1
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Long L, Huang Q, Song T, Dai Z. Myo-inositol rescued insulin resistance and dyslipidemia in db/db mice. J Appl Biomed 2024; 22:74-80. [PMID: 38912862 DOI: 10.32725/jab.2024.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 06/12/2024] [Indexed: 06/25/2024] Open
Abstract
Myo-inositol (MI), present in a variety of foods, is essential in several important processes of cell physiology. In this study, we explored the protective effects of MI against hyperglycemia and dyslipidemia in db/db mice, a typical animal model of type 2 diabetes mellitus (T2DM). MI supplement effectively suppressed the high plasma glucose and insulin levels and markedly relieved the insulin resistance (IR) in the db/db mice, comparable to metformin's effects. In MIN6 pancreatic β cells, MI also restrained the upsurge of insulin secretion stimulated by high-concentration glucose but had no impact on the promoted cell proliferation. Moreover, MI abated the enhanced plasma triglyceride and total cholesterol levels in the db/db mice. Notably, the lipid droplet formation of mesenchymal stem cells (MSCs) from db/db mice was significantly diminished after the treatment of MI, indicating that MI could effectively inhibit the differentiation of db/db mouse MSCs into adipocytes. However, MI regretfully failed to control obesity in db/db mice. This work proved that MI significantly helped db/db mice's metabolic disorders, indicating that MI has potential as an effective adjunctive treatment for hyperglycemia and dyslipidemia in T2DM patients.
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Affiliation(s)
- Lingzhi Long
- Hunan Provincial People's Hospital (The First-affiliated Hospital of Hunan Normal University), Department of Pharmacy, Changsha, China
| | - Qi Huang
- Hunan Provincial People's Hospital (The First-affiliated Hospital of Hunan Normal University), Department of Pharmacy, Changsha, China
| | - Tao Song
- Central South University, Xiangya Hospital, Department of Neurosurgery, Changsha, China
| | - Zhijie Dai
- The Second Xiangya Hospital of Central South University, Department of Metabolism and Endocrinology, National Clinical Research Center for Metabolic Diseases, Changsha, China
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2
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Case KC, Beltman RJ, Pflum MKH, Greenberg ML. Valproate regulates inositol synthesis by reducing expression of myo-inositol-3-phosphate synthase. Sci Rep 2023; 13:14844. [PMID: 37684289 PMCID: PMC10491628 DOI: 10.1038/s41598-023-41936-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 09/04/2023] [Indexed: 09/10/2023] Open
Abstract
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.
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Affiliation(s)
- Kendall C Case
- Department of Biological Sciences, Wayne State University, Detroit, MI, 48202, USA
| | - Rachel J Beltman
- Department of Chemistry, Wayne State University, Detroit, MI, 48202, USA
| | - Mary Kay H Pflum
- Department of Chemistry, Wayne State University, Detroit, MI, 48202, USA
| | - Miriam L Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, MI, 48202, USA.
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3
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Lazcano P, Schmidtke MW, Onu C, Greenberg ML. Phosphatidic acid inhibits inositol synthesis by inducing nuclear translocation of kinase IP6K1 and repression of myo-inositol-3-P synthase. J Biol Chem 2022; 298:102363. [PMID: 35963434 PMCID: PMC9478396 DOI: 10.1016/j.jbc.2022.102363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 07/25/2022] [Accepted: 07/28/2022] [Indexed: 11/17/2022] Open
Abstract
Inositol is an essential metabolite that serves as a precursor for structural and signaling molecules. Although perturbation of inositol homeostasis has been implicated in numerous human disorders, surprisingly little is known about how inositol levels are regulated in mammalian cells. A recent study in mouse embryonic fibroblasts demonstrated that nuclear translocation of inositol hexakisphosphate kinase 1 (IP6K1) mediates repression of myo-inositol-3-P synthase (MIPS), the rate-limiting inositol biosynthetic enzyme. Binding of IP6K1 to phosphatidic acid (PA) is required for this repression. Here, we elucidate the role of PA in IP6K1 repression. Our results indicate that increasing PA levels through pharmacological stimulation of phospholipase D (PLD) or direct supplementation of 18:1 PA induces nuclear translocation of IP6K1 and represses expression of the MIPS protein. We found that this effect was specific to PA synthesized in the plasma membrane, as endoplasmic reticulum–derived PA did not induce IP6K1 translocation. Furthermore, we determined that PLD-mediated PA synthesis can be stimulated by the master metabolic regulator 5′ AMP-activated protein kinase (AMPK). We show that activation of AMPK by glucose deprivation or by treatment with the mood-stabilizing drugs valproate or lithium recapitulated IP6K1 nuclear translocation and decreased MIPS expression. This study demonstrates for the first time that modulation of PA levels through the AMPK-PLD pathway regulates IP6K1-mediated repression of MIPS.
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Affiliation(s)
- Pablo Lazcano
- Department of Biological Sciences, Wayne State University, Detroit, MI, United States
| | - Michael W Schmidtke
- Department of Biological Sciences, Wayne State University, Detroit, MI, United States
| | - Chisom Onu
- Department of Biological Sciences, Wayne State University, Detroit, MI, United States
| | - Miriam L Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, MI, United States.
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4
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Káňovičová P, Čermáková P, Kubalová D, Bábelová L, Veselá P, Valachovič M, Zahumenský J, Horváth A, Malínský J, Balážová M. Blocking phosphatidylglycerol degradation in yeast defective in cardiolipin remodeling results in a new model of the Barth syndrome cellular phenotype. J Biol Chem 2021; 298:101462. [PMID: 34864056 PMCID: PMC8728584 DOI: 10.1016/j.jbc.2021.101462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/26/2021] [Accepted: 11/29/2021] [Indexed: 11/01/2022] Open
Abstract
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.
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Affiliation(s)
- Paulína Káňovičová
- Department of Membrane Biochemistry, Institute of Animal Biochemistry and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Petra Čermáková
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Dominika Kubalová
- Department of Membrane Biochemistry, Institute of Animal Biochemistry and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Lenka Bábelová
- Department of Membrane Biochemistry, Institute of Animal Biochemistry and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Petra Veselá
- Department of Functional Organization of Biomembranes, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Martin Valachovič
- Department of Membrane Biochemistry, Institute of Animal Biochemistry and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Jakub Zahumenský
- Department of Functional Organization of Biomembranes, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Anton Horváth
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Jan Malínský
- Department of Functional Organization of Biomembranes, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
| | - Mária Balážová
- Department of Membrane Biochemistry, Institute of Animal Biochemistry and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Bratislava, Slovakia.
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5
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Suliman M, Schmidtke MW, Greenberg ML. The Role of the UPR Pathway in the Pathophysiology and Treatment of Bipolar Disorder. Front Cell Neurosci 2021; 15:735622. [PMID: 34531727 PMCID: PMC8439382 DOI: 10.3389/fncel.2021.735622] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 08/09/2021] [Indexed: 11/13/2022] Open
Abstract
Bipolar disorder (BD) is a mood disorder that affects millions worldwide and is associated with severe mood swings between mania and depression. The mood stabilizers valproate (VPA) and lithium (Li) are among the main drugs that are used to treat BD patients. However, these drugs are not effective for all patients and cause serious side effects. Therefore, better drugs are needed to treat BD patients. The main barrier to developing new drugs is the lack of knowledge about the therapeutic mechanism of currently available drugs. Several hypotheses have been proposed for the mechanism of action of mood stabilizers. However, it is still not known how they act to alleviate both mania and depression. The pathology of BD is characterized by mitochondrial dysfunction, oxidative stress, and abnormalities in calcium signaling. A deficiency in the unfolded protein response (UPR) pathway may be a shared mechanism that leads to these cellular dysfunctions. This is supported by reported abnormalities in the UPR pathway in lymphoblasts from BD patients. Additionally, studies have demonstrated that mood stabilizers alter the expression of several UPR target genes in mouse and human neuronal cells. In this review, we outline a new perspective wherein mood stabilizers exert their therapeutic mechanism by activating the UPR. Furthermore, we discuss UPR abnormalities in BD patients and suggest future research directions to resolve discrepancies in the literature.
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Affiliation(s)
- Mahmoud Suliman
- Department of Biological Sciences, Wayne State University, Detroit, MI, United States
| | - Michael W Schmidtke
- Department of Biological Sciences, Wayne State University, Detroit, MI, United States
| | - Miriam L Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, MI, United States
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6
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Salsaa M, Aziz K, Lazcano P, Schmidtke MW, Tarsio M, Hüttemann M, Reynolds CA, Kane PM, Greenberg ML. Valproate activates the Snf1 kinase in Saccharomyces cerevisiae by decreasing the cytosolic pH. J Biol Chem 2021; 297:101110. [PMID: 34428448 PMCID: PMC8449051 DOI: 10.1016/j.jbc.2021.101110] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 08/19/2021] [Accepted: 08/20/2021] [Indexed: 11/27/2022] Open
Abstract
Valproate (VPA) is a widely used mood stabilizer, but its therapeutic mechanism of action is not understood. This knowledge gap hinders the development of more effective drugs with fewer side effects. Using the yeast model to elucidate the effects of VPA on cellular metabolism, we determined that the drug upregulated expression of genes normally repressed during logarithmic growth on glucose medium and increased levels of activated (phosphorylated) Snf1 kinase, the major metabolic regulator of these genes. VPA also decreased the cytosolic pH (pHc) and reduced glycolytic production of 2/3-phosphoglycerate. ATP levels and mitochondrial membrane potential were increased, and glucose-mediated extracellular acidification decreased in the presence of the drug, as indicated by a smaller glucose-induced shift in pH, suggesting that the major P-type proton pump Pma1 was inhibited. Interestingly, decreasing the pHc by omeprazole-mediated inhibition of Pma1 led to Snf1 activation. We propose a model whereby VPA lowers the pHc causing a decrease in glycolytic flux. In response, Pma1 is inhibited and Snf1 is activated, resulting in increased expression of normally repressed metabolic genes. These findings suggest a central role for pHc in regulating the metabolic program of yeast cells.
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Affiliation(s)
- Michael Salsaa
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA
| | - Kerestin Aziz
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA
| | - Pablo Lazcano
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA
| | - Michael W Schmidtke
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA
| | - Maureen Tarsio
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Maik Hüttemann
- Center for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, Michigan, USA
| | - Christian A Reynolds
- Department of Emergency Medicine, School of Medicine, Wayne State University, Detroit, Michigan, USA; Department of Biotechnology, University of Rijeka, Rijeka, Croatia
| | - Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Miriam L Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA.
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7
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Martín‐González J, Montero‐Bullón J, Lacal J. Dictyostelium discoideum as a non-mammalian biomedical model. Microb Biotechnol 2021; 14:111-125. [PMID: 33124755 PMCID: PMC7888446 DOI: 10.1111/1751-7915.13692] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 10/06/2020] [Accepted: 10/11/2020] [Indexed: 02/06/2023] Open
Abstract
Dictyostelium discoideum is one of eight non-mammalian model organisms recognized by the National Institute of Health for the study of human pathology. The use of this slime mould is possible owing to similarities in cell structure, behaviour and intracellular signalling with mammalian cells. Its haploid set of chromosomes completely sequenced amenable to genetic manipulation, its unique and short life cycle with unicellular and multicellular stages, and phenotypic richness encoding many human orthologues, make Dictyostelium a representative and simple model organism to unveil cellular processes in human disease. Dictyostelium studies within the biomedical field have provided fundamental knowledge in the areas of bacterial infection, immune cell chemotaxis, autophagy/phagocytosis and mitochondrial and neurological disorders. Consequently, Dictyostelium has been used to the development of related pharmacological treatments. Herein, we review the utilization of Dictyostelium as a model organism in biomedicine.
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Affiliation(s)
- Javier Martín‐González
- Molecular Genetics of Human Diseases GroupDepartment of Microbiology and GeneticsFaculty of BiologyUniversity of SalamancaCampus Miguel de UnamunoSalamancaE‐37007Spain
| | - Javier‐Fernando Montero‐Bullón
- Metabolic Engineering GroupDepartment of Microbiology and GeneticsUniversity of SalamancaCampus Miguel de UnamunoSalamancaE‐37007Spain
| | - Jesus Lacal
- Molecular Genetics of Human Diseases GroupDepartment of Microbiology and GeneticsFaculty of BiologyUniversity of SalamancaCampus Miguel de UnamunoSalamancaE‐37007Spain
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8
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Yue J, Zhong S, Luo A, Lai S, He T, Luo Y, Wang Y, Zhang Y, Shen S, Huang H, Wen S, Jia Y. Correlations Between Working Memory Impairment and Neurometabolites of the Prefrontal Cortex in Drug-Naive Obsessive-Compulsive Disorder. Neuropsychiatr Dis Treat 2021; 17:2647-2657. [PMID: 34421300 PMCID: PMC8373305 DOI: 10.2147/ndt.s296488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 07/12/2021] [Indexed: 01/06/2023] Open
Abstract
PURPOSE This study aimed to investigate the mechanism of working memory (WM) impairment in drug-naive obsessive-compulsive disorder (OCD) by using neuropsychological tests and proton magnetic resonance spectroscopy (1H-MRS). PATIENTS AND METHODS A total of 55 patients with drug-naive OCD and 55 healthy controls (HCs) were recruited for this study. The working memory (WM) was evaluated using the digit span test (DST), visual space memory test (VSMT), and the 2-back task and stroop color word test (SCWT). The bilateral metabolite levels of the prefrontal cortex (PFC) were evaluated by 1H-MRS, then determined the ratios of N-acetyl aspartate (NAA), choline-containing compounds (Cho), and myo-inositol (MI) to creatine (Cr). The independent sample t-test was used to analyse the differences in WM performance and neurometabolite ratios. Multivariate linear regression analysis was performed to screen the influential factors of WM, with an introduction level of 0.05 and a rejection level of 0.10. RESULTS 1) Patients with OCD performed significantly worse on DST (score), VSMT (score), 2-back task (accuracy rate), SCWT (execution time) when compared with HCs. 2) NAA/Cr and Cho/Cr in the left PFC (lPFC) and MI/Cr ratios in the bilateral PFC of OCD patients were significantly lower when compared to HCs. 3) For OCD patients, the NAA/Cr ratio in the lPFC was negatively correlated with the score of DST (forwards), the Cho/Cr ratio in the lPFC was positively correlated with the accuracy rate of 2-back task, and the MI/Cr ratio in the right PFC (rPFC) was positively correlated with the score of DST (forwards) and the accuracy rate of VSMT. We also found that the compulsive symptoms showed a positive correlation with MI/Cr ratio of the rPFC. CONCLUSION Drug-naive OCD patients have demonstrated WM impairments, including phonological loop, visual-spatial sketchpad and central executive system, and the WM impairments might be associated with hypometabolism in the PFC, especially the lPFC.
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Affiliation(s)
- Jihui Yue
- Department of Psychiatry, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong Province, People's Republic of China.,Department of Psychiatry, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, Guangdong Province, People's Republic of China
| | - Shuming Zhong
- Department of Psychiatry, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong Province, People's Republic of China
| | - Aimin Luo
- Department of Psychology, Guangdong Sanjiu Brain Hospital, Guangzhou, Guangdong Province, People's Republic of China
| | - Shunkai Lai
- Department of Psychiatry, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong Province, People's Republic of China
| | - Tingting He
- School of Management, Jinan University, Guangzhou, Guangdong Province, People's Republic of China
| | - Yuchong Luo
- Department of Psychiatry, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, Guangdong Province, People's Republic of China
| | - Ying Wang
- Medical Imaging Center, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong Province, People's Republic of China
| | - Yiliang Zhang
- Department of Psychiatry, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong Province, People's Republic of China
| | - Shiyi Shen
- School of Management, Jinan University, Guangzhou, Guangdong Province, People's Republic of China
| | - Hui Huang
- School of Management, Jinan University, Guangzhou, Guangdong Province, People's Republic of China
| | - Shenglin Wen
- Department of Psychiatry, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, Guangdong Province, People's Republic of China
| | - Yanbin Jia
- Department of Psychiatry, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong Province, People's Republic of China
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9
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Abstract
Interest in the coexistence of manic and depressive symptoms fostered hypotheses on neurobiological underpinnings of mixed states. Neurobiological properties of mixed states, however, have not been comprehensively described. The authors searched databases for articles on neurobiological markers related to mixed states. Results showed that mixed states are characterized by elevated central and peripheral monoamine levels, greater alterations in hypothalamic-pituitary-adrenal axis, increased inflammation, and greater circadian rhythms dysfunction than nonmixed forms. Furthermore, the magnitude of pathophysiologic alterations in mixed states exceeds those associated with nonmixed mania or depression and suggest that hyperactivation and hyperarousal are core features of mixed states.
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Affiliation(s)
- Alessio Simonetti
- Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, 1977 Butler Boulevard, Houston, TX 77030, USA; Department of Neurology and Psychiatry, Sapienza University of Rome, Rome, Italy; Centro Lucio Bini, Rome, Italy.
| | - Marijn Lijffijt
- Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, 1977 Butler Boulevard, Houston, TX 77030, USA; Michael E. DeBakey VA Medical Center, Houston, TX, USA
| | - Alan C Swann
- Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, 1977 Butler Boulevard, Houston, TX 77030, USA; Michael E. DeBakey VA Medical Center, Houston, TX, USA
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10
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Case KC, Salsaa M, Yu W, Greenberg ML. Regulation of Inositol Biosynthesis: Balancing Health and Pathophysiology. Handb Exp Pharmacol 2020; 259:221-260. [PMID: 30591968 DOI: 10.1007/164_2018_181] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Inositol is the precursor for all inositol compounds and is essential for viability of eukaryotic cells. Numerous cellular processes and signaling functions are dependent on inositol compounds, and perturbation of their synthesis leads to a wide range of human diseases. Although considerable research has been directed at understanding the function of inositol compounds, especially phosphoinositides and inositol phosphates, a focus on regulatory and homeostatic mechanisms controlling inositol biosynthesis has been largely neglected. Consequently, little is known about how synthesis of inositol is regulated in human cells. Identifying physiological regulators of inositol synthesis and elucidating the molecular mechanisms that regulate inositol synthesis will contribute fundamental insight into cellular processes that are mediated by inositol compounds and will provide a foundation to understand numerous disease processes that result from perturbation of inositol homeostasis. In addition, elucidating the mechanisms of action of inositol-depleting drugs may suggest new strategies for the design of second-generation pharmaceuticals to treat psychiatric disorders and other illnesses.
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Affiliation(s)
- Kendall C Case
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA
| | - Michael Salsaa
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA
| | - Wenxi Yu
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Miriam L Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA.
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11
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Bayraktar Bilen N, Titiz AP, Bilen S, Polat Gultekin B, Sahin Hamurcu M, Kalayci D. Optical coherence tomography and neurodegeneration in epilepsy. Eur J Ophthalmol 2019; 31:252-257. [PMID: 31645118 DOI: 10.1177/1120672119881982] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
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.
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Affiliation(s)
- Neslihan Bayraktar Bilen
- Department of Ophthalmology, Ankara Numune Training and Research Hospital, Ankara, Turkey.,Department of Neurology, Ankara Numune Training and Research Hospital, Ankara, Turkey
| | - Ayse Pinar Titiz
- Department of Ophthalmology, Ankara Numune Training and Research Hospital, Ankara, Turkey.,Department of Neurology, Ankara Numune Training and Research Hospital, Ankara, Turkey
| | - Sule Bilen
- Department of Ophthalmology, Ankara Numune Training and Research Hospital, Ankara, Turkey.,Department of Neurology, Ankara Numune Training and Research Hospital, Ankara, Turkey
| | - Burcu Polat Gultekin
- Department of Ophthalmology, Ankara Numune Training and Research Hospital, Ankara, Turkey.,Department of Neurology, Ankara Numune Training and Research Hospital, Ankara, Turkey
| | - Mualla Sahin Hamurcu
- Department of Ophthalmology, Ankara Numune Training and Research Hospital, Ankara, Turkey.,Department of Neurology, Ankara Numune Training and Research Hospital, Ankara, Turkey
| | - Defne Kalayci
- Department of Ophthalmology, Ankara Numune Training and Research Hospital, Ankara, Turkey.,Department of Neurology, Ankara Numune Training and Research Hospital, Ankara, Turkey
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12
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Direct Reprogramming of Human Neurons Identifies MARCKSL1 as a Pathogenic Mediator of Valproic Acid-Induced Teratogenicity. Cell Stem Cell 2019; 25:103-119.e6. [PMID: 31155484 DOI: 10.1016/j.stem.2019.04.021] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 02/19/2019] [Accepted: 04/26/2019] [Indexed: 12/24/2022]
Abstract
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.
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13
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Zhang L, Fan Z, Han Y, Xu L, Liu W, Bai X, Zhou M, Li J, Wang H. Valproic Acid Promotes Survival of Facial Motor Neurons in Adult Rats After Facial Nerve Transection: a Pilot Study. J Mol Neurosci 2018. [PMID: 29532368 DOI: 10.1007/s12031-018-1051-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Valproic acid (VPA), a medication primarily used to treat epilepsy and bipolar disorder, has been applied to the repair of central and peripheral nervous system injury. The present study investigated the effect of VPA on functional recovery, survival of facial motor neurons (FMNs), and expression of proteins in rats after facial nerve trunk transection by functional measurement, Nissl staining, TUNEL, immunofluorescence, and Western blot. Following facial nerve injury, all rats in group VPA showed a better functional recovery, which was significant at the given time, compared with group NS. The Nissl staining results demonstrated that the number of FMNs survival in group VPA was higher than that in group normal saline (NS). TUNEL staining showed that axonal injury of facial nerve could lead to neuronal apoptosis of FMNs. But treatment of VPA significantly reduced cell apoptosis by decreasing the expression of Bax protein and increased neuronal survival by upregulating the level of brain-derived neurotrophic factor (BDNF) and growth associated protein-43 (GAP-43) expression in injured FMNs compared with group NS. Overall, our findings suggest that VPA may advance functional recovery, reduce lesion-induced apoptosis, and promote neuron survival after facial nerve transection in rats. This study provides an experimental evidence for better understanding the mechanism of injury and repair of peripheral facial paralysis.
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Affiliation(s)
- Lili Zhang
- Department of Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China
- Department of Otolaryngology-Head and Neck Surgery, Yantai Affiliated Hospital of Binzhou Medical University, Yantai, 264199, China
| | - Zhaomin Fan
- Department of Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China
| | - Yuechen Han
- Department of Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China
| | - Lei Xu
- Department of Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China
| | - Wenwen Liu
- Shandong Provincial Key Laboratory of Otology, Jinan, 250022, China
| | - Xiaohui Bai
- Shandong Provincial Key Laboratory of Otology, Jinan, 250022, China
| | - Meijuan Zhou
- Shandong Provincial Key Laboratory of Otology, Jinan, 250022, China
| | - Jianfeng Li
- Shandong Provincial Key Laboratory of Otology, Jinan, 250022, China
- Institute of Eye and ENT, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250022, China
| | - Haibo Wang
- Department of Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China.
- Shandong Provincial Key Laboratory of Otology, Jinan, 250022, China.
- Institute of Eye and ENT, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, 250022, China.
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14
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Yu W, Daniel J, Mehta D, Maddipati KR, Greenberg ML. MCK1 is a novel regulator of myo-inositol phosphate synthase (MIPS) that is required for inhibition of inositol synthesis by the mood stabilizer valproate. PLoS One 2017; 12:e0182534. [PMID: 28817575 PMCID: PMC5560674 DOI: 10.1371/journal.pone.0182534] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 07/19/2017] [Indexed: 12/28/2022] Open
Abstract
Myo-inositol, the precursor of all inositol compounds, is essential for the viability of eukaryotes. Identifying the factors that regulate inositol homeostasis is of obvious importance to understanding cell function and the pathologies underlying neurological and metabolic resulting from perturbation of inositol metabolism. The current study identifies Mck1, a GSK3 homolog, as a novel positive regulator of inositol de novo synthesis in yeast. Mck1 was required for normal activity of myo-inositol phosphate synthase (MIPS), which catalyzes the rate-limiting step of inositol synthesis. mck1Δ cells exhibited a 50% decrease in MIPS activity and a decreased rate of incorporation of [13C6]glucose into [13C6]-inositol-3-phosphate and [13C6]-inositol compared to WT cells. mck1Δ cells also exhibited decreased growth in the presence of the inositol depleting drug valproate (VPA), which was rescued by supplementation of inositol. However, in contrast to wild type cells, which exhibited more than a 40% decrease in MIPS activity in the presence of VPA, the drug did not significantly decrease MIPS activity in mck1Δ cells. These findings indicate that VPA-induced MIPS inhibition is Mck1-dependent, and suggest a model that unifies two current hypotheses of the mechanism of action of VPA—inositol depletion and GSK3 inhibition.
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Affiliation(s)
- Wenxi Yu
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America
| | - Joshua Daniel
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America
| | - Dhara Mehta
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America
| | - Krishna Rao Maddipati
- Department of Pathology, Wayne State University, Detroit, Michigan, United States of America
| | - Miriam L. Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America
- * E-mail:
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15
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Metabolic abnormality in the right dorsolateral prefrontal cortex in patients with obsessive-compulsive disorder: proton magnetic resonance spectroscopy. Acta Neuropsychiatr 2017; 29:164-169. [PMID: 27748207 DOI: 10.1017/neu.2016.48] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Proton magnetic resonance spectroscopy (1H-MRS) was used to evaluate metabolic changes in the dorsolateral prefrontal cortex (DLPFC) in patients with obsessive-compulsive disorder (OCD). METHODS In total, 14 OCD patients (mean age 28.9±7.2 years) and 14 healthy controls (mean age 32.6±7.1 years) with no history of neurological and psychiatric illness participated in this study. Brain metabolite concentrations were measured from a localised voxel on the right DLPFC using a 3-Tesla 1H-MRS. RESULTS The metabolic concentration of myo-inositol in patients with OCD increased significantly by 52% compared with the healthy controls, whereas glutamine/glutamate was decreased by 11%. However, there were no significant differences in N-acetylaspartate, choline, lactate and lipid between the two groups. CONCLUSION These findings would be helpful to understand the pathophysiology of OCD associated with the brain metabolic abnormalities in the right DLPFC.
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16
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Tomimoto K, Akao T, Fukuda H. Phenotypes and brewing characteristics of sake yeast Kyokai no. 7 mutants resistant to valproate. JOURNAL OF THE INSTITUTE OF BREWING 2017. [DOI: 10.1002/jib.420] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Kazuya Tomimoto
- Brewing Microbiology Division; National Research Institute of Brewing; 3-7-1, Higashi-hiroshima Hiroshima 739-0046 Japan
| | - Takeshi Akao
- Brewing Microbiology Division; National Research Institute of Brewing; 3-7-1, Higashi-hiroshima Hiroshima 739-0046 Japan
| | - Hisashi Fukuda
- Planning and Management Division; National Research Institute of Brewing; 3-7-1, Higashi-hiroshima Hiroshima 739-0046 Japan
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17
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Tipping the scales: Lessons from simple model systems on inositol imbalance in neurological disorders. Eur J Cell Biol 2017; 96:154-163. [PMID: 28153412 DOI: 10.1016/j.ejcb.2017.01.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 01/18/2017] [Accepted: 01/21/2017] [Indexed: 11/20/2022] Open
Abstract
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.
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18
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Jadhav S, Russo S, Cowart LA, Greenberg ML. Inositol Depletion Induced by Acute Treatment of the Bipolar Disorder Drug Valproate Increases Levels of Phytosphingosine. J Biol Chem 2017; 292:4953-4959. [PMID: 28100786 DOI: 10.1074/jbc.m117.775460] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 01/17/2017] [Indexed: 12/13/2022] Open
Abstract
Bipolar disorder (BD) is a severe psychiatric illness affecting ∼1% of the world population. Valproate (VPA) and lithium, widely used for the treatment of BD, are not universally effective. These drugs have been shown to cause inositol depletion, but translating this observation to a specific therapeutic mechanism has been difficult, hampering the development of more effective therapies. We have shown previously in yeast that chronic VPA treatment induces the unfolded protein response due to increasing ceramide levels. To gain insight into the mechanisms activated during acute VPA treatment, we performed a genome-wide expression study in yeast treated with VPA for 30 min. We observed increased mRNA and protein levels of RSB1, which encodes an exporter of long chain bases dihydrosphingosine (DHS) and phytosphingosine (PHS), and further saw that VPA increased sensitivity of an rsb1Δ mutant to PHS, suggesting that VPA increases long chain base levels. Consistent with this, PHS levels were elevated in wild type and, to a greater extent, in rsb1Δ cells. Expression of ORM genes (negative regulators of PHS synthesis) and of fatty acid elongase genes FEN1 and SUR4 were decreased, and expression of YOR1 (exporter of PHS-1P) and DPL1 (lyase that degrades DHS-1P and PHS-1P) was increased. These effects were more pronounced in medium lacking inositol, and were mirrored by inositol starvation of an ino1Δ mutant. These findings provide a metabolic explanation as to how VPA-mediated inositol depletion causes increased synthesis of PHS and further support the therapeutic relevance of inositol depletion as a bipolar disorder treatment.
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Affiliation(s)
- Shyamalagauri Jadhav
- From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202
| | - Sarah Russo
- the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425, and.,the Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29425
| | - L Ashley Cowart
- the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425, and.,the Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29425
| | - Miriam L Greenberg
- From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202,
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19
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Distinctive gene expression profile in women with history of postpartum depression. Genomics 2016; 109:1-8. [PMID: 27816578 DOI: 10.1016/j.ygeno.2016.10.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 09/12/2016] [Accepted: 10/20/2016] [Indexed: 11/20/2022]
Abstract
Postpartum depression (PPD) is a disease which incorporates a variety of depressive states differing in nature and severity. To assist in the understanding of the pathogenesis of the disease, we aimed to ascertain a molecular mechanism underlying PPD development. We applied microarray technology to characterize gene expression of euthymic women with a history of PPD and compared the results with healthy controls. Our study demonstrated that women who considered euthymic on a clinical level, in fact, had an altered molecular profile when compared to participants with no PPD history. We identified nine genes significantly distinguished expression in post- depressive women; they may serve as a diagnostic tool for the detection of a predisposition to PPD. Our findings contribute significantly to the understanding of PPD etiology and its pathogenesis, offer a plausible explanation for the risk of the PPD recurrence, and may also contribute to clinical treatment.
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20
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Combined Transcriptomics and Chemical-Genetics Reveal Molecular Mode of Action of Valproic acid, an Anticancer Molecule using Budding Yeast Model. Sci Rep 2016; 6:35322. [PMID: 27734932 PMCID: PMC5062167 DOI: 10.1038/srep35322] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 09/28/2016] [Indexed: 12/16/2022] Open
Abstract
Valproic acid (VA) is a pharmacologically important histone deacetylase inhibitor that recently garnered attention as an anticancer agent. Since the molecular mechanisms behind the multiple effects of VA are unclear, this study was aimed to unravel the comprehensive cellular processes affected by VA and its molecular targets in vivo using budding yeast as a model organism. Interestingly, genome-wide transcriptome analysis of cells treated with VA showed differential regulation of 30% of the genome. Functional enrichment analysis of VA transcriptome evidenced alteration of various cellular processes including cell cycle, cell wall biogenesis, DNA repair, ion homeostasis, metabolism, stress response, transport and ribosomal biogenesis, etc. Moreover, our genetic screening analysis revealed VA molecular targets belonging to oxidative and osmotic stress, DNA repair, cell wall integrity, and iron homeostasis. Further, our results demonstrated the activation of mitogen-activated protein kinases (MAPKs) Hog1 (p38) and Slt2 (p44/42) upon VA treatment. Our results also exhibited that VA acts through alteration of mitochondrial, ER architecture and functions. Especially, VA effects were neutralized in cells lacking lipid particles. Altogether, our results deciphered the novel molecular insights and mechanistic links to strengthen our knowledge on diverse cellular effects of VA along with its probable therapeutic targets and detoxification approaches.
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21
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Jadhav S, Russo S, Cottier S, Schneiter R, Cowart A, Greenberg ML. Valproate Induces the Unfolded Protein Response by Increasing Ceramide Levels. J Biol Chem 2016; 291:22253-22261. [PMID: 27590340 DOI: 10.1074/jbc.m116.752634] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Indexed: 11/06/2022] Open
Abstract
Bipolar disorder (BD), which is characterized by depression and mania, affects 1-2% of the world population. Current treatments are effective in only 40-60% of cases and cause severe side effects. Valproate (VPA) is one of the most widely used drugs for the treatment of BD, but the therapeutic mechanism of action of this drug is not understood. This knowledge gap has hampered the development of effective treatments. To identify candidate pathways affected by VPA, we performed a genome-wide expression analysis in yeast cells grown in the presence or absence of the drug. VPA caused up-regulation of FEN1 and SUR4, encoding fatty acid elongases that catalyze the synthesis of very long chain fatty acids (C24 to C26) required for ceramide synthesis. Interestingly, fen1Δ and sur4Δ mutants exhibited VPA sensitivity. In agreement with increased fatty acid elongase gene expression, VPA increased levels of phytoceramide, especially those containing C24-C26 fatty acids. Consistent with an increase in ceramide, VPA decreased the expression of amino acid transporters, increased the expression of ER chaperones, and activated the unfolded protein response element (UPRE), suggesting that VPA induces the UPR pathway. These effects were rescued by supplementation of inositol and similarly observed in inositol-starved ino1Δ cells. Starvation of ino1Δ cells increased expression of FEN1 and SUR4, increased ceramide levels, decreased expression of nutrient transporters, and induced the UPR. These findings suggest that VPA-mediated inositol depletion induces the UPR by increasing the de novo synthesis of ceramide.
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Affiliation(s)
- Shyamalagauri Jadhav
- From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202
| | - Sarah Russo
- the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425, the Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29401, and
| | - Stéphanie Cottier
- the Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland
| | - Roger Schneiter
- the Department of Biology, University of Fribourg, 1700 Fribourg, Switzerland
| | - Ashley Cowart
- the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425, the Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29401, and
| | - Miriam L Greenberg
- From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202,
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22
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Frej AD, Clark J, Le Roy CI, Lilla S, Thomason PA, Otto GP, Churchill G, Insall RH, Claus SP, Hawkins P, Stephens L, Williams RSB. The Inositol-3-Phosphate Synthase Biosynthetic Enzyme Has Distinct Catalytic and Metabolic Roles. Mol Cell Biol 2016; 36:1464-79. [PMID: 26951199 PMCID: PMC4859692 DOI: 10.1128/mcb.00039-16] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 02/19/2016] [Accepted: 03/03/2016] [Indexed: 12/24/2022] Open
Abstract
Inositol levels, maintained by the biosynthetic enzyme inositol-3-phosphate synthase (Ino1), are altered in a range of disorders, including bipolar disorder and Alzheimer's disease. To date, most inositol studies have focused on the molecular and cellular effects of inositol depletion without considering Ino1 levels. Here we employ a simple eukaryote, Dictyostelium discoideum, to demonstrate distinct effects of loss of Ino1 and inositol depletion. We show that loss of Ino1 results in an inositol auxotrophy that can be rescued only partially by exogenous inositol. Removal of inositol supplementation from the ino1(-) mutant resulted in a rapid 56% reduction in inositol levels, triggering the induction of autophagy, reduced cytokinesis, and substrate adhesion. Inositol depletion also caused a dramatic generalized decrease in phosphoinositide levels that was rescued by inositol supplementation. However, loss of Ino1 triggered broad metabolic changes consistent with the induction of a catabolic state that was not rescued by inositol supplementation. These data suggest a metabolic role for Ino1 that is independent of inositol biosynthesis. To characterize this role, an Ino1 binding partner containing SEL1L1 domains (Q54IX5) and having homology to mammalian macromolecular complex adaptor proteins was identified. Our findings therefore identify a new role for Ino1, independent of inositol biosynthesis, with broad effects on cell metabolism.
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Affiliation(s)
- Anna D Frej
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, United Kingdom
| | - Jonathan Clark
- The Babraham Institute, Cambridge, Cambridgeshire, United Kingdom
| | - Caroline I Le Roy
- Department of Food and Nutritional Sciences, The University of Reading, Reading, Berkshire, United Kingdom
| | - Sergio Lilla
- Cancer Research UK Beatson Institute, Bearsden, Glasgow, United Kingdom
| | - Peter A Thomason
- Cancer Research UK Beatson Institute, Bearsden, Glasgow, United Kingdom
| | - Grant P Otto
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, United Kingdom
| | - Grant Churchill
- Department of Pharmacology, University of Oxford, Oxford, Oxfordshire, United Kingdom
| | - Robert H Insall
- Cancer Research UK Beatson Institute, Bearsden, Glasgow, United Kingdom
| | - Sandrine P Claus
- Department of Food and Nutritional Sciences, The University of Reading, Reading, Berkshire, United Kingdom
| | - Phillip Hawkins
- The Babraham Institute, Cambridge, Cambridgeshire, United Kingdom
| | - Len Stephens
- The Babraham Institute, Cambridge, Cambridgeshire, United Kingdom
| | - Robin S B Williams
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, United Kingdom
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23
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Yu W, Greenberg ML. Inositol depletion, GSK3 inhibition and bipolar disorder. FUTURE NEUROLOGY 2016; 11:135-148. [PMID: 29339929 DOI: 10.2217/fnl-2016-0003] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 03/04/2016] [Indexed: 12/31/2022]
Abstract
Valproic acid and lithium are widely used to treat bipolar disorder, a severe illness characterized by cycles of mania and depression. However, their efficacy is limited, and treatment is often accompanied by serious side effects. The therapeutic mechanisms of these drugs are not understood, hampering the development of more effective treatments. Among the plethora of biochemical effects of the drugs, those that are common to both may be more related to therapeutic efficacy. Two common outcomes include inositol depletion and GSK3 inhibition, which have been proposed to explain the efficacy of both valproic acid and lithium. Here, we discuss the inositol depletion and GSK3 inhibition hypotheses, and introduce a unified model suggesting that inositol depletion and GSK3 inhibition are inter-related.
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Affiliation(s)
- Wenxi Yu
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
| | - Miriam L Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
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24
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Deranieh RM, Shi Y, Tarsio M, Chen Y, McCaffery JM, Kane PM, Greenberg ML. Perturbation of the Vacuolar ATPase: A NOVEL CONSEQUENCE OF INOSITOL DEPLETION. J Biol Chem 2015; 290:27460-72. [PMID: 26324718 DOI: 10.1074/jbc.m115.683706] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Indexed: 11/06/2022] Open
Abstract
Depletion of inositol has profound effects on cell function and has been implicated in the therapeutic effects of drugs used to treat epilepsy and bipolar disorder. We have previously shown that the anticonvulsant drug valproate (VPA) depletes inositol by inhibiting myo-inositol-3-phosphate synthase, the enzyme that catalyzes the first and rate-limiting step of inositol biosynthesis. To elucidate the cellular consequences of inositol depletion, we screened the yeast deletion collection for VPA-sensitive mutants and identified mutants in vacuolar sorting and the vacuolar ATPase (V-ATPase). Inositol depletion caused by starvation of ino1Δ cells perturbed the vacuolar structure and decreased V-ATPase activity and proton pumping in isolated vacuolar vesicles. VPA compromised the dynamics of phosphatidylinositol 3,5-bisphosphate (PI3,5P2) and greatly reduced V-ATPase proton transport in inositol-deprived wild-type cells. Osmotic stress, known to increase PI3,5P2 levels, did not restore PI3,5P2 homeostasis nor did it induce vacuolar fragmentation in VPA-treated cells, suggesting that perturbation of the V-ATPase is a consequence of altered PI3,5P2 homeostasis under inositol-limiting conditions. This study is the first to demonstrate that inositol depletion caused by starvation of an inositol synthesis mutant or by the inositol-depleting drug VPA leads to perturbation of the V-ATPase.
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Affiliation(s)
- Rania M Deranieh
- From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202
| | - Yihui Shi
- From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202
| | - Maureen Tarsio
- the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210, and
| | - Yan Chen
- From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202
| | - J Michael McCaffery
- the Integrated Imaging Center, Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218
| | - Patricia M Kane
- the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210, and
| | - Miriam L Greenberg
- From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202,
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25
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Li X, Liu H, Fischhaber PL, Tang TS. Toward therapeutic targets for SCA3: Insight into the role of Machado-Joseph disease protein ataxin-3 in misfolded proteins clearance. Prog Neurobiol 2015; 132:34-58. [PMID: 26123252 DOI: 10.1016/j.pneurobio.2015.06.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 05/30/2015] [Accepted: 06/16/2015] [Indexed: 01/09/2023]
Abstract
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.
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Affiliation(s)
- Xiaoling Li
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Hongmei Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Paula L Fischhaber
- Department of Chemistry and Biochemistry, California State University Northridge, Northridge, CA 91330-8262, USA.
| | - Tie-Shan Tang
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
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26
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Villarreal FD, Kültz D. Direct Ionic Regulation of the Activity of Myo-Inositol Biosynthesis Enzymes in Mozambique Tilapia. PLoS One 2015; 10:e0123212. [PMID: 26066044 PMCID: PMC4466255 DOI: 10.1371/journal.pone.0123212] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 02/28/2015] [Indexed: 11/27/2022] Open
Abstract
Myo-inositol (Ins) is a major compatible osmolyte in many cells, including those of Mozambique tilapia (Oreochromis mossambicus). Ins biosynthesis is highly up-regulated in tilapia and other euryhaline fish exposed to hyperosmotic stress. In this study, enzymatic regulation of two enzymes of Ins biosynthesis, Ins phosphate synthase (MIPS) and inositol monophosphatase (IMPase), by direct ionic effects is analyzed. Specific MIPS and IMPase isoforms from Mozambique tilapia (MIPS-160 and IMPase 1) were selected based on experimental, phylogenetic, and structural evidence supporting their role for Ins biosynthesis during hyperosmotic stress. Recombinant tilapia IMPase 1 and MIPS-160 activity was assayed in vitro at ionic conditions that mimic changes in the intracellular milieu during hyperosmotic stress. The in vitro activities of MIPS-160 and IMPase 1 are highest at alkaline pH of 8.8. IMPase 1 catalytic efficiency is strongly increased during hyperosmolality (particularly for the substrate D-Ins-3-phosphate, Ins-3P), mainly as a result of [Na+] elevation. Furthermore, the substrate-specificity of IMPase 1 towards D-Ins-1-phosphate (Ins-1P) is lower than towards Ins-3P. Because MIPS catalysis results in Ins-3P this results represents additional evidence for IMPase 1 being the isoform that mediates Ins biosynthesis in tilapia. Our data collectively demonstrate that the Ins biosynthesis enzymes are activated under ionic conditions that cells are exposed to during hypertonicity, resulting in Ins accumulation, which, in turn, results in restoration of intracellular ion homeostasis. We propose that the unique and direct ionic regulation of the activities of Ins biosynthesis enzymes represents an efficient biochemical feedback loop for regulation of intracellular physiological ion homeostasis during hyperosmotic stress.
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Affiliation(s)
- Fernando D. Villarreal
- EcoPhysiological Proteomics Laboratory, Department of Animal Science, University of California Davis, One Shields Avenue, Davis, California 95616, United States of America
| | - Dietmar Kültz
- EcoPhysiological Proteomics Laboratory, Department of Animal Science, University of California Davis, One Shields Avenue, Davis, California 95616, United States of America
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Ye C, Greenberg ML. Inositol synthesis regulates the activation of GSK-3α in neuronal cells. J Neurochem 2014; 133:273-83. [PMID: 25345501 DOI: 10.1111/jnc.12978] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 10/10/2014] [Accepted: 10/13/2014] [Indexed: 12/26/2022]
Abstract
The synthesis of inositol provides precursors of inositol lipids and inositol phosphates that are pivotal for cell signaling. Mood stabilizers lithium and valproic acid, used for treating bipolar disorder, cause cellular inositol depletion, which has been proposed as a therapeutic mechanism of action of both drugs. Despite the importance of inositol, the requirement for inositol synthesis in neuronal cells is not well understood. Here, we examined inositol effects on proliferation of SK-N-SH neuroblastoma cells. The essential role of inositol synthesis in proliferation is underscored by the findings that exogenous inositol was dispensable for proliferation, and inhibition of inositol synthesis decreased proliferation. Interestingly, the inhibition of inositol synthesis by knocking down INO1, which encodes inositol-3-phosphate synthase, the rate-limiting enzyme of inositol synthesis, led to the inactivation of GSK-3α by increasing the inhibitory phosphorylation of this kinase. Similarly, the mood stabilizer valproic acid effected transient decreases in intracellular inositol, leading to inactivation of GSK-3α. As GSK-3 inhibition has been proposed as a likely therapeutic mechanism of action, the finding that inhibition of inositol synthesis results in the inactivation of GSK-3α suggests a unifying hypothesis for mechanism of mood-stabilizing drugs. Inositol is an essential metabolite that serves as a precursor for inositol lipids and inositol phosphates. We report that inhibition of the rate-limiting enzyme of inositol synthesis leads to the inactivation of glycogen synthase kinase (GSK) 3α by increasing inhibitory phosphorylation of this kinase. These findings have implications for the therapeutic mechanisms of mood stabilizers and suggest that inositol synthesis and GSK 3α activity are intrinsically related.
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Affiliation(s)
- Cunqi Ye
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA
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Zhang L, Di J. The transcriptional activator Ino2p dissociates from the yeast INM1 promoter in induction. DNA Cell Biol 2014; 33:863-8. [PMID: 25211324 DOI: 10.1089/dna.2014.2397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mood stabilizers lithium and valproates are widely used in the treatment of bipolar disorder. It has been shown that these drugs can affect the inositol monophosphatase activity and thus the inositol de novo biosynthesis. However, the molecular mechanism of this action has thus far been vague. As such, characterizing the regulation of the gene encoding inositol monophosphatase at the molecular level can help to understand the bipolar disorder. As the model organism, the inositol monophosphatase is encoded by INM1 in Saccharomyces cerevisiae. In this study, we showed, using real-time reverse transcriptase polymerase chain reaction analysis, that INM1 is expressed in the presence of inositol, suggesting that the presence of inositol is required for INM1 transcriptional activation. We also demonstrated, using chromatin immunoprecipitation, that Ino2p is present at the promoter under uninduced conditions. Upon induction, Ino2p dissociates from the INM1 promoter. Furthermore, chromatin remodelers Ino80p and Snf2p are recruited to INM1 promoter upon induction as well as histone acetylases Gcn5p and Esa1p. Altogether, we have provided the evidence which describes how the transcriptional activator and coactivators participate in INM1 activation.
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Affiliation(s)
- Lingzhi Zhang
- 1 Department of Emergency, Shengjing Hospital of China Medical University , Shenyang, China
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Chang P, Walker MC, Williams RSB. Seizure-induced reduction in PIP3 levels contributes to seizure-activity and is rescued by valproic acid. Neurobiol Dis 2013; 62:296-306. [PMID: 24148856 PMCID: PMC3898270 DOI: 10.1016/j.nbd.2013.10.017] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 09/11/2013] [Accepted: 10/11/2013] [Indexed: 12/31/2022] Open
Abstract
Phosphatidylinositol (3–5) trisphosphate (PIP3) is a central regulator of diverse neuronal functions that are critical for seizure progression, however its role in seizures is unclear. We have recently hypothesised that valproic acid (VPA), one of the most commonly used drugs for the treatment of epilepsy, may target PIP3 signalling as a therapeutic mode of action. Here, we show that seizure induction using kainic acid in a rat in vivo epilepsy model resulted in a decrease in hippocampal PIP3 levels and reduced protein kinase B (PKB/AKT) phosphorylation, measured using ELISA mass assays and Western blot analysis, and both changes were restored following VPA treatment. These finding were reproduced in cultured rat hippocampal primary neurons and entorhinal cortex–hippocampal slices during exposure to the GABA(A) receptor antagonist pentylenetetrazol (PTZ), which is widely used to generate seizures and seizure-like (paroxysmal) activity. Moreover, VPA's effect on paroxysmal activity in the PTZ slice model is blocked by phosphatidylinositol 3-kinase (PI3K) inhibition or PIP2 sequestration by neomycin, indicating that VPA's efficacy is dependent upon PIP3 signalling. PIP3 depletion following PTZ treatment may also provide a positive feedback loop, since enhancing PIP3 depletion increases, and conversely, reducing PIP3 dephosphorylation reduces paroxysmal activity and this effect is dependent upon AMPA receptor activation. Our results therefore indicate that PIP3 depletion occurs with seizure activity, and that VPA functions to reverse these effects, providing a novel mechanism for VPA in epilepsy treatment. In vivo seizure induction (using kainic acid) reduces hippocampal PIP3 levels. In vivo seizure induction (using kainic acid) reduces hippocampal phospho-PKB levels. Valproic acid protects against these reductions under seizure conditions only. Similar regulation is seen with PTZ-induced in vitro seizure activity. Seizure-induced PIP3 reduction causes a feedback activation of seizure activity.
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Affiliation(s)
- Pishan Chang
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK
| | - Matthew C Walker
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, WC1N 3BG, UK.
| | - Robin S B Williams
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK.
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De-Souza EA, Pimentel FSA, Machado CM, Martins LS, da-Silva WS, Montero-Lomelí M, Masuda CA. The unfolded protein response has a protective role in yeast models of classic galactosemia. Dis Model Mech 2013; 7:55-61. [PMID: 24077966 PMCID: PMC3882048 DOI: 10.1242/dmm.012641] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Classic galactosemia is a human autosomal recessive disorder caused by mutations in the GALT gene (GAL7 in yeast), which encodes the enzyme galactose-1-phosphate uridyltransferase. Here we show that the unfolded protein response pathway is triggered by galactose in two yeast models of galactosemia: lithium-treated cells and the gal7Δ mutant. The synthesis of galactose-1-phosphate is essential to trigger the unfolded protein response under these conditions because the deletion of the galactokinase-encoding gene GAL1 completely abolishes unfolded protein response activation and galactose toxicity. Impairment of the unfolded protein response in both yeast models makes cells even more sensitive to galactose, unmasking its cytotoxic effect. These results indicate that endoplasmic reticulum stress is induced under galactosemic conditions and underscores the importance of the unfolded protein response pathway to cellular adaptation in these models of classic galactosemia.
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Affiliation(s)
- Evandro A De-Souza
- Instituto de Bioquímica Médica Leopoldo de Meis, Programa de Biologia Molecular e Biotecnologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-590, Brazil
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31
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Deranieh RM, He Q, Caruso JA, Greenberg ML. Phosphorylation regulates myo-inositol-3-phosphate synthase: a novel regulatory mechanism of inositol biosynthesis. J Biol Chem 2013; 288:26822-33. [PMID: 23902760 DOI: 10.1074/jbc.m113.479121] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
myo-Inositol-3-phosphate synthase (MIPS) plays a crucial role in inositol homeostasis. Transcription of the coding gene INO1 is highly regulated. However, regulation of the enzyme is not well defined. We previously showed that MIPS is indirectly inhibited by valproate, suggesting that the enzyme is post-translationally regulated. Using (32)Pi labeling and phosphoamino acid analysis, we show that yeast MIPS is a phosphoprotein. Mass spectrometry analysis identified five phosphosites, three of which are conserved in the human MIPS. Analysis of phosphorylation-deficient and phosphomimetic site mutants indicated that the three conserved sites in yeast (Ser-184, Ser-296, and Ser-374) and humans (Ser-177, Ser-279, and Ser-357) affect MIPS activity. Both S296A and S296D yeast mutants and S177A and S177D human mutants exhibited decreased enzymatic activity, suggesting that a serine residue is critical at that location. The phosphomimetic mutations S184D (human S279D) and S374D (human S357D) but not the phosphodeficient mutations decreased activity, suggesting that phosphorylation of these two sites is inhibitory. The double mutation S184A/S374A caused an increase in MIPS activity, conferred a growth advantage, and partially rescued sensitivity to valproate. Our findings identify a novel mechanism of regulation of inositol synthesis by phosphorylation of MIPS.
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Valproic acid: an anticonvulsant drug with potent antinociceptive and anti-inflammatory properties. Naunyn Schmiedebergs Arch Pharmacol 2013; 386:575-87. [PMID: 23584602 DOI: 10.1007/s00210-013-0853-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2012] [Accepted: 03/11/2013] [Indexed: 01/02/2023]
Abstract
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.
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Seelan RS, Pisano MM, Greene RM, Casanova MF, Parthasarathy RN. Differential methylation of the gene encoding myo-inositol 3-phosphate synthase (Isyna1) in rat tissues. Epigenomics 2012; 3:111-24. [PMID: 21841945 DOI: 10.2217/epi.10.73] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
AIMS Myo-inositol levels are frequently altered in several brain disorders. Myo-inositol 3-phosphate synthase, encoded by the Isyna1 gene, catalyzes the synthesis of myo-inositol in cells. Very little is known about the mechanisms regulating Isyna1 expression in brain and other tissues. In this study, we have examined the role of DNA methylation in regulating Isyna1 expression in rat tissues. MATERIALS & METHODS Transfection analysis using in vitro methylated promoter constructs, Southern blot analysis of genomic DNA from various tissues digested with a methylation-sensitive enzyme and CpG methylation profiling of genomic DNA from different tissues were used to determine differential methylation of Isyna1 in tissues. Transfection analysis using plasmids harboring mutated CpG residues in the 5'-upstream region of Isyna1 was used to identify critical residues mediating promoter activity. RESULTS The -700 bp to -500 bp region (region 1) of Isyna1 exhibited increased methylation in brain cortex compared with other tissues; it also exhibited sex-specific methylation differences between matched male and female brain cortices. Mutation analysis identified one CpG residue in region 1 necessary for promoter activity in neuronal cells. A tissue-specific differentially methylated region (T-DMR) was found to be localized between +450 bp and +650 bp (region 3). This DMR was comparatively highly methylated in spleen, moderately methylated in brain cortex and poorly methylated in testis, consistent with mRNA levels observed in these tissues. CONCLUSION Rat Isyna1 exhibits tissue-specific DNA methylation. Brain DNA was uniquely methylated in the 5'-upstream region and displayed gender specificity. A T-DMR was identified within the gene body of Isyna1. These findings suggest that Isyna1 is regulated, in part, by DNA methylation and that significant alterations in methylation patterns during development could have a major impact on inositol phosphate synthase expression in later life.
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Affiliation(s)
- Ratnam S Seelan
- Molecular, Cellular & Craniofacial Biology, Birth Defects Center, University of Louisville, 501 S. Preston St, KY 40292, USA.
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Chen J, Korostyshevsky D, Lee S, Perlstein EO. Accumulation of an antidepressant in vesiculogenic membranes of yeast cells triggers autophagy. PLoS One 2012; 7:e34024. [PMID: 22529904 PMCID: PMC3329523 DOI: 10.1371/journal.pone.0034024] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 02/20/2012] [Indexed: 11/29/2022] Open
Abstract
Many antidepressants are cationic amphipaths, which spontaneously accumulate in natural or reconstituted membranes in the absence of their specific protein targets. However, the clinical relevance of cellular membrane accumulation by antidepressants in the human brain is unknown and hotly debated. Here we take a novel, evolutionarily informed approach to studying the effects of the selective-serotonin reuptake inhibitor sertraline/Zoloft® on cell physiology in the model eukaryote Saccharomyces cerevisiae (budding yeast), which lacks a serotonin transporter entirely. We biochemically and pharmacologically characterized cellular uptake and subcellular distribution of radiolabeled sertraline, and in parallel performed a quantitative ultrastructural analysis of organellar membrane homeostasis in untreated vs. sertraline-treated cells. These experiments have revealed that sertraline enters yeast cells and then reshapes vesiculogenic membranes by a complex process. Internalization of the neutral species proceeds by simple diffusion, is accelerated by proton motive forces generated by the vacuolar H+-ATPase, but is counteracted by energy-dependent xenobiotic efflux pumps. At equilibrium, a small fraction (10–15%) of reprotonated sertraline is soluble while the bulk (90–85%) partitions into organellar membranes by adsorption to interfacial anionic sites or by intercalation into the hydrophobic phase of the bilayer. Asymmetric accumulation of sertraline in vesiculogenic membranes leads to local membrane curvature stresses that trigger an adaptive autophagic response. In mutants with altered clathrin function, this adaptive response is associated with increased lipid droplet formation. Our data not only support the notion of a serotonin transporter-independent component of antidepressant function, but also enable a conceptual framework for characterizing the physiological states associated with chronic but not acute antidepressant administration in a model eukaryote.
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Affiliation(s)
- Jingqiu Chen
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Daniel Korostyshevsky
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Sean Lee
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Ethan O. Perlstein
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
- * E-mail:
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Chang P, Orabi B, Deranieh RM, Dham M, Hoeller O, Shimshoni JA, Yagen B, Bialer M, Greenberg ML, Walker MC, Williams RSB. The antiepileptic drug valproic acid and other medium-chain fatty acids acutely reduce phosphoinositide levels independently of inositol in Dictyostelium. Dis Model Mech 2012; 5:115-24. [PMID: 21876211 PMCID: PMC3255550 DOI: 10.1242/dmm.008029] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 07/14/2011] [Indexed: 12/11/2022] Open
Abstract
Valproic acid (VPA) is the most widely prescribed epilepsy treatment worldwide, but its mechanism of action remains unclear. Our previous work identified a previously unknown effect of VPA in reducing phosphoinositide production in the simple model Dictyostelium followed by the transfer of data to a mammalian synaptic release model. In our current study, we show that the reduction in phosphoinositide [PtdInsP (also known as PIP) and PtdInsP(2) (also known as PIP(2))] production caused by VPA is acute and dose dependent, and that this effect occurs independently of phosphatidylinositol 3-kinase (PI3K) activity, inositol recycling and inositol synthesis. In characterising the structural requirements for this effect, we also identify a family of medium-chain fatty acids that show increased efficacy compared with VPA. Within the group of active compounds is a little-studied group previously associated with seizure control, and analysis of two of these compounds (nonanoic acid and 4-methyloctanoic acid) shows around a threefold enhanced potency compared with VPA for protection in an in vitro acute rat seizure model. Together, our data show that VPA and a newly identified group of medium-chain fatty acids reduce phosphoinositide levels independently of inositol regulation, and suggest the reinvestigation of these compounds as treatments for epilepsy.
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Affiliation(s)
- Pishan Chang
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, TW20 0EX, UK
| | - Benoit Orabi
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, TW20 0EX, UK
| | - Rania M. Deranieh
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
| | - Manik Dham
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, TW20 0EX, UK
| | - Oliver Hoeller
- Department of Cellular and Molecular Pharmacology and the Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA
| | - Jakob A. Shimshoni
- Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Boris Yagen
- Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Meir Bialer
- Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Miriam L. Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
| | - Matthew C. Walker
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Robin S. B. Williams
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, TW20 0EX, UK
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Kronstad JW, Hu G, Choi J. The cAMP/Protein Kinase A Pathway and Virulence in Cryptococcus neoformans. MYCOBIOLOGY 2011; 39:143-50. [PMID: 22783095 PMCID: PMC3385117 DOI: 10.5941/myco.2011.39.3.143] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 08/30/2011] [Indexed: 05/21/2023]
Abstract
The basidiomycete fungus Cryptococcus neoformans is an important pathogen of immunocompromised people. The ability of the fungus to sense its environment is critical for proliferation and the generation of infectious propagules, as well as for adaptation to the mammalian host during infection. The conserved cAMP/protein kinase A pathway makes an important contribution to sensing, as demonstrated by the phenotypes of mutants with pathway defects. These phenotypes include loss of the ability to mate and to elaborate the key virulence factors capsule and melanin. This review summarizes recent work that reveals new targets of the pathway, new phenotypic consequences of signaling defects, and a more detailed understanding of connections with other aspects of cryptococcal biology including iron regulation, pH sensing, and stress.
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Affiliation(s)
- James W Kronstad
- The Michael Smith Laboratories, Department of Microbiology and Immunology, Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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Abstract
Anticonvulsant drugs are widely used in psychiatric indications. This includes alcohol and benzodiazepine withdrawal symptoms, panic and anxiety disorders, dementia, schizophrenia, and to some extent personality disorders. Besides pain syndromes, their main domain outside epilepsy, however, is bipolar disorder. Carbamazepine, valproate, and lamotrigine are meanwhile recognized mood stabilizers, but several other antiepileptic drugs have also been tried out with diverging or inconclusive results. Understanding the mechanisms of action and identifying similarities between anticonvulsants effective in bipolar disorder may also enhance our understanding of the underlying pathophysiology of the disorder.
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Affiliation(s)
- Heinz C R Grunze
- School of Neurology, Neurobiology and Psychiatry, University of Newcastle upon Tyne, UK.
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Ding D, Shi Y, Shaltiel G, Azab AN, Pullumbi E, Campbell A, Mehta DV, Agam G, Greenberg ML. Yeast bioassay for identification of inositol depleting compounds. World J Biol Psychiatry 2010; 10:893-9. [PMID: 18979283 DOI: 10.1080/15622970802485276] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Bipolar affective disorder is a chronic, severe, debilitating illness affecting 1-2% of the population. Valproate, along with lithium and carbamazepine, are the only drugs for which long-term efficacy has been established. However, these drugs are ineffective for, and not well tolerated by, a large number of patients and are also associated with teratogenicity and reproductive defects. Therefore, there is a substantial need to develop more effective anti-bipolar drugs. We have previously shown that valproate, like lithium, decreases intracellular inositol, which supports the inositol depletion hypothesis. We employed inositol depletion in yeast as a screening tool to identify potential new anti-bipolar medications. We show here that hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, ethylhexanoate, and methyloctanoate decrease intracellular inositol levels and increase the expression of INO1, the gene encoding myo-inositol-3-phosphate synthase (MIPS). Similar to valproate, these inositol-depleting carboxylic acids inhibited MIPS indirectly. A correlation was shown between cell growth inhibition and the increase in INO1 expression by the carboxylic acids, factors that were reversed in the presence of inositol. Inositol depletion in yeast may be exploited as an easy and inexpensive screening test for potential new inositol depleting anti-bipolar drugs.
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Affiliation(s)
- Daobin Ding
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
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Abstract
The anticonvulsant properties of VPA (valproic acid), a branched short-chain fatty acid, were serendipitously discovered in 1963. Since then, therapeutic roles of VPA have increased to include bipolar disorder and migraine prophylaxis, and have more recently been proposed in cancer, Alzheimer's disease and HIV treatment. These numerous therapeutic roles elevate VPA to near 'panacea' level. Surprisingly, the mechanisms of action of VPA in the treatment of many of these disorders remain unclear, although it has been shown to alter a wide variety of signalling pathways and a small number of direct targets. To analyse the mechanism of action of VPA, a number of studies have defined the structural characteristics of VPA-related compounds giving rise to distinct therapeutic and cellular effects, including adverse effects such as teratogenicity and hepatotoxicity. These studies raise the possibility of identifying target-specific novel compounds, providing better therapeutic action or reduced side effects. This short review will describe potential therapeutic pathways targeted by VPA, and highlight studies showing structural constraints necessary for these effects.
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Investigation of the H+–myo-inositol transporter (HMIT) as a neuronal regulator of phosphoinositide signalling. Biochem Soc Trans 2009; 37:1139-43. [DOI: 10.1042/bst0371139] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Phosphoinositide signalling regulates a series of important neuronal processes that are thought to be altered in mood disorders. Furthermore, mood-stabilizing drugs inhibit key enzymes that regulate phosphoinositide production and alter neuronal growth cone morphology in an inositol-reversible manner. Inositol is taken up by neurons from the extracellular fluid, presumably via membrane transporters; it can also be synthesized by the enzyme MIP-synthase (myo-inositol-1-phosphate synthase) and, in addition, it is generated by inositol phospholipid hydrolysis. The neuronal-specific HMIT (H+–myo-inositol transporter) represents a potential regulator of inositol signalling in neurons that warrants further investigation.
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Abstract
The inositol-depletion hypothesis was suggested to explain the therapeutic mechanism of mood-stabilizing drugs. Focus was previously on the phosphatidylinositol signalling pathway and on the regulatory roles of Ins(3,4,5)P3 and DAG (diacylglycerol). Recent findings indicate that inositol and inositol-containing molecules, including phosphoinositides and inositol phosphates, have signalling and regulatory roles in many cellular processes. This suggests that depleting inositol may lead to perturbation of a wide range of cellular functions, at least some of which may be associated with bipolar disorder.
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Guérin R, Beauregard PB, Leroux A, Rokeach LA. Calnexin regulates apoptosis induced by inositol starvation in fission yeast. PLoS One 2009; 4:e6244. [PMID: 19606215 PMCID: PMC2705804 DOI: 10.1371/journal.pone.0006244] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Accepted: 06/08/2009] [Indexed: 12/21/2022] Open
Abstract
Inositol is a precursor of numerous phospholipids and signalling molecules essential for the cell. Schizosaccharomyces pombe is naturally auxotroph for inositol as its genome does not have a homologue of the INO1 gene encoding inositol-1-phosphate synthase, the enzyme responsible for inositol biosynthesis. In this work, we demonstrate that inositol starvation in S. pombe causes cell death with apoptotic features. This apoptotic death is dependent on the metacaspase Pca1p and is affected by the UPR transducer Ire1p. Previously, we demonstrated that calnexin is involved in apoptosis induced by ER stress. Here, we show that cells expressing a lumenal version of calnexin exhibit a 2-fold increase in the levels of apoptosis provoked by inositol starvation. This increase is reversed by co-expression of a calnexin mutant spanning the transmembrane domain and C-terminal cytosolic tail. Coherently, calnexin is physiologically cleaved at the end of its lumenal domain, under normal growth conditions when cells approach stationary phase. This cleavage suggests that the two naturally produced calnexin fragments are needed to continue growth into stationary phase and to prevent cell death. Collectively, our observations indicate that calnexin takes part in at least two apoptotic pathways in S. pombe, and suggest that the cleavage of calnexin has regulatory roles in apoptotic processes involving calnexin.
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Affiliation(s)
- Renée Guérin
- Department of Biochemistry, Université de Montréal, Montréal, Québec, Canada
| | | | - Alexandre Leroux
- Department of Biochemistry, Université de Montréal, Montréal, Québec, Canada
| | - Luis A. Rokeach
- Department of Biochemistry, Université de Montréal, Montréal, Québec, Canada
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Seelan RS, Lakshmanan J, Casanova MF, Parthasarathy RN. Identification of myo-inositol-3-phosphate synthase isoforms: characterization, expression, and putative role of a 16-kDa gamma(c) isoform. J Biol Chem 2009; 284:9443-57. [PMID: 19188364 PMCID: PMC2666597 DOI: 10.1074/jbc.m900206200] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 02/02/2009] [Indexed: 11/06/2022] Open
Abstract
Myo-inositol is an important constituent of membrane phospholipids and is a precursor for the phosphoinositide signaling pathway. It is synthesized from glucose 6-phosphate by myo-inositol-3-phosphate synthase (IP synthase), a homotrimer composed of a 68-kDa polypeptide in most mammalian tissues. It is a putative target for mood-stabilizing drugs such as lithium and valproate. Here, we show that the rat gene (Isyna1) encoding this enzyme generates a number of alternatively spliced transcripts in addition to the fully spliced form that encodes the 68-kDa subunit (the alpha isoform). Specifically, we identify a small 16-kDa subunit (the gamma(c) isoform) derived by an intron retention mechanism and provide evidence for its existence in rat tissues. The gamma(c) isoform is highly conserved in mammals, but it lacks the catalytic domain while retaining the NAD(+) binding domain. Both alpha and gamma(c) isoforms are predominantly expressed in many rat tissues and display apparent stoichiometry in purified enzyme preparations. An IP synthase polyclonal antibody not only detects the alpha and gamma(c) isoforms but also several other isoforms in pancreas, intestine, and testis suggesting that the holoenzyme is composed of unique subunits in various tissues. Interestingly, the alpha isoform is not expressed in the intestine. IP synthase activity assays using purified alpha and gamma(c) isoforms indicate that the latter negatively modulates alpha isoform activity, possibly by competing for NAD(+) molecules. Our findings have important ramifications for understanding the mood stabilization process and suggest that inositol biosynthesis is a highly regulated and dynamic process.
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Affiliation(s)
- Ratnam S Seelan
- Department of Psychiatry, University of Louisville, Louisville, Kentucky 40202, USA.
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Ethylbutyrate, a valproate-like compound, exhibits inositol-depleting effects — A potential mood-stabilizing drug. Life Sci 2009; 84:38-44. [DOI: 10.1016/j.lfs.2008.10.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Revised: 10/19/2008] [Accepted: 10/28/2008] [Indexed: 11/23/2022]
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Marmol F. Lithium: bipolar disorder and neurodegenerative diseases Possible cellular mechanisms of the therapeutic effects of lithium. Prog Neuropsychopharmacol Biol Psychiatry 2008; 32:1761-71. [PMID: 18789369 DOI: 10.1016/j.pnpbp.2008.08.012] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Revised: 08/19/2008] [Accepted: 08/19/2008] [Indexed: 12/12/2022]
Abstract
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.
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Affiliation(s)
- Frederic Marmol
- Unitat de Farmacologia, Facultat de Medicina, Universitat de Barcelona, Casanova, 143, 08036 Barcelona, Spain.
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Song D, Du T, Li B, Cai L, Gu L, Li H, Chen Y, Hertz L, Peng L. Astrocytic alkalinization by therapeutically relevant lithium concentrations: implications for myo-inositol depletion. Psychopharmacology (Berl) 2008; 200:187-95. [PMID: 18506424 DOI: 10.1007/s00213-008-1194-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/27/2007] [Accepted: 04/27/2008] [Indexed: 11/29/2022]
Abstract
RATIONALE One theory for therapeutic effects of the lithium ion (Li+) in bipolar disorder is that myo-inositol, needed for phospholipase C-mediated signaling, is depleted by Li(+)-induced inhibition of inositolphosphate hydrolysis or of myo-inositol uptake, an effect demonstrated in cultured mouse astrocytes at high myo-inositol concentrations. In contrast, myo-inositol uptake is inhibited at low concentrations, reflecting that it occurs both by the high-affinity Na(+)-dependent myo-inositol transporter (SMIT) and the lower-affinity H(+)-dependent inositol transporter (HMIT). Increased intracellular pH (pHi) stimulates SMIT but inhibits HMIT, suggesting that the effect of Li+ could be caused by intracellular alkalinization. In this study, we therefore investigated Li+ effects on intracellular pH in astrocytes, measured by 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) fluorescence. RESULTS Chronic treatment with the therapeutically relevant Li+ concentration of 1 mM for 2 or 3 weeks increased pHi by approximately 0.10, whereas 0.5 mM was ineffective, and 2 mM caused a larger increase. The alkalinization resulted from acute stimulation of the Na+/H+ exchanger (NHE) by extracellular Li+, demonstrated after acid load with NH4Cl. In response to continuous stimulation, NHE1 mRNA was down-regulated, but protein was not. CONCLUSIONS Chronic treatment with pharmacologically relevant Li+ concentrations increases pHi in astrocytes, creating conditions for decreased uptake of high myo-inositol concentrations and increased uptake of low concentrations. The pharmacological relevance of this effect is supported by literature data suggesting brain acidosis in bipolar patients and by preliminary observations that carbamazepine and valproate also increase pHi in astrocytes. Stimulation of NHE1-stimulated sodium ion uptake might also trigger uptake of chloride ions and osmotically obliged water.
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Affiliation(s)
- Dan Song
- Department of Clinical Pharmacology, College of Basic Medical Sciences, China Medical University, Shenyang, People's Republic of China
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Azab AN, Ishak JF, Kaplanski J, Delbar V, Greenberg ML. Mechanisms of action of the mood stabilizer valproate: a focus on GSK-3 inhibition. FUTURE NEUROLOGY 2008. [DOI: 10.2217/14796708.3.4.433] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
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.
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Affiliation(s)
- Abed N Azab
- Ben-Gurion University of the Negev, School for Community Health Professions, Faculty of Health Sciences, PO Box 653, Beer-Sheva 84105, Israel
| | - Julia F Ishak
- Ben-Gurion University of the Negev, Medical School for International Health, Faculty of Health Sciences, PO Box 653, Beer-Sheva 84105, Israel
| | - Jacob Kaplanski
- Ben-Gurion University of the Negev, Department of Clinical Pharmacology, Faculty of Health Sciences, PO Box 653, Beer-Sheva 84105, Israel
| | - Vered Delbar
- Ben-Gurion University of the Negev, School for Community Health Professions, Faculty of Health Sciences, PO Box 653, Beer-Sheva 84105, Israel
| | - Miriam L Greenberg
- Wayne State University, Department of Biological Sciences, Detroit, MI 48202, USA
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Azab AN, Agam G, Kaplanski J, Delbar V, Greenberg ML. Inositol depletion: a good or bad outcome of valproate treatment? FUTURE NEUROLOGY 2008. [DOI: 10.2217/14796708.3.3.275] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
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.
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Affiliation(s)
- Abed N Azab
- Ben-Gurion University of the Negev, School for Community Health Professions, Faculty of Health Sciences, PO Box 653, Beer-Sheva 84105, Israel
| | - Galila Agam
- Ben-Gurion University of the Negev, Psychiatry Research Unit & Department of Clinical Biochemistry, Faculty of Health Sciences, PO Box 4600, Beer-Sheva 84170, Israel
| | - Jacob Kaplanski
- Ben-Gurion University of the Negev, Department of Clinical Pharmacology, Faculty of Health Sciences, PO Box 653, Beer-Sheva 84105, Israel
| | - Vered Delbar
- Ben-Gurion University of the Negev, School for Community Health Professions, Faculty of Health Sciences, PO Box 653, Beer-Sheva 84105, Israel
| | - Miriam L Greenberg
- Wayne State University, Department of Biological Sciences, Detroit, MI 48202, USA
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McGrath BM, McKay R, Dave S, Seres P, Weljie AM, Slupsky CM, Hanstock CC, Greenshaw AJ, Silverstone PH. Acute dextro-amphetamine administration does not alter brain myo-inositol levels in humans and animals: MRS investigations at 3 and 18.8 T. Neurosci Res 2008; 61:351-9. [PMID: 18508145 DOI: 10.1016/j.neures.2008.04.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Revised: 04/05/2008] [Accepted: 04/09/2008] [Indexed: 11/24/2022]
Abstract
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.
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Affiliation(s)
- Brent M McGrath
- Department of Psychiatry, University of Alberta, Edmonton, Alberta, Canada T6G 2B7.
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Microarray gene expression profiling of mouse brain mRNA in a model of lithium treatment. Psychiatr Genet 2008; 18:64-72. [DOI: 10.1097/ypg.0b013e3282fb0051] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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