Objective-
Drug-eluting stents eluting canonical mTOR (
mammalian target of rapamycin) inhibitors are widely used to treat
coronary artery disease but accelerate the development of
atherosclerosis within the
stent (neoatherosclerosis)-a leading cause of late
stent failure. We recently showed that canonical
mTOR inhibitors bind
FKBP12.6 (12.6-kDa
FK506-binding protein 12), displace it from
calcium release channels, resulting in activation of PKCα (
protein kinase Cα) and dissociation of p-120-catenin (p120) from VE-CAD (
vascular endothelial cadherin; promoting endothelial barrier dysfunction [EBD]). However, the relevance of these findings to
drug-eluting stents remains unknown. Newer generation direct mTOR
kinase inhibitors do not bind
FKBP12.6 and offer the potential of improving endothelial barrier function while maintaining antirestenotic efficacy, but their actual effects are unknown. We examined the effects of 2 different pharmacological targeting strategies-canonical mTOR inhibitor
everolimus and mTOR
kinase inhibitors Torin-2-on EBD after stenting. Approach and Results- Using the rabbit model of stenting and a combination of
Evans blue dye, confocal and scanning electron microscopy studies,
everolimus-eluting
stents resulted in long-term EBD compared with bare
metal stents. EBD was mitigated by using
stents that eluted mTOR
kinase inhibitors (Torin-2-eluting stent). At 60 days after
stent placement,
everolimus-eluting
stents demonstrated large areas of
Evans blue dye staining and evidence of p120 VE-CAD dissociation consistent with EBD. These findings were absent in bare
metal stents and significantly attenuated in Torin-2-eluting
stent. As proof of concept of the role of EBD in neoatherosclerosis, 100 days after stenting, animals were fed an enriched
cholesterol diet for an additional 30 days.
Everolimus-eluting
stents demonstrated significantly more macrophage infiltration (consistent with neoatherosclerosis) compared with both bare
metal stents and Torin-2-eluting
stent. Conclusions- Our results pinpoint interactions between
FKBP12.6 and canonical
mTOR inhibitors as a major cause of vascular permeability and neoatherosclerosis, which can be overcome by using mTOR
kinase inhibitors. Our study suggests further refinement of molecular targeting of the mTOR complex may be a promising strategy (Graphic Abstract).