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Ferroptosis has recently emerged as an iron-dependent form of nonapoptotic cell death, which is also a regulated necrosis process and a response to tumor suppression. However, whether ferroptosis is involved in ulcerative colitis (UC) is unknown. The aims of this study were to investigate whether the ferroptosis is involved in UC, particularly intestinal epithelial cell (IEC) death, and to analyze the effect of the nuclear factor kappa Bp65 subunit (NF-κBp65) on ferroptosis. The gene expression of ferroptosis-related proteins was assessed in intestinal mucosal samples from human UC. The experimental model of UC was induced with dextran sulfate sodium (DSS). Ferroptosis of IECs was evaluated, the effect of NF-κBp65 on ferroptosis was analyzed by using IEC-specific NF-κBp65-deleted mice (p65IEC-KO), and the ferroptosis signaling pathway was investigated in vitro and in vivo. The results showed that ferroptosis was significantly induced in the IECs from UC patients and mice with colitis, and the ferroptosis was mediated by endoplasmic reticulum (ER) stress signaling. The specific deletion of IEC NF-κBp65 clearly upregulated ferroptosis and exacerbated colitis, and the result showed that phosphorylated-NF-κBp65 significantly inhibited ER stress signaling by directly binding eukaryotic initiation factor 2α. These data indicate that ferroptosis contributes to UC via ER stress-mediated IEC cell death, and that NF-κBp65 phosphorylation suppresses ER stress-mediated IEC ferroptosis to alleviate UC. The results suggest that ferroptosis involves in IEC death in UC, NF-κBp65 play a critical role in the ferroptotic inhibition, and ferroptosis is a potential therapeutic target for UC.

Background: Mucosal epithelial apoptosis with non-specific inflammation is an essential pathological characteristic in portal hypertensive gastropathy (PHG). However, whether a coordinated crosstalk between myeloid cells and epithelial cells involved in PHG remains unclear. Methods: Gastric injury and mucosal apoptosis were examined in patients with PHG and the PHG model of p65ΔM/ΔM (myeloid cells specific NF-κBp65 deletion) and p65f/f (floxed p65) mice, PUMA-WT (PUMA wild-type) and PUMA-KO (PUMA knockout) mice. The interaction of IL-6, Fas, FasL, NF-κBp65 and PUMA expression was investigated, and the mechanisms underlying IL-6-regulated gastric epithelial apoptosis were analysed. Findings: IL-6, which is induced in the mucosa of PHG patients and mice, promotes FasL production via enhancing NF-κBp65 activation in myeloid cells, while blockage of IL-6 signaling by Tocilizumab or deletion of NF-κBp65 in myeloid cells attenuates the inflammatory response and Fas/FasL-mediated epithelial apoptosis in PHG. IL-6-driven FasL from myeloid cells combines with epithelial Fas receptor to encourage NF-κBp65/PUMA-mediated epithelial apoptosis in PHG, and inhibition of NF-κBp65 or knockout of PUMA dramatically alleviates Fas/FasL network-mediated epithelial apoptosis in PHG. Interpretation: These results indicate that IL-6 drives FasL generation via NF-κBp65 in myeloid cells to promote Fas/NF-κBp65/PUMA-mediated epithelial apoptosis in PHG. Funding: This work was supported by grants from the National Natural Science Foundation of China (U1501224, 81700536), the Natural Science Foundation Team Project of Guangdong Province (2018B03031200), the Science and Technology Developmental Special Foundation of Guangdong Province (2017B020226003), the Basic Research Programme of Young Teachers' Training Project of Sun Yat-sen University (17ykpy51), the Science and Technology Planning Projects of Guangzhou City (201604020118, 201604020002). Declaration of Interest: The authors declare that there are no conflicts of interest. Ethical Approval: The study protocol and the acquisition of the tissue samples were approved by the Institutional Review Board of The Third Affiliated Hospital of Sun Yat-Sen University.