Anti-inflammatory activities of Dictamnus dasycarpus Turcz., root bark on allergic contact dermatitis induced by dinitrofluorobenzene in mice

Ethnopharmacological relevance: The root bark of Dictamnus dasycaipus Turcz. is widely used as a medicinal herb for treatment of skin diseases such as eczema, pruritus and urticaria in China, Japan and Korea. Materials and methods: We investigated the effects of methanol extract of Dictamnus dasycaipus Turcz., root bark (MEDD) on ear thickness, ear weights, histopathological changes such as hyperplasia, edema, spongiosis and immune cell infiltration and cytokine productions in 1-fluoro-2,4-dinitrofluorobenzene (DNFB)-induced contact dermatitis (CD) mice. We also investigated its effects on degranulation of histamine and p-hexosaminidase and related mechanisms using RBL-2H3 cells. Results: Topical application of MEDD effectively inhibited enlargement of ear thickness and weight (P < 0.05). MEDD treatment also inhibited hyperplasia, edema and spongiosis induced by DNFB. Treatment with 300 mu g/ear of MEDD suppressed the increase in IFN-gamma and TNF-alpha levels (P < 0.05). In addition, treatment with >50 mu g/mL MEDD reduced the level of p-hexosaminidase release, while >100 mu g/mL MEDD lowered the level of histamine release in a dose-dependent manner (P < 0.05). Finally, MEDD treatment prevented phosphorylation of p38 MAPK induced by phorbol 12-myristate 13-acetate (PMA) and calcium ionophore A23187 in RBL-2H3 cells. Conclusions: These data indicate that root bark of Dictamnus dasycarpus Turcz. has the potential for use in the treatment of allergic skin diseases. Furthermore, they suggest that root bark of Dictamnus dasycarpus Turcz. is involved in decreasing degranulation of MCs via inhibition of the p38 MAPK pathway as well as in the inhibition of Th1 skewing reactions. (C) 2013 Elsevier Ireland Ltd. All rights reserved.