Sphingosine-1-phosphate drives astrocyte pyroptosis via activation of NLRC4 inflammasome in autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by deficits in social communication and cognitive functioning. Emerging evidence suggests that abnormal neuroinflammatory responses play a critical role in ASD pathogenesis. Our previous research studies have shown significantly elevated serum levels of Sphingosine-1-phosphate (S1P) in ASD patients, which correlate with clinical phenotypes. Given the key role of S1P in glial cells, we investigated its involvement in pyroptosis-related neuroinflammatory pathways. Mendelian randomization analysis revealed a genetic link between the pyroptosis-associated regulator CD122 and ASD risk. Consistent with this focus, blood samples from ASD patients showed elevated levels of key pyroptotic executioners (Caspase-1, GSDMD) and their downstream pro-inflammatory products (IL-1β, IL-18), confirming enhanced pyroptotic activity. In the BTBR mouse model, a validated ASD model, astrocytes exhibited increased expression of pyroptosis-related proteins and inflammatory cytokines, which were reversed following S1P depletion. Furthermore, hippocampal injection of S1P in wild-type mice induced astrocytic pyroptosis, confirming its direct pro-inflammatory effect. Mechanistic investigations identified NLRC4 as a key inflammasome component upregulated in astrocytes of BTBR mice. Suppression of Nlrc4 ameliorated cognitive deficits and social impairments in BTBR mice. Using astrocyte-specific Nlrc4 knockout models and in vitro assays, we demonstrated that S1P promotes astrocytic pyroptosis through NLRC4 activation, with ERK signaling identified as a critical downstream mediator in this process. These findings reveal a novel S1P-NLRC4-pyroptosis signaling axis in astrocytes that contributes to ASD-associated neuroinflammation, providing a potential molecular basis for targeted clinical intervention.