Analysis of the PKC-gamma-related immunocrossreactive region of a novel leukocyte protein gamma-rp

Mechanisms of neuronal cell death in ischemic stroke and their therapeutic implications

Ischemic stroke caused by arterial occlusion is the most common type of stroke, which is among the most frequent causes of disability and death worldwide. Current treatment approaches involve achieving rapid reperfusion either pharmacologically or surgically, both of which are time-sensitive; moreover, blood flow recanalization often causes ischemia/reperfusion injury. However, even though neuroprotective intervention is urgently needed in the event of stroke, the exact mechanisms of neuronal death during ischemic stroke are still unclear, and consequently, the capacity for drug development has remained limited. Multiple cell death pathways are implicated in the pathogenesis of ischemic stroke. Here, we have reviewed these potential neuronal death pathways, including intrinsic and extrinsic apoptosis, necroptosis, autophagy, ferroptosis, parthanatos, phagoptosis, and pyroptosis. We have also reviewed the latest results of pharmacological studies on ischemic stroke and summarized emerging drug targets with a focus on clinical trials. These observations may help to further understand the pathological events in ischemic stroke and bridge the gap between basic and translational research to reveal novel neuroprotective interventions.

Targeting pyroptosis to regulate ischemic stroke injury: Molecular mechanisms and preclinical evidences

Stroke is one of the leading causes of death worldwide with limited therapies. After ischemic stroke occurs, a robust sterile inflammatory response happens and lasts for days and determines neurological prognosis. Pyroptosis is an inflammatory programmed cell death characterized by cleavage of pore-forming proteins gasdermins as a result of activating caspases and inflammasomes. It has morphological characteristics of rapid plasma-membrane rupture and release of proinflammatory intracellular contents as well as cytokines. Recent researches implicate pyroptosis involvement in the pathogenesis of ischemic stroke and inhibition of pyroptosis attenuates ischemic brain injury. In this review, we discussed molecular mechanisms of pyroptosis, evidences for pyroptosis involvement in different kinds of the central nervous system cells, as well as potential inhibitors for intervention of pyroptosis. Based on the review, we hypothesize the feasibility of therapeutic strategies targeting pyroptosis in the context of ischemic stroke.

TMEM16F Aggravates Neuronal Loss by Mediating Microglial Phagocytosis of Neurons in a Rat Experimental Cerebral Ischemia and Reperfusion Model

Cerebral ischemia is a severe, acute condition, normally caused by cerebrovascular disease, and results in high rates of disability, and death. Phagoptosis is a newly recognized form of cell death caused by phagocytosis of viable cells, and has been reported to contribute to neuronal loss in brain tissue after ischemic stroke. Previous data indicated that exposure of phosphatidylserine to viable neurons could induce microglial phagocytosis of such neurons. Phosphatidylserine can be reversibly exposed to viable cells as a result of a calcium-activated phospholipid scramblase named TMEM16F. TMEM16F-mediated phospholipid scrambling on platelet membranes is critical for hemostasis and thrombosis, which plays an important role in Scott syndrome and has been confirmed by much research. However, few studies have investigated the association between TMEM16F and phagocytosis in ischemic stroke. In this study, a middle-cerebral-artery occlusion/reperfusion (MCAO/R) model was used in adult male Sprague-Dawley rats in vivo, and cultured neurons were exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) to simulate cerebral ischemia-reperfusion (I/R) injury in vitro. We found that the protein level of TMEM16F was significantly increased at 12 h after I-R injury both in vivo and in vitro, and reversible phosphatidylserine exposure was confirmed in neurons undergoing I/R injury in vitro. Additionally, we constructed a LV-TMEM16F-RNAi transfection system to suppress the expression of TMEM16F during and after cerebral ischemia. As a result, TMEM16F knockdown alleviated motor function injury and decreased the microglial phagocytosis of viable neurons in the penumbra through inhibiting the “eat-me” signal phosphatidylserine. Our data indicate that reducing neuronal phosphatidylserine-exposure via deficiency of TMEM16F blocks phagocytosis of neurons and rescues stressed-but-still-viable neurons in the penumbra, which may contribute to reducing infarct volume and improving functional recovering.

Mitochondrial function and brain Metabolic Score (BMS) in ischemic Stroke: Evaluation of "neuroprotectants" safety and efficacy

The initial and significant event developed in ischemic stroke is the sudden decrease in blood flow and oxygen supply to brain tissue, leading to dysfunction of the mitochondria. Many attempts were and are being made to develop new drugs and treatments that will save the ischemic brain, but the efficacy is not optimal and in many patients, irreversible damage to the brain will persist. We review a unique approach to evaluate mitochondrial function and microcirculatory hemodynamic in real time in vivo. Three out of four monitored physiological parameters are integrated into a new Brain Metabolic Score (BMS) calculated in real time and is correlated to Brain Oxygen Balance. The technology was adapted to various experimental as well as clinical situations for monitoring the brain in real time. The developed protocols could be used in testing the efficacy and safety of new drugs in experimental animals. Few models of brain monitoring during partial or complete ischemia were developed and used in naive animals or under brain activation protocols. It was found that mitochondrial function/dysfunction is the major and dominant parameter affecting the calculated Brain Metabolic Score. Using our monitoring system and protocols will provide direct information regarding the ability of the tested brain to provide enough oxygen consumed by the mitochondria in the "resting" or in the "activated" brain in vivo and in real-time. Preliminary studies, indicated that testing the efficacy and safety of new neuroprotectant drugs provided significant results to the R&D studies of ischemic stroke related to mitochondrial function.

Prolyl hydroxylase domain inhibitors: can multiple mechanisms be an opportunity for ischemic stroke?

Stroke and cerebrovascular disease are now the fifth most common cause of death behind other diseases such as heart, cancer and respiratory disease and accounts for approximately 40-50 fatalities per 100,000 people each year in the United States. Currently the only therapy for acute stroke, is intravenous administration of tissue plasminogen activator which was approved in 1996 by the FDA. Surprisingly no new treatments have come on the market since, although endovascular mechanical thrombectomy is showing promising results in trials. Recently focus has shifted towards a preventative therapy rather than trying to reverse or limit the amount of damage occurring following stroke onset. During one of the components of ischemia, hypoxia, a number of physiological changes occur within neurons which include the stabilization of hypoxia-inducible factors. The activity of these proteins is regulated by O₂, Fe²⁺, 2-OG and ascorbate-dependant hydroxylases which contain prolyl-4-hydroxylase domains (PHDs). PHD inhibitors are capable of pharmacologically activating the body's own endogenous adaptive response to low levels of oxygen and have therefore become an attractive therapeutic target for treating ischemia. They have been widely used in the periphery and have been shown to have a preconditioning and protective effect against a later and more severe ischemic insult. Currently there are a number of these agents in phase 1, 2 and 3 clinical trials for the treatment of anemia. In this review we assess the neuroprotective effects of PHD inhibitors, including dimethyloxalylglycine and deferoxamine and suggest that not all of their effects in the CNS are HIF-dependent. Unravelling new roles and a better understanding of the function of PHD inhibitors in the CNS may be of great benefit especially when investigating their use in the treatment of stroke and other ischemic diseases.

Preclinical Validation of the Therapeutic Potential of Glasgow Oxygen Level Dependent (GOLD) Technology: a Theranostic for Acute Stroke

In acute stroke patients, penumbral tissue is non-functioning but potentially salvageable within a time window of variable duration and represents target tissue for rescue. Reperfusion by thrombolysis and/or thrombectomy can rescue penumbra and improve stroke outcomes, but these treatments are currently available to a minority of patients. In addition to the utility of Glasgow Oxygen Level Dependent (GOLD) as an MRI contrast capable of detecting penumbra, its constituent perfluorocarbon (PFC) oxygen carrier, combined with normobaric hyperoxia, also represents a potential acute stroke treatment through improved oxygen delivery to penumbra. Preclinical studies were designed to test the efficacy of an intravenous oxygen carrier, the perfluorocarbon emulsion Oxycyte® (O-PFC), combined with normobaric hyperoxia (50% O₂) in both in vitro (neuronal cell culture) and in vivo rat models of ischaemic stroke. Outcome was assessed through the quantification of lipid peroxidation and oxidative stress levels, mortality, infarct volume, neurological scoring and sensorimotor tests of functional outcome in two in vivo models of stroke. Additionally, we investigated evidence for any positive or negative interactions with the thrombolytic recombinant tissue plasminogen activator (rt-PA) following embolus-induced stroke in rats. Treatment with intravenous O-PFC + normobaric hyperoxia (50% O₂) provided evidence of reduced infarct size and improved functional recovery. It did not exacerbate oxidative stress and showed no adverse interactions with rt-PA. The positive results and lack of adverse effects support human trials of O-PFC + 50% O₂ normobaric hyperoxia as a potential therapeutic approach. Combined with the diagnostic data presented in the preceding paper, O-PFC and normobaric hyperoxia is a potential theranostic for acute ischaemic stroke.

Neuronal Cell Death

Neuronal cell death occurs extensively during development and pathology, where it is especially important because of the limited capacity of adult neurons to proliferate or be replaced. The concept of cell death used to be simple as there were just two or three types, so we just had to work out which type was involved in our particular pathology and then block it. However, we now know that there are at least a dozen ways for neurons to die, that blocking a particular mechanism of cell death may not prevent the cell from dying, and that non-neuronal cells also contribute to neuronal death. We review here the mechanisms of neuronal death by intrinsic and extrinsic apoptosis, oncosis, necroptosis, parthanatos, ferroptosis, sarmoptosis, autophagic cell death, autosis, autolysis, paraptosis, pyroptosis, phagoptosis, and mitochondrial permeability transition. We next explore the mechanisms of neuronal death during development, and those induced by axotomy, aberrant cell-cycle reentry, glutamate (excitoxicity and oxytosis), loss of connected neurons, aggregated proteins and the unfolded protein response, oxidants, inflammation, and microglia. We then reassess which forms of cell death occur in stroke and Alzheimer's disease, two of the most important pathologies involving neuronal cell death. We also discuss why it has been so difficult to pinpoint the type of neuronal death involved, if and why the mechanism of neuronal death matters, the molecular overlap and interplay between death subroutines, and the therapeutic implications of these multiple overlapping forms of neuronal death.

Sustained diffusion reversal with in-bore reperfusion in monkey stroke models: Confirmed by prospective magnetic resonance imaging

Although early diffusion lesion reversal after recanalization treatment of acute ischaemic stroke has been observed in clinical settings, the reversibility of lesions observed by diffusion-weighted imaging remains controversial. Here, we present consistent observations of sustained diffusion lesion reversal after transient middle cerebral artery occlusion in a monkey stroke model. Seven rhesus macaques were subjected to endovascular transient middle cerebral artery occlusion with in-bore reperfusion confirmed by repeated prospective diffusion-weighted imaging. Early diffusion lesion reversal was defined as lesion reversal at 3 h after reperfusion. Sustained diffusion lesion reversal was defined as the difference between the ADC-derived pre-reperfusion maximal ischemic lesion volume (ADC_{D-P Match}) and the lesion on 4-week follow-up FLAIR magnetic resonance imaging. Diffusion lesions were spatiotemporally assessed using a 3-D voxel-based quantitative technique. The ADC_{D-P Match} was 9.7 ± 6.0% (mean ± SD) and the final infarct was 1.2-6.0% of the volume of the ipsilateral hemisphere. Early diffusion lesion reversal and sustained diffusion lesion reversal were observed in all seven animals, and the calculated percentages compared with their ADC_{D-P Match} ranged from 8.3 to 51.9% (mean ± SD, 26.9 ± 15.3%) and 41.7-77.8% (mean ± SD, 65.4 ± 12.2%), respectively. Substantial sustained diffusion lesion reversal and early reversal were observed in all animals in this monkey model of transient focal cerebral ischaemia.

Transient Vestibulopathy in Wallenberg's Syndrome: Pathologic Analysis

Objective

To report an unusual lateral medullary stroke (LMS) associated with transient unidirectional horizontal, nystagmus, and decreased horizontal vestibulo–ocular reflex (h-VOR) gain that mimicked a peripheral vestibulopathy. MRI suggested involvement of caudal medial vestibular nucleus (MVN); however, the rapid resolution of the nystagmus and improved h-VOR gain favored transient ischemia without infarction. Decreased h-VOR gain is expected with peripheral vestibular lesions within the labyrinth or superior vestibular nerve; less frequently lateral pontine strokes involving the vestibular root entry, the vestibular fascicle, or neurons within the MVN may be responsible. The h-VOR is typically normal in LMS.

Methods

Clinicopathologic examination of a 61-year-old man with an acute vestibular syndrome (AVS) and left LMS who died 3 weeks after the stroke. Postmortem brainstem analysis was performed.

Results

The stroke involved the lateral medulla and pontomedullary junction, near the MVN, sparing the cerebellum and pons. To explain transient vestibular findings there are two possible hypotheses; the first would be that the MVN survived the ischemic process and would be histologically intact, and the second that vestibular afferents in the horizontal semicircular canal were ischemic and recovered after the ischemic process. Neuropathological examination showed a left LMS whose extent matched that seen by imaging. Non-ocular motor signs correlated well with structures affected by the infarction. Neurons and glia within nearby MVN were spared, as predicted by the rapid normalization of the ocular motor signs. Although unlikely, the possibility of transient intralabyrinthine arteriolar ischemia cannot be excluded. Additionally, truncal lateropulsion was due to combined lateral vestibulospinal tract and lateral reticular nucleus infarction.

Conclusion

LMS may rarely be associated with an AVS that either represents or mimics a peripheral vestibulopathy. To our knowledge, this is the first neuropathologic examination of the brainstem of an LMS associated with transient vestibular findings occurring in the context of an anterior/posterior (AICA/PICA) cerebellar arterial variant stroke.

Neuroprotection of Gueichih-Fuling-Wan on cerebral ischemia/ reperfusion injury in streptozotocin-induced hyperglycemic rats via the inhibition of the cellular apoptosis pathway and neuroinflammation

Background: Risks of stroke link with complications of hyperglycemia. Gueichih-Fuling-Wan (GFW), according to Chinese Medical Code literature, has the promotion of blood circulation and attenuates the swollen plot. Recent pharmacological studies have pointed out its efficacy in patients with cerebral ischemia or diabetes. Therefore, this study determined whether GFW has the protection against cerebral ischemia/ reperfusion (I/R) injury in streptozotocin (STZ)-induced hyperglycemic rats and LPS-induced inflammation in BV-2 microglial cells.

Methods: Extracts of GFW were filtered and frozen to dry for use. Hyperglycemia was induced by intraperitoneal injection of 70 mg/kg STZ. Fourteen days after STZ injection, GFW (1, 2 and 4 g/kg) was orally administered once daily for seven days. Rats were subjected to cerebral ischemia/reperfusion and sacrificed for infarction analysis and neuronal apoptosis detection twenty-one days after STZ injection. MTT assay was used for cell viability; nitrite quantification and western blot analysis of iNOS and COX-2 were used to explore the effects of GFW on LPS-induced inflammation in BV-2 microglial cells.

Results: GFW significantly ameliorated cerebral infarction while dosage was more than 1 g/kg (by 38.03% at 2 g/kg and 52.44% at 4 g/kg), and attenuated neurological deficits by 23.48% (at 2 g/kg) and 47.25% (at 4 g/kg). Furthermore, GFW (2, 4 g/kg) notably decreased TUNEL- and cleaved caspase-3-positive cells in the immunohistochemical stain (P < 0.01 and P < 0.001, respectively). GFW remarkably increased in Bcl-2 and decreased in caspase-3 and Bax/Bcl-2 ratio protein expressions by Western blot. GFW (0.25, 0.5, 1 mg/ ml) significantly reduced LPS-induced NO production in BV-2 microglial cells. And GFW attenuated iNOS and COX-2 expression in LPS-treated BV-2 cells. Conclusions: In summary, GFW has good bioactivities to protect cerebral I/R injury in hyperglycemic rats, which might be due to inhibition of cellular apoptosis and neuroinflammation.

Long-term survival and regeneration of neuronal and vasculature cells inside the core region after ischemic stroke in adult mice

Focal cerebral ischemia results in an ischemic core surrounded by the peri-infarct region (penumbra). Most research attention has been focused on penumbra while the pattern of cell fates inside the ischemic core is poorly defined. In the present investigation, we tested the hypothesis that, inside the ischemic core, some neuronal and vascular cells could survive the initial ischemic insult while regenerative niches might exist many days after stroke in the adult brain. Adult mice were subjected to focal cerebral ischemia induced by permanent occlusion of distal branches of the middle cerebral artery (MCA) plus transient ligations of bilateral common carotid artery (CCA). The ischemic insult uniformly reduced the local cerebral blood flow (LCBF) by 90%. Massive cell death occurred due to multiple mechanisms and a significant infarction was cultivated in the ischemic cortex 24 h later. Nevertheless, normal or even higher levels of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) persistently remained in the core tissue, some NeuN-positive and Glut-1/College IV-positive cells with intact ultrastructural features resided in the core 7-14 days post stroke. BrdU-positive but TUNEL-negative neuronal and endothelial cells were detected in the core where extensive extracellular matrix infrastructure developed. Meanwhile, GFAP-positive astrocytes accumulated in the penumbra and Iba-1-positive microglial/macrophages invaded the core several days after stroke. The long term survival of neuronal and vascular cells inside the ischemic core was also seen after a severe ischemic stroke induced by permanent embolic occlusion of the MCA. We demonstrate that a therapeutic intervention of pharmacological hypothermia could save neurons/endothelial cells inside the core. These data suggest that the ischemic core is an actively regulated brain region with residual and newly formed viable neuronal and vascular cells acutely and chronically after at least some types of ischemic strokes.

Expanding the concept of neuroprotection for acute ischemic stroke: The pivotal roles of reperfusion and the collateral circulation

This review surveys the efforts taken to achieve clinically efficacious protection of the ischemic brain and underscores the necessity of expanding our purview to include the essential role of cerebral perfusion and the collateral circulation. We consider the development of quantitative strategies to measure cerebral perfusion at the regional and local levels and the application of these methods to elucidate flow-related thresholds of ischemic viability and to characterize the ischemic penumbra. We stress that the modern concept of neuroprotection must consider perfusion, the necessary substrate upon which ischemic brain survival depends. We survey the major mechanistic approaches to neuroprotection and review clinical neuroprotection trials, focusing on those phase 3 multicenter clinical trials for acute ischemic stroke that have been completed or terminated. We review the evolution of thrombolytic therapies; consider the lessons learned from the initial, negative multicenter trials of endovascular therapy; and emphasize the highly successful positive trials that have finally established a clinical role for endovascular clot removal. As these studies point to the brain's collateral circulation as key to successful reperfusion, we next review the anatomy and pathophysiology of collateral perfusion as it relates to ischemic infarction, as well as the molecular and genetic influences on collateral development. We discuss the current MR and CT-based diagnostic methods for assessing the collateral circulation and the prognostic significance of collaterals in ischemic stroke, and we consider past and possible future therapeutic directions.

A compressible scaffold for minimally invasive delivery of large intact neuronal networks

Millimeter to centimeter-sized injectable neural scaffolds based on macroporous cryogels are presented. The polymer-scaffolds are made from alginate and carboxymethyl-cellulose by a novel simple one-pot cryosynthesis. They allow surgical sterility by means of autoclaving, and present native laminin as an attachment motive for neural adhesion and neurite development. They are designed to protect an extended, living neuronal network during compression to a small fraction of the original volume in order to enable minimally invasive delivery. The scaffolds behave as a mechanical meta-material: they are soft at the macroscopic scale, enabling injection through narrow-bore tubing and potentially good cellular scaffold integration in soft target tissues such as the brain. At the same time, the scaffold material has a high local Young modulus, allowing protection of the neuronal network during injection. Based on macroscopic and nanomechanical characterization, the generic geometrical and mechanical design rules are presented, enabling macroporous cellular scaffold injectability.

Age-dependent modifications in vascular adhesion molecules and apoptosis after 48-h reperfusion in a rat global cerebral ischemia model

Stroke is one of the leading causes of death and permanent disability in the elderly. However, most of the experimental studies on stroke are based on young animals, and we hypothesised that age can substantially affect the stroke response. The two-vessel occlusion model of global ischemia by occluding the common carotid arteries for 15 min at 40 mmHg of blood pressure was carried out in 3- and 18-month-old male Sprague-Dawley rats. The adhesion molecules E- and P-selectin, cell adhesion molecules (CAMs), both intercellular (ICAM-1) and vascular (VCAM-1), as well as glial fibrillary acidic protein (GFAP), and cleaved caspase-3 were measured at 48 h after ischemia in the cerebral cortex and hippocampus using Western blot, qPCR and immunofluorescence techniques. Diametric expression of GFAP and a different morphological pattern of caspase-3 labelling, although no changes in the cell number, were observed in the neurons of young and old animals. Expression of E-selectin and CAMs was also modified in an age- and ischemia/reperfusion-dependent manner. The hippocampus and cerebral cortex had similar response patterns for most of the markers studied. Our data suggest that old and young animals present different time-courses of neuroinflammation and apoptosis after ischemic damage. On the other hand, these results suggest that neuroinflammation is dependent on age rather than on the different vulnerability described for the hippocampus and cerebral cortex. These differences should be taken into account in searching for therapeutic targets.

Effects of noninvasive facial nerve stimulation in the dog middle cerebral artery occlusion model of ischemic stroke

BACKGROUND AND PURPOSE

Facial nerve stimulation has been proposed as a new treatment of ischemic stroke because autonomic components of the nerve dilate cerebral arteries and increase cerebral blood flow when activated. A noninvasive facial nerve stimulator device based on pulsed magnetic stimulation was tested in a dog middle cerebral artery occlusion model.

METHODS

We used an ischemic stroke dog model involving injection of autologous blood clot into the internal carotid artery that reliably embolizes to the middle cerebral artery. Thirty minutes after middle cerebral artery occlusion, the geniculate ganglion region of the facial nerve was stimulated for 5 minutes. Brain perfusion was measured using gadolinium-enhanced contrast MRI, and ATP and total phosphate levels were measured using 31P spectroscopy. Separately, a dog model of brain hemorrhage involving puncture of the intracranial internal carotid artery served as an initial examination of facial nerve stimulation safety.

RESULTS

Facial nerve stimulation caused a significant improvement in perfusion in the hemisphere affected by ischemic stroke and a reduction in ischemic core volume in comparison to sham stimulation control. The ATP/total phosphate ratio showed a large decrease poststroke in the control group versus a normal level in the stimulation group. The same stimulation administered to dogs with brain hemorrhage did not cause hematoma enlargement.

CONCLUSIONS

These results support the development and evaluation of a noninvasive facial nerve stimulator device as a treatment of ischemic stroke.

Acid-sensing ion channels activation and hypoxia upregulate Homer1a expression

BACKGROUND

Recent studies have indicated that dynamic alterations in the structure of postsynaptic density (PSD) are involved in the pathogenesis of many central nervous system disorders, including ischemic stroke. Homer is the newly identified scaffolding protein located at PSD and regulates synaptic function. Homer1a, an immediate early gene, has been shown to be induced by several stimulations, such as glutamate, brain-derived neurotrophic factor, and trauma. However, whether acidosis mediated by acid-sensing ion channels (ASICs) and hypoxia during cerebral ischemia can change Homer1a expression remains to be determined.

RESULTS

We investigated that acidosis and hypoxia selectively and rapidly upregulated Homer1a expression, but not Homer1b/c in cultured cortical neurons. We also found that Homer1a exhibited induction expression in brain cortex of the middle cerebral artery occlusion (MCAO) rats. Additionally, acid-evoked Homer1a mRNA induction depended on extracellular signal-regulated kinase1/2 (ERK1/2) and Akt activity, and ASIC1a-mediated calcium influx whereas hypoxia depended only on ERK1/2 activity. Also, we demonstrated that continuous acidosis and hypoxia resulted in pronounced cell injury and Homer1a knockdown with small interfering RNA aggravated this damage induced by 3 h acid and hypoxia incubation in neuro-2a cells.

CONCLUSION

Homer1a might act as an activity-dependent regulator responding to extracellular stimuli during cerebral ischemia.

Infratentorial strokes for posterior circulation folks: clinical correlations for current translational therapeutics

Approximately 20 percent of all strokes will occur in the Infratentorial brain. This is within the vascular territory of the posterior vascular circulation. Very few clinical specifics are known about the therapeutic needs of this patient sub-population. Most evidence-based practices are founded from research about the treatment of anterior circulatory stroke. As a consequence, little is known about how stroke in the Infratentorial brain region would require a different approach. We characterized the neurovascular features of Infratentorial stroke, pathophysiological responses, and experimental models for further translational study.

mRNA redistribution during permanent focal cerebral ischemia

Translation arrest occurs in neurons following focal cerebral ischemia and is irreversible in penumbral neurons destined to die. Following global cerebral ischemia, mRNA is sequestered away from 40S ribosomal subunits as mRNA granules, precluding translation. Here, we investigated mRNA granule formation using fluorescence in situ histochemistry out to 8 h permanent focal cerebral ischemia using middle cerebral artery occlusion in Long Evans rats with and without diabetes. Neuronal mRNA granules colocalized with PABP, HuR, and NeuN, but not 40S or 60S ribosomal subunits, or organelle markers. The volume of brain with mRNA granule-containing neurons decreased exponentially with ischemia duration, and was zero after 8 h permanent focal cerebral ischemia or any duration of ischemia in diabetic rats. These results show that neuronal mRNA granule response has a limited range of insult intensity over which it is expressed. Identifying the limits of effective neuronal stress response to ischemia will be important for developing effective stroke therapies.

Neuroprotective effects of quetiapine on neuronal apoptosis following experimental transient focal cerebral ischemia in rats

OBJECTIVE

This study was undertaken in the belief that the atypical antipsychotic drug quetiapine could prevent apoptosis in the penumbra region following ischemia, taking into account findings that show 5-hydroxytryptamine-2 receptor blockers can prevent apoptosis.

METHODS

We created 5 groups, each containing 6 animals. Nothing was done on the K-I group used for comparisons with the other groups to make sure adequate ischemia had been achieved. The K-II group was sacrificed on the 1st day after transient focal cerebral ischemia and the K-III group on the 3rd day. The D-I group was administered quetiapine following ischemia and sacrificed on the 1st day while the D-II group was administered quetiapine every day following the ischemia and sacrificed on the 3rd day. The samples were stained with the immunochemical TUNEL method and the number of apoptotic cells were counted.

RESULTS

There was a significant difference between the first and third day control groups (K-II/K-III : p=0.004) and this indicates that apoptotic cell death increases with time. This increase was not encountered in the drug groups (D-I/D-II : p=1.00). Statistical analysis of immunohistochemical data revealed that quetiapine decreased the apoptotic cell death that normally increased with time.

CONCLUSION

Quetiapine is already in clinical use and is a safe drug, in contrast to many substances that are used to prevent ischemia and are not normally used clinically. Our results and the literature data indicate that quetiapine could help both as a neuronal protector and to resolve neuropsychiatric problems caused by the ischemia in cerebral ischemia cases.

Posterior circulation stroke: animal models and mechanism of disease

Posterior circulation stroke refers to the vascular occlusion or bleeding, arising from the vertebrobasilar vasculature of the brain. Clinical studies show that individuals who experience posterior circulation stroke will develop significant brain injury, neurologic dysfunction, or death. Yet the therapeutic needs of this patient subpopulation remain largely unknown. Thus understanding the causative factors and the pathogenesis of brain damage is important, if posterior circulation stroke is to be prevented or treated. Appropriate animal models are necessary to achieve this understanding. This paper critically integrates the neurovascular and pathophysiological features gleaned from posterior circulation stroke animal models into clinical correlations.

Selective ozone concentrations may reduce the ischemic damage after a stroke

Abstract Stroke is one of the most debilitating diseases, and it is unfortunate that only a small percentage of patients can be treated with thrombolytic agents. Consequently, there is an urgent need of finding an alternative procedure for reoxygenating the so-called penumbra at the earliest time as possible for reducing morbidity and disability. A preliminary, preclinical study has been carried out by using rat hippocampal and cortical brain slices subjected to oxygen-glucose deprivation. Oxygen-ozone gaseous mixture appeared to be effective in reverting damage of brain tissues, supporting the evaluation of this approach in well-designed clinical trials in stroke patients.

Potentiation of aspirin-induced cerebroprotection by minocycline: a therapeutic approach to attenuate exacerbation of transient focal cerebral ischaemia

Cerebrovascular disease is a major cause of mortality and disability in adults. Diabetes mellitus increases the risk of cerebral ischaemia and is associated with worse clinical outcome following an event. Upregulation of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) in diabetes appears to play a role in vascular complications of diabetes. We hypothesised that inhibition of MMP-2 and MMP-9 by minocycline can be potentiated by aspirin through inhibition of cyclooxygenase-2 and tissue plasminogen activator, resulting in amelioration of clinical cerebral ischaemia in diabetes. In the present study, cerebral ischaemia/reperfusion injury was induced in streptozotocin diabetic rats by 1 h middle cerebral artery occlusion and 24 h reperfusion. Infarct volume, cerebral oedema, neurological severity score and blood-brain barrier disruption were significantly increased in diabetic animals compared with the normoglycemic control group. The combination of aspirin and minocycline treatment significantly improved these parameters in diabetic animals. Moreover, this therapy was associated with significantly lower mortality and reduction in MMP-2 and MMP-9 levels. Our data indicate that combination of aspirin and minocycline therapy protects from the consequences of cerebral ischaemia in animal models of diabetes and is associated with inhibition of MMP-2 and MMP-9. Therefore, this combination therapy may represent a novel strategy to reduce the neurological complications of cerebral ischaemia in diabetes.

Effect of laser phototherapy on wound healing following cerebral ischemia by cryogenic injury

Laser phototherapy emerges as an alternative or auxiliary therapy for acute ischemic stroke, traumatic brain injury, degenerative brain disease, spinal cord injury, and peripheral nerve regeneration, but its effects are still controversial. We have previously found that laser phototherapy immunomodulates the response to focal brain damage. Following direct cortical cryogenic injury the effects of laser phototherapy on inflammation and repair was assessed after cryogenic injury (CI) to the central nervous system (CNS) of rats. The laser phototherapy was carried out with a 780 nm AlGaAs diode laser. The irradiation parameters were: power of 40 mW, beam area of 0.04 cm(2), energy density of 3 J/cm(2) (3s) in two points (0.12 J per point). Two irradiations were performed at 3 h-intervals, in contact mode. Rats (20 non-irradiated - controls and 20 irradiated) were used. The wound healing in the CNS was followed in 6 h, 1, 7 and 14 days after the last irradiation. The size of the lesions, the neuron cell viability percentages and the amount of positive GFAP labeling were statistically compared by ANOVA complemented by Tukey's test (p<0.05). The distribution of lymphocytes, leukocytes and macrophages were also analyzed. CI created focal lesions in the cortex represented by necrosis, edema, hemorrhage and inflammatory infiltrate. The most striking findings were: lased lesions showed smaller tissue loss than control lesions in 6 h. During the first 24 h the amount of viable neurons was significantly higher in the lased group. There was a remarkable increase in the amount of GFAP in the control group by 14 days. Moreover, the lesions of irradiated animals had fewer leukocytes and lymphocytes in the first 24 h than controls. Considering the experimental conditions of this study it was concluded that laser phototherapy exerts its effect in wound healing following CI by controlling the brain damage, preventing neuron death and severe astrogliosis that could indicate the possibility of a better clinical outcome.

Chronic fetal hypoxia produces selective brain injury associated with altered nitric oxide synthases

OBJECTIVE

The purpose of this study was to investigate the impact of chronic hypoxia on the nitric oxide synthase isoenzymes in specific brain structures.

STUDY DESIGN

Time-mated pregnant guinea pigs were exposed to 10.5% molecular oxygen for 14 days (animals with chronic fetal hypoxia; HPX) or room air (control animals; NMX); L-N6-(1-iminoethyl)-lysine (L-NIL; an inducible nitric oxide synthase inhibitor, 1 mg/kg/d) was administered to HPX group for 14 days (L-NIL + HPX). Fetal brains were harvested at term. Multilabeled immunofluorescence was used to generate a brain injury map. Laser capture microdissection and quantitative polymerase chain reaction were applied; cell injury markers, apoptosis activation, neuron loss, total nitric oxide, and the levels of individual nitric oxide synthase isoenzymes were quantified.

RESULTS

Chronic hypoxia causes selective fetal brain injury rather than global. Injury is associated with differentially affected nitric oxide synthases in both neurons and glial cells, with inducible macrophage-type nitric oxide synthase up-regulated at all injury sites. L-NIL attenuated the injury, despite continued hypoxia.

CONCLUSION

These studies demonstrate that chronic hypoxia selectively injures the fetal brain in part by the differential regulation of nitric oxide synthase isoenzymes in an anatomic- and cell-specific manner.

Rapid improvement of chronic stroke deficits after perispinal etanercept: three consecutive cases

BACKGROUND

Thrombolytic therapy reduces stroke size and disability by reperfusion and salvage of ischaemic penumbra. Emerging evidence suggests that retrieved penumbra may be the site of ongoing inflammatory pathology that includes extensive microglial activation. Microglial activation may be associated with excessive levels of tumour necrosis factor (TNF) and resultant neurotoxicity. Etanercept, a potent biologic TNF antagonist, reduces microglial activation in experimental models and has been therapeutically effective in models of brain and neuronal injury. Perispinal administration of etanercept, previously reported to be beneficial for the treatment of Alzheimer's disease, may facilitate delivery of etanercept into the brain.

OBJECTIVE

The objective of this report is to document the initial clinical response to perispinal etanercept in the first chronic stroke cohort so treated.

METHODS

Three consecutive patients with stable and persistent chronic neurological deficits due to strokes that had failed to resolve despite previous treatment and rehabilitation were evaluated at an outpatient clinic. They were treated off-label with perispinal etanercept as part of the clinic's practice of medicine.

RESULTS

All three patients had chronic hemiparesis, in addition to other stroke deficits. Their stroke distributions were right middle cerebral artery (MCA), brainstem (medulla) and left MCA. The two patients with MCA strokes had both received acute thrombolytic therapy. Each of the three patients was treated with an initial dose of perispinal etanercept 13, 35 and 36 months following their acute stroke, respectively. Significant clinical improvement following perispinal etanercept administration was observed in all patients. Onset of clinical response was evident within 10 minutes of perispinal injection in all patients. Improvements in hemiparesis, gait, hand function, hemi-sensory deficits, spatial perception, speech, cognition and behaviour were noted among the patients treated. Each patient received a second perispinal etanercept dose at 22-26 days after the first dose that was followed by additional clinical improvement.

CONCLUSIONS

Open-label administration of perispinal etanercept resulted in rapid neurological improvement in three consecutive patients with chronic neurological dysfunction due to strokes occurring 13-36 months earlier. These results suggest that stroke may result in chronic TNF-mediated pathophysiology that may be amenable to therapeutic intervention long after the acute event. Randomized clinical trials of perispinal etanercept for selected patients with chronic neurological dysfunction following stroke are indicated.

Neuroprotective effects of andrographolide in a rat model of permanent cerebral ischaemia

BACKGROUND AND PURPOSE

Andrographolide is a diterpenoid lactone isolated from a traditional medicinal herb, Andrographis paniculata. It possesses potent anti-inflammatory activity. The present study examined potential therapeutic effects of andrographolide on cerebral ischaemia using a rat model with permanent middle cerebral artery occlusion (pMCAO).

EXPERIMENTAL APPROACH

The MCA in rats was permanently occluded (by cautery), and 24 h later neurological effects were assessed with behavioural scores. Infarct volume and microglial activation were determined histologically. The p65 form of the transcription factor, nuclear factor-κB (NF-κB), was measured by Western blot, and cytokines by immunoassay of brain extracts.

KEY RESULTS

Andrographolide, given i.p. 1 h after pMCAO, reduced infarct volume with a maximum reduction of approximately 50% obtained at 0.1 mg·kg(-1). Neurological deficits were also reduced by andrographolide, reflecting a correlation between infarct volume and neurological deficits. pMCAO was found to induce activation of microglia and elevate tumour necrosis factor (TNF)-α, interleukin (IL)-1β and prostaglandin (PG)E(2) in the ischaemic brain areas. Andrographolide (0.1 mg·kg(-1)) significantly attenuated or abolished these effects. In addition, andrographolide suppressed the translocation of p65 from cytosol to nucleus, indicating reduced NF-κB activation.

CONCLUSIONS AND IMPLICATIONS

Andrographolide exhibited neuroprotective effects, with accompanying suppression of NF-κB and microglial activation, and reduction in the production of cytokines including TNF-α and IL-1β, and pro-inflammatory factors such as PGE(2). Our findings suggest that andrographolide may have therapeutic value in the treatment of stroke.

Krogh cylinders in retinal development, panretinal hypoperfusion and diabetic retinopathy

The volume of cells that a length of capillary supplies with O(2) is called a Krogh cylinder. This geometric 'tissue unit' was named after the Danish zoophysiologist and Nobel laureate August Krogh who made important discoveries in the fields of external and internal respiration in the first half of the last century. Krogh's ideas concerning tissue O(2) distribution can be extrapolated to retinal oxygenation by larger vessels (including arterioles, arteries and even veins) and by vessel groups within higher-order 'microvascular units' (including the choroid). During retinal development, for example, the difference in pO(2) levels within arteries and capillaries determines Krogh cylinders of different radius and establishes the periarterial capillary-free zone of His. The O(2) supply to the venous end of a tissue unit may be compromised during periods of reduced perfusion, increased O(2) consumption or hypoxaemia, resulting in an 'anoxic corner' of the Krogh cylinder. A funnel of hypometabolic (and therefore hypoxia-tolerant) cells will likely intervene between the necrotic cells and unaffected cells located closer to the O(2) source. Macular perivenular whitening heralds anoxic corners and/or hypoxic funnels owing to hypoperfusion within second-order microvascular units. In eyes with extensive retinal capillary closure from diabetes, Krogh cylinders surround the medium-sized arteries and veins that form arteriovenous shunts while traversing the midperipheral retina. These isolated tissue units incorporate an outer sheath of hypoxic cells within which vascular endothelial growth factor is upregulated. This 'angiogenic sheath' expands following retinal detachment; it corresponds to the hypoxia-tolerant funnel within capillary-based tissue units and to the cerebral penumbra after stroke.

Accumulation of macromolecules in brain parenchyma in acute phase of cerebral infarction/reperfusion

Ischemia-reperfusion injury is induced by recovery of blood flow after ischemia. This phenomenon is a main cause of ischemic brain injury. The integrity of the blood-brain barrier (BBB) fails after cerebral ischemia and reperfusion. Further elucidation of this phenomenon promotes to develop treatment strategies for ischemia-reperfusion injury. In the present study, we attempted to examine the time-dependent change of ischemia-reperfusion injury in relation to BBB disorders at acute phase in a transient middle cerebral artery occlusion (t-MCAO) model rat as a cerebral infarction and reperfusion model. Brain cell damage after the reperfusion was assessed by 2, 3, 5-triphenyltetrazolium chloride (TTC) staining. To clarify a time-dependent change of the integrity of BBB, fluorescein isothiocyanate (FITC)-dextran (150 kDa) was injected intravenously into t-MCAO rats, and time-dependent localization of FITC-dextran was monitored in ex vivo. As a result, obvious brain damage was firstly observed at 3 h after reperfusion following 1 h of MCAO. In contrast, the leakage of FITC-dextran from cerebral vessels was observed immediately after the reperfusion. The present data suggest that the integrity of BBB failed prior to the occurrence of serious brain damage induced by ischemia-reperfusion, and that macromolecules such as water-soluble polymers and proteins which cannot pass through the BBB under normal condition would reach brain parenchyma at early stage after reperfusion. These findings would be useful to establish a novel treatment strategy for reperfusion injury after cerebral infarction.

Upregulation of Dpysl2 and Spna2 gene expression in the rat brain after ischemic stroke

Ischemia activates the synthesis of potentially damaging and protective proteins in the central nervous system. Dihydropyrimidinase-like 2 (Dpysl2), a protein involved in neuronal differentiation and axonal guidance, and alpha-spectrin 2 (Spna2), a protein involved in maintaining neuronal membrane integrity, were found altered in various nervous system diseases. Modifications of Dpysl2 and Spna2 proteins have been reported in focal ischemic stroke, but their significance is not yet established. Therefore, this study was aimed to investigate the temporal expression of Dpysl2 and Spna2 genes in normal and stroke rat brain and to characterize stroke brains for cell areas, apoptosis, and microglia cells. The middle cerebral artery of rat brain was occluded and the brain tissue was sectioned for in situ hybridization of Dpysl2 and Spna2 genes, TUNEL, and OX-42 immunofluorescence staining. Dpysl2 and Spna2 mRNA expression was quantified by real-time RT-PCR. Characterization of stroke brain for apoptosis and microglia cells showed apoptotic cells and activated microglia, mainly in the infarct core of ipsilateral cortex and striatum of stroke brain. Significant upregulation of Dpysl2 and Spna2 mRNA expression in the penumbra region after stroke was observed predominantly in injured swollen cells in the cortex and striatum. Upregulation of Dpysl2 and Spna2 expression in hypertrophic cells in the penumbra regions of cortex and striatum of stroke brain indicates an early neuronal defense mechanism involving active neuronal repair, regeneration and development, as these genes are known to be involved in neurite outgrowth and plasticity.

Bioenergetics of cerebral ischemia: a cellular perspective

In cerebral ischemia survival of neurons, astrocytes, oligodendrocytes and endothelial cells is threatened during energy deprivation and/or following re-supply of oxygen and glucose. After a brief summary of characteristics of different cells types, emphasizing the dependence of all on oxidative metabolism, the bioenergetics of focal and global ischemia is discussed, distinguishing between events during energy deprivation and subsequent recovery attempt after re-circulation. Gray and white matter ischemia are described separately, and distinctions are made between mature and immature brains. Next comes a description of bioenergetics in individual cell types in culture during oxygen/glucose deprivation or exposure to metabolic inhibitors and following re-establishment of normal aerated conditions. Due to their expression of NMDA and non-NMDA receptors neurons and oligodendrocytes are exquisitely sensitive to excitotoxicity by glutamate, which reaches high extracellular concentrations in ischemic brain for several reasons, including failing astrocytic uptake. Excitotoxicity kills brain cells by energetic exhaustion (due to Na(+) extrusion after channel-mediated entry) combined with mitochondrial Ca(2+)-mediated injury and formation of reactive oxygen species. Many (but not all) astrocytes survive energy deprivation for extended periods, but after return to aerated conditions they are vulnerable to mitochondrial damage by cytoplasmic/mitochondrial Ca(2+) overload and to NAD(+) deficiency. Ca(2+) overload is established by reversal of Na(+)/Ca(2+) exchangers following Na(+) accumulation during Na(+)-K(+)-Cl(-) cotransporter stimulation or pH regulation, compensating for excessive acid production. NAD(+) deficiency inhibits glycolysis and eventually oxidative metabolism, secondary to poly(ADP-ribose)polymerase (PARP) activity following DNA damage. Hyperglycemia can be beneficial for neurons but increases astrocytic death due to enhanced acidosis.

Neuroprotection for ischemic stroke: past, present and future

Neuroprotection for ischemic stroke refers to strategies, applied singly or in combination, that antagonize the injurious biochemical and molecular events that eventuate in irreversible ischemic injury. There has been a recent explosion of interest in this field, with over 1000 experimental papers and over 400 clinical articles appearing within the past 6 years. These studies, in turn, are the outgrowth of three decades of investigative work to define the multiple mechanisms and mediators of ischemic brain injury, which constitute potential targets of neuroprotection. Rigorously conducted experimental studies in animal models of brain ischemia provide incontrovertible proof-of-principle that high-grade protection of the ischemic brain is an achievable goal. Nonetheless, many agents have been brought to clinical trial without a sufficiently compelling evidence-based pre-clinical foundation. At this writing, around 160 clinical trials of neuroprotection for ischemic stroke have been initiated. Of the approximately 120 completed trials, two-thirds were smaller early-phase safety-feasibility studies. The remaining one-third were typically larger (>200 subjects) phase II or III trials, but, disappointingly, only fewer than one-half of these administered neuroprotective therapy within the 4-6h therapeutic window within which efficacious neuroprotection is considered to be achievable. This fact alone helps to account for the abundance of "failed" trials. This review presents a close survey of the most extensively evaluated neuroprotective agents and classes and considers both the strengths and weakness of the pre-clinical evidence as well as the results and shortcomings of the clinical trials themselves. Among the agent-classes considered are calcium channel blockers; glutamate antagonists; GABA agonists; antioxidants/radical scavengers; phospholipid precursor; nitric oxide signal-transduction down-regulator; leukocyte inhibitors; hemodilution; and a miscellany of other agents. Among promising ongoing efforts, therapeutic hypothermia, high-dose human albumin therapy, and hyperacute magnesium therapy are considered in detail. The potential of combination therapies is highlighted. Issues of clinical-trial funding, the need for improved translational strategies and clinical-trial design, and "thinking outside the box" are emphasized.

Efficient control of transient wave forms to prevent spreading depolarizations

In various neurological disorders spatio-temporal excitation patterns constitute examples of excitable behavior emerging from pathological pathways. During migraine, seizure, and stroke an initially localized pathological state can temporarily spread indicating a transition from non-excitable to excitable behavior. We investigate these transient wave forms in the generic FitzHugh-Nagumo (FHN) system of excitable media. Our goal is to define an efficient control minimizing the volume of invaded tissue. The general point of such a therapeutic optimization is how to apply control theory in the framework of structures in differential geometry by regarding parameter plane M of the FHN system as a differentiable manifold endowed with a metric. We suggest to equip M with a metric given by pharmacokinetic-pharmacodynamic models of drug receptor interaction.

Imaging readouts as biomarkers or surrogate parameters for the assessment of therapeutic interventions

Surrogate markers and biomarkers based on imaging readouts providing predictive information on clinical outcome are of increasing importance in the preclinical and clinical evaluation of novel therapies. They are primarily used in studies designed to establish evidence that the therapeutic principle is valid in a representative patient population or in an individual. A critical step in the development of (imaging) surrogates is validation: correlation with established clinical endpoints must be demonstrated. Biomarkers must not fulfill such stringent validation criteria; however, they should provide insight into mechanistic aspects of the therapeutic intervention (proof-of-mechanism) or document therapy efficacy with prognostic quality with regard to the long-term clinical outcome (proof of concept). Currently used imaging biomarkers provide structural, physiological and metabolic information. Novel imaging approaches annotate structure with molecular signatures that are tightly linked to the pathophysiology or to the therapeutic principle. These cellular and molecular imaging methods yield information on drug biodistribution, receptor expression and occupancy, and/or intra- and intercellular signaling. The design of novel target-specific imaging probes is closely related to the development of the therapeutic agents and should be considered early in the discovery phase. Significant technical and regulatory hurdles have to be overcome to foster the use of imaging biomarkers for clinical drug evaluation.

Oncosis, the possible cell death pathway in astrocytes after focal cerebral ischemia

Swelling of astrocytes at early stage of cerebral ischemia has been reported, however, the fate and the cell death pathway of astrocytes are still unclear. Focal cerebral ischemia was induced in Sprague-Dawley rats by permanent occlusion of middle cerebral artery for 3 to 48 h. Haematoxylin and eosin (HE) staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), glial fibrillary acidic protein (GFAP), caspase-3 immunostaining, and double-staining with TUNEL and GFAP were carried out on consecutive sections. The ultrastructure was revealed by electron microscopy. Using electron microscope, apoptotic neurons were confirmed with condensed chromatin and apoptotic bodies. In the core of the infarct, clumps of heterochromatin around the edge of nucleus, vacuolar degeneration of the nucleus and leakage of chromatin were demonstrated at 3, 6, and 12 h respectively in the swelling astrocytes, which accorded with the process of oncosis; in the peripheral zone of the infarct, reactive astrocytes with nuclear membranes preserved demonstrated increased cell size and number and coexisted with oncotic astrocytes. Scattered GFAP-positive cells and ubiquitous caspase-3-positive cells were found in the core after 12 h following cerebral ischemia, and no cells positive for double-staining with TUNEL and GFAP were found in the ischemic regions, indicating that most GFAP-positive astrocytes did not die by apoptosis. Findings from present study demonstrate that after cerebral ischemia, oncosis may be the possible cell death pathway of astrocytes in the ischemic region, and oncotic astrocytes coexist with reactive astrocytes in the peripheral zone.

Subcellular Stress Response after Traumatic Brain Injury

Traumatic brain injury (TBI) initiates a complex genetic response that may include the expression of organelle specific stress genes. We investigated the effects of brain trauma on the expression of a number of stress genes by in situ hybridization and Western blot analysis including the endoplasmic reticulum (ER) stress gene grp78, ER protein processing enzymes calnexin and protein disulphide isomerase (PDI), the mitochondrial stress gene hsp60, and the cytoplasmic stress gene hsp70. Male Sprague-Dawley rats were subjected either to sham-surgery or moderate (1.8-2.2 atm) parasagittal fluid-percussion (F-P) brain injury followed by 30 min of either normoxic or hypoxic (30-40 mm Hg) gas levels. Expression of grp78 was increased in the ipsilateral cerebral cortex and dentate gyrus beginning 4 h after trauma plus hypoxia. Similarly, mRNA encoding the mitochondrial hsp60 was induced in the ipsilateral outer cortical layers at 4-24 h after TBI plus hypoxia. Calnexin and PDI mRNAs were not significantly altered following TBI with or without secondary hypoxia. In contrast, mRNA of the cytoplasmic hsp70 was strongly induced at 4 h after brain injury in multiple brain regions within the injured hemisphere, and this expression was greatly enhanced by secondary hypoxia. Because subcellular stress gene expression may reflect where unfolded or damaged proteins are abundant, these findings suggest that abnormal proteins are localized mainly in the cytoplasm, and to a lesser degree in the ER lumen and mitochondria after brain trauma. Thus, distinct parts of the cellular machinery respond to traumatic and metabolic stresses in specific ways.

Pathophysiology of Stroke Rehabilitation: Temporal Aspects of Neurofunctional Recovery

Stroke almost always causes an impairment of motor activity and function. Clinical recovery, though usually incomplete, is often highly dynamic and reflects the ability of the neuronal network to adapt. Mechanisms that underlie neuro-functional plasticity are now beginning to be understood. Albeit the enormous efforts undertaken to support the natural course of re-convalescence through rehabilitation, little has been done to relate possible effects of these therapeutic approaches to mechanisms of adaptive pathophysiology. The review presented here focuses on these mechanisms during the course of recovery post stroke. Next to an unmasking of latent network representations, other adaptive processes, such as excitatory metabolic stress, an imbalance in activating and inhibiting transmission, leading to salient hyperexcitability or mechanisms that consolidate novel connections prime the system's plastic capabilities. These pathophysiological processes potentially interact with rehabilitative interventions. They therefore form the foundation of positive, but possibly also negative recuperation under therapy.

Neurochemical and oedematous changes in 1,3-dinitrobenzene-induced astroglial injury in rat brain from a 1H-nuclear magnetic resonance perspective

1,3-Dinitrobenzene (1,3-DNB), an intermediate used in the chemical industry, has toxic effects in the brain and testes. It produces focal lesions with marked astroglial necrosis in the rat brain upon repeated administration. Astrocytic death occurs in parallel with elevated local blood flow and is followed by damage to the cerebral vasculature and neurones. (1)H-nuclear magnetic resonance spectroscopic analysis before the onset of astrocytic damage, showed a global elevation of lactate, whereas choline containing compounds increased in the non-vulnerable cerebral cortex, yet decreased in the vulnerable brainstem. Similarly, glutamate increased in the cerebral cortex, cerebellum and midbrain, but decreased in the susceptible brainstem. In vivo T2-weighted NMR imaging showed high signal intensities in brain nuclei shown to develop astroglial loss by conventional neuropathology at 24 hours after completion of dosing, but not at 6-10 hours. Hence the early neurochemical changes in susceptible areas contribute to the aetiology of degeneration, and those seen elsewhere may represent adaptive responses dependent on the particular phenotype of different cell groups and underlying metabolic relationships.

Neuroprotection of Cerebrolysin in tissue culture models of brain ischemia: post lesion application indicates a wide therapeutic window

All attempts to reduce neuronal damage after acute brain ischemia by the use of neuroprotective compounds have failed to prove efficacy in clinical trials so far. One of the main reasons might be the relatively narrow time window for intervention. In this study 2 different tissue culture models of ischemia, excitotoxic lesion by the use of glutamate and oxygen-glucose deprivation (OGD), were used to investigate the effects of delayed application of Cerebrolysin (Cere) on neuronal survival. This drug consists of low molecular weight peptides with neuroprotective and neurotrophic properties similar to naturally occurring growth factors. After both types of lesion, acute as well as delayed treatment with Cere resulted in a dose dependent and significant rescue of neurons. In the model of excitotoxic cell death significant drug effects were found even when the treatment started with a delay of 96 hours after addition of glutamate. In the OGD model pronounced effects were found after 48 hours delay of treatment, and even after 72 hours a small but significant rescue of neurons was detected. The neuroprotective effects of a single addition of Cerebrolysin to the culture medium resulted in significant protection until end of the experiments which was up to 2 weeks after the initial lesion. A shift of the efficacious dosages from low to high concentrations indicates that most likely active compounds are used up, indicating that multiple dosing might even increase the effect size. In conclusion the results indicate that Cere displays a relatively wide therapeutic time window which might be explained by a combination of acute neuroprotective properties and neurotrophic efficacy.

Noradrenergic agonists and antagonists influence migration of cortical spreading depression in rat-a possible mechanism of migraine prophylaxis and prevention of postischemic neuronal damage

Cortical spreading depression (CSD) is thought to be a neuronal mechanism that expands the penumbra zone after focal brain ischemia and that causes migraine aura. Both adrenergic agonists and antagonists significantly influence the size of the penumbra zone and decline the frequency of migraine. To study whether these compounds act by influencing CSD, we applied different drugs topically to an area of the exposed cortex of anesthetized adult rats and observed the migration of CSD-related DC potential deflections across the treated area. The adrenergic agonist norepinephrine (1 mmol/L) and the alpha(2)-agonist clonidine (0.56 mmol/L) blocked reversibly the migration of CSD. The beta-blocker propranolol (250 micromol/L to 1 mmol/L) dose-dependently diminished migration velocity or even blocked migration of CSD. The CSD blockade by the alpha(2)-antagonist yohimbine (1.75 mmol/L) was because of its action on inhibitory 5-HT(1A) receptors. None of the substances in the concentrations used had influence on regional cerebral blood flow or on systemic arterial blood pressure. The data suggest that the interference of these compounds with CSD may contribute to their beneficial therapeutic effect. The effect of beta-receptor antagonists in human migraine needs further exploration, since these drugs also work in migraine without aura.

Prophylactic activation of neuroprotective stress response pathways by dietary and behavioral manipulations

It is well established that when most types of cells, including neurons, are exposed to a mild stress they increase their ability to resist more severe stress. This "preconditioning" phenomenon involves up-regulation of genes that encode cytoprotective proteins such as heat-shock proteins and growth factors. We found that a similar beneficial cellular stress response can be induced in neurons throughout the brain by a "meal-skipping" dietary restriction (DR) regimen in rats and mice. DR is effective in protecting neurons and improving functional outcome in models of stroke, Alzheimer's, Parkinson's and Huntington's diseases. DR induces an increase in the levels of brain-derived neurotrophic factor (BDNF) and heat-shock proteins in neurons. DR also stimulates neurogenesis in the hippocampus, and BDNF plays a role in this effect of DR. Physical exercise and environmental enrichment are two other manipulations that have been shown to induce BDNF expression in the brain, presumably because it is a mild cellular stress. When taken together with epidemiological and clinical studies in humans, the data from animal studies suggest that it may be possible to reduce the risk for age-related neurodegenerative disorders through dietary and behavioral modifications that act by promoting neuronal plasticity and survival.