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Sökning: Lotta Agholme

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  • Agholme, Lotta, et al. (författare)
  • An In Vitro Model for Neuroscience: Differentiation of SH-SY5Y Cells into Cells with Morphological and Biochemical Characteristics of Mature Neurons
  • 2010
  • Ingår i: Journal of Alzheimer's Disease. - Ios Press. - 1387-2877. ; 20:4, s. 1069-1082
  • Tidskriftsartikel (refereegranskat)abstract
    • Neuroscience, including research on Alzheimers disease, is hampered by the lack of suitable in vitro models to study the human nervous system. To counteract this, many attempts to differentiate cell lines into more neuron-like cells have been performed, resulting in partial expression of neuronal features. Furthermore, it has been reported that neuroblastoma cell lines lack mature isoforms of tau. Our aim was to develop an improved in vitro model, generating sustainable cells with morphology and biochemistry of human, mature neurons. To obtain cells with neuronal differentiation and function, we investigated the effect of combining three-dimensional culturing of SH-SY5Y cells in extracellular matrix (ECM) gel with several factors reported to have neuro-differentiating effects. This resulted in cells with apparent neuronal morphology with long, extensively branched neurites. Further investigation revealed expression of several neurospecific markers including synapse protein Sv2 and nuclear marker NeuN, as well as the presence of synapses and axonal vesicle transport. In addition, these cells expressed mature tau isoforms, and tau protein expression was significantly increased compared to undifferentiated cells, reaching levels found in adult human brain. In conclusion, we found that pre-treatment with retinoic acid followed by ECM gel culturing in combination with brain derived neurotrophic factor, neuregulin beta(1), nerve growth factor, and vitamin D-3 treatment generated sustainable cells with unambiguous resemblance to adult neurons. These cells also expresses adult splicing forms of tau with neuronal localization, making this cellular in vitro model useful in many areas of neuroscience research, particularly the Alzheimers disease field.
  • Agholme, Lotta, et al. (författare)
  • Getting rid of intracellular Aβ- loss of cellular degradation leads to transfer between connected neurons
  • 2014
  • Ingår i: Current pharmaceutical design. - Bentham Science Publishers. - 1381-6128. ; 20:15, s. 2458-2468
  • Tidskriftsartikel (refereegranskat)abstract
    • The sporadic, late onset form of Alzheimers disease (AD) shares pathological hallmarks with the familial form; however, no clear reason for increased beta-amyloid (A beta) generation has been found in the former. It has long been speculated that the late onset form of AD is caused by reduced degradation and/or clearance of A beta. Indeed, both intracellular degradation systems, the proteasomal and lysosomal systems, have been shown to be defective in AD. Reduced proteasome activity increases levels of intracellular and secreted A beta. Furthermore, accumulation of improperly degraded A beta in the lysosomes causes lysosomal disruption and cell death. We recently showed that oligomeric A beta can be transmitted from one neuron to another, which causes neurotoxicity. In both the donating and receiving cells, A beta accumulates in the endo-lysosomal compartment. It is possible that ineffective degradation of A beta causes its transfer to neighboring neurons, thereby spreading AD pathology. This review summarizes the data underlying the idea of reduced A beta clearance and subsequent A beta spread in AD, and also suggests new therapeutic methods, which are aimed at targeting the degradation systems and synaptic transfer. By enhancing degradation of intracellular accumulated A beta, it can be possible to remove it and avoid A beta-induced neurodegeneration without disturbing the endogenously important pool of secreted A beta. Additionally, drugs targeted to inhibit the spread of intracellular toxic A beta aggregates may also be useful in stopping the progression of pathology, without affecting the level of A beta that normally occurs in the brain.
  • Agholme, Lotta, et al. (författare)
  • Low-dose γ-secretase inhibition increases secretion of Aβ peptides and intracellular oligomeric Aβ.
  • 2017
  • Ingår i: Molecular and cellular neurosciences. - 1095-9327. ; 85, s. 211-219
  • Tidskriftsartikel (refereegranskat)abstract
    • γ-Secretase inhibitors have been considered promising drug candidates against Alzheimer's disease (AD) due to their ability to reduce amyloid-β (Aβ) production. However, clinical trials have been halted due to lack of clinical efficacy and/or side effects. Recent in vitro studies suggest that low doses of γ-secretase inhibitors may instead increase Aβ production. Using a stem cell-derived human model of cortical neurons and low doses of the γ-secretase inhibitor DAPT, the effects on a variety of Aβ peptides were studied using mass spectrometry. One major focus was to develop a novel method for specific detection of oligomeric Aβ (oAβ), and this was used to study the effects of low-dose γ-secretase inhibitor treatment on intracellular oAβ accumulation. Low-dose treatment (2 and 20nM) with DAPT increased the secretion of several Aβ peptides, especially Aβx-42. Furthermore, using the novel method for oAβ detection, we found that 2nM DAPT treatment of cortical neurons resulted in increased oAβ accumulation. Thus, low dose-treatment with DAPT causes both increased production of long, aggregation-prone Aβ peptides and accumulation of intracellular Aβ oligomers, both believed to contribute to AD pathology.
  • Agholme, Lotta, et al. (författare)
  • Proteasome Inhibition Induces Stress Kinase Dependent Transport Deficits – Implications for Alzheimer’s Disease
  • 2014
  • Ingår i: Molecular and Cellular Neuroscience. - Elsevier. - 1044-7431. ; 58, s. 29-39
  • Tidskriftsartikel (refereegranskat)abstract
    • Alzheimer’s disease (AD) is characterized by accumulation of two misfolded and aggregated proteins, β-amyloid and hyperphosphorylated tau. Both cellular systems responsible for clearance of misfolded and aggregated proteins, the lysosomal and the proteasomal, have been shown to be malfunctioning in the aged brain and more so in AD patients. This malfunction could be the cause of β-amyloid and tau accumulation, eventually aggregating in plaques and tangles. We have investigated how decreased proteasome activity affects AD related pathophysiological changes of microtubule transport and stability, as well as tau phosphorylation. To do this, we used our recently developed neuronal model where human SH-SY5Y cells obtain neuronal morphology and function through differentiation. We found that exposure to low doses of the proteasome inhibitor MG-115 caused disturbed neuritic transport, together with microtubule destabilization and tau phosphorylation. Furthermore, reduced proteasome activity activated several kinases implicated in AD pathology, including JNK, c-Jun and ERK 1/2. Restoration of the microtubule transport was achieved by inhibiting ERK 1/2 activation, and simultaneous inhibition of both ERK 1/2 and c-Jun reversed the proteasome inhibition-induced tau phosphorylation. Taken together, this study suggests that a decrease in proteasome activity can, through activation of c-Jun and ERK 1/2, result in several events contributing to AD pathology. Restoring proteasome function or inhibiting ERK 1/2 and c-Jun could therefore be used as novel treatments against AD.
  • Agholme, Lotta (författare)
  • The involvement of degradation pathways and neuron-to-neuron transmission in Alzheimer’s disease
  • 2012
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Although the vast majority of Alzheimer’s disease (AD) cases are of the sporadic type, mutations causing the familial form have been the focus of AD research for decades. The disease is pathologically characterised by β-amyloid (Aβ) and tau protein aggregates in neuritic plaques and neurofibrillary tangles. Furthermore, it is known that AD pathology spreads throughout the brain, most often along the same anatomical pattern. However, so far no cause for the sporadic form of the disease has been found. Accumulation of protein aggregates as well as decreased activity of the protein degradation systems, lysosomes and proteasomes, is found in diseased brains. This indicates that defective degradation contributes to sporadic AD.The aim of this thesis was to develop an improved neuronal model, and study the effects of decreased proteasome function on tau phosphorylation and axonal transport. In addition, the effects on Aβ accumulation and generation upon proteasome inhibition were investigated. Finally, the possibility that intracellularly accumulated Aβ oligomers could be transferred from one neuron to another was tested.Differentiation of human SH-SY5Y neuroblastoma cells in an extracellular matrix gel, using a set of neurotrophic factors, resulted in cells with neuronal phenotype, expressing neuron specific markers and all six adult isoforms of tau. Within this neuronal model, we found that reduced proteasome activity inhibited neuritic transport, and caused tau phosphorylation in a c-Jun and ERK 1/2 dependent manner. Using proteasome inhibition in APP overexpressing cells, we found an autophagy dependent intralysosomal Aβ accumulation, together with elevation of intra- and extracellular concentrations of Aβ. Autophagy inhibition protected the cells from the toxicity induced by decreased proteasome activity. Finally, we could, as the first group, show that Aβ can be directly transferred from one neuron to another through connected neurites. Furthermore, accumulation of Aβ in the endo-lysosomal compartment of receiving cells caused toxicity and neurodegeneration.We believe that cells not able to degrade accumulated Aβ, due to increased generation or reduced degradative capacity, instead tries to clear its content through transfer to connected neurons. If not properly degraded in the receiving cell, this can accelerate AD pathology and cause neuritic and neuronal degeneration spreading throughout the brain. Increasing the activity of the degradative systems, or inhibiting transmission of Aβ between neurons could therefore be novel treatments for AD.
  • Armstrong, Andrea, et al. (författare)
  • Lysosomal Network Proteins as Potential Novel CSF Biomarkers for Alzheimers Disease
  • 2014
  • Ingår i: Neuromolecular medicine. - Humana Press. - 1535-1084. ; 16:1, s. 150-160
  • Tidskriftsartikel (refereegranskat)abstract
    • The success of future intervention strategies for Alzheimers disease (AD) will likely rely on the development of treatments starting early in the disease course, before irreversible brain damage occurs. The pre-symptomatic stage of AD occurs at least one decade before the clinical onset, highlighting the need for validated biomarkers that reflect this early period. Reliable biomarkers for AD are also needed in research and clinics for diagnosis, patient stratification, clinical trials, monitoring of disease progression and the development of new treatments. Changes in the lysosomal network, i.e., the endosomal, lysosomal and autophagy systems, are among the first alterations observed in an AD brain. In this study, we performed a targeted search for lysosomal network proteins in human cerebrospinal fluid (CSF). Thirty-four proteins were investigated, and six of them, early endosomal antigen 1 (EEA1), lysosomal-associated membrane proteins 1 and 2 (LAMP-1, LAMP-2), microtubule-associated protein 1 light chain 3 (LC3), Rab3 and Rab7, were significantly increased in the CSF from AD patients compared with neurological controls. These results were confirmed in a validation cohort of CSF samples, and patients with no neurochemical evidence of AD, apart from increased total-tau, were found to have EEA1 levels corresponding to the increased total-tau levels. These findings indicate that increased levels of LAMP-1, LAMP-2, LC3, Rab3 and Rab7 in the CSF might be specific for AD, and increased EEA1 levels may be a sign of general neurodegeneration. These six lysosomal network proteins are potential AD biomarkers and may be used to investigate lysosomal involvement in AD pathogenesis.
  • Bergström, Petra, et al. (författare)
  • Amyloid precursor protein expression and processing are differentially regulated during cortical neuron differentiation
  • 2016
  • Ingår i: Scientific Reports. - 2045-2322. ; 6
  • Tidskriftsartikel (refereegranskat)abstract
    • Amyloid precursor protein (APP) and its cleavage product amyloid beta (A beta) have been thoroughly studied in Alzheimer's disease. However, APP also appears to be important for neuronal development. Differentiation of induced pluripotent stem cells (iPSCs) towards cortical neurons enables in vitro mechanistic studies on human neuronal development. Here, we investigated expression and proteolytic processing of APP during differentiation of human iPSCs towards cortical neurons over a 100-day period. APP expression remained stable during neuronal differentiation, whereas APP processing changed. alpha-Cleaved soluble APP (sAPP alpha) was secreted early during differentiation, from neuronal progenitors, while beta-cleaved soluble APP (sAPP beta) was first secreted after deep-layer neurons had formed. Short A beta peptides, including A beta 1-15/16, peaked during the progenitor stage, while processing shifted towards longer peptides, such as A beta 1-40/42, when post-mitotic neurons appeared. This indicates that APP processing is regulated throughout differentiation of cortical neurons and that amyloidogenic APP processing, as reflected by A beta 1-40/42, is associated with mature neuronal phenotypes.
  • Domert, Jakob, et al. (författare)
  • Aggregated Alpha-Synuclein Transfer Efficiently between Cultured Human Neuron-Like Cells and Localize to Lysosomes
  • 2016
  • Ingår i: PLOS ONE. - PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 11:12
  • Tidskriftsartikel (refereegranskat)abstract
    • Parkinsons disease and other alpha-synucleinopathies are progressive neurodegenerative diseases characterized by aggregates of misfolded alpha-synuclein spreading throughout the brain. Recent evidence suggests that the pathological progression is likely due to neuron-to-neuron transfer of these aggregates between neuroanatomically connected areas of the brain. As the impact of this pathological spreading mechanism is currently debated, we aimed to investigate the transfer and subcellular location of alpha-synuclein species in a novel 3D co-culture human cell model based on highly differentiated SH-SY5Y cells. Fluorescently-labeled monomeric, oligomeric and fibrillar species of alpha-synuclein were introduced into a donor cell population and co-cultured with an EGFP-expressing acceptor-cell population of differentiated neuron-like cells. Subsequent transfer and colocalization of the different species were determined with confocal microscopy. We could confirm cell-to-cell transfer of all three alpha-synuclein species investigated. Interestingly the level of transferred oligomers and fibrils and oligomers were significantly higher than monomers, which could affect the probability of seeding and pathology in the recipient cells. Most alpha-synuclein colocalized with the lysosomal/endosomal system, both pre- and postsynaptically, suggesting its importance in the processing and spreading of alpha-synuclein.
  • Domert, Jakob, et al. (författare)
  • Spreading of Amyloid-β Peptides via Neuritic Cell-to-cell Transfer Is Dependent on Insufficient Cellular Clearance
  • 2014
  • Ingår i: Neurobiology of Disease. - Elsevier. - 0969-9961. ; 65, s. 82-92
  • Tidskriftsartikel (refereegranskat)abstract
    • The spreading of pathology through neuronal pathways is likely to be the cause of the progressive cognitive loss observed in Alzheimer's disease (AD) and other neurodegenerative diseases. We have recently shown the propagation of AD pathology via cell-to-cell transfer of oligomeric amyloid beta (Aβ) residues 1-42 (oAβ1-42) using our donor-acceptor 3-D co-culture model. We now show that different Aβ-isoforms (fluorescently labeled 1-42, 3(pE)-40, 1-40 and 11-42 oligomers) can transfer from one cell to another. Thus, transfer is not restricted to a specific Aβ-isoform. Although different Aβ isoforms can transfer, differences in the capacity to clear and/or degrade these aggregated isoforms result in vast differences in the net amounts ending up in the receiving cells and the net remaining Aβ can cause seeding and pathology in the receiving cells. This insufficient clearance and/or degradation by cells creates sizable intracellular accumulations of the aggregation-prone Aβ1-42 isoform, which further promotes cell-to-cell transfer; thus, oAβ1-42 is a potentially toxic isoform. Furthermore, cell-to-cell transfer is shown to be an early event that is seemingly independent of later appearances of cellular toxicity. This phenomenon could explain how seeds for the AD pathology could pass on to new brain areas and gradually induce AD pathology, even before the first cell starts to deteriorate, and how cell-to-cell transfer can act together with the factors that influence cellular clearance and/or degradation in the development of AD.
  • Kim, Woojin Scott, et al. (författare)
  • Increased ATP-binding cassette transporter A1 expression in Alzheimer's disease hippocampal neurons
  • 2010
  • Ingår i: Journal of Alzheimer's disease : JAD. - 1875-8908. ; 21:1, s. 193-205
  • Tidskriftsartikel (refereegranskat)abstract
    • ATP-binding cassette transporter A1 (ABCA1) reduces amyloid-beta burden in transgenic mouse models of Alzheimer's disease (AD). Associations between ABCA1 polymorphisms and AD risk are also established. Little is known regarding the regulation of ABCA1 expression in the brain and how this may be affected by AD. In the present study we assessed ABCA1 mRNA and protein expression in the hippocampus of AD cases compared to controls. ABCA1 was clearly expressed in hippocampal neurons and expression was increased two- to three-fold in AD cases. The increased hippocampal ABCA1 expression was associated with increased APOE and PUMA gene expression, implying an association with neuronal stress. Consistent with this, treatment of SK-N-SH neurons with amyloid-beta peptide resulted in a 48% loss in survival and a significant upregulation of ABCA1, APOE, and PUMA gene expression. Studies in young (2 month) and old (12 month) transgenic mice expressing a familial AD form of human amyloid-beta protein precursor and presenilin-1 revealed a significant age-dependent upregulation of hippocampal Abca1 compared to wild-type control mice. However, hippocampal Apoe and Puma gene expression were not correlated with increased Abca1 expression in mice. Our data indicate that ABCA1 is upregulated in AD hippocampal neurons potentially via an amyloid-beta-mediated pathway.
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