Abstract
In short-term animal models of ischemia, erythropoietin (EPO) signaling through the heterodimeric EPO receptor (EPOR)/β-common receptor (βCR) is believed to elicit tissue protective effects. However, large, randomized, controlled trials demonstrate that targeting a higher hemoglobin level by administering higher doses of EPO, which are more likely to activate the heterodimeric EPOR/βCR, is associated with an increase in adverse cardiovascular events. Thus, inhibition of long-term activation of the βCR may have therapeutic implications. This study aimed to design and evaluate the efficacy of novel computationally designed βCR inhibitory peptides (βIP). These novel βIPs were designed based on a truncated portion of Helix-A from EPO, specifically residues 11-26 (VLERYLLEAKEAEKIT). Seven novel peptides (P1 to P7) were designed. Peptide 7 (P7), VLERYLHEAKHAEKIT, demonstrated the most robust inhibitory activity. We also report here the ability of P7 to inhibit βCR-induced nitric oxide (NO) production and angiogenesis in human umbilical vein endothelial cells (HUVECs). Specifically, we found that P7 βIP completely abolished EPO-induced NO production. The inhibitory effect could be overcome with super physiological doses of EPO, suggesting a competitive inhibition. βCR-induced angiogenesis in HUVEC's was also abolished with treatment of P7 βIP, but P7 βIP did not inhibit vascular endothelial growth factor (VEGF)-induced angiogenesis. In addition, we demonstrate that the novel P7 βIP does not inhibit EPO-induced erythropoiesis with use of peripheral blood mononuclear cells (PBMCs). These results, for the first time, describe a novel, potent βCR peptide inhibitor that inhibit the actions of the βCR without affecting erythropoiesis.