[Show abstract][Hide abstract] ABSTRACT: Alzheimer´s disease (AD) is the most common neurodegenerative disorder. AD neuropathology is characterized by intracellular neurofibrillary tangles and extracellular β-amyloid deposits in the brain. To elucidate the complexity of AD pathogenesis a variety of transgenic mouse models have been generated. An ideal imaging system for monitoring β-amyloid plaque deposition in the brain of these animals should allow 3D-reconstructions of β-amyloid plaques via a single scan of an uncropped brain. Ultramicroscopy makes this possible by replacing mechanical slicing in standard histology by optical sectioning. It allows a time efficient analysis of the amyloid plaque distribution in the entire mouse brain with 3D cellular resolution. We herein labeled β-amyloid deposits in a transgenic mouse model of cerebral β-amyloidosis (APPPS1 transgenic mice) with two intraperitoneal injections of the amyloid-binding fluorescent dye methoxy-X04. Upon postmortem analysis the total number of β-amyloid plaques, the β-amyloid load (volume percent) and the amyloid plaque size distributions were measured in the frontal cortex of two age groups (2.5 versus 7-8.5 month old mice). Applying ultramicroscopy we found in a proof-of-principle study that the number of β-amyloid plaques increases with age. In our experiments we further observed an increase of large plaques in the older age group of mice. We demonstrate that ultramicroscopy is a fast, and accurate analysis technique for studying β-amyloid lesions in transgenic mice allowing the 3D staging of β-amyloid plaque development. This in turn is the basis to study neural network degeneration upon cerebral β-amyloidosis and to assess Aβ -targeting therapeutics.
PLoS ONE 05/2015; 10(5):e0125418. DOI:10.1371/journal.pone.0125418 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective. We examined the diagnostic value of subjective memory complaints (SMCs) assessed with a single item in a large cross-sectional cohort consisting of families with autosomal dominant Alzheimer’s disease (ADAD) participating in the Dominantly Inherited Alzheimer Network (DIAN). Methods. The baseline sample of 183 mutation carriers (MCs) and 117 noncarriers (NCs) was divided according to Clinical Dementia Rating (CDR) scale into preclinical (CDR 0; MCs: ; NCs: ), early symptomatic (CDR 0.5; MCs: ; NCs: ), and dementia stage (CDR ≥ 1; MCs: ; NCs: ). These groups were subdivided by the presence or absence of SMCs. Results. At CDR 0, SMCs were present in 12.1% of MCs and 9.2% of NCs . At CDR 0.5, SMCs were present in 66.7% of MCs and 62.5% of NCs . At CDR ≥ 1, SMCs were present in 96.4% of MCs. SMCs in MCs were significantly associated with CDR, logical memory scores, Geriatric Depression Scale, education, and estimated years to onset. Conclusions. The present study shows that SMCs assessed by a single-item scale have no diagnostic value to identify preclinical ADAD in asymptomatic individuals. These results demonstrate the need of further improvement of SMC measures that should be examined in large clinical trials.
BioMed Research International 04/2015; 2015. · 2.71 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mutations within the LRRK2 gene have been identified in Parkinson's disease (PD) patients and have been implicated in the dysfunction of several cellular pathways. Here, we explore how pathogenic mutations and the inhibition of LRRK2 kinase activity affect cytoskeleton dynamics in mouse and human cell systems. We generated and characterized a novel transgenic mouse model expressing physiological levels of human wild type and G2019S-mutant LRRK2. No neuronal loss or neurodegeneration was detected in midbrain dopamine neurons at the age of 12 months. Postnatal hippocampal neurons derived from transgenic mice showed no alterations in the seven parameters examined concerning neurite outgrowth sampled automatically on several hundred neurons using high content imaging. Treatment with the kinase inhibitor LRRK2-IN-1 resulted in no significant changes in the neurite outgrowth. In human fibroblasts we analyzed whether pathogenic LRRK2 mutations change cytoskeleton functions such as cell adhesion. To this end we compared the adhesion characteristics of human skin fibroblasts derived from six PD patients carrying one of three different pathogenic LRRK2 mutations and from four age-matched control individuals. The mutant LRRK2 variants as well as the inhibition of LRRK2 kinase activity did not reveal any significant cell adhesion differences in cultured fibroblasts. In summary, our results in both human and mouse cell systems suggest that neither the expression of wild type or mutant LRRK2, nor the inhibition of LRRK2 kinase activity affect neurite complexity and cellular adhesion.
PLoS ONE 04/2015; 10(4):e0118947. DOI:10.1371/journal.pone.0118947 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The prion paradigm has emerged as a unifying molecular principle for the pathogenesis of many age-related neurodegenerative diseases. This paradigm holds that a fundamental cause of specific disorders is the misfolding and seeded aggregation of certain proteins. The concept arose from the discovery that devastating brain diseases called spongiform encephalopathies are transmissible to new hosts by agents consisting solely of a misfolded protein, now known as the prion protein. Accordingly, "prion" was defined as a "proteinaceous infectious particle." As the concept has expanded to include other diseases, many of which are not infectious by any conventional definition, the designation of prions as infectious agents has become problematic. We propose to define prions as "proteinaceous nucleating particles" to highlight the molecular action of the agents, lessen unwarranted apprehension about the transmissibility of noninfectious proteopathies, and promote the wider acceptance of this revolutionary paradigm by the biomedical community. Expected final online publication date for the Annual Review of Neuroscience Volume 38 is July 08, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
[Show abstract][Hide abstract] ABSTRACT: Alzheimer Disease AD is a progressive neurodegenerative disorder, which is characterized by a variety of neuropathological abnormalities, such as the extracellular deposition of aggregated amyloid-‐beta peptide (Aβ) in the brain parenchyma. In brains of transgenic APPPS1 mice these β-‐amyloid deposits can be visualized and quantified by ultramicroscopy (UM) after staining by systemic dye loading and chemical clearing. We measured the total number of amyloid plaques, the amyloid load (volume percent) and the amyloid plaque size distributions in a defined volume in the frontal cortex of two age groups (2.5 versus 7.-‐8.5 mo). We demonstrate that UM is an easy, relative quick and direct method for counting uncropped β-amyloid deposits in 3D. Axons of motor and sensory neurons span long distances towards their targets. Tracing of these long nerves is a difficult task, as they are orientated in 3D, frequently split and generally do not take the shortest path to their target. In a neurodevelopmental project we applied UM to analyze axon guidance by growth factors as RET/GDNF. For this we visualized the topographic projections of motorneuron axons in the hind limb of mouse embryos.
11th Meeting of the German Neuroscience Society; 03/2015
[Show abstract][Hide abstract] ABSTRACT: An important early event in the pathogenesis of Alzheimer's disease (AD) is the aberrant polymerization and extracellular accumulation of amyloid-β peptide (Aβ). In young transgenic mice expressing the human Aβ-precursor protein (APP), deposits of Aβ can be induced by the inoculation of minute amounts of brain extract containing Aβ aggregates ("Aβ seeds"), indicative of a prion-like seeding phenomenon. Moreover, focal intracerebral injection of Aβ seeds can induce deposits not only in the immediate vicinity of the injection site, but, with time, also in distal regions of the brain. However, it remains uncertain whether the spatial progression of Aβ deposits occurs via nonsystematic diffusion from the injection site to proximal regions or via directed transit along neuroanatomical pathways. To address this question, we analyzed the spatiotemporal emergence of Aβ deposits in two different APP-transgenic mouse models that had been previously inoculated with Aβ seeds into the hippocampal formation. The results revealed a specific, neuroanatomically constrained pattern of induced Aβ deposits in structures corresponding to the limbic connectome, supporting the hypothesis that neuronal pathways act as conduits for the movement of proteopathic agents among brain regions, thereby facilitating the progression of disease.
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[Show abstract][Hide abstract] ABSTRACT: The dynamics of β-amyloid deposition and related second-order physiological effects, such as regional cerebral blood flow (rCBF), are key factors for a deeper understanding of Alzheimer's disease (AD). We present longitudinal in vivo data on the dynamics of β-amyloid deposition and the decline of rCBF in two different amyloid precursor protein (APP) transgenic mouse models of AD. Using a multiparametric positron emission tomography and magnetic resonance imaging approach, we demonstrate that in the presence of cerebral β-amyloid angiopathy (CAA), β-amyloid deposition is accompanied by a decline of rCBF. Loss of perfusion correlates with the growth of β-amyloid plaque burden but is not related to the number of CAA-induced microhemorrhages. However, in a mouse model of parenchymal β-amyloidosis and negligible CAA, rCBF is unchanged. Because synaptically driven spontaneous network activity is similar in both transgenic mouse strains, we conclude that the disease-related decline of rCBF is caused by CAA.
Nature Medicine 11/2014; 20(12). DOI:10.1038/nm.3734 · 28.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The soluble fraction of brain samples from patients with Alzheimer's disease contains highly biologically active amyloid-β seeds. In this study, we sought to assess the potency of soluble amyloid-β seeds derived from the brain and cerebrospinal fluid. Soluble Alzheimer's disease brain extracts were serially diluted and then injected into the hippocampus of young, APP transgenic mice. Eight months later, seeded amyloid-β deposition was evident even when the hippocampus received subattomole amounts of brain-derived amyloid-β. In contrast, cerebrospinal fluid from patients with Alzheimer's disease, which contained more than 10-fold higher levels of amyloid-β peptide than the most concentrated soluble brain extracts, did not induce detectable seeding activity in vivo. Similarly, cerebrospinal fluid from aged APP-transgenic donor mice failed to induce cerebral amyloid-β deposition. In comparison to the soluble brain fraction, cerebrospinal fluid largely lacked N-terminally truncated amyloid-β species and exhibited smaller amyloid-β-positive particles, features that may contribute to the lack of in vivo seeding by cerebrospinal fluid. Interestingly, the same cerebrospinal fluid showed at least some seeding activity in an in vitro assay. The present results indicate that the biological seeding activity of soluble amyloid-β species is orders of magnitude greater in brain extracts than in the cerebrospinal fluid.
[Show abstract][Hide abstract] ABSTRACT: Cerebral β-amyloidosis can be exogenously induced by the intracerebral injection of brain extracts containing aggregated β-amyloid (Aβ) into young, pre-depositing Aβ precursor protein- (APP) transgenic mice. Previous work has shown that the induction involves a prion-like seeding mechanism in which the seeding agent is aggregated Aβ itself. Here we report that the β-amyloid-inducing activity of Alzheimer's disease (AD) brain tissue or aged APP-transgenic mouse brain tissue is preserved, albeit with reduced efficacy, after formaldehyde fixation. Moreover, spectral analysis with amyloid conformation-sensitive luminescent conjugated oligothiophene dyes reveals that the strain-like properties of aggregated Aβ are maintained in fixed tissues. The resistance of Aβ seeds to inactivation and structural modification by formaldehyde underscores their remarkable durability, which in turn may contribute to their persistence and spread within the body. The present findings can be exploited to establish the relationship between the molecular structure of Aβ aggregates and the variable clinical features and disease progression of AD even in archived, formalin-fixed autopsy material.
[Show abstract][Hide abstract] ABSTRACT: Deposition of aggregated amyloid-β (Aβ) peptide in brain is an early event and hallmark pathology of Alzheimer's disease and cerebral Aβ angiopathy. Experimental evidence supports the concept that Aβ multimers can act as seeds and structurally corrupt other Aβ peptides by a self-propagating mechanism. Here we compare the induction of cerebral β-amyloidosis by intraperitoneal applications of Aβ-containing brain extracts in three Aβ-precursor protein (APP) transgenic mouse lines that differ in levels of transgene expression in brain and periphery (APP23 mice, APP23 mice lacking murine APP, and R1.40 mice). Results revealed that beta-amyloidosis induction, which could be blocked with an anti-Aβ antibody, was dependent on the amount of inoculated brain extract and on the level of APP/Aβ expression in the brain but not in the periphery. The induced Aβ deposits in brain occurred in a characteristic pattern consistent with the entry of Aβ seeds at multiple brain locations. Intraperitoneally injected Aβ could be detected in blood monocytes and some peripheral tissues (liver, spleen) up to 30 d after the injection but escaped histological and biochemical detection thereafter. These results suggest that intraperitoneally inoculated Aβ seeds are transported from the periphery to the brain in which corruptive templating of host Aβ occurs at multiple sites, most efficiently in regions with high availability of soluble Aβ.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 07/2014; 34(31):10264-10273. DOI:10.1523/JNEUROSCI.1608-14.2014 · 6.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Alzheimer's disease (AD) is characterized by neurotoxic amyloid-ß plaque formation in brain parenchyma and cerebral blood vessels known as cerebral amyloid angiopathy (CAA). Besides CAA, AD is strongly related to vascular diseases such as stroke and atherosclerosis. Cerebrovascular dysfunction occurs in AD patients leading to alterations in blood flow that might play an important role in AD pathology with neuronal loss and memory deficits. Platelets are the major players in hemostasis and thrombosis, but are also involved in neuroinflammatory diseases like AD. For many years, platelets were accepted as peripheral model to study the pathophysiology of AD because platelets display the enzymatic activities to generate amyloid-ß (Aß) peptides. In addition, platelets are considered to be a biomarker for early diagnosis of AD. Effects of Aß peptides on platelets and the impact of platelets in the progression of AD remained, however, ill-defined. The present study explored the cellular mechanisms triggered by Aß in platelets. Treatment of platelets with Aß led to platelet activation and enhanced generation of reactive oxygen species (ROS) and membrane scrambling, suggesting enhanced platelet apoptosis. More important, platelets modulate soluble Aß into fibrillar structures that were absorbed by apoptotic but not vital platelets. This together with enhanced platelet adhesion under flow ex vivo and in vivo and platelet accumulation at amyloid deposits of cerebral vessels of AD transgenic mice suggested that platelets are major contributors of CAA inducing platelet thrombus formation at vascular amyloid plaques leading to vessel occlusion critical for cerebrovascular events like stroke.
PLoS ONE 02/2014; 9(2):e90523. DOI:10.1371/journal.pone.0090523 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pathological, genetic, and biochemical hallmarks of Alzheimer's disease (AD) are linked to amyloid-β (Aβ) peptide aggregation. Especially misfolded Aβ42 peptide is sufficient to promote amyloid plaque formation. However, the cellular compartment facilitating the conversion of monomeric Aβ to aggregated toxic Aβ species remains unknown. In vitro models suggest lipid membranes to be the driving force of Aβ conversion. To this end, we generated two novel mouse models, expressing either membrane-anchored or nonanchored versions of the human Aβ42 peptide. Strikingly, membrane-anchored Aβ42 robustly accelerated Aβ deposition and exacerbated amyloid-associated toxicity upon crossing with Aβ precursor protein transgenic mice. These in vivo findings support the hypothesis that Aβ-membrane interactions play a pivotal role in early-onset AD as well as neuronal damage and provide evidence to study Aβ-membrane interactions as therapeutic targets.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 12/2013; 33(49):19284-94. DOI:10.1523/JNEUROSCI.2542-13.2013 · 6.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Dominantly Inherited Alzheimer's Network Trials Unit (DIAN-TU) was formed to direct the design and management of interventional therapeutic trials of international DIAN and autosomal dominant Alzheimer's disease (ADAD) participants. The goal of the DIAN-TU is to implement safe trials that have the highest likelihood of success while advancing scientific understanding of these diseases and clinical effects of proposed therapies. The DIAN-TU has launched a trial design that leverages the existing infrastructure of the ongoing DIAN observational study, takes advantage of a variety of drug targets, incorporates the latest results of biomarker and cognitive data collected during the observational study, and implements biomarkers measuring Alzheimer's disease (AD) biological processes to improve the efficiency of trial design. The DIAN-TU trial design is unique due to the sophisticated design of multiple drugs, multiple pharmaceutical partners, academics servings as sponsor, geographic distribution of a rare population and intensive safety and biomarker assessments. The implementation of the operational aspects such as home health research delivery, safety magnetic resonance imagings (MRIs) at remote locations, monitoring clinical and cognitive measures, and regulatory management involving multiple pharmaceutical sponsors of the complex DIAN-TU trial are described.
[Show abstract][Hide abstract] ABSTRACT: For several decades scientists have speculated that the key to understanding age-related neurodegenerative disorders may be found in the unusual biology of the prion diseases. Recently, owing largely to the advent of new disease models, this hypothesis has gained experimental momentum. In a remarkable variety of diseases, specific proteins have been found to misfold and aggregate into seeds that structurally corrupt like proteins, causing them to aggregate and form pathogenic assemblies ranging from small oligomers to large masses of amyloid. Proteinaceous seeds can therefore serve as self-propagating agents for the instigation and progression of disease. Alzheimer's disease and other cerebral proteopathies seem to arise from the de novo misfolding and sustained corruption of endogenous proteins, whereas prion diseases can also be infectious in origin. However, the outcome in all cases is the functional compromise of the nervous system, because the aggregated proteins gain a toxic function and/or lose their normal function. As a unifying pathogenic principle, the prion paradigm suggests broadly relevant therapeutic directions for a large class of currently intractable diseases.