Metabolic Dysfunction Governs Regulatory T Cell Inflammatory Response during Inflammatory Bowel Disease

Abstract Background Significant proportion of inflammatory bowel disease (IBD) patients respond inconsistently to therapies, underscoring disease complexity. Interleukin 21 (IL21) is highly expressed during IBD. In addition to T helper (Th) cells, inflammatory regulatory T cells (Tregs) have been linked to refractory IBD. Thus, we explored the metabolic role of IL21 in inducing Treg dysfunction and IBD. Methods Human Tregs and Th cells were subjected to transcriptional profiling and metabolic phenotyping. Colitis was induced in Rag1−/− mice by naïve CD4 T cell adoptive transfer. Results IL21 stimulation of human Tregs induced glycolysis and OXPHOS. In agreement, IL21 enhanced the expression of genes associated with glycolysis, anabolism, and OXPHOS, leading to inflammatory cytokine production. Mechanistically, we found disruption to mitochondrial integrity with concomitant activation of glycogen synthase kinase 3 (GSK3) β, a kinase known to prevent mitochondrial pyruvate metabolism. IL21-induced GSK3β activation was accompanied by pyruvate and lactate buildup. Notably, GSK3 inhibition or supplementation with membrane-permeable methyl pyruvate abrogated metabolic wiring of and inflammatory responses by IL21-stimulated Tregs and effector Th cells. These results suggest that impaired mitochondrial pyruvate metabolism is a feature of inflammatory CD4 T cells. Lastly, GSK3 inhibition prevented pathogenic CD4 T cell-induced colitis in mice, as evidenced by reduced Mouse Colon Histology Index and serum inflammatory cytokines. Conclusions IL21 engages Tregs in a hypermetabolic state that augments inflammatory cytokine production. Therefore, desensitizing CD4 T cells to IL21 may also augment Treg function during IBD. Supported by NIDDK award K01DK124358, the Center for Cell Signaling in Gastroenterology (P30DK084567), and the Mayo Clinic Center for Biomedical Discovery.