1
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Coyle JT. Passing the torch: The ascendance of the glutamatergic synapse in the pathophysiology of schizophrenia. Biochem Pharmacol 2024:116376. [PMID: 38906225 DOI: 10.1016/j.bcp.2024.116376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 06/11/2024] [Accepted: 06/18/2024] [Indexed: 06/23/2024]
Abstract
For nearly fifty years, the dopamine hypothesis has dominated our understanding of the pathophysiology of schizophrenia and provided the lone target for drug development. However, with the exception of clozapine, the dopamine D2 receptor antagonizing anti-psychotic drugs have little impact on the negative symptoms and cognitive deficits, aspects of the disorder that robustly predict outcome. Pathologic studies reveal cortical atrophy and wide-spread loss of glutamatergic synaptic spines, unexplained by dopaminergic malfunction. Recent genome-wide association studies indicate that at least thirty risk genes for schizophrenia encode proteins localized to the glutamatergic synapse and inhibit glutamate neurotransmission, especially at the NMDA receptor. To function, the NMDA receptor requires the binding of glycine (primarily in the cerebellum and brainstem) or D-serine (in forebrain) to the NR1 channel subunit of the NMDA receptor. Genetically silencing the gene (srr) encoding serine racemase, the biosynthetic enzyme for D-serine, results in forebrain NMDA receptor hypofunction. The srr-/- mice have 90 % loss of endogenous D-serine and approximately 70 % decrease in NMDA receptor function. Several animal models of schizophrenia are based on behavioral and pharmacologic strategies, which have negligible validity with regard to the fundamental etiology of schizophrenia. We summarize here the results of a mouse model, in which srr, one of the two dozen or more risk gene for schizophrenia that affect NMDA receptor function, has been inactivated. The srr-/- mice exhibit striking similarities to schizophrenia including cortical atrophy, loss of cortico-limbic glutamatergic synapses, increased sub-cortical dopamine release, EEG abnormalities, and cognitive impairments. The limited efficacy of drugs targeting the glutamatergic synapse on DSM-5 diagnosed criteria for schizophrenia used in clinical trials may reflect the fact that only 30 % of the patients have impaired glutamatergic neurotransmission, resulting from the genetic heterogeneity of the disorder.
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Affiliation(s)
- Joseph T Coyle
- Eben S Draper Professor of Psychiatry and Neuroscience Harvard Medical School (Emeritus), McLean Hospital, 115 Mill St, Belmont, MA 02478, United States.
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2
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Donlon J, Kumari P, Varghese SP, Bai M, Florentin OD, Frost ED, Banks J, Vadlapatla N, Kam O, Shad MU, Rahman S, Abulseoud OA, Stone TW, Koola MM. Integrative Pharmacology in the Treatment of Substance Use Disorders. J Dual Diagn 2024; 20:132-177. [PMID: 38117676 DOI: 10.1080/15504263.2023.2293854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
The detrimental physical, mental, and socioeconomic effects of substance use disorders (SUDs) have been apparent to the medical community for decades. However, it has become increasingly urgent in recent years to develop novel pharmacotherapies to treat SUDs. Currently, practitioners typically rely on monotherapy. Monotherapy has been shown to be superior to no treatment at all for most substance classes. However, many randomized controlled trials (RCTs) have revealed that monotherapy leads to poorer outcomes when compared with combination treatment in all specialties of medicine. The results of RCTs suggest that monotherapy frequently fails since multiple dysregulated pathways, enzymes, neurotransmitters, and receptors are involved in the pathophysiology of SUDs. As such, research is urgently needed to determine how various neurobiological mechanisms can be targeted by novel combination treatments to create increasingly specific yet exceedingly comprehensive approaches to SUD treatment. This article aims to review the neurobiology that integrates many pathophysiologic mechanisms and discuss integrative pharmacology developments that may ultimately improve clinical outcomes for patients with SUDs. Many neurobiological mechanisms are known to be involved in SUDs including dopaminergic, nicotinic, N-methyl-D-aspartate (NMDA), and kynurenic acid (KYNA) mechanisms. Emerging evidence indicates that KYNA, a tryptophan metabolite, modulates all these major pathophysiologic mechanisms. Therefore, achieving KYNA homeostasis by harmonizing integrative pathophysiology and pharmacology could prove to be a better therapeutic approach for SUDs. We propose KYNA-NMDA-α7nAChRcentric pathophysiology, the "conductor of the orchestra," as a novel approach to treat many SUDs concurrently. KYNA-NMDA-α7nAChR pathophysiology may be the "command center" of neuropsychiatry. To date, extant RCTs have shown equivocal findings across comparison conditions, possibly because investigators targeted single pathophysiologic mechanisms, hit wrong targets in underlying pathophysiologic mechanisms, and tested inadequate monotherapy treatment. We provide examples of potential combination treatments that simultaneously target multiple pathophysiologic mechanisms in addition to KYNA. Kynurenine pathway metabolism demonstrates the greatest potential as a target for neuropsychiatric diseases. The investigational medications with the most evidence include memantine, galantamine, and N-acetylcysteine. Future RCTs are warranted with novel combination treatments for SUDs. Multicenter RCTs with integrative pharmacology offer a promising, potentially fruitful avenue to develop novel therapeutics for the treatment of SUDs.
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Affiliation(s)
- Jack Donlon
- Cooper Medical School of Rowan University, Camden, New Jersey, USA
| | - Pooja Kumari
- Community Living Trent Highlands, Peterborough, Canada
| | - Sajoy P Varghese
- Addiction Recovery Treatment Services, Veterans Affairs Northern California Health Care System, University of California, Davis, Sacramento, California, USA
| | - Michael Bai
- Columbia University, New York, New York, USA
| | - Ori David Florentin
- Department of Psychiatry, Westchester Medical Center, Valhalla, New York, USA
| | - Emma D Frost
- Department of Neurology, Cooper University Health Care, Camden, New Jersey, USA
| | - John Banks
- Talkiatry Mental Health Clinic, New York, New York, USA
| | - Niyathi Vadlapatla
- Thomas Jefferson High School for Science and Technology, Alexandria, Virginia, USA
| | - Olivia Kam
- Stony Brook University Renaissance School of Medicine, Stony Brook, New York, USA
| | - Mujeeb U Shad
- Department of Psychiatry, University of Nevada Las Vegas, Las Vegas, Nevada, USA
| | - Shafiqur Rahman
- Department of Pharmaceutical Sciences, College of Pharmacy, South Dakota State University, Brookings, South Dakota, USA
| | - Osama A Abulseoud
- Department of Psychiatry and Psychology, Alix School of Medicine at Mayo Clinic, Phoenix, Arizona, USA
| | - Trevor W Stone
- Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, UK
| | - Maju Mathew Koola
- Department of Psychiatry and Behavioral Health, Cooper University Health Care, Cooper Medical School of Rowan University, Camden, New Jersey, USA
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3
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Souza INDO, Roychaudhuri R, de Belleroche J, Mothet JP. d-Amino acids: new clinical pathways for brain diseases. Trends Mol Med 2023; 29:1014-1028. [PMID: 37770379 DOI: 10.1016/j.molmed.2023.09.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 09/01/2023] [Accepted: 09/05/2023] [Indexed: 09/30/2023]
Abstract
Free d-amino acids (d-AAs) are emerging as a novel and important class of signaling molecules in many organs, including the brain and endocrine systems. There has been considerable progress in our understanding of the fundamental roles of these atypical messengers, with increasingly recognized implications in a wide range of neuropathologies, including schizophrenia (SCZ), epilepsy, Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), substance abuse, and chronic pain, among others. Research has enabled the discovery that d-serine, d-aspartate and more recently d-cysteine are essential for the healthy development and function of the central nervous system (CNS). We discuss recent progress that has profoundly transformed our vision of numerous physiological processes but has also shown how d-AAs are now offering therapeutic promise in clinical settings for several human diseases.
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Affiliation(s)
- Isis Nem de Oliveira Souza
- Biophotonics and Synapse Physiopathology Team, Laboratoire LuMIn UMR9024 Université Paris-Saclay, ENS Paris-Saclay, CNRS, CentraleSupelec, 91190 Gif-sur-Yvette, France; Molecular Pharmacology Laboratory, Biomedical Sciences Institute, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Robin Roychaudhuri
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Center for Birth Defects, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Jacqueline de Belleroche
- Neurogenetics Group, Division of Brain Sciences, Department of Medicine, Imperial College London, London, UK
| | - Jean-Pierre Mothet
- Biophotonics and Synapse Physiopathology Team, Laboratoire LuMIn UMR9024 Université Paris-Saclay, ENS Paris-Saclay, CNRS, CentraleSupelec, 91190 Gif-sur-Yvette, France.
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4
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Desai RI, Kangas BD, Luc OT, Solakidou E, Smith EC, Dawes MH, Ma X, Makriyannis A, Chatterjee S, Dayeh MA, Muñoz-Jaramillo A, Desai MI, Limoli CL. Complex 33-beam simulated galactic cosmic radiation exposure impacts cognitive function and prefrontal cortex neurotransmitter networks in male mice. Nat Commun 2023; 14:7779. [PMID: 38012180 PMCID: PMC10682413 DOI: 10.1038/s41467-023-42173-x] [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: 02/10/2023] [Accepted: 09/28/2023] [Indexed: 11/29/2023] Open
Abstract
Astronauts will encounter extended exposure to galactic cosmic radiation (GCR) during deep space exploration, which could impair brain function. Here, we report that in male mice, acute or chronic GCR exposure did not modify reward sensitivity but did adversely affect attentional processes and increased reaction times. Potassium (K+)-stimulation in the prefrontal cortex (PFC) elevated dopamine (DA) but abolished temporal DA responsiveness after acute and chronic GCR exposure. Unlike acute GCR, chronic GCR increased levels of all other neurotransmitters, with differences evident between groups after higher K+-stimulation. Correlational and machine learning analysis showed that acute and chronic GCR exposure differentially reorganized the connection strength and causation of DA and other PFC neurotransmitter networks compared to controls which may explain space radiation-induced neurocognitive deficits.
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Affiliation(s)
- Rajeev I Desai
- Department of Psychiatry, Harvard Medical School, Boston, MA, 02115, USA.
- Behavioral Biology Program, McLean Hospital, Belmont, MA, 02478, USA.
- Center for Drug Discovery, Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, 02115, USA.
| | - Brian D Kangas
- Department of Psychiatry, Harvard Medical School, Boston, MA, 02115, USA
- Behavioral Biology Program, McLean Hospital, Belmont, MA, 02478, USA
| | - Oanh T Luc
- Department of Psychiatry, Harvard Medical School, Boston, MA, 02115, USA
- Behavioral Biology Program, McLean Hospital, Belmont, MA, 02478, USA
| | - Eleana Solakidou
- Center for Drug Discovery, Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, 02115, USA
- Medical School, University of Crete, Heraklion, Greece
| | - Evan C Smith
- Center for Drug Discovery, Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, 02115, USA
| | - Monica H Dawes
- Department of Psychiatry, Harvard Medical School, Boston, MA, 02115, USA
- Behavioral Biology Program, McLean Hospital, Belmont, MA, 02478, USA
| | - Xiaoyu Ma
- Center for Drug Discovery, Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, 02115, USA
| | - Alexandros Makriyannis
- Center for Drug Discovery, Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, 02115, USA
| | | | - Maher A Dayeh
- Southwest Research Institute, San Antonio, TX, 78238, USA
- University of San Antonio, San Antonio, TX, 78249, USA
| | | | - Mihir I Desai
- Southwest Research Institute, San Antonio, TX, 78238, USA
- University of San Antonio, San Antonio, TX, 78249, USA
| | - Charles L Limoli
- Department of Radiation Oncology, University of California, Irvine, Orange, CA, 92697, USA
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5
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Toikumo S, Xu H, Gelernter J, Kember RL, Kranzler HR. Integrating human brain proteomic data with genome-wide association study findings identifies novel brain proteins in substance use traits. Neuropsychopharmacology 2022; 47:2292-2299. [PMID: 35941285 PMCID: PMC9630289 DOI: 10.1038/s41386-022-01406-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 06/13/2022] [Accepted: 07/16/2022] [Indexed: 11/09/2022]
Abstract
Despite the identification of a growing number of genetic risk loci for substance use traits (SUTs), the impact of these loci on protein abundance and the potential utility of relevant proteins as therapeutic targets are unknown. We conducted a proteome-wide association study (PWAS) in which we integrated human brain proteomes from discovery (Banner; N = 152) and validation (ROSMAP; N = 376) datasets with genome-wide association study (GWAS) summary statistics for 4 SUTs. The 4 samples comprised GWAS of European-ancestry individuals for smoking initiation [Smk] (N = 1,232,091), alcohol use disorder [AUD] (N = 313,959), cannabis use disorder [CUD] (N = 384,032), and opioid use disorder [OUD] (N = 302,585). We conducted transcriptome-wide association studies (TWAS) with human brain transcriptomic data to examine the overlap of genetic effects at the proteomic and transcriptomic levels and characterize significant genes through conditional, colocalization, and fine-mapping analyses. We identified 27 genes (Smk = 21, AUD = 3, CUD = 2, OUD = 1) that were significantly associated with cis-regulated brain protein abundance. Of these, 7 showed evidence for causality (Smk: NT5C2, GMPPB, NQO1, RHOT2, SRR and ACTR1B; and AUD: CTNND1). Cis-regulated transcript levels for 8 genes (Smk = 6, CUD = 1, OUD = 1) were associated with SUTs, indicating that genetic loci could confer risk for these SUTs by modulating both gene expression and proteomic abundance. Functional studies of the high-confidence risk proteins identified here are needed to determine whether they are modifiable targets and useful in developing medications and biomarkers for these SUTs.
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Affiliation(s)
- Sylvanus Toikumo
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
- Mental Illness Research, Education and Clinical Center, Crescenz VAMC, Philadelphia, PA, USA
| | - Heng Xu
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Joel Gelernter
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - Rachel L Kember
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
- Mental Illness Research, Education and Clinical Center, Crescenz VAMC, Philadelphia, PA, USA.
| | - Henry R Kranzler
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
- Mental Illness Research, Education and Clinical Center, Crescenz VAMC, Philadelphia, PA, USA.
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6
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Subcortical control of the default mode network: Role of the basal forebrain and implications for neuropsychiatric disorders. Brain Res Bull 2022; 185:129-139. [PMID: 35562013 PMCID: PMC9290753 DOI: 10.1016/j.brainresbull.2022.05.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 04/29/2022] [Accepted: 05/04/2022] [Indexed: 01/03/2023]
Abstract
The precise interplay between large-scale functional neural systems throughout the brain is essential for performance of cognitive processes. In this review we focus on the default mode network (DMN), one such functional network that is active during periods of quiet wakefulness and believed to be involved in introspection and planning. Abnormalities in DMN functional connectivity and activation appear across many neuropsychiatric disorders, including schizophrenia. Recent evidence suggests subcortical regions including the basal forebrain are functionally and structurally important for regulation of DMN activity. Within the basal forebrain, subregions like the ventral pallidum may influence DMN activity and the nucleus basalis of Meynert can inhibit switching between brain networks. Interactions between DMN and other functional networks including the medial frontoparietal network (default), lateral frontoparietal network (control), midcingulo-insular network (salience), and dorsal frontoparietal network (attention) are also discussed in the context of neuropsychiatric disorders. Several subtypes of basal forebrain neurons have been identified including basal forebrain parvalbumin-containing or somatostatin-containing neurons which can regulate cortical gamma band oscillations and DMN-like behaviors, and basal forebrain cholinergic neurons which might gate access to sensory information during reinforcement learning. In this review, we explore this evidence, discuss the clinical implications on neuropsychiatric disorders, and compare neuroanatomy in the human vs rodent DMN. Finally, we address technological advancements which could help provide a more complete understanding of modulation of DMN function and describe newly identified BF therapeutic targets that could potentially help restore DMN-associated functional deficits in patients with a variety of neuropsychiatric disorders.
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7
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Zengin G, Huri M. The sensory processing patterns of individuals with schizophrenia with comorbid substance use disorder. JOURNAL OF SUBSTANCE USE 2022. [DOI: 10.1080/14659891.2022.2071348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Gülşah Zengin
- Therapy and Rehabilitation Department, Nevşehir Hacı Bektaş Veli University, Nevşehir, Turkey
| | - Meral Huri
- Occupational Therapy Department, Hacettepe University, Ankara, Turkey
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8
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Takagi S, Puhl MD, Anderson T, Balu DT, Coyle JT. Serine Racemase Expression by Striatal Neurons. Cell Mol Neurobiol 2022; 42:279-289. [PMID: 32445040 PMCID: PMC7680280 DOI: 10.1007/s10571-020-00880-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 05/15/2020] [Indexed: 01/03/2023]
Abstract
D-serine is synthesized by serine racemase (SR) and is a co-agonist at forebrain N-methyl-D-aspartate receptors (NMDARs). D-serine and SR are expressed primarily in neurons, but not in quiescent astrocytes. In this study, we examined the localization of D-serine and SR in the mouse striatum and the effects of genetically silencing SR expression in GABAergic interneurons (iSR-/-). iSR-/- mice had substantially reduced SR expression almost exclusively in striatum, but only exhibited marginal D-serine reduction. SR positive cells in the striatum showed strong co-localization with dopamine- and cyclic AMP-regulated neuronal phosphoprotein (DARPP32) in wild type mice. Transgenic fluorescent reporter mice for either the D1 or D2 dopamine receptors exhibited a 65:35 ratio for co-localization with D1and D2 receptor positive cells, respectively. These results indicate that GABAergic medium spiny neurons receiving dopaminergic inputs in striatum robustly and uniformly express SR. In behavioral tests, iSR-/- mice showed a blunted response to the hedonic and stimulant effects of cocaine, without affecting anxiety-related behaviors. Because the cocaine effects have been shown in the constitutive SR-/- mice, the restriction of the blunted response to cocaine to iSR-/- mice reinforces the conclusion that D-serine in striatal GABAergic neurons plays an important role in mediating dopaminergic stimulant effects. Results in this study suggest that SR in striatal GABAergic neurons is synthesizing D-serine, not as a glutamatergic co-transmitter, but rather as an autocrine whereby the GABAergic neurons control the excitability of their NMDARs by determining the availability of the co-agonist, D-serine.
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Affiliation(s)
- Shunsuke Takagi
- Department of Psychiatry and Behavioral Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan,Department of Psychiatry, Tokyo Medical and Dental University Hospital, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan,Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan,Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA
| | - Matthew D. Puhl
- Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA
| | - Thea Anderson
- Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA
| | - Darrick T. Balu
- Department of Psychiatry, Harvard Medical School, 25 Shattuck Street, Boston, MA 02115, USA,Translational Psychiatry Laboratory, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA
| | - Joseph T. Coyle
- Laboratory for Psychiatric and Molecular Neuroscience, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA,Department of Psychiatry, Harvard Medical School, 25 Shattuck Street, Boston, MA 02115, USA
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9
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Folorunso OO, Harvey TL, Brown SE, Cruz C, Shahbo E, Ajjawi I, Balu DT. Forebrain expression of serine racemase during postnatal development. Neurochem Int 2021; 145:104990. [PMID: 33592203 PMCID: PMC8012237 DOI: 10.1016/j.neuint.2021.104990] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 01/25/2021] [Accepted: 02/10/2021] [Indexed: 12/23/2022]
Abstract
N-methyl-D-aspartate receptors (NMDARs) are important for synaptogenesis, synaptic maturation and refinement during the early postnatal weeks after birth. Defective synapse formation or refinement underlie cognitive and emotional abnormalities in various neurodevelopmental disorders (NDDs), including schizophrenia (Sz) and autism spectrum disorder (ASD). Serine racemase (SR) is a neuronal enzyme that produces D-serine, a co-agonist required for full NMDAR activation. NMDAR hypofunction as a result of genetic SR elimination and reduced synaptic availability of D-serine reduces neuronal dendritic arborization and spine density. In adult mouse brain, the expression of SR parallels that of NMDARs across forebrain regions including the striatum, amygdala, hippocampus, and medial prefrontal cortex (mPFC). However, there have yet to be studies providing a detailed characterization of the spatial and temporal expression of SR during early periods of synaptogenesis. Here, we examined the postnatal expression of SR in cortical and subcortical brain regions important for learning, memory and emotional regulation, during the first four weeks after birth. Using dual-antigen immunofluorescence, we demonstrate that the number of SR+ neurons steadily increases with postnatal age across the mPFC, amygdala, hippocampus and striatum. We also identified differences in the rate of SR protein induction both across and within brain regions. Analyzing existing human post-mortem brain in situ data, there was a similar developmental mRNA expression profile of SRR and GRIN1 (GluN1 subunit) from infancy through the first decade of life. Our findings further support a developmental role for D-serine mediated NMDAR activation regulating synaptogenesis and neural circuit refinement, which has important implications for the pathophysiology of Sz and other NDDs.
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Affiliation(s)
- Oluwarotimi O Folorunso
- Department of Psychiatry, Harvard Medical School, Boston, MA, 02115, United States; Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, 02478, United States
| | - Theresa L Harvey
- Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, 02478, United States
| | - Stephanie E Brown
- Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, 02478, United States
| | - Cristina Cruz
- Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, 02478, United States; Harvard University, Cambridge, MA, 02138, United States
| | - Ellie Shahbo
- Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, 02478, United States; Harvard University, Cambridge, MA, 02138, United States
| | - Ismail Ajjawi
- Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, 02478, United States; Harvard University, Cambridge, MA, 02138, United States
| | - Darrick T Balu
- Department of Psychiatry, Harvard Medical School, Boston, MA, 02115, United States; Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, 02478, United States.
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10
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Aguilar DD, Radzik LK, Schiffino FL, Folorunso OO, Zielinski MR, Coyle JT, Balu DT, McNally JM. Altered neural oscillations and behavior in a genetic mouse model of NMDA receptor hypofunction. Sci Rep 2021; 11:9031. [PMID: 33907230 PMCID: PMC8079688 DOI: 10.1038/s41598-021-88428-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 04/09/2021] [Indexed: 12/18/2022] Open
Abstract
Abnormalities in electroencephalographic (EEG) biomarkers occur in patients with schizophrenia and those clinically at high risk for transition to psychosis and are associated with cognitive impairment. Converging evidence suggests N-methyl-D-aspartate receptor (NMDAR) hypofunction plays a central role in the pathophysiology of schizophrenia and likely contributes to biomarker impairments. Thus, characterizing these biomarkers is of significant interest for early diagnosis of schizophrenia and development of novel treatments. We utilized in vivo EEG recordings and behavioral analyses to perform a battery of electrophysiological biomarkers in an established model of chronic NMDAR hypofunction, serine racemase knockout (SRKO) mice, and their wild-type littermates. SRKO mice displayed impairments in investigation-elicited gamma power that corresponded with reduced short-term social recognition and enhanced background (pre-investigation) gamma activity. Additionally, SRKO mice exhibited sensory gating impairments in both evoked-gamma power and event-related potential amplitude. However, other biomarkers including the auditory steady-state response, sleep spindles, and state-specific power spectral density were generally neurotypical. In conclusion, SRKO mice demonstrate how chronic NMDAR hypofunction contributes to deficits in certain translationally-relevant EEG biomarkers altered in schizophrenia. Importantly, our gamma band findings suggest an aberrant signal-to-noise ratio impairing cognition that occurs with NMDAR hypofunction, potentially tied to impaired task-dependent alteration in functional connectivity.
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Affiliation(s)
- David D Aguilar
- VA Boston Healthcare System, West Roxbury, MA, USA. .,Department of Psychiatry, Harvard Medical School, Boston, MA, USA.
| | - Leana K Radzik
- Department of Neuroscience, Stonehill College, Easton, MA, USA
| | - Felipe L Schiffino
- VA Boston Healthcare System, West Roxbury, MA, USA.,Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Oluwarotimi O Folorunso
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA.,Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, USA
| | - Mark R Zielinski
- VA Boston Healthcare System, West Roxbury, MA, USA.,Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Joseph T Coyle
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA.,Laboratory of Psychiatric and Molecular Neuroscience, McLean Hospital, Belmont, MA, USA
| | - Darrick T Balu
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA.,Translational Psychiatry Laboratory, McLean Hospital, Belmont, MA, USA
| | - James M McNally
- VA Boston Healthcare System, West Roxbury, MA, USA.,Department of Psychiatry, Harvard Medical School, Boston, MA, USA
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11
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Coyle JT, Ruzicka WB, Balu DT. Fifty Years of Research on Schizophrenia: The Ascendance of the Glutamatergic Synapse. Am J Psychiatry 2020; 177:1119-1128. [PMID: 33256439 PMCID: PMC8011846 DOI: 10.1176/appi.ajp.2020.20101481] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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12
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Billard JM. Changes in Serine Racemase-Dependent Modulation of NMDA Receptor: Impact on Physiological and Pathological Brain Aging. Front Mol Biosci 2018; 5:106. [PMID: 30555832 PMCID: PMC6282039 DOI: 10.3389/fmolb.2018.00106] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 11/09/2018] [Indexed: 02/02/2023] Open
Abstract
The N-methyl-D-Aspartate glutamate receptors (NMDARs) are pivotal for the functional and morphological plasticity that are required in neuronal networks for efficient brain activities and notably for cognitive-related abilities. Because NMDARs are heterogeneous in subunit composition and associated with multiple functional regulatory sites, their efficacy is under the tonic influence of numerous allosteric modulations, whose dysfunction generally represents the first step generating pathological states. Among the enzymatic candidates, serine racemase (SR) has recently gathered an increasing interest considering that it tightly regulates the production of d-serine, an amino acid now viewed as the main endogenous co-agonist necessary for NMDAR activation. Nowadays, SR deregulation is associated with a wide range of neurological and psychiatric diseases including schizophrenia, amyotrophic lateral sclerosis, and depression. This review aims at compelling the most recent experimental evidences indicating that changes in SR-related modulation of NMDARs also govern opposite functional dysfunctions in physiological and pathological (Alzheimer's disease) aging that finally results in memory disabilities in both cases. It also highlights SR as a relevant alternative target for new pharmacological strategies aimed at preventing functional alterations and cognitive impairments linked to the aging process.
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Coyle JT, Balu DT. The Role of Serine Racemase in the Pathophysiology of Brain Disorders. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2017; 82:35-56. [PMID: 29413527 PMCID: PMC5821497 DOI: 10.1016/bs.apha.2017.10.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The N-methyl-d-aspartate receptor (NMDAR) is unique in requiring two agonists to bind simultaneously to open its cation channel: the neurotransmitter, glutamate, and the coagonists, glycine, or d-serine. The Snyder laboratory was the first to clone serine racemase (SR), the enzyme that synthesizes d-serine, and to localize it immunocytochemically. Our laboratory has focused on the role of d-serine in brain disorders. Silencing the expression of SR, a risk gene for schizophrenia (SCZ), in mice (SR-/-), results in a phenotype that closely resembles SCZ including: cortical atrophy, reduced dendritic spine density and complexity, downregulation of parvalbumin-positive cortical GABAergic neurons, and cognitive impairments. This pathology can be reversed by treatment of SR-/- mice with d-serine in adulthood. SR-/- mice also exhibit abnormal response toward abusable substances, such as stimulants. They show reduced behavioral sensitization to d-amphetamine, but fail to extinguish it. Place preference to cocaine is altered, and the hedonic response to it is profoundly impaired as assessed by intracranial self-stimulation. d-cycloserine, a partial agonist at the NMDAR glycine modulatory site, shows therapeutic benefit for treating pathologic anxiety in combination with behavioral therapies. Studies in vitro with cortical culture and in vivo with middle cerebral artery occlusion show that silencing SR provides substantial protection against ischemic neuronal death. Finally, the switch of SR expression from neurons to reactive astrocytes after closed head trauma accounts for the reduced in vivo neuroplasticity, electroencephalogram abnormalities, and cognitive impairments.
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Affiliation(s)
- Joseph T Coyle
- Harvard Medical School, Boston, MA, United States; McLean Hospital, Belmont, MA, United States.
| | - Darrick T Balu
- Harvard Medical School, Boston, MA, United States; McLean Hospital, Belmont, MA, United States
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