Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Prostaglandins (PG) are highly unsaturated, cyclic fatty acids with 20 carbon atoms which are biosynthesized from dihomo-gamma-linolenic, arachidonic and eicosapentaenoic acids. These fatty acids are either ingested or are biosynthesized from linoleic and linolenic acids, respectively. The PG-precursor fatty acids are liberated from membrane phospholipids by phospholipase A and are converted to prostaglandins by the multienzyme complex PG-synthetase. The activity of the PG-system is influenced by extracellular hormonal, neural and mechanical stimuli and by intracellular factors such as ion-concentration and activity of the enzymes adenyl- and guanylcyclase. Prostaglandins are tissue hormones or autacoids which act on their receptors near their site of synthesis and degradation. The prostaglandin family constitutes a group of more than 10 natural occurring compounds showing a variety of biological actions. In arteries and veins the different PG:s have vasodilating as well as vasoconstricting effects. In addition, they are involved in the regulation of vascular smooth muscle proliferation. Within the kidney PG:s have vascular and tubular actions. They antagonize the effect of ADH, mediate renin secretion and are involved in the control of electrolyte balance. In the regulation of platelet aggregation and platelet adhesion PG:s have opposite functions: Prostacyclin which is synthesized in the vascular wall antagonizes the aggregating action of Thromboxane A2 which is formed in the platelets. A defect or an imbalance in the production of PG:s in the vascular wall, in platelets or in the kidney is assumed to play a pathogenetic role in a variety of cardiovascular and renal diseases such as in hypertension, atherosclerosis, persistent ductus arteriosus and Bartter's syndrome.
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PMID:[Prostaglandins in cardiovascular and renal function. Biochemical, physiological and clinical findings (author's transl)]. 10 97

It was shown that the action of phospholipase A2 on low density serum lipoproteins (LDL) in the presence of serum albumin led to decrease in the floatation coefficient. Lipase hydrolyzed LDL triglycerides after pretreatment of the latter with phospholipase A2. Due to the action of lipases the LDL residue loses its solubility and the cholesterol-rich precipitate forms. The loss of solubility of lipoproteins treated with lipases and proteinases may occur in vivo, underlying athermao formation, i.e. can thus serve as one of the factors in the pathogenesis of atherosclerosis.
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PMID:[Action of lipases on low-density serum lipoproteins]. 19 43

High density lipoprotein (HDL) was found in vitro to form myelin buds (liposomes) from washed crystals of free cholesterol (commercial or atheroma sources). This activity led to the progressive destruction and solubilization of the crystals. Low density and very low density lipoproteins did not have any effect. Liposome formation and solubilization were accelerated by calcium ions, phospholipase A and polyunsaturated lecithin (Lipostabil). Cholesterol crystals were nearly completely destroyed after 18 h incubation with HDL-Lipostabil.
Atherosclerosis 1978 Dec
PMID:The action of human high density lipoprotein on cholesterol crystals. Part 1. Light-microscopic observations. 21 76

We studied the effect of lysolecithin on the clearing of plasma cholesterol. The immediate and maximal conversion of plasma lecithin to lysolecithin was produced in rats by intravenous injection of phospholipase A. The changes which took place in the converted lysolecithin and of cholesterol were followed in rats which had previously received [32-P]phosphate and [14-C]cholesterol. We followed simultaneously the in vitro changes in blood removed immediately after the in vivo administration of phospholipase A. The experiments showed that a substantial part of the plasma lecithin was converted to lysolecithin within the first minute after intravenous administration of phospholipase A. In the course of 60 min of blood incubation, the ratio of plasmatic lysolecithin in the closed system continued to increase. At the same time the content of cholesterol also increased. In vivo, the converted lysolecithin was quickly released from the plasma, so that within 10 min the original lecithin content dropped to 15-5% depending on the dose of phospholipase A that had been administered. The content of sphingomyelin and lysolecithin, which increased only temporarily shortly after injection, did not alter during the experiment. The level of plasma cholesterol esters, however, dropped significantly, whereas the free cholesterol content increased. The molar ratio of the drop in lipid phosphorus and cholesterol esters in plasma after the administration of phospholipase A was similar. A significantly higher cholesterol content was found in the liver of animals treated with phospholipase A.
Atherosclerosis
PMID:Lysolecithin-dependent release of cholesterol from rat plasma. 114 30

Molecular graphics and molecular mechanics techniques have been used to study the mode of ligand binding and mechanism of action of the enzyme phospholipase A2. A substrate-enzyme complex was constructed based on the crystal structure of the apoenzyme. The complex was minimized to relieve initial strain, and the structural and energetic features of the resultant complex analyzed in detail, at the molecular and residue level. The minimized complex was then used as a basis for examining the action of the enzyme on modified substrates, binding of inhibitors to the enzyme, and possible reaction intermediate complexes. The model is compatible with the suggested mechanism of hydrolysis and with experimental data about stereoselectivity, efficiency of hydrolysis of modified substrates, and inhibitor potency. In conclusion, the model can be used as a tool in evaluating new ligands as possible substrates and in the rational design of inhibitors, for the therapeutic treatment of diseases such as rheumatoid arthritis, atherosclerosis, and asthma.
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PMID:Modeling of substrate and inhibitor binding to phospholipase A2. 140 62

Modification of the low density lipoprotein (LDL) core or surface lipids were shown to affect the cellular uptake of the lipoproteins and hence the formation of foam cell macrophages. In the present study phospholipase A2 treatment of LDL was shown to produce negatively charged lipoprotein with increased content of lysolechitine. This modified lipoprotein was taken up and degraded by J-774 A.1 macrophage-like cell line at enhanced rate (up to 97% when 10 units/ml of PLase A2 was used) in comparison to control LDL. This effect of PLase A2 was enzyme dose dependent. Competition experiments revealed that the uptake of PLase A2-LDL by the macrophages was specific and was mediated via the LDL receptor. Since PLase A2 was found to exist in various tissues, thus the production of PLase A2-LDL under certain pathological conditions can potentially contribute to foam cell formation and accelerated atherosclerosis.
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PMID:Phospholipase A2-modified LDL is taken up at enhanced rate by macrophages. 159 85

The immunoreactivity of human apolipoprotein B (apo B) towards 5 monoclonal antibodies was studied by enzyme immunoassay in native and in vitro oxidized low density lipoproteins (LDL). LDL oxidative modifications were obtained by incubation with either copper ions or an association of lipoxygenase and phospholipase A2. The monoclonal antibodies used in the inhibition analysis were directed to epitopes located in the amino-terminal region (1D1), in the middle part (2D8, L7, 4G3) and in the carboxy-terminal region (L3) of the apo B molecule. The results demonstrated that the immuno-reactivity of 1D1 epitope was little affected by LDL oxidation with copper ions or lipoxygenase plus phospholipase A2, whereas the immunoreactivity of the other epitopes were markedly decreased by these LDL modifications. Immunoreactivity changes were more important in L3 and L7 epitopes than in 2D8 and 4G3 epitopes. Since it is known that L3 and L7 epitopes are located in apo B domains rich in lipid-associated peptides whereas 1D1 is in a domain poor in such peptides, these results suggest a relationship between the lipid environment of an apo B epitope and its susceptibility to alteration by LDL oxidation.
Atherosclerosis 1991 Jul
PMID:Resistance to LDL oxidative modifications of an N-terminal apolipoprotein B epitope. 172 77

The effects of vitamin D3 on the production of prostacyclin (PGI2) by cultured rabbit vascular smooth muscle cells (VSMCs) were investigated. PGI2 synthesis by VSMCs was significantly increased in the presence of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and 1 alpha hydroxyvitamin D3 (1 alpha(OH)D3) at 48 hours [1,25(OH)2D3 greater than 1 alpha(OH)D3]. Physiological concentration of 1,25(OH)2D3 (10(-10) M) significantly increased the synthesis of PGI2. Further, we observed that treatment with 1,25(OH)2D3 significantly induced the activity of cyclooxygenase without changing the activity of phospholipase A2. These findings suggest that the mechanism of action of 1,25(OH)2D3 on the synthesis of PGI2 is mediated by the cyclooxygenase pathway. It seems possible that vitamin D3 is a vasoactive agent and may play a protective role in the development of atherosclerosis.
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PMID:Vitamin D3 stimulates the production of prostacyclin by vascular smooth muscle cells. 177 35

The effect of cigarette smoking on the levels of platelet-activating factor-like lipid(s) (PAF-LL) in plasma lipoproteins was studied. The subjects were 10 healthy male non-smokers (24 +/- 1.4 years old) and 13 healthy male habitual smokers (23 +/- 1.3 years old). Fasting venous blood was obtained and basal levels of PAF-LL in plasma lipoproteins were estimated. The acute effect of cigarette smoking was also studied in smokers. Plasma lipoproteins were separated by ultracentrifugation. Lipids were extracted and separated by thin-layer chromatography. The fraction with the same migration as authentic PAF was recovered and was shown to cause aggregation of human polymorphonuclear neutrophils. This activity was identified as PAF-LL because it was inactivated by phospholipase A2 and was blocked by CV-3988, an antagonist of the PAF receptor. PAF-LL was detected in LDL and HDL, but not in VLDL or in lipoprotein-deficient plasma. The levels of PAF-LL in LDL in non-smokers, and in smokers before and after smoking were 13 +/- 7.5, 16 +/- 14.9 and 190 +/- 179.0 pg/ml, and those in HDL were 12 +/- 5.2, 40 +/- 40.0 and 235 +/- 205.1 pg/ml, respectively. The values in both LDL and HDL in smokers increased significantly after smoking (P less than 0.05). After 30 min, the levels had returned almost to the pre-smoking levels. We conclude that cigarette smoking induces an increase in the levels of PAF or closely related lipid(s) in LDL and HDL, which may be related to smoking-induced atherosclerosis.
Atherosclerosis 1991 Mar
PMID:Effect of cigarette smoking on the levels of platelet-activating factor-like lipid(s) in plasma lipoproteins. 187 24

Phagocytes (P), i.e. neutrophils, monocytes and macrophages, may be involved as well as reactive oxygen species (ROS) in the initiation and development of atherosclerosis. Evidences for this assumption are the following; P and ROS are both able to damage endothelial cells whose dysfunction is crucial in the etiology of atherosclerosis. ROS generated by endothelial cells, smooth muscle cells or mainly blood cells such as neutrophils but also monocytes platelets and erythrocytes, peroxide directly endothelial cell membranes. Damage to cell membranes can be induced by P that adhere to, and release on endothelial cells large amounts of proteolytic and lipolytic enzymes. ROS can also induce formation in the blood of lipoperoxides which are often included in LDL (low density lipoproteins). These modified LDL are cytotoxic, possess phospholipase A2 activity and are recognized by the LDL scavenger receptor which is on the monocyte-macrophage membrane. The modified LDL are also immunogenic inducing formation of autoantibodies directed against them and normal LDL. Modified LDL and LDL immune complexes can be ingested by monocytes leading to foam cells and ROS. The damaged endothelial cells have an increased permeability to macromolecules, synthetize chemotactic factors, decrease their prostacyclin production and favour the adherence of neutrophils and monocytes to their surface. All these factors could increase ROS production and lipid peroxidation amplifying intra and extra-cellular accumulation of lipoperoxides in vascular walls. The ability of ROS and P to damage endothelial cells, to induce lipid peroxidation and thus to be involved in atherosclerosis relies on in vitro experimental results.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Oxygen, phagocytic cells and atheroma]. 265 11


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