Abstract 13: Targeting the PERK Pathway of ER Stress Response for Endothelium Protection and Restenosis Prevention:
A Paradigm for Developing Anti-thrombogenic Stents
Introduction: Cardiovascular disease is the leading cause of mortality and morbidity in the US. Reconstructions often fail due to the recurrent lumen narrowing, or restenosis. Stents eluting rapamycin or paclitaxel are deployed to inhibit the excessive proliferation of smooth muscle cells (SMCs), which is the core component of restenosis. However, these drugs cause collateral damage to endothelial cells (ECs) leading to stent thrombosis. To address this, our group initiated the first campaign of drug screening for compounds that selectively inhibit SMC proliferation without causing EC dysfunction. We recently identified lead compounds as such, which are inhibitors for protein kinase RNA-like endoplasmic reticulum kinase (PERK), an endoplasmic reticulum (ER) stress sensor. Here we evaluated PERK as a target for intervention of both SMC pathophysiology and EC dysfunction. Methods: Rat carotid artery balloon angioplasty was performed as a restenosis model. PDGF-BB and TNF-a were applied to primary human aortic SMCs and ECs, respectively, to mimic the in vivo pathogenic stimuli. Results: In balloon-injured arteries, both PERK phosphorylation and the expression of its downstream transcription factor ATF4 were increased compared to sham control. PERK activation was also observed in vitro in both SMCs and ECs stimulated with PDGF-BB and TNF-a, respectively. In SMCs, either selective inhibition (1μM GSK2606414) or siRNA knockdown of PERK abolished PDGF-BB induced de-differentiation and proliferation. In ECs, PERK antagonism abrogated TNF-a induced growth impairment and EC secretion of Tissue Factor (TF), which is the key initiator of thrombogenesis. Finally, in a pilot experiment, peri-adventitial application of GSK2606414 (25mg/kg, n=2 rats) reduced intima/media ratio by 80% and increased lumen area by ~ 2 fold compared to vehicle control (n=2) at 4 weeks post injury. Conclusion: Our results indicate an important role of PERK activation in promoting SMC phenotype switching and EC dysfunction in vitro as well as restenosis in vivo . Thus, PERK targeting represents a potential strategy to simultaneously achieve restenosis prevention and endothelium protection, with a long-term goal of developing anti-thrombogenic drug-eluting stents.