Pharmacological Actions of Adapalene on Platelet Function and Thrombosis through the PI3K/AKT Signaling Pathway

Background and aims: Given the global impact of Cardiovascular Disease (CVD) linked to abnormal platelet activation, there is an urgent demand for the development of safer and more effective antiplatelet agents.Adapalene, an FDA-approved anti-acne medication, has recently been repurposed as a third-generation synthetic retinoid for tumor treatment.The exploration of novel clinical applications represents a focused approach in the realm of drug discovery and development.Our research aimed to elucidate the impact of adapalene on platelet functionality and the associated molecular mechanisms.Method: Mouse or human platelets were thoroughly washed and then pretreated with adapalene or Dimethyl Sulfoxide (DMSO).Subsequently, their platelet aggregation capacities were assessed using an aggregometer.Flow cytometry was used to evaluate granule secretion and integrin IIb3 activation, while platelet spreading on fibrinogen was visualized via the staining of FITC-phalloidin.To evaluate the in vivo antithrombotic effects of adapalene, a mesenteric artery thrombus formation model induced by FeCl3 was utilized.Changes in critical signaling pathways were detected through Western blotting analysis.Results: Adapalene exhibited a concentrationdependent inhibition of thrombin-and ADP (adenosine diphosphate)-induced platelet aggregation.This was accompanied by reductions in the membrane translocation of CD62P and LAMP-1, as well as decreased ATP release.Furthermore, adapalene effectively attenuated integrin IIb3-mediated inside-out and outside-in signaling processes, impacting platelet adhesion and spreading.Key signaling pathways including Phosphoinositide 3 Kinase (PI3K)/Protein Kinase B (AKT)/Glycogen Synthase Kinase (GSK3), SRC proto-oncogene, nonreceptor Tyrosine Kinase (Src)/Spleen Tyrosine Kinase (Syk)/Phospholipase C Gamma 2 (PLC2), and Mitogen-Activated Protein Kinase (MAPK) were notably counteracted by adapalene.Intravenous administration of adapalene significantly prolonged mesenteric artery occlusion times in mice without a concurrent increase in tail bleeding events.Conclusions: Our findings uncovered a novel pharmacological mechanism of action of adapalene in suppressing platelet activity and thrombosis formation through the inhibition of agonist-induced platelet signal transduction pathways, specifically targeting the PI3K/AKT/GSK3, SRC/Syk/PLC2, and MAPK pathways.These results suggest that adapalene holds promise as a prospective therapeutic agent for the management and prophylaxis of thrombotic cardiovascular disorders.