Chemical consequences of cutaneous photoageing

Abstract

Human skin, in common with other organs, ages as a consequence of the passage of time, but in areas exposed to solar ultraviolet radiation, the effects of this intrinsic ageing process are exacerbated. In particular, both the severity and speed of onset of age-related changes, such as wrinkle formation and loss of elasticity, are enhanced in photoaged (also termed extrinsically aged) as compared with aged, photoprotected, skin. The anatomy of skin is characterised by two major layers: an outer, avascular, yet highly cellular and dynamic epidermis and an underlying vascularised, comparatively static and cell-poor, dermis. The structural consequences of photoageing are mainly evident in the extracellular matrix-rich but cell-poor dermis where key extracellular matrix proteins are particularly susceptible to photodamage. Most investigations to date have concentrated on the cell as both a target for and mediator of, ultraviolet radiation-induced photoageing. As the main effectors of dermal remodelling produced by cells (extracellular proteases) generally have low substrate specificity, we recently suggested that the differential susceptibility of key extracellular matrix proteins to the processes of photoageing may be due to direct, as opposed to cell-mediated, photodamage.In this review, we discuss the experimental evidence for ultraviolet radiation (and related reactive oxygen species)-mediated differential degradation of normally long lived dermal proteins including the fibrillar collagens, elastic fibre components, glycoproteins and proteoglycans. Whilst these components exhibit highly diverse primary and hence macro- and supra-molecular structures, we present evidence that amino acid composition alone may be a useful predictor of age-related protein degradation in both photoexposed and, as a consequence of differential oxidation sensitivity, photoprotected, tissues.

Skin rejuvenation using cosmetic products containing growth factors, cytokines, and matrikines: a review of the literature

“…Reactive oxygen species not only directly damage the skin structural proteins, but also induce overexpression of collagen-degrading matrix metalloproteinases and increase inflammation by the NF-κB pathway 10. In addition, ultraviolet light can directly damage the skin by causing nucleic acid strand breakage and by cross-linking and modifying the structural proteins and nucleic acids 4,11. Ultraviolet light also increases the accumulation of advanced glycation end-products, which can promote aging by several mechanisms 12…”

A dietary supplement improves facial photoaging and skin sebum, hydration and tonicity modulating serum fibronectin, neutrophil elastase 2, hyaluronic acid and carbonylated proteins

“…Cutaneous aging is the result of chronological or innate aging and sun-induced actinic damage that share the loss of normal elastic fiber functions as a key common feature [6]. Excessive exposure to the sun can cause severe photoaging as early as the second decade of life [7].…”

Ethanol extract ofTerminalia chebulafruit protects against UVB-induced skin damage

“…Ultraviolet (UV) irradiation accelerates ageing of the human skin, which is generally characterized by severe epidermal hyperplasia and skin elasticity reduction (Gilchrest 1996;Thurstan et al 2012). Three types of UV radiation are classified according to their wavelengths: UVA (320-400 nm), UVB (280-320 nm) and UVC (<280 nm).…”