Cytotoxic peptides with insulin‐releasing activities from skin secretions of the Italian stream frog Rana italica Rana italicaRana italica (Ranidae)

摘要

> Peptidomic analysis of norepinephrine‐stimulated skin secretions from Italian stream frog Rana italica led to the purification and characterization of two host‐defense peptides differing by a single amino acid residue belonging to the brevinin‐1 family (brevinin‐1ITa and ‐1ITb), a peptide belonging to the temporin family (temporin‐ITa) and a component identified as prokineticin Bv8. The secretions contained relatively high concentrations of the methionine‐sulphoxide forms of brevinin‐1ITa and ‐1ITb suggesting that these peptides may have a role as antioxidants in the skin of this montane frog. Brevinin‐1ITa (IVPFLLGMVPKLVCLITKKC) displayed potent cytotoxicity against non‐small cell lung adenocarcinoma A549 cells (LC ₅₀ ?=?18?μM), breast adenocarcinoma MDA‐MB‐231 cells (LC ₅₀ ?=?8?μM) and colorectal adenocarcinoma HT‐29 cells (LC ₅₀ ?=?18?μM), but the peptide was also strongly hemolytic against mouse erythrocytes (LC ₅₀ ?=?7?μM). Temporin‐ITa (VFLGAIAQALTSLLGKL.NH ₂ ) was between three and fivefold less potent against these cells. Brevinin‐1ITa inhibited growth of both Gram‐positive Staphylococcus epidermidis and Gram‐negative Escherichia coli as well as a strain of the opportunist yeast pathogen Candida parapsilosis , whereas temporin‐ITa was active only against S. epidermidis and C. parapsilosis . Both peptides stimulated the release of insulin from BRIN‐BD11 clonal β‐cells at concentrations ≥1?nM, but brevinin‐1ITa was cytotoxic