Learning Memory Deficits Research Articles

Transcriptional regulation of NRF1 on metabotropic glutamate receptors in a neonatal hypoxic‑ischemic encephalopathy rat model.

Neonatal hypoxic-ischemic encephalopathy (HIE) is a kind of brain injury that causes severe neurological disorders in newborns. Metabotropic glutamate receptors (mGluRs) and ionotropic glutamate receptors (iGluRs) are significantly associated with HIE and are involved in ischemia-induced excitotoxicity. This study aimed to investigate the upstream mechanisms of mGluRs and the transcriptional regulation by nuclear respiratory factor 1 (NRF1). The rat model of neonatal HIE was created using unilateral carotid artery ligation and in vitro oxygen-glucose deprivation paradigm. We used western blot, immunofluorescence, Nissl staining, and Morris water maze to investigate the impact of NRF1 on brain damage and learning memory deficit by HIE. We performed ChIP and luciferase activities to identify the transcriptional regulation of NRF1 on mGluRs. The neuronal NRF1 and some glutamatergic genes expression synchronously declined in infarcted tissues. The NRF1 overexpression effectively restored the expression of some glutamatergic genes and improved cognitive performance. NRF1 regulated some members of mGluRs and iGluRs in hypoxic-ischemic neurons. Finally, NRF1 is bound to the promoter regions of Grm1, Grm2, and Grm8 to activate their transcription. NRF1 is involved in the pathology of the neonatal HIE rat model, suggesting a novel therapeutic approach to neonatal HIE. NRF1 and some glutamatergic genes were synchronously downregulated in the infarcted brain of the neonatal HIE rat model. NRF1 overexpression could rescue cognitive impairment caused by the neonatal HIE rat model. NRF1 regulated the expressions of Grm1, Grm2, and Grm8, which activated their transcription by binding to the promoter regions.

Minocycline Ameliorated LPS-Induced Learning and Memory Impairment by Inhibiting Microglia and Astrocytes Activation in The Hippocampus

INTRODUCTION: Many studies support the notion that neuroinflammation involving glial cells may be the fundamental pathogenic event that lead to brain damage and degeneration in Alzheimer’s disease (AD). The effects of minocycline on glial cells activation in the lipopolysaccharide (LPS) rat model is studied here. MATERIALS AND METHODS: Fifty adult male Sprague Dawley rats were split into five groups: control, LPS, LPS-treated with minocycline 25 mg/kg, LPS-treated with minocycline 50 mg/kg, and LPS treated with memantine 10 mg/kg. For two weeks, rats were treated with minocycline and memantine intraperitoneally daily, while were injected with LPS intraperitoneally once on day 5. Morris water maze (MWM) test was performed to evaluate the learning and working memory behaviour. Immunohistochemistry and Western blot were performed to measure ionized calcium-binding adaptor molecule 1 (Iba-1) and glial fibrillary acidic protein (GFAP) expressions in the hippocampal tissue. RESULTS: LPS injection caused significant learning and working memory deficits (p<0.05) as well as increased expressions of Iba-1 and GFAP (p<0.05), indicating microglia and astrocytes activation, respectively. Minocycline treatment significantly improved learning and working memory performance (p<0.05) and reduced microglia/astrocytes activation (p<0.05) in a dose-dependent manner, similar to the effect of memantine. CONCLUSIONS: Our results suggest that minocycline modulates LPS-induced microglia and astrocytes activation as well as improves learning and working memory comparable to memantine. Thus, minocycline may have preventive-therapeutic effect in diseases involving neuroinflammation such as AD.

Electroacupuncture modulates gut microbiota in mice: A potential target in postoperative cognitive dysfunction.

The detailed mechanism of inflammation in postoperative cognitive dysfunction (POCD) is unclear. This study aimed to determine whether electroacupuncture (EA) ameliorates POCD by modulating gut microbial dysbiosis. Compared to the control group, mice in the EA group were treated at the acupoints Zusanli (ST36), Quchi (L111), Baihui (GV20), and Dazhui (GV14) 1 week before appendectomy. Novel object recognition and the Morris water maze tests were used to assess learning and spatial reference memory deficits, whereas hippocampus samples and stool samples were collected for central inflammatory tests and 16S-rRNA sequencing of intestinal flora, respectively. In amyloid precursor protein/presenilin 1 (APP/PS1) mice, EA enhanced spatial memory and learning deficits. The fecal microbial community was altered in APP/PS1 mice in the absence of EA following surgery. Among them, Coprococcus and Bacteroidetes were more abundant in the EA groups than in the control groups; however, Actinobacteriota, Helicobacteraceae, and Escherichia/shigella constitute the minor bacterial colonization in the EA groups. Furthermore, we found a significant negative correlation between Firmicutes and escape latency (Pearson correlation coefficient - 0.551, p < 0.01) and positive correlation between Proteobacteria and escape latency (Pearson correlation coefficient 0.462, p < 0.05). Electron microscopy revealed signs of blood-brain barrier (BBB) impairments and immunofluorescence images showed glial cells activated in the hippocampus of APP/PS mice without EA, and serum diamine oxidase levels were increased in these mice; whereas EA treatment significantly relieved the above pathological changes. Our findings implied that EA decreases hippocampal inflammation ofAPP/PS1 by upregulating benificial gut microbiota, reducing BBB and intestinal barrier dysfunction, thus alleviates postoperative cognitive dysfunction. This may provide a novel target in POCD management.

Identification of potential therapeutic and diagnostic characteristics of Alzheimer disease by targeting the miR-132-3p/FOXO3a-PPM1F axis in APP/PS1 mice

Alzheimer disease (AD) is a neurodegenerative disorder, which is characterized by progressive impairment of memory and cognition. Early diagnosis and treatment of AD has become a leading topic of research. In this study, we explored the effects of the miR-132-3p/FOXO3a-PPM1F axis on the onset of AD for possible early diagnosis and therapy. We found that miR-132-3p levels in the hippocampus and blood were drastically decreased in APP/PS1 mice from 9 months of age, and bi-directional manipulation of miR-132-3p levels induced magnified effects on learning memory behaviors, and manifestation of AD-related pathological characteristics and inflammatory cytokines in APP/PS1 mice of relevant ages. The hippocampal PPM1F expression levels were significantly elevated in APP/PS1 mice from 3 months of age, which was correlated with miR-132-3p levels at different ages. Overexpression of PPM1F remarkably accelerated the progression of learning memory deficits and associated pathological factors in APP/PS1 mice. Further, we showed that miR-132-3p modulated the expression of PPM1F via FOXO3a in HT22 cells. Finally, using peripheral blood samples of human study participants, we found that the miR-132-3p and PPM1F expression levels in patients with AD were also altered with prominent correlations. In conclusion, miR-132-3p indirectly regulates PPM1F expression by targeting FOXO3a, which could play an extensive role in contributing to the establishment of early diagnosis, treatment, and pathogenesis of AD.

Aluminium oxide nanoparticles compromise spatial memory performance and proBDNF-mediated neuronal function in the hippocampus of rats

BackgroundAlumina nanoparticles (aluminaNPs), which are widely used in a range of daily and medical fields, have been shown to penetrate blood-brain barrier, and distribute and accumulate in different brain areas. Although oral treatment of aluminaNPs induces hippocampus-dependent learning and memory impairments, characteristic effects and exact mechanisms have not been fully elucidated. Here, male adult rats received a single bilateral infusion of aluminaNPs (10 or 20 µg/kg of body weight) into the hippocampal region, and their behavioral performance and neural function were assessed.ResultsThe results indicated that the intra-hippocampus infusions at both doses of aluminaNPs did not cause spatial learning inability but memory deficit in the water maze task. This impairment was attributed to the effects of aluminaNP on memory consolidation phase through activation of proBDNF/RhoA pathway. Inhibition of the increased proBDNF by hippocampal infusions of p75NTR antagonist could effectively rescue the memory impairment. Incubation of aluminaNPs exaggerated GluN2B-dependent LTD induction with no effects on LTD expression in hippocampal slices. AluminaNP could also depress the amplitude of NMDA-GluN2B EPSCs. Meanwhile, increased reactive oxygen specie production was reduced by blocking proBDNF-p75NTR pathway in the hippocampal homogenates. Furthermore, the neuronal correlate of memory behavior was drastically weakened in the aluminaNP-infused groups. The dysfunction of synaptic and neuronal could be obviously mitigated by blocking proBDNF receptor p75NTR, implying the involvement of proBDNF signaling in aluminaNP-impaired memory process.ConclusionsTaken together, our findings provide the first evidence that the accumulation of aluminaNPs in the hippocampus exaggeratedly activates proBDNF signaling, which leads to neural and memory impairments.

SIRT1 Is Involved in the Neuroprotection of Pterostilbene Against Amyloid β 25-35-Induced Cognitive Deficits in Mice.

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by amyloid-β (Aβ) deposits and neurofibrillary tangles. Pterostilbene (PTE), a bioactive component mainly in blueberries, is found to have neuroprotective properties. However, the specific underlying mechanisms of PTE in protecting AD remain unclear. Herein, we explored its effects on Aβ25–35-induced neuronal damage in vivo and in vitro and further compared the roles with its structural analog resveratrol (RES) in improving learning–memory deficits. We found that intragastric administration of PTE (40 mg/kg) displayed more effective neuroprotection on Aβ25–35-induced cognitive dysfunction assessed using the novel object test, Y-maze test, and Morris water maze test. Then, we found that PTE improved neuronal plasticity and alleviated neuronal loss both in vivo and in vitro. Additionally, PTE upregulated the expression of sirtuin-1 (SIRT1) and nuclear factor erythroid 2-related factor 2 (Nrf2) and the level of superoxide dismutase (SOD), and inhibited mitochondria-dependent apoptosis in the Aβ25–35-treated group. However, SIRT1 inhibitor EX527 reversed the neuroprotection and induced a drop in mitochondrial membrane potential in PTE-treated primary cortical neurons. Our data suggest that PTE’s enhancing learning–memory ability and improving neuroplasticity might be related to inhibiting mitochondria-dependent apoptosis via the antioxidant effect regulated by SIRT1/Nrf2 in AD.

A53T α-synuclein induces neurogenesis impairment and cognitive dysfunction in line M83 transgenic mice and reduces the proliferation of embryonic neural stem cells

Dementia with Lewy body (DLB) is the second most common degenerative dementia after Alzheimer's disease. There is no therapeutic drug for DLB currently. It’s urgent for us to understand the pathological mechanism of dementia mediated by α-synuclein, as the main component of Lewy body. Here, we found that the A53T α-synuclein transgenic mice showed decreased nesting behavior starting from the age of 1 month. The results in Morris water maze test suggested that the 6-month-old mice had learning memory deficits. Golgi staining indicated that the apical neuronal dendritic spines of hippocampal CA1 neurons were significantly reduced in 6-month-old homozygotes and heterozygotes, although MAP2 protein expression revealed no significant difference in the hippocampus among wild-type mice, homozygotes and heterozygotes. In vitro, we proved mutant A53T α-synuclein decreased the dendritic branches and dendrite spines on the embryonic mice hippocampal neurons. Furthermore, Ki67 immunofluorescence staining identified that the Ki67-positive cells of the hippocampal dentate gyrus and subventricular zone were significantly reduced in 6-month-old homozygotes and heterozygotes, compared with age-matched wild-type mice. Similarly, when 6-month-old mice were injected with BrdU for one day, the immunostaining results also confirmed that BrdU-positive cells were significantly reduced in homozygous and heterozygous mice. Lastly, we transfected primary embryonic hippocampal neural stem cells with lentivirus vector expressing A53T α-synuclein in vitro. Both BrdU staining and Western blotting showed that A53T α-synuclein significantly decreased the proliferation of embryonic neural stem cells. Taken together, these data suggest that A53T α-synuclein can induce adult neurogenesis impairment and cognitive dysfunction. The A53T α-synuclein transgenic mice may be used as an animal model for DLB. Promoting adult neurogenesis may be a promising approach to treat DLB pathogenesis.

Total ginsenoside and Acorus tatarinowii volatile oil co-administration reverses learning memory deficits, reduces Aβ42 and AChE levels, and downregulates the PI3K/Akt/mTOR/Beclin-1 autophagic pathway in APP/PS1 double transgenic mice

Ethnopharmacological RelevanceThe combined application of ginseng and Shichangpu comes from the nootropic prescription—Dingzhi Xiaowan. One of the main effective components of ginseng is saponins. Studies have reported that its total saponins have significant neuroprotective effects, especially in anti-neuro-inflammation and anti-cognitive impairment. Shichangpu is a traditional Chinese medicine commonly used in clinical treatment of mental disorders such as dementia, amnesia, and epilepsy. One of the main active ingredients of Acorus tatarinowii is volatile oil, and research reports that its volatile oil also has a good neuroprotective effect. Previous research by the research team has shown its potential efficacy against Alzheimer's disease (AD). Aim of the studyAt present, the pathogenesis of Alzheimer's disease (AD) is not yet clear and the current treatment methods can only relief the related symptoms of AD. Our previous research found that the volatile oil of Acorus tatarinowii and components of ginsenosides, such as Rd, Rh2 and Rg1 can improve the learning and memory ability of AD mice. However, the effect and mechanism of volatile oil of Acorus tatarinowii combined with total ginsenosides on APP/PS1 double transgenic mice are still unknown. Materials and methodsIn this study, the effects of total ginsenoside and Acorus tatarinowii volatile oil co-administration on behavioral tests, amyloid β 42 (Aβ42) and acetylcholinesterase (AChE) levels, p-Akt, p-mTOR, LC3B, Bcl-2 and p62 expressions were investigated in APP/PS1 double transgenic mice. Furthermore, the PI3K/Akt/mTOR autophagic pathway was also studied and the structure of hippocampal neurons was observed. ResultsThe results showed that co-administrated treatment improved the learning and memory ability of mice in the water maze, passive avoidance and step-down tests, the swimming time and error times were shorten and incubation period was prolonged. And Aβ42 and AChE levels decreased, LC3B and Beclin-1 expressions declined, and number of autophagosomes reduced in the hippocampus of the APP/PS1 double transgenic mice, in contrary, the change of p-Akt, p-mTOR, P62 and Bcl-2 expressions were increased in the co-administrated treated mice compared with the untreated mice. We deduced that co-administrated therapy may firstly upregulate expressions of p-Akt, p-mTOR, P62 and Bcl-2, and then indirectly decrease the expression of LC3B and Beclin-1. ConclusionCollectively, all data indicated that total ginsenoside and Acorus tatarinowii volatile oil co-administration may play an autophagy inhibited role in preventing AD development by the PI3K/Akt/mTOR pathway.

Development and in vivo Evaluation of Hydroxy-α-Sanshool Intranasal Liposomes as a Potential Remedial Treatment for Alzheimer's Disease.

PurposeHydroxy-α-sanshool (HAS) improves cognitive dysfunction, but its structural instability has limited its clinical application. The present study was conducted to investigate the optimal formulation of hydroxy-α-sanshool liposomes (HAS-LPs) and its effect on ameliorating learning and memory disorders in an Alzheimer’s disease (AD) model.MethodsIn this study, HAS was prepared as HAS-LP using a thin film dispersion method. After selecting the optimal preparation conditions, HAS-LP was characterized using transmission electron microscopy (TEM) and by measuring the zeta potential, particle size, and in vitro drug release. Next, evaluated the effect of HAS-LP on the rat nasal mucosa and then applied it to AD mice. By performing behaviour experiments, pathological test and related pharmacokinetic parameters, we explored its effect on attenuating learning and memory impairment in mice.ResultsWhen the mass ratio of HAS:cholesterol:soybean lecithin was 1:4:16 and 15 mL of ultrapure water were added, the highest encapsulation efficiency and drug loading were obtained. HAS-LP had a particle size of 181.77 nm, a polydispersity index of 0.207 and a zeta potential of −53.8 mV, and it remained stable at 25 °C for 1 week and 4 °C for 8 weeks. Moreover, HAS-LP exhibited slow drug release and was highly consistent with the Higuchi release model. HAS-LP was not significantly toxic to the nasal mucosa and effectively alleviated D-galactose-induced learning memory deficits and protected mouse hippocampal neuronal cells. HAS-LP was highly enriched in plasma and brain tissue after administration via the nasal route and obtained some ability to target the brain.ConclusionHAS encapsulated in soybean lecithin and cholesterol was successfully developed, suggesting that treatment with the nanoparticles might reverse some AD symptoms. Therefore, these nanoparticles might be used as promising new candidates for the delivery of HAS to treat AD.

Blood brain barrier dysfunction caused by repeated Endothelin-1 injection leads to irreversible memory impairment.

Vascular dysfunction is being increasingly recognized as a major contributor to dementia burden. Repeated occurrence of vascular insults in small vessels results in Blood Brain Barrier (BBB) dysfunction potentially contributing to cognitive impairments. The small vessel infracts is seen as white matter hyperintensities in MRI of many patients. Postmortem studies have shown BBB damage in dementia including AD and accumulation blood-derived proteins as well as loss of BBB associated cells like pericytes. In view of such a scenario we wanted to establish an animal model to study multiple small vessel insults impacting BBB leading to learning and memory deficits. C57/BL6J mice aged 4-5 months was implanted with cannula on left side of the hemisphere. ET-1 (Endothelin- 1), a 21 amino acid vasoconstricting peptide was infused through guide cannula into the intracerebroventricular space of lateral ventricle. Mice were injected for 3 doses of ET-1 at intervals of 3 weeks over a period of 9 weeks. The animals were assessed for associative learning and spatial memory deficits with different behavioral task. Animals were perfused and brain was processed for immunohistochemistry to assess vascular pathology. To simulate the clinical conditions the animals were injected over a period of three weeks to make sure that animal completely recovers from first vascular insult and then subsequent insults were given. There was BBB leakage, discrepancies in the blood vessel integrity and loss of pericytes after multiple ET-1 injection. Further there was significant memory deficits in novel object task, contextual fear conditioning test and Morris water maze. Our results demonstrated that chronic vascular insults cause BBB dysfunction and cognitive deficits seen as memory impairment. We were able to establish that repeated vasoconstriction by ET-1 in small vessels leads to BBB breach resulting in irreversible learning and memory deficits. This animal model could help us to study molecular underpinnings of white matter hyperintensities.

Differential expression of long non-coding RNAs in the hippocampus of mice exposed to PM2.5 in Dalian, China.

Evidence is mounting that PM2.5 exposure could lead to learning disability, memory deficits, and cognitive impairment; however, the underlying mechanisms are still not well demonstrated yet. Long non-coding RNAs (LncRNAs) play a crucial role in many human diseases. Although the relationship of Alzheimer's disease (AD) and lncRNAs have been discovered, the role of lncRNA in AD-like phenotype induced by PM2.5 needs further exploration. In this study, we profiled the expression of messenger RNAs (mRNAs) and lncRNAs in hippocampus after confirming the AD-like changes in mice. Compared with the control group, a total of 478 mRNAs and 151 lncRNAs were dysregulated after PM2.5 exposure. ECM-receptor interaction, focal adhesion, complement and coagulation cascades, and AGE-RAGE signaling pathway were found dysregulated through lncRNA-co-expressed genes analysis based on the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Meanwhile, the genes related to microglia were significantly altered, such as CX3CR1, CD163, lncRNA Gm44750, and lncRNA Gm43509. Above evidences suggested that microglia-related lncRNAs dysregulation probably plays a crucial role in PM2.5exposure-associated learning and memory deficits.

A candidate gene of Alzheimer diseases was mutated in senescence-accelerated mouse prone (SAMP) 8 mice

The senescence-accelerated mouse prone (SAMP) 8 strain exhibits age-related learning and memory deficits (LMD) at 2 months of age. We have found strong association of chromosome 12 locus with learning memory deficit (LMD) phenotype in SAMP8 strain. In the course of searching candidate gene, here we identified solute carrier family 24 sodium/potassium/calcium exchanger member 4 (Slc24a4) in SAMP8 chromosome 12 LMD possessing one single nucleotide polymorphism causing amino acid replacement of Threonine at 413 position with Methionine. Since SLC24A4 has been postulated as a candidate of late onset Alzheimer's diseases (LOAD), we further analyze the functional importance of this polymorphism. By expressing Slc24a4 protein in HEK293 cells, here we showed polymorphic SAMP8 type Slc24a4-T413 M causing significant loss of calcium ion (Ca2+) transporter activity in cells compared with that of wild type mouse (Slc24a4-WT). However, no study yet shows any functional association of human SLC24A4 polymorphism with the onset of LOAD pathogenesis. Thus, our present finding may further help to clarify the importance of this ion exchanger with age related cognitive dysfunction.

MiR-216a-5p ameliorates learning-memory deficits and neuroinflammatory response of Alzheimer’s disease mice via regulation of HMGB1/NF-κB signaling

ObjectiveThe objective of this study was to explore whether miR-216a-5p could affect the learning-memory ability and inflammatory response of Alzheimer’s disease (AD) mice via regulation of the HMGB1/NF-κB pathway. MethodsMice were divided into the normal (wild-type C57BL/6 mice), AD (APP/PS1 double-transgenic mice), AD + miR-216a-5p, and AD + vector groups. The Morris water maze test was used to examine learning and memory ability. Nissl staining and TUNEL staining were performed to observe the survival and apoptosis of hippocampal neurons. In addition, Aβ deposition and the expression of inflammatory cytokines were determined, while miR-216a-5p expression and HMGB1/NF-κB pathway-related proteins were detected by qRT-PCR and Western blotting, respectively. ResultsAD mice exhibited decreased miR-216a-5p expression but increased HMGB-1 protein expression in the hippocampus, and these mice had a prolonged escape latency, fewer number of times crossing the platform location and shortened time in the target quadrant compared to those in normal mice. AD mice also had an elevated number of TUNEL-positive cells, increased deposition of Aβ, increased expression of inflammatory cytokines and decreased number of Nissl-positive cells. In addition, AD mice presented with downregulated expression of cytoplasmic NF-κB p65 protein but upregulated expression of nuclear NF-κB p65 protein. However, AD mice treated with miR-216a-5p exhibited significant improvements of the abovementioned parameters. The dual-luciferase reporter assay confirmed that HMGB1 is a target gene of miR-216a-5p. ConclusionMiR-216a-5p can improve learning-memory ability and attenuate the inflammatory response of AD mice through targeted inhibition of the HMGB1/NF-κB pathway.

Gulf War Agent Exposure Causes Dose‐Dependent Impairment of Memory Formation and Exercise Intolerance in a Mouse Model of Gulf War Illness

Gulf War Illness (GWI) is a chronic multi-symptom condition that still affects a third of veterans who served in the 1991 Persian Gulf War (GW). Latently-emerging and persistent symptoms fall into 5 general domains: neurological/cognition/mood, muscle/joint pain, respiratory, gastrointestinal disturbances and especially chronic fatigue. In particular, veterans exhibit CNS deficits in the neuropsychological domains of visuospatial abilities, attention/executive functioning, and learning/memory. GWI remains untreated due its poorly understood etiology and pathophysiology. It is suggested that GWI is a result of continuous exposure of military personnel to GW agents (pyridostigmine bromide, (PB), permethrin (PER), diethyltoluamide (DEET) and deployment/combat stress. To further investigate the cognitive manifestations of GWI pathophysiology, we studied the effects of chronic GW agent exposure in adult C57Bl/6N males utilizing a repeated measures design. The dosing paradigm consisted of 5 d/week for 28d of exposure to two doses of PB (6.5 mg/kg/d, 2x/d and 8.7 mg/kg/d, 1x/d; po), PER (1.3 mg/kg/d; top) in 70% ETOH, DEET (1650 mg/kg/d in DMSO) and stress 5 min/d (n=5–7/group). Two controls were included: sham (saline po, 70% ETOH and DMSO top) and sham/stress. Behavioral endpoints were measured at different timepoints post treatment (PT) up to PT160d. The 8.7 mg/kg/d dose was more effective in modeling cognitive deficits on the passive avoidance test since this group failed to avoid the aversive dark chamber at the 24h, and 7d and/or 3d retention timepoints at PT70. A repeat test at PT120 indicated that the 8.7 and sham/stress (P<.01) but not the 6.5 mg/kg/d group displayed retention of emotional reactivity memory at all test timepoints. In the novel object recognition test, performed at PT17, GW groupsbut not sham/stress displayed deficient memory retention at 24h (P<.01). On the Barnes Maze, no GW exposure effects on reference memory were noted during acquisition training nor a 24h acquisition probe trial. Since the neuropsychological deficits seen in GW chemical exposures can be exacerbated by comorbid mood-related conditions, animals were tested for anxiety and depression but no GW-specific effects were found. To model chronic fatigue, using a 5-day exercise endurance test we found that 8.7 mg/kg/d showed decreased latency to exhaustion at PT23 and PT161 compared to sham/stress (P<.05, P<.01). This effect could not be attributed to problems with motor coordination as measured on Suok and rotarod tests. In summary, the GW agent exposure paradigm produces specific cognitive deficits in associative aversive learning and novel object recognition memory but not visuospatial (reference) memory. GW agents also cause mice to tire faster during exercise without deficits in motor coordination. This animal model may be useful in examining common mechanisms underlying deficient cognitive performance and chronic fatigue in GWI.

Enhancing GABAergic signaling ameliorates aberrant gamma oscillations of olfactory bulb in AD mouse models

BackgroundBefore the deposition of amyloid-beta plaques and the onset of learning memory deficits, patients with Alzheimer’s disease (AD) experience olfactory dysfunction, typified by a reduced ability to detect, discriminate, and identify odors. Rodent models of AD, such as the Tg2576 and APP/PS1 mice, also display impaired olfaction, accompanied by aberrant in vivo or in vitro gamma rhythms in the olfactory pathway. However, the mechanistic relationships between the electrophysiological, biochemical and behavioral phenomena remain unclear.MethodsTo address the above issues in AD models, we conducted in vivo measurement of local field potential (LFP) with a combination of in vitro electro-olfactogram (EOG), whole-cell patch and field recordings to evaluate oscillatory and synaptic function and pharmacological regulation in the olfactory pathway, particularly in the olfactory bulb (OB). Levels of protein involved in excitation and inhibition of the OB were investigated by western blotting and fluorescence staining, while behavioral studies assessed olfaction and memory function.ResultsLFP measurements demonstrated an increase in gamma oscillations in the OB accompanied by altered olfactory behavior in both APP/PS1 and 3xTg mice at 3–5 months old, i.e. an age before the onset of plaque formation. Fewer olfactory sensory neurons (OSNs) and a reduced EOG contributed to a decrease in the excitatory responses of M/T cells, suggesting a decreased ability of M/T cells to trigger interneuron GABA release indicated by altered paired-pulse ratio (PPR), a presynaptic parameter. Postsynaptically, there was a compensatory increase in levels of GABAAR α1 and β3 subunits and subsequent higher amplitude of inhibitory responses. Strikingly, the GABA uptake inhibitor tiagabine (TGB) ameliorated abnormal gamma oscillations and levels of GABAAR subunits, suggesting a potential therapeutic strategy for early AD symptoms. These findings reveal increased gamma oscillations in the OB as a core indicator prior to onset of AD and uncover mechanisms underlying aberrant gamma activity in the OB.ConclusionsThis study suggests that the concomitant dysfunction of both olfactory behavior and gamma oscillations have important implications for early AD diagnosis: in particular, awareness of aberrant GABAergic signaling mechanisms might both aid diagnosis and suggest therapeutic strategies for olfactory damage in AD.

Metabolic, Phenotypic, and Neuropathological Characterization of the Tg4-42 Mouse Model for Alzheimer's Disease.

Background:Preclinical Alzheimer’s disease (AD) research strongly depends on transgenic mouse models that display major symptoms of the disease. Although several AD mouse models have been developed representing relevant pathologies, only a fraction of available mouse models, like the Tg4-42 mouse model, display hippocampal atrophy caused by the death of neurons as the key feature of AD. The Tg4-42 mouse model is therefore very valuable for use in preclinical research. Furthermore, metabolic biomarkers which have the potential to detect biochemical changes, are crucial to gain deeper insights into the pathways, the underlying pathological mechanisms and disease progression.Objective:We thus performed an in-depth characterization of Tg4-42 mice by using an integrated approach to analyze alterations of complex biological networks in this AD in vivo model.Methods:Therefore, untargeted NMR-based metabolomic phenotyping was combined with behavioral tests and immunohistological and biochemical analyses.Results:Our in vivo experiments demonstrate a loss of body weight increase in homozygous Tg4-42 mice over time as well as severe impaired learning behavior and memory deficits in the Morris water maze behavioral test. Furthermore, we found significantly altered metabolites in two different brain regions and metabolic changes of the glutamate/4-aminobutyrate-glutamine axis. Based on these results, downstream effects were analyzed showing increased Aβ42 levels, increased neuroinflammation as indicated by increased astro- and microgliosis as well as neuronal degeneration and neuronal loss in homozygous Tg4-42 mice.Conclusion:Our study provides a comprehensive characterization of the Tg4-42 mouse model which could lead to a deeper understanding of pathological features of AD. Additionally this study reveals changes in metabolic biomarker which set the base for future preclinical studies or drug development.

The Impact of Neonatal Methamphetamine on Spatial Learning and Memory in Adult Female Rats.

The present study was aimed at evaluating cognitive changes following neonatal methamphetamine exposure in combination with repeated treatment in adulthood of female Wistar rats. Pregnant dams and their pups were used in this study. One half of the offspring were treated indirectly via the breast milk of injected mothers, and the other half of pups were treated directly by methamphetamine injection. In the group with indirect exposure, mothers received methamphetamine (5 mg/ml/kg) or saline (1 ml/kg) between postnatal days (PD) 1–11. In the group with direct exposure, none of the mothers were treated. Instead, progeny were either: (1) treated with injected methamphetamine (5 mg/ml/kg); or (2) served as controls and received sham injections (no saline, just a needle stick) on PD 1–11. Learning ability and memory consolidation were tested on PD 70–90 in the Morris Water Maze (MWM) using three tests: Place Navigation Test, Probe Test, and Memory Recall Test. Adult female progeny were injected daily, after completion of the last trial of MWM tests, with saline or methamphetamine (1 mg/ml/kg). The effects of indirect/direct neonatal methamphetamine exposure combined with acute adult methamphetamine treatment on cognitive functions in female rats were compared. Statistical analyses showed that neonatal drug exposure worsened spatial learning and the ability to remember the position of a hidden platform. The study also demonstrated that direct methamphetamine exposure has a more significant impact on learning and memory than indirect exposure. The acute dose of the drug did not produce any changes in cognitive ability. Analyses of search strategies (thigmotaxis, scanning) used by females during the Place Navigation Test and Memory Recall Test confirmed all these results. Results from the present study suggested extensive deficits in learning skills and memory of female rats that may be linked to the negative impact of neonatal methamphetamine exposure.

Bioinformatics analysis and quantitative weight of evidence assessment to map the potential mode of actions of bisphenol A.

Bisphenol A (BPA) is a classical chemical contaminant in food, and the mode of action (MOA) of BPA remains unclear, constraining the progress of risk assessment. This study aims to assess the potential MOAs of BPA regarding reproductive/developmental toxicity, neurological toxicity, and proliferative effects on the mammary gland and the prostate potentially related to carcinogenesis by using the Comparative Toxicogenomics Database (CTD)-based bioinformatics analysis and the quantitative weight of evidence (QWOE) approach on the basis of the principles of Toxicity Testing in the 21st Century. The CTD-based bioinformatics analysis results showed that estrogen receptor 1, estrogen receptor 2, mitogen-activated protein kinase (MAPK) 1, MAPK3, BCL2 apoptosis regulator, caspase 3, BAX, androgen receptor, and AKT serine/threonine kinase 1 could be the common target genes, and the apoptotic process, cell proliferation, testosterone biosynthetic process, and estrogen biosynthetic process might be the shared phenotypes for different target organs. In addition, the KEGG pathways of the BPA-induced action might involve the estrogen signaling pathway and pathways in cancer. After the QWOE evaluation, two potential estrogen receptor-related MOAs of BPA-induced testis dysfunction and learning-memory deficit were proposed. However, the confidence and the human relevance of the two MOAs were moderate, prompting studies to improve the MOA-based risk assessment of BPA.

Gastrodin as a multi-target protective compound reverses learning memory deficits and AD-like pathology in APP/PS1 transgenic mice

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder. Evidence suggests that people can benefit from consumption of diets rich in plant phenolics because they can attenuate AD symptoms. The phenolic glucoside gastrodin is the main bioactive compound of Rhizoma Gastrodiae and is widely used for treating various neurological disorders. In this study, we assess whether long term oral administration of gastrodin can improve cognitive impairment and AD-like pathology. Our results showed that chronic gastrodin administration inhibits aggregation and disaggregate oligomeric and fibrillar species of Aβ42, prevents Aβ42 induced neurotoxicity in cell SH-SY5Y, decreases the levels of Aβ plaques and hyperphosphorylated tau, alleviates activation of glial cells and proinflammatory cytokines, attenuates oxidative stress in the APP/PS1 transgenic mice. The mechanisms underlying can be attributed to the inhibition levels of enzymes of Aβ and prevention GSK3β activity. Our results suggest that gastrodin might be a potential agent for thetreatment of AD.

Single bilateral injection of endothelin‐1 leads to temporary deficits in memory and synaptic dysfunction

AbstractBackgroundCerebral small vessel disease (SVD) has gained prominence worldwide as a major factor for cognitive impairment seen in dementia. Micro infracts causing elusive changes in cognitive function clinically will not get diagnosed are found to be the main risk factor for SVD. We were interested in creating micro infarcts rather than a severe insult to replicate small vessel damage, so we opted for Intra cerebroventricular (ICV) bilateral stereotaxic injection of endothelin‐1 (ET‐1) into lateral ventricles. Sub cortical injections of ET‐1 in brain has been used in many studies to accomplish long lasting vasoconstriction and gradual reperfusion causing lesion. Therefore, we tried to overcome this by injecting into lateral ventricles allowing it to spread through cerebrospinal fluid.MethodET‐1 (Endothelin‐ 1) a 21 amino acid vasoconstricting peptide was injected bilaterally into lateral ventricles of C57 mice. Some animals were injected unilaterally to see whether there are any motor deficits. Expression of CD31, a marker of endothelial cells was done by immunohistochemistry to assess vasoconstriction. Contextual fear conditioning, object recognition and Morris water maze task was performed to examine associative learning and spatial memory deficits. Gait and rotarod was performed to examine if there are any motor deficits. Synaptic plasticity was evaluated as activity dependent protein translation was measured in synaptoneurosomes prepared from hippocampus.ResultThe obstruction in cerebral blood flow due to vasoconstriction caused by ET‐1 injection leads to deficits in associative learning and spatial memory after 7 days. There was no change in gait or rotarod performance indicating no effect on motor function. However, the behavioral dysfunction was temporary and reversed after 30 days of ET‐1 treatment once the blood flow was restored. These changes were demonstrated as drop in the activity dependent protein translation after 7 days of ET‐1 injection and raise after 30 days of treatment as it is an indicator for synaptic plasticity.ConclusionBilateral injection of ET‐1 leads to prominent associative and spatial memory deficit and decline in activity dependent protein translation in hippocampus. Still these defects are reversible once the blood flow is restored. Unilateral injection of ET‐1 did not show any motor dysfunction.