Uremic Serum and Solutes Increases Post Vascular Interventional Thrombotic Risk through Altered Stability of Smooth Muscle Cell Tissue Factor
Background—Stent thrombosis (ST) – a post-interventional complication with a mortality of 50% - has an incidence that rises precipitously in patients at risk. Chronic renal failure (CRF) and end stage renal disease (ESRD) have emerged as one of the strongest ST risk factors, yet the mechanism remains elusive. Tissue factor (TF) is a crucial mediator of injury-related thrombosis and has been indicted as essential for ST. We posit that uremia modulates TF in the local vessel wall to induce post-interventional thrombosis in patients with ESRD.
Methods and Results—As a model of the de-endothelialized, post-interventional state, we exposed primary human vascular smooth muscle cells (vSMC) pretreated with uremic serum to coronary-like blood flow. vSMCs TF expression, activity, stability and post-translational modification were examined after treating vSMCs with uremic serum (obtained from patients on hemodialysis) or solutes. We found significantly greater clot formation following uremic serum exposure, which substantially reduced with the prior treatment with anti-TF neutralizing antibody. Uremic sera induced 2-3 fold higher TF expression and activity in vSMCs independent of diabetes. Relevant concentrations of isolated uremic solutes such as indole-3-acetic acid (IA; 3.5 μg/ml), indoxyl sulfate (IS; 25 μg/ml) and uric acid (UA; 80 μg/ml) recapitulated these effects in cell-culture and the flow loop model. We show further that TF undergoes ubiquitination at baseline and that uremic serum, IA, and IS significantly prolong TF half-life by inhibiting its ubiquitination.
Conclusions—The uremic milieu is profoundly thrombogenic and upregulates vSMC TF levels by increasing TF stability and decreasing its ubiquitination. Together, these data demonstrate for the first time that the post-translational regulation of TF in uremia may have a causative role in the increased ST risk observed in uremic patients. These data suggest that interventions that reduce vSMC TF may help prevent ST and that uremic solutes should be considered as novel risk factors for ST in CRF patients.
- Received May 15, 2012.
- Accepted November 13, 2012.
- Copyright © 2012, American Heart Association, Inc. All rights reserved. Unauthorized use prohibited