Expression analysis of TLR signaling pathway genes under lipopolysaccharide-induced and E. coli F17-infected sheep intestinal epithelial cells

Abstract

Escherichia coli (E. coli) F17 is one of the main pathogens causing diarrhea in young livestock. The specific F17 fimbriae and lipopolysaccharide (LPS) in the surface components of E. coli F17 induces immune activation via interacting with the intestinal epithelial cells (IECs)-expressed innate immune toll-like receptors (TLRs) signaling pathway. In this study, the expression patterns of eight canonical genes from the TLR signaling pathway (IL-6, IL-8, IL-1β, TLR4, MyD88, CD14, TNF-α and TRAF6) were analyzed in LPS-induced IECs, E. coli F17-infected IECs and ileum tissue of E. coli F17-infected lambs. The results showed that increased expression levels of all the studied genes were observed following post-LPS-induced and E. coli F17-infected treatment, with TLR4 having the highest up-regulated expression multiple (compared to NC, fold change = 17.94 and 20.11, respectively), and CD14 having the lowest up-regulated expression multiple (fold change = 2.68 and 1.59, respectively), and higher expression levels of all the studied TLR signaling pathway genes were observed in ileum tissue of E. coli F17 antagonistic (AN) lambs than in E. coli F17 sensitive (SE) lambs. Furthermore, when compared to LPS-induced IECs, E. coli F17-infected IECs showed a more pronounced increase in the expression of IL6, TLR4 and TNF-α, indicating the different roles of these genes in the IECs resistance to E. coli F17 infection. Our results demonstrate that the TLR signaling pathway likely promotes immune activation and provide the first evidence that TLRs have a significant potential to protect against E. coli F17 infections.

Keywords:

• Toll-like receptors signaling pathway
• Escherichia coli F17
• lipopolysaccharide
• intestinal epithelial cell

Ethics approval

The animal study was reviewed and approved by Experimental Animal Welfare 226 and the Ethical Institute of Animal Science, Yangzhou University (No: NFNC2020-NFY-6). All lamb experimental procedures were performed in accordance with the Regulations for the Administration of Affairs Concerning Experimental Animals approved by the State Council of the People’s Republic of China.

Disclosure statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Conceptualization: Ren ZM, Chen WH, Tesfaye G, Joram MM, Aynalem H and Sun W; Data curation: Ren ZM and Chen WH; Formal analysis: Ren ZM and Chen WH; Supervision: Sun W; Writing – original draft: Ren ZM; Writing – review and editing: Ren ZM, Chen WH and Sun W; Funding acquisition: Sun W. All authors read and approved the final manuscript.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China-CGIAR [32061143036], National Natural Science Foundation of China [31872333, 32172689], Major New Varieties of Agricultural Projects in Jiangsu Province [PZCZ201739], Key Research and Development Plan (modern agriculture) in Jiangsu Province [BE2018354] and Jiangsu Agricultural Science and Technology Innovation Fund [CX (18)2003].