Amyloid-beta antibody binding to cerebral amyloid angiopathy fibrils and risk for amyloid-related imaging abnormalities

Therapeutic antibodies have been developed to target amyloid-beta (Aβ), and some of these slow the progression of Alzheimer's disease (AD). However, they can also cause adverse events known as amyloid-related imaging abnormalities with edema (ARIA-E). We investigated therapeutic Aβ antibody binding to cerebral amyloid angiopathy (CAA) fibrils isolated from human leptomeningeal tissue to study whether this related to the ARIA-E frequencies previously reported by clinical trials. The binding of Aβ antibodies to CAA Aβ fibrils was evaluated in vitro using immunoprecipitation, surface plasmon resonance, and direct binding assay. Marked differences in Aβ antibody binding to CAA fibrils were observed. Solanezumab and crenezumab showed negligible CAA fibril binding and these antibodies have no reported ARIA-E cases. Lecanemab showed a low binding to CAA fibrils, consistent with its relatively low ARIA-E frequency of 12.6%, while aducanumab, bapineuzumab, and gantenerumab all showed higher binding to CAA fibrils and substantially higher ARIA-E frequencies (25-35%). An ARIA-E frequency of 24% was reported for donanemab, and its binding to CAA fibrils correlated with the amount of pyroglutamate-modified Aβ present. The findings of this study support the proposal that Aβ antibody-CAA interactions may relate to the ARIA-E frequency observed in patients treated with Aβ-based immunotherapies.

Thiamin dynamics during the adult life cycle of Atlantic salmon (Salmo salar)

Thiamin is an essential water-soluble B vitamin known for its wide range of metabolic functions and antioxidant properties. Over the past decades, reproductive failures induced by thiamin deficiency have been observed in several salmonid species worldwide, but it is unclear why this micronutrient deficiency arises. Few studies have compared thiamin concentrations in systems of salmonid populations with or without documented thiamin deficiency. Moreover, it is not well known whether and how thiamin concentration changes during the marine feeding phase and the spawning migration. Therefore, samples of Atlantic salmon (Salmo salar) were collected when actively feeding in the open Baltic Sea, after the sea migration to natal rivers, after river migration, and during the spawning period. To compare populations of Baltic salmon with systems without documented thiamin deficiency, a population of landlocked salmon located in Lake Vänern (Sweden) was sampled as well as salmon from Norwegian rivers draining into the North Atlantic Ocean. Results showed the highest mean thiamin concentrations in Lake Vänern salmon, followed by North Atlantic, and the lowest in Baltic populations. Therefore, salmon in the Baltic Sea seem to be consistently more constrained by thiamin than those in other systems. Condition factor and body length had little to no effect on thiamin concentrations in all systems, suggesting that there is no relation between the body condition of salmon and thiamin deficiency. In our large spatiotemporal comparison of salmon populations, thiamin concentrations declined toward spawning in all studied systems, suggesting that the reduction in thiamin concentration arises as a natural consequence of starvation rather than to be related to thiamin deficiency in the system. These results suggest that factors affecting accumulation during the marine feeding phase are key for understanding the thiamin deficiency in salmonids.

The interwoven fibril-like structure of amyloid-beta plaques in mouse brain tissue visualized using super-resolution STED microscopy

BACKGROUND

Standard neuropathologic analysis of Alzheimer's brain relies on traditional fluorescence microscopy, which suffers from limited spatial resolution due to light diffraction. As a result, it fails to reveal intricate details of amyloid plaques. While electron microscopy (EM) offers higher resolution, its extensive sample preparation, involving fixation, dehydration, embedding, and sectioning, can introduce artifacts and distortions in the complex brain tissue. Moreover, EM lacks molecular specificity and has limited field of view and imaging depth.

RESULTS

In our study, we employed super-resolution Stimulated Emission Depletion (STED) microscopy in conjunction with the anti-human APP recombinant antibody 1C3 fluorescently labelled with DyLightTM633 (1C3-DyLight633). This combination allowed us to visualize amyloidogenic aggregates in vitro and in brain sections from a 17-month-old 3×Tg-AD mouse with sub-diffraction limited spatial resolution. Remarkably, we achieved a spatial resolution of 29 nm in vitro and 62 nm in brain tissue sections, surpassing the capabilities of conventional confocal microscopy by 5-10 times. Consequently, we could discern individual fibrils within plaques, an achievement previously only possible with EM.

CONCLUSIONS

The utilization of STED microscopy represents a groundbreaking advancement in the field, enabling researchers to delve into the characterization of local mechanisms that underlie Amyloid (Aβ) deposition into plaques and their subsequent clearance. This unprecedented level of detail is especially crucial for comprehending the etiology of Alzheimer's disease and developing the next generation of anti-amyloid treatments. By facilitating the evaluation of drug candidates and non-pharmacological interventions aiming to reduce amyloid burden, STED microscopy emerges as an indispensable tool for driving scientific progress in Alzheimer's research.

Lecanemab, Aducanumab, and Gantenerumab - Binding Profiles to Different Forms of Amyloid-Beta Might Explain Efficacy and Side Effects in Clinical Trials for Alzheimer's Disease

Immunotherapy against amyloid-beta (Aβ) is a promising option for the treatment of Alzheimer's disease (AD). Aβ exists as various species, including monomers, oligomers, protofibrils, and insoluble fibrils in plaques. Oligomers and protofibrils have been shown to be toxic, and removal of these aggregates might represent an effective treatment for AD. We have characterized the binding properties of lecanemab, aducanumab, and gantenerumab to different Aβ species with inhibition ELISA, immunodepletion, and surface plasmon resonance. All three antibodies bound monomers with low affinity. However, lecanemab and aducanumab had very weak binding to monomers, and gantenerumab somewhat stronger binding. Lecanemab was distinctive as it had tenfold stronger binding to protofibrils compared to fibrils. Aducanumab and gantenerumab preferred binding to fibrils over protofibrils. Our results show different binding profiles of lecanemab, aducanumab, and gantenerumab that may explain clinical results observed for these antibodies regarding both efficacy and side effects.

In vivo imaging of alpha-synuclein with antibody-based PET

The protein alpha-synuclein (αSYN) plays a central role in synucleinopathies such as Parkinsons's disease (PD) and multiple system atrophy (MSA). Presently, there are no selective αSYN positron emission tomography (PET) radioligands that do not also show affinity to amyloid-beta (Aβ). We have previously shown that radiolabeled antibodies, engineered to enter the brain via the transferrin receptor (TfR), is a promising approach for PET imaging of intrabrain targets. In this study, we used this strategy to visualize αSYN in the living mouse brain. Five bispecific antibodies, binding to both the murine TfR and αSYN were generated and radiolabeled with iodine-125 or iodine-124. All bispecific antibodies bound to αSYN and mTfR before and after radiolabelling in an ELISA assay, and bound to brain sections prepared from αSYN overexpressing mice as well as human PD- and MSA subjects, but not control tissues in autoradiography. Brain concentrations of the bispecific antibodies were between 26-63 times higher than the unmodified IgG format 2 h post-injection, corresponding to about 1.5% of the injected dose per gram brain tissue. Additionally, intrastriatal αSYN fibrils were visualised with PET in an αSYN deposition mouse model with one of the bispecific antibodies, [¹²⁴I]RmAbSynO2-scFv8D3. However, PET images acquired in αSYN transgenic mice with verified brain pathology injected with [¹²⁴I]RmAbSynO2-scFv8D3 and [¹²⁴I]RmAb48-scFv8D3 showed no increase in antibody retention compared to WT mice. Despite successful imaging of deposited extracellular αSYN using a brain-penetrating antibody-based radioligand with no cross-specificity towards Aβ, this proof-of-concept study demonstrates challenges in imaging intracellular αSYN inclusions present in synucleinopathies.

ABBV-0805, a novel antibody selective for soluble aggregated α-synuclein, prolongs lifespan and prevents buildup of α-synuclein pathology in mouse models of Parkinson's disease

A growing body of evidence suggests that aggregated α-synuclein, the major constituent of Lewy bodies, plays a key role in the pathogenesis of Parkinson's disease and related α-synucleinopathies. Immunotherapies, both active and passive, against α-synuclein have been developed and are promising novel treatment strategies for such disorders. Here, we report on the humanization and pharmacological characteristics of ABBV-0805, a monoclonal antibody that exhibits a high selectivity for human aggregated α-synuclein and very low affinity for monomers. ABBV-0805 binds to a broad spectrum of soluble aggregated α-synuclein, including small and large aggregates of different conformations. Binding of ABBV-0805 to pathological α-synuclein was demonstrated in Lewy body-positive post mortem brains of Parkinson's disease patients. The functional potency of ABBV-0805 was demonstrated in several cellular assays, including Fcγ-receptor mediated uptake of soluble aggregated α-synuclein in microglia and inhibition of neurotoxicity in primary neurons. In vivo, the murine version of ABBV-0805 (mAb47) displayed significant dose-dependent decrease of α-synuclein aggregates in brain in several mouse models, both in prophylactic and therapeutic settings. In addition, mAb47 treatment of α-synuclein transgenic mice resulted in a significantly prolonged survival. ABBV-0805 selectively targets soluble toxic α-synuclein aggregates with a picomolar affinity and demonstrates excellent in vivo efficacy. Based on the strong preclinical findings described herein, ABBV-0805 has been progressed into clinical development as a potential disease-modifying treatment for Parkinson's disease.

Novel multivalent design of a monoclonal antibody improves binding strength to soluble aggregates of amyloid beta

Background

Amyloid-β (Aβ) immunotherapy is a promising therapeutic strategy in the fight against Alzheimer’s disease (AD). A number of monoclonal antibodies have entered clinical trials for AD. Some of them have failed due to the lack of efficacy or side-effects, two antibodies are currently in phase 3, and one has been approved by FDA. The soluble intermediate aggregated species of Aβ, termed oligomers and protofibrils, are believed to be key pathogenic forms, responsible for synaptic and neuronal degeneration in AD. Therefore, antibodies that can strongly and selectively bind to these soluble intermediate aggregates are of great diagnostic and therapeutic interest.

Methods

We designed and recombinantly produced a hexavalent antibody based on mAb158, an Aβ protofibril-selective antibody. The humanized version of mAb158, lecanemab (BAN2401), is currently in phase 3 clinical trials for the treatment of AD. The new designs involved recombinantly fusing single-chain fragment variables to the N-terminal ends of mAb158 antibody. Real-time interaction analysis with LigandTracer and surface plasmon resonance were used to evaluate the kinetic binding properties of the generated antibodies to Aβ protofibrils. Different ELISA setups were applied to demonstrate the binding strength of the hexavalent antibody to Aβ aggregates of different sizes. Finally, the ability of the antibodies to protect cells from Aβ-induced effects was evaluated by MTT assay.

Results

Using real-time interaction analysis with LigandTracer, the hexavalent design promoted a 40-times enhanced binding with avidity to protofibrils, and most of the added binding strength was attributed to the reduced rate of dissociation. Furthermore, ELISA experiments demonstrated that the hexavalent design also had strong binding to small oligomers, while retaining weak and intermediate binding to monomers and insoluble fibrils. The hexavalent antibody also reduced cell death induced by a mixture of soluble Aβ aggregates.

Conclusion

We provide a new antibody design with increased valency to promote binding avidity to an enhanced range of sizes of Aβ aggregates. This approach should be general and work for any aggregated protein or repetitive target.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40035-021-00258-x.

Alpha-Synuclein Protofibrils in Cerebrospinal Fluid: A Potential Biomarker for Parkinson's Disease

BACKGROUND

Currently, there is no established biomarker for Parkinson's disease (PD) and easily accessible biomarkers are crucial for developing disease-modifying treatments.

OBJECTIVE

To develop a novel method to quantify cerebrospinal fluid (CSF) levels of α-synuclein protofibrils (α-syn PF) and apply it to clinical cohorts of patients with PD and atypical parkinsonian disorders.

METHODS

A cohort composed of 49 patients with PD, 12 with corticobasal degeneration (CBD), 22 with progressive supranuclear palsy, and 33 controls, that visited the memory clinic but had no biomarker signs of Alzheimer's disease (AD, tau<350 pg/mL, amyloid-beta 42 (Aβ42)>530 pg/mL, and phosphorylated tau (p-tau)<60 pg/mL) was used in this study. The CSF samples were analyzed with the Single molecule array (Simoa) technology. Total α-synuclein (α-syn) levels were analyzed with a commercial ELISA-kit.

RESULTS

The assay is specific to α-syn PF, with no cross-reactivity to monomeric α-syn, or the β- and γ-synuclein variants. CSF α-syn PF levels were increased in PD compared with controls (62.1 and 40.4 pg/mL, respectively, p = 0.03), and CBD (62.1 and 34.2 pg/mL, respectively, p = 0.02). The accuracy of predicting PD using α-syn PF is significantly different from controls (area under the curve 0.68, p = 0.0097) with a sensitivity of 62.8% and specificity of 67.7%. Levels of total α-syn were significantly different between the PD and CBD groups (p = 0.04).

CONCLUSION

The developed method specifically quantifies α-syn PF in human CSF with increased concentrations in PD, but with an overlap with asymptomatic elderly controls.

The Uppsala APP deletion causes early onset autosomal dominant Alzheimer's disease by altering APP processing and increasing amyloid β fibril formation

Point mutations in the amyloid precursor protein gene (APP) cause familial Alzheimer's disease (AD) by increasing generation or altering conformation of amyloid β (Aβ). Here, we describe the Uppsala APP mutation (Δ690-695), the first reported deletion causing autosomal dominant AD. Affected individuals have an age at symptom onset in their early forties and suffer from a rapidly progressing disease course. Symptoms and biomarkers are typical of AD, with the exception of normal cerebrospinal fluid (CSF) Aβ42 and only slightly pathological amyloid-positron emission tomography signals. Mass spectrometry and Western blot analyses of patient CSF and media from experimental cell cultures indicate that the Uppsala APP mutation alters APP processing by increasing β-secretase cleavage and affecting α-secretase cleavage. Furthermore, in vitro aggregation studies and analyses of patient brain tissue samples indicate that the longer form of mutated Aβ, AβUpp1-42_Δ19-24, accelerates the formation of fibrils with unique polymorphs and their deposition into amyloid plaques in the affected brain.

Characterization of monomeric and soluble aggregated Aβ in Down's syndrome and Alzheimer's disease brains

The major characteristics of Alzheimer's disease (AD) are amyloid plaques, consisting of aggregated beta amyloid (Aβ) peptides, together with tau pathology (tangles, neuropil treads and dystrophic neurites surrounding the plaques), in the brain. Down's syndrome (DS) individuals are at increased risk to develop AD-type pathology; most DS individuals have developed substantial pathology already at the age of 40. DS individuals have an extra copy of chromosome 21, harbouring the amyloid precursor protein gene (APP). Our aim was to investigate the Aβ peptide pattern in DS and AD brains to investigate differences in their amyloid deposition and aggregation, respectively. Cortical tissue from patients with DS (with amyloid pathology), sporadic AD and controls were homogenized and fractionated into TBS (water soluble) and formic acid (water insoluble) fractions. Immunoprecipitation (IP) was performed using a variety of antibodies targeting different Aβ species including oligomeric Aβ. Mass spectrometry was then used to evaluate the presence of Aβ species in the different patient groups. A large number of Aβ peptides were identified including Aβ1-X, 2-X, 3-X, 4-X, 5-X, 11-X, and Aβ peptides extended N terminally of the BACE1 cleavage site and ending at amino 15 in the Aβ sequence APP/Aβ(-X to 15), as well as peptides post-translationally modified by pyroglutamate formation. Most Aβ peptides had higher abundance in AD and DS compared to controls, except the APP/Aβ(-X to 15) peptides which were most abundant in DS followed by controls and AD. Furthermore, the abundancies of AβX-40 and AβX-34 were increased in DS compared with AD. Aβ1-40, Aβ1-42, and Aβ4-42 were identified as the main constitutes of protofibrils (IP'd using mAb158) and higher relative Aβ1-42 signals were obtained compared with samples IP'd with 6E10 + 4G8, indicating that the protofibrils/oligomers were enriched with peptides ending at amino acid 42. All Aβ peptides found in AD were also present in DS indicating similar pathways of Aβ peptide production, degradation and accumulation, except for APP/Aβ(-X to 15). Likewise, the Aβ peptides forming protofibrils/oligomers in both AD and DS were similar, implying the possibility that treatment with clinical benefit in sporadic AD might also be beneficial for subjects with DS.

Efficient clearance of Aβ protofibrils in AβPP-transgenic mice treated with a brain-penetrating bifunctional antibody

Background

Amyloid-β (Aβ) immunotherapy is one of the most promising disease-modifying strategies for Alzheimer’s disease (AD). Despite recent progress targeting aggregated forms of Aβ, low antibody brain penetrance remains a challenge. In the present study, we used transferrin receptor (TfR)-mediated transcytosis to facilitate brain uptake of our previously developed Aβ protofibril-selective mAb158, with the aim of increasing the efficacy of immunotherapy directed toward soluble Aβ protofibrils.

Methods

Aβ protein precursor (AβPP)-transgenic mice (tg-ArcSwe) were given a single dose of mAb158, modified for TfR-mediated transcytosis (RmAb158-scFv8D3), in comparison with an equimolar dose or a tenfold higher dose of unmodified recombinant mAb158 (RmAb158). Soluble Aβ protofibrils and total Aβ in the brain were measured by enzyme-linked immunosorbent assay (ELISA). Brain distribution of radiolabeled antibodies was visualized by positron emission tomography (PET) and ex vivo autoradiography.

Results

ELISA analysis of Tris-buffered saline brain extracts demonstrated a 40% reduction of soluble Aβ protofibrils in both RmAb158-scFv8D3- and high-dose RmAb158-treated mice, whereas there was no Aβ protofibril reduction in mice treated with a low dose of RmAb158. Further, ex vivo autoradiography and PET imaging revealed different brain distribution patterns of RmAb158-scFv8D3 and RmAb158, suggesting that these antibodies may affect Aβ levels by different mechanisms.

Conclusions

With a combination of biochemical and imaging analyses, this study demonstrates that antibodies engineered to be transported across the blood-brain barrier can be used to increase the efficacy of Aβ immunotherapy. This strategy may allow for decreased antibody doses and thereby reduced side effects and treatment costs.

The Aβ protofibril selective antibody mAb158 prevents accumulation of Aβ in astrocytes and rescues neurons from Aβ-induced cell death

Background

Currently, several amyloid beta (Aβ) antibodies, including the protofibril selective antibody BAN2401, are in clinical trials. The murine version of BAN2401, mAb158, has previously been shown to lower the levels of pathogenic Aβ and prevent Aβ deposition in animal models of Alzheimer’s disease (AD). However, the cellular mechanisms of the antibody’s action remain unknown. We have recently shown that astrocytes effectively engulf Aβ₄₂ protofibrils, but store rather than degrade the ingested Aβ aggregates. In a co-culture set-up, the incomplete degradation of Aβ₄₂ protofibrils by astrocytes results in increased neuronal cell death, due to the release of extracellular vesicles, containing N-truncated, neurotoxic Aβ.

Methods

The aim of the present study was to investigate if the accumulation of Aβ in astrocytes can be affected by the Aβ protofibril selective antibody mAb158. Co-cultures of astrocytes, neurons, and oligodendrocytes, derived from embryonic mouse cortex, were exposed to Aβ₄₂ protofibrils in the presence or absence of mAb158.

Results

Our results demonstrate that the presence of mAb158 almost abolished Aβ accumulation in astrocytes. Consequently, mAb158 treatment rescued neurons from Aβ-induced cell death.

Conclusion

Based on these findings, we conclude that astrocytes may play a central mechanistic role in anti-Aβ immunotherapy.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1134-4) contains supplementary material, which is available to authorized users.

Rapid amyloid-β oligomer and protofibril accumulation in traumatic brain injury

Deposition of amyloid-β (Aβ) is central to Alzheimer's disease (AD) pathogenesis and associated with progressive neurodegeneration in traumatic brain injury (TBI). We analyzed predisposing factors for Aβ deposition including monomeric Aβ40, Aβ42 and Aβ oligomers/protofibrils, Aβ species with pronounced neurotoxic properties, following human TBI. Highly selective ELISAs were used to analyze N-terminally intact and truncated Aβ40 and Aβ42, as well as Aβ oligomers/protofibrils, in human brain tissue, surgically resected from severe TBI patients (n = 12; mean age 49.5 ± 19 years) due to life-threatening brain swelling/hemorrhage within one week post-injury. The TBI tissues were compared to post-mortem AD brains (n = 5), to post-mortem tissue of neurologically intact (NI) subjects (n = 4) and to cortical biopsies obtained at surgery for idiopathic normal pressure hydrocephalus patients (iNPH; n = 4). The levels of Aβ40 and Aβ42 were not elevated by TBI. The levels of Aβ oligomers/protofibrils in TBI were similar to those in the significantly older AD patients and increased compared to NI and iNPH controls (P < 0.05). Moreover, TBI patients carrying the AD risk genotype Apolipoprotein E epsilon3/4 (APOE ε3/4; n = 4) had increased levels of Aβ oligomers/protofibrils (P < 0.05) and of both N-terminally intact and truncated Aβ42 (P < 0.05) compared to APOE ε3/4-negative TBI patients (n = 8). Neuropathological analysis showed insoluble Aβ aggregates (commonly referred to as Aβ plaques) in three TBI patients, all of whom were APOE ε3/4 carriers. We conclude that soluble intermediary Aβ aggregates form rapidly after TBI, especially among APOE ε3/4 carriers. Further research is needed to determine whether these aggregates aggravate the clinical short- and long-term outcome in TBI.

Accumulation of amyloid-β by astrocytes result in enlarged endosomes and microvesicle-induced apoptosis of neurons

Background

Despite the clear physical association between activated astrocytes and amyloid-β (Aβ) plaques, the importance of astrocytes and their therapeutic potential in Alzheimer’s disease remain elusive. Soluble Aβ aggregates, such as protofibrils, have been suggested to be responsible for the widespread neuronal cell death in Alzheimer’s disease, but the mechanisms behind this remain unclear. Moreover, ineffective degradation is of great interest when it comes to the development and progression of neurodegeneration. Based on our previous results that astrocytes are extremely slow in degrading phagocytosed material, we hypothesized that astrocytes may be an important player in these processes. Hence, the aim of this study was to clarify the role of astrocytes in clearance, spreading and neuronal toxicity of Aβ.

Results

To examine the role of astrocytes in Aβ pathology, we added Aβ protofibrils to a co-culture system of primary neurons and glia. Our data demonstrates that astrocytes rapidly engulf large amounts of Aβ protofibrils, but then store, rather than degrade the ingested material. The incomplete digestion results in a high intracellular load of toxic, partly N-terminally truncated Aβ and severe lysosomal dysfunction. Moreover, secretion of microvesicles containing N-terminally truncated Aβ, induce apoptosis of cortical neurons.

Conclusions

Taken together, our results suggest that astrocytes play a central role in the progression of Alzheimer’s disease, by accumulating and spreading toxic Aβ species.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-016-0098-z) contains supplementary material, which is available to authorized users.

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

Amyloid-β (Aβ) 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 Aβ 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 Aβ protofibrils over Aβ monomers. Further, we confirm the presence of the target by showing that both antibodies efficiently immunoprecipitate soluble Aβ 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 Aβ42 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 Aβ protofibrils, with minimal binding to Aβ 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.

Radiation Dose to Patients from Radiopharmaceuticals: a Compendium of Current Information Related to Frequently Used Substances

This report provides a compendium of current information relating to radiation dose to patients, including biokinetic models, biokinetic data, dose coefficients for organ and tissue absorbed doses, and effective dose for major radiopharmaceuticals based on the radiation protection guidance given in Publication 60(ICRP, 1991). These data were mainly compiled from Publications 53, 80, and 106(ICRP, 1987, 1998, 2008), and related amendments and corrections. This report also includes new information for 82Rb-chloride, iodide (123I, 124I, 125I, and 131I) and 123I labeled 2ß-carbomethoxy 3ß-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (FPCIT).The coefficients tabulated in this publication will be superseded in due course by values calculated using new International Commission on Radiation Units and Measurements/International Commission on Radiological Protection adult and paediatric reference phantoms and Publication 103 methodology (ICRP,2007). The data presented in this report are intended for diagnostic nuclear medicine and not for therapeutic applications.

Specific uptake of an amyloid-β protofibril-binding antibody-tracer in AβPP transgenic mouse brain

Evidence suggests that amyloid-β (Aβ) protofibrils/oligomers are pathogenic agents in Alzheimer's disease (AD). Unfortunately, techniques enabling quantitative estimates of these species in patients or patient samples are still rather limited. Here we describe the in vitro and ex vivo characteristics of a new antibody-based radioactive ligand, [125I]mAb158, which binds to Aβ protofibrils with high affinity. [125I]mAb158 was specifically taken up in brain of transgenic mice expressing amyloid-β protein precursor (AβPP) as shown ex vivo. This was in contrast to [125I]mAb-Ly128 which does not bind to Aβ. The uptake of intraperitoneally-administered [125I]mAb158 into the brain was age- and time-dependent, and saturable in AβPP transgenic mice with modest Aβ deposition. Brain uptake was also found in young AβPP transgenic mice that were devoid of Aβ deposits, suggesting that [125I]mAb158 targets soluble Aβ protofibrils. The radioligand was diffusely located in the parenchyma, sometimes around senile plaques and only occasionally colocalized with cerebral amyloid angiopathy. A refined iodine-124-labeled version of mAb158 with much improved blood-brain barrier passage and a shorter plasma half-life might be useful for PET imaging of Aβ protofibrils.

31P NMR and computational studies on stereochemistry of conversion of phosphoramidate diesters into the corresponding phosphotriesters

31P NMR spectroscopy was used to investigate a stereochemical course of a nitrite-promoted conversion of phosphoramidate diesters into the corresponding phosphotriesters. It was found that this reaction occurred with almost complete epimerization at the phosphorus center and at the C1 atom in the amine moiety. On the basis of the 31P NMR data, a plausible mechanism for the reaction was proposed. The density functional theory calculation of the key step of the reaction, i.e., breaking of the P-N bond and formation of the P-O bond, suggested a one-step S(N)2(P) process with retention of configuration at the phosphorus center.

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.

Unwinding fibril formation of medin, the peptide of the most common form of human amyloid

Medin amyloid affects the medial layer of the thoracic aorta of most people above 50 years of age. The consequences of this amyloid are not completely known but the deposits may contribute to diseases such as thoracic aortic aneurysm and dissection or to the general diminished elasticity of blood vessels seen in elderly people. We show that the 50-amino acid residue peptide medin forms amyloid-like fibrils in vitro. With the use of Congo red staining, Thioflavin T fluorescence, electron microscopy, and a solid-phase binding assay on different synthetic peptides, we identified the last 18-19 amino acid residues to constitute the amyloid-promoting region of medin. We also demonstrate that the two C-terminal phenylalanines, previously suggested to be of importance for amyloid formation, are not required for medin amyloid formation.

Analysis of single Alzheimer solid plaque cores by laser capture microscopy and nanoelectrospray/tandem mass spectrometry

Aggregation of the 40-42 residue amyloid beta-peptide (Abeta) into amyloid plaques is a central event in Alzheimer's disease (AD) pathogenesis. Many proteins have by immunohistochemical techniques been shown to codeposit with Abeta in AD plaques. It is possible that some of these could seed Abeta aggregation and therefore be found in the actual core of the plaque. Here, we present a highly sensitive method for unbiased biochemical analysis of plaque cores. A mild purification protocol based on centrifugation and filtration was used to purify intact plaque cores from human AD brain. The purified plaques were dispensed on a glass slide and viewed in a laser capture microscope, and plaque cores were catapulted into a tube cap by a laser beam. After dissolution in formic acid, plaques were digested and analyzed by liquid chromatography coupled online to electrospray/tandem mass spectrometry. One single plaque was found to be sufficient for positive identification of the main amyloid component. Remarkably, Abeta was the only protein identified when 200 plaques were isolated and analyzed with the present method. Thus, it is possible that no proteins copolymerize with Abeta in the plaque cores and that Abeta alone is sufficient for formation of plaque cores. In support of this notion, core-like structures were observed after incubation of synthetic Abeta for 2 weeks. We suggest that the method described here could be used for the general analysis of amyloid aggregates and inclusion bodies found in other neurodegenerative disorders and that plaque cores in AD brain are molecularly homogeneous structures.

CLAC binds to aggregated Abeta and Abeta fragments, and attenuates fibril elongation

Deposition of amyloid beta-peptide (Abeta) into amyloid plaques is one of the invariant neuropathological features of Alzheimer's disease. Proteins that codeposit with Abeta are potentially important for the pathogenesis, and a recently discovered plaque-associated protein is the collagenous Alzheimer amyloid plaque component (CLAC). In this study, we investigated the molecular interactions between Abeta aggregates and CLAC using surface plasmon resonance spectroscopy and a solid-phase binding immunoassay. We found that CLAC binds to Abeta with high affinity, that the central region of Abeta is necessary and sufficient for CLAC interaction, and that the aggregation state of Abeta as well as the presence of negatively charged residues is important. We also show that this binding results in a reduced rate of fibril elongation. Taken together, we suggest that CLAC becomes involved at an intermediate stage in the pathogenesis by binding to Abeta fibrils, including fibrils formed from peptides with truncated N- or C-termini, and thereby slows their growth.

Collagenous Alzheimer amyloid plaque component assembles amyloid fibrils into protease resistant aggregates

Recently, a novel plaque-associated protein, collagenous Alzheimer amyloid plaque component (CLAC), was identified in brains from patients with Alzheimer's disease. CLAC is derived from a type II transmembrane collagen precursor protein, termed CLAC-P (collagen XXV). The biological function and the contribution of CLAC to the pathogenesis of Alzheimer's disease and plaque formation are unknown. In vitro studies indicate that CLAC binds to fibrillar, but not to monomeric, amyloid beta-peptide (Abeta). Here, we examined the effects of CLAC on Abeta fibrils using assays based on turbidity, thioflavin T binding, sedimentation analysis, and electron microscopy. The incubation of CLAC with preformed Abeta fibrils led to increased turbidity, indicating that larger aggregates were formed. In support of this contention, more Abeta was sedimented in the presence of CLAC, as determined by gel electrophoresis. Moreover, electron microscopy revealed an increased amount of Abeta fibril bundles in samples incubated with CLAC. Importantly, the frequently used thioflavin T-binding assay failed to reveal these effects of CLAC. Digestion with proteinase K or trypsin showed that Abeta fibrils, incubated together with CLAC, were more resistant to proteolytic degradation. Therefore, CLAC assembles Abeta fibrils into fibril bundles that have an increased resistance to proteases. We suggest that CLAC may act in a similar way in vivo.

Intraspecific sexual selection on a speciation trait, male coloration, in the Lake Victoria cichlid Pundamilia nyererei

The haplochromine cichlids of Lake Victoria constitute a classical example of explosive speciation. Extensive intra- and interspecific variation in male nuptial coloration and female mating preferences, in the absence of postzygotic isolation between species, has inspired the hypothesis that sexual selection has been a driving force in the origin of this species flock. This hypothesis rests on the premise that the phenotypic traits that underlie behavioural reproductive isolation between sister species diverged under sexual selection within a species. We test this premise in a Lake Victoria cichlid, by using laboratory experiments and field observations. We report that a male colour trait, which has previously been shown to be important for behavioural reproductive isolation between this species and a close relative, is under directional sexual selection by female mate choice within this species. This is consistent with the hypothesis that female choice has driven the divergence in male coloration between the two species. We also find that male territoriality is vital for male reproductive success and that multiple mating by females is common.

The genetic structure of adders (Vipera berus) in Fennoscandia: congruence between different kinds of genetic markers

In order to elucidate the colonization history of Fennoscandian adders (Vipera berus), the phylogeographical patterns of two nuclear sets of DNA markers (random amplified polymorphic DNA and microsatellite) are compared with that previously obtained from mitochondrial DNA. An eastern and a western lineage within Fennoscandian adders is readily distinguishable using both sets of nuclear markers, corroborating the hypothesis that the lineages stem from separate glacial refugia. Moreover, the same contact zones as were derived from mitochondrial data are clearly identifiable. Both sets of nuclear markers detect a high level of admixture across one zone in northern Finland, with introgression reaching far west into Sweden.

Characterization of the Alzheimer's disease-associated CLAC protein and identification of an amyloid beta-peptide-binding site

Amyloid beta-peptide (Abeta) deposition into amyloid plaques is one of the invariant neuropathological features of Alzheimer's disease. Other proteins co-deposit with Abeta in plaques, and one recently identified amyloid-associated protein is the collagen-like Alzheimer amyloid plaque component CLAC. It is not known how CLAC deposition affects Abeta plaque genesis and the progress of the disease. Here, we studied the in vitro properties of CLAC purified from a mammalian expression system. CLAC displays features characteristic of a collagen protein, e.g. it forms a partly protease-resistant triple-helical structure, exhibits an intermediate affinity for heparin, and is glycosylated. Purified CLAC was also used to investigate the interaction between CLAC and Abeta. Using a solid-phase binding assay, we show that CLAC bound with a similar affinity to aggregates formed by Abeta-(1-40) and Abeta-(1-42) and that the interaction was impaired by increasing salt concentrations. An 8-residue-long sequence located in non-collagenous domain 2 of CLAC was found to be crucial for the interaction with Abeta. These findings may be useful for future therapeutic interventions aimed at finding compounds that modulate the binding of CLAC to Abeta deposits.

Molecular Identification of AMY, an Alzheimer Disease Amyloid-Associated Protein

One of the neuropathological lesions characteristic of Alzheimer disease (AD) is the cerebral accumulation of the amyloid beta-peptide (A beta). Although numerous studies have demonstrated that A beta spontaneously forms amyloid in vitro, the molecular events underlying A beta amyloid formation in vivo are less well understood. Immunohistochemical studies have shown that other proteins colocalize with A beta in amyloid deposits in brain. The identity of one of these proteins, AMY, has so far remained elusive; therefore we attempted to purify AMY. The AMY protein was found to co-purify with A beta in insoluble fractions from human AD brain, and was absent in brains from control subjects. AMY immunoreactivity was primarily restricted to a 50-kDa and 100-kDa protein species. Interestingly, the chromatographic and immunological profile of AMY resembled the recently identified amyloid-associated protein CLAC, derived from a transmembrane collagen-like precursor, CLAC-P. Antibodies against AMY recognized CLAC-P expressed in mammalian cells. In addition, side-by-side comparisons of AD brain sections and extracts, using antibodies against both AMY and CLAC, respectively, resulted in almost identical staining patterns. Therefore, we conclude that the AMY immunoreactivity seen in association with amyloid in AD brain is due to the presence of the CLAC protein.

Central functions of the lumenal and peripheral thylakoid proteome of Arabidopsis determined by experimentation and genome-wide prediction

Experimental proteome analysis was combined with a genome-wide prediction screen to characterize the protein content of the thylakoid lumen of Arabidopsis chloroplasts. Soluble thylakoid proteins were separated by two-dimensional electrophoresis and identified by mass spectrometry. The identities of 81 proteins were established, and N termini were sequenced to validate localization prediction. Gene annotation of the identified proteins was corrected by experimental data, and an interesting case of alternative splicing was discovered. Expression of a surprising number of paralogs was detected. Expression of five isomerases of different classes suggests strong (un)folding activity in the thylakoid lumen. These isomerases possibly are connected to a network of peripheral and lumenal proteins involved in antioxidative response, including peroxiredoxins, m-type thioredoxins, and a lumenal ascorbate peroxidase. Characteristics of the experimentally identified lumenal proteins and their orthologs were used for a genome-wide prediction of the lumenal proteome. Lumenal proteins with a typical twin-arginine translocation motif were predicted with good accuracy and sensitivity and included additional isomerases and proteases. Thus, prime functions of the lumenal proteome include assistance in the folding and proteolysis of thylakoid proteins as well as protection against oxidative stress. Many of the predicted lumenal proteins must be present at concentrations at least 10,000-fold lower than proteins of the photosynthetic apparatus.

Improving the nurse-patient relationship: a multi-faceted approach

AIM

A Corporate Education Session was held to provide concrete strategies for overcoming several specific barriers in the daily nurse-patient relationship that negatively affect the patient, nurse, or both, and to provide the latest information about best practice as it affects nurses in renal care.

METHODOLOGY

The session was led by a moderator who presented three video case studies to the audience. Communication strategies for recognising and overcoming nurse-patient communication barriers were presented. The audience expressed their views about each case study using voting pads, and a panel of experts addressed the comments of the audience and discussed guidelines for best practice in renal care. The panel comprised three experienced renal nurses, a senior nephrologist, and an expert in social interaction.

CONCLUSIONS

Optimal treatment of patients with renal disease should include early treatment of anaemia, adequate levels of dialysis, and a multidisciplinary approach, responding to both the medical and the social needs of the patient.

Laboratory studies of the effects of carbohydrate consumption on wakefulness

Changes in wakefulness before and after exposure to carbohydrate intake were tested in 30 test persons. Changes in wakefulness were tested via EEG and subjective estimates. The intakes consisted of 400 ml glucose, 250 kcal (GI 100), 400 ml fructose, 209 kcal (GI 20), and 400 ml water. The study has indicated that intake of fructose, glucose and water had a similar stimulating effect on wakefulness in drowsy subjects immediately after intake. Our results also indicate that intake of fructose can lead to a delay in the development of drowsiness. Compared to water, a 20-30 minutes delay of the point in time when high-degree drowsiness developed, took place. There was no significant difference between glucose and water.

Colored microspheres for blood flow determinations twice in the same animal

The regional cochlear blood flow has been studied in the rabbit cochlea by mapping the distribution of non-radioactive microspheres in serial sections of plastic embedded cochleas. By using microspheres of two different colors injected at two different times, it is now possible to measure the 'regional' cochlear blood flow twice in the same animal.

Immunohistochemical procedures for the demonstration of peptide- and tyrosine hydroxylase-containing nerve fibers in cryostat sections of unfixed rapidly frozen tissue stored for long periods of time. A study on heart tissue

Traditional protocols for the immunohistochemical localization of peptides and tyrosine hydroxylase (TH) in nerve fibers in cryostat sections require the tissue to be thoroughly fixed and rinsed and to be processed for the cryostat sectioning and the immunohistochemical staining more or less directly after freezing. In the present study it was tested whether also unfixed, rapidly frozen tissue, conforming to guinea pig and bovine heart specimens, can be used for the visualization of neuropeptides [neuropeptide Y (NPY) and substance P (S P)] and TH in cryostat sections. The following observations were made: 1) NPY-immunoreactive (IR) and S P-IR nerve fibers could be clearly identified in both fixed and unfixed sections of this type of tissue. 2) TH-IR nerve fibers could be detected in unfixed tissue if the sections were post-fixed with aldehydes by the use of a two-step fixation process related to a sudden change of pH. However, the outlines of the nerve fibers were sometimes diffuse. 3) Storage of unfixed tissue for periods of up to 2.5 years at-80 degrees C did not lead to a decrease in immunoreactivity. 4) Somewhat higher concentrations of primary antibodies had to be used for sections of unfixed tissue than for sections of fixed tissue when the FITC method was used. This waste of antibodies was partly overcome by use of the biotin-streptavidin method. The glyoxylic acid induced catecholamine(CA)-fluorescence method for demonstration of sympathetic nerve fibers was also applied and was found to give optimal results after storage of tissue for up to 2.5 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary protein isolation by high-performance ion-exchange chromatography

Proteins excreted in urine, following renal failure, were analysed by high-performance anion-exchange chromatography and chromatofocusing. The analysis involved three steps: (1) removal of the low-molecular-weight fraction by rapid desalting, (2) anion exchange of the high-molecular-weight fraction by using combined salt and pH gradients and (3) further separation of the main peaks by chromatofocusing. The selection of the column and conditions were based on data obtained from electrophoretic titration curves. The purity of selected peaks was evaluated by sodium dodecyl sulphate polyacrylamide gel electrophoresis.