[Risk factors of atherosclerosis in childhood].
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Adolescent↗
Biomedical subjects
A Cerami
Publications and source records attributed to A Cerami.
Non-enzymatic modification of proteins by steroids: pathological implications for autoimmunity and glucocorticoid toxicity.
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Animals↗
Glucocorticoid-lens protein adducts in experimentally induced steroid cataracts.
The injection of glucocorticoids into the vitreous chamber of the rabbit eye results in the development of posterior subcapsular opacities. These lesions appear to be similar in morphology to human steroid-induced cataracts. Electron microscopic analysis revealed fiber cell separation, vacuolization, and changes within the matrix of the crystallins. Opacification could only be produced by glucocorticoids possessing a reactive C-20,21 hydroxylcarbonyl function, supporting the hypothesis that glucocorticoid addition products are involved in the induction of these lesions. The occurrence of glucocorticoid-lens proteins adducts was confirmed by tritium incorporation and by radioimmunoassay of protein hydrolysates obtained from these lenses.
17-alpha-Hydroxyprogesterone↗
Weight loss associated with an endotoxin-induced mediator from peritoneal macrophages: the role of cachectin (tumor necrosis factor).
Endotoxin-induced cells of the reticuloendothelial system were shown to produce mediator(s) that evoke a state of cachexia in recipient animals. The factor(s) responsible were assayed in endotoxin-resistant (C3H/HeJ) mice, which were injected with dialyzed conditioned medium obtained from lipopolysaccharide-induced peritoneal macrophages. The mice exhibited weight loss and anorexia, and they died if sufficient quantities of medium were administered. The syndrome was reversible if injections were discontinued. Endotoxin alone did not produce this effect, and no gross pathologic lesions were discernable in the treated animals. In this model system, cachexia appears to result from the action of soluble macromolecules produced by activated macrophages in vitro. Cachectin (murine tumor necrosis factor) is thought to play a central role in this phenomenon.
Animals↗
Identification of a novel, thiol-containing co-factor essential for glutathione reductase enzyme activity in trypanosomatids.
Soluble extracts of Trypanosoma brucei, T. cruzi, Leishmania mexicana and Crithidia fasciculata contain a novel enzyme capable of reducing oxidized glutathione by NADPH solely in the presence of an unidentified, dialyzable, heat stable co-factor. Evidence is presented showing that co-factor contains enzymatically reducible thiol group(s), essential for activity. The co-factor is possibly unique to the Kinetoplastida, since dialysate extracts from a wide selection of other organisms would not substitute for trypanosomatid co-factor preparations.
Animals↗
Nonenzymatic modification of lens crystallins by prednisolone induces sulfhydryl oxidation and aggregate formation: in vitro and in vivo studies.
Steroid-induced cataracts occur as a consequence of prolonged, therapeutic levels of glucocorticoids. Previous studies have shown that these lens opacities are associated with the occurrence of covalent glucocorticoid-lens protein adducts. In vitro, the glucocorticoid prednisolone nonenzymatically modifies the lysine residues of lens crystallins. This modification increases the reactivity of protein thiols and leads to the formation of high-molecular-weight, disulfide-linked aggregates. Prednisolone-induced aggregates result in an opalescence in the crystallins solution which is reversed by the addition of dithiothreitol. The acetylation of lens proteins prior to incubation inhibits both the incorporation of prednisolone and the development of opalescence. Gel filtration chromatography of the prednisolone lens protein incubations shows that the majority of the protein-incorporated prednisolone is associated with the disulfide-linked complexes. Similar analysis of proteins obtained from a human steroid-induced cataract demonstrates that prednisolone adducts which form in vivo are also present in reducible, high-molecular-weight complexes. These results implicate the nonenzymatic modification of lens crystallins in the cataractogenic effect of glucocorticoids and suggest possible pharmacological strategies in preventing this toxic manifestation of steroid therapy.
Acetylation↗
Protein glycosylation and the pathogenesis of atherosclerosis.
This review summarizes the progress of research in nonenzymatic glycosylation that is of potential relevance to atherosclerosis and relates this knowledge to the accelerated large-vessel disease observed in diabetics through a hypothetical model based on current concepts of atherogenesis. Critical new information has recently been obtained about complex glycosylation adducts, which form very slowly through a series of further reactions and rearrangements from the initial Amadori product. These adducts, called advanced glycosylation end products (AGE), are not reversible like the Amadori product. Thus, they continue to accumulate indefinitely on long-lived molecules such as collagen and nucleic acids. AGE covalently trap soluble plasma proteins, act as signals for macrophage recognition and uptake, and induce mutations in double-stranded plasmid DNA. Covalent trapping of low-density lipoproteins by AGE on collagen may promote excessive lipid accumulation in the arterial walls of diabetics, whereas trapping of von Willebrand factor by AGE may increase platelet adhesion and aggregation, leading to smooth muscle cell proliferation in the arterial intima. Recognition and uptake of AGE-protein derivatives by scavenging macrophages may further contribute to the process of atherogenesis by stimulating the release of such macrophage secretory products as macrophage-derived growth factor. Accumulation of AGE on smooth muscle cell DNA may also enhance proliferation of arterial smooth muscle cells by increasing the rate of mutations that affect growth control.
Arteriosclerosis↗
High-affinity-receptor-mediated uptake and degradation of glucose-modified proteins: a potential mechanism for the removal of senescent macromolecules.
Proteins that have been modified by long-term exposure to glucose accumulate advanced glycosylation end products (AGE) as a function of protein age. In these studies, we have characterized the interaction of AGE-protein with mouse peritoneal macrophages, using AGE-modified bovine serum albumin (AGE-BSA, prepared by incubation with glucose) as a probe. AGE-BSA was specifically bound to cells at 4 degrees C and was taken up and degraded at 37 degrees C; these processes were concentration dependent and saturable. Competition experiments with AGE-BSA, BSA incubated with phosphate-buffered saline rather than glucose, and yeast mannan demonstrated that macrophages specifically recognize AGE on proteins by a receptor that is completely distinct from the mannose/fucose receptor. Scatchard analysis of AGE-BSA binding data indicated that there are approximately 1.06 X 10(5) receptors per macrophage, with an affinity constant of 1.75 X 10(-11) M. Specific binding of AGE-BSA to the macrophage receptor was competitively inhibited by BSA that had been chemically coupled to a synthetic analogue of the specific AGE, 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole (FFI-BSA). FFI-BSA was also taken up by macrophages in a concentration-dependent, saturable manner. Prior incubation of macrophages with AGE-BSA failed to influence the subsequent uptake and degradation of added AGE-BSA. Thus, the AGE receptor does not appear to be down-regulated by exposure to AGE-proteins. Results from these studies suggest that AGE could act in vivo as a specific signal for recognition and degradation of senescent macromolecules. Incomplete removal of AGE-proteins by macrophages may ultimately give rise to some of the physiologic changes that occur with normal aging.
Aging↗
Modification of DNA by glucose 6-phosphate induces DNA rearrangements in an Escherichia coli plasmid.
Reducing sugars such as glucose or glucose 6-phosphate (Glc-6-P) have been shown previously to modify the amino groups of nucleotides and single-stranded DNA. We have examined the mutagenic effect of Glc-6-P-induced lesions in the double-stranded DNA plasmid pBR322. Seventeen mutants of the Ampr Tets phenotype were isolated from plasmid preparations whose transforming capacity had been decreased by incubation with Glc-6-P. A number of the mutant plasmids were found to have undergone gross DNA alterations, including insertions and deletions, as well as the development of multiple species originating from a single cell. The ability of an endogenous reducing sugar to induce extensive DNA rearrangements suggests that these lesions may be significant contributors to cellular mutation.
Chromosome Deletion↗
Hypothesis. Glucose as a mediator of aging.
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Adult↗
Increased levels of 16 alpha-hydroxyestrone-modified proteins in pregnancy and in systemic lupus erythematosus.
The ketolic estrogen 16 alpha-hydroxyestrone (16 alpha OHE) reacts with lysine residues, forming stable covalent adducts with proteins. To determine the extent of protein modification by 16 alpha OHE in vivo, we measured the level of 16 alpha OHE-lysine present within proteins of varying half-lives obtained from normal subjects, patients with systemic lupus erythematosus (SLE), and pregnant women. The latter groups have higher than normal levels of plasma 16 alpha OHE. The proteins analyzed were membrane proteins of the red cell and the lymphocyte and basement membrane proteins of the glomerulus. We report that elevated levels of plasma 16 alpha OHE led to increased formation of 16 alpha OHE-protein adducts and that the level of these adducts increases with the half-life of the protein. In the case of erythrocyte membrane proteins, pregnant women and women with SLE had significantly higher mean levels of 16 alpha OHE-lysine than normal women (normal, 5.2 pmol 16 alpha OHE-lysine/mmol leucine; SLE, 15.7; pregnant, 24.9). A similar elevation in the modification of lymphocyte proteins in women was found (normal, 15.6; SLE, 40.5). Since the degree of protein modification also was dependent on the ambient level of free 16 alpha OHE, these measurements provide a useful indicator of the long term 16 alpha OHE status of an individual. The modification of proteins by 16 alpha OHE may be a link in the relationship between female hormones, pregnancy, and systemic lupus erythematosus.
Adolescent↗
Recognition and uptake of human diabetic peripheral nerve myelin by macrophages.
Macrophages recognize and ingest several human proteins whose amino groups have been modified in vitro by specific chemical reagents. Because amino groups of human peripheral nerve myelin proteins become covalently modified in vivo by products of nonenzymatic glycosylation, we examined myelin/macrophage interactions using peripheral nerve myelin prepared from diabetic and nondiabetic patients. Intracellular accumulation of diabetic myelin increased with concentration in an apparently saturable fashion, reaching levels 3-4 times higher than those of age-matched nondiabetic samples. Low-temperature inhibition of cellular myelin accumulation further suggested that diabetic myelin uptake was associated with adsorptive endocytosis. Macrophage recognition and accumulation of nondiabetic myelin glycosylated in vitro increased with duration of sugar incubation, to a level nearly nine times that of the same sample incubated in buffer alone. Data from competition experiments with albumin and myelin glycosylated in vitro showed that recognition of human peripheral nerve myelin proteins by macrophages is specific for protein-bound products of nonenzymatic glycosylation. In vivo, such macrophage recognition of and interaction with nonenzymatic glycosylation products on diabetic peripheral nerve myelin could contribute to the pathogenesis of segmental demyelination.
Adult↗
Nonenzymatic glycosylation products on collagen covalently trap low-density lipoprotein.
Advanced nonenzymatic glycosylation products capable of cross-linking proteins accumulate on collagen in vivo in proportion to time-averaged blood glucose concentration. In this report, we have evaluated the ability of advanced nonenzymatic glycosylation products formed on collagen in vitro to covalently bind low-density lipoprotein (LDL) in a manner similar to that which occurs in human atherosclerotic lesions. At constant LDL concentration, covalent trapping increased linearly with the extent of advanced glycosylation product formation, from 1.42 +/- 0.15 to 4.46 +/- 0.36 micrograms LDL protein/mg collagen. At a constant level of collagen advanced glycosylation product, LDL binding increased as a function of increasing LDL concentration. At an LDL-cholesterol level of 103 mg/dl, covalent trapping of LDL by nonenzymatic glycosylation products on collagen averaged 3.2 times as much as control (P less than 0.01). These data indicate that LDL is bound specifically by reactive products generated by nonenzymatic glycosylation of collagen, and suggest that excessive LDL trapping by hyperglycemia-induced advanced glycosylation endproducts may contribute to the accelerated development of atherosclerosis in patients with diabetes mellitus.
Animals↗
Recombinant interleukin 1 suppresses lipoprotein lipase activity in 3T3-L1 cells.
Recombinant murine interleukin 1 (rIL 1) inhibits 3T3-L1 cell expression of lipoprotein lipase (LPL) activity when present in exceedingly dilute concentration (less than 10(-15) M). The extreme sensitivity of the adipocyte system to rIL 1 far exceeds that of the standard lymphocyte-activating factor assay. However, enzyme suppression is incomplete; even at micromolar concentrations, rIL 1 causes only about a 50% reduction in LPL activity. By contrast, cachectin (tumor necrosis factor) achieves nearly complete LPL suppression at subnanomolar concentrations. Concentrated solutions of rIL 1 are incapable of competing with radiolabeled cachectin for binding sites on 3T3-L1 cells. rIL 1-induced LPL suppression is abolished by the addition of a specific IL 1 neutralizing antiserum to the assay system. rIL 1 appears capable of influencing adipocyte expression of LPL, but apparently acts through a different mechanism than cachectin/TNF.
Adipose Tissue↗
Cachectin/tumor necrosis factor: production, distribution, and metabolic fate in vivo.
A highly specific radioreceptor assay for cachectin/tumor necrosis factor (TNF) was utilized to measure the time course of lipopolysaccharide (LPS)-induced hormone production in rabbits. Cachectin/TNF bioactivity was monitored in the same serum samples by measuring lipoprotein lipase (LPL) suppression in 3T3-L1 cells. Cachectin/TNF is produced in large quantities by LPS-treated rabbits without priming by bacillus Calmette Guérin, C. parvum, or other agents. Nanomolar concentrations of the hormone are achieved, with peak levels occurring at 2 hr postinjection; the hormone is rapidly cleared thereafter. In separate studies, mice were used to assess the distribution and metabolic fate of cachectin/TNF. Radioiodinated hormone is cleared from the plasma with a half-life of 6 to 7 min. Studies of the tissue distribution of label after injection demonstrate that liver, kidneys, skin, and gastrointestinal tract take up most of the hormone. Electrophoretic analysis of tissues recovered from injected animals suggests that the hormone is very rapidly degraded after binding.
Animals↗
Lipopolysaccharide-treated RAW 264.7 cells produce a mediator that inhibits lipoprotein lipase in 3T3-L1 cells.
RAW 264.7 cells upon stimulation with lipopolysaccharide secrete a protein mediator(s) that suppresses lipoprotein lipase activity in differentiated 3T3-L1 cells. The mediator(s), which is absent from unstimulated culture supernatants, is nondialyzable and thermolabile. Preliminary characterization suggests that this mediator(s) may be the same as that previously found in medium from lipopolysaccharide-treated thioglycollate-elicited mouse peritoneal macrophage cultures.
Adipose Tissue↗
Accumulation of advanced glycosylation endproducts on proteins and nucleic acids: role in ageing.
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Aging↗
Accumulation of diabetic rat peripheral nerve myelin by macrophages increases with the presence of advanced glycosylation endproducts.
We have previously shown that increased nonenzymatic glycosylation occurs in peripheral nervous tissue of diabetic humans and animals, primarily on the PO-protein of peripheral nerve myelin. The pathophysiologic mechanism by which this biochemical alteration leads to myelin breakdown and removal is not as yet understood. In the present study we show that advanced glycosylation end-product (AGE) adducts that form during long-term exposure of peripheral nerve myelin proteins to glucose in vitro and in vivo markedly alter the way in which myelin interacts with elicited macrophages. In this interaction, macrophages appear to specifically recognize AGEs on myelin, since AGE-BSA competes nearly as effectively as AGE-myelin, while neither unmodified BSA nor unmodified myelin compete. The failure of yeast mannan to interfere with macrophage recognition of AGE-myelin suggests that the mannose/fucose receptor does not mediate this process. Recognition of AGE-protein by macrophages is associated with endocytosis, as demonstrated by resistance of cell-associated radioactivity to removal by trypsin action, and by low temperature inhibition of ligand accumulation in the cellular fraction. 125I-labeled myelin that had been incubated in vitro with 50 mM glucose for 8 wk reached a steady state accumulation within thioglycolate-elicited macrophages that was five times greater than that of myelin incubated without glucose. Similarly, myelin isolated from rats having diabetes for 1.5-2.0 years duration had a steady state level that was 9 times greater than that of myelin from young rats, and 3.5 times greater than that of myelin from age-matched controls. In contrast, myelin isolated from rats having diabetes for 4-5 wk had the same degree of accumulation observed with myelin of age-matched normal rats. These data suggest that the amount of increased nonenzymatic glycosylation observed in the myelin of short-term diabetic rats had not yet resulted in the significant accumulation of AGE-myelin present both in vitro and in the long-term diabetic rats. The disappearance of acid-insoluble radioactivity from within the cells and the appearance of acid-soluble radioactivity released into the medium were very similar for the two groups, suggesting that the striking difference in accumulation seen between normal myelin and AGE-myelin is due primarily to increased uptake. Formation of irreversible AGE-adducts on myelin appears to promote the recognition and uptake of the modified myelin by macrophages. This interaction between AGE-myelin and macrophages may initiate or contribute to the segmental demyelination associated with diabetes and the normal aging of peripheral nerve.
Aging↗