- Title
- The implication of autophagy in cell fate of human bone marrow-derived mesenchymal stem cells exposed to titanium dioxide nanoparticles
- Creator
- Yu, Shunbang
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2020
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Titanium dioxide nanoparticles (TiO₂NPs) have become one of the most widely used nanomaterials, occupying over 70 % of the global production of pigment. Upon exposure, TiO₂NPs are capable of transposing to different organs and tissues. Therefore, a more in-depth description of the biological effects following exposure to different doses of this material is necessary to ensure safety during application of this material. Following a review of the available literature, three significant knowledge gaps have been identified: (1) mesenchymal stem cells (MSCs) which have been exposed to TiO₂NPs are understudied for autophagic reactions; (2) the interaction between cell death and survival of MSCs following exposure to TiO₂NPs is under-investigated; and (3) there has been a lack of investigation on the basal and fundamental mechanism for cell death following exposure to TiO₂NPs. The above knowledge gaps led to the development of three sets of aims, hypotheses, and approaches, which were covered by three individual studies. In Study 1 (Chapter 2), autophagic cell death, characterised by the upregulation of the p38/ERK/JNK pathway and absence of apoptosis, was detected in MSCs exposed to TiO₂NPs. Results obtained from Study 2 (Chapter 3) demonstrated that the MSCs undergoing autophagic cell death were related to an increase in extracellular Wnt protein levels, and increased GSK3β/β-catenin/cyclin D1 signalling pathway among cells in the same population. This suggests that autophagic cell death may result in release of survival- and proliferation-inducing signals. Study 3 (Chapter 4) demonstrated that TiO₂NPs may initiate cell death via dysregulation of the microRNA-21 (miR-21)/PTEN/AKT signalling pathway and impairment of glucose uptake abilities. The characteristics of the nanoparticles were determined by conducting multiple analyses. Precisely, the size distribution of the nanoparticles was measured by the light scattering method; density was determined via gas exchange method; specific area and porosity were measured with the Brunner-Emmet-Teller (BET) method; zeta potential was quantified by performing microelectrophoresis; crystal structure was assessed by X-ray Diffraction (XRD) method. The changes in molecular pathways, following exposure to TiO₂NPs, were detected via performing western blotting analysis for protein targets, or quantitative real-time polymerase chain reaction (RT-PCR) for miR-21. Autophagy and apoptosis were detected via quantification of LC3-II/LC3-I ratio and Caspase 3, Cleaved Caspase 3, and Cleaved PARP, respectively, by western blotting analysis. Manipulation of glucose uptake abilities was described by quantifying changes in Glucose Transporter (GLUT)1 and GLUT4 levels via western blotting analysis, and glucose uptake by the [3H]-2-deoxyglucose method. Pathway members were regulated by intervention with corresponding inhibitors or promoters. Specific details have been presented in the corresponding studies. The results indicated that the TiO2NPs could induce autophagic cell death in MSCs, which is characterised by the upregulation of the p38/ERK/JNK pathway. MSCs undergoing autophagic cell death is related to an increase in extracellular Wnt protein levels and is therefore linked to the stimulation of the GSK3β/β-catenin/cyclin D1 signalling pathway among the cell population. The TiO2NPs could dysregulate the miR-21/PTEN/AKT signalling pathway and reduce glucose uptake parameters, indicating that the observed cell death could be a result of deprival of energy metabolism abilities.
- Subject
- titanium dioxide nanoparticles; mesenchymal stem cells; autophagy; cell death; cell survival; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1423902
- Identifier
- uon:37991
- Rights
- Copyright 2020 Shunbang Yu
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 4 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 226 KB | Adobe Acrobat PDF | View Details Download |