See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/266027439 UV light and skin aging Article · September 2014 DOI: 10.1515/reveh-2014-0058 · Source: PubMed CITATIONS READS 4 73 2 authors, including: Jéssica EPS Silveira Natura Cosmeticos 5 PUBLICATIONS 21 CITATIONS SEE PROFILE Available from: Jéssica EPS Silveira Retrieved on: 13 April 2016 Rev Environ Health 2014; aop J é ssica Eleonora Pedroso Sanches Silveira * and D é bora Midori Myaki Pedroso UV light and skin aging Abstract: This article reviews current data about the rela- signs of aging. Physiological changes in aged skin include tionship between sun radiation and skin, especially with structural and biochemical changes as well as changes regards ultraviolet light and the skin aging process. The in neurosensory perception, permeability, response to benefits of sun exposition and the photoaging process are injury, repair capacity, and increased incidence of some discussed. Finally, the authors present a review of photopro- skin diseases (5) . tection agents that are commercially available nowadays. The skin aging process occurs in the epidermis and dermis. Although the number of cell layers remains stable, Keywords: photoaging; sun protection; ultraviolet (UV) the skin thins progressively over adult life at an accelerat- exposure. ing rate. The epidermis decreases in thickness by about 6.4% per decade on average, with an associated reduc- tion in epidermal cell numbers (6) , particularly in women. DOI 10.1515/reveh-2014-0058 Received August 4 , 2014 ; accepted August 15 , 2014 Further, dermis thickness decreases with age, and thin- ning is accompanied by a decrease in both vascularity and cellularity (5) . Aged skin turns dryer (7) , and this can be proven by Aging transepidermal water loss (TEWL) measurements. Base- line TEWL decreases with age, an observation believed to The process of aging begins at the moment of birth, but be due to the reduction of the water content of aged skin, people now live longer than ever before. This is due to which can be associated with a profound change in barrier the continued advancements in medicine involving new integrity. Although the number of sweat glands does not technologies for immunization, organ transplant, reduced change, sebum production decreases by as much as 60%. infection (1) and equipment to support life, which have all A reduction of the natural water and fat emulsion on the become more available. skin is also observed, as is water content in the stratum In many countries a demographic transition is occur- corneum. Global lipid content of the aged skin is reduced ring, involving aging of the population and reduced by as much as 65%. Changes in the amino acid compo- birthrates, as well as large-scale migrations. In the next sition in aged skin may reduce the amount of cutaneous 50 years, about one-third of women will be menopausal, natural moisturizing factor, thereby decreasing its capac- and anti-aging medicine will gain importance (2) because ity for water binding (5) . no one especially wants to continue to live in a way, in As skin ages, keratinocytes change shape, becom- which they also physically decline. Whereas cultural and ing shorter and fatter; by contrast, corneocytes become technical manipulations have brought about increased bigger due to decreased epidermal turnover. Enzymati- longevity, this has also shaped cultural and technical cally, active melanocytes decrease at a rate of 8% – 20% manipulations so that the side effects of longevity, includ- per decade, resulting in uneven pigmentation in elderly ing wrinkled skin, are increasingly treated. The eternal skin (5) . desire of people around the world is to live longer, to be As time goes by, skin becomes less resistant to shear- young longer, or at least to look younger (3) . ing forces and presents an increased vulnerability to insult Aging is a multisystem degenerative process that due to the flattening of the dermo-epidermal junction, involves the skin and the skin support systems, including which occurs as a result of the loss of dermal papillae and the bone, cartilage, and subcutaneous compartments (4) . the reduced interdigitation between layers. This flatten- However, skin transformations are the most perceptible ing begins in the sixth decade (6) . The smaller contiguous surface between the two layers also creates a reduced cellu- lar supply of nutrients and oxygen, leading to an increased *Corresponding author: J é ssica Eleonora Pedroso Sanches risk of dermo-epidermal separation, a process that may Silveira, Rod. Anhanguera, s/n, Km 30, 5 Polvilho, Cajamar, SP 07750-000, Natura, Sao Paulo, Brazil, explain the mechanism by which wrinkles form (8) . E-mail: [email protected] Inside the dermis, many changes also occur. For D é bora Midori Myaki Pedroso: Natura, Sao Paulo, Brazil example, the amount of glycosaminoglycans in the 2 Silveira and Pedroso: UV light and skin aging dermis declines with old age. The amount of hyal- changes in nail plate and there are fewer glands in aged uronic acid, elastin and collagen decreases as they are skin (3) . produced by fibroblasts, whose number also declines. In women, estrogen levels strongly influence skin Indeed, aging is inevitably associated with a decrease in integrity, that is, falling levels in midlife contribute to collagen turnover (due to a decrease in fibroblasts and earlier signs of aging. Furthermore, intrinsic aging pro- their collagen synthesis) as well as elastin. Elastin also ceeds at different rates in all organisms at genetically has higher degree of calcification in aged skin, with an determined pace; this is caused primarily by the buildup associated degradation of elastin fibers. In this case, of reactive oxygen species (ROS) as a by-product of cel- collagen crosslinks stabilize, whereas collagen bundles lular metabolism. ROS, in turn, cause damage to criti- become disorganized. The loss of molecular integrity of cal cellular components like membranes, enzymes, and the dermis leads to increased rigidity, decreased torsion deoxy ribonucleic acid (DNA) (5) . extensibility, and diminished elasticity, eroding faster in There is a great effect of ethnicity on aging, and it women than in men, with a concomitant increase in vul- is primarily related to differences in pigmentation. High nerability to tear-type injuries (5) . levels of pigmentation are protective with regards the Cutaneous aging is a mix of intrinsic aging (due to cumulative effects of photoaging, with African Americans inherent genetics) and extrinsic aging (due to environ- showing little cutaneous difference between exposed mental conditions like solar exposure) (7, 9) . However, the and unexposed sites (11) . Increased innate pigmentation interactions between chronological and photo-induced is related to ultraviolet (UV) damage protection, includ- aging are complex, and the quantification of only the ing less collagen decrease and DNA damage in darker- effect of sun-exposure is difficult to obtain. Hence, a study skinned people (13) . clinically quantified the effect of sun exposure on facial aging in terms of the appearance of new specific signs or in terms of increasing the classical signs of aging. This Extrinsic aging study seems to confirm that pigmentation heterogeneity is a pure photoaging sign, whereas sagging of tissues is Extrinsic skin aging process is characterized by striking essentially a result of chronological aging. Vascular dis- morphologic and physiologic changes that generally lead orders could be considered a precursor of future photo- to a premature aging of the skin. Prominent manifesta- aging. The appearance of wrinkles and skin texture are tions of the extrinsic skin aging process are coarse wrin- influenced by both extrinsic and intrinsic aging, depend- kles, solar elastosis, and pigment irregularities. These ing on the behavior of the individual and the amount of signs superimpose the intrinsic skin aging signs at chroni- sunlight to which he or she has been exposed (10) . cally exposed areas of the body (12) . Extrinsic factors are, to varying degrees, controllable and include exposure to sunlight, pollution or nicotine, Intrinsic aging repetitive muscle movements like squinting or frowning, and miscellaneous lifestyle components, including diet, Intrinsic aging of the skin occurs inevitably as a natural sleeping position, and overall health (14) . Repetitive facial consequence of physiological changes over time at vari- movements actually lead to fine lines and wrinkles. When able yet inalterable genetically determined rates (11) ; it we use a facial muscle, a groove forms beneath the surface is also characterized primarily by functional alterations of the skin, which is why we see lines forming with each than by gross morphological changes (12) . facial expression. As skin ages and loses its elasticity, the Within the skin, collagen production slows down and skin stops springing back to its line-free state, and these elastin has a bit less spring. Dead skin cells do not shed grooves become permanently etched on the face as fine as quickly, and turnover of new skin cells may decrease lines and wrinkles. When the skin elasticity declines in slightly. Although these changes usually begin in the middle age, the effects of gravity become evident. Gravity 20s, the signs of intrinsic aging are typically not visible causes the tip of the nose to droop, the ears to elongate, for decades (4) . The clinical manifestation of intrinsic the eyelids to fall, the jowls to form, and the upper lip to aging includes xerosis, laxity, wrinkles, slackness, and disappear as the lower lip becomes more pronounced. the appearance of a variety of benign neoplasms like seb- Resting your face in the same way every night for years orrheic keratosis and cherry angioma. At the same time, eventually also leads to wrinkles. As a person ages, sleep hair becomes depigmented, terminal hair converts to wrinkles become etched on the surface of the skin and no vellus hair, and loss of hair is increased. There are also longer disappear (4) .