title: Zileuton induces hemoglobin F synthesis in erythroid progenitors: role of the L-arginine-nitric oxide signaling pathway.
abstract: Induction of fetal hemoglobin (Hb F) is an important therapeutic tool in ameliorating complications of sickle cell disease. Nitric oxide has been implicated in the mechanism of Hb F synthesis induced by hydroxyurea (HU). This study examined whether zileuton (ZL), a structural analog of hydroxyurea, possessed Hb F-inducing properties and the potential role nitric oxide plays. ZL caused a dose-dependent increase in gamma-globin expression in K562 cells. This effect was confirmed by a dose-dependent increase in Hb F synthesis in erythroid progenitors from individuals with sickle cell anemia and normal hemoglobin genotypes. l-arginine had no effect on Hb F production; however, it dose-dependently inhibited ZL's ability to induce Hb F. The nitric oxide synthase inhibitor N(G)-monomethyl-l-arginine (l-NMMA) inhibited l-arginine's effect and restored ZL-mediated increase in Hb F synthesis. In addition, 8-PCPT-cGMP (8-(4-chlorophenylthio)guanosine 3',5'-cyclic monophosphate) inhibited ZL-mediated induction of Hb F synthesis. When comparing l-NMMA effects alone on ZL and HU, a partial reversal of increased Hb F synthesis was seen only with HU. Neither l-arginine alone nor l-arginine in combination with l-NMMA effected hydroxyurea-mediated induction of Hb F synthesis. This study demonstrates that ZL induces Hb F through a mechanism that involves l-arginine/nitric oxide/cGMP in a manner distinctly different from HU.
authors.affiliation: Department of Medicine, University of South Alabama Medical Center, Mobile, AL 36617, USA. jhaynes@usouthal.edu
authors.forename: Johnson
authors.initials: J
authors.lastname: Haynes
authors.forename: B Surendra
authors.initials: BS
authors.lastname: Baliga
authors.forename: Boniface
authors.initials: B
authors.lastname: Obiako
authors.forename: Solomon
authors.initials: S
authors.lastname: Ofori-Acquah
authors.forename: Betty
authors.initials: B
authors.lastname: Pace
mesh_terms: D000755:Anemia, Sickle Cell / Q000097:blood; D001120:Arginine / Q000494:pharmacology*; D016022:Case-Control Studies; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015672:Erythroid Precursor Cells / Q000378:metabolism*; D005319:Fetal Hemoglobin / Q000096:biosynthesis*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D006918:Hydroxyurea / Q000031:analogs & derivatives* / Q000494:pharmacology*; D020014:K562 Cells; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology
chemical_list: D009569:Nitric Oxide; D005319:Fetal Hemoglobin; D001120:Arginine; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP; C063449:zileuton; D006918:Hydroxyurea