Inhibitors of cyclooxygenase-2, but not cyclooxygenase-1 provide structural and functional protection against quinolinic acid-induced neurodegeneration

Selective COX-2 Inhibitors as Neuroprotective Agents in Traumatic Brain Injury

Traumatic brain injury (TBI) is a significant contributor to mortality and morbidity in people, both young and old. There are currently no approved therapeutic interventions for TBI. Following TBI, cyclooxygenase (COX) enzymes generate prostaglandins and reactive oxygen species that perpetuate inflammation, with COX-1 and COX-2 isoforms providing differing responses. Selective COX-2 inhibitors have shown potential as neuroprotective agents. Results from animal models of TBI suggest potential treatment through the alleviation of secondary injury mechanisms involving neuroinflammation and neuronal cell death. Additionally, early clinical trials have shown that the use of celecoxib improves patient mortality and outcomes. This review aims to summarize the therapeutic effects of COX-2 inhibitors observed in TBI animal models, highlighting pertinent studies elucidating molecular pathways and expounding upon their mechanistic actions. We then investigated the current state of evidence for the utilization of COX-2 inhibitors for TBI patients.

Akt / GSK3β / Nrf2 / HO-1 pathway activation by flurbiprofen protects the hippocampal neurons in a rat model of glutamate excitotoxicity

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that regulates redox homeostasis of the cell through regulation of the antioxidant response element genes transcription. Nrf2 also regulates the antiapoptotic Bcl-2 gene. Nrf2 degradation and nuclear translocation is regulated by upstream kinases Akt and GSK3β. Glutamate excitotoxicity is a process of neuronal cells death due to excessive activation of glutamate receptors. Glutamate excitotoxicity participates in the pathophysiology of several acute and chronic neurological conditions. In addition, glutamate excitotoxicity interrupts the PI3K/Akt prosurvival pathway so GSK3β remains active. Active GSK3β increases Nrf2 degradation, decreases Nrf2 nuclear translocation and increases Nrf2 nuclear export which decreases the ARE genes transcription such as, SOD, GSH synthesis enzyme and HO-1. Also, Bcl-2 transcription decreases. Flurbiprofen is a COX inhibitor. Previous studies showed that it has a neuroprotective effect in neurodegeneration and in focal cerebral ischemia/reperfusion model. In our research we aimed to test the hypothesis that flurbiprofen may have a neuroprotective effect in a rat model of glutamate-induced excitotoxicity and this neuroprotection may occur through modulation of (Akt/GSK3β/Nrf2/HO-1) pathway. Rats were divided into 4 groups; control, MSG (2.5 g/Kg, i.p), low dose FB (5 mg/kg, i.p) and high dose FB (10 mg/kg, i.p). We found that low and high doses FB decreased COX-2, PGE₂, NO and MDA and increased SOD and GSH in brain compared to MSG group. High dose was more effective than low dose. Western blotting analysis in hippocampus tissue showed that high dose FB increased p-Akt, p-GSK3β, nuclear Nrf2 and HO-1 and decreased cytosolic Nrf2 level in comparison with MSG group. Immunohistochemical analysis in hippocampus and cerebral cortex showed that high dose FB increased Bcl-2 and decreased Bax compared to MSG group. In addition, FB increased the number of intact neurons in hippocampus areas and cerebral cortex neurons and showed an anxiolytic-like action in OF and EPM tests. These findings suggest that FB has a neuroprotective effect in glutamate-induced excitotoxicity model through reduction of the glutamate excitotoxicity damage and activation of the survival pathway. These may occur due to modulation the survival pathway (Akt/GSK3β/Nrf2/HO-1) and inhibition of COX-2.

Celecoxib in a Preclinical Model of Repetitive Mild Traumatic Brain Injury: Hippocampal Learning Deficits Persist with Inflammatory and Excitotoxic Neuroprotection

Repetitive mild traumatic brain injuries (mTBIs) contribute to inflammation-induced neurodegeneration. Cycloxygenase (COX) enzymes produce inflammatory cytokines that influence the microglia response to neurotrauma. Celecoxib is a selective COX-2 inhibitor that is prescribed in some conditions of mTBI to alleviate symptoms of concussion, and has shown benefits in neurodegenerative conditions. We investigated molecular pathways of neuroinflammation in response to celecoxib treatment in a mouse model of repetetive mTBI. Fifteen mTBIs were delivered over 23 days in adult male C57BL/6J mice in one of four groups (control, celecoxib without impact, celecoxib with impact, and vehicle with impact). Cognitive function was assessed at 48 h and three months following the final mTBI. Morris Water Maze testing revealed impaired hippocampal spatial learning performance in the celecoxib treatment with the impact group compared to the vehicle with impact control in the acute phase, with celecoxib treatment providing no improvement compared with the control at chronic testing; mRNA analysis of the cerebral cortex and hippocampus revealed expression change, indicating significant improvement in microglial activation, inflammation, excitotoxicity, and neurodegeneration at chronic measurement. These data suggest that, in the acute phase following injury, celecoxib protected against neuroinflammation, but exacerbated clinical cognitive disturbance. Moreover, while there was evidence of neuroprotective alleviation of mTBI pathophysiology at chronic measurement, there remained no change in clinical features.

Celecoxib, ibuprofen, and indomethacin alleviate depression-like behavior induced by interferon-alfa in mice

Background Interferon-α (IFNα) therapy causes psychiatric side effects, including depression that may result in poor compliance of therapy. It is important to find alternative therapies for the prevention of IFNα induced depression. Non-steroidal anti-inflammatory drugs (NSAIDs) have been useful in depressive disorder. Therefore the effects of celecoxib, ibuprofen, and indomethacin were evaluated following IFNα-induced depression in mice. Methods Male albino mice weighing 26 ± 2 g were used. Depression was induced by IFNα (16 × 105 IU/kg, SC) for six consecutive days. Animals were first subject to the locomotor test, then the splash test and finally the forced swimming test (FST) on the 7th day. The NSAIDs were administered (IP) either one single dose before the test, or simultaneously with IFNα. Results locomotor activity was only impaired by ibuprofen high dose (75 mg/kg), thus it was not further evaluated. Following IFNα therapy depression-like behaviors were observed; significant changes during the splash test (grooming time 24 ± 7 sec vs. control 63 ± 7 sec), the FST (immobility time 166  ± 15 sec vs. control 128  ± 6 sec), and sucrose preference reduced to 64 ± 0.8%. The NSAIDs noticeably reduced the immobility time in FST, while grooming time was increased. Celecoxib and indomethacin single doses were effective while ibuprofen showed better antidepressant effects when it was administered along with IFNα. Conclusions The NSAIDs were able to prevent IFNα induced depression in mice. NSAIDs administration with IFNα does not interfere with clinical benefit effects of IFNα and they could also be useful to prevent IFNα psychiatric side effects, thus further clinical trials are suggested.

Design of selective COX-2 inhibitors in the (aza)indazole series. Chemistry, in vitro studies, radiochemistry and evaluations in rats of a [18F] PET tracer

A series of novel derivatives exhibiting high affinity and selectivity towards the COX-2 enzyme in the (aza) indazole series was developed. A short synthetic route involving a bromination/arylation sequence under microwave irradiation and direct C–H activation were established in the indazole and azaindazole series respectively. In vitro assays were conducted and structural modifications were carried out on these scaffolds to furnish compound 16 which exhibited effective COX-2 inhibitory activity, with IC₅₀ values of 0.409 µM and an excellent selectivity versus COX-1. Radiolabeling of this most potent derivative [¹⁸F]16 was achieved after boron ester release and the tracer was evaluated in vivo in a rat model of neuroinflammation. All chemistry, radiochemistry and biological experimental data are discussed.

Sertoli Cells Induce Systemic Donor-Specific Tolerance in Xenogenic Transplantation Model

Cell therapy is a potentially powerful tool in the treatment of many grave disorders including leukemia, immune deficiencies, autoimmune diseases, and diabetes. However, finding matched donors is challenging and recipients may suffer from the severe complications of systemic immune suppression. Sertoli cells, when cotransplanted with both allo- and xenograft tissues, promote graft acceptance in the absence of systemic immunosuppression. How Sertoli cells do this is not, as yet, clearly defined. We have examined the ability of Sertoli cells to produce systemic immune tolerance. For this purpose, Sertoli cells were injected into an otherwise normal C57/BL6 mouse host via the lateral tail vein. No other immunosuppressive protocols were applied. Six to 8 weeks posttransplantation, blood was collected for analysis of cytokine levels. Tolerance to donor cells was determined by mixed lymphocytic culture, and production of T-cell-dependent antibody was determined by an in vitro anti-sheep red blood cell plaque-forming assay. Results showed a marked modulation of immune cytokines in the transplanted mouse host and donor-specific transplantation tolerance was achieved. Tolerant mouse lymphocytes maintained a competent humoral antibody response. Additionally, C57/BL6 mice transplanted with rat Sertoli cells tolerated rat skin grafts significantly longer than control non-Sertoli cell transplanted mice. We conclude that systemic administration of rat Sertoli cells across xenogenic barrier induces transplantation tolerance without altering systemic immune competence. These data suggest that Sertoli cells may be used as a novel and potentially powerful tool in cell transplantation therapy.

Modulation of early stress-induced neurobiological changes: a review of behavioural and pharmacological interventions in animal models

Childhood adversity alters the predisposition to psychiatric disorders later in life. Those with psychiatric conditions and a history of early adversity exhibit a higher incidence of treatment resistance compared with individuals with no such history. Modulation of the influence early stress exerts over neurobiology may help to prevent the development of psychiatric disorders in some cases, while attenuating the extent of treatment resistance in those with established psychiatric disorders. This review aims to critically evaluate the ability of behavioural, environmental and pharmacologic interventions to modulate neurobiological changes induced by early stress in animal models. Databases were systematically searched to locate literature relevant to this review. Early adversity was defined as stress that resulted from manipulation of the mother-infant relationship. Analysis was restricted to animal models to enable characterisation of how a given intervention altered specific neurobiological changes induced by early stress. A wide variety of changes in neurobiology due to early stress are amenable to intervention. Behavioural interventions in childhood, exercise in adolescence and administration of epigenetic-modifying drugs throughout life appear to best modulate cellar and behavioural alterations induced by childhood adversity. Other pharmacotherapies, such as endocannabinoid system modulators, anti-inflammatories and antidepressants can also influence these neurobiological and behavioural changes that result from early stress, although findings are less consistent at present and require further investigation. Further work is required to examine the influence that behavioural interventions, exercise and epigenetic-modifying drugs exert over alterations that occur following childhood stress in human studies, before possible translational into clinical practice is possible.

Simultaneous inhibition of COX-2 and activation of PPAR-γ resulted in the same level and pattern of neuroprotection as they were targeted separately

The inflammatory response is an immune response of the body when exposed to internal and external stimuli. Cyclooxygenases (COX) are major inflammatory mediators implicated in inflammation. COX-2 is reported to be involved in neuroinflammation. Moreover, 15-Deoxy-D (12,14)-prostaglandin J2 (15d-PGJ2), an endogenous ligand of peroxisome proliferator-activated receptor gamma (PPAR-γ), has been demonstrated to have anti-inflammatory actions. In this study, we investigated whether co-therapy of a selective COX-2 inhibitor NS-398 and 15d-PGJ2 as a PPAR-γ ligand could exert additional neuroprotective effects in rat pheochromocytoma (PC12) cells. Our findings showed that 15d-PGJ2 and NS-398 suppress the apoptotic pathway in PC12 cells exposed to H(2)O(2) by attenuation of the Bax/Bcl-2 ratio. This effect was mediated through PPAR-γ, as it was reversed by GW9662 (a PPAR-γ inhibitor). Also, 15d-PGJ2 and NS-398 induced the Nrf2 signaling pathway and decreased NF-κB level in a PPAR-γ-dependent manner. We found that coadministration of a selective COX-2 inhibitor and a PPAR-γ ligand in PC12 cells has equal neuroprotective effect compared to their effects when used separately. Considering the higher affinity of 15d-PGJ2 for PPAR-γ than NS-398, it seems that the observed neuroprotection of this combination therapy was from 15d-PGJ2.

Translating the therapeutic potential of neurotrophic factors to clinical 'proof of concept': a personal saga achieving a career-long quest

While the therapeutic potential of neurotrophic factors has been well-recognized for over two decades, attempts to translate that potential to the clinic have been disappointing, largely due to significant delivery obstacles. Similarly, gene therapy (or gene transfer) emerged as a potentially powerful, new therapeutic approach nearly two decades ago and despite its promise, also suffered serious setbacks when applied to the human clinic. As advances continue to be made in both fields, ironically, they may now be poised to complement each other to produce a translational breakthrough. The accumulated data argue that gene transfer provides the 'enabling technology' that can solve the age-old delivery problems that have plagued the translation of neurotrophic factors as treatments for chronic central nervous system diseases. A leading translational program applying gene transfer to deliver a neurotrophic factor to rejuvenate and protect degenerating human neurons is CERE-120 (AAV2-NRTN). To date, over two dozen nonclinical studies and three clinical trials have been completed. A fourth (pivotal) clinical trial has completed all dosing and is currently evaluating safety and efficacy. In total, eighty Parkinson's disease (PD) subjects have thus far been dosed with CERE-120 (some 7 years ago), representing over 250 cumulative patient-years of exposure, with no serious safety issues identified. In a completed sham-surgery, double-blinded controlled trial, though the primary endpoint (the Unified Parkinson's Disease Rating Scale (UDPRS) motor off score measured at 12 months) did not show benefit from CERE-120, several important motor and quality of life measurements did, including the same UPDRS-motor-off score, pre-specified to also be measured at a longer, 18-month post-dosing time point. Importantly, not a single measurement favored the sham control group. This study therefore, provided important, well-controlled evidence establishing 'clinical proof of concept' for gene transfer to the CNS and the first controlled evidence for clinical benefit of a neurotrophic factor in a human neurodegenerative disease. This paper reviews the development of CERE-120, starting historically with the long-standing interest in the therapeutic potential of neurotrophic factors and continuing with selective accounts of past efforts to translate their potential to the clinic, eventually leading to the application of gene transfer and its role as the 'enabling technology'. Because of growing interest in translational R&D, including its practice in industry, the paper is uniquely oriented from the author's personal, quasi-autobiographic perspective and career-long experiences conducting translational research and development, with a focus on various translational neurotrophic factor programs spanning 30+ years in Big Pharma and development-stage biotech companies. It is hoped that by sharing these perspectives, practical insight and information might be provided to others also interested in translational R&D as well as neurotrophic factors and gene therapy, offering readers the opportunity to benefit from some of our successes, while possibly avoiding some of our missteps.

Nonsteroidal anti-inflammatory treatment prevents delayed effects of early life stress in rats

BACKGROUND

Early developmental insults can cause dysfunction within parvalbumin (PVB)-containing interneurons in the prefrontal cortex. The neuropsychiatric disorders associated with such dysfunction might involve neuroinflammatory processes. Cyclooxygenase-2 (COX-2) is a key mediator of inflammation and is therefore a potential target for preventive treatment. Here, we investigated whether the developmental trajectories of PVB expression and COX-2 induction in the prelimbic region of the prefrontal cortex are altered after maternal separation stress in male rats.

METHODS

Male rat pups were separated from their mother and littermates for 4 hours/day between postnatal Days 2 and 20. Western blotting and immunohistochemistry were used to analyze PVB and COX-2 expression in the prefrontal cortex and hippocampus. A separate cohort of animals was treated with a COX-2 inhibitor during preadolescence and analyzed for PVB, COX-2, and working memory performance.

RESULTS

We demonstrate that maternal separation causes a reduction of PVB and an increase in COX-2 expression in the prefrontal cortex in adolescence, with concurrent working memory deficits. Parvalbumin was not affected earlier in development. Prophylactic COX-2 inhibition preadolescence prevents PVB loss and improves working memory deficits induced by maternal separation.

CONCLUSIONS

These data are the first to show a preventive pharmacological intervention for the delayed effects of early life stress on prefrontal cortex interneurons and working memory. Our results suggest a possible mechanism for the relationship between early life stress and interneuron dysfunction in adolescence.

Neuroprotective effect of cyclooxygenase inhibitors in ICV-STZ induced sporadic Alzheimer's disease in rats

Sporadic Alzheimer's disease is an age-related neurological and psychiatric disorder characterized by impaired energy metabolism. Oxidative stress and neuroinflammation have been implicated in pathophysiology of sporadic type of dementia. The central streptozotocin administration induces behavioral and biochemical alterations resembling those in sporadic type of Alzheimer's patients. The present study was designed to investigate the effects of chronic pretreatment with cyclooxygenase-1 or cyclooxygenase-2 or cyclooxygenase-3 selective inhibitors on cognitive dysfunction and oxidative stress markers in intracerebroventricular streptozotocin-treated rats. Chronic treatment with valeryl salicylate (5 and 10 mg/kg, i.p.) and etoricoxib (5 and 10 mg/kg, i.p.) on a daily basis for a period of 21 days, beginning 1 h prior to first intracerebroventricular streptozotocin injection, significantly improved streptozotocin-induced cognitive impairment. However, phenacetin (20 and 40 mg/kg, i.p.) failed to restore the cognitive performances of streptozotocin-treated rats. Besides, improving cognitive dysfunction, chronic administration of highly selective cyclooxygenase-1 and/or cyclooxygenase-2 inhibitors (valeryl salicylate and etoricoxib, respectively), but not cyclooxygenase-3 inhibitor (phenacetin), significantly reduced elevated malondialdehyde, nitrite levels, and restored reduced glutathione and superoxide dismutase levels. Furthermore, cyclooxygenase-1 and/or cyclooxygenase-2 inhibitors significantly increased the survival of pyramidal neurons. In summary, we demonstrate for the first time that both cyclooxygenase-1 and cyclooxygenase-2 isoforms, but not cyclooxygenase-3, are involved in the progression of neuronal damage in intracerebroventricular streptozotocin-treated rats.

In vivo expression of cyclooxygenase-1 in activated microglia and macrophages during neuroinflammation visualized by PET with 11C-ketoprofen methyl ester

Cyclooxygenase (COX)-1 and -2 are prostanoid-synthesizing enzymes that play important roles in the regulation of neuroinflammation and in the development of neurodegenerative disorders. However, the specific functions of these isoforms are still unclear. We recently developed (11)C-labeled ketoprofen methyl ester as a PET probe that targets the COXs for imaging neuroinflammation, though its responsible isoform is yet to be determined. In the present study, we performed ex vivo and in vivo imaging studies with (11)C-ketoprofen methyl ester and determined the contributions of the COX isoforms during the neuroinflammatory process.

METHODS

To identify the COX isoform responsible for (11)C-ketoprofen methyl ester in the brain, we examined the ex vivo autoradiography of (11)C-ketoprofen methyl ester using COX-deficient mice. Time-dependent changes in accumulation of (11)C-ketoprofen methyl ester during the neuroinflammatory process were evaluated by PET in rats with hemispheric neuroinflammation induced by intrastriatal injection of lipopolysaccharide or quinolinic acid. In both rat models, cell-type specificity of COX isoform expression during neuroinflammation was identified immunohistochemically.

RESULTS

Ex vivo autoradiographic analysis of COX-deficient mice revealed a significant reduction of (11)C-ketoprofen methyl ester accumulation only in COX-1-deficient mice, not COX-2-deficient mice. PET of rats after intrastriatal injection of lipopolysaccharide showed a significant increase in accumulation of (11)C-ketoprofen methyl ester in the inflamed area. This increase was evident at the early phase of 6 h, peaked at day 1, and then returned to basal levels by day 7. In addition, immunohistochemical analysis revealed that the population of activated microglia and macrophages was elevated at the early phase with COX-1 expression but not COX-2. A significant increase in (11)C-ketoprofen methyl ester accumulation was also observed at day 1 after intrastriatal injection of quinolinic acid, with increased COX-1-expressing activated microglia and macrophages.

CONCLUSION

We have identified (11)C-ketoprofen methyl ester as a COX-1-selective PET probe, and using this, we have also demonstrated a time-dependent expression of COX-1 in activated microglia and macrophages during the neuroinflammatory process in the living brain. Thus, COX-1 may play a crucial role in the pathology of neuroinflammation and might be a critical target for the diagnosis and therapy of neurodegenerative disorders.

Highly reactive oxygen species: detection, formation, and possible functions

The so-called reactive oxygen species (ROS) are defined as oxygen-containing species that are more reactive than O(2) itself, which include hydrogen peroxide and superoxide. Although these are quite stable, they may be converted in the presence of transition metal ions, such as Fe(II), to the highly reactive oxygen species (hROS). hROS may exist as free hydroxyl radicals (HO·), as bound ("crypto") radicals or as Fe(IV)-oxo (ferryl) species and the somewhat less reactive, non-radical species, singlet oxygen. This review outlines the processes by which hROS may be formed, their damaging potential, and the evidence that they might have signaling functions. Since our understanding of the formation and actions of hROS depends on reliable procedures for their detection, particular attention is given to procedures for hROS detection and quantitation and their applicability to in vivo studies.

Licofelone attenuates quinolinic acid induced Huntington like symptoms: possible behavioral, biochemical and cellular alterations

Cyclo-oxygenase and lipoxygenase enzymes are involved in arachidonic acid metabolism. Emerging evidence indicates that cyclo-oxygenase and lipoxygenase inhibitors prevent neurodegenerative processes and related complications. Therefore, the present study has been designed to explore the neuroprotective potential of licofelone (dual COX-2/5-LOX inhibitor) against quinolinic acid induced Huntington like symptom in rats. Intrastriatal administration of quinolinic acid significantly caused reduction in body weight and motor function (locomotor activity, rotarod performance and beam walk test), oxidative defense (as evidenced by increased lipid peroxidation, nitrite concentration and decreased endogenous antioxidant enzymes), alteration in mitochondrial enzyme complex (I, II and IV) activities, raised TNF-α level and striatal lesion volume as compared to sham treated animals. Licofelone (2.5, 5 and 10 mg/kg) treatment significantly improved body weight, locomotor activity, rotarod performance, balance beam walk performance, oxidative defense, mitochondrial enzyme complex activities and attenuated TNF-α level and striatal lesion as compared to control (quinolinic acid). The present study highlights that licofelone attenuates behavioral, biochemical and cellular alterations against quinolinic acid induced neurotoxicity and this could be an important therapeutic avenue to ameliorate the Huntington like symptoms.

Inflammatory biomarkers and depression

Antidepressants, predominantly serotonin- and/or noradrenaline reuptake inhibiting drugs have several shortcomings. The exact pathophysiological mechanisms leading to serotonergic-, noradrenergic- or dopaminergic dysfunction are still unclear. An inflammatory mechanism has been postulated and will be discussed here including possible therapeutic advantages of cyclooxygenase-2 (COX-2) inhibitors. Differences in the activation of the enzyme indoleamine 2,3-dioxygenase (IDO) and in the tryptophan-kynurenine metabolism resulting in an increased tryptophan and serotonin degradation and probably in an increased production of quinolinic acid might play a key role in major depression (MD). These differences are associated with an imbalance in the glutamatergic neurotransmission, which may contribute to an overweight of N-methyl-D: -aspartate agonism in MD. The immunological imbalance results in an increased prostaglandin E₂ production and probably also in an increased COX-2 expression. Although there is strong evidence for the view that the interactions of the immune system, IDO, the serotonergic system and the glutamatergic neurotransmission play a key role in MD, several gaps, e.g. the roles of genetics, disease course, sex, different psychopathological states, etc., have to be bridged by intense further research. There were already hints that anti-inflammatory therapy might have beneficial effects in MD. COX-2 inhibitors, however, have been tested in animal models and in preliminary clinical studies showing favourable effects compared to placebo in MD. The effects of COX-2 inhibition in the CNS as well as the different components of the inflammatory system, the kynurenine-metabolism and the glutamatergic neurotransmission, however, still need careful further scientific evaluation including clinical studies in bigger samples of patients.

The impact of neuroimmune dysregulation on neuroprotection and neurotoxicity in psychiatric disorders--relation to drug treatment

An inflammatory pathogenesis has been postulated for schizophrenia and major depression (MD). In schizophrenia and depression, opposing patterns oftype-1 vs type-2 immune response seem to be associated with differences in the activation of the enzyme indoleamine 2,3-dioxygenase and in the tryptophan-kynurenine metabolism, resulting in increased production of kynurenic acid in schizophrenia and decreased production of kynurenic acid in depression. These differences are associated with an imbalance in the glutamatergic neurotransmission, which may contribute to an excessive agonist action of N-methyl-D-aspartate (NMDA) in depression and of NMDA antagonism in schizophrenia. Regarding the neuroprotective function of kynurenic acid and the neurotoxic effects of quinolinic acid (QUIN), different patterns of immune activation may also lead to an imbalance between the neuroprotective and the neurotoxic effects of the tryptophanlkynurenine metabolism. The differential activation of microglia cells and astrocytes may be an additional mechanism contributing to this imbalance. The immunological imbalance results in an inflammatory state combined with increased prostaglandin E2 production and increased cyclo-oxygenase-2 (COX-2) expression. The immunological effects of many existing antipsychotics and antidepressants, however, partly correct the immune imbalance and the excess production of the neurotoxic QUIN, COX-2 inhibitors have been tested in animal models of depression and in preliminary clinical trials, pointing to favorable effects in schizophrenia and in MD.

Interferon-gamma deficiency modifies the motor and co-morbid behavioral pathology and neurochemical changes provoked by the pesticide paraquat

In addition to nigrostriatal pathology and corresponding motor disturbances, Parkinson's disease (PD) is often characterized by co-morbid neuropsychiatric symptoms, most notably anxiety and depression. Separate lines of evidence indicate that inflammatory processes associated with microglial activation and cytokine release may be fundamental to the progression of both PD and its co-morbid psychiatric pathology. Accordingly, we assessed the contribution of the pro-inflammatory cytokine, interferon-gamma (IFN-gamma), to a range of PD-like pathology provoked by the ecologically relevant herbicide and dopamine (DA) toxin, paraquat. To this end, paraquat provoked overt motor impairment (reduced home-cage activity and impaired vertical climbing) and signs of anxiety-like behavior (reduced open field exploration) in wild-type but not IFN-gamma-deficient mice. Correspondingly, paraquat promoted somewhat divergent variations in neurochemical activity among wild-type and IFN-gamma null mice at brain sites important for both motor (striatum) and co-morbid affective pathologies (dorsal hippocampus, medial prefrontal cortex, and locus coeruleus). Specifically, the herbicide provoked a dosing regimen-dependent reduction in striatal DA levels that was prevented by IFN-gamma deficiency. In addition, the herbicide influenced serotonergic and noradrenergic activity within the dorsal hippocampus and medial prefrontal cortex; and elevated noradrenergic activity within the locus coeruleus. Although genetic ablation of IFN-gamma had relatively few effects on monoamine variations within the locus coeruleus and prefrontal cortex, loss of the pro-inflammatory cytokine did normalize the paraquat-induced noradrenergic alterations within the hippocampus. These findings further elucidate the functional implications of paraquat intoxication and suggest an important role for IFN-gamma in the striatal and motor pathology, as well as the co-morbid behavioral and hippocampal changes induced by paraquat.

A psychoneuroimmunological perspective to Emil Kraepelins dichotomy: schizophrenia and major depression as inflammatory CNS disorders

The Kraepelinian classification of psychiatric disorders, in particular the dichotomy of dementia praecox and manic-depressive psychosis is under discussion since a long time. In recent years, not only new research in the fields of psychopathology and clinical outcome, but also findings of biological markers in the areas of neurophysiology, neuroendocrinology, psychoneuroimmunology, genetics, or psychopharmacology show a big overlap between both groups of disorders. This overlap of symptoms and markers of both disorders intensified the discussion and the proposals for new criteria for the classification of psychiatric disorders. By means of findings from the field of psychoneuroimmunology and inflammation it will be shown that different pathological mechanisms in depression and schizophrenia may lead to the same final common pathway of inflammation. These mechanisms include the immunological balance between type-1 and type-2 immune activation which influences the tryptophan-degradating enzyme indoleamine 2,3-dioxygenase (IDO) in the CNS in opposite ways, leading to an altered availability of tryptophan and serotonin, and a disturbance of the kynurenine metabolism with an imbalance in favor of the production of the NMDA-receptor agonist quinolinic acid in depression and of the NMDA-receptor antagonist kynurenic acid in schizophrenia. In both disorders, however, an increased production of prostaglandin E2 and increased expression of cyclo-oxygenase-2 reflect a slight inflammatory process taking place probably in different regions of the CNS. Albeit this common inflammatory pathway--inflammation is a general pathway of the body as answer to a lot of different noxae and pathogens--the Kraepelinian dichotomy is important with respect to pathological mechanisms and therapeutic approaches, not only for further research in understanding the exact pathological mechanisms but also for the development of preventive strategies in high risk individuals and in patients. Opposite pathways regarding the immune activation, the neurotoxic versus neuroprotective kynurenine metabolites and the agonistic versus antagonistic effects on the NMDA receptor and the glutamatergic neurotransmission show despite a possible therapeutic advantage of anti-inflammatory therapy in both disorders that the Kraepelinian dichotomy still has a significant value from a biologic-psychiatric point of view.

Involvement of endogenous prostaglandin F2alpha on kainic acid-induced seizure activity through FP receptor: the mechanism of proconvulsant effects of COX-2 inhibitors

COX-2 and prostaglandins (PGs) might play important roles in epilepsy. In kainic acid-induced seizures, the brain largely increases PGD(2), first from COX-1 and later COX-2-induced PGF(2alpha). Pre-treatment with COX-2 inhibitors such as indomethacin, nimesulide, and celecoxib is known to aggravate kainic acid (KA)-induced seizure activity. However it is not known whether the proconvulsant effect of those non-steroidal anti-inflammatory drugs (NSAIDs) is due to changes in endogenous prostaglandins (PGs), or what types of PGs are involved. The purpose of this study was to determine the effect of intracisternally administered PGs on KA-induced seizures aggravated by pre- or post-treatment with COX-2 inhibitors. Systemic KA injection (10 mg/kg i.p.) in mice evoked mild seizure activity within 15 min. PGs were administrated intracisternally 20 min prior to KA administration. COX inhibitors (indomethacin, nimesulide, and ketoprofen, 10 mg/kg i.p.) were injected 1 h before or 15 min after KA. An additional COX-2 inhibitor, celecoxib, was administered orally. Intracisternally administered PGF(2alpha) (700 ng), but not PGD(2) (700 ng) or PGE(2) (700 ng) completely alleviated KA-induced seizures potentiated by COX-2 inhibitors, and also reduced KA-induced hippocampal neuronal death aggravated by indomethacin. PGF(2alpha) alone did not affect KA-induced seizures. However, an FP receptor antagonist, AL 8810 (10 or 50 ng) which is an 11beta-fluoro analogue of PGF(2alpha) potentiated KA-induced seizure activity dose-dependently. In summary, pre- or post-treatment with COX-2 inhibitors aggravates KA-induced seizures, which suggests to change the endogenous PGF(2alpha). Seizure-induced PGF(2alpha) might act as an endogenous anticonvulsant through FP receptors.

The immune-mediated alteration of serotonin and glutamate: towards an integrated view of depression

Beside the well-known deficiency in serotonergic neurotransmission as pathophysiological correlate of major depression (MD), recent evidence points to a pivotal role of increased glutamate receptor activation as well. However, cause and interaction of these neurotransmitter alterations are not understood. In this review, we present a hypothesis integrating current concepts of neurotransmission and hypothalamus-pituitary-adrenal (HPA) axis dysregulation with findings on immunological alterations and alterations in brain morphology in MD. An immune activation including increased production of proinflammatory cytokines has repeatedly been described in MD. Proinflammatory cytokines such as interleukin-2, interferon-gamma, or tumor necrosis factor-alpha activate the tryptophan- and serotonin-degrading enzyme indoleamine 2,3-dioxygenase (IDO). Depressive states during inflammatory somatic disorders are also associated with increased proinflammatory cytokines and increased consumption of tryptophan via activation of IDO. An enhanced consumption of serotonin and its precursor tryptophan through IDO activation could well explain the reduced availability of serotonergic neurotransmission in MD. An increased activation of IDO and its subsequent enzyme kynurenine monooxygenase by proinflammatory cytokines, moreover, leads to an enhanced production of quinolinic acid, a strong agonist of the glutamatergic N-methyl-D-aspartate receptor. In inflammatory states of the central nervous system, IDO is mainly activated in microglial cells, which preferentially metabolize tryptophan to the NMDA receptor agonist quinolinic acid, whereas astrocytes - counteracting this metabolism due to the lack of an enzyme of this metabolism - have been observed to be reduced in MD. Therefore the type 1/type 2 immune response imbalance, associated with an astrocyte/microglia imbalance, leads to serotonergic deficiency and glutamatergic overproduction. Astrocytes are further strongly involved in re-uptake and metabolic conversion of glutamate. The reduced number of astrocytes could contribute to both, a diminished counterregulation of IDO activity in microglia and an altered glutamatergic neurotransmission. Further search for antidepressant agents should take into account anti-inflammatory drugs, for example, cyclooxygenase-2 inhibitors, might exert antidepressant effects by acting on serotonergic deficiency, glutamatergic hyperfunction and antagonizing neurotoxic effects of quinolinic acid.

Effects of the adenosine A2A receptor antagonist SCH 58621 on cyclooxygenase-2 expression, glial activation, and brain-derived neurotrophic factor availability in a rat model of striatal neurodegeneration

Inhibition of adenosine A2A receptors (A2ARs) is neuroprotective in several experimental models of striatal diseases. However, the mechanisms elicited by A2AR blockade are only partially known, and critical aspects about the potential beneficial effects of A2AR antagonism in models of neurodegeneration still await elucidation. In the present study, we analyzed the influence of the selective A2AR antagonist SCH 58261 in a rat model of striatal excitotoxicity obtained by unilateral intrastriatal injection of quinolinic acid (QA). We found that SCH 58261 differently affected the expression of cyclooxygenase-2 (COX-2) induced by QA in cortex and striatum. The antagonist enhanced COX-2 expression in cortical neurons and prevented it in striatal microglia-like cells. Similarly, SCH 58261 differently regulated astrogliosis and microglial activation in the 2 brain regions. In addition, the A2AR antagonist prevented the QA-induced increase in striatal brain-derived neurotrophic factor levels. Because COX-2 activity has been linked to excitotoxic processes and because brain-derived neurotrophic factor depletion has been observed in mouse models as well as in patients with Huntington disease, we suggest that the final outcome of A2AR blockade (namely neuroprotection vs neurodegeneration) is likely to depend on the balance among its various and region-specific effects.

Cyclooxygenase inhibition attenuates 3-nitropropionic acid-induced neurotoxicity in rats: possible antioxidant mechanisms

Systemic administration of 3-nitropropionic acid (3-NP), a complex II inhibitor of the electron transport chain, causes motor and cognitive deficits that are associated with excitotoxicity and excessive free radical generation. Recently, cyclooxygenase (COX) inhibitors have been implicated as a neuroprotectant in the treatment of various neurological disorders. The present study was designed to investigate the effects of COX inhibitors in 3-NP-induced cognitive impairment and oxidative stress in rats. Intraperitoneal administration of 3-NP (20 mg/kg for 4 days) showed motor abnormalities and cognitive impairment in rats. Chronic treatment with naproxen (10 and 20 mg/kg) and valdecoxib (5 and 10 mg/kg) once daily for a period of 8 days beginning 4 days prior to 3-NP administration significantly improved 3-NP-induced motor and cognitive impairment in rats. Biochemical analysis revealed that systemic 3-NP administration significantly increased lipid peroxidation and nitrite levels, depleted reduced glutathione levels and reduced succinate dehydrogenase (SDH) activity in the brains of rats, whereas administration of naproxen, a nonselective COX inhibitor (10 and 20 mg/kg p.o.) and valdecoxib, a selective COX-2 inhibitor (5 and 10 mg/kg p.o.) significantly attenuated 3-NP-induced oxidative stress. Cyclooxygenase inhibitors also significantly restored the decreased SDH activity. The results of the present study clearly indicate that naproxen and valdecoxib showed protection against 3-NP-induced motor and cognitive impairment by decreasing oxidative stress.

Role of tissue-plasminogen activator (t-PA) in a mouse model of neonatal white matter lesions: interaction with plasmin inhibitors and anti-inflammatory drugs

Ibotenic acid injected intracerebrally over a broad dose range to 5-day-old mice induces cystic white matter (WM) lesions that mimic periventricular leukomalacia (PVL) of preterm infants. With both low (0.1 mug) and high (5 mug) ibotenic acid doses, tissue-plasminogen activator (t-PA) is involved in cyst formation. Subsequent cyst growth depends on high doses. We evaluated the effects of human recombinant tissue-plasminogen activator (hrt-PA), plasmin inhibitors (tranexamic acid, alpha2-antiplasmin, and aprotinin), and anti-inflammatory drugs (betamethasone, NS-398) in wild-type and t-PA(-/-) mice given high-dose or low-dose ibotenic acid. Intracerebral hrt-PA induced WM cystic lesions in t-PA(-/-) mice and had an additive effect when co-injected with high-dose ibotenic acid. Plasmin inhibitors reduced lesion growth in wild-type mice given high-dose, but not low-dose, ibotenic acid but had no effect in t-PA(-/-) mice. Similarly the anti-inflammatory drugs betamethasone and NS-398 (a cyclooxygenase 2 and NFkappaB inhibitor) were neuroprotective in wild-type animals exposed to high-dose, but not low-dose, ibotenic acid. Thus, the t-PA-dependent effect of low-dose ibotenic acid on cyst formation appeared independent from plasmin activity or inflammation. Conversely, a t-PA-dependent inflammatory process occurred with high-dose ibotenic acid. Potential strategies for PVL in preterm neonates may include fibrinolytic monitoring for prevention and anti-inflammatory agents for treatment.

Post-ischaemic treatment with the cyclooxygenase-2 inhibitor nimesulide reduces blood-brain barrier disruption and leukocyte infiltration following transient focal cerebral ischaemia in rats

Several studies suggest that cyclooxygenase (COX)-2 plays a pivotal role in the progression of ischaemic brain damage. In the present study, we investigated the effects of selective inhibition of COX-2 with nimesulide (12 mg/kg) and selective inhibition of COX-1 with valeryl salicylate (VAS, 12-120 mg/kg) on prostaglandin E(2) (PGE(2)) levels, myeloperoxidase (MPO) activity, Evans blue (EB) extravasation and infarct volume in a standardized model of transient focal cerebral ischaemia in the rat. Post-ischaemic treatment with nimesulide markedly reduced the increase in PGE(2) levels in the ischaemic cerebral cortex 24 h after stroke and diminished infarct size by 48% with respect to vehicle-treated animals after 3 days of reperfusion. Furthermore, nimesulide significantly attenuated the blood-brain barrier (BBB) damage and leukocyte infiltration (as measured by EB leakage and MPO activity, respectively) seen at 48 h after the initial ischaemic episode. These studies provide the first experimental evidence that COX-2 inhibition with nimesulide is able to limit BBB disruption and leukocyte infiltration following transient focal cerebral ischaemia. Neuroprotection afforded by nimesulide is observed even when the treatment is delayed until 6 h after the onset of ischaemia, confirming a wide therapeutic window of COX-2 inhibitors in experimental stroke. On the contrary, selective inhibition of COX-1 with VAS had no significant effect on the evaluated parameters. These data suggest that COX-2 activity, but not COX-1 activity, contributes to the progression of focal ischaemic brain injury, and that the beneficial effects observed with non-selective COX inhibitors are probably associated to COX-2 rather than to COX-1 inhibition.

Beneficial effects of rolipram in a quinolinic acid model of striatal excitotoxicity

Activity of c-AMP responsive element-binding protein (CREB) is decreased in Huntington's disease (HD). Such decrease was also described by our group in the quinolinic acid lesion model of striatal excitotoxicity. The phosphodiesterase type IV inhibitor rolipram increases CREB phosphorylation. Such drug has a protective effect in global ischaemia and embolism in rats. In this study, we sought to determine whether rolipram displays a neuroprotective effect in our rat model of HD. Animals were surgically administered QA and subsequently treated with rolipram daily up to 2 and 8 weeks respectively. After these time points, rats were sacrificed and immunohistochemical studies were performed in the striata. In the rolipram-treated animals, striatal lesion size was about 62% smaller that in the vehicle-treated ones at 2 weeks time point. Moreover, the surviving cell number was several times higher in the rolipram-treated animals than in the vehicle group at both time points. Rolipram also showed to be effective in increasing significantly the levels of activated CREB in the striatal spiny neurons, which accounts mostly for its beneficial effect in our rodent model of excitotoxicity. Our findings show that rolipram could be considered as a valid therapeutic approach for HD.

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.

Effect of resveratrol on 3-nitropropionic acid-induced biochemical and behavioural changes: possible neuroprotective mechanisms

Huntington's disease is a progressive, degenerative disease characterized by abnormal body movements called chorea, and a reduction of various mental abilities. 3-Nitropropionic acid, an inhibitor of complex II of the electron transport chain, causes Huntington's disease-like symptoms in rodents. Recently, it has been reported that oxidative stress, which is one of the pathological hallmarks of various neurodegenerative disorders, also plays an important role in the pathogenesis of Huntington's disease. The present study was designed to investigate effects of resveratrol, an antioxidant with cyclooxygenase I inhibitory activity, in the 3-nitropropionic acid-induced model of Huntington's disease. Intraperitoneal administration of 3-nitropropionic acid (20 mg/kg for 4 days) caused significant loss of body weight, a decline in motor function (locomotor activity, movement pattern and vacuous chewing movements) and poor retention of memory. Repeated treatment with resveratrol (5 and 10 mg/kg, orally), once daily for a period of 8 days beginning 4 days prior to 3-nitropropionic acid administration, significantly improved the 3-nitropropionic acid-induced motor and cognitive impairment. Biochemical analysis revealed that systemic 3-nitropropionic acid administration significantly increased lipid peroxidation, nitrite levels, and depleted reduced glutathione levels, and decreased succinate dehydrogenase activity in the brains of rats. The results of the present study indicate that resveratrol (5 and 10 mg/kg, orally) significantly reversed 3-nitropropionic acid-induced motor and cognitive impairment, and that the beneficial effects of resveratrol might be attributed to its antioxidant activity.

Neuroimmune-endocrine crosstalk in schizophrenia and mood disorders

This review focuses on possible causes and the impact of different immune states in schizophrenia and major depression. It discusses the fact that, in schizophrenia, an over-activation of the type 2 immune response may dominate, while the type 1 and the pro-inflammatory immune responses are over-activated in major depression. The consequence of these diverse immune states is the activation and, respectively, inhibition of different enzymes in tryptophan/kynurenine metabolism, which may lead to an overemphasis of N-methyl-D-aspartate (NMDA) receptor antagonism in schizophrenia and of NMDA-receptor agonism in depression, resulting in glutamatergic hypofunction in schizophrenia and glutamatergic hyperfunction in major depression. In addition, the activation of the type 1 and the pro-inflammatory immune responses in major depression result in increased serotonin degradation and a serotonergic deficit. While antipsychotics and antidepressants today mainly act on the dopaminergic-glutamatergic and the noradrenergic-serotonergic neurotransmission, anti-inflammatory and immune-modulating therapies might act more basically at the pathophysiological mechanism. The limitations of this concept, however, are critically discussed.

Enhanced cyclooxygenase-2 expression in olfactory-limbic forebrain following kainate-induced seizures

Cyclooxygenase-2 is expressed at low levels in a subset of neurons in CNS and is rapidly induced by a multiplicity of factors including seizure activity. A putative relationship exists between cyclooxygenase-2 induction and glutamatergic neurotransmission. Cyclooxygenase-1 is constitutively expressed in glial cells and has been specifically linked to microglia. In this study we evaluated cyclooxygenase-2 protein immunocytochemically and found markedly enhanced immunostaining primarily in olfactory-limbic regions at 2, 6 and 24 h following kainate-induced status epilepticus. Impressive enhanced cyclooxygenase-2 immunoreactivity was localized in anterior olfactory nucleus, tenia tecta, nucleus of the lateral olfactory tract, piriform cortex, lateral and basolateral amygdala, orbital frontal cortex, nucleus accumbens (shell) and associated areas of ventral striatum, entorhinal cortex, dentate gyrus granule cells and hilar neurons, hippocampal CA subfields and subiculum. Alternate sections were processed for dual immunocytochemical analysis utilizing c-Fos and cyclooxygenase-2 antiserum to examine the possibility that the neuronal induction of cyclooxygenase-2 was associated with seizure activity. Neurons that showed a timeline of cyclooxygenase-2 upregulation were found to possess c-Fos immunopositive nuclei. Additional results from all seizure groups showed cyclooxygenase-1 induction in microglia, which was confirmed by Western blot analysis of hippocampus. Western blot and real-time quantitative RT-PCR analysis showed significant upregulation of cyclooxygenase-2 expression, confirming its induction in neurons. These data indicate that cyclooxygenase-2 induction in a neuronal network can be a useful marker for pathways associated with seizure activity.

Neuroprotection in multiple sclerosis

In chronic inflammatory diseases like multiple sclerosis (MS), neuroprotection refers to strategies aimed at prevention of the irreversible damage of various neuronal and glial cell populations, and promoting regeneration. It is increasingly recognized that MS progression, in addition to demyelination, leads to substantial irreversible damage to, and loss of neurons, resulting in brain atrophy and cumulative disability. One of the most promising neuroprotective strategies involves the use of bone marrow derived stem cells. Both hematopoietic and non-hematopoietic (stromal) cells can, under certain circumstances, differentiate into cells of various neuronal and glial lineages. Neuronal stem cells have also been reported to suppress EAE by exerting direct in situ immunomodulating effects, in addition to their ability to provide a potential source for remyelination and neuroregeneration. Preliminary results from our laboratory indicate that intravenous or intracerebral/intraventricular injection of bone marrow derived stromal cells could differentiate in neuronal/glial cells and suppress the clinical signs of chronic EAE. Both bone marrow and neuronal stem cells may therefore have a therapeutic potential in MS. It seems that future treatment strategies for MS should combine immunomodulation with neuroprotective modalities to achieve maximal clinical benefit.

Down-regulation of microglial activation may represent a practical strategy for combating neurodegenerative disorders

Chronic neurodegenerative disorders are characterized by activation of microglia in the affected neural pathways. Peroxynitrite, prostanoids, and cytokines generated by these microglia can potentiate the excitotoxicity that contributes to neuronal death and dysfunction in these disorders--both by direct effects on neurons, and by impairing the capacity of astrocytes to sequester and metabolize glutamate. This suggests a vicious cycle in which the death of neurons leads to microglial activation, which in turn potentiates neuronal damage. If this model is correct, measures which down-regulate microglial activation may have a favorable effect on the induction and progression of neurodegenerative disease, independent of the particular trigger or target involved in a given disorder. Consistent with this possibility, the antibiotic minocycline, which inhibits microglial activation, shows broad utility in rodent models of neurodegeneration. Other agents which may have potential in this regard include PPARgamma agonists, genistein, vitamin D, COX-2 inhibitors, statins (and possibly policosanol), caffeine, cannabinoids, and sesamin; some of these agents could also be expected to be directly protective to neurons threatened with excitotoxicity. To achieve optimal clinical outcomes, regimens which down-regulate microglial activation could be used in conjunction with complementary measures which address other aspects of excitotoxicity.

Antiepileptic drugs and neuroprotection: current status and future roles

There has been a growing interest in the use of antiepileptic drugs (AEDs) for neuroprotection, and in the possible role of AEDs in disease modification (i.e., antiepileptogenesis). Increased understanding of the mechanisms underlying brain injury has led to advances in the study of neuroprotection. However, defining the clinical paradigm and selecting appropriate outcomes to detect neuroprotective effects present challenges to clinicians studying the neuroprotective properties of drugs. Established AEDs, such as phenytoin, phenobarbital, and carbamazepine, have shown neuroprotective activity in an ischemic/hypoxic model of neuronal injury. Animal model studies also have suggested that newer AEDs, such as levetiracetam, topiramate, and zonisamide, may have neuroprotective or antiepileptogenic properties. However, the prevention of epileptogenesis by an AED has yet to be demonstrated in clinical trials. The future of neuroprotection may involve established and newer AEDs, as well as other compounds, such as immunophilins, caspase inhibitors, endocannabinoids, and antioxidants.

Cyclooxygenase 2 (COX-2) inhibition increases the inflammatory response in the brain during systemic immune stimuli

Non-steroidal anti-inflammatory drugs (NSAIDs) and inhibitors of the cyclooxygenase (COX) pathways are currently recommended for the prevention and treatment of several inflammatory diseases, including neurodegenerative disorders. However non-selective blockade of COX was found to have pro-inflammatory properties, because they have the ability to alter the plasma glucocorticoid levels that play a critical role in the control of the innate immune response. The present study investigated the role of non-selective (ketorolac or indomethacin) or specific inhibitors of COX-1 (SC-560) and COX-2 (NS-398) in these effects. Mice challenged systemically with the endotoxin lipopolysaccharide (LPS) exhibited a robust hybridization signal for numerous inflammatory genes in vascular-associated cells of the brain and microglia across the cerebral tissue. Ketorolac, indomethacin and NS-398 significantly increased the ability of LPS to trigger such an innate immune response at time 3 h post challenge, whereas SC-560 failed to change gene expression in the brain of animals treated with the endotoxin. These data together with the crucial role of COX-2-derived prostaglandin E2 (PGE2) in the increase of glucocorticoids during systemic immune stimuli provide evidence that inhibition of this pathway results in an exacerbated early innate immune reaction. This may have a major impact on the use of these drugs in diseases where inflammation is believed to be a contributing and detrimental factor.

Novel method for in vivo hydroxyl radical measurement by microdialysis in fetal sheep brain in utero

Hydroxyl radical (.OH) is a reactive oxygen species produced during severe hypoxia, asphyxia, or ischemia that can cause cell death resulting in brain damage. Generation of .OH may occur in the fetal brain during asphyxia in utero. The very short half-life of .OH requires use of trapping agents such as salicylic acid or phenylalanine for detection, but their hydroxylated derivatives are either unstable, produced endogenously, or difficult to measure in the small volume of microdialysis samples. In the present study, we used terephthalic acid (TA), hydroxylation of which yields a stable and highly fluorometric isomer (excitation, 326 nm; emission, 432 nm). In vitro studies using .OH generated by the Fenton reaction showed that hydroxylated TA formed quickly (<10 s), was resistant to bleaching (<5% change in fluorescence), and permitted detection of <0.5 pmol .OH. In vivo studies were performed in fetal sheep using microdialysis probes implanted into the parasagittal cortex. The probe was perfused at 2 mul/min with artificial cerebrospinal fluid containing 5 mM TA, and samples were collected every 30 min. Fluorescence measured in 10 mul of dialysate was significantly greater than in the efflux from probes perfused without TA. High-performance liquid chromotography analysis showed that the fluorescence in dialysis samples was entirely due to hydroxylation of TA. Thus this study shows that it is possible to use TA as a trapping agent for detecting low concentrations of .OH both in vitro and in vivo and that low concentrations of .OH are present in fetal brain tissue and fluctuate with time.

Neuroprotection by encapsulated choroid plexus in a rodent model of Huntington’s disease

Choroid plexus from neonatal pigs was encapsulated in alginate microcapsules and transplanted into the rat striatum. Three days later, the same animals received unilateral injections of quinolinic acid (225 nmol) into the ipsilateral striatum. Choroid plexus transplants ameliorated the weight loss and motor impairments resulting from QA. Histological analysis demonstrated that choroid plexus transplants reduced the volume of striatal damage and protected ChAT-, but not NADPH-diaphorase-positive neurons. These data are the first to demonstrate that transplanted choroid plexus cells can protect striatal neurons from excitotoxic damage and that this strategy may ultimately prove relevant for the treatment of Huntington's disease.

Potential effects of tetrodotoxin exposure to human glial cells postulated using microarray approach

Sodium channels play an important role in many neurological disorders and also in prostate cancer. Tetrodotoxin (TTX), a blocker of voltage-gated sodium channels has been chiefly used as a molecular probe for the study and characterization of these channels. The regulation of gene expression in response for the exposure of TTX to glial cells which are reported to be involved in neurodegenerative process is poorly understood. Therefore, the present study aims to develop a repository of genes and map it on a few pivotal neurodegenerative pathways to speculate the effect of TTX. Using Affymetrix GeneChip (HG-U133A), we have selected a subset of 692 differentially expressed genes, several of which are-cullin 4A (CUL4A), ubiquitin carrier protein (E2-EPF), proteasome (prosome, macropain) subunit, beta type, 8 (large multifunctional protease 7) (PSMB8), protein tyrosine phosphatase type IVA (PTP4A1), intercellular adhesion molecule 1 (ICAM1), prostaglandin-endoperoxide synthase 2 (PTGS2), and caspase 1 (CASP1). These genes, which facilitate some of the neurodegenerative pathways, such as ubiquitin, proteasome, inflammation and kinases, were identified to be up- or down-regulated for the TTX treatment. Thus, the selected genes were further examined on ubiquitin-proteasome mediated inflammatory responses pathway as ample evidence for the role of glial cell-mediated inflammation in the neurodegenerative process are available. In summary, our result provides a basic understanding of the differentially expressed genes along with one of the possible pathway which may have been modulated by the exposure of TTX.

Sertoli cell grafts for Huntington's disease. An opinion

The role of inflammation in CNS diseases is controversial, but growing evidence suggests that anti-inflammatory agents can minimize and/or prevent neural degeneration and its associated behavioral consequences. Sertoli cells can be grafted into the CNS to locally deliver molecules with known trophic and anti-inflammatory effects on the surrounding tissue. When Sertoli cells are grafted into the 3-nitropropionic acid (3-NP) model of Huntington's disease the protective effects are quite similar to those obtained using systemic treatments with NSAIDS (Salzberg-Benhouse et al., J. Pharmacol. Exp. Ther. 306:218-228, 2003). While these data alone do not provide unequivocal support for the notion that Sertoli cell grafts exert their beneficial effects via modulating local inflammation, they do provide an interesting convergence between data sets. The benefits of Sertoli cell grafts should be more thoroughly examined in animal models of inflammation.