Effects of root bark extracts from Dictamnus dasycarpus on ICAM-1 expression and immune cell infiltration in human keratinocytes

The root bark of Dictamnus dasycarpus Turcz. (Rutaceae) is a well known anti-inflammatory agent for skin diseases such as eczema, pruritus and urticaria in Eastern countries.

We investigated the effects of methanolic extract of D. dasycarpus root bark (MEDD) on Intercellular Adhesion Molecule-1 (ICAM-1) expression, epidermal hyperplasia and immune cell infiltration in 1-fluoro-2,4-dinitrofluorobenzene (DNFB)-induced contact dermatitis (CD) mice. We also investigated its effects on the expression of ICAM-1, binding capacity to THP-1 cells, and phosphorylation of NF-κB in human keratinocytes (HaCaT cells).

Topical application of MEDD effectively inhibited ICAM-1 expression and epidermal hyperplasia in inflamed tissues. MEDD treatment also inhibited immune cell infiltration induced by DNFB. In addition, treatment with MEDD reduced the total amount of ICAM-1 in HaCaT cells and effectively lowered the capacity to bind to THP-1 cells. Finally, MEDD treatment prevented activation of the NF-κB pathway induced by TNF-α in HaCaT cells.

These data indicate that root bark of D. dasycarpus has the potential for treatment of inflammatory skin diseases as a complementary or alternative medicine to corticosteroids. In addition, they suggest that the anti-inflammatory effects of D. dasycarpus on CD are involved in the regulation of ICAM-1 expression through down-regulation of the NF-κB signaling pathway in keratinocytes.