Human apolipoprotein A-I and A-I mimetic peptides: potential for atherosclerosis reversal

Biomembrane-Derived Nanoparticles in Alzheimer's Disease Therapy: A Comprehensive Review of Synthetic Lipid Nanoparticles and Natural Cell-Derived Vesicles

Current therapies for Alzheimer's disease used in the clinic predominantly focus on reducing symptoms with limited capability to control disease progression; thus, novel drugs are urgently needed. While nanoparticles (liposomes, high-density lipoprotein-based nanoparticles) constructed with synthetic biomembranes have shown great potential in AD therapy due to their excellent biocompatibility, multifunctionality and ability to penetrate the BBB, nanoparticles derived from natural biomembranes (extracellular vesicles, cell membrane-based nanoparticles) display inherent biocompatibility, stability, homing ability and ability to penetrate the BBB, which may present a safer and more effective treatment for AD. In this paper, we reviewed the synthetic and natural biomembrane-derived nanoparticles that are used in AD therapy. The challenges associated with the clinical translation of biomembrane-derived nanoparticles and future perspectives are also discussed.

Post-Stroke Administration of L-4F Promotes Neurovascular and White Matter Remodeling in Type-2 Diabetic Stroke Mice

Patients with type 2 diabetes mellitus (T2DM) exhibit a distinct and high risk of ischemic stroke with worse post-stroke neurovascular and white matter (WM) prognosis than the non-diabetic population. In the central nervous system, the ATP-binding cassette transporter member A 1 (ABCA1), a reverse cholesterol transporter that efflux cellular cholesterol, plays an important role in high-density lipoprotein (HDL) biogenesis and in maintaining neurovascular stability and WM integrity. Our previous study shows that L-4F, an economical apolipoprotein A member I (ApoA-I) mimetic peptide, has neuroprotective effects via alleviating neurovascular and WM impairments in the brain of db/db-T2DM stroke mice. To further investigate whether L-4F has neurorestorative benefits in the ischemic brain after stroke in T2DM and elucidate the underlying molecular mechanisms, we subjected middle-aged, brain-ABCA1 deficient (ABCA1−B/−B), and ABCA1-floxed (ABCA1fl/fl) T2DM control mice to distal middle cerebral artery occlusion. L-4F (16 mg/kg, subcutaneous) treatment was initiated 24 h after stroke and administered once daily for 21 days. Treatment of T2DM-stroke with L-4F improved neurological functional outcome, and decreased hemorrhage, mortality, and BBB leakage identified by decreased albumin infiltration and increased tight-junction and astrocyte end-feet densities, increased cerebral arteriole diameter and smooth muscle cell number, and increased WM density and oligodendrogenesis in the ischemic brain in both ABCA1−B/−B and ABCA1fl/fl T2DM-stroke mice compared with vehicle-control mice, respectively (p < 0.05, n = 9 or 21/group). The L-4F treatment reduced macrophage infiltration and neuroinflammation identified by decreases in ED-1, monocyte chemoattractant protein-1 (MCP-1), and toll-like receptor 4 (TLR4) expression, and increases in anti-inflammatory factor Insulin-like growth factor 1 (IGF-1) and its receptor IGF-1 receptor β (IGF-1Rβ) in the ischemic brain (p < 0.05, n = 6/group). These results suggest that post-stroke administration of L-4F may provide a restorative strategy for T2DM-stroke by promoting neurovascular and WM remodeling. Reducing neuroinflammation in the injured brain may contribute at least partially to the restorative effects of L-4F independent of the ABCA1 signaling pathway.

Current Understanding of the Immunomodulatory Activities of High-Density Lipoproteins

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

The Apolipoprotein A-I Mimetic L-4F Attenuates Monocyte Activation and Adverse Cardiac Remodeling after Myocardial Infarction

Excessive inflammation after myocardial infarction (MI) can promote infarct expansion and adverse left ventricular (LV) remodeling. L-4F, a mimetic peptide of apolipoprotein A-I (apoA-I), exhibits anti-inflammatory and anti-atherogenic properties; however, whether L-4F imparts beneficial effects after myocardial infarction (MI) is unknown. Here we demonstrate that L-4F suppresses the expansion of blood, splenic, and myocardial pro-inflammatory monocytes and macrophages in a mouse model of reperfused MI. Changes in immune cell profiles were accompanied by alleviation of post-MI LV remodeling and dysfunction. In vitro, L-4F also inhibited pro-inflammatory and glycolytic gene expression in macrophages. In summary, L-4F treatment prevents prolonged and excessive inflammation after MI, in part through modulation of pro-inflammatory monocytes and macrophages, and improves post-MI LV remodeling. These data suggest that L-4F could be a used as a therapeutic adjunct in humans with MI to limit inflammation and alleviate the progression to heart failure.

Probing the Assembly of HDL Mimetic, Drug Carrying Nanoparticles Using Intrinsic Fluorescence

Reconstituted high-density lipoprotein (HDL) containing apolipoprotein A-I (Apo A-I) mimics the structure and function of endogenous (human plasma) HDL due to its function and potential therapeutic utility in atherosclerosis, cancer, neurodegenerative diseases, and inflammatory diseases. Recently, a new class of HDL mimetics has emerged, involving peptides with amino acid sequences that simulate the the primary structure of the amphipathic alpha helices within the Apo A-I protein. The findings reported in this communication were obtained using a similar amphiphilic peptide (modified via conjugation of a myristic acid residue at the amino terminal aspartic acid) that self-assembles (by itself) into nanoparticles while retaining the key features of endogenous HDL. The studies presented here involve the macromolecular assembly of the myristic acid conjugated peptide (MYR-5A) into nanomicellar structures and its characterization via steady-state and time-resolved fluorescence spectroscopy. The structural differences between the free peptide (5A) and MYR-5A conjugate were also probed, using tryptophan fluorescence, Fӧrster resonance energy transfer (FRET), dynamic light scattering, and gel exclusion chromatography. To our knowledge, this is the first report of a lipoprotein assembly generated from a single ingredient and without a separate lipid component. The therapeutic utility of these nanoparticles (due to their capablity to incorporate a wide range of drugs into their core region for targeted delivery) was also investigated by probing the role of the scavenger receptor type B1 in this process. SIGNIFICANCE STATEMENT: Although lipoproteins have been considered as effective drug delivery agents, none of these nanoformulations has entered clinical trials to date. A major challenge to advancing lipoprotein-based formulations to the clinic has been the availability of a cost-effective protein or peptide constituent, needed for the assembly of the drug/lipoprotein nanocomplexes. This report of a robust, spontaneously assembling drug transport system from a single component could provide the template for a superior, targeted drug delivery strategy for therapeutics of cancer and other diseases (Counsell and Pohland, 1982).

Association between Serum Lipid Profiles and Early Neurological Deterioration in Acute Ischemic Stroke

BACKGROUND

Dyslipidemia is associated with chronic cardiovascular disease. However, the effect of dyslipidemia on acute ischemic stroke is unclear. We hypothesized that dyslipidemia could contribute to early neurological deterioration (END) after ischemic stroke.

METHODS

A total of 410 acute ischemic stroke patients who were admitted to our stroke center within 24 hours after ictus were consecutively included in this study. END was defined as any new neurological symptoms/signs or any neurological worsening occurring during the admission and/or within 3 weeks after the index stroke. Multivariable logistic regression was used to examine the independent association between lipid indices and END.

RESULTS

Mean age was 68.2 ± 13.3 years, 241 (58.8%) were male, and 78 (19.0%) experienced END. Almost END occurred within 3 days after admission (n = 70, 89.7%), and the majority of END was stroke progression (n = 68, 87.1%). In univariate analysis, high-density lipoprotein (HDL)-cholesterol levels (per 1 mmol/L; odds ratio [OR] .37; 95% CI .17-.80; P = .012) and apolipoprotein B (apoB)/apoA-I ratio (per 1 increase; OR 3.71; 95% CI 1.48-9.29; P = .005) were associated with END. In the multivariable analysis, adjusted ORs of END for the highest quartile of HDL-cholesterol and apoB/apoA-I ratio were .42 (95% CI .19-.94; P = .034) and 2.37 (95% CI 1.02-5.53; P = .045), respectively. The ratio of apoB/apoA-I was associated with END in large artery atherosclerosis stroke but not in other stroke subtypes.

CONCLUSIONS

Independent association of low HDL-cholesterol and high apoB/apoA-I ratio with END warrants further research to investigate if correction of the lipid profile during the acute period of ischemic stroke could reduce the risk of END.

High-Density Lipoproteins: Nature's Multifunctional Nanoparticles

High-density lipoproteins (HDL) are endogenous nanoparticles involved in the transport and metabolism of cholesterol, phospholipids, and triglycerides. HDL is well-known as the "good" cholesterol because it not only removes excess cholesterol from atherosclerotic plaques but also has anti-inflammatory and antioxidative properties, which protect the cardiovascular system. Circulating HDL also transports endogenous proteins, vitamins, hormones, and microRNA to various organs. Compared with other synthetic nanocarriers, such as liposomes, micelles, and inorganic and polymeric nanoparticles, HDL has unique features that allow them to deliver cargo to specific targets more efficiently. These attributes include their ultrasmall size (8-12 nm in diameter), high tolerability in humans (up to 8 g of protein per infusion), long circulating half-life (12-24 h), and intrinsic targeting properties to different recipient cells. Various recombinant ApoA proteins and ApoA mimetic peptides have been recently developed for the preparation of reconstituted HDL that exhibits properties similar to those of endogenous HDL and has a potential for industrial scale-up. In this review, we will summarize (a) clinical pharmacokinetics and safety of reconstituted HDL products, (b) comparison of HDL with inorganic and other organic nanoparticles,

A Novel Anti-Inflammatory Effect for High Density Lipoprotein

High density lipoprotein has anti-inflammatory effects in addition to mediating reverse cholesterol transport. While many of the chronic anti-inflammatory effects of high density lipoprotein (HDL) are attributed to changes in cell adhesion molecules, little is known about acute signal transduction events elicited by HDL in endothelial cells. We now show that high density lipoprotein decreases endothelial cell exocytosis, the first step in leukocyte trafficking. ApoA-I, a major apolipoprotein of HDL, mediates inhibition of endothelial cell exocytosis by interacting with endothelial scavenger receptor-BI which triggers an intracellular protective signaling cascade involving protein kinase C (PKC). Other apolipoproteins within the HDL particle have only modest effects upon endothelial exocytosis. Using a human primary culture of endothelial cells and murine apo-AI knockout mice, we show that apo-AI prevents endothelial cell exocytosis which limits leukocyte recruitment. These data suggest that high density lipoprotein may inhibit diseases associated with vascular inflammation in part by blocking endothelial exocytosis.

Bioenergetic programming of macrophages by the apolipoprotein A-I mimetic peptide 4F

The apoA-I (apolipoprotein A-I) mimetic peptide 4F favours the differentiation of human monocytes to an alternatively activated M2 phenotype. The goal of the present study was to test whether the 4F-mediated differentiation of MDMs (monocyte-derived macrophages) requires the induction of an oxidative metabolic programme. 4F treatment induced several genes in MDMs that play an important role in lipid metabolism, including PPARγ (peroxisome-proliferator-activated receptor γ) and CD36. Addition of 4F was associated with a significant increase in FA (fatty acid) uptake and oxidation compared with vehicle treatment. Mitochondrial respiration was assessed by measurement of the OCR (oxygen-consumption rate). 4F increased basal and ATP-linked OCR as well as maximal uncoupled mitochondrial respiration. These changes were associated with a significant increase in ΔΨm (mitochondrial membrane potential). The increase in metabolic activity in 4F-treated MDMs was attenuated by etomoxir, an inhibitor of mitochondrial FA uptake. Finally, addition of the PPARγ antagonist T0070907 to 4F-treated MDMs reduced the expression of CD163 and CD36, cell-surface markers for M2 macrophages, and reduced basal and ATP-linked OCR. These results support our hypothesis that the 4F-mediated differentiation of MDMs to an anti-inflammatory phenotype is due, in part, to an increase in FA uptake and mitochondrial oxidative metabolism.

Cholesterol: the good, the bad, and the ugly - therapeutic targets for the treatment of dyslipidemia

Maintaining cholesterol and triglyceride (TG) levels within healthy limits is critical for decreasing the risk of heart disease. Dyslipidemia refers to the abnormal levels of lipids in the blood, including low high-density lipoprotein cholesterol (HDL-C), also known as good cholesterol, high low-density lipoprotein cholesterol (LDL-C), also known as bad cholesterol, and/or high TG levels that contribute to the development and progression of atherosclerosis. In this article we reviewed some of the current therapeutic targets for the treatment of dyslipidemia, with a primary focus on endothelial lipase and lecithin cholesterol acyl transferase for raising HDL-C, and the proprotein convertase subtilisin-like kexin type 9 (PCSK9), microsomal triglyceride transfer protein, and the messenger RNA of apolipoprotein B for lowering LDL-C. In addition, we reviewed the role of apolipoprotein AI (apoAI) in raising HDL-C, where we discuss three apoAI-based drugs under development. These are its mutated dimer (apoAI-Milano), a complex with phospholipids, and a mimetic peptide. Atherosclerosis, mainly because of dyslipidemia, is a leading cause of cardiovascular disease. Regarding the title of this article, the 'good' refers to HDL-C, the 'bad' refers to LDL-C, and the 'ugly' refers to atherosclerosis.

Anti-inflammatory mechanisms of apolipoprotein A-I mimetic peptide in acute respiratory distress syndrome secondary to sepsis

Acute respiratory distress syndrome (ARDS) due to sepsis has a high mortality rate with limited treatment options. High density lipoprotein (HDL) exerts innate protective effects in systemic inflammation. However, its role in ARDS has not been well studied. Peptides such as L-4F mimic the secondary structural features and functions of apolipoprotein (apo)A-I, the major protein component of HDL. We set out to measure changes in HDL in sepsis-mediated ARDS patients, and to study the potential of L-4F to prevent sepsis-mediated ARDS in a rodent model of lipopolysaccharide (LPS)-mediated acute lung injury, and a combination of primary human leukocytes and human ARDS serum. We also analyzed serum from non-lung disease intubated patients (controls) and sepsis-mediated ARDS patients. Compared to controls, ARDS demonstrates increased serum endotoxin and IL-6 levels, and decreased HDL, apoA-I and activity of anti-oxidant HDL-associated paraoxanase-1. L-4F inhibits the activation of isolated human leukocytes and neutrophils by ARDS serum and LPS in vitro. Further, L-4F decreased endotoxin activity and preserved anti-oxidant properties of HDL both in vitro and in vivo. In a rat model of severe endotoxemia, L-4F significantly decreased mortality and reduces lung and liver injury, even when administered 1 hour post LPS. Our study suggests the protective role of the apoA-I mimetic peptide L-4F in ARDS and gram-negative endotoxemia and warrant further clinical evaluation. The main protective mechanisms of L-4F are due to direct inhibition of endotoxin activity and preservation of HDL anti-oxidant activity.

Differential mRNA expression of seven genes involved in cholesterol metabolism and transport in the liver of atherosclerosis-susceptible and -resistant Japanese quail strains

Background

Two atherosclerosis-susceptible and -resistant Japanese quail (Coturnix japonica) strains obtained by divergent selection are commonly used as models to study atherosclerosis, but no genetic characterization of their phenotypic differences has been reported so far. Our objective was to examine possible differences in the expression of genes involved in cholesterol metabolism and transport in the liver between these two strains and to evaluate the value of this model to analyze the gene system affecting cholesterol metabolism and transport.

Methods

A factorial study with both strains (atherosclerosis-susceptible versus atherosclerosis-resistant) and two diets (control versus cholesterol) was carried out. The mRNA concentrations of four genes involved in cholesterol biosynthesis (HMGCR, FDFT1, SQLE and DHCR7) and three genes in cholesterol transport (ABCG5, ABCG8 and APOA1) were assayed using real-time quantitative PCR. Plasma lipids were also assayed.

Results

Expression of ABCG5 (control diet) and ABCG8 (regardless of dietary treatment) and expression of HMGCR, FDFT1 and SQLE (regardless of dietary treatment) were significantly higher in the atherosclerosis-resistant than in the atherosclerosis-susceptible strain. Plasma triglyceride and LDL levels, and LDL/HDL ratio were significantly higher in the atherosclerosis-susceptible than in the atherosclerosis-resistant strain fed the cholesterol diet. In the atherosclerosis-susceptible strain, ABCG5 expression regressed significantly and positively on plasma LDL level, whereas DHCR7 and SQLE expression regressed significantly and negatively on plasma triglyceride level.

Conclusions

Our results provide support for the hypothesis that the atherosclerosis-resistant strain metabolizes and excretes cholesterol faster than the atherosclerosis-susceptible strain. We have also demonstrated that these quail strains are a useful model to study cholesterol metabolism and transport in relation with atherosclerosis.

Preservation of biological function despite oxidative modification of the apolipoprotein A-I mimetic peptide 4F

Myeloperoxidase (MPO)-derived hypochlorous acid induces changes in HDL function via redox modifications at the level of apolipoprotein A-I (apoA-I). As 4F and apoA-I share structural and functional properties, we tested the hypothesis that 4F acts as a reactive substrate for hypochlorous acid (HOCl). 4F reduced the HOCl-mediated oxidation of the fluorescent substrate APF in a concentration-dependent manner (ED(50) ∼ 56 ± 3 μM). This reaction induced changes in the physical properties of 4F. Addition of HOCl to 4F at molar ratios ranging from 1:1 to 3:1 reduced 4F band intensity on SDS-PAGE gels and was accompanied by the formation of a higher molecular weight species. Chromatographic studies showed a reduction in 4F peak area with increasing HOCl and the formation of new products. Mass spectral analyses of collected fractions revealed oxidation of the sole tryptophan (Trp) residue in 4F. 4F was equally susceptible to oxidation in the lipid-free and lipid-bound states. To determine whether Trp oxidation influenced its apoA-I mimetic properties, we monitored effects of HOCl on 4F-mediated lipid binding and ABCA1-dependent cholesterol efflux. Neither property was altered by HOCl. These results suggest that 4F serves as a reactive substrate for HOCl, an antioxidant response that does not influence the lipid binding and cholesterol effluxing capacities of the peptide.

HDL Mimetic Peptide Administration Improves Left Ventricular Filling and Cardiac output in Lipopolysaccharide-Treated Rats

AIMS: Cardiac dysfunction is a complication of sepsis and contributes to morbidity and mortality. Since raising plasma apolipoprotein (apo) A-I and high density lipoprotein (HDL) concentration reduces sepsis complications, we tested the hypothesis that the apoA-I mimetic peptide 4F confers similar protective effects in rats treated with lipopolysaccharide (LPS). METHODS AND RESULTS: Male Sprague-Dawley (SD) rats were randomized to receive saline vehicle (n=13), LPS (10 mg/kg: n=16) or LPS plus 4F (10 mg/kg each: n=13) by intraperitoneal injection. Plasma cytokine and chemokine levels were significantly elevated 24 hrs after LPS administration. Echocardiographic studies revealed changes in cardiac dimensions that resulted in a reduction in left ventricular end-diastolic volume (LVEDV), stroke volume (SV) and cardiac output (CO) 24 hrs after LPS administration. 4F treatment reduced plasma levels of inflammatory mediators and increased LV filling, resulting in improved cardiac performance. Chromatographic separation of lipoproteins from plasma of vehicle, LPS and LPS+4F rats revealed similar profiles. Further analyses showed that LPS treatment reduced the agarose electrophoretic mobility of isolated HDL fractions. HDL-associated proteins were characterized by SDSPAGE and mass spectrometry. ApoA-I and apoA-IV were reduced while apoE content was increased in LPStreated rats. 4F treatment in vivo attenuated changes in HDL-associated apolipoproteins and increased the electrophoretic mobility of the particle. CONCLUSIONS: The ability of 4F to reduce inflammation and improve cardiac performance in LPS-treated rats may be due to its capacity to neutralize endotoxin and prevent adverse changes in HDL composition and function.

Can novel Apo A-I polymorphisms be responsible for low HDL in South Asian immigrants?

Coronary artery disease (CAD) is the leading cause of death in the world. Even though its rates have decreased worldwide over the past 30 years, event rates are still high in South Asians. South Asians are known to have low high-density lipoprotein (HDL) levels. The objective of this study was to identify Apolipoprotein A-I (Apo A-I) polymorphisms, the main protein component of HDL and explore its association with low HDL levels in South Asians. A pilot study on 30 South Asians was conducted and 12-h fasting samples for C-reactive protein, total cholesterol, HDL, low-density lipoprotein (LDL), triglycerides, Lipoprotein (a), Insulin, glucose levels, DNA extraction, and sequencing of Apo A-I gene were done. DNA sequencing revealed six novel Apo A-I single nucleotide polymorphisms (SNPs) in South Asians, one of which (rs 35293760, C938T) was significantly associated with low (<40 mg/dl) HDL levels (P = 0.004). The association was also seen with total cholesterol (P = 0.026) and LDL levels (P = 0.032). This pilot work has highlighted some of the gene-environment associations that could be responsible for low HDL and may be excess CAD in South Asians. Further larger studies are required to explore and uncover these associations that could be responsible for excess CAD risk in South Asians.

Synthesis and evaluation of a tri-tyrosine decorated dextran MR contrast agent for vulnerable plaque detection

This communication reports the synthesis, characterization and in vivo evaluation in mice of a new tri-tyrosine conjugated MR contrast agent, which may help to identify vulnerable plaques in atherosclerosis by targeting the lipid core.

The apolipoprotein A-I mimetic peptide 4F prevents defects in vascular function in endotoxemic rats

High density lipoprotein (HDL) and apolipoprotein A-I (apoA-I) reduce inflammatory responses to lipopolysaccharide (LPS). We tested the hypothesis that the apoA-I mimetic peptide 4F prevents LPS-induced defects in blood pressure and vascular reactivity. Systolic blood pressure (SBP) was measured in rats at baseline and 6 h after injection of LPS (10 mg/kg) or saline vehicle. Subgroups of LPS-treated rats also received 4F (10 mg/kg) or scrambled 4F (Sc-4F). LPS administration reduced SBP by 35% compared with baseline. 4F attenuated the reduction in SBP in LPS-treated rats (17% reduction), while Sc-4F was without effect. Ex vivo studies showed a reduced contractile response to phenylephrine (PE) in aortae of LPS-treated rats (ED(50) = 459 +/- 83 nM) compared with controls (ED(50) = 57 +/- 6 nM). This was associated with nitric oxide synthase 2 (NOS2) upregulation. 4F administration improved vascular contractility (ED(50) = 60 +/- 9 nM), reduced aortic NOS2 protein, normalized plasma levels of NO metabolites, and reduced mortality in LPS-treated rats. These changes were associated with a reduction in plasma endotoxin activity. In vivo administration of (14)C-4F and Bodipy-LPS resulted in their colocalization and retention in the HDL fraction. It is proposed that 4F promotes the localization of LPS to the HDL fraction, resulting in endotoxin neutralization. 4F may thus prevent LPS-induced hemodynamic changes associated with NOS2 induction.

Proteomics-derived cerebrospinal fluid markers of autopsy-confirmed Alzheimer's disease

The diagnostic performance of several candidate cerebrospinal fluid (CSF) protein biomarkers in neuropathologically confirmed Alzheimer's disease (AD), non-demented (ND) elderly controls and non-AD dementias (NADD) was assessed. Candidate markers were selected on the basis of initial two-dimensional gel electrophoresis studies or by literature review. Markers selected by the former method included apolipoprotein A-1 (ApoA1), haemopexin (HPX), transthyretin (TTR) and pigment epithelium-derived factor (PEDF), while markers identified from the literature included Abeta1-40, Abeta1-42, total tau, phosphorylated tau, alpha-1 acid glycoprotein (A1GP), haptoglobin, zinc alpha-2 glycoprotein (Z2GP) and apolipoprotein E (ApoE). Ventricular CSF concentrations of the markers were measured by enzyme-linked immunosorbent assay (ELISA). The concentrations of Abeta1-42, ApoA1, A1GP, ApoE, HPX and Z2GP differed significantly among AD, ND and NADD subjects. Logistic regression analysis for the diagnostic discrimination of AD from ND found that Abeta1-42, ApoA1 and HPX each had significant and independent associations with diagnosis. The CSF concentrations of these three markers distinguished AD from ND subjects with 84% sensitivity and 72% specificity, with 78% of subjects correctly classified. By comparison, using Abeta1-42 alone gave 79% sensitivity and 61% specificity, with 68% of subjects correctly classified. For the diagnostic discrimination of AD from NADD, only the concentration of Abeta1-42 was significantly related to diagnosis, with a sensitivity of 58%, specificity of 86% and 86% correctly classified. The results indicate that for the discrimination of AD from ND control subjects, measurement of a set of markers including Abeta1-42, ApoA1 and HPX improved diagnostic performance over that obtained by measurement of Abeta1-42 alone. For the discrimination of AD from NADD subjects, measurement of Abeta1-42 alone was superior.

The contribution of high density lipoprotein apolipoproteins and derivatives to serum paraoxonase-1 activity and function

High density lipoproteins (HDL) not only provide a serum transport vector for paraoxonase-1 (PON1) but also contribute to enzyme activity, stability and, consequently, function. The contribution of the apolipoprotein (apo) components of HDL to overall PON1 activity and function is not clearly established. ApoAI appears of major importance in defining serum PON1 activity and stability, but in the context of an interaction with the phospholipid fraction of HDL. This may involve a role in establishing the architecture of the HDL particle that optimally integrates the PON1 peptide. As the second, major structural peptide of HDL, apoAII may accomplish a similar role. These apolipoproteins, together with others associated with HDL, may also exert a more indirect influence on PON1 function by sequestering oxidised lipids that could compromise enzyme activity. The latter has been exploited therapeutically to give rise to apolipoprotein mimetic peptides that may be useful in limiting oxidative stress within the lipoprotein system, thus permitting PON1 activity to be maximally expressed.

Novel potent apoA-I peptide mimetics that stimulate cholesterol efflux and pre-beta particle formation in vitro

Reverse cholesterol transport (RCT) is believed to be the primary mechanism by which HDL and its major protein apoA-I protect against atherosclerosis. Starting from the inactive 22-amino acid peptide representing the consensus sequence of the class A amphipathic helical repeats of apoA-I, we designed novel peptides able to mobilize cholesterol from macrophages in vitro, and to stimulate the formation of 'nascent HDL' particles, with potency comparable to the entire apoA-I protein.

A reconstituted HDL containing V156K or R173C apoA-I exhibited anti-inflammatory activity in apo-E deficient mice and showed resistance to myeloperoxidase-mediated oxidation

It has been hypothesized that blood infusion of reconstituted HDL (rHDL) is a possible therapeutic strategy for the treatment of coronary artery disese. To compare short-term anti-inflammatory activity of wildtype (WT) apoA-I and point mutants, each rHDL containing WT, V156K, or R173C was infused into apo-E deficient atherosclerotic mice. Each rHDL was injected via the tail vein at a dosage of 120 mg/kg of body weight in 0.4 ml of tris-buffered saline (TBS), and blood was then collected at 24 and 48 h post-injection. Although regression activity was observed in each of the rHDL infused groups, a 30% reduction in the lipid-stained area of the aortic sinus was observed in the V156K and R173C-rHDL groups when compared to that of the WT-rHDL group, and this reduction was well correlated with an approximately 60% reduction in the accumulation of macrophages in the lesion area. Additionally, the groups that received the V156K and R173C-rHDL treatments showed smaller increases in the GOT, GPT, interleukin-6, myeloperoxidase (MPO) and lipid hydroperoxide (LPO) serum levels than those that received the WT-rHDL treatment. In addition, the strongest serum paraoxonase and ferric reducing ability was observed in the V156K and R173C-rHDL groups. In vitro nitration and chlorination of apoA-I by MPO treatment revealed that V156K-rHDL and R173C-rHDL were less susceptible to chlorination. Furthermore, rHDL treatment inhibited cellular uptake of oxidized LDL by macrophage cells and the production of proatherogenic species in culture media. In conclusion, blood infusions of the rHDLs exerted in vivo regression activity with anti-inflammatory and antioxidant activity in apo-E deficient mice and THP-1 cells, especially in those that were treated with V156K and R173C apoA-I.

Anti-inflammatory peptides grab on to the whiskers of atherogenic oxidized lipids

The peptide 4F is known to have potent anti-atherogenic activity. 4F is an 18 residue peptide that has a sequence capable of forming a class A amphipathic helix. Several other class A amphipathic helical, 18 residue peptides with the same polar face but with increasing Phe residues on the nonpolar face have been synthesized with varying degrees of biological activity. In this work we compared the properties of the original 2F peptide, modeled on the consensus sequence of the amphipathic helical segments of the apolipoprotein A-I with the peptide 4F that has two Leu residues replaced with Phe. We demonstrate that the more biologically active 4F peptide has the greatest affinity for binding to several molecular species of oxidized lipids. Lipoprotein particles can be formed by solubilizing 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) with peptides. These solubilized lipoprotein particles extract oxidized lipid from liposomes of POPC containing 5 mol% of oxidized lipid. The peptides with the strongest anti-atherogenic activity interact most strongly with the oxidized lipid. The results show that there is a correlation between the biological potency of these peptides and their ability to interact with certain specific cytotoxic lipids, suggesting that this interaction may contribute favourably to their biological properties.

Hemoglobin and its scavenger protein haptoglobin associate with apoA-1-containing particles and influence the inflammatory properties and function of high density lipoprotein

Hemoglobin (Hb) uniquely associates with proinflammatory HDL in atherogenic mice and coronary heart disease (CHD) patients. In this paper, we report that Hb and its scavenger proteins, haptoglobin (Hp) and hemopexin (Hx) are significantly increased in apoA-1-containing particles of HDL both in mouse models of hyperlipidemia and in CHD patients, when compared with wild type mice and healthy donors, respectively. We further demonstrate that the association of Hb, Hp, and Hx proteins with HDL positively correlates with inflammatory properties of HDL and systemic inflammation in CHD patients. Interestingly, HDL from Hp(-/-) mice under atherogenic conditions does not accumulate Hb and is anti-inflammatory, suggesting that (i) Hp is required for the association of Hb with HDL and (ii) Hb x Hp complexes regulate the inflammatory properties of HDL. Moreover, treatment of apoE(-/-) mice with an apoA-1 mimetic peptide resulted in significant dissociation of Hb x Hp complexes from HDL and improvement of HDL inflammatory properties. Our data strongly suggest that HDL can become proinflammatory via the Hb x Hp pathway in mice and humans, and dissociation of Hb x Hp x Hx complexes from apoA-1-containing particles of HDL may be a novel target for the treatment of CHD.

The cell cholesterol exporter ABCA1 as a protector from cardiovascular disease and diabetes

ATP-binding cassette transporter A1 (ABCA1) is an integral cell membrane protein that exports cholesterol from cells and suppresses macrophage inflammation. ABCA1 exports cholesterol by a multistep pathway that involves forming cell-surface lipid domains, solubilizing these lipids by apolipoproteins, binding of apolipoproteins to ABCA1, and activating signaling processes. Thus, ABCA1 behaves both as a lipid exporter and a signaling receptor. ABCA1 transcription is highly induced by sterols, and its expression and activity are regulated post-transcriptionally by diverse processes. ABCA1 mutations can reduce plasma HDL levels, accelerate cardiovascular disease, and increase the risk for type 2 diabetes. Genetic manipulations of ABCA1 expression in mice also affect plasma HDL levels, inflammation, atherogenesis, and pancreatic beta cell function. Metabolites elevated in individuals with the metabolic syndrome and diabetes destabilize ABCA1 protein and decrease cholesterol export from macrophages, raising the possibility that an impaired ABCA1 pathway contributes to the enhanced atherogenesis associated with common inflammatory and metabolic disorders. The ABCA1 pathway has therefore become a promising new therapeutic target for treating cardiovascular disease and diabetes.

Is HDL function as important as HDL quantity in the coronary artery disease risk assessment?

Over the past several decades, it has been clearly established that higher plasma concentrations of high-density lipoprotein (HDL) are related to lower risk of coronary artery disease (CAD). According to the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) guidelines, the HDL level of <40 mg/dL is considered low and is one of the CAD risk predictors. However, in the last decade, several studies have indicated the importance of the quality of HDL as another potential measure for CAD risk assessment. The loss of normal biological function of HDL particles as a result of multifactorial actions of chronic inflammation and acute phase responses has suggested a new potential pathway in the pathophysiology of atherosclerosis. The concept of "dysfunctional HDL" or "proinflammatory HDL," which exhibits chameleon-like properties of converting a positive force protecting arteries to a negative one, enhancing atherogenesis is now under active investigation. Measurements of this dysfunctional quality of HDL in cell-based or cell-free assays by analyzing anti-inflammatory functions may link these changes to in vivo assessments of vascular disease. This review provides details on functional and dysfunctional HDL and summarizes recent studies into dysfunctional HDL and its potential links to CAD.

Coronary artery diseases in South Asian immigrants: an update on high density lipoprotein role in disease prevention

Over the past several years, the overall prevalence and incidence of cardiovascular diseases (CVD) including coronary artery diseases (CAD) have declined in the United States (US) and in many developed countries. However, among South Asian in general and South Asian immigrants (SAIs) in particular, a disturbing trend toward high rates of CAD has been noted. This trend is associated with a high prevalence of conventional risk factors and metabolic syndrome in this population, yet these conventional risk factors may not account for the greater CAD risk among SAIs. A search for additional markers is warranted, to enable early detection and prevention of CAD in this high risk group. High density lipoprotein (HDL) is one of the predictor of CAD and is considered to be cardio-protective. However, some of the recent studies have shown that HDL is not only ineffective as an antioxidant but, paradoxically, appears to be pro-oxidant, and has been found to be associated with CAD. Such HDL is called dysfunctional HDL. We present here an overview CAD and CAD risk factors in general and dyslipidemias in particular in SAIs. In addition, the evolving theories on dysfunctional HDL and its impact on CAD are also briefly presented.

High density lipoprotein cholesterol: an evolving target of therapy in the management of cardiovascular disease

Since the pioneering work of John Gofman in the 1950s, our understanding of high density lipoprotein cholesterol (HDL-C) and its relationship to coronary heart disease (CHD) has grown substantially. Numerous clinical trials since the Framingham Study in 1977 have demonstrated an inverse relationship between HDL-C and one’s risk of developing CHD. Over the past two decades, preclinical research has gained further insight into the nature of HDL-C metabolism, specifically regarding the ability of HDL-C to promote reverse cholesterol transport (RCT). Recent attempts to harness HDL’s ability to enhance RCT have revealed the complexity of HDL-C metabolism. This review provides a detailed update on HDL-C as an evolving therapeutic target in the management of cardiovascular disease.

Regression of aortic valve stenosis by ApoA-I mimetic peptide infusions in rabbits

BACKGROUND AND PURPOSE

Aortic valve stenosis (AVS) is the most common valvular heart disease, and standard curative therapy remains open heart surgical valve replacement. The aim of our experimental study was to determine if apolipoprotein A-I (ApoA-I) mimetic peptide infusions could induce regression of AVS.

EXPERIMENTAL APPROACH

Fifteen New Zealand White male rabbits received a cholesterol-enriched diet and vitamin D(2) until significant AVS was detected by echocardiography. The enriched diet was then stopped to mimic cholesterol-lowering therapy and animals were allocated randomly to receive saline (control group, n=8) or an ApoA-I mimetic peptide (treated group, n=7), three times per week for 2 weeks. Serial echocardiograms and post mortem valve histology were performed.

KEY RESULTS

Aortic valve area increased significantly by 25% in the treated group after 14 days of treatment (P=0.012). Likewise, aortic valve thickness decreased by 21% in the treated group, whereas it was unchanged in controls (P=0.0006). Histological analysis revealed that the extent of lesions at the base of valve leaflets and sinuses of Valsalva was smaller in the treated group compared with controls (P=0.032). The treatment also reduced calcification, as revealed by the loss of the positive relationship observed in the control group (r=0.87, P=0.004) between calcification area and aortic valve thickness.

CONCLUSIONS AND IMPLICATIONS

Infusions of ApoA-I mimetic peptide lead to regression of experimental AVS. These positive results justify the further testing of high-density lipoprotein (HDL)-based therapies in patients with valvular aortic stenosis. Regression of aortic stenosis, if achieved safely, could transform the clinical treatment of this disease.

Emerging HDL-based therapies for atherothrombotic vascular disease

Statin therapy has been a significant advance in the management of dyslipidemia and atherothrombotic cardiovascular disease with a resultant 30% to 40% reduction in cardiovascular events; however, a significant number of events continue to occur in statin-treated patients, including in patients treated with high-dose statins targeted to achieve mean low-density lipoprotein cholesterol levels in the range of 60 to 80 mg/dL. Therefore, development and testing of new therapies that exploit the vascular protective effects of high-density lipoprotein (HDL) constitutes a rational and complementary approach. A number of HDL-based therapies are in various stages of development and testing. It is hoped that one or more of these new HDL-based therapies, if proven effective and safe, will become a part of our armamentarium against vaso-occlusive cardiovascular disease. A paradigm could emerge in which patients recovering from acute coronary syndromes and at high risk of recurrent events could be treated with rapid-acting HDL-based therapy, such as infusions of recombinant HDL or even HDL delipidation, followed by more sustained long-term HDL-based therapies, such as oral agents and perhaps even HDL-based gene therapy.

Excess coronary artery disease risk in South Asian immigrants: can dysfunctional high-density lipoprotein explain increased risk?

BACKGROUND

Coronary artery disease (CAD) is the leading cause of mortality and morbidity in the United States (US), and South Asian immigrants (SAIs) have a higher risk of CAD compared to Caucasians. Traditional risk factors may not completely explain high risk, and some of the unknown risk factors need to be explored. This short review is mainly focused on the possible role of dysfunctional high-density lipoprotein (HDL) in causing CAD and presents an overview of available literature on dysfunctional HDL.

DISCUSSION

The conventional risk factors, insulin resistance parameters, and metabolic syndrome, although important in predicting CAD risk, may not sufficiently predict risk in SAIs. HDL has antioxidant, antiinflammatory, and antithrombotic properties that contribute to its function as an antiatherogenic agent. Recent Caucasian studies have shown HDL is not only ineffective as an antioxidant but, paradoxically, appears to be prooxidant, and has been found to be associated with CAD. Several causes have been hypothesized for HDL to become dysfunctional, including Apo lipoprotein A-I (Apo A-I) polymorphisms. New risk factors and markers like dysfunctional HDL and genetic polymorphisms may be associated with CAD.

CONCLUSIONS

More research is required in SAIs to explore associations with CAD and to enhance early detection and prevention of CAD in this high risk group.

HDL Cholesterol: Physiology, Pathophysiology, and Management

Numerous epidemiological studies have identified high-density lipoprotein cholesterol (HDL) to be an independent risk factor for coronary heart disease (CHD). HDL is an emerging therapeutic target that could rival the impact of 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitors (statins) on LDL and CHD risk reduction. HDL metabolism, HDL kinetics, the concentration of various HDL subclasses, and other genetic factors affecting HDL functionality may all contribute to the anti-atherogenic properties of HDL; thus, standard plasma measurement may not capture the full range of HDL effects. Algorithms have been suggested to treat low HDL levels in subgroups of patients; however, no formal HDL target goals or treatment guidelines have been implemented as there is a lack of strong clinical evidence to support effective pharmacologic therapy for primary risk reduction. Available therapies have a modest impact on serum HDL levels; however, emerging therapies could have a more significant influence.

MIF is a noncognate ligand of CXC chemokine receptors in inflammatory and atherogenic cell recruitment

The cytokine macrophage migration inhibitory factor (MIF) plays a critical role in inflammatory diseases and atherogenesis. We identify the chemokine receptors CXCR2 and CXCR4 as functional receptors for MIF. MIF triggered G(alphai)- and integrin-dependent arrest and chemotaxis of monocytes and T cells, rapid integrin activation and calcium influx through CXCR2 or CXCR4. MIF competed with cognate ligands for CXCR4 and CXCR2 binding, and directly bound to CXCR2. CXCR2 and CD74 formed a receptor complex, and monocyte arrest elicited by MIF in inflamed or atherosclerotic arteries involved both CXCR2 and CD74. In vivo, Mif deficiency impaired monocyte adhesion to the arterial wall in atherosclerosis-prone mice, and MIF-induced leukocyte recruitment required Il8rb (which encodes Cxcr2). Blockade of Mif but not of canonical ligands of Cxcr2 or Cxcr4 in mice with advanced atherosclerosis led to plaque regression and reduced monocyte and T-cell content in plaques. By activating both CXCR2 and CXCR4, MIF displays chemokine-like functions and acts as a major regulator of inflammatory cell recruitment and atherogenesis. Targeting MIF in individuals with manifest atherosclerosis can potentially be used to treat this condition.

A Caucasian male with very low blood cholesterol and low apoA-II without evidence of atherosclerosis

BACKGROUND

It is well known that a high level of apolipoprotein (apo) A-II can be associated with familial combined hyperlipidaemia, and that high apolipoprotein profiles can contribute to the development of atherosclerosis. The serum lipoprotein/apolipoprotein profile of a Caucasian patient who had unusually low serum total cholesterol (83 mg dL(-1)) and triglyceride (28 mg dL(-1)) levels despite a high body mass index (33.5 kg m(-2)), is the subject of this report.

MATERIALS AND METHODS

Each lipoprotein was isolated from serum by sequential ultracentrifugation, and serum and lipoprotein lipids and proteins were determined. The cholesteryl ester (CE) conversion ability of lecithin:cholesterol acyltransferase and CE transfer activity of CE transfer protein were assayed, and the composition of apolipoprotein and lipoprotein(-1) was analyzed by electrophoresis and Western blot analysis.

RESULTS

Electrophoresis and immunodetection analyses revealed a 60% decrease in the apoA-II band intensity compared to normal reference serum. The decreased apoA-II was associated with reduced very low density lipoprotein-cholesterol and protein content, as well as a greater high-density lipoprotein (HDL)(2) size with high cholesterol content. The CE conversion activity and CE transfer activity of HDL(3) were almost totally lacking in the hypolipidaemic serum, although the expression level of lecithin:cholesterol acyltransferase was normal. Electron microscopy revealed that the obese patient had larger HDL(2) and HDL(3) particle sizes than those of reference serum.

CONCLUSION

These results suggest that a decreased apoA-II protein in serum and increased HDL-cholesterol and particle size might protect against hyperlipidaemia and the atherosclerotic process, even in a patient with severe obesity.

High-density lipoproteins: a therapeutic target for atherosclerotic cardiovascular disease

Despite great progress being made during the last two decades in cardiovascular disease prevention, especially by lowering low-density lipoprotein-cholesterol with statins, cardiovascular events continue to occur. Plasma high-density lipoprotein (HDL) exerts multiple protective effects on the arterial wall, through promotion of reverse cholesterol transport, prevention of endothelial dysfunction and inhibition of lipid oxidation. Therapeutic interventions raising plasma HDL levels or directly mimicking its beneficial effects represent the next frontier in the prevention and treatment of cardiovascular disease.

Apolipoprotein A1 Is a Stronger Prognostic Marker Than Are HDL and LDL Cholesterol for Cardiovascular Disease and Mortality in Elderly Men

The aim of this study was to compare apolipoprotein A1 (ApoA1) and B (ApoB) with high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) as markers for cardiovascular mortality and morbidity in elderly men. We analyzed serum ApoA1, ApoB, total cholesterol, HDL-C, and LDL-C in a group of 77-year-old men (n = 785). The results were correlated with data from the Swedish cause of death registry. Receiver-operating characteristic curves showed that, of the studied serum markers, ApoA1 was the best predictor for ischemic heart disease mortality (area under the curve = 0.724, 95% confidence interval, 0.691-0.755). There were also significant correlations between the apolipoproteins and other known risk markers for cardiovascular disease such as triglycerides, high-sensitivity C-reactive protein (hsCRP), and cystatin C. Serum ApoA1 is a better risk marker than are ApoB, ApoB/ApoA1 ratio, HDL-C, and LDL-C for cardiovascular disease and mortality in elderly men.

Emerging strategies for increasing high-density lipoprotein

High-density lipoprotein cholesterol is a potent and independent epidemiologic risk factor and is a proved antiatherosclerotic agent in animal models of atherosclerosis, acting through the principal mechanisms of accelerating cholesterol efflux and inhibiting oxidation and inflammation. Lifestyle modification increases serum levels by 5% to 15%, whereas niacin, the drug most widely used to increase high-density lipoprotein cholesterol, increases it by 25% to 35% at the highest doses. This review examines the potent methods of increasing high-density lipoprotein and/or enhancing reverse cholesterol transport, including cholesterol ester transfer protein inhibitors, apolipoprotein A-I Milano, D4F, the dual peroxisome proliferator-activated receptor agonists, and rimonabant, that are now in clinical trials. In conclusion, these new agents, used alone or in combination with existing therapies, carry the potential to markedly reduce the incidence of new coronary disease and cardiac events in this decade.

Oral amphipathic peptides as therapeutic agents

Cholesterol can promote inflammation by its ability to stimulate the production of reactive oxygen species that result in the formation of pro-inflammatory oxidised phospholipids. High-density lipoproteins (HDLs) are part of the innate immune response and can be either pro- or anti-inflammatory independently of plasma HDL-cholesterol levels. During systemic inflammation as occurs with atherosclerosis, Apolipoprotein A-I can be altered, reducing its ability to promote reverse cholesterol transport and HDL can become pro-inflammatory. Amphipathic peptides with either a class A amphipathic helix (D-4F) or a class G* amphipathic helix (D-[113-122]apoJ), or even those that are too small to form a helix (KRES and FREL) have some similar characteristics. Their interaction with lipids leads to a reduction in lipoprotein-lipid hydroperoxides that releases HDL-associated antioxidant enzymes, such as paraoxonase, therefore providing antiatherosclerosis and anti-inflammatory activity. In addition, the peptide D-4F stimulates the formation and cycling of pre-beta HDL. These amphipathic peptides appear to have therapeutic potential as oral agents.

Lipoproteins in inflammation and sepsis. II. Clinical aspects

BACKGROUND

Systemic inflammation and sepsis are accompanied by severe metabolic alterations, including insulin resistance together with increased levels of triglycerides (TGs) and decreases in high- and low-density lipoproteins. Clinical studies have clearly established a link between lipid metabolism and systemic inflammation. Lipoproteins were shown to neutralize LPS and to exert direct anti-inflammatory actions. High- and low-density lipoproteins are thus thought to be important regulators of the host immune response during endotoxemia, which may also have the potential of improving the care of patients with Gram-negative sepsis.

DISCUSSION

Nutritional lipids supplied during critical illness have been shown to modulate the host response to inflammation. In particular, inclusion of omega-3 fatty acids seems to have beneficial effects on cellular immunity and helps to maintain the balance between pro- and anti-inflammatory cytokines thereby preventing hyperinflammatory complications. In addition to improvements in the profile of lipid mediators generated, omega-3 fatty acids act as activating ligands of peroxisome proliferator-activated receptors and directly inhibit nuclear factor kappaB mediated proinflammatory signaling. We present an overview on the alterations in the metabolism of serum lipoproteins during sepsis and present data from clinical studies and discuss the significance of nutritional lipids and their role in immunomodulation with special emphasis on omega-3 fatty acids.

Proinflammatory high-density lipoprotein as a biomarker for atherosclerosis in patients with systemic lupus erythematosus and rheumatoid arthritis

OBJECTIVE

Women with systemic lupus erythematosus (SLE) have a 7-50-fold increased risk of coronary artery disease (CAD). In the general population, oxidized low-density lipoprotein (ox-LDL) increases the risk for CAD. Normal high-density lipoproteins (HDLs) protect LDL from oxidation; proinflammatory HDLs do not. This study was undertaken to determine whether patients with SLE, who have chronic inflammation that causes oxidative damage, have more proinflammatory HDL and higher levels of ox-LDL, thus predisposing them to atherosclerosis.

METHODS

One hundred fifty-four women with SLE, 48 women with rheumatoid arthritis (RA), and 72 healthy controls were studied. The ability of the patients' HDL to prevent oxidation of normal LDL was measured. Values >1.0 (the value assigned for LDL oxidation in the absence of HDL) after the addition of HDL indicated proinflammatory HDL. Plasma ox-LDL levels were measured as the amount of oxidation produced by the patient's LDL after the removal of HDL.

RESULTS

SLE patients had more proinflammatory HDL (mean +/- SD score 1.02 +/- 0.57, versus 0.68 +/- 0.28 in controls [P < 0.0001] and 0.81 +/- 0.22 in RA patients [P = 0.001 versus SLE patients]). A higher proportion of SLE patients had proinflammatory HDL: 44.7% of SLE patients versus 4.1% of controls and 20.1% of RA patients had scores >1.0 (P < 0.006 between all groups). Levels of ox-LDL correlated with levels of proinflammatory HDL (r = 0.37, P < 0.001). SLE patients with CAD had significantly higher proinflammatory HDL scores than patients without CAD (P < 0.001).

CONCLUSION

HDLs are proinflammatory in a significant proportion of SLE patients and are associated with elevated levels of ox-LDL. Abnormal HDLs impair the ability to prevent LDL oxidation and may predispose to atherosclerosis.

Current understanding of the role of high-density lipoproteins in atherosclerosis and senescence

Numerous epidemiologic and interventional studies revealed that high-density lipoprotein (HDL) is an important risk factor for coronary heart disease. There are several well documented HDL functions that may account for the antiatherogenic effects of this lipoprotein. The best recognized of these is the capacity of HDL to transport cholesterol from the periphery to the liver, and thereby prevent cholesterol deposition in the arterial wall. Further properties of HDL that may also be antiatherogenic include its potent anti oxidative and anti-inflammatory action. In addition, HDL seems to be involved in processes related to senescence at both the cellular and whole-organism level. Both protein components of HDL (such as apolipoprotein A-I) and its lipid components (such as, lysosphingolipids) appear to mediate the antiatherogenic and anti-aging effects of HDL. The purpose of this review is to summarize the novel functions of HDL that may protect from atherosclerosis and senescence.

Comparative proteomics of cerebrospinal fluid in neuropathologically-confirmed Alzheimer's disease and non-demented elderly subjects

OBJECTIVES

Diagnostic tests able to reveal Alzheimer's disease (AD) in living patients before cognitive ability is destroyed are urgently needed. Such tests must distinguish AD from other dementia causes, as well as differentiate subtle changes associated with normal aging from true pathology emergence. A single biomarker offering such diagnostic and prognostic capacities has eluded identification. Therefore, a valuable test for AD is likely to be based on a specific pattern of change in a set of proteins, rather than a single protein.

METHODS

We examined pooled cerebrospinal fluid (CSF) samples obtained from neuropathologically-confirmed AD (n=43) and non-demented control subjects (n=43) using 2-dimensional gel electrophoresis (2DE) proteomic methodology to detect differentially expressed proteins. Proteins exhibiting expression level differences between the pools were recovered and identified using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry.

RESULTS

Five differentially-expressed proteins with potential roles in amyloid-beta metabolism and vascular and brain physiology [apolipoprotein A-1 (Apo A-1), cathepsin D (CatD), hemopexin (HPX), transthyretin (TTR), and two pigment epithelium-derived factor (PEDF) isoforms] were identified. Apo A-1, CatD and TTR were significantly reduced in the AD pool sample, while HPX and the PEDF isoforms were increased in AD CSF.

DISCUSSION

These results suggest that multi-factor proteomic pattern analysis of the CSF may provide a means to diagnose and assess AD.

Preferable stimulation of PON1 arylesterase activity by phosphatidylcholines with unsaturated acyl chains or oxidized acyl chains at sn-2 position

To examine the effect of phospholipids on PON1 activities, purified PON1 was exposed to phospholipids prior to the determination of arylesterase and paraoxonase activities. Phosphatidylcholines with saturated acyl chains (C10-C16) showed a stimulation of both activities, chain length-dependent, with a greater stimulation of arylesterase activity, suggesting the implication of lipid bilayer in the stimulatory action. Such a preferable stimulation of arylesterase activity was more remarkable with phosphatidylcholines with polyunsaturated acyl chains or oxidized chains at sn-2 position, implying that the packing degree of acyl chain may be also important for the preferable stimulation of arylesterase activity. Separately, 1-palmitoyl-lysoPC also stimulated arylesterase activity preferably, indicating that the micellar formation of lipids around PON1 also contributes to the stimulatory action. Additionally, phosphatidylglycerols slightly enhanced arylesterase activity, but not paraoxonase activity. In contrast, phosphatidylserine and phosphatidic acid (> or =0.1 mM) inhibited both activities Further, such a preferable stimulation of arylesterase activity by phosphatidylcholines was also reproduced with VLDL-bound PON1, although to a less extent. These data indicate that phosphatidylcholines with polyunsaturated acyl chains or oxidized chain, or lysophosphatidylcholine cause a preferable stimulation of arylesterase activity, thereby contributing to the decrease in the ratio of paraoxonase activity to arylesterase activity.

ATP-binding cassette transporter A1: a cell cholesterol exporter that protects against cardiovascular disease

Blood high-density lipoprotein (HDL) levels are inversely related to risk for cardiovascular disease, implying that factors associated with HDL metabolism are atheroprotective. One of these factors is ATP-binding cassette transporter A1 (ABCA1), a cell membrane protein that mediates the transport of cholesterol, phospholipids, and other metabolites from cells to lipid-depleted HDL apolipoproteins. ABCA1 transcription is highly induced by sterols, a major substrate for cellular export, and its expression and activity are regulated posttranscriptionally by diverse processes. Liver ABCA1 initiates formation of HDL particles, and macrophage ABCA1 protects arteries from developing atherosclerotic lesions. ABCA1 mutations can cause a severe HDL deficiency syndrome characterized by cholesterol deposition in tissue macrophages and prevalent atherosclerosis. Genetic manipulations of ABCA1 expression in mice also affect plasma HDL levels and atherogenesis. Metabolites elevated in individuals with the metabolic syndrome and diabetes destabilize ABCA1 protein and decrease cholesterol export from macrophages. Moreover, oxidative modifications of HDL found in patients with cardiovascular disease reduce the ability of apolipoproteins to remove cellular cholesterol by the ABCA1 pathway. These observations raise the possibility that an impaired ABCA1 pathway contributes to the enhanced atherogenesis associated with common inflammatory and metabolic disorders. The ABCA1 pathway has therefore become an important new therapeutic target for treating cardiovascular disease.