Hyperbaric Oxygen Attenuates Cerebral Ischemia–Reperfusion Injury Through ROS-Dependent Remodeling of Microglial Mitochondrial Dynamics

Hyperbaric oxygen (HBO) shows neuroprotective potential in cerebral ischemia–reperfusion (CIR) injury, but its variable efficacy suggests that the underlying cellular mechanisms remain incompletely defined. We previously showed that HBO suppresses microglial NLRP3 inflammasome activation after CIR injury in a reactive oxygen species (ROS)-dependent manner; yet, how ROS couples to this effect remains unclear. Since mitochondria regulate ROS and inflammasome signaling, we investigated whether HBO modulates microglial mitochondrial dynamics in CIR injury. In adult male ICR mice (n = 71, 8–12 weeks) subjected to 60 min middle cerebral artery occlusion followed by 24 h reperfusion, HBO improved neurological function, reduced infarct area, and decreased ASC-positive microglia/macrophages. In lipopolysaccharide/nigericin-stimulated primary microglia, HBO suppressed IL-1β release, reduced mitochondrial fragmentation, preserved mitochondrial membrane potential, maintained mitofusin 2 (MFN2) protein level, and reduced DRP1 Ser616 phosphorylation without altering total DRP1 or FIS1 expression. MitoTEMPOL abolished HBO-mediated protection against mitochondrial fragmentation, MFN2 reduction, and DRP1 Ser616 phosphorylation in vitro. Edaravone, when combined with HBO, attenuated HBO-mediated neuroprotection and counteracted HBO-induced regulation of MFN2 and DRP1 Ser616 phosphorylation in vivo. These findings support ROS-dependent remodeling of microglial mitochondrial dynamics as a mechanism contributing to HBO-mediated suppression of inflammasome-associated inflammation after CIR injury.