Inhibitory activity of the flower buds of Lonicera japonica Thunb. against histamine production and L-histidine decarboxylase in human keratinocytes.

In previous studies we found that anionic surfactants such as sodium laurate (SL) and/or sodium dodecylsulfate (SDS) exert actions on epidermal keratinocytes rather than mast cells to give rise of histamine production and skin itching through increasing the expression of the 53-kDa active form of L-histidine decarboxylase (HDC). In addition, with treatment of SL in a three-dimensional human keratinocyte culture, increases in both the 53-kDa HDC and histamine production are detected and thus this culture assay is applied to screen anti-itching materials from natural resources. In this study, the inhibitory activity of "Kin-gin-ka" (flower buds of Lonicera japonica Thunb., FLJ) against histamine production and expression of the active form of HDC were examined in this culture assay. FLJ is a well-known traditional Chinese medicine, being used to treat fevers, coughs and some infectious diseases. The result showed both FLJ and chlorogenic acid had inhibitory activities against the expression of 53-kDa HDC and histamine production. However, chlorogenic acid showed a weaker effect on histamine production than that of FLJ, suggesting that other chemical constituents besides chlorogenic acid could contribute to the inhibitory activities. Thus, a further chemical study of FLJ is now under investigation.