Nanomedicine-based strategies for treatment of atherosclerosis

Optimization of RGD-modified Nano-liposomes Encapsulating Eptifibatide

BACKGROUND

Eptifibatide (Integrilin) is an intravenous (IV) peptide drug that selectively inhibits ligand binding to the platelet GP IIb/IIIa receptor. It is an efficient peptide drug, however has a short half-life. Therefore, antithrombotic agents like eptifibatide are required to become improved with a protected and targeted delivery system such as using nano-liposomes to the site of thrombus.

OBJECTIVES

The goal in the present report was to optimize encapsulation efficiency of the eptifibatide into Arg-Gly-Asp (RGD)-modified nano-liposomes (RMNL). As well, it was intended to evaluate the effect of sodium lauryl sulfate (SLS) on drug release.

MATERIALS AND METHODS

The effect of five independent variables including number of freeze/thawing cycles, concentration of eptifibatide, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), cholesterol, and dipalmitoyl-GRGDSPA peptide on drug entrapment efficiency (DEE) was investigated using response surface methodology (RSM). The effect of different concentrations of SLS on encapsulation and drug release from RMNL was also investigated. The size and morphology of RMNL were characterized using transmission electron microscopy (TEM).

RESULTS

The maximum DEE (38%) was obtained with 7 freeze/thawing cycles, 3.65 mmoL eptifibatide, 7 mM DSPC, 3 mM cholesterol, and 1 mM dipalmitoyl- GRGDSPA peptide. SLS has significantly increased the drug release from RMNL, although its effect on encapsulation efficiency was not significant.

CONCLUSIONS

The optimization of the formulations for valuable and expensive peptide drugs is essential to have the maximum encapsulation efficiency and the minimum experiments.

Enhancement of Anti-Inflammatory Activity of Curcumin Using Phosphatidylserine-Containing Nanoparticles in Cultured Macrophages

Macrophages are one kind of innate immune cells, and produce a variety of inflammatory cytokines in response to various stimuli, such as oxidized low density lipoprotein found in the pathogenesis of atherosclerosis. In this study, the effect of phosphatidylserine on anti-inflammatory activity of curcumin-loaded nanostructured lipid carriers was investigated using macrophage cultures. Different amounts of phosphatidylserine were used in the preparation of curcumin nanoparticles, their physicochemical properties and biocompatibilities were then compared. Cellular uptake of the nanoparticles was investigated using a confocal laser scanning microscope and flow cytometry analysis in order to determine the optimal phosphatidylserine concentration. In vitro anti-inflammatory activities were evaluated in macrophages to test whether curcumin and phosphatidylserine have interactive effects on macrophage lipid uptake behavior and anti-inflammatory responses. Here, we showed that macrophage uptake of phosphatidylserine-containing nanostructured lipid carriers increased with increasing amount of phosphatidylserine in the range of 0%–8%, and decreased when the phosphatidylserine molar ratio reached over 12%. curcumin-loaded nanostructured lipid carriers significantly inhibited lipid accumulation and pro-inflammatory factor production in cultured macrophages, and evidently promoted release of anti-inflammatory cytokines, when compared with curcumin or phosphatidylserine alone. These results suggest that the delivery system using PS-based nanoparticles has great potential for efficient delivery of drugs such as curcumin, specifically targeting macrophages and modulation of their anti-inflammatory functions.

Detection and treatment of atherosclerosis using nanoparticles

Atherosclerosis is the key pathogenesis of cardiovascular disease, which is a silent killer and a leading cause of death in the United States. Atherosclerosis starts with the adhesion of inflammatory monocytes on the activated endothelial cells in response to inflammatory stimuli. These monocytes can further migrate into the intimal layer of the blood vessel where they differentiate into macrophages, which take up oxidized low-density lipoproteins and release inflammatory factors to amplify the local inflammatory response. After accumulation of cholesterol, the lipid-laden macrophages are transformed into foam cells, the hallmark of the early stage of atherosclerosis. Foam cells can die from apoptosis or necrosis, and the intracellular lipid is deposed in the artery wall forming lesions. The angiogenesis for nurturing cells is enhanced during lesion development. Proteases released from macrophages, foam cells, and other cells degrade the fibrous cap of the lesion, resulting in rupture of the lesion and subsequent thrombus formation. Thrombi can block blood circulation, which represents a major cause of acute heart events and stroke. There are generally no symptoms in the early stages of atherosclerosis. Current detection techniques cannot easily, safely, and effectively detect the lesions in the early stages, nor can they characterize the lesion features such as the vulnerability. While the available therapeutic modalities cannot target specific molecules, cells, and processes in the lesions, nanoparticles appear to have a promising potential in improving atherosclerosis detection and treatment via targeting the intimal macrophages, foam cells, endothelial cells, angiogenesis, proteolysis, apoptosis, and thrombosis. Indeed, many nanoparticles have been developed in improving blood lipid profile and decreasing inflammatory response for enhancing therapeutic efficacy of drugs and decreasing their side effects. WIREs Nanomed Nanobiotechnol 2017, 9:e1412. doi: 10.1002/wnan.1412 For further resources related to this article, please visit the WIREs website.

Targeting and therapeutic peptides in nanomedicine for atherosclerosis

Peptides in atherosclerosis nanomedicine provide structural, targeting, and therapeutic functionality and can assist in overcoming delivery barriers of traditional pharmaceuticals. Moreover, their inherent biocompatibility and biodegradability make them especially attractive as materials intended for use in vivo In this review, an overview of nanoparticle-associated targeting and therapeutic peptides for atherosclerosis is provided, including peptides designed for cellular targets such as endothelial cells, monocytes, and macrophages as well as for plaque components such as collagen and fibrin. An emphasis is placed on recent advances in multimodal strategies and a discussion on current challenges and barriers for clinical applicability is presented.

Novel directions in inflammation as a therapeutic target in atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis is a chronic disease of the arterial wall largely driven by inflammation; hence, therapeutics targeting inflammatory pathways are considered an attractive strategy in atherosclerotic cardiovascular disease (ASCVD). The purpose of this review is to describe the randomized, placebo-controlled clinical trials currently investigating the impact of anti-inflammatory strategies in ASCVD patients, to discuss novel insights and targets into the role of innate immunity in atherosclerosis and to address the promise of local drug delivery as opposed to systemic therapies in atherosclerotic disease.

RECENT FINDINGS

The first clinical trials using systemic anti-inflammatory drugs in ASCVD patients might be able to strengthen the case for immunomodulation once showing an improved ASCVD outcome. Several specific targets in innate immunity bear therapeutic potential, of which some have already entered the clinical arena. To prevent immunosuppression by systemic effects, drug delivery systems are increasingly being applied to locally attenuate plaque inflammation.

SUMMARY

Anti-inflammatory therapies seem promising for future treatment of ASCVD. In view of the risk of immunosuppression in case of long term and systemic use of anti-inflammatory drugs, there is a clinical need for highly selective and targeted therapies in patients with atherosclerosis.

Recent Advances in Targeted, Self-Assembling Nanoparticles to Address Vascular Damage Due to Atherosclerosis

Self-assembling nanoparticles functionalized with targeting moieties have significant potential for atherosclerosis nanomedicine. While self-assembly allows the easy construction (and degradation) of nanoparticles with therapeutic or diagnostic functionality, or both, the targeting agent can direct them to a specific molecular marker within a given stage of the disease. Therefore, supramolecular nanoparticles have been investigated in the last decade as molecular imaging agents or explored as nanocarriers that can decrease the systemic toxicity of drugs by producing accumulation predominantly in specific tissues of interest. In this Progress Report, the pathogenesis of atherosclerosis and the damage caused to vascular tissue are described, as well as the current diagnostic and treatment options. An overview of targeted strategies using self-assembling nanoparticles is provided, including liposomes, high density lipoproteins, protein cages, micelles, proticles, and perfluorocarbon nanoparticles. Finally, an overview is given of current challenges, limitations, and future applications for personalized medicine in the context of atherosclerosis of self-assembling nanoparticles.

Atherosclerosis - A matter of unresolved inflammation

Atherosclerosis is commonly looked upon as a chronic inflammatory disease of the arterial wall arising from an unbalanced lipid metabolism and a maladaptive inflammatory response. However, atherosclerosis is not merely an inflammation of the vessel wall. In fact, the cardinal signs of unstable atherosclerotic lesions are primarily characteristics of failed resolution of a chronic inflammation. In contrast to acute inflammatory events which are typically self-limiting, atherosclerosis is an unresolved inflammatory condition, lacking the switch from the pro-inflammatory to the pro-resolving phase, the latter characterized by termination of inflammatory cell recruitment, removal of inflammatory cells from the site of inflammation by apoptosis and dead cell clearance, reprogramming of macrophages toward an anti-inflammatory, regenerative phenotype, and finally egress of effector cells and tissue regeneration. Here we present an overview on mechanisms of failed resolution contributing to atheroprogression and deliver a summary of novel therapeutic strategies to restore resolution in inflamed arteries.

Assessing Large-Vessel Endothelial Permeability Using Near-Infrared Fluorescence Imaging—Brief Report

Objective—

Loss of endothelial barrier function in arterial blood vessels is characteristic of vascular pathologies, including atherosclerosis. Here, we present a near-infrared fluorescence (NIRF) imaging methodology for quantifying endothelial permeability and macromolecular uptake in large arteries in the mouse and evaluate its applicability for studying mechanisms of vascular inflammation.

Approach and Results—

To validate the NIRF methodology, macrovascular inflammation was induced in C57bl/6 mice by local tumor necrosis factor-α stimulation of the carotid artery or in apolipoprotein E–deficient mice by Western diet for 4 weeks. Evans blue dye, serving as plasma protein marker and fluorescent in the near-infrared spectrum, was given intravenously at different doses. Carotids and aorta were excised, and Evans blue dye fluorescence was assessed through whole vessel scan in an infrared imaging system. NIRF correlated to extraction–absorbance methodology for Evans blue dye quantification and was superior at discriminating plasma protein accumulation in tumor necrosis factor-α–stimulated carotids. NIRF allowed for focal quantification of increased arterial wall Evans blue dye uptake in apolipoprotein E–deficient mice. Importantly, NIRF left vessels intact for subsequent histological analysis or quantification of leukocyte subpopulations by flow cytometry.

Conclusions—

The described NIRF methodology provides a sensitive and rapid tool to locate and quantify macromolecular uptake in the wall of arterial blood vessels in vascular pathologies in mice.

Annexin A1 counteracts chemokine-induced arterial myeloid cell recruitment

RATIONALE

Chemokine-controlled arterial leukocyte recruitment is a crucial process in atherosclerosis. Formyl peptide receptor 2 (FPR2) is a chemoattractant receptor that recognizes proinflammatory and proresolving ligands. The contribution of FPR2 and its proresolving ligand annexin A1 to atherosclerotic lesion formation is largely undefined.

OBJECTIVE

Because of the ambivalence of FPR2 ligands, we here investigate the role of FPR2 and its resolving ligand annexin A1 in atherogenesis.

METHODS AND RESULTS

Deletion of FPR2 or its ligand annexin A1 enhances atherosclerotic lesion formation, arterial myeloid cell adhesion, and recruitment. Mechanistically, we identify annexin A1 as an endogenous inhibitor of integrin activation evoked by the chemokines CCL5, CCL2, and CXCL1. Specifically, the annexin A1 fragment Ac2-26 counteracts conformational activation and clustering of integrins on myeloid cells evoked by CCL5, CCL2, and CXCL1 through inhibiting activation of the small GTPase Rap1. In vivo administration of Ac2-26 largely diminishes arterial recruitment of myeloid cells in a FPR2-dependent fashion. This effect is also observed in the presence of selective antagonists to CCR5, CCR2, or CXCR2, whereas Ac2-26 was without effect when all 3 chemokine receptors were antagonized simultaneously. Finally, repeated treatment with Ac2-26 reduces atherosclerotic lesion sizes and lesional macrophage accumulation.

CONCLUSIONS

Instructing the annexin A1-FPR2 axis harbors a novel approach to target arterial leukocyte recruitment. With the ability of Ac2-26 to counteract integrin activation exerted by various chemokines, delivery of Ac2-26 may be superior in inhibition of arterial leukocyte recruitment when compared with blocking individual chemokine receptors.