Towards improved understanding of the role of carboxypeptidase U in arterial thrombosis

Date: 19 December 2017

Venue: Campus Drie Eiken, Building O, room O.5 - Universiteitsplein 1 - 2610 Antwerp (Wilrijk)

Time: 4:00 PM - 6:00 PM

PhD candidate: Dorien Leenaerts

Principal investigator: Dirk Hendriks - Anne-Marie Lambeir

Short description: PhD defence Dorien Leenaerts- Department of Pharmaceutical Sciences


Arterial thrombosis is the result of an inappropriate activation of the hemostatic process upon rupture of an atherosclerotic plaque. The subsequent formation of a thrombus can result in the occlusion of a blood vessel supplying the heart or brain, leading to the development of myocardial infarction or ischemic stroke, respectively.

The fibrinolytic system is responsible for the proteolytic degradation of clots and is currently considered to contribute to the growth, stability and resorption capacity of thrombi. In this framework, the underlying hypothesis of this doctoral project was that the antifibrinolytic enzyme carboxypeptidase U (CPU) plays a role in arterial thrombosis.

In a first part of this thesis we developed a CPU generation assay, wherein unique characteristics – extent of proCPU activation, stability of CPU and the threshold level – are integrated. With this method we are now able to quantify the individual time course of CPU generation during coagulation and subsequent lysis. In addition to the CPU generation assay, we evaluated the CPU system in other in vitro systems that mimic the process of thrombus formation and lysis, by incorporating platelets, blood cells, spatial propagation and arterial flow. We provide novel evidence that the CPU system can also modulate fibrinolysis in more advanced hemostatic systems, but the extent of the effect appears to be dependent upon the exact experimental conditions.

Animal models mimicking arterial thrombosis are available, but tools to reliably measure CPU in pathological animal models have long been missing. In a second part, we optimized pre-analytical and analytical variables to enable accurate measurements in rat. Subsequently, the assays were used to explore the CPU system in two experimental stroke models. Results clearly indicate that the CPU pathway is activated upon cerebral ischemia.

In a third part, we demonstrated that CPU is detectable in the blood of patients presenting with acute myocardial infarction. Furthermore, we found evidence that the systemic levels are the result of a local generation of CPU at the thrombus site, as intracoronary blood samples contained more CPU than the peripheral samples from the same individuals.

In conclusion, the proCPU/CPU pathway is likely to be involved in arterial thrombus formation and data from this work serve as an incentive for further investigation in this field. Currently, the pharmaceutical industry evaluates CPU inhibitors in clinical trials. Ultimately, these investigations will uncover whether CPU inhibitors, alone or in combination with tPA, are beneficial in the treatment of arterial thrombosis.