Tyrosine-Induced Melanogenesis Shows Differences in Morphologic and Melanogenic Preferences of Melanosomes from Light and Dark Skin Types

Abstract

The quality, quantity and distribution of melanosomes in epidermis play a crucial role in the determination of skin color and its sensitivity to UV radiation. Melanocyte cultures originating from individuals with light and dark skin types were grown in media with varying concentration of L-tyrosine. Melanosomal melanin content and the size of the organelles were measured after subcellular fractionation. In light-skin type cells, increased melanin production resulted in a more elliptical shape of melanosomes. In melanosomes that constitutively produce more melanin, the tyrosine-induced melanogenesis caused enlargement in all dimensions. X-ray microanalysis provided evidence that the increase in sulfur content induced by high tyrosine concentration was more prominent in the melanosomes from light skin types. A ratio between pheomelanin and eumelanin found in light-skin type melanosomes by HPLC was increased more markedly than that in melanosomes from dark skin melanocytes. These findings suggest that the melanocytes of light-skinned individuals exhibit a preference for pheomelanogenesis. Pheomelanin production is a thiol-consuming process and that might increase the risk of oxidation stress in these cells. This fact, together with the limited ability of pheomelanin to absorb UV radiation may lead to an elevated skin cancer risk among light-skinned individuals.

18F-Flortaucipir Binding in Choroid Plexus: Related to Race and Hippocampus Signal

“…2). This observation agrees with human physiology, since melanin is produced by melanocytes in the skin, meninges, and CP [13] in both B/AA and W individuals, but to a greater extent in B/AA individuals [37]. However, high CP SUVR in light-skinned individuals could also point to additional factors contributing to CP FTP signal, which may include both off-target binding (e.g., iron deposits, Biondi rings, calcifications/mineralizations, MAO-A) and on-target binding (as observed within CP epithelial cells by Ikonomovic and colleagues) [38].…”

Increased Melanogenesis is a Risk Factor for Oxidative DNA Damage— Study on Cultured Melanocytes and Atypical Nevus Cells†

“…Regardless of the underlying mechanism, reduced glutathione concentration increases the risk of oxidative damage in these cells. Pigment cells with stimulated production of pheomelanin (26) are the best candidates for such increased risk.…”

The Skin–Brain Connection Hypothesis, Bringing Together CCL27-Mediated T-Cell Activation in the Skin and Neural Cell Damage in the Adult Brain

“…Dark pigment, eumelanin, protects skin cells from UV damage (50). In contrast, the yellow-red-colored pheomelanin is less effective in providing UV protection (51). Recently, Mitra et al have shown that pheomelanin may even promote oxidative DNA injury by generating free radicals in the absence of UV in fair skin individual (52).…”