Mineral metabolism, mania, and melancholia

Bartter Syndrome: A Systematic Review of Case Reports and Case Series

Background and Objectives: Bartter syndrome (BS) is a rare group of autosomal-recessive disorders that usually presents with hypokalemic metabolic alkalosis, occasionally with hyponatremia and hypochloremia. The clinical presentation of BS is heterogeneous, with a wide variety of genetic variants. The aim of this systematic review was to examine the available literature and provide an overview of the case reports and case series on BS. Materials and Methods: Case reports/series published from April 2012 to April 2022 were searched through Pubmed, JSTOR, Cochrane, ScienceDirect, and DOAJ. Subsequently, the information was extracted in order to characterize the clinical presentation, laboratory results, treatment options, and follow-up of the patients with BS. Results: Overall, 118 patients, 48 case reports, and 9 case series (n = 70) were identified. Out of these, the majority of patients were male (n = 68). A total of 21 patients were born from consanguineous marriages. Most cases were reported from Asia (73.72%) and Europe (15.25%). In total, 100 BS patients displayed the genetic variants, with most of these being reported as Type III (n = 59), followed by Type II (n = 19), Type I (n = 14), Type IV (n = 7), and only 1 as Type V. The most common symptoms included polyuria, polydipsia, vomiting, and dehydration. Some of the commonly used treatments were indomethacin, potassium chloride supplements, and spironolactone. The length of the follow-up time varied from 1 month to 14 years. Conclusions: Our systematic review was able to summarize the clinical characteristics, presentation, and treatment plans of BS patients. The findings from this review can be effectively applied in the diagnosis and patient management of individuals with BS, rendering it a valuable resource for nephrologists in their routine clinical practice.

Depressive-like behavior accompanies neuroinflammation in an animal model of bipolar disorder symptoms induced by ouabain

INTRODUCTION

A previous study from our Laboratory showed no alteration in inflammatory parameters seven days after ouabain (OUA) administration, a Na⁺K⁺ATPase inhibitor, which was previously considered only a mania model. However, the administration of OUA in rats was recently validated as a model of bipolar disorder (BD) symptoms, demonstrating that 14 days after single intracerebroventricular (ICV) administration, OUA also induces depressive-like behavior. Therefore, it is important to investigate the long-term effect of OUA on inflammatory parameters since this mechanism seems to play a key role in BD physiopathology.

METHODS

Adult male Wistar rats received a single ICV administration of OUA or artificial cerebrospinal fluid (aCSF). From the fourth day after the ICV infusion, the rats received saline or Lithium (Li) for 14 days. The open-field test was performed on the 7th day after OUA. On the 14th day, locomotion was re-evaluated, and the forced swimming test (FST) was used to evaluate depressive-like behavior. Inflammatory parameters were assessed in the frontal cortex and hippocampus.

RESULTS

OUA increased the locomotion of rats after seven days, considered a mania-like behavior. In the FST, OUA increased the time of immobility on the 14th day, considered a depressive-like behavior. Li reversed the mania-like behavior and partially reversed the depressive-like behavior. Furthermore, OUA increased the levels of interleukin (IL)-1β, IL-6, IL-10, TNF-α, and CINC-1 in the frontal cortex and hippocampus. Li treatment reverses all these inflammatory alterations.

CONCLUSION

This study suggests that the long-term Na⁺K⁺ATPase inhibition effects induce depressive-like behavior, which was accompanied by inflammation in the BD symptoms model.

NMDA receptor inhibition prevents intracellular sodium elevations in human olfactory neuroepithelial precursors derived from bipolar patients

Dysregulation of ion flux across membranes and glutamate-induced excitotoxicity appear to be important pathophysiologic abnormalities in bipolar illness. Understanding ion control and responses to ionic stress is important to decipher the pathogenesis of this disorder. Monensin alone significantly increased [Na]_i in ONPs from bipolar individuals (5.08 ± 0.71 vs baseline 3.13 ± 0.93, P = 0.03) and AP5 had no effect (2.0 ± 1.2 vs baseline 3.13 ± 0.93, P = 0.27). However, the combination of AP5 and monensin resulted in normalization of [Na]_i (3.25 ± 1.28 vs baseline 3.13 ± 0.93, P = 0.89). This effect was not observed in cells from non-bipolar individuals (monensin alone, 1.72 ± 1.10 vs baseline 2.42 ± 1.80, P = 0.25; AP5 alone, 1.37 ± 0.74 vs baseline 2.42 ± 1.80; AP5 combined with monensin, 1.53 ± 0.98 vs baseline 2.42 ± 1.80, P = 0.31). Sodium regulation is central to neuronal function and may be disturbed in patients with bipolar disorder. Monensin is an ionophore, meaning that it incorporates itself into the membrane and allows sodium to enter independent of cellular membrane proteins. While the mechanism remains obscure, the observation that the NMDA receptor antagonist, AP5, normalizes [Na]_i only in olfactory neuroepithelial precursors obtained from bipolar illness may provide novel insights into ion regulation in tissues from subjects with bipolar illness.

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.

Extra-synaptic modulation of GABAA and efficacy in bipolar disorder

BACKGROUND

Bipolar disorder type I is a severe psychiatric condition that leads to significant morbidity and mortality and whose treatment remains suboptimal. Its pathophysiology involves disturbance in the control of ionic fluxes so that when patients are either manic or depressed, the resting membrane potential of neurons is more depolarized than normal. Available mood stabilizers have a shared mechanism of normalizing ion flux by compensating for ionic abnormalities, and normalizing membrane potential.

HYPOTHESIS

Agents that significantly potentiate extrasynaptic GABA_A receptors are expected to be particularly effective in hyperpolarizing resting membrane potential in bipolar patients, thereby normalizing their membrane potential.

DISCUSSION

New neuroactive steroid-like agents are being tested in humans for depression and insomnia. These agents include brexanolone, ganaxolone, and gaboxadol. Brexanolone has been approved for the treatment of postpartum depression, ganaxolone is being studied for treatment-resistant depression, and gaboxadol development for the treatment of insomnia has been abandoned due to narrow therapeutic index. In addition to the current studies, these agents are expected to have particular efficacy in acute and prophylactic management of bipolar I disorder by hyperpolarizing the resting potential of neurons and antagonizing one of the most reproducible demonstrated biologic abnormalities of this illness.

Neurological Disorders and Risk of Arrhythmia

Neurological disorders including depression, anxiety, post-traumatic stress disorder (PTSD), schizophrenia, autism and epilepsy are associated with an increased incidence of cardiovascular disorders and susceptibility to heart failure. The underlying molecular mechanisms that link neurological disorders and adverse cardiac function are poorly understood. Further, a lack of progress is likely due to a paucity of studies that investigate the relationship between neurological disorders and cardiac electrical activity in health and disease. Therefore, there is an important need to understand the spatiotemporal behavior of neurocardiac mechanisms. This can be advanced through the identification and validation of neurological and cardiac signaling pathways that may be adversely regulated. In this review we highlight how dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis, autonomic nervous system (ANS) activity and inflammation, predispose to psychiatric disorders and cardiac dysfunction. Moreover, antipsychotic and antidepressant medications increase the risk for adverse cardiac events, mostly through the block of the human ether-a-go-go-related gene (hERG), which plays a critical role in cardiac repolarization. Therefore, understanding how neurological disorders lead to adverse cardiac ion channel remodeling is likely to have significant implications for the development of effective therapeutic interventions and helps improve the rational development of targeted therapeutics with significant clinical implications.

Review of animal models of bipolar disorder that alter ion regulation

BACKGROUND

Accurate modeling of psychiatric disorders in animals is essential for advancement in our understanding and treatment of the severe mental illnesses. Of the multiple models available for bipolar illness, the ones that disrupt ion flux are currently the only ones that meet the three criteria for validity: face validity, construct validity, and predictive validity.

METHODS

A directed review was performed to evaluate animal models for mania in which ion dysregulation was the key intervention.

RESULTS

Three models are identified. All focus on disruption of the sodium potassium pump. One is pharmacologic and requires surgical insertion of an intracerebroventricular (ICV) cannula and subsequent administration of ouabain. Two are genetic and are based on heterozygote knockout (KO) of the alpha2 or alpha3 subunits of the sodium pump. Alpha2 KOs are believed to have altered glial function, and they do not appear to have a full array of manic symptoms. Alpha3 KOs appear to be the best characterized animal model for bipolar disorder currently available.

CONCLUSION

Animal models that disrupt ion regulation are more inclined to model both mania and depression; and are thus the most promising models available. However, other models are important for demonstrating mechanisms in important pathophysiologic aspect of bipolar disorder.

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.

Targeting astrocytes in bipolar disorder

Astrocytes are homeostatic cells of the central nervous system, which are critical for development and maintenance of synaptic transmission and hence of synaptically connected neuronal ensembles. Astrocytic densities are reduced in bipolar disorder, and therefore deficient astroglial function may contribute to overall disbalance in neurotransmission and to pathological evolution. Classical anti-bipolar drugs (lithium salts, valproic acid and carbamazepine) affect expression of astroglial genes and modify astroglial signalling and homeostatic cascades. Many effects of both antidepressant and anti-bipolar drugs are exerted through regulation of glutamate homeostasis and glutamatergic transmission, through K(+) buffering, through regulation of calcium-dependent phospholipase A2 (that controls metabolism of arachidonic acid) or through Ca(2+) homeostatic and signalling pathways. Sometimes anti-depressant and anti-bipolar drugs exert opposite effects, and some effects on gene expression in drug treated animals are opposite in neurones vs. astrocytes. Changes in the intracellular pH induced by anti-bipolar drugs affect uptake of myo-inositol and thereby signalling via inositoltrisphosphate (InsP3), this being in accord with one of the main theories of mechanism of action for these drugs.

Cariprazine delays ouabain-evoked epileptiform spikes and loss of activity in rat hippocampal slices

In the only bipolar cycling in vitro model, rat hippocampal slices are treated with the sodium pump inhibitor ouabain, which induces epileptiform activity, followed by refractory activity loss that recovers and cycles back to epileptiform activity. Thus, clinical cycling seen in patients with bipolar disorder is modeled on a cellular level as alternating hyperactivity and hypoactivity interspersed with normal activity. In this study, we tested the ability of cariprazine a new antipsychotic candidate to block ouabain-induced changes in rat hippocampal slices. Cycling of population spikes and epileptiform bursts was evoked using an extracellular stimulation electrode located in the Schaeffer collaterals of 400-µm-thick rat hippocampal slices treated with ouabain (3.3μM) alone or in combination with cariprazine (1, 5, 25, and 50µM). Responses were recorded using an extracellular electrode placed in the cell body layer of the CA1 region. Cariprazine 25 and 50µM delayed ouabain-induced epileptiform burst onset and subsequent activity loss. Lower cariprazine concentrations were ineffective. Cariprazine delays the onset of ouabain-induced epileptiform bursts and the loss of spiking activity similarly to that previously demonstrated with the mood stabilizer lithium. These results suggest that cariprazine may have therapeutic potential for treatment of bipolar disorder.

Lithium: Molecular interactions, clinical actions

Lithium is one of the most widely used drugs in neuropsychopharmacology. Preclinical scientists have made several advances in ascertaining the molecular mechanisms of action of this cation; such as its ability to stabilize monoamine levels, to interact with second messengers, and its neuroprotective effects, possibly over suicidal behaviors. Nevertheless, there remains a gap of knowledge between the pharmacological advances and the number of reliable clinical trials, creating a lack of evidence-based medicine to support medical prescriptions. In this review we examine lithium’s molecular mechanisms of action and evaluate their relevance in clinical applications.

Neutralization of endogenous digitalis-like compounds alters catecholamines metabolism in the brain and elicits anti-depressive behavior

Depressive disorders are among the world's greatest public health problems. Na(+), K(+)-ATPase is the established receptor for the steroidal digitalis-like compounds (DLC). Alteration in brain Na(+), K(+)-ATPase and DLC have been detected in depressive disorders raising the hypothesis of their involvement in these pathology. The present study was designed to further elaborate this hypothesis by investigating the behavioral and biochemical consequences of neutralization in brain DLC activity attained by anti-ouabain antibodies administrations, in normal Sprague-Dawley (SD) and in the Flinders Sensitive Line (FSL) of genetically depressed rats. Chronic i.c.v. administration of anti-ouabain antibodies to FSL rats elicited anti-depressive behavior. Administration of anti-ouabain antibodies intracerebroventriculary (i.c.v.) to SD rats significantly changed the levels of catecholamines and their metabolites in the hippocampus, ventral tegmentum and nucleus accumbence. These results are in accordance with the notion that endogenous DLC may be involved in the manifestation of depressive disorders and suggests that alteration in their levels may be of significant therapeutic value.

Memantine reduces mania-like symptoms in animal models

Memantine, a selective antagonist of the N-methyl-D-aspartate receptor, is approved for the treatment of moderate to severe Alzheimer's disease. Ion dysregulation is thought to be involved in the pathophysiology of bipolar illness, suggesting that memantine may be effective in treating bipolar manic and/or depressive episodes. We utilized two preclinical models of mania that mimic pathophysiologic changes seen in bipolar illness to examine the potential efficacy of memantine in the treatment of this disorder. Locomotor hyperactivity of male Sprague-Dawley rats in an open field was induced with intracerebroventricular (ICV) administration of 10(-3) M ouabain. Memantine (2.5, 5 or 7.5mg/kg), lithium (6.75 mEq/kg), or vehicle were administered acutely via intraperitoneal injection immediately prior to ouabain, then chronically for 7 days (oral memantine 20, 30, and 40 mg/kg/day in water; lithium 2.4 g/kg food). In a second model of bipolar disorder, cycling between population spikes and epileptiform bursts was investigated in rat hippocampal slices treated with ouabain (3.3 μM) alone or in combination with memantine (0.5, 1.0, and 5.0 μM). Ouabain-induced hyperlocomotion was normalized with acute and chronic lithium and chronic use of memantine. Memantine delayed the onset of ouabain-induced-cycling in hippocampal slices. Memantine may have antimanic properties.

Effects of brain-derived neurotrophic factor on sodium-induced apoptosis in human olfactory neuroepithelial progenitor cells

Low levels of brain-derived neurotrophic factor (BDNF) peptide are linked to the pathophysiology of mood disorders. Several single-nucleotide polymorphisms (SNPs) across the BDNF gene (BDNF) have been associated with bipolar illness. Since both elevated intracellular sodium and apoptosis are believed to contribute to cellular dysfunction in bipolar disorder, it is important to determine the effect of exogenous BDNF on apoptosis induced by the high levels of intracellular sodium seen in ill bipolar patients. Human olfactory neuroepithelial progenitor cells were treated with monensin, a sodium ionophore that increases intracellular sodium and leads to apoptosis. Apoptosis was quantified with enzyme-linked immunosorbent assay (ELISA) for mono- and oligonucleosomes. Elevation of intracellular sodium concentration by monensin induced apoptosis. BDNF 100ng/mL pretreatment or co-treatment attenuated the monensin-induced apoptosis. Pretreatment with BDNF for 24h reduced monensin-induced apoptosis by 93%. Co-treatment of BDNF and monensin increased intracellular sodium concentration and reduced apoptosis by 66%. Monensin for 24h models a process that is believed to occur during ill phases of bipolar illness. Treatment with BDNF greatly attenuates or prevents monensin-induced apoptosis. The functional consequences of BDNF SNPs, known to be associated with bipolar illness, need to be examined.

Aberrant regulation of endogenous ouabain-like factor in bipolar subjects

Ill phases of bipolar illness are associated with abnormalities in ion regulation and intracellular ion concentrations. Previously, it has been reported that mania is characterised by lower circulating levels of ion regulating endogenous cardenolides, and that bipolar subjects lack the normal seasonal variation of these factors. Since endogenous cardenolides are elaborated in settings of extensive physical activity, euthymic bipolar and psychiatrically normal control subjects were asked to exercise to exhaustion. Plasma concentrations of endogenous cardenolides were measured at baseline, 60 min, peak exercise and post-recovery. Ouabain-like immunoreactive factor (OLF) was lower at baseline (0.005+/-S.D. 0.01 ng/mL in bipolar vs. 0.072+/-0.06 ng/mL in normal control subjects, P=0.019), lower at 60 min (0.007+/-S.D. 0.02 ng/mL in bipolar vs. 0.075+/-0.06 ng/mL in normal control subjects, P=0.029), and tended to be lower at peak exercise (0.009+/-S.D. 0.02 ng/mL in bipolar vs. 0.131+/-0.21 ng/mL in normal control subjects, P=0.15) in bipolar subjects compared to non-psychiatric controls. Other endogenous cardenolides did not vary significantly. The endogenous cardenolide, OLF, may be aberrantly controlled in bipolar illness.

Effect of ethacrynic acid on the sodium- and potassium-activated adenosine triphosphatase activity and expression in Old Order Amish bipolar individuals

BACKGROUND

There are numerous reports of abnormalities in the expression of the sodium- and potassium-activated adenosine triphosphatase (Na,K-ATPase) in response to an ionic stress with ethacrynic acid (ECA) challenge in bipolar subjects. However, all of these studies have been in out-bred populations. In an attempt to reduce the genetic variability associated with this observation, we examined this phenomenon within an isolated breeding population.

METHODS

We studied 36 lymphoblastoid cell lines obtained from Old Order Amish individuals who had bipolar disorder, type I (16), or were unaffected siblings of the same gender (9) or unrelated normal controls(11). Cells were treated with 10(-)(5)M ECA for 3 days after which Na,K-ATPase alpha1 protein expression and activity ([(3)H]-ouabain binding, (86)Rb-uptake, and intracellular sodium and potassium concentrations) were measured.

RESULTS

Cells from bipolar patients expressed less Na,K-ATPase as measured by immunoblot analysis after ECA treatment (0.94 + or - SD 0.13 relative units) compared to unaffected siblings (1.06 + or - 0.12, P = 0.029) and Old Order Amish normal controls (1.06 + or - 0.14, P = 0.0004). None of the other variables studied were different.

LIMITATIONS

This is a study of peripheral cells which do not express all of the Na,K-ATPase expressed in the brain. The observed difference is small.

CONCLUSIONS

Ethacrynic-acid-stimulated lymphoblast sodium pump expression in Old Order Amish bipolar subjects is reduced compared to Amish controls.

Response of sodium pump to ouabain challenge in human glioblastoma cells in culture

Bipolar disorder is a severe psychiatric condition that manifests with abnormalities in ion regulation. Previous studies have suggested that glia may be specifically involved in the pathophysiology of this condition. Since the potent sodium pump inhibitor, ouabain, has been used previously to model the ionic changes of bipolar illness, we investigated its effect of on sodium pump expression and activity in a human glioblastoma cell line. LN229 cells were grown with or without ouabain 10(-7) M for 3 days, and the effect of a therapeutic concentration of lithium was also examined. The mRNA transcription of sodium pump isoforms was determined by reverse transcriptase polymerase chain reaction (RT-PCR), and the protein expression of phosphorylated and non-phosphorylated pump isoforms was semi-quantified utilizing Western blot. Ouabain treatment caused an increase of some 6-fold in alpha1 protein expression and a doubling of alpha1 mRNA. alpha3 protein and alpha2 and alpha3 mRNA more than doubled. Lithium treatment alone had no effect, but lithium co-administered with ouabain normalized Na pump protein and mRNA expression for alpha1 and 2, but not alpha3. These results suggest that disturbance of ion regulation induces changes in glial cell sodium regulatory systems which are normalized by lithium treatment.

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

BACKGROUND

The sodium- and potassium-activated adenosine triphosphatase (Na+, K+-ATPase) is a major plasma membrane transporter for sodium and potassium. We recently suggested that bipolar disorders (BD) may be associated with alterations in brain Na+, K+-ATPase. We further conjectured that the differences in Na+, K+-ATPase in BD patients could result partially from genetic variations in Na+, K+-ATPase alpha isoforms.

METHODS

To test our hypothesis, we undertook a comprehensive study of 13 tagged single nucleotide polymorphisms (SNPs) across the three genes of the brain alpha isoforms of Na+, K+- ATPase (ATP1A1, ATP1A2, and ATP1A3, which encode the three alpha isoforms, alpha1, alpha2, and alpha3, respectively) identified using HapMap data and the Haploview algorithm. Altogether, 126 subjects diagnosed with BD from 118 families were genotyped (parents and affected siblings). Both individual SNPs and haplotypes were tested for association using family-based association tests as provided in the UNPHASED and PBAT set of programs.

RESULTS

Significant nominal association with BD was observed for six single SNPs (alpha1: rs11805078; alpha2: rs2070704, rs1016732, rs2854248, and rs2295623; alpha3: rs919390) in the three genes of Na+, K+-ATPase alpha isoforms. Haplotype analysis of the alpha2 isoform (ATP1A2 gene) showed a significant association with two loci haplotypes with BD (rs2295623: rs2070704; global p value = .0198, following a permutation test).

CONCLUSIONS

This study demonstrates for the first time that genetic variations in Na+, K+-ATPase are associated with BD, suggesting a role of this enzyme in the etiology of this disease.

Lithium: bipolar disorder and neurodegenerative diseases Possible cellular mechanisms of the therapeutic effects of lithium

Bipolar illness is a major psychiatric disorder that affects 1-3% of the worldwide population. Epidemiological studies have demonstrated that this illness is substantially heritable. However, the genetic characteristics remain unknown and a clear personality has not been identified for these patients. The clinical history of lithium began in mid-19th century when it was used to treat gout. In 1940, it was used as a substitute for sodium chloride in hypertensive patients. However, it was then banned, as it had major side effects. In 1949, Cade reported that lithium could be used as an effective treatment for bipolar disorder and subsequent studies confirmed this effect. Over the years, different authors have proposed many biochemical and biological effects of lithium in the brain. In this review, the main mechanisms of lithium action are summarised, including ion dysregulation; effects on neurotransmitter signalling; the interaction of lithium with the adenylyl cyclase system; inositol phosphate and protein kinase C signalling; and possible effects on arachidonic acid metabolism. However, none of the above mechanisms are definitive, and sometimes results have been contradictory. Recent advances in cellular and molecular biology have reported that lithium may represent an effective therapeutic strategy for treating neurodegenerative disorders like Alzheimer's disease, due to its effects on neuroprotective proteins like Bcl-2 and its actions on regulators of apoptosis and cellular resilience, such as GSK-3. However, results are contradictory and more specific studies into the use of lithium in therapeutic approaches for neurodegenerative diseases are required.

Positron emission tomography with fluorodeoxyglucose-F18 in an animal model of mania

Intracerebroventricular (ICV) administration of ouabain to young adult rats has been suggested to model human bipolar mania. In the human condition, mania and bipolar depression are both associated with reductions in frontal cerebral metabolism. We utilized [(18)F]-fluorodeoxyglucose [(18)FDG] positron emission tomography (PET) to visualize glucose uptake in animals receiving ICV ouabain. Animals received 5 microl of 10(-)(3) M ouabain ICV, were anesthetized with isoflurane inhalation, and administered intraperitoneally with 0.5 mCi of (18)FDG. PET data were collected over 20 min 1 hour later. Additionally, the effect of lithium was examined in animals receiving lithium in their diet for 1 week before the ICV ouabain injection. Data were analyzed with IDL Virtual Machine software. Brain glucose utilization as measured by (18)FDG uptake was significantly reduced in animals receiving ICV ouabain compared with those receiving equal volumes of artificial cerebrospinal fluid. Pretreatment with lithium normalized (18)FDG uptake. These results mirror human studies.

Mimicking human bipolar ion dysregulation models mania in rats

Psychiatric diseases in general, and bipolar illness in particular, are difficult to model in animals since the subjective nature of the core symptoms appears to preclude objective observation of behavioral changes. An adequate animal model of a psychiatric condition must fulfill three core criteria: share pathophysiological characteristics of the human condition (face validity), have similar behavioral manifestations as the human disease (construct validity), and improve with medications that improve the symptoms seen in afflicted humans (predictive validity). The ouabain model for bipolar illness mimics a widely reproduced biologic abnormality in mania: reduced sodium pump activity. An intracerebroventricular (ICV) administration of 5microL 10(-3)M ouabain induces motoric hyperactivity preventable by lithium, carbamazepine, and haloperidol. ICV ouabain may also produce environmentally dependent hypoactivity. The model, however, has not yet been examined for other potential manic behavior in rats such as reduced need for sleep, increased sexual activity, or increased irritability. While additional characterization of the model is required, the ouabain model for bipolar illness is the only available animal model that fulfills the three criteria for an adequate animal model for bipolar illness.

Involvement of Na(+), K(+)-ATPase and endogenous digitalis-like compounds in depressive disorders

BACKGROUND

Sodium and potassium-activated adenosine triphosphatase (Na(+), K(+)-ATPase) and endogenous digitalis-like compounds (DLC) in the brain have been implicated in the pathogenesis of mood disorders. This hypothesis was examined by the determination of Na(+), K(+)-ATPase/DLC system in parietal cortex of patients with different mood disorders and two animal models of depression.

METHODS

Na(+), K(+)-ATPase concentrations in human brain synaptosomal fractions, from patients with mood disorders, schizophrenia, and normal individuals, were determined by (3)H-ouabain binding assay. Alpha isoforms were quantified by Western blotting. Brain DLC were measured using sensitive enzyme linked immunosorbant assay (ELISA). The effects of ouabain and ouabain-antibodies on behavior were determined in two animal models of depression.

RESULTS

(3)H-ouabain binding in bipolar patients was significantly lower than in major depressed and schizophrenic patients. Na(+), K(+)-ATPase alpha isoforms in synaptosomal fractions were not different among the groups. DLC levels in the parietal cortex of bipolar patients were significantly higher than in normal individuals and depressed patients. Injection of lipopolysaccharide (intraperitoneally) to rats elicited depression-like symptoms, which were significantly attenuated by pre-injection of ouabain-antibodies. Injection of ouabain and ouabain-antibodies (intracerebroventricular) reduced depression-like symptoms in the forced swimming test in rats.

CONCLUSIONS

The results support the possibility that Na(+), K(+)-ATPase and endogenous DLC participate in the pathogenesis of depressive disorders.

[Lithium: 55 years of history in the therapy of bipolar affective disorder]

The clinical history of lithium began in mid-19th century when it was used to treat gout. It was subsequently administered as a substitute for sodium chloride and towards the end of 1940 its effects for the control of mania were discovered. At present it is used effectively for treatment of mania and for the prophylaxis of bipolar disorder. Though its effect on affective illnesses is evident, the same cannot be said of its mechanism of action, since in spite of the numerous studies performed to date it is still not known exactly how this ion acts. Many theories have been proposed, the most important of which are: normalisation of possible ionic alterations; interactions with the adenylyl cyclase cAMP system; effects on the phosphatidylinositol cycle; stabilisation of the levels of neuroprotective proteins; normalisation of the values of some cytosolic endopeptidases; etc. In any case, it has yet to be determined which of these is the principal factor responsible for lithium's therapeutic action, while at the same time the possibility cannot be totally ruled out that its precise mechanism of action is still to be discovered.

Differential response of bipolar and normal control lymphoblastoid cell sodium pump to ethacrynic acid

BACKGROUND

While the pathogenesis of manic-depressive, or bipolar, illness is unknown, an excess of intracellular sodium and calcium concentrations is thought to contribute to the development of the illness. Previous work has demonstrated a reduced adaptive response of the sodium pump to ethacrynic acid in lymphocytes obtained from bipolar subjects compared to psychiatrically normal controls.

METHODS

To further examine this phenomenon, we investigated several aspects of sodium pump response (transcription, translation, activity, and intracellular ion concentration) in lymphoblastoid cell lines derived from bipolar subjects and matched normal controls. Cells were treated with ethacrynic acid 100 microM for 3 days.

RESULTS

Normal control-derived cells exhibited an upregulation of sodium pump mRNA synthesis, protein expression, pump-specific binding and activity, and were able to maintain a normal intracellular sodium concentration. Cells derived from bipolar individuals did not alter sodium pump parameters in any way, and consequently, had a higher intracellular sodium concentration.

LIMITATIONS

While bipolar lymphoblasts were from an inbred Old Order Amish population, the normal controls were from an outbred population.

CONCLUSIONS

The results suggest that bipolar illness is associated with an abnormality in cellular sodium homeostatic regulation.

Intracerebroventricular administration of ouabain as a model of mania in rats

BACKGROUND

Human bipolar illness is characterized by mood state- and diagnosis-associated abnormalities of cellular cation distribution and transport. These include reduced sodium pump activity and expression and increased intracellular sodium. If these alterations are related to the pathophysiology of the disease, rather than secondary or ancillary abnormalities, then one would expect that modeling of these changes in vivo would produce lithium-preventable behavioral abnormalities.

METHODS

Ouabain, a potent inhibitor of the sodium pump, was administered intracerebroventricularly to male rats previously fed lithium-containing food or plain rat chow. Locomotion was then quantified in an open field.

RESULTS

Ouabain increased locomotion 300% over baseline. Lithium pretreatment prevented the ouabain-induced hyperlocomotion response.

CONCLUSION

Inhibition of central nervous system sodium pump with ouabain produces a plausible animal model of mania. This model may be useful for preclinical screening of potential mood stabilizers.

Effect of ethacrynic acid on sodium pump alpha isoforms in SH-SY5Y cells

BACKGROUND

Ethacrynic acid (ECA), a diuretic that has several cellular actions, increases expression of the sodium and potassium-activated adenosine triphosphatase (Na, K-ATPase or Na pump) in normal lymphocytes, but not in lymphocytes of bipolar patients. While this has been proposed to be important in the pathophysiology of bipolar illness, the response of neural tissues to ECA is unknown.

METHODS

Human neuroblastoma SH-SY5Y cells differentiated with 10-microM retinoic acid were treated with various ECA concentrations for 3 days, and changes in Na-pump alpha-isoform expression were quantified with densitometric analysis of Western bands.

RESULTS

Expression of alpha1 and alpha3 Na pump isoforms significantly increased with 10-5 M ECA. Cells treated with 10-6 or 10-7 M ECA showed no change in Na-pump expression, while cells treated with 10-4 M ECA died. The alpha2 isoform could not be detected in differentiated SH-SY5Y cells.

CONCLUSIONS

The effect of ECA on alpha1-isoform in neural tissue is similar to that observed in lymphocytes. As alpha3 isoform is not expressed in lymphocytes, however, we conclude that lymphocytes are an incomplete model of neural tissue.

Evaluation of neuroprotection by lithium and valproic acid against ouabain-induced cell damage

BACKGROUND

The pathophysiology of manic-depression may be associated with dysregulation of ion homeostasis. Ouabain is a potent inhibitor of the sodium-potassium adenosine triphosphatase and has been purported to mimic abnormalities seen in acute mania. As manic episodes are believed to be neurotoxic and mood stabilizers have recently been implicated as neuroprotectants, it is of interest to determine if lithium and valproic acid antagonize ouabain-induced neurotoxicity.

METHODS

Human neuroblastoma SH-SY5Y cells were differentiated for 12 days then pretreated with lithium or valproic acid for 24 h and then challenged with a 10 microM ouabain insult. Cellular damage was assessed with lactate dehydrogenase (LDH) release, and apoptotic potential of ouabain was evaluated with DNA fragmentation.

RESULTS

Ouabain significantly increased LDH release after 72 h of treatment. Lithium pretreatment at 1 mM diminished ouabain-induced LDH release. Valproic acid alone at 100 and 1000 micrograms/mL significantly increased LDH release from the cells. Furthermore, it significantly potentiated ouabain-induced LDH release. DNA fragmentation suggests that ouabain induces apoptosis.

CONCLUSIONS

Lithium at the therapeutic level of 1 mM limits the extent of cellular damage caused by 10 microM ouabain in SH-SY5Y cells as measured by LDH release. Valproic acid alone at the therapeutic concentration of 100 micrograms/mL induces LDH release and does not prevent ouabain-induced LDH release.

Ouabain induction of cycling of multiple spike responses in hippocampal slices is delayed by lithium

Alterations in sodium- and potassium-activated adenosine triphosphatase (Na,K-ATPase) activity have been associated with changes of mood states and lithium treatment in bipolar illness. We examined the effects of ouabain and lithium on evoked population responses in rat hippocampal slices. In vitro 3.3 microM ouabain induced cycling between epliptiform activity and unresponsiveness in 18.5% of slices. In vitro ouabain, at 1-10 microM, induced epileptiform multiple spike responses. In vivo lithium pretreatment for 10-21 days produced a significant delay in the onset of this ouabain-induced epileptiform activity compared to control animals. These findings are consistent with other work which suggests that Na, K-ATPase inhibition can both activate and suppress excitable tissues and that lithium pretreatment can mitigate these effects. The implications of these results and others regarding the pathophysiology of bipolar illness are discussed.

Endogenous digoxin-like immunoreactive factor (DLIF) serum concentrations are decreased in manic bipolar patients compared to normal controls

BACKGROUND

A decrease in sodium pump activity in erythrocytes has been associated with manic episodes of bipolar illness relative to euthymic moods. Since red blood cells are long-lived and lack a nucleus, it is likely that a plasma factor is responsible for the observed decrease in sodium pump activity.

METHODS

Utilizing a radioimmunoassay, we examined the serum concentrations of the digoxin-like immunoreactive factor (DLIF) in ill and well bipolar patients and compared the values to those of normal controls.

RESULTS

DLIF was significantly decreased in manic individuals as compared to normal controls (143.6+/-S.E.M. 20.94 vs. 296.6+/-12.76 pg digoxin equivalents/ml, respectively, F = 4.77, P<0.05), but not compared to euthymic bipolar subjects 213.8+/-86.92, P = 0.77). There were no significant differences in DLIF concentrations between manic and euthymic bipolar individuals (P = 0.8). Since relapse in bipolar patients appears to display a seasonal pattern, we also measured the plasma concentration of this factor over a 12-months period. Normal controls exhibited a seasonal pattern of change in serum DLIF concentrations with a nadir in the winter months. Plasma concentrations of DLIF in bipolar patients did not show a seasonal pattern and maintained low levels throughout the year.

LIMITATIONS

Due to the nonspecificity of our antibody, we could measure only total DLIF. Furthermore, it is unclear what the role of circulating DLIF, if any, may be on brain function.

CONCLUSION

DLIF may be involved in the pathophysiology of mania.

Alpha 2 isoform of the Na,K-adenosine triphosphatase is reduced in temporal cortex of bipolar individuals

BACKGROUND

The pathophysiology of bipolar illness has been associated with changes in transmembrane ion flux and redistribution of biologically active ions. The recent identification of multiple isoforms of Na,K-adenosine triphosphatase (ATPase) alpha and beta subunits raises the possibility of altered pump isoform expression.

METHODS

We determined Na,K-ATPase alpha subunit expression in postmortem temporal cortex gray matter from individuals suffering from bipolar disorder, schizoaffective disorder, schizophrenia, and matched normal controls. Quantification of isoform expression was accomplished via densitometric scanning of Western blots utilizing isoform-specific antibodies.

RESULTS

Bipolar individuals exhibited a significant reduction in the abundance of the alpha 2 isoform of Na,K-ATPase compared to normal controls. Schizophrenic and schizo-affective brains were not significantly different from normal controls.

CONCLUSION

These data suggest that previously observed abnormalities in regulation and distribution of ions in bipolar illness may be related to specific alpha 2 dysregulation.

Leukocyte transmembrane potential in bipolar illness

Abnormalities in ion regulation and distribution are commonly reported in bipolar disorder. In an effort to determine if these alter cellular physiological function, we determined the transmembrane potential (TMP) in mononuclear leukocytes from normal individuals and patients with bipolar illness either during normal phase or manic and hypomanic episodes. TMP was analyzed by flow cytometry using dihexyloxacarbocyanine iodide (DIOC6(3)), a cationic potential sensitive fluorescent dye. A normal range was established from measurements on leukocytes from 5 control individuals. TMP of manic and hypomanic patients was significantly hyperpolarized (P = 0.0036). The TMP of euthymic bipolar individuals was not different from normal controls. Pathologic moods in bipolar illness may be associated with altered cellular membrane physiology.

An animal model for mania: preliminary results

1. In human bipolar patients mania and bipolar depression are both characterized by decreased membrane Na,K-AtPase activity. Additionally, digoxin neurotoxicity in patients frequently presents with symptoms of mania or depression. 2. These findings suggest that central nervous system Na,K-ATPase inhibition may play a pathophysiologic role in bipolar illness. 3. The authors tested this hypothesis by administering intracerebroventricular (i.c.v.) ouabain to rats at sublethal doses. The authors then measured behavioral activity as total square crossings in an open field. 4. Motoric activity was significantly increased by i.c.v. administration of 5 microliters of ouabain at 10(-3) M. This preliminary study suggests that i.c.v. ouabain administration may provide a useful animal model of mania that is based on observed biochemical changes in humans.

The Na,K-ATPase hypothesis for bipolar illness

A cellular model for bipolar illness is presented. It is propounded that alterations in the activity of the membrane sodium- and potassium-activated adenosine triphosphatase pump (Na,K-ATPase) may be responsible for alterations in neuronal excitability and activity. Specifically, a reduction in Na,K-ATPase activity can lead to both mania and depression by increasing membrane excitability and decreasing neurotransmitter release, respectively. Supporting evidence is reviewed, and clinical and research implications are discussed.

Possible role of endogenous ouabain-like compounds in the pathophysiology of bipolar illness

A large number of studies have documented a mood-state-related decrease in blood cell sodium, potassium-activated adenosine triphosphatase (Na, K-ATPase) activity in acutely ill bipolar patients. While it has been proposed that this enzymatic change may be central to the pathophysiology of bipolar illness, its genesis has remained obscure. Recent advances in the isolation and characterization of endogenously produced ouabain- or digoxin-like compounds suggest a possible mechanism by which these mood-state-related changes can come about. We herein propose that the hypothalamic-pituitary-adrenal dysregulation frequently documented in major mood disorders may underlie a pathological increase in the production of endogenous ouabain-like compounds which excessively suppresses Na, K-ATPase activity and results in pathological mood and energy alteration.

The Na,K-ATPase hypothesis for manic-depression. II. The mechanism of action of lithium

A model as to how lithium may work in the treatment and prevention of manic-depression is presented. Lithium accumulates intracellularly, and accumulates preferentially in more active neurons. Intracellular accumulation of lithium displaces intracellular sodium, which, in turn, decreases intracellular calcium. A decrease of intracellular calcium normalizes neuron activity in both mania and depression. This model is supported by the majority of clinical and experimental data.

The Na,K-ATPase hypothesis for manic-depression. I. General considerations

An hypothesis is presented to explain and integrate experimental and clinical observations on manic-depressive (bipolar or biphasic) psychosis. The model is based on alterations in the activity of the sodium, potassium-activated adenosine triphosphatase (Na, K-ATPase) pump. A reduction in the activity of the Na,K-ATPase can be responsible for both phases of the disorder.

A trial of bendrofluazide in depression

There is evidence that depression may be associated with retention of sodium, and on recovery electrolyte changes return to normal (Shaw, 1966; Elithorn et al., 1966). In the premenstrual syndrome, psychiatric symptoms commonly occur, particularly depression; together with fluid retention. Thiazide diuretics, which cause excretion of water, potassium and sodium, are an effective form of treatment of the syndrome. In consequence, it would seem logical to assess the effects of a thiazide diuretic given to depressed patients.