RESUMEN
Olfactory dysfunction is increasingly recognized as an early indicator of Alzheimer's disease (AD). Aberrations in GABAergic function and the excitatory/inhibitory (E/I) balance within the olfactory bulb (OB) have been implicated in olfactory impairment during the initial stages of AD. While the neuregulin 1 (NRG1)/ErbB4 signaling pathway is known to regulate GABAergic transmission in the brain and is associated with various neuropsychiatric disorders, its specific role in early AD-related olfactory impairment remains incompletely understood. This study demonstrated that olfactory dysfunction preceded cognitive decline in young adult APP/PS1 mice and was characterized by reduced levels of NRG1 and ErbB4 in the OB. Further investigation revealed that deletion of ErbB4 in parvalbumin interneurons reduced GABAergic transmission and increased hyperexcitability in mitral and tufted cells (M/Ts) in the OB, thereby accelerating olfactory dysfunction in young adult APP/PS1 mice. Additionally, ErbB4 deficiency was associated with increased accumulation of Aß and BACE1-mediated cleavage of APP, along with enhanced CDK5 signaling in the OB. NRG1 infusion into the OB was found to enhance GABAergic transmission in M/Ts and alleviate olfactory dysfunction in young adult APP/PS1 mice. These findings underscore the critical role of NRG1/ErbB4 signaling in regulating GABAergic transmission and E/I balance within the OB, contributing to olfactory impairment in young adult APP/PS1 mice, and provide novel insights for early intervention strategies in AD. This work has shown that ErbB4 deficiency increased the burden of Aß, impaired GABAergic transmission, and disrupted the E/I balance of mitral and tufted cells (M/Ts) in the OB, ultimately resulting in olfactory dysfunction in young adult APP/PS1 mice. NRG1 could enhance GABAergic transmission, rescue E/I imbalance in M/Ts, and alleviate olfactory dysfunction in young adult APP/PS1 mice. OB: olfactory bulb, E/I: excitation/inhibition, Pr: probability of release, PV: parvalbumin interneurons, Aß: ß-amyloid, GABA: gamma-aminobutyric acid.
RESUMEN
BACKGROUND: Parvalbumin interneuron (PVI) activity synchronizes the medial prefrontal cortex circuit for normal cognitive function, and its impairment may contribute to schizophrenia (SZ). NMDA receptors in PVIs participate in these activities and form the basis for the NMDA receptor hypofunction hypothesis of SZ. However, the role of the GluN2D subunit, which is enriched in PVIs, in regulating molecular networks relevant to SZ is unknown. METHODS: Using electrophysiology and a mouse model with conditional deletion of GluN2D from PVIs (PV-GluN2D knockout [KO]), we examined the cell excitability and neurotransmission in the medial prefrontal cortex. Histochemical, RNA sequencing analysis and immunoblotting were conducted to understand molecular mechanisms. Behavioral analysis was conducted to test cognitive function. RESULTS: PVIs in the medial prefrontal cortex were found to express putative GluN1/2B/2D receptors. In a PV-GluN2D KO model, PVIs were hypoexcitable, whereas pyramidal neurons were hyperexcitable. Excitatory neurotransmission was higher in both cell types in PV-GluN2D KO, whereas inhibitory neurotransmission showed contrasting changes, which could be explained by reduced somatostatin interneuron projections and increased PVI projections. Genes associated with GABA (gamma-aminobutyric acid) synthesis, vesicular release, and uptake as well as those involved in formation of inhibitory synapses, specifically GluD1-Cbln4 and Nlgn2, and regulation of dopamine terminals were downregulated in PV-GluN2D KO. SZ susceptibility genes including Disc1, Nrg1, and ErbB4 and their downstream targets were also downregulated. Behaviorally, PV-GluN2D KO mice showed hyperactivity and anxiety behavior and deficits in short-term memory and cognitive flexibility. CONCLUSIONS: These findings demonstrate that GluN2D in PVIs serves as a point of convergence of pathways involved in the regulation of GABAergic synapses relevant to SZ.
Asunto(s)
Parvalbúminas , Esquizofrenia , Animales , Ratones , Interneuronas/fisiología , Ratones Noqueados , Proteínas del Tejido Nervioso/metabolismo , Parvalbúminas/metabolismo , Corteza Prefrontal/metabolismo , Receptor ErbB-4/metabolismo , Esquizofrenia/genética , Esquizofrenia/metabolismoRESUMEN
Alzheimer's disease (AD) is a neurodegenerative disorder characterized by a rapid accumulation of amyloid ß (Aß) protein in the hippocampus, which impairs synaptic structures and neuronal signal transmission, induces neuronal loss, and diminishes memory and cognitive functions. The present study investigated the impact of neuregulin 1 (NRG1)-ErbB4 signaling on the impairment of neural networks underlying hippocampal long-term potentiation (LTP) in 5xFAD mice, a model of AD with greater symptom severity than that of TG2576 mice. Specifically, we observed parvalbumin (PV)-containing hippocampal interneurons, the effect of NRG1 on hippocampal LTP, and the functioning of learning and memory. We found a significant decrease in the number of PV interneurons in 11-month-old 5xFAD mice. Moreover, synaptic transmission in the 5xFAD mice decreased at 6 months of age. The 11-month-old transgenic AD mice showed fewer inhibitory PV neurons and impaired NRG1-ErbB4 signaling than did wild-type mice, indicating that the former exhibit the impairment of neuronal networks underlying LTP in the hippocampal Schaffer-collateral pathway. In conclusion, this study confirmed the impaired LTP in 5xFAD mice and its association with aberrant NRG1-ErbB signaling in the neuronal network.
Asunto(s)
Envejecimiento/patología , Enfermedad de Alzheimer/patología , Región CA1 Hipocampal/patología , Potenciación a Largo Plazo/fisiología , Red Nerviosa/patología , Neuronas/patología , Envejecimiento/metabolismo , Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/metabolismo , Animales , Región CA1 Hipocampal/metabolismo , Cognición/fisiología , Modelos Animales de Enfermedad , Femenino , Interneuronas/metabolismo , Interneuronas/patología , Aprendizaje/fisiología , Masculino , Memoria/fisiología , Ratones , Ratones Transgénicos , Red Nerviosa/metabolismo , Neurregulina-1/metabolismo , Neuronas/metabolismo , Parvalbúminas/metabolismo , Receptor ErbB-4/metabolismo , Transducción de Señal/fisiología , Transmisión Sináptica/fisiologíaRESUMEN
Neuregulin 1 (NRG1)-induced activation of ErbB4 in parvalbumin (PV) inhibitory interneurons is reported to serve as a critical endogenous negative-feedback mechanism to repress brain epileptogenesis. Here, we investigated the seizure susceptibility and the role of NRG1-ErbB4 signaling in PV interneurons in the suppression of epileptic seizures for rats subject to early life hypoxia. Neonatal postnatal day 5 (P5) rats were exposed to intermittent hypoxia (IH) or control (CON) room air for 10 days. In the prefrontal cortex (PFC) of P54 rats, we determined the impact of neonatal IH exposures on the expression of PV, NRG1, ErbB4, and phosphorylated ErbB4 (p-ErbB4) during the seizure induction. Seizure susceptibility tests with the common convulsant agent pentylenetetrazole (PEN) at P54 revealed that rats subject to neonatal hypoxia exposure developed faster and more serious epileptic seizures. Neonatal IH exposures (1) decreased the number of PV cells in the PFC of P54 rats; (2) interrupted the expression of NRG1 gene; and (3) altered the activity of NRG1 on PV interneurons in the PFC after the seizure induction. Intracerebroventricular delivery of exogenous NRG1 before seizure induction by PEN significantly reduced the seizure susceptibility for neonatal IH-exposed rats. The ErbB4 inhibitor AG1478 inhibited the exogenous NRG1's effects on seizure susceptibility. Environmental enrichment (EE) rescued the abovementioned pathophysiological alterations and significantly attenuated the epileptic seizures after the seizure induction for neonatal IH-exposed rats. Our study indicated early life hypoxia exposure might increase the seizure susceptibility for rats and contribute to pathophysiological dysfunction of NRG1-ErbB4 signaling in PV interneurons in the suppression of epileptic seizures. EE might attenuate the increased seizure susceptibility for neonatal IH-exposed rats through rescuing pathophysiological alterations of NRG1-ErbB4 signaling in PV interneurons.
Asunto(s)
Encéfalo/fisiopatología , Hipoxia Encefálica/complicaciones , Hipoxia Encefálica/fisiopatología , Interneuronas/metabolismo , Neurregulina-1/metabolismo , Parvalbúminas/metabolismo , Receptor ErbB-4/metabolismo , Convulsiones/etiología , Animales , Animales Recién Nacidos , Encéfalo/patología , Recuento de Células , Susceptibilidad a Enfermedades , Femenino , Regulación de la Expresión Génica , Hipoxia Encefálica/genética , Inyecciones Intraventriculares , Neurregulina-1/genética , Pentilenotetrazol , Corteza Prefrontal/metabolismo , Corteza Prefrontal/patología , ARN Mensajero/genética , ARN Mensajero/metabolismo , Ratas Sprague-Dawley , Convulsiones/genética , Transducción de Señal , Regulación hacia ArribaRESUMEN
Traumatic brain injury (TBI) is a serious health problem in the world. However, little is known about the pathogenesis and molecular mechanisms of TBI. Here, we show that TBI activates neuregulin 1 (NRG1)-ErbB4 signaling, with an increased expression of NRG1 and ErbB4 in the traumatic region. Specifically knocking out ErbB4 in parvalbumin-positive (PV+) interneurons exacerbates motor function deficits in mice after TBI. Consistently, PV-ErbB4-/- mice showed larger necrotic area and more edema when compared with PV-ErbB4+/+ mice. Replenishment of NRG1 through intranasal application of the recombinant protein in PV-ErbB4+/+ mice enhanced neurological function. Moreover, using an in vitro neuronal culture system, we found that NRG1-ErbB4 signaling protects neurons from glutamate-induced death, and such protective effects could be diminished by GABA receptor antagonist. These results indicate that NRG-ErbB4 signaling protects cortical neurons from TBI-induced damage, and such effect is probably mediated by promoting GABA activity. Taken together, these findings unveil a previously unappreciated role for NRG1-ErB4 signaling in preventing neuronal cell death during functional recovery after TBI.
Asunto(s)
Lesiones Traumáticas del Encéfalo , Ácido Glutámico/metabolismo , Neurregulina-1/metabolismo , Neuronas/metabolismo , Neuroprotección/fisiología , Lóbulo Parietal , Receptor ErbB-4/metabolismo , Recuperación de la Función/fisiología , Transducción de Señal/fisiología , Ácido gamma-Aminobutírico/metabolismo , Animales , Conducta Animal/fisiología , Lesiones Traumáticas del Encéfalo/metabolismo , Lesiones Traumáticas del Encéfalo/patología , Lesiones Traumáticas del Encéfalo/fisiopatología , Muerte Celular/fisiología , Células Cultivadas , Modelos Animales de Enfermedad , Antagonistas del GABA/farmacología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Neurregulina-1/farmacología , Lóbulo Parietal/lesiones , Lóbulo Parietal/metabolismo , Lóbulo Parietal/patología , Lóbulo Parietal/fisiopatología , Receptor ErbB-4/deficienciaRESUMEN
Objective: To study the treating mechanism of α-humulene on the schizophrenic mice. Methods: The schizophrenic models were established by dizocilpine maleate (MK801), then different concentrations of α-humulene were used to treat the mice by intragastric administration. Open-field experiment and PPI test were carried out to evaluate the spontaneous activity and sensorimotor gating function of mice. Moreover, the frontal cortex MDA, NO levels and hippocampal NRG1, ErbB4 protein expression was detected. Results: The spontaneous activity, sensorimotor gating function, MDA, NO, NRG1 and ErbB4 levels were significantly changed in model mice when compared with normal mice (P < 0.01). Compared with model group, different concentrations of α-humulene notably inhibited spontaneous activity, improved PPI value, increased NO and MDA content, down-regulated ErbB4 and NRG1 protein expression (P < 0.05, P < 0.01). Conclusion: The schizophrenia abnormal behavior of mice was improved by α-humulene via down-regulating NRG1/ErbB4 signaling pathway, so as to achieve the purpose of treating schizophrenia.