A preliminary study of phosphodiesterases and adenylyl cyclase signaling pathway on red blood cell deformability of sickle cell patients

Abstract

Sickle cell disease (SCD) is an inherited hemoglobinopathy characterized by chronic anemia, intravascular hemolysis, and the occurrence of vaso-occlusive crises due to the mechanical obstruction of the microcirculation by poorly deformable red blood cells (RBCs). RBC deformability is a key factor in the pathogenesis of SCD, and is affected by various factors. In this study, we investigated the effects of adenylyl cyclase (AC) signaling pathway modulation and different phosphodiesterase (PDE) modulatory molecules on the deformability and mechanical stress responses of RBC from SCD patients (HbSS genotype) by applying 5 Pa shear stress with an ektacytometer (LORRCA). We evaluated RBC deformability before and after the application of shear stress. AC stimulation with Forskolin had distinct effects on RBC deformability depending on the application of 5 Pa shear stress. RBC deformability was increased by Forskolin before shear stress application but decreased after 5 Pa shear stress. AC inhibition with SQ22536 and protein kinase A (PKA) inhibition with H89 increased RBC deformability before and after the shear stress application. Non-selective PDE inhibition with Pentoxifylline increased RBC deformability. However, modulation of the different PDE types had distinct effects on RBC deformability, with PDE1 inhibition by Vinpocetine increasing deformability while PDE4 inhibition by Rolipram decreased RBC deformability after the shear stress application. The effects of the drugs varied greatly between patients suggesting some could benefit from one drug while others not. Developing drugs targeting the AC signaling pathway could have clinical applications for SCD, but more researches with larger patient cohorts are needed to identify the differences in the responses of sickle RBCs.

RBC-GEM: a Knowledge Base for Systems Biology of Human Red Blood Cell Metabolism

“…Over 80 proteins were found to have supporting experimental evidence for their presence and activity in RBCs, yet they were not detected across all proteomic studies. For example, at least six different phosphodiesterase proteins have been identified in RBCs with important roles in regulating cyclic nucleotide levels [95], yet none were found in the proteomic data. Proteins involved in the synthesis of blood group antigens also do not appear across proteomic studies [96,97].…”

“…signaling [95], degradation [128], and export [126]. Though early studies were unable to detect adenylosuccinate synthetase activity in RBCs [129], deep proteomic and metabolic tracing studies have demonstrated its presence and a residual activity [130].…”

Exploring unconventional attributes of red blood cells and their potential applications in biomedicine

“…For example, mitophagy agents in SCD mouse models reduced mitochondrial retention in RBCs and increased RBC lifespan, suggesting a promising therapeutic approach ( Jagadeeswaran et al, 2017 ). Similarly, RBC channel blockers and cAMP-pathway modulators were explored in SCD to counteract cell dehydration and deformability issues, respectively ( Ataga et al, 2008 ; Goskel et al, 2023 ; Toppet et al, 2000 ). The new knowledge that RBCs perform low levels of protein synthesis could also be therapeutically useful; thus, drugs enabling stop codon readthrough might be useful for patients with beta-thalassemia who have premature stop codons in their beta-globin gene ( Kar et al, 2020 ; Kumar et al, 2022 ).…”