Thrombopoietin (Tpo) Contributes To Platelet Activation In Human Diseases

Thrombopoietin (TPO) is a humoral growth factor that does not induce platelet aggregation per se, but primes platelet activation in response to several agonists. We investigated the potential contribution of TPO to platelet activation in human diseases. We found that higher TPO levels were associated with increased markers of in vivo platelet activation in patients with unstable angina, compared to patients with stable angina, and cigarette smokers, compared to nonsmokers. In vitro, the plasma from patients with unstable angina, but not from stable angina patients, and from cigarette smokers, primed platelet aggregation and monocyte-platelet binding, which were both reduced when an inhibitor of TPO was used. TPO may therefore enhance platelet activation in acute coronary syndromes and chronic smokers, thus participating to the pathogenesis of atherogenesis and of adverse cardiovascular events.