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Hydroxyurea induces the eNOS-cGMP pathway in endothelial cells.
Vladan P Cokic1, Bojana B Beleslin-Cokic, Melanija Tomic
1Institute of Medical Research, and the Institute of Endocrinology, Diabetes and Digestive and Diseases of Metabolism, Belgrade, Serbia and Montenegro.
Blood
|March 11, 2006
Summary
Hydroxyurea boosts nitric oxide (NO) production in endothelial cells by activating specific protein kinases. This mechanism may explain hydroxyurea's therapeutic effects in myeloproliferative diseases and sickle cell anemia.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Hydroxyurea is a known treatment for myeloproliferative diseases and sickle cell anemia.
- Previous research indicated hydroxyurea increases cyclic guanosine monophosphate (cGMP) in erythroid cells.
- Nitric oxide (NO) plays a crucial role in vascular function and has therapeutic implications.
Purpose of the Study:
- To investigate the effect of hydroxyurea on endothelial nitric oxide (NO) production.
- To elucidate the signaling pathways involved in hydroxyurea-induced NO synthesis in endothelial cells.
- To establish a novel mechanism for hydroxyurea's action in relevant diseases.
Main Methods:
- Utilized human umbilical vein endothelial cells (HUVECs) and a human bone marrow endothelial cell line (TrHBMEC).
- Assessed NO production and its inhibition using NO synthase (NOS) inhibitors like L-NAME.
- Investigated the roles of cAMP-dependent protein kinase (PKA) and protein kinase B (PKB/Akt) through specific inhibitors and by measuring protein phosphorylation (eNOS at Ser1177).
- Quantified intracellular levels of cyclic adenosine monophosphate (cAMP), cGMP, and calcium.
Main Results:
- Hydroxyurea significantly increased endothelial cell production of NO.
- This NO induction was dependent on both PKA and PKB/Akt activity.
- Hydroxyurea triggered rapid, transient phosphorylation of endothelial NO synthase (eNOS) at Ser1177 in a PKA-dependent manner.
- Elevated levels of cAMP, cGMP, and intracellular calcium were observed in response to hydroxyurea.
- NO production was blocked by NOS inhibitors, confirming the pathway.
Conclusions:
- Hydroxyurea stimulates NO production in endothelial cells through a mechanism involving PKA and PKB/Akt.
- The drug enhances eNOS phosphorylation, leading to increased NO synthesis.
- These findings reveal an additional pathway for hydroxyurea's action, potentially enhancing NO bioavailability and therapeutic efficacy in myeloproliferative disorders.