Submitted May 21, 2007
Accepted October 30, 2007
Hydroxyurea nitrosylates and activates soluble guanylyl cyclase in human erythroid cells
Vladan P Cokic, Silvana A Andric, Stanko S Stojilkovic, Constance T Noguchi, and Alan N. Schechter*
Laboatory of Experimental Hematology, Institute of Medical Research, Belgrade, Serbia and Montenegro
Section on Cellular Signaling, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
* Corresponding author; email: aschecht{at}helix.nih.gov.
Hydroxyurea, a drug widely used for treating myeloproliferative diseases, has also been approved for the treatment of sickle cell disease by raising fetal hemoglobin (HbF). We have shown that nitric oxide (NO) and the soluble guanylyl cyclase (sGC) pathways are involved in hydroxyurea-induction of HbF levels in erythroid progenitor cells (EPC). We demonstrate now that during erythroid differentiation, endothelial NO synthase mRNA and protein levels decline steadily, as does the production of NO derivatives and cAMP levels, but cGMP levels are stable. Hydroxyurea increased intracellular cGMP levels and cAMP levels in EPC. The NO donor, DEANONOate, induced much higher cGMP levels, but reduced cAMP levels. Hydroxyurea (1 mM) induced production of approximately 45 pM cGMP/min/ng of purified sGC, similar to induction by 1 µM of DEANONOate. We found that hydroxyurea and ProliNONOate produced iron-nitrosyl derivatives of sGC. Thus, we confirm that hydroxyurea can directly interact with the deoxy-heme of sGC, presumably by a free-radical nitroxide pathway, and activate cGMP production. These data add to an expanding appreciation of the role of hydroxyurea as an inducer of the NO/cGMP pathway in EPC. These mechanisms may also be involved in the cytostatic effects of hydroxyurea, as well as the induction of HbF.
