Neuroprotective effect of nicorandil in mice under deep hypothermic low flow

Objective To investigate the neuroprotective effect and possible mechanism of nicorandil in mice under deep hypothermic low flow (DHLF). Methods A total of 105 3-week-old male C57/BL-6 mice were randomly divided into 7 groups: sham operation, model, nicorandil (5, 10, and 20 mg/kg), nicorandil 20 mg/kg+ LY294002, and LY294002 groups (n=15 in each group). A DHLF model was induced. At 24 h after reperfusion, the brain tissues of mice were taken out for HE and TUNEL staining. The pathological changes of cerebral cortical neurons and apoptosis were observed. Western blot was used to detect the expression levels of the total Akt, phospho-Akt (p-Akt), Bcl-2, and Bax. Results HE pathological staining showed that cortical neuronal injury was reduced, the phenomena of cell membrane depression, nuclear condensation, concentrated dye, and the blurring of the nucleus were decreased significantly in nicorandil group. The morphology of neurons was basically restored to normal. TUNEL staining showed that the apoptosis index in various dose groups of nicorandil was decreased significantly compared with the model group (all P<0.05). Western blot analysis showed that the expression levels of p-Akt and Bcl-2 proteins increased significantly in various dose groups of nicorandil compared with the model group (all P<0.05), and the expression level of Bax protein was decreased significantly (all P<0.05). After adding the phosphatidylinositol 3-kinase (PI3K) specific inhibitor LY294002, there was no significant difference in neurons pathological injury in the cortex compared with the model group. There was no significant difference in the apoptosis index, and the expression levels of p-Akt, Bcl-2, and Bax compared with the model group. Conclusions Nicorandil has a certain neuroprotective effect in mice under DHLF. Its mechanism may be associated with the activation of PI3K/Akt signaling pathway, and then further regulation of the downstream protein Bcl-2 and Bax expression. Key words: Brain Ischemia; Reperfusion Injury; Hypothermia, Induced; Nicorandil; Apoptosis; Proto-Oncogene Proteins c-bcl-2; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; bcl-2-Associated X Protein; Neuroprotective Agents; Mice