Exosomes neutralize synaptic-plasticity-disrupting activity of Aβ assemblies in vivo

Background: Exosomes, small extracellular vesicles of endosomal origin, have been suggested to be involved in both the metabolism and aggregation of Alzheimer’s disease (AD)-associated amyloid β-protein (Aβ). Despite their ubiquitous presence and the inclusion of components which can potentially interact with Aβ, the role of exosomes in regulating synaptic dysfunction induced by Aβ has not been explored. Results: We here provide in vivo evidence that exosomes derived from N2a cells or human cerebrospinal fluid can abrogate the synaptic-plasticity-disrupting activity of both synthetic and AD brain-derived Aβ. Mechanistically, this effect involves sequestration of synaptotoxic Aβ assemblies by exosomal surface proteins such as PrPC rather than Aβ proteolysis. Conclusions: These data suggest that exosomes can counteract the inhibitory action of Aβ, which contributes to perpetual capability for synaptic plasticity

Linköping Studies in Science and Technology Dissertation No. 1361 Structure and Interactions of Human IgG-Fc

During the course of the research underlying this thesis, Daniel Kanmert wa

Structure and Interactions of Human IgG-Fc

This thesis involves structure and interaction studies of the Fc fragment of human IgG. For this purpose, hIgG-Fc of different subclasses were cloned and expressed in the eukaryotic host Pichia pastoris, where relevant protein modification at the post-translational level can be obtained. Sometimes, changes in pH, temperature and salt concentration or addition of moderate amounts of denaturants to a protein solution are associated with the protein forming non-natively folded states, such as the molten globule or the A state. IgG and some parts thereof are capable of forming another, so called alternatively folded state, usually induced by acidification in the presence of anions. This state is in many aspects related to the molten globule and the A state but with distinguishing properties related mainly to chemical stability and formation of oligomeric structures. The first part of this thesis describes two different alternatively folded states of hIgG-Fc of subclass 4. One of them was induced by decreasing the pH of the protein solution. Observed structural changes were highly dependent on the concentration of sodium chloride. The alternatively folded protein showed drastic changes in its secondary structure compared to the native protein and significant tertiary structure was lost. Moreover, it displayed an apparently increased chemical stability and had surface exposed hydrophobic patches resulting in the formation of higher order assemblies. In addition, it was shown for the first time that thermal induction of an alternatively folded state is also possible, with similar, but not identical, properties as the acid-induced state. Heat incubation for 20 hours at neutral pH and at a physiological salt concentration further resulted in the formation of protein aggregates. The dye Congo red had affinity for these aggregates, and when viewed under polarized light, it showed green birefringence. They also displayed binding of Thioflavin T and had a typical fibril appearance in the transmission electron microscope. Hence, the formed aggregates share key properties with structures constituting amyloid. The second part of this thesis is focused on interactions of the Fc-fragment with respect to both Fcγ-receptors on monocytes and the IgG autoantibody rheumatoid factor. Immune complexes and their binding to Fcγ-receptors are of pathogenic interest to rheumatoid arthritis. A surface mimic presenting full IgG molecules was designed as an in vitro immune complex model. Utilizing self-assembled monolayers composed of alkanethiolates with different chemical functionalities, the lateral IgG density could be tuned, enabling control of monocyte interaction with the surface. Importantly, the IgG molecules were homogeneously oriented to expose the Fc-fragment. The protein repellent properties of these  surfaces ensured that only differences in IgG concentration determined variations in cellular adhesion. In a separate study the specificities of IgG rheumatoid factor with respect to the different subclasses of hIgG-Fc were investigated, using sera from patients with early rheumatoid arthritis. Strikingly high IgG-RF reactivity against hIgG2-Fc was observed, together with raised levels against hIgG1-Fc and hIgG4-Fc. No reactivity against hIgG3-Fc was found

Short title: IgG Rheumatoid Factors in Early Rheumatoid Arthritis

N.B.: When citing this work, cite the original article. This is the authors ’ version of the following article

Identification of distinct physiochemical properties of the toxic prefibrillar species formed by Aβ peptide variants

The formation of amyloid-β peptide (Aβ) aggregates at an early stage during the self-assembly process is an important factor in the development of Alzheimer’s disease. The toxic effect is believed to be exerted by prefibrillar species of Aβ. It is therefore important to identify which prefibrillar species are toxic and characterize their distinct properties. In the present study, we investigated the in vitro aggregation behavior of Aβ-derived peptides possessing different levels of neurotoxic activity, using fluorescence spectroscopy in combination with transmission electron microscopy. The toxicity of various Aβ aggregates was assessed by using cultures of human neuroblastoma cells. Through combined use of the fluorescence probe 8-anilino-1-napthalenesulfonate (ANS) and the novel luminescent probe pentamer formyl thiophene acetic acid (p-FTAA), we were able to identify those Aβ peptide-derived prefibrillar species which exhibited cellular toxicity. In particular, species, which formed early during the aggregation process and showed strong p-FTAA and ANS fluorescence, were the species that possessed toxic activities. Moreover, by manipulating the aggregation conditions, it was possible to change the capacity of the Aβ peptide to form nontoxic versus toxic species.funding agencies|Swedish National Graduate School in Science, Technology and Mathematics Education Research (Fon-tD)||Swedish Alzheimers Foundation||Soderberg foundation||</p

Развитие хирургии на Могилевщине в конце ХVIII - начале ХХ веков

ЗДРАВООХРАНЕНИЕ РЕСПУБЛИКИ БЕЛАРУСЬИСТОРИЯ МЕДИЦИНЫХИРУРГИЯНа протяжении полутора веков – с момента разделов Речи Посполитой и вхождения белорусских земель в состав России и до советских времен – происходило постепенное развитие хирургической службы на территории Могилевской области. Ряд историко-социальных факторов, таких, как Отечественная война 1812 года, череда восстаний и подавление национальной культуры в середине 19 века, послужили причиной длительных задержек в становлении хирургической помощи на территории могилевщины. Созданное собственными силами общество могилевских врачей стало с середины 19 века центром получения новых медицинских знаний. Пришедшийся на это время период великих открытий в мировой медицине, развитие международных связей позволили энтузиастам хирургии, несмотря на административные проволочки, осваивать все более сложные вмешательства и оказывать квалифицированную хирургическую помощь.Surgery service in Mogilev region during one and a half centuries period has been gradually developing starting from the Rzhech Pospolita allotment and the Byelorussian Lands entry into Russia and till the Soviet period. Several historical and social factors, such as Patriotic War of 1812, a number of rebellions and the national culture repression in the middle of the 19th century have caused the prolonged delay of the surgical service formation in Mogilev region. Medical Society established by the Mogilev doctors has become the centre of the medical knowledge gaining since the middle of the 19th century. At the same time great discoveries in the field of medicine and the development of the international relations have enabled the enthusiastic surgeons of Mogilev to master more complicated surgical interventions and to provide skilled medical care despite the administrative delays

A highly sensitive novel immunoassay specifically detects low levels of soluble Aβ oligomers in human cerebrospinal fluid

Introduction: Amyloid β-protein oligomers play a key role in Alzheimer’s disease (AD), but well-validated assays that routinely detect them in cerebrospinal fluid (CSF) are just emerging. We sought to confirm and extend a recent study using the Singulex Erenna platform that reported increased mean CSF oligomer levels in AD. Methods: We tested four antibody pairs and chose one pair that was particularly sensitive, using 1C22, our new oligomer-selective monoclonal antibody, for capture. We applied this new assay to extracts of human brain and CSF. Results: A combination of 1C22 for capture and 3D6 for detection yielded an Erenna immunoassay with a lower limit of quantification of approximately 0.15 pg/ml that was highly selective for oligomers over monomers and detected a wide size-range of oligomers. Most CSFs we tested had detectable oligomer levels but with a large overlap between AD and controls and a trend for higher mean levels in mild cognitive impairment (MCI) than controls. Conclusion: Aβ oligomers are detectable in most human CSFs, but AD and controls overlap. MCI CSFs may have a modest elevation in mean value by this assay. Electronic supplementary material The online version of this article (doi:10.1186/s13195-015-0100-y) contains supplementary material, which is available to authorized users

Exosomes neutralize synaptic-plasticity-disrupting activity of A beta assemblies in vivo

Background: Exosomes, small extracellular vesicles of endosomal origin, have been suggested to be involved in both the metabolism and aggregation of Alzheimer&apos;s disease (AD)-associated amyloid beta-protein (A beta). Despite their ubiquitous presence and the inclusion of components which can potentially interact with A beta, the role of exosomes in regulating synaptic dysfunction induced by A beta has not been explored. Results: We here provide in vivo evidence that exosomes derived from N2a cells or human cerebrospinal fluid can abrogate the synaptic-plasticity-disrupting activity of both synthetic and AD brain-derived A beta. Mechanistically, this effect involves sequestration of synaptotoxic A beta assemblies by exosomal surface proteins such as PrPC rather than A beta proteolysis. Conclusions: These data suggest that exosomes can counteract the inhibitory action of A beta, which contributes to perpetual capability for synaptic plasticity.open115555sciescopu