B lymphocytes ameliorate Alzheimer's disease-like neuropathology via interleukin-35

Peripheral blood immune cell phenotypes and Alzheimer's disease: A mediation Mendelian randomization study

BackgroundAlzheimer's disease (AD) is a debilitating neurodegenerative disorder. Although peripheral immune cells have been implicated in the pathology of AD, the causal relationship between peripheral blood immune cells and AD remains to be fully elucidated.ObjectiveTo examine the association between peripheral blood immune cell phenotypes and AD, mediated by peripheral blood metabolite, a two-step Mendelian randomization (MR) analysis was performed.MethodsSummary statistics were obtained from the two largest independent cohorts. We explored bidirectional univariable MR analysis to explore causal associations and assessed the mediated proportion of peripheral blood metabolite phenotypes.ResultsThe proportion of IgD + CD38- B cells (Bm1) were found to increase the risk of AD in both the FinnGen database (p = 0.033) and the UK Biobank (p = 0.034). Conversely, hematopoietic stem cells were associated with a decreased risk of AD in the FinnGen database (p = 0.045) and the UK Biobank (p = 0.017). Mediation analysis revealed indirect effects of the proportion of Bm1 on AD through cysteine levels (β = 5 × 10-3), Acetylcarnitine (C2) to propionylcarnitine (C3) ratio (β = 4.5 × 10-3), and Gamma-glutamyl-alpha-lysine levels (β = 2.6 × 10-3), with mediated proportion of 19.4%, 16.9% and 9.6% of the total effect, respectively. Additionally, hematopoietic stem cells influenced AD through Glycolithocholate sulfate levels (β = 1.5 × 10-3), with a mediated proportion of 3.5%.ConclusionsOur findings demonstrate that two peripheral blood immune cell phenotypes impact the risk of AD. These immune cells may influence AD through various peripheral blood metabolite, identifying potential intervention targets for individuals at risk.

Peripheral and central neuroimmune mechanisms in Alzheimer's disease pathogenesis

Alzheimer's disease (AD) poses a growing global health challenge as populations age. Recent research highlights the crucial role of peripheral immunity in AD pathogenesis. This review explores how blood-brain barrier disruption allows peripheral immune cells to infiltrate the central nervous system (CNS), worsening neuroinflammation and disease progression. We examine recent findings on interactions between peripheral immune cells and CNS-resident microglia, forming a self-perpetuating inflammatory cycle leading to neuronal dysfunction. Moreover, this review emphasizes recent developments in the dysregulation of immune factors from both the periphery and CNS, and their impact on AD progression. With ongoing research and development of new therapeutic strategies, this review underscores the importance of modulating interactions between the peripheral immune system and CNS in AD therapy.

Fecal Microbiota Transplantation Improves Cognitive Function of a Mouse Model of Alzheimer's Disease

BACKGROUND

A growing body of evidence suggests a link between the gut microbiota and Alzheimer's disease (AD), although the underlying mechanisms remain elusive. This study aimed to investigate the impact of fecal microbiota transplantation (FMT) on cognitive function in a mouse model of AD.

METHODS

Four-month-old 5 × FAD (familial Alzheimer's disease) mice underwent antibiotic treatment to deplete their native gut microbiota. Subsequently, they received FMT either weekly or every other day. After 8 weeks, cognitive function and β-amyloid (Aβ) load were assessed through behavioral testing and pathological analysis, respectively. The composition of the gut microbiota was analyzed using 16S rRNA sequencing.

RESULTS

Initial weekly FMT failed to alleviate memory deficits or reduce brain Aβ pathology in 5 × FAD mice. In contrast, FMT administered every other day effectively restored gut dysbiosis in 5 × FAD mice and decreased Aβ pathology and lipopolysaccharide levels in the colon and hippocampus. Mechanistically, FMT reduced the expression of amyloid β precursor protein, β-site APP cleaving enzyme 1, and presenilin-1, potentially by inhibiting the Toll-like receptor 4/inhibitor of kappa B kinase β/nuclear factor kappa-B signaling pathway. However, the cognitive benefits of FMT on 5 × FAD mice diminished over time.

CONCLUSION

These findings demonstrate the dose- and time-dependent efficacy of FMT in mitigating AD-like pathology, underscoring the potential of targeting the gut microbiota for AD treatment.

Immune conversations at the border: meningeal immunity in health and disease

The brain and spinal cord, collectively known as the central nervous system, are encapsulated by an overlapping series of membranes known as the meninges. Once considered primarily a physical barrier for central nervous system protection, the bordering meninges are now recognized as highly immunologically active. The meninges host diverse resident immune cells and serve as a critical interface with peripheral immunity, playing multifaceted roles in maintaining central nervous system homeostasis, responding to pathogenic threats, and neurological disorders. This review summarizes recent advancements in our understanding of meningeal immunity including its structural composition, physiological functions, and role in health and disease.

Skull bone marrow and skull meninges channels: redefining the landscape of central nervous system immune surveillance

The understanding of neuroimmune function has evolved from concepts of immune privilege and protection to a new stage of immune interaction. The discovery of skull meninges channels (SMCs) has opened new avenues for understanding central nervous system (CNS) immunity. Here, we characterize skull bone marrow and SMCs by detailing the anatomical structures adjacent to the skull, the differences between skull and peripheral bone marrow, mainstream animal processing methods, and the role of skull bone marrow in monitoring various CNS diseases. Additionally, we highlight several unresolved issues based on current research findings, aiming to guide future research directions.

Identifying Neuro-Inflammatory Biomarkers of Generalized Anxiety Disorder from Lymphocyte Subsets Based on Machine Learning Approaches

INTRODUCTION

Activation of the inflammatory response system is involved in the pathogenesis of generalized anxiety disorder (GAD). The purpose of this study was to identify and characterize inflammatory biomarkers in the diagnosis of GAD based on machine learning algorithms.

METHODS

The evaluation of peripheral immune parameters and lymphocyte subsets was performed on patients with GAD. Multivariable linear regression was used to explore the association between lymphocyte subsets and the severity of GAD. Receiver operating characteristic (ROC) analysis was used to determine the predictive value of these immunological parameters for GAD. Machine learning technology was applied to classify the collected data from patients in the GAD and healthy control groups.

RESULTS

Of the 340 patients enrolled, 171 were GAD patients, and 169 were non-GAD patients as healthy control. The levels of neutrophil, monocytes, and systemic immune-inflammation index (SII) were significantly elevated in GAD patients (p < 0.01), and the count and proportion of immune cells, including CD3+CD4+ T cells, CD3+CD8+ T cells, CD19+ B cells, and CD3-CD16+CD56+ NK cells (p < 0.001), have undergone large changes. The classification analysis conducted by machine learning using a weighted ensemble-L2 algorithm demonstrated an accuracy of 95.00 ± 2.04% in assessing the predictive value of these lymphocyte subsets in GAD. In addition, the feature importance analysis score is 0.255, which was much more predictive of GAD severity than for other lymphocyte subsets.

CONCLUSION

In the presented work, we show the level of lymphocyte subsets altered in GAD. Lymphocyte subsets, specifically CD3+CD4+ T %, can serve as neuroinflammatory biomarkers for GAD diagnostics. Furthermore, the application of machine learning offers a highly efficient approach for investigating neuroinflammatory biomarkers and predicting GAD. Our research has provided novel insights into the involvement of cellular immunity in GAD and highlighted the potential predictive value and therapeutic targets of lymphocyte subsets in this disorder.

Agarwood as a potential therapeutic for Alzheimer's disease: Mechanistic insights and target identification

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, memory loss, and functional impairments. Despite extensive research, its pathogenesis remains incompletely understood, and effective treatments are limited. This study explored the therapeutic potential of agarwood in AD by integrating network pharmacology, protein-protein interaction (PPI) network analysis, and single-cell expression analysis. The results revealed that agarwood compounds may modulate key inflammatory genes such as NFKB1, STAT1, and TLR4, alleviating neuroinflammation; enhance the expression of HSP90 and regulate KDR signaling to improve blood-brain barrier (BBB) integrity; and promote the activity of PTPN11 and CXCR4 to support oligodendrocyte precursor cell (OPC) repair and remyelination. Single-cell expression analysis highlighted cell-type-specific expression patterns, particularly in OPCs and endothelial cells, underscoring their relevance in AD pathology. Agarwood's multi-dimensional therapeutic potential positions it as a promising candidate for the development of novel AD treatments.

MiRNA-501-3p and MiRNA-502-3p: A Promising Biomarker Panel for Alzheimer's Disease

INTRODUCTION

Alzheimer's disease (AD) lacks a less invasive and early detectable biomarker. Here, we investigated the biomarker potential of miR-501-3p and miR-502-3p using different AD sources.

METHODS

MiR-501-3p and miR-502-3p expressions were evaluated in AD CSF exosomes, serum exosomes, familial and sporadic AD fibroblasts and B-lymphocytes by qRT-PCR analysis. Further, miR-501-3p and miR-502-3p expressions were analyzed in APP, Tau cells and media exosomes.

RESULTS

MiR-501-3p and miR-502-3p expressions were significantly upregulated in AD CSF exosomes relative to controls. MiRNA levels were high in accordance with amyloid plaque and NFT density in multiple brain regions. Similarly, both miRNAs were elevated in AD and MCI serum exosomes compared to controls. MiR-502-3p expression was high in fAD and sAD B-lymphocytes. Finally, miR-501-3p and miR-502-3p expression were elevated intracellularly and secreted extracellularly in response to APP and Tau pathology.

DISCUSSION

These results suggest that miR-501-3p and miR-502-3p could be promising biomarkers for AD.

Novel method for detection of Aβ and Iso-D7-Aβ N-terminus-specific B cells and Iso-D7-Aβ-specific antibodies

Alzheimer's disease (AD) is a multifactorial systemic disease that is triggered, at least in part, by the accumulation of β-amyloid (Aβ) peptides in the brain, but it also depends on immune system-mediated regulation. Recent studies suggest that B cells may play a role in AD development and point to the accumulation of clonally expanded B cells in AD patients. However, the specificity of the clonally expanded B cells is unknown, and the contribution of Aβ-specific B cells to AD pathology development is unclear. In this study, we have developed a novel method to identify Aβ-specific B cells by flow cytometry using fluorescent tetramers. The suggested method also enables the identification of B-cell clones specific to a more pathology-provoking form of Aβ with an isomerized Asp7 residue (Iso-D7-Aβ) that accumulates in elderly people and in AD patients. The method has been verified using mice immunized with antigens containing the isomerized or non-isomerized Aβ N-terminus peptides. In addition, we describe a new method for the detection of Iso-D7-Aβ-specific antibodies, which was tested on mouse serum. These methods are of potential importance in research aimed at studying AD and may be also utilized for diagnostic and therapeutic purposes.

Peripheral Immune Cells Contribute to the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder with progressive memory and cognitive loss. Neuroinflammation is a central mechanism involved in the progression of AD. With the disruption of the blood-brain barrier (BBB), peripheral immune cells and inflammatory molecules enter into AD brain. However, the exact relationship between peripheral immune cells and AD remains unknown due to various challenges. This study aimed to investigate the potential causal association between peripheral immune cells and AD by using a two-sample Mendelian randomization (TSMR) analysis. We conducted a TSMR to decipher the causal relationship between AD and 731 types of peripheral immune cell parameters from the TBNK, regulatory T cell (Treg), myeloid cell, monocyte, maturation stages of T cell, dendritic cell (DC), and B cell panels.  Various analytical methods were employed, including inverse variance weighting (IVW), MR Egger, and weighted median methods. The Cochran's Q statistic, MR-Egger intercept, and MR-PRESSO tests were used to verify the heterogeneity and horizontal pleiotropy of the results. To further verify our results, we also conducted a replication analysis. The analysis identified CD33 on CD14 + monocyte (OR = 1.03; 95% CI, 1.01-1.04; p = 1.14E-04; adjust-p = 0.042) had an increased risk association for AD, which was verified by the replication study. CD33 on CD33dim HLA DR + CD11b- cell (OR = 1.02; 95% CI, 1.01-1.04; p = 2.87E-04; adjust-p = 0.035) had an increased risk association for AD, while secreting CD4 regulatory T cell %CD4 regulatory T cell (OR = 0.97; 95% CI, 0.96-0.99; p = 1.90E-04; adjust-p = 0.046) and CD25 on switched memory B cell (OR = 0.95; 95% CI, 0.92-0.98; p = 2.87E-04; adjust-p = 0.042) were discovered to be related to a lower risk of AD. However, the causal effect of these three immune cells on AD was insufficiently validated in the replication analysis. The MR analysis suggests a potential causal relationship between peripheral immune cells and the risk of AD. Further extensive research is needed on the specific role of peripheral immune cells in AD.

Risk Factors and Diagnostic Model Construction of Chronic Pain with Cognitive Impairment

Background

Cognitive impairment (CI) is frequently observed in patients with chronic pain (CP). CP progression increases the risk of dementia and accelerates Alzheimer's disease pathogenesis. However, risk diagnostic models and biomarkers for CP-related CI remain insufficient. Previous research has highlighted the relationships between several complete blood count parameters for CP or CI-related diseases, such as Alzheimer's disease, while the specific values of complete blood count parameters in CP-related CI patients remain unclear. This study aimed to explore the correlation between complete blood count parameters and CP-related CI to establish a risk diagnostic model for the early detection of CP-related CI.

Methods

This cross-sectional study was conducted at West China Hospital, Sichuan University. The Montreal Cognitive Assessment (MoCA) was used to classify patients into either the CP with CI group or the CP without CI group. Univariate analysis and multivariate logistic regression analysis were used to screen the related factors of CP-related CI for constructing a risk diagnostic model, and the model was evaluated using receiver operating characteristic (ROC) curve analysis.

Results

The study ultimately included 163 eligible patients. Based on analysis, age (OR, 1.037 [95% CI, 1.007-1.070]; P=0.018), duration of pain (OR, 2.546 [95% CI, 1.099-6.129]; P=0.032), VAS score (OR, 1.724 [95% CI, 0.819-3.672]; P=0.153), LMR (OR, 0.091 [95% CI, 0.024-0.275]; P<0.001), absolute neutrophil value (OR, 0.306 [95% CI, 0.115-0.767]; P=0.014), and lymphocyte percentage (OR, 6.551 [95% CI, 2.143-25.039]; P=0.002) were identified as critical factors of CP-related CI. The diagnostic model was evaluated by the ROC curve, demonstrating good diagnostic value with an area under the curve (AUC) of 0.803, a sensitivity of 0.603 and a specificity of 0.871.

Conclusion

The risk diagnostic model developed in this study for CP-related CI has significant value and enables clinicians to customize interventions based on each patient's needs.

Approaches for studying neuroimmune interactions in Alzheimer's disease

Peripheral immune cells play an important role in the pathology of Alzheimer's disease (AD), impacting processes such as amyloid and tau protein aggregation, glial activation, neuronal integrity, and cognitive decline. Here, we examine cutting-edge strategies - encompassing animal and cellular models - used to investigate the roles of peripheral immune cells in AD. Approaches such as antibody-mediated depletion, genetic ablation, and bone marrow chimeras in mouse models have been instrumental in uncovering T, B, and innate immune cell disease-modifying functions. However, challenges such as specificity, off-target effects, and differences between human and mouse immune systems underscore the need for more human-relevant models. Emerging multicellular models replicating critical aspects of human brain tissue and neuroimmune interactions increasingly offer fresh insights into the role of immune cells in AD pathogenesis. Refining these methodologies can deepen our understanding of immune cell contributions to AD and support the development of novel immune-related therapeutic interventions.

Advancements in Single-Cell RNA Sequencing Research for Neurological Diseases

Neurological diseases are a major cause of the global burden of disease. Although the mechanisms of the occurrence and development of neurological diseases are not fully clear, most of them are associated with cells mediating neuroinflammation. Yet medications and other therapeutic options to improve treatment are still very limited. Single-cell RNA sequencing (scRNA-seq), as a delightfully potent breakthrough technology, not only identifies various cell types and response states but also uncovers cell-specific gene expression changes, gene regulatory networks, intercellular communication, and cellular movement trajectories, among others, in different cell types. In this review, we describe the technology of scRNA-seq in detail and discuss and summarize the application of scRNA-seq in exploring neurological diseases, elaborating the corresponding specific mechanisms of the diseases as well as providing a reliable basis for new therapeutic approaches. Finally, we affirm that scRNA-seq promotes the development of the neuroscience field and enables us to have a deeper cellular understanding of neurological diseases in the future, which provides strong support for the treatment of neurological diseases and the improvement of patients' prognosis.

The Emerging Role of Immunoglobulins and Complement in the Stimulation of Neuronal Activity and Repair: Not as Simple as We Thought

Neurologic disorders such as traumatic brain injury, multiple sclerosis, Alzheimer's disease, and drug-resistant epilepsy have a high socioeconomic impact around the world. Current therapies for these disorders are often not effective. This creates a demand for the development of new therapeutic approaches to treat these disorders. Recent data suggest that autoreactive naturally occurring immunoglobulins produced by subsets of B cells, called B1 B cells, combined with complement, are actively involved in the processes of restoration of neuronal functions during pathological conditions and remyelination. The focus of this review is to discuss the possibility of creating specific therapeutic antibodies that can activate and fix complement to enhance neuronal survival and promote central nervous system repair after injuries associated with many types of neurodegenerative diseases.

β-Amyloids and Immune Responses Associated with Alzheimer's Disease

Alzheimer's disease (AD) is associated with the accumulation of β-amyloids (Aβs) and the formation of Aβ plaques in the brain. Various structural forms and isoforms of Aβs that have variable propensities for oligomerization and toxicity and may differentially affect the development of AD have been identified. In addition, there is evidence that β-amyloids are engaged in complex interactions with the innate and adaptive immune systems, both of which may also play a role in the regulation of AD onset and progression. In this review, we discuss what is currently known about the intricate interplay between β-amyloids and the immune response to Aβs with a more in-depth focus on the possible roles of B cells in the pathogenesis of AD.

EBF1 is a potential biomarker for predicting progression from mild cognitive impairment to Alzheimer's disease: an in silico study

Introduction

The prediction of progression from mild cognitive impairment (MCI) to Alzheimer's disease (AD) is an important clinical challenge. This study aimed to identify the independent risk factors and develop a nomogram model that can predict progression from MCI to AD.

Methods

Data of 141 patients with MCI were obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. We set a follow-up time of 72 months and defined patients as stable MCI (sMCI) or progressive MCI (pMCI) according to whether or not the progression of MCI to AD occurred. We identified and screened independent risk factors by utilizing weighted gene co-expression network analysis (WGCNA), where we obtained 14,893 genes after data preprocessing and selected the soft threshold β = 7 at an R 2 of 0.85 to achieve a scale-free network. A total of 14 modules were discovered, with the midnightblue module having a strong association with the prognosis of MCI. Using machine learning strategies, which included the least absolute selection and shrinkage operator and support vector machine-recursive feature elimination; and the Cox proportional-hazards model, which included univariate and multivariable analyses, we identified and screened independent risk factors. Subsequently, we developed a nomogram model for predicting the progression from MCI to AD. The performance of our nomogram was evaluated by the C-index, calibration curve, and decision curve analysis (DCA). Bioinformatics analysis and immune infiltration analysis were conducted to clarify the function of early B cell factor 1 (EBF1).

Results

First, the results showed that 40 differentially expressed genes (DEGs) related to the prognosis of MCI were generated by weighted gene co-expression network analysis. Second, five hub variables were obtained through the abovementioned machine learning strategies. Third, a low Montreal Cognitive Assessment (MoCA) score [hazard ratio (HR): 4.258, 95% confidence interval (CI): 1.994-9.091] and low EBF1 expression (hazard ratio: 3.454, 95% confidence interval: 1.813-6.579) were identified as the independent risk factors through the Cox proportional-hazards regression analysis. Finally, we developed a nomogram model including the MoCA score, EBF1, and potential confounders (age and gender). By evaluating our nomogram model and validating it in both internal and external validation sets, we demonstrated that our nomogram model exhibits excellent predictive performance. Through the Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes Genomes (KEGG) functional enrichment analysis, and immune infiltration analysis, we found that the role of EBF1 in MCI was closely related to B cells.

Conclusion

EBF1, as a B cell-specific transcription factor, may be a key target for predicting progression from MCI to AD. Our nomogram model was able to provide personalized risk factors for the progression from MCI to AD after evaluation and validation.

Immunotherapy in Alzheimer's disease: focusing on the efficacy of gantenerumab on amyloid-β clearance and cognitive decline

Gantenerumab, a human monoclonal antibody (mAb), has been thought of as a potential agent to treat Alzheimer's disease (AD) by specifically targeting regions of the amyloid-β (Aβ) peptide sequence. Aβ protein accumulation in the brain leads to amyloid plaques, causing neuroinflammation, oxidative stress, neuronal damage, and neurotransmitter dysfunction, thereby causing cognitive decline in AD. Gantenerumab involves disrupting Aβ aggregation and promoting the breakdown of larger Aβ aggregates into smaller fragments, which facilitates the action of Aβ-degrading enzymes in the brain, thus slowing down the progression of AD. Moreover, Gantenerumab acts as an opsonin, coating Aβ plaques and enhancing their recognition by immune cells, which, combined with its ability to improve the activity of microglia, makes it an intriguing candidate for promoting Aβ plaque clearance. Indeed, the multifaceted effects of Gantenerumab, including Aβ disaggregation, enhanced immune recognition, and improved microglia activity, may position it as a promising therapeutic approach for AD. Of note, reports suggest that Gantenerumab, albeit its capacity to reduce or eliminate Aβ, has not demonstrated effectiveness in reducing cognitive decline. This review, after providing an overview of immunotherapy approaches that target Aβ in AD, explores the efficacy of Gantenerumab in reducing Aβ levels and cognitive decline.

Loss of Mitochondrial Tusc2/Fus1 Triggers a Brain Pro-Inflammatory Microenvironment and Early Spatial Memory Impairment

Brain pathological changes impair cognition early in disease etiology. There is an urgent need to understand aging-linked mechanisms of early memory loss to develop therapeutic strategies and prevent the development of cognitive impairment. Tusc2 is a mitochondrial-resident protein regulating Ca2+ fluxes to and from mitochondria impacting overall health. We previously reported that Tusc2-/- female mice develop chronic inflammation and age prematurely, causing age- and sex-dependent spatial memory deficits at 5 months old. Therefore, we investigated Tusc2-dependent mechanisms of memory impairment in 4-month-old mice, comparing changes in resident and brain-infiltrating immune cells. Interestingly, Tusc2-/- female mice demonstrated a pro-inflammatory increase in astrocytes, expression of IFN-γ in CD4+ T cells and Granzyme-B in CD8+T cells. We also found fewer FOXP3+ T-regulatory cells and Ly49G+ NK and Ly49G+ NKT cells in female Tusc2-/- brains, suggesting a dampened anti-inflammatory response. Moreover, Tusc2-/- hippocampi exhibited Tusc2- and sex-specific protein changes associated with brain plasticity, including mTOR activation, and Calbindin and CamKII dysregulation affecting intracellular Ca2+ dynamics. Overall, the data suggest that dysregulation of Ca2+-dependent processes and a heightened pro-inflammatory brain microenvironment in Tusc2-/- mice could underlie cognitive impairment. Thus, strategies to modulate the mitochondrial Tusc2- and Ca2+- signaling pathways in the brain should be explored to improve cognitive health.

Single cell transcriptome analysis identified a unique neutrophil type associated with Alzheimer's disease

BACKGROUND

Neutrophils play an essential role in Alzheimer's disease (AD) pathology. However, the extent of their heterogeneity remains poorly explored, particularly in the context of developing novel therapies targeting these cells.

RESULTS

We investigate the population structure of neutrophils purified from peripheral blood samples of AD mice. Utilizing single cell RNA sequencing, we comprehensively map neutrophil populations into six distinct clusters and find that the Neu-5 subset is specially enriched in AD mice. This subset exhibits fewer specific granules and a lower mature score. Gene ontology (GO) analysis reveals that genes involved in cytokine-mediated signaling are downregulated in the Neu-5 cluster. Furthermore, we identify the Ccrl2 gene is specifically upregulated in this subgroup, which is confirmed by flow cytometry in AD mice. Finally, immunohistochemical staining indicates that CCRL2 protein is increased in the brains of AD mice.

CONCLUSIONS

We identify a unique CCRL2 positive neutrophil cluster, that is specifically enriched in the peripheral blood of AD mice.

Neuroinflammation in Alzheimer's disease: insights from peripheral immune cells

Alzheimer's disease (AD) is a serious brain disorder characterized by the presence of beta-amyloid plaques, tau pathology, inflammation, neurodegeneration, and cerebrovascular dysfunction. The presence of chronic neuroinflammation, breaches in the blood-brain barrier (BBB), and increased levels of inflammatory mediators are central to the pathogenesis of AD. These factors promote the penetration of immune cells into the brain, potentially exacerbating clinical symptoms and neuronal death in AD patients. While microglia, the resident immune cells of the central nervous system (CNS), play a crucial role in AD, recent evidence suggests the infiltration of cerebral vessels and parenchyma by peripheral immune cells, including neutrophils, T lymphocytes, B lymphocytes, NK cells, and monocytes in AD. These cells participate in the regulation of immunity and inflammation, which is expected to play a huge role in future immunotherapy. Given the crucial role of peripheral immune cells in AD, this article seeks to offer a comprehensive overview of their contributions to neuroinflammation in the disease. Understanding the role of these cells in the neuroinflammatory response is vital for developing new diagnostic markers and therapeutic targets to enhance the diagnosis and treatment of AD patients.

Peripheral immune function and Alzheimer's disease: a living systematic review and critical appraisal

BACKGROUND

A growing body of literature examines the relationship between peripheral immune function and Alzheimer's Disease (AD) in human populations. Our living systematic review summarizes the characteristics and findings of these studies, appraises their quality, and formulates recommendations for future research.

METHODS

We searched the electronic databases PubMed, PsycINFO, and Web of Science, and reviewed references of previous reviews and meta-analyses to identify human studies examining the relationship between any peripheral immune biomarkers and AD up to September 7th, 2023. We examined patterns of reported statistical associations (positive, negative, and null) between each biomarker and AD across studies. Evidence for each biomarker was categorized into four groups based on the proportion of studies reporting different associations: corroborating a positive association with AD, a negative association, a null association, and presenting contradictory findings. A modified Newcastle-Ottawa scale (NOS) was employed to assess the quality of the included studies.

FINDINGS

In total, 286 studies were included in this review. The majority were cross-sectional (n = 245, 85.7%) and hospital-based (n = 248, 86.7%), examining relationships between 187 different peripheral immune biomarkers and AD. Cytokines were the most frequently studied group of peripheral immune biomarkers. Evidence supported a positive association with AD for six biomarkers, including IL-6, IL-1β, IFN-γ, ACT, IL-18, and IL-12, and a negative association for two biomarkers, including lymphocytes and IL-6R. Only a small proportion of included studies (n = 22, 7.7%) were deemed to be of high quality based on quality assessment.

INTERPRETATION

Existing research on peripheral immune function and AD exhibits substantial methodological variations and limitations, with a notable lack of longitudinal, population-based studies investigating a broad range of biomarkers with prospective AD outcomes. The extent and manner in which peripheral immune function can contribute to AD pathophysiology remain open questions. Given the biomarkers that we identified to be associated with AD, we posit that targeting peripheral immune dysregulation may present a promising intervention point to reduce the burden of AD.

Near-Infrared-II Imaging Revealed Hypothermia Regulates Neuroinflammation Following Brain Injury by Increasing the Glymphatic Influx

Advanced in vivo imaging techniques have facilitated the comprehensive visual exploration of animal biological processes, leading to groundbreaking discoveries such as the glymphatic system. However, current limitations of macroscopic imaging techniques impede the precise investigation of physiological parameters regulating this specialized lymphatic transport system. While NIR-II fluorescence imaging has demonstrated advantages in peripheral lymphatic imaging, there are few reports regarding its utilization in the glymphatic system. To address this, a noninvasive transcranial macroscopic NIR-II fluorescence imaging model is developed using a cyanine dye-protein coupled nanoprobe. NIR-II imaging with high temporal and spatial resolution reveals that hypothermia can increase the glymphatic influx by reducing the flow rate of cerebrospinal fluid. In addition, respiratory rate, respiratory amplitude, and heart rate all play a role in regulating the glymphatic influx. Thus, targeting the glymphatic influx may alter the trajectory of immune inflammation following brain injury, providing therapeutic prospects for treating brain injury with mild hypothermia.

Roles of Cytokines in Alzheimer's Disease

The neuroimmune system is a collection of immune cells, cytokines, and the glymphatic system that plays a pivotal role in the pathogenesis and progression of Alzheimer's disease (AD). Of particular focus are cytokines, a group of immune signaling molecules that facilitate communication among immune cells and contribute to inflammation in AD. Extensive research has shown that the dysregulated secretion of certain cytokines (IL-1β, IL-17, IL-12, IL-23, IL-6, and TNF-α) promotes neuroinflammation and exacerbates neuronal damage in AD. However, anti-inflammatory cytokines (IL-2, IL-3, IL-33, and IL-35) are also secreted during AD onset and progression, thereby preventing neuroinflammation. This review summarizes the involvement of pro- and anti-inflammatory cytokines in AD pathology and discusses their therapeutic potential.

Association of peripheral B cells and delirium: combined single-cell sequencing and Mendelian randomization analysis

Background

Delirium seriously affects the prognosis of patients and greatly reduces the ability to work and live. Peripheral inflammatory events may contribute to the development of delirium, the mechanism of which is still unclear. There is a lack of effective diagnostic and treatments for delirium in clinical practice. The study aims to investigate alterations in peripheral immune cell subsets under inflammatory stress and to explore causal associations with delirium.

Methods

Single-cell transcriptional sequencing data of human peripheral blood mononuclear cells (PBMC) before and after lipopolysaccharide (LPS) intervention were processed by the Seurat package in R software. PBMC subsets and cellular markers were defined after downscaling and clustering by the Harmony algorithm to identify characteristic subsets in the context of inflammatory stress. Subsequently, a two-sample Mendelian randomization (MR) study was used to explore the causal associations of these inflammation-related PBMC subsets and their molecular phenotypes with delirium. Based on publicly available genetic data, the study incorporated 70 PBMC-associated immune traits, including 8 types of circulating immune cells, 33 B cell subsets and molecular phenotypes, 13 T cell subsets, and 16 B cell-associated cytokines. The results were also validated for robustness, heterogeneity, and horizontal pleiotropy.

Results

Under LPS-induced inflammatory stress, B cells, T cells, monocytes, and dendritic cells in human PBMC showed significant activation and quantitative changes. Of these, only lymphocyte and B cell counts were causally associated with delirium risk. This risk link is also seen in the TNF pathway. Further studies of B cells and their subsets revealed that this association may be related to unswitched memory B cells and CD27 expressed on memory B cells. Annotation of the screened SNPs revealed significant polymorphisms in CD27 and CD40 annotated by rs25680 and rs9883798, respectively. The functions of the key annotated genes may be related to the regulation of immune responses, cell differentiation, proliferation, and intercellular interactions.

Conclusion

The present study revealed the potential possibility that B cell, memory B cell subset, and TNF-related molecules may be involved in the development of delirium due to peripheral inflammation, which can provide clues for further investigation of delirium prevention and treatment strategies.

Complement-mediated synapse loss in Alzheimer's disease: mechanisms and involvement of risk factors

The complement system is increasingly recognized as a key player in the synapse loss and cognitive impairments observed in Alzheimer's disease (AD). In particular, the process of complement-dependent synaptic pruning through phagocytosis is over-activated in AD brains, driving detrimental excessive synapse elimination and contributing to synapse loss, which is the strongest neurobiological correlate of cognitive impairments in AD. Herein we review recent advances in characterizing complement-mediated synapse loss in AD, summarize the underlying mechanisms, and discuss the possible involvement of AD risk factors such as aging and various risk genes. We conclude with an overview of key questions that remain to be addressed.

Intruders or protectors - the multifaceted role of B cells in CNS disorders

B lymphocytes are immune cells studied predominantly in the context of peripheral humoral immune responses against pathogens. Evidence has been accumulating in recent years on the diversity of immunomodulatory functions that B cells undertake, with particular relevance for pathologies of the central nervous system (CNS). This review summarizes current knowledge on B cell populations, localization, infiltration mechanisms, and function in the CNS and associated tissues. Acute and chronic neurodegenerative pathologies are examined in order to explore the complex, and sometimes conflicting, effects that B cells can have in each context, with implications for disease progression and treatment outcomes. Additional factors such as aging modulate the proportions and function of B cell subpopulations over time and are also discussed in the context of neuroinflammatory response and disease susceptibility. A better understanding of the multifactorial role of B cell populations in the CNS may ultimately lead to innovative therapeutic strategies for a variety of neurological conditions.

Peripheral inflammation and neurocognitive impairment: correlations, underlying mechanisms, and therapeutic implications

Cognitive impairments, such as learning and memory deficits, may occur in susceptible populations including the elderly and patients who are chronically ill or have experienced stressful events, including surgery, infection, and trauma. Accumulating lines of evidence suggested that peripheral inflammation featured by the recruitment of peripheral immune cells and the release of pro-inflammatory cytokines may be activated during aging and these conditions, participating in peripheral immune system-brain communication. Lots of progress has been achieved in deciphering the core bridging mechanism connecting peripheral inflammation and cognitive impairments, which may be helpful in developing early diagnosis, prognosis evaluation, and prevention methods based on peripheral blood circulation system sampling and intervention. In this review, we summarized the evolving evidence on the prevalence of peripheral inflammation-associated neurocognitive impairments and discussed the research advances in the underlying mechanisms. We also highlighted the prevention and treatment strategies against peripheral inflammation-associated cognitive dysfunction.

Blood tau-PT217 contributes to the anesthesia/surgery-induced delirium-like behavior in aged mice

INTRODUCTION

Blood phosphorylated tau at threonine 217 (tau-PT217) is a newly established biomarker for Alzheimer's disease and postoperative delirium in patients. However, the mechanisms and consequences of acute changes in blood tau-PT217 remain largely unknown.

METHODS

We investigated the effects of anesthesia/surgery on blood tau-PT217 in aged mice, and evaluated the associated changes in B cell populations, neuronal excitability in anterior cingulate cortex, and delirium-like behavior using positron emission tomography imaging, nanoneedle technology, flow cytometry, electrophysiology, and behavioral tests.

RESULTS

Anesthesia/surgery induced acute increases in blood tau-PT217 via enhanced generation in the lungs and release from B cells. Tau-PT217 might cross the blood-brain barrier, increasing neuronal excitability and inducing delirium-like behavior. B cell transfer and WS635, a mitochondrial function enhancer, mitigated the anesthesia/surgery-induced changes.

DISCUSSION

Acute increases in blood tau-PT217 may contribute to brain dysfunction and postoperative delirium. Targeting B cells or mitochondrial function may have therapeutic potential for preventing or treating these conditions.

Current views on meningeal lymphatics and immunity in aging and Alzheimer's disease

Alzheimer's disease (AD) is an aging-related form of dementia associated with the accumulation of pathological aggregates of amyloid beta and neurofibrillary tangles in the brain. These phenomena are accompanied by exacerbated inflammation and marked neuronal loss, which altogether contribute to accelerated cognitive decline. The multifactorial nature of AD, allied to our still limited knowledge of its etiology and pathophysiology, have lessened our capacity to develop effective treatments for AD patients. Over the last few decades, genome wide association studies and biomarker development, alongside mechanistic experiments involving animal models, have identified different immune components that play key roles in the modulation of brain pathology in AD, affecting its progression and severity. As we will relay in this review, much of the recent efforts have been directed to better understanding the role of brain innate immunity, and particularly of microglia. However, and despite the lack of diversity within brain resident immune cells, the brain border tissues, especially the meninges, harbour a considerable number of different types and subtypes of adaptive and innate immune cells. Alongside microglia, which have taken the centre stage as important players in AD research, there is new and exciting evidence pointing to adaptive immune cells, namely T and B cells found in the brain and its meninges, as important modulators of neuroinflammation and neuronal (dys)function in AD. Importantly, a genuine and functional lymphatic vascular network is present around the brain in the outermost meningeal layer, the dura. The meningeal lymphatics are directly connected to the peripheral lymphatic system in different mammalian species, including humans, and play a crucial role in preserving a "healthy" immune surveillance of the CNS, by shaping immune responses, not only locally at the meninges, but also at the level of the brain tissue. In this review, we will provide a comprehensive view on our current knowledge about the meningeal lymphatic vasculature, emphasizing its described roles in modulating CNS fluid and macromolecule drainage, meningeal and brain immunity, as well as glial and neuronal function in aging and in AD.