Oxana Klementieva

Verified email at med.lu.se

Lunds universitet



Scopus Publications

Scopus Publications

  • Early-life stress elicits peripheral and brain immune activation differently in wild type and 5xFAD mice in a sex-specific manner
    S. Bachiller, I. Hidalgo, M. G. Garcia, A. Boza-Serrano, A. Paulus, Q. Denis, C. Haikal, O. Manouchehrian, O. Klementieva, J. Y. Li, C. J. Pronk, G. K. Gouras, and T. Deierborg

    Journal of Neuroinflammation, eISSN: 17422094, Published: December 2022 Springer Science and Business Media LLC
    Abstract Background The risk of developing Alzheimer’s disease (AD) is modulated by genetic and environmental factors. Early-life stress (ELS) exposure during critical periods of brain development can impact later brain function and health, including increasing the risk of developing AD. Microglial dysfunction and neuroinflammation have been implicated as playing a role in AD pathology and may be modulated by ELS. To complicate matters further, sex-specific effects have been noted in response to ELS and in the incidence and progression of AD. Methods Here, we subjected male and female mice with either a wild type or 5xFAD familial AD-model background to maternal separation (MS) from postnatal day 2 to 14 to induce ELS. Results We detected hippocampal neuroinflammatory alterations already at postnatal day 15. By 4 months of age, MS mice presented increased immobility time in the forced swim test and a lower discrimination index in the novel object recognition memory test compared to controls. We found altered Bdnf and Arc expression in the hippocampus and increased microglial activation in the prefrontal cortex due to MS in a sex-dependent manner. In 5xFAD mice specifically, MS exacerbated amyloid-beta deposition, particularly in females. In the periphery, the immune cell population was altered by MS exposure. Conclusion Overall, our results demonstrate that MS has both short- and long-term effects on brain regions related to memory and on the inflammatory system, both in the brain and periphery. These ELS-related effects that are detectable even in adulthood may exacerbate pathology and increase the risk of developing AD via sex-specific mechanisms.

  • Recommendations for addressing the translational gap between experimental and clinical research on amyloid diseases
    Miriam Solomon, Vito Foderà, Annette Eva Langkilde, Perry Elliott, Fabrizio Tagliavini, Trevor Forsyth, Oxana Klementieva, and Vittorio Bellotti

    Journal of Translational Medicine, eISSN: 14795876, Published: December 2022 Springer Science and Business Media LLC
    AbstractThis paper is a report of recommendations for addressing translational challenges in amyloid disease research. They were developed during and following an international online workshop organized by the LINXS Institute of Advanced Neutron and X-Ray Science in March 2021. Key suggestions include improving cross-cultural communication between basic science and clinical research, increasing the influence of scientific societies and journals (vis-à-vis funding agencies and pharmaceutical companies), improving the dissemination of negative results, and strengthening the ethos of science.

  • Correlative imaging to resolve molecular structures in individual cells: Substrate validation study for super-resolution infrared microspectroscopy
    Agnes Paulus, Sahana Yogarasa, Mustafa Kansiz, Isak Martinsson, Gunnar K. Gouras, Tomas Deierborg, Anders Engdahl, Ferenc Borondics, and Oxana Klementieva

    Nanomedicine: Nanotechnology, Biology, and Medicine, ISSN: 15499634, eISSN: 15499642, Published: July 2022 Elsevier BV

  • Parkinson's disease and multiple system atrophy patient iPSC-derived oligodendrocytes exhibit alpha-synuclein-induced changes in maturation and immune reactive properties
    Carla Azevedo, Gabriel Teku, Yuriy Pomeshchik, Juan F. Reyes, Margarita Chumarina, Kaspar Russ, Ekaterina Savchenko, Anna Hammarberg, Nuno Jorge Lamas, Anna Collin, Gunnar K. Gouras, Oxana Klementieva, Martin Hallbeck, Ricardo Taipa, Mauno Vihinen, and Laurent Roybon

    Proceedings of the National Academy of Sciences of the United States of America, ISSN: 00278424, eISSN: 10916490, Volume: 119, Published: 22 March 2022 Proceedings of the National Academy of Sciences
    Significance Our results demonstrate the existence of early cellular pathways and network alterations in oligodendrocytes in the alpha-synucleinopathies Parkinson’s disease and multiple system atrophy. They further reveal the involvement of an immune component triggered by alpha-synuclein protein, as well as a connection between (epi)genetic changes and immune reactivity in multiple system atrophy. The knowledge generated in this study could be used to devise novel therapeutic approaches to treat synucleinopathies.

  • The intracellular milieu of Parkinson’s disease patient brain cells modulates alpha-synuclein protein aggregation
    Nadja Gustavsson, Ekaterina Savchenko, Oxana Klementieva, and Laurent Roybon

    Acta Neuropathologica Communications, eISSN: 20515960, Published: December 2021 Springer Science and Business Media LLC
    AbstractRecent studies suggest that brain cell type specific intracellular environments may play important roles in the generation of structurally different protein aggregates that define neurodegenerative diseases. Using human induced pluripotent stem cells (hiPSC) and biochemical and vibrational spectroscopy techniques, we studied whether Parkinson’s disease (PD) patient genomes could modulate alpha-synuclein (aSYN) protein aggregates formation. We found increased β-sheets and aggregated aSYN in PD patient hiPSC-derived midbrain cells, compared to controls. Importantly, we discovered that aSYN protein aggregation is modulated by patient brain cells’ intracellular milieus at the primary nucleation phase. Additionally, we found changes in the formation of aSYN fibrils when employing cellular extracts from familial PD compared to idiopathic PD, in a Thioflavin T-based fluorescence assay. The data suggest that changes in cellular milieu induced by patient genomes trigger structural changes of aSYN potentially leading to the formation of strains having different structures, properties and seeding propensities.

  • Correlative optical photothermal infrared and X-ray fluorescence for chemical imaging of trace elements and relevant molecular structures directly in neurons
    Nadja Gustavsson, Agnes Paulus, Isak Martinsson, Anders Engdahl, Kadda Medjoubi, Konstantin Klementiev, Andrea Somogyi, Tomas Deierborg, Ferenc Borondics, Gunnar K. Gouras, and Oxana Klementieva

    Light: Science and Applications, ISSN: 20955545, eISSN: 20477538, Published: December 2021 Springer Science and Business Media LLC
    AbstractAlzheimer’s disease (AD) is the most common cause of dementia, costing about 1% of the global economy. Failures of clinical trials targeting amyloid-β protein (Aβ), a key trigger of AD, have been explained by drug inefficiency regardless of the mechanisms of amyloid neurotoxicity, which are very difficult to address by available technologies. Here, we combine two imaging modalities that stand at opposite ends of the electromagnetic spectrum, and therefore, can be used as complementary tools to assess structural and chemical information directly in a single neuron. Combining label-free super-resolution microspectroscopy for sub-cellular imaging based on novel optical photothermal infrared (O-PTIR) and synchrotron-based X-ray fluorescence (S-XRF) nano-imaging techniques, we capture elemental distribution and fibrillary forms of amyloid-β proteins in the same neurons at an unprecedented resolution. Our results reveal that in primary AD-like neurons, iron clusters co-localize with elevated amyloid β-sheet structures and oxidized lipids. Overall, our O-PTIR/S-XRF results motivate using high-resolution multimodal microspectroscopic approaches to understand the role of molecular structures and trace elements within a single neuronal cell.

  • Erratum: Human iPSC-derived hippocampal spheroids: An innovative tool for stratifying Alzheimer disease patient-specific cellular phenotypes and developing therapies (Stem Cell Reports (2020) 15(1) (256–273), (S2213671120301922), (10.1016/j.stemcr.2020.06.001))
    Yuriy Pomeshchik, Oxana Klementieva, Jeovanis Gil, Isak Martinsson, Marita Grønning Hansen, Tessa de Vries, Anna Sancho-Balsells, Kaspar Russ, Ekaterina Savchenko, Anna Collin, Ana Rita Vaz, Silvia Bagnoli, Benedetta Nacmias, Claire Rampon, Sandro Sorbi, Dora Brites, György Marko-Varga, Zaal Kokaia, Melinda Rezeli, Gunnar K. Gouras, and Laurent Roybon

    Stem Cell Reports, ISSN: 22136711, Pages: 2838, Published: 9 November 2021 Elsevier BV

  • Nano‐infrared imaging of primary neurons
    Raul O. Freitas, Adrian Cernescu, Anders Engdahl, Agnes Paulus, João E. Levandoski, Isak Martinsson, Elke Hebisch, Christophe Sandt, Gunnar Keppler Gouras, Christelle N. Prinz, Tomas Deierborg, Ferenc Borondics, and Oxana Klementieva

    Cells, eISSN: 20734409, Published: October 2021 MDPI AG
    Alzheimer’s disease (AD) accounts for about 70% of neurodegenerative diseases and is a cause of cognitive decline and death for one-third of seniors. AD is currently underdiagnosed, and it cannot be effectively prevented. Aggregation of amyloid-β (Aβ) proteins has been linked to the development of AD, and it has been established that, under pathological conditions, Aβ proteins undergo structural changes to form β-sheet structures that are considered neurotoxic. Numerous intensive in vitro studies have provided detailed information about amyloid polymorphs; however, little is known on how amyloid β-sheet-enriched aggregates can cause neurotoxicity in relevant settings. We used scattering-type scanning near-field optical microscopy (s-SNOM) to study amyloid structures at the nanoscale, in individual neurons. Specifically, we show that in well-validated systems, s-SNOM can detect amyloid β-sheet structures with nanometer spatial resolution in individual neurons. This is a proof-of-concept study to demonstrate that s-SNOM can be used to detect Aβ-sheet structures on cell surfaces at the nanoscale. Furthermore, this study is intended to raise neurobiologists’ awareness of the potential of s-SNOM as a tool for analyzing amyloid β-sheet structures at the nanoscale in neurons without the need for immunolabeling.

  • Amyloid structural changes studied by infrared microspectroscopy in bigenic cellular models of alzheimer’s disease
    Agnes Paulus, Anders Engdahl, Yiyi Yang, Antonio Boza-Serrano, Sara Bachiller, Laura Torres-Garcia, Alexander Svanbergsson, Megg G. Garcia, Gunnar K. Gouras, Jia-Yi Li, Tomas Deierborg, and Oxana Klementieva

    International Journal of Molecular Sciences, ISSN: 16616596, eISSN: 14220067, Published: 1 April 2021 MDPI AG
    Alzheimer’s disease affects millions of lives worldwide. This terminal disease is characterized by the formation of amyloid aggregates, so-called amyloid oligomers. These oligomers are composed of β-sheet structures, which are believed to be neurotoxic. However, the actual secondary structure that contributes most to neurotoxicity remains unknown. This lack of knowledge is due to the challenging nature of characterizing the secondary structure of amyloids in cells. To overcome this and investigate the molecular changes in proteins directly in cells, we used synchrotron-based infrared microspectroscopy, a label-free and non-destructive technique available for in situ molecular imaging, to detect structural changes in proteins and lipids. Specifically, we evaluated the formation of β-sheet structures in different monogenic and bigenic cellular models of Alzheimer’s disease that we generated for this study. We report on the possibility to discern different amyloid signatures directly in cells using infrared microspectroscopy and demonstrate that bigenic (amyloid-β, α-synuclein) and (amyloid-β, Tau) neuron-like cells display changes in β-sheet load. Altogether, our findings support the notion that different molecular mechanisms of amyloid aggregation, as opposed to a common mechanism, are triggered by the specific cellular environment and, therefore, that various mechanisms lead to the development of Alzheimer’s disease.

  • Human iPSC-Derived Hippocampal Spheroids: An Innovative Tool for Stratifying Alzheimer Disease Patient-Specific Cellular Phenotypes and Developing Therapies
    Yuriy Pomeshchik, Oxana Klementieva, Jeovanis Gil, Isak Martinsson, Marita Grønning Hansen, Tessa de Vries, Anna Sancho-Balsells, Kaspar Russ, Ekaterina Savchenko, Anna Collin, Ana Rita Vaz, Silvia Bagnoli, Benedetta Nacmias, Claire Rampon, Sandro Sorbi, Dora Brites, György Marko-Varga, Zaal Kokaia, Melinda Rezeli, Gunnar K. Gouras, and Laurent Roybon

    Stem Cell Reports, ISSN: 22136711, Pages: 256-273, Published: 14 July 2020 Elsevier BV
    Summary The hippocampus is important for memory formation and is severely affected in the brain with Alzheimer disease (AD). Our understanding of early pathogenic processes occurring in hippocampi in AD is limited due to tissue unavailability. Here, we report a chemical approach to rapidly generate free-floating hippocampal spheroids (HSs), from human induced pluripotent stem cells. When used to model AD, both APP and atypical PS1 variant HSs displayed increased Aβ42/Aβ40 peptide ratios and decreased synaptic protein levels, which are common features of AD. However, the two variants differed in tau hyperphosphorylation, protein aggregation, and protein network alterations. NeuroD1-mediated gene therapy in HSs-derived progenitors resulted in modulation of expression of numerous genes, including those involved in synaptic transmission. Thus, HSs can be harnessed to unravel the mechanisms underlying early pathogenic changes in the hippocampi of AD patients, and provide a robust platform for the development of therapeutic strategies targeting early stage AD.

  • Super-Resolution Infrared Imaging of Polymorphic Amyloid Aggregates Directly in Neurons
    Oxana Klementieva, Christophe Sandt, Isak Martinsson, Mustafa Kansiz, Gunnar K. Gouras, and Ferenc Borondics

    Advanced Science, eISSN: 21983844, Published: 1 March 2020 Wiley
    Abstract Loss of memory during Alzheimer's disease (AD), a fatal neurodegenerative disorder, is associated with neuronal loss and the aggregation of amyloid proteins into neurotoxic β‐sheet enriched structures. However, the mechanism of amyloid protein aggregation is still not well understood due to many challenges when studying the endogenous amyloid structures in neurons or in brain tissue. Available methods either require chemical processing of the sample or may affect the amyloid protein structure itself. Therefore, new approaches, which allow studying molecular structures directly in neurons, are urgently needed. A novel approach is tested, based on label‐free optical photothermal infrared super‐resolution microspectroscopy, to study AD‐related amyloid protein aggregation directly in the neuron at sub‐micrometer resolution. Using this approach, amyloid protein aggregates are detected at the subcellular level, along the neurites and strikingly, in dendritic spines, which has not been possible until now. Here, a polymorphic nature of amyloid structures that exist in AD transgenic neurons is reported. Based on the findings of this work, it is suggested that structural polymorphism of amyloid proteins that occur already in neurons may trigger different mechanisms of AD progression.

  • Poly(propylene imine) dendrimers with histidine-maltose shell as novel type of nanoparticles for synapse and memory protection
    Ester Aso, Isak Martinsson, Dietmar Appelhans, Christiane Effenberg, Nuria Benseny-Cases, Josep Cladera, Gunnar Gouras, Isidre Ferrer, and Oxana Klementieva

    Nanomedicine: Nanotechnology, Biology, and Medicine, ISSN: 15499634, eISSN: 15499642, Pages: 198-209, Published: April 2019 Elsevier BV
    Poly(propylene imine) dendrimers have been shown to be promising 3-dimensional polymers for the use in the pharmaceutical and biomedical applications. Our aims of this study were first, to synthesize a novel type of dendrimer with poly(propylene imine) core and maltose-histidine shell (G4HisMal) assessing if maltose-histidine shell can improve the biocompatibility and the ability to cross the blood-brain barrier, and second, to investigate the potential of G4HisMal to protect Alzheimer disease transgenic mice from memory impairment. Our data demonstrate that G4HisMal has significantly improved biocompatibility and ability to cross the blood-brain barrier in vivo. Therefore, we suggest that a maltose-histidine shell can be used to improve biocompatibility and ability to cross the blood-brain barrier of dendrimers. Moreover, G4HisMal demonstrated properties for synapse and memory protection when administered to Alzheimer disease transgenic mice. Therefore, G4HisMal can be considered as a promising drug candidate to prevent Alzheimer disease via synapse protection.

  • Generation of an induced pluripotent stem cell line (CSC-46) from a patient with Parkinson's disease carrying a novel p.R301C mutation in the GBA gene
    Nadja Gustavsson, Ana Marote, Yuriy Pomeshchik, Kaspar Russ, Carla Azevedo, Margarita Chumarina, Stefano Goldwurm, Anna Collin, Luisa Pinto, António J. Salgado, Oxana Klementieva, Laurent Roybon, and Ekaterina Savchenko

    Stem Cell Research, ISSN: 18735061, eISSN: 18767753, Published: January 2019 Elsevier BV
    Mutations in the glucocerebrosidase (GBA) gene have been associated with the development of Parkinson's disease (PD). An induced pluripotent stem cell (iPSC) line was generated from a 60-year old patient diagnosed with PD and carrying a new mutation variant p.R301C in GBA. Using non-integrating Sendai virus-based technology, we utilized OCT3/4, SOX2, c-MYC and KLF4 transcription factors to reprogram skin fibroblasts into iPSCs. The generated iPSC line retained the mutation, displayed expression of common pluripotency markers, differentiated into the three germ layers, and exhibited normal karyotype. The iPSC line can be further used for studying PD pathogenesis.

  • S100A9-Driven Amyloid-Neuroinflammatory Cascade in Traumatic Brain Injury as a Precursor State for Alzheimer’s Disease
    Chao Wang, Igor A. Iashchishyn, Jonathan Pansieri, Sofie Nyström, Oxana Klementieva, John Kara, Istvan Horvath, Roman Moskalenko, Reza Rofougaran, Gunnar Gouras, Gabor G. Kovacs, S. K. Shankar, and Ludmilla A. Morozova-Roche

    Scientific Reports, eISSN: 20452322, Published: 1 December 2018 Springer Science and Business Media LLC
    Pro-inflammatory and amyloidogenic S100A9 protein is an important contributor to Alzheimer’s disease (AD) pathology. Traumatic brain injury (TBI) is viewed as a precursor state for AD. Here we have shown that S100A9-driven amyloid-neuroinflammatory cascade was initiated in TBI and may serve as a mechanistic link between TBI and AD. By analyzing the TBI and AD human brain tissues, we demonstrated that in post-TBI tissues S100A9, produced by neurons and microglia, becomes drastically abundant compared to Aβ and contributes to both precursor-plaque formation and intracellular amyloid oligomerization. Conditions implicated in TBI, such as elevated S100A9 concentration, acidification and fever, provide strong positive feedback for S100A9 nucleation-dependent amyloid formation and delay in its proteinase clearance. Consequently, both intracellular and extracellular S100A9 oligomerization correlated with TBI secondary neuronal loss. Common morphology of TBI and AD plaques indicated their similar initiation around multiple aggregation centers. Importantly, in AD and TBI we found S100A9 plaques without Aβ. S100A9 and Aβ plaque pathology was significantly advanced in AD cases with TBI history at earlier age, signifying TBI as a risk factor. These new findings highlight the detrimental consequences of prolonged post-TBI neuroinflammation, which can sustain S100A9-driven amyloid-neurodegenerative cascade as a specific mechanism leading to AD development.

  • Nano-scale Infrared Imaging of β-sheet Structures in Synaptic Junctions of Primary Neurons Isolated from Transgenic Mice
    O. Klementieva, J. Mathurin, A. Engdahl, R. Freitas, K. Willen, P. Uvdal, L.M. Miller, and G. Gouras

    International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, ISSN: 21622027, eISSN: 21622035, Volume: 2018-September, Published: 25 October 2018 IEEE
    Aβ is a class of aggregation-prone proteins, which may misfold into stable, β-sheet rich fibrils. Aβ is linked to the development of synaptic pathology in Alzheimer's disease (AD). However, a main question in the AD field is how Aβ contributes to AD neuropathology? Up to now there is little evidence for protein structural changes in diseased neuron. Our aim is to study the distribution of β-sheet structures in AD transgenic neurons in order to uncover sub-cellular mechanism(s) by which amyloid β-sheet structures are involved in AD pathology.

  • Prion-like seeding and nucleation of intracellular amyloid-β
    Tomas T. Olsson, Oxana Klementieva, and Gunnar K. Gouras

    Neurobiology of Disease, ISSN: 09699961, eISSN: 1095953X, Volume: 113, Pages: 1-10, Published: May 2018 Elsevier BV
    Alzheimer's disease (AD) brain tissue can act as a seed to accelerate aggregation of amyloid-β (Aβ) into plaques in AD transgenic mice. Aβ seeds have been hypothesized to accelerate plaque formation in a prion-like manner of templated seeding and intercellular propagation. However, the structure(s) and location(s) of the Aβ seeds remain unknown. Moreover, in contrast to tau and α-synuclein, an in vitro system with prion-like Aβ has not been reported. Here we treat human APP expressing N2a cells with AD transgenic mouse brain extracts to induce inclusions of Aβ in a subset of cells. We isolate cells with induced Aβ inclusions and using immunocytochemistry, western blot and infrared spectroscopy show that these cells produce oligomeric Aβ over multiple replicative generations. Further, we demonstrate that cell lysates of clones with induced oligomeric Aβ can induce aggregation in previously untreated N2a APP cells. These data strengthen the case that Aβ acts as a prion-like protein, demonstrate that Aβ seeds can be intracellular oligomers and for the first time provide a cellular model of nucleated seeding of Aβ.

  • 3D membrane segmentation and quantification of intact thick cells using cryo soft X-ray transmission microscopy: A pilot study
    Rubén Cárdenes, Chong Zhang, Oxana Klementieva, Stephan Werner, Peter Guttmann, Christoph Pratsch, Josep Cladera, and Bart H. Bijnens

    PLoS ONE, eISSN: 19326203, Published: April 2017 Public Library of Science (PLoS)
    Structural analysis of biological membranes is important for understanding cell and sub-cellular organelle function as well as their interaction with the surrounding environment. Imaging of whole cells in three dimension at high spatial resolution remains a significant challenge, particularly for thick cells. Cryo-transmission soft X-ray microscopy (cryo-TXM) has recently gained popularity to image, in 3D, intact thick cells (∼10μm) with details of sub-cellular architecture and organization in near-native state. This paper reports a new tool to segment and quantify structural changes of biological membranes in 3D from cryo-TXM images by tracking an initial 2D contour along the third axis of the microscope, through a multi-scale ridge detection followed by an active contours-based model, with a subsequent refinement along the other two axes. A quantitative metric that assesses the grayscale profiles perpendicular to the membrane surfaces is introduced and shown to be linearly related to the membrane thickness. Our methodology has been validated on synthetic phantoms using realistic microscope properties and structure dimensions, as well as on real cryo-TXM data. Results demonstrate the validity of our algorithms for cryo-TXM data analysis.

  • Pre-plaque conformational changes in Alzheimer's disease-linked Aβ and APP
    O. Klementieva, K. Willén, I. Martinsson, B. Israelsson, A. Engdahl, J. Cladera, P. Uvdal, and G. K. Gouras

    Nature Communications, eISSN: 20411723, Published: 13 March 2017 Springer Science and Business Media LLC
    Reducing levels of the aggregation-prone Aβ peptide that accumulates in the brain with Alzheimer's disease (AD) has been a major target of experimental therapies. An alternative approach may be to stabilize the physiological conformation of Aβ. To date, the physiological state of Aβ in brain remains unclear, since the available methods used to process brain tissue for determination of Aβ aggregate conformation can in themselves alter the structure and/or composition of the aggregates. Here, using synchrotron-based Fourier transform infrared micro-spectroscopy, non-denaturing gel electrophoresis and conformational specific antibodies we show that the physiological conformations of Aβ and amyloid precursor protein (APP) in brain of transgenic mouse models of AD are altered before formation of amyloid plaques. Furthermore, focal Aβ aggregates in brain that precede amyloid plaque formation localize to synaptic terminals. These changes in the states of Aβ and APP that occur prior to plaque formation may provide novel targets for AD therapy.

  • Microspectroscopy (μFTIR) reveals co-localization of lipid oxidation and amyloid plaques in human Alzheimer disease brains
    Núria Benseny-Cases, Oxana Klementieva, Marine Cotte, Isidre Ferrer, and Josep Cladera

    Analytical Chemistry, ISSN: 00032700, eISSN: 15206882, Pages: 12047-12054, Published: 16 December 2014 American Chemical Society (ACS)
    Amyloid peptides are the main component of one of the characteristic pathological hallmarks of Alzheimer's disease (AD): senile plaques. According to the amyloid cascade hypothesis, amyloid peptides may play a central role in the sequence of events that leads to neurodegeneration. However, there are other factors, such as oxidative stress, that may be crucial for the development of the disease. In the present paper, we show that it is possible, by using Fourier tranform infrared (FTIR) microscopy, to co-localize amyloid deposits and lipid peroxidation in tissue slides from patients affected by Alzheimer's disease. Plaques and lipids can be analyzed in the same sample, making use of the characteristic infrared bands for peptide aggregation and lipid oxidation. The results show that, in samples from patients diagnosed with AD, the plaques and their immediate surroundings are always characterized by the presence of oxidized lipids. As for samples from non-AD individuals, those without amyloid plaques show a lower level of lipid oxidation than AD individuals. However, it is known that plaques can be detected in the brains of some non-AD individuals. Our results show that, in such cases, the lipid in the plaques and their surroundings display oxidation levels that are similar to those of tissues with no plaques. These results point to lipid oxidation as a possible key factor in the path that goes from showing the typical neurophatological hallmarks to suffering from dementia. In this process, the oxidative power of the amyloid peptide, possibly in the form of nonfibrillar aggregates, could play a central role.

  • Effect of poly(propylene imine) glycodendrimers on β-amyloid aggregation in vitro and in APP/PS1 transgenic mice, as a model of brain amyloid deposition and alzheimer's disease
    O. Klementieva, E. Aso, D. Filippini, N. Benseny-Cases, M. Carmona, S. Juvés, D. Appelhans, J. Cladera, and I. Ferrer

    Biomacromolecules, ISSN: 15257797, eISSN: 15264602, Pages: 3570-3580, Published: 14 October 2013 American Chemical Society (ACS)
    Poly(propylene imine) (PPI) glycodendrimers are promising candidates as drug carriers and antiamyloidogenic and antiprionic agents. In this study the anti-β-amyloid capacity of PPI glycodendrimers of the fourth and fifth generations was investigated in vitro and in vivo. We assessed distinct PPI glycodendrimers including G4mDS and G5mDS, with electroneutral maltose shell, and G4mOS and G4m-IIIOS, with cationic maltose or maltotriose shell. Our results show that in vitro PPI maltose dendrimers reduce the toxicity of Aβ(1-42). However, only the electroneutral maltose dendrimers G4mDS and G5mDS reduce the toxicity of Alzheimer's disease brain extracts in SH-SY5Y neuroblastoma cells. PPI maltose dendrimers with electroneutral or cationic surface penetrate the cytoplasm of cultured cells, and they reach the brain when administered intranasally. Both cationic G4mOS and electroneutral G4mDS are able to modify the total burden of β-amyloid in APP/PS1 mice. The studied dendrimers did not reverse memory impairment in APP/PS1 mice following chronic administration; moreover, cationic G4mOS caused cognitive decline in nontransgenic mice. In spite of the capacity of G4mDS and G4mOS to cross the blood-brain barrier and modulate Aβ aggregation in APP/PS1 mice, further studies are needed to learn how to reduce the harmful effects of maltose dendrimers in vivo.

  • Granular non-fibrillar aggregates and toxicity in Alzheimer's disease
    Nuria Benseny-Cases, Oxana Klementieva, Jan Maly, and Josep Cladera

    Current Alzheimer Research, ISSN: 15672050, eISSN: 18755828, Pages: 962-971, Published: 2012 Bentham Science Publishers Ltd.
    Granular non-fibrillar aggregates (GNAs) are identified as possible toxic species in Alzheimer's disease. GNAs form on the surface of negatively charged biological membranes and as a consequence of an acidic environment, off the polymerization pathway at neutral pH. Aβ (1-40) GNAs disturb the bilayer structure of model membranes and seem to be more toxic to cells with negatively charged membranes (consequence of chronic pre-apoptosis). GNAs may be relevant in physiological situations associated to Alzheimer's disease: a local acidic pH at the cell surface (consequence of lipid oxidation or other cell insults) and acidification as a consequence of vascular events causing hypoxia. Together with previous descriptions of granular aggregates with poly-glutamine peptides related to Huntington's disease and the SH3 domain of PI3, GNAs related to Alzheimer's disease are a further example of a possible common aggregation and toxicity mechanism in conformational diseases. GNAs may represent a new pharmacological target in Alzheimer's disease.

  • In vitro oligomerization and fibrillogenesis of Amyloid-beta peptides
    Núria Benseny-Cases, Oksana Klementieva, and Josep Cladera

    Subcellular Biochemistry, ISSN: 03060225, Pages: 53-74, Published: 29 May 2012 Springer Netherlands
    The amyloid beta Ab(1-40) and Ab(1-42) peptides are the main components of the fibrillar plaques characteristically found in the brains affected by Alzheimer's disease. Fibril formation has been thoroughly studied in vitro using synthetic amyloid peptides and has been described to be a nucleation dependent polymerization process. During this process, defined by a slow nucleation phase followed by a rapid exponential elongation reaction, a whole range of aggregated species (low and high molecular weight aggregates) precede fibril formation. Toxic species related to the onset and development of Alzheimer's disease are thought to be found among these prefibrillar aggregates. Two main procedures are used to experimentally monitor fibril formation kinetics: through the measurement of the light scattered by the different peptide aggregates and using the fluorescent dye thioflavin T, which fluorescence increases when specifically interacting with amyloid fibrils. Reproducibility may, however, be difficult to achieve when measuring and characterizing fibril formation kinetics. This fact is mainly due to the difficulty in experimentally handling amyloid peptides, which is directly related to the difficulty of having them in a monomeric form at the beginning of the polymerization process. This has to do mainly with the type of solvent used for the preparation of the peptide stock solutions (water, DMSO, TFE, HFIP) and the control of determinant physicochemical parameters such as pH. Moreover, kinetic progression turns out to be highly dependent on the type of peptide counter-ion used, which will basically determine the duration of the nucleation phase and the rate at which high molecular weight oligomers are formed. Centrifugation and filtration procedures used in the preparation of the peptide stock solutions will also greatly influence the duration of the fibril formation process. In this chapter, a survey of the alluded experimental procedures is provided and a general frame is proposed for the interpretation of the fibril formation kinetics, intended to integrate the results from the different experimental approaches. The significance of the different aggregated species in terms of cell toxicity will be discussed. Special emphasis will be given to the influence of pH on the structural and toxic characteristics of amyloid aggregates, an aspect that may be particularly relevant in some specific physiological conditions.

  • Phosphorus dendrimers affect Alzheimer's (Aβ <inf>1-28</inf>) peptide and MAP-Tau protein aggregation
    Tomasz Wasiak, Maksim Ionov, Krzysztof Nieznanski, Hanna Nieznanska, Oxana Klementieva, Maritxell Granell, Josep Cladera, Jean-Pierre Majoral, Anne Marie Caminade, and Barbara Klajnert

    Molecular Pharmaceutics, ISSN: 15438384, eISSN: 15438392, Pages: 458-469, Published: 5 March 2012 American Chemical Society (ACS)
    Alzheimer's disease (AD) is characterized by pathological aggregation of β-amyloid peptides and MAP-Tau protein. β-Amyloid (Aβ) is a peptide responsible for extracellular Alzheimer's plaque formation. Intracellular MAP-Tau aggregates appear as a result of hyperphosphorylation of this cytoskeletal protein. Small, oligomeric forms of Aβ are intermediate products that appear before the amyloid plaques are formed. These forms are believed to be most neurotoxic. Dendrimers are highly branched polymers, which may find an application in regulation of amyloid fibril formation. Several biophysical and biochemical methods, like circular dichroism (CD), fluorescence intensity of thioflavin T and thioflavin S, transmission electron microscopy, spectrofluorimetry (measuring quenching of intrinsic peptide fluorescence) and MTT-cytotoxicity assay, were applied to characterize interactions of cationic phosphorus-containing dendrimers of generation 3 and generation 4 (CPDG3, CPDG4) with the fragment of amyloid peptide (Aβ(1-28)) and MAP-Tau protein. We have demonstrated that CPDs are able to affect β-amyloid and MAP-Tau aggregation processes. A neuro-2a cell line (N2a) was used to test cytotoxicity of formed fibrils and intermediate products during the Aβ(1-28) aggregation. It has been shown that CPDs might have a beneficial effect by reducing the system toxicity. Presented results suggest that phosphorus dendrimers may be used in the future as agents regulating the fibrilization processes in Alzheimer's disease.

  • Dendrimers antiamyloidogenic potential in neurodegenerative diseases
    Núria Benseny-Cases, Oxana Klementieva, and Josep Cladera

    New Journal of Chemistry, ISSN: 11440546, eISSN: 13699261, Pages: 211-216, Published: February 2012 Royal Society of Chemistry (RSC)
    Dendrimers have been shown to be capable of interfering in vitro with the formation of the amyloid fibrillar structures typically related to the onset and development of the so-called conformational diseases, such as Alzheimer's disease and prion diseases. This makes dendrimers potentially useful as compounds that could prevent or inhibit the action of the cytotoxic amyloid species. In the present paper we summarise the works on the interaction of dendrimers with amyloid peptides related to Alzheimer and prion diseases and take it as the basis from which to focus on some developments that will contribute to enhance the potential of dendrimers as antiamyloidogenic agents. An important first set of works was dedicated to the characterization of the effects of positively charged PAMAM and phosphorous dendrimers on the polymerization processes of different amyloid peptides. However, due to the inherent toxicity of positively charged dendrimers, the research has moved towards the design of more biocompatible dendrimers such as glycodendrimers. This sugar-decorated dendrimers have shown as well their capacity to interact with amyloids, a low level of cell toxicity has been measured for different cell lines and they have shown interesting properties as antiamyloidogenic agents. Other surface-decorated dendrimeric structures are finally also taken into account.

  • Dense shell glycodendrimers as potential nontoxic anti-amyloidogenic agents in Alzheimer's disease. Amyloid-dendrimer aggregates morphology and cell toxicity
    Oxana Klementieva, Núria Benseny-Cases, Alejandro Gella, Dietmar Appelhans, Brigitte Voit, and Josep Cladera

    Biomacromolecules, ISSN: 15257797, eISSN: 15264602, Pages: 3903-3909, Published: 14 November 2011 American Chemical Society (ACS)
    Dendrimers have been proved to interact with amyloids, although most of dendrimers assayed in amyloidogenic systems are toxic to cells. The development of glycodendrimers, poly(propyleneimine) (PPI) dendrimers decorated with maltose (Mal), represents the possibility of using dendrimers with a low intrinsic toxicity. In the present paper we show that fourth (PPI-G4-Mal) and fifth (PPI-G5-Mal) generation glycodendrimers have the capacity to interfere with Alzheimer's amyloid peptide Aβ(1-40) fibrilization. The interaction is generation dependent: PPI-G5-Mal blocks amyloid fibril formation generating granular nonfibrillar amorphous aggregates, whereas PPI-G4-Mal generates clumped fibrils at low dendrimer-peptide ratios and amorphous aggregates at high ratios. Both PPI-G4-Mal and PPI-G5-Mal are nontoxic to PC12 and SH-SY5Y cells. PPI-G4-Mal reduces amyloid toxicity by clumping fibrils together, whereas amorphous aggregates are toxic to PC12 cells. The results show that glycodendrimers are promising nontoxic agents in the search for anti-amyloidogenic compounds. Fibril clumping may be an anti-amyloid toxicity strategy.