PubMed Health⌕ Search

Biomedical subjects

O H Morand

Publications and source records attributed to O H Morand.

10 recordsLinked to original sources
PubMed1997

Human monocyte-derived macrophages express an approximately 120-kD Ox-LDL binding protein with strong identity to CD68.

A protein that specifically binds oxidized LDL (Ox-LDL) has recently been characterized in mouse peritoneal macrophages and identified as macrosialin, a protein with a molecular weight of 95 kD. First, the present work shows that human monocyte-derived macrophages express a membrane protein with a molecular weight of approximately 120 kD that selectively binds Ox-LDL. Second, we tested whether this approximately 120-kD Ox-LDL binding protein had any relation to CD68, the human homologue of macrosialin. The following evidence was obtained to support the role of CD68 as an Ox-LDL binding protein: (1) Ligand blots with Ox-LDL and Western blots with Ki-M6, an anti-human CD68 monoclonal antibody, revealed a single band with a molecular weight of approximately 120 kD under reducing and nonreducing condition. (2) The expression patterns of the approximately 120-kD Ox-LDL binding membrane protein and of CD68 paralleled each other during monocyte/macrophage differentiation. (3) Digestion with N-glycosidase F demonstrated that both CD68 and the Ox-LDL binding protein are glycoproteins; both showed a similar shift of approximately 18 kD in apparent molecular weight. (4) CD68, probed with monoclonal antibody Ki-M6, and the approximately 120-kD Ox-LDL binding protein were coprecipitated with EMB11, another anti-CD68 antibody. About 5000 molecules of CD68 are expressed on the cell surface of human macrophages. Ligation of 125I-Ki-M6 to cells leads to its internalization and degradation. This capacity would be sufficient to allow for the specific uptake and degradation of Ox-LDL. Taken together, these data support a role for CD68 as a specific Ox-LDL binding protein in human monocyte-derived macrophages.

Amidohydrolases↗
PubMed1997

Ro 48-8.071, a new 2,3-oxidosqualene:lanosterol cyclase inhibitor lowering plasma cholesterol in hamsters, squirrel monkeys, and minipigs: comparison to simvastatin.

2,3-Oxidosqualene:lanosterol cyclase (OSC, E.C. 5.4.99.7) represents a unique target for a cholesterol lowering drug. Partial inhibition of OSC should reduce synthesis of lanosterol and subsequent sterols, and also stimulate the production of epoxysterols that repress HMG-CoA reductase expression, generating a synergistic, self-limited negative regulatory loop. Hence, the pharmacological properties of Ro 48-8.071, a new OSC inhibitor, were compared to that of an HMG-CoA reductase inhibitor, simvastatin. Ro 48-8.071 blocked human liver OSC and cholesterol synthesis in HepG2 cells in the nanomolar range; in cells it triggered the production of monooxidosqualene, dioxidosqualene, and epoxycholesterol. It was safe in hamsters, squirrel monkeys and Göttingen minipigs at pharmacologically active doses, lowering LDL approximately 60% in hamsters, and at least 30% in the two other species, being at least as efficacious as safe doses of simvastatin. The latter was hepatotoxic in hamsters at doses > 30 mumol/kg/day limiting its window of efficacy. Hepatic monooxidosqualene increased dose-dependently after treatment with Ro 48-8.071, up to approximately 20 micrograms/g wet liver or less than 1% of hepatic cholesterol, and it was inversely correlated with LDL levels. Ro 48-8.071 did not reduce coenzyme Q10 levels in liver and heart of hamsters, and importantly did not trigger an overexpression of hepatic HMG-CoA reductase, squalene synthase, and OSC itself. In strong contrast, simvastatin stimulated these enzymes dramatically, and reduced coenzyme Q10 levels in liver and heart. Altogether these findings clearly differentiate the OSC inhibitor Ro 48-8.071 from simvastatin, and support the view that OSC is a distinct key component in the regulation of the cholesterol synthesis pathway.

Acetates↗
PubMed1996

Decrease in scavenger receptor expression in human monocyte-derived macrophages treated with granulocyte macrophage colony-stimulating factor.

To determine whether scavenger receptors are susceptible to regulation by granulocyte macrophage colony-stimulating factor (GM-CSF), a macrophage-specific cytokine, human monocytes were differentiated into macrophages in the absence or presence of 20 U/mL GM-CSF. Binding, uptake, and degradation of acetylated LDL (Ac-LDL) and oxidized LDL (Ox-LDL) were measured. Treatment with GM-CSF resulted in a significant twofold to threefold decrease in the number of binding sites for Ac-LDL and Ox-LDL on the surface of macrophages without affecting the affinity of the receptor for these ligands. Competition experiments revealed that two binding sites were responsible for the recognition and uptake of Ac-LDL; one specific for Ac-LDL and one that recognized both Ac-LDL and Ox-LDL. No binding site specific for Ox-LDL could be detected in either control or GM-CSF-treated macrophages. Treatment of human monocyte-derived macrophages with GM-CSF resulted in a decrease of the Ac-LDL/Ox-LDL receptor but did not affect the binding site specific for Ac-LDL. Northern blot analysis showed that mRNA levels of both types I and II scavenger receptor were reduced in macrophages differentiated in the presence of GM-CSF. Human macrophages that were differentiated in the presence of GM-CSF accumulated approximately 50% fewer cholesteryl esters. Taken together, these results indicate that GM-CSF can downregulate both types I and II scavenger receptor in human monocyte-derived macrophages, which might have implications for foam cell formation.

Base Sequence↗
PubMed1992

Effects of chronic aortic coarctation on atherosclerosis and arterial lipid accumulation in the Watanabe hereditary hyperlipidemic (WHHL) rabbit.

The effects of high blood pressure on atherosclerosis were examined in the Watanabe heritable hyperlipidemic (WHHL) rabbit. For this purpose, the subdiaphragmatic aorta of rabbits was partially ligated (coarctation) to increase blood pressure. Atherosclerosis was assessed 4 months later by morphometric analyses and quantitation of arterial lipids. Results were compared to control WHHL rabbits with matched plasma triglycerides and cholesterol levels. A marked increase in atherosclerotic lesions was observed in the thoracic aorta of the hypertensive rabbits without qualitative changes in its morphometric features. The cross sectional area of the atherosclerotic plaques of the ascending and descending aorta in the hypertensive rabbits was two- and six-times larger than in normotensive rabbits, respectively. Lesions represented 12.0% +/- 3.5% of the total medial cross sectional area of the descending aorta of normotensive rabbits, versus 45.0% +/- 5.7% in hypertensive rabbits. No lesions were observed downstream of the coarctation in hypertensive rabbits, nor in the normotensive rabbits. Accumulation of cholesterol and choline-containing phospholipids in the descending aorta of hypertensive rabbits was increased 3.2- and 1.5-fold, respectively, when compared to normotensive rabbits. Hypertension did not change the unesterified cholesterol/total cholesterol and sphingomyelin/lecithin + lysolecithin molar ratios. In conclusion, chronic coarctation enhances the atherosclerotic response in WHHL rabbits in the high blood pressure compartment, and reduces the variability of this response.

Animals↗
PubMed1990

A rapid selection for animal cell mutants with defective peroxisomes.

Chinese hamster ovary (CHO) cells take up and incorporate 9-(1'-pyrene)nonanol (P9OH) into phospholipids and neutral lipids. Exposure of P9OH-labeled cells to long wavelength ultraviolet (UV) light causes cell death, because excitation of the pyrene moiety generates reactive oxygen species. CHO mutant cells deficient in plasmalogen biosynthesis and peroxisome assembly (Zoeller, R.A. and Raetz, C.R.H. (1986) Proc. Natl. Acad. Sci. USA 83, 5170-5174) are much more resistant to P9OH/UV treatment than are wild-type cells. This phenotype is explained by a 7.5-fold reduction of P9OH incorporation into the ethanolamine-linked phospholipids in the mutant cells and 2.4- to 6-fold reduction of P9OH incorporation into all other phospholipids and triglycerides, suggesting a general defect in fatty alcohol metabolism. [U-14C]Hexadecanol incorporation into the phospholipids of the mutant cells is also impaired. In contrast, the fatty acid analog, 9-(1'-pyrene)nonanoic acid, is incorporated into cells two times more rapidly by the mutants than by the wild type. Resistance to P9OH/UV treatment affords a simple, new method for the selection of animal cell mutants defective in peroxisome biogenesis.

Animals↗
PubMed1989

Cytoplasmic requirement for peroxisome biogenesis in Chinese hamster ovary cells.

Hybrids constructed by fusion of wild-type Chinese hamster ovary cells (CHO-K1) to peroxisome-deficient CHO mutants (ZR-78.1) contain normal peroxisomes, demonstrating that the mutation(s) are recessive. "Nuclear hybrids" prepared by fusion of CHO-K1 karyoplasts to mutant ZR-78.1 occasionally fail to regain intact peroxisomes (approximately 1/300 cells). These peroxisome-deficient nuclear hybrids closely resemble the original mutant cells by biochemical criteria, but their modal chromosome number is 36-38, the same as that of CHO hybrids generated from intact cells. When the peroxisome-deficient nuclear hybrids are fused to wild-type cytoplasts, a fraction of the fusion products (at least 70%) continue to propagate normal peroxisomes indefinitely. Peroxisome biogenesis cannot be reinitiated in cells of mutant ZR-78.1 by fusion to wild-type cytoplasts. Our results suggest that a wild-type nucleus by itself is necessary but not sufficient for restoration of normal peroxisome biogenesis and that a cytoplasmic component of wild-type cells, possibly a normal peroxisome, is also required.

Animals↗
PubMed1988

A possible role for plasmalogens in protecting animal cells against photosensitized killing.

Chinese hamster ovary (CHO) cells incorporate 12-(1'-pyrene) dodecanoic acid (P12) into membrane lipids. Exposure of P12-labeled cells to long wavelength ultraviolet light causes cell killing, presumably because excitation of the pyrene moiety (a photosensitizer) leads to the generation of reactive oxygen species. Cytotoxicity is dependent upon the concentration of P12 used to label the cells, and time of UV exposure, and the presence of oxygen during irradiation. CHO mutant cells deficient in plasmalogen biosynthesis and peroxisome assembly (Zoeller, R.A., and Raetz, C.R.H. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 5170-5174) are several orders of magnitude more sensitive to P12/UV treatment than wild-type cells, permitting direct selection of one wild-type cell in 1 X 10(4) mutant cells. A major factor responsible for the P12/UV hypersensitivity of these mutants appears to be the absence of plasmalogens. Supplementation of the mutants with 1-O-hexadecyl-sn-glycerol restores plasmalogen levels and nearly normal resistance to P12/UV treatment, whereas the biogenesis of peroxisomes is not restored. The P12/UV hypersensitivity of the plasmalogen-deficient mutants, together with the selective, P12/UV-induced decomposition of plasmalogens in wild-type cells, documented in the accompanying manuscript, suggest that the vinyl ether linkage of plasmalogens plays a direct role in protecting animal cell membranes against certain oxidative stresses.

Animals↗
PubMed1988

Disappearance of plasmalogens from membranes of animal cells subjected to photosensitized oxidation.

Chinese hamster ovary cells (CHO-K1) photosensitized with 12-(1'-pyrene)dodecanoic acid (P12) are killed when exposed to long wavelength ultraviolet (UV) light (greater than 300 nm). Mutants deficient in plasmalogen biosynthesis are hypersensitive to this treatment. We now demonstrate that plasmenylethanolamine is rapidly and preferentially destroyed when CHO-K1 cells, photosensitized either with P12 or merocyanine 540, are irradiated with light of the appropriate wavelength. Using [2-14C]ethanolamine, [1-14C]hexadecanol, or [U-14C]hexadecanol to follow the turnover of plasmenylethanolamine, we show that 2-monoacylglycerophosphoethanolamine, formic acid, and pentadecanal are formed during P12/UV treatment of CHO-K1 cells, but not of mutant cells deficient in plasmalogen synthesis. The decomposition of plasmenylethanolamine is O2-dependent, is enhanced in D2O, and is reduced in the presence of sodium azide. The process may be explained, in part, by the cycloaddition of singlet oxygen to the vinyl ether linkage of plasmenylethanolamine, generating a dioxetane intermediate that would be expected to decompose under physiological conditions to the observed products. An additional possibility is the formation of an allylic hydroperoxide at the 1'-carbon of the alkyl moiety by an "ene" reaction of singlet oxygen, or by radical-mediated oxidation, followed by metabolism or chemical decomposition of the hydroperoxide. Given the P12/UV hypersensitivity of plasmalogen-deficient mutants, we suggest that plasmalogens might protect animal cell membranes from singlet oxygen and/or radical-initiated oxidation by functioning as scavengers and decomposing to products that can be reutilized.

Animals↗