Glutamine supplementation improves the activity and immunosuppressive action of induced regulatory T cells in vitro and in vivo

Background: Glutamine is crucial for the activation and efficacy of T cells, and may play a role in regulating the immune environment. This study aimed to investigate the potential role of glutamine in the activation and proliferation of induced regulatory T cells (iTregs). Methods: CD4 + CD45RA + T cells were sorted from peripheral blood mononuclear cells and cultured to analyze iTreg differentiation. Glutamine was then added to the culture system to evaluate the effects of glutamine on iTregs by determining oxidative phosphorylation (OXPHOS), apoptosis, and cytokine secretion. Additionally, a humanized murine graft- versus -host disease (GVHD) model was constructed to confirm the efficacy of glutaminetreated iTregs in vivo . Results: After being cultured in vitro , glutamine significantly enhanced the levels of Foxp3, CTLA-4, CD39, CD69, IL -10, TGF-8, and Ki67 (CTLA-4, IL -10, TGF-8 are immunosuppressive markers of iTregs) compared with that of the control iTregs ( P < 0.05). Furthermore, the growth curve showed that the proliferative ability of glutaminetreated iTregs was better than that of the control iTregs ( P < 0.01). Compared with the control iTregs, glutamine supplementation significantly increased oxygen consumption rates and ATP production ( P < 0.05), significantly downregulated Annexin V and Caspase 3, and upregulated BCL2 ( P < 0.05). However, GPNA significantly reversed the effects of glutamine ( P < 0.05). Finally, a xeno-GVHD mouse model was successfully established to confirm that glutamine-treated iTregs increased the mice survival rate, delayed weight loss, and alleviated colon injury. Conclusion: Glutamine supplementation can improve the activity and immunosuppressive action of iTregs, and the possible mechanisms by which this occurs are related to cell proliferation, apoptosis, and OXPHOS.