RESUMEN
Two-thirds of signaling hormones and one-third of approved drugs exert their effects by binding and modulating the G protein-coupled receptors (GPCRs) activation. While the activation mechanism for monomeric GPCRs has been well-established, little is known about GPCRs in dimeric form. Here, by combining transition pathway generation, extensive atomistic simulation-based Markov state models, and experimental signaling assays, we reveal an asymmetric, stepwise millisecond allosteric activation mechanism for the metabotropic glutamate receptor subtype 5 receptor (mGlu5), an obligate dimeric class C GPCR. The dynamic picture is presented that agonist binding induces dimeric ectodomains compaction, amplified by the precise association of the cysteine-rich domains, ultimately loosely bringing the intracellular 7-transmembrane (7TM) domains into proximity and establishing an asymmetric TM6-TM6 interface. The active inter-domain interface enhances their intra-domain flexibility, triggering the activation of micro-switches crucial for downstream signal transduction. Furthermore, we show that the positive allosteric modulator stabilizes both the active inter-domain 7TM interface and an open, extended intra-domain ICL2 conformation. This stabilization leads to the formation of a pseudo-cavity composed of the ICL2, ICL3, TM3, and C-terminus, which facilitates G protein coordination. Our strategy may be generalizable for characterizing millisecond events in other allosteric systems.
Asunto(s)
Multimerización de Proteína , Receptor del Glutamato Metabotropico 5 , Receptor del Glutamato Metabotropico 5/metabolismo , Receptor del Glutamato Metabotropico 5/química , Receptor del Glutamato Metabotropico 5/genética , Regulación Alostérica , Humanos , Células HEK293 , Transducción de Señal , Simulación de Dinámica Molecular , Animales , Dominios Proteicos , Unión ProteicaRESUMEN
BACKGROUND: The group-I metabotropic glutamate receptor subtype 5 (mGlu5) has been implicated in methamphetamine exposure in animals and in human cognition. Because people with methamphetamine use disorder (MUD) exhibit cognitive deficits, we evaluated mGlu5 in people with MUD and controls and tested its association with cognitive performance. METHODS: Positron emission tomography was performed to measure the total VT of [18F]FPEB, a radiotracer for mGlu5, in brains of participants with MUD (abstinent from methamphetamine for at least 2 weeks, N = 14) and a control group (N = 14). Drug use history questionnaires and tests of verbal learning, spatial working memory, and executive function were administered. Associations of VT with methamphetamine use, tobacco use, and cognitive performance were tested. RESULTS: MUD participants did not differ from controls in global or regional VT, and measures of methamphetamine use were not correlated with VT. VT was significantly higher globally in nonsmoking vs smoking participants (main effect, P = .0041). MUD participants showed nonsignificant weakness on the Rey Auditory Verbal Learning Task and the Stroop test vs controls (P = .08 and P = .13, respectively) with moderate to large effect sizes, and significantly underperformed controls on the Spatial Capacity Delayed Response Test (P = .015). Across groups, Rey Auditory Verbal Learning Task performance correlated with VT in the dorsolateral prefrontal cortex and superior frontal gyrus. CONCLUSION: Abstinent MUD patients show no evidence of mGlu5 downregulation in brain, but association of VT in dorsolateral prefrontal cortex with verbal learning suggests that medications that target mGlu5 may improve cognitive performance.
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Trastornos Relacionados con Anfetaminas , Encéfalo , Fumar Cigarrillos , Metanfetamina , Tomografía de Emisión de Positrones , Receptor del Glutamato Metabotropico 5 , Adulto , Femenino , Humanos , Masculino , Trastornos Relacionados con Anfetaminas/metabolismo , Trastornos Relacionados con Anfetaminas/diagnóstico por imagen , Trastornos Relacionados con Anfetaminas/fisiopatología , Encéfalo/metabolismo , Encéfalo/efectos de los fármacos , Encéfalo/diagnóstico por imagen , Estimulantes del Sistema Nervioso Central/farmacología , Estimulantes del Sistema Nervioso Central/administración & dosificación , Fumar Cigarrillos/metabolismo , Cognición/efectos de los fármacos , Función Ejecutiva/efectos de los fármacos , Función Ejecutiva/fisiología , Metanfetamina/administración & dosificación , Metanfetamina/farmacología , Pruebas Neuropsicológicas , Receptor del Glutamato Metabotropico 5/metabolismoRESUMEN
RATIONALE: Anti-Myelin oligodendrocyte glycoprotein (MOG) and anti-metabotropic glutamate receptor 5 (mGluR5) double antibody positive encephalitis characterized by optic neuritis is extremely rare. We present a case of overlapping syndrome of MOG-IgG-associated disease and anti-mGluR5 encephalitis manifested as optic neuritis. PATIENT CONCERNS: A 60-year-old Chinses woman presented to the hospital with progressive vision loss and headache for 1 week. The cerebrospinal fluid examination was within the normal range. Visual evoked potentials study disclosed prolonged latency of P100 bilaterally. Fundus examination revealed indistinct boundaries of both optic discs. Her brain magnetic resonance imaging showed patchy hyperintensity in the posterior horn of the left ventricle and the left optic nerve. Her serum was positive for anti-MOG and anti-mGluR5 antibodies. DIAGNOSIS: The patient was diagnosed with overlapping syndrome of anti-MOG antibody-associated disease and anti-mGluR5 encephalitis mainly based on the clinical symptoms and further test of the antibody in serum. INTERVENTIONS AND OUTCOMES: She was subsequently subjected to empirical treatment with intravenous methylprednisolone. After discharge, she was given a tapering dose of oral prednisone, alongside mycophenolate mofetil. On outpatient follow-up, her symptoms showed no relapse after 1 month, and her condition remained stable. LESSONS: Early recognition of autoimmune encephalitis is crucial. The detection of cerebrospinal fluid and serum of autoimmune encephalitis and demyelinating diseases of the CNS, including MOG-IgG and mGluR5-IgG, should be strengthened in order to make a precise diagnosis and develop a comprehensive treatment plan in a timely manner.
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Autoanticuerpos , Glicoproteína Mielina-Oligodendrócito , Neuritis Óptica , Receptor del Glutamato Metabotropico 5 , Humanos , Femenino , Neuritis Óptica/diagnóstico , Neuritis Óptica/inmunología , Neuritis Óptica/tratamiento farmacológico , Persona de Mediana Edad , Glicoproteína Mielina-Oligodendrócito/inmunología , Autoanticuerpos/sangre , Encefalitis/diagnóstico , Encefalitis/inmunología , Encefalitis/tratamiento farmacológico , Metilprednisolona/uso terapéutico , Imagen por Resonancia Magnética , SíndromeRESUMEN
INTRODUCTION: Traumatic brain injury (TBI) is a complex pathophysiological process, and increasing attention has been paid to the important role of post-synaptic density (PSD) proteins, such as glutamate receptors. Our previous study showed that a PSD protein Arc/Arg3.1 (Arc) regulates endoplasmic reticulum (ER) stress and neuronal necroptosis in traumatic injury in vitro. AIM: In this study, we investigated the expression, regulation and biological function of Arc in both in vivo and in vitro experimental TBI models. RESULTS: Traumatic neuronal injury (TNI) induced a temporal upregulation of Arc in cortical neurons, while TBI resulted in sustained increase in Arc expression up to 24 h in rats. The increased expression of Arc was mediated by the activity of metabotropic glutamate receptor 5 (mGluR5), but not dependent on the intracellular calcium (Ca2+) release. By using inhibitors and antagonists, we found that TNI regulates Arc expression via Gq protein and protein turnover. In addition, overexpression of Arc protects against TBI-induced neuronal injury and motor dysfunction both in vivo and in vitro, whereas the long-term cognitive function was not altered. To determine the role of Arc in mGluR5-induced protection, lentivirus-mediated short hairpin RNA (shRNA) transfection was performed to knockdown Arc expression. The mGluR5 agonist (RS)-2-chloro-5-hydroxyphenylglycine (CHPG)-induced protection against TBI was partially prevented by Arc knockdown. Furthermore, the CHPG-induced attenuation of Ca2+ influx after TNI was dependent on Arc activation and followed regulation of AMPAR subunits. The results of Co-IP and Ca2+ imaging showed that the Arc-Homer1 interaction contributes to the CHPG-induced regulation of intracellular Ca2+ release. CONCLUSION: In summary, the present data indicate that the mGluR5-mediated Arc activation is a protective mechanism that attenuates neurotoxicity following TBI through the regulation of intracellular Ca2+ hemostasis. The AMPAR-associated Ca2+ influx and ER Ca2+ release induced by Homer1-IP3R pathway might be involved in this protection.
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Lesiones Traumáticas del Encéfalo , Proteínas del Citoesqueleto , Proteínas de Andamiaje Homer , Proteínas del Tejido Nervioso , Neuronas , Ratas Sprague-Dawley , Receptor del Glutamato Metabotropico 5 , Animales , Lesiones Traumáticas del Encéfalo/metabolismo , Lesiones Traumáticas del Encéfalo/patología , Receptor del Glutamato Metabotropico 5/metabolismo , Receptor del Glutamato Metabotropico 5/antagonistas & inhibidores , Masculino , Proteínas del Tejido Nervioso/metabolismo , Proteínas del Tejido Nervioso/genética , Proteínas del Citoesqueleto/metabolismo , Proteínas del Citoesqueleto/genética , Proteínas del Citoesqueleto/biosíntesis , Ratas , Proteínas de Andamiaje Homer/metabolismo , Neuronas/metabolismo , Neuronas/efectos de los fármacos , Modelos Animales de Enfermedad , Células Cultivadas , Corteza Cerebral/metabolismo , Calcio/metabolismo , Glicina/análogos & derivados , FenilacetatosRESUMEN
We used light-sensitive drugs to identify the brain region-specific role of mGlu5 metabotropic glutamate receptors in the control of pain. Optical activation of systemic JF-NP-26, a caged, normally inactive, negative allosteric modulator (NAM) of mGlu5 receptors, in cingulate, prelimbic, and infralimbic cortices and thalamus inhibited neuropathic pain hypersensitivity. Systemic treatment of alloswitch-1, an intrinsically active mGlu5 receptor NAM, caused analgesia, and the effect was reversed by light-induced drug inactivation in the prelimbic and infralimbic cortices, and thalamus. This demonstrates that mGlu5 receptor blockade in the medial prefrontal cortex and thalamus is both sufficient and necessary for the analgesic activity of mGlu5 receptor antagonists. Surprisingly, when the light was delivered in the basolateral amygdala, local activation of systemic JF-NP-26 reduced pain thresholds, whereas inactivation of alloswitch-1 enhanced analgesia. Electrophysiological analysis showed that alloswitch-1 increased excitatory synaptic responses in prelimbic pyramidal neurons evoked by stimulation of presumed BLA input, and decreased BLA-driven feedforward inhibition of amygdala output neurons. Both effects were reversed by optical silencing and reinstated by optical reactivation of alloswitch-1. These findings demonstrate for the first time that the action of mGlu5 receptors in the pain neuraxis is not homogenous, and suggest that blockade of mGlu5 receptors in the BLA may limit the overall analgesic activity of mGlu5 receptor antagonists. This could explain the suboptimal effect of mGlu5 NAMs on pain in human studies and validate photopharmacology as an important tool to determine ideal target sites for systemic drugs.
Asunto(s)
Luz , Receptor del Glutamato Metabotropico 5 , Receptor del Glutamato Metabotropico 5/metabolismo , Receptor del Glutamato Metabotropico 5/antagonistas & inhibidores , Animales , Masculino , Ratones , Neuralgia/metabolismo , Tálamo/efectos de los fármacos , Tálamo/metabolismo , Complejo Nuclear Basolateral/metabolismo , Complejo Nuclear Basolateral/efectos de los fármacos , Analgésicos/farmacología , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/metabolismo , Ratones Endogámicos C57BLRESUMEN
Multiple studies have shown that astrocytes in the medullary dorsal horn (MDH) play an important role in the development of pathologic pain. However, little is known about the structural reorganization of the peripheral astrocytic processes (PAP), the main functional part of the astrocyte, in MDH in neuropathic state. For this, we investigated the structural relationship between PAP and their adjacent presynaptic axon terminals and postsynaptic dendrites in the superficial laminae of the MDH using electron microscopical immunohistochemistry for ezrin, a marker for PAP, and quantitative analysis in a rat model of neuropathic pain following chronic constriction injury of the infraorbital nerve (CCI-ION). We found that, compared to controls, in rats with CCI-ION, (1) the number, % area, surface density, and volume fraction of ezrin-positive (+) PAP, as well as the fraction of synaptic edge apposed by ezrin + PAP and the degree of its coverage of presynaptic axon terminals and postsynaptic dendrites increased significantly, (2) these effects were abolished by administration of the mGluR5 antagonist 2-methyl-6-(phenylethynyl) pyridine (MPEP). These findings indicate that PAP undergoes structural reorganization around the central synapses of sensory afferents following nerve injury, suggest that it may be mediated by mGluR5, and may represent the structural basis for enhancing astrocyte-neuron interaction in neuropathic pain.
Asunto(s)
Astrocitos , Modelos Animales de Enfermedad , Neuralgia , Ratas Sprague-Dawley , Asta Dorsal de la Médula Espinal , Animales , Astrocitos/metabolismo , Astrocitos/patología , Neuralgia/patología , Neuralgia/metabolismo , Masculino , Asta Dorsal de la Médula Espinal/metabolismo , Asta Dorsal de la Médula Espinal/patología , Ratas , Bulbo Raquídeo/metabolismo , Bulbo Raquídeo/patología , Receptor del Glutamato Metabotropico 5/metabolismo , Proteínas del Citoesqueleto/metabolismo , Dendritas/metabolismo , Dendritas/patología , Terminales Presinápticos/metabolismo , Terminales Presinápticos/patología , Terminales Presinápticos/ultraestructuraRESUMEN
Potentiation of metabotropic glutamate receptor subtype 5 (mGluR5) function produces antipsychotic-like and pro-cognitive effects in animal models of schizophrenia and can reverse cognitive deficits induced by N-methyl-D-aspartate type glutamate receptor (NMDAR) antagonists. However, it is currently unknown if mGluR5 positive allosteric modulators (PAMs) can modulate NMDAR antagonist-induced alterations in extracellular glutamate levels in regions underlying these cognitive and behavioral effects, such as the medial prefrontal cortex (mPFC). We therefore assessed the ability of the mGluR5 PAM, 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl) benzamide (CDPPB), to reduce elevated extracellular glutamate levels induced by the NMDAR antagonist, dizocilpine (MK-801), in the mPFC. Male Sprague-Dawley rats were implanted with a guide cannula aimed at the mPFC and treated for ten consecutive days with MK-801 and CDPPB or their corresponding vehicles. CDPPB or vehicle was administered thirty minutes before MK-801 or vehicle each day. On the final day of treatment, in vivo microdialysis was performed, and samples were collected every thirty minutes to analyze extracellular glutamate levels. Compared to animals receiving only vehicle, administration of MK-801 alone significantly increased extracellular levels of glutamate in the mPFC. This effect was not observed in animals administered CDPPB before MK-801, nor in those administered CDPPB alone, indicating that CDPPB decreased extracellular glutamate release stimulated by MK-801. Results indicate that CDPPB attenuates MK-801 induced elevations in extracellular glutamate in the mPFC. This effect of CDPPB may underlie neurochemical adaptations associated with the pro-cognitive effects of mGluR5 PAMs in rodent models of schizophrenia.
Asunto(s)
Benzamidas , Maleato de Dizocilpina , Antagonistas de Aminoácidos Excitadores , Ácido Glutámico , Corteza Prefrontal , Pirazoles , Ratas Sprague-Dawley , Receptor del Glutamato Metabotropico 5 , Animales , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/metabolismo , Masculino , Maleato de Dizocilpina/farmacología , Receptor del Glutamato Metabotropico 5/metabolismo , Receptor del Glutamato Metabotropico 5/antagonistas & inhibidores , Ácido Glutámico/metabolismo , Antagonistas de Aminoácidos Excitadores/farmacología , Regulación Alostérica/efectos de los fármacos , Benzamidas/farmacología , Pirazoles/farmacología , Ratas , MicrodiálisisRESUMEN
Our previous study has identified that glutamate in the red nucleus (RN) facilitates the development of neuropathic pain through metabotropic glutamate receptors (mGluR). Here, we further explored the actions and possible molecular mechanisms of red nucleus mGluR â (mGluR1 and mGluR5) in the development of neuropathic pain induced by spared nerve injury (SNI). Our data indicated that both mGluR1 and mGluR5 were constitutively expressed in the RN of normal rats. Two weeks after SNI, the expressions of mGluR1 and mGluR5 were significantly boosted in the RN contralateral to the nerve injury. Administration of mGluR1 antagonist LY367385 or mGluR5 antagonist MTEP to the RN contralateral to the nerve injury at 2 weeks post-SNI significantly ameliorated SNI-induced neuropathic pain. However, unilateral administration of mGluRâ agonist DHPG to the RN of normal rats provoked a significant mechanical allodynia, this effect could be blocked by LY367385 or MTEP. Further studies indicated that the expressions of TNF-α and IL-1ß in the RN were also elevated at 2 weeks post-SNI. Administration of mGluR1 antagonist LY367385 or mGluR5 antagonist MTEP to the RN at 2 weeks post-SNI significantly inhibited the elevations of TNF-α and IL-1ß. However, administration of mGluR â agonist DHPG to the RN of normal rats significantly enhanced the expressions of TNF-α and IL-1ß, these effects were blocked by LY367385 or MTEP. These results suggest that activation of red nucleus mGluR1 and mGluR5 facilitate the development of neuropathic pain by stimulating the expressions of TNF-α and IL-1ß. mGluR â maybe potential targets for drug development and clinical treatment of neuropathic pain.
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Interleucina-1beta , Neuralgia , Ratas Sprague-Dawley , Receptor del Glutamato Metabotropico 5 , Receptores de Glutamato Metabotrópico , Núcleo Rojo , Factor de Necrosis Tumoral alfa , Animales , Neuralgia/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Receptores de Glutamato Metabotrópico/antagonistas & inhibidores , Receptores de Glutamato Metabotrópico/agonistas , Masculino , Receptor del Glutamato Metabotropico 5/metabolismo , Receptor del Glutamato Metabotropico 5/antagonistas & inhibidores , Interleucina-1beta/metabolismo , Interleucina-1beta/biosíntesis , Factor de Necrosis Tumoral alfa/metabolismo , Factor de Necrosis Tumoral alfa/antagonistas & inhibidores , Ratas , Núcleo Rojo/metabolismo , Núcleo Rojo/efectos de los fármacosRESUMEN
Numerous findings confirm that the metabotropic glutamate receptors (mGluRs) are involved in the conditioned place preference (CPP) induced by morphine. Here we focused on the role of mGluR5 in the nucleus accumbens (NAc) as a main site of glutamate action on the rewarding effects of morphine. Firstly, we investigated the effects of intra-NAc administrating mGluR5 antagonist 3-((2-Methyl-1,3-thiazol-4-yl) ethynyl) pyridine hydrochloride (MTEP; 1, 3, and 10 µg/µl saline) on the extinction and the reinstatement phase of morphine CPP. Moreover, to determine the downstream signaling cascades of mGluR5 in morphine CPP, the protein levels of stromal interaction molecules (STIM1 and 2) in the NAc and hippocampus (HPC) were measured by western blotting. The behavioral data indicated that the mGluR5 blockade by MTEP at the high doses of 3 and 10 µg facilitated the extinction of morphine-induced CPP and attenuated the reinstatement to morphine in extinguished rats. Molecular results showed that the morphine led to increased levels of STIM proteins in the HPC and increased the level of STIM1 without affecting STIM2 in the NAc. Furthermore, intra-NAc microinjection of MTEP (10 µg) in the reinstatement phase decreased STIM1 in the NAc and HPC and reduced the STIM2 in the HPC. Collectively, our data show that morphine could facilitate brain reward function in part by increasing glutamate-mediated transmission through activation of mGluR5 and modulation of STIM proteins. Therefore, these results highlight the therapeutic potential of mGluR5 antagonists in morphine use disorder.
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Extinción Psicológica , Morfina , Núcleo Accumbens , Piridinas , Receptor del Glutamato Metabotropico 5 , Tiazoles , Animales , Núcleo Accumbens/efectos de los fármacos , Núcleo Accumbens/metabolismo , Receptor del Glutamato Metabotropico 5/metabolismo , Receptor del Glutamato Metabotropico 5/antagonistas & inhibidores , Masculino , Extinción Psicológica/efectos de los fármacos , Extinción Psicológica/fisiología , Morfina/farmacología , Morfina/administración & dosificación , Tiazoles/farmacología , Tiazoles/administración & dosificación , Ratas , Piridinas/farmacología , Piridinas/administración & dosificación , Ratas Sprague-Dawley , Antagonistas de Aminoácidos Excitadores/farmacología , Antagonistas de Aminoácidos Excitadores/administración & dosificación , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Narcóticos/farmacología , Narcóticos/administración & dosificación , Relación Dosis-Respuesta a DrogaRESUMEN
BACKGROUND: Elucidating biological mechanisms contributing to bipolar disorder (BD) is key to improved diagnosis and treatment development. With converging evidence implicating the metabotropic glutamate receptor 5 (mGlu5) in the pathology of BD, here, we therefore test the hypothesis that recently identified deficits in mGlu5 are associated with functional brain differences during emotion processing in BD. METHODS: Positron emission tomography (PET) with [18F]FPEB was used to measure mGlu5 receptor availability and functional imaging (fMRI) was performed while participants completed an emotion processing task. Data were analyzed from 62 individuals (33 ± 12 years, 45 % female) who completed both PET and fMRI, including individuals with BD (n = 18), major depressive disorder (MDD: n = 20), and psychiatrically healthy comparisons (HC: n = 25). RESULTS: Consistent with some prior reports, the BD group displayed greater activation during fear processing relative to MDD and HC, notably in right lateralized frontal and parietal brain regions. In BD, (but not MDD or HC) lower prefrontal mGlu5 availability was associated with greater activation in bilateral pre/postcentral gyri and cuneus during fear processing. Furthermore, greater prefrontal mGlu5-related brain activity in BD was associated with difficulties in psychomotor function (r≥0.904, p≤0.005) and attention (r≥0.809, p≤0.028). LIMITATIONS: The modest sample size is the primary limitation. CONCLUSIONS: Deficits in prefrontal mGlu5 in BD were linked to increased cortical activation during fear processing, which in turn was associated with impulsivity and attentional difficulties. These data further implicate an mGlu5-related mechanism unique to BD. More generally these data suggest integrating PET and fMRI can provide novel mechanistic insights.
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Trastorno Bipolar , Trastorno Depresivo Mayor , Emociones , Imagen por Resonancia Magnética , Tomografía de Emisión de Positrones , Corteza Prefrontal , Receptor del Glutamato Metabotropico 5 , Humanos , Femenino , Trastorno Bipolar/fisiopatología , Trastorno Bipolar/diagnóstico por imagen , Trastorno Bipolar/metabolismo , Receptor del Glutamato Metabotropico 5/metabolismo , Masculino , Adulto , Corteza Prefrontal/fisiopatología , Corteza Prefrontal/diagnóstico por imagen , Corteza Prefrontal/metabolismo , Trastorno Depresivo Mayor/fisiopatología , Trastorno Depresivo Mayor/diagnóstico por imagen , Trastorno Depresivo Mayor/metabolismo , Emociones/fisiología , Persona de Mediana Edad , Adulto Joven , Miedo/fisiologíaAsunto(s)
Encefalitis , Trastornos Psicóticos , Receptor del Glutamato Metabotropico 5 , Humanos , Receptor del Glutamato Metabotropico 5/metabolismo , Trastornos Psicóticos/etiología , Encefalitis/complicaciones , Encefalitis/inmunología , Mioclonía/etiología , Ataxia , Femenino , Masculino , AdultoRESUMEN
The expression of metabotropic glutamate receptor 5 (mGluR5) is subject to developmental regulation and undergoes significant changes in neuropsychiatric disorders and diseases. Visualizing mGluR5 by fluorescence imaging is a highly desired innovative technology for biomedical applications. Nevertheless, there are substantial problems with the chemical probes that are presently accessible. In this study, we have successfully developed a two-photon fluorogenic probe, mGlu-5-TP, based on the structure of mGluR5 antagonist 6-methyl-2-(phenylethynyl)pyridine (MPEP). Due to this antagonist-based probe selectively recognizes mGluR5, high expression of mGluR5 on living SH-SY5Y human neuroblastoma cells has been detected during intracellular inflammation triggered by lipopolysaccharides (LPS). Of particular significance, the probe can be employed along with two-photon fluorescence microscopy to enable real-time visualization of the mGluR5 in Aß fiber-treated neuronal cells, thereby establishing a connection to the progression of Alzheimer's disease (AD). These results revealed that the probe can be a valuable imaging tool for studying mGluR5-related diseases in the nervous system.
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Colorantes Fluorescentes , Neuronas , Piridinas , Receptor del Glutamato Metabotropico 5 , Receptor del Glutamato Metabotropico 5/metabolismo , Receptor del Glutamato Metabotropico 5/antagonistas & inhibidores , Humanos , Colorantes Fluorescentes/química , Colorantes Fluorescentes/síntesis química , Neuronas/metabolismo , Piridinas/química , Piridinas/farmacología , Línea Celular Tumoral , Lipopolisacáridos/farmacología , Fotones , Imagen Óptica , Péptidos beta-Amiloides/metabolismo , Péptidos beta-Amiloides/análisisRESUMEN
Diets high in sucrose and fat are becoming more prevalent the world over, accompanied by a raised prevalence of cardiovascular diseases, cancers, diabetes, obesity, and metabolic syndrome. Clinical studies link unhealthy diets with the development of mental health disorders, particularly depression. Here, we investigate the effects of 12 days of sucrose consumption administered as 2 L of 25% sucrose solution daily for 12 days in Göttingen minipigs on the function of brain receptors involved in reward and motivation, regulating feeding, and pre- and post-synaptic mechanisms. Through quantitative autoradiography of cryostat sections containing limbic brain regions, we investigated the effects of sucrose restricted to a 1-h period each morning, on the specific binding of [3H]raclopride on dopamine D2/3 receptors, [3H]UCB-J at synaptic vesicle glycoprotein 2A (SV2A), [3H]MPEPγ at metabotropic glutamate receptor subtype 5 (mGluR5) and [3H]SR141716A at the cannabinoid receptor 1 (CB1). Compared to control diet animals, the sucrose group showed significantly lower [3H]UCB-J and [3H]MPEPγ binding in the prefrontal cortex. The sucrose-consuming minipigs showed higher hippocampal CB1 binding, but unaltered dopamine D2/3 binding compared to the control group. We found that the sucrose diet reduced the synaptic density marker while increasing CB1 binding in limbic brain structures, which may subserve maladaptive changes in appetite regulation and feeding. Further studies of the effects of diets and lifestyle habits on brain neuroreceptor and synaptic density markers are warranted.
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Sacarosa , Porcinos Enanos , Animales , Porcinos , Sacarosa/administración & dosificación , Masculino , Receptor del Glutamato Metabotropico 5/metabolismo , Receptores de Cannabinoides/metabolismo , Sinapsis/metabolismo , Sinapsis/efectos de los fármacos , Receptor Cannabinoide CB1/metabolismo , Receptores de Dopamina D2/metabolismo , Encéfalo/metabolismo , Encéfalo/efectos de los fármacos , Femenino , Receptores de Dopamina D3/metabolismoRESUMEN
PURPOSE OF REVIEW: This focused, narrative review mostly describes our team's investigations into the potential inflammatory mechanisms that contribute to the development of cancer-related gastrointestinal (GI) mucositis and its associated symptoms. This review summarizes details of our clinical and preclinical findings to test the role of inflammation in the development and occurrence of these cancer-related conditions. RECENT FINDINGS: GI mucositis (GIM) is a common, distressing condition reported by cancer patients. GIM is often clustered with other behaviors including fatigue, pain, anorexia, depression, and diarrhea. It is hypothesized that there is a common biologic mechanism underpinning this symptom cluster. Our multi-platform investigations revealed that GIM and its associated cluster of behaviors may be triggered by local inflammation spreading systemically causing pro-inflammatory-mediated toxicities, leading to alterations in immune, metabolic, and nervous system functions and activities. For example, behavioral toxicities related to local irradiation for non-metastatic cancer may be triggered by mGluR5 activation influencing prolonged T cell as well as NF-κB transcription factor activities. Thus, interventions targeting inflammation and associated pathways may be a reasonable strategy to alleviate GIM and its symptom cluster. SUMMARY: GIM may be a sign of a broader systemic inflammatory response triggered by cancer or its treatment. Addressing GIM and its associated symptoms primarily involves supportive care strategies focused on relieving symptoms, promoting healing, and preventing complications.
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Mucositis , Neoplasias , Humanos , Neoplasias/complicaciones , Mucositis/etiología , Inflamación/fisiopatología , Depresión/etiología , Fatiga/etiología , Fatiga/fisiopatología , Receptor del Glutamato Metabotropico 5 , Síndrome de Respuesta Inflamatoria Sistémica/fisiopatología , Anorexia/etiología , Anorexia/fisiopatología , FN-kappa B/metabolismo , Diarrea/etiología , Enfermedades Gastrointestinales/etiología , Enfermedades Gastrointestinales/fisiopatología , Dolor/etiologíaRESUMEN
BACKGROUND: Partial negative allosteric modulators (NAM) of the metabotropic glutamate 5 (mGlu5) receptor are an excellent alternative to full antagonists and NAMs because they retain therapeutic effects and have a much broader therapeutic window. Here, we investigated whether partial mGlu5 NAM, 2-(2-(3-methoxyphenyl)ethynyl)-5-methylpyridine (M-5MPEP), induced a fast and sustained antidepressant-like effect, characteristic of rapid-acting antidepressant drugs (RAADs) like ketamine, in mice. METHODS: A tail suspension test (TST) was used to investigate acute antidepressant-like effects. Sustained effects were studied 24 h after the four intraperitoneal (ip) administrations using the splash test, designed to measure apathy-like state, the sucrose preference test (SPT), reflecting anhedonia, and the TST. Western blot and ELISA techniques were used to measure brain-derived neurotrophic factor (BDNF) and selected protein levels. METHODS: A tail suspension test (TST) was used to investigate acute antidepressant-like effects. Sustained effects were studied 24 h after the four intraperitoneal (ip) administrations using the splash test, designed to measure apathy-like state, the sucrose preference test (SPT), reflecting anhedonia, and the TST. Western blot and ELISA techniques were used to measure brain-derived neurotrophic factor (BDNF) and selected protein levels. CONCLUSION: Partial mGlu5 receptor NAM, M-5MPEP, induced rapid and sustained antidepressant-like effects in the BDNF-dependent mechanism and enhanced (R)-ketamine action in mice, indicating both substances' convergent mechanisms of action and the possibility of their practical use in treating depression as RAAD.
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Antidepresivos , Factor Neurotrófico Derivado del Encéfalo , Suspensión Trasera , Ketamina , Piridinas , Receptor del Glutamato Metabotropico 5 , Animales , Masculino , Ratones , Regulación Alostérica/efectos de los fármacos , Anhedonia/efectos de los fármacos , Antidepresivos/farmacología , Conducta Animal/efectos de los fármacos , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Depresión/tratamiento farmacológico , Modelos Animales de Enfermedad , Ketamina/farmacología , Ketamina/administración & dosificación , Piridinas/farmacología , Receptor del Glutamato Metabotropico 5/metabolismo , Receptor del Glutamato Metabotropico 5/antagonistas & inhibidoresRESUMEN
This study aimed to assess whether brief recall of methamphetamine (MA) memory, when combined with ketamine (KE) treatment, may prevent stress-primed MA memory reinstatement. Combining 3-min recall and KE facilitated MA memory extinction and resistance to subsequent stress-primed reinstatement. Such combination also produced glutamate metabotropic receptor 5 (mGluR5) upregulation in animals' medial prefrontal cortex (mPFC) γ-amino-butyric acid (GABA) neuron. Accordingly, chemogenetic methods were employed to bi-directionally modulate mPFC GABA activity. Following brief recall and KE-produced MA memory extinction, intra-mPFC mDlx-Gi-coupled-human-muscarinic-receptor 4 (hM4Di)-infused mice receiving compound 21 (C21) treatment showed eminent stress-primed reinstatement, while their GABA mGluR5 expression seemed to be unaltered. Intra-mPFC mDlx-Gq-coupled-human-muscarinic-receptor 3 (hM3Dq)-infused mice undergoing C21 treatment displayed MA memory extinction and resistance to stress-provoked reinstatement. These results suggest that combining a brief recall and KE treatment and exciting mPFC GABA neuron may facilitate MA memory extinction and resistance to stress-primed recall. mPFC GABA neuronal activity plays a role in mediating brief recall/KE-produced effects on curbing the stress-provoked MA seeking.
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Extinción Psicológica , Ketamina , Recuerdo Mental , Metanfetamina , Corteza Prefrontal , Receptor del Glutamato Metabotropico 5 , Estrés Psicológico , Animales , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/metabolismo , Metanfetamina/farmacología , Ketamina/farmacología , Masculino , Ratones , Recuerdo Mental/efectos de los fármacos , Estrés Psicológico/tratamiento farmacológico , Estrés Psicológico/psicología , Receptor del Glutamato Metabotropico 5/metabolismo , Extinción Psicológica/efectos de los fármacos , Memoria/efectos de los fármacos , Ácido gamma-Aminobutírico/metabolismo , Ratones Endogámicos C57BLRESUMEN
Posttranslational modifications regulate the properties and abundance of synaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors that mediate fast excitatory synaptic transmission and synaptic plasticity in the central nervous system. During long-term depression (LTD), protein tyrosine phosphatases (PTPs) dephosphorylate tyrosine residues in the C-terminal tail of AMPA receptor GluA2 subunit, which is essential for GluA2 endocytosis and group I metabotropic glutamate receptor (mGluR)-dependent LTD. However, as a selective downstream effector of mGluRs, the mGluR-dependent PTP responsible for GluA2 tyrosine dephosphorylation remains elusive at Schaffer collateral (SC)-CA1 synapses. In the present study, we find that mGluR5 stimulation activates Src homology 2 (SH2) domain-containing phosphatase 2 (SHP2) by increasing phospho-Y542 levels in SHP2. Under steady-state conditions, SHP2 plays a protective role in stabilizing phospho-Y869 of GluA2 by directly interacting with GluA2 phosphorylated at Y869, without affecting GluA2 phospho-Y876 levels. Upon mGluR5 stimulation, SHP2 dephosphorylates GluA2 at Y869 and Y876, resulting in GluA2 endocytosis and mGluR-LTD. Our results establish SHP2 as a downstream effector of mGluR5 and indicate a dual action of SHP2 in regulating GluA2 tyrosine phosphorylation and function. Given the implications of mGluR5 and SHP2 in synaptic pathophysiology, we propose SHP2 as a promising therapeutic target for neurodevelopmental and autism spectrum disorders.
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Endocitosis , Depresión Sináptica a Largo Plazo , Proteína Tirosina Fosfatasa no Receptora Tipo 11 , Receptores AMPA , Receptores de Glutamato Metabotrópico , Receptores AMPA/metabolismo , Animales , Fosforilación , Endocitosis/fisiología , Depresión Sináptica a Largo Plazo/fisiología , Receptores de Glutamato Metabotrópico/metabolismo , Proteína Tirosina Fosfatasa no Receptora Tipo 11/metabolismo , Proteína Tirosina Fosfatasa no Receptora Tipo 11/genética , Ratas , Tirosina/metabolismo , Receptor del Glutamato Metabotropico 5/metabolismo , Sinapsis/metabolismo , Ratones , Humanos , Neuronas/metabolismoRESUMEN
Metabotropic glutamate receptors belong to a family of G protein-coupled receptors that are obligate dimers and possess a large extracellular ligand-binding domain that is linked via a cysteine-rich domain to their 7-transmembrane domain1. Upon activation, these receptors undergo a large conformational change to transmit the ligand binding signal from the extracellular ligand-binding domain to the G protein-coupling 7-transmembrane domain2. In this manuscript, we propose a model for a sequential, multistep activation mechanism of metabotropic glutamate receptor subtype 5. We present a series of structures in lipid nanodiscs, from inactive to fully active, including agonist-bound intermediate states. Further, using bulk and single-molecule fluorescence imaging, we reveal distinct receptor conformations upon allosteric modulator and G protein binding.
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Ligandos , Dominios Proteicos , Receptor del Glutamato Metabotropico 5 , Humanos , Regulación Alostérica/efectos de los fármacos , Fluorescencia , Modelos Moleculares , Unión Proteica , Receptor del Glutamato Metabotropico 5/agonistas , Receptor del Glutamato Metabotropico 5/química , Receptor del Glutamato Metabotropico 5/metabolismo , Imagen Individual de Molécula , Proteínas de Unión al GTP Heterotriméricas/metabolismoRESUMEN
ABSTRACT: Objective: This study aimed to explore the impact of heat stress (HS) on glutamate transmission-dependent expression levels of interleukin-1ß (IL-1ß) and IL-18 in BV-2 microglial cells. Methods: BV-2 microglial cells were cultured in vitro , with cells maintained at 37°C serving as the control. The HS group experienced incubation at 40°C for 1 h, followed by further culturing at 37°C for 6 or 12 h. The experimental group was preincubated with glutamate, the glutamate antagonist riluzole, or the mGluR5 agonist, 2-chloro-5-hydroxyphenylglycine (CHPG), before HS. Glutamate content in BV-2 culture supernatant was assessed using colorimetric assay. Moreover, mRNA expression levels of EAAT3 and/or mGluR5 in BV-2 cells were determined via quantitative polymerase chain reaction. Interleukins (IL-1ß and IL-18) in cell culture supernatant were measured using enzyme-linked immunosorbent assay. Western blot analysis was employed to assess protein levels of IL-1ß and IL-18 in BV-2 cells. Results: HS induced a significant release of glutamate and increased the expression levels of mGluR5 and EAAT3 in BV-2 cells. It also triggered the expression levels and release of proinflammatory factors, such as IL-1ß and IL-18, synergizing with the effects of glutamate treatment. Preincubation with both riluzole and CHPG significantly reduced HS-induced glutamate release and mitigated the increased expression levels and release of IL-1ß and IL-18 induced by HS. Conclusion: The findings confirmed that microglia could be involved in HS primarily through glutamate metabolisms, influencing the expression levels and release of IL-1ß and IL-18.
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Ácido Glutámico , Interleucina-18 , Interleucina-1beta , Microglía , Interleucina-18/metabolismo , Interleucina-1beta/metabolismo , Microglía/metabolismo , Microglía/efectos de los fármacos , Animales , Ácido Glutámico/metabolismo , Ratones , Respuesta al Choque Térmico , Línea Celular , Receptor del Glutamato Metabotropico 5/metabolismo , Riluzol/farmacologíaRESUMEN
Bergamot essential oil shows anxiolytic-relaxant effects devoid of sedative action and motor impairment typical of benzodiazepines. Considering the potential for clinical of these effects, it is important to understand the underlying mechanisms of the phytocomplex. Modulation of glutamate group I and II metabotropic receptors is involved in stress and anxiety disorders, in cognition and emotions and increases locomotor activity and wakefulness. Interestingly, early data indicate that bergamot essential oil modulates glutamatergic transmission in specific manifestations of the central nervous system. The aim of this work is to investigate if selective antagonists of metabotropic glutamate 2/3 and 5 receptors affect behavioral parameters modulated by the phytocomplex. Male Wistar rats were used to measure behavioral parameters to correlate anxiety and motor activity using elevated plus maze (EPM), open field (OF), and rotarod tasks. Bergamot essential oil increases in EPM the time spent in open/closed arms and reduces total number of entries. The essential oil also increases immobility in EPM and OF and not affect motor coordination in rotarod. Pretreatment with the metabotropic glutamate antagonists does not affect the time spent in open/close arms, however, differently affects motor behavior measured after administration of phytocomplex. Particularly, glutamate 2/3 antagonist reverts immobility and glutamate 5 antagonist potentiates this parameter induced by the phytocomplex. Our data show that modulation of both metabotropic glutamate receptors is likely involved in some of behavioral effects of bergamot essential oil.