Shishihakuhito, a Kampo Medicine for Atopic Dermatitis, Prevents Lipopolysaccharide-induced Activation of NF-KB-dependent Transcription in C6 Rat Glioma Cells

摘要

Shishihakuhito has been recently demonstrated to be effective in the treatment of atopic dermatitis. However the molecular mechanism underlying the beneficial effects of the Kampo medicine on the dermatologic disorder remains to be elucidated. As the first step to reveal the molecular mechanism of the action of Shishihakuhito, we examined the effects of the Kampo medicine on NF-KB-dependent transcription which plays central roles in inflammation in vivo, in C6 rat glioma cells treated with lipopolysaccharide (LPS). Our reporter gene assays showed that the Kampo medicine reduced LPS-inducible increase in NF-KB-dependent transcription, which plays a crucial role in induction of COX-2 gene expression, in a concentration-dependent manner, and actually prevented LPS-inducible increase in COX-2 gene transcription. Also among three crude drugs constituting Shishihakuhito, namely Gardenia Fruit, Phellodendron Bark and Glycyrrhiza, the activity to inhibit LPS-inducible increase in NF-KB-dependent transcription was identified only in Phellodendron Bark. In addition, this crude drug prevented the activation of NF-icB-dependent transcription in a concentration-dependent manner in C6 cells. Furthermore, as examined by Western blot analysis, Shishihakuhito and Phellodendron Bark appeared to inhibit LPS-induced IkBoc degradation in C6 cells. These results suggest that the Kampo medicine may inhibit LPS-induced NF-KB-dependent transcription probably by inhibiting IkB degradation, thereby preventing inflammation in vivo.