Apolipoprotein A-IV regulates coagulation and ischemic stroke by potentiating activated protein C

Inflammation is crucial in regulating coagulation and hemostasis. While prior research shows that apolipoprotein A-IV (ApoA-IV) has anti-inflammatory and antiplatelet effects, its specific impact on coagulation remains unclear.

To investigate the effects of ApoA-IV on the coagulation system, including its interactions with potential targets and the underlying mechanisms.

Plasma ApoA-IV levels in deep vein thrombosis patients were tested by enzyme-linked immunosorbent assay. The effects of ApoA-IV on coagulation were assessed through thromboelastography. Potential interactions and mechanisms were analyzed using surface plasmon resonance and AlphaFold 3. Mice bleeding and stroke models were employed to evaluate the effects on hemostasis and thrombosis.

ApoA-IV levels were reduced in deep vein thrombosis patients and correlated with increased thrombotic risk. Thromboelastography showed that ApoA-IV treatment delayed clot reaction and kinetic times while decreasing thrombus generation angle and maximum amplitude, highlighting its crucial role in inhibiting coagulation and platelet aggregation. We identified ApoA-IV as a functional activator of activated protein C (APC), with critical interactions occurring at residues 144 to 148 within the exosite loop of the APC protease domain. In animal models, anti-ApoA-IV antibody administration shortened bleeding time but exacerbated ischemic stroke outcomes. Notably, inhibitory peptide HE5, which inhibits ApoA-IV-APC interaction, effectively counteracted the anticoagulant activity of ApoA-IV.

These findings establish ApoA-IV as a pivotal regulator of coagulation and hemostasis, primarily through enhancing APC activity. This research advances our understanding of the interplay between inflammation, lipid metabolism, and thrombosis, offering insights for developing novel antithrombotic therapies.