The amyloid hypothesis of Alzheimer's disease at 25 years

Acute Restraint Stress Induces Long-Lasting Synaptic Enhancement by Inhibiting AMPK Activation in AD Model Mice

BACKGROUND

Alzheimer's disease (AD) is characterized by a gradual synaptic loss. The progression of AD severely affects late-phase long-term potentiation (L-LTP), which is essential for long-term memory consolidation.

AIM

We have previously demonstrated the beneficial effects of acute restraint stress (ARS) on hippocampal LTP in AD mouse models. This study aimed to verify the effects and potential mechanisms of ARS on the maintenance of hippocampal L-LTP in two AD mouse models.

MATERIALS AND METHODS

5xFAD and Tg2576 mice underwent a 30-min body immobilization protocol to induce ARS, followed by electrophysiological recordings of L-LTP (> 3 h) in the CA1 region of thehippocampus.

RESULTS

The ARS-exposed group exhibited significantly enhanced L-LTP compared to the control group. Maintenance of L-LTP requires new protein synthesis and signaling via the mammalian target of rapamycin (mTOR) pathway. Our findings revealed that ARS increased hippocampal adenosine triphosphate (ATP) production and reduced AMPK activity. Inactivation of AMPK and subsequent activation of the mTOR pathway were strongly associated with the ARS-facilitated enhancement of L-LTP. Furthermore, our experiments using the mTOR inhibitor rapamycin demonstrated that it effectively prevented the enhancement of L-LTP following ARS, underscoring the pivotal role of mTOR in this process.

CONCLUSION

ARS may significantly modify AMPK activation and mTOR regulation in L-LTP, potentially triggering the mechanisms of long-term memory consolidation in AD mouse model mice. Identifying these underlying mechanisms could help promote the development of novel pharmaceutical agents for the treatment of AD.

Decoding TGR5: A comprehensive review of its impact on cerebral diseases

Currently, unraveling the enigmatic realm of drug targets for cerebral disorders poses a formidable challenge. Takeda G protein-coupled receptor 5 (TGR5), also known as G protein-coupled bile acid receptor 1, is a specific bile acid receptor. Widely distributed across various tissues, TGR5 orchestrates a myriad of biological functions encompassing inflammation, energy metabolism, fatty acid metabolism, immune responses, cellular proliferation, apoptosis, and beyond. Alongside its well-documented implications in liver diseases, obesity, type 2 diabetes, tumors, and cardiovascular diseases, a growing body of evidence accentuates the pivotal role of TGR5 in cerebral diseases. Thus, this comprehensive review aimed to scrutinize the current insights into the pathological mechanisms involving TGR5 in cerebral diseases, while contemplating its potential as a promising therapeutic target for cerebral diseases.

Alzheimer's Disease Diagnosis and Management in the Age of Amyloid Monoclonal Antibodies

Alzheimer's disease (AD) is the most common neurodegenerative disorder, and for providers the term AD is often avoided, favoring generic terms like memory loss or dementia. This is partly not only by limitations in using diagnostics and busy clinics but also by a sense that an AD diagnosis will not lead to a meaningful change in management. However, a turning point has occurred with advancements in diagnostics and disease-modifying therapies. Additionally, AD prevention therapies are not too far into the future. This review will cover AD clinical presentation and symptomatic management with focus on AD diagnostics and disease-modifying therapies.

Social and contextual memory impairments induced by Amyloid-β oligomers are rescued by Sigma-1 receptor activation

Sigma-1 receptors (S1Rs) are widely expressed throughout the central nervous system and modulate neuron intracellular calcium levels, leading to changes in neurotransmitter release and neuronal activity. They also interact with various proteins and signaling pathways, playing a key role in regulating synaptic plasticity in brain areas such as the hippocampus, thereby influencing learning and memory processes. This opens a research avenue to explore S1R modulation as a potential therapeutic target in diseases involving hippocampal synaptic alterations and compromised cognitive processes, such as Alzheimer's disease (AD). Here, we hypothesize that pharmacological activation of S1R could counteract synaptic plasticity deficits and hippocampal-dependent cognitive alterations in an early-stage amyloidosis model of Alzheimer's disease, induced by intracerebroventricular (icv) administration of Aβ1-42 oligomers (oAβ1-42). For that purpose, we investigate ex vivo CA3-CA1 synaptic plasticity, while in vivo, we performed open field habituation and social recognition tasks to assess contextual and social memory, respectively. Our data show that pharmacological activation of S1Rs with the selective agonist PRE-084 counteract oAβ1-42 deleterious effects on CA3-CA1 long-term synaptic plasticity (LTP), and hippocampal-dependent contextual and social memory, without alterations of spontaneous behaviors. Together, these results provide further evidence for the role of S1Rs in ameliorating hippocampal synaptic and contextual memory dysfunctions and introduce novel insight into their involvement in early amyloid-induced social memory deficits, highlighting their potential for developing comprehensive treatments for early AD. Also, the absence of adverse behavioral outcomes associated with PRE-084 treatment suggests a favorable safety profile in preclinical models, supporting its potential as a therapeutic option.

Gut Microbiota Mediates Neuroinflammation in Alzheimer's Disease: Unraveling Key Factors and Mechanistic Insights

The gut microbiota, the complex community of microorganisms that inhabit the gastrointestinal tract, has emerged as a key player in the pathogenesis of neurodegenerative disorders, including Alzheimer's disease (AD). AD is characterized by progressive cognitive decline and neuronal loss, associated with the accumulation of amyloid-β plaques, neurofibrillary tangles, and neuroinflammation in the brain. Increasing evidence suggests that alterations in the composition and function of the gut microbiota, known as dysbiosis, may contribute to the development and progression of AD by modulating neuroinflammation, a chronic and maladaptive immune response in the central nervous system. This review aims to comprehensively analyze the current role of the gut microbiota in regulating neuroinflammation and glial cell function in AD. Its objective is to deepen our understanding of the pathogenesis of AD and to discuss the potential advantages and challenges of using gut microbiota modulation as a novel approach for the diagnosis, treatment, and prevention of AD.

Alzheimer's disease risk ABCA7 p.A696S variant disturbs the microglial response to amyloid pathology in mice

The adenosine triphosphate-binding cassette transporter A7 (ABCA7) gene is ranked as one of the top susceptibility loci for Alzheimer's disease (AD). While ABCA7 mediates lipid transport across cellular membranes, ABCA7 loss of function has been shown to exacerbate amyloid-β (Aβ) pathology and compromise microglial function. Our family-based study uncovered an extremely rare ABCA7 p.A696S variant that was substantially segregated with the development of AD in 3 African American families. Using the knockin mouse model, we investigated the effects of ABCA7-A696S substitution on amyloid pathology and brain immune response in 5xFAD transgenic mice. Importantly, our study demonstrated that ABCA7-A696S substitution reduces amyloid plaque-associated microgliosis and increases dystrophic neurites around amyloid deposits compared to control mice. We also found increased X-34-positive amyloid plaque burden in 5xFAD mice with ABCA7-A696S substitution, while there was no evident difference in insoluble Aβ levels between mouse groups. Thus, ABCA7-A696S substitution may disrupt amyloid compaction resulting in aggravated neuritic dystrophy due to insufficient microglia barrier function. In addition, we observed that ABCA7-A696S substitution disturbs the induction of proinflammatory cytokines interleukin 1β and interferon γ in the brains of 5xFAD mice, although some disease-associated microglia gene expression, including Trem2 and Tyrobp, are upregulated. Lipidomics also detected higher total lysophosphatidylethanolamine levels in the brains of 5xFAD mice with ABCA7-A696S substitution than controls. These results suggest that ABCA7-A696S substitution might compromise the adequate innate immune response to amyloid pathology in AD by modulating brain lipid metabolism, providing novel insight into the pathogenic mechanisms mediated by ABCA7. ONE SENTENCE SUMMARY: A rare Alzheimer's disease risk ABCA7 p.A696S variant compromises microglial response to amyloid pathology.

Oligodendrocytes in Alzheimer's disease pathophysiology

Our understanding of Alzheimer's disease (AD) has transformed from a purely neuronal perspective to one that acknowledges the involvement of glial cells. Despite remarkable progress in unraveling the biology of microglia, astrocytes and vascular elements, the exploration of oligodendrocytes in AD is still in its early stages. Contrary to the traditional notion of oligodendrocytes as passive bystanders in AD pathology, emerging evidence indicates their active participation in and reaction to amyloid and tau pathology. Oligodendrocytes undergo a functional transition to a disease-associated state, engaging in immune modulation, stress responses and cellular survival. Far from being inert players, they appear to serve a dual role in AD pathogenesis, potentially offering defense mechanisms against pathology while also contributing to disease progression. This Review explores recent advancements in understanding the roles of oligodendrocytes and their myelin sheaths in the context of AD, shedding light on their complex interactions within the disease pathology.

Identification of benzimidazole-6-carboxamide based inhibitors of secretory glutaminyl cyclase for the treatment of Alzheimer's disease

The formation of the pyroglutamate variant of amyloid beta (pGlu-Aβ), which is extremely hydrophobic, rapidly aggregating, and highly neurotoxic, is mediated by the action of secretory glutaminyl cyclase (sQC). The pGlu-Aβ often acts as a seed for the aggregation of the full length Aβ and contributes to the overall load of Aβ plaques in Alzheimer's disease (AD). Therefore, inhibiting sQC is a potential approach to limit the formation of pGlu-Aβ and to modify the progression of AD. This study presents two novel molecules containing benzimidazole-6-carboxamide, namely LSB-09 and LSB-24, as promising sQC inhibitors. These inhibitors demonstrated moderate toxicity in human neuroblastoma cell lines and possessed IC50 values in the micromolar range (40 and 4 μM for LSB-09 and LSB-24, respectively). Additionally, the X-ray crystal structure of the sQC-LSB-09 complex revealed a unique binding mode, and a systematic computational investigation elucidated the binding mode for LSB-24. The binding mode of these two benzimidazole-6-carboxamide inhibitors offers a potential platform for designing attractive lead candidates against sQC.

Impact of Amidation on Aβ25-35 Aggregation

Toxic oligomeric species are suspected in the etiology of Alzheimer's disease. The full-length Aβ42 can be studied by the fragment Aβ25-35 as it retains neurotoxicity. According to experimental studies, amidation of the Aβ25-35 carboxyl terminal decreases fibrillation activity while retaining its neurotoxic properties. Our molecular dynamics simulation studied the aggregation of the Aβ25-35 trimer from two initial structures (fibril and randomized helical structures) in their amidated and nonamidated forms. Comparing the amidated and nonamidated systems, the results suggest that antiparallel chains are dominant in nonamidated systems, while the amide group leads to parallel chains. In terms of secondary structures, a higher helix content with a corresponding decrease in β-sheet content is observed as a consequence of amidation. Despite the variation in secondary structures, the chain-chain contacts are still mediated by the Gly motif (GxxxG) and Ile residues in both amidated and nonamidated systems. As neurotoxicity does not change upon amidation, our results imply that clumping of peptides sustained by the Gly motif is a greater contributing factor to toxicity than secondary and quaternary structures.

HCN2 deficiency correlates with memory deficits and hyperexcitability of dCA1 pyramidal neurons in Alzheimer's disease

BACKGROUND

Abnormal excitability of hippocampal neurons may lead to dysfunction of neural circuits and then causes cognitive impairments in Alzheimer's disease (AD). However, the underlying mechanisms remain to be fully elucidated.

METHODS

Electrophysiology was performed to examine the intrinsic excitability of CA1 neurons and the activity of the hyperpolarization-activated cyclic nucleotide-gated ion channels (HCNs) of CA1 neurons in wild type (WT) and hAPP-J20 mice. The activity of CA1 pyramidal neurons (PNs) was modulated with chemogenetics. The activity of HCNs was regulated with nonselective facilitator (cAMP) or inhibitor (ZD7288) of HCNs. Immunohistochemical staining or western blotting were performed to examine the expression of HCN1 and HCN2 in the hippocampus of WT and hAPP-J20 mice, or AD patients and non-AD controls. AAVs were injected to specifically modulate the expression of HCN2 in dorsal CA1 (dCA1) PNs. Cognitive performance of mice was assessed with behavioral tests.

RESULTS

dCA1 PNs were more excitable in hAPP-J20 mice, but the excitability of PNs in the ventral CA1 (vCA1) or PV neurons was comparable between WT and hAPP-J20 mice. The activity of the HCNs was reduced in dCA1 PNs of hAPP-J20 mice, and pharmacologically increasing the activity of HCNs attenuated the hyperexcitability of dCA1 PNs in hAPP-J20 mice, suggesting that the reduced activity of HCNs is associated with the hyperexcitability of dCA1 PNs in hAPP-J20 mice. The expression of HCN2 but not HCN1 was reduced in the hippocampus of hAPP-J20 mice, and the expression of HCN2 was also reduced in the hippocampus of AD patients, suggesting that dysregulation of HCN2 is associated with the reduced activity of HCNs in AD. Overexpressing HCN2 rescued the activity of HCNs, attenuated the hyperexcitability of dCA1 PNs and improved memory of hAPP-J20 mice, and knocking down HCN2 impaired the function of HCNs, increased the excitability of dCA1 PNs and led to memory deficits in WT mice.

CONCLUSIONS

Our data suggest that dysregulation of HCNs, particularly HCN2, contributes to the abnormal excitability of CA1 PNs in AD mice and probably in AD patients as well, and thus provide new insights into the mechanisms underlying the aberrant activity or excitability of hippocampal neurons in AD.

Cellular Prion Protein and Amyloid-β Oligomers in Alzheimer's Disease-Are There Connections?

Alzheimer's disease (AD) is the most common cause of dementia worldwide. Pathological deposits of neurotoxin proteins within the brain, such as amyloid-β and hyperphosphorylated tau tangles, are prominent features in AD. The prion protein (PrP) is involved in neurodegeneration via its conversion from the normal cellular form (PrPC) to the infection prion protein scrapie (PrPSc) form. Some studies indicated that post-translationally modified PrPC isoforms play a fundamental role in AD pathological progression. Several studies have shown that the interaction of Aβ oligomers (Aβos) with the N-terminal residues of the PrPC protein region appears critical for neuronal toxicity. PrPC-Aβ binding always occurs in AD brains and is never detected in non-demented controls, and the binding of Aβ aggregates to PrPC is restricted to the N-terminus of PrPC. In this study, we aimed to gather all of the recent information about the connections between PrPC and AD, with potential clinical implications.

The p3 peptides (Aβ17-40/42) rapidly form amyloid fibrils that cross-seed with full-length Aβ

The p3 peptides, Aβ17-40/42, are a common alternative cleavage product of the amyloid precursor protein, and are found in diffuse amyloid deposits of Alzheimer's and Down Syndrome brains. The p3 peptides have been mis-named 'non-amyloidogenic'. Here we show p340/42 peptides rapidly form amyloid fibrils, with kinetics dominated by secondary nucleation. Importantly, cross-seeding experiments, with full-length Aβ induces a strong nucleation between p3 and Aβ peptides. The cross-seeding interaction is highly specific, and occurs only when the C-terminal residues are matched. We have imaged membrane interactions with p3, and monitored Ca2+ influx and cell viability with p3 peptide. Together this data suggests the N-terminal residues influence, but are not essential for, membrane disruption. Single particle analysis of TEM images indicates p3 peptides can form ring-like annular oligomers. Patch-clamp electrophysiology, shows p342 oligomers are capable of forming large ion-channels across cellular membranes. A role for p3 peptides in disease pathology should be considered as p3 peptides are cytotoxic and cross-seed Aβ fibril formation in vitro.

ApoE2 affects insulin signaling in the hippocampus and spatial cognition of aged mice in a sex-dependent manner

Apolipoprotein E (APOE) has garnered significant attention as one of the most influential genetic risk factors for Alzheimer's disease (AD). While the pathogenic role of APOE4 in sporadic AD has been extensively studied, research on the protective effects of the APOE2 genotype and its underlying mechanisms remains limited. Additionally, the existence of sex differences in the protective effects of ApoE2 continues to be a topic of debate. In this study, we utilized humanized ApoE2- and ApoE3- target replacement mice to examine the sex-specific effects of ApoE2 on cognition. Compared with female ApoE3 mice, we found significantly lower spatial cognitive ability and impaired hippocampal synaptic ultrastructure in aged female ApoE2 mice, accompanied by reduced insulin signaling of the hippocampus. Further analyses by target metabolomics and transcriptomic analyses revealed that female ApoE2 mice exhibit an age-related decline in hippocampal inositol levels, and that alterations in inositol levels lower insulin signaling. Importantly, inositol supplementation was found to alleviate peripheral glucose intolerance, enhance insulin signaling, and ultimately improve cognitive function. Interestingly, these differences were not observed between male ApoE2 and ApoE3 mice. The research findings not only provide new insights into the impact of ApoE2 on cognition but also offer a new strategy for cognitive improvement through inositol supplementation in older women.

Ultrasensitive Assays Detect Different Conformations of Plasma β Amyloids

With the developments of ultrasensitive technologies such as immunomagnetic reduction (IMR) assay, single molecule array (SIMOA) assay, electrochemiluminescence immunoassay (ECLIA), the assay of blood-based amyloid 1-42 (Aβ1-42) becomes possible. However, the changes in measured plasma Aβ1-42 concentrations in Alzheimer's disease (AD) compared to cognitively unimpaired subjects (CU) are inconsistent. A possible reason for the inconsistency regarding various conformations of Aβ1-42 in plasma is explored in this study. Three samples with equal amounts of Aβ1-42 but different proportions of monomers and oligomers of Aβ1-42 were prepared. The Aβ1-42 composition of monomers and oligomers in samples was analyzed with Western blot. Identically diluted versions of these three samples were assayed with IMR and SIMOA for Aβ1-42 concentrations. The three diluted samples showed similar levels of Aβ1-42 assayed with IMR, whereas much lower levels for samples with more oligomers assayed with SIOMA. The results imply that IMR detects both monomers and oligomers of Aβ1-42. The measured levels of Aβ1-42 are independent of the proportions of monomer or oligomer Aβ1-42 but depend on the total amounts of Aβ1-42. In the case of SIMOA, monomers of Aβ1-42 are the primary target measured. By comparing Aβ1-42 concentrations of the plasma using IMR and SIMOA, the significant difference in plasma Aβ1-42 levels using IMR in AD compared to CU is mainly due to the formations of oligomeric Aβ1-42. Therefore, if the target molecules are monomers of Aβ1-42, SIMOA is the method of choice. Still, if the target molecules should include monomers, small and large oligomers, IMR would be an optimal consideration. In the future, the clinical implications of the proportion of oligomeric Aβ1-42 need to be elucidated.

Low-intensity pulsed ultrasound enhances delivery of 30 nm Q10 for improving mental and memory disorder in APP/PS1 mice

Patients with Alzheimer's disease (AD) often experience mental and memory disorders with poor outcomes. Coenzyme Q10 can degrade formaldehyde (FA) and improve Alzheimer-related symptoms, but its ability to cross the blood-brain barrier (BBB) is limited. This study investigated whether low-intensity pulsed ultrasound (LIPUS) enhances 30 nm Q10 delivery and improve symptoms in AD model mice. Here, 30 nm Q10 was prepared by encapsulating Q10 in liposomes coupled with PEG, creating PEG-Q10@NPs under 30 nm in diameter. Wild-type mice and APPswe/PS1dE9 mice (a familial AD model) received 30 nm Q10 via intraperitoneal injection, or a combination of 30 nm Q10 and LIPUS (50 or 100 100 mW/cm2). Then the mice's anxiety-like and depression-like behaviors and biochemical index were evaluated. We found that the combination therapy of LIPUS at 100 mW/cm2 and 30 nm Q10 was more effective in ameliorating psychosis in AD mice than individual treatments with 30 nm Q10. This effectiveness was linked to higher levels of brain Q10, serotonin (5-HT), and dopamine (DA), along with lower levels of FA and plaques. Especially, excessive FA directly inactivated 5-HT and DA in vitro. The enhanced cellular uptake of Q10 and improved BBB permeability facilitated by LIPUS were confirmed in both cultured cells and wild-type mice. Unexpectedly, LIPUS at the different intensity only partially alleviated anxiety and depression symptoms and memory deficits in AD mice. Hence, this combination therapy of LIPUS and 30 nm Q10 is an innovative strategy for ameliorating mental and cognitive disorders in AD.

Small-Molecule Inhibitors of Amyloid Beta: Insights from Molecular Dynamics-Part A: Endogenous Compounds and Repurposed Drugs

The amyloid hypothesis is the predominant model of Alzheimer's disease (AD) pathogenesis, suggesting that amyloid beta (Aβ) peptide is the primary driver of neurotoxicity and a cascade of pathological events in the central nervous system. Aβ aggregation into oligomers and deposits triggers various processes, such as vascular damage, inflammation-induced astrocyte and microglia activation, disrupted neuronal ionic homeostasis, oxidative stress, abnormal kinase and phosphatase activity, tau phosphorylation, neurofibrillary tangle formation, cognitive dysfunction, synaptic loss, cell death, and, ultimately, dementia. Molecular dynamics (MD) is a powerful structure-based drug design (SBDD) approach that aids in understanding the properties, functions, and mechanisms of action or inhibition of biomolecules. As the only method capable of simulating atomic-level internal motions, MD provides unique insights that cannot be obtained through other techniques. Integrating experimental data with MD simulations allows for a more comprehensive understanding of biological processes and molecular interactions. This review summarizes and evaluates MD studies from the past decade on small molecules, including endogenous compounds and repurposed drugs, that inhibit amyloid beta. Furthermore, it outlines key considerations for future MD simulations of amyloid inhibitors, offering a potential framework for studies aimed at elucidating the mechanisms of amyloid beta inhibition by small molecules.

γ-Secretase modulator resistance of an aggressive Alzheimer-causing presenilin mutant can be overcome in the heterozygous patient state by a set of advanced compounds

BACKGROUND

Amyloid-β peptide (Aβ) species of 42 or 43 amino acids in length (Aβ42/43) trigger Alzheimer´s disease (AD) and are produced in abnormal amounts by mutants of the γ-secretase subunit presenilin-1 (PS1), which represent the primary cause of familial AD (FAD). Lowering these peptides by γ-secretase modulators (GSMs) is increasingly considered a safe strategy to treat AD since these compounds do not affect the overall cleavage of γ-secretase substrates. GSMs were shown to modulate not only wild-type (WT) γ-secretase but also FAD mutants, expanding their potential use also to the familial form of the disease. Unlike most other FAD mutants, the very aggressive PS1 L166P mutant is largely resistant to GSMs. However, these data were mostly obtained from overexpression models, which mimic more the less relevant homozygous state rather than the heterozygous patient situation.

METHODS

Mouse embryonic fibroblast and induced pluripotent stem cell-derived neuronal PS1 L166P knock-in (KI) cell models were treated with various GSMs and Aβ responses were assessed by immunoassays and/or gel-based analysis.

RESULTS

We identified GSMs that lower Aβ42 and/or Aβ43 when PS1 L166P is heterozygous, as it is the case in affected patients, and could reduce the amount of pathogenic Aβ species towards WT levels. RO7019009 was the most potent of these compounds, reducing both pathogenic species and concomitantly increasing the short Aβ37 and Aβ38, of which the latter has been associated with delayed AD progression. Another effective compound, the structurally novel indole-type GSM RO5254601 specifically acts on the Aβ42 product line leading to a selective increase of the beneficial Aβ38. Interestingly, we further found that this class of GSMs can bind not only one, but both presenilin fragments suggesting that it targets γ-secretase at an unusual binding site.

CONCLUSION

Our data show that even highly refractory presenilin FAD mutants are in principle tractable with GSMs extending the possibilities for potential clinical studies in FAD with suitable GSM molecules.

The Potential Mechanism and the Role of Antioxidants in Mitigating Oxidative Stress in Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent cause of dementia and a significant contributor to health issues and mortality among older individuals. This condition involves a progressive deterioration in cognitive function and the onset of dementia. Recent advancements suggest that the development of AD is more intricate than its underlying brain abnormalities alone. In addition, Alzheimer's disease, metabolic syndrome, and oxidative stress are all intricately linked to one another. Increased concentrations of circulating lipids and disturbances in glucose homeostasis contribute to the intensification of lipid oxidation, leading to a gradual depletion of the body's antioxidant defenses. This heightened oxidative metabolism adversely impacts cell integrity, resulting in neuronal damage. Pathways commonly acknowledged as contributors to AD pathogenesis include alterations in synaptic plasticity, disorganization of neurons, and cell death. Abnormal metabolism of some membrane proteins is thought to cause the creation of amyloid (Aβ) oligomers, which are extremely hazardous to neurotransmission pathways, especially those involving acetylcholine. The interaction between Aβ oligomers and these neurotransmitter systems is thought to induce cellular dysfunction, an imbalance in neurotransmitter signaling, and, ultimately, the manifestation of neurological symptoms. Antioxidants have a significant impact on human health since they may improve the aging process by combating free radicals. Neurodegenerative diseases are currently incurable; however, they may be effectively managed. An appealing alternative is the utilization of natural antioxidants, such as polyphenols, through diet or dietary supplements, which offer numerous advantages. Within this framework, we have extensively examined the importance of oxidative stress in the advancement of Alzheimer's disease, as well as the potential influence of antioxidants in mitigating its effects.

Reduced protein solubility - cause or consequence in amyloid disease?

In this perspective, we ask the question whether the apparently lower solubility of specific proteins in amyloid disease is a cause or consequence of the protein deposition seen in such diseases. We focus on Alzheimer's disease and start by reviewing the experimental evidence of disease-associated reduction in the measured concentration of amyloid β peptide, Aβ42, in cerebrospinal fluid. We propose a series of possible physicochemical explanations for these observations. These include a reduced solubility, a reduced apparent solubility, as well as a long-lived metastable state manifested in healthy individuals as a free concentration of Aβ42 in the solution phase above the solubility limit. For each scenario, we discuss whether it is most likely a cause or a consequence of the observed protein deposition in the disease.

Krüppel-like factor 9 alleviates Alzheimer's disease via IDE-mediated Aβ degradation

The deposition of β-amyloid (Aβ) in the brain is a crucial factor in the pathogenesis of Alzheimer's disease (AD). Insulin-degrading enzyme (IDE) plays a critical role in the balance between Aβ production and degradation. However, the regulatory mechanisms of IDE are not yet fully understood. Therefore, uncovering additional IDE regulatory mechanisms will help elucidate the pathogenesis of AD and identify key therapeutic targets for this disease. This study revealed that global Krüppel-like factor 9-mutant (Klf9-/-) mice exhibited impaired cognitive function. Additionally, we found that Klf9 expression in hippocampal tissue was reduced in APPswe/PS1dE9 (APP/PS1) mice. This study also showed that Klf9 stimulates IDE expression and promotes the Aβ degradation process by directly binding to IDE and activating its transcription. Silencing IDE blocked the Klf9-induced Aβ degradation process. We stereotactically injected an adeno-associated virus to selectively overexpress IDE (AAV-IDE) in the hippocampal neurons of Klf9-/- mice and found that the overexpression of IDE in hippocampal neurons ameliorated cognitive deficits and reduced the Aβ content in Klf9-/- mice. Additionally, we also stereotactically injected AAV-Klf9 into the hippocampal neurons of APP/PS1 mice and found that overexpression of Klf9 in hippocampal neurons ameliorated cognitive deficits and reduced Aβ levels in APP/PS1 mice. These findings suggest that downregulation of Klf9 may be a key factor in AD progression, as it reduces Aβ clearance by decreasing IDE expression. Overexpression or activation of Klf9 may be a potential strategy for preventing the pathogenesis of AD.

Identifying risk factors for Alzheimer's disease from multivariate longitudinal clinical data using temporal pattern mining

BACKGROUND

Patient data contain a wealth of information that could aid in understanding the onset and progression of disease. However, the task of modelling clinical data, which consist of multiple heterogeneous time series of different lengths, measured at different time intervals, is a complex one. A growing body of research has applied temporal pattern mining to this problem to identify common patterns in clinical attributes over time. However, the vast majority of these algorithms use techniques that are not ideally suited to clinical data. We present an efficient and scalable framework designed specifically for temporal pattern mining of real-world clinical data. Our framework combines temporal abstraction, an extended version of the efficient pattern-growth algorithm, TPMiner, the concepts of relative risk and the odds ratio to identify interesting and high-risk patterns and multiprocessing to improve computational efficiency. A complete set of cut-off values for discretisation and interpretation of the data is provided and is applicable to studies on ageing populations in general. We name this framework Clinical Temporal Pattern Mining or C-TPM.

RESULTS

The framework is applied to data from two real-world studies of Alzheimer's disease (AD). The patterns discovered were predictive of AD in survival analysis models with a Concordance index of up to 0.87 and contain clinically relevant variables. A visualisation module provides a clear picture of the discovered patterns for ease of interpretability.

CONCLUSIONS

The framework provides an effective and scalable method of modelling multivariate, longitudinal clinical data and can identify patterns in uncommon diseases and those that progress slowly over time. It is generalisable to clinical data from other medical domains as well as non-clinical data.

Reduced SH3RF3 may protect against Alzheimer's disease by lowering microglial pro-inflammatory responses via modulation of JNK and NFkB signaling

Understanding how high-risk individuals are protected from Alzheimer's disease (AD) may illuminate potential therapeutic targets. We identified protective genetic variants in SH3RF3/POSH2 that delayed the onset of AD among individuals carrying the PSEN1 G206A mutation. SH3RF3 acts as a JNK pathway scaffold and activates NFκB signaling. While effects of SH3RF3 knockdown in human neurons were subtle, including decreased ptau S422, knockdown in human microglia significantly reduced inflammatory cytokines in response to either a viral mimic or oAβ42. This was associated with reduced activation of JNK and NFκB pathways in response to these stimuli. Pharmacological inhibition of JNK or NFκB signaling phenocopied SH3RF3 knockdown. We also found PSEN1 G206A microglia had reduced inflammatory response to oAβ42. Thus, further reduction of microglial inflammatory responses in PSEN1 G206A mutant carriers by protective variants in SH3RF3 might reduce the link between amyloid and neuroinflammation to subsequently delay the onset of AD.

Functional and effective EEG connectivity patterns in Alzheimer's disease and mild cognitive impairment: a systematic review

Background

Alzheimer's disease (AD) might be best conceptualized as a disconnection syndrome, such that symptoms may be largely attributable to disrupted communication between brain regions, rather than to deterioration within discrete systems. EEG is uniquely capable of directly and non-invasively measuring neural activity with precise temporal resolution; connectivity quantifies the relationships between such signals in different brain regions. EEG research on connectivity in AD and mild cognitive impairment (MCI), often considered a prodromal phase of AD, has produced mixed results and has yet to be synthesized for comprehensive review. Thus, we performed a systematic review of EEG connectivity in MCI and AD participants compared with cognitively healthy older adult controls.

Methods

We searched PsycINFO, PubMed, and Web of Science for peer-reviewed studies in English on EEG, connectivity, and MCI/AD relative to controls. Of 1,344 initial matches, 124 articles were ultimately included in the systematic review.

Results

The included studies primarily analyzed coherence, phase-locked, and graph theory metrics. The influence of factors such as demographics, design, and approach was integrated and discussed. An overarching pattern emerged of lower connectivity in both MCI and AD compared to healthy controls, which was most prominent in the alpha band, and most consistent in AD. In the minority of studies reporting greater connectivity, theta band was most commonly implicated in both AD and MCI, followed by alpha. The overall prevalence of alpha effects may indicate its potential to provide insight into nuanced changes associated with AD-related networks, with the caveat that most studies were during the resting state where alpha is the dominant frequency. When greater connectivity was reported in MCI, it was primarily during task engagement, suggesting compensatory resources may be employed. In AD, greater connectivity was most common during rest, suggesting compensatory resources during task engagement may already be exhausted.

Conclusion

The review highlighted EEG connectivity as a powerful tool to advance understanding of AD-related changes in brain communication. We address the need for including demographic and methodological details, using source space connectivity, and extending this work to cognitively healthy older adults with AD risk toward advancing early AD detection and intervention.

Quantification and correlation of amyloid-β plaque load, glial activation, GABAergic interneuron numbers, and cognitive decline in the young TgF344-AD rat model of Alzheimer's disease

Background

Animal models of Alzheimer's disease (AD) are essential tools for investigating disease pathophysiology and conducting preclinical drug testing. In this study, we examined neuronal and glial alterations in the hippocampus and medial prefrontal cortex (mPFC) of young TgF344-AD rats and correlated these changes with cognitive decline and amyloid-β plaque load.

Methods

We compared TgF344-AD and non-transgenic littermate rats aged 7-8 months of age. We systematically quantified β-amyloid plaques, astrocytes, microglia, four different subtypes of GABAergic interneurons (calretinin-, cholecystokinin-, parvalbumin-, and somatostatin-positive neurons), and newly generated neurons in the hippocampus. Spatial learning and memory were assessed using the Barnes maze test.

Results

Young TgF344-AD rats had a large number of amyloid plaques in both the hippocampus and mPFC, together with a pronounced increase in microglial cell numbers. Astrocytic activation was significant in the mPFC. Cholecystokinin-positive cell numbers were decreased in the hippocampus of transgenic rats, but calretinin-, parvalbumin-, and somatostatin-positive cell numbers were not altered. Adult neurogenesis was not affected by genotype. TgF344-AD rats had spatial learning and memory impairments, but this cognitive deficit did not correlate with amyloid plaque number or cellular changes in the brain. In the hippocampus, amyloid plaque numbers were negatively correlated with cholecystokinin-positive neuron and microglial cell numbers. In the mPFC, amyloid plaque number was negatively correlated with the number of astrocytes.

Conclusion

Pronounced neuropathological changes were found in the hippocampus and mPFC of young TgF344-AD rats, including the loss of hippocampal cholecystokinin-positive interneurons. Some of these neuropathological changes were negatively correlated with amyloid-β plaque load, but not with cognitive impairment.

The effects of amyloidosis and aging on glutamatergic and GABAergic synapses, and interneurons in the barrel cortex and non-neocortical brain regions

Previous studies on changes in the distribution of GABAergic interneurons and excitation/inhibition (E/I) balance in Alzheimer's disease (AD) and aging were mainly conducted in the neocortex and hippocampus. However, the limbic system is the primary and crucial location for AD progression. Therefore, in this study, we utilized AD and aging mouse models to investigate the E/I balance and the distribution of parvalbumin (PV)- and somatostatin (SST)-expressing cells in S1BF (barrel field of primary somatosensory cortex, barrel cortex), CA1 hippocampal area and brain regions beyond the neocortex and hippocampus, including retrosplenial cortex (RSC, which is composed of RSG and RSA), piriform cortex (Pir), amygdala (BMA), and hypothalamus (DM). We discovered that amyloidosis may disrupt the alignment of excitatory pre- and postsynaptic quantities. Amyloidosis reduces the quantity of synapses and SST cells, but does not impact the counts of PV cells. By contrast, aging is linked to a decline in synapses, I/E ratios, SST and PV cells. Amyloidosis affects the S1BF and BMA, while aging may harm all studied regions, including the S1BF, RSC, hippocampus, Pir, BMA, and DM. Aging mostly affects synapses and I/E ratios in Pir, BMA, and DM, and PV and SST interneurons in the hippocampus.

Changes in Adsorption, Aggregation, and Diffusion Nature of Amyloid β on a Lipid Membrane in an Open System

The aggregation and accumulation of amyloid β 42 (Aβ42) peptides on the surface of brain cells is associated with Alzheimer's disease (AD); however, the underlying molecular mechanisms remain unclear. Herein, we used a unique brain-mimetic open system that continuously flows Aβ42 solution to analyze the initial aggregation and adsorptive nature of Aβ42 at physiological concentrations on the lipid membrane. The open system accelerated the adsorption and dimerization kinetics. Upon the addition of Aβ42, monomeric Aβ42 was dominant on the lipid bilayer surface in the closed system with no flow, whereas dimers and high-order oligomers were dominant in the open system. Closed and open systems exhibited different oligomerization kinetics, lipid-Aβ42 interactions, and diffusive properties of monomers and oligomers. These results indicate the specific adsorptive and diffusive nature of Aβ42 on the cell membrane. The open system may help in elucidating the molecular mechanisms underlying AD progression.

Alzheimer-mutant γ-secretase complexes stall amyloid β-peptide production

Missense mutations in the amyloid precursor protein (APP) and presenilin-1 (PSEN1) cause early-onset familial Alzheimer's disease (FAD) and alter proteolytic production of secreted 38-to-43-residue amyloid β-peptides (Aβ) by the PSEN1-containing γ-secretase complex, ostensibly supporting the amyloid hypothesis of pathogenesis. However, proteolysis of APP substrate by γ-secretase is processive, involving initial endoproteolysis to produce long Aβ peptides of 48 or 49 residues followed by carboxypeptidase trimming in mostly tripeptide increments. We recently reported evidence that FAD mutations in APP and PSEN1 cause deficiencies in early steps in processive proteolysis of APP substrate C99 and that this results from stalled γ-secretase enzyme-substrate and/or enzyme-intermediate complexes. These stalled complexes triggered synaptic degeneration in a Caenorhabditis elegans model of FAD independently of Aβ production. Here, we conducted full quantitative analysis of all proteolytic events on APP substrate by γ-secretase with six additional PSEN1 FAD mutations and found that all six are deficient in multiple processing steps. However, only one of these (F386S) was deficient in certain trimming steps but not in endoproteolysis. Fluorescence lifetime imaging microscopy in intact cells revealed that all six PSEN1 FAD mutations lead to stalled γ-secretase enzyme-substrate/intermediate complexes. The F386S mutation, however, does so only in Aβ-rich regions of the cells, not in C99-rich regions, consistent with the deficiencies of this mutant enzyme only in trimming of Aβ intermediates. These findings provide further evidence that FAD mutations lead to stalled and stabilized γ-secretase enzyme-substrate and/or enzyme-intermediate complexes and are consistent with the stalled process rather than the products of γ-secretase proteolysis as the pathogenic trigger.

Microvascular dysfunction in a murine model of Alzheimer's disease using intravital microscopy

Alzheimer's disease (AD) is a complex neurocognitive disorder. Early theories of AD sought to identify a single unifying explanation underlying AD pathogenesis; however, evolving evidence suggests it is a multifactorial, systemic disease, involving multiple systems. Of note, vascular dysfunction, encompassing both cerebral and peripheral circulation, has been implicated in AD pathogenesis. This pilot study used intravital microscopy to assess differences in responsiveness of gluteal muscle arterioles between a transgenic AD mouse model (APP/PS1; Tg) and wild-type (C57BL/6; WT) mice to further elucidate the role of vascular dysfunction in AD. Arteriole diameters were measured in response to acetylcholine (10-9 to 10-5 M), phenylephrine (10-9 to 10-5 M), histamine (10-9 to 10-4 M) and compound 48/80 (10-9 to 10-3 M). Tg mice demonstrated a trend toward reduced vasodilatory response to acetylcholine with a significant difference at 10-5 M (36.91 vs. 69.55%: p = 0.0107) when compared to WT. No significant differences were observed with histamine, compound 48/80 or phenylephrine; however, a trend toward reduced vasoconstriction to phenylephrine was observed in Tg mice at higher concentrations. Mean net diameter change (resting to maximum) also differed significantly (p = 0.0365) between WT (19.11 μm) and Tg mice (11.13 μm). These findings suggest reduced vascular responsiveness may contribute to the systemic vascular deficits previously observed in AD models. Future research using diverse models and broader variables could further elucidate peripheral vascular dysfunction's role in AD pathogenesis, including its impact on motor symptoms and disease progression. Such insights may inform the development of vascular-targeted therapeutic strategies.

Cordycepin mediates neuroprotection against apoptosis via ERK/CREB signaling activation in Aβ1-42-induced neuronal cell models

The aggregation of β-amyloid (Aβ) peptides has been associated with the onset of Alzheimer's disease (AD) by causing neurotoxicity due to oxidative stress and apoptosis. Cordycepin is a natural derivative of the nucleoside adenosine that displays potent antioxidant, antitumor, anti-inflammatory, and neuroprotective properties. However, the mechanism of the neuroprotective effect of cordycepin toward Aβ-induced neurotoxicity, as well as underlying mechanisms, is still unclear. In this study, we found that cordycepin conferred neuroprotection to catecholaminergic PC12 neuronal cell cultures exposed to Aβ1-42-insult by reducing the production of reactive oxygen species, restoring the mitochondrial membrane potential, and inhibiting apoptosis. Cordycepin stimulated the phosphorylation of extracellular signal-regulated kinase (ERK) and cyclic AMP-responsive element-binding protein (CREB) in a time- and concentration-dependent manner. Inhibition of the ERK pathway reduced the neuroprotective effect of cordycepin. Similar results were obtained with hippocampal HT22 neuronal cell cultures. Cumulatively, these findings suggest that cordycepin-induced neuroprotection toward Aβ1-42 neurotoxic insult may involve activation of the ERK/CREB pathway. This study expands our knowledge of the neuroprotective function of cordycepin and suggests that it holds promise as a natural lead compound for drug development in AD.

TMF Attenuates Cognitive Impairment and Neuroinflammation by Inhibiting the MAPK/NF-κB Pathway in Alzheimer's Disease: A Multi-Omics Analysis

The rising prevalence of Alzheimer's disease (AD) underscores the urgent need for novel therapeutic agents derived from natural sources. Among flavonoids, 3',4',5,7-tetramethoxyflavone (TMF), a structural analog of luteolin, has gained attention for its favorable pharmacokinetics and potential neuroprotective properties. Despite the significant neuroprotective effects and favorable pharmacokinetics of TMF, its efficacy and mechanism of action in AD remain unclear. This study explored TMF's pharmacological effects in AD models, highlighting its ability to improve memory and cognitive deficits in APP/PS1 mice. TMF reduced Aβ plaques, NFTs formation, and glial activation while suppressing neuroinflammation through the MAPK/NF-κB pathway. Further analysis in LPS-induced BV2 cells revealed TMF's ability to reduce microglial activation. These findings highlight the anti-neuroinflammatory activity of TMF, suggesting its potential as a treatment for AD.

Nanoscale drug formulations for the treatment of Alzheimer's disease progression

Alzheimer's disease (AD) is a devastating neurodegenerative disorder with no effective disease-modifying treatments. The blood-brain barrier hinders drug delivery to the brain, limiting therapeutic efficacy. Nanoparticle-based systems have emerged as promising tools to overcome these challenges. This review highlights recent advances in nanoparticle technologies for AD treatment, including liposomes, polymeric, inorganic, and biomimetic nanoparticles. These nanoparticles improve drug delivery across the blood-brain barrier, improve stability and bioavailability, and enable targeted delivery to affected brain regions. Functionalization strategies further enhance their therapeutic potential. Multifunctional nanoparticles combining therapeutic and diagnostic properties offer theranostic approaches. While progress has been made, challenges related to safety, targeting precision, and clinical translation remain. Future perspectives emphasize the need for collaborative efforts to optimize nanoparticle design, conduct rigorous studies, and accelerate the development of effective nanotherapeutics. With continued innovation, nanoparticle-based delivery systems hold great promise for revolutionizing AD treatment.

Precuneus Activity during Retrieval Is Positively Associated with Amyloid Burden in Cognitively Normal Older APOE4 Carriers

The precuneus is a site of early amyloid-beta (Aβ) accumulation. Previous cross-sectional studies reported increased precuneus fMRI activity in older adults with mild cognitive deficits or elevated Aβ. However, longitudinal studies in early Alzheimer's disease (AD) are lacking and the relationship to the Apolipoprotein-E (APOE) genotype is unclear. Investigating the PREVENT-AD dataset, we assessed how baseline and longitudinal precuneus activity during successful memory retrieval relates to future Aβ and tau burden and change in memory performance. We further studied the moderation by APOE4 genotype. We included 165 older adults (age, 62.8 ± 4.4 years; 113 female; 66 APOE4 carriers) who were cognitively normal at baseline with a family history of AD. All participants performed task-fMRI at baseline and underwent 18F-flortaucipir-PET and 18F-NAV4694-Aβ-PET on average 5 years later. We found that higher baseline activity and greater longitudinal increase in precuneus activity were associated with higher Aβ burden in APOE4 carriers but not noncarriers. We observed no effects of precuneus activity on tau burden. Finally, APOE4 noncarriers with low baseline precuneus activity exhibited better longitudinal performance in an independent memory test compared with (1) noncarriers with higher baseline activity and (2) APOE4 carriers. Our findings suggest that higher task-related precuneus activity during memory retrieval at baseline and over time are associated with greater Aβ burden in cognitively normal APOE4 carriers. Our results further indicate that the absence of "hyperactivation" and the absence of the APOE4 allele is related with better future cognitive outcomes in cognitively normal older adults at risk for AD.

Sex differences in the neuroinflammatory signaling pathway: effect of miRNAs on fatty acid synthesis in microglia

BACKGROUND

Significant sex differences exist in the prevalence and incidence of Alzheimer's disease (AD). Notably, testosterone has been reported to regulate cognitive functions in the brain, with low serum testosterone levels correlating with increased AD risk. However, the specific mechanisms underlying this relationship remain unclear. Recent studies have demonstrated that microglia, the primary innate immune cells in the brain, play a crucial role in AD development. Therefore, this study aimed to explore sex differences in microglial function, specifically focusing on the role of testosterone in miRNA-mediated regulation of microglial gene expression.

METHODS

Microglia were isolated from pooled hippocampal tissue of five 8-month-old male and female mice. Total RNA was extracted and subjected to miRNA microarray analysis. The mouse microglial cell line MG6 was used for in vitro experiments. Following testosterone treatment, miRNA, gene, and protein expression levels were investigated. An inflammatory response was induced using lipopolysaccharide (LPS) stimulation, and subsequent p65 phosphorylation was assessed.

RESULTS

Sex-dependent differences were observed in miRNA-mediated biological processes, with males exhibiting greater changes. Male-enriched miRNAs were associated with fatty acid synthesis and metabolism pathways. In MG6 cells, testosterone treatment upregulated the expression of several miRNAs enriched in male microglia, particularly those targeting genes related to fatty acid synthesis. Additionally, testosterone significantly reduced the gene expression of fatty acid synthase (FASN). This testosterone-induced inhibition of FASN expression attenuated NF-κB/p65 phosphorylation. Consequently, the suppression of FASN expression led to reduced expression and secretion of tumor necrosis factor-alpha following LPS stimulation in MG6 cells.

CONCLUSIONS

These findings suggest that testosterone modulates inflammation in male microglia by regulating fatty acid synthesis, potentially contributing to the observed sex differences in AD pathogenesis.

Amyloid-β predominant Alzheimer's disease neuropathologic change

Different subsets of Alzheimer's disease neuropathologic change (ADNC), including the intriguing set of individuals with severe/widespread amyloid-β (Aβ) plaques but no/mild tau tangles [Aβ-predominant (AP)-ADNC], may have distinct genetic and clinical features. Analysing National Alzheimer's Coordinating Center data, we stratified 1187 participants into AP-ADNC (n = 95), low Braak primary age-related tauopathy (PART; n = 185), typical-ADNC (n = 832) and high-Braak PART (n = 75). AP-ADNC differed in some clinical features and genetic polymorphisms in the APOE, SNX1, WNT3/MAPT and IGH genes. We conclude that AP-ADNC differs from classical ADNC with implications for in vivo studies.

Massive changes in gene expression and their cause(s) can be a unifying principle in the pathobiology of Alzheimer's disease

Understanding of the biology of Alzheimer's disease (AD) has long been fragmented, with various investigators concentrating on amyloid beta (Aβ) or tau, inflammation, cell death pathways, misfolded proteins, glia, and more. Yet data from multiple authors has repeatedly shown altered expression of myriad genes related to these seemingly disparate phenomena. In 2022, Morgan et al. organized the massive data on changes in AD in a meticulous survey of the literature and related these changes to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Their data showed that 91% of the known KEGG pathways are involved in AD and that many of these pathways are represented by the known cellular/molecular phenomena of AD. Such data then raise the fundamental question: What mechanism(s) may be responsible for such widespread changes in gene expression? We review evidence for a unifying model based on sequestrations in stress granules and alteration of nucleocytoplasmic transport in AD. HIGHLIGHTS: In Alzheimer's disease (AD), critical changes take place in neurons before the appearance of plaques or tangles. Addressing these early changes provides a path to early detection and effective intervention in AD.

HEBE: A novel chimeric chronokine for ameliorating memory deficits in Alzheimer's disease

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder characterized by amyloid-β and Tau protein depositions, with treatments focusing on single proteins have shown limited success due to the complexity of pathways involved. This study explored the potential of chronokines -proteins that modulate aging-related processes- as an alternative therapeutic approach. Specifically, we focused on a novel pleiotropic chimeric protein named HEBE, combining s-KL, sTREM2 and TIMP2, guided by bioinformatic analyses to ensure the preservation of each protein's conformation, crucial for their functions. In vitro studies confirmed HEBE's stability and enzymatic activities, even suggesting it has different activities compared to the individual chronokines. In vivo experiments on APP/Tau mice revealed improved learning and memory functions with HEBE treatment, along with decreased levels of phosphorylated Tau and minor effects on amyloid-β levels. These findings suggest that HEBE is as a promising therapeutic candidate for ameliorating memory deficits and reducing pTau in an AD mouse model.

Self-Assembled BODIPY@Au Core-Shell Structures for Durable Neuroprotective Phototherapy

BODIPY analogs are promising photosensitizers for molecular phototherapy; however, they exhibit high dark cytotoxicity and limited singlet oxygen generation capacity. In this study, we developed self-assembled core-shell nanophotosensitizers by linking a bipyridine group to BODIPY (Bpy-BODIPY) and promoting J-aggregation on gold nanourchins. This design enhances photostability and reduces the energy gap between the lowest singlet excited state and the lower triplet state, facilitating efficient singlet oxygen production. We characterized these nanophotosensitizers using UV-visible spectroscopy, transmission electron microscopy (TEM), surface-enhanced Raman spectroscopy (SERS) and dynamic light scattering (DLS), which confirmed the formation of the desired core-shell structure and J-aggregates. Notably, Bpy-BODIPY@Au significantly suppresses tau protein aggregation and enhances neuroprotective action, even in the presence of a phosphatase inhibitor. This work broadens the application of BODIPY chemistry to nanoagents for neuroprotective therapy.

Polyphenols as Wnt/β-catenin pathway modulators: A promising strategy in clinical neurodegeneration

Polyphenols, a diverse group of naturally occurring compounds found in plants, have garnered significant attention for their potential therapeutic properties in treating neurodegenerative diseases (NDs). The Wnt/β-catenin (WβC) signaling pathway, a crucial player in neurogenesis, neuronal survival, and synaptic plasticity, is involved in several cellular mechanisms related to NDs. Dysregulation of this pathway is a hallmark in the development of various NDs. This study explores multiple polyphenolic compounds, such as flavonoids, stilbenes, lignans, and phenolic acids, and their potential to protect the nervous system. It provides a comprehensive analysis of their effects on the WβC pathway, elucidating their modes of action. The study highlights the dual function of polyphenols in regulating and protecting the nervous system, providing reassurance about the research benefits. This review provides a comprehensive analysis of the results obtained from both in vitro studies and in vivo research, shedding light on how these substances influence the various components of the pathway. The focus is mainly on the molecular mechanisms that allow polyphenols to reduce oxidative stress, inflammation, and apoptotic processes, ultimately improving the function and survival of neurons. This study aims to offer a thorough understanding of the potential of polyphenols in targeting the WβC signaling pathway, which could lead to the development of innovative therapeutic options for NDs.

A network aggregation model for amyloid- β dynamics and treatment of Alzheimer's diseases at the brain scale

Neurodegenerative diseases are associated with the assembly of specific proteins into oligomers and fibrillar aggregates. At the brain scale, these protein assemblies can diffuse through the brain and seed other regions, creating an autocatalytic protein progression. The growth and transport of these assemblies depend on various mechanisms that can be targeted therapeutically. Here, we use spatially-extended nucleation-aggregation-fragmentation models for the dynamics of prion-like neurodegenerative protein-spreading in the brain to study the effect of different drugs on whole-brain Alzheimer's disease progression.

Screening for Anti-Aβ Aggregation Activity of Marine Fungal Natural Products Based on a Gold Nanoparticle Method

Screening Aβ aggregation inhibitors (AAIs) is important for Alzheimer's disease drug discovery. However, common cellular or biochemical methods are not suitable for high-throughput natural product screening. A gold nanoparticle (GNP) screening method was employed in this study to screen marine fungal crude extracts and pure compounds for quick AAI discovering. The anti-Aβ aggregation activity was further inspected using transmission electron microscopic (TEM) observation, and the interaction between active molecules and different Aβ species was revealed by molecular docking. The results indicated that the fungal extracts DLS2008001(M), BM3T2(M), DLEN2008005(M), TBG1-16(P), and TBG1-13(P) showed activity comparable to the positive control human serum albumin at the concentration of 500 µg/mL; 10 pure compounds also displayed moderate anti-aggregation activity, particularly nidulin, aspergillusidone G, and butyrolactone I. The inspection of anti-Aβ aggregation effect through TEM further demonstrated that extracts TBG1-16(P), DLS2008001(M), and BM3T2(M) dramatically inhibited the formation of Aβ aggregates. Molecular docking displayed low binding energies and key interactions of nidulin, aspergillusidone G, and butyrolactone I, with nine types of Aβ peptides. These findings indicate that the GNP method is efficient in screening AAIs and reveal marine fungal natural products as valuable sources of small molecular AAIs.

Linking higher amyloid beta 1-38 (Aβ(1-38)) levels to reduced Alzheimer's disease progression risk

INTRODUCTION

The beneficial effects of amyloid beta 1-38, or Aβ(1-38), on Alzheimer's disease (AD) progression in humans in vivo remain controversial. We investigated AD patients' cerebrospinal fluid (CSF) Aβ(1-38) and AD progression.

METHODS

Cognitive function and diagnostic change were assessed annually for 3 years in 177 Aβ-positive participants with subjective cognitive decline (SCD), mild cognitive impairment (MCI), and dementia from the German Center for Neurodegenerative Diseases (DZNE) longitudinal cognitive impairment and dementia study (DELCODE) cohort using the Mini-Mental State Examination (MMSE), Preclinical Alzheimer's Cognitive Composite (PACC), Clinical Dementia Rating (CDR), and National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria. Mixed linear and Cox regression analyses were conducted. CSF was collected at baseline.

RESULTS

Higher Aβ(1-38) levels were associated with slower PACC (p = 0.001) and slower CDR Sum of Boxes (CDR-SB) (p = 0.002) but not MMSE decline. Including Aβ(1-40) beyond Aβ(1-38) in the model confirmed an association of Aβ(1-38) with slower PACC decline (p = 0.005), but not with CDR-SB or MMSE decline. In addition, higher Aβ(1-38) baseline levels were associated with a reduced dementia conversion risk.

DISCUSSION

Further research is needed to understand the role of Aβ(1-38) in AD and its potential for future therapeutic strategies.

HIGHLIGHTS

This study not only replicates but also extends the existing findings on the role of Aβ(1-38) (amyloid beta 1-38) in Alzheimer's disease (AD) in humans in vivo. Higher baseline Aβ(1-38) levels were associated with a decreased risk of conversion to AD dementia in subjective cognitive decline (SCD) and mild cognitive impairment (MCI). Different linear-mixed regression models suggest an association between higher Aβ(1-38) baseline levels and slower Preclinical Alzheimer's Cognitive Composite (PACC) and Clinical Dementia Rating Sum of Boxes (CDR-SB) decline. Including Aβ(1-40) beyond Aβ(1-38) in the model confirmed a link between Aβ(1-38) and PACC decline, but showed no association of Aβ(1-38) on CDR-SB and Mini-Mental State Examination (MMSE) decline. The impact of short Aβ isoforms in AD progression might have been under-investigated These findings underscore the urgent need for additional research on the role of these shorter Aβ peptides in AD, as they may hold key insights for future therapeutic strategies.

Local molecular and connectomic contributions of tau-related neurodegeneration

Neurodegeneration in Alzheimer's disease (AD) is known to be mostly driven by tau neurofibrillary tangles. However, both tau and neurodegeneration exhibit variability in their distribution across the brain and among individuals, and the relationship between tau and neurodegeneration might be influenced by several factors. I aimed to map local molecular and connectivity characteristics that affect the association between tau pathology and neurodegeneration. The current study was conducted on the cross-sectional tau-PET and longitudinal T1-weighted MRI scan data of 186 participants from the ADNI dataset including 71 cognitively unimpaired (CU) and 115 mild cognitive impairment (MCI) individuals. Furthermore, the normative molecular profile of a region was defined using neurotransmitter receptor densities, gene expression, T1w/T2w ratio (myelination), FDG-PET (glycolytic index, glucose metabolism, and oxygen metabolism), and synaptic density. I found that the excitatory-inhibitory (E:I) ratio, myelination, synaptic density, glycolytic index, and functional connectivity are linked with deviation in the relationship between tau and neurodegeneration. Furthermore, there was spatial similarity between tau pathology and glycolytic index, synaptic density, and functional connectivity across brain regions. The current study demonstrates that the regional susceptibility to tau-related neurodegeneration is associated with specific molecular and connectomic characteristics of the affected neural systems. I found that the molecular and connectivity architecture of the human brain is linked to the different effects of tau pathology on downstream neurodegeneration.

C/EBPβ in Alzheimer's disease: An integrative regulator of pathological mechanisms

Alzheimer's disease (AD) stands as one of the most prevalent neurodegenerative disorders, characterized by a progressive decline in cognitive function, neuroinflammation, amyloid-beta (Aβ) plaques, and neurofibrillary tangles (NFTs). With the global aging population, the incidence of AD continues to rise, yet current therapeutic strategies remain limited in their ability to significantly alleviate cognitive impairments. Therefore, a deeper understanding of the molecular mechanisms underlying AD is imperative for the development of more effective treatments. In recent years, the transcription factor C/EBPβ has emerged as a pivotal regulator in several pathological processes of AD, including neuroinflammation, lipid metabolism, Aβ processing, and tau phosphorylation. Through intricate post-translational modifications, C/EBPβ modulates these processes and may influence the progression of AD on multiple fronts. This review systematically explores the multifaceted roles of C/EBPβ in the pathogenesis of AD, delving into its crucial involvement in neuroinflammation, Aβ production, tau pathology, and lipid metabolism dysregulation. Furthermore, we critically assess therapeutic strategies targeting C/EBPβ, examining the challenges and opportunities in regulating this factor. By synthesizing the latest research findings, we offer a more comprehensive understanding of the role of C/EBPβ in AD and discuss its potential as a therapeutic intervention target.

Female sex is linked to a stronger association between sTREM2 and CSF p-tau in Alzheimer's disease

In Alzheimer's disease (AD), Aβ triggers p-tau secretion, which drives tau aggregation. Therefore, it is critical to characterize modulators of Aβ-related p-tau increases which may alter AD trajectories. Here, we assessed whether factors known to alter tau levels in AD modulate the association between fibrillar Aβ and secreted p-tau181 determined in the cerebrospinal fluid (CSF). To assess potentially modulating effects of female sex, younger age, and ApoE4, we included 322 ADNI participants with cross-sectional/longitudinal p-tau181. To determine effects of microglial activation on p-tau181, we included 454 subjects with cross-sectional CSF sTREM2. Running ANCOVAs for nominal and linear regressions for metric variables, we found that women had higher Aβ-related p-tau181 levels. Higher sTREM2 was associated with elevated p-tau181, with stronger associations in women. Similarly, ApoE4 was related to higher p-tau181 levels and faster p-tau181 increases, with stronger effects in female ApoE4 carriers. Our results show that sex alone modulates the Aβ to p-tau axis, where women show higher Aβ-dependent p-tau secretion, potentially driven by elevated sTREM2-related microglial activation and stronger effects of ApoE4 carriership in women.

Defining benefit: Clinically and biologically meaningful outcomes in the next-generation Alzheimer's disease clinical care pathway

To understand the potential benefits of emerging Alzheimer's disease (AD) therapies within and beyond clinical trial settings, there is a need to advance current outcome measurements into meaningful information relevant to all stakeholders. The relationship between the impact on disease biology and clinically measurable outcomes in cognition, function, and behavior must be considered when defining the meaningful benefit of early AD therapies. In this review, we discuss: (1) the lack of consideration for biomarkers in the current concept of meaningfulness in AD; (2) the lack of gold standards for determining minimal biologically and clinically important differences (MBCIDs) in AD trials; (3) how the treatment benefits of disease-modifying treatments are cumulative and increase over time; and (4) the different concepts of meaningfulness among key stakeholders. This review utilizes the future clinical biological framework of AD and aims to further integrate and expand the parameters of meaningful benefits toward a precision medicine framework. HIGHLIGHTS: Definition of meaningful benefit from Alzheimer's disease (AD) treatment varies across disease stage and stakeholder perspectives. Observable and meaningful outcomes must consider the clinical-biological nature of AD. Statistically significant effects or outcomes do not always equate to clinically meaningfulness. Assessment tools must reflect stage-specific subtle changes following treatment. Real-world evidence will support consensus, definition, and interpretation of clinical meaningfulness.

An overview of the genes and biomarkers in Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia and neurodegenerative disease characterized by neurofibrillary tangles (NFTs) and amyloid plaque. Familial AD is caused by mutations in the APP, PSEN1, and PSEN2 genes and these mutations result in the early onset of the disease. Sporadic AD usually affects older adults over the age of 65 years and is, therefore classified as late-onset AD (LOAD). Several risk factors associated with LOAD including the APOE gene have been identified. Moreover, GWAS studies have identified a wide array of genes and polymorphisms that are associated with LOAD risk. Currently, the diagnosis of AD involves the evaluation of memory and personality changes, cognitive impairment, and medical and family history to rule out other diseases. Laboratory tests to assess the biomarkers in the body fluids as well as MRI, CT, and PET scans to analyze the presence of plaques and NFTs are also included in the diagnosis of AD. It is important to diagnose AD before the onset of clinical symptoms, i.e. during the preclinical stage, to delay the progression and for better management of the disease. Research has been conducted to identify biomarkers of AD in the CSF, serum, saliva, and urine during the preclinical stage. Current research has identified several biomarkers and potential biomarkers in the body fluids that enhance diagnostic accuracy. Aside from genetics, other factors such as diet, physical activity, and lifestyle factors may influence the risk of developing AD. Clinical trials are underway to find potential biomarkers, diagnostic measures, and treatments for AD mainly in the preclinical stage. This review provides an overview of the genes and biomarkers of AD.

Nanomaterials-mediated lysosomal regulation: a robust protein-clearance approach for the treatment of Alzheimer's disease

Alzheimer's disease is a debilitating, progressive neurodegenerative disorder characterized by the progressive accumulation of abnormal proteins, including amyloid plaques and intracellular tau tangles, primarily within the brain. Lysosomes, crucial intracellular organelles responsible for protein degradation, play a key role in maintaining cellular homeostasis. Some studies have suggested a link between the dysregulation of the lysosomal system and pathogenesis of neurodegenerative diseases, including Alzheimer's disease. Restoring the normal physiological function of lysosomes hold the potential to reduce the pathological burden and improve the symptoms of Alzheimer's disease. Currently, the efficacy of drugs in treating Alzheimer's disease is limited, with major challenges in drug delivery efficiency and targeting. Recently, nanomaterials have gained widespread use in Alzheimer's disease drug research owing to their favorable physical and chemical properties. This review aims to provide a comprehensive overview of recent advances in using nanomaterials (polymeric nanomaterials, nanoemulsions, and carbon-based nanomaterials) to enhance lysosomal function in treating Alzheimer's disease. This review also explores new concepts and potential therapeutic strategies for Alzheimer's disease through the integration of nanomaterials and modulation of lysosomal function. In conclusion, this review emphasizes the potential of nanomaterials in modulating lysosomal function to improve the pathological features of Alzheimer's disease. The application of nanotechnology to the development of Alzheimer's disease drugs brings new ideas and approaches for future treatment of this disease.

Communicating scientific evidence: drugs for Alzheimer's disease as a case study

This paper reviews the scientific evidence on new anti-amyloid monoclonal antibodies for treating Alzheimer's disease as a case study for improving scientific evidence communication. We introduce five guidelines condensed from the biomedical evidence literature but adapted to the short format of science communication in e.g. journal opinion pieces and newspaper articles. Given the major importance and recent confusion regarding the discussed drugs, with certain disagreements seen e.g. between FDA and EMA, the suggested guidelines may be useful to clinicians discussing with their patients and to scientists communicating the evidence in balance. More generally, we hope that the guidelines may help us to improve communication of scientific evidence on complex topics in opinion pieces in the scientific literature, in advocacy, and in media appearances.

Elevation of ganglioside degradation pathway drives GM2 and GM3 within amyloid plaques in a transgenic mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that accounts for two-thirds of all dementia cases, and age is the strongest risk factor. In addition to the amyloid hypothesis, lipid dysregulation is now recognized as a core component of AD pathology. Gangliosides are a class of membrane lipids of the glycosphingolipid family and are enriched in the central nervous system (CNS). Ganglioside dysregulation has been implicated in various neurodegenerative diseases, including AD, but the spatial distribution of ganglioside dysregulation with respect to amyloid-beta (Aβ) deposition is not well understood. To address this gap, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) was employed to investigate the age-dependent expression profiles of the A-series ganglioside species GD1a, GM1, GM2, and GM3 in the APP/PS1 transgenic mouse model of AD in which age-dependent amyloid-beta (Aβ) plaques develop. This study utilized a dual-resolution approach in combination with whole-brain imaging for comprehensive detection of ganglioside expression across neuroanatomical regions via high-resolution imaging of the cerebral cortex and hippocampus to investigate plaque-associated ganglioside alterations. The results revealed age-dependent changes in the complex gangliosides GM1 and GD1a across white and gray matter regions in both wildtype and APP/PS1 mice. Significantly greater levels of simple gangliosides GM2 and GM3 were observed in the cortex and dentate gyrus of the hippocampus in transgenic mice at 12 and 18 m than in age-matched controls. The accumulation of GM3 colocalized with Aβ plaques in aged APP/PS1 mice and correlated with Hexa gene expression, suggesting that ganglioside degradation is a mechanism for the accumulation of GM3. This work is the first to demonstrate that age-related ganglioside dysregulation is spatiotemporally associated with Aβ plaques using sophisticated MSI and reveals novel mechanistic insights into lipid regulation in AD.

Roles of blood monocytes carrying TREM2R47H mutation in pathogenesis of Alzheimer's disease and its therapeutic potential in APP/PS1 mice

INTRODUCTION

The triggering receptor expressed on myeloid cells 2 (TREM2) arginine-47-histidine (R47H) mutation is a significant risk for Alzheimer's disease (AD) with unclear mechanisms. Previous studies focused on microglial amyloid-β (Aβ) phagocytosis with less attention on the impact of TREM2R47H mutation on blood monocytes.

METHODS

Bone marrow transplantation (BMT) models were used to assess the contribution of blood monocytes carrying TREM2R47H mutation to AD.

RESULTS

Aβ phagocytosis was compromised in mouse monocytes carrying the TREM2R47H mutation. Transplantation of bone marrow cells (BMCs) carrying TREM2R47H mutation increased cerebral Aβ burden and aggravated AD-type pathologies. Moreover, the replacement of TREM2R47H-BMCs restored monocytic Aβ phagocytosis, lowered Aβ levels in the blood and brain, and improved cognitive function.

DISCUSSION

Our study reveals that blood monocytes carrying the TREM2R47H mutation substantially contribute to the pathogenesis of AD, and correcting the TREM2R47H mutation in BMCs would be a potential therapeutic approach for those carrying this mutation.

HIGHLIGHTS

TREM2R47H mutation compromises the Aβ phagocytosis of blood monocytes. Blood monocytes carrying TREM2R47H mutation contribute substantially to AD pathogenesis. Correction of the TREM2R47H mutation in bone marrow cells ameliorates AD pathologies and cognitive impairments.