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

Effects of Cyclooxygenase Inhibitors on Apoptotic Neuroretinal Cells

Glaucoma is characterized by a loss of retinal ganglion cells (RGC) which is associated with a decrease of visual function. Neuroprotective agents as a new therapeutic strategy could prevent the remaining neurons from apoptotic cell death. Previous studies have shown the involvement of the Cyclooxygenase (COX)-2 signalling in the apoptotic death of neurons. Herein we investigated the neuroprotective effect of COX-1/COX-2- and selective COX-2- inhibitors on apoptotic. R28, a neuroretinal cell line and determined the PGE(2) levels by ELISA. Furthermore we investigated differences in protein expression in the cells after exposure to elevated pressure compared to untreated cells by ProteinChip analysis.In addition, a protein profiling study of the cells after exposure to elevated pressure was performed. The protein expression profiles were measured by SELDI-TOF (Surface Enhanced Laser Desorption/Ionization-time of flight) Protein Chips. The protein identification was performed by mass spectrometry (MS).It could be shown that COX-2 inhibition significantly prevented the cells from apoptosis and reduced the PGE(2) concentrations. Selective COX-2 inhibitors were significant more potent than non-selective inhibitors or COX-1 inhibitors. We found differently expressed protein patterns in neuroretinal cells cultured at atmospheric pressure compared to those cells exposed to elevated pressure with or without celecoxib respectively. We identified three biomarkers, ubiquitin, HSP10 and NDKB, which were differently expressed in the groups. However, our data indicates a distinct neuroprotective effect of COX-2 inhibition. The local treatment with selective COX-2 inhibitors might provide an innovative strategy of therapeutic intervention for glaucoma.

Cytosolic phospholipase A2 alpha inhibition prevents neuronal NMDA receptor-stimulated arachidonic acid mobilization and prostaglandin production but not subsequent cell death

Phospholipase A(2) (PLA(2)) enzymes encompass a superfamily of at least 13 extracellular and intracellular esterases that hydrolyze the sn-2 fatty acyl bonds of phospholipids to yield fatty acids and lysophospholipids. The purpose of this study was to characterize which phospholipase paralog regulates NMDA receptor-mediated arachidonic acid (AA) release. Using mixed cortical cell cultures containing both neurons and astrocytes, we found that [(3)H]-AA released into the extracellular medium following NMDA receptor stimulation (100 microM) increased with time and was completely prevented by the addition of the NMDA receptor antagonist MK-801 (10 microM) or by removal of extracellular Ca(2+). Neither diacylglycerol lipase inhibition (RHC-80267; 10 microM) nor selective inhibition of Ca(2+)-independent PLA(2) [bromoenol lactone (BEL); 10 microM] alone had an effect on NMDA receptor-stimulated release of [(3)H]-AA. Release was prevented by methyl arachidonyl fluorophosphonate (MAFP) (5 microM) and AACOCF(3) (1 microM), inhibitors of both cytosolic PLA(2) (cPLA(2)) and Ca(2+)-independent PLA(2) isozymes. This inhibition effectively translated to block of NMDA-induced prostaglandin (PG) production. An inhibitor of p38MAPK, SB 203580 (7.5 microM), also significantly reduced NMDA-induced PG production providing suggestive evidence for the role of cPLA(2)alpha. Its involvement in release was confirmed using cultures derived from mice deficient in cPLA(2)alpha, which failed to produce PGs in response to NMDA receptor stimulation. Interestingly, neither MAFP, AACOCF(3) nor cultures derived from cPLA(2)alpha null mutant animals showed any protection against NMDA-mediated neurotoxicity, indicating that inhibition of this enzyme may not be a viable protective strategy in disorders of the cortex involving over-activation of the NMDA receptor.

Seizure-induced up-regulation of P-glycoprotein at the blood-brain barrier through glutamate and cyclooxygenase-2 signaling

Increased expression of drug efflux transporters at the blood-brain barrier accompanies epileptic seizures and complicates therapy with antiepileptic drugs. This study is concerned with identifying mechanistic links that connect seizure activity to increased P-glycoprotein expression at the blood-brain barrier. In this regard, we tested the hypothesis that seizures increase brain extracellular glutamate, which signals through an N-methyl-d-aspartate (NMDA) receptor and cyclooxygenase-2 (COX-2) in brain capillaries to increase blood-brain barrier P-glycoprotein expression. Consistent with this hypothesis, exposing isolated rat or mouse brain capillaries to glutamate for 15 to 30 min increased P-glycoprotein expression and transport activity hours later. These increases were blocked by 5H-dibenzo[a,d]cyclohepten-5,10-imine (dizocilpine maleate) (MK-801), an NMDA receptor antagonist, and by celecoxib, a selective COX-2 inhibitor; no such glutamate-induced increases were seen in brain capillaries from COX-2-null mice. In rats, intracerebral microinjection of glutamate caused locally increased P-glycoprotein expression in brain capillaries. Moreover, using a pilocarpine status epilepticus rat model, we observed seizure-induced increases in capillary P-glycoprotein expression that were attenuated by administration of indomethacin, a COX inhibitor. Our findings suggest that brain uptake of some antiepileptic drugs can be enhanced through COX-2 inhibition. Moreover, they provide insight into one mechanism that underlies drug resistance in epilepsy and possibly other central nervous system 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.

Celecoxib as an adjunct in the treatment of depressive or mixed episodes of bipolar disorder: a double-blind, randomized, placebo-controlled study

OBJECTIVE

To investigate whether the cox-2 inhibitor celecoxib has antidepressant effects in bipolar disorder (BD) patients during depressive or mixed phases.

METHODS

We studied 28 DSM-IV BD patients who were experiencing a depressive or mixed episode and were on a stable dose of a mood stabilizer or atypical antipsychotic medication. Subjects were randomized to receive 6 weeks of double-blind placebo or celecoxib (400 mg/day) treatment. Current mood stabilizer or antipsychotic medication remained at the same doses during the trial.

RESULTS

Intention-to-treat analysis showed that the patients receiving celecoxib had lower Hamilton Depression Rating Scale (HamD) scores after 1 week of treatment compared to the patients receiving placebo, but this difference was not statistically significant (p = 0.09). The improvement in the first week of treatment was statistically significant when the analysis included only the subjects who completed the full 6-week trial (p = 0.03). The two groups did not differ significantly on depressive or manic symptoms from the second week until the end of the trial. Celecoxib was well tolerated with the exception of two subjects who dropped out of the study due to rash.

CONCLUSIONS

Our findings suggest that adjunctive treatment with celecoxib may produce a rapid-onset antidepressant effect in BD patients experiencing depressive or mixed episodes.

A cyclooxygenase-2 inhibitor ameliorates behavioral impairments induced by striatal administration of epidermal growth factor

Consistent with the hypothesis that neuroinflammatory processes contribute to the neuropathology of schizophrenia, the protein levels of epidermal growth factor (EGF) and its receptor ErbB1 are abnormal in patients with schizophrenia. To evaluate neuropathological significance of this abnormality, we established an animal model for behavioral deficits by administering EGF into the striatum and evaluated the effects of cyclooxygenase-2 (Cox-2) inhibitor celecoxib. Intracranial infusion of EGF into the striatum of adult male rats activated ErbB1 and induced neurobehavioral impairments observed in several schizophrenia models. Unilateral EGF infusion to the striatum lowered prepulse inhibition (PPI) in a dose-dependent manner and impaired latent learning of active shock avoidance without affecting basal learning ability. Bilateral EGF infusion similarly affected PPI. In contrast, EGF infusion to the nucleus accumbens did not induce a behavioral deficit. Intrastriatal EGF infusion also increased Cox-2 expression, elevated tyrosine hydroxylase activity, and upregulated the levels of dopamine and its metabolites. Subchronic administration of celecoxib (10 mg/kg, p.o.) ameliorated the abnormalities in PPI and latent learning as well as normalized dopamine metabolism. We conclude that this EGF-triggered neuroinflammatory process is mediated in part by Cox-2 activity and perturbs dopamine metabolism to generate neurobehavioral abnormalities.

Protective effects of 15-deoxy-Delta12,14-prostaglandin J2 against glutamate-induced cell death in primary cortical neuron cultures: induction of adaptive response and enhancement of cell tolerance primarily through up-regulation of cellular glutathione

There is increasing evidence to suggest that reactive oxygen species, including a variety of lipid oxidation products and other physiologically existing oxidative stimuli, can induce an adaptive response and enhance cell tolerance. In the present study, by using cultured cortical neurons, we investigated the effect of electrophilic lipids, such as 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) and 4-hydroxy-2-nonenal (4-HNE) against the cell death induced by H(2)O(2) and glutamate. Pre-treatment with both 15d-PGJ(2) and 4-HNE at sublethal concentrations resulted in a significant protective effect against oxidative stress, and 15d-PGJ(2), in particular, exhibited a complete protective effect against glutamate-induced neuronal cell death. Pre-treatment with 15d-PGJ(2) increased the intracellular glutathione (GSH) as well as the gene expression of glutamate-cysteine ligase (GCL), the rate-limiting enzyme of GSH synthesis. 15d-PGJ(2) protected cells from glutamate-induced GSH depletion, while the inhibition of cellular GSH synthesis by buthionine sulfoximine abolished the adaptive response induced by 15d-PGJ(2). These findings indicate that at low levels, 15d-PGJ(2) acts as a potent survival mediator against glutamate-induced insults via the induction of an adaptive response primarily through the up-regulation of the intracellular GSH synthesis.

Neuronal Cyclooxygenase-2 Activity and Prostaglandins PGE2, PGD2, and PGF2α Exacerbate Hypoxic Neuronal Injury in Neuron-enriched Primary Culture

Cyclooxygenase-2 (COX-2) activity has been implicated in the pathogenesis of cerebral ischemia. To determine whether COX-2 activity within the neuron itself exacerbates hypoxic neuronal injury, neuron-enriched cultures were subjected to anoxia. Treatment with COX-2 selective antagonists decreased cell death. Neurons cultured from homozygous COX-2 gene disrupted mice were resistant to hypoxia compared to those of heterozygotes. Infection of primary neurons with AAV expressing COX-2 exacerbated cell death compared to neurons infected with enhanced green fluorescent protein (EGFP) control vector. Addition of PGE2, PGD2 or PGF2 alpha to the medium exacerbated injury, suggesting that the deleterious effects of COX-2 overexpression in hypoxia could be mediated by direct receptor mediated effects of prostaglandins. Overexpression of COX-2 did not increase expression of cyclin D1 or phosphoretinoblastoma protein (pRb), or cleavage of caspase 3 suggesting that this cell cycle mechanism does not mediate COX-2 toxicity in this model.

A liquid chromatography/mass spectrometric method for simultaneous analysis of arachidonic acid and its endogenous eicosanoid metabolites prostaglandins, dihydroxyeicosatrienoic acids, hydroxyeicosatetraenoic acids, and epoxyeicosatrienoic acids in rat brain tissue

A sensitive, specific, and robust liquid chromatography/mass spectrometric (LC/MS) method was developed and validated that allows simultaneous analysis of arachidonic acid (AA) and its cyclooxygenase, cytochrome P450, and lipoxygenase pathway metabolites prostaglandins (PGs), dihydroxyeicosatrienoic acids (DiHETrEs), hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs), including PGF(2alpha), PGE(2), PGD(2), PGJ(2), 14,15-DiHETrE, 11,12-DiHETrE, 8,9-DiHETrE, 5,6-DiHETrE, 20-HETE, 15-HETE, 12-HETE, 9-HETE, 8-HETE, 5-HETE, 14,15-EET, 11,12-EET, 8,9-EET, and 5,6-EET in rat brain tissues. Deuterium labeled PGF(2alpha)-d(4), PGD(2)-d(4), 15(S)-HETE-d(8), 14,15-EET-d(8), 11,12-EET-d(8), 8,9-EET-d(8), and AA-d(8) were used as internal standards. Solid phase extraction was used for sample preparation. A gradient LC/MS method using a C18 column and electrospray ionization source under negative ion mode was optimized for the best sensitivity and separation within 35 min. The method validation, including LC/MS instrument qualification, specificity, calibration model, accuracy, precision (without brain matrix and with brain matrix), and extraction efficiency were performed. The linear ranges of the calibration curves were 2-1000 pg for PGs, DiHETrEs, HETEs, and EETs, 10-2400 pg for PGE(2) and PGD(2), and 20-2000 ng for AA, respectively.

Cell death in rat cerebellar granule neurons induced by hydrogen peroxide in vitro: mechanisms and protection by adenosine receptor ligands

Oxidative stress, resulting from excessive production of reactive oxygen species (ROS), is a pathological state that causes profound cellular damage and eventual death resulting from the overactivation of glutamate receptors, and the generation of nitric oxide, superoxide and hydrogen peroxide (H(2)O(2)). As such, H(2)O(2) represents an important model for studying the neuropathology of oxidative stress in a variety of CNS disorders. The effects of H(2)O(2) on the viability of post-natal cerebellar granule neurons (CGNs), the nature of the cell death involved and the potential protection by adenosine receptors against the damage were examined in the current study. Hydrogen peroxide (10-400 microM) reduced CGN viability in a concentration- and time-dependent manner. The addition of catalase (100 U/ml) prevented this effect, and the non-specific COX inhibitor aspirin (1 mM) also alleviated the damage. A combination of H(2)O(2) (5 microM) and Cu(2+) (0.5 mM) resulted in a significant damage that was not prevented by the hydroxyl radical scavenger mannitol (50 mM). The permeability transition pore blocker cyclosporin A, the caspase-3 inhibitor Z-DEVD-fmk (40 microM) and the PARP-1 inhibitor DPQ (10 microM) each significantly protected against peroxide damage. While the A(1) adenosine receptor agonist CPA and the A(2A) receptor antagonist ZM241385 (each at 100 nM) elicited protection, the A(1) adenosine receptor blocker DPCPX and the A(2A) receptor agonist CGS21680 (each at 100 nM) showed no effect. The data demonstrate that H(2)O(2) induced oxidative stress in CGNs, involving both apoptotic and necrotic death, and this can be ameliorated by A(1) receptor activation or A(2A) receptor blockade.

Parecoxib is neuroprotective in spontaneously hypertensive rats after transient middle cerebral artery occlusion: a divided treatment response?

Background

Anti-inflammatory treatment affects ischemic damage and neurogenesis in rodent models of cerebral ischemia. We investigated the potential benefit of COX-2 inhibition with parecoxib in spontaneously hypertensive rats (SHRs) subjected to transient middle cerebral artery occlusion (tMCAo).

Methods

Sixty-four male SHRs were randomized to 90 min of intraluminal tMCAo or sham surgery. Parecoxib (10 mg/kg) or isotonic saline was administered intraperitoneally (IP) during the procedure, and twice daily thereafter. Nineteen animals were euthanized after 24 hours, and each hemisphere was examined for mRNA expression of pro-inflammatory cytokines and COX enzymes by quantitative RT-PCR. Twenty-three tMCAo animals were studied with diffusion and T₂ weighted MRI within the first 24 hours, and ten of the SHRs underwent follow-up MRI six days later. Thirty-three SHRs were given 5-bromo-2'-deoxy-uridine (BrdU) twice daily on Day 4 to 7 after tMCAo. Animals were euthanized on Day 8 and the brains were studied with free-floating immunohistochemistry for activated microglia (ED-1), hippocampal granule cell BrdU incorporation, and neuronal nuclei (NeuN). Infarct volume estimation was done using the 2D nucleator and Cavalieri principle on NeuN-stained coronal brain sections. The total number of BrdU⁺ cells in the dentate gyrus (DG) of the hippocampus was estimated using the optical fractionator.

Results

We found a significant reduction in infarct volume in parecoxib treated animals one week after tMCAo (p < 0.03). Cortical ADC values in the parecoxib group were markedly less increased on Day 8 (p < 0.01). Interestingly, the parecoxib treated rats were segregated into two subgroups, suggesting a responder vs. non-responder phenomenon. We found indications of mRNA up-regulation of IL-1β, IL-6, TNF-α and COX-2, whereas COX-1 remained unaffected. Hippocampal granule cell BrdU incorporation was not affected by parecoxib treatment. Presence of ED-1⁺ activated microglia in the hippocampus was related to an increase in BrdU uptake in the DG.

Conclusion

IP parecoxib administration during tMCAo was neuroprotective, as evidenced by a large reduction in mean infarct volume and a lower cortical ADC increment. Increased pro-inflammatory cytokine mRNA levels and hippocampal granule cell BrdU incorporation remained unaffected.

Differential effects of cyclooxygenase inhibitors on intracerebroventricular colchicine-induced dysfunction and oxidative stress in rats

Alzheimer's disease is a progressive neurological and psychiatric disorder. Oxidative stress and neuroinflammation have been implicated in pathophysiology of Alzheimer's disease. Inflammatory cells, such as astrocytes and microglia, are activated in areas of the brain affected by amyloid plaques and inflammatory mediators including cytokines, chemokines, prostaglandins, oxygen free radicals and reactive nitrogen species may have a crucial role in Alzheimer's disease pathogenesis. Central administration of colchicine, a microtubule-disrupting agent, causes loss of cholinergic neurons and cognitive dysfunction that is associated with excessive free radical generation. The present study was aimed to evaluate the effects of cyclooxygenase inhibitors against colchicine-induced cognitive dysfunction and oxidative stress in rats. Following intracerebroventricular (i.c.v.) administration of colchicine (15 microg/5 microl), rats exhibited poor retention of memory in Morris water maze and elevated plus maze task paradigms and oxidative stress in rats. Chronic treatment with naproxen (per se; 20 and 40 mg/kg, p.o.) or valdecoxib (per se; 5 and 10 mg/kg, p.o.) daily respectively for a period of 25 days beginning 4 days prior to colchicine injection significantly improved colchicine-induced cognitive impairment. Intracerebroventricular colchicine injection resulted in free radical generation characterized by alterations in oxidative stress markers with a significant increase in malondialdehyde and nitrite levels and depletion of reduced glutathione levels in the brains of rats. It also caused a decrease in acetylcholinesterase activity. Besides, improving cognitive dysfunction, chronic administration of cyclooxygenase inhibitors (naproxen and valdecoxib) significantly reduced elevated malondialdehyde, nitrite levels and restored reduced glutathione levels and acetylcholinesterase activity. The results of the present study indicated that naproxen (per se; 20 and 40 mg/kg, p.o.) or valdecoxib (per se; 5 and 10 mg/kg, p.o.) treatment has a neuroprotective role against colchicine-induced cognitive impairment and associated oxidative stress. The present findings further support the potential use of cyclooxygenase inhibitors in treatment of neurodegenerative diseases such as Alzheimer's disease.

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.

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.

Inhibition of nNOS and COX-2 expression by lutein in acute retinal ischemia

OBJECTIVE

Lutein is a major nutrient in the retina. Lutein has an antioxidative effect and protects against macular degeneration and retinal degenerative disease. However, the mechanism of lutein is not clear in retinal degeneration, and a role for lutein is not known in ischemic injury. In this study, an ischemia-induced rat retina was examined to determine the effect of the lutein on ischemic retinal cell death.

METHODS

We used a transient ischemia model of high intraocular pressure in the rat. Lutein (Kemin Foods, LC) was injected into the intraperitoneal or intravitreous before ischemia. Retinal degeneration was observed by light microscopy 24 h after ischemia. Expressions of neuronal nitric oxide synthase (nNOS) and cyclo-oxygenase-2 (COX-2) were detected by western blot analysis at various times after retinal ischemia.

RESULTS

The nNOS and COX-2 expression levels were increased early in ischemic control retinas, but these increases were inhibited by lutein. In addition, the inhibitory effect of lutein was observed to be dose dependent. Further, ischemia-induced cell death was inhibited by lutein. Lutein-injected ischemic retina appeared similar to normal retina.

CONCLUSION

This study investigated the protective effect of lutein on retinal ischemia and the inhibitory effect of nNOS and COX-2 expressions. These results suggest that a supplement with lutein may have the potential to inhibit ischemic cell death by this mechanism in the neural retina.

Increases in COX II mRNA in the rat spinal cord induced by cauda equina traction

This article investigated the time response of COX II induction by traction of the cauda equina assessed by a quantified RT-PCR method. Under deep GOI anesthesia, male Wistar rats were fixed in the prone position and a laminectomy of the dorsal part of the first and second sacral vertebrae was performed. Following, COX II-mRNA levels in the cervical, thoracic, lumbar, sacral, and caudal segments were measured at 2, 4, 6, and 24 h after traction by a quantified RT-PCR method. After cauda equina traction, significant levels of COX II mRNA were detected in all segments of the spinal cord examined. Maximum levels in each segment were determined 4 h after traction of the cauda equina. Particularly in the sacrocaudal segments significantly higher levels of COX II mRNA were measured 24 h after traction. These results indicate that significant induction of spinal COX II mRNA was caused by cauda equina traction and that such induction plays a regulatory role in the nociceptive pain pathway.

A time course analysis of cyclooxygenase-2 suggests a role in spatial memory retrieval in rats

We previously showed a role for COX-2 in spatial memory retention. In that study we investigated the effects of post-training intrahippocampal infusion of celecoxib as a COX-2-specific inhibitor on spatial memory retention. Those infusions impaired spatial memory retention in the Morris water maze. In the present study a time course analysis of role of COX-2 in spatial memory was conducted. Here stereotaxic surgery was employed for the bilateral implantation of guide cannulas into the CA1 region of the hippocampus. Training trials were started after recovery of the animals. Immediately after last trial of training on third day, the celecoxib (0.1M) was infused bilaterally and testing trials, were performed 1, 2, 3, and 7 days after celecoxib infusions. Significant alterations were observed in escape latency and traveled distance 2 and 3 days after celecoxib infusions. The maximum impairment was obtained 72 h after the infusions. The data suggests that the effect of celecoxib is transient and that its effect on performance is likely caused by a problem in memory retrieval. Quantification analyses of the immunostaining of COX-2-containing neurons in the dorsal hippocampus show that celecoxib infusions significantly reduced (P<0.05) COX-2 immunoreactivity for the animals that were tested 3 days after the drug infusion. Results from the behavioral study along with the findings from immunohistochemical analyses suggest that COX-2 has significant role in spatial memory retrieval. Moreover, the memory deficits induced by the infusions continuously persists for 3 days.

NMDA and group I metabotropic glutamate receptors activation modulates substance P release from the arcuate nucleus and median eminence

Glutamate participates in the regulation of secretion of several neuropeptides, including substance P (SP). Glutamate acts through ionotropic (iGluR) and metabotropic (mGluR) receptors. We have investigated whether glutamate receptor agonists and antagonists could affect SP release from the arcuate nucleus and the median eminence (ARC/ME). An increase in SP-like immunoreactivity (SP-LI) release from ARC/ME was induced by glutamate and N-methyl-D-aspartate (NMDA). This increase was prevented by D-(-)-2-amino-5-phosphono pentanoic acid (DAP5) (0.1mM), a specific NMDA antagonist and by (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) (0.1 mM), a selective antagonist of group I mGluR. The selective non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3(1H-4H)-dione (DNQX) (0.1mM) and (RS)-alpha-methyl-4-tetrazolylphenylglycine (MTPG) (0.1 mM), a group II and III mGluRs antagonist, did not affect the stimulatory effect of glutamate. A group I selective agonist, (S)-3,5-dihydroxyphenylglycine (DHPG) induced a significant increase in SP-LI release. Supporting the participation of nitric oxide (NO) in the effect of glutamate on SP-LI release, NAME (0.5 mM), a NO synthase inhibitor, reduced the glutamate-induced increase in SP-LI release from ARC/ME. Similarly, glutamate did not induce an increase in SP-LI release in the presence of meloxicam (0.1 mM) (a cyclooxygenase-2 (COX-2) specific inhibitor) indicating that prostaglandins production may also be involved in the glutamate effect. These data indicate that glutamate increases SP-LI release from the ARC/ME by acting through NMDA and group I mGluRs in the male rat. This stimulatory effect could be mediated by nitric oxide and prostaglandin production.

Mitochondrial inhibition and oxidative stress: reciprocating players in neurodegeneration

Although the etiology for many neurodegenerative diseases is unknown, the common findings of mitochondrial defects and oxidative damage posit these events as contributing factors. The temporal conundrum of whether mitochondrial defects lead to enhanced reactive oxygen species generation, or conversely, if oxidative stress is the underlying cause of the mitochondrial defects remains enigmatic. This review focuses on evidence to show that either event can lead to the evolution of the other with subsequent neuronal cell loss. Glutathione is a major antioxidant system used by cells and mitochondria for protection and is altered in a number of neurodegenerative and neuropathological conditions. This review also addresses the multiple roles for glutathione during mitochondrial inhibition or oxidative stress. Protein aggregation and inclusions are hallmarks of a number of neurodegenerative diseases. Recent evidence that links protein aggregation to oxidative stress and mitochondrial dysfunction will also be examined. Lastly, current therapies that target mitochondrial dysfunction or oxidative stress are discussed.

Celecoxib augmentation of continuously ill patients with schizophrenia

BACKGROUND

Previous reports have demonstrated a beneficial effect of celecoxib adjunctive therapy for patients with an acute exacerbation of schizophrenia. We investigated the effects of celecoxib augmentation of atypical antipsychotic medications for continuously symptomatic outpatient subjects with schizophrenia to further extend these findings. We hypothesized that celecoxib augmentation therapy would improve psychopathology ratings compared with placebo.

METHODS

Thirty-eight symptomatic outpatient subjects meeting DSM-IV criteria for schizophrenia and on a stable dose of an atypical antipsychotic medication for at least three months were randomized to receive 8 weeks of double blind placebo or celecoxib (400 mg/day) augmentation. Measures of psychopathology, functional disability, and extrapyramidal side effects were performed throughout the study.

RESULTS

The treatment cohorts did not differ on any of the clinical outcome measures.

CONCLUSIONS

Celecoxib augmentation of continuously ill outpatient subjects with schizophrenia did not improve clinical symptoms or measures of disability.

Cyclooxygenase-2-specific inhibitor improves functional outcomes, provides neuroprotection, and reduces inflammation in a rat model of traumatic brain injury

OBJECTIVE

Increases in brain cyclooxygenase-2 (COX2) are associated with the central inflammatory response and with delayed neuronal death, events that cause secondary insults after traumatic brain injury. A growing literature supports the benefit of COX2-specific inhibitors in treating brain injuries.

METHODS

DFU [5,5-dimethyl-3(3-fluorophenyl)-4(4-methylsulfonyl)phenyl-2(5)H)-furanone] is a third-generation, highly specific COX2 enzyme inhibitor. DFU treatments (1 or 10 mg/kg intraperitoneally, twice daily for 3 d) were initiated either before or after traumatic brain injury in a lateral cortical contusion rat model.

RESULTS

DFU treatments initiated 10 minutes before injury or up to 6 hours after injury enhanced functional recovery at 3 days compared with vehicle-treated controls. Significant improvements in neurological reflexes and memory were observed. DFU initiated 10 minutes before injury improved histopathology and altered eicosanoid profiles in the brain. DFU 1 mg/kg reduced the rise in prostaglandin E2 in the brain at 24 hours after injury. DFU 10 mg/kg attenuated injury-induced COX2 immunoreactivity in the cortex (24 and 72 h) and hippocampus (6 and 72 h). This treatment also decreased the total number of activated caspase-3-immunoreactive cells in the injured cortex and hippocampus, significantly reducing the number of activated caspase-3-immunoreactive neurons at 72 hours after injury. DFU 1 mg/kg amplified potentially anti-inflammatory epoxyeicosatrienoic acid levels by more than fourfold in the injured brain. DFU 10 mg/kg protected the levels of 2-arachidonoyl glycerol, a neuroprotective endocannabinoid, in the injured brain.

CONCLUSION

These improvements, particularly when treatment began up to 6 hours after injury, suggest exciting neuroprotective potential for COX2 inhibitors in the treatment of traumatic brain injury and support the consideration of Phase I/II clinical trials.

Chronic lithium administration to rats selectively modifies 5-HT2A/2C receptor-mediated brain signaling via arachidonic acid

The effects of chronic lithium administration on regional brain incorporation coefficients k* of arachidonic acid (AA), a marker of phospholipase A2 (PLA2) activation, were determined in unanesthetized rats administered i.p. saline or 1 mg/kg i.p. (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), a 5-HT2A/2C receptor agonist. After injecting [1-(14)C]AA intravenously, k* (brain radioactivity/integrated plasma radioactivity) was measured in each of 94 brain regions by quantitative autoradiography. Studies were performed in rats fed a LiCl or a control diet for 6 weeks. In the control diet rats, DOI significantly increased k* in widespread brain areas containing 5-HT2A/2C receptors. In the LiCl-fed rats, the significant positive k* response to DOI did not differ from that in control diet rats in most brain regions, except in auditory and visual areas, where the response was absent. LiCl did not change the head turning response to DOI seen in control rats. In summary, LiCl feeding blocked PLA2-mediated signal involving AA in response to DOI in visual and auditory regions, but not generally elsewhere. These selective effects may be related to lithium's therapeutic efficacy in patients with bipolar disorder, particularly its ability to ameliorate hallucinations in that disease.

Age-related loss of neuronal nicotinic receptor expression in the aging mouse hippocampus corresponds with cyclooxygenase-2 and PPAR? expression and is altered by long-term NS398 administration

Age-related changes in the mammalian dorsal hippocampus are associated with diminished expression of neuronal nicotinic acetylcholine receptors (nAChR), which is particularly severe in pathologies such as those associated with dementias, including Alzheimer's disease. Because the mouse is a useful model for age-related decline in nAChR expression in the basal forebrain and limbic system, we used immunohistochemistry to examine the influence of long-term (12-month) oral administration of nicotine and/or the cyclooxygenase-2 (COX-2) preferring non-steroidal anti-inflammatory drug (NSAID) NS398 on nAChR alpha4, alpha5, alpha7, and beta4 expression in the C57BL/6 mouse. Inhibitory neurons of the dorsal hippocampus that express nAChRs also constitutively express COX-2 and the peroxisome proliferator-antagonist receptor subtype gamma-2 (PPAR gamma2) which is also a target of NS398. Administration of NS398 correlated with retention of nAChR alpha4 and to a lesser extent nAChR beta4, but not nAChR alpha5 or alpha7, but nicotine exhibited no similar effect. Nicotine and NS398 co-administration abolished the NS398-related effect on nAChR alpha4 retention. These results provide evidence that the interaction during aging between oral administration of nicotine and NSAIDs are not straightforward and could even be antagonistic when combined.

Prostanoids, not reactive oxygen species, mediate COX-2-dependent neurotoxicity

The prostaglandin synthesizing enzyme cyclooxygenase-2 (COX-2) has emerged as a critical pathogenic factor in brain diseases associated with activation of N-methyl-D-aspartate (NMDA) receptors, including stroke and neurodegenerative diseases. However, the COX-2 reaction products responsible for these deleterious effects have not been identified. In particular, the relative contribution to the neurotoxicity of COX-2-derived prostanoids and reactive oxygen species has not been defined. We found that the brain damage produced by direct injection of NMDA into the somatosensory cortex is attenuated by the COX-2 inhibitor NS-398 or in COX-2-null mice, but that the associated production of free radicals is not. Furthermore, COX-2 inhibition reduces the lesions even if the deleterious effects of free radicals are eliminated by the scavenger superoxide dismutase. The protection exerted by NS-398 is counteracted by a stable analog of prostaglandin E2. The findings directly implicate COX-2-derived prostanoids, rather then radicals, in the COX-2-dependent component of the damage mediated by NMDA receptors and strengthen the rationale for using COX-2 inhibitors in the treatment of neurological diseases associated with glutamate neurotoxicity.

Naproxen reduces excitotoxic neurodegeneration in vivo with an extended therapeutic window

The purpose of this study was to examine the optimal dose and therapeutic window of opportunity of the nonsteroidal anti-inflammatory drug naproxen in an animal model of excitotoxic neuronal injury. Injection of N-methyl-D-aspartate (NMDA; 18-20 nmol) into the CA1 region of the left hippocampus resulted in significant brain edema as measured by the percentage of total forebrain water content that occurred 24 h after intrahippocampal microinjection of NMDA with approximately 50% loss of CA1 neurons assessed 72 h later. Naproxen pretreatment (20 mg/kg) resulted in significantly less brain edema. Ten, 15, or 20 mg/kg naproxen, administered systemically 1 day (b.i.d.) before and for 3 days after (b.i.d.) NMDA injection, attenuated the neuronal damage by 27.2 +/- 7.8, 39.6 +/- 11.1, and 57.0 +/- 5.2%, respectively. By comparison, a single dose of MK-801 (2 mg/kg i.p.) given 20 min before NMDA injection inhibited subsequent hippocampal injury by 65.6 +/- 8.8%. Most importantly, neuroprotection was still evident when naproxen treatment (20 mg/kg i.p.) was initiated 6 h after NMDA microinjection. Protection was lost if administration of naproxen was delayed for 20 h. These findings demonstrate that naproxen can prevent excitotoxic neuronal injury in vivo, that it is nearly as effective as direct NMDA receptor antagonism, and that it has an extended therapeutic time window. As such, naproxen may be a particularly promising pharmaceutical for the treatment of neurological diseases associated with overactivation of NMDA receptors.

Clinical variability in Rett syndrome

The clinical variability of Rett syndrome, associated with mutations in the MECP2 gene, varies from classically symptomatic female patients to asymptomatic female patients, and male patients who have none of the diagnostic features considered pathognomonic of this disease. Multiple factors contribute to this variability. In our studies, mutations closer to the amino-terminus, prior to amino acid 255, led to severe clinical manifestations, such as inability to walk, severe dysphagia, and urinary organic acid abnormalities, compared with mutations toward the carboxyl-terminus. However, we found no correlation between severity and mutation type (missense versus nonsense). Despite the importance of mutation location to clinical severity, the widely varying severity within the same mutation suggests that in females, X-chromosome inactivation or other epigenetic phenomena also have roles in determining severity. We propose that stages 1 and 2 of the disease are a consequence of failed, time-linked, postnatal expression of MeCP2 in cerebellar neurons. This, in association with glutamate N-methyl-D-aspartate receptor-mediated neuroexcitotoxic injury to the differentiating neurons, results in the transient age-specific autistic-like behavior, motor, and cognitive dysfunction associated with these stages.

Chronic lithium administration potentiates brain arachidonic acid signaling at rest and during cholinergic activation in awake rats

Studies were performed to determine if the reported 'proconvulsant' action of lithium in rats given cholinergic drugs is related to receptor-initiated phospholipase A2 signaling via arachidonic acid. Regional brain incorporation coefficients k* of intravenously injected [1-14C]arachidonic acid, which represent this signaling, were measured by quantitative autoradiography in unanesthetized rats at baseline and following administration of subconvulsant doses of the cholinergic muscarinic agonist, arecoline. In rats fed LiCl for 6 weeks to produce a therapeutically relevant brain lithium concentration, the mean baseline values of k* in brain auditory and visual areas were significantly greater than in rats fed control diet. Arecoline at doses of 2 and 5 mg/kg intraperitoneally increased k* in widespread brain areas in rats fed the control diet as well as the LiCl diet. However, the arecoline-induced increments often were significantly greater in the LiCl-fed than in the control diet-fed rats. Lithium's elevation of baseline k* in auditory and visual regions may correspond to its ability in humans to increase auditory and visual evoked responses. Additionally, its augmentation of the k* responses to arecoline may underlie its reported 'proconvulsant' action with cholinergic drugs, as arachidonic acid and its eicosanoid metabolites can increase neuronal excitability and seizure propagation.

A novel dehydroepiandrosterone analog improves functional recovery in a rat traumatic brain injury model

The purpose of this study was to investigate the efficacy of a novel steroid, fluasterone (DHEF, a dehydroepiandrosterone (DHEA) analog), at improving functional recovery in a rat model of traumatic brain injury (TBI). The lateral cortical impact model was utilized in two studies of efficacy and therapeutic window. DHEF was given (25 mg/kg, intraperitoneally) at the initial time point and once a day for 2 more days. Study A included four groups: sham injury, vehicle treated (n = 22); injured, vehicle treated (n = 30); injured, pretreated (5-10 min prior to injury, n = 24); and injured, posttreated (initial dose 30 min postinjury, n = 15). Study B (therapeutic window) included five groups: sham injury, vehicle treated (n = 17); injured, vehicle treated (n = 26); and three posttreatment groups: initial dose at 30 min (n = 18), 2 h (n = 23), or 12 h (n = 16) postinjury. Three criteria were used to grade functional recovery. In study A, DHEF improved beam walk performance both with pretreatment (79%) and 30-min posttreatment group (54%; p < 0.01, Dunnett vs. injured vehicle). In study B, the 12-h posttreatment group showed a 97% improvement in beam walk performance (p < 0.01, Dunnett). The 30-min and 12-h posttreatment groups showed a decreased incidence of falls from the beam, which reached statistical significance (p < 0.05, Dunnett). Tests of memory (Morris water maze) and neurological reflexes both revealed significant improvements in all DHEF treatment groups. In cultured rat mesangial cells, DHEF (and DHEA) potently inhibited interleukin-1beta-induced cyclooxygenase-2 (COX2) mRNA and prostaglandin (PGE2) production. In contrast, DHEF treatment did not alter injury-induced COX2 mRNA levels in the cortex or hippocampus. However, DHEF (and DHEA) relaxed ex vivo bovine middle cerebral artery preparations by about 30%, with an IC(50) approximately 40 microM. This was a direct effect on the vascular smooth muscle, independent of the endothelial cell layer. Fluasterone (DHEF) treatments improved functional recovery in a rat TBI model. Possible mechanisms of action for this novel DHEA analog are discussed. These findings suggest an exciting potential use for this agent in the clinical treatment of traumatic brain injury.