Cleaved High Molecular Weight Kininogen Induces Endothelial Progenitor Cell Senescence by Stimulation of JNK/FOXO4/MnSOD Pathway.

High molecular weight kininogen (HK) is a major component of plasma kallikrein-kinin system (KKS), and is cleaved to its active form (HKa) upon the activation of this system. Although the KKS activation is widely involved in a variety of pathological settings, the activities of its activation product HKa remain largely unknown. Recently we have reported that HKa accelerates the onset of endothelial progenitor cell (EPC) senescence by induction of reactive oxygen species (Arterioscler Thromb Vasc Biol. 2011;31:883), whereas the mechanism is not clear. In this study, we investigated whether HKa induces EPC senescence via stimulation of c-Jun N-terminal kinases (JNK)-related pathway.

Human EPCs were treated with HKa in different concentrations for 72 hours, which were followed by the measurement of phospharylation of JNK at Thr183/tyr185 and transcription factor FOXO4 at Thr451, as well as expression of Mn-superoxide dismutase (MnSOD) at protein and mRNA level. To narrow down the functional domain of HKa, recombinant proteins of human HK heavy chain (HC, 19–380aa) and light chain (LC, 390–644aa) were generated for determining which domain(s) mediates the effect of HKa.

In a concentration-dependent manner, HKa treatment induced phosphorylation of JNK at Thr183/Tyr185, and its downstream phosphorylation of transcription factor FOXO4 at Thr451. Concomitantly, HKa upregulated the expression of MnSOD at protein and mRNA levels as measured by Western blot and real time RT-PCR. However, it did not affect the expression of catalase. Similar to HKa, the heavy chain (HC), but not the light chain, increased the percentage of senescent EPCs (63%±6.6 for HC v.s. 77.5%±6.02 for HKa). Moreover, HC at 100 nM increased FOXO4 phosphorylation at Thr451 and the expression of MnSOD in EPCs. Besides, both of HKa and its HC stimulated the production of intracellular H₂O₂.

These above results demonstrate that HKa accelerates the onset of EPC senescence by stimulating JNK/FOXO4/MnSOD pathway, and its effect is mediated by the HC.

No relevant conflicts of interest to declare.