ApoA-I-Directed Therapies for the Management of Atherosclerosis

A Genome-Wide Association Study of Genetic Variants of Apolipoprotein A1 Levels and Their Association with Vitamin D in Korean Cohorts

Dyslipidemia is an important independent risk factor for cardiovascular disease (CVD). Specifically, apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), and the ApoB/A1 ratio have been linked to CVD. We conducted a genome-wide association study meta-analysis of two Korean cohorts containing a total of 12,924 patients to identify novel single nucleotide polymorphisms (SNPs) associated with ApoA1 and ApoB levels and the ApoB/A1 ratio. Additionally, an expression quantitative trait locus (eQTL) and differentially expressed genes (DEGs) analysis were performed. The statistically significant eQTL, DEG, and Gene Ontology (GO) results were used to explore the predicted interaction networks and retrieve the interacting genes and proteins. We identified three novel SNPs (rs11066280, p = 3.46 × 10−21; rs1227162, p = 2.98 × 10−15; rs73216931, p = 5.62 × 10−9) associated with ApoA1. SNP rs73216931 was an eQTL for KMT5A in the pancreas and whole blood. The network analysis revealed that HECTD4 and MYL2:LINC1405 are associated with AKT1. Our in silico analysis of ApoA1 genetic variants revealed heart muscle-related signals. ApoA1 also correlated positively with vitamin D, and genes associated with ApoA1 and vitamin D were found. Our data imply that more research into ApoA1 is needed to understand the links between dyslipidemia and CVD and vitamin D and CVD.

Apolipoprotein A1 Modulates Teff/Treg Balance Through Scavenger Receptor Class B Type I-Dependent Mechanisms in Experimental Autoimmune Uveitis

Purpose

Experimental autoimmune uveitis (EAU) is a representative animal model of human uveitis. In this study, we investigated whether apolipoprotein A1 (APOA1) can alleviate EAU and explored its underlying mechanism.

Methods

Mice were immunized with interphotoreceptor retinoid-binding protein 1-20 and treated with APOA1 or vehicle. The retinas, draining lymph nodes (DLNs), and spleens were analyzed. Isolated T cells were used for proliferation, differentiation, and function assays in vitro. Selective inhibitors and pathway agonists were used to study signaling pathways. The effect of APOA1 on peripheral blood mononuclear cells (PBMCs) from uveitis patients was also examined.

Results

Administration of APOA1 ameliorated EAU. APOA1 suppressed pathogenic CD4+ T cell expansion in DLNs and spleen, and decreased the infiltration of effector T (Teff) cells into retina. APOA1 also inhibited T cell proliferation and T helper 1 cell differentiation in vitro and promoted regulatory T (Treg) cell differentiation. APOA1 restricted inflammatory cytokine production from lipopolysaccharide-stimulated PBMCs. Mechanistic studies revealed that the effect of APOA1 was mediated by scavenger receptor class B type I (SR-BI) and downstream signals including phosphatidylinositol 3-kinase/Protein kinase B (PKB, or Akt), p38 mitogen-activated protein kinase, and nuclear factor–κB.

Conclusions

APOA1 ameliorates EAU by regulating the Teff/Treg partially through SR-BI. Our results suggest that APOA1 can be a therapeutic alternative for autoimmune uveitis.

Interaction of Lipids, Mean Platelet Volume, and the Severity of Coronary Artery Disease Among Chinese Adults: A Mediation Analysis

Objective

Currently, coronary artery disease (CAD) is regarded as one of the leading global disease burdens. Evidence proved that platelet activation in dyslipidemia induced CAD, however, their interaction has not been well-established in vivo. This study aims to assess the mediation effects of mean platelet volume (MPV) in lipids and the severity of CAD.

Methods

We prospectively enrolled 5,188 consecutive subjects who underwent coronary angiography between 2015 and 2020. Participants were grouped according to their CAD events, which was defined as stenosis ≥50% in at least one coronary artery, and whose severity was evaluated by the Gensini score (GS). A lipid index was drawn by principal component analysis to weight related lipid parameters including total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), non-HDL-C, apolipoprotein (apo) A1 B. The interaction of lipids and MPV in atherosclerosis was evaluated by the mediation analysis.

Results

Lipid index increased with elevated GS irrespective of statin status (not on statin: β = 0.100, p < 0.001; on statin: β = 0.082, p < 0.001). Multiple linear regression indicated positive correlation between MPV and GS after adjustment (β = 0.171, p < 0.001). Subjects in the highest MPV tertile had higher levels of atherogenic lipid parameters and lipid index (p < 0.001). The adjusted odds ratios were greater among individuals undergoing statin medications who had high GS and higher MPV levels by elevated lipid index tertiles [1.168 (0.893–1.528) vs. 2.068 (1.552–2.756) vs. 1.764 (1.219–2.551)]. The combination of lipid index and MPV provided better prediction for high GS than individual lipid index or MPV, as shown by receiver-operating characteristic (ROC) curves (areas under ROC curves were 0.700 and 0.673 in subjects on or not on statin treatment, respectively). Significantly, mediation analysis revealed the mediation interaction of lipid index on GS by MPV, whose effect size reached 20.71 and 20.07% in participants with or without statin medications.

Conclusion

The increased risk of dyslipidemia on CAD was partly enhanced by elevated MPV levels, whose mediating effect was around 20%.

HDL and reverse cholesterol transport in humans and animals: Lessons from pre-clinical models and clinical studies

The ability to accept cholesterol from cells and to promote reverse cholesterol transport (RCT) represents the best characterized antiatherogenic function of HDL. Studies carried out in animal models have unraveled the multiple mechanisms by which these lipoproteins drive cholesterol efflux from macrophages and cholesterol uptake to the liver. Moreover, the influence of HDL composition and the role of lipid transporters have been clarified by using suitable transgenic models or through experimental design employing pharmacological or nutritional interventions. Cholesterol efflux capacity (CEC), an in vitro assay developed to offer a measure of the first step of RCT, has been shown to associate with cardiovascular risk in several human cohorts, supporting the atheroprotective role of RCT in humans as well. However, negative data in other cohorts have raised concerns on the validity of this biomarker. In this review we will present the most relevant data documenting the role of HDL in RCT, as assessed in classical or innovative methodological approaches.

Exosome-Mediated Transfer of Anti-miR-33a-5p from Transduced Endothelial Cells Enhances Macrophage and Vascular Smooth Muscle Cell Cholesterol Efflux

Atherosclerosis is a disease of large- and medium-sized arteries that is caused by cholesterol accumulation in arterial intimal cells, including macrophages and smooth muscle cells (SMC). Cholesterol accumulation in these cells can be prevented or reversed in preclinical models-and atherosclerosis reduced-by transgenesis that increases expression of molecules that control cholesterol efflux, including apolipoprotein AI (apoAI) and ATP-binding cassette subfamily A, member 1 (ABCA1). In a previous work, we showed that transduction of arterial endothelial cells (EC)-with a helper-dependent adenovirus (HDAd) expressing apoAI-enhanced EC cholesterol efflux in vitro and decreased atherosclerosis in vivo. Similarly, overexpression of ABCA1 in cultured EC increased cholesterol efflux and decreased inflammatory gene expression. These EC-targeted gene-therapy strategies might be improved by concurrent upregulation of cholesterol-efflux pathways in other intimal cell types. Here, we report modification of this strategy to enable delivery of therapeutic nucleic acids to cells of the sub-endothelium. We constructed an HDAd (HDAdXMoAntimiR33a5p) that expresses an antagomiR directed at miR-33a-5p (a microRNA that suppresses cholesterol efflux by silencing ABCA1). HDAdXMoAntimiR33a5p contains a sequence motif that enhances uptake of anti-miR-33a-5p into exosomes. Cultured EC release exosomes containing small RNA, including miR-33a-5p. After transduction with HDAdXMoAntimiR33a5p, EC-derived exosomes containing anti-miR-33a-5p accumulate in conditioned medium (CM). When this CM is added to macrophages or SMC, anti-miR-33a-5p is detected in these target cells. Exosome-mediated transfer of anti-miR-33a-5p reduces miR-33a-5p by ∼65-80%, increases ABCA1 protein by 1.6-2.2-fold, and increases apoAI-mediated cholesterol efflux by 1.4-1.6-fold (all p ≤ 0.01). These effects were absent in macrophages and SMC incubated in exosome-depleted CM. EC transduced with HDAdXMoAntimiR33a5p release exosomes that can transfer anti-miR-33a-5p to other intimal cell types, upregulating cholesterol efflux from these cells. This strategy provides a platform for genetic modification of intimal and medial cells, using a vector that transduces only EC.

Targeting Foam Cell Formation in Atherosclerosis: Therapeutic Potential of Natural Products

Foam cell formation and further accumulation in the subendothelial space of the vascular wall is a hallmark of atherosclerotic lesions. Targeting foam cell formation in the atherosclerotic lesions can be a promising approach to treat and prevent atherosclerosis. The formation of foam cells is determined by the balanced effects of three major interrelated biologic processes, including lipid uptake, cholesterol esterification, and cholesterol efflux. Natural products are a promising source for new lead structures. Multiple natural products and pharmaceutical agents can inhibit foam cell formation and thus exhibit antiatherosclerotic capacity by suppressing lipid uptake, cholesterol esterification, and/or promoting cholesterol ester hydrolysis and cholesterol efflux. This review summarizes recent findings on these three biologic processes and natural products with demonstrated potential to target such processes. Discussed also are potential future directions for studying the mechanisms of foam cell formation and the development of foam cell-targeted therapeutic strategies.

Biological Consequences of Dysfunctional HDL

Epidemiological studies have suggested an inverse correlation between high-density lipoprotein (HDL) cholesterol levels and the risk of cardiovascular disease. HDLs promote reverse cholesterol transport (RCT) and possess several putative atheroprotective functions, associated to the anti-inflammatory, anti-thrombotic and anti-oxidant properties as well as to the ability to support endothelial physiology. The assumption that increasing HDL-C levels would be beneficial on cardiovascular disease (CVD), however, has been questioned as, in most clinical trials, HDL-C-raising therapies did not result in improved cardiovascular outcomes. These findings, together with the observations from Mendelian randomization studies showing that polymorphisms mainly or solely associated with increased HDL-C levels did not decrease the risk of myocardial infarction, shift the focus from HDL-C levels toward HDL functional properties. Indeed, HDL from atherosclerotic patients not only exhibit impaired atheroprotective functions but also acquire pro-atherogenic properties and are referred to as "dysfunctional" HDL; this occurs even in the presence of normal or elevated HDL-C levels. Pharmacological approaches aimed at restoring HDL functions may therefore impact more significantly on CVD outcome than drugs used so far to increase HDL-C levels. The aim of this review is to discuss the pathological conditions leading to the formation of dysfunctional HDL and their role in atherosclerosis and beyond.

Association of apolipoprotein A1 and A5 polymorphisms with stroke subtypes in Han Chinese people in Taiwan

BACKGROUND AND PURPOSES

Stroke is a leading cause of death and serious disability worldwide. Now, evidences indicate that dyslipidemia may play an important role in stroke. APOA1 and APOA5 involve in lipid metabolism. In this study, we investigated the association of APOA1 rs670 and APOA5 rs662799 with different stroke subtypes in the Han Chinese population of Taiwan.

METHODS

A total of 1751 participants, including 459 control subjects, 606 large artery atherosclerosis (LAA), 339 small vessel occlusion (SVO), and 347 hypertensive intracranial hemorrhage (HICH), were enrolled. The presence of rs670 and rs662799 was analyzed through polymerase chain react ion and matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry.

RESULTS

Notably, the frequency of the rs662799 C allele was significantly lower in the SVO patients than in the controls (24.36% vs. 29.74%, P = 0.024). The frequencies of heterozygote TC [odd ratio (OR) = 0.732, 95% confidence interval (CI) = 0.544-0.984, P = 0.038] and TC + CC (OR = 0.719, 95% CI = 0.542-0.953, P = 0.022) genotypes were significantly lower in the SVO patients than in the controls. In addition, triglyceride levels in individuals carrying the rs662799 TC + CC genotype were significantly higher than in those carrying the TT genotype, especially in older age, female, and body mass index (BMI) ≥ 25 groups. On the contrary, the low-density lipoprotein-cholesterol (LDL-C) was significantly lower in rs662799 TC + CC genotype than TT genotype. The BMI was significantly lower in subjects with rs662799 TC + CC genotype than those with TT genotype, especially in older age and female. High-density lipoprotein-cholesterol (HDL-C) levels were higher in individuals carrying the rs670 GG genotype than in those carrying the AG + AA genotype, especially in BMI < 25 group. Logistic regression analysis showed that the rs662799 C allele (TC + CC) was an independent protective factor for SVO after adjustment for conventional risk factors (OR = 0.709, 95% CI = 0.526-0.956; P = 0.024).

CONCLUSION

GG genotype of rs670 is correlated with high serum HDL-C levels, whereas TC + CC genotype of rs662799 is associated with high serum triglyceride and low LDL and BMI levels. In addition, the rs662799 C allele (TC + CC) is an independent protective factor for SVO in the Han Chinese population in Taiwan.

ABCA1 Overexpression in Endothelial Cells In Vitro Enhances ApoAI-Mediated Cholesterol Efflux and Decreases Inflammation

Atherosclerosis, a disease of blood vessels, is driven by cholesterol accumulation and inflammation. Gene therapy that removes cholesterol from blood vessels and decreases inflammation is a promising approach for prevention and treatment of atherosclerosis. In previous work, we reported that helper-dependent adenoviral (HDAd) overexpression of apolipoprotein A-I (apoAI) in endothelial cells (ECs) increases cholesterol efflux in vitro and reduces atherosclerosis in vivo. However, the effect of HDAdApoAI on atherosclerosis is partial. To improve this therapy, we considered concurrent overexpression of ATP-binding cassette subfamily A, member 1 (ABCA1), a protein that is required for apoAI-mediated cholesterol efflux. Before attempting combined apoAI/ABCA1 gene therapy, we tested whether an HDAd that expresses ABCA1 (HDAdABCA1) increases EC cholesterol efflux, whether increased cholesterol efflux alters normal EC physiology, and whether ABCA1 overexpression in ECs has anti-inflammatory effects. HDAdABCA1 increased EC ABCA1 protein (∼3-fold; p < 0.001) and apoAI-mediated cholesterol efflux (2.3-fold; p = 0.007). Under basal culture conditions, ABCA1 overexpression did not alter EC proliferation, metabolism, migration, apoptosis, nitric oxide production, or inflammatory gene expression. However, in serum-starved, apoAI-treated EC, ABCA1 overexpression had anti-inflammatory effects: decreased inflammatory gene expression (∼50%; p ≤ 0.02 for interleukin [IL]-6, tumor necrosis factor [TNF]-α, and vascular cell adhesion protein-1); reduced lipid-raft Toll-like receptor 4 (80%; p = 0.001); and a trend towards increased nitric oxide production (∼55%; p = 0.1). In ECs stimulated with lipopolysaccharide, ABCA1 overexpression markedly decreased inflammatory gene expression (∼90% for IL-6 and TNF-α; p < 0.001). Therefore, EC ABCA1 overexpression has no toxic effects and counteracts the two key drivers of atherosclerosis: cholesterol accumulation and inflammation. In vivo testing of HDAdABCA1 is warranted.

Pharmacological Intervention to Modulate HDL: What Do We Target?

The cholesterol concentrations of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) have traditionally served as risk factors for cardiovascular disease. As such, novel therapeutic interventions aiming to raise HDL cholesterol have been tested in the clinical setting. However, most trials led to a significant increase in HDL cholesterol with no improvement in cardiovascular events. The complexity of the HDL particle, which exerts multiple physiological functions and is comprised of a number of subclasses, has raised the question as to whether there should be more focus on HDL subclass and function rather than cholesterol quantity. We review current data regarding HDL subclasses and subclass-specific functionality and highlight how current lipid modifying drugs such as statins, cholesteryl ester transfer protein inhibitors, fibrates and niacin often increase cholesterol concentrations of specific HDL subclasses. In addition this review sets out arguments suggesting that the HDL3 subclass may provide better protective effects than HDL2.

Apo A-I (Apolipoprotein A-I) Vascular Gene Therapy Provides Durable Protection Against Atherosclerosis in Hyperlipidemic Rabbits

OBJECTIVE

Gene therapy that expresses apo A-I (apolipoprotein A-I) from vascular wall cells has promise for preventing and reversing atherosclerosis. Previously, we reported that transduction of carotid artery endothelial cells with a helper-dependent adenoviral (HDAd) vector expressing apo A-I reduced early (4 weeks) fatty streak development in fat-fed rabbits. Here, we tested whether the same HDAd could provide long-term protection against development of more complex lesions.

APPROACH AND RESULTS

Fat-fed rabbits (n=25) underwent bilateral carotid artery gene transfer, with their left and right common carotids randomized to receive either a control vector (HDAdNull) or an apo A-I-expressing vector (HDAdApoAI). Twenty-four additional weeks of high-fat diet yielded complex intimal lesions containing lipid-rich macrophages as well as smooth muscle cells, often in a lesion cap. Twenty-four weeks after gene transfer, high levels of apo A-I mRNA (median ≥250-fold above background) were present in all HDAdApoAI-treated arteries. Compared with paired control HDAdNull-treated arteries in the same rabbit, HDAdApoAI-treated arteries had 30% less median intimal lesion volume (P=0.03), with concomitant reductions (23%-32%) in intimal lipid, macrophage, and smooth muscle cell content (P≤0.05 for all). HDAdApoAI-treated arteries also had decreased intimal inflammatory markers. VCAM-1 (vascular cell adhesion molecule-1)-stained area was reduced by 36% (P=0.03), with trends toward lower expression of ICAM-1 (intercellular adhesion molecule-1), MCP-1 (monocyte chemoattractant protein 1), and TNF-α (tumor necrosis factor-α; 13%-39% less; P=0.06-0.1).

CONCLUSIONS

In rabbits with severe hyperlipidemia, transduction of vascular endothelial cells with an apo A-I-expressing HDAd yields at least 24 weeks of local apo A-I expression that durably reduces atherosclerotic lesion growth and intimal inflammation.

Modulating cholesterol efflux capacity to improve cardiovascular disease

PURPOSE OF REVIEW

Low HDL-cholesterol (HDL-C) levels are predictive of incident atherosclerotic cardiovascular disease events. However, the use of medication to raise HDL-C levels has not consistently shown clinical benefit. As a result, studies have shifted toward HDL function, specifically cholesterol efflux, which has been inversely associated with prevalent subclinical atherosclerosis as well as subsequent atherosclerotic cardiovascular disease events. The purpose of this review is to summarize the effects of current medications and interventions on cholesterol efflux capacity.

RECENT FINDINGS

Medications for cardiovascular health, including statins, fibrates, niacin, and novel therapeutics, are reviewed for their effect on cholesterol efflux. Differences in population studied and assay used are addressed appropriately. Lifestyle interventions, including diet and exercise, are also included in the review.

SUMMARY

The modification of cholesterol efflux capacity (CEC) by current medications and interventions has been investigated in both large randomized control trials and smaller observational cohorts. This review serves to compile the results of these studies and evaluate CEC modulation by commonly used medications. Altering CEC could be a novel therapeutic approach to improving cardiovascular risk profiles.