Inhibition of MiRNA-125b Decreases Cerebral Ischemia/Reperfusion Injury by Targeting CK2α/NADPH Oxidase Signaling

Cerebral ischemia-reperfusion (I/R) injury involves multiple independently fatal terminal pathways. CK2α/NADPH oxidase is an important signaling pathway associated with ischemia-reperfusion injury, and miR-125b can regulate oxidative stress-related injury. In this study, we investigated whether the effect of miR-125b in rat brain I/R injury occurs through its modulation of the CK2α/NADPH oxidase pathway.

Rats were subjected to 2 h of cerebral ischemia followed by 24 h of reperfusion to establish an I/R injury model. Neurological deficit was evaluated using a five-point score. Infarct volume was evaluated with 2, 3, 5-triphenyltetrazolium chloride (TTC) staining, and RT-PCR was used to detect expressions of miR125b and CK2α. We then examined the association between miR-125b expression and the CK2α/NADPH oxidative signaling pathway in a PC-12 cell oxygen-glucose deprivation and reoxygenation (OGD/R) injury model. Transfection with miR-125b mimics, an miR-125b inhibitor, and luciferase reporter gene plasmid was accomplished using commercial kits. In these cells, Western blots were used to detect the levels of expression of CK2α, cleaved caspase-3, NOX2, and NOX4. RT-PCR was used to detect the expressions of CK2α, miR125b, NOX2, and NOX4. We evaluated Lactate Dehydrogenase (LDH) level, NADPH oxidase activity, and caspase-3 activity using commercial kits. Mitochondrial reactive oxygen species (ROS) were measured by fluorescence microscopy. For both PC-12 cells and rat brains, histological analyses were conducted to observe morphological changes, and apoptosis was measured using a commercial kit.

I/R rats exhibited an increase in neurological deficit score, infarct volume, and cellular apoptosis, along with miR-125b elevation and CK2α downregulation. OGD/R treatment increased PC-12 cells' injuries, cellular apoptosis, and ROS levels. These changes were associated with miR-125b elevation, CK2α downregulation and activations of NOX2 and NOX4, mimicking our in vivo findings. All of these effects were reversed by the inhibition of miR-125b, confirming a strong correlation between miR-125b activity and the CK2α/NADPH oxidase signaling pathway.

Based on these observations, we conclude that inhibition of miR-125b protects the rat brain from I/R injury by regulating the CK2α/NADPH oxidative signaling pathway.