Inhibition of Interleukin-4 and β-Hexosaminidase Release in RBL-2H3 Cells by Compounds Isolated from Lobelia chinensis

Lobelia chinensis Lour. has commonly been used in traditional Chinese medicine for the treatment of antidote, diuretic, diarrhea, and inflammation. This study aimed to identify the active compounds in an aqueous extract of L. chinensis responsible for its anti-atopic effect in vitro using RBL-2H3 cells. A chemical investigation of secondary metabolites in an aqueous extract of L. chinensis led to the isolation of nine chemical constituents, which included the four marker compounds, and these were evaluated for their inhibitory effects on IL-4 mRNA expression and the release of β-hexosaminidase in propidium iodide-induced RBL-2H3 cells. We found diosmetin and fraxidin inhibited cellular IL-4 mRNA expression, and that diosmetin and 6,8-dimethoxycoumarin inhibited DNP-specific IgE-induced degranulation in these cells. Our study suggests that diosmetin, fraxidin, and 6,8-dimethoxycoumarin are potential candidates for the treatment of atopic diseases.

Diosmetin and Its Glycoside, Diosmin, Improve Atopic DermatitisLike Lesions in 2,4-Dinitrochlorobenzene-Induced Murine Models

Naturally derived diosmetin and its glycoside diosmin are known to be effective in treating inflammatory disease. This study was performed to determine whether diosmin and diosmetin have the effect of improving atopic dermatitis in a 2,4-dinitrochlorobenzen (DNCB)-induced atopic dermatitis (AD) model. DNCB was used to establish AD model in hairless mice. Skin moisture, serum immunoglobulin E (IgE), interleukin 4 (IL-4), and histological analysis were performed to measure the effectiveness of diosmin and diosmetine to improve AD. IL-4 levels were also measured in RBL-2H3 cells. Administration of diosmetin or diosmin orally inhibited the progress of DNCB-induced AD-like lesions in murine models by inhibiting transdermal water loss (TEWL) and increasing skin hydration. Diosmetin or diosmin treatment also reduced IgE and IL-4 levels in AD-induced hairless mouse serum samples. However, in the in vitro assay, only diosmetin, not diosmin, reduced the expression level of IL-4 mRNA in RBL-2H3 cells. Diosmin and diosmetine alleviated the altered epidermal thickness and immune cell infiltration in AD. Diosmin is considered effective in the cure of AD and skin inflammatory diseases by being converted into diosmetin in the body by pharmacokinetic metabolism. Thus, oral administration of diosmetin and diosmin might be a useful agent for the treatment of AD and cutaneous inflammatory diseases.

Dioscorea japonica Thunb. Ethanolic Extract Attenuated Oxazolone-Induced Atopic Dermatitis-like Skin Lesions in BALB/c Mice

The rhizomes of Dioscorea japonica Thunb. are widely consumed as food and also used to treat diabetes and polyuria in Korea. This study was undertaken to study the anti-atopic dermatitis effects of a 95% ethanolic extract (DJE) of D. japonica in an oxazolone-stimulated murine model of atopic dermatitis (AD). The therapeutic effects of DJE on AD-like skin lesions were assessed on both ears. DJE (1%) or dexamethasone (0.5%; the positive control) were applied to skin lesions for three weeks. Serum levels of IgE and IL-4 were assessed by ELISA (enzyme-linked immunosorbent assay). Histopathological examinations were performed by hematoxylin and eosin (H&E) and toluidine blue staining and revealed DJE significantly reduced dermal thickness and inflammatory cell infiltration when applied to oxazolone-treated ear skin. DJE-treated AD mice also showed lower serum levels of IgE and IL-4 than oxazolone-stimulated controls. Our findings demonstrate DJE might be a useful safe, topical agent for the treatment of atopic diseases.

Dihydrobenzofuran Neolignans Isolated from Euonymus alatus Leaves and Twigs Attenuated Inflammatory Responses in the Activated RAW264.7 Macrophage Cells

Anti-inflammatory effects of dihydrobenzofuran neolignans isolated from Euonymus alatus leaves and twigs were evaluated in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. Six neolignans, (+)- simulanol (1), (+)-dehydrodiconiferyl alcohol (2), (-)-simulanol (3), (-)-dehydrodiconiferyl alcohol (4), (+)-dihydrodehyrodiconiferyl alcohol (5), threo-buddlenol B (6) effectively inhibited the production of nitric oxide (NO) induced by LPS, and the activity of iNOS. (-)-dehydrodiconiferyl alcohol (4), which showed the most potent inhibitory activity, attenuated the activity of iNOS enzyme and also the expression of iNOS and COX-2 proteins. The subsequent production of pro-inflammatory cytokines, interleukin-1β, interleukin-6, tumor necrosis factor-α and prostaglandin E2 were also inhibited by the pretreatment of RAW264.7 cells with (-)-dehydrodiconiferyl alcohol (4). These neolignans are thought to contribute to anti-inflammatory effects of E. alatus, and expected to be potential candidates to prevent/treat inflammation-related diseases.