The role of elastases secreted by fibroblasts in wrinkle formation: Implication through selective inhibition of elastase activity

We have previously demonstrated that decreases in skin elasticity, accompan ied by increases in the tortuosity of elastic fibers, are important early e vents in wrinkle formation. In order to study the role of elastases in the degeneration of elastic fibers during wrinkle formation we examined the eff ects of an inhibitor of skin fibroblast elastase, N-phenethylphosphonyl-L-l eucyl-L-tryptophane (NPLT), on wrinkle formation in hairless mice skin foll owing UV irradiation. Dorsal skins of hairless mice were exposed daily to U V light for 18 weeks at doses of 65-95 mJ/cm(2) and treated topically with 100 muL of 1 mM NPLT immediately after each UV irradiation. Wrinkles on dor sal skins were evaluated from week 6 through week 18. The daily exposure of mouse skin to UV light with less than I minimal erythemal dose significant ly enhanced the activity of elastase in the exposed skin by week 4, and the elevated levels of elastase activity were significantly reduced by the in vitro incubation with NPLT in a dose-dependent manner to a level similar to that in unexposed mice skin, indicating that NPLT can efficiently inhibit the UV-inducible elastase activity. Topical application of NPLT significant ly suppressed wrinkle formation when compared with vehicle controls by week 15 of treatment (P < 0.05). Histochemistry of elastic fibers with Orcein s taining demonstrated that there were no obvious decreases of the fine elast ic fibers in UV-exposed NPLT-treated skin in contrast to their marked decre ases in the UV-exposed vehicle-treated skin. These findings suggest that sk in fibroblast elastase plays a decisive role in wrinkle formation through t he degeneration of elastic fiber.