Effect of recombinant human erythropoietin on endothelial cell apoptosis

Background Recombinant human erythropoietin (rHuEPO) induces endothelial ce ll growth and angiogenesis in vitro. The mechanisms are unknown. Because an increase in endothelial cell survival could play a role in this process, w e examined the effect of rHuEPO on lipopolysaccharide (LPS)-induced apoptos is in bovine pulmonary artery endothelial cells (BPAECs). Methods. Four groups of cells were studied. The first group was preincubate d in serum-free medium followed by treatment with LPS. The second group was preincubated with rHuEPO followed by LPS. The third group was treated with only rHuEPO. Control cells were cultured in the absence of rHuEPO and LPS. Apoptosis was determined by Bow cytometric DNA analysis, propidium iodide staining, cellular DNA fragmentation by ELISA, and gel electrophoresis. Results. LPS-treated cells showed an increase in hypodiploid DNA (36.4 +/- 6.1%) compared with controls (9.8 +/- 3.3%, P< 0.001). Preincubation with r HuEPO decreased this effect to 14.7 +/- 5.1% (P < 0.001). Apoptosis determi ned by propidium iodide was observed in 33 +/- 8% of LPS-treated cells, but in only 9 +/- 3% of cells preincubated with rHuEPO cells (P < 0.001). Simi larly, DNA fragmentation was decreased in rHuEPO pretreated cells compared with LPS alone (0.155 OD +/- 0.02 vs. 0.538 +/- 0.09 OD, P < 0.001). DNA br eakdown was observed in only LPS-treated cells. Conclusions. These results suggest that rHuEPO prevents LPS-induced apoptos is in endothelial cells. This protective effect could be an important facto r in the action of rHuEPO on vascular endothelium.