The molecular mechanism of EPO regulates the angiogenesis after cerebral is-chemia through AMPK-KLF2 signaling pathway

In this study, the molecular mechanism by which EPO regulates the angiogenesis after cerebral ischemia through AMPK-KLF2 signaling pathway was investigated. Methods: Sixty healthy, male, C57BL/6 mice were randomly divided into three groups of 20 mice: a sham group, the middle cerebral artery occlusion (MCAO) group, and a MCAO+EPO treatment group. The MCAO model was established using a modified ZeaLonga method. Mice in the EPO treatment group were injected with EPO immediately after repalusion (5000 IU/kg), and EPO was injected the following day. The number of mouse deaths and neurologic function scores were recorded during the experiment. On day 7 after cerebral ischemia, brain tissue proteins were extracted. The following proteins expressions were detected by western blot assay: EPO, vascular endothelial growth factor (VEGE), vascular endothelial growth factor receptor (KDR), adenosine activated protein kinase (AMPK), and alpha HIF-1 alpha alpha (HIF-1 alpha), KLF2 and nitric oxide synthase (eNOS). Results: Compared with the MCAO group, the survival rate of mice in the EPO group was significantly improved and neurological function was significantly improved (P < 0.01). Western blot results showed that the content of EPO in brain tissue in MCAO group significantly increased compared with sham group. The content of EPO in the brain tissue of mice in the MCAO+EPO treatment group was significantly higher than in that of the MCAO group, which indicates that EPO increased the content of EPO in mouse brain tissue. Compared with the sham group, the protein expression of vascular endothelial growth factor (VEGE) and its receptor (KDR) in brain tissue of the MCAO group significantly decreased. However, the protein expression of VEGE and its receptor KDR in brain tissue of rats treated with MCAO+EPO was significantly higher than in that of the MCAO group. Thus, in this study, EPO was associated with vascular endothelial differentiation after cerebral ischemia in mice. The results of AMPK and KLF2 showed that the expression levels of AMPK and KLF2 in brain tissues of MCAO group mice significantly decreased compared with the sham group. However, the expression levels of AMPK and KLF2 in brain tissues of mice treated with MCAO+EPO were significantly higher than those in the MCAO group. Thus, EPO can activate AMPK and upregulate the expression of the transcription factor KLF2. The protein expression of HIF-1 alpha in the brain tissue of mice in the MCAO group significantly increased compared with the sham group. However, the expression of HIF-1 alpha in mice brain tissues in the MCAO+EPO treatment group was significantly lower than in that of the MCAO group, indicating that EPO was involved in regulating HIF-1 alpha expression. The eNOS results showed that, compared with Sham group, the protein expression of eNOS in brain tissue of MCAO group mice significantly decreased. In the MCAO+EPO treatment group, the protein expression of eNOS was significantly higher in the brain tissue of the mice than in that of the MCAO group, indicating that EPO was involved in the synthesis of NO and promoted the angiogenesis. Conclusion: EPO promotes VEGE and its receptor (KDR) expression and participates in the regulation of HIF-1 alpha and eNOS protein expression through the activation of AMPK-KLF2 signaling pathways to promote new vascular development after cerebral ischemia.