The neurobiology of bipolar disorder: focus on signal transduction pathways and the regulation of gene expression

A critical evaluation of dynamical systems models of bipolar disorder

Bipolar disorder (BD) is a mood disorder involving recurring (hypo)manic and depressive episodes. The inherently temporal nature of BD has inspired its conceptualization using dynamical systems theory, which is a mathematical framework for understanding systems that evolve over time. In this paper, we provide a critical review of the dynamical systems models of BD. Owing to the heterogeneity of methodological and experimental designs in computational modeling, we designed a structured approach that parallels the appraisal of animal models by their face, predictive, and construct validity. This tool, the validity appraisal guide for computational models (VAG-CM), is not an absolute measure of validity, but rather a guide for a more objective appraisal of models in this review. We identified 26 studies published before November 18, 2021 that proposed generative dynamical systems models of time-varying signals in BD. Two raters independently applied the VAG-CM to the included studies, obtaining a mean Cohen's κ of 0.55 (95% CI [0.45, 0.64]) prior to establishing consensus ratings. Consensus VAG-CM ratings revealed three model/study clusters: data-driven models with face validity, theory-driven models with predictive validity, and theory-driven models lacking all forms of validity. We conclude that future modeling studies should employ a hybrid approach that first operationalizes BD features of interest using empirical data to achieve face validity, followed by explanations of those features using generative models with components that are homologous to physiological or psychological systems involved in BD, to achieve construct validity. Such models would be best developed alongside long-term prospective cohort studies involving a collection of multimodal time-series data. We also encourage future studies to extend, modify, and evaluate the VAG-CM approach for a wider breadth of computational modeling studies and psychiatric disorders.

Endogenous Cardiac Steroids in Bipolar Disorder: State of the Art

Bipolar disorder (BD) is a severe psychiatric illness with a poor prognosis and problematic, suboptimal, treatments. Treatments, borne of an understanding of the pathoetiologic mechanisms, need to be developed in order to improve outcomes. Dysregulation of cationic homeostasis is the most reproducible aspect of BD pathophysiology. Correction of ionic balance is the universal mechanism of action of all mood stabilizing medications. Endogenous sodium pump modulators (collectively known as endogenous cardiac steroids, ECS) are steroids which are synthesized in and released from the adrenal gland and brain. These compounds, by activating or inhibiting Na⁺, K⁺-ATPase activity and activating intracellular signaling cascades, have numerous effects on cell survival, vascular tone homeostasis, inflammation, and neuronal activity. For the past twenty years we have addressed the hypothesis that the Na⁺, K⁺-ATPase-ECS system may be involved in the etiology of BD. This is a focused review that presents a comprehensive model pertaining to the role of ECS in the etiology of BD. We propose that alterations in ECS metabolism in the brain cause numerous biochemical changes that underlie brain dysfunction and mood symptoms. This is based on both animal models and translational human results. There are data that demonstrate that excess ECS induce abnormal mood and activity in animals, while a specific removal of ECS with antibodies normalizes mood. There are also data indicating that circulating levels of ECS are lower in manic individuals, and that patients with BD are unable to upregulate synthesis of ECS under conditions that increase their elaboration in non-psychiatric controls. There is strong evidence for the involvement of ion dysregulation and ECS function in bipolar illness. Additional research is required to fully characterize these abnormalities and define future clinical directions.

Prediction of lithium response using genomic data

Predicting lithium response prior to treatment could both expedite therapy and avoid exposure to side effects. Since lithium responsiveness may be heritable, its predictability based on genomic data is of interest. We thus evaluate the degree to which lithium response can be predicted with a machine learning (ML) approach using genomic data. Using the largest existing genomic dataset in the lithium response literature (n = 2210 across 14 international sites; 29% responders), we evaluated the degree to which lithium response could be predicted based on 47,465 genotyped single nucleotide polymorphisms using a supervised ML approach. Under appropriate cross-validation procedures, lithium response could be predicted to above-chance levels in two constituent sites (Halifax, Cohen’s kappa 0.15, 95% confidence interval, CI [0.07, 0.24]; and Würzburg, kappa 0.2 [0.1, 0.3]). Variants with shared importance in these models showed over-representation of postsynaptic membrane related genes. Lithium response was not predictable in the pooled dataset (kappa 0.02 [− 0.01, 0.04]), although non-trivial performance was achieved within a restricted dataset including only those patients followed prospectively (kappa 0.09 [0.04, 0.14]). Genomic classification of lithium response remains a promising but difficult task. Classification performance could potentially be improved by further harmonization of data collection procedures.

Exemplar scoring identifies genetically separable phenotypes of lithium responsive bipolar disorder

Predicting lithium response (LiR) in bipolar disorder (BD) may inform treatment planning, but phenotypic heterogeneity complicates discovery of genomic markers. We hypothesized that patients with "exemplary phenotypes"-those whose clinical features are reliably associated with LiR and non-response (LiNR)-are more genetically separable than those with less exemplary phenotypes. Using clinical data collected from people with BD (n = 1266 across 7 centers; 34.7% responders), we computed a "clinical exemplar score," which measures the degree to which a subject's clinical phenotype is reliably predictive of LiR/LiNR. For patients whose genotypes were available (n = 321), we evaluated whether a subgroup of responders/non-responders with the top 25% of clinical exemplar scores (the "best clinical exemplars") were more accurately classified based on genetic data, compared to a subgroup with the lowest 25% of clinical exemplar scores (the "poor clinical exemplars"). On average, the best clinical exemplars of LiR had a later illness onset, completely episodic clinical course, absence of rapid cycling and psychosis, and few psychiatric comorbidities. The best clinical exemplars of LiR and LiNR were genetically separable with an area under the receiver operating characteristic curve of 0.88 (IQR [0.83, 0.98]), compared to 0.66 [0.61, 0.80] (p = 0.0032) among poor clinical exemplars. Variants in the Alzheimer's amyloid-secretase pathway, along with G-protein-coupled receptor, muscarinic acetylcholine, and histamine H1R signaling pathways were informative predictors. This study must be replicated on larger samples and extended to predict response to other mood stabilizers.

Using human stem cells as a model system to understand the neural mechanisms of alcohol use disorders: Current status and outlook

Alcohol use disorders (AUDs), which include alcohol abuse and dependence, are among the most common types of neuropsychiatric disorders in the United States (U.S.). Approximately 14% of the U.S. population is affected in a single year, thus placing a tremendous burden on individuals from all socioeconomic backgrounds. Animal models have been pivotal in revealing the basic mechanisms of how alcohol impacts neuronal function, yet there are currently limited effective therapies developed based on these studies. This is mainly due to a limited understanding of the exact cellular and molecular mechanisms underlying AUDs in humans, which leads to a lack of targeted therapeutics. Furthermore, compounding factors including genetic background, gene copy number variants, single nucleotide polymorphisms (SNP) as well as environmental and social factors that affect and promote the development of AUDs are complex and heterogeneous. Recent developments in stem cell biology, especially the human induced pluripotent stem (iPS) cell development and differentiation technologies, has provided us a unique opportunity to model neuropsychiatric disorders like AUDs in a manner that is highly complementary to animal studies, but that maintains fidelity with complex human genetic contexts. Patient-specific neuronal cells derived from iPS cells can then be used for drug discovery and precision medicine, e.g. for pathway-directed development in alcoholism. Here, we review recent work employing iPS cell technology to model and elucidate the genetic, molecular and cellular mechanisms of AUDs in a human neuronal background and provide our perspective on future development in this direction.

Application of induced pluripotent stem cells to understand neurobiological basis of bipolar disorder and schizophrenia

The etiology of neuropsychiatric disorders, such as schizophrenia and bipolar disorder, usually involves complex combinations of genetic defects/variations and environmental impacts, which hindered, for a long time, research efforts based on animal models and patients' non-neuronal cells or post-mortem tissues. However, the development of human induced pluripotent stem cell (iPSC) technology by the Yamanaka group was immediately applied to establish cell research models for neuronal disorders. Since then, techniques to achieve highly efficient differentiation of different types of neural cells following iPSC modeling have made much progress. The fast-growing iPSC and neural differentiation techniques have brought valuable insights into the pathology and neurobiology of neuropsychiatric disorders. In this article, we first review the application of iPSC technology in modeling neuronal disorders and discuss the progress in the accompanying neural differentiation. Then, we summarize the progress in iPSC-based research that has been accomplished so far regarding schizophrenia and bipolar disorder.

Effects of Lithium Monotherapy for Bipolar Disorder on Gene Expression in Peripheral Lymphocytes

BACKGROUND

This study investigated the effect of lithium monotherapy on peripheral lymphocyte gene expression in bipolar disorder (BD).

METHOD

Twenty-two medication-free bipolar subjects (11 hypomanic, 11 depressed) were started on lithium monotherapy. Closely matched healthy subjects (n = 15) were included as controls but did not receive treatment. Blood RNA samples were collected at baseline and after 2 and 8 weeks of treatment. RNA expression was measured using the Affymetrix GeneChip® Human Gene 1.0 ST Array followed by Ingenuity pathways analysis. The results for the contrast of weeks 2 and 8 were not significantly different and were combined.

RESULTS

In BD subjects, 56 genes showed significant (false discovery rate <0.1) expression changes from baseline; the effect sizes and directions for all of these were similar at weeks 2 and 8. Among these were immune-related genes (IL5RA, MOK, IFI6, and RFX2), purinergic receptors (P2RY14, P2RY2, and ADORA3) and signal transduction-related genes (CAMK1 and PIK3R6). Pathway and upstream regulator analysis also revealed that lithium altered several immune- and signal transduction-related functions. Differentially expressed genes did not correlate with week 8 clinical response, but other genes involved in protein synthesis and degradation did.

CONCLUSION

Peripheral gene expression may serve as a biomarker of lithium effect.

Differential responses to lithium in hyperexcitable neurons from patients with bipolar disorder

Bipolar disorder is a complex neuropsychiatric disorder that is characterized by intermittent episodes of mania and depression; without treatment, 15% of patients commit suicide. Hence, it has been ranked by the World Health Organization as a top disorder of morbidity and lost productivity. Previous neuropathological studies have revealed a series of alterations in the brains of patients with bipolar disorder or animal models, such as reduced glial cell number in the prefrontal cortex of patients, upregulated activities of the protein kinase A and C pathways and changes in neurotransmission. However, the roles and causation of these changes in bipolar disorder have been too complex to exactly determine the pathology of the disease. Furthermore, although some patients show remarkable improvement with lithium treatment for yet unknown reasons, others are refractory to lithium treatment. Therefore, developing an accurate and powerful biological model for bipolar disorder has been a challenge. The introduction of induced pluripotent stem-cell (iPSC) technology has provided a new approach. Here we have developed an iPSC model for human bipolar disorder and investigated the cellular phenotypes of hippocampal dentate gyrus-like neurons derived from iPSCs of patients with bipolar disorder. Guided by RNA sequencing expression profiling, we have detected mitochondrial abnormalities in young neurons from patients with bipolar disorder by using mitochondrial assays; in addition, using both patch-clamp recording and somatic Ca(2+) imaging, we have observed hyperactive action-potential firing. This hyperexcitability phenotype of young neurons in bipolar disorder was selectively reversed by lithium treatment only in neurons derived from patients who also responded to lithium treatment. Therefore, hyperexcitability is one early endophenotype of bipolar disorder, and our model of iPSCs in this disease might be useful in developing new therapies and drugs aimed at its clinical treatment.

Alterations in Gene Expression in Depression: Prospects for Personalize Patient Treatment

The number of people around the world suffering from depression has dramatically increased in last few decades. It has been predicted that by 2020 depression will become the second most common cause of disability. Furthermore, depression is often misdiagnosed and confused with other psychiatric disorders showing similar symptoms, i.e., anxiety and bipolar disorder, due to the fact that diagnosing is often carried out by medical workers who are not psychiatrically trained. These facts prompt us to prepare this review which focuses on alterations in gene expression in depression. We believe that an in-depth knowledge of molecular bases of behavior in depression and other mood disorders would be of a great benefit for the correct diagnosing of these disorders, as well as for prescribing a treatment that best suits each individual depending on expression alterations in depression-related genes. Therefore, the main aim of this review is to promote further translational research on the biochemistry of mood disorders and take the results further for the design of new targeted therapeutics that can be used for personalized treatment with minimal adverse effects.

EEG power, cordance and coherence differences between unipolar and bipolar depression

INTRODUCTION

Understanding the biological underpinnings of unipolar (UD) and bipolar depression (BD) is vital for avoiding inappropriate treatment through the misdiagnosis of bipolar patients in their first depressive episode. One plausible way to distinguish between UD and BD is to compare EEG brain dynamics to identify potential neurophysiological biomarkers. Here we aimed to test group differences in EEG power, cordance and coherence values between UD and BD.

METHODS

Twenty-five bipolar and 56 unipolar depression patients were recruited. Sociodemographic and clinical variables were collected in addition to resting state EEG. Data was analyzed with multivariate and repeated analyses of variance where parametric assumptions were met.

RESULTS

Accordingly, we did not find any differences in the EEG absolute power and frontal asymmetry indexes between UD and BD. Regarding cordance, significant group differences were observed in the right theta cordance values (p=0.031). Regarding coherence, BD patients (as compared to UD) exhibited greater central-temporal theta (p=0.003), and parietal-temporal alpha (p=0.007) and theta (p=0.001) coherence. Lastly, less alpha coherence in BD was present at right frontal-central (p=0.007) and central inter-hemispheric (p=0.019) regions.

CONCLUSIONS

Our results demonstrate that EEG cordance and coherence values have potential to discriminate between UD and BD. The loss of temporal synchronization in the frontal interhemispheric and right sided frontolimbic neuronal networks may be a unique feature that distinguishes between BD and UD.

The neurobiology of bipolar disorder: identifying targets for specific agents and synergies for combination treatment

Bipolar disorder (BD) is a chronic psychiatric illness described by severe changes in mood. Extensive research has been carried out to understand the aetiology and pathophysiology of BD. Several hypotheses have been postulated, including alteration in genetic factors, protein expression, calcium signalling, neuropathological alteration, mitochondrial dysfunction and oxidative stress in BD. In the following paper, we will attempt to integrate these data in a manner which is to understand targets of treatment and how they may be, in particular, relevant to combination treatment. In summary, the data suggested that BD might be associated with neuronal and glial cellular impairment in specific brain areas, including the prefrontal cortex. From molecular and genetics: (1) alterations in dopaminergic system, through catechol-O-aminotransferase; (2) decreased expression and polymorphism on brain-derived neurotrophic factor; (3) alterations cyclic-AMP responsive element binding; (4) dysregulation of calcium signalling, including genome-wide finding for voltage-dependent calcium channel α-1 subunit are relevant findings in BD. Future studies are now necessary to understand how these molecular pathways interact and their connection to the complex clinical manifestations observed in BD.

Alteration of cyclic-AMP response element binding protein in the postmortem brain of subjects with bipolar disorder and schizophrenia

BACKGROUND

Abnormalities of cyclic-AMP (cAMP) response element binding protein (CREB) function has been suggested in bipolar (BP) illness and schizophrenia (SZ), based on both indirect and direct evidence. To further elucidate the role of CREB in these disorders, we studied CREB expression and function in two brain areas implicated in these disorders, i.e., dorsolateral prefrontal cortex (DLPFC) and cingulate gyrus (CG).

METHODS

We determined CREB protein expression using Western blot technique, CRE-DNA binding using gel shift assay, and mRNA expression using real-time RT-polymerase chain reaction (qPCR) in DLPFC and CG of the postmortem brain of BP (n=19), SZ (n=20), and normal control (NC, n=20) subjects.

RESULTS

We observed that CREB protein and mRNA expression and CRE-DNA binding activity were significantly decreased in the nuclear fraction of DLPFC and CG obtained from BP subjects compared with NC subjects. However, the protein and mRNA expression and CRE-DNA binding in SZ subjects was significantly decreased in CG, but not in DLPFC, compared with NC.

CONCLUSION

These studies thus indicate region-specific abnormalities of CREB expression and function in both BP and SZ. They suggest that abnormalities of CREB in CG may be associated with both BP and SZ, but its abnormality in DLPFC is specific to BP illness.

Reduced regulatory T cells are associated with higher levels of Th1/TH17 cytokines and activated MAPK in type 1 bipolar disorder

Bipolar disorder (BD) has been associated with an immunologic imbalance shown by increased peripheral inflammatory markers. The underlying mechanisms of this phenomenon may include changes in circulating cells and differential activation of mitogen-activated protein kinases (MAPKs). Twenty-seven euthymic female subjects with BD type I (all medicated) and 24 age- and sex-matched controls were recruited in this study. Lymphocytes were isolated and stimulated in vitro to assess Th1/Th17/Th2 cytokines (IL-2, IL-4, IL-6, IL-10, IL-17, IFN-γ and TNF-α) and MAPK phosphorylation. The expression of phospho-MAPKs, a large panel of lymphocyte subsets and cytokines were assessed by multi-color flow cytometry. BD patients had reduced proportions of natural T regulatory cells (CD4+ CD25+ FoxP3+) (p<0.01) in parallel to higher cytokine production (all p<0.01) than healthy controls. In particular, BD was associated with a strong bias to Th1 rather than Th2 profile. There was an expansion of senescence-associated cells (CD8+ CD28-) in BD (p<0.0001). T cells of BD patients had an increased p-ERK signaling (p<0.0001), indicating lymphocyte activation. Our data suggest that multiple molecular and cellular mechanisms may contribute to the immunologic imbalance observed in BD. In addition, our data concur to an early senescence process in these patients.

A comparative genomic study in schizophrenic and in bipolar disorder patients, based on microarray expression profiling meta-analysis

Schizophrenia affecting almost 1% and bipolar disorder affecting almost 3%–5% of the global population constitute two severe mental disorders. The catecholaminergic and the serotonergic pathways have been proved to play an important role in the development of schizophrenia, bipolar disorder, and other related psychiatric disorders. The aim of the study was to perform and interpret the results of a comparative genomic profiling study in schizophrenic patients as well as in healthy controls and in patients with bipolar disorder and try to relate and integrate our results with an aberrant amino acid transport through cell membranes. In particular we have focused on genes and mechanisms involved in amino acid transport through cell membranes from whole genome expression profiling data. We performed bioinformatic analysis on raw data derived from four different published studies. In two studies postmortem samples from prefrontal cortices, derived from patients with bipolar disorder, schizophrenia, and control subjects, have been used. In another study we used samples from postmortem orbitofrontal cortex of bipolar subjects while the final study was performed based on raw data from a gene expression profiling dataset in the postmortem superior temporal cortex of schizophrenics. The data were downloaded from NCBI's GEO datasets.

A hybrid likelihood model for sequence-based disease association studies

In the past few years, case-control studies of common diseases have shifted their focus from single genes to whole exomes. New sequencing technologies now routinely detect hundreds of thousands of sequence variants in a single study, many of which are rare or even novel. The limitation of classical single-marker association analysis for rare variants has been a challenge in such studies. A new generation of statistical methods for case-control association studies has been developed to meet this challenge. A common approach to association analysis of rare variants is the burden-style collapsing methods to combine rare variant data within individuals across or within genes. Here, we propose a new hybrid likelihood model that combines a burden test with a test of the position distribution of variants. In extensive simulations and on empirical data from the Dallas Heart Study, the new model demonstrates consistently good power, in particular when applied to a gene set (e.g., multiple candidate genes with shared biological function or pathway), when rare variants cluster in key functional regions of a gene, and when protective variants are present. When applied to data from an ongoing sequencing study of bipolar disorder (191 cases, 107 controls), the model identifies seven gene sets with nominal p-values0.05, of which one MAPK signaling pathway (KEGG) reaches trend-level significance after correcting for multiple testing.

Inexpensive, high-throughput sequencing has transformed the field of case-control association studies. For the first time, it may be possible to identify the genetic underpinnings of complex diseases, by sequencing the DNA of hundreds (even thousands) of cases and controls and comparing patterns of DNA sequence variation. However, complex diseases are likely to be caused by many variants, some of which are very rare. Taken one at a time, the association between variant and disease phenotype may not be detectable by current statistical methods. One strategy is to identify regions where important variants occur by “collapsing” variants into groups. Here, we present a new collapsing approach, capable of detecting subtle genetic differences between cases and controls. We show, in extensive simulations and using a benchmark set of genes involved in human triglyceride levels, that the approach is potentially more powerful than existing methods. We apply the new method to an ongoing sequencing study of bipolar cases and controls and identify a set of genes found in neuronal synapses, which may be implicated in bipolar disorder.

Evidence for disease and antipsychotic medication effects in post-mortem brain from schizophrenia patients

Extensive research has been conducted on post-mortem brain tissue in schizophrenia (SCZ), particularly the dorsolateral prefrontal cortex (DLPFC). However, to what extent the reported changes are due to the disorder itself, and which are the cumulative effects of lifetime medication remains to be determined. In this study, we employed label-free liquid chromatography-mass spectrometry-based proteomic and proton nuclear magnetic resonance-based metabonomic profiling approaches to investigate DLPFC tissue from two cohorts of SCZ patients grouped according to their lifetime antipsychotic dose, together with tissue from bipolar disorder (BPD) subjects, and normal controls (n=10 per group). Both techniques showed profound changes in tissue from low-cumulative-medication SCZ subjects, but few changes in tissue from medium-cumulative-medication subjects. Protein expression changes were validated by Western blot and investigated further in a third group of subjects who were subjected to high-cumulative-medication over the course of their lifetime. Furthermore, key protein expression and metabolite level changes correlated significantly with lifetime antipsychotic dose. This suggests that the detected changes are present before antipsychotic therapy and, moreover, may be normalized with treatment. Overall, our analyses revealed novel protein and metabolite changes in low-cumulative-medication subjects associated with synaptogenesis, neuritic dynamics, presynaptic vesicle cycling, amino acid and glutamine metabolism, and energy buffering systems. Most of these markers were altered specifically in SCZ as determined by analysis of the same brain region from BPD patients.

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.

Evaluation of citrate synthase activity in brain of rats submitted to an animal model of mania induced by ouabain

Bipolar disorder (BD) is a psychiatric disorder characterized by alternating episodes of mania and depression. The intracerebroventricular (i.c.v) administration of ouabain (a Na(+)/K(+)-ATPase inhibitor) in rats has been used as an animal model of mania, because present face, construct and predictive validities. Several studies strongly suggest that mitochondrial dysfunction play a central role in the pathophysiology of BD. Citrate synthase (CS) is an enzyme localized in the mitochondrial matrix and represents one of the most important steps of Krebs cycle. The aim of this study was to investigate CS activity in brain of rats after the administration of ouabain. Adult male Wistar rats received a single i.c.v. administration of ouabain (10(-2) and 10(-3) M) or vehicle (control group). Locomotor activity was measured using the open field task. CS activity was measured in the brain of rats immediately (1 h) and 7 days after ouabain administration. Our results showed that spontaneous locomotion was increased 1 h after ouabain administration, and that the hyperlocomotion persists 7 days after the administration. Moreover, CS activity was inhibited immediately after the administration of ouabain in the prefrontal cortex at the doses of 10(-3) and 10(-2) M. This inhibition remains by 7 days after the administration of ouabain. On the other hand, it was not observed any difference in CS activity in the hippocampus and striatum. Considering that inhibition of CS activity may reflect a mitochondrial dysfunction, it is tempting to speculate that the reduction of brain energy metabolism might be related to the pathophysiology of BD.

Antidepressants are a rational complementary therapy for the treatment of Alzheimer's disease

There is a high prevalence rate (30-50%) of Alzheimer's disease (AD) and depression comorbidity. Depression can be a risk factor for the development of AD or it can be developed secondary to the neurodegenerative process. There are numerous documented diagnosis and treatment challenges for the patients who suffer comorbidity between these two diseases. Meta analysis studies have provided evidence for the safety and efficacy of antidepressants in treatment of depression in AD patients. Preclinical and clinical studies show the positive role of chronic administration of selective serotonin reuptake inhibitor (SSRI) antidepressants in hindering the progression of the AD and improving patient performance. A number of clinical studies suggest a beneficial role of combinatorial therapies that pair antidepressants with FDA approved AD drugs. Preclinical studies also demonstrate a favorable effect of natural antidepressants for AD patients. Based on the preclinical studies there are a number of plausible antidepressants effects that may modulate the progression of AD. These effects include an increase in neurogenesis, improvement in learning and memory, elevation in the levels of neurotrophic factors and pCREB and a reduction of amyloid peptide burden. Based on this preclinical and clinical evidence, antidepressants represent a rational complimentary strategy for the treatment of AD patients with depression comorbidity.

Electroconvulsive seizure increases phosphorylation of PKC substrates, including GAP-43, MARCKS, and neurogranin, in rat brain

Protein kinase C (PKC) has been suggested as a molecular target related to the pathogenetic and therapeutic mechanisms of mood disorders in which electroconvulsive seizure (ECS) is effective. However, the reports concerning the effects of ECS on PKC are anecdotal and need further clarification. In this study, we examined the effects of ECS treatment on the phosphorylation of PKC substrates, including GAP-43, MARCKS, and neurogranin. Immunoblot using anti-p-PKC substrate antibodies revealed that a single ECS treatment induced temporal changes in the phosphorylation level of PKC substrates in rat brain, reflecting the effects on PKC activity. Phosphorylation of GAP-43 and MARCKS, representative PKC substrates related to synaptic remodeling, increased from 5 to 30 min, after a transient decrease at 0 min immediately after ECS, and returned to basal levels at 60 min in rat frontal cortex, hippocampus, and cerebellum. Phosphorylation of neurogranin, another PKC substrate, showed a similar pattern of temporal changes in the frontal cortex and hippocampus. Immunohistochemical analysis revealed that p-GAP-43 and p-MARCKS were densely stained throughout the neuronal cells of the prefrontal cortex and hippocampus, and the Purkinje cells of cerebellum, after ECS treatment. Brief and transient activation of PKC may be translated into long-term biochemical changes, resulting in synaptic plasticity. Taken together, the acute effects of ECS on PKC activity, which could be an underpinning of long-term biochemical changes induced by ECS, may contribute to understand the molecular mechanism of ECS.

Neurobiological trait abnormalities in bipolar disorder

Dissecting trait neurobiological abnormalities in bipolar disorder (BD) from those characterizing episodes of mood disturbance will help elucidate the aetiopathogenesis of the illness. This selective review highlights the immunological, neuroendocrinological, molecular biological and neuroimaging abnormalities characteristic of BD, with a focus on those likely to reflect trait abnormalities by virtue of their presence in euthymic patients or in unaffected relatives of patients at high genetic liability for illness. Trait neurobiological abnormalities of BD include heightened pro-inflammatory function and hypothalamic-pituitary-adrenal axis dysfunction. Dysfunction in the intracellular signal transduction pathway is indicated by elevated protein kinase A activity and altered intracellular calcium signalling. Consistent neuroimaging abnormalities include the presence of ventricular enlargement and white matter abnormalities in patients with BD, which may represent intermediate phenotypes of illness. In addition, spectroscopy studies indicate reduced prefrontal cerebral N-acetylaspartate and phosphomonoester concentrations. Functional neuroimaging studies of euthymic patients implicate inherently impaired neural networks subserving emotional regulation, including anterior limbic, ventral and dorsal prefrontal regions. Despite heterogeneous samples and conflicting findings pervading the literature, there is accumulating evidence for the existence of neurobiological trait abnormalities in BD at various scales of investigation. The aetiopathogenesis of BD will be better elucidated by future clinical research studies, which investigate larger and more homogenous samples and employ a longitudinal design to dissect neurobiological abnormalities that are underlying traits of the illness from those related to episodes of mood exacerbation or pharmacological treatment.

Lithium: a key to the genetics of bipolar disorder

Since the 1950s, lithium salts have been the main line of treatment for bipolar disorder (BD), both as a prophylactic and as an episodic treatment agent. Like many psychiatric conditions, BD is genetically and phenotypically heterogeneous, but evidence suggests that individuals who respond well to lithium treatment have more homogeneous clinical and molecular profiles. Response to lithium seems to cluster in families and can be used as a predictor for recurrence of BD symptoms. While molecular studies have provided important information about possible genes involved in BD predisposition or in lithium response, neither the mechanism of action of this drug nor the genetic profile of bipolar disorder is, as yet, completely understood.

Prioritizing risk pathways: a novel association approach to searching for disease pathways fusing SNPs and pathways

MOTIVATION

Complex diseases are generally thought to be under the influence of one or more mutated risk genes as well as genetic and environmental factors. Many traditional methods have been developed to identify susceptibility genes assuming a single-gene disease model ('single-locus methods'). Pathway-based approaches, combined with traditional methods, consider the joint effects of genetic factor and biologic network context. With the accumulation of high-throughput SNP datasets and human biologic pathways, it becomes feasible to search for risk pathways associated with complex diseases using bioinformatics methods. By analyzing the contribution of genetic factor and biologic network context in KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways, we proposed an approach to prioritize risk pathways for complex diseases: Prioritizing Risk Pathways fusing SNPs and pathways (PRP). A risk-scoring (RS) measurement was used to prioritize risk biologic pathways. This could help to demonstrate the pathogenesis of complex diseases from a new perspective and provide new hypotheses. We introduced this approach to five complex diseases and found that these five diseases not only share common risk pathways, but also have their specific risk pathways, which is verified by literature retrieval.

Mitochondrial dysfunction and psychiatric disorders

Mitochondrial oxidative phosphorylation is the major ATP-producing pathway, which supplies more than 95% of the total energy requirement in the cells. Damage to the mitochondrial electron transport chain has been suggested to be an important factor in the pathogenesis of a range of psychiatric disorders. Tissues with high energy demands, such as the brain, contain a large number of mitochondria, being therefore more susceptible to reduction of the aerobic metabolism. Mitochondrial dysfunction results from alterations in biochemical cascade and the damage to the mitochondrial electron transport chain has been suggested to be an important factor in the pathogenesis of a range of neuropsychiatric disorders, such as bipolar disorder, depression and schizophrenia. Bipolar disorder is a prevalent psychiatric disorder characterized by alternating episodes of mania and depression. Recent studies have demonstrated that important enzymes involved in brain energy are altered in bipolar disorder patients and after amphetamine administration, an animal model of mania. Depressive disorders, including major depression, are serious and disabling. However, the exact pathophysiology of depression is not clearly understood. Several works have demonstrated that metabolism is impaired in some animal models of depression, induced by chronic stress, especially the activities of the complexes of mitochondrial respiratory chain. Schizophrenia is a devastating mental disorder characterized by disturbed thoughts and perception, alongside cognitive and emotional decline associated with a severe reduction in occupational and social functioning, and in coping abilities. Alterations of mitochondrial oxidative phosphorylation in schizophrenia have been reported in several brain regions and also in platelets. Abnormal mitochondrial morphology, size and density have all been reported in the brains of schizophrenic individuals. Considering that several studies link energy impairment to neuronal death, neurodegeneration and disease, this review article discusses energy impairment as a mechanism underlying the pathophysiology of some psychiatric disorders, like bipolar disorder, depression and schizophrenia.

Lithium response and genetic variation in the CREB family of genes

Bipolar disorder (BD) is a severe psychiatric disorder that affects 1% of the population. Recently, there have been many attempts to identify specific genes that are involved in BD; however, the task of finding susceptibility genes is not easy due to the complexity of the disorder. Since lithium (Li) has been used for over 40 years now as an effective prophylactic agent and response to Li treatment seems to be, at least in part, genetically determined, classification according to Li response is a manner through which more homogeneous populations can be obtained for investigation. It has previously been suggested that Li exerts an effect on signal transduction pathways, such as the cyclic adenosine monophosphate (cAMP) pathway. We carried out an association study of BD with CREB1, CREB2 and CREB3 genes, located at ch 2q32.3-q34, 22q13.1 and 9pter-p22.1, respectively. A total of three promoter single nucleotide polymorphisms (SNP), 14 SNPs in the UTR, 6 exonic and 15 intronic SNPs were investigated for their frequency and haplotype distribution in a BD sample of 180 lithium responders and 69 nonresponders and 127 controls using a SNaPshot multiplex reaction from Applied Biosystems, a modified fluorescent single base pair extension procedure. Following correction for multiple testing, our results suggest that the CREB1-1H SNP (G/A change, P < 0.002) and the CREB1-7H SNP (T/C change, P < 0.002) may be associated with BD and/or lithium response.

Decreased protein kinase C (PKC) in platelets of pediatric bipolar patients: effect of treatment with mood stabilizing drugs

Pediatric bipolar disorder (PBD) is a major public health concern, however, its neurobiology is poorly understood. We, therefore, studied the role of protein kinase C (PKC) in the pathophysiology of bipolar illness. We determined PKC activity and immunolabeling of various PKC isozymes (i.e., PKC alpha, PKC betaI, PKC betaII, and PKC delta) in the cytosol and membrane fractions of platelets obtained from PBD patients and normal control subjects. PKC activity and PKC isozymes were also determined after 8 weeks of pharmacotherapy of PBD patients (n=16) with mood stabilizers. PKC activity and the protein expression of PKC betaI and betaII, but not PKC alpha or PKC delta, were significantly decreased in both membrane as well as cytosol fractions of platelets obtained from medication-free PBD patients compared with normal control subjects. Eight weeks of pharmacotherapy resulted in significantly increased PKC activity but no significant changes in any of the PKC isozymes in PBD patients. These results indicate that decreases of specific PKC isozymes and decreased PKC activity may be associated with the pathophysiology of PBD and that pharmacotherapy with mood stabilizing drugs results in an increase and normalization of PKC activity along with improvement in clinical symptoms.

Protein kinase C inhibition by tamoxifen antagonizes manic-like behavior in rats: implications for the development of novel therapeutics for bipolar disorder

RATIONALE

In the context of bipolar disorder (BPD) research it was demonstrated that administration of the structurally dissimilar mood stabilizers lithium and valproate produced a striking reduction in protein kinase C (PKC) in rat brain. In a small clinical study, tamoxifen (a PKC inhibitor) had antimanic efficacy. However, both lithium and valproate exert many biochemical changes and attribution of therapeutic relevance to any molecular findings needs to be based on linking them to behavioral effects.

OBJECTIVES

The present study was designed to explore such relationship by studying the effects of PKC inhibition in amphetamine-induced behavioral animal models of mania and changes in GAP-43.

METHODS

The effects of two daily tamoxifen (1 mg/kg) i.p. injections on acute or chronic (7 injections) amphetamine (0.5 mg/kg) -induced behaviors and GAP-43 phosphorylation were tested.

RESULTS

The study demonstrates that tamoxifen significantly reduced amphetamine-induced hyperactivity in a large open field without affecting spontaneous activity levels and normalized amphetamine-induced increase in visits to the center of an open field (representing risk-taking behavior). Tamoxifen also attenuated amphetamine-induced phosphorylation of GAP-43, a result that is consistent with the behavioral findings.

CONCLUSIONS

These results support the possibility that PKC signaling may play an important role in the pathophysiology and treatment of BPD. These findings may have direct clinical implications as they offer a new avenue for attempts to develop more specific drugs for the disorder.

Effects of lithium and valproate on hippocampus citrate synthase activity in an animal model of mania

Some studies suggest that mitochondrial dysfunction may be related to the pathophysiology of bipolar disorder. In this work, we evaluated the activity of citrate synthase in rats, and the effects of the treatment with mood stabilizers (lithium and valproate) on the enzyme activity. In the first experiment (reversal treatment), amphetamine or saline were administered to rats for 14 days, and between day 8 and 14, rats were treated with either lithium, valproate or saline. In the second experiment (prevention treatment), rats were pretreated with lithium, valproate or saline, and between day 8 and 14, rats were administered amphetamine or saline. In reversal and prevention models, amphetamine administration significantly inhibited citrate synthase activity in rat hippocampus. In amphetamine-pretreated animals, valproate administration reversed citrate synthase activity inhibition induced by amphetamine. In the prevention model, pretreatment with lithium prevented amphetamine-induced citrate synthase inhibition. Our results showed that amphetamine inhibited citrate synthase activity and that valproate reversed and lithium prevented the enzyme inhibition.

Effects of acute and chronic valproate treatments on p-CREB levels in the rat amygdala and nucleus accumbens

Valproate may exert its effects by modulating signalling pathways controlling gene expression as they are known to alter both CREB and ERK pathways in the rat hippocampus and frontal cortex. The action of valproate on these signalling pathways has not been studied yet in limbic areas such as the nucleus accumbens and the amygdala which are central for the regulation of emotional behaviors. To this aim, the effect of valproate on phosphorylated CREB (p-CREB) and ERK (p-ERK) in the amygdala and nucleus accumbens, by using immunohistochemical and Western blot analysis, was investigated. The immunohistochemistry was followed by a stereological quantification of the number of immunoreactive cells. Acute valproate (80 mg/kg, i.p.) increased the density of p-CREB-positive cells and enhanced p-CREB, but not p-ERK, protein levels in the amygdala and the accumbens. In contrast, following chronic valproate (80 mg/kg/day for 4 weeks) p-CREB and p-ERK protein levels were markedly attenuated in the amygdala, while the number of p-CREB immunoreactive cells was increased in the accumbens. These data suggest that valproate exert differential effects depending on the brain region examined, the duration and the dose of treatment. The increasing effect of chronic valproate on p-CREB levels in the accumbens is consistent with previous studies in the cortex and the hippocampus, while the decrease of amygdalar p-CREB levels might be specific to mood stabilizers compared to antidepressant drugs, and might be linked to the anti-manic action of valproate.

Gene expression analysis of bipolar disorder reveals downregulation of the ubiquitin cycle and alterations in synaptic genes

Bipolar affective disorder is a severe psychiatric disorder with a strong genetic component but unknown pathophysiology. We used microarray technology to determine the expression of approximately 22,000 mRNA transcripts in post-mortem tissue from two brain regions in patients with bipolar disorder and matched healthy controls. Dorsolateral prefrontal cortex tissue from a cohort of 70 subjects and orbitofrontal cortex tissue from a separate cohort of 30 subjects was investigated. The final analysis included 30 bipolar and 31 control subjects for the dorsolateral prefrontal cortex and 10 bipolar and 11 control subjects for the orbitofrontal cortex. Differences between disease and control groups were identified using a rigorous statistical analysis with correction for confounding variables and multiple testing. In the orbitofrontal cortex, 393 differentially expressed transcripts were identified by microarray analysis and a representative subset was validated by quantitative real-time PCR. Pathway analysis revealed significant upregulation of genes involved in G-protein coupled receptor signalling and response to stimulus (in particular the immune response), while genes relating to the ubiquitin cycle and intracellular transport showed coordinated downregulation in bipolar disorder. Additionally, several genes involved in synaptic function were significantly downregulated in bipolar disorder. No significant changes in gene expression were observed in the dorsolateral prefrontal cortex using microarray analysis or quantitative real-time PCR. Our findings implicate the orbitofrontal cortex as a region prominently involved in bipolar disorder and indicate that diverse processes are affected. Overall, our results suggest that dysregulation of the ubiquitin pathway and synaptic function may be central to the disease process.

Lithium increases nerve growth factor levels in the rat hippocampus in an animal model of mania

Pharmacological studies suggest that neurotrophins may play a role in the effects of lithium and valproate on mood regulation. In this study, we tested the hypotheses that lithium and valproate would reverse and prevent the behavioral and biochemical effects of amphetamine, using a rat model of mania. In the reversal treatment, male Wistar rats were first administered D-amphetamine or saline for 14 days, and then, between days 8-14, rats were treated with lithium, valproate or saline. In the prevention treatment, rats were pretreated with lithium, valproate or saline, and then, between days 8-14, rats were administered D-amphetamine or saline. Locomotor behavior was assessed using the open-field task and hippocampal nerve growth factor levels were determined by enzyme-linked immunosorbent assay. Both lithium and valproate reversed and prevented D-amphetamine-induced hyperactivity. Lithium increased nerve growth factor content in rat hippocampus in both experiments, but this effect was blocked with the co-administration of D-amphetamine. No significant effects on nerve growth factor levels were observed with valproate or D-amphetamine alone. These findings suggest that nerve growth factor may play a role in the neurotrophic effects of lithium but do not support the hypotheses that the nerve growth factor/TrkA pathway is involved in the pathophysiology of bipolar disorder.

Effects of mood stabilizers on hippocampus BDNF levels in an animal model of mania

There is an emerging body of data suggesting that mood disorders are associated with decreased brain-derived neurotrophic factor (BDNF). The present study aims to investigate the effects of the mood stabilizers lithium (Li) and valproate (VPT) in an animal model of bipolar disorder. In the first experiment (acute treatment), rats were administered D-amphetamine (AMPH) or saline for 14 days, and then between day 8 and 14, rats were treated with either Li, VPT or saline. In the second experiment (maintenance treatment), rats were pretreated with Li, VPT or saline, and then between day 8 and 14, rats were administered AMPH or saline. In both experiments, locomotor activity was measured using the open-field test and BDNF levels were measured in rat hippocampus by sandwich-ELISA. Li and VPT reversed AMPH-induced behavioral effects in the open-field test in both experiments. In the first experiment, Li increased BDNF levels in rat hippocampus. In the second experiment, AMPH decreased BDNF levels and Li and VPT increased BDNF levels in rat hippocampus. Our results suggest that the present model fulfills adequate face, construct and predictive validity as an animal model of mania.

Investigating responders to lithium prophylaxis as a strategy for mapping susceptibility genes for bipolar disorder

Attempts to map susceptibility genes for bipolar disorder have been complicated by genetic complexity of the illness and, above all by heterogeneity. This paper reviews the genetic research of bipolar disorder aiming to reduce the heterogeneity by focusing on definite responders to long-term lithium treatment. The available evidence strongly suggests that lithium-responsive bipolar disorder is the core bipolar phenotype, characterized by a more prominent role of genetic factors. Responders to lithium have typically a family history of bipolar disorder (often responsive to lithium). They differ from responders to other mood stabilizing drugs in their family histories as well as in other clinical characteristics. The molecular genetic investigations of bipolar disorder responsive to lithium indicate possibly several loci linked to and/or associated with the illness. A combination of research strategies employing multiple methods such as linkage, association, and gene-expression studies will be needed to clarify which of these represent true susceptibility loci.

A proton magnetic resonance spectroscopy investigation of the dorsolateral prefrontal cortex in acute mania

BACKGROUND

Several neurochemical abnormalities have been reported in bipolar disorder (BD), but the exact mechanisms that underlie its pathophysiology remain to be elucidated. Proton magnetic resonance spectroscopy (1HMRS) allows in vivo measurements of certain neurometabolites in the human brain. 1HMRS was used to investigate the dorsolateral prefrontal cortex (DLPFC) in bipolar subjects during a manic or mixed phase. N-acetyl-L-aspartate (NAA), choline-containing molecules (Cho), creatine plus phosphocreatine (Cr) and myoinositol (Ino) were measured.

METHOD

Ten bipolar patients (nine manic, one mixed), diagnosed by a semi-structured clinical interview (SCID), and ten age- and gender-matched healthy volunteers were studied. Absolute neurometabolites levels were measured from two 8 cm3 voxels placed in left and right DLPFC using a short TE 1HMRS method at 1.5 T. T1- and T2-weighted anatomical magnetic resonance imaging was performed to exclude any neuroanatomical abnormality.

RESULTS

No significant differences were found for NAA, Cho, Cr, Ino, NAA/Cr, Cho/Cr or Ino/Cr between patients and controls. Manic/mixed patients had significantly higher left-to-right myoinositol ratios in DLPFC (p = 0.044).

CONCLUSIONS

Increased left-to-right myoinositol ratios in the DLPFC in bipolar patients during acute mania may represent a dysfunction in the phosphoinositide-signaling pathway. Longitudinal studies with larger samples of unmedicated patients assessing pre- and post-treatment times will be required for further clarification of the time course of these abnormalities and the relationship with treatment effects.

Fisiopatologia do transtorno afetivo bipolar: o que mudou nos últimos 10 anos?

Apesar dos crescentes esforços para o entendimento da neurobiologia do transtorno afetivo bipolar (TAB), sua exata fisiopatologia permanece indeterminada. Inicialmente, a pesquisa estava voltada para o estudo das aminas biogênicas, devido aos efeitos dos diversos agentes psicofarmacológicos. Mais recentemente, evidências apontam que disfunções nos sistemas de sinalização intracelular e de expressão gênica podem estar associadas ao TAB. Estas alterações podem estar associadas a interrupções nos circuitos reguladores do humor, como sistema límbico, estriado e córtex pré-frontal, sendo que os efeitos neuroprotetores do uso crônico dos estabilizadores de humor podem reverter este processo patológico. Este artigo tem como objetivo trazer uma atualização dos achados recentes sobre a neuroquímica do TAB.

Genética do transtorno bipolar

O Transtorno bipolar (TB) possui alta prevalência na população mundial e causa perdas significativas na vida dos portadores. É uma doença cuja herança genética se caracteriza por mecanismos complexos de transmissão envolvendo múltiplos genes. Na tentativa de identificar genes de vulnerabilidade para o TB, várias estratégias de investigação genética têm sido utilizadas. Estudos de ligação apontam diversas regiões cromossômicas potencialmente associadas ao TB, cujos marcadores ou genes podem ser candidatos para os estudos de associação. Genes associados aos sistemas monoaminérgicos e vias de sinalização intracelulares são candidatos para investigação da etiologia genética do TB. Novas técnicas de mapeamento de expressão gênica em tecidos especializados apontam para novos genes cujas mutações possam ser responsáveis pelo aparecimento da doença. Em virtude da complexidade do modo de transmissão do TB e de sua heterogeneidade fenotípica, muitas dificuldades são encontradas na determinação desses genes de vulnerabilidade. Até o momento, há apenas resultados preliminares identificando alguns genes associados à vulnerabilidade para desenvolver o TB. Entretanto, a compreensão crescente dos mecanismos epigenéticos de controle da expressão gênica e a abordagem dimensional dos transtornos mentais podem colaborar nas investigações futuras em genética psiquiátrica.

Identification of lithium-regulated genes in cultured lymphoblasts of lithium responsive subjects with bipolar disorder

Lithium, a common drug for the treatment of bipolar disorder (BD), requires chronic administration to prevent recurrences of the illness. The necessity for long-term treatment suggests that changes in genes expression are involved in the mechanism of its action. We studied effects of lithium on gene expression in lymphoblasts from BD patients, all excellent responders to lithium prophylaxis. Gene expression was analyzed using cDNA arrays that included a total of 2400 cDNAs. We found that chronic lithium treatment at a therapeutically relevant concentration decreased the expression of seven genes in lymphoblasts from lithium responders. Five of these candidate lithium-regulated genes, including alpha1B-adrenoceptor (alpha1B-AR), acetylcholine receptor protein alpha chain precursor (ACHR), cAMP-dependent 3',5'-cyclic phosphodiesterase 4D (PDE4D), substance-P receptor (SPR), and ras-related protein RAB7, were verified by Northern blotting analysis in lithium responders. None of these genes were regulated by lithium in healthy control subjects. When we compared the expression of these five genes between bipolar subjects and healthy control subjects at baseline, prior to lithium administration, we found that alpha1B-AR gene expression was higher in bipolar subjects than in healthy control subjects. Our findings indicate that alpha1B-AR may play an important role in the mechanism of action of lithium treatment.

Drug-induced decrease of protein kinase a activity reveals alteration in BDNF expression of bipolar affective disorder

Bipolar affective disorder (BAD) is a severe disease whose molecular and cellular bases are not well known. The aim of the present study was to probe the cAMP signaling downstream targets by pharmacologically manipulating the protein kinase A (PKA) enzyme, along with the assessment of brain-derived neurotrophic factor (BDNF) expression in lymphoblasts. The time course of lymphoblast PKA activity (up to 72 h) revealed optimal activity at 24 h. Then, the enzyme activity and protein levels of PKA Calpha subunit and phopsho-cAMP responsive element binding (CREB) were assayed in lymphoblasts derived from 12 BAD and 12 control (CT) subjects and cultured for 24 h in the presence of cAMP analog drugs. The results indicated that basal PKA activity and PKA Calpha subunit immunolabeling are increased in cells from BAD compared with controls. Enzyme activity was increased by Sp-isomer in BAD and in CT's cells, without change in protein levels. In contrast, the Rp-isomer decreased enzyme activity and protein levels. In drug-naive conditions, there was no change in BDNF expression of BAD cells compared with CT cells. Treatment with Sp-isomer induced increased BDNF in both groups, while treatment with Rp-isomer induced a significant decrease in BDNF expression of BAD compared with CT. The p-CREB changes followed changes in BDNF levels, with increased and decreased Sp-isomer and Rp-isomer treatment, respectively. Our results suggest that mood disorder is associated with PKA upregulation and this could mask alteration in BDNF expression, because slowing down of PKA signaling results in a decrease of BDNF expression. These findings, combined with previous reports, provide a new insight to explain pharmacological features in different diagnostic groups.

Amygdala cyclic adenosine monophosphate response element binding protein phosphorylation in patients with mood disorders: effects of diagnosis, suicide, and drug treatment

BACKGROUND

Signal transduction abnormalities have been identified in patients with bipolar (BD) and major depressive (MDD) disorders and are targets for lithium and antidepressant drugs. A key downstream target for signal transduction pathways is the transcription factor cyclic adenosine monophosphate (cAMP) response element binding protein (CREB). Therefore, we measured the levels of phosphorylated CREB (pCREB) in the amygdala, a region critical to emotional processing and important in the pathophysiology of both BD and MDD.

METHODS

Human postmortem amygdala sections were generously provided by the Stanley Foundation Neuropathology Consortium. Samples consisted of subjects with MDD, BD, schizophrenia (SCZ), and nonpsychiatric-nonneurologic comparison subjects (n = 15 per group). Levels of pCREB were measured by immunohistochemistry, relative to total cell number.

RESULTS

There were no differences between diagnostic groups--control subjects and subjects with BD, MDD, or SCZ--but increased numbers of pCREB stained cells were found in several amygdalar nuclei in subjects who had died by suicide. In contrast, patients treated with lithium at the time of death had significantly lower pCREB levels in the same region.

CONCLUSIONS

These results suggest that CREB activity may be an important factor in the neurobiology of suicide and the well-documented antisuicidal effect of lithium.

Chronic lithium treatment inhibits pilocarpine-induced mossy fiber sprouting in rat hippocampus

Lithium remains the gold standard in the treatment of bipolar disorder. Long-term treatment with lithium may lead to specific adaptational changes in gene expression that contribute to a neuroprotective effect. In this study, the pilocarpine model of spontaneous limbic epilepsy was used to induce mossy fiber sprouting (axonal growth of the dentate granule cells that synapse on the pyramidal cells of the CA3 region) to examine the prophylactic neuroprotective effects of lithium in vivo. There were four groups of animals: pilocarpine treated (Pil+/Li-); pilocarpine treated followed by lithium (Pil+/Li+); lithium alone (Pil-/Li+); control (Pil-/Li-). Timm staining was used to obtain density measurements in the stratum oriens and the inner molecular layer of the hippocampus. Mossy fiber density was higher in the pilocarpine-treated animals compared to controls. Chronic lithium following pilocarpine treatment attenuated the density of mossy fibers but lithium alone had no effect. No changes in hilar volume or neuronal number were detected using stereological procedures. The ability of lithium to attenuate activation-induced reorganization in the hippocampus provides evidence for its role as a neuroprotective agent in an in vivo model that may be relevant to its clinical effects in bipolar disorder.