Infrared plus visible light and heat from natural sunlight participate in the expression of MMPs and type I procollagen as well as infiltration of inflammatory cell in human skin in vivo.
BACKGROUND
Compared with the detailed characterization of the ultraviolet (UV) response in human skin, the effects of infrared (IR) and other regions of the sunlight are scarce.


OBJECTIVE
To determine the participation of IR/visible light and heat components of the sunlight on matrix metalloproteinases (MMPs) and type I procollagen expression, and inflammatory cell infiltration in human skin in vivo.


METHODS
The buttocks of 16 healthy volunteers (aged 24-43 years, 10 male and 6 female) were irradiated with a 1.1-3 minimal erythema dose (MED) of natural sunlight. To determine the differential effects of UV, IR/visible rays and solar heat alone, the exposed sites were covered with either a UV filter or black cloth, respectively, during irradiation. Skin samples were taken 24h later.


RESULTS
IR/visible light spectrum of sunlight significantly increased MMP-1 and MMP-9 expression and decreased type I procollagen expression. Solar heat also contributed to the increased MMP-1 expression. Only the UV region recruited neutrophils into the dermis, while UV, IR/visible light and heat contributed to macrophage infiltration.


CONCLUSIONS
IR/visible light and heat of natural sunlight, in addition to UV, play a role in modulating the expressions of MMPs and procollagen, and inflammatory cell infiltration in human skin.
Cho
Soyun
S
Department of Dermatology, Seoul National University College of Medicine, Seoul, Republic of Korea.
Lee
Min Jung
MJ
Kim
Mi Sun
MS
Lee
Serah
S
Kim
Yoon Kyung
YK
Lee
Dong Hun
DH
Lee
Chae Wook
CW
Cho
Kwang Hyun
KH
Chung
Jin Ho
JH
D000328:Adult; D024042:Collagen Type I / Q000378:metabolism*; D015536:Down-Regulation; D004790:Enzyme Induction; D004794:Enzyme Repression; D005260:Female; D006358:Hot Temperature; D006801:Humans; D007259:Infrared Rays; D008264:Macrophages / Q000528:radiation effects*; D008297:Male; D020781:Matrix Metalloproteinase 1 / Q000096:biosynthesis; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis; D053505:Matrix Metalloproteinases, Secreted / Q000096:biosynthesis* / Q000235:genetics; D020556:Neutrophil Infiltration / Q000528:radiation effects*; D012333:RNA, Messenger / Q000378:metabolism; D012867:Skin / Q000201:enzymology / Q000276:immunology / Q000378:metabolism / Q000528:radiation effects*; D013472:Sunlight; D014466:Ultraviolet Rays
D024042:Collagen Type I; D012333:RNA, Messenger; D053505:Matrix Metalloproteinases, Secreted; C522361:MMP2 protein, human; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; C522360:MMP1 protein, human; D020781:Matrix Metalloproteinase 1