Swedish Alzheimer's disease variant perturbs activity of retrograde molecular motors and causes widespread derangement of axonal transport pathways.

Experimental studies in flies, mice, and humans suggest a significant role of impaired axonal transport in the pathogenesis of Alzheimer's disease (AD). The mechanisms underlying these impairments in axonal transport, however, remain poorly understood. Here we report that the Swedish familial AD mutation causes a standstill of the amyloid precursor protein (APP) in the axons at the expense of its reduced anterograde transport. The standstill reflects the perturbed directionality of the axonal transport of APP, which spends significantly more time traveling in the retrograde direction. This ineffective movement is accompanied by an enhanced association of dynactin-1 with APP, which suggests that reduced anterograde transport of APP is the result of enhanced activation of the retrograde molecular motor dynein by dynactin-1. The impact of the Swedish mutation on axonal transport is not limited to the APP vesicles since it also reverses the directionality of a subset of early endosomes, which become enlarged and aberrantly accumulate in distal locations. In addition, it also reduces the trafficking of lysosomes due to their less effective retrograde movement. Altogether, our experiments suggest a pivotal involvement of retrograde molecular motors and transport in the mechanisms underlying impaired axonal transport in AD and reveal significantly more widespread derangement of axonal transport pathways in the pathogenesis of AD.

Immunotherapy targeting the C-terminal domain of TDP-43 decreases neuropathology and confers neuroprotection in mouse models of ALS/FTD.

Effective therapies are urgently needed to safely target TDP-43 pathology as it is closely associated with the onset and development of devastating diseases such as frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP) and amyotrophic lateral sclerosis (ALS). In addition, TDP-43 pathology is present as a co-pathology in other neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Our approach is to develop a TDP-43-specific immunotherapy that exploits Fc gamma-mediated removal mechanisms to limit neuronal damage while maintaining physiological TDP-43 function. Thus, using both in vitro mechanistic studies in conjunction with the rNLS8 and CamKIIa inoculation mouse models of TDP-43 proteinopathy, we identified the key targeting domain in TDP-43 to accomplish these therapeutic objectives. Targeting the C-terminal domain of TDP-43 but not the RNA recognition motifs (RRM) reduces TDP-43 pathology and avoids neuronal loss in vivo. We demonstrate that this rescue is dependent on Fc receptor-mediated immune complex uptake by microglia. Furthermore, monoclonal antibody (mAb) treatment enhances phagocytic capacity of ALS patient-derived microglia, providing a mechanism to restore the compromised phagocytic function in ALS and FTD patients. Importantly, these beneficial effects are achieved while preserving physiological TDP-43 activity. Our findings demonstrate that a mAb targeting the C-terminal domain of TDP-43 limits pathology and neurotoxicity, enabling clearance of misfolded TDP-43 through microglia engagement, and supporting the clinical strategy to target TDP-43 by immunotherapy. SIGNIFICANCE STATEMENT: TDP-43 pathology is associated with various devastating neurodegenerative disorders with high unmet medical needs such as frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS) and Alzheimer's disease. Thus, safely and effectively targeting pathological TDP-43 represents a key paradigm for biotechnical research as currently there is little in clinical development. After years of research, we have determined that targeting the C-terminal domain of TDP-43 rescues multiple patho-mechanisms involved in disease progression in two animal models of FTD/ALS. In parallel, importantly, our studies establish that this approach does not alter the physiological functions of this ubiquitously expressed and indispensable protein. Together, our findings substantially contribute to the understanding of TDP-43 pathobiology and support the prioritization for clinical testing of immunotherapy approaches targeting TDP-43.

Preclinical characterization and IND-enabling safety studies for PNT001, an antibody that recognizes cis-pT231 tau.

BACKGROUND: The cis-conformer of tau phosphorylated at threonine-231 (cis-pT231 tau) is hypothesized to contribute to tauopathies. PNT001 is a humanized, monoclonal antibody that recognizes cis-pT231 tau. PNT001 was characterized to assess clinical development readiness. METHODS: Affinity and selectivity were assessed by surface plasmon resonance and enzyme-linked immunosorbent assay. Immunohistochemistry (IHC) was performed with brain sections from human tauopathy patients and controls. Real-time quaking-induced conversion (RT-QuIC) was used to assess whether PNT001 reduced tau seeds from Tg4510 transgenic mouse brain. Murine PNT001 was evaluated in vivo in the Tg4510 mouse. RESULTS: The affinity of PNT001 for a cis-pT231 peptide was 0.3 to 3 nM. IHC revealed neurofibrillary tangle-like structures in tauopathy patients with no detectable staining in controls. Incubation of Tg4510 brain homogenates with PNT001 lowered seeding in RT-QuIC. Multiple endpoints were improved in the Tg4510 mouse. No adverse findings attributable to PNT001 were detected in Good Laboratory Practice safety studies. DISCUSSION: The data support clinical development of PNT001 in human tauopathies.

Development of GMP-1 a molecular chaperone network modulator protecting mitochondrial function and its assessment in fly and mice models of Alzheimer's disease.

Mitochondrial dysfunction is an early feature of Alzheimer's disease (AD) and may play an important role in the pathogenesis of disease. It has been shown that amyloid beta peptide (Aß) and amyloid precursor protein (APP) interact with mitochondria contributing to the mitochondrial dysfunction in AD. Prevention of abnormal protein targeting to mitochondria can protect normal mitochondrial function, increase neuronal survival and at the end, ameliorate symptoms of AD and other neurodegenerative disorders. First steps of mitochondrial protein import are coordinated by molecular chaperones Hsp70 and Hsp90 that bind to the newly synthesized mitochondria-destined proteins and deliver them to the protein import receptors on the surface of organelle. Here, we have described the development of a novel compound named GMP-1 that disrupts interactions between Hsp70/Hsp90 molecular chaperones and protein import receptor Tom70. GMP-1 treatment of SH-SY5Y cells results in decrease in mitochondria-associated APP and protects SH-SY5Y cells from toxic effect of Aß1-42 exposure. Experiments in drosophila and mice models of AD demonstrated neuroprotective effect of GMP-1 treatment, improvement in memory and behaviour tests as well as restoration of mitochondrial function.

Nortriptyline inhibits aggregation and neurotoxicity of alpha-synuclein by enhancing reconfiguration of the monomeric form.

The pathology of Parkinson's disease and other synucleinopathies is characterized by the formation of intracellular inclusions comprised primarily of misfolded, fibrillar α-synuclein (α-syn). One strategy to slow disease progression is to prevent the misfolding and aggregation of its native monomeric form. Here we present findings that support the contention that the tricyclic antidepressant compound nortriptyline (NOR) has disease-modifying potential for synucleinopathies. Findings from in vitro aggregation and kinetics assays support the view that NOR inhibits aggregation of α-syn by directly binding to the soluble, monomeric form, and by enhancing reconfiguration of the monomer, inhibits formation of toxic conformations of the protein. We go on to demonstrate that NOR inhibits the accumulation, aggregation and neurotoxicity of α-syn in multiple cell and animal models. These findings suggest that NOR, a compound with established safety and efficacy for treatment of depression, may slow progression of α-syn pathology by directly binding to soluble, native, α-syn, thereby inhibiting pathological aggregation and preserving its normal functions.

Late-stage α-synuclein accumulation in TNWT-61 mouse model of Parkinson's disease detected by diffusion kurtosis imaging.

Diffusion kurtosis imaging (DKI) by measuring non-Gaussian diffusion allows an accurate estimation of the distribution of water molecule displacement and may correctly characterize microstructural brain changes caused by neurodegeneration. The aim of this study was to evaluate the ability of DKI to detect changes induced by α-synuclein (α-syn) accumulation in α-syn over-expressing transgenic mice (TNWT-61) in both gray matter (GM) and white matter (WM) using region of interest (ROI) and tract-based spatial statistics analyses, respectively, and to explore the relationship between α-syn accumulation and DKI metrics in our regions of interest. Fourteen-month-old TNWT-61 mice and wild-type (WT) littermates underwent in vivo DKI scanning using the Bruker Avance 9.4 Tesla magnetic resonance imaging system. ROI analysis in the GM regions substantia nigra, striatum, hippocampus, sensorimotor cortex, and thalamus and tract-based spatial statistics analysis in WM were performed. Immunohistochemistry for α-syn was performed in TNWT-61 mice and correlated with DKI findings. We found increased kurtosis and decreased diffusivity values in GM regions such as the thalamus and sensorimotor cortex, and in WM regions such as the external and internal capsule, mamillothalamic tract, anterior commissure, cingulum, and corpus callosum in TNWT-61 mice as compared to WT mice. Furthermore, we report for the first time that α-syn accumulation is positively correlated with kurtosis and negatively correlated with diffusivity in the thalamus. The study provides evidence of an association between the amount of α-syn and the magnitude of DKI metric changes in the ROIs, with the potential of improving the clinical diagnosis of Parkinson's disease. We propose diffusion kurtosis imaging as a sensitive method for detecting human α-synuclein accumulation-induced changes in brain tissue, which may be reflective of Parkinson disease stage. Boxplots show the averaged mean kurtosis (orange) and mean diffusivity (blue) under the results of the analysis (*p < 0.05) in brains of wild-type (WT) and α-synuclein over-expressing (TNWT-61) mice. This approach might represent a novel biomarker for the early diagnosis of Parkinson's disease. Read the Editorial Highlight for this article on page 1117.

Influence of Lentiviral ß-Synuclein Overexpression in the Hippocampus of a Transgenic Mouse Model of Alzheimer's Disease on Amyloid Precursor Protein Metabolism and Pathology.

BACKGROUND: ß-Synuclein (ß-Syn) is a member of the highly homologous synuclein protein family. The most prominent family member, α-synuclein (α-Syn), abnormally accumulates in so-called Lewy bodies, one of the major pathological hallmarks of α-synucleinopathies. Notably, parts of the peptide backbone, called the nonamyloid component, are also found in amyloid plaques. However, ß-Syn seems to have beneficial effects by reducing α-Syn aggregation, and amyloid antiaggregatory activity has been described. OBJECTIVE: The aim of the study was to analyze if wild-type ß-Syn can counteract functional and pathological changes in a murine Alzheimer model over different time periods. METHODS: At the onset of pathology, lentiviral particles expressing human ß-Syn were injected into the hippocampus of transgenic mice overexpressing human amyloid precursor protein with Swedish and London mutations (APPSL). An empty vector served as the control. Behavioral analyses were performed 1, 3 and 6 months after injection followed by biochemical and histological examinations of brain samples. RESULTS: ß-Syn expression was locally concentrated and rather modest, but nevertheless changed its effect on APP expression and plaque load in a time- and concentration-dependent manner. Interestingly, the phosphorylation of glycogen synthase kinase 3 beta was enhanced in APPSL mice expressing human ß-Syn, but an inverse trend was observed in wild-type animals. CONCLUSION: The initially reported beneficial effects of ß-Syn could be partially reproduced, but locally elevated levels of ß-Syn might also cause neurodegeneration. To enlighten the controversial pathological mechanism of ß-Syn, further examinations considering the relationship between concentration and exposure time of ß-Syn are needed.

Neuroinflammation and related neuropathologies in APPSL mice: further value of this in vivo model of Alzheimer's disease.

BACKGROUND: Beyond cognitive decline, Alzheimer's disease (AD) is characterized by numerous neuropathological changes in the brain. Although animal models generally do not fully reflect the broad spectrum of disease-specific alterations, the APPSL mouse model is well known to display early plaque formation and to exhibit spatial learning and memory deficits. However, important neuropathological features, such as neuroinflammation and lipid peroxidation, and their progression over age, have not yet been described in this AD mouse model. METHODS: Hippocampal and neocortical tissues of APPSL mice at different ages were evaluated. One hemisphere from each mouse was examined for micro- and astrogliosis as well as concomitant plaque load. The other hemisphere was evaluated for lipid peroxidation (quantified by a thiobarbituric acid reactive substances (TBARS) assay), changes in Aß abundance (Aß38, Aß40 and Aß42 analyses), as well as determination of aggregated Aß content (Amorfix A4 assay). Finally, correlation analyses were performed to illustrate the time-dependent correlation between neuroinflammation and Aß load (soluble, insoluble, fibrils), or lipid peroxidation, respectively. RESULTS: As is consistent with previous findings, neuroinflammation starts early and shows strong progression over age in the APPSL mouse model. An analyses of concomitant Aß load and plaque deposition revealed a similar progression, and high correlations between neuroinflammation markers and soluble or insoluble Aß or fibrillar amyloid plaque loads were observed. Lipid peroxidation, as measured by TBARS levels, correlates well with neuroinflammation in the neocortex but not the hippocampus. The hippocampal lipid peroxidation correlated strongly with the increase of LOC positive fiber load, whereas neocortical TBARS levels were unrelated to amyloidosis. CONCLUSIONS: These data illustrate for the first time the progression of major AD related neuropathological features other than plaque load in the APPSL mouse model. Specifically, we demonstrate that microgliosis and astrocytosis are prominent aspects of this AD mouse model. The strong correlation of neuroinflammation with amyloid burden and lipid peroxidation underlines the importance of these pathological factors for the development of AD. The new finding of a different relation of lipid peroxidation in the hippocampus and neocortical regions show that the model might contribute to the understanding of complex pathological mechanisms and their interplay in AD.

Amyloid precursor protein induces reactive astrogliosis.

AIM: Astrocytes respond to stressors by acquiring a reactive state characterized by changes in their morphology and function. Molecules underlying reactive astrogliosis, however, remain largely unknown. Given that several studies observed increase in the Amyloid Precursor Protein (APP) in reactive astrocytes, we here test whether APP plays a role in reactive astrogliosis. METHODS: We investigated whether APP instigates reactive astroglios by examining in vitro and in vivo the morphology and function of naive and APP-deficient astrocytes in response to APP and well-established stressors. RESULTS: Overexpression of APP in cultured astrocytes led to remodeling of the intermediate filament network, enhancement of cytokine production, and activation of cellular programs centered around the interferon (IFN) pathway, all signs of reactive astrogliosis. Conversely, APP deletion abrogated remodeling of the intermediate filament network and blunted expression of IFN-stimulated gene products in response to lipopolysaccharide. Following traumatic brain injury (TBI), mouse reactive astrocytes also exhibited an association between APP and IFN, while APP deletion curbed the increase in glial fibrillary acidic protein observed canonically in astrocytes in response to TBI. CONCLUSIONS: The APP thus represents a candidate molecular inducer and regulator of reactive astrogliosis. This finding has implications for understanding pathophysiology of neurodegenerative and other diseases of the nervous system characterized by reactive astrogliosis and opens potential new therapeutic avenues targeting APP and its pathways to modulate reactive astrogliosis.

Time course and progression of wild type α-synuclein accumulation in a transgenic mouse model.

BACKGROUND: Progressive accumulation of α-synuclein (α-Syn) protein in different brain regions is a hallmark of synucleinopathic diseases, such as Parkinson's disease, dementia with Lewy bodies and multiple system atrophy. α-Syn transgenic mouse models have been developed to investigate the effects of α-Syn accumulation on behavioral deficits and neuropathology. However, the onset and progression of pathology in α-Syn transgenic mice have not been fully characterized. For this purpose we investigated the time course of behavioral deficits and neuropathology in PDGF-ß human wild type α-Syn transgenic mice (D-Line) between 3 and 12 months of age. RESULTS: These mice showed progressive impairment of motor coordination of the limbs that resulted in significant differences compared to non-transgenic littermates at 9 and 12 months of age. Biochemical and immunohistological analyses revealed constantly increasing levels of human α-Syn in different brain areas. Human α-Syn was expressed particularly in somata and neurites of a subset of neocortical and limbic system neurons. Most of these neurons showed immunoreactivity for phosphorylated human α-Syn confined to nuclei and perinuclear cytoplasm. Analyses of the phenotype of α-Syn expressing cells revealed strong expression in dopaminergic olfactory bulb neurons, subsets of GABAergic interneurons and glutamatergic principal cells throughout the telencephalon. We also found human α-Syn expression in immature neurons of both the ventricular zone and the rostral migratory stream, but not in the dentate gyrus. CONCLUSION: The present study demonstrates that the PDGF-ß α-Syn transgenic mouse model presents with early and progressive accumulation of human α-Syn that is accompanied by motor deficits. This information is essential for the design of therapeutical studies of synucleinopathies.

Amyloid precursor protein induces reactive astrogliosis.

We present in vitro and in vivo evidence demonstrating that Amyloid Precursor Protein (APP) acts as an essential instigator of reactive astrogliosis. Cell-specific overexpression of APP in cultured astrocytes led to remodelling of the intermediate filament network, enhancement of cytokine production and activation of cellular programs centred around the interferon (IFN) pathway, all signs of reactive astrogliosis. Conversely, APP deletion in cultured astrocytes abrogated remodelling of the intermediate filament network and blunted expression of IFN stimulated gene (ISG) products in response to lipopolysaccharide (LPS). Following traumatic brain injury (TBI), mouse reactive astrocytes also exhibited an association between APP and IFN, while APP deletion curbed the increase in glial fibrillary acidic protein (GFAP) observed canonically in astrocytes in response to TBI. Thus, APP represents a molecular inducer and regulator of reactive astrogliosis.

MRI in dementia.

With cognitive disorders increasingly common, clinicians urgently need faster and more accurate tools to classify such disorders and to noninvasively monitor therapeutic interventions. In this review, we provide information on MRI techniques that enable the study of the morphology, neuronal integrity, and metabolism of dementing illnesses. In addition, we explore the usefulness of such techniques as surrogate markers of these diseases.

BACE1-cleavage of Sez6 and Sez6L is elevated in Niemann-Pick type C disease mouse brains.

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 ß-amyloid precursor protein (APP) by ß-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.

Diffusion Kurtosis Imaging Detects Microstructural Alterations in Brain of α-Synuclein Overexpressing Transgenic Mouse Model of Parkinson's Disease: A Pilot Study.

Evidence suggests that accumulation and aggregation of α-synuclein contribute to the pathogenesis of Parkinson's disease (PD). The aim of this study was to evaluate whether diffusion kurtosis imaging (DKI) will provide a sensitive tool for differentiating between α-synuclein-overexpressing transgenic mouse model of PD (TNWT-61) and wild-type (WT) littermates. This experiment was designed as a proof-of-concept study and forms a part of a complex protocol and ongoing translational research. Nine-month-old TNWT-61 mice and age-matched WT littermates underwent behavioral tests to monitor motor impairment and MRI scanning using 9.4 Tesla system in vivo. Tract-based spatial statistics (TBSS) and the DKI protocol were used to compare the whole brain white matter of TNWT-61 and WT mice. In addition, region of interest (ROI) analysis was performed in gray matter regions such as substantia nigra, striatum, hippocampus, sensorimotor cortex, and thalamus known to show higher accumulation of α-synuclein. For the ROI analysis, both DKI (6 b-values) protocol and conventional (2 b-values) diffusion tensor imaging (cDTI) protocol were used. TNWT-61 mice showed significant impairment of motor coordination. With the DKI protocol, mean, axial, and radial kurtosis were found to be significantly elevated, whereas mean and radial diffusivity were decreased in the TNWT-61 group compared to that in the WT controls with both TBSS and ROI analysis. With the cDTI protocol, the ROI analysis showed decrease in all diffusivity parameters in TNWT-61 mice. The current study provides evidence that DKI by providing both kurtosis and diffusivity parameters gives unique information that is complementary to cDTI for in vivo detection of pathological changes that underlie PD-like symptomatology in TNWT-61 mouse model of PD. This result is a crucial step in search for a candidate diagnostic biomarker with translational potential and relevance for human studies.

Tracking of magnetite labeled nanoparticles in the rat brain using MRI.

This study was performed to explore the feasibility of tracing nanoparticles for drug transport in the healthy rat brain with a clinical MRI scanner. Phantom studies were performed to assess the R1 ( =  1/T1) relaxivity of different magnetically labeled nanoparticle (MLNP) formulations that were based on biodegradable human serum albumin and that were labeled with magnetite of different size. In vivo MRI measurements in 26 rats were done at 3T to study the effect and dynamics of MLNP uptake in the rat brain and body. In the brain, MLNPs induced T1 changes were quantitatively assessed by T1 relaxation time mapping in vivo and compared to post-mortem results from fluorescence imaging. Following intravenous injection of MLNPs, a visible MLNP uptake was seen in the liver and spleen while no visual effect was seen in the brain. However a histogram analysis of T1 changes in the brain demonstrated global and diffuse presence of MLNPs. The magnitude of these T1 changes scaled with post-mortem fluorescence intensity. This study demonstrates the feasibility of tracking even small amounts of magnetite labeled NPs with a sensitive histogram technique in the brain of a living rodent.

Increased efflux of amyloid-ß peptides through the blood-brain barrier by muscarinic acetylcholine receptor inhibition reduces pathological phenotypes in mouse models of brain amyloidosis.

The formation and accumulation of toxic amyloid-ß peptides (Aß) in the brain may drive the pathogenesis of Alzheimer's disease. Accordingly, disease-modifying therapies for Alzheimer's disease and related disorders could result from treatments regulating Aß homeostasis. Examples are the inhibition of production, misfolding, and accumulation of Aß or the enhancement of its clearance. Here we show that oral treatment with ACI-91 (Pirenzepine) dose-dependently reduced brain Aß burden in AßPPPS1, hAßPPSL, and AßPP/PS1 transgenic mice. A possible mechanism of action of ACI-91 may occur through selective inhibition of muscarinic acetylcholine receptors (AChR) on endothelial cells of brain microvessels and enhanced Aß peptide clearance across the blood-brain barrier. One month treatment with ACI-91 increased the clearance of intrathecally-injected Aß in plaque-bearing mice. ACI-91 also accelerated the clearance of brain-injected Aß in blood and peripheral tissues by favoring its urinal excretion. A single oral dose of ACI-91 reduced the half-life of interstitial Aß peptide in pre-plaque mhAßPP/PS1d mice. By extending our studies to an in vitro model, we showed that muscarinic AChR inhibition by ACI-91 and Darifenacin augmented the capacity of differentiated endothelial monolayers for active transport of Aß peptide. Finally, ACI-91 was found to consistently affect, in vitro and in vivo, the expression of endothelial cell genes involved in Aß transport across the Blood Brain Brain (BBB). Thus increased Aß clearance through the BBB may contribute to reduced Aß burden and associated phenotypes. Inhibition of muscarinic AChR restricted to the periphery may present a therapeutic advantage as it avoids adverse central cholinergic effects.

Impact of ApoB-100 expression on cognition and brain pathology in wild-type and hAPPsl mice.

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.

In vivo and ex vivo imaging of amyloid-ß cascade aggregates with a Pronucleon™ peptide.

Accumulation of amyloid-ß (Aß) cascade aggregates is considered a hallmark of Alzheimer's disease (AD). Current dogma holds that the appearance of Aß oligomers and larger aggregates occur many years prior to plaque formation associated with the advanced and irreparable neurocognitive decline characteristic of AD. This premise is the impetus to identify these Aß precursor structures prior to advanced plaque development. The Pronucleon™ technology platform is comprised of a novel series of engineered peptides that provide a unique readout when associated with beta-rich fiber and oligomeric Aß. This technology has been applied to Ex Vivo tissue sections and In Vivo mouse models of AD to determine the potential utility of these synthetic peptides as potential imaging agents. In Ex Vivo studies, the Pronucleon™ peptide binds plaque like structures in brain sections obtained from transgenic mice overexpressing hAPP with both the human Swedish and London Aß mutations. In Vivo, Pronucleon™ peptide administered peripherally can localize to the brain and label plaques throughout the brain in transgenic mice. Taken together, the data suggest that Pronucleon™ could provide a new imaging tool for Aß cascade elements that precede advanced plaque and fibril formation, thereby advancing early diagnosis and treatment opportunities.

Modulation of γ-secretase by EVP-0015962 reduces amyloid deposition and behavioral deficits in Tg2576 mice.

BACKGROUND: A hallmark of Alzheimer's disease is the presence of senile plaques in human brain primarily containing the amyloid peptides Aß42 and Aß40. Many drug discovery efforts have focused on decreasing the production of Aß42 through γ-secretase inhibition. However, identification of γ-secretase inhibitors has also uncovered mechanism-based side effects. One approach to circumvent these side effects has been modulation of γ-secretase to shift Aß production to favor shorter, less amyloidogenic peptides than Aß42, without affecting the overall cleavage efficiency of the enzyme. This approach, frequently called γ-secretase modulation, appears more promising and has lead to the development of new therapeutic candidates for disease modification in Alzheimer's disease. RESULTS: Here we describe EVP-0015962, a novel small molecule γ-secretase modulator. EVP-0015962 decreased Aß42 in H4 cells (IC50 = 67 nM) and increased the shorter Aß38 by 1.7 fold at the IC50 for lowering of Aß42. AßTotal, as well as other carboxyl-terminal fragments of amyloid precursor protein, were not changed. EVP-0015962 did not cause the accumulation of other γ-secretase substrates, such as the Notch and ephrin A4 receptors, whereas a γ-secretase inhibitor reduced processing of both. A single oral dose of EVP-0015962 (30 mg/kg) decreased Aß42 and did not alter AßTotal peptide levels in a dose-dependent manner in Tg2576 mouse brain at an age when overt Aß deposition was not present. In Tg2576 mice, chronic treatment with EVP-0015962 (20 or 60 mg/kg/day in a food formulation) reduced Aß aggregates, amyloid plaques, inflammatory markers, and cognitive deficits. CONCLUSIONS: EVP-0015962 is orally bioavailable, detected in brain, and a potent, selective γ-secretase modulator in vitro and in vivo. Chronic treatment with EVP-0015962 was well tolerated in mice and lowered the production of Aß42, attenuated memory deficits, and reduced Aß plaque formation and inflammation in Tg2576 transgenic animals. In summary, these data suggest that γ-secretase modulation with EVP-0015962 represents a viable therapeutic alternative for disease modification in Alzheimer's disease.

A longitudinal study of behavioral deficits in an AßPP transgenic mouse model of Alzheimer's disease.

Elucidating the age-dependent alterations in transgenic (Tg) mice overexpressing amyloid-ß protein precursor (AßPP) is important for understanding the pathogenesis of Alzheimer's disease (AD) and designing experimental therapies. Cross-studies have previously characterized some time-dependent behavioral and pathological alterations in AßPP Tg mice, however, a more comprehensive longitudinal study is needed to fully examine the progressive nature of behavioral deficits in these mice. In order to better understand the age- and gender-dependent progression of behavioral alterations, we performed a longitudinal study wherein Tg mice overexpressing human AßPP751 with the London (V717I) and Swedish (K670M/N671L) mutations under the regulatory control of the neuron specific murine (m)Thy-1 promoter (mThy1-hAßPP751) were behaviorally analyzed at 3 months and then re-tested at 6 and 9 months of age. The results show that there was an age-associated impairment in learning in the water maze task and habituation in the hole-board task. Motor coordination of the mThy1-hAßPP751 Tg mice was well-preserved throughout the investigated life span however, gender-specific deficits were observed in spontaneous activity and thigmotaxis. Neuropathologically, mThy1-hAßPP751 Tg mice displayed a progressive increase in the number of Aß plaques and mean plaque size in the cortex and hippocampus from 3 to 6 and from 6 to 9 months of age. Taken together, these results indicate that the mThy1-hAßPP751 Tg mice model AD from the early onset of the disease through to later stages, allowing them to be utilized at numerous points during the timeline for drug test designs.