STING Activation in Macrophages and Microglia Drives Poststroke Inflammation: Implications for Neuroinflammatory Mechanisms and Therapeutic Interventions

ABSTRACT Background Monocyte‐derived macrophages and microglia initially adopt an anti‐inflammatory phenotype following stroke but later transition to a pro‐inflammatory state. The mechanisms underlying this phenotypic shift remain unclear. This study investigates the activation dynamics of molecular signaling pathways in macrophages and microglia after stroke. Methods We utilized publicly available single‐cell RNA sequencing datasets to examine the activation dynamics of molecular signaling pathways alongside the pro‐inflammatory phenotype of macrophages and microglia. Male C57BL/6 mice underwent transient middle cerebral artery occlusion (tMCAO), with the STING inhibitor H151 administered to tMCAO mice. Neurobehavioral performance was assessed using rotarod, foot fault, novel object recognition, and water maze tests at 5‐, 7‐, 10‐, and 14‐days post‐stroke. Primary microglia and bone marrow‐derived macrophages were cultured for in vitro experiments. Results Single‐cell sequencing data indicated that the activation of STING and subsequent type I interferon signaling drove the phenotypic shift of microglia and macrophages toward a pro‐inflammatory state in the stroke lesion. Immunostaining demonstrated that the emergence of pro‐inflammatory microglia and macrophages aligned with the activation time course of STING and type I interferon signaling. Continuous phagocytosis by macrophages and microglia led to STING activation, which triggered type I interferon signaling and promoted the phenotypic shift. Inhibition of STING signaling prevented this transition, reduced neuroinflammation, and conferred protection against ischemic stroke. Conclusion These findings elucidated the critical role of STING‐mediated type I interferon signaling in driving post‐stroke neuroinflammation and underscored the potential of STING inhibition as a therapeutic strategy for alleviating neuroinflammatory responses following stroke.