Responses of Black and White Skin to Solar-Simulating Radiation: Differences in DNA Photodamage, Infiltrating Neutrophils, Proteolytic Enzymes Induced, Keratinocyte Activation, and IL-10 Expression

Abstract

Black skin is more resistant to the deleterious effects of ultraviolet radiation than white skin. A higher melanin content and a different melanosomal dispersion pattern in the epidermis are thought to be responsible for this. Our purpose was to compare skin responses in black and white skin following exposure to solar-simulating radiation (SSR) to further investigate the photoprotective properties of black skin. Six volunteers of skin phototype I-III (white) were exposed to (doses measured directly with a Waldmann UV detector device) 12,000-18,000 mJ per cm2 (2 MED) of SSR and compared with six volunteers of skin phototype VI (black) exposed to 18,000 mJ per cm2 (<1 MED) of SSR. The presence and distribution of skin pigment, DNA photodamage, infiltrating neutrophils, photoaging associated proteolytic enzymes, keratinocyte activation, and the source of interleukin 10 (IL-10) in skin biopsies taken before and after exposure were studied. In all white skinned subjects, 12,000-18,000 mJ per cm2 of SSR induced DNA damage in epidermal and dermal cells, an influx of neutrophils, active proteolytic enzymes, and diffuse keratinocyte activation. Additionally, in three of the white skinned volunteers IL-10 positive neutrophils were found to infiltrate the epidermis. Except for DNA damage in the supra basal epidermis, none of these changes was found in black skinned subjects. Increased skin pigmentation appears to be primarily responsible for the observed differences in skin responses. Our data could provide an explanation as to why black skin is less susceptible to sunburn, photoaging, and skin carcinogenesis.

Ethnic skin types: are there differences in skin structure and function?1

“…they burn more and tan less than a person with higher pigmentation. In this respect Rijken et al [28] recently compared the responses of black and white skin to solar-simulating radiation and except for some DNA damage in the suprabasal epidermis the subjects with skin of colour did not show any increase in neutrophils, active proteolytic enzymes and diffuse keratinocyte activation unlike the Caucasians. Thus, it would appear that Asian skin has other mechanisms than the presence of melanin to protect against UV irradiation.…”

Survey on skin aging status and related influential factors in Southeast China

“…The patterns of skin aging are characterized by ethnic specificity among different peoples (Chung et al, 2001;Rijken et al, 2004); for example, pigmentation and wrinkling patterns in yellow skin share little common features with those in white skin (Roh et al, 2001). Nouveau-Richard et al(2005) reported main skin aging features progress differently in Chinese and French women, and Zhao et al(1998) investigated 470 healthy people in Northeast China to explore skin damage resulting from solar ultraviolet (UV) radiation.…”

La genètica de la pigmentació humana i de la predisposició al càncer de pell

“…A més, la mala resposta de la pell a l'exposició al sol, amb l'aparició de cremades i la impossibilitat de bronzejat, és també un indicador d'una major susceptibilitat al càncer de pell, sobretot al melanoma. En individus amb trets de pigmentació més foscos i amb millor tolerància al sol, la incidència de neoplàsies cutànies és menor a causa del nivell més elevat de melanina epidèrmica, la qual exerceix com a factor fotoprotector, capaç d'absorbir la radiació UV (Liu i altres, 2013;Rijken i altres, 2004;Scherer i Kumar, 2010).…”