Novel analgesic peptides from the tree frog of Hyla japonica.

Two novel analgesic peptides (Analgesin-HJ, FWPVI-NH2 and Analgesin-HJ(I5T), FWPVT-NH2) were identified from the skin of the tree frog, Hyla japonica. There are 171 amino acid residues in the precursor encoding analgesin-HJs. The precursor contains 10 copies of mature peptide, which include 9 copies of analgesin-HJ and one copy of analgesin-HJ(I5T). Results from analgesic experiments using mice models including abdominal writhing induced by acetic acid, formalin-induced paw licking, and thermal pain test indicated that this two peptides exerted comparable analgesic activities with morphine. In addition, they had ability to inhibit inflammatory factor secretion induced by lipopolysaccharides (LPS). Considering their easy production, storage, transfer and potential analgesic activity, analgesin-HJs might be exciting leading compounds or templates for the development of novel analgesic agent. In addition, this study might facilitate to understand skin defensive mechanism of amphibians.