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Microplastic exposure induces hepatotoxicity through oxidative stress: an investigation into the molecular mechanism
Thesis (MSc)--Stellenbosch University, 2024.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613805995884544 |
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| access_status_str | Open Access |
| author | Bristow, Paolo Timothy |
| author2 | Abdul, Naeem Sheik |
| author_browse | Abdul, Naeem Sheik Bristow, Paolo Timothy |
| author_facet | Abdul, Naeem Sheik Bristow, Paolo Timothy |
| author_sort | Bristow, Paolo Timothy |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131600 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:41:59.323Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131600 Microplastic exposure induces hepatotoxicity through oxidative stress: an investigation into the molecular mechanism Bristow, Paolo Timothy Abdul, Naeem Sheik Marnewick, Jeanine L. Stellenbosch University. Faculty of Science. Dept. of Biochemistry. Polystyrene -- Molecular aspects Microplastics -- Health aspects Oxidative stress Polystyrene microplastics -- Mechanism of action Hepatotoxicology Liver cells -- Effect of stress on Microplastics -- Toxicology UCTD Thesis (MSc)--Stellenbosch University, 2024. ENGLISH ABSTRACT: Polystyrene microplastics (PSMP) are ubiquitous contaminants of the biosphere, this makes human exposure inevitable. Numerous studies have provided evidence that PSMP can bioaccumulate in human organs such as the liver. The liver is rich in mitochondria and, facilitates first pass metabolism and detoxification of xenobiotics. These factors make the liver a target for PSMP toxicity. A unifying endpoint of PSMP toxicity has been linked to oxidative stress, however the molecular mechanisms involved in this are not elucidated in human liver cells. The production of reactive oxygen species (ROS) at complex I, II and III in the electron transport chain (ETC) occurs when electrons escape and interact with the abundant surrounding oxygen. In this way alterations in metabolic function directly lead to changes in ROS production. This study sets out to determine the molecular mechanism behind PSMP’s induced oxidative stress using luminometric, spectrophotometric, fluorometric and protein expression techniques. This study tested the toxic effects of three selected PSMP concentrations (5, 75, 200 μg/mL) to estimate the effect of low, intermediate and high exposure levels. Results showed that PSMP disrupted metabolic function and decreased ATP output while increasing intracellular ROS in a dose dependent manner. Data further indicates that oxidative stress and apoptosis were induced as indicated by the increase in MDA levels (biomarker for lipid peroxidation) and caspase 3 activation for all tested concentrations. The levels of GSH and GSSG supported the role of the antioxidant system in overcoming PSMP induced oxidative stress, however catalase activity was significantly decreased. This prompted further investigation into the molecular mechanisms which revealed that PSMP treatment upregulated the expression of the mitochondrial SOD2 along with cytoplasmic SOD1 and catalase. The data showed upregulation of NRF, the master transcription factor of the antioxidant response. The project conclude that the upregulated antioxidant expression was not enough to detoxify the ROS and could not prevent oxidative stress. This study provides insight into the molecular mechanisms of PSMP induced hepatotoxicity and may aid in understanding and predicting the contamination risks of this neglected but ubiquitous toxin. This is of particular importance to developing countries where the risk of PSMP exposure is high due to the lack of infrastructure for dealing with the plastic burden. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Masters 2025-01-28T13:34:47Z 2025-01-28T13:34:47Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131600 en Stellenbosch University ix, ii, 127 pages : illustrations, maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Polystyrene -- Molecular aspects Microplastics -- Health aspects Oxidative stress Polystyrene microplastics -- Mechanism of action Hepatotoxicology Liver cells -- Effect of stress on Microplastics -- Toxicology UCTD Bristow, Paolo Timothy Microplastic exposure induces hepatotoxicity through oxidative stress: an investigation into the molecular mechanism |
| title | Microplastic exposure induces hepatotoxicity through oxidative stress: an investigation into the molecular mechanism |
| title_full | Microplastic exposure induces hepatotoxicity through oxidative stress: an investigation into the molecular mechanism |
| title_fullStr | Microplastic exposure induces hepatotoxicity through oxidative stress: an investigation into the molecular mechanism |
| title_full_unstemmed | Microplastic exposure induces hepatotoxicity through oxidative stress: an investigation into the molecular mechanism |
| title_short | Microplastic exposure induces hepatotoxicity through oxidative stress: an investigation into the molecular mechanism |
| title_sort | microplastic exposure induces hepatotoxicity through oxidative stress an investigation into the molecular mechanism |
| topic | Polystyrene -- Molecular aspects Microplastics -- Health aspects Oxidative stress Polystyrene microplastics -- Mechanism of action Hepatotoxicology Liver cells -- Effect of stress on Microplastics -- Toxicology UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131600 |
| work_keys_str_mv | AT bristowpaolotimothy microplasticexposureinduceshepatotoxicitythroughoxidativestressaninvestigationintothemolecularmechanism |