Ginkgo biloba has been advocated as a neuroprotective agent for several years in glaucoma. In this study, immunohistochemistry was used to identify known potential molecular targets of Ginkgo biloba related to retinal ganglion cell (RGC) apoptosis in experimental glaucoma, including amyloid precursor protein (APP), Aß, cytochrome c, caspase-3 and tumor necrosis factor receptor-1 (TNF-R1). Furthermore, using apoptotic inducers related to mechanisms implicated in glaucoma, namely Dimethyl sulphoxide (DMSO), ultraviolet C (UVC) and Sodium Azide (NaN3), the effects of the terpenoid fraction of Ginkgo biloba (Ginkgolide A, Ginkgolide B and Bilobalide) were investigated separately in cultured retinal ganglion cells (RGC-5). Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and morphological analysis of DMSO treated RGC-5 was performed using Hoechst 33342 stain. Immunohistochemistry showed a strong inverse correlation between Aß and APP in ocular hypertension (OHT) animals, with APP and Aß accumulation peaking at 1 and 12 weeks after intraocular pressure (IOP) elevation respectively. Cytochrome c and TNF-R1 expression peaked at 3 weeks, and active caspase 3 activity at 12 weeks after IOP elevation. 1% DMSO, UV40, 1mM NaN3 and 50μM Aβ25-35 dose dependently reduced RGC-5 survival at 24 hours by 27%, 20%, 35% and 27% respectively. These effects were inhibited by Ginkgolide A, Ginkgolide B and Bilobalide in different assays at different levels. In these experiments, all three compounds showed a dose-related response although some intrinsic toxicity was observed with Ginkgolide A. Ginkgolide B had the most profound neuroprotective effects in the majority of assays at a concentration range of 0.5-5μg/ml, whereas Ginkgolide A and Bilobalide had variable activity. Although the effect of simultaneous administration of all three fractions was not assessed, work in this thesis suggest that Ginkgolide B can be neuroprotective to RGCs in preventing apoptosis and cell death, therefore may be of use as a neuroprotective strategy in glaucoma management.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:625771 |
| Date | January 2012 |
| Creators | Baltmr, A. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1343626/ |
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