TY - JOUR T1 - Neutrophils prevent rectal bleeding in ulcerative colitis by peptidyl-arginine deiminase-4-dependent immunothrombosis JF - Gut JO - Gut SP - 2414 LP - 2429 DO - 10.1136/gutjnl-2021-324725 VL - 71 IS - 12 AU - Moritz Leppkes AU - Aylin Lindemann AU - Stefanie Gößwein AU - Susanne Paulus AU - Dominik Roth AU - Anne Hartung AU - Eva Liebing AU - Sebastian Zundler AU - Miguel Gonzalez-Acera AU - Jay V Patankar AU - Fabrizio Mascia AU - Kristina Scheibe AU - Markus Hoffmann AU - Stefan Uderhardt AU - Christine Schauer AU - Sebastian Foersch AU - Clemens Neufert AU - Michael Vieth AU - Georg Schett AU - Raja Atreya AU - Anja A Kühl AU - Andre Bleich AU - Christoph Becker AU - Martin Herrmann AU - Markus F Neurath Y1 - 2022/12/01 UR - http://gut.bmj.com/content/71/12/2414.abstract N2 - Objective Bleeding ulcers and erosions are hallmarks of active ulcerative colitis (UC). However, the mechanisms controlling bleeding and mucosal haemostasis remain elusive.Design We used high-resolution endoscopy and colon tissue samples of active UC (n = 36) as well as experimental models of physical and chemical mucosal damage in mice deficient for peptidyl-arginine deiminase-4 (PAD4), gnotobiotic mice and controls. We employed endoscopy, histochemistry, live-cell microscopy and flow cytometry to study eroded mucosal surfaces during mucosal haemostasis.Results Erosions and ulcerations in UC were covered by fresh blood, haematin or fibrin visible by endoscopy. Fibrin layers rather than fresh blood or haematin on erosions were inversely correlated with rectal bleeding in UC. Fibrin layers contained ample amounts of neutrophils coaggregated with neutrophil extracellular traps (NETs) with detectable activity of PAD. Transcriptome analyses showed significantly elevated PAD4 expression in active UC. In experimentally inflicted wounds, we found that neutrophils underwent NET formation in a PAD4-dependent manner hours after formation of primary blood clots, and remodelled clots to immunothrombi containing citrullinated histones, even in the absence of microbiota. PAD4-deficient mice experienced an exacerbated course of dextrane sodium sulfate-induced colitis with markedly increased rectal bleeding (96 % vs 10 %) as compared with controls. PAD4-deficient mice failed to remodel blood clots on mucosal wounds eliciting impaired healing. Thus, NET-associated immunothrombi are protective in acute colitis, while insufficient immunothrombosis is associated with rectal bleeding.Conclusion Our findings uncover that neutrophils induce secondary immunothrombosis by PAD4-dependent mechanisms. Insufficient immunothrombosis may favour rectal bleeding in UC.Data are available in a public, open access repository. Data sharing not applicable as no datasets generated and/or analysed for this study. Data are available upon reasonable request. All data relevant to the study are included in the article or uploaded as supplementary information. All data relevant to the study are included in the article or uploaded as supplementary information.RNAseq studies are made available in a public, open access repository (Accession: E-MTAB-10824). Additional data are available upon reasonable request. ER -