Saireito, a traditional Chinese medicine, suppressed photodamage and reduction of lymphatic vessel density in UVB-irradiated skin.

A single high-dose ultraviolet B (UVB) exposure on the skin induces acute inflammatory responses, such as an increase in proinflammatory cytokines, hyperpermeability and dilation of blood and lymphatic vessels, and infiltration of inflammatory cells. These responses result in different cutaneous disorders characterized by erythema, edema formation, and extracellular matrix degradation. Saireito (SRT), a traditional Chinese medicine, has been used to treat various inflammatory diseases in Japan. SRT was also suggested to improve lymphedema after radiotherapy in a clinical study, and it was found to have a protective effect against UV irradiation in vitro. Based on these findings, we aimed to investigate the effect of SRT on UVB-induced photodamage. We pretreated HR-1 hairless mice with SRT (625 or 1250 mg/kg) for 3 weeks before a single UVB (250 mJ/cm2) irradiation. SRT treatment attenuated UVB-induced increases in erythema, transepidermal water loss, and edema formation at 72 h post-irradiation. SRT treatment also suppressed UVB-induced inflammatory cell infiltration and collagen degradation. Furthermore, at 24 h post-irradiation, SRT treatment inhibited UVB-induced upregulation of proinflammatory cytokines and reduction in lymphatic vessel density associated with upregulation of VEGF-C expression. These results suggest that SRT could attenuate UVB-induced photodamage. This protective effect of SRT involves suppression of upregulation of proinflammatory cytokines and improvement of lymphatic function in the early stage of inflammation.