Faculty Bibliography

BACKGROUND: High density lipoproteins (HDLs) are thought to be atheroprotective and to reduce the risk of cardiovascular disease (CVD). Besides their antioxidant, antithrombotic, anti-inflammatory, anti-apoptotic properties in the vasculature, HDLs also improve glucose metabolism in skeletal muscle. SCOPE OF THE REVIEW: Herein, we review the functional role of HDLs to improve metabolic disorders, especially those involving insulin resistance and to induce regression of CVD with a particular focus on current pharmacological treatment options as well as lifestyle interventions, particularly exercise. MAJOR CONCLUSIONS: Functional properties of HDLs continue to be considered important mediators to reverse metabolic dysfunction and to regress atherosclerotic cardiovascular disease. Lifestyle changes are often recommended to reduce the risk of CVD, with exercise being one of the most important of these. Understanding how exercise improves HDL function will likely lead to new approaches to battle the expanding burden of obesity and the metabolic syndrome.

Cardinal events in atherogenesis are the retention of apolipoprotein B-containing lipoproteins in the arterial wall and the reaction of macrophages to these particles. My laboratory has been interested in both the cell biological events producing apolipoprotein B-containing lipoproteins, as well as in the reversal of the damage they cause in the plaques formed in the arterial wall. In the 2013 George Lyman Duff Memorial Lecture, as summarized in this review, I covered 3 areas of my past, present, and future interests, namely, the regulation of hepatic very low density lipoprotein production by the degradation of apolipoprotein B100, the dynamic changes in macrophages in the regression of atherosclerosis, and the application of nanoparticles to both image and treat atherosclerotic plaques.

Atherosclerosis, caused in part by monocytes in plaques, continues to be a disease that afflicts the modern world. Whilst significant steps have been made in treating this chronic inflammatory disease, questions remain on how to prevent monocyte and macrophage accumulation in atherosclerotic plaques. Junctional Adhesion Molecule C (JAM-C) expressed by vascular endothelium directs monocyte transendothelial migration in a unidirectional manner leading to increased inflammation. Here we show that interfering with JAM-C allows reverse-transendothelial migration of monocyte-derived cells, opening the way back out of the inflamed environment. To study the role of JAM-C in plaque regression we used a mouse model of atherosclerosis, and tested the impact of vascular JAM-C expression levels on monocyte reverse transendothelial migration using human cells. Studies in-vitro under inflammatory conditions revealed that overexpression or gene silencing of JAM-C in human endothelium exposed to flow resulted in higher rates of monocyte reverse-transendothelial migration, similar to antibody blockade. We then transplanted atherosclerotic, plaque-containing aortic arches from hyperlipidemic ApoE-/- mice into wild-type normolipidemic recipient mice. JAM-C blockade in the recipients induced greater emigration of monocyte-derived cells and further diminished the size of atherosclerotic plaques. Our findings have shown that JAM-C forms a one-way vascular barrier for leukocyte transendothelial migration only when present at homeostatic copy numbers. We have also shown that blocking JAM-C can reduce the number of atherogenic monocytes/macrophages in plaques by emigration, providing a novel therapeutic strategy for chronic inflammatory pathologies.

Cellular metabolism is increasingly recognized as a controller of immune cell fate and function. MicroRNA-33 (miR-33) regulates cellular lipid metabolism and represses genes involved in cholesterol efflux, HDL biogenesis, and fatty acid oxidation. Here, we determined that miR-33-mediated disruption of the balance of aerobic glycolysis and mitochondrial oxidative phosphorylation instructs macrophage inflammatory polarization and shapes innate and adaptive immune responses. Macrophage-specific Mir33 deletion increased oxidative respiration, enhanced spare respiratory capacity, and induced an M2 macrophage polarization-associated gene profile. Furthermore, miR-33-mediated M2 polarization required miR-33 targeting of the energy sensor AMP-activated protein kinase (AMPK), but not cholesterol efflux. Notably, miR-33 inhibition increased macrophage expression of the retinoic acid-producing enzyme aldehyde dehydrogenase family 1, subfamily A2 (ALDH1A2) and retinal dehydrogenase activity both in vitro and in a mouse model. Consistent with the ability of retinoic acid to foster inducible Tregs, miR-33-depleted macrophages had an enhanced capacity to induce forkhead box P3 (FOXP3) expression in naive CD4+ T cells. Finally, treatment of hypercholesterolemic mice with miR-33 inhibitors for 8 weeks resulted in accumulation of inflammation-suppressing M2 macrophages and FOXP3+ Tregs in plaques and reduced atherosclerosis progression. Collectively, these results reveal that miR-33 regulates macrophage inflammation and demonstrate that miR-33 antagonism is atheroprotective, in part, by reducing plaque inflammation by promoting M2 macrophage polarization and Treg induction.

BACKGROUND: Diabetes mellitus (DM) and metabolic syndrome are important targets for secondary prevention in cardiovascular disease. However, the prevalence in patients undergoing elective percutaneous coronary intervention (PCI) is not well defined. We aimed to analyze the prevalence and characteristics of patients undergoing PCI with previously unrecognized prediabetes, diabetes and metabolic syndrome. METHODS: Data were collected from 740 patients undergoing elective PCI between November 2010 and March 2013 at a tertiary referral center. Prevalence of DM and prediabetes was evaluated using Hemoglobin A1c (A1c >/= 6.5% for DM, A1c 5.7-6.4% for prediabetes). A modified definition was used for metabolic syndrome [3 or more of the following criteria: body mass index (BMI) >/=30 kg/m2; triglycerides >/= 150 mg/dL; high density lipoprotein <40 mg/dL in men and <50 mg/dL in women; systolic blood pressure >/= 130 mmHg and/or diastolic >/= 85 mmHg; A1c >/= 5.7% or on therapy]. RESULTS: Mean age was 67 years, median BMI was 28.2 kg/m2 , and 39% had known DM. Of those without known DM, 8.3% and 58.5% met A1c criteria for DM and for prediabetes at time of PCI. Overall, 54.9% met criteria for metabolic syndrome (69.2% of patients with DM and 45.8% of patients without DM). CONCLUSION: Among patients undergoing elective PCI, a substantial number were identified with new DM, prediabetes, and/or metabolic syndrome. Routine screening for an abnormal glucometabolic state at the time of revascularization may be useful for identifying patients who may benefit from additional targeting of modifiable risk factors

BACKGROUND: Patients undergoing cardiovascular procedures remain at increased risk for myocardial infarction, stroke, and cardiovascular death. Risk factor control in this patient population remains suboptimal and would likely benefit from strategies targeting education, lifestyle, and healthy behaviors. DESIGN: The IMPACT trial is a 400-subject prospective randomized trial designed to compare different cardiovascular prevention strategies in subjects following a cardiovascular intervention. The trial began enrollment in the Spring of 2012 and is randomizing subjects in a 1:1:1 manner to usual care, a one-time cardiovascular prevention consult, or a one-time cardiovascular prevention consult plus behavioral intervention program (telephone-based motivational interviewing and tailored text messages) over a 6-month period. The primary end point is non-high-density lipoprotein cholesterol. Secondary end points include other plasma lipid values, metabolic risk, smoking cessation, physical activity, dietary intake, medication use and adherence, and quality of life. CONCLUSIONS: The IMPACT trial provides data on different management strategies for risk factor optimization in subjects following cardiovascular procedures. The results will provide a platform for the continued development of novel multidisciplinary interventions in this high-risk population.

Tumor-associated macrophages (TAMs) are increasingly investigated in cancer immunology and are considered a promising target for better and tailored treatment of malignant growth. Although TAMs also have high diagnostic and prognostic value, TAM imaging still remains largely unexplored. Here, we describe the development of reconstituted high-density lipoprotein (rHDL)-facilitated TAM PET imaging in a breast cancer model. METHODS: Radiolabeled rHDL nanoparticles incorporating the long-lived positron-emitting nuclide (89)Zr were developed using 2 different approaches. The nanoparticles were composed of phospholipids and apolipoprotein A-I (apoA-I) in a 2.5:1 weight ratio. (89)Zr was complexed with deferoxamine (also known as desferrioxamine B, desferoxamine B), conjugated either to a phospholipid or to apoA-I to generate (89)Zr-PL-HDL and (89)Zr-AI-HDL, respectively. In vivo evaluation was performed in an orthotopic mouse model of breast cancer and included pharmacokinetic analysis, biodistribution studies, and PET imaging. Ex vivo histologic analysis of tumor tissues to assess regional distribution of (89)Zr radioactivity was also performed. Fluorescent analogs of the radiolabeled agents were used to determine cell-targeting specificity using flow cytometry. RESULTS: The phospholipid- and apoA-I-labeled rHDL were produced at 79% +/- 13% (n = 6) and 94% +/- 6% (n = 6) radiochemical yield, respectively, with excellent radiochemical purity (>99%). Intravenous administration of both probes resulted in high tumor radioactivity accumulation (16.5 +/- 2.8 and 8.6 +/- 1.3 percentage injected dose per gram for apoA-I- and phospholipid-labeled rHDL, respectively) at 24 h after injection. Histologic analysis showed good colocalization of radioactivity with TAM-rich areas in tumor sections. Flow cytometry revealed high specificity of rHDL for TAMs, which had the highest uptake per cell (6.8-fold higher than tumor cells for both DiO@Zr-PL-HDL and DiO@Zr-AI-HDL) and accounted for 40.7% and 39.5% of the total cellular DiO@Zr-PL-HDL and DiO@Zr-AI-HDL in tumors, respectively. CONCLUSION: We have developed (89)Zr-labeled TAM imaging agents based on the natural nanoparticle rHDL. In an orthotopic mouse model of breast cancer, we have demonstrated their specificity for macrophages, a result that was corroborated by flow cytometry. Quantitative macrophage PET imaging with our (89)Zr-rHDL imaging agents could be valuable for noninvasive monitoring of TAM immunology and targeted treatment.

In mouse models of atherosclerosis, normalization of hyperlipidemia promotes macrophage emigration and regression of atherosclerotic plaques in part by the Liver X Receptor (LXR)-mediated induction of the chemokine receptor CCR7. Here we report that LXRalpha serine 198 (S198) phosphorylation modulates CCR7 expression. Low levels of S198 phosphorylation are observed in plaque macrophages in the regression environment where high levels of CCR7 expression are observed. Consistent with these findings, CCR7 gene expression in human and mouse macrophages cell lines is induced when LXRalpha at S198 is non-phosphorylated. In bone marrow derived-macrophages (BMDMs) we also observe induction of CCR7 by ligands that promote non-phosphorylated LXRalpha S198 and this is lost in LXR deficient BMDMs. LXRalpha occupancy at the CCR7 promoter is enhanced and histone modifications associated with gene repression are reduced in RAW264.7 cells expressing non-phosphorylated (RAW-LXRalphaS198A) compared to phosphorylated LXRalpha (RAW-LXRalphaWT). Expression profiling from ligand treated RAW-LXRalphaS198A compared to RAW-LXRalphaWT cells revealed induction of cell migratory and anti-inflammatory genes, and repression of pro-inflammatory genes. Modeling of LXRalpha S198 in non-phosphorylated and phosphorylated states identified phosphorylation-dependent conformational changes in the hinge region commensurate with sites for protein interaction. Therefore, gene transcription is regulated by LXRalpha S198 phosphorylation including anti-atherogenic genes like CCR7.

Inflammation drives atherosclerotic plaque progression and rupture, and is a compelling therapeutic target. Consequently, attenuating inflammation by reducing local macrophage accumulation is an appealing approach. This can potentially be accomplished by either blocking blood monocyte recruitment to the plaque or increasing macrophage apoptosis and emigration. Because macrophage proliferation was recently shown to dominate macrophage accumulation in advanced plaques, locally inhibiting macrophage proliferation may reduce plaque inflammation and produce long-term therapeutic benefits. To test this hypothesis, we used nanoparticle-based delivery of simvastatin to inhibit plaque macrophage proliferation in apolipoprotein E deficient mice (Apoe-/- ) with advanced atherosclerotic plaques. This resulted in rapid reduction of plaque inflammation and favorable phenotype remodeling. We then combined this short-term nanoparticle intervention with an eight-week oral statin treatment, and this regimen rapidly reduced and continuously suppressed plaque inflammation. Our results demonstrate that pharmacologically inhibiting local macrophage proliferation can effectively treat inflammation in atherosclerosis.