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)

We studied the ability of rat basophilic leukemia (RBL-2H3) cells stimulated with either IgE/antigen or calcium ionophore, A23187, to synthesize LTC4 and PGD2 after addition of exogenous arachidonic acid. RBL-2H3 cells preferentially synthesized PGD2 in response to stimulation with low concentrations of antigen or A23187 while higher concentrations also resulted in a marked synthesis of LTC4. The synthesis of LTC4 was dependent upon initial activation of 5-lipoxygenase by IgE/antigen or A23187, since arachidonic acid lone failed to induce LTC4 synthesis. Following the addition of IgE/antigen or A23187 alone, the synthesis of PGD2 and LTC4 was essentially complete by 10 min. To determine whether a limitation of substrate precluded further eicosanoid synthesis, exogenous arachidonic acid was added to washed cells 15-145 min following the initial stimulation with IgE/antigen or A23187, PGD2 and LTC4 synthesis was resumed following the addition of arachidonic acid to washed prestimulated cells, demonstrating that the termination of eicosanoid synthesis in RBL-2H3 cells was nor caused by the inactivation of cyclooxygenase and 5-lipoxygenase. DNP-lysine was added to cells previously stimulated with IgE/antigen to stop receptor aggregation and this greatly inhibited subsequent production of LTC4 following the addition of arachidonic acid, suggesting that ongoing stimulation of Fc epsilon XsRI was required for LTC4 synthesis in this setting. These results indicate that the magnitude of a physiologic stimulus (IgE/antigen) can profoundly affect the arachidonate metabolites produced by mast cells and that the synthesis of these metabolites quickly becomes limited by substrate availability rather than the activity of cyclooxygenase or 5-lipoxygenase.
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PMID:Arachidonate-induced eicosanoid synthesis in RBL-2H3 cells: stimulation with antigen or A23187 induces prolonged activation of 5-lipoxygenase. 881 55

Poly-2'-O-(2,4-dinitrophenyl)poly[A] (DNP-poly[A] is a potent inhibitor of reverse transcriptases from a variety of sources (I. Kang and J. H. Wang, J. Biol. Chem. 269:12024-12031, 1994). In the present study, its inhibitory effect on the reverse transcriptase (RT) from Moloney murine leukemia virus (MuLV) was investigated. DNP-poly[A] was found to enter the virus spontaneously and to completely inhibit the RT within 30 min at 0 degree C. The inhibitor was also spontaneously transported into isolated human lymphocytes and leukocytes at 37 degrees C. Animal studies have demonstrated the effectiveness of DNP-poly[A] as an antiviral drug when administered intraperitoneally at various doses from 1 to 100 mg/kg of body weight. MuLV-infected mice show the presence of RT in their blood as well as increased numbers of leukocytes. After the administration of DNP-poly[A] at a dosage of 100 mg/kg of body weight three times a week over a 3-week period, RT could no longer be detected by an ultrasensitive RT-PCR assay. Autopsy showed that the spleens of infected but untreated mice were enlarged 2- to 10-fold, with fused nodules and the proliferation of large abnormal lymphocytes, whereas the spleens of infected but treated mice resembled the normal spleens of uninfected control mice. These observations indicate that further study of DNP-poly[A] as a general antiretroviral agent is desirable.
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PMID:Inhibition of murine leukemia virus with poly-2'-O-(2,4-dinitrophenyl)poly[A]. 889 Nov 36

Two antisense poly-2'-O-(2,4-dinitrophenyl)-oligoribonucleotides (poly-DNP-RNA) have been synthesized and tested for the treatment of murine leukemia. Compound I was designed as a bifunctional inhibitor of either the reverse transcriptase (RT) activity or viral envelope synthesis in Moloney murine leukemia virus (MMLV). Compound II was designed as a trifunctional inhibitor of either RT activity or envelope synthesis or protease synthesis in MMLV. Administration of either I or II to MMLV-infected mice for 3 weeks decreased viremia gradually to below the level detectable by RT-PCR. Viremia did not reappear 8 weeks after termination of treatment, when most of the mice were killed for autopsy. All infected but untreated mice died within 6 months with enlarged spleens that exhibited abnormal histologic signs and were found by PCR to contain the DNA of integrated viral genome. The infected mice that had been treated subsequently with adequate dosage of compound I or II had normal spleens, continued to live on, and had no integrated MMLV genome in their spleen and bone marrow samples. The effective i.p. dosage (ED50) for compounds I and II are 0.25 and 0.1 mg/kg, respectively, which are 200-fold to 500-fold lower than that of the monofunctional RT inhibitor poly-DNP-oligo A. The estimated effective oral dosage of compound II is 1.2 mg/kg.
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PMID:Effective treatment of murine leukemia with antisense poly-2'O-(2,4-dinitrophenyl)-oligoribonucleotides. 1019 88

Aggregation of cell surface receptors by multivalent ligand can trigger a variety of cellular responses. A well-studied receptor that responds to aggregation is the high affinity receptor for IgE (FcepsilonRI), which is responsible for initiating allergic reactions. To quantify antigen-induced aggregation of IgE-FcepsilonRI complexes, we have developed a method based on multiparameter flow cytometry to monitor both occupancy of surface IgE combining sites and association of antigen with the cell surface. The number of bound IgE combining sites in excess of the number of bound antigens, the number of bridges between receptors, provides a quantitative measure of IgE-FcepsilonRI aggregation. We demonstrate our method by using it to study the equilibrium binding of a haptenated fluorescent protein, 2,4-dinitrophenol-coupled B-phycoerythrin (DNP25-PE), to fluorescein isothiocyanate-labeled anti-DNP IgE on the surface of rat basophilic leukemia cells. The results, which we analyze with the aid of a mathematical model, indicate how IgE-FcepsilonRI aggregation depends on the total concentrations of DNP25-PE and surface IgE. As expected, we find that maximal aggregation occurs at an optimal antigen concentration. We also find that aggregation varies qualitatively with the total concentration of surface IgE as predicted by an earlier theoretical analysis.
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PMID:Quantifying aggregation of IgE-FcepsilonRI by multivalent antigen. 1023 59

The degranulation of mast cells in an allergic response is initiated by the aggregation of high-affinity IgE receptors (Fc epsilon RI) by IgE and antigen. Recently it has been shown that such degranulation can be inhibited by cross-linking Fc epsilon RI and low-affinity IgG receptors (Fc gamma RII) which are also expressed by mast cells. The ability of various monoclonal antibodies to block the degranulation of rat basophil leukaemia (RBL) cells sensitized with IgE antidinitrophenyl (DNP) antibodies has been investigated. Sensitized cells were challenged with immune complexes formed using varying concentrations of antigen, and of both high- and low-valency antigen. It is reported here that rat IgG1 antibodies, which are associated in the rat with a Th1-type response, act as highly effective blocking antibodies over a wide concentration range. Rat IgG2a antibodies, which are associated with a Th2-type response, were able only to inhibit degranulation when immune complexes were formed with very low concentrations of high-valency antigen (DNP32-HSA). Under these conditions, some inhibitory activity was seen with high-affinity murine IgA anti-DNP but not with low-affinity rat IgG2b anti-DNP antibody-containing immune complexes. In addition to this inhibitory activity, IgG2a antibodies were shown to be capable of inducing degranulation of cells via unoccupied Fc epsilon RI. These results demonstrate that blocking activity may arise via both inhibitory receptors and by masking of antigen.
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PMID:The effectiveness of different rat IgG subclasses as IgE-blocking antibodies in the rat basophil leukaemia cell model. 1023 46

Rat basophilic leukemia (RBL) cells resemble mucosal mast cells (MMC) and develop few secretory granules under normal culture conditions. RBL cells have been used for the study of secretion and for the possible involvement of MMC in food allergies and irritable bowel syndrome (IBS). The flavonoid quercetin is one of very few molecules that inhibit RBL cell proliferation and constitutive histamine release; it also induces synthesis of rat mast cell protease (RMCP) II and accumulation of secretory granules. Even though quercetin is available as a food supplement over the counter, some early studies had indicated it may be carcinogenic. We, therefore, compared the effect of quercetin to that of other flavonoids with similar structure. Flavone, kaempferol, myricetin and morin were investigated for their action on RBL cell secretion of beta-hexosaminidase stimulated by anti-DNP serum and DNP-BSA, as well as on secretory granule development. Quercetin, myricetin and kaempferol inhibited RBL cell secretion significantly only at 10(-4) M. Flavone inhibited secretion at 10(-4), 10(-5) and 10(-6) M; it also maximally induced secretory granule accumulation as evidenced by light and electron microscopy. In contrast, morin which differs structurally only by one extra hydroxyl group had minimal effect. These results indicate that flavone is capable of inhibiting stimulated secretion and inducing secretory granule development at reasonable concentrations.
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PMID:Differential effect of flavonoids on inhibition of secretion and accumulation of secretory granules in rat basophilic leukemia cells. 1040 73

The need to modify tumor cells in order to render them more "immunogenic" was based on the assumption that normal, nonmodified tumor cells are non- or weakly immunogenic and as such are unable to raise an efficient protective immune response. Various methods for "xenogenization" (modification of tumor cells) were suggested: induction of new foreign antigens, treatment with either chemicals or enzymes and use of mutagens. Xenogenized tumor cells by their coupling to proteins, and use of chemicals like DTIC (5-[3,3-dimethyl- 1-triazeno]-imidazole-4-carboxamide), TZC (8-carbamoyl-3-methyl-imidazo[5, 1-d]- 1,2,3,5-tetrazin-4 [3H]-one 8-carbamoyl-3-[2-chloroethyl] imidazole [5,1 -d]- 1,2,3,5-tetrazin-4[3H]-one) and antiemetic drugs, were tested in experimental models of murine leukemia. Non-tumorigenic clones, xenogenization with DNA hypomethylating agents, aryl-triazine derivatives and DTIC were evaluated for their induction of protective immune response in murine lymphoma. Murine plasmacytoma cells were used for immunization after treatment with glutaraldehyde. Viral modifications of tumor cells were evaluated for their ability to induce a protective tumor response in model systems of rat fibrosarcoma, liver metastatic rat tumor cells, lymphoid tumor cells and hamster tumor cells. In the case of human cancer, attempts were reported to use DNP-conjugated melanoma cells, mutagenic triazine compounds, an autologous colon tumor cell bacillus Calmette-Guerin (BCG) vaccine and genetically engineered vaccines for immunization. The general conclusion drawn from experimental tumor models and for human cancer is, that although modified tumor cells were found to be partially effective in experimental models, it is still necessary to provide more data in order to determine the effective use of xenogenized human tumor cells for immunotherapy.
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PMID:Use of xenogenized (modified) tumor cells for treatment in experimental tumor and in human neoplasia. 1091 65

Basophils and mast cells contain a peculiar class of inflammatory granules that discharge their content upon antigen-mediated crosslinking of IgE-membrane receptors. The pathways for granule biogenesis and exocytosis in these cells are still largely obscure. In this study we employed the rat basophilic leukemia (RBL)/mast cell line to verify the hypothesis that inflammatory granules share common bioactive molecules and functional properties with lysosomes. We demonstrate that inflammatory granules, as identified by the monoclonal 5G10 antibody (which recognises an integral membrane protein) or by Toluidine Blue staining, have an intralumenal acidic pH, possess lysosomal enzymes and are accessible by fluid-phase and membrane endocytosis markers. In addition, we studied the targeting, subcellular localisation and regulated secretion of the lysosomal aspartic protease cathepsin D (CD) as affected by IgE receptor stimulation in order to obtain information on the pathways for granule biogenesis and exocytosis. Stimulation with DNP-BSA of specific IgE-primed RBL cells led to a prompt release of processed forms of CD, along with other mature lysosomal hydrolases. This release could be prevented by addition of EGTA, indicating that it was dependent on extracellular calcium influx. Antigen stimulation also induced exocytosis of immature CD forms accumulated by ammonium chloride, suggesting the existence of an intermediate station in the pathway for granule biogenesis still sensitive to regulated exocytosis. The targeting of molecules to secretory granules may occur via either a mannose-6-phosphate-dependent or mannose-6-phosphate-independent pathway. We conclude that endosomes and lysosomes in basophils/mast cells can act as regulated secretory granules or actually identify with them.
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PMID:The lysosomal protease cathepsin D is efficiently sorted to and secreted from regulated secretory compartments in the rat basophilic/mast cell line RBL. 1095 26

There are conflicting reports in the literature as to whether palmitoylethanolamide affects the function of mast cell-related cell lines in vitro, in contrast to the well-documented effects of this compound upon mast cell function in vivo. In the present study, we have reinvestigated the effects of palmitoylethanolamide upon antigen-induced release of [3H]serotonin and beta-hexosaminidase from rat basophilic leukemia RBL-2H3 cells and compared these effects with those of 2-arachidonoylglycerol, anandamide and R1-methanandamide. RBL-2H3 cells were sensitized with a monoclonal anti-DNP IgE, after which they were stimulated with antigen (DNP-HSA). Palmitoylethanolamide produced a small, but significant reduction in antigen-stimulated [3H]serotonin release at high concentrations, whereas anandamide was without effect. In contrast, 2-arachidonoylglycerol and methanandamide increased the antigen-stimulated release of both [3H]serotonin and beta-hexosaminidase. It is concluded that in RBL-2H3 cells, these cannabimimetic fatty acid derivatives do not have potent stabilizing effects upon antigen-induced degranulation.
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PMID:Effects of the cannabimimetic fatty acid derivatives 2-arachidonoylglycerol, anandamide, palmitoylethanolamide and methanandamide upon IgE-dependent antigen-induced beta-hexosaminidase, serotonin and TNF alpha release from rat RBL-2H3 basophilic leukaemic cells. 1148 41

IgE plays a central role in allergic reactions. Some anti-IgE antibodies (HMK-12, 6HD5) inhibit the binding of IgE to the FcepsilonRI of mast cells/basophilic leukemia cells (PT-18, RBL/2H3), but less inhibition is seen with the anti-allotypic JKS-6 and the anti-idiotypic Eb-1. Anti-IgE HMK-12 can detach bound IgE molecules from the FcepsilonRI. When mast cells or basophils were incubated with monoclonal anti-DNP-IgE SPE-7, washed and treated with anti-IgE HMK-12, anti-IgE/IgE complexes were found in the supernatant. Similar results were obtained with the Fab fragment of HMK-12. Mice injected with anti-DNP-IgE SPE-7 and later with DNP-BSA had the typical systemic anaphylactic shock. However, if they were injected with the anti-IgE antibody (HMK-12) before the challenge, they did not get an anaphylactic shock. In the sera of mice injected with monoclonal IgE SPE-7 and anti-IgE antibody (HMK-12), IgE/anti-IgE complexes were detected. No passive cutaneous anaphylaxis occurred if the rats were injected with anti-IgE antibodies before the challenge. In summary, anti-IgE antibodies can remove IgE antibodies from the FcepsilonRI; anti-IgE/IgE complexes can be detected in vitro and in vivo, and anti-IgE antibodies can inhibit IgE-mediated systemic or local anaphylactic reactions.
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PMID:Rat monoclonal anti-murine IgE antibody removes IgE molecules already bound to mast cells or basophilic leukemia cells, resulting in the inhibition of systemic anaphylaxis and passive cutaneous anaphylaxis. 1203 98


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