No abstract

Exposure to solar radiation is a major cause of environmental human skin damage. The main constituent of solar UV light is UVA radiation (320-400 nm); however, the need for protection against UVA has been marginalized for a long time. As a result, there is still a lack of useful agents for UVA protection. In this study, the effect of silymarin (SM) and its main constituent silybin (SB) pre-treatment on UVA-stimulated damage to primary human dermal fibroblasts were carried out. The cells were pre-treated for 1 h with SB or SM and then were exposed to UVA light, using a solar simulator. The effect of SB and SM on reactive oxygen species (ROS) and glutathione (GSH) level, caspase-3 activity, single-strand breaks (SSB) formation and protein level of matrix metalloproteinase-1 (MMP-1), heme oxygenase-1 (HO-1), and heat shock protein (HSP70) was evaluated. Treatment with both SM and SB resulted in a reduction in UVA-stimulated ROS generation and SSB production, as well as in the prevention of GSH depletion, a decrease in the activation of caspase-3 and protein level of MMP-1. They also moderately increased HO-1 level and reduced HSP70 level. Our data showed that both SM and SB are non-phototoxic and have UVA-photoprotective potential and could be useful agents for UV-protective dermatological preparations.

No abstract

Quercetin, one of the most abundant polyphenols in the plant kingdom has been shown to be photodegraded on exposure to UV light. Despite the fact, it is a component of several dermatological preparations. Its phototoxic potential has not been evaluated to date. The aim of this study was to assess whether photo-induced degradation of quercetin is linked to phototoxic effects on living cells. Its dihydro derivative, taxifolin, was included in the study. For evaluation, the 3T3 Neutral Red Uptake Phototoxicity Test according to OECD TG 432 was used. To better approximate human skin, HaCaT keratinocytes, normal human epidermal keratinocytes and dermal fibroblasts were used, apart from the Balb/c 3T3 cell line. Quercetin showed a dose-dependent photodegradation in aqueous and organic environments and a phototoxic effect on all used cells. Quercetin pretreatment and following UVA exposure resulted in increased reactive oxygen species production and intracellular glutathione level depletion in human dermal fibroblasts. Taxifolin was found completely nonphototoxic and photostable. As only in vitro methodology was used, further studies using 3D skin models and/or human volunteers are needed to confirm whether exposure to sunlight, tanning sunbeds and/or phototherapy in people using cosmetics containing quercetin is a health risk.

The ultraviolet (UV) part of solar radiation can permanently affect skin tissue. UVA photons represent the most abundant UV component and stimulate the formation of intracellular reactive oxygen species (ROS), leading to oxidative damage to various biomolecules. Several plant-derived polyphenols are known as effective photoprotective agents. This study evaluated the potential of quercetin (QE) and its structurally related flavonoid taxifolin (TA) to reduce UVA-caused damage to human primary dermal fibroblasts (NHDF) and epidermal keratinocytes (NHEK) obtained from identical donors. Cells pre-treated with QE or TA (1 h) were then exposed to UVA light using a solar simulator. Both flavonoids effectively prevented oxidative damage, such as ROS generation, glutathione depletion, single-strand breaks formation and caspase-3 activation in NHDF. These protective effects were accompanied by stimulation of Nrf2 nuclear translocation, found in non-irradiated and irradiated NHDF and NHEK, and expression of antioxidant proteins, such as heme oxygenase-1, NAD(P)H:quinone oxidoreductase 1 and catalase. For most parameters, QE was more potent than TA. On the other hand, TA demonstrated protection within the whole concentration range, while QE lost its protective ability at the highest concentration tested (75 μM), suggesting its pro-oxidative potential. In summary, QE and TA demonstrated UVA-protective properties in NHEK and NHDF obtained from identical donors. However, due to the in vitro phototoxic potential of QE, published elsewhere and discussed herein, further studies are needed to evaluate QE safety in dermatological application for humans as well as to confirm our results on human skin ex vivo and in clinical trials.