Effect of erythropoietin on expression of integrin-β1 in hippocampus of neonatal rats with hypoxic-ischemic brain damage

Abstract

Objective To investigate the effect of erythropoietin (EPO) on the expression of integrin-β1 in hippocampus of neonatal rats after hypoxic- ischemic brain damage (HIBD) and to discuss the neuroprotective mechanisms for EPO. Methods Neonatal Sprague-Dawley rats of 7 days old were randomly divided into 3 groups by random number table method (24 cases in each group): sham-operated group, HIBD group and EPO treated group(EPO group), then each group was further divided into 4 subgroups (n=6) based on different time points following the injection of 9 g/L or EPO (6 h, 24 h, 3 d, 7 d). The expressions of integrin-β1 and integrin-β1 gene in hippocampus were determined by Western blot and real-time fluorescent quantitative PCR(RT-qPCR). Results By Western blot method: integrin-β1 had low expression in the hippocampus of the sham-operated group at each time point, which had no significant difference(0.47±0.22, 0.45±0.18, 0.54±0.24, 0.53±0.22, F=0.223, P=0.879). The expression of integrin-β1 in HIBD group was increased at first and then decreased, which had a significant difference(0.62±0.16, 1.42±0.32, 1.13±0.37, 0.81±0.21, F=11.809, P=0.000). In the EPO group the expression of integrin-β1 was rising significantly at 24 h and 7 d and showed two peaks (0.64±0.21, 1.10±0.37, 0.96±0.30, 1.19±0.31, F=3.741, P=0.028). Compared with the sham-operated group at corresponding time points, the integrin-β1 protein expression showed significant increase at 24 h and on 3 d in HIBD group and 24 h, 3 d, and 7 d in EPO group (all P<0.05). By RT-qPCR: there was no significant difference in the gene expression of integrin-β1 in hippocampus of the sham-operated group at different time points (0.31±0.13, 0.33±0.16, 0.34±0.15, 0.32±0.17, F=0.036, P=0.990). Gene expression of integrin-β1 in HIBD group was increased at first and then decreased and the summit was at 24 h point(0.72±0.35, 1.39±0.33, 0.95±0.24, 0.61±0.25). The difference between each time point was statistically significant (F=8.022, P=0.001). Integrin-β1 gene expression of EPO group showed two peaks at 24 h and on 7 d(0.77±0.30, 1.09±0.27, 0.90±0.38, 1.17±0.36), and there was a significant difference between 6 h group and 7 d group (P<0.05). Compared with the sham-operated group at corresponding time points, the expression of integrin-β1 gene in between HIBD group and EPO group was extremely higher(all P<0.05). Besides, the gene expression of integrin-β1 in EPO group was higher than that in the HIBD group on 7 d with statistically significant difference (P<0.05). Conclusion Erythropoietin can upregulate the expression of integrin-β1 in the recovery phase of HIBD, which may be one of the beneficial effects of EPO for HIBD. Key words: Erythropoietin; Integrin-β1; Hypoxic-ischemic brain damage