Mitochondrial complex III-derived ROS amplify immunometabolic changes in astrocytes and promote dementia pathology.

Neurodegenerative disorders alter mitochondrial functions, including the production of reactive oxygen species (ROS). Mitochondrial complex III (CIII) generates ROS implicated in redox signalling, but its triggers, temporal dynamics, targets and disease relevance are not clear. Here, using site-selective suppressors and genetic manipulations together with live mitochondrial ROS imaging and multiomic profiling, we show that CIII is a dominant source of ROS production in astrocytes exposed to neuropathology-related stimuli. Astrocytic CIII ROS production is dependent on nuclear factor-κB and the mitochondrial sodium-calcium exchanger (NCLX) and causes oxidation of select cysteines within immune- and metabolism-associated proteins linked to neurological disease. CIII ROS amplify metabolomic and pathology-associated transcriptional changes in astrocytes, with STAT3 activity as a major mediator, and facilitate neuronal toxicity. Therapeutic suppression of CIII ROS in mice decreases dementia-linked tauopathy and neuroimmune cascades and extends lifespan. Our findings establish CIII ROS as an important immunometabolic signal transducer and tractable therapeutic target in neurodegenerative disease.