Association between sodium- and potassium-activated adenosine triphosphatase alpha isoforms and bipolar disorders

Single-Quantum Sodium MRI at 3T for the Separation of Mono- and Bi-T2 Sodium Signals

Sodium magnetic resonance imaging (MRI) is highly sensitive to cellular ionic balance due to tenfold difference in sodium concentration across membranes, actively maintained by the sodium-potassium (Na+-K+) pump. Disruptions in this pump or membrane integrity, as seen in neurological disorders like epilepsy, multiple sclerosis, bipolar disease, and mild traumatic brain injury, lead to increased intracellular sodium. However, this cellular-level alteration is often masked by the dominant extracellular sodium signal, making it challenging to distinguish sodium populations with mono- vs. bi-exponential transverse (T2) decays - especially given the low signal-to-noise ratio (SNR) even at an advanced clinical field of 3 Tesla. Here, we propose a novel technique that leverages intrinsic difference in T2 decays by acquiring single-quantum images at multiple echo times (TEs) and applying voxel-wise matrix inversion for accurate signal separation. Using numerical models, agar phantoms, and human subjects, we achieved high separation accuracy in phantoms (95.8% for mono-T2 and 72.5-80.4% for bi-T2) and demonstrated clinical feasibility in humans. This approach may enable early detection of neurological disorders and early assessment of treatment responses at the cellular level using sodium MRI at 3T.

The Mechanisms of Lithium Action: The Old and New Findings

Despite lithium's presence in modern psychiatry for three-quarters of a century, the mechanisms of its therapeutic action have not been fully elucidated. This article presents the evolution of the views on these mechanisms, and both the old and new findings are discussed. Among the old mechanisms, lithium's effect on the purinergic system; electrolyte metabolism; membrane transport; and second messenger systems, namely, cyclic nucleotide and phosphatidylinositol (PI), glycogen synthase kinase-3beta (GSK-3β), brain-derived neurotrophic factor, and neurotransmitters, are discussed. The new data were obtained from in vitro studies, molecular biology, and genetic research. They showed the effects of lithium on the immune system, biological rhythms, telomere functions, and mitochondria. In this article, each lithium mechanism is considered in the light of its association with the pathogenesis of bipolar disorder or/and as a marker of the lithium response. Although not exhaustive, this review elucidates the multiple potential mechanisms of lithium action. It was also observed that many seemingly "old" mechanisms have experienced a resurgence in research conducted during the 21st century. Additionally, many studies converged on the previously postulated mechanisms of lithium inhibiting GSK-3β and PI.

Differentially Altered Metabolic Pathways in the Amygdala of Subjects with Schizophrenia, Bipolar Disorder and Major Depressive Disorder

Background and hypothesis

A growing number of studies implicate a key role for metabolic processes in psychiatric disorders. Recent studies suggest that ketogenic diet may be therapeutically effective for subgroups of people with schizophrenia (SCZ), bipolar disorder (BPD) and possibly major depressive disorder (MDD). Despite this promise, there is currently limited information regarding brain energy metabolism pathways across these disorders, limiting our understanding of how brain metabolic pathways are altered and who may benefit from ketogenic diets. We conducted gene expression profiling on the amygdala, a key region involved in in the regulation of mood and appetitive behaviors, to test the hypothesis that amygdala metabolic pathways are differentially altered between these disorders.

Study Design

We used a cohort of subjects diagnosed with SCZ, BPD or MDD, and non-psychiatrically ill control subjects (n=15/group), together with our bioinformatic 3-pod analysis consisting of full transcriptome pathway analysis, targeted pathway analysis, leading-edge gene analysis and iLINCS perturbagen analysis.

Study Results

We identified differential expression of metabolic pathways in each disorder. Subjects with SCZ displayed downregulation of mitochondrial respiration and nucleotide metabolism pathways. In comparison, we observed upregulation of mitochondrial respiration pathways in subjects with MDD, while subjects with BPD displayed enrichment of pathways involved in carbohydrate metabolism. Several pathways associated with brain metabolism including immune system processes and calcium ion transport were also differentially altered between diagnosis groups.

Conclusion

Our findings suggest metabolic pathways are differentially altered in the amygdala in these disorders, which may impact approaches for therapeutic strategies.

Involvement of the Na+, K+-ATPase α1 Isoform and Endogenous Cardiac Steroids in Depression- and Manic-like Behaviors

Bipolar disorder (BD) is a severe and common chronic mental illness characterized by recurrent mood swings between depression and mania. The biological basis of the disease is poorly understood, and its treatment is unsatisfactory. Na+, K+-ATPase is a major plasma membrane transporter and signal transducer. The catalytic α subunit of this enzyme is the binding site for cardiac steroids. Three α isoforms of the Na+, K+-ATPase are present in the brain. Previous studies have supported the involvement of the Na+, K+-ATPase and endogenous cardiac steroids (ECS) in the etiology of BD. Decreased brain ECS has been found to elicit anti-manic and anti-depressive-like behaviors in mice and rats. However, the identity of the specific α isoform involved in these behavioral effects is unknown. Here, we demonstrated that decreasing ECS through intracerebroventricular (i.c.v.) administration of anti-ouabain antibodies (anti-Ou-Ab) decreased the activity of α1+/- mice in forced swimming tests but did not change the activity in wild type (wt) mice. This treatment also affected exploratory and anxiety behaviors in α1+/- but not wt mice, as measured in open field tests. The i.c.v. administration of anti-Ou-Ab decreased brain ECS and increased brain Na+, K+-ATPase activity in wt and α1+/- mice. The serum ECS was lower in α1+/- than wt mice. In addition, a study in human participants demonstrated that serum ECS significantly decreased after treatment. These results suggest that the Na+, K+-ATPase α1 isoform is involved in depressive- and manic-like behaviors and support that the Na+, K+-ATPase/ECS system participates in the etiology of BD.

Socrates: A Novel N-Ethyl-N-nitrosourea-Induced Mouse Mutant with Audiogenic Epilepsy

Epilepsy is one of the common neurological diseases that affects not only adults but also infants and children. Because epilepsy has been studied for a long time, there are several pharmacologically effective anticonvulsants, which, however, are not suitable as therapy for all patients. The genesis of epilepsy has been extensively investigated in terms of its occurrence after injury and as a concomitant disease with various brain diseases, such as tumors, ischemic events, etc. However, in the last decades, there are multiple reports that both genetic and epigenetic factors play an important role in epileptogenesis. Therefore, there is a need for further identification of genes and loci that can be associated with higher susceptibility to epileptic seizures. Use of mouse knockout models of epileptogenesis is very informative, but it has its limitations. One of them is due to the fact that complete deletion of a gene is not, in many cases, similar to human epilepsy-associated syndromes. Another approach to generating mouse models of epilepsy is N-Ethyl-N-nitrosourea (ENU)-directed mutagenesis. Recently, using this approach, we generated a novel mouse strain, soc (socrates, formerly s8-3), with epileptiform activity. Using molecular biology methods, calcium neuroimaging, and immunocytochemistry, we were able to characterize the strain. Neurons isolated from soc mutant brains retain the ability to differentiate in vitro and form a network. However, soc mutant neurons are characterized by increased spontaneous excitation activity. They also demonstrate a high degree of Ca2+ activity compared to WT neurons. Additionally, they show increased expression of NMDA receptors, decreased expression of the Ca2+-conducting GluA2 subunit of AMPA receptors, suppressed expression of phosphoinositol 3-kinase, and BK channels of the cytoplasmic membrane involved in protection against epileptogenesis. During embryonic and postnatal development, the expression of several genes encoding ion channels is downregulated in vivo, as well. Our data indicate that soc mutation causes a disruption of the excitation-inhibition balance in the brain, and it can serve as a mouse model of epilepsy.

Ouabain Reverts CUS-Induced Disruption of the HPA Axis and Avoids Long-Term Spatial Memory Deficits

Ouabain (OUA) is a cardiotonic steroid that modulates Na+, K+ -ATPase activity. OUA has been identified as an endogenous substance that is present in human plasma, and it has been shown to be associated with the response to acute stress in both animals and humans. Chronic stress is a major aggravating factor in psychiatric disorders, including depression and anxiety. The present work investigates the effects of the intermittent administration of OUA (1.8 μg/kg) during the chronic unpredictable stress (CUS) protocol in a rat's central nervous system (CNS). The results suggest that the intermittent OUA treatment reversed CUS-induced HPA axis hyperactivity through a reduction in (i) glucocorticoids levels, (ii) CRH-CRHR1 expression, and by decreasing neuroinflammation with a reduction in iNOS activity, without interfering with the expression of antioxidant enzymes. These changes in both the hypothalamus and hippocampus may reflect in the rapid extinction of aversive memory. The present data demonstrate the ability of OUA to modulate the HPA axis, as well as to revert CUS-induced long-term spatial memory deficits.

Chemical Element Profiling in the Sera and Brain of Bipolar Disorders Patients and Healthy Controls

Bipolar Disorder (BD) is a severe recurrent affective mood disorder characterized by a wide range of lifelong mood swings, varying between depressive and manic states. BD affects more than 1% of the world's population irrespective of nationality, ethnic origin, or socioeconomic status and is one of the main causes of disability among young people, leading to cognitive and functional impairment and raised mortality, particularly death by suicide. Trace elements play a vital role in many biochemical and physiological processes. Compelling evidence shows that element toxicity might play a crucial role in the onset and progression of neurodegenerative disorders, but their involvement in mood disorders has been scarcely studied. In the present investigation, we determined the concentration of 26 elements in the serum of BD patients before and after treatment and in postmortem brain samples from BD patients and compared them with matched controls. The only element that was reduced significantly in the serum following treatment was vanadium (V). Furthermore, the concentration of Al, B, Cu, K, Mg and V were significantly lower in the pre-frontal cortex of BD patients compared with those of the controls. A comparison of Spearman's rank correlation coefficients between the elements in the serum and brain of BD patients and control groups pointed to boron and aluminum as being involved in the disease. These results suggest that there is a disturbance in the elements' homeostasis and the inter-elements' relationship in the brain of BD patients and advocate a thorough examination of the possible involvement of chemical elements in different stages of the disease.

Potential of Heterogeneous Compounds as Antidepressants: A Narrative Review

Depression is a globally widespread disorder caused by a complicated interplay of social, psychological, and biological factors. Approximately 280 million people are suffering from depression worldwide. Traditional frontline antidepressants targeting monoamine neurotransmitters show unsatisfactory effects. The development and application of novel antidepressants for dissimilar targets are on the agenda. This review characterizes the antidepressant effects of multiple endogenous compounds and/or their targets to provide new insight into the working mechanism of antidepressants. We also discuss perspectives and challenges for the generation of novel antidepressants.

Endogenous Cardiac Steroids in Bipolar Disorder: State of the Art

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

Influence of Nitric Oxide-Cyclic GMP and Oxidative STRESS on Amyloid-β Peptide Induced Decrease of Na,K-ATPase Activity in Rat Hippocampal Slices

Amyloid-β peptide (Aβ) has been shown to cause synaptic dysfunction and can render neurons vulnerable to excitotoxicity and oxidative stress. Na,K-ATPase plays an important role to maintain cell ionic equilibrium and it can be modulated by N-methyl-D-aspartate (NMDA)-nitric oxide (NO)-cyclic GMP pathway. Disruption of NO synthase (NOS) activity and reactive oxygen species (ROS) production could lead to changes in Na,K-ATPase isoforms' activities that may be detrimental to the cells. Our aim was to evaluate the signaling pathways of Aβ in relation to NMDA-NOS-cyclic GMP versus oxidative stress on α₁-/α_2,3-Na,K-ATPase activities in rat hippocampal slices. Aβ_1-40 induced a concentration-dependent increase of NOS activity and increased cyclic guanosine monophosphate (cGMP), TBARS (thiobarbituric acid reactive substances), and 3-Nitrotyrosine (3-NT)-modified protein levels in rat hippocampal slices. The increase in NOS activity and cyclic GMP levels induced by Aβ_1-40 was completely blocked by MK-801 (inhibitor of NMDA receptor) and L-NAME (inhibitor of NOS) pre-treatment but changes in TBARS levels were only partially blocked by both compounds. The Aβ treatment also decreased Na,K-ATPase activity which was reverted by N-nitro-L-arginine methyl ester hydrochloride (L-NAME) but not by MK-801 pre-treatment. The decrease in enzyme activity induced by Aβ was isoform-specific since only α₁-Na,K-ATPase was affected. These findings suggest that the activation of NMDA-NOS signaling cascade linked to α_2,3-Na,K-ATPase activity may mediate an adaptive, neuroprotective response to Aβ in rat hippocampus.

Ouabain induces memory impairment and alter the BDNF signaling pathway in an animal model of bipolar disorder: Cognitive and neurochemical alterations in BD model

BACKGROUND

The present study aims to evaluate the effects of ouabain on memory and neurotrophic parameters in the brains of rats.

METHODS

Wistar rats received an intracerebroventricular (ICV) injection of ouabain or artificial cerebrospinal fluid (aCSF). Seven and 14 days after ICV administration, the animals were subjected to the open-field and splash tests. Furthermore, the pro-BDNF, BDNF, TrkB, and CREB were assessed in the frontal cortex and hippocampus of the rats, in both seven and 14 days after ICV injection. The memory of the animals was tested by novel object recognition test (NOR) and inhibitory avoidance task (IA), only 14 days after ICV administration.

RESULTS

Ouabain increased locomotion and exploration in the animals seven days after its administration; however, 14 days after ICV, these behavioral parameters return to the basal level. Seven days after ouabain administration increased grooming behavior in the splash test; on the other hand, seven days after ouabain injection decreased the grooming behavior, which is considered an anhedonic response. Besides, ouabain decreased recognition index in the NOR and decreased aversive memory in the IA, when compared to the control group. The levels of pro-BDNF and BDNF decreased in the frontal cortex seven days after ouabain; but its receptor (TrkB) and CREB decreased seven and 14 days after ouabain, in both cerebral structures evaluated.

CONCLUSION

Ouabain-induced animal model of BD is an excellent model to assess memory alteration, observed in bipolar patients. Besides, the memory impairment induced by ouabain seems to be related to BDNF signaling pathway alterations.

Role of endogenous ouabain in the etiology of bipolar disorder

Background

Bipolar disorder is a severe psychiatric illness with poor prognosis and problematic and suboptimal treatments. Understanding the pathoetiologic mechanisms may improve treatment and outcomes.

Discussion

Dysregulation of cationic homeostasis is the most reproducible aspect of bipolar pathophysiology. Correction of ionic balance is the universal mechanism of action of all mood stabilizing medications. Recent discoveries of the role of endogenous sodium pump modulators (which include ‘endogenous ouabain’) in regulation of sodium and potassium distribution, inflammation, and activation of key cellular second messenger systems that are important in cell survival, and the demonstration that these stress-responsive chemicals may be dysregulated in bipolar patients, suggest that these compounds may be candidates for the coupling of environmental stressors and illness onset. Specifically, individuals with bipolar disorder appear to be unable to upregulate endogenous ouabain under conditions that require it, and therefore may experience a relative deficiency of this important regulatory hormone. In the absence of elevated endogenous ouabain, neurons are unable to maintain their normal resting potential, become relatively depolarized, and are then susceptible to inappropriate activation. Furthermore, sodium pump activity appears to be necessary to prevent inflammatory signals within the central nervous system. Nearly all available data currently support this model, but additional studies are required to solidify the role of this system.

Conclusion

Endogenous ouabain dysregulation appears to be a reasonable candidate for understanding the pathophysiology of bipolar disorder.

Characterization of Severe and Extreme Behavioral Problems in Patients With Alternating Hemiplegia of Childhood

BACKGROUND

Alternating hemiplegia of childhood often manifests severe or extreme behavioral problems, the nature of which remains to be fully characterized.

METHODS

We analyzed 39 consecutive patients with alternating hemiplegia of childhood for occurrence of behavioral problems and categorized those by severity: mild (not requiring intervention), moderate (requiring intervention but no risk), severe (minor risk to self, others, or both), and extreme (major risk). We then analyzed behavioral manifestations, concurrent morbidity, and medication responses in patients with severe or extreme symptoms.

RESULTS

Two patients had mild behavioral problems, five moderate, 10 severe, six extreme, and 16 none. Extreme cases exhibited disruptive behaviors escalating to assaults. Triggers, when present, included peer-provocation, low frustration tolerance, limits set by others, and sleep disruption. Reversible psychotic symptoms occurred in two patients: in one triggered by infection and trihexyphenidyl, and in another triggered by sertraline. Of the 16 patients with severe or extreme symptoms, 13 had concurrent neuropsychiatric diagnoses. Occurrence of severe or extreme symptoms did not correlate with age, puberty, severity of intellectual disability, or mutation status (P > 0.05). A multidisciplinary team including mental health professionals comanaged all patients with severe or extreme symptoms with either behavioral therapy, medications, or both. When considering medications prescribed to more than four patients, medicines that demonstrated efficacy or partial efficacy in more than 50% of patients were alpha-adrenergic agonists and selective-serotonin-reuptake-inhibitors.

CONCLUSIONS

Patients with alternating hemiplegia of childhood (41%) often experience severe or extreme behavioral problems and, rarely, medication-triggered psychotic symptoms. These observations are consistent with current understanding of underlying alternating hemiplegia of childhood brain pathophysiology. Increasing awareness of these behavioral problems facilitates alternating hemiplegia of childhood management and anticipatory guidance.

Na+, K+-ATPase α Isoforms and Endogenous Cardiac Steroids in Prefrontal Cortex of Bipolar Patients and Controls

Bipolar disorder is a chronic multifactorial psychiatric illness that affects the mood, cognition, and functioning of about 1–2% of the world’s population. Its biological basis is unknown, and its treatment is unsatisfactory. The α1, α2, and α3 isoforms of the Na⁺, K⁺-ATPase, an essential membrane transporter, are vital for neuronal and glial function. The enzyme and its regulators, endogenous cardiac steroids like ouabain and marinobufagenin, are implicated in neuropsychiatric disorders, bipolar disorder in particular. Here, we address the hypothesis that the α isoforms of the Na⁺, K⁺-ATPase and its regulators are altered in the prefrontal cortex of bipolar disease patients. The α isoforms were determined by Western blot and ouabain and marinobufagenin by specific and sensitive immunoassays. We found that the α2 and α3 isoforms were significantly higher and marinobufagenin levels were significantly lower in the prefrontal cortex of the bipolar disease patients compared with those in the control. A positive correlation was found between the levels of the three α isoforms in all samples and between the α1 isoform and ouabain levels in the controls. These results are in accordance with the notion that the Na⁺, K⁺-ATPase-endogenous cardiac steroids system is involved in bipolar disease and suggest that it may be used as a target for drug development.

HDAC inhibitors reverse mania-like behavior and modulate epigenetic regulatory enzymes in an animal model of mania induced by Ouabain

BACKGROUND

The etiology of bipolar disorder (BD) is multifactorial, involving both environmental and genetic factors. Current pharmacological treatment is associated with several side effects, which are the main reason patients discontinue treatment. Epigenetic alterations have been studied for their role in the pathophysiology of BD, as they bridge the gap between gene and environment.

OBJECTIVE

Evaluate the effects of histone deacetylase inhibitors on behavior and epigenetic enzymes activity in a rat model of mania induced by ouabain.

METHODS

Adult male rats were subjected to a single intracerebroventricular injection of ouabain (10^-3 M) followed by 7 days of valproate (200 mg/kg) or sodium butyrate (600 mg/kg) administration. Locomotor and exploratory activities were evaluated in the open-field test. Histone deacetylase, DNA methyltransferase, and histone acetyltransferase activity were assessed in the frontal cortex, hippocampus, and striatum.

RESULTS

Ouabain induced hyperactivity in rats, which was reversed by valproate and sodium butyrate treatment. Ouabain did not alter the activity of any of the enzymes evaluated. However, valproate and sodium butyrate decreased the activity of histone deacetylase and DNA methyltransferase. Moreover, there was a positive correlation between these two enzymes.

CONCLUSION

These results suggest that targeting epigenetic mechanisms may play an important role in mania-like behavior management.

Validation of the animal model of bipolar disorder induced by Ouabain: face, construct and predictive perspectives

A particular challenge in the development of a bipolar disorder (BD) model in animals is the complicated clinical course of the condition, characterized by manic, depressive and mixed mood episodes. Ouabain (OUA) is an inhibitor of Na⁺/K⁺-ATPase enzyme. Intracerebroventricular (ICV) injection of this drug in rats has been regarded a proper model to study BD by mimic specific manic symptoms, which are reversed by lithium (Li), an important mood stabilizer drug. However, further validation of this experimental approach is required to characterize it as an animal model of BD, including depressive-like behaviors. The present study aimed to assess manic- and depressive-like behaviors, potential alteration in the hypothalamic-pituitary-adrenal (HPA) system and oxidative stress parameters after a single OUA ICV administration in adult male Wistar rats. Moreover, we evaluated Li effects in this experimental setting. Data show that OUA ICV administration could constitute a suitable model for BD since the injection of the drug triggered manic- and depressive-like behaviors in the same animal. Additionally, the OUA model mimics significant physiological and neurochemical alterations detected in BD patients, including an increase in oxidative stress and change in HPA axis. Our findings suggest that decreased Na⁺/K⁺-ATPase activity detected in bipolar patients may be linked to increased secretion of glucocorticoid hormones and oxidative damage, leading to the marked behavioral swings. The Li administration mitigated these pathological changes in the rats. The proposed OUA model is regarded as suitable to simulate BD by complying with all validities required to a proper animal model of the psychiatric disorder.

Circadian Disruptions in the Myshkin Mouse Model of Mania Are Independent of Deficits in Suprachiasmatic Molecular Clock Function

BACKGROUND

Alterations in environmental light and intrinsic circadian function have strong associations with mood disorders. The neural origins underpinning these changes remain unclear, although genetic deficits in the molecular clock regularly render mice with altered mood-associated phenotypes.

METHODS

A detailed circadian and light-associated behavioral characterization of the Na+/K+-ATPase α3 Myshkin (Myk/+) mouse model of mania was performed. Na+/K+-ATPase α3 does not reside within the core circadian molecular clockwork, but Myk/+ mice exhibit concomitant disruption in circadian rhythms and mood. The neural basis of this phenotype was investigated through molecular and electrophysiological dissection of the master circadian pacemaker, the suprachiasmatic nuclei (SCN). Light input and glutamatergic signaling to the SCN were concomitantly assessed through behavioral assays and calcium imaging.

RESULTS

In vivo assays revealed several circadian abnormalities including lengthened period and instability of behavioral rhythms, and elevated metabolic rate. Grossly aberrant responses to light included accentuated resetting, accelerated re-entrainment, and an absence of locomotor suppression. Bioluminescent recording of circadian clock protein (PERIOD2) output from ex vivo SCN revealed no deficits in Myk/+ molecular clock function. Optic nerve crush rescued the circadian period of Myk/+ behavior, highlighting that afferent inputs are critical upstream mediators. Electrophysiological and calcium imaging SCN recordings demonstrated changes in the response to glutamatergic stimulation as well as the electrical output indicative of altered retinal input processing.

CONCLUSIONS

The Myshkin model demonstrates profound circadian and light-responsive behavioral alterations independent of molecular clock disruption. Afferent light signaling drives behavioral changes and raises new mechanistic implications for circadian disruption in affective disorders.

High-fructose corn syrup consumption in adolescent rats causes bipolar-like behavioural phenotype with hyperexcitability in hippocampal CA3-CA1 synapses

BACKGROUND AND PURPOSE

Children and adolescents are the top consumers of high-fructose corn syrup (HFCS) sweetened beverages. Even though the cardiometabolic consequences of HFCS consumption in adolescents are well known, the neuropsychiatric consequences have yet to be determined.

EXPERIMENTAL APPROACH

Adolescent rats were fed for a month with 11% weight/volume carbohydrate containing HFCS solution, which is similar to the sugar-sweetened beverages of human consumption. The metabolic, behavioural and electrophysiological characteristics of HFCS-fed rats were determined. Furthermore, the effects of TDZD-8, a highly specific GSK-3B inhibitor, on the HFCS-induced alterations were further explored.

KEY RESULTS

HFCS-fed adolescent rats displayed bipolar-like behavioural phenotype with hyperexcitability in hippocampal CA3-CA1 synapses. This hyperexcitability was associated with increased presynaptic release probability and increased readily available pool of AMPA receptors to be incorporated into the postsynaptic membrane, due to decreased expression of the neuron-specific α3-subunit of Na⁺ /K⁺ -ATPase and an increased ser⁸⁴⁵ -phosphorylation of GluA1 subunits (AMPA receptor subunit) respectively. TDZD-8 treatment was found to restore behavioural and electrophysiological disturbances associated with HFCS consumption by inhibition of GSK-3B, the most probable mechanism of action of lithium for its mood-stabilizing effects.

CONCLUSION AND IMPLICATIONS

This study shows that HFCS consumption in adolescent rats led to a bipolar-like behavioural phenotype with neuronal hyperexcitability, which is known to be one of the earliest endophenotypic manifestations of bipolar disorder. Inhibition of GSK-3B with TDZD-8 attenuated hyperexcitability and restored HFCS-induced behavioural alterations.

Na⁺, K⁺-ATPase Signaling and Bipolar Disorder

Bipolar disorder (BD) is a severe and common chronic mental illness characterized by recurrent mood swings between depression and mania. The biological basis of the disease is poorly understood and its treatment is unsatisfactory. Although in past decades the "monoamine hypothesis" has dominated our understanding of both the pathophysiology of depressive disorders and the action of pharmacological treatments, recent studies focus on the involvement of additional neurotransmitters/neuromodulators systems and cellular processes in BD. Here, evidence for the participation of Na⁺, K⁺-ATPase and its endogenous regulators, the endogenous cardiac steroids (ECS), in the etiology of BD is reviewed. Proof for the involvement of brain Na⁺, K⁺-ATPase and ECS in behavior is summarized and it is hypothesized that ECS-Na⁺, K⁺-ATPase-induced activation of intracellular signaling participates in the mechanisms underlying BD. We propose that the activation of ERK, AKT, and NFκB, resulting from ECS-Na⁺, K⁺-ATPase interaction, modifies neuronal activity and neurotransmission which, in turn, participate in the regulation of behavior and BD. These observations suggest Na⁺, K⁺-ATPase-mediated signaling is a potential target for drug development for the treatment of BD.

Are Polyunsaturated Fatty Acids Implicated in Histaminergic Dysregulation in Bipolar Disorder?: AN HYPOTHESIS

Bipolar disorder (BD) is an extremely disabling psychiatric disease, characterized by alternate states of mania (or hypomania) and depression with euthymic states in between. Currently, patients receive pharmacological treatment with mood stabilizers, antipsychotics, and antidepressants. Unfortunately, not all patients respond well to this type of treatment. Bipolar patients are also more prone to heart and metabolic diseases as well as a higher risk of suicide compared to the healthy population. For a correct brain function is indispensable a right protein and lipids (e.g., fatty acids) balance. In particular, the amount of fatty acids in the brain corresponds to a 50–70% of the dry weight. It has been reported that in specific brain regions of BD patients there is a reduction in the content of unsaturated n-3 fatty acids. Accordingly, a diet rich in n-3 fatty acids has beneficial effects in BD patients, while their absence or high levels of saturated fatty acids in the diet are correlated to the risk of developing the disease. On the other hand, the histamine system is likely to be involved in the pathophysiology of several psychiatric diseases such as BD. Histamine is a neuromodulator involved in arousal, motivation, and energy balance; drugs acting on the histamine receptor H3 have shown potential as antidepressants and antipsychotics. The histaminergic system as other neurotransmission systems can be altered by fatty acid membrane composition. The purpose of this review is to explore how polyunsaturated fatty acids content alterations are related to the histaminergic system modulation and their impact in BD pathophysiology.

Reduction in endogenous cardiac steroids protects the brain from oxidative stress in a mouse model of mania induced by amphetamine

OBJECTIVES

Bipolar disorder (BD) is a severe mental illness characterized by episodes of mania and depression. Numerous studies have implicated the involvement of endogenous cardiac steroids (CS), and their receptor, Na⁺, K⁺ -ATPase, in BD. The aim of the present study was to examine the role of brain oxidative stress in the CS-induced behavioral effects in mice.

METHODS

Amphetamine (AMPH)-induced hyperactivity, assessed in the open-field test, served as a model for manic-like behavior in mice. A reduction in brain CS was obtained by specific and sensitive anti-ouabain antibodies. The level of oxidative stress was tested in the hippocampus and frontal cortex by measuring the activity of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), as well as the levels of antioxidant non-protein thiols (NPSH) and oxidative damage biomarkers thiobarbituric acid reactive substances (TBARS) and protein carbonyl (PC).

RESULTS

AMPH administration resulted in a marked hyperactivity and increased oxidative stress, as manifested by increased SOD activity, decreased activities of CAT and GPx, reduced levels of NPSH and increased levels of TBARS and PC. The administration of anti-ouabain antibodies, which reduced the AMPH-induced hyperactivity, protected against the concomitant oxidative stress in the brain.

CONCLUSIONS

Our results demonstrate that oxidative stress participates in the effects of endogenous CS on manic-like behavior induced by AMPH. These finding support the notion that CS and oxidative stress may be associated with the pathophysiology of mania and BD.

Gene-wide Association Study Reveals RNF122 Ubiquitin Ligase as a Novel Susceptibility Gene for Attention Deficit Hyperactivity Disorder

Attention Deficit Hyperactivity Disorder (ADHD) is a common childhood-onset neurodevelopmental condition characterized by pervasive impairment of attention, hyperactivity, and/or impulsivity that can persist into adulthood. The aetiology of ADHD is complex and multifactorial and, despite the wealth of evidence for its high heritability, genetic studies have provided modest evidence for the involvement of specific genes and have failed to identify consistent and replicable results. Due to the lack of robust findings, we performed gene-wide and pathway enrichment analyses using pre-existing GWAS data from 607 persistent ADHD subjects and 584 controls, produced by our group. Subsequently, expression profiles of genes surpassing a follow-up threshold of P-value < 1e-03 in the gene-wide analyses were tested in peripheral blood mononucleated cells (PBMCs) of 45 medication-naive adults with ADHD and 39 healthy unrelated controls. We found preliminary evidence for genetic association between RNF122 and ADHD and for its overexpression in adults with ADHD. RNF122 encodes for an E3 ubiquitin ligase involved in the proteasome-mediated processing, trafficking, and degradation of proteins that acts as an essential mediator of the substrate specificity of ubiquitin ligation. Thus, our findings support previous data that place the ubiquitin-proteasome system as a promising candidate for its involvement in the aetiology of ADHD.

Cognitive flexibility impairment and reduced frontal cortex BDNF expression in the ouabain model of mania

Central infusion of the Na+/K+-ATPase inhibitor, ouabain in rats serves as an animal model of mania because it leads to hyperactivity, as well as reproduces ion dysregulation and reduced brain-derived neurotrophic factor (BDNF) levels similar to that observed in bipolar disorder. Bipolar disorder is also associated with cognitive inflexibility and working memory deficits. It is unknown whether ouabain treatment in rats leads to similar cognitive flexibility and working memory deficits. The present study examined the effects of an intracerebral ventricular infusion of ouabain in rats on spontaneous alternation, probabilistic reversal learning and BDNF expression levels in the frontal cortex. Ouabain treatment significantly increased locomotor activity, but did not affect alternation performance in a Y-maze. Ouabain treatment selectively impaired reversal learning in a spatial discrimination task using an 80/20 probabilistic reinforcement procedure. The reversal learning deficit in ouabain-treated rats resulted from an impaired ability to maintain a new choice pattern (increased regressive errors). Ouabain treatment also decreased sensitivity to negative feedback during the initial phase of reversal learning. Expression of BDNF mRNA and protein levels was downregulated in the frontal cortex which also negatively correlated with regressive errors. These findings suggest that the ouabain model of mania may be useful in understanding the neuropathophysiology that contributes to cognitive flexibility deficits and test potential treatments to alleviate cognitive deficits in bipolar disorder.

The sensitivity of Na+, K+ ATPase as an indicator of blood diseases

BACKGROUND

Blood-related hereditary diseases are widespread in Eastern and SouthWestern regions of Saudi Arabia until recently. In this study, we used Na⁺, K⁺ATPase as an enzymatic indicator for the diagnosis of the diseases.

MATERIALS AND METHODS

Individuals with different blood diseases (iron deficiency (n=13), anemia (n=14), thalassemia (n=16) and sickle cell anemia (n=12) were studied for Na⁺, K⁺-ATPase activity in the plasma membrane of red blood cell and compared with those of the healthy ones (n=20) of the same age and gender living in Jeddah, Saudi Arabia.

RESULTS

There was a significant elevation in the specific activity of Na⁺, K⁺ATPase in individuals with anemia compared with those of control (0.0094 + 0.001 nmol / mg protein/min versus 0.0061 ± 0.001). On the other hand, there was a significant reduction in enzyme activity in thalassemia (0.0028 ± 0.002 nmol / mg protein/min) and sickle cell anemia cases (0.0042 ±0.001 nmol / mg protein/min) compared to the control group. The cut off value for Na⁺, K⁺ATPase activity is 0.005 µmol Pi/min-showing 94% sensitivity and 93% specificity for the differentiation of blood abnormality.

CONCLUSION

It can be recommended that the activity of Na⁺, K⁺-ATPase can be used for the diagnosis of individuals with blood diseases/disorders.

Correlative study of peripheral ATP1A1 gene expression level to anxiety severity score on major depressive disorder patients

BACKGROUND

Major depressive disorder (MDD) frequently co-occurs with other psychiatric problems. Our previous study showed that ATP1A1 gene expression level was significantly decreased in MDD patients. This research explores the potential correlations between the ATP1A1 expression level reduction and MDD patients' clinical manifestation.

METHODS

All participant patients were diagnosed by Diagnostic and Statistical Manual of Mental Disorders - 4th edition (DSM-IV). Hamilton rating scale for depression (HAM-D) and anxiety (HAM-A) were applied to group patients into different categories. ATP1A1 expression level was measured by reverse transcript real-time polymerase chain reaction.

RESULTS

ATP1A1 expression levels of all MDD subgroups showed significant reduction compared to the control group (p<0.01). Further, the trend of ATP1A1 expression level reduction is significantly related to MDD patients' HAM-A scores (p<0.01). However, there was no significance between ATP1A1 level and HAM-D scores (p>0.05).

CONCLUSIONS

ATP1A1 expression level reduction is related to MDD anxiety score, which may be an explanation for the clinical manifestations and the underlining physiological mechanisms.

A novel de novo mutation in ATP1A3 and childhood-onset schizophrenia

We describe a child with onset of command auditory hallucinations and behavioral regression at 6 yr of age in the context of longer standing selective mutism, aggression, and mild motor delays. His genetic evaluation included chromosomal microarray analysis and whole-exome sequencing. Sequencing revealed a previously unreported heterozygous de novo mutation c.385G>A in ATP1A3, predicted to result in a p.V129M amino acid change. This gene codes for a neuron-specific isoform of the catalytic α-subunit of the ATP-dependent transmembrane sodium–potassium pump. Heterozygous mutations in this gene have been reported as causing both sporadic and inherited forms of alternating hemiplegia of childhood and rapid-onset dystonia parkinsonism. We discuss the literature on phenotypes associated with known variants in ATP1A3, examine past functional studies of the role of ATP1A3 in neuronal function, and describe a novel clinical presentation associated with mutation of this gene.

Endogenous cardiac steroids in animal models of mania

OBJECTIVES

Bipolar disorder (BD) is a complex psychiatric disorder characterized by mania and depression. Alterations in brain Na(+) , K(+) -ATPase and cardiac steroids (CSs) have been detected in BD, raising the hypothesis of their involvement in this pathology. The present study investigated the behavioral and biochemical consequences of a reduction in endogenous brain CS activity in animal models of mania.

METHODS

Amphetamine (AMPH)-induced hyperactivity in BALB/c and black Swiss mice served as a model of mania. Behavior was evaluated in the open-field test in naïve mice or in mice treated with anti-ouabain antibodies. CS levels were determined by enzyme-linked immunosorbent assay (ELISA), using sensitive and specific anti-ouabain antibodies. Extracellular signal-regulated kinase (ERK) and protein kinase B (Akt) phosphorylation levels in the frontal cortex were determined by western blot analysis.

RESULTS

Administration of AMPH to BALB/c and black Swiss mice resulted in a marked increase in locomotor activity, accompanied by a threefold increase in brain CSs. The lowering of brain CSs by the administration of anti-ouabain antibodies prevented the hyperactivity and the increase in brain CS levels. AMPH caused an increase in phosphorylated ERK (p-ERK) and phosphorylated Akt (p-Akt) levels in the frontal cortex, which was significantly reduced by administration of the antibodies. A synthetic 'functional antagonist' of CSs, 4-(3'α-15'β-dihydroxy-5'β-estran-17'β-yl) furan-2-methyl alcohol, also resulted in attenuation of AMPH-induced hyperactivity.

CONCLUSIONS

These results are in accordance with the notion that malfunctioning of the Na(+) , K(+) -ATPase/CS system may be involved in the manifestation of mania and identify this system as a potential new target for drug development.

Animal models of bipolar mania: The past, present and future

Bipolar disorder (BD) is the sixth leading cause of disability in the world according to the World Health Organization and affects nearly six million (∼2.5% of the population) adults in the United State alone each year. BD is primarily characterized by mood cycling of depressive (e.g., helplessness, reduced energy and activity, and anhedonia) and manic (e.g., increased energy and hyperactivity, reduced need for sleep, impulsivity, reduced anxiety and depression), episodes. The following review describes several animal models of bipolar mania with a focus on more recent findings using genetically modified mice, including several with the potential of investigating the mechanisms underlying 'mood' cycling (or behavioral switching in rodents). We discuss whether each of these models satisfy criteria of validity (i.e., face, predictive, and construct), while highlighting their strengths and limitations. Animal models are helping to address critical questions related to pathophysiology of bipolar mania, in an effort to more clearly define necessary targets of first-line medications, lithium and valproic acid, and to discover novel mechanisms with the hope of developing more effective therapeutics. Future studies will leverage new technologies and strategies for integrating animal and human data to reveal important insights into the etiology, pathophysiology, and treatment of BD.

Non-motor symptoms in genetically defined dystonia: Homogenous groups require systematic assessment

INTRODUCTION

Dystonia is a movement disorder involving sustained or intermittent muscle contractions resulting in abnormal movements and postures. Identification of disease causing genes has allowed examination of genetically homogenous groups. Unlike the motor symptoms, non-motor characteristics are less clearly defined, despite their impact on a patient's quality of life. This review aims to examine the evidence for non-motor symptoms, addressing cohort size and methods of assessment in each study.

METHODS

A systematic and standardised search strategy was used to identify the published literature relating to psychiatric symptoms, cognition, sleep disorders, sensory abnormalities and pain in each of the genetically determined dystonias. Studies were divided according to cohort size, method of assessment and whether comparison was made to an appropriate control group.

RESULTS

Ninety-five articles were identified including reported clinical histories (n = 42), case reports and smaller case series (n = 12), larger case series (n = 23) and case-control cohorts (n = 18). Psychiatric symptoms were the most frequently investigated with anxiety, depression and Obsessive-Compulsive disorder being most common. Cognitive impairment involved either global deficits or isolated difficulties in specific domains. Disturbances to sleep were most common in the dopa-responsive dystonias. Sensory testing in DYT1 cases identified an intermediate subclinical phenotype.

CONCLUSION

Non-motor symptoms form an integral component of the dystonia phenotype. However, future studies should involve a complete assessment of all symptom subtypes in order to understand the frequency and gene-specificity of these symptoms. This will enable early symptom identification, appropriate clinical management, and provide additional outcome measures in future clinical trials.

Endogenous cardiotonic steroids in kidney failure: a review and an hypothesis

In response to progressive nephron loss, volume and humoral signals in the circulation have increasing relevance. These signals, including plasma sodium, angiotensin II, and those related to volume status, activate a slow neuromodulatory pathway within the central nervous system (CNS). The slow CNS pathway includes specific receptors for angiotensin II, mineralocorticoids, and endogenous ouabain (EO). Stimulation of the pathway leads to elevated sympathetic nervous system activity (SNA) and increased circulating EO. The sustained elevation of circulating EO (or ouabain) stimulates central and peripheral mechanisms that amplify the impact of SNA on vascular tone. These include changes in synaptic plasticity in the brain and sympathetic ganglia that increase preganglionic tone and amplify ganglionic transmission, amplification of the impact of SNA on arterial tone in the vascular wall, and the reprogramming of calcium signaling proteins in arterial myocytes. These increase SNA, raise basal and evoked arterial tone, and elevate blood pressure (BP). In the setting of CKD, we suggest that sustained activation/elevation of the slow CNS pathway, plasma EO, and the cardiotonic steroid marinobufagenin, comprises a feed-forward system that raises BP and accelerates kidney and cardiac damage. Block of the slow CNS pathway and/or circulating EO and marinobufagenin may reduce BP and slow the progression to ESRD.

Variants in Ion Channel Genes Link Phenotypic Features of Bipolar Illness to Specific Neurobiological Process Domains

Recent advances in genome-wide association studies are pointing towards a major role for voltage-gated ion channels in neuropsychiatric disorders and, in particular, bipolar disorder (BD). The phenotype of BD is complex, with symptoms during mood episodes and deficits persisting between episodes. We have tried to elucidate the common neurobiological mechanisms associated with ion channel signaling in order to provide a new perspective on the clinical symptoms and possible endophenotypes seen in BD patients. We propose a model in which the multiple variants in genes coding for ion channel proteins would perturb motivational circuits, synaptic plasticity, myelination, hypothalamic-pituitary-adrenal axis function, circadian neuronal rhythms, and energy regulation. These changes in neurobiological mechanisms would manifest in endophenotypes of aberrant reward processing, white matter hyperintensities, deficits in executive function, altered frontolimbic connectivity, increased amygdala activity, increased melatonin suppression, decreased REM latency, and aberrant myo-inositol/ATP shuttling. The endophenotypes result in behaviors of poor impulse control, motivational changes, cognitive deficits, abnormal stress response, sleep disturbances, and energy changes involving different neurobiological process domains. The hypothesis is that these disturbances start with altered neural circuitry during development, following which multiple environmental triggers may disrupt the neuronal excitability balance through an activity-dependent molecular process, resulting in clinical mood episodes.

Electrogenic properties of the Na⁺/K⁺ ATPase control transitions between normal and pathological brain states

Ionic concentrations fluctuate significantly during epileptic seizures. In this study, using a combination of in vitro electrophysiology, computer modeling, and dynamical systems analysis, we demonstrate that changes in the potassium and sodium intra- and extracellular ion concentrations ([K(+)] and [Na(+)], respectively) during seizure affect the neuron dynamics by modulating the outward Na(+)/K(+) pump current. First, we show that an increase of the outward Na(+)/K(+) pump current mediates termination of seizures when there is a progressive increase in the intracellular [Na(+)]. Second, we show that the Na(+)/K(+) pump current is crucial in maintaining the stability of the physiological network state; a reduction of this current leads to the onset of seizures via a positive-feedback loop. We then present a novel dynamical mechanism for bursting in neurons with a reduced Na(+)/K(+) pump. Overall, our study demonstrates the profound role of the current mediated by Na(+)/K(+) ATPase on the stability of neuronal dynamics that was previously unknown.

Signaling function of Na,K-ATPase induced by ouabain against LPS as an inflammation model in hippocampus

BACKGROUND

Ouabain (OUA) is a newly recognized hormone that is synthesized in the adrenal cortex and hypothalamus. Low doses of OUA can activate a signaling pathway by interaction with Na,K-ATPase, which is protective against a number of insults. OUA has central and peripheral anti-inflammatory effects. Lipopolysaccharide (LPS), via toll-like receptor 4 activation, is a widely used model to induce systemic inflammation. This study used a low OUA dose to evaluate its effects on inflammation induced by LPS injection in rats.

METHODS

Adult male Wistar rats received acute intraperitoneal (ip) OUA (1.8 μg/kg) or saline 20 minutes before LPS (200 μg/kg, ip) or saline injection. Some of the animals had their femoral artery catheterized in order to assess arterial blood pressure values before and after OUA administration. Na,K-ATPase activity, cytokine mRNA levels, apoptosis-related proteins, NF-κB activation brain-derived neurotrophic factor BDNF, corticosterone and TNF-α levels were measured.

RESULTS

OUA pretreatment decreased mRNA levels of the pro-inflammatory cytokines, inducible nitric oxide synthase (iNOS) and IL-1β, which are activated by LPS in the hippocampus, but with no effect on serum measures of these factors. None of these OUA effects were linked to Na,K-ATPase activity. The involvement of the inflammatory transcription factor NF-κB in the OUA effect was indicated by its prevention of LPS-induced nuclear translocation of the NF-κB subunit, RELA (p65), as well as the decreased cytosol levels of the NF-κB inhibitor, IKB, in the hippocampus. OUA pretreatment reversed the LPS-induced glial fibrillary acidic protein (GFAP) activation and associated inflammation in the dentate gyrus. OUA also prevented LPS-induced increases in the hippocampal Bax/Bcl2 ratio suggesting an anti-apoptotic action in the brain.

CONCLUSION

Our results suggest that a low dose of OUA has an important anti-inflammatory effect in the rat hippocampus. This effect was associated with decreased GFAP induction by LPS in the dentate gyrus, a brain area linked to adult neurogenesis.

Natriuretic hormones in brain function

Natriuretic hormones (NH) include three groups of compounds: the natriuretic peptides (ANP, BNP and CNP), the gastrointestinal peptides (guanylin and uroguanylin), and endogenous cardiac steroids. These substances induce the kidney to excrete sodium and therefore participate in the regulation of sodium and water homeostasis, blood volume, and blood pressure (BP). In addition to their peripheral functions, these hormones act as neurotransmitters or neuromodulators in the brain. In this review, the established information on the biosynthesis, release and function of NH is discussed, with particular focus on their role in brain function. The available literature on the expression patterns of each of the NH and their receptors in the brain is summarized, followed by the evidence for their roles in modulating brain function. Although numerous open questions exist regarding this issue, the available data support the notion that NH participate in the central regulation of BP, neuroprotection, satiety, and various psychiatric conditions, including anxiety, addiction, and depressive disorders. In addition, the interactions between the different NH in the periphery and the brain are discussed.

Histone deacetylase inhibitors reverse manic-like behaviors and protect the rat brain from energetic metabolic alterations induced by ouabain

Studies have revealed alterations in mitochondrial complexes in the brains of bipolar patients. However, few studies have examined changes in the enzymes of the tricarboxylic acid cycle. Several preclinical studies have suggested that histone deacetylase inhibitors may have antimanic effects. The present study aims to investigate the effects of lithium, valproate and sodium butyrate, a histone deacetylase inhibitor, on the activity of tricarboxylic acid cycle enzymes in the brains of rats subjected to an animal model of mania induced by ouabain. Wistar rats received a single intracerebroventricular injection of ouabain or cerebrospinal fluid. Starting on the day following the intracerebroventricular injection, the rats were treated for 7days with intraperitoneal injections of saline, lithium, valproate or sodium butyrate. Risk-taking behavior, locomotor and exploratory activities were measured using the open-field test. Citrate synthase, succinate dehydrogenase, and malate dehydrogenase were examined in the frontal cortex and hippocampus. All treatments reversed ouabain-related risk-taking behavior and hyperactivity in the open-field test. Ouabain inhibited tricarboxylic acid cycle enzymes in the brain, and valproate and sodium butyrate but not lithium reversed this ouabain-induced dysfunction. Thus, protecting the tricarboxylic acid cycle may contribute to the therapeutic effects of histone deacetylase inhibitors.

RNA-sequencing of the brain transcriptome implicates dysregulation of neuroplasticity, circadian rhythms and GTPase binding in bipolar disorder

RNA-sequencing (RNA-seq) is a powerful technique to investigate the complexity of gene expression in the human brain. We used RNA-seq to survey the brain transcriptome in high-quality postmortem dorsolateral prefrontal cortex from 11 individuals diagnosed with bipolar disorder (BD) and from 11 age- and gender-matched controls. Deep sequencing was performed, with over 350 million reads per specimen. At a false discovery rate of <5%, we detected five differentially expressed (DE) genes and 12 DE transcripts, most of which have not been previously implicated in BD. Among these, Prominin 1/CD133 and ATP-binding cassette-sub-family G-member2 (ABCG2) have important roles in neuroplasticity. We also show for the first time differential expression of long noncoding RNAs (lncRNAs) in BD. DE transcripts include those of serine/arginine-rich splicing factor 5 (SRSF5) and regulatory factor X4 (RFX4), which along with lncRNAs have a role in mammalian circadian rhythms. The DE genes were significantly enriched for several Gene Ontology categories. Of these, genes involved with GTPase binding were also enriched for BD-associated SNPs from previous genome-wide association studies, suggesting that differential expression of these genes is not simply a consequence of BD or its treatment. Many of these findings were replicated by microarray in an independent sample of 60 cases and controls. These results highlight common pathways for inherited and non-inherited influences on disease risk that may constitute good targets for novel therapies.

Genetic association of LMAN2L gene in schizophrenia and bipolar disorder and its interaction with ANK3 gene polymorphism

Recent studies have shown that bipolar disorder (BPD) and schizophrenia (SZ) share some common genetic risk factors. This study aimed to examine the association between candidate single nucleotide polymorphisms (SNPs) identified from genome-wide association studies (GWAS) and risk of BPD and SZ. A total of 715 patients (244 BPD and 471 SZ) and 593 controls were genotyped using the Sequenom MassARRAY platform. We showed a positive association between LMAN2L (rs6746896) and risk of both BPD and SZ in a pooled population (P-value=0.001 and 0.009, respectively). Following stratification by ethnicity, variants of the ANK3 gene (rs1938516 and rs10994336) were found to be associated with BPD in Malays (P-value=0.001 and 0.006, respectively). Furthermore, an association exists between another variant of LMAN2L (rs2271893) and SZ in the Malay and Indian ethnic groups (P-value=0.003 and 0.002, respectively). Gene-gene interaction analysis revealed a significant interaction between the ANK3 and LMAN2L genes (empirical P=0.0107). Significant differences were shown between patients and controls for two haplotype frequencies of LMAN2L: GA (P=0.015 and P=0.010, for BPD and SZ, respectively) and GG (P=0.013 for BPD). Our study showed a significant association between LMAN2L and risk of both BPD and SZ.

Expression of the G72/G30 gene in transgenic mice induces behavioral changes

The G72/G30 gene complex is a candidate gene for schizophrenia and bipolar disorder. However, G72 and G30 mRNAs are expressed at very low levels in human brain, with only rare splicing forms observed. We report here G72/G30 expression profiles and behavioral changes in a G72/G30 transgenic mouse model. A human BAC clone containing the G72/G30 genomic region was used to establish the transgenic mouse model, on which gene expression studies, western blot and behavioral tests were performed. Relative to their minimal expression in humans, G72 and G30 mRNAs were highly expressed in the transgenic mice, and had a more complex splicing pattern. The highest G72 transcript levels were found in testis, followed by cerebral cortex, with very low or undetectable levels in other tissues. No LG72 (the long putative isoform of G72) protein was detected in the transgenic mice. Whole-genome expression profiling identified 361 genes differentially expressed in transgenic mice compared with wild-type, including genes previously implicated in neurological and psychological disorders. Relative to wild-type mice, the transgenic mice exhibited fewer stereotypic movements in the open field test, higher baseline startle responses in the course of the prepulse inhibition test, and lower hedonic responses in the sucrose preference test. The transcriptome profile changes and multiple mouse behavioral effects suggest that the G72 gene may play a role in modulating behaviors relevant to psychiatric disorders.

Decreased Na+/K+ ATPase α1 (ATP1A1) gene expression in major depression patients’ peripheral blood

Major depression affects the central nervous system and thereafter the autonomic nervous system, immune system, and endocrine system. Na+/K+ ATPase, as a major mediator of cellular transmembrane ionic gradients, plays an important role in nervous signal transduction. Three types of Na+/K+ ATPase α subunit isoforms (ATP1A1, ATP1A2, and ATP1A3) are found in brain but vary in the type of cell and level of expression. It has been confirmed that reduced expression of ATP1A2 and ATP1A3 are related to depressive disorder. However, there is no reported correlation between ATP1A1 and major depression. This study investigated the potential correlation between ATP1A1 gene expression level and major depression. The expression levels of ATP1A1 gene in the peripheral circulation of both depressive patients and healthy human controls were quantified by using reverse transcripted quantitative polymerase chain reaction. Statistical analysis showed a significant decrease of ATP1A1 expression level in major depression patients when compared to that of healthy controls (P<0.01). The differences of gene nucleotide sequences and protein structures among ATP1A1, ATP1A2, and ATP1A3 were also illustrated. This study demonstrates, for the first time, that ATP1A1 gene expression level is significantly associated with major depression and suggests that ATP1A1 could be a significant molecular marker for diagnosis.

Frontal lobe bioenergetic metabolism in depressed adolescents with bipolar disorder: a phosphorus-31 magnetic resonance spectroscopy study

OBJECTIVES

To compare the concentrations of high-energy phosphorus metabolites associated with mitochondrial function in the frontal lobe of depressed adolescents with bipolar disorder (BD) and healthy controls (HC).

METHODS

We used in vivo phosphorus-31 magnetic resonance spectroscopy ((31) P-MRS) at 3 Tesla to measure phosphocreatine (PCr), beta-nucleoside triphosphate (β-NTP), inorganic phosphate (Pi), and other neurometabolites in the frontal lobe of eight unmedicated and six medicated adolescents with bipolar depression and 24 adolescent HCs.

RESULTS

Analysis of covariance, including age as a covariate, revealed differences in PCr (p=0.037), Pi (p=0.017), and PCr/Pi (p=0.002) between participant groups. Percentage neurochemical differences were calculated with respect to mean metabolite concentrations in the HC group. Post-hoc Tukey-Kramer analysis showed that unmedicated BD participants had decreased Pi compared with both HC (17%; p=0.038) and medicated BD (24%; p=0.022). The unmedicated BD group had increased PCr compared with medicated BD (11%; p=0.032). The PCr/Pi ratio was increased in unmedicated BD compared with HC (24%; p=0.013) and with medicated BD (39%; p=0.002). No differences in β-NTP or pH were observed.

CONCLUSIONS

Our results support the view that frontal lobe mitochondrial function is altered in adolescent BD and may have implications for the use of Pi as a biomarker. These findings join volumetric studies of the amygdala, and proton MRS studies of n-acetyl aspartate in pointing to potential differences in neurobiology between pediatric and adult BD.

Psychiatric disorders in rapid-onset dystonia-parkinsonism

OBJECTIVE

Rapid-onset dystonia-parkinsonism (RDP) is caused by a variety of missense mutations in the ATP1A3 gene. Psychiatric comorbidity has been reported, although systematic examination of psychiatric disease in individuals with RDP is lacking. This study examines psychiatric morbidity for 23 patients with RDP in 10 families with family member control subjects and in 3 unrelated patients with RDP, totaling 56 individuals.

METHODS

Twenty-nine ATP1A3 mutation-positive individuals were examined; 26 exhibited motor symptoms (motor manifesting carrier [MMC]) and 3 did not (nonmotor manifesting carriers [NMC]). Twenty-seven ATP1A3 mutation-negative participants (noncarriers [NC]) were included. Rates of psychiatric illness for patients with RDP and related asymptomatic gene mutation carriers were compared with those for related nonmutation carriers. Outcome measures included the Unified Parkinson's Disease Rating Scale, Burke-Fahn-Marsden Dystonia Rating Scale, Instrumental Activities of Daily Living, Composite International Diagnostic Interview, Structured Clinical Interview for DSM-IV, Hamilton Depression Scale, Hamilton Anxiety Scale, and Yale-Brown Obsessive-Compulsive Scale.

RESULTS

NMC participants did not report any history of psychiatric disorder. Findings in MMC and NC groups included anxiety (MMC 48, NC 41%), mood (MMC 50%, NC 22%), psychotic (MMC 19%, NC 0%), and substance abuse/dependence (MMC 38%, NC 27%).

CONCLUSIONS

ATP1A3 mutations cause a wide spectrum of motor and nonmotor features. Psychotic symptoms tended to emerge before or concurrent with motor symptom onset, suggesting that this could be another expression of the ATP1A3 gene mutation.

New insights into behaviour using mouse ENU mutagenesis

Identifying genes involved in behavioural disorders in man is a challenge as the cause is often multigenic and the phenotype is modulated by environmental cues. Mouse mutants are a valuable tool for identifying novel pathways underlying specific neurological phenotypes and exploring the influence both genetic and non-genetic factors. Many human variants causing behavioural disorders are not gene deletions but changes in levels of expression or activity of a gene product; consequently, large-scale mouse ENU mutagenesis has the advantage over the study of null mutants in that it generates a range of point mutations that frequently mirror the subtlety and heterogeneity of human genetic lesions. ENU mutants have provided novel and clinically relevant functional information on genes that influence many aspects of mammalian behaviour, from neuropsychiatric endophenotypes to circadian rhythms. This review will highlight some of the most important findings that have been made using this method in several key areas of neurological disease research.

Hippocampal levels and activity of the sodium/potassium transporting ATPase subunit α-3 (AT1A3) are paralleling memory training in the multiple T-maze in the C57BL/6J mouse

Although the sodium/potassium transporting ATPase subunit alpha-3 (AT1A3) has been linked to memory mechanisms in rodents, regulation of this ATPase in terms of activity and complex levels by memory performance in a land maze has not been shown so far. It was therefore the aim of the study to link memory retrieval in the multiple T-Maze (MTM) to AT1A3 protein levels and activity. C57BL/6J mice were trained in the MTM and euthanized 6h following memory retrieval. Hippocampal membrane proteins were prepared by ultracentrifugation and run on blue native gel electrophoresis (BN-PAGE). Enzyme activity was evaluated using an in-gel method. AT1A3 protein was characterized using mass spectrometry (nano-LC-ESI-MS/MS). On BN-PAGE a single band was observed at 240 kDa, which corresponds to the dimeric form of the enzyme. Higher levels of AT1A3 complex were seen in trained mice. Also ATPase activity was higher in trained mice, and was observed both at 110 and at 240 kDa. Mass spectrometry unambiguously identified AT1A3 with 98.91% sequence coverage. A series of novel AT1A3 phosphorylation sites were detected. Taken together, it was shown that increased AT1A3 protein levels for the dimer as well as AT1A3 activity represented by the monomer and the dimer were paralleling memory training in the MTM. This may be relevant for understanding the role of the catalytic hydrolysis of ATP coupled with the exchange of sodium and potassium ions across the plasma membrane that generates the electrochemical gradient of sodium and potassium ions. Herein, we provide evidence for a possible role of AT1A3 in memory mechanisms and support previous findings using different animal models for memory formation.

Genetic suppression of agrin reduces mania-like behavior in Na+ , K+ -ATPase α3 mutant mice

Myshkin mice heterozygous for an inactivating mutation in the neuron-specific Na(+) ,K(+) -ATPase α3 isoform show behavior analogous to mania, including an abnormal endogenous circadian period. Agrin is a proteoglycan implicated as a regulator of synapses that has been proposed to inhibit activity of Na(+) ,K(+) -ATPase α3. We examined whether the mania-related behavior of Myshkin mice could be rescued by a reduction in the expression of agrin through genetic knockout. The suppression of agrin reduced hyperambulation and holeboard exploration, restored anxiety-like behavior (or reduced risk-taking behavior), improved prepulse inhibition and shortened the circadian period. Hence, agrin is important for regulating mania-like behavior and circadian rhythms. In Myshkin mice, the suppression of agrin increased brain Na(+) ,K(+) -ATPase activity by 11 ± 4%, whereas no effect on Na(+) ,K(+) -ATPase activity was detected when agrin was suppressed in mice without the Myshkin mutation. These results introduce agrin as a potential therapeutic target for the treatment of mania and other neurological disorders associated with reduced Na(+) ,K(+) -ATPase activity and neuronal hyperexcitability.

New triggers and non-motor findings in a family with rapid-onset dystonia-parkinsonism

BACKGROUND

A woman from Italy presented with dystonic leg symptoms at the age of 59. Rapid-onset dystonia-parkinsonism (RDP) was not suspected until 3 affected children (2 male, 1 female) with presentations consistent with the disorder were recognized.

METHODS

The mother and four of her children (3 with and 1 without dystonia) were evaluated with an extensive battery including standardized history questionnaire and rating scales. In addition, all four children had cognitive testing and three of the four children had psychiatric interviews.

RESULTS

In this family, a T613M mutation in the ATP1A3 gene was confirmed, the most common mutation present in patients with RDP. The proband's limb dystonia was atypical of RDP, symptoms of the others affected included dysarthria, asymmetric limb dystonia, and dysphagia more consistent with RDP. The two sons developed dystonia-parkinsonism in adolescence after consuming large amounts of alcohol. All 3 of those with psychiatric interviews reached diagnosable thresholds for mood disorder (bipolar or dysthymia) and some form of anxiety disorder.

CONCLUSIONS

The phenotype and age of onset is broader than previously reported in RDP, suggesting that it could be under-reported. Prior to this study, neuropsychologic symptoms associated with RDP were under-appreciated. Those patients who are at risk or suspected of having RDP should be cautioned to avoid excessive alcohol intake. Further study is needed to assess if the cognitive and psychiatric features are part of a broader RDP phenotype and this may have implications for future research into genetic susceptibility for psychiatric disease.