RESUMO
Syntenin-1 is a PDZ domain-containing intracellular scaffold protein involved in exosome production, synapse formation, and synaptic plasticity. We tested whether syntenin-1 can regulate learning and memory through its effects on synaptic plasticity. Specifically, we investigated the role of syntenin-1 in contextual and cued fear conditioning and extinction of conditioned fear using syntenin-1 knockout (KO) mice. Genetic disruption of syntenin-1 had little effect on contextual and cued fear memory. However, syntenin-1 KO mice exhibited selective impairment in cued fear extinction retention. This extinction retention deficit in syntenin-1 KO mice was associated with reduced c-Fos-positive neurons in the basolateral amygdala (BLA) and infralimbic cortex (IL) after extinction training and increased c-Fos-positive neurons in the BLA after an extinction retention test. Our results suggest that syntenin-1 plays an important role in extinction of cued fear memory by modulating neuronal activity in the BLA and IL.
Assuntos
Córtex Cerebral/metabolismo , Extinção Psicológica/fisiologia , Medo/fisiologia , Memória/fisiologia , Sinteninas/genética , Tonsila do Cerebelo/metabolismo , Animais , Sinais (Psicologia) , Camundongos , Camundongos Knockout , Neurônios/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Sinteninas/metabolismoRESUMO
The abnormal expression and function of myelin-related proteins contribute to nervous system dysfunction associated with neuropsychiatric disorders; however, the underlying mechanism of this remains unclear. We found here that breast carcinoma amplified sequence 1 (BCAS1), a basic protein abundant in the brain, was expressed specifically in oligodendrocytes and Schwann cells, and that its expression level was decreased by demyelination. This suggests that BCAS1 is a novel myelin-associated protein. BCAS1 knockout mice displayed schizophrenia-like behavioral abnormalities and a tendency toward reduced anxiety-like behaviors. Moreover, we found that the loss of BCAS1 specifically induced hypomyelination and the expression of inflammation-related genes in the brain. These observations provide a novel insight into the functional link between oligodendrocytes and inflammation and/or abnormal behaviors.
Assuntos
Encéfalo/metabolismo , Doenças Desmielinizantes/genética , Proteínas de Neoplasias/metabolismo , Oligodendroglia/metabolismo , Animais , Encéfalo/patologia , Doenças Desmielinizantes/patologia , Inflamação/genética , Camundongos Knockout , Proteína Básica da Mielina/genética , Proteína Básica da Mielina/metabolismo , Bainha de Mielina/metabolismo , Bainha de Mielina/patologia , Proteínas de Neoplasias/deficiência , Esquizofrenia/genética , Esquizofrenia/patologia , Ativação Transcricional/genética , Regulação para CimaRESUMO
Glioma is an aggressive and incurable disease, and is frequently accompanied by augmented platelet-derived growth factor (PDGF) signaling. Overexpression of PDGF-B ligand characterizes a specific subclass of glioblastoma multiforme, but the significance of the ligand remains to be elucidated. For this end, we implanted a glioma-cell line transfected with PDGF-BB-overexpressing vector (GL261-PDGF-BB) or control vector (GL261-vector) into wild-type mouse brain, and examined the effect of glioma-derived PDGF on the tumor microenvironment. The volume of GL261-PDGF-BB rapidly increased compared with GL261-vector. Recruitment of many PDGF receptor (PDGFR)-α and Olig2-positive oligodendrocyte precursor cells and frequent hemorrhages were observed in GL261-PDGF-BB but not in GL261-vector. We then implanted GL261-PDGF-BB into the mouse brain with and without Pdgfra gene inactivation, corresponding to PDGFRα-knockout (KO) and Flox mice, respectively. The recruitment of oligodendrocyte precursor cells was largely suppressed in PDGFRα-KO than in Flox, whereas the volume of GL261-PDGF-BB was comparable between the two genotypes. Frequent hemorrhage and increased IgG-leakage were associated with aberrant vascular structures within the area where many recruited oligodendrocyte precursor cells accumulated in Flox. In contrast, these vascular phenotypes were largely normalized in PDGFRα-KO. Increased matrix metalloproteinase-9 in recruited oligodendrocyte precursor cells and decreased claudin-5 in vasculature may underlie the vascular abnormality. Glioma-derived PDGF-B signal induces cancer stroma characteristically seen in high-grade glioma, and should be therapeutically targeted to improve cancer microenvironment.
Assuntos
Neoplasias Encefálicas/patologia , Glioblastoma/patologia , Oligodendroglia/fisiologia , Proteínas Proto-Oncogênicas c-sis/fisiologia , Células-Tronco/fisiologia , Animais , Antineoplásicos Hormonais/farmacologia , Neoplasias Encefálicas/tratamento farmacológico , Permeabilidade Capilar/fisiologia , Linhagem Celular Tumoral , Hemorragia Cerebral/etiologia , Colágeno/fisiologia , Feminino , Técnicas de Inativação de Genes , Vetores Genéticos , Glioblastoma/tratamento farmacológico , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transplante de Neoplasias , Fenótipo , Tamoxifeno/farmacologia , Transfecção , Carga TumoralRESUMO
BACKGROUND: Serine racemase (SR) catalyzes the production of d-serine, a co-agonist of the N-methyl-d-aspartate receptor (NMDAR). A previous report shows the contribution of SR in the NMDAR-mediated neuronal cell death process. METHODS AND RESULTS: To analyze the intrinsic role of SR in the cell death process, we established the epithelial human embryonic kidney 293T (HEK293T) cell lines expressing wild-type SR (SR-WT), catalytically inactive mutant SR (SR-K56G), and catalytically hyperactive mutant SR (SR-Q155D). To these cell lines, staurosporine (STS), which induces apoptosis, was introduced. The cells expressing SR-WT and SR-Q155D showed resistance to STS-induced apoptosis, compared with nontransfected HEK293T cells and cells expressing SR-K56G. The SR-WT cells also showed a significant higher viability than the SR-QD cells. Furthermore, we detected elevated phosphorylation levels of Bcl-2 at serine-70 and Akt at serine-473 and threonine-308, which are related to cell survival, in the cells expressing SR-WT and SR-Q155D. From the results of metabolite analysis, we found elevated levels of acetyl CoA and ATP in cells expressing SR-WT. CONCLUSION: Because SR has two enzymatic activities, namely, racemization and α, ß-elimination, and SR-Q155D shows enhanced racemization and reduced α, ß-elimination activities, we concluded that the racemization reaction catalyzed by SR may have a more protective role against apoptosis than the α, ß-elimination reaction. Moreover, both of these activities are important for maximal survival and elevated levels of acetyl CoA and ATP. GENERAL SIGNIFICANCE: Our findings reveal the NMDAR-independent roles of SR in metabolism and cell survival.
Assuntos
Apoptose , Metabolismo , Racemases e Epimerases/metabolismo , Animais , Caspase 3/metabolismo , Citocromos c/metabolismo , Glicólise/efeitos dos fármacos , Células HEK293 , Humanos , L-Serina Desidratase/metabolismo , Metabolômica , Camundongos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Modelos Biológicos , Fosforilação/efeitos dos fármacos , Complexo Piruvato Desidrogenase/metabolismo , Estaurosporina/farmacologia , Transfecção , Proteína de Morte Celular Associada a bcl/metabolismoRESUMO
Although coordinated molecular signaling through excitatory and modulatory neurotransmissions is critical for the induction of immediate early genes (IEGs), which lead to effective changes in synaptic plasticity, the intracellular mechanisms responsible remain obscure. Here we measured the expression of IEGs and used bioluminescence imaging to visualize the expression of Bdnf when GPCRs, major neuromodulator receptors, were stimulated. Stimulation of pituitary adenylate cyclase-activating polypeptide (PACAP)-specific receptor (PAC1), a Gαs/q-protein-coupled GPCR, with PACAP selectively activated the calcineurin (CN) pathway that is controlled by calcium signals evoked via NMDAR. This signaling pathway then induced the expression of Bdnf and CN-dependent IEGs through the nuclear translocation of CREB-regulated transcriptional coactivator 1 (CRTC1). Intracerebroventricular injection of PACAP and intraperitoneal administration of MK801 in mice demonstrated that functional interactions between PAC1 and NMDAR induced the expression of Bdnf in the brain. Coactivation of NMDAR and PAC1 synergistically induced the expression of Bdnf attributable to selective activation of the CN pathway. This CN pathway-controlled expression of Bdnf was also induced by stimulating other Gαs- or Gαq-coupled GPCRs, such as dopamine D1, adrenaline ß, CRF, and neurotensin receptors, either with their cognate agonists or by direct stimulation of the protein kinase A (PKA)/PKC pathway with chemical activators. Thus, the GPCR-induced expression of IEGs in coordination with NMDAR might occur via the selective activation of the CN/CRTC1/CREB pathway under simultaneous excitatory and modulatory synaptic transmissions in neurons if either the Gαs/adenylate cyclase/PKA or Gαq/PLC/PKC-mediated pathway is activated.
Assuntos
Calcineurina/metabolismo , Cálcio/metabolismo , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Neurônios/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Receptores de Polipeptídeo Hipofisário Ativador de Adenilato Ciclase/metabolismo , Animais , Calcineurina/genética , Inibidores de Calcineurina/farmacologia , Células Cultivadas , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/genética , Embrião de Mamíferos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/genética , Proteínas Imediatamente Precoces/genética , Proteínas Imediatamente Precoces/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/efeitos dos fármacos , Polipeptídeo Hipofisário Ativador de Adenilato Ciclase/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/genética , Receptores de Polipeptídeo Hipofisário Ativador de Adenilato Ciclase/genética , Transdução de Sinais/efeitos dos fármacos , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
D-Aspartate is an endogenous free amino acid in the brain, endocrine tissues, and exocrine tissues in mammals, and it plays several physiological roles. In the testis, D-aspartate is detected in elongate spermatids, Leydig cells, and Sertoli cells, and implicated in the synthesis and release of testosterone. In the hippocampus, D-aspartate strongly enhances N-methyl-D-aspartate receptor-dependent long-term potentiation and is involved in learning and memory. The existence of aspartate racemase, a candidate enzyme for D-aspartate production, has been suggested. Recently, mouse glutamic-oxaloacetic transaminase 1-like 1 (Got1l1) has been reported to synthesize substantially D-aspartate from L-aspartate and to be involved in adult neurogenesis. In this study, we investigated the function of Got1l1 in vivo by generating and analyzing Got1l1 knockout (KO) mice. We also examined the enzymatic activity of recombinant Got1l1 in vitro. We found that Got1l1 mRNA is highly expressed in the testis, but it is not detected in the brain and submandibular gland, where D-aspartate is abundant. The D-aspartate contents of wild-type and Got1l1 KO mice were not significantly different in the testis and hippocampus. The recombinant Got1l1 expressed in mammalian cells showed L-aspartate aminotransferase activity, but lacked aspartate racemase activity. These findings suggest that Got1l1 is not the major aspartate racemase and there might be an as yet unknown D-aspartate-synthesizing enzyme.
Assuntos
Isomerases de Aminoácido/metabolismo , Ácido D-Aspártico/metabolismo , Isomerases de Aminoácido/química , Isomerases de Aminoácido/genética , Animais , Encéfalo/enzimologia , Encéfalo/metabolismo , Feminino , Hipocampo/enzimologia , Hipocampo/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos ICR , Camundongos Knockout , Testículo/enzimologia , Testículo/metabolismoRESUMO
D-Serine and glycine are coagonists of NMDA receptors (NMDARs), but their relative contributions for several NMDAR-dependent processes are unclear. We now report that the alanine-serine-cysteine transporter-1 (Asc-1) mediates release of both D-serine and glycine from neurons, and, in turn, this modulates NMDAR synaptic activity. Asc-1 antiporter activity is enhanced by D-isoleucine (D-Ile), which releases D-serine and glycine from Asc-1-transfected cells, primary neuronal cultures, and hippocampal slices. D-Ile has no effect on astrocytes, which do not express Asc-1. We show that D-Ile enhances the long-term potentiation (LTP) in rat and mouse hippocampal CA1 by stimulating Asc-1-mediated endogenous D-serine release. D-Ile effects on synaptic plasticity are abolished by enzymatically depleting D-serine or by using serine racemase knock-out (SR-KO) mice, confirming its specificity and supporting the notion that LTP depends mostly on D-serine release. Conversely, our data also disclose a role of glycine in activating synaptic NMDARs. Although acute enzymatic depletion of D-serine also drastically decreases the isolated NMDAR synaptic potentials, these responses are still enhanced by D-Ile. Furthermore, NMDAR synaptic potentials are preserved in SR-KO mice and are also enhanced by D-Ile, indicating that glycine overlaps with D-serine binding at synaptic NMDARs. Altogether, our results disclose a novel role of Asc-1 in regulating NMDAR-dependent synaptic activity by mediating concurrent non-vesicular release of D-serine and glycine. Our data also highlight an important role of neuron-derived D-serine and glycine, indicating that astrocytic D-serine is not solely responsible for activating synaptic NMDARs.
Assuntos
Sistema y+ de Transporte de Aminoácidos/fisiologia , Glicina/metabolismo , Neurônios/metabolismo , Receptores de N-Metil-D-Aspartato/fisiologia , Serina/metabolismo , Sinapses/fisiologia , Animais , Animais Recém-Nascidos , Células Cultivadas , Células HEK293 , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Plasticidade Neuronal/fisiologia , Ratos , Ratos Sprague-Dawley , Transmissão Sináptica/fisiologiaRESUMO
Neuroligin (NLGN) 3 is a postsynaptic cell adhesion protein organizing synapse formation through two different types of transsynaptic interactions, canonical interaction with neurexins (NRXNs) and a recently identified noncanonical interaction with protein tyrosine phosphatase (PTP) δ. Although, NLGN3 gene is known as a risk gene for neurodevelopmental disorders such as autism spectrum disorder (ASD) and intellectual disability (ID), the pathogenic contribution of the canonical NLGN3-NRXN and noncanonical NLGN3-PTPδ pathways to these disorders remains elusive. In this study, we utilized Nlgn3 mutant mice selectively lacking the interaction with either NRXNs or PTPδ and investigated their social and memory performance. Neither Nlgn3 mutants showed any social cognitive deficiency in the social novelty recognition test. However, the Nlgn3 mutant mice lacking the PTPδ pathway exhibited significant decline in the social conditioned place preference (sCPP) at the juvenile stage, suggesting the involvement of the NLGN3-PTPδ pathway in the regulation of social motivation and reward. In terms of learning and memory, disrupting the canonical NRXN pathway attenuated contextual fear conditioning while disrupting the noncanonical NLGN3-PTPδ pathway enhanced it. Furthermore, disruption of the NLGN3-PTPδ pathway negatively affected the remote spatial reference memory in the Barnes maze test. These findings highlight the differential contributions of the canonical NLGN3-NRXN and noncanonical NLGN3-PTPδ synaptogenic pathways to the regulation of higher order brain functions associated with ASD and ID.
Assuntos
Transtorno do Espectro Autista , Moléculas de Adesão Celular Neuronais , Deficiência Intelectual , Proteínas de Membrana , Proteínas do Tecido Nervoso , Animais , Camundongos , Transtorno do Espectro Autista/genética , Moléculas de Adesão Celular , Moléculas de Adesão Celular Neuronais/genética , Moléculas de Adesão Celular Neuronais/metabolismo , Cognição , Aprendizagem em Labirinto , Mudança Social , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismoRESUMO
Background: Neurodegenerative processes in Alzheimer's disease (AD) are associated with excitotoxicity mediated by the N-methyl-D-aspartate receptor (NMDAR). D-Serine is an endogenous co-agonist necessary for NMDAR-mediated excitotoxicity. In the mammalian brain, it is produced by serine racemase (SRR) from L-serine, suggesting that dysregulation of L-serine, D-serine, or SRR may contribute to AD pathogenesis. Objective and methods: We examined the contributions of D-serine to AD pathology in the AppNL-G-F/NL-G-F gene knock-in (APPKI) mouse model of AD. We first examined brain SRR expression levels and neuropathology in APPKI mice and then assessed the effects of long-term D-serine supplementation in drinking water on neurodegeneration. To further confirm the involvement of endogenous D-serine in AD progression, we generated Srr gene-deleted APPKI (APPKI-SRRKO) mice. Finally, to examine the levels of brain amino acids, we conducted liquid chromatography-tandem mass spectrometry. Results: Expression of SRR was markedly reduced in the retrosplenial cortex (RSC) of APPKI mice at 12 months of age compared with age-matched wild-type mice. Neuronal density was decreased in the hippocampal CA1 region but not altered significantly in the RSC. D-Serine supplementation exacerbated neuronal loss in the hippocampal CA1 of APPKI mice, while APPKI-SRRKO mice exhibited attenuated astrogliosis and reduced neuronal death in the hippocampal CA1 compared with APPKI mice. Furthermore, APPKI mice demonstrated marked abnormalities in the cortical amino acid levels that were partially reversed in APPKI-SRRKO mice. Conclusion: These findings suggest that D-serine participates in the regional neurodegenerative process in the hippocampal CA1 during the amyloid pathology of AD and that reducing brain D-serine can partially attenuate neuronal loss and reactive astrogliosis. Therefore, regulating SRR could be an effective strategy to mitigate NMDAR-dependent neurodegeneration during AD progression.
RESUMO
The retrieval of fear memories induces two opposing processes, reconsolidation, and extinction. The memory reconsolidation is an active process that involves gene expression and updates an existing memory. It is hypothesized that blockade of reconsolidation by manipulating the neurobiological factors, which are mechanistically involved in the process, could weaken or disrupt the original fear memory. The N-methyl-D-aspartate (NMDA) receptor and hippocampal neurogenesis play crucial roles in hippocampus-dependent memory processes, including reconsolidation. Using contextual fear conditioning paradigm with multiple retrievals, we attempted to weaken the original contextual fear memory by repeatedly disrupting retrieval-induced reconsolidation via downregulation of NMDA receptor signaling and inhibition of neurogenesis. In the first experiment, prior to fear conditioning, NMDA receptor signaling was downregulated by the genetic reduction of its co-agonist, D-serine, and the neurogenesis was dampened by focal X-ray irradiation on the hippocampus. We found that simultaneous D-serine reduction and neurogenesis dampening resulted in a progressive decrease in freezing following each retrieval, leading to an attenuation of remote contextual fear memory on day 28. In the second experiment using the same behavioral protocols, after conditioning, pharmacological approaches were conducted to simultaneously block D-serine signaling and neurogenesis, resulting in a similar suppressive effect on the remote fear memory. The present findings provide insights for understanding the role of D-serine-mediated NMDA receptor signaling and neurogenesis in memory retrieval and the maintenance of remote fear memory, and improving the efficacy of exposure-based therapy for the treatment of post-traumatic stress disorder (PTSD).
RESUMO
Tauopathies differ in terms of the brain regions that are affected. In Alzheimer's disease, basal forebrain and hippocampus are mainly involved, while frontotemporal lobar degeneration affects the frontal and temporal lobes and subcortical nuclei including striatum. Over 90% of human cases of tauopathies are sporadic, although the majority of established tau-transgenic mice have had mutations. This prompted us to establish transgenic mice expressing wild-type human tau (Tg601). Old (>14 months old) Tg601 mice displayed decreased anxiety in the elevated plus maze test and impaired place learning in the Morris water maze test. Immunoblotting of brain tissue identified that soluble tau multimer was increased with aging even though insoluble tau was not observed. In the striatum of old Tg601, the level of AT8- or AT180-positive tau was decreased compared with that of other regions, while PHF-1-positive tau levels remained equal. Phosphorylated tau-positive axonal dilations were present mainly in layers V and VI of the prefrontal cortex. Loss of synaptic dendritic spine and decreased immunohistochemical level of synaptic markers were observed in the nucleus accumbens. In vivo 2-[(18)F]fluoro-2-deoxy-d-glucose positron emission tomography analysis also showed decreased activity exclusively in the nucleus accumbens of living Tg601 mice. In Tg601 mice, the axonal transport defect in the prefrontal cortex-nucleus accumbens pathway may lead to decreased anxiety behavior. Differential distribution of hyperphosphorylated tau may cause region-specific neurodegeneration.
Assuntos
Núcleo Accumbens/metabolismo , Sinapses/metabolismo , Tauopatias/metabolismo , Proteínas tau/metabolismo , Análise de Variância , Animais , Western Blotting , Modelos Animais de Doenças , Imuno-Histoquímica , Camundongos , Camundongos Knockout , Degeneração Neural/metabolismo , Degeneração Neural/patologia , Emaranhados Neurofibrilares/metabolismo , Emaranhados Neurofibrilares/patologia , Núcleo Accumbens/patologia , Fosforilação , Tomografia por Emissão de Pósitrons , Sinapses/patologia , Tauopatias/patologia , Distribuição TecidualRESUMO
D-Serine is detected in the brain and acts as a coagonist at the "glycine-site" of the NMDA-type glutamate receptor. Although D-serine can be directly produced from L-serine by serine racemase (SR), the relative contribution of SR in D-serine formation in vivo is not known. Pathological roles of brain D-serine mediating NMDA receptor overactivation are suggested in studies using in vitro culture systems. However, we have recently demonstrated the differential SR protein expression in vivo and in culture. Here, we reported an approximately 90% decrease in forebrain D-serine content in SR knock-out (KO) mice. We also found a reduced neurotoxicity induced by NMDA- and Abeta(1-42)- peptide injections into the forebrain in SR KO mice. These results suggest that SR is the major enzyme for D-serine production in the brain, D-serine is the predominant endogenous coagonist of the NMDA receptor in the forebrain, and D-serine may be involved in controlling the extent of NMDA receptor-mediated neurotoxic insults observed in disorders including Alzheimer's disease. The control of SR activity and D-serine level in the brain may lead to a novel strategy for neuroprotection against various neurodegenerative diseases.
Assuntos
Peptídeos beta-Amiloides/toxicidade , N-Metilaspartato/toxicidade , Síndromes Neurotóxicas/etiologia , Neurotoxinas/toxicidade , Fragmentos de Peptídeos/toxicidade , Racemases e Epimerases/deficiência , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Cromatografia Líquida de Alta Pressão/métodos , Modelos Animais de Doenças , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Síndromes Neurotóxicas/metabolismo , Síndromes Neurotóxicas/patologia , Síndromes Neurotóxicas/prevenção & controle , Serina/metabolismoRESUMO
Extinction-based exposure therapy is widely used for the treatment of anxiety disorders, such as post-traumatic stress disorder (PTSD). D-serine, an endogenous co-agonist at the glycine-binding site of the N-methyl-D-aspartate-type glutamate receptor (NMDAR), has been shown to be involved in extinction of fear memory. Recent findings suggest that the length of time between the initial learning and an extinction session is a determinant of neural mechanism involved in fear extinction. However, how D-serine is involved in extinction of fear memory at different timings remains unclear. In the present study, we investigated the role of D-serine in immediate, delayed and post-retrieval extinction (P-RE) of contextual fear memory using wild-type (WT) and serine racemase (SRR) knockout (KO) mice that exhibit 90% reduction in D-serine content in the hippocampus. We found that SRR disruption impairs P-RE, facilitates immediate extinction (IE), but has no effect on delayed extinction (DE) of contextual fear memories. The impaired P-RE of contextual fear memory in SRRKO mice was associated with increased expression of the GluA1 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptor (AMPAR) in the hippocampal synaptic membrane fraction after P-RE, and this increase of AMPAR and impaired P-RE were rescued by the administration of D-serine to SRRKO mice. Our findings suggest that D-serine is differentially involved in the regulation of contextual fear extinction depending on the timing of behavioral intervention, and that combining D-serine or other drugs, enhancing the NMDAR function, with P-RE may achieve optimal outcomes for the treatment of PTSD.
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Diabetic retinopathy (DR) is a leading cause of blindness. DR is recognized as a microvascular disease and inner retinal neurodegeneration. In the course of retinal neurodegeneration, N-methyl-D-aspartate receptor (NMDAR)-mediated excitotoxicity is involved. Full activation of NMDAR requires binding of agonist glutamate and coagonist glycine or D-serine. D-Serine is produced from L-serine by serine racemase (SRR) and contributes to retinal neurodegeneration in rodent models of DR. However, the involvement of SRR in both neurodegeneration and microvascular damage in DR remains unclear. Here, we established diabetic model of SRR knockout (SRR-KO) and control wild-type (WT) mice by streptozotocin injection. Six months after the onset of diabetes, the number of survived retinal ganglion cells was higher in SRR-KO mice than that of WT mice. The reduction of thickness of inner retinal layer (IRL) was attenuated in SRR-KO mice than that of WT mice. Moreover, the number of damaged acellular capillaries was lower in SRR-KO mice than that of WT mice. Our results suggest the suppression of SRR activity may have protective effects in DR.
Assuntos
Retinopatia Diabética/patologia , Microvasos/patologia , Neurônios/patologia , Racemases e Epimerases/genética , Animais , Retinopatia Diabética/enzimologia , Camundongos , Camundongos Knockout , EstreptozocinaRESUMO
Glucocorticoid receptor (GR) is crucial for signaling mediated by stress-induced high levels of glucocorticoids. The lateral nucleus of the amygdala (LA) is a key structure underlying auditory-cued fear conditioning. Here, we demonstrate that genetic disruption of GR in the LA (LAGRKO) resulted in an auditory-cued fear memory deficit for strengthened conditioning. Furthermore, the suppressive effect of a single restraint stress (RS) prior to conditioning on auditory-cued fear memory in floxed GR (control) mice was abolished in LAGRKO mice. Optogenetic induction of long-term depression (LTD) at auditory inputs to the LA reduced auditory-cued fear memory in RS-exposed LAGRKO mice, and in contrast, optogenetic induction of long-term potentiation (LTP) increased auditory-cued fear memory in RS-exposed floxed GR mice. These findings suggest that prior stress suppresses fear conditioning-induced LTP at auditory inputs to the LA in a GR-dependent manner, thereby protecting animals from encoding excessive cued fear memory under stress conditions.
Assuntos
Tonsila do Cerebelo/fisiologia , Medo/psicologia , Memória/fisiologia , Receptores de Glucocorticoides/genética , Estresse Psicológico/metabolismo , Estimulação Acústica , Tonsila do Cerebelo/anatomia & histologia , Animais , Condicionamento Psicológico , Corticosterona/sangue , Sinais (Psicologia) , Medo/fisiologia , Imobilização , Integrases/genética , Integrases/metabolismo , Potenciação de Longa Duração/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Optogenética/métodos , Receptores de Glucocorticoides/deficiência , Estresse Psicológico/fisiopatologia , Estresse Psicológico/psicologiaRESUMO
Chronic inflammation is a pathophysiology of insulin resistance in metabolic diseases, such as obesity and type 2 diabetes. Adipose tissue macrophages (ATMs) play important roles in this inflammatory process. SIRT1 is implicated in the regulation of glucose metabolism in some metabolic tissues, such as liver or skeletal muscle. This study was performed to investigate whether SIRT1 in macrophages played any roles in the regulation of inflammation and glucose metabolism. Myeloid cell-specific SIRT1-knockout mice were originally generated and analyzed under chow-fed and high-fat-fed conditions. Myeloid cell-specific SIRT1 deletion impaired insulin sensitivity and glucose tolerance assessed by the glucose- or insulin-tolerance test, which was associated with the enhanced expression of inflammation-related genes in epididymal adipose tissue of high-fat-fed mice. Interestingly, the M1 ATMs from the SIRT1-knockout mice showed more hypoxic and inflammatory phenotypes than those from control mice. The expressions of some inflammatory genes, such as Il1b and Nos2, which were induced by in vitro hypoxia treatment, were further enhanced by SIRT1 deletion along with the increased acetylation of HIF-1α in cultured macrophages. These results suggest that deletion of SIRT1 in myeloid cells impairs glucose metabolism by enhancing the hypoxia and inflammatory responses in ATMs, thereby possibly representing a novel therapeutic target for metabolic diseases, such as type 2 diabetes.
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Syntenin-1 is an intracellular PDZ protein that binds multiple proteins and regulates protein trafficking, cancer metastasis, exosome production, synaptic formation, and IL-5 signaling. However, the functions of Syntenin-1 have not yet been clearly characterized in detail, especially in vivo. In this study, we generated a Syntenin-1 knock out (KO) mouse strain and analyzed the role(s) of Syntenin-1 in IL-5 signaling, because the direct interaction of Syntenin-1 with the cytoplasmic domain of the IL-5 receptor α subunit and the regulation of IL-5 signaling by Syntenin-1 have been reported. Unexpectedly, the number of IL-5-responding cells was normal and the levels of fecal immunoglobulins were rather higher in the Syntenin-1 KO mice. We also found that IgA and IgM production of splenic B cells stimulated in vitro was increased in Syntenin-1 KO mice. In addition, we showed that a distribution of intestinal microbial flora was influenced in Syntenin-1 KO mice. Our data indicate that Syntenin-1 negatively regulates the intestinal immunoglobulin production and has a function to maintain the intestinal homeostasis in vivo. The analysis of Syntenin-1 KO mice may provide novel information on not only mucosal immunity but also other functions of Syntenin-1 such as cancer metastasis and neural development.
Assuntos
Imunoglobulinas/biossíntese , Intestinos/imunologia , Sinteninas/metabolismo , Animais , Formação de Anticorpos/genética , Microbioma Gastrointestinal/genética , Homeostase/genética , Imunidade nas Mucosas/genética , Interleucina-5/metabolismo , Intestinos/microbiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transdução de Sinais/genética , Sinteninas/genéticaRESUMO
Platelet derived growth factor (PDGF) plays a pivotal role in the remodeling of connective tissues. Emerging data indicate the distinctive role of PDGF receptor-α (PDGFRα) in this process. In the present study, the Pdgfra gene was systemically inactivated in adult mouse (α-KO mouse), and the role of PDGFRα was examined in the subcutaneously implanted sponge matrices. PDGFRα expressed in the fibroblasts of Pdgfra-preserving control mice (Flox mice), was significantly reduced in the sponges in α-KO mice. Neovascularized areas were largely suppressed in the α-KO mice than in the Flox mice, whereas the other parameters related to the blood vessels and endothelial cells were similar. The deposition of collagen and fibronectin and the expression of collagen 1a1 and 3a1 genes were significantly reduced in α-KO mice. There was a significantly decrease in the number and dividing fibroblasts in the α-KO mice, and those of macrophages were similar between the two genotypes. Hepatocyte growth factor (Hgf) gene expression was suppressed in Pdgfra-inactivated fibroblasts and connective tissue. The findings implicate the role of PDGFRα-dependent ECM and HGF production in fibroblasts that promotes the remodeling of connective tissue and suggest that PDGFRα may be a relevant target to regulate connective tissue remodeling.
Assuntos
Tecido Conjuntivo/metabolismo , Receptor alfa de Fator de Crescimento Derivado de Plaquetas/metabolismo , Animais , Vasos Sanguíneos/efeitos dos fármacos , Vasos Sanguíneos/metabolismo , Contagem de Células , Colágeno/metabolismo , Tecido Conjuntivo/efeitos dos fármacos , Matriz Extracelular/efeitos dos fármacos , Matriz Extracelular/metabolismo , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Fibronectinas/metabolismo , Imunofluorescência , Fator de Crescimento de Hepatócito/metabolismo , Implantes Experimentais , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neovascularização Fisiológica/efeitos dos fármacos , Pele/citologia , Tamoxifeno/farmacologiaRESUMO
D-Serine, an endogenous coagonist of the N-methyl-D-aspartate receptor (NMDAR), is widely distributed in the central nervous system and is synthesized from L-serine by serine racemase (SR). NMDAR plays an important role in pain processing including central sensitization that eventually causes hyperalgesia. To elucidate the roles of D-serine and SR in pain transmission, we evaluated the behavioral changes and spinal nociceptive processing induced by formalin using SR knock-out (KO) mice. We found that SR is mainly distributed in lamina II of the dorsal horn of the spinal cord in wild-type (WT) mice. Although the formalin injected subcutaneously induced the biphasic pain response of licking in SR-KO and WT mice, the time spent on licking was significantly longer in the SR-KO mice during the second phase of the formalin test. The number of neurons immunopositive for c-Fos and phosphorylated extracellular signal-regulated kinase (p-ERK), which are molecular pain markers, in laminae I-II of the ipsilateral dorsal horn was significantly larger in the SR-KO mice. Immunohistochemical staining revealed that the distribution of SR changed from being broad to being concentrated in cell bodies after the formalin injection. On the other hand, the expression level of the cytosolic SR in the ipsilateral dorsal horn significantly decreased. Oral administration of 10 mM D-serine in drinking water for one week cancelled the difference in pain behaviors between WT and SR-KO mice in phase 2 of the formalin test. These findings demonstrate that the SR-KO mice showed increased sensitivity to inflammatory pain and the WT mice showed translocation of SR and decreased SR expression levels after the formalin injection, which suggest a novel antinociceptive mechanism via SR indicating an important role of D-serine in pain transmission.