Aqueous extract of erigeron annuus ameliorates OVA-induced atopic dermatitis-like skin lesions through modulation of Th2-mediated immune responses and MAPK signaling

Context Atopic dermatitis is a chronic inflammatory skin disorder characterized by epidermal barrier dysfunction and dysregulated type 2 helper T cell (Th2)-mediated immune responses. Erigeron annuus (L.) Desf. is traditionally used for inflammatory conditions, but its effects on atopic dermatitis remain unclear.Objective This study evaluated the protective effects of E. annuus aqueous extract (EA) and associated mechanisms.Materials and methods Atopic dermatitis-like lesions were induced in 5-week-old female BALB/c mice by repeated epicutaneous ovalbumin (OVA) sensitization, and EA was orally administered for six weeks. Epidermal barrier function, histopathology, immunoglobulins, cytokines, and mitogen-activated protein kinase (MAPK) signaling were evaluated. Pyromeconic acid (PA), a representative constituent of EA, was examined in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages.Results EA attenuated dermatitis-like lesions and reduced dermatitis scores in OVA-sensitized mice. EA decreased transepidermal water loss, increased skin hydration, restored filaggrin expression, and reduced epidermal and dermal thickening, mast cell infiltration, CD4+/CD8+ T-cell accumulation, splenomegaly, serum total and OVA-specific IgE, and skin interleukin-4 and interleukin-13 levels. EA also reduced extracellular signal-regulated kinase and p38 phosphorylation and interleukin-1β expression in dorsal skin. PA suppressed MAPK activation and inflammatory mediator expression in LPS-stimulated macrophages.Discussion and conclusion EA attenuated OVA-induced atopic dermatitis-like inflammation in association with improved epidermal barrier function, reduced Th2-associated immune responses, and attenuated MAPK signaling. PA showed anti-inflammatory activity in vitro, although its contribution to the in vivo effects of EA remains to be established. EA warrants further investigation as a plant-derived candidate for complementary intervention in atopic dermatitis.