Abstract
Reactive oxygen species (ROS) are necessary for normal cell signaling and the antimicrobial defense of the skin. However excess production of ROS can disrupt the cellular redox balance and overwhelm the cellular antioxidant (AO) capacity, leading to oxidative stress. In the skin, oxidative stress plays a key role in driving both extrinsic and intrinsic aging. Sunlight exposure has also been a major contributor to extrinsic photoaging of the skin as its oxidising components disrupt both redox- and iron-homeostasis, promoting oxidative damage to skin cells and tissue constituents. Upon oxidative insults, the interplay between excess accumulation of ROS and redox-active labile iron (LI) and its detrimental consequences to the skin are often overlooked. In this review we have revisited the oxidative mechanisms underlying skin damage and aging by focussing on the concerted action of ROS and redox-active LI in the initiation and progression of intrinsic and extrinsic skin aging processes. Based on these, we propose to redefine the selection criteria for skin antiaging and photoprotective ingredients to include natural antioxidants (AOs) exhibiting robust redox–balancing and/or iron-chelating properties. This would promote the concept of natural-based or bio-inspired bifunctional anti-aging and photoprotective ingredients for skincare and sunscreen formulations with both AO and iron-chelating properties.
Highlights
Skin, as the largest organ in the body, is crucial for sensing and vitamin D synthesis
Under conditions of oxidative stress, electrophiles and reactive oxygen species (ROS) act to modify the reactive cysteine residues of Kelch-like Echassociated protein 1 (Keap1) which will inhibit its activity as an E3 ligase component. This leads to the stabilisation of nuclear factor erythroid 2-related factor 2 (Nrf2) and its translocation to the nucleus, where it forms a heterodimer with other transcription factors, such as small Maf, which in turn binds to the 50 -upstream Cis-acting regulatory sequence, termed AO response elements (ARE) or electrophile response elements (EpRE), located in the promoter region of genes encoding various AOs and phase II detoxifying enzymes, [220] and thereby promotes the transcription of over 250 genes
With a clear shift of the consumer market from synthetic compounds to natural-based and bio-inspired skincare and sunscreen ingredients, it is necessary to adopt a systematic approach to evaluate the effectiveness of current natural products in the market, in order to identify opportunities to improve the future of skincare and sunscreen formulations
Summary
As the largest organ in the body, is crucial for sensing and vitamin D synthesis It provides a major barrier for protecting the body against environmental chemical and physical assaults and pathogens, while insulating and regulating its temperature to avoid uncontrolled water and solutes loss [1,2]. Under conditions of oxidative stress, excess production of ROS can be detrimental for the cells and body especially in the presence of high levels of harmful labil iron (LI). This is because LI can catalyse the production of highly reactive species.
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