Welcome to the AD/PD™ 2024 Interactive Program
The conference will officially run on Western European Standard Time (Lisbon, UTC+0)
To convert the conference times to your local time Click Here
DISENTANGLING THE FUNCTION OF LYSOSOMAL LOCALIZED PRESENILIN2 IN NEURONS AND BRAIN: RELEVANCE FOR ALZHEIMER’S DISEASE PATHOGENESIS
Abstract
Aims
Presenilin2(PSEN2)/γ-secretase complexes are restricted in their localization to late endosomes and lysosomes, in stark contrast to the broadly distributed PSEN1/γ-secretase complexes. This underscores the existence of complex-specific substrate pools potentially revealing distinct contributions to Alzheimer’s disease(AD) pathology. Moreover, PSEN2/γ-secretase is the main generator of intracellular Aβ42, a highly toxic pool that surges prior to plaque pathology and coincides well with synaptic dysfunction.
Methods
To unravel PSEN2 specific contributions to AD pathology, we generated APPNLGF knock-in(APPKI) mice models deficient for PSEN2 or expressing the familial AD-linked mutant variant N141I(FAD-PSEN2).
Results
Curiously, both models show an accelerated plaque pathology and dystrophic neurite occurrence, albeit even earlier in the APPxFADPSEN2. As predicted, knocking out PSEN2 resulted in a relative abundance of shorter Aβ peptides whereas introduction of the FADPSEN2 variant drives the production towards longer more aggregation prone Aβ species. At the behavioral level, this accelerated pathology coincides with working memory deficits, strongly linked to the CA3 region of the hippocampus in which PSEN2 appears to be more highly expressed. Long-term potentiation(LTP) recordings in the mossy fibers of the CA3 region show significant decreases in LTP amplitude in both the APPKIxPSEN2KO and APPKIxFADPSEN2. Additionally, ultrastructural analysis shows significant reduction in mossy fiber synapse area. Interestingly, hippocampal neurons with altered PSEN2 expression present with endolysosomal defects including enlarged lysosomes and reduced lysosomal calcium release. Additionally, pre-and postsynaptic channels are significantly downregulated at the neuronal cell surface.
Conclusions
Here we collected strong support for the unique way in which PSEN2 may contribute to AD pathology. We argue that due to its restricted localization, mutations or deficiencies in PSEN2 lead to endolysosomal defects that, we propose, impact on synaptic alterations and provide a molecular mechanism for the observed synaptic defects and memory deficits.
ADDITIVE AND SYNERGISTIC EFFECTS OF TSPO AND AMYLOID-Β AS PREDICTORS OF LONGITUDINAL PTAU217 CHANGES
Abstract
Aims
It has been proposed that microglia-released proinflammatory factors reactive to amyloid plaques constitute an early event leading to tau pathology. Here we applied multiple biomarkers to assess whether the rate of p-tau-217 change, an early marker of tau pathology, depends on baseline levels of amyloid and neuroinflammation.
Methods
We included 78 individuals from the TRIAD cohort. Brain inflammation, tangles and amyloid-β (Aβ) were assessed at baseline via [11C]PBR28-PET, [18F]MK6240-PET and [18F]AZD4694-PET. Plasma pTau217 was quantified at baseline and follow-up (1.9 years±0.6). Voxel-based regression models evaluated the relationship between PET biomarkers at baseline and the yearly change in pTau217. Models evaluating the associations with [18F]AZD4694-PET were adjusted for [18F]MK6240-PET and [11C]PBR28-PET voxel-wise and vice-versa, adjusting for age and sex and correcting for multiple comparisons. Cut-off for TSPO positivity was generated using the mean SUVR value of the CUY individuals plus 2.5 s.d. in ROIs. Aβ positivity was defined as neocortical Aβ-PET SUVR ≥ 1.55.
Results
Positive associations were found between baseline levels of TSPO- and Aβ-PET and yearly change of plasma pTau217 (Fig.1A). No significant clusters with tau-PET survived RFT. A significant correlation between PET SUVR and pTau217 change was found in TSPO-positive individuals (P<0.001) and in Aβ-positive individuals (P=0.01) (Fig.1B). The interaction between Aβ and TSPO predicting the change in pTau217 was the model with the highest R2 and the lowest AIC values (Fig.2).
Conclusions
These results support the hypothesis that microglial activation and Aβ pathology facilitate tau phosphorylation independently and interactively, while tau-PET does not reflect this process. Our results also suggest that microglial abnormalities might be an early upstream event, presumably before tangle formation.
ANTAGONISM AND GENETIC DEPLETION OF L-TYPE CALCIUM CHANNEL CAV1.2 RESTRICT AMYLOID PATHOLOGY THROUGH DIVERGENT MECHANISMS
Abstract
Aims
Dysfunction of the endosomal-lysosomal network is a key feature of Alzheimer’s disease (AD) pathology. We recently reported that treatment with the L-type calcium channel (LTCC) antagonist isradipine age-dependently reduced dysfunctional endo-lysosomes vacuoles surrounding amyloid plaques in the 5XFAD mouse model of amyloid pathology. Intracellular calcium plays a role in the biogenesis and maturation of autophagosomes and lysosomes via a variety of intracellular signaling cascades. Here, we compared the effect of the LTCC antagonist isradipine and neuronal and microglial genetic ablation of the LTCC Cav1.2 on amyloid and endo-lysosomal pathology in 5XFAD mice.
Methods
We first confirmed that LTCC antagonists reduce AD pathology and cognitive deficits using human postmortem data from the National Alzheimer's Coordinating Center (NACC) database. We then treated 5XFAD mice with isradipine via subcutaneous pellets, or knocked out Cav1.2 on neurons or microglia using Cre-loxp technology. We measured pathology in 5XFAD mice using immunohistochemistry for lysosomes, amyloid plaques, and microglia and measured mechanisms of autophagic regulation using Western blotting and qPCR.
Results
We found that LTCC antagonist treatment in humans was significantly assocated with reduced pathology and protected cognition. In our mouse studies, we found that isradipine treatment upregulated the expression of several autophagy-associated genes in 5XFAD mice as well as in N2A cells in vitro. We also found that isradipine treatment decreased protein levels of β secretase 1 (BACE1). Loss of Cav1.2 on neurons phenocopied effect of isradipine on amyloid and dystrophic neurites but not autophagic gene expression.
Conclusions
Antaognism of the LTCC Cav1.2 reduces pathology in both humans and the 5XFAD mouse model of amyloid pathology. While neuronal knockout of the LTCC Cav1.2 recapitulates reduced pathology in 5XFAD mice, it appears to do so via mechanisms distinct from the LTCC antagonist isradipine.
MOLECULAR MECHANISMS UNDERLYING A REVERSIBLE STATE OF HYPOMETABOLISM IN SPORADIC PARKINSON’S DISEASE
Abstract
Aims
Sporadic Parkinson’s Disease (sPD) is a progressive neurodegenerative disorder caused by multiple genetic and environmental factors with largely unknown aetiology. Prominent pathological culprits in patients are alterations in mitochondrial metabolism. However, their relevance at different stages of disease progression specifically in humans remains largely elusive and needs further investigations in human cellular models.
Methods
Thus, here we used human induced pluripotent stem cells (hiPSCs) from late-onset sPD patients and healthy individuals for disease modelling. A multilayered -omics study (single cell transcriptomics, proteomics and metabolomics) was performed on neuronal precursor cells and thereof derived neurons and mitochondrial function was assessed.
Results
Our results show, that cells derived from sPD patients exhibit mitochondrial complex I deficiency next to a state of hypometabolism. The multilayered -Omics analysis allowed us to identify the citric acid cycle on the level of the α-ketoglutarate dehydrogenase complex (OGDHC) as being the bottleneck in sPD metabolism. Notably, a follow-up of patients about 10 years after the initial biopsy reveals a high correlation between OGDHC activity changes in our hiPSC-derived cellular model and the disease progression in the original patients. In addition, the alterations in cellular metabolism such as the glucose metabolization and the activity of the OGDHC were restored by interfering with the enhanced SHH signal transduction mediated by sPD-specific alterations in primary cilia function in sPD.
Conclusions
In sum, this model integrates sPD-associated mitochondrial dysfunction with metabolic alterations into one comprehensive mechanistic model. In addition, the results suggest that inhibiting overactive SHH signalling may potentially contribute to new neuroprotective therapies during the early stages of sPD, thus preventing or halting disease progress.
AGE-RELATED DIFFERENCES OF LOCUS COEULEUS PROJECTIONS MEASURED BY PROBABILISTIC TRACTOGRAPHY
Abstract
Aims
The locus coeruleus (LC) is an important noradrenergic nucleus in the dorsolateral pons that supplies noradrenaline to the brain through extensive cortical and subcortical projections. Recent studies established that the LC is vulnerable to aging, but how these projections differ between age groups and how they are affected by common age-related comorbidities is not fully clear.
Methods
Here, we employ probabilistic tractography to characterize structural connectivity of the LC across aging using 3T diffusion-weighted MRI in a population-based cohort aged from 18 to 88 years of age (Cambridge Centre for Ageing and Neuroscience cohort, n=640). We assess associations between age and connectivity, as well as common aging-related comorbidities, such as subjective memory problems, hypertension and diabetes. Age-related differences were assessed using Spearman’s rank correlation, whereas comorbidity-related changes were investigated using Mann-Whitney U-tests, corrected for age, biological sex and education.
Results
The tractogram of the LC contained connections consistent with previous tractography and tracer studies. LC connectivity exhibited a marked decrease in older participants to a variety of brain areas including frontal and temporal regions, as well as the bilateral thalami and the left caudate (Spearman’s R < -0.2, pFDR<0.001). Participants with subjective memory problems exhibited increased LC connectivity to the ventral anterior cingulate cortex (p<0.0032). Participants with hypertension and diabetes exhibited decreased LC connectivity to the left middle frontal gyrus, the right amygdala and bilateral thalami (0.0001<p<0.014).
Conclusions
These results highlight how the structural connectivity of the LC changes throughout aging, and imply that its connections are further affected by common aging-related disorders.
SINGLE-CELL MULTI-REGION DISSECTION OF ALZHEIMER’S DISEASE REVEALS SELECTIVELY VULNERABLE NEURONS
Abstract
Aims
Alzheimer’s disease (AD) is the leading cause of dementia worldwide, but the cellular architecture of brain regions involved in AD and its molecular mechanisms across genes, pathways, and cell types remain poorly understood.
Methods
We report a multi-region single-cell transcriptomic atlas of the aged human brain covering 1.3 million cells from 283 post-mortem human brain samples across six brain regions, 48 individuals, and multiple stages of AD. We validate our findings with orthogonal datasets and data modalities, including single-cell RNA-seq across 400 individuals, RNAscope and IHC in human post-mortem tissue and mouse models.
Results
We identify 76 cell types, including region-specific subtypes of excitatory and inhibitory neurons and glia, two thalamic astrocyte subtypes absent from the neocortex, and a previously uncharacterized inhibitory interneuron population unique to the thalamus and distinct from canonical inhibitory subclasses. We identify region-specific excitatory and inhibitory neuron subtypes and neuronal circuits depleted in AD across brain regions. We provide evidence for the involvement of the Reelin signaling pathway in modulating vulnerability and resilience of both excitatory and inhibitory neurons in AD, revealing a convergence of factors associated with cellular vulnerability in sporadic AD and resilience to autosomal dominant AD. We develop a scalable gene module discovery method, which we use to identify and annotate cellular expression programs and reveal cell-type-specific and region-specific modules altered in AD and associated with diverse pathological variables. We reveal an astrocyte program with cognitive resilience to AD pathology, tying choline metabolism and polyamine biosynthesis in astrocytes to preserved cognitive function late in life.
Conclusions
Overall, our work provides a valuable brain-region-specific atlas of the aging brain and provides important insights into cellular vulnerability, response, and resilience to Alzheimer’s disease.
ENHANCED DELIVERY OF A LOW DOSE OF MONOCLONAL ANTIBODY VIA FOCUSED ULTRASOUND IN A MOUSE MODEL OF ALZHEIMER’S DISEASE
Abstract
Aims
Lecanemab, a human IgG1 monoclonal antibody targeting oligomer, protofibrils and fibril forms of beta-amyloid, has been reported to reduce amyloid pathology and improve impaired cognition after administration of a high dose (10 mg/kg) of the drug in Alzheimer’s disease (AD). The purpose of this study was to investigate the therapeutic efficacy and the associated molecular mechanisms of a lower dose of lecanemab (1 mg/kg) with enhanced delivery via focused ultrasound (FUS) in a mouse model of AD.
Methods
We used 6-month-old WT and 5xFAD mouse model. The FUS with microbubbles opened the blood–brain barrier (BBB) of the hippocampus for the delivery of lecanemab. The combined therapy of FUS and 1mg/kg of lecanemab was performed three times in total and each treatment was performed biweekly.
Results
In feasibility study, the FUS-mediated BBB opening increased the delivery of Aducanumab (3mg/kg) into the brain by approximately 8 times. The FUS-mediated immunotherapy induced significantly less cognitive decline and decreased the level of amyloid plaques in 5×FAD mice compared with monoclonal antibody alone. we also noted increased activated phagocytic microglia without hemorrhage in 5×FAD mice treated with low dose of Aducanumab. We performed RNA sequencing and identified that enriched canonical pathways including phagosome formation, neuroinflammation signaling and synaptic plasticity were altered in 5xFAD mice. The dose dependant of reduction of lecanemab immunotherapy down to 1mg/kg and its role of mitigation of cognitive impariment and neuropathological findings will be presented.
Conclusions
The major roadblock of current immunotherapy in AD are lacking of efficacy of drug treatment, including the role of a pro-inflammatory response and subsequent vascular side effects. Our study will elucidate that FUS-mediated delivery at lower and safer concentration of lecanemab will be suitable strategy for an immunotherapeutic approach in AD.
EFFECTS OF TAU DELETION AND TAU INDUCTION ON NEURODEGENERATION IN A MOUSE MODEL OF CEREBRAL ΒETA-AMYLOIDOSIS
Abstract
Aims
Brain deposition of amyloid-β (Aβ) is the first pathogenic event along the Alzheimer´s disease (AD) continuum and starts at least 20 years before clinical disease onset. Clinical trials are increasingly shifted to pre-symptomatic disease phases and thus, it is important to understand the link between Aβ-deposition and downstream events, namely Tau-pathology and neurodegeneration. Increasing Neurofilament-light-chain (NfL) concentrations in CSF and blood appear as promising biomarkers of neurodegeneration and disease progression in various brain disorders, including AD. Similarly, NfL increases in mouse models with amyloid-pathology, such as APPPS1-transgenic mice. However, it remains unknown whether the Aβ-aggregation itself or downstream processes, in particular Tau-related changes, lead to rising NfL-concentrations. Therefore, the objective of this study was to elucidate the contribution of Tau to neurodegeneration in APPPS1 mice.
Methods
APPPS1 mice and APPPS1 mice with reduced or lack of endogenous Tau (APPPS1,Tau+/- and APPPS1,Tau-/-) were studied. Additionally, APPPS1 mice with induced Tau-pathology (by seeded induction) were investigated. Brains were analysed biochemically and neuropathologically. CSF and blood were collected and are now analysed with non-targeted chromatography-mass spectrometry. In addition, NfL was measured using the Simoa platform.
Results
Our results indicate that Aβ-load is not affected in 6- and 12-months-old APPPS1 mice in the absence of Tau expression. Similarly, no robust effect on amyloid-associated pathology and glial activation was found, and age-related increases of NfL were similar in APPPS1 mice with or without endogenous Tau. Analysis of APPPS1 mice with induced Tau-pathology and a more comprehensive CSF proteome analysis are ongoing.
Conclusions
Our preliminary data indicate that endogenous Tau is not a mediator of neurodegeneration in APPPS1 mice. The effect of Tau lesion induction in amyloid-laden brains on NfL-levels is ongoing and will be presented at the meeting.
PRE-RECORDED: PRESENILIN-1 AFFECTS MITOCHONDRIA IN CULTURED HIPPOCAMPAL NEURONS: FUNCTIONAL IMPLICATIONS
Abstract
Abstract Body
Abstract: Presenilin 1 (PS1) is a transmembrane proteolytic subunit of γ-secretase that cleaves amyloid precursor protein. Mutations in PS1 (mPS1) are associated with early-onset familial Alzheimer’s disease (AD). The link between mPS1, mitochondrial calcium regulation and AD has been studied extensively in different test systems. Despite the emerging role of mPS1 in AD, there is a paucity of information on the link between PS1 and neuronal cell death, a hallmark of AD. In the present study, we employed the selective mitochondrial uncoupler carbonyl cyanide chlorophenylhydrazone (CCCP) and compared reactivity of mPS1-transfected cultured rat hippocampal neurons with PS1 and control neurons, in situation of impaired mitochondrial functions. CCCP caused a slow rise in cytosolic and mitochondrial calcium in all three groups of neurons, with the mPS1 neurons demonstrating a higher and faster rise than that seen in PS1 neurons or controls. Consequently, mPS1 mitochondria were more depolarized by CCCP, measured by TMRM, a mitochondrial voltage indicator, than the other two groups. Morphologically, CCCP produced acute rise in filopodial density than the other two groups, which were similarly affected by the drug. Finally, mPS1 transfected neurons tended to die from prolonged exposure to CCCP, sooner than the other two groups. These results indicate that mPS1 neurons are associated with a lower ability to regulate excess cytosolic calcium.