Number Of NeuN-positive Neurons Research Articles

Shati/Nat8l Overexpression Improves Cognitive Decline by Upregulating Neuronal Trophic Factor in Alzheimer's Disease Model Mice.

Alzheimer's disease (AD) is a type of dementia characterized by the deposition of amyloid β, a causative protein of AD, in the brain. Shati/Nat8l, identified as a psychiatric disease related molecule, is a responsive enzyme of N-acetylaspartate (NAA) synthesis. In the hippocampi of AD patients and model mice, the NAA content and Shati/Nat8l expression were reported to be reduced. Having recently clarified the involvement of Shati/Nat8l in cognitive function, we examined the recovery effect of the hippocampal overexpression of Shati/Nat8l in AD model mice (5XFAD). Shati/Nat8l overexpression suppressed cognitive dysfunction without affecting the Aβ burden or number of NeuN-positive neurons. In addition, brain-derived neurotrophic factor mRNA was upregulated by Shati/Nat8l overexpression in 5XFAD mice. These results suggest that Shati/Nat8l overexpression prevents cognitive dysfunction in 5XFAD mice, indicating that Shati/Nat8l could be a therapeutic target for AD.

Ndufs4 ablation decreases synaptophysin expression in hippocampus

Altered function of mitochondrial respiratory chain in brain cells is related to many neurodegenerative diseases. NADH Dehydrogenase (Ubiquinone) Fe-S protein 4 (Ndufs4) is one of the subunits of mitochondrial complex I and its mutation in human is associated with Leigh syndrome. However, the molecular biological role of Ndufs4 in neuronal function is poorly understood. In this study, upon Ndufs4 expression confirmation in NeuN-positive neurons, and GFAP-positive astrocytes in WT mouse hippocampus, we found significant decrease of mitochondrial respiration in Ndufs4-KO mouse hippocampus. Although there was no change in the number of NeuN positive neurons in Ndufs4-KO hippocampus, the expression of synaptophysin, a presynaptic protein, was significantly decreased. To investigate the detailed mechanism, we silenced Ndufs4 in Neuro-2a cells and we observed shorter neurite lengths with decreased expression of synaptophysin. Furthermore, western blot analysis for phosphorylated extracellular regulated kinase (pERK) revealed that Ndufs4 silencing decreases the activity of ERK signalling. These results suggest that Ndufs4-modulated mitochondrial activity may be involved in neuroplasticity via regulating synaptophysin expression.

Altered White Matter and Layer VIb Neurons in Heterozygous Disc1 Mutant, a Mouse Model of Schizophrenia.

Increased white matter neuron density has been associated with neuropsychiatric disorders including schizophrenia. However, the pathogenic features of these neurons are still largely unknown. Subplate neurons, the earliest generated neurons in the developing cortex have also been associated with schizophrenia and autism. The link between these neurons and mental disorders is also not well established. Since cortical layer VIb neurons are believed to be the remnant of subplate neurons in the adult rodent brain, in this study, we aimed to examine the cytoarchitecture of neurons in cortical layer VIb and the underlying white matter in heterozygous Disc1 mutant (Het) mice, a mouse model of schizophrenia. In the white matter, the number of NeuN-positive neurons was quite low in the external capsule; however, the density of these cells was found increased (54%) in Het mice compared with wildtype (WT) littermates. The density of PV-positive neurons was unchanged in the mutants. In the cortical layer VIb, the density of CTGF-positive neurons increased (21.5%) in Het mice, whereas the number of Cplx3-positive cells reduced (16.1%) in these mutants, compared with WT mice. Layer VIb neurons can be classified by their morphological characters. The morphology of Type I pyramidal neurons was comparable between genotypes while the dendritic length and complexity of Type II multipolar neurons were significantly reduced in Het mice. White matter neurons and layer VIb neurons receive synaptic inputs and modulate the process of sensory information and sleep/arousal pattern. Aberrances of these neurons in Disc1 mutants implies altered brain functions in these mice.

Altered expression of parvalbumin immunoreactivity in rat main olfactory bulb following pilocarpine-induced status epilepticus

Epilepsy is a chronic neurological disease characterized by spontaneous recurrent seizures and caused by various factors and mechanisms. Malfunction of the olfactory bulb is frequently observed in patients with epilepsy. However, the morphological changes in the olfactory bulb during epilepsy-induced neuropathology have not been elucidated. Therefore, in the present study, we investigated the expression of parvalbumin (PV), one of the calcium-binding proteins, and morphological changes in the rat main olfactory bulb (MOB) following pilocarpine-induced status epilepticus (SE). Pilocarpine-induced SE resulted in neuronal degeneration in the external plexiform layer (EPL) and glomerular layer (GL) of the MOB. PV immunoreactivity was observed in the neuronal somas and processes in the EPL and GL of the control group. However, six hours after pilocarpine administration, PV expression was remarkably decreased in the neuronal processes compared to the somas and the average number of PV-positive interneurons was significantly decreased. Three months after pilocarpine treatment, the number of PV-positive interneurons was also significantly decreased compared to the 6 hour group in both layers. In addition, the number of NeuN-positive neurons was also significantly decreased in the EPL and GL following pilocarpine treatment. In double immunofluorescence staining for PV and MAP2, the immunoreactivity for MAP2 around the PV-positive neurons was significantly decreased three months after pilocarpine treatment. Therefore, the present findings suggest that decreases in PV-positive GABAergic interneurons and dendritic density in the MOB induced impaired calcium buffering and reciprocal synaptic transmission. Thus, these alterations may be considered key factors aggravating olfactory function in patients with epilepsy.

Downregulation of spinal angiotensin converting enzyme 2 is involved in neuropathic pain associated with type 2 diabetes mellitus in mice

We have previously reported that the spinal angiotensin (Ang) system is involved in the modulation of streptozotocin (STZ)-induced diabetic neuropathic pain in mice. An important drawback of this model however is the fact that the neuropathic pain is independent of hyperglycemia and produced by the direct stimulation of peripheral nerves. Here, using the leptin deficient ob/ob mouse as a type 2 diabetic model, we examined whether the spinal Ang system was involved in naturally occuring diabetic neuropathic pain. Blood glucose levels were increased in ob/ob mice at 5–15 weeks of age. Following the hyperglycemia, persistent tactile and thermal hyperalgesia were observed at 11–14 and 9–15 weeks of age, respectively, which was ameliorated by insulin treatment. At 12 weeks of age, the expression of Ang-converting enzyme (ACE) 2 in the spinal plasma membrane fraction was decreased in ob/ob mice. Spinal ACE2 was expressed in neurons and microglia but the number of NeuN-positive neurons was decreased in ob/ob mice. In addition, the intrathecal administration of Ang (1-7) and SB203580, a p38 MAPK inhibitor, attenuated hyperalgesia in ob/ob mice. The phosphorylation of spinal p38 MAPK was also attenuated by Ang (1-7) in ob/ob mice. These inhibitory effects of Ang (1-7) were prevented by A779, a Mas receptor antagonist. In conclusion, we revealed that the Ang (1-7)-generating system is downregulated in ob/ob mice and is accompanied by a loss of ACE2-positive neurons. Furthermore, Ang (1-7) decreased the diabetic neuropathic pain through inhibition of p38 MAPK phosphorylation via spinal Mas receptors.

Cranial irradiation induces axon initial segment dysfunction and neuronal injury in the prefrontal cortex and impairs hippocampal coupling.

BackgroundRadiation therapy for brain tumors commonly induces cognitive dysfunction. The prefrontal cortex (PFC) is crucial for a diverse array of cognitive processes, however, its role in radiation-induced cognitive dysfunction is unknown. We previously found that cranial irradiation impairs neuroplasticity along the hippocampal–PFC pathway. Herein, we hypothesized that brain irradiation directly affects the firing properties of PFC neurons, contributing to deficits in neuronal functions.MethodsIn vivo recordings were used to monitor the firing activities of PFC neurons and local field potentials in both PFC and hippocampal CA1/subicular regions after cranial irradiation of Sprague Dawley rats. We further assessed the impacts of irradiation on axon initial segments (AISs) with immunofluorescence assays of PFC slices.ResultsWe found that PFC neurons exhibited increased excitation 3 days after radiation and the timing of increased excitation coincided with elongation of the AIS. At 2 weeks, excitation levels returned to nearly normal levels however the population of spontaneously firing neurons decreased. While the number of NeuN-positive neurons in the PFC was not different, persistent neuronal injury, manifested as ATF-3 staining, was present at 2 weeks. Radiation also disrupted communication along the hippocampal–PFC pathway, with elongation of the phase lag between regions. Analysis of paired-pulse ratios suggested that this was secondary to presynaptic dysfunction.ConclusionsCranial irradiation excited and injured surviving PFC neurons and was associated with a partial block of PFC’s functional coupling to the hippocampus. These deficits in the PFC may contribute to radiation-induced cognitive dysfunction.

Improvement in mitochondrial function underlies the effects of ANNAO tablets on attenuating cerebral ischemia-reperfusion injuries.

ANNAO tablets derive from Chinese classical prescriptions of Angong Niuhuang Pills with modified compositions, which have been singly or combined used for stoke associated neurological disorders. However the underlying mechanism is not yet well-defined, the present study investigated its anti-ischemic effects in rat middle cerebral artery occlusion (MCAO) model and focused on mitochondrial quality control. Rats were subjected to 2 h of brain ischemia followed by 1 day or up to 7 days of reperfusion. Vehicle, ANNAO tablets or Edaravone were given at 1h after the start of reperfusion for 1 day or successive 7 days in MCAO rats. For the behavior assessment, Longa test and modified Neurological Severity Scores (m NSS) test were performed. Following the behavioral assessment, we assessed the protein expressions related to mitochondrial function. Moreover, we also assessed the neuroprotective effects of ANNAO tablets by immunohistochemical analysis. Compared with sham rats, ANNAO tablets improved the behavioral performance and decreased the infarction volume in the MCAO rats. Western blotting results showed that ANNAO tablets altered the expression level of multiple proteins related to mitochondrial function, elevated the ratio of Bcl-2/Bax and inhibited the apoptosis. Additionally, ANNAO tablets increased the number of NeuN positive neurons. The obtained data demonstrated that ANNAO tablets exhibited an obvious anti-cerebral ischemia-reperfusion effect, which could be attributed to the improvement of mitochondrial quality control.

Cathepsin K Knockout Exacerbates Haemorrhagic Transformation Induced by Recombinant Tissue Plasminogen Activator After Focal Cerebral Ischaemia in Mice.

Severe haemorrhagic transformation (HT), a common complication of recombinant tissue plasminogen activator (rtPA) treatment, predicts poor clinical outcomes in acute ischaemic stroke. The search for agents to mitigate this effect includes investigating biomolecules involved in neovascularization. This study examines the role of Cathepsin K (Ctsk) in rtPA-induced HT after focal cerebral ischaemia in mice. After knockout of Ctsk, the gene encoding Ctsk, the outcomes of Ctsk+/+ and Ctsk-/- mice were compared 24h after rtPA-treated cerebral ischaemia with respect to HT severity, neurological deficits, brain oedema, infarct volume, number of apoptotic neurons and activated microglia/macrophage, blood-brain barrier integrity, vascular endothelial growth factor (VEGF) expression and Akt-mTOR pathway activation. We observed that haemoglobin levels, brain oedema and infarct volume were significantly greater and resulted in more severe neurological deficits in Ctsk-/- than in Ctsk+/+ mice. Consistent with our hypothesis, the number of NeuN-positive neurons was lower and the number of TUNEL-positive apoptotic neurons and activated microglia/macrophage was higher in Ctsk-/- than in Ctsk+/+ mice. Ctsk knockout mice exhibited more severe blood-brain barrier (BBB) disruption, with microvascular endothelial cells exhibiting greater VEGF expression and lower ratios of phospo-Akt/Akt and phospo-mTOR/mTOR than in Ctsk+/+ mice. This study is the first to provide molecular insights into Ctsk-regulated HT after cerebral ischaemia, suggesting that Ctsk deficiency may disrupt the BBB via Akt/mTOR/VEGF signalling, resulting in neurological deficits and neuron apoptosis. Ctsk administration has the potential as a novel modality for improving the safety of rtPA treatment following stroke.

Hyaluronic acid-based hydrogel enhances neuronal survival in spinal cord slice cultures from postnatal mice

Numerous biomaterials based on extracellular matrix-components have been developed. It was our aim to investigate whether a hyaluronic acid-based hydrogel improves neuronal survival and tissue preservation in organotypic spinal cord slice cultures. Organotypic spinal cord slice cultures were cultured for 4 days invitro (div), either on hyaluronic acid-based hydrogel (hyaluronic acid-gel group), collagen gel (collagen group), directly on polyethylene terephthalate membrane inserts (control group), or in the presence of soluble hyaluronic acid (soluble hyaluronic acid group). Cultures were immunohistochemically stained against neuronal antigen NeuN and analyzed by confocal laser scanning microscopy. Histochemistry for choline acetyltransferance, glial fibrillary acidic protein, and Griffonia simplicifolia isolectin B4 followed by quantitative analysis was performed to assess motorneurons and different glial populations. Confocal microscopic analysis showed a 4-fold increase in the number of NeuN-positive neurons in the hyaluronic acid-gel group compared to both collagen (p < 0.001) and control groups (p < 0.001). Compared to controls, organotypic spinal cord slice cultures maintained on hyaluronic acid-based hydrogel showed 5.9-fold increased survival of choline acetyltransferance-positive motorneurons (p = 0.008), 2-fold more numerous resting microglial cells in the white matter (p = 0.031), and a 61.4% reduction in the number of activated microglial cells within the grey matter (p = 0.05). Hyaluronic acid-based hydrogel had a shear modulus (G') of ≈1200 Pascals (Pa), which was considerably higher than the ≈25 Pa measured for collagen gel. Soluble hyaluronic acid failed to improve tissue preservation. In conclusion, hyaluronic acid-based hydrogel improves neuronal and - most notably - motorneuron survival in organotypic spinal cord slice cultures and microglial activation is limited. The positive effects of hyaluronic acid-based hydrogel may at least in part be due to its mechanical properties.

Effects of Aβ25–35 on neurogenesis in the adult mouse subventricular zone and dentate gyrus

It has been demonstrated that neuorgenesis driven by neural precursor cells persists well into the adult period. This study was to observe the effects of Amyloid-beta (25–35) peptide (Aβ25–35) on neurogenesis in the subventricular zone and dentate gyrus of adult mouse brain. Aggregated Aβ25–35(1 mg/ml, 3 μl) was injected into the lateral ventricle of adult mouse. Animals were transcardially perfused with 4% paraformaldehyde in PBS, respectively at 5, 10, 20, 30 days after the Aβ25–35 injection. All the animals were injected with BrdU (50 mg/kg, i. p) to label the neural precursor cells 24 h before the each perfusion. NeuN immunofluorescence and BrdU immunohistology were performed. It was found that Aβ25–35 could injure the mature neurons and decrease the number of NeuN positive neurons. It also showed that Aβ25–35 inhibited neurogenesis and significantly decreased the number of BrdU positive cells in the dentate gyrus of hippocampus, but it had no obvious effects on neurogenesis in the subventricular zone. The present results indicated that Aβ25–35 could impair neurogenesis in the hippocampus of adult mouse brain.

An immunohistochemical study of neuronal and glial cell reactions in retinae of rats with experimental glaucoma.

Glaucoma is a common disease seen in the eye clinic, but its associated pathological processes, especially the role of glial cells in glaucomatous retinae, are still under debate. The aim of the present work was to study the responses of astrocytes, Müller cells and microglia in retinae of rats with experimental glaucoma. Glaucoma was induced in adult male Wistar rats by cauterizing limbal-derived veins and the changes in glial fibrillary acidic protein (GFAP), OX42, OX18, OX6 and EDI expression were studied by immunohistochemical staining. Neuronal cell viability was studied by immunostaining with the neuronal nuclei (NeuN) antibody. In the experimental glaucomatous eyes, a significant drop in the number of NeuN-positive neurons was observed from 7 days postoperation and beyond in both the ganglion cell layer and inner nuclear layer. The expression of GFAP and OX42 was increased during the first 2 months after operation and reduced in rats at 3 and 4 months. OX6 and OX18 immunoreactivity was induced in some microglia of both glaucomatous and sham-operated control eyes. Possible mechanisms of the reaction of astrocytes, Müller cells and microglia in neuronal degeneration following glaucoma are discussed.