Anti-inflammatory effect of Amomum xanthioides in a mouse atopic dermatitis model

Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disorder. The present study investigated the effects of Amomum xanthioides extract (AXE) on AD-like skin inflammation using a Dermatophagoides farinae extract (DFE) and 2,4-dinitrochlorobenzene (DNCB)-induced mouse AD model. Hematoxylin and eosin staining results demonstrated that repeated DFE/DNCB exposure markedly increased the thickening of the dermis and epidermis, in addition to the infiltration of eosinophils and mast cells. However, oral administration of AXE reduced these histopathological alterations in a dose-dependent manner. Elevated serum histamine, total and DFE-specific immunoglobulin E (IgE), and IgG2a were also decreased by treatment with AXE. In addition, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) results demonstrated that the mRNA expression of tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-4, IL-13, IL-31 and IL-17A was reduced in ear skin following AXE administration in AD mice. Fluorescence-activated cell sorting demonstrated that the population of CD4+/IL-4+, CD4+/IFN-γ+ and CD4+/IL-17A+ cells in draining lymph nodes was also significantly decreased in AXE-treated mice compared with AD mice without AXE treatment. Furthermore, keratinocytes that were stimulated with TNF-α and IFN-γ exhibited increased gene expression of pro-inflammatory cytokines and chemokines, including TNF-α, IL-1β, IL-6, IL-8, C-C motif chemokine ligand (CCL)17 and CCL22, as determined by RT-qPCR. However, upregulation of these genes was reduced by AXE pretreatment. Based on these results, we hypothesize that AXE may be useful in the treatment of allergic skin inflammation, particularly AD.