Rosmarinic Acid Attenuates -Induced Inflammation via Regulating TLR9/NF-κB Signaling Pathway and Intestinal Microbiota.

() infection disrupts the homeostasis of the intestinal microbiota, causing an intestinal inflammatory response and posing a great threat to human and animal health. The unreasonable use of antibiotics has led to an increase in the prevalence of drug-resistant , increasing the difficulty of controlling . Therefore, new drug strategies and research are urgently needed to control . Rosmarinic acid (RA) is a natural phenolic acid with various pharmacological activities, including antioxidant, anti-inflammatory and antibacterial properties. However, the protective effects and mechanism of RA on intestinal inflammation and the gut microbial disorders caused by have not been fully elucidated. In this study, RAW264.7 cells, MCECs and BALB/c mice were challenged with to assess the protective effects and mechanisms of RA. The results showed that RA enhanced the phagocytic ability of RAW264.7 cells, reduced the invasion and adhesion ability of in MCECs, and inhibited -induced inflammation in cells. Moreover, RA inhibited the activation of the NF-κB signaling pathway by upregulating TLR9 expression. Importantly, we found that RA provided protection against and increased the diversity and abundance of the intestinal microbiota in mice. Compared with infection control, RA significantly increased the abundance of and and decreased the abundance of , and . However, RA failed to alleviate -induced inflammation and lost its regulatory effects on the TLR9/NF-κB signaling pathway after destroying the gut microbiota with broad-spectrum antibiotics. These results indicated that RA attenuated -induced inflammation by regulating the TLR9/NF-κB signaling pathway and maintaining the homeostasis of the gut microbiota. Our study provides a new strategy for preventing -induced intestinal inflammation.