Prostacyclin Analogues Inhibit Platelet Reactivity, Extracellular Vesicle Release and Thrombus Formation in Patients with Pulmonary Arterial Hypertension

(1) Background: Prostacyclin analogues (epoprostenol, treprostinil, and iloprost) induce vasodilation in pulmonary arterial hypertension (PAH) but also inhibit platelet function. (2) Objectives: We assessed platelet function in PAH patients treated with prostacyclin analogues and not receiving prostacyclin analogues. (3) Methods: Venous blood was collected from 42 patients treated with prostacyclin analogues (49.5 +/- 15.9 years, 81% female) and 38 patients not receiving prostacyclin analogues (55.5 +/- 15.6 years, 74% female). Platelet reactivity was analyzed by impedance aggregometry using arachidonic acid (AA; 0.5 mM), adenosine diphosphate (ADP; 6.5 mu M), and thrombin receptor-activating peptide (TRAP; 32 mu M) as agonists. In a subset of patients, concentrations of extracellular vesicles (EVs) from all platelets (CD61(+)), activated platelets (CD61(+)/CD62P(+)), leukocytes (CD45(+)), and endothelial cells (CD146(+)) were analyzed by flow cytometry. Platelet-rich thrombus formation was measured using a whole blood perfusion system. (4) Results: Compared to controls, PAH patients treated with prostacyclin analogues had lower platelet reactivity in response to AA and ADP (p = 0.01 for both), lower concentrations of platelet and leukocyte EVs (p <= 0.04), delayed thrombus formation (p <= 0.003), and decreased thrombus size (p = 0.008). Epoprostenol did not affect platelet reactivity but decreased the concentrations of platelet and leukocyte EVs (p <= 0.04). Treprostinil decreased platelet reactivity in response to AA and ADP (p <= 0.02) but had no effect on the concentrations of EVs. All prostacyclin analogues delayed thrombus formation and decreased thrombus size (p <= 0.04). (5) Conclusions: PAH patients treated with prostacyclin analogues had impaired platelet reactivity, EV release, and thrombus formation, compared to patients not receiving prostacyclin analogues.

Automated summary

The study showed that PAH patients treated with prostacyclin analogues had impaired platelet reactivity, EV release, and thrombus formation compared to those not receiving prostacyclin analogues.