The protective role of melanin against UV damage in human skin

Abstract

Human skin is repeatedly exposed to UVR that influences the function and survival of many cell types and is regarded as the main causative factor in the induction of skin cancer. It has been traditionally believed that skin pigmentation is the most important photoprotective factor, as melanin, besides functioning as a broadband UV absorbent, has antioxidant and radical scavenging properties. Besides, many epidemiological studies have shown a lower incidence for skin cancer in individuals with darker skin compared to those with fair skin. Skin pigmentation is of great cultural and cosmetic importance, yet the role of melanin in photoprotection is still controversial. This article outlines the major acute and chronic effects of UVR on human skin, the properties of melanin, the regulation of pigmentation and its effect on skin cancer prevention.

Figure 1. Melanin Content in Skin of Different Ethnicity

Histological detection of melanin content using Fontana-Masson staining. Melanin content in the basal layers of the epidermis is substantially higher in Black skin compared to Asian or White skin, although the number of melanocytes is virtually identical in skins of different ethnicity.

Figure 2. CPD in Skin of Different Ethnicity

Immunohistochemical detection of CPDs in skin of different ethnicities immediately after UVR. The fluorescence detection technique uses the binding of FITC-labeled antibodies that are reactive with DNA photoproducts. A considerably higher amount of CPDs is detected in White skin compared to Asian or Black skin.