High-Density Lipoprotein Infusions

Molecular mechanisms of the regulatory action of high-density lipoproteins on the endothelial function

Endothelial dysfunction underlies the pathogenesis of many diseases, primarily cardiovascular diseases. Epidemiological studies have shown an inverse dependence between the plasma level of high-density lipoproteins (HDL) and cardiovascular diseases. The results of experimental studies indicate that the antiatherogenic effect of HDL is associated not only with their participation in the reverse transport of excess cholesterol, but also with their regulatory effect on the functions of cells of various organs and tissues, including endothelial cells. The purpose of this review is to consider recent data on the participation of plasma receptors and related intracellular signaling pathways in the mechanism of protective effect of HDL on endothelial cell functions. Understanding the mechanisms of cell function regulation under the influence of HDL is an important step for the development of new ways of pharmacological correction of impaired endothelial functions and creation of effective endothelial protection drugs.

Multivalent Display of ApoAI Peptides on the Surface of Tobacco Mosaic Virus Nanotubes Improves Cholesterol Efflux

Atherosclerosis is a progressive cardiovascular disease in which cholesterol-rich plaques build up within arteries, increasing the risk of thrombosis, myocardial infarction, and stroke. One promising therapeutic approach is the use of high-density lipoprotein (HDL) biomimetic formulations based on ApoAI peptides that promote cholesterol efflux from plaques, ultimately leading to cholesterol excretion. Here, we describe the multivalent display of ApoAI peptides on the surface of protein nanotubes derived from the plant virus tobacco mosaic virus (TMV) and protein nanoparticles using virus-like particles from bacteriophage Qβ. Bioconjugation yielded ApoAI conjugates varying in size and morphology. We tested ABCA1-mediated cholesterol efflux using macrophage foam cells, the mitigation of reactive oxygen species in endothelial cells, and wound healing in endothelial cells. We found that the multivalent ApoAI platform, in particular the TMV-based nanotube, significantly improved the efficacy of cholesterol efflux compared to free peptides, Qβ nanoparticle formulations, and traditional HDL therapy. Finally, to better understand the mechanistic basis of enhanced cholesterol efflux, we used confocal microscopy to show that while native TMV was taken up by cells, TMV-ApoAI remained at the exterior of foam cell membranes and efflux was documented using fluorescent cholesterol. Together, these data highlight that high aspect ratio materials with multivalent display of ApoAI peptides offer unique capabilities promoting efficient cholesterol efflux and may find applications in cardiovascular therapy.

Infusions of Large Synthetic HDL Containing Trimeric apoA-I Stabilize Atherosclerotic Plaques in Hypercholesterolemic Rabbits

BACKGROUND

Among strategies to reduce the remaining risk of cardiovascular disease, interest has focused on using infusions of synthetic high-density lipoprotein (sHDL).

METHODS

New Zealand rabbits underwent a perivascular injury at both carotids and were randomly allocated into 2 protocols: (1) a single-dose study, where rabbits were treated with a single infusion of sHDL containing a trimeric form of human apoA-I (TN-sHDL, 200 mg/kg) or with Placebo; (2) a multiple-dose study, where 4 groups of rabbits were treated 5 times with Placebo or TN-sHDL at different doses (8, 40, 100 mg/kg). Plaque changes were analysed in vivo by intravascular ultrasound. Blood was drawn from rabbits for biochemical analyses and cholesterol efflux capacity evaluation.

RESULTS

In both protocols, atheroma volume in the Placebo groups increased between the first and the second intravascular ultrasound evaluation. A stabilization or a slight regression was instead observed vs baseline in the TN-sHDL-treated groups (P < 0.005 vs Placebo after infusion). TN-sHDL treatment caused a sharp rise of plasma-free cholesterol levels and a significant increase of total cholesterol efflux capacity. Histologic analysis of carotid plaques showed a reduced macrophage accumulation in TN-sHDL-treated rabbits compared with Placebo (P < 0.05).

CONCLUSIONS

Our results demonstrate that acute and subacute treatments with TN-sHDL are effective in stabilizing atherosclerotic plaques in a rabbit model. This effect appears to be related to a reduced intraplaque accumulation of inflammatory cells. Besides recent failures in proving its efficacy, sHDL treatment remains a fascinating therapeutic option for the reduction of cardiovascular risk.