Browsing by Subject "confocal microscopy"

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  • Huovila, Tiina (Helsingfors universitet, 2017)
    Autophagy is a pathway for cells to degrade intracellular components that are no longer needed or are detrimental for the cells. It is essential for cell homeostasis and survival and has been related to various diseases and pathophysiology. Autophagy is a complex process and there are still several unclear und unknown aspects to it. Regulation of autophagy is essential to prevent unwanted and escess activation, and several pathways and molecules, both stimulatory and inhibitory, are included. Different signaling pathways are sensitive to a variety of environmental clues. Two main autophagy pathways are mTOR-dependent pathway and mTOR-independent pathway. Induction of autophagy in the latter pathway is dependent on the interaction of Bcl-2 and Beclin 1. Prolyl oligopeptidase (PREP) is a peptidase enzyme that has several substrates. PREP-inhibition by KYP-2047 can reduce aggregation of α-synuclein in two ways: by increasing rate of autophagy and by decreasing dimerization. The aim of this study was to find out how PREP affects the interaction between Bcl-2 and Beclin 1 and how this affects autophagy. Based on previous studies, PREP-inhibition seems to increase the amount of Beclin 1 and to affect the phosphorylation of Bcl-2 and Beclin 1, leading to dissociation of the complex. Hypothesis was to see differences in colocalization of Bcl-2 and Beclin 1 in cells treated with different PREP-modifications and for PREP-inhibition to decrease the colocalization. Human embryonic kidney cells 293 (HEK-293) and hPREP knockout cell line created from them by using CRISPR/Cas9-silencing were used in the experiments. Two experiments were performed on regular HEK-cells: inhibitor experiment with KYP-2047 (1 or 10 µM) and overexpression experiment (transfection with either active or inactive hPREP plasmid). After immunofluorescence staining, cells were analysed with confocal microscope and colocation analysis of Bcl-2 and Beclin 1 was performed. The intensity of Beclin 1 in the nuclei was stronger than in other parts of the cell in all samples, which could indicate a stronger activity of its nuclear tasks compared to autophagy. However, the antibody used for immunofluorescence has most likely caused this staining pattern. Based on previous knowledge, it was expected to see differences in colocalization of Bcl-2 and Beclin 1 in cells treated with different PREP-modifications. However, there were no significant differences in colocalization of Beclin 1 and Bcl-2 in any of the experiments but it was nearly 100 percent in all treatments. Since rate of autophagy in cells was not detected, it is impossible to determine, if there were changes in autophagy that were not reflected as changes in colocalization of these two proteins. It is possible that even a small change in colocalization can affect the rate of autophagy or there might be subpopulations where the interaction is interrupted and these changes are so small that they are not detectable with the methods used in this experiment. Both Bcl-2 and Beclin 1 also have functions not related to autophagy, which could be one reason behind the results gained in this study.
  • Niemi, Liisa (Helsingfors universitet, 2016)
    Extracellular vesicles are cell-derived vesicles which consist of two lipid layers. Extracellular vesicles involve in intercellular communication, maintaining of homeostase and development of pathophysiological states in human body. Extracellular vesicles are promising biomarkers and drug carriers in future. The aim of this study was to develop a method based on time resolved fluorescence microscopy and autologous extracellular vesicles labelled with environmentally sensitive fluorescent probes for studying the distribution of mitose-inhibitor paclitaxel in prostate cancer cells (PC-3) carried by extracellular vesicles. The efficacy of paclitaxel loaded extracellular vesicles was compared to synthetic liposomes. The two subpopulations of extracellular vesicles, exosome -and microvesicle-enriched, were isolated from the PC-3 cell media by differential ultracentrifugation. The size distribution and particle concentration of extracellular vesicles was determined by nanoparticle tracking analysis. DSPC-Cholesterol liposomes were prepared by reverse-phase evaporation method and the size distribution of the liposomes was determined by dynamic laser diffraction and nanoparticle tracking analysis. Paclitaxel was loaded into the liposomes in hydration phase and into the extracellular vesicles by incubating vesicles and paclitaxel. Unbound paclitaxel was removed from samples by ultracentrifugation. The the dose-dependent sytotoxicity of paclitaxel loaded extracellular vesicles and liposomes was evaluated with Alamar Blue viability assay. The release and distribution of paclitaxel from extracellular vesicles in living PC-3 cells was investigated by confocal microscopy and time-resolved fluorescence microscopy. The exosomes had approximately 50 nm smaller diameter than microvesicles and exosome particle concentrations were significantly higher compared to microvesicles. According to viability assays conducted with wide range of concentrations, paclitaxel loaded in microvesicles were slightly more effective than paclitaxel loaded in exosomes. The time-resolved fluorescence microscopy was useful method for investigating the release and distribution of extracellular vesicle bound paclitaxel, since we succesfully detected changes in Paclitaxel-OregonGreen fluorescence lifetime in different phases of the drug delivery process. With confocal microscopy we detected that paclitaxel loaded extracellular vesicles were already uptaken inside the cells after two hours of incubation and after few hours, paclitaxel was detected in microtubules of PC-3 cells and killed PC-3 cells. Extracellular vesicles may improve the accumulation of paclitaxel into tumor cells thus preventing the side-effects of paclitaxel. Nevertheless, PC-3 cell derived extracellular vesicles have ability to increase the PC-3 cell viability, which limits their potential use as drug carrier due to safety issues. In addition, extracellular vesicles characterization and isolation methods lack standardization and the isolation of exosomes and microvesicles is impossible due to this fact. Extracellular vesicles involvement in physiological and pathophysiological states should be investigated throughoutly and their safety as drug carriers should be examined both in animal and human.