Cleaved High-Molecular-Weight Kininogen Accelerates the Onset of Endothelial Progenitor Cell Senescence by Induction of Reactive Oxygen Species
Objective—Cleaved high-molecular-weight kininogen (HKa), an activation product of the plasma kallikrein-kinin system, inhibits endothelial cell functions. We questioned whether HKa affects the function of endothelial progenitor cells (EPCs) and accelerates their senescence.
Methods and Results—Treatment with HKa for 2 weeks markedly inhibited the formation of large colonies and proliferation of EPCs on collagen surfaces, whereas HKa did not affect collagen-mediated EPC adhesion and survival. Concomitantly, treated EPCs displayed flattened and giant cell morphological changes and formation of intracellular vacuoles. As determined by acidic β-galactosidase staining, HKa increased senescent EPCs by 2- and >3-fold after culture for 1 and 2 weeks, respectively. In addition, HKa suppressed the telomerase activity of EPCs. HKa concentration-dependently increased the generation of intracellular reactive oxygen species (ROS) and markedly upregulated p38 kinase phosphorylation and prosenescence molecule p16INK4a expression. SB203580, a p38 inhibitor, attenuated the level of HKa-enhanced p16INK4a expression. Either quenching of ROS or inhibition of p38 kinase prevented HKa-induced EPC senescence.
Conclusion—HKa accelerates the onset of EPC senescence by activating the ROS–p38 kinase–p16INK4a signaling cascade. This novel activity of HKa points out the likelihood of HKa serving as an endogenous inducer of EPC senescence.
- Received September 10, 2010.
- Accepted January 3, 2011.
- © 2011 American Heart Association, Inc.