Microglial Activation Mediates Drp1-Dependent Mitochondrial Fission and Neuronal Apoptosis in a Lipopolysaccharide-Induced Model of Cognitive Dysfunction.

Neuroimmune dysregulation, characterized by microglial overactivation and imbalances in mitochondrial dynamics within the central nervous system represents a core pathological mechanism in postoperative cognitive dysfunction (POCD). This study investigated the neuroinflammation-mitochondrial interaction through the establishment of in vivo and in vitro models using lipopolysaccharide (LPS). Findings indicated that LPS-induced microglial overactivation was associated with marked upregulation of mitochondrial fission proteins, including phosphorylated Drp1 at Ser616, mitochondrial Drp1, and Fis1, along with downregulation of mitofusin-2. These alterations promoted mitochondrial fragmentation in hippocampal neurons, which subsequently led to mitochondrial membrane potential depolarization, adenosine triphosphate depletion, and excessive production of reactive oxygen species. This cascade further activated the intrinsic apoptotic pathway via Bax/Bcl-2 imbalance and caspase-9/3 activation. Conversely, administration of the Drp1 inhibitor Mdivi-1 reduced microglial activation, attenuated inflammatory cytokine levels, restored mitochondrial network integrity and function, inhibited neuronal apoptosis, and ameliorated LPS-induced spatial memory impairment in behavioral assays. These findings indicate that microglial activation-induced mitochondrial fission plays a pivotal role in inflammation-related cognitive impairment. Moreover, they highlight mitochondrial fission as a promising therapeutic target for intervention in POCD.