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Li J, Ye J. Chronic intermittent hypoxia induces cognitive impairment in Alzheimer's disease mouse model via postsynaptic mechanisms. Sleep Breath 2024; 28:1197-1205. [PMID: 38267641 DOI: 10.1007/s11325-023-02970-6] [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: 12/20/2022] [Revised: 12/04/2023] [Accepted: 12/06/2023] [Indexed: 01/26/2024]
Abstract
PURPOSE Obstructive sleep apnea (OSA) is highly comorbid with Alzheimer's disease (AD) and may represent a risk factor for inducing or accelerating cognitive impairment in AD. Chronic intermittent hypoxia (CIH) has been considered to be a predictor of developing cognitive decline and AD. However, the precise underlying mechanisms by which CIH contributes to cognitive impairment remain unknown. In the present study, we examined the effects of CIH on cognition and hippocampal function in APP/PS1 mice, an animal model of AD. METHODS Wild-type (WT) and APP/PS1 mice were subjected to one of the following conditions for 2 weeks: (1) sham condition (continuous room air) or (2) CIH condition. The oxygen concentration of the CIH condition transitioned from 5 to 21%. Behavioral tests, electrophysiological recording, real-time polymerase chain reaction, and Western blot were used to assess the effect of CIH on cognitive performance and synaptic plasticity. RESULTS CIH exposure did not affect motor coordination, general locomotor activity, anxiety, or willingness to explore. However, behavioral test results indicated that APP/PS1-CIH mice showed more spatial learning and memory deficits. CIH induced long-term potentiation (LTP) dysfunction of the hippocampus in WT mice. These effects were aggravated in APP/PS1 mice. The N-methyl-D-aspartic acid receptor (NMDAR) NR1 subunit and postsynaptic density 95 (PSD95) in the hippocampus of WT and APP/PS1 mice were downregulated. CONCLUSIONS These findings showed that a postsynaptic mechanism was involved in the effect of CIH on cognitive impairment.
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Affiliation(s)
- Juan Li
- Department of Otorhinolaryngology-Head and Neck Surgery, Beijing Tsinghua Changgung Hospital, School of Clinical Medicine, Tsinghua University, Beijing, 102218, China
| | - Jingying Ye
- Department of Otorhinolaryngology-Head and Neck Surgery, Beijing Tsinghua Changgung Hospital, School of Clinical Medicine, Tsinghua University, Beijing, 102218, China.
- Institute for Precision Medicine, Tsinghua University, Beijing, 100084, China.
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Wiseman RL, Bigos KL, Dastgheyb RM, Barker PB, Rubin LH, Slusher BS. Brain N -acetyl-aspartyl-glutamate is associated with cognitive function in older virally suppressed people with HIV. AIDS 2024; 38:1003-1011. [PMID: 38411600 PMCID: PMC11062820 DOI: 10.1097/qad.0000000000003871] [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: 09/10/2023] [Revised: 02/05/2024] [Accepted: 02/14/2024] [Indexed: 02/28/2024]
Abstract
OBJECTIVES Cognitive impairment persists in virally suppressed people with HIV (VS-PWH) especially in higher order domains. One cortical circuit, linked to these domains, is regulated by N -acetyl-aspartyl glutamate (NAAG), the endogenous agonist of the metabotropic glutamate receptor 3. The enzyme glutamate carboxypeptidase II (GCPII) catabolizes NAAG and is upregulated in aging and disease. Inhibition of GCPII increases brain NAAG and improves learning and memory in rodent and primate models. DESIGN As higher order cognitive impairment is present in VS-PWH, and NAAG has not been investigated in earlier magnetic resonance spectroscopy studies (MRS), we investigated if brain NAAG levels measured by MRS were associated with cognitive function. METHODS We conducted a retrospective analysis of 7-Tesla MRS data from a previously published study on cognition in older VS-PWH. The original study did not separately quantify NAAG, therefore, work for this report focused on relationships between regional NAAG levels in frontal white matter (FWM), left hippocampus, left basal ganglia and domain-specific cognitive performance in 40 VS-PWH after adjusting for confounds. Participants were older than 50 years, negative for affective and neurologic disorders, and had no prior 3-month psychoactive-substance use. RESULTS Higher NAAG levels in FWM were associated with better attention/working memory. Higher left basal ganglia NAAG related to better verbal fluency. There was a positive relationship between hippocampal NAAG and executive function which lost significance after correction for confounds. CONCLUSION These data suggest brain NAAG serves as a biomarker of cognition in VS-PWH. Pharmacological modulation of brain NAAG warrants investigation as a therapeutic approach for cognitive deficits in VS-PWH.
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Affiliation(s)
- Robyn L. Wiseman
- Department of Pharmacology and Molecular Sciences
- Johns Hopkins Drug Discovery
- Department of Medicine, Division of Clinical Pharmacology
| | - Kristin L. Bigos
- Department of Pharmacology and Molecular Sciences
- Department of Medicine, Division of Clinical Pharmacology
- Department of Psychiatry and Behavioral Sciences
| | | | - Peter B. Barker
- Russell H. Morgan Department of Radiology and Radiological Sciences
| | - Leah H. Rubin
- Department of Psychiatry and Behavioral Sciences
- Department of Neurology
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health
| | - Barbara S. Slusher
- Department of Pharmacology and Molecular Sciences
- Johns Hopkins Drug Discovery
- Department of Medicine, Division of Clinical Pharmacology
- Department of Psychiatry and Behavioral Sciences
- Department of Neurology
- Department of Oncology
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Yang JJ, Liu YX, Wang YF, Ge BY, Wang Y, Wang QS, Li S, Zhang JJ, Jin LL, Hong JS, Yin SM, Zhao J. Anti-epileptic and Neuroprotective Effects of Ultra-low Dose NADPH Oxidase Inhibitor Dextromethorphan on Kainic Acid-induced Chronic Temporal Lobe Epilepsy in Rats. Neurosci Bull 2024; 40:577-593. [PMID: 37973720 PMCID: PMC11127903 DOI: 10.1007/s12264-023-01140-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 06/24/2023] [Indexed: 11/19/2023] Open
Abstract
Neuroinflammation mediated by microglia and oxidative stress play pivotal roles in the development of chronic temporal lobe epilepsy (TLE). We postulated that kainic acid (KA)-Induced status epilepticus triggers microglia-dependent inflammation, leading to neuronal damage, a lowered seizure threshold, and the emergence of spontaneous recurrent seizures (SRS). Extensive evidence from our laboratory suggests that dextromethorphan (DM), even in ultra-low doses, has anti-inflammatory and neuroprotective effects in many animal models of neurodegenerative disease. Our results showed that administration of DM (10 ng/kg per day; subcutaneously via osmotic minipump for 4 weeks) significantly mitigated the residual effects of KA, including the frequency of SRS and seizure susceptibility. In addition, DM-treated rats showed improved cognitive function and reduced hippocampal neuronal loss. We found suppressed microglial activation-mediated neuroinflammation and decreased expression of hippocampal gp91phox and p47phox proteins in KA-induced chronic TLE rats. Notably, even after discontinuation of DM treatment, ultra-low doses of DM continued to confer long-term anti-seizure and neuroprotective effects, which were attributed to the inhibition of microglial NADPH oxidase 2 as revealed by mechanistic studies.
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Affiliation(s)
- Jing-Jing Yang
- College of Basic Medical Sciences, Dalian Medical University, Dalian, 116044, China
- Department of Neurology, The First Affiliated Hospital of Dalian Medical University, Dalian, 116011, China
- National and Local Joint Engineering Research Center for Drug Research and Development of Neurodegenerative Diseases, Dalian, 116044, China
| | - Ying-Xin Liu
- College of Basic Medical Sciences, Dalian Medical University, Dalian, 116044, China
- National and Local Joint Engineering Research Center for Drug Research and Development of Neurodegenerative Diseases, Dalian, 116044, China
| | - Yan-Fang Wang
- College of Basic Medical Sciences, Dalian Medical University, Dalian, 116044, China
- National and Local Joint Engineering Research Center for Drug Research and Development of Neurodegenerative Diseases, Dalian, 116044, China
| | - Bi-Ying Ge
- National and Local Joint Engineering Research Center for Drug Research and Development of Neurodegenerative Diseases, Dalian, 116044, China
| | - Ying Wang
- Department of Neurology, The First Affiliated Hospital of Dalian Medical University, Dalian, 116011, China
| | - Qing-Shan Wang
- National and Local Joint Engineering Research Center for Drug Research and Development of Neurodegenerative Diseases, Dalian, 116044, China
- School of Public Health, Dalian Medical University, Dalian, 116044, China
| | - Sheng Li
- College of Basic Medical Sciences, Dalian Medical University, Dalian, 116044, China
- National and Local Joint Engineering Research Center for Drug Research and Development of Neurodegenerative Diseases, Dalian, 116044, China
| | - Jian-Jie Zhang
- College of Basic Medical Sciences, Dalian Medical University, Dalian, 116044, China
- Department of Neurology, The First Affiliated Hospital of Dalian Medical University, Dalian, 116011, China
| | - Ling-Ling Jin
- National and Local Joint Engineering Research Center for Drug Research and Development of Neurodegenerative Diseases, Dalian, 116044, China
| | - Jau-Shyong Hong
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, Durham, NC, 27709, USA
| | - Sheng-Ming Yin
- College of Basic Medical Sciences, Dalian Medical University, Dalian, 116044, China.
- National and Local Joint Engineering Research Center for Drug Research and Development of Neurodegenerative Diseases, Dalian, 116044, China.
| | - Jie Zhao
- College of Basic Medical Sciences, Dalian Medical University, Dalian, 116044, China.
- National and Local Joint Engineering Research Center for Drug Research and Development of Neurodegenerative Diseases, Dalian, 116044, China.
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Becker I, Wang-Eckhardt L, Eckhardt M. NAAG synthetase deficiency has only low influence on pathogenesis in a Canavan disease mouse model. J Inherit Metab Dis 2024; 47:230-243. [PMID: 38011891 DOI: 10.1002/jimd.12693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 11/14/2023] [Accepted: 11/15/2023] [Indexed: 11/29/2023]
Abstract
Canavan disease (CD) is a leukodystrophy caused by mutations in the N-acetylaspartate (NAA) hydrolase aspartoacylase (ASPA). Inability to degrade NAA and its accumulation in the brain results in spongiform myelin degeneration. NAA is mainly synthesized by neurons, where it is also a precursor of the neuropeptide N-acetylaspartylglutamate (NAAG). Hydrolysis of this peptide by glutamate carboxypeptidases is an additional source of extracellular NAA besides the instant neuronal release of NAA. This study examines to what extent NAA released from NAAG contributes to NAA accumulation and pathogenesis in the brain of Aspanur7/nur7 mutant mice, an established model of CD. Towards this aim, Aspanur7/nur7 mice with additional deficiencies in NAAG synthetase genes Rimklb and/or Rimkla were generated. Loss of myelin in Aspanur7/nur7 mice was not significantly affected by Rimkla and Rimklb deficiency and there was also no obvious change in the extent of brain vacuolation. Astrogliosis was slightly reduced in the forebrain of Rimkla and Rimklb double deficient Aspanur7/nur7 mice. However, only minor improvements at the behavioral level were found. The brain NAA accumulation in CD mice was, however, not significantly reduced in the absence of NAAG synthesis. In summary, there was only a weak tendency towards reduced pathogenic symptoms in Aspanur7/nur7 mice deficient in NAAG synthesis. Therefore, we conclude that NAAG metabolism has little influence on NAA accumulation in Aspanur7/nur7 mice and development of pathological symptoms in CD.
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Affiliation(s)
- Ivonne Becker
- Institute of Biochemistry and Molecular Biology, Medical Faculty, University of Bonn, Bonn, Germany
| | - Lihua Wang-Eckhardt
- Institute of Biochemistry and Molecular Biology, Medical Faculty, University of Bonn, Bonn, Germany
| | - Matthias Eckhardt
- Institute of Biochemistry and Molecular Biology, Medical Faculty, University of Bonn, Bonn, Germany
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Zhuang Y, Xu X, Li H, Niu F, Yang M, Ge Q, Lu S, Deng Y, Wu H, Zhang B, Liu B. Megf10-related engulfment of excitatory postsynapses by astrocytes following severe brain injury. CNS Neurosci Ther 2023; 29:2873-2883. [PMID: 37081759 PMCID: PMC10493650 DOI: 10.1111/cns.14223] [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: 11/03/2022] [Revised: 01/13/2023] [Accepted: 01/18/2023] [Indexed: 04/22/2023] Open
Abstract
AIMS To investigate astrocyte-related phagocytosis of synapses in the ipsilateral hippocampus after traumatic brain injury (TBI). METHODS We performed controlled cortical impact to simulate TBI in mice. Seven days postinjury, we performed cognitive tests, synapse quantification, and examination of astrocytic phagocytosis in association with Megf10 expression. RESULTS During the subacute stage post-TBI, we found a reduction in excitatory postsynaptic materials in the ipsilateral hippocampus, which was consistent with poor performance in the cognitive test. The transcriptome data suggested that robust phagocytosis was responsible for this process. Coincidently, we identified phagocytic astrocytes containing secondary lysosomes that were wrapped around the synapses in the ipsilateral hippocampus. Moreover, a significant increase in the co-location of GFAP and PSD-95 in the CA1 region suggested astrocytic engulfment of excitatory postsynaptic proteins. After examining the reported phagocytic pathways, we found that both the transcription level and protein expression of Megf10 were elevated. Co-immunofluorescence of GFAP and Megf10 demonstrated that the expression of Megf10 was spatially upregulated in astrocytes, exclusively in the CA1 region, and was related to the astrocytic engulfment of PSD-95. CONCLUSION Our study elaborated that the Megf10-related astrocytic engulfment of PSD-95 in the CA1 region of the ipsilateral hippocampus aggravated cognitive dysfunction following severe TBI.
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Affiliation(s)
- Yuan Zhuang
- Department of Neurosurgery, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Xiaojian Xu
- Beijing Key Laboratory of Central Nervous System InjuryBeijing Neurosurgical Institute, Capital Medical UniversityBeijingChina
| | - Hao Li
- Department of Neurosurgery, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Fei Niu
- Beijing Key Laboratory of Central Nervous System InjuryBeijing Neurosurgical Institute, Capital Medical UniversityBeijingChina
| | - Mengshi Yang
- Department of Neurosurgery, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Qianqian Ge
- Department of Neurosurgery, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Shenghua Lu
- Department of Neurosurgery, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Yu Deng
- Department of Neurosurgery, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Hongbin Wu
- Department of Neurosurgery, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Bin Zhang
- Department of Intensive Care Unit, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Baiyun Liu
- Department of Neurosurgery, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
- Beijing Key Laboratory of Central Nervous System InjuryBeijing Neurosurgical Institute, Capital Medical UniversityBeijingChina
- Center for Nerve Injury and RepairBeijing Institute of Brain DisordersBeijingChina
- China National Clinical Research Center for Neurological DiseasesBeijingChina
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6
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Becker I, Eckhardt M. An enzymatic fluorimetric assay for determination of N-acetylaspartate. Anal Biochem 2023; 667:115083. [PMID: 36804395 DOI: 10.1016/j.ab.2023.115083] [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: 12/01/2022] [Revised: 01/27/2023] [Accepted: 02/11/2023] [Indexed: 02/17/2023]
Abstract
N-acetylaspartate (NAA) is an abundant metabolite in the mammalian brain and a precursor of the neuropeptide N-acetylaspartylglutamate (NAAG). The physiological role of NAA is not fully understood and requires further studies. We here describe the development of a coupled enzymatic fluorimetric assay for the determination of NAA in biological samples. Deproteinized tissue extracts are first passed through a strong cation exchange column to remove aspartate. NAA in the sample is hydrolysed by aspartoacylase and released aspartate oxidized using l-aspartate oxidase. Generated H2O2 is measured with peroxidase in a fluorimetric assay using Ampliflu Red. The limit of detection and the lower limit of quantification are 1.0 μM (10 pmol/well) and 3.3 μM (33 pmol/well), respectively, with a linear range to 100 μM. Specificity of the assay was confirmed using samples from mice deficient in NAA synthase Nat8l that were spiked with NAA. Analysis of samples from aspartoacylase-deficient mice showed a 2 to 3-fold increase in brain NAA concentration, in line with previous reports. Mice lacking NAAG synthetases had a slightly reduced (-10%) brain NAA level. Thus, the new fluorimetric enzymatic assay is useful to perform sensitive and large scale quantification of NAA in biological samples without the need for expensive equipment.
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Affiliation(s)
- Ivonne Becker
- Institute of Biochemistry and Molecular Biology, Medical Faculty, University of Bonn, Nussallee 11, 53115, Bonn, Germany
| | - Matthias Eckhardt
- Institute of Biochemistry and Molecular Biology, Medical Faculty, University of Bonn, Nussallee 11, 53115, Bonn, Germany.
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7
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Lawrence AJ, Prado MA. Editorial: Exciting developments in neurochemistry research and publishing. J Neurochem 2022; 162:151-155. [PMID: 35524403 DOI: 10.1111/jnc.15595] [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: 02/14/2022] [Revised: 02/22/2022] [Accepted: 02/23/2022] [Indexed: 12/01/2022]
Abstract
In this editorial, we are happy to connect with our community to explain the changes introduced to the Journal of Neurochemistry over the last year and provide some insights into new developments and exciting opportunities. We anticipate these developments, which are strongly guided to increase transparency and support early career researchers, will increase the value of the Journal of Neurochemistry for the authors and readers. Ultimately, we hope to improve the author experience with the Journal of Neurochemistry and continue to be the leading venue for fast dissemination of exciting new research focusing on how molecules, cells and circuits regulate the nervous system in health and disease.
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Affiliation(s)
- Andrew J Lawrence
- The Florey Institute of Neuroscience & Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Marco A Prado
- University of Western Ontario, Robarts Research Institute, London, Ontario, Canada
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Li K, Lu M, Cui M, Wang X, Zheng Y. The regulatory role of NAAG-mGluR3 signaling on cortical synaptic plasticity after hypoxic ischemia. Cell Commun Signal 2022; 20:55. [PMID: 35443669 PMCID: PMC9022257 DOI: 10.1186/s12964-022-00866-8] [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: 01/20/2022] [Accepted: 03/25/2022] [Indexed: 11/14/2022] Open
Abstract
Background Synapses can adapt to changes in the intracerebral microenvironment by regulation of presynaptic neurotransmitter release and postsynaptic neurotransmitter receptor expression following hypoxic ischemia (HI) injury. The peptide neurotransmitter N-acetylaspartylglutamate (NAAG) exerts a protective effect on neurons after HI and may be involved in maintaining the function of synaptic networks. In this study, we investigated the changes in the expression of NAAG, glutamic acid (Glu) and metabotropic glutamate receptors (mGluRs), as well as the dynamic regulation of neurotransmitters in the brain after HI, and assessed their effects on synaptic plasticity of the cerebral cortex. Methods Thirty-six Yorkshire newborn pigs (3-day-old, males, 1.0–1.5 kg) were selected and randomly divided into normal saline (NS) group (n = 18) and glutamate carboxypeptidase II inhibition group (n = 18), both groups were divided into control group, 0–6 h, 6–12 h, 12–24 h, 24–48 h and 48–72 h groups (all n = 3) according to different post-HI time. The content of Glu and NAAG after HI injury were detected by 1H-MRS scanning, immunofluorescence staining of mGluRs, synaptophysin (syph) along with postsynaptic density protein-95 (PSD95) and transmission electron microscopy were performed. ANOVA, Tukey and LSD test were used to compare the differences in metabolite and protein expression levels among subgroups. Correlation analysis was performed using Pearson analysis with a significance level of α = 0.05. Results We observed that the NAAG and mGluR3 expression levels in the brain increased and then decreased after HI and was significantly higher in the 12–24 h (P < 0.05, Tukey test). There was a significant positive correlation between Glu content and the expression of mGluR1/mGluR5 after HI with r = 0.521 (P = 0.027) and r = 0.477 (P = 0.045), respectively. NAAG content was significantly and positively correlated with the level of mGluR3 expression (r = 0.472, P = 0.048). When hydrolysis of NAAG was inhibited, the expression of synaptic protein PSD95 and syph decreased significantly. Conclusions After 12–24 h of HI injury, there was a one-time elevation in NAAG levels, which was consistent with the corresponding mGluR3 receptor expression trend; the NAAG maintains cortical synaptic plasticity and neurotransmitter homeostasis by inhibiting presynaptic glutamate vesicle release, regulating postsynaptic density proteins and postsynaptic receptor expression after pathway activation. Video abstract
Supplementary Information The online version contains supplementary material available at 10.1186/s12964-022-00866-8.
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Affiliation(s)
- Kexin Li
- Department of Radiology, Shengjing Hospital of China Medical University, No. 36, Sanhao Street, Heping District, Shenyang, 110004, People's Republic of China
| | - Meng Lu
- Department of Radiology, Shengjing Hospital of China Medical University, No. 36, Sanhao Street, Heping District, Shenyang, 110004, People's Republic of China
| | - Mengxu Cui
- Department of Radiology, Shengjing Hospital of China Medical University, No. 36, Sanhao Street, Heping District, Shenyang, 110004, People's Republic of China
| | - Xiaoming Wang
- Department of Radiology, Shengjing Hospital of China Medical University, No. 36, Sanhao Street, Heping District, Shenyang, 110004, People's Republic of China.
| | - Yang Zheng
- Department of Radiology, Shengjing Hospital of China Medical University, No. 36, Sanhao Street, Heping District, Shenyang, 110004, People's Republic of China.
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Dogra S, Conn PJ. Metabotropic glutamate receptors as emerging targets for the treatment of schizophrenia. Mol Pharmacol 2022; 101:275-285. [PMID: 35246479 PMCID: PMC9092465 DOI: 10.1124/molpharm.121.000460] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 02/22/2022] [Indexed: 11/22/2022] Open
Abstract
Accumulating evidence of glutamatergic abnormalities in the brains of schizophrenia patients has led to efforts to target various components of glutamatergic signaling as potential new approaches for schizophrenia. Exciting research suggests that metabotropic glutamate (mGlu) receptors could provide a fundamentally new approach for better symptomatic relief in schizophrenia patients. In preclinical studies, the mGlu5 receptor positive allosteric modulators (PAMs) have efficacy in animal models relevant for all symptom domains in schizophrenia. Interestingly, biased pure mGlu5 receptor PAMs that do not potentiate coupling of mGlu5 receptors to NMDA receptors lack neurotoxic effects associated with mGlu5 PAMs that enhance coupling to N-methyl-D-aspartate (NMDA) receptors or have allosteric agonist activity (ago-PAMs). This provides a better therapeutic profile for treating schizophrenia-like symptoms. Additionally, the mGlu1 receptor PAMs modulate dopamine release in the striatum, which may contribute to their antipsychotic-like effects. Besides group I mGlu (mGlu1 and mGlu5) receptors, agonists of mGlu2/3 receptor also induce robust antipsychotic-like and pro-cognitive effects in rodents and may be effective in treating symptoms of schizophrenia in a selective group of patients. Additionally, mGlu2/4 receptor heterodimers modulate glutamatergic neurotransmission in the prefrontal cortex at selective synapses activated in schizophrenia and, therefore, hold potential as novel antipsychotics. Excitingly, the mGlu3 receptor activation can enhance cognition in rodents suggesting that mGlu3 receptor agonist/PAM could provide a novel approach for the treatment of cognitive deficits in schizophrenia. Collectively, the development of mGlu receptor-specific ligands may provide an alternative approach to meet the clinical need for safer and efficacious therapeutics for schizophrenia. Significance Statement The currently available antipsychotic medications do not show significant efficacy for treating negative symptoms and cognitive deficits in schizophrenia. Emerging preclinical and clinical literature suggests that pharmacological targeting of metabotropic glutamate receptors could potentially provide an alternative approach for designing safer and efficacious therapeutics for treating schizophrenia.
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Morland C, Nordengen K. N-Acetyl-Aspartyl-Glutamate in Brain Health and Disease. Int J Mol Sci 2022; 23:ijms23031268. [PMID: 35163193 PMCID: PMC8836185 DOI: 10.3390/ijms23031268] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/20/2022] [Accepted: 01/21/2022] [Indexed: 02/04/2023] Open
Abstract
N-acetyl-aspartyl-glutamate (NAAG) is the most abundant dipeptide in the brain, where it acts as a neuromodulator of glutamatergic synapses by activating presynaptic metabotropic glutamate receptor 3 (mGluR3). Recent data suggest that NAAG is selectively localized to postsynaptic dendrites in glutamatergic synapses and that it works as a retrograde neurotransmitter. NAAG is released in response to glutamate and provides the postsynaptic neuron with a feedback mechanisms to inhibit excessive glutamate signaling. A key regulator of synaptically available NAAG is rapid degradation by the extracellular enzyme glutamate carboxypeptidase II (GCPII). Increasing endogenous NAAG—for instance by inhibiting GCPII—is a promising treatment option for many brain disorders where glutamatergic excitotoxicity plays a role. The main effect of NAAG occurs through increased mGluR3 activation and thereby reduced glutamate release. In the present review, we summarize the transmitter role of NAAG and discuss the involvement of NAAG in normal brain physiology. We further present the suggested roles of NAAG in various neurological and psychiatric diseases and discuss the therapeutic potential of strategies aiming to enhance NAAG levels.
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Affiliation(s)
- Cecilie Morland
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, The Faculty of Mathematics and Natural Sciences, University of Oslo, 1068 Oslo, Norway
- Correspondence: (C.M.); (K.N.); Tel.: +47-22844937; (C.M.); +47-23073580 (K.N.)
| | - Kaja Nordengen
- Department of Neurology, Oslo University Hospital, 0424 Oslo, Norway
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, 0318 Oslo, Norway
- Correspondence: (C.M.); (K.N.); Tel.: +47-22844937; (C.M.); +47-23073580 (K.N.)
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The PGRMC1 Antagonist AG-205 Inhibits Synthesis of Galactosylceramide and Sulfatide. Cells 2021; 10:cells10123520. [PMID: 34944026 PMCID: PMC8700550 DOI: 10.3390/cells10123520] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 12/07/2021] [Accepted: 12/10/2021] [Indexed: 02/05/2023] Open
Abstract
Sulfatide synthesis in the human renal cancer cell line SMKT-R3 was strongly inhibited in the presence of low µM concentrations of AG-205, a progesterone receptor membrane component 1 (PGRMC1) antagonist. This was also the case in Chinese hamster ovary (CHO) cells stably transfected with UDP-galactose: ceramide galactosyltransferase and cerebroside sulfotransferase, the two enzymes required for sulfatide synthesis. In CHO cells synthesizing galactosylceramide but not sulfatide, galactosylceramide was also strongly reduced, suggesting an effect at the level of galactolipid synthesis. Notably, AG-205 inhibited galactosylceramide synthesis to a similar extent in wild type CHO cells and cells that lack PGRMC1 and/or PGRMC2. In vitro enzyme activity assays showed that AG-205 is an inhibitor of UDP-galactose: ceramide galactosyltransferase, but not cerebroside sulfotransferase. This study shows that PGRMC1 is only one of several targets of AG-205 and should be used with caution, especially in studies using cells synthesizing galactosylceramide and sulfatide.
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