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

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.

Dose-dependent changes in neuroinflammatory and arachidonic acid cascade markers with synaptic marker loss in rat lipopolysaccharide infusion model of neuroinflammation

Background

Neuroinflammation, caused by six days of intracerebroventricular infusion of bacterial lipopolysaccharide (LPS), stimulates rat brain arachidonic acid (AA) metabolism. The molecular changes associated with increased AA metabolism are not clear. We examined effects of a six-day infusion of a low-dose (0.5 ng/h) and a high-dose (250 ng/h) of LPS on neuroinflammatory, AA cascade, and pre- and post-synaptic markers in rat brain. We used artificial cerebrospinal fluid-infused brains as controls.

Results

Infusion of low- or high-dose LPS increased brain protein levels of TNFα, and iNOS, without significantly changing GFAP. High-dose LPS infusion upregulated brain protein and mRNA levels of AA cascade markers (cytosolic cPLA₂-IVA, secretory sPLA₂-V, cyclooxygenase-2 and 5-lipoxygenase), and of transcription factor NF-κB p50 DNA binding activity. Both LPS doses increased cPLA₂ and p38 mitogen-activated protein kinase levels, while reducing protein levels of the pre-synaptic marker, synaptophysin. Post-synaptic markers drebrin and PSD95 protein levels were decreased with high- but not low-dose LPS.

Conclusions

Chronic LPS infusion has differential effects, depending on dose, on inflammatory, AA and synaptic markers in rat brain. Neuroinflammation associated with upregulated brain AA metabolism can lead to synaptic dysfunction.

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.

A review of research trends in physiological abnormalities in autism spectrum disorders: immune dysregulation, inflammation, oxidative stress, mitochondrial dysfunction and environmental toxicant exposures

Recent studies have implicated physiological and metabolic abnormalities in autism spectrum disorders (ASD) and other psychiatric disorders, particularly immune dysregulation or inflammation, oxidative stress, mitochondrial dysfunction and environmental toxicant exposures ('four major areas'). The aim of this study was to determine trends in the literature on these topics with respect to ASD. A comprehensive literature search from 1971 to 2010 was performed in these four major areas in ASD with three objectives. First, publications were divided by several criteria, including whether or not they implicated an association between the physiological abnormality and ASD. A large percentage of publications implicated an association between ASD and immune dysregulation/inflammation (416 out of 437 publications, 95%), oxidative stress (all 115), mitochondrial dysfunction (145 of 153, 95%) and toxicant exposures (170 of 190, 89%). Second, the strength of evidence for publications in each area was computed using a validated scale. The strongest evidence was for immune dysregulation/inflammation and oxidative stress, followed by toxicant exposures and mitochondrial dysfunction. In all areas, at least 45% of the publications were rated as providing strong evidence for an association between the physiological abnormalities and ASD. Third, the time trends in the four major areas were compared with trends in neuroimaging, neuropathology, theory of mind and genetics ('four comparison areas'). The number of publications per 5-year block in all eight areas was calculated in order to identify significant changes in trends. Prior to 1986, only 12 publications were identified in the four major areas and 51 in the four comparison areas (42 for genetics). For each 5-year period, the total number of publications in the eight combined areas increased progressively. Most publications (552 of 895, 62%) in the four major areas were published in the last 5 years (2006-2010). Evaluation of trends between the four major areas and the four comparison areas demonstrated that the largest relative growth was in immune dysregulation/inflammation, oxidative stress, toxicant exposures, genetics and neuroimaging. Research on mitochondrial dysfunction started growing in the last 5 years. Theory of mind and neuropathology research has declined in recent years. Although most publications implicated an association between the four major areas and ASD, publication bias may have led to an overestimation of this association. Further research into these physiological areas may provide insight into general or subset-specific processes that could contribute to the development of ASD and other psychiatric disorders.

Imaging brain signal transduction and metabolism via arachidonic and docosahexaenoic acid in animals and humans

The polyunsaturated fatty acids (PUFAs), arachidonic acid (AA, 20:4n-6) and docosahexaenoic acid (DHA, 22:6n-3), important second messengers in brain, are released from membrane phospholipid following receptor-mediated activation of specific phospholipase A(2) (PLA(2)) enzymes. We developed an in vivo method in rodents using quantitative autoradiography to image PUFA incorporation into brain from plasma, and showed that their incorporation rates equal their rates of metabolic consumption by brain. Thus, quantitative imaging of unesterified plasma AA or DHA incorporation into brain can be used as a biomarker of brain PUFA metabolism and neurotransmission. We have employed our method to image and quantify effects of mood stabilizers on brain AA/DHA incorporation during neurotransmission by muscarinic M(1,3,5), serotonergic 5-HT(2A/2C), dopaminergic D(2)-like (D(2), D(3), D(4)) or glutamatergic N-methyl-d-aspartic acid (NMDA) receptors, and effects of inhibition of acetylcholinesterase, of selective serotonin and dopamine reuptake transporter inhibitors, of neuroinflammation (HIV-1 and lipopolysaccharide) and excitotoxicity, and in genetically modified rodents. The method has been extended for the use with positron emission tomography (PET), and can be employed to determine how human brain AA/DHA signaling and consumption are influenced by diet, aging, disease and genetics.

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 neuroinflammation impacts the recruitment of adult-born neurons into behaviorally relevant hippocampal networks

Growing evidence suggests that adult-born granule cells integrate into hippocampal networks and are required for proper cognitive function. Although neuroinflammation is involved in many disorders associated with cognitive impairment, it remains unknown whether it impacts the recruitment of adult-born neurons into behaviorally relevant hippocampal networks. Under similar behavioral conditions, exploration-induced expression of the immediate-early gene Arc in hippocampal cells has been linked to cellular activity observed by electrophysiological recording. By detecting exploration-induced Arc protein expression, we investigated whether neuroinflammation alters the recruitment of adult-born neurons into behaviorally relevant hippocampal networks. Neuroinflammation was induced in rats by intra-cerebroventricular infusion of lipopolysaccharide for 28 days. Animals received bromodeoxyuridine injections starting on day 29 (5 days) and were euthanized two months later. Persistent lipopolysaccharide-induced neuroinflammation was reliably detected by microglial activation in the hippocampus. Neuroinflammation did not impact the number of adult-born neurons but did alter their migration pattern through the granule cell layer. There was a positive correlation between the density of activated microglia and alterations in the fraction of existing granule neurons expressing Arc, suggesting that neuroinflammation induced a long-term disruption of hippocampal network activity. The proportion of adult-born neurons expressing behaviorally induced Arc was significantly lower in lipopolysaccharide-treated rats than in controls. This observation supports the fact that neuroinflammation significantly impacts adult-born neurons recruitment into hippocampal networks encoding spatial information.

Mitochondria, oligodendrocytes and inflammation in bipolar disorder: evidence from transcriptome studies points to intriguing parallels with multiple sclerosis

Gene expression studies of bipolar disorder (BPD) have shown changes in transcriptome profiles in multiple brain regions. Here we summarize the most consistent findings in the scientific literature, and compare them to data from schizophrenia (SZ) and major depressive disorder (MDD). The transcriptome profiles of all three disorders overlap, making the existence of a BPD-specific profile unlikely. Three groups of functionally related genes are consistently expressed at altered levels in BPD, SZ and MDD. Genes involved in energy metabolism and mitochondrial function are downregulated, genes involved in immune response and inflammation are upregulated, and genes expressed in oligodendrocytes are downregulated. Experimental paradigms for multiple sclerosis demonstrate a tight link between energy metabolism, inflammation and demyelination. These studies also show variabilities in the extent of oligodendrocyte stress, which can vary from a downregulation of oligodendrocyte genes, such as observed in psychiatric disorders, to cell death and brain lesions seen in multiple sclerosis. We conclude that experimental models of multiple sclerosis could be of interest for the research of BPD, SZ and MDD.

Inflammatory markers and their relationships with leptin and insulin from acute mania to full remission in bipolar disorder

BACKGROUND

Weight gain and increased production of leptin may be associated with immuno-modulation and insulin resistance in bipolar disorder. The links among inflammatory markers, leptin, and insulin of bipolar patients from acute mania to full remission remain unclear.

METHODS

Thirty-three healthy, bipolar I patients under 45 years of age were enrolled. We measured the circulating levels of high-sensitivity C-reactive protein (hs-CRP), anti-inflammatory mediators (interleukin-1 receptor antagonist [IL-1Ra] and soluble tumor necrosis factor receptor 1 [sTNF-R1]), leptin, and insulin during acute mania and subsequent partial and full remission. The results were compared with 33 age- and gender-matched healthy subjects.

RESULTS

The levels of IL-1Ra and hs-CRP of bipolar patients in both acute mania and partial remission were significantly higher than their levels of control subjects. The hs-CRP level of bipolar patients was also elevated in full remission. The elevation of IL-1Ra and hs-CRP levels in acute mania was independent of each other. They were also independent of the body mass index (BMI) and levels of leptin and insulin measurements. The levels of leptin were all positively associated with insulin levels in the normal subjects and bipolar patients in three phases. However, a significant relationship between leptin and immunoparameter was only seen in full remission with sTNF-R1 (r=0.51). Furthermore, IL-1Ra was inversely correlated with sTNF-R1 (r=-0.37, p<0.05) during partly remission, and while levels of IL-1Ra tended to normalize when patients remitted, levels of hs-CRP and sTNF-R1 showed the opposite trend.

CONCLUSIONS

Activated inflammation was found in acute mania, as evidenced by high levels of IL-1Ra, hs-CRP, and sTNF-R1. The production of leptin may be more tightly linked to insulin than the immunomodulators. Chronic inflammation may exist in bipolar patients and is reflected by elevations of IL-1Ra and hs-CRP levels in acute mania and persistent higher hs-CRP in full remission.

Affective symptoms are associated with markers of inflammation and immune activation in bipolar disorders but not in schizophrenia

OBJECTIVE

Elevated levels of inflammation are reported in bipolar disorders (BP), but how this relates to affective symptoms is unclear. We aimed to determine if immune markers that consistently have been reported elevated in BP were associated with depressive and manic symptoms, and if this was specific for BP.

METHODS

From a catchment area, 112 BP patients were included together with 153 schizophrenia (SCZ) patients and 239 healthy controls. Depression and mania were assessed and the patients were grouped into depressed, neutral, and elevated mood. We measured the immune markers tumor necrosis factor receptor 1 (sTNF-R1), interleukin 1 receptor antagonist (IL-1Ra), interleukin 6 (IL-6), high sensitive C-reactive protein (hsCRP), osteoprotegerin (OPG) and von Willebrand factor (vWf) which have been found increased in severe mental disorders.

RESULTS

In BP all inflammatory markers were lowest in depressed state, with significant group differences after control for confounders with respect to TNF-R1 (p = 0.04), IL-1Ra (p = 0.02), OPG (p = 0.004) and IL-6 (p = 0.005). STNF-R1 was positively correlated with the item elevated mood (p = 0.02) whereas sad mood was negatively correlated with OPG (p = 0.0003), IL-1Ra (p = 0.001) and IL-6 (p = 0.006). Compared to controls the neutral mood group had significantly higher levels of OPG (p = 0.0003) and IL-6 (p = 0.005), and the elevated mood group had higher levels of TNF-R1 (p = 0.000005) and vWf (p = 0.002). There were no significant associations between affective states orsymptoms in SCZ.

CONCLUSIONS

The current associations between inflammatory markers and affective symptomatology in BP and not SCZ suggest that immune related mechanisms are associated with core psychopathology of BP.

Effect of valproic acid through regulation of NMDA receptor-ERK signaling in sleep deprivation rats

Although the effect of mood stabilizer valproic acid (VPA) through multiple signaling pathways has been shown, its therapeutic mechanism is still largely unknown. We investigated the effect of VPA (200 mg/kg, every 12 h) in sleep deprivation (SD) rats (72 h), the manic-like animal model, focusing on the N-methyl-D: -aspartic acid (NMDA) receptor and signaling mediators of synaptic plasticity such as extracellular signal-regulated protein kinase (ERK), cAMP response element-binding protein (CREB), B cell chronic lymphocytic leukemia/lymphoma 2 (BCL2), and brain-derived neurotrophic factor (BDNF). SD reduced the expression of the NR2B subunit of the NMDA receptor in the frontal cortex and hippocampus but did not affect the expression of NR1 and NR2A subunits. In comparison, VPA inhibited the SD-induced reduction of NR2B expression in both brain regions. In addition, SD attenuated ERK phosphorylation in the frontal cortex and hippocampus, whereas VPA prevented the attenuation. VPA also protected the SD-induced decrease of CREB phosphorylation, BCL2 expression, and BDNF expression in the frontal cortex but not in the hippocampus. These results indicate that VPA could regulate NMDA receptor-ERK signaling in SD rats, preventing the SD-induced decrease of the expression of NR2B subunit and the activation of ERK signaling mediators such as ERK, CREB, BCL2, and BDNF.

Expression profiling in neuropsychiatric disorders: emphasis on glutamate receptors in bipolar disorder

Functional genomics and proteomics approaches are being employed to evaluate gene and encoded protein expression changes with the tacit goal to find novel targets for drug discovery. Genome-wide association studies (GWAS) have attempted to identify valid candidate genes through single nucleotide polymorphism (SNP) analysis. Furthermore, microarray analysis of gene expression in brain regions and discrete cell populations has enabled the simultaneous quantitative assessment of relevant genes. The ability to associate gene expression changes with neuropsychiatric disorders, including bipolar disorder (BP), and their response to therapeutic drugs provides a novel means for pharmacotherapeutic interventions. This review summarizes gene and pathway targets that have been identified in GWAS studies and expression profiling of human postmortem brain in BP, with an emphasis on glutamate receptors (GluRs). Although functional genomic assessment of BP is in its infancy, results to date point towards a dysregulation of GluRs that bear some similarity to schizophrenia (SZ), although the pattern is complex, and likely to be more complementary than overlapping. The importance of single population expression profiling of specific neurons and intrinsic circuits is emphasized, as this approach provides informative gene expression profile data that may be underappreciated in regional studies with admixed neuronal and non-neuronal cell types.

Insulin dysfunction and allostatic load in bipolar disorder

Bipolar disorder (BD) is associated with substantial morbidity, as well as premature mortality. Available evidence indicates that 'stress-sensitive' chronic medical disorders, such as cardiovascular disease, obesity and Type 2 diabetes mellitus, are critical mediators and/or moderators of BD. Changes in physiologic systems implicated in allostasis have been proposed to impact brain structures and neurocognition, as well as medical comorbidity in this population. For example, abnormalities in insulin physiology, for example, insulin resistance, hyperinsulinemia and central insulinopenia, are implicated as effectors of allostatic load in BD. Insulin's critical role in CNS physiological (e.g., neurotrophism and synaptic plasticity) and pathophysiological (e.g., neurocognitive deficits, pro-apoptosis and amyloid deposition) processes is amply documented. This article introduces the concept that insulin is a mediator of allostatic load in the BD and possibly a therapeutic target.

Preliminary findings regarding proinflammatory markers and brain-derived neurotrophic factor among adolescents with bipolar spectrum disorders

Mood symptoms in adult bipolar disorder are associated with increased proinflammatory markers and decreased brain-derived neurotrophic factor (BDNF). We examined serum interleukin-6, high-sensitivity C-reactive protein (hsCRP), and BDNF among 30 bipolar disorder adolescents. Hypomanic/manic symptoms were positively associated with hsCRP. BDNF levels were negatively associated with interleukin-6. Forty percent had cardiovascular high-risk hsCRP levels. Larger longitudinal studies are warranted.

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.

Resilient emotionality and molecular compensation in mice lacking the oligodendrocyte-specific gene Cnp1

Altered oligodendrocyte structure and function is implicated in major psychiatric illnesses, including low cell number and reduced oligodendrocyte-specific gene expression in major depressive disorder (MDD). These features are also observed in the unpredictable chronic mild stress (UCMS) rodent model of the illness, suggesting that they are consequential to environmental precipitants; however, whether oligodendrocyte changes contribute causally to low emotionality is unknown. Focusing on 2'-3'-cyclic nucleotide 3'-phosphodiesterase (Cnp1), a crucial component of axoglial communication dysregulated in the amygdala of MDD subjects and UCMS-exposed mice, we show that altered oligodendrocyte integrity can have an unexpected functional role in affect regulation. Mice lacking Cnp1 (knockout, KO) displayed decreased anxiety- and depressive-like symptoms (i.e., low emotionality) compared with wild-type animals, a phenotypic difference that increased with age (3-9 months). This phenotype was accompanied by increased motor activity, but was evident before neurodegenerative-associated motor coordination deficits (≤ 9-12 months). Notably, Cnp1(KO) mice were less vulnerable to developing a depressive-like syndrome after either UCMS or chronic corticosterone exposure. Cnp1(KO) mice also displayed reduced fear expression during extinction, despite normal amygdala c-Fos induction after acute stress, together implicating dysfunction of an amygdala-related neural network, and consistent with proposed mechanisms for stress resiliency. However, the Cnp1(KO) behavioral phenotype was also accompanied by massive upregulation of oligodendrocyte- and immune-related genes in the basolateral amygdala, suggesting an attempt at functional compensation. Together, we demonstrate that the lack of oligodendrocyte-specific Cnp1 leads to resilient emotionality. However, combined with substantial molecular changes and late-onset neurodegeneration, these results suggest the low Cnp1 seen in MDD may cause unsustainable and maladaptive molecular compensations contributing to the disease pathophysiology.

Morphometric post-mortem studies in bipolar disorder: possible association with oxidative stress and apoptosis

Despite extensive research in the last decades, the pathophysiology of bipolar disorder (BD) remains unclear. Access to post-mortem brain tissue of subjects who had BD offers an opportunity to investigate neurobiology and this approach has led to some progress, particularly, due to the availability of more sophisticated molecular and cellular biological methodologies and well characterized brain collections over the past decade. Here we review the findings of morphometric post-mortem studies in BD and interpret them in the context of a potential physiopathological mechanism involving oxidative stress and apoptosis. A review of the literature was conducted to identify post-mortem studies that investigated cellular changes such as number, density and size of neurons and glia, in brains of subjects with BD. We found decreased density of neurons and glia and decreased size of neurons in frontal and subcortical areas of the brain. Based on recent studies that found evidence of increased apoptosis and oxidative stress in BD, we hypothesize that the cell abnormalities described are due to an increase in the apoptotic process that can be triggered, through its intrinsic pathway, by the existence of an exacerbated production of reactive oxygen species and oxidative damage in the disease.

Altered neuroinflammatory, arachidonic acid cascade and synaptic markers in postmortem Alzheimer's disease brain

Alzheimer's disease (AD), a progressive neurodegenerative disorder, is the leading cause of dementia in the elderly. A recent positron emission tomography imaging study demonstrated upregulated brain arachidonic acid (AA) metabolism in AD patients. Further, a mouse model of AD shows an increase in AA-releasing cytosolic phospholipase A(2) (cPLA(2)) in brain, and a reduction in cPLA(2) activity ameliorated cognitive deficits. These observations led us to hypothesize that there is an upregulation of AA cascade and neuroinflammatory markers in the brain of AD patients. To test this hypothesis, we measured protein and mRNA levels of AA cascade, neuroinflammatory and synaptic markers in postmortem frontal cortex from 10 AD patients and 10 age-matched controls. Consistent with our hypothesis, AD frontal cortex showed significant increases in protein and mRNA levels of cPLA(2)-IVA, secretory sPLA(2)-IIA, cyclooxygenase-1 and -2, membrane prostaglandin (PG) synthase-1 and lipoxygenase-12 and -15. Calcium-independent iPLA(2)-VIA and cytosolic PGE(2) synthase were decreased. In addition, interleukin-1β, tumor necrosis factor-α, glial fibrillary acidic protein and CD11b were increased. AD postmortem brain also showed signs of cellular injury, including decreased synaptophysin and drebrin, pre- and postsynaptic markers. These results indicate that increased AA cascade and inflammatory markers could contribute to AD pathology. Altered brain AA cascade enzymes could be considered therapeutic targets for future drug development.

Features of microglia and neuroinflammation relevant to environmental exposure and neurotoxicity

Microglia are resident cells of the brain involved in regulatory processes critical for development, maintenance of the neural environment, injury and repair. They belong to the monocytic-macrophage lineage and serve as brain immune cells to orchestrate innate immune responses; however, they are distinct from other tissue macrophages due to their relatively quiescent phenotype and tight regulation by the CNS microenvironment. Microglia actively survey the surrounding parenchyma and respond rapidly to changes such that any disruption to neural architecture or function can contribute to the loss in regulation of the microglia phenotype. In many models of neurodegeneration and neurotoxicity, early events of synaptic degeneration and neuronal loss are accompanied by an inflammatory response including activation of microglia, perivascular monocytes, and recruitment of leukocytes. In culture, microglia have been shown to be capable of releasing several potentially cytotoxic substances, such as reactive oxygen intermediates, nitric oxide, proteases, arachidonic acid derivatives, excitatory amino acids, and cytokines; however, they also produce various neurotrophic factors and quench damage from free radicals and excitotoxins. As the primary source for pro-inflammatory cytokines, microglia are implicated as pivotal mediators of neuroinflammation and can induce or modulate a broad spectrum of cellular responses. Neuroinflammation should be considered as a balanced network of processes whereby subtle modifications can shift the cells toward disparate outcomes. For any evaluation of neuroinflammation and microglial responses, within the framework of neurotoxicity or degeneration, one key question in determining the consequence of neuroinflammation is whether the response is an initiating event or the consequence of tissue damage. As examples of environmental exposure-related neuroinflammation in the literature, we provide an evaluation of data on manganese and diesel exhaust particles.

Convergent functional genomic studies of ω-3 fatty acids in stress reactivity, bipolar disorder and alcoholism

Omega-3 fatty acids have been proposed as an adjuvant treatment option in psychiatric disorders. Given their other health benefits and their relative lack of toxicity, teratogenicity and side effects, they may be particularly useful in children and in females of child-bearing age, especially during pregnancy and postpartum. A comprehensive mechanistic understanding of their effects is needed. Here we report translational studies demonstrating the phenotypic normalization and gene expression effects of dietary omega-3 fatty acids, specifically docosahexaenoic acid (DHA), in a stress-reactive knockout mouse model of bipolar disorder and co-morbid alcoholism, using a bioinformatic convergent functional genomics approach integrating animal model and human data to prioritize disease-relevant genes. Additionally, to validate at a behavioral level the novel observed effects on decreasing alcohol consumption, we also tested the effects of DHA in an independent animal model, alcohol-preferring (P) rats, a well-established animal model of alcoholism. Our studies uncover sex differences, brain region-specific effects and blood biomarkers that may underpin the effects of DHA. Of note, DHA modulates some of the same genes targeted by current psychotropic medications, as well as increases myelin-related gene expression. Myelin-related gene expression decrease is a common, if nonspecific, denominator of neuropsychiatric disorders. In conclusion, our work supports the potential utility of omega-3 fatty acids, specifically DHA, for a spectrum of psychiatric disorders such as stress disorders, bipolar disorder, alcoholism and beyond.

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.

Post-synaptic scaffolding protein interactions with glutamate receptors in synaptic dysfunction and Alzheimer's disease

Alzheimer's disease (AD) is characterized clinically by an insidious decline in cognition. Much attention has been focused on proposed pathogenic mechanisms that relate Aβ plaque and neurofibrillary tangle pathology to cognitive symptoms, but compelling evidence now identifies early synaptic loss and dysfunction, which precede plaque and tangle formation, as the more probable initiators of cognitive impairment. Glutamate-mediated transmission is severely altered in AD. Glutamate receptor expression is most markedly altered in regions of the AD brain that show the greatest pathological changes. Signaling via glutamate receptors controls synaptic strength and plasticity, and changes in these parameters are likely to contribute to memory and cognitive deficits in AD. Glutamate receptor expression and activity are modulated by interactions with post-synaptic scaffolding proteins that augment the strength and direction of signal cascades initiated by glutamate receptor activity. Scaffold proteins offer promising targets for more focused and effective drug therapy. In consequence, interest is developing into the roles these proteins play in neurological disease. In this review we discuss disruptions to excitatory neurotransmission at the level of glutamate receptor-post-synaptic scaffolding protein interactions that may contribute to synaptic dysfunction in AD.

Elevation of cerebrospinal fluid interleukin-1ß in bipolar disorder

BACKGROUND

In recent years, a role for the immune system in the pathogenesis of psychiatric diseases has gained increased attention. Although bipolar disorder appears to be associated with altered serum cytokine levels, a putative immunological contribution to its pathophysiology remains to be established. Hitherto, no direct analyses of cerebrospinal fluid (CSF) cytokines in patients with bipolar disorder have been performed.

METHODS

We analyzed CSF cytokine concentrations in euthymic patients with diagnosed bipolar disorder type I (n = 15) or type II (n = 15) and healthy volunteers (n = 30) using an immunoassay-based protein array multiplex system.

RESULTS

The mean interleukin (IL)-1ß level (4.2 pg/mL, standard error of the mean [SEM] 0.5) was higher and the IL-6 level (1.5 pg/mL, SEM 0.2) was lower in euthymic bipolar patients than in healthy volunteers (0.8 pg/mL, SEM 0.04, and 2.6 pg/mL, SEM 0.2, respectively). Patients with 1 or more manic/hypomanic episodes during the last year showed significantly higher levels of IL-1ß (6.2 pg/mL, SEM 0.8; n = 9) than patients without a recent manic/hypomanic episode (3.1 pg/mL, SEM 1.0; n = 10).

LIMITATIONS

All patients were in an euthymic state at the time of sampling. Owing to the large variety of drugs prescribed to patients in the present study, influence of medication on the cytokine profile cannot be ruled out.

CONCLUSION

Our findings show an altered brain cytokine profile associated with the manifestation of recent manic/hypomanic episodes in patients with bipolar disorder. Although the causality remains to be established, these findings may suggest a pathophysiological role for IL-1ß in bipolar disorder.

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.

Recent advances in psychoneuroimmunology: Inflammation in psychiatric disorders

Psychiatric disorders are common and complex and their precise biological underpinnings remain elusive. Multiple epidemiological, molecular, genetic and gene expression studies suggest that immune system dysfunction may contribute to the risk for developing psychiatric disorders including schizophrenia, bipolar disorder, and major depressive disorder. However, the precise mechanisms by which inflammation-related events confer such risk are unclear. In this review, we examine the peripheral and central evidence for inflammation in psychiatric disorders and the potential molecular mechanisms implicated including inhibition of neurogenesis, apoptosis, the HPA-axis, the role of brain-derived neurotrophic factor and the interplay between the glutamatergic, dopaminergic and serotonergic neurotransmitter systems.

Anti-inflammatory effects of chronic aspirin on brain arachidonic acid metabolites

Pro-inflammatory and anti-inflammatory mediators derived from arachidonic acid (AA) modulate peripheral inflammation and its resolution. Aspirin (ASA) is a unique non-steroidal anti-inflammatory drug, which switches AA metabolism from prostaglandin E₂ (PGE₂) and thromboxane B₂ (TXB₂) to lipoxin A₄ (LXA₄) and 15-epi-LXA₄. However, it is unknown whether chronic therapeutic doses of ASA are anti-inflammatory in the brain. We hypothesized that ASA would dampen increases in brain concentrations of AA metabolites in a rat model of neuroinflammation, produced by a 6-day intracerebroventricular infusion of bacterial lipopolysaccharide (LPS). In rats infused with LPS (0.5 ng/h) and given ASA-free water to drink, concentrations in high-energy microwaved brain of PGE₂, TXB₂ and leukotriene B₄ (LTB₄) were elevated. In rats infused with artificial cerebrospinal fluid, 6 weeks of treatment with a low (10 mg/kg/day) or high (100 mg/kg/day) ASA dose in drinking water decreased brain PGE₂, but increased LTB₄, LXA₄ and 15-epi-LXA₄ concentrations. Both doses attenuated the LPS effects on PGE₂, and TXB₂. The increments in LXA₄ and 15-epi-LXA₄ caused by high-dose ASA were significantly greater in LPS-infused rats. The ability of ASA to increase anti-inflammatory LXA₄ and 15-epi-LXA₄ and reduce pro-inflammatory PGE₂ and TXB₂ suggests considering aspirin further for treating clinical neuroinflammation.

Disturbed choline plasmalogen and phospholipid fatty acid concentrations in Alzheimer's disease prefrontal cortex

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by brain deposition of senile (neuritic) plaques containing amyloid-β, neurofibrillary tangles, synaptic loss, neuroinflammation, and overexpression of arachidonic acid (AA, 20:4n-6) metabolizing enzymes. Lipid concentration changes have been reported in different brain regions, but often partially or as a percent of the total concentration. In this study, we measured absolute concentrations (per gram wet weight) of a wide range of lipids in postmortem prefrontal cortex (Brodmann area 9) from 10 AD patients and 9 non-AD controls. Mean total brain lipid, phospholipid, cholesterol, and triglyceride concentrations did not differ significantly between AD and controls. There was a significant 73% decrease in plasmalogen choline, but no difference in other measured phospholipids. Fatty acid concentrations in total phospholipid did not differ from control. However, docosahexaenoic acid (DHA, 22:6n-3) was reduced in ethanolamine glycerophospholipid and choline glycerophospholipid, but increased in phosphatidylinositol. AA was reduced in choline glycerophospholipid, but increased in phosphatidylinositol, while docosatetraenoic acid (22:4n-6), an AA elongation product, was reduced in total brain lipid, cholesteryl ester and triglyceride. These lipid changes, which suggest extensive membrane remodeling, may contribute to membrane instability and synaptic loss in AD and reflect neuroinflammation.

Valproate uncompetitively inhibits arachidonic acid acylation by rat acyl-CoA synthetase 4: relevance to valproate's efficacy against bipolar disorder

BACKGROUND

The ability of chronic valproate (VPA) to reduce arachidonic acid (AA) turnover in brain phospholipids of unanesthetized rats has been ascribed to its inhibition of acyl-CoA synthetase (Acsl)-mediated activation of AA to AA-CoA. Our aim was to identify a rat Acsl isoenzyme that could be inhibited by VPA in vitro.

METHODS

Rat Acsl3-, Acsl6v1- and Acsl6v2-, and Acsl4-flag proteins were expressed in E. coli, and the ability of VPA to inhibit their activation of long-chain fatty acids to acyl-CoA was estimated using Michaelis-Menten kinetics.

RESULTS

VPA uncompetitively inhibited Acsl4-mediated conversion of AA and of docosahexaenoic (DHA) but not of palmitic acid to acyl-CoA, but did not affect AA conversion by Acsl3, Acsl6v1 or Acsl6v2. Acsl4-mediated conversion of AA to AA-CoA showed substrate inhibition and had a 10-times higher catalytic efficiency than did conversion of DHA to DHA-CoA. Butyrate, octanoate, or lithium did not inhibit AA activation by Acsl4.

CONCLUSIONS

VPA's ability to inhibit Acsl4 activation of AA and of DHA to their respective acyl-CoAs, when related to the higher catalytic efficiency of AA than DHA conversion, may account for VPA's selective reduction of AA turnover in rat brain phospholipids, and contribute to VPA's efficacy against bipolar disorder.

Swift Acetate Glial Assay (SAGA): an accelerated human ¹³C MRS brain exam for clinical diagnostic use

We demonstrate a robust procedure for the quantitative characterization of glial metabolism in human brain. In the past, the slope of the uptake and production of enriched label at steady state were used to determine metabolic rates, requiring the patient to be in the magnet for 120-160 min. In the present method, (13)C cerebral metabolite profiles were acquired at steady state alone on a routine clinical MR scanner in 25.6 min. Results obtained from the new short method (SAGA) were comparable to those achieved in a conventional, long method and effective for determination of glial metabolic rate in posterior-parietal and frontal brain regions.

A genetic network model of cellular responses to lithium treatment and cocaine abuse in bipolar disorder

Background

Lithium is an effective treatment for Bipolar Disorder (BD) and significantly reduces suicide risk, though the molecular basis of lithium's effectiveness is not well understood. We seek to improve our understanding of this effectiveness by posing hypotheses based on new experimental data as well as published data, testing these hypotheses in silico, and posing new hypotheses for validation in future studies. We initially hypothesized a gene-by-environment interaction where lithium, acting as an environmental influence, impacts signal transduction pathways leading to differential expression of genes important in the etiology of BD mania.

Results

Using microarray and rt-QPCR assays, we identified candidate genes that are differentially expressed with lithium treatment. We used a systems biology approach to identify interactions among these candidate genes and develop a network of genes that interact with the differentially expressed candidates. Notably, we also identified cocaine as having a potential influence on the network, consistent with the observed high rate of comorbidity for BD and cocaine abuse. The resulting network represents a novel hypothesis on how multiple genetic influences on bipolar disorder are impacted by both lithium treatment and cocaine use. Testing this network for association with BD and related phenotypes, we find that it is significantly over-represented for genes that participate in signal transduction, consistent with our hypothesized-gene-by environment interaction. In addition, it models related pharmacogenomic, psychiatric, and chemical dependence phenotypes.

Conclusions

We offer a network model of gene-by-environment interaction associated with lithium's effectiveness in treating BD mania, as well as the observed high rate of comorbidity of BD and cocaine abuse. We identified drug targets within this network that represent immediate candidates for therapeutic drug testing. Posing novel hypotheses for validation in future work, we prioritized SNPs near genes in the network based on functional annotation. We also developed a "concept signature" for the genes in the network and identified additional candidate genes that may influence the system because they are significantly associated with the signature.

Pathways underlying neuroprogression in bipolar disorder: focus on inflammation, oxidative stress and neurotrophic factors

There is now strong evidence of progressive neuropathological processes in bipolar disorder (BD). On this basis, the current understanding of the neurobiology of BD has shifted from an initial focus on monoamines, subsequently including evidence of changes in intracellular second messenger systems and more recently to, incorporating changes in inflammatory cytokines, corticosteroids, neurotrophins, mitochondrial energy generation, oxidative stress and neurogenesis into a more comprehensive model capable of explaining some of the clinical features of BD. These features include progressive shortening of the inter-episode interval with each recurrence, occurring in consort with reduced probability of treatment response as the illness progresses. To this end, emerging data shows that these biomarkers may differ between early and late stages of BD in parallel with stage-related structural and neurocognitive alterations. This understanding facilitates identification of rational therapeutic targets, and the development of novel treatment classes. Additionally, these pathways provide a cogent explanation for the efficacy of seemingly diverse therapies used in BD, that appear to share common effects on oxidative, inflammatory and neurotrophic pathways.

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.

Lithium modifies brain arachidonic and docosahexaenoic metabolism in rat lipopolysaccharide model of neuroinflammation

Neuroinflammation, caused by 6 days of intracerebroventricular infusion of a low dose of lipopolysaccharide (LPS; 0.5 ng/h), stimulates brain arachidonic acid (AA) metabolism in rats, but 6 weeks of lithium pretreatment reduces this effect. To further understand this action of lithium, we measured concentrations of eicosanoids and docosanoids generated from AA and docosahexaenoic acid (DHA), respectively, in high-energy microwaved rat brain using LC/MS/MS and two doses of LPS. In rats fed a lithium-free diet, low (0.5 ng/h)- or high (250 ng/h)-dose LPS compared with artificial cerebrospinal fluid increased brain unesterified AA and prostaglandin E(2) concentrations and activities of AA-selective Ca(2+)-dependent cytosolic phospholipase A(2) (cPLA(2))-IV and Ca(2+)-dependent secretory sPLA(2). LiCl feeding prevented these increments. Lithium had a significant main effect by increasing brain concentrations of lipoxygenase-derived AA metabolites, 5- hydroxyeicosatetraenoic acid (HETE), 5-oxo-eicosatetranoic acid, and 17-hydroxy-DHA by 1.8-, 4.3- and 1.9-fold compared with control diet. Lithium also increased 15-HETE in high-dose LPS-infused rats. Ca(2+)-independent iPLA(2)-VI activity and unesterified DHA and docosapentaenoic acid (22:5n-3) concentrations were unaffected by LPS or lithium. This study demonstrates, for the first time, that lithium can increase brain 17-hydroxy-DHA formation, indicating a new and potentially important therapeutic action of lithium.

DHA deficiency and prefrontal cortex neuropathology in recurrent affective disorders

Increasing evidence suggests that docosahexaenoic acid [DHA, 22:6(n-3)], the principal (n-3) fatty acid in brain gray matter, has neurotrophic and neuroprotective properties. Preliminary clinical evidence also suggests that the perinatal accrual, and the subsequent dietary maintenance of, cortical DHA is positively associated with cortical gray matter volumes. The pathophysiology of recurrent affective disorders, including unipolar and bipolar depression, is associated with (n-3) fatty acid deficiency, DHA deficits, impaired astrocyte mediated vascular coupling, neuronal shrinkage, and reductions in gray matter volume in the prefrontal cortex (PFC). Preclinical studies have also observed neuronal shrinkage and indices of astrocyte pathology in the DHA-deficient rat brain. Together, this body of evidence supports the proposition that DHA deficiency increases vulnerability to neuronal atrophy in the PFC of patients with affective disorders. Because projections from the PFC modulate multiple limbic structures involved in affective regulation, this represents one plausible mechanism by which (n-3) fatty acid deficiency may increase vulnerability to recurrent affective disorders.

Brain lipid concentrations in bipolar disorder

Reduced concentrations of docosahexaenoic acid (DHA, 22:6n-3) and arachidonic acid (AA, 20:4n-6) have been reported in the postmortem bipolar disorder (BD) brain. Additionally, an increased prevalence of BD has been related to low dietary intake of fish, and dietary supplements containing fish products or DHA have been reported to ameliorate BD symptoms. These observations suggest that brain lipid metabolism, particularly involving DHA, is disturbed in BD. To test this suggestion, concentrations of different lipids were measured using internal standards in postmortem frontal cortex from eight BD patients and six matched controls. Compared with control cortex, the BD cortex showed no statistically significant difference in mean concentrations (per gram wet weight) of "stable" lipids (total lipid, total phospholipid, individual phospholipids, or cholesterol), of unesterified fatty acids, or of esterified DHA or AA within stable lipids. Fractional esterified AA and DHA concentrations also did not differ significantly between groups. Some fatty acid concentration differences were found in low-abundant cholesteryl ester. These results do not support the hypothesis of disturbed brain lipid concentrations, including concentrations of AA and DHA, in BD. Positron emission tomography might be used, however, to see if brain AA or DHA kinetics are disturbed in the disease.

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.

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.