Rosmarinic Acid Inhibits PRV Replication by Regulating Oxidative Stress Through the Nrf2 Signaling Pathway

Pseudorabies (PR) is an acute and highly contagious disease caused by the pseudorabies virus (PRV). This virus has a wide range of susceptible hosts and has caused major economic losses to the global swine industry. While rosmarinic acid possesses broad antioxidant and antiviral properties, its efficacy against PRV has remained unexplored. Therefore, this study aimed to evaluate the anti-PRV activity of rosmarinic acid and to elucidate its underlying mechanism, with a focus on the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway. The results revealed that rosmarinic acid exhibited potent, concentration-dependent antiviral activity in vitro, with a half-maximal inhibitory concentration (IC50) of 0.02654 mg/mL, a half-maximal cytotoxic concentration (CC50) of 0.1043 mg/mL, and a selectivity index (SI) of 3.9. Rosmarinic acid inhibited virus adsorption, entry, and intracellular replication. It also significantly suppressed the expression of the gB protein. In a mouse model, rosmarinic acid treatment (200 mg/kg) significantly enhanced the survival rate to 28.5%. This treatment reduced the viral load in the brain, lungs, kidneys, heart, and spleen. It also alleviated the tissue damage caused by PRV infection. Furthermore, rosmarinic acid counteracted PRV-induced oxidative stress by elevating the activity of the antioxidant factors SOD and CAT and reducing the level of the oxidative factor MDA. Network pharmacology analyses predicted the Nrf2 signaling pathway as a key target for rosmarinic acid. Subsequent mechanistic studies confirmed that rosmarinic acid upregulated the expression of the Nrf2, HO-1, GPX, SOD, and CAT genes, as well as Nrf2 and HO-1 proteins, thereby promoting the nuclear translocation of Nrf2. These results identify rosmarinic acid as a promising anti-PRV agent that acts through multi-phase viral inhibition and activation of the Nrf2-mediated antioxidant defense, suggesting its potential as a novel pharmacological strategy against PRV.