Browsing by Author "Louw, Letitia"
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- ItemInvestigation into potential endocrine disruptive effects of Sceletium tortuosum(Stellenbosch : Stellenbosch University, 2018-03) Louw, Letitia; Smith, Carine; Swart, Amanda C.; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: Depression has been recognised by the World Health Organisation (WHO) as the leading cause of disability, affecting an estimated 300 million people globally. To date antidepressants are prescribed as the first step in the treatment strategy. However, finding the appropriate antidepressant is often a lengthy process and is usually accompanied by side effects. A major and often unexpected side effect is reduced sexual function, which has been reported to aggravate depression and could possibly lead to poor compliance to medication. Sceletium tortuosum is a native South African plant, which has exhibited both antidepressant and anxiolytic properties. Although the exact mechanism of action remains to be elucidated, there are currently two hypotheses which attempt to explain it’s mechanism of action. Firstly, it has been reported to act in the same manner as a selective serotonin reuptake inhibitor (SSRI), binding to the serotonin transporter and preventing the reuptake of serotonin (5-HT) and thus leading to an increase of 5-HT in the synaptic cleft. On the other hand, it has been reported to act as a monoamine releasing agent (MRA) which assists with the release of monoamine vesicles from the presynaptic neuron, also resulting in an increase of 5-HT in the synaptic cleft. A strong correlation exists between depression and the hyper-activation of the hypothalamus-pituitary-adrenal (HPA) axis. On the other hand, antidepressants and MRA’s have been associated with endocrine disruption. Although a human safety study has illustrated that S.tortuosum is safe for consumption, it was recently reported to decrease sex steroid hormone levels including androstenedione (A4) and testosterone (T) in the H295R cell line, but conclusive remarks could not be formulated. The objective of this thesis was to establish whether Trimesemine™ (Tri; a mesembrine-rich S.tortuosum) could adversely affect gonadal steroid synthesis. HEK293 cells were transfected with 17βHSD type 5 (17βHSD5) cDNA, resulting in the overexpression of the 17βHSD5 enzyme, which is responsible for the conversion of A4 to T. Previous studies within our group used Trimesemine™ at doses ranging from 0.0001 mg/ml to 1 mg/ml. For this study narrower ranges were chosen. The cells were treated with Tri™ at proven effective dose (0.01 mg/ml) and high (0.5 mg/ml) dose, the supernatant was removed after 24 hours and the samples were analysed by UPC2-MS/MS. Routinely euthanized mice were accessed immediately after the culling to obtain viable tissue for primary cultures. Testes were removed, decapsulated and a mixed culture was plated. After 24 hours the cells were treated with lower and high doses of Tri™, following another 24 hours the supernatant was removed and the samples were analysed with UPLC-MS/MS. Ovaries were collected, dissociated and plated. The mixed culture was allowed to stabilise for 24 hours. This was followed by treatment with Tri™ at lower and high doses for a period of 24 hours, the supernatant was removed and the samples were analysed with UPLC-MS/MS. At the lower dose Tri™ did not appear to have any effect on A4, T and estradiol (E2). However, the high dose of Tri™ appeared to decrease A4 (mixed testicular culture) and T (HEK293 cells), possibly via inhibition of the 3βHSD or 17βHSD enzymes. In contrast no there did not appear to be estrogenic effects. In conclusion, low dose Tri™ did not appear to exhibit endocrine disruptive properties in vitro. These doses are comparable to those recommended for consumer use. The adverse effect elicited by the high dose Tri™ could be used as a marker for overdose, provided that basal levels of the hormones are known. These positive results indicates endocrine safety in vitro, but in vivo data is required for conclusive confirmation.