P0057 METTL3 potentiates aged CD4+T cell response via programming effector differentiation in elderly ulcerative colitis

Abstract Background The burden of IBD in the elderly is increasing globally. However, the mechanisms underlying the age-related IBD susceptibility remain unclear. Aging leads to a progressive functional decline of the immune system, rendering the elderly increasingly susceptible to inflammatory and autoimmune disease. As a fundamental mRNA modification, N6-methyladenosine (m6A) participates in various pathological processes. However, the role of METTL3-mediated m6A RNA modification in elderly IBD remains unclear. Herein, we sought to determine the role of immunosenescence in age-dependent colitis and to explore the underlying mechanisms. Methods Young (2-3 months), middle-aged (10-12 months), and aged (20-24 months) mice were established models of colitis by 2% dextran sulfate sodium salt (DSS) treatment. We detected the senescence-associated-β-galactosidase (SA-β-Gal) activity in lymphocytes isolated from colon of mice. Single-cell and bulk RNA-seq of colonic immune cells in mice with different ages were performed to investigate the precise molecular mechanisms. CD4+CD25-CD45RBhi T cell adoptive transfer model was used to further analyze the role of senescent CD4+T cells in colitis. Mettl3fl/lfCd4Cre mice were obtained to explicit role of METTL3 in regulating CD4+T cell senescence. Results Ageing increased the severity of DSS-induced colitis. CD4+T cell senescence was implicated in the progression of aging-related experimental colitis, exhibiting an increase of SA-β-Gal and accumulation of CD4+ effector memory T (TEM) cells in colon. Aged colonic CD4+ T cells generate higher levels of IFN-γ and IL-17 comparing to young colonic CD4+ T cells. Single-cell analysis revealed that aging increased colonic CD4+ TEM cells, which were associated with T cell-mediated cytotoxicity and cytokine-mediated signaling pathway. Adoptive transfer of aged CD4+CD25-CD45RBhi T cells to Rag-/- mice induced more severe colitis compared with young CD4+CD25-CD45RBhi T cells transfer. Aged CD4+T potentiates Th1/Th17/Tfh differentiation and exacerbates the progression of colitis. METTL3 was increased in aged colonic CD4+T cells. Inhibiting METTL3 in CD4+T cell protects from cellular senescence, effector differentiation and colitis. Conclusion These results provide a significant insight into the contribution of senescent CD4+ T cells to age-dependent colitis and provide an attractive possibility that targeting T cell specifically might be a potential strategy to treat elderly IBD patients.