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Kartha S, Ghimire P, Winkelstein BA. Inhibiting spinal secretory phospholipase A 2 after painful nerve root injury attenuates established pain and spinal neuronal hyperexcitability by altering spinal glutamatergic signaling. Mol Pain 2021; 17:17448069211066221. [PMID: 34919471 PMCID: PMC8721705 DOI: 10.1177/17448069211066221] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Neuropathic injury is accompanied by chronic inflammation contributing to the onset and maintenance of pain after an initial insult. In addition to their roles in promoting immune cell activation, inflammatory mediators like secretory phospholipase A2 (sPLA2) modulate nociceptive and excitatory neuronal signaling during the initiation of pain through hydrolytic activity. Despite having a known role in glial activation and cytokine release, it is unknown if sPLA2 contributes to the maintenance of painful neuropathy and spinal hyperexcitability later after neural injury. Using a well-established model of painful nerve root compression, this study investigated if inhibiting spinal sPLA2 7 days after painful injury modulates the behavioral sensitivity and/or spinal dorsal horn excitability that is typically evident. The effects of sPLA2 inhibition on altered spinal glutamatergic signaling was also probed by measuring spinal intracellular glutamate levels and spinal glutamate transporter (GLAST and GLT1) and receptor (mGluR5, GluR1, and NR1) expression. Spinal sPLA2 inhibition at day 7 abolishes behavioral sensitivity, reduces both evoked and spontaneous neuronal firing in the spinal cord, and restores the distribution of neuronal phenotypes to those of control conditions. Inhibiting spinal sPLA2 also increases intracellular glutamate concentrations and restores spinal expression of GLAST, GLT1, mGluR5, and GluR1 to uninjured expression with no effect on NR1. These findings establish a role for spinal sPLA2 in maintaining pain and central sensitization after neural injury and suggest this may be via exacerbating glutamate excitotoxicity in the spinal cord.
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Affiliation(s)
- Sonia Kartha
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
| | - Prabesh Ghimire
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
| | - Beth A Winkelstein
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA.,Department of Neurosurgery, University of Pennsylvania, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
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2
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Monson EA, Trenerry AM, Laws JL, Mackenzie JM, Helbig KJ. Lipid droplets and lipid mediators in viral infection and immunity. FEMS Microbiol Rev 2021; 45:fuaa066. [PMID: 33512504 PMCID: PMC8371277 DOI: 10.1093/femsre/fuaa066] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 12/02/2020] [Indexed: 12/14/2022] Open
Abstract
Lipid droplets (LDs) contribute to key pathways important for the physiology and pathophysiology of cells. In a homeostatic view, LDs regulate the storage of neutral lipids, protein sequestration, removal of toxic lipids and cellular communication; however, recent advancements in the field show these organelles as essential for various cellular stress response mechanisms, including inflammation and immunity, with LDs acting as hubs that integrate metabolic and inflammatory processes. The accumulation of LDs has become a hallmark of infection, and is often thought to be virally driven; however, recent evidence is pointing to a role for the upregulation of LDs in the production of a successful immune response to viral infection. The fatty acids housed in LDs are also gaining interest due to the role that these lipid species play during viral infection, and their link to the synthesis of bioactive lipid mediators that have been found to have a very complex role in viral infection. This review explores the role of LDs and their subsequent lipid mediators during viral infections and poses a paradigm shift in thinking in the field, whereby LDs may play pivotal roles in protecting the host against viral infection.
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Affiliation(s)
- Ebony A Monson
- School of Life Sciences, La Trobe University, Melbourne, Australia, 3083
| | - Alice M Trenerry
- Department of Microbiology and Immunology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia, 3000
| | - Jay L Laws
- School of Life Sciences, La Trobe University, Melbourne, Australia, 3083
| | - Jason M Mackenzie
- Department of Microbiology and Immunology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia, 3000
| | - Karla J Helbig
- School of Life Sciences, La Trobe University, Melbourne, Australia, 3083
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3
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Htwe YM, Wang H, Belvitch P, Meliton L, Bandela M, Letsiou E, Dudek SM. Group V Phospholipase A 2 Mediates Endothelial Dysfunction and Acute Lung Injury Caused by Methicillin-Resistant Staphylococcus Aureus. Cells 2021; 10:1731. [PMID: 34359901 PMCID: PMC8304832 DOI: 10.3390/cells10071731] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 06/25/2021] [Accepted: 07/03/2021] [Indexed: 12/12/2022] Open
Abstract
Lung endothelial dysfunction is a key feature of acute lung injury (ALI) and clinical acute respiratory distress syndrome (ARDS). Previous studies have identified the lipid-generating enzyme, group V phospholipase A2 (gVPLA2), as a mediator of lung endothelial barrier disruption and inflammation. The current study aimed to determine the role of gVPLA2 in mediating lung endothelial responses to methicillin-resistant Staphylococcus aureus (MRSA, USA300 strain), a major cause of ALI/ARDS. In vitro studies assessed the effects of gVPLA2 inhibition on lung endothelial cell (EC) permeability after exposure to heat-killed (HK) MRSA. In vivo studies assessed the effects of intratracheal live or HK-MRSA on multiple indices of ALI in wild-type (WT) and gVPLA2-deficient (KO) mice. In vitro, HK-MRSA increased gVPLA2 expression and permeability in human lung EC. Inhibition of gVPLA2 with either the PLA2 inhibitor, LY311727, or with a specific monoclonal antibody, attenuated the barrier disruption caused by HK-MRSA. LY311727 also reduced HK-MRSA-induced permeability in mouse lung EC isolated from WT but not gVPLA2-KO mice. In vivo, live MRSA caused significantly less ALI in gVPLA2 KO mice compared to WT, findings confirmed by intravital microscopy assessment in HK-MRSA-treated mice. After targeted delivery of gVPLA2 plasmid to lung endothelium using ACE antibody-conjugated liposomes, MRSA-induced ALI was significantly increased in gVPLA2-KO mice, indicating that lung endothelial expression of gVPLA2 is critical in vivo. In summary, these results demonstrate an important role for gVPLA2 in mediating MRSA-induced lung EC permeability and ALI. Thus, gVPLA2 may represent a novel therapeutic target in ALI/ARDS caused by bacterial infection.
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Affiliation(s)
| | | | | | | | | | | | - Steven M. Dudek
- Division of Pulmonary, Critical Care, Sleep and Allergy, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA; (Y.M.H.); (H.W.); (P.B.); (L.M.); (M.B.); (E.L.)
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4
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Samuchiwal SK, Balestrieri B. Harmful and protective roles of group V phospholipase A 2: Current perspectives and future directions. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1864:819-826. [PMID: 30308324 DOI: 10.1016/j.bbalip.2018.10.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Revised: 09/27/2018] [Accepted: 10/01/2018] [Indexed: 12/17/2022]
Abstract
Group V Phospholipase A2 (Pla2g5) is a member of the PLA2 family of lipid-generating enzymes. It is expressed in immune and non-immune cell types and is inducible during several pathologic conditions serving context-specific functions. In this review, we recapitulate the protective and detrimental functions of Pla2g5 investigated through preclinical and translational approaches. This article is part of a Special Issue entitled Novel functions of phospholipase A2 Guest Editors: Makoto Murakami and Gerard Lambeau.
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Affiliation(s)
- Sachin K Samuchiwal
- Department of Medicine, Harvard Medical School, Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Barbara Balestrieri
- Department of Medicine, Harvard Medical School, Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA 02115, USA.
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5
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Phospholipase A 2 catalysis and lipid mediator lipidomics. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1864:766-771. [PMID: 30905345 DOI: 10.1016/j.bbalip.2018.08.010] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 08/10/2018] [Accepted: 08/16/2018] [Indexed: 01/09/2023]
Abstract
Phospholipase A2 (PLA2) enzymes are the upstream regulators of the eicosanoid pathway liberating free arachidonic acid from the sn-2 position of membrane phospholipids. Free intracellular arachidonic acid serves as a substrate for the eicosanoid biosynthetic enzymes including cyclooxygenases, lipoxygenases, and cytochrome P450s that lead to inflammation. The Group IVA cytosolic (cPLA2), Group VIA calcium-independent (iPLA2), and Group V secreted (sPLA2) are three well-characterized human enzymes that have been implicated in eicosanoid formation. In this review, we will introduce and summarize the regulation of catalytic activity and cellular localization, structural characteristics, interfacial activation and kinetics, substrate specificity, inhibitor binding and interactions, and the downstream implications for eicosanoid biosynthesis of these three important PLA2 enzymes.
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Karray A, Bou Ali M, Kharrat N, Gargouri Y, Bezzine S. Antibacterial, antifungal and anticoagulant activities of chicken PLA2 group V expressed in Pichia pastoris. Int J Biol Macromol 2017; 108:127-134. [PMID: 29129630 DOI: 10.1016/j.ijbiomac.2017.11.045] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Revised: 11/07/2017] [Accepted: 11/08/2017] [Indexed: 02/02/2023]
Abstract
Secretory class V phospholipase A2 (PLA2-V) has been shown to be involved in inflammatory processes in cellular studies, but the biochemical and physical properties of this important enzyme have been unclear. As a first step towards understanding the structure, function and regulation of this PLA2, we report the expression and characterization of PLA2-V from chicken (ChPLA2-V). The ChPLA2-V cDNA was synthesized from chicken heart polyA mRNA by RT-PCR, and an expression construct containing the PLA2 was established. After expression in Pichia pastoris cells, the active enzyme was purified. The purified ChPLA2-V protein was biochemically and physiologically characterized. The recombinant ChPLA2-V has an absolute requirement for Ca2+ for enzymatic activity. The optimum pH for this enzyme is pH 8.5 in Tris-HCl buffer with phosphatidylcholine as substrate. ChPLA2-V was found to display potent Gram-positive and Gram-negative bactericidal activity and antifungal activity in vitro. The purified enzyme ChPLA2-V with much stronger anticoagulant activity compared with the intestinal and pancreatic chicken PLA2-V was approximately 10 times more active. Chicken group V PLA2, like mammal one, may be considered as a future therapeutic agents against fungal and bacterial infections and as an anticoagulant agent.
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Affiliation(s)
- Aida Karray
- Laboratoire de Biochimie et de Génie Enzymatique des Lipases, ENIS Route de Soukra, université de Sfax, Tunisia
| | - Madiha Bou Ali
- Laboratoire de Biochimie et de Génie Enzymatique des Lipases, ENIS Route de Soukra, université de Sfax, Tunisia
| | - Nedia Kharrat
- Laboratoire de Biochimie et de Génie Enzymatique des Lipases, ENIS Route de Soukra, université de Sfax, Tunisia
| | - Youssef Gargouri
- Laboratoire de Biochimie et de Génie Enzymatique des Lipases, ENIS Route de Soukra, université de Sfax, Tunisia
| | - Sofiane Bezzine
- Laboratoire de Biochimie et de Génie Enzymatique des Lipases, ENIS Route de Soukra, université de Sfax, Tunisia.
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7
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Montenegro-Burke JR, Sutton JA, Rogers LM, Milne GL, McLean JA, Aronoff DM. Lipid profiling of polarized human monocyte-derived macrophages. Prostaglandins Other Lipid Mediat 2016; 127:1-8. [PMID: 27871801 PMCID: PMC6053630 DOI: 10.1016/j.prostaglandins.2016.11.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 11/11/2016] [Indexed: 12/31/2022]
Abstract
The highly orchestrated transcriptional and metabolic reprogramming during activation drastically transforms the main functions and physiology of human macrophages across the polarization spectrum. Lipids, for example, can modify protein function by acting remotely as signaling molecules but also locally by altering the physical properties of cellular membranes. These changes play key roles in the functions of highly plastic immune cells due to their involvement in inflammation, immune responses, phagocytosis and wound healing processes. We report an analysis of major membrane lipids of distinct phenotypes of resting (M0), classically activated (M1), alternatively activated (M2a) and deactivated (M2c) human monocyte derived macrophages from different donors. Samples were subjected to supercritical fluid chromatography-ion mobility-mass spectrometry analysis, which allowed separations based on lipid class, facilitating the profiling of their fatty acid composition. Different levels of arachidonic acid mobilization as well as other fatty acid changes were observed for different lipid classes in the distinct polarization phenotypes, suggesting the activation of highly orchestrated and specific enzymatic processes in the biosynthesis of lipid signaling molecules and cell membrane remodeling. Thromboxane A2 production appeared to be a specific marker of M1 polarization. These alterations to the global composition of lipid bi-layer membranes in the cell provide a potential methodology for the definition and determination of cellular and tissue activation states.
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Affiliation(s)
- J Rafael Montenegro-Burke
- Department of Chemistry, Vanderbilt University, Nashville, TN, 37235, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN, 37235, USA; Vanderbilt Institute for Integrative Biosystems Research and Education, Vanderbilt University, Nashville, TN, 37235, USA; Center for Innovative Technology, Vanderbilt University, Nashville, TN 37235, USA
| | - Jessica A Sutton
- Division of Infectious Diseases, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA; Department of Microbiology and Immunology, Meharry Medical College School of Medicine, Nashville, TN, 37208, USA; Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Lisa M Rogers
- Division of Infectious Diseases, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Ginger L Milne
- Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - John A McLean
- Department of Chemistry, Vanderbilt University, Nashville, TN, 37235, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN, 37235, USA; Vanderbilt Institute for Integrative Biosystems Research and Education, Vanderbilt University, Nashville, TN, 37235, USA; Center for Innovative Technology, Vanderbilt University, Nashville, TN 37235, USA
| | - David M Aronoff
- Vanderbilt Institute for Integrative Biosystems Research and Education, Vanderbilt University, Nashville, TN, 37235, USA; Division of Infectious Diseases, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA; Department of Microbiology and Immunology, Meharry Medical College School of Medicine, Nashville, TN, 37208, USA; Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.
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8
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Jung KH, Baek H, Shin D, Lee G, Park S, Lee S, Choi D, Kim W, Bae H. Protective Effects of Intratracheally-Administered Bee Venom Phospholipase A2 on Ovalbumin-Induced Allergic Asthma in Mice. Toxins (Basel) 2016; 8:toxins8100269. [PMID: 27669297 PMCID: PMC5086630 DOI: 10.3390/toxins8100269] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 09/14/2016] [Indexed: 12/27/2022] Open
Abstract
Asthma is a common chronic disease characterized by bronchial inflammation, reversible airway obstruction, and airway hyperresponsiveness (AHR). Current therapeutic options for the management of asthma include inhaled corticosteroids and β2 agonists, which elicit harmful side effects. In the present study, we examined the capacity of phospholipase A2 (PLA2), one of the major components of bee venom (BV), to reduce airway inflammation and improve lung function in an experimental model of asthma. Allergic asthma was induced in female BALB/c mice by intraperitoneal administration of ovalbumin (OVA) on days 0 and 14, followed by intratracheal challenge with 1% OVA six times between days 22 and 30. The infiltration of immune cells, such as Th2 cytokines in the lungs, and the lung histology, were assessed in the OVA-challenged mice in the presence and absence of an intratracheal administration of bvPLA2. We showed that the intratracheal administration of bvPLA2 markedly suppressed the OVA-induced allergic airway inflammation by reducing AHR, overall area of inflammation, and goblet cell hyperplasia. Furthermore, the suppression was associated with a significant decrease in the production of Th2 cytokines, such as IL-4, IL-5, and IL-13, and a reduction in the number of total cells, including eosinophils, macrophages, and neutrophils in the airway.
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Affiliation(s)
- Kyung-Hwa Jung
- Department of Physiology, College of Korean Medicine, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemoon-gu, Seoul 130-701, Korea.
| | - Hyunjung Baek
- Department of Physiology, College of Korean Medicine, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemoon-gu, Seoul 130-701, Korea.
| | - Dasom Shin
- Department of Physiology, College of Korean Medicine, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemoon-gu, Seoul 130-701, Korea.
| | - Gihyun Lee
- Department of Physiology, College of Korean Medicine, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemoon-gu, Seoul 130-701, Korea.
| | - Sangwon Park
- Department of Physiology, College of Korean Medicine, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemoon-gu, Seoul 130-701, Korea.
| | - Sujin Lee
- Department of Physiology, College of Korean Medicine, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemoon-gu, Seoul 130-701, Korea.
| | - Dabin Choi
- Department of Physiology, College of Korean Medicine, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemoon-gu, Seoul 130-701, Korea.
| | - Woojin Kim
- Department of Physiology, College of Korean Medicine, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemoon-gu, Seoul 130-701, Korea.
| | - Hyunsu Bae
- Department of Physiology, College of Korean Medicine, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemoon-gu, Seoul 130-701, Korea.
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9
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Oberčkal J, Kovačič L, Šribar J, Leonardi A, Dolinar K, Pucer Janež A, Križaj I. On the role of protein disulfide isomerase in the retrograde cell transport of secreted phospholipases A2. PLoS One 2015; 10:e0120692. [PMID: 25763817 PMCID: PMC4357439 DOI: 10.1371/journal.pone.0120692] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 01/25/2015] [Indexed: 11/29/2022] Open
Abstract
Following the finding that ammodytoxin (Atx), a neurotoxic secreted phospholipase A2 (sPLA2) in snake venom, binds specifically to protein disulfide isomerase (PDI) in vitro we show that these proteins also interact in living rat PC12 cells that are able to internalize this group IIA (GIIA) sPLA2. Atx and PDI co-localize in both differentiated and non-differentiated PC12 cells, as shown by fluorescence microscopy. Based on a model of the complex between Atx and yeast PDI (yPDI), a three-dimensional model of the complex between Atx and human PDI (hPDI) was constructed. The Atx binding site on hPDI is situated between domains b and b’. Atx interacts hPDI with an extensive area on its interfacial binding surface. The mammalian GIB, GIIA, GV and GX sPLA2s have the same fold as Atx. The first three sPLA2s have been detected intracellularly but not the last one. The models of their complexes with hPDI were constructed by replacement of Atx with the respective mammalian sPLA2 in the Atx—hPDI complex and molecular docking of the structures. According to the generated models, mammalian GIB, GIIA and GV sPLA2s form complexes with hPDI very similar to that with Atx. The contact area between GX sPLA2 and hPDI is however different from that of the other sPLA2s. Heterologous competition of Atx binding to hPDI with GV and GX sPLA2s confirmed the model-based expectation that GV sPLA2 was a more effective inhibitor than GX sPLA2, thus validating our model. The results suggest a role of hPDI in the (patho)physiology of some snake venom and mammalian sPLA2s by assisting the retrograde transport of these molecules from the cell surface. The sPLA2–hPDI model constitutes a valuable tool to facilitate further insights into this process and into the (patho)physiology of sPLA2s in relation to their action intracellularly.
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Affiliation(s)
- Jernej Oberčkal
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Lidija Kovačič
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Jernej Šribar
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Adrijana Leonardi
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Klemen Dolinar
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Anja Pucer Janež
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Igor Križaj
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
- * E-mail:
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Immobilized IL-8 Triggers Phagocytosis and Dynamic Changes in Membrane Microtopology in Human Neutrophils. Ann Biomed Eng 2015; 43:2207-19. [PMID: 25582838 DOI: 10.1007/s10439-014-1242-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 12/29/2014] [Indexed: 10/24/2022]
Abstract
The interaction of leukocytes with surface bound ligands can be limited by the location of the molecules relative to the surface topology of the cell. In this report, we examine the dynamic response of neutrophils to IL-8-fractalkine chimera immobilized on bead surfaces, taking into account changes in receptor occupancy resulting from changes in surface topography. As a readout for receptor signaling, we observe the dynamics of calcium release in neutrophils following contact with the IL-8 coated surface. After a delay that depended on the initial area of contact and the surface density of IL-8, the cell began to phagocytose the IL-8 coated bead. This appeared to be a pre-requisite for release of calcium, which typically followed shortly after the initiation of phagocytosis. In separate experiments, effective kinetic coefficients for the formation of bonds between immobilized IL-8 and receptors on the cell surface were determined. Using these coefficients, we were able to estimate the number of bound receptors in the nascent contact zone. Kinetic modeling of the signaling response predicted that cell spreading and a concomitant increase in the density of occupied receptors would be required for the experimentally observed calcium dynamics. Postulating that there is an increase in receptor occupancy resulting from smoothing of the cell surface as it is stretched over the bead enabled us to obtain model predictions consistent with experimental observations. This study reveals the likely importance of membrane microtopology as a rate-limiting property and potential means of regulation of cell responses stimulated by two-dimensional surface interactions.
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11
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RHEE HAEJIN, JI LITING, KIM SEUNGHYUK, LEE JONGHO. Human group V secretory phospholipase A2 is associated with lipid rafts and internalized in a flotillin-dependent pathway. Int J Mol Med 2013; 32:1126-36. [DOI: 10.3892/ijmm.2013.1492] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 08/23/2013] [Indexed: 11/06/2022] Open
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12
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Pniewska E, Pawliczak R. The involvement of phospholipases A2 in asthma and chronic obstructive pulmonary disease. Mediators Inflamm 2013; 2013:793505. [PMID: 24089590 PMCID: PMC3780701 DOI: 10.1155/2013/793505] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 01/02/2013] [Accepted: 02/27/2013] [Indexed: 12/21/2022] Open
Abstract
The increased morbidity, mortality, and ineffective treatment associated with the pathogenesis of chronic inflammatory diseases such as asthma and chronic obstructive pulmonary disease (COPD) have generated much research interest. The key role is played by phospholipases from the A2 superfamily: enzymes which are involved in inflammation through participation in pro- and anti-inflammatory mediators production and have an impact on many immunocompetent cells. The 30 members of the A2 superfamily are divided into 7 groups. Their role in asthma and COPD has been studied in vitro and in vivo (animal models, cell cultures, and patients). This paper contains complete and updated information about the involvement of particular enzymes in the etiology and course of asthma and COPD.
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Affiliation(s)
- Ewa Pniewska
- Department of Immunopathology, Faculty of Biomedical Sciences and Postgraduate Training, Medical University of Lodz, 7/9 Zeligowskiego Street, Building 2, Room 122, 90-752 Lodz, Poland
| | - Rafal Pawliczak
- Department of Immunopathology, Faculty of Biomedical Sciences and Postgraduate Training, Medical University of Lodz, 7/9 Zeligowskiego Street, Building 2, Room 122, 90-752 Lodz, Poland
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13
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Henderson WR, Ye X, Lai Y, Ni Z, Bollinger JG, Tien YT, Chi EY, Gelb MH. Key role of group v secreted phospholipase A2 in Th2 cytokine and dendritic cell-driven airway hyperresponsiveness and remodeling. PLoS One 2013; 8:e56172. [PMID: 23451035 PMCID: PMC3581544 DOI: 10.1371/journal.pone.0056172] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 01/07/2013] [Indexed: 11/23/2022] Open
Abstract
Background Previous work has shown that disruption of the gene for group X secreted phospholipase A2 (sPLA2-X) markedly diminishes airway hyperresponsiveness and remodeling in a mouse asthma model. With the large number of additional sPLA2s in the mammalian genome, the involvement of other sPLA2s in the asthma model is possible – in particular, the group V sPLA2 (sPLA2-V) that like sPLA2-X is highly active at hydrolyzing membranes of mammalian cells. Methodology and Principal Findings The allergen-driven asthma phenotype was significantly reduced in sPLA2-V-deficient mice but to a lesser extent than observed previously in sPLA2-X-deficient mice. The most striking difference observed between the sPLA2-V and sPLA2-X knockouts was the significant impairment of the primary immune response to the allergen ovalbumin (OVA) in the sPLA2-V−/− mice. The impairment in eicosanoid generation and dendritic cell activation in sPLA2-V−/− mice diminishes Th2 cytokine responses in the airways. Conclusions This paper illustrates the diverse roles of sPLA2s in the immunopathogenesis of the asthma phenotype and directs attention to developing specific inhibitors of sPLA2-V as a potential new therapy to treat asthma and other allergic disorders.
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Affiliation(s)
- William R Henderson
- Center for Allergy and Inflammation, UW Medicine at South Lake Union, Department of Medicine, University of Washington, Seattle, Washington, United States of America.
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14
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A novel C(28)-hydroxylated lupeolic acid suppresses the biosynthesis of eicosanoids through inhibition of cytosolic phospholipase A2. Biochem Pharmacol 2012; 84:681-91. [DOI: 10.1016/j.bcp.2012.06.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Revised: 06/13/2012] [Accepted: 06/14/2012] [Indexed: 11/23/2022]
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Muñoz NM, Desai A, Meliton LN, Meliton AY, Zhou T, Leff AR, Dudek SM. Group V phospholipase A(2) increases pulmonary endothelial permeability through direct hydrolysis of the cell membrane. Pulm Circ 2012; 2:182-92. [PMID: 22837859 PMCID: PMC3401872 DOI: 10.4103/2045-8932.97604] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Acute lung injury (ALI) is characterized by inflammatory disruption of the alveolar–vascular barrier, resulting in severe respiratory compromise. Inhibition of the intercellular messenger protein, Group V phospholipase A2 (gVPLA2), blocks vascular permeability caused by LPS both in vivo and in vitro. In this investigation we studied the mechanism by which recombinant gVPLA2 increases permeability of cultured human pulmonary endothelial cells (EC). Exogenous gVPLA2 (500 nM), a highly hydrolytic enzyme, caused a significant increase in EC permeability that began within minutes and persisted for >10 hours. However, the major hydrolysis products of gVPLA2 (Lyso-PC, Lyso-PG, LPA, arachidonic acid) did not cause EC structural rearrangement or loss of barrier function at concentrations <10 μM. Higher concentrations (≥ 30 μM) of these membrane hydrolysis products caused some increased permeability but were associated with EC toxicity (measured by propidium iodide incorporation) that did not occur with barrier disruption by gVPLA2 (500 nM). Pharmacologic inhibition of multiple intracellular signaling pathways induced by gVPLA2 activity (ERK, p38, PI3K, cytosolic gIVPLA2) also did not prevent EC barrier disruption by gVPLA2. Finally, pretreatment with heparinase to prevent internalization of gVPLA2 did not inhibit EC barrier disruption by gVPLA2. Our data thus indicate that gVPLA2 increases pulmonary EC permeability directly through action as a membrane hydrolytic agent. Disruption of EC barrier function does not depend upon membrane hydrolysis products, gVPLA2 internalization, or upregulation of downstream intracellular signaling.
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Affiliation(s)
- Nilda M Muñoz
- Philippine Foundation for Lung Health, Research and Development, Inc. and Research and Biotechnology Division, St. Luke's Medical Center, Quezon City, Philippines
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Differences between group X and group V secretory phospholipase A(2) in lipolytic modification of lipoproteins. Cell Mol Biol Lett 2012; 17:459-78. [PMID: 22706677 PMCID: PMC6275602 DOI: 10.2478/s11658-012-0019-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 05/31/2012] [Indexed: 11/20/2022] Open
Abstract
Secretory phospholipases A(2) (sPLA(2)s) are a diverse family of low molecular mass enzymes (13-18 kDa) that hydrolyze the sn-2 fatty acid ester bond of glycerophospholipids to produce free fatty acids and lysophospholipids. We have previously shown that group X sPLA(2) (sPLA(2)-X) had a strong hydrolyzing activity toward phosphatidylcholine in low-density lipoprotein (LDL) linked to the formation of lipid droplets in the cytoplasm of macrophages. Here, we show that group V sPLA(2) (sPLA(2)-V) can also cause the lipolysis of LDL, but its action differs remarkably from that of sPLA(2)-X in several respects. Although sPLA(2)-V released almost the same amount of fatty acids from LDL, it released more linoleic acid and less arachidonic acid than sPLA(2)-X. In addition, the requirement of Ca(2+) for the lipolysis of LDL was about 10-fold higher for sPLA(2)-V than sPLA(2)-X. In fact, the release of fatty acids from human serum was hardly detectable upon incubation with sPLA(2)-V in the presence of sodium citrate, which contrasted with the potent response to sPLA(2)-X. Moreover, sPLA(2)-X, but not sPLA(2)-V, was found to specifically interact with LDL among the serum proteins, as assessed by gel-filtration chromatography as well as sandwich enzyme-immunosorbent assay using anti-sPLA(2)-X and anti-apoB antibodies. Surface plasmon resonance studies have revealed that sPLA2-X can bind to LDL with high-affinity (K(d) = 3.1 nM) in the presence of Ca(2+). Selective interaction of sPLA(2)-X with LDL might be involved in the efficient hydrolysis of cell surface or intracellular phospholipids during foam cell formation.
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Dennis EA, Cao J, Hsu YH, Magrioti V, Kokotos G. Phospholipase A2 enzymes: physical structure, biological function, disease implication, chemical inhibition, and therapeutic intervention. Chem Rev 2011; 111:6130-85. [PMID: 21910409 PMCID: PMC3196595 DOI: 10.1021/cr200085w] [Citation(s) in RCA: 804] [Impact Index Per Article: 61.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Edward A. Dennis
- Department of Chemistry and Biochemistry and Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093-0601
| | - Jian Cao
- Department of Chemistry and Biochemistry and Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093-0601
| | - Yuan-Hao Hsu
- Department of Chemistry and Biochemistry and Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093-0601
| | - Victoria Magrioti
- Laboratory of Organic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Athens 15771, Greece
| | - George Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Athens 15771, Greece
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Murakami M, Taketomi Y, Sato H, Yamamoto K. Secreted phospholipase A2 revisited. J Biochem 2011; 150:233-55. [PMID: 21746768 DOI: 10.1093/jb/mvr088] [Citation(s) in RCA: 150] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Phospholipase A(2) (PLA(2)) catalyses the hydrolysis of the sn-2 position of glycerophospholipids to yield fatty acids and lysophospholipids. So far, more than 30 enzymes that possess PLA(2) or related activity have been identified in mammals. About one third of these enzymes belong to the secreted PLA(2) (sPLA(2)) family, which comprises low molecular weight, Ca(2+) requiring, secreted enzymes with a His/Asp catalytic dyad. Individual sPLA(2)s display distinct localizations and enzymatic properties, suggesting their specialized biological roles. However, in contrast to intracellular PLA(2)s, whose roles in signal transduction and membrane homoeostasis have been well documented, the biological roles of sPLA(2)s in vivo have remained obscure until recently. Over the past decade, information fuelled by studies employing knockout and transgenic mice as well as specific inhibitors, in combination with lipidomics, has clarified when and where the different sPLA(2) isoforms are expressed, which isoforms are involved in what types of pathophysiology, and how they exhibit their specific functions. In this review, we highlight recent advances in PLA(2) research, focusing mainly on the physiological functions of sPLA(2)s and their modes of action on 'extracellular' phospholipid targets versus lipid mediator production.
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Affiliation(s)
- Makoto Murakami
- Lipid Metabolism Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
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Madsen JJ, Linderoth L, Subramanian AK, Andresen TL, Peters GH. Secretory phospholipase A2 activity toward diverse substrates. J Phys Chem B 2011; 115:6853-61. [PMID: 21561115 DOI: 10.1021/jp112137b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have studied secretory phospholipase A(2)-IIA (sPLA(2)) activity toward different phospholipid analogues by performing biophysical characterizations and molecular dynamics simulations. The phospholipids were natural substrates, triple alkyl phospholipids, a prodrug anticancer etherlipid, and an inverted ester. The latter were included to study head group-enzyme interactions. Our simulation results show that the lipids are optimally placed into the binding cleft and that water molecules can freely reach the active site through a well-defined pathway; both are indicative that these substrates are efficiently hydrolyzed, which is in good agreement with our experimental data. The phospholipid analogue with three alkyl side chains forms aggregates of different shapes with no well-defined sizes due to its cone-shape structure. Phosphatidylglycerol and phosphatidylcholine head groups interact with specific charged residues, but relatively large fluctuations are observed, suggesting that these interactions are not necessarily important for stabilizing substrate binding to the enzyme.
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Affiliation(s)
- Jesper J Madsen
- Department of Chemistry, Technical University of Denmark, Kgs. Lyngby, Denmark
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20
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Ji JE, Kim SK, Ahn KH, Choi JM, Jung SY, Jung KM, Jeon HJ, Kim DK. Ceramide induces serotonin release from RBL-2H3 mast cells through calcium mediated activation of phospholipase A2. Prostaglandins Other Lipid Mediat 2011; 94:88-95. [DOI: 10.1016/j.prostaglandins.2011.01.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Revised: 12/28/2010] [Accepted: 01/04/2011] [Indexed: 11/30/2022]
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21
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Rosenson RS. After FRANCIS: next steps in the clinical evaluation of varespladib methyl. Future Cardiol 2011; 7:11-8. [DOI: 10.2217/fca.10.118] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Secretory phospholipase A2 (sPLA2) represents a family of isoenzymes that participate in lipoprotein and inflammatory pathways, mediate atherosclerosis and enhance myocardial ischemic injury. The Fewer Recurrent Acute Coronary Events with Near-term Cardiovascular Inflammatory Suppression (FRANCIS) trial (NCT00743925) was a Phase II trial designed to examine the effects of varespladib methyl, a small-molecule inhibitor of sPLA2, on plasma biomarkers in patients with acute coronary syndrome (ACS) who were treated with atorvastatin 80 mg and standard-of-care daily. Varespladib methyl significantly reduced low-density lipoprotein cholesterol and inflammatory biomarkers in ACS subjects treated with standard-of-care and atorvastatin 80 mg daily. There was a nonsignificant reduction in major adverse cardiovascular events at study completion; however, positive trends remained for unstable angina and myocardial infarction. In order to achieve the widespread use of varespladib methyl in ACS patients, completion of a prospective, randomized placebo-controlled trial in ACS patients and stable coronary artery disease patients with increased sPLA2 activity will be required.
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Affiliation(s)
- Robert S Rosenson
- Mount Sinai School of Medicine, Box 1030, One Gustave L Levy Place, New York, NY 10029, USA
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Murakami M, Taketomi Y, Miki Y, Sato H, Hirabayashi T, Yamamoto K. Recent progress in phospholipase A₂ research: from cells to animals to humans. Prog Lipid Res 2010; 50:152-92. [PMID: 21185866 DOI: 10.1016/j.plipres.2010.12.001] [Citation(s) in RCA: 368] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mammalian genomes encode genes for more than 30 phospholipase A₂s (PLA₂s) or related enzymes, which are subdivided into several classes including low-molecular-weight secreted PLA₂s (sPLA₂s), Ca²+-dependent cytosolic PLA₂s (cPLA₂s), Ca²+-independent PLA₂s (iPLA₂s), platelet-activating factor acetylhydrolases (PAF-AHs), lysosomal PLA₂s, and a recently identified adipose-specific PLA. Of these, the intracellular cPLA₂ and iPLA₂ families and the extracellular sPLA₂ family are recognized as the "big three". From a general viewpoint, cPLA₂α (the prototypic cPLA₂ plays a major role in the initiation of arachidonic acid metabolism, the iPLA₂ family contributes to membrane homeostasis and energy metabolism, and the sPLA₂ family affects various biological events by modulating the extracellular phospholipid milieus. The cPLA₂ family evolved along with eicosanoid receptors when vertebrates first appeared, whereas the diverse branching of the iPLA₂ and sPLA₂ families during earlier eukaryote development suggests that they play fundamental roles in life-related processes. During the past decade, data concerning the unexplored roles of various PLA₂ enzymes in pathophysiology have emerged on the basis of studies using knockout and transgenic mice, the use of specific inhibitors, and information obtained from analysis of human diseases caused by mutations in PLA₂ genes. This review focuses on current understanding of the emerging biological functions of PLA₂s and related enzymes.
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Affiliation(s)
- Makoto Murakami
- Lipid Metabolism Project, The Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan.
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Yano T, Fujioka D, Saito Y, Kobayashi T, Nakamura T, Obata JE, Kawabata K, Watanabe K, Watanabe Y, Mishina H, Tamaru S, Kugiyama K. Group V secretory phospholipase A2 plays a pathogenic role in myocardial ischaemia-reperfusion injury. Cardiovasc Res 2010; 90:335-43. [PMID: 21169294 DOI: 10.1093/cvr/cvq399] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
AIMS Group V secretory phospholipase A(2) (sPLA(2)-V) is highly expressed in the heart. This study examined (i) the role of sPLA(2)-V in myocardial ischaemia-reperfusion (I/R) injury and (ii) the cooperative action of sPLA(2)-V and cytosolic PLA(2) (cPLA(2)) in myocardial I/R injury, using sPLA(2)-V knockout (sPLA(2)V(-/-)) mice. METHODS AND RESULTS Myocardial I/R injury was created by 1 h ligation of the left anterior descending coronary artery, followed by 24 h of reperfusion. The sPLA(2)V(-/-) mice had a 44% decrease in myocardial infarct size, a preservation of echocardiographic LV function (%fractional shortening: 40 ± 3.5 vs. 21 ± 4.6, respectively), and lower content of leucotriene B(4) (LTB(4)) and thromboxane B(2) (TXB(2)) (40 and 37% lower, respectively) in the ischaemic myocardium after I/R compared with wild-type (WT) mice. Intraperitoneal administration of AACOCF3 or MAFP, inhibitors of cPLA(2) activity, decreased myocardial infarct size and myocardial content of LTB(4) and TXB(2) in both genotyped mice. The decrease in myocardial infarct size and content of LTB(4) and TXB(2) after cPLA(2) inhibitor administration was greater in WT mice than in sPLA(2)V(-/-) mice. I/R increased phosphorylation of extracellular signal-related kinase 1/2, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinases in the ischaemic myocardium in association with cPLA(2) phosphorylation. The I/R-induced increase in the phosphorylation of p38 and cPLA(2) was less in sPLA(2)-V(-/-) mice than in WT mice. Pretreatment with the p38 inhibitor SB202190 suppressed an increase in cPLA(2) phosphorylation after I/R in WT mice. CONCLUSION sPLA(2)-V plays an important role in the pathogenesis of myocardial I/R injury partly in concert with the activation of cPLA(2).
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Affiliation(s)
- Toshiaki Yano
- Department of Internal Medicine II, Faculty of Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 1110 Shimokato, Yamanashi, Chuo 409-3898, Japan
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Lai Y, Oslund RC, Bollinger JG, Henderson WR, Santana LF, Altemeier WA, Gelb MH, Hallstrand TS. Eosinophil cysteinyl leukotriene synthesis mediated by exogenous secreted phospholipase A2 group X. J Biol Chem 2010; 285:41491-500. [PMID: 20974857 DOI: 10.1074/jbc.m110.153338] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Secreted phospholipase A(2) group X (sPLA(2)-X) has recently been identified in the airways of patients with asthma and may participate in cysteinyl leukotriene (CysLT; C(4), D(4), and E(4)) synthesis. We examined CysLT synthesis and arachidonic acid (AA) and lysophospholipid release by eosinophils mediated by recombinant human sPLA(2)-X. We found that recombinant sPLA(2)-X caused marked AA release and a rapid onset of CysLT synthesis in human eosinophils that was blocked by a selective sPLA(2)-X inhibitor. Exogenous sPLA(2)-X released lysophospholipid species that arise from phospholipids enriched in AA in eosinophils, including phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine as well as plasmenyl phosphatidylcholine and phosphatidylethanolamine. CysLT synthesis mediated by sPLA(2)-X but not AA release could be suppressed by inhibition of cPLA(2)α. Exogenous sPLA(2)-X initiated Ser(505) phosphorylation of cPLA(2)α, an intracellular Ca(2+) flux, and translocation of cPLA(2)α and 5-lipoxygenase in eosinophils. Synthesis of CysLTs in response to sPLA(2)-X or lysophosphatidylcholine was inhibited by p38 or JNK inhibitors but not by a MEK 1/2 inhibitor. A further increase in CysLT synthesis was induced by the addition of sPLA(2)-X to eosinophils under conditions of N-formyl-methionyl-leucyl-phenylalanine-mediated cPLA(2)α activation. These results indicate that sPLA(2)-X participates in AA and lysophospholipid release, resulting in CysLT synthesis in eosinophils through a mechanism involving p38 and JNK MAPK, cPLA(2)α, and 5-lipoxygenase activation and resulting in the amplification of CysLT synthesis during cPLA(2)α activation. Transactivation of eosinophils by sPLA(2)-X may be an important mechanism leading to CysLT formation in the airways of patients with asthma.
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Affiliation(s)
- Ying Lai
- Division of Pulmonary and Critical Care, University of Washington, Seattle, Washington 98195, USA
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Rosenson RS, Hislop C, Elliott M, Stasiv Y, Goulder M, Waters D. Effects of varespladib methyl on biomarkers and major cardiovascular events in acute coronary syndrome patients. J Am Coll Cardiol 2010; 56:1079-88. [PMID: 20863951 DOI: 10.1016/j.jacc.2010.06.015] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2010] [Revised: 05/19/2010] [Accepted: 06/01/2010] [Indexed: 11/16/2022]
Abstract
OBJECTIVES The purpose of this study was to investigate the effects of varespladib on cardiovascular biomarkers in acute coronary syndrome patients. BACKGROUND Secretory phospholipase A(2) (sPLA(2)) represents a family of proatherogenic enzymes that hydrolyze lipoprotein phospholipids, increasing their affinity for intimal proteoglycans; contribute to cholesterol loading of macrophages by nonscavenger receptor mediated pathways; and activate inflammatory pathways. In prospective studies, high sPLA(2)-IIA levels predicted major adverse cardiovascular events in acute coronary syndrome (ACS) and stable coronary heart disease patients. METHODS This randomized, double-blind, prospective controlled clinical trial (phase 2B) was designed to investigate the effects of sPLA(2) inhibition with varespladib 500 mg daily versus placebo as adjunctive therapy to atorvastatin 80 mg daily on biomarkers (low-density lipoprotein cholesterol [LDL-C], high-sensitivity C-reactive protein [hsCRP], and sPLA(2)-IIA levels), major adverse cardiovascular events (unstable angina, myocardial infarction, death), and safety. In all, 625 ACS subjects were randomized within 96 h of the index event and treated for a minimum of 6 months. RESULTS After 8 weeks (primary efficacy end point), varespladib/atorvastatin reduced mean LDL-C levels from baseline by 49.6% compared with 43.4% with placebo/atorvastatin (p = 0.002). Respective 8-week median reductions in sPLA(2)-IIA levels were 82.4% and 15.6% (p < 0.0001), and hsCRP levels were lowered by 75.0% and 71.0% (p = 0.097). At 24 weeks, respective reductions with varespladib and placebo were as follows: LDL-C 43.5% versus 37.6% (p < 0.05), hsCRP 79.8% versus 77.0% (p = 0.02), and sPLA(2)-IIA 78.5% versus 6.4% (p < 0.0001). Major adverse cardiovascular events were not different from placebo 6 months post-randomization (7.3% varespladib vs. 7.7% placebo). No treatment differences in elevated liver function studies on >1 occasion were observed. CONCLUSIONS Varespladib therapy effectively reduced LDL-C and inflammatory biomarkers in ACS patients treated with conventional therapy including atorvastatin 80 mg daily. There were no treatment differences in clinical cardiovascular events. (FRANCIS [Fewer Recurrent Acute Coronary Events With Near-Term Cardiovascular Inflammation Suppression]-ACS Trial: A Study of the Safety and Efficacy of A 002 in Subjects With Acute Coronary Syndromes; NCT00743925).
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Rosenson RS, Fraser H, Trias J, Hislop C. Varespladib methyl in cardiovascular disease. Expert Opin Investig Drugs 2010; 19:1245-55. [DOI: 10.1517/13543784.2010.517193] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Boilard E, Lai Y, Larabee K, Balestrieri B, Ghomashchi F, Fujioka D, Gobezie R, Coblyn JS, Weinblatt ME, Massarotti EM, Thornhill TS, Divangahi M, Remold H, Lambeau G, Gelb MH, Arm JP, Lee DM. A novel anti-inflammatory role for secretory phospholipase A2 in immune complex-mediated arthritis. EMBO Mol Med 2010; 2:172-87. [PMID: 20432503 PMCID: PMC3058614 DOI: 10.1002/emmm.201000072] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Phospholipase A2 (PLA2) catalyses the release of arachidonic acid for generation of lipid mediators of inflammation and is crucial in diverse inflammatory processes. The functions of the secretory PLA2 enzymes (sPLA2), numbering nine members in humans, are poorly understood, though they have been shown to participate in lipid mediator generation and the associated inflammation. To further understand the roles of sPLA2 in disease, we quantified the expression of these enzymes in the synovial fluid in rheumatoid arthritis and used gene-deleted mice to examine their contribution in a mouse model of autoimmune erosive inflammatory arthritis. Contrary to expectation, we find that the group V sPLA2 isoform plays a novel anti-inflammatory role that opposes the pro-inflammatory activity of group IIA sPLA2. Mechanistically, group V sPLA2 counter-regulation includes promotion of immune complex clearance by regulating cysteinyl leukotriene synthesis. These observations identify a novel anti-inflammatory function for a PLA2 and identify group V sPLA2 as a potential biotherapeutic for treatment of immune-complex-mediated inflammation.
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Affiliation(s)
- Eric Boilard
- Division of Rheumatology, Immunology and Allergy and Partners Asthma Center, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
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Lapointe S, Brkovic A, Cloutier I, Tanguay JF, Arm JP, Sirois MG. Group V secreted phospholipase A2 contributes to LPS-induced leukocyte recruitment. J Cell Physiol 2010; 224:127-34. [PMID: 20232296 DOI: 10.1002/jcp.22106] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Secreted phospholipases A(2) (sPLA(2)s) are well known for their contribution in the biosynthesis of inflammatory eicosanoids. These enzymes also participate in the inflammatory process by regulating chemokine production and protein expression of adhesion molecules. The majority of sPLA(2) isoforms are up-regulated by proinflammatory stimuli such as bacterial lipopolysaccharide (LPS), which predominantly increases the expression of group V sPLA(2) (sPLA(2)-V). Furthermore, it has recently been shown that sPLA(2)-V is a critical messenger in the regulation of cell migration during allergic airway responsiveness. Herein, we investigated the effect of sPLA(2)-V on LPS-mediated leukocyte recruitment and its capacity to modulate adhesion molecule expression. We conducted our study in the murine air pouch model, using sPLA(2)-V null mice (sPLA(2)-V(-/-)) and control wild-type (WT) littermates. We observed that LPS (1 microg/ml)-mediated leukocyte emigration in sPLA(2)-V(-/-) was attenuated by 52% and 86% upon 6 and 12 h of treatment respectively, as compared to WT mice. In WT mice, treatment with the cell-permeable sPLA(2) inhibitor (12-epi-scalaradial; SLD) reduced LPS-mediated leukocyte recruitment by 67%, but had no additional inhibitory effect in sPLA(2)-V(-/-) mice. Protein analyses from the air pouch skin were carried out upon LPS-challenge, and the expression of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 were both significantly reduced in sPLA(2)-V(-/-) mice as compared to control WT mice. Together, our data demonstrate the role of sPLA(2)-V in LPS-induced ICAM-1 and VCAM-1 protein overexpression and leukocyte recruitment, supporting the contribution of sPLA(2)-V in the development of inflammatory innate immune responses.
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Affiliation(s)
- Stéphanie Lapointe
- Research Centre, Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada
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Murakami M, Taketomi Y, Girard C, Yamamoto K, Lambeau G. Emerging roles of secreted phospholipase A2 enzymes: Lessons from transgenic and knockout mice. Biochimie 2010; 92:561-82. [PMID: 20347923 DOI: 10.1016/j.biochi.2010.03.015] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Accepted: 03/18/2010] [Indexed: 11/15/2022]
Abstract
Among the emerging phospholipase A(2) (PLA(2)) superfamily, the secreted PLA(2) (sPLA(2)) family consists of low-molecular-mass, Ca(2+)-requiring extracellular enzymes with a His-Asp catalytic dyad. To date, more than 10 sPLA(2) enzymes have been identified in mammals. Individual sPLA(2)s exhibit unique tissue and cellular localizations and enzymatic properties, suggesting their distinct pathophysiological roles. Despite numerous enzymatic and cell biological studies on this enzyme family in the past two decades, their precise in vivo functions still remain largely obscure. Recent studies using transgenic and knockout mice for several sPLA(2) enzymes, in combination with lipidomics approaches, have opened new insights into their distinct contributions to various biological events such as food digestion, host defense, inflammation, asthma and atherosclerosis. In this article, we overview the latest understanding of the pathophysiological functions of individual sPLA(2) isoforms fueled by studies employing transgenic and knockout mice for several sPLA(2)s.
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Affiliation(s)
- Makoto Murakami
- Biomembrane Signaling Project, The Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan.
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The role of mast cell-derived secreted phospholipases A2 in respiratory allergy. Biochimie 2010; 92:588-93. [PMID: 20219624 DOI: 10.1016/j.biochi.2010.02.030] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Accepted: 02/19/2010] [Indexed: 11/23/2022]
Abstract
Secreted phospholipases A(2) (sPLA(2)s) are molecules released in plasma and biological fluids of patients with systemic inflammatory, autoimmune and allergic diseases. These molecules exert proinflammatory effects by either enzymatic-mechanisms or through binding to surface molecules expressed on inflammatory cells. sPLA(2)s are released at low levels in the normal airways and tend to increase during respiratory allergies (e.g., rhinitis and bronchial asthma) as the result of local secretion. Several sPLA(2) isoforms are expressed in the human lung and some of them (e.g., group IIA and group X) are released in the airways of patients with rhinitis or asthma. Mast cells play a major role in the pathogenesis of respiratory allergies and other chronic inflammatory lung diseases. Recent evidence indicates that mast cells purified from human lung express most of the sPLA(2) isoforms so far described. IgE-mediated activation of these cells induce the release of sPLA(2)s suggesting that mast cells are a main source of extracellular sPLA(2)s during allergic reactions. Once released, sPLA(2)s may contribute to the generation of eicosanoids (e.g., PGD(2) and LTC(4)) and to the release of preformed mediators (e.g., histamine) by an autocrine loop involving the interaction of sPLA(2)s with surface molecules such as heparan sulphate proteoglycans or the M-type receptor. Thus, mast cell-derived sPLA(2)s may play an important role in the initiation and amplification of the inflammatory reactions in patients with allergic rhinitis and bronchial asthma.
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Fast method for monitoring phospholipase A2 activity by liquid chromatography-electrospray ionization mass spectrometry. J Chromatogr A 2009; 1216:5249-55. [PMID: 19486990 DOI: 10.1016/j.chroma.2009.05.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 05/08/2009] [Accepted: 05/11/2009] [Indexed: 01/24/2023]
Abstract
A new liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method for the fast determination of phospholipase A(2) (PLA(2)) activity has been developed. For the first time, the method allows the parallel detection of glycerophosphatidylcholine (GroPCho) as PLA(2) substrate as well as of its products fatty acid (FA) and lyso-GroPCho. ESI-MS was carried out in negative ion mode, detecting the FA as [M-H](-) ions and the lyso-GroPCho and GroPCho as acetate adducts [M+Ac](-). Utilizing a fast gradient on a short C(5)-modified silica gel column with 3 microm particles, five GroPChos, five FAs and six lyso-GroPChos could be separated according to their chain length in less than 3 min. A very high average chromatographic efficiency of 41,200 theoretical plates (plate height 0.5 microm) was achieved for the separation of the GroPChos. The method was applied for monitoring the release of arachidonic acid (20:4 FA) and 1-stearoyl-lyso-sn-GroPCho (18:0 GroPCho) from unilamellar vesicles of 1-stearoyl-2-arachidonoyl-sn-GroPCho (18:0/20:4 GroPCho). With a limit of detection of 0.5 pmol (total amount injected on column) for the FAs and lyso-GroPChos and 1.5 pmol for the GroPChos as well as a linear range of 1.5 decades, the method has proven to be suitable for the monitoring of different secretory PLA(2) (sPLA(2)) conversions. Furthermore, it was applied to screen a small library of PLA(2) inhibitors for their activity towards sPLA(2) type V and snake venom of Bothrops moojeni. In both cases, active samples could be directly identified. With its short analysis time, its high chromatographic efficiency and the parallel detection of substrate and all products, the developed LC-ESI-MS method is well suited for the analysis of PLA(2) activity.
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Ruipérez V, Astudillo AM, Balboa MA, Balsinde J. Coordinate regulation of TLR-mediated arachidonic acid mobilization in macrophages by group IVA and group V phospholipase A2s. THE JOURNAL OF IMMUNOLOGY 2009; 182:3877-83. [PMID: 19265167 DOI: 10.4049/jimmunol.0804003] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Macrophages can be activated through TLRs for a variety of innate immune responses. In contrast with the wealth of data existing on TLR-dependent gene expression and resultant cytokine production, very little is known on the mechanisms governing TLR-mediated arachidonic acid (AA) mobilization and subsequent eicosanoid production. We have previously reported the involvement of both cytosolic group IVA phospholipase A(2) (cPLA(2)) and secreted group V phospholipase A(2) (sPLA(2)-V) in regulating the AA mobilization response of macrophages exposed to bacterial LPS, a TLR4 agonist. In the present study, we have used multiple TLR agonists to define the role of various PLA(2)s in macrophage AA release via TLRs. Activation of P388D(1) and RAW2647.1 macrophage-like cells via TLR1/2, TLR2, TLR3, TLR4, TLR6/2, and TLR7, but not TLR5 or TLR9, resulted in AA mobilization that appears to involve the activation of both cPLA(2) and sPLA(2) but not of calcium-independent phospholipase A(2). Furthermore, inhibition of sPLA(2)-V by RNA interference or by two cell-permeable compounds, namely scalaradial and manoalide, resulted in a marked reduction of the phosphorylation of ERK1/2 and cPLA(2) via TLR1/2, TLR2, TLR3, and TLR4, leading to attenuated AA mobilization. Collectively, the results suggest a model whereby sPLA(2)-V contributes to the macrophage AA mobilization response via various TLRs by amplifying cPLA(2) activation through the ERK1/2 phosphorylation cascade.
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Affiliation(s)
- Violeta Ruipérez
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, and Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Valladolid, Spain
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Muñoz NM, Meliton AY, Meliton LN, Dudek SM, Leff AR. Secretory group V phospholipase A2 regulates acute lung injury and neutrophilic inflammation caused by LPS in mice. Am J Physiol Lung Cell Mol Physiol 2009; 296:L879-87. [PMID: 19286925 DOI: 10.1152/ajplung.90580.2008] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
We investigated the regulatory role of 14-kDa secretory group V phospholipase A(2) (gVPLA(2)) in the development of acute lung injury (ALI) and neutrophilic inflammation (NI) caused by intratracheal administration of LPS. Experiments were conducted in gVPLA(2) knockout (pla2g5(-/-)) mice, which lack the gene, and gVPLA(2) wild-type littermate control (pla2g5(+/+)) mice. Indices of pulmonary injury were evaluated 24 h after intratracheal administration of LPS. Expression of gVPLA(2) in microsections of airways and mRNA content in lung homogenates were increased substantially in pla2g5(+/+) mice after LPS-administered compared with saline-treated pla2g5(+/+) mice. By contrast, expression of gVPLA(2) was neither localized in LPS- nor saline-treated pla2g5(-/-) mice. LPS also caused 1) reduced transthoracic static compliance, 2) lung edema, 3) neutrophilic infiltration, and 4) increased neutrophil myeloperoxidase activity in pla2g5(+/+) mice. These events were attenuated in pla2g5(-/-) mice exposed to LPS or in pla2g5(+/+) mice receiving MCL-3G1, a neutralizing MAb directed against gVPLA(2), before LPS administration. Our data demonstrate that gVPLA(2) is an inducible protein in pla2g5(+/+) mice but not in pla2g5(-/-) mice within 24 h after LPS treatment. Specific inhibition of gVPLA(2) with MCL-3G1 or gene-targeted mice lacking gVPLA(2) blocks ALI and attenuates NI caused by LPS.
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Affiliation(s)
- Nilda M Muñoz
- Dept. of Medicine, M6076, Univ. of Chicago, 5841 S. Maryland Ave., Chicago, IL 60637, USA
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Leite JO, Vaishnav U, Puglisi M, Fraser H, Trias J, Fernandez ML. A-002 (Varespladib), a phospholipase A2 inhibitor, reduces atherosclerosis in guinea pigs. BMC Cardiovasc Disord 2009; 9:7. [PMID: 19222850 PMCID: PMC2653470 DOI: 10.1186/1471-2261-9-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Accepted: 02/17/2009] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND The association of elevated serum levels of secretory phospholipase A2 (sPLA2) in patients with cardiovascular disease and their presence in atherosclerotic lesions suggest the participation of sPLA2 enzymes in this disease. The presence of more advanced atherosclerotic lesions in mice that overexpress sPLA2 enzymes suggest their involvement in the atherosclerotic process. Therefore, the sPLA2 family of enzymes could provide reasonable targets for the prevention and treatment of atherosclerosis. Thus, A-002 (varespladib), an inhibitor of sPLA2enzymes, is proposed to modulate the development of atherosclerosis. METHODS Twenty-four guinea pigs were fed a high saturated fat, high cholesterol diet (0.25%) for twelve weeks. Animals were treated daily with A-002 (n = 12) or vehicle (10% aqueous acacia; n = 12) by oral gavage. After twelve weeks, animals were sacrificed and plasma, heart and aorta were collected. Plasma lipids were measured by enzymatic methods, lipoprotein particles size by nuclear magnetic resonance, aortic cytokines by a colorimetric method, and aortic sinus by histological analyses. RESULTS Plasma total cholesterol, HDL cholesterol and triglycerides were not different among groups. However, the levels of inflammatory cytokines interleukin (IL)-10, IL-12 and granulocyte-macrophage colony-stimulating factor (GM-CSF) were significantly reduced in the treatment group. This group also had a significant 27% reduction in cholesterol accumulation in aorta compared with placebo group. Morphological analysis of aortic sinus revealed that the group treated with A-002 reduced atherosclerotic lesions by 24%. CONCLUSION The use of A-002 may have a beneficial effect in preventing diet-induced atherosclerosis in guinea pigs.
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Affiliation(s)
- Jose O Leite
- Department of Nutritional Sciences, University of Connecticut, Storrs, CT, USA.
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Abstract
Introduction The secretory phospholipase A2 (sPLA2) family provides a seemingly endless array of potential biological functions that is only beginning to be appreciated. In humans, this family comprises 9 different members that vary in their tissue distribution, hydrolytic activity, and phospholipid substrate specificity. Through their lipase activity, these enzymes trigger various cell-signaling events to regulate cellular functions, directly kill bacteria, or modulate inflammatory responses. In addition, some sPLA2’s are high affinity ligands for cellular receptors. Objective This review merely scratches the surface of some of the actions of sPLA2s in innate immunity, inflammation, and atherosclerosis. The goal is to provide an overview of recent findings involving sPLA2s and to point to potential pathophysiologic mechanisms that may become targets for therapy.
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Lambeau G, Gelb MH. Biochemistry and physiology of mammalian secreted phospholipases A2. Annu Rev Biochem 2008; 77:495-520. [PMID: 18405237 DOI: 10.1146/annurev.biochem.76.062405.154007] [Citation(s) in RCA: 406] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Phospholipases A(2) (PLA2s) are esterases that hydrolyze the sn-2 ester of glycerophospholipids and constitute one of the largest families of lipid hydrolyzing enzymes. The mammalian genome contains 10 enzymatically active secreted PLA2s (sPLA2s) and two sPLA2-related proteins devoid of lipolytic enzymatic activity. In addition to the well-established functions of one of these enzymes in digestion of dietary phospholipids and another in host defense against bacterial infections, accumulating evidence shows that some of these sPLA2s are involved in arachidonic acid release from cellular phospholipids for the biosynthesis of eicosanoids, especially during inflammation. More speculative results suggest the involvement of one or more sPLA2s in promoting atherosclerosis and cancer. In addition, the mammalian genome encodes several types of sPLA2-binding proteins, and mounting evidence shows that sPLA2s may have functions related to binding to cellular target proteins in a manner independent of their lipolytic enzymatic activity.
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Affiliation(s)
- Gérard Lambeau
- Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Université de Nice-Sophia-Antipolis, 06560 Valbonne, France.
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38
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Multiple roles of phospholipase A2 during lung infection and inflammation. Infect Immun 2008; 76:2259-72. [PMID: 18411286 DOI: 10.1128/iai.00059-08] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Tian W, Wijewickrama GT, Kim JH, Das S, Tun MP, Gokhale N, Jung JW, Kim KP, Cho W. Mechanism of regulation of group IVA phospholipase A2 activity by Ser727 phosphorylation. J Biol Chem 2007; 283:3960-71. [PMID: 18065419 DOI: 10.1074/jbc.m707345200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although group IVA cytosolic phospholipase A(2) (cPLA(2)alpha) has been reported to be phosphorylated at multiple Ser residues, the mechanisms by which phosphorylation at different sites regulates cPLA(2)alpha activities are not fully understood. To explore the possibility that phosphorylation of Ser(727) modulates cellular protein-protein interactions, we measured the effect of Ser(727) mutations on the interaction of cPLA(2)alpha with a reported cPLA(2)alpha-binding protein, p11. In vitro activity assays and membrane binding measurements by surface plasmon resonance analysis showed that a heterotetramer (A2t) of p11 and annexin A2, but not p11 or annexin A2 alone, directly binds cPLA(2)alpha via Ser(727), which keeps the enzyme from binding the membrane and catalyzing the phospholipid hydrolysis. Phosphorylation of Ser(727) disrupts this inhibitory cPLA(2)alpha-A2t interaction, thereby activating cPLA(2)alpha. Subcellular translocation and activity measurements in HEK293 cells cotransfected with cPLA(2)alpha and p11 also showed that p11, in the form of A2t, inhibits cPLA(2)alpha by the same mechanism and that phosphorylation of Ser(727) activates cPLA(2)alpha by interfering with the inhibitory cPLA(2)alpha-A2t interaction. Collectively, these studies provide new insight into the regulatory mechanism of cPLA(2)alpha through Ser(727) phosphorylation.
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Affiliation(s)
- Wen Tian
- Department of Chemistry, University of Illinois, Chicago, Illinois 60607, USA
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40
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Abstract
The Foerster resonance energy transfer-based sensor, PENN, measures intracellular phospholipase A(2) (PLA(2)) activity in living cells and small organisms. In an attempt to modify the probe for the detection of particular isoforms, we altered the sn-2 fatty acid in such a way that either one or three of the Z double bonds in arachidonic acid were present in the sensor molecule. Arachidonic-acid-mimicking fatty acids were prepared by copper-mediated coupling reactions. Probes with a single double bond in the 5-position exhibited favorable substrate properties for secretory PLA(2)s. In vitro experiments with the novel unsaturated doubly labeled phosphatidylethanolamine derivatives showed preferred cleavage of the sensor PENN2 (one double bond) by the physiologically important group V sPLA(2), while the O-methyl-derivative PMNN2 was accepted best by the isoform from hog pancreas. For experiments in living cells, we demonstrated that bioactivation via S-acetylthioethyl (SATE) groups is essential for probe performance. Surprisingly, membrane-permeant versions of the new sensors that contained double bonds, PENN2 and PENN3, were only cleaved to a minor extent in HeLa cells while the saturated form, PENN, was well accepted.
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Affiliation(s)
- Oliver Wichmann
- O. Wichmann, Dr. C. Schultz, European Molecular Biology Laboratorium, Gene Expression Programme, Meyerhofstrasse 1, 69117 Heidelberg (Germany), Fax: (+49) 6221-387206, E-mail:
| | - Michael H. Gelb
- Dr. M. H. Gelb, Department of Chemistry and Biochemistry, Campus Box 351700, Seattle, WA 98195 (USA)
| | - Carsten Schultz
- O. Wichmann, Dr. C. Schultz, European Molecular Biology Laboratorium, Gene Expression Programme, Meyerhofstrasse 1, 69117 Heidelberg (Germany), Fax: (+49) 6221-387206, E-mail:
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Ruipérez V, Casas J, Balboa MA, Balsinde J. Group V phospholipase A2-derived lysophosphatidylcholine mediates cyclooxygenase-2 induction in lipopolysaccharide-stimulated macrophages. THE JOURNAL OF IMMUNOLOGY 2007; 179:631-8. [PMID: 17579085 DOI: 10.4049/jimmunol.179.1.631] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Activation of macrophages and macrophage cell lines by bacterial LPS elicits a delayed phase of PG biosynthesis that appears to be entirely mediated by cyclooxygenase-2 (COX-2). In previous work, we found that a catalytically active group V secreted phospholipase A(2) (sPLA(2)-V) was required for COX-2 induction, but the nature of the sPLA(2)-V metabolite involved was not defined. In this study, we identify lysophosphatidylcholine (lysoPC) as the sPLA(2)-V downstream mediator involved in COX-2 induction by LPS-stimulated macrophages. Inhibition of sPLA(2)-V by RNA interference or by the cell-permeable compound scalaradial blocked LPS-induced COX-2 expression, and this inhibition was overcome by incubating the cells with a nonhydrolyzable lysoPC analog, but not by arachidonic acid or oleic acid. Moreover, inhibition of sPLA(2)-V by scalaradial also prevented the activation of the transcription factor c-Rel, and such an inhibition was also selectively overcome by the lysoPC analog. Collectively, these results support a model whereby sPLA(2)-V hydrolysis of phospholipids upon LPS stimulation results in lysoPC generation, which in turn regulates COX-2 expression by a mechanism involving the transcriptional activity of c-Rel.
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Affiliation(s)
- Violeta Ruipérez
- Institute of Molecular Biology and Genetics, Spanish National Research Council and University of Valladolid School of Medicine, Valladolid, Spain
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42
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Kikawada E, Bonventre JV, Arm JP. Group V secretory PLA2 regulates TLR2-dependent eicosanoid generation in mouse mast cells through amplification of ERK and cPLA2alpha activation. Blood 2007; 110:561-7. [PMID: 17369491 PMCID: PMC1924482 DOI: 10.1182/blood-2006-10-052258] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2006] [Accepted: 02/06/2007] [Indexed: 01/28/2023] Open
Abstract
Mast cells may be activated through Toll-like receptors (TLRs) for the dose- and time-dependent release of eicosanoids. However, the signaling mechanisms of TLR-dependent rapid eicosanoid generation are not known. We previously reported a role for group V secretory phospholipase A(2) (PLA(2)) in regulating phagocytosis of zymosan and the ensuing eicosanoid generation in mouse resident peritoneal macrophages, suggesting a role for the enzyme in innate immunity. In the present study, we have used gene knockout mice to define an essential role for MyD88 and cytosolic PLA(2)alpha in TLR2-dependent eicosanoid generation. Furthermore, in mast cells lacking group V secretory PLA(2), the time course of phosphorylation of ERK1/2 and of cPLA(2)alpha was markedly truncated, leading to attenuation of eicosanoid generation in response to stimulation through TLR2, but not through c-kit or FcepsilonRI. These findings provide the first dissection of the mechanisms of TLR-dependent rapid eicosanoid generation, which is MyD88-dependent, requires cPLA(2)alpha, and is amplified by group V sPLA(2) through its regulation of the sequential phosphorylation and activation of ERK1/2 and cPLA(2)alpha. The findings support the suggestion that group V sPLA(2) regulates innate immune responses.
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Affiliation(s)
- Eriya Kikawada
- Department of Medicine, Harvard Medical School, Boston, MA, USA
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43
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Kuwata H, Fujimoto C, Yoda E, Shimbara S, Nakatani Y, Hara S, Murakami M, Kudo I. A novel role of group VIB calcium-independent phospholipase A2 (iPLA2gamma) in the inducible expression of group IIA secretory PLA2 in rat fibroblastic cells. J Biol Chem 2007; 282:20124-32. [PMID: 17475622 DOI: 10.1074/jbc.m611883200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Group IIA secretory phospholipase A(2) (sPLA(2)-IIA) is a prototypic sPLA(2) enzyme that may play roles in modification of eicosanoid biosynthesis as well as antibacterial defense. In several cell types, inducible expression of sPLA(2) by pro-inflammatory stimuli is attenuated by group IVA cytosolic PLA(2) (cPLA(2)alpha) inhibitors such as arachidonyl trifluoromethyl ketone, leading to the proposal that prior activation of cPLA(2)alpha is required for de novo induction of sPLA(2). However, because of the broad specificity of several cPLA(2)alpha inhibitors used so far, a more comprehensive approach is needed to evaluate the relevance of this ambiguous pathway. Here, we provide evidence that the induction of sPLA(2)-IIA by pro-inflammatory stimuli requires group VIB calcium-independent PLA(2) (iPLA(2)gamma), rather than cPLA(2)alpha, in rat fibroblastic 3Y1 cells. Results with small interfering RNA unexpectedly showed that the cytokine induction of sPLA(2)-IIA in cPLA(2)alpha knockdown cells, in which cPLA(2)alpha protein was undetectable, was similar to that in replicate control cells. By contrast, knockdown of iPLA(2)gamma, another arachidonyl trifluoromethyl ketone-sensitive intracellular PLA(2), markedly reduced the cytokine-induced expression of sPLA(2)-IIA. Supporting this finding, the R-enantiomer of bromoenol lactone, an iPLA(2)gamma inhibitor, suppressed the cytokine-induced sPLA(2)-IIA expression, whereas (S)-bromoenol lactone, an iPLA(2)beta inhibitor, failed to do so. Moreover, lipopolysaccharide-stimulated sPLA(2)-IIA expression was also abolished by knockdown of iPLA(2)gamma. These findings open new insight into a novel regulatory role of iPLA(2)gamma in stimulus-coupled sPLA(2)-IIA expression.
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Affiliation(s)
- Hiroshi Kuwata
- Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555
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Henderson WR, Chi EY, Bollinger JG, Tien YT, Ye X, Castelli L, Rubtsov YP, Singer AG, Chiang GKS, Nevalainen T, Rudensky AY, Gelb MH. Importance of group X-secreted phospholipase A2 in allergen-induced airway inflammation and remodeling in a mouse asthma model. ACTA ACUST UNITED AC 2007; 204:865-77. [PMID: 17403936 PMCID: PMC2118555 DOI: 10.1084/jem.20070029] [Citation(s) in RCA: 150] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Arachidonic acid metabolites, the eicosanoids, are key mediators of allergen-induced airway inflammation and remodeling in asthma. The availability of free arachidonate in cells for subsequent eicosanoid biosynthesis is controlled by phospholipase A2s (PLA2s), most notably cytosolic PLA2-α. 10 secreted PLA2s (sPLA2s) have also been identified, but their function in eicosanoid generation is poorly understood. We investigated the role of group X sPLA2 (sPLA2-X), the sPLA2 with the highest in vitro cellular phospholipolysis activity, in acute and chronic mouse asthma models in vivo. The lungs of sPLA2-X−/− mice, compared with those of sPLA2-X+/+ littermates, had significant reduction in ovalbumin-induced infiltration by CD4+ and CD8+ T cells and eosinophils, goblet cell metaplasia, smooth muscle cell layer thickening, subepithelial fibrosis, and levels of T helper type 2 cell cytokines and eicosanoids. These data direct attention to sPLA2-X as a novel therapeutic target for asthma.
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Affiliation(s)
- William R Henderson
- Center for Allergy and Inflammation, Department of Medicine, University of Washington, Seattle, WA 98109, USA.
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Ohtsuki M, Taketomi Y, Arata S, Masuda S, Ishikawa Y, Ishii T, Takanezawa Y, Aoki J, Arai H, Yamamoto K, Kudo I, Murakami M. Transgenic expression of group V, but not group X, secreted phospholipase A2 in mice leads to neonatal lethality because of lung dysfunction. J Biol Chem 2006; 281:36420-33. [PMID: 17008322 DOI: 10.1074/jbc.m607975200] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In an effort to elucidate the functions of secreted phospholipase A2 (sPLA2) enzymes in vivo, we generated transgenic (Tg) mice for group V sPLA2 (sPLA2-V) and group X sPLA2 (sPLA2-X), which act potently on phosphatidylcholine in vitro. We found that sPLA2-V Tg mice died in the neonatal period because of respiratory failure. The lungs of sPLA2-V Tg mice exhibited atelectasis with thickened alveolar walls and narrow air spaces, accompanied by infiltration of macrophages and only modest changes in eicosanoid levels. This severe pulmonary defect in sPLA2-V Tg mice was attributable to marked reduction of the lung surfactant phospholipids, phosphatidylcholine and phosphatidylglycerol. Given that the expression of sPLA2-V is greatly elevated in human lungs with severe inflammation, our present results raise the intriguing possibility that this isozyme may contribute to ongoing surfactant hydrolysis often observed in the lungs of patients with respiratory distress syndrome. In contrast, sPLA2-X Tg neonates displayed minimal abnormality of the respiratory tract with normal alveolar architecture and surfactant composition. This unexpected result was likely because sPLA2-X protein existed as an inactive zymogen in most tissues. The active form of sPLA2-X was detected in tissues with inflammatory granulation in sPLA2-X Tg mice. These results suggest that sPLA2-X mostly remains inactive under physiological conditions and that its proteolytic activation occurs during inflammation or other as yet unidentified circumstances in vivo.
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Affiliation(s)
- Mitsuhiro Ohtsuki
- Department of Health Chemistry, School of Pharmaceutical Sciences and Center for Biotechnology, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
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Gorovetz M, Baekelandt M, Berner A, Trope' CG, Davidson B, Reich R. The clinical role of phospholipase A2 isoforms in advanced-stage ovarian carcinoma. Gynecol Oncol 2006; 103:831-40. [PMID: 16919315 DOI: 10.1016/j.ygyno.2006.06.042] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2006] [Revised: 06/07/2006] [Accepted: 06/22/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVE To analyze the expression of phospholipase A2 (PLA2) isoforms and its relationship with matrix metalloproteinase (MMP) expression and clinical parameters in advanced-stage (FIGO III-IV) ovarian carcinoma. METHODS Seventy-seven fresh frozen effusions from ovarian carcinoma patients were studied for messenger RNA (mRNA) expression of 10 secretory PLA2 (sPLA2) isoforms (IB, IIA/D/E/F, III, V, X, XII and XIII), the PLA2 receptor (sPLA2R), cytoplasmic PLA2 (cPLA2), PLA2-activating protein (PLAP) and MMP-2 using reverse transcription polymerase chain reaction (RT-PCR). Phosphorylated cPLA2 (p-cPLA2) protein expression was studied in 52 effusions using immunohistochemistry. MMP-2 and MMP-9 activity was evaluated in 22 and 20 effusions, respectively, using zymography. Expression was analyzed for correlation with clinicopathologic parameters, chemotherapy status and survival. RESULTS PLA2 isoforms, sPLA2R, PLAP and MMP-2 mRNA was expressed in >95% of specimens. p-cPLA2 protein was expressed in 46/52 (88%) effusions. MMP-2 activity was found in all specimens, while that of MMP-9 was detected in 19/20 effusions. MMP-2 was found to be co-expressed with p-cPLA2 (p=0.003) and sPLA2-IIA (p=0.021). Lower expression of sPLA2-IIA (p<0.001) and higher expression of sPLA2-V (p=0.038) and sPLA2-XIII (p=0.001) was found in post-chemotherapy effusions. In univariate survival analysis, higher levels of sPLA2-V correlated with better overall (OS, p=0.021) and progression-free (PFS, p=0.025) survival. For patients with post-chemotherapy effusions, FIGO stage IV and higher PLAP mRNA expression correlated with worse OS (p=0.005 for both PLAP and stage), while higher PLAP (p=0.025) and sPLA2-XII (p=0.027) levels and FIGO stage IV (p<0.001) correlated with shorter PFS. In Cox multivariate analysis, PLAP expression (p=0.022) and FIGO stage (p=0.036) independently predicted poor OS, while higher sPLA2-XII levels (p=0.04) and FIGO stage (p=0.003) were independent predictors of shorter PFS. CONCLUSIONS The present study documents for the first time expression of PLA2 isoforms, sPLA2R and PLAP in ovarian carcinoma. PLA2 isoenzyme expression differs in pre- and post-chemotherapy specimens. PLAP and sPLA2-XII may be independent predictors of poor outcome for patients with post-chemotherapy effusions.
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MESH Headings
- Adenocarcinoma, Clear Cell/metabolism
- Adenocarcinoma, Clear Cell/mortality
- Adenocarcinoma, Clear Cell/pathology
- Adenocarcinoma, Mucinous/metabolism
- Adenocarcinoma, Mucinous/mortality
- Adenocarcinoma, Mucinous/pathology
- Adult
- Aged
- Ascitic Fluid/metabolism
- Cystadenocarcinoma, Serous/metabolism
- Cystadenocarcinoma, Serous/mortality
- Cystadenocarcinoma, Serous/pathology
- DNA Primers
- Disease-Free Survival
- Female
- Gene Expression Regulation, Neoplastic
- Humans
- Immunohistochemistry
- Matrix Metalloproteinase 2/genetics
- Matrix Metalloproteinase 2/metabolism
- Matrix Metalloproteinase 9/genetics
- Matrix Metalloproteinase 9/metabolism
- Matrix Metalloproteinases/genetics
- Matrix Metalloproteinases/metabolism
- Middle Aged
- Neoplasm Staging
- Neoplasms, Glandular and Epithelial/metabolism
- Neoplasms, Glandular and Epithelial/mortality
- Neoplasms, Glandular and Epithelial/pathology
- Norway
- Ovarian Neoplasms/metabolism
- Ovarian Neoplasms/mortality
- Ovarian Neoplasms/pathology
- Phospholipases/genetics
- Phospholipases/metabolism
- Prognosis
- Protein Isoforms
- Reverse Transcriptase Polymerase Chain Reaction
- Survival Analysis
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Affiliation(s)
- Michal Gorovetz
- Department of Pharmacology and Experimental Therapeutics, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Israel, and Department of Gynecologic Oncology, National Hospital-Norwegian Radium Hospital, Oslo, Norway
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47
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Winget JM, Pan YH, Bahnson BJ. The interfacial binding surface of phospholipase A2s. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1260-9. [PMID: 16962825 DOI: 10.1016/j.bbalip.2006.08.002] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2006] [Revised: 07/19/2006] [Accepted: 08/01/2006] [Indexed: 11/17/2022]
Abstract
For membrane-associated enzymes, which access substrate from either a monolayer or bilayer of the aggregate substrate, the partitioning from the aqueous phase to this phospholipid interface is critical for catalysis. Despite a large and expanding body of knowledge regarding interfacial enzymes, the biophysical steps involved in interfacial recognition and adsorption remain relatively poorly understood. The surface of the enzyme that contacts the phospholipid surface is referred to as its interfacial binding surface, or more simply, its i-face. The interaction of a protein's i-face with the aggregate substrate may simply control access to substrate. However, it can be more complex, and this interaction often serves to allosterically activate the enzyme on this surface. First we briefly review what is currently known about i-face structure and function for a prototypical interfacial enzyme, the secreted Phospholipase A2 (PLA2). Then we develop, characterize, compare, and discuss models of the PLA2 i-face across a subset of five homologous PLA2 family members, groups IA, IB, IIA, V, and X. A homology model of human group-V is included in this comparison, suggesting that a similar approach could be used to explore interfacial function of any of the PLA2 family members. Despite moderate sequence identity, structural homology and sequence similarity are well conserved. We find that the residues predicted to be interfacial, while conserved structurally, are not highly conserved in sequence. Implications for this divergence on interfacial selectivity are discussed.
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Affiliation(s)
- Jason M Winget
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA
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48
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Yedgar S, Cohen Y, Shoseyov D. Control of phospholipase A2 activities for the treatment of inflammatory conditions. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1373-82. [PMID: 16978919 DOI: 10.1016/j.bbalip.2006.08.003] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Accepted: 08/01/2006] [Indexed: 01/10/2023]
Abstract
Phospholipase-A2 (PLA2) enzymes hydrolyze cell membrane phospholipids to produce arachidonic acid (AA) and lyso-phospholipids (LysoPL), playing a key role in the production of inflammatory lipid mediators, mainly eicosanoids. They are therefore considered pro-inflammatory enzymes and their inhibition has long been recognized as a desirable therapeutic target. However, attempts to develop suitable PLA2 inhibitors for the treatment of inflammatory diseases have yet to succeed. This is due to their functional and structural diversity, and their homeostatic and even anti-inflammatory roles in certain circumstances. In the present review we outline the diversity and functions of PLA2 isoforms, and their interplay in the induction and inhibition of inflammatory processes, with emphasis on discussing approaches for therapeutic manipulation of PLA2 activities.
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Affiliation(s)
- Saul Yedgar
- Department of Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
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49
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Balestrieri B, Arm JP. Group V sPLA2: classical and novel functions. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1280-8. [PMID: 16945583 DOI: 10.1016/j.bbalip.2006.07.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2006] [Revised: 07/20/2006] [Accepted: 07/25/2006] [Indexed: 10/24/2022]
Abstract
Group V sPLA(2) is unique among the family of secretory sPLA(2) enzymes in being able to bind to cell membranes through both interfacial-binding and through binding to proteoglycan. The function of group V sPLA(2) as an enzyme and its cross-talk with cPLA(2)alpha in initiating eicosanoid generation is well documented. Evidence, though, is emerging on the ability of this molecule to act as a regulator of several intracellular and extracellular pathways independently of its ability to provide arachidonic acid for eicosanoid generation, acting within the cell or as a secreted enzyme. In this article we will provide an overview of the properties of the enzyme and how they relate to our current understanding of its function.
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Affiliation(s)
- Barbara Balestrieri
- Department of Medicine, Harvard Medical School, Brigham and Women's Hospital, Boston, MA 02115, USA
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50
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Triggiani M, Granata F, Frattini A, Marone G. Activation of human inflammatory cells by secreted phospholipases A2. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1289-300. [PMID: 16952481 DOI: 10.1016/j.bbalip.2006.07.003] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2006] [Revised: 07/07/2006] [Accepted: 07/17/2006] [Indexed: 10/24/2022]
Abstract
Secreted phospholipases A(2) (sPLA(2)s) are enzymes detected in serum and biological fluids of patients with various inflammatory, autoimmune and allergic disorders. Different isoforms of sPLA(2)s are expressed and released by human inflammatory cells, such as neutrophils, eosinophils, T cells, monocytes, macrophages and mast cells. sPLA(2)s generate arachidonic acid and lysophospholipids thus contributing to the production of bioactive lipid mediators in inflammatory cells. However, sPLA(2)s also activate human inflammatory cells by mechanisms unrelated to their enzymatic activity. Several human and non-human sPLA(2)s induce degranulation of mast cells, neutrophils and eosinophils and activate exocytosis in macrophages. In addition some, but not all, sPLA(2) isoforms promote cytokine and chemokine production from macrophages, neutrophils, eosinophils, monocytes and endothelial cells. These effects are primarily mediated by binding of sPLA(2)s to specific membrane targets (heparan sulfate proteoglycans, M-type, N-type or mannose receptors) expressed on effector cells. Thus, sPLA(2)s may play an important role in the initiation and amplification of inflammatory reactions by at least two mechanisms: production of lipid mediators and direct activation of inflammatory cells. Selective inhibitors of sPLA(2)-enzymatic activity and specific antagonists of sPLA(2) receptors are current being tested for pharmacological treatment of inflammatory and autoimmune diseases.
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Affiliation(s)
- Massimo Triggiani
- Division of Clinical Immunology and Allergy, Center for Basic and Clinical Immunology Research (CISI), University of Naples Federico II, 80131 Naples, Via Pansini 5, Italy.
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