| Summary: | <i>Pyrus ussuriensis Maxim</i>, a pear commonly known as “Sandolbae” in Korea, is used as a traditional herbal medicine for asthma, cough, and fever in Korea, China, and Japan. <i>P. ussuriensis Maxim</i> leaves (PUL) have therapeutic effects on atopic dermatitis (AD). However, there are no reports on the efficacy of specific components of PUL. In the present study, activity-guided isolation of PUL was used to determine the compounds with potent activity. Astragalin was identified as the major component of the chloroform-soluble fraction of PUL (PULC) using High-performance liquid chromatography (HPLC) analysis. Astragalin and PULC were tested in vitro and in vivo for their effects against AD. PULC and astragalin dose-dependently inhibited the production of nitric oxide (NO) in mouse macrophage (RAW 264.7) cells, and interleukin (IL)-6 and IL-1β in tumor necrosis factor (TNF-α)/interferon γ (IFNγ) induced HaCaT cells. In the AD mice model, PULC and astragalin application significantly reduced dermatitis severity, scratching behavior, and trans-epidermal water loss (TEWL) when compared to that of 2, 4-dinitrochlorobenzene-treated NC/Nga mice. Additionally, they normalized skin barrier function by decreasing immunoglobulin E (IgE) levels in the serum. Filaggrin and involucrin protein levels were normalized by PULC treatment in HaCaT cells and skin lesions. These results indicate that PULC and astragalin ameliorate AD-like symptoms by alleviating both pro-inflammatory cytokines and immune stimuli in vitro and in vivo in animal models. Therefore, PULC and astragalin might be effective therapeutic agents for the treatment of AD.
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