Decreased OPA1 expression increases neuronal vulnerability to ischaemic stroke during ageing: Role of Timm8b as a therapeutic target.

Abstract

Ischaemic stroke stands as a major global driver of mortality and disability, with advancing age significantly worsening patient outcomes. Mitochondrial impairment plays a pivotal role in both ischaemia-triggered neuronal damage and ageing, yet its precise role in age-related neuronal stroke susceptibility and regulatory mechanisms remains a key unresolved question. To address this, we applied weighted gene coexpression network analysis (WGCNA) to the GSE212336 dataset, identifying 65 mitochondrial genes downregulated with age-most notably OPA1. OPA1 gradually declined with age in murine models and humans, and decreased further post-stroke. Neuronal-specific OPA1 knockout in aged mice with distal middle cerebral artery occlusion (dMCAO) notably worsened mitochondrial cristae disruption, enlarged infarct volumes, and increased neuronal loss. Proteomic analyses showed OPA1 deficiency and ischaemia both reduce Timm8b expression. Timm8b overexpression effectively preserved mitochondrial ultrastructure, mitigated ischaemic damage in heterozygous OPA1-deficient mice while diminished in homozygotes, restored OPA1 dimerization, and alleviated neuronal apoptosis and infarct expansion in aged ischaemic brains. Collectively, this work uncovers a novel regulatory axis: ageing reduces OPA1 and exacerbates ischaemic damage, while Timm8b downregulated by OPA1 depletion protects mitochondria, restores OPA1 function, and reduces ischaemic harm, highlighting Timm8b as a promising therapeutic target for age-related stroke.