Disruption of the Pum2 axis Aggravates neuronal damage following cerebral Ischemia-Reperfusion in mice☆

Stroke remains a leading cause of disability and mortality worldwide, with mitochondrial dysfunction closely linked to ischemic injury. This study explores the Norad-Pum2-Mff axis as a key regulator of mitochondrial function following ischemia-reperfusion (I/R) injury. Using an oxygen-glucose deprivation/reoxygenation (OGD/R) model, Mff protein levels were significantly elevated post-OGD/R, while mRNA levels remained unchanged, suggesting post-transcriptional regulation. Pumilio2 (Pum2), an RNA-binding protein, was shown to inhibit Mff translation, while Norad, a long non-coding RNA, sequestered Pum2, alleviating this inhibition. We observed decreased Pum2 levels and binding capacity to Mff mRNA, alongside increased Norad levels and binding to Pum2 in neurons after OGD/R. Overexpression of Pum2 in neurons reduced Mff levels, mitigated mitochondrial fragmentation, and alleviated neuronal injury. In a mouse model of middle cerebral artery occlusion/reperfusion (MCAO/R), Pum2 overexpression further improved mitochondrial morphology, reduced infarct volume, and enhanced neurobehavioral recovery. These findings suggest that targeting the Norad-Pum2-Mff axis could provide a promising therapeutic strategy for ischemic stroke by restoring mitochondrial function and reducing neuronal damage.