Antimicrobial peptides from amphibian skin: What do they tell us?

Amphibian skill secretions contain many biologically active compounds, such as biogenic amines, complex alkaloids, or peptides. Within the latter clas s molecules, a large number of peptide antibiotics has been isolated and ch aracterized from different amphibian species. Antimicrobial peptides are co nsidered the effector molecules of innate immunity, acting as a first line of defense against bacterial infections, by perturbing the phospholipid bil ayer of the target cell membrane. These gene-encoded molecules are synthesi zed as inactive precursors and in several cases their proparts were shown t o have highly conserved structures es. It has also been demonstrated that t he promoter regions of inducible peptide antibiotics are often regulated by the transcriptional control machinery NF-kB/IkB alpha. In amphibia of Rana and Bombina genera, inhibition of transcription of the genes encoding anti microbial peptides has been obtained by,glucocorticoid treatment, which cau ses an increase of IkB alpha synthesis. Moreover, determination of the stru cture of a number of genes coding for antimicrobial peptides in amphibia ha s actually shown that their promoter regions contain recognition sites for nuclear factors. (C) 1999 John Wiley & Sons, Inc.