Abnormal Lipoproteins Trigger Oxidative Stress-Mediated Apoptosis of Renal Cells in LCAT Deficiency.

Familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is a rare genetic disease caused by the loss of function mutations in the LCAT gene. LCAT deficiency is characterized by an abnormal lipoprotein profile with severe reduction in plasma levels of high-density lipoprotein (HDL) cholesterol and the accumulation of lipoprotein X (LpX). Renal failure is the major cause of morbidity and mortality in FLD patients; the pathogenesis of renal disease is only partly understood, but abnormalities in the lipoprotein profile could play a role in disease onset and progression. Serum and lipoprotein fractions from LCAT deficient carriers and controls were tested for renal toxicity on podocytes and tubular cells, and the underlying mechanisms were investigated at the cellular level. Both LpX and HDL from LCAT-deficient carriers triggered oxidative stress in renal cells, which culminated in cell apoptosis. These effects are partly explained by lipoprotein enrichment in unesterified cholesterol and ceramides, especially in the HDL fraction. Thus, alterations in lipoprotein composition could explain some of the nephrotoxic effects of LCAT deficient lipoproteins on podocytes and tubular cells.

Body Mass Index Modulates the Impact of Short-Term Exposure to Air Particulate Matter on High-Density Lipoprotein Function.

Air particulate matter (PM) exposure has been associated with increased cardiovascular risk, especially in obesity. By triggering inflammation and oxidative stress, PM could impact atheroprotection by high-density lipoproteins (HDL). The aim of the study was to assess the relationship between short-term exposure to PM and HDL function, and the modifying effect of body mass index (BMI). Daily exposures to PM10 and PM2.5 of 50 subjects with overweight/obesity and 41 healthy volunteers with BMI < 30 kg/m2 were obtained from fixed monitoring stations. HDL function was assessed as promotion of nitric oxide (NO) release by endothelial cells and reduction in cholesterol in macrophages. HDL-induced NO release progressively declined with the increase in BMI. No association was found between HDL function and PM exposure, but a modifying effect of BMI was observed. The positive association between PM10 exposure at day −1 and NO production found at normal BMI values was lost in participants with higher BMI. Similar results were obtained for the reduction in macrophage cholesterol. The loss of the compensatory response of HDL function to PM exposure at increasing BMI levels could contribute to the endothelial dysfunction induced by PM and help to explain the susceptibility of subjects with obesity to air pollution.

HDL-mediated reduction of cholesterol content inhibits the proliferation of prostate cancer cells induced by LDL: Role of ABCA1 and proteasome inhibition.

High-density lipoproteins (HDL) are well known for their atheroprotective function, mainly due to their ability to remove cell cholesterol and to exert antioxidant and anti-inflammatory activities. Through the same mechanisms HDL could also affect the development and progression of tumors. Cancer cells need cholesterol to proliferate, especially in hormone-dependent tumors, as prostate cancer (PCa). Aim of the study was to investigate the ability of HDL to modulate cholesterol content and metabolism in androgen receptor (AR)-positive and AR-null PCa cell lines and the consequences on cell proliferation. HDL inhibited colony formation of LNCaP and PC3 cells. HDL reduced cell cholesterol content and proliferation of LNCaP cells loaded with low-density lipoproteins but were not effective on PC3 cells. Here, the expression of the ATP-binding cassette transporter A1 (ABCA1) was markedly reduced due to proteasome degradation. Bortezomib, a proteasome inhibitor, restored ABCA1 expression and HDL ability to promote cholesterol removal from PC3; consequently, HDL inhibited the proliferation of PC3 cells induced by LDL only after bortezomib pre-treatment. In conclusion, the antiproliferative activity of HDL on AR-positive and AR-null PCa cells also rely on cholesterol removal, a process in which the ABCA1 transporter plays a key role.

High-density lipoproteins: A promising tool against cancer.

High-density lipoproteins (HDL) are well known for their protective role against the development and progression of atherosclerosis. Atheroprotection is mainly due to the key role of HDL within the reverse cholesterol transport, and to their ability to exert a series of antioxidant and anti-inflammatory activities. Through the same mechanisms HDL could also affect cancer cell proliferation and tumor progression. Many types of cancers share common alterations of cellular metabolism, including lipid metabolism. In this context, not only fatty acids but also cholesterol and its metabolites play a key role. HDL were shown to reduce cancer cell content of cholesterol, overall rewiring cholesterol homeostasis. In addition, HDL reduce oxidative stress and the levels of pro-inflammatory molecules in cancer cells and in the tumor microenvironment (TME). Here, HDL can also help in reverting tumor immune escape and in inhibiting angiogenesis. Interestingly, HDL are good candidates for drug delivery, targeting antineoplastic agents to the tumor mass mainly through their binding to the scavenger receptor BI. Since they could affect cancer development and progression per se, HDL-based drug delivery systems may render cancer cells more sensitive to antitumor agents and reduce the development of drug resistance.

Air Pollution: Another Threat to HDL Function.

Epidemiological studies have consistently demonstrated a positive association between exposure to air pollutants and the incidence of cardiovascular disease, with the strongest evidence for particles with a diameter < 2.5 µm (PM2.5). Therefore, air pollution has been included among the modifiable risk factor for cardiovascular outcomes as cardiovascular mortality, acute coronary syndrome, stroke, heart failure, and arrhythmias. Interestingly, the adverse effects of air pollution are more pronounced at higher levels of exposure but were also shown in countries with low levels of air pollution, indicating no apparent safe threshold. It is generally believed that exposure to air pollution in the long-term can accelerate atherosclerosis progression by promoting dyslipidemia, hypertension, and other metabolic disorders due to systemic inflammation and oxidative stress. Regarding high density lipoproteins (HDL), the impact of air pollution on plasma HDL-cholesterol levels is still debated, but there is accumulating evidence that HDL function can be impaired. In particular, the exposure to air pollution has been variably associated with a reduction in their cholesterol efflux capacity, antioxidant and anti-inflammatory potential, and ability to promote the release of nitric oxide. Further studies are needed to fully address the impact of various air pollutants on HDL functions and to elucidate the mechanisms responsible for HDL dysfunction.

LIPA gene mutations affect the composition of lipoproteins: Enrichment in ACAT-derived cholesteryl esters.

BACKGROUND AND AIMS: Cholesteryl ester storage disease (CESD) due to LIPA gene mutations is characterized by hepatic steatosis, hypercholesterolemia and hypoalphalipoproteinemia, exposing affected patients to an increased cardiovascular risk. Further insights into the impact of LIPA gene mutations on lipid/lipoprotein metabolism are limited. Aim of the study was to investigate the effect of carrying one or two mutant LIPA alleles on lipoprotein composition and function. METHODS: Lipoproteins were isolated from 6 adult CESD patients, 5 relatives carrying one mutant LIPA allele (carriers) and 12 sex/age matched controls. Lipid profile, lipoprotein mass composition and the fatty acid distribution of cholesteryl esters (CEs) were assessed. HDL function was evaluated as the ability to promote nitric oxide release by endothelial cells. RESULTS: Despite the lipid-lowering therapy, total cholesterol, LDL-cholesterol and triglycerides were increased in CESD patients compared to controls, while HDL-cholesterol was reduced. Carriers also displayed elevated total and LDL-cholesterol. Very low and intermediate density lipoproteins from CESD patients and carriers were enriched in CEs compared to the control ones, with a concomitant reduction of triglycerides. Fatty acid composition of CEs in serum and lipoproteins showed a depletion of linoleate content in CESD patients, due to the reduced LCAT activity. In CESD HDL, fatty acid distribution of CEs was shifted towards saturated ones, if compared to control HDL. The changes in HDL composition did not affect HDL ability to promote nitric oxide release by endothelial cells. CONCLUSIONS: LIPA gene mutations significantly affected plasma levels and lipid composition of lipoproteins, likely contributing to the increased cardiovascular risk of affected patients.

Role of Lipoproteins in the Microenvironment of Hormone-Dependent Cancers.

The tumor microenvironment (TME) is an attractive target to develop novel strategies for hormone-dependent cancers. Several molecules in the TME can favor tumor development and progression, including lipoproteins. Lipoproteins are taken up by cancer cells, providing them with cholesterol and fatty acids. Cholesterol regulates cell signaling and it is converted into a series of bioactive metabolites, including hormones. The conflicting results of epidemiological and interventional studies suggest that the local availability of lipoproteins in the TME is more relevant for cancer biology than their circulating levels. Thus, reducing lipoprotein uptake and stimulating cell cholesterol efflux to high-density lipoproteins (HDLs) can represent a novel adjuvant strategy for cancer management. HDL-like particles can also act as drug delivery systems for tumor targeting.

Lipid accumulation impairs lysosomal acid lipase activity in hepatocytes: Evidence in NAFLD patients and cell cultures.

AIMS: It has been hypothesized that the activity of lysosomal acid lipase (LAL), a key enzyme involved in lipid metabolism, is involved in the NAFLD phenotype. To clarify the role of LAL in NAFLD, we studied 164 consecutive patients with biopsy-proven NAFLD and fat-loaded HepG2 cells. METHODS: LAL activity was measured (i) on dried blood spots (DBS) from NAFLD patients and dyslipidemic subjects without fatty liver and (ii) on liver biopsies from NAFLD patients. LAL activity and expression were evaluated in HepG2 cells cultured in the presence of free fatty acids (FAs), with or without a PPAR-alpha agonist. RESULTS: LAL activity was significantly reduced in patients with NAFLD compared to dyslipidemic subjects. LAL activity measured in liver biopsies from NAFLD patients was highly correlated to that measured on DBS and was independent of LAL expression in the liver. In a fully adjusted model, LAL activity on DBS was associated only with platelets and, when normalized by platelet count, it did not differ according to fibrosis stage. In vitro, FA loading of HepG2 fully replicated the impairment of LAL activity observed in NALFD patients. In these cells, the activation of PPAR-alpha receptors prevented and corrected FA-induced LAL impairment, by stimulating FA oxidation and LAL expression. CONCLUSIONS: LAL activity is reduced in NAFLD patients, independently from disease progression. In vitro, impaired LAL activity induced by FA loading was rescued by PPAR-alpha activation. These data suggest that the pharmacological modulation of LAL should be explored in the management of NAFLD patients.

Treatment with fibrates is associated with higher LAL activity in dyslipidemic patients.

Lysosomal acid lipase (LAL) is responsible for the hydrolysis of cholesteryl esters (CE) and triglycerides (TG) within the lysosomes; generated cholesterol and free fatty acids (FFA) are released in the cytosol where they can regulate their own synthesis and metabolism. When LAL is not active, as in case of genetic mutations, CE and TG accumulate in the lysosomal compartment, while the lack of release of cholesterol and FFA in the cytosol leads to an upregulation of their synthesis. Thus, LAL plays a central role in the intracellular homeostasis of lipids. Since there are no indications about the effect of different lipid-lowering agents on LAL activity, aim of the study was to address the relationship between LAL activity and the type of lipid-lowering therapy in a cohort of dyslipidemic patients. LAL activity was measured on dried blood spot from 120 patients with hypercholesterolemia or mixed dyslipidemia and was negatively correlated to LDL-cholesterol levels. Among enrolled patients, ninety-one were taking one or more lipid-lowering drugs, as statins, fibrates, ezetimibe and omega-3 polyunsaturated fatty acids. When patients were stratified according to the type of lipid-lowering treatment, i.e. untreated, taking statins or taking fibrates, LAL activity was significantly higher in those with fibrates, even after adjustment for sex, age, BMI, lipid parameters, liver function, metabolic syndrome, diabetes and statin use. In a subset of patients tested after 3 months of treatment with micronized fenofibrate, LAL activity raised by 21%; the increase was negatively correlated with baseline LAL activity. Thus, the use of fibrates is independently associated with higher LAL activity in dyslipidemic patients, suggesting that the positive effects of PPAR-α activation on cellular and systemic lipid homeostasis can also include an improved LAL activity.

Recombinant LCAT (Lecithin:Cholesterol Acyltransferase) Rescues Defective HDL (High-Density Lipoprotein)-Mediated Endothelial Protection in Acute Coronary Syndrome.

Objective- Aim of this study was to evaluate changes in LCAT (lecithin:cholesterol acyltransferase) concentration and activity in patients with an acute coronary syndrome, to investigate if these changes are related to the compromised capacity of HDL (high-density lipoprotein) to promote endothelial nitric oxide (NO) production, and to assess if rhLCAT (recombinant human LCAT) can rescue the defective vasoprotective HDL function. Approach and Results- Thirty ST-segment-elevation myocardial infarction (STEMI) patients were enrolled, and plasma was collected at hospital admission, 48 and 72 hours thereafter, at hospital discharge, and at 30-day follow-up. Plasma LCAT concentration and activity were measured and related to the capacity of HDL to promote NO production in cultured endothelial cells. In vitro studies were performed in which STEMI patients' plasma was added with rhLCAT and HDL vasoprotective activity assessed by measuring NO production in endothelial cells. The plasma concentration of the LCAT enzyme significantly decreases during STEMI with a parallel significant reduction in LCAT activity. HDL isolated from STEMI patients progressively lose the capacity to promote NO production by endothelial cells, and the reduction is related to decreased LCAT concentration. In vitro incubation of STEMI patients' plasma with rhLCAT restores HDL ability to promote endothelial NO production, possibly related to significant modification in HDL phospholipid classes. Conclusions- Impairment of cholesterol esterification may be a major factor in the HDL dysfunction observed during acute coronary syndrome. rhLCAT is able to restore HDL-mediated NO production in vitro, suggesting LCAT as potential therapeutic target for restoring HDL functionality in acute coronary syndrome.

Dysfunctional HDL as a Therapeutic Target for Atherosclerosis Prevention.

Hypercholesterolemia is one of the main risk factors for the development of atherosclerosis. Among the various lipoprotein classes, however, high density lipoproteins (HDL) are inversely associated with the incidence of atherosclerosis, since they are able to exert a series of atheroprotective functions. The central role of HDL within the reverse cholesterol transport, their antioxidant and anti-inflammatory properties and their ability to preserve endothelial homeostasis are likely responsible for HDL-mediated atheroprotection. However, drugs that effectively raise HDL-C failed to result in a decreased incidence of cardiovascular event, suggesting that plasma levels of HDL-C and HDL function are not always related. Several evidences are showing that different pathologic conditions, especially those associated with an inflammatory response, can cause dramatic alterations of HDL protein and lipid cargo resulting in HDL dysfunction. Established and investigational drugs designed to affect lipid metabolism and to increase HDL-C are only partly effective in correcting HDL dysfunction.

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.

Effect of soy on metabolic syndrome and cardiovascular risk factors: a randomized controlled trial.

BACKGROUND: Cardiovascular diseases are currently the commonest cause of death worldwide. Different strategies for their primary prevention have been planned, taking into account the main known risk factors, which include an atherogenic lipid profile and visceral fat excess. METHODS: The study was designed as a randomized, parallel, single-center study with a nutritional intervention duration of 12 weeks. Whole soy foods corresponding to 30 g/day soy protein were given in substitution of animal foods containing the same protein amount. RESULTS: Soy nutritional intervention resulted in a reduction in the number of MetS features in 13/26 subjects. Moreover, in the soy group we observed a significant improvement of median percentage changes for body weight (-1.5 %) and BMI (-1.5 %), as well as for atherogenic lipid markers, namely TC (-4.85 %), LDL-C (-5.25 %), non-HDL-C (-7.14 %) and apoB (-14.8 %). Since the majority of the studied variables were strongly correlated, three factors were identified which explained the majority (52 %) of the total variance in the whole data set. Among them, factor 1, which loaded lipid and adipose variables, explained the 22 % of total variance, showing a statistically significant difference between treatment arms (p = 0.002). CONCLUSIONS: The inclusion of whole soy foods (corresponding to 30 g/day protein) in a lipid-lowering diet significantly improved a relevant set of biomarkers associated with cardiovascular risk.

Plasma cholesterol homeostasis, HDL remodeling and function during the acute phase reaction.

Acute phase reaction (APR) is a systemic inflammation triggered by several conditions associated with lipid profile alterations. We evaluated whether APR also associates with changes in cholesterol synthesis and absorption, HDL structure, composition, and cholesterol efflux capacity (CEC). We analyzed 59 subjects with APR related to infections, oncologic causes, or autoimmune diseases and 39 controls. We detected no difference in markers of cholesterol synthesis and absorption. Conversely, a significant reduction of LpA-I- and LpAI:AII-containing HDL (-28% and -44.8%, respectively) and of medium-sized HDL (-10.5%) occurred in APR. Total HDL CEC was impaired in APR subjects (-18%). Evaluating specific CEC pathways, we found significant reductions in CEC by aqueous diffusion and by the transporters scavenger receptor B-I and ABCG1 (-25.5, -41.1 and -30.4%, respectively). ABCA1-mediated CEC was not affected. Analyses adjusted for age and gender provided similar results. In addition, correcting for HDL-cholesterol (HDL-C) levels, the differences in aqueous diffusion total and ABCG1-CEC remained significant. APR subjects displayed higher levels of HDL serum amyloid A (+20-folds; P = 0.003). In conclusion, APR does not associate with cholesterol synthesis and absorption changes but with alterations of HDL composition and a marked impairment of HDL CEC, partly independent of HDL-C serum level reduction.

Depletion in LpA-I:A-II particles enhances HDL-mediated endothelial protection in familial LCAT deficiency.

The aim of this study was to evaluate the vasoprotective effects of HDL isolated from carriers of LCAT deficiency, which are characterized by a selective depletion of LpA-I:A-II particles and predominance of preß migrating HDL. HDLs were isolated from LCAT-deficient carriers and tested in vitro for their capacity to promote NO production and to inhibit vascular cell adhesion molecule-1 (VCAM-1) expression in cultured endothelial cells. HDLs from carriers were more effective than control HDLs in promoting eNOS activation with a gene-dose-dependent effect (PTrend = 0.048). As a consequence, NO production induced by HDL from carriers was significantly higher than that promoted by control HDL (1.63 ± 0.24-fold vs. 1.34 ± 0.07-fold, P = 0.031). HDLs from carriers were also more effective than control HDLs in inhibiting the expression of VCAM-1 (homozygotes, 65.0 ± 8.6%; heterozygotes, 53.1 ± 7.2%; controls, 44.4 ± 4.1%; PTrend = 0.0003). The increased efficiency of carrier HDL was likely due to the depletion in LpA-I:A-II particles. The in vitro findings might explain why carriers of LCAT deficiency showed flow-mediated vasodilation and plasma-soluble cell adhesion molecule concentrations comparable to controls, despite low HDL-cholesterol levels. These results indicate that selective depletion of apoA-II-containing HDL, as observed in carriers of LCAT deficiency, leads to an increased capacity of HDL to stimulate endothelial NO production, suggesting that changes in HDL apolipoprotein composition may be the target of therapeutic interventions designed to improve HDL functionality.

Persistent changes in lipoprotein lipids after a single infusion of ascending doses of MDCO-216 (apoA-IMilano/POPC) in healthy volunteers and stable coronary artery disease patients.

BACKGROUND AND AIMS: Effects of single ascending doses of MDCO-216 on plasma lipid and lipoprotein levels were assessed in human healthy volunteers and in patients with stable coronary artery disease (CAD). METHODS: MDCO-216 was infused at a single dose of 5, 10, 20, 30 or 40 mg/kg over 2 h and blood was collected at 2, 4, 8, 24, 48, 168 and 720 h after start of infusion (ASOI). Lipoprotein lipids were assessed by FLPC and by 1H NMR. RESULTS: Plasma concentrations of free cholesterol (FC) displayed a rapid and dose-dependent rise, peaking at 8 h, but remaining above baseline until 48 h ASOI, whereas levels of esterified cholesterol (CE) increased at lower doses but not at higher doses, and even decreased below baseline at the highest dose. Plasma cholesterol esterification rate (CER) decreased with a first nadir between 4 and 8 h and a second nadir at 48 h ASOI. Taken over all subjects receiving MDCO-216, the increase in FC at 8 h correlated inversely with the drop in CER at 4 h but positively with the increase in basal and scavenger receptor class B type I (SR-BI)-mediated cholesterol efflux capacities at 2 h ASOI. Upon FPLC analysis, FC was found to increase first in high density lipoproteins (HDL) and very low density lipoproteins (VLDL) and later (at 48 or 168 h ASOI) in low density lipoproteins (LDL). CE initially decreased in LDL and HDL but after 24 h started to increase in VLDL and LDL whereas HDL-CE was still below baseline at 48 h. Phospholipids (PL) showed the same pattern as FC. Triglycerides (TG) also rose rapidly, most prominently in VLDL, but also in LDL and HDL. Apolipoprotein E (Apo-E) in VLDL increased at 4-8 h but returned to baseline at 24 h ASOI. 1H NMR analysis showed a rapid and dose-dependent increase in HDL particle size, peaking at 2 h and returning to baseline at 24 h, and a small increase in HDL particle concentration. After infusion of the 40 mg/kg dose, LDL and VLDL-particles also increased in number and size. CONCLUSIONS: A single administration of MDCO-216 caused rapid changes in lipid levels and lipoprotein composition, some of which persisted for at least 7 days.

An Essential Role for Liver ERα in Coupling Hepatic Metabolism to the Reproductive Cycle.

Lipoprotein synthesis is controlled by estrogens, but the exact mechanisms underpinning this regulation and the role of the hepatic estrogen receptor α (ERα) in cholesterol physiology are unclear. Utilizing a mouse model involving selective ablation of ERα in the liver, we demonstrate that hepatic ERα couples lipid metabolism to the reproductive cycle. We show that this receptor regulates the synthesis of cholesterol transport proteins, enzymes for lipoprotein remodeling, and receptors for cholesterol uptake. Additionally, ERα is indispensable during proestrus for the generation of high-density lipoproteins efficient in eliciting cholesterol efflux from macrophages. We propose that a specific interaction with liver X receptor α (LXRα) mediates the broad effects of ERα on the hepatic lipid metabolism.

Protective Effects of HDL Against Ischemia/Reperfusion Injury.

Several lines of evidence suggest that, besides being a strong independent predictor of the occurrence of primary coronary events, a low plasma high density lipoprotein (HDL) cholesterol level is also associated with short- and long-term unfavorable prognosis in patients, who have recovered from a myocardial infarction, suggesting a direct detrimental effect of low HDL on post-ischemic myocardial function. Experiments performed in ex vivo and in vivo models of myocardial ischemia/reperfusion (I/R) injury have clearly shown that HDL are able to preserve cardiac function when given before ischemia or at reperfusion; the protective effects of HDL against I/R injury have been also confirmed in other tissues and organs, as brain and hind limb. HDL were shown to act on coronary endothelial cells, by limiting the increase of endothelium permeability and promoting vasodilation and neoangiogenesis, on white blood cells, by reducing their infiltration into the ischemic tissue and the release of pro-inflammatory and matrix-degrading molecules, and on cardiomyocytes, by preventing the activation of the apoptotic cascade. Synthetic HDL retains the cardioprotective activity of plasma-derived HDL and may become a useful adjunctive therapy to improve clinical outcomes in patients with acute coronary syndromes or undergoing coronary procedures.

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

HDL (high-density lipoproteins) exert anti-thrombotic activities by preventing platelet adhesion and activation and by stimulating the protein C pathway and fibrinolysis. The aim of the present study was to assess the effect of plasma-derived and synthetic HDL on endothelial and monocyte expression of TF (tissue factor), the primary initiator of coagulation. HDL inhibited TF expression and activity in stimulated endothelial cells and monocytes in a dose-dependent way. Synthetic HDL fully retain the ability to inhibit TF expression in a dose-dependent manner; lipid-free apoA-I (apolipoprotein A-I) was not effective and neither was sphingosine 1-phosphate involved. HDL-mediated TF inhibition was due to a modulation of cellular cholesterol content through the interaction with SR-BI (scavenger receptor BI); downstream, HDL inhibited the activation of p38 MAPK (mitogen-activated protein kinase) and the repression of the PI3K (phosphoinositide 3-kinase) pathway responsible for TF expression. In vivo, human apoA-I-transgenic mice displayed a reduced aortic TF expression compared with wild-type animals and TF plasma levels were increased in subjects with low HDL-C (HDL-cholesterol) levels compared with high HDL-C subjects. Thus the anti-thrombotic activity of HDL could also be mediated by the inhibition of TF expression and activity in endothelial cells and monocytes; synthetic HDL retain the inhibitory activity of plasma-derived HDL, supporting the hypothesis that synthetic HDL infusion may be beneficial in the setting of acute coronary syndrome.

Cholesterol trafficking-related serum lipoprotein functions in children with cholesteryl ester storage disease.

OBJECTIVE: Serum lipoproteins influence cell cholesterol content by delivering and removing cholesterol to/from cells, functions mainly exerted by LDL and HDL, respectively. Especially in the case of HDL, structure and composition are crucial for function, beyond serum levels. Cholesteryl ester storage disease (CESD) is caused by LIPA gene mutations and reduced activity of lysosomal acid lipase (LAL), the enzyme responsible for hydrolysis of cholesteryl esters and TG. CESD patients typically present dyslipidaemia, liver damage and premature atherosclerosis. The objective of this work was to evaluate serum HDL cholesterol efflux capacity (CEC) and serum cholesterol loading capacity (CLC) in CESD pediatric patients and to study lipoprotein qualitative modifications. METHODS: HDL CEC was evaluated by radioisotopic techniques, serum CLC was measured by a fluorimetric assay, HDL subclasses were determined by two-dimensional electrophoresis. RESULTS: CESD patients (n = 3) displayed on average increased LDL cholesterol (+163%; p = 0.019), TG (+203; p = 0.012), phospholipids (+40%; p = 0.024) and lower HDL cholesterol (-57%; p = 0.012) compared to controls (n = 9). CESD HDL CEC was impaired both as a whole (average reduction of 26%; p < 0.0001) and with respect to specific membrane cholesterol transporters (-23% for aqueous diffusion; p = 0.005; -32% for ABCA1-efflux; p = 0.0002; -60% for SR-BI-efflux; p < 0.0001; -42% for ABCG1-efflux p = 0.0003). A marked reduction in the pre-ß HDL concentration (-69%; p = 0.012) was detected. Finally, CESD serum CLC was significantly increased (+21%; p = 0.0007). CONCLUSION: These new data demonstrate that the pro-atherogenic modifications of serum include disturbances in lipoprotein functions involved in cell cholesterol homeostasis occurring from very early age in CESD patients.