Hemoglobin-bound platelets correlate with the increased platelet activity in hemoglobin E/β-thalassemia

Area of Science:

• Hematology
• Vascular Biology
• Thalassemia Research

Background:

• Platelet hyperactivity contributes to vascular issues in hemoglobin E/β-thalassemia (HbE/β-thal).
• Elevated plasma-free hemoglobin (Hb) in HbE/β-thal patients correlates with platelet activation.
• Hb-bound platelets have not been previously quantified in HbE/β-thal.

Purpose of the Study:

• To determine levels of Hb-bound platelets in HbE/β-thal patients.
• To investigate the association between Hb-bound platelets and platelet activity in HbE/β-thal.

Main Methods:

• Flow cytometry was used to quantify Hb-bound platelets and platelet activation markers (P-selectin, aGP IIb/IIIa) in 26 HbE/β-thal patients and 22 healthy controls.
• Plasma Hb levels were measured using a chemiluminescence assay.
• In vitro experiments assessed the effect of patient-derived Hb on healthy platelets.

Main Results:

• HbE/β-thal patients exhibited significantly higher levels of Hb-bound platelets and plasma Hb compared to healthy subjects.
• In vitro, Hb from HbE/β-thal patients increased Hb-bound platelets in healthy subjects' platelets, partially inhibited by anti-GPIbα.
• Hb-bound platelets positively correlated with plasma Hb and markers of platelet activation, including baseline and ADP-stimulated P-selectin and ADP-induced aGP IIb/IIIa expression.

Conclusions:

• HbE/β-thal patients present with increased Hb-bound platelets.
• Elevated Hb-bound platelets are associated with enhanced baseline platelet activation and reactivity in HbE/β-thal.