Extracellular vesicles of Fusobacterium nucleatum compromise intestinal barrier through targeting RIPK1-mediated cell death pathway

Abstract

Microbial factors that mediate microbes-host interaction in ulcerative colitis (UC), a chronic disease seriously affecting human health, are not fully known. The emerging oncobacterium Fusobacterium nucleatum (Fn) secretes extracellular vesicles carrying several types of harmful molecules in the intestine which can alter microbes-host interaction, especially the epithelial homeostasis in UC. However, the mechanism is not yet clear. Previously, we isolated EVs by the ultracentrifugation of Fn culture media and characterized them as the potent inducer of pro-inflammatory cytokines. Here, we examined the mechanism in detail. We found that in macrophage/Caco-2 co-cultures, FnEVs significantly promoted epithelial barrier loss and oxidative stress damage, which are related to epithelial necroptosis caused by the activation of receptor-interacting protein kinase 1 (RIPK1) and receptor-interacting protein kinase 3 (RIPK3). Furthermore, FnEVs promoted the migration of RIPK1 and RIPK3 into necrosome in Caco2 cells. Notably, these effects were reversed by TNF-α neutralizing antibody or Necrostatin-1 (Nec-1), a RIPK1 inhibitor. This suggested that FADD-RIPK1-caspase-3 signaling is involved in the process. Moreover, the observed effects were verified in the murine colitis model treated with FnEVs or by adoptive transfer of FnEVs-trained macrophages. In conclusion, we propose that RIPK1-mediated epithelial cell death promotes FnEVs-induced gut barrier disruption in UC and the findings can be used as the basis to further investigate this disease.

Fusobacterium nucleatum Acts as a Pro-carcinogenic Bacterium in Colorectal Cancer: From Association to Causality

“…Fourth, like other gram-negative bacteria, F. nucleatum can release extracellular vesicles (EVs) or outer membrane vesicles (OMVs) ( Liu et al, 2019 ; Liu L. et al, 2021 ), which contain a large number of bioactive substances and participate in bacteria-bacteria or bacteria-host cells communications ( Macia et al, 2019 ). By isolating and purifying F. nucleatum (ATCC 23726)-derived EVs, researchers verified that EVs’ surface protein, FomA, could bind to TLR2 on the intestinal epithelial cells and then modulate innate immunity ( Martin-Gallausiaux et al, 2020 ).…”

“…By isolating and purifying F. nucleatum (ATCC 23726)-derived EVs, researchers verified that EVs’ surface protein, FomA, could bind to TLR2 on the intestinal epithelial cells and then modulate innate immunity ( Martin-Gallausiaux et al, 2020 ). F. nucleatum EVs’ can also disrupt the intestinal epithelial barrier by activating the FADD-RIPK1-caspase3 signaling pathway to promote necrosis of intestinal epithelial cells ( Liu L. et al, 2021 ). Furthermore, Engevik et al (2021) used OMVs isolated from F. nucleatum (ATCC 10953) to stimulate colonic epithelial cells and found the production of the proinflammatory cytokines IL-8 and TNF increased.…”

The Fruits of Paris polyphylla Inhibit Colorectal Cancer Cell Migration Induced by Fusobacterium nucleatum-Derived Extracellular Vesicles

“…It has been reported that F. nucleatum -derived EVs induce inflammation via TLR2 pathway in intestinal epithelial cells (IECs), and these effects are similar to those observed with whole F. nucleatum bacteria on IECs [ 29 ]. Other studies also demonstrated that F. nucleatum -derived EVs markedly promoted epithelial barrier loss and oxidative stress in Caco-2 cells [ 30 ] and induced intestinal inflammation [ 31 ]. We first isolated EVs from F. nucleatum and investigated their effect on CRC proliferation.…”

PANoptosis: A New Insight Into Oral Infectious Diseases

“…The results of co-immunoprecipitation studies revealed the interaction between RIPK1 and RIPK3 in F. nucleatum OMVs-treated cells. This was abrogated by anti-TNF-α or Nec-1, indicating that F. nucleatum -OMVs upregulate RIPK1 and RIPK3 and promote formation of the necrosome, ultimately causing necroptosis and impairing epithelial barrier function ( 76 ).…”