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Hassan JJ, Lieske A, Dörpmund N, Klatt D, Hoffmann D, Kleppa MJ, Kustikova OS, Stahlhut M, Schwarzer A, Schambach A, Maetzig T. A Multiplex CRISPR-Screen Identifies PLA2G4A as Prognostic Marker and Druggable Target for HOXA9 and MEIS1 Dependent AML. Int J Mol Sci 2021; 22:ijms22179411. [PMID: 34502319 PMCID: PMC8431012 DOI: 10.3390/ijms22179411] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 08/25/2021] [Accepted: 08/25/2021] [Indexed: 12/03/2022] Open
Abstract
HOXA9 and MEIS1 are frequently upregulated in acute myeloid leukemia (AML), including those with MLL-rearrangement. Because of their pivotal role in hemostasis, HOXA9 and MEIS1 appear non-druggable. We, thus, interrogated gene expression data of pre-leukemic (overexpressing Hoxa9) and leukemogenic (overexpressing Hoxa9 and Meis1; H9M) murine cell lines to identify cancer vulnerabilities. Through gene expression analysis and gene set enrichment analyses, we compiled a list of 15 candidates for functional validation. Using a novel lentiviral multiplexing approach, we selected and tested highly active sgRNAs to knockout candidate genes by CRISPR/Cas9, and subsequently identified a H9M cell growth dependency on the cytosolic phospholipase A2 (PLA2G4A). Similar results were obtained by shRNA-mediated suppression of Pla2g4a. Remarkably, pharmacologic inhibition of PLA2G4A with arachidonyl trifluoromethyl ketone (AACOCF3) accelerated the loss of H9M cells in bulk cultures. Additionally, AACOCF3 treatment of H9M cells reduced colony numbers and colony sizes in methylcellulose. Moreover, AACOCF3 was highly active in human AML with MLL rearrangement, in which PLA2G4A was significantly higher expressed than in AML patients without MLL rearrangement, and is sufficient as an independent prognostic marker. Our work, thus, identifies PLA2G4A as a prognostic marker and potential therapeutic target for H9M-dependent AML with MLL-rearrangement.
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MESH Headings
- Apoptosis
- Biomarkers, Tumor/genetics
- Biomarkers, Tumor/metabolism
- CRISPR-Cas Systems
- Cell Proliferation
- Gene Expression Regulation, Neoplastic
- Group IV Phospholipases A2/antagonists & inhibitors
- Group IV Phospholipases A2/genetics
- High-Throughput Screening Assays
- Homeodomain Proteins/genetics
- Homeodomain Proteins/metabolism
- Humans
- Leukemia, Myeloid, Acute/genetics
- Leukemia, Myeloid, Acute/metabolism
- Leukemia, Myeloid, Acute/pathology
- Myeloid Ecotropic Viral Integration Site 1 Protein/genetics
- Myeloid Ecotropic Viral Integration Site 1 Protein/metabolism
- Tumor Cells, Cultured
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Affiliation(s)
- Jacob Jalil Hassan
- Institute of Experimental Hematology, Hannover Medical School, 30625 Hannover, Germany; (J.J.H.); (A.L.); (N.D.); (D.K.); (D.H.); (M.-J.K.); (O.S.K.); (M.S.); (A.S.); (A.S.)
| | - Anna Lieske
- Institute of Experimental Hematology, Hannover Medical School, 30625 Hannover, Germany; (J.J.H.); (A.L.); (N.D.); (D.K.); (D.H.); (M.-J.K.); (O.S.K.); (M.S.); (A.S.); (A.S.)
- Department of Pediatric Hematology and Oncology, Hannover Medical School, 30625 Hannover, Germany
| | - Nicole Dörpmund
- Institute of Experimental Hematology, Hannover Medical School, 30625 Hannover, Germany; (J.J.H.); (A.L.); (N.D.); (D.K.); (D.H.); (M.-J.K.); (O.S.K.); (M.S.); (A.S.); (A.S.)
- Department of Pediatric Hematology and Oncology, Hannover Medical School, 30625 Hannover, Germany
| | - Denise Klatt
- Institute of Experimental Hematology, Hannover Medical School, 30625 Hannover, Germany; (J.J.H.); (A.L.); (N.D.); (D.K.); (D.H.); (M.-J.K.); (O.S.K.); (M.S.); (A.S.); (A.S.)
| | - Dirk Hoffmann
- Institute of Experimental Hematology, Hannover Medical School, 30625 Hannover, Germany; (J.J.H.); (A.L.); (N.D.); (D.K.); (D.H.); (M.-J.K.); (O.S.K.); (M.S.); (A.S.); (A.S.)
| | - Marc-Jens Kleppa
- Institute of Experimental Hematology, Hannover Medical School, 30625 Hannover, Germany; (J.J.H.); (A.L.); (N.D.); (D.K.); (D.H.); (M.-J.K.); (O.S.K.); (M.S.); (A.S.); (A.S.)
| | - Olga S. Kustikova
- Institute of Experimental Hematology, Hannover Medical School, 30625 Hannover, Germany; (J.J.H.); (A.L.); (N.D.); (D.K.); (D.H.); (M.-J.K.); (O.S.K.); (M.S.); (A.S.); (A.S.)
| | - Maike Stahlhut
- Institute of Experimental Hematology, Hannover Medical School, 30625 Hannover, Germany; (J.J.H.); (A.L.); (N.D.); (D.K.); (D.H.); (M.-J.K.); (O.S.K.); (M.S.); (A.S.); (A.S.)
| | - Adrian Schwarzer
- Institute of Experimental Hematology, Hannover Medical School, 30625 Hannover, Germany; (J.J.H.); (A.L.); (N.D.); (D.K.); (D.H.); (M.-J.K.); (O.S.K.); (M.S.); (A.S.); (A.S.)
- Department of Hematology, Hemostasis, Oncology and Stem Cell Transplantation, Hannover Medical School, 30625 Hannover, Germany
| | - Axel Schambach
- Institute of Experimental Hematology, Hannover Medical School, 30625 Hannover, Germany; (J.J.H.); (A.L.); (N.D.); (D.K.); (D.H.); (M.-J.K.); (O.S.K.); (M.S.); (A.S.); (A.S.)
- Division of Hematology/Oncology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Tobias Maetzig
- Institute of Experimental Hematology, Hannover Medical School, 30625 Hannover, Germany; (J.J.H.); (A.L.); (N.D.); (D.K.); (D.H.); (M.-J.K.); (O.S.K.); (M.S.); (A.S.); (A.S.)
- Department of Pediatric Hematology and Oncology, Hannover Medical School, 30625 Hannover, Germany
- Correspondence:
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David S, López-Vales R. Bioactive Lipid Mediators in the Initiation and Resolution of Inflammation after Spinal Cord Injury. Neuroscience 2021; 466:273-297. [PMID: 33951502 DOI: 10.1016/j.neuroscience.2021.04.026] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/22/2021] [Accepted: 04/23/2021] [Indexed: 12/12/2022]
Abstract
Neuroinflammation is a prominent feature of the response to CNS trauma. It is also an important hallmark of various neurodegenerative diseases in which inflammation contributes to the progression of pathology. Inflammation in the CNS can contribute to secondary damage and is therefore an excellent therapeutic target for a range of neurological conditions. Inflammation in the nervous system is complex and varies in its fine details in different conditions. It involves a wide variety of secreted factors such as chemokines and cytokines, cell adhesion molecules, and different cell types that include resident cell of the CNS, as well as immune cells recruited from the peripheral circulation. Added to this complexity is the fact that some aspects of inflammation are beneficial, while other aspects can induce secondary damage in the acute, subacute and chronic phases. Understanding these aspects of the inflammatory profile is essential for developing effective therapies. Bioactive lipids constitute a large group of molecules that modulate the initiation and the resolution of inflammation. Dysregulation of these bioactive lipid pathways can lead to excessive acute inflammation, and failure to resolve this by specialized pro-resolution lipid mediators can lead to the development of chronic inflammation. The focus of this review is to discuss the effects of bioactive lipids in spinal cord trauma and their potential for therapies.
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Affiliation(s)
- Samuel David
- Centre for Research in Neuroscience, BRaIN Program, The Research Institute of the McGill University Health Centre, 1650 Cedar Avenue, Montreal, Quebec H3G 1A4, Canada.
| | - Rubén López-Vales
- Departament de Biologia Cellular, Fisiologia i Inmunologia, Institut de Neurociències, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia, Spain
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3
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Cytosolic phospholipase A 2-α participates in lipid body formation and PGE 2 release in human neutrophils stimulated with an L-amino acid oxidase from Calloselasma rhodostoma venom. Sci Rep 2020; 10:10976. [PMID: 32620771 PMCID: PMC7334223 DOI: 10.1038/s41598-020-67345-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 06/05/2020] [Indexed: 12/02/2022] Open
Abstract
Cr-LAAO, an l-amino acid oxidase isolated from Calloselasma rhodosthoma snake venom, has been demonstrated as a potent stimulus for neutrophil activation and inflammatory mediator production. However, the mechanisms involved in Cr-LAAO induced neutrophil activation has not been well characterized. Here we investigated the mechanisms involved in Cr-LAAO-induced lipid body (also known as lipid droplet) biogenesis and eicosanoid formation in human neutrophils. Using microarray analysis, we show for the first time that Cr-LAAO plays a role in the up-regulation of the expression of genes involved in lipid signalling and metabolism. Those include different members of phospholipase A2, mostly cytosolic phospholipase A2-α (cPLA2-α); and enzymes involved in prostaglandin synthesis including cyclooxygenases 2 (COX-2), and prostaglandin E synthase (PTGES). In addition, genes involved in lipid droplet formation, including perilipin 2 and 3 (PLIN 2 and 3) and diacylglycerol acyltransferase 1 (DGAT1), were also upregulated. Furthermore, increased phosphorylation of cPLA2-α, lipid droplet biogenesis and PGE2 synthesis were observed in human neutrophils stimulated with Cr-LAAO. Treatment with cPLA2-α inhibitor (CAY10650) or DGAT-1 inhibitor (A922500) suppressed lipid droplets formation and PGE2 secretion. In conclusion, we demonstrate for the first time the effects of Cr-LAAO to regulate neutrophil lipid metabolism and signalling.
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Vandenberghe LTM, Heindryckx B, Smits K, Popovic M, Szymanska K, Bonte D, Peelman L, Deforce D, De Sutter P, Van Soom A, De Schauwer C. Intracellular localisation of platelet-activating factor during mammalian embryo development in vitro: a comparison of cattle, mouse and human. Reprod Fertil Dev 2018; 31:658-670. [PMID: 30458920 DOI: 10.1071/rd18146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 10/05/2018] [Indexed: 11/23/2022] Open
Abstract
Platelet-activating factor (PAF) is a well-known marker for embryo quality and viability. For the first time, we describe an intracellular localisation of PAF in oocytes and embryos of cattle, mice and humans. We showed that PAF is represented in the nucleus, a signal that was lost upon nuclear envelope breakdown. This process was confirmed by treating the embryos with nocodazole, a spindle-disrupting agent that, as such, arrests the embryo in mitosis, and by microinjecting a PAF-specific antibody in bovine MII oocytes. The latter resulted in the absence of nuclear PAF in the pronuclei of the zygote and reduced further developmental potential. Previous research indicates that PAF is released and taken up from the culture medium by preimplantation embryos invitro, in which bovine serum albumin (BSA) serves as a crucial carrier molecule. In the present study we demonstrated that nuclear PAF does not originate from an extracellular source because embryos cultured in polyvinylpyrrolidone or BSA showed similar levels of PAF in their nuclei. Instead, our experiments indicate that cytosolic phospholipase A2 (cPLA2) is likely to be involved in the intracellular production of PAF, because treatment with arachidonyl trifluoromethyl ketone (AACOCF3), a specific cPLA2 inhibitor, clearly lowered PAF levels in the nuclei of bovine embryos.
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Affiliation(s)
- L T M Vandenberghe
- Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - B Heindryckx
- Ghent-Fertility and Stem cell Team (G-FaST), Department for Reproductive Medicine, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium
| | - K Smits
- Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - M Popovic
- Ghent-Fertility and Stem cell Team (G-FaST), Department for Reproductive Medicine, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium
| | - K Szymanska
- Physiology Group, Department of Basic Medical Sciences, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium
| | - D Bonte
- Ghent-Fertility and Stem cell Team (G-FaST), Department for Reproductive Medicine, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium
| | - L Peelman
- Department of Nutrition, Genetics and Ethology, Faculty of Veterinary Medicine, Ghent University, Heidestraat 19, 9820 Merelbeke, Belgium
| | - D Deforce
- Laboratory of Pharmaceutical Biotechnology, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium
| | - P De Sutter
- Ghent-Fertility and Stem cell Team (G-FaST), Department for Reproductive Medicine, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium
| | - A Van Soom
- Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - C De Schauwer
- Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
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5
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Robichaud PP, Boulay K, Munganyiki JÉ, Surette ME. Fatty acid remodeling in cellular glycerophospholipids following the activation of human T cells. J Lipid Res 2013; 54:2665-77. [PMID: 23894206 DOI: 10.1194/jlr.m037044] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Changes in fatty acid (FA) and glycerophospholipid (GPL) metabolism associated with cell cycle entry are not fully understood. In this study FA-GPL remodeling was investigated in resting and proliferating primary human T cells. Significant changes were measured in the composition and distribution of FAs in GPLs following receptor activation of human T cells. The FA distribution of proliferating T cells was very similar to that of the human Jurkat T cell line and when the stimulus was removed from proliferating T cells, they stopped proliferating and the FA distribution largely reverted back to that of resting T cells. The cellular content of saturated and monounsaturated FAs was significantly increased in proliferating cells, which was associated with an induction of FA synthase and stearoyl-CoA desaturase-1 gene expression. Additionally, cellular arachidonate was redistributed in GPLs in a distinct pattern that was unlike any other FAs. This redistribution was associated with an induction of CoA-dependent and CoA-independent remodeling. Accordingly, significant changes in the expression of several acyl-CoA synthetases, lysophospholipid acyltransferases, and phospholipase A2 were measured. Overall, these results suggest that metabolic pathways are activated in proliferating T cells that may represent fundamental changes associated with human cell proliferation.
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6
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Sanford SD, Yun BG, Leslie CC, Murphy RC, Pfenninger KH. Group IVA phospholipase A₂ is necessary for growth cone repulsion and collapse. J Neurochem 2012; 120:974-84. [PMID: 22220903 DOI: 10.1111/j.1471-4159.2012.07651.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The repellent semaphorin 3A (Sema3A) causes growth cone turning or collapse by triggering cytoskeletal rearrangements and detachment of adhesion sites. Growth cone detachment is dependent on eicosanoid activation of protein kinase C epsilon (PKCε), but the characterization of the phospholipase A(2) (PLA(2) ) that releases arachidonic acid (AA) for eicosanoid synthesis has remained elusive. Here, we show, in rat dorsal root ganglion (DRG) neurons, that Sema3A stimulates PLA(2) activity, that Sema3A-induced growth cone turning and collapse are dependent on the release of AA, and that the primary PLA(2) involved is the group IV α isoform (GIVA). Silencing GIVA expression renders growth cones resistant to Sema3A-induced collapse, and GIVA inhibition reverses Sema3A-induced repulsion into attraction. These studies identify a novel, early step in Sema3A-signaling and a PLA(2) necessary for growth cone repulsion and collapse.
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Affiliation(s)
- Staci D Sanford
- Department of Pediatrics, Neuroscience Program, and Colorado Intellectual and Developmental Disabilities Research Center, University of Colorado School of Medicine, Aurora, Colorado, USA
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Dumas E, Martel C, Neagoe PE, Bonnefoy A, Sirois MG. Angiopoietin-1 but not angiopoietin-2 promotes neutrophil viability: Role of interleukin-8 and platelet-activating factor. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:358-67. [DOI: 10.1016/j.bbamcr.2011.12.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 12/06/2011] [Accepted: 12/07/2011] [Indexed: 01/15/2023]
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8
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Flamand N, Picard S, Lemieux L, Pouliot M, Bourgoin SG, Borgeat P. Effects of pyrrophenone, an inhibitor of group IVA phospholipase A2, on eicosanoid and PAF biosynthesis in human neutrophils. Br J Pharmacol 2006; 149:385-92. [PMID: 16967052 PMCID: PMC1978440 DOI: 10.1038/sj.bjp.0706879] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND AND PURPOSE The biosynthesis of leukotrienes (LT) and platelet-activating factor (PAF) involves the release of their respective precursors, arachidonic acid (AA) and lyso-PAF by the group IVA PLA2 (cPLA2alpha). This paper aims at characterizing the inhibitory properties of the cPLA2alpha inhibitor pyrrophenone on eicosanoids and PAF in human neutrophils (PMN). EXPERIMENTAL APPROACH Freshly isolated human PMN were activated with physiological and pharmacological agents (fMLP, PAF, exogenous AA, A23187 and thapsigargin) in presence and absence of the cPLA2alpha inhibitor pyrrophenone and biosynthesis of LT, PAF, and PGE2 was measured. KEY RESULTS Pyrrophenone potently inhibited LT, PGE2 and PAF biosynthesis in PMN with IC50s in the range of 1-20 nM. These inhibitory effects of pyrrophenone were specific (the consequence of substrate deprivation), as shown by the reversal of inhibition by exogenous AA and lyso-PAF. Comparative assessment of pyrrophenone, methyl-arachidonoyl-fluoro-phosphonate (MAFP) and arachidonoyl-trifluoromethylketone (AACOCF3) demonstrated that pyrrophenone was more specific and 100-fold more potent than MAFP and AACOCF3 for the inhibition of LT biosynthesis in A23187-activated PMN. The inhibitory effect of pyrrophenone on LT biosynthesis was reversible as LT biosynthesis was recovered when pyrrophenone-treated PMN were washed with autologous plasma. No alteration of phospholipase D (PLD) activity in fMLP-activated PMN was observed with up to 10 microM pyrrophenone, suggesting that the cPLA2alpha inhibitor does not directly inhibit PLD. CONCLUSIONS AND IMPLICATIONS Pyrrophenone is a more potent and specific cPLA2alpha inhibitor than MAFP and AACOCF3 and represents an excellent pharmacological tool to investigate the biosynthesis and the biological roles of eicosanoids and PAF.
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Affiliation(s)
- N Flamand
- Département d'anatomic et de physiologie, Centre de Recherche en Rhumatologie et Immunologie, Centre de recherche du CHUQ (CHUL), Faculté de Médecine, Université Laval Québec, Canada
| | - S Picard
- Département d'anatomic et de physiologie, Centre de Recherche en Rhumatologie et Immunologie, Centre de recherche du CHUQ (CHUL), Faculté de Médecine, Université Laval Québec, Canada
| | - L Lemieux
- Département d'anatomic et de physiologie, Centre de Recherche en Rhumatologie et Immunologie, Centre de recherche du CHUQ (CHUL), Faculté de Médecine, Université Laval Québec, Canada
| | - M Pouliot
- Département d'anatomic et de physiologie, Centre de Recherche en Rhumatologie et Immunologie, Centre de recherche du CHUQ (CHUL), Faculté de Médecine, Université Laval Québec, Canada
| | - S G Bourgoin
- Département d'anatomic et de physiologie, Centre de Recherche en Rhumatologie et Immunologie, Centre de recherche du CHUQ (CHUL), Faculté de Médecine, Université Laval Québec, Canada
| | - P Borgeat
- Département d'anatomic et de physiologie, Centre de Recherche en Rhumatologie et Immunologie, Centre de recherche du CHUQ (CHUL), Faculté de Médecine, Université Laval Québec, Canada
- Author for correspondence:
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Gambero A, Thomazzi SM, Cintra ACO, Landucci ECT, De Nucci G, Antunes E. Signalling pathways regulating human neutrophil migration induced by secretory phospholipases A2. Toxicon 2004; 44:473-81. [PMID: 15450921 DOI: 10.1016/j.toxicon.2004.06.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Revised: 06/02/2004] [Accepted: 06/04/2004] [Indexed: 11/18/2022]
Abstract
This study was designed to elucidate the signalling pathways by which secretory phospholipases A2 (sPLA2s) induce in vitro neutrophil migration. The cell migration assays were performed with Naja mocambique venom PLA2 (sPLA2 with high catalytic activity), bothropstoxin-I (sPLA2 devoid of catalytic activity) and platelet-activating factor (PAF), using a 48-well microchemotaxis chamber. Both the non-selective protein kinase inhibitor staurosporine (30-300 nM) and the selective protein kinase C (PKC) inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpyperazine (H7; 50-200 microM) as well as the Gi inactivator pertussis toxin (30-300 nM) caused a concentration-dependent inhibition of the neutrophil migration induced by either N. mocambique venom PLA2 (100 microg/ml) or bothropstoxin-I (100 microg/ml). Pertussis toxin nearly abolished PAF-induced migration, while staurosporine and H7 partly (but significantly) inhibited the chemotactic responses to PAF. The dual inhibitor of cytosolic PLA2 and Ca2+ -independent PLA2 (iPLA2), arachidonil-trifluoromethyl-ketone (ATK; 0.2-20 microM), or the specific iPLA2 inhibitor bromoenol lactone (1-30 microM) caused a concentration-dependent inhibition of the migration induced by either sPLA2s. At the maximal concentration used for each compound, the migration was almost suppressed. In contrast, both of these compounds caused only slight inhibitions of PAF-induced migration. No rise in intracellular Ca2+ was observed in neutrophil-stimulated sPLA2, as determined in cells preloaded with fura 2-AM. In the experimental condition used, pertussis toxin, staurosporine, H7, ATK or bromoenol lactone did not induce cytotoxic effects, according to MTT assay. Our results suggest that activation of an endogenous PLA2 through activation of GTP-binding protein and PKC is the main mechanism by which exogenous sPLA2s cause neutrophil migration.
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Affiliation(s)
- Alessandra Gambero
- Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas UNICAMP, PO Box 6111, 13084-970, Brazil
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10
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Rubin BB, Downey GP, Koh A, Degousee N, Ghomashchi F, Nallan L, Stefanski E, Harkin DW, Sun C, Smart BP, Lindsay TF, Cherepanov V, Vachon E, Kelvin D, Sadilek M, Brown GE, Yaffe MB, Plumb J, Grinstein S, Glogauer M, Gelb MH. Cytosolic phospholipase A2-alpha is necessary for platelet-activating factor biosynthesis, efficient neutrophil-mediated bacterial killing, and the innate immune response to pulmonary infection: cPLA2-alpha does not regulate neutrophil NADPH oxidase activity. J Biol Chem 2004; 280:7519-29. [PMID: 15475363 PMCID: PMC2409062 DOI: 10.1074/jbc.m407438200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of a cytosolic phospholipase A(2)-alpha (cPLA(2)-alpha) in neutrophil arachidonic acid release, platelet-activating factor (PAF) biosynthesis, NADPH oxidase activation, and bacterial killing in vitro, and the innate immune response to bacterial infection in vivo was examined. cPLA(2)-alpha activity was blocked with the specific cPLA(2)-alpha inhibitor, Pyrrolidine-1 (human cells), or by cPLA(2) -alpha gene disruption (mice). cPLA(2)-alpha inhibition or gene disruption led to complete suppression of neutrophil arachidonate release and PAF biosynthesis but had no effect on neutrophil NADPH oxidase activation, FcgammaII/III or CD11b surface expression, primary or secondary granule secretion, or phagocytosis of Escherichia coli in vitro. In contrast, cPLA(2)-alpha inhibition or gene disruption diminished neutrophil-mediated E. coli killing in vitro, which was partially rescued by exogenous arachidonic acid or PAF but not leukotriene B(4). Following intratracheal inoculation with live E. coli in vivo, pulmonary PAF biosynthesis, inflammatory cell infiltration, and clearance of E. coli were attenuated in cPLA(2)-alpha(-/-) mice compared with wild type littermates. These studies identify a novel role for cPLA(2)-alpha in the regulation of neutrophil-mediated bacterial killing and the innate immune response to bacterial infection.
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Affiliation(s)
- Barry B Rubin
- Division of Vascular Surgery and Toronto General Hospital Research Institute of the University Health Network, University of Toronto, Toronto, Ontario M5G 2C4, Canada.
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11
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Choisy SCM, Hancox JC, Arberry LA, Reynolds AM, Shattock MJ, James AF. Evidence for a Novel K+Channel Modulated by α1A-Adrenoceptors in Cardiac Myocytes. Mol Pharmacol 2004; 66:735-48. [PMID: 15322267 DOI: 10.1124/mol.104.000760] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Accumulating evidence suggests that steady-state K(+) currents modulate excitability and action potential duration, particularly in cardiac cell types with relatively abbreviated action potential plateau phases. Despite representing potential drug targets, at present these currents and their modulation are comparatively poorly characterized. Therefore, we investigated the effects of phenylephrine [PE; an alpha(1)-adrenoceptor (alpha(1)-AR) agonist] on a sustained outward K(+) current in rat ventricular myocytes. Under K(+) current-selective conditions at 35 degrees C and whole-cell patch clamp, membrane depolarization elicited transient (I(t)) and steady-state (I(ss)) outward current components. PE (10 microM) significantly decreased I(ss) amplitude, without significant effect on I(t). Preferential modulation of I(ss) by PE was confirmed by intracellular application of the voltage-gated K(+) channel blocker tetraethylammonium, which largely inhibited I(t) without affecting the PE-sensitive current (I(ss,PE)). I(ss,PE) had the properties of an outwardly rectifying steady-state K(+)-selective conductance. Acidification of the external solution or externally applied BaCl(2) or quinidine strongly inhibited I(ss,PE). However, I(ss,PE) was not abolished by anandamide, ruthenium red, or zinc, inhibitors of TASK acid-sensitive background K(+) channels. Furthermore, the PE-sensitive current was partially inhibited by external administration of high concentrations of tetraethylammonium and 4-aminopyridine, which are voltage-gated K(+) channel-blockers. Power spectrum analysis of I(ss,PE) yielded a large unitary conductance of 78 pS. I(ss,PE) resulted from PE activation of the alpha(1A)-AR subtype, involved a pertussis toxin-insensitive G-protein, and was independent of cytosolic Ca(2+). These results collectively demonstrate that alpha(1A)-AR activation results in the inhibition of an outwardly rectifying steady-state K(+) current with properties distinct from previously characterized cardiac K(+) channels.
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Affiliation(s)
- Stéphanie C M Choisy
- Department of Physiology and Cardiovascular Research Laboratories, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 1TD, United Kingdom
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Kell PJ, Creer MH, Crown KN, Wirsig K, McHowat J. Inhibition of Platelet-Activating Factor (PAF) Acetylhydrolase by Methyl Arachidonyl Fluorophosphonate Potentiates PAF Synthesis in Thrombin-Stimulated Human Coronary Artery Endothelial Cells. J Pharmacol Exp Ther 2003; 307:1163-70. [PMID: 14560038 DOI: 10.1124/jpet.103.055392] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have previously demonstrated that thrombin stimulation of endothelial cells results in increased membrane-associated, Ca(2+)-independent phospholipase A2 (iPLA2) activity, accelerated hydrolysis of membrane plasmalogen phospholipids, and production of several biologically active phospholipid metabolites, including prostacyclin and platelet-activating factor (PAF) that is abolished by pretreatment with the iPLA2-selective inhibitor bromoenol lactone. This study was designed to further investigate the role of alternative PLA2 inhibitors, including methyl arachidonyl fluorophosphonate (MAFP, an inhibitor of cytosolic PLA2 isoforms), on phospholipid turnover and PAF production from thrombin-stimulated human coronary artery endothelial cells (HCAECs). Paradoxically, pretreatment of HCAEC with MAFP (5-25 microM) resulted in a significant increase in PAF production in both unstimulated and thrombin-stimulated cells that was found to be a direct result of inhibition of PAF acetylhydrolase (PAF-AH) activity. Pretreatment with MAFP did not significantly inhibit HCAEC PLA2 activity, possibly due to the localization of PLA2 activity in the membrane fraction rather than the cytosol. Bromoenol lactone did not inhibit PAF-AH activity, even at concentrations as high as 20 microM. We conclude that MAFP augments thrombin-stimulated PAF production by inhibition of PAF catabolism without affecting membrane-associated iPLA2 activity.
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Affiliation(s)
- Pamela J Kell
- Department of Pathology, St. Louis University School of Medicine, 1402 S. Grand Blvd., St. Louis, MO 63104, USA
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Lie WJ, Homburg CHE, Kuijpers TW, Knol EF, Mul FPJ, Roos D, Tool ATJ. Regulation and kinetics of platelet-activating factor and leukotriene C4 synthesis by activated human basophils. Clin Exp Allergy 2003; 33:1125-34. [PMID: 12911788 DOI: 10.1046/j.1365-2222.2003.01726.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Allergic disease is the result of an interplay of many different cell types, including basophils and mast cells, in combination with various inflammatory lipid mediators, such as platelet-activating factor (PAF) and leukotrienes (LT). LTC4 synthesis by human basophils has been studied quite extensively. However, not much is known about the synthesis of PAF by human basophils. OBJECTIVE In this study, we have made a comprehensive comparison between the kinetics of PAF and LTC4 synthesis, in highly purified basophils, activated with different stimuli or with combinations of stimuli. METHODS Synthesis of PAF and LTC4 by human basophils was determined with commercially available assay kits. The basophils were activated with C5a, fMLP, PMA, allergen or anti-IgE, in the absence and presence of IL-3 and/or in combination with elevation of cytosolic free Ca2+ by the sarcoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin. RESULTS Most stimuli were found to induce both PAF and LTC4 synthesis. PAF synthesis and LTC4 release were enhanced by preincubation of the basophils with IL-3 or by elevation of cytosolic free Ca2+ by thapsigargin. Incubation of human basophils with IL-3 alone or thapsigargin alone did not result in detectable synthesis of PAF and LTC4, whereas the combination of the two resulted in high amounts of PAF and LTC4 synthesis. Depending on the stimulus used, LTC4 release was 5-100-fold higher than PAF synthesis. In addition, PAF, but not LTC4, was transiently detected, probably due to PAF degradation. LTC4 and PAF synthesis was strongly blocked by inhibitors of cytosolic phospholipase A2, indicating that this enzyme is involved in PAF and LTC4 synthesis by activated human basophils. CONCLUSION This study provides a first comprehensive comparison of PAF and LTC4 synthesis in highly purified human basophils, stimulated with a variety of stimuli.
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Affiliation(s)
- W J Lie
- Sanquin Research at CLB, and Landsteiner Laboratory, Academic Medical Centre, University of Amsterdam, Amsterdam
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