Contextual and cued fear conditioning test using a video analyzing system in mice

Periodontitis-induced neuroinflammation impacts dendritic spine immaturity and cognitive impairment

OBJECTIVE

This study investigated the spinal changes in ligature-induced periodontitis and the role of periodontitis in cognitive impairment.

METHODS

Twenty mice were randomized into the control and chronic periodontitis (CP) groups, with the latter receiving ligature-induced periodontitis. Cognitive performance was assessed by fear conditioning test. Periodontal inflammation and alveolar bone resorption were evaluated by micro-computed tomography and histopathology. The hippocampal microglial activation was evaluated by immunohistochemistry (IHC). The expressions of hippocampal cytokines (TNF-α, iNOS, IL-1β, IL-4, IL-10, and TREM2) were measured by reverse transcription-polymerase chain reaction. The morphology and density of the dendritic spines were determined by Golgi-Cox staining.

RESULTS

The CP mice reported significant inflammatory cell infiltration and alveolar bone resorption, with marked increases in cytokine levels (TNF-α, iNOS, IL-1β, and TREM2) in the brain. Moreover, the CP mice showed significantly reduced freezing to the conditioned stimulus in the cued and contextual tests, indicating impaired memory. Further analyses revealed, in the hippocampus of the CP mice, enhanced microglial activation, decreased dendritic spine density, and increased proportion of thin dendritic spines.

CONCLUSIONS

Periodontitis-induced neuroinflammation may impair the cognitive function by activating hippocampal microglia and inducing dendritic spine immaturity.

Phenotypic Insights Into Anti-IgLON5 Disease in IgLON5-Deficient Mice

BACKGROUND AND OBJECTIVES

Anti-IgLON5 disease is an autoimmune neurodegenerative disorder characterized by various phenotypes, notably sleep and movement disorders and tau pathology. Although the disease is known to be associated with the neuronal cell adhesion protein IgLON5, the physiologic function of IgLON5 remains elusive. There are conflicting views on whether autoantibodies cause loss of function, activation of IgLON5, or inflammation-associated neuronal damage, ultimately leading to the disease. We generated IgLON5 knockout (-/-) mice to investigate the functions of IgLON5 and elucidate the pathomechanism of anti-IgLON5 disease.

METHODS

IgLON5 knockout (-/-) mice underwent behavioral tests investigating motor function, psychiatric function (notably anxiety and depression), social and exploratory behaviors, spatial learning and memory, and sensory perception. Histologic analysis was conducted to investigate tau aggregation in mice with tauopathy.

RESULTS

IgLON5-/- mice had poorer performance in the wire hang and rotarod tests (which are tests for motor function) than wild-type mice. Moreover, IgLON5-/- mice exhibited decreased anxiety-like behavior and/or hyperactivity in behavior tests, including light/dark transition test and open field test. IgLON5-/- mice also exhibited poorer remote memory in the contextual fear conditioning test. However, neither sleeping disabilities assessed by EEG nor tau aggregation was detected in the knockout mice.

DISCUSSION

These results suggest that IgLON5 is associated with activity, anxiety, motor ability, and contextual fear memory. Comparing the various phenotypes of anti-IgLON5 disease, anti-IgLON5 disease might partially be associated with loss of function of IgLON5; however, other phenotypes, such as sleep disorders and tau aggregation, can be caused by gain of function of IgLON5 and/or neuronal damage due to inflammation. Further studies are needed to elucidate the role of IgLON5 in the pathogenesis of anti-IgLON5 diseases.

Differential contribution of canonical and noncanonical NLGN3 pathways to early social development and memory performance

Neuroligin (NLGN) 3 is a postsynaptic cell adhesion protein organizing synapse formation through two different types of transsynaptic interactions, canonical interaction with neurexins (NRXNs) and a recently identified noncanonical interaction with protein tyrosine phosphatase (PTP) δ. Although, NLGN3 gene is known as a risk gene for neurodevelopmental disorders such as autism spectrum disorder (ASD) and intellectual disability (ID), the pathogenic contribution of the canonical NLGN3-NRXN and noncanonical NLGN3-PTPδ pathways to these disorders remains elusive. In this study, we utilized Nlgn3 mutant mice selectively lacking the interaction with either NRXNs or PTPδ and investigated their social and memory performance. Neither Nlgn3 mutants showed any social cognitive deficiency in the social novelty recognition test. However, the Nlgn3 mutant mice lacking the PTPδ pathway exhibited significant decline in the social conditioned place preference (sCPP) at the juvenile stage, suggesting the involvement of the NLGN3-PTPδ pathway in the regulation of social motivation and reward. In terms of learning and memory, disrupting the canonical NRXN pathway attenuated contextual fear conditioning while disrupting the noncanonical NLGN3-PTPδ pathway enhanced it. Furthermore, disruption of the NLGN3-PTPδ pathway negatively affected the remote spatial reference memory in the Barnes maze test. These findings highlight the differential contributions of the canonical NLGN3-NRXN and noncanonical NLGN3-PTPδ synaptogenic pathways to the regulation of higher order brain functions associated with ASD and ID.

Effects of omega-3 supplementation on anxiety-like behaviors and neuroinflammation in Wistar rats following cafeteria diet-induced obesity

ABSTRACTObjetives: Omega-3 (n3) fatty acids have been studied as an option to alleviate the harmful effects of obesity. However, its role in obesity-related behavioral changes is still controversial. This study aimed to evaluate the effects of n3 on behavior and neuroinflammation in obese animals. Methods: Male Wistar rats were divided into four groups: control diet (CT), CT+n3, cafeteria diet (CAF), and CAF+n3. Diet was administered for 13 weeks, and n3 was supplemented during the last 5 weeks. Metabolic and biochemical parameters were evaluated, as well as anxiety-like behaviors. Immunoblots were conducted in the animals' cerebral cortex and hippocampus to assess changes in neuroinflammatory markers.Results: CAF-fed animals showed higher weight gain, visceral adiposity, fasting glucose, total cholesterol, triglycerides, and insulin levels, and n3 improved the lipid profile and restored insulin sensitivity. CAF-fed rats showed anxiety-like behaviors in the open field and light-dark box tasks but not in the contextual aversive conditioning. Omega-3 did not exert any effect on these behaviors. Regarding neuroinflammation, diet and supplementation acted in a region-specific manner. In the hippocampus, CAF reduced claudin-5 expression with no effect of n3, indicating a brain-blood barrier disruption following CAF. Furthermore, in the hippocampus, the glial fibrillary acidic protein (GFAP) and toll-like receptor 4 (TLR-4) were reduced in treated obese animals. However, n3 could not reverse the TLR-4 expression increase in the cerebral cortex.Discussion: Although n3 may protect against some neuroinflammatory manifestations in the hippocampus, it does not seem sufficient to reverse the increase in anxiolytic manifestations caused by CAF.

Brain-enriched guanylate kinase-associated protein, a component of the post-synaptic density protein complexes, contributes to learning and memory

Brain-enriched guanylate kinase-associated protein (BEGAIN) is highly enriched in the post-synaptic density (PSD) fraction and was identified in our previous study as a protein associated with neuropathic pain in the spinal dorsal horn. PSD protein complexes containing N-methyl-D-aspartate receptors are known to be involved in neuropathic pain. Since these PSD proteins also participate in learning and memory, BEGAIN is also expected to play a crucial role in this behavior. To verify this, we first examined the distribution of BEGAIN in the brain. We found that BEGAIN was widely distributed in the brain and highly expressed in the dendritic regions of the hippocampus. Moreover, we found that BEGAIN was concentrated in the PSD fraction of the hippocampus. Furthermore, immunoelectron microscopy confirmed that BEGAIN was localized at the asymmetric synapses. Behavioral tests were performed using BEGAIN-knockout (KO) mice to determine the contribution of BEGAIN toward learning and memory. Spatial reference memory and reversal learning in the Barns circular maze test along with contextual fear and cued fear memory in the contextual and cued fear conditioning test were significantly impaired in BEGAIN-KO mice compared to with those in wild-type mice. Thus, this study reveals that BEGAIN is a component of the post-synaptic compartment of excitatory synapses involved in learning and memory.

Impact of NLRP3 Depletion on Aging-Related Metaflammation, Cognitive Function, and Social Behavior in Mice

Immunosenescence and chronic inflammation associated with old age accompany brain aging and the loss of complex behaviors. Neuroinflammation in the hippocampus plays a pivotal role in the development of cognitive impairment and anxiety. However, the underlying mechanisms have not been fully explained. In this study, we aimed to investigate the disruption of insulin signaling and the mechanisms underlying metabolic inflammation ("metaflammation") in the brains of wild-type (WT) and NLRP3 knockout (KO) mice of different ages. We found a significant upregulation of the NLRP3 inflammasome in the hippocampus during aging, leading to an increase in the expression of phosphorylated metaflammation proteinases and inflammatory markers, along with an increase in the number of senescent cells. Additionally, metaflammation causes anxiety and impairs social preference behavior in aged mice. On the other hand, deletion of NLRP3 improves some behavioral and biochemical characteristics associated with aging, such as signal memory, neuroinflammation, and metabolic inflammation, but not anxious behavior. These results are associated with reduced IL-18 signaling and the PKR/IKKβ/IRS1 pathway as well as the SASP phenotype. In NLRP3 gene deletion conditions, PKR is down-regulated. Therefore, it is likely that slowing aging through various NLRP3 inhibition mechanisms will lessen the corresponding cognitive decline with aging. Thus, the genetic knockout of the NLRP3 inflammasome can be seen as a new therapeutic strategy for slowing down central nervous system (CNS) aging.

Possible role of locus coeruleus neuronal loss in age-related memory and attention deficits

Introduction

Aging is associated with a decline in cognitive abilities, including memory and attention. It is generally accepted that age-related histological changes such as increased neuroinflammatory glial activity and a reduction in the number of specific neuronal populations contribute to cognitive aging. Noradrenergic neurons in the locus coeruleus (LC) undergo an approximately 20 % loss during ageing both in humans and mice, but whether this change contributes to cognitive deficits is not known. To address this issue, we asked whether a similar loss of LC neurons in young animals as observed in aged animals impairs memory and attention, cognitive domains that are both influenced by the noradrenergic system and impaired in aging.

Methods

For that, we treated young healthy mice with DSP-4, a toxin that specifically kills LC noradrenergic neurons. We compared the performance of DSP-4 treated young mice with the performance of aged mice in models of attention and memory. To do this, we first determined the dose of DSP-4, which causes a similar 20 % neuronal loss as is typical in aged animals.

Results

Young mice treated with DSP-4 showed impaired attention in the presence of distractor and memory deficits in the 5-choice serial reaction time test (5-CSRTT). Old, untreated mice showed severe deficits in both the 5-CSRTT and in fear extinction tests.

Discussion

Our data now suggest that a reduction in the number of LC neurons contributes to impaired working memory and greater distractibility in attentional tasks but not to deficits in fear extinction. We hypothesize that the moderate loss of LC noradrenergic neurons during aging contributes to attention deficits and working memory impairments.

Combination of epigallocatechin 3 gallate and curcumin improves D-galactose and normal-aging associated memory impairment in mice

Previously, we observed curcumin improves aging-associated memory impairment in D-galactose (D-gal) and normal-aged (NA) mice. Evidence showed that multiple agents can be used in managing aging-induced memory dysfunction, drawn by the contribution of several pathways. Curcumin and Epigallocatechin 3 gallate (EGCG) combination substantially reduced the oxidative stress that commonly mediates aging. This study examined the combined effect of EGCG and curcumin on memory improvement in two recognized models, D-gal and normal-aged (NA) mice. The co-administration of EGCG and curcumin significantly (p < 0.05) increased retention time detected by passive avoidance (PA) and freezing response determined in contextual fear conditioning (CFC) compared to the discrete administration of EGCG or curcumin. Biochemical studies revealed that the combination of EGCG and curcumin remarkably ameliorated the levels (p < 0.05) of glutathione, superoxide dismutase, catalase, advanced oxidation protein products, nitric oxide, and lipid peroxidation compared to the monotherapy of EGCG or curcumin in mice hippocampi. The behavioral and biochemical studies revealed that the combination of EGCG and curcumin showed better improvement in rescuing aging-associated memory disorders in mice. EGCG and curcumin combination could serve as a better choice in managing aging-related memory disorders.

Comprehensive behavioral analyses of mice with a glycine receptor alpha 4 deficiency

Glycine receptors (GlyRs) are ligand-gated chloride channels comprising alpha (α1-4) and β subunits. The GlyR subunits play major roles in the mammalian central nervous system, ranging from regulating simple sensory information to modulating higher-order brain function. Unlike the other GlyR subunits, GlyR α4 receives relatively little attention because the human ortholog lacks a transmembrane domain and is thus considered a pseudogene. A recent genetic study reported that the GLRA4 pseudogene locus on the X chromosome is potentially involved in cognitive impairment, motor delay and craniofacial anomalies in humans. The physiologic roles of GlyR α4 in mammal behavior and its involvement in disease, however, are not known. Here we examined the temporal and spatial expression profile of GlyR α4 in the mouse brain and subjected Glra4 mutant mice to a comprehensive behavioral analysis to elucidate the role of GlyR α4 in behavior. The GlyR α4 subunit was mainly enriched in the hindbrain and midbrain, and had relatively lower expression in the thalamus, cerebellum, hypothalamus, and olfactory bulb. In addition, expression of the GlyR α4 subunit gradually increased during brain development. Glra4 mutant mice exhibited a decreased amplitude and delayed onset of the startle response compared with wild-type littermates, and increased social interaction in the home cage during the dark period. Glra4 mutants also had a low percentage of entries into open arms in the elevated plus-maze test. Although mice with GlyR α4 deficiency did not show motor and learning abnormalities reported to be associated in human genomics studies, they exhibited behavioral changes in startle response and social and anxiety-like behavior. Our data clarify the spatiotemporal expression pattern of the GlyR α4 subunit and suggest that glycinergic signaling modulates social, startle, and anxiety-like behaviors in mice.

Inflammatory Skin Disease Causes Anxiety Symptoms Leading to an Irreversible Course

Intense itching significantly reduces the quality of life, and atopic dermatitis is associated with psychiatric conditions, such as anxiety and depression. Psoriasis, another inflammatory skin disease, is often complicated by psychiatric symptoms, including depression; however, the pathogenesis of these mediating factors is poorly understood. This study used a spontaneous dermatitis mouse model (KCASP1Tg) and evaluated the psychiatric symptoms. We also used Janus kinase (JAK) inhibitors to manage the behaviors. Gene expression analysis and RT-PCR of the cerebral cortex of KCASP1Tg and wild-type (WT) mice were performed to examine differences in mRNA expression. KCASP1Tg mice had lower activity, higher anxiety-like behavior, and abnormal behavior. The mRNA expression of S100a8 and Lipocalin 2 (Lcn2) in the brain regions was higher in KCASP1Tg mice. Furthermore, IL-1β stimulation increased Lcn2 mRNA expression in astrocyte cultures. KCASP1Tg mice had predominantly elevated plasma Lcn2 compared to WT mice, which improved with JAK inhibition, but behavioral abnormalities in KCASP1Tg mice did not improve, despite JAK inhibition. In summary, our data revealed that Lcn2 is closely associated with anxiety symptoms, but the anxiety and depression symptoms caused by chronic skin inflammation may be irreversible. This study demonstrated that active control of skin inflammation is essential for preventing anxiety.

ILF3 prion-like domain regulates gene expression and fear memory under chronic stress

The prion-like domain (PrLD) is a class of intrinsically disordered regions. Although its propensity to form condensates has been studied in the context of neurodegenerative diseases, the physiological role of PrLD remains unclear. Here, we investigated the role of PrLD in the RNA-binding protein NFAR2, generated by a splicing variant of the Ilf3 gene. Removal of the PrLD in mice did not impair the function of NFAR2 required for survival, but did affect the responses to chronic water immersion and restraint stress (WIRS). The PrLD was required for WIRS-sensitive nuclear localization of NFAR2 and WIRS-induced changes in mRNA expression and translation in the amygdala, a fear-related brain region. Consistently, the PrLD conferred resistance to WIRS in fear-associated memory formation. Our study provides insights into the PrLD-dependent role of NFAR2 for chronic stress adaptation in the brain.

Downregulating PTBP1 Fails to Convert Astrocytes into Hippocampal Neurons and to Alleviate Symptoms in Alzheimer's Mouse Models

Conversion of astroglia into functional neurons has been considered a promising therapeutic strategy for neurodegenerative diseases. Recent studies reported that downregulation of the RNA binding protein, polypyrimidine tract-binding protein 1 (PTBP1), converts astrocytes into neurons in situ in multiple mouse brain regions, consequently improving pathologic phenotypes associated with Parkinson's disease, RGC loss, and aging. Here, we demonstrate that PTBP1 downregulation using an astrocyte-specific AAV-mediated shRNA system fails to convert hippocampal astrocytes into neurons in both male and female wild-type (WT) and β-amyloid (5×FAD) and tau (PS19) Alzheimer's disease (AD) mouse models and fails to reverse synaptic/cognitive deficits and AD-associated pathology in male mice. Similarly, PTBP1 downregulation cannot convert astrocytes into neurons in the striatum and substantia nigra in both male and female WT mice. Together, our study suggests that cell fate conversion strategy for neurodegenerative disease therapy through manipulating one single gene, such as PTBP1, warrants more rigorous scrutiny.SIGNIFICANCE STATEMENT Our results do not support some of the recent extraordinary and revolutionary claims that resident astrocytes can be directly and efficiently converted into neurons. Our study is critical for the field of neural regeneration and degeneration. In addition, our study is financially important because it may prevent other researchers/organizations from wasting a vast amount of time and resources on relevant investigations.

Curcumin improves D-galactose and normal-aging associated memory impairment in mice: In vivo and in silico-based studies

Aging-induced memory impairment is closely associated with oxidative stress. D-Galactose (D-gal) evokes severe oxidative stress and mimics normal aging in animals. Curcumin, a natural flavonoid, has potent antioxidant and anti-aging properties. There are several proteins like glutathione S-transferase A1 (GSTA1), glutathione S-transferase omega-1 (GSTO1), kelch-like ECH-associated protein 1 (KEAP1), beta-secretase 1 (BACE1), and amine oxidase [flavin-containing] A (MAOA) are commonly involved in oxidative stress and aging. This study aimed to investigate the interaction of curcumin to these proteins and their subsequent effect on aging-associated memory impairment in two robust animal models: D-Gal and normal aged (NA) mice. The aging mice model was developed by administering D-gal intraperitoneally (i.p). Mice (n = 64) were divided into the eight groups (8 mice in each group): Vehicle, Curcumin-Control, D-gal (100mg/kg; i.p), Curcumin + D-gal, Astaxanthin (Ast) + D-gal, Normal Aged (NA), Curcumin (30mg/kg Orally) + NA, Ast (20mg/kg Orally) + NA. Retention and freezing memories were assessed by passive avoidance (PA) and contextual fear conditioning (CFC). Molecular docking was performed to predict curcumin binding with potential molecular targets. Curcumin significantly increased retention time (p < 0.05) and freezing response (p < 0.05) in PA and CFC, respectively. Curcumin profoundly ameliorated the levels of glutathione, superoxide dismutase, catalase, advanced oxidation protein products, nitric oxide, and lipid peroxidation in mice hippocampi. In silico studies revealed favorable binding energies of curcumin with GSTA1, GSTO1, KEAP1, BACE1, and MAOA. Curcumin improves retention and freezing memory in D-gal and nature-induced aging mice. Curcumin ameliorates the levels of oxidative stress biomarkers in mice. Anti-aging effects of curcumin could be attributed to, at least partially, the upregulation of antioxidant enzymes through binding with GSTA1, GSTO1, KEAP1, and inhibition of oxidative damage through binding with BACE1 and MAOA.

Reversible Suppression of Fear Memory Recall by Transient Circadian Arrhythmia

We tested the hypothesis that a temporary period of circadian arrhythmia would transiently impair recall of an aversive memory in Siberian hamsters (Phodopus sungorus). Unlike mice or rats, circadian arrhythmia is easily induced in this species by a one-time manipulation of their ambient lighting [i.e., the disruptive phase shift (DPS) protocol]. Hamsters were conditioned to associate footshocks with a shock chamber (context) and with a predictive auditory tone (cue), and then exposed to the DPS protocol. Following DPS, animals either became arrhythmic (ARR), reentrained to the light-dark cycle (ENT), or became arrhythmic for &lt; 14 days before their circadian locomotor rhythms spontaneously recovered and reentrained (ARR-ENT). Tests for contextual memory showed that freezing was decreased 9–10 days post-DPS when both ARR and ARR-ENT groups were arrhythmic. Once ARR-ENT animals reentrained (day 41), however, freezing was elevated back to Pre-DPS levels and did not differ from those observed in ENT hamsters. ENT animals maintained high levels of freezing at both time points, whereas, freezing remained low in ARR hamsters. In contrast to contextual responses, cued responses were unaffected by circadian arrhythmia; all three groups exhibited elevated levels of freezing in response to the tones. The differential impact of circadian arrhythmia on contextual versus cued associative memory suggests that arrhythmia preferentially impacts memory processes that depend on the hippocampus.

Memantine Disrupts Motor Coordination through Anxiety-like Behavior in CD1 Mice

Memantine is an FDA approved drug for the treatment of Alzheimer’s disease. It reduces neurodegeneration in the hippocampus and cerebral cortex through the inhibition of extrasynaptic NMDA receptors in patients and mouse models. Potentially, it could prevent neurodegeneration in other brain areas and caused by other diseases. We previously used memantine to prevent functional damage and to retain morphology of cerebellar neurons and Bergmann glia in an optogenetic mouse model of spinocerebellar ataxia type-1 (SCA1). However, before suggesting wider use of memantine in clinics, its side effects must be carefully evaluated. Blockers of NMDA receptors are controversial in terms of their effects on anxiety. Here, we investigated the effects of chronic application of memantine over 9 weeks to CD1 mice and examined rotarod performance and anxiety-related behaviors. Memantine-treated mice exhibited an inability to adapt to anxiety-causing conditions which strongly affected their rotarod performance. A tail suspension test revealed increased signs of behavioral despair. These data provide further insights into the potential deleterious effects of memantine which may result from the lack of adaptation to novel, stressful conditions. This effect of memantine may affect the results of tests used to assess motor performance and should be considered during clinical trials of memantine in patients.

Geraniol enhances inhibitory inputs to the paraventricular thalamic nucleus and induces sedation in mice

BACKGROUND

Plant extracts with sedative effects have a long history of clinical use for treating insomnia and epilepsy. Geraniol (GE), a plant-derived acyclic monoterpene, reduces locomotion and prolongs barbiturate-induced anesthesia in rats. However, the mechanisms of GE in sedation remain elusive.

PURPOSE

This study aimed to investigate the mechanisms of GE in sedation in mice.

METHODS

GE was administered systemically by nebulization and intraperitoneal injection. Open field tests, acute seizure tests, and electroencephalogram (EEG) recordings were performed to examine the sedative effects of GE in mice. The time of loss of the righting reflex and return of the righting reflex were recorded in anesthesia experiments to examine the effect of GE on anesthesia. In vitro c-Fos staining and in vivo fiber photometry recordings were performed to detect the activity change of the paraventricular thalamic nucleus (PVT). Microinjection of GE into PVT and related behavioral tests were performed to confirm that PVT was a critical target for GE. Whole-cell recordings were performed to dissect the effects of GE on PVT neurons via GABAA receptors. Molecular docking was performed to examine the interaction between GE and GABAA receptor subunits.

RESULTS

We found that GE reduced locomotion, relieved acute seizures, altered the EEG, and facilitated general anesthesia in mice. Next, we found that GE decreased c-Fos expression and suppressed the calcium activity in PVT. Microinjection of GE into PVT reduced locomotion and facilitated anesthesia. Furthermore, electrophysiology results showed that GE induced dramatic membrane hyperpolarization and suppressed the activity of PVT neurons, mainly by prolonging spontaneous inhibitory postsynaptic currents and inducing tonic inhibitory currents. Molecular docking results indicated that the β3 subunit might be a potential target for GE.

CONCLUSION

By combined using behavioral tests, immunohistochemistry, calcium recording, and electrophysiology, we systematically revealed that GE inhibits PVT and induces sedation in mice. Essential oils have long been considered part of traditional medicine, and they are playing a critical role in aromatherapy. Since GE has a comparatively ideal safety property and multiple delivery methods, GE has great application potential in aromatherapy. Our study also provides a potential candidate for further development of sedatives and anaesthetics.

Metabolic reprogramming in astrocytes results in neuronal dysfunction in intellectual disability

Astrocyte aerobic glycolysis provides vital trophic support for central nervous system neurons. However, whether and how astrocytic metabolic dysregulation contributes to neuronal dysfunction in intellectual disability (ID) remain unclear. Here, we demonstrate a causal role for an ID-associated SNX27 mutation (R198W) in cognitive deficits involving reshaping astrocytic metabolism. We generated SNX27R196W (equivalent to human R198W) knock-in mice and found that they displayed deficits in synaptic function and learning behaviors. SNX27R196W resulted in attenuated astrocytic glucose uptake via GLUT1, leading to reduced lactate production and a switch from homeostatic to reactive astrocytes. Importantly, lactate supplementation or a ketogenic diet restored neuronal oxidative phosphorylation and reversed cognitive deficits in SNX27R196W mice. In summary, we illustrate a key role for astrocytic SNX27 in maintaining glucose supply and glycolysis and reveal that altered astrocytic metabolism disrupts the astrocyte-neuron interaction, which contributes to ID. Our work also suggests a feasible strategy for treating ID by restoring astrocytic metabolic function.

Long-term exercise pre-training attenuates Alzheimer's disease-related pathology in a transgenic rat model of Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia. Despite enormous efforts around the world, there remains no effective cure for AD. This study was performed to investigate the effects of long-term exercise pretreatment on the typical pathology of AD in a novel transgenic AD rat model. Male 2-month-old animals were divided into the following groups: wild-type (WT) rats, AD rats, and AD rats with treadmill exercise pretreatment (AD-Exe). After exercise pretreatment, the Barnes maze task, passive avoidance task, and cued fear conditioning test were performed to test learning and memory function. The elevated plus maze, open field test, sucrose preference test, and forced swim test were conducted to measure anxious-depressive-like behavior. Immunofluorescence staining, Golgi staining, transmission electron microscopy, Western blot analysis, F-Jade C staining, TUNEL staining, and related assay kits were conducted to measure Aβ plaques, tau hyperphosphorylation, neuronal damage, neuronal degeneration, dendritic spine density, synapses, synaptic vesicles, mitochondrial morphology, mitochondrial dynamic, oxidative stress, and neuroinflammation. Behavioral tests revealed that long-term exercise pretreatment significantly alleviated learning and memory dysfunction and anxious-depressive-like behaviors in AD animals. In addition, exercise pretreatment attenuated amyloid-β deposition and tau hyperphosphorylation and preserved spine density, synapses, and presynaptic vesicles. Exercise also inhibited neuronal damage, neuronal apoptosis, and neuronal degeneration. Additional studies revealed the imbalance of mitochondrial dynamics was significantly inhibited by exercise pretreatment accompanied by a remarkable suppression of oxidative stress and neuroinflammation. Our findings suggest that long-term exercise pretreatment alleviated behavioral deficits and typical pathologies of the AD rat model, supporting long-term exercise pretreatment as a potential approach to delay the progression of AD.

Abnormal lipid droplets accumulation induced cognitive deficits in obstructive sleep apnea syndrome mice via JNK/SREBP/ACC pathway but not through PDP1/PDC pathway

The mechanisms of chronic intermittent hypoxia (CIH)-induced cognitive deficits remain unclear. Here, our study found that about 3 months CIH treatment induced lipid droplets (LDs) accumulation in hippocampal nerve and glia cells of C57BL/6 mice, and caused severe neuro damage including neuron lesions, neuroblast (NB) apoptosis and abnormal glial activation. Studies have shown that the neuronal metabolism disorders might contribute to the CIH induced-hippocampal impairment. Mechanistically, the results showed that pyruvate dehydrogenase complex E1ɑ subunit (PDHA1) and the pyruvate dehydrogenase complex (PDC) activator pyruvate dehydrogenase phosphatase 1 (PDP1) did not noticeable change after intermittent hypoxia. Consistent with those results, the level of Acetyl-CoA in hippocampus did not significantly change after CIH exposure. Interestingly, we found that CIH produced large quantities of ROS, which activated the JNK/SREBP/ACC pathway in nerve and glia cells. ACC catalyzed the carboxylation of Acetyl-CoA to malonyl-CoA and then more lipid acids were synthesized, which finally caused aberrant LDs accumulation. Therefore, the JNK/SREBP/ACC pathway played a crucial role in the cognitive deficits caused by LDs accumulation after CIH exposure. Additionally, LDs were peroxidized by the high level of ROS under CIH conditions. Together, lipid metabolic disorders contributed to nerve and glia cells damage, which ultimately caused behavioral dysfunction. An active component of Salvia miltiorrhiza, SMND-309, dramatically alleviated these injuries and improved cognitive deficits of CIH mice.

Neuronal Menin Overexpression Rescues Learning and Memory Phenotype in CA1-Specific α7 nAChRs KD Mice

The perturbation of nicotinic cholinergic receptors is thought to underlie many neurodegenerative and neuropsychiatric disorders, such as Alzheimer's and schizophrenia. We previously identified that the tumor suppressor gene, MEN1, regulates both the expression and synaptic targeting of α7 nAChRs in the mouse hippocampal neurons in vitro. Here we sought to determine whether the α7 nAChRs gene expression reciprocally regulates the expression of menin, the protein encoded by the MEN1 gene, and if this interplay impacts learning and memory. We demonstrate here that α7 nAChRs knockdown (KD) both in in vitro and in vivo, initially upregulated and then subsequently downregulated menin expression. Exogenous expression of menin using an AAV transduction approach rescued α7 nAChRs KD mediated functional and behavioral deficits specifically in hippocampal (CA1) neurons. These effects involved the modulation of the α7 nAChR subunit expression and functional clustering at the synaptic sites. Our data thus demonstrates a novel and important interplay between the MEN1 gene and the α7 nAChRs in regulating hippocampal-dependent learning and memory.

Neuron-specific ablation of eIF5A or deoxyhypusine synthase leads to impairments in growth, viability, neurodevelopment, and cognitive functions in mice

Eukaryotic initiation factor 5A (eIF5A)†,‡ is an essential protein that requires a unique amino acid, hypusine, for its activity. Hypusine is formed exclusively in eIF5A post-translationally via two enzymes, deoxyhypusine synthase (DHPS) and deoxyhypusine hydroxylase. Each of the genes encoding these proteins, Eif5a, Dhps, and Dohh, is required for mouse embryonic development. Variants in EIF5A or DHPS were recently identified as the genetic basis underlying certain rare neurodevelopmental disorders in humans. To investigate the roles of eIF5A and DHPS in brain development, we generated four conditional KO mouse strains using the Emx1-Cre or Camk2a-Cre strains and examined the effects of temporal- and region-specific deletion of Eif5a or Dhps. The conditional deletion of Dhps or Eif5a by Emx1 promotor-driven Cre expression (E9.5, in the cortex and hippocampus) led to gross defects in forebrain development, reduced growth, and premature death. On the other hand, the conditional deletion of Dhps or Eif5a by Camk2a promoter-driven Cre expression (postnatal, mainly in the CA1 region of the hippocampus) did not lead to global developmental defects; rather, these KO animals exhibited severe impairment in spatial learning, contextual learning, and memory when subjected to the Morris water maze and a contextual learning test. In both models, the Dhps-KO mice displayed more severe impairment than their Eif5a-KO counterparts. The observed defects in the brain, global development, or cognitive functions most likely result from translation errors due to a deficiency in active, hypusinated eIF5A. Our study underscores the important roles of eIF5A and DHPS in neurodevelopment.

NLRP3 Inflammasome Blocking as a Potential Treatment of Central Insulin Resistance in Early-Stage Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a devastating neurodegenerative disorder. In recent years, attention of researchers has increasingly been focused on studying the role of brain insulin resistance (BIR) in the AD pathogenesis. Neuroinflammation makes a significant contribution to the BIR due to the activation of NLRP3 inflammasome. This study was devoted to the understanding of the potential therapeutic roles of the NLRP3 inflammasome in neurodegeneration occurring concomitant with BIR and its contribution to the progression of emotional disorders.

METHODS

To test the impact of innate immune signaling on the changes induced by Aβ1-42 injection, we analyzed animals carrying a genetic deletion of the Nlrp3 gene. Thus, we studied the role of NLRP3 inflammasomes in health and neurodegeneration in maintaining brain insulin signaling using behavioral, electrophysiological approaches, immunohistochemistry, ELISA and real-time PCR.

RESULTS

We revealed that NLRP3 inflammasomes are required for insulin-dependent glucose transport in the brain and memory consolidation. Conclusions NLRP3 knockout protects mice against the development of BIR: Taken together, our data reveal the protective role of Nlrp3 deletion in the regulation of fear memory and the development of Aβ-induced insulin resistance, providing a novel target for the clinical treatment of this disorder.

Secondary hypoxic ischemia alters neurobehavioral outcomes, neuroinflammation, and oxidative stress in mice exposed to controlled cortical impact

Objective

Hypoxic ischemia (HI) is a secondary insult that can cause fatal neurologic outcomes after traumatic brain injury (TBI), ranging from mild cognitive deficits to persistent vegetative states. We here aimed to unravel the underlying pathological mechanisms of HI injury in a TBI mouse model.

Methods

Neurobehavior, neuroinflammation, and oxidative stress were assessed in a mouse model of controlled cortical impact (CCI) injury followed by HI. Mice underwent CCI alone, CCI followed by HI, HI alone, or sham operation. HI was induced by one-vessel carotid ligation with 1 hour of 8% oxygen in nitrogen. Learning and memory were assessed using the novel object recognition test, contextual and cued fear conditioning, and Barnes maze test. Brain cytokine production and oxidative stress-related components were measured.

Results

Compared to TBI-only animals, TBI followed by HI mice exhibited significantly poorer survival and health scores, spatial learning and memory in the Barnes maze test, discrimination memory in the novel object recognition test, and fear memory following contextual and cued fear conditioning. Malondialdehyde levels were significantly lower, whereas glutathione peroxidase activity was significantly higher in TBI followed by HI mice compared to TBI-only and sham counterparts, respectively. Interleukin-6 levels were significantly higher in TBI followed by HI mice compared to both TBI-only and sham animals.

Conclusion

Post-traumatic HI aggravated deficits in spatial, fear, and discrimination memory in an experimental TBI mouse model. Our results suggest that increased neuroinflammation and oxidative stress contribute to HI-induced neurobehavioral impairments after TBI.

Long-term molecular differences between resilient and susceptible mice after a single traumatic exposure

BACKGROUND AND PURPOSE

PTSD is a heterogeneous disorder induced by trauma, resulting in severe long-term impairments of an individual's mental health. Interestingly, PTSD does not develop in every individual; thus, some individuals are more resilient than others. However, the underlying molecular mechanisms are poorly understood. Here, we aimed at shedding light on these processes.

EXPERIMENTAL APPROACH

We used a single-trauma PTSD model in mice to induce long-term maladaptive behaviours and profiled the mice four weeks post-trauma into resilient or susceptible individuals. The phenotype's classification was based on their individual responses in different behavioural experiments. We analysed microbiome, circulating endocannabinoids, and long-term changes in brain phospholipid and transcript levels.

KEY RESULTS

We found a plethora of molecular differences between resilient and susceptible individuals across multiple molecular domains, including lipidome, transcriptome, and gut microbiome. Some of these differences were stable even several weeks after the trauma, indicating the long-term impact of traumatic stimuli on the organism's physiology. Furthermore, the integration of these multi-layered molecular data revealed that resilient and susceptible individuals have very distinct molecular signatures across various physiological systems.

CONCLUSIONS AND IMPLICATIONS

We showed that trauma induces individual-specific behavioural responses that, in combination with a longitudinal characterization of mice, can be used to identify distinct sub-phenotypes within the trauma-exposed group. These groups differ significantly not only in their behaviour but also in specific molecular aspects across a variety of tissues and brain regions. This approach may reveal new targets and predictive biomarkers for the pharmacological treatment and prognosis of stress-related disorders.

Translational relevance of behavioral, neural, and electroencephalographic profiles in a mouse model of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a severe, long-term psychological disorder triggered by distressing events. The neural basis and underlying mechanisms of PTSD are not completely understood. Therefore, it is important to determine the pathology of PTSD using reliable animal models that mimic the symptoms of patients. However, the lack of evidence on the clinical relevance of PTSD animal models makes it difficult to interpret preclinical studies from a translational perspective. In this study, we performed a comprehensive screening of the behavioral, neuronal, glial, and electroencephalographic (EEG) profiles in the single prolonged stress and electric foot shock (SPS&S) mouse model. Based on the clinical features of PTSD, we observed fearful and excessive responses to trauma-related environments in the SPS&S mouse model that lasted longer than 14 days. The mice exhibited a defective and strong resistance to the extinction of fear memories caused by auditory cues and also showed enhanced innate fear induced by visual stimuli with concomitant phobias and anxiety. Furthermore, neurons, astrocytes, and microglia in PTSD-related brain regions were activated, supporting abnormal brain activation and neuroimmune changes. EEG assessment also revealed decreased power and impaired coupling strength between cortical regions. These results demonstrated that the SPS&S mouse model recapitulates the behavioral symptoms as well as neural and EEG profiles of PTSD patients, justifying the preclinical use of this mouse model.

Pharmacological Screening of Viola odorata L. for Memory-Enhancing Effect via Modulation of Oxidative Stress and Inflammatory Biomarkers

Purpose: Alzheimer disease (AD) is a progressive neurodegenerative disorder that is caused by neuroinflammation and oxidative stress. The present study aimed to characterize and then investigate the memory-enhancing potential of Viola odorata methanolic extract in lipopolysaccharide (LPS)–treated mice.

Methods:V. odorata characterization was done by using the GCMS technique. Neuroinflammation was induced by the intracerebroventricular administration of LPS at a dose of 12 µg. Animals were divided randomly into six groups (n = 10). Group I was normal control, which was given vehicle. Group II was disease control, which received LPS (12 µg) via the intracerebroventricular route. Group III was standard, which was administered with donepezil (3 µg) orally for 21 days. Groups IV–VI were the treatment groups, which were administered with the extract at 100, 200, and 400 mg/kg dose levels orally respectively for 21 days. Groups III–VI received LPS (12 µg) on the first day along with their treatments. During the treatment, the animals were assessed for memory retention by employing different behavioral paradigms namely elevated plus maze, passive avoidance, foot shock and open field. Various mediators [endogenous antioxidants, neurotransmitters, and acetylcholinesterase (AChE)] involved in the pathogenesis of AD were quantified by using the UV spectrophotometric method.

Results: Extract-treated groups showed a remarkable improvement in cognitive impairment in all behavioral paradigms. Oxidative stress biomarkers, that is, superoxide dismutase, catalase, and glutathione were raised dose-dependently in the treatment groups with a dose-dependent decrease in the malonaldehyde and AChE levels in the brains of the treated animals. The treatment groups showed decreased levels of inflammatory biomarkers, that is, tumor necrosis factor–alpha, nuclear factor kappa light-chain enhancer of activated β-cells, and cyclo-oxygenase, which supports the therapeutic effectiveness of the treatment.

Conclusion: Based on behavioral, oxidative stress biomarker, and neuroinflammatory data, it is concluded that V. odorata possesses memory-enhancing activity and may prove a beneficial role in the management of AD.

IGF-1 facilitates extinction of conditioned fear

Insulin-like growth factor-1 (IGF-1) plays a key role in synaptic plasticity, spatial learning, and anxiety-like behavioral processes. While IGF-1 regulates neuronal firing and synaptic transmission in many areas of the central nervous system, its signaling and consequences on excitability, synaptic plasticity, and animal behavior dependent on the prefrontal cortex remain unexplored. Here, we show that IGF-1 induces a long-lasting depression of the medium and slow post-spike afterhyperpolarization (mAHP and sAHP), increasing the excitability of layer 5 pyramidal neurons of the rat infralimbic cortex. Besides, IGF-1 mediates a presynaptic long-term depression of both inhibitory and excitatory synaptic transmission in these neurons. The net effect of this IGF-1-mediated synaptic plasticity is a long-term potentiation of the postsynaptic potentials. Moreover, we demonstrate that IGF-1 favors the fear extinction memory. These results show novel functional consequences of IGF-1 signaling, revealing IGF-1 as a key element in the control of the fear extinction memory.

Loss of Ftsj1 perturbs codon-specific translation efficiency in the brain and is associated with X-linked intellectual disability

FtsJ RNA 2'-O-methyltransferase 1 (FTSJ1) gene has been implicated in X-linked intellectual disability (XLID), but the molecular pathogenesis is unknown. We show that Ftsj1 is responsible for 2'-O-methylation of 11 species of cytosolic transfer RNAs (tRNAs) at the anticodon region, and these modifications are abolished in Ftsj1 knockout (KO) mice and XLID patient-derived cells. Loss of 2'-O-methylation in Ftsj1 KO mouse selectively reduced the steady-state level of tRNA^Phe in the brain, resulting in a slow decoding at Phe codons. Ribosome profiling showed that translation efficiency is significantly reduced in a subset of genes that need to be efficiently translated to support synaptic organization and functions. Ftsj1 KO mice display immature synaptic morphology and aberrant synaptic plasticity, which are associated with anxiety-like and memory deficits. The data illuminate a fundamental role of tRNA modification in the brain through regulation of translation efficiency and provide mechanistic insights into FTSJ1-related XLID.

NLRP3 deficiency-induced hippocampal dysfunction and anxiety-like behavior in mice

Neuroinflammation has been classified as a trigger of behavioral alterations and cognitive impairments in many neurological conditions, including Alzheimer's disease, major depression, anxiety and others. Regardless of the cause of neuroinflammation, key molecules, which sense neuropathological conditions, are intracellular multiprotein signaling inflammasomes. Increasing evidence shows that the inflammatory response, mediated by activated nucleotide-binding oligomerization domain-, leucine-rich repeat- and pyrin domain-containing 3 (NLRP3) inflammasomes, is associated with the onset and progression of a wide range of diseases of the CNS. However, whether the NLRP3 inflammasome in the CNS is involved in the learning, development of anxiety and adult neurogenesis remains elusive. Therefore, the present study was designed to assess NLRP3 inflammasome contribution in anxiety and reveal its potential involvement in the experimental acquisition of fear responses and hippocampal neurogenesis. Behavioral, immunohistochemical and electrophysiological alterations were measured to evaluate role of neuroinflammation in the limbic system of mice. In this study, we describe interrelated neurophysiological mechanisms, which culminate in absence of NLRP3 inflammasome in young 4 months mice. These include the following: anxious behavior and deterioration in learning and memory of fear conditioning; impairment of adult neurogenesis; reduction and altered morphology of astrocytes in the brain; hyperexcitability in basolateral amygdala (BLA); impaired activation in axons of pyramidal cells of CA1 hippocampal zone in NLRP3 KO mice particularly via the Schaffer collateral pathway; and impaired synaptic transduction in pyramidal cells mediated by an embarrassment of neurotransmitter release from presynaptic site in CA3 hippocampal zone. The present study has demonstrated the novel findings that basal level of NLRP3 inflammasome in the brain of young mice is required for conditioning-induced plasticity in the ventral hippocampus and the basolateral amygdala. The deletion of NLRP3 impair synaptic transduction and caused anxiety-like behavior and labored fear learning, suggesting that low grade inflammation, mediated by NLRP3 expression, play a key role in memory consolidation.

Vasopressin escape and memory impairment in a model of chronic syndrome of inappropriate secretion of antidiuretic hormone in mice

Recently, chronic hyponatremia, even mild, has shown to be associated with poor quality of life and high mortality. The mechanism by which hyponatremia contributes to those symptoms, however, remains to be elucidated. Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a primary cause of hyponatremia. Appropriate animal models are crucial for investigating the pathophysiology of SIADH. A rat model of SIADH has been generally used and mouse models have been rarely used. In this study, we developed a mouse model of chronic SIADH in which stable and sustained hyponatremia occurred after 3-week continuous infusion of the vasopressin V2 receptor agonist 1-desamino-8-D-arginine vasopressin (dDAVP) and liquid diet feeding to produce chronic water loading. Weight gain in chronic SIADH mice at week 2 and 3 after starting dDAVP injection was similar to that of control mice, suggesting that the animals adapted to chronic hyponatremia and grew up normally. AQP2 expression in the kidney, which reflects the renal action of vasopressin, was decreased in dDAVP-infused water-loaded mice as compared with control mice that received the same dDAVP infusion but were fed pelleted chow. These results suggest that "vasopressin escape" occurred, which is an important process for limiting potentially fatal severe hyponatremia. Behavioral analyses using the contextual and cued fear conditioning test and T-maze test demonstrated cognitive impairment, especially working memory impairment, in chronic SIADH mice, which was partially restored after correcting hyponatremia. Our results suggest that vasopressin escape occurred in chronic SIADH mice and that chronic hyponatremia contributed to their memory impairment.

Mice with cleavage-resistant N-cadherin exhibit synapse anomaly in the hippocampus and outperformance in spatial learning tasks

N-cadherin is a homophilic cell adhesion molecule that stabilizes excitatory synapses, by connecting pre- and post-synaptic termini. Upon NMDA receptor (NMDAR) activation by glutamate, membrane-proximal domains of N-cadherin are cleaved serially by a-disintegrin-and-metalloprotease 10 (ADAM10) and then presenilin 1(PS1, catalytic subunit of the γ-secretase complex). To assess the physiological significance of the initial N-cadherin cleavage, we engineer the mouse genome to create a knock-in allele with tandem missense mutations in the mouse N-cadherin/Cadherin-2 gene (Cdh2 R714G, I715D, or GD) that confers resistance on proteolysis by ADAM10 (GD mice). GD mice showed a better performance in the radial maze test, with significantly less revisiting errors after intervals of 30 and 300 s than WT, and a tendency for enhanced freezing in fear conditioning. Interestingly, GD mice reveal higher complexity in the tufts of thorny excrescence in the CA3 region of the hippocampus. Fine morphometry with serial section transmission electron microscopy (ssTEM) and three-dimensional (3D) reconstruction reveals significantly higher synaptic density, significantly smaller PSD area, and normal dendritic spine volume in GD mice. This knock-in mouse has provided in vivo evidence that ADAM10-mediated cleavage is a critical step in N-cadherin shedding and degradation and involved in the structure and function of glutamatergic synapses, which affect the memory function.

Trisomy 21-induced dysregulation of microglial homeostasis in Alzheimer's brains is mediated by USP25

Down syndrome (DS), caused by trisomy of chromosome 21, is the most significant risk factor for early-onset Alzheimer's disease (AD); however, underlying mechanisms linking DS and AD remain unclear. Here, we show that triplication of homologous chromosome 21 genes aggravates neuroinflammation in combined murine DS-AD models. Overexpression of USP25, a deubiquitinating enzyme encoded by chromosome 21, results in microglial activation and induces synaptic and cognitive deficits, whereas genetic ablation of Usp25 reduces neuroinflammation and rescues synaptic and cognitive function in 5×FAD mice. Mechanistically, USP25 deficiency attenuates microglia-mediated proinflammatory cytokine overproduction and synapse elimination. Inhibition of USP25 reestablishes homeostatic microglial signatures and restores synaptic and cognitive function in 5×FAD mice. In summary, we demonstrate an unprecedented role for trisomy 21 and pathogenic effects associated with microgliosis as a result of the increased USP25 dosage, implicating USP25 as a therapeutic target for neuroinflammation in DS and AD.

Neuroprotective Effect of Cudrania tricuspidata Fruit Extracts on Scopolamine-Induced Learning and Memory Impairment

Cudrania tricuspidata has diverse biological activities, such as antioxidant, anti-inflammatory, anticancer, and neuroprotective effects. This study investigated the protective effects of C. tricuspidata fruit extracts (CTFE) against scopolamine (SCO)-induced neuron impairment. The neuroprotective effects of CTFE on SCO-induced memory dysfunction were confirmed in mice using the Barnes maze test. The results showed that co-treatment of SCO and CTFE increased the stay time in the target zone compared with SCO treatment alone. Similarly, the results obtained by the fear conditioning test revealed that SCO-CTFE co-treatment induced the freezing action time under both the contextual fear condition and the cued fear condition compared with SCO treatment alone. Moreover, we showed that CTFE reduced the SCO-induced acetylcholinesterase (AChE) activity, thereby increasing the acetylcholine concentration in mice hippocampal tissues. Consistent with the improvement of memory and recognition function in vivo, our in vitro results showed that CTFE induced cAMP response element binding protein (CREB) and extracellular regulated kinase 1/2 (ERK1/2) activity in PC12 cells and reduced SCO-induced AChE activity. In addition, the microarray results of the hippocampal tissue support our data showing that CTFE affects gene expressions associated with neurogenesis and neuronal cell differentiation markers such as spp1 and klk6. Overall, CTFE exerts a neuroprotective effect via regulation of the CREB and ERK1/2 signaling pathways and could be a therapeutic candidate for neurodegenerative diseases.

Protrudin-deficient mice manifest depression-like behavior with abnormalities in activity, attention, and cued fear-conditioning

Protrudin is a protein that resides in the membrane of the endoplasmic reticulum and is highly expressed in the nervous system. Although mutations in the human protrudin gene (ZFYVE27, also known as SPG33) give rise to hereditary spastic paraplegia (HSP), the physiological role of the encoded protein has been largely unclear. We therefore generated mice deficient in protrudin and subjected them to a battery of behavioral tests designed to examine their intermediate phenotypes. The protrudin-deficient mice were found to have a reduced body size and to manifest pleiotropic behavioral abnormalities, including hyperactivity, depression-like behavior, and deficits in attention and fear-conditioning memory. They exhibited no signs of HSP, however, consistent with the notion that HSP-associated mutations of protrudin may elicit neural degeneration, not as a result of a loss of function, but rather as a result of a gain of toxic function. Overall, our results suggest that protrudin might play an indispensable role in normal neuronal development and behavior.

Visually cued fear conditioning test for memory impairment related to cortical function

AIM

Fear conditioning tests are intended to elucidate a subject's ability to associate a conditioned stimulus with an aversive, unconditioned stimulus, such as footshock. Among these tests, a paradigm related to precise cortical functions would be increasingly important in drug screening for disorders such as schizophrenia and dementia. Therefore, we established a new fear conditioning paradigm using a visual cue in mice. In addition, the validity of the test was evaluated using a genetically engineered mouse, heterozygous deficient in Mdga1 (Mdga1+/-), which is related to schizophrenia.

RESULTS

Mice were given footshocks associated with a visual cue of moving gratings at training in 25-minute sessions. The mice showed the conditioned response of freezing behavior to the visual stimulus at testing 24 hours after the footshocks. In the test for validation, the Mdga1+/- deficient mice showed significantly less freezing than wild-type mice.

CONCLUSION

The visually cued fear conditioning paradigm with moving gratings has been established, which is experimentally useful to evaluate animal cortical functions. The validity of the test was confirmed for Mdga1-deficient mice with possible deficiency in cortical functions.

Selective neuronal degeneration in MATR3 S85C knock-in mouse model of early-stage ALS

A missense mutation, S85C, in the MATR3 gene is a genetic cause for amyotrophic lateral sclerosis (ALS). It is unclear how the S85C mutation affects MATR3 function and contributes to disease. Here, we develop a mouse model that harbors the S85C mutation in the endogenous Matr3 locus using the CRISPR/Cas9 system. MATR3 S85C knock-in mice recapitulate behavioral and neuropathological features of early-stage ALS including motor impairment, muscle atrophy, neuromuscular junction defects, Purkinje cell degeneration and neuroinflammation in the cerebellum and spinal cord. Our neuropathology data reveals a loss of MATR3 S85C protein in the cell bodies of Purkinje cells and motor neurons, suggesting that a decrease in functional MATR3 levels or loss of MATR3 function contributes to neuronal defects. Our findings demonstrate that the MATR3 S85C mouse model mimics aspects of early-stage ALS and would be a promising tool for future basic and preclinical research.

Distinct signals in medial and lateral VTA dopamine neurons modulate fear extinction at different times

Dopamine (DA) neurons are thought to encode reward prediction error (RPE), in addition to other signals, such as salience. While RPE is known to support learning, the role of salience in learning remains less clear. To address this, we recorded and manipulated VTA DA neurons in mice during fear extinction. We applied deep learning to classify mouse freezing behavior, eliminating the need for human scoring. Our fiber photometry recordings showed DA neurons in medial and lateral VTA have distinct activity profiles during fear extinction: medial VTA activity more closely reflected RPE, while lateral VTA activity more closely reflected a salience-like signal. Optogenetic inhibition of DA neurons in either region slowed fear extinction, with the relevant time period for inhibition differing across regions. Our results indicate salience-like signals can have similar downstream consequences to RPE-like signals, although with different temporal dependencies.

Germinated Brown Rice Attenuates Cell Death in Vascular Cognitive Impaired Mice and Glutamate-Induced Toxicity In HT22 Cells

Germinated brown rice (GBR) with unpolishing, soaking, and germinating processes can improve the texture, flavor, and nutritional value, including GABA and phenolic contents. The effect of GBR was first investigated in vascular cognitive impaired mice and glutamate-induced toxicity in HT22 cells with respect to standard pure GABA. Feeding mice with GBR for 5 weeks showed neuroprotection. In this study, the modified bilateral common carotid artery occlusion mice model was mild but a significant difference in cognitive impairment was still shown. Like pure GABA, GBR decreased cognitive deficits in memory behavioral tests and significantly attenuated hippocampal neuronal cell death at P < 0.001. Similarly to 0.125 μM of GABA, 100 μg/mL of GBR increased HT22 cell viability after glutamate toxicity. GBR affected less apoptotic cell death and less blocking by the GABA_A antangonist bicuculline in comparison to GABA. When the results are taken together, the underlying mechanism of GBR protection may mediate though the GABA_A receptor and its phenolic contents.

Forebrain excitatory neuron-specific SENP2 knockout mouse displays hyperactivity, impaired learning and memory, and anxiolytic-like behavior

Sentrin/SUMO-specific protease 2 (SENP2) is a member of SENPs family involved in maturation of SUMO precursors and deSUMOylation of specific target, and is highly expressed in the central nervous system (CNS). Although SENP2 has been shown to modulate embryonic development, fatty acid metabolism, atherosclerosis and epilepsy, the function of SENP2 in the CNS remains poorly understood. To address the role of SENP2 in the CNS and its potential involvement in neuropathology, we generated SENP2 conditional knockout mice by crossing floxed SENP2 mice with CaMKIIα-Cre transgenic mice. Behavioral tests revealed that SENP2 ablation induced hyper-locomotor activity, anxiolytic-like behaviors, spatial working memory impairment and fear-associated learning defect. In line with these observations, our RNA sequencing (RNA-seq) data identified a variety of differential expression genes that are particularly enriched in locomotion, learning and memory related biologic process. Taken together, our results indicated that SENP2 plays a critical role in emotional and cognitive regulation. This SENP2 conditional knockout mice model may help reveal novel mechanisms that underlie a variety of neuropsychiatric disorders associated with anxiety and cognition.

Overview on Emotional Behavioral Testing in Rodent Models of Pediatric Epilepsy

Psychiatric and cognitive disturbances are the most common comorbidities of epileptic disorders in children. The successful treatment of these comorbidities faces many challenges including their etiologically heterogonous nature. Translational neurobehavioral research in age-tailored and clinically relevant rodent seizure models offers a controlled setting to investigate emotional and cognitive behavioral disturbances, their causative factors, and potentially novel treatment interventions. In this review, we propose a conceptual framework that provides a nonsubjective approach to rodent emotional behavioral testing with a focus on the clinically relevant outcome of behavioral response adaptability. We also describe the battery of neurobehavioral tests that we tailored to seizure models with prominent amygdalo-hippocampal involvement, including testing panels for anxiety-like, exploratory, and hyperactive behaviors (the open-field and light-dark box tests), depressive-like behaviors (the forced swim test), and visuospatial navigation (Morris water maze). The review also discusses the modifications we introduced to active avoidance testing in order to simultaneously test auditory and hippocampal-dependent emotionally relevant learning and memory. When interpreting the significance and clinical relevance of the behavioral responses obtained from a given testing panel, it is important to avoid a holistic disease-based approach as a specific panel may not necessarily mirror a disease entity. The analysis of measurable behavioral responses has to be performed in the context of outcomes obtained from multiple related and complementary neurobehavioral testing panels. Behavioral testing is also complemented by mechanistic electrophysiological and molecular investigations.

Tsukushi is essential for the development of the inner ear

Tsukushi (TSK)—a small, secreted, leucine-rich-repeat proteoglycan—interacts with and regulates essential cellular signaling cascades. However, its functions in the mouse inner ear are unknown. In this study, measurement of auditory brainstem responses, fluorescence microscopy, and scanning electron microscopy revealed that TSK deficiency in mice resulted in the formation of abnormal stereocilia in the inner hair cells and hearing loss but not in the loss of these cells. TSK accumulated in nonprosensory regions during early embryonic stages and in both nonprosensory and prosensory regions in late embryonic stages. In adult mice, TSK was localized in the organ of Corti, spiral ganglion cells, and the stria vascularis. Moreover, loss of TSK caused dynamic changes in the expression of key genes that drive the differentiation of the inner hair cells in prosensory regions. Finally, our results revealed that TSK interacted with Sox2 and BMP4 to control stereocilia formation in the inner hair cells. Hence, TSK appears to be an essential component of the molecular pathways that regulate inner ear development.

Direct activation of G-protein-gated inward rectifying K+ channels promotes nonrapid eye movement sleep

STUDY OBJECTIVES

A major challenge in treating insomnia is to find effective medicines with fewer side effects. Activation of G-protein-gated inward rectifying K+ channels (GIRKs) by GABAB agonists baclofen or γ-hydroxybutyric acid (GHB) promotes nonrapid eye movement (NREM) sleep and consolidates sleep. However, baclofen has poor brain penetration, GHB possesses abuse liability, and in rodents both drugs cause spike-wave discharges (SWDs), an absence seizure activity. We tested the hypothesis that direct GIRK activation promotes sleep without inducing SWD using ML297, a potent and selective GIRK activator.

METHODS

Whole-cell patch-clamp recordings from hypocretin/orexin or hippocampal neurons in mouse brain slices were made to study neuronal excitability and synaptic activity; spontaneous activity, locomotion, contextual and tone-conditioned memory, and novel object recognition were assessed. Electroencephalogram/electromyogram (EEG/EMG) recordings were used to study GIRK modulation of sleep.

RESULTS

ML297, like baclofen, caused membrane hyperpolarization, decreased input resistance, and blockade of spontaneous action potentials. Unlike baclofen, ML297 (5-10 µM) did not cause significant depression of postsynaptic excitatory and inhibitory currents (EPSCs-IPSCs), indicating preferential postsynaptic inhibition. ML297 (30 mg/kg, i.p.) inhibited wake activity and locomotion, and preferentially increased NREM sleep without altering EEG delta power, REM sleep, inducing SWDs, or impairing conditioned memory and novel object recognition.

CONCLUSIONS

This study finds that direct activation of neuronal GIRK channels modulates postsynaptic membrane excitability and prolongs NREM sleep without changing sleep intensity, inducing SWDs, or impairing memory in rodents. These results suggest that direct GIRK activation with a selective compound may present an innovative approach for the treatment of chronic insomnia.

Up-regulation of miR-106a targets LIMK1 and contributes to cognitive impairment induced by isoflurane anesthesia in mice

BACKGROUND

Postoperative cognitive dysfunction (POCD) had a great relationship with anesthesia during surgery, and miRNAs have been found involved in anesthesia-induced cognitive impairment.

OBJECTIVE

To explore the role and potential mechanism of miR-106a in isoflurane anesthesia-induced cognitive impairment.

METHODS

Adult male mice were treated with isoflurane anesthesia; Morris water maze tests and fear conditioning tests were performed; and expression levels of miR-106a and LIMK1 were determined by quantitative real-time PCR (qRT-PCR) and western blot. Dual luciferase reporter assay was used to determine the binding of miR-106a and 3'UTR of LIMK1. To verify the role of miR-106a, antagomir of miR-106a were intrahippocampally injected. Finally, expression of BCL2 apoptosis regulator (Bcl-2), LIM domain kinase 1 (LIMK1), BCL2-associated X, apoptosis regulator (Bax) and cleaved caspase3 was determined by western blot.

RESULTS

In isoflurane anesthesia-treated group (IS), the percentage of target quadrant dwell time was significantly lower and the escape latency was significantly higher than in the control group (sham), and the freezing behavior of IS was significantly less in contextual fear conditioning tests. Expression levels of miR-106a were increased and those of LIMK1 were decreased in response to IS. Dual luciferase reporter assay showed that miR-106a could bind with the 3'UTR of LIMK1. Decreased expression levels of miR-106a improved the cognitive impairment of the mice treated with isoflurane. Intrahippocampally injected antagomir of miR-106a also increased LIMK1 and Bcl-2 levels, decreased the BAX and cleaved caspase3 expression levels in the mice treated with isoflurane.

CONCLUSION

Decrease of LIMK1 expression by miR-106a played an important role in isoflurane anesthesia-induced cognitive impairment.

Differential effects of stress exposure via two types of restraint apparatuses on behavior and plasma corticosterone level in inbred male BALB/cAJcl mice

Aims

Restraint stress is one of the most widely used experimental methods for generating rodent models of stress‐induced neuropsychiatric disorders, such as depression and anxiety. Although various types of restraint apparatuses have been used to expose animals to stress, the magnitudes of the effects of stress exposure via different types of restraint apparatuses on physiology and behavior have not been compared in the same environment. Here, we investigated the effects of stress exposure via two types of restraint apparatuses on body weight, locomotor activity, anxiety‐ and depression‐related behaviors, and plasma corticosterone levels in mice.

Methods

Adult male BALB/cAJcl mice were restrained by placing them in either a well‐ventilated plastic conical tube or a tapered plastic film envelope for 6 hours per day for 10 or 21 consecutive days. Mice were weighed during and after the stress period and were subjected to a battery of behavioral tests, including light/dark transition, open field, elevated plus maze, Porsolt forced swim, tail suspension, and sucrose preference tests, starting on the day after the last stress session. Plasma corticosterone levels were measured in another cohort of mice on the 1st and the 21st stress sessions and after the Porsolt forced swim test.

Results

Exposure to repeated stress via the two above mentioned types of restraint apparatuses caused body weight loss, heightened locomotor activity, altered immobility during forced swim, and increased plasma corticosterone levels, and some of these results differed between the restraint stress protocols. Film‐restraint–stressed mice had significantly lower body weights than tube‐restraint–stressed mice. Film‐restraint–stressed mice exhibited significantly higher or lower immobility during forced swim than tube‐restraint–stressed mice, depending on the test time. Additionally, the stress‐induced increase in plasma corticosterone levels was found to be higher in film‐restraint–stressed mice than in tube‐restraint–stressed mice.

Conclusion

Our results indicate that film‐restraint stress has more pronounced effects on body weight, depression‐related behavior, and corticosterone response than tube‐restraint stress in mice. These findings may help guide which restraint stress procedures to use, depending on the objectives of a given study, in generating animal models of stress‐induced neuropsychiatric disorders.

This study investigated the effects of stress exposure via two types of restraint apparatuses, a well‐ventilated plastic conical tube and a tapered plastic film envelope, on body weights, behaviors, and plasma corticosterone levels in male BALB/cAJcl mice. Film‐restraint stress had more pronounced effects on body weight, depression‐related behavior, and corticosterone response than tube‐restraint stress, which may help guide which restraint stress procedures to use in generating animal models of stress‐induced disorders.

A Freely Available, Self-Calibrating Software for Automatic Measurement of Freezing Behavior

Freezing behavior is commonly used as a measure of associative fear memory. It can be measured by a trained observer, but this task is time-consuming and subject to variation. Commercially available software packages can also be used to quantify freezing; however, they can be expensive and usually require various parameters to be adjusted by the researcher, leading to additional work and variability in results. With this in mind, we developed Phobos, a freely available, self-calibrating software that measures freezing in a set of videos using a brief manual quantification performed by the user to automatically adjust parameters. To optimize the software, we used four different video sets with different features in order to determine the most relevant parameters, the amount of videos needed for calibration and the minimum criteria to consider it reliable. The results of four different users were compared in order to test intra- and interobserver variability in manual and automated freezing scores. Our results suggest that Phobos can be an inexpensive, simple and reliable tool for measurement of fear-related behavior, with intra- and interuser variability similar to that obtained with manual scoring.

Comprehensive behavioral analysis of heterozygous Syngap1 knockout mice

AIMS

Synaptic Ras GTPase-activating protein 1 (SYNGAP1) regulates synaptic plasticity through AMPA receptor trafficking. SYNGAP1 mutations have been found in human patients with intellectual disability (ID) and autism spectrum disorder (ASD). Almost every individual with SYNGAP1-related ID develops epilepsy, and approximately 50% have ASD. SYNGAP1-related ID is estimated to account for at least 1% of ID cases. In mouse models with Syngap1 mutations, strong cognitive and affective dysfunctions have been reported, yet some findings are inconsistent across studies. To further understand the behavioral significance of the SYNGAP1 gene, we assessed various domains of behavior in Syngap1 heterozygous mutant mice using a behavioral test battery.

METHODS

Male mice with a heterozygous mutation in the Syngap1 gene (Syngap1-/+ mice) created by Seth Grant's group were subjected to a battery of comprehensive behavioral tests, which examined general health, and neurological screens, rotarod, hot plate, open field, light/dark transition, elevated plus maze, social interaction, prepulse inhibition, Porsolt forced swim, tail suspension, gait analysis, T-maze, Y-maze, Barnes maze, contextual and cued fear conditioning, and home cage locomotor activity. To control for type I errors due to multiple-hypothesis testing, P-values below the false discovery rate calculated by the Benjamini-Hochberg method were considered as study-wide statistically significant.

RESULTS

Syngap1-/+ mice showed increased locomotor activity, decreased prepulse inhibition, and impaired working and reference spatial memory, consistent with preceding studies. Impairment of context fear memory and increased startle reflex in Syngap1 mutant mice could not be reproduced. Significant decreases in sensitivity to painful stimuli and impaired motor function were observed in Syngap1-/+ mice. Decreased anxiety-like behavior and depression-like behavior were noted, although increased locomotor activity is a potential confounding factor of these phenotypes. Increased home cage locomotor activity indicated hyperlocomotor activity not only in specific behavioral test conditions but also in familiar environments.

CONCLUSION

In Syngap1-/+ mice, we could reproduce most of the previously reported cognitive and emotional deficits. The decreased sensitivity to painful stimuli and impaired motor function that we found in Syngap1-/+ mice are consistent with the common characteristics of patients with SYNGAP-related ID. We further confirmed that the Syngap1 heterozygote mouse recapitulates the symptoms of ID and ASD patients.

Animal Models of PTSD: A Critical Review

The goals of animal research in post-traumatic stress disorder (PTSD) include better understanding the neurophysiological etiology of PTSD, identifying potential targets for novel pharmacotherapies, and screening drugs for their potential use as PTSD treatment in humans. Diagnosis of PTSD relies on a patient interview and, as evidenced by changes to the diagnostic criteria in the DSM-5, an adequate description of this disorder in humans is a moving target. Therefore, it may seem insurmountable to model the construct of PTSD in animals such as rodents. Fortunately, the neural circuitry involved in fear and anxiety, thought to be essential to the etiology of PTSD in humans, is highly conserved throughout evolution. Furthermore, many symptoms can be modeled using behavioral tests that have face, construct, and predictive validity. Because PTSD is precipitated by a definite traumatic experience, animal models can simulate the induction of PTSD, and test causal factors with longitudinal designs. Accordingly, several animal models of physical and psychological trauma have been established. This review discusses the widely used animal models of PTSD in rodents, and overviews their strengths and weaknesses in terms of face, construct, and predictive validity.