Liver injury caused by the irrational use of acetaminophen (APAP) represents a significant challenge in the field of public health. In clinical treatment, apart from N—acetylcysteine (NAC), the only approved antidote, there are extremely limited effective intervention measures for APAP-induced hepatotoxicity. Therefore, exploring novel liver-protecting drugs and elucidating their mechanisms of action is of great scientific significance and clinical value. Rosmarinic acid (RA), as a natural polyphenolic compound, has been proven to have significant antioxidant activity. Previous studies have shown that it has a protective effect against drug-induced liver injury. Nevertheless, the precise protective mechanism of RA in APAP-induced acute liver injury (AILI) has not been fully defined. This study was based on an AILI mouse model to systematically explore the liver-protecting effect of RA and its underlying molecular mechanisms. The research results showed that pretreatment with RA could notably mitigate liver pathological injury. It could decrease the activities of ALT and AST in the serum, suppress the liver inflammatory reaction, and reverse the decline in the levels of CAT, T-AOC, SOD, and GSH caused by APAP. Meanwhile, RA could enhance antioxidant defense capabilities by activating the Keap1/Nrf2/HO-1 signaling pathway, regulate the xCT/GPX4 axis to inhibit lipid peroxidation, and thus block the process of ferroptosis. In conclusion, this study confirmed that RA exerts a protective effect against AILI by regulating the Keap1/Nrf2/HO-1 axis to enhance antioxidant capacity and inhibit ferroptosis through the xCT/GPX4 pathway. Our research provides a theoretical basis for RA as a potential therapeutic agent for APAP-induced liver injury.

Salmonella enteritidis (SE) 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 SE, increasing the difficulty of controlling SE. Therefore, new drug strategies and research are urgently needed to control SE. 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 SE have not been fully elucidated. In this study, RAW264.7 cells, MCECs and BALB/c mice were challenged with SE 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 SE in MCECs, and inhibited SE-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 SE and increased the diversity and abundance of the intestinal microbiota in mice. Compared with infection control, RA significantly increased the abundance of Firmicutes and Acidibacteria and decreased the abundance of Proteobacteria, Epsilonbacteraeota and Bacteroidota. However, RA failed to alleviate SE-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 SE-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 SE-induced intestinal inflammation.