OBJECTIVE: Based on the emerging importance of the wingless (Wnt) pathways in inflammation and vascular biology, we hypothesized a role for Dickkopf-1 (DKK-1), a major modulator of Wnt signaling, in atherogenesis and plaque destabilization. METHODS AND RESULTS: We report increased levels of DKK-1 in experimental (ApoE(-/-) mice) and clinical (patients with coronary artery disease [n=80] and patients with carotid plaque [n=47]) atherosclerosis, both systemically (serum) and within the lesion, with particularly high levels in advanced and unstable disease. We identified platelets as an important cellular source of DKK-1 as shown by in vitro experiments and by immunostaining of thrombus material obtained at the site of plaque rupture in patients with acute ST-elevation myocardial infarction, with strong immunoreactivity in platelet aggregates. Our in vitro experiments identified a role for platelet- and endothelial-derived DKK-1 in platelet-dependent endothelial activation, promoting enhanced release of inflammatory cytokines. These inflammatory effects of DKK-1 involved inhibition of the Wnt/beta-catenin pathway and activation of nuclear factor kappaB. CONCLUSIONS: Our findings identify DKK-1 as a novel mediator in platelet-mediated endothelial cell activation. The demonstration of enhanced DKK-1 expression within advanced carotid plaques may suggest that this DKK-1-driven inflammatory loop could be operating within the atherosclerotic lesion.
OBJECTIVE: Based on the emerging importance of the wingless (Wnt) pathways in inflammation and vascular biology, we hypothesized a role for Dickkopf-1 (DKK-1), a major modulator of Wnt signaling, in atherogenesis and plaque destabilization. METHODS AND RESULTS: We report increased levels of DKK-1 in experimental (ApoE(-/-) mice) and clinical (patients with coronary artery disease [n=80] and patients with carotid plaque [n=47]) atherosclerosis, both systemically (serum) and within the lesion, with particularly high levels in advanced and unstable disease. We identified platelets as an important cellular source of DKK-1 as shown by in vitro experiments and by immunostaining of thrombus material obtained at the site of plaque rupture in patients with acute ST-elevation myocardial infarction, with strong immunoreactivity in platelet aggregates. Our in vitro experiments identified a role for platelet- and endothelial-derived DKK-1 in platelet-dependent endothelial activation, promoting enhanced release of inflammatory cytokines. These inflammatory effects of DKK-1 involved inhibition of the Wnt/beta-catenin pathway and activation of nuclear factor kappaB. CONCLUSIONS: Our findings identify DKK-1 as a novel mediator in platelet-mediated endothelial cell activation. The demonstration of enhanced DKK-1 expression within advanced carotid plaques may suggest that this DKK-1-driven inflammatory loop could be operating within the atherosclerotic lesion.