LAUSR

&NA; Vanillin is used in a variety of food, chemical, and pharmaceutical applications, and exhibits anti‐inflammatory properties. However, there are no reports about the effects of vanillin on lipopolysaccharide (LPS)‐induced mastitis. In this study, we explored the effects of vanillin on the subsequent inflammatory response and blood–milk barrier in LPS‐induced mastitis. Results showed that vanillin suppressed the inflammatory response by a) inhibiting myeloperoxidase activity; b) decreasing the production of pro‐inflammatory mediators which include tumor necrosis factor alpha (Tnf‐&agr;; from 128.5 ± 14.59 to 67.51 ± 10.88,pg/mL, P < 0.01), interleukin‐6 (Il‐6; from 531.5 ± 196.4 to 109.3 ± 24.14, pg/mL, P < 0.05), interleukin‐1&bgr; (Il‐1&bgr;; from 2569 ± 1648 to 731.8 ± 171.7, pg/mL, P < 0.05), inducible nitric oxide synthase (Inos), and cyclooxygenase‐2 (Cox‐2); and c) repairing the blood‐milk barrier by increasing the protein levels of the tight junction proteins, including zona occludens 1 (Zo‐1), claudin‐3, and occludin. In vitro experiment, Vanillin can inhibit LPS‐induced inflammation and enhance the protein levels of tight junction proteins. Further studies have shown that vanillin inhibits inflammation by inhibiting mitogen‐activated protein kinases (MAPKs) and nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐&kgr;B) signaling pathways. Our findings showed that vanillin protects mammary gland from LPS‐induced mastitis by enhancing the blood–milk barrier and inhibiting the inflammatory response.