Abstracts Category : Other

Assessment ofthe effect of selected African plants on an in vitro model ofParkinson's disease

by Keagile Hilda Lepule

Parkinsons disease (PD) is an incurable, progressivedisease characterised by loss of dopaminergic neurons in thesubstantia nigra of the brain. The main cause of dopaminergicneuron loss is attributed to oxidative stress and mitochondrialdysfunction. Although treatments are available, focus is placed onsymptomatic relief, and thus over time disease progression stilloccurs. Herbal remedies offer a wide range of chemical entitiesthat may prove beneficial in treating neurodegeneration. The aim ofthis study was to evaluate the neuroprotective effects of selectedAfrican medicinal plants using 6- hydroxydopamine (6-OHDA)-inducedcytotoxicity in the SH-SY5Y human neuroblastoma cell line as modelof PD. Eight plants, used ethnomedicinally for the treatment ofneurological disorders, were extracted using methanol and acetoneultrasonic maceration. Neurotoxicity was induced by exposing cellsto 33.3 M 6- OHDA for 2 h, followed by 24 h incubation with thecrude extracts. Neuroprotection was initially assessed using thesulforhodamine B staining assay. Plants that displayedneuroprotective activity (Acokanthera oppositifolia, Boophanedisticha and Xysmalobium undulatum) were further assessed (0.5- 15g/mL) using mechanistic assays. Reduced glutathione (GSH) content,mitochondrial membrane potential, reactive oxygen species (ROS)levels, intracellular calcium (Ca2+) flux and adenosinetriphosphate (ATP) levels were assessed using the monochlorobamineadduct formation, JC-1 ratiometric, dihydrodichlorofluoresceincleavage assays, Fura-2 AM and a bioluminescence assay kit,respectively. Cell morphology was visualized using phase contrastand polarisation-optical transmitted light differentialinterference contrast (PlasDIC) microscopy. 6-Hydroxydopaminereduced cell density by 91% and increasing ROS (3-fold) and GSH(2-fold) levels. Mitochondrial depolarisation (2-fold) wasevident, most likely due to blockage of mitochondrial complex Iwith subsequent ROS leakage. Reduced glutathione levels increasedadaptively possibly in response to the ensuing oxidation. Crudeextracts attenuated cytotoxicity by reducing ROS, sustaining ATPproduction and maintaining threshold intracellular Ca2+ effects.This was confirmed by microscopic analyses. A trend for greaterprotection at lower concentrations was observed. Results suggestthat intermediate-polarity extracts of A. oppositifolia, B.disticha and X. undulatum may assist with reducing the detrimentaleffects associated with PD. In conclusion, extracts of A.oppositifolia, B. disticha and X. undulatum offer in vitroneuroprotective effects.Advisors/Committee Members: Steenkamp, Vanessa (advisor), Nell, Margo Judith (coadvisor), Cordier, Werner (coadvisor).