Ornithine decarboxylase supports ILC3 responses in infectious and autoimmune colitis through positive regulation of IL-22 transcription. Ornithine decarboxylase supports ILC3 responses in infectious and autoimmune colitis through positive regulation of IL-22 transcription

Group 3 innate lymphoid cells (ILC3s) are RORγT+ lymphocytes that are predominately enriched in mucosal tissues and produce IL-22 and IL-17A. They are the innate counterparts of Th17. While Th17 lymphocytes utilize unique metabolic pathways in their differentiation program, it is unknown whether ILC3s make similar metabolic adaptations. We employed single-cell RNA sequencing and metabolomic profiling of intestinal ILC subsets to identify an enrichment of polyamine biosynthesis in ILC3s, converging on the rate-limiting enzyme ornithine decarboxylase (ODC1). In vitro and in vivo studies demonstrated that exogenous supplementation with the polyamine putrescine or its biosynthetic substrate, ornithine, enhanced ILC3 production of IL-22. Conditional deletion of ODC1 in ILC3s impaired mouse antibacterial defense against C. rodentium infection, which was associated with a decrease in anti-microbial peptide production by the intestinal epithelium. Furthermore, in a model of anti-CD40 colitis, deficiency of ODC1 in ILC3s markedly reduced the production of IL-22 and severity of inflammatory colitis. We conclude that cell-intrinsic polyamine biosynthesis facilitates efficient defense against enteric pathogens as well as augments autoimmune colitis, thus representing an attractive target to modulate ILC3 function in intestinal disease. Overall design: Untreated (n=2), IL23-stimulated (n=2), putrescine-treated (n=2), and IL-23-stimulated and putrescine-treated (n=2) MNK-3. WT CCR6+ ILC3 (n=2) and ODC1 KO CCR6+ ILC3 (n=2).

3型先天淋巴细胞（Group 3 innate lymphoid cells, ILC3s）是RORγT+淋巴细胞，主要富集于黏膜组织，可分泌白细胞介素22（IL-22）与白细胞介素17A（IL-17A），是辅助性T细胞17（Th17）的先天同源细胞。尽管辅助性T细胞17在分化过程中依赖独特的代谢通路，但目前尚不明确ILC3s是否存在类似的代谢适应性改变。本研究通过对肠道ILC亚群开展单细胞RNA测序（single-cell RNA sequencing）与代谢组学分析（metabolomic profiling），发现ILC3s中多胺生物合成通路显著富集，并聚焦于限速酶鸟氨酸脱羧酶（ornithine decarboxylase, ODC1）。体外与体内实验证实，外源性补充多胺腐胺（polyamine putrescine）或其生物合成底物鸟氨酸，可增强ILC3分泌IL-22的能力。在ILC3s中条件性敲除ODC1，会损伤小鼠对抗鼠柠檬酸杆菌（C. rodentium）感染的抗菌防御能力，该效应与肠上皮细胞分泌抗菌肽水平下降相关。此外，在抗CD40结肠炎模型中，ILC3s缺失ODC1可显著降低IL-22的分泌水平，并缓解炎症性结肠炎的严重程度。综上，细胞内在的多胺生物合成通路既可促进机体有效抵抗肠道病原体感染，又可加剧自身免疫性结肠炎，因此该通路可作为调控肠道疾病中ILC3功能的潜在靶点。实验整体设计：未处理组（n=2）、IL-23刺激组（n=2）、腐胺处理组（n=2）、IL-23联合腐胺处理组（n=2）的MNK-3细胞；野生型CCR6阳性ILC3组（n=2）与ODC1敲除CCR6阳性ILC3组（n=2）。