Anti-photoaging effects of chitosan oligosaccharide in ultraviolet-irradiated hairless mouse skin

Skin photoaging (SP) is a premature skin-aging damage after repeated exposure to ultraviolet (UV) radiation, mainly characterized by oxidative stress and inflammatory disequilibrium, which makes skin show the typical symptoms of photoaging such as coarse wrinkling, dryness, irregular pigmentation and laxity. Chitosan oligosaccharide (COS), a natural polysaccharide with good humectant property, is the depolymerized product of chitosan with various biological activities, among which the antioxidant and anti-inflammatory effects have been frequently reported in recent years. However, no existing invivo study indicates whether COS has direct protective effect on UV-induced SP. In the current research, we investigated the potential preventive effect of COS against UV-caused damage in hairless mouse dorsal skin. The data showed that COS, by topical application after each UV-radiation for 10 weeks, effectively inhibited the undesirable changes on the skin induced by UV. To be specific, COS obviously alleviated the macroscopic and histopathological damages of mice skin, via mitigating the disrupted collagenous fibers, as well as improving the relative content of type I collagen and the amount of total collagen. Furthermore, COS effectively inhibited the levels of pro-inflammatory cytokines such as TNF-α, IL-1β and IL-6, and markedly improved the activities of antioxidant enzymes (SOD, GSH-Px, CAT), as well as the content of skin hydroxyproline and moisture. These findings demonstrated that this natural polysaccharide attenuated UV-induced SP, at least in part, by virtue of favorable regulation of antioxidant and anti-inflammatory status, which presumably worked in concert to maintain the morphology and level of dermal collagen.