Background: Platelets are essential in atherothrombosis, a common cause of heart attack and stroke. We recently identified apolipoprotein A-IV (apoA-IV) as an endogenous inhibitor of atherothrombosis through competitive blockade of the αIIbβ3 platelet integrin (Nat. Commun. 2018). Mutational studies suggest the D5 and D13 N-terminal residues are essential in this interaction. Structural analysis indicates an interface between the N- and C-termini that may partially mask its platelet binding site. Interestingly, common apoA-IV C-terminal polymorphisms, Q360H and T347S, are linked to an increased risk of cardiovascular disease as high as 2-fold, however, the mechanism behind this phenomenon remains unknown.

Aims: To determine whether apoA-IV C-terminal polymorphisms, Q360H and T347S, reduces its affinity for the αIIbβ3 integrin and thus, its endogenous inhibition of thrombosis.

Methods: Site-directed mutagenesis was used to generate Q360H and T347S apoA-IV plasmids and proteins were subsequently expressed in E. coli BL21 cells. Light transmittance aggregometry was used to measure platelet aggregation following either ADP or collagen agonist in human samples of platelet-rich plasma (PRP) or gel-filtered platelets. Thrombus formation was measured under shear conditions by flowing human whole blood across collagen-coated microcapillary perfusion chambers under a real-time fluorescence microscope.

Results: Our data demonstrates the apoA-IV inhibitory effect is completely abrogated in the Q360H polymorphism. Our preliminary data also suggests this effect is significantly reduced in the T347S polymorphism. These results were consistent using ADP or collagen-induced platelet aggregation in either PRP or gel-filtered platelets and in human whole-blood under high shear.

Conclusions: These data identify a novel mechanism that may explain the elevated risk of cardiovascular disease in individuals with apoA-IV polymorphisms, Q360H and T347S. Our findings also contribute to our understanding of the link between lipid metabolism and cardiovascular disease, our collective understanding of pathologies leading to atherothrombosis, and may guide personalized based treatments of cardiovascular disease.
* denotes equal contribution.

« Back to ISTH 2020 Congress

ISTH Congress Abstracts - https://abstracts.isth.org/abstract/apolipoprotein-a-iv-is-an-endogenous-inhibitor-of-thrombosis-the-roles-of-polymorphisms-in-the-risk-of-cardiovascular-disease/