Mechanism Of Fusobacterium Nucleatum Activating ERS Pathway In The Development Of Crohn's Disease

Objective:there is increasing evidence that members of the intestinal flora,especially F.nucleatum,are associated with crohn's disease?CD?,but the specific mechanism by which F.nucleatum promotes CD development is not clear.This study will explore the mechanism of the activation of the ERS signaling pathway by F.nucleatum in the generation of CD.Methods:we first examined nucleolus abundance and its effect on CD disease activity,and explored whether nucleolus abundance increased intestinal inflammation and facilitated destruction of the intestinal mucosal barrier in vitro and in vivo.Select the same months of raw C57 male mice were randomly divided into normal control group?group C?,dextran sodium sulfate?DSS?,with F.nucleatum infection group?Fn?,with F.nucleatum+dextran sodium sulfate group?Fn+DSS group?and F.nucleatum+dextran sodium sulfate+4-PBA group?Fn+DSS+4-PBA group?,6 mice in each group.All mice were fed 2 mg/ml streptomycin in their drinking water for 3 days to ensure a consistent routine microbiome.In the Fn group,the Fn+DSS group,and the Fn+DSS+4-PBA group,clostridium nucleophilus?10⁹CFU/ml?was injected once daily through gavage for two weeks.In the Fn+DSS+4-PBA group,mice were intraperitoneally injected with 4-PBA at a dose of 100 g per mouse every 3 days,and then gavage with clostridium nucleophilus?10⁹CFU/ml?for 2 weeks one hour after4-PBA inoculation.To induce colitis,3%?wt/vol?DSS was added to the drinking water of the mice.Once a day,animal weight,water and food consumption,morbidity,fecal consistency,and the presence of large amounts of blood in feces or anus were measured or observed.On day 7 after induction with DSS,the animals were rapidly euthanized by inhalation of CO₂,the colon and cecum were rapidly separated,the colon was photographed and used for length measurements,and feces and blood were gently removed with 4°C PBS.A small portion of the colon was immobilized in paraformaldehyde for histological staining?H&E?and fluorescence in situ hybridization?FISH?,and another portion was immediately frozen in liquid nitrogen for PCR or Western blot analysis.Results:clostridium nucleophilus enriched CD tissue in 41.21%of patients,and was associated with CD clinical course,clinical activity and refractory behavior?P<0.05?.In addition,mice treated with Fn+DSS+4-PBA showed slower weight loss and lower disease activity index.Mice treated with Fn+DSS+4-PBA showed lower levels of BIP and XBP1 and higher levels of zo-1 and Occludin in the inflammatory tissues.The histological score of Fn+DSS was significantly higher than that of mice treated with 4-PBA.F.ucleatum infection is involved in CD development and activates the ER stress?ERS?pathway to promote destruction of the intestinal mucosal barrier.In mechanism,F.nucleatum up-regulates CARD3 to activate the ERS pathway,and promotes F.nucleatum-mediated mucosal barrier damage in vivo and in vitro.Conclusion:F.ucleatum coordinates molecular networks involving CARD3 and ERS to control the CD process.Measurement and targeting of F.nucleatum and related pathways will provide valuable insights into the prevention and treatment of CD.