Thesis
Purification of plant derived molecules that modulate sphingolipid enzymes in cancer and inflammation
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde.
- Date of award
- 2021
- Thesis identifier
- T16015
- Person Identifier (Local)
- 201664709
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- There is a constant need to discover new anticancer and anti-inflammatory compounds that can be developed as medicines. Sphingosine kinase 1 (SK1) and dihydroceramide desaturase (Des1) have been demonstrated to have a key role in sphingolipid metabolism and are potential targets for anticancer/anti-inflammatory therapeutics. This study aims to screen a plant library collected during field work in Egypt and then to isolate new anticancer and anti-inflammatory compounds with activity against SK1 and/ or Des1. This aim was achieved using plant extracts tested on breast cancer cell viability, proliferation and SK1 and/or Des1 protein expression. Bio-assay guided fractionation and isolation of compounds using flash column, silica gel column chromatography and preparative TLC techniques, followed by structure elucidation using 1D and 2D spectroscopic analysis enabled identification of compounds that met the criteria above. Cell proliferation was determined using [3H]-thymidine incorporation assay. Western blotting technique was used to determine the effect of isolated compounds on the targeted enzymes SK1/Des1 as well as the apoptotic pathway (PARP). There were three major findings. First, three plant species Gomphocarpus sinaicus, Urginea maritima and Pancratium tortuosum exhibited anticancer activity. Second, narciclasine was isolated for the first time from P. tortuosum and was demonstrated to inhibit cell proliferation (p<0.05) and to reduce SK1 and Des1 expression in MDA-MB-231 and MCF7-7L breast cancer cells. Narciclasine also induced PARP cleavage (a marker for apoptosis) and reduced expression of Ki67 and phosphorylated AKT levels (a marker for cell survival). The reduced expression of SK1 and Des1 in response to narciclasine was independent of the ubiquitin-proteasomal pathway, suggesting that this compound might affect the transcriptional/translational regulation of SK1 and Des1. Finally, narciclasine also exhibited ant-inflammatory activity as evidenced by its ability to prevent TNFα-stimulated degradation of IκB and to inhibit NFkB- and AP1-dependent transcriptional activity in keratinocytes. Third, a mixture of cardenolide glycosides were isolated from G. sinaicus and shown to inhibit cell proliferation (p<0.05), reduce expression of SK1 and Des1 and induce modest PARP cleavage in MDA-MB-231 and MCF-7L cells. This mixture contained humistratin and calactin and/or calotropin. These compounds reduced SK1 expression by inducing its proteasomal degradation, while the reduction in Des1 expression may be via a transcriptional/translational mechanism and is independent of ubiquitin-proteasomal degradation pathway. The mixture also exhibited anti-inflammatory activity in inhibiting NFkB- and AP-1-dependent transcriptional activity in keratinocytes. Narciclasine and the cardenolide glycoside mixture are potential anticancer/anti-inflammatory compounds require further studies in order to establish whether these compounds might be usefully exploited to treat cancer and inflammatory disease.
- Advisor / supervisor
- Pyne, Susan
- Pyne, Nigel
- Grey, Sandy
- Resource Type
- DOI
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PDF of thesis T16015 | 2021-10-13 | Public | Download |