Oxidative stress mechanisms regulating g-globin gene transcription in sickle cell disease
Abstract:
Sickle cell disease (SCD) is the most common inherited monogenic disorder affecting the ß-globin
gene, leading to the production of sickled-shaped red blood cells (RBCs). Patients with SCD suffer from
severe anemia and painful vasoocclusive crises, which are both exacerbated by increased oxidative
stress. Induction of normal, but developmentally silenced ¿-globin gene of fetal hemoglobin (HbF)
expression reduces RBC sickling-mediated vasoocclusion, and anemia, consequently ameliorating
clinical severity of SCD. Reducing oxidative stress also improves SCD phenotypic severity. Yet
effective treatment options remain limited. Understanding the pathogenesis of the erythroid
mechanisms regulating oxidative stress and factors engaged in silencing ¿-globin gene, is of substantial
value to SCD patients. Our data uncovered an unanticipated role for mediators of oxidative stress in
RBC sickling, and in regulating the transcriptional regulatory machinery that represses ¿-globin genes
as well as epigenetic enzyme components associated with ¿-globin to ß-globin gene switch in erythroid
progenitors. Here, to extend our studies, we will in vitro and in vivo genetically and/or chemically
manipulate these mediators of oxidative stress and the regulated pathways using a SCD mouse model,
and determine their effects on ¿-globin gene regulation, and thus sickling, and their mechanism of
action on the transcriptional regulatory machinery that silences ¿-globin gene during sickle RBC
production. We will also determine the contribution of these mediators in epigenetic DNA and histone
modifications associated with ¿-globin
to ß-globin gene switch during sickle RBC production. Because
stress erythropoiesis compensates for anemia caused by oxidative damage to the RBCs, we will further
validate the effects of these mediators of oxidative stress on stress erythropoiesis in splenic
hematopoietic tissue and examine their role in chronic erythroid stress-response, specifically in
erythroid terminal maturation and enucleation. We strongly believe that our studies will provide novel
and unprecedented insights into the exact mechanisms regulating ¿-globin gene silencing and ¿-globin
to ß-globin gene switch in SCD, as well as ineffective erythroid maturation and enucleation. Our long-
term goal is to identify remediable sickle erythroid abnormalities to improve SCD pathophysiology. In
addition, our studies will lay the foundation for more rational approaches to therapies that better
alleviate SCD clinical symptoms.