Background: The skin has evolved an epithelial defence mechanism which is characterized by antimicrobial peptides that inactivate various microorganisms and exhibit stimulatory activities bridging innate and adaptive immunity. Dermcidin (DCD) is a newly isolated antimicrobial peptide produced by the eccrine sweat glands in the skin. Recently, the DCD peptides DCD-1 and DCD-1L have been shown to display in vitro microbicidal activities against bacteria and viruses.
Objectives: Because some skin-derived antimicrobial peptides activate keratinocytes, we investigated whether DCD-1L would also trigger keratinocyte activation.
Methods: Normal human keratinocytes were used in this study. The ability of DCD-1L to induce the production of cytokines/chemokines by keratinocytes was determined by enzyme-linked immunosorbent assay, and various inhibitors were used to investigate the stimulatory mechanism of DCD-1L. Mitogen-activated protein kinase (MAPK) phosphorylation and NF-kappaB activation were analysed by Western blotting.
Results: DCD-1L stimulated keratinocytes to generate cytokines and chemokines including tumour necrosis factor-alpha, interleukin-8 (CXCL8), interferon-inducible protein 10 (CXCL10) and macrophage inflammatory protein-3alpha (CCL20). To determine the molecular mechanism involved, we showed that DCD-1L-mediated cytokine/chemokine production was controlled by both G-protein and MAPK pathways, as evidenced by the inhibitory effects of pertussis toxin and specific inhibitors for p38 and ERK, but not for JNK, on DCD-1L-induced keratinocyte activation. Furthermore, we confirmed that DCD-1L could induce phosphorylation of p38 and ERK, and noticeably upregulated NF-kappaB activation.
Conclusions: Taken together, the new activity of DCD-1L to stimulate the production of cytokines/chemokines by keratinocytes provides novel evidence for the implication of DCD, beyond its microbicidal ability, in skin immunity.