Saireito Improves Lymphatic Function and Prevents UVB-Induced Acute Inflammation and Photodamage in HR-1 Hairless Mice

A single high-dose ultraviolet B (UVB) exposure on the skin induces acute inflammatory responses, such as an increase in proinflammatory cytokines (e.g., IL-6 and IL-1β), hyperpermeability and dilation of blood and lymphatic vessels, and infiltration of inflammatory cells. These responses result in different cutaneous disorders characterized by erythema, epidermal hyperplasia, edema formation, and extracellular matrix degradation. Saireito extract (SRT), a traditional Chinese medicine, has been used to treat various inflammatory diseases in Japan, and SRT and its major active components (e.g., saikosaponins and baicalin) were reported to downregulate proinflammatory cytokines. Moreover, SRT has a protective effect against UV irradiation in vitro. Based on these findings, we aimed to investigate the effect of SRT on UVB-induced photodamage and structural change in the vasculature. We pretreated male HR-1 hairless mice with SRT (625 or 1250 mg/kg) for 3 weeks before a single UVB (250 mJ/cm(2)) irradiation. SRT treatment attenuated UVB-induced increases in erythema, transepidermal water loss, and edema formation at 72 h after irradiation. SRT treatment also suppressed UVB-induced inflammatory cell infiltration and collagen degradation. Furthermore, at 24 h after 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.