UVA Light Stimulates the Production of Cathepsin G and Elastase-Like Enzymes by Dermal Fibroblasts: A Possible Contribution to the Remodeling of Elastotic Areas in Sun-Damaged Skin

Abstract

Solar elastosis is characterized by accumulation of large amounts of material staining similarly to elastin in the dermis. The nature of this material and the process responsible for its accumulation are still unknown. Elastolytic proteases have important functions in the catabolism of the interstitial matrix and can also generate, by the digestion of the interstitial proteins, soluble peptides which can induce collagen and elastin synthesis and deposition. We investigated whether (i) elastolytic enzymes can be detected in samples from sunexposed and nonexposed skin, and (ii) ultraviolet (UV) rays influence the production of elastolytic activities in cultured dermal fibroblasts. Immunoelectron microscopy showed a positive reaction for neutrophil elastase and cathepsin G in fibroblast like cells from specimens of sunexposed areas. Little or no reaction was found in biopsies of sunprotected skin. Fibroblast cultures from sunexposed skin expressed higher levels of hydrolytic activity against synthetic substrates of elastases and cathepsin G than those obtained from sunprotected areas. Irradiation with UVA strongly stimulated the production of these activities in fibroblasts from sunprotected sites. No significant change was detected in parallel sets of cultures after UVB irradiation. Inhibition experiments indicated that the elastaselike activity expressed by fibroblasts can be attributed to at least two enzymes.