Photoprotection of bacterial-derived melanin against ultraviolet A-induced cell death and its potential application as an active sunscreen.
BACKGROUND
The increase in the incidence of non-melanoma skin tumours, photoaging, and immunosuppression demand for more effective sunscreen on ultraviolet A (UVA) irradiation.


OBJECTIVE
The aim of the study is to evaluate the photoprotective effects of a bacterial-derived melanin against UVA-induced damages in vitro and in vivo. Methods Human fibroblasts were used to assess the role of the bacterial-derived melanin on cell viability against UVA. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and nuclear morphology were employed to evaluate the photoprotection at the cellular level. Fluorometric assays were performed to detect the formation of reactive oxygen species (ROS) in the cells. Evaluations of the bacterial-derived melanin as a sunscreen were measured by transmission test and persistent pigment darkening on human skin.


RESULTS
Bacterial-derived melanin efficiently scavenged ROS in the fibroblasts after UVA irradiation. The cell viability of xeroderma pigmentosum (XP) fibroblast treated with varied doses of melanin increased dramatically in comparison with untreated control and the treated XP fibroblasts became more resistant to UVA-induced apoptosis than normal fibroblasts. Although the relative transmission didn't change too much with different concentration of bacterial-derived melanin, this melanin could keep UVA-irradiated skin from pigment darkening and act as an active sunscreen on skin.


CONCLUSIONS
The bacterial-derived melanin provided significant protection to fibroblast cell and human skin against the UVA radiation. It has the potential to be developed as an active sunscreen for the patients with photosensitivity skin to sun exposure.
Geng
J
J
State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.
Tang
W
W
Wan
X
X
Zhou
Q
Q
Wang
X-J
XJ
Shen
P
P
Lei
T-C
TC
Chen
X-D
XD
D000287:Administration, Topical; D000328:Adult; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000528:radiation effects*; D016166:Free Radical Scavengers / Q000008:administration & dosage; D006801:Humans; D008543:Melanins / Q000008:administration & dosage*; D008875:Middle Aged; D010787:Photosensitivity Disorders / Q000188:drug therapy* / Q000473:pathology; D011549:Pseudomonas; D017382:Reactive Oxygen Species / Q000378:metabolism; D012867:Skin / Q000187:drug effects / Q000528:radiation effects; D013473:Sunscreening Agents / Q000008:administration & dosage*; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014983:Xeroderma Pigmentosum / Q000188:drug therapy / Q000473:pathology
D016166:Free Radical Scavengers; D008543:Melanins; D017382:Reactive Oxygen Species; D013473:Sunscreening Agents