Contribution of blood-brain barrier-related blood-borne factors for Alzheimer’s disease vs. vascular dementia diagnosis: A pilot study

Towards a better diagnosis and treatment of dementia: Identifying common and distinct neuropathological mechanisms in Alzheimer's and vascular dementia

Alzheimer's disease (AD) and vascular dementia (VaD) together contribute to almost 90 % of all dementia cases leading to major health challenges of our time with a substantial global socioeconomic burden. While in AD, the improved understanding of Amyloid beta (Aß) mismetabolism and tau hyperphosphorylation as pathophysiological hallmarks has led to significant clinical breakthroughs, similar advances in VaD are lacking. After comparing the clinical presentation, including risk factors, disease patterns, course of diseases and further diagnostic parameters for both forms of dementia, we highlight the importance of shared pathomechanisms found in AD and VaD: Endothelial damage, blood brain barrier (BBB) breakdown and hypoperfusion inducing oxidative stress and inflammation and thus trophic uncoupling in the neurovascular unit. A dysfunctional endothelium and BBB lead to the accumulation of neurotoxic molecules and Aß through impaired clearance, which in turn leads to neurodegeneration. In this context we discuss possible neuropathological parameters, which might serve as biomarkers and thus improve diagnostic accuracy or reveal targets for novel therapeutic strategies for both forms of dementia.

Diagnostic and discriminative accuracy of plasma phosphorylated tau 217 for symptomatic Alzheimer's disease in a Chinese cohort

BACKGROUND

Plasma phosphorylated tau at threonine 217 (p-tau217) measured with an ultrasensitive immunoassay method has been demonstrated to be an optimal biomarker for Alzheimer's disease (AD).

OBJECTIVES

The aim of this study was to establish the reference interval for plasma p-tau217 in Chinese individuals and evaluate its diagnostic value in symptomatic AD.

DESIGN, SETTING, PARTICIPANTS

We recruited 150 cognitively unimpaired (CU) individuals, 60 patients with AD dementia, 30 patients with mild cognitive impairment (MCI) due to AD, 40 patients with frontotemporal lobar degeneration (FTLD), and 70 patients with subcortical ischaemic vascular dementia (SIVD).

MEASUREMENTS

The concentrations of plasma p-tau217, total tau, amyloid-beta (Aβ)42 and Aβ40 were measured with a single-molecule array.

RESULTS

Plasma p-tau217 outperformed other biomarkers in discriminating AD patients from CU controls, FTLD patients, and SIVD patients (AUC = 0.983, 0.936, 0.892) and discriminating MCI patients from CU controls (AUC = 0.943). The plasma p-tau217 level was negatively correlated with memory in patients with symptomatic AD.

CONCLUSION

The diagnostic accuracy of plasma p-tau217 was exceptional for AD, even at early stages, in the Chinese population.

Biomarkers of cellular senescence predict risk of mild cognitive impairment: Results from the lifestyle interventions for elders (LIFE) study

OBJECTIVES

Cellular senescence, characterized by a marked and multifactorial senescence-associated secretory phenotype (SASP), is a potential unifying mechanism of aging and chronic disease. Most studies of the SASP have focused on frailty and other functional outcomes. Senescent cells have been detected in the brains of patients with Alzheimer's disease, but few studies have examined associations between plasma SASP markers and cognition. The objective of this study was to examine the cross-sectional and longitudinal associations between plasma SASP markers and mild cognitive impairment among older adults at high risk of mobility disability.

DESIGN

The Lifestyle Interventions for Elders (LIFE) study was a randomized controlled trial of a group-based physical activity program compared to a "successful aging" health education program to assess effects on major mobility disability that was conducted from February 2010 to December 2013.

SETTING

Recruitment occurred at eight centers in the United States.

PARTICIPANTS

We included 1,373 participants enrolled in the study with baseline measures of 27 biomarkers of cellular senescence and adjudication of mild cognitive impairment (MCI) and dementia at baseline and 24-month follow-up. At baseline, participants were aged 70-80, sedentary, and at high risk of mobility disability.

MEASUREMENTS

A neuropsychological assessment was administered at baseline and 24 months post-randomization. At both timepoints, a clinical adjudication committee determined whether individuals had a diagnosis of cognitively normal, MCI, or dementia; individuals with dementia at baseline were excluded. The concentrations of 26 of the 27 plasma proteins identified as components of the SASP were measured with commercially available Luminex xMAP multiplex magnetic bead-based immunoassays analyzed on the MAGPIX System while 1 protein (Activin A) was measured using an enzyme-linked immunosorbent assay.

RESULTS

Logistic regression models were used to examine the associations of each senescence biomarker, in quartiles, with baseline or incident MCI. Models stratified by clinical site and adjusted for intervention assignment, age, gender, race, and education. Among 1,373 participants, 117 (8.5%) were diagnosed with MCI at baseline. Increasing quartiles of myeloperoxidase (MPO) was associated with higher odds of MCI compared to quartile 1 (Q2: OR = 1.34, 95% CI: 0.74-2.45; Q3: OR = 1.43, 95% CI: 0.80-2.59; Q4: OR = 1.79, 95% CI: 1.02-3.22). Additionally, matrix metalloproteinase 1 (MMP1) quartiles 2-4 had lower odds of MCI compared to quartile 1 (Q2: OR = 0.61, 95% CI: 0.35-1.02; Q3: OR = 0.58, 95% CI: 0.33-0.98; Q4: OR = 0.64, 95% CI: 0.37-1.08). Of the 1,256 cognitively unimpaired participants at baseline, 141 (11.2%) were diagnosed with incident MCI or dementia at the 24-month follow-up. Compared to quartile 1, increasing baseline quartiles of MPO (Q2: OR = 1.10, 95% CI: 0.63-1.92; Q3: OR = 1.36, 95% CI: 0.80-2.33; Q4: OR = 1.92, 95% CI: 1.16-3.25) and matrix metalloproteinase 7 (MMP7, Q2: OR = 0.88, 95% CI: 0.47-1.62; Q3: OR = 1.46, 95% CI: 0.85-2.55; Q4: OR = 2.14, 95% CI: 1.28-3.65) were associated with increased odds of MCI or dementia at 24 months.

CONCLUSIONS

Among older adults at high risk of mobility disability, high plasma MPO was cross-sectionally and, along with MMP7, longitudinally associated with increased odds of MCI and dementia. In contrast, high MMP1 was cross-sectionally associated with reduced odds of MCI.

Inhibition of PGAM5 hyperactivation reduces neuronal apoptosis in PC12 cells and experimental vascular dementia rats

PURPOSE

The incidence of vascular dementia (VaD), as one of the main types of dementia in old age, has been increasing year by year, and exploring its pathogenesis and seeking practical and effective treatment methods are undoubtedly the key to solving this problem. Phosphoglycerate translocase 5 (PGAM5), as a crossroads of multiple signaling pathways, can lead to mitochondrial fission, which in turn triggers the onset and development of necroptosis, and thus PGAM5 may be a novel target for the prevention and treatment of vascular dementia.

METHODS

Animal model of vascular dementia was established by Two-vessel occlusion (2-VO) method, and cellular model of vascular dementia was established by oxygen glucose deprivation (OGD) method. Neuronal damage was detected in vivo and in vitro in different groups using different concentrations of the PGAM5-specific inhibitor LFHP-1c, and necroptosis and mitochondrial dynamics-related factors were determined.

RESULTS

In vivo experiments, 10 mg/kg-1 and 20 mg/kg-1 LFHP-1c improved cognitive deficits, reduced neuronal edema and vacuoles, increased the number of nissl bodies, and it could modulate the expression of Caspase family and Bcl-2 family related proteins and mRNAs and ameliorate neuronal damage. Simultaneously, in vitro experiments, 5 μM, 10 μM and 20 μM LFHP-1c increased the activity and migration number of model cells, reduced the number of apoptotic cells, ameliorated the excessive accumulation of intracellular reactive oxygen species, inhibited the over-activation of caspase-family and Bcl-2-family related proteins and mRNAs, and improved the mitochondrial dynamics of the fission and fusion states. Moreover, in vivo and in vitro experiments have shown that LFHP-1c can also upregulate the expression level of BDNF, inhibit the expression content of TNF-α and ROS, regulate the expression of proteins and mRNAs related to the RIPK1/RIPK3/MLKL pathway and mitochondrial dynamics, and reduce neuronal apoptosis.

CONCLUSIONS

Inhibition of PGAM5 expression level can reduce neuronal damage caused by chronic cerebral ischemia and hypoxia, which mainly prevents necroptosis by targeting the RIPK1/RIPK3/MLKL signaling pathway and regulates the downstream mitochondrial dynamics homeostasis system to prevent excessive mitochondrial fission, thus improving cognition and exerting cerebroprotective effects.

Perinatal hypoxia-mediated neurodevelopment abnormalities in congenital heart disease mouse model

BACKGROUND

Cyanotic congenital heart disease (CHD) in children has been associated with neurodevelopmental abnormalities, although the underlying mechanisms remain largely unknown. Multiple factors are likely involved in this process. This research aims to explore the potential effects of hypoxia and vascular system-derived factors in neurodevelopmental outcomes in offspring.

METHODS

Mouse aorta endothelial cells (MEC) and amygdala neurons were isolated to investigate the effects of hypoxia on pro-inflammatory cytokine release, gene expression, redox balance, mitochondrial function, and epigenetic modifications. A CHD mouse model was established to evaluate the impact of perinatal hypoxia on fetal brain development. Estrogen receptor β (ERβ) expression in endothelial cells was modulated using Tie2-driven lentivirus both in vitro and in vivo study to assess the vascular system's contribution to hypoxia-mediated neurodevelopmental abnormalities.

RESULTS

Hypoxia exposure, along with factors released from MEC, led to altered gene expression, oxidative stress, mitochondrial dysfunction, and epigenetic modifications in amygdala neurons. In the CHD mouse model, perinatal hypoxia resulted in compromised vascular function, altered gene expression, disrupted redox balance in brain tissues, and impaired behavioral outcomes in offspring. Prenatal expression of ERβ in endothelial cells partially ameliorated these neurodevelopmental abnormalities, while prenatal knockdown of ERβ mimicked the effects of perinatal hypoxia.

CONCLUSIONS

Hypoxia, combined with endothelial cell-derived factors, induces epigenetic changes in neurons. In the CHD mouse model, perinatal hypoxia causes vascular dysfunction, altered gene expression, and redox imbalance in brain tissues, leading to behavioral impairments in offspring. Prenatal expression of ERβ in endothelial cells mitigates these effects, suggesting that modulating gene expression in the vascular system during pregnancy could play a protective role against hypoxia-induced neurodevelopmental abnormalities in CHD.

Monogenic causes of cerebral small vessel disease- models for vascular cognitive impairment and dementia?

PURPOSE OF REVIEW

Recent advancements in molecular biomarkers and therapeutic options for Alzheimer's disease have brought into focus the need for greater progress in the second most common cause of dementia, vascular cognitive impairment and dementia (VCID). We examine how the study of monogenic causes of VCID has contributed to the understanding of its pathophysiology and potential biomarker and treatment research.

RECENT FINDINGS

It is widely accepted that conditions which disrupt the cerebral small vessels contribute to vascular pathologies including stroke and cerebral microbleeds, ultimately leading to vascular cognitive impairment and dementia. Among these conditions are a range of monogenic small vessel diseases (SVDs) such as CADASIL, CARASIL, Fabry disease and COL4A-related disorders.

SUMMARY

This review indicates the importance of furthering research into monogenic SVDs in order to gain insight into the pathomechanisms of VCID more broadly. Monogenic conditions are easier to model than sporadic VCID and can serve as a guide for identifying biomarkers for diagnosis, monitoring and intervention outcomes.

The Link Between Matrix Metalloproteinases and Alzheimer's Disease Pathophysiology

Alzheimer's disease (AD) is a major contributor to dementia and the most common neurodegenerative disorder. In AD pathophysiology, matrix metalloproteinases (MMPs)-proteolytic enzymes, best known to be responsible for remodeling and degradation of the extracellular matrix-were suggested to play an important role. Due to the diverse nature of the published data and frequent inconsistent results presented in available papers, it was considered essential to analyze all aspects of MMP literature with respect to AD pathophysiology and attempt to outline a unifying concept for understanding their role in AD. Thus, the main contribution of this review article is to summarize the most recent research on the participation of MMP in AD pathophysiology obtained using the cell cultures to understand the molecular principles of their action. Furthermore, an updated comprehensive view regarding this topic based exclusively on papers from human studies is provided as well. It can be concluded that determining the exact role of any particular MMPs in the AD pathophysiology holds promise for establishing their role as potential biomarkers reflecting the severity or progression of this disease or for developing new therapeutic agents targeting the processes that lead to AD.

Fluid biomarkers of the neurovascular unit in cerebrovascular disease and vascular cognitive disorders: A systematic review and meta-analysis

Background

The disruption of the neurovascular unit (NVU), which maintains the integrity of the blood brain barrier (BBB), has been identified as a critical mechanism in the development of cerebrovascular and neurodegenerative disorders. However, the understanding of the pathophysiological mechanisms linking NVU dysfunction to the disorders is incomplete, and reliable blood biomarkers to measure NVU dysfunction are yet to be established. This systematic review and meta-analysis aimed to identify biomarkers associated with BBB dysfunction in large vessel disease, small vessel disease (SVD) and vascular cognitive disorders (VCD).

Methods

A literature search was conducted in PubMed, EMBASE, Scopus and PsychINFO to identify blood biomarkers related to dysfunction of the NVU in disorders with vascular pathologies published until 20 November 2023. Studies that assayed one or more specific markers in human serum or plasma were included. Quality of studies was assessed using the Newcastle-Ottawa Quality Assessment Scale. Effects were pooled and methodological heterogeneity examined using the random effects model.

Results

A total of 112 studies were included in this review. Where study numbers allowed, biomarkers were analysed using random effect meta-analysis for VCD (1 biomarker; 5 studies) and cerebrovascular disorders, including stroke and SVD (9 biomarkers; 29 studies) while all remaining biomarkers (n = 17 biomarkers; 78 studies) were examined through qualitative analysis. Results of the meta-analysis revealed that cerebrospinal fluid/serum albumin quotient (Q-Alb) reliably differentiates VCD patients from healthy controls (MD = 2.77; 95 % CI = 1.97-3.57; p < 0.0001) while commonly measured biomarkers of endothelial dysfunction (VEGF, VCAM-1, ICAM-1, vWF and E-selectin) and neuronal injury (NfL) were significantly elevated in vascular pathologies. A qualitative assessment of non-meta-analysed biomarkers revealed NSE, NfL, vWF, ICAM-1, VCAM-1, lipocalin-2, MMP-2 and MMP-9 levels to be upregulated in VCD, although these findings were not consistently replicated.

Conclusions

This review identifies several promising biomarkers of NVU dysfunction which require further validation. A panel of biomarkers representing multiple pathophysiological pathways may offer greater discriminative power in distinguishing possible disease mechanisms of VCD.

Exposure to the World Trade Center Particulate Matter Alters the Gut-Brain Axis in Early Onset Alzheimer's Disease Mice

Background

The September 11, 2001, catastrophe unleashed widespread destruction beyond the World Center (WTC), with fires and toxic gases leaving lasting impacts. First responders at Ground Zero faced prolonged exposure to hazardous particulate matter (PM), resulting in chronic health challenges. Among the multitude of health concerns, the potential association between the WTCPM and Alzheimer's disease (AD) has emerged as an area of intense inquiry, probing the intricate interplay between environmental factors and neurodegenerative diseases.

Objective

We posit that a genetic predisposition to AD in mice results in dysregulation of the gut-brain axis following chronic exposure to WTCPM. This, in turn, may heighten the risk of AD-like symptoms in these individuals.

Methods

3xTg-AD and WT mice were intranasally administered with WTCPM collected at Ground Zero within 72 hours after the attacks. Working memory and learning and recognition memory were monitored for 4 months. Moreover, brain transcriptomic analysis and gut barrier permeability along with microbiome composition were examined.

Results

Our findings underscore the deleterious effects of WTCPM on cognitive function, as well as notable alterations in brain genes associated with synaptic plasticity, pro-survival, and inflammatory signaling pathways. Complementary, chronic exposure to the WTCPM led to increased gut permeability in AD mice and altered bacteria composition and expression of functional pathways in the gut.

Conclusions

Our results hint at a complex interplay between gut and brain axis, suggesting potential mechanisms through which WTCPM exposure may exacerbate cognitive decline. Identifying these pathways offers opportunities for tailored interventions to alleviate neurological effects among first responders.

Molecular biomarkers for vascular cognitive impairment and dementia

As disease-specific interventions for dementia are being developed, the ability to identify the underlying pathology and dementia subtypes is increasingly important. Vascular cognitive impairment and dementia (VCID) is the second most common cause of dementia after Alzheimer disease, but progress in identifying molecular biomarkers for accurate diagnosis of VCID has been relatively limited. In this Review, we examine the roles of large and small vessel disease in VCID, considering the underlying pathophysiological processes that lead to vascular brain injury, including atherosclerosis, arteriolosclerosis, ischaemic injury, haemorrhage, hypoperfusion, endothelial dysfunction, blood-brain barrier breakdown, inflammation, oxidative stress, hypoxia, and neuronal and glial degeneration. We consider the key molecules in these processes, including proteins and peptides, metabolites, lipids and circulating RNA, and consider their potential as molecular biomarkers alone and in combination. We also discuss the challenges in translating the promise of these biomarkers into clinical application.

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.

Exposure to World Trade Center Dust Exacerbates Cognitive Impairment and Evokes a Central and Peripheral Pro-Inflammatory Transcriptional Profile in an Animal Model of Alzheimer's Disease

BACKGROUND

The terrorist attacks on September 11, 2001, on the World Trade Center (WTC) led to intense fires and a massive dense cloud of toxic gases and suspended pulverized debris. In the subsequent years, following the attack and cleanup efforts, a cluster of chronic health conditions emerged among First Responders (FR) who were at Ground Zero for prolonged periods and were repeatedly exposed to high levels of WTC particulate matter (WTCPM). Among those are neurological complications which may increase the risk for the development of Alzheimer's disease (AD) later in life.

OBJECTIVE

We hypothesize that WTCPM dust exposure affects the immune cross-talking between the periphery and central nervous systems that may induce brain permeability ultimately promoting AD-type phenotype.

METHODS

5XFAD and wild-type mice were intranasally administered with WTCPM dust collected at Ground Zero within 72 h after the attacks. Y-maze assay and novel object recognition behavioral tests were performed for working memory deficits and learning and recognition memory, respectively. Transcriptomic analysis in the blood and hippocampus was performed and confirmed by RT qPCR.

RESULTS

Mice exposed to WTCPM dust exhibited a significant impairment in spatial and recognition short and long-term memory. Furthermore, the transcriptomic analysis in the hippocampal formation and blood revealed significant changes in genes related to immune-inflammatory responses, and blood-brain barrier disruption.

CONCLUSION

These studies suggest a putative peripheral-brain immune inflammatory cross-talking that may potentiate cognitive decline, identifying for the first time key steps which may be therapeutically targetable in future studies in WTC FR.