RORψt⁺CD4⁺T cells promote IL-23R-mediated neuronal cell apoptosis in the central nervous system

Abstract Transcription factors T-bet and RORψt play a crucial role in neuronal autoimmunity, and mice deficient in these two factors do not develop experimental autoimmune encephalomyelitis (EAE). The independent role of T-bet and RORψt in the pathogenesis of EAE and how they help induce apoptosis of neurons in the central nervous system (CNS) during neuronal autoimmunity is unclear. In the present study, we showed that myelin oligodendrocyte glycoprotein (MOG 35-55 ) peptide-specific Th1 cells deficient in RORψt could cross BBB but fail to induce apoptosis of neurons and EAE. Pathogenic Th17 cell-derived cytokines GM-CSF, TNF-α, IL-17A, and IL-21 significantly increase the surface expression of IL-23R on neuronal cells. Furthermore, we showed that, in EAE, neurons in the brain and spinal cord express IL-23R. IL-23-IL-23R signaling in neuronal cells caused phosphorylation of STAT3 (Ser727 and Tyr705) and induced cleaved caspase 3 and cleaved poly (ADP-ribose) polymerase-1 (PARP-1) molecules in an IL-23R-dependent manner and caused apoptosis. Thus, we provided a mechanism where we showed that T-bet is required to recruit pathogenic Th17 cells and RORψt expression to drive the apoptosis of IL-23R + neurons in the CNS and cause EAE. Understanding detailed molecular mechanisms will help to design better strategies to control neuroinflammation and autoimmunity. GRAPHICAL ABSTRACT One Sentence Summary IL-23-IL-23R signaling promotes apoptosis of CNS neurons.