Search

Senile plaques frequently contain Aβ-pE(3), a N-terminally truncated Aβ species that is more closely linked to AD compared to other Aβ species. Tau protein is highly phosphorylated at several residues in AD, and specifically phosphorylation at Ser202/Thr205 is known to be increased in AD. Several studies suggest that formation of plaques and tau phosphorylation might be linked to each other. To evaluate if Aβ-pE(3) and ptau Ser202/Thr205 levels correlate in human and transgenic AD mouse models, we analyzed human cortical and hippocampal brain tissue of different Braak stages as well as murine brain tissue of two transgenic mouse models for levels of Aβ-pE(3) and ptau Ser202/Thr205 and correlated the data. Our results show that Aβ-pE(3) formation is increased at early Braak stages while ptau Ser202/Thr205 mostly increases at later stages. Further analyses revealed strongest correlations between the two pathologies in the temporal, frontal, cingulate, and occipital cortex, however correlation in the hippocampus was weaker. Evaluation of murine transgenic brain tissue demonstrated a slow but steady increase of Aβ-pE(3) from 6 to 12 months of age in the cortex and hippocampus of APPSL mice, and a very early and strong Aβ-pE(3) increase in 5xFAD mice. ptau Ser202/Thr205 levels increased at the age of 9 months in APPSL mice and at 6 months in 5xFAD mice. Our results show that Aβ-pE(3) and ptau Ser202/Thr205 levels strongly correlate in human as well as murine tissues, suggesting that tau phosphorylation might be amplified by Aβ-pE(3)., Competing Interests: JN, MD, SF, TL and BHP are employees of QPS Austria GmbH. This does not alter our adherence to PLOS ONE policies on sharing data and materials. Vivoryon AG provided antibody msAβ-pE(3).

Alzheimer's disease can be modelled by different transgenic mouse strains. To gain deeper insight into disease model mechanisms, the previously described Tg4-42 mouse was analysed for transgene integration. On RNA/DNA level the transgene integration resulted in more than 20 copy numbers and further caused a deletion of exon 2 of the retinoic acid receptor beta. These findings were also confirmed on protein level with highly decreased retinoic acid receptor beta protein levels in homozygous Tg4-42 mice and may have an impact on the previously described phenotype of homozygous Tg4-42 mice to be solely dependent on amyloid-ß 4-42 expression. Since hemizygous mice show no changes in RARB protein levels it can be concluded that the previously described phenotype of these mice should not be affected by the retinoic acid receptor beta gene knockout. In order to fully understand the results of transgenesis, it is extremely advisable to determine the genome integration site and the basic structure of the inserted transgenes. This can be carried out for instance by next-generation sequencing techniques. Our results thus suggest that a detailed characterization of new disease models using the latest genomics technologies prior to functional studies could be a valuable tool to avoid an unexpected genetic influence on the animals' phenotype that is not only based on the inserted transgene. This would also significantly improve the selection of mouse models that are best suited for therapeutic development and basic research.

It is intriguing that a rare, inherited lysosomal storage disorder Niemann-Pick type C (NPC) shares similarities with Alzheimer's disease (AD). We have previously reported an enhanced processing of β-amyloid precursor protein (APP) by β-secretase (BACE1), a key enzyme in the pathogenesis of AD, in NPC1-null cells. In this work, we characterized regional and temporal expression and processing of the recently identified BACE1 substrates seizure protein 6 (Sez6) and seizure 6-like protein (Sez6L), and APP, in NPC1-/- (NPC1) and NPC1+/+ (wt) mouse brains. We analysed 4-weeks old brains to detect the earliest changes associated with NPC, and 10-weeks of age to identify changes at terminal disease stage. Sez6 and Sez6L were selected due to their predominant cleavage by BACE1, and their potential role in synaptic function that may contribute to presentation of seizures and/or motor impairments in NPC patients. While an enhanced BACE1-cleavage of all three substrates was detected in NPC1 vs. wt-mouse brains at 4-weeks of age, at 10-weeks increased proteolysis by BACE1 was observed for Sez6L in the cortex, hippocampus and cerebellum of NPC1-mice. Interestingly, both APP and Sez6L were found to be expressed in Purkinje neurons and their immunostaining was lost upon Purkinje cell neurodegeneration in 10-weeks old NPC1 mice. Furthermore, in NPC1- vs. wt-mouse primary cortical neurons, both Sez6 and Sez6L showed increased punctuate staining within the endolysosomal pathway as well as increased Sez6L and BACE1-positive puncta. This indicates that a trafficking defect within the endolysosomal pathway may play a key role in enhanced BACE1-proteolysis in NPC disease. Overall, our findings suggest that enhanced proteolysis by BACE1 could be a part of NPC disease pathogenesis. Understanding the basic biology of BACE1 and the functional impact of cleavage of its substrates is important to better evaluate the therapeutic potential of BACE1 against AD and, possibly, NPC disease., Competing Interests: The authors have declared that no competing interests exist.

Alzheimer's disease is characterized by accumulation of amyloid plaques and tau aggregates in several cortical brain regions. Tau phosphorylation causes formation of neurofibrillary tangles and neuropil threads. Phosphorylation at tau Ser202/Thr205 is well characterized since labeling of this site is used to assign Braak stage based on occurrence of neurofibrillary tangles. Only little is known about the spatial and temporal phosphorylation profile of other phosphorylated tau (ptau) sites. Here, we investigate total tau and ptau at residues Tyr18, Ser199, Ser202/Thr205, Thr231, Ser262, Ser396, Ser422 as well as amyloid-β plaques in human brain tissue of AD patients and controls. Allo- and isocortical brain regions were evaluated applying rater-independent automated quantification based on digital image analysis. We found that the level of ptau at several residues, like Ser199, Ser202/Thr205, and Ser422 was similar in healthy controls and Braak stages I to IV but was increased in Braak stage V/VI throughout the entire isocortex and transentorhinal cortex. Quantification of ThioS-stained plaques showed a similar pattern. Only tau phosphorylation at Tyr18 and Thr231 was already significantly increased in the transentorhinal region at Braak stage III/IV and hence showed a progressive increase with increasing Braak stages. Additionally, the increase in phosphorylation relative to controls was highest at Tyr18, Thr231 and Ser199. By contrast, Ser396 tau and Ser262 tau showed only a weak phosphorylation in all analyzed brain regions and only minor progression. Our results suggest that the ptau burden in the isocortex is comparable between all analyzed ptau sites when using a quantitative approach while levels of ptau at Tyr18 or Thr231 in the transentorhinal region are different between all Braak stages. Hence these sites could be crucial in the pathogenesis of AD already at early stages and therefore represent putative novel therapeutic targets.

Introduction: Amyloid-β (Aβ) aggregation is thought to be a major pathogenic event underlying the neuropathology of Alzheimer's disease (AD). The development of new drugs inhibiting the Aβ aggregation process is, therefore, important. SEN1500, an orally bioavailable and CNS-penetrant Aβ aggregation inhibitor, has previously been shown to reduce spatial learning and memory deficits in an APP transgenic mouse model. To verify that the pharmacological properties of SEN1500 are not unique to this model, we investigated brain Aβ pathology, neuroinflammation, as well as memory in a different mouse model of AD expressing the human amyloid precursor protein with Swedish and London mutations (APP SL )., Materials & Methods: APP SL transgenic mice and non-transgenic littermates were treated with SEN1500 via food pellets from three months of age for four months. At the end of the treatment, animals were tested for memory deficits using the contextual fear conditioning test and brain tissue was analyzed for soluble and insoluble amyloid-β1-38, -40, -42, β-amyloid plaques, β-sheet plaque cores, as well as for astrocytosis and activated microglia., Results: SEN1500 treatment lowered insoluble Aβ levels and β-amyloid plaque load in the brain compared with control-treated APP SL mice. Activated microglia were significantly reduced in the cortex but not the hippocampus of SEN1500-treated APP SL mice. Memory deficits of APP SL mice could not be rescued by SEN1500., Discussion: SEN1500 is not only able to reduce Aβ pathology and activated microglia but also to improve learning and memory as previously shown, making SEN1500 a potential candidate for human AD treatment. This Aβ aggregation inhibitor could be a promising therapeutic agent for the disease-modifying treatment of AD., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: Synucleinopathies such as Parkinson's disease or multiple system atrophy are characterized by Lewy bodies in distinct brain areas. These aggregates are mainly formed by α-synuclein inclusions, a protein crucial for synaptic functions in the healthy brain. Transgenic animal models of synucleinopathies are frequently based on over-expression of human wild type or mutated α-synuclein under the regulatory control of different promoters. A promising model is the Line 61 α-synuclein transgenic mouse that expresses the transgene under control of the Thy-1 promoter., Results: Here, we show an extended characterization of this mouse model over age. To this end, we analyzed animals for the progression of human and mouse protein expression levels in different brain areas as well as motor and memory deficits. Our results show, that Line 61 mice exhibited an age dependent increase of α-synuclein protein levels in the hippocampus but not the striatum. While murine α-synuclein was also increased with age, it was lower expressed in Line 61 mice than in non-transgenic littermates. At the age of 9 months animals exhibited increased neuroinflammation. Furthermore, we found that Line 61 mice showed severe motor deficits as early as 1 month of age as assessed by the wire hanging and nest building tests. At later ages, initial motor deficits were validated with the RotaRod, pasta gnawing and beam walk tests. At 8 months of age animals exhibited emotional memory deficits as validated with the contextual fear conditioning test., Conclusion: In summary, our results strengthen and further expand our knowledge about the Line 61 mouse model, emphasizing this mouse model as a valuable in vivo tool to test new compounds directed against synucleinopathies.

During their lifetime, people are commonly exposed to several vascular risk factors that may affect brain ageing and cognitive function. In the last few years, increasing evidence suggests that pathological plasma lipid profiles contribute to the pathogenesis of late-onset Alzheimer's disease. Importantly, hypercholesterolemia, especially elevated low-density lipoprotein cholesterol values, that is, increased apolipoprotein B-100 (ApoB-100) levels, represents an independent risk factor. In this study, the effects of ApoB-100 overexpression, either alone or in combination with cerebral expression of human amyloid precursor protein (hAPP), on cognitive functions and brain pathology were assessed. Our results show that ApoB-100 overexpression induces memory decline and increases cerebral lipid peroxidation and amyloid beta levels compared to those in wild-type animals. Although double-transgenic ApoBxAPP animals did not develop more distinct behavioral deficits than single-transgenic hAPP littermates, hApoB-100 expression caused additional pathophysiological features, such as high LDL and low HDL-cholesterol levels, increased lipid peroxidation, and pronounced ApoB-100 accumulation in cerebral vessels. Thus, our results indicate that ApoBxAPP mice might better reflect the situation of elderly humans than hAPPsl overexpression alone., (Copyright © 2013 Elsevier Inc. All rights reserved.)