COX-2, a synaptically induced enzyme, is expressed by excitatory neurons at postsynaptic sites in rat cerebral cortex

Spinal cyclooxygenase-2 is involved in development of allodynia after nerve injury in rats

Increased spinal cyclooxygenase activity is associated with nociception induced by tissue inflammation. In the present study, we examined the changes of cyclooxygenase-1 and cyclooxygenase-2 protein expression in several regions of the CNS associated with pain perception, and the role of spinal cyclooxygenase activity in the development of allodynia following nerve injury. Allodynia was induced by ligation of the left L5 and L6 spinal nerves in rats. Using western blot analysis, we found that the cyclooxygenase-2 protein levels in the dorsal spinal cord and thalamus (but not in the ventral spinal cord, cingulate cortex and locus coeruleus) increased significantly one day after nerve ligation, compared with those in the sham animals. The cyclooxygenase-2 protein levels in the above tissues were similar in nerve-injured and sham animals three and 14 days after surgery. In contrast, cyclooxygenase-1 protein was not detectable in any of the neural tissues examined one, three, and 14 days after nerve injury. In the behavioral experiments, we observed that intrathecal injection of 100microg of indomethacin immediately or one day after nerve ligation attenuated the development of tactile allodynia. However, intrathecal injection of indomethacin had no effect on established allodynia two weeks after nerve injury.Collectively, our results suggest that cyclooxygenase-2 is preferentially up-regulated in the dorsal spinal cord and thalamus in response to nerve injury in rats. Spinal cyclooxygenase-2 probably plays an important role in the early development, but not in the maintenance, of tactile allodynia caused by the nerve injury in this rat model of neuropathic pain.

Prolonged cyclooxygenase-2 induction in neurons and glia following traumatic brain injury in the rat

Cyclooxygenase-2 (COX2) is a primary inflammatory mediator that converts arachidonic acid into precursors of vasoactive prostaglandins, producing reactive oxygen species in the process. Under normal conditions COX2 is not detectable, except at low abundance in the brain. This study demonstrates a distinctive pattern of COX2 increases in the brain over time following traumatic brain injury (TBI). Quantitative lysate ribonuclease protection assays indicate acute and sustained increases in COX2 mRNA in two rat models of TBI. In the lateral fluid percussion model, COX2 mRNA is significantly elevated (>twofold, p < 0.05, Dunnett) at 1 day postinjury in the injured cortex and bilaterally in the hippocampus, compared to sham-injured controls. In the lateral cortical impact model (LCI), COX2 mRNA peaks around 6 h postinjury in the ipsilateral cerebral cortex (fivefold induction, p < 0.05, Dunnett) and in the ipsilateral and contralateral hippocampus (two- and six-fold induction, respectively, p < 0.05, Dunnett). Increases are sustained out to 3 days postinjury in the injured cortex in both models. Further analyses use the LCI model to evaluate COX2 induction. Immunoblot analyses confirm increased levels of COX2 protein in the cortex and hippocampus. Profound increases in COX2 protein are observed in the cortex at 1-3 days, that return to sham levels by 7 days postinjury (p < 0.05, Dunnett). The cellular pattern of COX2 induction following TBI has been characterized using immunohistochemistry. COX2-immunoreactivity (-ir) rises acutely (cell numbers and intensity) and remains elevated for several days following TBI. Increases in COX2-ir colocalize with neurons (MAP2-ir) and glia (GFAP-ir). Increases in COX2-ir are observed in cerebral cortex and hippocampus, ipsilateral and contralateral to injury as early as 2 h postinjury. Neurons in the ipsilateral parietal, perirhinal and piriform cortex become intensely COX2-ir from 2 h to at least 3 days postinjury. In agreement with the mRNA and immunoblot results, COX2-ir appears greatest in the contralateral hippocampus. Hippocampal COX2-ir progresses from the pyramidal cell layer of the CA1 and CA2 region at 2 h, to the CA3 pyramidal cells and dentate polymorphic and granule cell layers by 24 h postinjury. These increases are distinct from those observed following inflammatory challenge, and correspond to brain areas previously identified with the neurological and cognitive deficits associated with TBI. While COX2 induction following TBI may result in selective beneficial responses, chronic COX2 production may contribute to free radical mediated cellular damage, vascular dysfunction, and alterations in cellular metabolism. These may cause secondary injuries to the brain that promote neuropathology and worsen behavioral outcome.

Preservation of neural function in the perinate by high PGE(2) levels acting via EP(2) receptors

Despite increasingly frequent and longer lasting hypoxic episodes during progressive labor, the neonate is alert and vigorous at birth. We investigated whether high levels of PGs during the perinatal period assist in preserving neural function after such "stressful" hypoxic events. Visual evoked potentials (VEPs) and electroretinograms (ERGs) were recorded before and 45 min after mild moderate asphyxic hypoxia (two 4-min asphyxic-hypoxic periods induced by interrupting ventilation at 8-min intervals) in newborn piglets <12 h old treated or not treated with inhibitors of PG synthase (ibuprofen or diclofenac) with or without PG analogs. At 45 min after the hypoxic episode, P2 and b-wave amplitudes were slightly decreased and latencies were delayed. These changes in the VEP and ERG returned to near normal by 120 min. Ibuprofen and diclofenac decreased brain and retinal PG levels and markedly intensified 45 min after hypoxia-induced changes in VEP and ERG, but cerebral and retinal blood flows improved. Combined treatment with PG synthase inhibitor in combination with 16,16-dimethyl-PGE(2) (a PGE(2) analog), but not with PGI(2) and PGF(2alpha) analogs, and in combination with the EP(2) receptor agonist butaprost (but not EP(1) or EP(3) agonists), prevented ibuprofen- and diclofenac-aggravated postasphyxia electrophysiological changes. In conclusion, high levels of PGE(2) in nervous tissue, via actions on EP(2) receptors, seem to contribute to preservation of neural function in the perinate subjected to frequent hypoxic events.

Advances in secondary spinal cord injury: role of apoptosis

The outcome of spinal cord injury depends on the extent of secondary damage produced by a series of cellular and molecular events initiated by the primary trauma. This article reviews the evidence that secondary spinal cord injury involves the apoptotic as well as necrotic death of neurons and glial cells. Also discussed are the major factors that can contribute to cell death, such as glutamatergic excitotoxicity, free radical damage, cytokines, and inflammation. The development of innovative therapeutic strategies to reduce secondary spinal cord injury depends on an increased understanding of secondary injury mechanisms at the molecular and biochemical level. Such therapeutic interventions may include the use of antiapoptotic drugs, free radical scavengers, and anti-inflammatory agents. These could be targeted to block key reactions on cellular and molecular injury cascades, thus reducing secondary tissue damage, minimizing side effects, and improving functional recovery.

The potential role of fatty acids in attention-deficit/hyperactivity disorder

As currently defined, attention-deficit/hyperactivity disorder (ADHD) encompasses a broad constellation of behavioural and learning problems and its definition and diagnosis remain controversial. The aetiology of ADHD is acknowledged to be both complex and multifactorial. The proposal considered here is that at least some features of ADHD may reflect an underlying abnormality of fatty acid metabolism. Clinical and biochemical evidence is discussed which suggests that a functional deficiency of certain long-chain polyunsaturated fatty acids could contribute to many of the features associated with this condition. The implications in terms of fatty acid treatment proposals are also discussed; such a form of treatment is relatively safe compared to existing pharmacological interventions, although further studies are still needed in order to evaluate its potential efficacy in the management of ADHD symptoms.

Distribution and cellular localization of prostacyclin synthase in human brain

Prostacyclin (PGI(2)) is a labile, lipid-derived metabolite of arachidonic acid synthesized through the sequential action of cyclo-oxygenase (COX) and prostacyclin synthase (PGIS). In addition to its well-characterized vasodilatory and thrombolytic effects, an increasing number of studies report an important role of PGI(2) in nociception in various animal species. In this study we investigated the regional distribution of PGIS in human brain by immunohistochemistry and in situ hybridization. PGIS-immunoreactive (ir) protein was localized to blood vessels throughout the brain. Neuronal cells and glial cells, such as microglia and oligodendrocytes, also showed intense labeling. The strongest expression of PGIS was seen in large principal neurons, such as pyramidal cells of the cortex, pyramidal cells of the hippocampus, and Purkinje cells of the cerebellum. Abundance of PGIS mRNA was observed in blood vessels and large neurons and correlated well with the immunohistochemical findings. The expression of PGIS in human brain was further demonstrated by immunoblotting and detection of 6-keto-PGF (1alpha), the stable degradation product of prostacyclin in human brain homogenate. These results demonstrate a widespread expression of PGIS in the central nervous system and suggest a potentially important role of prostacylin in modulating neuronal activity in human brain.

Rat pulmonary cyclooxygenase-2 expression in response to endotoxin challenge: differential regulation in the various types of cells in the lung

Cyclooxygenase (Cox), the key enzyme of prostanoid synthesis, consists of the two isoforms Cox-1 and Cox-2, both recently noted to be constitutively expressed in rat lungs with a distinct profile of cellular distribution. The responsiveness of pulmonary Cox-1 and Cox-2 expression to intravascular endotoxin lipopolysaccharide (LPS) administration was investigated in isolated, ventilated rat lungs, buffer-perfused with or without admixture of rat plasma. Immunohistochemical staining intensity was measured by a previously described method of silver enhancement and epipolarization image analysis. Both the Cox-1 mRNA, quantified in the whole lung homogenate, and the cellular localization of Cox-1 were unchanged in response to LPS. In contrast, time- and dose-dependent up-regulation of Cox-2 mRNA (lung homogenate) occurred, and differential LPS reactivity at the cellular level was observed. Up-regulation of Cox-2 in cell types expressing this enzyme already under baseline conditions was noted in bronchial epithelial cells, bronchial and vascular smooth muscle cells, cells within the BALT and myocytes of the large hilar veins. De novo induction of Cox-2 occurred in endothelial cells and the majority of alveolar macrophages. Down-regulation of Cox-2 was observed in perivascular and peribronchial macrophage-like cells. Moreover, differential impact of plasma components was noted: for the large majority of cells, CD14 surface expression correlated with Cox-2 responsiveness to LPS independent of plasma, whereas the presence of plasma components was a prerequisite for the LPS response in CD14-negative cells. LPS did not provoke physiological changes in the perfused lungs, but markedly enhanced baseline prostanoid generation. We conclude that LPS-induced Cox-2 regulation occurs in a complex, cell-specific manner, which may be relevant for pathogenetic sequelae in septic lung injury and acute respiratory failure.

Outcome of children in the indomethacin intraventricular hemorrhage prevention trial

BACKGROUND

For preterm infants, intraventricular hemorrhage (IVH) may be associated with adverse neurodevelopmental outcome. We have demonstrated that early low-dose indomethacin treatment is associated with a decrease in both the incidence and severity of IVH in very low birth weight preterm infants. In addition, we hypothesized that the early administration of low-dose indomethacin would not be associated with an increase in the incidence of neurodevelopmental handicap at 4.5 years of age in our study children.

METHODS

To test this hypothesis, we provided neurodevelopmental follow-up for the 384 very low birth weight survivors of the Multicenter Randomized Indomethacin IVH Prevention Trial. Three hundred thirty-seven children (88%) were evaluated at 54 months' corrected age, and underwent neurodevelopmental examinations, including the Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R), the Peabody Picture Vocabulary Test-Revised (PPVT-R), and standard neurologic examinations.

RESULTS

Of the 337 study children, 170 had been randomized to early low-dose indomethacin therapy and 167 children had received placebo. Twelve (7%) of the 165 indomethacin children and 11 (7%) of the 158 placebo children who underwent neurologic examinations were found to have cerebral palsy. For the 233 English-monolingual children for whom cognitive outcome data follow, the mean gestational age was significantly younger for the children who received indomethacin than for those who received placebo. In addition, although there were no differences in the WPPSI-R or the PPVT-R scores between the 2 groups, analysis of the WPPSI-R full-scale IQ by function range demonstrated significantly less mental retardation among those children randomized to early low-dose indomethacin (for the indomethacin study children, 9% had an IQ <70, 12% had an IQ of 70-80, and 79% had an IQ >80, compared with the placebo group, for whom 17% had an IQ <70, 18% had an IQ of 70-80, and 65% had an IQ >80). Indomethacin children also experienced significantly less difficulty with vocabulary skills as assessed by the PPVT-R when compared with placebo children.

CONCLUSIONS

These data suggest that, for preterm neonates, the early administration of low-dose indomethacin therapy is not associated with adverse neurodevelopmental function at 54 months' corrected age.

Cyclooxygenase-2 contributes to functional hyperemia in whisker-barrel cortex

The prostanoid-synthesizing enzyme cyclooxygenase-2 (COX-2) is expressed in selected cerebral cortical neurons and is involved in synaptic signaling. We sought to determine whether COX-2 participates in the increase in cerebral blood flow produced by synaptic activity in the somatosensory cortex. In anesthetized mice, the vibrissae were stimulated mechanically, and cerebral blood flow was recorded in the contralateral somatosensory cortex by a laser-Doppler probe. We found that the COX-2 inhibitor NS-398 attenuates the increase in somatosensory cortex blood flow produced by vibrissal stimulation. Furthermore, the flow response was impaired in mice lacking the COX-2 gene, whereas the associated increase in whisker-barrel cortex glucose use was not affected. The increases in cerebral blood flow produced by hypercapnia, acetylcholine, or bradykinin were not attenuated by NS-398, nor did they differ between wild-type and COX-2 null mice. The findings provide evidence for a previously unrecognized role of COX-2 in the mechanisms coupling synaptic activity to neocortical blood flow and provide an insight into one of the functions of constitutive COX-2 in the CNS.

Upregulation of COX-2 during cardiac allograft rejection

BACKGROUND

The hypothesis that cyclooxygenase-2 (COX-2) is involved in the myocardial inflammatory response during cardiac allograft rejection was investigated using a rat heterotopic abdominal cardiac transplantation model.

METHODS AND RESULTS

COX-2 mRNA and protein in the myocardium of rejecting cardiac allografts were significantly elevated 3 to 5 days after transplantation compared with syngeneic controls (n=3, P<0.05). COX-2 upregulation paralleled in time and extent the upregulation of iNOS mRNA, protein, and enzyme activity in this model. COX-2 immunostaining was prominent in macrophages infiltrating the rejecting allografts and in damaged cardiac myocytes. Prostaglandin (PG) levels in rejecting allografts were also higher than in native hearts. Because NO has been reported to modulate PG synthesis by COX-2, additional transplants were performed using animals treated with a selective COX-2 inhibitor (SC-58125) and a selective inhibitor of the inducible nitric oxide synthase (iNOS) N-aminomethyl-L-lysine. At posttransplant day 5, inhibitor administration resulted in a significant reduction of COX-2 mRNA expression (3764+/-337 versus 5110+/-141 arbitrary units, n=3, P<0.05) and iNOS enzymatic activity (1.7+/-0.4 versus 22.8+/-14. 4 nmol/mg protein, n=3, P<0.01) compared with vehicle-treated allogeneic transplants. Allograft survival in treated animals was increased modestly from 5.4 to 6.4 days (P<0.05). However, apoptosis of cardiac myocytes (TUNNEL method) was only marginally reduced relative to vehicle controls in treated graft recipients. The intensity of allograft rejection was also similar in the treated and untreated allografts.

CONCLUSIONS

The data indicates that COX-2 expression is enhanced in parallel with iNOS in the myocardium during cardiac allograft rejection.

Cyclooxygenase-2 contributes to functional hyperemia in whisker-barrel cortex

The prostanoid-synthesizing enzyme cyclooxygenase-2 (COX-2) is expressed in selected cerebral cortical neurons and is involved in synaptic signaling. We sought to determine whether COX-2 participates in the increase in cerebral blood flow produced by synaptic activity in the somatosensory cortex. In anesthetized mice, the vibrissae were stimulated mechanically, and cerebral blood flow was recorded in the contralateral somatosensory cortex by a laser-Doppler probe. We found that the COX-2 inhibitor NS-398 attenuates the increase in somatosensory cortex blood flow produced by vibrissal stimulation. Furthermore, the flow response was impaired in mice lacking the COX-2 gene, whereas the associated increase in whisker-barrel cortex glucose use was not affected. The increases in cerebral blood flow produced by hypercapnia, acetylcholine, or bradykinin were not attenuated by NS-398, nor did they differ between wild-type and COX-2 null mice. The findings provide evidence for a previously unrecognized role of COX-2 in the mechanisms coupling synaptic activity to neocortical blood flow and provide an insight into one of the functions of constitutive COX-2 in the CNS.

Inflammation and stroke: putative role for cytokines, adhesion molecules and iNOS in brain response to ischemia

Ischemic stroke is a leading cause of death and disability in developed countries. Yet, in spite of substantial research and development efforts, no specific therapy for stroke is available. Several mechanism for neuroprotection have been explored including ion channels, excitatory amino acids and oxygen radicals yet none has culminated in an effective therapeutic effect. The review article on "inflammation and stroke" summarizes key data in support for the possibility that inflammatory cells and mediators are important contributing and confounding factors in ischemic brain injury. In particular, the role of cytokines, endothelial cells and leukocyte adhesion molecules, nitric oxide and cyclooxygenase (COX-2) products are discussed. Furthermore, the potential role for certain cytokines in modulation of brain vulnerability to ischemia is also reviewed. The data suggest that novel therapeutic strategies may evolve from detailed research on some specific inflammatory factors that act in spatial and temporal relationships with traditionally recognized neurotoxic factors. The dual nature of some mediators in reformatting of brain cells for resistance or sensitivity to injury demonstrate the delicate balance needed in interventions based on anti-inflammatory strategies.

Inhibition of cyclooxygenase 2 by nimesulide decreases prostaglandin E2 formation but does not alter brain edema or clinical recovery after closed head injury in rats

Recently, the enzyme cyclooxygenase (COX) has been recognized to exist as constitutive (COX-1) and inducible isoforms (COX-2). In previous studies, drugs that were inhibitors of both COX-1 and COX-2 failed to decrease brain edema formation or improve Neurological Severity Score (NSS) after closed head trauma (CHT), although some did decrease prostaglandin-E2 (PGE2) formation. The present study examined whether or not a specific inhibitor of COX-2 (nimesulide) exerts a beneficial effect after CHT in rats. Halothane-anesthetized rats (n = 8 in each group) were randomly assigned to one of four groups: surgery, no CHT, no drug (group 1); surgery, no CHT, nimesulide 30 mg/kg intraperitoneally (IP) (group 2); surgery, CHT, no drug (group 3); and surgery, CHT, nimesulide 30 mg/kg IP (group 4). NSS was determined at 1 and 24 h, and brain tissue PGE2 concentration and water content were determined after killing at 24 h. Treatment with nimesulide did not improve NSS (NSS at 24 h = 11+/-6 [median +/- range] in group 3 and 12+/-4 in group 4) or edema formation (brain water content at 24 h = 84.3+/-1.8% [mean +/- SD] in group 3 and 83.8+/-1.9% in group 4). However, nimesulide did decrease cortical and hypothalamic PGE2 formation by 41% and 47%, respectively during the first hour of incubation after brain tissue sampling. The authors conclude that although nimesulide does reduce tissue PGE2 formation, it does not exert a beneficial effect on brain tissue edema or functional activity after CHT in rats.

Alzheimer's disease and inflammation: a review of cellular and therapeutic mechanisms

1. Of the neurodegenerative diseases that cause dementia, Alzheimer's disease (AD) is the most common. Three major pathologies characterize the disease: senile plaques, neurofibrillary tangles and inflammation. We review the literature on events contributing to the inflammation and the treatments thought to target this pathology. 2. The senile plaques of AD consist primarily of complexes of the beta-amyloid protein. This protein is central to the pathogenesis of the disease. 3. Inflammatory microglia are consistently associated with senile plaques in AD, although the classic inflammatory response (immunoglobulin and leucocyte infiltration) is absent. beta-Amyloid fragments appear to mediate such inflammatory mechanisms by activating the complement pathway in a similar fashion to immunoglobulin. 4. Epidemiological studies have identified a reduced risk of AD in patients with arthritis and in leprosy patients treated with anti-inflammatory drugs. Longitudinal studies have shown that the consumption of anti-inflammatory medications reduces the risk of AD only in younger patients (< 75 years). 5. There is a considerable body of in vitro evidence indicating that the inflammatory response of microglial cells is reduced by non-steroidal anti-inflammatory drugs (NSAID). However, no published data are available concerning the effects of these medications on brain pathology in AD. 6. Cyclo-oxygenase 2 enzyme is constitutively expressed in neurons and is up-regulated in degenerative brain regions in AD. Non-steroidal anti-inflammatory drugs may reduce this expression. 7. Platelets are a source of beta-amyloid and increased platelet activation and increased circulating beta-amyloid have been identified in AD. Anti-platelet medication (including NSAID) would prevent such activation and its potentially harmful consequences. 8. Increased levels of luminal beta-amyloid permeabilizes the blood-brain barrier (BBB) and increases vasoconstriction of arterial vessels, paralleling the alterations observed with infection and inflammation. Cerebral amyloidosis is highly prevalent in AD, compromising the BBB and vasoactivity. Anti-inflammatory medications may alleviate these problems.

Induction of cyclooxygenase-2 in the rat brain after a mild episode of focal ischemia without tissue inflammation or neural cell damage

Cyclooxygenase-2, a key enzyme in prostanoid synthesis, is induced by inflammatory stimuli and it is associated with cell death after cerebral ischemia. Here we evaluated whether cyclooxygenase-2 was induced after a short (10-min) episode of focal ischemia, mild enough not to cause inflammation or cell death. One-hour ischemia leading to brain infarct was studied for comparative purposes. Induction of cyclooxygenase-2 mRNA and protein was detected after both 10-min and 1-h ischemia. However, signs of edema were only apparent after 1-h, but not 10-min ischemia, and only rats subjected to 1-h ischemia had developed brain infarct at 4 days. Therefore, cyclooxygenase-2, not linked with neural cell death or inflammation, is induced after focal ischemia.

Dietary modulation of prostanoid synthesis in the aging process: role of cyclooxygenase-2

To investigate the role of cyclooxygenase (COX) as a mediator for prostaglandin synthesis in relation to generation of reactive oxidant species (ROS), we quantitated the COX-derived ROS generation and the gene expression of COX-2, an inducible form of COX in aged kidney. In addition, the modulation by dietary restriction was investigated. COX-derived ROS generation increased with age in ad libitum (AL) rats, but dietary restriction (DR) suppressed the level. The amounts of COX-2 protein and mRNA increased with age in AL rats but maintained at low levels in DR group. It was found that the binding characteristics of a nuclear transcription factor, NF-kappaB were altered by aging. The binding activity of NF-kappaB in aged kidney was significantly enhanced with the corresponding increase in mRNA and protein levels. These increases were closely in parallel to the increased ROS generation and gene expression of COX-2. The COX activity shown by NF-kappaB activation and the ROS generation by COX-mediated process were all modulated by DR. Our results suggest that the upregulation of COX-2 during aging may play an important role in many age-related diseases associated with aging process. And this upregulation was attenuated by DR. We propose that the modulation of the redox-sensitive transcription factor may well be a part of the mechanisms underpinning the anti-oxidative action of DR.

Biochemical changes in prostanoids and cerebral expression of cyclooxygenase (COX)-1 and COX-2 during morphine sulfate infusion in the newborn piglet

To examine the biochemical regulation of morphine sulfate (MS) on prostanoid synthesis, conscious newborn piglets received a bolus dose of 100 microg/kg followed by a continuous infusion dose of 100 microg/kg/h. The control group received equivalent volume bolus and continuous infusion of 5% dextrose. Blood samples were drawn from the femoral artery and sagittal sinus vein before, during and after infusion for measurement of prostanoids. The expression of mRNAs encoding cyclooxygenases (COX)-1 and -2 in the brainstem, thalamus, cortex, and cerebellum of the newborn piglets were also examined. Systemic PGE2 levels declined substantially during and post MS infusion (p < 0.01), whereas sagittal sinus vein PGE2 levels increased following the bolus dose (p < 0.01) and at 4 h of continuous infusion (p < 0.01). MS infusion did not affect systemic 6-ketoPGF1alpha levels, however, in the cerebral circulation 6-ketoPGF1alpha levels increased 146% (p < 0.01) following the bolus dose and remained elevated throughout the infusion and post infusion times. Systemic TxB2 levels increased transiently at 4 h (p < 0.01) and sagittal sinus vein TxB2 increased at 0.5 and 1 h (p < 0.01) during continuous infusion. RT-PCR assays revealed a 1.5- (p < 0.001) to 4-fold (p < 0.001) increased expression of COX-1 mRNA in the MS-infused brain samples. In contrast, no differences in COX-2 mRNA were detected between the groups. These data imply that MS may have significant effects on prostanoid synthesis in the newborn. The data further show that the MS-induced prostanoid responses appear to be mediated via COX-1.

Cyclooxygenase-2 selective inhibitors aggravate kainic acid induced seizure and neuronal cell death in the hippocampus

Cyclooxygenase-2 (COX-2) in the brain is expressed constitutively and also increased in pathological conditions such as seizure, cerebral ischemia, and inflammation. This study examined the role of COX-2 in kainic acid-induced seizure and in the following neuronal death by using selective inhibitors. Systemic kainate injection (50 mg/kg; i.p.) in mice evoked seizure within 15 min and led to 29% mortality within 2 h. TUNEL-positive neuronal death peaked at 3 days after injection and was prominent in CA(3a) regions of the hippocampus. NS-398 or celecoxib (10 mg/kg, COX-2 selective inhibitor) and indomethacin (5 mg/kg, nonselective inhibitor) exaggerated kainic acid-induced seizure activity and mortality. COX-2 selective inhibitors induced the seizure at earlier onset and more severe mortality within the first hour than indomethacin and aspirin. NS-398 also aggravated kainic acid-induced TUNEL positive neuronal death and decreased Cresyl violet stained viable neurons, and extended lesions to CA(1) and CA(3b). Kainic acid increased the levels of PGD(2), PGF(2a) and PG E(2) in the hippocampus immediately after injection. Indomethacin attenuated the production of basal and kainic acid-induced prostaglandins. In contrast, NS-398 failed to reduce until the first 30 min after kainic acid injection, during which the animals were severely seizured. It has been challenged the endogenous PGs might have anticonvulsant properties. Thus, COX-2 selective inhibitor, including nonselective inhibitor such as indomethacin, aggravated kainic acid-induced seizure activity and the following hippocampal neuronal death even with variable prostaglandin levels.

Selective targeting of cyclooxygenase-2 reveals its role in renal medullary interstitial cell survival

Renal medullary interstitial cells (MICs) are a major site of cyclooxygenase (COX)-mediated PG synthesis. These studies examined the role of COX in MIC survival. Immunoblot and nuclease protection demonstrate that cultured MICs constitutively express COX2, with little constitutive COX1 expression. SC-58236, a COX2-selective inhibitor, but not SC-58560, a COX1 inhibitor, preferentially blocks PGE2 synthesis in MICs. Transduction with a COX2 antisense adenovirus reduced MIC COX2 protein expression and also decreased PGE2 production. Antisense downregulation of COX2 was associated with MIC death, whereas a control adenovirus was without effect. Similarly, the COX2-selective inhibitor SC-58236 (30 microM) and several nonselective COX-inhibiting nonsteroidal anti-inflammatory drugs (NSAIDs), including sulindac, ibuprofen, and indomethacin, all caused MIC death. In contrast, SC-58560, a COX1-selective inhibitor, was 100-fold less potent for inducing MIC death than its structural congener SC-58236. NSAID-induced MIC death was associated with DNA laddering and nuclear fragmentation, consistent with apoptosis. These results suggest that COX2 plays an important role in MIC survival. COX2 inhibition may contribute to NSAID-associated injury of the renal medulla.

Expression of cyclooxygenase-2 mRNA after global ischemia is regulated by AMPA receptors and glucocorticoids

BACKGROUND AND PURPOSE

Cyclooxygenase-2 (COX-2) is implicated in ischemic neuronal death. In focal ischemia, its mRNA induction is mediated through N-methyl-D-aspartic acid (NMDA) receptors and phospholipase A(2). Because mechanisms of neuronal death involving COX-2 in global ischemia are unclear, we studied the time course and regulation of COX-2 expression in rat brain global ischemia.

METHODS

Global ischemia was induced by a 4-vessel occlusion method. COX-2 mRNA levels were demonstrated with in situ hybridization and COX-2 protein with immunocytochemistry. Several animals were pretreated with MK-801, an NMDA receptor antagonist; 2, 3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX), an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist; and dexamethasone.

RESULTS

In the cortex, the CA3 hippocampal region and dentate gyrus expression of COX-2 mRNA peaked at 4 to 8 hours, while in the CA1 region COX-2 mRNA levels were high at 4 to 24 hours. COX-2 protein was induced in the corresponding regions at 12 to 24 hours, but in the CA1 neurons the protein was still seen at 3 days. COX-2 mRNA induction in the cortex was inhibited by NBQX and dexamethasone and in CA1 neurons was inhibited by NBQX. MK-801 did not suppress COX-2 induction.

CONCLUSIONS

COX-2 is differentially induced in the cortex and hippocampal structures after global ischemia. The prolonged COX-2 expression in the vulnerable CA1 neurons is regulated by AMPA receptors, suggesting that COX-2 expression is likely to be associated with AMPA receptor-mediated neuronal death in global ischemia. Glucocorticoids may not be efficiently used to inhibit ischemia-induced COX-2 expression in the hippocampus.

Regional distribution of cyclooxygenase-2 in the hippocampal formation in Alzheimer's disease

Cyclooxygenase-2 (COX-2), a key enzyme in prostanoid biosynthesis, may represent an important therapeutic target in Alzheimer's disease (AD). In the present study, we explored the regulation of COX-2 in the hippocampal formation in sporadic AD. Using semiquantitative immunocytochemical techniques, we found that in AD cases (vs. age-matched controls) neurons of the CA1-CA4 subdivisions of the hippocampal pyramidal layer showed elevation of COX-2 signal; COX-2 levels correlated with amyloid plaque density. In contrast, the level of COX-2 immunostaining in the dentate gyrus granule neurons was not elevated in AD. No expression of COX-2 in cells with glial morphology was found in any case examined. In parallel, in vitro studies found that neurons derived from transgenic mice with neuronal overexpression of COX-2 are more susceptible to beta-amyloid (Abeta) toxicity, with potentiation of redox impairment. The results indicate elevated expression of neuronal COX-2 in subregions of the hippocampal formation in AD and that such elevation may potentiate Abeta-mediated oxidative stress.

Interpreting the clinical significance of the differential inhibition of cyclooxygenase-1 and cyclooxygenase-2

The International Consensus Meeting on the Mode of Action of COX-2 Inhibition (ICMMAC) brought together 17 international experts in arthritis, gastroenterology and pharmacology on 5 6 December 1997. The meeting was convened to provide a definition of COX-2 specificity and to consider the clinical relevance of COX-2-specific agents. These compounds are a new class of drugs that specifically inhibit the enzyme COX-2 while having no effect on COX-1 across the whole therapeutic dose range. The objectives of the meeting were to review the currently available data regarding the roles and biology of COX-1 and COX-2, and to foster a consensus definition on COX-2 specificity. At the present time, no guidelines exist for the in vitro and in vivo assessment of COX specificity, and it was felt that consensus discussion might clarify some of these issues. The meeting also reviewed recent clinical data on COX-2-specific inhibitors. The following article reflects discussion at this meeting and provides a consensus definition of COX-2-specific inhibitors.

Restricted cyclooxygenase-2 expression in the central nervous system following acute and delayed-type hypersensitivity responses to bacillus Calmette-Guérin

The expression of cyclooxygenase-2, a key enzyme in prostaglandin and thromboxane synthesis in inflammation, was studied immunohistochemically in in vivo models of acute and chronic inflammatory responses in rat central nervous system. In the acute inflammatory response to intracranial injection of heat-killed bacillus Calmette-Guérin as well as in the immune-mediated, delayed-type hypersensitivity response to the same pathogen, cyclooxygenase-2 expression was restricted to major infiltrating haematogenous cell populations such as neutrophils and mononuclear phagocytes, while the expression of the enzyme by brain non-neuronal resident cells (astrocytes, microglia, perivascular cells) appeared to be limited to perivascular cells of the blood vessels in the vicinity of the lesion and in the surrounding area. On the basis of their morphology and location, these perivascular cells were identified as perivascular macrophages, but we could not rule out the possibility that some endothelial cells also expressed cyclooxygenase-2. The constitutive neuronal cyclooxygenase-2 was not affected by the ongoing inflammation. Interestingly, in spite of the extensive astrocyte and microglial reaction occurring over a broad area surrounding the inflammatory lesions, there was no obvious cyclooxygenase-2 staining in these cells. These data indicate that the up-regulation of cyclooxygenase-2 expression in acute and chronic, immune-mediated lesions in the brain parenchyma is remarkably restricted to the lesion site. Since cyclooxygenase metabolites can regulate important functions of resident as well as infiltrating cells, the increased synthesis of prostaglandins and thromboxanes, which is likely to occur as a consequence of the expression of cycloxygenase-2 at the lesion site, might represent an important component of the inflammatory processes within the brain.

Distribution of cyclooxygenase-1 and cyclooxygenase-2 mRNAs and proteins in human brain and peripheral organs

We used the techniques of reverse transcriptase-polymerase chain reaction, Western blotting and immunohistochemistry to evaluate the expression of cyclooxygenase (COX)-1 and -2 in brain and peripheral organs of Alzheimer disease (AD) and control cases. We found both COX-1 and COX-2 to be constitutively expressed in all organs tested, i.e., brain, heart, liver, kidney, spleen and intestine. COX-2 was substantially upregulated in affected areas of AD brain and in infarcted areas of human heart. COX-1 was only mildly upregulated in AD brain. Immunohistochemically, COX-2 was strongly expressed in the perinuclear, dendritic and axonal areas of pyramidal neurons, with enhanced staining in AD. These data suggest a special role for COX-2 in neuronal function.

Synaptic clustering of AMPA receptors by the extracellular immediate-early gene product Narp

Narp (neuronal activity-regulated pentraxin) is a secreted immediate-early gene (IEG) regulated by synaptic activity in brain. In this study, we demonstrate that Narp possesses several properties that make it likely to play a key role in excitatory synaptogenesis. Narp is shown to be selectively enriched at excitatory synapses on neurons from both the hippocampus and spinal cord. Overexpression of recombinant Narp increases the number of excitatory but not inhibitory synapses in cultured spinal neurons. In transfected HEK 293T cells, Narp interacts with itself, forming large surface clusters that coaggregate AMPA receptor subunits. Moreover, Narp-expressing HEK 293T cells can induce the aggregation of neuronal AMPA receptors. These studies support a model in which Narp functions as an extracellular aggregating factor for AMPA receptors.

The clinical potential of cyclooxygenase-2-specific inhibitors

Emerging evidence suggests that cyclooxygenase-2 (COX-2) has diverse physiologic and pathophysiologic functions. It is expressed constitutively in the developing kidney and brain, playing a role in their proper maturation and function. Further, COX-2 expression may be up-regulated at certain sites: in the kidney during sodium restriction; in the microglia of cognitive centers within the hippocampus and cortex in Alzheimer's disease; and in intestinal adenomas and colon tumors. On the basis of COX-2 expression in Alzheimer's disease and colon cancer, COX-2-specific inhibitors may find clinical utility in the prevention or treatment of these conditions. Despite this apparently optimistic outlook for future uses of COX-2 inhibitors, most of the findings supporting this perspective are based on in vitro and in vivo models and must be rigorously corroborated in human studies, some of which are already planned.

Selective cyclooxygenase-2 inhibitors

The identification of COX-2 less than a decade ago has been followed by an unprecedented period of discovery and drug development. An awareness of the existence of two COX isoforms has led to potential novel insights into disease pathogenesis (arthritis, Alzheimer's disease, cancer) and the regulation of normal physiology (brain, kidney). The preliminary in vivo experience with COX-2-selective inhibitors has provided evidence for proof of concept for the COX-1 and COX-2 hypothesis, namely that the selective inhibition of COX-2-derived prostaglandins is sufficient to inhibit inflammation and is nonulcerogenic. It may be that we have moved closer to the "better aspirin" envisioned by Sir John Vane for the treatment of degenerative and inflammatory arthritides; however, caution is still warranted. Some toxicities of current NSAIDs may result from COX-2 inhibition, as in the kidney and brain; such side effects may be shared by the selective compounds. In addition, unexpected toxicities may arise simply because new chemical compounds will be widely prescribed. Finally, since the efficacy of traditional NSAIDs derives largely from their capacity to inhibit COX-2, it may be that the COX-2 selective drugs will not prove to be therapeutically superior to available agents. Given the well-recognized toxicity of NSAIDs, however, the availability of COX-2-selective agents promises to provide significant advantage to patients with chronic diseases, such as RA and OA.

The febrile response to lipopolysaccharide is blocked in cyclooxygenase-2(-/-), but not in cyclooxygenase-1(-/-) mice

Various lines of evidence have implicated inducible cyclooxygenase-2 (COX-2) in fever production. Thus, its expression is selectively enhanced in brain after peripheral exogenous (e.g., lipopolysaccharide [LPS]) or endogenous (e.g., interleukin-1) pyrogen administration, while selective COX-2 inhibitors suppress the fever induced by these pyrogens. In this study, we assessed the febrile response to LPS of congenitally constitutive COX-1 (COX-1-/-) and COX-2 (COX-2-/-)-deficient C57BL/6J-derived mice. COX-1+/- and COX-2+/- mice were also evaluated; controls were wild-type C57BL/6J mice (Jackson Labs.). All the animals were pretrained daily for two weeks to the experimental procedures. LPS was injected intraperitoneally at 1 microgram/mouse; pyrogen-free saline (PFS) was the vehicle and control solution. Core temperatures (Tcs) were recorded using thermocouples inserted 2 cm into the colon. The presence of the COX isoforms was determined in cerebral blood vessels immunocytochemically after the experiments, without knowledge of the functional results. The data showed that the wild-type, COX-1+/-, and COX-1-/- mice all responded to LPS with a 1 degrees C rise in Tc within 1 h; the fever gradually abated over the next 4 h. By contrast, COX-2+/- and COX-2-/- mice displayed no Tc rise after LPS. PFS did not affect the Tc of any animal. It would appear therefore that COX-2 is necessary for LPS-induced fever production.

Oxidative damage of cardiomyocytes is limited by extracellular regulated kinases 1/2-mediated induction of cyclooxygenase-2

Oxidative stress causes cardiac damage following ischemia/reperfusion and in response to anthracyclines. Extracellular signal-regulated kinases (ERK) 1/2 are activated by oxidative stress in cardiac myocytes and protect cardiac myocytes from apoptosis. Prostaglandins (PG) also protect cells from injury in a number of tissues, including the cardiomyocyte. Cyclooxygenase (COX) the rate-limiting enzyme in PG biosynthesis has two isoforms, the constitutive COX-1 and an inducible COX-2. Here, we examined the effects of two oxidative stresses, hydrogen peroxide (H2O2) and the anthracycline doxorubicin on the activity of ERK1/2 and the expression of COX isoforms and PG formation in neonatal rat primary cardiomyocytes. These cells expressed COX-1 at rest and both COX isoforms on treatment with phorbol 12-myristate 13-acetate. Exposure to 50 microM H2O2 for 10 min or doxorubicin at 10 and 100 micrograms/ml caused expression of COX-2 that was prevented by free radical scavengers. COX-2 induction was associated with activation of ERK1/2 and the specific ERK-inhibitor PD098059 abolished COX-2 expression. Treatment of cells with decoy oligonucleotides corresponding to COX-2 promoter elements implicated the AP-1 and NF-kappaB-2 but not the NF-kappaB-1 in the transcription of COX-2. Induction of COX-2 mRNA and protein was accompanied by increased prostacyclin formation, which was abolished by the selective COX-2 inhibitor, NS-398, and PD098059. H2O2 and doxorubicin enhanced the release of lactate dehydrogenase and free radical scavengers prevented this. NS-398 enhanced the release of lactate dehydrogenase in response to H2O2 and doxorubicin, whereas the injury was prevented by iloprost, a stable prostacyclin analogue. In cardiomyocytes cell injury by H2O2 and doxorubicin is limited by an increase in prostacyclin formation that reflects induction of COX-2 mediated by ERK1/2 activation.

The neuromessenger platelet-activating factor in plasticity and neurodegeneration

Synaptic activation leads to the formation of arachidonic acid, platelet-activating factor (PAF, 1-O-alkyl-2-acyl-sn-3-phosphocholine) and other lipid messengers. PAF is a potent bioactive phospholipid in synaptic plasticity. PAF enhances presynaptic glutamate release, is a retrograde messenger in long-term potentiation and enhances memory formation. PAF also couples synaptic events with gene expression by stimulating a FOS/JUN/AP-1 transcriptional signaling system, as well as transcription of COX-2 (inducible prostaglandin synthase). Since the COX-2 gene is also involved in synaptic plasticity, the PAF-COX-2 pathway may have physiological significance. Seizures, ischemia and other forms of brain injury promote phospholipase A2 (PLA2) overactivation, resulting in the accumulation of bioactive lipids at the synapse. PAF, under these pathological conditions, behaves as a neuronal injury messenger by at least two mechanisms: (a) enhancing glutamate release; and, (b) by sustained augmentation of COX-2 transcription. These events link PAF with neurodegeneration. The upstream intracellular pathways of signal transduction involved in neuronal or photoreceptor cell apoptosis are not well understood and involve stress sensitive kinases. PAF is a transcriptional activator of the COX-2 gene. BN 50730, a potent intracellular PAF antagonist, blocks COX-2 induction. COX-2 transcription and protein expression are upregulated in the hippocampus in kainic acid induced epileptogenesis. There is a selectively elevated induction of COX-2 (72-fold) by kainic acid preceding neuronal cell death. BN 50730 administered by i.c.v. injection blocks seizure-induced COX-2 induction. Overall, PAF is a dual modulator of neural function and becomes an endogenous neurotoxin when over produced.

FMR1 gene expression in olfactory neuroblasts from two males with fragile X syndrome

The fragile X mental retardation 1 gene (FMR1) mutation is strongly correlated with specific and marked neurobehavioral and neuroanatomical abnormalities. The protein product, FMRP, is highly expressed in neurons of the normal mammalian brain, and absent or in low levels in leukocytes from individuals with fragile X (FraX)-associated mental impairment. Inferences which arise from these findings are that FMRP has a critical role in the development and functioning of the brain, and that leukocyte-derived molecular assessments provide a good indicator of FMR1 expression in that organ. This latter conclusion appears true in most cases even though the typical FMR1 mutation is an unstable triplet repeat expansion which demonstrates somatic heterogeneity within and across tissues. Blood to brain correspondence in FraX patients has only rarely been confirmed by the direct study of human brain specimens and, to our knowledge, it has never been studied in living individuals with the FMR1 mutation. In this report, we describe the FMR1 patterns in olfactory neuroblasts (ON) from two living brothers with expansion mutations in their leukocytes who are mentally retarded and autistic. ON were chosen for study because they are accessible neurons closely linked to the brain. In both subjects, the ON genotype was highly, but not perfectly, consistent with that observed in leukocytes. Protein phenotypes across tissues were completely consistent showing the absence of FMRP-immunoreactivity (-ir). These results augment the limited amount of direct evidence which indicates that FMR1 mutation patterns in leukocytes are a good, albeit potentially fallible, reflection of such patterns in the brain. This report further demonstrates the feasibility of using ON samples to evaluate the FMR1 mutation in humans in vivo.

Expression of COX-2 by normal and reactive astrocytes in the adult rat central nervous system

We have used a previously characterized antiserum against cycloxygenase-2 (COX-2) together with cold methanol fixation to immunohistochemically locate the protein in astrocytes in rat brain. Although in cerebral cortex most enzyme was located in neuronal perikarya as previously described, a number of glial fibrillary acidic protein (GFAP)-positive astrocytes were also labeled. No COX-2-positive neurons were seen in the cerebellum, but here also a subset of GFAP+ astrocytes was present which contained the enzyme. The number of COX-2-positive astrocytes increased considerably after injection of the neurotoxin kainate into the cerebellum. These immunohistochemical data were supported by semiquantitative RT-PCR results, which were used to assess the levels of COX-2 mRNA relative to the housekeeping gene hypoxanthine phosphoribosyl transferase. PGE2 levels were measured in contralateral and lesioned cerebellum to correlate changes in COX-2 immunoreactivity and mRNA with physiological events. PGE2 levels increased by 230% in the lesioned cerebellar hemispheres in comparison to the contralateral ones. We discuss the possibility that the targets for astrocytic prostaglandins might include both autocrine effects and paracrine responses of neurons, lymphocytes and capillary endothelial cells.

The induction of pain: an integrative review

The highly disagreeable sensation of pain results from an extraordinarily complex and interactive series of mechanisms integrated at all levels of the neuroaxis, from the periphery, via the dorsal horn to higher cerebral structures. Pain is usually elicited by the activation of specific nociceptors ('nociceptive pain'). However, it may also result from injury to sensory fibres, or from damage to the CNS itself ('neuropathic pain'). Although acute and subchronic, nociceptive pain fulfils a warning role, chronic and/or severe nociceptive and neuropathic pain is maladaptive. Recent years have seen a progressive unravelling of the neuroanatomical circuits and cellular mechanisms underlying the induction of pain. In addition to familiar inflammatory mediators, such as prostaglandins and bradykinin, potentially-important, pronociceptive roles have been proposed for a variety of 'exotic' species, including protons, ATP, cytokines, neurotrophins (growth factors) and nitric oxide. Further, both in the periphery and in the CNS, non-neuronal glial and immunecompetent cells have been shown to play a modulatory role in the response to inflammation and injury, and in processes modifying nociception. In the dorsal horn of the spinal cord, wherein the primary processing of nociceptive information occurs, N-methyl-D-aspartate receptors are activated by glutamate released from nocisponsive afferent fibres. Their activation plays a key role in the induction of neuronal sensitization, a process underlying prolonged painful states. In addition, upon peripheral nerve injury, a reduction of inhibitory interneurone tone in the dorsal horn exacerbates sensitized states and further enhance nociception. As concerns the transfer of nociceptive information to the brain, several pathways other than the classical spinothalamic tract are of importance: for example, the postsynaptic dorsal column pathway. In discussing the roles of supraspinal structures in pain sensation, differences between its 'discriminative-sensory' and 'affective-cognitive' dimensions should be emphasized. The purpose of the present article is to provide a global account of mechanisms involved in the induction of pain. Particular attention is focused on cellular aspects and on the consequences of peripheral nerve injury. In the first part of the review, neuronal pathways for the transmission of nociceptive information from peripheral nerve terminals to the dorsal horn, and therefrom to higher centres, are outlined. This neuronal framework is then exploited for a consideration of peripheral, spinal and supraspinal mechanisms involved in the induction of pain by stimulation of peripheral nociceptors, by peripheral nerve injury and by damage to the CNS itself. Finally, a hypothesis is forwarded that neurotrophins may play an important role in central, adaptive mechanisms modulating nociception. An improved understanding of the origins of pain should facilitate the development of novel strategies for its more effective treatment.

Inhibition of prostanoid synthesis protects against neuronal damage induced by focal ischemia in rat brain

Changes in prostanoids concentration and effects of the non-specific COX inhibitor indomethacin on prostanoids levels and extension of tissue damage were studied following focal ischemia induction in the fronto-parietal region of rat brain. Ischemia was induced in animals bearing a transcerebral microdialysis probe by injection of Rose Bengal, a photosensitive dye, followed by light activation. Prostanoid levels were determined in the dialysate using immunoenzymatic techniques. PGD2 levels rose significantly up to 237+/-22 pg/ml compared to a basal level measured before ischemia induction which was below the detection limit. TXB2 changes were smaller and had a different time course. Treatment with indomethacin abolished the ischemia-induced PGD2 release and reduced the extent of injury to the area by 43+/-3.7%. These results suggest that prostanoid release may play an important role in neurodegenerative processes and that cyclooxygenase inhibitors may contribute to protect against cerebral tissue damage.

Role of cyclooxygenase 2 in acute spinal cord injury

Cyclooxygenase, or prostaglandin G/H synthase, is the rate-limiting step in the production of prostaglandins. A new isoform, cyclooxygenase-2 (COX-2), has been cloned that is induced during inflammation in leukocytes and by synaptic activity in neurons. The objectives of this study are to determine the nature of COX-2 expression in normal and traumatized rat spinal cord, and to determine the effects of selective COX-2 inhibition on functional recovery following spinal cord injury. Using a weight-drop model of spinal cord injury, COX-2 mRNA expression was studied with in situ hybridization. COX-2 protein expression was examined by immunohistochemistry and Western analysis. Finally, using the highly selective COX-2 inhibitor, 1-[(4-methylsufonyl)phenyl]-3-tri-fluro-methyl-5-[(4-flur o)phenyl]prazole (SC58125), the effect of COX-2 inhibition on functional outcome following a spinal cord injury was determined. COX-2 was expressed in the normal adult rat spinal cord. COX-2 mRNA and protein production were increased following injury with increases in COX-2 mRNA production detectable at 2 h following injury. Increased levels of COX-2 protein were detectable for at least 48 h following traumatic spinal cord injury. Selective inhibition of COX-2 activity with SC58125 resulted in improved mean Basso, Beattie, and Bresnahan scores in animals with 12.5- and 25-g/cm spinal cord injuries; however, the effect was significant only for the 12.5g/cm injury group (p=0.0001 vs. p=0.0643 in the 25-g/cm group). These data demonstrate that COX-2 mRNA and protein expression are induced by spinal cord injury, and that selective inhibition of COX-2 improves functional outcome following experimental spinal cord injury.

PGE2, via EP3 receptors, regulates brain nitric oxide synthase in the perinatal period

We tested the hypothesis that high prostaglandin levels during the perinatal period might regulate brain nitric oxide synthase (nNOS) expression. nNOS and cyclooxygenase (COX)-2 mRNAs were higher in brain cortex and the periventricular area of newborn rats and pigs compared with adult brain. Nitric oxide synthase activity was also 2. 5- to 4-fold higher in newborn than in adult brain. Administration of nonselective COX inhibitor ibuprofen or COX-2 inhibitor nimesulide every 8 h for 24 h to newborn rats and pigs reduced prostaglandin levels and caused comparable reductions in nNOS mRNA, protein, and activity to levels of adults; COX inhibitor-induced changes were prevented by cotreatment with PGE2 analog, 16, 16-dimethyl-PGE2, and agonist for the EP3 receptor of PGE2, sulprostone, but not by PGI2 analog carbaprostacyclin, PGD2, EP1 receptor agonist 17-phenyl trinor-PGE2, and EP2 agonist butaprost. Concordant observations were made in vitro and revealed that nNOS expression (detected by NADPH diaphorase reactivity) mostly present in neurons of the deeper cortical layers was reduced by COX inhibitor, and this effect was prevented by EP3 agonist. In conclusion, high levels of PGE2 in neonatal brain contribute to the increased expression of nNOS by acting on EP3 receptors; this positive interaction between PGE2 and nNOS might be required physiologically for normal brain development.

Cyclooxygenase-2 expression is increased in frontal cortex of Alzheimer's disease brain

Many epidemiological studies suggest that use of nonsteroidal anti-inflammatory drugs delays or slows the clinical expression of Alzheimer's disease, but the mechanism by which these drugs might affect pathophysiological processes relevant to Alzheimer's disease has been unclear. Non-steroidal anti-inflammatory drugs are presumed to act by inhibiting cyclooxygenase, a key enzyme in the metabolism of membrane-derived arachidonic acid into prostaglandins. In recent years, two distinct isoforms of cyclooxygenase have been characterized, a constitutive form, cyclooxygenase-1, and a mitogen-inducible form, cyclooxygenase-2. Cyclooxygenase-2 has been identified in rodent brain. Excitotoxic lesions cause up-regulation of cyclooxygenase-2 expression coincident with the onset of expression of markers of apoptosis; cyclooxygenase-2 thus represents a possible target of non-steroidal anti-inflammatory drug action in neurodegenerative mechanisms. In the present study, we examined cyclooxygenase-2 gene expression in Alzheimer's disease and control cases. We found up-regulation of cyclooxygenase-2 expression in Alzheimer's disease frontal cortex. Further, we found that synthetic beta-amyloid peptides induced cyclooxygenase-2 expression in SH-SY5Y neuroblastoma cells in vitro, suggesting a mechanism for cyclooxygenase-2 up-regulation in Alzheimer's disease. These findings support the investigation of selective cyclooxygenase-2 inhibitors for the treatment of Alzheimer's disease.

Cyclooxygenase and inflammation in Alzheimer's disease: experimental approaches and clinical interventions

Many epidemiological studies suggest that use of non-steroidal anti-inflammatory drugs (NSAIDs) delay or slow the clinical expression of Alzheimer's disease (AD). While it has been demonstrated that neurodegeneration in AD is accompanied by specific inflammatory mechanisms, including activation of the complement cascade and the accumulation and activation of microglia, the mechanism by which NSAIDs might affect these or other pathophysiological processes relevant to AD has been unclear. New evidence that cyclooxygenase (COX) is involved in neurodegeneration along with the development of selective COX inhibitors has led to renewed interest in the therapeutic potential of NSAIDs in AD.

Cyclooxygenase-2 inhibition prevents delayed death of CA1 hippocampal neurons following global ischemia

The inducible isoform of the enzyme cyclooxygenase-2 (COX2) is an immediate early gene induced by synaptic activity in the brain. COX2 activity is an important mediator of inflammation, but it is not known whether COX2 activity is pathogenic in brain. To study the role of COX2 activity in ischemic injury in brain, expression of COX2 mRNA and protein and the effect of treatment with a COX2 inhibitor on neuronal survival in a rat model of global ischemia were determined. Expression of both COX2 mRNA and protein was increased after ischemia in CA1 hippocampal neurons before their death. There was increased survival of CA1 neurons in rats treated with the COX2-selective inhibitor SC58125 [1-[(4-methylsulfonyl) phenyl]-3-trifluoro-methyl-5-[(4-fluoro)phenyl] pyrazole] before or after global ischemia compared with vehicle controls. Furthermore, hippocampal prostaglandin E2 concentrations 24 h after global ischemia were decreased in drug-treated animals compared with vehicle-treated controls. These results suggest that COX2 activity contributes to CA1 neuronal death after global ischemia.

Localization of cyclooxygenase-2 and prostaglandin E2 receptor EP3 in the rat lumbar spinal cord

Cyclooxygenase-2 (COX-2) is now considered to be the major constitutively expressed COX isozyme in the central nervous system. The present immunocytochemical study details localization of COX-2 immunoreactivity in rat spinal cord along with the expression of prostaglandin E2 receptor subtype EP3. Prominent COX-2 staining was observed in the nuclear envelope of neurons throughout the spinal cord, especially in the superficial dorsal horn laminae and motoneurons of lamina IX, as well as in glial cells of the white matter. Expression of EP3 receptor was strictly confined to afferent terminal areas in the superficial dorsal horns.