Abstract
Background: Novel approaches to photoprotection must go beyond classical MED measurements, as discoveries on the effect of UV radiation on skin paints a more complex and multi-pronged scenario with multitude of skin cell types involved. Of these, photoimmunoprotection emerges as a crucial factor that protects against skin cancer and photoaging. A novel immune parameter is enabled by the precise knowledge of the wavelength and dose of solar radiation that induces photoimmunosupression. Natural substances, that can play different roles in photoprotection as antioxidant, immune regulation, and DNA protection as well as its possible ability as sunscreen are the new goals in cosmetic industry.Objective: To analyze the effect of a specific natural extract from Polypodium leucotomos (PLE, Fernblock®), as part of topical sunscreen formulations to protect from photoimmunosuppression, as well as other deleterious biological effects of UV radiation.Methods: The possible sunscreen effect of PLE was analyzed by including 1% (w/w) PLE in four different galenic formulations containing different combinations of UVB and UVA organic and mineral filters. In vitro sun protection factor (SPF), UVA protection factor (UVA-PF), contact hypersensitivity factor (CHS), and human immunoprotection factor (HIF) were estimated following the same protocol as ISO 24443:2012 for in vitro UVA-PF determination.Results: PLE-containing formulations significantly reduced UV radiation reaching to skin. Combination of UVB and UVA filters with PLE increased SPF and UVAPF significantly. PLE also increased UV immune protection, by elevating the contact hypersensitivity factor and the human immunoprotective factor of the sunscreen formulations.Conclusion: This study confirms the double role of PLE in photoprotection. Together to the biological activity shown in previous works, the UV absorption properties of PLE confers a booster effect when it is supplemented in topical sunscreens increasing the protection not only at level of erythema and permanent pigment darkening but also against two photoimmunoprotection factors.
Highlights
The skin is the first barrier of the organism against aggression
Polypodium leucotomos extract (PLE) extract was included in four experimental galenic formulations similar to those used in sunscreen formulations, containing different types of UVB and UVA organic and mineral filters together with PLE at 1% (Table 1)
The different concentrations of PLE diluted in distilled water increased absorbance in the UV spectrum, gradually from 250 to 400 nm, reaching a peak around 290 nm (Figure 2)
Summary
The skin is the first barrier of the organism against aggression. Biological aggression usually brings to mind pathogens, e.g., viruses or bacteria. The skin protects from mechanical and radiation damage The latter is crucial due to the constant irradiation of the Earth’s surface with sun rays, which contain a significant amount of UV photons. UV radiation comprises photons from ∼100 to 400 nm in wavelength, of which those between 290 and 400 nm have significant biological effects at earth surface. Short-term deleterious effects are sunburn, oxidative stress as well as skin pigmentation changes leading in the longterm an increase in photoaging damage as well as the probability of photocarcinogenesis. Sunburn refers to the destruction of epidermal tissue, and includes redness and swelling, blood vessel dilation and inflammation. These processes are collectively known as erythema. That can play different roles in photoprotection as antioxidant, immune regulation, and DNA protection as well as its possible ability as sunscreen are the new goals in cosmetic industry
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