Pulsatilla Saponin B4 Ameliorates LPS-Induced Inflammatory Response by Inhibiting IL-17RA and MAPK/NF-κB Signaling in Bovine Mammary Epithelial Cells and Mastitis Mouse Model

Bovine mastitis is a persistent and challenging illness in dairy industry, bringing about devastating economic losses to the sector. The longstanding over-reliance on antibiotic therapy has raised severe public health concerns, highlighting the critical need to develop safe and effective alternative regimens. Pulsatilla saponin B4 (PSB4), a plant-derived triterpenoid saponin, has been shown to regulate inflammation. However, the effect of PSB4 on mastitis in lactating cows has not been elucidated. The aim of this study was to explore the anti-inflammatory property and the molecular mechanisms of PSB4 in bovine mammary epithelial cells (BMECs) and mouse mastitis model. In cultured cells, PSB4 alleviated LPS-induced inflammatory reaction by suppressing the expression of pro-inflammatory mediators in BMECs. Notably, RNA-seq analysis indicated that the anti-inflammatory effect of PSB4 was correlated with IL-17RA and NF-κB signaling, with subsequent Western blot validation. Moreover, BMECs were stimulated with recombinant interleukin-17A (rIL-17A) to induce inflammation and challenged with Taltz to specifically inhibit IL-17RA signaling. The results showed that PSB4 reversed the rIL-17A-induced upregulation of elements within the IL-17RA pathway and its downstream MAPK/NF-κB cascade, including their downstream effectors. Furthermore, Taltz blocked the efficacy of PSB4 in protecting against LPS-induced inflammation. In vivo, PSB4 alleviated the inflammatory damage of mammary gland, pro-inflammatory mediator levels in mammary gland tissue and se-rum, while blocking the activation of IL-17RA signal along with downstream MAPK/NF-κB signal in LPS-induced mouse mastitis model. Taken together, studies in both BMECs and mice demonstrated that PSB4 alleviates mastitis by inhibiting IL-17RA signaling and downstream MAPK/NF-κB pathway, which may be a new strategy and a target for the management of mastitis.