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Meghnem D, Leong E, Pinelli M, Marshall JS, Di Cara F. Peroxisomes Regulate Cellular Free Fatty Acids to Modulate Mast Cell TLR2, TLR4, and IgE-Mediated Activation. Front Cell Dev Biol 2022; 10:856243. [PMID: 35756999 PMCID: PMC9215104 DOI: 10.3389/fcell.2022.856243] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Accepted: 04/12/2022] [Indexed: 11/17/2022] Open
Abstract
Mast cells are specialized, tissue resident, immune effector cells able to respond to a wide range of stimuli. MCs are involved in the regulation of a variety of physiological functions, including vasodilation, angiogenesis and pathogen elimination. In addition, MCs recruit and regulate the functions of many immune cells such as dendritic cells, macrophages, T cells, B cells and eosinophils through their selective production of multiple cytokines and chemokines. MCs generate and release multi-potent molecules, such as histamine, proteases, prostanoids, leukotrienes, heparin, and many cytokines, chemokines, and growth factors through both degranulation dependent and independent pathways. Recent studies suggested that metabolic shifts dictate the activation and granule content secretion by MCs, however the metabolic signaling promoting these events is at its infancy. Lipid metabolism is recognized as a pivotal immunometabolic regulator during immune cell activation. Peroxisomes are organelles found across all eukaryotes, with a pivotal role in lipid metabolism and the detoxification of reactive oxygen species. Peroxisomes are one of the emerging axes in immunometabolism. Here we identified the peroxisome as an essential player in MCs activation. We determined that lack of functional peroxisomes in murine MCs causes a significant reduction of interleukin-6, Tumor necrosis factor and InterleukinL-13 following immunoglobulin IgE-mediated and Toll like receptor 2 and 4 activation compared to the Wild type (WT) BMMCs. We linked these defects in cytokine release to defects in free fatty acids homeostasis. In conclusion, our study identified the importance of peroxisomal fatty acids homeostasis in regulating mast cell-mediated immune functions.
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Affiliation(s)
- Dihia Meghnem
- Dalhousie Human Immunology and Inflammation Group, Department of Microbiology and Immunology, Dalhousie University, Halifax, NS, Canada
- Department of Pediatrics, Nova Scotia Health Authority IWK, Halifax, NS, Canada
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS, Canada
| | - Edwin Leong
- Department of Pathology, Dalhousie University, Halifax, NS, Canada
| | - Marinella Pinelli
- Department of Pediatrics, Nova Scotia Health Authority IWK, Halifax, NS, Canada
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS, Canada
| | - Jean S. Marshall
- Dalhousie Human Immunology and Inflammation Group, Department of Microbiology and Immunology, Dalhousie University, Halifax, NS, Canada
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS, Canada
- Department of Pathology, Dalhousie University, Halifax, NS, Canada
- *Correspondence: Jean S. Marshall, ; Francesca Di Cara,
| | - Francesca Di Cara
- Department of Pediatrics, Nova Scotia Health Authority IWK, Halifax, NS, Canada
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS, Canada
- *Correspondence: Jean S. Marshall, ; Francesca Di Cara,
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Park JW, Jeon YJ, Lee JC, Ahn SR, Ha SW, Bang SY, Park EK, Yi SA, Lee MG, Han JW. Destabilization of TNF-α mRNA by Rapamycin. Biomol Ther (Seoul) 2013; 20:43-9. [PMID: 24116273 PMCID: PMC3792200 DOI: 10.4062/biomolther.2012.20.1.043] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 12/22/2011] [Accepted: 12/27/2011] [Indexed: 11/24/2022] Open
Abstract
Stimulation of mast cells through the high affinity IgE receptor (FcεRI) induces degranulation, lipid mediator release, and cytokine secretion leading to allergic reactions. Although various signaling pathways have been characterized to be involved in the FcεRI-mediated responses, little is known about the precious mechanism for the expression of tumor necrosis factor-α (TNF-α) in mast cells. Here, we report that rapamycin, a specific inhibitor of mammalian target of rapamycin (mTOR), reduces the expression of TNF-α in rat basophilic leukemia (RBL-2H3) cells. IgE or specific antigen stimulation of RBL-2H3 cells increases the expression of TNF-α and activates various signaling molecules including S6K1, Akt and p38 MAPK. Rapamycin specifically inhibits antigen-induced TNF-α mRNA level, while other kinase inhibitors have no effect on TNF-α mRNA level. These data indicate that mTOR signaling pathway is the main regulation mechanism for antigen-induced TNF-α expression. TNF-α mRNA stability analysis using reporter construct containing TNF-α adenylate/uridylate-rich elements (AREs) shows that rapamycin destabilizes TNF-α mRNA via regulating the AU-rich element of TNF-α mRNA. The antigen-induced activation of S6K1 is inhibited by specific kinase inhibitors including mTOR, PI3K, PKC and Ca2+chelator inhibitor, while TNF-α mRNA level is reduced only by rapamycin treatment. These data suggest that the effects of rapamycin on the expression of TNF-α mRNA are not mediated by S6K1 but regulated by mTOR. Taken together, our results reveal that mTOR signaling pathway is a novel regulation mechanism for antigen-induced TNF-α expression in RBL-2H3 cells.
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Affiliation(s)
- Jong-Woo Park
- Research Center for Epigenome Regulation, School of Pharmacy, Sungkyunkwan University, Suwon 440-746, Republic of Korea
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Michael C. Madden Mitchell Friedman. INHIBITION OF ARACHIDONIC ACID ESTERIFICATION IN HUMAN AIRWAY EPITHELIAL CELLS EXPOSED TO OZONE IN VITRO. Inhal Toxicol 2008. [DOI: 10.1080/089583798197466] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Tomita M, Baker RC, Ando S, Santoro TJ. Arachidonoyl-phospholipid remodeling in proliferating murine T cells. Lipids Health Dis 2004; 3:1. [PMID: 14754461 PMCID: PMC343295 DOI: 10.1186/1476-511x-3-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2003] [Accepted: 01/30/2004] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Previous studies have shown that the functional capacity of T cells may be modulated by the composition of fatty acids within, and the release of fatty acids from membrane phospholipids, particularly containing arachidonic acid (AA). The remodeling of AA within membrane phospholipids of resting and proliferating CD4+ and CD8+ T cells is examined in this study. RESULTS Splenic T cells were cultured in the presence or absence of anti-CD3 mAb for 48 h then labeled with [3H]AA for 20 min. In unstimulated cells, labeled AA was preferentially incorporated into the phosphoglycerides, phosphatidylcholine (PC) followed by phosphatidylinositol (PI) and phosphatidylethanolamine (PE). During a subsequent chase in unlabeled medium unstimulated CD4+ and CD8+ T cells demonstrated a significant and highly selective transfer of free, labeled AA into the PC pool. In contrast, proliferating CD4+ and CD8+ T cells distributed labeled [3H]AA predominantly into PI followed by PC and PE. Following a chase in AA-free medium, a decline in the content of [3H]AA-PC was observed in association with a comparable increase in [3H]AA-PE. Subsequent studies revealed that the cold AA content of all PE species was increased in proliferating T cells compared with that in non-cycling cells, but that enrichment in AA was observed only in the ether lipid fractions. Finally, proliferating T cells preincubated with [3H]AA exhibited a significant loss of labeled arachidonate in the PC fraction and an equivalent gain in labeled AA in 1-alk-1'-enyl-2-arachidonoyl-PE during a chase in unlabeled medium. CONCLUSION This apparent unidirectional transfer of AA from PC to ether-containing PE suggests the existence of a CoA-independent transacylase system in T cells and supports the hypothesis that arachidonoyl phospholipid remodeling may play a role in the regulation of cellular proliferation.
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Affiliation(s)
- Michiyo Tomita
- Departments of Internal Medicine, University of North Dakota, Grand Forks, ND 58203, USA
| | - Rodney C Baker
- Department of Pharmacology & Toxicology, University of Mississippi, Jackson, MS 39216. USA
| | - Soichiro Ando
- Department of Medicine, Juntendo University, Tokyo, Japan
| | - Thomas J Santoro
- Departments of Internal Medicine, University of North Dakota, Grand Forks, ND 58203, USA
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Naesse EP, Schreurs O, Helgeland K, Schenck K, Steinsvoll S. Matrix metalloproteinases and their inhibitors in gingival mast cells in persons with and without human immunodeficiency virus infection. J Periodontal Res 2004; 38:575-82. [PMID: 14632920 DOI: 10.1034/j.1600-0765.2003.00687.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND Mast cells are a prominent cell type in the gingival infiltrate in periodontitis. In this study we examined the expression by gingival mast cells of matrix metalloproteinases, MMP-1, MMP-2, MMP-8 and the tissue inhibitors of metalloproteinases, TIMP-1 and TIMP-2. METHODS Gingival specimens from 12 human immunodeficiency virus-negative (HIV-) and 15 HIV-positive (HIV+) patients with chronic marginal periodontitis (CMP), and from 10 HIV- and four HIV+ controls with clinically healthy gingiva (HG) were examined after double immunofluorescence staining for mast cell tryptase, combined with antibodies for MMP-1, MMP-2, MMP-8 or their inhibitors TIMP-1 and TIMP-2. RESULTS In the HIV+CMP, HIV+HG and HIV-CMP groups, all mast cells expressed MMP-1 and MMP-8, whereas a smaller proportion (40-60%) in the HIV-HG controls displayed such staining. The former groups also displayed a significantly higher proportion (39-64%) of mast cells expressing MMP-2 as compared with the HIV-HG group (21-31%). All groups displayed similar proportions of TIMP-1 expressing mast cells (86-100%), whereas significantly increased proportions of TIMP-2+ mast cells were seen in the HIV+CMP, HIV+HG and HIV-CMP groups (18-25%) as compared with the HIV-HG group (8-13%). Mast cells were the cell type that most prominently expressed MMP-1 and MMP-8. MMP-2 expression was also strong in mast cells, but was also similarly expressed in other cell types. CONCLUSION The chronically inflamed periodontal lesions in the present study appeared with little evidence of mast cell degranulation. The results show, however, that mast cells in inflamed gingiva have the potential to degrade extracellular matrix if appropriately triggered.
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Affiliation(s)
- E P Naesse
- Department of Oral Biology, University of Oslo, Oslo, Norway
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Tkaczyk C, Okayama Y, Woolhiser MR, Hagaman DD, Gilfillan AM, Metcalfe DD. Activation of human mast cells through the high affinity IgG receptor. Mol Immunol 2002; 38:1289-93. [PMID: 12217397 DOI: 10.1016/s0161-5890(02)00077-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Mast cells are known to participate in the induction of inflammation through interaction of antigen with specific IgE bound to the high affinity receptor for IgE (FcepsilonRI). Human mast cells, derived from CD34(+) hematopoietic precursors, not only express FcepsilonRI but also express high affinity receptors for IgG (FcgammaRI), the latter only after IFN-gamma exposure. Human mast cells that express FcgammaRI are activated following FcgammaRI aggregation, either using antibodies directed to the receptor or through IgG bound to the receptor. This activation results in degranulation, with the release of granule-associated mediators, and the generation of metabolites of arachidonic acid and secretion of chemokines and cytokines. These observations provide evidence that human mast cells may also be recruited into inflammation through IgG-dependent mechanisms.
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Affiliation(s)
- Christine Tkaczyk
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Building 10, Room 11C205, 10 Center Drive MSC 1881, Bethesda, MD 2089-1881, USA
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Diaz BL, Fujishima H, Kanaoka Y, Urade Y, Arm JP. Regulation of prostaglandin endoperoxide synthase-2 and IL-6 expression in mouse bone marrow-derived mast cells by exogenous but not endogenous prostanoids. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 168:1397-404. [PMID: 11801681 DOI: 10.4049/jimmunol.168.3.1397] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Mouse bone marrow-derived mast cells (BMMC), stimulated with stem cell factor, IL-1beta, and IL-10, secrete IL-6 and demonstrate a delayed phase of PGD(2) generation that is dependent upon the induced expression of PG endoperoxide synthase (PGHS)-2. We have examined the potential for exogenous prostanoids, acting in a paracrine fashion, and endogenous prostanoids, acting in an autocrine fashion, to regulate PGHS-2 induction and IL-6 secretion in mouse BMMC. Exogenous PGE(2), which acts through G protein-coupled receptors, and 15-deoxy-Delta(12,14)-PGJ(2), which is a ligand for peroxisome proliferator-activated receptor (PPAR)gamma, elicited a 2- to 3-fold amplification of PGHS-2 induction, delayed-phase PGD(2) generation, and IL-6 secretion in response to stem cell factor, IL-1beta, and IL-10. The effect of PGE(2) was reproduced by the E prostanoid (EP)1 receptor agonist 17-trinor-PGE(2), and the EP1/EP3 agonist, sulprostone, but not the EP2 receptor agonist, butaprost. Although BMMC express PPARgamma, the effects of 15-deoxy-Delta(12,14)-PGJ(2) were not reproduced by the PPARgamma agonists, troglitazone and ciglitazone. PGHS-2 induction, but not IL-6 secretion, was impaired in cPLA(2)-deficient BMMC. However, there was no impairment of PGHS-2 induction in BMMC deficient in hematopoietic PGD synthase or PGHS-1 in the presence or absence of the PGHS-2 inhibitor, NS-398. Thus, although exogenous prostanoids may contribute to amplification of the inflammatory response by augmenting PGD(2) generation and IL-6 secretion from mast cells, endogenous prostanoids do not play a role.
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Affiliation(s)
- Bruno L Diaz
- Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
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Affiliation(s)
- C Tkaczyk
- Laboratory of Allergic Diseases, National Institutes of Allergy and Inflammatory Diseases, National Institutes of Health, Building 10, Room 11C213, MSC 1881, 10 Center Drive, Bethesda, MD 20892-1881, USA
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Fonteh AN, LaPorte T, Swan D, McAlexander MA. A decrease in remodeling accounts for the accumulation of arachidonic acid in murine mast cells undergoing apoptosis. J Biol Chem 2001; 276:1439-49. [PMID: 11022038 DOI: 10.1074/jbc.m006551200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The goal of this study was to examine arachidonic acid (AA) metabolism by murine bone marrow-derived mast cells (BMMC) during apoptosis induced by cytokine depletion. BMMC deprived of cytokines for 12-48 h displayed apoptotic characteristics. During apoptosis, levels of AA, but not other unsaturated fatty acids, correlated with the percentage of apoptotic cells. A decrease in both cytosolic phospholipase A(2) expression and activity indicated that cytosolic phospholipase A(2) did not account for AA mobilization during apoptosis. Free AA accumulation is also unlikely to be due to decreases in 5-lipoxygenase and/or cyclooxygenase activities, since BMMC undergoing apoptosis produced similar amounts of leukotriene B(4) and significantly greater amounts of PGD(2) than control cells. Arachidonoyl-CoA synthetase and CoA-dependent transferase activities responsible for incorporating AA into phospholipids were not altered during apoptosis. However, there was an increase in arachidonate in phosphatidylcholine (PC) and neutral lipids concomitant with a 40.7 +/- 8.1% decrease in arachidonate content in phosphatidylethanolamine (PE), suggesting a diminished capacity of mast cells to remodel arachidonate from PC to PE pools. Further evidence of a decrease in AA remodeling was shown by a significant decrease in microsomal CoA-independent transacylase activity. Levels of lyso-PC and lyso-PE were not altered in cells undergoing apoptosis, suggesting that the accumulation of lysophospholipids did not account for the decrease in CoA-independent transacylase activity or the induction of apoptosis. Together, these data suggest that the mole quantities of free AA closely correlated with apoptosis and that the accumulation of AA in BMMC during apoptosis was mediated by a decreased capacity of these cells to remodel AA from PC to PE.
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Affiliation(s)
- A N Fonteh
- Department of Internal Medicine, Pulmonary and Critical Care Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27154, USA.
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Chilton FH, Fonteh AN, Surette ME, Triggiani M, Winkler JD. Control of arachidonate levels within inflammatory cells. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1299:1-15. [PMID: 8555241 DOI: 10.1016/0005-2760(95)00169-7] [Citation(s) in RCA: 182] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- F H Chilton
- Department of Internal Medicine, Bowman Gray School of Medicine, Winston-Salem, NC 27157, USA
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Shipley MM, Dillwith JW, Bowman AS, Essenberg RC, Sauer JR. Distribution of arachidonic acid among phospholipid subclasses of lone star tick salivary glands. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 1994; 24:663-670. [PMID: 8069331 DOI: 10.1016/0965-1748(94)90053-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The subclass composition of choline- and ethanolamine-containing phospholipids was determined by analysis of acyl-linked fatty acids released by base hydrolysis of diradylglycerobenzoates formed from lone star tick salivary gland diacyl, alkylacyl and alkenylacyl phospholipids. The diacyl subclass comprises 87% of all choline-containing phospholipids, while th alkylacyl subclass comprises c. 9% and the alkenylacyl subclass c. 4%. The diacyl subclass comprises 72-77% of ethanolamine-containing phospholipids and about 14 and 13% of this subclass of phospholipid are alkylacyl and alkenylacyl lipids, respectively. Arachidonic acid (20:4) is the most abundant fatty acid (28% of all fatty acids) esterified in the alkylacyl form of phosphatidylcholine (PC) and it comprises 17% of the fatty acids in alkenylacyl-PC. The alkylacyl form of phosphatidylethanolamine (PE) is also rich in 20:4 (24%) while the alkenylacyl-PE subclass contains only 9% 20:4. Despite the relatively high amounts of 20:4 within the ether-linked phospholipids, the majority of the salivary gland 20:4 (> 83%) is found in the diacyl phospholipid subclass because of the preponderence of this subclass in tick salivary glands. Isolated salivary glands incorporated [3H]-20:4 primarily (> 98%) into the sn-2 position of diacyl PC > PE, with some incorporation into triglycerides. Continued incubation in the absence of labeled 20:4 demonstrated remodeling of [3H]-20:4 from PC into PE, and from the diacyl subclass to the alkylacyl subclass in the choline containing phospholipids.
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Affiliation(s)
- M M Shipley
- Department of Entomology, Oklahoma State University, Stillwater 74078
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Ishimoto T, Akiba S, Sato T, Fujii T. Contribution of phospholipases A2 and D to arachidonic acid liberation and prostaglandin D2 formation with increase in intracellular Ca2+ concentration in rat peritoneal mast cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 219:401-6. [PMID: 7508386 DOI: 10.1111/j.1432-1033.1994.tb19952.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The contribution of phospholipases A2 (PLA2) and D (PLD) activation to arachidonic acid liberation and prostaglandin D2 (PGD2) formation was studied in stimulated rat peritoneal mast cells. Stimulation of the cells with ionomycin induced time-dependent and Ca(2+)-concentration-dependent increase in arachidonic acid liberation and PGD2 formation, and the Ca(2+)-dependent increase was especially remarkable at extracellular Ca2+ concentration higher than 200 microM. Staurosporine did not induce any effect on the arachidonic acid liberation, indicating that protein kinase C is not involved in the liberation. Addition of ethanol to the cells decreased the ionomycin-stimulated arachidonic acid liberation to 40% of the control, while it decreased the PGD2 formation almost completely, with the increase in phosphatidylethanol formation. Propranolol, a phosphatidate phosphohydrolase inhibitor, caused similar effects. p-Bromophenacyl bromide, a PLA2 inhibitor, inhibited partially the arachidonic acid liberation. The inhibition of the liberation by combination of p-bromophenacyl bromide and ethanol was additive and reached approximately 90%. Under the conditions used p-bromophenacyl bromide did not influence significantly the PLD activity assessed by the phosphatidylethanol formation. Histamine release was decreased by ethanol treatment to 35% of the control. These results suggest that more than half of the total arachidonic acid liberation is mediated by the sequential pathway of PLD/phosphatidate phosphohydrolase/diacylglycerol lipase and more than half of histamine release is also dependent on PLD activation, while the PGD2 formation is fully mediated by the pathway. PLA2 also contributes to arachidonic acid liberation but to a lower extent.
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Affiliation(s)
- T Ishimoto
- Department of Biochemistry, Kyoto Pharmaceutical University, Japan
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13
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Winkler JD, Sung CM, Hubbard WC, Chilton FH. Evidence for different mechanisms involved in the formation of lyso platelet-activating factor and the calcium-dependent release of arachidonic acid from human neutrophils. Biochem Pharmacol 1992; 44:2055-66. [PMID: 1449523 DOI: 10.1016/0006-2952(92)90109-v] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Recent studies suggest that the first step in platelet-activating factor (PAF) biosynthesis, 1-alkyl-2-lyso-GPC (lyso PAF) formation, may be initiated by the selective transfer of arachidonate from 1-alkyl-2-arachidonoyl-GPC to an acceptor lyso phospholipid by a CoA-independent transacylase activity (CoA-IT). The present study was designed to determine whether the formation of 1-alkyl-2-lyso-GPC and the release of arachidonic acid can occur by different mechanisms. These experiments examined both the formation of 1-[3H]alkyl-2-lyso-GPC from 1-[3H]alkyl-2-acyl-GPC and the release of arachidonic acid from membrane phospholipids as determined by GC/MS in neutrophil homogenates under various conditions. The addition of unlabelled lyso phospholipids to neutrophil homogenates stimulated the time-dependent formation of 1-[3H]alkyl-2-lyso-GPC from 1-[3H]alkyl-2-acyl-GPC. Without exogenous lyso phospholipids, little 1-[3H]alkyl-2-lyso-GPC was formed in this reaction. The activity which catalyzed the formation of 1-[3H]alkyl-2-lyso-GPC had characteristics identical to CoA-IT as indicated by the fact that both reactions were: independent of Ca2+, Mg2+, CoA and CoA fatty acids, located in microsomal fractions, and stable in 10 mM dithiothreitol. In sharp contrast to the aforementioned reaction, addition of lyso phospholipids did not affect the quantity of arachidonic acid released from membrane phospholipids. Furthermore, there was a Ca(2+)-independent release of arachidonic acid from membrane phospholipid that was increased 4 to 5-fold after the addition of 5 mM Ca2+. Finally, Ca(2+)-dependent arachidonic acid release was inhibited by putative phospholipase A2 inhibitors, aristolochic acid and scalaradial, at concentrations where neither the production of 1-[3H]alkyl-2-lyso-GPC nor Ca(2+)-independent arachidonic acid release was altered. Together these data imply that there may be different mechanisms involved in the formation of 1-alkyl-2-lyso-GPC and arachidonic acid from membrane phospholipids.
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Affiliation(s)
- J D Winkler
- Division of Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, PA 19406
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14
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Triggiani M, Fonteh AN, Chilton FH. Factors that influence the proportions of platelet-activating factor and 1-acyl-2-acetyl-sn-glycero-3-phosphocholine synthesized by the mast cell. Biochem J 1992; 286 ( Pt 2):497-503. [PMID: 1530582 PMCID: PMC1132925 DOI: 10.1042/bj2860497] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Recent studies have demonstrated that inflammatory cells can be divided into two groups depending on the type of 2-acetylated phospholipids [1-radyl-2-acetyl-sn-glycero-3-phosphocholine (GPC)] they produce: those that produce predominantly platelet-activating factor (PAF), and those that produce predominantly its 1-acyl analogue (1-acyl-2-acetyl-GPC; AAGPC) [Triggiani, Schleimer, Warner & Chilton (1991) J. Immunol. 147, 660-666]. The present study has examined the factors that regulate the production of these two molecules in mouse bone marrow-derived mast cells (BMMC). Initial experiments indicated that PAF and AAGPC were catabolized by BMMC in a differential manner via two pathways: the first, exclusive for AAGPC, involved a 1-acyl hydrolase that removed the long chain at the sn-1 position of the molecule, and the second, common to AAGPC and PAF, involved acetylhydrolase that removed the acetate at the sn-2 position of the two molecules. Experiments were next designed to identify conditions where the differential catabolism of AAGPC and PAF could be eliminated in order to uncover other factors that regulate the proportions of AAGPC and PAF produced. Phenylmethanesulphonyl fluoride (PMSF) completely blocked the 1-acylhydrolase activity while having little or no effect on the acetyl hydrolase activity, thereby eliminating the influence of the catabolic pathway unique to AAGPC. Moreover, PMSF did not alter the release of arachidonic acid from phospholipid subclasses. PMSF-treated BMMC produced larger quantities of AAGPC than of PAF. The AAGPC/PAF ratio detected in PMSF-treated BMMC was very similar to the ratio of arachidonate contained in and released from 1-acyl-/1-alkyl-linked phosphatidylcholine (PC). BMMC supplemented with arachidonic acid in culture for 3 days increased their total arachidonic acid content in PC as well as the ratio of 1-acyl-2-arachidonoyl-GPC to 1-alkyl-2-arachidonoyl-GPC. These changes resulted in parallel and significant increases in both the total amount of 1-radyl-2-acetyl-GPC and the AAGPC/PAF ration in BMMC. These data indicate that the AAGPC/PAF ratio produced by inflammatory cells is regulated by at least two factors: (1) differential catabolism of these two molecules, and (2) the distribution of arachidonate in 1-acyl- and 1-alkyl-2-arachidonyl-GPC. These observations support the concept of a common pathway for AAGPC and PAF biosynthesis in which the two precursor molecules are 1-acyl-2-arachidonoyl-GPC and 1-alkyl-2-arachidonoyl-GPC, respectively.
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Affiliation(s)
- M Triggiani
- Division of Clinical Immunology, Johns Hopkins University School of Medicine
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15
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O'Sullivan M, Chilton F, Huggins EM, McCall C. Lipopolysaccharide priming of alveolar macrophages for enhanced synthesis of prostanoids involves induction of a novel prostaglandin H synthase. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42073-x] [Citation(s) in RCA: 164] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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