Elevated β-secretase 1 expression mediates CD4+ T cell dysfunction via PGE2 signalling in Alzheimer's disease

Dissecting the immune response of CD4+ T cells in Alzheimer's disease

The formation of amyloid-β (Aβ) plaques is a neuropathological hallmark of Alzheimer's disease (AD), however, these pathological aggregates can also be found in the brains of cognitively unimpaired elderly population. In that context, individual variations in the Aβ-specific immune response could be key factors that determine the level of Aβ-induced neuroinflammation and thus the propensity to develop AD. CD4+ T cells are the cornerstone of the immune response that coordinate the effector functions of both adaptive and innate immunity. However, despite intensive research efforts, the precise role of these cells during AD pathogenesis is still not fully elucidated. Both pathogenic and beneficial effects have been observed in various animal models of AD, as well as in humans with AD. Although this functional duality of CD4+ T cells in AD can be simply attributed to the vast phenotype heterogeneity of this cell lineage, disease stage-specific effect have also been proposed. Therefore, in this review, we summarized the current understanding of the role of CD4+ T cells in the pathophysiology of AD, from the aspect of their antigen specificity, activation, and phenotype characteristics. Such knowledge is of practical importance as it paves the way for immunomodulation as a therapeutic option for AD treatment, given that currently available therapies have not yielded satisfactory results.

Safety concerns associated with BACE1 inhibitors - past, present, and future

INTRODUCTION

BACE1 (beta-site amyloid precursor protein cleaving enzyme 1) inhibitors have shown promise in treating Alzheimer's disease (AD) by reducing amyloid-beta (Aβ) production. However, clinical trials of inhibitors such as atabecestat, verubecestat, and lanabecestat have faced challenges, including limited efficacy and significant adverse effects.

AREAS COVERED

This narrative review discusses randomized-controlled trials of BACE1 inhibitors. Literature searches were conducted using PubMed and Web of Science for studies from 2010 to 2024. Association with BACE1's widespread expression beyond the brain shows adverse effects such as anxiety, depressive symptoms, and hepatotoxicity.

EXPERT OPINION

The trial results underscore the need for CNS-specific BACE1 inhibitors to reduce adverse effects. Future research should focus on optimizing drug design and identifying additional therapeutic avenues, such as prostate cancer and insulin resistance.

Elevated BACE1 and IFNγ+ T Cells in Patients with Cognitive Impairment and the 5xFAD Mouse Model

The dysregulation of T cell differentiation was associated with cognitive impairment. Recently, the peripheric β-secretase (BACE1) has been suggested as a regulator of T cell differentiation, which was increased in both cognitive impairment (CI) and type 2 diabetes mellitus (T2DM) in CI patients. However, the relationship between T cell dysfunction and CI remains unclear. To address this question, we measured T cell subtypes and BACE1 enzyme activity in a clinical cohort and 5xFAD mice. We found that both IFNγ+ Th1 and Tc1 cells were increased in the CI and T2DM-CI groups, which were associated with worsening cognitive function. The elevated IFNγ + Th1 and Tc1 cells were also observed in 8-month-old 5xFAD mice. The elevated BACE1-mediated INSR cleavage was associated with increased IFNγ + Th1 and Tc1 cells. These findings demonstrate the potential role of elevated BACE1 in IFNγ+ T cells and CI.

Brain derived β-interferon is a potential player in Alzheimer's disease pathogenesis and cognitive impairment

BACKGROUND

Recent research has postulated that the activation of cGAS-STING-interferon signalling pathways could be implicated in the pathogenesis of Alzheimer's disease (AD). However, the precise types of interferons and related cytokines, both from the brain and periphery, responsible for cognitive impairment in patients with AD remain unclear.

METHODS

A total of 131 participants (78 [59.5%] female and 53 [40.5%] male; mean [SD] age, 61.5 [7.6] years) with normal cognition and cognitive impairment from the China Aging and Neurodegenerative Initiative cohort were included. CSF and serum IFNα-2a, IFN-β, IFN-γ, TNF-α, IL-6, IL-10, MCP-1and CXCL-10 were tested. The correlation between these interferons and related cytokines with AD core biomarkers in the CSF and plasma, cognition performance, and brain MRI measures were analysed.

RESULTS

We found that only CSF IFN-β levels were significantly elevated in Alzheimer's disease compared to normal cognition. Furthermore, CSF IFN-β levels were significantly associated with AD core biomarkers (CSF P-tau and Aβ42/Aβ40 ratio) and cognitive performance (MMSE and CDR score). Additionally, the CSF IFN-β levels were significantly correlated with the typical pattern of brain atrophy in AD (such as hippocampus, amygdala, and precuneus). In contrast, CSF IL-6 levels were significantly elevated in non-AD cognitively impaired patients compared to other groups. Moreover, CSF IL-6 levels were significantly associated with cognitive performance in non-AD individuals and correlated with the vascular cognitive impairment-related MRI markers (such as white matter hyperintensity).

CONCLUSION

Our findings demonstrate that distinct inflammatory molecules are associated with different cognitive disorders. Notably, CSF IFN-β levels are significantly linked to the pathology and cognitive performance of AD, identifying this interferon as a potential target for AD therapy.

Trolox, Ferulic, Sinapic, and Cinnamic Acid Derivatives of Proline and GABA with Antioxidant and/or Anti-Inflammatory Properties

Degenerative conditions, such as neurodegenerative disorders (Alzheimer's disease (AD), Parkinson's disease (PD)) and cardiovascular diseases, are complex, multifactorial disorders whose pathophysiology has not been fully elucidated yet. As a result, the available treatment options cannot eliminate these diseases radically, but only alleviate the symptoms. Both inflammatory processes and oxidation are key factors in the development and evolution of neurodegeneration, while acetylcholinesterase inhibitors are the most used therapeutic options against AD. In this work, following the multi-targeting compound approach, we designed and synthesized a series of proline and gamma-aminobutyric acid (GABA) amides with various acidic moieties that possess an antioxidant and/or anti-inflammatory potency. Proline is the pharmacophore of nootropic drugs (e.g., piracetam) used for memory improvement, while GABA is the main inhibitory neurotransmitter in the central nervous system. The designed molecules were subjected to a preliminary screening of their bioactivity in antioxidant and anti-inflammatory assays, as well as against acetylcholinesterase. Most of the synthesized compounds could inhibit lipid peroxidation (IC50 as low as 8 μΜ) and oxidative protein glycation (inhibition of up to 48%) and reduce the 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH). In addition, all of the compounds were moderate inhibitors of lipoxygenase (LOX) (up to 46% at 100 μΜ) and could decrease carrageenan-induced paw edema in rats by up to 55%. Finally, some of the compounds were moderate acetylcholinesterase inhibitors (IC50 as low as 219 μΜ). The results confirmed the design rationale, indicating that the compounds could be further optimized as multi-targeting molecules directed against degenerative conditions.

Modeling the neuroimmune system in Alzheimer's and Parkinson's diseases

Parkinson's disease (PD) and Alzheimer's disease (AD) are neurodegenerative disorders caused by the interaction of genetic, environmental, and familial factors. These diseases have distinct pathologies and symptoms that are linked to specific cell populations in the brain. Notably, the immune system has been implicated in both diseases, with a particular focus on the dysfunction of microglia, the brain's resident immune cells, contributing to neuronal loss and exacerbating symptoms. Researchers use models of the neuroimmune system to gain a deeper understanding of the physiological and biological aspects of these neurodegenerative diseases and how they progress. Several in vitro and in vivo models, including 2D cultures and animal models, have been utilized. Recently, advancements have been made in optimizing these existing models and developing 3D models and organ-on-a-chip systems, holding tremendous promise in accurately mimicking the intricate intracellular environment. As a result, these models represent a crucial breakthrough in the transformation of current treatments for PD and AD by offering potential for conducting long-term disease-based modeling for therapeutic testing, reducing reliance on animal models, and significantly improving cell viability compared to conventional 2D models. The application of 3D and organ-on-a-chip models in neurodegenerative disease research marks a prosperous step forward, providing a more realistic representation of the complex interactions within the neuroimmune system. Ultimately, these refined models of the neuroimmune system aim to aid in the quest to combat and mitigate the impact of debilitating neuroimmune diseases on patients and their families.

Bioinformatic identification and experiment validation reveal 6 hub genes, promising diagnostic and therapeutic targets for Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disease that can cause dementia. We aim to screen out the hub genes involved in AD based on microarray datasets.

METHODS

Gene expression profiles GSE5281 and GSE28146 were retrieved from Gene Expression Omnibus database to acquire differentially expressed genes (DEGs). Gene Ontology and pathway enrichment were conducted using DAVID online tool. The STRING database and Cytoscape tools were employed to analyze protein-protein interactions and identify hub genes. The predictive value of hub genes was assessed by principal component analysis and receiver operating characteristic curves. AD mice model was constructed, and histology was then observed by hematoxylin-eosin staining. Gene expression levels were finally determined by real-time quantitative PCR.

RESULTS

We obtained 197 overlapping DEGs from GSE5281 and GSE28146 datasets. After constructing protein-protein interaction network, three highly interconnected clusters were identified and 6 hub genes (RBL1, BUB1, HDAC7, KAT5, SIRT2, and ITGB1) were selected. The hub genes could be used as basis to predict AD. Histological abnormalities of brain were observed, suggesting successful AD model was constructed. Compared with the control group, the mRNA expression levels of RBL1, BUB1, HDAC7, KAT5 and SIRT2 were significantly increased, while the mRNA expression level of ITGB1 was significantly decreased in AD groups.

CONCLUSION

RBL1, BUB1, HDAC7, KAT5, SIRT2 and ITGB1 are promising gene signatures for diagnosis and therapy of AD.

Neuroimmune mechanisms underlying Alzheimer's disease: Insights into central and peripheral immune cell crosstalk

Alzheimer's disease (AD) is a highly life-threatening neurodegenerative disease. Dysregulation of the immune system plays a critical role in promoting AD, which has attracted extensive attention recently. Central and peripheral immune responses are involved in the pathogenesis of AD. Immune changes precede Aβ-associated senile plaque formation and tau-related neurofibrillary tangles, which are the recognised pathological features of AD. Therefore, elucidating immune-related mechanisms underlying the development of AD can help to prevent and treat AD at the source by blocking its progression before the development of pathological changes. To understand the specific pathogenesis of AD, it is important to examine the role of central and peripheral immunity in AD. This review summarises immune-related mechanisms underlying the pathogenesis of AD, focusing on the effect of various central and peripheral immune cells, and describes the possible crosstalk between central and peripheral immunity during the development of AD. This review provides novel insights into the treatment of AD and offers a new direction for immune-related research on AD in the future.

Integrated analysis and identification of hub genes as novel biomarkers for Alzheimer’s disease

Alzheimer’s disease (AD) is an intractable and progressive neurodegenerative disorder that can lead to severe cognitive decline, impaired speech, short-term memory loss, and finally an inability to function in daily life. For patients, their families, and even all of society, AD can impart great emotional pressure and economic costs. Therefore, this study aimed to investigate potential diagnostic biomarkers of AD. Using the Gene Expression Omnibus (GEO) database, the expression profiles of genes were extracted from the GSE5281, GSE28146, and GSE48350 microarray datasets. Then, immune-related genes were identified by the intersections of differentially expressed genes (DEGs). Functional enrichment analyses, including Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, Disease Ontology (DO), and Gene Set Enrichment Analysis (GSEA), were performed. Subsequently, random forest models and least absolute shrinkage and selection operator regression were used to further screen hub genes, which were then validated using receiver operating characteristic (ROC) curve analysis. Finally, 153 total immune-related DEGs were identified in relation to AD. DO analysis of these immune-related DEGs showed that they were enriched in “lung disease,” “reproductive system disease,” and “atherosclerosis.” Single GSEA of hub genes showed that they were particularly enriched in “oxidative phosphorylation.” ROC analysis of AGAP3 yielded an area under the ROC curve of 0.878 for GSE5281, 0.727 for GSE28146, and 0.635 for GSE48350. Moreover, immune infiltration analysis demonstrated that AGAP3 was related to follicular helper T cells, naïve CD4 T cells, naïve B cells, memory B cells, macrophages M0, macrophages M1, macrophages M2, resting natural killer (NK) cells, activated NK cells, monocytes, neutrophils, eosinophils, and activated mast cells. These results indicate that identifying immune-related DEGs might enhance the current understanding of the development and prognosis of AD. Furthermore, AGAP3 not only plays a vital role in AD progression and diagnosis but could also serve as a valuable target for further research on AD.

Insights into T-cell dysfunction in Alzheimer's disease

T cells, the critical immune cells of the adaptive immune system, are often dysfunctional in Alzheimer's disease (AD) and are involved in AD pathology. Reports highlight neuroinflammation as a crucial modulator of AD pathogenesis, and aberrant T cells indirectly contribute to neuroinflammation by secreting proinflammatory mediators via direct crosstalk with glial cells infiltrating the brain. However, the mechanisms underlying T‐cell abnormalities in AD appear multifactorial. Risk factors for AD and pathological hallmarks of AD have been tightly linked with immune responses, implying the potential regulatory effects of these factors on T cells. In this review, we discuss how the risk factors for AD, particularly Apolipoprotein E (ApoE), Aβ, α‐secretase, β‐secretase, γ‐secretase, Tau, and neuroinflammation, modulate T‐cell activation and the association between T cells and pathological AD hallmarks. Understanding these associations is critical to provide a comprehensive view of appropriate therapeutic strategies for AD.