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Sunscreens with broad-spectrum absorption decrease the trans to cis photoisomerization of urocanic acid in the human
Photochemistry and Photobiology
|September 1, 1994
Summary
UV light exposure causes urocanic acid (UCA) isomerization in skin, potentially leading to immunosuppression. Sunscreens, especially broad-spectrum ones, can reduce UV-induced cis-UCA formation, limiting its accumulation.
Area of Science:
- Photochemistry
- Dermatology
- Immunology
Background:
- Trans to cis photoisomerization of urocanic acid (UCA) in skin is implicated in UV-induced immunosuppression.
- Understanding factors affecting cis-UCA formation is crucial for photoprotection strategies.
Purpose of the Study:
- To investigate the influence of skin type and low SPF sunscreens on UV-induced cis-UCA formation.
- To assess the protective efficacy of sunscreens against cis-UCA accumulation in human skin.
Main Methods:
- Exposure of human skin to artificial UV light.
- Topical application of various sunscreens with low SPF.
- Measurement of cis-UCA formation and accumulation.
- Theoretical modeling of cis-UCA diffusion and elimination.
Main Results:
- Skin type had minimal impact on the rate of cis-UCA formation.
- Topical sunscreens reduced UV-induced cis-UCA formation.
- Higher SPF and broad-spectrum sunscreens were more effective in preventing cis-UCA formation.
- Cis-UCA accumulates in the stratum corneum and may diffuse into deeper epidermal layers.
Conclusions:
- Sunscreens, particularly broad-spectrum, high-SPF formulations, can mitigate UV-induced cis-UCA formation.
- The accumulation and potential diffusion of cis-UCA highlight the need for effective photoprotection.
- Desquamation is the primary mechanism for cis-UCA elimination from the stratum corneum.