Ubiquitin promotes Escherichia coli HPI-induced duodenitis through the TLR4/Myd88/NF-κB pathway

Abstract The high-pathogenicity island (HPI), carried by Yersinia pestis , is an essential pathogenic component of the virulence distributed in Escherichia coli (E. coli). As an NF-κB pathway activator, Ubiquitin (Ub) is crucial in the inflammatory response. However, the molecular mechanismsof Ub in the TLR4/Myd88/NF-κB signaling pathway induced by HPI in E. coli is still unclear. In our experiment, Ub was overexpressed usingsmall intestinal epithelial cells (in vitro), and BALB/c mouse models (in vivo) infected with E. coli HPI and analysed by using qPCR, ELISA, immunofluorescence, immunohistochemistry, and H&E staining assays. We demonstrated that E. coli HPI can promote the expression of TLR4, NF-κB, and Ub in. IPEC-J2 cells. Immunofluorescence and Immunohistochemistry analysis revealed that TLR4 and NF-κB key factor in the E. coli HPI group were expressed, and the NF-κB p65 protein translocated to the nucleus. Further research showed that the mRNA expression levels of TLR4, MyD88, NF-κB, IL-1β, and TNF-α were significantly increased in the Ub overexpression group and BALB/c mice group. H&E staining assay showed that Ub overexpression with IPEC-J2 cells have thecharacteristics of elongated, rounded, fragmented, duodenal villi diminished, and the surface was covered with many sloughed necrotic cells, indicating that exacerbating cell damage and duodenitis. Taken together, this study suggested that E. coli HPI can activate NF-κB via increasing the expression of Ub, andUb can exacerbate E. coli HPI-induced duodenitis through the TLR4/MyD88/NF-κB signaling pathway.