Restored microRNA-326-5p Inhibits Neuronal Apoptosis and Attenuates Mitochondrial Damage via Suppressing STAT3 in Cerebral Ischemia/Reperfusion Injury.

Studies have greatly explored the role of microRNAs (miRNAs) in cerebral ischemia/reperfusion injury (CI/RI). But the specific mechanism of miR-326-5p in CI/RI is still elusive. Hence, this study was to unmask the mechanism of miR-326-5p/signal transducer and activator of transcription-3 (STAT3) axis in CI/RI. Two models (oxygen and glucose deprivation [OGD] in primary rat cortical neurons and middle cerebral artery occlusion [MCAO] in Sprague-Dawley rats) were established to mimic CI/RI in vitro and in vivo, respectively. Loss- and gain-of function assays were performed with OGD-treated neurons and with MCAO rats. Afterward, viability, apoptosis, oxidative stress and mitochondrial membrane potential in OGD-treated neurons were tested, as well as pathological changes, apoptosis and mitochondrial membrane potential in brain tissues of MCAO rats. Mitofusin-2 (Mfn2), miR-326-5p and STAT3 expression in OGD-treated neurons and in brain tissues of MCAO rats were detected. Mfn2 and miR-326-5p were reduced, and STAT3 was elevated in OGD-treated neurons and brain tissues of MCAO rats. miR-326-5p targeted and negatively regulated STAT3 expression. Restoring miR-326-5p or reducing STAT3 reinforced viability, inhibited apoptosis and oxidative stress, increased mitochondrial membrane potential and increased Mfn2 expression in OGD-treated neurons. Up-regulating miR-326-5p or down-regulating STAT3 relieved pathological changes, inhibited apoptosis and elevated mitochondrial membrane potential and Mfn2 expression in brain tissues of rats with MCAO. This study elucidates that up-regulated miR-326-5p or down-regulated STAT3 protects against CI/RI by elevating Mfn2 expression.