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Traxoprodil Produces Antidepressant-Like Behaviors in Chronic Unpredictable Mild Stress Mice through BDNF/ERK/CREB and AKT/FOXO/Bim Signaling Pathway. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2023; 2023:1131422. [PMID: 36819781 PMCID: PMC9937761 DOI: 10.1155/2023/1131422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 01/07/2023] [Accepted: 01/17/2023] [Indexed: 02/12/2023]
Abstract
Traxoprodil is a selective N-methyl-d-aspartate receptor subunit 2B (NR2B) receptor inhibitor with rapid and long-lasting antidepressant effects. However, the appropriate dosage, duration of administration, and underlying mechanism of traxoprodil's antidepressant effects remain unclear. The purpose of this study is to compare the antidepressant effects of traxoprodil in different doses and different durations of administration and to explore whether traxoprodil exerts antidepressant effects via the brain-derived neurotrophic factor/extracellular signal-regulated kinase/cAMP-response element binding protein (BDNF/ERK/CREB) and protein kinase B/Forkhead box O/building information modelling (AKT/FOXO/Bim) signaling pathway. Mice were randomly divided into control group, chronic unpredictable mild stress (CUMS) + vehicle group, CUMS + traxoprodil (10 mg/kg, 20 mg/kg, and 40 mg/kg) groups, and CUMS + fluoxetine (5 mg/kg) group, followed by a forced swimming test, tail suspension test, and sucrose preference test. Western blotting and immunohistochemistry were used to measure the protein expression of BDNF, p-ERK1/2, p-CREB, NR2B, AKT, FOXO1, FOXO3a, and Bim. Compared with the control group, CUMS treatment increased immobility time; decreased sucrose preference; reduced expression of BDNF, p-ERK1/2, and p-CREB; and increased expression of AKT, FOXO, and Bim in the hippocampus. These alterations were ameliorated by administration of 20 mg/kg or 40 mg/kg of traxoprodil after 7 or 14 days of administration and with 10 mg/kg of traxoprodil or 5 mg/kg of fluoxetine after 21 days of administration. At the 7-day and 14-day timepoints, traxoprodil displayed dose-dependent antidepressant effects, with 20 and 40 mg/kg doses of traxoprodil producing rapid and strong antidepressant effects. However, at 21 days of administration, 10 and 20 mg/kg doses of traxoprodil exerted more pronounced antidepressant effects. The mechanism of traxoprodil's antidepressant effects may be closely related to the BDNF/ERK/CREB and AKT/FOXO/Bim signaling pathway.
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Phytoestrogen genistein modulates neuron-microglia signaling in a mouse model of chronic social defeat stress. Neuropharmacology 2022; 206:108941. [PMID: 34990615 DOI: 10.1016/j.neuropharm.2021.108941] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Revised: 12/26/2021] [Accepted: 12/29/2021] [Indexed: 01/20/2023]
Abstract
Microglia, resident immune cells in the brain, are shown to mediate the crosstalk between psychological stress and depression. Interestingly, increasing evidence indicates that sex hormones, particularly estrogen, are involved in the regulation of immune system. In this study, we aimed to understand the potential effects of chronic social defeat stress (CSDS) and genistein (GEN), an estrogenic compound of the plant origin, on neuron-microglia interactions in the mouse hippocampus. The time spent in the avoidance zone in the social interaction test was increased by CSDS 1 day after the exposure, while the avoidance behavior returned to control levels 14 days after the CSDS exposure. Similar results were obtained from the elevated plus-maze test. However, the immobility time in the forced swim test was increased by CSDS 14 days after the exposure, and the depression-related behavior was in part alleviated by GEN. The numerical densities of microglia in the hippocampus were increased by CSDS, and they were decreased by GEN. The voxel densities of synaptic structures and synaptic puncta colocalized with microglia were decreased by CSDS, and they were increased by GEN. Neither CSDS nor GEN affected the gene expressions of major pro-inflammatory cytokines. Conversely, the expression levels of genes related to neurotrophic factors were decreased by CSDS, and they were partially reversed by GEN. These findings show that GEN may in part alleviate stress-related symptoms, and the effects of GEN may be associated with the modulation of neuron-microglia signaling via chemokines and neurotrophic factors in the hippocampus.
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Jia Z, Yang J, Cao Z, Zhao J, Zhang J, Lu Y, Chu L, Zhang S, Chen Y, Pei L. Baicalin ameliorates chronic unpredictable mild stress-induced depression through the BDNF/ERK/CREB signaling pathway. Behav Brain Res 2021; 414:113463. [PMID: 34280458 DOI: 10.1016/j.bbr.2021.113463] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 07/07/2021] [Accepted: 07/09/2021] [Indexed: 01/29/2023]
Abstract
Brain-derived neurotrophic factor (BDNF) can activate the extracellular regulated protein kinase (ERK)/cAMP response element binding protein (CREB) cascade revealing an important role in antidepressant effects. Here, we studied the neuroprotective effect of baicalin (BA) in mice with chronic unpredictable mild stress (CUMS)-induced via a BDNF/ERK/CREB signaling pathway. Depression was induced via six weeks of CUMS in male ICR mice, and drug therapy was given simultaneously for the last three weeks. Cognitive dysfunctions were then evaluated via sucrose preference test (SPT), open field test (OFT), Morris water maze test (MWM), tail suspension test (TST), and novelty suppressed feeding test (NSF). Western blot and real-time PCR were then used to detect the relative expression of ERK, CREB, p-ERK, and p-CREB. Integrated optical density (IOD) tests of p-ERK and p-CREB were then evaluated via immunofluorescence. The behavior results showed that the cognitive dysfunctions increased in the CUMS group versus the control (CON) group (p < 0.01). There were decreases in fluoxetine (FLU) and BA groups (p < 0.05, p < 0.01). The protein ratios of p-ERK/ERK, p-CREB/CREB and ERK mRNA, and CREB mRNA expression decreased in the CUMS group (p < 0.01) and markedly increased in the FLU and BA groups (p < 0.05, p < 0.01). The IOD value of the p-ERK and p-CREB in the CUMS group was decreased versus the CON group (p < 0.01), and these changes were improved via BA and FLU treatment (p < 0.05, p < 0.01). This study indicated that BA can improve cognitive functions and has antidepressant effects in mice, which may be associated with activation of the BDNF/ERK/CREB signaling pathway in the hippocampus.
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Affiliation(s)
- Zhixia Jia
- Hebei University of Chinese Medicine, Shijiazhuang, Hebei, China
| | - Jiali Yang
- Hebei University of Chinese Medicine, Shijiazhuang, Hebei, China
| | - Zhuoqing Cao
- Hebei University of Chinese Medicine, Shijiazhuang, Hebei, China
| | - Jing Zhao
- Hebei Key Laboratory of Turbidity, Hebei Academy of Chinese Medicine Sciences, Shijiazhuang, Hebei, 050011, China
| | - Jinhu Zhang
- Hebei Key Laboratory of Turbidity, Hebei Academy of Chinese Medicine Sciences, Shijiazhuang, Hebei, 050011, China
| | - Ye Lu
- Hebei Key Laboratory of Turbidity, Hebei Academy of Chinese Medicine Sciences, Shijiazhuang, Hebei, 050011, China
| | - Li Chu
- Hebei University of Chinese Medicine, Shijiazhuang, Hebei, China
| | - Shaodan Zhang
- The Second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China.
| | - Yuan Chen
- The Second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China.
| | - Lin Pei
- Hebei Key Laboratory of Turbidity, Hebei Academy of Chinese Medicine Sciences, Shijiazhuang, Hebei, 050011, China.
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Kubicova L, Chobot V. Potential of kynurenine metabolites in drug development against neurodegenerative diseases. Neural Regen Res 2021; 16:308-309. [PMID: 32859788 PMCID: PMC7896208 DOI: 10.4103/1673-5374.290897] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- Lenka Kubicova
- Division of Molecular Systems Biology, Department of Ecogenomics and Systems Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | - Vladimir Chobot
- Division of Molecular Systems Biology, Department of Ecogenomics and Systems Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria
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Antoniuk S, Bijata M, Ponimaskin E, Wlodarczyk J. Chronic unpredictable mild stress for modeling depression in rodents: Meta-analysis of model reliability. Neurosci Biobehav Rev 2019; 99:101-116. [DOI: 10.1016/j.neubiorev.2018.12.002] [Citation(s) in RCA: 185] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 12/03/2018] [Accepted: 12/03/2018] [Indexed: 01/01/2023]
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Wang JQ, Mao L. The ERK Pathway: Molecular Mechanisms and Treatment of Depression. Mol Neurobiol 2019; 56:6197-6205. [PMID: 30737641 DOI: 10.1007/s12035-019-1524-3] [Citation(s) in RCA: 140] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 02/01/2019] [Indexed: 11/30/2022]
Abstract
Major depressive disorder is a chronic debilitating mental illness. Its pathophysiology at cellular and molecular levels is incompletely understood. Increasing evidence supports a pivotal role of the mitogen-activated protein kinase (MAPK), in particular the extracellular signal-regulated kinase (ERK) subclass of MAPKs, in the pathogenesis, symptomatology, and treatment of depression. In humans and various chronic animal models of depression, the ERK signaling was significantly downregulated in the prefrontal cortex and hippocampus, two core areas implicated in depression. Inhibiting the ERK pathway in these areas caused depression-like behavior. A variety of antidepressants produced their behavioral effects in part via normalizing the downregulated ERK activity. In addition to ERK, the brain-derived neurotrophic factor (BDNF), an immediate upstream regulator of ERK, the cAMP response element-binding protein (CREB), a transcription factor downstream to ERK, and the MAPK phosphatase (MKP) are equally vulnerable to depression. While BDNF and CREB were reduced in their activity in the prefrontal cortex and hippocampus of depressed animals, MKP activity was enhanced in parallel. Chronic antidepressant treatment readily reversed these neurochemical changes. Thus, ERK signaling in the depression-implicated brain regions was disrupted during the development of depression, which contributes to the long-lasting and transcription-dependent neuroadaptations critical for enduring depression-like behavior and the therapeutic effect of antidepressants.
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Affiliation(s)
- John Q Wang
- Department of Biomedical Sciences, University of Missouri-Kansas City, School of Medicine, 2411 Holmes Street, Rm. M3-213, Kansas City, MO, USA. .,Department of Anesthesiology, University of Missouri-Kansas City, School of Medicine, 2411 Holmes Street, Kansas City, MO, USA.
| | - Limin Mao
- Department of Biomedical Sciences, University of Missouri-Kansas City, School of Medicine, 2411 Holmes Street, Rm. M3-213, Kansas City, MO, USA
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Chaki S. Beyond Ketamine: New Approaches to the Development of Safer Antidepressants. Curr Neuropharmacol 2018; 15:963-976. [PMID: 28228087 PMCID: PMC5652016 DOI: 10.2174/1570159x15666170221101054] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 02/08/2017] [Accepted: 02/15/2017] [Indexed: 12/28/2022] Open
Abstract
Background: Ketamine has been reported to exert rapid and sustained antidepressant effects in patients with depression, including patients with treatment-resistant depression. However, ketamine has several drawbacks such as psychotomimetic/dissociative symptoms, abuse potential and neurotoxicity, all of which prevent its routine use in daily clinical practice. Methods: Therefore, development of novel agents with fewer safety and usage concerns for the treatment of depression has been actively investigated. From this standpoint, searching for active substances (stereoisomers and metabolites) and agents acting on the N-methyl-D-aspartate (NMDA) receptor have recently gained much attention. Results: The first approach includes stereoisomers of ketamine, (R)-ketamine and (S)-ketamine. Although (S)-ketamine has been considered as the active stereoisomer of racemic ketamine, recently, (R)-ketamine has been demonstrated to exert even more prolonged antidepressant effects in animal models than (S)-ketamine. Moreover, ketamine is rapidly metabolized into several metabolites, and some metabolites are speculated as being active substances exerting antidepressant effects. Of such metabolites, one in particular, namely, (2R,6R)-hydroxynorketamine, has been reported to be responsible for the antidepressant effects of ketamine. The second approach includes agents acting on the NMDA receptor, such as glycine site modulators and GluN2B subunit-selective antagonists. These agents have been tested in patients with treatment-resistant depression, and have been found to exhibit rapid antidepressant effects like ketamine. Conclusion: The above approaches may be useful to overcome the drawbacks of ketamine. Elucidation of the mechanisms of action of ketamine may pave the way for the development of antidepressant that are safer, but as potent and rapidly acting as ketamine.
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Affiliation(s)
- Shigeyuki Chaki
- Research Headquarters, Taisho Pharmaceutical Co., Ltd., 1-403 Yoshino-cho, Kita-ku, Saitama 331-9530. Japan
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Grassi D, Franz H, Vezzali R, Bovio P, Heidrich S, Dehghanian F, Lagunas N, Belzung C, Krieglstein K, Vogel T. Neuronal Activity, TGFβ-Signaling and Unpredictable Chronic Stress Modulate Transcription of Gadd45 Family Members and DNA Methylation in the Hippocampus. Cereb Cortex 2018; 27:4166-4181. [PMID: 28444170 DOI: 10.1093/cercor/bhx095] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 04/04/2017] [Indexed: 02/06/2023] Open
Abstract
Neuronal activity is altered in several neurological and psychiatric diseases. Upon depolarization not only neurotransmitters are released but also cytokines and other activators of signaling cascades. Unraveling their complex implication in transcriptional control in receiving cells will contribute to understand specific central nervous system (CNS) pathologies and will be of therapeutically interest. In this study we depolarized mature hippocampal neurons in vitro using KCl and revealed increased release not only of brain-derived neurotrophic factor (BDNF) but also of transforming growth factor beta (TGFB). Neuronal activity together with BDNF and TGFB controls transcription of DNA modifying enzymes specifically members of the DNA-damage-inducible (Gadd) family, Gadd45a, Gadd45b, and Gadd45g. MeDIP followed by massive parallel sequencing and transcriptome analyses revealed less DNA methylation upon KCl treatment. Psychiatric disorder-related genes, namely Tshz1, Foxn3, Jarid2, Per1, Map3k5, and Arc are transcriptionally activated and demethylated upon neuronal activation. To analyze whether misexpression of Gadd45 family members are associated with psychiatric diseases, we applied unpredictable chronic mild stress (UCMS) as established model for depression to mice. UCMS led to reduced expression of Gadd45 family members. Taken together, our data demonstrate that Gadd45 family members are new putative targets for UCMS treatments.
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Affiliation(s)
- Daniela Grassi
- Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,Department of Basic Biomedical Sciences, Faculty of Biomedical Science and Health, Universidad Europea de Madrid, Madrid, Spain
| | - Henriette Franz
- Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Riccardo Vezzali
- Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Patrick Bovio
- Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Stefanie Heidrich
- Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Fariba Dehghanian
- Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Natalia Lagunas
- Inserm U 930, Université François Rabelais, 37200 Tours, France
| | | | - Kerstin Krieglstein
- Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Tanja Vogel
- Department of Molecular Embryology, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
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Zhang MW, Zhang SF, Li ZH, Han F. 7,8-Dihydroxyflavone reverses the depressive symptoms in mouse chronic mild stress. Neurosci Lett 2016; 635:33-38. [PMID: 27773794 DOI: 10.1016/j.neulet.2016.10.035] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 10/18/2016] [Accepted: 10/19/2016] [Indexed: 01/09/2023]
Abstract
7,8-Dihydroxyflavone (7,8-DHF) is a naturally-occurring flavone which possesses good bioavailability. Due to its ability to cross the blood-brain barrier, previous studies have demonstrated that 7,8-DHF was a potent tropomyosin-related kinase B (TrkB) agonist, and produced antidepressant-like effects in mouse forced swimming test and tail suspension test. However, it has not been evaluated in chronic mild stress (CMS), a classical depression model modulating the processes of major depression in human. In the present study, we not only evaluated the depressive-like behaviors, but also measured the key proteins of TrkB signaling in mice exposed to CMS. Our results firstly found that long term but not single injection of 7,8-DHF restored the depressive-like behaviors in sucrose preference test and novelty suppressed feeding test. In addition, 7,8-DHF not only increased TrkB phosphorylation and brain-derived neurotrophic factor (BDNF) levels, but also activated the expression of TrkB downstream synaptic proteins such as PSD95 and synaptophysin. Furthermore, the TrkB antagonist K252a blocked the antidepressant-like effects of 7,8-DHF. In summary, the present results demonstrated that chronic 7,8-DHF treatment exerted significant antidepressant-like effects, which were likely attributed to regulating TrkB signaling and thus promoting synaptic protein expression.
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Affiliation(s)
- Min-Wang Zhang
- Department of Encephalopathy (II), Zhengzhou Traditional Chinese Medicine Hospital, Zhengzhou 450007, Henan province, PR China
| | - She-Feng Zhang
- Henan Province Chinese medicine research institute, Zhengzhou 450004, Henan province, PR China
| | - Zhen-Hua Li
- Department of Encephalopathy (II), Zhengzhou Traditional Chinese Medicine Hospital, Zhengzhou 450007, Henan province, PR China
| | - Fang Han
- Department of Encephalopathy (II), Zhengzhou Traditional Chinese Medicine Hospital, Zhengzhou 450007, Henan province, PR China.
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Wang J, Duan P, Cui Y, Li Q, Shi Y. Geniposide alleviates depression-like behavior via enhancing BDNF expression in hippocampus of streptozotocin-evoked mice. Metab Brain Dis 2016; 31:1113-22. [PMID: 27311609 DOI: 10.1007/s11011-016-9856-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 06/09/2016] [Indexed: 01/15/2023]
Abstract
Clinical and preclinical data suggest that diabetes is often psychological complications such as depression. Geniposide (GP), a major compound in Gardenia jasminoides Ellis with both medicinal and nutritional values, has been previously confirmed to exert anti-diabetic and anti-depressive activities. The present study attempted to observe anti-depressive mechanisms of GP in streptozotocin (STZ) evoked diabetic mice by involving brain-derived neurotrophic factor (BDNF), for the first time. Mice were given GP daily (50, and 100 mg/kg, ig) or reference drugs FHMH [fluoxetine hydrochloride (FH, 10 mg/kg, ig) combined with metformin hydrochloride (MH, 100 mg/kg, ig)] for 3 weeks. The forced swimming test (FST) was performed to observe depression-like behavior, and serum and brain tissues were used for neurochemical and fluorescent quantitative reverse transcription PCR analyses. STZ induced excessively increased blood sugar and immobility time in FST, in a manner attenuated by GP and FHMH administration. GP administration further elevated BDNF levels, and up-regulated the mRNA expression of BDNF and tropomyosin-related kinase B (TrkB) in hippocampus of diabetic mice. In addition, STZ induced the excessive level of serum corticosterone (CORT), while GP did not influence on it in diabetic mice. Taken together, these findings indicate that GP can alleviate depression-like behavior in STZ-evoked diabetic mice, and suggest its mechanisms may partially be ascribed to up-regulating BDNF expression in brain.
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Affiliation(s)
- Junming Wang
- Collaborative Innovation Center for Respiratory Disease Diagnosis and Treatment & Chinese Medicine Development of Henan Province, Henan University of Traditional Chinese Medicine, Zhengzhou, 450046, China.
- College of Pharmacy, Henan University of Traditional Chinese Medicine, East Jinshui Road & Boxue Road, Zhengzhou, 450046, China.
| | - Peili Duan
- College of Pharmacy, Henan University of Traditional Chinese Medicine, East Jinshui Road & Boxue Road, Zhengzhou, 450046, China
| | - Ying Cui
- Collaborative Innovation Center for Respiratory Disease Diagnosis and Treatment & Chinese Medicine Development of Henan Province, Henan University of Traditional Chinese Medicine, Zhengzhou, 450046, China
- College of Pharmacy, Henan University of Traditional Chinese Medicine, East Jinshui Road & Boxue Road, Zhengzhou, 450046, China
| | - Qing Li
- College of Pharmacy, Henan University of Traditional Chinese Medicine, East Jinshui Road & Boxue Road, Zhengzhou, 450046, China
| | - Yanran Shi
- College of Pharmacy, Henan University of Traditional Chinese Medicine, East Jinshui Road & Boxue Road, Zhengzhou, 450046, China
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The Gut-Brain Axis, BDNF, NMDA and CNS Disorders. Neurochem Res 2016; 41:2819-2835. [PMID: 27553784 DOI: 10.1007/s11064-016-2039-1] [Citation(s) in RCA: 131] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 08/09/2016] [Accepted: 08/17/2016] [Indexed: 02/08/2023]
Abstract
Gastro-intestinal (GI) microbiota and the 'gut-brain axis' are proving to be increasingly relevant to early brain development and the emergence of psychiatric disorders. This review focuses on the influence of the GI tract on Brain-Derived Neurotrophic Factor (BDNF) and its relationship with receptors for N-methyl-D-aspartate (NMDAR), as these are believed to be involved in synaptic plasticity and cognitive function. NMDAR may be associated with the development of schizophrenia and a range of other psychopathologies including neurodegenerative disorders, depression and dementias. An analysis of the routes and mechanisms by which the GI microbiota contribute to the pathophysiology of BDNF-induced NMDAR dysfunction could yield new insights relevant to developing novel therapeutics for schizophrenia and related disorders. In the absence of GI microbes, central BDNF levels are reduced and this inhibits the maintenance of NMDAR production. A reduction of NMDAR input onto GABA inhibitory interneurons causes disinhibition of glutamatergic output which disrupts the central signal-to-noise ratio and leads to aberrant synaptic behaviour and cognitive deficits. Gut microbiota can modulate BDNF function in the CNS, via changes in neurotransmitter function by affecting modulatory mechanisms such as the kynurenine pathway, or by changes in the availability and actions of short chain fatty acids (SCFAs) in the brain. Interrupting these cycles by inducing changes in the gut microbiota using probiotics, prebiotics or antimicrobial drugs has been found promising as a preventative or therapeutic measure to counteract behavioural deficits and these may be useful to supplement the actions of drugs in the treatment of CNS disorders.
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