Inhibition of VCAM-1 expression in endothelial cells by reconstituted high density lipoproteins

Apolipoprotein A1 and high-density lipoprotein limit low-density lipoprotein transcytosis by binding SR-B1

Atherosclerosis results from the deposition and oxidation of LDL and immune cell infiltration in the sub-arterial space leading to arterial occlusion. Studies have shown that transcytosis transports circulating LDL across endothelial cells lining blood vessels. LDL transcytosis is initiated by binding to either scavenger receptor B1 (SR-B1) or activin A receptor-like kinase 1 on the apical side of endothelial cells leading to its transit and release on the basolateral side. HDL is thought to partly protect individuals from atherosclerosis due to its ability to remove excess cholesterol and act as an antioxidant. Apolipoprotein A1 (APOA1), an HDL constituent, can bind to SR-B1, raising the possibility that APOA1/HDL can compete with LDL for SR-B1 binding, thereby limiting LDL deposition in the sub-arterial space. To examine this possibility, we used in vitro approaches to quantify the internalization and transcytosis of fluorescent LDL in coronary endothelial cells. Using microscale thermophoresis and affinity capture, we find that SR-B1 and APOA1 interact and that binding is enhanced when using the cardioprotective variant of APOA1 termed Milano (APOA1-Milano). In male mice, transiently increasing the levels of HDL reduced the acute deposition of fluorescently labeled LDL in the atheroprone inner curvature of the aorta. Reduced LDL deposition was also observed when increasing circulating wild-type APOA1 or the APOA1-Milano variant, with a more robust inhibition from the APOA1-Milano. The results suggest that HDL may limit SR-B1-mediated LDL transcytosis and deposition, adding to the mechanisms by which it can act as an atheroprotective particle.

High-density lipoprotein protects vascular endothelial cells from indoxyl sulfate insults through its antioxidant ability

Chronic kidney disease (CKD) patients have a high risk of cardiovascular disease. Indoxyl sulfate (IS) is a uremic toxin that has been shown to inhibit nitric oxide production and cause cell senescence by inducing oxidative stress. High-density lipoprotein (HDL) has a protective effect on the cardiovascular system; however, its impacts on IS-damaged endothelial cells are still unknown. This study aimed to explore the effects of exogenous supplement of HDL on vascular endothelial cells in a uremia-mimic environment. Tube formation, migration, adhesion, and senescence assays were used to evaluate the cell function of human aortic endothelial cells (HAECs). Reactive oxygen species generation was measured by using Amplex red assay. L-NAME and MCI186 were used as a nitric oxide synthase inhibitor and a free radical scavenger, respectively. HDL exerted anti-inflammatory and antioxidant effects via HIF-1α/HO-1 activation and IL-1β/TNF-α/IL-6 inhibition in IS-stimulated HAECs. HDL improved angiogenesis ability through upregulating Akt/eNOS/VEGF/SDF-1 in IS-stimulated HAECs. HDL decreased endothelial adhesiveness via downregulating VCAM-1 and ICAM-1 in IS-stimulated HAECs. Furthermore, HDL reduced cellular senescence via upregulating SIRT1 and downregulating p53 in IS-stimulated HAECs. Importantly, the above beneficial effects of HDL were mainly due to its antioxidant ability. In conclusion, HDL exerted a comprehensive protective effect on vascular endothelial cells against damage from IS through its antioxidant ability. The results of this study might provide a theoretical basis for potential HDL supplementation in CKD patients with endothelial damage.

Dynamic Resistance Exercise Alters Blood ApoA-I Levels, Inflammatory Markers, and Metabolic Syndrome Markers in Elderly Women

Combined endurance and dynamic-resistance exercise has important anti-inflammatory effects, altering vascular endothelial function, and helping to prevent and treat aging-related metabolic syndrome (MS). We studied changes in 40 elderly women aged ≥ 65 years (control group (no MS), n = 20, mean age: 68.23 ± 2.56 years; MS group, n = 19, mean age: 71.42 ± 5.87 years; one left). The exercise program comprised dynamic-resistance training using elastic bands, three times weekly, for six months. We analyzed body composition, blood pressure, physical fitness, and MS-related blood variables including ApoA-I, antioxidant factors, and inflammatory markers. After the program, the MS group showed significant reductions in waist-hip ratio, waist circumference, diastolic blood pressure, blood insulin, and HOMA-IR, and a significant increase in HSP70 (p < 0.05). Both groups showed significant increases in ApoA-I levels, ApoA-I/HDL-C ratio, SOD2, IL-4, and IL-5 levels (p < 0.05). Active-resistance training-induced changes in ApoA-I were significantly positively correlated with changes in HDL-C and HSP70, and significantly negatively correlated with changes in triglycerides, C-reactive protein, and TNF-α (p < 0.05). Active-resistance training qualitatively altered HDL, mostly by altering ApoA-I levels, relieving vascular inflammation, and improving antioxidant function. This provides evidence that dynamic-resistance exercise can improve physical fitness and MS risk factors in elderly women.

Low HDL Cholesterol Efflux Capacity Indicates a Fatal Course of COVID-19

Plasma membrane cholesterol is required for proper trafficking and localization of receptors that facilitate severe acute respiratory syndrome coronavirus 2 infection. High-density lipoproteins (HDL) mobilize plasma membrane cholesterol, and HDL-cholesterol levels are associated with the severity of COVID-19 disease and mortality. However, HDL-cholesterol levels poorly reflect the function of this complex family of particles, and a detailed assessment of COVID-19-associated changes in HDL functionality and its prognostic value is lacking. In the present study, we assessed HDL cholesterol efflux capacity, HDL anti-inflammatory and antioxidant properties, and changes in HDL composition and metabolism in COVID-19 (n = 48) and non-COVID pneumonia patients (n = 32). COVID-19 infection markedly reduced the activity of lecithin-cholesteryl-acyltransferase and functional parameters of HDL, such as the cholesterol efflux capacity, arylesterase activity of paraoxonase 1, and anti-oxidative capacity of apoB-depleted serum when compared to non-COVID pneumonia at baseline, paralleled by markedly reduced levels of HDL-cholesterol. Of particular interest, low HDL cholesterol efflux capacity was associated with increased mortality risk in COVID-19 patients, independent of HDL-C levels. Our results highlight profound effects of COVID-19 infection on HDL function, metabolism, and composition. Low HDL cholesterol efflux capacity indicates a fatal course of COVID-19, independent of HDL-cholesterol levels.

Dietary Strategies to Improve Cardiovascular Health: Focus on Increasing High-Density Lipoprotein Functionality

Cardiovascular disease is one of the leading causes of morbidity and mortality worldwide, with increasing incidence. A cornerstone of cardiovascular disease prevention is lifestyle modification through dietary changes to influence various risk factors such as obesity, hypertension and diabetes. The effects of diet on cardiovascular health are complex. Some dietary components and metabolites directly affect the composition and structure of high-density lipoproteins (HDL) and increase anti-inflammatory and vasoprotective properties. HDLs are composed of distinct subpopulations of particles of varying size and composition that have several dynamic and context-dependent functions. The identification of potential dietary components that improve HDL functionality is currently an important research goal. One of the best-studied diets for cardiovascular health is the Mediterranean diet, consisting of fish, olive oil, fruits, vegetables, whole grains, legumes/nuts, and moderate consumption of alcohol, most commonly red wine. The Mediterranean diet, especially when supplemented with extra virgin olive oil rich in phenolic compounds, has been shown to markedly improve metrics of HDL functionality and reduce the burden, or even prevent the development of cardiovascular disease. Particularly, the phenolic compounds of extra virgin olive oil seem to exert the significant positive effects on HDL function. Moreover, supplementation of anthocyanins as well as antioxidants such as lycopene or the omega-3 fatty acid eicosapentaenoic acid improve parameters of HDL function. In this review, we aim to highlight recent discoveries on beneficial dietary patterns as well as nutritional components and their effects on cardiovascular health, focusing on HDL function.

Fetal High-Density Lipoproteins: Current Knowledge on Particle Metabolism, Composition and Function in Health and Disease

Cholesterol and other lipids carried by lipoproteins play an indispensable role in fetal development. Recent evidence suggests that maternally derived high-density lipoprotein (HDL) differs from fetal HDL with respect to its proteome, size, and function. Compared to the HDL of adults, fetal HDL is the major carrier of cholesterol and has a unique composition that implies other physiological functions. Fetal HDL is enriched in apolipoprotein E, which binds with high affinity to the low-density lipoprotein receptor. Thus, it appears that a primary function of fetal HDL is the transport of cholesterol to tissues as is accomplished by low-density lipoproteins in adults. The fetal HDL-associated bioactive sphingolipid sphingosine-1-phosphate shows strong vasoprotective effects at the fetoplacental vasculature. Moreover, lipoprotein-associated phospholipase A2 carried by fetal-HDL exerts anti-oxidative and athero-protective functions on the fetoplacental endothelium. Notably, the mass and activity of HDL-associated paraoxonase 1 are about 5-fold lower in the fetus, accompanied by an attenuation of anti-oxidative activity of fetal HDL. Cholesteryl ester transfer protein activity is reduced in fetal circulation despite similar amounts of the enzyme in maternal and fetal serum. This review summarizes the current knowledge on fetal HDL as a potential vasoprotective lipoprotein during fetal development. We also provide an overview of whether and how the protective functionalities of HDL are impaired in pregnancy-related syndromes such as pre-eclampsia or gestational diabetes mellitus.

Effects of lipoproteins on endothelial cells and macrophages function and its possible implications on fetal adverse outcomes associated to maternal hypercholesterolemia during pregnancy

Hypercholesterolemia is one of the main risk factors associated with atherosclerosis and cardiovascular disease, the leading cause of death worldwide. During pregnancy, maternal hypercholesterolemia develops, and it can occur in a physiological (MPH) or supraphysiological (MSPH) manner, where MSPH is associated with endothelial dysfunction and early atherosclerotic lesions in the fetoplacental vasculature. In the pathogenesis of atherosclerosis, endothelial activation and endothelial dysfunction, characterized by an imbalance in the bioavailability of nitric oxide, contribute to the early stages of this disease. Macrophages conversion to foam cells, cholesterol efflux from these cells and its differentiation into a pro- or anti-inflammatory phenotype are also important processes that contribute to atherosclerosis. In adults it has been reported that native and modified HDL and LDL play an important role in endothelial and macrophage function. In this review it is proposed that fetal lipoproteins could be also relevant factors involved in the detrimental vascular effects described in MSPH. Changes in the composition and function of neonatal lipoproteins compared to adults has been reported and, although in MSPH pregnancies the fetal lipid profile does not differ from MPH, differences in the lipidomic profiles of umbilical venous blood have been reported, which could have implications in the vascular function. In this review we summarize the available information regarding the effects of lipoproteins on endothelial and macrophage function, emphasizing its possible implications on fetal adverse outcomes associated to maternal hypercholesterolemia during pregnancy.

Obesity-Related Changes in High-Density Lipoprotein Metabolism and Function

In obese individuals, atherogenic dyslipidemia is a very common and important factor in the increased risk of cardiovascular disease. Adiposity-associated dyslipidemia is characterized by low high-density lipoprotein cholesterol (HDL-C) levels and an increase in triglyceride-rich lipoproteins. Several factors and mechanisms are involved in lowering HDL-C levels in the obese state and HDL quantity and quality is closely related to adiponectin levels and the bioactive lipid sphingosine-1-phosphate. Recent studies have shown that obesity profoundly alters HDL metabolism, resulting in altered HDL subclass distribution, composition, and function. Importantly, weight loss through gastric bypass surgery and Mediterranean diet, especially when enriched with virgin olive oil, is associated with increased HDL-C levels and significantly improved metrics of HDL function. A thorough understanding of the underlying mechanisms is crucial for a better understanding of the impact of obesity on lipoprotein metabolism and for the development of appropriate therapeutic approaches. The objective of this review article was to summarize the newly identified changes in the metabolism, composition, and function of HDL in obesity and to discuss possible pathophysiological consequences.

High density lipoprotein cholesterol and apolipoprotein A-I are associated with greater cerebral perfusion in multiple sclerosis

BACKGROUND

The pathophysiological mechanisms underlying the associations of multiple sclerosis (MS) neurodegeneration serum cholesterol profiles is currently unknown.

OBJECTIVE

To determine associations between lipid profile measures and cerebral perfusion-based indices in MS patients.

METHODS

Seventy-seven MS patients underwent 3 T MRI. Cerebral blood volume (CBV), time-to-peak (TTP) and mean transit time (MTT) measures were computed from dynamic susceptibility contrast (DSC) perfusion-weighted imaging (PWI) for normal-appearing brain tissue (NABT), GM, cortex, deep gray matter (DGM) and thalamus. Total cholesterol, low and high-density lipoprotein cholesterol (LDL-C and HDL-C) and the apolipoproteins (Apo), ApoA-I, ApoA-II, ApoB, ApoC-II and ApoE levels were measured in plasma. Age and body mass index (BMI)-adjusted correlations were used to assess the associations between PWI and lipid profile measures.

RESULTS

Higher HDL-C levels were associated with shorter MTT, which are indicative of greater perfusion, in NABT (p = 0.012), NAWM (p = 0.021), GM (p = 0.009), cortex (p = 0.014), DGM p = 0.015; and thalamus p = 0.015). The HDL-C-associated apolipoproteins, ApoA-I and ApoA-II, were associated with shorter MTT of the same brain regions (all p < 0.028). HDL-C and ApoA-I levels were also associated with shorter TTP, indicative of faster cerebral blood delivery. ApoC-II was associated with lower nCBV of the GM and cortex (p = 0.035 and p = 0.014, respectively).

CONCLUSION

The HDL pathway is associated with better global brain perfusion and faster cerebral blood delivery as measured by shorter MTT and TTP, respectively. ApoC-II may be associated with lower cortical and DGM perfusion.

Sex-related associations of high-density lipoprotein cholesterol with aortic stiffness and endothelial glycocalyx integrity in treated hypertensive patients

Smoking, a well-recognized major cardiovascular (CV) risk factor, impairs endothelial function and increases aortic stiffness which indicates subclinical organ damage in hypertensive patients. Loss of endothelial glycocalyx (EG) integrity, as part of the endothelium, represents endothelial dysfunction. The authors aimed to investigate the role of increased HDL cholesterol levels (HDL-C), which usually are considered protective against CV disease, in aortic stiffness and endothelial integrity in middle-aged treated hypertensive patients regarding smoking habit. The authors studied 193 treated hypertensive patients ≥40 years (mean age = 61±11 years, 58% females), divided in four groups regarding sex and smoking. Increased perfusion boundary region of the 5-9 μm diameter sublingual arterial microvessels (PBR_5-9 ) was measured as a noninvasive accurate index of reduced EG thickness. Aortic stiffness was estimated by carotid-femoral pulse wave velocity (PWV). In the whole population, an inverse weak relationship was found between HDL-C and PWV (r = -.15, P = .03) and PBR_5-9 (ρ = -.15, P = .03). Moreover, HDL-C was negatively related to PBR_5-9 in males (r = -.29, P = .008) either smokers (r = -.35, P < .05) or non-smokers (r = -.27, P < .05) and PWV in female non-smokers (r = -.28, P = .009). In a multiple linear regression analysis, using age, weight, smoking, HDL-C, and LDL-C as independent variables, we found that HDL-C independently predicts PWV in the whole population (β = -.14, P = .02) and PBR_5-9 in male hypertensive patients (β = -.28, P = .01). Higher HDL-C levels are associated with reduced aortic stiffness in hypertensive patients, while they protect EG and subsequently endothelial function in middle-aged, treated hypertensive male patients (either smokers or not).

HDL therapy today: from atherosclerosis, to stent compatibility to heart failure

Epidemiologically, high-density lipoprotein (HDL) cholesterol levels have been inversely associated to cardiovascular (CV) events, although a Mendelian Randomisation Study had failed to establish a clear causal role. Numerous atheroprotective mechanisms have been attributed to HDL, the main being the ability to promote cholesterol efflux from arterial walls; anti-inflammatory effects related to HDL ligands such as S1P (sphingosine-1-phosphate), resolvins and others have been recently identified. Experimental studies and early clinical investigations have indicated the potential of HDL to slow progression or induce regression of atherosclerosis. More recently, the availability of different HDL formulations, with different phospholipid moieties, has allowed to test other indications for HDL therapy. Positive reports have come from studies on coronary stent biocompatibility, where the use of HDL from different sources reduced arterial cell proliferation and thrombogenicity. The observation that low HDL-C levels may be associated with an enhanced risk of heart failure (HF) has also suggested that HDL therapy may be applied to this condition. HDL infusions or apoA-I gene transfer were able to reverse heart abnormalities, reduce diastolic resistance and improve cardiac metabolism. HDL therapy may be effective not only in atherosclerosis, but also in other conditions, of relevant impact on human health.Key messagesHigh-density lipoproteins have as a major activity that of removing excess cholesterol from tissues (particularly arteries).Knowledge on the activity of high-density lipoproteins on health have however significantly widened.HDL-therapy may help to improve stent biocompatibility and to reduce peripheral arterial resistance in heart failure.

HDL from an Alzheimer's disease perspective

PURPOSE OF REVIEW

We review current knowledge regarding HDL and Alzheimer's disease, focusing on HDL's vasoprotective functions and potential as a biomarker and therapeutic target for the vascular contributions of Alzheimer's disease.

RECENT FINDINGS

Many epidemiological studies have observed that circulating HDL levels associate with decreased Alzheimer's disease risk. However, it is now understood that the functions of HDL may be more informative than levels of HDL cholesterol (HDL-C). Animal model studies demonstrate that HDL protects against memory deficits, neuroinflammation, and cerebral amyloid angiopathy (CAA). In-vitro studies using state-of-the-art 3D models of the human blood-brain barrier (BBB) confirm that HDL reduces vascular Aβ accumulation and attenuates Aβ-induced endothelial inflammation. Although HDL-based therapeutics have not been tested in clinical trials for Alzheimer's disease , several HDL formulations are in advanced phase clinical trials for coronary artery disease and atherosclerosis and could be leveraged toward Alzheimer's disease .

SUMMARY

Evidence from human studies, animal models, and bioengineered arteries supports the hypothesis that HDL protects against cerebrovascular dysfunction in Alzheimer's disease. Assays of HDL functions relevant to Alzheimer's disease may be desirable biomarkers of cerebrovascular health. HDL-based therapeutics may also be of interest for Alzheimer's disease, using stand-alone or combination therapy approaches.

ApoA-I deficiency increases cortical amyloid deposition, cerebral amyloid angiopathy, cortical and hippocampal astrogliosis, and amyloid-associated astrocyte reactivity in APP/PS1 mice

Background

Alzheimer’s disease (AD) is defined by amyloid beta (Aβ) plaques and neurofibrillary tangles and characterized by neurodegeneration and memory loss. The majority of AD patients also have Aβ deposition in cerebral vessels known as cerebral amyloid angiopathy (CAA), microhemorrhages, and vascular co-morbidities, suggesting that cerebrovascular dysfunction contributes to AD etiology. Promoting cerebrovascular resilience may therefore be a promising therapeutic or preventative strategy for AD. Plasma high-density lipoproteins (HDL) have several vasoprotective functions and are associated with reduced AD risk in some epidemiological studies and with reduced Aβ deposition and Aβ-induced inflammation in 3D engineered human cerebral vessels. In mice, deficiency of apoA-I, the primary protein component of HDL, increases CAA and cognitive dysfunction, whereas overexpression of apoA-I from its native promoter in liver and intestine has the opposite effect and lessens neuroinflammation. Similarly, acute peripheral administration of HDL reduces soluble Aβ pools in the brain and some studies have observed reduced CAA as well. Here, we expand upon the known effects of plasma HDL in mouse models and in vitro 3D artery models to investigate the interaction of amyloid, astrocytes, and HDL on the cerebrovasculature in APP/PS1 mice.

Methods

APP/PS1 mice deficient or hemizygous for Apoa1 were aged to 12 months. Plasma lipids, amyloid plaque deposition, Aβ protein levels, protein and mRNA markers of neuroinflammation, and astrogliosis were assessed using ELISA, qRT-PCR, and immunofluorescence. Contextual and cued fear conditioning were used to assess behavior.

Results

In APP/PS1 mice, complete apoA-I deficiency increased total and vascular Aβ deposition in the cortex but not the hippocampus compared to APP/PS1 littermate controls hemizygous for apoA-I. Markers of both general and vascular neuroinflammation, including Il1b mRNA, ICAM-1 protein, PDGFRβ protein, and GFAP protein, were elevated in apoA-I-deficient APP/PS1 mice. Additionally, apoA-I-deficient APP/PS1 mice had elevated levels of vascular-associated ICAM-1 in the cortex and hippocampus and vascular-associated GFAP in the cortex. A striking observation was that astrocytes associated with cerebral vessels laden with Aβ or associated with Aβ plaques showed increased reactivity in APP/PS1 mice lacking apoA-I. No behavioral changes were observed.

Conclusions

ApoA-I-containing HDL can reduce amyloid pathology and astrocyte reactivity to parenchymal and vascular amyloid in APP/PS1 mice.

Electronic supplementary material

The online version of this article (10.1186/s13195-019-0497-9) contains supplementary material, which is available to authorized users.

Association between Cardiac Remodeling and Metabolic Alteration in an Experimental Model of Obesity Induced by Western Diet

The high consumption of fat and sugar contributes to the development of obesity and co-morbidities, such as dyslipidemia, hypertension, and cardiovascular disease. The aim of this study was to evaluate the association between dyslipidemia and cardiac dysfunction induced by western diet consumption. Wistar rats were randomly divided into two experimental groups and fed ad libitum for 20 weeks with a control diet (Control, n = 12) or a high-sugar and high-fat diet (HSF, n = 12). The HSF group also received water + sucrose (25%). Evaluations included feed and caloric intake; body weight; plasma glucose; insulin; uric acid; HOMA-IR; lipid profile: [total cholesterol (T-chol), high-density lipoprotein (HDL), non-HDL Chol, triglycerides (TG)]; systolic blood pressure, and Doppler echocardiographic. Compared to the control group, animals that consumed the HSF diet presented higher weight gain, caloric intake, feed efficiency, insulin, HOMA-IR, and glucose levels, and lipid profile impairment (higher TG, T-chol, non-HDL chol and lower HDL). HSF diet was also associated with atrial-ventricular structural impairment and systolic-diastolic dysfunction. Positive correlation was also found among the following parameters: insulin versus estimated LV mass (r = 0.90, p = 0.001); non-HDL versus deceleration time (r = 0.46, p = 0.02); TG versus deceleration time (r = 0.50, p = 0.01). In summary, our results suggest cardiac remodeling lead by western diet is associated with metabolic parameters.

HDL cholesterol levels and endothelial glycocalyx integrity in treated hypertensive patients

Endothelial dysfunction indicates target organ damage in hypertensive patients. The integrity of endothelial glycocalyx (EG) plays a vital role in vascular permeability, inflammation and elasticity, and finally to cardiovascular disease. The authors aimed to investigate the role of increased HDL cholesterol (HDL-C) levels, which usually are considered protective against cardiovascular disease, in EG integrity in older hypertensive patients. The authors studied 120 treated hypertensive patients older than 50 years were divided regarding HDL-C tertiles in group HDL_H (HDL-C ≥ 71 mg/dL, upper HDL-C tertile) and group HDL_L (HDL-C < 71 mg/dL, two lower HDL-C tertiles). Increased perfusion boundary region (PBR) of the sublingual arterial microvessels (ranging from 5 to 9 µm) using Sideview Darkfield imaging (Microscan, Glycocheck) was measured as a non-invasive accurate index of reduced EG thickness. PBR 5-9 was significantly decreased in group HDL_H (P = 0.04). In the whole population, HDL-C was inversely but moderately related to PBR 5-9 (r = -0.22, P = 0.01). In a multiple linear regression analysis model, using age, BMI, smoking habit, HDL-C, LDL-C, and office SBP, as independent variables, the authors found that BMI (β = 0.25, P = 0.006) independently predicted PBR 5-9 in the whole population. In older hypertensive patients, HDL-C ranging between 71 and 101 mg/dL might moderately protect EG and subsequently endothelial function. Future studies in several groups of low- or high-risk hypertensives are needed in order to evaluate the beneficial role of extremely elevated HDL-C regarding cardiovascular risk evaluation as well as endothelial glycocalyx as a novel index of target organ damage in essential hypertension.

Diet-Modulated Lipoprotein Metabolism and Vascular Inflammation Evaluated by 18F-fluorodeoxyglucose Positron Emission Tomography

Vascular inflammation plays a central role in atherosclerosis, from initiation and progression to acute thrombotic complications. Modified low-density lipoproteins (LDLs) and apoB-containing particles stimulate plaque inflammation by interacting with macrophages. Loss of function of high-density lipoprotein (HDL) for preventing LDL particles from oxidative modification in dyslipidemic states may amplify modified LDL actions, accelerating plaque inflammation. Diets are one of the most important factors that can affect these processes of lipoprotein oxidation and vascular inflammation. Recently, ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has emerged as a reliable noninvasive imaging modality for identifying and quantifying vascular inflammation within atherosclerotic lesions based on the high glycolytic activity of macrophages infiltrating active atherosclerotic plaques. Vascular inflammation evaluated by FDG PET has been positively related to metabolic syndrome components and traditional risk factors of cardiovascular disease, including high-sensitivity C-reactive protein, body mass index, and insulin resistance. A positive association of vascular inflammation with endothelial dysfunction, resistin levels, pericardial adipose tissue, and visceral fat area has also been reported. In contrast, HDL cholesterol and adiponectin have been inversely related to vascular inflammation detected by FDG PET. Because of its reproducibility, serial FDG PET shows potential for tracking the effects of dietary interventions and other systemic and local antiatherosclerotic therapies for plaque inflammation.

High Density Lipoproteins Inhibit Oxidative Stress-Induced Prostate Cancer Cell Proliferation

Recent evidence suggests that oxidative stress can play a role in the pathogenesis and the progression of prostate cancer (PCa). Reactive oxygen species (ROS) generation is higher in PCa cells compared to normal prostate epithelial cells and this increase is proportional to the aggressiveness of the phenotype. Since high density lipoproteins (HDL) are known to exert antioxidant activities, their ability to reduce ROS levels and the consequent impact on cell proliferation was tested in normal and PCa cell lines. HDL significantly reduced basal and H₂O₂-induced oxidative stress in normal, androgen receptor (AR)-positive and AR-null PCa cell lines. AR, scavenger receptor BI and ATP binding cassette G1 transporter were not involved. In addition, HDL completely blunted H₂O₂-induced increase of cell proliferation, through their capacity to prevent the H₂O₂-induced shift of cell cycle distribution from G0/G1 towards G2/M phase. Synthetic HDL, made of the two main components of plasma-derived HDL (apoA-I and phosphatidylcholine) and which are under clinical development as anti-atherosclerotic agents, retained the ability of HDL to inhibit ROS production in PCa cells. Collectively, HDL antioxidant activity limits cell proliferation induced by ROS in AR-positive and AR-null PCa cell lines, thus supporting a possible role of HDL against PCa progression.

Low high-density lipoprotein cholesterol and particle concentrations are associated with greater levels of endothelial activation markers in Multi-Ethnic Study of Atherosclerosis participants

BACKGROUND

High-density lipoproteins (HDL) are well characterized for their role in reverse cholesterol transport but may confer other cardiovascular benefits-specifically, HDL may suppress the endothelial activation cascade in the initiating stages of atherogenesis.

OBJECTIVE

It was the primary aim of this study to examine the relations of HDL cholesterol (HDL-C), total HDL particle (HDL-P) concentrations, and HDL-P subclasses with circulating levels of endothelial activation markers in a subcohort of Multi-Ethnic Study of Atherosclerosis participants.

METHODS

HDL-C was measured by enzymatic assay, and total HDL-P and subclass concentrations were assessed by nuclear magnetic resonance spectroscopy. Concentrations of circulating endothelial activation markers were determined through immunoassay. Multivariable linear regression was used to determine the cross-sectional associations between HDL variables and endothelial markers with statistical adjustment for age, race/ethnicity, sex, education, systolic blood pressure, hypertension medication use, body mass index, smoking status, lipid-lowering medication use, serum creatinine, diabetes, low-density lipoprotein cholesterol, and coronary artery calcium.

RESULTS

HDL-C and HDL-P were found to be inversely associated with soluble vascular cell adhesion molecule-1, soluble vascular intracellular adhesion molecule-1, sL-selectin, and sP-selectin; HDL-P was additionally inversely associated with sE-selectin. Participants with low levels of HDL-C (<40 mg/dL) or HDL-P (<25th percentile) showed 3%-12% higher mean levels of soluble vascular cell adhesion molecule and compared with those above these levels (all P < .01).

CONCLUSION

Coupled with previous evidence, our findings suggest a modest to moderate relation of HDL and circulating levels of endothelial activation markers in humans. Whether this relationship may have clinical implications in suppressing atherogenesis or coronary heart disease development requires additional research.

Effect of two lipid-lowering strategies on high-density lipoprotein function and some HDL-related proteins: a randomized clinical trial

BACKGROUND

The influence of lipid-lowering therapy on high-density lipoprotein (HDL) is incompletely understood. We compared the effect of two lipid-lowering strategies on HDL functions and identified some HDL-related proteins.

METHODS

Thirty two patients were initially screened and HDLs of 21 patients were finally analyzed. Patients were randomized to receive atorvastatin 20 mg (n = 11) or atorvastatin 5 mg/ezetimibe 10 mg combination (n = 10) for 8 weeks. The cholesterol efflux capacity and other anti-inflammatory functions were assessed based on HDLs of the participants before and after treatment. Pre-specified HDL proteins of the same HDL samples were measured.

RESULTS

The post-treatment increase in cholesterol efflux capacities was similar between the groups (35.6% and 34.6% for mono-therapy and combination, respectively, p = 0.60). Changes in nitric oxide (NO) production, vascular cell adhesion molecule-1 (VCAM-1) expression, and reactive oxygen species (ROS) production were similar between the groups. The baseline cholesterol efflux capacity correlated positively with apolipoprotein (apo)A1 and C3, whereas apoA1 and apoC1 showed inverse associations with VCAM-1 expression. The changes in the cholesterol efflux capacity were positively correlated with multiple HDL proteins, especially apoA2.

CONCLUSIONS

Two regimens increased the cholesterol efflux capacity of HDL comparably. Multiple HDL proteins, not limited to apoA1, showed a correlation with HDL functions. These results indicate that conventional lipid therapy may have additional effects on HDL functions with changes in HDL proteins.

TRIAL REGISTRATION

ClinicalTrials.gov, number NCT02942602 .

The protective effect of apolipoprotein in models of trophoblast invasion and preeclampsia

Preeclampsia is a hypertensive disorder of pregnancy. It is associated with abnormal placentation via poor placental invasion of the uterine vasculature by trophoblast cells, leading to poor placental perfusion, oxidative stress, and inflammation, all of which are implicated in its pathogenesis. A dyslipidemia characterized by low plasma levels of high-density lipoproteins (HDL) and elevated triglycerides has been described in preeclampsia. Apolipoprotein A-I (apoA-I), a constituent of HDL is an anti-inflammatory agent. This study investigated whether apoA-I protects against hypertension and adverse placental changes in a proinflammatory cytokine (TNF-α)-induced model of preeclampsia. Further, this study investigated whether apoA-I protects against the inhibitory effect of TNF-α in a human in vitro model of trophoblast invasion. Administration of apoA-I to pregnant mice before infusion with TNF-α resulted in a significant reduction in the cytokine-induced increase in systolic blood pressure. MRI measurement of T2 relaxation, a parameter that is tissue specific and sensitive to physiological changes within tissues, showed a reversal of TNF-α-induced placental changes. Preincubation of endothelial cells with apoA-I protected against the TNF-α-induced inhibition of HTR-8/SVneo (trophoblast) cell integration into endothelial (UtMVEC) networks. These data suggest that a healthy lipid profile may affect pregnancy outcomes by priming endothelial cells in preparation for trophoblast invasion.

Inflammation and the pathogenesis of atherosclerosis in systemic lupus erythematosus

Atherosclerosis is a complicated inflammatory process characterized by the interactions of numerous different moieties including lipids, enzymes, endothelial cells, cytokines, chemokines, leukocytes, adhesion molecules, complement and antibodies. As in the pathogenesis of many lupus disease processes, the increased risk of atherosclerosis seen in systemic lupus erythematosus (SLE) is likely due to the complex interplay of many of these inflammatory mediators. Expanding our understanding of the pathogenesis of atherosclerosis in SLE is critical if we are to improve the quality of care and reduce mortality in this vulnerable population.

HDL as a prognostic biomarker for coronary atherosclerosis: the role of inflammation

INTRODUCTION

Emerging evidence suggests that the role of high density lipoprotein (HDL) in the atherosclerotic process is not as clear as previously thought, since atheroprotective HDL becomes atherogenic in states of increased inflammatory processes.

AREAS COVERED

In this review we aim to elucidate the role of HDL as a prognostic biomarker and we discuss therapeutic approaches that aim to increase HDL and their possible clinical benefit.

EXPERT OPINION

Given the structural variability and biological complexity of the HDL particle, its role in the atherosclerotic process is far from clear. According to current evidence, the atheroprotective role of HDL turns atherogenic in states of increased inflammatory processes, while even minor alterations in systemic inflammation are likely to hinder the endothelial protective effects of HDL. In accordance, significant data have revealed that HDL-related drugs may be effective in reducing cardiovascular mortality; however they are not as encouraging or unanimous as expected. Possible future goals could be to quantify either HDL subclasses or functions in an attempt to reach safer conclusions as to the prognostic importance of HDL in coronary atherosclerosis. Having achieved that, a more targeted therapy that would aim to raise either HDL functionality or to remodel HDL structure would be more easily designed.

Plasma-derived and synthetic high-density lipoprotein inhibit tissue factor in endothelial cells and monocytes

Atheroprotection mediated by high-density lipoproteins could also be related to their ability to inhibit the expression of tissue factor, the main activator of the coagulation cascade, in endothelial cells and in monocytes.

Pathophysiology and Medical Treatment of Carotid Artery Stenosis

Stroke is the third leading cause of mortality. Approximately 80 to 85% strokes are ischemic due to carotid artery stenosis (CAS). The prevalence of significant CAS is 7% in women and 9% in men. Severe asymptomatic CAS varies from 0 to 3.1%. Prevalence of symptomatic CAS is high in patients with peripheral arterial disease. CAS is due to atherosclerosis, the major risk factors for which include dyslipidemia, hypertension, diabetes, obesity, cigarette smoking, advanced glycation end products (AGEs) and its receptors (RAGE, soluble RAGE [sRAGE]), lack of exercise and C-reactive protein (CRP). This article discusses the basic mechanism of atherosclerosis and the mechanisms by which these risk factors induce atherosclerosis. The role of AGEs and its receptors in the development and progression of CAS has been discussed in detail. Lifestyle changes and medical treatment of CAS such as lifestyle changes, lipid-lowering agents, antihypertensive agents, antidiabetic drugs, anti-AGE therapy, measures to elevate soluble receptors of AGE (sRAGE, esRAGE). CRP-lowering agents have been discussed in detail. The drugs especially lipid-lowering agents, and antihypertensive and antidiabetic drugs suppress, regress, and slow the progression of CAS. The possible role of lowering the levels of AGEs and raising the levels of sRAGE in the treatment of CAS has been proposed. Lifestyle changes besides medical treatment have been stressed. Lifestyle changes and medical treatment not only would slow the progression of CAS but would also regress the CAS.

Accelerated vascular disease in systemic lupus erythematosus: role of macrophage

Atherosclerosis is a chronic inflammatory condition that is considered a major cause of death worldwide. Striking phenomena of atherosclerosis associated with systemic lupus erythematosus (SLE) is its high incidence in young patients. Macrophages are heterogeneous cells that differentiate from hematopoietic progenitors and reside in different tissues to preserve tissue integrity. Macrophages scavenge modified lipids and play a major role in the development of atherosclerosis. When activated, macrophages secret inflammatory cytokines. This activation triggers apoptosis of cells in the vicinity of macrophages. As such, macrophages play a significant role in tissue remodeling including atherosclerotic plaque formation and rupture. In spite of studies carried on identifying the role of macrophages in atherosclerosis, this role has not been studied thoroughly in SLE-associated atherosclerosis. In this review, we address factors released by macrophages as well as extrinsic factors that may control macrophage behavior and their effect on accelerated development of atherosclerosis in SLE.

Dysfunctional HDL: from structure-function-relationships to biomarkers

Reduced plasma levels of HDL-C are associated with an increased risk of CAD and myocardial infarction, as shown in various prospective population studies. However, recent clinical trials on lipid-modifying drugs that increase plasma levels of HDL-C have not shown significant clinical benefit. Notably, in some recent clinical studies, there is no clear association of higher HDL-C levels with a reduced risk of cardiovascular events observed in patients with existing CAD. These observations have prompted researchers to shift from a cholesterol-centric view of HDL towards assessing the function and composition of HDL particles. Of importance, experimental and translational studies have further demonstrated various potential antiatherogenic effects of HDL. HDL has been proposed to promote macrophage reverse cholesterol transport and to protect endothelial cell functions by prevention of oxidation of LDL and its adverse endothelial effects. Furthermore, HDL from healthy subjects can directly stimulate endothelial cell production of nitric oxide and exert anti-inflammatory and antiapoptotic effects. Of note, increasing evidence suggests that the vascular effects of HDL can be highly heterogeneous and HDL may lose important anti-atherosclerotic properties and turn dysfunctional in patients with chronic inflammatory disorders. A greater understanding of mechanisms of action of HDL and its altered vascular effects is therefore critical within the context of HDL-targeted therapies.

Effects of established hypolipidemic drugs on HDL concentration, subclass distribution, and function

The knowledge of an inverse relationship between plasma high-density lipoprotein cholesterol (HDL-C) concentrations and rates of cardiovascular disease has led to the concept that increasing plasma HDL-C levels would be protective against cardiovascular events. Therapeutic interventions presently available to correct the plasma lipid profile have not been designed to specifically act on HDL, but have modest to moderate effects on plasma HDL-C concentrations. Statins, the first-line lipid-lowering drug therapy in primary and secondary cardiovascular prevention, have quite modest effects on plasma HDL-C concentrations (2-10%). Fibrates, primarily used to reduce plasma triglyceride levels, also moderately increase HDL-C levels (5-15%). Niacin is the most potent available drug in increasing HDL-C levels (up to 30%), but its use is limited by side effects, especially flushing.The present chapter reviews the effects of established hypolipidemic drugs (statins, fibrates, and niacin) on plasma HDL-C levels and HDL subclass distribution, and on HDL functions, including cholesterol efflux capacity, endothelial protection, and antioxidant properties.

Understanding high-density lipoprotein function in disease: recent advances in proteomics unravel the complexity of its composition and biology

Although the epidemiology of high-density lipoprotein (HDL) cholesterol and cardiovascular risk has been consistent, pharmacologic interventions to increase HDL-cholesterol by delaying HDL catabolism did not translate into reduction in cardiovascular risk. HDL particles are small, protein-rich when compared to other plasma lipoprotein classes. Latest progresses in proteomics technology have dramatically increased our understanding of proteins carried by HDL. In addition to proteins with well-established functions in lipid transport, iron transport proteins, members of the complement pathway, and proteins involved in immune function and acute phase response were repeatedly identified on HDL particles. With the unraveling of the complexity of the HDL proteome, different laboratories have started to monitor its changes in various disease states. In addition, dynamic aspects of HDL subgroups are being discovered. These recent studies clearly illustrate the promise of HDL proteomics for deriving new biomarkers for disease diagnosis and to measure the effectiveness of current and future treatment regimens. This review summarizes recent advances in proteomics and lipidomics helping to understand HDL function in health and disease.

HDL and atherosclerosis: Insights from inherited HDL disorders

Plasma high density lipoproteins (HDL) comprise a highly heterogeneous family of lipoprotein particles, differing in density, size, surface charge, and lipid and protein composition. Epidemiological studies have shown that plasma HDL level inversely correlates with atherosclerotic cardiovascular disease. The most relevant atheroprotective function of HDL is to promote the removal of cholesterol from macrophages within the arterial wall and deliver it to the liver for excretion in a process called reverse cholesterol transport. In addition, HDLs can contribute to the maintenance of endothelial cell homeostasis and have potent antioxidant properties. It has been long suggested that individual HDL subclasses may differ in terms of their functional properties, but which one is the good particle remains to be defined. Inherited HDL disorders are rare monogenic diseases due to mutations in genes encoding proteins involved in HDL metabolism. These disorders are not only characterized by extremely low or high plasma HDL levels but also by an abnormal HDL subclass distribution, and thus represent a unique tool to understand the relationship between plasma HDL concentration, HDL function, and HDL-mediated atheroprotection. This article is part of a Special Issue entitled Linking transcription to physiology in lipodomics.

HDL-mediated mechanisms of protection in cardiovascular disease

Low plasma levels of HDL-cholesterol (HDL-C) represent a strong and independent risk factor for cardiovascular disease. HDL particles display a wide spectrum of atheroprotective activities, which include effluxing cellular cholesterol, diminishing cellular death, decreasing vascular constriction, reducing inflammatory response, protecting from pathological oxidation, combating bacterial infection, lessening platelet activation, regulating gene expression by virtue of microRNAs, and improving glucose metabolism. It remains presently indeterminate as to whether some biological activities of HDL are more relevant for the protection of the endothelium from atherogenesis when compared with others. The multitude of such activities raises the question of a proper assay to assess HDL functionality ex vivo. Together with clear understanding of molecular mechanisms underlying atheroprotective properties of HDL, such assay will provide a basis to resolve the ultimate question of the HDL field to allow the development of efficient HDL-targeting therapies.

High-density lipoproteins and cerebrovascular integrity in Alzheimer's disease

Cerebrovascular dysfunction significantly contributes to the clinical presentation and pathoetiology of Alzheimer's disease (AD). Deposition and aggregation of β-amyloid (Aβ) within vascular smooth muscle cells leads to inflammation, oxidative stress, impaired vasorelaxation, and disruption of blood-brain barrier integrity. Midlife vascular risk factors, such as hypertension, cardiovascular disease, diabetes, and dyslipidemia, increase the relative risk for AD. These comorbidities are all characterized by low and/or dysfunctional high-density lipoproteins (HDL), which itself is a risk factor for AD. HDL performs a wide variety of critical functions in the periphery and CNS. In addition to lipid transport, HDL regulates vascular health via mediating vasorelaxation, inflammation, and oxidative stress and promotes endothelial cell survival and integrity. Here, we summarize clinical and preclinical data examining the involvement of HDL, originating from the circulation and from within the CNS, on AD and hypothesize potential synergistic actions between the two lipoprotein pools.

High-density lipoprotein and atherosclerosis regression: evidence from preclinical and clinical studies

High-density lipoprotein (HDL) particles transport (among other molecules) cholesterol (HDL-C). In epidemiological studies, plasma HDL-C levels have an inverse relationship to the risk of atherosclerotic cardiovascular disease. It has been assumed that this reflects the protective functions of HDL, which include their ability to promote cholesterol efflux. Yet, several recent pharmacological and genetic studies have failed to demonstrate that increased plasma levels of HDL-C resulted in decreased cardiovascular disease risk, giving rise to a controversy regarding whether plasma levels of HDL-C reflect HDL function, or that HDL is even as protective as assumed. The evidence from preclinical and (limited) clinical studies shows that HDL can promote the regression of atherosclerosis when the levels of functional particles are increased from endogenous or exogenous sources. The data show that regression results from a combination of reduced plaque lipid and macrophage contents, as well as from a reduction in its inflammatory state. Although more research will be needed regarding basic mechanisms and to establish that these changes translate clinically to reduced cardiovascular disease events, that HDL can regress plaques suggests that the recent trial failures do not eliminate HDL from consideration as an atheroprotective agent but rather emphasizes the important distinction between HDL function and plasma levels of HDL-C.

HDL-cholesterol in coronary artery disease risk: function or structure?

High-density lipoproteins (HDL) are inversely related with coronary artery disease (CAD) and HDL-cholesterol is the only standardized and reproducible parameter available to estimate plasma concentration of these lipoproteins. However, pharmacological interventions intended to increase HDL-cholesterol have not been consistently associated to an effective CAD risk reduction. Among patients with a myocardial infarction, 43 and 44% of men and women, respectively, had normal plasma levels of HDL-cholesterol, whereas genetic studies have failed to show a causal association between HDL-cholesterol and CAD risk. Instead, HDL functionality seems to be the target to be evaluated, but the existing methods are still poorly reproducible and far to be adapted to the clinical laboratory. HDL subclasses rise as a potential alternative for the evaluation of CAD risk; HDL subclasses are a surrogate of intravascular metabolism of these lipoproteins and probably of their functionality. Low levels of large HDL and increased proportions of small particles are the most remarkable features associated to an increased risk of type 2 diabetes mellitus (T2DM) or CAD. However, inflammation and other environmental factors are related with abnormal HDL structure, and, as a consequence, more prospective studies are needed to better support the clinical usefulness of HDL subclasses. New insights from proteome and lipidome profiles of HDL will provide potential HDL-related biomarkers in the coming years.

GPR109A and vascular inflammation

GPR109A has generated expanding interest since its discovery as the receptor for niacin a decade ago, along with deorphanisation as the receptor for endogenous ligand 3-hydroxy-butyrate shortly after. This interest is generated especially because of the continuing exploration of niacin's "pleiotropic" mechanisms of action and its potential in the "cross-talk" between metabolic and inflammatory pathways. As GPR109A's primary pharmacological ligand in clinical use, niacin has been used for over 50 years in the treatment of cardiovascular disease, mainly due to its favourable effects on plasma lipoproteins. However, it has become apparent that niacin also possesses lipoprotein-independent effects that influence inflammatory pathways mediated through GPR109A. In addition to its G-protein-mediated effects, recent evidence has emerged to support alternative GPR109A signalling via adaptive protein β-arrestins. In this article, we consider the role of GPR109A and its downstream effects in the context of atherosclerosis and vascular inflammation, along with insights into strategy for future drug development.

High density lipoproteins and endothelial functions: mechanistic insights and alterations in cardiovascular disease

Prospective population studies in the primary prevention setting have shown that reduced plasma levels of HDL cholesterol are associated with an increased risk of coronary disease and myocardial infarction. Experimental and translational studies have further revealed several potential anti-atherogenic effects of HDL, including protective effects on endothelial cell functions. HDL has been suggested to protect endothelial cell functions by prevention of oxidation of LDL and its adverse endothelial effects. Moreover, HDL from healthy subjects can directly stimulate endothelial cell production of nitric oxide and anti-inflammatory, anti-apoptotic, and anti-thrombotic effects as well as endothelial repair processes. However, several recent clinical trials using HDL cholesterol-raising agents, such as torcetrapib, dalcetrapib, and niacin, did not demonstrate a significant reduction of cardiovascular events in patients with coronary disease. Of note, growing evidence suggests that the vascular effects of HDL can be highly heterogeneous and vasoprotective properties of HDL are altered in patients with coronary disease. Characterization of underlying mechanisms and understanding of the clinical relevance of this "HDL dysfunction" is currently an active field of cardiovascular research. Notably, in some recent studies no clear association of higher HDL cholesterol levels with a reduced risk of cardiovascular events was observed in patients with already established coronary disease. A greater understanding of mechanisms of action of HDL and its altered vascular effects is therefore critical within the context of HDL-targeted therapies. In this review, we will address different effects of HDL on endothelial cell functions potentially relevant to atherosclerotic vascular disease and explore molecular mechanisms leading to "dysfunctional HDL".

Epigallocatechin 3-gallate inhibits 7-ketocholesterol-induced monocyte-endothelial cell adhesion

7-Ketocholesterol (7KC) induces monocytic adhesion to endothelial cells, and induces arteriosclerosis while high-density lipoprotein (HDL) inhibits monocytic adhesion to the endothelium. Epigallocatechin 3-gallate (EGCG) was found to have a protective effect against arteriosclerosis. Therefore, the purpose of this study was to examine the possible HDL-like mechanisms of EGCG in endothelial cells by investigating whether EGCG inhibits 7KC-induced monocyte-endothelial cell adhesion by activating HDL-dependent signal transduction pathways. 7KC and/or EGCG were added to human endothelial cells (ISO-HAS), and the adhesion of pro-monocytic U937 cells was examined. The expression of genes associated with HDL effects such as Ca(2+)/calmodulin-dependent kinase II (CaMKKII), liver kinase B (LKD1), PSD-95/Dlg/ZO-1 kinase 1 (PDZK1), phosphatidylinositol 3-kinase (PI3K), intercellular adhesion molecule-1 (ICAM-1), monocyte chemotactic protein-1 (MCP-1), and endothelial nitric oxide synthase (eNOS) was examined by RT-PCR, and ICAM-1 protein expression was evaluated by western blot (WB). Production of reactive oxygen species (ROS) was examined with H2DCFDA. 7KC significantly induced adhesion of U937 cells to human endothelial cells while significantly increasing gene expressions of ICAM-1 and MCP-1 and decreasing eNOS and CaMKKII gene expressions. EGCG inhibited 7KC-induced monocytic adhesion to endothelial cells, and induced expression of eNOS and several genes involved in the CaMKKII pathway. Stimulation of endothelial cells with EGCG produced intracellular ROS, whereas treatment with N-acetylcysteine (NAC) blocked EGCG-induced expression of eNOS and CaMKKII. These results suggest that inhibition of monocyte-endothelial cell adhesion by EGCG is associated with CaMKKII pathway activation by ROS. Inhibition of 7KC-induced monocyte-endothelial cell adhesion induced by EGCG may function similarly to HDL.

The lipid-bound apolipoprotein A-I cysteine mutant (N74C) inhibits the activation of NF-κB, JNK and p38 in endotoxemic mice and RAW264.7 cells

Our previous studies showed that recombinant high-density lipoprotein (rHDL) rHDL74 exhibited higher anti-inflammatory capabilities compared to wild-type rHDL (rHDLwt), while rHDL228 showed hyper-proinflammation. In this paper, we further investigated the potential mechanisms involved in their different inflammatory functions using two models: endotoxemic mice and the RAW264.7 inflammation model. Our results showed that 24 h after the injection of lipopolysaccharide (LPS), mice treated with rHDL74 had a significant decrease in plasma CRP (P<0.01 vs. rHDLwt; P<0.01 vs. LPS), MCP-1 (P<0.05 vs. rHDLwt; P<0.01 vs. LPS) and CD14 (P<0.01 vs. LPS) compared with the mice treated with rHDLwt or the controls that received LPS only. Similar to our previous study, rHDL228 increased the plasma level of CRP (P<0.05 vs. LPS) and MCP-1 (P<0.01 vs. LPS). Our immunohistochemistry and western blot analysis showed that rHDL74 inhibited the activation of NF-κB in endotoxemic mice and JNK and p38 in the RAW264.7 inflammation model, while rHDL228 exacerbated the activation of NF-κB and ERK. In summary, our data suggest that rHDL74 exhibits higher anti-inflammatory activity by decreasing inflammatory factors and inhibiting the activation of NF-κB, JNK and p38, while rHDL228 appears to be hyper-proinflammation by increasing these inflammatory factors and aggravating the activation of NF-κB and ERK.

New roles of HDL in inflammation and hematopoiesis

High-density lipoprotein (HDL) levels are inversely associated with coronary heart disease due to HDL's ability to transport excess cholesterol in arterial macrophages to the liver for excretion [i.e., reverse cholesterol transport (RCT)]. However, recent advances highlight additional atheroprotective roles for HDL beyond bulk cholesterol removal from cells through RCT. By promoting cellular free cholesterol (FC) efflux, HDL and its apolipoproteins (apoA-I and apoE) decrease plasma membrane FC and lipid raft content in immune and hematopoietic stem cells, decreasing inflammatory and cell proliferation signaling pathways. HDL and apoA-I also dampen inflammatory signaling pathways independent of cellular FC efflux. In addition, HDL lipid and protein cargo provide protection against parasitic and bacterial infection, endothelial damage, and oxidant toxicity. Here, current knowledge is reviewed regarding the role of HDL and its apolipoproteins in regulating cellular cholesterol homeostasis, highlighting recent advances on novel functions and mechanisms by which HDLs regulate inflammation and hematopoiesis.

ApoA-1 infusion reduces arterial cholesterol and myocardial lesions in a rat model of cardiac dysfunction and insulin resistance

OBJECTIVE

Low plasma high-density lipoprotein cholesterol (HDL-C) concentration is associated with the metabolic syndrome (MetS) and increased prevalence of cardiovascular disease (CVD). Animal and human studies report infusion of apolipoprotein A-1 (apoA-1) can reduce endothelial dysfunction, and/or induce regression of atherosclerosis. However, the direct mechanisms underlying the vascular benefits of either apoA-1 or HDL-C remain unclear. In this study, we assessed the ability of reconstituted HDL (rHDL) to improve vascular complications of MetS, including left ventricular (LV)-hypertrophy, arterial cholesterol deposition and myocardial lesion development.

METHODS AND RESULTS

Obese insulin resistant (IR) JCR:LA-cp rats were infused with rHDL (0.4 mg/kg) over 3 days before assessing cardiac function (Echocardiography) at days 7 and 50 post-infusion, as well as haematoxylin and eosin staining of myocardial lesions at day 50. Acute ex vivo arterial cholesterol deposition was assessed with acute infusion of rHDL ex-vivo. Infusion of rHDL partially corrected abnormal diastolic compliance (18%; *p<0.05) and improved parameters of cardiac function in IR rats. Further, acute rHDL infusion in carotid vessels reduced remnant lipoprotein associated-cholesterol deposition (30-86%; **p<0.01) ex vivo in IR and male Wistar rats and reduced (41%; *p<0.05) the frequency of early-stage myocardial lesions in IR rats.

CONCLUSION

Short-term infusion of rHDL may beneficially reduce chronic vascular sequelae of MetS, including temporary improvement in LV-dysfunction, acute reduction of acute arterial cholesterol deposition and the development of early-stage myocardial lesions in the JCR:LA-cp rat.

Systemic lupus erythematosus and cardiovascular disease: prediction and potential for therapeutic intervention

Patients with systemic lupus erythematosus have a significantly increased risk of cardiovascular events due to atherosclerosis. Traditional cardiac risk factors cannot fully explain this increased risk. Recent evidence strongly suggests that atherosclerotic plaque is largely driven by inflammation and an active immunological response, in contrast to the long-held belief that plaque is a passive accumulation of lipids in the arterial wall. Current approaches to the prevention of atherosclerosis in systemic lupus erythematosus involve targeting modifiable cardiac risk factors. Future preventive strategies may include therapies that counteract the immunologic responses that lead to plaque formation.

Pleiotropic effects of thyroid hormones: learning from hypothyroidism

Hypothyroidism induces several metabolic changes that allow understanding some physiopathological mechanisms. Under experimental hypothyroid conditions in rats, heart and kidney are protected against oxidative damage induced by ischemia reperfusion. An increased resistance to opening of the permeability transition pore seems to be at the basis of such protection. Moreover, glomerular filtration rate of hypothyroid kidney is low as a result of adenosine receptors-induced renal vasoconstriction. The vascular tone of aorta is also regulated by adenosine in hypothyroid conditions. In other context, thyroid hormones regulate lipoprotein metabolism. High plasma level of LDL cholesterol is a common feature in hypothyroidism, due to a low expression of the hepatic LDL receptor. In contrast, HDL-cholesterol plasma levels are variable in hypothyroidism; several proteins involved in HDL metabolism and structure are expressed at lower levels in experimental hypothyroidism. Based on the positive influence of thyroid hormones on lipoprotein metabolism, thyromimetic drugs are promising for the treatment of dyslipidemias. In summary, hypothyroid status has been useful to understand molecular mechanisms involved in ischemia reperfusion, regulation of vascular function and intravascular metabolism of lipoproteins.

Scavenger receptor class B, type I: a promising immunotherapy target

Scavenger receptor class B, type I (SR-BI) is a crucial molecule in lipid metabolism, since the interaction of high-density lipoproteins (HDLs) with SR-BI is involved in reverse cholesterol transport and cholesterol efflux. Recent findings also underscore a critical role of SR-BI in antimicrobial and immune responses. SR-BI is not only highly expressed in liver and steroidogenic glands, but also in endothelial cells, macrophages and dendritic cells. SR-BI mainly mediates anti-inflammatory responses, which may be altered by dysfunctional HDLs produced in several diseases. Moreover, SR-BI has been involved in the capture and cross-presentation of antigens from viruses, bacteria and parasites. It thus works as a pattern-recognition receptor that interacts with both damage-associated molecular patterns and pathogen-associated molecular patterns. These new findings in the microbiology and immunology fields present SR-BI as an unexplored therapeutic target that warrants further basic and applied research.

Down-regulation of endothelial TLR4 signalling after apo A-I gene transfer contributes to improved survival in an experimental model of lipopolysaccharide-induced inflammation

The protective effects of high-density lipoprotein (HDL) under lipopolysaccharide (LPS) conditions have been well documented. Here, we investigated whether an effect of HDL on Toll-like receptor 4 (TLR4) expression and signalling may contribute to its endothelial-protective effects and to improved survival in a mouse model of LPS-induced inflammation and lethality. HDL cholesterol increased 1.7-fold (p < 0.005) and lung endothelial TLR4 expression decreased 8.4-fold (p < 0.005) 2 weeks after apolipoprotein (apo) A-I gene transfer. Following LPS administration in apo A-I gene transfer mice, lung TLR4 and lung MyD88 mRNA expression, reflecting TLR4 signalling, were 3.0-fold (p < 0.05) and 2.1-fold (p < 0.05) lower, respectively, than in LPS control mice. Concomitantly, LPS-induced lung neutrophil infiltration, lung oedema and mortality were significantly attenuated following apo A–I transfer. In vitro, supplementation of HDL or apo A–I to human microvascular endothelial cells-1 24 h before LPS administration reduced TLR4 expression, as assessed by fluorescent-activated cell sorting, and decreased the LPS-induced MyD88 mRNA expression and NF-κB activity, independently of LPS binding. In conclusion, HDL reduces TLR4 expression and signalling in endothelial cells, which may contribute significantly to the protective effects of HDL in LPS-induced inflammation and lethality.