Pro-rich
antimicrobial peptides are a group of linear
peptides of innate immunity isolated from mammals and invertebrates, and characterised by a high content of
proline residues (up to 50%). Members of this group are predominantly active against Gram-negative bacterial species which they kill by a non-lytic mechanism, at variance with the majority of the known
antimicrobial peptides. Evidence is accumulating that the Pro-rich
peptides enter the cells without membrane lysis and, once in the cytoplasm, bind to, and inhibit the activity of specific molecular targets essential to bacterial growth, thereby causing cell death. This mode of action makes these
peptides suitable for
drug development efforts. In addition to antibacterial action,
PR-39, one of the better characterised Pro-rich
peptides from mammals, exerts other potentially exploitable
biological activities, such as induction of
syndecan expression in mesenchymal cells and inhibition of the
NADPH oxidase activity of neutrophils, suggesting a role of this
peptide in
wound repair and
inflammation.
PR-39 also exerts a protective effect in various animal models of
ischemia-reperfusion injury, preventing the post-ischemic
oxidant production, and is a potent inducer of angiogenesis both in vitro and in vivo. Although the physiological relevance of all these effects has not yet been established, the above observations underscore the therapeutic potential of this
peptide in a number of complex processes such as
inflammation,
wound repair,
ischemia-reperfusion injury, and angiogenesis.