Age dependent increase of elastase type protease activity in mouse skin - Effect of UV-irradiation

The effect of chronological aging and photoaging (UV-radiation) on elastase -type enzyme activity of hairless mouse skin was studied. Aging resulted in the increase of elastase type endopeptidase activity extractable from mous e skins. Both chronic UVA and UVB radiation resulted in a significant incre ase of elastase type activity. PBS extracted only small part of the elastas e activity, UV-A produced an increase of about 90-120% according to the typ e of irradiation (xenon or UV-A SUN) and UV-B produced a 72% increase. Extr action by Triton X-100 suggested that most of the activity is bound to cell s and fibrous structures. EDTA inhibited 80-90% of the elastase activity in chronologically aged skin extracts and also the activity induced by UVA ra diation suggesting that metallo-elastase(s) are involved, About 30% of the WE induced activity could only be inhibited by EDTA and about 50% by PMSF s uggesting that irradiation by UVB increased more serine endopeptidase activ ity but also MMP-activity. Chronic UVA radiation produced an increase of sk in elastase activity equivalent to that observed after 24 months of aging i n non-irradiated animals (similar to 100 weeks) corresponding to similar to 90% of total life span of these mice. The total increase produced by UVB w as less, but the strong increase of a serine elastase, presumably from PMN- s, appear to produce a much more pronounced biological activity as shown by the presence of fibronectin degradation products in skin extracts. Such de gradation products were shown to exert harmful effects on tissues. These re sults may well have biological significance and distinguish chronological a ging and photoaging. (C) 2000 Elsevier Science S.A. All rights reserved.