C oronary heart disease is the leading cause of death worldwide, and at least 7 million patients die of this disease each year (386 324 people in the United States alone).1 Acute myocardial infarction (AMI) is the most severe type of coronary heart disease and the most frequent cause of heart failure, and it impairs the quality of life and inflates medical costs. Timely and successful revascularization therapy for AMI reduces short-term mortality, and current standard medical therapy with angiotensin-converting enzyme inhibitors and β-blockers ameliorates the development of post-myocardial infarction heart failure. However, these recent advances in therapeutic intervention for AMI are associated with an increased prevalence of heart failure with high long-term mortality, which remains a serious concern.2 In the United States, 5.1 million people experienced heart failure in 2010, and 274 601 people died of heart failure in 2009. 1 Therefore, there is an urgent need for preventive treatment to avoid plaque destabilization and rupture, which directly cause AMI. Clinical Perspective on p 906Rupture-prone unstable atherosclerotic plaques feature monocyte/macrophage infiltration, lipid core formation, and fibrous cap thinning by matrix metalloproteinases (MMPs). 3 Recent reports suggest that monocytes are functionally polarized into at least 2 major subsets: Inflammatory monocytes (CD14 high in mice). 4 Inflammatory monocytes are found in the peripheral blood of patients with AMI, 5 Background-Preventing atherosclerotic plaque destabilization and rupture is the most reasonable therapeutic strategy for acute myocardial infarction. Therefore, we tested the hypotheses that (1) inflammatory monocytes play a causative role in plaque destabilization and rupture and (2) the nanoparticle-mediated delivery of pitavastatin into circulating inflammatory monocytes inhibits plaque destabilization and rupture. Methods and Results-We used a model of plaque destabilization and rupture in the brachiocephalic arteries of apolipoprotein E-deficient (ApoE −/− ) mice fed a high-fat diet and infused with angiotensin II. The adoptive transfer of CCR2 +/+ Ly-6C high inflammatory macrophages, but not CCR2 −/− leukocytes, accelerated plaque destabilization associated with increased serum monocyte chemoattractant protein-1 (MCP-1), monocyte-colony stimulating factor, and matrix metalloproteinase-9. We prepared poly(lactic-co-glycolic) acid nanoparticles that were incorporated by Ly-6G − CD11b+ monocytes and delivered into atherosclerotic plaques after intravenous administration. Intravenous treatment with pitavastatin-incorporated nanoparticles, but not with control nanoparticles or pitavastatin alone, inhibited plaque destabilization and rupture associated with decreased monocyte infiltration and gelatinase activity in the plaque. Pitavastatin-incorporated nanoparticles inhibited MCP-1-induced monocyte chemotaxis and the secretion of MCP-1 and matrix metalloproteinase-9 from cultured macrophages. Furthermore, the nanoparticle-mediated a...

Objective-Inflammatory monocytes/macrophages produce various proteinases, including matrix metalloproteinases, and degradation of the extracellular matrix by these activated proteinases weakens the mechanical strength of atherosclerotic plaques, which results in a rupture of the plaque. Peroxisome proliferator-activated receptor-γ induces a polarity shift of monocytes/macrophages toward less inflammatory phenotypes and has the potential to prevent atherosclerotic plaque ruptures. Therefore, we hypothesized that nanoparticle-mediated targeted delivery of the peroxisome proliferatoractivated receptor-γ agonist pioglitazone into circulating monocytes could effectively inhibit plaque ruptures in a mouse model. Approach and Results-We prepared bioabsorbable poly(lactic-co-glycolic-acid) nanoparticles containing pioglitazone (pioglitazone-NPs). Intravenously administered poly(lactic-co-glycolic-acid) nanoparticles incorporated with fluorescein isothiocyanate were found in circulating monocytes and aortic macrophages by flow cytometric analysis. Weekly intravenous administration of pioglitazone-NPs (7 mg/kg per week) for 4 weeks decreased buried fibrous caps, a surrogate marker of plaque rupture, in the brachiocephalic arteries of ApoE −/− mice fed a high-fat diet and infused with angiotensin II. In contrast, administration of control-NPs or an equivalent dose of oral pioglitazone treatment produced no effects. Pioglitazone-NPs inhibited the activity of matrix metalloproteinases and cathepsins in the brachiocephalic arteries. Pioglitazone-NPs regulated inflammatory cytokine expression and also suppressed the expression of extracellular matrix metalloproteinase inducer in bone marrow-derived macrophages. Conclusions-Nanoparticle-mediated delivery of pioglitazone inhibited macrophage activation and atherosclerotic plaque ruptures in hyperlipidemic ApoE −/− mice. These results demonstrate a promising strategy with a favorable safety profile to prevent atherosclerotic plaque ruptures.

Myocardial ischemia-reperfusion (IR) injury limits the therapeutic effect of early reperfusion therapy for acute myocardial infarction (AMI), in which the recruitment of inflammatory monocytes plays a causative role. Here we develop bioabsorbable poly-lactic/glycolic acid (PLGA) nanoparticles incorporating irbesartan, an angiotensin II type 1 receptor blocker with a peroxisome proliferator-activated receptor (PPAR)γ agonistic effect (irbesartan-NP). In a mouse model of IR injury, intravenous PLGA nanoparticles distribute to the IR myocardium and monocytes in the blood and in the IR heart. Single intravenous treatment at the time of reperfusion with irbesartan-NP (3.0 mg kg−1 irbesartan), but not with control nanoparticles or irbesartan solution (3.0 mg kg−1), inhibits the recruitment of inflammatory monocytes to the IR heart, and reduces the infarct size via PPARγ-dependent anti-inflammatory mechanisms, and ameliorates left ventricular remodeling 21 days after IR. Irbesartan-NP is a novel approach to treat myocardial IR injury in patients with AMI.

Administration of drugs and other therapeutic agents has been the central strategy of contemporary medicine for cardiovascular disease. The use of drug delivery systems (DDS) includes micelles, liposomes, polymeric nanoparticles, dendrimers, carbon nanotubes, and crystalline metals. Nano-DDS modify in vivo drug kinetics, depending on (patho)physiological mechanisms such as retard excretion, vascular permeability, and incorporation by mononuclear phagocyte systems, which constitute the 'passive-targeting' property of nano-DDS. These properties of nano-DDS are applicable to inflammatory diseases including atherosclerosis. Atherosclerotic plaque destabilization and rupture account for the majority of acute myocardial infarction, for which inflammatory monocytes and macrophages play critical roles. In our experience, polymeric nanoparticles have been delivered to inflammatory monocytes and macrophages in an atherosclerotic mouse model. Nano-DDS loaded with pioglitazone reduced Ly6C inflammatory monocytes and increased Ly6C non-inflammatory monocytes in the peripheral blood, and induced M2 macrophage-associated genes in the aorta. Pioglitazone-nanoparticles finally stabilized atherosclerotic plaques assessed by a decrease in the number of buried fibrous caps in the plaque. Application of nano-DDS is a unique and promising approach to prevent life-threatening cardiovascular events including acute myocardial infarction by regulating inflammation in the cardiovascular system.

NP-mediated cell-selective statin delivery may be a more effective and integrative strategy for therapeutic neovascularization in patients with severe organ ischemia.