1412 AMP-IBP5, an antimicrobial peptide derived from insulin-like growth factor-binding protein 5, triggers human keratinocyte activation

Abstract

Besides exhibiting direct microbicidal properties, antimicrobial peptides also display various immunomodulatory functions, including keratinocyte production of cytokines and chemokines, proliferation, migration and wound healing. Recently, a novel antimicrobial peptide named AMP- IBP5 (antimicrobial peptide derived from insulin-like growth factor-binding protein 5) was shown to exhibit antimicrobial activity against numerous pathogens, even at concentrations comparable to those of well-known antimicrobial peptides, such as human β-defensins and LL-37. However, the immunomodulatory role of AMP-IBP5 in cutaneous tissue is still not well understood. In the current study, we investigated whether AMP-IBP5 might trigger human keratinocyte activation and clarified the underlying molecular mechanism. The results revealed that among various cytokines, chemokines and growth factors tested in normal human keratinocytes, AMP-IBP5 selectively increased the production of interleukin (IL-8) and vascular endothelial growth factor (VEGF). Moreover, AMP-IBP5 markedly enhanced keratinocyte migration (assessed by in vitro wound closure assay,) and proliferation (analyzed using BrdU incorporation and XTT assays). AMP-IBP5-induced keratinocyte activation was mediated by Mas-related gene (Mrg) X1-X4 receptors with MAPK and NF-κB pathways working downstream, as evidenced by the inhibitory effects of MrgX1-X4 siRNAs and ERK-, JNK-, p38- and NF-κB-specific inhibitors. Indeed, we confirmed that AMP-IBP5 induced ERK, JNK, p38 and IB phosphorylation. Furthermore, AMP-IBP5-induced VEGF but not IL-8 production correlated with an increase in intracellular cAMP. In conclusion, these observations suggest that in addition to its antimicrobial function, AMP-IBP5 might contribute to wound healing process through activation of human keratinocytes.