Modulation of paraoxonase-2 in human dermal fibroblasts by UVA-induced oxidative stress: A new potential marker of skin photodamage.

Paraoxonase-2 (PON2) is an intracellular protein, that exerts a protective role against cell oxidative stress and apoptosis. Genetic and environmental factors (i.e. dietary factors, cigarette smoke, drugs) are able to modulate cellular PON2 levels. The effect of ultraviolet A radiation (UVA), the oxidizing component of sunlight, on PON2 in human dermal fibroblasts (HuDe) has not been previously explored. Excessive UVA radiation is known to cause direct and indirect skin damage by influencing intracellular signalling pathways through oxidative stress mediated by reactive oxygen species (ROS) that modulate the expression of downstream genes involved in different processes, e.g. skin photoaging and cancer. The aim of this study was, therefore, to investigate the modulation of PON2 in terms of protein expression and enzyme activity in HuDe exposed to UVA (270 kJ/m2). Our results show that PON2 is up-regulated immediately after UVA exposure and that its levels and activity decrease in the post-exposure phase, in a time-dependent manner (2-24 h). The trend in PON2 levels mirror the time-course study of UVA-induced ROS. To confirm this, experiments were also performed in the presence of a SPF30 sunscreen used as shielding agent to revert modulation of PON2 at 0 and 2 h post-UVA exposure where other markers of photo-oxidative stress were also examined (NF-KB, γH2AX, advanced glycation end products). Overall, our results show that the upregulation of PON2 might be related to the increase in intracellular ROS and may play an important role in mitigation of UVA-mediated damage and in the prevention of the consequences of UV exposure, thus representing a new marker of early-response to UVA-induced damage in skin fibroblasts.

Oleuropein-Rich Gellan Gum/Alginate Films as Innovative Treatments against Photo-Induced Skin Aging.

Olea europaea L. leaf extracts (OLEs) represent highly value-added agro-industrial byproducts, being promising sources of significant antioxidant compounds, such as their main component, oleuropein. In this work, hydrogel films based on low-acyl gellan gum (GG) blended with sodium alginate (NaALG) were loaded with OLE and crosslinked with tartaric acid (TA). The films' ability to act as an antioxidant and photoprotectant against UVA-induced photoaging, thanks to their capability to convey oleuropein to the skin, were examined with the aim of a potential application as facial masks. Biological in vitro performances of the proposed materials were tested on normal human dermal fibroblasts (NhDFs), both under normal conditions and after aging-induced UVA treatment. Overall, our results clearly show the intriguing properties of the proposed hydrogels as effective and fully naturally formulated anti-photoaging smart materials for potential use as facial masks.

Insights on the UV-Screening Potential of Marine-Inspired Thiol Compounds.

One of the major threats to skin aging and the risk of developing skin cancer is excessive exposure to the sun's ultraviolet radiation (UVR). The use of sunscreens containing different synthetic, organic, and inorganic UVR filters is one of the most widespread defensive measures. However, increasing evidence suggests that some of these compounds are potentially eco-toxic, causing subtle damage to the environment and to marine ecosystems. Resorting to natural products produced in a wide range of marine species to counteract UVR-mediated damage could be an alternative strategy. The present work investigates marine-inspired thiol compounds, derivatives of ovothiol A, isolated from marine invertebrates and known to exhibit unique antioxidant properties. However, their potential use as photoprotective molecules for biocompatible sunscreens and anti-photo aging formulations has not yet been investigated. Here, we report on the UVR absorption properties, photostability, and in vitro UVA shielding activities of two synthetic ovothiol derivatives, 5-thiohistidine and iso-ovothiol A, by spectrophotometric and fluorimetric analysis. We found that the UVA properties of these compounds increase upon exposure to UVA and that their absorption activity is able to screen UVA rays, thus reducing the oxidative damage induced to proteins and lipids. The results of this work demonstrate that these novel marine-inspired compounds could represent an alternative eco-friendly approach for UVR skin protection.