Effect of hydroxyurea on G gamma chain fetal hemoglobin synthesis by sickle-cell disease patients

Targeted therapeutic management based on phytoconstituents for sickle cell anemia focusing on molecular mechanisms: Current trends and future perspectives

The global epidemic of Sickle cell anemia (SCA) is causing thousands of children to die. SCA, a genetic disorder affecting the hemoglobin-globin chain, affects millions globally. The primary physiological issue in these patients is the polymerization of sickle hemoglobin within their red blood cells (RBCs) during their deoxygenating state. The RBC undergoes a sickle shape due to the polymerization of mutant hemoglobin within it and membrane deformation during anoxic conditions. To prevent complications, it is essential to effectively stop the sickling of RBCs of the patients. Various medications have been studied for treating SCA patients, focusing on antisickling, γ-globulin induction, and antiplatelet action. Natural and synthetic anti-sickling agents can potentially reduce patient clinical morbidity. Numerous clinical trials focused on using natural remedies for the symptomatic therapy of SCA. Medicinal plants and phytochemical agents have antisickling properties. Recent studies on plant extracts' natural compounds have primarily focused on in vitro RBCs sickling studies, with limited data on in vivo studies. This review discussed the potential role of phytoconstituents in the management of SCA.

Newer aspects of the pathophysiology of sickle cell disease vaso-occlusion

Sickle cell disease is an inherited disorder of hemoglobin (Hb) synthesis, caused by a single nucleotide substitution (GTG>GAG) at the sixth codon of the beta-globin gene, leading to the production of a defective form of Hb, Hb S. When deoxygenated, Hb S polymerizes, damaging the sickle erythrocyte and it is this polymerization that is the primary indispensable event in the molecular pathogenesis of sickle cell disease. Hb S polymerization results in a series of cellular alterations in red cell morphology and function that shorten the red cell life span and leads to vascular occlusion. Sickle cell disease vaso-occlusion is now known to constitute a complex multifactorial process characterized by recurrent vaso-occlusion, ischemia-reperfusion injury, and oxidative stress with consequent vascular endothelial cell activation that induces a chronic inflammatory state in sickle cell disease individual and is propagated by elevated levels of circulating inflammatory cytokines. Activation of the endothelium results in the induction of endothelial adhesion molecule expression that mediates red and white cell adhesion to the vessel wall and the formation of heterocellular aggregates, followed by secondary red cell trapping, all of which contribute to reduced blood flow and eventually obstruction of the micro-circulation. Reduced nitric oxide bioavailability, caused principally by its consumption by cell-free Hb, liberated during intravascular hemolysis, contributes to this process by facilitating vasoconstriction and adhesion molecule activity.