Lysophosphatidylcholine in phospholipase A-modified LDL triggers secretion of angiopoietin 2.

Background And Aims: Secretory phospholipase A (PLA) hydrolyzes LDL phospholipids generating modified LDL particles (PLA-LDL) with increased atherogenic properties. Exocytosis of Weibel-Palade bodies (WPB) releases angiopoietin 2 (Ang2) and externalizes P-selectin, which both play important roles in vascular inflammation. Here, we investigated the effects of PLA-LDL on exocytosis of WPBs.

The effect of intakes of fish and Camelina sativa oil on atherogenic and anti-atherogenic functions of LDL and HDL particles: A randomized controlled trial.

Background And Aims: Omega-3 fatty acids are known to have several cardioprotective effects. Our aim was to investigate the effects of intakes of fish and Camelina sativa oil (CSO), rich in alpha-linolenic acid, on the atherogenic and anti-atherogenic functions of LDL and HDL particles.

Methods: Altogether, 88 volunteers with impaired glucose metabolism were randomly assigned to CSO (10 g of alpha-linolenic acid/day), fatty fish (4 fish meals/week), lean fish (4 fish meals/week) or control group for 12 weeks.

Susceptibility of low-density lipoprotein particles to aggregate depends on particle lipidome, is modifiable, and associates with future cardiovascular deaths.

Aims: Low-density lipoprotein (LDL) particles cause atherosclerotic cardiovascular disease (ASCVD) through their retention, modification, and accumulation within the arterial intima. High plasma concentrations of LDL drive this disease, but LDL quality may also contribute. Here, we focused on the intrinsic propensity of LDL to aggregate upon modification.

Human mast cell neutral proteases generate modified LDL particles with increased proteoglycan binding.

Background And Aims: Subendothelial interaction of LDL with extracellular matrix drives atherogenesis. This interaction can be strengthened by proteolytic modification of LDL. Mast cells (MCs) are present in atherosclerotic lesions, and upon activation, they degranulate and release a variety of neutral proteases.

Chymase released from hypoxia-activated cardiac mast cells cleaves human apoA-I at Tyr and compromises its cardioprotective activity.

ApoA-I, the main structural and functional protein of HDL particles, is cardioprotective, but also highly sensitive to proteolytic cleavage. Here, we investigated the effect of cardiac mast cell activation and ensuing chymase secretion on apoA-I degradation using isolated rat hearts in the Langendorff perfusion system. Cardiac mast cells were activated by injection of compound 48/80 into the coronary circulation or by low-flow myocardial ischemia, after which lipid-free apoA-I was injected and collected in the coronary effluent for cleavage analysis.

Carboxyl-Terminal Cleavage of Apolipoprotein A-I by Human Mast Cell Chymase Impairs Its Anti-Inflammatory Properties.

Objective: Apolipoprotein A-I (apoA-I) has been shown to possess several atheroprotective functions, including inhibition of inflammation. Protease-secreting activated mast cells reside in human atherosclerotic lesions. Here we investigated the effects of the neutral proteases released by activated mast cells on the anti-inflammatory properties of apoA-I.

Apolipoprotein A-I mimetic peptide 4F blocks sphingomyelinase-induced LDL aggregation.

Lipolytic modification of LDL particles by SMase generates LDL aggregates with a strong affinity for human arterial proteoglycans and may so enhance LDL retention in the arterial wall. Here, we evaluated the effects of apoA-I mimetic peptide 4F on structural and functional properties of the SMase-modified LDL particles. LDL particles with and without 4F were incubated with SMase, after which their aggregation, structure, and proteoglycan binding were analyzed.

Acidification of the intimal fluid: the perfect storm for atherogenesis.

Atherosclerotic lesions are often hypoxic and exhibit elevated lactate concentrations and local acidification of the extracellular fluids. The acidification may be a consequence of the abundant accumulation of lipid-scavenging macrophages in the lesions. Activated macrophages have a very high energy demand and they preferentially use glycolysis for ATP synthesis even under normoxic conditions, resulting in enhanced local generation and secretion of lactate and protons.

Spontaneous remodeling of HDL particles at acidic pH enhances their capacity to induce cholesterol efflux from human macrophage foam cells.

HDL particles may enter atherosclerotic lesions having an acidic intimal fluid. Therefore, we investigated whether acidic pH would affect their structural and functional properties. For this purpose, HDL(2) and HDL(3) subfractions were incubated for various periods of time at different pH values ranging from 5.

Conformational changes of apoB-100 in SMase-modified LDL mediate formation of large aggregates at acidic pH.

During atherogenesis, the extracellular pH of atherosclerotic lesions decreases. Here, we examined the effect of low, but physiologically plausible pH on aggregation of modified LDL, one of the key processes in atherogenesis. LDL was treated with SMase, and aggregation of the SMase-treated LDL was followed at pH 5.

Oxidative inactivation of lactonase activity of purified human paraoxonase 1 (PON1).

Paraoxonase1 (PON1), one of HDL-associated antioxidant proteins, is known to lose its activity in vivo systems under oxidative stress. Here, we examined the effect of various oxidants on lactonase activity of PON1, and tried to protect the lactonase activity from oxidative inactivation. Among the oxidative systems tested, the ascorbate/Cu(2+) system was the most potent in inactivating the lactonase activity of purified PON1; in contrast to a limited role of Fe(2+), Cu(2+) (0.

Degradation of very long chain dicarboxylic polyunsaturated fatty acids in mouse hepatocytes, a peroxisomal process.

Polyunsaturated fatty acids can be omega-oxidized to dicarboxylic polyunsaturated fatty acids (DC-PUFA), bioactive compounds which cause vasodilatation and activation of PPARalpha and gamma. DC-PUFA can be shortened by beta-oxidation, and to determine whether mitochondria and/or peroxisomes are responsible for this degradation 20-carboxy-[1-(14)C]-eicosatetraenoic acid (20-COOH-AA) was synthesized and given to hepatocytes from mouse models with peroxisomal dysfunctions. In contrast to wild type cells, hepatocytes from mice with liver-selective elimination of peroxisomes, due to Pex5p deficiency, failed to produce (14)CO(2) and labeled acid-soluble oxidation products, indicating that peroxisomes are involved in the degradation of 20-COOH-AA.

Rice albumin N-terminal (Asp-His-His-Gln) prevents against copper ion-catalyzed oxidations.

Chromatographic separation of soluble proteins from rice (Oryza sativa L.) yielded a major albumin protein (16 kDa), with the DHHQVYSPGEQ sequence in the N terminus, showing antioxidant action. The rice albumin was more potent than other rice proteins in preventing Cu2+-induced low-density lipoprotein (LDL) oxidation.

Differential effect of lysophospholipids on activities of human plasma paraoxonase1, either soluble or lipid-bound.

Interaction of paraoxonase1 (PON1) with lysophospholipids was examined with respect to activity regulation and binding property. Paraoxonase activity of purified PON1 was partially inhibited by palmitoyl-lysophosphatidyl-glycerol (palmitoyl-lysoPG) and lysophosphatidylinositol (lysoPI), which had a stimulatory effect on arylesterase and diazoxonase activities. The selective inhibition of paraoxonase activity by palmitoyl-lysoPG, characterized by noncompetitiveness and charge interaction, was also observed with HDL- or dimyristoylphosphatidylcholine (DMPC)-bound PON1.

Apolipoprotein A-I-mimetic peptides with antioxidant actions.

To augment antioxidant action of apolipoprotein A-I (Apo A-I)-mimetic peptide, the peptide F3,6,14,18 18A (DWFKAFYDKVAEKFKEAF) was modified by incorporating antioxidant amino acid residues. Introduction of His residue at position 2 or 3 at N-terminal of the peptide remarkably enhanced antioxidant action against Cu2+ oxidation of LDL and the capability of sequestering Cu2+. Likewise, the substitution of Ala for Cys residue at position 12 increased antioxidant action against Cu2+ oxidation of LDL.

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

To examine the effect of phospholipids on PON1 activities, purified PON1 was exposed to phospholipids prior to the determination of arylesterase and paraoxonase activities. Phosphatidylcholines with saturated acyl chains (C10-C16) showed a stimulation of both activities, chain length-dependent, with a greater stimulation of arylesterase activity, suggesting the implication of lipid bilayer in the stimulatory action. Such a preferable stimulation of arylesterase activity was more remarkable with phosphatidylcholines with polyunsaturated acyl chains or oxidized chains at sn-2 position, implying that the packing degree of acyl chain may be also important for the preferable stimulation of arylesterase activity.

Broad-spectrum antioxidant peptides derived from His residue-containing sequences present in human paraoxonase 1.

Hydroxyl or peroxyl radicals and hypochlorous acid (HOCl) are known to cause the oxidation of lipoproteins. Here, we examined Cu(2+)-binding property of paraoxonase 1 (PON1), and antioxidant actions of peptides, resembling His residue-containing sequences in PON1, against oxidations by Cu(2+), peroxyl radicals or HOCl. When Cu(2+)-binding property of PON1 was examined spectrophotometrically, the maximal Cu(2+) binding was achieved at 1:1 molar ratio of PON1: Cu(2+).

Effect of 3,4-dihydroxyphenylalanine on Cu(2+)-induced inactivation of HDL-associated paraoxonasel and oxidation of HDL; inactivation of paraoxonasel activity independent of HDL lipid oxidation.

Paraoxonasel (PON1), one of HDL-asssociated antioxidant proteins, is known to be sensitive to oxidative stress. Here, the effect of endogenous reducing compounds on Cu(2+)-mediated inactivation of PON1 was examined. Cu(2+)-mediated inactivation of PON1 was enhanced remarkably by catecholamines, but not by uric acid or homocysteine.

Preferential inhibition of paraoxonase activity of human paraoxonase 1 by negatively charged lipids.

To determine the causes responsible for a preferential decrease of paraoxonase activity, which has been observed in the serum of patients with cardiovascular diseases, the inactivation or inhibition of paraoxonase 1 (PON1) by various endogenous factors was examined using paraoxon or phenyl acetate as a substrate. When purified PON1 was incubated with various endogenous oxidants or aldehydes, they failed to cause a preferential reduction of paraoxonase activity, suggesting no participation of the inactivation mechanism in the preferential loss of paraoxonase activity. Next, when we examined the inhibition of PON1 activity by endogenous lipids, monoenoic acids such as palmitoleic acid or oleic acid inhibited paraoxonase activity preferentially, in contrast to a parallel inhibition of both activities by polyunsaturated or saturated acids.

Copper ions and hypochlorite are mainly responsible for oxidative inactivation of paraoxon-hydrolyzing activity in human high density lipoprotein.

Paraoxon-hydrolyzing activity of HDL (HDL-PON1) is known to lose its activity under oxidative stress condition. Here, we attempted to elucidate the possible causes for the oxidative inactivation of HDL-PON1 in vivo system. Of various oxidative systems, ascorbate/Cu2+ system was the most potent in inactivating the paraoxon-hydrolyzing activity of purified PON1 (PON1).

Oxidative inactivation of paraoxonase1, an antioxidant protein and its effect on antioxidant action.

Paraoxonase1 (PON1), one of antioxidant proteins to protect low density lipoprotein (LDL) from the oxidation, is known to lose its activity in the oxidative environment. Here, we attempted to elucidate the possible mechanisms for the oxidative inactivation of PON1, and to examine the capability of hydroxyl radicals-inactivated PON1 to prevent against LDL oxidation. Of various oxidative systems, the ascorbate/Cu2+ system was the most potent in inactivating the purified PON1 (PON1) as well as HDL-bound PON1 (HDL-PON1).

Beneficial effect of oleoylated lipids on paraoxonase 1: protection against oxidative inactivation and stabilization.

The effect of lipids on PON1 (paraoxonase 1), one of antioxidant proteins in high-density lipoprotein, was investigated in respect to inhibition, protection against oxidative inactivation, and stabilization. When the effect of lipids on the PON1 activity was examined, a remarkable inhibition was expressed by polyenoic fatty acids (C18:2-C20:5). Linoleic acid, the most potent ( K(i), 3.