title: Epithelial-mesenchymal interaction during UVB-induced up-regulation of neutral endopeptidase.
abstract: We recently reported that overexpression of the elastase NEP (neutral endopeptidase) by fibroblasts plays a pivotal role in the mechanism of UVB-induced skin wrinkling by degrading dermal elastic fibres. Since UVB does not penetrate to the dermis, we hypothesized that factors secreted by UVB-exposed keratinocytes in the epidermis trigger fibroblasts in the dermis to increase their expression of NEP which then degrades the elastic fibres. In the present study, we characterized the epithelial-mesenchymal interaction between keratinocytes and fibroblasts which leads to increased expression of NEP. Human fibroblasts co-cultured with UVB-exposed human keratinocytes in cell inserts significantly increased their expression of NEP at the transcriptional, translational and enzymatic levels. Neutralizing antibodies to IL (interleukin)-1α or GM-CSF (granulocyte/macrophage colony-stimulating factor) significantly abolished the increased expression of NEP at the enzymatic levels in human fibroblasts co-cultured with UVB-exposed human keratinocytes, whereas neutralizing antibodies to IL-6, IL-8 or TNFα (tumour necrosis factor α) had no such effect. The addition of IL-1α or GM-CSF, but not TNFα, IL-6 or IL-8, at concentrations ranging from 1 to 10 nM, significantly stimulated the expression of NEP in human fibroblasts at the transcriptional and translational levels. These findings suggest that IL-1α and GM-CSF are intrinsic cytokines secreted by UVB-exposed keratinocytes that stimulate expression of NEP by fibroblasts.
authors.affiliation: School of Bioscience and Biotechnology, Tokyo University of Technology, 1404-1 Katakura, Hachioji, Tokyo, 192-0982, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakajima
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Ezaki
authors.forename: Tomoyashu
authors.initials: T
authors.lastname: Nagai
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Yoshioka
authors.forename: Genji
authors.initials: G
authors.lastname: Imokawa
mesh_terms: D002478:Cells, Cultured; D018920:Coculture Techniques; D016207:Cytokines / Q000494:pharmacology / Q000502:physiology; D000078404:Epidermal Cells; D005347:Fibroblasts / Q000201:enzymology*; D052816:Foreskin / Q000166:cytology; D015870:Gene Expression; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D006801:Humans; D053582:Interleukin-1alpha / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D015603:Keratinocytes / Q000378:metabolism / Q000528:radiation effects*; D008297:Male; D015260:Neprilysin / Q000235:genetics* / Q000378:metabolism; D019899:Paracrine Communication; D014466:Ultraviolet Rays; D015854:Up-Regulation / Q000528:radiation effects*
chemical_list: D016207:Cytokines; D053582:Interleukin-1alpha; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D015260:Neprilysin