Targeting innate immunity to protect and cure Alzheimer's disease: opportunities and pitfalls

A Proteomic Approach Identified TFEB as a Key Player in the Protective Action of Novel CB2R Bitopic Ligand FD22a against the Deleterious Effects Induced by β-Amyloid in Glial Cells

Neurodegenerative diseases (NDDs) are progressive multifactorial disorders of the nervous system sharing common pathogenic features, including intracellular misfolded protein aggregation, mitochondrial deficit, and inflammation. Taking into consideration the multifaceted nature of NDDs, development of multitarget-directed ligands (MTDLs) has evolved as an attractive therapeutic strategy. Compounds that target the cannabinoid receptor type II (CB2R) are rapidly emerging as novel effective MTDLs against common NDDs, such as Alzheimer's disease (AD). We recently developed the first CB2R bitopic/dualsteric ligand, namely FD22a, which revealed the ability to induce neuroprotection with fewer side effects. To explore the potential of FD22a as a multitarget drug for the treatment of NDDs, we investigated here its ability to prevent the toxic effect of β-amyloid (Aβ25-35 peptide) on human cellular models of neurodegeneration, such as microglia (HMC3) and glioblastoma (U87-MG) cell lines. Our results displayed that FD22a efficiently prevented Aβ25-35 cytotoxic and proinflammatory effects in both cell lines and counteracted β-amyloid-induced depression of autophagy in U87-MG cells. Notably, a quantitative proteomic analysis of U87-MG cells revealed that FD22a was able to potently stimulate the autophagy-lysosomal pathway (ALP) by activating its master transcriptional regulator TFEB, ultimately increasing the potential of this novel CB2R bitopic/dualsteric ligand as a multitarget drug for the treatment of NDDs.

Mind the Gap: Unraveling the Intricate Dance Between Alzheimer's Disease and Related Dementias and Bone Health

PURPOSE OF REVIEW

This review examines the linked pathophysiology of Alzheimer's disease/related dementia (AD/ADRD) and bone disorders like osteoporosis. The emphasis is on "inflammaging"-a low-level inflammation common to both, and its implications in an aging population.

RECENT FINDINGS

Aging intensifies both ADRD and bone deterioration. Notably, ADRD patients have a heightened fracture risk, impacting morbidity and mortality, though it is uncertain if fractures worsen ADRD. Therapeutically, agents targeting inflammation pathways, especially Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) and TNF-α, appear beneficial for both conditions. Additionally, treatments like Sirtuin 1 (SIRT-1), known for anti-inflammatory and neuroprotective properties, are gaining attention. The interconnectedness of AD/ADRD and bone health necessitates a unified treatment approach. By addressing shared mechanisms, we can potentially transform therapeutic strategies, enriching our understanding and refining care in our aging society. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

Passive Immunotherapies Targeting Amyloid-β in Alzheimer's Disease: A Quantitative Systems Pharmacology Perspective

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by amyloid-β (Aβ) protein accumulation in the brain. Passive immunotherapies using monoclonal antibodies for targeting Aβ have shown promise for AD treatment. Indeed, recent US Food and Drug Administration approval of aducanumab and lecanemab, alongside positive donanemab Phase III results demonstrated clinical efficacy after decades of failed clinical trials for AD. However, the pharmacological basis distinguishing clinically effective from ineffective therapies remains unclear, impeding development of potent therapeutics. This study aimed to provide a quantitative perspective for effectively targeting Aβ with antibodies. We first reviewed the contradicting results associated with the amyloid hypothesis and the pharmacological basis of Aβ immunotherapy. Subsequently, we developed a quantitative systems pharmacology (QSP) model that describes the non-linear progression of Aβ pathology and the pharmacologic actions of the Aβ-targeting antibodies. Using the QSP model, we analyzed various scenarios for effective passive immunotherapy for AD. The model revealed that binding exclusively to the Aβ monomer has minimal effect on Aβ aggregation and plaque reduction, making the antibody affinity toward Aβ monomer unwanted, as it could become a distractive mechanism for plaque reduction. Neither early intervention, high brain penetration, nor increased dose could yield significant improvement of clinical efficacy for antibodies targeting solely monomers. Antibodies that bind all Aβ species but lack effector function exhibited moderate effects in plaque reduction. Our model highlights the importance of binding aggregate Aβ species and incorporating effector functions for efficient and early plaque reduction, guiding the development of more effective therapies for this devastating disease. SIGNIFICANCE STATEMENT: Despite previous unsuccessful attempts spanning several decades, passive immunotherapies utilizing monoclonal antibodies for targeting amyloid-beta (Aβ) have demonstrated promise with two recent FDA approvals. However, the pharmacological basis that differentiates clinically effective therapies from ineffective ones remains elusive. Our study offers a quantitative systems pharmacology perspective, emphasizing the significance of selectively targeting specific Aβ species and importance of antibody effector functions. This perspective sheds light on the development of more effective therapies for this devastating disease.

Fabrication of a polymer brush-functionalized porphyrin-based covalent organic framework for enrichment of N-glycopeptides

A surface-initiated atom transfer radical polymerization method combining click chemistry was employed to prepare a novel porphyrin-based covalent organic framework composite grafted with polymer brushes (TAPBB@GMA@AMA@Cys) for the specific enrichment of N-glycopeptides. The material successfully realized the high efficiency enrichment of N-glycopeptides with good selectivity (1:1000), low detection limit (0.2 fmol/μL), and high loading capacity (133.3 mg·g-1). The TAPBB@GMA@AMA@Cys was successfully applied to actual sample analysis; 235 N-glycopeptides related to 125 glycoproteins and 210 N-glycopeptides related to 121 glycoproteins were recognized from the serum of normal individuals and Alzheimer's disease patients, respectively. Gene ontology studies of molecular functions, cellular components, and biological processes have revealed that identified glycoproteins are strongly associated with neurodegenerative diseases involving innate immune responses, basement membranes, calcium binding, and receptor binding. The above results confirm the surprising potential of materials in glycoproteomics research and practical sample applications.

Blood-brain barrier dysfunction and Alzheimer's disease: associations, pathogenic mechanisms, and therapeutic potential

Alzheimer's disease (AD) is a common neurodegenerative disorder characterized by the accumulation of amyloid-beta (Aβ), hyperphosphorylation of tau, and neuroinflammation in the brain. The blood-brain barrier (BBB) limits solutes from circulating blood from entering the brain, which is essential for neuronal functioning. Focusing on BBB function is important for the early detection of AD and in-depth study of AD pathogenic mechanisms. However, the mechanism of BBB alteration in AD is still unclear, which hinders further research on therapeutics that target the BBB to delay the progression of AD. The exact timing of the vascular abnormalities in AD and the complex cause-and-effect relationships remain uncertain. Thus, it is necessary to summarize and emphasize this process. First, in this review, the current evidence for BBB dysfunction in AD is summarized. Then, the interrelationships and pathogenic mechanisms between BBB dysfunction and the risk factors for AD, such as Aβ, tau, neuroinflammation, apolipoprotein E (ApoE) genotype and aging, were analyzed. Finally, we discuss the current status and future directions of therapeutic AD strategies targeting the BBB. We hope that these summaries or reviews will allow readers to better understand the relationship between the BBB and AD.

Role of inflammation in the socioeconomic inequalities of neurocognitive disorders

BACKGROUND

Socioeconomic position has been shown to be associated with inflammation. However, little is known about the role of inflammation in socioeconomic inequalities in relation to neurocognitive disorders in later life and the potential underlying inflammatory mechanisms. This study has used longitudinal data to investigate the mediation effects of inflammation in the relationship between socioeconomic position and neurocognitive disorders in older adults.

METHODS

Using data from the English Longitudinal Study of Ageing (ELSA, n = 4,815), we ascertained neurocognitive disorders using a recognised consensus criterion and included the following categories: (1) No Cognitive Impairment (NOCI) (2) Cognitive Impairment No Dementia (CIND) and (3) Dementia. We examined whether socioeconomic position (education, occupation, and wealth) measured in 2008/09 was associated with neurocognitive disorders measured in 2018/19. Mediation analyses were carried out to investigate the role of inflammatory markers [C-Reactive Protein (CRP), plasma fibrinogen and white blood cells (WBC)] in the association between socioeconomic inequalities and subsequent neurocognitive disorders. Sensitivity analyses were conducted to assess the mediating role of lifestyle behaviours and body mass index (BMI).

RESULTS

Higher education, occupation and wealth were longitudinally associated with a lower likelihood of cognitive impairment and dementia. WBC mediated the association between latent socioeconomic position and CIND [β = -0.037 (CI: -0.06 to -0.01)], but not the association with dementia. Indirect effects were attenuated but remained significant when other mediators, such as lifestyle behaviours and BMI were considered. In a separate analysis accounting for main confounders, CRP and fibrinogen mediated the association between education and CIND, all three inflammatory biomarkers mediated the association of occupation and CIND, while WBC mediated the association between wealth and CIND.

CONCLUSION

These findings emphasise that socioeconomic inequalities in mid and later life could contribute to the prevalence of neurocognitive disorders in later life. Our results provide some evidence for the biological embedding of WBC in the association between socioeconomic inequalities and cognitive impairment via elevated inflammation. Future studies should explore other plausible biological mechanisms.

T1AM/TAAR1 System Reduces Inflammatory Response and β-Amyloid Toxicity in Human Microglial HMC3 Cell Line

Microglial dysfunction is one of the hallmarks and leading causes of common neurodegenerative diseases (NDDs), including Alzheimer's disease (AD) and Parkinson's disease (PD). All these pathologies are characterized by aberrant aggregation of disease-causing proteins in the brain, which can directly activate microglia, trigger microglia-mediated neuroinflammation, and increase oxidative stress. Inhibition of glial activation may represent a therapeutic target to alleviate neurodegeneration. Recently, 3-iodothyronamine (T1AM), an endogenous derivative of thyroid hormone (TH) able to interact directly with a specific GPCR known as trace amine-associated receptor 1 (TAAR1), gained interest for its ability to promote neuroprotection in several models. Nevertheless, T1AM's effects on microglial disfunction remain still elusive. In the present work we investigated whether T1AM could inhibit the inflammatory response of human HMC3 microglial cells to LPS/TNFα or β-amyloid peptide 25-35 (Aβ25-35) stimuli. The results of ELISA and qPCR assays revealed that T1AM was able to reduce microglia-mediated inflammatory response by inhibiting the release of proinflammatory factors, including IL-6, TNFα, NF-kB, MCP1, and MIP1, while promoting the release of anti-inflammatory mediators, such as IL-10. Notably, T1AM anti-inflammatory action in HMC3 cells turned out to be a TAAR1-mediated response, further increasing the relevance of the T1AM/TAAR1 system in the management of NDDs.

Shared genetic loci between Alzheimer's disease and multiple sclerosis: Crossroads between neurodegeneration and immune system

BACKGROUND

Neuroinflammation is involved in the pathophysiology of Alzheimer's disease (AD), including immune-linked genetic variants and molecular pathways, microglia and astrocytes. Multiple Sclerosis (MS) is a chronic, immune-mediated disease with genetic and environmental risk factors and neuropathological features. There are clinical and pathobiological similarities between AD and MS. Here, we investigated shared genetic susceptibility between AD and MS to identify putative pathological mechanisms shared between neurodegeneration and the immune system.

METHODS

We analysed GWAS data for late-onset AD (N cases = 64,549, N controls = 634,442) and MS (N cases = 14,802, N controls = 26,703). Gaussian causal mixture modelling (MiXeR) was applied to characterise the genetic architecture and overlap between AD and MS. Local genetic correlation was investigated with Local Analysis of [co]Variant Association (LAVA). The conjunctional false discovery rate (conjFDR) framework was used to identify the specific shared genetic loci, for which functional annotation was conducted with FUMA and Open Targets.

RESULTS

MiXeR analysis showed comparable polygenicities for AD and MS (approximately 1800 trait-influencing variants) and genetic overlap with 20% of shared trait-influencing variants despite negligible genetic correlation (rg = 0.03), suggesting mixed directions of genetic effects across shared variants. conjFDR analysis identified 16 shared genetic loci, with 8 having concordant direction of effects in AD and MS. Annotated genes in shared loci were enriched in molecular signalling pathways involved in inflammation and the structural organisation of neurons.

CONCLUSIONS

Despite low global genetic correlation, the current results provide evidence for polygenic overlap between AD and MS. The shared loci between AD and MS were enriched in pathways involved in inflammation and neurodegeneration, highlighting new opportunities for future investigation.

Immunosenescence and Aging: Neuroinflammation Is a Prominent Feature of Alzheimer's Disease and Is a Likely Contributor to Neurodegenerative Disease Pathogenesis

Alzheimer's disease (AD) is a chronic multifactorial and complex neuro-degenerative disorder characterized by memory impairment and the loss of cognitive ability, which is a problem affecting the elderly. The pathological intracellular accumulation of abnormally phosphorylated Tau proteins, forming neurofibrillary tangles, and extracellular amyloid-beta (Aβ) deposition, forming senile plaques, as well as neural disconnection, neural death and synaptic dysfunction in the brain, are hallmark pathologies that characterize AD. The prevalence of the disease continues to increase globally due to the increase in longevity, quality of life, and medical treatment for chronic diseases that decreases the mortality and enhance the survival of elderly. Medical awareness and the accurate diagnosis of the disease also contribute to the high prevalence observed globally. Unfortunately, no definitive treatment exists that can be used to modify the course of AD, and no available treatment is capable of mitigating the cognitive decline or reversing the pathology of the disease as of yet. A plethora of hypotheses, ranging from the cholinergic theory and dominant Aβ cascade hypothesis to the abnormally excessive phosphorylated Tau protein hypothesis, have been reported. Various explanations for the pathogenesis of AD, such as the abnormal excitation of the glutamate system and mitochondrial dysfunction, have also been suggested. Despite the continuous efforts to deliver significant benefits and an effective treatment for this distressing, globally attested aging illness, multipronged approaches and strategies for ameliorating the disease course based on knowledge of the underpinnings of the pathogenesis of AD are urgently needed. Immunosenescence is an immune deficit process that appears with age (inflammaging process) and encompasses the remodeling of the lymphoid organs, leading to alterations in the immune function and neuroinflammation during advanced aging, which is closely linked to the outgrowth of infections, autoimmune diseases, and malignant cancers. It is well known that long-standing inflammation negatively influences the brain over the course of a lifetime due to the senescence of the immune system. Herein, we aim to trace the role of the immune system in the pathogenesis of AD. Thus, we explore alternative avenues, such as neuroimmune involvement in the pathogenesis of AD. We determine the initial triggers of neuroinflammation, which is an early episode in the pre-symptomatic stages of AD and contributes to the advancement of the disease, and the underlying key mechanisms of brain damage that might aid in the development of therapeutic strategies that can be used to combat this devastating disease. In addition, we aim to outline the ways in which different aspects of the immune system, both in the brain and peripherally, behave and thus to contribute to AD.

Role of chronic neuroinflammation in neuroplasticity and cognitive function: A hypothesis

OBJECTIVE

Evaluating the efficacy of 3,6'-dithioPomalidomide in 5xFAD Alzheimer's disease (AD) mice to test the hypothesis that neuroinflammation is directly involved in the development of synaptic/neuronal loss and cognitive decline.

BACKGROUND

Amyloid-β (Aβ) or tau-focused clinical trials have proved unsuccessful in mitigating AD-associated cognitive impairment. Identification of new drug targets is needed. Neuroinflammation is a therapeutic target in neurodegenerative disorders, and TNF-α a pivotal neuroinflammatory driver.

NEW HYPOTHESIS

AD-associated chronic neuroinflammation directly drives progressive synaptic/neuronal loss and cognitive decline. Pharmacologically mitigating microglial/astrocyte activation without altering Aβ generation will define the role of neuroinflammation in AD progression.

MAJOR CHALLENGES

Difficulty of TNF-α-lowering compounds reaching brain, and identification of a therapeutic-time window to preserve the beneficial role of neuroinflammatory processes.

LINKAGE TO OTHER MAJOR THEORIES

Microglia/astroglia are heavily implicated in maintenance of synaptic plasticity/function in healthy brain and are disrupted by Aβ. Mitigation of chronic gliosis can restore synaptic homeostasis/cognitive function.

Patchouli alcohol ameliorates the learning and memory impairments in an animal model of Alzheimer's disease via modulating SIRT1

BACKGROUND

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases. Patchouli alcohol (PA), a major active ingredient isolated from Pogostemonis Herba, exhibits extensive bioactivity in the central nervous system (CNS) and exerts neuroprotective effects.

PURPOSE

This study aimed to investigate the anti-AD effects of PA in an animal model of AD and to elucidate the underlying molecular mechanisms.

METHODS

The gas chromatography (GC) was used to determine the ability of PA to pass the blood-brain barrier (BBB) in rats after oral administration. The sporadic AD rat model was established by intracerebroventricularly (ICV) injection with streptozotocin (STZ). PA (25 and 50 mg/kg) was given to rat orally once daily for 42 consecutive days. Morris water maze (MWM) test was performed to determine the learning and memory functions of the STZ-induced AD rats. EX527, a silent information regulator 1 (SIRT1) selective inhibitor, was used to investigate the involvement of SIRT1 in the anti-AD effects of PA in rats.

RESULTS

PA could penetrate the BBB. MWM test results showed that PA could significantly ameliorate the learning and memory deficits induced by STZ in rats. Meanwhile, PA enhanced the expression of SIRT1, and markedly alleviated the tau pathology by inhibiting the hyperacetylation (at the site of Lys174) and hyperphosphorylation (at the sites of Thr181, Thr205, Ser396 and Ser404) of tau protein. PA also efficiently suppressed the activation of microglia and astrocytes, and the beta-amyloid (Aβ) expression and the deacetylation of nuclear factor-kappa B (NF-κB) at Lys 310 (K310) in the STZ-treated AD rats. EX527, a SIRT1 selective inhibitor, could partially abolish the cognitive deficits improving effect of PA and inhibit the down-regulation of acetylated tau and acetylated NF-κB p65, suggesting that PA exhibited neuroprotective effects against AD via upregulating SIRT1.

CONCLUSION

This study reported for the first time that PA could penetrate the BBB to exert its protective effects on the brain after a single-dose oral administration. The current experimental findings also amply demonstrated that PA could improve the cognitive and memory impairments in the STZ-induced AD rat model. The underlying mechanisms involve the alleviations of neuroinflammation, tau pathology and Aβ deposition via modulating of SIRT1 and NF-κB pathways. All these findings strongly suggest that PA is a promising naturally occurring compound worthy of further development into an anti-AD pharmaceutical.

Modifiable Innate Biology within the Gut–Brain Axis for Alzheimer’s Disease

Alzheimer’s disease (AD) is a prototypical inflammation-associated loss of cognitive function, with approximately 90% of the AD burden associated with invading myeloid cells controlling the function of the resident microglia. This indicates that the immune microenvironment has a pivotal role in the pathogenesis of the disease. Multiple peripheral stimuli, conditioned by complex and varied interactions between signals that stem at the intestinal level and neuroimmune processes, are involved in the progression and severity of AD. Conceivably, the targeting of critical innate immune signals and cells is achievable, influencing immune and metabolic health within the gut–brain axis. Considerable progress has been made, modulating many different metabolic and immune alterations that can drive AD development. However, non-pharmacological strategies targeting immunometabolic processes affecting neuroinflammation in AD treatment remain general and, at this point, are applied to all patients regardless of disease features. Despite these possibilities, improved knowledge of the relative contribution of the different innate immune cells and molecules comprising the chronically inflamed brain network to AD pathogenesis, and elucidation of the network hierarchy, are needed for planning potent preventive and/or therapeutic interventions. Moreover, an integrative perspective addressing transdisciplinary fields can significantly contribute to molecular pathological epidemiology, improving the health and quality of life of AD patients. This review is intended to gather modifiable immunometabolic processes based on their importance in the prevention and management of AD.

Identification of Immune Hub Genes Associated With Braak Stages in Alzheimer’s Disease and Their Correlation of Immune Infiltration

Background

Alzheimer’s disease (AD) is the most common type of neurodegenerative disease. Tau pathology is one of the pathological features of AD, and its progression is closely related to the progress of AD. Immune system dysfunction is an important mediator of Tau pathological progression, but the specific molecular mechanism is still unclear. The purpose of this study is to determine the immune hub genes and peripheral immune cell infiltration associated with the Braak stages, and the molecular mechanisms between them.

Methods

In this study, 60 samples with different Braak stages in the GSE106241 dataset were used to screen Braak stages-related immune hub genes by using the WGCNA package in R and cytoHubba plugin. The temporal lobe expression data in the Alzdata database were used to verify the results. The correlation between the expression level of immune core genes and the pathological features of AD was analyzed to evaluate the abundance of peripheral immune cell infiltration and screened Braak stages-related cells. Finally, we used correlation analysis of immune hub genes and immune cells and Gene Set Enrichment Analysis (GSEA) of them.

Results

Seven genes (GRB2, HSP90AA1, HSPA4, IGF1, KRAS, PIK3R1, and PTPN11) were identified as immune core genes after the screening of the test datasets and validation of independent data. Among them, Kirsten rat sarcoma viral oncogene homolog (KRAS) and Phosphoinositide-3-Kinase Regulatory Subunit 1 (PIK3R1) were the most closely related to Tau and Aβ pathology in AD. In addition, the ImmuneScore increased gradually with the increase of Braak stages. Five types of immune cells (plasma cells, T follicular helper cells, M2 macrophage, activated NK cells, and eosinophils) were correlated with Braak stages. KRAS and PIK3R1 were the immune core genes most related to the abnormal infiltration of peripheral immune cells. They participated in the regulation of the pathological process of AD through axon guidance, long-term potentiation, cytokine–cytokine receptor interaction, RNA polymerase, etc.

Conclusion

The KRAS and PIK3R1 genes were identified as the immune hub genes most associated with Tau pathological progress in AD. The abnormal infiltration of peripheral immune cells mediated by these cells was involved in the Tau pathological process. This provides new insights for AD.

Uncommon Noninvasive Biomarkers for the Evaluation and Monitoring of the Etiopathogenesis of Alzheimer's Disease

Background:

Alzheimer´s disease (AD) is the most widespread dementia in the world, followed by vascular dementia. Since AD is a heterogeneous disease that shows several varied phenotypes, it is not easy to make an accurate diagnosis, so it arises when the symptoms are clear and the disease is already very advanced. Therefore, it is important to find out biomarkers for AD early diagnosis that facilitate treatment or slow down the disease. Classic biomarkers are obtained from cerebrospinal fluid and plasma, along with brain imaging by positron emission tomography. Attempts have been made to discover uncommon biomarkers from other body fluids, which are addressed in this update.

Objective:

This update aims to describe recent biomarkers from minimally invasive body fluids for the patients, such as saliva, urine, eye fluid or tears.

Methods:

Biomarkers were determined in patients versus controls by single tandem mass spectrometry, and immunoassays. Metabolites were identified by nuclear magnetic resonance, and microRNAs with genome-wide high-throughput real-time polymerase chain reaction-based platforms.

Results:

Biomarkers from urine, saliva, and eye fluid were described, including peptides/proteins, metabolites, and some microRNAs. The association with AD neuroinflammation and neurodegeneration was analyzed, highlighting the contribution of matrix metalloproteinases, the immune system and microglia, as well as the vascular system.

Conclusion:

Unusual biomarkers have been developed, which distinguish each stage and progression of the disease, and are suitable for the early AD diagnosis. An outstanding relationship of biomarkers with neuroinflammation and neurodegeneration was assessed, clearing up concerns of the etiopathogenesis of AD.

Associations of plasma soluble CD22 levels with brain amyloid burden and cognitive decline in Alzheimer's disease

CD22 has been suggested to contribute to Alzheimer's disease (AD) pathogenesis by inhibiting microglial amyloid β (Aβ) phagocytosis. Soluble CD22 (sCD22) generated by cleavage from cell membranes may be a marker of inflammation and microglial dysfunction; but alterations of sCD22 levels in AD and their correlation with AD biomarkers remain unclear. Plasma sCD22 levels were measured in cognitively normal non-AD participants and patients with preclinical AD and AD dementia from a Chinese cohort and the Australian Imaging, Biomarkers and Lifestyle Flagship Study of Ageing. Plasma sCD22 levels were elevated in patients with preclinical and dementia AD. Plasma sCD22 levels were negatively correlated with cerebrospinal fluid (CSF) Aβ42 levels and Aβ42/Aβ40, and positively correlated with CSF phosphorylated tau levels and brain Aβ burden, but negatively correlated with cognitive function. Moreover, higher plasma sCD22 levels were associated with faster cognitive decline during follow-up. These findings suggest that CD22 plays important roles in AD development, and that sCD22 is a potential biomarker for AD.

Greater diffusion restriction in white matter in Preclinical Alzheimer's disease

OBJECTIVE

The Alzheimer's Continuum is biologically defined by beta-amyloid deposition which, at the earliest stages, is superimposed upon white matter degeneration in aging. However, the extent to which these co-occurring changes are characterized is relatively under-explored. The goal of this study was to use Diffusional Kurtosis Imaging (DKI) and biophysical modeling to detect and describe amyloid-related white matter changes in preclinical Alzheimer's disease (AD).

METHODS

Cognitively unimpaired participants ages 45-85 completed brain MRI, amyloid PET (florbetapir), neuropsychological testing, and other clinical measures at baseline in a cohort study. We tested whether beta amyloid-negative (AB-) and -positive (AB+) participants differed on DKI-based conventional (i.e. Fractional Anisotropy [FA], Mean Diffusivity [MD], Mean Kurtosis [MK]) and modeling (i.e. Axonal Water Fraction [AWF], extra-axonal radial diffusivity [D_e,⊥ ]) metrics, and whether these metrics were associated with other biomarkers.

RESULTS

We found significantly greater diffusion restriction (higher FA/AWF, lower MD/ D_e,⊥ ) in white matter in AB+ than AB- (partial η² = 0.08-0.19), more notably in the extra-axonal space within primarily late-myelinating tracts. Diffusion metrics predicted amyloid status incrementally over age (AUC=0.84) with modest yet selective associations, where AWF (a marker of axonal density) correlated with speed/executive functions and neurodegeneration, whereas D_e,⊥ (a marker of gliosis/myelin repair) correlated with amyloid deposition and white matter hyperintensity volume.

INTERPRETATION

These results support prior evidence of a non-monotonic change in diffusion behavior, where an early increase in diffusion restriction is hypothesized to reflect inflammation and myelin repair prior to an ensuing decrease in diffusion restriction, indicating glial and neuronal degeneration. This article is protected by copyright. All rights reserved.

Review of evidence implicating the plasminogen activator system in blood-brain barrier dysfunction associated with Alzheimer's disease

Elucidating the pathogenic mechanisms of Alzheimer’s disease (AD) to identify therapeutic targets has been the focus of many decades of research. While deposition of extracellular amyloid-beta plaques and intraneuronal neurofibrillary tangles of hyperphosphorylated tau have historically been the two characteristic hallmarks of AD pathology, therapeutic strategies targeting these proteinopathies have not been successful in the clinics. Neuroinflammation has been gaining more attention as a therapeutic target because increasing evidence implicates neuroinflammation as a key factor in the early onset of AD disease progression. The peripheral immune response has emerged as an important contributor to the chronic neuroinflammation associated with AD pathophysiology. In this context, the plasminogen activator system (PAS), also referred to as the vasculature’s fibrinolytic system, is emerging as a potential factor in AD pathogenesis. Evolving evidence suggests that the PAS plays a role in linking chronic peripheral inflammatory conditions to neuroinflammation in the brain. While the PAS is better known for its peripheral functions, components of the PAS are expressed in the brain and have been demonstrated to alter neuroinflammation and blood-brain barrier (BBB) permeation. Here, we review plasmin-dependent and -independent mechanisms by which the PAS modulates the BBB in AD pathogenesis and discuss therapeutic implications of these observations.

Discerning the Role of Blood Brain Barrier Dysfunction in Alzheimer’s Disease

Alzheimer’s disease (AD) is the most common form of neurodegenerative disease. The predominant characteristics of AD are the accumulation of amyloid-β (Aβ) and hyperphosphorylated tau in the brain. Blood brain barrier (BBB) dysfunction as one of the causative factors of cognitive impairment is increasingly recognized in the last decades. However, the role of BBB dysfunction in AD pathogenesis is still not fully understood. It remains elusive whether BBB dysfunction is a consequence or causative fact of Aβ pathology, tau pathology, neuroinflammation, or other conditions. In this review, we summarized the major findings of BBB dysfunction in AD and the reciprocal relationships between BBB dysfunction, Aβ pathology, tau pathology, and neuroinflammation. In addition, the implications of BBB dysfunction in AD for delivering therapeutic drugs were presented. Finally, we discussed how to better determine the underlying mechanisms between BBB dysfunction and AD, as well as how to explore new therapies for BBB regulation to treat AD in the future.

The Potential Role of Cytokines and Growth Factors in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is one of the most prominent neurodegenerative diseases, which impairs cognitive function in afflicted individuals. AD results in gradual decay of neuronal function as a consequence of diverse degenerating events. Several neuroimmune players (such as cytokines and growth factors that are key players in maintaining CNS homeostasis) turn aberrant during crosstalk between the innate and adaptive immunities. This aberrance underlies neuroinflammation and drives neuronal cells toward apoptotic decline. Neuroinflammation involves microglial activation and has been shown to exacerbate AD. This review attempted to elucidate the role of cytokines, growth factors, and associated mechanisms implicated in the course of AD, especially with neuroinflammation. We also evaluated the propensities and specific mechanism(s) of cytokines and growth factors impacting neuron upon apoptotic decline and further shed light on the availability and accessibility of cytokines across the blood-brain barrier and choroid plexus in AD pathophysiology. The pathogenic and the protective roles of macrophage migration and inhibitory factors, neurotrophic factors, hematopoietic-related growth factors, TAU phosphorylation, advanced glycation end products, complement system, and glial cells in AD and neuropsychiatric pathology were also discussed. Taken together, the emerging roles of these factors in AD pathology emphasize the importance of building novel strategies for an effective therapeutic/neuropsychiatric management of AD in clinics.

Triggering Innate Immune Receptors as New Therapies in Alzheimer's Disease and Multiple Sclerosis

Multiple sclerosis and Alzheimer's disease are two complex neurodegenerative diseases involving the immune system. So far, available treatments provide at best mild improvements to patients' conditions. For decades now, a new set of molecules have been used to modulate and regulate the innate immunity in these pathologies. Most studies have been carried out in rodents and some of them have reported tremendous beneficial effects on the disease course. The modulation of innate immune cells is of great interest since it provides new hope for patients. In this review, we will briefly overview the therapeutic potential of some molecules and receptors in multiple sclerosis and Alzheimer's disease and how they could be used to exploit new therapeutic avenues.