Chronic lithium and sodium valproate both decrease the concentration of myo-inositol and increase the concentration of inositol monophosphates in rat brain

Cellular and molecular mechanisms of aspartoacylase and its role in Canavan disease

Canavan disease is an autosomal recessive and lethal neurological disorder, characterized by the spongy degeneration of the white matter in the brain. The disease is caused by a deficiency of the cytosolic aspartoacylase (ASPA) enzyme, which catalyzes the hydrolysis of N-acetyl-aspartate (NAA), an abundant brain metabolite, into aspartate and acetate. On the physiological level, the mechanism of pathogenicity remains somewhat obscure, with multiple, not mutually exclusive, suggested hypotheses. At the molecular level, recent studies have shown that most disease linked ASPA gene variants lead to a structural destabilization and subsequent proteasomal degradation of the ASPA protein variants, and accordingly Canavan disease should in general be considered a protein misfolding disorder. Here, we comprehensively summarize the molecular and cell biology of ASPA, with a particular focus on disease-linked gene variants and the pathophysiology of Canavan disease. We highlight the importance of high-throughput technologies and computational prediction tools for making genotype-phenotype predictions as we await the results of ongoing trials with gene therapy for Canavan disease.

Valproate regulates inositol synthesis by reducing expression of myo-inositol-3-phosphate synthase

Inositol depletion is a hypothesized mechanism of action of mood stabilization drugs used in the treatment of bipolar disorder. It was previously reported that the mood stabilizer valproate (VPA) increased phosphorylation of myo-inositol-3-phosphate synthases (MIPS), the rate limiting enzyme of inositol synthesis. Phosphosites were identified and examination of site-directed mutants suggested that phosphorylation leads to decreased enzymatic activity. In this study, we examined the extent of MIPS phosphorylation in response to VPA and used two interaction screens to identify protein kinases that interact with MIPS. Using an epitope tagged MIPS construct, we determined the fraction of phosphorylated MIPS to be very low (less than 2% of total), and we could not detect phosphorylation of untagged MIPS in response to VPA. In vitro analyses of phosphorylation revealed that putative protein kinases, PKC and CKII, have low specificity toward MIPS. These findings suggest that VPA likely depletes inositol via a mechanism other than MIPS phosphorylation. Consistent with this, mRNA levels of the MIPS-encoding gene INO1 and MIPS protein levels were significantly reduced during the mid-log growth phase in response to VPA treatment. These findings suggest that the mechanism whereby VPA causes inositol depletion is by reducing expression of the rate-limiting enzyme MIPS.

Antisense Oligonucleotide Therapy for the Nervous System: From Bench to Bedside with Emphasis on Pediatric Neurology

Antisense oligonucleotides (ASOs) are disease-modifying agents affecting protein-coding and noncoding ribonucleic acids. Depending on the chemical modification and the location of hybridization, ASOs are able to reduce the level of toxic proteins, increase the level of functional protein, or modify the structure of impaired protein to improve function. There are multiple challenges in delivering ASOs to their site of action. Chemical modifications in the phosphodiester bond, nucleotide sugar, and nucleobase can increase structural thermodynamic stability and prevent ASO degradation. Furthermore, different particles, including viral vectors, conjugated peptides, conjugated antibodies, and nanocarriers, may improve ASO delivery. To date, six ASOs have been approved by the US Food and Drug Administration (FDA) in three neurological disorders: spinal muscular atrophy, Duchenne muscular dystrophy, and polyneuropathy caused by hereditary transthyretin amyloidosis. Ongoing preclinical and clinical studies are assessing the safety and efficacy of ASOs in multiple genetic and acquired neurological conditions. The current review provides an update on underlying mechanisms, design, chemical modifications, and delivery of ASOs. The administration of FDA-approved ASOs in neurological disorders is described, and current evidence on the safety and efficacy of ASOs in other neurological conditions, including pediatric neurological disorders, is reviewed.

Blocking phosphatidylglycerol degradation in yeast defective in cardiolipin remodeling results in a new model of the Barth syndrome cellular phenotype

Barth syndrome (BTHS) is an inherited mitochondrial disorder characterized by a decrease in total cardiolipin and the accumulation of its precursor monolysocardiolipin due to the loss of the transacylase enzyme tafazzin. However, the molecular basis of BTHS pathology is still not well understood. Here we characterize the double mutant pgc1Δtaz1Δ of Saccharomyces cerevisiae deficient in phosphatidylglycerol-specific phospholipase C and tafazzin as a new yeast model of BTHS. Unlike the taz1Δ mutant used to date, this model accumulates phosphatidylglycerol, thus better approximating the human BTHS cells. We demonstrate that increased phosphatidylglycerol in this strain leads to more pronounced mitochondrial respiratory defects and an increased incidence of aberrant mitochondria compared to the single taz1Δ mutant. We also show that the mitochondria of the pgc1Δtaz1Δ mutant exhibit a reduced rate of respiration due to decreased cytochrome c oxidase and ATP synthase activities. Finally, we determined that the mood-stabilizing anticonvulsant valproic acid has a positive effect on both lipid composition and mitochondrial function in these yeast BTHS models. Overall, our results show that the pgc1Δtaz1Δ mutant better mimics the cellular phenotype of BTHS patients than taz1Δ cells, both in terms of lipid composition and the degree of disruption of mitochondrial structure and function. This favors the new model for use in future studies.

Repeated fluoxetine treatment induces transient and long-term astrocytic plasticity in the medial prefrontal cortex of normal adult rats

Fluoxetine (Flx)-induced neuronal plasticity plays an important role in the effective treatment of depression and mood disorders. It is less understood whether repeated Flx treatment induces astrocytic plasticity that outlasts the presence of the drug in the body. We showed previously that Flx-induced neuronal plasticity in the medial prefrontal cortex (mPFC) persisted up to 20 days after the treatment. In this study, adult rats were subjected to a 15-day repeated Flx treatment at a daily dose of 20 mg/kg body weight. Astrocytic metabolites and markers were assessed in the mPFC at day 1 (d1) and day 20 (d20) after the treatment. Significant transient reductions in the concentrations of astrocytic metabolites taurine and myo-inositol and the expressions of glial fibrillary acidic protein (GFAP) and aquaporin-4 (AQP4) were observed in the mPFC of Flx-treated rats at d1, which recovered to the control levels at d20. Further, Flx treatment resulted in long-lasting changes in Kir4.1 expression in the mPFC, which remained downregulated at d20. The expression of 5-HT_1A receptor in the mPFC of Flx-treated rats was downregulated at d1 but became upregulated at d20. In summary, repeated Flx treatment induces both transient and long-term astrocytic plasticity in the mPFC of adult rats. The changes observed at d1 are consistent with disturbed water homeostasis and astrocytic de-maturation in the mPFC. The persistent changes in the expressions of Kir4.1 and 5-HT_1A at d20, presumably of the astrocytic origin, might have contributed to the long-term neurotrophic effects of repeated Flx treatment in the mPFC.

Transcriptional analysis of sodium valproate in a serotonergic cell line reveals gene regulation through both HDAC inhibition-dependent and independent mechanisms

Sodium valproate (VPA) is a histone deacetylase (HDAC) inhibitor, widely prescribed in the treatment of bipolar disorder, and yet the precise modes of therapeutic action for this drug are not fully understood. After exposure of the rat serotonergic cell line RN46A to VPA, RNA-sequencing (RNA-Seq) analysis showed widespread changes in gene expression. Analysis by four bioinformatic pipelines revealed as many as 230 genes were significantly upregulated and 72 genes were significantly downregulated. A subset of 23 differentially expressed genes was selected for validation using the nCounter® platform, and of these we obtained robust validation for ADAM23, LSP1, MAOB, MMP13, PAK3, SERPINB2, SNAP91, WNT6, and ZCCHC12. We investigated the effect of lithium on this subset and found four genes, CDKN1C, LSP1, SERPINB2, and WNT6 co-regulated by lithium and VPA. We also explored the effects of other HDAC inhibitors and the VPA analogue valpromide on the subset of 23 selected genes. Expression of eight of these genes, CDKN1C, MAOB, MMP13, NGFR, SHANK3, VGF, WNT6 and ZCCHC12, was modified by HDAC inhibition, whereas others did not appear to respond to several HDAC inhibitors tested. These results suggest VPA may regulate genes through both HDAC-dependent and independent mechanisms. Understanding the broader gene regulatory effects of VPA in this serotonergic cell model should provide insights into how this drug works and whether other HDAC inhibitor compounds may have similar gene regulatory effects, as well as highlighting molecular processes that may underlie regulation of mood.

In-silico studies on Myo inositol-1-phosphate synthase of Leishmania donovani in search of anti-leishmaniasis

Myo-inositol is one of the vital nutritional requirements for the Leishmania parasites' survival and virulence in the mammalian host. . Myo-inositol-1-phosphate synthase (MIPS) is responsible for the synthesis of myo-inositol in Leishmania, which plays a vital role in Leishmania's virulence to mammalian hosts. Earlier studies suggest MIP synthase as a potential drug target against which valproate was used as a drug. So, MIP synthase can be used as a target for anti-leishmanial drugs, and its inhibition may help in preventing leishmaniasis. The present study aims to identify valproate's potent analogs as drugs against MIP synthase of L. donovani (Ld-MIPS) with minimum side effects and toxicity to host.In this study, the three-dimensional structure of Ld-MIPS was built, followed by active site prediction. Ligand-based virtual screening was done using hybrid similarity recognition methods. The best 123 valproate analogs were filtered based on their quantitative structure activity relationship (QSAR) properties and were docked against Ld-MIPS using FlexX, PyRx and iGEMDOCK software. The topmost five ligands were selected for molecular dynamics simulation and pharmacokinetic analysis based on the docking score. Simulation studies up to 30 ns revealed that all five lead molecules bound with Ld-MIPS throughout MD simulation and there was no variation in their backbone. All the chosen inhibitors exhibited good pharmacokinetics/ADMET predictions with an excellent absorption profile, metabolism, oral bioavailability, solubility, excretion, and minimal toxicity, suggesting that these inhibitors may further be developed as anti-leishmaniasis drugs to prevent the spread of leishmaniasis.Communicated by Ramaswamy H. Sarma.

Optical coherence tomography and neurodegeneration in epilepsy

PURPOSE

To compare optical coherence tomography measurements; central macular thickness, ganglion cell complex, and retinal nerve fiber layer thickness in patients with epilepsy versus healthy controls.

METHODS

We evaluated 28 eyes of 28 patients with epilepsy and 34 eyes of 34 healthy subjects. Central macular thickness, ganglion cell complex, and retinal nerve fiber layer thickness measurements were performed by spectral-domain optical coherence tomography.

RESULTS

Superior and superotemporal quadrant ganglion cell complex, average, and superior quadrant retinal nerve fiber layer thickness measurements were significantly lower in epilepsy group compared to healthy control subjects. Central macular thickness was significantly lower in polytherapy group compared to monotherapy group. Ganglion cell complex and retinal nerve fiber layer thickness measurements were not significantly different between polytherapy and monotherapy groups.

CONCLUSION

The present study shows that epileptic patients taking antiepileptic drugs have reduced ganglion cell complex and retinal nerve fiber layer thickness compared to healthy controls. This can be related to the epileptic process in the brain. Optical coherence tomography may be a useful tool for showing the neurodegeneration in patients with epilepsy.

Direct Reprogramming of Human Neurons Identifies MARCKSL1 as a Pathogenic Mediator of Valproic Acid-Induced Teratogenicity

Human pluripotent stem cells can be rapidly converted into functional neurons by ectopic expression of proneural transcription factors. Here we show that directly reprogrammed neurons, despite their rapid maturation kinetics, can model teratogenic mechanisms that specifically affect early neurodevelopment. We delineated distinct phases of in vitro maturation during reprogramming of human neurons and assessed the cellular phenotypes of valproic acid (VPA), a teratogenic drug. VPA exposure caused chronic impairment of dendritic morphology and functional properties of developing neurons, but not those of mature neurons. These pathogenic effects were associated with VPA-mediated inhibition of the histone deacetylase (HDAC) and glycogen synthase kinase-3 (GSK-3) pathways, which caused transcriptional downregulation of many genes, including MARCKSL1, an actin-stabilizing protein essential for dendritic morphogenesis and synapse maturation during early neurodevelopment. Our findings identify a developmentally restricted pathogenic mechanism of VPA and establish the use of reprogrammed neurons as an effective platform for modeling teratogenic pathways.

Influence of Myo-inositol Plus Ethanolamine on Plasmalogens and Cell Viability during Oxidative Stress

Previously, we demonstrated that treatment of rats with myo-inositol plus ethanolamine (ME) elevated brain ethanolamine plasmalogens (PE-Pls) and protected against phosphine-induced oxidative stress. Here we tested the hypothesis that ME treatment elevates PE-Pls in a neuro-2A (N2A) cell culture system and protects against hydrogen peroxide (H₂O₂)-induced oxidative stress, and we assessed the effects of treatments using myo-inositol with or without (+/-) ethanolamine on ethanolamine phospholipids (PLs) and cell viability following H₂O₂ exposure. Cells were treated with equimolar amounts (500 μM) of myo-inositol, ethanolamine (Etn), or their combination (ME) for 24 h, followed by an additional 24 h exposure to 650 μM H₂O₂. NMR analyses evaluated the treatment effects on Etn PLs, while LC-MS/MS analyses assessed the molecular species of Etn PLs preferentially affected by ME and H₂O₂ treatments, especially PE-Pls and their degradation byproducts-lysophosphatidylethanolamine (LPE) and glycerophosphoethanolamine (GPE). Only ME influenced the cellular levels of PLs. ME yielded a 3-fold increase in PE-Pls and phosphatidylethanolamine (PE) ( p < 0.001) and a preferential 60% increase in PE-Pls containing saturated and monounsaturated fatty acids (SFA+MUFA), while polyunsaturated fatty acid (PUFA) species increased by only 10%. Exposing cells to 650 μM H₂O₂ caused a significant cell death (56% viability), a 27% decrease in PE-Pls, a 201% increase in PUFA-rich LPE, and a ca. 3-fold increase in GPE. H₂O₂ had no impact on PE, suggesting that LPE and GPE were primarily the byproducts of PE-Pls (not PE) degradation. Surprisingly, ME pretreatment ameliorated H₂O₂ effects and significantly increased cell survival to 80% ( p < 0.05). Cellular PE-Pls levels prior to H₂O₂ treatment were highly correlated ( R² = 0.95) with cell survival, suggesting a relationship between PE-Pls and cell protection. Data suggest that a preferential increase in PE-Pls containing SFA+MUFA species may protect cells from oxidative stress. Such studies aid in our understanding of the neuroprotective mechanisms that may be associated with plasmalogens and the relevance of these phospholipids to neurodegenerative diseases/disorders.

Alterations in anterior cingulate cortex myoinositol and aggression in veterans with suicidal behavior: A proton magnetic resonance spectroscopy study

Studies investigating the neurochemical changes that correspond with suicidal behavior (SB) have not yielded conclusive results. Suicide correlates such as aggression have been used to explore risk factors for SB. Yet the neurobiological basis for the association between aggression and SB is unclear. Aggression and SB are both prevalent in veterans relative to civilian populations. The current study evaluated the relationship between brain chemistry in the anterior (ACC) and the posterior cingulate cortex (POC), as well as the relationship between aggression and SB in a veteran population using proton magnetic resonance spectroscopy (¹H-MRS). Single-voxel MRS data at 3 Tesla (T) were acquired from the ACC and POC voxels using a 2-dimensional J-resolved point spectroscopy sequence and quantified using the ProFit algorithm. Participants also completed a structured diagnostic interview and a clinical battery. Our results showed that the myoinositol (mI)/H2O ratio in the ACC and POC was significantly higher in veterans who reported SB when compared to veterans who did not. The two groups did not differ significantly with regard to other metabolites. Second, verbal aggression and SB measures positively correlated with mI/H2O in the ACC. Finally, verbal aggression mediated the relationship between mI/H2O in the ACC and SB.

Application of magnetic resonance spectroscopy in geriatric mood disorders

The prevalence of mood disorders in the rapidly-growing older adult population merits attention due to the likelihood of increased medical comorbidities, risk of hospitalization or institutionalization, and strains placed on caregivers and healthcare providers. Magnetic resonance spectroscopy (MRS) quantifies biochemical compounds in vivo, and has been used specifically for analyses of neural metabolism and bioenergetics in older adults with mood disorders, usually via proton or phosphorous spectroscopy. While yet to be clinically implemented, data gathered from research subjects may help indicate potential biomarkers of disease state or trait or putative drug targets. Three prevailing hypotheses for these mood disorders are used as a framework for the present review, and the current biochemical findings within each are discussed with respect to particular metabolites and brain regions. This review covers studies of MRS in geriatric mood disorders and reveals persisting gaps in research knowledge, especially with regard to older age bipolar disorder. Further MRS work, using higher field strengths and larger sample sizes, is warranted in order to better understand the neurobiology of these prevalent late-life disorders.

Proton spectroscopy of the thalamus in a homogeneous sample of patients with easy-to-control juvenile myoclonic epilepsy

Objective

Juvenile myoclonic epilepsy (JME) is a subtype of genetically determined generalized epilepsy that does not present abnormalities on conventional magnetic resonance imaging. The aim of this study was to identify metabolic alterations in the thalamus in a clinically homogeneous sample of patients with easy-to-control JME, using short-echo time proton magnetic resonance spectroscopy (MRS).

Materials and Methods

We performed single-voxel (2 cm × 2 cm × 2 cm), short-echo time (TE = 35 ms) proton MRS of the thalamus in 21 patients with JME and in 14 healthy age-matched controls. We quantified N-acetylaspartate (NAA), total NAA, creatine (Cr), choline, and myo-inositol (MI), as well as the sum of glutamate and glutamine signals, all scaled to internal water content, and we calculated metabolite ratios using Cr as a reference. Values of p < 0.05 were considered significant.

Results

The MI level and the MI/Cr ratio were significantly lower in the thalami of patients diagnosed with JME than in those of the controls. Other metabolites and their ratios did not differ significantly between the two groups.

Conclusion

In our sample of 21 JME patients, we identified lower levels of MI in the thalamus. No significant abnormalities were observed in the concentrations or ratios of other metabolites.

Tipping the scales: Lessons from simple model systems on inositol imbalance in neurological disorders

Inositol and inositol-containing compounds have signalling and regulatory roles in many cellular processes, suggesting that inositol imbalance may lead to wide-ranging changes in cellular functions. Indeed, changes in inositol-dependent signalling have been implicated in various diseases and cellular functions such as autophagy, and these changes have often been proposed as therapeutic targets. However, few studies have highlighted the links between inositol depletion and the downstream effects on inositol phosphates and phosphoinositides in disease states. For this research, many advances have employed simple model systems that include the social amoeba D. discoideum and the yeast S. cerevisiae, since these models enable a range of experimental approaches that are not possible in mammalian models. In this review, we discuss recent findings initiated in simple model systems and translated to higher model organisms where the effect of altered inositol, inositol phosphate and phosphoinositide levels impact on bipolar disorder, Alzheimer disease, epilepsy and autophagy.

Toward therapeutic targets for SCA3: Insight into the role of Machado-Joseph disease protein ataxin-3 in misfolded proteins clearance

Machado-Joseph disease (MJD, also known as spinocerebellar ataxia type 3, SCA3), an autosomal dominant neurological disorder, is caused by an abnormal expanded polyglutamine (polyQ) repeat in the ataxin-3 protein. The length of the expanded polyQ stretch correlates positively with the severity of the disease and inversely with the age at onset. To date, we cannot fully explain the mechanism underlying neurobiological abnormalities of this disease. Yet, accumulating reports have demonstrated the functions of ataxin-3 protein in the chaperone system, ubiquitin-proteasome system, and aggregation-autophagy, all of which suggest a role of ataxin-3 in the clearance of misfolded proteins. Notably, the SCA3 pathogenic form of ataxin-3 (ataxin-3(exp)) impairs the misfolded protein clearance via mechanisms that are either dependent or independent of its deubiquitinase (DUB) activity, resulting in the accumulation of misfolded proteins and the progressive loss of neurons in SCA3. Some drugs, which have been used as activators/inducers in the chaperone system, ubiquitin-proteasome system, and aggregation-autophagy, have been demonstrated to be efficacious in the relief of neurodegeneration diseases like Huntington's disease (HD), Parkinson's (PD), Alzheimer's (AD) as well as SCA3 in animal models and clinical trials, putting misfolded protein clearance on the list of potential therapeutic targets. Here, we undertake a comprehensive review of the progress in understanding the physiological functions of ataxin-3 in misfolded protein clearance and how the polyQ expansion impairs misfolded protein clearance. We then detail the preclinical studies targeting the elimination of misfolded proteins for SCA3 treatment. We close with future considerations for translating these pre-clinical results into therapies for SCA3 patients.

Age-dependent decreases of high energy phosphates in cerebral gray matter of patients with bipolar I disorder: a preliminary phosphorus-31 magnetic resonance spectroscopic imaging study

OBJECTIVES

To identify abnormalities in high energy phosphate cerebral metabolism in euthymic bipolar disorder.

METHODS

Phosphorus-31 magnetic resonance spectroscopic imaging ((31)P MRSI) data were acquired from the entire brain of 9 euthymic adults with bipolar disorder and 13 healthy adults. Estimates of phosphocreatine (PCr) and adenosine triphosphate (ATP) in homogeneous gray and white matter were obtained by tissue regression analysis.

RESULTS

Analyses of covariance revealed the effect of age to be significantly different between bipolar and healthy groups for concentrations of PCr (p=0.0018) and ATP (p=0.013) in gray matter. These metabolites were negatively correlated with age in gray matter in bipolar subjects while PCr was positively correlated with age in gray matter of healthy subjects. Additionally, age-corrected concentrations of PCr in gray matter were significantly elevated in bipolar subjects (p=0.0048).

LIMITATIONS

Given that this cross-sectional study possessed a small sample and potentially confounding effects of medication status, we recommend a larger, longitudinal study to more robustly study relationships between bioenergetic impairment and duration of disease.

CONCLUSIONS

Our results suggest bioenergetic impairment related to mitochondrial function may be progressive in multi-episode bipolar subjects as they age.

Making the White Matter Matters: Progress in Understanding Canavan's Disease and Therapeutic Interventions Through Eight Decades

Canavan's disease (CD) is a fatal autosomal recessive pediatric leukodystrophy in which patients show severe neurodegeneration and typically die by the age of 10, though life expectancy in patients can be highly variable. Currently, there is no effective treatment for CD; however, gene therapy seems to be a feasible approach to combat the disease. Being a monogenic defect, the disease provides an excellent model system to develop gene therapy approaches that can be extended to other monogenic leukodystrophies and neurodegenerative diseases. CD results from mutations in a single gene aspartoacylase which hydrolyses N-acetyl aspartic acid (NAA) which accumulates in its absences. Since CD is one of the few diseases that show high NAA levels, it can also be used to study the enigmatic biological role of NAA. The disease was first described in 1931, and this review traces the progress made in the past 8 decades to understand the disease by enumerating current hypotheses and ongoing palliative measures to alleviate patient symptoms in the context of the latest advances in the field.

Comparative modeling and virtual screening for the identification of novel inhibitors for myo-inositol-1-phosphate synthase

Myo-inositol-1-phosphate (MIP) synthase is a key enzyme in the myo-inositol biosynthesis pathway. Disruption of the inositol signaling pathway is associated with bipolar disorders. Previous work suggested that MIP synthase could be an attractive target for the development of anti-bipolar drugs. Inhibition of this enzyme could possibly help in reducing the risk of a disease in patients. With this objective, three dimensional structure of the protein was modeled followed by the active site prediction. For the first time, computational studies were carried out to obtain structural insights into the interactive behavior of this enzyme with ligands. Virtual screening was carried out using FILTER, ROCS and EON modules of the OpenEye scientific software. Natural products from the ZINC database were used for the screening process. Resulting compounds were docked into active site of the target protein using FRED (Fast Rigid Exhaustive Docking) and GOLD (Genetic Optimization for Ligand Docking) docking programs. The analysis indicated extensive hydrogen bonding network and hydrophobic interactions which play a significant role in ligand binding. Four compounds are shortlisted and their binding assay analysis is underway.

Molecular actions and clinical pharmacogenetics of lithium therapy

Mood disorders, including bipolar disorder and depression, are relatively common human diseases for which pharmacological treatment options are often not optimal. Among existing pharmacological agents and mood stabilizers used for the treatment of mood disorders, lithium has a unique clinical profile. Lithium has efficacy in the treatment of bipolar disorder generally, and in particular mania, while also being useful in the adjunct treatment of refractory depression. In addition to antimanic and adjunct antidepressant efficacy, lithium is also proven effective in the reduction of suicide and suicidal behaviors. However, only a subset of patients manifests beneficial responses to lithium therapy and the underlying genetic factors of response are not exactly known. Here we discuss preclinical research suggesting mechanisms likely to underlie lithium's therapeutic actions including direct targets inositol monophosphatase and glycogen synthase kinase-3 (GSK-3) among others, as well as indirect actions including modulation of neurotrophic and neurotransmitter systems and circadian function. We follow with a discussion of current knowledge related to the pharmacogenetic underpinnings of effective lithium therapy in patients within this context. Progress in elucidation of genetic factors that may be involved in human response to lithium pharmacology has been slow, and there is still limited conclusive evidence for the role of a particular genetic factor. However, the development of new approaches such as genome-wide association studies (GWAS), and increased use of genetic testing and improved identification of mood disorder patients sub-groups will lead to improved elucidation of relevant genetic factors in the future.

Effects of normal aging and SCN1A risk-gene expression on brain metabolites: evidence for an association between SCN1A and myo-inositol

Previously reported MRS findings in the aging brain include lower N-acetylaspartate (NAA) and higher myo-inositol (mI), total creatine (Cr) and choline-containing compound (Cho) concentrations. Alterations in the sodium channel voltage gated type I, alpha subunit SCN1A variant rs10930201 have been reported to be associated with several neurological disorders with cognitive deficits. MRS studies in SCN1A-related diseases have reported striking differences in the mI concentrations between patients and controls. In a study on 'healthy aging', we investigated metabolite spectra in a sample of 83 healthy volunteers and determined their age dependence. We also investigated a potential link between SCN1A and mI. We observed a significantly negative association of NAA (p = 0.004) and significantly positive associations of mI (p ≤ 0.001), Cr (p ≤ 0.001) and Cho (p = 0.034) with age in frontal white matter. The linear association of Cho ends at the age of about 50 years and is followed by an inverted 'U'-shaped curve. Further, mI was higher in C allele carriers of the SCN1A variant rs10930201. Our results corroborated the age-related changes in metabolite concentrations, and found evidence for a link between SCN1A and frontal white matter mI in healthy subjects.

Inositol-related gene knockouts mimic lithium's effect on mitochondrial function

The inositol-depletion hypothesis proposes that lithium attenuates phosphatidylinositol signaling. Knockout (KO) mice of two genes (IMPA1 or Slc5a3), each encoding for a protein related to inositol metabolism, were studied in comparison with lithium-treated mice. Since we previously demonstrated that these KO mice exhibit a lithium-like neurochemical and behavioral phenotype, here we searched for pathways that may mediate lithium's/the KO effects. We performed a DNA-microarray study searching for pathways affected both by chronic lithium treatment and by the KO of each of the genes. The data were analyzed using three different bioinformatics approaches. We found upregulation of mitochondria-related genes in frontal cortex of lithium-treated, IMPA1 and Slc5a3 KO mice. Three out of seven genes differentially expressed in all three models, Cox5a, Ndufs7, and Ndufab, all members of the mitochondrial electron transfer chain, have previously been associated with bipolar disorder and/or lithium treatment. Upregulation of the expression of these genes was verified by real-time PCR. To further support the link between mitochondrial function and lithium's effect on behavior, we determined the capacity of chronic low-dose rotenone, a mitochondrial respiratory chain complex I inhibitor, to alter lithium-induced behavior as measured by the forced-swim and the amphetamine-induced hyperlocomotion paradigms. Rontenone treatment counteracted lithium's effect on behavior, supporting the proposition suggested by the bioinformatics analysis for a mitochondrial function involvement in behavioral effects of lithium mediated by inositol metabolism alterations.The results provide support for the notion that mitochondrial dysfunction is linked to bipolar disorder and can be ameliorated by lithium. The phenotypic similarities between lithium-treated wild-type mice and the two KO models suggest that lithium may affect behavior by altering inositol metabolism.

Delay of iris flower senescence by cytokinins and jasmonates

It is not known whether tepal senescence in Iris flowers is regulated by hormones. We applied hormones and hormone inhibitors to cut flowers and isolated tepals of Iris × hollandica cv. Blue Magic. Treatments with ethylene or ethylene antagonists indicated lack of ethylene involvement. Auxins or auxin inhibitors also did not change the time to senescence. Abscisic acid (ABA) hastened senescence, but an inhibitor of ABA synthesis (norflurazon) had no effect. Gibberellic acid (GA3 ) slightly delayed senescence in some experiments, but in other experiments it was without effect, and gibberellin inhibitors [ancymidol or 4-hydroxy-5-isopropyl-2-methylphenyltrimethyl ammonium chloride-1-piperidine carboxylate (AMO-1618)] were ineffective as well. Salicylic acid (SA) also had no effect. Ethylene, auxins, GA3 and SA affected flower opening, therefore did reach the flower cells. Jasmonates delayed senescence by about 2.0 days. Similarly, cytokinins delayed senescence by about 1.5-2.0 days. Antagonists of the phosphatidylinositol signal transduction pathway (lithium), calcium channels (niguldipine and verapamil), calmodulin action [fluphenazine, trifluoroperazine, phenoxybenzamide and N-(6-aminohexyl)-5-chloro-1-naphtalenesulfonamide hydrochloride (W-7)] or protein kinase activity [1-(5-isoquinolinesulfonyl)-2-methylpiperazine hydrochloride (H-7), N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide hydrochloride (H-8) and N-(2-aminoethyl)-5-isoquinolinesulfonamide dihydrochloride (H-9)] had no effect on senescence, indicating no role of a few common signal transduction pathways relating to hormone effects on senescence. The results indicate that tepal senescence in Iris cv. Blue Magic is not regulated by endogenous ethylene, auxin, gibberellins or SA. A role of ABA can at present not be excluded. The data suggest the hypothesis that cytokinins and jasmonates are among the natural regulators.

Valproic acid: an anticonvulsant drug with potent antinociceptive and anti-inflammatory properties

Valproic acid (VA) is a major antiepileptic drug, used for several therapeutic indications. It has a wide activity spectrum, reflecting on mechanisms of action that are not fully understood. The objectives of this work were to study the effects of VA on acute models of nociception and inflammation in rodents. VA (0.5, 1, 10, 25, and 50 mg/kg, p.o.) effects were evaluated on the carrageenan-induced paw edema, carrageenan-induced peritonitis, and plantar tests in rats, as well as by the formalin test in mice. The HE staining and immunohistochemistry assay for TNF-α in carrageenan-induced edema, from paws of untreated and VA-treated rats, were also carried out. VA decreased paw edema after carrageenan, and maximum effects were seen with doses equal to or higher than 10 mg/kg. VA also preserved the tissue architecture as assessed by the HE staining. Immunohistochemical studies revealed that VA significantly reduced TNF-α immunostaining in carrageenan-inflamed rat paws. In addition, the anti-inflammatory action of VA was potentiated by pentoxifylline (a phosphodiesterase inhibitor, known to inhibit TNF-α production), but not by sodium butyrate or by suberoylanilide hydroxamic acid (SAHA), nonspecific and specific inhibitors, respectively, of histone deacetylase. However, the decrease in the number of positive TNF-α cells in the rat paw was drastically potentiated in the VA + SAHA associated group. VA also reduced leukocytes and myeloperoxidase (MPO) releases to the peritoneal exudate, in the carrageenan-induced peritonitis. Although in the formalin test, VA inhibited both phases, the inhibition was mainly on the second phase. Furthermore, VA significantly increased the reaction time to thermal stimuli, as assessed by the plantar test. VA is a multi-target drug, presenting potent antinociceptive and anti-inflammatory properties at a lower dose range. These effects are partly dependent upon its inhibitory action on TNF-α-related pathways. However, the participation of the HDAC inhibition with the VA anti-inflammatory action cannot be ruled out. Inflammatory processes are associated with free radical damage and oxidative stress, and their blockade by VA could also explain the present results.

Chronic treatment with lithium or valproate modulates the expression of Homer1b/c and its related genes Shank and Inositol 1,4,5-trisphosphate receptor

Homer proteins are associated with both dopaminergic and glutamatergic function. In addition, these proteins are implicated in many signal transduction pathways that are also putative targets of the mood stabilizers lithium and valproate (VPA). This study investigated the effect of in vivo chronic administration of therapeutically-relevant doses of lithium and VPA on the expression of the inducible (Homer1a and ania-3) and constitutive (Homer1b/c) isoforms of the Homer1 gene in rat brain, and of two other Homer-related genes: Inositol 1,4,5 trisphosphate receptor (IP3R) and Shank. Homer1b/c was significantly decreased in cortex by VPA, and in striatal and accumbal subregions by both lithium and VPA. Both mood stabilizers reduced Homer1b/c expression in the dorsolateral caudate-putamen, while only VPA decreased gene expression in all other striatal subregions. Shank and IP3R were downregulated by both mood stabilizers in the cortex. Neither chronic lithium nor VPA affected Homer immediate-early genes. These results suggest that lithium and VPA similarly modulate the expression of structural postsynaptic genes with topographic specificity in cortical and subcortical regions. Thus, Homer may represent an additional molecular substrate for mood stabilizers, and a potential link with dopaminergic function.

Lithium citrate as treatment of Canavan disease

Canavan disease is a rare autosomal recessive leukodystrophy characterized by abnormal accumulation of N-acetyl aspartate (NAA) in brain white matter. Currently, there is no cure for this disease, and management of patients consists mainly of treating symptoms. We describe a 3-month-old girl who was hospitalized for poor head control and decreased muscle tone. A battery of laboratory and genetic (homozygous mutation p.C218X) analysis revealed the presence of Canavan disease. Lithium citrate was initiated at a dosage of 45 mg/kg per day after diagnosis. Periodic controls of thyroid and liver function, and lithium levels in blood showed that this drug was sure and well tolerated. After 1 year of treatment, NAA levels decreased by approximately 20% in the brain region, urinary NAA levels showed a reduction of 80%, and patient improved alertness and visual tracking but continued with no heat support, axial hypotonia, and spastic diplegia. In our patient, the results obtained after drug administration are important with respect to the decrease in NAA and more discreet in clinical improvement. However, given the absence of adverse effects and limited treatment options, lithium citrate may be a good alternative to stop the progression of the disease and improve the quality of life of patients.

Creatine metabolism and psychiatric disorders: Does creatine supplementation have therapeutic value?

Athletes, body builders, and military personnel use dietary creatine as an ergogenic aid to boost physical performance in sports involving short bursts of high-intensity muscle activity. Lesser known is the essential role creatine, a natural regulator of energy homeostasis, plays in brain function and development. Creatine supplementation has shown promise as a safe, effective, and tolerable adjunct to medication for the treatment of brain-related disorders linked with dysfunctional energy metabolism, such as Huntington's Disease and Parkinson's Disease. Impairments in creatine metabolism have also been implicated in the pathogenesis of psychiatric disorders, leaving clinicians, researchers and patients alike wondering if dietary creatine has therapeutic value for treating mental illness. The present review summarizes the neurobiology of the creatine-phosphocreatine circuit and its relation to psychological stress, schizophrenia, mood and anxiety disorders. While present knowledge of the role of creatine in cognitive and emotional processing is in its infancy, further research on this endogenous metabolite has the potential to advance our understanding of the biological bases of psychopathology and improve current therapeutic strategies.

Synaptic polarity depends on phosphatidylinositol signaling regulated by myo-inositol monophosphatase in Caenorhabditis elegans

Although neurons are highly polarized, how neuronal polarity is generated remains poorly understood. An evolutionarily conserved inositol-producing enzyme myo-inositol monophosphatase (IMPase) is essential for polarized localization of synaptic molecules in Caenorhabditis elegans and can be inhibited by lithium, a drug for bipolar disorder. The synaptic defect of IMPase mutants causes defects in sensory behaviors including thermotaxis. Here we show that the abnormalities of IMPase mutants can be suppressed by mutations in two enzymes, phospholipase Cβ or synaptojanin, which presumably reduce the level of membrane phosphatidylinositol 4,5-bisphosphate (PIP₂). We also found that mutations in phospholipase Cβ conferred resistance to lithium treatment. Our results suggest that reduction of PIP₂ on plasma membrane is a major cause of abnormal synaptic polarity in IMPase mutants and provide the first in vivo evidence that lithium impairs neuronal PIP₂ synthesis through inhibition of IMPase. We propose that the PIP₂ signaling regulated by IMPase plays a novel and fundamental role in the synaptic polarity.

Lithium-induced suicidal erythrocyte death

Lithium (Li+), an effective drug for treatment of bipolar disorders, is known to alter several Ca²+ transporting systems. Increased cellular Ca²+ has in turn been shown to stimulate eryptosis, the suicidal death of erythrocytes. Eryptosis is characterised by exposure of phosphatidylserine (PS) at the erythrocyte surface and by cell shrinkage. The present experiments explored whether Li+ influences eryptosis. In erythrocytes from healthy volunteers, cytosolic Ca²+ activity (Fluo-3 fluorescence), cell volume (forward scatter) and PS exposure (annexin V binding) were determined by fluorescence-activated cell sorting analysis. Exposure to Li+ (≥ 1 mM) did not significantly modify forward scatter but significantly increased cytosolic Ca²+ activity (within 3 h) and annexin binding (within 48 h). The effect was paralleled by increase of cellular adenosine triphosphate concentration. Glucose depletion (24 h) strongly increased PS exposure, an effect significantly enhanced in the presence of Li+ (≥ 1 mM). In conclusion, Li+ triggers suicidal erythrocyte death, an effect at least partially due to increase of cytosolic Ca²+ activity.

Lithium and valproate and their possible effects on themyo-inositol second messenger system in healthy volunteers and bipolar patients

Over 25 years ago it was suggested that the mechanism by which lithium was clinically effective may be due to a stabilizing effect on the phosphoinositol second messenger system (PI-cycle), which has multiple effects within cells. It was proposed that lithium, which is an inhibitor of one of the key enzymes in the PI-cycle, acted to lower myo-inositol concentrations; termed the 'inositol-depletion hypothesis'. Initial animal evidence supported this hypothesis, and also suggested that it was possible that sodium valproate could affect the PI-cycle. Since the first magnetic resonance studies in this area in the early 1990s many studies have examined various aspects of this hypothesis in both healthy volunteers and patients utilizing magnetic resonance spectroscopy (MRS). The present review considers research in this area and concludes that, despite initial promise, current evidence suggests that it is unlikely that either lithium or valproate produce clinically relevant changes in myo-inositol concentrations or the PI-cycle. These findings do not suggest that lithium-induced changes in the PI-cycle are the primary mechanism by which lithium or valproate exert their beneficial clinical effects in bipolar disorder. Nonetheless, given the current technical and clinical limitations of the literature to date, this conclusion cannot be considered completely definitive.

Lithium citrate reduces excessive intra-cerebral N-acetyl aspartate in Canavan disease

Our group has previously reported the first clinical application of lithium in a child affected by Canavan disease. In this study, we aimed to assess the effects of lithium on N-acetyl aspartate (NAA) as well as other end points in a larger cohort. Six patients with clinical, laboratory and genetic confirmation of Canavan disease were recruited and underwent treatment with lithium. The battery of safety and efficacy testing performed before and after sixty days of treatment included Gross Motor Function Testing (GMFM), Magnetic Resonance Imaging (MRI) Proton Magnetic Spectroscopy (H-MRS) as well as blood work. The medication was safe without any clinical or laboratory evidence for toxicity. Parental reports indicated improvement in alertness and social interactions. GMFM did not show statistically significant improvement in motor development. H-MRS documented an overall drop in NAA which was statistically significant in the basal ganglia. T1 measurements recorded on MRI studies suggested a mild improvement in myelination in the frontal white matter after treatment. Diffusion Tensor Imaging was available in two patients and suggested micro-structural improvement in the corpus callosum. The results suggest that lithium administration may be beneficial in patients with Canavan disease.

Valproic acid- and lithium-sensitivity in prs mutants of Saccharomyces cerevisiae

Prs [PRPP (phosphoribosyl pyrophosphate) synthetase] catalyses the transfer of pyrophosphate from ATP to ribose 5-phosphate, thereby activating the pentose sugar for incorporation into purine and pyrimidine nucleotides. The Saccharomyces cerevisiae genome contains five genes, PRS1-PRS5, whose products display characteristic PRPP and bivalent-cation-binding sites of Prs polypeptides. Deletion of one or more of the five PRS genes has far-reaching and unexpected consequences, e.g. impaired cell integrity, temperature-sensitivity and sensitivity to VPA (valproic acid) and LiCl. CTP pools in prs1Delta and prs3Delta are reduced to 12 and 31% of the wild-type respectively, resulting in an imbalance in phospholipid metabolism which may have an impact on the intracellular inositol pool which is affected by the administration of either VPA or LiCl. Overexpression of CTP synthetase in prs1Delta prs3Delta strains partially reverses the VPA-sensitive phenotype. Yeast two-hybrid screening revealed that Prs3 and the yeast orthologue of GSK3 (glycogen synthase kinase 3), Rim11, a serine/threonine kinase involved in several signalling pathways, interact with each other. Furthermore, Prs5, an essential partner of Prs3, which also interacts with GSK3 contains three neighbouring phosphorylation sites, typical of GSK3 activation. These studies on yeast PRPP synthetases bring together and expand the current theories for the mood-stabilizing effects of VPA and LiCl in bipolar disorder.

Lithium and valproate protect against dextro-amphetamine induced brain choline concentration changes in bipolar disorder patients

BACKGROUND

Lithium may affect brain choline concentrations, and this effect has been proposed to potentially explain its clinical efficacy. Since dextro-amphetamine is a useful human model of mania, we were interested in determining firstly whether dextro-amphetamine would alter brain choline concentrations, and secondly to determine if lithium would protect against any such changes in bipolar patients. In addition, we wanted to determine if valproate would also have any effects upon choline levels.

METHODS

Healthy controls (n=18) were compared with euthymic Bipolar Disorder patients (Type I and Type II) who were taking lithium (n=14) or valproate (n=11). We utilized (1)H-magnetic resonance spectroscopy ((1)H-MRS) in a 3.0T scanner to examine brain choline/phosphocholine+creatine (Cho/Cr) ratios. Changes in this ratio were measured to determine any changes in choline concentrations in the temporal lobe.

RESULTS

The results showed that administration of dextro-amphetamine decreased the Cho/Cr ratios. In contrast, in both the lithium-treated and valproate-treated patients this decrease was not seen; this attenuation in the change in Cho/Cr ratio changes was statistically significant. It should be noted that Cho/Cr ratios were significantly higher at baseline in the controls compared to both groups of patients, which may have influenced the results.

CONCLUSIONS

These findings are the first to examine the effects of dextro-amphetamine on brain choline concentrations. They show that while in controls dextro-amphetamine decreases choline concentrations, lithium and valproate both appear to protect against this effect in bipolar patients. However, as brain ratios were measured rather than the absolute concentration of choline, and these ratios were lowered in patients at baseline, these results must be regarded as preliminary and require replication in future studies.

Metabonomic analysis identifies molecular changes associated with the pathophysiology and drug treatment of bipolar disorder

Bipolar affective disorder is a severe and debilitating psychiatric condition characterized by the alternating mood states of mania and depression. Both the molecular pathophysiology of the disorder and the mechanism of action of the mainstays of its treatment remain largely unknown. Here, (1)H NMR spectroscopy-based metabonomic analysis was performed to identify molecular changes in post-mortem brain tissue (dorsolateral prefrontal cortex) of patients with a history of bipolar disorder. The observed changes were then compared to metabolic alterations identified in rat brain following chronic oral treatment with either lithium or valproate. This is the first study to use (1)H NMR spectroscopy to study post-mortem bipolar human brain tissue, and it is the first to compare changes in disease brain with changes induced in rat brain following mood stabilizer treatment. Several metabolites were found to be concordantly altered in both the animal and human tissues. Glutamate levels were increased in post-mortem bipolar brain, while the glutamate/glutamine ratio was decreased following valproate treatment, and gamma-aminobutyric acid levels were increased after lithium treatment, suggesting that the balance of excitatory/inhibitory neurotransmission is central to the disorder. Both creatine and myo-inositol were increased in the post-mortem brain but depleted with the medications. Lastly, the level of N-acetyl aspartate, a clinically important metabolic marker of neuronal viability, was found to be unchanged following chronic mood stabilizer treatment. These findings promise to provide new insight into the pathophysiology of bipolar disorder and may be used to direct research into novel therapeutic strategies.

Rapid beta-oxidation of eicosapentaenoic acid in mouse brain: an in situ study

Analyses of brain phospholipid fatty acid profiles reveal a selective deficiency and enrichment in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), respectively. In order to account for this difference in brain fatty acid levels, we hypothesized that EPA is more rapidly beta-oxidized upon its entry into the brain. Wild-type C57BL/6 mice were perfused with either (14)C-EPA or (14)C-DHA via in situ cerebral perfusion for 40s, followed by a bicarbonate buffer to wash out the residual radiolabeled polyunsaturated fatty acid (PUFA) in the capillaries. (14)C-PUFA-perfused brains were extracted for chemical analyses of neutral lipid and phospholipid fatty acids. Based on the radioactivity in aqueous, total lipid, neutral lipid and phospholipid fractions, volume of distribution (V(D), microl/g) was calculated. The V(D) between (14)C-EPA- and (14)C-DHA-perfused samples was not statistically different for total lipid, neutral lipids or total phospholipids. However, the V(D) of (14)C-EPA in the aqueous fraction was 2.5 times higher than that of (14)C-DHA (p=0.025), suggesting a more extensive beta-oxidation than DHA. Furthermore, radiolabeled palmitoleic acid, a fatty acid that can be synthesized de novo, was detected in brain phospholipids from (14)C-EPA but not from (14)C-DHA-perfused mice suggesting that beta-oxidation products of EPA were recycled into endogenous fatty acid biosynthetic pathways. These findings suggest that low levels of EPA in brain phospholipids compared to DHA may be the result of its rapid beta-oxidation upon uptake by the brain.

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.

Chronic lithium salt treatment reduces CRE/CREB-directed gene transcription and reverses its upregulation by chronic psychosocial stress in transgenic reporter gene mice

The molecular mechanism of action of the mood stabilizer lithium is assumed to involve changes in gene expression leading to neuronal adaptation. The transcription factor CREB (cAMP-responsive element binding protein) regulates the expression of many genes and has been implicated in important brain functions and the action of psychogenic agents. We here investigated the effect of lithium on cAMP-responsive element (CRE)/CREB-mediated gene transcription in the brain, using transgenic reporter mice that express the luciferase reporter gene under the control of four copies of the rat somatostatin gene promoter CRE. Chronic (21 days) but not acute (24 h) treatment with lithium (7.5 mmol/kg) significantly decreased CRE/CREB-directed gene expression in hippocampus, cortex, hypothalamus, and striatum to 60-70%, and likewise reduced CREB phosphorylation. As bipolar disorder is also considered as a stress-related disorder, the effect of lithium was determined in mice submitted to a paradigm for chronic psychosocial stress. As shown before, stress for 25 days significantly increased CRE/CREB-directed gene expression in several brain regions by 100-150%. Treatment of stressed mice with lithium decreased stress-induced CRE/CREB-directed gene expression to control levels in nearly all brain regions and likewise reduced CREB phosphorylation. Chronic lithium treatment induced beta-catenin accumulation and decreased cAMP levels, indicating an inhibitory effect of lithium on glycogen synthase kinase 3 and the adenylate cyclase/protein kinase A signalling cascade, which are known to modulate CREB activity. We here for the first time show that lithium regulates CRE/CREB-directed gene transcription in vivo and suggest CREB as a putative mediator of the neuronal adaptation after chronic lithium treatment.

Mechanisms of action of the mood stabilizer valproate: a focus on GSK-3 inhibition

Valproate is the most widely prescribed antiepileptic drug worldwide, and it is also used in the treatment of bipolar affective disorder, migraine headache and cancer. However, the therapeutic mechanism of action of valproate in these illness states is not understood. This article reviews the pharmacological effects of valproate that may explain its therapeutic efficacy. It focuses on the hypothesis that inhibition of glycogen synthase kinase-3 by valproate is a crucial therapeutic mechanism of this drug in the treatment of bipolar affective disorder. Other cellular pathways and signaling molecules that are targets of valproate (such as inositol de novo biosynthesis, histone deacetylase, protein kinase C, γ-aminobutyric acid, the extracellular signal-regulated kinase pathway and others) are also discussed.

Inositol depletion: a good or bad outcome of valproate treatment?

Bipolar affective disorder is a severe and chronic disabling illness affecting 1.5% of the general population. Lithium, valproate and other mood stabilizers are used to treat bipolar disorder; however, these are ineffective for, and not tolerated by, a significant percentage of patients, underscoring the urgent need for better medications. Although not universally accepted, the inositol-depletion hypothesis is one of the main hypotheses suggested to explain the therapeutic mechanism of mood-stabilizing drugs. This paper reviews the relevance of the inositol-depletion hypothesis, paying special attention to the inhibition of inositol de novo synthesis by valproate. It also discusses inositol supplementation as a treatment strategy for multiple neurological disorders, including prophylactic use against valproate-induced neural tube defects.

Acute dextro-amphetamine administration does not alter brain myo-inositol levels in humans and animals: MRS investigations at 3 and 18.8 T

The pathophysiological underpinnings of bipolar disorder are not fully understood. However, they may be due in part to changes in the phosphatidylinositol second messenger system (PI-cycle) generally, or changes in myo-inositol concentrations more specifically. Dextro-amphetamine has been used as a model for mania in several human studies as it causes similar subjective and physiological symptoms. We wanted to determine if dextro-amphetamine altered myo-inositol concentrations in vivo as it would clearly define a mechanism linking putative changes in the PI-cycle to the subjective psychological changes seen with dextro-amphetamine administration. Fifteen healthy human volunteers received a baseline scan, followed by second scan 75 min after receiving a 25 mg oral dose of dextro-amphetamine. Stimulated echo proton magnetic resonance spectroscopy (MRS) scans were preformed at 3.0 Tesla (T) in the dorsal medial prefrontal cortex (DMPFC). Metabolite data were adjusted for tissue composition and analyzed using LCModel. Twelve adult male rats were treated acutely with a 5-mg/kg intraperitoneal dose of dextro-amphetamine. After 1 h rats were decapitated and the brains were rapidly removed and frozen until dissection. Rat brains were dissected into frontal, temporal, and occipital cortical areas, as well as hippocampus. Tissue was analyzed using a Varian 18.8 T spectrometer. Metabolites were identified and quantified using Chenomx Profiler software. The main finding in the present study was that myo-inositol concentrations in the DMPFC of human volunteers and in the four rat brain regions were not altered by acute dextro-amphetamine. While it remains possible that the PI-cycle may be involved in the pathophysiology of bipolar disorder, it is not likely that the subjective and physiological of dextro-amphetamine are mediated, directly or indirectly, via alternations in myo-inositol concentrations.

The mood stabilizer valproate inhibits both inositol- and diacylglycerol-signaling pathways in Caenorhabditis elegans

The antiepileptic valproate (VPA) is widely used in the treatment of bipolar disorder, although the mechanism of its action in the disorder is unclear. We show here that VPA inhibits both inositol phosphate and diacylglycerol (DAG) signaling in Caenorhabditis elegans. VPA disrupts two behaviors regulated by the inositol-1,4,5-trisphosphate (IP(3)): defecation and ovulation. VPA also inhibits two activities regulated by DAG signaling: acetylcholine release and egg laying. The effects of VPA on DAG signaling are relieved by phorbol ester, a DAG analogue, suggesting that VPA acts to inhibit DAG production. VPA reduces levels of DAG and inositol-1-phosphate, but phosphatidylinositol-4,5-bisphosphate (PIP(2)) is slightly increased, suggesting that phospholipase C-mediated hydrolysis of PIP(2) to form DAG and IP(3) is defective in the presence of VPA.

Mitochondrial DNA-dependent effects of valproate on mitochondrial calcium levels in transmitochondrial cybrids

Calcium plays important roles in various cellular processes. Using transmitochondrial hybrid cells (cybrids) carrying fluorescent calcium indicators, we previously found two mitochondrial DNA (mtDNA) polymorphism sites, 8701 and 10398, that alter intracellular calcium signalling and mitochondrial pH. The 10398A polymorphism is reportedly associated with bipolar disorder, Parkinson's disease, Alzheimer's disease, and cancer, whereas 10398G is associated with longevity. In bipolar disorder, elevation of intracellular calcium levels in the platelets and lymphocytes is a well-replicated finding. Thus, we examined whether two mood stabilizers, lithium and valproate, affect the intracellular calcium signalling in cybrids with these mtDNA polymorphisms. After cybrids with 8701A/10398A and 8701G/10398G (three cell lines for each) derived from healthy controls were pretreated with lithium (0.75 mm or 1.5 mm) or valproate (0.6 mm or 1.2 mm) for 7 d, they were stimulated by 10 mum histamine. Valproate decreased mitochondrial calcium levels, compared with untreated cybrids, only in cybrids with 8701A/10398A. Moreover, valproate decreased cytosolic calcium levels at plateau after stimulation in cybrids with 8701A/10398A. These finding suggest that valproate may stabilize intracellular calcium only in cells with high mitochondrial calcium levels.

Cellular plasticity cascades in the pathophysiology and treatment of bipolar disorder

Bipolar disorder (BPD) is characterized by recurrent episodes of disturbed affect including mania and depression as well as changes in psychovegetative function, cognitive performance, and general health. A growing body of data suggests that BPD arises from abnormalities in synaptic and neuronal plasticity cascades, leading to aberrant information processing in critical synapses and circuits. Thus, these illnesses can best be conceptualized as genetically influenced disorders of synapses and circuits rather than simply as deficits or excesses in individual neurotransmitters. In addition, commonly used mood-stabilizing drugs that are effective in treating BPD have been shown to target intracellular signaling pathways that control synaptic plasticity and cellular resilience. In this article we draw on clinical, preclinical, neuroimaging, and post-mortem data to discuss the neurobiology of BPD within a conceptual framework while highlighting the role of neuroplasticity in the pathophysiology and treatment of this disorder.