Aberrant neuronal excitation promotes neuroinflammation in the primary motor cortex of ischemic stroke mice.

Current treatments for ischemic stroke aim to achieve rapid reperfusion with intravenous thrombolysis and/or endovascular thrombectomy, which have proven to attenuate disability. Despite the significant progress in reperfusion therapies, functional recovery remains inconsistent, primarily due to ongoing neuronal excitotoxicity and neuroinflammation. In this study we investigated the relationship between neuronal activity and neuroinflammation in an ischemic mouse model using chemogenetic techniques. MCAO cerebral ischemia model was established in mice; in vitro oxygen-glucose deprivation/reoxygenation (OGD/R) was established in PC12 neurons. By measuring c-Fos expression, we showed that MCAO caused the activation of both excitatory and inhibitory neurons within the M1 primary motor cortex, which subsequently induced reactive activation of local microglia through the secretion of unique neuronal extracellular vesicles (EVs). Chemogenetic inhibition of abnormal neuronal activity in stroke-affected cortical neurons reversed microglia activation and reduced neuronal apoptosis. By analyzing the miRNAs in EVs from the ischemic M1 cortex, we found that miR-128-3p was significantly downregulated in ischemia-challenged neurons and their EVs, leading to neuronal injury and proinflammatory polarization of microglia. Intravenous injection of miR-128-3p mimics significantly improved neuronal survival, reduced neuroinflammation accompanied by better functional recovery after ischemic stroke. In summary, stroke-induced abnormal neuronal activity reduces miR-128-3p levels in ischemic neurons and EVs, leading to increased microglia activation and neuronal injury after a stroke. The study highlights that inhibiting abnormal neuronal activity or delivering miR-128-3p-enriched EVs as novel methods for stroke treatment.