The impact of avobenzone and oxybenzone on fibroblast and keratinocyte membranes. Searching for the role of lipids in the effect of UV filters on skin cells.

In this work, the effects of two UV filters - avobenzone and oxybenzone - on the membranes of fibroblasts and keratinocytes in ex vivo model systems (Langmuir monolayers) and cell line experiments were examined. The goal of these studies was to analyze the significance of lipid structures in the mechanism of UV filter-induced toxicity to skin cells. Monolayers composed of lipids characteristic of mammalian cell membranes - namely phosphatidylcholine (SOPC), sphingomyelin (SM), cholesterol (Chol) and ceramides (Ceramide 22 and Ceramide 17) - were used as model systems. Both mixed monolayers mimicking fibroblast and keratinocyte membranes and one-component lipid films were investigated. The surface pressure/area measurements and penetration studies were done, and Brewster angle microscopy was applied to verify the morphology of the studied systems. It was found that avobenzone has a stronger impact on molecular organization of skin cell model membranes than oxybenzone; however, its effect is concentration-limited. Both UV filters exhibited stronger affinity to Chol, SM and SOPC monolayers than to ceramides, which are the lipids characteristic for skin cells. Therefore, it can be suggested that ceramides may hinder the penetration of UV filter molecules into the interior of skin cells. Cell line model studied with SEM microscopy suggested that UV filters alter the skin cell membrane. Finally, it was summarized that the mechanism of UV filter toxicity is complex, but one of its important elements is the impact on the organization of lipid structures.