Interactions between neutrophil-derived antimicrobial peptides and airway epithelial cells

Most antimicrobial peptides have been discovered based on activity-guided purification procedures, which used assays to determine their antimicrobial activity. Nevertheless, recent studies have shown that antimicrobial peptides also exert a range of other functions. Based on these observations, antimicrobial peptides are now not only implicated in host defense against infection but also in other immune reactions, inflammation, and wound-repair processes. The activities of neutrophil defensins and the cathelicidin hCAP-18/LL-37, antimicrobial peptides that are abundantly expressed in the human neutrophil, are the subject of an increasing number of studies. Exposure to neutrophil defensins and hCAP-18/LL-37 results in increases in mediator expression and release, chemotaxis, and proliferation of inflammatory and epithelial cells and fibroblasts, and the mechanisms underlying these effects have been partly elucidated. This review is focused on the effects of neutrophil defensins and hCAP-18/LL-37 on airway epithelial cells.