Intake of hemoglobin by the hemoglobin-haptoglobin receptor CD163 leads to a distinct alternative non–foam cell antiinflammatory macrophage phenotype that was previously considered atheroprotective. Here, we reveal an unexpected but important pathogenic role for these macrophages in atherosclerosis. Using human atherosclerotic samples, cultured cells, and a mouse model of advanced atherosclerosis, we investigated the role of intraplaque hemorrhage on macrophage function with respect to angiogenesis, vascular permeability, inflammation, and plaque progression. In human atherosclerotic lesions, CD163⁺ macrophages were associated with plaque progression, microvascularity, and a high level of HIF1α and VEGF-A expression. We observed irregular vascular endothelial cadherin in intraplaque microvessels surrounded by CD163⁺ macrophages. Within these cells, activation of HIF1α via inhibition of prolyl hydroxylases promoted VEGF-mediated increases in intraplaque angiogenesis, vascular permeability, and inflammatory cell recruitment. CD163⁺ macrophages increased intraplaque endothelial VCAM expression and plaque inflammation. Subjects with homozygous minor alleles of the SNP rs7136716 had elevated microvessel density, increased expression of CD163 in ruptured coronary plaques, and a higher risk of myocardial infarction and coronary heart disease in population cohorts. Thus, our findings highlight a nonlipid-driven mechanism by which alternative macrophages promote plaque angiogenesis, leakiness, inflammation, and progression via the CD163/HIF1α/VEGF-A pathway.

Intraplaque hemorrhage (IPH) is a phenomenon observed in advanced atherosclerotic plaques. Paterson1 was the first to propose vasa vasorum as the source of IPH. Barger et al2 described an abundance of plaque microvessels found in diseased coronary arteries compared with healthy ones and proposed that plaque neovascularization plays an important role in the pathogenesis of atherosclerosis. A postmortem study from our group established a critical relationship between erythrocyte extravasation in coronary atherosclerotic plaques (measured by the red blood cell membrane sialoglycoprotein glycophorin A) and necrotic core enlargement and plaque progression.3 In a different postmortem study, plaque macrophages were found to be 2- to 4-fold more abundant in patients with symptomatic cardiovascular disease, and the adjacent microvessel network was found to be denser.4 Kockx et al5 showed that perivascular foam cells in areas of high microvascular density within carotid plaques frequently contained platelets and erythrocytes. Phagocytosis of red blood cells was shown to be a trigger for macrophage activation in both in vitro and in vivo. It was also shown that macrophages were particularly abundant around newly formed leaky microvessels.5–7 This and other emerging data support the notion that IPH plays a causal role in promoting plaque progression via deposition of free cholesterol from red blood cells.8–10 The effect of plaque hemorrhage translates into higher plaque burden and vulnerability, which are demonstrable in imaging modalities such as magnetic resonance imaging, intravascular ultrasound, and near infrared spectroscopy.11,12 Here, we summarize recent progress made in our understanding of the collective role of IPH, angiogenesis, macrophages, and iron metabolism in atherosclerotic plaque progression. In a recent article, Sun et al13 examined the effect of the blood pressure on carotid plaque IPH diagnosed by magnetic resonance imaging in an asymptomatic …

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).

Background: The “very late” clinical outcomes for durable polymer drug‐eluting stents and bare metal stents ( BMSs ) have been shown to be dissimilar in clinical studies. Conceptually, the long‐term vascular compatibility of BMSs is still regarded to be superior to drug‐eluting stents; however, no pathologic study to date has specifically addressed this issue. We evaluated the very late (≥1 year) pathologic responses to durable polymer drug‐eluting stents (cobalt–chromium [CoCr] everolimus‐eluting stents [ EESs ] and stainless steel sirolimus‐eluting stents [ SS ‐ SESs ]) versus BMSs (CoCr‐ BMSs ). Methods and Results: From the CVP ath stent registry, we studied a total of 119 lesions (40 CoCr‐ EESs , 44 SS ‐ SES s, 35 CoCr‐ BMS s) from 92 autopsy cases with a duration ranging from 1 to 5 years. Sections of stented coronary segments were pathologically analyzed. Inflammation score and the percentage of struts with giant cells were lowest in CoCr‐ EESs (median inflammation score: 0.6; median percentage of struts with giant cells: 3.8%) followed by CoCr‐ BMSs (median inflammation score: 1.3 [ P <0.01]; median percentage of struts with giant cells: 8.9% [ P =0.02]) and SS‐ SESs (median inflammation score: 1.7 [ P <0.01]; median percentage of struts with giant cells: 15.3% [ P <0.01]). Polymer delamination was observed exclusively in SS ‐ SESs and was associated with increased inflammatory and giant cell reactions. The prevalence of neoatherosclerosis with CoCr‐ EESs (50%) was significantly less than with SS ‐ SESs (77%, P =0.02) but significantly greater than with CoCr‐ BMSs (20%, P <0.01). Conclusions: CoCr‐ EESs , SS ‐ SESs , and BMSs each demonstrated distinct vascular responses. CoCr‐ EESs demonstrated the least inflammation, near‐equivalent healing to BMSs , and lower neointimal formation. These results challenge the belief that BMSs have superior biocompatibility compared with some polymeric coated drug‐eluting stents and may have implications for future stent design.