Browsing by Author "Keet, Lana"

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    Development of in vitro models to investigate the anti-inflammatory properties of Cyclopia Maculata and other South African herbal teas : a comparative study
    (Stellenbosch : Stellenbosch University, 2015-04) Keet, Lana; Gelderblom, W. C. A.; Riedel, S.; Swart, Amanda C.; Stellenbosch University. Faculty of Science. Dept. of Biochemistry.
    ENGLISH ABSTRACT: Chronic inflammation is suggested to contribute to cancer development and therefore a potential target for chemoprevention. In the skin, keratinocytes and macrophages play an integral part in acute and chronic inflammation, with interleukin 1-α (IL-1α) and tumor necrosis factor α (TNF-α) as key cytokines governing this process. Green tea (Camellia sinensis) and the South African herbal teas, rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.) displayed antiinflammatory effects in mouse and human skin. To further investigate the antiinflammatory properties of green tea and the herbal teas, rooibos and honeybush (C. subternata and C. maculata) herbal teas, suitable cell culture models were developed and validated utilising human keratinocytes (HaCaT) and monocyte (THP- 1) derived macrophages. Aqueous extracts of the green tea and unfermented herbal teas were prepared and their chemical composition determined by high performance liquid chromatography (HPLC) and the antioxidant activity characterised utilising different antioxidant assays. Green tea and rooibos exhibited similar antioxidant activities while C. maculata displayed the lowest overall antioxidant activity of all the extracts, despite possessing the highest mangiferin level, the major polyphenol in honeybush. The modulation of cytokine release was studied in (i) an UVB-induced pre-exposure HaCaT model monitoring the accumulation of IL-1α and (ii) a LPS stimulated THP-1 macrophage model monitoring the TNF-α release, utilising both a pre-exposure and co-exposure extract regimens. In the pre-exposure HaCaT inflammatory model the UVB-induced IL-1α was decreased by the green tea extract while a far weaker response was obtained with the rooibos extract. Both the honeybush extracts displayed a significant effect in the reduction of IL-1α with C. subternata exhibiting a slight increased protection at a lower extract concentration. In the pre-exposure THP-1 derived macrophage model, green tea and the herbal tea extracts inhibited TNF-α release in a dose dependent manner in the absence of an overt loss in cell viability and apoptosis at lower extract concentrations, suggesting a typical anti-inflammatory effect. In the co-exposure model, the different extracts also exhibited an anti-inflammatory effect at the lowest concentrations in the absence of apoptosis while at higher extract concentrations the effect was masked by a decrease in cell viability and increased apoptosis. C. maculata exhibit differential effects when considering the inhibition of cytokine production and, depending on the cell model, either exhibited a weaker or stronger effect when compared to C. subternata and rooibos. Phenolic diversity of the different teas is likely to explain the differential effects in the antioxidant assays and cell culture models with respect to the regulation of the production of the inflammatory markers. Proposed mechanism for the anti-inflammatory effects include the modulation of oxidative stress via various pathways and the subsequent down regulation of nuclear factor kappa β (NFκB) and activated protein-1 (AP-1) which are key regulators of cytokine production governing the inflammatory response.