Blood-brain barrier leakage in Alzheimer's disease: From discovery to clinical relevance

Glucose-modified BSA/procyanidin C1 NPs penetrate the blood-brain barrier and alleviate neuroinflammation in Alzheimer's disease models

Alzheimer's disease (AD) is a chronic neurodegenerative disease with high prevalence, long duration and poor prognosis. The blood-brain barrier (BBB) is a physiologic barrier in the central nervous system, which hinders the entry of most drugs into the brain from the blood, thus affecting the efficacy of drugs for AD. Natural products are recognized as one of the promising and unique therapeutic approaches to treat AD. To improve the efficiency and therapeutic effect of the drug across the BBB, a natural polyphenolic compound, procyanidin C-1 (C1) was encapsulated in glucose-functionalized bovine serum albumin (BSA) nanoparticles to construct Glu-BSA/C1 NPs in our study. Glu-BSA/C1 NPs exhibited good stability, slow release, biocompatibility and antioxidant properties. In addition, Glu-BSA/C1 NPs penetrated the BBB, accumulated in the brain by targeting Glut1, and maintained the BBB integrity both in vitro and in vivo. Moreover, Glu-BSA/C1 NPs alleviated memory impairment of 5 × FAD mice by reducing Aβ deposition and Tau phosphorylation and promoting neurogenesis. Mechanistically, Glu-BSA/C1 NPs significantly activated the PI3K/AKT pathway and inhibited the NLRP3/Caspase-1/IL-1β pathway thereby suppressing neuroinflammation. Taken together, Glu-BSA/C1 NPs could penetrate the BBB and mitigate neuroinflammation in AD, which provides a new therapeutic approach targeting AD.

Feasibility of measuring blood-brain barrier permeability using ultra-short echo time radial magnetic resonance imaging

BACKGROUND AND PURPOSE

The purpose of this study is to evaluate the feasibility of using 3-dimensional (3D) ultra-short echo time (UTE) radial imaging method for measurement of the permeability of the blood-brain barrier (BBB) to gadolinium-based contrast agent. In this study, we propose to use the golden-angle radial sparse parallel (GRASP) method with 3D center-out trajectories for UTE, hence named as 3D UTE-GRASP. We first examined the feasibility of using 3D UTE-GRASP dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI) for differentiating subtle BBB disruptions induced by focused ultrasound (FUS). Then, we examined the BBB permeability changes in Alzheimer's disease (AD) pathology using Alzheimer's disease transgenic mice (5xFAD) at different ages.

METHODS

For FUS experiments, we used four Sprague Dawley rats at similar ages where we compared BBB permeability of each rat receiving the FUS sonication with different acoustic power (0.4-1.0 MPa). For AD transgenic mice experiments, we included three 5xFAD mice (6, 12, and 16 months old) and three wild-type mice (4, 8, and 12 months old).

RESULTS

The result from FUS experiments showed a progressive increase in BBB permeability with increase of acoustic power (p < .05), demonstrating the sensitivity of DCE-MRI method for detecting subtle changes in BBB disruption. Our AD transgenic mice experiments suggest an early BBB disruption in 5xFAD mice, which is further impaired with aging.

CONCLUSION

The results in this study substantiate the feasibility of using the proposed 3D UTE-GRASP method for detecting subtle BBB permeability changes expected in neurodegenerative diseases, such as AD.

Systemic inflammation in Aβ1-40-induced Alzheimer's disease model: New translational opportunities

Alzheimer disease (AD) is the most frequent cause of dementia, and the most common neurodegenerative disease, which is characterized by memory impairment, neuronal death, and synaptic loss in the hippocampus. Sporadic late-onset AD, which accounts for over 95 % of disease cases, is a multifactorial pathology with complex etiology and pathogenesis. Nowadays, neuroinflammation is considered the third most important component of AD pathogenesis in addition to amyloid peptide generation and deposition. Neuroinflammation is associated with the impairment of blood-brain barrier and leakage of inflammatory mediators into the periphery with developing systemic inflammatory responses. Systemic inflammation is currently considered one of the therapeutic targets for AD treatment, that necessitates in-depth study of this phenomenon in appropriate non-transgenic animal models. This study was aimed to explore systemic inflammatory manifestations in rats with Aβ1-40-induced AD. The impairment of spatial memory and cognitive flexibility in Aβ1-40-lesioned rats was accompanied by pronounced systemic inflammation, which was confirmed by commonly accepted biomarkers: increased hematological indices of systemic inflammation (NLR, dNLR, LMR, PLR and SII), signs of anemia of inflammation or chronic diseases, and pro-inflammatory polarized activation of circulating phagocytes. In addition, markers of systemic inflammation strongly correlated with disorders of remote cognitive flexibility in Aβ1-40-lesioned rats. These results indicate, that Aβ1-40-induced AD model permits the investigation of specific element of the disease - systemic inflammation in addition to well reproduced neuroinflammation and impairment of spatial memory and cognitive flexibility. It increases translational value of this well-known model.

Association between elevated blood-brain barrier permeability and the risk of progressive cognitive decline: A longitudinal study

BACKGROUND

The breakdown of the blood-brain barrier (BBB) is intricately linked to the onset and advancement of cognitive impairment and dementia. This investigation explores the correlation between blood-brain barrier permeability, assessed through the cerebrospinal fluid/serum albumin ratio (QAlb), in a clinical cohort and the evolution of cognitive decline.

METHODS

This prospective observational cohort study included 295 participants. Cognitive decline progression was characterized by an escalation in the overall deterioration scale and/or clinical dementia rating scores. The investigation delves into the correlation between blood-brain barrier permeability and the advancement of cognitive impairment among patients.

RESULTS

The APOE 4 allele and diabetes mellitus among individuals exhibited increased BBB permeability (P < 0.05). Moreover, AD patients exhibited the highest QAlb levels, signifying elevated BBB permeability compared to individuals with MCI and SCD (P < 0.05). After mean 17 months following up, 117 patients (51.31 %) were identified as experiencing cognitive decline progression, and we found that only AD diagnosis, CDR, and QAlb (All P < 0.05) were significant predictors of cognitive decline progression.

CONCLUSION

Our study emphasizes the clinical relevance of QAlb in detecting individuals with an elevated risk of cognitive decline. It suggests that heightened BBB permeability could contribute to clinical deterioration and serves as a plausible therapeutic target.

Molecular Mechanisms of Ischemic Stroke: A Review Integrating Clinical Imaging and Therapeutic Perspectives

Ischemic stroke poses a significant global health challenge, necessitating ongoing exploration of its pathophysiology and treatment strategies. This comprehensive review integrates various aspects of ischemic stroke research, emphasizing crucial mechanisms, therapeutic approaches, and the role of clinical imaging in disease management. It discusses the multifaceted role of Netrin-1, highlighting its potential in promoting neurovascular repair and mitigating post-stroke neurological decline. It also examines the impact of blood-brain barrier permeability on stroke outcomes and explores alternative therapeutic targets such as statins and sphingosine-1-phosphate signaling. Neurocardiology investigations underscore the contribution of cardiac factors to post-stroke mortality, emphasizing the importance of understanding the brain-heart axis for targeted interventions. Additionally, the review advocates for early reperfusion and neuroprotective agents to counter-time-dependent excitotoxicity and inflammation, aiming to preserve tissue viability. Advanced imaging techniques, including DWI, PI, and MR angiography, are discussed for their role in evaluating ischemic penumbra evolution and guiding therapeutic decisions. By integrating molecular insights with imaging modalities, this interdisciplinary approach enhances our understanding of ischemic stroke and offers promising avenues for future research and clinical interventions to improve patient outcomes.

Developmental priming of early cerebrovascular ageing: Implications across a lifetime

INTRODUCTION

Neurological conditions such as Alzheimer's disease and stroke represent a substantial health burden to the world's ageing population. Cerebrovascular dysfunction is a key contributor to these conditions, affecting an individual's risk profile, age of onset, and severity of neurological disease. Recent data shows that early-life events, such as maternal health during pregnancy, birth weight and exposure to environmental toxins can 'prime' the vascular system for later changes. With age, blood vessels can become less flexible and more prone to damage. This can lead to reduced blood flow to the brain, which is associated with cognitive decline and an increased risk of stroke and other cerebrovascular diseases. These in turn increase the risk of vascular dementia and Alzheimer's disease.

OBJECTIVES

We aim to explore how early life factors influence cerebrovascular health, ageing and disease.

METHODS

We have reviewed recently published literature from epidemiological studies, clinical cases and basic research which explore mechanisms that contribute to cerebrovascular and blood-brain barrier dysfunction, with a particularly focus on those that assess contribution of early-life events or vascular priming to subsequent injury.

RESULTS

Perinatal events have been linked to acute cerebrovascular dysfunction and long-term structural reorganisation. Systemic disease throughout the lifetime that produce inflammatory or oxidative stress may further sensitise the cerebrovasculature to disease and contribute to neurodegeneration.

CONCLUSIONS

By identifying these early-life determinants and understanding their mechanisms, scientists aim to develop strategies for preventing or mitigating cerebrovascular ageing-related issues.

Progressive Age-Associated Blood-Brain Barrier Leak/Dysfunction-Nexus of Neurodegenerative Disease Using MRI Markers to Identify Preclinical Disease and Potential New Targets for Future Treatments

This review article focuses on the upstream pertinent pathophysiology leading to neurodegenerative disease. Specifically, the nexus appears to be blood-brain barrier (BBB) leakiness resulting in a two-prong inflammatory disease spectrum damaging the microvasculature and corrupting protein synthesis and degradation with accumulating misfolded toxic proteins. The suboptimal results of removing misfolded proteins mean a new approach to disease in the preclinical state is required aimed at other targets. Validated noninvasive imaging and serologic biomarkers of early preclinical disease implemented in the high-risk patient cohort along with periodic surveillance once effective treatments are developed will be required. This review discusses the physiology and pathophysiology of the BBB, new MRI imaging techniques identifying the leak, and altered fluid dynamic effects in the preclinical state. The risk factors for disease development, preventative measures, and potential treatment targets are also discussed.

Cognitive decline, Aβ pathology, and blood-brain barrier function in aged 5xFAD mice

BACKGROUND

Patients with Alzheimer's disease (AD) develop blood-brain barrier dysfunction to varying degrees. How aging impacts Aβ pathology, blood-brain barrier function, and cognitive decline in AD remains largely unknown. In this study, we used 5xFAD mice to investigate changes in Aβ levels, barrier function, and cognitive decline over time.

METHODS

5xFAD and wild-type (WT) mice were aged between 9.5 and 15.5 months and tested for spatial learning and reference memory with the Morris Water Maze (MWM). After behavior testing, mice were implanted with acute cranial windows and intravenously injected with fluorescent-labeled dextrans to assess their in vivo distribution in the brain by two-photon microscopy. Images were processed and segmented to obtain intravascular intensity, extravascular intensity, and vessel diameters as a measure of barrier integrity. Mice were sacrificed after in vivo imaging to isolate brain and plasma for measuring Aβ levels. The effect of age and genotype were evaluated for each assay using generalized or cumulative-linked logistic mixed-level modeling and model selection by Akaike Information Criterion (AICc). Pairwise comparisons were used to identify outcome differences between the two groups.

RESULTS

5xFAD mice displayed spatial memory deficits compared to age-matched WT mice in the MWM assay, which worsened with age. Memory impairment was evident in 5xFAD mice by 2-threefold higher escape latencies, twofold greater cumulative distances until they reach the platform, and twice as frequent use of repetitive search strategies in the pool when compared with age-matched WT mice. Presence of the rd1 allele worsened MWM performance in 5xFAD mice at all ages but did not alter the rate of learning or probe trial outcomes. 9.5-month-old 15.5-month-old 5xFAD mice had twofold higher brain Aβ40 and Aβ42 levels (p < 0.001) and 2.5-fold higher (p = 0.007) plasma Aβ40 levels compared to 9.5-month-old 5xFAD mice. Image analysis showed that vessel diameters and intra- and extravascular dextran intensities were not significantly different in 9.5- and 15.5-month-old 5xFAD mice compared to age-matched WT mice.

CONCLUSION

5xFAD mice continue to develop spatial memory deficits and increased Aβ brain levels while aging. Given in vivo MP imaging limitations, further investigation with smaller molecular weight markers combined with advanced imaging techniques would be needed to reliably assess subtle differences in barrier integrity in aged mice.

The VEGFs/VEGFRs system in Alzheimer's and Parkinson's diseases: Pathophysiological roles and therapeutic implications

The vascular endothelial growth factors (VEGFs) and their cognate receptors (VEGFRs), besides their well-known involvement in physiological angiogenesis/lymphangiogenesis and in diseases associated to pathological vessel formation, play multifaceted functions in the central nervous system (CNS). In addition to shaping brain development, by controlling cerebral vasculogenesis and regulating neurogenesis as well as astrocyte differentiation, the VEGFs/VEGFRs axis exerts essential functions in the adult brain both in physiological and pathological contexts. In this article, after describing the physiological VEGFs/VEGFRs functions in the CNS, we focus on the VEGFs/VEGFRs involvement in neurodegenerative diseases by reviewing the current literature on the rather complex VEGFs/VEGFRs contribution to the pathogenic mechanisms of Alzheimer's (AD) and Parkinson's (PD) diseases. Thereafter, based on the outcome of VEGFs/VEGFRs targeting in animal models of AD and PD, we discuss the factual relevance of pharmacological VEGFs/VEGFRs modulation as a novel and potential disease-modifying approach for these neurodegenerative pathologies. Specific VEGFRs targeting, aimed at selective VEGFR-1 inhibition, while preserving VEGFR-2 signal transduction, appears as a promising strategy to hit the molecular mechanisms underlying AD pathology. Moreover, therapeutic VEGFs-based approaches can be proposed for PD treatment, with the aim of fine-tuning their brain levels to amplify neurotrophic/neuroprotective effects while limiting an excessive impact on vascular permeability.

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.

Effect of Vascular Risk Factors on Blood-Brain Barrier and Cerebrospinal Fluid Biomarkers Along the Alzheimer's Disease Continuum: A Retrospective Observational Study

BACKGROUND

Blood-brain barrier (BBB) dysfunction could favor the pathogenesis and progression of Alzheimer's disease (AD). Vascular risk factors (VRF) could worsen BBB integrity, thus promoting neurode generation.

OBJECTIVE

To investigate BBB permeability and its relation with VRF along the AD continuum (ADc). Cerebrospinal fluid (CSF) Amyloid (A) and p-tau (T) levels were used to stratify patients.

METHODS

We compared CSF/plasma albumin ratio (QAlb) of 131 AD patients and 24 healthy controls (HC). APOE genotype and VRF were evaluated for each patient. Spearman's Rho correlation was used to investigate the associations between Qalb and CSF AD biomarkers. Multivariate regression analyses were conducted to explore the relationship between Qalb and AD biomarkers, sex, age, cognitive status, and VRF.

RESULTS

QAlb levels did not show significant difference between ADc patients and HC (p = 0.984). However, QAlb was significantly higher in A + T-compared to A + T+ (p = 0.021). In ADc, CSF p-tau demonstrated an inverse correlation with QAlb, a finding confirmed in APOE4 carriers (p = 0.002), but not in APOE3. Furthermore, in APOE4 carriers, sex, hypertension, and hypercholesterolemia were associated with QAlb (p = 0.004, p = 0.038, p = 0.038, respectively), whereas only sex showed an association in APOE3 carriers (p = 0.026).

CONCLUSIONS

BBB integrity is preserved in ADc. Among AT categories, A + T-have a more permeable BBB than A + T+. In APOE4 carriers, CSF p-tau levels display an inverse association with BBB permeability, which in turn, seems to be affected by VRF. These data suggest a possible relationship between BBB efficiency, VRF and CSF p-tau levels depending on APOE genotype.

Risk of cognitive decline progression is associated to increased blood-brain-barrier permeability: A longitudinal study in a memory unit clinical cohort

INTRODUCTION

This study examined the relationship between blood-brain-barrier permeability (BBBp), measured by cerebrospinal fluid/serum albumin ratio (QAlb), and cognitive decline progression in a clinical cohort.

METHODS

This prospective observational study included 334 participants from the BIODEGMAR cohort. Cognitive decline progression was defined as an increase in Global Deterioration Scale and/or Clinical Dementia Rating scores. Associations between BBBp, demographics, and clinical factors were explored.

RESULTS

Male sex, diabetes mellitus, and cerebrovascular burden were associated with increased log-QAlb. Vascular cognitive impairment patients had the highest log-QAlb levels. Among the 273 participants with valid follow-up data, 154 (56.4%) showed cognitive decline progression. An 8% increase in the hazard of clinical worsening was observed for each 10% increase in log-QAlb.

DISCUSSION

These results suggest that increased BBBp in individuals with cognitive decline may contribute to clinical worsening, pointing to potential targeted therapies. QAlb could be a useful biomarker for identifying patients with a worse prognosis.

Blood-brain barrier permeability is associated with different neuroinflammatory profiles in Alzheimer's disease

INTRODUCTION

Inflammation is an important player in Alzheimer's disease (AD), whose effects can be influenced by the blood-brain barrier (BBB). Here, we investigated the relationship between BBB permeability, indicated by cerebrospinal fluid (CSF)/plasma albumin quotient (Qalb), and CSF indexes of neuroinflammation in a cohort of biologically defined AD patients.

METHODS

Fifty-nine consecutive patients with mild cognitive impairment (MCI) or early AD (Mini-Mental State Examination [MMSE] >22) underwent CSF analysis for inflammatory cytokines (interleukin [IL]-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, Il-10, IL-12, IL-13, IL-17, tumor necrosis factor-α [TNF-α], interferon-γ [IFN-γ], granulocyte-monocyte colony-stimulating factor [GM-CSF], granulocyte colony-stimulating factor [G-CSF]). Using backward stepwise linear regression analysis, we explored the potential influence of each cytokine CSF level on Qalb considering age, sex, and apolipoprotein E (APOE) as covariates.

RESULTS

Higher levels of IL-4 (β = 0.356, 0.005) and IL-8 (β = 0.249, 0.05) were associated with higher Qalb values, while macrophage inflammatory protein-1α (MIP-1β) (β = -0.274; p = 0.032) and TNF-α (β = -0.248; p = 0.031) showed a significant negative association with BBB permeability. Age was also positively associated with Qalb (β = 0.283; p = 0.016).

CONCLUSIONS

Despite the overall integrity of the BBB, its permeability could either influence or be influenced by central neuroinflammation, reflected by CSF cytokine levels. This is in line with previous studies that showed that patients with a more intact barrier are those with more prominent neurodegeneration. Our findings suggest that different neuroinflammatory profiles can be associated with different levels of BBB permeability in AD.

Reexamining the Causes and Effects of Cholesterol Deposition in the Brains of Patients with Alzheimer's Disease

Alzheimer's disease (AD) is a degenerative disease of the central nervous system. Numerous studies have shown that imbalances in cholesterol homeostasis in the brains of AD patients precede the onset of clinical symptoms. In addition, cholesterol deposition has been observed in the brains of AD patients even though peripheral cholesterol does not enter the brain through the blood‒brain barrier (BBB). Studies have demonstrated that cholesterol metabolism in the brain is associated with many pathological conditions, such as amyloid beta (Aβ) production, Tau protein phosphorylation, oxidative stress, and inflammation. In 2022, some scholars put forward a new hypothesis of AD: the disease involves lipid invasion and its exacerbation of the abnormal metabolism of cholesterol in the brain. In this review, by discussing the latest research progress, the causes and effects of cholesterol retention in the brains of AD patients are analyzed and discussed. Additionally, the possible mechanism through which AD may be improved by targeting cholesterol is described. Finally, we propose that improving the impairments in cholesterol removal observed in the brains of AD patients, instead of further reducing the already impaired cholesterol synthesis in the brain, may be the key to preventing cholesterol deposition and improving the corresponding pathological symptoms.

Thinking outside the black box: are the brain endothelial cells the new main target in Alzheimer's disease?

The blood-brain barrier is the interface through which the brain interacts with the milieu and consists mainly of a sophisticated network of brain endothelial cells that forms blood vessels and selectively moves molecules inside and outside the brain through multiple mechanisms of transport. Although brain endothelial cell function is crucial for brain homeostasis, their role in neurodegenerative diseases has historically not been considered with the same importance as other brain cells such as microglia, astroglia, neurons, or even molecules such as amyloid beta, Tau, or alpha-synuclein. Alzheimer's disease is the most common neurodegenerative disease, and brain endothelial cell dysfunction has been reported by several groups. However, its impairment has barely been considered as a potential therapeutic target. Here we review the most recent advances in the relationship between Alzheimer's disease and brain endothelial cells commitment and analyze the possible mechanisms through which their alterations contribute to this neurodegenerative disease, highlighting their inflammatory phenotype and the possibility of an impaired secretory pattern of brain endothelial cells that could contribute to the progression of this ailment. Finally, we discuss why shall brain endothelial cells be appreciated as a therapeutic target instead of solely an obstacle for delivering treatments to the injured brain in Alzheimer's disease.

Cell membrane-based nanomaterials for therapeutics of neurodegenerative diseases

Central nervous system (CNS) diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), glioblastoma (GBM), and peripheral nerve injury have been documented as incurable diseases, which lead to serious impacts on human health especially prevalent in the aging population worldwide. Most of the treatment strategies fail due to low efficacy, toxicity, and poor brain penetration. Recently, advancements in nanotechnology have helped alleviate the challenges associated with the application of cell membrane-based nanomaterials against CNS diseases. In the following review, the existing types of cell membrane-based nanomaterials systems which have improved therapeutic efficacy for CNS diseases would be described. A summary of recent progress in the incorporation of nanomaterials in cell membrane-based production, separation, and analysis will be provided. Addition to, challenges relate to large-scale manufacturing of cell membrane-based nanomaterials and future clinical trial of such platforms will be discussed.

Mammalian Models in Alzheimer's Research: An Update

A form of dementia distinct from healthy cognitive aging, Alzheimer's disease (AD) is a complex multi-stage disease that currently afflicts over 50 million people worldwide. Unfortunately, previous therapeutic strategies developed from murine models emulating different aspects of AD pathogenesis were limited. Consequently, researchers are now developing models that express several aspects of pathogenesis that better reflect the clinical situation in humans. As such, this review seeks to provide insight regarding current applications of mammalian models in AD research by addressing recent developments and characterizations of prominent transgenic models and their contributions to pathogenesis as well as discuss the advantages, limitations, and application of emerging models that better capture genetic heterogeneity and mixed pathologies observed in the clinical situation.

Proteasome inhibition protects blood-brain barrier P-glycoprotein and lowers Aβ brain levels in an Alzheimer's disease model

BACKGROUND

Loss of P-glycoprotein (P-gp) at the blood-brain barrier contributes to amyloid-β (Aβ) brain accumulation in Alzheimer's disease (AD). Using transgenic human amyloid precursor protein (hAPP)-overexpressing mice (Tg2576), we previously showed that Aβ triggers P-gp loss by activating the ubiquitin-proteasome pathway, which leads to P-gp degradation. Furthermore, we showed that inhibiting the ubiquitin-activating enzyme (E1) prevents P-gp loss and lowers Aβ accumulation in the brain of hAPP mice. Based on these data, we hypothesized that repurposing the FDA-approved proteasome inhibitor, bortezomib (Velcade®; BTZ), protects blood-brain barrier P-gp from degradation in hAPP mice in vivo.

METHODS

We treated hAPP mice with the proteasome inhibitor BTZ or a combination of BTZ with the P-gp inhibitor cyclosporin A (CSA) for 2 weeks. Vehicle-treated wild-type (WT) mice were used as a reference for normal P-gp protein expression and transport activity. In addition, we used the opioid receptor agonist loperamide as a P-gp substrate in tail flick assays to indirectly assess P-gp transport activity at the blood-brain barrier in vivo. We also determined P-gp protein expression by Western blotting, measured P-gp transport activity levels in isolated brain capillaries with live cell confocal imaging and assessed Aβ plasma and brain levels with ELISA.

RESULTS

We found that 2-week BTZ treatment of hAPP mice restored P-gp protein expression and transport activity in brain capillaries to levels found in WT mice. We also observed that hAPP mice displayed significant loperamide-induced central antinociception compared to WT mice indicating impaired P-gp transport activity at the blood-brain barrier of hAPP mice in vivo. Furthermore, BTZ treatment prevented loperamide-induced antinociception suggesting BTZ protected P-gp loss in hAPP mice. Further, BTZ-treated hAPP mice had lower Aβ40 and Aβ42 brain levels compared to vehicle-treated hAPP mice.

CONCLUSIONS

Our data indicate that BTZ protects P-gp from proteasomal degradation in hAPP mice, which helps to reduce Aβ brain levels. Our data suggest that the proteasome system could be exploited for a novel therapeutic strategy in AD, particularly since increasing Aβ transport across the blood-brain barrier may prove an effective treatment for patients.

Administration of recombinant FOXN1 protein attenuates Alzheimer's pathology in mice

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia in older adults and characterized by progressive loss of memory and cognitive functions that are associated with amyloid-beta (Aβ) plaques and neurofibrillary tangles. Immune cells play an important role in the clearance of Aβ deposits and neurofibrillary tangles. T cells are the major component of the immune system. The thymus is the primary organ for T cell generation. T cell development in the thymus depends on thymic epithelial cells (TECs). However, TECs undergo both qualitative and quantitative loss over time. We have previously reported that a recombinant (r) protein containing FOXN1 and a protein transduction domain can increase the number of TECs and subsequently increases the number of T cells in mice. In this study we determined the ability of rFOXN1 to affect cognitive performance and AD pathology in mice.

METHODS

Aged 3xTg-AD and APP/PS1 AD mice were injected with rFOXN1 or control protein. Cognitive performance, AD pathology, the thymic microenvironment and immune cells were then analyzed.

RESULTS

Administration of rFOXN1 into AD mice improves cognitive performance and reduces Aβ plaque load and phosphorylated tau in the brain. This is related to rejuvenating the aged thymic microenvironment, which results in enhanced T cell generation in the thymus, leading to increased number of T cells, especially IFNγ-producing T cells, in the spleen and the choroid plexus (CP), enhanced expression of immune cell trafficking molecules in the CP, and increased migration of monocyte-derived macrophages into the brain. Furthermore, the production of anti-Aβ antibodies in the serum and the brain, and the macrophage phagocytosis of Aβ are enhanced in rFOXN1-treated AD mice.

CONCLUSIONS

Our results suggest that rFOXN1 protein has the potential to provide a novel approach to treat AD patients.

ABCB1 and ABCG2 Regulation at the Blood-Brain Barrier: Potential New Targets to Improve Brain Drug Delivery

The drug efflux transporters ABCB1 and ABCG2 at the blood-brain barrier limit the delivery of drugs into the brain. Strategies to overcome ABCB1/ABCG2 have been largely unsuccessful, which poses a tremendous clinical problem to successfully treat central nervous system (CNS) diseases. Understanding basic transporter biology, including intracellular regulation mechanisms that control these transporters, is critical to solving this clinical problem.In this comprehensive review, we summarize current knowledge on signaling pathways that regulate ABCB1/ABCG2 at the blood-brain barrier. In Section I, we give a historical overview on blood-brain barrier research and introduce the role that ABCB1 and ABCG2 play in this context. In Section II, we summarize the most important strategies that have been tested to overcome the ABCB1/ABCG2 efflux system at the blood-brain barrier. In Section III, the main component of this review, we provide detailed information on the signaling pathways that have been identified to control ABCB1/ABCG2 at the blood-brain barrier and their potential clinical relevance. This is followed by Section IV, where we explain the clinical implications of ABCB1/ABCG2 regulation in the context of CNS disease. Lastly, in Section V, we conclude by highlighting examples of how transporter regulation could be targeted for therapeutic purposes in the clinic. SIGNIFICANCE STATEMENT: The ABCB1/ABCG2 drug efflux system at the blood-brain barrier poses a significant problem to successful drug delivery to the brain. The article reviews signaling pathways that regulate blood-brain barrier ABCB1/ABCG2 and could potentially be targeted for therapeutic purposes.

Cooperation between neurovascular dysfunction and Aβ in Alzheimer's disease

The amyloid-β (Aβ) hypothesis was once believed to represent the pathogenic process of Alzheimer's disease (AD). However, with the failure of clinical drug development and the increasing understanding of the disease, the Aβ hypothesis has been challenged. Numerous recent investigations have demonstrated that the vascular system plays a significant role in the course of AD, with vascular damage occurring prior to the deposition of Aβ and neurofibrillary tangles (NFTs). The question of how Aβ relates to neurovascular function and which is the trigger for AD has recently come into sharp focus. In this review, we outline the various vascular dysfunctions associated with AD, including changes in vascular hemodynamics, vascular cell function, vascular coverage, and blood-brain barrier (BBB) permeability. We reviewed the most recent findings about the complicated Aβ-neurovascular unit (NVU) interaction and highlighted its vital importance to understanding disease pathophysiology. Vascular defects may lead to Aβ deposition, neurotoxicity, glial cell activation, and metabolic dysfunction; In contrast, Aβ and oxidative stress can aggravate vascular damage, forming a vicious cycle loop.

The effects of high plasma levels of Aβ1-42 on mononuclear macrophage in mouse models of Alzheimer's disease

More and more evidences are proving that microglia play a crucial role in the pathogenesis of Alzheimer's disease (AD) and the plasma Aβ_1-42 levels significantly increased 15 years before the onset of dominantly inherited AD. However, the effects of high plasma levels of Aβ_1-42 on mononuclear macrophage, the peripheral counterparts of microglia, remain unclear. In the present study, we used APP/PS1 transgenic (Tg) mice and a parabiotic model of wild type (Wt) mice and Tg mice (Parabiotic Wt-Tg, Pa (Wt-Tg)) to investigate the effects of high plasma levels of Aβ_1-42 on peripheral mononuclear macrophage. Our results showed that in the early stage of Tg mice (7 months) and Pa (Wt-Tg) mice (4 months), the proportions of pro-inflammatory macrophages in peritoneal cavity, myeloid derived suppressor cells (MDSCs) in spleen, granulocyte-monocyte progenitors (GMPs) in bone marrow, and the plasma levels of interleukin-6 (IL-6) were significantly decreased. While the proportions of pro-inflammatory macrophages, MDSCs, GMPs, and the plasma levels of IL-6 and tumor necrosis factor (TNF)-α, as well as the numbers of bone marrow-derived macrophages (BMDMs) in mice brain were increased in the late stage of Tg mice (11 months) and Pa (Wt-Tg) mice (8 months). In addition, the proportions of monocytes in spleen and the proliferation of bone marrow cells (BMCs) were enhanced consistently, and the phagocytic function of macrophages kept stably after high plasma levels of Aβ_1-42 sustaining stimulation. These results demonstrated that high plasma levels of Aβ_1-42 play a biphasic regulating role at different stages of the disease, namely inhibiting effects on peripheral pro-inflammatory macrophages in the early stage of AD model, while promoting effects in the late stage of AD model. The mechanism behind this may be associated with their effects on MDSCs in spleen and myeloid progenitor cells in bone marrow. Therefore, intervening the effects of plasma Aβ_1-42 on pro-inflammatory macrophages might offer a new therapeutic approach to AD.

The Rare Marine Bioactive Compounds in Neurological Disorders and Diseases: Is the Blood-Brain Barrier an Obstacle or a Target?

The blood-brain barrier (BBB) is a dynamic barrier separating neurocytes and brain tissues from blood that is extremely sealed and strictly regulated by transporters such as aquaporin-4 (AQP-4), glucose transporter (GLUT), and specialized tight junctional complexes (TJCs) including tight junctions (TJs), adherens junctions (AJs), and Zonulae occludens (ZOs). With specifically selective transcellular and paracellular permeability, the BBB maintains a homeostatic microenvironment to protect the central nervous system (CNS). In recent years, increasing attention has been paied to the importance of BBB disruption and dysfunction in the pathology of neurological disorders and diseases, such as Alzheimer's diseases (AD), Parkinson diseases (PD), stroke and cerebral edema. However, the further research on how the integral structure and function of BBB are altered under the physiological or pathological conditions is still needed. Focusing on the ultrastructural features of the BBB and combining the latest research on associated proteins and transporters, physiological regulation and pathological change of the BBB were elucidated. By summarizing the protective effects of known bioactive compounds derived from marine life on the BBB, this review aims to highlight the BBB as a key to the treatment of several major neurological diseases instead of a normally described obstacle to drug absorption and transport. Overall, the BBB's morphological characteristics and physiological function and their regulation provide the theoretical basis for the study on the BBB and inspire the diagnosis of and therapy for neurological diseases.

Receptor-mediated drug delivery of bispecific therapeutic antibodies through the blood-brain barrier

Therapeutic antibody drug development is a rapidly growing sector of the pharmaceutical industry. However, antibody drug development for the brain is a technical challenge, and therapeutic antibodies for the central nervous system account for ~3% of all such agents. The principal obstacle to antibody drug development for brain or spinal cord is the lack of transport of large molecule biologics across the blood-brain barrier (BBB). Therapeutic antibodies can be made transportable through the blood-brain barrier by the re-engineering of the therapeutic antibody as a BBB-penetrating bispecific antibody (BSA). One arm of the BSA is the therapeutic antibody and the other arm of the BSA is a transporting antibody. The transporting antibody targets an exofacial epitope on a BBB receptor, and this enables receptor-mediated transcytosis (RMT) of the BSA across the BBB. Following BBB transport, the therapeutic antibody then engages the target receptor in brain. RMT systems at the BBB that are potential conduits to the brain include the insulin receptor (IR), the transferrin receptor (TfR), the insulin-like growth factor receptor (IGFR) and the leptin receptor. Therapeutic antibodies have been re-engineered as BSAs that target the insulin receptor, TfR, or IGFR RMT systems at the BBB for the treatment of Alzheimer's disease and Parkinson's disease.

Recent Advancements in Nanomaterials: A Promising Way to Manage Neurodegenerative Disorders

Neurodegenerative diseases (NDs) such as dementia, Alzheimer's disease, Parkinson's disease, frontotemporal dementia, and amyotrophic lateral sclerosis are some of the most prevalent disorders currently afflicting healthcare systems. Many of these diseases share similar pathological hallmarks, including elevated oxidative stress, mitochondrial dysfunction, protein misfolding, excitotoxicity, and neuroinflammation, all of which contribute to the deterioration of the nervous system's structure and function. The development of diagnostic and therapeutic materials in the monitoring and treatment of these diseases remains challenging. One of the biggest challenges facing therapeutic and diagnostic materials is the blood-brain barrier (BBB). The BBB is a multifunctional membrane possessing a plethora of biochemical, cellular, and immunological features that ensure brain homeostasis by preventing the entry and accumulation of unwanted compounds. With regards to neurodegenerative diseases, the recent application of tailored nanomaterials (nanocarriers and nanoparticles) has led to advances in diagnostics and therapeutics. In this review, we provide an overview of commonly used nanoparticles and their applications in NDs, which may offer new therapeutic strategies for the prevention and treatment of neurodegenerative diseases.

The Lipid Invasion Model: Growing Evidence for This New Explanation of Alzheimer's Disease

The Lipid Invasion Model (LIM) is a new hypothesis for Alzheimer's disease (AD) which argues that AD is a result of external lipid invasion to the brain, following damage to the blood-brain barrier (BBB). The LIM provides a comprehensive explanation of the observed neuropathologies associated with the disease, including the lipid irregularities first described by Alois Alzheimer himself, and accounts for the wide range of risk factors now identified with AD, all of which are also associated with damage to the BBB. This article summarizes the main arguments of the LIM, and new evidence and arguments in support of it. The LIM incorporates and extends the amyloid hypothesis, the current main explanation of the disease, but argues that the greatest cause of late-onset AD is not amyloid-β (Aβ) but bad cholesterol and free fatty acids, let into the brain by a damaged BBB. It suggests that the focus on Aβ is the reason why we have made so little progress in treating the disease in the last 30 years. As well as offering new perspectives for further research into the diagnosis, prevention, and treatment of AD, based on protecting and repairing the BBB, the LIM provides potential new insights into other neurodegenerative diseases such as Parkinson's disease and amyotrophic lateral sclerosis/motor neuron disease.

Preserved blood-brain barrier and neurovascular coupling in female 5xFAD model of Alzheimer's disease

Introduction

Dysfunction of the cerebral vasculature is considered one of the key components of Alzheimer's disease (AD), but the mechanisms affecting individual brain vessels are poorly understood.

Methods

Here, using in vivo two-photon microscopy in superficial cortical layers and ex vivo imaging across brain regions, we characterized blood-brain barrier (BBB) function and neurovascular coupling (NVC) at the level of individual brain vessels in adult female 5xFAD mice, an aggressive amyloid-β (Aβ) model of AD.

Results

We report a lack of abnormal increase in adsorptive-mediated transcytosis of albumin and preserved paracellular barrier for fibrinogen and small molecules despite an extensive load of Aβ. Likewise, the NVC responses to somatosensory stimulation were preserved at all regulatory segments of the microvasculature: penetrating arterioles, precapillary sphincters, and capillaries. Lastly, the Aβ plaques did not affect the density of capillary pericytes.

Conclusion

Our findings provide direct evidence of preserved microvascular function in the 5xFAD mice and highlight the critical dependence of the experimental outcomes on the choice of preclinical models of AD. We propose that the presence of parenchymal Aβ does not warrant BBB and NVC dysfunction and that the generalized view that microvascular impairment is inherent to Aβ aggregation may need to be revised.

Nanoparticle-Based Drug Delivery Systems: An Inspiring Therapeutic Strategy for Neurodegenerative Diseases

Neurodegenerative diseases are common, incurable neurological disorders with high prevalence, and lead to memory, movement, language, and intelligence impairments, threatening the lives and health of patients worldwide. The blood-brain barrier (BBB), a physiological barrier between the central nervous system and peripheral blood circulation, plays an important role in maintaining the homeostasis of the intracerebral environment by strictly regulating the transport of substances between the blood and brain. Therefore, it is difficult for therapeutic drugs to penetrate the BBB and reach the brain, and this affects their efficacy. Nanoparticles (NPs) can be used as drug transport carriers and are also known as nanoparticle-based drug delivery systems (NDDSs). These systems not only increase the stability of drugs but also facilitate the crossing of drugs through the BBB and improve their efficacy. In this article, we provided an overview of the types and administration routes of NPs, highlighted the preclinical and clinical studies of NDDSs in neurodegenerative diseases, and summarized the combined therapeutic strategies in the management of neurodegenerative diseases. Finally, the prospects and challenges of NDDSs in recent basic and clinical research were also discussed. Above all, NDDSs provide an inspiring therapeutic strategy for the treatment of neurodegenerative diseases.

Engineered nanomaterials that exploit blood-brain barrier dysfunction fordelivery to the brain

The blood-brain barrier (BBB) is a highly regulated physical and functional boundarythat tightly controls the transport of materials between the blood and the brain. There is an increasing recognition that the BBB is dysfunctional in a wide range of neurological disorders; this dysfunction can be symptomatic of the disease but can also play a role in disease etiology. BBB dysfunction can be exploited for the delivery of therapeutic nanomaterials. Forexample, there can be a transient, physical disruption of the BBB in diseases such as brain injury and stroke, which allows temporary access of nanomaterials into the brain. Physicaldisruption of the BBB through external energy sources is now being clinically pursued toincrease therapeutic delivery into the brain. In other diseases, the BBB takes on new properties that can beleveraged by delivery carriers. For instance, neuroinflammation induces the expression ofreceptors on the BBB that can be targeted by ligand-modified nanomaterials and theendogenous homing of immune cells into the diseased brain can be hijacked for the delivery ofnanomaterials. Lastly, BBB transport pathways can be altered to increase nanomaterial transport. In this review, we will describe changes that can occur in the BBB in disease, and how these changes have been exploited by engineered nanomaterials forincreased transport into the brain.

Blood-Brain Barrier Dysfunction in Normal Aging and Neurodegeneration: Mechanisms, Impact, and Treatments

Cerebral endothelial cells and their linking tight junctions form a unique, dynamic and multi-functional interface, the blood-brain barrier (BBB). The endothelium is regulated by perivascular cells and components forming the neurovascular unit. This review examines BBB and neurovascular unit changes in normal aging and in neurodegenerative disorders, particularly focusing on Alzheimer disease, cerebral amyloid angiopathy and vascular dementia. Increasing evidence indicates BBB dysfunction contributes to neurodegeneration. Mechanisms underlying BBB dysfunction are outlined (endothelium and neurovascular unit mediated) as is the BBB as a therapeutic target including increasing the uptake of systemically delivered therapeutics across the BBB, enhancing clearance of potential neurotoxic compounds via the BBB, and preventing BBB dysfunction. Finally, a need for novel biomarkers of BBB dysfunction is addressed.

Mitochondrial oxidative stress in brain microvascular endothelial cells: Triggering blood-brain barrier disruption

Blood-brain barrier disruption plays an important role in central nervous system diseases. This review provides information on the role of mitochondrial oxidative stress in brain microvascular endothelial cells in cellular dysfunction, the disruption of intercellular junctions, transporter dysfunction, abnormal angiogenesis, neurovascular decoupling, and the involvement and aggravation of vascular inflammation and illustrates related molecular mechanisms. In addition, recent drug and nondrug therapies targeting cerebral vascular endothelial cell mitochondria to repair the blood-brain barrier are discussed. This review shows that mitochondrial oxidative stress disorder in brain microvascular endothelial cells plays a key role in the occurrence and development of blood-brain barrier damage and may be critical in various pathological mechanisms of blood-brain barrier damage. These new findings suggest a potential new strategy for the treatment of central nervous system diseases through mitochondrial modulation of cerebral vascular endothelial cells.

Aducanumab-Hope or Disappointment for Alzheimer's Disease

In June 2021, the world was informed about a new drug for Alzheimer's disease approved by the FDA. Aducanumab (BIIB037, ADU), being a monoclonal antibody IgG1, is the newest AD treatment. The activity of the drug is targeted towards amyloid β, which is considered one of the main causes of Alzheimer's disease. Clinical trials have revealed time- and dose-dependent activity towards Aβ reduction, as well as cognition improvement. Biogen, the company responsible for conducting research and introducing the drug to the market, presents the drug as a solution to cognitive impairment, but its limitations, costs, and side effects are controversial. The framework of the paper focuses on the mechanism of aducanumab's action along with the positive and negative sides of the therapy. The review presents the basis of the amyloid hypothesis that is the cornerstone of therapy, as well as the latest information about aducanumab, its mechanism of action, and the possibility of the use of the drug.

Mechanisms of Blood-Brain Barrier Protection by Microbiota-Derived Short-Chain Fatty Acids

Impairment of the blood-brain barrier (BBB) integrity is implicated in the numerous neurological disorders associated with neuroinflammation, neurodegeneration and aging. It is now evident that short-chain fatty acids (SCFAs), mainly acetate, butyrate and propionate, produced by anaerobic bacterial fermentation of the dietary fiber in the intestine, have a key role in the communication between the gastrointestinal tract and nervous system and are critically important for the preservation of the BBB integrity under different pathological conditions. The effect of SCFAs on the improvement of the compromised BBB is mainly based on the decrease in paracellular permeability via restoration of junctional complex proteins affecting their transcription, intercellular localization or proteolytic degradation. This review is focused on the revealed and putative underlying mechanisms of the direct and indirect effects of SCFAs on the improvement of the barrier function of brain endothelial cells. We consider G-protein-coupled receptor-mediated effects of SCFAs, SCFAs-stimulated acetylation of histone and non-histone proteins via inhibition of histone deacetylases, and crosstalk of these signaling pathways with transcriptional factors NF-κB and Nrf2 as mainstream mechanisms of SCFA's effect on the preservation of the BBB integrity.

Mesenchymal and Neural Stem Cell-Derived Exosomes in Treating Alzheimer's Disease

As the most common form of dementia and a progressive neurodegenerative disorder, Alzheimer's disease (AD) affects over 10% world population with age 65 and older. The disease is neuropathologically associated with progressive loss of neurons and synapses in specific brain regions, deposition of amyloid plaques and neurofibrillary tangles, neuroinflammation, blood-brain barrier (BBB) breakdown, mitochondrial dysfunction, and oxidative stress. Despite the intensive effort, there is still no cure for the disorder. Stem cell-derived exosomes hold great promise in treating various diseases, including AD, as they contain a variety of anti-apoptotic, anti-inflammatory, and antioxidant components. Moreover, stem cell-derived exosomes also promote neurogenesis and angiogenesis and can repair damaged BBB. In this review, we will first outline the major neuropathological features associated with AD; subsequently, a discussion of stem cells, stem cell-secreted exosomes, and the major exosome isolation methods will follow. We will then summarize the recent data involving the use of mesenchymal stem cell- or neural stem cell-derived exosomes in treating AD. Finally, we will briefly discuss the challenges, perspectives, and clinical trials using stem cell-derived exosomes for AD therapy.

Coxsackievirus B3 infects and disrupts human induced-pluripotent stem cell derived brain-like endothelial cells

Coxsackievirus B3 (CVB3) is a significant human pathogen that is commonly found worldwide. CVB3 among other enteroviruses, are the leading causes of aseptic meningo-encephalitis which can be fatal especially in young children. How the virus gains access to the brain is poorly-understood, and the host-virus interactions that occur at the blood-brain barrier (BBB) is even less-characterized. The BBB is a highly specialized biological barrier consisting primarily of brain endothelial cells which possess unique barrier properties and facilitate the passage of nutrients into the brain while restricting access to toxins and pathogens including viruses. To determine the effects of CVB3 infection on the BBB, we utilized a model of human induced-pluripotent stem cell-derived brain-like endothelial cells (iBECs) to ascertain if CVB3 infection may alter barrier cell function and overall survival. In this study, we determined that these iBECs indeed are susceptible to CVB3 infection and release high titers of extracellular virus. We also determined that infected iBECs maintain high transendothelial electrical resistance (TEER) during early infection despite possessing high viral load. TEER progressively declines at later stages of infection. Interestingly, despite the high viral burden and TEER disruptions at later timepoints, infected iBEC monolayers remain intact, indicating a low degree of late-stage virally-mediated cell death, which may contribute to prolonged viral shedding. We had previously reported that CVB3 infections rely on the activation of transient receptor vanilloid potential 1 (TRPV1) and found that inhibiting TRPV1 activity with SB-366791 significantly limited CVB3 infection of HeLa cervical cancer cells. Similarly in this study, we observed that treating iBECs with SB-366791 significantly reduced CVB3 infection, which suggests that not only can this drug potentially limit viral entry into the brain, but also demonstrates that this infection model could be a valuable platform for testing antiviral treatments of neurotropic viruses. In all, our findings elucidate the unique effects of CVB3 infection on the BBB and shed light on potential mechanisms by which the virus can initiate infections in the brain.

Reconsidering the role of blood-brain barrier in Alzheimer's disease: From delivery to target

The existence of a selective blood-brain barrier (BBB) and neurovascular coupling are two unique central nervous system vasculature features that result in an intimate relationship between neurons, glia, and blood vessels. This leads to a significant pathophysiological overlap between neurodegenerative and cerebrovascular diseases. Alzheimer's disease (AD) is the most prevalent neurodegenerative disease whose pathogenesis is still to be unveiled but has mostly been explored under the light of the amyloid-cascade hypothesis. Either as a trigger, bystander, or consequence of neurodegeneration, vascular dysfunction is an early component of the pathological conundrum of AD. The anatomical and functional substrate of this neurovascular degeneration is the BBB, a dynamic and semi-permeable interface between blood and the central nervous system that has consistently been shown to be defective. Several molecular and genetic changes have been demonstrated to mediate vascular dysfunction and BBB disruption in AD. The isoform ε4 of Apolipoprotein E is at the same time the strongest genetic risk factor for AD and a known promoter of BBB dysfunction. Low-density lipoprotein receptor-related protein 1 (LRP-1), P-glycoprotein, and receptor for advanced glycation end products (RAGE) are examples of BBB transporters implicated in its pathogenesis due to their role in the trafficking of amyloid-β. This disease is currently devoid of strategies that change the natural course of this burdening illness. This unsuccess may partly be explained by our misunderstanding of the disease pathogenesis and our inability to develop drugs that are effectively delivered to the brain. BBB may represent a therapeutic opportunity as a target itself or as a therapeutic vehicle. In this review, we aim to explore the role of BBB in the pathogenesis of AD including the genetic background and detail how it can be targeted in future therapeutic research.

Utilizing Reduced Labeled Proton Clearance to Identify Preclinical Alzheimer Disease with 3D ASL MRI

Addressing the seminal pathophysiology in Alzheimer disease (AD) is the next logical focus for effective intervention, given the initial disappointing and more recent possibly encouraging results of monoclonal antibody trials. Endothelial cell dysfunction-induced blood-brain barrier leak with associated prolonged capillary mean transit time (cMTT) and glymphatic outflow dysfunction is the most proximal events in the degeneration cascade. Sensitive and reproducible markers are required to both identify early disease and assess future treatment trial outcomes. Two participants, with mild cognitive impairment (MCI) and one with AD, were evaluated clinically prior to MRI in this small case series report. From seven 3D turbo gradient and spin echo (TGSE) pulsed arterial spin echo (PASL) MRI sequences six homologous region of interest in bitemporal, bifrontal, and biparietal lobes for each sequence were examined and plotted against time. By choosing late perfusion times during cMTT phase of perfusion linear analysis of signal decay could be utilized. A reference axial FLAIR sequence was also obtained. Slope of the linear analysis correlated to the rate of labeled proton clearance with reduced clearance occurring in AD participants compared to normal participants in our previous study. Whether similar differences in clearance rate extend to either MCI or early AD was investigated. Participants were categorized by clinical phenotype before MRI and compared to previously published phenotype cohorts: n = 18 normal/healthy, n = 6 AD, n = 3 MCI. Significant differences in labeled proton clearance rates between AD and MCI/control phenotypes within bilateral temporal lobes (left p = 0.004, right p = 0.002) and within bilateral frontal lobes AD versus controls (left p = 0.001, right p = 0.008) and AD versus MCI (left p = 0.001, right p = 0.001) were found. This noninvasive MRI technique has potential for identifying MCI transition to AD.

Fucoidan ameliorates LPS-induced neuronal cell damage and cognitive impairment in mice

The incidence of cognitive impairment is rising globally, but there is no effective therapy. Recent studies showed that fucoidan (Fuc), a sulfated polysaccharide enriched in brown algae, is widely used due to its anti-inflammatory, antioxidant, and prebiotic effects. However, the effects and mechanisms of Fuc on lipopolysaccharide (LPS)-induced neuronal cell damage and cognitive impairment in mice need to be explored further. In the present study, we found that Fuc treatment protected HT22 cells from LPS-induced damage by inhibiting the activation of NLRP3 inflammasomes. Fuc exerted neuroprotective effects in mice with LPS-induced cognitive impairment by ameliorating neuroinflammation, promoting neurogenesis, and reducing blood-brain barrier and intestinal barrier permeability. Mechanistically, Fuc supplement significantly restructured the gut microbiota composition, which may be related to glucose and fructose metabolism. In conclusion, Fuc ameliorated LPS-induced neuronal cell damage and cognitive impairment in mice, suggesting that Fuc may be a medicinal and food homologous functional agent to improve cognitive function.

Transgenic animal models to explore and modulate the blood brain and blood retinal barriers of the CNS

The unique environment of the brain and retina is tightly regulated by blood-brain barrier and the blood-retinal barrier, respectively, to ensure proper neuronal function. Endothelial cells within these tissues possess distinct properties that allow for controlled passage of solutes and fluids. Pericytes, glia cells and neurons signal to endothelial cells (ECs) to form and maintain the barriers and control blood flow, helping to create the neurovascular unit. This barrier is lost in a wide range of diseases affecting the central nervous system (CNS) and retina such as brain tumors, stroke, dementia, and in the eye, diabetic retinopathy, retinal vein occlusions and age-related macular degeneration to name prominent examples. Recent studies directly link barrier changes to promotion of disease pathology and degradation of neuronal function. Understanding how these barriers form and how to restore these barriers in disease provides an important point for therapeutic intervention. This review aims to describe the fundamentals of the blood-tissue barriers of the CNS and how the use of transgenic animal models led to our current understanding of the molecular framework of these barriers. The review also highlights examples of targeting barrier properties to protect neuronal function in disease states.

Manual acupuncture benignly regulates blood-brain barrier disruption and reduces lipopolysaccharide loading and systemic inflammation, possibly by adjusting the gut microbiota

BACKGROUND

Blood-brain barrier (BBB) disruption and gut microbiota dysbiosis play crucial roles in Alzheimer's disease (AD). Lipopolysaccharide (LPS) stimulation triggered by gut microbial dysbiosis is an important factor in BBB disruption and systemic inflammation, but the mechanism of acupuncture regulation of BBB disruption via the gut microbiota in AD is not clear.

OBJECTIVE

The current study evaluated the effect of manual acupuncture (MA) on BBB dysfunction in APP/PS1 mice and examined the mechanism of gut microbiota by acupuncture in AD.

METHODS

Acupoints were applied to Baihui (GV20), Yintang (GV29), and Zusanli (ST36) in the MA group. Mice in the manual acupuncture plus antibiotics (MAa) group received antibiotics and acupuncture, while mice in the probiotics (P) group received probiotics. Alterations in spatial learning and memory, the gut microbiota, tightly connected structure and permeability of BBB, and the expression of LPS and inflammatory factors in each group were assessed.

RESULTS

Compared to the normal (N) group, cognitive ability was significantly impaired, the gut microbiota composition was markedly altered, the BBB was significantly disrupted, and the expression of LPS in serum and brain, serum TNF-α, and IL-1β were significantly increased in the AD group (p < 0.01). These changes were inhibited in the MA and P groups (p < 0.01 or p < 0.05), and antibiotics reversed the benign regulatory effects of MA (p < 0.01 or p < 0.05).

CONCLUSION

Manual acupuncture benignly modulated the gut microbiota and BBB dysfunction, reduced LPS, TNF-α, and IL-1β. These effects were comparable to probiotics. The decrease in LPS load and systemic inflammation may play important roles in the regulation of BBB dysfunction by acupuncture, and the gut microbiota may be a potential target for the benign regulation of BBB disruption by acupuncture.

The Role of Blood-Brain Barrier Dysfunction in Mild Cognitive Impairment: a Scientometric and Visualization Analysis from 2000 to 2021

Mild cognitive impairment (MCI) is a pathological stage between normal cognitive aging and dementia. The blood-brain barrier (BBB) breakdown is emerging as an early biomarker of MCI. This study aimed to visually analyze the literatures related to MCI caused by BBB dysfunction in recent 20 years, systematically identify collaboration networks, track research trends, highlight current hot spots, and predict future frontiers in this field. The related literatures published from 2000 to 2021 were obtained from the Web of Science with the search term "mild cognitive impairment and (blood-brain barrier or neurovascular unit or neurovascular coupling)". VOSviewer software was used to present knowledge map, CiteSpace software was used to extract literature information and make tables, including the top most influential countries, authors, institutions, periodicals, keywords, and references. A total of 333 literatures were used for visual analysis. After 2013, the literatures in the field of BBB dysfunction-induced MCI showed an increased trend in terms of year of publication and quantity of material, with more than 40 publications published each year. USA, England, China, and Sweden cooperated closely. In terms of institutions, Harvard Med Sch ranked first in the number of papers published, followed by Mstricht Univ and Univ Washington. In terms of journals, three of the top five co-cited journals belonged to USA, the other two journals were Neurobiol Aging and J Alzheimers DIS, which were from England and Netherlands respectively. A total of 1752 authors were identified, with Abhay P Sagare the most published and Zlokovic BV the most cited. Keyword emergence detection analysis showed that inflammation, oxidative stress, and memory were new research hot spot in this field. Overall, the research on BBB dysfunction-induced MCI is booming. In the future, cooperation and communication between different countries and institutions should be strengthened.