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At least 1,225 records · Page 68Linked to original sources
PubMed1999

Effects of NTE-122, a novel acyl-CoA:cholesterol acyltransferase inhibitor, on cholesterol esterification and high-density lipoprotein-induced cholesterol efflux in macrophages.

We investigated the effects of a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, NTE-122 (trans-1,4-bis[[1-cyclohexyl-3-(4-dimethylamino phenyl)ureido]methyl]cyclohexane), on ACAT activities in macrophages originating from several species and high-density lipoprotein (HDL)-induced cholesterol efflux in phorbol 12-myristate 13-acetate (PMA)-treated THP-1 cells. NTE-122 inhibited cell-free ACAT activities in human PMA-treated THP-1 cells and mouse J774.1 cells with IC50 values of 0.88 and 360 nM, respectively. NTE-122 competively inhibited the ACAT activity in PMA-treated THP-1 cells. NTE-122 also inhibited cellular ACAT activities in PMA-treated THP-1 cells, rat peritoneal macrophages and J774.1 cells with IC50 values of 3.5, 84 and 6800 nM, respectively. Furthermore, NTE-122 prevented cholesterol accumulation in PMA-treated THP-1 cells incubated with acetylated low density lipoprotein, simultaneously with HDL, while it caused accumulation of a significant amount of free cholesterol in the absence and even in the presence of HDL. NTE-122 also enhanced HDL-induced cholesterol efflux from established foam cells converted from PMA-treated THP-1 cells. These results suggest that NTE-122, capable of inhibiting macrophage ACAT activity in humans more strongly than those in the other species, exhibits anti-atherogenic effects by preventing the foam cell formation and enhancing the foam cell regression in humans.

Aniline Compounds↗
PubMed2004

Reduction in photostability by the esterification of beta-cryptoxanthin.

Liposomes, in which beta-carotene, beta-cryptoxanthin, zeaxanthin, beta-cryptoxanthin palmitate or beta-cryptoxanthin acetate had been embedded, were irradiated by UVA, and the rate of degradation of each carotenoid was measured. There was no significant difference in the degradation rate between beta-carotene, beta-cryptoxanthin and zeaxanthin. The degradation rates of beta-cryptoxanthin palmitate and beta-cryptoxanthin acetate were faster than that of beta-cryptoxanthin, and the degradation rate of beta-cryptoxanthin palmitate was faster than that of beta-cryptoxanthin acetate.

Carotenoids↗
PubMedDate not supplied

Metabolic conversions of trichothecene mycotoxins: de-esterification reactions using cell-free extracts of Fusarium.

A crude cell-free extract from cultures of Fusarium sp. strain C37410-90 possessed significant esterase activity and hydrolyzed the trichothecene mycotoxin 3-acetyldeoxynivalenol (3-AcDON) to deoxynivalenol (DON) in high yield. Smaller amounts of 15-acetyl- and 3,15-diacetyl-esters of DON were also formed. The extract was capable of hydrolyzing a range of natural and semisynthetic trichothecene esters, and showed a high degree of regioselectivity towards position 3. 3,4,15-Triacetylscirpentriol (TAS) was efficiently hydrolyzed to 4,15-diacetoxyscirpenol (DAS), and no further transformation was observed. The enzyme activity was partially purified.

Biotransformation↗
PubMed1996

Preferential esterification of arachidonic acid into ethanolamine phospholipids in epithelial cells from ovine endometrium.

In sheep, the pulsatile release of prostaglandin F2 alpha by the endometrium is necessary to achieve luteolysis which occurs at the end of the oestrous cycle. The production of prostaglandins is known to depend upon the availability of arachidonic acid, the fatty acid precursor of prostaglandin biosynthesis. Consequently, the mechanisms controlling intracellular amounts of arachidonate may be involved in the regulation of prostaglandin synthesis. Since arachidonic acid is mostly found in phospholipids and the endometrial epithelium is the primary source of prostaglandin F2 alpha during luteolysis, the fate of arachidonic acid when incorporated into epithelial cells from the ovine uterus was investigated. Endometrial epithelial cells isolated from cyclic ewes at day 15 after oestrus were cultured in the presence of [3H]arachidonic acid. Incorporation and distribution of the radiolabelled arachidonic acid into the various phospholipid classes were examined using HPLC. We observed that ethanolamine glycerophospholipids contained 61% of the total tritiated arachidonic acid incorporated into cellular lipids, whereas phosphatidylinositols, phosphatidylcholines and phosphatidylserines contained 17%, 13% and 4.7%, respectively. In addition, the radioactivity measured within phosphatidylethanolamines was preferentially detected in the 1-alkenyl-2-acyl (44%) forms of ethanolamine phospholipids, also called plasmalogens. The kinetic study of arachidonic acid uptake into ethanolamine phospholipids showed that arachidonic acid was rapidly esterified into the diacyl forms and then uptake decreased, whereas the incorporation increased continuously into the plasmalogen forms for at least 24 h. These results demonstrate that the primary pool of esterified arachidonic acid is found in ethanolamine plasmalogens of epithelial cells from the ovine endometrium. The high arachidonate content of ethanolamine plasmalogens suggests that these phospholipids play a crucial role in the control of arachidonic acid availability and ultimately in the regulation of prostaglandin synthesis.

Animals↗
PubMed1985

Effect of high-density lipoproteins on cholesterol efflux and esterification in lipid-enriched human skin fibroblasts.

The ability of high-density lipoprotein (HDL) to reduce the cholesterol content was studied in cultured fibroblasts enriched with cholesterol esters. Incubation of cholesterol-enriched cells with HDL in a final concentration of 1 g protein/l for 24 h reduced the total and esterified cholesterol content by 23% as compared with control fibroblasts incubated with albumin. Similar cholesterol efflux was obtained with HDL isolated from lecithin:cholesterol acyltransferase (LCAT)-deficient plasma. The HDL3 subfraction isolated by rate-zonal ultracentrifugation contained the major part of the cholesterol-depleting effect. HDL or HDL3 decreased CoA:cholesterol acyltransferase (ACAT) activity to 5% of the level found in control fibroblasts within 8 h of incubation. These findings suggest that ACAT activity is sensitive to a pool of intracellular cholesterol, which can be mobilized by the addition of HDL to the culture medium, and that ACAT activity is a useful measure of cholesterol efflux from cultured fibroblasts.

Cells, Cultured↗
PubMed1978

An example of the oxidative de-esterification of an isopropyl ester. Its role in the metabolism of the herbicide flampropisopropyl.

1. Two mammalian metabolites of the herbicidal ester, flamprop-isopropyl (BARNON), have been characterized as products of omega-hydroxylation of the isopropoxycarbonyl grouping (-CO2 CHMe 2). 2. Hydroxylation at the methine group of this moiety, to afford an unstable lactol (-CO2C(OH)Me2) and thence the corresponding carboxylic acid also appears to occur. On the basis of experiments with rat liver microsomes, this pathway to the acid may be as important as the esterase-catalysed route. 3. Biomimetic oxidation studies with peroxytrifluoroacetic acid of a simple model of the herbicide (isopropyl acetate) have provided confirmation of the feasibility of the novel biotransformation.

Anilides↗