Antioxidants add protection to a broad-spectrum sunscreen.
BACKGROUND
Exposure of human skin to ultraviolet radiation (UVR) results in erythema, pigment darkening, skin cancer and photoageing. In addition to conventional organochemical and the physical-mineral type sunscreens (SS), other non-SS protective strategies have been investigated, including antioxidants (AOx) and topical DNA repair enzymes.


OBJECTIVE
To investigate whether AOx could improve the protection provided by a broad-spectrum sunscreen (SS) preparation.


METHODS
Volunteers were exposed to repetitive solar-simulated (ss)UVR at 1.5 times minimal erythema dose for four consecutive days. Thirty minutes before each exposure and 6, 24 and 48 h after the last exposure, the test materials [vehicle, SS (sun protection factor 25) alone, AOx alone and SS plus AOx] were applied to four different sites. Another two sites received ssUVR only, or SS plus AOx only, and a third site was left untreated (neither ssUVR or product). Erythema and pigmentation were measured using a Mexameter. Biopsy specimens were taken 72 h after the last irradiation. The thickness of the stratum corneum and epidermis were measured by microscopy. Expression of cytokeratins (CKs), matrix metalloproteinases (MMPs) and CD1a-positive Langerhans cells (LCs) analysed by immunohistochemical staining, and relative expression levels were compared between all seven sites.


RESULTS
AOx alone did not reduce erythema. There was a significant reduction in pigmentation, and the product almost completely protected against LC depletion. AOx plus SS gave better protection against pigment formation and CK5/6 induction than SS alone. AOx alone protected against ssUVR-induced hyperproliferation, as shown by epidermal thickness and CK16 biomarkers, and was better than SS alone. Interestingly, although protection against induction of MMP-9, a marker of photoageing, did not reach significance when either SS or AOx were applied separately, there was complete protection against MMP-9 induction when these were combined.


CONCLUSIONS
Non-SS materials such as AOx can contribute significantly to sun protection when added to a broad-spectrum SS and applied topically to human skin in vivo.
Wu
Y
Y
Department of Dermatology, No. 1 Hospital of China Medical University, Shenyang, China.
Matsui
M S
MS
Chen
J Z S
JZ
Jin
X
X
Shu
C-M
CM
Jin
G-Y
GY
Dong
G-H
GH
Wang
Y-K
YK
Gao
X-H
XH
Chen
H-D
HD
Li
Y-H
YH
D000975:Antioxidants / Q000627:therapeutic use*; D049109:Cell Proliferation / Q000187:drug effects; D004359:Drug Therapy, Combination; D004817:Epidermis / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects; D004890:Erythema / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007633:Keratins / Q000378:metabolism; D007801:Langerhans Cells / Q000378:metabolism / Q000528:radiation effects; D020782:Matrix Metalloproteinases / Q000378:metabolism; D008543:Melanins / Q000096:biosynthesis; D011832:Radiation Injuries / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D015595:Skin Aging / Q000187:drug effects / Q000528:radiation effects; D012880:Skin Pigmentation / Q000187:drug effects / Q000528:radiation effects; D013473:Sunscreening Agents / Q000627:therapeutic use*; D014466:Ultraviolet Rays / Q000009:adverse effects
D000975:Antioxidants; D008543:Melanins; D013473:Sunscreening Agents; D007633:Keratins; D020782:Matrix Metalloproteinases