Collagen Fragments Inhibit Hyaluronan Synthesis in Skin Fibroblasts in Response to Ultraviolet B (UVB)

Abstract

UVB irradiation causes characteristic features of skin aging including remodeling of the dermal extracellular matrix. A key feature during this process is the up-regulation of matrix metalloproteinases and cleavage of collagen. Hyaluronic acid (HA), a major component of the dermal matrix, decreases after chronic UVB exposure. However, the factors that govern the decline of HA synthesis during the course of actinic aging are largely unknown. The aim of the present study was to explore whether collagen degradation causes inhibition of HA synthesis in human skin fibroblasts. After treatment of fibroblasts with collagen fragments (CF) in vitro, resolution of the actin cytoskeleton and inhibition of HA secretion occurred because of specific down-regulation of hyaluronan synthase 2 (HAS2) expression. The ␣ v ␤ 3 -agonist, RGDS, latrunculin A, and an inhibitor of Rho-activated kinase inhibited HAS2 expression. Conversely, blocking antibodies to ␣ v ␤ 3 abolished the down-regulation of HAS2 and the cytoskeletal effects. Furthermore, inhibition of cofilin phosphorylation in response to CF was prevented by ␣ v ␤ 3 -blocking antibodies. The key role of ERK signaling was shown by reduced nuclear accumulation of phosphoERK and of ELK-1 phosphorylation in response to CF. In addition, the ERK inhibitor PD98059 reduced HAS2 expression. Also, UVB irradiation of fibroblasts caused down-regulation of HAS2, which was sensitive to matrix metalloproteinase inhibitors and to ␣ v ␤ 3 -blocking antibodies. In conclusion, these data suggest that CF activate ␣ v ␤ 3 -integrins and in turn inhibit Rho kinase (ROCK) signaling and nuclear translocation of phosphoERK, resulting in reduced HAS2 expression. Therefore, a novel mechanism is presented how proteolytic collagen cleavage may inhibit HA synthesis in dermal fibroblasts during extrinsic skin aging.

The decreased secretion of hyaluronan by older human fibroblasts under physiological conditions is mainly associated with the down-regulated expression of hyaluronan synthases but not with the expression levels of hyaluronidases

“…Taken together, these results for HAS expression seem to indicate that the expression of HAS, especially HAS2, at both the gene and protein levels, mainly reflects the secretion levels of HA. These results are consistent with another study using UVB-exposed skin fibroblasts, which demonstrated that HAS2 is the predominant isoform expressed in skin fibroblasts and the extent of HAS2 down-regulation correlated with the UVB-induced decrease of HA secretion (Röck et al 2011).…”

“…In relation to the age-dependent impairment in wound healing, aging fibroblasts have a defect in their phenotypic maturation that is required for tissue remodeling and the closure of wounds because of the dysfunction of HA-dependent CD44/epidermal growth factor receptor signaling. The cellular mechanisms of UVB-induced changes in HA in skin cells and tissues have been studied in detail (Südel et al 2005;Averbeck et al 2006;Dai et al 2007;Röck et al 2011), and it has been shown that the loss of HA is closely associated with phenotypic characteristics of skin photo-aging (Margelin et al 1996;Takahashi et al 1995Takahashi et al , 1996. In contrast, the effects of chronological aging on HA are much less well understood.…”

Hyaluronan Synthase 2 Protects Skin Fibroblasts against Apoptosis Induced by Environmental Stress

“…On the other hand, a series of reports from the Fischer group (42) demonstrated that chronic UVB exposure caused a significant loss of HA from the dermis of mouse skin and decreased gene expression of all three HAS enzymes in the dermis. The UVB-induced down-regulation of Has2 was mediated by the activation of ␣ V ␤ 3 -integrin induced by collagen fragments (18). Another group reported that a single UVB exposure caused an increase in chondroitin sulfate but not in other glycosaminoglycans, including HA, in human skin (43).…”

“…Studies from different groups have shown that HAS2 plays a predominant role in inducible HA synthesis in fibroblasts exposed to growth factors (15,16), including fibroblasts undergoing transformation to myofibroblasts (17). Furthermore, down-regulation of Has2 gene expression is responsible for the inhibition of HA synthesis in skin fibroblasts in response to certain environmental stressors, such as UVB irradiation (18). The activity of HAS enzymes can be regulated at the transcriptional level (15,16,19,20) or at the posttranslational level by phosphorylation (21), OGlcNAcylation (22), or ubiquitination (23).…”

Effect of Adipose-Derived Stem Cells on Induced Photoaging in the Skin of Adult Guinea Pig: Histological and Immunohistochemical Study

“…Also, amplified AP-1 transcription induced collagen degradation by upregulating MMPs production in both fibroblasts and damaged keratinocytes [9] . Moreover, although UVB had short wave lengths, about 5% of UVB rays could reach dermal papillae and affect dermal fibroblasts [46] . Coinciding, degenerated fibroblasts were detected in the photoaged subgroup of the present study.…”