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Rezaie AR, Giri H. Anticoagulant and signaling functions of antithrombin. J Thromb Haemost 2020; 18:3142-3153. [PMID: 32780936 PMCID: PMC7855051 DOI: 10.1111/jth.15052] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 07/25/2020] [Accepted: 08/04/2020] [Indexed: 12/19/2022]
Abstract
Antithrombin (AT) is a major plasma glycoprotein of the serpin superfamily that regulates the proteolytic activity of the procoagulant proteases of both intrinsic and extrinsic pathways. Two important structural features that participate in the regulatory function of AT include a mobile reactive center loop that binds to active site of coagulation proteases, trapping them in the form of inactive covalent complexes, and a basic D-helix that binds to therapeutic heparins and heparan sulfate proteoglycans (HSPGs) on vascular endothelial cells. The binding of D-helix of AT by therapeutic heparins promotes the reactivity of the serpin with coagulation proteases by several orders of magnitude by both a conformational activation of the serpin and a template (bridging) mechanism. In addition to its essential anticoagulant function, AT elicits a potent anti-inflammatory signaling response when it binds to distinct vascular endothelial cell HSPGs, thereby inducing prostacyclin synthesis. Syndecans-4 has been found as a specific membrane-bound HSPG receptor on endothelial cells that relays the signaling effect of AT to the relevant second messenger molecules in the signal transduction pathways inside the cell. However, following cleavage by coagulation proteases and/or by spontaneous conversion to a latent form, AT loses both its anti-inflammatory activity and high-affinity interaction with heparin and HSPGs. Interestingly, these low-affinity heparin conformers of AT elicit potent proapoptotic and antiangiogenic activities by also binding to specific HSPGs by unknown mechanisms. This review article will summarize current knowledge about mechanisms through which different conformers of AT exert their serine protease inhibitory and intracellular signaling functions in these biological pathways.
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Affiliation(s)
- Alireza R. Rezaie
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Hemant Giri
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
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2
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Mitchell JA, Kirkby NS. Eicosanoids, prostacyclin and cyclooxygenase in the cardiovascular system. Br J Pharmacol 2019; 176:1038-1050. [PMID: 29468666 PMCID: PMC6451069 DOI: 10.1111/bph.14167] [Citation(s) in RCA: 119] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 01/19/2018] [Accepted: 01/29/2018] [Indexed: 12/30/2022] Open
Abstract
Eicosanoids represent a diverse family of lipid mediators with fundamental roles in physiology and disease. Within the eicosanoid superfamily are prostanoids, which are specifically derived from arachidonic acid by the enzyme cyclooxygenase (COX). COX has two isoforms; COX-1 and COX-2. COX-2 is the therapeutic target for the nonsteroidal anti-inflammatory drug (NSAID) class of pain medications. Of the prostanoids, prostacyclin, first discovered by Sir John Vane in 1976, remains amongst the best studied and retains an impressive pedigree as one of the fundamental cardiovascular protective pathways. Since this time, we have learnt much about how eicosanoids, COX enzymes and prostacyclin function in the cardiovascular system, knowledge that has allowed us, for example, to harness the power of prostacyclin as therapy to treat pulmonary arterial hypertension and peripheral vascular disease. However, there remain many unanswered questions in our basic understanding of the pathways, and how they can be used to improve human health. Perhaps, the most important and controversial outstanding question in the field remains; 'how do NSAIDs produce their much publicized cardiovascular side-effects?' This review summarizes the history, biology and cardiovascular function of key eicosanoids with particular focus on prostacyclin and other COX products and discusses how our knowledge of these pathways can applied in future drug discovery and be used to explain the cardiovascular side-effects of NSAIDs. LINKED ARTICLES: This article is part of a themed section on Eicosanoids 35 years from the 1982 Nobel: where are we now? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.8/issuetoc.
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Affiliation(s)
- Jane A Mitchell
- Cardiothoracic PharmacologyNational Heart and Lung InstituteLondonUK
| | - Nicholas S Kirkby
- Cardiothoracic PharmacologyNational Heart and Lung InstituteLondonUK
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3
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Kispert S, Marentette J, McHowat J. Cigarette smoking promotes bladder cancer via increased platelet-activating factor. Physiol Rep 2019; 7:e13981. [PMID: 30756528 PMCID: PMC6372534 DOI: 10.14814/phy2.13981] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 12/18/2018] [Accepted: 12/20/2018] [Indexed: 02/06/2023] Open
Abstract
Cigarette smoking is the number one risk factor for bladder cancer development and epidemiological data suggest that nearly half of all bladder cancer patients have a history of smoking. In addition to stimulating the growth of a primary tumor, it has been shown that there is a correlation between smoking and tumor metastasis. Platelet activating factor (PAF) is expressed on the cell surface of the activated endothelium and, through binding with the PAF-receptor (PAF-R), facilitates transendothelial migration of cells in the circulation (McHowat et al. Biochemistry 40:14921-14931; 2001). In this study, we show that the exposure of bladder cancer cells to cigarette smoke extract (CSE) results in increased PAF accumulation and increased expression of the PAF-R. Furthermore, treatment with CSE increases adherence of bladder cancer cells to bladder endothelial cells and could be abrogated by pretreatment with ginkgolide B. Immunohistochemical analysis of tumor biopsy samples from bladder cancer patients who smoked revealed increased PAF and the PAF-R in tumor regions when compared to normal tissue. These data highlight a pathway in bladder cancer that is influenced by CSE which could facilitate primary tumor growth and increase metastatic potential. Targeting of the PAF-PAFR interaction could serve as a beneficial therapeutic target for managing further growth of a developing tumor.
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Affiliation(s)
- Shannon Kispert
- Department of BiologyUniversity of North GeorgiaOakwoodGeorgia
| | - John Marentette
- Skaggs School of Pharmacy and Pharmaceutical SciencesUniversity of Colorado Anschutz Medical CampusAuroraColorado
| | - Jane McHowat
- Department of PathologySaint Louis University School of MedicineSt. LouisMissouri
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4
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Turk J, White TD, Nelson AJ, Lei X, Ramanadham S. iPLA 2β and its role in male fertility, neurological disorders, metabolic disorders, and inflammation. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1864:846-860. [PMID: 30408523 DOI: 10.1016/j.bbalip.2018.10.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Revised: 10/26/2018] [Accepted: 10/29/2018] [Indexed: 02/06/2023]
Abstract
The Ca2+-independent phospholipases, designated as group VI iPLA2s, also referred to as PNPLAs due to their shared homology with patatin, include the β, γ, δ, ε, ζ, and η forms of the enzyme. The iPLA2s are ubiquitously expressed, share a consensus GXSXG catalytic motif, and exhibit organelle/cell-specific localization. Among the iPLA2s, iPLA2β has received wide attention as it is recognized to be involved in membrane remodeling, cell proliferation, cell death, and signal transduction. Ongoing studies implicate participation of iPLA2β in a variety of disease processes including cancer, cardiovascular abnormalities, glaucoma, and peridonditis. This review will focus on iPLA2β and its links to male fertility, neurological disorders, metabolic disorders, and inflammation.
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Affiliation(s)
- John Turk
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, United States of America
| | - Tayleur D White
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States of America; Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Alexander J Nelson
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States of America; Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Xiaoyong Lei
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States of America; Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Sasanka Ramanadham
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States of America; Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL, United States of America.
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5
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Selectivity of phospholipid hydrolysis by phospholipase A 2 enzymes in activated cells leading to polyunsaturated fatty acid mobilization. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1864:772-783. [PMID: 30010011 DOI: 10.1016/j.bbalip.2018.07.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 07/08/2018] [Accepted: 07/10/2018] [Indexed: 12/14/2022]
Abstract
Phospholipase A2s are enzymes that hydrolyze the fatty acid at the sn-2 position of the glycerol backbone of membrane glycerophospholipids. Given the asymmetric distribution of fatty acids within phospholipids, where saturated fatty acids tend to be present at the sn-1 position, and polyunsaturated fatty acids such as those of the omega-3 and omega-6 series overwhelmingly localize in the sn-2 position, the phospholipase A2 reaction is of utmost importance as a regulatory checkpoint for the mobilization of these fatty acids and the subsequent synthesis of proinflammatory omega-6-derived eicosanoids on one hand, and omega-3-derived specialized pro-resolving mediators on the other. The great variety of phospholipase A2s, their differential substrate selectivity under a variety of pathophysiological conditions, as well as the different compartmentalization of each enzyme and accessibility to substrate, render this class of enzymes also key to membrane phospholipid remodeling reactions, and the generation of specific lipid mediators not related with canonical metabolites of omega-6 or omega-3 fatty acids. This review highlights novel findings regarding the selective hydrolysis of phospholipids by phospholipase A2s and the influence this may have on the ability of these enzymes to generate distinct lipid mediators with essential functions in biological processes. This brings a new understanding of the cellular roles of these enzymes depending upon activation conditions.
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Abstract
Phospholipases are lipolytic enzymes that hydrolyze phospholipid substrates at specific ester bonds. Phospholipases are widespread in nature and play very diverse roles from aggression in snake venom to signal transduction, lipid mediator production, and metabolite digestion in humans. Phospholipases vary considerably in structure, function, regulation, and mode of action. Tremendous advances in understanding the structure and function of phospholipases have occurred in the last decades. This introductory chapter is aimed at providing a general framework of the current understanding of phospholipases and a discussion of their mechanisms of action and emerging biological functions.
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Kispert SE, Marentette J, Campian EC, Isbell TS, Kuenzel H, McHowat J. Cigarette smoke-induced urothelial cell damage: potential role of platelet-activating factor. Physiol Rep 2017; 5:5/5/e13177. [PMID: 28270596 PMCID: PMC5350181 DOI: 10.14814/phy2.13177] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 01/30/2017] [Accepted: 02/02/2017] [Indexed: 11/24/2022] Open
Abstract
Cigarette smoking is an environmental risk factor associated with a variety of pathologies including cardiovascular disease, inflammation, and cancer development. Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic inflammatory bladder disease with multiple etiological contributors and risk factors associated with its development, including cigarette smoking. Previously, we determined that cigarette smoking was associated with bladder wall accumulation of platelet activating factor (PAF), a potent inflammatory mediator that facilitates transendothelial cell migration of inflammatory cells from the circulation. PAF has been shown to reduce expression of tight junctional proteins which could ultimately lead to increased urothelial cell permeability. In this study, we observed that cigarette smoke extract (CSE) treatment of human urothelial cells increases PAF production and PAF receptor expression and reduces wound healing ability. After exposure to cigarette smoke for 6 months, wild-type C57BL/6 mice displayed urothelial thinning and destruction which was not detected in iPLA2β-/- (enzyme responsible for PAF production) animals. We also detected increased urinary PAF concentration in IC/BPS patients when compared to controls, with an even greater increase in urinary PAF concentration in smokers with IC/BPS These data indicate that cigarette smoking is associated with urothelial cell damage that may be a result of increased PAF-PAF receptor interaction. Inhibition of iPLA2β activity or blocking of the PAF-PAF receptor interaction could serve as a potential therapeutic target for managing cigarette smoke-induced bladder damage.
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Affiliation(s)
- Shannon E Kispert
- Department of Pathology, Saint Louis University School of Medicine, Saint Louis, Missouri
| | - John Marentette
- Department of Pathology, Saint Louis University School of Medicine, Saint Louis, Missouri
| | - E Cristian Campian
- Department of Obstetrics, Gynecology & Women's Health, Saint Louis University School of Medicine, Saint Louis, Missouri
| | - T Scott Isbell
- Department of Pathology, Saint Louis University School of Medicine, Saint Louis, Missouri
| | - Hannah Kuenzel
- Department of Pathology, Saint Louis University School of Medicine, Saint Louis, Missouri
| | - Jane McHowat
- Department of Pathology, Saint Louis University School of Medicine, Saint Louis, Missouri
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Kispert S, Schwartz T, McHowat J. Cigarette Smoke Regulates Calcium-Independent Phospholipase A2 Metabolic Pathways in Breast Cancer. THE AMERICAN JOURNAL OF PATHOLOGY 2017; 187:1855-1866. [DOI: 10.1016/j.ajpath.2017.04.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 03/24/2017] [Accepted: 04/04/2017] [Indexed: 11/25/2022]
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Marentette J, Kolar G, McHowat J. Increased susceptibility to bladder inflammation in smokers: targeting the PAF-PAF receptor interaction to manage inflammatory cell recruitment. Physiol Rep 2015; 3:3/12/e12641. [PMID: 26660553 PMCID: PMC4760457 DOI: 10.14814/phy2.12641] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Chronic bladder inflammation can result in a significant reduction in quality of life. Smoking remains a leading preventable risk factor in many diseases. Despite the large amount of evidence supporting the risks of smoking, roughly 45 million people in the United States remain smokers. The impact of cigarette smoking on inflammation is well established, but how smoking promotes bladder inflammation is currently unknown. The aim of this study was to determine if cigarette smoke exposure impacts inflammatory cell adherence to bladder endothelial cells and if targeting the platelet‐activating factor (PAF)–PAF receptor (PAFR) interaction could be beneficial in managing bladder inflammation. In response to cigarette smoke extract (CSE) incubation, bladder endothelial cells from human or mouse displayed increased PAF accumulation, decreased PAF‐AH activity, and increased inflammatory cell adherence. Inhibition of endothelial cell calcium‐independent phospholipase A2β (iPLA2β) with (S)‐BEL, to block PAF production, prevented adherence of inflammatory cells. Pretreatment of inflammatory cells with PAFR antagonists, ginkgolide B or WEB2086 significantly reduced the number of adhered cells to bladder endothelium. Wild‐type mice exposed to cigarette smoke displayed increased presence of inflammatory infiltration which was absent in iPLA2β−/− mice and those exposed to room air. In conclusion, cigarette smoke exposure increases endothelial cell PAF accumulation and increased inflammatory cell adherence. Inhibition of PAF accumulation or PAFR antagonism markedly attenuated inflammatory cell adherence to bladder endothelial cells. The results detailed in this study highlight to potential therapeutic targets for managing bladder inflammation.
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Affiliation(s)
- John Marentette
- Department of Pathology, Saint Louis University School of Medicine, St. Louis, Missouri
| | - Grant Kolar
- Department of Pathology, Saint Louis University School of Medicine, St. Louis, Missouri
| | - Jane McHowat
- Department of Pathology, Saint Louis University School of Medicine, St. Louis, Missouri
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10
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Rauckhorst AJ, Pfeiffer DR, Broekemeier KM. The iPLA2γ is identified as the membrane potential sensitive phospholipase in liver mitochondria. FEBS Lett 2015. [DOI: 10.1016/j.febslet.2015.07.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Kirkby NS, Reed DM, Edin ML, Rauzi F, Mataragka S, Vojnovic I, Bishop-Bailey D, Milne GL, Longhurst H, Zeldin DC, Mitchell JA, Warner TD. Inherited human group IVA cytosolic phospholipase A2 deficiency abolishes platelet, endothelial, and leucocyte eicosanoid generation. FASEB J 2015; 29:4568-78. [PMID: 26183771 PMCID: PMC4608906 DOI: 10.1096/fj.15-275065] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 07/06/2015] [Indexed: 12/25/2022]
Abstract
Eicosanoids are important vascular regulators, but the phospholipase A2
(PLA2) isoforms supporting their production within the cardiovascular
system are not fully understood. To address this, we have studied platelets,
endothelial cells, and leukocytes from 2 siblings with a homozygous loss-of-function
mutation in group IVA cytosolic phospholipase A2
(cPLA2α). Chromatography/mass spectrometry was used to determine
levels of a broad range of eicosanoids produced by isolated vascular cells, and in
plasma and urine. Eicosanoid release data were paired with studies of cellular
function. Absence of cPLA2α almost abolished eicosanoid synthesis
in platelets (e.g., thromboxane A2, control 20.5 ±
1.4 ng/ml vs. patient 0.1 ng/ml) and leukocytes
[e.g., prostaglandin E2 (PGE2), control
21.9 ± 7.4 ng/ml vs. patient 1.9 ng/ml], and this was
associated with impaired platelet activation and enhanced inflammatory responses.
cPLA2α-deficient endothelial cells showed reduced, but not
absent, formation of prostaglandin I2 (prostacyclin; control 956 ±
422 pg/ml vs. patient 196 pg/ml) and were primed for inflammation.
In the urine, prostaglandin metabolites were selectively influenced by
cPLA2α deficiency. For example, prostacyclin metabolites were
strongly reduced (18.4% of control) in patients lacking cPLA2α,
whereas PGE2 metabolites (77.8% of control) were similar to healthy
volunteer levels. These studies constitute a definitive account, demonstrating the
fundamental role of cPLA2α to eicosanoid formation and cellular
responses within the human circulation.—Kirkby, N. S., Reed, D. M., Edin, M.
L., Rauzi, F., Mataragka, S., Vojnovic, I., Bishop-Bailey, D., Milne, G. L.,
Longhurst, H., Zeldin, D. C., Mitchell, J. A., Warner, T. D. Inherited human group
IVA cytosolic phospholipase A2 deficiency abolishes platelet, endothelial,
and leucocyte eicosanoid generation.
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Affiliation(s)
- Nicholas S Kirkby
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
| | - Daniel M Reed
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
| | - Matthew L Edin
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
| | - Francesca Rauzi
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
| | - Stefania Mataragka
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
| | - Ivana Vojnovic
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
| | - David Bishop-Bailey
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
| | - Ginger L Milne
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
| | - Hilary Longhurst
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
| | - Darryl C Zeldin
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
| | - Jane A Mitchell
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
| | - Timothy D Warner
- *National Heart and Lung Institute, Imperial College London, London, United Kingdom; William Harvey Research Institute, Queen Mary University of London, London, United Kingdom; National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA; Department of Comparative Biomedical Sciences, Royal Veterinary College, London, United Kingdom; Department of Pharmacology and Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA; and Immunology Department, Barts Health and the London National Health Service Trust, London, United Kingdom
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Kispert SE, Marentette JO, McHowat J. Enhanced breast cancer cell adherence to the lung endothelium via PAF acetylhydrolase inhibition: a potential mechanism for enhanced metastasis in smokers. Am J Physiol Cell Physiol 2014; 307:C951-6. [PMID: 25186013 DOI: 10.1152/ajpcell.00218.2014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cancer deaths are primarily caused by distant metastases, rather than by primary tumor growth; however, the role of smoking in metastasis remains unclear. We demonstrated previously that endothelial cell platelet-activating factor (PAF) production results in enhanced inflammatory cell recruitment to the lung. We propose that endothelial cell PAF accumulation plays a role in cancer cell migration to distal locations. We used cigarette smoke extract (CSE) to inhibit the activity of endothelial cell PAF acetylhydrolase (PAF-AH), which hydrolyzes and inactivates PAF, and determined whether this results in increased endothelial cell PAF accumulation and breast cancer adherence. Incubation of human lung microvascular endothelial cells (HMVEC-L) with CSE resulted in a significant inhibition of PAF-AH activity that was accompanied by increased PAF production and adherence of highly invasive MDA-MB-231 breast cancer cells. Pretreatment of HMVEC-L with (S)-bromoenol lactone to inhibit calcium-independent phospholipase A2β (iPLA2β, which initiates endothelial cell PAF production) prior to CSE exposure resulted in complete inhibition of MDA-MB-231 cell adherence. Similarly, pretreatment of MDA-MB-231 cells with the PAF receptor antagonist Ginkgo biloba resulted in inhibition of adherence to the endothelium. Immunoblot analysis indicated an increase in MDA-MB-231 cell PAF receptor expression with CSE exposure. Taken together, our data indicate that CSE exposure increases endothelial cell PAF production, resulting in enhanced adherence of tumor cells to the endothelium. Our in vitro data indicate that increased tumor cell adherence would lead to enhanced metastasis formation in smokers. Potential therapeutic targets include endothelial cell iPLA2β or the tumor cell PAF receptor.
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Affiliation(s)
- Shannon E Kispert
- Department of Pathology, Saint Louis University School of Medicine, St. Louis, Missouri
| | - John O Marentette
- Department of Pathology, Saint Louis University School of Medicine, St. Louis, Missouri
| | - Jane McHowat
- Department of Pathology, Saint Louis University School of Medicine, St. Louis, Missouri
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13
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Abstract
At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.
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Affiliation(s)
- Paul N Hopkins
- Cardiovascular Genetics, Department of Internal Medicine, University of Utah, Salt Lake City, Utah, USA.
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14
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Lei X, Bone RN, Ali T, Wohltmann M, Gai Y, Goodwin KJ, Bohrer AE, Turk J, Ramanadham S. Genetic modulation of islet β-cell iPLA₂β expression provides evidence for its impact on β-cell apoptosis and autophagy. Islets 2013; 5:29-44. [PMID: 23411472 PMCID: PMC3662380 DOI: 10.4161/isl.23758] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
β-cell apoptosis is a significant contributor to β-cell dysfunction in diabetes and ER stress is among the factors that contributes to β-cell death. We previously identified that the Ca²⁺-independent phospholipase A₂β (iPLA₂β), which in islets is localized in β-cells, participates in ER stress-induced β-cell apoptosis. Here, direct assessment of iPLA₂β role was made using β-cell-specific iPLA₂β overexpressing (RIP-iPLA₂β-Tg) and globally iPLA₂β-deficient (iPLA₂β-KO) mice. Islets from Tg, but not KO, express higher islet iPLA₂β and neutral sphingomyelinase, decrease in sphingomyelins, and increase in ceramides, relative to WT group. ER stress induces iPLA₂β, ER stress factors, loss of mitochondrial membrane potential (∆Ψ), caspase-3 activation, and β-cell apoptosis in the WT and these are all amplified in the Tg group. Surprisingly, β-cells apoptosis while reduced in the KO is higher than in the WT group. This, however, was not accompanied by greater caspase-3 activation but with larger loss of ∆Ψ, suggesting that iPLA₂β deficiency impacts mitochondrial membrane integrity and causes apoptosis by a caspase-independent manner. Further, autophagy, as reflected by LC3-II accumulation, is increased in Tg and decreased in KO, relative to WT. Our findings suggest that (1) iPLA₂β impacts upstream (UPR) and downstream (ceramide generation and mitochondrial) pathways in β-cells and (2) both over- or under-expression of iPLA₂β is deleterious to the β-cells. Further, we present for the first time evidence for potential regulation of autophagy by iPLA₂β in islet β-cells. These findings support the hypothesis that iPLA₂β induction under stress, as in diabetes, is a key component to amplifying β-cell death processes.
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Affiliation(s)
- Xiaoyong Lei
- Department of Cell, Developmental, and Integrative Biology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Robert N. Bone
- Department of Pathology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Tomader Ali
- Department of Cell, Developmental, and Integrative Biology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Mary Wohltmann
- Department of Medicine; Mass Spectrometry Resource; Division of Endocrinology, Metabolism and Lipid Research; Washington University School of Medicine; St. Louis, MO USA
| | - Ying Gai
- Department of Cell, Developmental, and Integrative Biology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Karen J. Goodwin
- Department of Cell, Developmental, and Integrative Biology; University of Alabama at Birmingham; Birmingham, AL USA
| | - Alan E. Bohrer
- Department of Medicine; Mass Spectrometry Resource; Division of Endocrinology, Metabolism and Lipid Research; Washington University School of Medicine; St. Louis, MO USA
| | - John Turk
- Department of Medicine; Mass Spectrometry Resource; Division of Endocrinology, Metabolism and Lipid Research; Washington University School of Medicine; St. Louis, MO USA
| | - Sasanka Ramanadham
- Department of Cell, Developmental, and Integrative Biology; University of Alabama at Birmingham; Birmingham, AL USA
- Correspondence to: Sasanka Ramanadham,
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Taha AY, Gao F, Ramadan E, Cheon Y, Rapoport SI, Kim HW. Upregulated expression of brain enzymatic markers of arachidonic and docosahexaenoic acid metabolism in a rat model of the metabolic syndrome. BMC Neurosci 2012; 13:131. [PMID: 23110484 PMCID: PMC3531256 DOI: 10.1186/1471-2202-13-131] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Accepted: 10/05/2012] [Indexed: 12/22/2022] Open
Abstract
Background In animal models, the metabolic syndrome elicits a cerebral response characterized by altered phospholipid and unesterified fatty acid concentrations and increases in pro-apoptotic inflammatory mediators that may cause synaptic loss and cognitive impairment. We hypothesized that these changes are associated with phospholipase (PLA2) enzymes that regulate arachidonic (AA, 20:4n-6) and docosahexaenoic (DHA, 22:6n-6) acid metabolism, major polyunsaturated fatty acids in brain. Male Wistar rats were fed a control or high-sucrose diet for 8 weeks. Brains were assayed for markers of AA metabolism (calcium-dependent cytosolic cPLA2 IVA and cyclooxygenases), DHA metabolism (calcium-independent iPLA2 VIA and lipoxygenases), brain-derived neurotrophic factor (BDNF), and synaptic integrity (drebrin and synaptophysin). Lipid concentrations were measured in brains subjected to high-energy microwave fixation. Results The high-sucrose compared with control diet induced insulin resistance, and increased phosphorylated-cPLA2 protein, cPLA2 and iPLA2 activity and 12-lipoxygenase mRNA, but decreased BDNF mRNA and protein, and drebrin mRNA. The concentration of several n-6 fatty acids in ethanolamine glycerophospholipids and lysophosphatidylcholine was increased, as was unesterified AA concentration. Eicosanoid concentrations (prostaglandin E2, thromboxane B2 and leukotriene B4) did not change. Conclusion These findings show upregulated brain AA and DHA metabolism and reduced BDNF and drebrin, but no changes in eicosanoids, in an animal model of the metabolic syndrome. These changes might contribute to altered synaptic plasticity and cognitive impairment in rats and humans with the metabolic syndrome.
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Affiliation(s)
- Ameer Y Taha
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA
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16
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Cheon Y, Kim HW, Igarashi M, Modi HR, Chang L, Ma K, Greenstein D, Wohltmann M, Turk J, Rapoport SI, Taha AY. Disturbed brain phospholipid and docosahexaenoic acid metabolism in calcium-independent phospholipase A(2)-VIA (iPLA(2)β)-knockout mice. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1821:1278-86. [PMID: 22349267 PMCID: PMC3393806 DOI: 10.1016/j.bbalip.2012.02.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 01/25/2012] [Accepted: 02/03/2012] [Indexed: 10/14/2022]
Abstract
Calcium-independent phospholipase A(2) group VIA (iPLA(2)β) releases docosahexaenoic acid (DHA) from phospholipids in vitro. Mutations in the iPLA(2)β gene, PLA2G6, are associated with dystonia-parkinsonism and infantile neuroaxonal dystrophy. To understand the role of iPLA(2)β in brain, we applied our in vivo kinetic method using radiolabeled DHA in 4 to 5-month-old wild type (iPLA(2)β(+/+)) and knockout (iPLA(2)β(-/-)) mice, and measured brain DHA kinetics, lipid concentrations, and expression of PLA(2), cyclooxygenase (COX), and lipoxygenase (LOX) enzymes. Compared to iPLA(2)β(+/+) mice, iPLA(2)β(-/-) mice showed decreased rates of incorporation of unesterified DHA from plasma into brain phospholipids, reduced concentrations of several fatty acids (including DHA) esterified in ethanolamine- and serine-glycerophospholipids, and increased lysophospholipid fatty acid concentrations. DHA turnover in brain phospholipids did not differ between genotypes. In iPLA(2)β(-/-) mice, brain levels of iPLA(2)β mRNA, protein, and activity were decreased, as was the iPLA(2)γ (Group VIB PLA(2)) mRNA level, while levels of secretory sPLA(2)-V mRNA, protein, and activity and cytosolic cPLA(2)-IVA mRNA were increased. Levels of COX-1 protein were decreased in brain, while COX-2 protein and mRNA were increased. Levels of 5-, 12-, and 15-LOX proteins did not differ significantly between genotypes. Thus, a genetic iPLA(2)β deficiency in mice is associated with reduced DHA metabolism, profound changes in lipid-metabolizing enzyme expression (demonstrating lack of redundancy) and of phospholipid fatty acid content of brain (particularly of DHA), which may be relevant to neurologic abnormalities in humans with PLA2G6 mutations.
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Affiliation(s)
- Yewon Cheon
- National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
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17
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Majed BH, Khalil RA. Molecular mechanisms regulating the vascular prostacyclin pathways and their adaptation during pregnancy and in the newborn. Pharmacol Rev 2012; 64:540-82. [PMID: 22679221 DOI: 10.1124/pr.111.004770] [Citation(s) in RCA: 173] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Prostacyclin (PGI(2)) is a member of the prostanoid group of eicosanoids that regulate homeostasis, hemostasis, smooth muscle function and inflammation. Prostanoids are derived from arachidonic acid by the sequential actions of phospholipase A(2), cyclooxygenase (COX), and specific prostaglandin (PG) synthases. There are two major COX enzymes, COX1 and COX2, that differ in structure, tissue distribution, subcellular localization, and function. COX1 is largely constitutively expressed, whereas COX2 is induced at sites of inflammation and vascular injury. PGI(2) is produced by endothelial cells and influences many cardiovascular processes. PGI(2) acts mainly on the prostacyclin (IP) receptor, but because of receptor homology, PGI(2) analogs such as iloprost may act on other prostanoid receptors with variable affinities. PGI(2)/IP interaction stimulates G protein-coupled increase in cAMP and protein kinase A, resulting in decreased [Ca(2+)](i), and could also cause inhibition of Rho kinase, leading to vascular smooth muscle relaxation. In addition, PGI(2) intracrine signaling may target nuclear peroxisome proliferator-activated receptors and regulate gene transcription. PGI(2) counteracts the vasoconstrictor and platelet aggregation effects of thromboxane A(2) (TXA(2)), and both prostanoids create an important balance in cardiovascular homeostasis. The PGI(2)/TXA(2) balance is particularly critical in the regulation of maternal and fetal vascular function during pregnancy and in the newborn. A decrease in PGI(2)/TXA(2) ratio in the maternal, fetal, and neonatal circulation may contribute to preeclampsia, intrauterine growth restriction, and persistent pulmonary hypertension of the newborn (PPHN), respectively. On the other hand, increased PGI(2) activity may contribute to patent ductus arteriosus (PDA) and intraventricular hemorrhage in premature newborns. These observations have raised interest in the use of COX inhibitors and PGI(2) analogs in the management of pregnancy-associated and neonatal vascular disorders. The use of aspirin to decrease TXA(2) synthesis has shown little benefit in preeclampsia, whereas indomethacin and ibuprofen are used effectively to close PDA in the premature newborn. PGI(2) analogs have been used effectively in primary pulmonary hypertension in adults and have shown promise in PPHN. Careful examination of PGI(2) metabolism and the complex interplay with other prostanoids will help design specific modulators of the PGI(2)-dependent pathways for the management of pregnancy-related and neonatal vascular disorders.
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Affiliation(s)
- Batoule H Majed
- Harvard Medical School, Brigham and Women's Hospital, Division of Vascular Surgery, 75 Francis St., Boston, MA 02115, USA
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Abstract
Phospholipids are present in all living organisms. They are a major component of all biological membranes, along with glycolipids and cholesterol. Enzymes aimed at cleaving the various bonds in phospholipids, namely phospholipases, are consequently widespread in nature, playing very diverse roles from aggression in snake venom to signal transduction, lipid mediators production, and digestion in humans. Although all phospholipases target phospholipids as substrates, they vary in the site of action on the phospholipids molecules, physiological function, mode of action, and their regulation. Significant studies on phospholipases characterization, physiological role, and industrial potential have been conducted worldwide. Some of them have been directed for biotechnological advances, such as gene discovery and functional enhancement by protein engineering. Others reported phospholipases as virulence factors and major causes of pathophysiological effects. In this introductory chapter, we provide brief details of different phospholipases.
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Affiliation(s)
- Ahmed Aloulou
- National School of Engineers of Sfax, University of Sfax, Sfax, Tunisia.
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19
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Sharma J, Young DM, Marentette JO, Rastogi P, Turk J, McHowat J. Lung endothelial cell platelet-activating factor production and inflammatory cell adherence are increased in response to cigarette smoke component exposure. Am J Physiol Lung Cell Mol Physiol 2012; 302:L47-55. [PMID: 21984569 PMCID: PMC3349370 DOI: 10.1152/ajplung.00179.2011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 10/03/2011] [Indexed: 12/30/2022] Open
Abstract
An early event in the pathogenesis of emphysema is the development of inflammation associated with accumulation of polymorphonuclear leukocytes (PMN) in small airways, and inflammatory cell recruitment from the circulation involves migration across endothelial and epithelial cell barriers. Platelet-activating factor (PAF) promotes transendothelial migration in several vascular beds, and we postulated that increased PAF production in the airways of smokers might enhance inflammatory cell recruitment and exacerbate inflammation. To examine this possibility, we incubated human lung microvascular endothelial cells (HMVEC-L) with cigarette smoke extract (CSE) and found that CSE inhibits PAF-acetylhydrolase (PAF-AH) activity. This enhances HMVEC-L PAF production and PMN adherence, and adherence is blocked by PAF receptor antagonists (CV3988 or ginkgolide B). CSE also inhibited PAF-AH activity of lung endothelial cells isolated from wild-type (WT) and iPLA(2)β knockout mice, and with WT cells, CSE enhanced PAF production and RAW 264.7 cell adherence. In contrast, CSE did not affect PAF production or RAW 264.7 cell adherence to iPLA(2)β-null cells, suggesting that iPLA(2)β plays an important role in PAF production by lung endothelial cells. These findings suggest that inhibition of PAF-AH by components of cigarette smoke may initiate or exacerbate inflammatory lung disease by enhancing PAF production and promoting accumulation of inflammatory cells in small airways. In addition, iPLA(2)β is identified as a potential target for therapeutic interventions to reduce airway inflammation and the progression of chronic lung disease.
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Affiliation(s)
- Janhavi Sharma
- Department of Pathology, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA
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20
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Joseph EK, Levine JD. Sexual dimorphism in endothelin-1 induced mechanical hyperalgesia in the rat. Exp Neurol 2011; 233:505-12. [PMID: 22155617 DOI: 10.1016/j.expneurol.2011.11.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2011] [Revised: 10/26/2011] [Accepted: 11/22/2011] [Indexed: 01/20/2023]
Abstract
While the onset of mechanical hyperalgesia induced by endothelin-1 was delayed in female rats, compared to males, the duration was much longer. Given that the repeated test stimulus used to assess nociceptive threshold enhances hyperalgesia, a phenomenon we have referred to as stimulus-induced enhancement of hyperalgesia, we also evaluated for sexual dimorphism in the impact of repeated application of the mechanical test stimulus on endothelin-1 hyperalgesia. In male and female rats, endothelin-1 induced hyperalgesia is already maximal at 30 min. At this time stimulus-induced enhancement of hyperalgesia, which is observed only in male rats, persisted for 3-4h. In contrast, in females, it develops only after a very long (15 day) delay, and is still present, without attenuation, at 45 days. Ovariectomy eliminated these differences between male and female rats. These findings suggest marked, ovarian-dependent sexual dimorphism in endothelin-1 induced mechanical hyperalgesia and its enhancement by repeated mechanical stimulation.
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Affiliation(s)
- Elizabeth K Joseph
- Department of Medicine and Oral and Maxillofacial Surgery, University of California, San Francisco, CA 94143-0440, USA
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21
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Ueno N, Taketomi Y, Yamamoto K, Hirabayashi T, Kamei D, Kita Y, Shimizu T, Shinzawa K, Tsujimoto Y, Ikeda K, Taguchi R, Murakami M. Analysis of two major intracellular phospholipases A(2) (PLA(2)) in mast cells reveals crucial contribution of cytosolic PLA(2)α, not Ca(2+)-independent PLA(2)β, to lipid mobilization in proximal mast cells and distal fibroblasts. J Biol Chem 2011; 286:37249-63. [PMID: 21880721 DOI: 10.1074/jbc.m111.290312] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mast cells release a variety of mediators, including arachidonic acid (AA) metabolites, to regulate allergy, inflammation, and host defense, and their differentiation and maturation within extravascular microenvironments depend on the stromal cytokine stem cell factor. Mouse mast cells express two major intracellular phospholipases A(2) (PLA(2)s), namely group IVA cytosolic PLA(2) (cPLA(2)α) and group VIA Ca(2+)-independent PLA(2) (iPLA(2)β), and the role of cPLA(2)α in eicosanoid synthesis by mast cells has been well documented. Lipidomic analyses of mouse bone marrow-derived mast cells (BMMCs) lacking cPLA(2)α (Pla2g4a(-/-)) or iPLA(2)β (Pla2g6(-/-)) revealed that phospholipids with AA were selectively hydrolyzed by cPLA(2)α, not by iPLA(2)β, during FcεRI-mediated activation and even during fibroblast-dependent maturation. Neither FcεRI-dependent effector functions nor maturation-driven phospholipid remodeling was impaired in Pla2g6(-/-) BMMCs. Although BMMCs did not produce prostaglandin E(2) (PGE(2)), the AA released by cPLA(2)α from BMMCs during maturation was converted to PGE(2) by microsomal PGE synthase-1 (mPGES-1) in cocultured fibroblasts, and accordingly, Pla2g4a(-/-) BMMCs promoted microenvironmental PGE(2) synthesis less efficiently than wild-type BMMCs both in vitro and in vivo. Mice deficient in mPGES-1 (Ptges(-/-)) had an augmented local anaphylactic response. These results suggest that cPLA(2)α in mast cells is functionally coupled, through the AA transfer mechanism, with stromal mPGES-1 to provide anti-anaphylactic PGE(2). Although iPLA(2)β is partially responsible for PGE(2) production by macrophages and dendritic cells, it is dispensable for mast cell maturation and function.
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Affiliation(s)
- Noriko Ueno
- Lipid Metabolism Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 256-8506, Japan
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22
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McHowat J, Gullickson G, Hoover RG, Sharma J, Turk J, Kornbluth J. Platelet-activating factor and metastasis: calcium-independent phospholipase A2β deficiency protects against breast cancer metastasis to the lung. Am J Physiol Cell Physiol 2011; 300:C825-32. [PMID: 21228317 DOI: 10.1152/ajpcell.00502.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We determined the contribution of calcium-independent phospholipase A(2)β (iPLA(2)β) to lung metastasis development following breast cancer injection into wild-type (WT) and iPLA(2)β-knockout (iPLA(2)β-KO) mice. WT and iPLA(2)β-KO mice were injected in the mammary pad with 200,000 E0771 breast cancer cells. There was no difference in primary tumor size between WT and iPLA(2)β-KO mice at 27 days postinjection. However, we observed an 11-fold greater number of breast cancer cells in the lungs of WT mice compared with iPLA(2)β-KO animals (P < 0.05). Isolated WT lung endothelial cells demonstrated a significant increase in platelet-activating factor (PAF) production when stimulated with thrombin [1 IU/ml, 10 min, 4,330 ± 555 vs. 15,227 ± 1,043 disintegrations per minute (dpm), P < 0.01] or TNF-α (10 ng/ml, 2 h, 16,532 ± 538 dpm, P < 0.01). Adherence of E0771 cells to WT endothelial cells was increased by thrombin (4.8 ± 0.3% vs. 70.9 ± 6.3, P < 0.01) or TNF-α (60.5 ± 4.3, P < 0.01). These responses were blocked by pretreatment with the iPLA(2)β-selective inhibitor (S)-bromoenol lactone and absent in lung endothelial cells from iPLA(2)β-KO mice. These data indicate that endothelial cell iPLA(2)β is responsible for PAF production and adherence of E0771 cells and may play a role in cancer cell migration to distal locations.
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Affiliation(s)
- Jane McHowat
- Department of Pathology, Saint Louis University School of Medicine, Missouri 63104, 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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