Hippocampal CA3-CA1 synaptic rescue via DHHC2-mediated PSD95 palmitoylation stabilization

Background: Depression is a mental disorder that poses a serious threat to human health. Adult hippocampal neurogenesis (AHN) is closely associated with the efficacy of antidepressants. Chronic treatment with corticosterone (CORT), a well-validated pharmacological stressor, induces depressive-like behaviors and suppresses AHN in experimental animals. However, the possible mechanisms of chronic CORT action remain elusive. Methods: A chronic CORT treatment (0.1 mg/mL, drinking water for 4 weeks) was applied to prepare a mouse model of depression. Immunofluorescence was performed to analyze the hippocampal neurogenesis lineage, and immunoblotting, immunofluorescence, electron microscopy, and adeno-associated virus (AAV) expressing a pH-sensitive tandemly tagged light chain 3 (LC3) protein were used to analyze neuronal autophagy. AAV-hSyn-miR30-shRNA was used to knock down autophagy-related gene 5 (Atg5) expression in the neurons. Results: Chronic CORT induces depressive-like behaviors and

Down syndrome (DS) is a high-incidence genetic pathology characterized by severe impairment of cognitive functions, including declarative memory. Impairment of hippocampus-dependent long-term memory in DS appears to be related to anatomo-functional alterations of the hippocampal trisynaptic circuit formed by the dentate gyrus (DG) granule cells - CA3 pyramidal neurons - CA1 pyramidal neurons. No therapies exist to improve cognitive disability in individuals with DS. In previous studies we demonstrated that pharmacotherapy with fluoxetine restores neurogenesis, granule cell number and dendritic morphology in the DG of the Ts65Dn mouse model of DS. The goal of the current study was to establish whether treatment rescues the impairment of synaptic connectivity between the DG and CA3 that characterizes the trisomic condition. Euploid and Ts65Dn mice were treated with fluoxetine during the first two postnatal weeks and examined 45-60 days after treatment cessation. Untreated Ts65Dn mice had

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with growing major health impacts, particularly in countries with aging populations. The examination of neural circuit mechanisms in AD mouse models is a recent focus for identifying new AD treatment strategies. We hypothesize that age-progressive changes of both long-range and local hippocampal neural circuit connectivity occur in AD. Recent advancements in viral-genetic technologies provide new opportunities for semi-quantitative mapping of cell-type-specific neural circuit connections in AD mouse models. We applied a recently developed monosynaptic rabies tracing method to hippocampal neural circuit mapping studies in AD model mice to determine how local and global circuit connectivity to hippocampal CA1 excitatory neurons may be altered in the single APP knock-in (APP-KI) AD mouse model. To determine age-related AD progression, we measured circuit connectivity in age-matched littermate control and AD model mice at

INTRODUCTION: Individuals with Down syndrome (DS) exhibit neurological deficits throughout life including the development of in Alzheimer's disease (AD) pathology and cognitive impairment. At the cellular level, dysregulation in neuronal gene expression is observed in postmortem human brain and mouse models of DS/AD. To date, RNA-sequencing (RNA-seq) analysis of hippocampal neuronal gene expression including the characterization of discrete circuit-based connectivity in DS remains a major knowledge gap. We postulate that spatially characterized hippocampal neurons display unique gene expression patterns due, in part, to dysfunction of the integrity of intrinsic circuitry. METHODS: We combined laser capture microdissection to microisolate individual neuron populations with single population RNA-seq analysis to determine gene expression analysis of CA1 and CA3 pyramidal neurons and dentate gyrus granule cells located in the hippocampus, a region critical for learning, memory, and synapti

Mnemonic discrimination, a cognitive process that relies on hippocampal pattern separation, is one of the first memory domains to decline in aging and preclinical Alzheimer's disease. We tested whether functional connectivity (FC) within the entorhinal-hippocampal circuit, measured with high-resolution resting state fMRI, is associated with mnemonic discrimination and amyloid-β (Aβ) pathology in a sample of 64 cognitively normal human older adults (mean age, 71.3 ± 6.4 years; 67% female). FC was measured between entorhinal-hippocampal circuit nodes with known anatomical connectivity, as well as within cortical memory networks. Aβ pathology was measured with 18F-florbetapir-PET, and neurodegeneration was assessed with subregional volume from structural MRI. Participants performed both object and spatial versions of a mnemonic discrimination task outside of the scanner and were classified into low-performing and high-performing groups on each task using a median split. Low object mnemoni

The subiculum (SUB), a hippocampal formation structure, is among the earliest brain regions impacted in Alzheimer's disease (AD). Toward a better understanding of AD circuit-based mechanisms, we mapped synaptic circuit inputs to dorsal SUB using monosynaptic rabies tracing in the 5xFAD mouse model by quantitatively comparing the circuit connectivity of SUB excitatory neurons in age-matched controls and 5xFAD mice at different ages for both sexes. Input-mapped brain regions include the hippocampal subregions (CA1, CA2, CA3), medial septum and diagonal band, retrosplenial cortex, SUB, postsubiculum (postSUB), visual cortex, auditory cortex, somatosensory cortex, entorhinal cortex, thalamus, perirhinal cortex (Prh), ectorhinal cortex, and temporal association cortex. We find sex- and age-dependent changes in connectivity strengths and patterns of SUB presynaptic inputs from hippocampal subregions and other brain regions in 5xFAD mice compared with control mice. Significant sex differences

In this chapter we have explored the hypothesis that reactive synaptogenesis is an adaptive mechanism that can compensate for loss of a fraction of a defined neuronal population. Partial cell loss occurs during the course of aging, neurodegenerative diseases, and minor traumatic brain injuries. As cells are lost or as their function severely declines, new connections made by healthy neurons from within the population can assume parallel functions (homotypic sprouting), or fibers from converging pathways (heterotypic sprouting) can act to boost weakened signals and maintain functional stability. When cell death (or disease) progresses to the point where the pathway is broken, sprouting can no longer maintain information flow along the circuit and thus is unable to preserve function, unless new circuits can also be compensatory as, for example, after unilateral injury. We have analyzed the consequences of cell loss on the nature of circuit regrowth within the primary hippocampal circuits

Vesicular Zn2+ (zinc) is released at synapses and has been demonstrated to modulate neuronal responses. However, mechanisms through which dysregulation of zinc homeostasis may potentiate neuronal dysfunction and neurodegeneration are not well-understood. We previously reported that accumulation of soluble amyloid beta oligomers (AβO) at synapses correlates with synaptic loss and that AβO localization at synapses is regulated by synaptic activity and enhanced by the release of vesicular Zn2+ in the hippocampus, a brain region that deteriorates early in Alzheimer's disease (AD). Significantly, drugs regulating zinc homeostasis inhibit AβO accumulation and improve cognition in mouse models of AD. We used both sexes of a transgenic mouse model lacking synaptic Zn2+ (ZnT3KO) that develops AD-like cognitive impairment and neurodegeneration to study the effects of disruption of Zn2+ modulation of neurotransmission in cognition, protein expression and activation, and neuronal excitability. Her

Brain-derived neurotrophic factor (BDNF) protects hippocampal neurons from glutamate excitotoxicity as determined by analysis of chromatin condensation, through activation of extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3-kinase (PI3-K) signaling pathways. However, it is still unknown whether BDNF also prevents the degeneration of axons and dendrites, and the functional demise of synapses, which would be required to preserve neuronal activity. Herein, we have studied the time-dependent changes in several neurobiological markers, and the regulation of proteolytic mechanisms in cultured rat hippocampal neurons, through quantitative western blot and immunocytochemistry. Calpain activation peaked immediately after the neurodegenerative input, followed by a transient increase in ubiquitin-conjugated proteins and increased abundance of cleaved-caspase-3. Proteasome and calpain inhibition did not reproduce the protective effect of BDNF and caspase inhibition in prevent

In the present study, we have attempted to elucidate the effects of the intra-arterial injection of microglia on the global ischemia-induced functional and morphological deficits of hippocampal CA1 neurons. When PKH26-labeled immortalized microglial cells, GMIR1, were injected into the subclavian artery, these exogenous microglia were found to accumulate in the hippocampus at 24 h after ischemia. In hippocampal slices prepared from medium-injected rats subjected to ischemia 48 h earlier, synaptic dysfunctions including a significant reduction of synaptic responses and a marked reduction of long-term potentiation (LTP) of the CA3-CA1 Schaffer collateral synapses were observed. At this stage, however, neither significant neuronal degeneration nor gliosis was observed in the hippocampus. At 96 h after ischemia, there was a total loss of the synaptic activity and a marked neuronal death in the CA1 subfield. In contrast, the basal synaptic transmission and LTP of the CA3-CA1 synapses were w

Persistent microglial inflammation is a detrimental contributor to the progression of Parkinson disease (PD) pathology and related issues such as impaired adult hippocampal neurogenesis (AHN) and cognition. We conducted a 10-week exercise program with MPTP-treated mice to determine whether neuroinflammation can be addressed by aerobic exercise and elucidate its underlying regulatory mechanisms. Ten weeks of exercise significantly reduced PD-related pathology and enhanced AHN and memory. These changes were linked to a reduction in neuronal apoptosis, microglial inflammation, and NLRP3 inflammasome activation. In cultured microglia, fibril α-synuclein reduced FNDC5/irisin protein levels and induced NLRP3 inflammasome formation and IL-1β production, which could be diminished by recombinant irisin treatment. Interestingly, "runner serum" isolated from exercising rodents enhanced FNDC5/irisin expression and reduced NLRP3 inflammasome components and IL-1β secretion in α-synuclein-treated mic

Investigating long-term potentiation (LTP) in disease models provides essential mechanistic insight into synaptic dysfunction and relevant behavioral changes in many neuropsychiatric and neurological diseases. Toxoplasma (T) gondii is an intracellular parasite causing bizarre changes in host's mind including losing inherent fear of life-threatening situations. We examined hippocampal-dependent behavior as well as in vivo short- and long-term synaptic plasticity (STP and LTP) in rats with latent toxoplasmosis. Rats were infected by T. gondii cysts. Existence of REP-529 genomic sequence of the parasite in the brain was detected by RT-qPCR. Four and eight weeks after infection, spatial, and inhibitory memories of rats were assessed by Morris water maze and shuttle box tests, respectively. Eight weeks after infection, STP was assessed in dentate gyrus (DG) and CA1 by double pulse stimulation of perforant pathway and Shaffer collaterals, respectively. High frequency stimulation (HFS) was ap

Alzheimer's disease (AD) pathology begins decades prior to onset of clinical symptoms, and the entorhinal cortex and hippocampus are among the first and most extensively impacted brain regions. The TgF344-AD rat model, which more fully recapitulates human AD pathology in an age-dependent manner, is a next generation preclinical rodent model for understanding pathophysiological processes underlying the earliest stages of AD (Cohen et al., 2013). Whether synaptic alterations occur in hippocampus prior to reported learning and memory deficit is not known. Furthermore, it is not known if specific hippocampal synapses are differentially affected by progressing AD pathology, or if synaptic deficits begin to appear at the same age in males and females in this preclinical model. Here, we investigated the time-course of synaptic changes in basal transmission, paired-pulse ratio, as an indirect measure of presynaptic release probability, long-term potentiation (LTP), and dendritic spine density

Cellular activity in the CA1 area of the hippocampus waxes and wanes at theta frequency (4-8 Hz) during exploratory behavior of rats. Perisomatic inhibition onto pyramidal cells tends to be strongest out of phase with pyramidal cell activity, whereas dendritic inhibition is strongest in phase with pyramidal cell activity. Synaptic plasticity also varies across the theta cycle, from strong long-term potentiation (LTP) to long-term depression (LTD), putatively corresponding to encoding and retrieval phases for information patterns encoded by pyramidal cell activity (Hasselmo et al. (2002a) Neural Comput 14:793-817). The mechanisms underpinning the phasic changes in plasticity are not clear, but it is likely that inhibition plays a role by affecting levels of electrical activity and calcium concentration at synapses. We explore the properties of synaptic plasticity during theta at Schaffer collateral synapses on CA1 pyramidal neurons and the influence of spatially and temporally targeted

The marginal efficiency observed with the existing therapies in Alzheimer's Disease (AD) can be attributed to the timing of the treatment. The beneficiaries of symptomatic or disease-modifying therapy for AD are mild-cognitive-impairment (MCI) or late-stage dementia patients. At this stage, the pathological features are already advanced and irreversible, as the shift in biomarker levels starts in a continuum 15-20 years prior. Early intervention, therefore, is a plausible solution to this issue. Consequently, we selected 3 month-old 5XFAD AD mice as an early intervention model. We administered cannabidiol (CBD) and plasmid brain-derived neurotrophic factor (BDNF) encapsulated in liposome nanoparticles, functionalized with penetratin and mannose for brain-targeting, as a therapy. Neuroinflammation is emerging as a key driver of AD progression by its interaction with amyloid plaques and phosphorylated tau. Therefore, CBD, which is anti-inflammatory and neuroprotective, was used. BDNF, a

Affective disorders such as depression, anxiety disorders and suicidality are major contributors to global psychiatry. The "chemical imbalance" theory has been traditionally used; however recent research suggests that neurotransmitter dysfunction may represent an important early contributor within a broader, bidirectional cascade of cellular changes. Stress responses and neural circuits are disrupted by dysregulation of the serotonergic, noradrenergic, dopaminergic, GABAergic, and glutamatergic systems, which leads to oxidative stress, excitotoxicity, neuroinflammation, and decreased trophic support. Reduced brain-derived neurotrophic factor (BDNF) signaling, dendritic retraction, synapse loss, and apoptotic susceptibility are the common pathways that result in both amygdala hyperactivity and structural atrophy in the hippocampus and prefrontal cortex. Rumination, fear, anhedonia, cognitive impairment, and suicidal ideation are clinical manifestations of the ensuing circuit failure. Th

Microglia-neuron contacts have been shown to regulate neural network activity through the formation and elimination of synapses. The pathogenesis of major depressive disorder is accompanied by a decline in brain-derived neurotrophic factor (BDNF) signaling, associated with increased microglia activity that disrupts cognitive function. The actions of both typical and rapid-acting antidepressant drugs, which have been shown to increase BDNF signaling through the tropomyosin receptor kinase B (TrkB) receptor, decrease microglia activation and the levels of pro-inflammatory cytokines. Examining the link between BDNF signaling and the microglial pro-inflammatory response, we demonstrate that TrkB signaling elicits the neuronal secretion of CD22 (Siglec-2), a sialic acid-binding immunoglobulin-type lectin, to inhibit microglial activation and alleviate depression-like symptoms. In a male chronic mild stress (CMS) mouse model of depression decreased expression of the postsynaptic scaffolding

OBJECTIVE: This study aims to elucidate the pharmacological basis and antidepressant mechanisms of a combined extract from Eucommia ulmoides Oliv. And Gastrodia elata Bl. (Eucommia-Gastrodia extract), employing an integrated strategy that combines UHPLC-QTOF-MS analysis, network pharmacology, molecular docking, and in vivo validation. METHODOLOGY: This research integrated computational approaches network pharmacology, molecular docking and in vivo experimental investigations. Initially, the active constituents of the EGE were identified through ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS). Potential targets related to depression were predicted using the Traditional Chinese Medicine Systems Pharmacology Database (TCMSP) and SwissADME. Protein-protein interaction (PPI) networks were constructed via the STRING database, followed by the development of a comprehensive "drug-active ingredient-target-disease" network. Fu

INTRODUCTION: Gestational intermittent hypoxia (GIH), which serves as a model for obstructive sleep apnea (OSA), is associated with adverse maternal and neonatal outcomes, especially cognitive impairments in offspring. Growing evidence supports that the anti-inflammatory actions of melatonin significantly influence the peripartum environment and contribute to the mitigation of neurodegeneration. However, the full impact of GIH on offspring cognition and the molecular mechanisms by which melatonin modulates these effects remain uncertain. Thus, in this study, we explored the neurobiological changes in GIH-exposed offspring and the mechanism underlying maternal melatonin supplementation in preventing these alterations using a murine model. METHODS: C57BL/6J mice were exposed to GIH between gestational Days 15 and 21. Concurrently, dams received either vehicle or melatonin. The Morris water maze test was employed to evaluate offspring cognitive function, after which the offspring were eut

Brain-derived neurotrophic factor (BDNF) is one of the most distributed and extensively studied neurotrophins in the mammalian brain. BDNF signals through the tropomycin receptor kinase B (TrkB) and the low affinity p75 neurotrophin receptor (p75NTR). BDNF plays an important role in proper growth, development, and plasticity of glutamatergic and GABAergic synapses and through modulation of neuronal differentiation, it influences serotonergic and dopaminergic neurotransmission. BDNF acts as paracrine and autocrine factor, on both pre-synaptic and post-synaptic target sites. It is crucial in the transformation of synaptic activity into long-term synaptic memories. BDNF is considered an instructive mediator of functional and structural plasticity in the central nervous system (CNS), influencing dendritic spines and, at least in the hippocampus, the adult neurogenesis. Changes in the rate of adult neurogenesis and in spine density can influence several forms of learning and memory and can

Aging and various neurodegenerative diseases cause significant reduction in adult neurogenesis and simultaneous increase in quiescent neural stem cells (NSCs), which impact the brain's regenerative capabilities. To deal with this challenging issue, current treatments involve stem cell transplants or prevention of neurodegeneration; however, the efficacy or success of this process remains limited. Therefore, extensive and focused investigation is highly demanding to overcome this challenging task. Here, we have designed an efficient peptide-based EphA4 receptor-targeted ligand through an in silico approach. Further, this strategy involves chemical conjugation of the peptide with adipose tissue stem cell-derived EV (Exo-pep-11). Interestingly, our newly designed engineered EV, Exo-pep-11, targets NSC through EphA4 receptors, which offers promising therapeutic advantages by stimulating NSC proliferation and subsequent differentiation. Our result demonstrates that NSC successfully internal

The blood-brain barrier (BBB) poses a substantial obstacle to the successful delivery of therapeutics to the central nervous system (CNS). The transnasal route has been extensively explored, but success rates have been modest due to challenges related to the precise anatomical placement of drugs, the small volumes that the olfactory cleft can accommodate and short drug residence times due to mucociliary clearance. Here, to address these issues, we have developed a surgical technique known as the minimally invasive nasal depot (MIND), which allows the accurate placement of depot drugs into the submucosal space of the olfactory epithelium of rats. This technique exploits the unique anatomy of the olfactory apparatus to enable transnasal delivery of drugs into the CNS, bypassing the BBB. In our rat model, a bony window is created in the animal snout to expose the submucosal space. Using the MIND technique, we have successfully delivered oligonucleotides to the CNS in Sprague-Dawley and Lo

Brain-derived neurotrophic factor (BDNF) plays an important role in synaptic development and plasticity. It is a promising therapeutic target for improving neurofunctional outcomes after traumatic brain injury (TBI). However, the delivery of BDNF faces several significant challenges including limited entry into the CNS due to blood-brain barrier (BBB), short half-life, and potential side effects. The use of viral vectors like AAV to deliver the BDNF gene directly to the brain has shown promise in animal models. However, issues with host immunogenicity and limited biodistribution remain. Herein, we report a successful restoration of cognitive function of a TBI mouse model by efficient delivery of BDNF mRNA loaded to a novel lipid nanoparticle (DA6 LNP). DA6 LNPs loaded with either luciferase mRNA or GFP mRNA were internalized by astrocytes and dose dependently expressed the corresponding protein. Two consecutive intravenous injections of DA6 LNPs loaded with BDNF mRNA to a TBI mouse mod

Recent research on Alzheimer's disease (AD) focuses on processes prior to amyloid-beta plaque deposition accounting for the progress of the disease. However, early mechanisms of AD are still poorly understood and predictors of the disease in the pre-plaque stage essential for initiating an early therapy are lacking. Behavioral and psychological symptoms of dementia (BPSD) and potentially impaired cognition may serve as predictors and early clinical diagnostic markers for AD. To investigate potential BPSD and cognitive impairments in association with neuronal cell development as such markers for AD in the pre-plaque stage, female APP23 mice at eight, 19 and 31 weeks of age and corresponding control animals were tested for BPSD (elevated zero maze; sucrose preference test), motor coordination (rotarod), spatial memory and reversal learning (Morris water maze) and hippocampal neurogenesis as a neuronal correlate for hippocampus-dependent behavior. To evaluate a potential therapeutic effec

BACKGROUND: Rhubarb, traditionally used in China for neurological disorders, has recently attracted considerable scientific attention for its neuroprotective and cerebrovascular benefits. The main therapeutic components of rhubarb are anthraquinones, including emodin, aloe-emodin, chrysophanol, rhein, and physcion. Accumulating experimental evidence indicates that anthraquinones are of importance in neurodegenerative diseases (NDDs), such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis. However, as a promising candidate for drug development, the mechanisms by which anthraquinones treat NDDs have not been systematically reviewed. Therefore, this article outlines the anti-neurodegenerative effects of anthraquinones, focusing on their molecular mechanisms. OBJECTIVE: This article reviews recent research progress of anthraquinones in NDDs, focusing on their potential targets and pathways to provide new ideas for the intervention and treatment of ND

OBJECTIVE: Given the limitations of current treatments for Alzheimer's disease (AD), this study aims to comprehensively evaluate the therapeutic efficacy of human umbilical cord mesenchymal stem cells (hUCMSCs) in AD mouse models through a systematic review and meta-analysis. Additionally, we explore the impact of transplantation dose and route on treatment outcomes to identify the optimal window for clinical application. METHODS: In accordance with the PRISMA guidelines, we systematically searched four major databases to identify randomized controlled trials involving hUCMSCs in AD mouse models. We used the standardized mean difference (SMD) to synthesize effect sizes and performed subgroup analyses based on pre-defined transplantation routes and doses. RESULTS: A total of 13 studies were included in the analysis. The meta-analysis revealed that hUCMSCs transplantation significantly improved spatial learning and memory in AD model mice, with a marked reduction in escape latency (SMD =

Decline in mitochondrial quality is a prominent pathological feature of Alzheimer's disease (AD), manifested by impaired energy metabolism, disrupted mitochondrial biogenesis, abnormal mitochondrial dynamics, and defective mitophagy. Increasing evidence indicates that mitochondrial dysfunction contributes to the exacerbation of amyloid-β (Aβ) deposition and tau protein hyperphosphorylation, thereby accelerating AD pathogenesis. Of particular interest, physical exercise has been shown to effectively enhance mitochondrial quality and help prevent or slow the progression of AD, largely through the activation of key signaling pathways such as adenosine monophosphate-activated protein kinase (AMPK) and sirtuin 1 (SIRT1). However, regular physical activity may not be feasible for individuals in the prodromal or clinical stages of AD. In this context, exercise mimetics-compounds that pharmacologically simulate the molecular effects of exercise-have emerged as a promising alternative intervent