Abstract
Exposure to sun and especially to ultraviolet radiation (UVR) exerts well known detrimental effects on skin which are implicated in malignancy. UVR induces production of cyclobutane pyrimidine dimers (CPDs), immediately during exposure and even hours after the exposure, these latter being called dark-CPDs, as consequence of the effects of different reactive species that are formed. Fernblock® (FB), an aqueous extract of Polypodium leucotomos, has proven to have photoprotective and antioxidant effects on skin. The aim of our work was to investigate the potential photoprotective effect of FB against dark-CPD formation. Murine melanocytes (B16-F10) were exposed to UVA radiation and the production of dark-CPDs and different reactive oxygen and nitrogen species (ROS and RNS) was measured. Significant dark-CPD formation could be seen at 3 h after UVA irradiation, which was inhibited by the pre-treatment of cells with FB. Formation of nitric oxide, superoxide and peroxynitrite was increased after irradiation, consistent with the increased CPD formation. FB successfully reduced the production of these reactive species. Hence, these results show how dark-CPDs are formed in UVA irradiated melanocytes, and that FB acts as a potential antioxidant and ROS scavenger, preventing the DNA damage induced by sun exposure.
Highlights
As the largest organ of the human body, the skin, and the epidermis, acts as a barrier against environmental damaging agents [1]
Dark-cyclobutane pyrimidine dimers (CPDs) are produced by successive reactions between reactive oxygen species (ROS), RNS and melanin degradation products that lead to the formation of an excited triplet carbonyl, which transfers its energy to DNA [4,5,6,7]
Prevention of NO, O2 ̄ and ONOOproduction by FB, might impede the formation of dioxetane intermediates that lead to excited triplet carbonyls, which are responsible for the energy transfer to DNA and the subsequent formation of dark-CPDs. These results show how dark-CPDs are formed in UVA irradiated melanocytes through the action of successive reactions between ROS and RNS, and that FB acts as a potential antioxidant and ROS and RNS scavenger, preventing the formation of DNA
Summary
As the largest organ of the human body, the skin, and the epidermis, acts as a barrier against environmental damaging agents [1]. Ultraviolet radiation (UVR) is one of the most extensively studied agents due to its DNA-damaging effects [1,2]. The UVR that reaches the skin can be classified into three different types according to the wavelength spectrum. UVA (320–400 nm) accounts for 95% of the UVR and has been linked to the immediate and persistent pigment darkening, as well as the generation of reactive oxygen species (ROS) [1,2]. UVB (290–320 nm) represents 5% of UVR and is associated with delayed pigment darkening and the direct alteration of DNA nucleotide structure [1,2].
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