Increased membrane-associated protein kinase C activity and translocation in blood platelets from bipolar affective disorder patients

New Advances in the Pharmacology and Toxicology of Lithium: A Neurobiologically Oriented Overview

Over the last six decades, lithium has been considered the gold standard treatment for the long-term management of bipolar disorder due to its efficacy in preventing both manic and depressive episodes as well as suicidal behaviors. Nevertheless, despite numerous observed effects on various cellular pathways and biologic systems, the precise mechanism through which lithium stabilizes mood remains elusive. Furthermore, there is recent support for the therapeutic potential of lithium in other brain diseases. This review offers a comprehensive examination of contemporary understanding and predominant theories concerning the diverse mechanisms underlying lithium's effects. These findings are based on investigations utilizing cellular and animal models of neurodegenerative and psychiatric disorders. Recent studies have provided additional support for the significance of glycogen synthase kinase-3 (GSK3) inhibition as a crucial mechanism. Furthermore, research has shed more light on the interconnections between GSK3-mediated neuroprotective, antioxidant, and neuroplasticity processes. Moreover, recent advancements in animal and human models have provided valuable insights into how lithium-induced modifications at the homeostatic synaptic plasticity level may play a pivotal role in its clinical effectiveness. We focused on findings from translational studies suggesting that lithium may interface with microRNA expression. Finally, we are exploring the repurposing potential of lithium beyond bipolar disorder. These recent findings on the therapeutic mechanisms of lithium have provided important clues toward developing predictive models of response to lithium treatment and identifying new biologic targets. SIGNIFICANCE STATEMENT: Lithium is the drug of choice for the treatment of bipolar disorder, but its mechanism of action in stabilizing mood remains elusive. This review presents the latest evidence on lithium's various mechanisms of action. Recent evidence has strengthened glycogen synthase kinase-3 (GSK3) inhibition, changes at the level of homeostatic synaptic plasticity, and regulation of microRNA expression as key mechanisms, providing an intriguing perspective that may help bridge the mechanistic gap between molecular functions and its clinical efficacy as a mood stabilizer.

Intracellular Signaling Cascades in Bipolar Disorder

Bipolar spectrum disorders carry a significant public health burden. Disproportionately high rates of suicide, incarceration, and comorbid medical conditions necessitate an extraordinary focus on understanding the intricacies of this disease. Elucidating granular, intracellular details seems to be a necessary preamble to advancing promising therapeutic opportunities. In this chapter, we review a wide range of intracellular mechanisms including mitochondrial energetics, calcium signaling, neuroinflammation, the microbiome, neurotransmitter metabolism, glycogen synthase kinase 3-beta (GSK3β), protein kinase C (PKC) and diacylglycerol (DAG), and neurotrophins (especially BDNF), as well as the glutamatergic, dopaminergic, purinergic, and neurohormonal systems. Owing to the relative lack of understanding and effective therapeutic options compared to the rest of the spectrum, special attention is paid in the chapter to the latest developments in bipolar depression. Likewise, from a therapeutic standpoint, special attention should be paid to the pervasive mechanistic actions of lithium as a means of amalgamating numerous, disparate cascades into a digestible cognitive topology.

Protein and mRNA expression of protein kinase C (PKC) in the postmortem brain of bipolar and schizophrenic subjects

Abnormalities of protein kinase C (PKC) have been implicated in the pathophysiology of bipolar (BP) illness. This is primarily based on studies of PKC in platelets of BP patients. Whether such abnormalities of PKC activity and isoforms exist in the brain is unclear. We have therefore determined PKC activity, protein and mRNA expression of PKC isoforms in the prefrontal cortex (PFC), cingulate cortex (CING) and temporal cortex (TEMP) from BP (n = 19), schizophrenic (SZ) (n = 20) and normal control (NC) (n = 25) subjects. The brain samples were obtained from the Harvard Brain Bank, and the subjects were diagnosed according to DSM-IV criteria. Protein levels were determined using Western blot technique and mRNA levels were determined using real-time PCR (qPCR) method. We found that there was a significant decrease in the PKC activity in the cytosol and membrane fractions of PFC and TEMP obtained from BP subjects but not from SZ subjects. When we compared the expression of PKC isozymes, we found that the protein and mRNA expression of several isozymes was significantly decreased in the PFC (i.e., PKCα, PKCβI, PKCβII and PKCε) and TEMP (i.e., PKCα, PKCβI, PKCβII, PKCε and PKCγ) of BP subjects, but not in the CING. Overall, there was no difference in the mRNA or protein expression of PKC isozymes between SZ and NC subjects in any of the three brain areas we studied. Our results show that there is a region-specific decrease of certain PKC isozymes in the membrane and cytosol fractions of BP but not SZ subjects.

Protein kinase C isoforms as a target for manic-like behaviors and oxidative stress in a dopaminergic animal model of mania

Bipolar disorder (BD) is a chronic condition characterized by severe mood swings alternating between episodes of mania and depression. Evidence indicates that protein kinase C (PKC) and oxidative stress are important therapeutic targets for BD. However, what PKC isoforms that are precisely involved in this effect are unknown. Therefore, we evaluated the effects of the intracerebroventricular (ICV) injection of PKC inhibitors (lithium (Li), tamoxifen (TMX), PKCα inhibitor (iPKCα), PKCγ inhibitor (iPKCγ), and PKCε inhibitor (iPKCε)) on the manic-like behaviors and oxidative stress parameters (4-hydroxy-2-nonenal (4-HNE), 8-isoprostane (8-ISO), carbonyl groups, 3-nitrotyrosine (3-NT), glutathione peroxidase (GPx) and glutathione reductase (GR)) in the brains of rats submitted to the model of mania induced by methamphetamine (m-AMPH). Animals received a single ICV infusion of artificial cerebrospinal fluid, Li, TMX, iPKCα, iPKCγ or iPKCε followed by an intraperitoneal injection of saline or m-AMPH before the behavioral analysis (open-field task). Oxidative stress was evaluated in the striatum, frontal cortex, and hippocampus. ICV injection of Li, TMX or iPKCε blocked the m-AMPH-induced increase in the manic-like behaviors - crossings, rearings, visits to the center, sniffing, and grooming. ICV infusion of iPKCα triggered a decrease in these behaviors induced by m-AMPH. Besides, the iPKCε administration significantly prevented the oxidative damage to lipids and proteins, as well as disturbances in the activity of antioxidant enzymes induced by m-AMPH. The findings of the present study suggest that PKCε isoform is strongly implied in the antimanic and antioxidant effects of Li, TMX, and the other PKC inhibitors in the model of mania.

Statin-specific inhibition of Rab-GTPase regulates cPKC-mediated IKs internalization

Statins are prescribed for prevention and treatment of coronary artery disease. Statins have different cholesterol lowering abilities, with rosuvastatin and atorvastatin being the most effective, while statins like simvastatin and fluvastatin having lower effectiveness. Statins, in addition to their cholesterol lowering effects, can prevent isoprenylation of Rab-GTPase proteins, a protein family important for the regulation of membrane-bound protein trafficking. Here we show that endosomal localization of Rab-GTPases (Rab5, Rab7 and Rab11) was inhibited in a statin-specific manner, with stronger effects by fluvastatin, followed by simvastatin and atorvastatin, and with a limited effect by rosuvastatin. Fluvastatin inhibition of Rab5 has been shown to mediate cPKC-dependent trafficking regulation of the cardiac delayed rectifier KCNQ1/KCNE1 channels. We observed statin-specific inhibition of channel regulation consistent with statin-specific Rab-GTPase inhibition both in heterologous systems and cardiomyocytes. Our results uncover a non-cholesterol-reducing statin-specific effect of statins. Because Rab-GTPases are important regulators of membrane trafficking they may underlie statin specific pleiotropic effects. Therefore, statin-specificity may allow better treatment tailoring.

Valproate for acute mania

BACKGROUND

Bipolar disorder is a severe and common mental disorder where patients experience recurrent symptoms of elevated or irritable mood, depression, or a combination of both. Treatment is usually with psychiatric medication, including mood stabilisers, antidepressants and antipsychotics. Valproate is an effective maintenance treatment for bipolar disorder. However, evidence assessing the efficacy of valproate in the treatment of acute mania is less robust, especially when comparing it to some of the newer antipsychotic agents. This review is an update of a previous Cochrane Review (last published 2003) on the role of valproate in acute mania.

OBJECTIVES

To assess the efficacy and tolerability of valproate for acute manic episodes in bipolar disorder compared to placebo, alternative pharmacological treatments, or a combination pharmacological treatments, as measured by the treatment of symptoms on specific rating scales for individual episodes in paediatric, adolescent and adult populations.

SEARCH METHODS

We searched Ovid MEDLINE (1950- ), Embase (1974- ), PsycINFO (1967- ) and the Cochrane Central Register of Controlled Trials (CENTRAL) to 28 September 2018. We had also conducted an earlier search of these databases in the Cochrane Common Mental Disorders Controlled Trials Register (CCMDCTR) (all years to 6 June 2016). We also searched the World Health Organization (WHO) trials portal (ICTRP) and clinicaltrials.gov in September 2018, to identify any additional unpublished or ongoing studies.

SELECTION CRITERIA

Single- and double-blind, randomised controlled trials comparing valproate with placebo, alternative antimanic treatments, or a combination of pharmacological treatments. We also considered studies where valproate was used as an adjunctive treatment in combination with another agent separately from studies where it was used in monotherapy. We included male and female patients of all ages and ethnicity with bipolar disorder.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed data extraction and methodological quality assessment. For analysis, we used the odds ratio (OR) for binary efficacy outcomes and the mean difference (MD) or standardised mean difference (SMD) for continuously distributed outcomes.

MAIN RESULTS

Twenty-five trials (3252 participants) compared valproate with either placebo or alternative antimanic treatments to alleviate the symptoms of acute mania. For efficacy, our primary outcome was response rate. For tolerability, our primary outcome was the number of participants with any adverse effect. This meta-analysis included studies focusing on children, adolescents, as well as adults with a range of severity of manic symptoms. The majority of studies focused on adult men and women (aged 18 and above), were conducted in inpatient settings and completed in the US. Five studies in this review focused on children and adolescents (aged 18 and under) so that the review covers an age range from 3 - 82 years. Seven studies contained outpatient participants in some form. Nine studies included data that has been collected outside the US, namely Iran (4 studies), India (3 studies), China (1 study), or across several international countries (1 study).In adults, high-quality evidence found that valproate induces a slightly higher response compared to placebo (45% vs 29%, OR 2.05, 95% CI 1.32 to 3.20; 4 studies, 869 participants). Moderate-quality evidence found there was probably little or no difference in response rates between valproate and lithium (56% vs 62%, OR 0.80, 95% CI 0.48 to 1.35; 3 studies, 356 participants). In adults, low-quality evidence found there may be little or no difference in response rate between valproate and olanzapine (38% vs 44%, OR 0.77, 95% CI 0.48 to 1.25; 2 studies, 667 participants).In the children and adolescent population, the evidence regarding any difference in response rates between valproate and placebo was uncertain (23% vs 22%, OR 1.11, 95% CI 0.51 to 2.38; 1 study, 151 participants, very low-quality evidence). Low-quality evidence found that the response rate of participants receiving valproate may be lower compared to risperidone (23% vs 66%, OR 0.16, 95% CI 0.08 to 0.29; 1 study, 197 participants). The evidence regarding any difference in response rates between valproate and lithium was uncertain (23% vs 34%, OR 0.57, 95% CI 0.31 to 1.07; 1 study, 197 participants, very low-quality evidence).In terms of tolerability in adults, moderate-quality evidence found that there are probably more participants receiving valproate who experienced any adverse events compared to placebo (83% vs 75%, OR 1.63, 95% CI 1.13 to 2.36; 3 studies, 745 participants). Low-quality evidence found there may be little or no difference in tolerability between valproate and lithium (78% vs 86%, OR 0.61, 95% CI 0.25 to 1.50; 2 studies, 164 participants). We did not obtain primary tolerability outcome data on the olanzapine comparison.Within the children and adolescent population, the evidence regarding any difference between valproate or placebo was uncertain (67% vs 60%, OR 1.39, 95% CI 0.71 to 2.71; 1 study, 150 participants, very low-quality evidence). We did not obtain primary tolerability outcome data on the lithium or risperidone comparisons.

AUTHORS' CONCLUSIONS

There is evidence that valproate is an efficacious treatment for acute mania in adults when compared to placebo. By contrast, there is no evidence of a difference in efficacy between valproate and placebo for children and adolescents. Valproate may be less efficacious than olanzapine in adults, and may also be inferior to risperidone as a monotherapy treatment for paediatric mania. Generally, there is uncertain evidence regarding whether valproate causes more or less side effects than the other main antimanic therapies. However, evidence suggests that valproate causes less weight gain and sedation than olanzapine.

Lithium-induced gene expression alterations in two peripheral cell models of bipolar disorder

Objectives: The aim of our study was to investigate molecular mechanisms of lithium action by studying the gene expression profile of peripheral cell models generated from bipolar patients (BD) and healthy controls (HC). Methods: EBV-immortalised lymphoblastoid cells (LCLs) and fibroblast cells from BD and HC were incubated with either lithium chloride or plain medium for 3 weeks. We first conducted a microarray gene expression study. The most promising differentially regulated genes in terms of lithium-associated or disorder-associated pathways were then replicated by quantitative real-time PCR (qRT-PCR). Results: The pooled microarray analysis showed 459 genes to be differentially regulated in BD compared to HC and 58 due to lithium treatment in LCLs, and 295 genes to be differentially regulated in BD compared to HC and five due to lithium treatment in fibroblasts. After correction for multiple comparison, EPHB1 disorder × treatment interactions remained significant in LCLs validated by qRT-PCR. In the control group, lithium influenced the expression of ANP32E, PLEKHA2, KCNK1, PRKCH, ST3GAL6 and AIF1. In bipolar and control fibroblast cells lithium treatment decreased FGF9 expression. Conclusions: The differentially regulated genes in our study add evidence for the relevance of inflammation, neuronal/glial development, phosphatidylinositol second-messenger pathway and ion channels in the mode of action of lithium.

Fluvastatin inhibits Rab5-mediated IKs internalization caused by chronic Ca2+-dependent PKC activation

Statins, in addition to their cholesterol lowering effects, can prevent isoprenylation of Rab GTPase proteins, a key protein family for the regulation of protein trafficking. Rab-GTPases have been shown to be involved in the control of membrane expression level of ion channels, including one of the major cardiac repolarizing channels, IKs. Decreased IKs function has been observed in a number of disease states and associated with increased propensity for arrhythmias, but the mechanism underlying IKs decrease remains elusive. Ca²⁺-dependent PKC isoforms (cPKC) are chronically activated in variety of human diseases and have been suggested to acutely regulate IKs function. We hypothesize that chronic cPKC stimulation leads to Rab-mediated decrease in IKs membrane expression, and that can be prevented by statins. In this study we show that chronic cPKC stimulation caused a dramatic Rab5 GTPase-dependent decrease in plasma membrane localization of the IKs pore forming subunit KCNQ1, reducing IKs function. Our data indicates fluvastatin inhibition of Rab5 restores channel localization and function after cPKC-mediated channel internalization. Our results indicate a novel statin anti-arrhythmic effect that would be expected to inhibit pathological electrical remodeling in a number of disease states associated with high cPKC activation. Because Rab-GTPases are important regulators of membrane trafficking they may underlie other statin pleiotropic effects.

Genetic Overlap Between Alzheimer's Disease and Bipolar Disorder Implicates the MARK2 and VAC14 Genes

Background: Alzheimer's disease (AD) and bipolar disorder (BIP) are complex traits influenced by numerous common genetic variants, most of which remain to be detected. Clinical and epidemiological evidence suggest that AD and BIP are related. However, it is not established if this relation is of genetic origin. Here, we applied statistical methods based on the conditional false discovery rate (FDR) framework to detect genetic overlap between AD and BIP and utilized this overlap to increase the power to identify common genetic variants associated with either or both traits. Methods: We obtained genome wide association studies data from the International Genomics of Alzheimer's Project part 1 (17,008 AD cases and 37,154 controls) and the Psychiatric Genetic Consortium Bipolar Disorder Working Group (20,352 BIP cases and 31,358 controls). We used conditional QQ-plots to assess overlap in common genetic variants between AD and BIP. We exploited the genetic overlap to re-rank test-statistics for AD and BIP and improve detection of genetic variants using the conditional FDR framework. Results: Conditional QQ-plots demonstrated a polygenic overlap between AD and BIP. Using conditional FDR, we identified one novel genomic locus associated with AD, and nine novel loci associated with BIP. Further, we identified two novel loci jointly associated with AD and BIP implicating the MARK2 gene (lead SNP rs10792421, conjunctional FDR = 0.030, same direction of effect) and the VAC14 gene (lead SNP rs11649476, conjunctional FDR = 0.022, opposite direction of effect). Conclusion: We found polygenic overlap between AD and BIP and identified novel loci for each trait and two jointly associated loci. Further studies should examine if the shared loci implicating the MARK2 and VAC14 genes could explain parts of the shared and distinct features of AD and BIP.

Neuro-Immune Hemostasis: Homeostasis and Diseases in the Central Nervous System

Coagulation and the immune system interact in several physiological and pathological conditions, including tissue repair, host defense, and homeostatic maintenance. This network plays a key role in diseases of the central nervous system (CNS) by involving several cells (CNS resident cells, platelets, endothelium, and leukocytes) and molecular pathways (protease activity, complement factors, platelet granule content). Endothelial damage prompts platelet activation and the coagulation cascade as the first physiological step to support the rescue of damaged tissues, a flawed rescuing system ultimately producing neuroinflammation. Leukocytes, platelets, and endothelial cells are sensitive to the damage and indeed can release or respond to chemokines and cytokines (platelet factor 4, CXCL4, TNF, interleukins), and growth factors (including platelet-derived growth factor, vascular endothelial growth factor, and brain-derived neurotrophic factor) with platelet activation, change in capillary permeability, migration or differentiation of leukocytes. Thrombin, plasmin, activated complement factors and matrix metalloproteinase-1 (MMP-1), furthermore, activate intracellular transduction through complement or protease-activated receptors. Impairment of the neuro-immune hemostasis network induces acute or chronic CNS pathologies related to the neurovascular unit, either directly or by the systemic activation of its main steps. Neurons, glial cells (astrocytes and microglia) and the extracellular matrix play a crucial function in a “tetrapartite” synaptic model. Taking into account the neurovascular unit, in this review we thoroughly analyzed the influence of neuro-immune hemostasis on these five elements acting as a functional unit (“pentapartite” synapse) in the adaptive and maladaptive plasticity and discuss the relevance of these events in inflammatory, cerebrovascular, Alzheimer, neoplastic and psychiatric diseases. Finally, based on the solid reviewed data, we hypothesize a model of neuro-immune hemostatic network based on protein–protein interactions. In addition, we propose that, to better understand and favor the maintenance of adaptive plasticity, it would be useful to construct predictive molecular models, able to enlighten the regulating logic of the complex molecular network, which belongs to different cellular domains. A modeling approach would help to define how nodes of the network interact with basic cellular functions, such as mitochondrial metabolism, autophagy or apoptosis. It is expected that dynamic systems biology models might help to elucidate the fine structure of molecular events generated by blood coagulation and neuro-immune responses in several CNS diseases, thereby opening the way to more effective treatments.

Protein Kinase C Activity and Delayed Recovery of Sleep-Wake Cycle in Mouse Model of Bipolar Disorder

OBJECTIVE

Previous studies reported the delayed recovery group after circadian rhythm disruption in mice showed higher quinpiroleinduced locomotor activity. This study aimed to compare not only Protein Kinase C (PKC) activities in frontal, striatal, hippocampus and cerebellum, but also relative PKC activity ratios among brain regions according to recovery of circadian rhythm.

METHODS

The circadian rhythm disruption protocol was applied to eight-week-old twenty male Institute Cancer Research mice. The circadian rhythm recovery patterns were collected through motor activities measured by Mlog system. Depressive and manic proneness were examined by forced swim test and quinpirole-induced open field test respectively. Enzyme-linked immunosorbent assay was employed to measure PKC activities.

RESULTS

The delayed recovery group presented greater locomotor activities than the early recovery group (p=0.033). The delayed recovery group had significantly lower frontal PKC activity than the other (p=0.041). The former showed lower frontal/cerebellar PKC activity ratio (p=0.047) but higher striatal/frontal (p=0.038) and hippocampal/frontal (p=0.007) PKC activities ratios than the latter.

CONCLUSION

These findings support potential mechanism of delayed recovery after circadian disruption in bipolar animal model could be an alteration of relative PKC activities among mood regulation related brain regions. It is required to investigate the PKC downstream signaling related to the delayed recovery pattern.

Neuro-Coagulopathy: Blood Coagulation Factors in Central Nervous System Diseases

Blood coagulation factors and other proteins, with modulatory effects or modulated by the coagulation cascade have been reported to affect the pathophysiology of the central nervous system (CNS). The protease-activated receptors (PARs) pathway can be considered the central hub of this regulatory network, mainly through thrombin or activated protein C (aPC). These proteins, in fact, showed peculiar properties, being able to interfere with synaptic homeostasis other than coagulation itself. These specific functions modulate neuronal networks, acting both on resident (neurons, astrocytes, and microglia) as well as circulating immune system cells and the extracellular matrix. The pleiotropy of these effects is produced through different receptors, expressed in various cell types, in a dose- and time-dependent pattern. We reviewed how these pathways may be involved in neurodegenerative diseases (amyotrophic lateral sclerosis, Alzheimer's and Parkinson's diseases), multiple sclerosis, ischemic stroke and post-ischemic epilepsy, CNS cancer, addiction, and mental health. These data open up a new path for the potential therapeutic use of the agonist/antagonist of these proteins in the management of several central nervous system diseases.

Role of Protein Kinase C in Bipolar Disorder: A Review of the Current Literature

Bipolar disorder (BD) is a major health problem. It causes significant morbidity and imposes a burden on the society. Available treatments help a substantial proportion of patients but are not beneficial for an estimated 40-50%. Thus, there is a great need to further our understanding the pathophysiology of BD to identify new therapeutic avenues. The preponderance of evidence pointed towards a role of protein kinase C (PKC) in BD. We reviewed the literature pertinent to the role of PKC in BD. We present recent advances from preclinical and clinical studies that further support the role of PKC. Moreover, we discuss the role of PKC on synaptogenesis and neuroplasticity in the context of BD. The recent development of animal models of BD, such as stimulant-treated and paradoxical sleep deprivation, and the ability to intervene pharmacologically provide further insights into the involvement of PKC in BD. In addition, the effect of PKC inhibitors, such as tamoxifen, in the resolution of manic symptoms in patients with BD further points in that direction. Furthermore, a wide variety of growth factors influence neurotransmission through several molecular pathways that involve downstream effects of PKC. Our current understanding identifies the PKC pathway as a potential therapeutic avenue for BD.

Serum phosphatidylinositol as a biomarker for bipolar disorder liability

OBJECTIVES

Individuals with bipolar disorder (BPD) exhibit alterations in their phospholipid levels. It is unclear whether these alterations are a secondary consequence of illness state, or if phospholipids and illness risk overlap genetically. If the latter were true, then phospholipids might provide key insights into the pathophysiology of the illness. Therefore, we rank-ordered phospholipid classes by their genetic overlap with BPD risk in order to establish which class might be most informative in terms of increasing our understanding of illness pathophysiology.

METHODS

Analyses were conducted in a sample of 558 individuals, unselected for BPD, from 38 extended pedigrees (average family size=14.79, range=2-82). We calculated a coefficient of relatedness for all family members of nine individuals with BPD in the sample (N=185); this coefficient was set to be zero in unrelated individuals (N=373). Then, under an endophenotype ranking value (ERV) approach, this scalar index was tested against 13 serum-based phospholipid concentrations in order to rank-order lipid classes by their respective overlap with BPD risk.

RESULTS

The phosphatidylinositol class was significantly heritable (h² =0.26, P=6.71 × 10^-05 ). It was the top-ranked class, and was significantly associated with BPD risk after correction for multiple testing (β=-1.18, P=2.10 × 10^-03 , ERV=0.49).

CONCLUSIONS

We identified a peripheral biomarker, serum-based phosphatidylinositol, which exhibits a significant association with BPD risk. Therefore, given that phosphatidylinositol and BPD risk share partially common etiology, it seems that this lipid class warrants further investigation, not only in terms of treatment, but also as a promising diagnostic and risk marker.

Increased PKC activity and altered GSK3β/NMDAR function drive behavior cycling in HINT1-deficient mice: bipolarity or opposing forces

Mice with histidine triad nucleotide-binding protein 1 (HINT1) deletion exhibit manic-like symptoms that evolve into depressive-like behavior in response to stressful paradigms. Molecular and electrophysiological studies have indicated that HINT1^−/− mice exhibit increased PKC, PKA, and GSK3β activities, as well as glutamate N-methyl-D-aspartate receptor (NMDAR)/α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic receptor (AMPAR) and NR2B/NR2A subunit ratios. Pharmacological interventions stabilized their behavior but through different mechanisms. GSK3β inhibitors and valproate directly attenuated the expression of the manic-like symptoms, whereas PKC inhibition, lamotrigine, or risperidone promoted NMDAR-mediated depressive-like behaviors that counterbalanced the preexisting manic-like symptoms. Naïve HINT1^−/− mice exposed to stressful paradigms rapidly manifested depressive-like behaviors in subsequent stressful situations, a capacity that persisted for a couple of weeks thereafter. During the depressive-like phase, citalopram, amitriptyline and MK801 precipitated manic-like behaviors in stressed HINT1^−/− mice. Notably, the antagonism of NMDARs prevented HINT1^−/− mice from alternating behaviors in response to stress. A comparison with “manic” Black Swiss mice indicated that in HINT1^−/− mice, PKC supports manic-like symptoms and reduces the expression of depressive-like behaviors via activation of GSK3β and regulation of NR2B-enriched NMDARs. HINT1^−/− mice represent a suitable model for studying human BPD and may facilitate the identification of novel targets and drugs to treat this mental disorder.

DGKH genetic risk variant influences gene expression in bipolar affective disorder

BACKGROUND

DGKH is a replicated risk gene of bipolar disorder (BD). However, the pathophysiological role of the coded protein, diacylglycerol kinase eta, remains elusive.

METHODS

In this proof-of-concept study we isolated mRNA from peripheral blood and fibroblasts of heterozygote DGKH risk variants carriers (risk haplotype rs994856/rs9525580/rs9525584 GAT) with bipolar disorder and non-risk variant carriers with and without bipolar disorder. Gene expression of DGKH1, DGKH2, INPP5E, PI4K2B, PIK4CA, PLCG2, PRKCA, PRKCD, PRKCE and PRKCH was analysed by qRT PCR.

RESULTS

DGKH1 expression was increased in peripheral blood of risk variant carriers (p=0.027). In fibroblast cells, PRKCD expression was significantly increased in DGKH GAT carriers (p=0.037). Patients with a current depressive episode had lower PRKCD levels and lithium treatment was associated with increased PRKCA expression (p=0.005, and p=0.033).

LIMITATIONS

No homozygote risk variant carriers and no healthy risk variant carriers were included due to their infrequency. Bipolar patients carrying the GAT haplotype were older with marginal significance, as age had also an influence on DGKH expression levels but not on PRKCD levels, replication with better age-matched samples and also bigger samples are needed.

CONCLUSIONS

The results add evidence for the role of fibroblast cells and peripheral blood as useful tools in the functional characterisation of risk gene variants. Also a combination of genotyping and peripheral gene expression analysis could proof useful in the search of biomarkers for endophenotypes. Furthermore, we could confirm the role of the inositol-1,4,5-triphosphate second messenger pathway and protein kinase C in the pathogenesis of BD.

Inositol depletion, GSK3 inhibition and bipolar disorder

Valproic acid and lithium are widely used to treat bipolar disorder, a severe illness characterized by cycles of mania and depression. However, their efficacy is limited, and treatment is often accompanied by serious side effects. The therapeutic mechanisms of these drugs are not understood, hampering the development of more effective treatments. Among the plethora of biochemical effects of the drugs, those that are common to both may be more related to therapeutic efficacy. Two common outcomes include inositol depletion and GSK3 inhibition, which have been proposed to explain the efficacy of both valproic acid and lithium. Here, we discuss the inositol depletion and GSK3 inhibition hypotheses, and introduce a unified model suggesting that inositol depletion and GSK3 inhibition are inter-related.

Protein kinase C inhibition rescues manic-like behaviors and hippocampal cell proliferation deficits in the sleep deprivation model of mania

BACKGROUND

Recent studies revealed that bipolar disorder may be associated with deficits of neuroplasticity. Additionally, accumulating evidence has implicated alterations of the intracellular signaling molecule protein kinase C (PKC) in mania.

METHODS

Using sleep deprivation (SD) as an animal model of mania, this study aimed to examine the possible relationship between PKC and neuroplasticity in mania. Rats were subjected to SD for 72 h and tested behaviorally. In parallel, SD-induced changes in hippocampal cell proliferation were evaluated with bromodeoxyuridine (BrdU) labeling. We then examined the effects of the mood stabilizer lithium, the antipsychotic agent aripiprazole, and the PKC inhibitors chelerythrine and tamoxifen on both behavioral and cell proliferation impairments induced by SD. The antidepressant fluoxetine was used as a negative control.

RESULTS

We found that SD triggered the manic-like behaviors such as hyperlocomotion and increased sleep latency, and reduced hippocampal cell proliferation. These alterations were counteracted by an acute administration of lithium and aripiprazole but not of fluoxetine, and only a single administration of aripiprazole increased cell proliferation on its own. Importantly, SD rats exhibited increased levels of phosphorylated synaptosomal-associated protein 25 (SNAP-25) in the hippocampus and prefrontal cortex, suggesting PKC overactivity. Moreover, PKC inhibitors attenuated manic-like behaviors and rescued cell proliferation deficits induced by SD.

CONCLUSIONS

Our findings confirm the relevance of SD as a model of mania, and provide evidence that antimanic agents are also able to prevent SD-induced decrease of hippocampal cell proliferation. Furthermore, they emphasize the therapeutic potential of PKC inhibitors, as revealed by their antimanic-like and pro-proliferative properties.

The effect of deficient muscarinic signaling on commonly reported biochemical effects in schizophrenia and convergence with genetic susceptibility loci in explaining symptom dimensions of psychosis

With the advent of DSM 5 criticism has generally centered on a lack of biological validity of the diagnostic criteria. Part of the problem in describing a nosology of psychosis is the tacit assumption of multiple genetic causes each with an incremental loading on the clinical picture that fails to differentiate a clear underlying pathophysiology of high impact. The aim of this paper is to consolidate a primary theory of deficient muscarinic signaling underlying key clinical features of schizophrenia and its regulation by several important genetic associations including neuregulin, DISC and dysbindin. Secondary reductions in markers for GABAergic function and changes in the levels of interneuron calcium binding proteins parvalbumin and calbindin can be attributed to dysfunctional muscarinic transduction. A parallel association exists for cytokine production. The convergent pathway hypothesis is likewise used to model dopaminergic and glutamatergic theories of schizophrenia. The negative symptom dimension is correlated with dysfunction of Akt and ERK transduction, a major point of convergence. The present paradigm predicts the importance of a recent finding of a deletion in a copy number variant of PLCB1 and its potential use if replicated, as one of the first testable biological markers differentiating schizophrenia from bipolar disorder and further subtyping of schizophrenia into deficit and non-deficit. Potential limitations of PLCB1 as a prospective marker are also discussed.

Tamoxifen use for the management of mania: a review of current preclinical evidence

RATIONALE

Preliminary data on the efficacy of tamoxifen in reducing manic symptoms of bipolar disorder (BD) suggest that this agent may be a potential treatment for the management of this psychiatric disorder. However, the antimanic properties of tamoxifen have not been fully elucidated, hampering the development and/or use of mood-stabilising drugs that may share its same therapeutic mechanisms of action. Notably, we may gain a greater understanding of the neurobiological and therapeutic properties of tamoxifen by using suitable animal models of mania.

OBJECTIVES

Here, we review the preclinical studies that have evaluated the effects of tamoxifen to provide an overview of the current progress in our understanding of its antimanic actions, highlighting the critical role of protein kinase C (PKC) as a therapeutic target for the treatment of BD.

CONCLUSIONS

To date, this field has struggled to make significant progress, and the organisation of an explicit battery of tests is a valuable tool for assessing a number of prominent facets of BD, which may provide a greater understanding of the entire scope of this disease.

Second messenger/signal transduction pathways in major mood disorders: moving from membrane to mechanism of action, part II: bipolar disorder

In this second of two articles on second messenger/signal transduction cascades in major mood disorders, we will review the evidence in support of intracellular dysfunction and its rectification in the etiopathogenesis and treatment of bipolar disorder (BD). The importance of these cascades is highlighted by lithium's (the gold standard in BD psychopharmacology) ability to inhibit multiple critical loci in second messenger/signal transduction cascades including protein kinase C (involved in the IP3/PIP2 pathway) and GSK-3β (canonically identified in the Wnt/Fz/Dvl/GSK-3β cascade). As a result, and like major depressive disorder (MDD), more recent pathophysiological studies and rational therapeutic targets have been directed at these and other intracellular mediators. Even in the past decade, intracellular dysfunction in numerous neuroprotective/apoptotic cascades appears important in the pathophysiology and may be a future target for pharmacological interventions of BD.

Increased density of AKAP5-expressing neurons in the anterior cingulate cortex of subjects with bipolar disorder

Brain anatomical abnormalities as well as cognitive and emotional processing deficits have been reported for the prefrontal cortex in bipolar disorder, which are in part attributable to cellular and laminar abnormalities in postsynaptic protein expression. A kinase anchoring protein (AKAP) 5/79 plays a key role in postsynaptic signalling of excitatory synapses. We aimed to reveal if the cellular expression of AKAP5/79 protein is altered in the anterior cingulate cortex and the dorsolateral prefrontal cortex in bipolar disorder. Ten subjects with bipolar disorder and ten control cases were investigated by use of immunohistochemical and morphometric techniques. Compared with controls in subjects with bipolar disorder, the numerical density of AKAP5-expressing neurons was significantly increased in the left (p = 0.002) and right (p = 0.008) anterior cingulate cortex. Layer-specific counting revealed that left side layers II (p = 0.000), III (p = 0.001) and V (p = 0.005) as well as right side layers III (p = 0.007), IV (p = 0.007) and V (p = 0.004) had significantly increased AKAP5-positive cell densities in bipolar disorder. In contrast, no statistically significant differences were found for the dorsolateral prefrontal cortex. However, we observed a more intense intraneuronal immunostaining in both prefrontal areas in bipolar disorder patients. Elevated cell numbers and increased intracellular expression of AKAP, together with the altered expression patterns of most intracellular interaction partners of this protein in bipolar disorder as known from the literature, might point to disease-related abnormalities of the AKAP-associated signalosome in prefrontal cortex neurons.

Experimental evidence for the involvement of PDLIM5 in mood disorders in hetero knockout mice

Background

Reports indicate that PDLIM5 is involved in mood disorders. The PDLIM5 (PDZ and LIM domain 5) gene has been genetically associated with mood disorders; it’s expression is upregulated in the postmortem brains of patients with bipolar disorder and downregulated in the peripheral lymphocytes of patients with major depression. Acute and chronic methamphetamine (METH) administration may model mania and the evolution of mania into psychotic mania or schizophrenia-like behavioral changes, respectively.

Methods

To address whether the downregulation of PDLIM5 protects against manic symptoms and cause susceptibility to depressive symptoms, we evaluated the effects of reduced Pdlim5 levels on acute and chronic METH-induced locomotor hyperactivity, prepulse inhibition, and forced swimming by using Pdlim5 hetero knockout (KO) mice.

Results

The homozygous KO of Pdlim5 is embryonic lethal. The effects of METH administration on locomotor hyperactivity and the impairment of prepulse inhibition were lower in Pdlim5 hetero KO mice than in wild-type mice. The transient inhibition of PDLIM5 (achieved by blocking the translocation of protein kinase C epsilon before the METH challenge) had a similar effect on behavior. Pdlim5 hetero KO mice showed increased immobility time in the forced swimming test, which was diminished after the chronic administration of imipramine. Chronic METH treatment increased, whereas chronic haloperidol treatment decreased, Pdlim5 mRNA levels in the prefrontal cortex. Imipramine increased Pdlim5 mRNA levels in the hippocampus.

Conclusion

These findings are partially compatible with reported observations in humans, indicating that PDLIM5 is involved in psychiatric disorders, including mood disorders.

Protein kinase C, an elusive therapeutic target?

Protein kinase C (PKC) has been a tantalizing target for drug discovery ever since it was first identified as the receptor for the tumour promoter phorbol ester in 1982. Although initial therapeutic efforts focused on cancer, additional indications--including diabetic complications, heart failure, myocardial infarction, pain and bipolar disorder--were targeted as researchers developed a better understanding of the roles of eight conventional and novel PKC isozymes in health and disease. Unfortunately, both academic and pharmaceutical efforts have yet to result in the approval of a single new drug that specifically targets PKC. Why does PKC remain an elusive drug target? This Review provides a short account of some of the efforts, challenges and opportunities in developing PKC modulators to address unmet clinical needs.

Platelet protein kinase C and brain-derived neurotrophic factor levels in borderline personality disorder patients

Borderline personality disorder (BPD) is a prevalent and difficult to treat psychiatric condition characterized by abrupt mood swings, intense anger and depression, unstable interpersonal relationships, impulsive self-destructive behavior and a suicide rate of approximately 10%. Possible underlying molecular dysregulations in BPD have not been well explored. Protein kinase C (PKC) and brain-derived neurotrophic factor (BDNF) have both been implicated in affective disorders, but their role in BPD has not been examined. Platelets were isolated from blood obtained from 24 medication-free BPD patients and 18 healthy control subjects. PKC-α, phosphorylated-PKC-α (p-PKCα), PKC-βII, and BDNF were measured in platelet homogenates by immunoblotting. In the males, platelet BDNF and PKC-α levels were lower in patients than controls. p-PKC-α and PKC-βII were lower at trend levels. In the entire sample, platelet p-PKCα and PKC-α activity were lower, at a trend level, in patients compared to controls. This is the first report to our knowledge of PKC and BDNF activity in BPD and calls for replication. These findings are consistent with altered PKC and BDNF activity in a range of neuropsychiatric conditions including bipolar disorder, depression and suicide.

Regionally selective activation and differential regulation of ERK, JNK and p38 MAP kinase signalling pathway by protein kinase C in mood modulation

A growing body of evidence indicates that the extracellular signal-regulated kinase (ERK) pathway may participate in the neuronal modulation of depression. p38MAPK and c-Jun-N-terminal kinase/stress-activated protein kinase (JNK/SAPK) also belong to the MAPK family which mainly function as mediators of cellular stresses. Since increasing evidence implicates stress as an important factor in vulnerability to depressive illnesses, the involvement of ERK, JNK and p38MAPK pathways in the modulation of mood was investigated in the forced swim test (FST) and tail suspension test (TST). The effect produced by a single acute session of FST and TST on hippocampal and cortical MAPK expression and phosphorylation was investigated by immunoblotting experiments. In the hippocampus of animals exposed to FST and TST, an intensive, PKC-dependent, ERK1, ERK2, JNK, and p38MAPK phosphorylation was observed. In the frontal cortex, the FST and TST produced a PKC-dependent increase of ERK2 and p38MAPK phosphorylation, a PKC-independent activation of JNK and cAMP response element-binding protein (CREB) whereas any involvement of ERK1 was detected. The PKC blocker calphostin C (0.05-0.1 μg i.c.v.), the MEK inhibitor U0126 (10-20 μg i.c.v.), the p38MAPK inhibitor SB203580 (5-20 μg i.c.v.) and the JNK inhibitor II (0.5-5 μg i.c.v.), produced antidepressant-like behaviour without altering locomotor activity. These results illustrate a differentially mediated activation of MAPK in hippocampus and frontal cortex of animals exposed to behavioural despair paradigms. An antidepressant-like phenotype produced by acute blockade of MAPK signalling was also demonstrated.

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.

Regulation of protein kinases and coregulatory interplay of S-100beta and serotonin transporter on serotonin levels in diabetic rat brain

Protein kinases are critical component in the regulation of signal transduction pathways, including neurotransmitters. Our previous studies have shown that serotonin (5-HT) altered under diabetic condition was accompanied by alterations of protein kinase C-alpha (PKC-alpha) and CaMKII, and those alterations were reversed after insulin administration. The current study showed that alloxan-induced diabetic animals revealed hyperglycemia and was associated with an increase in the content of 5-HT, PKC-alpha expression and PKC activity (P < 0.05) simultaneously in striatum (ST), midbrain (MB), pons medulla (PM), cerebellum (CB), and cerebral cortex (CCX) from 7 days to 60 days. Although the 5-HT levels in hippocampus (HC) and hypothalamus (HT) were not altered, the PKC-alpha expression and PKC activity showed increases (P < 0.05) in level in HC. Insulin administration reversed all these changes to a normal level. In contrast, the in vitro study has shown that the 5-HT levels correlated with PKC-alpha expressions as well as PKC activity (P < 0.05) only in ST, MB, and CB either after induction with phorbol 12-myristate 13-acetate (PMA) or blocking with chelerythrine, whereas PM and CCX remained elevated (P < 0.05), implying a regulatory role for PKC-alpha only in ST, MB, and CB. However, our consecutive studies have shown that the 5-HT level in PM was regulated by p38-mitogen-activated protein kinase (p38-MAPK) both in vivo and in vitro, whereas the 5-HT level in CCX was coregulated by S-100beta by protein-protein interaction with serotonin transporter (SERT) via 8-bromoadenosine 3',5'-cyclic monophosphate sodium salt (8-Br-cAMP)-induced cAMP/PKAII pathway(s).

Protein kinase C inhibitors: rationale for use and potential in the treatment of bipolar disorder

Bipolar disorder is one of the most severely debilitating of all medical illnesses. For a large number of patients, outcomes are quite poor. The illness results in tremendous suffering for patients and their families and commonly impairs functioning and workplace productivity. Risks of increased morbidity and mortality, unfortunately, are frequent occurrences as well. Until recently, little has been known about the specific molecular and cellular underpinnings of bipolar disorder. Such knowledge is crucial for the prospect of developing specific targeted therapies that are more effective and that have a more rapid onset of action than currently available treatments. Exciting recent data suggest that regulation of certain signalling pathways may be involved in the aetiology of bipolar disorder and that these pathways may be profitably targeted to treat the disorder. In particular, mania is associated with overactive protein kinase C (PKC) intracellular signalling, and recent genome-wide association studies of bipolar disorder have implicated an enzyme that reduces the activation of PKC. Importantly, the current mainstays in the treatment of mania, lithium (a monovalent cation) and valproate (a small fatty acid) indirectly inhibit PKC. In addition, recent clinical studies with the relatively selective PKC inhibitor tamoxifen add support to the relevance of the PKC target in bipolar disorder. Overall, a growing body of work both on a preclinical and clinical level indicates that PKC signalling may play an important role in the pathophysiology and treatment of bipolar disorder. The development of CNS-penetrant PKC inhibitors may have considerable benefit for this devastating illness.

Molecular neurobiology of bipolar disorder: a disease of 'mood-stabilizing neurons'?

Although the role of a genetic factor is established in bipolar disorder, causative genes or robust genetic risk factors have not been identified. Increased incidence of subcortical hyperintensity, altered calcium levels in cells derived from patients and neuroprotective effects of mood stabilizers suggest vulnerability or impaired resilience of neurons in bipolar disorder. Mitochondrial dysfunction or impaired endoplasmic reticulum stress response is suggested to play a role in the neurons' vulnerability. Progressive loss or dysfunction of 'mood-stabilizing neurons' might account for the characteristic course of the illness. The important next step in the neurobiological study of bipolar disorder is identification of the neural systems that are responsible for this disorder.

Molecular mechanisms of stress-induced prefrontal cortical impairment: implications for mental illness

The symptoms of mental illness often involve weakened regulation of thought, emotion, and behavior by the prefrontal cortex. Exposure to stress exacerbates symptoms of mental illness and causes marked prefrontal cortical dysfunction. Studies in animals have revealed the intracellular signaling pathways activated by stress exposure that induce profound prefrontal cortical impairment: Excessive dopamine stimulation of D1 receptors impairs prefrontal function via cAMP intracellular signaling, leading to disconnection of prefrontal networks, while excessive norepinephrine stimulation of alpha1 receptors impairs prefrontal function via phosphatidylinositol-protein kinase C intracellular signaling. Genetic studies indicate that the genes disrupted in serious mental illness (bipolar disorder and schizophrenia) often encode for the intracellular proteins that serve as brakes on the intracellular stress pathways. For example, disrupted in schizophrenia 1 (DISC1) normally regulates cAMP levels, while regulator of G protein signaling 4 (RGS4) and diacylglycerol kinase (DGKH)-the molecule most associated with bipolar disorder- normally serve to inhibit phosphatidylinositol-protein kinase C intracellular signaling. Patients with mutations resulting in loss of adequate function of these genes likely have weaker endogenous regulation of these stress pathways. This may account for the vulnerability to stress and the severe loss of PFC regulation of behavior, thought, and affect in these illnesses. This review highlights the signaling pathways onto which genetic vulnerability and stress converge to impair PFC function and induce debilitating symptoms such as thought disorder, disinhibition, and impaired working memory.

Hyperactive intracellular calcium dynamics in B lymphoblasts from patients with bipolar I disorder

Substantial evidence implicates abnormalities of intracellular calcium (Ca2+) dynamics in the pathophysiology of bipolar disorder (BD). However, the precise mechanisms underlying such disturbances are poorly understood. To further elaborate the nature of altered intracellular Ca2+ signalling dynamics that occur in BD, we examined receptor- and store-operated Ca2+ responses in B lymphoblast cell lines (BLCLs), which have been found in earlier studies to 'report' BD-associated disturbances. Basal Ca2+ concentrations ([Ca2+]B), and lysophosphatidic acid (LPA)- and thapsigargin-stimulated Ca2+ responses were determined in BLCLs from 52 BD-I patients and 30 healthy comparison subjects using fura-2, and ratiometric fluorometry. ANOVA revealed a significant effect of diagnosis, but not gender, on [Ca2+]B (F1,63=4.4, p=0.04) and the rate of rise (F1,63=5.2, p=0.03) of LPA-stimulated Ca2+ responses in BLCLs from patients compared with those from healthy subjects. A significant genderxdiagnosis interaction on the LPA-induced rate of rise (F1,63=4.6, p=0.03) was accounted for by a faster rate of rise (97%) in BLCLs from BD-I males compared with healthy males but not in those from female patients compared with healthy females. A genderxdiagnosis interaction in thapsigargin-evoked Ca2+ influx (F1,61=3.8, p=0.05) resulted from a significantly higher peak [Ca2+]influx (24%) in BLCLs from female compared with male patients. The results suggest more rapid LPA-stimulated Ca2+ responses occur in BLCLs from BD-I patients compared with controls, which are probably mediated, in part, by canonical transient receptor potential type 3 (TRPC3)-like channels. Additionally, this study highlights sex-dependent differences that can occur in the pathophysiological disturbances involved in BD.

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.

Effects of calmodulin and protein kinase C modulators on transient Ca2+ increase and capacitative Ca2+ entry in human platelets: relevant to pathophysiology of bipolar disorder

Disturbed intracellular calcium (Ca(2+)) homeostasis has been implicated in bipolar disorder, which mechanisms may be involved in the dysregulation of protein kinase C (PKC) and calmodulin systems. In this study, we investigated a transient intracellular Ca(2+) increase induced by thapsigargin, an inhibitor of sarco/endoplasmic reticulum Ca(2+)-ATPase pump (SERCA), and a capacitative Ca(2+) entry followed by addition of extracellular Ca(2+), in the presence or absence of PKC/calmodulin modulators in the platelets of healthy subjects in order to elucidate the role of SERCA in Ca(2+) homeostasis and to assess how both PKC and calmodulin systems regulate the two Ca(2+) responses. Moreover, we also examined the thapsigargin-elicited transient Ca(2+) increase and capacitative Ca(2+) entry in patients with mood disorders. PKC and calmodulin systems have opposite regulatory effects on the transient Ca(2+) increase and capacitative Ca(2+) entry in the platelets of normal subjects. The inhibitory effect of PKC activation on capacitative Ca(2+) entry is significantly increased and the stimulatory effect of PKC inhibition is significantly decreased in bipolar disorder compared to major depressive disorder and normal controls. These results suggest the possibility that increased PKC activity may activate the inhibitory effect of capacitative Ca(2+) entry in bipolar disorder. However, this is a preliminary study using a small sample, thus further studies are needed to examine the PKC and calmodulin modulators on the capacitative Ca(2+) entry in a larger sample.

Modulation of phosphoinositide-protein kinase C signal transduction by omega-3 fatty acids: implications for the pathophysiology and treatment of recurrent neuropsychiatric illness

The phosphoinositide (PI)-protein kinase C (PKC) signal transduction pathway is initiated by pre- and postsynaptic Galphaq-coupled receptors, and regulates several clinically relevant neurochemical events, including neurotransmitter release efficacy, monoamine receptor function and trafficking, monoamine transporter function and trafficking, axonal myelination, and gene expression. Mounting evidence for PI-PKC signaling hyperactivity in the peripheral (platelets) and central (premortem and postmortem brain) tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, coupled with evidence that PI-PKC signal transduction is down-regulated in rat brain following chronic, but not acute, treatment with antipsychotic, mood-stabilizer, and antidepressant medications, suggest that PI-PKC hyperactivity is central to an underlying pathophysiology. Evidence that membrane omega-3 fatty acids act as endogenous antagonists of the PI-PKC signal transduction pathway, coupled with evidence that omega-3 fatty acid deficiency is observed in peripheral and central tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, support the hypothesis that omega-3 fatty acid deficiency may contribute to elevated PI-PKC activity in these illnesses. The data reviewed in this paper outline a potential molecular mechanism by which omega-3 fatty acids could contribute to the pathophysiology and treatment of recurrent neuropsychiatric illness.

Cellular plasticity cascades: genes-to-behavior pathways in animal models of bipolar disorder

BACKGROUND

Despite extensive research, the molecular/cellular underpinnings of bipolar disorder (BD) remain to be fully elucidated. Recent data has demonstrated that mood stabilizers exert major effects on signaling that regulate cellular plasticity; however, a direct extrapolation to mechanisms of disease demands proof that manipulation of candidate genes, proteins, or pathways result in relevant behavioral changes.

METHODS

We critique and evaluate the behavioral changes induced by manipulation of cellular plasticity cascades implicated in BD.

RESULTS

Not surprisingly, the behavioral data suggest that several important signaling molecules might play important roles in mediating facets of the complex symptomatology of BD. Notably, the protein kinase C and extracellular signal-regulated kinase cascades might play important roles in the antimanic effects of mood stabilizers, whereas glycogen synthase kinase (GSK)-3 might mediate facets of lithium's antimanic/antidepressant actions. Glucocorticoid receptor (GR) modulation also seems to be capable to inducing affective-like changes observed in mood disorders. And Bcl-2, amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors, and inositol homeostasis represent important pharmacological targets for mood stabilizers, but additional behavioral research is needed to more fully delineate their behavioral effects.

CONCLUSIONS

Behavioral data support the notion that regulation of cellular plasticity is involved in affective-like behavioral changes observed in BD. These findings are leading to the development of novel therapeutics for this devastating illness.

Selective translocation of protein kinase c isozymes by PAF in rabbit platelets

The action of platelet activating factor (PAF) on subcellular distribution and activity of protein kinase C (PKC) isoforms in rabbit platelets was analyzed. The results showed an increase of PKC alpha in membrane fraction, concomitantly with a decrease in cytosolic fraction after 5 min PAF treatment, indicating that a translocation of PKC alpha occurred. In addition, PKC zeta was redistributed in a "reverse" form, from the membrane to cytosolic fraction after PAF treatment. PAF induced an increase of PKC alpha activity, whereas a decrease rather than increase in PKC zeta was observed by using immunoprecipitation assays. In addition, some results indicated that PI3 kinase activation was not involved in PAF-induced PKC zeta translocation as occur in several cells and with other agonists. These actions were time- and concentration-dependent, and were inhibited by the treatment with a PAF antagonist. No translocation was observed when the platelets were incubated with lysoPAF, a PAF related compound. The redistribution of PKC isoforms take place through the activation of high specificity PAF binding sites. The pretreatment of the rabbit platelets with staurosporine, a putative inhibitor of PKC, completely blocked the PAF-evoked aggregation without affecting to PAF-evoked shape change and serotonin release. All together, these data could suggest that the specific translocation of PKC isoforms play an important role in the activation of rabbit platelets.

Lithium and valproic acid treatments reduce PKC activation and receptor-G protein coupling in platelets of bipolar manic patients

Dysregulated protein kinase C (PKC) distribution and activation, and abnormal receptor-G protein coupling, have been implicated in the pathophysiology of bipolar affective disorder (BD). The therapeutic effectiveness of lithium has also been correlated with its ability to reduce PKC activation and G protein-mediated signaling. We examine the cellular distribution and activation of PKC and receptor-G protein coupling in blood platelets from normal controls, patients with BD mania or schizophrenia during treatment-free state, and after lithium or valproic acid administration. PKC activity was measured under basal and 50 nM phorbol 12-myristate, 13-acetate (PMA), 1 microM serotonin or 0.5 U/ml thrombin-stimulated conditions. The coupling of G proteins to serotonin or thrombin receptors were assessed by serotonin or thrombin-mediated [35S]GTPgammaS binding to membrane Galpha proteins. The results demonstrate that membrane-associated PKC activity and stimulus-induced PKC translocation are increased in BD manic, whereas stimulus-elicited PKC translocation is attenuated in schizophrenic patients. Lithium and valproic acid treatments attenuated the stimulus-induced PKC translocations to a similar degree and decreased PKC activity in both cytosolic and membranous fractions after two weeks of drug administration. An increase in 5-HT or thrombin stimulated [35S]GTPgammaS binding to Galpha proteins was detected in BD manic but not in schizophrenic patients although basal [35S]GTPgammaS binding was not different across the diagnostic groups. Lithium and valproic acid treatments similarly reduced receptor-G protein coupling with comparable time courses. Thus, increased membrane-associated PKC, cytosol to membrane PKC translocation and receptor-G protein coupling in platelets of BD manic patients were alleviated by lithium or valproic acid treatments.

Initial conditions of psychotropic drug response: studies of serotonin transporter long promoter region (5-HTTLPR), serotonin transporter efficiency, cytokine and kinase gene expression relevant to depression and antidepressant outcome

The Hypothesis of Initial Conditions posits that differences in psychotropic drug response result from individual differences in receptor site kinetics, and differences in the sensitivity of downstream receptor-linked responses. This work examines data consistent with the hypothesis, specific to genetic and kinetic differences of the serotonin (5-HT) transporter (SERT), as they may be linked to divergent antidepressant response (ADR). The mechanisms for divergent ADR in association with different initial SERT function are considered within the context of SERT trafficking as sensitive to various different kinase and cytokine signals, some of which are dependent on the 5-HTTLPR polymorphism of the SERT gene. Pilot data suggest that human lymphocytes show kinase changes similar to those found in rat brain with ADT. These studies additionally suggest that ADT prompts a shift in cytokine gene expression toward a greater anti-inflammatory/inflammatory ratio. These latter findings are discussed within the context of a literature suggesting increased inflammatory cytokine levels in depression, and recent observations of increased temperature associated with depression. In sum, the data suggest the opportunity to identify response dependent protein (RDP) expression patterns that may differ with dichotomous ADR, and suggest new insights into understanding the mechanisms of psychotropic drug response through an understanding of initial differences in potential for psychotropic drug target regulation during therapy.

Distinctions between bipolar and unipolar depression

This is a review of the studies comparing unipolar and bipolar depression, with focus on the course, symptomatology, neurobiology, and psychosocial literatures. These are reviewed with one question in mind: does the evidence support diagnosing bipolar and unipolar depressions as the same disorder or different? The current nomenclature of bipolar and unipolar disorders has resulted in research that compares these disorders as a whole, without considering depression separately from mania within bipolar disorder. Future research should investigate two broad categories of depression and mania as separate disease processes that are highly comorbid.

Neurobiological findings in bipolar II disorder compared with findings in bipolar I disorder

OBJECTIVE

To determine whether there are consistent neurobiological differences between patients with bipolar I disorder (BD I) and those with bipolar II disorder (BD II).

METHOD

We reviewed the literature in areas where the most consistent neurobiological findings have been reported for bipolar disorder, specifically, neuroimaging and brain metabolism. The imaging studies reviewed examined structure, using magnetic resonance imaging (MRI), and function, using functional MRI, positron emission tomography, and single photon emission computed tomography. We used magnetic resonance spectroscopy to examine brain chemistry. We reviewed those metabolic studies that examined cell calcium, 3-methoxy-4-hydroxyphenylglycol, and protein kinase C.

RESULTS

Some genetic studies suggest that there may be differences between BD II and BD I patients. However, our review of the imaging and metabolic studies identified few studies directly comparing these 2 groups. In those studies, there were few differences, if any, and these were not consistent.

CONCLUSIONS

While genetic data suggest there may be differences between BD II patients and BD I patients, the neurobiological findings to date do not provide support. However, this may be owing to the small number of studies directly comparing the 2 groups and also to the fact that those carried out have not been adequately powered to detect possible small true differences. This is an important issue because, if there are no neurobiological differences, it would be anticipated that similar treatments would be similarly effective in both groups. Given the importance of understanding whether there are neurochemical differences between these groups, further research in this area is clearly needed.

[Neuropatological and neurochemical abnormalities in bipolar disorder]

OBJECTIVES

Postmortem, pharmacological, neuroimaging, and animal model studies have demonstrated a possible association of intracellular signaling mechanisms in the pathophysiology of bipolar disorder. The objective of this paper is to review the findings in neuropathology and cellular biochemistry.

METHODS

We performed a MEDLINE research, between 1980-2003, using bipolar disorder, signaling, second messengers, and postmortem as keywords, and cross-references.

RESULTS

Neuropathological studies reported a decrease in neuronal and glial cells, mainly in the prefrontal cortex of bipolar patients. Neurochemical studies reported dysfunction in cAMP, phosphoinositide, Wnt/GSK-3b, and intracellular Ca++ pathways in these patients.

CONCLUSION

The neuropathological and neurochemical abnormalities demonstrated in BD may be related to the pathophysiology of this disorder and the effects of mood stabilizers. However, further studies are needed to clarify the role of the intracellular signaling cascade in the pathogenesis of this disorder.

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.

Serotonin-mediated phosphorylation of extracellular regulated kinases in platelets of patients with panic disorder versus controls

Phosphorylation of extracellular signal-regulated kinases (ERK 1/2) represents a converging intracellular signalling pathway which is involved in the modulation of gene transcription and may contribute to the feed-back regulation of neurotransmitter receptor functioning. The purpose of the current study was to investigate the serotonin-mediated phosphorylation of ERK 1/2 in platelets from patients (n = 17) with panic disorder, with respect to healthy volunteers (n = 17). Patients presented a severe symptomatology as assessed by the self-report rating scales for panic-agoraphobic (PAS-SR) and mood (MOOD-SR) spectrum, and by Clinical Global Impression Severity Scale (CGI-S). In platelets from healthy volunteers, serotonin induced a rapid increase of ERK 1/2 phosphorylation with a transient monophasic kinetic. The dose-response curves showed this effect was concentration dependent with an average of the EC(50) value of 22.8 +/- 2.4 microM. Platelet pre-incubation with 5HT(1A) and 5HT(2A) antagonists, pindobind and ritanserin, significantly inhibited serotonin-mediated kinase activation with an EC(50) of 3.2 +/- 0.2 and 1.99 +/- 0.08 nM, respectively, suggesting an involvement of these specific receptor subtypes in serotonin-mediated response. Furthermore, the 5HT(1A) and 5HT(2A) agonists, 8-hydroxy-N,N-dipropyl-aminotetralin (8OH-DPAT) and 1-(2,5-dimethoxy)-4-iodophenyl-2-aminopropane (DOI), were able to modulate ERK 1/2 phosphorylation in a concentration-dependent manner with an EC(50) value of 3.1 +/- 0.2 and 76 +/- 4.5 nM, respectively. ERK 1/2 phosphorylation was not observed after serotonin treatment of platelets from drug-free panic disorder patients, suggesting an alteration in intracellular phosphorylative pathways. Since ERK 1/2 responsiveness to other stimulus, such as collagen and thrombin, was comparable in platelets from healthy volunteers and patients, our results suggested that a specific alteration of serotonergic system occurred in panic disorder. Further studies to investigate 5HT(1A) and 5HT(2A) receptor expression and threonine phosphorylation levels showed that, nevertheless no significant differences in the receptor expression levels were detected, an increase of both 5HT receptor phosphorylation, on threonine residues, occurred in platelet from panic patients with respect to controls, suggesting that a reduction of serotonin receptor functioning was involved in the loss of serotonin responsiveness in panic.

Avoiding drug-induced switching in patients with bipolar depression

Antidepressant-induced switching is a major risk during the treatment of bipolar depression. Despite several clinical studies, questions remain regarding both the definition of these mood switches and the most appropriate therapeutic strategy to avoid this adverse effect. This review will first briefly consider the current guidelines for the acute treatment of bipolar depression. We will then review the mechanisms of action of antidepressant and mood stabilisers, and the switches induced by various types of antidepressant treatments, or triggered by antidepressant withdrawal, as well as by atypical antipsychotics. We then will address the risk of mood switch according to the type of mood stabiliser used. The propensity to mood switches in bipolar patients is subject to individual differences. Therefore we will describe both the clinical and biological characteristics of patients prone to mood switches under antidepressant treatment. However, the clinical characteristics of the depressive syndrome may also be a key determinant for mood switches. Various data help identify the most appropriate drug management strategies for avoiding mood switches during the treatment of bipolar depression. Selective serotonin reuptake inhibitors appear to be the drugs of first-choice because of the low associated risk of mood switching. Antidepressants must be associated with a mood stabiliser and the most effective in the prevention of switches seems to be lithium. Whatever the mood stabiliser used, effective plasma levels must be ensured. The optimal duration of antidepressant treatment for bipolar depression is still an open issue - prolonged treatments after recovery may be unnecessary and may facilitate mood elation. Moreover, some mood episodes with mixed symptoms can be worsened by antidepressants pointing to the need for a better delineation of the categories of symptoms requiring antidepressant treatment. Finally, as a result of this review, we suggest some propositions to define drug-induced switches in bipolar patients, and to try to delineate which strategies should be recommended in clinical practice to reduce as far as possible the risk of mood switch during the treatment of bipolar depression.