Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The arachidonate lipoxygenase from rat basophilic leukemia cells (RBL-1) is widely utilized as a model to dissect the primary enzymatic reactions leading to leukotriene formation. The purpose of the present study was to optimize the specific activity of 5-lipoxygenase prepared from a high speed supernatant of RBL-1 cell homogenates. Activation of 5-lipoxygenase was observed in the presence of micromolar levels of calcium. A synergistic enhancement of 5-lipoxygenase was observed upon addition of equally low levels of ATP; maximal activation was induced by 5 microM CaCl2 plus 5 microM ATP. Addition of a microsomal-membrane preparation and NADPH further augmented 5-HETE biosynthesis. High concentrations (330 microM) of NADPH reversed the microsomal-induced stimulation of RBL-1 5-lipoxygenase, resulting in enzyme inhibition.
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PMID:Optimization of cofactors which regulate RBL-1 arachidonate 5-lipoxygenase. 274 90

Eicosanoids regulate a wide spectrum of cellular processes including cell proliferation. We have shown previously that lipoxygenase metabolites of arachidonic acid modulate normal human hematopoiesis by in vitro colony assays. In this study we investigated the role of lipoxygenase metabolites in regulating the proliferation of several malignant hematopoietic cell lines, including K562 and EM-2 (chronic myelogenous leukemia blasts), HL-60 (promyelocytic leukemia cells), and U937 (malignant histiocytes). Piriprost, a specific inhibitor of 5-lipoxygenase, inhibits proliferation of these cell lines up to 95% with 50% cell inhibition at approximately 3 x 10(-5) M. Other less specific lipoxygenase inhibitors such as caffeic acid, nordihydroguaiaretic acid, and BW755C have similar activity in a [3H]-thymidine incorporation assay. In contrast, indomethacin, which is a cyclooxygenase inhibitor, has no suppressive effect in these assays. Inhibition by these drugs is completely reversible. Several nonhematopoietic malignant cell lines do not appear to be affected by these drugs. Two specific lipoxygenase metabolites, leukotriene B4 and leukotriene D4, stimulate leukemia cell line proliferation to 150% of control levels when added directly to cell cultures. These data suggest that certain lipoxygenase products, perhaps leukotrienes, are critical for the proliferation of malignant hematopoietic cells in vitro.
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PMID:Antiproliferative effects of lipoxygenase inhibitors on malignant human hematopoietic cell lines. 290 62

Using cultured bovine aortic endothelial cells, the effects of MCI-186, a radical scavenger, were studied on arachidonic acid metabolism and on the cell injury caused by 15-HPETE. MCI-186 at 3 X 10(-5) M enhanced prostacyclin production in the intact endothelial cells without affecting phospholipase A2. When endothelial cell homogenates were used as an enzyme source, it was found that MCI-186 stimulated the conversion of arachidonic acid to prostacyclin like phenol, perhaps by trapping OH radicals produced in the process of the conversion of PGG2 to PGH2. On the other hand, MCI-186 was found to inhibit lipoxygenase metabolism of arachidonic acid in cell free homogenates of rat basophilic leukemia cells. The lipoxygenase inhibition caused by 3 X 10(-5) M MCI-186 was almost equivalent to that caused by 3 X 10(-6) M BW 755C. MCI-186 remarkably protected against endothelial cell damage caused by 15-HPETE. 3 X 10(-5) M of 15-HPETE caused endothelial cell death in about 60% of the population: however, pretreatment of the cells with 10(-5) M of MCI-186 or concomitant addition of 10(-5) M of MCI-186 with 15-HPETE to the cultures prevented the cell death completely. These results suggest that MCI-186 may become an unique anti-ischemic drug.
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PMID:Preventive effect of MCI-186 on 15-HPETE induced vascular endothelial cell injury in vitro. 314 37

The enzyme responsible for 15-lipoxygenation of arachidonic acid was purified to homogeneity from human eosinophil-enriched leukocytes using a combination of ammonium sulfate precipitation, hydrophobic interaction chromatography, and high pressure liquid chromatography on hydroxyapatite and cation-exchange columns. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified protein revealed a single major band (apparent Mr 70,000). Amino acid sequence analysis yielded a single N-terminal sequence. Comparison of the N-terminal 15 residues reveals 71% sequence identity to the rabbit reticulocyte lipoxygenase and 36% sequence identity to the rat basophilic leukemia 5-lipoxygenase. In contrast, sequence identity to the soybean lipoxygenase-1 is not observed. These results demonstrate that human 15-lipoxygenase can be isolated from eosinophil-enriched leukocytes and is accessible for direct sequence analysis. Furthermore, we present initial evidence that the mammalian lipoxygenases constitute an homologous family of enzymes. The availability of homogeneous human 15-lipoxygenase will play a key role in elucidating other relationships in this family of enzymes.
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PMID:Arachidonate 15-lipoxygenase (omega-6 lipoxygenase) from human leukocytes. Purification and structural homology to other mammalian lipoxygenases. 335 88

A full-length cDNA clone encoding 5-lipoxygenase, a key enzyme in the formation of leukotrienes, was isolated from a rat basophilic leukemia cell lambda gt11 cDNA library. The 2.5-kilobase (kb) cDNA insert, whose identity was confirmed by hybrid-select translation and DNA sequence analysis, has a 2.0-kb open reading frame encoding a protein of Mr approximately 77,600 and includes 60 base pairs of 5'-untranslated region and 0.4 kb of 3'-untranslated region to the polyadenylation signal. The deduced amino acid sequence shows significant homology with published sequences for the rabbit reticulocyte lipoxygenase and soybean lipoxygenase-1; it also contains sequences similar to a consensus sequence found in several calcium-dependent membrane-binding proteins. The cDNA recognizes a 2.6-kb mRNA species which is detected in all tissues but is particularly abundant in RNA from lung.
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PMID:Isolation and characterization of a cDNA clone encoding rat 5-lipoxygenase. 341 84

Arachidonate 5-lipoxygenase of rat basophilic leukemia (RBL-1) cells was purified more than 1000-fold by gel filtration and anion exchange protein-high performance liquid chromatography (HPLC). Physical properties of the purified 5-lipoxygenase such as molecular weight (74,000-76,000), N-terminal sequence (30 amino acids), and amino acid composition were determined. The purified enzyme converted [14C]arachidonic acid at 20 degrees to [14C] 5-hydroperoxyeicosatetraenoic acid (5-HPETE) and to [14C]dihydroxyeicosatetraenoic acids (diHETEs). Utilizing [14C] 5(S)HPETE as substrate, the purified enzyme also converted the hydroperoxy acid to [14C]diHETES. The [14C]diHETE reaction products were identified primarily (greater than 80% of recovered radioactivity) as the nonenzymatic hydrolysis products of leukotriene A4 (i.e., 6-trans-leukotriene B4 and 12-epi-6-trans-leukotriene B4) by reverse phase HPLC, scanning spectrophotometry, and gas chromatography-mass spectrometry. The bioconversion of [14C] arachidonate and [14C]5(S)HPETE to reaction products by the purified enzyme was dependent on the presence of both Ca2+ and ATP. The enzymatic activities were inhibited in a similar manner by the lipoxygenase inhibitors nordihydroguaiaretic acid, diphenyldisulfide, and SK&F 86002. The data provide evidence that RBL-1 cell 5-lipoxygenase and leukotriene A4 synthetase activities reside on a single monomeric protein with a free N-terminus and that they possess similar biochemical characteristics.
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PMID:Purification, characterization, and structural properties of a single protein from rat basophilic leukemia (RBL-1) cells possessing 5-lipoxygenase and leukotriene A4 synthetase activities. 378 38

The use of rat basophilic leukemia (RBL-1) cell-line as a biosynthetic source of arachidonic acid metabolites has been previously described. We have developed a rapid and effective procedure for the extraction of lipoxygenase and cyclooxygenase products. The cells grown in spinner cultures were harvested and washed in phosphate buffer and stimulated by calcium ionophore A23187. The ethanolic extract of the cells was dried, dissolved in 20% methanol acidified with acetic acid and applied to octadecyl reversed phase cartridge (Backer C18). The cartridge was washed with 50% methanol (4 ml). Prostaglandins were eluted with 75% methanol (4 ml) and leukotrienes and related compounds with 100% methanol (4 ml). The identification of the fractions was carried out with pure standards. The recoveries of radiolabelled compounds ranged from 70% to 90%. This system can therefore accomplish an initial separation of major arachidonate metabolites and be applied in investigating metabolic pathways of arachidonic acid in different experimental conditions.
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PMID:Purification of arachidonic acid metabolites from cell cultures by octadecyl reversed phase cartridges. 393 Mar 18

Some eukaryotic cells in culture synthesize a variety of lipoxygenase and/or cyclooxygenase products when stimulated by appropriate agonists. Under normal nutritional conditions, these products are derived from the polyunsaturated fatty acid (PUFA) 5,8,11,14-eicosatetraenoic acid (ETA), arachidonic acid, which before metabolism must be liberated from cellular lipids by deesterification. If the cellular lipids are preloaded with 5,8,11,14,17-eicosapentaenoic acid (EPA) and cells are then stimulated to metabolize the PUFAs, levels of cyclooxygenase and lipoxygenase products synthesized are altered. Cyclooxygenase products decrease, while lipoxygenase products are not significantly affected and may even increase. The decrease in the production of cyclooxygenase products results from reduced utilization of the substrate (ETA). Decreased prostaglandin production by rat basophil leukemia-1 cells preloaded with EPA and radiolabeled with [3H]ETA and [14C]EPA can also be demonstrated by high-performance liquid chromatographic analyses of [3H]- and [14C] radiolabeled metabolites in culture fluids of cells stimulated to metabolize PUFA by the Ca2+ ionophore A23187.
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PMID:Eicosapentaenoic acid: its effects on arachidonic acid metabolism by cells in culture. 608 16

Arachidonate 5-lipoxygenase was partially purified from rat basophilic leukemia cells with the aid of ATP as a ligand linked to Sepharose. The enzyme produced predominantly 5-hydroperoxy-6,8,11,14-eicosatetraenoic acid. Calcium ion was required for the enzyme activity (0.1 mM for half maximal activity), and the calcium-dependent reaction was stimulated by ATP and several nucleotides. 5,8,11,14,17-Eicosapentaenoic acid was converted to its 5-hydroperoxy derivative at a higher rate than arachidonate oxygenation. 5,8,11-Eicosatrienoic acid as substrate was almost as active as arachidonic acid. Among various lipoxygenase inhibitors tested, cirsiliol, a flavone derivative, was the most potent.
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PMID:Studies on arachidonate 5-lipoxygenase of rat basophilic leukemia cells. 608 6

Previous studies in a line of rat basophilic leukemia (RBL 1) cells have indicated that the slow reacting substance (SRS) made during stimulation with the divalent cation ionophore, A23187, is derived from arachidonic acid (AA). In the present report, various inhibitors of AA metabolism were compared with regard to their effects on SRS formation and incorporation of radioactivity from [1-14C]-AA into known metabolites of the lipoxygenase and cyclooxygenase pathways. An apparently close parallel between lipoxygenase product formation and SRS synthesis is demonstrated. In addition, exogenous 5-hydroperoxy-eicosatetraenoic acid (5-HPETE) has been shown to markedly enhance SRS synthesis, even when A23187 is absent. The data provide very strong evidence that SRS is produced through the lipoxygenase pathway.
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PMID:Effect of the 5-hydroperoxide of eicosatetraenoic acid and inhibitors of the lipoxygenase pathway on the formation of slow reacting substance by rat basophilic leukemia cells; direct evidence that slow reacting substance is a product of the lipoxygenase pathway. 610 10


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