Galectin-3 accelerates the progression of cerebral infarction by regulating the ERK/ROS/BRD4-mediated P2X7R/MerTK balance in microglia

Galectin-3 disrupts microglial P2X7R/MerTK balance after stroke • ERK/ROS/BRD4 axis mediates Gal-3-induced P2X7R upregulation • Gal-3 promotes cGAS-STING inflammation and apoptosis via HIF1α/P2X7R • TD-139 restores P2X7R/MerTK balance and reduces cerebral infarction • Targeting Gal-3 improves motor, cognitive, and grip strength in MCAO rats This study demonstrates that Galectin-3 (Gal3) exacerbates cerebral infarction progression by modulating the P2X7R/MerTK equilibrium in microglia via the ERK/BRD4/HIF1α signaling axis, with reactive oxygen species (ROS) serving as a potential intermediate mediator linking ERK activation to BRD4 upregulation based on prior literature evidence. Single-cell transcriptomic analysis revealed that ischemia drives microglia from a homeostatic state to an activated disease phenotype, and virtual Gal3 knockout predicted corresponding downregulation of BRD4. Using a rat model of cerebral infarction, we found that the Gal3 inhibitor TD-139 significantly reduced infarct volume, promoted M2 polarization of microglia, and improved neurological function in behavioral assays. Mechanistic investigations in BV2 microglia revealed that Gal3 activates ERK1/2, leading to ROS accumulation, BRD4 upregulation, and subsequent HIF1α-mediated P2X7R transcription, while suppressing KLF4 and MerTK. This cascade increased P2X7R expression and suppressed MerTK/KLF4 expression, generating a pro-inflammatory and pro-apoptotic microenvironment. Notably, pharmacological inhibition of Gal3 enhanced efferocytosis and reduced apoptosis, whereas P2X7R blockade exerted similar neuroprotective effects. These findings identify Gal3 as a key regulator of microglial polarization via the experimentally validated ERK/BRD4/HIF1α-P2X7R signaling cascade, where P2X7R activation concurrently triggers cGAS-STING-mediated pro-inflammatory/pyroptotic responses and suppresses the KLF4/MerTK efferocytosis axis. Targeting this regulatory network could provide therapeutic benefits in cerebral infarction by shifting microglia toward the neuroprotective M2 phenotype and facilitating inflammation resolution. Targeting this pathway could provide therapeutic benefits in cerebral infarction by shifting microglia toward the neuroprotective M2 phenotype and facilitating inflammation resolution. Data were analysed using one-way ANOVA followed by Tukey's post-hoc test for multiple comparisons; P < 0.05 was considered statistically significant.