Date Published: February 7, 2017
Publisher: Public Library of Science
Author(s): Toshiyuki Komatsu, Suguru Sasaki, Yuki Manabe, Takashi Hirata, Tatsuya Sugawara, Andrzej T Slominski.
Astaxanthin, a carotenoid found mainly in seafood, has potential clinical applications due to its antioxidant activity. In this study, we evaluated the effect of dietary astaxanthin derived from Haematococcus pluvialis on skin photoaging in UVA-irradiated hairless mice by assessing various parameters of photoaging. After chronic ultraviolet A (UVA) exposure, a significant increase in transepidermal water loss (TEWL) and wrinkle formation in the dorsal skin caused by UVA was observed, and dietary astaxanthin significantly suppressed these photoaging features. We found that the mRNA expression of lympho-epithelial Kazal-type-related inhibitor, steroid sulfatase, and aquaporin 3 in the epidermis was significantly increased by UVA irradiation for 70 days, and dietary astaxanthin significantly suppressed these increases in mRNA expression to be comparable to control levels. In the dermis, the mRNA expression of matrix metalloprotease 13 was increased by UVA irradiation and significantly suppressed by dietary astaxanthin. In addition, HPLC-PDA analysis confirmed that dietary astaxanthin reached not only the dermis but also the epidermis. Our results indicate that dietary astaxanthin accumulates in the skin and appears to prevent the effects of UVA irradiation on filaggrin metabolism and desquamation in the epidermis and the extracellular matrix in the dermis.
The skin functions as the outermost barrier of the body and is in direct contact with the environment, which causes physical damage. Skin can regulate the local and global homeostasis by sensing the environment [1, 2]. However, chronic exposure to ultraviolet (UV) radiation from the sun contributes to skin photoaging, which is clinically characterized by dryness, pigmentation, laxity, and deep wrinkling [3, 4]. UV radiation comprises wavelengths from 200 to 400 nm, and is further divided into three sections: UVA (320–400 nm), UVB (280–320 nm), and UVC (200–280 nm). Although UVC is filtered out by atmospheric ozone for the most part, both UVA and UVB radiation can reach the Earth’s surface and cause biological consequence to the skin [5, 6]. UVB radiation critically damages cellular macromolecules and induces the formation of reactive oxygen species. Exposure to UVB radiation is the primary cause of skin cancer in humans and animals . Despite being weakly carcinogenic as compared to UVB, UVA radiation contributes up to 95% of the total UV exposure and plays a substantial role in photoaging of the human skin . UVA is able to penetrate the dermis, resulting in damage to dermal collagen and elastin, while UVB mainly affects the epidermis and causes DNA damage . Therefore, dietary supplementation with molecules that can effectively accumulate in the dermis could protect the skin from UVA-induced damage such as photoaging.
Diverse UV radiation plays an important role in the skin and regulates body homeostasis both on the local [30–32] and systemic levels [33–35]. To our knowledge, this is one of the first in vivo studies evaluating the protective effect of dietary astaxanthin against skin photoaging induced by UVA radiation. Intrinsic and chronological skin aging is characterized by atrophy of the skin with loss of elasticity and slowed metabolic activity. Quantitatively different from intrinsic aging, skin photoaging, which is clinically characterized by dryness, pigmentation, laxity, and deep wrinkling, occurs as a result of the accumulation of environmental damage, particularly exposure to ultraviolet radiation [3, 4]. It was suggested that exposure to UVA contributes to photodamage in human skin, because UVA accounts for approximately 95% of personal exposure to solar radiation . In this study, we found that dietary supplementation with astaxanthin effectively prevented features of photoaging, such as the increase of TEWL and wrinkle formation, in the dorsal skin of mice exposed to UVA irradiation. Based on the body weight, the calculated astaxanthin intake in the condition of this study was 20–200 mg per day for human. However, it seems that lower dose is enough to be effective for human, because the absorption of carotenoids in mice is generally smaller than in human . It has been reported that the concentration of plasma astaxanthin in human after 3 mg/day ingestion of astaxanthin for 12-week was 62±25 pmol/mL, as similar as the plasma astaxanthin level of 0.01% Ax group in this study (92±48 pmol/mL) .