The interaction of procoagulant platelets with neutrophil granulocytes - Potential impact on thromboinflammation

Abstract

The aim of this MD thesis was to investigate the interaction of procoagulant platelets with neutrophil granulocytes. This interaction was recently proposed to play an important role in the setting of immunothrombosis, where (hyper-)inflammatory diseases trigger a pro-thrombotic setting with increased risk of thrombosis and embolism. For the purpose of this MD project, laboratory models were developed that allowed further quantification of platelet-neutrophil interplay. Washed platelets were subjected to established agonists in order to induce different platelet subpopulations. The resulting distinguishable platelet subpopulations included resting, activated and procoagulant platelets. The procoagulant effects of the latter have at least partially been attributed to the presence of PS on the platelet surface. Basically, two endpoints in platelet-neutrophil interaction were defined. First, platelet-neutrophil aggregate (PNA) formation was assessed in a flow-cytometric approach. A microscopic assay was then established to visualize and quantify the effects on release of NETs. Activated and procoagulant platelets appeared to have a similar potential in stimulating PNA formation. CD62-P plays a key role in mediating PNA formation although interestingly, subsequent inhibition experiments with anti-CD62P and anti-PS point towards at least one additional factor involved in aggregation. Namely, procoagulant platelets demonstrated to be less affected by CD62P blockade and to a certain degree showed sensitivity to PS inhibition. Ultimately, release of neutrophil extracellular traps (NETs) from neutrophils was observed to be higher when co-incubated with procoagulant platelets as compared to NET release by stimulation from solely activated platelets. The obtained data in this MD thesis support the hypothesis that procoagulant platelets are equipped with additional unique pro-NETotic properties which may favour pathological thrombus formation.