Newly developed apolipoprotein A-I mimetic peptide promotes macrophage reverse cholesterol transport in vivo

A novel apoA-I mimetic peptide suppresses atherosclerosis by promoting physiological HDL function in apoE-/- mice

BACKGROUND AND PURPOSE

Apolipoprotein A-I (apoA-I) mimetic peptides (AAMPs) are short peptides that can mimic the physiological effects of apoA-I, including the suppression of atherosclerosis by reversely transporting peripheral cholesterol to the liver. As the hydrophobicity of apoA-I is considered important for its lipid transport, novel AAMPs were designed and synthesized in this study by gradually increasing the hydrophobicity of the parent peptide, and their anti-atherosclerotic effects were tested.

EXPERIMENTAL APPROACH

Seventeen new AAMPs (P1-P17) with incrementally increased hydrophobicity were designed and synthesized by replacing the amino acids 221-240 of apoA-I (VLESFKVSFLSALEEYTKKL). Their effects on cholesterol efflux were evaluated. Their cytotoxicity and haemolytic activity were also measured. The in vitro mechanism of the action of the new peptides was explored. Adult apolipoprotein E^-/- mice were used to evaluate the anti-atherosclerotic activity of the best candidate, and the mechanistic basis of its anti-atherosclerotic effects was explored.

KEY RESULTS

Seventeen new AAMPs (P1-P17) were synthesized, and their cholesterol efflux activity and cytotoxicity were closely related to their hydrophobicity. P12 (FLEKLKELLEHLKELLTKLL) was the best candidate and most strongly promoted cholesterol efflux among the non-toxic peptides (P1-P12). With its phospholipid affinity, P12 facilitated cholesterol transport through the ATP-binding cassette transporter A1. In vivo, P12 exhibited prominent anti-atherosclerotic activity via coupling with HDL.

CONCLUSION AND IMPLICATIONS

P12 featured adequate hydrophobicity, which ensured its efficient binding with cytomembrane phospholipids, cholesterol and HDL, and provided a basis for its ability to reversely transport cholesterol and treat atherosclerosis.

Anti-atherosclerotic effects of an improved apolipoprotein A-I mimetic peptide

BACKGROUND

Apolipoprotein (Apo)A-I is a major protein component of high-density lipoprotein (HDL) that causes cholesterol efflux from peripheral cells through ATP-binding cassette transporter A1 (ABCA1) and the generation of HDL. Furthermore, it has a possible protective function against atherosclerotic cardiovascular disease (ASCVD). We previously developed a novel ApoA-I mimetic peptide without phospholipids (Fukuoka University ApoA-I Mimetic Peptide, FAMP). According to our previous studies, FAMP had an anti-arteriosclerotic effect. Since the required dose and reaction time of conventional FAMP were relatively large and short, respectively, we newly developed an improved FAMP (i-FAMP).

METHODS AND RESULTS

We synthesized four candidate i-FAMPs, i-FAMP-D1, -D2, -D3 and -D4, and examined which i-FAMP has greater cholesterol efflux capacity than FAMP in A172 human glioblastoma cells transiently transfected with human ABCA1 cDNA. Only i-FAMP-D1 showed significantly greater cholesterol efflux capacity than conventional FAMP. i-FAMP-D1 formed stronger α-helical conformations than FAMP as assessed by circular dichroism spectra. Thus, we selected i-FAMP-D1 for further experiments. i-FAMP-D1 had a greater atheroprotective effect than FAMP in ApoE knockout mice. In addition, i-FAMP-D1 activated cholesterol efflux from macrophage to HDL more strongly than FAMP and increased cholesterol excretion from liver to feces.

CONCLUSION

These results suggest that i-FAMP-D1 has a stronger anti-atherosclerotic effect than conventional FAMP.

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.

Cholesterol transport system: An integrated cholesterol transport model involved in atherosclerosis

Atherosclerosis, the pathological basis of most cardiovascular disease (CVD), is closely associated with cholesterol accumulation in the arterial intima. Excessive cholesterol is removed by the reverse cholesterol transport (RCT) pathway, representing a major antiatherogenic mechanism. In addition to the RCT, other pathways are required for maintaining the whole-body cholesterol homeostasis. Thus, we propose a working model of integrated cholesterol transport, termed the cholesterol transport system (CTS), to describe body cholesterol metabolism. The novel model not only involves the classical view of RCT but also contains other steps, such as cholesterol absorption in the small intestine, low-density lipoprotein uptake by the liver, and transintestinal cholesterol excretion. Extensive studies have shown that dysfunctional CTS is one of the major causes for hypercholesterolemia and atherosclerosis. Currently, several drugs are available to improve the CTS efficiently. There are also several therapeutic approaches that have entered into clinical trials and shown considerable promise for decreasing the risk of CVD. In recent years, a variety of novel findings reveal the molecular mechanisms for the CTS and its role in the development of atherosclerosis, thereby providing novel insights into the understanding of whole-body cholesterol transport and metabolism. In this review, we summarize the latest advances in this area with an emphasis on the therapeutic potential of targeting the CTS in CVD patients.

Investigational therapies for hypercholesterolemia

INTRODUCTION

Cardiovascular morbidity and mortality are of increasing concern, not only to patients but also to the health care profession and service providers. The preventative benefit of treatment of dyslipidaemia is unquestioned but there is a large, so far unmet need to improve clinical outcome. There are exciting new discoveries of targets that may translate into improved clinical outcome. Areas covered: This review highlights some new pathways in cholesterol and triglyceride metabolism and examines new targets, new drugs and new molecules. The review includes the results of recent trials of relatively new drugs that have shown benefit in cardiovascular endpoint outcomes, drugs that have been licenced without endpoint trials yet available and new drugs that have not yet been licenced but have produced exciting results in animal studies and some in early phase 2 human studies. Expert opinion: The new areas that have been discovered as the cause of dyslipidaemia have opened up a host of new targets for new drugs including antisense RNA's, microRNA's and human monoclonal antibodies. The plethora of new targets and new drugs has made it an extraordinarily exciting time in the development of therapeutics to combat atherosclerosis.

Common links between metabolic syndrome and inflammatory bowel disease: Current overview and future perspectives

Metabolic syndrome (MS) features a constellation of central obesity, dyslipidemia, impaired glucose metabolism and often hypertension joined by insulin resistance and chronic inflammation. All these elements greatly raise patient's risk of cardiovascular disease and type 2 diabetes, resulting in an increased mortality. Metabolic syndrome affects approximately 20-25% of the world's adult population and thus it is essential to study its pathophysiology and seek new pharmacological targets. There is a thoroughly studied link between MS and inflammatory diseases of the gastrointestinal (GI) system, i.e. steatohepatitis. However, recent findings also indicate similarities in pathophysiological features between MS and inflammatory bowel disease (IBD), including adipose tissue dysregulation, inadequate immune response, and inflammation. In this review we aim to outline the pathophysiology of MS and emphasize the aspects revealed recently, such as mineralocorticoid activity, involvement of sex hormones and an accompanying increase in prolactin secretion. More importantly, we focus on the common links between MS and IBD. Finally, we describe new strategies and drug targets that may be utilized in MS therapy, namely adiponectin mimetics, GLP-1-based multi agonists, ABCA1 agonists and possible role of miRNA. We also discuss the possible utility of selected agents as adjuvants in IBD therapy.

High-Density Lipoprotein Mimetics: a Therapeutic Tool for Atherosclerotic Diseases

Clinical trials and epidemiological studies have revealed a negative correlation between serum high-density lipoprotein (HDL) cholesterol levels and the risk of cardiovascular events. Currently, statin treatment is the standard therapy for cardiovascular diseases, reducing plasma low-density lipoprotein (LDL) cholesterol levels. However, more than half of the patients have not been able to receive the beneficial effects of this treatment.The reverse cholesterol transport pathway has several potential anti-atherogenic properties. An important approach to HDL-targeted therapy is the optimization of HDL cholesterol levels and function in the blood to enhance the removal of circulating cholesterol and to prevent or mitigate inflammation that causes atherosclerosis. Cholesteryl ester transfer protein inhibitors increase HDL cholesterol levels in humans, but whether they reduce the risk of atherosclerotic diseases is unknown. HDL therapies using HDL mimetics, including reconstituted HDL, apolipoprotein (Apo) A-IMilano, ApoA-I mimetic peptides, or full-length ApoA-I, are highly effective in animal models. In particular, the Fukuoka University ApoA-I-mimetic peptide (FAMP) effectively removes cholesterol via the ABCA1 transporter and acts as an anti-atherosclerotic agent by enhancing the biological functions of HDL without elevating HDL cholesterol levels.Our literature review suggests that HDL mimetics have significant atheroprotective potential and are a therapeutic tool for atherosclerotic diseases.