FPR2/ALX stimulation modulates microglia and natural killer cells to restrict autoimmune astrocytopathy

Autoantibody- and complement-mediated cytotoxicity can cause autoimmune astrocytopathy that leads to CNS inflammatory demyelination. Formyl peptide receptor 2 (FPR2/ALX) governs the activation and propagation of immune response. However, the precise role of FPR2/ALX in neuroinflammation and the effect of FPR2/ALX stimulation on autoimmune astrocytopathy are poorly understood. Using a mouse model of autoimmune astrocytopathy induced by AQP4-IgG- and complement-mediated cytotoxicity, we found that the stimulation of FPR2/ALX with the small-molecule agonist Quin-C1 led to reduced brain lesion volume, astrocyte loss and demyelination. This was accompanied by enhanced anti-inflammatory activity of microglia and reduced infiltration of lymphocytes in the brain. FPR2/ALX stimulation also led to increased phosphorylation of SYK and AKT in mice with autoimmune astrocytopathy. Notably, the benefits of FPR2/ALX stimulation were attenuated in mice with autoimmune astrocytopathy after microglial depletion using the CSF1R inhibitor PLX5622 or natural killer (NK) cell depletion using an anti-NK1.1 monoclonal antibody. Additionally, the protective effects of FPR2/ALX stimulation were diminished in mice with autoimmune astrocytopathy that received the SYK inhibitor R406. Collectively, our findings demonstrate that FPR2/ALX stimulation may represent a promising therapeutic strategy to attenuate detrimental neuroinflammation in autoimmune astrocytopathy by modulating microglia and NK cells. FPR2/ALX stimulation suppresses autoimmune astrocytopathy: Using a mouse model of autoimmune astrocytopathy, we demonstrated that FPR2/ALX stimulation with the small molecule Quin-C1 reduces the CNS infiltration of lymphocytes and augments the anti-inflammatory activity of microglia, leading to attenuated astrocyte pathology induced by AQP4-IgG and complement-mediated attacks. Mechanistically, the benefits of FPR2/ALX stimulation using Quin-C1 involve microglia, natural killer (NK) cells, and SYK-AKT signaling.