Cyclosporine A improves spatial memory following chronic cerebral hypoperfusion in rats by down-regulation of NADPH oxidase 4

Abstract

Objective To investigate the protection effect of cyclosporine A on spatial memory following chronic cerebral hypoperfusion in rats and its possible mechanism. Methods Sixty SD rats were randomly divided into sham operation, vehicle, low-dose cyclosporine A, medium-dose cyclosporine A, and high-dose cyclosporine A groups. A chronic cerebral hypoperfusion model was prepared by permanent bilateral ligation of bilateral common carotid arteries. From 46 days after modeling, olive oil 1 ml/d was used for intragastric administration in the sham-operation group and the vehicle group. Cyclosporine A 3 mg/kg, 6 mg/kg, and 12 mg/kg were administrated intragastrically in the low-dose, medium-dose and high-dose cyclosporine A groups, respectively, once a day for 14 days. The spatial memory was assessed using Morris water maze test. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to detect the expression of NADPH oxidase 4 (NOX4) mRNA in the cerebral cortex. Immunohistochemical staining and Western blot were used to detect the expression of NOX4 protein in the cerebral cortex. Results The Morris water maze test showed that the escape latencies in all cyclosporine A groups were significantly shorter than the vehicle group (all P<0.05). Immunohistochemical staining showed that the percentages of the NOX4-positive cells in the sham-operation, vehicle, low-dose, medium-dose, and high-dose cyclosporine A groups were 4.43%±0.37%, 37.44%±4.76%, 18.05%±2.91%, 12.51%±3.4%, and 11.06%±1.74%, respectively (F=262.021, P<0.001), the vehicle group was significantly higher than the sham-operation group (P<0.01), and all cyclosporine A groups were significantly less than the vehicle group (all P<0.01). RT-PCR showed that the expression levels of NOX4 mRNA in cerebral cortex in the sham-operation, vehicle, low-dose, medium-dose, and high-dose cyclosporine A groups were 0.36±0.03, 1.04±0.04, 0.58±0.02, 0.49±0.01, and 0.40±0.02, respectively (F=1 324.941, P<0.001), all cyclosporine A groups were significantly lower than the vehicle group (all P<0.01). Western blot showed that the expression levels of NOX4 protein in cerebral cortex in the sham-operation, vehicle, low-dose, medium-dose, and high-dose cyclosporine A groups were 0.02±0.01, 0.27±0.04, 0.09±0.02, 0.06±0.02, and 0.06±0.01, respectively (F=222.692, P<0.001), all cyclosporine A groups was significantly lower than the vehicle group (all P<0.01). Conclusion Cyclosporine A may improve spatial memory following chronic cerebral hypoperfusion in rats by down-regulation of NOX4. Key words: Brain Ischemia; Cyclosporine; NADPH Oxidase; Cognition Disorders; Maze Learning; Memory; Neuroprotective Agents; Disease Models, Animal; Rats