Reconstituted HDL: a therapy for atherosclerosis and beyond

CIGB-258 Exerts Potent Anti-Inflammatory Activity against Carboxymethyllysine-Induced Acute Inflammation in Hyperlipidemic Zebrafish via the Protection of Apolipoprotein A-I

Inflammation and atherosclerosis are intimately associated via the production of dysfunctional high-density lipoproteins (HDL) and modification of apolipoprotein (apo) A-I. A putative interaction between CIGB-258 and apoA-I was investigated to provide mechanistic insight into the protection of HDL. The protective activity of CIGB-258 was tested in the CML-mediated glycation of apoA-I. The in vivo anti-inflammatory efficacy was compared in paralyzed hyperlipidemic zebrafish and its embryo in the presence of CML. Treatment of CML induced greater glycation extent of HDL/apoA-I and proteolytic degradation of apoA-I. In the presence of CML, however, co-treatment of CIGB-258 inhibited the glycation of apoA-I and protected the degradation of apoA-I, exerting enhanced ferric ion reduction ability. Microinjection of CML (500 ng) into zebrafish embryos resulted in acute death with the lowest survivability with severe developmental defects with interleukin (IL)-6 production. Conversely, a co-injection of CIGB-258 or Tocilizumab produced the highest survivability with a normal development speed and morphology. In hyperlipidemic zebrafish, intraperitoneal injection of CML (500 μg) caused the complete loss of swimming ability and severe acute death with only 13% survivability 3 h post-injection. A co-injection of the CIGB-258 resulted in a 2.2-fold faster recovery of swimming ability than CML alone, with higher survivability of approximately 57%. These results suggest that CIGB-258 protected hyperlipidemic zebrafish from the acute neurotoxicity of CML. Histological analysis showed that the CIGB-258 group had 37% lower infiltration of neutrophils in hepatic tissue and 70% lower fatty liver changes than those of the CML-alone group. The CIGB-258 group exhibited the smallest IL-6 expression in the liver and the lowest blood triglyceride level. CIGB-258 displayed potent anti-inflammatory activity in hyperlipidemic zebrafish by inhibiting apoA-I glycation, promoting rapid recovery from the paralysis of CML toxicity and suppression of IL-6, and lowering fatty liver changes.

Boosting Cholesterol Efflux from Foam Cells by Sequential Administration of rHDL to Deliver MicroRNA and to Remove Cholesterol in a Triple-Cell 2D Atherosclerosis Model

Cardiovascular disease, the leading cause of mortality worldwide, is primarily caused by atherosclerosis, which is characterized by lipid and inflammatory cell accumulation in blood vessels and carotid intima thickening. Although disease management has improved significantly, new therapeutic strategies focused on accelerating atherosclerosis regression must be developed. Atherosclerosis models mimicking in vivo-like conditions provide essential information for research and new advances toward clinical application. New nanotechnology-based therapeutic opportunities have emerged with apoA-I nanoparticles (recombinant/reconstituted high-density lipoproteins, rHDL) as ideal carriers to deliver molecules and the discovery that microRNAs participate in atherosclerosis establishment and progression. Here, a therapeutic strategy to improve cholesterol efflux is developed based on a two-step administration of rHDL consisting of a first dose of antagomiR-33a-loaded rHDLs to induce adenosine triphosphate-binding cassette transporters A1 overexpression, followed by a second dose of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine rHDLs, which efficiently remove cholesterol from foam cells. A triple-cell 2D-atheroma plaque model reflecting the cellular complexity of atherosclerosis is used to improve efficiency of the nanoparticles in promoting cholesterol efflux. The results show that sequential administration of rHDL potentiates cholesterol efflux indicating that this approach may be used in vivo to more efficiently target atherosclerotic lesions and improve prognosis of the disease.

Current Understanding of the Immunomodulatory Activities of High-Density Lipoproteins

Lipoproteins interact with immune cells, macrophages and endothelial cells - key players of the innate and adaptive immune system. High-density lipoprotein (HDL) particles seem to have evolved as part of the innate immune system since certain HDL subspecies contain combinations of apolipoproteins with immune regulatory functions. HDL is enriched in anti-inflammatory lipids, such as sphingosine-1-phosphate and certain saturated lysophospholipids. HDL reduces inflammation and protects against infection by modulating immune cell function, vasodilation and endothelial barrier function. HDL suppresses immune cell activation at least in part by modulating the cholesterol content in cholesterol/sphingolipid-rich membrane domains (lipid rafts), which play a critical role in the compartmentalization of signaling pathways. Acute infections, inflammation or autoimmune diseases lower HDL cholesterol levels and significantly alter HDL metabolism, composition and function. Such alterations could have a major impact on disease progression and may affect the risk for infections and cardiovascular disease. This review article aims to provide a comprehensive overview of the immune cell modulatory activities of HDL. We focus on newly discovered activities of HDL-associated apolipoproteins, enzymes, lipids, and HDL mimetic peptides.

Reconstituted high density lipoprotein (rHDL), a versatile drug delivery nanoplatform for tumor targeted therapy

rHDL is a synthesized drug delivery nanoplatform exhibiting excellent biocompatibility, which possesses most of the advantages of HDL. rHDL shows almost no toxicity and can be degraded to non-toxic substances in vivo. The severe limitation of the application of various antitumor agents is mainly due to their low bioavailability, high toxicity, poor stability, etc. Favorably, antitumor drug-loaded rHDL nanoparticles (NPs), which are known as an important drug delivery system (DDS), help to change the situation a lot. This DDS shows an outstanding active-targeting ability towards tumor cells and improves the therapeutic effect during antitumor treatment while overcoming the shortcomings mentioned above. In the following text, we will mainly focus on the various applications of rHDL in tumor targeted therapy by describing the properties, preparation, receptor active-targeting ability and antitumor effects of antineoplastic drug-loaded rHDL NPs.

Radiolabeled liposomes and lipoproteins as lipidic nanoparticles for imaging and therapy

Radiolabeled lipidic nanoparticles, particularly liposomes and lipoproteins, are of great interest as agents for imaging and therapy, due not only to their peculiar physicochemical and biological properties, but also to their great versatility and the ability to manipulate them to obtain the desired properties. This review provides an overview of radionuclide labeling strategies for preparing diagnostic and therapeutic nanoparticles based on liposomes and lipoproteins that have been developed to date, as well as the main quality control methods and in vivo applications.

Protein Backbone and Average Particle Dynamics in Reconstituted Discoidal and Spherical HDL Probed by Hydrogen Deuterium Exchange and Elastic Incoherent Neutron Scattering

Lipoproteins are supramolecular assemblies of proteins and lipids with dynamic characteristics critically linked to their biological functions as plasma lipid transporters and lipid exchangers. Among them, spherical high-density lipoproteins are the most abundant forms of high-density lipoprotein (HDL) in human plasma, active participants in reverse cholesterol transport, and associated with reduced development of atherosclerosis. Here, we employed elastic incoherent neutron scattering (EINS) and hydrogen-deuterium exchange mass spectrometry (HDX-MS) to determine the average particle dynamics and protein backbone local mobility of physiologically competent discoidal and spherical HDL particles reconstituted with human apolipoprotein A-I (apoA-I). Our EINS measurements indicated that discoidal HDL was more dynamic than spherical HDL at ambient temperatures, in agreement with their lipid-protein composition. Combining small-angle neutron scattering (SANS) with contrast variation and MS cross-linking, we showed earlier that the most likely organization of the three apolipoprotein A-I (apoA-I) chains in spherical HDL is a combination of a hairpin monomer and a helical antiparallel dimer. Here, we corroborated those findings with kinetic studies, employing hydrogen-deuterium exchange mass spectrometry (HDX-MS). Many overlapping apoA-I digested peptides exhibited bimodal HDX kinetics behavior, suggesting that apoA-I regions with the same amino acid composition located on different apoA-I chains had different conformations and/or interaction environments.

Artificial High Density Lipoprotein Nanoparticles in Cardiovascular Research

Lipoproteins are endogenous nanoparticles which are the major transporter of fats and cholesterol in the human body. They play a key role in the regulatory mechanisms of cardiovascular events. Lipoproteins can be modified and manipulated to act as drug delivery systems or nanocarriers for contrast agents. In particular, high density lipoproteins (HDL), which are the smallest class of lipoproteins, can be synthetically engineered either as nascent HDL nanodiscs or spherical HDL nanoparticles. Reconstituted HDL (rHDL) particles are formed by self-assembly of various lipids and apolipoprotein AI (apo-AI). A variety of substances including drugs, nucleic acids, signal emitting molecules, or dyes can be loaded, making them efficient nanocarriers for therapeutic applications or medical diagnostics. This review provides an overview about synthesis techniques, physicochemical properties of rHDL nanoparticles, and structural determinants for rHDL function. We discuss recent developments utilizing either apo-AI or apo-AI mimetic peptides for the design of pharmaceutical rHDL formulations. Advantages, limitations, challenges, and prospects for clinical translation are evaluated with a special focus on promising strategies for the treatment and diagnosis of atherosclerosis and cardiovascular diseases.

HDL-apoA-I induces the expression of angiopoietin like 4 (ANGPTL4) in endothelial cells via a PI3K/AKT/FOXO1 signaling pathway

BACKGROUND

High Density Lipoprotein (HDL) and its main protein component, apolipoprotein A-I (apoA-I), have numerous atheroprotective functions on various tissues including the endothelium. Therapies based on reconstituted HDL containing apoA-I (rHDL-apoA-I) have been used successfully in patients with acute coronary syndrome, peripheral vascular disease or diabetes but very little is known about the genomic effects of rHDL-apoA-I and how they could contribute to atheroprotection.

OBJECTIVE

The present study aimed to understand the endothelial signaling pathways and the genes that may contribute to rHDL-apoA-I-mediated atheroprotection.

METHODS

Human aortic endothelial cells (HAECs) were treated with rHDL-apoA-I and their total RNA was analyzed with whole genome microarrays. Validation of microarray data was performed using multiplex RT-qPCR. The expression of ANGPTL4 in EA.hy926 endothelial cells was determined by RT-qPCR and Western blotting. The contribution of signaling kinases and transcription factors in ANGPTL4 gene regulation by HDL-apoA-I was assessed by RT-qPCR, Western blotting and immunofluorescence using chemical inhibitors or siRNA-mediated gene silencing.

RESULTS

It was found that 410 transcripts were significantly changed in the presence of rHDL-apoA-I and that angiopoietin like 4 (ANGPTL4) was one of the most upregulated and biologically relevant molecules. In validation experiments rHDL-apoA-I, as well as natural HDL from human healthy donors or from transgenic mice overexpressing human apoA-I (TgHDL-apoA-I), increased ANGPTL4 mRNA and protein levels. ANGPTL4 gene induction by HDL was direct and was blocked in the presence of inhibitors for the AKT or the p38 MAP kinases. TgHDL-apoA-I caused phosphorylation of the transcription factor forkhead box O1 (FOXO1) and its translocation from the nucleus to the cytoplasm. Importantly, a FOXO1 inhibitor or a FOXO1-specific siRNA enhanced ANGPTL4 expression, whereas administration of TgHDL-apoA-I in the presence of the FOXO1 inhibitor or the FOXO1-specific siRNA did not induce further ANGPTL4 expression. These data suggest that FOXO1 functions as an inhibitor of ANGPTL4, while HDL-apoA-I blocks FOXO1 activity and induces ANGPTL4 through the activation of AKT.

CONCLUSION

Our data provide novel insights into the global molecular effects of HDL-apoA-I on endothelial cells and identify ANGPTL4 as a putative mediator of the atheroprotective functions of HDL-apoA-I on the artery wall, with notable therapeutic potential.

Templated high density lipoprotein nanoparticles as potential therapies and for molecular delivery

High density lipoproteins (HDLs) are dynamic natural nanoparticles best known for their role in cholesterol transport and the inverse correlation that exists between blood HDL levels and the risk of developing coronary heart disease. In addition, enhanced HDL-cholesterol uptake has been demonstrated in several human cancers. As such, the use of HDL as a therapeutic and as a vehicle for systemic delivery of drugs and as imaging agents is increasingly important. HDLs exist on a continuum from the secreted HDL-scaffolding protein, apolipoprotein A-1 (Apo A1), to complex, spherical "mature" HDLs. Aspects of HDL particles including their size, shape, and surface chemical composition are being recognized as critical to their diverse biological functions. Here we review HDL biology; strategies for synthesizing HDLs; data supporting the clinical use and benefit of directly administered HDL; a rationale for developing synthetic methods for spherical, mature HDLs; and, the potential to employ HDLs as therapies, imaging agents, and drug delivery vehicles. Importantly, methods that utilize nanoparticle templates to control synthetic HDL size, shape, and surface chemistry are highlighted.

Anti-inflammatory functions of apolipoprotein A-I and high-density lipoprotein are preserved in trimeric apolipoprotein A-I

Raising high-density lipoprotein (HDL) levels is proposed as an attractive target to treat cardiovascular disease. However, a number of clinical studies examining the effect of HDL-raising therapies have been prematurely halted due to futility. Therefore there is a need for alternative therapies. Infusion of reconstituted HDL (rHDL) particles is still considered as a viable approach to increasing HDL levels. In this study we have profiled the anti-inflammatory effects of a trimeric-HDL particle. We show that trimeric apoA-I and rHDL particles promote cholesterol efflux to a similar rate as native apoA-I particles in both ABCA1-dependent and -independent pathways. Trimeric particles inhibited ICAM-1 and VCAM-1 expression and the ability of the endothelium to capture monocytes under shear flow. Monocyte activation, CD11b-dependent adhesion, and monocyte recruitment under shear flow conditions were perturbed by the trimeric particles. Our data suggest that trimeric rHDL particles can be constructed without any loss of function, preserving the anti-inflammatory effects of HDL that are key to its in vivo actions.

Neutrophil activation is attenuated by high-density lipoprotein and apolipoprotein A-I in in vitro and in vivo models of inflammation

OBJECTIVE

Neutrophils play a key role in the immune response but can undesirably exacerbate inflammation. High-density lipoproteins (HDL) are antiinflammatory particles, exerting beneficial cardiovascular influences. We determined whether HDL exerts antiinflammatory effects on neutrophils and explored the mechanisms by which these occur.

METHODS AND RESULTS

CD11b on activated human neutrophils was significantly attenuated by apolipoprotein A-I (apoA-I) and HDL. The effects of apoA-I were mediated via ABCA1, whereas the effects of HDL were via scavenger receptor BI. Both were associated with a reduction in the abundance of lipid rafts, and a strong correlation between raft abundance and CD11b activation was observed. ApoA-I and HDL reduced neutrophil adhesion to a platelet monolayer under shear flow, as well as neutrophil spreading and migration. ApoA-I also inhibited leukocyte recruitment to the endothelium in an acute in vivo model of inflammation. Finally, infusion of reconstituted HDL in patients with peripheral vascular disease was demonstrated to significantly attenuate neutrophil activation.

CONCLUSION

We describe here a novel role for HDL and apoA-I in regulating neutrophil activation using in vitro, in vivo, and clinical approaches. We also show that these effects of HDL and apoA-I involve a mechanism requiring changes in membrane domain content rather than in cholesterol efflux per se.

Nanotechnology for synthetic high-density lipoproteins

Atherosclerosis is the disease mechanism responsible for coronary heart disease (CHD), the leading cause of death worldwide. One strategy to combat atherosclerosis is to increase the amount of circulating high-density lipoproteins (HDL), which transport cholesterol from peripheral tissues to the liver for excretion. The process, known as reverse cholesterol transport, is thought to be one of the main reasons for the significant inverse correlation observed between HDL blood levels and the development of CHD. This article highlights the most common strategies for treating atherosclerosis using HDL. We further detail potential treatment opportunities that utilize nanotechnology to increase the amount of HDL in circulation. The synthesis of biomimetic HDL nanostructures that replicate the chemical and physical properties of natural HDL provides novel materials for investigating the structure-function relationships of HDL and for potential new therapeutics to combat CHD.