[Show abstract][Hide abstract] ABSTRACT: Exposure of human skin to solar ultraviolet (UV) irradiation induces matrix metalloproteinase-1 (MMP-1) activity, which degrades type I collagen fibrils. Type I collagen is the most abundant protein in skin and constitutes the majority of skin connective tissue (dermis). Degradation of collagen fibrils impairs the structure and function of skin that characterize skin aging. Decorin is the predominant proteoglycan in human dermis. In model systems, decorin binds to and protects type I collagen fibrils from proteolytic degradation by enzymes such as MMP-1. Little is known regarding alterations of decorin in response to UV irradiation. We found that solar-simulated UV irradiation of human skin in vivo stimulated substantial decorin degradation, with kinetics similar to infiltration of polymorphonuclear (PMN) cells. Proteases that were released from isolated PMN cells degraded decorin in vitro. A highly selective inhibitor of neutrophil elastase blocked decorin breakdown by proteases released from PMN cells. Furthermore, purified neutrophil elastase cleaved decorin in vitro and generated fragments with similar molecular weights as those resulting from protease activity released from PMN cells, and as observed in UV-irradiated human skin. Cleavage of decorin by neutrophil elastase significantly augmented fragmentation of type I collagen fibrils by MMP-1. Taken together, these data indicate that PMN cell proteases, especially neutrophil elastase, degrade decorin, and this degradation renders collagen fibrils more susceptible to MMP-1 cleavage. These data identify decorin degradation and neutrophil elastase as potential therapeutic targets for mitigating sun exposure-induced collagen fibril degradation in human skin.
PLoS ONE 08/2013; 8(8):e72563. DOI:10.1371/journal.pone.0072563 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Proteoglycans, a family of glycosaminoglycan (GAG) conjugated proteins, are important constituents of human skin connective tissue (dermis) and are essential for maintaining mechanical strength of the skin. Age-related alterations of dermal proteoglycans have not been fully elucidated. We quantified transcripts of 20 known interstitial proteoglycans in human skin and found that decorin was the most highly expressed. Decorin was predominantly produced by dermal fibroblasts. Decorin was localized in dermal extracellular matrix with GAG bound to type I collagen fibrils. Analysis of decorin extracted from young (21-30 years) and aged (>80 years) sun-protected human buttock skin revealed that decorin molecular size in aged skin is significantly smaller than in young skin. The average size of decorin protein did not alter, indicating size of GAG chain is reduced in aged, compared to young skin. This age-dependent alteration of decorin GAG may contribute to skin fragility of elderly people.
[Show abstract][Hide abstract] ABSTRACT: Ultraviolet (UV) irradiation from the sun is the major cause of keratinocyte skin cancer. Transcription factor Snail plays an important role in epithelial-to-mesenchymal transition and epithelial tumor formation.
The aims of this study are to determine the regulation of Snail expression of ultraviolet (UV) irradiation on Snail expression in human skin in vivo, and the mechanisms by which UV irradiation induces Snail expression, in human keratinocytes.
Real-time RT-PCR was employed to measure Snail expression in human skin in vivo and cultured human keratinocytes. Luciferase assay and electrophoretic mobility shift assay (EMSA) were employed to investigate transcriptional regulation of the in Snail gene promoter.
Ultraviolet (UV) irradiation transiently induces Snail expression in human skin in vivo and cultured human keratinocytes. Snail induction is significantly reduced by specific inhibitors of ERK, p38 or JNK, indicating each of the three major mitogen-activated protein kinase (MAPK) pathways participate in Snail regulation. AP-1 transcription factor complex, a downstream target of MAPK signaling, is required for Snail induction. Inhibition of AP-1 activity by over-expression of dominant-negative c-Jun substantially reduces Snail induction. Analyses of the Snail promoter, revealed the presence of an AP-1 binding site. EMSA assay demonstrated that UV irradiation specifically induced c-Jun binding to this AP-1 site. Mutation of the AP-1-binding site completely blocked protein binding and inhibited UV irradiation-induced Snail promoter activity.
UV irradiation induces Snail gene expression in human skin keratinocytes. This induction is mediated by MAPK-AP-1 dependent signaling pathway. Elevated expression of Snail in response to chronic UV irradiation in human skin may contribute to UV irradiation-induced skin tumor development.