Somatic gene transfer of human ApoA-I inhibits atherosclerosis progression in mouse models

Serum apolipoprotein A-I depletion is causative to silica nanoparticles-induced cardiovascular damage

The rapid development of nanotechnology has greatly benefited modern science and engineering and also led to an increased environmental exposure to nanoparticles (NPs). While recent research has established a correlation between the exposure of NPs and cardiovascular diseases, the intrinsic mechanisms of such a connection remain unclear. Inhaled NPs can penetrate the air-blood barrier from the lung to systemic circulation, thereby intruding the cardiovascular system and generating cardiotoxic effects. In this study, on-site cardiovascular damage was observed in mice upon respiratory exposure of silica nanoparticles (SiNPs), and the corresponding mechanism was investigated by focusing on the interaction of SiNPs and their encountered biomacromolecules en route. SiNPs were found to collect a significant amount of apolipoprotein A-I (Apo A-I) from the blood, in particular when the SiNPs were preadsorbed with pulmonary surfactants. While the adsorbed Apo A-I ameliorated the cytotoxic and proinflammatory effects of SiNPs, the protein was eliminated from the blood upon clearance of the NPs. However, supplementation of Apo A-I mimic peptide mitigated the atherosclerotic lesion induced by SiNPs. In addition, we found a further declined plasma Apo A-I level in clinical silicosis patients than coronary heart disease patients, suggesting clearance of SiNPs sequestered Apo A-I to compromise the coronal protein's regular biological functions. Together, this study has provided evidence that the protein corona of SiNPs acquired in the blood depletes Apo A-I, a biomarker for prediction of cardiovascular diseases, which gives rise to unexpected toxic effects of the nanoparticles.

Dose-Response Association Between High-Density Lipoprotein Cholesterol and Stroke: A Systematic Review and Meta-Analysis of Prospective Cohort Studies

INTRODUCTION

Studies investigating the effect of high-density lipoprotein cholesterol (HDL-C) on stroke and stroke subtypes have reached inconsistent conclusions. The purpose of our study was to clarify the dose-response association between HDL-C level and risk of total stroke and stroke subtypes by a systematic review and meta-analysis.

METHODS

We performed a systematic search of PubMed, Embase, and Web of Science databases through July 30, 2020, for prospective cohort studies that reported the HDL-C-stroke association and extracted the estimate that was adjusted for the greatest number of confounding factors. Restricted cubic splines were used to evaluate the linear and nonlinear dose-response associations.

RESULTS

We included 29 articles, which reported on 62 prospective cohort studies including 900,501 study participants and 25,678 with stroke. The summary relative risk per 1-mmol/L increase in HDL-C level for total stroke was 0.82 (95% CI, 0.76-0.89; I² = 42.9%; n = 18); ischemic stroke (IS), 0.75 (95% CI, 0.69-0.82; I² = 50.1%; n = 22); intracerebral hemorrhage (ICH), 1.21 (95% CI, 1.04-1.42; I² = 33.4%; n = 10); and subarachnoid hemorrhage (SAH), 0.98 (95% CI, 0.96-1.00; I² = 0%; n = 7). We found a linear inverse association between HDL-C level and risk of total stroke and SAH, a nonlinear inverse association for IS risk, but a linear positive association for ICH risk. The strength and the direction of the effect size estimate for total stroke, IS, ICH, and SAH remained stable for most subgroups. We found no publication bias with Begg's test and Egger's test for the association of HDL-C level with risk of total stroke, IS, and ICH.

CONCLUSION

A high HDL-C level is associated with reduced risk of total stroke and IS and an increased risk of ICH.

Improvement of Endothelial Dysfunction of Berberine in Atherosclerotic Mice and Mechanism Exploring through TMT-Based Proteomics

Atherosclerosis is a multifactorial vascular disease triggered by disordered lipid metabolism, characterized by chronic inflammatory injury, and initiated by endothelial dysfunction. Berberine is the main active alkaloid of the herbal medicine Coptidis Rhizoma (Huanglian). Notably, berberine has been shown to have beneficial effects against atherosclerosis. However, the mechanisms of berberine in preventing atherosclerosis are still unclear. This study is aimed at investigating the effects and mechanisms of berberine in protecting the aorta and ameliorating atherosclerosis in apolipoprotein E-deficient (ApoE^−/−) mice. Here, we demonstrated that berberine reduced serum lipid levels, antagonized hepatic lipid accumulation, improved intima-media thickening, and alleviated atherosclerotic lesions in ApoE^−/− mice fed a western-type diet for 12 weeks. Meanwhile, berberine reduced aortic reactive oxygen species (ROS) generation and reduced the serum levels of malondialdehyde (MDA), oxidized low-density lipoprotein (ox-LDL), and interleukin-6 (IL-6). In aortic ring assay, berberine restored aortic endothelium-dependent vasodilatation in vivo and in vitro. Furthermore, 4,956 proteins were identified by proteomic analysis, and 199 differentially expressed proteins regulated by berberine were found to be involved in many biological pathways, such as mitochondrial dysfunction, fatty acid β-oxidation I, and FXR/RXR activation. Summarily, these data suggested that berberine ameliorates endothelial dysfunction and protects against atherosclerosis, and thus may be a promising therapeutic candidate for atherosclerosis.

Statins for Treatment of Dyslipidemia in Chronic Kidney Disease

Dyslipidemia is a potent cardiovascular (CV) risk factor in the general population. Elevated low-density lipoprotein cholesterol (LDL-C) and/or low high-density lipoprotein (HDL-C) are well-established CV risk factors, but more precise determinants of risk include increased apoprotein B (ApoB), lipoprotein(a) [Lp(a)], intermediate and very low-density lipoprotein (IDL-C, VLDL-C; “remnant particles”), and small dense LDL particles. Lipoprotein metabolism is altered in association with declining glomerular filtration rate such that patients with non dialysis-dependent chronic kidney disease (CKD) have lower levels of HDL-C, higher triglyceride, ApoB, remnant IDL-C, remnant VLDL-C, and Lp(a), and a greater proportion of oxidized LDL-C. Similar abnormalities are prevalent in hemodialysis (HD) patients, who often manifest proatherogenic changes in LDL-C in the absence of increased levels. Patients treated with peritoneal dialysis (PD) have a similar but more severe dyslipidemia compared to HD patients due to stimulation of hepatic lipoprotein synthesis by glucose absorption from dialysate, increased insulin levels, and selective protein loss in the dialysate analogous to the nephrotic syndrome. In the dialysis-dependent CKD population, total cholesterol is directly associated with increased mortality after controlling for the presence of malnutrition–inflammation.

Treatment with statins reduces CV mortality in the general population by approximately one third, irrespective of baseline LDL-C or prior CV events. Statins have similar, if not greater, efficacy in altering the lipid profile in patients with dialysis-dependent CKD (HD and PD) compared to those with normal renal function, and are well tolerated in CKD patients at moderate doses (≤ 20 mg/day atorvastatin or simvastatin). Statins reduce C-reactive protein as well as lipid moieties such as ApoB, remnants IDL and VLDL-C, and oxidized and small dense LDL-C fraction. Large observational studies demonstrate that statin treatment is independently associated with a 30% – 50% mortality reduction in patients with dialysis-dependent CKD (similar between HD- and PD-treated patients). One recent randomized controlled trial evaluated the ability of statin treatment to reduce mortality in type II diabetics treated with HD (“4D”); the primary end point of death from cardiac cause, myocardial infarction, and stroke was not significantly reduced. However, results of this trial may not apply to other end-stage renal disease populations. Two ongoing randomized controlled trials (SHARP and AURORA) are underway evaluating the effect of statins on CV events and death in patients with CKD (including patients treated with HD and PD). Recruitment to future trials should be given a high priority by nephrologists and, until more data are available, consideration should be given to following published guidelines for the treatment of dyslipidemia in CKD. Additional consideration could be given to treating all dialysis patients felt to be at risk of CV disease (irrespective of cholesterol level), given the safety and potential efficacy of statins. This is especially relevant in patients treated with PD, given their more atherogenic lipid profile and the lack of randomized controlled trials in this population.

The Mechanism of Bisphenol A Atherogenicity Involves Apolipoprotein A-I Downregulation through NF-κB Activation

Apolipoprotein A-I (apoA-I) is the major protein component of high-density lipoproteins (HDL), mediating many of its atheroprotective properties. Increasing data reveal the pro-atherogenic effects of bisphenol A (BPA), one of the most prevalent environmental chemicals. In this study, we investigated the mechanisms by which BPA exerts pro-atherogenic effects. For this, LDLR-/- mice were fed with a high-fat diet and treated with 50 µg BPA/kg body weight by gavage. After two months of treatment, the area of atherosclerotic lesions in the aorta, triglycerides and total cholesterol levels were significantly increased, while HDL-cholesterol was decreased in BPA-treated LDLR-/- mice as compared to control mice. Real-Time PCR data showed that BPA treatment decreased hepatic apoA-I expression. BPA downregulated the activity of the apoA-I promoter in a dose-dependent manner. This inhibitory effect was mediated by MEKK1/NF-κB signaling pathways. Transfection experiments using apoA-I promoter deletion mutants, chromatin immunoprecipitation, and protein-DNA interaction assays demonstrated that treatment of hepatocytes with BPA induced NF-κB signaling and thus the recruitment of p65/50 proteins to the multiple NF-κB binding sites located in the apoA-I promoter. In conclusion, BPA exerts pro-atherogenic effects downregulating apoA-I by MEKK1 signaling and NF-κB activation in hepatocytes.

A potential risk factor for paraoxonase 1: in silico and in-vitro analysis of the biological activity of proton-pump inhibitors†

Objectives

Proton-pump inhibitors (PPIs) are drugs commonly utilized by about 7% of adults in the world. Recent researches have shown that there are countless and severe side effects of these drugs. This situation has raised concern among clinicians and patients alike. The purpose of this study is to contribute the novel drug discovery and development technology and toxicology field by researching interactions of PPIs on paraoxonase 1.

Methods

In this study, the paraoxonase 1 enzyme was purified from human serum by using rapid and straightforward chromatographic techniques. Subsequently, the inhibition effects of pantoprazole, omeprazole, and esomeprazole, PPIs, were investigated on paraoxonase 1. Besides, molecular docking studies were performed to unravel the binding mechanism between the enzyme and drugs.

Key findings

All drugs showed potent inhibitory activities. IC50 of the drugs values were 54.780 ± 0.524, 86.470 ± 0.818 and 93.390 ± 0.885 mm and Ki constants were found as 39.895 ± 0.005 mm, 70.112 ± 0.010 mm and 78.868 ± 0.008 mm, respectively. The binding scores observed in silico studies were found to agree with the obtained from in-vitro experimental results.

Conclusions

We observed that the drugs decreased PON1 activity at low concentrations. The results show that adjusting the dosages of these medications is a crucial case for each patient. The physicians should more carefully interpret whether there is an essential indication before prescribing PPIs and, if there is, to approve the proper dosing for the situation.

BMP1 5'UTR + 104 T/C gene variation: can be a predictive marker for serum HDL and apoprotein A1 levels in male patients with coronary heart disease

Apolipoprotein A1 (Apo A1), the major protein of HDL, is secreted as a proprotein and then is cleaved by C-terminal procollagen endoproteinase/bone morphogenetic protein-1 (BMP1). BMP1 stimulates the conversion of newly secreted proapo A1 to its phospholipid-binding form. Therefore, genetic variations of BMP1 gene may affect serum ApoA1 and HDL levels. We aimed to investigate the effects of the functional 5'UTR + 104 (T/C) variant of BMP1 on serum ApoA1 and HDL levels and risk of coronary heart disease (CHD) in this study. The BMP1 5'UTR + 104 (T/C) (rs143383) variation was determined in 131 male patients with CHD and 51 male controls by real-time polymerase chain reaction technique. ApoA1 levels were measured by immunoturbidimetry. The serum Apo-A1 levels were found higher in controls with the BMP1-CC genotype than those with the T-allele (p < 0.001). Our findings show the association of this variation with serum ApoA1 and HDL-C levels which increase in the order of CT < TT < CC in the controls. No effect was found on ApoA1 and HDL-C levels in CHD patients, as it was observed in the controls. However, the BMP1-TT genotype was associated with higher triglyceride (TG) levels as compared to C-allele (p = 0.009). These discrepancies could be due to statin therapy which has dominant effects on lowering cholesterol levels comparing to TG levels. Our results indicated that the BMP1 5'UTR + 104 (T/C) variation may affect the serum ApoA1 and lipoprotein levels depending on statin therapy so that contributes to the development of CHD.

In Vivo Gene Transfer to the Rabbit Common Carotid Artery Endothelium

The goal of this method is to introduce a transgene into the endothelium of isolated segments of both rabbit common carotid arteries. The method achieves focal endothelial-selective transgenesis, thereby allowing an investigator to determine the biological roles of endothelial-expressed transgenes and to quantify the in vivo transcriptional activity of DNA sequences in large artery endothelial cells. The method uses surgical isolation of rabbit common carotid arteries and an arteriotomy to deliver a transgene-expressing viral vector into the arterial lumen. A short incubation period of the vector in the lumen, with subsequent aspiration of the lumen contents, is sufficient to achieve efficient and durable expression of the transgene in the endothelium, with no detectable transduction or expression outside of the isolated arterial segment. The method allows assessment of the biological activities of transgene products both in normal arteries and in models of human vascular disease, while avoiding systemic effects that could be caused either by targeting gene delivery to other sites (e.g. the liver) or by the alternative approach of delivering genetic constructs to the endothelium by germ line transgenesis. Application of the method is limited by the need for a skilled surgeon and anesthetist, a well-equipped operating room, the costs of purchasing and housing rabbits, and the need for expertise in gene-transfer vector construction and use. Results obtained with this method include: transgene-related alterations in arterial structure, cellularity, extracellular matrix, or vasomotor function; increases or reductions in arterial inflammation; alterations in vascular cell apoptosis; and progression, retardation, or regression of diseases such as intimal hyperplasia or atherosclerosis. The method also allows measurement of the ability of native and synthetic DNA regulatory sequences to alter transgene expression in endothelial cells, providing results that include: levels of transgene mRNA, levels of transgene protein, and levels of transgene enzymatic activity.

Oral Apolipoprotein A-I Mimetic D-4F Lowers HDL-Inflammatory Index in High-Risk Patients: A First-in-Human Multiple-Dose, Randomized Controlled Trial

A single dose of the apolipoprotein (apo)A-I mimetic peptide D-4F rendered high-density lipoprotein (HDL) less inflammatory, motivating the first multiple-dose study. We aimed to assess safety/tolerability, pharmacokinetics, and pharmacodynamics of daily, orally administered D-4F. High-risk coronary heart disease (CHD) subjects added double-blinded placebo or D-4F to statin for 13 days, randomly assigned 1:3 to ascending cohorts of 100, 300, then 500 mg (n = 62; 46 men/16 women). D-4F was safe and well-tolerated. Mean ± SD plasma D-4F area under the curve (AUC, 0-8h) was 6.9 ± 5.7 ng/mL*h (100 mg), 22.7 ± 19.6 ng/mL*h (300 mg), and 104.0 ± 60.9 ng/mL*h (500 mg) among men, higher among women. Whereas placebo dropped HDL inflammatory index (HII) 28% 8 h postdose (range, 1.25-0.86), 300-500 mg D-4F effectively halved HII: 1.35-0.57 and 1.22-0.63, respectively (P < 0.03 vs. placebo). Oral D-4F peptide dose predicted HII suppression, whereas plasma D-4F exposure was dissociated, suggesting plasma penetration is unnecessary. In conclusion, oral D-4F dosing rendered HDL less inflammatory, affirming oral D-4F as a potential therapy to improve HDL function.

Could high-density lipoprotein cholesterol predict increased cardiovascular risk?

PURPOSE OF REVIEW

Serum high-density lipoprotein (HDL) is considered to be protective against cardiovascular disease. However, there is emerging evidence that under certain conditions the HDL molecule can become dysfunctional and proinflammatory, paradoxically leading to increased risk of cardiovascular disease. This review will provide a brief outline of the potential mechanisms by which HDL can become atherogenic and summarize some of the clinical evidence on this topic.

RECENT FINDINGS

HDL metabolism, structure, and function in addition to its level can be profoundly altered under conditions of marked oxidative stress and chronic inflammation. These abnormalities, in turn, lead to impaired reverse cholesterol transport, increased systemic oxidative stress/inflammation, and endothelial dysfunction that subsequently may contribute to atherogenesis and progression of cardiovascular disease.

SUMMARY

Association of serum HDL cholesterol level with outcomes is not only dependent on its serum concentration but also on the qualities/properties of this lipoprotein at a given point in time. Hence, it is essential that future studies examining association of HDL with risk of cardiovascular disease take into account the complexities of HDL metabolism and function and address the impact of the HDL particle as a whole (quantity as well as various properties) on atherosclerosis and cardiovascular outcomes.

Local Vascular Gene Therapy With Apolipoprotein A-I to Promote Regression of Atherosclerosis

OBJECTIVE

Gene therapy, delivered directly to the blood vessel wall, could potentially prevent atherosclerotic lesion growth and promote atherosclerosis regression. Previously, we reported that a helper-dependent adenoviral (HDAd) vector expressing apolipoprotein A-I (apoA-I) in carotid endothelium of fat-fed rabbits reduced early (4 weeks) atherosclerotic lesion growth. Here, we tested whether the same HDAd-delivered to the existing carotid atherosclerotic lesions-could promote regression.

APPROACH AND RESULTS

Rabbits (n=26) were fed a high-fat diet for 7 months, then treated with bilateral carotid gene transfer. One carotid was infused with an HDAd expressing apoA-I (HDAdApoAI) and the other with a control nonexpressing HDAd (HDAdNull). The side with HDAdApoAI was randomized. Rabbits were then switched to regular chow, lowering their plasma cholesterols by over 70%. ApoA-I mRNA and protein were detected in HDAdApoAI-transduced arteries. After 7 weeks of gene therapy, compared with HDAdNull-treated arteries in the same rabbits, HDAdApoAI-treated arteries had significantly less vascular cell adhesion molecule-1 expression (28%; P=0.04) along with modest but statistically insignificant trends toward decreased intimal lesion volume, lipid and macrophage content, and intercellular adhesion molecule-1 expression (9%-21%; P=0.1-0.4). Post hoc subgroup analysis of rabbits with small-to-moderate-sized lesions (n=20) showed that HDAdApoAI caused large reductions in lesion volume, lipid content, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 expression (30%-50%; P≤0.04 for all). Macrophage content was reduced by 30% (P=0.06). There was a significant interaction (P=0.02) between lesion size and treatment efficacy.

CONCLUSIONS

Even when administered on a background of aggressive lowering of plasma cholesterol, local HDAdApoAI vascular gene therapy may promote rapid regression of small-to-moderate-sized atherosclerotic lesions.

Targeting high-density lipoproteins: increasing de novo production versus decreasing clearance

Although cardiovascular mortality has been decreasing in industrialized countries, there continues to be a substantial residual risk; thus, novel therapeutic agents and new targets of therapy have been sought. One highly plausible therapeutic target is high-density lipoprotein (HDL). HDL is a key player in reverse cholesterol transport and possesses a slew of other cardioprotective properties; however, recent trials with agents known to increase HDL levels have generally not shown any reduction in cardiovascular events. Further analysis of these trials suggest that fibrates have consistently reduced some cardiovascular outcomes, at least in the subgroup of patients with high serum triglycerides and low HDL cholesterol (HDLc) levels. Since fibrates, unlike niacin or cholesterol ester transfer protein inhibitors, increase HDLc level mostly through the stimulation of apolipoprotein A-I production, it is suggested that the quality and functionality of HDL are enhanced when de novo synthesis rather than inhibition of turnover is the mechanism of increasing HDL level. In this communication, the evidence for and against the cardioprotective properties of HDL is reviewed and the contemporary clinical trials are discussed.

HDL cholesterol and stroke risk: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND AND PURPOSE

Accurate identification of risk factors for stroke is important for public health promotion and disease prevention. HDL cholesterol is a potential risk factor, yet its role in stroke risk is unclear, as is whether HDL cholesterol content or particle number might be a better indicator of stroke risk. Furthermore, the degree to which ethnicity moderates the risk is unknown. As such, the current study examines the associations between incident stroke and both HDL cholesterol concentration and particle number, and assesses the moderating role of race and ethnicity.

METHODS

The sample is a racially diverse cohort of US adults between the ages of 45-84 years enrolled in the Multi-Ethnic Study of Atherosclerosis between 2000 and 2002 and followed until December 2011. The associations among cholesterol content and stroke risk, particle number and stroke risk, and the interaction with race were explored.

RESULTS

The incidence of stroke was 2.6%. HDL cholesterol concentration (mmol/L) (Hazard Ratio (HR) = .56; 95% Confidence Interval (CI): .312-.988) and number of large HDL particles (μmol/L) (HR = .52, CI: .278-.956) were associated with lower stroke risk. When interactions with race were evaluated, the relationship between both HDL variables and stroke were significant in Blacks, but not other races.

CONCLUSIONS

Higher HDL cholesterol and a higher concentration of large particles are associated with lower risk of stroke in Blacks. Further research is needed to elucidate the mechanisms by which HDL subfractions may differentially affect stroke outcome in different races/ethnicities.

Perhexiline activates KLF14 and reduces atherosclerosis by modulating ApoA-I production

Recent genome-wide association studies have revealed that variations near the gene locus encoding the transcription factor Krüppel-like factor 14 (KLF14) are strongly associated with HDL cholesterol (HDL-C) levels, metabolic syndrome, and coronary heart disease. However, the precise mechanisms by which KLF14 regulates lipid metabolism and affects atherosclerosis remain largely unexplored. Here, we report that KLF14 is dysregulated in the liver of 2 dyslipidemia mouse models. We evaluated the effects of both KLF14 overexpression and genetic inactivation and determined that KLF14 regulates plasma HDL-C levels and cholesterol efflux capacity by modulating hepatic ApoA-I production. Hepatic-specific Klf14 deletion in mice resulted in decreased circulating HDL-C levels. In an attempt to pharmacologically target KLF14 as an experimental therapeutic approach, we identified perhexiline, an approved therapeutic small molecule presently in clinical use to treat angina and heart failure, as a KLF14 activator. Indeed, in WT mice, treatment with perhexiline increased HDL-C levels and cholesterol efflux capacity via KLF14-mediated upregulation of ApoA-I expression. Moreover, perhexiline administration reduced atherosclerotic lesion development in apolipoprotein E-deficient mice. Together, these results provide comprehensive insight into the KLF14-dependent regulation of HDL-C and subsequent atherosclerosis and indicate that interventions that target the KLF14 pathway should be further explored for the treatment of atherosclerosis.

A new model of reverse cholesterol transport: enTICEing strategies to stimulate intestinal cholesterol excretion

Cardiovascular disease (CVD) remains the largest cause of mortality in most developed countries. Although recent failed clinical trials and Mendelian randomization studies have called into question the high-density lipoprotein (HDL) hypothesis, it remains well accepted that stimulating the process of reverse cholesterol transport (RCT) can prevent or even regress atherosclerosis. The prevailing model for RCT is that cholesterol from the artery wall must be delivered to the liver where it is secreted into bile before leaving the body through fecal excretion. However, many studies have demonstrated that RCT can proceed through a non-biliary pathway known as transintestinal cholesterol excretion (TICE). The goal of this review is to discuss the current state of knowledge of the TICE pathway, with emphasis on points of therapeutic intervention.

Excessive centrifugal fields damage high density lipoprotein

HDL is typically isolated ultracentrifugally at 40,000 rpm or greater, however, such high centrifugal forces are responsible for altering the recovered HDL particle. We demonstrate that this damage to HDL begins at approximately 30,000 rpm and the magnitude of loss increases in a rotor speed-dependent manner. The HDL is affected by elevated ultracentrifugal fields resulting in a lower particle density due to the shedding of associated proteins. To circumvent the alteration of the recovered HDL, we utilize a KBr-containing density gradient and a lowered rotor speed of 15,000 rpm to separate the lipoproteins using a single 96 h centrifugation step. This recovers the HDL at two density ranges; the bulk of the material has a density of about 1.115 g/ml, while lessor amounts of material are recovered at >1.2 g/ml. Thus, demonstrating the isolation of intact HDL is possible utilizing lower centrifuge rotor speeds.

HDL biogenesis, remodeling, and catabolism

In this chapter, we review how HDL is generated, remodeled, and catabolized in plasma. We describe key features of the proteins that participate in these processes, emphasizing how mutations in apolipoprotein A-I (apoA-I) and the other proteins affect HDL metabolism. The biogenesis of HDL initially requires functional interaction of apoA-I with the ATP-binding cassette transporter A1 (ABCA1) and subsequently interactions of the lipidated apoA-I forms with lecithin/cholesterol acyltransferase (LCAT). Mutations in these proteins either prevent or impair the formation and possibly the functionality of HDL. Remodeling and catabolism of HDL is the result of interactions of HDL with cell receptors and other membrane and plasma proteins including hepatic lipase (HL), endothelial lipase (EL), phospholipid transfer protein (PLTP), cholesteryl ester transfer protein (CETP), apolipoprotein M (apoM), scavenger receptor class B type I (SR-BI), ATP-binding cassette transporter G1 (ABCG1), the F1 subunit of ATPase (Ecto F1-ATPase), and the cubulin/megalin receptor. Similarly to apoA-I, apolipoprotein E and apolipoprotein A-IV were shown to form discrete HDL particles containing these apolipoproteins which may have important but still unexplored functions. Furthermore, several plasma proteins were found associated with HDL and may modulate its biological functions. The effect of these proteins on the functionality of HDL is the topic of ongoing research.

An experimentally robust model of monomeric apolipoprotein A-I created from a chimera of two X-ray structures and molecular dynamics simulations

High-density lipoprotein (HDL) retards atherosclerosis by accepting cholesterol from the artery wall. However, the structure of the proposed acceptor, monomeric apolipoprotein A-I (apoA-I), the major protein of HDL, is poorly understood. Two published models for monomeric apoA-I used cross-linking distance constraints to derive best fit conformations. This approach has limitations. (i) Cross-linked peptides provide no information about secondary structure. (ii) A protein chain can be folded in multiple ways to create a best fit. (iii) Ad hoc folding of a secondary structure is unlikely to produce a stable orientation of hydrophobic and hydrophilic residues. To address these limitations, we used a different approach. We first noted that the dimeric apoA-I crystal structure, (Δ185-243)apoA-I, is topologically identical to a monomer in which helix 5 forms a helical hairpin, a monomer with a hydrophobic cleft running the length of the molecule. We then realized that a second crystal structure, (Δ1-43)apoA-I, contains a C-terminal structure that fits snuggly via aromatic and hydrophobic interactions into the hydrophobic cleft. Consequently, we combined these crystal structures into an initial model that was subjected to molecular dynamics simulations. We tested the initial and simulated models and the two previously published models in three ways: against two published data sets (domains predicted to be helical by H/D exchange and six spin-coupled residues) and against our own experimentally determined cross-linking distance constraints. We note that the best fit simulation model, superior by all tests to previously published models, has dynamic features of a molten globule with interesting implications for the functions of apoA-I.

In vivo efficacy of HDL-like nanolipid particles containing multivalent peptide mimetics of apolipoprotein A-I

We have observed that molecular constructs based on multiple apoA-I mimetic peptides attached to a branched scaffold display promising anti-atherosclerosis functions in vitro. Building on these promising results, we now describe chronic in vivo studies to assess anti-atherosclerotic efficacy of HDL-like nanoparticles assembled from a trimeric construct, administered over 10 weeks either ip or orally to LDL receptor-null mice. When dosed ip, the trimer-based nanolipids markedly reduced plasma LDL-cholesterol levels by 40%, unlike many other apoA-I mimetic peptides, and were substantially atheroprotective. Surprisingly, these nanoparticles were also effective when administered orally at a dose of 75 mg/kg, despite the peptide construct being composed of l-amino acids and being undetectable in the plasma. The orally administered nanoparticles reduced whole aorta lesion areas by 55% and aortic sinus lesion volumes by 71%. Reductions in plasma cholesterol were due to the loss of non-HDL lipoproteins, while plasma HDL-cholesterol levels were increased. At a 10-fold lower oral dose, the nanoparticles were marginally effective in reducing atherosclerotic lesions. Intriguingly, analogous results were obtained with nanolipids of the corresponding monomeric peptide. These nanolipid formulations provide an avenue for developing orally efficacious therapeutic agents to manage atherosclerosis.

Apolipoprotein A-I and adenosine triphosphate-binding cassette transporter A1 expression alleviates lipid accumulation in hepatocytes

BACKGROUND AND AIM

Abnormal lipid metabolism may contribute to the pathogenesis of non-alcoholic steatohepatitis. ATP-binding cassette transporter A1 (ABCA1) mediates the transport of cholesterol and phospholipids from cells to high density lipoprotein apolipoproteins. The lipidation of apolipoprotein A-I (apoA-I) by ABCA1 is the rate-limiting step in reverse cholesterol transport and the generation of plasma high density lipoprotein. Here, we examined the effect of apoA-I or ABCA1 overexpression on hepatic lipid levels in BEL-7402 cells.

METHODS

Human ABCA1 or apoA-I was overexpressed in BEL-7402 hepatocytes by transfection and human apoA-I was overexpressed via adenoviral vector in C57BL/6J mice with MCD diet.

RESULTS

Overexpression of either apoA-I or ABCA1 resulted in an increase in cholesterol efflux and a decrease in cellular fatty acids and triglycerides. However, after repression of ABCA1 by its siRNA, overexpression of apoA-I failed to decrease both cellular fatty acids and triglycerides. ApoA-I or ABCA1 overexpression also resulted in a decrease in the expression of the endoplasmic reticulum stress-related proteins GRP78 and SREBP-1. Overexpression of apoA-I in mice also reduced hepatic lipid levels.

CONCLUSIONS

Expression of apoA-I or ABCA1 can reduce steatosis by decreasing lipid storage in hepatocytes through lipid transport and may also reduce endoplasmic reticulum stress, further lessening hepatic steatosis.

Molecules that mimic apolipoprotein A-I: potential agents for treating atherosclerosis

Certain amphipathic α-helical peptides can functionally mimic many of the properties of full-length apolipoproteins, thereby offering an approach to modulate high-density lipoprotein (HDL) for combating atherosclerosis. In this Perspective, we summarize the key findings and advances over the past 25 years in the development of peptides that mimic apolipoproteins, especially apolipoprotein A-I (apoA-I). This assemblage of information provides a reasonably clear picture of the state of the art in the apolipoprotein mimetic field, an appreciation of the potential for such agents in pharmacotherapy, and a sense of the opportunities for optimizing the functional properties of HDL.

Mimicry of high-density lipoprotein: functional peptide-lipid nanoparticles based on multivalent peptide constructs

We describe an approach for engineering peptide-lipid nanoparticles that function similarly to high-density lipoprotein (HDL). Branched, multivalent constructs, bearing multiple 23- or 16-amino-acid peptides, were designed, synthesized, and combined with phospholipids to produce nanometer-scale discoidal HDL-like particles. A variety of biophysical techniques were employed to characterize the constructs, including size exclusion chromatography, analytical ultracentrifuge sedimentation, circular dichroism, transmission electron microscopy, and fluorescence spectroscopy. The nanoparticles functioned in vitro (human and mouse plasma) and in vivo (mice) to rapidly remodel large native HDLs into small lipid-poor HDL particles, which are key acceptors of cholesterol in reverse cholesterol transport. Fluorescent labeling studies showed that the constituents of the nanoparticles readily distributed into native HDLs, such that the peptide constructs coexisted with apolipoprotein A-I (apoA-I), the main structural protein in HDLs. Importantly, nanolipid particles containing multivalent peptides promoted efficient cellular cholesterol efflux and were functionally superior to those derived from monomeric apoA-I mimetic peptides. The multivalent peptide-lipid nanoparticles were also remarkably stable toward enzymatic digestion in vitro and displayed long half-lives and desirable pharmacokinetic profiles in mice, providing a real practical advantage over previously studied linear or tandem helical peptides. Encouragingly, a two-week exploratory efficacy study in a widely used animal model for atherosclerosis research (LDLr-null mice) using nanoparticles constructed from a trimeric peptide demonstrated an exceptional 50% reduction in the plasma total cholesterol levels compared to the control group. Altogether, the studies reported here point to an attractive avenue for designing synthetic, HDL-like nanoparticles, with potential for treating atherosclerosis.

Apolipoprotein A-I inhibits LPS-induced atherosclerosis in ApoE(-/-) mice possibly via activated STAT3-mediated upregulation of tristetraprolin

AIM

To investigate the effects of the major component of high-density lipoprotein apolipoprotein A-I (apoA-I) on the development of atherosclerosis in LPS-challenged ApoE(-/-) mice and the underlying mechanisms.

METHODS

Male ApoE-KO mice were daily injected with LPS (25 μg, sc) or PBS for 4 weeks. The LPS-challenged mice were intravenously injected with rAAV-apoA-I-GFP or rAAV-GFP. After the animals were killed, blood, livers and aortas were collected for biochemical and histological analyses. For ex vivo experiments, the abdominal cavity macrophages were harvested from each treatment group of mice, and cultured with autologous serum, then treated with LPS.

RESULTS

Chronic administration of LPS in ApoE(-/-) mice significantly increased the expression of inflammatory cytokines (TNF-α, IL-1β, IL-6, and MCP-1), increased infiltration of inflammatory cells, and enhanced the development of atherosclerosis. In LPS-challenged mice injected with rAAV-apoA-I-GFP, viral particles and human apoA-I were detected in the livers, total plasma human apoA-I levels were grammatically increased; HDL-cholesterol level was significantly increased, TG and TC were slightly increased. Furthermore, overexpression of apoA-I significantly suppressed the expression of proinflammatory cytokines, reduced the infiltration of inflammatory cells, and decreased the extent of atherosclerotic lesions. Moreover, overexpression of apoA-I significantly increased the expression of the cytokine mRNA-destabilizing protein tristetraprolin (TTP), and phosphorylation of JAK2 and STAT3 in aortas. In ex vivo mouse macrophages, the serum from mice overexpressing apoA-I significantly increased the expression of TTP, accompanied by accelerated decay of mRNAs of the inflammatory cytokines.

CONCLUSION

ApoA-I potently suppresses LPS-induced atherosclerosis by inhibiting the inflammatory response possibly via activation of STAT3 and upregulation of TTP.

High-density lipoprotein function, dysfunction, and reverse cholesterol transport

Although high high-density lipoprotein (HDL)-cholesterol levels are associated with decreased cardiovascular risk in epidemiological studies, recent genetic and pharmacological findings have raised doubts about the beneficial effects of HDL. Raising HDL levels in animal models by infusion or overexpression of apolipoprotein A-I has shown clear vascular improvements, such as delayed atherosclerotic lesion progression and accelerated lesion regression, along with increased reverse cholesterol transport. Inflammation and other factors, such as myeloperoxidase-mediated oxidation, can impair HDL production and HDL function, with regard to its reverse cholesterol transport, antioxidant, and anti-inflammatory activities. Thus, tests of HDL function, which have not yet been developed as routine diagnostic assays, may prove useful and be a better predictor of cardiovascular risk than HDL-cholesterol levels.

High-density lipoprotein cholesterol: How High

The high-density lipoprotein cholesterol (HDL-C) is considered anti-atherogenic good cholesterol. It is involved in reverse transport of lipids. Epidemiological studies have found inverse relationship of HDL-C and coronary heart disease (CHD) risk. When grouped according to HDL-C, subjects having HDL-C more than 60 mg/dL had lesser risk of CHD than those having HDL-C of 40-60 mg/dL, who in turn had lesser risk than those who had HDL-C less than 40 mg/dL. No upper limit for beneficial effect of HDL-C on CHD risk has been identified. The goals of treating patients with low HDL-C have not been firmly established. Though many drugs are known to improve HDL-C concentration, statins are proven to improve CHD risk and mortality. Cholesteryl ester transfer protein (CETP) is involved in metabolism of HDL-C and its inhibitors are actively being screened for clinical utility. However, final answer is still awaited on CETP-inhibitors.

Apolipoprotein E mimetic is more effective than apolipoprotein A-I mimetic in reducing lesion formation in older female apo E null mice

OBJECTIVE

The apolipoprotein E mimetic peptide Ac-hE18A-NH(2), capable of reducing plasma cholesterol and possessing anti-inflammatory properties, was compared with the well-studied anti-atherogenic apoA-I mimetic peptide 4F for reducing lesion formation in female apoE null mice with already existing lesions.

METHODS AND RESULTS

In initial experiments, Ac-hE18A-NH(2) was administered retro-orbitally two or three times weekly for 6-8 weeks, while peptide 4F was administered intraperitoneally every day for the same period. Age matched controls were injected with saline every day. At the end of the treatment period, plasma cholesterol levels of Ac-hE18A-NH(2) administered mice were significantly lower than in 4F and control mice. However, both 4F and Ac-hE18A-NH(2) showed reduced lesion areas in en face lesion analysis to a similar extent compared to the control group, while paraoxonase-1 (PON-1) activity was increased only in the Ac-hE18A-NH(2) group. In the third experiment, both peptides were administered at the same dose, frequency, and route of administration. The reduction in en face lesions with Ac-hE18A-NH(2) was significantly greater than the 4F and control groups, although lesions in 4F-treated mice were also significantly reduced compared with controls. Both peptide groups had significantly reduced plasma lipid hydroperoxides, but only the Ac-hE18A-NH(2) group had significantly reduced serum amyloid A levels. HDL and plasma inflammatory indices were significantly reduced in both peptide groups compared with controls.

CONCLUSIONS

Although both peptides had similar anti-inflammatory properties, Ac-hE18A-NH(2) was more effective in inhibiting lesions than 4F at the same dose, frequency, and route of administration, perhaps due to its cholesterol reducing properties.

Hepatocyte-specific ABCA1 transfer increases HDL cholesterol but impairs HDL function and accelerates atherosclerosis

AIMS

The ATP-binding cassette transporter A1 (ABCA1) lipidates apolipoprotein (apo) A-I. The hypothesis that hepatocyte-specific ABCA1 overexpression results in high-density lipoprotein (HDL) dysfunction was evaluated by comparing the effects of murine ABCA1 (AdABCA1) and human apo A-I (AdA-I) transfer on lipoprotein profile, HDL function, and progression of atherosclerosis.

METHODS AND RESULTS

Gene transfer in male and female C57BL/6 apo E(-/-) mice was performed at the age of 3 months with E1E3E4-deleted adenoviral vectors containing hepatocyte-specific expression cassettes. Atherosclerosis was quantified at baseline and 56 days later in AdABCA1, AdA-I, and control mice. HDL cholesterol after AdA-I transfer was 1.7-fold (P < 0.001) and 1.8-fold (P < 0.001) higher in male and female mice, respectively, and potently inhibited atherosclerosis progression compared with respective controls. Notwithstanding a 1.4-fold (P < 0.01) and a 1.7-fold (P < 0.01) increase of HDL cholesterol in male and female mice, respectively, after AdABCA1 transfer, the intima was 2.2-fold (P < 0.001) larger in male and 1.3-fold (P = NS) larger in female mice compared with respective controls. HDL isolated from control and AdA-I mice but not from AdABCA1 mice enhanced endothelial progenitor cell (EPC) migration in vitro and reduced endothelial cell death in vitro after serum and growth factor withdrawal. Scavenger receptor class B type I (SR-BI) protein level in the liver was significantly lower in AdABCA1 mice than in control and AdA-I mice.

CONCLUSION

Hepatocyte-specific ABCA1 transfer decreases SR-BI protein level in the liver and abrogates beneficial effects of HDL on EPCs and endothelial cells. Decreased HDL function may underlie accelerated atherosclerosis in AdABCA1 apo E(-/-)mice.

Gene therapy for dyslipidemia: a review of gene replacement and gene inhibition strategies

Despite numerous technological and pharmacological advances and more detailed knowledge of molecular etiologies, cardiovascular diseases remain the leading cause of morbidity and mortality worldwide claiming over 17 million lives a year. Abnormalities in the synthesis, processing and catabolism of lipoprotein particles can result in severe hypercholesterolemia, hypertriglyceridemia or low HDL-C. Although a plethora of antidyslipidemic pharmacological agents are available, these drugs are relatively ineffective in many patients with Mendelian lipid disorders, indicating the need for new and more effective interventions. In vivo somatic gene therapy is one such intervention. This article summarizes current strategies being pursued for the development of clinical gene therapy for dyslipidemias that cannot effectively be treated with existing drugs.

The HDL hypothesis: does high-density lipoprotein protect from atherosclerosis?

There is unequivocal evidence of an inverse association between plasma high-density lipoprotein (HDL) cholesterol concentrations and the risk of cardiovascular disease, a finding that has led to the hypothesis that HDL protects from atherosclerosis. This review details the experimental evidence for this "HDL hypothesis". In vitro studies suggest that HDL has a wide range of anti-atherogenic properties but validation of these functions in humans is absent to date. A significant number of animal studies and clinical trials support an atheroprotective role for HDL; however, most of these findings were obtained in the context of marked changes in other plasma lipids. Finally, genetic studies in humans have not provided convincing evidence that HDL genes modulate cardiovascular risk. Thus, despite a wealth of information on this intriguing lipoprotein, future research remains essential to prove the HDL hypothesis correct.

AAV gene therapy as a means to increase apolipoprotein (Apo) A-I and high-density lipoprotein-cholesterol levels: correction of murine ApoA-I deficiency

BACKGROUND

Inherited apolipoprotein (Apo) A-I deficiency is an orphan disorder characterized by high-density lipoprotein (HDL)-cholesterol deficiency and premature atherosclerosis. Constitutive over-expression of ApoA-I might provide a means to treat this disease. The present study provides a comprehensive evaluation of adeno-associated virus (AAV)-mediated ApoA-I gene delivery to express human (h)ApoA-I and correct the low HDL-cholesterol phenotype associated with ApoA-I deficiency.

METHODS

In an effort to maximize AAV-mediated gene expression, we performed head-to-head comparisons of recombinant AAVs with pseudotype capsids 1, 2, 6 and 8 administered by different routes with the use of five different liver-specific promoters in addition to cytomegalovirus as single-stranded or as self-complementary (sc) AAV vectors.

RESULTS

Intravenous administration of 1 x 10(13) gc/kg scAAV8, in combination with the liver-specific promoter LP1, in female ApoA-I(-/-) mice resulted in hApoA-I expression levels of 634 +/- 69 mg/l, which persisted for the duration of the study (15 weeks). This treatment resulted in full recovery of HDL-cholesterol levels with correction of HDL particle size and apolipoprotein composition. In addition, we observed increased adrenal cholesterol content and a significant increase in bodyweight in treated mice.

CONCLUSIONS

The present study demonstrates that systemic delivery of a scAAV8 vector provides a means for efficient liver expression of hApoA-I, thereby correcting the lipid abnormalities associated with murine ApoA-I deficiency. Importantly, the study demonstrates that AAV-based gene therapy can be used to express therapeutic proteins at a high level for a prolonged period of time and, as such, provides a basis for further development of this strategy to treat hApoA-I deficiency.

Regulation of expression of apolipoprotein A-I by selenium status in human liver hepatoblastoma cells

BACKGROUND

Cardiomyopathy is common to areas with low selenium (Se) intake and in patients receiving total parenteral nutrition. Although controversial, a few studies have suggested a protective role for Se in coronary heart disease on the basis of modulation of high-density lipoproteins (HDL).

AIMS OF THE STUDY

In this study, the role of Se as a positive regulator of expression of a key HDL, apolipoprotein A-I (apoA-I), has been evaluated in human hepatoblastoma (HepG2) cell culture model. We further examined if the transcription of apoA-I, driven by the nuclear hormone receptor, peroxisome-proliferator activated receptor, PPARalpha, was trans-repressed by the presence of the oxidative stress-responsive transcription factor, NF-kappaB.

METHODS

Modulation of expression of apoA-I and activation of nuclear NF-kappaB subunit p65 and PPARalpha by Se status were evaluated by Western blot and luciferase-based assays. Interaction of p65 with PPARalpha was evaluated by immunoprecipitation.

RESULTS

HepG2 cultured in media with Se (100 nM) demonstrated an increase in the expression of apoA-I when compared to Se-deficient cells. A similar trend was also seen in mice that were supplemented with 0.4 ppm of Se as sodium selenite. Treatment of Se-supplemented cells with bacterial lipopolysaccharide (LPS) showed induction of apoA-I. Supplementation of hepatocytes with Se decreased the nuclear levels of p65, which prevented its interaction with PPARalpha to modulate apoA-I transcription.

CONCLUSION

Our results suggest that supplementation of hepatocytes with Se mitigates oxidative stress-dependent repression of apoA-I expression by suppressing the NF-kappaB pathway, which allows PPARalpha to effectively drive the expression of apoA-I.

HDL: bridging past and present with a look at the future

Clinical and epidemiological studies have shown that HDLs, a class of plasma lipoproteins, heterogeneous in size and density, have an atheroprotective role attributed, for years, to their capacity to promote the efflux of cholesterol from activated cholesterol-loaded arterial macrophages. Recent studies, however, have recognized that the physical heterogeneity of HDLs is associated with multiple functions that involve both the protein and the lipid components of these particles. ApoA-I, quantitatively the major protein constituent, has an amphipathic structure suited for transport of lipids. It readily interacts with the ATP-binding cassette transporter ABCA1, the SR-B1 scavenger receptor; activates the enzyme lecithin-cholesterol acyl transferase (LCAT), which is critical for HDL maturation. It also has antioxidant and antiinflammatory properties, along with the HDL-associated enzymes paraoxonase, platelet activating factor acetylhydrolase (PAF), and glutathione peroxidase. Regarding the lipid moiety, an atheroprotective role has been recognized for lysosphingolipids, particularly sphingosine-1-phosphate (S1P). All of these atheroprotective functions are lost in the post-translational dependent dysfunctional plasma HDLs of subjects with systemic inflammation, coronary heart disease, diabetes, and chronic renal disease. The emerging notion that particle quality has more predictive power than quantity has stimulated further exploration of the HDL proteome, already revealing unsuspected pro- or antiatherogenic proteins/peptides associated with HDL.

Safety, pharmacokinetics, and pharmacodynamics of oral apoA-I mimetic peptide D-4F in high-risk cardiovascular patients

Patients with coronary heart disease or equivalent risk received a single dose of 30, 100, 300, or 500 mg of unformulated D-4F (n = 8, each dose) or placebo (n = 8) under fasting conditions. An additional 10 patients received 500 mg (n = 8) or placebo (n = 2) with a low-fat meal. There were no significant trends in any safety parameter. D-4F was detectable in plasma at all doses with a T(max) of 30 min, 1 h, and 2 h for 30, 100, and > or = 300 mg, respectively. The area under the curve((0-t)) was 27.81 ng/hr/ml and 54.71 ng/hr/ml for the 300 mg and 500 mg dose groups, respectively, and 17.96 ng/hr/ml for the 500 mg dose given with food. HDL from each time point for each subject was tested for its ability to inhibit LDL-induced monocyte chemotactic activity in cultures of human aortic endothelial cells. The values obtained were normalized to 1.0 for LDL alone to obtain the HDL inflammatory index. This index significantly improved at 4 h at the 300 mg dose and at 2 h at the 500 mg dose compared with placebo (P < 0.05). There were no changes in plasma lipid or lipoprotein levels. We conclude that unformulated D-4F has low bioavailability that is improved under fasting conditions, and that a single dose of D-4F is safe and well tolerated and may improve the HDL anti-inflammatory index.

Anti-atherogenic effects of seabuckthorn (Hippophaea rhamnoides) seed oil

Seabuckthorn (SBT) seed oil is a rich source of unsaturated fatty acids, phytosterols, carotenoids and flavonoids, which are known to have significant anti-atherogenic and cardioprotective activity. The anti-atherogenic activity of supercritical CO(2) extracted SBT seed oil was evaluated in white albino rabbits fed on high cholesterol diet for 60 days. The study was performed on 20 male healthy rabbits divided into four groups of 5 animals each. Group I - control, group II - SBT seed oil, group III - cholesterol (1%) for 60 days, group IV - cholesterol+SBT seed oil. After 30 days of high cholesterol diet, group IV rabbits received 1 ml of SBT seed oil daily for 30 days. Blood total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C) and triglyceride (TG) levels were measured before and after the administration of SBT seed oil. The vasorelaxant activity of the seed oil was studied in vitro using aortic ring model technique and changes in isometric force were recorded using a polygraphic recording system. Accumulation of cholesterol in the aorta was studied using Sudan-IV staining technique. SBT seed oil feeding to normal rabbits for 18 days caused a significant decline in plasma cholesterol, LDL-C, atherogenic index (AI) and LDL/HDL ratio. The HDL-C levels, HDL-C/TC ratio (HTR) and vasorelaxant activity of the aorta were significantly increased. In cholesterol-fed animals the TC, TG, LDL-C and AI were significantly increased and showed a decline following seed oil administration. The increase in HDL-C was more marked in seed oil treated hypercholesterolemic animals. The acetylcholine-induced vasorelaxant activity was significantly decreased in cholesterol-fed animals and could be restored to that of normal values by seed oil administration. These observations suggest that supercritical CO(2) extracted SBT seed oil has significant anti-atherogenic and cardioprotective activity.

Increasing apoA-I production as a target for CHD risk reduction

Dyslipidemia leading to coronary heart diseases (CHD) enables venues to prevent or treat CHD by other strategies than only lowering serum LDL cholesterol (LDL-C) concentrations, which is currently the most frequently targeted change. Unlike LDL-C, elevated high-density lipoprotein cholesterol (HDL-C) concentrations may protect against the development of CHD as demonstrated in numerous large-scale epidemiological studies. In this review we describe that besides elevating serum HDL-C concentrations by increasing alpha-HDL particles, approaches to elevate HDL-C concentrations by increasing pre-beta HDL particle concentrations seems more attractive. Besides infusion of apoA-I(Milano), using apoA-I mimetics, or delipidation of alpha-HDL particles, elevating de novo apoA-I production may be a suitable target to functionally increase pre-beta HDL particle concentrations. Therefore, a detailed description of the molecular pathways underlying apoA-I synthesis and secretion, completed with an overview of known effects of pharmacological and nutritional compounds on apoA-I synthesis will be presented. This knowledge may ultimately be applied in developing dietary intervention strategies to elevate apoA-I production and serum HDL-C concentrations and consequently lower CHD risk.

Gene transfer of wild-type apoA-I and apoA-I Milano reduce atherosclerosis to a similar extent

Background

The atheroprotective effects of systemic delivery of either apolipoprotein A-I (wtApoA-I) or the naturally occurring mutant ApoA-I Milano (ApoA-I_M) have been established in animal and human trials, but direct comparison studies evaluating the phenotype of ApoA-I or ApoAI-Milano knock-in mice or bone marrow transplantated animals with selectively ApoA-I or ApoAI-Milano transduced macrophages give conflicting results regarding the superior performance of either one. We therefore sought to compare the two forms of apoA-I using liver-directed somatic gene transfer in hypercholesterinemic mice – a model which is most adequately mimicking the clinical setting.

Methods and results

Vectors based on AAV serotype 8 (AAV2.8) encoding wtApoA-I, ApoA-I_M or green fluorescent protein (GFP) as control were constructed. LDL receptor deficient mice were fed a Western Diet. After 8 weeks the AAV vectors were injected, and 6 weeks later atherosclerotic lesion size was determined by aortic en face analysis. Expression of wtApoA-I reduced progression of atherosclerosis by 32% compared with control (p = 0.02) and of ApoA-I_M by 24% (p = 0.04). There was no significant difference between the two forms of ApoA-I in inhibiting atherosclerosis progression.

Conclusion

Liver-directed AAV2.8-mediated gene transfer of wtApoA-I and ApoA-I_M each significantly reduced atherosclerosis progression to a similar extent.

Astaxanthin ameliorates features of metabolic syndrome in SHR/NDmcr-cp

Glucose and lipid metabolic parameters play crucial roles in metabolic syndrome and its major feature of insulin resistance. This study was designed to investigate whether dietary astaxanthin oil (ASX-O) has potential effects on metabolic syndrome features in an SHR/NDmcr-cp (cp/cp) rat model. Oral administration of ASX (50 mg/kg/day) for 22 weeks induced a significant reduction in arterial blood pressure in SHRcp. It also significantly reduced the fasting blood glucose level, homeostasis index of insulin resistance (HOMA-IR), and improved insulin sensitivity. The results also showed an improved adiponectin level, a significant increase in high-density lipoprotein cholesterol, a significant decrease in plasma levels of triglycerides, and non-esterified fatty acids. Additionally, ASX showed significant effects on the white adipose tissue by decreasing the size of the fat cells. These results suggest that ASX ameliorates insulin resistance by mechanisms involving the increase of glucose uptake, and by modulating the level of circulating lipid metabolites and adiponectin.

High-Density Lipoprotein Cholesterol: A Potential Therapeutic Target for Prevention of Coronary Artery Disease

High-density lipoprotein cholesterol has an important role in the pathophysiology of coronary artery disease. High-density lipoprotein cholesterol is becoming an increasingly important prognostic and therapeutic target. The purpose of this paper is to review the biochemical pathways involved in reverse cholesterol transport and to discuss potential, clinically based high-density lipoprotein therapies that may contribute to reduction in risk of atherosclerosis.

Selective proteolysis of apolipoprotein B-100 by Arg-gingipain mediates atherosclerosis progression accelerated by bacterial exposure

Epidemiological studies suggest the association of periodontal infections with atherosclerosis, however, the mechanism underlying this association remains poorly understood. Porphyromonas gingivalis is the primary etiologic agent of adult periodontitis and produces a unique class of cysteine proteinases consisting of Arg-gingipain (Rgp) and Lys-gingipain (Kgp). To elucidate key mechanisms for progression of atherosclerosis by P. gingivalis infection, we tested the effects of the disruption of genes encoding Rgp and/or Kgp and inhibitors specific for the respective enzymes on atherosclerosis progression in apolipoprotein E-knockout mice. Repeated intravenous injection of wild-type P. gingivalis resulted in an increase in atherosclerotic lesions as well as an increase in the serum LDL cholesterol and a decrease of HDL cholesterol in these animals. LDL particles in P. gingivalis-injected animals were modified as a result of selective proteolysis of apoB-100 in LDL particles. This modification of LDL by P. gingivalis resulted in an increase in LDL uptake by macrophages and consequent foam cell formation in vitro. The atherosclerotic changes induced by P. gingivalis infection were attenuated by disruption of Rgp-encoding genes or by an Rgp-specific inhibitor. Our results indicate that degradation of apoB-100 by Rgp plays a crucial role in the promotion of atherosclerosis by P. gingivalis infection.

Persistent liver expression of murine apoA-l using vectors based on adeno-associated viral vectors serotypes 5 and 1

Plasma levels of high-density lipoprotein-cholesterol (HDL-C) and apolipoprotein A-l (apoA-l) are inversely related to risk for coronary heart disease. Overexpression of apoA-l inhibits atherosclerosis in animal models. A method of stably expressing apoA-l using somatic gene transfer would be of interest. Pseudotyped adeno-associated virus (AAV) vectors comprised of inverted terminal repeats from AAV serotype 2 have been used for liver-directed gene transfers. We hypothesized that liver-directed gene transfer of apoA-l using vectors based on AAV serotypes 1 and 5 would result in higher-level, prolonged expression of apoA-l and increased HDL-C. To test this hypothesis we injected apoA-l-/- mice via the tail vein with either AAV2, AAV1 or AAV5 vectors encoding the murine apoA-l cDNA driven by the liver-specific thyroxine binding globulin promoter. Plasma levels of murine apoA-l and HDL-C were highest in mice injected with the AAV1-based vector and lowest in mice injected with the AAV2-based vector. Expression of apoA-l was stable up to 1 year after vector injection. These results indicate that AAV5 and AAV1 are more effective vectors for achieving higher levels of stable transgene expression of apoA-l after liver-directed gene transfer than AAV2. Furthermore, AAV1-based vectors generate higher apoA-l levels than AAV5-based vectors. It is possible that the levels of expression achieved using these vectors will be therapeutic in preventing atherosclerosis.

PPAR delta: a dagger in the heart of the metabolic syndrome

Obesity is a growing threat to global health by virtue of its association with insulin resistance, glucose intolerance, hypertension, and dyslipidemia, collectively known as the metabolic syndrome or syndrome X. The nuclear receptors PPARalpha and PPARgamma are therapeutic targets for hypertriglyceridemia and insulin resistance, respectively, and drugs that modulate these receptors are currently in clinical use. More recent work on the less-described PPAR isotype PPARdelta has uncovered a dual benefit for both hypertriglyceridemia and insulin resistance, highlighting the broad potential of PPARdelta in the treatment of metabolic disease. PPARdelta enhances fatty acid catabolism and energy uncoupling in adipose tissue and muscle, and it suppresses macrophage-derived inflammation. Its combined activities in these and other tissues make it a multifaceted therapeutic target for the metabolic syndrome with the potential to control weight gain, enhance physical endurance, improve insulin sensitivity, and ameliorate atherosclerosis.

Gene therapy for lipoprotein disorders

Existing approaches to the treatment of refractory hypercholesterolaemia, severe hypertriglyceridaemia, low levels of high-density lipoprotein cholesterol and certain inherited disorders of intracellular lipid metabolism are ineffective in a substantial number of patients. Somatic gene therapy is considered to be a potential approach to the therapy of several of these lipid disorders. In many cases preclinical proof-of-principle studies have already been performed, and in one (homozygous familial hypercholesterolaemia) a clinical trial has been conducted. Other clinical gene therapy trials for dyslipidaemia are likely to be initiated within the next several years.

Persistence of high density lipoprotein particles in obese mice lacking apolipoprotein A-I

Obese mice without leptin (ob/ob) or the leptin receptor (db/db) have increased plasma HDL levels and accumulate a unique lipoprotein referred to as LDL/HDL1. To determine the role of apolipoprotein A-I (apoA-I) in the formation and accumulation of LDL/HDL1, both ob/ob and db/db mice were crossed onto an apoA-I-deficient (apoA-I(-/-)) background. Even though the obese apoA-I(-/-) mice had an expected dramatic decrease in HDL levels, the LDL/HDL1 particle persisted. The cholesterol in this lipoprotein range was associated with both alpha- and beta-migrating particles, confirming the presence of small LDLs and large HDLs. Moreover, in the obese apoA-I(-/-) mice, LDL particles were smaller and HDLs were more negatively charged and enriched in apoE compared with controls. This LDL/HDL1 particle was rapidly remodeled to the size of normal HDL after injection into C57BL/6 mice, but it was not catabolized in obese apoA-I(-/-) mice even though plasma hepatic lipase (HL) activity was increased significantly. The finding of decreased hepatic scavenger receptor class B type I (SR-BI) protein levels may explain the persistence of LDL/HDL1 in obese apoA-I(-/-) mice. Our studies suggest that the maturation and removal of large HDLs depends on the integrity of a functional axis of apoA-I, HL, and SR-BI. Moreover, the presence of large HDLs without apoA-I provides evidence for an apoA-I-independent pathway of cholesterol efflux, possibly sustained by apoE.

HDL as a target in the treatment of atherosclerotic cardiovascular disease

Lipid abnormalities are among the key risk factors for cardiovascular disease. Indeed, lipid-modifying drugs - in particular, the statins, which primarily lower plasma levels of low-density lipoprotein (LDL) cholesterol - considerably reduce the risk of cardiovascular events, leading to their widespread use. Nevertheless, it seems that there might be limits to the degree of benefit that can be achieved by lowering LDL-cholesterol levels alone, which has led to increased interest in targeting other lipid-related risk factors for cardiovascular disease, such as low levels of high-density lipoprotein (HDL) cholesterol. In this article, we first consider the mechanisms that underlie the protective effect of HDL cholesterol, and then discuss several strategies that have recently emerged to increase levels of HDL cholesterol to treat cardiovascular disease, including nuclear receptor modulation, inhibition of cholesteryl ester transfer protein and infusion of apolipoprotein/phospholipid complexes.

Gene therapy of atherosclerosis

Atherosclerosis and related diseases are the leading cause of death in Western world. The disease process begins with the formation of fatty streaks already during the first decade of life but does not manifest clinically until several decades later. Gene therapy is a potential new way to target multiple factors playing a role in the development and progression of atherosclerosis. A great number of genes involved in the development of atherosclerosis have been identified and have been tested both in vitro and in vivo as potential new targets for therapy. Pre-clinical experiments have shown the feasibility and safety of several gene therapy applications for the treatment of atherosclerosis and clinical trials have also provided evidence for the applicability of gene therapy for the treatment of cardiovascular diseases. In this review we discuss vectors and potential gene therapy approaches for intervention and therapy of atherosclerosis.