Zhiyue Wang,1,2,* Bowen Li,1,2,* Liqing Bao,1– 3,* Yu Chen,1,2 Jinhua Yang,1,2 Fangqi Xu,1– 3 Shang Shi,4 Wanlu Chen,2,5 Boding Wang,2,5 Yang Liu1,2 

1Department of Pancreatic and Gastrointestinal Surgery Division, Ningbo No.2 hospital, Ningbo, People’s Republic of China; 2Ningbo Key Laboratory of Intestinal Microecology and Human Major Diseases, Ningbo, People’s Republic of China; 3Department of Cixi Biomedical Research Institute, Wenzhou Medical University, Ningbo, People’s Republic of China; 4Department of Breast Surgery, Ningbo Medical Center Lihuili Hospital, Ningbo, People’s Republic of China; 5Department of Neurosurgery, Ningbo No.2 hospital, Ningbo, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Yang Liu; Boding Wang, Email lyang712@icloud.com; wangboding06@126.com

Background: Inflammatory bowel disease (IBD) is affected by interactions between intestinal microbial factors, abnormal inflammation, and an impaired intestinal mucosal barrier. Neutrophils (NE) are key players in IBD. Fusobacterium nucleatum (F. nucleatum) is reported to contribute to IBD progression. However, the relationship between F. nucleatum, abnormal inflammation, and intestinal barrier impairment should be interpreted to understand the role of F. nucleatum in IBD.
Methods: Dextran sulfate sodium (DSS)-induced colitis model was established and mice were orally administered with F. nucleatum. F. nucleatum colonization was confirmed by fluorescence in situ hybridization (FISH) and PCR. Intestinal barrier impairment was investigated by tight junction protein expression. Immuno-histochemistry (IHC) for Ly6G and flow cytometry detection to measure NE chemotaxis in mouse colon tissues. Caco-2 monolayers were used to evaluate epithelial integrity and permeability in vitro. A transwell model involving caco-2 cells and NE co-culture was used to assess NE chemotaxis. NE chemokines were measured by ELISA. A mouse model of NE exhaustion using an anti-Ly6G antibody was used to identify the role of NEs in F. nucleatum-induced colitis. Transcriptome sequencing and bioinformatics analysis were applied to screen cytokines and signaling pathways.
Results: Administration of F. nucleatum aggravated colitis in the DSS model. F. nucleatum infection downregulates ZO-1 and Occludin expression and increases intestinal permeability. Additionally, F. nucleatum-induced NE chemotaxis decreases the integrity and permeability of the caco-2 monolayer. F. nucleatum-induced NE chemotaxis is dependent on IEC-derived interleukin 8 (IL-8) secretion, mediated by the TLR2/ERK signaling pathway. In addition, NE exhaustion in mice inhibited F. nucleatum-induced intestinal barrier impairment and colitis.
Conclusion: F. nucleatum improves NE chemotaxis by infecting intestinal epithelial cells (IECs) to secrete IL-8 and aggravate intestinal barrier impairment, contributing to the progression of intestinal inflammation. Examining and eliminating F. nucleatum could be a valuable microbiome-based method for IBD surveillance and prevention.

Keywords: inflammatory bowel disease, IBD, Fusobacterium nucleatum, neutrophil chemotaxis, IL-8, intestinal barrier impairment