Inhibitory effect of Isatis tinctoria L. water extract on DNCB-induced atopic dermatitis in BALB/c mice and HaCaT cells

BACKGROUND: Isatis tinctoria L (PLG) is a medicinal herb from the roots of Isatis indigotica Fort (Family Cruciferae). Previous studies have shown that PLG has anti-inflammatory and therapeutic effects against conditions such as acute and chronic hepatitis, various respiratory inflammations, and cancer. The purpose of this study was to define the pharmacological effects of PLG on inflammatory reactions and skin hyperkeratosis, which are the main symptoms of atopic dermatitis (AD), in vivo and in vitro. METHODS: For the AD in vivo experiment, 2,4-dinitrochlorobenzene (DNCB) induction and oral administration of PLG were performed on male BALB/c mice for four weeks. For in vitro experiments, keratinocytes were activated using TNF-α/IFN-γ in cultured human keratinocyte (HaCaT) cells. PLG inhibited inflammatory chemokine production and blocked the nuclear translocation of NF-κB p65 in activated keratinocytes. RESULTS: As a result of oral administration of PLG, dermis and epidermis thickening, as well as eosinophil and mast cell infiltration, were attenuated in AD skin lesions. In addition, the levels of immunoglobulin E (IgE), pro-inflammatory cytokines, and the MAPK/NF-κB signaling pathway were decreased in serum and dorsal skin tissues. Furthermore, PLG inhibited inflammatory chemokine production and blocked the nuclear translocation of NF-κB p65 in activated keratinocytes. In addition, epigoitrin and adenosine, the standard compounds of PLG, were identified as candidate AD compounds. CONCLUSIONS: These results indicate that PLG is a potent therapeutic agent for attenuating symptoms of AD. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13020-022-00624-5.