Abstract
The repetitive exposure of skin to ultraviolet B (UVB) preferentially elicits wrinkling while ultraviolet A (UVA) predominantly elicits sagging. In chronically UVB or UVA-exposed rat skin there is a similar tortuous deformation of elastic fibers together with decreased skin elasticity, whose magnitudes are greater in UVB-exposed skin than in UVA-exposed skin. Comparison of skin elasticity with the activity of matrix metalloproteinases (MMPs) in the dermis of ovariectomized rats after UVB or UVA irradiation demonstrates that skin elasticity is more significantly decreased in ovariectomized rats than in sham-operated rats, which is accompanied by a reciprocal increase in elastase activity but not in the activities of collagenases I or IV. Clinical studies using animal skin and human facial skin demonstrated that topical treatment with a specific inhibitor or an inhibitory extract of skin fibroblast-derived elastase distinctly attenuates UVB and sunlight-induced formation of wrinkling. Our results strongly indicated that the upregulated activity of skin fibroblast-derived elastase plays a pivotal role in wrinkling and/or sagging of the skin via the impairment of elastic fiber configuration and the subsequent loss of skin elasticity.
Highlights
IntroductionFacial wrinkles and sagging are the most prominent characteristics by which skin aging is recognized
Facial wrinkles and sagging are the most prominent characteristics by which skin aging is recognized.the mechanism(s) of UV-induced wrinkling and sagging of the skin remains poorly elucidated.This poor mechanistic understanding of UV radiation-induced wrinkling and sagging is mainly due to the following two issues: (1) there are experimental limitations to using human skin for inducing such photo-aging phenomena, which require at least one year; (2) skin behaves as a stress organ, which exerts the neuroendocrine system in response to UV radiation to release stress neurotransmitters, neuropeptides, and hormones [1,2]
These findings suggest that the Ue* and Uv* changes observed in human facial skin resemble the actinic aging caused by chronic UV exposure and that this animal model could serve as a useful and reliable tool to analyze the mechanism(s) involved in the UV-induced formation of wrinkling and sagging
Summary
Facial wrinkles and sagging are the most prominent characteristics by which skin aging is recognized. No such changes were observed in the dorsal skin of mice where a temporary groove was produced, if not followed by UVB irradiation These findings suggest that early wrinkle formation in the corners of the eyes occurs as a result of the immobilization of transient wrinkles, seen as laugh grooves in the corners of the eyes, due to the loss of skin elasticity induced by frequent exposure to sunlight. UVA but not after UVB irradiation, which may reflect a difference in the frequency balance of wrinkling and sagging observed between UVB and UVA These findings suggest that the Ue* and Uv* changes observed in human facial skin resemble the actinic aging caused by chronic UV exposure and that this animal model could serve as a useful and reliable tool to analyze the mechanism(s) involved in the UV-induced formation of wrinkling and sagging.
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