Alzheimer's Disease-like Phenotype Research Articles

Ethyl gallate ameliorates diabetes-induced Alzheimer's disease-like phenotype in rats via activation of α7 nicotinic receptors and mitigation of oxidative stress

Cognitive decline, an important comorbidity of type 2 diabetes (T2D), is attributed to oxidative stress and impaired cholinergic signaling in the brain. The α7 nicotinic acetylcholine receptor (α7nAChR) is densely distributed in the hippocampus and cortex, and exerts neuroprotective and procognitive actions. Ethyl gallate (EG), a natural phenolic antioxidant compound, showed high in-silico binding affinity towards α7nAChR and brain penetrability. Therefore, the present study aimed to evaluate the involvement of α7nAChR in the potential of EG to ameliorate T2D-induced Alzheimer's disease-like condition. T2D was induced by intraperitoneal (i.p.) injection of streptozotocin (35 mg/kg) in rats on high-fat diet. Diabetic animals were treated with EG (10 and 20 mg/kg, i.p.) for four weeks, and their learning and memory performance was evaluated by the Morris water maze (MWM). Further, the brains were subjected to biochemical analysis of antioxidants like glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT), and oxidative stress marker malonaldehyde (MDA). While diabetic rats showed a significant decline in cognitive performance in the MWM, a substantial improvement was noticed following EG treatment. Further, the diabetes-associated reductions in GSH, SOD, and CAT levels, along with increased MDA contents in the brain, were effectively restored by EG. Interestingly, pre-treatment with α7nAChR antagonist methyllycaconitine (1 mg/kg, i.p.) attenuated the effects of EG on behavioral and biochemical parameters. The results suggest that EG may augment cholinergic signaling in the brain via α7nAChR to mitigate oxidative stress, consequently alleviating T2D-associated dementia. Therefore, EG could be a potential candidate for addressing cognitive impairment comorbid with T2D.

Ferroptotic Potency of ISM1 Expression in the Drug-Induced Alzheimer's Disease-Like Phenotype Under the Influence of Betulin.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by two main pathological mechanisms, mostly hyperphosphorylated tau and amyloid-β toxicity. Although many studies focus on these basic mechanisms, ferroptosis draws attention as an important pathway responsible for neurodegeneration in AD. There is no definitive treatment for AD but alternative phytochemicals to drugs come into prominence. Betulin is usually obtained from the birch tree. It is an abundant triterpene and has a high antioxidant capacity. Isthmin-1 (ISM1) is a secreted adipokine. In this study, we investigated the potential treatment of AD in the ferroptosis-ISM1-betulin triangle. For this, we created an AD model with okadaic acid (200 ng/kg)) in 36 Wistar albino male rats and treated with betulin (20 mg/kg/day, i.p). We evaluated ISM1 gene expression, iron accumulation, and total oxidative metabolism parameters (TAS, TOS, OSI) in hippocampal tissue. We analyzed cognitive recovery in AD with Morris Water Maze Test and general locomotor activity, explore, and anti-anxiolytic effect with Open Field Test. We compared the obtained data with metabolic and genetic results. In conclusion, betulin may have a role in neuronal ferroptotic mechanisms by reducing iron accumulation by ISM1 regulation. Betulin may have a role in neuronal ferroptotic mechanisms by reducing iron accumulation by ISM1 regulation. Although this study suggests the corrective effect of betulin and ISM1 on cognitive gain and anxiety, it is the first study to show the total antioxidant capacity of betulin in AD.

Insulin-incubated palladium clusters alleviate Alzheimer's disease-like phenotypes in a preclinical mouse model.

Insulin-incubated palladium clusters alleviate Alzheimer's disease-like phenotypes in a preclinical mouse model.

Cdc42GAP deficiency contributes to the Alzheimer's disease phenotype.

Alzheimer's disease, the most common cause of dementia, is a chronic degenerative disease with typical pathological features of extracellular senile plaques and intracellular neurofibrillary tangles and a significant decrease in the density of neuronal dendritic spines. Cdc42 is a member of the small G protein family that plays an important role in regulating synaptic plasticity and is regulated by Cdc42GAP, which switches Cdc42 from active GTP-bound to inactive GDP-bound states regulating downstream pathways via effector proteins. However, few studies have focused on Cdc42 in the progression of Alzheimer's disease. In a heterozygous Cdc42GAP mouse model that exhibited elevated Cdc42-GTPase activity accompanied by increased Cdc42-PAK1-cofilin signalling, we found impairments in cognitive behaviours, neuron senescence, synaptic loss with depolymerization of F-actin and the pathological phenotypes of Alzheimer's disease, including phosphorylated tau (p-T231, AT8), along with increased soluble and insoluble Aβ1-42 and Aβ1-40, which are consistent with typical Alzheimer's disease mice. Interestingly, these impairments increased significantly with age. Furthermore, the results of quantitative phosphoproteomic analysis of the hippocampus of 11-month-old GAP mice suggested that Cdc42GAP deficiency induces and accelerates Alzheimer's disease-like phenotypes through activation of GSK-3β by dephosphorylation at Ser9, Ser389 and/or phosphorylation at Tyr216. In addition, overexpression of dominant-negative Cdc42 in the primary hippocampal and cortical neurons of heterozygous Cdc42GAP mice reversed synaptic loss and tau hyperphosphorylation. Importantly, the Cdc42 signalling pathway, Aβ1-42, Aβ1-40 and GSK-3β activity were increased in the cortical sections of Alzheimer's disease patients compared with those in healthy controls. Together, these data indicated that Cdc42GAP is involved in regulating Alzheimer's disease-like phenotypes such as cognitive deficits, dendritic spine loss, phosphorylated tau (p-T231, AT8) and increased soluble and insoluble Aβ1-42 and Aβ1-40, possibly through the activation of GSK-3β, and these impairments increased significantly with age. Thus, we provide the first evidence that Cdc42 is involved in the progression of Alzheimer's disease-like phenotypes, which may provide new targets for Alzheimer's disease treatment.

ACE2/ANG-(1-7)/Mas receptor axis activation prevents inflammation and improves cognitive functions in streptozotocin induced rat model of Alzheimer's disease-like phenotypes

Activation of the renin-angiotensin system (RAS), by Angiotensin converting enzyme/Angiotensin II/Angiotensin receptor-1 (ACE/Ang II/AT1 R) axis elicits amyloid deposition and cognitive impairment. Furthermore, ACE2 induced release of Ang-(1-7) binds with the Mas receptor and autoinhibits ACE/Ang II/AT1 axis activation. Inhibition of ACE by perindopril has been reported to improve memory in preclinical settings. However, the functional significance and mechanism by which ACE2/Mas receptor regulate cognitive functions and amyloid pathology is not known. The present study is aimed to determine the role of ACE2/Ang-(1–7)/Mas receptor axis in STZ induced rat model of Alzheimer's disease (AD). We have used pharmacological, biochemical and behavioural approaches to identify the role of ACE2/Ang-(1–7)/Mas receptor axis activation on AD-like pathology in both in vitro and invivo models. STZ treatment enhances ROS formation, inflammation markers and NFκB/p65 levels which are associated with reduced ACE2/Mas receptor levels, acetylcholine activity and mitochondrial membrane potential in N2A cells. DIZE mediated ACE2/Ang-(1–7)/Mas receptor axis activation resulted in reduced ROS generation, astrogliosis, NFκB level and inflammatory molecules and improved mitochondrial functions along with Ca2+ influx in STZ treated N2A cells. Interestingly, DIZE induced activation of ACE2/Mas receptor significantly restored acetylcholine levels and reduced amyloid-beta and phospho-tau deposition in cortex and hippocampus that resulted in improved cognitive function in STZ induced rat model of AD-like phenotypes. Our data indicate that ACE2/Mas receptor activation is sufficient to prevented cognitive impairment and progression of amyloid pathology in STZ induced rat model of AD-like phenotypes. These findings suggest the potential role of ACE2/Ang-(1–7)/Mas axis in AD pathophysiology by regulating inflammation cognitive functions.

Patients carrying the mutation p.R406W in MAPT present with non-conforming phenotypic spectrum.

The missense mutation p.R406W in microtubule-associated protein tau leads to frontotemporal lobar degeneration with an amnestic, Alzheimer's disease-like phenotype with an autosomal dominant pattern of inheritance. In 2003, we described the pedigree of a Belgian family, labelled ADG, with 28 p.R406W patients. Over 18 years follow-up, we extended the family with 10 p.R406W carriers and provided an in-depth clinical description of the patients. Additionally, genetic screening was used to identify p.R406W carriers in Belgian cohorts of frontotemporal dementia and Alzheimer's disease patients and to calculate p.R406W frequency. In the frontotemporal dementia cohort, we found four p.R406W carriers (n = 647, 0.62%) and three in the Alzheimer's disease cohort (n = 1134, 0.26%). Haplotype sharing analysis showed evidence of a shared haplotype suggesting that they are descendants of a common ancestor. Of the p.R406W patients, we describe characteristics of neuropsychological, imaging and fluid biomarkers as well as neuropathologic examination. Intriguingly, the phenotypic spectrum among the p.R406W patients ranged from typical behavioural variant frontotemporal dementia to clinical Alzheimer's disease, based on CSF biomarker analysis and amyloid PET scan. Heterogeneous overlap syndromes existed in between, with highly common neuropsychiatric symptoms like disinhibition and aggressiveness, which occurred in 100% of frontotemporal dementia and 58% of clinical Alzheimer's disease patients. This was also the case for memory problems, 89% in frontotemporal dementia and 100% in clinical Alzheimer's disease patients. Median age at death was significantly lower in patients with frontotemporal dementia (68 years) compared to clinical Alzheimer's disease patients (79 years), although the sizes of the sub-cohorts are limited and do not allow prognostic predictions. Post-mortem brain analysis of one p.R406W patient with behavioural variant frontotemporal dementia revealed frontotemporal lobar degeneration with tau pathology. Notably, neuropathological investigation showed only 3R tau isoforms in the absence of 4R tau reactivity, an unusual finding in microtubule-associated protein tau-related frontotemporal lobar degeneration. No traces of amyloid pathology were present. Prevalence of the p.R406W mutation was relatively high in both frontotemporal dementia and Alzheimer's disease Belgian patient cohorts. These findings grant new insights into genotype-phenotype correlations of p.R406W carriers. They may help in further unravelling of the pathophysiology of this tauopathy and in facilitating the identification of patients with p.R406W-related frontotemporal lobar degeneration, both in clinical diagnostic and research settings.

Mesenchymal stem cell-derived extracellular vesicles ameliorate Alzheimer's disease-like phenotypes in a preclinical mouse model.

Alzheimer's disease (AD) is an irreversible neurodegenerative disorder that affects more than 44 million people worldwide. Despite the high disease burden, there is no effective treatment for people suffering from AD. Mesenchymal stem cells (MSCs) are multipotent stromal cells that have been widely studied due to their therapeutic potential. However, administration of cells has been found to have a multitude of limitations. Recently, extracellular vesicles (EVs) derived from MSCs have been studied as a therapeutic candidate, as they exhibit similar immunoprotective and immunomodulatory abilities as the host human MSCs.Methods: To test the potential therapeutic effects of MSC EVs, human bone-marrow derived MSCs were grown in three-dimensional (3D) cell culture, and small EVs were harvested using differential ultracentrifugation. These small EVs were given to non-transgenic (NT) or 5XFAD (5 familial Alzheimer's disease mutations) mice intranasally (IN) every 4 days for 4 months. The mice were then required to perform a variety of behavioral assays to measure changes in learning and memory. Afterwards, immunohistochemistry was performed on brain slices to measure amyloid beta (Aβ) and glial fibrillary acidic protein (GFAP) levels.Results: The data revealed that 5XFAD mice that received hMSC-EV treatment behaved significantly better in cognitive tests than saline treated 5XFAD mice, with no significant change between EV-treated 5XFAD mice and NT mice. Additionally, we found lower Aβ plaque load in the hippocampus of the EV-treated mice. Finally, less colocalization between GFAP and Aβ plaques was found in the brain of EV-treated mice compared to saline.Conclusions: Taken together, these data suggest that IN administration of MSC-derived EVs can slow down AD pathogenesis.

Thymoquinone administration ameliorates Alzheimer's disease-like phenotype by promoting cell survival in the hippocampus of amyloid beta1–42 infused rat model

BackgroundThymoquinone (TQ), a biologically active ingredient of Nigella sativa, has anti-inflammatory, anti-oxidative and neuroprotective properties. Therefore, it could be a good candidate in the recovery of Alzheimer`s disease (AD) pathology rather than current symptomatic reliefs. PurposeIn the present study, we examined the molecular healing effects of TQ in amyloid beta 1–42 (Aβ1–42) peptide-infused AD rat hippocampus. Study designA micro-osmotic pump containing aggregated Aβ1–42 was cannulated into the hippocampus of adult female rats. After two weeks infusion, the dose of TQ (10 mg/kg or 20 mg/kg) was determined according to the HPLC results of cerebrospinal fluid and TQ was given to rats intragastrically for 15 days. MethodsThe memory performance of rats was determined by Morris water maze test. Afterwards, the acetylcholinesterase (AChE) level were measured by ELISA. Histopathological examinations of hippocampal tissue were performed for cell survival by Nissl staining, for detection of amyloid plaque deposits by Congo red staining and for determination of degenerating neurons by Fluoro Jade C staining. MicroRNA/mRNA levels and protein expressions of AD-related genes and proteins were analyzed by Real-Time Polymerase Chain Reaction and Western Blotting, respectively. ResultsAdministration of TQ enhanced the memory performance of Aβ1–42 infused rats and it also ameliorated the neuronal loss in the cornu ammonis (CA1), but not in the dentate gyrus (DG). In addition, TQ treatment decreased the fibril deposition whose accumulation was significantly higher in the Aβ1–42-infused animals compared to that of the control group. The expression profiles of mir29c and Bax which significantly upregulated in the Aβ1–42-infused animals were attenuated by TQ. Furthermore, administration of TQ decreased the expressions of Aβ, phosphorylated-tau, and BACE-1 proteins. There was no significant therapeutic effect of TQ on the AKT/GSK3β or MAPK signaling pathways which were affected due to Aβ1–42 infusion. ConclusionTQ has the capacity to recover the neuropathology by removing Aβ plaques and by restoring neuron viability. All might have established the molecular basement of the consolidation in the memory observed by means of TQ treatment.

Decreased glucose transporter 1 expression at the blood-brain barrier exacerbates Alzheimer disease-like phenotypes in mouse models

Decreased glucose transporter 1 expression at the blood-brain barrier exacerbates Alzheimer disease-like phenotypes in mouse models

Adaptive reprogramming of brain mitochondrial biology during preconditioning prevents the sporadic Alzheimer's disease-like phenotype

Adaptive reprogramming of brain mitochondrial biology during preconditioning prevents the sporadic Alzheimer's disease-like phenotype

Exaggerated [Ca2+]I Signaling and Alzheimer's Disease-Like Phenotypes of PS1M146V Mice are Attenuated by Decreasing Brain InsP3R-1 Protein Levels

Familial Alzheimer's disease (FAD) is linked to mutations in the presenilin (PS) homologs. FAD mutations have several cellular consequences, including exaggerated intracellular Ca2+ ([Ca2+]i) signaling - enhanced sensitivity to agonists of ER Ca2+ release and increased magnitudes of [Ca2+]i signals. Single channel recordings suggest exaggerated [Ca2+]i signaling is due to a gain-of-function interaction between FAD mutant PS and the inositol 1,4,5-trisphosphate receptor (InsP3R). However, the in vivo significance of the PS-InsP3R interaction to exaggerated [Ca2+]i signaling and the contribution of exaggerated [Ca2+]i signaling to the development of AD are unknown. If exaggerated [Ca2+]i signaling is InsP3R-dependent, we hypothesize that decreasing InsP3R protein expression will normalize [Ca2+]i signaling. Therefore, we crossed the Opisthotonus (Opt) mouse, deficient in InsP3R1 protein, to the PS1M146V knock-in (PS1KIN) AD mouse model to investigate the contribution of InsP3R-1-mediated [Ca2+]i release to exaggerated [Ca2+]i signaling, and the role of exaggerated [Ca2+]i signaling to the AD-like phenotypes of this mouse model. We observed that the Opt allele normalizes exaggerated [Ca2+]i release in vitro and ex vivo. Interestingly, in young (5wk) and mature (3 mth) PS1KIN mice we observed that the Opt allele normalized aberrantly activated hippocampal biochemical pathways and the enhancement of CA3-CA1 early long-term potentiation present in these mice - phenotypes that mirror the early hippocampal hyperactivity in patients that later develop AD. These findings indicate that FAD mutant PS-associated exaggerated [Ca2+]i signaling is InsP3R1-dependent and a early event in Alzheimer's disease.

Spinocerebellar ataxia 17 (SCA17) and Huntington’s disease-like 4 (HDL4)

Spinocerebellar ataxia 17 (SCA17) or Huntington's disease-like-4 is a neurodegenerative disease caused by the expansion above 44 units of a CAG/CAA repeat in the coding region of the TATA box binding protein (TBP) gene leading to an abnormal expansion of a polyglutamine stretch in the corresponding protein. Alleles with 43 and 44 repeats have been identified in sporadic cases and their pathogenicity remains uncertain. Furthermore, incomplete penetrance of pathological alleles with up to 49 repeats has been suggested. The imperfect nature of the repeat makes intergenerational instability extremely rare and de novo mutations are most likely the result of partial duplications. This is one of the rarer forms of autosomal dominant cerebellar ataxia but the associated phenotype is often severe, involving various systems (cerebral cortex, striatum, and cerebellum), with extremely variable age at onset (range: 3-75 years) and clinical presentation. This gene is thought to account for a small proportion of patients with a Huntington's disease-like phenotype and cerebellar signs. Parkinson's disease-like, Creutzfeldt-Jakob disease-like and Alzheimer disease-like phenotypes have also been described with small SCA17 expansions. The abnormal protein is expressed at the same level as its normal counterpart and forms neuronal intranuclear inclusions containing other proteins involved in protein folding or degradation. The increase in the size of the glutamine stretch enhances transcription in vitro, probably leading to transcription deregulation. Interestingly, the TBP protein mutated in SCA17 is recruited in the inclusions of other polyglutaminopathies, suggesting its involvement in the transcription down-regulation observed in these diseases.

Full Reversal of Alzheimer's Disease-Like Phenotype in a Mouse Model with Conditional Overexpression of Glycogen Synthase Kinase-3

Glycogen synthase kinase-3 (GSK-3) is a ubiquitously expressed serine/threonine kinase that is particularly abundant in the CNS. Dysregulation of GSK-3 activity is believed to play a key role in the pathogenesis of CNS chronic disorders such as Alzheimer's disease (AD), bipolar disorder, and Huntington's disease, and of metabolic disorders such as type II diabetes. Accordingly, GSK-3 inhibitors have been postulated as therapeutic tools for these diseases. Interestingly, pathophysiological and pharmacological regulation of GSK-3 is affected by an amplification mechanism that applies both to inhibition and activation. The possibility therefore exists that sustained inhibition or activation might persist after cessation of the initial trigger. Regarding AD, GSK-3 has been shown to accumulate in pretangle neurons. Furthermore, GSK-3 phosphorylates tau in most serine and threonine residues hyperphosphorylated in PHF (paired helical filament)-tau and GSK-3 activity contributes both to beta-amyloid production and to beta-amyloid-mediated neuronal death. In good agreement, mice with conditional overexpression of GSK-3 in forebrain neurons (Tet/GSK-3beta mice) recapitulate aspects of AD neuropathology such as tau hyperphosphorylation, apoptotic neuronal death, and reactive astrocytosis as well as spatial learning deficit. Here, we exploit the conditional system used to generate Tet/GSK-3beta mice to explore whether the biochemical, histopathological, and behavioral consequences of increased GSK-3 activity are susceptible to revert after restoration of normal GSK-3 levels. Here, we show that transgene shutdown in symptomatic mice leads to normal GSK-3 activity, normal phospho-tau levels, diminished neuronal death, and suppression of the cognitive deficit, thus further supporting the potential of GSK-3 inhibitors for AD therapeutics.