Chemical traits of cerebral amyloid angiopathy in familial British-, Danish-, and non-Alzheimerʼs dementias

Familial British dementia (FBD) and familial Danish dementia (FDD) are autosomal dominant forms of dementia caused by mutations in the integral membrane protein 2B (ITM2B, also known as BRI2) gene. Secretase processing of mutant BRI2 leads to secretion and deposition of BRI2-derived amyloidogenic peptides, ABri and ADan that resemble APP/β-amyloid (Aβ) pathology, which is characteristic of Alzheimer's disease (AD). Amyloid pathology in FBD/FDD manifests itself predominantly in the microvasculature by ABri/ADan containing cerebral amyloid angiopathy (CAA). While ABri and ADan peptide sequences differ only in a few C-terminal amino acids, CAA in FDD is characterized by co-aggregation of ADan with Aβ, while in contrast no Aβ deposition is observed in FBD. The fact that FDD patients display an earlier and more severe disease onset than FBD suggests a potential role of ADan and Aβ co-aggregation that promotes a more rapid disease progression in FDD compared to FBD. It is therefore critical to delineate the chemical signatures of amyloid aggregation in these two vascular dementias. This in turn will increase the knowledge on the pathophysiology of these diseases and the pathogenic role of heterogenous amyloid peptide interactions and deposition, respectively. Herein, we used matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) in combination with hyperspectral, confocal microscopy based on luminescent conjugated oligothiophene probes (LCO) to delineate the structural traits and associated amyloid peptide patterns of single CAA in postmortem brain tissue of patients with FBD, FDD as well as sporadic CAA without AD (CAA+) that show pronounced CAA without parenchymal plaques. The results show that CAA in both FBD and FDD consist of N-terminally truncated- and pyroglutamate-modified amyloid peptide species (ADan and ABri), but that ADan peptides in FDD are also extensively C-terminally truncated as compared to ABri in FBD, which contributes to hydrophobicity of ADan species. Further, CAA in FDD showed co-deposition with Aβ x-42 and Aβ x-40 species. CAA+ vessels were structurally more mature than FDD/FBD CAA and contained significant amounts of pyroglutamated Aβ. When compared with FDD, Aβ in CAA+ showed more C-terminal and less N-terminally truncations. In FDD, ADan showed spatial co-localization with Aβ3pE-40 and Aβ3-40 but not with Aβx-42 species. This suggests an increased aggregation propensity of Aβ in FDD that promotes co-aggregation of both Aβ and ADan. Further, CAA maturity appears to be mainly governed by Aβ content based on the significantly higher 500/580 patterns observed in CAA+ than in FDD and FBD, respectively. Together this is the first study of its kind on comprehensive delineation of Bri2 and APP-derived amyloid peptides in single vascular plaques in both FDD/FBD and sporadic CAA that provides new insight in non-AD-related vascular amyloid pathology. (Figure presented.

Fluid biomarkers of extracellular matrix remodelling across neurological diseases

Neurological diseases constitute a major health and socioeconomic issue. Despite an enormous amount of research going on globally, the prevalence and mortality of neurological disorders are still rising. This has placed a big pressure on health-care systems for biomarker development to be able to detect early stages of the disease and to predict clinical outcomes in patients. The fact that biochemical changes in the brain can be reflected in blood or cerebrospinal fluid paves the way for the fluid biomarkers to become beneficial, cost-effective, and easily accessible tools in neuroscience. The ambition of this thesis was to investigate if measurements of extracellular matrix proteins in human body fluids have a potential to characterise neurological conditions. The findings presented in this thesis suggest that several extracellular matrix proteins may serve as novel cerebrospinal fluid biomarkers for outcome prediction following traumatic brain injury. In addition, they showed a novel diagnostic biomarker potential to differentiate vascular dementia from Alzheimer’s disease, the two most common types of dementia with largely overlapping symptoms. Moreover, their levels in cerebrospinal fluid may represent complex biochemical changes of the brain’s extracellular matrix in patients with idiopathic normal pressure hydrocephalus and in patients who received cranial radiotherapy. These findings may lead to a better understanding of the role of extracellular matrix remodelling across neurological diseases and may contribute to the management and development of future therapies

Differences in fall-related characteristics across cognitive disorders

Approximately 40-60% of falls in the elderly lead to injuries, resulting in disability and loss of independence. Despite the higher prevalence of falls and morbidity rates in cognitively impaired individuals, most fall risk assessments fail to account for mental status. In addition, successful fall prevention programmes in cognitively normal adults have generally failed in patients with cognitive impairment. Identifying the role of pathological aging on fall characteristics can improve the sensitivity and specificity of fall prevention approaches. This literature review provides a thorough investigation into fall prevalence and fall risk factors, the accuracy of fall risk assessments, and the efficacy of fall prevention strategies in individuals with diverse cognitive profiles. We show that fall-related characteristics differ between cognitive disorders and fall risk assessment tools as well as fall prevention strategies should critically consider each patient's cognitive status to facilitate the identification of fallers at an earlier stage and support clinical decision-making.ISSN:1663-436

Serum Brevican as a Biomarker of Cerebrovascular Disease in an Elderly Cognitively Impaired Cohort

In the brain, the extracellular matrix (ECM) composition shapes the neuronal microenvironment and can undergo substantial changes with cerebral pathology. Brevican is integral to the formation of the ECM's neuroprotective perineuronal nets (PNNs). Decreased brevican levels were reported in vascular dementia (VaD) but not in Alzheimer's disease (AD). However, the status of brevican in clinical cohorts with high concomitance of AD pathological burden and cerebrovascular disease (CeVD) is unclear. In this study, 32 non-cognitively impaired (NCI), 97 cognitively impaired no dementia (CIND), 46 AD, and 23 VaD participants recruited from memory clinics based in Singapore underwent neuropsychological and neuroimaging assessments, together with measurements of serum brevican. Association analyses were performed between serum brevican and neuroimaging measures of CeVDs, including white matter hyperintensities (WMHs), lacunes, cortical infarcts, and cerebral microbleeds. Using an aggregated score for CeVD burden, only CIND participants showed lower brevican levels with higher CeVD compared to those with lower CeVD burden (p = 0.006). Among the CeVD subtypes assessed, only elevated WMH burden was associated with lower brevican levels (OR = 2.7; 95% CI = 1.3-5.5). Our findings suggest that brevican deficits may play a role in early cerebrovascular damage in participants at risk of developing dementia

Brevican and Neurocan Peptides as Potential Cerebrospinal Fluid Biomarkers for Differentiation Between Vascular Dementia and Alzheimer's Disease

BACKGROUND: Brevican and neurocan are central nervous system-specific extracellular matrix proteoglycans. They are degraded by extracellular enzymes, such as metalloproteinases. However, their degradation profile is largely unexplored in cerebrospinal fluid (CSF).OBJECTIVE: The study aim was to quantify proteolytic peptides derived from brevican and neurocan in human CSF of patients with Alzheimer's disease (AD) and vascular dementia (VaD) compared with controls.METHODS: The first cohort consisted of 75 individuals including 25 patients with AD, 7 with mild cognitive impairment (MCI) diagnosed with AD upon follow-up, 10 patients with VaD or MCI diagnosed with VaD upon follow-up, and 33 healthy controls and cognitively stable MCI patients. In the second cohort, 31 individuals were included (5 AD patients, 14 VaD patients and 12 healthy controls). Twenty proteolytic peptides derived from brevican (n = 9) and neurocan (n = 11) were quantified using high-resolution parallel reaction monitoring mass spectrometry.RESULTS: In the first cohort, the majority of CSF concentrations of brevican and neurocan peptides were significantly decreased inVaDas compared withADpatients (AUC = 0.83.0.93, p≤0.05) and as compared with the control group (AUC = 0.79.0.87, p ≤ 0.05). In the second cohort, CSF concentrations of two brevican peptides (B87, B156) were significantly decreased in VaD compared with AD (AUC = 0.86.0.91, p ≤ 0.05) and to controls (AUC = 0.80.0.82, p ≤ 0.05), while other brevican and neurocan peptides showed a clear trend to be decreased in VaD compared with AD (AUC = 0.64.80, p > 0.05). No peptides differed between AD and controls.CONCLUSION: Brevican and neurocan peptides are potential diagnostic biomarkers for VaD, with ability to separate VaD from AD

Chemical imaging of sphingolipids and phospholipids at the single amyloid-β plaque level in post-mortem human Alzheimer’s disease brain

Lipids dysregulations have been critically implicated in Alzheimer’s disease (AD) pathology. Chemical analysis of amyloid-β (Aβ) plaque pathology in transgenic AD mouse models has demonstrated alterations in the microenvironment in direct proximity to Aβ plaque pathology. In mouse studies, differences in lipid patterns linked to structural polymorphism among Aβ pathology, such as diffuse, immature, and mature fibrillary aggregate have also been reported. To date, no comprehensive analysis of neuronal lipids microenvironment changes in human AD tissue has been performed. Here, for the first time we leverage matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) though high speed and spatial resolution commercial time-of-light instrument, as well as high mass resolution in-house developed orbitrap system to characterize the lipid microenvironment in postmortem human brain tissue from AD patients carrying Presenilin 1 mutations (PSEN 1) that lead to familial forms of AD (fAD). Interrogation of the spatially resolved MSI data on a single Aβ plaque allowed us to verify nearly 40 sphingolipid and phospholipid species from diverse subclasses being enriched and depleted in relation to the Aβ deposits. This included monosialo-gangliosides (GM), ceramide monohexosides (HexCer), ceramide-1-phosphates (CerP), ceramide phosphoethanolamine conjugates (PE-Cer), sulfatides (ST), as well as phosphatidylinositols (PI), phosphatidylethanolamines (PE), and phosphatidic acid (PA) species (including Lyso-forms). Indeed, many of the sphingolipids species overlap with the species previously seen in transgenic AD mouse models. Interestingly, in comparison to the animal studies, we observed an increased localization of PE and PI species containing arachidonic acid (AA). These finding are highly relevant, demonstrating for the first time Aβ plaque pathology-related alteration in the lipid microenvironment in humans. They provide a basis for development of potential lipid biomarkers for AD characterization and insight into human-specific molecular pathway alterations

Galectin-3 is elevated in CSF and is associated with A beta deposits and tau aggregates in brain tissue in Alzheimer's disease

Galectin-3 (Gal-3) is a beta-galactosidase binding protein involved in microglial activation in the central nervous system (CNS). We previously demonstrated the crucial deleterious role of Gal-3 in microglial activation in Alzheimer’s disease (AD). Under AD conditions, Gal-3 is primarily expressed by microglial cells clustered around Aβ plaques in both human and mouse brain, and knocking out Gal-3 reduces AD pathology in AD-model mice. To further unravel the importance of Gal-3-associated infammation in AD, we aimed to investigate the Gal-3 infammatory response in the AD continuum. First, we measured Gal-3 levels in neocortical and hippocampal tissue from early-onset AD patients, including genetic and sporadic cases. We found that Gal-3 levels were signifcantly higher in both cortex and hippocampus in AD subjects. Immunohistochemistry revealed that Gal-3+microglial cells were associated with amyloid plaques of a larger size and more irregular shape and with neurons containing tau-inclusions. We then analyzed the levels of Gal-3 in cerebrospinal fuid (CSF) from AD patients (n=119) compared to control individuals (n=36). CSF Gal-3 levels were elevated in AD patients compared to controls and more strongly correlated with tau (p-Tau181 and t-tau) and synaptic markers (GAP-43 and neurogranin) than with amyloid-β. Lastly, principal component analysis (PCA) of AD biomarkers revealed that CSF Gal-3 clustered and associated with other CSF neuroinfammatory markers, including sTREM-2, GFAP, and YKL-40. This neuroinfammatory component was more highly expressed in the CSF from amyloid-β positive (A+), CSF p-Tau181 positive (T+), and biomarker neurodegeneration positive/negative (N+/−) (A+T+N+/−) groups compared to the A+T−N− group. Overall, Gal-3 stands out as a key pathological biomarker of AD pathology that is measurable in CSF and, therefore, a potential target for disease-modifying therapies involving the neuroinfammatory response.Ministerio de Ciencia, Innovación y Universidades de España RTI2018-098645-B-100Ministerio de Ciencia, Innovación y Universidades, RTI2018-098645-B-100 y PID2021-124096OB-100Instituto de Salud Carlos III de España - 20/00448Fondos FEDER de la Unión Europea - PI18/01556 y PI21/00914Consejería de Economía, Innovación, Ciencia y Empleo de la Junta de Andalucía. España - P18-RT-137

Dynamics of cerebrospinal fluid levels of matrix metalloproteinases in human traumatic brain injury

Abstract Matrix metalloproteinases (MMPs) are extracellular enzymes involved in the degradation of extracellular matrix (ECM) proteins. Increased expression of MMPs have been described in traumatic brain injury (TBI) and may contribute to additional tissue injury and blood–brain barrier damage. The objectives of this study were to determine longitudinal changes in cerebrospinal fluid (CSF) concentrations of MMPs after acute TBI and in relation to clinical outcomes, with patients with idiopathic normal pressure hydrocephalus (iNPH) serving as a contrast group. The study included 33 TBI patients with ventricular CSF serially sampled, and 38 iNPH patients in the contrast group. Magnetic bead-based immunoassays were utilized to measure the concentrations of eight MMPs in ventricular human CSF. CSF concentrations of MMP-1, MMP-3 and MMP-10 were increased in TBI patients (at baseline) compared with the iNPH group (p < 0.001), while MMP-2, MMP-9 and MMP-12 did not differ between the groups. MMP-1, MMP-3 and MMP-10 concentrations decreased with time after trauma (p = 0.001–0.04). Increased concentrations of MMP-2 and MMP-10 in CSF at baseline were associated with an unfavourable TBI outcome (p = 0.002–0.02). Observed variable pattern of changes in MMP concentrations indicates that specific MMPs serve different roles in the pathophysiology following TBI, and are in turn associated with clinical outcomes

Amyloid Plaque Polymorphism is Associated with Distinct Lipid Accumulations Revealed by Trapped Ion Mobility Mass Spectrometry Imaging (TIMS MSI)

Understanding of Alzheimer’s disease (AD) pathophysiology, requires molecular assessment of how key pathological factors, specifically amyloid β (Aβ) plaques, influence the surrounding microenvironment. Here, neuronal lipids are particularly of interest as these are implicated in pathological- and neurodegenerative processes in AD. The exact molecular characteristics of the cellular environment in direct proximity to Aβ plaques are however still not known, not in the least due to high molecular complexity of lipid species but also due to the lacking spatial resolution, sensitivity, and specificity of analytical approaches. Likewise, how such micro environmental changes differ, across structurally polymorphic Aβ features - such as diffuse, immature and mature, fibrillary structures - has been a challenge, requiring complemental, multimodal imaging approaches. Herein, we used matrix assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) trapped ion mobility spectrometry Time-of-Flight (TIMS TOF) in combination with hyperspectral microscopy to probe lipidomic microenvironment associated with structural polymorphism of Aβ plaque in transgenic mouse model of Alzheimer’s disease (tgAPPSWE).Integrated multivariate imaging data analysis revealed alteration of multiple lipid species showing a general, Aβ associated enrichment/depletion patterns. The hyperspectral imaging strategy further delineated unique distribution of PA, PE-Cer and PI lipids to more/less aggregated Aβ fibrillary structures present within individual Aβ plaques at different timepoints of progressing plaque pathology. Using an elaborate on tissue and ex situ validation approach, the unique possibility to obtain gas-phase isobar and isomer separations through TIMS TOF, facilitated unambiguous identification of lipid isomers that showed plaque pathology associated localizations. Finally, we followed AD pathology associated lipid changes over time, identifying plaque growth and maturation to be characterized by peripheral accumulation of PI (40:6). Together, these data demonstrate the potential of multimodal imaging approaches to overcome limitations associated with conventional advanced MS imaging applications. This allowed for differentiation of both distinct lipid components in a complex micro environment, as well as their correlation to disease relevant amyloid plaque polymorphs