Time-dependent effects of lithium on the agonist-stimulated accumulation of second messenger inositol 1,4,5-trisphosphate in SH-SY5Y human neuroblastoma cells

Common changes in rat cortical gene expression after valproate or lithium treatment particularly affect pre- and post-synaptic pathways that regulate four neurotransmitters systems

OBJECTIVES

We have postulated that common changes in gene expression after treatment with different therapeutic classes of psychotropic drugs contribute to their common therapeutic mechanisms of action.

METHODS

To test this hypothesis, we measured levels of cortical coding and non-coding RNA using GeneChip® Rat Exon 1.0 ST Array after treatment with vehicle (chow only), chow containing 1.8 g lithium carbonate/kg (n = 10) or chow containing 12 g sodium valproate/kg (n = 10) for 28 days. Differences in levels of RNA were identified using JMP Genomics 13 and the Panther Gene Ontology Classification System was used to identify potential consequences of RNA.

RESULTS

Compared to vehicle treatment, levels of cortical RNA for 543 and 583 coding and non-coding RNAs were different after treatment with valproate and lithium, respectively. Moreover, levels of 323 coding and non-coding RNAs were altered in a highly correlated way by treatment with valproate and lithium, changes that would impact on cholinergic, glutamatergic, serotonergic and dopaminergic neurotransmission as well as on voltage gated ion channels.

CONCLUSIONS

Our study suggests that treating with mood stabilisers cause many common changes in levels of RNA which will impact on CNS function, particularly affecting post-synaptic muscarinic receptor functioning and the release of multiple neurotransmitters.

IP3 accumulation and/or inositol depletion: two downstream lithium's effects that may mediate its behavioral and cellular changes

Lithium is the prototype mood stabilizer but its mechanism is still unresolved. Two hypotheses dominate-the consequences of lithium's inhibition of inositol monophosphatase at therapeutically relevant concentrations (the 'inositol depletion' hypothesis), and of glycogen-synthase kinase-3. To further elaborate the inositol depletion hypothesis that did not decisively determine whether inositol depletion per se, or phosphoinositols accumulation induces the beneficial effects, we utilized knockout mice of either of two inositol metabolism-related genes-IMPA1 or SMIT1, both mimic several lithium's behavioral and biochemical effects. We assessed in vivo, under non-agonist-stimulated conditions, ³H-inositol incorporation into brain phosphoinositols and phosphoinositides in wild-type, lithium-treated, IMPA1 and SMIT1 knockout mice. Lithium treatment increased frontal cortex and hippocampal phosphoinositols labeling by several fold, but decreased phosphoinositides labeling in the frontal cortex of the wild-type mice of the IMPA1 colony strain by ~50%. Inositol metabolites were differently affected by IMPA1 and SMIT1 knockout. Inositoltrisphosphate administered intracerebroventricularly affected bipolar-related behaviors and autophagy markers in a lithium-like manner. Namely, IP₃ but not IP₁ reduced the immobility time of wild-type mice in the forced swim test model of antidepressant action by 30%, an effect that was reversed by an antagonist of all three IP₃ receptors; amphetamine-induced hyperlocomotion of wild-type mice (distance traveled) was 35% reduced by IP₃ administration; IP₃ administration increased hippocampal messenger RNA levels of Beclin-1 (required for autophagy execution) and hippocampal and frontal cortex protein levels ratio of Beclin-1/p62 by about threefold (p62 is degraded by autophagy). To conclude, lithium affects the phosphatidylinositol signaling system in two ways: depleting inositol, consequently decreasing phosphoinositides; elevating inositol monophosphate levels followed by phosphoinositols accumulation. Each or both may mediate lithium-induced behavior.

Micropatterning of Porous Silicon Films by Direct Laser Writing

In this study, we demonstrate that porous silicon films can be ablated by the pulsed nitrogen laser of a commercial MALDI mass spectrometer. The extent of laser-induced ablation was found to depend on the doping level and surface chemistry of the porous silicon film. Using direct laser writing with or without a mask, micropatterns were generated on the porous silicon surface. These micropatterns were subsequently used to guide the growth of mammalian cells including neuroblastoma. Excellent selectivity of cell growth toward the laser-ablated regions was established.

Metabolic depression in hibernation and major depression: an explanatory theory and an animal model of depression

Metabolic depression, an adaptive biological process for energy preservation, is responsible for torpor, hibernation and estivation. We propose that a form of metabolic depression, and not mitochondrial dysfunction, is the process underlying the observed hypometabolism, state-dependent neurobiological changes and vegetative symptoms of major depression in humans. The process of metabolic depression is reactivated via differential gene expression in response to perceived adverse stimuli in predisposed persons. Behavior inhibition by temperament, anxiety disorders, genetic vulnerabilities, and early traumatic experiences predispose persons to depression. The proposed theory is supported by similarities in the presentation and neurobiology of hibernation in bears and major depression and explains the yet unexplained neurobiological changes of depression. Although, gene expression is suppressed in other hibernators by deep hypothermia, bears were chosen because they hibernate with mild hypothermia. Pre-hibernation in bears and major depression with atypical features are both characterized by fat storage through overeating, oversleeping, and decreased mobility. Hibernation in bears and major depression with melancholic features are characterized by withdrawal from the environment, lack of energy, loss of weight from not eating and burning stored fat, changes in sleep pattern, and the following similar neurobiological findings: reversible subclinical hypothyroidism; increased concentration of serum cortisol; acute phase protein response; low respiratory quotient; oxidative stress response; decreased neurotransmitter levels; and changes in cyclic-adenosine monophosphate-binding activity. Signaling systems associated with protein phosphorylation, transcription factors, and gene expression are responsible for the metabolic depression process during pre-hibernation and hibernation. Antidepressants and mood stabilizers interfere with the hibernation process and produce their therapeutic effects by normalizing the fluctuation of activities in the different signaling systems, which are down-regulated during hibernation and depression and up-regulated during exodus from hibernation and the hypomanic or manic phase of mood disorders. The ways individuals cognitively perceive, understand, communicate, and react to the vegetative symptoms of depression, from downregulation in energy production, and in the absence of known medical causes, produce the other characteristics of depression including guilt, helplessness, hopelessness, suicidal phenomena, agitation, panic attacks, psychotic symptoms, and sudden switch to hypomanic or manic episodes. The presence of one or more of these characteristics depends on the person's neuropsychological function, its social status between the others, and the other's response to the person. Neurobiological changes associated with metabolic depression during entrance, maintenance, and exodus from hibernation in bears is suggested as a natural animal model of human depression and mood disorders.

Predicting response to lithium in mood disorders: role of genetic polymorphisms

Lithium is considered to be the first choice mood stabilizer in recurrent mood disorders. Its widespread and large-scale use is the result of its proven efficacy. In spite of this fact, patients have been observed to show a variable response to lithium treatment: in some cases it is completely effective in preventing manic or depressive relapses, while in other cases it appears to show no influence on the disease course. The possible definition of a genetic liability profile for adverse effects and efficacy will be of great help, as lithium therapy needs at least 6 months to be effective in stabilizing mood disorders. During the last few years, a number of groups have reported possible liability genes. Lithium long-term prophylactic efficacy has been associated with serotonin transporter protein, tryptophan hydroxylase and inositol polyphosphate 1-phosphatase variants. A number of other candidate genes and anonymous markers did not yield positive associations. Therefore, even if some positive results have been reported, no unequivocal susceptibility gene for lithium efficacy has been identified. Although the available data may not currently allow a meaningful prediction of lithium response, future research is aimed at the development of individualized treament of mood disorders, including the possibility of 'pharmacological genetic counseling'.

Lithium long-term treatment in mood disorders: clinical and genetic predictors

Lithium is the most widely used long-term treatment for recurrent mood disorders. Despite its proven efficacy, patients show a variable response, ranging from complete efficacy to no influence at all. This paper reviews possible predictors of response focusing on molecular genetic studies. The functional polymorphism in the upstream regulatory region of the serotonin transporter gene (5-HTTLPR) has been associated with lithium long-term efficacy in two independent studies, marginal associations have been reported for tryptophan hydroxylase and inositol polyphosphate 1-phosphatase (INPP1). A number of other candidate genes and anonymous markers did not yield positive associations. Therefore, even though some positive results have been reported, no unequivocal susceptibility gene for lithium efficacy has been identified.

Exclusion of the Darier's disease gene, ATP2A2, as a common susceptibility gene for bipolar disorder

Bipolar affective disorder is a genetically complex psychiatric disorder with a population prevalence of approximately 1%. We have previously reported cosegregation of bipolar affective disorder and Darier's disease, a dominant skin disorder with a neuropsychiatric component. The gene for Darier's disease was mapped to chromosome 12q23-q24.1 and linkage studies by us and others have subsequently implicated this region as harbouring a susceptibility gene for bipolar affective disorder. In this study we have investigated the Darier's disease gene ATP2A2, the calcium pumping ATPase SERCA2, as a potential susceptibility gene for bipolar disorder under the hypothesis that variations in SERCA2 have pleiotropic effects in brain. Support for this hypothesis comes from clinical evidence of neuropsychiatric abnormalities in Darier's disease, genetic data produced in our study showing non-random clustering of missense mutations in ATP2A2 in neuropsychiatric Darier patients, and functional data demonstrating the role of SERCA2 in intracellular calcium regulation. In a panel of 15 unrelated bipolar patients from multiply affected families showing increased allele sharing at markers in the 12q23-q24.1 region, we performed mutational screening of the ATP2A2 coding sequence, promoter regions, and 3' untranslated region and identified six sequence variations. These were analysed in a large sample of bipolar patients (n = 324) and control subjects (n = 327). Analysis of allele and genotype distributions for all six variations, and of haplotype frequencies showed no evidence for the involvement of ATP2A2 in producing susceptibility to bipolar disorder.

P2Y2 purinergic and M3 muscarinic acetylcholine receptors activate different phospholipase C-beta isoforms that are uniquely susceptible to protein kinase C-dependent phosphorylation and inactivation

Activation of phospholipase C-beta (PLC-beta) by G protein-coupled receptors typically results in rapid but transient second messenger generation. Although PLC-beta deactivation may contribute to the transient nature of this response, the mechanisms governing PLC-beta deactivation are poorly characterized. We investigated the involvement of protein kinase C (PKC) in the termination of PLC-beta activation induced by endogenous P2Y(2) purinergic receptors and transfected M(3) muscarinic acetylcholine receptors (mAChR) in Chinese hamster ovary cells. Activation of P2Y(2) receptors causes Galpha(q/11) to associate with PLC-beta3, whereas M(3) mAChR activation causes Galpha(q/11) to associate with both PLC-beta1 and PLC-beta3 in these cells. Phosphorylation of PLC-beta3, but not PLC-beta1, is induced by activating either P2Y(2) receptors or M(3) mAChR. We demonstrate that PKC rather than protein kinase A mediates the G protein-coupled receptor-induced phosphorylation of PLC-beta3. The PKC-mediated phosphorylation of PLC-beta3 diminishes the interaction of Galpha(q/11) with PLC-beta3, thereby contributing to the termination PLC-beta3 activity. These findings indicate that the distinct temporal profiles of PLC activation by P2Y(2) receptors and mAChR may arise from the differential activation of PLC-beta1 and PLC-beta3 by the receptors, coupled with a selective PKC-mediated negative feedback mechanism that targets PLC-beta3 but not PLC-beta1.

The high affinity inositol transport system--implications for the pathophysiology and treatment of bipolar disorder

The 'inositol-depletion hypothesis' postulates that the therapeutic effects of lithium are due to inhibition of inositol monophosphatase, which leads to depletion of brain cells of myo-inositol and consequently to dampening of phosphoinositide (PI) signaling. This article examines the potential relevance of an alternative mechanism for inositol depletion: inhibition of myo-inositol uptake that proceeds via the sodium/myo-inositol cotransport (SMIT). We discuss recent in vitro experiments that show a pronounced downregulation of SMIT after chronic treatment with lithium, carbamazepine, and valproate at therapeutically relevant concentrations. It is concluded that downregulation of SMIT could represent a common mechanism of action of mood stabilizers.

ATP2A2 mutations in Darier's disease and their relationship to neuropsychiatric phenotypes

Darier's disease (DD) is a rare, dominantly inherited disorder that affects the skin producing a variety of types of lesion. Close examination of lesional DD skin shows the presence of abnormal keratinization (epidermal differentiation) and acantholysis (loss of cohesion) of keratinocytes. A number of clinical studies have described the co-occurrence of various neurological and psychiatric symptoms with DD, including mood disorders, epilepsy, mental retardation and a slowly progressive encephalopathy. A single locus for DD has been mapped to chromosome 12q23-q24.1, and a variety of missense, nonsense, frameshift and splicing mutations in the ATP2A2 gene have been described recently in families with DD. This gene encodes the sarcoplasmic/endoplasmic reticulum calcium-pumping ATPase SERCA2, which has a central role in intra-cellular calcium signalling. In this study, we performed mutation analysis on ATP2A2 in 19 unrelated DD patients, of whom 10 had neuropsychiatric phenotypes. We identified and verified 17 novel mutations predicting conservative and non-conservative amino acid changes, potential premature translation terminations and potential altered splicing. Our findings confirm that mutations in ATP2A2 are associated with DD. In neuropsychiatric cases, there was a non-random clustering of mutations in the 3' end of the gene ( P = 0.01), and a predominance of the missense type (70% versus 38% in DD patients). This supports the hypothesis that the DD gene has pleiotropic effects in brain and that mutations in SERCA2 are implicated in the pathogenesis of neuropsychiatric disorders.

Lithium reduces tau phosphorylation: effects in living cells and in neurons at therapeutic concentrations

BACKGROUND

The mechanism of action of lithium remains to be determined satisfactorily. Recent studies suggested a possible role in inhibiting glycogen synthase kinase-3 (GSK-3), previously shown to phosphorylate the protein tau. Tau is expressed mainly in neurons, where it functions to stabilize microtubules in a phosphorylation-dependent manner.

METHODS

Neurons and transfected non-neuronal cells were treated with lithium and the phosphorylation of tau at multiple epitopes examined by western blotting and by immunocytochemistry. Using green fluorescent protein as a tag we examined the effects of lithium on phosphorylated tau in living cells.

RESULTS

Lithium reversibly reduced tau phosphorylation at therapeutic concentrations, and even at high concentrations did not alter neuronal morphology. Green fluorescent protein tagged-tau when phosphorylated by GSK-3 was diffusely distributed; treatment with lithium resulted in association with microtubules and then bundle formation. Removing lithium allowed observation of the dissolution of bundles and gradual dissociation of tau from microtubules in living cells.

CONCLUSIONS

Lithium may have multiple effects in brain, but at least one action is demonstrated to be a relative inhibition of GSK-3-induced tau phosphorylation. These results carry implications for future studies of the actions of mood-stabilizing drugs and indeed of the molecular mechanisms of affective disorders.

Effect of concomitant beta-adrenoceptor stimulation on alpha 1-adrenoceptor-mediated increase of inositol-1,4,5-trisphosphate mass in adult rat cardiomyocytes

The aim of the present study was to investigate the accumulation of inositol-1,4,5-trisphosphate (IP3) in isolated adult rat ventricular cardiomyocytes after alpha 1- and beta-adrenoceptor stimulation, separate and in combination, in order to elucidate a possible influence of concomitant beta-adrenoceptor stimulation on the alpha 1-adrenoceptor stimulated response. IP3 was measured by a radioligand binding assay based on an (1,4,5)IP3-specific binding protein from bovine adrenal cortex. The basal IP3 content was 4.06 +/- 0.31 pmol/mg protein (N = 56). alpha 1-Adrenoceptor stimulation resulted in a rapid increase in the IP3 level, which reached a plateau, 50-80% above basal level, at 10-30 sec. The plateau lasted at least up to 120 sec., while at 300 sec. there was no significant difference between control values and values after alpha 1-adrenoceptor stimulation. Li+ did not affect either the basal IP3 level, or the magnitude or time course of alpha 1-adrenoceptor-stimulated IP3 accumulation. Combined adrenoceptor stimulation gave a similar response as separate alpha 1-adrenoceptor stimulation, whereas there was no significant change in the IP3 level after beta-adrenoceptor stimulation. No inhibitory influence of simultaneous beta-adrenoceptor stimulation on the alpha 1-adrenoceptor-stimulated increase of IP3 mass was revealed.

The antibipolar drug valproate mimics lithium in stimulating glutamate release and inositol 1,4,5-trisphosphate accumulation in brain cortex slices but not accumulation of inositol monophosphates and bisphosphates

Valproic acid and lithium are effective antibipolar drugs. We recently showed that lithium stimulated the release of glutamate in monkey and mouse cerebral cortex slices, which, through activation of the N-methyl-D-aspartate receptor, increased accumulation of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]. We show here that valproate behaves similarly to lithium in that at therapeutic concentrations it stimulates glutamate release and Ins(1,4,5)P3 accumulation in mouse cerebral cortex slices. The fact that these two effects are a common denominator for two structurally unrelated antibipolar drugs suggests that these effects are important in their antibipolar action. The effects of maximal concentrations of lithium and valproate on glutamate release are additive, suggesting different mechanisms for release, which are discussed. The additivity of the two drugs on glutamate release is consistent with the clinical benefit of combining the two drugs in the treatment of subsets of bipolar patients, e.g., in rapid cycling manic-depression. Unlike lithium, valproate does not increase accumulation of inositol monophosphates, inositol bisphosphates, or inositol 1,3,4-trisphosphate. This is additional evidence against the "inositol depletion" hypothesis, which states that, by trapping inositol in the form of inositol monophosphates and certain inositol polyphosphates, lithium exerts its antimanic action by inhibiting resynthesis of phosphoinositides with resultant blunting of Ins(1,4,5)P3 signaling.

Phosphoinositide signalling in human neuroblastoma cells: biphasic effect of Li+ on the level of the inositolphosphate second messengers

Lithium has a biphasic effect of the agonist-dependent accumulation of Ins(1,4,5)P3 in human neuroblastoma SH-SY5Y cells. These effects consist of a transient reduction, followed by a long-lasting increase in Ins(1,4,5)P3 as compared to controls. The Li+ effects are dose dependent, and were observed at concentrations used in the treatment of bipolar disorders, and thus may have therapeutic implications. The mechanism of the Li+ effect on Ins(1,4,5)P3 accumulation requires further investigation. The transient reduction of Ins(1,4,5)P3 was observed under conditions where Li+ causes only a moderate increase in the inositol mono- and bi-phosphates. Supplementation with exogenous inositol had no effect on the level of Ins(1,4,5)P3, indicating that the mechanism of the Li(+)-dependent reduction of Ins(1,4,5)P3 is not due to inositol depletion. Li+ did not interfere with degradation of Ins(1,4,5)P3 after receptor-blockage with atropine, suggesting that Li+ has no direct effect on the Ins(1,4,5)P3 metabolizing enzymes. A direct effect of Li+ on the phospholipase C is also unlikely. Entry of Ca2+ into the cells is an important factor, which affects agonist-stimulated accumulation of Ins(1,4,5)P3, as well as absolute values of Li(+)-dependent increase in Ins(1,4,5)P3; however, it is not essential for the manifestation of Li+ effects. Our results also show that manifestation of Li+ effects in human neuroblastoma cells requires the stimulation of muscarinic receptors and activation of PLCs, PKCs, and/or that other staurosporine/H-7/GF 109203X-sensitive protein kinases are involved in the regulation of Ins(1,4,5)P3 during the plateau phase of ACh-stimulation. We also suggest an important role for these enzymes in the Li(+)-dependent elevation of Ins(1,4,5)P3.