Abstract 5258: SDF1-Triggered Erk-2 Activation In Endothelial Progenitor Cells In Patients With Coronary Artery Disease And Healthy Controls: Role For Adhesion And Migration
Endothelial progenitor cells (EPCs) are a heterogeneous group of bone marrow-derived precursor cells that circulate in peripheral blood and are recruited to sites of vascular injury or tissue damage. The underlying relevant intracellular signalling cascades are poorly characterized. EPCs were isolated from healthy volunteers and from patients with severe coronary artery disease (CAD; stable coronary 3-vessel disease) by density gradient centrifugation and cultured for 4 days under endothelial selection pressure prior to stimulation with the chemokine stromal-derived factor-1 (SDF-1; 100 nM, 30sec-5min). Western blot analysis revealed not only an enhanced phosphorylation of Akt (S473), but also a selective activation of Erk-2 after 60–90sec (baseline (densitometry): 8±2, 60sec: 50±18, 90sec: 134±17 arbitrary units; AU) with a maximum after 3–5min (3min: 232±34, 5min: 232±13 AU; n=3, p<0.05). The SDF-1-triggered Erk-2-phosphorylation could be blocked by pretreatment of EPCs with the Erk-inhibitor PD98059 (10μM, 30min), the Akt-phosphorylation by the PI3-kinase-inhibitor wortmannin. In contrast, EPCs from patients with CAD were characterized by a temporally delayed and quantitatively attenuated Erk-2-phosphorylation (baseline: 1.2±0.3, maximum after 5min: 150±46 AU; n=4, p<0.05). Functionally, pretreatment of EPCs with PD98059 (10μM, 30min; n=3, p<0.05) inhibited SDF-1-triggered migration (modified Boyden chambers; control: 21901±3136, PD: 10187±886 cells/hpf) and adhesion under physiological shear stress (2 dynes/cm2; control: 52±4, PD: 26±3 cells/hpf). Compared to healthy controls, SDF-1-triggered dynamic adhesion of EPCs from patients with coronary 3-vessel disease was significantly diminished (control: 52±4, CAD: 21±3 cells/hpf; n=4, p<0.05). These data identify Erk-2 as a chemokine-activated signaling molecule that regulates migration and adhesion in EPCs and is down-regulated in association with functional defects in EPCs of patients with CAD. Erk-2 may be a potential novel target of EPC-based regenerative strategies for the therapy of ischemic vascular disease.