Neural stem cells respond to extracellular succinate via SUCNR1/GPR91 to ameliorate chronic neuroinflammation


Neural stem cell (NSC) transplantation induces recovery in animal models of central nervous system (CNS) diseases, in part by modulating adaptive and innate immune responses. Since metabolism governs the phenotype and function of immune cells, the aim of this thesis was to investigate whether NSCs have the ability to regulate the immunometabolic components underpinning neuroinflammation. Herein I have identified a new mechanism by which transplanted somatic and directly-induced NSCs counteract CNS-compartmentalised chronic inflammation in mice. NSC transplantation reduces the immunometabolite succinate in the cerebrospinal fluid, while decreasing the burden of mononuclear phagocyte (MP) infiltration and secondary CNS damage. Mechanistically, the anti-inflammatory activity of NSCs arises in response to succinate released by inflammatory MPs, which activates succinate receptor 1 (SUCNR1)/GPR91 on NSCs, thus initiating prostaglandin E2 secretion and extracellular succinate scavenging. This work uncovers a succinate-SUCNR1 axis in NSCs that clarifies how stem cells respond to inflammatory metabolic signals to inhibit the activation of pro-inflammatory MPs in the chronically inflamed brain.