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Thrombin Generation Is Associated With Extracellular Vesicle and Leukocyte Lipid Membranes in Atherosclerotic
Majd B Protty1, Victoria J Tyrrell1, Keith Allen-Redpath2
1Systems Immunity University Institute, Cardiff University, United Kingdom (M.B.P., V.J.T., A.A.H., D.C., P.V.J., V.B.O.D.).
Insights
Aminophospholipids (aPLs) on extracellular vesicles (EVs) significantly increase thrombin generation in atherosclerotic cardiovascular disease (ASCVD). Targeting EVs offers a novel antithrombotic strategy for ASCVD patients.
Area of Science:
- Cardiovascular Science
- Thrombosis Research
- Lipidomics
Background:
- Thrombosis risk in atherosclerotic cardiovascular disease (ASCVD) is elevated and not fully addressed by current therapies.
- The role of membrane aminophospholipids (aPLs) in ASCVD thrombotic risk is currently unknown.
- This study investigates aPL composition and its contribution to thrombin generation in ASCVD patients.
Purpose of the Study:
- To characterize the aPL composition of circulating membranes in ASCVD patients.
- To determine the contribution of external-facing aPLs to plasma thrombin generation.
- To explore novel antithrombotic targets in ASCVD.
Main Methods:
- Thrombin generation measured using purified factor assays on platelets, leukocytes, and extracellular vesicles (EVs).
- Lipidomics used to determine aPL composition of resting/activated cells and EV membranes.
- Comparison between patients with acute coronary syndrome, stable coronary artery disease, positive risk factors, and healthy controls.
Main Results:
- External-facing aPLs were significantly elevated on activated EVs, platelets, and leukocytes.
- Higher thrombin generation observed on EVs from acute coronary syndrome patients compared to controls, correlated with EV counts and phosphatidylserine exposure.
- Leukocyte and platelet aPLs and thrombin generation were not significantly impacted by disease, despite higher circulating leukocyte counts.
Conclusions:
- EV membrane aPLs significantly support elevated thrombin generation in ASCVD.
- Leukocytes may contribute to thrombosis, while platelets appear less involved.
- Targeting EV formation, clearance, or aPL-coagulation factor interactions presents a novel antithrombotic strategy for ASCVD.
Background:
Clotting, leading to thrombosis, requires interactions of coagulation factors with the membrane aminophospholipids (aPLs) phosphatidylserine and phosphatidylethanolamine. Atherosclerotic cardiovascular disease (ASCVD) is associated with elevated thrombotic risk, which is not fully preventable using current therapies. Currently, the contribution of aPL to thrombotic risk in ASCVD is not known. Here, the aPL composition of circulating membranes in ASCVD of varying severity will be characterized along with the contribution of external facing aPL to plasma thrombin generation in patient samples.
Methods:
Thrombin generation was measured using a purified factor assay on platelet, leukocyte, and extracellular vesicles (EVs) from patients with acute coronary syndrome (n=24), stable coronary artery disease (n=18), and positive risk factor (n=23) and compared with healthy controls (n=24). aPL composition of resting/activated platelet and leukocytes and EV membranes was determined using lipidomics.
Results:
External facing aPLs were detected on EVs, platelets, and leukocytes, elevating significantly following cell activation. Thrombin generation was higher on the surface of EVs from patients with acute coronary syndrome than healthy controls, along with increased circulating EV counts. Thrombin generation correlated significantly with externalized EV phosphatidylserine, plasma EV counts, and total EV membrane surface area. In contrast, aPL levels and thrombin generation from leukocytes and platelets were not impacted by disease, although circulating leukocyte counts were higher in patients.
Conclusions:
The aPL membrane of EV supports an elevated level of thrombin generation in patient plasma in ASCVD. Leukocytes may also play a role although the platelet membrane did not seem to contribute. Targeting EV formation/clearance and developing strategies to prevent the aPL surface of EV interacting with coagulation factors represents a novel antithrombotic target in ASCVD.
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