Submitted on October 22, 2008
Revised on May 13, 2009
Accepted on June 9, 2009
Erythropoietin activates nitric oxide synthase in murine erythrocytes
Deyan Nikolaev Mihov1, Johannes Vogel2, Max Gassmann3, and Anna Bogdanova2*
1 University of Zurich, Zurich Center for Integrative Human Physiology (ZHIP)
2 Institute of Vereinary Physiology and Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich
3 Institute of Veterinary Physiology
* To whom correspondence should be addressed. E-mail: annab{at}access.unizh.ch.
Erythropoietin (Epo) is the main regulator of erythrocyte production and a potent cytoprotective factor. It was suggested that some of Epo cytoprotective properties are due to its regulation of nitric oxide (NO) production. Recently, functionally active endothelial type NO synthase was discovered in mature murine and human red blood cells (RBC-eNOS). The goal of the present study was to characterize the effect of physiologic and therapeutic doses of Epo on RBC-eNOS function. We found that recombinant human Epo (rHuEpo) binds specifically to mouse erythrocytes. Epo binding sites are not equally distributed through the RBC population but prevail in reticulocytes and young erythrocytes with about 105 receptors/cell, in comparison to adult and old erythrocytes with 1-4 receptors/cell. The treatment of mouse erythrocytes with rHuEpo resulted in a time- and dose-dependent up-regulation of NO production, mediated via activation of the PI3K/Akt pathway and RBC-eNOS phosphorylation at Ser-1177. Finally, when erythrocytes were incubated in L-arginine-free medium, rHuEpo treatment resulted in upregulation of superoxide radical production with concomitant shifting of the cellular redox state towards more oxidized. Epo-induced changes in erythrocyte redox potential were absent in erythrocytes from eNOS deficient mice.
