Faculty Bibliography

Background: Immune cells, particularly myeloid-derived ones, play a pivotal role in the microenvironment of breast cancer. Because of the high diagnostic and therapeutic values of these immune cells, they have been extensively investigated, mostly invasively. Therefore, non-invasive breast cancer immune cell imaging methods can have great impact on diagnosis, disease management, and evaluation of therapy. Here, we describe the development of a high-density lipoprotein (HDL) -based positron emission tomography (PET) nano-tracer to noninvasively image immune cells in a breast cancer model. Methods: Radiolabeled HDL-based nano-tracers were developed by using two different approaches that incorporated the long-lived positron-emitting nuclide ⁸⁹Zr into HDL. The nano-tracers are composed of the phospholipid DMPC and apolipoprotein A-I (apoA-I) in a 2.5 : 1 weight ratio. DFO chelators, conjugated to either phospholipids or apoA-I proteins, were used to complex with ⁸⁹Zr to generate ⁸⁹Zr-PL-HDL (phospholipid-labeled) or ⁸⁹Zr-AI-HDL (apoA-1- labeled). In vivo evaluation was carried out in an orthotropic mouse model of breast cancer and included pharmacokinetic analysis, biodistribution studies, and PET imaging. Ex vivo radioautography and histology analyses of tumor tissues were performed to assess regional distribution of the nano-tracers. Fluorescent analogs of the nanotracers were used to determine cell-targeting specificity by using flow cytometry. Results: ⁸⁹Zr-PL-HDL (phospholipid-labeled) was produced in 79 +/- 13% (n = 6) radiochemical yield; ⁸⁹Zr-AI-HDL (apoA-I-labeled), 94 +/- 6% (n = 6). Both nano-tracers had at least 99% radiochemical purity. Intravenous administration of both nano-tracers resulted in high tumor radioactivity accumulation (16.5 +/- 2.8 %ID/g for ⁸⁹Zr-PL-HDL and 8.6 +/- 1.3 %ID/g for ⁸⁹Zr-AI-HDL) at 24 hours post injection. Radioautography and histology analyses showed high colocalization of radioactivity with macrophage-rich areas in tumors. Flow cytometry revealed high accumulation of the nano-tracers in myeloid-derived immune cells (preferentially in tumor-associated macrophages and monocytes, followed by dendritic cells and neutrophils), whereas low uptake was observed in endothelial cells and tumor cells (n = 4). Conclusions: Based on natural HDL particles, we have developed immune cell-targeting PET nano-tracers. In an orthotropic mouse model of breast cancer, we have demonstrated their specificity for myeloid-derived immune cells. Quantitative immune cell PET imaging with our ⁸⁹Zr-PET nano-tracers could be valuable for non-invasive diagnosis of breast cancer and evaluation of immunotherapy response. (Figure Presented)

TRPV4 ion channel mediates vascular mechanosensitivity and vasodilation. Here, we sought to explore whether non-mechanical activation of TRPV4 could limit vascular inflammation and atherosclerosis. We found that GSK1016790A, a potent and specific small-molecule agonist of TRPV4, induces the phosphorylation and activation of eNOS partially through the AMPK pathway. Moreover, GSK1016790A inhibited TNF-alpha-induced monocyte adhesion to human endothelial cells. Mice given GSK1016790A showed increased phosphorylation of eNOS and AMPK in the aorta and decreased leukocyte adhesion to TNF-alpha-inflamed endothelium. Importantly, oral administration of GSK1016790A reduced atherosclerotic plaque formation in ApoE deficient mice fed a Western-type diet. Together, the present study suggests that pharmacological activation of TRPV4 may serve as a potential therapeutic approach to treat atherosclerosis.

Liver X receptors (LXR) are oxysterol-activated nuclear receptors that play a central role in reverse cholesterol transport (RCT) through upregulation of ATP-binding Cassette transporters (ABCA1 and ABCG1) that mediate cellular cholesterol efflux. Mouse models of atherosclerosis exhibit reduced atherosclerosis and enhanced regression of established plaques upon LXR activation. However, the coregulatory factors that affect LXR-dependent gene activation in macrophages remain to be elucidated. To identify novel regulators of LXR that modulate its activity, we used affinity purification and mass spectrometry to analyze nuclear LXRalpha complexes, and identified poly(ADP-ribose) polymerase-1 (PARP-1) as an LXR-associated factor. In fact, PARP-1 interacted with both LXRalpha and LXRbeta. Both depletion of PARP-1 and inhibition of PARP-1 activity augmented LXR ligand-induced ABCA1 expression in the RAW 264.7 macrophage line and primary bone marrow derived macrophages, but did not affect LXR-dependent expression of other target genes, ABCG1 and SREBP-1c. Chromatin immunoprecipitation experiments confirmed PARP-1 recruitment at the LXR response element in the promoter of the ABCA1 gene. Further, we demonstrated that LXR is poly(ADP-ribosyl)ated by PARP-1, a potential mechanism by which PARP-1 influences LXR function. Importantly, the PARP inhibitor, 3-aminobenzamide, enhanced macrophage ABCA1-mediated cholesterol efflux to the lipid-poor apolipoprotein AI (apoA-I). These findings shed light on the important role of PARP-1 on LXR-regulated lipid homeostasis. Understanding the interplay between PARP-1 and LXR may provide insights into developing novel therapeutics for treating atherosclerosis.

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.