Abstract
BackgroundUVA rays present in sunlight are able to reach the dermal skin layer generating reactive oxygen species (ROS) responsible for oxidative damage, alterations in gene expression, DNA damage, leading to cell inflammation, photo-ageing/-carcinogenesis. Sunscreens contain UV filters as active ingredients that absorb/reflect/dissipate UV radiation: their efficiency depends on their spectral profile and photostability which should then be reflected in biological protection of underlying skin.MethodsA set of new UV filters was synthesized, and the most photostable one was compared to BMDBM, a widely used UVA filter. Cultured human dermal fibroblasts were exposed to UVA radiation which was filtered by a base cream containing or not UV filters placed above cell culture wells. The endpoints measured were: cell viability (MTT assay), ROS generation (DCFH-DA assay), mitochondrial function (JC-1 assay), DNA integrity (Comet assay) and gene expression (MMP-1, COL1A1) by RT-qPCR.ResultsThe new UV filter resulted more efficient than BMDBM in preserving cell viability, mitochondrial functionality and oxidative DNA damage, despite similar inhibition levels of intracellular ROS. Moreover, expression of genes involved in dermal photoageing were positively affected by the filtering action of the tested molecules.ConclusionsThe experimental model proposed was able to validate the efficacy of the new UV filter, taking into account important cellular events related to UV-induced intracellular oxidative stress, often underestimated in the assessments of these compounds.General SignificanceThe model may be used to compare the actual biological protection of commercial sunscreens and suncare products aside from their SPF and UVA-PF values.
Highlights
UV radiation represents 5% of the total solar radiation reaching the earth’s surface, and is divided into two spectral regions: UVA (320–400 nm) and UVB (290–320 nm) constituting,96% and,4%, respectively, and both are responsible for the carcinogenic effect associated with sunlight overexposure [1]
UV filters are the active ingredients of sunscreens able to absorb/reflect/dissipate UV radiation reducing the amount of UV light reaching the viable skin layers [6], and two important requisites which determine their efficacy are their spectral profile and their photostability
benzoxazine 1 (BOX 1) has no substituents on the benzoxazine ring nor on the phenyl group in position 3 and it absorbs throughout the whole UVB range and partly in the UVA one
Summary
UV radiation represents 5% of the total solar radiation reaching the earth’s surface, and is divided into two spectral regions: UVA (320–400 nm) and UVB (290–320 nm) constituting ,96% and ,4%, respectively, and both are responsible for the carcinogenic effect associated with sunlight overexposure [1]. From UVB, UVA rays are able to penetrate further into the dermal layers of skin where they are absorbed by skin chromophores triggering the generation of reactive oxygen species (ROS) in the resident dermal fibroblasts and in extra-cellular structures [2] This contributes to oxidative damage, alterations in gene expression, DNA damage, leading to cell inflammation, photoageing and photocarcinogenesis [3,4,5]. UV filters are the active ingredients of sunscreens able to absorb/reflect/dissipate UV radiation reducing the amount of UV light reaching the viable skin layers [6], and two important requisites which determine their efficacy are their spectral profile and their photostability Their absorbance spectra should remain unaltered throughout the whole exposure period guaranteeing uniform and sufficient UVA/B coverage, which implies that they should be photochemically stable. Sunscreens contain UV filters as active ingredients that absorb/reflect/dissipate UV radiation: their efficiency depends on their spectral profile and photostability which should be reflected in biological protection of underlying skin
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