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- Vahdat Shariatpanahi, Aida, 1982-
(author)
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The Importance of Macrophages, Lipid Membranes and Seeding in Experimental AA Amyloidosis
- 2019
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Doctoral thesis (other academic/artistic)abstract
- Amyloidosis is a group of protein misfolding diseases caused by tissue deposition of fibrillary protein aggregates termed amyloid. Amyloid A (AA) amyloidosis is a systemic form of amyloidosis that occurs as a complication of chronic inflammatory diseases, such as rheumatoid arthritis, familial Mediterranean fever and chronic infections, such as tuberculosis. AA amyloid is derived from the precursor protein serum amyloid A and is deposited in several organs preferably kidneys, liver and spleen. AA amyloidosis can be induced in mice by long standing inflammatory stimulation and concurrent administration of tissue extracts of AA amyloid, referred to as amyloid enhancing factor (AEF), reduces the time for amyloid deposition in the marginal zone of the spleen from 5 weeks to 2 days. The general aim of this thesis was to investigate the mechanisms involved in the development of AA amyloid in the mouse model of AA amyloidosis.Amyloid was induced in inflamed mice by injection of AEF and amyloid toxicity to splenic macrophages was investigated. We found that the marginal zone macrophages were very sensitive to amyloid formation and increasing amyloid load caused progressive depletion of these cells, whereas red pulp macrophages and metallophilic marginal zone macrophages appeared unaffected. To clarify the role of splenic macrophages in amyloidogenesis, macrophages were depleted by clodronate containing liposomes. We displayed that in the absence of splenic macrophages, especially marginal zone macrophages, amyloid formation was delayed implying a crucial role of macrophages in amyloid formation.The effect of lipid membranes on amyloid formation was studied and we showed that liposomes exhibited an amyloidogenic effect in inflamed mice although not as powerful as AEF. Following the fate of the liposomes, we showed that liposomes were rapidly cleared by uptake in the spleen and liver and colocalized with lysosomes. A tentative mechanism might be that accumulation of liposomes in lysosomes interfere with the SAA degradation process facilitating amyloid formation.Finally the conformational properties of two AEF (AEF1 and AEF2) preparations were studied using conformation sensitive luminescent-conjugated oligothiophenes (LCOs). We found that AEF1 and AEF2 displayed significantly different ultrastructure as well as conformation and consequently induced different cytotoxicity in vitro. Inducing amyloid formation in inflamed mice by AEF1 and AEF2 revealed that the polymorph of the amyloid aggregates was replicated in vivo.In summary, the results obtained in this thesis indicate an important role for macrophages for the formation of amyloid. The existence of amyloid strains has long been an in vitro finding, but the finding that AEF ultrastructure drives the morphology of newly formed amyloid in vivo opens up for new studies that can help us to understand the formation of homologous and heterologous fibrils. Thus, the fundamental mechanisms of various amyloid diseases are similar and the results presented in the thesis can increase the understanding of other amyloid diseases.
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- Orfanidis, Kyriakos, et al.
(author)
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Evaluation of tubulin β-3 as a novel senescence-associated gene in melanocytic malignant transformation.
- 2017
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In: Pigment Cell & Melanoma Research. - : Blackwell Munksgaard. - 1755-1471 .- 1755-148X. ; 30:2, s. 243-254
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Journal article (peer-reviewed)abstract
- Malignant melanoma might develop from melanocytic nevi in which the growth-arrested state has been broken. We analyzed the gene expression of young and senescent human melanocytes in culture and compared the gene expression data with a dataset from nevi and melanomas. A concordant altered gene expression was identified in 84 genes when comparing the growth-arrested samples with proliferating samples. TUBB3, which encodes the microtubule protein tubulin β-3, showed a decreased expression in senescent melanocytes and nevi and was selected for further studies. Depletion of tubulin β-3 caused accumulation of cells in the G2/M phase and decreased proliferation and migration. Immunohistochemical assessment of tubulin β-3 in benign lesions revealed strong staining in the superficial part of the intradermal components, which faded with depth. In contrast, primary melanomas exhibited staining without gradient in a disordered pattern and strong staining of the invasive front. Our results describe an approach to find clinically useful diagnostic biomarkers to more precisely identify cutaneous malignant melanoma and present tubulin β-3 as a candidate marker. This article is protected by copyright. All rights reserved.
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- Panahi, Aida Vahdat Shariat, et al.
(author)
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Lipid membranes accelerate amyloid formation in the mouse model of AA amyloidosis
- 2019
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In: Amyloid. - : Informa UK Limited. - 1350-6129 .- 1744-2818. ; 26:1, s. 34-44
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Journal article (peer-reviewed)abstract
- Introduction:AA amyloidosis develops as a result of prolonged inflammation and is characterized by deposits of N-terminal proteolytic fragments of the acute phase reactant serum amyloid A (SAA). Macrophages are usually found adjacent to amyloid, suggesting their involvement in the formation and/or degradation of the amyloid fibrils. Furthermore, accumulating evidence suggests that lipid membranes accelerate the fibrillation of different amyloid proteins.Methods:Using an experimental mouse model of AA amyloidosis, we compared the amyloidogenic effect of liposomes and/or amyloid-enhancing factor (AEF). Inflammation was induced by subcutaneous injection of silver nitrate followed by intravenous injection of liposomes and/or AEF to accelerate amyloid formation.Results:We showed that liposomes accelerate amyloid formation in inflamed mice, but the amyloidogenic effect of liposomes was weaker compared with AEF. Regardless of the induction method, amyloid deposits were mainly found in the marginal zones of the spleen and coincided with the depletion of marginal zone macrophages, while red pulp macrophages and metallophilic marginal zone macrophages proved insensitive to amyloid deposition.Conclusions:We conclude that increased intracellular lipid content facilitates AA amyloid fibril formation and show that the mouse model of AA amyloidosis is a suitable system for further mechanistic studies.
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- Södergren, Anna, 1985-
(author)
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Formation and Relevance of Platelet Subpopulations
- 2018
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Doctoral thesis (other academic/artistic)abstract
- Platelets are important players in the hemostatic system, acting as guardians of vessel integrity. When they come across a breach in the vessel wall, they quickly adhere to the damaged surface, secrete activating and adhesive compounds from their secretory granules, recruit additional platelets into a growing platelet plug and support the action of the coagulation system. In the past decades, it has become clear that platelets form functionally different platelet subpopulations. The aggregatory platelets build the platelet plug, whereas the procoagulant subpopulation support and direct the actions of the coagulation system. The aim of this thesis was to examine the formation and features of the different platelet subpopulations, and elucidate their respective roles in hemostasis.Platelet lysosomal secretion is not well characterized. In Paper I, we found that lysosomal secretion, detected as LAMP-1 surface exposure, occur upon potent platelet stimulation including secondary activation by ADP. This is regulated by the endothelial platelet inhibitors nitric oxide and prostacyclin. As observed in Paper II, lysosomal secretion might also be of clinical relevance as a quality indicator for platelet concentrates used for transfusion, an area were quality control may become increasingly important in the future. Among several evaluated platelet activation markers, platelet LAMP-1 exposure and the ability to form procoagulant platelets may be useful as novel indicators of platelet responsiveness. Moreover, the ability to form procoagulant platelets varies extensively between individuals, something we established in Paper III. Here we also present a novel flow cytometry protocol enabling the simultaneous investigation of 6 different platelet activation markers. Using this protocol we investigate the formation of procoagulant platelets and reveal that only a subpopulation of platelets may become procoagulant. Further we show that this is dependent on the agonist stimulation applied. Finally in Paper IV, we explore the influence of the procoagulant platelet subpopulation on different aspects of hemostasis. While platelet aggregation was not affected, the fraction of procoagulant platelets was found to strongly correlate to peak thrombin generation, and to be associated with plasma cholesterol levels.In conclusion, this thesis presents evidence for the use of LAMP-1 surface exposure and the formation of a procoagulant platelet subpopulation as potential indicators of platelet activation potential. The formation of procoagulant platelets varies extensively between individuals, influence hemostasis and is associated with the known risk factor cholesterol. Thus, the formation of a procoagulant platelet subpopulation may be a candidate biomarker for cardiovascular disease, to be explored in the future.
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