Arachidonic Acid-Modified Lovastatin Discoidal Reconstituted High Density Lipoprotein Markedly Decreases the Drug Leakage during the Remodeling Behaviors Induced by Lecithin Cholesterol Acyltransferase

Current targeting strategies and advanced nanoplatforms for atherosclerosis therapy

Atherosclerosis is one of the major causes of death worldwide, and it is closely related to many cardiovascular diseases, such as stroke, myocardial infraction and angina. Although traditional surgical and pharmacological interventions can effectively retard or slow down the progression of atherosclerosis, it is very difficult to prevent or even reverse this disease. In recent years, with the rapid development of nanotechnology, various nanoagents have been designed and applied to different diseases including atherosclerosis. The unique atherosclerotic microenvironment with signature biological components allows nanoplatforms to distinguish atherosclerotic lesions from normal tissue and to approach plaques specifically. Based on the process of atherosclerotic plaque formation, this review summarises the nanodrug delivery strategies for atherosclerotic therapy, trying to provide help for researchers to understand the existing atherosclerosis management approaches as well as challenges and to reasonably design anti-atherosclerotic nanoplatforms.

Reactive oxygen species (ROS)-responsive size-reducible nanoassemblies for deeper atherosclerotic plaque penetration and enhanced macrophage-targeted drug delivery

Nanoparticle-based therapeutics represent potential strategies for treating atherosclerosis; however, the complex plaque microenvironment poses a barrier for nanoparticles to target the dysfunctional cells. Here, we report reactive oxygen species (ROS)-responsive and size-reducible nanoassemblies, formed by multivalent host-guest interactions between β-cyclodextrins (β-CD)-anchored discoidal recombinant high-density lipoprotein (NP³_ST) and hyaluronic acid-ferrocene (HA-Fc) conjugates. The HA-Fc/NP³_ST nanoassemblies have extended blood circulation time, specifically accumulate in atherosclerotic plaque mediated by the HA receptors CD44 highly expressed in injured endothelium, rapidly disassemble in response to excess ROS in the intimal and release smaller NP³_ST, allowing for further plaque penetration, macrophage-targeted cholesterol efflux and drug delivery. In vivo pharmacodynamicses in atherosclerotic mice shows that HA-Fc/NP³_ST reduces plaque size by 53%, plaque lipid deposition by 63%, plaque macrophage content by 62% and local inflammatory factor level by 64% compared to the saline group. Meanwhile, HA-Fc/NP³_ST alleviates systemic inflammation characterized by reduced serum inflammatory factor levels. Collectively, HA-Fc/NP³_ST nanoassemblies with ROS-responsive and size-reducible properties exhibit a deeper penetration in atherosclerotic plaque and enhanced macrophage targeting ability, thus exerting effective cholesterol efflux and drug delivery for atherosclerosis therapy.

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HA-Fc/NP³_ST is designed for long blood circulation and deep plaque penetration.

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Nanoassemblies are formed by multivalent host-guest interactions of β-CD/ferrocene.

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Release of NP³_ST triggered by excess ROS aims for macrophage-targeted drug delivery.

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FRET method is utilized to characterize the ROS-responsiveness of nanoassemblies.

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Biomimic cell coculture model is constructed to simulate the atherosclerotic plaque.

Surface-modified nanotherapeutics targeting atherosclerosis

Atherosclerosis is a chronic and metabolic-related disease that is a serious threat to human health. Currently available diagnostic and therapeutic measures for atherosclerosis lack adequate efficiency which requires promising alternative approaches. Nanotechnology-based nano-delivery systems allow for new perspectives for atherosclerosis therapy. Surface-modified nanoparticles could achieve highly effective therapeutic effects by binding to specific receptors that are abnormally overexpressed in atherosclerosis, with less adverse effects on non-target tissues. The main purpose of this review is to summarize the research progress and design ideas to target atherosclerosis using a variety of ligand-modified nanoparticle systems, discuss the shortcomings of current vector design, and look at future development directions. We hope that this review will provide novel research strategies for the design and development of nanotherapeutics targeting atherosclerosis.

Anchoring β-CD on simvastatin-loaded rHDL for selective cholesterol crystals dissolution and enhanced anti-inflammatory effects in macrophage/foam cells

Macrophage/foam cells and cholesterol crystals (CCs) have been regarded as the central triggers of maladaptive inflammation in atherosclerotic plaque. Despite the tremendous progress of recombinant high-density lipoprotein (rHDL) serving for targeted drug delivery to alleviate inflammation in macrophage/foam cells, the active attempt to modulate/improve its CCs dissolution capacity remains poorly explored. The untreated CCs can seriously aggravate inflammation and threaten plaque stability. Based on the superb ability of β-cyclodextrin (β-CD) to bind CCs and promote cholesterol efflux, simvastatin-loaded discoidal-rHDL (ST-d-rHDL) anchored with β-CD (βCD-ST-d-rHDL) was constructed. We verified that βCD-ST-d-rHDL specifically bound and dissolved CCs extracellularly and intracellularly. Furthermore, anchoring β-CD onto the surface of ST-d-rHDL enhanced its cholesterol removal ability in RAW 264.7 cell-derived foam cells characterized by accelerated cholesterol efflux, reduced intracellular lipid deposition, and improved cell membrane fluidity/permeability. Finally, βCD-ST-d-rHDL exerted efficient drug delivery and effective anti-inflammatory effects in macrophage/foam cells. Collectively, anchoring β-CD onto the surface of ST-d-rHDL for selective CCs dissolution, accelerated cholesterol efflux, and improved drug delivery represents an effective strategy to enhance anti-inflammatory effects for the therapy of atherosclerosis.

Nanotechnology for Targeted Therapy of Atherosclerosis

Atherosclerosis is the major cause of heart attack and stroke that are the leading causes of death in the world. Nanomedicine is a powerful tool that can be engineered to target atherosclerotic plaques for therapeutic and diagnosis purposes. In this review, advances in designing nanoparticles with therapeutic effects on atherosclerotic plaques known as atheroprotective nanomedicine have been summarized to stimulate further development and future translation.

Supramolecular copolymer modified statin-loaded discoidal rHDLs for atherosclerotic anti-inflammatory therapy by cholesterol efflux and M2 macrophage polarization

Foam cells with the pro-inflammatory macrophage phenotype (M1) play an essential role in atherosclerosis progression. Either cellular cholesterol removal or drug intervention was reported to polarize M1 into the anti-inflammatory phenotype (M2) for atherosclerosis regression. These might be realized simultaneously by drug-loaded discoidal reconstituted high-density lipoproteins (d-rHDLs) with the functions of cellular cholesterol efflux and targeted drug delivery on macrophages. However, cholesterol reception can drive the remodelling of d-rHDLs, which serves to release drugs specifically in the atherosclerotic plaque but might incur premature drug leakage in blood circulation. Given that, the proposed strategy is to inhibit the remodelling behaviour of the carrier in blood circulation and responsively accelerate it under the atherosclerotic microenvironmental stimulus. Herein, atorvastatin calcium-loaded d-rHDL was modified by a PEGylated ferrocene/β-cyclodextrin supramolecular copolymer (PF/TC) to construct ROS-responsive PF/TC-AT-d-rHDL, which is expected to possess plasma stability and biosafety as well as triggered drug release by cholesterol efflux promotion. As a result, PF/TC-AT-d-rHDL could responsively dissemble into β-cyclodextrin modified AT-d-rHDL under the ROS-triggered dissociation of PF/TC, therefore exhibiting increased cholesterol efflux from the cholesterol donor and drug release through the remodelling behaviour of the carrier in vitro. Moreover, PF/TC-AT-d-rHDL enhanced cellular cholesterol removal in foam cells after response to ROS, inhibiting intracellular lipid deposition compared with other d-rHDL carriers. Interestingly, cellular drug uptake was significantly promoted upon cellular cholesterol removal by restoring the permeability and fluidity of foam cell membranes as indicated by flow cytometry and fluorescence polarization analysis, respectively. Importantly, compared with untreated foam cells, PF/TC-AT-d-rHDL obviously increased the ratio of M2/M1 by 6.3-fold, which was even higher than the effect of PF/TC-d-rHDL (3.4-fold) and free drugs (1.9-fold), revealing that PF/TC-AT-d-rHDL synergistically promoted the M2 polarization of macrophages. Accordingly, PF/TC-AT-d-rHDL boosted the secretion of anti-inflammatory cytokines and inhibited that of inflammatory cytokines. Collectively, PF/TC-AT-d-rHDL exerted synergistic M2 polarization effects on foam cells for atherosclerotic immunomodulatory therapy via responsively mediating cholesterol efflux and delivering drugs.

Shuttle/sink model composed of β-cyclodextrin and simvastatin-loaded discoidal reconstituted high-density lipoprotein for enhanced cholesterol efflux and drug uptake in macrophage/foam cells

Targeting drug delivery to macrophage/foam cells is challenged owing to the poor cell permeability and fluidity resulting from the massive accumulation of intracellular cholesterol in atherosclerosis (AS). Discoidal reconstituted high-density lipoprotein (d-rHDL) has been well regarded as a potential drug delivery system for AS by virtue of its plaque-targeting and cholesterol removal abilities, while the latter is compromised by the high activation energy of cholesterol efflux. It is reported that a low concentration of β-cyclodextrin (β-CD) can function as a cholesterol shuttle to promote cholesterol efflux from cells to the extracellular acceptors (cholesterol sink, such as HDL particles), but it is still unknown whether the combination of β-CD with a drug-loaded d-rHDL can function as a shuttle/sink model to promote the remodeling and drug release of the d-rHDL carrier after accelerating the cholesterol efflux. Furthermore, it is interesting to investigate whether enhanced cholesterol efflux can improve the cellular drug uptake by restoring the permeability and fluidity of the cell membrane. Here, simvastatin-loaded d-rHDL (ST-d-rHDL) was combined with different concentrations of β-CD. Compared with ST-d-rHDL alone, the cholesterol removal ability of ST-d-rHDL combined with 0.5 mM of β-CD increased by 31-fold after incubation for 6 h and the cumulative drug release of ST-d-rHDL increased by two-fold during the initial 1 h in an acellular mimetic system. In macrophage/foam cells, 0.5 mM of β-CD showed superior promoting effects in the cholesterol removal ability and remodeling of ST-d-rHDL compared to 0.1 mM of β-CD. The high concentration of β-CD at 2 mM displayed a low efficiency for accelerating cholesterol efflux, which might function as a cholesterol sink rather than a cholesterol shuttle. Moreover, the permeability and fluidity of the cell membrane were improved by combining 0.5 mM of β-CD with ST-d-rHDL, which exhibited an enhanced cellular drug uptake and inhibiting effect on the intracellular lipid deposition and secretion of inflammatory cytokine. Collectively, combination of β-CD and ST-d-rHDL as a shuttle/sink model could enhance cholesterol efflux and drug uptake to suppress inflammation in macrophage/foam cells.

Endocytic recycling as cellular trafficking fate of simvastatin-loaded discoidal reconstituted high-density lipoprotein to coordinate cholesterol efflux and drug influx

Reconstituted high-density lipoproteins (rHDLs) hold promise as nanocarriers for atherosclerosis-targeted delivery, with biofunctions typified by mediating cholesterol efflux. The paradox is how rHDL offloads the delivered drugs into atherosclerotic foam cells, while simultaneously transferring cholesterol out of cells. Herein, simvastatin-loaded discoidal rHDL (ST-d-rHDL), constructed based on established paradigms, was employed to investigate its basic trafficking mechanism in foam cells. As proved, ST-d-rHDL was resecreted via lysosomal and Golgi apparatus-recycling endosome-mediated pathways following clathrin-mediated endocytosis. And the resecretion ratio reached 60% within 6-h chase with excessive ST-d-rHDLs. During the rHDL resecretion, 39% of cellular cholesterol efflux was detected, accompanied by 85% of the encapsulated cargo released intracellularly. Furthermore, the recycling rate was demonstrated to be promoted by smaller rHDL size and higher cellular lipid contents. Collectively, endocytic recycling confers the synergism in ST-d-rHDL to coordinate cholesterol efflux and intracellular drug release, providing new insights into design of biofunctional rHDL.

Roles of Reconstituted High-Density Lipoprotein Nanoparticles in Cardiovascular Disease: A New Paradigm for Drug Discovery

Epidemiological results revealed that there is an inverse correlation between high-density lipoprotein (HDL) cholesterol levels and risks of atherosclerotic cardiovascular disease (ASCVD). Mounting evidence supports that HDLs are atheroprotective, therefore, many therapeutic approaches have been developed to increase HDL cholesterol (HDL-C) levels. Nevertheless, HDL-raising therapies, such as cholesteryl ester transfer protein (CETP) inhibitors, failed to ameliorate cardiovascular outcomes in clinical trials, thereby casting doubt on the treatment of cardiovascular disease (CVD) by increasing HDL-C levels. Therefore, HDL-targeted interventional studies were shifted to increasing the number of HDL particles capable of promoting ATP-binding cassette transporter A1 (ABCA1)-mediated cholesterol efflux. One such approach was the development of reconstituted HDL (rHDL) particles that promote ABCA1-mediated cholesterol efflux from lipid-enriched macrophages. Here, we explore the manipulation of rHDL nanoparticles as a strategy for the treatment of CVD. In addition, we discuss technological capabilities and the challenge of relating preclinical in vivo mice research to clinical studies. Finally, by drawing lessons from developing rHDL nanoparticles, we also incorporate the viabilities and advantages of the development of a molecular imaging probe with HDL nanoparticles when applied to ASCVD, as well as gaps in technology and knowledge required for putting the HDL-targeted therapeutics into full gear.

Cellular Vehicles Based on Neutrophils Enable Targeting of Atherosclerosis

Given the multiple interactions between neutrophils (NEs) and atherosclerosis (AS), in this study, we exploited NEs as cellular vehicles loaded with cationic liposomes for actively targeting atherosclerotic sites. The cellular vehicles based on NEs possess efficient internalization of cationic liposomes and sensitive response to the chemotaxis of atherosclerotic inflammatory cells, which ultimately realize the targeted delivery of the cargos into the target cells in vitro. Moreover, these effects also translated to significant enhancement of the accumulation of NEs' cargos into the atherosclerotic plaque in vivo after administering NE vehicles to the AS animal model. Consequently, cellular vehicles based on NEs could be a novel strategy for targeted delivery of payloads into atherosclerotic plaque, which would facilitate theranostics for AS and the development of anti-AS drugs to manage the disease.

Reconstituted high-density lipoproteins: novel biomimetic nanocarriers for drug delivery

High-density lipoproteins (HDL) are naturally-occurring nanoparticles that are biocompatible, non-immunogenic and completely biodegradable. These endogenous particles can circulate for an extended period of time and transport lipids, proteins and microRNA from donor cells to recipient cells. Based on their intrinsic targeting properties, HDL are regarded as promising drug delivery systems. In order to produce on a large scale and to avoid blood borne pollution, reconstituted high-density lipoproteins (rHDL) possessing the biological properties of HDL have been developed. This review summarizes the biological properties and biomedical applications of rHDL as drug delivery platforms. It focuses on the emerging approaches that have been developed for the generation of biomimetic nanoparticles rHDL to overcome the biological barriers to drug delivery, aiming to provide an alternative, promising avenue for efficient targeting transport of nanomedicine.

Plaque-hyaluronidase-responsive high-density-lipoprotein-mimetic nanoparticles for multistage intimal-macrophage-targeted drug delivery and enhanced anti-atherosclerotic therapy

Increasing evidence has highlighted the pivotal role that intimal macrophage (iMΦ) plays in the pathophysiology of atherosclerotic plaques, which represents an attractive target for atherosclerosis treatment. In this work, to address the insufficient specificity of conventional reconstituted high-density lipoprotein (rHDL) for iMΦ and its limited cholesterol efflux ability, we designed a hyaluronan (HA)-anchored core-shell rHDL. This nanoparticle achieved efficient iMΦ-targeted drug delivery via a multistage-targeting approach, and excellent cellular cholesterol removal. It contained a biodegradable poly (lactic-co-glycolic acid) (PLGA) core within a lipid bilayer, and apolipoprotein A-I (apoA-I) absorbing on the lipid bilayer was covalently decorated with HA. The covalent HA coating with superior stability and greater shielding was favorable for not only minimizing the liver uptake but also facilitating the accumulation of nanoparticles at leaky endothelium overexpressing CD44 receptors in atherosclerotic plaques. The ultimate iMΦ homing was achieved via apoA-I after HA coating degraded by hyaluronidase (HAase) (abundant in atherosclerotic plaque). The multistage-targeting mechanism was revealed on the established injured endothelium-macrophage co-culture dynamic system. Upon treatment with HAase in vitro, the nanoparticle HA-(C)-PLGA-rHDL exhibited a greater cholesterol efflux capacity compared with conventional rHDL (2.43-fold). Better targeting efficiency toward iMΦ and attenuated liver accumulation were further proved by results from ex vivo imaging and iMΦ-specific fluorescence localization. Ultimately, HA-(C)-PLGA-rHDL loaded with simvastatin realized the most potent anti-atherogenic efficacies in model animals over other preparations. Thus, the HAase-responsive HDL-mimetic nanoparticle was shown in this study to be a promising nanocarrier for anti-atherogenic therapy, in the light of efficient iMΦ-targeted drug delivery and excellent function of mediating cellular cholesterol efflux.

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.