1. Broad-Spectrum Sunscreens Offer Protection Against Urocanic Acid Photoisomerization by Artificial Ultraviolet Radiation in Human Skin1 
Renate G. van der Molen, Coby Out-Luiting, Hansjürgen Driller, Frans H.J. Claas, Henk K. Koerten, A. Mieke Mommaas 
Journal of Investigative Dermatology 
Volume 115, Issue 3, Pages (September 2000)
DOI: /j x
Copyright © 2000 The Society for Investigative Dermatology, Inc Terms and Conditions

2. Figure 1
Dose–response curves of in vivo and ex vivo UCA photoisomerization in human skin. The mean percentage of cis-UCA (±SEM) rose after in vivo (solid line) UV irradiation with increasing UV doses until a photostationary plateau was reached of 52% cis-UCA with a dose of 100 mJ per cm2 (n = 4). After ex vivo (dotted line) irradiation of human skin a plateau of 44% cis-UCA was reached after a dose of 200 mJ per cm2 (n = 4).
Journal of Investigative Dermatology  , DOI: ( /j x)
Copyright © 2000 The Society for Investigative Dermatology, Inc Terms and Conditions

3. Figure 2
Sunscreens can significantly reduce cis-UCA formation after in vivo exposure to single or repeated UV irradiations of 100 mJ per cm2. The mean percentages of cis-UCA (±SEM) are shown for single exposure (□, n = 14) and irradiation for four consecutive days (▪, n = 18). With both UV protocols all sunscreens showed significant protection against the UV-induced increase of cis-UCA, although at different levels (p < 0.01). Significantly, more cis-UCA was found in the sunscreen protected groups after repeated UV exposures compared with values found after a single dose (p < 0.05). Comparing the protective capacity of the sunscreens with the same SPF (B10 and T10) after a single dose showed significantly better protection by sunscreen T10 (p < 0.01). Also after repeated UV exposures T10 showed significantly better protection than B10 (p < 0.01). Cis-UCA percentages found with the vehicle were comparable with the percentages found after UV exposure without sunscreen.
Journal of Investigative Dermatology  , DOI: ( /j x)
Copyright © 2000 The Society for Investigative Dermatology, Inc Terms and Conditions

4. Figure 3
In vivo sunscreen protection against UCA photoisomerization is correlated with the SPF. For both the organic sunscreens B and physical sunscreens T the SPF was plotted against the percentages of cis-UCA (data from Figure 2) found at each SPF. Two regression lines for each sunscreen type are drawn through the observations made after single and repeated exposures (equations are shown). After a single exposure using the sunscreen type B the regression line crosses the x-axis at ±SPF 20 and after repeated UV exposure this occurs with ±SPF 23. For sunscreen type T the regression line crosses the x-axis at ±SPF 11 after a single UV exposure and at ±SPF 13 after repeated UV exposures.
Journal of Investigative Dermatology  , DOI: ( /j x)
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5. Figure 4
After ex vivo exposure of skin to 200 mJ per cm2 UV all sunscreens showed significant protection against UCA photoisomerization. The mean percentages of cis-UCA (±SEM) are shown (n = 7, for each bar). All sunscreens afforded significant protection against the UV-induced increase of cis-UCA (p < 0.01). Comparing the sunscreens with the same SPF (B10 and T10) showed significantly better protection by sunscreen T10 after UV exposure (p < 0.01). Cis-UCA percentages found with the vehicles were comparable with the percentages found after UV exposure without sunscreen.
Journal of Investigative Dermatology  , DOI: ( /j x)
Copyright © 2000 The Society for Investigative Dermatology, Inc Terms and Conditions

6. Figure 5
A broad absorption spectrum is more important for good protection against UV-induced isomerization of UCA than the penetration characteristics of a sunscreen. The mean percentages of cis-UCA (±SEM) are shown (n = 7, for each bar). Values were increased from 0.8% in nonexposed skin to 51% (□) after in vivo exposure with an UV dose of 100 mJ per cm2 without quartz glass and to 50% with quartz glass (▪). Again there was a significant difference in the percentages of cis-UCA when comparing the sunscreens B10 and T10 (p < 0.01). Application of T10 or B10 either directly on the skin or on quartz glass did not result in a significant difference between the two application methods. Organic sunscreen AB10 with a broad absorption spectrum showed comparable (not significantly different) protection as physical suncreen T10 with the same SPF of 10, although it was significantly different from B10 (p < 0.01).
Journal of Investigative Dermatology  , DOI: ( /j x)
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7. Figure 6
UV absorption spectra of the three sunscreens with SPF 10 and vehicle. Spectra were obtained by spectrophotometric measurements of the formulations applied as a thin layer (1 mg per cm2) on quartz glass. Sunscreen AB10 (––––) and T10 (–··–··–··) show absorption/reflection in both the UVB and UVA range. Sunscreen B10 (–––) mainly absorbs UVB wavelengths. The vehicle (········) shows minimal to no absorption.
Journal of Investigative Dermatology  , DOI: ( /j x)
Copyright © 2000 The Society for Investigative Dermatology, Inc Terms and Conditions

8. Figure 7
Sunscreens show differential protection against UV-induced modulation of the MECLR (n = 7). Data are expressed as percentages of control, nonirradiated skin (first bar) ±SEM (*p < 0.01). The 100% control responses were (±4400) cpm. Hardly any proliferation (< 500 cpm) was found in cultures containing only responder peripheral blood mononuclear cells. After 200 mJ per cm2 MECLR responses of nonprotected skin were significantly reduced to 17% as compared with control, nonirradiated skin. Sunscreens AB10 and T10 both completely prevented this reduction. MECLR responses with sunscreen B10 were significantly suppressed to 81%. Responses with the vehicle were reduced, comparable with the UV irradiated skin without sunscreen.
Journal of Investigative Dermatology  , DOI: ( /j x)
Copyright © 2000 The Society for Investigative Dermatology, Inc Terms and Conditions