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Taketomi Y, Murakami M. Regulatory Roles of Phospholipase A2 Enzymes and Bioactive Lipids in Mast Cell Biology. Front Immunol 2022; 13:923265. [PMID: 35833146 PMCID: PMC9271868 DOI: 10.3389/fimmu.2022.923265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 05/30/2022] [Indexed: 11/26/2022] Open
Abstract
Lipids play fundamental roles in life as an essential component of cell membranes, as a major source of energy, as a body surface barrier, and as signaling molecules that transmit intracellular and intercellular signals. Lipid mediators, a group of bioactive lipids that mediates intercellular signals, are produced via specific biosynthetic enzymes and transmit signals via specific receptors. Mast cells, a tissue-resident immune cell population, produce several lipid mediators that contribute to exacerbation or amelioration of allergic responses and also non-allergic inflammation, host defense, cancer and fibrosis by controlling the functions of microenvironmental cells as well as mast cell themselves in paracrine and autocrine fashions. Additionally, several bioactive lipids produced by stromal cells regulate the differentiation, maturation and activation of neighboring mast cells. Many of the bioactive lipids are stored in membrane phospholipids as precursor forms and released spatiotemporally by phospholipase A2 (PLA2) enzymes. Through a series of studies employing gene targeting and lipidomics, several enzymes belonging to the PLA2 superfamily have been demonstrated to participate in mast cell-related diseases by mobilizing unique bioactive lipids in multiple ways. In this review, we provide an overview of our current understanding of the regulatory roles of several PLA2-driven lipid pathways in mast cell biology.
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Solinski HJ, Kriegbaum MC, Tseng PY, Earnest TW, Gu X, Barik A, Chesler AT, Hoon MA. Nppb Neurons Are Sensors of Mast Cell-Induced Itch. Cell Rep 2020; 26:3561-3573.e4. [PMID: 30917312 PMCID: PMC6490177 DOI: 10.1016/j.celrep.2019.02.089] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 01/25/2019] [Accepted: 02/21/2019] [Indexed: 02/06/2023] Open
Abstract
Itch is an unpleasant skin sensation that can be triggered by exposure to many chemicals, including those released by mast cells. The natriuretic polypeptide b (Nppb)-expressing class of sensory neurons, when activated, elicits scratching responses in mice, but it is unclear which itch-inducing agents stimulate these cells and the receptors involved. Here, we identify receptors expressed by Nppb neurons and demonstrate the functional importance of these receptors as sensors of endogenous pruritogens released by mast cells. Our search for receptors in Nppb neurons reveals that they express leukotriene, serotonin, and sphingosine-1-phosphate receptors. Targeted cell ablation, calcium imaging of primary sensory neurons, and conditional receptor knockout studies demonstrate that these receptors induce itch by the direct stimulation of Nppb neurons and neurotransmission through the canonical gastrin-releasing peptide (GRP)-dependent spinal cord itch pathway. Together, our results define a molecular and cellular pathway for mast cell-induced itch.
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Affiliation(s)
- Hans Jürgen Solinski
- Molecular Genetics Section, National Institute of Dental and Craniofacial Research, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Mette C Kriegbaum
- Molecular Genetics Section, National Institute of Dental and Craniofacial Research, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Pang-Yen Tseng
- Molecular Genetics Section, National Institute of Dental and Craniofacial Research, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Thomas W Earnest
- Molecular Genetics Section, National Institute of Dental and Craniofacial Research, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Xinglong Gu
- Molecular Genetics Section, National Institute of Dental and Craniofacial Research, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Arnab Barik
- National Center for Complementary and Integrative Health, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Alexander T Chesler
- National Center for Complementary and Integrative Health, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Mark A Hoon
- Molecular Genetics Section, National Institute of Dental and Craniofacial Research, NIH, 35A Convent Drive, Bethesda, MD 20892, USA.
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Yagnik D, Hills F. Urate crystals induce macrophage PAF‑AH secretion which is differentially regulated by TGFβ1 and hydrocortisone. Mol Med Rep 2018; 18:3506-3512. [DOI: 10.3892/mmr.2018.9323] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 06/13/2018] [Indexed: 11/06/2022] Open
Affiliation(s)
- Darshna Yagnik
- Department of Natural Sciences, Biomarker Research Group, School of Science and Technology, Middlesex University, The Burroughs, London NW4 4BT, UK
| | - Frank Hills
- Department of Natural Sciences, Biomarker Research Group, School of Science and Technology, Middlesex University, The Burroughs, London NW4 4BT, UK
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Chen X, Wang K, Xu W, Ma Q, Chen M, Du L, Mo M, Wang Y, Shen J. Discovery of Potent and Orally Active Lipoprotein-Associated Phospholipase A2 (Lp-PLA2) Inhibitors as a Potential Therapy for Diabetic Macular Edema. J Med Chem 2016; 59:2674-87. [PMID: 26927682 DOI: 10.1021/acs.jmedchem.5b01930] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Lipoprotein-associated phospholipase A2 (Lp-PLA2) is considered to be a promising therapeutic target for several inflammation-associated diseases. Herein, we describe the discovery of a series of pyrimidone derivatives as Lp-PLA2 inhibitors. Systematic structural modifications led to the identification of several pyrimidone compounds with promising in vitro inhibitory potency and pharmacokinetic properties. Compound 14c, selected for in vivo evaluation, demonstrated decent pharmacokinetic profiles and robust inhibitory potency against Lp-PLA2 in Sprague-Dawley (SD) rats. Furthermore, 14c significantly inhibited retinal thickening in STZ-induced diabetic SD rats as a model of diabetic macular edema (DME) after oral dosing for 4 weeks. Taken together, these results suggested that 14c can serve as a valuable lead in the search for new Lp-PLA2 inhibitors for prevention and/or treatment of DME.
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Affiliation(s)
- Xinde Chen
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zuchongzhi Road, Shanghai 201203, China
| | - Kai Wang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zuchongzhi Road, Shanghai 201203, China
| | - Wenwei Xu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zuchongzhi Road, Shanghai 201203, China
| | - Quanxin Ma
- Laboratory Animal Research Center, Zhejiang Chinese Medical University , Hangzhou 310053, China
| | - Minli Chen
- Laboratory Animal Research Center, Zhejiang Chinese Medical University , Hangzhou 310053, China
| | - Lili Du
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zuchongzhi Road, Shanghai 201203, China
| | - Mingguang Mo
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zuchongzhi Road, Shanghai 201203, China
| | - Yiping Wang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zuchongzhi Road, Shanghai 201203, China
| | - Jianhua Shen
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zuchongzhi Road, Shanghai 201203, China
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Jarvie JL, Wang H, Kinney GL, Snell-Bergeon J, Hokanson JE, Eckel RH. Lipoprotein-associated phospholipase A2 distribution among lipoproteins differs in type 1 diabetes. J Clin Lipidol 2016; 10:577-86. [PMID: 27206945 DOI: 10.1016/j.jacl.2016.01.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2013] [Revised: 12/16/2015] [Accepted: 01/03/2016] [Indexed: 01/07/2023]
Abstract
BACKGROUND LpPLA2 mass and activity have been variably related to cardiovascular disease risk, and the distribution of LpPLA2 in patients with type 1 diabetes (T1D), wherein cardiovascular disease risk is high despite normal or higher levels of high-density lipoprotein (HDL) cholesterol, is unknown. OBJECTIVE To determine whether there are differences in the distribution of LpPLA2 mass and activity across lipoproteins and their association with coronary artery calcium (CAC) in patients with T1D. METHODS Men with T1D (n = 19) not on statins, with and without CAC progression, and men without diabetes matched for HDL cholesterol (n = 25) had lipoproteins separated by fast protein liquid chromatography. RESULTS Both LpPLA2 mass and activity were found within low-density lipoprotein (LDL) and HDL pools with more LpPLA2 mass being associated with HDL (54% vs 44%; P-value <.001) and more LpPLA2 activity being associated with LDL (56% vs 40%; P value = .02). In T1D, more LpPLA2 activity was associated with large- or less-dense LDL compared to those without diabetes. However, no difference in LpPLA2 activity or mass between lipoprotein subfractions was observed between all groups, and there was no relationship between LpPLA2 activity or mass and its distribution and CAC score progression in healthy or T1D men. CONCLUSION LpPLA2 is found in both LDL and HDL and is distributed differently in men with T1D without any relationship to CAC score progression.
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Affiliation(s)
- Jennifer L Jarvie
- Department of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA
| | - Hong Wang
- Department of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA
| | - Gregory L Kinney
- Barbara Davis Center for Childhood Diabetes, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA
| | - Janet Snell-Bergeon
- Barbara Davis Center for Childhood Diabetes, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA
| | - John E Hokanson
- Department of Epidemiology, Colorado School of Public Health, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA
| | - Robert H Eckel
- Department of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA.
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Chen X, Xu W, Wang K, Mo M, Zhang W, Du L, Yuan X, Xu Y, Wang Y, Shen J. Discovery of a Novel Series of Imidazo[1,2-a]pyrimidine Derivatives as Potent and Orally Bioavailable Lipoprotein-Associated Phospholipase A2 Inhibitors. J Med Chem 2015; 58:8529-41. [DOI: 10.1021/acs.jmedchem.5b01024] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Xinde Chen
- State Key Laboratory of Drug
Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Wenwei Xu
- State Key Laboratory of Drug
Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Kai Wang
- State Key Laboratory of Drug
Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Mingguang Mo
- State Key Laboratory of Drug
Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Wei Zhang
- State Key Laboratory of Drug
Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Lili Du
- State Key Laboratory of Drug
Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Xiaojing Yuan
- State Key Laboratory of Drug
Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Yechun Xu
- State Key Laboratory of Drug
Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Yiping Wang
- State Key Laboratory of Drug
Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Jianhua Shen
- State Key Laboratory of Drug
Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
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Alevizos M, Karagkouni A, Vasiadi M, Sismanopoulos N, Makris M, Kalogeromitros D, Theoharides TC. Rupatadine inhibits inflammatory mediator release from human laboratory of allergic diseases 2 cultured mast cells stimulated by platelet-activating factor. Ann Allergy Asthma Immunol 2013; 111:542-7. [PMID: 24267366 DOI: 10.1016/j.anai.2013.08.025] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 08/23/2013] [Accepted: 08/25/2013] [Indexed: 02/04/2023]
Abstract
BACKGROUND Mast cells are involved in allergy and inflammation by the secretion of multiple mediators, including histamine, cytokines, and platelet-activating factor (PAF), in response to different triggers, including emotional stress. PAF has been associated with allergic inflammation, but there are no clinically available PAF inhibitors. OBJECTIVE To investigate whether PAF could stimulate human mast cell mediator release and whether rupatadine (RUP), a dual histamine-1 and PAF receptor antagonist, could inhibit the effect of PAF on human mast cells. METHODS Laboratory of allergic diseases 2 cultured mast cells were stimulated with PAF (0.001, 0.01, and 0.1 μmol/L) and substance P (1 μmol/L) with or without pretreatment with RUP (2.5 and 25 μmol/L), which was added 10 minutes before stimulation. Release of β-hexosaminidase was measured in supernatant fluid by spectrophotoscopy, and histamine, interleukin-8, and tumor necrosis factor were measured by enzyme-linked immunosorbent assay. RESULTS PAF stimulated a statistically significant release of histamine, interleukin-8, and tumor necrosis factor (0.001-0.1 μmol/L) that was comparable to that stimulated by substance P. Pretreatment with RUP (25 μmol/L) for 10 minutes inhibited this effect. In contrast, pretreatment of laboratory of allergic diseases 2 cells with diphenhydramine (25 μmol/L) did not inhibit mediator release, suggesting that the effect of RUP was not due to its antihistaminic effect. CONCLUSION PAF stimulates human mast cell release of proinflammatory mediators that is inhibited by RUP. This action endows RUP with additional properties in treating allergic inflammation.
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Affiliation(s)
- Michail Alevizos
- Laboratory of Molecular Immunopharmacology and Drug Discovery, Department of Molecular Physiology and Pharmacology, Tufts University School of Medicine, Boston, Massachusetts; Present address: Department of Internal Medicine, Jacoby Medical Center, New York, New York
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8
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Jiang Z, Fehrenbach ML, Ravaioli G, Kokalari B, Redai IG, Sheardown SA, Wilson S, Macphee C, Haczku A. The effect of lipoprotein-associated phospholipase A2 deficiency on pulmonary allergic responses in Aspergillus fumigatus sensitized mice. Respir Res 2012; 13:100. [PMID: 23140447 PMCID: PMC3546878 DOI: 10.1186/1465-9921-13-100] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 11/06/2012] [Indexed: 12/05/2022] Open
Abstract
Background Lipoprotein-associated phospholipase A2 (Lp-PLA2)/platelet-activating factor acetylhydrolase (PAF-AH) has been implicated in the pathogenesis of cardiovascular disease. A therapeutic targeting of this enzyme was challenged by the concern that increased circulating platelet activating factor (PAF) may predispose to or increase the severity of the allergic airway response. The aim of this study was to investigate whether Lp-PLA2 gene deficiency increases the risk of PAF and IgE-mediated inflammatory responses in vitro and in vivo using mouse models. Methods Lp-PLA2-/- mice were generated and back crossed to the C57BL/6 background. PAF-AH activity was measured using a hydrolysis assay in serum and bronchoalveolar lavage (BAL) samples obtained from mice. Aspergillus fumigatus (Af)-specific serum was prepared for passive allergic sensitization of mice in vivo and mast cells in vitro. β- hexosaminidase release was studied in bone marrow derived mast cells sensitized with Af-specific serum or DNP-IgE and challenged with Af or DNP, respectively. Mice were treated with lipopolysaccharide (LPS) and PAF intratracheally and studied 24 hours later. Mice were sensitized either passively or actively against Af and were studied 48 hours after a single intranasal Af challenge. Airway responsiveness to methacholine, inflammatory cell influx in the lung tissue and BAL, immunoglobulin (ELISA) and cytokine (Luminex) profiles were compared between the wild type (WT) and Lp-PLA2-/- mice. Results PAF-AH activity was reduced but not completely abolished in Lp-PLA2-/- serum or by in vitro treatment of serum samples with a high saturating concentration of the selective Lp-PLA2 inhibitor, SB-435495. PAF inhalation significantly enhanced airway inflammation of LPS treated WT and Lp-PLA2-/- mice to a similar extent. Sensitized WT and Lp-PLA2-/- bone-marrow derived mast cells released β-hexosaminidase following stimulation by allergen or IgE crosslinking to equivalent levels. Wild type and Lp-PLA2-/- mice responded to passive or active allergic sensitization by significant IgE production, airway inflammation and hyperresponsiveness after Af challenge. BAL cell influx was not different between these strains while IL-4, IL-5, IL-6 and eotaxin release was attenuated in Lp-PLA2-/- mice. There were no differences in the amount of total IgE levels in the Af sensitized WT and Lp-PLA2-/- mice. Conclusions We conclude that Lp-PLA2 deficiency in C57BL/6 mice did not result in a heightened airway inflammation or hyperresponsiveness after PAF/LPS treatment or passive or active allergic sensitization and challenge.
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Affiliation(s)
- Zhilong Jiang
- Pulmonary, Allergy and Critical Care Division, University of Pennsylvania, Philadelphia, PA, USA
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Xiao Q, Pepe AE, Wang G, Luo Z, Zhang L, Zeng L, Zhang Z, Hu Y, Ye S, Xu Q. Nrf3-Pla2g7 interaction plays an essential role in smooth muscle differentiation from stem cells. Arterioscler Thromb Vasc Biol 2012; 32:730-44. [PMID: 22247257 DOI: 10.1161/atvbaha.111.243188] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Phospholipase A2, group 7 (Pla2g7) is an important mediator in cardiovascular development and diseases because of its divergent physiological and pathological functions in inflammation and oxidative stress. However, little is known about the functional role of Pla2g7 in smooth muscle cell (SMC) differentiation from stem cells. METHODS AND RESULTS In the present study, embryonic stem cells were cultivated on collagen IV-coated plates to allow SMC differentiation. Pla2g7 gene expression and activity were upregulated significantly following 4 to 14 days of cell differentiation and colocalized with SMC differentiation markers in the differentiated SMCs. Knockdown of Pla2g7 resulted in downregulation of smooth muscle-specific markers in vitro and impairment of SMC differentiation in vivo, whereas enforced expression of Pla2g7 enhanced SMC differentiation and increased reactive oxygen species generation. Importantly, enforced expression of Pla2g7 significantly increased the binding of serum response factor to SMC differentiation gene promoters, resulting in SMC differentiation, which was abolished by free radical scavenger and flavoprotein inhibitor of NADPH oxidase but not hydrogen peroxide inhibitor. Moreover, we demonstrated that nuclear factor erythroid 2-related factor 3 (Nrf3) regulates Pla2g7 gene expression through direct binding to the promoter regions of Pla2g7 gene. CONCLUSION Our findings demonstrated that Pla2g7 plays a crucial physiological role in SMC differentiation from stem cells, and the fine interactions between Nrf3 and Pla2g7 are essential for SMC differentiation.
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Affiliation(s)
- Qingzhong Xiao
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, United Kingdom.
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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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The role of lipoprotein-associated phospholipase A2 in atherosclerosis may depend on its lipoprotein carrier in plasma. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:327-38. [PMID: 19272461 DOI: 10.1016/j.bbalip.2009.02.015] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 02/06/2009] [Accepted: 02/19/2009] [Indexed: 01/28/2023]
Abstract
Platelet-activating factor (PAF) acetylhydrolase exhibits a Ca(2+)-independent phospholipase A2 activity and degrades PAFas well as oxidized phospholipids (oxPL). Such phospholipids are accumulated in the artery wall and may play key roles in vascular inflammation and atherosclerosis. PAF-acetylhydrolase in plasma is complexed to lipoproteins; thus it is also referred to as lipoprotein-associated phospholipase A2 (Lp-PLA2). Lp-PLA2 is primarily associated with low-density lipoprotein (LDL), whereas a small proportion of circulating enzyme activity is also associated with high-density lipoprotein (HDL). The majority of the LDL-associated Lp-PLA2 (LDL-Lp-PLA2) activity is bound to atherogenic small-dense LDL particles and it is a potential marker of these particles in plasma. The distribution of Lp-PLA2 between LDL and HDL is altered in various types of dyslipidemias. It can be also influenced by the presence of lipoprotein (a) [Lp(a)] when plasma levels of this lipoprotein exceed 30 mg/dl. Several lines of evidence suggest that the role of plasma Lp-PLA2 in atherosclerosis may depend on the type of lipoprotein particle with which this enzyme is associated. In this regard, data from large Caucasian population studies have shown an independent association between the plasma Lp-PLA2 levels (which are mainly influenced by the levels of LDL-Lp-PLA2) and the risk of future cardiovascular events. On the contrary, several lines of evidence suggest that HDL-associated Lp-PLA2 may substantially contribute to the HDL antiatherogenic activities. Recent studies have provided evidence that oxPL are preferentially sequestered on Lp(a) thus subjected to degradation by the Lp(a)-associated Lp-PLA2. These data suggest that Lp(a) may be a potential scavenger of oxPL and provide new insights into the functional role of Lp(a) and the Lp(a)-associated Lp-PLA2 in normal physiology as well as in inflammation and atherosclerosis. The present review is focused on recent advances concerning the Lp-PLA2 structural characteristics, the molecular basis of the enzyme association with distinct lipoprotein subspecies, as well as the potential role of Lp-PLA2 associated with different lipoprotein classes in atherosclerosis and cardiovascular disease.
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12
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PAF-acetylhydrolase expressed during megakaryocyte differentiation inactivates PAF-like lipids. Blood 2009; 113:6699-706. [PMID: 19395675 DOI: 10.1182/blood-2008-11-186312] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Platelet activating factor (PAF) and PAF-like lipids induce inflammatory responses in target cells. These lipid mediators are inactivated by PAF-acetylhydrolase (PAF-AH). The PAF signaling system affects the growth of hematopoietic CD34(+) cells, but roles for PAF-AH in this process are unknown. Here, we investigated PAF-AH function during megakaryopoiesis and found that human CD34(+) cells accumulate this enzymatic activity as they differentiate toward megakaryocytes, consistent with the expression of mRNA and protein for the plasma PAF-AH isoform. Inhibition of endogenous PAF-AH activity in differentiated megakaryocytes increased formation of lipid mediators that signaled the PAF receptor (PAFR) in fully differentiated human cells such as neutrophils, as well as megakaryocytes themselves. PAF-AH also controlled megakaryocyte alpha(IIb)beta(3)-dependent adhesion, cell spreading, and mobility that relied on signaling through the PAFR. Together these data suggest that megakaryocytes generate PAF-AH to modulate the accumulation of intracellular phospholipid mediators that may detrimentally affect megakaryocyte development and function.
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13
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Khodoun M, Strait R, Orekov T, Hogan S, Karasuyama H, Herbert DR, Köhl J, Finkelman FD. Peanuts can contribute to anaphylactic shock by activating complement. J Allergy Clin Immunol 2009; 123:342-51. [PMID: 19121857 DOI: 10.1016/j.jaci.2008.11.004] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Revised: 11/07/2008] [Accepted: 11/10/2008] [Indexed: 10/21/2022]
Abstract
BACKGROUND Peanut allergy is the most common food-related cause of lethal anaphylaxis and, unlike other food allergies, typically persists into adulthood. Resistance to digestion and dendritic cell activation by the major peanut allergen Ara h 1 are reported to contribute to its allergenicity. OBJECTIVE We sought to evaluate whether peanut molecules might also promote anaphylaxis through an innate immune mechanism. METHODS Naive mice were treated with a beta-adrenergic receptor antagonist and long-acting IL-4 to increase sensitivity to vasoactive mediators and injected with peanut extract (PE). Shock was detected and quantified by means of rectal thermometry. Gene-deficient mice and specific antagonists were used to determine the roles of specific cell types, complement, Fc receptors, and vasoactive mediators in shock pathogenesis. RESULTS PE induces dose-dependent shock. PE activates complement in vivo in mice and in vitro in mice and human subjects. C3a and, to a lesser extent, stimulatory immunoglobulin receptors contribute to PE-induced shock. PE-induced shock depends more on macrophages and basophils than on mast cells. Platelet-activating factor and, to a lesser extent, histamine contribute to PE-induced shock. PE induces shock in the absence of the adaptive immune system. LPS contamination is not responsible for PE-induced shock. PE and IgE-mediated mast cell degranulation synergistically induce shock. Tree nuts have similar effects to PE, and skim milk and egg white do not. CONCLUSION Peanuts can contribute to shock by causing production of C3a, which stimulates macrophages, basophils, and mast cells to produce platelet-activating factor and histamine.
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Affiliation(s)
- Marat Khodoun
- Cincinnati Veterans Affairs Medical Center, Cincinnati, Ohio; Division of Immunology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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14
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Karabina SA, Ninio E. Plasma PAF-acetylhydrolase: an unfulfilled promise? Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1351-8. [PMID: 16807087 DOI: 10.1016/j.bbalip.2006.05.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Revised: 05/04/2006] [Accepted: 05/08/2006] [Indexed: 01/04/2023]
Abstract
Plasma Platelet-activating-Factor (PAF)-acetylhydrolase (PAF-AH also named lipoprotein-PLA(2) or PLA(2)G7 gene) is secreted by macrophages, it degrades PAF and oxidation products of phosphatidylcholine produced upon LDL oxidation and/or oxidative stress, and thus is considered as a potentially anti-inflammatory enzyme. Cloning of PAF-AH has sustained tremendous promises towards the use of PAF-AH recombinant protein in clinical situations. The reason for that stems from the numerous animal models of inflammation, atherosclerosis or sepsis, where raising the levels of circulating PAF-AH either through recombinant protein infusion or through the adenoviral gene transfer showed to be beneficial. Unfortunately, neither in human asthma nor in sepsis the recombinant PAF-AH showed sufficient efficacy. One of the most challenging questions nowadays is as to whether PAF-AH is pro- or anti-atherogenic in humans, as PAF-AH may possess a dual pro- and anti-inflammatory role, depending on the concentration and the availability of potential substrates. It is equally possible that the plasma level of PAF-AH is a diagnostic marker of ongoing atherosclerosis.
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Affiliation(s)
- Sonia-Athina Karabina
- INSERM U525, Université Pierre et Marie Curie-Paris6, Faculté de Médecine Pierre et Marie Curie, 91, bd de l'Hôpital 75634 Paris cedex 13, France
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15
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Lee WS, Kim MJ, Beck YI, Park YD, Jeong TS. Lp-PLA2 inhibitory activities of fatty acid glycerols isolated from Saururus chinensis roots. Bioorg Med Chem Lett 2005; 15:3573-5. [PMID: 15961310 DOI: 10.1016/j.bmcl.2005.05.056] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2005] [Revised: 05/03/2005] [Accepted: 05/16/2005] [Indexed: 11/23/2022]
Abstract
(R)-Glycerol-monolinoleate 4 and (R)-glycerol-monostearate 5 were isolated from the ethyl acetate extracts of Saururus chinensis roots and (R)- or (S)-fatty acid glycerols 4 and 5 were synthesized for confirming their structures and evaluating their inhibitory activities against Lp-PLA(2). The (R)-4 and (S)-4 exhibited Lp-PLA(2) inhibitory activities with IC(50) values of 45.0 and 52.0 microM, respectively.
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Affiliation(s)
- Woo Song Lee
- National Research Laboratory of Lipid Metabolism and Atherosclerosis, Korea Research Institute of Bioscience and Biotechnology, 52 Oun, Yusong, Daejeon 305-333, Republic of Korea
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Castro Faria Neto HC, Stafforini DM, Prescott SM, Zimmerman GA. Regulating inflammation through the anti-inflammatory enzyme platelet-activating factor-acetylhydrolase. Mem Inst Oswaldo Cruz 2005; 100 Suppl 1:83-91. [PMID: 15962103 DOI: 10.1590/s0074-02762005000900014] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Platelet-activating factor (PAF) is one of the most potent lipid mediators involved in inflammatory events. The acetyl group at the sn-2 position of its glycerol backbone is essential for its biological activity. Deacetylation induces the formation of the inactive metabolite lyso-PAF. This deacetylation reaction is catalyzed by PAF-acetylhydrolase (PAF-AH), a calcium independent phospholipase A2 that also degrades a family of PAF-like oxidized phospholipids with short sn-2 residues. Biochemical and enzymological evaluations revealed that at least three types of PAF-AH exist in mammals, namely the intracellular types I and II and a plasma type. Many observations indicate that plasma PAF AH terminates signals by PAF and oxidized PAF-like lipids and thereby regulates inflammatory responses. In this review, we will focus on the potential of PAF-AH as a modulator of diseases of dysregulated inflammation.
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Affiliation(s)
- Hugo C Castro Faria Neto
- Laboratório de Imunofarmacologia, Departamento de Fisiologia e Farmacodinâmica, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, RJ, Brasil
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17
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Loers G, Aboul-Enein F, Bartsch U, Lassmann H, Schachner M. Comparison of myelin, axon, lipid, and immunopathology in the central nervous system of differentially myelin-compromised mutant mice: a morphological and biochemical study. Mol Cell Neurosci 2005; 27:175-89. [PMID: 15485773 DOI: 10.1016/j.mcn.2004.06.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2004] [Revised: 05/27/2004] [Accepted: 06/08/2004] [Indexed: 01/06/2023] Open
Abstract
The present study was carried out to compare different myelin-compromised mouse mutants with regard to myelin morphology in relation to axon-, lipid-, and immunopathology as a function of age. Mouse mutants deficient in the myelin-associated glycoprotein (MAG) and myelin basic protein (MBP) display subtle and severe myelin pathologies in the central nervous system (CNS), respectively. Animals doubly deficient in MAG and the neural cell adhesion molecule (NCAM) show defects similar to those present in MAG single mutants while mice deficient in MAG and the nonreceptor type tyrosine kinase Fyn are severely hypomyelinated, in addition to the MAG-specific myelin abnormalities. These mutant mice showed distinct myelin pathologies in different regions of the central nervous system and generally displayed a decrease in axonal integrity with age. Myelin pathology did not correlate locally with axon transection and with an involvement of the immune system as seen by numbers of CD3-positive lymphocytes and MAC-3-positive macrophages. Interestingly, the degree of these cellular abnormalities also did not correlate with abnormalities in levels of phospholipids, arachidonic acid, cholesterol, and apolipoprotein E (apoE). Moreover, these changes in lipid metabolism, including immune system-related arachidonic acid, preceded cellular pathology. The combined observations point to differences, but also similarities in the relation of myelin, axon, and immunopathology with genotype, and to a common aggravation of the phenotype with age.
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Affiliation(s)
- Gabriele Loers
- Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, D-20251 Hamburg, Germany
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18
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Lie WJ, Homburg CHE, Kuijpers TW, Knol EF, Mul FPJ, Roos D, Tool ATJ. Regulation and kinetics of platelet-activating factor and leukotriene C4 synthesis by activated human basophils. Clin Exp Allergy 2003; 33:1125-34. [PMID: 12911788 DOI: 10.1046/j.1365-2222.2003.01726.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Allergic disease is the result of an interplay of many different cell types, including basophils and mast cells, in combination with various inflammatory lipid mediators, such as platelet-activating factor (PAF) and leukotrienes (LT). LTC4 synthesis by human basophils has been studied quite extensively. However, not much is known about the synthesis of PAF by human basophils. OBJECTIVE In this study, we have made a comprehensive comparison between the kinetics of PAF and LTC4 synthesis, in highly purified basophils, activated with different stimuli or with combinations of stimuli. METHODS Synthesis of PAF and LTC4 by human basophils was determined with commercially available assay kits. The basophils were activated with C5a, fMLP, PMA, allergen or anti-IgE, in the absence and presence of IL-3 and/or in combination with elevation of cytosolic free Ca2+ by the sarcoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin. RESULTS Most stimuli were found to induce both PAF and LTC4 synthesis. PAF synthesis and LTC4 release were enhanced by preincubation of the basophils with IL-3 or by elevation of cytosolic free Ca2+ by thapsigargin. Incubation of human basophils with IL-3 alone or thapsigargin alone did not result in detectable synthesis of PAF and LTC4, whereas the combination of the two resulted in high amounts of PAF and LTC4 synthesis. Depending on the stimulus used, LTC4 release was 5-100-fold higher than PAF synthesis. In addition, PAF, but not LTC4, was transiently detected, probably due to PAF degradation. LTC4 and PAF synthesis was strongly blocked by inhibitors of cytosolic phospholipase A2, indicating that this enzyme is involved in PAF and LTC4 synthesis by activated human basophils. CONCLUSION This study provides a first comprehensive comparison of PAF and LTC4 synthesis in highly purified human basophils, stimulated with a variety of stimuli.
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Affiliation(s)
- W J Lie
- Sanquin Research at CLB, and Landsteiner Laboratory, Academic Medical Centre, University of Amsterdam, Amsterdam
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Karasawa K, Harada A, Satoh N, Inoue K, Setaka M. Plasma platelet activating factor-acetylhydrolase (PAF-AH). Prog Lipid Res 2003; 42:93-114. [PMID: 12547653 DOI: 10.1016/s0163-7827(02)00049-8] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The platelet-activating factor-acetylhydrolase (PAF-AH) is an enzyme which catalyzes the hydrolysis of acetyl ester at the sn-2 position of PAF. The family of PAF-AHs consists of two intracellular isoforms (Ib and II), and one secreted isoform (plasma). These PAF-AHs show different biochemical characteristics and molecular structures. Plasma PAF-AH and intracellular isoform, II degrade not only PAF but also oxidatively fragmented phospholipids with potent biological activities. Among these PAF-AHs, plasma PAF-AH has been the target of many clinical studies in inflammatory diseases, such as asthma, sepsis, and vascular diseases, because the plasma PAF-AH activity in the patients with these diseases is altered when compared with normal individuals. Finding a genetic deficiency in the plasma PAF-AH opened the gate in elucidating the protecting role of this enzyme in inflammatory diseases. The most common loss-of-function mutation, V279F, is found in more than 30% of Japanese subjects (4% homozygous, 27% heterozygous). This single nucleotide polymorphism in plasma PAF-AH and the resulting enzymatic deficiency is thought to be a genetic risk factor in various inflammatory diseases in Japanese subjects. Administration of recombinant plasma PAF-AH or transfer of the plasma PAF-AH gene improves pathology in animal models. Therefore, substitution of plasma PAF-AH would be an effective in the treatment of the patients with the inflammatory diseases and a novel clinical approach. In addition, the detection of polymorphisms in the plasma PAF-AH gene and abnormalities in enzyme activity would be beneficial in the diagnosis of the inflammatory diseases.
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Affiliation(s)
- Ken Karasawa
- Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa, Japan.
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20
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Tselepis AD, John Chapman M. Inflammation, bioactive lipids and atherosclerosis: potential roles of a lipoprotein-associated phospholipase A2, platelet activating factor-acetylhydrolase. ATHEROSCLEROSIS SUPP 2002; 3:57-68. [PMID: 12573364 DOI: 10.1016/s1567-5688(02)00045-4] [Citation(s) in RCA: 229] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
It is well established that inflammation is an integral feature of atherosclerosis and of the cardiovascular diseases which it underlies. Oxidative stress is also recognized as a key actor in atherogenesis, in which it is closely associated with the inflammatory response and bioactive lipid formation. Several bioactive lipids have been identified in the atherosclerotic plaque, including the potent inflammatory mediator platelet activating factor (PAF), PAF-like lipids, oxidised phospholipids (oxPL) and lysophosphatidylcholine (lyso-PC). Recent evidence has established a central role of two phospholipases (PL) in atherogenesis, the non-pancreatic Type II secretory phospholipase A(2) (sPLA(2)) and the lipoprotein-associated PLA(2)-alternatively termed as PAF-acetylhydrolase (PAF-AH). sPLA(2) is calcium-dependent and hydrolyses the sn-2 acyl group of glycerophospholipids of lipoproteins and cell membranes to produce lyso-PC and free fatty acids. It is also implicated in isoprostane production from oxPL. sPLA(2) is an acute phase reactant, which is upregulated by inflammatory cytokines and may represent a new independent risk factor for coronary heart disease. In contrast to sPLA(2), PAF-AH is calcium-independent and is specific for short acyl groups at the sn-2 position of the phospholipid substrate and with the exception of PAF, can equally hydrolyze oxPL to generate lyso-PC and oxidized fatty acids. Thus PAF-AH plays a key role in the degradation of proinflammatory oxPL and in the generation of lyso-PC and oxidized fatty acids. PAF-AH equally can also hydrolyze short-chain diacylglycerols, triacylglycerols, and acetylated alkanols, and displays a PLA(1) activity. Whereas sPLA(2) may represent a new independent risk factor for coronary artery disease, the potential relevance of PAF-AH to atherosclerosis remains the subject of debate, and recent results suggest that the potential role of the LDL-associated PAF-AH in atherogenesis may be distinct to that of the HDL-associated enzyme. This review is focused on the main structural and catalytic features of plasma PAF-AH, on the association of the enzyme with distinct lipoprotein particle subspecies, on its cellular sources, and finally on the potential significance of this lipoprotein-associated PLA(2) in cardiovascular disease.
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21
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Abstract
Phospholipase A2 (PLA2) catalyzes the hydrolysis of the sn-2 position of membrane glycerophospholipids to liberate arachidonic acid (AA), a precursor of eicosanoids including prostaglandins and leukotrienes. The same reaction also produces lysophosholipids, which represent another class of lipid mediators. So far, at least 19 enzymes that possess PLA2 activity have been identified and cloned in mammals. The secretory PLA2 (sPLA2) family, in which 10 isozymes have been identified, consists of low-molecular weight, Ca2+-requiring secretory enzymes that have been implicated in a number of biological processes, such as modification of eicosanoid generation, inflammation, and host defense. The cytosolic PLA2 (cPLA2) family consists of three enzymes, among which cPLA2alpha has been paid much attention by researchers as an essential component of the initiation of AA metabolism. The activation of cPLA2alpha is tightly regulated by Ca2+ and phosphorylation. The Ca2+-independent PLA2 (iPLA2) family contains two enzymes and may play a major role in phospholipid remodeling. The platelet-activating factor (PAF) acetylhydrolase (PAF-AH) family contains four enzymes that exhibit unique substrate specificity toward PAF and/or oxidized phospholipids. Degradation of these bioactive phospholipids by PAF-AHs may lead to the termination of inflammatory reaction and atherosclerosis.
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Affiliation(s)
- Ichiro Kudo
- Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, Tokyo, Japan.
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22
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Suckling KE, Macphee CH. Lipoprotein-associated phospholipase A2: a target directed at the atherosclerotic plaque. Expert Opin Ther Targets 2002; 6:309-14. [PMID: 12223071 DOI: 10.1517/14728222.6.3.309] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is so named because it is found in human plasma largely associated with low-density lipoprotein (LDL). It is secreted by macrophages and able to hydrolyse oxidised fatty acids from oxidised phospholipids in LDL thereby releasing pro-atherogenic lysophosphatidylcholine and fatty acids. Inhibition of this enzyme activity was proposed to be antiatherogenic and this hypothesis has been confirmed both in vitro and in animal studies using specific inhibitors. In addition, the enzyme has been shown to be present in human atherosclerotic plaques and to be a potential risk factor for coronary heart disease in epidemiological studies. However, Lp-PLA(2) is identical to platelet-activating factor acetylhydrolase (PAF-AH), whose activity is regarded as antiatherogenic. The role of this enzyme in humans, represented as Lp-PLA(2) or PAF-AH, remains to be clarified. Specific and potent inhibitors of Lp-PLA(2) have been described and help address this question. This is a novel approach directed specifically towards processes in atherogenesis which take place in the artery wall. Innovative strategies for clinical development are required to progress novel molecular strategies such as this.
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Affiliation(s)
- Keith E Suckling
- Artherosclerosis Research, GlaxoSmithkline, Medicines Research Centre, Stevenage, Herts, UK.
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23
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Affiliation(s)
- M Murakami
- Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
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24
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Macphee CH. Lipoprotein-associated phospholipase A2: a potential new risk factor for coronary artery disease and a therapeutic target. Curr Opin Pharmacol 2001; 1:121-5. [PMID: 11714085 DOI: 10.1016/s1471-4892(01)00024-8] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The recognition that atherosclerosis represents an inflammatory disease has begun to shift interest towards novel therapies that could specifically target the underlying inflammatory component of atherogenesis. Like low-density lipoprotein, an ideal new drug target would be a modifiable plasma risk factor that not only reflects the ongoing inflammatory process but also actively promotes it. Lipoprotein-associated phospholipase A2, also known as platelet-activating factor acetylhydrolase, is a new risk factor that may have the potential to fulfil these requirements.
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Affiliation(s)
- C H Macphee
- Department of Vascular Biology, SmithKline Beecham Pharmaceuticals, Harlow, Essex, UK.
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25
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Murakami M, Koduri RS, Enomoto A, Shimbara S, Seki M, Yoshihara K, Singer A, Valentin E, Ghomashchi F, Lambeau G, Gelb MH, Kudo I. Distinct arachidonate-releasing functions of mammalian secreted phospholipase A2s in human embryonic kidney 293 and rat mastocytoma RBL-2H3 cells through heparan sulfate shuttling and external plasma membrane mechanisms. J Biol Chem 2001; 276:10083-96. [PMID: 11106649 DOI: 10.1074/jbc.m007877200] [Citation(s) in RCA: 148] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We analyzed the ability of a diverse set of mammalian secreted phospholipase A(2) (sPLA(2)) to release arachidonate for lipid mediator generation in two transfected cell lines. In human embryonic kidney 293 cells, the heparin-binding enzymes sPLA(2)-IIA, -IID, and -V promote stimulus-dependent arachidonic acid release and prostaglandin E(2) production in a manner dependent on the heparan sulfate proteoglycan glypican. In contrast, sPLA(2)-IB, -IIC, and -IIE, which bind weakly or not at all to heparanoids, fail to elicit arachidonate release, and addition of a heparin binding site to sPLA(2)-IIC allows it to release arachidonate. Heparin nonbinding sPLA(2)-X liberates arachidonic acid most likely from the phosphatidylcholine-rich outer plasma membrane in a glypican-independent manner. In rat mastocytoma RBL-2H3 cells that lack glypican, sPLA(2)-V and -X, which are unique among sPLA(2)s in being able to hydrolyze phosphatidylcholine-rich membranes, act most likely on the extracellular face of the plasma membrane to markedly augment IgE-dependent immediate production of leukotriene C(4) and platelet-activating factor. sPLA(2)-IB, -IIA, -IIC, -IID, and -IIE exert minimal effects in RBL-2H3 cells. These results are also supported by studies with sPLA(2) mutants and immunocytostaining and reveal that sPLA(2)-dependent lipid mediator generation occur by distinct (heparanoid-dependent and -independent) mechanisms in HEK293 and RBL-2H3 cells.
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Affiliation(s)
- M Murakami
- Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
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26
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Kato M, Mano H, Ota A, Konomi K, Nakata K. Platelet activating factor degradation in tear fluid from guinea pigs with allergic conjunctivitis. J Ocul Pharmacol Ther 2001; 17:83-91. [PMID: 11327052 DOI: 10.1089/108076801750125757] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The purpose of this study was to investigate the role of platelet-activating factor (PAF) and PAF acetylhydrolase (AH) in conjunctiva. The influence of PAF on conjunctival vascular permeability and the presence of PAF or its metabolites in tears from guinea pigs with allergic conjunctivitis were investigated. We instilled PAF to the eyes of guinea pigs and evaluated vascular permeability. Tear samples were collected from passively sensitized guinea pigs, and the concentration of PAF and its metabolites determined by liquid chromatography-tandem mass spectrometry. Exogenous PAF degradation in tear samples was evaluated with or without diisopropyl fluorophosphate (DFP). Topically applied PAF increased vascular permeability in conjunctiva. In the tear samples from guinea pigs with allergic conjunctivitis, PAF could not be detected. However, 40 +/- 6 ng/ml of lyso-platelet activating factor (lyso-PAF) and 230 +/- 50 ng/ml of 1-alkyl-2-acyl-sn-glycero-3-phosphocholine were detected at 10 min after challenge. Exogenous PAF was rapidly degraded in the tear samples from guinea pigs with allergic conjunctivitis, but not from normal guinea pigs. This PAF degradation was inhibited by DFP. These results suggest that PAF in the tear fluid is quickly hydrolyzed to lyso-PAF by PAF AH, which may be released or activated in allergic conjunctivitis.
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Affiliation(s)
- M Kato
- Ophthalmic Research Division, Santen Pharmaceutical Co., Lt., Nara, Japan
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27
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Tjoelker LW, Stafforini DM. Platelet-activating factor acetylhydrolases in health and disease. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1488:102-23. [PMID: 11080681 DOI: 10.1016/s1388-1981(00)00114-1] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The platelet-activating factor (PAF) acetylhydrolases catalyze hydrolysis of the sn-2 ester bond of PAF and related pro-inflammatory phospholipids and thus attenuate their bioactivity. One secreted (plasma) and four intracellular isozymes have been described. The intracellular isozymes are distinguished by differences in primary sequence, tissue localization, subunit composition, and substrate preferences. The most thoroughly characterized intracellular isoform, Ib, is a G-protein-like complex with two catalytic subunits (alpha1 and alpha2) and a regulatory beta subunit. The beta subunit is a product of the LIS1 gene, mutations of which cause Miller-Dieker lissencephaly. Isoform II is a single polypeptide that is homologous to the plasma PAF acetylhydrolase and has antioxidant activity in several systems. Plasma PAF acetylhydrolase is also a single polypeptide with a catalytic triad of amino acids that is characteristic of the alpha/beta hydrolases. Deficiency of this enzyme has been associated with a number of pathologies. The most common inactivating mutation, V279F, is found in >30% of randomly surveyed Japanese subjects (4% homozygous, 27% heterozygous). The prevalence of the mutant allele is significantly greater in patients with asthma, stroke, myocardial infarction, brain hemorrhage, and nonfamilial cardiomyopathy. Preclinical studies have demonstrated that recombinant plasma PAF acetylhydrolase can prevent or attenuate pathologic inflammation in a number of animal models. In addition, preliminary clinical results suggest that the recombinant enzyme may have pharmacologic potential in human inflammatory disease as well. These observations underscore the physiological importance of the PAF acetylhydrolases and point toward new approaches for controlling pathologic inflammation.
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Murakami M, Tada K, Nakajima K, Kudo I. Regulation of prostaglandin, leukotriene, and platelet-activating factor metabolism in mast cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2000; 469:37-42. [PMID: 10667307 DOI: 10.1007/978-1-4615-4793-8_6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Affiliation(s)
- M Murakami
- Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, Tokyo, Japan
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29
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Asano K, Okamoto S, Fukunaga K, Shiomi T, Mori T, Iwata M, Ikeda Y, Yamaguchi K. Cellular source(s) of platelet-activating-factor acetylhydrolase activity in plasma. Biochem Biophys Res Commun 1999; 261:511-4. [PMID: 10425216 DOI: 10.1006/bbrc.1999.1066] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Platelet activating factor (PAF) is immediately degraded and inactivated in the bloodstream by plasma PAF acetylhydrolase (PAF-AH). Although plasma PAF-AH-like activity was secreted in vitro from various cell types such as macrophages and hepatocytes, the exact cellular source(s) of this enzyme activity in vivo remains unclear. There is a naturally-occurring missense mutation (V279F) in the plasma PAF-AH gene in the Japanese population which results in complete loss of the enzyme activity. We analyzed 52 Japanese who had received an allogeneic bone marrow transplant and maintained donor-derived hematopoiesis. Ten recipients had chimeric plasma PAF-AH genotypes between the donor-derived peripheral blood leukocytes and the recipient-derived epithelial cells of buccal mucosa. Multiple regression analysis demonstrated that PAF-AH activity in plasma depended on the donor's genotype (standardized regression coefficient = 0.68, P < 0.0001), but not on the recipient's genotype (p = 0.48). One recipient who was a V279F homozygote in leukocytes and wild type homozygote in buccal mucosa had undetectable PAF-AH activity in plasma. We conclude that most of the PAF-AH activity in human plasma originates from hematopoietic lineage cells.
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Affiliation(s)
- K Asano
- Department of Medicine, Keio University School of Medicine, Tokyo, 160-8582, Japan.
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30
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Affiliation(s)
- S Soubeyrand
- Department of Biochemistry, University of Montreal, Guy-Bernier Research Centre, Quebec, Canada
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31
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Moon TC, Murakami M, Ashraf MD, Kudo I, Chang HW. Regulation of cyclooxygenase-2 and endogenous cytokine expression by bacterial lipopolysaccharide that acts in synergy with c-kit ligand and Fc epsilon receptor I crosslinking in cultured mast cells. Cell Immunol 1998; 185:146-52. [PMID: 9636692 DOI: 10.1006/cimm.1998.1284] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Emerging evidence has suggested the pivotal role of mast cells in a host defense against bacterial infection. In this paper, we report that bacterial lipopolysaccharide (LPS) is a potent enhancer of the cytokine- and IgE-dependent delayed responses of IL-3-dependent mouse bone marrow-derived cultured mast cells (BMMC). LPS, although showing minimal effects, significantly augmented the c-kit ligand (KL)- or IgE-dependent expression of cyclooxygenase (COX)-2 and the attendant delayed PGD2 generation, with IL-10 and IL-4 acting as potentiating and inhibitory cytokines, respectively. The COX-2-inducing activity of LPS was mimicked by exogenous IL-1 beta. Assessment of endogenous cytokine induction revealed that IL-1 beta expression was stimulated by either LPS or exogenous IL-1 beta. IL-6 expression occurred in parallel with COX-2 expression. IL-10 expression, which lagged behind COX-2 expression, depended on exogenous IL-10, but not on LPS and IL-1 beta. Thus, LPS and IL-1 beta exhibited similar biological activities in terms of COX-2 and endogenous cytokine expression. However, adding an antibody against the type I IL-1 receptor to BMMC, which abrogated the effects of IL-1 beta, failed to neutralize the effects of LPS. These results suggest that LPS activates BMMC through the signal transduction pathway shared with exogenous IL-1 beta, rather than exerting its action indirectly via the production of endogenous IL-1 beta.
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Affiliation(s)
- T C Moon
- College of Pharmacy, Yeungnam University, Gyonsan, Korea
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