Plasma ProteomeSignatures in Sickle Cell Anemia andthe Effect of Hydroxyurea Treatment

Abstract Sickle Cell Anaemia (SCA) is a monogenic blood disorder caused by a mutation in the β-globin gene, yet it presents with marked clinical variability. Although hydroxyurea (HU) is an established therapy, its precise mechanism of action remains incompletely understood. Plasma proteins represent valuable biomarkers for elucidating disease mechanisms and treatment responses. In this study, plasma proteome profiling of 31 healthy controls and 76 SCA patients identified 43 differentially abundant proteins (DAPs) that form a highly interconnected interaction network. Proteins with increased abundance in SCA were largely associated with immune and inflammatory responses, whereas those with reduced levels were linked to coagulation and proteolytic pathways. HU therapy was associated with elevated levels of haptoglobin (HP) and hemopexin (HPX), key mediators of free hemoglobin scavenging. We also identified several previously unreported plasma proteins altered in SCA, broadening the landscape of potential biomarkers and HU-responsive targets. Many DAPs significantly correlated with clinical indices, such as transfusion frequency, vaso-occlusive crises, white blood cell counts, and platelet counts, offering insights into disease mechanisms and potential utility in disease management. Notably, overlap with β-thalassemia-associated signatures suggests shared pathophysiological pathways between these hemoglobinopathies. Collectively, these findings provide a strong foundation for translational validation in larger, independent cohorts.