Abstract
Skin secretions of amphibians, which contain a large amount of bioactive compounds, play an essential role in their survival. For instance, some toxic or irritant secretions can protect them against predators. Due to the pharmacological and bioactive characteristics of the components in amphibian skin secretion, these secretions have been considered as one of the world’s richest source of such agents.In this study, the skin secretions of the frogs Odorrana livida, Hylarana latouchii and Phyllomedusa sauvagii were collected from the dorsal surface and immediately frozen in liquid nitrogen. Afterwards, a series of molecular techniques, including mRNA isolation, cDNA library construction, PCR, agarose gel analysis and DNA sequencing were applied. The novel peptide sequences were deduced from cloned cDNAs and then confirmed by using MALDI-TOF mass spectrometry and MS/MS fragmentation sequencing. Finally, three novel peptides were chemically-synthesised.
The determination of the therapeutic bioactivities of the three novel peptides was carried out by a series of assays. QUB-1384, exhibited BK-receptor agonist-like functions which induced the contraction of rat bladder and uterus tissues. QUB-1906 is a Bowman-Birk inhibitor which could efficiently inhibit the activity of trypsin. The novel dermaseptin peptide, QUB-2949, had broad-spectrum anticancer activities against human cancer cell lines including PC-3 (ATCC-CRL-1435), U251MG (ecacc-09063001), H157 (ATCC-CRL-5802), MCF-7 (ATCC-HTB-22) and MDA-MB-435S (ATCC-HTB-129). Meanwhile, like other dermaseptin peptides, QUB-2949 showed effective growth inhibitory activity against the standard Gram-negative bacterium Escherichia coli (NCTC 10418), the standard Gram-positive bacterium Staphylococcus aureus (NCTC 10788), the pathogenic yeast Candida albicans (NCPF 1467), the drug-resistant bacterium Enterococcus faecalis (ATCC 29212), Methicillin-resistant Staphylococcus aureus (MRSA) (ATCC BAA-2094) and Pseudomonas aeruginosa (NCTC 13437). In addition, according to the results of haemolysis assay and HMEC-1 MTT assay, all the peptides exhibited low cytotoxicity.
In conclusion, three novel peptides were found and assessed in this project. The multifunction and low cytotoxicity of these bioactive peptides make them promising candidates for natural drug discovery and provide new prospect for clinical treatments.
| Date of Award | Jul 2018 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Christopher Shaw (Supervisor), Tianbao Chen (Supervisor), Mei Zhou (Supervisor) & Lei Wang (Supervisor) |