The deposition of amyloid-? (A?) is one of the major neuropathological hallmarks of Alzheimer's disease (AD). In the case of sporadic AD, an imbalance in A? in production and clearance seems to be the reason for an enhanced A? accumulation. Besides a systematic clearance through the blood-brain barrier, A? is cleared from the brain by A?-degrading enzymes. The metalloprotease neprilysin (NEP) is an important A?-degrading enzyme as shown by numerous in vitro, in vivo, and reverse genetics studies. 5XFAD mice represent an early-onset AD mouse model which develops plaque pathology starting with 2 months of age in addition to robust behavioral deficits at later time points. By crossing 5XFAD mice with homozygous NEP-knock-out mice (NEP-/-), we show that hemizygous NEP deficiency aggravates the behavioral and neuropathological phenotype of 5XFAD mice. We found that 5XFAD mice per se showed strongly decreased NEP expression levels compared to wildtype mice, which was aggravated by NEP reduction. 5XFAD/NEP+/- mice demonstrated impairment in spatial working memory and increased astrocytosis in all studied brain areas, in addition to an overall increased level of soluble A?42 as well as region-specific increases in extracellular A? deposition. Surprisingly, in young mice, a more abundant cortical A? plaque pathology was observed in 5XFAD compared to 5XFAD/NEP+/- mice. Additionally, young 5XFAD/NEP+/- as well as hemi and homozygous NEP knockout mice showed elevated levels of endothelin-converting enzyme 1 (ECE1), suggesting a mutual regulation of ECE1 and NEP at young ages. The present data indicate that NEP mainly degrades soluble A? peptides, which confirms previous observations. Increased ECE1 levels correlated well with the strongly reduced extracellular plaque load in young 5XFAD/NEP+/- mice and might suggest a reciprocal effect between ECE and NEP activities in A? degradation.
The pathogenesis of Alzheimer's disease (AD) is believed to be closely dependent on deposits of neurotoxic amyloid-? peptides (A?), which become abundantly present throughout the central nervous system in advanced stages of the disease. The different A? peptides existing are generated by subsequent cleavage of the amyloid-? protein precursor (A?PP) and may vary in length and differ at their C-terminus. Despite extensive studies on the most prevalent species A?40 and A?42, A? peptides with other C-termini such as A?38 have not received much attention. In the present study, we used a highly specific and sensitive antibody against A?38 to analyze the distribution of this A? species in cases of sporadic and familial AD, as well as in the brains of a series of established transgenic AD mouse models. We found A?38 to be present as vascular deposits in the brains of the majority of sporadic AD cases, whereas it is largely absent in non-demented control cases. A?38-positive extracellular plaques were virtually limited to familial cases. Interestingly we observed A?38-positive plaques not only among familial cases due to A?PP mutations, but also in cases of familial AD caused by presenilin (PSEN) mutations. Furthermore we demonstrate that A?38 deposits in the form of extracellular plaques are common in several AD transgenic mouse models carrying either only A?PP, or combinations of A?PP, PSEN1, and tau transgenes.
Autosomal dominant familial Alzheimer's disease (AD) is associated with mutations in the A?PP, PSEN1, and PSEN2 genes. The clinical phenotype associated with A?PP mutations is mainly characterized by dementia or by strokes related to cerebral amyloid angiopathy (CAA). We present a comprehensive clinical, neuropathological, genetic, and biochemical study on a patient affected by familial AD associated with the I716F mutation in the A?PP gene. The clinical phenotype was characterized by early age of onset of 47 years, and rapidly progressive cerebellar ataxia, myoclonic jerks, rigidity, and dementia reminiscent of Creutzfeldt-Jakob disease (CJD), followed by a prolonged persistent vegetative state. Neuropathological evaluation of the proband revealed AD-related pathology but also ?-synucleinopathy compatible with dementia with Lewy bodies neocortical stage or Parkinson's disease corresponding to Braak stage 6. Tau-pathology in the form of neurofibrillary degeneration corresponded to stage VI according to the Braak classification. The severe A? pathology included CAA, numerous plaques, and deposition of N-truncated pyroglutamate-modified A? peptides. Remarkably, pyroglutamate A? oligomers were also present intracellularly in Purkinje cells corresponding to the ataxic phenotype. The detection of a CJD-like phenotype expands the spectrum of clinical presentations associated with familial AD. Our study supports the concept that the neuropathology of familial AD expands beyond the classical AD-related pathology as defined by plaques and tangles. Finally, we provide evidence for the first time that oligomeric pyroglutamate A? is present in a specific pattern correlating with the clinical symptoms of a patient with A?PP I716F mutation.
The objectives of this study were the evaluation of flexor tendon pulley rupture of the fingers in the crimp grip position using magnetic resonance imaging (MRI) and the comparison of the results with MRI in the neutral position in a cadaver study.
Although N-truncated A? variants are known to be the main constituent of amyloid plaques in the brains of patients with Alzheimer's disease, their potential as targets for pharmacological intervention has only recently been investigated. In the last few years, the Alzheimer field has experienced a paradigm shift with the ever increasing understanding that targeting amyloid plaques has not led to a successful immunotherapy. On the other hand, there can be no doubt that the amyloid cascade hypothesis is central to the etiology of Alzheimer's disease, raising the question as to why it is apparently failing to translate into the clinic. In this review, we aim to refocus the amyloid hypothesis integrating N-truncated A? peptides based on mounting evidence that they may represent better targets than full-length A?. In addition to A? peptides starting with an Asp at position 1, a variety of different N-truncated A? peptides have been identified starting with amino residue Ala-2, pyroglutamylated Glu-3, Phe-4, Arg-5, His-6, Asp-7, Ser-8, Gly-9, Tyr-10 and pyroglutamylated Glu-11. Certain forms of N-truncated species are better correlates for early pathological changes found pre-symptomatically more often than others. There is also evidence that, together with full-length A?, they might be physiologically detectable and are naturally secreted by neurons. Others are known to form soluble aggregates, which have neurotoxic properties in transgenic mouse models. It has been clearly demonstrated by several groups that some N-truncated A?s dominate full-length A? in the brains of Alzheimer's patients. We try to address which of the N-truncated variants may be promising therapeutic targets and which enzymes might be involved in the generation of these peptides.
According to the modified amyloid hypothesis the main event in the pathogenesis of Alzheimer's disease (AD) is the deposition of neurotoxic amyloid ?-peptide (A?) within neurons. Additionally to full-length peptides, a great diversity of N-truncated A? variants is derived from the larger amyloid precursor protein (APP). Vast evidence suggests that A?x??? isoforms play an important role triggering neurodegeneration due to its high abundance, amyloidogenic propensity and toxicity. Although N-truncated and A?x??? species have been pointed as crucial players in AD etiology, the A??-x isoforms have not received much attention.
Current histopathological classification and TNM staging have limited accuracy in predicting survival and stratifying patients for appropriate treatment. The goal of the study is to determine whether the expression pattern of functionally important regulatory proteins can add additional values for more accurate classification and prognostication of non-small lung cancer (NSCLC).
One of the central research questions on the etiology of Alzheimer's disease (AD) is the elucidation of the molecular signatures triggered by the amyloid cascade of pathological events. Next-generation sequencing allows the identification of genes involved in disease processes in an unbiased manner. We have combined this technique with the analysis of two AD mouse models: (1) The 5XFAD model develops early plaque formation, intraneuronal A? aggregation, neuron loss, and behavioral deficits. (2) The Tg4-42 model expresses N-truncated A?4-42 and develops neuron loss and behavioral deficits albeit without plaque formation. Our results show that learning and memory deficits in the Morris water maze and fear conditioning tasks in Tg4-42 mice at 12?months of age are similar to the deficits in 5XFAD animals. This suggested that comparative gene expression analysis between the models would allow the dissection of plaque-related and -unrelated disease relevant factors. Using deep sequencing differentially expressed genes (DEGs) were identified and subsequently verified by quantitative PCR. Nineteen DEGs were identified in pre-symptomatic young 5XFAD mice, and none in young Tg4-42 mice. In the aged cohort, 131 DEGs were found in 5XFAD and 56 DEGs in Tg4-42 mice. Many of the DEGs specific to the 5XFAD model belong to neuroinflammatory processes typically associated with plaques. Interestingly, 36 DEGs were identified in both mouse models indicating common disease pathways associated with behavioral deficits and neuron loss.
The amyloid hypothesis in Alzheimer disease (AD) considers amyloid ? peptide (A?) deposition causative in triggering down-stream events like neurofibrillary tangles, cell loss, vascular damage and memory decline. In the past years N-truncated A? peptides especially N-truncated pyroglutamate A?pE3-42 have been extensively studied. Together with full-length A?1-42 and A?1-40, N-truncated A?pE3-42 and A?4-42 are major variants in AD brain. Although A?4-42 has been known for a much longer time, there is a lack of studies addressing the question whether A?pE3-42 or A?4-42 may precede the other in Alzheimers disease pathology.
The Arctic mutation (p.E693G/p.E22G)fs within the ?-amyloid (A?) region of the ?-amyloid precursor protein gene causes an autosomal dominant disease with clinical picture of typical Alzheimers disease. Here we report the special character of Arctic AD neuropathology in four deceased patients.
Reductions in adult neurogenesis have been documented in the original 3xTg mouse model of Alzheimers disease (AD), notably occurring at the same age when spatial memory deficits and amyloid plaque pathology appeared. As this suggested reduced neurogenesis was associated with behavioral deficits, we tested whether activity and pharmacological stimulation could prevent memory deficits and modify neurogenesis and/or neuropathology in the 3xTg model backcrossed to the C57Bl/6 strain. We chronically administered the antidepressant fluoxetine to one group of mice, allowed access to a running wheel in another, and combined both treatments in a third cohort. All treatments lasted for 11 months. The female 3xTg mice failed to exhibit any deficits in spatial learning and memory as measured in the Morris water maze, indicating that when backcrossed to the C57Bl/6 strain, the 3xTg mice lost the behavioral phenotype that was present in the original 3xTg mouse maintained on a hybrid background. Despite this, the backcrossed 3xTg mice expressed prominent intraneuronal amyloid beta (A?) levels in the cortex and amygdala, with lower levels in the CA1 area of the hippocampus. In the combined cohort, fluoxetine treatment interfered with exercise and reduced the total distance run. The extent of A? neuropathology, the tau accumulations, or BDNF levels, were not altered by prolonged exercise. Thus, neuropathology was present but not paralleled by spatial memory deficits in the backcrossed 3xTg mouse model of AD. Prolonged exercise for 11 months did improve the long-term survival of newborn neurons generated during middle-age, whereas fluoxetine had no effect. We further review and discuss the relevant literature in this respect.
Give and take both: A bis(benzimidazolate)-capped biomimetic [2Fe-2S] cluster has been characterized in different protonation states, both in the diferric and mixed-valent forms. Protonation does not lead to structural changes of the [2Fe-2S] core, but facilitates its reduction and causes pronounced valence localization in the mixed-valent state. Concerted proton and electron transfer back to the diferric cluster emulates a key step in the function of mitochondrial Rieske proteins (see scheme).
To study the value of 3.0-Tesla magnetic resonance imaging for baseline and follow-up assessment of epiphyseal finger phalanx stress fractures in a collective of 7 consecutive adolescent climbing athletes.
The current review covers proteinopathies an umbrella term for neurodegenerative disorders that are characterized by the accumulation of specific proteins within neurons or in the brain parenchyma. Most prevalent examples for typical proteinopathies are Alzheimers disease and Parkinsons disease. In healthy brain, these proteins are unstructured as a monomer, serving most likely as the physiological form. In a disease condition, the unstructured proteins experience a conformational change leading to small oligomers that eventually will aggregate into higher order structures. Prion disease is an exception within the family of proteinopathies as the aggregated prion protein is highly infectious and can self-aggregate and propagate. Recent reports might implicate a prion-like spread of misfolded proteins in Alzheimers and Parkinsons disease; however there are evident differences in comparison to prion diseases. As proteinopathies are caused by the aggregation of disease-typical proteins with an ordered structure, active and passive immunization protocols have been used to expose model systems to therapeutic antibodies that bind to the aggregates thereby inhibiting the prolongation into higher ordered fibrils or dissolving the existing fibrillar structure. While most of the immunization treatments have been only carried out in preclinical model systems overexpressing the disease-relevant aggregating protein, other approaches are already in clinical testing. Taking the core concept of proteinopathies with conformationally altered protein aggregates into account, immunization appears to be a very promising therapeutic option for neurodegenerative disorders.
N-truncated A?4-42 is highly abundant in Alzheimer disease (AD) brain and was the first A? peptide discovered in AD plaques. However, a possible role in AD aetiology has largely been neglected. In the present report, we demonstrate that A?4-42 rapidly forms aggregates possessing a high aggregation propensity in terms of monomer consumption and oligomer formation. Short-term treatment of primary cortical neurons indicated that A?4-42 is as toxic as pyroglutamate A?3-42 and A?1-42. In line with these findings, treatment of wildtype mice using intraventricular A? injection induced significant working memory deficits with A?4-42, pyroglutamate A?3-42 and A?1-42. Transgenic mice expressing A?4-42 (Tg4-42 transgenic line) developed a massive CA1 pyramidal neuron loss in the hippocampus. The hippocampus-specific expression of A?4-42 correlates well with age-dependent spatial reference memory deficits assessed by the Morris water maze test. Our findings indicate that N-truncated A?4-42 triggers acute and long-lasting behavioral deficits comparable to AD typical memory dysfunction.
There is pivotal evidence that tau pathology can be triggered by amyloid-? (A?) pathology in experimental systems. On the other side, studies on human brain specimen have elucidated that tau pathology may occur before amyloid pathology is present indicating that in principle tau pathology could also trigger A? aggregation. To address this question, we have crossed 5XFAD mice coexpressing human mutant APP695 with the Swedish, Florida, and London mutations and human mutant presenilin-1 (PS1) with the M146L and L286V mutations with the PS19 model overexpressing human mutant tau with the P301S mutation. The resulting triple transgenic model 5XFAD/PS19 has been characterized at 3 and 9 months of age. A dramatic aggravation of hyperphosphorylated tau pathology together with a dramatically increased inflammatory response and a loss of synapses and hippocampal CA1 neurons in aged 5XFAD/PS19 mice were observed. Extracellular amyloid deposits were unaltered. These data support the assumption of tau pathology being downstream of amyloid pathology, suggesting that both pathologies together trigger the severe neuron loss in the hippocampus in the 5XFAD/PS19 mouse model.
The progressive accumulation of extracellular amyloid plaques in the brain is a common hallmark of Alzheimers disease (AD). We recently identified a novel species of A? phosphorylated at serine residue 8 with increased propensity to form toxic aggregates as compared to non-phosphorylated species. The age-dependent analysis of A? depositions using novel monoclonal phosphorylation-state specific antibodies revealed that phosphorylated A? variants accumulate first inside of neurons in a mouse model of AD already at 2 month of age. At higher ages, phosphorylated A? is also abundantly detected in extracellular plaques. Besides a large overlap in the spatiotemporal deposition of phosphorylated and non-phosphorylated A? species, fractionized extraction of A? from brains revealed an increased accumulation of phosphorylated A? in oligomeric assemblies as compared to non-phosphorylated A? in vivo. Thus, phosphorylated A? could represent an important species in the formation and stabilization of neurotoxic aggregates, and might be targeted for AD therapy and diagnosis.
Pyroglutamate-modified amyloid-? (A?(pE3)) peptides are gaining considerable attention as potential key participants in the pathology of Alzheimer disease (AD) due to their abundance in AD brain, high aggregation propensity, stability, and cellular toxicity. Transgenic mice that produce high levels of A?(pE3-42) show severe neuron loss. Recent in vitro and in vivo experiments have proven that the enzyme glutaminyl cyclase catalyzes the formation of A?(pE3). In this minireview, we summarize the current knowledge on A?(pE3), discussing its discovery, biochemical properties, molecular events determining formation, prevalence in the brains of AD patients, Alzheimer mouse models, and potential as a target for therapy and as a diagnostic marker.
Laser treatment of benign prostatic obstruction (BPO) has become more prevalent in recent years. Although multiple surgical approaches exist, there is confusion about laser-tissue interaction, especially in terms of physical aspects and with respect to the optimal treatment modality.
In the present review, we summarize the current achievements of modelling early intraneuronal A? (amyloid ?-peptide) accumulation in transgenic mice with the resulting pathological consequences. Of special importance will be to discuss recent developments and the translation of the results to AD (Alzheimers disease). N-terminally truncated A?pE3 (A? starting with pyroglutamate at position 3) represents a major fraction of all A? peptides in the brain of AD patients. Recently, we generated a novel mAb (monoclonal antibody), 9D5, that selectively recognizes oligomeric assemblies of A?pE3 and demonstrated the potential involvement of oligomeric A?pE3 in vivo using transgenic mouse models as well as human brains from sporadic and familial AD cases. 9D5 showed an unusual staining pattern with almost non-detectable plaques in sporadic AD patients and non-demented controls. Interestingly, in sporadic and familial AD cases prominent intraneuronal staining was observed. Moreover, passive immunization of 5XFAD mice with 9D5 significantly reduced overall A? levels and stabilized behavioural deficits. In summary, we have demonstrated that intraneuronal A? is a valid risk factor in model systems and AD patients. This feature of AD pathology was successful in identifying novel low-molecular-mass oligomeric A?-specific antibodies for diagnosis and therapy.
Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) that has been reported to reduce the risk of developing Alzheimers disease (AD). Its preventive effects in AD are likely pleiotropic as ibuprofen displays both anti-inflammatory activity by inhibition of cyclooxygenases and anti-amyloidogenic activity by modulation of ?-secretase. In order to study the anti-inflammatory properties of ibuprofen independent of its anti-amyloidogenic activity, we performed a long-term treatment study with ibuprofen in 5XFAD mice expressing a presenilin-1 mutation that renders this AD model resistant to ?-secretase modulation. As expected, ibuprofen treatment for 3 months resulted in a reduction of the inflammatory reaction in the 5XFAD mouse model. Importantly, an unchanged amyloid beta (A?) plaque load, an increase in soluble A?42 levels, and an aggravation of some behavioral parameters were noted, raising the question whether suppression of inflammation by nonsteroidal anti-inflammatory drug is beneficial in AD.
Pyroglutamate-modified A? (A?pE3-42) peptides are gaining considerable attention as potential key players in the pathology of Alzheimer disease (AD) due to their abundance in AD brain, high aggregation propensity, stability, and cellular toxicity. Overexpressing A?pE3-42 induced a severe neuron loss and neurological phenotype in TBA2 mice. In vitro and in vivo experiments have recently proven that the enzyme glutaminyl cyclase (QC) catalyzes the formation of A?pE3-42. The aim of the present work was to analyze the role of QC in an AD mouse model with abundant A?pE3-42 formation. 5XFAD mice were crossed with transgenic mice expressing human QC (hQC) under the control of the Thy1 promoter. 5XFAD/hQC bigenic mice showed significant elevation in TBS, SDS, and formic acid-soluble A?pE3-42 peptides and aggregation in plaques. In 6-month-old 5XFAD/hQC mice, a significant motor and working memory impairment developed compared with 5XFAD. The contribution of endogenous QC was studied by generating 5XFAD/QC-KO mice (mouse QC knock-out). 5XFAD/QC-KO mice showed a significant rescue of the wild-type mice behavioral phenotype, demonstrating the important contribution of endogenous mouse QC and transgenic overexpressed QC. These data clearly demonstrate that QC is crucial for modulating A?pE3-42 levels in vivo and prove on a genetic base the concept that reduction of QC activity is a promising new therapeutic approach for AD.
N-terminally truncated A? peptides starting with pyroglutamate (A?pE3) represent a major fraction of all A? peptides in the brain of Alzheimer disease (AD) patients. A?pE3 has a higher aggregation propensity and stability and shows increased toxicity compared with full-length A?. In the present work, we generated a novel monoclonal antibody (9D5) that selectively recognizes oligomeric assemblies of A?pE3 and studied the potential involvement of oligomeric A?pE3 in vivo using transgenic mouse models as well as human brains from sporadic and familial AD cases. 9D5 showed an unusual staining pattern with almost nondetectable plaques in sporadic AD patients and non-demented controls. Interestingly, in sporadic and familial AD cases prominent intraneuronal and blood vessel staining was observed. Using a novel sandwich ELISA significantly decreased levels of oligomers in plasma samples from patients with AD compared with healthy controls were identified. Moreover, passive immunization of 5XFAD mice with 9D5 significantly reduced overall A? plaque load and A?pE3 levels, and normalized behavioral deficits. These data indicate that 9D5 is a therapeutically and diagnostically effective monoclonal antibody targeting low molecular weight A?pE3 oligomers.
The disturbed metabolism of beta-amyloid peptides generated from amyloid precursor protein is widely considered as a main factor during the pathogenesis of Alzheimers disease. A neuropathological hallmark in the brains from cases with Alzheimers disease are senile plaques mainly composed of hardly soluble beta-amyloid peptides comprising up to 43 amino acids. Age-dependent cortical beta-amyloidosis was also shown in several transgenic mice and old individuals from various mammalian species, e.g., non-human primates. Beta-amyloid(1-42) is believed to be the main component in the core of senile plaques, whereas less hydrophobic beta-amyloid(1-40) predominantly occurs in the outer rim of plaques. Amino-terminally truncated pyroglutamyl-beta-amyloid(pE3-x) was recently found to be a beta-amyloid species of high relevance to the progression of the disease. While a few biochemical studies provided data on the co-occurrence of several beta-amyloid forms, their concomitant histochemical detection is still lacking. Here, we present a novel triple immunofluorescence labelling of amino- and differently carboxy-terminally truncated beta-amyloid peptides in cortical plaques from a case with Alzheimers disease, senile macaques and baboons, and triple transgenic mice with age-dependent beta-amyloidosis and tau hyperphosphorylation. Additionally, beta-amyloid(pE3-x) and total beta-amyloid were concomitantly detected with beta-amyloid peptides ending with amino acid 40 or 42, respectively. Simultaneous staining of several beta-amyloid species reveals for instance vascular amyloid containing beta-amyloid(pE3-x) in Alzheimers disease and monkeys, and may contribute to the further elucidation of beta-amyloidosis in neurodegenerative disorders and animal models.
The beta-amyloid precursor protein (APP) represents a type I transmembrane glycoprotein that is ubiquitously expressed. In the brain, it is a key player in the molecular pathogenesis of Alzheimer disease. Its physiological function is however less well understood. Previous studies showed that APP is up-regulated in prostate, colon, pancreatic tumor, and oral squamous cell carcinoma. In this study, we show that APP has an essential role in growth control of pancreatic and colon cancer. Abundant APP staining was found in human pancreatic adenocarcinoma and colon cancer tissue. Interestingly, treating pancreatic and colon cancer cells with valproic acid (VPA, 2-propylpentanoic acid), a known histone deacetylase (HDAC) inhibitor, leads to up-regulation of GRP78, an endoplasmic reticulum chaperone immunoglobulin-binding protein. GRP78 is involved in APP maturation and inhibition of tumor cell growth by down-regulation of APP and secreted soluble APPalpha. Trichostatin A, a pan-HDAC inhibitor, also lowered APP and increased GRP78 levels. In contrast, treating cells with valpromide, a VPA derivative lacking HDAC inhibitory properties, had no effect on APP levels. VPA did not modify the level of epidermal growth factor receptor, another type I transmembrane protein, and APLP2, a member of the APP family, demonstrating the specificity of the VPA effect on APP. Small interfering RNA-mediated knockdown of APP also resulted in significantly decreased cell growth. Based on these observations, the data suggest that APP down-regulation via HDAC inhibition provides a novel mechanism for pancreatic and colon cancer therapy.
Environmental enrichment has been used in a variety of transgenic mouse models of Alzheimers disease (AD), however, with conflicting results. Here we studied the influence of environmental enrichment in a severely affected AD mouse model, showing a multiplicity of pathological alterations including hippocampal neuron loss. APP/PS1KI and wild type (WT) control mice were housed under standard conditions or in enriched cages equipped with various objects and running wheels. Amyloid plaque load, motor and working memory performance, axonopathy, as well as CA1 neuron number and hippocampal neurogenesis were assessed. Although a partial improvement in motor performance was observed, 4 months of enriched housing showed no beneficial effects in terms of working memory, A? plaque pathology, or neuron loss in APP/PS1KI mice. In addition, no changes in hippocampal neurogenesis and even an aggravation of the axonal phenotype were detected with a tendency toward a premature death. The APP/PS1KI model represents a model for mild to severe AD showing early behavioral deficits starting at 2 months of age with fast deterioration. Therefore our data might suggest that physical activity and enriched environment might be more beneficial in patients with mild cognitive impairment than in patients with incipient AD.
Despite of long-standing evidence that beta-amyloid (Abeta) peptides have detrimental effects on synaptic function, the relationship between Abeta, synaptic and neuron loss is largely unclear. During the last years there is growing evidence that early intraneuronal accumulation of Abeta peptides is one of the key events leading to synaptic and neuronal dysfunction. Many studies have been carried out using transgenic mouse models of Alzheimers disease (AD) which have been proven to be valuable model systems in modern AD research. The present review discusses the impact of intraneuronal Abeta accumulation on synaptic impairment and neuron loss and provides an overview of currently available AD mouse models showing these pathological alterations.
In the present report, we extend previous findings in the 5XFAD mouse model and demonstrate that these mice develop an age-dependent motor phenotype in addition to working memory deficits and reduced anxiety levels as demonstrated in an elevated plus maze task. Employing a variety of N- and C-terminal specific A? antibodies, abundant intraneuronal and plaque-associated pathology, including accumulation of pyroglutamate A?, was observed as early as the age of 3 months. Using unbiased stereology, we demonstrate that the 5XFAD mice develop a significant selective neuron loss in layer 5 of the cortex, leaving the overall neuron number of the total frontal cortex and hippocampus unaffected. This observation coincides with the accumulation of intraneuronal A? peptides only in cortical Layer 5, but not in CA1, despite comparable APP expression levels. The motor phenotype correlates with abundant spinal cord pathology, as demonstrated by abundant intraneuronal A? accumulation and extracellular plaque deposition. In addition, comparable to the APP/PS1KI mouse model, 5XFAD mice develop an age-dependent axonopathy likely contributing to the behavioral deficits.
In contrast to extracellular plaque and intracellular tangle pathology, the presence and relevance of intraneuronal Abeta in Alzheimers disease (AD) is still a matter of debate. Human brain tissue offers technical challenges such as post-mortem delay and uneven or prolonged tissue fixation that might affect immunohistochemical staining. In addition, previous studies on intracellular Abeta accumulation in human brain often used antibodies targeting the C-terminus of Abeta and differed strongly in the pretreatments used. To overcome these inconsistencies, we performed extensive parametrical testing using a highly specific N-terminal Abeta antibody detecting the aspartate at position 1, before developing an optimal staining protocol for intraneuronal Abeta detection in paraffin-embedded sections from AD patients. To rule out that this antibody also detects the beta-cleaved APP C-terminal fragment (beta-CTF, C99) bearing the same epitope, paraffin-sections of transgenic mice overexpressing the C99-fragment were stained without any evidence for cross-reactivity in our staining protocol. The staining intensity of intraneuronal Abeta in cortex and hippocampal tissue of 10 controls and 20 sporadic AD cases was then correlated to patient data including sex, Braak stage, plaque load, and apolipoprotein E (ApoE) genotype. In particular, the presence of one or two ApoE4 alleles strongly correlated with an increased accumulation of intraneuronal Abeta peptides. Given that ApoE4 is a major genetic risk factor for AD and is involved in neuronal cholesterol transport, it is tempting to speculate that perturbed intracellular trafficking is involved in the increased intraneuronal Abeta aggregation in AD.
The staining protocols so far applied to study intracellular Abeta accumulation in human tissue have been inconsistent with varying use of heat and formic acid (FA) for antigen retrieval. Microwave heat treatment has been reported to enhance the staining of intraneuronal Abeta as compared to no or enzymatic pretreatment. FA is widely used to increase the staining of plaque pathology in AD, yet the effect of FA on intraneuronal Abeta staining has been reported to be low and similar to the effect of heat or even to counteract the enhancing effect of heat pretreatment on intraneuronal Abeta immunohistochemical detection. To overcome these inconsistencies, there is a need for optimization of the staining protocol for intraneuronal Abeta detection and more knowledge is required concerning the effects of the different antigen retrieval methods. In the present work, we optimized the staining protocol for intraneuronal Abeta in paraffin-embedded sections in relation to heat and FA using four different mouse models known to accumulate intraneuronal Abeta peptides. It was found that FA is essential for the staining of highly aggregated intraneuronal Abeta peptides in AD transgenic mouse tissue.
Perioperative haemorrhage is still the major complication of transurethral resection of the prostate (TURP) for benign enlargement of the prostate. Photoselective vaporisation of the prostate (PVP) with the potassium-titanyl-phosphate (KTP) laser has been shown to achieve instant tissue ablation with excellent haemostatic properties. Our aim was to determine the tissue removal capacity, coagulation and haemostatic property of the novel 1,470 nm diode laser, ex vivo and in vivo. We evaluated two prototype diode laser systems at 1,470 nm in an ex vivo, isolated, blood-perfused, porcine kidney model (n = 5; 10 W-50 W) and in an in vivo investigation of beagle prostate (n = 4; 100 W) to assess vaporisation capacities and coagulation properties at different generator settings. The diode laser evaluation was compared with an 80 W KTP laser in the porcine model. After the laser treatment we performed a histological examination to compare the depth of coagulation and vaporisation. The diode laser system (50 W) showed significantly lower (P < 0.0001) capacities for tissue removal than the 80 W KTP laser (0.96 mm +/- 0.17 mm and 5.93 mm +/- 0.25 mm, respectively, P < 0.0001), while coagulation zones were significantly (P < 0.001) larger in diode laser-treated kidneys (3,39 mm +/- 0.93 mm and 1.27 mm +/- 0.13 mm, respectively). In vivo, the diode laser displayed rapid ablation of prostatic tissue with no intraoperative haemorrhage. Histological examination revealed coagulation zones of 2.30 mm (+/-0.26) at 100 W in the diode laser-treated prostates.
The presence of Abeta(pE3) (N-terminal truncated Abeta starting with pyroglutamate) in Alzheimers disease (AD) has received considerable attention since the discovery that this peptide represents a dominant fraction of Abeta peptides in senile plaques of AD brains. This was later confirmed by other reports investigating AD and Downs syndrome postmortem brain tissue. Importantly, Abeta(pE3) has a higher aggregation propensity, and stability, and shows an increased toxicity compared to full-length Abeta. We have recently shown that intraneuronal accumulation of Abeta(pE3) peptides induces a severe neuron loss and an associated neurological phenotype in the TBA2 mouse model for AD. Given the increasing interest in Abeta(pE3), we have generated two novel monoclonal antibodies which were characterized as highly specific for Abeta(pE3) peptides and herein used to analyze plaque deposition in APP/PS1KI mice, an AD model with severe neuron loss and learning deficits. This was compared with the plaque pattern present in brain tissue from sporadic and familial AD cases. Abundant plaques positive for Abeta(pE3) were present in patients with sporadic AD and familial AD including those carrying mutations in APP (arctic and Swedish) and PS1. Interestingly, in APP/PS1KI mice we observed a continuous increase in Abeta(pE3) plaque load with increasing age, while the density for Abeta(1-x ) plaques declined with aging. We therefore assume that, in particular, the peptides starting with position 1 of Abeta are N-truncated as disease progresses, and that, Abeta(pE3) positive plaques are resistant to age-dependent degradation likely due to their high stability and propensity to aggregate.
In the present work, we investigated the level of IgM autoantibodies directed against different A? epitopes as potential diagnostic biomarker for Alzheimers disease (AD). Anti-A? autoantibody levels were measured in 75 plasma samples from patients with AD, individuals with mild cognitive impairment (MCI), and healthy age- and sex-matched controls (HC). To validate the presence of anti-A? IgMs, pooled plasma samples were subjected to gel-filtration analysis. The mean level of pGluA?-IgM (N-terminal truncated starting at position three with pyroglutamate) was significantly decreased in AD patients as compared to HC. In the group of MCI patients there was a significant positive correlation between pGluA?-IgM and cognitive decline analyzed by MMSE (rho = 0.58, d.f. = 13, p = 0.022). These observations indicate that the level of IgM autoantibodies against pGluA? is a promising plasma biomarker for AD and correlates with the cognitive status of individuals at risk to develop AD.
To evaluate, ex vivo and in vivo, the tissue-removal capacity and coagulation properties of a diode laser emitting light at 940 nm, as in the search for potential therapeutic strategies for benign prostatic hyperplasia that cause less morbidity than transurethral resection of the prostate (TURP), various types of lasers have been tested.
Abeta accumulation has an important function in the etiology of Alzheimers disease (AD) with its typical clinical symptoms, like memory impairment and changes in personality. However, the mode of this toxic activity is still a matter of scientific debate. We used the APP/PS1KI mouse model for AD, because it is the only model so far which develops 50% hippocampal CA1 neuron loss at the age of 1 year. Previously, we have shown that this model develops severe learning deficits occurring much earlier at the age of 6 months. This observation prompted us to study the anatomical and cellular basis at this time point in more detail. In the current report, we observed that at 6 months of age there is already a 33% CA1 neuron loss and an 18% atrophy of the hippocampus, together with a drastic reduction of long-term potentiation and disrupted paired pulse facilitation. Interestingly, at 4 months of age, there was no long-term potentiation deficit in CA1. This was accompanied by reduced levels of pre- and post-synaptic markers. We also observed that intraneuronal and total amount of different Abeta peptides including N-modified, fibrillar and oligomeric Abeta species increased and coincided well with CA1 neuron loss. Overall, these data provide the basis for the observed robust working memory deficits in this mouse model for AD at 6 months of age.
Studies in animals have reported that normalized or elevated Cu levels can inhibit or even remove Alzheimers disease-related pathological plaques and exert a desirable amyloid-modifying effect. We tested engineered nanocarriers composed of diverse core-shell architectures to modulate Cu levels under physiological conditions through bypassing the cellular Cu uptake systems. Two different nanocarrier systems were able to transport Cu across the plasma membrane of yeast or higher eukaryotic cells, CS-NPs (core-shell nanoparticles) and CMS-NPs (core-multishell nanoparticles). Intracellular Cu levels could be increased up to 3-fold above normal with a sublethal dose of carriers. Both types of carriers released their bound guest molecules into the cytosolic compartment where they were accessible for the Cu-dependent enzyme SOD1. In particular, CS-NPs reduced Abeta levels and targeted intracellular organelles more efficiently than CMS-NPs. Fluorescently labeled CMS-NPs unraveled a cellular uptake mechanism, which depended on clathrin-mediated endocytosis in an energy-dependent manner. In contrast, the transport of CS-NPs was most likely driven by a concentration gradient. Overall, nanocarriers depending on the nature of the surrounding shell functioned by mediating import of Cu across cellular membranes, increased levels of bioavailable Cu, and affected Abeta turnover. Our studies illustrate that Cu-charged nanocarriers can achieve a reasonable metal ion specificity and represent an alternative to metal-complexing agents. The results demonstrate that carrier strategies have potential for the treatment of metal ion deficiency disorders.
It has previously been shown that immune complexes (IC) of a given biomarker with class M immunoglobulins (IgM) provide better performances compared to the unbound biomarker in a number of cancer entities. In the present work, we investigated IC of IgM-Abeta as a potential biomarker for Alzheimers disease (AD). Abeta-IgM concentration has been measured in 75 plasma samples from patients with AD, individuals with mild cognitive impairment (MCI), and healthy age- and sex-matched controls (HC). To characterize the fractions associated with Abeta, pooled plasma samples were subjected to gel-filtration analysis. Size-separated fractions were analyzed for the presence of Abeta using a sandwich ELISA assay. A strong reactivity was observed in the high molecular weight IgM (>500 kDa) and 150 kDa (IgG) fractions indicating that blood Abeta is strongly associated with antibodies. Using an ELISA assay detecting Abeta-IgM complexes, we observed that high levels of Abeta-IgMs were detectable in HC and MCI patients; however, there was no significant difference to the AD group.
To study the configuration of the proximal interphalangeal joint volar plate (VP) in the crimp grip position (metacarpophalangeal joint at 0° to 45° flexion, proximal interphalangeal joint at 90° to 100° flexion, and distal interphalangeal joint at 0° to 10° hyperextension) using magnetic resonance imaging techniques in healthy volunteers and cadaver fingers and to compare the results with histological sections.
Gangliosides are important players for controlling neuronal function and are directly involved in AD pathology. They are among the most potent stimulators of A? production, are enriched in amyloid plaques and bind amyloid beta (A?). However, the molecular mechanisms linking gangliosides with AD are unknown. Here we identified the previously unknown function of the amyloid precursor protein (APP), specifically its cleavage products A? and the APP intracellular domain (AICD), of regulating GD3-synthase (GD3S). Since GD3S is the key enzyme converting a- to b-series gangliosides, it therefore plays a major role in controlling the levels of major brain gangliosides. This regulation occurs by two separate and additive mechanisms. The first mechanism directly targets the enzymatic activity of GD3S: Upon binding of A? to the ganglioside GM3, the immediate substrate of the GD3S, enzymatic turnover of GM3 by GD3S was strongly reduced. The second mechanism targets GD3S expression. APP cleavage results, in addition to A? release, in the release of AICD, a known candidate for gene transcriptional regulation. AICD strongly down regulated GD3S transcription and knock-in of an AICD deletion mutant of APP in vivo, or knock-down of Fe65 in neuroblastoma cells, was sufficient to abrogate normal GD3S functionality. Equally, knock-out of the presenilin genes, presenilin 1 and presenilin 2, essential for A? and AICD production, or of APP itself, increased GD3S activity and expression and consequently resulted in a major shift of a- to b-series gangliosides. In addition to GD3S regulation by APP processing, gangliosides in turn altered APP cleavage. GM3 decreased, whereas the ganglioside GD3, the GD3S product, increased A? production, resulting in a regulatory feedback cycle, directly linking ganglioside metabolism with APP processing and A? generation. A central aspect of this homeostatic control is the reduction of GD3S activity via an A?-GM3 complex and AICD-mediated repression of GD3S transcription.
Increasing evidence suggests an important function of the ?-amyloid precursor protein (APP) in malignant disease in humans; however, the biological basis for this evidence is not well understood at present. To understand the role of APP in transformed pluripotent stem cells, we studied its expression levels in human testicular germ cell tumors using patient tissues, model cell lines, and an established xenograft mouse model. In the present study, we demonstrate the cooperative expression of APP with prominent pluripotency-related genes such as Sox2, NANOG, and POU5F1 (Oct3/4). The closest homologue family member, APLP2, showed no correlation to these stem cell factors. In addition, treatment with histone deacetylase (HDAC) inhibitors suppressed the levels of APP and stem cell markers. Loss of pluripotency, either spontaneously or as a consequence of treatment with an HDAC inhibitor, was accompanied by decreased APP protein levels both in vitro and in vivo. These observations suggest that APP represents a novel and specific biomarker in human transformed pluripotent stem cells that can be selectively modulated by HDAC inhibitors.
Pyroglutamate-modified A? peptides at amino acid position three (A?(pE3-42)) are gaining considerable attention as potential key players in the pathogenesis of Alzheimer disease (AD). A?(pE3-42) is abundant in AD brain and has a high aggregation propensity, stability and cellular toxicity. The aim of the present work was to study the direct effect of elevated A?(pE3-42) levels on ongoing AD pathology using transgenic mouse models. To this end, we generated a novel mouse model (TBA42) that produces A?(pE3-42). TBA42 mice showed age-dependent behavioral deficits and A?(pE3-42) accumulation. The A? profile of an established AD mouse model, 5XFAD, was characterized using immunoprecipitation followed by mass spectrometry. Brains from 5XFAD mice demonstrated a heterogeneous mixture of full-length, N-terminal truncated, and modified A? peptides: A?(1-42), A?(1-40), A?(pE3-40), A?(pE3-42), A?(3-42), A?(4-42), and A?(5-42). 5XFAD and TBA42 mice were then crossed to generate transgenic FAD42 mice. At 6 months of age, FAD42 mice showed an aggravated behavioral phenotype compared with single transgenic 5XFAD or TBA42 mice. ELISA and plaque load measurements revealed that A?(pE3) levels were elevated in FAD42 mice. No change in A?(x)(-42) or other A? isoforms was discovered by ELISA and mass spectrometry. These observations argue for a seeding effect of A?(pE-42) in FAD42 mice.
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