An exploration of the experiences and utility of functional electrical stimulation for foot drop in people with multiple sclerosis.

Purpose: Functional electrical stimulation (FES) is effective in improving walking in people with multiple sclerosis (MS) with foot drop. There is limited research exploring people's experiences of using this device. This study aims to explore the utility, efficacy, acceptability, and impact on daily life of the device in people with MS.Methods: An interpretative phenomenological approach was employed. Ten participants who had used FES for 12 months were interviewed. Transcripts were analysed, and emergent themes identified.Results: Nine participants continued to use the device. Three relevant super-ordinate themes were identified; impact of functional electrical stimulation, sticking with functional electrical stimulation, and autonomy and control. Participants reported challenges using the device; however, all reported positive physical and psychological benefits. Intrinsic and external influences such as; access to professional help, the influence of others, an individual's ability to adapt, and experiences using the device, influenced their decisions to continue with the device. A thematic model of these factors was developed.Conclusions: This study has contributed to our understanding of people with MS experiences of using the device and will help inform prescribing decisions and support the continued, appropriate use of FES over the longer term.Implications for RehabilitationPeople with multiple sclerosis using functional electrical stimulation report benefits in many aspects of walking, improved psychological well-being and increased engagement in valued activities.A number of challenges impact on functional electrical stimulation use. Factors such as; a positive experience using the device, access to professional help, the influence of others, a strong sense of personal autonomy and an individual's ability to adapt, influence an individual's decision to continue using functional electrical stimulation.Clinicians prescribing functional electrical stimulation should be aware of these factors so that the right support and guidance can be provided to people with multiple sclerosis, thus improving outcomes and compliance over the long term.

Evaluating the Effect of Functional Electrical Stimulation Used for Foot Drop on Aspects of Health-Related Quality of Life in People with Multiple Sclerosis: A Systematic Review.

BACKGROUND: Multiple sclerosis (MS) is a common degenerative neurologic condition resulting in walking difficulties. Foot drop is a common walking impairment in MS that can affect health-related quality of life (HRQOL). Functional electrical stimulation (FES) can improve walking in people with MS, but its effect on HRQOL is not well established. This review investigated the effect of FES used for foot drop on HRQOL in adults with MS. METHODS: A systematic search was performed using CINAHL, MEDLINE, Cochrane Library, PubMed, and PEDro online databases. Inclusion and exclusion criteria were applied to select eligible studies. Data were extracted, and two reviewers independently rated the quality of the studies using the Effective Public Health Practice Project assessment tool. RESULTS: Eight studies were eligible for review; seven were of moderate-to-strong methodological quality and one was weak. Seven studies demonstrated significant positive effects of FES on different aspects of HRQOL as measured by the 29-item Multiple Sclerosis Impact Scale, 36-item Short Form Health Status Survey, Canadian Occupational Performance Measure, and Psychosocial Impact of Assistive Devices Scale. CONCLUSIONS: This review provides preliminary evidence that FES has a positive effect on aspects of HRQOL in people with MS; however, the variety of HRQOL outcomes used makes it difficult to determine definitive conclusions. Future larger-scale randomized studies with long-term follow-up are recommended to better understand the effect of FES on HRQOL. This will inform prescribing decisions and support compliance with FES over the longer-term.

The clinical- and cost-effectiveness of functional electrical stimulation and ankle-foot orthoses for foot drop in Multiple Sclerosis: a multicentre randomized trial.

OBJECTIVE: To compare the clinical- and cost-effectiveness of ankle-foot orthoses (AFOs) and functional electrical stimulation (FES) over 12 months in people with Multiple Sclerosis with foot drop. DESIGN: Multicentre, powered, non-blinded, randomized trial. SETTING: Seven Multiple Sclerosis outpatient centres across Scotland. SUBJECTS: Eighty-five treatment-naïve people with Multiple Sclerosis with persistent (>three months) foot drop. INTERVENTIONS: Participants randomized to receive a custom-made, AFO (n = 43) or FES device (n = 42). OUTCOME MEASURES: Assessed at 0, 3, 6 and 12 months; 5-minute self-selected walk test (primary), Timed 25 Foot Walk, oxygen cost of walking, Multiple Sclerosis Impact Scale-29, Multiple Sclerosis Walking Scale-12, Modified Fatigue Impact Scale, Euroqol five-dimension five-level questionnaire, Activities-specific Balance and Confidence Scale, Psychological Impact of Assistive Devices Score, and equipment and National Health Service staff time costs of interventions. RESULTS: Groups were similar for age (AFO, 51.4 (11.2); FES, 50.4(10.4) years) and baseline walking speed (AFO, 0.62 (0.21); FES 0.73 (0.27) m/s). In all, 38% dropped out by 12 months (AFO, n = 21; FES, n = 11). Both groups walked faster at 12 months with device (P < 0.001; AFO, 0.73 (0.24); FES, 0.79 (0.24) m/s) but no difference between groups. Significantly higher Psychological Impact of Assistive Devices Scores were found for FES for Competence (P = 0.016; AFO, 0.85(1.05); FES, 1.53(1.05)), Adaptability (P = 0.001; AFO, 0.38(0.97); FES 1.53 (0.98)) and Self-Esteem (P = 0.006; AFO, 0.45 (0.67); FES 1 (0.68)). Effects were comparable for other measures. FES may offer value for money alternative to usual care. CONCLUSION: AFOs and FES have comparable effects on walking performance and patient-reported outcomes; however, high drop-outs introduces uncertainty.

A comparison of the initial orthotic effects of functional electrical stimulation and ankle-foot orthoses on the speed and oxygen cost of gait in multiple sclerosis.

BACKGROUND: Foot drop affects walking in people with multiple sclerosis (pwMS). This study compares the initial orthotic effects of two treatments for foot drop: ankle-foot orthoses (AFO) and functional electrical stimulation (FES), on the speed and oxygen cost of walking in MS. METHOD AND MATERIALS: Seventy-eight pwMS were randomised to receive AFO or FES (ODFS PACE (OML, Salisbury, UK)). Participants completed the 25-ft walk test (25ftWT) and 5-min self-selected walk test (5minSSWT), from which oxygen cost was determined, with and without their device. Between-, within- and sub-group analyses (based on baseline walking speed of <0.8 m/s (slow) or ≥0.8 m/s (fast)) were undertaken. RESULTS: No significant differences between baseline measures were observed. The AFO group walked significantly slower than the FES group (5minSSWT, p = 0.037, 0.11 m/s). The AFO group walked significantly slower with than without AFO (25ftWT, p = 0.037), particularly in the fast-walking group ( p = 0.011). The slow-walking FES group walked significantly faster with FES than without (25ftWT; p = 0.029, 5minSSWT; p = 0.037). There were no differences in the fast-walking FES group or in the oxygen cost for either device. CONCLUSION: AFO reduced walking speed, particularly in fast walkers. FES increased walking speed in slow, but not fast walkers.

Functional Electrical Stimulation for Foot Drop in Multiple Sclerosis: A Systematic Review and Meta-Analysis of the Effect on Gait Speed.

OBJECTIVE: To review the efficacy of functional electrical stimulation (FES) used for foot drop in people with multiple sclerosis (pwMS) on gait speed in short and long walking performance tests. DATA SOURCES: Five databases (Cochrane Library, CINAHL, Embase, MEDLINE, and PubMed) and reference lists were searched. STUDY SELECTION: Studies of both observational and experimental design where gait speed data in pwMS could be extracted were included. DATA EXTRACTION: Data were independently extracted and recorded. Methodologic quality was assessed using the Effective Public Health Practice Project tool. DATA SYNTHESIS: Nineteen studies (described in 20 articles) recruiting 490 pwMS were identified and rated as moderate or weak, with none gaining a strong rating. All studies rated weak for blinding. Initial and ongoing orthotic and therapeutic effects were assessed regarding the effect of FES on gait speed in short and long walking tests. Meta-analyses of the short walk tests revealed a significant initial orthotic effect (t=2.14, P=.016), with a mean increase in gait speed of .05m/s, and ongoing orthotic effect (t=2.81, P=.003), with a mean increase of .08m/s. There were no initial or ongoing effects on gait speed in long walk tests and no therapeutic effect on gait speed in either short or long walk tests. CONCLUSIONS: FES used for foot drop has a positive initial and ongoing effect on gait speed in short walking tests. Further fully powered randomized controlled trials comparing FES with alternative treatments are required.

The murine version of BAN2401 (mAb158) selectively reduces amyloid-ß protofibrils in brain and cerebrospinal fluid of tg-ArcSwe mice.

Amyloid-ß (Aß) immunotherapy for Alzheimer's disease (AD) has good preclinical support from transgenic mouse models and clinical data suggesting that a long-term treatment effect is possible. Soluble Aß protofibrils have been shown to exhibit neurotoxicity in vitro and in vivo, and constitute an attractive target for immunotherapy. Here, we demonstrate that the humanized antibody BAN2401 and its murine version mAb158 exhibit a strong binding preference for Aß protofibrils over Aß monomers. Further, we confirm the presence of the target by showing that both antibodies efficiently immunoprecipitate soluble Aß aggregates in human AD brain extracts. mAb158 reached the brain and reduced the brain protofibril levels by 42% in an exposure-dependent manner both after long-term and short-term treatment in tg-ArcSwe mice. Notably, a 53% reduction of protofibrils/oligomers in cerebrospinal fluid (CSF) that correlated with reduced brain protofibril levels was observed after long-term treatment, suggesting that CSF protofibrils/oligomers could be used as a potential biomarker. No change in native monomeric Aß42 could be observed in brain TBS extracts after mAb158-treatment in tg-ArcSwe mice. By confirming the specific ability of mAb158 to selectively bind and reduce soluble Aß protofibrils, with minimal binding to Aß monomers, we provide further support in favor of its position as an attractive new candidate for AD immunotherapy. BAN2401 has undergone full phase 1 development, and available data indicate a favorable safety profile in AD patients.

Immunotherapy targeting α-synuclein protofibrils reduced pathology in (Thy-1)-h[A30P] α-synuclein mice.

Several lines of evidence suggest that accumulation of aggregated alpha-synuclein (α-synuclein) in the central nervous system (CNS) is an early pathogenic event in Parkinson's disease and other Lewy body disorders. In recent years, animal studies have indicated immunotherapy with antibodies directed against α-synuclein as a promising novel treatment strategy. Since large α-synuclein oligomers, or protofibrils, have been demonstrated to possess pronounced cytotoxic properties, such species should be particularly attractive as therapeutic targets. In support of this, (Thy-1)-h[A30P] α-synuclein transgenic mice with motor dysfunction symptoms were found to display increased levels of α-synuclein protofibrils in the CNS. An α-synuclein protofibril-selective monoclonal antibody (mAb47) was evaluated in this α-synuclein transgenic mouse model. As measured by ELISA, 14month old mice treated for 14weeks with weekly intraperitoneal injections of mAb47 displayed significantly lower levels of both soluble and membrane-associated protofibrils in the spinal cord. Besides the lower levels of pathogenic α-synuclein demonstrated, a reduction of motor dysfunction in transgenic mice upon peripheral administration of mAb47 was indicated. Thus, immunotherapy with antibodies targeting toxic α-synuclein species holds promise as a future disease-modifying treatment in Parkinson's disease and related disorders.

Monoclonal antibodies selective for α-synuclein oligomers/protofibrils recognize brain pathology in Lewy body disorders and α-synuclein transgenic mice with the disease-causing A30P mutation.

Inclusions of intraneuronal alpha-synuclein (α-synuclein) can be detected in brains of patients with Parkinson's disease and dementia with Lewy bodies. The aggregation of α-synuclein is a central feature of the disease pathogenesis. Among the different α-synuclein species, large oligomers/protofibrils have particular neurotoxic properties and should therefore be suitable as both therapeutic and diagnostic targets. Two monoclonal antibodies, mAb38F and mAb38E2, with high affinity and strong selectivity for large α-synuclein oligomers were generated. These antibodies, which do not bind amyloid-beta or tau, recognize Lewy body pathology in brains from patients with Parkinson's disease and dementia with Lewy bodies and detect pathology earlier in α-synuclein transgenic mice than linear epitope antibodies. An oligomer-selective sandwich ELISA, based on mAb38F, was set up to analyze brain extracts of the transgenic mice. The overall levels of α-synuclein oligomers/protofibrils were found to increase with age in these mice, although the levels displayed a large interindividual variation. Upon subcellular fractionation, higher levels of α-synuclein oligomers/protofibrils could be detected in the endoplasmic reticulum around the age when behavioral disturbances develop. In summary, our novel oligomer-selective α-synuclein antibodies recognize relevant pathology and should be important tools to further explore the pathogenic mechanisms in Lewy body disorders. Moreover, they could be potential candidates both for immunotherapy and as reagents in an assay to assess a potential disease biomarker.

The Arctic amyloid-ß precursor protein (AßPP) mutation results in distinct plaques and accumulation of N- and C-truncated Aß.

The Arctic (p. E693G) mutation in the amyloid-ß precursor protein (AßPP) facilitates amyloid-ß (Aß) protofibril formation and generates clinical symptoms of Alzheimer's disease (AD). Here, molecular details of Aß in post mortem brain were investigated with biochemical and morphological techniques. The basic structure of Arctic plaques resembled cotton wool plaques. However, they appeared ring-formed with Aß42-specific antibodies, but were actually targetoid, since the periphery and center of many parenchymal Aß deposits stained differently with mid-domain, N- and C-terminal Aß antibodies. Aß fibrils were similar in shape, albeit shorter than in sporadic AD brain, when examined by electron microscopy. Aßwild-type and Aßarctic codeposited and parenchymal deposits were highly enriched in both N- and C-terminally truncated Aß. In contrast, cerebral amyloid angiopathy (CAA) contained a substantial amount of Aß1-40. The absence of plaques with cores of fibrillary Aß might be due to the scarcity of full-length Aß, although other mechanisms could be involved. Our findings are discussed in relation to mechanisms and relevance of amyloid formation and to the clinical features of AD.

Observations in APP bitransgenic mice suggest that diffuse and compact plaques form via independent processes in Alzheimer's disease.

Studies of familial Alzheimer's disease suggest that misfolding and aggregation of amyloid-ß (Aß) peptides initiate the pathogenesis. The Arctic mutation of Aß precursor protein (APP) results in AD, and Arctic Aß is more prone to form Aß protofibrils and extracellular deposits. Herein is demonstrated that the burden of diffuse Aß deposits but not compact plaques is increased when tg-Swe mice are crossed with tg-ArcSwe mice synthesizing low levels of Arctic Aß. The diffuse deposits in bitransgenic mice, which contain primarily wild-type Aß42, accumulate in regions both with and without transgene expression. However, APP processing, when compared with tg-Swe, remains unchanged in young bitransgenic mice, whereas wild-type Aß42 aggregation is accelerated and fibril architecture is altered in vitro and in vivo when a low level of Arctic Aß42 is introduced. Thus, the increased number of diffuse deposits is likely due to physical interactions between Arctic Aß and wild-type Aß42. The selective increase of a single type of parenchymal Aß deposit suggests that different pathways lead to formation of diffuse and compact plaques. These findings could have general implications for Alzheimer's disease pathogenesis and particular relevance to patients heterozygous for the Arctic APP mutation. Moreover, it further illustrates how Aß neuropathologic features can be manipulated in vivo by mechanisms similar to those originally conceptualized in prion research.

Heavy-chain complementarity-determining regions determine conformation selectivity of anti-aß antibodies.

BACKGROUND/AIMS: Amyloid-ß (Aß) protofibrils are neurotoxic soluble intermediates in the Aß aggregation process eventually forming senile plaques in Alzheimer's disease. This Aß species is a potential biomarker for Alzheimer's disease and also a promising target for immunotherapy. In this study, we investigated the characteristics of conformation-dependent Aß antibodies specific for Aß protofibrils. METHODS: Mice were immunized with Aß protofibrils to generate hybridomas producing Aß-specific monoclonal antibodies. Binding of antibodies to different Aß conformations was investigated with inhibition ELISA. The antibodies' complementarity-determining region (CDR) sequences were determined and compared. RESULTS: A majority of the antibodies were of the IgM class, all selectively binding to aggregated Aß. Two IgG antibodies were generated: one with selective affinity for Aß protofibrils and the other bound Aß in all conformations. A high degree of similarity between the heavy-chain CDRs of the conformation-dependent antibodies was found, and all high-affinity Aß antibodies displayed a high degree of sequence similarity in the light-chain CDRs. CONCLUSION: Sequence similarity in the heavy-chain CDRs is associated with conformation selectivity of the antibodies, while sequence similarity in the light-chain CDRs correlates with the affinity for Aß.

Sensitive detection of Aß protofibrils by proximity ligation--relevance for Alzheimer's disease.

BACKGROUND: Protein aggregation plays important roles in several neurodegenerative disorders. For instance, insoluble aggregates of phosphorylated tau and of Aß peptides are cornerstones in the pathology of Alzheimer's disease. Soluble protein aggregates are therefore potential diagnostic and prognostic biomarkers for their cognate disorders. Detection of the aggregated species requires sensitive tools that efficiently discriminate them from monomers of the same proteins. Here we have established a proximity ligation assay (PLA) for specific and sensitive detection of Aß protofibrils via simultaneous recognition of three identical determinants present in the aggregates. PLA is a versatile technology in which the requirement for multiple target recognitions is combined with the ability to translate signals from detected target molecules to amplifiable DNA strands, providing very high specificity and sensitivity. RESULTS: For specific detection of Aß protofibrils we have used a monoclonal antibody, mAb158, selective for Aß protofibrils in a modified PLA, where the same monoclonal antibody was used for the three classes of affinity reagents required in the assay. These reagents were used for detection of soluble Aß aggregates in solid-phase reactions, allowing detection of just 0.1 pg/ml Aß protofibrils, and with a dynamic range greater than six orders of magnitude. Compared to a sandwich ELISA setup of the same antibody the PLA increases the sensitivity of the Aß protofibril detection by up to 25-fold. The assay was used to measure soluble Aß aggregates in brain homogenates from mice transgenic for a human allele predisposing to Aß aggregation. CONCLUSIONS: The proximity ligation assay is a versatile analytical technology for proteins, which can provide highly sensitive and specific detection of Aß aggregates - and by implication other protein aggregates of relevance in Alzheimer's disease and other neurodegenerative disorders.

Animal models of amyloid-beta-related pathologies in Alzheimer's disease.

In the early 1990s, breakthrough discoveries on the genetics of Alzheimer's disease led to the identification of missense mutations in the amyloid-beta precursor protein gene. Research findings quickly followed, giving insights into molecular pathogenesis and possibilities for the development of new types of animal models. The complete toolbox of transgenic techniques, including pronuclear oocyte injection and homologous recombination, has been applied in the Alzheimer's disease field, to produce overexpressors, knockouts, knockins and regulatable transgenics. Transgenic models have dramatically advanced our understanding of pathogenic mechanisms and allowed therapeutic approaches to be tested. Following a brief introduction to Alzheimer's disease, various nontransgenic and transgenic animal models are described in terms of their values and limitations with respect to pathogenic, therapeutic and functional understandings of the human disease.

An amyloid-beta protofibril-selective antibody prevents amyloid formation in a mouse model of Alzheimer's disease.

Human genetics link Alzheimer's disease pathogenesis to excessive accumulation of amyloid-beta (Abeta) in brain, but the symptoms do not correlate with senile plaque burden. Since soluble Abeta aggregates can cause synaptic dysfunctions and memory deficits, these species could contribute to neuronal dysfunction and dementia. Here we explored selective targeting of large soluble aggregates, Abeta protofibrils, as a new immunotherapeutic strategy. The highly protofibril-selective monoclonal antibody mAb158 inhibited in vitro fibril formation and protected cells from Abeta protofibril-induced toxicity. When the mAb158 antibody was administered for 4 months to plaque-bearing transgenic mice with both the Arctic and Swedish mutations (tg-ArcSwe), Abeta protofibril levels were lowered while measures of insoluble Abeta were unaffected. In contrast, when treatment began before the appearance of senile plaques, amyloid deposition was prevented and Abeta protofibril levels diminished. Therapeutic intervention with mAb158 was however not proven functionally beneficial, since place learning depended neither on treatment nor transgenicity. Our findings suggest that Abeta protofibrils can be selectively cleared with immunotherapy in an animal model that display highly insoluble Abeta deposits, similar to those of Alzheimer's disease brain.

Amyloid-beta protofibril levels correlate with spatial learning in Arctic Alzheimer's disease transgenic mice.

Oligomeric assemblies of amyloid-beta (Abeta) are suggested to be central in the pathogenesis of Alzheimer's disease because levels of soluble Abeta correlate much better with the extent of cognitive dysfunctions than do senile plaque counts. Moreover, such Abeta species have been shown to be neurotoxic, to interfere with learned behavior and to inhibit the maintenance of hippocampal long-term potentiation. The tg-ArcSwe model (i.e. transgenic mice with the Arctic and Swedish Alzheimer mutations) expresses elevated levels of Abeta protofibrils in the brain, making tg-ArcSwe a highly suitable model for investigating the pathogenic role of these Abeta assemblies. In the present study, we estimated Abeta protofibril levels in the brain and cerebrospinal fluid of tg-ArcSwe mice, and also assessed their role with respect to cognitive functions. Protofibril levels, specifically measured with a sandwich ELISA, were found to be elevated in young tg-ArcSwe mice compared to several transgenic models lacking the Arctic mutation. In aged tg-ArcSwe mice with considerable plaque deposition, Abeta protofibrils were approximately 50% higher than in younger mice, whereas levels of total Abeta were exponentially increased. Young tg-ArcSwe mice showed deficits in spatial learning, and individual performances in the Morris water maze were correlated inversely with levels of Abeta protofibrils, but not with total Abeta levels. We conclude that Abeta protofibrils accumulate in an age-dependent manner in tg-ArcSwe mice, although to a far lesser extent than total Abeta. Our findings suggest that increased levels of Abeta protofibrils could result in spatial learning impairment.

Design, synthesis, and evaluation in vitro of quinoline-8-carboxamides, a new class of poly(adenosine-diphosphate-ribose)polymerase-1 (PARP-1) inhibitor.

Poly(ADP-ribose)polymerase-1 is an important target enzyme in drug design; inhibitors have a wide variety of therapeutic activities. A series of quinoline-8-carboxamides was designed to maintain the required pharmacophore conformation through an intramolecular hydrogen bond. 3-Substituted quinoline-8-carboxamides were synthesized by Pd-catalyzed couplings (Suzuki, Sonogashira, Stille) to 3-iodoquinoline-8-carboxamide, an efficient process that introduces diversity in the final step. 2-Substituted quinoline-8-carboxamides were prepared by selective Pd-catalyzed couplings at the 2-position of 2,8-dibromoquinoline, followed by lithium-bromine exchange of the intermediate 2-(alkyl/aryl)-8-bromoquinolines and reaction with trimethylsilyl isocyanate. The intramolecular hydrogen bond was confirmed by X-ray and by NMR. The SAR of the 3-substituted compounds for inhibition of human recombinant PARP-1 activity showed a requirement for a small narrow group. Substituents in the 2-position increased potency, with the most active 2-methylquinoline-8-carboxamide having IC(50) = 500 nM (IC(50) = 1.8 microM for 5-aminoisoquinolin-1-one (5-AIQ, a standard water-soluble inhibitor)).

The Arctic Alzheimer mutation favors intracellular amyloid-beta production by making amyloid precursor protein less available to alpha-secretase.

Mutations within the amyloid-beta (Abeta) domain of the amyloid precursor protein (APP) typically generate hemorrhagic strokes and vascular amyloid angiopathy. In contrast, the Arctic mutation (APP E693G) results in Alzheimer's disease. Little is known about the pathologic mechanisms that result from the Arctic mutation, although increased formation of Abeta protofibrils in vitro and intraneuronal Abeta aggregates in vivo suggest that early steps in the amyloidogenic pathway are facilitated. Here we show that the Arctic mutation favors proamyloidogenic APP processing by increased beta-secretase cleavage, as demonstrated by altered levels of N- and C-terminal APP fragments. Although the Arctic mutation is located close to the alpha-secretase site, APP harboring the Arctic mutation is not an inferior substrate to a disintegrin and metalloprotease-10, a major alpha-secretase. Instead, the localization of Arctic APP is altered, with reduced levels at the cell surface making Arctic APP less available for alpha-secretase cleavage. As a result, the extent and subcellular location of Abeta formation is changed, as revealed by increased Abeta levels, especially at intracellular locations. Our findings suggest that the unique clinical symptomatology and neuropathology associated with the Arctic mutation, but not with other intra-Abeta mutations, could relate to altered APP processing with increased steady-state levels of Arctic Abeta, particularly at intracellular locations.

The Arctic Alzheimer mutation facilitates early intraneuronal Abeta aggregation and senile plaque formation in transgenic mice.

The Arctic mutation (APP E693G) is unique, since it is located within the amyloid-beta (Abeta) sequence and leads to Alzheimer's disease (AD). Arctic Abeta peptides more easily form Abeta protofibrils in vitro, but little is known about the pathogenic mechanism of the Arctic mutation in vivo. Here, we analyzed APP transgenic mice with both the Swedish and Arctic mutations (tg-APPArcSwe) and transgenic mice with the Swedish mutation alone (tg-APPSwe). Intense intraneuronal Abeta-immunoreactive staining was present in young tg-APPArcSwe mice, but not in tg-APPSwe mice. Intracellular Abeta aggregates in tg-APPArcSwe were strongly stained by antibodies recognizing the N-terminus of Abeta, while those recognizing the C-terminus of Abeta stained weakly. The Abeta aggregates inside neurons increased with age and predated extracellular Abeta deposition in both tg-APPArcSwe and tg-APPSwe mice. Senile plaque deposition was markedly accelerated in tg-APPArcSwe mice, as compared to tg-APPSwe mice. We conclude that the Arctic mutation causes AD by facilitating amyloidosis through early accumulation of intracellular Abeta aggregates in association with a rapid onset of senile plaque deposition.

Amyloid-beta oligomers are inefficiently measured by enzyme-linked immunosorbent assay.

Amyloid-beta (Abeta) peptide levels are widely measured by enzyme-linked immunosorbent assay (ELISA) in Alzheimer's disease research. Here, we show that oligomerization of Abeta results in underestimated Abeta ELISA levels. The implications are that comprehensive analysis of soluble Abeta requires either sample pretreatment at denaturing conditions or novel conformation-dependent immunoassays. Our findings might be of relevance for many neurodegenerative disorders in which soluble protein aggregates are the main neurotoxic species.