Differential cellular distribution and dynamics of HSP70, cyclooxygenase-2, and c-Fos in the rat brain after transient focal ischemia or kainic acid

Immunohistochemistry in postmortem diagnosis of acute cerebral hypoxia and ischemia: A systematic review

BACKGROUND

: Discovery of evidence of acute brain ischemia or hypoxia and its differentiation from agonal hypoxia represents a task of interest but extremely difficult in forensic neuropathology. Generally, more than 50% of forensic autopsies indicate evidence of brain induced functional arrest of the organ system, which can be the result of a hypoxic/ischemic brain event. Even if the brain is the target organ of hypoxic/ischemic damage, at present, there are no specific neuropathological (macroscopic and histological) findings of hypoxic damage (such as in drowning, hanging, intoxication with carbon monoxide) or acute ischemia. In fact, the first histological signs appear after at least 4 to 6 hours. Numerous authors have pointed out how an immunohistochemical analysis could help diagnose acute cerebral hypoxia/ischemia.Data sources: This review was based on articles published in PubMed and Scopus databases in the past 25 years, with the following keywords "immunohistochemical markers," "acute cerebral ischemia," "ischemic or hypoxic brain damage," and "acute cerebral hypoxia".

OBJECTIVES

: Original articles and reviews on this topic were selected. The purpose of this review is to analyze and summarize the markers studied so far and to consider the limits of immunohistochemistry that exist to date in this specific field of forensic pathology.

RESULTS

: We identified 13 markers that had been examined (in previous studies) for this purpose. In our opinion, it is difficult to identify reliable and confirmed biomarkers from multiple studies in order to support a postmortem diagnosis of acute cerebral hypoxia/ischemia. Microtubule-associated protein 2 (MAP2) is the most researched marker in the literature and the results obtained have proven to be quite useful.

CONCLUSION

Immunohistochemistry has provided interesting and promising results, but further studies are needed in order to confirm and apply them in standard forensic practice.

Stoichiometric Analysis of Shifting in Subcellular Compartmentalization of HSP70 within Ischemic Penumbra

The heat shock protein (HSP) 70 is considered the main hallmark in preclinical studies to stain the peri-infarct region defined area penumbra in preclinical models of brain ischemia. This protein is also considered as a potential disease modifier, which may improve the outcome of ischemic damage. In fact, the molecule HSP70 acts as a chaperonine being able to impact at several level the homeostasis of neurons. Despite being used routinely to stain area penumbra in light microscopy, the subcellular placement of this protein within area penumbra neurons, to our knowledge, remains undefined. This is key mostly when considering studies aimed at deciphering the functional role of this protein as a determinant of neuronal survival. The general subcellular placement of HSP70 was grossly reported in studies using confocal microscopy, although no direct visualization of this molecule at electron microscopy was carried out. The present study aims to provide a direct evidence of HSP70 within various subcellular compartments. In detail, by using ultrastructural morphometry to quantify HSP70 stoichiometrically detected by immuno-gold within specific organelles we could compare the compartmentalization of the molecule within area penumbra compared with control brain areas. The study indicates that two cell compartments in control conditions own a high density of HSP70, cytosolic vacuoles and mitochondria. In these organelles, HSP70 is present in amount exceeding several-fold the presence in the cytosol. Remarkably, within area penumbra a loss of such a specific polarization is documented. This leads to the depletion of HSP70 from mitochondria and mostly cell vacuoles. Such an effect is expected to lead to significant variations in the ability of HSP70 to exert its physiological roles. The present findings, beyond defining the neuronal compartmentalization of HSP70 within area penumbra may lead to a better comprehension of its beneficial/detrimental role in promoting neuronal survival.

Neuroinflammation, neuronal damage or cognitive impairment associated with mechanical ventilation: A systematic review of evidence from animal studies

PURPOSE

Long-term cognitive impairment is a complication of critical illness survivors. Beside its lifesaving role, mechanical ventilation has potential complications. The aim of this study is to systematically review the evidence collected in animal studies that correlate mechanical ventilation with neuroinflammation, neuronal damage and cognitive impairment.

METHODS

We searched MEDLINE and EMBASE databases for studies published from inception until August 31st, 2020, that enrolled mechanically ventilated animals and reported on neuroinflammation or neuronal damage markers changes or cognitive-behavioural impairment.

RESULTS

Of 5583 studies, 11 met inclusion criteria. Mice, rats, pigs were used. Impact of MV: 4 out of 7 studies reported higher neuroinflammation markers in MV-treated animals and 3 studies reported no differences; 7 out of 8 studies reported a higher neuronal damage and 1 reported no differences; 2 out of 2 studies reported cognitive decline up to 3 days after MV. Higher Tidal volumes are associated with higher changes in brain or serum markers.

CONCLUSION

Preclinical evidence suggests that MV induces neuroinflammation, neuronal damage and cognitive impairment and these are worsened if sub-optimal MV settings are applied. Future studies, with appropriate methodology, are necessary to evaluate for serum monitoring strategies.

TRIAL REGISTRATION NUMBER

CRD42019148935.

Study of Protein Expression in Peri-Infarct Tissue after Cerebral Ischemia

In this work, we report our study of protein expression in rat peri-infarct tissue, 48 h after the induction of permanent focal cerebral ischemia. Two proteomic approaches, gel electrophoresis with mass spectrometry and combined fractional diagonal chromatography (COFRADIC), were performed using tissue samples from the periphery of the induced cerebral ischemic lesions, using tissue from the contra-lateral hemisphere as a control. Several protein spots (3408) were identified by gel electrophoresis, and 11 showed significant differences in expression between peri-infarct and contra-lateral tissues (at least 3-fold, p < 0.05). Using COFRADIC, 5412 proteins were identified, with 72 showing a difference in expression. Apart from blood-related proteins (such as serum albumin), both techniques showed that the 70 kDa family of heat shock proteins were highly expressed in the peri-infarct tissue. Further studies by 1D and 2D western blotting and immunohistochemistry revealed that only one member of this family (the inducible form, HSP72 or HSP70i) is specifically expressed by the peri-infarct tissue, while the majority of this family (the constitutive form, HSC70 or HSP70c) is expressed in the whole brain. Our data support that HSP72 is a suitable biomarker of peri-infarct tissue in the ischemic brain.

In vivo theranostics at the peri-infarct region in cerebral ischemia

The use of theranostics in neurosciences has been rare to date because of the limitations imposed on the free delivery of substances to the brain by the blood-brain barrier. Here we report the development of a theranostic system for the treatment of stroke, a leading cause of death and disability in developed countries. We first performed a series of proteomic, immunoblotting and immunohistological studies to characterize the expression of molecular biomarkers for the so-called peri-infarct tissue, a key region of the brain for stroke treatment. We confirmed that the HSP72 protein is a suitable biomarker for the peri-infarct region, as it is selectively expressed by at-risk tissue for up to 7 days following cerebral ischemia. We also describe the development of anti-HSP72 vectorized stealth immunoliposomes containing imaging probes to make them traceable by conventional imaging techniques (fluorescence and MRI) that were used to encapsulate a therapeutic agent (citicoline) for the treatment of cerebral ischemia. We tested the molecular recognition capabilities of these nano-platforms in vitro together with their diagnostic and therapeutic properties in vivo, in an animal model of cerebral ischemia. Using MRI, we found that 80% of vectorized liposomes were located on the periphery of the ischemic lesion, and animals treated with citicoline encapsulated on these liposomes presented lesion volumes up to 30% smaller than animals treated with free (non-encapsulated) drugs. Our results show the potential of nanotechnology for the development of effective tools for the treatment of neurological diseases.

In vivo imaging of induction of heat-shock protein-70 gene expression with fluorescence reflectance imaging and intravital confocal microscopy following brain ischaemia in reporter mice

PURPOSE

Stroke induces strong expression of the 72-kDa heat-shock protein (HSP-70) in the ischaemic brain, and neuronal expression of HSP-70 is associated with the ischaemic penumbra. The aim of this study was to image induction of Hsp-70 gene expression in vivo after brain ischaemia using reporter mice.

METHODS

A genomic DNA sequence of the Hspa1b promoter was used to generate an Hsp70-mPlum far-red fluorescence reporter vector. The construct was tested in cellular systems (NIH3T3 mouse fibroblast cell line) by transient transfection and examining mPlum and Hsp-70 induction under a challenge. After construct validation, mPlum transgenic mice were generated. Focal brain ischaemia was induced by transient intraluminal occlusion of the middle cerebral artery and the mice were imaged in vivo with fluorescence reflectance imaging (FRI) with an intact skull, and with confocal microscopy after opening a cranial window.

RESULTS

Cells transfected with the Hsp70-mPlum construct showed mPlum fluorescence after stimulation. One day after induction of ischaemia, reporter mice showed a FRI signal located in the HSP-70-positive zone within the ipsilateral hemisphere, as validated by immunohistochemistry. Live confocal microscopy allowed brain tissue to be visualized at the cellular level. mPlum fluorescence was observed in vivo in the ipsilateral cortex 1 day after induction of ischaemia in neurons, where it is compatible with penumbra and neuronal viability, and in blood vessels in the core of the infarction.

CONCLUSION

This study showed in vivo induction of Hsp-70 gene expression in ischaemic brain using reporter mice. The fluorescence signal showed in vivo the induction of Hsp-70 in penumbra neurons and in the vasculature within the ischaemic core.

Fresh green tea and gallic acid ameliorate oxidative stress in kainic acid-induced status epilepticus

Green tea is one of the most-consumed beverages due to its taste and antioxidative polyphenols. However, the protective effects of green tea and its constituent, gallic acid (GA), against kainic acid (KA)-induced seizure have not been studied. We investigated the effect of fresh green tea leaf (GTL) and GA on KA-induced neuronal injury in vivo and in vitro. The results showed that GTL and GA reduced the maximal seizure classes, predominant behavioral seizure patterns, and lipid peroxidation in male FVB mice with status epilepticus (SE). GTL extract and GA provided effective protection against KA-stressed PC12 cells in a dose-dependent manner. In the protective mechanism study, GTL and GA decreased Ca(2+) release, ROS, and lipid peroxidation from KA-stressed PC12 cells. Western blot results revealed that mitogen-activated protein kinases (MAPKs), RhoA, and COX-2 expression were increased in PC12 cells under KA stress, and expression of COX-2 and p38 MAPK, but not RhoA, was significantly reduced by GTL and GA. Furthermore, GTL and GA were able to reduce PGE(2) production from KA-stressed PC12 cells. Taken together, the results showed that GTL and GA provided neuroprotective effects against excitotoxins and may have a clinical application in epilepsy.

Pu-Erh tea and GABA attenuates oxidative stress in kainic acid-induced status epilepticus

Background

Pu-Erh tea is one of the most-consumed beverages due to its taste and the anti-anxiety-producing effect of the gamma-aminobutyric acid (GABA) if contains. However the protective effects of Pu-Erh tea and its constituent, GABA to kainic acid (KA)-induced seizure have not been fully investigated.

Methods

We analyzed the effect of Pu-Erh tea leaf (PETL) and GABA on KA-induced neuronal injury in vivo and in vitro.

Results

PETL and GABA reduced the maximal seizure classes, predominant behavioral seizure patterns, and lipid peroxidation in male FVB mice with status epilepticus. PETL extracts and GABA were effective in protecting KA-treated PC12 cells in a dose-dependent manner and they decreased Ca²⁺ release, ROS production and lipid peroxidation from KA-stressed PC12 cells. Western blot results revealed that mitogen-activated protein kinases (MAPKs), RhoA and cyclo-oxygenase-2 (COX-2) expression were increased in PC12 cells under KA stress, and PETL and GABA significantly reduced COX-2 and p38 MAPK expression, but not that of RhoA. Furthermore, PETL and GABA reduced PGE₂ production from KA-induced PC12 cells.

Conclusions

Taken together, PETL and GABA have neuroprotective effects against excitotoxins that may have clinical applications in epilepsy.

The lung and the brain: a dangerous cross-talk

Brain or lung injury or both are frequent causes of admission to intensive care units and are associated with high morbidity and mortality rates. Mechanical ventilation, which is commonly used in the management of these critically ill patients, can induce an inflammatory response, which may be involved in distal organ failure. Thus, there may be a complex crosstalk between the lungs and other organs, including the brain. Interestingly, survivors from acute lung injury/acute respiratory distress syndrome frequently have some cognitive deterioration at hospital discharge. Such neurologic dysfunction might be a secondary marker of injury and the neuroanatomical substrate for downstream impairment of other organs. Brainlung interactions have received little attention in the literature, but recent evidence suggests that both the lungs and brain can promote inflammation through common mediators. The present commentary discusses the main physiological issues related to brain-lung interactions.

Sesamin ameliorates oxidative stress and mortality in kainic acid-induced status epilepticus by inhibition of MAPK and COX-2 activation

BACKGROUND

Kainic acid (KA)-induced status epilepticus (SE) was involved with release of free radicals. Sesamin is a well-known antioxidant from sesame seeds and it scavenges free radicals in several brain injury models. However the neuroprotective mechanism of sesamin to KA-induced seizure has not been studied.

METHODS

Rodents (male FVB mice and Sprague-Dawley rats) were fed with sesamin extract (90% of sesamin and 10% sesamolin), 15 mg/kg or 30 mg/kg, for 3 days before KA subcutaneous injection. The effect of sesamin on KA-induced cell injury was also investigated on several cellular pathways including neuronal plasticity (RhoA), neurodegeneration (Caspase-3), and inflammation (COX-2) in PC12 cells and microglial BV-2 cells.

RESULTS

Treatment with sesamin extract (30 mg/kg) significantly increased plasma α-tocopherol level 50% and 55.8% from rats without and with KA treatment, respectively. It also decreased malondialdehyde (MDA) from 145% to 117% (p=0.017) and preserved superoxide dismutase from 55% of the vehicle control mice to 81% of sesamin-treated mice, respectively to the normal levels (p=0.013). The treatment significantly decreased the mortality from 22% to 0% in rats. Sesamin was effective to protect PC12 cells and BV-2 cells from KA-injury in a dose-dependent manner. It decreased the release of Ca2+, reactive oxygen species, and MDA from PC12 cells. Western blot analysis revealed that sesamin significantly reduced ERK1/2, p38 mitogen-activated protein kinases, Caspase-3, and COX-2 expression in both cells and RhoA expression in BV-2 cells. Furthermore, Sesamin was able to reduce PGE2 production from both cells under KA-stimulation.

CONCLUSIONS

Taken together, it suggests that sesamin could protect KA-induced brain injury through anti-inflammatory and partially antioxidative mechanisms.

Injurious mechanical ventilation affects neuronal activation in ventilated rats

Introduction

Survivors of critical illness often have significant long-term brain dysfunction, and routine clinical procedures like mechanical ventilation (MV) may affect long-term brain outcome. We aimed to investigate the effect of the increase of tidal volume (Vt) on brain activation in a rat model.

Methods

Male Sprague Dawley rats were randomized to three groups: 1) Basal: anesthetized unventilated animals, 2) low Vt (LVt): MV for three hours with Vt 8 ml/kg and zero positive end-expiratory pressure (ZEEP), and 3) high Vt (HVt) MV for three hours with Vt 30 ml/kg and ZEEP. We measured lung mechanics, mean arterial pressure (MAP), arterial blood gases, and plasma and lung levels of cytokines. We used immunohistochemistry to examine c-fos as a marker of neuronal activation. An additional group of spontaneously breathing rats was added to discriminate the effect of surgical procedure and anesthesia in the brain.

Results

After three hours on LVt, PaO₂ decreased and PaCO₂ increased significantly. MAP and compliance remained stable in MV groups. Systemic and pulmonary inflammation was higher in MV rats than in unventilated rats. Plasma TNFα was significantly higher in HVt than in LVt. Immunopositive cells to c-fos in the retrosplenial cortex and thalamus increased significantly in HVt rats but not in LVt or unventilated rats.

Conclusions

MV promoted brain activation. The intensity of the response was higher in HVt animals, suggesting an iatrogenic effect of MV on the brain. These findings suggest that this novel cross-talking mechanism between the lung and the brain should be explored in patients undergoing MV.

Prophylactic, prandial rofecoxib treatment lacks efficacy against acute PTZ-induced seizure generation and kindling acquisition

PURPOSE

The goal of this study was to determine whether prophylactic prandial administration of rofecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, could alter seizure generation, kindling acquisition, and/or kindling maintenance in the mouse pentylenetetrazole (PTZ) epilepsy model.

METHODS

Male CD-1 mice were fed ad libitum with control chow or chow formulated to deliver 30 mg/kg/day rofecoxib. After 5 days, mice were treated with a single dose of 40 or 55 mg/kg PTZ (acute paradigm) or 40 mg/kg PTZ delivered daily (kindling paradigm). Seizure severity was scored on a four-point behavioral scale and COX-2 expression was assessed in brain slices from a subset of mice 3 h or 72 h after acute PTZ or following establishment of kindling.

KEY FINDINGS

Hippocampal COX-2 expression was transiently upregulated 3 h after an acute PTZ-induced convulsion and returned to baseline levels within 72 h, whereas it remained elevated for at least 72 h after the final seizure in the kindling paradigm. Despite this increase, chronic rofecoxib treatment did not attenuate the severity of acute PTZ-induced seizures and failed to alter kindling development or maintenance.

SIGNIFICANCE

The present study demonstrates that prophylactic, prandial rofecoxib treatment lacks efficacy against acute PTZ-induced seizure generation and kindling acquisition, and does not reverse the kindled state once established.

Kainic Acid-induced F-344 Rat model of Mesial Temporal Lobe Epilepsy: Gene Expression and Canonical Pathways

Mesial temporal lobe epilepsy (MTLE) is a severe neurological condition of unknown pathogenesis for which several animal models have been developed. To obtain a better understanding of the underlying molecular mechanisms and identify potential biomarkers of lesion progression, we used a rat kainic acid (KA) treatment model of MTLE coupled with global gene expression analysis to examine temporal (four hours, days 3, 14, or 28) gene regulation relative to hippocampal histopathological changes. The authors recommend reviewing the companion histopathology paper ( Sharma et al. 2008 ) to get a better understanding of the work presented here. Analysis of filtered gene expression data using Ingenuity Pathways Analysis (Ingenuity Systems, http://www.ingenuity.com ) revealed that a number of genes pertaining to neuronal plasticity (RhoA, Rac1, Cdc42, BDNF, and Trk), neurodegeneration (Caspase3, Calpain 1, Bax, a Cytochrome c, and Smac/Diablo), and inflammation/immune-response pathways (TNF-α, CCL2, Cox2) were modulated in a temporal fashion after KA treatment. Expression changes for selected genes known to have a role in neuronal plasticity were subsequently validated by quantitative polymerase chain reaction (qPCR). Notably, canonical pathway analysis revealed that a number of genes within the axon guidance signaling canonical pathway were up-regulated from Days 3 to 28, which correlated with aberrant mossy fiber (MF) sprouting observed histologically beginning at Day 6. Importantly, analysis of the gene expression data also identified potential biomarkers for monitoring neurodegeneration (Cox2) and neuronal/synaptic plasticity (Kalrn).

THE EFFECT OF NORMOVOLEMIC HEMODILUTION ON C-FOS PROTEIN IMMUNOREACTIVITY IN THE POSTISCHEMIC RAT BRAIN CORTEX

The hemodilution effect was evaluated in the parietal, temporal, and basal regions of postischemic rat brain neocortex by the immunohistochemical detection of the c-Fos protein. Rats were subjected to the four-vessel-occlusion and the hemodilution was used in one group of animals. Coronal sections of rat brains were used for immunohistochemical processing of c-Fos protein after different postischemic reperfusion intervals. The number of c-Fos positive neuronal nuclei was significantly decreased in the hemodilution group after 4 h of reperfusion in the parietal and basal neocortex compared to the reperfusion without hemodilution.

Distinct pattern of microglial response, cyclooxygenase-2, and inducible nitric oxide synthase expression in the aged rat brain after excitotoxic damage

Microglial and inflammatory responses to acute damage in aging are still poorly understood, although the aged brain responds differently to injury, showing poor lesion outcome. In this study, excitotoxicity was induced by intrastriatal injection of N-methyl-D-aspartate in adult (3-4 months) and aged (22-24 months) rats. Cryostat brain sections were processed for the analysis of microglial response by lectin histochemistry and cyclooxygenase 2 (COX2) and inducible nitric oxide synthase (iNOS) expression by immunohistochemistry and confocal analysis. Aged injured animals showed more widespread area of microglial response at 12 hr postlesion (hpl) and greater microglia/macrophage density at 3 days postlesion (dpl). However, aged reactive microglia showed prevalence of ramified morphologies and fewer amoeboid/round forms. Aged injured animals presented a diminished area of COX2 expression, but a significantly larger density of COX2(+) cells, with higher numbers of COX2(+) neurons during the first 24 hpl and COX2(+) microglia/macrophages later. In contrast, the amount of COX2(+) neutrophils was diminished in the aged. iNOS was more rapidly induced in the aged injured striatum, with higher cell density at 12 hpl, when expression was mainly neuronal. From 1 dpl, both the iNOS(+) area and the density of iNOS(+) cells were reduced in the aged, with lower numbers of iNOS(+) neurons, microglia/macrophages, neutrophils, and astrocytes. In conclusion, excitotoxic damage in aging induces a distinct pattern of microglia/macrophage response and expression of inflammatory enzymes, which may account for the changes in lesion outcome in the aged, and highlight the importance of using aged animals for the study of acute age-related insults.

Pharmacologic suppression of oxidative damage and dendritic degeneration following kainic acid-induced excitotoxicity in mouse cerebrum

Intense seizure activity associated with status epilepticus and excitatory amino acid (EAA) imbalance initiates oxidative damage and neuronal injury in CA1 of the ventral hippocampus. We tested the hypothesis that dendritic degeneration of pyramidal neurons in the CA1 hippocampal area resulting from seizure-induced neurotoxicity is modulated by cerebral oxidative damage. Kainic acid (KA, 1 nmol/5 microl) was injected intracerebroventricularly to C57Bl/6 mice. F2-isoprostanes (F2-IsoPs) and F4-neuroprostanes (F4-NeuroPs) were used as surrogate measures of in vivo oxidative stress and biomarkers of lipid peroxidation. Nitric oxide synthase (NOS) activity was quantified by evaluating citrulline level and pyramidal neuron dendrites and spines were evaluated using rapid Golgi stains and a Neurolucida system. KA produced severe seizures in mice immediately after its administration and a significant (p<0.001) increase in F2-IsoPs, F4-NeuroPs and citrulline levels were seen 30 min following treatment. At the same time, hippocampal pyramidal neurons showed significant (p<0.001) reduction in dendritic length and spine density. In contrast, no significant change in neuronal dendrite and spine density or F2-IsoP, F4-NeuroPs and citrulline levels were found in mice pretreated with vitamin E (alpha-tocopherol, 100mg/kg, i.p.) for 3 days, or with N-tert-butyl-alpha-phenylnitrone (PBN, 200mg/kg, i.p.) or ibuprofen (inhibitors of cyclooxygenase, COX, 14 microg/ml of drinking water) for 2 weeks prior to KA treatment. These findings indicate novel interactions among free radical-induced generation of F2-IsoPs and F4-NeuroPs, nitric oxide and dendritic degeneration, closely associate oxidative damage to neuronal membranes with degeneration of the dendritic system, and point to possible interventions to limit severe damage in acute neurological disorders.

Antiinflammatory and neuroprotective actions of COX2 inhibitors in the injured brain

Overexpression of COX2 appears to be both a marker and an effector of neural damage after a variety of acquired brain injuries, and in natural or pathological aging of the brain. COX2 inhibitors may be neuroprotective in the brain by reducing prostanoid and free radical synthesis, or by directing arachidonic acid down alternate metabolic pathways. The arachidonic acid shunting hypothesis proposes that COX2 inhibitors' neuroprotective effects may be mediated by increased formation of potentially beneficial eicosanoids. Under conditions where COX2 activity is inhibited, arachidonic acid accumulates or is converted to eicosanoids via lipoxygenases and cytochrome P450 (CYP) epoxygenases. Several P450 eicosanoids have been demonstrated to have beneficial effects in the brain and/or periphery. We suspect that arachidonic acid shunting may be as important to functional recovery after brain injuries as altered prostanoid formation per se. Thus, COX2 inhibition and arachidonic acid shunting have therapeutic implications beyond the suppression of prostaglandin synthesis and free radical formation.

Roles of prostaglandin synthesis in excitotoxic brain diseases

Cyclooxygenase (COX) is a rate-limiting enzyme in prostaglandin synthesis. COX consists of two isoforms, constitutive COX-1 and inducible COX-2. We have first found that COX-2 expression in the brain is tightly regulated by neuronal activity under physiological conditions, and electroconvulsive seizure robustly induces COX-2 mRNA in the brain. Our recent in-depth studies reveal COX-2 expression is divided into two phases, early in neurons and late in non-neuronal cells, such as endothelial cells or astrocytes. In this review, we present that early synthesized COX-2 facilitates the recurrence of hippocampal seizures in rapid kindling model, and late induced COX-2 stimulates hippocampal neuron loss after kainic acid treatment. Hence, we consider the potential role of COX-2 inhibitors as a new therapeutic drug for a neuronal loss after seizure or focal cerebral ischemia. The short-term and sub-acute medication of selective COX-2 inhibitors that suppresses an elevation of prostaglandin E(2) (PGE(2)) may be an effective treatment to prevent neuronal loss after onset of neuronal excitatory diseases. This review also discusses a novel role of vascular endothelial cells in brain diseases. We found that these cells produce PGE(2) by synthesizing COX-2 and microsomal prostaglandin E synthase-1 (mPGES-1) in response to excitotoxicity and neuroinflammation. We also show a possible mechanisms of neuronal damage associated with seizure via astrocytes and endothelial cells. Further analysis of the interaction among neurons, astrocytes and endothelial cells may provide a better understanding of the processes of neuropathological disorders, as well as facilitating the development of new treatments.

Postanoxic damage of microglial cells is mediated by xanthine oxidase and cyclooxygenase

Brain ischemia and the following reperfusion are important causes for brain damage and leading causes of brain morbidity and human mortality. Numerous observations exist describing the neuronal damage during ischemia/reperfusion, but the outcome of such conditions towards glial cells still remains to be elucidated. Microglia are resident macrophages in the brain. In this study, we investigated the anoxia/reoxygenation caused damage to a microglial cell line via determination of energy metabolism, free radical production by dichlorofluorescein fluorescence and nitric oxide production by Griess reagent. Consequences of oxidant production were determined by measurements of protein oxidation and lipid peroxidation, as well. By using site-specific antioxidants and inhibitors of various oxidant-producing pathways, we identified major sources of free radical production in the postanoxic microglial cells. The protective influences of these compounds were tested by measurements of cell viability and apoptosis. Although, numerous free radical generating systems may contribute to the postanoxic microglial cell damage, the xanthine oxidase- and the cyclooxygenase-mediated oxidant production seems to be of major importance.

Expression of transcription factors CREB and c-Fos in the brains of terminal Creutzfeldt-Jakob disease cases

Expression levels and localization of transcription factors cAMP response element binding protein (CREB(1) and CREB(2)) and c-Fos, as well as levels of up-stream mitogen-activated protein kinases/extracellular signal-regulated kinases (ERK-1 and ERK-2) and p38 kinase, were examined in the brains (frontal cortex) of eleven cases with Creutzfeldt-Jakob disease (CJD) and five age-matched controls. Preserved expression levels of ERK-1-P, ERK-2-P and p38-P were observed in CJD. However, significantly reduced levels, as revealed by gel electrophoresis and Western blotting, and reduced numbers of immunoreactive nuclei, as seen by immunohistochemistry, to CREB, CREB-P, c-Fos and c-Fos-P were found in CJD when compared with controls. These observations point to exhausted CREB and c-Fos brain responses, in spite of preserved up-stream signaling kinases, thus favoring cell death in terminal stages of CJD.

[C-fos protein expression in the parietal cortex and olfactory tubercle in the hypoxic rat brain]

INTRODUCTION

We have attempted to identify which parts of the brain react to ischemic attack using the four-vessel occlusion model in rats.

MATERIAL AND METHODS

We have monitored the expression of c-fos protein in the parietal cortex (R3 and T3) and in the olfactory tubercle (R4 and T4), regions which are supplied with blood by different arteries. The four-vessel occlusion was performed using the Pulsinelli's method and rats were divided into two groups: total ischemia (ligation of four blood vessels or coagulation of the vertebral artheries with bilateral ligation of carotid arteries - R group) and transient ischemic attack (ligation of four blood vessels or coagulation of the vertebral arteries with bilateral repeated ligation of carotid arteries - T group of rats, the so-called preconditioned group). Each of these groups had a control group.

RESULTS AND CONCLUSION

The results showed pronounced expression of c-fos neurons in T group of rats which can explain longer survival of neurons. We believe that this model can serve as a good starting point to developing new approaches to the therapy of brain ischemia.

Contributions of cyclooxygenase-2 to neuroplasticity and neuropathology of the central nervous system

Cyclooxygenase (COX) enzymes, or prostaglandin-endoperoxide synthases (PTGS), are heme-containing bis-oxygenases that catalyze the first committed reaction in metabolism of arachidonic acid (AA) to the potent lipid mediators, prostanoids and thromboxanes. Two isozymes of COX enzymes (COX-1 and COX-2) have been identified to date. This review will focus specifically on the neurobiological and neuropathological consequences of AA metabolism via the COX-2 pathway and discuss the potential therapeutic benefit of COX-2 inhibition in the setting of neurological disease. However, given the controversy surrounding the use of COX-2 selective inhibitors with respect to cardiovascular health, it will be important to move beyond COX to identify which down-stream effectors are responsible for the deleterious and/or potentially protective effects of COX-2 activation in the setting of neurological disease. Important advances toward this goal are highlighted herein. Identification of unique effectors in AA metabolism could direct the development of new therapeutics holding significant promise for the prevention and treatment of neurological disorders.

Oral treatment with rofecoxib reduces hippocampal excitotoxic neurodegeneration

The purpose of this study was to determine whether the selective cyclooxygenase-2 (COX-2) inhibitor rofecoxib [4-[4-(methylsulfonyl)phenyl]-3-phenyl-2(5H)-furanone] could effectively prevent hippocampal neuronal injury in an animal model of excitotoxic neurodegeneration. COX-2 protein levels increased between 3 and 6 h, peaked at 12 h, and declined to near baseline levels 24 h after injection of N-methyl-d-aspartate (NMDA; 18 nmol) into the CA1 region of the left hippocampus. Mice that were fed ad libitum a control rodent diet for 4 days before and 3 days after injection of NMDA demonstrated marked neuronal loss in the primary cell layers of the ipsilateral CA1, CA3, and dentate gyrus (50, 30, and 20% cell loss, respectively). This injury was potently and dose-dependently reduced by feeding animals a diet standardized to deliver 15 or 30 mg/kg rofecoxib per day. Neurodegeneration in the CA1 region was reduced by 30.1 +/- 5.6 and 51.5 +/- 9.0%, respectively; in the CA3 by 64.6 +/- 12.4 and 69.0 +/- 14.1%, respectively; and in the dentate gyrus by 47.8 +/- 15.2 and 58.0 +/- 18.2%, respectively. Moreover, rofecoxib chow slightly but significantly reduced injury-induced brain edema. These findings demonstrate that rofecoxib can ameliorate excitotoxic neuronal injury in vivo and, as such, may be a particularly promising pharmaceutical for the treatment of neurological diseases associated with overactivation of NMDA receptors.

Modulatory role of cyclooxygenase-2 in cerebrovascular coupling

To investigate the role of cyclooxygenase-2 (COX-2) in the cerebrovascular coupling, hemodynamic and neuronal responses to forepaw stimulation were measured in alpha-chloralose-anesthetized rats (N = 18) before and after intravenous administration of Meloxicam (MEL), a preferential COX-2 inhibitor, and following a bolus of prostaglandin E(2) (PGE(2)), a prominent vasodilatatory product of COX-2 catalyzed metabolism of arachidonic acid. The cerebral blood flow (CBF) and blood-oxygenation-level-dependent (BOLD) response was quantified using continuous arterial spin labeling magnetic resonance imaging. Neuronal activity was measured by recording somatosensory-evoked potentials (SEPs) via intracranial electrodes. Both MEL and PGE(2) had a significant effect on the activation-elicited CBF (P < 10(-6)) and BOLD (P < 10(-6)) responses, without affecting the baseline perfusion. Meloxicam decreased brain COX enzymatic activity by 57 +/- 14% and decreased the stimulation-induced CBF response to 32 +/- 2% and BOLD to 46 +/- 1% of their respective pre-drug amplitudes. In turn, PGE(2) bolus resulted in a partial recovery of functional hyperemia, with the CBF response recovering to 52 +/- 3% and the BOLD response to 56 +/- 2% of their values prior to MEL administration. There was no concomitant decrease in either amplitudes or latencies of SEP components. These findings suggest a modulatory role of COX-2 products in the cerebrovascular coupling and provide evidence for existence of a functional metabolic buffer.

Regional distribution of the prostaglandin E2 receptor EP1 in the rat brain: accumulation in Purkinje cells of the cerebellum

Prostaglandin E2 (PGE2), is a major prostanoid produced by the activity of cyclooxygenases (COX) in response to various physiological and pathological stimuli. PGE2 exerts its effects by activating four specific E-type prostanoid receptors (EP1, EP2, EP3, and EP4). In the present study, we analyzed the expression of the PGE2 receptor EP1 (mRNA and protein) in different regions of the adult rat brain (hippocampus, hypothalamus, striatum, prefrontal cerebral cortex, parietal cortex, brain stem, and cerebellum) using reverse transcription- polymerase chain reaction, Western blotting, and immunohistochemical methods. On a regional basis, levels of EP1 mRNA were the highest in parietal cortex and cerebellum. At the protein level, we found very strong expression of EP1 in cerebellum, as revealed by Western blotting experiments. Furthermore, the present study provides for the first time evidence that the EP1 receptor is highly expressed in the cerebellum, where the Purkinje cells displayed very high immunolabeling of their perikaryon and dendrites, as observed in the immunohistochemical analysis. Results from the present study indicate that the EP1 prostanoid receptor is expressed in specific neuronal populations, which possibly determine the region-specific response to PGE2.

Induction of heat shock proteins by hyperglycemic cerebral ischemia

Hyperglycemia worsens the neuronal death induced by cerebral ischemia. A previous study demonstrated that diabetic hyperglycemia suppressed the expression of heat shock protein 70 (HSP70) in the liver. The objective of this study is to determine whether hyperglycemia exacerbates ischemic brain damage by suppressing the expression of heat shock proteins (HSPs) in the brain. Both normoglycemic and hyperglycemic rats were subjected to a transient global cerebral ischemia of 15 min and followed by 0.5, 1 and 3 h of reperfusion. The expression of stress-related genes and levels of HSP proteins were determined by DNA microarray, immunocytochemistry and Western blot analyses. The results showed that hyperglycemic ischemia upregulated the expressions of hsp70, hsp90A, hsp90B, heat shock cognate 71 kD protein (hsc70) and mthsp70. Protein levels of HSP70 and HSP60 were enhanced by hyperglycemia compared with normoglycemia. The results suggested that hyperglycemia-exacerbated ischemic brain damage is not mediated by the suppression of the HSPs. The increased levels of HSPs and mthsp70 suggest that the cell and the mitochondrion had strong stress responses to hyperglycemic ischemia.

Post-seizures amygdaloallocortical microvascular lesion leading to atrophy and memory impairment

Although the incidence of seizures after a cerebrovascular event including intracerebral hemorrhage has been widely recognized, the present studies have demonstrated that generalized convulsive seizures can cause multifocal amygdaloallocortical hemorrhage and tissue necrosis, the origin of which remains to be established. The seizure-elicited amygdaloallocortical injured area, which we refer to as a focal injury-prone area (FIPA), was caused by cholinergic stimulation of the ventroposterolateral and thalamic reticular nuclei. The amygdaloallocortical injury was preceded by focal absence of neuronal COX-2 and presence of microvascular immunoreactivity to the pro-inflammatory cytokines, IL-1beta and TNF-alpha. The microvascular inflammation was followed by edema and multifocal amygdaloallocortical microhemorrhages, leading to atrophy and cognitive impairment. On the basis of the present results, we conclude that generalized convulsive seizures may be at the origin of amygdaloallocortical microvascular injury suggesting that, in addition to anticonvulsant treatment, an appropriate clinical evaluation and therapy for seizures-associated cerebrovascular accidents should be considered.

Cyclooxygenase-2 activity contributes to neuronal expression of cyclin D1 after anoxia/ischemia in vitro and in vivo

Cyclooxygenase-2 (COX-2) activity has been implicated in the pathogenesis of neuronal cell death in ischemia and other diseases, but the mechanism by which COX-2 exacerbates cell death is unknown. COX-2 activity is known to induce expression of cyclin D1 in neoplastic cells, and cyclin D1 expression can induce cell death in postmitotic neurons. In the present study, the role of COX-2 and cyclin D1 in neuronal cell death induced by anoxia and ischemia was examined. Treatment with the COX-2 specific inhibitor (NS 398 25 microM) and cyclin D1 inhibitor (flavopiridol 1 microM) increased neuronal survival and inhibited DNA fragmentation after anoxia. NS-398 suppressed anoxia-induced expression of cyclin D1. Flavopiridol inhibited the anoxia-induced increased expression of cyclin D1, but had no effect on COX-2 expression. Treatment with the selective COX-2 inhibitor, SC58125, had no affect on COX-2 expression but partially suppressed cyclin D1 expression in the cortex following middle cerebral artery occlusion in vivo. These results show that COX-2 activity is required for cyclin D1 expression after ischemia in vivo and anoxia in vitro. These data provide support for the hypothesis that cyclin D1 expression is an important mechanism by which COX-2 activity exacerbates ischemic neuronal death.

Wide therapeutic time window for nimesulide neuroprotection in a model of transient focal cerebral ischemia in the rat

Results from several studies indicate that cyclooxygenase-2 (COX-2) is involved in ischemic brain injury. The purpose of this study was to evaluate the neuroprotective effects of the selective COX-2 inhibitor nimesulide on cerebral infarction and neurological deficits in a standardized model of transient focal cerebral ischemia in rats. Three doses of nimesulide (3, 6 and 12 mg/kg; i.p.) or vehicle were administered immediately after stroke and additional doses were given at 6, 12, 24, 36 and 48 h after ischemia. In other set of experiments, the effect of nimesulide was studied in a situation in which its first administration was delayed for 3-24 h after ischemia. Total, cortical and subcortical infarct volumes and functional outcome (assessed by neurological deficit score and rotarod performance) were determined 3 days after ischemia. The effect of nimesulide on prostaglandin E(2) (PGE(2)) levels in the injured brain was also investigated. Nimesulide dose-dependently reduced infarct volume and improved functional recovery when compared to vehicle. Of interest is the finding that neuroprotection conferred by nimesulide (reduction of infarct size and neurological deficits and improvement of rotarod performance) was also observed when treatment was delayed until 24 h after ischemia. Further, administration of nimesulide in a delayed treatment paradigm completely abolished PGE(2) accumulation in the postischemic brain, suggesting that COX-2 inhibition is a promising therapeutic strategy for cerebral ischemia to target the late-occurring inflammatory events which amplify initial damage.

Hypothermia and stroke: the pathophysiological background

Hypothermia to mitigate ischemic brain tissue damage has a history of about six decades. Both in clinical and experimental studies of hypothermia, two principal arbitrary patterns of core temperature lowering have been defined: mild (32-35 degrees C) and moderate hypothermia (30-33 degrees C). The neuroprotective effectiveness of postischemic hypothermia is typically viewed with skepticism because of conflicting experimental data. The questions to be resolved include the: (i) postischemic delay; (ii) depth; and (iii) duration of hypothermia. However, more recent experimental data have revealed that a protected reduction in brain temperature can provide sustained behavioral and histological neuroprotection, especially when thermoregulatory responses are suppressed by sedation or anesthesia. Conversely, brief or very mild hypothermia may only delay neuronal damage. Accordingly, protracted hypothermia of 32-34 degrees C may be beneficial following acute cerebral ischemia. But the pathophysiological mechanism of this protection remains yet unclear. Although reduction of metabolism could explain protection by deep hypothermia, it does not explain the robust protection connected with mild hypothermia. A thorough understanding of the experimental data of postischemic hypothermia would lead to a more selective and effective clinical therapy. For this reason, we here summarize recent experimental data on the application of hypothermia in cerebral ischemia, discuss problems to be solved in the experimental field, and try to draw parallels to therapeutic potentials and limitations.

Effects of nimesulide on kainate-induced in vitro oxidative damage in rat brain homogenates

BACKGROUND

The cyclooxygenase-2 inhibitor nimesulide is able to reduce kainate-induced oxidative stress in vivo. Here we investigate if this effect is mediated by the direct antioxidant properties of nimesulide using a well-characterized in vitro model of kainate toxicity.

RESULTS

Exposure of rat brain homogenates to kainate (12 mM) caused a significant (p < 0.01) increase in the concentrations of malondialdehyde and 4-hydroxy-alkenals and a significant (p < 0.01) decrease in sulfhydryl levels. High concentrations of nimesulide (0.6-1.6 mM) reduced the extent of lipid peroxidation and the decline in both total and non-protein sulfhydryl levels induced by kainate in a concentration-dependent manner.

CONCLUSIONS

Our results suggest that the neuroprotective effects of nimesulide against kainate-induced oxidative stress in vivo are not mediated through its direct free radical scavenging ability because the concentrations at which nimesulide is able to reduce in vitro kainate excitotoxicity are excessively higher than those attained in plasma after therapeutic doses.

The selective cyclooxygenase-2 inhibitor rofecoxib suppresses brain inflammation and protects cholinergic neurons from excitotoxic degeneration in vivo

Brain inflammatory processes underlie the pathogenesis of Alzheimer's disease, and non-steroidal anti-inflammatory drugs have a protective effect in the disease. The aim of this work was to study in vivo whether attenuation of brain inflammatory response to excitotoxic insult by the selective cyclooxygenase-2 inhibitor, rofecoxib, may prevent neurodegeneration, as a contribution to a better understanding of the role inflammation plays in the pathology of Alzheimer's disease. We investigated, by immunohistochemical methods, glia reaction, the activation of p38 mitogen-activated protein kinase (p38MAPK) pathway with an antibody selective for the phosphorylated form of the enzyme and the number of choline acetyltransferase-positive neurons and, by in vivo microdialysis, cortical extracellular levels of acetylcholine following the injection of quisqualic acid into the right nucleus basalis of adult rats. Seven days after injection, a marked reduction in the number of choline acetyltransferase-positive neurons was found, along with an intense glia reaction, selective activation of p38MAPK at the injection site and a significant decrease in the extracellular levels of acetylcholine in the cortex ipsilateral to the injection site. The loss of cholinergic neurons persisted for at least up to 28 days. Rofecoxib (3 mg/kg/day, starting 1 h prior to injection of quisqualic acid) treatment for 7 days significantly attenuated glia activation and prevented the loss of choline acetyltransferase-positive cells and a decrease in cortical acetylcholine release. The prevention of cholinergic cell loss by rofecoxib occurred concomitantly with the inhibition of p38MAPK phosphorylation. Our findings suggest an important role of brain inflammatory reaction in cholinergic degeneration and demonstrate a neuroprotective effect of rofecoxib, presumably mediated through the inhibition of p38MAPK phosphorylation.

Hyperbilirubinemia protects against focal ischemia in rats

Heme oxygenase-1 (HO1) catalyzes oxidation of the heme molecule in concert with NADPH-cytochrome P450 reductase following the specific cleavage of heme into carbon monoxide, iron, and biliverdin, which is rapidly metabolized to bilirubin. HO1 is a stress-inducible protein that protects cells against oxidative injury, but its protective mechanism is not fully understood. The Eizai hyperbilirubinemic rat (EHBR), a mutant strain derived from the Sprague-Dawley rat (SDR), has a mutation in the gene for the canalicular multispecific organic anion transporter, which results in a phenotype of hyperbilirubinemia, and thus is a model of Dubin-Johnson syndrome in humans. In this study, we compared EHBR and SDR with regard to neuronal death induced by 2 hr of occlusion of the middle cerebral artery and reperfusion. In EHBR, the area that was immunoreactive for microtubule-associated protein-2 was significantly reduced, and the HO1-immunoreactive area was smaller than that in SDR. These results suggest that bilirubin has essentially a neuroprotective effect against focal ischemia and may participate in HO1-induced neuroprotection.

Cyclooxygenase-2 mRNA expression is associated with c-fos mRNA expression and transient water ADC reduction detected with diffusion MRI during acute focal ischemia in rats

Cyclooxygenase-2 (COX-2) plays an important role in the development of injury during cerebral ischemia and inhibition of its activity can reduce infarct size. COX-2 expression during acute ischemia is caused by activation of post-synaptic glutamate receptors, which occurs during spreading depression and ischemic depolarization. Both of these phenomena cause a reduction in the apparent diffusion coefficient of water (ADC), which can be detected with diffusion-weighted magnetic resonance imaging. The reduction is believed to be caused by cellular swelling that occurs as cells depolarize. The goal of this work was to determine the spatial relationship between cyclooxygenase-2 mRNA (cox-2) expression, c-fos mRNA expression and ADC reduction during acute focal cerebral ischemia. Adult rats were subjected to either 30- or 60-min permanent occlusion of the middle cerebral artery. A 2-Tesla scanner was used to acquire diffusion-weighted echo-planar images throughout the ischemic period, which were used to calculate ADC maps. Cox-2 and c-fos mRNA were detected with (35)S in situ hybridization. The results indicate that, for rats subjected to 60-min ischemia, cox-2 was observed in superficial layers of cortex, where transient ADC reduction and c-fos expression were observed. The same was true for most rats subjected to 30-min ischemia. However, in a small number of rats of the 30-min group, cox-2 mRNA expression was observed in regions exhibiting transient and persistent ADC reduction with no c-fos expression. The results suggest that cox-2 mRNA expression during acute MCA occlusion is caused by either or both spreading depression and transient ischemic depolarization.

Neuroprotective efficacy of nimesulide against hippocampal neuronal damage following transient forebrain ischemia

Cyclooxygenase-2 is involved in the inflammatory component of the ischemic cascade, playing an important role in the delayed progression of the brain damage. The present study evaluated the pharmacological effects of the selective cyclooxygenase-2 inhibitor nimesulide on delayed neuronal death of hippocampal CA1 neurons following transient global cerebral ischemia in gerbils. Administration of therapeutically relevant doses of nimesulide (3, 6 and 12 mg/kg; i.p.) 30 min before ischemia and at 6, 12, 24, 48 and 72 h after ischemia significantly (P<0.01) reduced hippocampal neuronal damage. Treatment with a single dose of nimesulide given 30 min before ischemia also resulted in a significant increase in the number of healthy neurons in the hippocampal CA1 sector 7 days after ischemia. Of interest is the finding that nimesulide rescued CA1 pyramidal neurons from ischemic death even when treatment was delayed until 24 h after ischemia (34+/-9% protection). Neuroprotective effect of nimesulide is still evident 30 days after the ischemic episode, providing the first experimental evidence that cyclooxygenase-2 inhibitors confer a long-lasting neuroprotection. Oral administration of nimesulide was also able to significantly reduce brain damage, suggesting that protective effects are independent of the route of administration. The present study confirms the ability of cyclooxygenase-2 inhibitors to reduce brain damage induced by cerebral ischemia and indicates that nimesulide can provide protection when administered for up to 24 h post-ischemia.

Pharmacology of celecoxib in rat brain after kainate administration

Prostaglandin E(2) (PGE(2)) is the major prostaglandin produced both centrally and in the periphery in models of acute and chronic inflammation, and its formation in both locations is blocked by cyclooxygenase-2 (COX-2) inhibitors such as celecoxib. In animal models of inflammation, PGE(2) inhibition in the brain may occur secondarily to a peripheral action by inhibiting local PG formation that elicits increased firing of pain fibers and consequent activation of PG synthesis in the central nervous system (CNS). Celecoxib was studied in the kainate-induced seizure model in the rat, a model of direct central prostaglandin induction, to determine whether it can act directly in the CNS. In the kainate-treated rat brain there was increased PGE(2), PGF(2alpha), and PGD(2) production, with COX activity and PGE(2) formation increased about 7-fold over normal. We quantitated mRNA levels for enzymes involved in the prostaglandin biosynthetic pathways and found that both COX-2 and PGE synthase (PGEs) mRNA levels were increased in the brain; no changes were found for expression of COX-1 or PGD synthase mRNA. By Western blot analysis, COX-2 and PGEs were induced in total brain, hippocampus, and cortex, but not in the spinal cord. Immunohistological studies showed that COX-2 protein expression was enhanced in neurons. Dexamethasone treatment reduced the expression of both COX-2 and PGEs in kainate-treated animals. Celecoxib reduced the elevated PGE(2) levels in brain of kainate-treated rats and inhibited induced COX activity, demonstrating the ability of this compound to act on COX-2 in CNS. Doses of celecoxib that inhibited brain COX-2 were lower than those needed for anti-inflammatory activity in adjuvant arthritis, demonstrating a potent direct central action of the compound.

Expression of inducible nitric oxide synthase and cyclooxygenase-2 after excitotoxic damage to the immature rat brain

It is well established that after adult brain damage the enzymes cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) play an important role in the inflammatory processes and oxidative stress, which are considered to be the leading factors contributing to delayed cell death. The contribution of these enzymes to postnatal brain damage, however, is poorly understood. In our study, excitotoxic lesions were induced by the injection of N-methyl-D-aspartate in the cortex of postnatal day 9 rats. After different survival times ranging from 4 hr to 7 days post-lesion, brain sections were processed for the immunocytochemical demonstration of COX-2 and iNOS and double labeling with neuronal, glial and neutrophil markers. First and maximal de novo induction of iNOS and COX-2 expression was found at 10 hr post-lesion. Expression of both enzymes started to diminish at 24 hr, reaching basal levels at day 3. iNOS-expressing cells were mainly identified as infiltrated neutrophils as well as highly ramified protoplasmic astrocytes closely associated with blood vessels. Moreover, scattered iNOS-positive neurons were found at the lesion borders. In contrast, COX-2 was mainly observed in reactive microglial cells and neuronal cells. COX-2-positive neurons were found within the degenerating area at 10 hr and at the borders of the lesion later on. This study shows that maximal iNOS and COX-2 expression precedes the period of massive neuronal death observed at 24 hr post-lesion, and may therefore contribute to the evolution of the inflammatory response and the neurodegenerative process after an excitotoxic lesion to the postnatal brain.

Cyclooxygenase-2 inhibition protects cultured cerebellar granule neurons from glutamate-mediated cell death

Primary insults to the brain can initiate glutamate release that may result in excitotoxicity followed by neuronal cell death. This secondary process is mediated by both N-methyl-D-aspartate (NMDA) and non-NMDA receptors in vivo and requires new gene expression. Neuronal cyclooxygenase-2 (COX2) expression is upregulated following brain insults, via glutamatergic and inflammatory mechanisms. The products of COX2 are bioactive prostanoids and reactive oxygen species that may play a role in neuronal survival. This study explores the role of neuronal COX2 in glutamate excitotoxicity using cultured cerebellar granule neurons (day 8 in vitro). Treatment with excitotoxic concentrations of glutamate or kainate transiently induced COX2 mRNA (two- and threefold at 6 h, respectively, p < 0.05, Dunnett) and prostaglandin production (five- and sixfold at 30 min, respectively, p < 0.05, Dunnett). COX2 induction peaked at toxic concentrations of these excitatory amino acids. Surprisingly, NMDA, L-quisqualate, and trans-ACPD did not induce COX2 mRNA at any concentration tested. The glutamate receptor antagonist NBQX (5 microM, AMPA/kainate receptor) completely inhibited kainate-induced COX2 mRNA and partially inhibited glutamate-induced COX2 (p < 0.05, Dunnett). Other glutamate receptor antagonists, such as MK-801 (1 microM, NMDA receptor) or MCPG (500 microM, class 1 metabotropic receptors), partially attenuated glutamate-induced COX2 mRNA. These antagonists all reduced steady-state COX2 mRNA (p < 0.05, Dunnett). To determine whether COX2 might be an effector of excitotoxic cell death, cerebellar granule cells were pretreated (24 h) with the COX2-specific enzyme inhibitor, DFU (5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl) phenyl-2((5)H)-furanone) prior to glutamate challenge. DFU (1 to 1000 nM) completely protected cultured neurons from glutamate-mediated neurotoxicity. Approximately 50% protection from NMDA-mediated neurotoxicity, and no protection from kainate-mediated neurotoxicity was observed. Therefore, glutamate-mediated COX2 induction contributes to excitotoxic neuronal death. These results suggest that glutamate, NMDA, and kainate neurotoxicity involve distinct excitotoxic pathways, and that the glutamate and NMDA pathways may intersect at the level of COX2.

Cyclooxygenase inhibition as a strategy to ameliorate brain injury

Cyclooxygenase (COX) is the obligate, rate-limiting enzyme for the conversion of arachidonic acid into prostaglandins. Two COX enzymes have been identified: a constitutively expressed COX-1 and an inducible, highly regulated COX-2. Widely used to treat chronic inflammatory disorders, COX inhibitors have shown promise in attenuating inflammation associated with brain injury. However, the use of COX inhibition in the treatment of brain injury has met with mixed success. This review summarizes our current understanding of COX expression in the central nervous system and the effects of COX inhibitors on brain injury. Three major targets for COX inhibition in the treatment brain injury have been identified. These are the cerebrovasculature, COX-2 expression by vulnerable neurons, and the neuroinflammatory response. Evidence suggests that given the right treatment paradigm, COX inhibition can influence each of these three targets. Drug interactions and general considerations for administrative paradigms are also discussed. Although therapies targeted to specific prostaglandin species, such as PGE2, might prove more ameliorative for brain injury, at the present time non-specific COX inhibitors and COX-2 specific inhibitors are readily available to researchers and clinicians. We believe that COX inhibition will be a useful, ameliorative adjunct in the treatment of most forms of brain injury.

Mechanisms of prostaglandin E2-induced interleukin-6 release in astrocytes: possible involvement of EP4-like receptors, p38 mitogen-activated protein kinase and protein kinase C

The expression of cyclooxygenase-2 (COX-2) and the synthesis of prostaglandin E2 (PGE2) as well as of cytokines such as interleukin-6 (IL-6) have all been suggested to propagate neuropathology in different brain disorders such as HIV-dementia, prion diseases, stroke and Alzheimer's disease. In this report, we show that PGE2-stimulated IL-6 release in U373 MG human astroglioma cells and primary rat astrocytes. PGE2-induced intracellular cAMP formation was mediated via prostaglandin E receptor 2 (EP2), but inhibition of cAMP formation and protein kinase A or blockade of EP1/EP2 receptors did not affect PGE2-induced IL-6 synthesis. This indicates that the cAMP pathway is not part of PGE2-induced signal transduction cascade leading to IL-6 release. The EP3/EP1-receptor agonist sulprostone failed to induce IL-6 release, suggesting an involvement of EP4-like receptors. PGE2-activated p38 mitogen-activated kinase (p38 MAPK) and protein kinase C (PKC). PGE2-induced IL-6 synthesis was inhibited by specific inhibitors of p38 MAPK (SB202190) and PKC (GF203190X). Although, up to now, EP receptors have only rarely been linked to p38 MAPK or PKC activation, these results suggest that PGE2 induces IL-6 via an EP4-like receptor by the activation of PKC and p38 MAPK via an EP4-like receptor independently of cAMP.

Temporospatial expression of HSP72 and c-JUN, and DNA fragmentation in goat hippocampus after global cerebral ischemia

The role of gene induction (expression of HSP72 and c-JUN proteins) and delayed ischemic cell death (in situ labeling of DNA fragmentation) have been investigated in the goat hippocampus after transient global cerebral ischemia. The animals were subjected to 20-min ischemia (bilateral occlusion of the external carotid arteries plus bilateral jugular vein compression) and allowed to reperfuse for 2 h, and then 1, 3, and 7 days. Histological signs of cell loss were not found in the hippocampus at 2 h, 1 day, or 3 days of reperfusion. However, such an ischemic insult produced extensive, selective, and delayed degeneration in the hippocampus, as 68% of the neurons in CA1 had died at 7 days, but cell loss was not detected in CA3 and dentate gyrus fields. Concomitantly, a high percentage of TUNEL-positive CA1 neurons (60+/-9%, mean +/- SEM) was seen at 7 days, but not at the earlier time points. Mild induction of HSP72 was detected in the goat hippocampus after ischemia. The maximum percentage of HSP72-positive neurons (10-15%) was shown at 3 days of reperfusion and was concentrated mainly in the CA3 field, subiculum, and hilus, rather than in the CA1 field, whereas HSP72 expression was hardly detected at 7 days. At this later time point, scattered induction of nuclear c-JUN was found in a few neurons. The results show that: 1) postischemic delayed neuronal death selectively affects the CA1 field in the goat hippocampus, a phenomenon which seems to take longer to develop than in previously reported rodent models; and 2) postischemic expression of c-JUN does not appear to be related to cell death or survival, while the inability of most CA1 neurons to express HSP72 could contribute to neuronal death.

Selective vulnerability to kainate-induced oxidative damage in different rat brain regions

Some markers of oxidative injury were measured in different rat brain areas (hippocampus, cerebral cortex, striatum, hypothalamus, amygdala/piriform cortex and cerebellum) after the systemic administration of an excitotoxic dose of kainic acid (KA, 9 mg kg(-1) i.p.) at two different sampling times (24 and 48 h). Kainic acid was able to lower markedly (P < 0.05) the glutathione (GSH) levels in hippocampus, cerebellum and amygdala/piriform cortex (maximal reduction at 24 h). In a similar way, lipid peroxidation, as assessed by malonaldehyde and 4-hydroxyalkenal levels, significantly increased (P < 0.05) in hippocampus, cerebellum and amygdala/piriform cortex mainly at 24 h after KA. In addition, hippocampal superoxide dismutase (SOD) activity decreased significantly (P < 0.05) with respect to basal levels by 24 h after KA application. On the other hand, brain areas such as hypothalamus, striatum and cerebral cortex seem to be less susceptible to KA excitotoxicity. According to these findings, the pattern of oxidative injury induced by systemically administered KA seems to be highly region-specific. Further, our results have shown that a lower antioxidant status (GSH and SOD) seems not to play an important role in the selective vulnerability of certain brain regions because it correlates poorly with increases in markers of oxidative damage.

Changes in the levels of nitric oxide synthase and protein kinase C gamma following kainic acid receptor activation in the rat spinal cord

In this study, we evaluated the levels of nitric oxide synthase, both neuronal and induced (nNOS and iNOS, respectively), cyclooxygenase-1 and 2 (COX-1 and COX-2) and protein kinase C gamma (PKCgamma) and correlated these with algogenic behavior following spinal kainic acid (KA) receptor activation in rats. Thirty adult male Sprague-Dawley rats were randomly assigned into six groups (n=5). Groups A, B, and C received 0.5 g kainic acid intrathecally and were analyzed at 3, 6, 24 h after injection, respectively. Groups D, E, and F received saline and were analyzed at 3, 6, 24 h after injection, respectively. We observed for behavioral changes in the rats following intrathecal KA injection and analyzed the protein levels of NOS, COX and PKCgamma by Western blotting techniques. Importantly, we clarified the potential roles of PKCgamma in the regulation of nNOS and COX-2 following intrathecal injection with KA in the rat spinal cord. COX-2 protein was detected but not significantly changed in the lumbosacral spinal cord at 3, 6, and 24 h following intrathecal KA injection (P>0.05). In contrast, nNOS protein was detected at higher levels in comparison with normal spinal cord at 6 and 24 h after intrathecal administration of KA (P<0.05). PKCgamma also increased significantly at 3, 6, and 24 h after intrathecal KA injection when compared with the baseline level (P<0.05). On the other hand, COX-1 and iNOS were not detected in either normal or KA treated spinal cords. These results provide strong in vivo evidence to support the idea that nNOS but not COX-2, plays an important role in spinal KA receptor activation. Furthermore, up-regulation of PKCgamma is involved in KA induced algogenic behavior in rats.

The Cycloxygenase-2 inhibitor SC58236 is neuroprotective in an in vivo model of focal ischemia in the rat

Focal ischemia was induced in the fronto-parietal region of rat brain, by injection of Rose Bengal, followed by light activation. Focal ischemia was accompanied by formation of PGD(2) peaking 60-90 min post irradiation and declining thereafter. Increased Cycloxygenase-2 (COX-2) expression was also observed. Control ischemic rats showed distinct morphological alterations with necrosis of neurons, glial cells and blood vessels, surrounded by a halo with pyknotic cells with cytoplasm swelling and vacuolization. Compound SC58236, a selective COX-2 inhibitor, dose-dependently prevented, ischemia-induced eicosanoid formation (area under the curve (AUC) of controls: 3.11 +/- 0.87; AUC of 20 mg/kg SC58236: 0.39 +/- 0.24), and caused significant reduction of damaged area (30.7 and 18.9% at SC58236 20 and 6.6 mg/kg), suggesting that selective inhibitors of COX-2 are neuroprotective.

The selective cyclooxygenase-2 inhibitor rofecoxib reduces kainate-induced cell death in the rat hippocampus

Treatment of male Sprague-Dawley rats with kainic acid (10 mg/kg, i.p.) triggered limbic seizures in 60% of the animals starting within 30 min and lasting for about 6 h. Cyclooxygenase-2 (COX-2) mRNA was strongly induced in the pyramidal cells of the hippocampus, in the amygdala and the piriform cortex after 8 h, as shown by in situ hybridization, and returned to control levels after 72 h. At this time marked cell loss occurred in the CA1-CA3 areas of the hippocampus. We hypothesize that rofecoxib, a selective COX-2 inhibitor, might abbreviate the late neurotoxicity, possibly associated with COX-2 induction. Animals which developed seizures were treated for 3 days with rofecoxib (10 mg/kg, i.p., n = 12) starting 6 or 8 h after kainic acid injection. Histological staining of viable cells confirmed that rofecoxib treatment selectively diminished cell loss in the hippocampus. The TdT-mediated dUTP nick end labelling (TUNEL) technique was used to estimate delayed cell death. Abundant TUNEL-positive cells were detected in seizure rats 72 h after kainic acid injection in pyramidal cells of the hippocampus (CA1-CA3), in cells of the thalamus, the amygdala and the piriform cortex. Treatment with rofecoxib selectively and significantly (P < 0.05) attenuated the number of TUNEL-positive cells in the hippocampus, whereas the cells of the thalamus, amygdala and piriform cortex were not protected. Therefore we conclude that COX-2 might contribute to cell death of pyramidal cells of the hippocampus as a consequence of limbic seizures.

Interleukin-1beta induces cyclooxygenase-2 and prostaglandin E(2) synthesis in human neuroblastoma cells: involvement of p38 mitogen-activated protein kinase and nuclear factor-kappaB

Prostaglandins (PGs), which are generated by the enzymatic activity of cyclooxygenase (COX)-1 and -2, modulate several functions in the CNS such as the generation of fever, the sleep/wake cycle, and the perception of pain. Moreover, the neuronal induction of COX-2 has been linked to neuroinflammatory aspects of Alzheimer's disease (AD). The regulation of COX expression in neuronal cells is only partly understood and has been mainly linked to synaptic activity. In pathophysiological situations, however, cytokines may be potent stimulators of neuronal COX expression. Here we show that interleukin (IL)-1beta induces COX-2 mRNA and protein synthesis and the release of PGE(2) in the human neuroblastoma cell line SK-N-SH. We further demonstrate that both a free radical scavenger and an inhibitor of p38 mitogen-activated protein kinase (MAPK) reduce IL-1beta-induced synthesis of COX-2. IL-1beta induces p38 MAPK phosphorylation and activation of the nuclear factor-kappaB independently from each other. Our data suggest that IL-1beta-induced COX-2 expression in SK-N-SH cells is regulated by different mechanisms, presumably involving mRNA transcription and mRNA stability. The ability of p38 MAPK to augment COX-2 expression in human neuroblastoma cells, as shown here, suggests that p38 MAPK may be involved in neuronal expression of COX-2 in AD.