Mechanisms of vascular endothelial growth factor receptor 2 expression regulation by erythropoietin in a premature rat model of periventricular white matter damage

Abstract

Objective To explore the mechanisms of vascular endothelial growth factor receptor 2 (VEGFR2) expression regulated by recombinant human erythropoietin (rh-EPO) in a premature rat model of periventricular white matter damage. Methods Sprague-Dawley rats aged three days were randomly divided into five groups: sham group without hypoxia-ischemia (HI), HI group (HI with saline administration), HI+erythropoietin (EPO) group, HI+erythropoietin receptor (EPOR) antagonist group and HI+EPO+EPOR antagonist group. Rat pups were either subjected to permanent ligation of the right common carotid artery and 6% O2+94% N2 for two hours (HI) or sham operated and exposed to normal air (sham). After the operation, rats in the HI+EPOR antagonist and HI+EPO+EPOR antagonist groups received a single intraventricular injection of EPOR antagonist (5 μl). Four hours after the operation, rats in the HI+EPO and HI+EPO+EPOR antagonist groups received a single intraperitoneal injection of rh-EPO (5 U/g). Western-blot was performed to detect EPOR, phosphorylated EPOR (p-EPOR), extracellular regulated protein kinases (ERK) and phosphorylated ERK (p-ERK) at 60 and 90 minutes after the models were established successfully, and also used to analyze the expression of VECFR2 on day 2 and 4. Analysis of variance and SNK test were used as statistical methods. Results At 60 and 90 minutes after model establishment, the expression of EPOR protein in rat brain tissues was increased in HI (1.717±0.206 and 1.416±0.242), HI+EPO (2.557±0.222 and 2.111±0.159) and HI+EPO+EPOR antagonist (1.547±0.170 and 1.452±0.250) groups as compared with that in sham group (1.095±0.182 and 0.751±0.136), that in HI+EPO group was higher than that in HI and HI+EPO+EPOR antagonist groups, and that in HI+EPOR antagonist group (1.088±0.160 and 1.020±0.174) was lower than that in HI group. All differences were statistically significant (F=30.154 and 20.265, both P 0.05). Conclusions ERK signaling pathways will be affected by EPO binding to EPOR. As a result, VEGFR2 expression was increased leading to enhanced angiogenesis in a premature rat model of periventricular white matter damage. Key words: Leukomalacia, periventricular; Infant, premature, diseases; Erythropoietin; Vascular endothelial growth factor receptor-2; Disease models, animal