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 γ-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 NG-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.
ASJC Scopus subject areas
- Cell Biology