| 1. |
- Agholme, Lotta
(författare)
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The involvement of degradation pathways and neuron-to-neuron transmission in Alzheimer’s disease
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)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.
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| 2. |
- Andin, Josefine, et al.
(författare)
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Environmental enrichment induces changes in the mRNA expression of rat EAAC1 and NMDA but not in AMPA
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Interaction with the environment has a key role in refining the neuronal circuitry required for normal brain function throughout life. Profound effects of enriched environment has been shown on neuronal strucrure and chemistry in experimental animals. Epidemiological studies imply that this is true also in man, thus cognitive stimulation has a protective effect on neurodegeneration, e.g. Alzheimer's disease. Glutamatergic corticocortical pathways are imperative for cognitive functions, such as memory and learning, and long term porenriation relies on the AMPA and NMDAglutamate rcceptors. The glutamate signalling is also dependent on a fine-runed transport system, in the hippocampus primarily by theglutamate transporter EAACl. In this study we show how environmental enrichment modulates these parts of the glutamarergic system using in siru hybridization. This work demonstrates for the first time that environmental enrichment modulates the mRNA expression of EAAC1 which is significantly decreased in hippocampal and cortical areas. We also provide further evidence about the upregulation of NMDA mRNA after environmental enrichement, and show it to have a regionally and hemisphere specific regulation. The current work also confirms that AMPA mRNA is nor per se changed by environmental enrichment in adult animals. Taken together, our results extend the knowledge of the glutamatergic system and its modulation by environmental enrichment and could contribute to the development of strategies aimed at limiting pathological changes associated with glutamatergic dysfunctions.
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| 3. |
- Bauer, Susanne
(författare)
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Cell type-specific translatome analysis of mouse models of three genetic neurodegenerative diseases
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The burden neurodegenerative diseases place on patients, their loved ones, and the healthcare system is significant, and despite extensive research efforts, there is currently no cure. Since degenerative changes in the brain can begin years before symptoms appear, early intervention is critical. Additionally, neurodegenerative diseases target certain brain regions and neuron types early on. A more comprehensive understanding of the affected cells during the presymptomatic phase is therefore crucial for an effective and targeted intervention. Herein, we isolated, sequenced, and analyzed translatome samples from six neuronal cell types in knock-in mouse models of three monogenic neurodegenerative diseases at a presymptomatic stage: genetic Creutzfeldt-Jakob disease (gCJD), fatal familial insomnia (FFI), and Huntington’s disease (HD). To obtain the translatome samples, we used RiboTag to immunoprecipitate HA-tagged ribosomes with their translating mRNAs from targeted cell types. We analyzed six cell types across two brain regions: cerebral and cerebellar glutamatergic and GABAergic neurons, and cerebral parvalbumin (PV) and somatostatin (SST)-expressing neurons. In the first paper, we focused our analysis on the prion diseases, gCJD (E200K) and FFI (D178N). Here observed a similar response of SST+ neurons, a cell type not previously reported as affected, in both disease models. This was characterized by upregulation of ribosomeassociated genes, and downregulation of cytoskeleton and synapse-associated genes in FFI. Weighted gene co-expression network analysis of SST+ neurons pointed towards the downregulation of mTOR inhibition as a potential mechanism underlying the observed gene expression changes. In the second paper, we analyzed a 129S4-HdhQ200 knock-in mouse model of HD. Histological and behavioral assessment revealed pathological changes in the striatum and cerebellum at 9 months and a later, mild behavioral phenotype. Translatome analysis indicated a surprisingly strong response in reportedly resistant glutamatergic neurons of the cerebellum, marked by upregulation of cell cycle regulators Ccnd1 and chromobox protein genes. In the third paper, we aimed to compare disease-specific responses of PV+ neurons across the three disease models. This analysis revealed a milder response in HD compared to prion disease at comparable disease stages. Functional analysis further indicated PV+ neurons may respond differently in the investigated diseases, showing upregulation of immune response-associated pathways in gCJD, neurodegenerative-disease pathways in FFI, and autophagy in HD. Lastly, the generation of mouse models such as were used in papers I-III requires stable and predictable transgene expression without interfering with the expression of endogenous genes. In the fourth paper, we conducted a pilot study to compare three potential loci, Rpl6, Rpl7, and Eef1a1, as potential safe harbors for transgene integration. Preliminary results indicated that the Rpl6 locus may be best suited for our purposes. Furthermore, this work generated a novel dataset consisting of translatome profiles of six cell types in three neurodegenerative disease models. This provides gene expression data at a previously unavailable level of cellular resolution, especially in prion disease. We believe that this data will serve as a valuable resource for future research and help expand our understanding of the early molecular mechanisms in neurodegenerative disease beyond the scope of this thesis.
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| 4. |
- Domert, Jakob, 1986-
(författare)
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Neuron-to-neuron propagation of neurodegenerative proteins; relation to degradative systems
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Alzheimer’s disease (AD) and Parkinson’s disease (PD) are defined by neurodegeneration and accumulations of misfolded proteins that spread through the brain in a well characterized manner. In AD these accumulations consist mainly of β-amyloid (Aβ) and tau, while in PD, α-synuclein (α-syn) make up the characteristic lewy pathology. The general aim of this thesis was to investigate mechanisms associated with neurotoxic peptide activity by Aβ, tau and α-syn in relation to cellular degradation and transfer with a cell-to-cell transfer model system. We found that intercellular transfer of oligomeric Aβ occurs independently of isoform. However, the amount of transfer correlates with each isoforms ability to resist degradation or cellular clearance. The Aβ1-42 isoform showed particular resistance to clearance, which resulted in higher levels of cell-to-cell transfer of the isoform and lysosomal stress caused by accumulation. As Aβ accumulations can inhibit the proteasomal degradation we investigated how reduced proteasomal degradation affected neuron-like cells. We found increased levels of phosphorylated tau protein, disturbed microtubule stability and impaired neuritic transport after reduced proteasomal activity. These changes was partly linked to c-Jun and ERK 1/2 kinase activity. We could also show that α-syn transferred from cell-to-cell in our model system, with a higher degree of transfer for the larger oligomer and fibrillar species. Similar to Aβ, α-syn mainly colocalized with lysosomes, before and after transfer. Lastly, we have developed our cell-to-cell transfer system into a model suitable for high throughput screening (HTS). The type of cells have been upgraded from SH-SY5Y cells to induced pluripotent stem cells (iPSCs), with a differentiation profile more similar to mature neurons. The next step will be screening a small molecular library for substances with inhibitory effect on cell-to-cell transfer of Aβ peptides. The importance of the degradative systems in maintaining protein homeostasis and prevent toxic accumulations in general is well known. Our findings shows the importance of these systems for neurodegenerative diseases and also highlight the link between degradation and cell-to-cell transfer. To restore or enhance the degradative systems would be an interesting avenue to treat neurodegenerative diseases. Another way would be to inhibit the transfer of misfolded protein aggregates. By using the HTS model we developed, a candidate substance with good inhibitory effect on transfer can hopefully be found.
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| 5. |
- Elander, Louise, 1980-, et al.
(författare)
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Prostaglandin E2 receptors in IL-1β induced anorexia
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Anorexia in response to immune challenge by Interleukin-1β (IL-1β) has been shown to be dependent on Prostaglandin E2 (PGE2) produced by the inducible enzyme microsomal prostaglandin E synthase-1 (mPGES-1). However, it is not known which of the four known PGE2 receptors EP1-4, encoded by the genes Ptger 1-4, that mediates the PGE2-induced anorexia. Here we examined food intake in mice deficient in EP1, EP2 and EP3, respectively, during normal conditions and following treatment with IL-1β. Neither of the gene deletions affected baseline food intake, and all the three genotypes displayed anorexia following IL-1β injection, similar to wild type mice. Previous work has demonstrated that the EP3 receptor is critical for the generation of fever, and that EP1 and EP3 receptors mediate inflammationinduced activation of the hypothalamic-pituitary-adrenal (HPA) axis. The present data, showing intact anorexigenic responses in EP1 and EP3 deficient mice, as well as in mice with deletion of the EP2 receptor, hence suggest that PGE2-elicited acute phase responses are mediated by distinct set or sets of PGE2-receptors.
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| 6. |
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| 7. |
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| 8. |
- Haj-Hosseini, Neda, 1980-, et al.
(författare)
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Stereotactic Brain Tumor Optical Biopsy
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To provide guidance for targeting diagnostic tumor tissue and to avoid vessel rupture during the biopsy procedure an application specific fiber optic probe was devel-oped. The setup incorporated an in-house developed fluorescence spectroscopy system for 5-aminolevulinic acid (5-ALA) induced protopophyrin IX (PpIX) for detection in the tumor, and laser Doppler flowmeter (LDF) system for measurement of blood perfusion. Fluorescence and blood flow were recorded millimeter-wise towards the pre-calculated target. In conclusion, the optical probe made real-time detection of tumor possible and has a potential for vessel detection during the biopsy procedures. Moreover, the PpIX fluorescence, autofluorescence and blood flow in the tumor could be studied at precise positions in the brain and the tumor. In the next step, further anal-ysis will be added.
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| 9. |
- Hallbeck, Martin, et al.
(författare)
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Effect of Stimulation of the Paraventricular Hypothalamic Nucleus on Noxious-Evoked Fos-immunoreactlvity In the Rat lumbar Spinal Cord
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The paraventricular nucleus of the hypothalamus (PVH) provides a prominent descending projection to the superficial dorsal horn, and contains a number of neuropeptides that are know to influence nociceptive processing. In the present study, we injected formalin subcutaneously into the hind paws of unanesthetized rats and studied the noxious-evoked Fos protein expression in the dorsal horn following simultaneous unilateral injection of the glutamate receptor agonist kainic acid into the PVH. Although some cases displayed less Fos-inununoreactivity in the lumbar spinal cord on the side ipsilateral to the PVH activation than on the contralateral side, others displayed no side differences, and one case showed more labeling in the ipsilateral dorsal horn than on the contralateral side, Because different parts of the PVH were activated in the different experiments, the present observations suggest that the different peptide expressing populations of spinal cordprojecting neurons in PVH may have different, and perhaps opposing functions in the spinal dorsal horn.
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| 10. |
- Hallbeck, Martin, 1970-
(författare)
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Peptidergic projections from the rat paraventricular hypothalamic nucleus to the spinal cord
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The survival of the organism is dependent on keeping a balanced internal milieu in an ever-changing environment The process to achieve this balance is called homeostasis and it is accomplished by the consonant action of the endocrine system and the autonomic nervous system. Specific parts of the central nervous system (CNS) control these systems in response to various sensory inputs. One of the key sites for the coordinated action of these two homeostasis systems is the paraventricular hypothalamic nucleus (PVH). Tirrough its projections to the pituitary the PVH controls the release of different hormones. In addition, it projects heavily to brain stem and spinal cord autonomic centers. Furthermore, the PVH projects to the superficial layers of the spinal cord, where nerve fibers conveying pain and temperature modalities terminate. Thus, in addition to its motor control of the homeostasis system, the PVH may influence the processing of sensory inputs that are important for homeostatic regulation. The aim of this thesis was to investigate some aspects of the organization and function of the neuronal pathways projecting from the PVH to the spinal cord in the rat.Vasopressin, which is a peptide that is synthesized by PVH neurons, has been proposed to regulate several different processes in the spinal cord. However, the source of vasopressin fibers within the spinal cord has been a matter of some dispute. Thus, firstly, we investigated the distribution of neurons expressing vasopressin mRNA in the naive rat, thereby providing the first complete screening of the CNS for this neuropeptide at the mRNA level. The results confmn some earlier work, but also demonstrate several new sites of vasopressin mRNA synthesis. Some sites previously thought to produce vasopressin displayed no vasopressin mRNA. Our results show that the PVH is the only putative site of spinally-projecting vasopressin neurons in the naive rat Hence, all functions exerted by vasopressin in the spinal cord are likely to be controlled by the PVH.Secondly, we examined the neurochemical profile of the PVH neurons that project to the spinal cord. We show that 41% of these neurons express dynorphin mRNA, 20% express enkephalin mRNA, 38% express oxytocin mRNA, and 42% express vasopressin mRNA. This is the first time that dynorphin has been shown in PVH neurons with spinal projections, and the figures for the other peptides are substantially higher than what has been reported in previous shldies. In addition, we demonstrate that each of the spinal cord projecting subdivisions of the PVH displays distinct peptide expression patterns.Thirdly, we investigated the physiological effect of the PVH on nociceptive transmission in the spinal cord dorsal horn. However, with the present experimental approach we could not show a consistent effect of PVH stimulation on nociceptive neurons in the spinal dorsal horn. The varying results we achieved are ascribed to the functional heterogeneity of the PVH as revealed by our previous studies.The present data contribute to the nnderstanding of the complex organization of the PVH. The parcellation of peptide-expressing neurons into distinct spinal cord projecting subnuclei is likely to reflect distinct functional roles of these subnuclei, and may provide the anatomical basis for the ability of the PVH to control many different processes in the spinal cord The nnderstanding of the physiological profile of these different subnuclei will provide insight into the control of homeostasis.
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