Modeling Alzheimer's disease: from past to future

Mesenchymal Stem Cells from Familial Alzheimer's Patients Express MicroRNA Differently

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the predominant form of dementia globally. No reliable diagnostic, predictive techniques, or curative interventions are available. MicroRNAs (miRNAs) are vital to controlling gene expression, making them valuable biomarkers for diagnosis and prognosis. This study examines the transcriptome of olfactory ecto-mesenchymal stem cells (MSCs) derived from individuals with the PSEN1(A431E) mutation (Jalisco mutation). The aim is to determine whether this mutation affects the transcriptome and expression profile of miRNAs and their target genes at different stages of asymptomatic, presymptomatic, and symptomatic conditions. Expression microarrays compare the MSCs from mutation carriers with those from healthy donors. The results indicate a distinct variation in the expression of miRNAs and mRNAs among different symptomatologic groups and between individuals with the mutation. Using bioinformatics tools allows us to identify target genes for miRNAs, which in turn affect various biological processes and pathways. These include the cell cycle, senescence, transcription, and pathways involved in regulating the pluripotency of stem cells. These processes are closely linked to inter- and intracellular communication, vital for cellular functioning. These findings can enhance our comprehension and monitoring of the disease's physiological processes, identify new disorder indicators, and develop innovative treatments and diagnostic tools for preventing or treating AD.

Improved Quantification of MicroPET/CT Imaging Using CT-derived Scaling Factors

Purpose

Combined micro-PET/CT scanners are widely employed to investigate models of brain disorders in rodents using PET-based coregistration. We examined if CT-based coregistration could improve estimates of brain dimensions and consequently estimates of nondisplaceable binding potential (BPND) in rodent PET studies.

Procedures

PET and CT scans were acquired on 5 female and 5 male CD-1 mice with PET and CT scans were acquired on 5 female and 5 male CD-1 mice with 3-[18F]fluoro-5-(2-pyridinylethynyl)benzonitrile ([18F]FPEB), a radiotracer for the metabotropic glutamate receptor subtype 5 (mGluR5). In the proposed PET/CT (PTCT) approach, the tracer-specific standard volume was dimension-customized to each animal using the scaling factors from CT-to-standard CT coregistration to simplify PET-to-standard PET coregistration (i.e., 3 CT- and 6 PET-derived parameters). For comparison, conventional PET-based coregistration was performed with 9 (PT9) or 12 (PT12) parameters. PET frames were transferred to the standard space by the three approaches (PTCT, PT9, and PT12) to obtain regional time-activity curves (TACs) and BPND in 14 standard volumes of interest (VOIs). Lastly, CT images of the animals were transferred to the standard space by CT-based parameters from PTCT and with the scaling factors replaced with those from PET-based PT9 to evaluate agreement of the skull to the standard CT.

Results

The PET-based approaches showed various degrees of underestimations of scaling factors in the posterior-anterior-direction compared to PTCT, which resulted in negatively proportional overestimation of radioactivity in the cerebellum (reference region) up to 20%, and proportional, more prominent underestimation of BPND in target regions down to -50%. The skulls of individual animals agreed with the standard skull for scaling factors from PTCT but not for the scaling factors from PT9, which suggested inaccuracy of the latter.

Conclusions

The results indicated that conventional PET-based coregistration approaches could yield biased estimates of BPND due to erroneous estimates of brain dimensions when applied to tracers for which the cerebellum serves as reference region. The proposed PTCT provides evidence of a quantitative improvement over PET-based approaches for brain studies using micro-PET/CT scanners.

Preclinical Models for Alzheimer's Disease: Past, Present, and Future Approaches

A robust preclinical disease model is a primary requirement to understand the underlying mechanisms, signaling pathways, and drug screening for human diseases. Although various preclinical models are available for several diseases, clinical models for Alzheimer's disease (AD) remain underdeveloped and inaccurate. The pathophysiology of AD mainly includes the presence of amyloid plaques and neurofibrillary tangles (NFT). Furthermore, neuroinflammation and free radical generation also contribute to AD. Currently, there is a wide gap in scientific approaches to preventing AD progression. Most of the available drugs are limited to symptomatic relief and improve deteriorating cognitive functions. To mimic the pathogenesis of human AD, animal models like 3XTg-AD and 5XFAD are the primarily used mice models in AD therapeutics. Animal models for AD include intracerebroventricular-streptozotocin (ICV-STZ), amyloid beta-induced, colchicine-induced, etc., focusing on parameters such as cognitive decline and dementia. Unfortunately, the translational rate of the potential drug candidates in clinical trials is poor due to limitations in imitating human AD pathology in animal models. Therefore, the available preclinical models possess a gap in AD modeling. This paper presents an outline that critically assesses the applicability and limitations of the current approaches in disease modeling for AD. Also, we attempted to provide key suggestions for the best-fit model to evaluate potential therapies, which might improve therapy translation from preclinical studies to patients with AD.

Synthetic, Cell-Derived, Brain-Derived, and Recombinant β-Amyloid: Modelling Alzheimer's Disease for Research and Drug Development

Alzheimer's disease (AD) is the most common cause of dementia in the elderly, characterised by the accumulation of senile plaques and tau tangles, neurodegeneration, and neuroinflammation in the brain. The development of AD is a pathological cascade starting according to the amyloid hypothesis with the accumulation and aggregation of the β-amyloid peptide (Aβ), which induces hyperphosphorylation of tau and promotes the pro-inflammatory activation of microglia leading to synaptic loss and, ultimately, neuronal death. Modelling AD-related processes is important for both studying the molecular basis of the disease and the development of novel therapeutics. The replication of these processes is often achieved with the use of a purified Aβ peptide. However, Aβ preparations obtained from different sources can have strikingly different properties. This review aims to compare the structure and biological effects of Aβ oligomers and aggregates of a higher order: synthetic, recombinant, purified from cell culture, or extracted from brain tissue. The authors summarise the applicability of Aβ preparations for modelling Aβ aggregation, neurotoxicity, cytoskeleton damage, receptor toxicity in vitro and cerebral amyloidosis, synaptic plasticity disruption, and cognitive impairment in vivo and ex vivo. Further, the paper discusses the causes of the reported differences in the effect of Aβ obtained from the sources mentioned above. This review points to the importance of the source of Aβ for AD modelling and could help researchers to choose the optimal way to model the Aβ-induced abnormalities.

An integrated genome and phenome-wide association study approach to understanding Alzheimer's disease predisposition

Genome-wide association studies (GWAS) have identified common single nucleotide polymorphisms (SNPs) that increase late-onset Alzheimer's disease (LOAD) risk. To identify additional LOAD-associated variants and provide insight into underlying disease biology, we performed a phenome-wide association study on 23 known LOAD-associated SNPs and 4:1 matched control SNPs using UK Biobank data. LOAD-associated SNPs were significantly enriched for associations with 8/778 queried traits, including 3 platelet traits. The strongest enrichment was for platelet distribution width (PDW) (p = 1.2 × 10-5), but increased PDW was not associated with LOAD susceptibility in Mendelian randomization analysis. Of 384 PDW-associated SNPs identified by prior GWAS, 36 were nominally associated with LOAD risk (17,008 cases; 37,154 controls) and 5 survived false-discovery rate correction. Associations confirmed known LOAD risk loci near PICALM, CD2AP, SPI1, and NDUFAF6, and identified a novel risk locus in epidermal growth factor receptor. Integrating GWAS and phenome-wide association study data reveals substantial pleiotropy between genetic determinants of LOAD and of platelet morphology, and for the first time implicates epidermal growth factor receptor - a mediator of β-amyloid toxicity - in Alzheimer's disease susceptibility.

High-throughput screening for amyloid-β binding natural small-molecules based on the combinational use of biolayer interferometry and UHPLC−DAD-Q/TOF-MS/MS

Discovery of drugs rapidly and effectively is an important aspect for Alzheimer's disease (AD). In this study, a novel high-throughput screening (HTS) method aims at screening the small-molecules with amyloid-β (Aβ) binding affinity from natural medicines, based on the combinational use of biolayer interferometry (BLI) and ultra-high-performance liquid chromatography coupled with diode-array detector and quadrupole/time-of-flight tandem mass spectrometry (UHPLC−DAD-Q/TOF-MS/MS) has been firstly developed. Briefly, the components in natural medicines disassociated from biotinylated Aβ were collected to analyze their potential Aβ binding affinity by UHPLC−DAD-Q/TOF-MS/MS. Here, baicalein was confirmed to exhibit the highest binding affinity with Aβ in Scutellaria baicalensis. Moreover, polyporenic acid C (PPAC), dehydrotumulosic acid (DTA), and tumulosic acid (TA) in Kai-Xin-San (KXS) were also identified as potent Aβ inhibitors. Further bioactivity validations indicated that these compounds could inhibit Aβ fibrillation, improve the viability in Aβ-induced PC-12 cells, and decrease the Aβ content and improve the behavioral ability in Caenorhabditis elegans. The molecular docking results confirmed that PPAC, DTA, and TA possessed good binding properties with Aβ. Collectively, the present study has provided a novel and effective HTS method for the identification of natural inhibitors on Aβ fibrillation, which may accelerate the process on anti-AD drugs discovery and development.

Synaptic dysfunction in early phases of Alzheimer's Disease

The synapse is the locus of plasticity where short-term alterations in synaptic strength are converted to long-lasting memories. In addition to the presynaptic terminal and the postsynaptic compartment, a more holistic view of the synapse includes the astrocytes and the extracellular matrix to form a tetrapartite synapse. All these four elements contribute to synapse health and are crucial for synaptic plasticity events and, thereby, for learning and memory processes. Synaptic dysfunction is a common pathogenic trait of several brain disorders. In Alzheimer's Disease, the degeneration of synapses can be detected at the early stages of pathology progression before neuronal degeneration, supporting the hypothesis that synaptic failure is a major determinant of the disease. The synapse is the place where amyloid-β peptides are generated and is the target of the toxic amyloid-β oligomers. All the elements constituting the tetrapartite synapse are altered in Alzheimer's Disease and can synergistically contribute to synaptic dysfunction. Moreover, the two main hallmarks of Alzheimer's Disease, i.e., amyloid-β and tau, act in concert to cause synaptic deficits. Deciphering the mechanisms underlying synaptic dysfunction is relevant for the development of the next-generation therapeutic strategies aimed at modifying the disease progression.

Protective effect of co-administration of caffeine and piracetam on scopolamine-induced amnesia in Wistar rats

Alzheimer's disease is a cerebrovascular disorder characterized by progressive loss of the mental capabilities. The novel therapeutic agent piracetam is a cyclic derivative of γ-aminobutyric acid and one of the oldest recognized synthetic nootropics. Piracetam improves cognitive function without stimulation or sedation. Caffeine is a central nervous system stimulant with nootropic activity. Caffeine promotes the performance of tasks that involve working memory to a limited extent, and it also retards cognitive decline in healthy individuals. The present study aimed to determine the protective effect of co-administering piracetam and caffeine on scopolamine-induced amnesia in rats. Pre-treatment with caffeine and piracetam decreased scopolamine-induced cognitive damage and amnesia. The preventive response was demonstrated by an improved learning tendency. The mechanism responsible for these effects requires further investigation. The co-administration of caffeine and piracetam has potential as a novel therapeutic strategy for combating amnesia.

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Piracetam improves cognitive function with no stimulation or sedation on CNS.

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Caffeine is CNS stimulant which is reported for nootropic activity.

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Caffeine and piracetam pre-treatment decreased scopolamine-induced cognitive damage and amnesia.

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The preventive response was reported by an improvement in learning tendency.

Microfluidic Platforms to Unravel Mysteries of Alzheimer's Disease: How Far Have We Come?

Alzheimer’s disease (AD) is a significant health concern with enormous social and economic impact globally. The gradual deterioration of cognitive functions and irreversible neuronal losses are primary features of the disease. Even after decades of research, most therapeutic options are merely symptomatic, and drugs in clinical practice present numerous side effects. Lack of effective diagnostic techniques prevents the early prognosis of disease, resulting in a gradual deterioration in the quality of life. Furthermore, the mechanism of cognitive impairment and AD pathophysiology is poorly understood. Microfluidics exploits different microscale properties of fluids to mimic environments on microfluidic chip-like devices. These miniature multichambered devices can be used to grow cells and 3D tissues in vitro, analyze cell-to-cell communication, decipher the roles of neural cells such as microglia, and gain insights into AD pathophysiology. This review focuses on the applications and impact of microfluidics on AD research. We discuss the technical challenges and possible solutions provided by this new cutting-edge technique to understand disease-associated pathways and mechanisms.

Looking at Alzheimer's Disease Pathogenesis from the Nuclear Side

Alzheimer’s disease (AD) is a neurodegenerative disorder representing the most common form of dementia. It is biologically characterized by the deposition of extracellular amyloid-β (Aβ) senile plaques and intracellular neurofibrillary tangles, constituted by hyperphosphorylated tau protein. The key protein in AD pathogenesis is the amyloid precursor protein (APP), which is cleaved by secretases to produce several metabolites, including Aβ and APP intracellular domain (AICD). The greatest genetic risk factor associated with AD is represented by the Apolipoprotein E ε4 (APOE ε4) allele. Importantly, all of the above-mentioned molecules that are strictly related to AD pathogenesis have also been described as playing roles in the cell nucleus. Accordingly, evidence suggests that nuclear functions are compromised in AD. Furthermore, modulation of transcription maintains cellular homeostasis, and alterations in transcriptomic profiles have been found in neurodegenerative diseases. This report reviews recent advancements in the AD players-mediated gene expression. Aβ, tau, AICD, and APOE ε4 localize in the nucleus and regulate the transcription of several genes, part of which is involved in AD pathogenesis, thus suggesting that targeting nuclear functions might provide new therapeutic tools for the disease.

Human Dental Pulp Stem Cells Display a Potential for Modeling Alzheimer Disease-Related Tau Modifications

We present here the first description of tau in human dental pulp stem cells (DPSCs) evidenced by RT-PCR data on expression of the gene MAPT and by immunocytochemical detection of epitopes by 12 anti-tau antibodies. The tau specificity of eight of these antibodies was confirmed by their affinity to neurofibrillary tangles (NFTs) in Alzheimer's disease (AD) postmortem brain samples. We therefore used DPSCs and AD brain samples as a test system for determining the probability of the involvement of tau epitopes in the mechanisms converting tau into NFT in AD. Three antibodies to non-phosphorylated and seven antibodies to phosphorylated epitopes bound tau in both DPSCs and AD NFTs, thus suggesting that their function was not influenced by inducers of formation of NFTs in the AD brain. In contrast, AT100, which recognizes a hyperphosphorylated epitope, did not detect it in the cytoplasm of DPSCs but detected it in AD brain NFTs, demonstrating its AD diagnostic potential. This indicated that the phosphorylation/conformational events required for the creation of this epitope do not occur in normal cytoplasm and are a part of the mechanism (s) leading to NFT in AD brain. TG3 bound tau in the cytoplasm and in mitotic chromosomes but did not find it in nuclei. Collectively, these observations characterize DPSCs as a novel tau-harboring neuronal lineage long-term propagable in vitro cellular system for the normal conformational state of tau sites, detectable by antibodies, with their state in AD NFTs revealing those involved in the pathological processes converting tau into NFTs in the course of AD. With this information, one can model the interaction of tau with inducers and inhibitors of hyperphosphorylation toward NFT-like aggregates to search for drug candidates. Additionally, the clonogenicity of DPSCs provides the option for generation of cell lineages with CRISPR-mutagenized genes of familial AD modeling.

Reconstruction of Alzheimer's Disease Cell Model In Vitro via Extracted Peripheral Blood Molecular Cells from a Sporadic Patient

The establishment of human-induced pluripotent stem cell (iPSC) models from sporadic Alzheimer's disease (sAD) patients is necessary and could potentially benefit research into disease etiology and therapeutic strategies. However, the development of sAD iPSC models is still limited due to the multifactorial nature of the disease. Here, we extracted peripheral blood mononuclear cells (PBMCs) from a patient with sAD and induced them into iPSC by introducing the Sendai virus expressing Oct3/4, Sox2, c-Myc, and Klf4, which were subsequently induced into neural cells to build the cell model of AD. Using alkaline phosphatase staining, immunofluorescence staining, karyotype analysis, reverse transcription-polymerase chain reaction (RT-PCR), and teratoma formation in vitro, we demonstrated that the iPSC derived from PMBCs (PBMC-iPSC) had a normal karyotype and potential to differentiate into three embryonic layers. Immunofluorescence staining and quantitative real-time polymerase chain reaction (qPCR) suggested that PBMC-iPSCs were successfully differentiated into neural cells. Detection of beta-amyloid protein oligomer (AβO), beta-amyloid protein 1-40 (Aβ 1-40), and beta-amyloid protein 1-42 (Aβ 1-42) indicated that the AD cell model was satisfactorily constructed in vitro. In conclusion, this study has successfully generated an AD cell model with pathological features of beta-amyloid peptide deposition using PBMC from a patient with sAD.

Development, optimisation and evaluation of chitosan nanoparticles of alendronate against Alzheimer's disease in intracerebroventricular streptozotocin model for brain delivery

The current study aimed to develop alendronate (ALN)-loaded chitosan nanoparticles (CS-ALN-NPs) for brain delivery via intranasal route. These CS-ALN-NPs reduced the peripheral side effects and released ALN directly to brain. These NPs were formulated through ionic gelation technique by mixing sodium tripolyphosphate (1.5 mg/ml) in ALN-CS (1.75 mg/ml) solution. CS-ALN-NPs attained 135.75 ± 5.80 nm, 0.21 ± 0.013, 23.8 ± 3.69 mV, 72.46 ± 0.879% and 30.92 ± 0.375% mean particle size, PDI, zeta potential, entrapment efficiency and loading capacity, respectively. Furthermore, the TEM and SEM analysis of CS-ALN-NPs, respectively, revealed the particle size in 200 nm range and spherical shape. The in vitro and ex vivo release profile revealed a sustained drug release through CS-ALN-NPs as compared to pure drug solution. Also these NPs acquired a high concentration in mice brain and better pharmacokinetic profile than ALN solution (intranasal) CS-ALN-NPs were then evaluated against intracerebroventricular-streptozotocin (ICV-STZ) induced Alzheimer's disease (AD)-like pathologies in mice. The intranasal CS-ALN-NP altered the ICV-STZ induced neurobehavioral, neurochemical and histopathological changes in mice. These effects were significant to those of ALN solution (intranasal). The neuroprotective potential of CS-ALN-NPs observed in ICV-STZ mice model of AD may be a promising brain-targeted delivery system for AD treatment along with further extensive exploration at both pre-clinical and clinical edge. HIGHLIGHTS CS-ALN-NPs were developed and optimised to overcome the poor pharmacokinetic profile and associated side effects of ALN CS-ALN-NPs showed particle size within 200 nm range as well as controlled and sustained release in in vitro release study These optimised NPs of ALN attained higher brain:blood ratio and better pharmacokinetic profile (Cmax, tmax, AUC) CS-ALN-NPs markedly altered ICV STZ induced impairment in cognitive functions of mice and changes in APP processing, neuroinflammatory cytokines and other biochemical parameters in mice hippocampus.

A Three-Dimensional Alzheimer's Disease Cell Culture Model Using iPSC-Derived Neurons Carrying A246E Mutation in PSEN1

Alzheimer's disease (AD) is a chronic brain disorder characterized by progressive intellectual decline and memory and neuronal loss, caused mainly by extracellular deposition of amyloid-β (Aβ) and intracellular accumulation of hyperphosphorylated tau protein, primarily in areas implicated in memory and learning as prefrontal cortex and hippocampus. There are two forms of AD, a late-onset form that affects people over 65 years old, and the early-onset form, which is hereditable and affect people at early ages ~45 years. To date, there is no cure for the disease; consequently, it is essential to develop new tools for the study of processes implicated in the disease. Currently, in vitro AD three-dimensional (3D) models using induced pluripotent stem cells (iPSC)-derived neurons have broadened the horizon for in vitro disease modeling and gained interest for mechanistic studies and preclinical drug discovery due to their potential advantages in providing a better physiologically relevant information and more predictive data for in vivo tests. Therefore, this study aimed to establish a 3D cell culture model of AD in vitro using iPSCs carrying the A246E mutation. We generated human iPSCs from fibroblasts from a patient with AD harboring the A246E mutation in the PSEN1 gene. Cell reprogramming was performed using lentiviral vectors with Yamanaka's factors (OSKM: Oct4, Sox2, Klf4, and c-Myc). The resulting iPSCs expressed pluripotency genes (such as Nanog and Oct4), alkaline phosphatase activity, and pluripotency stem cell marker expression, such as OCT4, SOX2, TRA-1-60, and SSEA4. iPSCs exhibited the ability to differentiate into neuronal lineage in a 3D environment through dual SMAD inhibition as confirmed by Nestin, MAP2, and Tuj1 neural marker expression. These iPSC-derived neurons harbored Aβ oligomers confirmed by Western Blot (WB) and immunostaining. With human iPSC-derived neurons able to produce Aβ oligomers, we established a novel human hydrogel-based 3D cell culture model that recapitulates Aβ aggregation without the need for mutation induction or synthetic Aβ exposure. This model will allow the study of processes implicated in disease spread throughout the brain, the screening of molecules or compounds with therapeutic potential, and the development of personalized therapeutic strategies.

Neuroprotective Effect of Nerve Growth Factor Loaded in Porous Silicon Nanostructures in an Alzheimer's Disease Model and Potential Delivery to the Brain

Nerve growth factor (NGF) plays a vital role in reducing the loss of cholinergic neurons in Alzheimer's disease (AD). However, its delivery to the brain remains a challenge. Herein, NGF is loaded into degradable oxidized porous silicon (PSiO₂ ) carriers, which are designed to carry and continuously release the protein over a 1 month period. The released NGF exhibits a substantial neuroprotective effect in differentiated rat pheochromocytoma PC12 cells against amyloid-beta (Aβ)-induced cytotoxicity, which is associated with Alzheimer's disease. Next, two potential localized administration routes of the porous carriers into murine brain are investigated: implantation of PSiO₂ chips above the dura mater, and biolistic bombardment of PSiO₂ microparticles through an opening in the skull using a pneumatic gene gun. The PSiO₂ -implanted mice are monitored for a period of 8 weeks and no inflammation or adverse effects are observed. Subsequently, a successful biolistic delivery of these highly porous microparticles into a live-mouse brain is demonstrated for the first time. The bombarded microparticles are observed to penetrate the brain and reach a depth of 150 µm. These results pave the way for using degradable PSiO₂ carriers as potential localized delivery systems for NGF to the brain.

A mathematical model demonstrating the role of interstitial fluid flow on the clearance and accumulation of amyloid β in the brain

A system of partial differential equations is developed to describe the formation and clearance of amyloid β (Aβ) and the subsequent buildup of Aβ plaques in the brain, which are associated with Alzheimer's disease. The Aβ related proteins are divided into five distinct categories depending on their size. In addition to enzymatic degradation, the clearance via diffusion and the outflow of interstitial fluid (ISF) into the surrounding cerebral spinal fluid (CSF) are considered. Treating the brain tissue as a porous medium, a simplified two-dimensional circular geometry is assumed for the transverse section of the brain leading to a nonlinear, coupled system of PDEs. Asymptotic analysis is carried out for the steady states of the spatially homogeneous system in the vanishingly small limit of Aβ clearance rate. The PDE model is studied numerically for two cases, a spherically symmetric case and a more realistic 2D asymmetric case, allowing for non-uniform boundary conditions. Our investigations demonstrate that ISF advection is a key component in reproducing the clinically observed accumulation of plaques on the outer boundaries. Furthermore, ISF circulation serves to enhance Aβ clearance over diffusion alone and that non-uniformities in ISF drainage into the CSF can lead to local clustering of plaques. Analysis of the model also demonstrates that plaque formation does not directly correspond to the high presence of toxic oligomers.

Curcumin-loaded self-nanomicellizing solid dispersion system: part II: in vivo safety and efficacy assessment against behavior deficit in Alzheimer disease

Curcumin (CUR), a natural polyphenolic compound, is considered as one of the most potential candidates against Alzheimer disease (AD) by targeting multiple pathologies such as amyloid-beta, tau phosphorylation, and oxidative stress. Poor physicochemical profile and oral bioavailability (BA) are the major contributors to its failure in clinical trials. Lack of success in numerous drug clinical trials for the treatment of AD urges the need of repositioning of CUR. To overcome its limitation and enhance oral BA, Novel CUR Formulation (NCF) was developed using self-nanomicellizing solid dispersion strategy which displayed 117-fold enhancement in oral BA of CUR. NCF was tested using SH-SY5Y695 APP human neuroblastoma cell line against the cytotoxicity induced by copper metal ion, H₂O₂, and Aβ42 oligomer and compared with CUR control. The safety and efficacy of NCF on mice AD-like behavioral deficits (open field, novel objective recognition, Y-maze, and Morris water maze tests) were assessed in transgenic AD (APPSwe/PS1deE9) mice model. In SH-SY5Y695 APP human neuroblastoma cell line, NCF showed better safety and efficacy against the cytotoxicity due to the significantly enhancement of cellular uptake. It not only prevents the deterioration of cognitive functions of the aged APPSwe/PS1deE9 mice during aging but also reverses the cognitive functions to their much younger age which is also better than the currently available approved options. Moreover, NCF was proved as well tolerated with no appearance of any significant toxicity via oral administration. The results of the study demonstrated the potential of NCF to improve the efficacy of CUR without compromising its safety profile, and pave the way for clinical development for AD.

Modelling Alzheimer's disease: Insights from in vivo to in vitro three-dimensional culture platforms

Alzheimer's disease (AD) is the most common form of dementia and is characterized by progressive memory loss, impairment of other cognitive functions, and inability to perform activities of daily life. The key to understanding AD aetiology lies in the development of effective disease models, which should ideally recapitulate all aspects pertaining to the disease. A plethora of techniques including in vivo, in vitro, and in silico platforms have been utilized in developing disease models of AD over the years. Each of these approaches has revealed certain essential characteristics of AD; however, none have managed to fully mimic the pathological hallmarks observed in the AD human brain. In this review, we will provide details into the genesis, evolution, and significance of the principal methods currently employed in modelling AD, the advantages and limitations faced in their application, including the headways made by each approach. This review will focus primarily on two-dimensional and three-dimensional in vitro modelling of AD, which during the last few years has made significant breakthroughs in the areas of AD pathology and therapeutic screening. In addition, a glimpse into state-of-the-art neural tissue engineering techniques incorporating biomaterials and microfluidics technologies is provided, which could pave the way for the development of more accurate and comprehensive AD models in the future.

No evidence in support of a prodromal respiratory control signature in the TgF344-AD rat model of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative condition disturbing major brain networks, including those pivotal to the motor control of breathing. The aim of this study was to examine respiratory control in the TgF344-AD transgenic rat model of AD. At 8-11 months of age, basal minute ventilation and ventilatory responsiveness to chemostimulation were equivalent in conscious wild-type (WT) and TgF344-AD rats. Under urethane anesthesia, basal diaphragm and genioglossus EMG activities were similar in WT and TgF344-AD rats. The duration of phenylbiguanide-induced apnoea was significantly shorter in TgF344-AD rats compared with WT. Following bilateral cervical vagotomy, diaphragm and genioglossus EMG responsiveness to chemostimulation were intact in TgF344-AD rats. Amyloid precursor protein C-terminal fragments were elevated in the TgF344-AD brainstem, in the absence of amyloid-β accumulation or alterations in tau phosphorylation. Brainstem pro-inflammatory cytokine concentrations were not increased in TgF344-AD rats. We conclude that neural control of breathing is preserved in TgF344-AD rats at this stage of the disease.

Human-specific approaches to brain research for the 21st century: a South American perspective

The 21st century paradigm in toxicology, which emphasizes mechanistic understanding and species-relevant modeling of human biology and pathophysiology, is gaining traction in the wider biosciences through a global workshop series organized by the BioMed21 Collaboration. The second of this series, entitled Emerging Technology Toward Pathway-Based Human Brain Research, was held in Brazil in 2017, bringing together leading South American and international scientists, research funders and other stakeholders. The aims were to foster strategic scientific dialogue and identify actionable consensus recommendations as a first step toward a roadmap for 21st century, human-specific health research and funding in the region.

Deficits in synaptic function occur at medial perforant path-dentate granule cell synapses prior to Schaffer collateral-CA1 pyramidal cell synapses in the novel TgF344-Alzheimer's Disease Rat Model

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 at two hippocampal synapses in male and ovariectomized female TgF344-AD rats and wildtype littermates, prior to reported behavioral deficits. Decreased basal synaptic transmission begins at medial perforant path-dentate granule cell (MPP-DGC) synapses prior to Schaffer-collateral-CA1 (CA3-CA1) synapses, in the absence of a change in paired-pulse ratio (PPR) or dendritic spine density. N-methyl-d-aspartate receptor (NMDAR)-dependent LTP magnitude is unaffected at CA3-CA1 synapses at 6, 9, and 12months of age, but is significantly increased at MPP-DGC synapses in TgF344-AD rats at 6months only. Sex differences were only observed at CA3-CA1 synapses where the decrease in basal transmission occurs at a younger age in males versus females. These are the first studies to define presymptomatic alterations in hippocampal synaptic transmission in the TgF344-AD rat model. The time course of altered synaptic transmission mimics the spread of pathology through hippocampus in human AD and provides support for this model as a valuable preclinical tool in elucidating pathological mechanisms of early synapse dysfunction in AD.

Human induced pluripotent stem cells as a research tool in Alzheimer's disease

Human-induced pluripotent stem cells (iPSCs) offer a novel, timely approach for investigating the aetiology of neuropsychiatric disorders. Although we are starting to gain more insight into the specific mechanisms that cause Alzheimer's disease and other forms of dementia, this has not resulted in therapies to slow the pathological processes. Animal models have been paramount in studying the neurobiological processes underlying psychiatric disorders. Nonetheless, these human conditions cannot be entirely recapitulated in rodents. Human cell models derived from patients' cells now offer new hope for improving our understanding of the early molecular stages of these diseases, through to validating therapeutics. The impact of dementia is increasing, and a new model to investigate the early stages of this disease is heralded as an essential, new platform for translational research. In this paper, we review current literature using iPSCs to study Alzheimer's disease, describe drug discovery efforts using this platform, and discuss the future potential for this technology in psychiatry research.

Analysis of FDA-approved imaging agents

The development of imaging agents was initially driven following the discovery of X-ray technologies, but quickly evolved and expanded to include radiolabeling of cells and tissues to assist disease diagnosis and progression. The first imaging agents preceded the Great War but the field did not gain momentum until the 1950s. The approval rate for imaging NMEs continued at a high level for the remainder of the 20th century, but substantially decreased thereafter. This decline in approval rates corresponds with industry consolidation. Such losses have stabilized, but could have important implications for a field that has conveyed direct benefits to medicine and that could ensure the future of the wider biopharmaceutical industry.

Extracellular low-n oligomers of tau cause selective synaptotoxicity without affecting cell viability

INTRODUCTION

Tau-mediated toxicity in Alzheimer's disease is thought to operate through low-n oligomers, rather than filamentous aggregates. However, the nature of oligomers and pathways of toxicity are poorly understood. Therefore, we investigated structural and functional aspects of highly purified oligomers of a pro-aggregant tau species.

METHODS

Purified oligomers of the tau repeat domain were characterized by biophysical and structural methods. Functional aspects were investigated by cellular assays ((3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay of cell viability, lactate dehydrogenase release assay [for cell toxicity], reactive oxygen species production, and calcium assay), combined with analysis of neuronal dendritic spines exposed to oligomers.

RESULTS

Purified low-n oligomers are roughly globular, with sizes around 1.6 to 5.4 nm, exhibit an altered conformation, but do not have substantial β-structure. Treatment of primary neurons with oligomers impairs spine morphology and density, accompanied by increased reactive oxygen species and intracellular calcium, but without affecting cell viability (by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay of cell viability and lactate dehydrogenase release assay [for cell toxicity]).

DISCUSSION

Tau oligomers are toxic to synapses but not lethal to cells.

Prion-like disorders and Transmissible Spongiform Encephalopathies: An overview of the mechanistic features that are shared by the various disease-related misfolded proteins

Prion diseases or Transmissible Spongiform Encephalopathies (TSEs) are a group of fatal neurodegenerative disorders affecting several mammalian species. Its causative agent, disease-associated prion protein (PrP^d), is a self-propagating β-sheet rich aberrant conformation of the cellular prion protein (PrP^C) with neurotoxic and aggregation-prone properties, capable of inducing misfolding of PrP^C molecules. PrP^d is the major constituent of prions and, most importantly, is the first known example of a protein with infectious attributes. It has been suggested that similar molecular mechanisms could be shared by other proteins implicated in diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis or systemic amyloidoses. Accordingly, several terms have been proposed to collectively group all these disorders. Through the stringent evaluation of those aspects that characterise TSE-causing prions, in particular propagation and spread, strain variability or transmissibility, we will discuss whether terms such as "prion", "prion-like", "prionoid" or "propagon" can be used when referring to the aetiological agents of the above other disorders. Moreover, it will also be discussed whether the term "infectious", which defines a prion essential trait, is currently misused when referring to the other misfolded proteins.

KCa3.1 constitutes a pharmacological target for astrogliosis associated with Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia and is characterized by a progression from decline of episodic memory to a global impairment of cognitive function. Astrogliosis is a hallmark feature of AD, and reactive gliosis has been considered as an important target for intervention in various neurological disorders. We previously found in astrocyte cultures that the expression of the intermediate conductance calcium-activated potassium channel KCa3.1 was increased in reactive astrocytes induced by TGF-β, while pharmacological blockade or genetic deletion of KCa3.1 attenuated astrogliosis. In this study, we sought to suppress reactive gliosis in the context of AD by inhibiting KCa3.1 and evaluate its effects on the cognitive impairment using murine animal models such as the senescence-accelerated mouse prone 8 (SAMP8) model that exhibits some AD-like symptoms. We found KCa3.1 expression was increased in reactive astrocytes as well as neurons in the brains of both SAMP8 mice and Alzheimer's disease patients. Blockade of KCa3.1 with the selective inhibitor TRAM-34 in SAMP8 mice resulted in a decrease in astrogliosis as well as microglia activation, and moreover an attenuation of memory deficits. Using KCa3.1 knockout mice, we further confirmed that deletion of KCa3.1 reduced the activation of astrocytes and microglia, and rescued the memory loss induced by intrahippocampal Aβ_1-42 peptide injection. We also found in astrocyte cultures that blockade of KCa3.1 or deletion of KCa3.1 suppressed Aβ oligomer-induced astrogliosis. Our data suggest that KCa3.1 inhibition might represent a promising therapeutic strategy for AD treatment.

Animal models for prion-like diseases

Prion diseases or Transmissible Spongiform Encephalopathies (TSEs) are a group of fatal neurodegenerative disorders affecting several mammalian species being Creutzfeldt-Jacob Disease (CJD) the most representative in human beings, scrapie in ovine, Bovine Spongiform Encephalopathy (BSE) in bovine and Chronic Wasting Disease (CWD) in cervids. As stated by the "protein-only hypothesis", the causal agent of TSEs is a self-propagating aberrant form of the prion protein (PrP) that through a misfolding event acquires a β-sheet rich conformation known as PrP(Sc) (from scrapie). This isoform is neurotoxic, aggregation prone and induces misfolding of native cellular PrP. Compelling evidence indicates that disease-specific protein misfolding in amyloid deposits could be shared by other disorders showing aberrant protein aggregates such as Alzheimer's Disease (AD), Parkinson's Disease (PD), Amyotrophic lateral sclerosis (ALS) and systemic Amyloid A amyloidosis (AA amyloidosis). Evidences of shared mechanisms of the proteins related to each disease with prions will be reviewed through the available in vivo models. Taking prion research as reference, typical prion-like features such as seeding and propagation ability, neurotoxic species causing disease, infectivity, transmission barrier and strain evidences will be analyzed for other protein-related diseases. Thus, prion-like features of amyloid β peptide and tau present in AD, α-synuclein in PD, SOD-1, TDP-43 and others in ALS and serum α-amyloid (SAA) in systemic AA amyloidosis will be reviewed through models available for each disease.