Development of in vitro models to investigate the anti-inflammatory properties of Cyclopia Maculata and other South African herbal teas : a comparative study

Keet, Lana (2015-04)

Thesis (MSc)--Stellenbosch University, 2015.

Thesis

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.

AFRIKAANSE OPSOMMING: Kroniese inflammasie van die vel kan bydra tot die ontwikkeling van kanker en is dus ’n potensiële area om te teiken in die voorkoming van velkanker. Keratinosiete en makrofage speel ’n integrale rol in akute en chroniese inflammasie van die vel en TNF-α en IL-1α is die belangrikste sitokiene wat hierdie proses inisieer. Dit is bekend dat ekstrakte van groen tee (Camellia sinensis) en die Suid-Afrikaanse kruietees, rooibos (Aspalathus linearis) en heuningbos (Cyclopia spp.) ‘n anti-inflammatoriese effek op die vel van muise en mense het. Om die anti-inflammatoriese aktiwitieit van groen tee, rooibos en 2 heuningbos kruietees (C. subternata en C. maculata) verder te ondersoek en te definieer is geskikte selkultuurmodelle ontwikkel en gevalideer deur gebruik te maak van menslike keratinosiete (HaCaT) en monosiet (THP-1) afgeleide makrofage. Water ekstrakte van groen tee en ongefermenteerde kruietees is voorberei en die chemiese samestelling deur hoë druk vloeistof chromatografie (HDLC) bepaal. ‘n Verskeidenheid van antioksidant bepalingstoetse is gebruik om die antioksidant aktiwiteit van die ekstrakte te meet. Groen tee en rooibos het soortgelyke antioksidant aktiwiteite getoon, terwyl C. maculata die swakste algehele aktiwiteit getooon het, ten spyte van die teenwoordigheid van hoёr vlakke van mangiferin, die belangrikste polifenoliese verbinding in heuningbos. Modulasie van sitokiene is verder bestudeer in (i) ’n UVB-geïnduseerde vooraf-blootstelling HaCaT model, waartydens akkumulering van IL-1α gemonitor is en (ii) ‘n lipopolisakkaried (LPS)-gestimuleerde THP-1 makrofaag model, waar die vrystelling van TNF-α gemonitor is. Vir die THP-1 model is beide die voor en gelyktydige blootstelling benaderings vir die ekstrakte met LPS gebruik. In die keratinosiet model, waar die selle aan ekstrakte blootgestel is voor UVB bestraing, is IL-1α beduidend verlaag deur die groen tee ekstrak, terwyl ’n swakker reaksie gesien is met rooibos. Beide heuningbos ekstrakte het ’n beduidende invloed in die vermindering van IL-1α getoon, waar C. subternata ’n effense verhoogde beskerming teen selsterfte by ‘n laer ekstrakkonsentrasie toon. Blootstelling van die makrofage aan al vier ekstrakte voor LPS stimulasie (vooraf-blootstelling), het gelei tot inhibisie van TNF-α vrystelling op ’n dosis afhanklike wyse en die afwesigheid van apoptose en selsterftes by lae ekstrak konsentrasievlakke. Hierdie waarnemings dui op ’n tipiese antiinflammatoriese effek. In die gelyktydige-blootstelling model verlaag al die ekstrakte TNF-α vrystelling teen die laagste ekstrak konsentrasievlakke, in die afwesigheid van apoptose en met geen effek op seldood nie. Hoёr ekstrak konsentrasievlakke het sitotoksisiteit en verhoogde apoptose getoon, dus was die anti-inflammatoriese effek gemaskeer. C. maculata toon ‘n variërende effek met betrekking tot antioksidant aktiwiteit en die bekamping van sitokien produksie, afhangend van die model wat bestudeer is. Die verskeidenheid fenoliese verbindings teenwoordig in die verskillende tee ekstrakte is waarskynlik die rede vir die effekte wat waargeneem is tydens antioksidant toetsing en selkultuurmodelle. Die anti-inflammatoriese meganismes wat deur hierdie studie voorgestel word sluit die modulasie van oksidatiewe stres via verskeie metaboliese paaie in. Modulasie van oksidatiewe stres lei tot af-regulering van kernfaktor-kappaB (NF-κB) en aktiveerderproteïen- 1(AP-1), wat sleutel reguleerders van sitokien produksie tydens inflammatoriese respons is.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/97030
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