induced by an experimental paradigm of excitotoxicity.

Novel treatments after experimental brain injury

Perinatal hypoxic-ischaemic encephalopathy(HIE) is being studied in laboratory models that allow the delayed cascade of events triggered by the energetic insult to be examined in detail. The concept of the 'excitotoxic cascade' provides a conceptual framework for thinking about the pathogenesis of HIE. Major events in the cascade triggered by hypoxia-ischaemia include overstimulation of N-methyl-D-aspartate type glutamate receptors, calcium entry into cells, activation of calcium-sensitive enzymes such as nitric oxide synthase, production of oxygen free radicals, injury to mitochondria, leading in turn to necrosis or apoptosis. New experimental approaches to salvaging brain tissue from the effects of HIE include inhibition of neuronal nitric oxide synthase, administration of neuronal growth factors, and inhibition of the caspase enzymes that execute apoptosis. Recent experimental work suggests that these approaches may be effective during a longer 'therapeutic window' after the insult, because they are acting on events that are relatively delayed. Application of modest hypothermia may allow these agents to be neuroprotective at even longer intervals after hypoxia-ischaemia.

The use of quantitative RT-PCR to measure mRNA expression in a rat model of focal ischemia--caspase-3 as a case study

Quantitative reverse transcription and polymerisation chain reaction (RT-PCR) using Taqman¿trade mark omitted¿ fluorogenic probes has been used to measure changes in gene expression in the cerebral cortex of rats in the permanent middle cerebral artery occlusion (pMCAO) model of focal ischemia. The mRNA levels of three housekeeping genes have been analysed in this model to determine which gene showed least change following experimental insult. In the lesioned cortex, beta-actin mRNA increased at 24 h, while the levels of cyclophilin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) did not change. We have also used this methodology to examine modulations in the level of caspase-3 mRNA during focal ischemia in the rat. Caspase-3 mRNA showed a 41% increase at 6 h post-MCAO, which was specific to the lesioned cortex. This change became more pronounced with time, showing an increase of 220% at 24 h. This methodology enables changes in mRNA expression to be analysed more sensitively and quantitatively than other available techniques and highlights the need for careful choice of control or housekeeping genes used for RNA comparisons.

The selective vulnerability of striatopallidal neurons

The different types of striatal neuron show a range of vulnerabilities to a variety of insults. This can be clearly seen in Huntington's disease where a well mapped pattern of pathological events occurs. Medium spiny projection (MSP) neurons are the first striatal cells to be affected as the disease progresses whilst interneurons, in particular the NADPH diaphorase positive ones, are spared even in the late stages of the disease. The MSP neurons themselves are also differentially affected. The death of MSP neurons in the patch compartment of the striatum precedes that in the matrix compartment and the MSP neurons of the dorsomedial caudate nucleus degenerate before those in the ventral lateral putamen. The enkephalin positive striatopallidal MSP neurons are also more vulnerable than the substance P/dynorphin MSP neurons. We review the potential causes of this selective vulnerability of striatopallidal neurons and discuss the roles of endogenous glutamate, nitric oxide and calcium binding proteins. It is concluded that MSP neurons in general are especially susceptible to disruptions of cellular respiration due to the enormous amount of energy they expend on maintaining unusually high transmembrane potentials. We go on to consider a subpopulation of enkephalinergic striatopallidal neurons in the rat which are particularly vulnerable. This subpopulation of neurons readily undergo apoptosis in response to experimental manipulations which affect dopamine and/or corticosteroid levels. We speculate that the cellular mechanisms underlying this cell death may also operate in degenerative disorders such as Huntington's disease thereby imposing an additional level of selectivity on the pattern of degeneration. The possible contribution of the selective death of striatopallidal neurons to a number of clinically important psychiatric conditions including obsessive compulsive disorders and Tourette's syndrome is also discussed.

DNA damage and DNA damage-inducible protein Gadd45 following ischemia in the P7 neonatal rat

Cerebral ischemia in adult rodents leads to the production of several types of lesions in the genomic DNA, followed by the activation of the damage-response indicator Gadd45. Our purpose was to investigate the structural changes that occur in chromatin DNA and repair processes after ischemic injury in neonatal brain. Neonatal ischemia was induced by the permanent left MCA occlusion in association with 1 h occlusion of the left common carotid artery in 7-day-old Wistar pups. Oligonucleosome fragments that are recognized as the characteristic DNA ladder was observed in a delayed fashion. Double-strand breaks result in high molecular weight fragments of 50- and 300-kbp as demonstrated by pulsed-field gel electrophoresis, and visualized by the TUNEL assay at 24 h of recovery. In contrast, DNA single-strand breaks, shown by the use of DNA polymerase I-mediated biotin-dATP nick translation were not so abundant. Gadd45 immunoreactivity was sequentially increased in vulnerable neurons in the infarct (4 to 24 h) and in sublethally injured neurons in the penumbra (24-48 h). Taken together, these findings suggest that Gadd45 responds to DNA damage following neonatal ischemia. Furthermore, repairing processes seem to be more active in the penumbra and therefore Gadd45 could have also a protective role in cerebral ischemia.

Caspase-8 and caspase-3 are expressed by different populations of cortical neurons undergoing delayed cell death after focal stroke in the rat

A number of studies have provided evidence that neuronal cell loss after stroke involves programmed cell death or apoptosis. In particular, recent biochemical and immunohistochemical studies have demonstrated the expression and activation of intracellular proteases, notably caspase-3, which act as both initiators and executors of the apoptotic process. To further elucidate the involvement of caspases in neuronal cell death induced by focal stroke we developed a panel of antibodies and investigated the spatial and temporal pattern of both caspase-8 and caspase-3 expression. Our efforts focused on caspase-8 because its "apical" position within the enzymatic cascade of caspases makes it a potentially important therapeutic target. Constitutive expression of procaspase-8 was detectable in most cortical neurons, and proteolytic processing yielding the active form of caspase-8 was found as early as 6 hr after focal stroke induced in rats by permanent middle cerebral artery occlusion. This active form of caspase-8 was predominantly seen in the large pyramidal neurons of lamina V. Active caspase-3 was evident only in neurons located within lamina II/III starting at 24 hr after injury and in microglia throughout the core infarct at all times examined. Terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling, gel electrophoresis of DNA, and neuronal cell quantitation indicated that there was an early nonapoptotic loss of cortical neurons followed by a progressive elimination of neurons with features of apoptosis. These data indicate that the pattern of caspase expression occurring during delayed neuronal cell death after focal stroke will vary depending on the neuronal phenotype.

Genetically modified mice in neuropharmacology

Since the first transgenic mouse was reported in 1980, genetically engineered mice have become an invaluable biological tool for better understanding of physiological and pathological processes in many fields of biomedical research. The transgenic technology allows researchers to carry out specific genetic manipulation in all cells of a laboratory animal, and makes it possible to dissect gene function in a living organism. In the field of neurosciences these animals have contributed greatly to shed light on basic mechanisms of brain function as well as to generate useful animal models for studying human neurological disorders. In this review, the different techniques available for generating specific mutations in the mouse genome will be described, from pronuclear microinjection to gene targeting in embryonic stem cells, and to the second generation of inducible and conditional knockout mice. Then, the impact of transgenic mouse models as an alternative or additional approach to neuropharmacology will be discussed, not only for the study of molecular mechanisms in the central nervous system but also for the identification of new biological targets for innovative pharmacological therapy.

Caspases as treatment targets in stroke and neurodegenerative diseases

Apoptosis is one of the most exciting and intensely investigated areas of biology and medicine today. Cysteine proteases called caspases serve as the executioners of apoptosis, a form of cell suicide. Hypoxic/ischemic cell death proceeds in part, by apoptosis, particularly within the periinfarct zone or ischemic penumbra. During ischemia, activated caspases dismantle the cell by cleaving multiple substrates including cytoskeletal proteins and enzymes essential for cell repair. Strategies that inhibit caspase activity block cell death in experimental models of mild ischemia, and preserve neurological function. The therapeutic window for caspase inhibition is substantially longer than for glutamate receptor antagonists, and treatment combinations with both classes of drugs decrease ischemic injury and expand the treatment window synergistically. Hence, the caspases are now recognized as novel therapeutic targets for central nervous system diseases in which cell death is prominent. This article will review the evidence and the potential importance of caspase inhibition to cerebral ischemia and briefly summarize an emerging body of data implicating caspases in cell death accompanying neurodegenerative disorders.