Chronic NMDA administration to rats up-regulates frontal cortex cytosolic phospholipase A2 and its transcription factor, activator protein-2

The Neurobiology of Bipolar Disorder

Bipolar disorders are severe and have a high prevalence; despite this, the neurobiological mechanisms are far from being elucidated, and this limits the development of new treatments. Although the aetiology of bipolar disorders is not yet fully understood, it is accepted that the disorder(s) may result from the interaction between genetic factors that cause susceptibility and predisposing, precipitating and perpetuating environmental factors, such as stress and traumatic events. A pathophysiological formulation of the disease suggests that dysfunctions in intracellular biochemical cascades, oxidative stress and mitochondrial dysfunction impair the processes linked to neuronal plasticity, leading to cell damage and the consequent loss of brain tissue that has been identified in post-mortem and neuroimaging studies. The data we have reviewed suggests that peripheral biomarkers related to hormones, inflammation, oxidative stress and neurotrophins are altered in bipolar disorders, especially during acute mood episodes. Together, these changes have been associated with a systemic toxicity of the disease and the damage resulting from multiple episodes. Systemic toxicity related to recurrent episodes in bipolar disorder may influence brain anatomical changes associated with the progression of stress and neuroplasticity in bipolar disorder and the response to treatment.

Minor Physical Anomalies in Bipolar Disorder

OBJECTIVE

High-arched palate is more frequent in schizophrenia and bipolar disorder (BD). Upto 40% of patients develop schizophrenia in 22q11.2 Deletion Syndrome manifested with cleft lip and palate, which originate from the first pharyngeal arch in embryo. The auricle also originates from the dorsal ends of the first and second pharyngeal arches; hence, we aimed to determine the associations between auricular anomalies and BD.

METHODS

We screened for 36 minor physical anomalies of the auricle in 146 patients with BD.

RESULTS

7 out of the of 36 assessed anomalies highly differed between healthy subjects and BD patients. A regression model including the differing anomalies predicted healthy subjects and BD-patients by 78.8% and 68.5%, respectively.

CONCLUSIONS

Assessing minor anomalies in psychiatric disorders may help to discover novel pathogenesis pathways and even new endophenotypes.

Lamotrigine as a mood stabilizer: insights from the pre-clinical evidence

INTRODUCTION

Lamotrigine (LTG) is a well-established anticonvulsant that is also approved for the prevention of mood relapses in bipolar disorder. However, the mechanisms underlying LTG mood stabilizing effects remain unclear. Areas covered: Herein, the pre-clinical evidence concerning LTG's' mode of action in depression and mania is reviewed. Bottlenecks and future perspectives for this expanding and promising field are also discussed. Pre-clinical studies have indicated that neurotransmitter systems, especially serotoninergic, noradrenergic and glutamatergic, as well as non-neurotransmitter pathways such as inflammation and oxidative processes might play a role in LTG's antidepressant effects. The mechanisms underlying LTG's anti-manic properties remain to be fully explored, but the available pre-clinical evidence points out to the role of glutamatergic neurotransmission, possibly through AMPA-receptors. Expert opinion: A major limitation of current pre-clinical investigations is that there are no experimental models that recapitulate the complexity of bipolar disorder. Significant methodological differences concerning time and dose of LTG treatment, administration route, animal strains, and behavioral paradigms also hamper the reproducibility of the findings, leading to contradictory conclusions. Moreover, the role of other mechanisms (e.g. inositol phosphate and GSK3β pathways) implicated in the mode of action of different mood-stabilizers must also be consolidated with LTG.

Retraction

Retraction: "Aging is associated with altered inflammatory, arachidonic acid cascade, and synaptic markers, influenced by epigenetic modifications, in the human frontal cortex" by Keleshian VL, Modi HR, Rapoport SI, Rao JS. The above article from Journal of Neurochemistry, published online on 17 February 2013 in Wiley Online Library (wileyonlinelibrary.com) and in volume 121, issue 1, pp. 63-73, has been retracted by agreement between the corresponding author Stanley Rapoport, the Journal's Editor-in-Chief, Jörg Schulz, and John Wiley & Sons Ltd. The Editorial Office was contacted by the author Stanley Rapoport with the request to retract this and a related publication (see below), informing the Editor-in-Chief that the National Institutes of Health (NIH) had found Dr. Jagadeesh S. Rao guilty of research misconduct by falsifying data in the referenced paper. The Editorial Office was forwarded a letter, signed by investigation committee members on behalf of NIH and NIA, which states: "[…] The National Institutes of Health (NIH) investigated allegations of research misconduct involving the falsification of data in "Aging is associated with altered inflammatory, arachidonic acid cascade, and synaptic markers, influenced by epigenetic modifications, in the human frontal cortex." Keleshian VL, Modi HR, Rapoport SI, Rao JS. Journal of Neurochemistry 2013 Apr; 125(1): 63-73. Based on the unanimous decision of a five member committee, composed of NIH investigators, NIH found that Dr. Jagadeesh Rao, corresponding author, knowingly and intentionally committed research misconduct by falsifying data in Figures 1A, 1G, 3G, and 4D in the manuscript(s) listed above. Dr. Rao was solely responsible for the falsification and all other authors were uninvolved. The report was submitted to the HHS Office of Research Integrity for its review. Because Dr. Rao was the corresponding author, Dr. Stanley I. Rapoport, Senior Advisor for the former Laboratory of Brain Physiology and Metabolism Section, is acting for Dr. Rao, who was his representative, and approves this request to retract this publication using the recommended language, in italics above." A related paper has also been retracted: Rao JS, Ertley RN, Rapoport SI, Bazinet RP, Lee HJ. (2007) Chronic NMDA administration to rats up-regulates frontal cortex cytosolic phospholipase A₂ and its transcription factor, activator protein-2. J. Neurochem. 102: 1918-1927. References Keleshian V. L., Modi H. R., Rapoport S. I. and Rao J. S. (2013) Aging is associated with altered inflammatory, arachidonic acid cascade, and synaptic markers, influenced by epigenetic modifications, in the human frontal cortex. J. Neurochem. 125, 63-73. Rao J. S., Ertley R. N., Rapoport S. I., Bazinet R. P. and Lee H. J. (2007) Chronic NMDA administration to rats up-regulates frontal cortex cytosolic phospholipase A₂ and its transcription factor, activator protein-2. J. Neurochem. 102, 1918-1927.

Reconsidering Dietary Polyunsaturated Fatty Acids in Bipolar Disorder: A Translational Picture

Inflammation is an important mediator of pathophysiology in bipolar disorder. The omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acid (PUFA) metabolic pathways participate in several inflammatory processes and have been linked through epidemiologic and clinical studies to bipolar disorder and its response to treatment. We review the proposed role of PUFA metabolism in neuroinflammation, modulation of brain PUFA metabolism by antimanic medications in rodent models, and anti-inflammatory pharmacotherapy in bipolar disorder and in major depressive disorder (MDD). Although the convergence of findings between preclinical and postmortem clinical data is compelling, we investigate why human trials of PUFA as treatment are mixed. We view the biomarker and treatment study findings in light of the evidence for the hypothesis that arachidonic acid hypermetabolism contributes to bipolar disorder pathophysiology and propose that a combined high n-3 plus low n-6 diet should be tested as an adjunct to current medication in future trials.

Ionotropic glutamate receptors: Which ones, when, and where in the mammalian neocortex

A multitude of 18 iGluR receptor subunits, many of which are diversified by splicing and RNA editing, localize to >20 excitatory and inhibitory neocortical neuron types defined by physiology, morphology, and transcriptome in addition to various types of glial, endothelial, and blood cells. Here we have compiled the published expression of iGluR subunits in the areas and cell types of developing and adult cortex of rat, mouse, carnivore, bovine, monkey, and human as determined with antibody- and mRNA-based techniques. iGluRs are differentially expressed in the cortical areas and in the species, and all have a unique developmental pattern. Differences are quantitative rather than a mere absence/presence of expression. iGluR are too ubiquitously expressed and of limited use as markers for areas or layers. A focus has been the iGluR profile of cortical interneuron types. For instance, GluK1 and GluN3A are enriched in, but not specific for, interneurons; moreover, the interneurons expressing these subunits belong to different types. Adressing the types is still a major hurdle because type-specific markers are lacking, and the frequently used neuropeptide/CaBP signatures are subject to regulation by age and activity and vary as well between species and areas. RNA-seq reveals almost all subunits in the two morphofunctionally characterized interneuron types of adult cortical layer I, suggesting a fairly broad expression at the RNA level. It remains to be determined whether all proteins are synthesized, to which pre- or postsynaptic subdomains in a given neuron type they localize, and whether all are involved in synaptic transmission. J. Comp. Neurol. 525:976-1033, 2017. © 2016 Wiley Periodicals, Inc.

Mitochondrial dysfunction in bipolar disorder: Evidence, pathophysiology and translational implications

Bipolar disorder (BD) is a chronic psychiatric illness characterized by severe and biphasic changes in mood. Several pathophysiological mechanisms have been hypothesized to underpin the neurobiology of BD, including the presence of mitochondrial dysfunction. A confluence of evidence points to an underlying dysfunction of mitochondria, including decreases in mitochondrial respiration, high-energy phosphates and pH; changes in mitochondrial morphology; increases in mitochondrial DNA polymorphisms; and downregulation of nuclear mRNA molecules and proteins involved in mitochondrial respiration. Mitochondria play a pivotal role in neuronal cell survival or death as regulators of both energy metabolism and cell survival and death pathways. Thus, in this review, we discuss the genetic and physiological components of mitochondria and the evidence for mitochondrial abnormalities in BD. The final part of this review discusses mitochondria as a potential target of therapeutic interventions in BD.

Management of bipolar depression with lamotrigine: an antiepileptic mood stabilizer

The efficacy of lamotrigine in the treatment of focal epilepsies have already been reported in several case reports and open studies, which is thought to act by inhibiting glutamate release through voltage-sensitive sodium channels blockade and neuronal membrane stabilization. However, recent findings have also illustrated the importance of lamotrigine in alleviating the depressive symptoms of bipolar disorder, without causing mood destabilization or precipitating mania. Currently, no mood stabilizers are available having equal efficacy in the treatment of both mania and depression, two of which forms the extreme sides of the bipolar disorder. Lamotrigine, a well established anticonvulsant has received regulatory approval for the treatment and prevention of bipolar depression in more than 30 countries worldwide. Lamotrigine, acts through several molecular targets and overcomes the major limitation of other conventional antidepressants by stabilizing mood from “below baseline” thereby preventing switches to mania or episode acceleration, thus being effective for bipolar I disorder. Recent studies have also suggested that these observations could also be extended to patients with bipolar II disorder. Thus, lamotrigine may supposedly fulfill the unmet requirement for an effective depression mood stabilizer.

Implications of glial nitric oxide in neurodegenerative diseases

Nitric oxide (NO) is a pleiotropic janus-faced molecule synthesized by nitric oxide synthases (NOS) which plays a critical role in a number of physiological and pathological processes in humans. The physiological roles of NO depend on its local concentrations, as well as its availability and the nature of downstream target molecules. Its double-edged sword action has been linked to neurodegenerative disorders. Excessive NO production, as the evoked by inflammatory signals, has been identified as one of the major causative reasons for the pathogenesis of several neurodegenerative diseases. Moreover, excessive NO synthesis under neuroinflammation leads to the formation of reactive nitrogen species and neuronal cell death. There is an intimate relation between microglial activation, NO and neuroinflammation in the human brain. The role of NO in neuroinflammation has been defined in animal models where this neurotransmitter can modulate the inflammatory process acting on key regulatory pathways, such as those associated with excitotoxicity processes induced by glutamate accumulation and microglial activation. Activated glia express inducible NOS and produce NO that triggers calcium mobilization from the endoplasmic reticulum, activating the release of vesicular glutamate from astroglial cells resulting in neuronal death. This change in microglia potentially contributes to the increased age-associated susceptibility and neurodegeneration. In the current review, information is provided about the role of NO, glial activation and age-related processes in the central nervous system (CNS) that may be helpful in the isolation of new therapeutic targets for aging and neurodegenerative diseases.

Reduced mRNA expression of PTGDS in peripheral blood mononuclear cells of rapid-cycling bipolar disorder patients compared with healthy control subjects

BACKGROUND

Disturbances related to the arachidonic acid cascade and prostaglandin metabolism may be involved in the pathophysiology of bipolar disorder, as supported by a recent genome-wide association study meta-analysis; however, evidence from clinical studies on a transcriptional level is lacking. Two enzymes in the arachidonic acid cascade are the prostaglandin D synthase (PTGDS), which catalyzes the conversion of prostaglandin H2 to prostaglandin D2 (PGD2), and the aldo-keto reductase family 1 member C3 (AKR1C3), which catalyzes the reduction of PGD2. We aimed to test the hypothesis that mRNA expression of PTGDS and AKR1C3 is deregulated in rapid-cycling disorder patients in a euthymic or current affective state compared with healthy control subjects, and that expression alters with affective states.

METHODS

PTGDS and AKR1C3 mRNA expression in peripheral blood mononuclear cells was measured in 37 rapid-cycling bipolar disorder patients and 40 age- and gender-matched healthy control subjects using reverse transcription quantitative real-time polymerase chain reaction. Repeated measurements of PTGDS and AKR1C3 mRNA expression were obtained in various affective states during 6-12 months and compared with repeated measurements in healthy control subjects.

RESULTS

Adjusted for age and gender, PTGDS mRNA expression was down-regulated in rapid-cycling bipolar disorder patients in a euthymic, depressive, and manic/hypomanic state compared with healthy control subjects. No difference in PTGDS mRNA expression was observed between affective states. AKR1C3 mRNA expression did not differ between bipolar disorder patients in any affective state or in comparison with healthy control subjects.

CONCLUSIONS

The results suggest a role for aberrantly-regulated PTGDS mRNA expression in rapid-cycling bipolar disorder. The sample size was limited; replication of the findings in larger, independent samples is warranted to further explore the role of the arachidonic acid cascade and prostaglandin metabolism as a potential therapeutic target in bipolar disorder.

A genome-wide linkage scan of bipolar disorder in Latino families identifies susceptibility loci at 8q24 and 14q32

A genome-wide nonparametric linkage screen was performed to localize Bipolar Disorder (BP) susceptibility loci in a sample of 3757 individuals of Latino ancestry. The sample included 963 individuals with BP phenotype (704 relative pairs) from 686 families recruited from the US, Mexico, Costa Rica, and Guatemala. Non-parametric analyses were performed over a 5 cM grid with an average genetic coverage of 0.67 cM. Multipoint analyses were conducted across the genome using non-parametric Kong & Cox LOD scores along with Sall statistics for all relative pairs. Suggestive and significant genome-wide thresholds were calculated based on 1000 simulations. Single-marker association tests in the presence of linkage were performed assuming a multiplicative model with a population prevalence of 2%. We identified two genome-wide significant susceptibly loci for BP at 8q24 and 14q32, and a third suggestive locus at 2q13-q14. Within these three linkage regions, the top associated single marker (rs1847694, P = 2.40 × 10(-5)) is located 195 Kb upstream of DPP10 in Chromosome 2. DPP10 is prominently expressed in brain neuronal populations, where it has been shown to bind and regulate Kv4-mediated A-type potassium channels. Taken together, these results provide additional evidence that 8q24, 14q32, and 2q13-q14 are susceptibly loci for BP and these regions may be involved in the pathogenesis of BP in the Latino population.

RETRACTED: Increased neuroinflammatory and arachidonic acid cascade markers, and reduced synaptic proteins, in the postmortem frontal cortex from schizophrenia patients

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editors. The National Institutes of Health has found that Dr. Jagadeesh S. Rao engaged in research misconduct by falsifying data. Data in Figures 1A, 1E, 3E and 3F were falsified. Dr. Rao was solely responsible for the falsification. None of the other authors are implicated in any way.

Propylisopropylacetic acid (PIA), a constitutional isomer of valproic acid, uncompetitively inhibits arachidonic acid acylation by rat acyl-CoA synthetase 4: a potential drug for bipolar disorder

BACKGROUND

Mood stabilizers used for treating bipolar disorder (BD) selectively downregulate arachidonic acid (AA) turnover (deacylation-reacylation) in brain phospholipids, when given chronically to rats. In vitro studies suggest that one of these, valproic acid (VPA), which is teratogenic, reduces AA turnover by inhibiting the brain long-chain acyl-CoA synthetase (Acsl)4 mediated acylation of AA to AA-CoA. We tested whether non-teratogenic VPA analogues might also inhibit Acsl4 catalyzed acylation, and thus have a potential anti-BD action.

METHODS

Rat Acsl4-flag protein was expressed in Escherichia coli, and the ability of three VPA analogues, propylisopropylacetic acid (PIA), propylisopropylacetamide (PID) and N-methyl-2,2,3,3-tetramethylcyclopropanecarboxamide (MTMCD), and of sodium butyrate, to inhibit conversion of AA to AA-CoA by Acsl4 was quantified using Michaelis-Menten kinetics.

RESULTS

Acsl4-mediated conversion of AA to AA-CoA in vitro was inhibited uncompetitively by PIA, with a Ki of 11.4mM compared to a published Ki of 25mM for VPA, while PID, MTMCD and sodium butyrate had no inhibitory effect.

CONCLUSIONS

PIA's ability to inhibit conversion of AA to AA-CoA by Acsl4 in vitro suggests that, like VPA, PIA may reduce AA turnover in brain phospholipids in unanesthetized rats, and if so, may be effective as a non-teratogenic mood stabilizer in BD patients.

Upregulated expression of brain enzymatic markers of arachidonic and docosahexaenoic acid metabolism in a rat model of the metabolic syndrome

Background

In animal models, the metabolic syndrome elicits a cerebral response characterized by altered phospholipid and unesterified fatty acid concentrations and increases in pro-apoptotic inflammatory mediators that may cause synaptic loss and cognitive impairment. We hypothesized that these changes are associated with phospholipase (PLA₂) enzymes that regulate arachidonic (AA, 20:4n-6) and docosahexaenoic (DHA, 22:6n-6) acid metabolism, major polyunsaturated fatty acids in brain. Male Wistar rats were fed a control or high-sucrose diet for 8 weeks. Brains were assayed for markers of AA metabolism (calcium-dependent cytosolic cPLA₂ IVA and cyclooxygenases), DHA metabolism (calcium-independent iPLA₂ VIA and lipoxygenases), brain-derived neurotrophic factor (BDNF), and synaptic integrity (drebrin and synaptophysin). Lipid concentrations were measured in brains subjected to high-energy microwave fixation.

Results

The high-sucrose compared with control diet induced insulin resistance, and increased phosphorylated-cPLA₂ protein, cPLA₂ and iPLA₂ activity and 12-lipoxygenase mRNA, but decreased BDNF mRNA and protein, and drebrin mRNA. The concentration of several n-6 fatty acids in ethanolamine glycerophospholipids and lysophosphatidylcholine was increased, as was unesterified AA concentration. Eicosanoid concentrations (prostaglandin E₂, thromboxane B₂ and leukotriene B₄) did not change.

Conclusion

These findings show upregulated brain AA and DHA metabolism and reduced BDNF and drebrin, but no changes in eicosanoids, in an animal model of the metabolic syndrome. These changes might contribute to altered synaptic plasticity and cognitive impairment in rats and humans with the metabolic syndrome.

Brain glutamate levels measured by magnetic resonance spectroscopy in patients with bipolar disorder: a meta-analysis

OBJECTIVES

Bipolar disorder (BD) is a common and highly disabling disease characterized by substantial cognitive and functional impairment. The exact neurobiological mechanisms underlying the expression of symptoms in this condition remain unknown but there is growing evidence that glutamate might play an important role. Using proton magnetic resonance spectroscopy (¹H-MRS), a number of studies have examined brain glutamate/glutamine levels in patients with bipolar disorder, but they have produced conflicting results. The objective of this paper was to conduct a systematic review and meta-analysis of the literature on brain glutamate/glutamine in BD as measured by ¹H-MRS.

METHODS

A Medline search for the period January 1980-April 2010 was conducted to identify published studies that used ¹H-MRS to measure glutamate + glutamine (Glx), the Glx/creatine (Cr) ratio, glutamate (Glu), or the Glu/Cr ratio in any brain region in adult or child/adolescent patients with BD and healthy subjects. A meta-analysis of the pooled data was conducted.

RESULTS

BD patients were found to have increased Glx compared to healthy subjects when all brain areas were combined. This finding remained true in medicated and non-medicated patients, and in frontal brain areas in adults. There was a non-significant trend (p = 0.09) for an increase in whole-brain Glx/Cr and Glu in patients compared with healthy subjects. No significant difference was found in Glu/Cr.

CONCLUSIONS

The results of this meta-analysis suggest that brain Glx levels are elevated in BD patients and support the idea that glutamate might play an important role in the pathophysiology of BD.

Lamotrigine blocks NMDA receptor-initiated arachidonic acid signalling in rat brain: implications for its efficacy in bipolar disorder

An up-regulated brain arachidonic acid (AA) cascade and a hyperglutamatergic state characterize bipolar disorder (BD). Lamotrigine (LTG), a mood stabilizer approved for treating BD, is reported to interfere with glutamatergic neurotransmission involving N-methyl-d-aspartate receptors (NMDARs). NMDARs allow extracellular calcium into the cell, thereby stimulating calcium-dependent cytosolic phospholipase A2 (cPLA2) to release AA from membrane phospholipid. We hypothesized that LTG, like other approved mood stabilizers, would reduce NMDAR-mediated AA signalling in rat brain. An acute subconvulsant dose of NMDA (25 mg/kg) or saline was administered intraperitoneally to unanaesthetized rats that had been treated p.o. daily for 42 d with vehicle or a therapeutically relevant dose of LTG (10 mg/kg.d). Regional brain AA incorporation coefficients k* and rates J in, and AA signals, were measured using quantitative autoradiography after intravenous [1-14C]AA infusion, as were other AA cascade markers. In chronic vehicle-treated rats, acute NMDA compared to saline increased k* and J in in widespread regions of the brain, as well as prostaglandin (PG)E2 and thromboxane B2 concentrations. Chronic LTG treatment compared to vehicle reduced brain cyclooxygenase (COX) activity, PGE2 concentration, and DNA-binding activity of the COX-2 transcription factor, NF-κB. Pretreatment with chronic LTG blocked the acute NMDA effects on AA cascade markers. In summary, chronic LTG like other mood stabilizers blocks NMDA-mediated signalling involving the AA metabolic cascade. Since markers of the AA cascade and of NMDAR signalling are up-regulated in the post-mortem BD brain, mood stabilizers generally may be effective in BD by dampening NMDAR signalling and the AA cascade.

Brain anticonvulsant protection of mice given chronic carbamazepine under various fatty acid and magnesium diet conditions

The anticonvulsant and mood stabilizer drug carbamazepine (CBZ) was evaluated for anti-seizure activity after drug pretreatment of young weaning mice given various oil-based diets. These diets had various mono-(MUFA) and poly-(PUFA) unsaturated fatty acid contents, were associated or not with magnesium deprivation, and were given over the entire experimental period (34 days). The diets included a commercial and three purified synthetic diets (n-6 PUFA, n-3 PUFA and MUFA-based chows containing 5% corn/sunflower oils 1:3, 5% rapeseed oil and 5% high oleic acid sunflower oil/sunflower oil 7:3, respectively). A 10-days CBZ treatment (50 mg/kg/day fragmented in two daily intraperitoneal injections of 25 mg/kg) was given 20 days after initiating diet administration and evaluations of mice was performed 4 days after arrest of CBZ in various seizure tests. In these conditions, CBZ pretreatment still exhibited anticonvulsant protection especially in magnesium-deficient animals. Ethosuximide (ESM)-like profiles under MUFA and n-3 PUFA diets and unusual GABA(A)ergic profile under n-6 PUFA diet in magnesium-deficiency dependent audiogenic seizures (MDDAS) test as well as protection against NMDA-induced seizures in all lipid (n-3 PUFA>MUFA and n-6 PUFA) diet conditions were observed in CBZ-pretreated mice. By highlighting ESM-like and anti-NMDA mechanisms previously induced by an n-3 PUFA diet, present CBZ anticonvulsant properties suggest brain protective targets common to CBZ and n-3 PUFAs.

Epigenetic modifications in frontal cortex from Alzheimer's disease and bipolar disorder patients

Alzheimer's disease (AD) and bipolar disorder (BD) are progressive brain disorders. Upregulated mRNA and protein levels of neuroinflammatory and arachidonic acid (AA) markers with loss of synaptic markers (synaptophysin and drebrin) have been reported in brain tissue from AD and BD patients. We hypothesized that some of these changes are associated with epigenetic modifications of relevant genes. To test this, we measured gene-specific CpG methylation, global DNA methylation and histone modifications in postmortem frontal cortex from BD (n=10) and AD (n=10) patients and respective age-matched controls (10 per group). AD and BD brains showed several epigenetic similarities, including global DNA hypermethylation, and histone H3 phosphorylation. These changes were associated with hypo- and hypermethylation of CpG islands in cyclooxygenase-2 and brain-derived neurotrophic factor promoter regions, respectively. Only the AD brain showed hyper- and hypomethylated CpG islands in promoter regions for cAMP response element-binding protein and nuclear transcription factor kappa B genes, respectively. Only the BD brain demonstrated increased global histone H3 acetylation and hypermethylation of the promotor region for the drebrin-like protein gene. There was no significant epigenetic modification for 12-lipooxygenase or p450 epoxygenase in either illness. Many observed epigenetic changes were inversely related to respective changes in mRNA and protein levels. These epigenetic modifications involving neuroinflammatory, AA cascade and synaptic markers may contribute to progression in AD and BD and identify new targets for drug development.

Neuroinflammation and synaptic loss

Neuroinflammation plays a critical role in the progression of many neurodegenerative, neuropsychiatric and viral diseases. In neuroinflammation, activated microglia and astrocytes release cytokines and chemokines as well as nitric oxide, which in turn activate many signal transduction pathways. The cytokines, interleukin-1 beta and tumor necrosis factor alpha, regulate transcription of a number of genes within the brain, which can lead to the formation of pro-inflammatory products of the arachidonic acid cascade. Formation of pro-inflammatory agents and associated cytotoxic products during neuroinflammation can be detrimental to neurons by altering synaptic proteins. Neuroinflammation as well as excitotoxic insults reduce synaptic markers such as synaptophysin and drebrin. Neurodegenerative, neuropsychiatric illnesses and viral infections are accompanied by loss of both pre- and post-synaptic proteins. These synaptic changes may contribute to the progressive cognitive decline and behavioral changes associated with these illnesses.

Neuroprotection by mefenamic acid against D-serine: involvement of oxidative stress, inflammation and apoptosis

Mefenamic acid, a non-steroidal antiinflammatory drug (NSAID), directly and dose-dependently exhibits neuroprotective activity. In our study, we investigated the effects of mefenamic acid against d-serine on oxidative stress in the hippocampus, cortex and cerebellum of rats. Furthermore, the potential inflammatory and apoptotic effects of d-serine and potential protective effect of mefenamic acid were determined at mRNA and protein levels of TNF-α, IL-1β, Bcl-2 and Bax. We found that d-serine significantly increased oxidative stress, levels of inflammation- and apoptosis-related molecules in a region specific manner. Mefenamic acid treatment provided significant protection against the elevation of lipid peroxidation, protein oxidation, levels of TNF-α, IL-1β and Bax. As a conclusion, we suggest that d-serine, as a potential neurodegenerative agent, may have a pivotal role in the regulation of oxidative stress, inflammation and apoptosis; and NSAIDs, such as mefenamic acid, may assist other therapeutics in treating disorders where d-serine-induced neurotoxic mechanisms are involved in.

GluN3 subunit-containing NMDA receptors: not just one-trick ponies

The two GluN3 subunits were the last NMDA receptor subunits to be cloned some 15 years ago. Strikingly, despite the steadily growing interest in their function, their physiological role remains elusive. The original billing as dominant-negative modulators of classical NMDA receptors composed of GluN1 and GluN2 subunits has given way to proposals of much more complex functions, including roles in synaptogenesis and synaptic plasticity. In addition, GluN3 subunits in the absence of GluN2 surprisingly assemble with GluN1 into excitatory glycine receptors. This review provides an overview of the unique spatial and temporal expression patterns of the GluN3 subunits, discusses proposed functions and physiological roles for receptors comprising these subunits, and briefly summarizes their putative involvement in several neural diseases.

RETRACTED: Dysregulated glutamate and dopamine transporters in postmortem frontal cortex from bipolar and schizophrenic patients

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of The National Institutes of Health has found that the first author, Dr. Jagadeesh S. Rao engaged in research misconduct by falsifying data in “Dysregulated glutamate and dopamine transporters in postmortem frontal cortex from bipolar and schizophrenic patients”. Rao JS, Kellom M, Reese EA, Rapoport SI, Kim HW. J. Affect Disord. 136(1–2):63–71. 2012. Data in Figures 2A, 2B, 3A, 3B and 4A were falsified.

Chronic olanzapine treatment decreases arachidonic acid turnover and prostaglandin E₂ concentration in rat brain

The atypical antipsychotic, olanzapine (OLZ), is used to treat bipolar disorder, but its therapeutic mechanism of action is not clear. Arachidonic acid (AA, 20:4n-6) plays a critical role in brain signaling and an up-regulated AA metabolic cascade was reported in postmortem brains from bipolar disorder patients. In this study, we tested whether, similar to the action of the mood stabilizers lithium, carbamazepine and valproate, chronic OLZ treatment would reduce AA turnover in rat brain. We administered OLZ (6 mg/kg/day) or vehicle i.p. to male rats once daily for 21 days. A washout group received 21 days of OLZ followed by vehicle on day 22. Two hours after the last injection, [1-¹⁴C]AA was infused intravenously for 5 min, and timed arterial blood samples were taken. After the rat was killed at 5 min, its brain was microwaved, removed and analyzed. Chronic OLZ decreased plasma unesterified AA concentration, AA incorporation rates and AA turnover in brain phospholipids. These effects were absent after washout. Consistent with reduced AA turnover, OLZ decreased brain cyclooxygenase activity and the brain concentration of the proinflammatory AA-derived metabolite, prostaglandin E₂, In view of up-regulated brain AA metabolic markers in bipolar disorder, the abilities of OLZ and the mood stabilizers to commonly decrease prostaglandin E₂, and AA turnover in rat brain phospholipids, albeit by different mechanisms, may be related to their efficacy against the disease.

Increased neuroinflammatory and arachidonic acid cascade markers, and reduced synaptic proteins, in brain of HIV-1 transgenic rats

Background

Cognitive impairment has been reported in human immune deficiency virus-1- (HIV-1-) infected patients as well as in HIV-1 transgenic (Tg) rats. This impairment has been linked to neuroinflammation, disturbed brain arachidonic acid (AA) metabolism, and synapto-dendritic injury. We recently reported upregulated brain AA metabolism in 7- to 9-month-old HIV-1 Tg rats. We hypothesized that these HIV-1 Tg rats also would show upregulated brain inflammatory and AA cascade markers and a deficit of synaptic proteins.

Methods

We measured protein and mRNA levels of markers of neuroinflammation and the AA cascade, as well as pro-apoptotic factors and synaptic proteins, in brains from 7- to 9-month-old HIV-1 Tg and control rats.

Results

Compared with control brain, HIV-1 Tg rat brain showed immunoreactivity to glycoprotein 120 and tat HIV-1 viral proteins, and significantly higher protein and mRNA levels of (1) the inflammatory cytokines interleukin-1β and tumor necrosis factor α, (2) the activated microglial/macrophage marker CD11b, (3) AA cascade enzymes: AA-selective Ca²⁺-dependent cytosolic phospholipase A₂ (cPLA₂)-IVA, secretory sPLA₂-IIA, cyclooxygenase (COX)-2, membrane prostaglandin E₂ synthase, 5-lipoxygenase (LOX) and 15-LOX, cytochrome p450 epoxygenase, and (4) transcription factor NF-κBp50 DNA binding activity. HIV-1 Tg rat brain also exhibited signs of cell injury, including significantly decreased levels of brain-derived neurotrophic factor (BDNF) and drebrin, a marker of post-synaptic excitatory dendritic spines. Expression of Ca²⁺-independent iPLA₂-VIA and COX-1 was unchanged.

Conclusions

HIV-1 Tg rats show elevated brain markers of neuroinflammation and AA metabolism, with a deficit in several synaptic proteins. These changes are associated with viral proteins and may contribute to cognitive impairment. The HIV-1 Tg rat may be a useful model for understanding progression and treatment of cognitive impairment in HIV-1 patients.

Altered arachidonic acid cascade enzymes in postmortem brain from bipolar disorder patients

Mood stabilizers that are approved for treating bipolar disorder (BD), when given chronically to rats, decrease expression of markers of the brain arachidonic metabolic cascade, and reduce excitotoxicity and neuroinflammation-induced upregulation of these markers. These observations, plus evidence for neuroinflammation and excitotoxicity in BD, suggest that arachidonic acid (AA) cascade markers are upregulated in the BD brain. To test this hypothesis, these markers were measured in postmortem frontal cortex from 10 BD patients and 10 age-matched controls. Mean protein and mRNA levels of AA-selective cytosolic phospholipase A(2) (cPLA(2)) IVA, secretory sPLA(2) IIA, cyclooxygenase (COX)-2 and membrane prostaglandin E synthase (mPGES) were significantly elevated in the BD cortex. Levels of COX-1 and cytosolic PGES (cPGES) were significantly reduced relative to controls, whereas Ca(2+)-independent iPLA(2)VIA, 5-, 12-, and 15-lipoxygenase, thromboxane synthase and cytochrome p450 epoxygenase protein and mRNA levels were not significantly different. These results confirm that the brain AA cascade is disturbed in BD, and that certain enzymes associated with AA release from membrane phospholipid and with its downstream metabolism are upregulated. As mood stabilizers downregulate many of these brain enzymes in animal models, their clinical efficacy may depend on suppressing a pathologically upregulated cascade in BD. An upregulated cascade should be considered as a target for drug development and for neuroimaging in BD.

Imaging upregulated brain arachidonic acid metabolism in HIV-1 transgenic rats

Human immunodeficiency virus (HIV)-associated infection involves the entry of virus-bearing monocytes into the brain, followed by microglial activation, neuroinflammation, and upregulated arachidonic acid (AA) metabolism. The HIV-1 transgenic (Tg) rat, a noninfectious HIV-1 model, shows neurologic and behavioral abnormalities after 5 months of age. We hypothesized that brain AA metabolism would be elevated in older HIV-1 Tg rats in vivo. Arachidonic acid incorporation from the plasma into the brain of unanesthetized 7-to-9-month-old rats was imaged using quantitative autoradiography, after [1-(14)C]AA infusion. Brain phospholipase (PLA(2)) activities and eicosanoid concentrations were measured, and enzymes were localized by immunostaining. AA incorporation coefficients k* and rates J(in), measures of AA metabolism, were significantly higher in 69 of 81 brain regions in HIV-1 Tg than in control rats, as were activities of cytosolic (c)PLA(2)-IV, secretory (s)PLA(2), and calcium independent (i)PLA(2)-VI, as well as prostaglandin E(2) and leukotriene B(4) concentrations. Immunostaining of somatosensory cortex showed elevated cPLA(2)-IV, sPLA(2)-IIA, and cyclooxygenase-2 in neurons. Brain AA incorporation and other markers of AA metabolism are upregulated in HIV-1 Tg rats, in which neurologic changes and neuroinflammation have been reported. Positron emission tomography with [1-(11)C]AA could be used to test whether brain AA metabolism is upregulated in HIV-1-infected patients, in relation to cognitive and behavioral disturbances.

Signal transduction pathways in the pathophysiology of bipolar disorder

Signal transduction pathways and genes associated with cellular life and death have received much attention in bipolar disorder (BPD) and provide scientists with molecular targets for understanding the biological basis of BPD. In this chapter, we describe the signal transduction pathways involved in the molecular biology of BPD and the indications for the mechanisms of disease and treatment. We discuss the BPD literature with respect to the disease itself and the effects of mood stabilizer treatment on cellular receptors, including G-protein-coupled receptors, glutamate receptors, and tyrosine receptor kinase. We also discuss the intracellular alterations observed in BPD to second messenger systems, such as cyclic adenosine monophosphate (cAMP), protein kinase A, phosphoinositide pathways, glycogen synthase kinase-3, protein kinase B, Wnt, and arachidonic acid. We describe how receptor activation and modulation of second messengers occurs, and how transcription factors are activated and altered in this disease (e.g., the transcription factors ?-catenin, cAMP response element binding protein, heat shock transcription factor-1, and activator protein-1). Abnormalities in intracellular signal transduction pathways could generate a functional discrepancy in numerous neurotransmitter systems, which may explain the varied clinical symptoms observed in BPD. The influence of mood stabilizers on transcription factors may be important in connecting the regulation of gene expression to neuroplasticity and cellular resilience.

Is there a role for the nuclear receptor PPARγ in neuropsychiatric diseases?

The aetiology of psychiatric diseases such as depression or schizophrenia remains largely unknown, even though multiple theories have been proposed. Although monoamine theory is the cornerstone of available pharmacological therapies, relapses, incomplete control of symptoms or failure in treatment occur frequently. From an inflammatory/immune point of view, both entities share several common hallmarks in their pathophysiology, e.g. neuroendocrine/immune alterations, structural/functional abnormalities in particular brain areas, and cognitive deficits, suggesting a dysregulated inflammatory-related component of these diseases that better explains the myriad of symptoms presented by affected individuals. In this review we aimed to explore the role and relevance of inflammatory related lipids (prostanoids) derived from arachidonic acid metabolism by identification of new inflammatory markers and possible pharmacological/dietary modulation of these compounds, with the aim of improving some of the symptoms developed by individuals affected with psychiatric diseases (a critical review of basic and clinical studies about inflammatory-related arachidonic acid metabolism on neuropsychiatric diseases is included). As a specific candidate, one of these immunoregulatory lipids, the anti-inflammatory prostaglandin 15d-PGJ₂ and its nuclear receptor peroxisome proliferator-activated nuclear receptor (PPARγ) could be used as a biological marker for psychiatric diseases. In addition, its pharmacological activation can be considered as a multi-faceted therapeutic target due to its anti-inflammatory/antioxidant/anti-excitotoxic/pro-energetic profile, reported in some inflammatory-related scenarios (neurological and stress-related diseases). PPARs are activated by a great variety of compounds, the most relevant being the currently prescribed group of anti-diabetic drugs thiazolidinediones, and some cannabinoids (both endocannabinoids, phytocannabinoids or synthetic), as possible novel therapeutical strategy.

Extracellular-derived calcium does not initiate in vivo neurotransmission involving docosahexaenoic acid

In vitro studies show that docosahexaenoic acid (DHA) can be released from membrane phospholipid by Ca(2+)-independent phospholipase A(2) (iPLA(2)), Ca(2+)-independent plasmalogen PLA(2) or secretory PLA(2 (sPLA2)), but not by Ca(2+)-dependent cytosolic PLA(2) (cPLA2), which selectively releases arachidonic acid (AA). Since glutamatergic NMDA (N-methyl-D-aspartate) receptor activation allows extracellular Ca(2+) into cells, we hypothesized that brain DHA signaling would not be altered in rats given NMDA, to the extent that in vivo signaling was mediated by Ca(2+)-independent mechanisms. Isotonic saline, a subconvulsive dose of NMDA (25 mg/kg), MK-801, or MK-801 followed by NMDA was administered i.p. to unanesthetized rats. Radiolabeled DHA or AA was infused intravenously and their brain incorporation coefficients k*, measures of signaling, were imaged with quantitative autoradiography. NMDA or MK-801 compared with saline did not alter k* for DHA in any of 81 brain regions examined, whereas NMDA produced widespread and significant increments in k* for AA. In conclusion, in vivo brain DHA but not AA signaling via NMDA receptors is independent of extracellular Ca(2+) and of cPLA(2). DHA signaling may be mediated by iPLA(2), plasmalogen PLA(2), or other enzymes insensitive to low concentrations of Ca(2+). Greater AA than DHA release during glutamate-induced excitotoxicity could cause brain cell damage.

Chronic imipramine but not bupropion increases arachidonic acid signaling in rat brain: is this related to 'switching' in bipolar disorder?

Agents effective against mania in bipolar disorder are reported to decrease turnover of arachidonic acid (AA) in phospholipids and expression of calcium-dependent AA-selective cytosolic phospholipase A(2) (cPLA(2)) in rat brain. In contrast, fluoxetine, an antidepressant that is reported to switch bipolar depressed patients to mania, increases cPLA(2) expression and AA turnover in rat brain. We therefore hypothesized that antidepressants that increase switching to mania generally increase cPLA(2) and AA turnover in brain. To test this hypothesis, adult male CDF-344 rats were administered imipramine and bupropion, with reported high and low switching rates, respectively, at daily doses of 10 and 30 mg kg(-1) i.p., respectively, or i.p. saline (control) for 21 days. Frontal cortex expression of different PLA(2) enzymes and AA turnover rates in brain when the rats were unanesthetized were measured. Compared with chronic saline, chronic imipramine but not bupropion significantly increased cortex cPLA(2) mRNA activity, protein and phosphorylation, expression of the cPLA(2) transcription factor, activator protein-2alpha (AP-2alpha) and AA turnover in phospholipids. Protein levels of secretory phospholipase A(2), calcium-independent phospholipase A(2), cyclooxygenase (COX)-1 and COX-2 were unchanged, and prostaglandin E(2) was unaffected. These results, taken with prior data on chronic fluoxetine in rats, suggest that antidepressants that increase the switching tendency of bipolar depressed patients to mania do so by increasing AA recycling and metabolism in brain. Mania in bipolar disorder thus may involve upregulated brain AA metabolism.

Increased excitotoxicity and neuroinflammatory markers in postmortem frontal cortex from bipolar disorder patients

Reports of cognitive decline, symptom worsening and brain atrophy in bipolar disorder (BD) suggest that the disease progresses over time. The worsening neuropathology may involve excitotoxicity and neuroinflammation. We determined protein and mRNA levels of excitotoxicity and neuroinflammatory markers in postmortem frontal cortex from 10 BD patients and 10 age-matched controls. The brain tissue was matched for age, postmortem interval and pH. The results indicated statistically significant lower protein and mRNA levels of the N-methyl-D-aspartate receptors, NR-1 and NR-3A, but significantly higher protein and mRNA levels of interleukin (IL)-1beta, the IL-1 receptor (IL-1R), myeloid differentiation factor 88, nuclear factor-kappa B subunits, and astroglial and microglial markers (glial fibrillary acidic protein, inducible nitric oxide synthase, c-fos and CD11b) in postmortem frontal cortex from BD compared with control subjects. There was no significant difference in mRNA levels of tumor necrosis factor alpha or neuronal nitric oxide synthase in the same region. These data show the presence of excitotoxicity and neuroinflammation in BD frontal cortex, with particular activation of the IL-R cascade. The changes may account for reported evidence of disease progression in BD and be a target for future therapy.

Quantitative contributions of diet and liver synthesis to docosahexaenoic acid homeostasis

Dietary requirements for maintaining brain and heart docosahexaenoic acid (DHA, 22:6n-3) homeostasis are not agreed on, in part because rates of liver DHA synthesis from circulating alpha-linolenic acid (alpha-LNA, 18:3n-3) have not been quantified. These rates can be estimated using intravenous radiotracer- or heavy isotope-labeled alpha-LNA infusion. In adult unanesthetized male rats, such infusion shows that liver synthesis-secretion rates of DHA from alpha-LNA markedly exceed brain and heart DHA synthesis rates and the brain DHA consumption rate, and that liver but not heart or brain synthesis is upregulated when dietary n-3 PUFA content is reduced. These rate differences reflect much higher expression of DHA-synthesizing enzymes in liver, and upregulation of liver but not heart or brain enzyme expression by reduced dietary n-3 PUFA content. A noninvasive intravenous [U-(13)C]alpha-LNA infusion method that produces steady-state liver tracer metabolism gives exact liver DHA synthesis-secretion rates and could be extended for human studies.

Is aspirin useful in patients on lithium? A pharmacoepidemiological study related to bipolar disorder

OBJECTIVES

Administration to rats of mood stabilizers approved for bipolar disorder (BD) downregulates markers of the brain arachidonic acid (AA, 20:4n-6) metabolic cascade, including phospholipase A(2) (PLA(2)) and cyclooxygenase (COX) expression. We hypothesized that other agents that target the brain AA cascade, nonsteroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids, also would ameliorate BD symptoms.

METHODS

Medication histories on subjects who had been prescribed lithium were collected from the Netherlands PHARMO Record Linkage System. Data were stratified according to drug classes that inhibit PLA(2) and/or COX enzymes, and duration of use. Incidence density (ID) of medication events (dose increase or substance change) was used as a proxy for clinical worsening. ID ratios in patients with the inhibitors plus lithium were compared to ratios in patients using lithium alone.

RESULTS

Low-dose acetylsalicylic acid (aspirin) significantly reduced the ID ratio of medication events, independent of use duration. The ID ratios of NSAIDs and glucocorticoids did not differ significantly from 1.0 if prescribed for > or =180 or > or =90 days, but exceeded 1.0 with shorter use. Selective COX-2 inhibitors had no significant effect and multiagent administration increased the ID ratio above 1.0.

CONCLUSIONS

Low-dose aspirin produced a statistically significant duration-independent reduction in the relative risk of clinical deterioration in subjects on lithium, whereas other NSAIDs and glucocorticoids did not. These tentative findings could be tested on larger databases containing detailed information about diagnosis and disease course, as well as by controlled clinical trials.

Altered expression of apoptotic factors and synaptic markers in postmortem brain from bipolar disorder patients

Bipolar disorder (BD) is a progressive psychiatric disorder characterized by recurrent changes of mood and is associated with cognitive decline. There is evidence of excitotoxicity, neuroinflammation, upregulated arachidonic acid (AA) cascade signaling and brain atrophy in BD patients. These observations suggest that BD pathology may be associated with apoptosis as well as with disturbed synaptic function. To test this hypothesis, we measured mRNA and protein levels of the pro-apoptotic (Bax, BAD, caspase-9 and caspase-3) and anti-apoptotic factors (BDNF and Bcl-2) and of pre- and post-synaptic markers (synaptophysin and drebrin), in postmortem prefrontal cortex (Brodmann area 9) from 10 BD patients and 10 age-matched controls. Consistent with the hypothesis, BD brains showed significant increases in protein and mRNA levels of the pro-apoptotic factors and significant decreases of levels of the anti-apoptotic factors and the synaptic markers, synaptophysin and drebrin. These differences may contribute to brain atrophy and progressive cognitive changes in BD.

Chronic NMDA administration to rats increases brain pro-apoptotic factors while decreasing anti-Apoptotic factors and causes cell death

BACKGROUND

Chronic N-Methyl-d-aspartate (NMDA) administration to rats is reported to increase arachidonic acid signaling and upregulate neuroinflammatory markers in rat brain. These changes may damage brain cells. In this study, we determined if chronic NMDA administration (25 mg/kg i.p., 21 days) to rats would alter expression of pro- and anti-apoptotic factors in frontal cortex, compared with vehicle control.

RESULTS

Using real time RT-PCR and Western blotting, chronic NMDA administration was shown to decrease mRNA and protein levels of anti-apoptotic markers Bcl-2 and BDNF, and of their transcription factor phospho-CREB in the cortex. Expression of pro-apoptotic Bax, Bad, and 14-3-3zeta was increased, as well as Fluoro-Jade B (FJB) staining, a marker of neuronal loss.

CONCLUSION

This alteration in the balance between pro- and anti-apoptotic factors by chronic NMDA receptor activation in this animal model may contribute to neuronal loss, and further suggests that the model can be used to examine multiple processes involved in excitotoxicity.

Bipolar disorder and mechanisms of action of mood stabilizers

Bipolar disorder (BD) is a major medical and social burden, whose cause, pathophysiology and treatment are not agreed on. It is characterized by recurrent periods of mania and depression (Bipolar I) or of hypomania and depression (Bipolar II). Its inheritance is polygenic, with evidence of a neurotransmission imbalance and disease progression. Patients often take multiple agents concurrently, with incomplete therapeutic success, particularly with regard to depression. Suicide is common. Of the hypotheses regarding the action of mood stabilizers in BD, the "arachidonic acid (AA) cascade" hypothesis is presented in detail in this review. It is based on evidence that chronic administration of lithium, carbamazepine, sodium valproate, or lamotrigine to rats downregulated AA turnover in brain phospholipids, formation of prostaglandin E(2), and/or expression of AA cascade enzymes, including cytosolic phospholipase A(2), cyclooxygenase-2 and/or acyl-CoA synthetase. The changes were selective for AA, since brain docosahexaenoic or palmitic acid metabolism, when measured, was unaffected, and topiramate, ineffective in BD, did not modify the rat brain AA cascade. Downregulation of the cascade by the mood stabilizers corresponded to inhibition of AA neurotransmission via dopaminergic D(2)-like and glutamatergic NMDA receptors. Unlike the mood stabilizers, antidepressants that increase switching of bipolar depression to mania upregulated the rat brain AA cascade. These observations suggest that the brain AA cascade is a common target of mood stabilizers, and that bipolar symptoms, particularly mania, are associated with an upregulated cascade and excess AA signaling via D(2)-like and NMDA receptors. This review presents ways to test these suggestions.

Targeting prostaglandin E2 EP1 receptors prevents seizure-associated P-glycoprotein up-regulation

Up-regulation of the blood-brain barrier efflux transporter P-glycoprotein in central nervous system disorders results in restricted brain access and limited efficacy of therapeutic drugs. In epilepsies, seizure activity strongly triggers expression of P-glycoprotein. Here, we identified the prostaglandin E2 receptor, EP1, as a key factor in the signaling pathway that mediates seizure-induced up-regulation of P-glycoprotein at the blood-brain barrier. In the rat pilocarpine model, status epilepticus significantly increased P-glycoprotein expression by 92 to 197% in the hippocampal hilus and granule cell layer as well as the piriform cortex. The EP1 receptor antagonist 8-chlorodibenz[b,f][1,4]oxazepine-10(11H)-carboxylic acid, 2-[1-oxo-3-(4-pyridinyl)propyl]hydrazide hydrochloride (SC-51089) abolished seizure-induced P-glycoprotein up-regulation and retained its expression at the control level. The control of P-glycoprotein expression despite prolonged seizure activity suggests that EP1 receptor antagonism will also improve antiepileptic drug efficacy. Preliminary evidence for this concept has been obtained using a massive kindling paradigm during which animals received a subchronic SC-51089 treatment. After withdrawal of the EP1 receptor antagonist, a low dose of the P-glycoprotein substrate phenobarbital resulted in an anticonvulsant effect in this pretreated group, whereas the same dosage of phenobarbital did not exert a significant effect in the respective control group. In conclusion, our data demonstrate that EP1 is a key signaling factor in the regulatory pathway that drives P-glycoprotein up-regulation during seizures. These findings suggest new intriguing possibilities to prevent and interrupt P-glycoprotein overexpression in epilepsy. Future studies are necessary to further evaluate the appropriateness of the strategy to enhance the efficacy of antiepileptic drugs.

Imaging elevated brain arachidonic acid signaling in unanesthetized serotonin transporter (5-HTT)-deficient mice

Certain polymorphisms reduce serotonin (5-HT) reuptake transporter (5-HTT) function and increase susceptibility to psychiatric disorders. Heterozygous (5-HTT(+/-))-deficient mice, models for humans with these polymorphisms, have elevated brain 5-HT concentrations and behavioral abnormalities. As postsynaptic 5-HT(2A/2C) receptors are coupled to cytosolic phospholipase A(2) (cPLA(2)), which releases arachidonic acid (AA) from membrane phospholipid, 5-HTT-deficient mice may have altered brain AA signaling and metabolism. To test this hypothesis, signaling was imaged as an AA incorporation coefficient k(*) in unanesthetized homozygous knockout (5-HTT(-/-)), 5-HTT(+/-) and wild-type (5-HTT(+/+)), mice following saline (baseline) or 1.5 mg/kg s.c. DOI, a partial 5-HT(2A/2C) receptor agonist. Enzyme activities, metabolite concentrations, and head-twitch responses to DOI were also measured. Baseline k(*) was widely elevated by 20-70% in brains of 5-HTT(+/-) and 5-HTT(-/-) compared to 5-HTT(+/+) mice. DOI increased k(*) in 5-HTT(+/+) mice, but decreased k(*) in 5-HTT-deficient mice. Brain cPLA(2) activity was elevated in 5-HTT-deficient mice; cyclooxygenase activity and prostaglandin E(2) and F(2alpha) and thromboxane B(2) concentrations were reduced. Head-twitch responses to DOI, although robust in 5-HTT(+/+) and 5-HTT(+/-) mice, were markedly fewer in 5-HTT(-/-) mice. Pretreatment with para-chlorophenylalanine, a 5-HT synthesis inhibitor, restored head twitches in 5-HTT(-/-) mice to levels in 5-HTT(+/+) mice. We propose that increased baseline values of k(*) in 5-HTT-deficient mice reflect tonic cPLA(2) stimulation through 5-HT(2A/2C) receptors occupied by excess 5-HT, and that reduced k(*) and head-twitch responses to DOI reflected displacement of receptor-bound 5-HT by DOI with a lower affinity. Increased baseline AA signaling in humans having polymorphisms with reduced 5-HTT function might be identified using positron emission tomography.

Intracellular- and extracellular-derived Ca(2+) influence phospholipase A(2)-mediated fatty acid release from brain phospholipids

Docosahexaenoic acid (DHA) and arachidonic acid (AA) are found in high concentrations in brain cell membranes and are important for brain function and structure. Studies suggest that AA and DHA are hydrolyzed selectively from the sn-2 position of synaptic membrane phospholipids by Ca(2+)-dependent cytosolic phospholipase A(2) (cPLA(2)) and Ca(2+)-independent phospholipase A(2) (iPLA(2)), respectively, resulting in increased levels of the unesterified fatty acids and lysophospholipids. Cell studies also suggest that AA and DHA release depend on increased concentrations of Ca(2+), even though iPLA(2) has been thought to be Ca(2+)-independent. The source of Ca(2+) for activation of cPLA(2) is largely extracellular, whereas Ca(2+) released from the endoplasmic reticulum can activate iPLA(2) by a number of mechanisms. This review focuses on the role of Ca(2+) in modulating cPLA(2) and iPLA(2) activities in different conditions. Furthermore, a model is suggested in which neurotransmitters regulate the activity of these enzymes and thus the balanced and localized release of AA and DHA from phospholipid in the brain, depending on the primary source of the Ca(2+) signal.

Acute but not chronic donepezil increases muscarinic receptor-mediated signaling via arachidonic acid in unanesthetized rats

Donepezil, an acetylcholinesterase (AChE) inhibitor used for treating Alzheimer's disease patients, is thought to act by increasing brain extracellular acetylcholine (ACh), and ACh binding to cholinergic receptors. Muscarinic receptors are coupled to cytosolic phospholipase A2 (cPLA2) activation and arachidonic acid (AA) release from synaptic membrane phospholipid. This activation can be imaged in rodents as an AA incorporation coefficient k*, using quantitative autoradiography. Acute and chronic effects of donepezil on the AA signal, k* for AA, were measured in 81 brain regions of unanesthetized rats. Twenty min after a single oral dose (3.0 mg/kg) of donepezil, k* was increased significantly in 37 brain regions, whereas k* did not differ from control 7 h afterwards or following chronic (21 days) of donepezil. Pretreatment with atropine prevented the 20-min increments in k* following donepezil. Donepezil also increased the brain ACh concentration and reduced brain AChE activity, but did not change cPLA2 activity, regardless of administration regimen. These results show that donepezil acutely increases the brain AA signal that is mediated by ACh acting at muscarinic receptors, but that this signal is rapidly desensitized despite continued elevated brain ACh concentration. In contrast, the AA signal in response to arecoline was not altered following donepezil.

Arachidonic acid and the brain

Kinetic methods in unanesthetized rodents have shown that turnover rates of arachidonic acid (AA) and docosahexaenoic acid (DHA) in brain membrane phospholipids are rapid and energy consuming and that phospholipase A(2) (PLA(2)) and acyl-CoA synthetase enzymes that regulate turnover are specific for one or the other PUFA. Thus, AA turnover in brain phospholipids was reduced, and AA-selective cytosolic cPLA(2) or acyl-CoA synthetase, as well as cyclooxygenase (COX)-2, were downregulated in brains of rats given drugs effective against bipolar disorder, whereas DHA turnover and expression of DHA-selective calcium-independent iPLA(2) were unchanged. Additionally, the brain AA and DHA cascades can be altered reciprocally by dietary or genetic conditions. Thus, following 15 wk of dietary (n-3) PUFA deprivation, DHA loss from rat brain was slowed because of reduced iPLA(2) and COX-1 expression, whereas AA-selective cPLA(2), sPLA(2), and COX-2 were upregulated, as were AA and docosapentaenoic acid concentrations. Measured rates of AA and DHA incorporation into brain represent their respective rates of metabolic consumption, because these PUFA are not synthesized de novo or converted significantly from their precursors in brain. In healthy human volunteers, positron emission tomography (PET) was used to show that the brain consumes AA and DHA at respective rates of 17.8 and 4.6 mg/d, whereas in patients with Alzheimer disease, AA consumption is elevated. In the future, PET could be used to relate human brain rates of AA and DHA consumption to liver PUFA metabolism and dietary PUFA intake.

Chronic d-amphetamine depresses an imaging marker of arachidonic acid metabolism in rat brain

Acute d-amphetamine (d-Amph) administration to rats leads to the release of arachidonic acid (AA, 20:4n-6) as a second messenger following indirect agonism at dopamine D2-like receptors in the brain. We hypothesized that chronically administered d-Amph in rats also would alter brain AA metabolism and signalling. To test this, adult male rats were injected i.p. daily for 2 wk with saline or 2.5 mg/kg d-Amph. After a 1-d washout, the unanaesthetized rats were injected acutely with i.v. saline, 1 mg/kg quinpirole (a D2-like receptor agonist) or 5.0 mg/kg SKF-38393 (a D1-like receptor agonist), followed by i.v. [1-14C]AA. The AA incorporation coefficient k* (brain radioactivity/integrated plasma radioactivity), a marker of AA signalling and metabolism, was quantified using autoradiography in each of 62 brain regions. Compared with chronic saline, chronic d-Amph widely decreased baseline values of k* in brain regions having D2-like receptors. On the other hand, chronic amphetamine did not alter the k* responses to quinpirole seen in chronic saline-treated rats. SKF-38393 had minimal effects on k* in both chronic saline-treated and amphetamine-treated rats, consistent with D1-like receptors not being coupled to AA signalling. The ability of chronic d-Amph after 1-d washout to down-regulate baseline values of k* probably reflects neuroplastic changes in brain AA signalling, and may correspond to depressive behaviours noted following withdrawal from chronic amphetamine in humans and in rats.

Brain arachidonic and docosahexaenoic acid cascades are selectively altered by drugs, diet and disease

Metabolic cascades involving arachidonic acid (AA) and docosahexaenoic acid (DHA) within brain can be independently targeted by drugs, diet and pathological conditions. Thus, AA turnover and brain expression of AA-selective cytosolic phospholipase A(2) (cPLA(2)), but not DHA turnover or expression of DHA-selective Ca(2+)-independent iPLA(2), are reduced in rats given agents effective against bipolar disorder mania, whereas experimental excitotoxicity and neuroinflammation selectively increase brain AA metabolism. Furthermore, the brain AA and DHA cascades are altered reciprocally by dietary n-3 polyunsaturated fatty acid (PUFA) deprivation in rats. DHA loss from brain is slowed and iPLA(2) expression is decreased, whereas cPLA(2) and COX-2 are upregulated, as are brain concentrations of AA and its elongation product, docosapentaenoic acid (DPA). Positron emission tomography (PET) has shown that the normal human brain consumes 17.8 and 4.6 mg/day, respectively, of AA and DHA, and that brain AA consumption is increased in Alzheimer disease patients. In the future, PET could help to determine how human brain AA or DHA consumption is influenced by diet, aging or disease.

Regulation of brain polyunsaturated fatty acid uptake and turnover

The brain is particularly enriched in glycerophospholipids with either arachidonic or docosahexaenoic acid esterified in the stereospecifically numbered-2 position. In this paper, we review how combining a kinetic approach to study the uptake and turnover of arachidonic and docosahexaenoic acids within brain phospholipids of unanesthetized rats, along with chronic administration of antimanic drugs (lithium, valproate and carbamazepine), have advanced our understanding of how polyunsaturated fatty acids (PUFA) enter the brain, and the mechanisms that regulate their turnover within brain phospholipids. The incorporation rates of arachidonic and docosahexaenoic acid from the plasma unesterified pool into brain phospholipids closely approximate independent measures of their consumption rates by the brain, suggesting this is quantitatively the major pool for uptake of these PUFA. Antimanic drugs (lithium and carbamazepine) that downregulate the activity of the calcium-dependent cytosolic phospholipase A(2) (cPLA(2)) transcription factor AP-2, and in turn the expression and activity of cPLA(2,) lead to a selective downregulation in brain arachidonic acid turnover. Furthermore, targeting arachidonoyl-CoA formation via ordered, non-competitive inhibition of an acyl-CoA synthetase with valproate also selectively decreases brain arachidonic acid turnover. Drugs that increase brain cPLA(2) activity (N-methyl-d-aspartic acid and fluoxetine) are correlated with increased turnover of arachidonic acid in brain phospholipids. Altered PUFA metabolism has been implicated in several neurological disorders, including bipolar disorder and Alzheimer's disease. Identifying the enzymes that regulated brain PUFA metabolism could lead to new therapeutic approaches for these disorders.

Amyloid beta peptide and NMDA induce ROS from NADPH oxidase and AA release from cytosolic phospholipase A2 in cortical neurons

Increase in oxidative stress has been postulated to play an important role in the pathogenesis of a number of neurodegenerative diseases including Alzheimer's disease. There is evidence for involvement of amyloid-beta peptide (Abeta) in mediating the oxidative damage to neurons. Despite yet unknown mechanism, Abeta appears to exert action on the ionotropic glutamate receptors, especially the N-methyl-D-aspartic acid (NMDA) receptor subtypes. In this study, we showed that NMDA and oligomeric Abeta(1-42) could induce reactive oxygen species (ROS) production from cortical neurons through activation of NADPH oxidase. ROS derived from NADPH oxidase led to activation of extracellular signal-regulated kinase 1/2, phosphorylation of cytosolic phospholipase A(2)alpha (cPLA(2)alpha), and arachidonic acid (AA) release. In addition, Abeta(1-42)-induced AA release was inhibited by d(-)-2-amino-5-phosphonopentanoic acid and memantine, two different NMDA receptor antagonists, suggesting action of Abeta through the NMDA receptor. Besides serving as a precursor for eicosanoids, AA is also regarded as a retrograde messenger and plays a role in modulating synaptic plasticity. Other phospholipase A(2) products such as lysophospholipids can perturb membrane phospholipids. These results suggest an oxidative-degradative mechanism for oligomeric Abeta(1-42) to induce ROS production and stimulate AA release through the NMDA receptors. This novel mechanism may contribute to the oxidative stress hypothesis and synaptic failure that underline the pathogenesis of Alzheimer's disease.

Mode of action of mood stabilizers: is the arachidonic acid cascade a common target?

Bipolar disorder is a major medical, social and economic burden worldwide. However, the mechanisms of action of effective antibipolar disorder drugs remain elusive. In this paper, we review studies using a neuropharmacological approach in unanesthetized rats, combined with kinetic, biochemical and molecular biology techniques, showing that chronic administration of three Food and Drug Administration-approved mood stabilizers (lithium, valproate and carbamazepine) at therapeutically relevant doses, selectively target the brain arachidonic acid (AA) cascade. Whereas chronic lithium and carbamazepine decrease the binding activity of activator protein-2 and in turn the transcription, translation and activity of its AA-selective calcium-dependent phospholipase A(2) gene product, valproate appears to be a non-competitive inhibitor of long-chain acyl-CoA synthetase. The net overlapping effects of the three drugs are decreased turnover of AA but not of docosahexaenoic acid in rat brain phospholipids, and decreased brain cyclooxygenase-2 and prostaglandin E(2). Although these observations support the hypothesis proposed by Rapoport and colleagues that the AA cascade is a common target of mood stabilizers, this hypothesis is not necessarily exclusive of other targets. Targeting the AA cascade with drugs or diet may be a useful therapeutic approach in bipolar disorder, and examining the AA cascade in patients might help in better understanding the disease.

Effect of the dysbindin gene on antimanic agents in patients with bipolar I disorder

OBJECTIVE

We previously reported an association between dysbindin gene (DTNBP1) variants and bipolar I disorder (BID). This paper expands upon previous findings suggesting that DTNBP1 variants may play a role in the response to acute mood stabilizer treatment.

METHODS

A total of 45 BID patients were treated with antimanic agents (lithium, valproate, or carbamazepine) for an average of 36.52 (+/-19.87) days. After treatment, the patients were evaluated using the Clinical Global Impression (CGI) scale and the Young Mania Rating Scale (YMRS) and genotyped for their DTNBP1 variants (rs3213207 A/G, rs1011313 C/T, rs2005976 G/A, rs760761 C/T and rs2619522 A/C).

RESULTS

There was no association between the variants investigated and response to mood stabilizer treatment, even after considering possible stratification factors.

CONCLUSION

Although the small number of subjects is an important limitation in our study, DTNBP1 does not seem to be involved in acute antimanic efficacy.

Chronic NMDA administration increases neuroinflammatory markers in rat frontal cortex: cross-talk between excitotoxicity and neuroinflammation

Chronic N-Methyl-D: -aspartate (NMDA) administration, a model of excitotoxicity, and chronic intracerebroventricular lipopolysaccharide infusion, a model of neuroinflammation, are reported to upregulate arachidonic acid incorporation and turnover in rat brain phospholipids as well as enzymes involved in arachidonic acid metabolism. This suggests cross-talk between signaling pathways of excitotoxicity and of neuroinflammation, involving arachidonic acid. To test whether chronic NMDA administrations to rats can upregulate brain markers of neuroinflammation, NMDA (25 mg/kg i.p.) or vehicle (1 ml saline/kg i.p.) was administered daily to adult male rats for 21 days. Protein and mRNA levels of cytokines and other inflammatory markers were measured in the frontal cortex using immunoblot and real-time PCR. Compared with chronic vehicle, chronic NMDA significantly increased protein and mRNA levels of interleukin-1beta, tumor necrosis factor alpha, glial fibrillary acidic protein and inducible nitric oxide synthase. Chronic NMDA receptor overactivation results in increased levels of neuroinflammatory markers in the rat frontal cortex, consistent with cross-talk between excitotoxicity and neuroinflammation. As both processes have been reported in a number of human brain diseases, NMDA receptor inhibitors might be of use in treating neuroinflammation in these diseases.

Antimanic therapies target brain arachidonic acid signaling: lessons learned about the regulation of brain fatty acid metabolism

Bipolar disorder is a major medical, social and economic burden worldwide. However, the biochemical basis of the disorder and the mechanisms of action of effective antibipolar disorder drugs remain elusive. In this paper, we review how combining a kinetic approach to studying the turnover of fatty acids within brain phospholipids of unanesthetized rats along with chronic administration of antimanic drugs (lithium, valproate and carbamazepine) at therapeutically relevant doses, shows that the brain arachidonic acid cascade is a common target of these drugs. The overlapping effects of the three drugs are decreased turnover of arachidonic acid but not of docosahexaenoic acid in rat brain phospholipids, and decreased brain cyclooxygenase-2 and prostaglandin E(2). Whereas lithium and carbamazepine target the transcription of the arachidonic acid-selective calcium-dependent cytosolic phospholipase A(2), valproate is a non-competitive inhibitor of an arachidonic acid-selective acyl-CoA synthetase. Two potential models of bipolar disorder, chronic N-methyl-d-aspartate and n-3 polyunsaturated fatty acid deprivation, opposite to the antimanic drugs, increase the turnover and markers of the arachidonic acid cascade in rat brain. These observations support the hypothesis proposed by Rapoport and colleagues that the arachidonic acid cascade is a common target of mood stabilizers and that by targeting substrate-specific enzymes the turnover of individual fatty acids can be regulated within the brain.

Chronic N-methyl-D-aspartate administration increases the turnover of arachidonic acid within brain phospholipids of the unanesthetized rat

Whereas antibipolar drug administration to rats reduces brain arachidonic acid turnover, excessive N-methyl-d-aspartate (NMDA) signaling is thought to contribute to bipolar disorder symptoms and may increase arachidonic acid turnover in rat brain phospholipids. To determine whether chronic NMDA would increase brain arachidonic acid turnover, rats were daily administered NMDA (25 mg/kg, ip) or vehicle for 21 days. In unanesthetized rats, on day 21, [1-(14)C]arachidonic acid was infused intravenously and arterial blood plasma was sampled until the animal was euthanized at 5 min and its microwaved brain was subjected to chemical and radiotracer analysis. Using equations from our in vivo fatty acid model, we found that compared with controls, chronic NMDA increased the net rate of incorporation of plasma unesterified arachidonic acid into brain phospholipids (25-34%) as well as the turnover of arachidonic acid within brain phospholipids (35-58%). These changes were absent at 3 h after a single NMDA injection. The changes, opposite to those after chronic administration of antimanic drugs to rats, suggest that excessive NMDA signaling via arachidonic acid may be a model of upregulated arachidonic acid turnover in brain phospholipids.