Activity of erythrocyte Na,K-ATPase in manic patients

Imipramine Can Be Effective on Depressive-Like Behaviors, but Not on Neurotrophic Factor Levels in an Animal Model for Bipolar Disorder Induced by Ouabain

INTRODUCTION

Despite possible risks of mania switching with the long-term use of antidepressants in patients with bipolar disorder (BD), these drugs may help in depressive episodes. Alterations in neurotrophic factor levels seem to be involved in the pathophysiology of BD. The present study aimed to evaluate the effect of acute treatment of imipramine on behavior and neurotrophic levels in rats submitted to the animal model for BD induced by ouabain.

METHODS

Wistar rats received a single intracerebroventricular (ICV) injection of artificial cerebrospinal fluid or ouabain (10^-3 M). Following the ICV administration, the rats were treated for 14 days with saline (NaCl 0.9%, i.p.), lithium (47.5 mg/kg, i.p.), or valproate (200 mg/kg, i.p.). On the 13^th and 14^th days of treatment, the animals received an additional injection of saline or imipramine (10 mg/kg, i.p.). Behavior tests were evaluated 7 and 14 days after ICV injection. Adrenal gland weight and concentrations of ACTH were evaluated. Levels of neurotrophins BDNF, NGF, NT-3, and GDNF were measured in the frontal cortex and hippocampus by ELISA test.

RESULTS

The administration of ouabain induced mania- and depressive-like behavior in the animals 7 and 14 days after ICV, respectively. The treatment with lithium and valproate reversed the mania-like behavior. All treatments were able to reverse most of the depressive-like behaviors induced by ouabain. Moreover, ouabain increased HPA-axis parameters in serum and decreased the neurotrophin levels in the frontal cortex and hippocampus. All treatments, except imipramine, reversed these alterations.

CONCLUSION

It can be suggested that acute administration of imipramine alone can be effective on depressive-like symptoms but not on neurotrophic factor alterations present in BD.

Na+/K+-ATPase and lipid peroxidation in forebrain cortex and hippocampus of sleep-deprived rats treated with therapeutic lithium concentration for different periods of time

Lithium (Li) is a typical mood stabilizer and the first choice for treatment of bipolar disorder (BD). Despite an extensive clinical use of Li, its mechanisms of action remain widely different and debated. In this work, we studied the time-course of the therapeutic Li effects on ouabain-sensitive Na⁺/K⁺-ATPase in forebrain cortex and hippocampus of rats exposed to 3-day sleep deprivation (SD). We also monitored lipid peroxidation as malondialdehyde (MDA) production. In samples of plasma collected from all experimental groups of animals, Li concentrations were followed by ICP-MS. The acute (1 day), short-term (7 days) and chronic (28 days) treatment of rats with Li resulted in large decrease of Na⁺/K⁺-ATPase activity in both brain parts. At the same time, SD of control, Li-untreated rats increased Na⁺/K⁺-ATPase along with increased production of MDA. The SD-induced increase of Na⁺/K⁺-ATPase and MDA was attenuated in Li-treated rats. While SD results in a positive change of Na⁺/K⁺-ATPase, the inhibitory effect of Li treatment may be interpreted as a pharmacological mechanism causing a normalization of the stress-induced shift and return the Na⁺/K⁺-ATPase back to control level. We conclude that SD alone up-regulates Na⁺/K⁺-ATPase together with increased peroxidative damage of lipids. Chronic treatment of rats with Li before SD, protects the brain tissue against this type of damage and decreases Na⁺/K⁺-ATPase level back to control level.

Pathways-based analyses of whole-genome association study data in bipolar disorder reveal genes mediating ion channel activity and synaptic neurotransmission

Despite known heritability, the complex genetic architecture of bipolar disorder (likely including trait, locus and allelic heterogeneity, as well as genetic interactions) has confounded genetic discovery for many years. Even modern day whole genome association studies (WGAS) using over half a million common SNPs have implicated only a handful of genes at the genomewide level. Temporally coincident with this series of WGAS, a host of pathways-based analyses (PBAs) have emerged as novel computational approaches in the examination of large-scale datasets, but thus far rarely have been applied to WGAS data in psychiatric disorders. Here, we report a series of PBAs conducted using exploratory visual analysis, an analytic and visualization software tool for examining genomic data, to examine results from the National Institutes of Mental Health and Wellcome-Trust Case Control Consortium WGAS in bipolar disorder. Consistent with a host of prior linkage findings, some candidate gene association studies, and recent WGAS, our strongest findings suggest involvement of ion channel structural and regulatory genes, including voltage-gated ion channels and the broader ion channel group that comprises both voltage- and ligand-gated channels. Moreover, we found only modest overlap in the particular genes driving the significance of these gene sets across the analyses. This observation strongly suggests that variation in ion channel genes, as a class of genes, may contribute to the susceptibility of bipolar disorder and that heterogeneity may figure prominently in the genetic architecture of this susceptibility.

Effect of lithium and sodium valproate ions on resting membrane potentials in neurons: an hypothesis

In an attempt to understand the therapeutic effects of lithium and sodium valproate in stabilizing the moods in manic depressive illness, the well-known Goldman-Hodgkin-Katz (G-H-K) equation is modified to include a fourth ion, such as a lithium ion or a sodium ion. The modified G-H-K equation is used to calculate the resting membrane potential in neurons. These calculations show that the resting membrane potential is depolarized depending upon the relative concentration of the lithium ion and upon its relative permeability. These calculations suggest that the resting membrane potential may be hyperpolarized in bipolar patients before treatment, and that the lithium ion perhaps depolarizes the resting membrane potential back to the normal level. They further support the prevailing hypothesis that manic-depressive illness may be caused by the hyperpolarization of the resting membrane potential, which, in turn, may be caused by the changes in ionic conductance (permeability) of the membranes. Sodium ions in sodium valproate do not significantly affect the resting membrane potential since they do not significantly change in the serum.

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.

The upregulation of Na+,K(+)-ATPase pump numbers in lymphocytes from the first-degree unaffected relatives of patients with manic depressive psychosis in response to in vitro lithium and sodium ethacrynate

Patients with manic depressive disorder (DSM-III-R bipolar disorder) have an abnormality of the Na+,K(+)-ATPase pumps in their lymphocytes: the pump numbers do not upregulate to stimulation with lithium and ethacrynate. We have now investigated the in vitro adaptive responses of lymphocyte Na+,K(+)-ATPase pumps in the first-degree unaffected relatives of patients with a clear history of manic depressive disorder. The lymphocytes of the healthy relatives upregulated their Na+,K(+)-ATPase pumps normally, suggesting that the abnormal response that we have previously observed in patients with the disorder reflects a complex relation between the biochemical phenotype and the development of clinical symptoms.

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.

Cation transport mediated by Na+,K(+)-adenosine triphosphatase in lymphoblastoma cells from patients with bipolar I disorder, their relatives, and unrelated control subjects

In an investigation of cation transport in bipolar affective disorder, we have measured parameters related to Na+,K(+)-adenosine triphosphatase, the enzyme that carries out active transport of sodium and potassium, in lymphoblastoid cells cultured from patients with bipolar affective disorder, age-matched nonaffected family relatives, and unrelated control subjects. Patients had lower ion transport per cell and per transport enzyme site than did related or unrelated control subjects. The rate of transport per cell appeared higher in nonaffected relatives of patients than in unrelated control subjects, though this difference did not reach significance. These data suggest that abnormally regulated ion transport may be associated with bipolar affective disorder independently of clinical state.

Erythrocyte membrane structure in bipolar affective disorder: a non-replication

Fifteen bipolar patients were compared with sixteen controls in an attempt to replicate the findings of Pettegrew et al. in 1982 of decreased fluidity in the hydrocarbon core of the erythrocyte membrane. No significant differences were seen between groups. The present control group shows very similar membrane characteristics to the original control series; however, the bipolar patient group is not similar. Possible explanations are discussed.

Erythrocyte membrane sodium-potassium adenosine triphosphatase activity in affective disorders

Erythrocyte membrane Na+,K(+)-ATPase activity was studied in drug naive patients with bipolar (BP) mania (n = 62) and unipolar (UP) depression (n = 60) and normal controls (n = 66). Compared to controls there was a significantly decreased Na+,K(+)-ATPase activity in UP depressives but no change in BP manics. However, lithium treatment caused a significant increase in Na+,K(+)-ATPase activity although there was no correlation between plasma lithium levels and enzyme activity. Plasma cortisol correlated inversely with Na+,K(+)-ATPase in UP depressives. Interestingly, the lithium responders [less than 50% Beck Rafaelson's Mania Rating Scale (BRMS) score] showed a significant increase in Na+,K(+)-ATPase activity compared to lithium nonresponders (greater than 50% BRMS score). These observations indicate that monitoring of Na+,K(+)-ATPase activity during lithium therapy is useful to predict a therapeutic response.

Altered in vitro adaptive responses of lymphocyte Na+,K(+)-ATPase in patients with manic depressive psychosis

When lymphocytes from healthy subjects are incubated in lithium (8 mM) or ethacrynate (1 microM) they show a time-dependent adaptive response, which consists of a significant increase in the number of Na+,K(+)-ATPase molecules in the lymphocyte membrane. We have studied the lymphocytes from nine euthymic drug-free patients with a history of manic depressive psychosis, and have found that this normal adaptive response was absent. It was also absent from the lymphocytes of euthymic patients taking lithium. We conclude that this altered in vitro adaptive response of lymphocyte Na+,K(+)-ATPase represents an enduring trait marker in manic depressive psychosis.

The effect of lithium on cation transport measured in vivo in patients suffering from bipolar affective illness

We have investigated cation transport in vivo in patients being treated with lithium for bipolar affective illness by studying the disposition of rubidium after an oral load of rubidium chloride. The rate of erythrocyte cation transport was increased in the patients when compared with matched healthy volunteers. However, the rate of in-vivo erythrocyte rubidium accumulation in the euthymic treated patients was significantly lower than in a matched group of unmedicated manic patients. The regulation of specific pathways for cation transport may be altered in individuals predisposed to affective illness.

The measurement of transmembrane cation transport in vivo in acute manic illness

We have used a novel technique to assess the transport of cations across the erythrocyte membrane in vivo in unmedicated patients suffering an acute manic illness. The results show that erythrocyte cation transport via the sodium-pump enzyme Na+,K+-ATPase is increased in manic patients compared with healthy controls.

A review of the biochemical and neuropharmacological actions of lithium

The pharmacological actions central to the therapeutic effects of lithium have not yet been established, despite almost 40 years of clinical use and scientific investigation. We review the biochemical and neuropharmacological data relating to this problem and attempt to identify profitable areas for further research.

Erythrocyte 3H-ouabain binding and digitalis treatment in ethanol addicted patients

The binding of 3H-ouabain to human erythrocytes was analyzed in a population of hospitalized male ethanol addicted patients under long term digitalis treatment. In the non-alcoholic patient group the long term digitalis treatment induced an increase in Bmax and Kd values; such modification was not observed in the alcoholic patients. Chronic alcohol intake itself induced an increase in 3H-ouabain kinetic parameters. These observations confirm that ouabain binding to human erythrocytes is subject to pharmacological and toxicological regulation and that adaptive changes in peripheral tissues can be useful in predicting possible parallel modifications in other less accessible tissues.

Erythrocyte membrane sodium-potassium and magnesium ATPase in primary affective disorder

Erythrocyte membrane Mg2+ ATPase and Na+-K+ ATPase were measured in patients with affective disorder, their well relatives, and normal controls during euthymic moods. On the average, the Mg2+ ATPase activity was high in subjects belonging to affective disorder families. However, the difference between normal and affective disordered individuals was not statistically significant. Only the well individuals from affective disorder pedigrees as a group had significantly higher than normal Mg2+ ATPase activity (p less than 0.05). The Na+-K+ ATPase activity was similar for all the groups, including normal, bipolar manic-depressive (with or without lithium), unipolar depressive, and well individuals. Lithium treatment did not seem to have any effect on Mg2+ ATPase. Even though the values of Na+-K+ ATPase in the lithium-treated group were high, it is not certain that this was due to lithium per se.

Especial considerations for neurotoxicological research

In recent years, there has been much impetus toward a definition of behavior in terms of underlying biological events. Such correlations have been attempted in several areas ranging from learning and memory to neurological disease. Increased information concerning the relation between behavior and neurobiological mechanisms is especially important in the area of neurotoxicology. It is often abnormal behavior that is a first sign of exposure to a neurotoxic agent and such changes may give clues as to the anatomical or chemical sites of attack on the nervous system. These clues might also lead to the development of a therapeutic treatment as to the development of tests designed to reveal exposure to a toxic agent at levels below those causing gross behavioral change. Unfortunately, there is a relatively small amount of literature reporting on both behavioral and biological disturbances caused by a toxic agent in the same experimental animal. However, a variety of methodological advances combined with a growing interest in neurotoxicology is gradually changing this. Increased information concerning the role of defined nerve pathways and the means of action of their chemical constituents offers an opportunity to bring about a deepening understanding of neurotoxic events. This review will suggest how new pharmacological findings can be applied to neurotoxicology. Examples of human and animal exposure to toxic materials will be used and current problems will be shown to be major determinants of future research directions.

Tissue vanadium levels in manic-depressive psychosis

The vanadium content of hair, whole blood, serum and urine was estimated by neutron activation analysis in samples from manic patients, depressed patients, recovered manic patients, recovered depressed patients and normal controls. The results suggest that manic patients have significantly raised vanadium levels in hair which fall towards control levels with recovery, but there are no significant differences in the mean vanadium content of whole blood or serum. In contrast, depressed patients have raised levels of vanadium in whole blood and serum which appear to fall with recovery. Levels of vanadium in serum correlate strongly with those in whole blood, but neither shows significant correlation with vanadium in hair for either patients or controls. Hair and blood probably serve as indicator tissues for differing aspects of vanadium metabolism.

Pharmacodynamics and pharmacokinetics of digoxin in the presence of lithium

Previous biochemical and clinical data suggest there may be an interaction between digoxin and lithium. The pharmacodynamics and pharmacokinetics of an intravenous infusion of digoxin were studied in six male subjects before and after 2 weeks treatment with lithium carbonate. The effects of lithium on sodium pump activity, intracellular electrolytes and extracellular electrolytes were studied. No significant interaction between digoxin and lithium was found. No significant effects of lithium on sodium pump activity or electrolyte concentrations were found.