Hippocampal Neuronal Loss Research Articles

MicroRNA-410 inhibition of the TIMP2-dependent MAPK pathway confers neuroprotection against oxidative stress-induced apoptosis after ischemic stroke in mice

Ischemic stroke (IS) is an acute cerebral event characterized by a high incidence rate, high disability rate as well as a high mortality. More recently, accumulative literature has provided evidence highlighting the role played by microRNAs (miRs) in the development of neurons. Hence, the aim of the present study was to investigate the neuroprotective role of miR-410 in IS. Microarray-based gene expression profiling of AMI was conducted in order to identify differentially expressed genes (DEGs) and the corresponding miRs regulating these genes. IS models were established to assess neurology on a scoring basis. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activity and malondialdehyde (MDA) were all subsequently assessed. The functional role of miR-410 in IS was determined based on ectopic expression, knockdown and reporter assay experiments in hippocampal neurons. The expressions of microRNA-410, TIMP2, ERK, p38MAPK, JNK were all examined accordingly. The survival rate was assessed by MTT assay, and cell cycle and apoptosis by flow cytometry. After the loss of hippocampal neurons, infarct size as well as oxidative stress injury had been detected, microarray technology revealed that TIMP2 was differentially expressed in IS and that miR-410 regulated TIMP2. Initial observations revealed elevated levels of TIMP2 expression and MDA activity, in addition to evidence obtained indicated that the MAPK pathway had been activated along with decreased SOD, GSH-Px activity and miR-410 expression in IS mice. Ectopic expression of miR-410 was observed to inactivate the MAPK pathway, TIMP2 expression and hippocampal neuron apoptosis, while elevated hippocampal neuron survival rates and cell cycle entry were detected. Furthermore, TIMP2 as a direct target gene of miR-410, was determined to be negatively regulated by miR-410, while the MAPK pathway was found to be inhibited following TIMP2 knockdown. Our results revealed that the overexpression of miR-410 could ameliorate hippocampal neuron loss, reduce infarct size and oxidative stress injury in IS mice. Taken together, the key evidence of the current study elucidated the distinct nature of the inhibitory effect on IS as a result of overexpressed miR-410 whereby the conferral of neuroprotection was observed in oxidative stress-induced apoptosis post IS through the TIMP2-dependent repression of the MAPK pathway in mice.

RTMS ameliorated depressive-like behaviors by restoring HPA axis balance and prohibiting hippocampal neuron apoptosis in a rat model of depression

Repetitive transcranial magnetic stimulation (rTMS) has been widely used to treat depression. The mechanistic basis for the effects of rTMS is not well understood, although previous studies have suggested that it involves the regulation of hypothalamic-pituitary-adrenocortical (HPA) axis and protection of hippocampal neurons. We investigated this in the present study using a chronic unpredictable mild stress (CUMS) paradigm in Sprague-Dawley rats. The rats were subjected to rTMS for 15 consecutive days, and body weight, sucrose consumption, and locomotor activity were evaluated. B cell lymphoma-2-associated X protein (Bax) expression was assessed by immunohistochemistry; cell morphology was examined by Nissl staining; and adrenocorticotropic hormone (ACTH) and cortisol (CORT) levels in the hippocampus were measured by enzyme-linked immunosorbent assay. CUMS decreased body weight and sucrose consumption in rats along with horizontal/vertical distance traveled in the open field test. Rats subjected to CUMS also showed increased levels of Bax as well as ACTH and CORT; the hippocampal neurons in these animals had abnormal morphology and were reduced in number. rTMS reversed these changes and improved depression-like behaviors. Thus, rTMS abrogates the loss of hippocampal neurons and restores the balance of the HPA axis in the treatment of depression.

The effects of safranal, a constitute of saffron, and metformin on spatial learning and memory impairments in type-1 diabetic rats: behavioral and hippocampal histopathological and biochemical evaluations

Safranal is one of saffron constituents and has antioxidant and neuroprotective properties. Metformin is used as an anti-diabetic drug. This study was planned to investigate the separate and combined treatment effects of safranal and metformin on diabetes-induced learning and memory impairments by behavioral and hippocampal histopathological and biochemical evaluations. Diabetes was induced by intraperitoneal injection of streptozotocin (STZ), treatments with safranal (0.025, 0.1 and 0.4 mg/kg), metformin (50 and 200 mg/kg), and a combination of low doses of this chemicals were initiated after confirmation of diabetes and continued for 37 days. Blood glucose concentration was measured before and on days 15, 25 and 35 after injection of streptozotocin. Learning and memory tested using Morris Water Maze (MWM) on days 40–45 and on day 45 hippocampal specimens were collected for determination of malodialdehyde (MDA), tumor necrosis factor-alpha (TNF-α) and Caspase-3 levels and superoxide dismutase (SOD) activity. The hippocampus was also designed for light microscopy evaluation. Hyperglycemia, spatial learning and memory impairments, hippocampal neuron loss, increase of hippocampal MDA, TNF-α and caspase-3 levels and decrease of SOD activity were observed in diabetic rats. Safranal (0.1 and 0.4 mg/kg), metformin (200 mg/kg) and safranal (0.025 mg/kg) with metformin (50 mg/kg) improved the above-mentioned behavioral, histopathological and biochemical changes. Safranal and metformin and their combination improved learning and memory impairments in STZ-induced diabetic rats. Antioxidant, anti-inflammatory and antiapoptotic mechanisms might be involved. It is recommended that safranal be considered for diabetes management.

Glutathione peroxidase-1 overexpressing transgenic mice are protected from neurotoxicity induced by microcystin-leucine-arginine.

Although it has been well-recognized that microcystin-leucine-arginine (MCLR), the most common form of microcystins, induces neurotoxicity, little is currently known about the underlying mechanism for this neurotoxicity. Here, we found that MCLR (10 ng/μL/mouse, i.c.v.) induces significant neuronal loss in the hippocampus of mice. MCLR-induced neurotoxicity was accompanied by oxidative stress, as shown by a significant increase in the level of 4-hydroxynonenal, protein carbonyl, and reactive oxygen species (ROS). Superoxide dismutase-1 (SOD-1) activity was significantly increased, but glutathione peroxidase (GPx) level was significantly decreased following MCLR insult. In addition, MCLR significantly inhibited GSH/GSSG ratio, and significantly induced NFκB DNA binding activity. Because reduced activity of GPx appeared to be critical for the imbalance between activities of SODs and GPx, we utilized GPx-1 overexpressing transgenic mice to ascertain the role of GPx-1 in this neurotoxicity. Genetic overexpression of GPx-1 or NFκB inhibitor pyrrolidine dithiocarbamate (PDTC) significantly attenuated MCLR-induced hippocampal neuronal loss in mice. However, PDTC did not exert any additive effect on neuroprotection mediated by GPx-1 overexpression, indicating that NFκB is a neurotoxic target of MCLR. Combined, these results suggest that MCLR-induced neurotoxicity requires oxidative stress associated with failure in compensatory induction of GPx, possibly through activation of the transcription factor NFκB.

Effect of LGI1 antibody-positive IgG on hippocampal neuron survival: a preliminary study.

Anti-leucine-rich glioma inactivated 1 (anti-LGI1) encephalitis is one of the most frequently encountered forms of autoimmune encephalitis. Many patients with anti-LGI1 encephalitis develop permanent hippocampal neuron loss and chronic neuropsychiatric symptoms, suggesting that LGI antibodies (Ab) might have a neurotoxic action. To investigate this hypothesis, purified serum IgG of three patients with anti-LGI1 encephalitis and six healthy controls were incubated with cultured primary hippocampal neurons obtained from newborn mice. Nontreated cells were used as controls. The viability of IgG-treated neurons was evaluated by propidium iodide staining. Apoptotic mechanisms were assessed by JC-1 assay and mRNA expression level measurement of apoptosis-related genes using real-time PCR. The effect of IgG treatment on calcium influx was analyzed by fluo-4 calcium imaging. LGI1-Ab+ IgG increased the number of propidium iodide positive neurons, reduced mitochondrial membrane potentials, upregulated caspase-3 and Bax mRNA expression levels and downregulated Bcl-2 mRNA expression levels of neurons. LGI1-Ab+ IgG-treated neurons showed lower calcium staining than healthy controls IgG-treated and non-IgG-treated neurons. Our results indicate a neurotoxic role of LGI1-Ab. This neurotoxicity is likely mediated through induction of apoptosis and reduction of calcium currents.

Anti-TNF-α restricts dengue virus-induced neuropathy.

Proinflammatory TNF-α facilitates dengue virus (DENV) infection in endovascular dysfunction and neurotoxicity. The introduction of TNF-α blocking therapy with Abs is performed to test its therapeutic effect in this study. In DENV-infected mice, TNF-α production in the brain accompanied the progression of neurotoxicity and encephalitis. DENV infection caused the loss of hippocampal neurons with TNF-α expression around damaged regions, and immunostaining showed the induction of apoptosis in hippocampal neurons. TNF-α was expressed in active microglia and astrocytes in DENV-infected mice. TNF-α facilitated DENV-induced neurotoxicity in vitro in murine Neuro-2a cells. Using a currently established encephalitic mouse model in which DENV infection causes progressive hunchback posture, limbic seizures, limbic weakness, paralysis, and lethality 7 days postinfection, we showed that TNF-α transgenic mice represented the progressive disease development and administration of neutralizing TNF-α Ab reduced dengue encephalitis and mortality. These results demonstrate an immunopathogenesis of TNF-α for mediating DENV-induced encephalitis-associated neurotoxicity and that targeting TNF-α can be used as a strategy against dengue encephalitis.

Association of Induced Hyperhomocysteinemia with Alzheimer's Disease-Like Neurodegeneration in Rat Cortical Neurons After Global Ischemia-Reperfusion Injury.

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disorder that results in massive hippocampal and neocortical neuronal loss leading to dementia and eventual death. The exact cause of Alzheimer's disease is not fully explored, although a number of risk factors have been recognized, including high plasma concentration of homocysteine (Hcy). Hyperhomocysteinemia (hHcy) is considered a strong, independent risk factor for stroke and dementia. However, the molecular background underlying these mechanisms linked with hHcy and ischemic stroke is not fully understood. Paper describes rat model of global forebrain ischemia combined with the experimentally induced hHcy. Global ischemia-reperfusion injury (IRI) was developed by 4-vessels occlusion lasting for 15min followed by reperfusion period of 72h. hHcy was induced by subcutaneous injection of 0.45µmol/g of Hcy in duration of 14 days. The results showed remarkable neural cell death induced by hHcy in the brain cortex and neurodegeneration is further aggravated by global IRI. We demonstrated degeneration of cortical neurons, alterations in number and morphology of tissue astrocytes and dysregulation of oxidative balance with increased membrane protein oxidation. Complementary to, an immunohistochemical analysis of tau protein and β-amyloid peptide showed that combination of hHcy with the IRI might lead to the progression of AD-like pathological features. Conclusively, these findings suggest that combination of risk factor hHcy with IRI aggravates neurodegeneration processes and leads to development of AD-like pathology in cerebral cortex.

A role for astrocyte-derived amyloid β peptides in the degeneration of neurons in an animal model of temporal lobe epilepsy.

Kainic acid, an analogue of the excitatory neurotransmitter glutamate, can trigger seizures and neurotoxicity in the hippocampus and other limbic structures in a manner that mirrors the neuropathology of human temporal lobe epilepsy (TLE). However, the underlying mechanisms associated with the neurotoxicity remain unclear. Since amyloid-β (Aβ) peptides, which are critical in the development of Alzheimer's disease, can mediate toxicity by activating glutamatergic NMDA receptors, it is likely that the enhanced glutamatergic transmission that renders hippocampal neurons vulnerable to kainic acid treatment may involve Aβ peptides. Thus, we seek to establish what role Aβ plays in kainic acid-induced toxicity using in vivo and in vitro paradigms. Our results show that systemic injection of kainic acid to adult rats triggers seizures, gliosis and loss of hippocampal neurons, along with increased levels/processing of amyloid precursor protein (APP), resulting in the enhanced production of Aβ-related peptides. The changes in APP levels/processing were evident primarily in activated astrocytes, implying a role for astrocytic Aβ in kainic acid-induced toxicity. Accordingly, we showed that treating rat primary cultured astrocytes with kainic acid can lead to increased Aβ production/secretion without any compromise in cell viability. Additionally, we revealed that kainic acid reduces neuronal viability more in neuronal/astrocyte co-cultures than in pure neuronal culture, and this is attenuated by precluding Aβ production. Collectively, these results indicate that increased production/secretion of Aβ-related peptides from activated astrocytes can contribute to neurotoxicity in kainic acid-treated rats. Since kainic acid administration can lead to neuropathological changes resembling TLE, it is likely that APP/Aβ peptides derived from astrocytes may have a role in TLE pathogenesis.

AMPA Receptor Antagonist Perampanel Ameliorates Post-Stroke Functional and Cognitive Impairments

Perampanel (PER), a noncompetitive α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor antagonist, clinically used for seizure control, has been reported to exert neuroprotective effects in experimental models of neurodegenerative diseases. However, few studies have investigated the therapeutic effects of PER in brain injury including stroke. Our aim was to investigate the neuroprotective potential of PER using a rat transient middle cerebral artery occlusion (MCAO) model. Sprague–Dawley rats underwent 90-min MCAO followed by intraperitoneal PER administration at a dose of 1.5 mg/kg. Infarct volumes, neurological deficits, and immunological analyses were performed at 7 days after MCAO. PER significantly reduced infarct volumes (p < 0.05) and improved motor function (p < 0.05) compared with vehicle. Immunological analysis showed that PER significantly inhibited microglial activation, pro-inflammatory cytokine expression, and oxidative stress compared with vehicle. Moreover, PER suppressed neurodegeneration in the cortical ischemic boundary zone, via downregulation of Bcl-2-associated x and upregulation of Bcl-extra-large with Akt activation. In addition, post-stroke secondary neuronal damage and cognitive impairments, using the Y-maze test, were assessed 30 days after MCAO. PER significantly improved spatial working memory, which was accompanied by hippocampal CA1 neuronal loss and cortical thinning, compared with vehicle. These results indicate that PER attenuates infarct volumes and motor function deficits possibly through its anti-inflammatory, antioxidant, and anti-apoptotic activities, mediated via activation of phosphatidylinositol 3-kinase (PI3K)/Akt pathways in the acute ischemic phase, and further ameliorates post-stroke cognitive impairments via the suppression of secondary neuronal damage in the chronic ischemic phase.

Long noncoding ribonucleic acid NKILA induces the endoplasmic reticulum stress/autophagy pathway and inhibits the nuclear factor‐k‐gene binding pathway in rats after intracerebral hemorrhage

Long noncoding RNAs (lncRNAs) have emerged as an important class of molecules that have been associated with brain function and neurological disease, but the expression profiles of lncRNAs after intracerebral hemorrhage (ICH) remain to be elucidated. In this study, we determined the expression pattern of nuclear factor-k-gene binding (NF-kB) interacting lncRNA (NKILA) after ICH and examined its respective effects on the endoplasmic reticulum stress (ERS)/autophagy pathway, hippocampal neuron loss, and the NF-kB pathway after type VII collagenase-induced ICH in rats. The regulatory mechanisms of NKILA were investigated by an intraperitoneal injection of small interfering (siRNA) against NKILA into rats after ICH. NKILA inhibition mediated by siRNA against NKILA was shown to significantly reduce ERS and autophagy, activate the NF-kB pathway, decrease neurological deficits, brain edema, and injury, and induce blood-brain barrier breakdown, further leading to hippocampal neuron loss and the production of inflammation cytokines. Taken together, the demonstration that NKILA induces the ERS/autophagy pathway and inhibits the NF-kB pathway after ICH supports the concept that NKILA functions as a novel target that is required for the attenuation of brain injuries after ICH.

Down-regulation of Long Noncoding RNA MALAT1 Protects Hippocampal Neurons Against Excessive Autophagy and Apoptosis via the PI3K/Akt Signaling Pathway in Rats with Epilepsy.

Epilepsy is a common chronic brain disorder and is characterized by an enduring predisposition to generate seizures. The hippocampus is especially vulnerable to seizure-induced damage. In this study, we explore the ability of long noncoding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) to influence the autophagy and apoptosis of hippocampal neurons in epilepsy and the underlying mechanism involving the PI3K/Akt signaling pathway. Seventy-two Sprague-Dawley rats were assigned to normal, sham, Ep, Ep + si-NC, Ep + si-MALAT1, and Ep + si-MALAT1 + LY groups. Fluorescence in situ hybridization kit was employed to determine the MALAT1 in the brain tissues. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blotting were performed to determine the expression of MALAT1, mRNAs, and proteins. The autophagy of hippocampal neurons was evaluated under a transmission electron microscope and their apoptosis was evaluated using TUNEL staining. We found that MALAT1 and c-Met were enriched while microRNA-101 (miR-101) decreased in rats with epilepsy. The demonstration showed that MALAT1 binds to miR-101, thus regulating c-Met. In rats with epilepsy, MALAT1 depletion mediated by anti-MALAT1 siRNA resulted in activation of PI3K/Akt signaling pathway and loss of hippocampal neurons. LY294002, an inhibitor of PI3K/Akt signaling pathway, could reverse the events caused by MALAT1 knockdown. Taken together, these findings indicate that down-regulation of MALAT1 activates the PI3K/Akt signaling pathway to protect hippocampal neurons against autophagy and apoptosis in rats with epilepsy.

Effects of Huangpu Tongqiao capsule on apoptosis of Alzheimer's disease cell model

The loss of hippocampal neurons is one of the main pathological features of Alzheimer's disease (AD), which is related to the apoptosis of hippocampal neurons. Huangpu Tongqiao capsule is used for the treatment of AD, but the underlying mechanism is still unclear. This study is to investigate the mechanism of neuroprotective effect of Huangpu Tongqiao capsule in the treatment of AD, through observing the effect of Huangpu Tongqiao capsule containing serum on cell injury of primary cultured hippocampal neurons induced by Aβ₂₅₋₃₅ via inhibiting the cell apoptosis. Primary cultured hippocampal neurons were cultured and identified by MAP-2 immunofluorescence staining, and cell growth state was observed by inverted microscope. The Huangpu Tongqiao capsule containing serum was prepared using the method of serum pharmacology. MTT assays were used to measure the optimum concentration range of Huangpu Tongqiao capsule containing serum, and optimum Aβ concentration for establishing the AD model. After primary cultured hippocampal neurons AD cell model was induced by Aβ₂₅₋₃₅, cell survival rate was detected by MTT, cell apoptosis rate was assayed by flow cytometry, and protein expressions of Bax, Cyt C and caspase-3 were determined by Western blot analysis. The results showed that the primary cultured hippocampal neurons were cultured successfully, and cells grew mature at seventh days; Compared with normal group, the survival rate of hippocampal neurons in AD cell model group was decreased, the apoptosis rate of hippocampal neurons was increased, and the protein expressions of Bax, Cyt C and caspase-3 were increased (P<0.05, P<0.01); Compared with AD cell model group, the survival rate of hippocampal neurons in Huangpu Tongqiao capsule containing serum group was increased, the apoptosis rate of hippocampal neurons was decreased, and the protein expressions of Bax, Cyt C and caspase-3 were decreased (P<0.05, P<0.01). These findings suggest that Huangpu Tongqiao capsule containing serum has a neuroprotective effect on cell injury of the primary cultured hippocampal neurons induced by Aβ₂₅₋₃₅, and its effect on the treatment of AD is associated with the inhibition the apoptosis of hippocampal neurons.

Investigation of the effect of Ginkgo biloba leaf extract on spatial memory impairment and hippocampal neuronal loss caused by diabetes induced by streptozotocin in rats

ABSTRACT Background and Aim: Learning and memory defect occurs following chronic diabetes with uncontrolled blood glucose. Ginkgo leaf extract improves brain blood flow. Also it contains antioxidant components and has shown beneficial effects in neurological diseases. In this study we investigated the effects of Ginkgo leaf extract on spatial memory impairment and hippocampal neuronal loss caused by diabetes. Material and Methods: This experimental study included 28 adult male Sparague-Dawley rats. The rats were made diabetic by injection of streptozotocin (STZ: 60 mg/kg). Ginkgo leaf extract (40 mg/kg) was administrated orally every day for two weeks and its effects on memory impairment and hippocampal tissue damage were investigated. Spatial memory was assessed in Morris water maze for four days. Then, the brains of the animals were extracted and after tissue staining hippocampal tissue damage were evaluated by neuronal count. Results: Latency to find the platform in water maze were significantly increased in STZ group compared to that in the control group (p<0.05). While, administration of the Ginkgo extract in STZ injected animals significantly reduced the latency to find the platform (p<0.05). In addition, STZ reduced hippocampal neuronal count (p<0.001) and administration of the Ginkgo extract in STZ injected animals significantly improved hippocampal neuronal loss (p<0.01). Conclusion: Ginkgo leaf extract significantly improved spatial memory impairment and hippocampal neuronal loss, induced by diabetes.

D-galactose and aluminium chloride induced rat model with cognitive impairments

Cognitive impairments and cholinergic dysfunctions have been well reported in old age disorders including Alzheimer’s disease (AD). d-galactose (D-gal) has been reported as a senescence agent while aluminium act as a neurotoxic metal, but little is known about their combined effects at different doses. The aim of this study was to establish an animal model with cognitive impairments by comparing the effects of different doses of co-administrated D-gal and aluminium chloride (AlCl3). In this study male albino wistar rats were administered with D-gal 60 mg/kg.bwt intra peritoneally (I.P) injected and AlCl3 (100, 200, or 300 mg/kg.bwt.) was orally administered once daily for 10 consecutive weeks. Performance of the rats were evaluated through behavioural assessments; Morris water maze (MWM) and open field tests (OFT); histopathological examination was performed on the hippocampus; moreover biochemical measurements of acetylcholinesterase (AChE) and hyperphosphorylated tau protein (p-tau) were examined. The results of this experiment on rats treated with D-gal 60 + AlCl3 200 mg/kg.bwt showed near ideal cognitive impairments. The rats exhibited an obvious memory and learning deficits, marked neuronal loss in hippocampus, showed increase in AChE activities and high expression of p-tau within the tissues of the brain. This study concludes that D-gal 60 + AlCl3 200 mg/kg.bwt as the ideal dose for mimicking AD like cognitive impairments in albino wistar rats. It is also crucial to understand the pathogenesis of this neurodegenerative disease and for drug discovery.

Virus antigen-specific CD8 T cells contribute to brain atrophy during Theiler’s murine encephalomyelitis virus (TMEV) infection of the CNS.

Abstract Brain atrophy is a central feature of numerous neurological diseases for which the contribution of immune cells remains poorly defined. For example, in human multiple sclerosis, clonally expanded CD8 T cells have been observed in proximity to lesions, but their role in mediating brain atrophy has yet to be elucidated. This study aims to define how antigen-specific CD8 T cells contribute to brain atrophy in the TMEV model of neuroinflammation. Specific MHC class I haplotypes have been shown to dictate neuropathology and functional outcomes in mice following intracranial infection with TMEV. In this study, we demonstrate that transgenic FVB mice which express the H-2Db class I molecule rapidly clear picornavirus infection but at the cost of a novel neurodegenerative phenotype consistent with brain atrophy. Following TMEV infection out to four months, FVB mice expressing the Db class I molecule display increased lateral ventricular volume via T2-weighted MRI and hippocampal neuron loss by hematoxylin and eosin staining. Furthermore, these transgenic FVB mice present enhanced brain infiltration of virus-specific CD8 T cells for the immunodominant Db:VP2121–130 epitope. To address these findings mechanistically, we inhibited the Db:VP2121–130 epitope-specific CD8 T cell response and monitored the effect on brain atrophy. This inhibition strategy resulted in a reduction in brain atrophy to levels comparable to wild-type FVB controls. Not confounded by persistent infection or demyelination, these studies are the first to demonstrate antigen-specific CD8 T cells have the capacity to induce brain atrophy in a murine model of neurodegeneration.

Elevated MeCP2 in Mice Causes Neurodegeneration Involving Tau Dysregulation and Excitotoxicity: Implications for the Understanding and Treatment of MeCP2 Triplication Syndrome.

Expression of MeCP2 mustbe carefully regulated as a reduction or increase results in serious neurological disorders. We are studying transgenic mice in which the MeCP2 gene is expressed at about three times higher than the normal level. Male MeCP2-Tg mice, but not female mice, suffer motor and cognitive deficits and die at 18-20weeks of age. MeCP2-Tg mice display elevated GFAP and Tau expression within the hippocampus and cortex followed by neuronal loss in these brain regions. Loss of Purkinje neurons, but not of granule neurons in the cerebellar cortex is also seen. Exposure of cultured cortical neurons to either conditioned medium from astrocytes (ACM) derived from male MeCP2-Tg mice or normal astrocytes in which MeCP2 is expressed at elevated levels promotes their death. Interestingly, ACM from male, but not female MeCP2-Tg mice, displays this neurotoxicity reflecting the gender selectivity of neurological symptoms in mice. Male ACM, but not female ACM, contains highly elevated levels of glutamate, and its neurotoxicity can be prevented by MK-801, indicating that it is caused by excitotoxicity. Based on the close phenotypic resemblance of MeCP2-Tg mice to patients with MECP2 triplication syndrome, we suggest for the first time that the human syndrome is a neurodegenerative disorder resulting from astrocyte dysfunctionthat leads to Tau-mediated excitotoxic neurodegeneration. Loss of cortical and hippocampal neurons may explain the mental retardation and epilepsy in patients, whereas ataxia likely results from the loss of Purkinje neurons.

Oxytocin Inhibits Corticosterone-induced Apoptosis in Primary Hippocampal Neurons

Stress is an adaptive and coordinated response to endogenous or exogenous stressors that pose an unpleasant and aversive threat to an individual’s homeostasis and wellbeing. Glucocorticoids, corticosterone (CORT) in rodents and cortisol in humans, are adrenal steroids which are released in response to stressful stimuli. Although they help individuals to cope with stress, their overexposure in animals has been implicated in hippocampal dysfunction and neuronal loss. Oxytocin (OT) plays an active role in adaptive stress-related responses and protects hippocampal synaptic plasticity and memory during stress. In this study, we showed that OT protects primary mouse hippocampal neurons from CORT-induced apoptosis. OT receptors (OTR) were expressed in primary mouse hippocampal neurons and glial cells. CORT induced apoptosis in hippocampal neurons, but had no effect on apoptosis in glial cells. OT inhibited CORT-induced apoptosis in primary hippocampal neurons. OT was unable to protect primary hippocampal neurons prepared from OTR KO mice from CORT-induced apoptosis. These results indicate that OT has inhibitory effects on CORT-induced neuronal death in primary hippocampal neurons via acting on OTR. The findings suggest a therapeutic potential of OT in the treatment of stress-related disorders.

Synaptic Alterations in Mouse Models for Alzheimer Disease-A Special Focus on N-Truncated Abeta 4-42.

This commentary reviews the role of the Alzheimer amyloid peptide Aβ on basal synaptic transmission, synaptic short-term plasticity, as well as short- and long-term potentiation in transgenic mice, with a special focus on N-terminal truncated Aβ4-42. Aβ4-42 is highly abundant in the brain of Alzheimer’s disease (AD) patients. It demonstrates increased neurotoxicity compared to full length Aβ, suggesting an important role in the pathogenesis of AD. Transgenic Tg4-42 mice, a model for sporadic AD, express human Aβ4-42 in Cornu Ammonis (CA1) neurons, and develop age-dependent hippocampal neuron loss and neurological deficits. In contrast to other transgenic AD mouse models, the Tg4-42 model exhibits synaptic hyperexcitability, altered synaptic short-term plasticity with no alterations in short- and long-term potentiation. The outcomes of this study are discussed in comparison with controversial results from other AD mouse models.

The Pilocarpine Model of Temporal Lobe Epilepsy and EEG Monitoring Using Radiotelemetry System in Mice

Temporal lobe epilepsy (TLE) is a common neurological disorder in adulthood. For translational studies of chronic epilepsy, pilocarpine-induced status epilepticus (SE) is frequently selected to recapitulate spontaneous recurrent seizures (SRS). Here we present a protocol of SE induction by intraperitoneal (i.p.) injection of pilocarpine and monitoring of chronic recurring seizures in live animals using a wireless telemetry video and electroencephalogram (EEG) system. We demonstrated notable behavioral changes that need attention after pilocarpine injection and their correlation with hippocampal neuronal loss at 7 days and 6 weeks post-pilocarpine. We also describe the experimental procedures of electrode implantation for video and EEG recording, and analysis of the frequency and duration of chronic recurrent seizures. Finally, we discuss the possible reasons why the expected results are not achieved in each case. This provides a basic overview of modeling chronic epilepsy in mice and guidelines for troubleshooting. We believe this protocol can serve as a baseline for suitable models of chronic epilepsy and epileptogenesis.

The Pilocarpine Model of Temporal Lobe Epilepsy and EEG Monitoring Using Radiotelemetry System in Mice.

Temporal lobe epilepsy (TLE) is a common neurological disorder in adulthood. For translational studies of chronic epilepsy, pilocarpine-induced status epilepticus (SE) is frequently selected to recapitulate spontaneous recurrent seizures (SRS). Here we present a protocol of SE induction by intraperitoneal (i.p.) injection of pilocarpine and monitoring of chronic recurring seizures in live animals using a wireless telemetry video and electroencephalogram (EEG) system. We demonstrated notable behavioral changes that need attention after pilocarpine injection and their correlation with hippocampal neuronal loss at 7 days and 6 weeks post-pilocarpine. We also describe the experimental procedures of electrode implantation for video and EEG recording, and analysis of the frequency and duration of chronic recurrent seizures. Finally, we discuss the possible reasons why the expected results are not achieved in each case. This provides a basic overview of modeling chronic epilepsy in mice and guidelines for troubleshooting. We believe this protocol can serve as a baseline for suitable models of chronic epilepsy and epileptogenesis.