Effect of erythropoietin on endothelial cell apoptosis induced by high glucose

Erythropoietin (Epo) has been reported to inhibit apoptosis of neuron and erythroid cells. In this study, we examined an effect of high glucose on apoptosis of endothelial cells and investigated an anti-apoptotic effect of Epo. Human aortic endothelial cells were incubated with normal or high glucose for 72 h, and apoptotic cells were detected by TUNEL assay. Simultaneously, Epo (100 U/ml) was added to the high glucose medium to examine an inhibitory effect on the apoptosis induced by high glucose. Activity of caspase-3 was also measured using a specific substrate. To investigate a possible mechanism of Epo's action on apoptosis, phosphorylation of Akt was examined by applying Epo. Incubation with high glucose increased apoptosis of endothelial cells, whereas this effect was prevented by co-incubation with Epo. Caspase-3 activity was also increased (1.4-fold) by incubation with high glucose, and the activation of caspase-3 was normalized to the control level by co-incubation with Epo. Furthermore, Epo-induced phosphorylation of Akt in dose-dependent manner. In conclusion, we demonstrated that incubation with high glucose activated caspase-3 and induced apoptosis of endothelial cells. Epo was shown to phosphorylate Akt, leading to the inhibition of caspase-3 activation and apoptosis induced by high glucose. These results suggest that reduced production of Epo in patients with end-stage of nephropathy may accelerate diabetic angiopathy and that replacing therapy with Epo might inhibit endothelial cell apoptosis and diabetic angiopathy.