The effects of Sutherlandia frutescens and Fumonisin B1 on Jurkat cells.

Abstract

The medicinal plant Sutherlandia frutescens (SF) is commonly consumed in South Africa, and is traditionally applied to a range of ailments. Yet its popularity stems from the use of SF as a cancer treatment. This plant contains a range of active compounds including L-canavanine (L-CAV), D-pinitol and gamma (γ)-aminobutyric acid, all of which contribute to the therapeutic properties of SF. It is also endorsed by the South African Ministry of Health as a supplementary treatment for HIV/AIDS. Maize is the staple crop of South Africa, and can be frequently contaminated by the mycotoxin fumonisin B1 (FB1). The mycotoxin is linked to an extensive list of livestock diseases. Although little is known about its role in human disease, FB1 has been epidemiologically linked to oesophageal cancer in South Africa. Both SF and FB1 have been shown to promote apoptosis, and the effect(s) of consuming both in combination is currently unknown. The principle aim of this study was to determine whether SF and FB1 had either synergistic or antagonising effects in combination, by investigating immune cell toxicity Jurkat cells. Apoptotic parameters such as caspase activation, mitochondrial depolarisation, phosphatidylserine (PS) externalisation and ATP quantification were analysed. Levels of caspase activation were highest in cells treated with SF only (caspase-3: 86.79 RLU, no significance compared to other treatments; caspase-8: 40.1 RLU, significance compared to other treatments [p<0.05]; caspase-9: 11.07 RLU, significance compared to FB1 and control treatments [p<0.05]). ATP levels were significantly highest in SF-treated cells compared to other treatments (8.17 RLU, [p<0.05]). Mitochondrial depolarisation was also highest in SF-treated Jurkat cells at 18.5% depolarisation with no significance compared to other treatments, however PS externalisation were significantly lower in SF-treated cells compared with other treatments (3.69% [p<0.05]). Oxidative stress parameters were also investigated, including thiobutyric acid reactive species (TBARS), Glutathione (GSH) and Reactive Nitrogen Species (RNS) assays. TBARS levels were significantly higher in FB1 treated cells (OD 1.95, [p<0.05]) compared to SF and control. Glutathione and RNS levels were also lowest in FB1-treated cells. The data suggests that SF induces apoptosis, characteristic of its nature as an anti-cancer treatment, and FB1 induces oxidative stress, which is characteristic of its carcinogenic properties. Based on this preliminary study, it appears that FB1 and SF both synergises and antagonises the other in combination, yet further investigation is needed into its effects in vivo.