Abstract: In order to study the molecular mechanism of IPEC-J2 injury induced by Salmonella, we stimulated IPEC-J2 with Salmonella and collected the cells and culture supernatant at pointed times. The expression of tight junction proteins, inflammation-related proteins, cell proliferation-related proteins and the content of lactate dehydrogenase (LDH) were detected by fluorescence quantitative PCR or ELISA to confirm that Salmonella could cause IPEC-J2 damage. We also further explored the regulation of NF-κB/β-catenin signaling pathway in Salmonella induced-IPEC-J2 injury using NF-κB inhibitors and small interference RNA. The results showed that, compared with the control group, the mRNA expression levels of tight junction proteins ZO-1 and Occludin in the Salmonella-infected group were extremely significantly decreased at 6 and 24 h after infection (P<0.01); the production of pro-inflammatory cytokines TNF-α, IL-8, and the release of LDH, were extremely significantly increased at 6, 12 and 24 h after infection (P<0.01), and the mRNA expression of NF-κB p65 was also extremely significantly increased at 1, 3 and 6 h after infection (P<0.01); and the mRNA expression of cell proliferation proteins cyclin D1 and c-Myc significantly decreased at 6, 12 and 24 h after infection (P<0.05), and the mRNA expression of transcription regulatory factor β-catenin was extremely significantly decreased at 24 h after infection (P<0.01). Compared with Salmonella-infected group, the mRNA expression levels of ZO-1 and Occludin in the inhibitor+Salmonella-infected group were extremely significantly increased at 12 and 18 h (P<0.01), while the levels of NF-κB p65, TNF-α, IL-8 and LDH content were extremely significantly decreased at all time points (P<0.01); the levels of β-catenin, cyclin D1 and c-Myc were extremely significantly decreased at each time point in siRNA-β-catenin+Salmonella treatment group (P<0.01), the release of LDH extremely significantly increased at 6 and 12 h (P<0.01), but no significant increase at 18 h after infection (P>0.05). The results showed that Salmonella activated the NF-κB signaling pathway, promoted the production of pro-inflammatory cytokines, and aggravated the IPEC-J2 damage; meanwhile, Salmonella inhibited the β-catenin signaling pathway, decreased the expression of cell proliferation proteins and tight junction proteins, and affected the cell repair, which leads to the imbalance between cell damage and cell repair, and finally presents cell damage. This study revealed the molecular mechanism of IPEC-J2 damage caused by Salmonella from the perspective of NF-κB/β-catenin signaling pathway.

Key words: Salmonella, IPEC-J2, NF-κB signaling pathway, β-catenin signaling pathway