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Biomedical subjects

A L Catapano

Publications and source records attributed to A L Catapano.

At least 19 recordsLinked to original sources
PubMed2006

Role of vitamin E-coated membrane in reducing advanced glycation end products in hemodialysis patients: a pilot study.

INTRODUCTION: Advanced glycation end products (AGEs) are markers of oxidative stress. AIMS: To assess if a vitamin-E-coated dialyzer affects plasma AGE levels and endothelial function in hemodialysis patients. METHODS: 16 patients were dialyzed with a synthetic modified cellulose membrane (SMC, n = 8) or a vitamin E-coated dialyzer (n = 8), respectively. At week 32 endothelial function was determined as brachial artery flow-mediated dilatation (FMD). Total AGEs, free pentosidine (FP), protein-bound pentosidine (BP) and autoantibodies against oxidized LDL (ox-LDL-autoantibodies) were assessed at baseline (T0) and at 16, 32, 40 and 42 weeks (T16, T32, T40 and T42). RESULTS: At T16 and T32 FP and BP were lower in vitamin E than in SMC (T 16: 88.7 +/- 8.96 vs. 124.2 +/- 11.90 pmol/ml plasma; p = 0.04, and 22.9 +/- 2.99 vs. 32.8 +/- 2.98 pmol/mg proteins; p = 0.04. T32: 78.7 +/- 8.54 vs. 123.7 +/- 10.15 pmol/ml plasma; p = 0.007, and 19.9 +/- 2.0 vs. 33.67 +/- 2.41 pmol/mg proteins; p = 0.001). In vitamin E, AGEs were lower at T32, T40 and T42 (946.7 +/- 80.91 vs. 1,351.2 +/- 179.33 AU/ml, p = 0.05; 986.9 +/- 59.63 vs. 1,509.9 +/- 154.17 AU/ml, p = 0.013; 890.3 +/- 73.70 vs. 1,453.9 +/- 153.16 AU/ml, p = 0.009). At T32 AGEs, ox-LDL autoantibodies and FMD were inversely correlated (R = -0.70 p = 0.007 and R = -0.59, p = 0.04, respectively). CONCLUSIONS: Vit E-coated membrane reduces plasma AGEs levels and AGEs values are negatively correlated with FMD.

Aged↗
PubMed2006

Triglyceride-rich lipoproteins from hypertriglyceridemic subjects induce a pro-inflammatory response in the endothelium: Molecular mechanisms and gene expression studies.

Triglyceride-rich lipoproteins (TGRLs) are a cardiovascular risk factor and induce endothelial dysfunction. In the present study we investigated the effects of TGRLs from type IV hyperlipidemic and normolipidemic subjects on endothelial activation focusing on the effects on intracellular pathways and gene expression. A total of 54 subjects, 30 hypertriglyceridemic (triglyceride (TG) levels 284+/-101 mg/dl) and 23 normotriglyceridemic (TG levels 109+/-40 mg/dl) were enrolled as lipoprotein donors. TGRLs were isolated from hypertriglyceridemic (H-TGRL) and normotriglyceridemic (N-TGRL) subjects. RNA from human endothelial cells incubated with N-TGRL or H-TGRL was prepared for cDNA microarray analyses. Western blotting was used to study intracellular signaling pathways. Regulated genes were further studied with real-time PCR, immunofluorescence and FACS. Furthermore, a protein/DNA array and chromatin-immunoprecipitation were used to identify transcription factors involved in the observed effects. Both N-TGRL and H-TGRL activated ERK1/2 and p38 MAPK. However, there were differences in the pattern of upregulated target genes between the two types of lipoproteins in HUVECs and/or HAECs: PAI-1, VCAM-1, ELAM-1 and MCP-1 were upregulated by both N-TGRL and H-TGRL, while PECAM-1, IL-6 and ADAMTs1 were selectively upregulated by H-TGRL. Chromatin immunoprecipitation analysis demonstrated the involvement of transcription factors NF-kB and CREB in the activation of these genes. These results support the possible involvement of hypertriglyceridemic TGRLs in endothelial dysfunction via induction of a pro-inflammatory and pro-thrombotic state.

Adult↗
PubMed2005

Effect of the Toll-like receptor 4 (TLR-4) variants on intima-media thickness and monocyte-derived macrophage response to LPS.

OBJECTIVES: Toll-like receptor 4 (TLR-4) is believed to contribute to the initiation and progression of atherosclerosis. The association of the D299G polymorphism of the TLR-4 gene with the progression of coronary and carotid atherosclerosis, risk of cardiovascular events and myocardial infarction is controversial. We have investigated whether the presence of the D299G polymorphism and the co-segregated T399I polymorphism affects the intima-media thickness (IMT) in the general population. SUBJECTS: The PLIC study population (n = 1256) was genotyped for the D299G and the T399I polymorphisms. RESULTS: The presence of both the D299G and T399I alleles was observed in the 13.0% of the population, carriers of the T399I alone were 1.8% and of the D299G alone were 0.9%. No difference in IMT was detected within the carriers of the D299G and T399I alleles and the wild-type subjects in the PLIC population. Furthermore, we investigated whether monocyte from D299G to T399I subjects present a defective response to CD40, interleukin (IL)-6, monocyte chemotactic protein (MCP)-1, cyclo-oxygenase (COX)-2 and PTX3 expression induced by lipopolysaccharide (LPS). When the monocyte-derived macrophages of these subjects were challenged with LPS (1 mug mL(-1)), no impact of the polymorphisms on the induction of CD40, MCP-1 and PTX3 was observed. Only IL-6 and COX-2 induction by LPS resulted reduced in the D299G/T399I carriers. CONCLUSION: The presence of the D299G and T399I polymorphisms of the TLR-4 gene does not play a major role on the progression of carotid atherosclerosis. Macrophages from the subjects carrying the polymorphisms show an impaired response to LPS limited only to a IL-6 and COX-2.

Alleles↗
PubMed2005

Liver X receptor and retinoic X receptor agonists modulate the expression of genes involved in lipid metabolism in human endothelial cells.

The cooperation of liver X receptors (LXRs) alpha and beta, and retinoic X receptor (RXR) modulate the expression of several genes involved in lipid metabolism in hepatocyte and macrophages. Using cDNA microarray technology, we have shown previously that several of these genes are also expressed in endothelial cells. In the present study, we investigated whether the activation of LXR and RXR affects the expression of genes involved in lipid metabolism in human endothelial cells. Relative expression of ABCA-1, CETP, SR-B1, EL, LPL, PLTP, ApoE and LDLR was investigated in HUVECs, human fibroblasts (hFB) and HepG2 cells by quantitative real-time PCR. For CETP and EL mRNA expression, the results were HUVECs > hFB > HEPG2; for PLTP, LDLR and LPL: hFB > HUVECs > HEPG2; for SR-B1 and ApoE: HEPG2 > HUVECs > hFB; and for ABCA-1 HEPG2: > hFB > HUVECs. Incubation of HUVECs with LXR agonists as 22-(R)-hydroxycholesterol (22-(R)-HC) or T0901317-induced ABCA1 (20.1- and 17.8-fold), LPL (3.46- and 7.03-fold) and CETP (6.34- and 3.98-fold) expression; EL, LDLR and SR-B1 expression was induced only upon incubation with T0901317 (2.40-, 2.83- and 2.19-fold, respectively) while 22-(R)-HC had no effect on EL and SR-B1 expression (0.8- and 0.9-fold) and decreased LDLR expression (0.4-fold). No effect of either 22-(R)-HC or T0901317 on PLTP and ApoE expression was observed. The RXR agonist, 9-cis retinoic acid (9CRA) alone induced the expression of CETP, LPL and SR-B1 (2.8-, 8.2- and 2.4-fold). No effect of 9CRA on ABCA-1, EL, PLTP, ApoE, and LDLR expression was observed. Association of 9CRA with 22-(R)-HC or T0901317 increased the expression of CETP and LPL while no effect on ABCA-1 or LDLR was observed. Activation of LXRs and RXRs in endothelial cells represents a new target of LXR and RXR agonist in the arterial wall. Modulation of gene expression in the endothelium should be taken into account when studying the effects of LXR and RXR agonists on lipid metabolism in the arterial wall.

ATP Binding Cassette Transporter 1↗
PubMed2004

HDL3 induces cyclooxygenase-2 expression and prostacyclin release in human endothelial cells via a p38 MAPK/CRE-dependent pathway: effects on COX-2/PGI-synthase coupling.

OBJECTIVE: In endothelial cells, cyclooxygenase-1 (COX-1) and COX-2 both contribute to prostacyclin production. Recent findings suggest that COX-2 contributes significantly to systemic prostacyclin synthesis in humans; whether COX-2 inhibition is related to an increased cardiovascular risk is undergoing debate. HDLs have been shown to increase prostacyclin synthesis, thus in the present study we investigated the molecular mechanisms involved in this effect in endothelial cells. METHODS AND RESULTS: HDL3 (30 microg/mL) induced COX-2 expression in a time- and dose-dependent manner. COX-2 was found mainly in the perinuclear area where it co-localizes with PGI synthase. Transient transfection experiments showed that CRE is required for HDL-induced COX-2 transcription, and we demonstrated that p38 MAPK activation by HDL3 is involved in COX-2 mRNA transcription and stabilization. As a consequence of COX-2-induction by HDL3 prostacyclin production increased, incubation with a COX-2 selective inhibitor blocked this effect. Moreover, HDL3 increased caveolin-1 phosphorylation, thus promoting PGI-synthase shuttling from the membrane to the perinuclear area. CONCLUSIONS: We conclude that in endothelial cells, HDL modulates COX-2/PGI-S activity via both p38 MAPK-dependent COX-2 mRNA stability and transcription and both caveolin-1-dependent PGI-synthase shuttling and COX-2 coupling. The understanding of these mechanisms may provide new insights into the antiatherogenic role of HDL.

Caveolin 1↗
PubMed2004

Lipid lowering activity of drugs affecting cholesterol absorption.

AIM: Dietary cholesterol absorption, endogenous cholesterol synthesis and biliary cholesterol excretion regulate whole body cholesterol balance as a result of biotransformation into bile acids or direct cholesterol excretion. Recent studies have significantly advanced our understanding of intestinal sterol absorption at molecular level. This review concentrates on two major issues: the mechanisms of sterol absorption, and the currently available or experimental drugs that affect this pathway. DATA SYNTHESIS: Nuclear hormone receptors, such as the liver X, farnesoid X and retinoid X receptors, regulate the absorption of dietary sterols by modulating the transcription of several genes involved in cholesterol metabolism, The ABC proteins transport dietary cholesterol from enterocytes back to the intestinal lumen, thus limiting the amount of absorbed cholesterol. By means of the same mechanism, ABC transporters also provide an efficient barrier against the absorption of plant sterols. Phytosterols, bile acid sequestrants, ezetimibe and ACAT inhibitors are possible means of affecting these pathways. CONCLUSION: In addition to providing an insight into the molecular mechanisms of sterol absorption, these recent findings may lead to new therapeutic options for the treatment of hypercholesterolemia. This is particularly true in the case of patients at high risk of coronary artery disease requiring aggressive lipid-lowering therapy combining a statin with drugs affecting cholesterol absorption in order to ensure the optimal management of dyslipidemia.

Anticholesteremic Agents↗
PubMed2004

Native LDL and oxidized LDL modulate cyclooxygenase-2 expression in HUVECs through a p38-MAPK, NF-kappaB, CRE dependent pathway and affect PGE2 synthesis.

Native low density lipoproteins (n-LDL) and oxidized low density lipoproteins (Ox-LDL) play a central role in atherogenesis and possess a wide variety of biological properties. We investigated whether n-LDL or Ox-LDL modulate cyclooxygenase-1 and -2 (Cox-1 and Cox-2) expression and prostaglandins release in human endothelial cells via an MAPK-dependent pathway. HUVECs were incubated in the presence of n-LDL or Ox-LDL (30 micro g/ml for both) for 2-15 h. Real-time PCR, western blotting and immunocytochemistry were used to investigate Cox-1 and Cox-2 expression. N-LDL and Ox-LDL induced Cox-2 expression in a time- and dose-dependent manner. The Cox-2 protein was strongly induced 2 h after exposure to n-LDL or Ox-LDL, the induction was maximal after 4 h and sustained for at least 8 h. The effect was specific for Cox-2, as Cox-1 expression was not modulated either by n-LDL or by Ox-LDL. The induction of Cox-2 expression was mainly dependent on the activation of p38 MAPK. Transient transfection analysis using a Cox-2 promoter showed that n-LDL and Ox-LDL exert their effects at the transcriptional level via NF-kappaB and CREB activation. N-LDL and Ox-LDL increased PGE2 release in a Cox-2-dependent manner while TXA2 and PGI2 release were not affected either by n-LDL or Ox-LDL. The finding that n-LDL and Ox-LDL induces Cox-2 in human endothelial cells through a p38 MAPK, NF-kappaB, CREB dependent pathway thus modulating PGE2 release, suggests a new mechanism by which these lipoproteins induce endothelial dysfunction, sustaining inflammatory processes in the arterial wall.

Cells, Cultured↗
PubMed2003

Gene expression and intracellular pathways involved in endothelial dysfunction induced by VLDL and oxidised VLDL.

OBJECTIVES: The molecular mechanisms underlying the relationship between elevated plasma concentrations of triglyceride-rich lipoproteins and coronary artery disease remain uncertain. In the present work, we investigated the gene expression pattern and intracellular pathways in human endothelial cells incubated with very low density lipoproteins (VLDL). Moreover, as VLDL can enter the arterial wall and undergo oxidative modification, we compared the VLDL-induced expression pattern with the one of oxidised VLDL (Ox-VLDL). METHODS: Total RNA from endothelial cells incubated with 75 microg/ml VLDL or Ox-VLDL and total RNA from endothelial cells under basal conditions were hybridised to identical microarrays containing 8411 genes. Seven clusters of expression profiles were identified. This pattern was validated by quantitative real-time PCR of selected genes. The intracellular pathway involved in VLDL or Ox-VLDL mediated endothelial responses were also investigated. RESULTS AND CONCLUSION: VLDL predominantly activated the ERK1/2 pathway while P38 MAPK was the main target of Ox-VLDL. CREB and NF-kappa B were activated by both VLDL and Ox-VLDL. Real-time PCR demonstrated that VLDL induced matrix metalloproteinase-2 (5.47+/-1.74 fold), CD38 (2.38+/-0.23) and transforming growth factor-alpha (2.51+/-0.30) expression. Ox-VLDL was found to induce interleukin-15 (2.10+/-0.48) and macrophage migration inhibitory factor (3.19+/-0.07) expression. In addition, several genes implicated in endothelial cell activation and damage/proliferation were identified by the array analysis. Ox-VLDL was found to promote the generation of reactive oxygen species and exert a cytotoxic effect, while VLDL lacks these effects. These findings confirm the involvement of VLDL and Ox-VLDL in endothelial dysfunction and suggest new genes and molecular mechanisms involved in these actions.

Cell Death↗
PubMed2002

Apoptosis and proliferation of endothelial cells in early atherosclerotic lesions: possible role of oxidised LDL.

BACKGROUND AND AIM: Evidence for apoptosis has been found in advanced atherosclerotic lesions, but the factors triggering it are poorly understood. Oxidised low-density lipoproteins (LDLs) are cytotoxic to a variety of cells and induce the apoptosis of smooth muscle cells (SMC), fibroblast, macrophages and endothelial cells in vitro. The aim of this study was to investigate apoptotic cell death in the early phases of aortic atherosclerosis in rabbits, and whether oxidised LDLs colocalize ex vivo with apoptotic cells in atherosclerotic lesions in cholesterol-fed rabbits. METHODS AND RESULTS: Male albino New Zealand rabbits were fed a standard diet or a diet containing 1.2% cholesterol for 60 days. The aortic arch of each animal was sectioned and stained with antibodies against SMC, endothelial cells, macrophages and oxidised LDLs or for proteins involved in apoptotic pathways such as Fas, Bax, Bcl2, and caspase 3. The nuclei in adjacent sections were stained with Hoechst 33258, TUNEL and for the proliferating cell nuclear antigen (PCNA). Early atherosclerotic lesions were characterised by intimal thickening and the presence of SMC and macrophages. The percentage of apoptotic cells, calculated as the ratio of TUNEL-positive nuclei to total nuclei was 32.6 +/- 3.73% in the lesions and 55.9 +/- 2.36% in the endothelium. As it has been reported that nuclei undergoing active gene transcription can be TUNEL positive, we evaluated the percentage of PCNA-positive cells, which proved to be 45.2 +/- 4.68% along the endothelium and 22.3 +/- 2.7% in the intima. The true percentage of apoptotic cells was therefore about 10% in both cases. Fas, Bax and caspase3 signals were mainly located in the endothelium and SMC proximal to the lumen, whereas Bcl2 colocalized with macrophages and SMC deeper in the lesions. Abundant oxidised LDL epitopes were detected in areas of lipid accumulation and along the endothelium, mainly in the areas in which TUNEL and PCNA-positive cells were localised. CONCLUSIONS: Our findings may be taken as ex vivo indications of an apoptotic and proliferating role of oxidised LDLs as previously shown in vitro, and may at least partially account for the endothelial dysfunction that can be rapidly induced by hypercholesterolemia.

Animals↗
PubMed2001

Epitope mapping analysis of apolipoprotein B-100 using a surface plasmon resonance-based biosensor.

Using a surface plasmon resonance (SPR)-based biosensor (BIA-technology), we have studied the interaction of ten different murine monoclonal antibodies (mAbs, all IgG(1)), raised against the main protein constituent of human low density lipoprotein (LDL), i.e. the apolipoprotein B-100 (apoB-100). These mAbs identify distinct domains on apoB-100, relevant to LDL-receptor interaction: epitopes in the amino-terminal region (mAbs L7, L9, L10 and L11: aa 1-1297) and in the middle region (mAb 6B: aa 1480-1693; mAbs 2A, 3B: aa 2152-2377; mAbs 9A, L2 and L4: aa 2657-3248) of native apoB-100. A multisite binding analysis was performed to further characterize the epitopes recognized by all these mAbs. A rabbit anti-mouse IgG(1)-Fc antibody (RAM.Fc) was first coupled to the gold surface in order to capture one anti-human apoB-100 mAb. ApoB-100 protein was subsequently injected and allowed to react with this immobilized, oriented antibody. Multisite binding assays were then performed, by sequentially flowing other mAbs, in different orders, over the sensing surface. The capacity of each mAb to interact with the entrapped apoB-100 in a multimolecular complex was monitored in real time by SPR. The results achieved were comparable to those obtained by western immunoblotting using the same reagents. However, SPR ensures a more detailed epitope identification, demonstrating that BIA-technology can be successfully used for mapping distinct epitopes on apoB-100 protein in solution dispensing with labels and secondary tracers; moreover, compared with conventional immunoassays, it is significantly time saving (CNR-P.F. MADESS 2).

Animals↗
PubMed2001

Overexpression of inducible heat shock protein 70 in Cos-1 cells fails to protect from cytotoxicity of oxidized ldls.

Oxidized low density lipoproteins (OxLDLs) are believed to play a central role in atherogenesis and to possess a wide variety of biological properties; among them, OxLDLs are cytotoxic to cultured vascular cells in that they induce necrosis and apoptosis. Moreover, OxLDLs are known to induce the expression of heat shock protein 70 (Hsp70), a protein that protects cells from several cytotoxic stimuli. To determine whether Hsp70 can protect cells against OxLDL-induced cytotoxicity, COS-1 cells were transfected with a construct containing human Hsp70. A number of cell lines permanently expressing Hsp70 were obtained, 1 of which (cos-Hsp70/10, with high Hsp70 expression) was selected for further studies. Hsp70 overexpression protected cells from toxic stimuli, such as H(2)O(2), UV irradiation, and heat shock, suggesting that the overexpressed protein was functional. When incubated with OxLDLs, however, the clone overexpressing Hsp70 showed a significant decrease in viability, as determined by the [(3)H]adenine release assay (319.8+/-3.16% of control for transfected cells versus 217.6+/-6.08% for control cells exposed to 100 microgram protein/mL of OxLDL), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (12.5+/-0.9% versus 28.9+/-1.99% of control, respectively), and LDH release (48.4+/-0.04% versus 15.2+/-0.06% of control cells). The increased expression of BAX and the decreased expression of Bcl-2 (a proapoptotic and an antiapoptotic protein, respectively) in cos-Hsp70/10 cells and in control cells on incubation with OxLDLs suggested that overexpression of Hsp70 did not confer protection against apoptosis induced by OxLDLs. The analysis of nucleosome content and the nuclear staining with Hoechst 33258 confirmed this finding. These data suggest that overexpression of Hsp70 not only fails to protect COS-1 cells against OxLDL-induced apoptosis but rather confers a higher sensitivity to the cytotoxic action of these lipoproteins. Thus, the Hsp70 response, although induced by OxLDLs, cannot protect cells from lipoprotein toxicity.

Animals↗
PubMed2000

Treatment of severe hypercholesterolemia in apolipoprotein E-deficient mice by intramuscular injection of plasmid DNA.

We report on systemic delivery and long-term biological effects of apolipoprotein E (apoE) obtained by intramuscular (i.m.) plasmid DNA injection. ApoE plays an important role in lipoprotein catabolism and apoE knock-out mice develop severe hypercholesterolemia and diffuse atherosclerosis. We have injected apoE-deficient mice with 80 microg of a plasmid vector (pCMV-E3) encoding the human apoE3 cDNA under the control of the CMV promoter-enhancer in both posterior legs. Local expression of the transgene was demonstrated throughout 16 weeks. Human apoE3 recombinant protein reached 0.6 ng/ml serum level. After i.m. injection of pCMV-E3 expression vector the mean serum cholesterol concentrations decreased from 439 +/- 57 mg/dl to 253 +/- 99 mg/dl (P < 0.05) 2 weeks after injection and persisted at a significantly reduced level throughout the 16 weeks observation period (P < 0.005). Serum cholesterol was unaffected and reached an absolute level of 636 +/- 67 mg/dl in control groups. Finally, injection of pCMV-E3 into apoE-deficient mice resulted in a redistribution of cholesterol content between lipoprotein fractions, with a marked decrease in VLDL, IDL and LDL cholesterol content and an increase in HDL cholesterol. These results demonstrate that severe hypercholesterolemia in apoE-deficient mice can be effectively reversed by i.m. DNA injection, and indicate that this approach could represent a useful tool to correct several hyperlipidemic conditions resulting in atherosclerosis.

Analysis of Variance↗
PubMed2000

Low density lipoprotein oxidation, antioxidants, and atherosclerosis.

Oxidized low density lipoproteins (LDLs) are believed to be the most atherogenic form of LDL. However, although a number of experimental data support this concept, the protective role of antioxidants that may prevent LDL oxidation in atherosclerosis is only partially confirmed by studies in humans. Observational and epidemiologic data as well as randomized trials failed to provide clear-cut indications because of mixed results on the protective role of antioxidants against cardiovascular diseases. In spite of the lack of a general consensus, recent data reinforce the concept that a regular intake of antioxidants present in food blocks the progression of atherosclerosis and that the reduced oxidisability of LDL may represent a good marker to follow the action of antioxidants. When it becomes possible to monitor the efficacy of any antioxidant therapy with validated markers of oxidation, the potential influence of vitamins and antioxidants on coronary artery disease will eventually be resolved.

Antioxidants↗
PubMed2000

Oxidized lipoproteins and endothelium.

Endothelium is an early target of pro-atherosclerotic events, which may result in functional and morphological perturbations. Oxidized low density lipoproteins, an atherogenic factor with strong cytotoxicity, may potentially contribute to altered endothelial function through the activation of a stress response, which would rescue cells to full vitality, or, conversely, by leading to cell death. Evidence is presented here for the ability of chemically oxidized low density lipoproteins to induce the synthesis of the inducible form of heat shock protein 70 in cultured human endothelial cells, and for the association of epitopes of these modified lipoproteins with apoptotic endothelial cells in aortic sections from hypercholesterolemic rabbits.

Animals↗
PubMed2000

Identification of domains in apoA-I susceptible to proteolysis by mast cell chymase. Implications for HDL function.

When stimulated, rat serosal mast cells degranulate and secrete a cytoplasmic neutral protease, chymase. We studied the fragmentation of apolipoprotein (apo) A-I during proteolysis of HDL(3) by chymase, and examined how chymase-dependent proteolysis interfered with the binding of eight murine monoclonal antibodies (Mabs) against functional domains of apoA-I. Size exclusion chromatography of HDL(3) revealed that proteolysis for up to 24 h did not alter the integrity of the alpha-migrating HDL, whereas a minor peak containing particles of smaller size with prebeta mobility disappeared after as little as 15 min of incubation. At the same time, generation of a large (26 kDa) polypeptide containing the N-terminus of apoA-I was detected. This large fragment and other medium-sized fragments of apoA-I produced after prolonged treatment with chymase were found to be associated with the alphaHDL; meanwhile, small lipid-free peptides were rapidly produced. Incubation of HDL(3) with chymase inhibited binding of Mab A-I-9 (specific for prebeta(1)HDL) most rapidly (within 15 min) of the eight studied Mabs. This rapid loss of binding was paralleled by a similar reduction in the ability of HDL(3) to induce high-affinity efflux of cholesterol from macrophage foam cells, indicating that proteolysis had destroyed an epitope that is critical for this function. In sharp contrast, prolonged degradation of HDL(3) by chymase failed to reduce the ability of HDL(3) to activate LCAT, even though it led to modification of three epitopes in the central region of apoA-I that are involved in lecithin cholesterol acyltransferase (LCAT) activation. This differential sensitivity of the two key functions of HDL(3) to the proteolytic action of mast cell chymase is compatible with the notion that, in reverse cholesterol transport, intactness of apoA-I is essential for prebeta(1)HDL to promote the high-affinity efflux of cellular cholesterol, but not for the alpha-migrating HDL particles to activate LCAT.

Animals↗
PubMed1999

Oxysterols from oxidized LDL are cytotoxic but fail to induce hsp70 expression in endothelial cells.

Oxidized low density lipoprotein (OxLDL) possesses several proatherogenic characteristics, among which a marked cytotoxicity. In vitro, cytotoxicity of OxLDL to endothelial cells is associated with an increase in the expression of the inducible form of heat shock protein 70 (hsp70), generally regarded as a cytoprotective protein. Oxidized derivatives of cholesterol which form upon LDL oxidation are cytotoxic. Moreover, most of the OxLDL cytotoxicity is due to its lipid moiety, in particular to oxysterols. In this report we demonstrate that although oxysterols identified in OxLDL are cytotoxic, they cannot trigger the increase in hsp70 expression observed with intact oxidized lipoproteins. We speculate therefore that oxysterols may represent the most toxic form of oxidized lipids in LDL because they cannot activate a rescue mechanism (i.e. the hsp response) and may contribute significantly to cell death within atherosclerotic plaques.

Apoptosis↗
PubMed1999

Antioxidants and coronary artery disease.

The protective role of antioxidants in experimental models of atherosclerosis is only partially confirmed by studies in man. Observational and epidemiologic data, as well as randomized trials failed to provide clear cut indications, because of mixed results on the protective role of antioxidants against cardiovascular diseases. In spite of the lack of a general consensus, recent data reinforce the concept that a regular intake of antioxidants present in food limits the progression of atherosclerosis. When it will be possible to monitor the efficacy of any antioxidant therapy with validated markers of oxidation, the potential influence of vitamins and antioxidants on coronary artery disease may eventually be resolved.

Animals↗