UV-light-induced signal cascades and skin aging

Photoageing is the superposition of chronic ultraviolet (UV)-induced damage on intrinsic ageing and accounts for most age-associated changes in skin appearance. It is triggered by receptor-initiated signalling, mitochondrial damage, protein oxidation and telomere-based DNA damage responses. Photodamaged skin displays variable epidermal thickness, dermal elastosis, decreased/fragmented collagen, increased matrix-degrading metalloproteinases, inflammatory infiltrates and vessel ectasia. The development of cosmetically pleasing sunscreens that protect against both UVA and UVB irradiation as well as products such as tretinoin that antagonize the UV signalling pathways leading to photoageing are major steps forward in preventing and reversing photoageing. Improved understanding of the skin's innate UV protective mechanisms has also given rise to several novel treatment concepts that promise to revolutionize this field within the coming decade. Such advances should not only allow for the improved appearance of skin in middle age and beyond, but also greatly reduce the accompanying burden of skin cancer.

Photoageing: mechanism, prevention and therapy.

As the proportion of the ageing population in industrialized countries continues to increase, the dermatological concerns of the aged grow in medical importance. Intrinsic structural changes occur as a natural consequence of ageing and are genetically determined. The rate of ageing is significantly different among different populations, as well as among different anatomical sites even within a single individual. The intrinsic rate of skin ageing in any individual can also be dramatically influenced by personal and environmental factors, particularly the amount of exposure to ultraviolet light. Photodamage, which considerably accelerates the visible ageing of skin, also greatly increases the risk of cutaneous neoplasms. As the population ages, dermatological focus must shift from ameliorating the cosmetic consequences of skin ageing to decreasing the genuine morbidity associated with problems of the ageing skin. A better understanding of both the intrinsic and extrinsic influences on the ageing of the skin, as well as distinguishing the retractable aspects of cutaneous ageing (primarily hormonal and lifestyle influences) from the irretractable (primarily intrinsic ageing), is crucial to this endeavour.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1468-2494.2007.00415.x

Intrinsic and extrinsic factors in skin ageing: a review.

Aging is a complex, multifactorial process resulting in several functional and esthetic changes in the skin. These changes result from intrinsic as well as extrinsic processes, such as ultraviolet radiation. Recent advances in skin biology have increased our understanding of skin homeostasis and the aging process, as well as the mechanisms by which ultraviolet radiation contributes to photoaging and cutaneous disease. These advances in skin biology have led to the development of a diversity of treatments aimed at preventing aging and rejuvenating the skin. The focus of this review is the mechanism of photoaging and the pathophysiology underlying the treatments specifically designed for its prevention and treatment. Learning objectives At the conclusion of this learning activity, participants should be familiar with the mechanism of photoaging, the treatments for photoaging, and the data that supports the use of these treatments.

Photoaging: Mechanisms and repair

The effects of chronic sun exposure on skin are readily apparent when skin not typically exposed to the sun and skin regularly exposed to the sun are compared While the sun is not the only aetiological factor in the dynamic process of skin ageing, it is the primary exogenous cause among several internal and environmental elements Thus, photo-ageing, the main focus of this article, is a subset of extrinsic skin ageing The influence of the sun in extrinsic skin ageing, as well as its role in potentially altering the normal course of intrinsic (also known as natural or cellular) ageing, is discussed Telomeres, the specialized structures found at the ends of chromosomes, are believed to be integral to cellular ageing as well as in the development of cancer The ageing process, both intrinsic and extrinsic, is also believed to be influenced by the formation of free radicals, also known as reactive oxygen species The loss of collagen is considered the characteristic histological finding in aged skin Wrinkling and pigmentary changes are directly associated with photo-ageing and are considered its most salient cutaneous manifestations Such photodamage represents the cutaneous signs of premature ageing In addition, deleterious consequences of chronic sun exposure, specifically various forms of photo-induced skin cancer, are also linked to acute and chronic sun exposure The only known strategies aimed at preventing photo-ageing include sun avoidance, using sunscreens to block or reduce skin exposure to UV radiation, using retinoids to inhibit collagenase synthesis and to promote collagen production, and using anti-oxidants, particularly in combination, to reduce and neutralize free radicals

https://onlinelibrary.wiley.com/doi/pdf/10.1002/path.2098

Skin ageing and its treatment

https://www.jidonline.org/article/S0022-202X(15)30269-4/pdf

Joo Heung Lee

Papers

Topical N-acetyl cysteine and genistein prevent ultraviolet-light-induced signaling that leads to photoaging in human skin in vivo