Polyunsaturated fatty acids partially reproduce the role of melanocytes in the epidermal melanin unit

Abstract

The incidence rate of melanoma is higher in fair-skinned than in dark-skinned individuals. In negroid skin there is more eumelanin which is present in all skin layers and fewer polyunsaturated fatty acids (PUFA) than in caucasoid skin. The western diet, which is rich in omega-6 polyunsaturated fatty acids, is associated with more proneness to cancer including cutaneous melanoma. To study the respective influence of omega-6 PUFA and low phototype melanocytes on redox status -basal and following UV irradiation-, we used epidermal reconstructs. The addition of polyunsaturated fatty acids as well as the presence of low phototype melanocytes affected basal status similarly except for catalase activity, which decreased significantly in polyunsaturated fatty acid-supplemented reconstructs. Following UV, polyunsaturated fatty acids and low phototype melanocytes increased lipid and protein oxidative damage without affecting direct DNA damage. However, polyunsaturated fatty acids increased epidermal apoptosis whereas low phototype melanocytes decreased it. Since our data suggest that an omega-6 PUFA rich-diet may increase oxidative damage in melanocytes without inducing apoptosis, the long-term net outcome could be cumulated mutations and an increased risk of skin cancer, especially melanoma.

Anti‐oxidant defence mechanism in vitiliginous skin increases with skin type

“…Our previous studies demonstrated in melanocyte cultures and in reconstructed epidermis, 24–28 a correlation between cellular antioxidants and the phototype of the donors. In vivo , it has been shown that thioredoxin reductase correlate with skin phototypes with a linear increase from fair to dark skin 29 .…”

Serum Fatty Acids and Risk of Cutaneous Melanoma: A Population-Based Case-Control Study

“…Subjects whose blood samples were separated or stored more than 24 hours after collection and whose samples were not available for other reasons were excluded from analyses, leaving 51 cases and their matched controls. A dermatologist determined each participant's phototype using the Fitzpatrick phototyping scale [22] and collected information about family history of melanoma, sun exposure, and other anamnestic characteristics.…”

“…Laboratory studies have reported toxic effects of fatty acids such as linoleic and arachidonic acid on distinct cell types such as leukemia cells [17], rabbit renal cells [18], human endothelial cells [19], and murine and human melanoma cell lines [20], with different potential mechanisms including in vivo isomerization into trans fatty acids [21]. In epidermal reconstructs, n-6 PUFAs administration resulted in increased epidermal oxidative damage, possibly leading to accumulated mutations and increased risk of skin cancer, especially melanoma [22]. …”

Catalase overexpression reduces UVB-induced apoptosis in a human xeroderma pigmentosum reconstructed epidermis

“…Similarly, treatment of RE with a-tocopherol (a natural antioxidant) or polyunsaturated fatty acids (PUFA), which increased lipid, protein and DNA oxidation and apoptosis due to ROS production, did not increase CPD formation. 42,43 The significant effect of catalase overexpression on the reduction of UVB-induced apoptosis without affecting CPD formation-the main UVB-induced DNA photoproduct-is surprising. We have recently demonstrated that UVB induces ROS production at two distinct chronologic stages: immediately following irradiation and 2-3 h after irradiation.…”