P0052F.nucleatum remodels glycerophospholipid metabolism to activate immunogenic intestinal dendritic cells in Crohn’s pathogenesis

Background Crohn’s disease is driven by gene–microbiota–immune crosstalk. Fusobacterium nucleatum, enriched in patients, stimulates myeloid dendritic cells (DCs) to exacerbate colitis, but how remains obscure. DC activation depends on metabolic reprogramming; glycerophospholipid imbalance is central to IBD. Phosphatidylcholine (PC) is hydrolyzed to lysophosphatidylcholine (LysoPC) by phospholipase A1, encoded by PLA1A, whose expression rises in IBD. Resultant PC remodeling fuels DC immunogenicity and T-cell priming. Whether F. nucleatum exploits PLA1A-mediated PC remodeling to activate DCs and worsen colitis is unknown. Methods Colon/fecal 16S rRNA from CD patients and controls quantified F. nucleatum; DSS colitis and GM-CSF/IL-4 bone-marrow-DCs were used for in-vivo/in-vitro modeling. UPLC-MS/MS untargeted metabolomics plus MSEA mapped PC/LysoPC glycerophospholipid shifts. IL-1β, IL-6, TNF-α, IFN-γ and PLA1A were profiled by WB/qPCR; LysoPC quantified with ELISA, immunogenic DCs by flow, co-localization by IF. DESeq2 identified differential genes; two-tailed t-test or ANOVA with GraphPad Prism 10.0 plotted results. Results 16S rRNA profiling of CD fecal and mucosal samples showed elevated F. nucleatum, prompting DSS-colitis mice gavaged with the bacterium. IF/FISH confirmed F. nucleatum–DC co-localization; these mice lost more weight, displayed higher histology and DAI scores, and released more colonic IL-1β, IL-6, TNF-α and IFN-γ. Flow cytometry revealed an expanded immunogenic DC fraction in lamina propria and in BMDCs co-cultured with F. nucleatum. Untargeted metabolomics and RNA-seq of infected BMDCs intersected at glycerophospholipid and sphingomyelin pathways, with glycerophospholipid metabolism most enriched. F. nucleatum shifted the PC/LysoPC balance toward LysoPC, an effect mirrored by ELISA and accompanied by up-regulation of PC-hydrolyzing enzymes, especially PLA1A, corroborated in public IBD datasets. Pharmacologic blockade of PLA1A with MAFP in vitro restored PC levels, curtailed LysoPC accumulation, reversed the immunogenic DC surge, and attenuated cytokine release. In DSS-colitis mice, MAFP together with F. nucleatum lessened weight loss, DAI, colon shortening, histopathology scores, colonic cytokines and immunogenic DC expansion. Thus, F. nucleatum drives PC remodeling via PLA1A, generating LysoPC that licenses immunogenic DC differentiation and intensifies colitis; targeting this lipid loop offers a therapeutic avenue. Conclusion: F.nucleatum promotes the synthesis of LysoPC by upregulating the expression of PLA1A, thereby leading to the differentiation of immunogenic DCs and the secretion of inflammatory factors, ultimately exacerbating intestinal inflammation. Conflict of interest: Ms. Wang, Jiayun: No conflict of interest Zhang, Hongjie: No conflict of interest Zhao, Xiaojing: No conflict of interest Wang, Shu: No conflict of interest