A Cannabinoid Type 1 Receptor Antagonist Impairs Spatial Memory and Increases the Tau Gene Expression in an Animal Model of the Alzheimer's Disease.

Alzheimer's disease (AD) is characterized by progressive cognitive decline and a reduction in hippocampal neurotrophins, in which trimethytin (TMT) infusion causes tangles and neuronal dysfunction, creating an AD-like model in rats. Previous studies have demonstrated that crocin, which has anti-inflammatory properties, can enhance learning, memory acquisition, and cognitive behavior. This study aimed to assess the combined impact of aerobic exercise and crocin on memory, learning, and hippocampal Tau and neurotrophins gene expression in AD-like model rats. Forty male Sprague Dawley rats were randomly divided into five groups: (1) healthy control, (2) Alzheimer's control, (3) endurance training, (4) crocin consumption, and (5) endurance training + crocin. Alzheimer's induction was achieved in groups 2-5 through intraperitoneal injection of 8 mg/kg TMT. Rats in groups 3 and 5 engaged in treadmill running three sessions per week, 15-30 min per session, at a speed of 15-20 m/min for eight weeks, and groups 4 and 5 received daily crocin supplementation of 25 mg/kg. Alzheimer's induction with TMT showed significant reduction in memory, learning, NGF, BDNF, and TrkB gene expression, and increase in tau gene expression (all p < 0.05). Notably, endurance training and crocin consumption separately significantly increased memory, learning, NGF, BDNF, and TrkB gene expression while significantly decreasing tau gene expression (all p < 0.05). Importantly, combined endurance training with crocin yielded the most profound effects on memory (p = 0.001), NGF (p = 0.002), BDNF (p = 0.001), and TrkB (p = 0.003) gene expression (p < 0.005), as well as a reduction in tau gene expression (p = 0.001). These findings underscore the possible impact of endurance training, particularly when coupled with crocin, on enhancing memory, learning, and neurotrophin gene expression and reducing tau gene expression in Alzheimer's rats. These results highlight the possibility of synergistic interventions for improved therapeutic outcomes.

Shifting balance from neurodegeneration to regeneration of the brain: a novel therapeutic approach to Alzheimer's disease and related neurodegenerative conditions.

Objective To explore the protective effect and mechanism of the dihydromyricetin (DHM) on cognitive dysfunction in Alzheimer’s disease (AD) rat model. Methods The AD model of rats was established by injecting Aβ1-42 oligomolymer into the hippocampus. According to the random number table, 30 successfully constructed AD model rats were divided into AD group, AD+ DHM1 group and AD+ DHM2 group, with 10 in each group.And the rats in the three groups were intraperitoneally injected with normal saline, 100 mg/kg DHM and 200 mg/kg DHM for 21 days, respectively.Another 10 rats with body mass matching were taken as the control group.Morris water maze was used to evaluate the spatial learning and memory ability of rats in each group, the expression of inflammatory cytokines were detected by Elisa, and the expressions of AMPK and SIRT1 proteins were detected by Western blot. Results Compared with the control group, the escape incubation period of rats in AD group was prolonged, and the difference was statistically significant (day 5 : (10.36±2.80)s, (22.40±2.98)s; t=-18.63, P<0.05). Compared with AD group, the escape latency of rats in AD+ DHM1 group and AD+ DHM2 group were shortened (day 5: AD+ DHM1 group (15.68±3.06) s, AD+ DHM2 group (18.85±3.22) s; t=10.65, 4.13, both P<0.05). Compared with AD group, rats in AD+ DHM1 group and AD+ DHM2 group had more crossing times ((1.87±0.76), (2.75±0.63) and (3.78±0.71); t=-6.86, -9.83, both P<0.05), and the target quadrant residence time were extended ((17.08±1.99) s, (16.33±4.33) s, (22.59±4.21) s; t= 28.5, 8.63, both P<0.05). Compared with the control group, the levels of IL-1β, IL-6 and TNF-α in the serum and hippocampus of the AD group were significantly increased (serum: t=4.98, 7.87, 5.43, all P<0.05; hippocampus: t=11.13, 30.50, 23.38, all P<0.05). Compared with the AD group, the levels of IL-1β, IL-6 and TNF-α in the serum and hippocampus of the AD+ DHM1 group and the AD+ DHM2 group were significantly decreased, the difference was statistically significant(serum: AD+ DHM1 group t=-4.13, -10.70, -9.22, AD+ DHM2 group t=-1.75, -3.63, -18.75, all P<0.05; hippocampus: AD+ DHM1 group t=-69.13, -15.13, -6.50, AD+ DHM2 group t=-10.25, -39.00, -8.00, all P<0.05). Compared with the control group, the expression of p-AMPK/AMPK protein and SIRT1 protein in the AD group were decreased.The expression of the two proteins in the AD+ DHM1 group and the AD+ DHM2 group were increased, comparing with those of AD group, and the difference was statistically significant(all P<0.05). Conclusion DHM exerts protective role in AD model rats, which may be related to the activation of AMPK/SIRT1 pathway and the inhibition of inflammatory response. Key words: Dihydromyricetin; Alzheimer’s disease; Cognitive function; AMPK; SIRT1; Inflammatory responses; Rat

Alzheimer's disease is characterized by impairment in episodic memory and visuospatial skills, which is related to the deterioration of glutamatergic synapses within the entorhinal cortex-hippocampal circuit. While electroacupuncture shows therapeutic promise for Alzheimer's disease, its underlying mechanisms remain poorly understood. This study investigated whether the effects of electroacupuncture on spatial memory involves improving synaptic plasticity in this circuit using triple-transgenic Alzheimer's disease mice. The intervention consisted of a 4-week daily electroacupuncture treatment at DU20/DU24 acupoints or sham treatment. Our findings revealed that electroacupuncture triggered a cascade of neuroplastic events, leading to significant cognitive improvements. Crucially, these therapeutic effects were completely abrogated by chemogenetic inhibition of the entorhinal cortex-hippocampal CA1 circuit, establishing its causal necessity. Our multi-level analyses revealed that electroacupuncture attenuated tau hyperphosphorylation, restored dendritic spine density, and boosted long-term potentiation. This was accompanied by an increase in crucial synaptic proteins and activation of the NMDAR-CaMKII-CREB signaling cascade. The key findings of this study reveal a multi-level neurorestorative cascade induced by electroacupuncture, by simultaneously reducing tau pathology, rebuilding synaptic architecture, and enhancing synaptic function in the entorhinal-hippocampal circuit, driven by the NMDAR-CaMKII-CREB pathway. Collectively, these results provide evidence that electroacupuncture ameliorates spatial memory deficits in Alzheimer's disease model mice by specifically enhancing synaptic plasticity in the entorhinal cortex-hippocampal circuit.

Hippocampal-cortical dialogue, during which hippocampal ripple oscillations support information transfer, is necessary for long-term consolidation of spatial memories. Whereas a vast amount of work has been carried out to understand the cellular and molecular mechanisms involved in the impairments of memory formation in Alzheimer’s disease (AD), far less work has been accomplished to understand these memory deficiencies at the network-level interaction that may underlie memory processing. We recently demonstrated that freely moving 8 to 9-month-old APP/PS1 mice, a model of AD, are able to learn a spatial reference memory task despite a major deficit in Sharp-Wave Ripples (SWRs), the integrity of which is considered to be crucial for spatial memory formation. In order to test whether reconfiguration of hippocampal-cortical dialogue could be responsible for the maintenance of this ability for memory formation, we undertook a study to identify causal relations between hippocampal and cortical circuits in epochs when SWRs are generated in hippocampus. We analyzed the data set obtained from multielectrode intracranial recording of transgenic and wild-type mice undergoing consolidation of spatial memory reported in our previous study. We applied Directed Transfer Function, a connectivity measure based on Granger causality, in order to determine effective coupling between distributed circuits which express oscillatory activity in multiple frequency bands. Our results showed that hippocampal-cortical coupling in epochs containing SWRs was expressed in the two frequency ranges corresponding to ripple (130–180 Hz) and slow gamma (20–60 Hz) band. The general features of connectivity patterns were similar in the 8 to 9-month-old APP/PS1 and wild-type animals except that the coupling in the slow gamma range was stronger and spread to more cortical sites in APP/PS1 mice than in the wild-type group. During the occurrence of SWRs, the strength of effective coupling from the cortex to hippocampus (CA1) in the ripple band undergoes sharp increase, involving cortical areas that were different in the two groups of animals. In the wild-type group, retrosplenial cortex and posterior cingulate cortex interacted with the hippocampus most strongly, whereas in the APP/PS1 group more anterior structures interacted with the hippocampus, that is, anterior cingulate cortex and prefrontal cortex. This reconfiguration of cortical-hippocampal interaction pattern may be an adaptive mechanism responsible for supporting spatial memory consolidation in AD mice model.

Alzheimer’s disease (AD) is a degenerative neurological disease that primarily affects the elderly. Drug therapy is the main strategy for AD treatment, but current treatments suffer from poor efficacy and a number of side effects. Non-drug therapy is attracting more attention and may be a better strategy for treatment of AD. Hypoxia is one of the important factors that contribute to the pathogenesis of AD. Multiple cellular processes synergistically promote hypoxia, including aging, hypertension, diabetes, hypoxia/obstructive sleep apnea, obesity, and traumatic brain injury. Increasing evidence has shown that hypoxia may affect multiple pathological aspects of AD, such as amyloid-beta metabolism, tau phosphorylation, autophagy, neuroinflammation, oxidative stress, endoplasmic reticulum stress, and mitochondrial and synaptic dysfunction. Treatments targeting hypoxia may delay or mitigate the progression of AD. Numerous studies have shown that oxygen therapy could improve the risk factors and clinical symptoms of AD. Increasing evidence also suggests that oxygen therapy may improve many pathological aspects of AD including amyloid-beta metabolism, tau phosphorylation, neuroinflammation, neuronal apoptosis, oxidative stress, neurotrophic factors, mitochondrial function, cerebral blood volume, and protein synthesis. In this review, we summarized the effects of oxygen therapy on AD pathogenesis and the mechanisms underlying these alterations. We expect that this review can benefit future clinical applications and therapy strategies on oxygen therapy for AD.

Gliosis and dendritic loss is reported to be secondary to the amyloid beta (Aß) and hyperphosphorylated tau (hp‐tau) production in Alzheimer’s disease(AD) brain. STZ administration is reported to induce sporadic AD. Previous clinical or preclinical studies on effect of rTMS treatment in AD patients or APP23 mice showed cognitive improvement alone or as adjuvant therapy along‐with amelioration of the glial aggravation in the hippocampus. However, studies on the effect of magnetic field stimulation on the gliosis related dendritic trimming in animal models of sporadic AD is elusive. Therefore, in the present study we have looked in to the effect of extremely low frequency magnetic field stimulation (ELF‐MF; 17.96µT, 50Hz, 2hr/day) for one month post‐injection of STZ (bilateral, 3mg/kg). Total 45 animals were (ethical no. 937/IAEC/2016) randomly divided into five groups: Control, Sham, AD, Sham+MF and AD+MF. After assessing retention of spatial and avoidance memory using Morris water maze and passive avoidance step down test on 30th day, animals were sacrificed and tissues processed for oxidative stress and immunofluorescence, Golgi‐Cox staining. Behavioural analysis revealed spatial memory improvement with no effect on the avoidance memory loss in AD+MF group as compared to AD group. We also found significant decrease in superoxide dismutase, catalase, GSH and increase in malon‐di‐aldehyde (MDA) in AD group. ELF‐MF treatment only reduced MDA level in hippocampus and frontal cortex. GFAP, IBA‐1 and hp‐tau (ser356) positive cells were found to be reduced in AD+MF group, as compared to all groups except Control. Sholl analysis revealed partial improvement of reduction in the number of intersection, bifurcation and length in basal and apical dendrite in the AD group after ELF‐MF treatment in CA3 layer. These findings suggests dual role of ELF‐MF exposure on STZ model of AD showing improvement of spatial memory by reducing the gliosis induced dendritic loss. However, inability to manage oxidative stress due to STZ, which may lead to avoidance memory deficit even after exposure period of one month.

Dual Role of Low Frequency Magnetic Field on Neuroinflammation Induced Dendritic Trimming And Memory Impairment on Rat Model of Sporadic Alzheimer’s Disease

Viral Vector–mediated Delivery of Estrogen Receptor-α to the Hippocampus Improves Spatial Learning in Estrogen Receptor-α Knockout Mice

ObjectiveThis study aims to apply the virtual radial arm maze (VRAM) task to find spatial working memory and reference memory impairments in patients of amnestic mild cognitive impairment (aMCI) and Alzheimer’s disease (AD). Spatial memory functions between aMCI converters and nonconverters are also compared using VRAM results.MethodsWe assessed the spatial memory in 20 normal controls, 20 aMCI, and 20 mild AD subjects using VRAM. The Mini-Mental State Examination, Clinical Dementia Rating scale, and other neuropsychological tests were given to the subjects in conjunction with the VRAM test. Scores in working memory errors and reference memory errors were compared among the three groups using repeated measures analysis of variance. In addition, aMCI patients were followed-up after 5 years and surveyed for AD conversion rate.ResultsIn AD patients, both spatial working and reference memory were impaired. However, in aMCI subjects, only spatial reference memory was impaired. Significant spatial reference memory impairment was found in the aMCI converter group when compared to the nonconverter group.ConclusionSpatial working memory is less impaired in aMCI while reference memory is similarly damaged in AD. In aMCI patients, more severe spatial reference memory deficit is a neuropsychological marker for AD conversion. VRAM may be well utilized in humans to assess spatial memory in normal aging, in aMCI, and in AD.

Forebrain cholinergic neuronal loss is strongly correlated with the memory impairment of Alzheimer’s disease (AD). Current therapeutic options provide short term symptomatic relief and only minimally affect disease progression. Thus, any potential stem cell therapy with the ability to reverse the cell loss and halt the disease progression would be a valuable therapeutic option. The overarching aim of this thesis was to investigate the ability of transplanted neural progenitor cells to restore cognitive function in mouse models of Alzheimer’s disease. A dual reporter system was employed to identify specific populations of mouse embryonic stem (mES) cells, with mcherry (a red florescent protein) targeted to the ROSA26 (thumpd 3) promoter and β lactamase-T2A-β- galactosidase targeted to the Lhx8 promoter, designed to enrich cultured cells for cholinergic progenitors. Two different mouse models of AD, the acquired immunotoxin based model and the genetic triple transgenic model of AD (3xTg-AD), were validated using two behavioural paradigms measuring hippocampal (spatial memory) and cortical (declarative memory) function via a modified water maze and novel object recognition paradigm. Immunotoxin treated mice were later implanted with neural precursor cells and their cognitive function was then evaluated post-transplantation. In the first chapter (chapter3), the immunotoxin mouse model was investigated. The model uses mu-p75-saporin, a ribosomal inactivating toxin directed against the p75 nerve growth factor receptor, to cause the degeneration of forebrain cholinergic neurons as observed in AD. Intracerebroventricular injections of mu-p75- saporin caused cholinergic cell loss which was behaviourally correlated with spatial memory deficits in the water maze but intact recognition memory in novel object paradigm. Post mortem analyses revealed a reduction in the number of choline acetyltransferase (ChAT) positive cells in the principle regions providing cholinergic innervations to the hippocampus. Together, these data suggests that mu- p75-saporin treated mice represent a suitable model for the investigation of spatial memory deficits in future stem cell experiments. In chapter four, the 3xTg-AD mouse model was investigated. 3xTg-AD mice express three human transgenes, the amyloid precursor protein (APPswe), presenilin 1 (PS1M146V), and tau (tauP301L), and exhibit age related insoluble Aβ and neurofibrillary tangle (NFT) pathologies, as observed in human AD patients. Cognitive function in 3xTg-AD mice was assessed at 12 - 14 months and 16 - 18 months of age, again using the same modified water maze and novel object recognition paradigms. Deficits in recognition memory were observed in both male and female 3xTg-AD mice at both age points. However, in the water maze both WT and 3xTg-AD mice exhibited spatial memory deficits, making the data inconclusive. Tau based tangle pathology was detected in the hippocampus, amygdala and cortex of transgenic mice; however Aβ pathology was completely absent in the aforementioned regions. Due to the lack of Aβ pathology, the model was not used for future stem cell transplantation studies.In chapter five, the cholinergic differentiation potential of the Lhx8-AMP-T2A-lacZ‐FneoF reporter cell line was characterised under monolayer and neurosphere culture conditions. Lhx8 is a vital transcription factor involved in cholinergic differentiation. In the monolayer Lhx8+ cell culture a very low number of cholinergic neurons were detected at day 18 of differentiation. A moderately higher number of cholinergic neurons were detected in the neurosphere cultures therefore neural precursor cells obtained from neurosphere culture conditions were selected for use in future transplantation experiments. In the final experimental study, immunotoxin treated mice were implanted with neural precursor cells derived from neurosphere culture. The mice were first injected with mu-p75-saporin and their spatial memory was assessed using the water maze paradigm. After a month, treated and control mice were injected with 100,000 neural precursor cells (bilaterally administered into the hippocampus) and were behaviourally assessed again to detect any potential effects of cell transplantation on cognitive function. Whilst treatment with mu-p75-saporin induced a cognitive decline in spatial memory as measured using the water maze and altered nesting behaviour in treated mice, cell transplantation was only able to influence the nesting behaviour, with the behavioural deficits observed in the water maze remaining unchanged. Implanted cells were detected in the hippocampus and expressed proteins were indicative of a neuronal phenotype, demonstrating that the transplanted cells were able to survive in the brain over the experimental period. In conclusion, this thesis demonstrates that the implantation of neural precursor cells derived using a specific knock-in fluorescent reporter cell line has the potential to improve cognitive function in an acquired mouse model of AD. These preliminary studies indicate that further investigations are warranted and suggest that this approach could serve as an important model system in which to study brain development and neurodegenerative processes.

According to available evidence, prolonged or chronic exposure to stress is detrimental to various brain structures, including the hippocampus. The current study examined the expression of two critical blood-brain barrier receptors required for amyloid-beta clearance to understand better the mechanism by which chronic stress impairs learning and memory in patients with Alzheimer's disease (AD). Rats were randomly assigned to one of two groups in this study: experiment 1 and experiment 2. Each main group was then divided into four subgroups. Rats were bilaterally injected with streptozotocin (STZ, 3mg/kg, twice) using the intracerebroventricular (ICV) technique to induce the Alzheimer's model. Additionally, they were subjected to foot shock (1mA, 1Hz) for 10s every 60s (1h/day) for ten consecutive days prior to and following STZ injection. The Morris Water Maze (MWM) test was used to assess spatial learning and memory. Real-time PCR was used to determine Low-density lipoprotein receptor-related protein-1 (LRP1) and receptor for advanced glycation end-products (RAGE) mRNA levels in the hippocampus. Moreover, the animals' body weights were determined as physiological parameters in all groups. The results indicated that 10-day chronic electric foot shock stress reduced body weight, impaired spatial learning and memory, decreased hippocampal LRP1 mRNA expression, and increased hippocampal RAGE mRNA expression in a rat AD model. It can be concluded that chronic stress in conjunction with AD alters the expression of LRP1 and RAGE in the hippocampus. The findings pave the way for scientists to develop novel treatment strategies for AD.

In early stages of Alzheimer's disease (AD), soluble amyloid-β (Aβ) is a key player disrupting neuronal activity and contributing to cognitive decline in advanced stages of the disease. Although the hippocampus has been a central focus in prior research because of its susceptibility to Aβ-induced alterations, a comprehensive understanding of the temporal progression of early AD pathology requires exploring interconnected brain regions. The posterior parietal cortex (PPC), collaborating closely with the hippocampus and involved in various memory processes, particularly spatial memory formation, holds particular significance. Investigating the function of the PPC is imperative because it may contribute to early AD characteristics and provide a more holistic perspective on disease progression. To address this gap, we examined the relationship between neural oscillations and memory processes in both the PPC and hippocampus, in a mouse model of early hippocampal amyloidosis generated by intracerebroventricular oligomeric Aβ1-42 (oAβ1-42) injection. By performing in vivo oscillatory activity recordings from these regions in alert animals, together with spatial and habituation memory tests (Barnes maze and open field habituation), we found oAβ1-42 to induce significant alterations in PPC oscillatory activity. These changes emerged several days after hippocampal disturbances showed as aberrant synaptic plasticity and network activity. Additionally, significant alterations of stereotyped behaviours were not found. Our results provide an electrophysiological substrate for persistent spatial memory deficits and the temporal progression pattern of the early deleterious effects caused by Aβ. Furthermore, investigating PPC oscillatory activity might be a valuable approach for early detection and intervention in AD. KEY POINTS: Posterior parietal cortex (PPC), in close collaboration with the hippocampus, has been implicated in various memory processes disrupted in early Alzheimer's disease models. A mouse model of early Alzheimer's-like hippocampal amyloidosis generated by intracerebroventricular oligomeric Aβ1-42 (oAβ1 42) injection was used to examine the relationship between neural oscillations and memory processes in both the PPC and hippocampus. oAβ1-42 induces alterations in spatial and habituation memory, associated with PPC aberrant oscillatory activity, several days after hippocampal synaptic plasticity and network activity disturbances were found. We provide an electrophysiological PPC-mediated substrate for persistent spatial memory deficits and the temporal progression pattern of the early oscillatory deleterious effects caused by Aβ.

Expression of long-lasting synaptic plasticity and long-term memory requires new protein synthesis, which can be repressed by phosphorylation of eukaryotic initiation factor 2α subunit (eIF2α). It was reported previously that eIF2α phosphorylation is elevated in the brains of Alzheimer’s disease (AD) patients and AD model mice. Therefore, we determined whether suppressing eIF2α kinases could alleviate synaptic plasticity and memory deficits in AD model mice. The genetic deletion of the eIF2α kinase PERK prevented enhanced eIF2α phosphorylation, as well as deficits in protein synthesis, synaptic plasticity, and spatial memory in APP/PS1 AD model mice. Similarly, deletion of another eIF2α kinase, GCN2, prevented impairments of synaptic plasticity and spatial memory defects displayed in the APP/PS1 mice. Our findings implicate aberrant eIF2α phosphorylation as a novel molecular mechanism underlying AD-related synaptic pathophysioloy and memory dysfunction and suggest that PERK and GCN2 are potential therapeutic targets for the treatment of individuals with AD.

CaMKII Activation in the Entorhinal Cortex Disrupts Previously Encoded Spatial Memory