Abstract B23: The anticancer properties of South African herbal teas utilizing an in vitro pre-exposure anti-inflammatory UVB/keratinocyte model

Abstract

Abstract The incidence of skin cancer, resulting from exposure to UVB irradiation, has become a global concern as it continues to rise rapidly with the non-melanoma skin cancers, comprised of basal cell carcinoma and squamous cell carcinoma, being the most frequently diagnosed in Caucasian populations. Chronic inflammation is suggested to contribute to cancer development and therefore poses 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 anti-inflammatory effects in mouse and human skin. To further investigate the anti-inflammatory properties of green tea and the herbal teas, rooibos and honeybush (C. subternata and C. maculata) herbal teas, a pre-exposure UVB-irradiated/keratinocytes cell culture model was developed and validated utilizing human keratinocytes (HaCaT) utilizing the intracellular accumulation of IL-1α as endpoint. Aqueous extracts of the green tea and unfermented herbal teas were prepared, their polyphenolic composition determined by high performance liquid chromatography (HPLC) and their antioxidant activity characterized utilizing different antioxidant assays. Green tea and rooibos exhibited similar antioxidant activities while C. maculata displayed the lowest overall antioxidant activity mainly due to a high mangiferin level, the major polyphenol in honeybush. UVB-induced IL-1α was decreased by pre-exposing the keratinocytes to the green tea extract for 16 hrs prior to UVB-irradiation while a far weaker response was obtained with the rooibos extract. Both the honeybush extracts displayed a significant anti-inflammatory effect in the reduction of IL-1α with C. subternata exhibiting a slightly increased protection at a lower extract concentration. Flavonoid diversity of the teas is likely to explain the differential effects regarding their antioxidant and anti-inflammatory activities. Proposed mechanisms for the anti-inflammatory effects include the modulation of UVB-induced 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. Citation Format: Lana Keet, Sylvia Riedel, Amanda C. Swart, E Joubert, WCA Gelderblom. The anticancer properties of South African herbal teas utilizing an in vitro pre-exposure anti-inflammatory UVB/keratinocyte model [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr B23.