Remifentanil protects neurological function of rats with cerebral ischemia-reperfusion injury via NR2B/CaMKIIα signaling pathway

The effects of remifentanil were studied on cerebral ischemia-reperfusion injury (IRI) in rats, and its regulatory effect was explored on the N-methyl D-aspartate receptor subtype 2B (NR2B)/calcium/calmodulin-dependent protein kinase type II subunit alpha (CaMKII) signaling pathway in cerebral tissues. A total of 40 Sprague-Dawley rats were randomly assigned into sham group, model group, low-dose group (remifentanil injected into the caudal veins at 2 μg/kg) and high-dose group (remifentanil injected into the caudal veins at 10 μg/kg). Then, in the model, low-dose and high-dose groups, the rat model of cerebral IRI was established through middle cerebral artery occlusion (namely, ischemia for 1 h and reperfusion for 2 h), while no thread was inserted into the rats in the sham group. Neurological function of rats in each group was evaluated, and the cerebral infarct size was measured using 2,3,5-triphenyltetrazolium chloride (TTC) staining. Moreover, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining was performed to determine the neuronal apoptosis level, and mitochondrial membrane potential was measured via JC-1 assay. Moreover, the reactive oxygen species (ROS) level in neurons and the malondialdehyde (MDA) content in cerebral tissues were determined using 2',7'-dichlorofluorescin diacetate (DCFH-DA) assay and enzyme-linked immunosorbent assay (ELISA), respectively. Finally, the expression levels of apoptosis-associated proteins and the NR2B/CaMKIIα signaling pathway-associated proteins in cerebral tissues were measured by Western blotting. Remifentanil preconditioning substantially decreased the neurological score of rats (p<0.01), cerebral infarct size (p<0.01), neuronal apoptosis level (p<0.01), ROS level in neurons (p<0.01), MDA content (p<0.01) and expression levels of cysteinyl aspartate specific proteinase-3 (Caspase-3), NR2B, phosphorylated CaMKIIα (p-CaMKIIα) and p-cAMP responsive element binding protein (p-CREB) (p<0.01), but it increased the mitochondrial membrane potential (p<0.01) and B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated X protein (Bax) ratio (p<0.01). Remifentanil can repress the NR2B/ CaMKIIα signaling pathway in the neurons of rats with cerebral IRI to decrease the p-CREB expression, ROS level and MDA content in neurons, neuronal apoptosis level and cerebral infarct size, and increase the mitochondrial membrane potential, thereby protecting the neurological function.