Kaempferol-7-O-Glucoside Ameliorates Atopic Dermatitis via the TSLP-Mediated JAK2/STAT5 Signaling Axis

Background/Objectives: Thymic stromal lymphopoietin (TSLP) is central to the pathogenesis of atopic dermatitis (AD) and a promising therapeutic target. However, developing small-molecule TSLP inhibitors is challenging due to the difficulty in disrupting the TSLP-TSLPR interface. This study aimed to explore naturally sourced blockers of the TSLP-TSLPR interaction and identify novel candidate compounds for AD treatment. Methods: HuT78 cells were stimulated with PMA, ionomycin, and TSLP to establish an AD model. Inflammatory cytokines were measured by qRT-PCR and ELISA. JAK/STAT signaling was analyzed by Western blot. In female BALB/c mice, DNCB-induced AD-like skin lesions were topically treated with test compounds, followed by histopathological and immunohistochemical assessment. Results: Eight compounds were screened, and their key structural features were elucidated via structure-activity relationship (SAR) analysis. Among them, kaempferol-7-O-glucoside (K-7-G) emerged as the most potent candidate. It interfered with the TSLP-TSLPR interaction, selectively inhibited TSLP-mediated JAK2/STAT5 phosphorylation, and significantly downregulated IL-4 (p < 0.0001) and IL-13 (p < 0.001) levels. Topical application of 1% K-7-G significantly alleviated AD-like symptoms in a mouse model, decreasing dorsal skin thickness, dermatitis score, and scratching frequency while restoring the expression of filaggrin, loricrin, and occludin (p < 0.0001). Meanwhile, it significantly reduced key inflammatory mediators in a concentration-dependent manner, including TSLP, IL-4, IL-13, TNF-α, IFN-γ, and IgE. Conclusions: This study demonstrates that K-7-G is a novel natural TSLP inhibitor capable of blocking the TSLP-TSLPR signaling pathway and effectively improving AD symptoms. Further research may explore its therapeutic potential in other inflammatory diseases.