Efficacy of chronic BACE1 inhibition in PS2APP mice depends on the regional A beta deposition rate and plaque burden at treatment initiation

Beta secretase (BACE) inhibitors are promising therapeutic compounds currently in clinical phase II/III trials. Preclinical [F-18]-florbetaben (FBB) amyloid PET imaging facilitates longitudinal monitoring of amyloidosis in Alzheimer's disease (AD) mouse models. Therefore, we applied this theranostic concept to investigate, by serial FBB PET, the efficacy of a novel BACE1 inhibitor in the PS2APP mouse, which is characterized by early and massive amyloid deposition. Methods: PS2APP and C57BU6 (WT) mice were assigned to treatment (PS2APP: N=13;WT: N=11) and vehicle control (PS2APP: N=13;WT: N=11) groups at the age of 9.5 months. All animals had a baseline PET scan and follow-up scans at two months and after completion of the four-month treatment period. In addition to this longitudinal analysis of cerebral amyloidosis by PET, we undertook biochemical amyloid peptide quantification and histological amyloid plaque analyses after the final PET session. Results: BACE1 inhibitor-treated transgenic mice revealed a progression of the frontal cortical amyloid signal by 8.4 +/- 2.2% during the whole treatment period, which was distinctly lower when compared to vehicle-treated mice (15.3 +/- 4.4%, p10% of the increase in controls showed only 40% attenuation with BACE1 inhibition. BACE1 inhibition in mice with lower amyloidosis at treatment initiation showed a higher efficacy in attenuating progression to PET. A predominant reduction of small plaques in treated mice indicated a main effect of BACE1 on inhibition of de novo amyloidogenesis. Conclusions: This theranostic study with BACE1 treatment in a transgenic AD model together with amyloid PET monitoring indicated that progression of amyloidosis is more effectively reduced in regions with low initial plaque development and revealed the need of an early treatment initiation during amyloidogenesis

β-secretase inhibition prevents structural spine plasticity deficits in AppNL-G-F mice

All clinical BACE1-inhibitor trials for the treatment of Alzheimer's Disease (AD) have failed due to insufficient efficacy or side effects like worsening of cognitive symptoms. However, the scientific evidence to date suggests that BACE1-inhibition could be an effective preventative measure if applied prior to the accumulation of amyloid-beta (Aβ)-peptide and resultant impairment of synaptic function. Preclinical studies have associated BACE1-inhibition-induced cognitive deficits with decreased dendritic spine density. Therefore, we investigated dose-dependent effects of BACE1-inhibition on hippocampal dendritic spine dynamics in an APP knock-in mouse line for the first time. We conducted in vivo two-photon microscopy in the stratum oriens layer of hippocampal CA1 neurons in 3.5-month-old AppNL-G-FGFP-M mice over 6 weeks to monitor the effect of potential preventive treatment with a high and low dose of the BACE1-inhibitor NB-360 on dendritic spine dynamics. Structural spine plasticity was severely impaired in untreated AppNL-G-FGFP-M mice, although spines were not yet showing signs of degeneration. Prolonged high-dose BACE1-inhibition significantly enhanced spine formation, improving spine dynamics in the AD mouse model. We conclude that in an early AD stage characterized by low Aβ-accumulation and no irreversible spine loss, BACE1-inhibition could hold the progressive synapse loss and cognitive decline by improving structural spine dynamics

BACE1 Inhibitor MK-8931 Alters Formation but Not Stability of Dendritic Spines

Beta-site amyloid-precursor-protein cleaving enzyme 1 (BACE1) is the rate limiting protease in the production of the amyloid-beta peptide (A beta), which is considered to be the causative agent in the pathogenesis of Alzheimer's Disease (AD). Therefore, the therapeutic potential of pharmacological BACE1 inhibitors is currently tested in clinical trials for AD treatment. To ensure a positive clinical outcome it is crucial to identify and evaluate adverse effects associated with BACE1 inhibition. Preclinical studies show that chronic blockade of BACE1 activity alters synaptic functions and leads to loss of dendritic spines. To assess the mechanism of synapse loss, dendritic spine dynamics of pyramidal layer V cells were monitored by in vivo two-photon microscopy in the somatosensory cortex of mice, treated with the BACE1 inhibitor MK-8931. MK-8931 treatment significantly reduced levels of A beta 40 and density of dendritic spines in the brain. However, the steady decline in dendritic spine density specifically resulted from a diminished formation of new spines and not from a loss of stable spines. Furthermore, the described effects on spine formation were transient and recovered after inhibitor withdrawal. Since MK-8931 inhibition did not completely abolish spine formation, our findings suggest that carefully dosed inhibitors might be therapeutically effective without affecting the structural integrity of excitatory synapses if given at an early disease stage

Increase of TREM2 during Aging of an Alzheimer's Disease Mouse Model Is Paralleled by Microglial Activation and Amyloidosis

Heterozygous missense mutations in the triggering receptor expressed on myeloid cells 2 (TREM2) have been reported to significantly increase the risk of developing Alzheimer's disease (AD). Since TREM2 is specifically expressed by microglia in the brain, we hypothesized that soluble TREM2 (sTREM2) levels may increase together with in vivo biomarkers of microglial activity and amyloidosis in an AD mouse model as assessed by small animal positron-emission-tomography (it PET). In this cross-sectional study, we examined a strong amyloid mouse model (PS2APP) of four age groups by mu PET with H-18-GE180 (glial activation) and F-18]-florbetaben (amyloidosis), followed by measurement of sTREM2 levels and amyloid levels in the brain. Pathology affected brain regions were compared between tracers (dice similarity coefficients) and pseudo-longitudinally. (PET results of both tracers were correlated with terminal TREM2 levels. The brain sTREM2 levels strongly increased with age of PS2APP mice (5 vs. 16 months: +211%, p 0.001), and correlated highly with mu PET signals of microglial activity (R = 0.89, p < 0.001) and amyloidosis (R = 0.92, p < 0.001). Dual p,,PET enabled regional mapping of glial activation and amyloidosis in the mouse brain, which progressed concertedly leading to a high overlap in aged PS2APP mice (dice similarity 67%). Together, these results substantiate the use of in vivo mu PET measurements in conjunction with post mortem sTREM2 in future anti-inflammatory treatment trials. Taking human data into account sTREM2 may increase during active amyloid deposition

MOVING: A User-Centric Platform for Online Literacy Training and Learning

Part of the Progress in IS book series (PROIS)In this paper, we present an overview of the MOVING platform, a user-driven approach that enables young researchers, decision makers, and public administrators to use machine learning and data mining tools to search, organize, and manage large-scale information sources on the web such as scientific publications, videos of research talks, and social media. In order to provide a concise overview of the platform, we focus on its front end, which is the MOVING web application. By presenting the main components of the web application, we illustrate what functionalities and capabilities the platform offer its end-users, rather than delving into the data analysis and machine learning technologies that make these functionalities possible

Chronic PPARγ Stimulation Shifts Amyloidosis to Higher Fibrillarity but Improves Cognition.

We undertook longitudinal β-amyloid positron emission tomography (Aβ-PET) imaging as a translational tool for monitoring of chronic treatment with the peroxisome proliferator-activated receptor gamma (PPARγ) agonist pioglitazone in Aβ model mice. We thus tested the hypothesis this treatment would rescue from increases of the Aβ-PET signal while promoting spatial learning and preservation of synaptic density. Here, we investigated longitudinally for 5 months PS2APP mice (N = 23; baseline age: 8 months) and App NL-G-F mice (N = 37; baseline age: 5 months) using Aβ-PET. Groups of mice were treated with pioglitazone or vehicle during the follow-up interval. We tested spatial memory performance and confirmed terminal PET findings by immunohistochemical and biochemistry analyses. Surprisingly, Aβ-PET and immunohistochemistry revealed a shift toward higher fibrillary composition of Aβ-plaques during upon chronic pioglitazone treatment. Nonetheless, synaptic density and spatial learning were improved in transgenic mice with pioglitazone treatment, in association with the increased plaque fibrillarity. These translational data suggest that a shift toward higher plaque fibrillarity protects cognitive function and brain integrity. Increases in the Aβ-PET signal upon immunomodulatory treatments targeting Aβ aggregation can thus be protective

Data on specificity of [F-18]GE180 uptake for TSPO expression in rodent brain and myocardium

Data in this article show radioligand uptake (to gamma counter and positron-emission-tomography) as well as polymerase chain reaction analyses of 18 kDa translocator protein (TSPO) quantification. We confirmed specificity of [F-18]GE180 binding of rodent brain and myocardium by blocking experiments with prior application of non-radioactive GE180, using dynamic in vivo positron emission-tomography and ex vivo gamma counter measurements. Expression of TSPO was compared between rodent brain and myocardium by quantitative polymerase chain reaction

Comparison of F-18-T807 and F-18-THK5117 PET in a Mouse Mode of Tau Pathology

Positron-emission-tomography (PET) imaging of tau pathology has facilitated development of anti-tau therapies. While members of the arylquinoline and pyridoindole families have been the most frequently used tau radioligands so far, analyses of their comparative performance in vivo are scantly documented. Here, we conducted a head-to-head PET comparison of the arylquinoline (18)FT807 and the pyridoindole (18)FTHK5117 PET in a mouse model of tau pathology. PET recordings were obtained in groups of (N = 5-7) P301S and wild-type (WT) mice at 6 and 9 months of age. Volume-of-interest based analysis (standard-uptake-value ratio, SUVR) was used to calculate effect sizes (Cohen's d) for each tracer and age. Statistical parametric mapping (SPM) was used to assess regional similarity (dice coefficient) of tracer binding alterations for the two tracers. Immunohistochemistry staining of neurofibrillary tangles was performed for validation ex vivo. Significantly elevated F-18-T807 binding in the brainstem of P301S mice was already evident at 6 months (+14%, p < 0.01, d = 1.64), and increased further at 9 months (+23%, p < 0.001, d = 2.70). F-18-THK5117 indicated weaker increases and effect sizes at 6 months (+5%, p < 0.05, d = 1.07) and 9 months (+10%, p < 0.001, d = 1.49). Regional similarity of binding of the two tracers was high (71%) at 9 months. F-18-T807 was more sensitive than F-18-THK5117 to tau pathology in this model, although both tracers present certain obstacles, which need to be considered in the design of longitudinal preclinical tau imaging studies

Untersuchung der Pharmakodynamik und Effektivität der präventiven BACE1‐Inhibierung gegen die Alzheimer Demenz unter Verwendung und Charakterisierung des APP‐Knock‐In Mausmodells

Die Alzheimer Demenz (AD) stellt im Zeitalter des demographischen Wandels global eine zunehmende medizinische, ökonomische und gesellschaftliche Herausforderung dar. Die Zahl der Betroffenen lag 2018 bei 50 Millionen Menschen weltweit, wobei sich diese Zahl laut Prognosen des „World Alzheimer Report 2018 “ bis 2050 verdreifachen wird. Die AD führt unter anderem zu einem progressiven Verlust kognitiver Funktionen und Gedächtnisleistungen sowie zu einer Atrophie bestimmter Hirnareale. Die Diagnoseverfahren zur Feststellung der chronischen, neurodegenerativen Erkrankung des zentralen Nervensystems werden stetig verbessert. Allerdings existieren derzeit weder präventive noch kurative Wirkstoffe, welche das Ausbrechen oder Fortschreiten der Krankheit unterbinden könnten. Einen Erklärungsansatz für die Entstehung der Alzheimer Demenz auf molekularer Ebene bietet die Amyloid‐Kaskaden‐Hypothese, welche als Ursache die Akkumulation und Aggregation des Amyloid‐Beta (Aβ)‐Peptids postuliert, wodurch fortführend Synapsen und Neurone geschädigt werden und degenerieren. Das Aβ‐Peptid entsteht durch die sequenzielle Spaltung des Amyloid‐Vorläufer‐Proteins (APP) durch die β‐Sekretase BACE1 und die γ‐Sekretase. In den letzten Jahrzehnten wurde deshalb intensiv die direkte Hemmung der BACE1‐Sekretase als Therapieansatz verfolgt, um eine Reduktion der Aβ‐Generierung zu bewirken. Äußerst wirksame, nicht‐peptidische BACE‐Inhibitoren wurden entwickelt und für klinische Studien zugelassen. Die klinischen Studien mussten allerdings aufgrund einer unzureichenden Wirkung des Inhibitors sowie infolge von Nebenwirkungen, wie der Verschlechterung der kognitiven Leistung, vorzeitig abgebrochen werden. Neuste Erkenntnisse legen die Vermutung nahe, dass eine therapeutische Intervention mittels BACE‐Inhibition in einem präklinischem AD‐Stadium und somit vor der Manifestierung klinischer Symptome erfolgen muss. Eine weitere Herausforderung wird es sein, eine ausgewogene BACE-Inhibitor Dosierung zu ermitteln, die Wirksamkeit und klinische Sicherheit gewährleistet. Im ersten Teil dieser Dissertation wurde der Verlauf und die Ausprägung der Pathologie des Knock‐In Alzheimer Mausmodells APPNL–G–F (APP‐Knock‐In) tiefergehend untersucht. Diese Untersuchung sollte klären, ob das APP‐Knock‐In Mausmodell ein frühes AD‐Stadium widerspiegelt und sich als Modell eignet, die Effektivität einer präventiven und ausgewogenen BACE‐Inhibitor Intervention zu ermitteln. Mittels Kleintier‐Positronen‐Emissions‐Tomographie (μPET) wurde eine parallele Zunahme der Aβ‐Last und der Neuroinflammation beobachtet. Die in vivo 2‐Photonen mikroskopischen Intervalluntersuchung dendritischer Spines des Stratum Oriens der CA1‐Region des Hippocampus zeigte eine Beeinträchtigung der strukturellen Plastizität der Postsynapsen abseits von Aβ‐Ablagerungen. Ein Rückgang in der Spine‐Dichte konnte allerdings nicht festgestellt werden. Diese Beobachtungen bieten einen möglichen Erklärungsansatz für die darüber hinaus observierten hippocampusabhängigen Lern‐ und Gedächtnisdefizite des APP‐Knock‐In Mausmodells im Morris‐Wasserlabyrinth. Zusammenfassend zeigten die Observierungen, dass das APP‐Knock‐In Mausmodell ein frühes Stadium der Alzheimer Demenz widerspiegelt. Im zweiten Teil der Arbeit wurde anschließend die Effektivität einer präventiven BACE‐Inhibition mittels des potenten BACE‐Inhibitors NB‐360 im APP‐Knock‐In Mausmodell untersucht. Zunächst wurde eine NB‐360‐Dosierung ermittelt, welche eine signifikante Hemmung der AD‐Pathologie im APP‐Knock‐In Mausmodell bewirkte ohne gravierende Nebenwirkungen auszulösen. Mittels Intravitalmikroskopischen Untersuchungen konnte beobachtet werden, dass die im APP‐Knock‐In Mausmodell observierte Beeinträchtigung der strukturellen Plastizität dendritischer Spines des Stratum oriens der CA1‐Region des Hippocampus abseits von Aβ‐Ablagerungen unter der frühzeitigen Intervention mittels einer hohen NB‐360‐Dosierung behoben werden konnte. Im Wildtyp bewirkte die hohe Dosierung des BACE‐Inhibitors NB‐360 allerdings eine signifikante Abnahme in der Bildung neuer dendritischer Spines. Unter einer niedrig dosierten NB‐360‐Behandlung wurde im APPKnock‐In Mausmodell kein signifikanter Effekt auf die strukturelle Plastizität dendritischer Spines beobachtet. Im Wildtyp waren die Ergebnisse unter der niedrigen NB‐360‐Behandlung nicht ganz eindeutig. Der Therapieansatz einer präventiven BACE‐Inhibition bedingt zudem eine langfristige Verabreichung des Inhibitors, weshalb anschließend die Langzeitapplikation der hohen NB‐360‐Dosierung auf die Entwicklung der Aβ‐Last sowie auf die Neuroiflammation mittels μPET untersucht wurde. Unter der präventiven und langfristigen BACE‐Inhibitor Behandlung konnte eine signifikante Senkung der kortikalen Aβ‐Last sowie der hippocampalen und kortikalen Neuroinflammation im APP‐Knock‐In Mausmodell beobachtet werden. Darüber hinaus wurde eine signifikante Verbesserung der kognitiven Leistung unter der langfristigen BACE‐Inhibitor Behandlung mittels NB‐360 festgestellt. Zusammenfassend zeigten diese Daten, dass die präventive BACE1‐Inhibition eine valide therapeutische Behandlung bei der Alzheimer Demenz darstellt ‐ Vorausgesetzt der Applikationszeitpunkt und die Dosierung des BACE1‐Inhibitors werden adäquat gewählt.In an age of demographic aging, Alzheimer’s dementia (AD) represents a global medical, economic and social challenge. In 2018, the number of people affected was 50 million worldwide and according to the World Alzheimer Report of 2018 this number will triple by 2050. AD is characterized by a progressive loss of cognitive functions as well as an atrophy of certain brain areas. Diagnostic procedures for detecting the chronic neurodegenerative disease of the central nervous system are constantly being improved. However, there are currently neither preventive nor curative therapeutic agents that could stop the onset or progression of the disease. An explanation for the development of Alzheimer’s dementia at the molecular level is provided by the amyloid‐cascade‐hypothesis, postulating the accumulation and aggregation of the amyloid‐beta (Aβ)‐peptide as the central pathogenic event, which is followed by synaptic and neuronal damage and degeneration. The Aβ‐peptide is produced by the sequential cleavage of the amyloid precursor protein (APP) by the β‐secretase BACE1 followed by the γ‐secretase. Therefore, the direct inhibition of the BACE1‐secretase has been intensively pursued in the last decades as a therapeutic approach to reduce the generation of Aβ. Highly effective, non‐peptidic BACE‐inhibitors have been developed and approved for clinical trials. However, the clinical trials had to be terminated prematurely due to an insufficient effect of the inhibitor as well as side effects such as cognitive worsening. Recent findings suggest that a therapeutic intervention targeting BACE1‐inhibition must be performed at a preclinical AD‐stage and thus before the onset of clinical symptoms. A further challenge will be to find a suitable therapeutic dosage of a BACE1‐inhibitor that reconciles both: efficacy and clinical safety. In the first part of this thesis, the course of AD‐pathology expressed by the knock‐in mouse model APPNL–G–F(APP‐knock‐in) was investigated in detail. Based on this investigation the efficacy of preventive BACE‐inhibitor treatment in this AD mouse model was evaluated in the second part of this study. The longitudinally monitoring of amyloidogenesis and neuroinflammation using small animal positron‐emission‐tomography (μPET) revealed a parallel increase in Aβ‐load and neuroinflammation in APP‐knock‐In mice. Investigating the structural plasticity of dendritic spines in the Stratum oriens of the CA1‐region of the hippocampus by using 2‐photon in vivo microscopy, a significant reduction in the formation of new dendritic spines was observed in the distance of Aβ‐deposits. A decrease in Spine‐Density was not detected. The in vivo detected impairment of synaptic plasticity also offers a possible explanation for the further observed hippocampus‐dependent learning and memory deficits in the APP‐knock‐in mouse model using the Morris water maze test. In summary, the observations confirmed that the mouse model reflects an early stage of Alzheimer’s dementia. In the second part of this thesis, the effectiveness of a preventive BACE‐inhibitor treatment in the APP‐knock‐in mouse model was analyzed. First APP‐knock‐in mice were treated with two different dosages of the potent, blood‐brain barrier penetrating BACE‐inhibitor NB‐360 to determine which dose successfully inhibits the AD‐pathology without side effects. Using intravital microscopy, it was observed that the high dosage of NB‐360 enhanced significantly the initial reduced spine‐formation rate in APP‐knock‐in mice. In wild type mice, the higher dosage of NB‐360 resulted in a significant decrease in the formation of new dendritic spines. No significant effect on the structural plasticity of dendritic spines was observed in the APP‐knock‐in mouse model under low‐dose NB360‐treatment. In wild type mice, the results were not entirely clear under the low dose NB360‐treatment. The therapeutic approach of a preventive BACE‐inhibitor treatment also requires long‐term administration of such a therapeutic agent. Therefore, the effects of a preventive, long‐term BACE‐inhibitor intervention, with the therapeutically effective high dosage of NB‐360, were investigated by monitoring the course of amyloidogenesis and neuroinflammation using longitudinal μPET‐imaging. The therapeutical approach of a preventive, long‐term BACEinhibition with the higher dosed NB‐360‐Inhibitor was able to significantly reduce the cortical Aβ‐load as well as the hippocampal and cortical neuroinflammation in the APP‐knockin mouse model. In addition, a significant improvement in cognitive performance was observed under long‐term BACE inhibitor treatment with high dosed NB‐360. In summary, these data showed that preventive BACE1‐inhibition is a valid therapeutic treatment for Alzheimer’s dementia ‐ provided that the timing and dosage of the BACE1‐inhibitor are appropriately chosen