The inhibitory effect of ergosterol, a bioactive constituent of a traditional Japanese herbal medicine saireito on the activity of mucosal-type mast cells

Mucosal inflammation in ulcerative colitis (UC) is presumed to be regulated primarily by type 2 T helper cell immune responses and mucosal mast cells in the colon are thought to play an important role in the pathogenesis of the mucosal inflammation. Saireito, a Japanese herbal medicine of standardized quality, originating from traditional Chinese medicine (Kampo medicine), is composed of two different Kampo medicines (shosaikoto and goreisan) and is often used for UC in Japan. In this study, we examined the direct effects of these Kampo medicines and their constituents on the antigen-induced degranulation of mucosal-type mast cells. Mucosal-type murine bone marrow-derived mast cells (mBMMCs) were pretreated by these drugs for 24 h, and immunoglobulin E (IgE) receptor-triggered degranulation of mBMMCs was assessed by β-hexosaminidase release. Goreisan showed inhibitory effects on degranulation of mBMMCs in a dose-dependent manner. Among the five constituent medicinal herbs of goreisan, Poria and Polyporus had the inhibitory effects on mBMMCs. Ergosterol, a principal and common component of Poria and Polyporus, also suppressed the degranulation of mBMMCs. Our results provide a molecular basis to explain a portion of the beneficial therapeutic properties of saireito on UC.