Inositol monophosphatase activity in brain and lymphocyte-derived cell lines of bipolar patients

Neuropsychological Characterization of Autosomal Recessive Intellectual Developmental Disorder 59 Associated with IMPA1 (MRT59)

Biallelic loss of function of IMPA1 causes autosomal recessive intellectual developmental disorder 59 (MRT59, OMIM #617323). MRT59 has been reported to present with significant intellectual disability and disruptive behavior, but little is known about the neurocognitive pattern of those patients. Thus, the aims of this study were: (1) to assess the cognitive profile of these patients, and (2) to evaluate their functional dependence levels. Eighteen adults, aged 37 to 89 years, participated in this study: nine MRT59 patients, five heterozygous carriers and four non-carrier family members. All of them were from a consanguineous family living in Northeast Brazil. All IMPA1 patients had the (c.489_493dupGGGCT) pathogenic variant in homozygosis. For cognitive assessment, the WASI battery was applied in nine MRT59 patients and compared to heterozygous carriers and non-carrier family members. Functional dependence was evaluated using the functional independence measure (FIM). Patients showed moderate to severe intellectual disability and severe functional disabilities. Heterozygous carriers did not differ from non-carriers. MRT59 patients should be followed up by health professionals in an interdisciplinary way to understand their cognitive disabilities and functional needs properly.

Lithium-associated anterior cingulate neurometabolic profile in euthymic Bipolar I disorder: A 1H-MRS study

OBJECTIVE

In the treatment of Bipolar disorder (BD), achieving euthymia is highly complex and usually requires a combination of mood stabilizers. The mechanism of action in stabilizing mood has not been fully elucidated, but alterations in N-Acetylaspartate (NAA), Myo-Inositol (mI) and Choline (Cho) have been implicated. Proton magnetic resonance spectroscopy (¹H-MRS) is the gold standard technique for measuring brain NAA, Cho and mI in vivo. The objective of this study was to investigate the association of lithium use in BD type I and brain levels of NAA, mI and Cho in the (anterior cingulate cortex) ACC.

METHODS

129 BD type I subjects and 79 healthy controls (HC) were submitted to a 3-Tesla brain magnetic resonance imaging scan (¹H-MRS) using a PRESS ACC single voxel (8cm³) sequence.

RESULTS

BD patients exhibited higher NAA and Cho levels compared to HC. Lithium prescription was associated with lower mI (combination + monotherapy) and higher NAA levels (monotherapy).

CONCLUSION

The results observed add to the knowledge about the mechanisms of action of mood stabilizers on brain metabolites during euthymia. Additionally, the observed decrease in mI levels associated with lithium monotherapy is an in vivo finding that supports the inositol-depletion hypothesis of lithium pharmacodynamics.

Cellular models to study bipolar disorder: A systematic review

BACKGROUND

There is an emerging interest in the use of cellular models to study psychiatric disorders. We have systematically reviewed the application of cellular models to understand the biological basis of bipolar disorder (BD).

METHOD

Published scientific literature in MEDLINE, PsychINFO and SCOPUS databases were identified with the following search strategy: [(Lymphoblastoid OR Lymphoblast OR Fibroblast OR Pluripotent OR Olfactory epithelium OR Olfactory mucosa) AND (Bipolar disorder OR Lithium OR Valproate OR Mania)]. Studies were included if they had used cell cultures derived from BD patients.

RESULTS

There were 65 articles on lymphoblastoid cell lines, 14 articles on fibroblasts, 4 articles on olfactory neuronal epithelium (ONE) and 2 articles on neurons reprogrammed from induced pluripotent stem cell lines (IPSC). Several parameters have been studied, and the most replicated findings are abnormalities in calcium signaling, endoplasmic reticulum (ER) stress response, mitochondrial oxidative pathway, membrane ion channels, circadian system and apoptosis related genes. These, although present in basal state, seem to be accentuated in the presence of cellular stressors (e.g. oxidative stress--rotenone; ER stress--thapsigargin), and are often reversed with in-vitro lithium.

CONCLUSION

Cellular modeling has proven useful in BD, and potential pathways, especially in cellular resilience related mechanisms have been identified. These findings show consistency with other study designs (genome-wide association, brain-imaging, and post-mortem brain expression). ONE cells and IPSC reprogrammed neurons represent the next generation of cell models in BD. Future studies should focus on family-based study designs and combine cell models with deep sequencing and genetic manipulations.

Inhibition of inositol monophosphatase (IMPase) at the calbindin-D28k binding site: molecular and behavioral aspects

Bipolar-disorder (manic-depressive illness) is a severe chronic illness affecting ∼1% of the adult population. It is treated with mood-stabilizers, the prototypic one being lithium-salts (lithium), but it has life threatening side-effects and a significant number of patients fail to respond. The lithium-inhibitable enzyme inositol-monophosphatase (IMPase) is one of the viable targets for lithium's mechanism of action. Calbindin-D28k (calbindin) up-regulates IMPase activity. The IMPase-calbindincomplex was modeled using the program MolFit. The in-silico model indicated that the 55-66 amino-acid segment of IMPase anchors calbindin via Lys59 and Lys61 with a glutamate in between (Lys-Glu-Lys motif) and that the motif interacts with residues Asp24 and Asp26 of calbindin. We found that differently from wildtype calbindin, IMPase was not activated by mutated calbindin in which Asp24 and Asp26 were replaced by alanine. Calbindin's effect was significantly reduced by a linear peptide with the sequence of amino acids 58-63 of IMPase (peptide 1) and by six amino-acid linear peptides including at least part of the Lys-Glu-Lys motif. The three amino-acid peptide Lys-Glu-Lys or five amino-acid linear peptides containing this motif were ineffective. Mice administered peptide 1 intracerebroventricularly exhibited a significant anti-depressant-like reduced immobility in the forced-swim test. Based on the sequence of peptide 1, and to potentially increase the peptide's stability, cyclic and linear pre-cyclic analog peptides were synthesized. One cyclic peptide and one linear pre-cyclic analog peptide inhibited calbindin-activated brain IMPase activity in-vitro. Our findings may lead to the development of molecules capable of inhibiting IMPase activity at an alternative site than that of lithium.

Lithium: the pharmacodynamic actions of the amazing ion

Lithium has been used for the treatment of mood disorders for over 60 years, yet the exact mechanisms by which it exerts its therapeutic effects remain unclear. Two enzymatic chains or pathways emerge as targets for lithium: inositol monophosphatase within the phosphatidylinositol signalling pathway and the protein kinase glycogen synthase kinase 3. Lithium inhibits these enzymes through displacing the normal cofactor magnesium, a vital regulator of numerous signalling pathways. Here we provide an overview of evidence, supporting a role for the inhibition of glycogen synthase kinase 3 and inositol monophosphatase in the pharmacodynamic actions of lithium. We also explore how inhibition of these enzymes by lithium can lead to downstream effects of clinical relevance, both for mood disorders and neurodegenerative diseases. Establishing a better understanding of lithium's mechanisms of action may allow the development of more effective and more tolerable pharmacological agents for the treatment of a range of mental illnesses, and provide clearer insight into the pathophysiology of such disorders.

Genetic control of lithium sensitivity and regulation of inositol biosynthetic genes

Lithium (Li(+)) is a common treatment for bipolar mood disorder, a major psychiatric illness with a lifetime prevalence of more than 1%. Risk of bipolar disorder is heavily influenced by genetic predisposition, but is a complex genetic trait and, to date, genetic studies have provided little insight into its molecular origins. An alternative approach is to investigate the genetics of Li(+) sensitivity. Using the social amoeba Dictyostelium, we previously identified prolyl oligopeptidase (PO) as a modulator of Li(+) sensitivity. In a link to the clinic, PO enzyme activity is altered in bipolar disorder patients. Further studies demonstrated that PO is a negative regulator of inositol(1,4,5)trisphosphate (IP(3)) synthesis, a Li(+) sensitive intracellular signal. However, it was unclear how PO could influence either Li(+) sensitivity or risk of bipolar disorder. Here we show that in both Dictyostelium and cultured human cells PO acts via Multiple Inositol Polyphosphate Phosphatase (Mipp1) to control gene expression. This reveals a novel, gene regulatory network that modulates inositol metabolism and Li(+) sensitivity. Among its targets is the inositol monophosphatase gene IMPA2, which has also been associated with risk of bipolar disorder in some family studies, and our observations offer a cellular signalling pathway in which PO activity and IMPA2 gene expression converge.

PtdIns(3,4,5)P3 and inositol depletion as a cellular target of mood stabilizers

Lithium (Li+) is the mood stabilizer most frequently used in the treatment of bipolar mood disorder; however, its therapeutic mechanism is unknown. In the 1980s, Berridge and colleagues proposed that Li+ treatment acts via inhibition of IMPase (inositol monophosphatase) to deplete the cellular concentration of myo-inositol. Inositol depletion is also seen with the alternative mood stabilizers VPA (valproic acid) and CBZ (carbamazepine), suggesting a common therapeutic action. All three drugs cause changes in neuronal cell morphology and cell chemotaxis; however, it is unclear how reduced cellular inositol modulates these changes in cell behaviour. It is often assumed that reduced inositol suppresses Ins(1,4,5)P3, a major intracellular signal molecule, but there are other important phosphoinostide-based signal molecules in the cell. In the present paper, we discuss evidence that Li+ has a substantial effect on PtdIns(3,4,5)P3, an important signal molecule within the nervous system. As seen for Ins(1,4,5)P3 signalling, suppression of PtdIns(3,4,5)P3 signalling also occurs via an inositol-depletion mechanism. This has implications for the cellular mechanisms controlling phosphoinositide signalling, and offers insight into the genetics underlying risk of bipolar mood disorder.

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.

Possible involvement of post-dopamine D2 receptor signalling components in the pathophysiology of schizophrenia

Par-4 has been suggested to mediate dopamine neurotransmission. Dopamine D2 receptor (DRD2) activation induces a signalling complex of AKT1, PP2A and beta-arrestin2 which dephosphorylates/inactivates AKT1 thereby activating GSK-3beta, transducing dopamine-dependent behaviour. DRD2 activation also results in down-regulation of PKA activity. Among other substrates PKA phosphorylates GSK-3beta. Prolonged DRD2 activation leads to its 'desensitization' which involves GRKs and beta-arrestins. beta-arrestin1 binds to phosphorylated receptors preventing further G-protein stimulation. This study examined whether Par-4, beta-arrestin1, AKT1 and GSK-3beta are involved in the pathophysiology of schizophrenia. Lymphocytes obtained from schizophrenia and bipolar patients and healthy controls recruited from the Beer-Sheva Mental Health Center were transformed by Epstein-Barr virus (EBV) into lymphocyte-derived cell lines (LDCL). Post-mortem brain samples were obtained from the Rebecca L. Cooper Brain Bank, Parkville, Australia. The study was approved by the IRB committees of Beer-Sheva, Israel and Parkville, Australia. Levels of the specific proteins were assayed by Western blotting. beta-arrestin1 protein levels were significantly ~2-fold increased in LDCL from schizophrenia patients while Par-4 protein levels were unaltered. A 63% significant decrease was found in frontal cortex phospho-Ser9-GSK-3beta protein levels in schizophrenia but not in those of AKT1, Par-4 or beta-arrestin1. Elevated beta-arrestin1 protein levels in LDCL and decreased phospho-Ser9-GSK-3beta protein levels in post-mortem frontal cortex of schizophrenia patients vs. control groups support the possible involvement of these proteins in the pathophysiology of schizophrenia. However, since we did not find differences in beta-arrestin1, AKT1 and Par-4 protein levels in post-mortem frontal cortex of schizophrenia patients and although GSK-3beta participates in other signalling cascades we can not rule out the possibility that the differences found reflect deviation in DRD2 signalling.

A promoter haplotype of the inositol monophosphatase 2 gene (IMPA2) at 18p11.2 confers a possible risk for bipolar disorder by enhancing transcription

Lithium is an effective mood stabilizer for bipolar disorder patients and its therapeutic effect may involve inhibition of inositol monophosphatase activity. In humans, the enzyme is encoded by two genes, IMPA1 and IMPA2. IMPA2 maps to 18p11.2, a genomic interval for which evidence of linkage to bipolar disorder has been supported by several reports. We performed a genetic association study in Japanese cohorts (496 patients with bipolar disorder and 543 control subjects). Interestingly, we observed association of IMPA2 promoter single nucleotide polymorphisms (SNPs) (-461C and -207T) with bipolar disorder, the identical SNPs reported previously in a different population. In vitro promoter assay and genetic haplotype analysis showed that the combination of (-461C)-(-207T)-(-185A) drove enhanced transcription and the haplotypes containing (-461C)-(-207T)-(-185A) contributed to risk for bipolar disorder. Expression study on post-mortem brains revealed increased transcription from the IMPA2 allele that harbored (-461C)-(-207T)-(-185A) in the frontal cortex of bipolar disorder patients. The examination of allele-specific expressions in post-mortem brains did not support genomic imprinting of IMPA2, which was suggested nearby genomic locus. Contrasting to a prior report, therapeutic concentrations of lithium could not suppress the transcription of IMPA2 mRNA, and the mood-stabilizing effect of lithium is, if IMPA2 was one of the targets of lithium, deemed to be generated via inhibition of enzymatic reaction rather than transcriptional suppression. In conclusion, the present study suggests that a promoter haplotype of IMPA2 possibly contributes to risk for bipolar disorder by elevating IMPA2 levels in the brain, albeit the genetic effect varies among populations.

Interaction of calbindin D28k and inositol monophosphatase in human postmortem cortex: possible implications for bipolar disorder

OBJECTIVES

Therapeutically relevant concentrations of lithium (Li) exert an uncompetitive inhibition on inositol monophosphatase (IMPase). It has recently been shown that calbindin D28k (calbindin) activates IMPase. Purified calbindin attaches to a specific amino acid sequence on purified IMPase enhancing its activity by several hundred fold. We studied whether calbindin activates IMPase in postmortem human brain crude homogenate, whether differences in calbindin levels between lymphocytes and brain may be responsible for our previous finding of reduced IMPase activity in lymphocytes but not brain of bipolar patients, and whether calbindin protein levels are altered in postmortem brain from bipolar patients versus control subjects and schizophrenic and major depressive patients.

METHODS

IMPase activity in human postmortem brain specimens with or without 10 microM human recombinant calbindin was quantified spectrophotometrically in an enzyme-linked immunosorbent assay (ELISA) reader. Calbindin protein levels in postmortem brain were determined using Western blot analysis.

RESULTS

Supplementation of human recombinant calbindin to postmortem human brain crude homogenate enhanced IMPase activity by 3.5-fold. No difference in postmortem temporal cortex calbindin protein levels was found between bipolar patients versus comparison groups. Two-fold higher calbindin protein levels were found in Li-treated bipolar patients compared with other bipolar patients. Subchronic Li treatment in mice did not affect brain calbindin protein levels significantly. Chronic Li treatment reduced calbindin protein levels in the frontal cortex but not in the hippocampus.

CONCLUSIONS

Calbindin is a physiological activator of IMPase in human brain. Protein levels of calbindin are not altered in postmortem temporal cortex of bipolar patients.

Low GSK-3beta in schizophrenia as a consequence of neurodevelopmental insult

Glycogen synthase kinase-3 (GSK-3) is a protein kinase highly abundant in brain and involved in signal transduction cascades, particularly neurodevelopment. Its activity and protein levels have been reported to be over 40% lower in postmortem frontal cortex of schizophrenic patients. GSK-3beta in occipital cortex of schizophrenic patients was not reduced, suggesting regional specificity. There was no reduction in GSK-3beta protein levels in fresh and immortalized lymphocytes and both GSK-3 activity and GSK-3beta mRNA levels in fresh lymphocytes from schizophrenic patients. In the schizophrenia-related neonatal ventral hippocampal lesion rat model, we measured GSK-3beta protein levels and GSK-3 activity in the frontal cortex. GSK-3beta protein levels in lesioned rats were significantly lower than in sham rats, favoring perinatal insult as a cause of low GSK-3beta in schizophrenia. Taken together, these studies suggest that low GSK-3 in postmortem brain of schizophrenic patients is a late consequence of perinatal neurodevelopmental insult in schizophrenia. In rats, acute or chronic cold restraint stress did not change GSK-3beta protein levels. Chronic treatment of rats with lithium, valproate, haloperidol or clozapine did not change rat cortical GSK-3beta protein levels ex vivo, supporting the concept that low GSK-3beta in schizophrenia is not secondary to stress or drug treatment. Our initial findings of low GSK-3beta protein levels in postmortem brain have been replicated by another group. Our own group has found additionally that GSK-3beta mRNA levels were 40% lower in postmortem dorsolateral prefrontal cortex (DLPFC) of schizophrenic patients, supporting our previous findings. Further studies will be aimed at determining whether nonspecific neonatal damage or only specific factors cause low GSK-3 as a late effect. We plan to study whether low GSK-3beta activity is associated with biochemical effects such as elevated beta-catenin levels.

Valproate decreases inositol biosynthesis

BACKGROUND

Lithium and valproate (VPA) are used for treating bipolar disorder. The mechanism of mood stabilization has not been elucidated, but the role of inositol has gained substantial support. Lithium inhibition of inositol monophosphatase, an enzyme required for inositol recycling and de novo synthesis, suggested the hypothesis that lithium depletes brain inositol and attenuates phosphoinositide signaling. Valproate also depletes inositol in yeast, Dictyostelium, and rat neurons. This raised the possibility that the effect is the result of myo-inositol-1-phosphate (MIP) synthase inhibition.

METHODS

Inositol was measured by gas chromatography. Human prefrontal cortex MIP synthase activity was assayed in crude homogenate. INO1 was assessed by Northern blotting. Growth cones morphology was evaluated in cultured rat neurons.

RESULTS

We found a 20% in vivo reduction of inositol in mouse frontal cortex after acute VPA administration. As hypothesized, inositol reduction resulted from decreased MIP synthase activity: .21-.28 mmol/LVPA reduced the activity by 50%. Among psychotropic drugs, the effect is specific to VPA. Accordingly, only VPA upregulates the yeast INO1 gene coding for MIP synthase. The VPA derivative N-methyl-2,2,3,3,-tetramethyl-cyclopropane carboxamide reduces MIP synthase activity and has an affect similar to that of VPA on rat neurons, whereas another VPA derivative, valpromide, poorly affects the activity and has no affect on neurons.

CONCLUSIONS

The rate-limiting step of inositol biosynthesis, catalyzed by MIP synthase, is inhibited by VPA; inositol depletion is a first event shown to be common to lithium and VPA.

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.

Lithium inhibitable enzymes in postmortem brain of bipolar patients

Despite considerable ongoing efforts at the epidemiological, genetic and molecular level, the etiology of bipolar disorder had not yet been elucidated. To study possible contributing components to the pathophysiology of this disorder, we have hypothesized that levels of enzymes inhibited by therapeutically relevant lithium ion concentrations in the brain of patients may differ from those in normal controls and may be involved in the etiology of the disorder. Three Li-inhibitable enzymes were studied in postmortem brain samples of bipolar patients and normal controls. The expression and function of the two enzymes that are obviously involved in signaling cascades, IMPase, involved in the second messenger system of the phosphatidylinositol cycle, and GSK-3, a mediator of an array of signaling cascades, were not found to be different in postmortem frontal and occipital cortex of bipolar patients and normal controls. Only PAP phosphatase protein levels, but not its mRNA levels or enzymatic activity, were found to be significantly decreased in frontal cortex of bipolar patients compared with normal controls.

Search for a common mechanism of mood stabilizers

Manic-depression, or bipolar affective disorder, is a prevalent mental disorder with a global impact. Mood stabilizers have acute and long-term effects and at a minimum are prophylactic for manic or depressive poles without detriment to the other. Lithium has significant effects on mania and depression, but may be augmented or substituted by some antiepileptic drugs. The biochemical basis for mood stabilizer therapies or the molecular origins of bipolar disorder is unknown. One approach to this problem is to seek a common target of all mood stabilizers. Lithium directly inhibits two evolutionarily conserved signal transduction pathways. It both suppresses inositol signaling through depletion of intracellular inositol and inhibits glycogen synthase kinase-3 (GSK-3), a multifunctional protein kinase. A number of GSK-3 substrates are involved in neuronal function and organization, and therefore present plausible targets for therapy. Valproic acid (VPA) is an antiepileptic drug with mood-stabilizing properties. It may indirectly reduce GSK-3 activity, and can up-regulate gene expression through inhibition of histone deacetylase. These effects, however, are not conserved between different cell types. VPA also inhibits inositol signaling through an inositol-depletion mechanism. There is no evidence for GSK-3 inhibition by carbamazepine, a second antiepileptic mood stabilizer. In contrast, this drug alters neuronal morphology through an inositol-depletion mechanism as seen with lithium and VPA. Studies on the enzyme prolyl oligopeptidase and the sodium myo-inositol transporter support an inositol-depletion mechanism for mood stabilizer action. Despite these intriguing observations, it remains unclear how changes in inositol signaling underlie the origins of bipolar disorder.

Myo-inositol-1-phosphate (MIP) synthase: a possible new target for antibipolar drugs

Inositol metabolism is well characterized in yeast at a molecular level, and yeast is the only eukaryote in which genetic, molecular and functional genomic approaches to identify lithium. valproate and inositol targets may be combined readily. It has been shown that lithium inhibits yeast inositol monophosphatase (encoded by INM1 and INM2), and both valproate and lithium reduce intracellular inositol. Unlike lithium, valproate causes a decrease in intracellular inositol-1-phosphate as well. suggesting that myo-inositol-1-P (MIP) synthase is a site of valproate action in the yeast PI cycle. MIP synthase is the rate-limiting step in inositol biosynthesis and is highly regulated in response to inositol. Yeast genes that are affected by both lithium and valproate in the phosphoinositide pathways (INO1 increased over 10-fold, INO2 increased twofold and INM1 decreased about twofold) have been identified. It has also been reported previously that both lithium and inositol mildly up-regulate IMPA1 (encoding mammalian inositol monophosphatase) expression in human cells. These findings indicate that IMPA is regulated only mildly by lithium, and therefore may not be the major target in the inositol pathway. Given the substantial evidence for the role of inositol in the mechanism of action of lithium and valproate. the opposing and mild effects of lithium on the genes encoding inositol monophosphatase in yeast and human cells, but the powerful effect of lithium and valproate on INO1 in yeast, it is hypothesized that human hIANO1 is a factor in the psychopharmacology of mood stabilizers.

GSK-3 parameters in lymphocytes of schizophrenic patients

Glycogen synthase kinase-3 (GSK-3) is a highly conserved serine/threonine protein kinase that is involved in the signal transduction cascades of multiple cellular processes. GSK-3 has two isoforms, designated alpha and beta. GSK-3beta protein levels and GSK-3 enzyme activity have been reported to be reduced by over 40% in postmortem frontal cortex of schizophrenic patients. GSK-3 is also present in peripheral tissue such as lymphocytes. In this study we aimed to find whether the reduction in brain GSK-3beta measures is reflected in peripheral tissue of schizophrenic patients. Fresh lymphocytes from schizophrenic patients showed no difference in GSK-3 alpha and GSK-3beta mRNA levels, GSK-3beta protein levels, or total GSK-3 (alpha+beta) enzyme activity compared with findings in control subjects. In addition, lymphocyte-derived cell lines from schizophrenic patients did not differ in their GSK-3beta protein levels from levels in normal control subjects. The results rule out the use of lymphocyte GSK-3 as a marker for central GSK-3 abnormalities in schizophrenia.

Reduced inositol content in lymphocyte-derived cell lines from bipolar patients

OBJECTIVES

The study aimed to determine whether low inositol content and uptake previously reported in brain and peripheral tissue of bipolar patients are also reflected in lymphocyte-derived cell lines from these patients.

METHODS

Inositol content and uptake were studied in lymphocyte-derived cell lines grown in vitro for at least five generations to eliminate influences of drug treatment. Inositol content was studied gas chromatographically and inositol uptake by following 3H-inositol incorporation at various concentrations.

RESULTS

Inositol levels of cell lines derived from bipolar patients were significantly lower than those of cell lines from controls.

CONCLUSIONS

Low inositol content in lymphocyte-derived cell lines from bipolar patients corroborates previous findings in frontal cortex and in lymphoblastoid cell lines and are consistent with the notion that the phosphatidylinositol signaling system is involved in the pathophysiology of this disorder.