Masters Degrees (Physiological Sciences)
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Browsing Masters Degrees (Physiological Sciences) by Subject "Anti-inflammatory"
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- ItemEvaluation of the therapeutic potential of green rooibos (Aspalathus linearis) extract in neurological disease(Stellenbosch : Stellenbosch University, 2021-04) Sibanda, Melusi; Smith, Carine; Powrie, Yigael SL; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: The intricate relationship between oxidative stress and neuroinflammation has been demonstrated in the aetiology of most neurodegenerative diseases. Current pharmacological treatments of these diseases have limitations and side effects. This has led to extensive investigations of novel therapeutic approaches to modify the course of these conditions. Globally, phytochemicals, especially polyphenols, have been investigated in vitro and in vivo for their antioxidant and anti-inflammatory properties. Aspalathus linearis (Rooibos) is one such plant. Although unfermented (green) rooibos is well known for its antioxidant capacity, no information is available on its neuroprotective capacity. Aim: This study aimed to establish the neuroprotection potential of unfermented rooibos extract in neuronal cells and astrocytes. In addition, an evaluation of the antioxidant and anti-inflammatory capacity, as well as potential mechanism of action of rooibos in neuroprotection was done in vivo in a zebrafish larval model. Method: Antioxidant properties of unfermented rooibos were quantified using cell-free systems (DPPH, ORAC and xanthine/xanthine oxidase). Green rooibos extract (Green oxithinTM) neuroprotective capacity was assessed in mouse neuroblastoma (Neuro-2a) cells exposed to different concentrations of hydrogen peroxide (250 or 125 μM) after a 24-hour treatment with different rooibos extract concentrations (12.5, 25, 50 and 100 μg/mL), as well as in human astrocytes treated with varying concentrations of rooibos extract (800, 400, 200, 100 and 50 μg/ml) and exposed to 20 μg/mL of E.coli lipopolysaccharide (LPS). MCP-1 secretion by astrocytes were determined by ELISA and XTT assay was used to assess cell viability. Intracellular ROS was quantified as a parameter of cellular redox status and MAO-A inhibition as further indicators of neuroprotection. Moreover, an in vivo PTZ-induced seizure model was employed to probe GABA receptor modulation as potential mechanism of action of rooibos. Results: Green rooibos scavenged free radicals of both exogenous and endogenous origin in a dose dependent manner with a similar profile activity to vitamins C or E. Green rooibos extract protected N2a cells, predominantly at the assault of a lethal concentration (250 μM) of H2O2 where up to 15% (p<0.0001) cell survival was observed. Intracellular ROS levels were significantly reduced (p<0.0001) at both 250 and 125 μM H2O2. In a dose dependent way, MCP-1 production decreased significantly in cells pre-treated with rooibos (p<0.0024). Finally, current data generated in zebrafish do not support a GABA receptor-associated mechanism of action rooibos. Conclusion: Green rooibos extract modulated the production of MCP-1 by astrocytes and mildly inhibited MAO-A.