Thesis (MSc)--Stellenbosch University, 2015. / 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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/97030 |
| Date | 04 1900 |
| Creators | Keet, Lana |
| Contributors | Gelderblom, W. C. A., Riedel, S., Swart, A. C., Stellenbosch University. Faculty of Science. Dept. of Biochemistry. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xvii, 139 pages : illustrations (some colour) |
| Rights | Stellenbosch University |
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