- Title
- The anti-inflammatory effects of Sutherlandia Frutescens in a cell and animal model
- Creator
- Fortuin-Seedat, Maleeha
- Subject
- Medicinal Plant -- South Africa
- Date Issued
- 2019
- Date
- 2019
- Type
- Thesis
- Type
- Doctoral
- Type
- PhD
- Identifier
- http://hdl.handle.net/10948/44617
- Identifier
- vital:38167
- Description
- The South African medicinal plant, Sutherlandia frutescens has anti-diabetic, antiinflammatory and antioxidant properties. Many of the mediators of inflammation are also involved in obesity and diabetes. Furthermore, T2D can either induce inflammation, or exacerbate the inflammatory response by maintaining imbalances between pro-and anti-inflammatory mediators. Two macrophage sub-populations involved in the regulation of immune responses have been defined. These are classically activated macrophages (M1) which stimulate inflammation, and alternatively activated macrophages (M2), which show anti-inflammatory activity. Therefore it is hypothesised that S. frutescens can potentially regulate macrophage polarization states which, in turn, influence metabolic immunomodulatory processes. The aims of this study were firstly to identify the mechanisms(s) by which S. frutescens could improve the low-grade inflammatory status in obese and T2D individuals using a transgenic mouse model of obesity, and secondly to determine the immunomodulating properties of S. frutescens in the human monocytic THP-1 cell line. Groups of nine week old male db/db mice were gavaged daily with water (vehicle control), Vildagliptin (10mL kg-1)(positive medication control) or hot aqueous S. frutescens extract at concentrations of 5mg, 50mg, 250mg kg-1 for 4 weeks. Body weight and fasting plasma glucose levels were determined weekly. The potential for hot aqueous S. frutescens extract to lower postprandial hyperglycaemia and promote insulin sensitivity was determined by an oral glucose tolerance test (OGTT) after a 16 hour fast, and an insulin radioimmunoassay (RIA) after a 4 hour fast before termination. After 4 weeks of hot aqueous S. frutescens treatment the total percentage body weight of 13 week old db/db mice was reduced, but hyperglycaemia was not prevented. Human THP-1 monocytes were stimulated to differentiate into macrophages with phorbol-12myristate-13acetate (PMA) and cultured under pro-inflammatory conditions (M1) or anti-inflammatory conditions (M2). Cell viability and anti-proliferative effects of LPS and S. frutescens extracts were determined. The effect of hot aqueous and ethanolic S. frutescens extracts on M1 and M2 macrophage cell surface markers was investigated by flow cytometry using CD86 (M1) and CD206 (M2). The effect of the S. frutescens extracts on three signalling pathways and a pro-inflammatory mediator activated in an LPS-induced inflammatory response were determined using Western blotting. Changes in mRNA gene expression levels of downstream transcription factors, cytokines and chemokines associated with M1 and M2 polarised macrophages were investigated using qRT-PCR. Both ethanolic and hot aqueous S. frutescens extracts reduced cytotoxicity caused by LPS. S. frutescens extracts alone did not alter cell viability. Furthermore, both hot and ethanolic S. frutescens extracts reduced expression of the M1 marker CD86 and nonsignificantly induced expression of an M2 marker CD206, following LPS stimulation. Following M2 induction, the M1 and M2 cell surface markers were reverted to baseline M0 macrophage expression by both S. frutescens extracts. The S. frutescens extracts mediated immune-regulatory activity through suppression of the pro-inflammatory p38 MAPK and NFκB signalling pathways and regulated apoptosis through the ERK1/2 pathway. The hot aqueous S. frutescens extract exerted anti-inflammatory effects through the IKK pathway and/ or GSK3β signalling pathway. This thesis demonstrates that S. frutescens promotes macrophage homeostasis by maintaining the balance between M1 and M2 macrophages during pro-and antiinflammatory immune responses. The regulation may occur during the activation and polarization process, via rapid deactivation of M1 macrophages and a decrease in need for macrophages to switch to an M2 phenotype. Furthermore S. frutescens is hypothesised to play a role in the regulation of the GSK3β signalling which plays a central role in regulating inflammation associated with pathophysiological conditions such as IR, T2D and obesity via the PI3K/Akt pathway.
- Format
- xxviii, 202 leaves
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of
- Language
- English
- Rights
- Nelson Mandela University
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NMU School of BioMolecular and Chemical Sciences
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Fortuin-Seedat, M 212389874 Thesis Dec 2019.pdf | 5 MB | Adobe Acrobat PDF | View Details Download |