Eugenol alleviates transmissible gastroenteritis virus-induced intestinal epithelial injury by regulating NF-κB signaling pathway.

Increasing evidence supports the ability of eugenol to maintain intestinal barrier integrity and anti-inflammatory and ; however, whether eugenol alleviates virus-mediated intestinal barrier damage and inflammation remains a mystery. Transmissible gastroenteritis virus (TGEV), a coronavirus, is one of the main causative agents of diarrhea in piglets and significantly impacts the global swine industry. Here, we found that eugenol could alleviate TGEV-induced intestinal functional impairment and inflammatory responses in piglets. Our results indicated that eugenol improved feed efficiency in TGEV-infected piglets. Eugenol not only increased serum immunoglobulin concentration () but also significantly decreased serum inflammatory cytokine concentration () in TGEV-infected piglets. In addition, eugenol also significantly decreased the expression of mRNA and the phosphorylation level of protein in the jejunum mucosa of TGEV-infected piglets. Eugenol increased villus height and the ratio of villus height to crypt depth in the jejunum and ileum, and decreased serum D-lactic acid levels. Importantly, eugenol increased tight junction protein () and mRNA expression levels of nutrient transporter-related genes ( and ) in the jejunum mucosa of TGEV-infected piglets. Meanwhile, compared with TGEV-infected IPEC-J2 cells, treatment with eugenol reduced the cell cytopathic effect, attenuated the inflammatory response. Interestingly, eugenol did not increase the expression of and in IPEC-J2 cells. However, western blot and immunofluorescence results showed that eugenol restored TGEV-induced down-regulation of ZO-1 and Occludin, while BAY11-7082 (The NF-κB specific inhibitor) enhanced the regulatory ability of eugenol. Our findings demonstrated that eugenol attenuated TGEV-induced intestinal injury by increasing the expression of and , which may be related to the inhibition of signaling pathway. Eugenol may offer some therapeutic opportunities for coronavirus-related diseases.