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Eucalyptol Inhibits Agonist-induced Platelet Function and Thrombus Formation in Mice


Blood clots or thrombi result from inappropriate platelet activation due to injury or disease. Once a clot forms within the vasculature, it can reduce or block the blood supply to vital organs.

Thus, anti-platelet drugs are vital to prevent or treat thrombotic diseases. But the available medicines may cause adverse events like gastrointestinal issues and bleeding.

Essential oils could be an alternative to traditional treatments. However, there´s little information about their effects on thrombosis.

Thinking about that, researchers at the University of Reading (UK) investigated the effects of eucalyptol (1,8-cineole) on agonists-induced platelet activation, thrombus formation under arterial flow, and hemostasis in mice.


Study Overview

Methods

Agonist-induced Platelet Aggregation Assays

To determine the impact of eucalyptol on platelet activation, Alatawi and colleagues (2021) performed aggregation assays with various agonists.

First, they isolated human platelets and incubated them with a vehicle or eucalyptol at different concentrations. After that, they stimulated the platelets with varying concentrations of Glycoprotein VI (GPVI) agonists such as collagen and cross-linked collagen-related peptide (CPR-XL).

They repeated these experiments using platelet-rich plasma (PRP) to see the modulatory effect of eucalyptol in the presence of plasma proteins.


Integrin αIIbβ3 Signaling

Integrin αIIbβ3 is a platelet surface receptor involved in platelet aggregation. For that, the receptor must change from a low-affinity to a high-affinity state for fibrinogen and von Willebrand factor (vWF).

To determine eucalyptol´s effect on this event, the researchers measured the levels of fibrinogen binding in platelets stimulated by CRP-XL, thrombin, and ADP.


Granule Secretion in Platelets

Platelets contain different granules that they secrete under agonist stimulation to increase platelet activation and thrombus formation.

The researchers used flow cytometry to measure P-selectin exposure on the platelet´s surface upon stimulation with agonists to assess granule secretion. They also measured ATP secretion in isolated platelets using a lumi-aggregometer.


Calcium Mobilisation in Platelets

Because calcium is a critical mediator of platelet activation, the group analyzed the eucalyptol´s impact on intracellular calcium mobilization in human PRP or isolated platelets upon agonists activation.


Hemostasis

Hemostasis is the body´s defense against excessive bleeding following a vascular injury. To assess eucalyptol´s effect on hemostasis, the group also performed a tail-bleeding assay in mice.


Thrombus Formation

Platelet aggregation after a vascular injury culminates in thrombus formation to seal the damaged area and prevent bleeding.

Experiments modelling platelet aggregation were necessary to determine eucalyptol´s (1,8-cineole) impact on whole-blood thrombus formation under arterial flow conditions.