Sickle cell disease (SCD) is a worldwide distributed hereditary red cell disorder characterized by chronic hemolytic anemia in association with acute and chronic life-threatening complications mainly related to acute vaso-occlusive events (VOCs) due to amplified inflammatory response and defective pro-resolving events.
Imatinib is an oral Tyrosine (Tyr)-kinase inhibitor, developed for the treatment of chronic myeloid leukemia (CML). Few case reports on SCD patients with CML undergoing imatinib treatment highlight the beneficial impact of imatinib on severity and recurrence of acute VOCs in SCD. In red blood cells (RBCs), Imatinib has been shown to interfere with Tyr-phosphorylation state of the integral membrane protein band 3, affecting RBC microparticle formation. Here, we study the actions of Imatinib on a model of acute VOCs using humanized SCD mice (Hbatm1(HBA)TowHbbtm2(HBG1,HBB*)Tow). We treated SCD and control healthy mice (AA, Hbatm1(HBA)Tow Hbbtm3(HBG1,HBB)Tow) (n=6-7 animals in each group) with Imatinib 50 mg/Kg/d for 2 weeks before hypoxia/Reoxygenation (H/R) stress used to mimic acute VOCs. Under normoxia, we found that in SCD mice Imatinib significantly reduced (i) Tyr-phosphorylation state of sickle red cell membrane proteins; (ii) the amount of phosphatidyl-serine (PS)+ sickle RBCs; and (iii) the release of erythroid microparticles, which was associated with accumulation of hemichromes and a more efficient erythrophagocytosis compared to vehicle treated animals. In SCD mice exposed to H/R stress, imatinib significantly decreased the H/R-induced (i) increase in peripheral neutrophil count; (ii) lung inflammatory cell infiltrate; (iii) kidney inflammatory cell infiltrate. In the lung of H/R SCD mice, Imatinib inhibited the H/R induced NF-kB activation and prevented the up-regulation of (i) pro-inflammatory cytokines such as ET-1; (ii) vascular endothelial activation markers (VCAM-1, ICAM-1); (iii) pro-fibrotic markers such as PDGF-B and (iv) the activation of UPR system. In the kidney of H/R SCD mice, Imatinib significantly reduced H/R induced expression of ET-1, VCAM-1 and E-selectin, which were again associated with inhibition of NF-kB. In addition, Imatinib significantly upregulated the expression of the microRNAs miR200a/b, which has been described to reduce renal fibrosis. Finally, in isolated aorta from Imatinib treated SCD exposed to H/R stress, a significant reduction in vascular activation markers was observed compared to vehicle treated animals. Collectively, our data indicate that Imatinib acts on multiple targets, modulating signal transduction and reducing inflammatory vasculopathy and extracellular matrix remodeling process related to VOC in SCD. Thus, Imatinib might represent a new therapeutic tool in clinical management of SCD patients.
El Nemer:Imara: Research Funding.
Asterisk with author names denotes non-ASH members.