Abstract Number: OC 73.5
Meeting: ISTH 2022 Congress
Theme: Platelets and Megakaryocytes » Platelet Function and Interactions
Background: Immune thrombocytopenia (ITP) is an autoantibody-mediated bleeding disorder with increased clearance of platelets and megakaryocyte dysfunction. Previously, we showed that antibody-mediated desialylation plays a pivotal role in pathophysiology of ITP, leading to impaired platelet adhesion and megakaryocyte differentiation via FcγRIIA receptor.
Aims: In current study, we aim to investigate whether spleen tyrosine kinase (Syk) inhibition can alter platelet dysfunction and desialylation in ITP.
Methods: Using in vitro cell culture and flow cytometry methods, we analyzed the impact of Syk inhibitors R406 and PRT318. Role of FcγRIIA was studied by crosslinking anti CD32 clone AT-10 with the secondary Fab2 antibody to stimulate the receptor. Platelet function was determined as CD62P and PAC1 expression, and apoptosis as mitochondrial-transmembrane potential (Δψ) depolarization and phosphatidylserine (PS) externalization. Human ITP AAb-induced platelet desialylation was analyzed using a lectin binding assay (LBA) after incubation of platelets with ITP or healthy donor sera and flow cytometry.
Results: Our data shows that Syk inhibition can effectively alter antibody-mediated biological effects in ITP. Activation of FcyRIIA via crosslinking resulted in significant increase in apoptosis and desialylation markers. R406 and PRT318 significantly inhibited apoptosis (mean %PS externalization ±SEM: 27.9±2.1 vs. 9.1±2.3 and 2.1±90.50 respectively, p < 0.001) and desialylation (mean FI±SEM 2.15±0.17 vs 1.25±0.10 and 0.93±0.16 respectively, p < 0.01). Sera from ITP patients induced desialylation in healthy washed platelets, which could be inhibited with both R406 and PRT318 (mean FI±SEM 1.62±0.10 vs 1.13±0.04 and 0.93±0.05 respectively, p < 0.01). In ongoing studies, we explore the opportunity to restore impaired proplatelet formation by megakaryocytes with Syk-inhibition, and investigate the possibility of reverting desialylation in an established ex vivo model of thrombopoiesis.
Conclusion(s): Our data indicates that Syk-inhibition might be a promising approach to prevent antibody-mediated platelet desialylation in ITP and might serve as a potential therapeutic approach to prevent patient complications during pathogenesis of ITP.
To cite this abstract in AMA style:
Singh A, Toma F, Althaus K, Backchoul T. Investigations to assess Impact of Syk-inhibition on antibody-mediated desialylation: novel implications on therapy for immune thrombocytopenia [abstract]. https://abstracts.isth.org/abstract/investigations-to-assess-impact-of-syk-inhibition-on-antibody-mediated-desialylation-novel-implications-on-therapy-for-immune-thrombocytopenia/. Accessed September 21, 2023.« Back to ISTH 2022 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/investigations-to-assess-impact-of-syk-inhibition-on-antibody-mediated-desialylation-novel-implications-on-therapy-for-immune-thrombocytopenia/