Regulation of Human Skin Pigmentation in situ by Repetitive UV Exposure: Molecular Characterization of Responses to UVA and/or UVB

Abstract

Ultraviolet (UV) radiation is a major environmental factor that affects pigmentation in human skin and can eventually result in various types of UV-induced skin cancers. The effects of various wavelengths of UV on melanocytes and other types of skin cells in culture have been studied but little is known about gene expression patterns in situ following in situe exposure of human skin to different types of UV (UVA and/or UVB). Paracrine factors expressed by keratinocytes and/or fibroblasts that affect skin pigmentation might be regulated differently by UV, as might their corresponding receptors expressed on melanocytes. To test the hypothesis that different mechanisms are involved in the pigmentary responses of the skin to different types of UV, we used immunohistochemical and whole human genome microarray analyses to characterize human skin in situ to examine how melanocyte-specific proteins and paracrine melanogenic factors are regulated by repetitive exposure to different types of UV compared with unexposed skin as a control. The results show that gene expression patterns induced by UVA or UVB are distinct, UVB eliciting dramatic increases in a large number of genes involved in pigmentation as well as in other cellular functions, while UVA had little or no effect on those. The expression patterns characterize the distinct responses of the skin to UVA or UVB, and identify several potential previously unidentified factors involved in UV-induced responses of human skin.

Melanogenesis inhibition in mice using a low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum garnet laser: a pilot study

“…*p < 0.008 versus control to modulate a large number of genes involved in the pigmentation pathway. In contrast, UVA was not capable of inducing pigmentation-related genes [31]. In our previous observation, we found that after laser toning, UVA-induced melanosis was rather responsive to increasing numbers of laser passes in human (according to Western blotting results).…”

Influence of Repetitive UVA Stimulation on Skin Protection Capacity and Antioxidant Efficacy

“…We found that 4 repetitive low-dose UVA irradiations alone caused an increasing stimulation of the skin's capacity to cope with oxidative stress by +36% compared to the baseline level. Therefore, the beneficial effect of moderate sunlight exposure of the skin is obviously not limited to vitamin D formation [18] , pigmentation [19] or increased expression of antimicrobial peptides [20] .…”

Thymol and Thymus Vulgaris L. activity against UVA- and UVB-induced damage in NCTC 2544 cell line

“…UVA exposure leads to several lesions, overproduction of ROS (Reactive Oxygen Species) [11], lipid peroxidation (LPO) [4,12] oxidized basis (8-oxo-dG or thymine-glycole), abasic sites and single strand breaks (SSB) [10,12,13]. UVB, absorbed by the epidermis, cause sunburn, erythema and tanning [8] because it is able to induce expression of genes involved in melanin synthesis [14]. UVB is directly absorbed by the proteins and the nucleic acids and leads to the cyclobutane-pyrimidine dimers (CPDs) and pyrimidine pyrimidone photoproducts as the principal DNA lesions [13].…”