FOXO3 and autoimmune disease: Spermidine exerts a protective role in mouse experimental models of autoimmune diseases, such as multiple sclerosis and psoriasis, by activating the Forkhead box protein O3 (FOXO3) pathway and thus suppressing the production of inflammatory cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-6 (Li et al., 2020).