Regional changes in rat brain inositol monophosphatase 1 (IMPase 1) activity with chronic lithium treatment

Neural tube defects: role of lithium carbonate exposure in embryonic neural development in a murine model

BACKGROUND

Lithium carbonate (Li₂CO₃) is widely used in the treatment of clinical-affective psychosis. Exposure to Li₂CO₃ during pregnancy increases the risk of neural tube defects (NTDs) in offspring, which are severe birth defects of the central nervous system. The mechanism of Li₂CO₃-induced NTDs remains unclear.

METHODS

C57BL/6 mice were injected with different doses of Li₂CO₃ intraperitoneally on gestational day 7.5 (GD7.5), and embryos collected at GD11.5 and GD13.5. The mechanisms of Li₂CO₃ exposure-induced NTDs were determined utilizing immunohistochemistry, western blotting, EdU imaging, enzymatic method, gas chromatography-mass spectrometry (GC-MS), ELISA and HE staining.

RESULTS

The NTDs incidence was 33.7% following Li₂CO₃ exposure. Neuroepithelial cell proliferation and phosphohistone H3 level were significantly increased in NTDs embryos, compared with control group (P < 0.01), while the expressing levels of p53 and caspase-3 were significantly decreased. IMPase and GSK-3β activity was inhibited in Li₂CO₃-treated maternal and embryonic neural tissues (P < 0.01 and P < 0.05, respectively), along with decreased levels of inositol and metabolites, compared with control groups (P < 0.01).

CONCLUSIONS

Lithium-induced NTDs model in C57BL/6 mice was established. Enhanced cell proliferation and decreased apoptosis following lithium exposure were closely associated with the impairment of inositol biosynthesis, which may contribute to lithium-induced NTDs.

IMPACT

Impairment of inositol biosynthesis has an important role in lithium exposure-induced NTDs in mice model. Lithium-induced NTDs model on C57BL/6 mice was established. Based on this NTDs model, lithium-induced impairment of inositol biosynthesis resulted in the imbalance between cell proliferation and apoptosis, which may contribute to lithium-induced NTDs. Providing evidence to further understand the molecular mechanisms of lithium-induced NTDs and enhancing its primary prevention.

Lithium effects on serine-threonine kinases activity: High throughput kinomic profiling of lymphoblastoid cell lines from excellent-responders and non-responders bipolar patients

Objectives: Lithium is the leading mood stabiliser for maintenance treatment in bipolar disorder (BD). However, response to lithium is heterogeneous with more than 60% of patients experiencing partial or no response. In vitro and in vivo molecular studies have reported the implication of kinases in the pathophysiology of BD.Methods: Since kinases are putative targets for lithium therapeutic action, we conducted the first pilot study using kinase array technology to evaluate the global serine/threonine kinases (STK) profiles in cell lines from BD I subtype patients classified as lithium excellent-responders (ER) and non-responder (NR) to lithium treatment.Results: We found significant differences in the basal STK profiles between ER and NR to lithium. We also tested lithium influence on the global STK profile and found no significant difference between ER vs NR cell lines.Conclusions: The results obtained in this exploratory study suggest that multiplex kinase activity profiling could provide a complementary approach in the study of biomarkers of therapeutic response in BD.

High-Throughput Cell-Based Screening Using Scintillation Proximity Assay for the Discovery of Inositol Phosphatase Inhibitors

Inositol monophosphatase is a potential drug target for developing lithium-mimetic agents for the treatment of bipolar disorder. Enzyme-based assays have been traditionally used in compound screening to identify inositol monophosphatase inhibitors. A cell-based screening assay in which the compound needs to cross the cell membrane before reaching the target enzyme offers a new approach for discovering novel structure leads of the inositol monophosphatase inhibitor. The authors have recently reported a high-throughput measurement of G-protein-coupled receptor activation by determining inositol phosphates in cell extracts using scintillation proximity assay. This cell-based assay has been modified to allow the determination of inositol monophosphatase activity instead of G-protein-coupled receptors. The enzyme is also assayed in its native form and physiological environment. The authors have applied this cell-based assay to the high-throughput screening of a large compound collection and identified several novel inositol monophosphatase inhibitors. ( Journal of Biomolecular Screening 2004:132-140)

Role of autophagy inhibitors and inducers in modulating the toxicity of trimethyltin in neuronal cell cultures

Trimethyltin (TMT) is a triorganotin compound which determines neurodegeneration of specific brain areas particularly damaging the limbic system. Earlier ultrastructural studies indicated the formation of autophagic vacuoles in neurons after TMT intoxication. However, no evaluation has been attempted to determine the role of the autophagic pathway in TMT neurotoxicity. To assess the contribution of autophagy to TMT-induced neuronal cell death, we checked the vulnerability of neuronal cultures to TMT after activation or inhibition of autophagy. Our results show that autophagy inhibitors (3-methyladenine and L-asparagine) greatly enhanced TMT neurotoxicity. Conversely, known activators of autophagy, such as lithium and rapamycin, displayed neuroprotection against this toxic compound. Due to its diverse targets, the action of lithium was complex. When lithium was administered according to a chronic treatment protocol (6 days pretreatment) it was able to rescue both hippocampal and cortical neurons from TMT (or from glutamate toxicity used as reference). This effect was accompanied by an increased phosphorylation of glycogen synthase kinase 3 which is a known target for lithium neuroprotection. If the pre-incubation time was reduced to 2 h (acute treatment protocol), lithium was still able to counteract TMT toxicity in hippocampal but not in cortical neurons. The neuroprotective effect of lithium acutely administered against TMT in hippocampal neurons can be completely reverted by an excess of inositol and is possibly related to the inactivation of inositol monophosphatase, a key regulator of autophagy. These data indicate that TMT neurotoxicity can be dramatically modified, at least in vitro, by lithium addition which seems to act through different mechanisms if acutely or chronically administered.

Interaction networks of lithium and valproate molecular targets reveal a striking enrichment of apoptosis functional clusters and neurotrophin signaling

The overall neurobiological mechanisms by which lithium and valproate stabilize mood in bipolar disorder patients have yet to be fully defined. The therapeutic efficacy and dissimilar chemical structures of these medications suggest that they perturb both shared and disparate cellular processes. To investigate key pathways and functional clusters involved in the global action of lithium and valproate, we generated interaction networks formed by well-supported drug targets. Striking functional similarities emerged. Intersecting nodes in lithium and valproate networks highlighted a strong enrichment of apoptosis clusters and neurotrophin signaling. Other enriched pathways included MAPK, ErbB, insulin, VEGF, Wnt and long-term potentiation indicating a widespread effect of both drugs on diverse signaling systems. MAPK1/3 and AKT1/2 were the most preponderant nodes across pathways suggesting a central role in mediating pathway interactions. The convergence of biological responses unveils a functional signature for lithium and valproate that could be key modulators of their therapeutic efficacy.

Enhanced function of prefrontal serotonin 5-HT(2) receptors in a rat model of psychiatric vulnerability

Prefrontal serotonin 5-HT(2) receptors have been linked to the pathogenesis and treatment of affective disorders, yet their function in psychiatric vulnerability is not known. Here, we examine the effects of 5-HT(2) receptors in a rat model of psychiatric vulnerability using electrophysiology, gene expression, and behavior. Following the early stress of chronic maternal separation, we found that serotonin has atypical 5-HT(2) receptor-mediated excitatory effects in the adult prefrontal cortex that were blocked by the 5-HT(2A) receptor antagonist MDL 100907. In the absence of a serotonergic agonist, the intrinsic excitability of the prefrontal cortex was not enhanced relative to controls. Yet, in response to stimulation of 5-HT(2) receptors, adult animals with a history of early stress exhibit heightened prefrontal network activity in vitro, enhanced immediate early gene expression in vivo, and potentiated head shake behavior. These changes arise in the absence of any major alteration of prefrontal 5-HT(2A/C) mRNA expression or 5-HT(2) receptor binding. Our microarray results and quantitative PCR validation provide insight into the molecular changes that accompany such enhanced 5-HT(2) receptor function in adult animals following early stress. We observed persistent prefrontal transcriptome changes, with significant enrichment of genes involved in cellular developmental processes, regulation of signal transduction, and G-protein signaling. Specific genes regulated by early stress were validated in an independent cohort, and several altered genes were normalized by chronic blockade of 5-HT(2) receptors in adulthood. Together, our results demonstrate enhanced prefrontal 5-HT(2) receptor function and persistent alterations in prefrontal gene expression in a rat model of psychiatric vulnerability.

Effect of prolonged phenytoin administration on rat brain gene expression assessed by DNA microarrays

Preliminary clinical trials have recently shown that phenytoin, an antiepileptic drug, may also be beneficial for treatment of bipolar disorder. To examine molecular mechanisms of action of phenytoin as a potential mood stabilizer, DNA microarrays were used to study the effect of phenytoin on gene expression in the hippocampus and frontal cortex of Sprague-Dawley rats. While our particular interest is in bipolar disorder, this is the first DNA microarray study on the effect of phenytoin in brain tissue, in general. As compared with control rats, treated rats had 508 differentially expressed genes in the hippocampus and 62 in the frontal cortex. Phenytoin modulated the expression of genes which may affect neurotransmission, e.g. glutamate decarboxylase 1 (Gad1) and gamma-aminobutyric acid A receptor, alpha 5 (Gabra5). Phenytoin also exerted an effect on neuroprotection-related genes, namely the survival-promoting and antioxidant genes v-akt murine thymoma viral oncogene homolog 1 (Akt1), FK506 binding protein 12-rapamycin associated protein 1 (Frap1), glutathione reductase (Gsr) and glutamate cysteine ligase catalytic subunit (Gclc). The expression of genes potentially associated with mechanisms of mood regulation such as adenylate cyclase-associated protein 1 (Cap1), Glial Fibrillary Acidic Protein (Gfap) and prodynorphin (Pdyn) was also altered. Some of the above genes are regarded as targets of classical mood stabilizers and their modulation supports the clinical observation that phenytoin may have mood-stabilizing effects. The results may provide new insights regarding the mechanism of action of phenytoin and genes found differentially expressed following phenytoin administration may play a role in the pathophysiology of either bipolar disorder or epilepsy.

Review of lithium effects on brain and blood

Clinicians have long used lithium to treat manic depression. They have also observed that lithium causes granulocytosis and lymphopenia while it enhances immunological activities of monocytes and lymphocytes. In fact, clinicians have long used lithium to treat granulocytopenia resulting from radiation and chemotherapy, to boost immunoglobulins after vaccination, and to enhance natural killer activity. Recent studies revealed a mechanism that ties together these disparate effects of lithium. Lithium acts through multiple pathways to inhibit glycogen synthetase kinase-3beta (GSK3 beta). This enzyme phosphorylates and inhibits nuclear factors that turn on cell growth and protection programs, including the nuclear factor of activated T cells (NFAT) and WNT/beta-catenin. In animals, lithium upregulates neurotrophins, including brain-derived neurotrophic factor (BDNF), nerve growth factor, neurotrophin-3 (NT3), as well as receptors to these growth factors in brain. Lithium also stimulates proliferation of stem cells, including bone marrow and neural stem cells in the subventricular zone, striatum, and forebrain. The stimulation of endogenous neural stem cells may explain why lithium increases brain cell density and volume in patients with bipolar disorders. Lithium also increases brain concentrations of the neuronal markers n-acetyl-aspartate and myoinositol. Lithium also remarkably protects neurons against glutamate, seizures, and apoptosis due to a wide variety of neurotoxins. The effective dose range for lithium is 0.6-1.0 mM in serum and >1.5 mM may be toxic. Serum lithium levels of 1.5-2.0 mM may have mild and reversible toxic effects on kidney, liver, heart, and glands. Serum levels of >2 mM may be associated with neurological symptoms, including cerebellar dysfunction. Prolonged lithium intoxication >2 mM can cause permanent brain damage. Lithium has low mutagenic and carcinogenic risk. Lithium is still the most effective therapy for depression. It "cures" a third of the patients with manic depression, improves the lives of about a third, and is ineffective in about a third. Recent studies suggest that some anticonvulsants (i.e., valproate, carbamapazine, and lamotrigene) may be useful in patients that do not respond to lithium. Lithium has been reported to be beneficial in animal models of brain injury, stroke, Alzheimer's, Huntington's, and Parkinson's diseases, amyotrophic lateral sclerosis (ALS), spinal cord injury, and other conditions. Clinical trials assessing the effects of lithium are under way. A recent clinical trial suggests that lithium stops the progression of ALS.

Brain lithium, N-acetyl aspartate and myo-inositol levels in older adults with bipolar disorder treated with lithium: a lithium-7 and proton magnetic resonance spectroscopy study

OBJECTIVES

We investigated the relationship between brain lithium levels and the metabolites N-acetyl aspartate (NAA) and myo-inositol (myo-Ino) in the anterior cingulate cortex of a group of older adults with bipolar disorder (BD).

METHODS

This cross-sectional assessment included nine subjects (six males and three females) with bipolar I disorder and currently treated with lithium, who were examined at McLean Hospital's Geriatric Psychiatry Research Program and Brain Imaging Center. The subjects' ages ranged from 56 to 85 years (66.0 +/- 9.7 years) and all subjects had measurements of serum and brain lithium levels. Brain lithium levels were assessed using lithium magnetic resonance spectroscopy. All subjects also had proton magnetic resonance spectroscopy to obtain measurements of NAA and myo-Ino.

RESULTS

Brain lithium levels were associated with higher NAA levels [df = (1, 8), Beta = 12.53, t = 4.09, p < 0.005] and higher myo-Ino levels [df = (1, 7), F = 16.81, p < 0.006]. There were no significant effects of serum lithium levels on any of the metabolites.

CONCLUSION

Our findings of a relationship between higher brain lithium levels and elevated NAA levels in older adult subjects with BD may support previous evidence of lithium's neuroprotective, neurotrophic, and mitochondrial function-enhancing effects. Elevated myo-Ino related to elevated brain lithium levels may reflect increased inositol monophosphatase (IMPase) activity, which would lead to an increase in myo-Ino levels. This is the first study to demonstrate alterations in NAA and myo-Ino in a sample of older adults with BD treated with lithium.

MRI study of the cerebellum in young bipolar patients

Prior studies demonstrate structural abnormalities of cerebellar vermis in adult bipolar patients. Cerebella of 16 young bipolar patients (mean age+/-S.D.=15.5+/-3.4) and 21 healthy controls (mean age+/-S.D.=16.9+/-3.8) were examined using magnetic resonance imaging. The volumes of right, left and total cerebellum, vermis, and areas of vermal regions V1 (lobules I-V), V2 (lobules VI-VII), and V3 (lobules VIII-X) were measured. Analysis of covariance, with age, gender, and intra-cranial brain volume as covariates, revealed no significant differences in cerebellum or vermis measures between patients and controls; however, there was a trend to smaller vermis V2 areas in patients (p=0.06). The number of previous affective episodes and vermis area V2 were inversely correlated (partial correlation coefficient=-0.97, P=0.001) in the male bipolar patient group. Our results are preliminary, but consistent with the findings from studies in adult bipolar patients suggesting the involvement of structural changes in cerebellar vermis in the pathophysiology of bipolar disorder.

Transcriptomic approach to the study of osmoregulation in the European eel Anguilla anguilla

In euryhaline teleosts, osmoregulation is a fundamental and dynamic process that is essential for the maintenance of ion and water balance, especially when fish migrate between fresh water (FW) and sea water (SW) environments. The European eel has proved to be an excellent model species to study the molecular and physiological adaptations associated with this osmoregulatory plasticity. The life cycle of the European eel includes two migratory periods, the second being the migration of FW eels back to the Sargasso Sea for reproduction. Various anatomical and physiological changes allow the successful transition to SW. The aim of this study was to use a microarray approach to screen the osmoregulatory tissues of the eel for changes in gene expression following acclimation to SW. Tissues were sampled from fish at selected intervals over a 5-mo period following FW/SW transfer, and RNA was isolated. Suppressive subtractive hybridization was used for enrichment of differentially expressed genes. Microarrays comprising 6,144 cDNAs from brain, gill, intestine, and kidney libraries were hybridized with appropriate targets and analyzed; 229 differentially expressed clones with unique sequences were identified. These clones represented the sequences for 95 known genes, with the remaining sequences (59%) being unknown. The results of the microarray analysis were validated by quantification of 28 differentially expressed genes by Northern blotting. A number of the differentially expressed genes were already known to be involved in osmoregulation, but the functional roles of many others, not normally associated with ion or water transport, remain to be characterized.

Lithium treatment effects on Myo-inositol in adolescents with bipolar depression

BACKGROUND

The neurochemical effects of lithium in adolescents with bipolar disorder largely are unknown. This study used proton magnetic resonance spectroscopy (1H MRS) to identify the in vivo effects of lithium on myo-inositol (mI) concentrations in adolescent bipolar depression.

METHODS

Twenty-eight adolescents (12-18 years old) with bipolar I disorder, current episode depressed, received open-label lithium 30 mg/kg, adjusted to achieve serum levels of 1.0-1.2 mEq/L. The mI concentrations in the medial as well as the left and right lateral prefrontal cortices were measured at baseline, day 7, and day 42 of treatment. Changes in mI concentrations over time were analyzed.

RESULTS

Significant main effects of time were observed for mI concentrations in the medial (p = .03) and right lateral (p = .05) prefrontal cortices. Baseline concentrations of mI were not significantly different from day 7 or day 42 concentrations. However, mI concentrations on day 42 were significantly higher than those on day 7 (p = .02) in both regions.

CONCLUSIONS

This study demonstrates that prefrontal mI concentrations do not significantly change from baseline after acute and chronic lithium treatment in adolescents with bipolar depression. Further investigation of the effect of lithium on mI is warranted to better understand possible mechanisms by which lithium exerts antidepressant activity.

Lithium alters regional rat brain myo-inositol at 2 and 4 weeks: an ex-vivo magnetic resonance spectroscopy study at 18.8 T

Lithium has been the mainstay of treatment for bipolar disorder. Early studies suggest that lithium acts via inositol depletion. This study assesses the effect of 1, 2 and 4 weeks of lithium treatment on myo-inositol concentrations across several brain regions. Thirty-six Sprague-Dawley rats were treated for 2 weeks with an intraperitoneal injection of either 1 mmol/kg/day, twice daily lithium chloride (n=18) or placebo (2 ml/kg of saline) (n=18). The rats were separated into three groups: 1 week, 2 weeks and 4 weeks. Brains were dissected into prefrontal, temporal and occipital cortical areas, as well as hippocampus, and analyzed at 18.8 T. Myo-inositol was quantified using the Chenomx Profiler software. Lithium did not alter myo-inositol concentrations at 1 week. A significant reduction exists in myo-inositol concentrations in lithium-treated rats at 2 and 4 weeks, across all four brain regions. Studies suggest brain region-specific alterations in myo-inositol concentrations among bipolar patients. Our findings suggest that lithium-induced reduction of myo-inositol is more global.

Lithium modulation of the human inositol monophosphatase 2 (IMPA2) promoter

The inositol-signaling pathway is a therapeutic target for lithium in the treatment of bipolar disorder. Inositol monophosphatases (IMPases) play a key role in inositol signaling. Lithium's ability to inhibit IMPase 1 is well known, but its effect on IMPase 2 or on the transcriptional regulation of these genes has not been studied. Here, we report the identification and characterization of the minimal promoter of IMPA2 (encoding IMPase 2) in HeLa (epithelial) and SK-N-AS (neuronal) cells. IMPA2 promoter activity appears to be contributed by different elements in the 5' flanking region, suggesting that the gene is differentially regulated in neuronal and non-neuronal cells. Furthermore, IMPA2 promoter activity in both cell lines is downregulated, in a dose-dependent manner, by lithium after treatment for only 24h. This effect is also observed in vivo. Our results suggest a possible role for IMPA2 in bipolar disorder.

Increased inositol-monophosphatase activity by lithium treatment in bipolar patients

Inhibition of inositol monophosphatase (IMPase) enzyme is the target mechanism of action of lithium. However, increased activity of mRNA levels by lithium has been reported. These two diverse effects were shown after relatively short periods of lithium administration. The aim of this study was to observe the effect of prolonged use of lithium on IMPase activity. The authors investigated IMPase activities in fresh erythrocytes and leukocytes in 63 bipolar patients (42 euthymic, 8 depressive, 13 manic episodes) and 16 control subjects. We found that erythrocyte IMPase activity was higher in lithium treated euthymic patients than non-lithium treated patients. The duration of lithium use was positively correlated with leukocyte IMPase activity. Increased IMPase activity by chronic lithium use suggests an up-regulation of the enzyme activity.

Antioxidant enzyme activities and oxidative stress in affective disorders

Recent data from several reports indicate that free radicals are involved in the biochemical mechanisms underlying neuropsychiatric disorders in human. The results of several reports suggest that lower antioxidant defences against lipid peroxidation exist in patients with depression and that there is a therapeutic benefit from antioxidant supplementation in unstable manic-depressive patients. We investigated the antioxidant enzyme status and the indices of oxidative stress and lipid peroxidation end products in erythrocytes from patients with affective disorder. For this purpose, we measured superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) activities, as well as malondialdehyde (MDA) and nitric oxide (NO) levels in patients with affective disorders (n=30) in both pre- and post-treatment periods, and in a control group (n=21). CAT activities were significantly decreased in both pre-, and post-treatment periods in patients compared to the control group. GSH-Px activity in the pre-treatment period in the patients was significantly lower than both post-treatment patient and control groups. MDA levels were increased in both pre-, and post-treatment patient groups compared to the control group. NO level was lower in the pre-treatment patient group than in the control group. There were statistically significant correlations between SOD and MDA, and SOD and NO in the pre-treatment patient and control groups. Because the overall study sample was small, and the post-treatment patient group was even smaller, it can tentatively be suggested that the antioxidant system is impaired during a mood episode in patients with affective disorders, normalizing at the end of the episode.