The gradual deterioration of cognitive functions in Alzheimer’s disease is paralleled by a hierarchical progression of amyloid-beta and tau brain pathology. Recent findings indicate that toxic ...oligomers of amyloid-beta may cause propagation of pathology in a prion-like manner, although the underlying mechanisms are incompletely understood. Here we show that small extracellular vesicles, exosomes, from Alzheimer patients’ brains contain increased levels of amyloid-beta oligomers and can act as vehicles for the neuron-to-neuron transfer of such toxic species in recipient neurons in culture. Moreover, blocking the formation, secretion or uptake of exosomes was found to reduce both the spread of oligomers and the related toxicity. Taken together, our results imply that exosomes are centrally involved in Alzheimer’s disease and that they could serve as targets for development of new diagnostic and therapeutic principles.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Telomerase reverse transcriptase (TERT) activity is up-regulated in several types of tumors including glioblastoma (GBM). In the present study, 128 primary glioblastoma patients were examined for ...single nucleotide polymorphisms of TERT in blood and in 92 cases for TERT promoter mutations in tumors. TERT promoter mutations were observed in 86% of the tumors and of these, C228T (-124 bp upstream start codon) was detected in 75% and C250T (-146 bp) in 25% of cases. TERT promoter mutations were associated with shorter overall survival (11 vs. 20 months p = 0.002 and 12 vs. 20, p = 0.04 for C228T and C250T, respectively). The minor alleles of rs2736100 and rs10069690 SNP's, located in intron 2 and the promotor regions, respectively, were associated with an increased risk of developing GBM (p = 0.004 and 0.001). GBM patients having both TERT promoter mutations and being homozygous carriers of the rs2853669 C-allele displayed significantly shorter overall survival than those with the wild type allele. The rs2853669 SNP is located in a putative Ets2 binding site in the promoter (-246 bp upstream start codon) close to the C228T and C250T mutation hot spots. Interleukin-6 (IL-6) expression regulated by TERT promoter status and polymorphism, what leads us to think that TERT and IL-6 plays a significant role in GBM, where specific SNPs increase the risk of developing GBM while the rs2853669 SNP and specific mutations in the TERT promoter of the tumor lead to shorter survival.
Parkinson's 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.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The misfolding of transactive response DNA-binding protein (TDP-43) is a major contributor to the pathogenesis of TDP-43 proteinopathies, including amyotrophic lateral sclerosis and frontotemporal ...lobar degeneration with TDP-43 inclusions, but also plays a role in other neurodegenerative diseases including Alzheimer’s disease. It is thought that different truncations at the N- and C-termini of TDP-43 contribute to its misfolding and aggregation in the brain, and that these aberrant TDP-43 fragments contribute to disease. Despite this, little is known about whether different truncation events influence the protein’s transmissibility between cells, and how this cell to cell transfer occurs. In this study, we use a well-established cellular model to study the efficiency by which full-length and truncated TDP-43 fragments are transferred between neuron-like cells. We demonstrate that preservation of the N-terminus of TDP-43 enhances its transmissibility between cells, and that this protein transmission occurs in a manner exclusive of extracellular vesicles, instead requiring cellular proximity for efficient propagation. These data indicate that the N-terminus of TDP-43 might be a useful target in the generation of therapeutics to limit the spread of TDP-43 pathology.
Alzheimer's disease (AD) is an incurable, progressive and devastating neurodegenerative disease. Pathogenesis of AD is associated with the aggregation and accumulation of amyloid beta (Aβ), a major ...neurotoxic mediator that triggers neuroinflammation and memory impairment. Recently, we found that cellulose ether compounds (CEs) have beneficial effects against prion diseases by inhibiting protein misfolding and replication of prions, which share their replication mechanism with Aβ. CEs are FDA-approved safe additives in foods and pharmaceuticals. Herein, for the first time we determined the therapeutic effects of the representative CE (TC-5RW) in AD using in vitro and in vivo models. Our in vitro studies showed that TC-5RW inhibits Aβ aggregation, as well as neurotoxicity and immunoreactivity in Aβ-exposed human and murine neuroblastoma cells. In in vivo studies, for the first time we observed that single and weekly TC-5RW administration, respectively, improved memory functions of transgenic 5XFAD mouse model of AD. We further demonstrate that TC-5RW treatment of 5XFAD mice significantly inhibited Aβ oligomer and plaque burden and its associated neuroinflammation via regulating astrogliosis, microgliosis and proinflammatory mediator glial maturation factor beta (GMFβ). Additionally, we determined that TC-5RW reduced lipopolysaccharide-induced activated gliosis and GMFβ in vitro. In conclusion, our results demonstrate that CEs have therapeutic effects against Aβ pathologies and cognitive impairments, and direct, potent anti-inflammatory activity to rescue neuroinflammation. Therefore, these FDA-approved compounds are effective candidates for developing therapeutics for AD and related neurodegenerative diseases associated with protein misfolding.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
We sought to analyse the androgen receptor (AR) in glioblastoma (GBM) due to the location of the AR gene on chromosome X, often reported with shorter survival and higher prevalence of GBM among ...males. Copy number (CN) and mRNA expression of AR were tested with droplet digital PCR in 91 fresh‐frozen GBM samples and 170 formalin‐fixed, paraffin‐embedded samples collected at Linköping University Hospital. The fresh‐frozen cohort was also subjected to pyrosequencing methylation analysis of 17 CpG sites in the AR promoter. Additionally, the gene expression of AR was analysed in the fresh‐frozen cohort and The Cancer Genome Atlas (TCGA) cohort of isocitrate dehydrogenase wild‐type primary GBM (135 females and 219 males). The association of AR expression and overall survival (OS) was tested with Kaplan–Meier log rank analysis after dichotomisation by maximally selected rank statistics. We found that AR CN alterations were more common in female GBM. AR gene expression correlated with methylation levels of different CpG sites in males and females but there was no difference in expression between sexes. Survival analysis of TCGA cohort revealed the opposite effect of AR overexpression on OS of males and females, with high AR expression correlating with shorter OS in females and longer OS in males. Additional gene set enrichment analysis showed that AR expression correlated with DNA repair response, especially in the male group. In summary, we found that high AR gene expression in GBM exhibits sex‐dependent effects on patient survival, which, for males, is linked to DNA repair response.
Glioblastoma (GBM) is more common among males; however, the reason for sex differences remains largely unknown. Through molecular analyses of androgen receptor (AR) in GBM samples, we found that AR is commonly expressed in tumours of both sexes, but copy number alterations of the gene coding for AR are more frequent in females. Additionally, high AR expression correlates with worse survival among females but better survival among males.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Recently, extracellular vesicles (EVs), such as exosomes, have been proposed to play an influential role in the cell-to-cell spread of neurodegenerative diseases, including the intercellular ...transmission of α-synuclein (α-syn). However, the regulation of EV biogenesis and its relation to Parkinson’s disease (PD) is only partially understood. The generation of EVs through the ESCRT-independent pathway depends on the hydrolysis of sphingomyelin by neutral sphingomyelinase 2 (nSMase2) to produce ceramide, which causes the membrane of endosomal multivesicular bodies to bud inwards. nSMase2 is sensitive to oxidative stress, a common process in PD brains; however, little is known about the role of sphingomyelin metabolism in the pathogenesis of PD. This is the first study to show that inhibiting nSMase2 decreases the transfer of oligomeric aggregates of α-syn between neuron-like cells. Furthermore, it reduced the accumulation and aggregation of high molecular weight α-syn. Hypoxia, as a model of oxidative stress, reduced the levels of nSMase2, but not its enzymatic activity, and significantly altered the lipid composition of cells without affecting EV abundance or the transfer of α-syn. These data show that altering sphingolipids can mitigate the spread of α-syn, even under hypoxic conditions, potentially suppressing PD progression.
The sporadic, late onset form of Alzheimer's disease (AD) shares pathological hallmarks with the familial form; however, no clear reason for increased β-amyloid (Aβ) 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 Aβ. 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 Aβ. Furthermore, accumulation of improperly degraded Aβ in the lysosomes causes lysosomal disruption and cell death. We recently showed that oligomeric Aβ can be transmitted from one neuron to another, which causes neurotoxicity. In both the donating and receiving cells, Aβ accumulates in the endo-lysosomal compartment. It is possible that ineffective degradation of Aβ causes its transfer to neighboring neurons, thereby spreading AD pathology. This review summarizes the data underlying the idea of reduced Aβ clearance and subsequent Aβ 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 Aβ, it can be possible to remove it and avoid Aβ-induced neurodegeneration without disturbing the endogenously important pool of secreted Aβ. Additionally, drugs targeted to inhibit the spread of intracellular toxic Aβ aggregates may also be useful in stopping the progression of pathology, without affecting the level of Aβ that normally occurs in the brain.
Amyloid beta peptide (Aβ) is the main component of extraneuronal senile plaques typical of Alzheimer's disease (AD) brains. Although Aβ is produced by normal neurons, it is shown to accumulate in ...large amounts within neuronal lysosomes in AD. We have recently shown that under normal conditions the majority of Aβ is localized extralysosomally, while oxidative stress significantly increases intralysosomal Aβ content through activation of macroautophagy. It is also suggested that impaired Aβ secretion and resulting intraneuronal increase of Aβ can contribute to AD pathology. However, it is not clear how Aβ is distributed inside normal neurons, and how this distribution is effected when Aβ secretion is inhibited.
Using retinoic acid differentiated neuroblastoma cells and neonatal rat cortical neurons, we studied intracellular distribution of Aβ by double immunofluorescence microscopy for Aβ40 or Aβ42 and different organelle markers. In addition, we analysed the effect of tetanus toxin-induced exocytosis inhibition on the intracellular distribution of Aβ.
Under normal conditions, Aβ was found in the small cytoplasmic granules in both neurites and perikarya. Only minor portion of Aβ was colocalized with trans-Golgi network, Golgi-derived vesicles, early and late endosomes, lysosomes, and synaptic vesicles, while the majority of Aβ granules were not colocalized with any of these structures. Furthermore, treatment of cells with tetanus toxin significantly increased the amount of intracellular Aβ in both perikarya and neurites. Finally, we found that tetanus toxin increased the levels of intralysosomal Aβ although the majority of Aβ still remained extralysosomally.
Our results indicate that most Aβ is not localized to Golgi-related structures, endosomes, lysosomes secretory vesicles or other organelles, while the suppression of Aβ secretion increases intracellular intra- and extralysosomal Aβ.
PDF
