Search Results (31)

Background:/ Over the past decade, increasing evidence has shifted attention from the brain to the gut microbiota (MB) as a source and site of systemic dissemination of amyloid-β (Aβ), an APP derivative responsible for plaque formation in the brains of Alzheimer’s disease (AD) patients. Furthermore, AD patients and APP/PS1 mice, a transgenic model of AD, exhibit dysbiosis. Objectives: Using APP/PS1 mice treated from 2 to 8 months of age, we studied ileal and colonic epithelial integrity, intestinal barrier (IB) integrity assessed through tight junction (TJ) protein expression, local immune system, the presence/increase in Aβ expression in enterocytes, and the protective effects of synbiotic treatment. Methods: The tissue was stained with Periodic Acid-Schiff and Alcian Blue to evaluate epithelial morphology and mucus production, and immunohistochemistry was performed to assess TJs, immune markers, and Aβ expression. Results: Our results demonstrate that colonic and ileal epithelium of 8-month-old APP/PS1 mice displays IB impairment in term of alterations of goblet cells staining and TJ protein expression and signs of immune involvement. The ileum was more severely affected, showing a reduced epithelial surface area, decreased lysozyme production, and fewer tuft cells. Long-term synbiotic treatment largely prevented APP/PS1 mouse changes and caused a significant increase in Aβ expression in all treated mice. Conclusions: These findings support the belief in early intestinal involvement in AD and highlight the potential of the microbiota as a target for early intervention aimed at modifying the progression to neurodegeneration. Increased epithelial Aβ labeling after treatment raises the possibility of intestinal management of Aβ, which requires further validation. Full article

Aging and Alzheimer’s disease (AD) are associated with profound changes in glial cell morphology and signaling. This study investigates the three-dimensional morphology of microglia and the intracellular localization of phosphorylated SMAD proteins as downstream effectors of transforming growth factor β (TGF-β) signaling in the amyloid precursor protein and presenilin-1 (APP/PS1) transgenic mouse model of Alzheimer’s disease. Using confocal microscopy and Simple Neurite Tracer software, we reconstructed and quantitatively analyzed glial cell morphology in aged wild-type and APP/PS1 mice. Immunofluorescence staining revealed altered pSMAD2 distribution in microglia, suggesting impaired canonical TGF-β signaling. Our findings indicate a disturbed glial morphology and dysfunctional TGF-β signaling cascade in the APP/PS1 model, underlining their potential role in Alzheimer’s disease pathogenesis. Full article

Stem cell therapies, including mesenchymal (MSCs) and haematopoietic stem cells (HSCs), have shown promise in neurodegenerative diseases. Here, we investigated the therapeutic effects of a defined combination of unmanipulated MSCs and CD34⁺ HSCs, termed Neuro-Cells (NC), in a murine model of Alzheimer’s disease (AD), the APPswe/PS1dE9 mouse. At 12 months of age, mice received intracisternal injections of NC (1.39 × 10⁶ MSCs + 5 × 10⁵ HSCs) or vehicle. After 45 days, behavioural testing, immunohistochemical analyses of amyloid plaque density (APD), and cortical gene expression profiling were conducted. NC-treated APP/PS1 mice exhibited preserved object recognition memory and reduced anxiety-like behaviours, contrasting with deficits observed in untreated transgenic controls. Histologically, NC treatment significantly reduced the density of small amyloid plaques (<50 μm²) in the hippocampus and thalamus, and total plaque burden in the thalamus. Gene expression analysis revealed that NC treatment normalised or reversed disease-associated changes in insulin receptor (IR) signalling and neurotrophic pathways. Specifically, NC increased expression of Bdnf, Irs2, and Pgc-1α, while attenuating aberrant upregulation of Insr, Igf1r, and markers of ageing and AD-related pathology (Sirt1, Gdf15, Arc, Egr1, Cldn5). These findings indicate that NC therapy mitigates behavioural and molecular hallmarks of AD, potentially via restoration of BDNF and insulin receptor-mediated signalling. Full article

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by memory loss and cognitive decline, with women being disproportionately affected in both prevalence and severity. A key feature of AD is synaptic loss, particularly around amyloid-β (Aβ) aggregates, which correlates strongly with the severity of dementia. Oligomeric Aβ is believed to be the primary driver of synaptic dysfunction by impairing excitatory neurotransmission through interactions with synaptic receptors, including N-methyl-D-aspartate (NMDA) receptors. However, the influence of sex on these synaptic changes and NMDA receptor mislocalization in AD is not well understood. This study examined potential sex-specific differences in synaptotoxicity and the role of extrasynaptic GluN2B-containing NMDA receptors in AD pathogenesis using the APP/PS1 double transgenic mouse model. Although both male and female mice showed a similar amyloid burden and cognitive impairments, synaptic alterations were slightly less severe in females, suggesting subtle sex differences in synaptic pathology. Both sexes exhibited the mislocalization of GluN2B subunits to extrasynaptic areas, which was linked to reduced PSD-95 levels and the synaptic accumulation of Aβ_1–42. Intrahippocampal injections of DL-TBOA confirmed the role of extrasynaptic GluN2B-containing NMDA receptors in memory dysfunction. These findings emphasize the importance of targeting synaptic receptor trafficking to address AD-related memory deficits, potentially offering a therapeutic approach for both sexes. Full article

Background: The excessive accumulation of Aβ plays a critical role in the development of Alzheimer’s disease. However, the therapeutic potential of drugs like curcumin is often limited by low biocompatibility and BBB permeability. In this study, we developed a nanomaterial, BP-PEG-Tar@Cur, which was designed to enhance the biocompatibility of (curcumin) Cur, target Aβ, and augment BBB permeability through near-infrared (NIR) photothermal effects. Methods: Soluble Aβ, ThT fluorescence, and Aβ depolymerization fluorescence experiments were conducted to evaluate the ability of BP-PEG-Tar@Cur to inhibit Aβ aggregation and dissociate Aβ fibrils. Cell uptake assays were performed to confirm the targeting ability of BP-PEG-Tar@Cur towards Aβ. In vitro mitochondrial ROS clearance and in vivo detection of inflammatory factors were used to assess the anti-inflammatory and antioxidant properties of the nanodrug. Water maze behavioral experiments were conducted to evaluate the effect of BP-PEG-Tar@Cur on spatial memory, learning ability, and behavioral disorders in AD mice. Results: The nanodrug effectively inhibited Aβ aggregation and dissociated Aβ fibrils in vitro. BP-PEG-Tar@Cur demonstrated efficiency in curbing ROS overproduction in mitochondria and dampening the activation of microglia and astrocytes triggered by Aβ aggregation. Water maze behavioral experiments revealed that BP-PEG-Tar@Cur enhanced spatial memory, learning ability, and alleviated behavioral disorders in AD mice. Conclusions: Collectively, these findings demonstrate that BP-PEG-Tar@Cur has the potential to be an effective targeted drug for inhibiting Aβ aggregation and improving cognitive impairment in AD mice. Full article

Alzheimer’s disease (AD) is the most common cause of dementia, and no cure is currently available. The β-amyloid cascade of AD and neurofibrillary tangles are the basis of the current understanding of AD pathogenesis, driving drug investigation and other discoveries. Up until now, no AD models have entirely validated the β-amyloid cascade hypothesis. AD models must be capable of recapitulating the critical events of this pathology, including β-amyloid plaques and neurofibrillary tangles. The development of plaques is probably derived from the amyloid precursor protein (APP) and presenilin 1 (PS1) familial Alzheimer’s disease (FAD) mutations, while the tangle-like pathology is determined by tau mutations. Transgenic mouse models struggle to replicate the entire spectrum of AD, particularly neuronal death stemming from β-amyloid and tau pathologies. Furthermore, the success of these transgenic mice often relies on the overexpression of APP transgenes enclosing FAD-associated mutations at levels beyond physiological. Ultimate species-specific discrepancies in genome and protein composition between the human and the mouse may hinder the accurate recapitulation of AD pathological events in mouse models. Although none of the AD models fully mirrors human pathology, these experimental in vivo animal models have provided valuable insights into β-amyloid toxicity and the overall pathophysiological basis of AD. Therefore, these experimental models have been widely used in the preclinical evaluation of therapeutic strategies and have played a pivotal role in the development of immunotherapies for AD. In this review, we sum up the main transgenic mouse models used for AD research, whether they are APP mutation-based mice, APP plus presenilin mutation-based mice, or tau mutation-based mice. The specific characteristics of each mouse model and the significance of their use for AD research, focusing on their current advantages and disadvantages, as well as on the progress made and the forthcoming challenges in replicating this neurodegenerative disease, are also highlighted. Full article

Alzheimer’s disease (AD) is marked by impaired cognitive functions, particularly in learning and memory, owing to complex and diverse mechanisms. Methionine restriction (MR) has been found to exert a mitigating effect on brain oxidative stress to improve AD. However, the bidirectional crosstalk between the gut and brain through which MR enhances learning and memory in AD, as well as the effects of fecal microbiota transplantation (FMT) from MR mice on AD mice, remains underexplored. In this study, APP/PS1 double transgenic AD mice were used and an FMT experiment was conducted. 16S rRNA gene sequencing, targeted metabolomics, and microbial metabolite short-chain fatty acids (SCFAs) of feces samples were analyzed. The results showed that MR reversed the reduction in SCFAs induced by AD, and further activated the free fatty acid receptors, FFAR2 and FFAR3, as well as the transport protein MCT1, thereby signaling to the brain to mitigate inflammation and enhance the learning and memory capabilities. Furthermore, the FMT experiment from methionine-restricted diet mouse donors showed that mice receiving FMT ameliorated Alzheimer’s learning and memory ability through SCFAs. This study offers novel non-pharmaceutical intervention strategies for AD prevention. Full article

Alzheimer’s disease (AD) is a devastating disorder with a global prevalence estimated at 55 million people. In clinical studies administering certain anti-beta-amyloid (Aβ) antibodies, amyloid-related imaging abnormalities (ARIAs) have emerged as major adverse events. The frequency of these events is higher among apolipoprotein ε4 allele carriers (APOE4) compared to non-carriers. To reflect patients most at risk for vascular complications of anti-Aβ immunotherapy, we selected an APPswe/PS1dE9 transgenic mouse model bearing the human APOE4 gene (APPPS1:E4) and compared it with the same APP/PS1 mouse model bearing the human APOE3 gene (APOE ε3 allele; APPPS1:E3). Using histological and biochemical analyses, we characterized mice at three ages: 8, 12, and 16 months. Female and male mice were assayed for general cerebral fibrillar and pyroglutamate (pGlu-3) Aβ deposition, cerebral amyloid angiopathy (CAA), microhemorrhages, apoE and cholesterol composition, astrocytes, microglia, inflammation, lysosomal dysfunction, and neuritic dystrophy. Amyloidosis, lipid deposition, and astrogliosis increased with age in APPPS1:E4 mice, while inflammation did not reveal significant changes with age. In general, APOE4 carriers showed elevated Aβ, apoE, reactive astrocytes, pro-inflammatory cytokines, microglial response, and neuritic dystrophy compared to APOE3 carriers at different ages. These results highlight the potential of the APPPS1:E4 mouse model as a valuable tool in investigating the vascular side effects associated with anti-amyloid immunotherapy. Full article

Alzheimer’s disease (AD) is characterized by a loss of neurons in the cortex and subcortical regions. Previously, we showed that the progressive degeneration of subcortical monoaminergic (MAergic) neurons seen in human AD is recapitulated in the APP_swe/PS1ΔE9 (APP/PS) transgenic mouse model. Because degeneration of cholinergic (Ach) neurons is also a prominent feature of AD, we examined the integrity of the Ach system in the APP/PS model. The overall density of Ach fibers is reduced in APP/PS1 mice at 12 and 18 months of age but not at 4 months of age. Analysis of basal forebrain Ach neurons shows no loss of Ach neurons in the APP/PS model. Thus, since MAergic systems show overt cell loss at 18 months of age, the Ach system is less vulnerable to neurodegeneration in the APP/PS1 model. We also examined whether the proximity to Aβ deposition affected the degeneration of Ach and 5-HT afferents. We found that the areas closer to the edges of compact Aβ deposits exhibit a more severe loss of afferents than the areas that are more distal to Aβ deposits. Collectively, the results indicate that the APP/PS model recapitulates the degeneration of multiple subcortical neurotransmitter systems, including the Ach system. In addition, the results indicate that Aβ deposits cause global as well as local toxicity to subcortical afferents. Full article

Alzheimer’s disease (AD) stands as the most prevalent neurodegenerative disorder, characterized by a multitude of pathological manifestations, prominently marked by the aggregation of amyloid beta. Recent investigations have revealed a compelling association between excessive adiposity and glial activation, further correlating with cognitive impairments. Additionally, alterations in levels of insulin-like growth factor 1 (IGF-1) have been reported in individuals with metabolic conditions accompanied by memory dysfunction. Hence, our research endeavors to comprehensively explore the impact of IGF-1 on the hippocampus and adipose tissue in the context of Alzheimer’s disease. To address this, we have conducted an in-depth analysis utilizing APP/PS2 transgenic mice, recognized as a well-established mouse model for Alzheimer’s disease. Upon administering IGF-1 injections to the APP/PS2 mice, we observed notable alterations in their behavioral patterns, prompting us to undertake a comprehensive transcriptomic analysis of both the hippocampal and adipose tissues. Our data unveiled significant modifications in the functional profiles of these tissues. Specifically, in the hippocampus, we identified changes associated with synaptic activity and neuroinflammation. Concurrently, the adipose tissue displayed shifts in processes related to fat browning and cell death signaling. In addition to these findings, our analysis enabled the identification of a collection of long non-coding RNAs and circular RNAs that exhibited significant changes in expression subsequent to the administration of IGF-1 injections. Furthermore, we endeavored to predict the potential roles of these identified RNA molecules within the context of our study. In summary, our study offers valuable transcriptome data for hippocampal and adipose tissues within an Alzheimer’s disease model and posits a significant role for IGF-1 within both the hippocampus and adipose tissue. Full article

Alzheimer’s disease (AD) is an irreversible neurodegenerative disease that affects millions of people worldwide. AD does not have a cure and most drug development efforts in the AD field have been focused on targeting the amyloid pathway based on the “amyloid cascade hypothesis”. However, in addition to the amyloid pathway, substantial evidence also points to dysregulated neuronal calcium (Ca²⁺) signaling as one of the key pathogenic events in AD, and it has been proposed that pharmacological agents that stabilize neuronal Ca²⁺ signaling may act as disease-modifying agents in AD. In previous studies, we demonstrated that positive allosteric regulators (PAMs) of the Sarco/endoplasmic reticulum Ca²⁺ ATPase (SERCA) pump might act as such Ca²⁺ stabilizing agents. In the present study, we report the development of a novel SERCA PAM agent, compound NDC-1173. To test the effectiveness of this compound, we performed behavioral studies with the APP/PS1 transgenic AD mouse model. We also evaluated effects of this compound on expression of endoplasmic reticulum (ER) stress genes in the hippocampus of APP/PS1 mice. The results of this study support the hypothesis that the SERCA pump is a potential novel therapeutic drug target and that NDC-1173 is a promising lead molecule for developing disease-modifying agents in AD. Full article

Mitochondrial bioenergetics and dynamics (alterations in morphology and motility of mitochondria) play critical roles in neuronal reactions to varying energy requirements in health and disease. In Alzheimer’s disease (AD), mitochondria undergo excessive fission and become less motile. The mechanisms leading to these alterations are not completely clear. Here, we show that collapsin response mediator protein 2 (CRMP2) is hyperphosphorylated in AD and that is accompanied by a decreased interaction of CRMP2 with Drp1, Miro 2, and Mitofusin 2, which are proteins involved in regulating mitochondrial morphology and motility. CRMP2 was hyperphosphorylated in postmortem brain tissues of AD patients, in brain lysates, and in cultured cortical neurons from the double transgenic APP/PS1 mice, an AD mouse model. CRMP2 hyperphosphorylation and dissociation from its binding partners correlated with increased Drp1 recruitment to mitochondria, augmented mitochondrial fragmentation, and reduced mitochondrial motility. (S)-lacosamide ((S)-LCM), a small molecule that binds to CRMP2, decreased its phosphorylation at Ser 522 and Thr 509/514, and restored CRMP2′s interaction with Miro 2, Drp1, and Mitofusin 2. This was paralleled by decreased Drp1 recruitment to mitochondria, diminished mitochondrial fragmentation, and improved motility of the organelles. Additionally, (S)-LCM-protected cultured cortical AD neurons from cell death. Thus, our data suggest that CRMP2, in a phosphorylation-dependent manner, participates in the regulation of mitochondrial morphology and motility, and modulates neuronal survival in AD. Full article

A mis-metabolism of transition metals (i.e., copper, iron, and zinc) in the brain has been recognised as a precursor event for aggregation of Amyloid-β plaques, a pathological hallmark of Alzheimer’s disease (AD). However, imaging cerebral transition metals in vivo can be extremely challenging. As the retina is a known accessible extension of the central nervous system, we examined whether changes in the hippocampus and cortex metal load are also mirrored in the retina. Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to visualise and quantify the anatomical distribution and load of Cu, Fe, and Zn in the hippocampus, cortex, and retina of 9-month-old Amyloid Precursor Protein/Presenilin 1 (APP/PS1, n = 10) and Wild Type (WT, n = 10) mice. Our results show a similar metal load trend between the retina and the brain, with the WT mice displaying significantly higher concentrations of Cu, Fe, and Zn in the hippocampus (p < 0.05, p < 0.0001, p < 0.01), cortex (p < 0.05, p = 0.18, p < 0.0001) and the retina (p < 0.001, p = 0.01, p < 0.01) compared with the APP/PS1 mice. Our findings demonstrate that dysfunction of the cerebral transition metals in AD is also extended to the retina. This could lay the groundwork for future studies on the assessment of transition metal load in the retina in the context of early AD. Full article

Melatonin, insulin, and Δ9-tetrahydrocannabinol (THC) have been shown to reverse cognitive deficits and attenuate neuropathologies in transgenic mouse models of Alzheimer’s disease (AD) when used individually. Here, we evaluated the therapeutic properties of long-term intranasal treatment with a novel nanoformulation containing melatonin, insulin, and THC in aged APPswe/PS1ΔE9 (APP/PS1) mice, a transgenic model of AD. Transgenic mice at the age of 12 months were intranasally administered with a new nanoformulation containing melatonin, insulin, and THC at doses of 0.04, 0.008, and 0.02 mg/kg, respectively, once daily for 3 months. The spatial memory of the mice was assessed using the radial arm water maze (RAWM) test before and after drug treatment. Brain tissues were collected at the end of the treatment period for the assessment of Aβ load, tauopathy state, and markers of mitochondrial function. The RAWM test revealed that the treatment with the melatonin–insulin–THC (MIT) nasal spray improved the spatial learning memory of APP/PS1 mice significantly. Results of protein analyses of brain homogenates indicated that MIT treatment significantly decreased the tau phosphorylation implicated in tau toxicity (p < 0.05) and the expression of CKMT1 associated with mitochondrial dysfunction. Moreover, MIT significantly decreased the expression of two mitochondrial fusion-related proteins, Mfn2 and Opa1 (p < 0.01 for both), while increasing the expression of a mitophagy regulator, Parkin, suggesting a compensatory enhancement of mitophagy due to MIT-promoted mitochondrial fusion. In conclusion, this study was the first to demonstrate the ability of an MIT nanoformulation to improve spatial memory in AD mice through its multi-targeting effects on Aβ production, tau phosphorylation, and mitochondrial dynamics. Thus, MIT may be a safe and effective therapeutic for AD. Full article

Neurogenesis plays a crucial role in cognitive processes. During aging and in Alzheimer’s disease (AD), altered neurogenesis and neuroinflammation are evident both in C57BL/6J, APP_Swe/PS1_dE9 (Tg) mice and humans. AD pathology may slow down upon drug treatment, for example, in a previous study of our group P33, a putative neuroprotective agent was found to exert advantageous effects on the elevated levels of APP, Aβ, and neuroinflammation. In the present study, we aimed to examine longitudinal alterations in neurogenesis, neuroinflammation and AD pathology in a transgenic (Tg) mouse model, and assessed the putative beneficial effects of long-term P33 treatment on AD-specific neurological alterations. Hippocampal cell proliferation and differentiation were significantly reduced between 8 and 12 months of age. Regarding neuroinflammation, significantly elevated astrogliosis and microglial activation were observed in 6- to 7-month-old Tg animals. The amounts of the molecules involved in the amyloidogenic pathway were altered from 4 months of age in Tg animals. P33-treatment led to significantly increased neurogenesis in 9-month-old animals. Our data support the hypothesis that altered neurogenesis may be a consequence of AD pathology. Based on our findings in the transgenic animal model, early pharmacological treatment before the manifestation of AD symptoms might ameliorate neurological decline. Full article