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

Differences in intracellular protein levels in monocytes and CD4+ lymphocytes between bipolar depressed patients and healthy controls: A pilot study with tyramine-based signal-amplified flow cytometry

BACKGROUND

Molecular biomarkers for bipolar disorder (BD) that distinguish it from other manifestations of depressive symptoms remain unknown. The aim of this study was to determine if a very sensitive tyramine-based signal-amplification technology for flow cytometry (CellPrint™) could facilitate the identification of cell-specific analyte expression profiles of peripheral blood cells for bipolar depression (BPD) versus healthy controls (HCs).

METHODS

The diagnosis of psychiatric disorders was ascertained with Mini International Neuropsychiatric Interview for DSM-5. Expression levels for eighteen protein analytes previously shown to be related to bipolar disorder were assessed with CellPrint™ in CD4⁺ T cells and monocytes of bipolar patients and HCs. Implementation of protein-protein interaction (PPI) network and pathway analysis was subsequently used to identify new analytes and pathways for subsequent interrogations.

RESULTS

Fourteen drug-naïve or -free patients with bipolar I or II depression and 17 healthy controls (HCs) were enrolled. The most distinguishable changes in analyte expression based on t-tests included GSK3β, HMGB1, IRS2, phospho-GSK3αβ, phospho-RELA, and TSPO in CD4⁺ T cells and calmodulin, GSK3β, IRS2, and phospho-HS1 in monocytes. Subsequent PPI and pathway analysis indicated that prolactin, leptin, BDNF, and interleukin-3 signal pathways were significantly different between bipolar patients and HCs.

LIMITATION

The sample size of the study was small and 2 patients were on medications.

CONCLUSION

In this pilot study, CellPrint™ was able to detect differences in cell-specific protein levels between BPD patients and HCs. A subsequent study including samples from patients with BPD, major depressive disorder, and HCs is warranted.

Akkouh I, Hughes T, Frei E, A. Andreassen O, Djurovic S. Using iPSC Models to Understand the Role of Estrogen in Neuron-Glia Interactions in Schizophrenia and Bipolar Disorder

Schizophrenia (SCZ) and bipolar disorder (BIP) are severe mental disorders with a considerable disease burden worldwide due to early age of onset, chronicity, and lack of efficient treatments or prevention strategies. Whilst our current knowledge is that SCZ and BIP are highly heritable and share common pathophysiological mechanisms associated with cellular signaling, neurotransmission, energy metabolism, and neuroinflammation, the development of novel therapies has been hampered by the unavailability of appropriate models to identify novel targetable pathomechanisms. Recent data suggest that neuron-glia interactions are disturbed in SCZ and BIP, and are modulated by estrogen (E2). However, most of the knowledge we have so far on the neuromodulatory effects of E2 came from studies on animal models and human cell lines, and may not accurately reflect many processes occurring exclusively in the human brain. Thus, here we highlight the advantages of using induced pluripotent stem cell (iPSC) models to revisit studies of mechanisms underlying beneficial effects of E2 in human brain cells. A better understanding of these mechanisms opens the opportunity to identify putative targets of novel therapeutic agents for SCZ and BIP. In this review, we first summarize the literature on the molecular mechanisms involved in SCZ and BIP pathology and the beneficial effects of E2 on neuron-glia interactions. Then, we briefly present the most recent developments in the iPSC field, emphasizing the potential of using patient-derived iPSCs as more relevant models to study the effects of E2 on neuron-glia interactions.

Cellular calcium in bipolar disorder: systematic review and meta-analysis

Calcium signalling has long been implicated in bipolar disorder, especially by reports of altered intracellular calcium ion concentrations ([Ca²⁺]). However, the evidence has not been appraised critically. We carried out a systematic review and meta-analysis of studies of cellular calcium indices in bipolar disorder. 2281 records were identified and 117 screened, of which 32 were eligible and 21 were suitable for meta-analyses. The latter each involved up to 642 patients and 404 control subjects. We found that basal free intracellular [Ca²⁺] is increased in bipolar disorder, both in platelets and in lymphocytes. The effect size is 0.55, with an estimated elevation of 29%. It is observed in medication-free patients. It is present in mania and bipolar depression, but data are equivocal for euthymia. Cells from bipolar disorder individuals also show an enhanced [Ca²⁺] response to stimulation with 5-HT or thrombin, by an estimated 25%, with an effect size of 0.63. In studies which included other diagnoses, intracellular basal [Ca²⁺] was higher in bipolar disorder than in unipolar depression, but not significantly different from schizophrenia. Functional parameters of cellular Ca²⁺ (e.g. calcium transients), and neuronal [Ca²⁺], have been much less investigated, and no firm conclusions can be drawn. In summary, there is a robust, medium effect size elevation of basal and stimulated free intracellular [Ca²⁺] in bipolar disorder. The results suggest altered calcium functioning in the disorder, and encourage further investigations into the underlying mechanisms, and the implications for pathophysiology and therapeutics.

Lithium effects on serine-threonine kinases activity: High throughput kinomic profiling of lymphoblastoid cell lines from excellent-responders and non-responders bipolar patients

Objectives: Lithium is the leading mood stabiliser for maintenance treatment in bipolar disorder (BD). However, response to lithium is heterogeneous with more than 60% of patients experiencing partial or no response. In vitro and in vivo molecular studies have reported the implication of kinases in the pathophysiology of BD.Methods: Since kinases are putative targets for lithium therapeutic action, we conducted the first pilot study using kinase array technology to evaluate the global serine/threonine kinases (STK) profiles in cell lines from BD I subtype patients classified as lithium excellent-responders (ER) and non-responder (NR) to lithium treatment.Results: We found significant differences in the basal STK profiles between ER and NR to lithium. We also tested lithium influence on the global STK profile and found no significant difference between ER vs NR cell lines.Conclusions: The results obtained in this exploratory study suggest that multiplex kinase activity profiling could provide a complementary approach in the study of biomarkers of therapeutic response in BD.

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.

Calcium as a Trojan horse in mental diseases-The role of PMCA and PMCA-interacting proteins in bipolar disorder and schizophrenia

Although first mentions about calcium disturbances in psychiatric diseases appeared more than 30 years ago, the most recent genomic and proteomic findings confirmed a significant role of Ca²⁺ and Ca²⁺-regulated pathways in development of neuropathological processes, including bipolar disorder and schizophrenia. Moreover, last decades have shown that due to multifactorial nature of both diseases, impairment in neuronal calcium homeostasis may depend not only on disturbed Ca²⁺ entry system, but also on altered extrusion system. A pivotal role in Ca²⁺ clearance mechanism is played by plasma membrane Ca²⁺-ATPase (PMCA), the enzyme responsible for returning the elevated levels of cytosolic Ca²⁺ back to the resting state. In this paper we summarize the current knowledge about the role of PMCA in bipolar disorder and schizophrenia pathologies, as well as the contribution of several proteins that by interaction with PMCA modify signal transduction mechanisms.

Mania

PURPOSE OF REVIEW

Primary mania and hypomania in full or subsyndromal forms are the defining features of bipolar disorder and are common in neurologic patients, as are manic syndromes precipitated by medications used to treat neurologic disorders. This article addresses the diagnosis, pathophysiology, treatment, and course of bipolar disorder after a manic episode as well as mania as a manifestation of neurologic disease.

RECENT FINDINGS

Mania can be a primary psychiatric disorder but can also be a symptom of a neurologic disorder, especially right-sided cerebrovascular disease. Treatments (such as corticosteroids and dopaminergic agents) for neurologic illnesses regularly induce mania. The neurobiology of primary mania and bipolar disorder involves alterations in intracellular signaling, changes in gene expression, neural network interactions, and apoptosis. Except when induced by time-limited treatment with a provoking agent, mania tends to be highly recurrent and to alternate or be exhibited alongside depression. Symptoms of mania become more complex and treatment refractory with time, although effective treatment improves the long-term outcome.

SUMMARY

Behavioral manifestations of mania may be more obvious than affective symptoms, especially in patients with aprosodia. Atypical antipsychotic drugs are often first-line acute treatments, but the evidence supporting their long-term prophylactic efficacy is questionable. In addition to being an established mood stabilizer, lithium has putative neuroprotective properties, although a side effect can be impaired memory.

Increased platelet intracellular calcium ion concentration is specific to bipolar disorder

BACKGROUND

Increased baseline ([Ca(2+)]B) and agonist-stimulated ([Ca(2+)]s) free intracellular calcium ion concentrations ([Ca(2+)]i) are well-replicated findings in bipolar disorder, but whether this finding is specific to that condition and if so, whether it is a marker of the mood disorder or a feature seen in other disorders such as psychosis has remained unclear.

METHODS

Platelet [Ca(2+)]i was assessed in 15 inpatients with psychotic and nonpsychotic mania, 17 schizophrenia inpatients, and 17 matched controls.

RESULTS

Platelet [Ca(2+)]B and [Ca(2+)]s were significantly higher than controls in bipolar disorder but not schizophrenia. Variability of [Ca(2+)]B was significantly increased in bipolar disorder regardless of the presence of psychosis, but not in schizophrenia.

LIMITATIONS

Use of antipsychotic drugs by the majority of both patient groups may have obscured elevated [Ca(2+)]i in schizophrenia, or may have masked a difference between psychotic and nonpsychotic bipolar disorder. Measurement of [Ca(2+)]i is too labor intensive to become a routine test for diagnosis or prediction of treatment response.

CONCLUSIONS

Elevated intracellular Ca(2+) signaling may be a marker of primary cellular hyperactivity that could contribute to comorbid conditions such as hypertension and neuronal apoptosis. Since lithium and carbamazepine attenuate increased [Ca(2+)]i, further research may demonstrate a correlation between normalization of [Ca(2+)]i and response to one of these medications, and further research may clarify whether a subgroup of patients may respond well to calcium channel antagonists.

Multiple levels of impaired neural plasticity and cellular resilience in bipolar disorder: developing treatments using an integrated translational approach

OBJECTIVES

This paper reviews the neurobiology of bipolar disorder (BD), particularly findings associated with impaired cellular resilience and plasticity.

METHODS

PubMed/Medline articles and book chapters published over the last 20 years were identified using the following keyword combinations: BD, calcium, cytokines, endoplasmic reticulum (ER), genetics, glucocorticoids, glutamate, imaging, ketamine, lithium, mania, mitochondria, neuroplasticity, neuroprotection, neurotrophic, oxidative stress, plasticity, resilience, and valproate.

RESULTS

BD is associated with impaired cellular resilience and synaptic dysfunction at multiple levels, associated with impaired cellular resilience and plasticity. These findings were partially prevented or even reversed with the use of mood stabilizers, but longitudinal studies associated with clinical outcome remain scarce.

CONCLUSIONS

Evidence consistently suggests that BD involves impaired neural plasticity and cellular resilience at multiple levels. This includes the genetic and intra- and intercellular signalling levels, their impact on brain structure and function, as well as the final translation into behaviour/cognitive changes. Future studies are expected to adopt integrated translational approaches using a variety of methods (e.g., microarray approaches, neuroimaging, genetics, electrophysiology, and the new generation of -omics techniques). These studies will likely focus on more precise diagnoses and a personalized medicine paradigm in order to develop better treatments for those who need them most.

The CACNA1C risk allele selectively impacts on executive function in bipolar type I disorder

OBJECTIVE

Calcium channels are important for converting electrical activity into biochemical events. A single nucleotide polymorphism (SNP) (rs1006737) in the CACNA1C gene has been strongly associated with increased risk for Bipolar disorder (BD) in genome-wide association studies. Recently, this same SNP has been reported to influence executive function in schizophrenia and controls, but it remains unclear whether this SNP affects behaviour, especially cognition in subjects with BD.

METHOD

A total of 109 BD type I subjects and 96 controls were genotyped for CACNA1C rs1006737 and assessed with an executive function tests battery [Wechsler Adult Intelligence Scale III (WAIS-III) Letter-Number Sequence subtest (WAIS-LNS), digit span (WAISDS), trail making test (TMT), and WCST (Wisconsin Card Sorting Test)].

RESULTS

In patients with BD, the CACNA1C genotype Met/Met was associated with worse performance on all four executive function tests compared to Val/Val. No influence of CACNA1C was observed in the cognitive performance of healthy controls.

CONCLUSION

Our data indicate for the first time that the CACNA1C risk allele is likely associated with executive dysfunction as a trait in BD, as this association was found regardless the presence of mood symptoms. Larger studies should evaluate the potential influence of CACNA1C on other cognitive domains in BD.

The impact of the CACNA1C risk allele on limbic structures and facial emotions recognition in bipolar disorder subjects and healthy controls

INTRODUCTION

Impairments in facial emotion recognition (FER) have been reported in bipolar disorder (BD) during all mood states. FER has been the focus of functional magnetic resonance imaging studies evaluating differential activation of limbic regions. Recently, the α1-C subunit of the L-type voltage-gated calcium channel (CACNA1C) gene has been described as a risk gene for BD and its Met allele found to increase CACNA1C mRNA expression. In healthy controls, the CACNA1C risk (Met) allele has been reported to increase limbic system activation during emotional stimuli and also to impact on cognitive function. The aim of this study was to investigate the impact of CACNA1C genotype on FER scores and limbic system morphology in subjects with BD and healthy controls.

MATERIAL AND METHODS

Thirty-nine euthymic BD I subjects and 40 healthy controls were submitted to a FER recognition test battery and genotyped for CACNA1C. Subjects were also examined with a 3D 3-Tesla structural imaging protocol.

RESULTS

The CACNA1C risk allele for BD was associated to FER impairment in BD, while in controls nothing was observed. The CACNA1C genotype did not impact on amygdala or hippocampus volume neither in BD nor controls.

LIMITATIONS

Sample size.

CONCLUSION

The present findings suggest that a polymorphism in calcium channels interferes FER phenotype exclusively in BD and doesn't interfere on limbic structures morphology.

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.