Betulin Attenuates TGF-ß1- and PGE2-Mediated Inhibition of NK Cell Activity to Suppress Tumor Progression and Metastasis in Mice.

Transforming growth factor (TGF)-ß1 and prostaglandin E2 (PGE2) are humoral factors critically involved in the induction of immunosuppression in the microenvironment of various types of tumors, including melanoma. In this study, we identified a natural compound that attenuated TGF-ß1- and PGE2-induced immunosuppression and examined its effect on B16 melanoma growth in mice. By screening 502 natural compounds for attenuating activity against TGF-ß1- or PGE2-induced suppression of cytolysis in poly(I:C)-stimulated murine splenocytes, we found that betulin was the most potent compound. Betulin also reduced TGF-ß1- and PGE2-induced downregulation of perforin and granzyme B mRNA expression and cell surface expression of NKG2D and CD69 in natural killer (NK) cells. Cell depletion and coculture experiments showed that NK cells, dendritic cells, B cells, and T cells were necessary for the attenuating effects of betulin. Structure-activity relationship analysis revealed that two hydroxyl groups at positions C3 and C28 of betulin, their cis-configuration, and methyl group at C30 played crucial roles in its attenuating activity. In a subcutaneous implantation model of B16 melanoma in mice, intratumor administration of betulin and LY2157299, a TGF-ß1 type I receptor kinase inhibitor, significantly retarded the growth of B16 melanoma. Notably, betulin increased significantly the number of CD69 positive NK cells in tumor sites at early stages of post-tumor cell injection. Our data suggest that betulin inhibits the growth of B16 melanoma by enhancing NK cell activity through attenuating the immunosuppressive tumor microenvironment.

Antipruritic effects of Sophora flavescens on acute and chronic itch-related responses in mice.

To find new antipruritic herbal medicines for pruritus, we screened the methanol extracts of seven herbal medicines which have been used to treat dermatologic diseases, testing them on mouse models of acute and chronic itch. When administrated perorally (p.o.) at a dose of 200 mg/kg, methanol extracts of Sophora flavescens and Cnidium monnieri, but not the others, significantly inhibited a serotonin (5-HT)-induced itch-related response (scratching) and the spontaneous scratching of NC mice, a mouse model of atopic dermatitis. The inhibitory effect of Sophora flavescens was stronger than that of Cnidium monnieri. The methanol extract from Sophora flavescens (50-200 mg/kg) inhibited 5-HT-induced scratching in a dose-dependent manner, without any effects on the locomotor activity. These results suggest that Sophora flavescens and its constituents widely affect acute and chronic pruritus, and are possible as new antipruritic agents.