IDDF2024-ABS-0244 Fusobacterium nucleatum affects anti-TNF responsiveness through activating NAD+ salvage pathway in ulcerative colitis

<h3>Background</h3> The effect and mechanism of microbiota involvement in the anti-TNF treatment of UC remains to be revealed. <h3>Methods</h3> We collected UC tissues and stool samples. Stool samples were collected to observe the effect of faecal bacteria from NRUC and RUC patients on IFX treatment in mice. Cells incubated with <i>Fn,</i> NAD⁺ inhibitor or NAMPT-targeting siRNA conducted RNA-seq analysis and metabolomics analysis, then the expression of mRNAs, proteins and the contents of NAM, NMN and NAD⁺ were verified. Mice were treated with ABX, fecal bacteria, <i>Fn</i>, DSS, Adezmapimod or FK866 to observe intestinal mucosal injury and pathological changes. <h3>Results</h3> Mice in NR+DSS+IFX group exhibited rapid weight loss, higher DAI, shorter colon size ratio and disruption of mucosal structures than mice treated with DSS+IFX or NR+DSS+IFX. The abundance of <i>Lactobacillus</i> and <i>Fusobacterium</i> in tissues of NR+DSS+IFX group was significantly increased.<i> Fn</i> was abundant in NRUC tissues ((<i>P</i> &lt; 0.01). Compared with control cells, the expression of NAD⁺, NMN, NAM, p-ERK, p-P38 was significantly increased, and the expression of ZO-1 and Occludin was downregulated in cells infected with <i>Fn.</i> These effects were attenuated by exposure to FK866, knockdown of NAMPT. Mice treated with <i>Fn+</i>DSS+IFX developed significantly rapid weight loss, higher DAI, shorter colon size ratio and disruption of mucosal structures, higher content of NAD⁺, NMN, NAM, upregulated expression of NAMPT, p-P38, downregulated expression of ZO-1 and Occludin, higher secretion of IL-6, IL-18 and TNF-α in serum and tissues than mice treated with DSS+IFX,which were attenuated by exposure to Adezmapimod or FK866. <h3>Conclusions</h3> Gut microbiota plays an important role in anti-TNF resistance in UC. We identified that <i>Fn</i> was enriched in NRUC tissues from patients. <i>Fn</i> orchestrates a molecular network involving NAMPT and NAD⁺ slvage pathways to control the responsiveness of anti-TNF therapy in UC. Measuring and targeting<i> Fn</i> and its associated pathways will yield valuable insights into the prevention and treatment for drug resistance of <i>Fn</i> -related UC.