Neuroprotective effects of erythropoietin and carbamylated erythropoietin on focal cerebral ischemia

Abstract

Objective To study the neuroprotective effect and the mechanism of carbamylated erythropoietin (CEPO) on ischemic brain injury, and compare it with erythropoietin (EPO). Methods Focal cerebral ischemia/reperfusion models were induced by occlusion of the middle cerebral artery using the intraluminal filament technique. Four groups (control group, EPO 5 μg/kg treatment group, EPO 50μg/kg treatment group and CEPO 50 μg/kg treatment group) were chosen (n=6). The cerebral blood flow was monitored through a Laser-Doppler flow probe. The slices of brain tissue were stained with cresyl-violet and the cerebral volume of infarction and edema was measured by ImageJ software. The apoptotic cells were detected with TUNEL staining. The inducible NO synthase (iNOS) positive cells were observed by immunohistochemistry. Results Compared with the control group, the EPO 50 μg/kg treatment and CEPO 50 μg/kg treatment groups showed significantly decreased infarct and edema volume, and lower scores of national institutes of health stroke scale. The numbers ofiNOS positive cells in the ischemic cortex of the EPO 50 μg/kg treatment and CEPO 50 μg/kg treatment groups were statistically smaller than those of the control group (P＜0.05). The numbers of apoptotic cells in the ischemic cortex ofthe EPO 50 μg/kg treatment and CEPO 50 μg/kg treatment groups ([43.6±10.1] cells,[40.5±9.8] cells) were obviously smaller than those of the control group ([94.2±15.2] cells, P＜0.05).Conclusion Lower dose of EPO (5 μg/kg) has no brain protective effect. Treatment with CEPO 50μg/kg and EPO 50 μg/kg have equal roles in increasing the cerebral blood flow, decreasing the neurological deficit scores and volume of infarct and edema, and boosting the anti-apoptosis by means of inhibiting the expression of iNOS. Key words: Erythropoietin; Carbamylated erythropoietin; Cerebral ischemia; Reperfusion; Inducible NO synthase