Anti-ageing skin effects of Korean bamboo salt on SKH1 hairless mice

Bamboo salt is generated by baking bamboo and sea salt and is used as a traditional food or medicine. The aim of this study was to investigate the anti-ageing skin effects of Korean bamboo salt and to compare the antioxidant, anti-ageing and anti-inflammatory effects of various salts, including purified salt, solar salt, bath solar salt, Masada solar salt, 1-time baked bamboo salt (1× bamboo salt), and 9-times baked bamboo salt (9× bamboo salt). Based on the content of mineral elements, pH, OH groups and redox potential amperometric analysis, the 9× bamboo salt showed the most antioxidant components and characteristics compared to the other salts. The in vitro results showed that the 9× bamboo salt could inhibit oxidative damage by hydrogen peroxide (H2O2) treatment in HaCaT keratinocytes, and its effect was better than that of the other salts. In an in vivo experiment, SHK-1 hairless mice were treated with UV (ultraviolet) radiation to induce ageing. The epidermal thickness and epidermal structures were then assessed by phenotypic and histological analyses. The 0.2% 9× bamboo salt- and 1× bamboo salt-treated mice had a thinner epidermis than the control mice, and the sebaceous glands were almost intact with a regular arrangement that was similar to those in the normal group. Compared with the UV-treated group (control group) and other salt-treated groups, the 9× bamboo salt- and 1× bamboo salt-treated groups had higher dermal collagen and elastic fibre content. Fewer mast cells were observed in the 9× bamboo salt- and 1× bamboo salt-treated groups than in the control group. The activities of the skin antioxidant-related enzymes superoxide dismutase (SOD) and catalase (CAT) in the 9× bamboo salt- and 1× bamboo salt-treated groups were higher than those in other groups and similar to those in the normal group, but lipid peroxide (LPO) activity and carbonylated protein levels showed the opposite trends. Furthermore, the 9× bamboo salt- and 1× bamboo salt-treated groups had protein contents similar to those of the normal group. In addition, the 9× bamboo salt and 1× bamboo salt effectively down-regulated the expression of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) and up-regulated the expression of tissue inhibitor expression of matrix metalloproteinase-1 (TIMP-1), matrix metalloproteinase-2 (TIMP-2), SOD and CAT compared to the other salts at a concentration of 0.2% (p < 0.05). These results suggest that at appropriate concentrations, bamboo salt could prevent skin ageing induced by ultraviolet radiation b (UVB) photodamage.