Lithium prevents aberrant NMDA-induced F-actin reorganization in neurons

Alternations of vitamin D and cognitive function in first-diagnosed and drug-naïve BD patients: Physical activity as a moderator

BACKGROUND

The pathophysiological mechanism of cognitive impairments of bipolar disorder (BD) has not yet been completely revealed. It is well known that Vitamin D and physical activity (PA) are associated with BD. However, specific links between Vitamin D and cognitive deficits in BD are still unclear.

METHOD

The serum levels of vitamin D were measured. The cognitive performances of 102 first-diagnosed and drug-naïve BD patients were evaluated for analysis. The repeatable battery for the assessment of neuropsychological status (RBANS) and the Stroop Color-Word test was used in this study. PA was collected by international physical activity questionnaire.

RESULT

Patients with BD had high levels of serum vitamin D. Furthermore, immediate and delayed memory was negatively associated with vitamin D levels in patients' group. The serum levels of vitamin D in patients with low PA were positively associated with memory. However, increased PA attenuated the protective effect of vitamin D on executive cognition.

CONCLUSION

It is concluded that the increased levels of vitamin D were observed in the serum of patients with BD. Thus, it is found that more PA is less beneficial to cognition of patients with BD than longer resting.

INF2-mediated actin filament reorganization confers intrinsic resilience to neuronal ischemic injury

During early ischemic brain injury, glutamate receptor hyperactivation mediates neuronal death via osmotic cell swelling. Here we show that ischemia and excess NMDA receptor activation cause actin to rapidly and extensively reorganize within the somatodendritic compartment. Normally, F-actin is concentrated within dendritic spines. However, <5 min after bath-applied NMDA, F-actin depolymerizes within spines and polymerizes into stable filaments within the dendrite shaft and soma. A similar actinification occurs after experimental ischemia in culture, and photothrombotic stroke in mouse. Following transient NMDA incubation, actinification spontaneously reverses. Na+, Cl-, water, and Ca2+ influx, and spine F-actin depolymerization are all necessary, but not individually sufficient, for actinification, but combined they induce activation of the F-actin polymerization factor inverted formin-2 (INF2). Silencing of INF2 renders neurons vulnerable to cell death and INF2 overexpression is protective. Ischemia-induced dendritic actin reorganization is therefore an intrinsic pro-survival response that protects neurons from death induced by cell edema.

Growth cone macropinocytosis of neurotrophin receptor and neuritogenesis are regulated by neuron navigator 1

Neuron navigator 1 (Nav1) is a cytoskeleton-associated protein expressed during brain development that is necessary for proper neuritogenesis, but the underlying mechanisms are poorly understood. Here we show that Nav1 is present in elongating axon tracts during mouse brain embryogenesis. We found that depletion of Nav1 in cultured neurons disrupts growth cone morphology and neurotrophin-stimulated neuritogenesis. In addition to regulating both F-actin and microtubule properties, Nav1 promotes actin-rich membrane ruffles in the growth cone and promotes macropinocytosis at those membrane ruffles, including internalization of the TrkB receptor for the neurotrophin brain-derived neurotropic factor (BDNF). Growth cone macropinocytosis is important for downstream signaling, neurite targeting, and membrane recycling, implicating Nav1 in one or more of these processes. Depletion of Nav1 also induces transient membrane blebbing via disruption of signaling in the Rho GTPase signaling pathway, supporting the novel role of Nav1 in dynamic actin-based membrane regulation at the cell periphery. These data demonstrate that Nav1 works at the interface of microtubules, actin, and plasma membrane to organize the cell periphery and promote uptake of growth and guidance cues to facilitate neural morphogenesis during development.

[Lithium in the psychopharmacology of affective disorders and mechanisms of its effects on cellular physiology]

However, despite successful use of lithium in the treatment of affective disorders for almost 40 years, the mechanisms of its therapeutic action are still poorly understood. This review presents and summarizes the current literature about the use of lithium in treatment of affective disorders, as well as its effects on cellular physiology, with a separate description of the effect of this ion on the functioning of nerve tissue and ion-molecular mechanisms.

[Bipolar disorder vulnerability: The vitamin D path]

OBJECTIVES

Bipolar disorder (BD) etiopathogenesis is still not well elucidated. It has recently been proven that 25-hydroxy vitamin D (25OHD) has an anti-inflammatory and neuroprotective role. Our objectives were to measure 25OHD plasma levels in patients with BD in acute decompensation and compare them with patients with schizophrenia (SCZ) or schizoaffective disorder (SAD) and with healthy controls.

METHODS

This is a cross-sectional case-control study including male inpatients with a decompensation of their disease who were diagnosed with BD, SCZ or SAD according to DSM-5 criterias. The control group was constituted by unrelated healthy subjects, age-and-sex matched.

RESULTS

The 25OHD level was significantly higher only in patients with BD compared to controls. 25OHD was also positively correlated to the PANSS scale (r = 0.282, p < 0.001) and to different MOCA scores (r = 0.326, p = 0.006) as well as aspects related to abstraction, attention and memory capacity. Multivariate analysis found that BD acute decompensation was independently related to the rise in plasma 25OHD (p = 0.012; OR =1.157, [1.032 -1.297]).

CONCLUSION

Our study shows that BD acute decompensation is associated with the rise in plasma 25OHD synthesis. However, the vitamin D dosage relevance as a biomarker of this disease warrants a verification in other studies.

Omega-3 Polyunsaturated Fatty Acid Deficiency and Progressive Neuropathology in Psychiatric Disorders: A Review of Translational Evidence and Candidate Mechanisms

Meta-analytic evidence indicates that mood and psychotic disorders are associated with both omega-3 polyunsaturated fatty acid (omega-3 PUFA) deficits and progressive regional gray and white matter pathology. Although the association between omega-3 PUFA insufficiency and progressive neuropathological processes remains speculative, evidence from translational research suggests that omega-3 PUFA insufficiency may represent a plausible and modifiable risk factor not only for enduring neurodevelopmental abnormalities in brain structure and function, but also for increased vulnerability to neurodegenerative processes. Recent evidence from human neuroimaging studies suggests that lower omega-3 PUFA intake/status is associated with accelerated gray matter atrophy in healthy middle-aged and elderly adults, particularly in brain regions consistently implicated in mood and psychotic disorders, including the amygdala, anterior cingulate, hippocampus, prefrontal cortex, and temporal cortex. Human neuroimaging evidence also suggests that both low omega-3 PUFA intake/status and psychiatric disorders are associated with reductions in white matter microstructural integrity and increased rates of white matter hyperintensities. Preliminary evidence suggests that increasing omega-3 PUFA status is protective against gray matter atrophy and deficits in white matter microstructural integrity in patients with mood and psychotic disorders. Plausible mechanisms mediating this relationship include elevated pro-inflammatory signaling, increased synaptic regression, and reductions in cerebral perfusion. Together these associations encourage additional neuroimaging research to directly investigate whether increasing omega-3 PUFA status can mitigate neuropathological processes in patients with, or at high risk for, psychiatric disorders.

The Stress-Inducible Protein DRR1 Exerts Distinct Effects on Actin Dynamics

Cytoskeletal dynamics are pivotal to memory, learning, and stress physiology, and thus psychiatric diseases. Downregulated in renal cell carcinoma 1 (DRR1) protein was characterized as the link between stress, actin dynamics, neuronal function, and cognition. To elucidate the underlying molecular mechanisms, we undertook a domain analysis of DRR1 and probed the effects on actin binding, polymerization, and bundling, as well as on actin-dependent cellular processes. Methods: DRR1 domains were cloned and expressed as recombinant proteins to perform in vitro analysis of actin dynamics (binding, bundling, polymerization, and nucleation). Cellular actin-dependent processes were analyzed in transfected HeLa cells with fluorescence recovery after photobleaching (FRAP) and confocal microscopy. Results: DRR1 features an actin binding site at each terminus, separated by a coiled coil domain. DRR1 enhances actin bundling, the cellular F-actin content, and serum response factor (SRF)-dependent transcription, while it diminishes actin filament elongation, cell spreading, and actin treadmilling. We also provide evidence for a nucleation effect of DRR1. Blocking of pointed end elongation by addition of profilin indicates DRR1 as a novel barbed end capping factor. Conclusions: DRR1 impacts actin dynamics in several ways with implications for cytoskeletal dynamics in stress physiology and pathophysiology.

Bipolar disorder in youth is associated with increased levels of vitamin D-binding protein

Genetic, dietary, and inflammatory factors contribute to the etiology of major mood disorders (MMD), thus impeding the identification of specific biomarkers to assist in diagnosis and treatment. We tested association of vitamin D and inflammatory markers in 36 adolescents with bipolar disorder (BD) and major depressive disorder (MDD) forms of MMD and without MMD (non-mood control). We also assessed the overall level of inflammation using a cell-based reporter assay for nuclear factor kappa-B (NFκB) activation and measuring antibodies to oxidized LDL. We found that these factors were similar between non-mood and MMD youth. To identify potential biomarkers, we developed a screening immunoprecipitation-sequencing approach based on inflammatory brain glia maturation factor beta (GMFβ). We discovered that a homolog of GMFβ in human plasma is vitamin D-binding protein (DBP) and validated this finding using immunoprecipitation with anti-DBP antibodies and mass spectrometry/sequencing analysis. We quantified DBP levels in participants by western blot. DBP levels in BD participants were significantly higher (136%) than in participants without MMD (100%). The increase in DBP levels in MDD participants (121.1%) was not statistically different from these groups. The DBP responds early to cellular damage by binding of structural proteins and activating inflammatory cells. A product of enzymatic cleavage of DBP has been described as macrophage-activating factor. Circulating DBP is comprised of heterogenous high and low molecular fractions that are only partially recognized by mono- and polyclonal ELISA and are not suitable for the quantitative comparison of DBP in non-mood and MDD participants. Our data suggest DBP as a marker candidate of BD warranting its validation in a larger cohort of adolescent and adult MMD patients.

An Oldie but Goodie: Lithium in the Treatment of Bipolar Disorder through Neuroprotective and Neurotrophic Mechanisms

Lithium has been used for the treatment of bipolar disorder (BD) for the last sixty or more years, and recent studies with more reliable designs and updated guidelines have recommended lithium to be the treatment of choice for acute manic, mixed and depressive episodes of BD, along with long-term prophylaxis. Lithium’s specific mechanism of action in mood regulation is progressively being clarified, such as the direct inhibition on glycogen synthase kinase 3β, and its various effects on neurotrophic factors, neurotransmitters, oxidative metabolism, apoptosis, second messenger systems, and biological systems are also being revealed. Furthermore, lithium has been proposed to exert its treatment effects through mechanisms associated with neuronal plasticity. In this review, we have overviewed the clinical aspects of lithium use for BD, and have focused on the neuroprotective and neurotrophic effects of lithium.

Synaptic Plasticity, Metaplasticity and Depression

The development of a persistent depressive affective state has for some time been thought to result from persistent alterations in neurotransmitter-mediated synaptic transmission. While the identity of those transmitters has changed over the years, the literature has lacked mechanistic connections between the neurophysiological mechanisms they regulate, and how these mechanisms alter neuronal function, and, hence, affective homeostasis. This review will examine recent work that suggests that both long-term activity-dependent changes in synaptic strength (“plasticity”), and shifting set points for the ease of induction of future long-term changes (“metaplasticity”), may be critical to establishing and reversing a depressive behavioral state. Activity-dependent long-term synaptic plasticity involves both strengthening and weakening of synaptic connections associated with a dizzying array of neurochemical alterations that include synaptic insertion and removal of a number of subtypes of AMPA, NMDA and metabotropic glutamate receptors, changes in presynaptic glutamate release, and structural changes in dendritic spines. Cellular mechanisms of metaplasticity are far less well understood. Here, we will review the growing evidence that long-term synaptic changes in glutamatergic transmission, in brain regions that regulate mood, are key determinants of affective homeostasis and therapeutic targets with immense potential for drug development.

Therapeutic Mechanisms of Lithium in Bipolar Disorder: Recent Advances and Current Understanding

Lithium is the most effective and well established treatment for bipolar disorder, and it has a broad array of effects within cellular pathways. However, the specific processes through which therapeutic effects occur and are maintained in bipolar disorder remain unclear. This paper provides a timely update to an authoritative review of pertinent findings that was published in CNS Drugs in 2013. A literature search was conducted using the Scopus database, and was limited by year (from 2012). There has been a resurgence of interest in lithium therapy mechanisms, perhaps driven by technical advancements in recent years that permit the examination of cellular mechanisms underpinning the effects of lithium-along with the reuptake of lithium in clinical practice. Recent research has further cemented glycogen synthase kinase 3β (GSK3β) inhibition as a key mechanism, and the inter-associations between GSK3β-mediated neuroprotective, anti-oxidative and neurotransmission mechanisms have been further elucidated. In addition to highly illustrative cellular research, studies examining higher-order biological systems, such as circadian rhythms, as well as employing innovative animal and human models, have increased our understanding of how lithium-induced changes at the cellular level possibly translate to changes at behavioural and clinical levels. Neural circuitry research is yet to identify clear mechanisms of change in bipolar disorder in response to treatment with lithium, but important structural findings have demonstrated links to the modulation of cellular mechanisms, and peripheral marker and pharmacogenetic studies are showing promising findings that will likely inform the exploration for predictors of lithium treatment response. With a deeper understanding of lithium's therapeutic mechanisms-from the cellular to clinical levels of investigation-comes the opportunity to develop predictive models of lithium treatment response and identify novel drug targets, and recent findings have provided important leads towards these goals.

Bipolar disorder and antibodies against the N-methyl-d-aspartate receptor: A gate to the involvement of autoimmunity in the pathophysiology of bipolar illness

The high prevalence of comorbidity between bipolar disorder (BD) and other medical conditions, including autoimmune diseases, supports the hypothesis of the nature of BD as a biological illness category. Hence, an immune dysregulation process may play an important role in the development of at least certain subtypes of BD. Increasing evidence also suggests that the N-methyl-d-aspartate receptor (NMDAR) may be relevant in the pathophysiology of BD. A possible key mechanism underlying the physiopathology of certain autoimmune diseases that may present with affective symptoms might be the production of anti-NMDAR auto-antibodies (auto-Abs). The best characterized autoimmune anti-NMDAR disease is the anti-NMDAR encephalitis. It has been found that 4% of these patients present isolated, mostly affective, psychiatric manifestations during their illness. An interesting suggestion emerged from this overview is that the same mechanisms that trigger affective symptoms in patients with increased anti-NMDAR auto-Abs levels could be involved in the physiopathology of at least a subgroup of BD. Future studies are needed to characterize the relationship between anti-NMDAR auto-Abs and BD.

GSK3β inhibition promotes synaptogenesis in Drosophila and mammalian neurons

The PI3K-dependent activation of AKT results in the inhibition of GSK3β in most signaling pathways. These kinases regulate multiple neuronal processes including the control of synapse number as shown for Drosophila and rodents. Alzheimer disease's patients exhibit high levels of circulating GSK3β and, consequently, pharmacological strategies based on GSK3β antagonists have been designed. The approach, however, has yielded inconclusive results so far. Here, we carried out a comparative study in Drosophila and rats addressing the role of GSK3β in synaptogenesis. In flies, the genetic inhibition of the shaggy-encoded GSK3β increases the number of synapses, while its upregulation leads to synapse loss. Likewise, in three weeks cultured rat hippocampal neurons, the pharmacological inhibition of GSK3β increases synapse density and Synapsin expression. However, experiments on younger cultures (12 days) yielded an opposite effect, a reduction of synapse density. This unexpected finding seems to unveil an age- and dosage-dependent differential response of mammalian neurons to the stimulation/inhibition of GSK3β, a feature that must be considered in the context of human adult neurogenesis and pharmacological treatments for Alzheimer's disease based on GSK3β antagonists.