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1.
  • Fu, Huamei, 1979, et al. (author)
  • Changes in the ratio between FPR and FPRL1 triggered superoxide production in human neutrophils-a tool in analysing receptor specific events
  • 2008
  • In: Journal of Immunological Methods. - : Elsevier BV. - 0022-1759. ; 331:1-2, s. 50-8
  • Journal article (peer-reviewed)abstract
    • Neutrophils express the G protein-coupled N-formyl peptide receptor (FPR) as well as its closely related homologue, formyl peptide like receptor 1 (FPRL1), and activation of these receptors induce a release of superoxide anions. The magnitude of the responses induced by the two peptide agonists fMLF and WKYMVM, specific for FPR and FPRL1, respectively, was found to be very variable in different neutrophil populations. The ratio between the FPR and FPRL1 triggered respiratory burst was, however, very constant and close to 1. The ratio was changed in neutrophils that were desensitized as well as when the signaling through either of the receptors was inhibited by receptor specific antagonists or by a PIP(2) binding peptide. The FPR/FPRL1 ratio was not changed in primed neutrophils or in differentiated HL-60 cells. We show that the change in the ratio, calculated from the amount of radical release in neutrophils triggered with FPR and FPRL1 specific agonists can be used as a valuable tool to find/identify receptor specific/selective changes mediated by peptides/proteins/drugs, as well as to identify cells from patients or groups of patients that diverge from normal cells in their FPR/FPRL1 triggered functions.
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2.
  • Aspberg, A., et al. (author)
  • Cartilage oligomeric matrix protein forms protein complexes with synovial lubricin via non-covalent and covalent interactions
  • 2017
  • In: Osteoarthritis and Cartilage. - : Elsevier BV. - 1063-4584. ; 25:9, s. 1496-1504
  • Journal article (peer-reviewed)abstract
    • Objective: Understanding the cartilage surface structure, lost in arthritic disease, is essential for developing strategies to effectively restore it. Given that adherence of the lubricating protein, lubricin, to the cartilage surface is critical for boundary lubrication, an interaction with cartilage oligomeric matrix protein (COMP) was investigated. COMP, an abundant cartilage protein, is known to be important for matrix formation. Design: Synovial fluid (SF) from arthritic patients was used to detect possible COMP-lubricin complexes by immunological methods. Recombinant (RC) COMP and lubricin fragments were expressed to characterize this bonding and mass spectrometry employed to specifically identify the cysteines involved in inter-protein disulfide bonds. Results: COMP-lubricin complexes were identified in the SF of arthritic patients by Western blot, co-immunoprecipitation and sandwich ELISA. RC fragment solid-phase binding assays showed that the C-terminal (amino acids (AA) 518-757) of COMP bound non-covalently to the N-terminal of lubricin (AA 105-202). Mass spectrometry determined that although cysteines throughout COMP were involved in binding with lubricin, the cysteines in lubricin were primarily focused to an N-terminal region (AA 64-86). The close proximity of the non-covalent and disulfide binding domains on lubricin suggest a two-step mechanism to strongly bind lubricin to COMP. Conclusion: These data demonstrate that lubricin forms a complex network with COMP involving both non-covalent and covalent bonds. This complex between lubricin and the cartilage protein COMP can be identified in the SF of patients with arthritis conditions including osteoarthritis (OA) and rheumatoid arthritis (RA). (C) 2017 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.
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3.
  • Björkman, Lena, 1965, et al. (author)
  • Data on the NADPH-oxidase activity induced by WKYMVm and galectin-3 in bone marrow derived and exudated neutrophils isolated from four different mouse strains.
  • 2017
  • In: Data in brief. - : Elsevier BV. - 2352-3409. ; 10, s. 349-353
  • Journal article (peer-reviewed)abstract
    • Neutrophils are the key players in inflammatory reactions and the release of superoxide through the NADPH-oxidase upon neutrophil activation contributes to bacterial clearance and surrounding tissue damage. Here we describe data on the mouse neutrophil NADPH-oxidase activation induced by the mouse formyl peptide receptor (Fpr) agonist WKYMVm and galectin-3. Neutrophils isolated from bone marrow, peritoneal exudated, and in vitro TNFα primed bone marrow neutrophils from four different laboratory strains (C57BL/6, DBA/1, BALB/c and NMRI) were used. Both Fpr agonist and galectin-3 activated neutrophils to release superoxide. No differences were observed in the amounts of superoxide released from neutrophils derived from four different strains.
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4.
  • Björkman, Lena, 1965, et al. (author)
  • Larixol is not an inhibitor of Gαi containing G proteins and lacks effect on signaling mediated by human neutrophil expressed formyl peptide receptors
  • 2024
  • In: Biochemical Pharmacology. - 0006-2952 .- 1873-2968. ; 220
  • Journal article (peer-reviewed)abstract
    • Neutrophils express several G protein-coupled receptors (GPCRs) connected to intracellular Gαi or Gαq containing G proteins for down-stream signaling. To dampen GPCR mediated inflammatory processes, several inhibitors targeting the receptors and/or their down-stream signals, have been developed. Potent and selective inhibitors for Gαq containing G proteins are available, but potent and specific inhibitors of Gαi containing G proteins are lacking. Recently, Larixol, a compound extracted from the root of Euphorbia formosana, was shown to abolish human neutrophil functions induced by N-formyl-methionyl-leucyl-phenylalanine (fMLF), an agonist recognized by formyl peptide receptor 1 (FPR1) which couple to Gαi containing G proteins. The inhibitory effect was suggested to be due to interference with/inhibition of signals transmitted by βγ complexes of the Gαi containing G proteins coupled to FPR1. In this study, we applied Larixol, obtained from two different commercial sources, to determine the receptor- and G protein- selectivity of this compound in human neutrophils. However, our data show that Larixol not only lacks inhibitory effect on neutrophil responses mediated through FPR1, but also on responses mediated through FPR2, a Gαi coupled GPCR closely related to FPR1. Furthermore, Larixol did not display any features as a selective inhibitor of neutrophil responses mediated through the Gαq coupled GPCRs for platelet activating factor and ATP. Hence, our results imply that the inhibitory effects described for the root extract of Euphorbia formosana are not mediated by Larixol and that the search for a selective inhibitor of G protein dependent signals generated by Gαi coupled neutrophil GPCRs must continue.
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5.
  • Björkman, Lena, 1965, et al. (author)
  • Neutrophil recruitment to inflamed joints can occur without cellular priming.
  • 2019
  • In: Journal of leukocyte biology. - 1938-3673. ; 105:6, s. 1123-1130
  • Journal article (peer-reviewed)abstract
    • Recruitment of neutrophils from blood to tissues is a cardinal event in inflammation during which neutrophils switch from a resting, naive state to a preactivated, primed phenotype; the priming process is characterized by alterations in the composition of cell surface adhesins, for example, shedding of l-selectin and mobilization of granule-stored integrins to the cell surface. Ligation of chemotactic receptors and interactions with the endothelial lining are established triggers of neutrophil priming and in line with this, in vivo transmigrated neutrophils obtained from tissues are typically highly primed. We here characterize the priming of neutrophils brought about by in vivo recruitment from blood to inflamed joints by the analyses of synovial fluid and blood from patients with inflammatory arthritis. For comparisons, we used controlled in vivo models of neutrophil transmigration to skin of healthy subjects. In contrast to the residing view and in vivo transmigrated neutrophils from skin models, neutrophils from synovial fluid were often surprisingly resting and phenotypically very similar to naive cells isolated from peripheral blood; synovial fluid cells often retained l-selectin and had undergone minimal up-regulation of integrin receptors. In complete agreement with our in vivo findings, cell-free synovial fluid was potently chemotactic without triggering alteration of surface receptors also in vitro. We conclude that tissue recruitment of neutrophils does not by default trigger l-selectin shedding and granule mobilization, and the chemoattractant(s) guiding neutrophils to synovial fluid apparently operate without inducing cellular priming.
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6.
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7.
  • Björkman, Lena, 1965, et al. (author)
  • Serum amyloid A mediates human neutrophil production of reactive oxygen species through a receptor independent of formyl peptide receptor like-1
  • 2008
  • In: Journal of Leukocyte Biology. - : Oxford University Press (OUP). - 0741-5400 .- 1938-3673. ; 83:2, s. 245-53
  • Journal article (peer-reviewed)abstract
    • Serum amyloid A (SAA) is one of the acute-phase reactants, a group of plasma proteins that increases immensely in concentration during microbial infections and inflammatory conditions, and a close relationship between SAA levels and disease activity in rheumatoid arthritis (RA) has been observed. RA is an inflammatory disease, where neutrophils play important roles, and SAA is thought to participate in the inflammatory reaction by being a neutrophil chemoattractant and inducer of proinflammatory cytokines. The biological effects of SAA are reportedly mediated mainly through formyl peptide receptor like-1 (FPRL1), a G protein-coupled receptor (GPCR) belonging to the formyl peptide receptor family. Here, we confirmed the affinity of SAA for FPRL1 by showing that stably transfected HL-60 cells expressing FPRL1 were activated by SAA and that the response was inhibited by the use of the FPRL1-specific antagonist WRWWWW (WRW4). We also show that SAA activates the neutrophil NADPH-oxidase and that a reserve pool of receptors is present in storage organelles mobilized by priming agents such as TNF-alpha and LPS from Gram-negative bacteria. The induced activity was inhibited by pertussis toxin, indicating the involvement of a GPCR. However, based on FPRL1-specific desensitization and use of FPRL1 antagonist WRW4, we found the SAA-mediated effects in neutrophils to be independent of FPRL1. Based on these findings, we conclude that SAA signaling in neutrophils is mediated through a GPCR, distinct from FPRL1. Future identification and characterization of the SAA receptor could lead to development of novel, therapeutic targets for treatment of RA.
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8.
  • Björkman, Lena, 1965, et al. (author)
  • The Neutrophil Response Induced by an Agonist for Free Fatty Acid Receptor 2 (GPR43) Is Primed by Tumor Necrosis Factor Alpha and by Receptor Uncoupling from the Cytoskeleton but Attenuated by Tissue Recruitment
  • 2016
  • In: Molecular and Cellular Biology. - : Informa UK Limited. - 0270-7306 .- 1098-5549. ; 36:20, s. 2583-2595
  • Journal article (peer-reviewed)abstract
    • Ligands with improved potency and selectivity for free fatty acid receptor 2 (FFA2R) have become available, and we here characterize the neutrophil responses induced by one such agonist (Cmp1) and one antagonist (CATPB). Cmp1 triggered an increase in the cytosolic concentration of Ca2+, and the neutrophils were then desensitized to Cmp1 and to acetate, a naturally occurring FFA2R agonist. The antagonist CATPB selectively inhibited responses induced by Cmp1 or acetate. The activated FFA2R induced superoxide anion secretion at a low level in naive blood neutrophils. This response was largely increased by tumor necrosis factor alpha (TNF-alpha) in a process associated with a recruitment of easily mobilizable granules, but neutrophils recruited to an aseptic inflammation in vivo were nonresponding. Superoxide production induced by Cmp1 was increased in latrunculin A-treated neutrophils, but no reactivation of desensitized FFA2R was induced by this drug, suggesting that the cytoskeleton is not directly involved in terminating the response. The functional and regulatory differences between the receptors that recognize short-chain fatty acids and formylated peptides, respectively, imply different roles of these receptors in the orchestration of inflammation and confirm the usefulness of a selective FFA2R agonist and antagonist as tools for the exploration of the precise role of the FFA2R.
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9.
  • Björkman, Lena, 1965, et al. (author)
  • The proinflammatory activity of recombinant serum amyloid A is not shared by the endogenous protein in the circulation.
  • 2010
  • In: Arthritis and rheumatism. - : Wiley. - 1529-0131 .- 0004-3591. ; 62:6, s. 1660-5
  • Journal article (peer-reviewed)abstract
    • OBJECTIVE: Elevated serum levels of the acute-phase protein serum amyloid A (SAA) are a marker for active rheumatoid arthritis (RA), and SAA can also be found in the tissues of patients with active RA. Based on a number of studies with recombinant SAA (rSAA), the protein has been suggested to be a potent proinflammatory mediator that activates human neutrophils, but whether endogenous SAA shares these proinflammatory activities has not been directly addressed. The present study was undertaken to investigate whether SAA in the plasma of patients with RA possesses proinflammatory properties and activates neutrophils in a manner similar to that of the recombinant protein. METHODS: Neutrophil activation was monitored by flow cytometry, based on L-selectin shedding from cell surfaces. Whole blood samples from healthy subjects and from RA patients with highly elevated SAA levels were studied before and after stimulation with rSAA as well as purified endogenous SAA. RESULTS: Recombinant SAA potently induced cleavage of L-selectin from neutrophils and in whole blood samples. Despite highly elevated SAA levels, L-selectin was not down-regulated on RA patient neutrophils as compared with neutrophils from healthy controls. Spiking SAA-rich whole blood samples from RA patients with rSAA, however, resulted in L-selectin shedding. In addition, SAA purified from human plasma was completely devoid of neutrophil- or macrophage-activating capacity. CONCLUSION: The present findings show that rSAA is proinflammatory but that this activity is not shared by endogenous SAA, either when present in the circulation of RA patients or when purified from plasma during an acute-phase response.
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10.
  • Björkman, Lena, 1965 (author)
  • The Role Of Serum Amyloid A In Inflammatory Disease - Proinflammatory Mediator Or Inert Biomarker?
  • 2010
  • Doctoral thesis (other academic/artistic)abstract
    • Abstract: Neutrophils are phagocytes of the innate immune system with prominent roles in host defense and are also believed to be important in autoimmune diseases such as rheumatoid arthritis (RA) by accumulating in inflamed joints and contribute to tissues destruction. Neutrophils differentiate in the bone-marrow and are mature cells when entering circulation with a cytoplasm packed with granules that contain toxic substances in addition to receptors that can be up-regulated to the cell surface during activation. Migration into the affected tissue is directed by mediators from the inflamed site which guides neutrophils along a chemotactic gradient and transfers the cell from resting- into a primed state. The inflammatory process triggers a systemic acute phase response characterized by the production of acute phase proteins (APP). The most prominent APP is serum amyloid A (SAA), the concentration of which can increase thousand fold in response to infection, aseptic inflammation or trauma. Patients with RA often have chronically elevated SAA in blood and joints and SAA has been implicated in the pathogenesis of RA. Recombinant SAA (rSAA) has been suggested to possess proinflammatory activities and act as a chemoattractant for neutrophils via a receptor called FPR2. A peptide (PBP10) with intracellular inhibitory activity was shown to allow discrimination between neutrophil signals mediated by FPR2 and the closely related FPR1. Next, the receptor specificity for rSAA was studied by use of PBP10 and another FPR2 specific inhibitor WRW4. rSAA affinity for FPR2 in transfected cell lines was corroborated and rSAA indeed activated primary human neutrophils. However, FPR2 was not responsible for mediating activation of primary human neutrophils by rSAA. Next, proinflammatory activity of rSAA was compared to that of endogenous SAA in circulation of RA patients. Using a sensitive marker for neutrophil activation in peripheral blood, endogenous SAA in circulation lacked proinflammatory activity and thus differed functionally from rSAA. Synovial neutrophils from patients with inflammatory arthritis and elevated SAA in joint fluid were next studied with respect to activation status. Synovial neutrophils displayed a surprisingly resting phenotype despite having transmigrated from peripheral blood to a compartment with endogenous SAA. Endogenous SAA, both in circulation and in joints, lack the proinflammatory properties present in the recombinant molecule. Key-words: neutrophils, serum amyloid A, rheumatoid arthritis ISBN: 978-91-628-8050-7
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11.
  • Christenson, Karin, et al. (author)
  • Collection of in vivo transmigrated neutrophils from human skin.
  • 2014
  • In: Methods in molecular biology (Clifton, N.J.). - Totowa, NJ : Humana Press. - 1940-6029. ; 1124, s. 39-52
  • Research review (peer-reviewed)abstract
    • A wealth of knowledge on the life and death of human neutrophils has been obtained by the in vitro study of isolated cells derived from peripheral blood. However, neutrophils are of main importance, physiologically as well as pathologically, after they have left circulation and transmigrated to extravascular tissues. The journey from blood to tissue is complex and eventful, and tissue neutrophils are in many aspects distinct from the cells left in circulation. Here we describe how to obtain human tissue neutrophils in a controlled experimental setting from aseptic skin lesions created by the application of negative pressure. One protocol enables the direct analysis of the blister content, infiltrating leukocytes as well as exudate fluid, and is a simple method to follow multiple parameters of aseptic inflammation in vivo. Also described is the skin chamber technique, a method based on denuded skin blisters which are subsequently covered by collection chambers filled with autologous serum. Although slightly more artificial as compared to analysis of the blister content directly, the cellular yield of this skin chamber method is sufficient to perform a large number of functional analyses of in vivo transmigrated cells.
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12.
  • Christenson, Karin, et al. (author)
  • Endogenous Acute Phase Serum Amyloid A Lacks Pro-Inflammatory Activity, Contrasting the Two Recombinant Variants That Activate Human Neutrophils through Different Receptors.
  • 2013
  • In: Frontiers in immunology. - : Frontiers Media SA. - 1664-3224. ; 4
  • Journal article (peer-reviewed)abstract
    • Most notable among the acute phase proteins is serum amyloid A (SAA), levels of which can increase 1000-fold during infections, aseptic inflammation, and/or trauma. Chronically elevated SAA levels are associated with a wide variety of pathological conditions, including obesity and rheumatic diseases. Using a recombinant hybrid of the two human SAA isoforms (SAA1 and 2) that does not exist in vivo, numerous in vitro studies have given rise to the notion that acute phase SAA is a pro-inflammatory molecule with cytokine-like properties. It is however unclear whether endogenous acute phase SAA per se mediates pro-inflammatory effects. We tested this in samples from patients with inflammatory arthritis and in a transgenic mouse model that expresses human SAA1. Endogenous human SAA did not drive production of pro-inflammatory IL-8/KC in either of these settings. Human neutrophils derived from arthritis patients displayed no signs of activation, despite being exposed to severely elevated SAA levels in circulation, and SAA-rich sera also failed to activate cells in vitro. In contrast, two recombinant SAA variants (the hybrid SAA and SAA1) both activated human neutrophils, inducing L-selectin shedding, production of reactive oxygen species, and production of IL-8. The hybrid SAA was approximately 100-fold more potent than recombinant SAA1. Recombinant hybrid SAA and SAA1 activated neutrophils through different receptors, with recombinant SAA1 being a ligand for formyl peptide receptor 2 (FPR2). We conclude that even though recombinant SAAs can be valuable tools for studying neutrophil activation, they do not reflect the nature of the endogenous protein.
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13.
  • Christenson, Karin, et al. (author)
  • In vivo-transmigrated human neutrophils are resistant to antiapoptotic stimulation.
  • 2011
  • In: Journal of leukocyte biology. - : Oxford University Press (OUP). - 1938-3673 .- 0741-5400. ; 90:6, s. 1055-63
  • Journal article (peer-reviewed)abstract
    • Neutrophils respond to microbial invasion or injury by transmigration from blood to tissue. Transmigration involves cellular activation and degranulation, resulting in altered levels of surface receptors and changed responsiveness to certain stimuli. Thus, fundamental functional changes are associated with neutrophil transmigration from blood to tissue. Neutrophils isolated from peripheral blood spontaneously enter apoptosis, a process that can be accelerated or delayed by different pro- or antiapoptotic factors. How tissue neutrophils that have transmigrated in vivo regulate cell death is poorly understood. In this study, in vivo-transmigrated neutrophils (tissue neutrophils) were collected using a skin chamber technique and compared with blood neutrophils from the same donors with respect to regulation of cell death. Skin chamber fluid contained a variety of cytokines known to activate neutrophils and regulate their lifespan. Freshly prepared tissue neutrophils had elevated activity of caspase 3/7 but were fully viable; spontaneous cell death after in vitro culture was also similar between blood and tissue neutrophils. Whereas apoptosis of cultured blood neutrophils was delayed by soluble antiapoptotic factors (e.g., TLR ligands), tissue neutrophils were completely resistant to antiapoptotic stimulation, even though receptors were present and functional. In vitro transmigration of blood neutrophils into skin chamber fluid did not fully confer resistance to antiapoptotic stimulation, indicating that a block of antiapoptotic signaling occurs specifically during in vivo transmigration. We describe a novel, functional alteration that takes place during in vivo transmigration and highlights the fact that life and death of neutrophils may be regulated differently in blood and tissue.
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14.
  • Christenson, Karin, et al. (author)
  • Regulation of Neutrophil Apoptosis Differs after in vivo Transmigration to Skin Chambers and Synovial Fluid: A Role for Inflammasome-Dependent Interleukin-1 beta Release
  • 2013
  • In: Journal of Innate Immunity. - : S. Karger AG. - 1662-811X .- 1662-8128. ; 5:4, s. 377-388
  • Journal article (peer-reviewed)abstract
    • Short-lived neutrophils are major players in inflammation, arriving early to infected and/or injured tissues. After performed duty, neutrophils are programmed to die by apoptosis and are thereafter rapidly cleared by other phagocytes. In vitro, modulation of the apoptotic process has been thoroughly investigated in neutrophils isolated from peripheral blood, but less is known about the regulation of this process in neutrophils derived from extravascular tissues. We recently demonstrated that neutrophils having transmigrated in vivo, obtained from experimental skin chambers of healthy human subjects, are resistant to the death-delaying signals induced by a range of antiapoptotic stimuli. In the current study, we show that skin chamber neutrophils spontaneously secrete high levels of antiapoptotic interleukin (IL)-1 beta which delays neutrophil apoptosis. Contrary to skin chamber fluid, synovial fluid from patients with rheumatic arthritis contained only moderate levels of IL-1 beta, and neutrophils taken from this site were fully responsive to antiapoptotic stimulation during in vitro culture. Our data demonstrate that resistance to antiapoptotic stimulation is not a general feature of tissue neutrophils and imply that autocrine IL-1 beta signaling could be an important factor in determining how life and death of neutrophils is regulated in inflamed tissues.
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15.
  • Christenson, Karin, et al. (author)
  • Serum amyloid A inhibits apoptosis of human neutrophils via a P2X7-sensitive pathway independent of formyl peptide receptor-like 1
  • 2008
  • In: Journal of Leukocyte Biology. - : Oxford University Press (OUP). - 0741-5400 .- 1938-3673. ; 83:1, s. 139-48
  • Journal article (peer-reviewed)abstract
    • Neutrophil apoptosis is important for the termination of inflammatory reactions, in that it ensures placid clearance of these potently cytotoxic cells. Various proinflammatory cytokines delay neutrophil apoptosis, which may result in accumulation of these cells, sometimes accompanied by tissue destruction, potentially leading to various inflammatory disease states. Rheumatoid arthritis (RA) is characterized frequently by elevated levels of the acute-phase reactant serum amyloid A (SAA) in circulation and in tissues. SAA is emerging as a cytokine-like molecule with the ability to activate various proinflammatory processes, many of which involve signaling via the formyl peptide receptor-like 1 (FPRL1). In this study, we show that SAA, purified from plasma from RA patients or in recombinant form, suppressed apoptosis of human neutrophils. Blocking FPRL1 did not lessen the antiapoptotic effects of SAA, implying the action of a receptor distinct from FPRL1. In contrast, antagonists of the nucleotide receptor P2X7 abrogated the antiapoptotic effect of SAA completely but did not block intracellular calcium transients evoked by SAA stimulation. Based on these results and also the finding that blocking P2X7 inhibited antiapoptotic actions of unrelated stimuli (LPS and GM-CSF), we propose that P2X7 is a general mediator of antiapoptotic signaling in neutrophils rather than a bona fide SAA receptor.
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16.
  • Dahlgren, Claes, 1949, et al. (author)
  • G protein coupled pattern recognition receptors expressed in neutrophils: Recognition, activation/modulation, signaling and receptor regulated functions.
  • 2022
  • In: Immunological reviews. - : Wiley. - 1600-065X .- 0105-2896. ; 314:1, s. 69-92
  • Research review (peer-reviewed)abstract
    • Neutrophils, the most abundant white blood cell in human blood, express receptors that recognize damage/microbial associated pattern molecules of importance for cell recruitment to sites of inflammation. Many of these receptors belong to the family of G protein coupled receptors (GPCRs). These receptor-proteins span the plasma membrane in expressing cells seven times and the down-stream signaling rely in most cases on an activation of heterotrimeric G proteins. The GPCRs expressed in neutrophils recognize a number of structurally diverse ligands (activating agonists, allosteric modulators, and inhibiting antagonists) and share significant sequence homologies. Studies of receptor structure and function have during the last 40years generated important information on GPCR biology in general; this knowledge aids in the overall understanding of general pharmacological principles, governing regulation of neutrophil function and inflammatory processes, including novel leukocyte receptor activities related to ligand recognition, biased/functional selective signaling, allosteric modulation, desensitization, and reactivation mechanisms as well as communication (receptor transactivation/cross-talk) between GPCRs. This review summarizes the recent discoveries and pharmacological hallmarks with focus on some of the neutrophil expressed pattern recognition GPCRs. In addition, unmet challenges, including recognition by the receptors of diverse ligands and how biased signaling mediate different biological effects are described/discussed.
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17.
  • Dahlgren, Claes, 1949, et al. (author)
  • Neutrophil Signaling That Challenges Dogmata of G Protein-Coupled Receptor Regulated Functions
  • 2020
  • In: ACS Pharmacology and Translational Science. - : American Chemical Society (ACS). - 2575-9108. ; 3:2, s. 203-220
  • Research review (peer-reviewed)abstract
    • Activation as well as recruitment of neutrophils, the most abundant leukocyte in human blood, to sites of infection/inflammation largely rely on surface-exposed chemoattractant receptors. These receptors belong to the family of 7-transmembrane domain receptors also known as G protein-coupled receptors (GPCRs) due to the fact that part of the downstream signaling relies on an activation of heterotrimeric G proteins. The neutrophil GPCRs share significant sequence homologies but bind many structurally diverse activating (agonistic) and inhibiting (antagonistic) ligands, ranging from fatty acids to purines, peptides, and lipopeptides. Recent structural and functional studies of neutrophil receptors have generated important information on GPCR biology in general; this knowledge aids in the overall understanding of general pharmacological principles, governing regulation of neutrophil function and inflammatory processes, including novel leukocyte receptor activities related to ligand recognition, biased/functional selective signaling, allosteric modulation, desensitization mechanisms and reactivation, and communication (cross-talk) between GPCRs. This review summarizes the recent discoveries and pharmacological hallmarks with focus on neutrophil GPCRs. In addition, unmet challenges are dealt with, including recognition by the receptors of diverse ligands and how biased signaling mediates different biological effects. © 2020 American Chemical Society.
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18.
  • Dahlstrand Rudin, Agnes, et al. (author)
  • The neutrophil subset defined by CD177 expression is preferentially recruited to gingival crevicular fluid in periodontitis
  • 2021
  • In: Journal of Leukocyte Biology. - : WILEY. - 0741-5400 .- 1938-3673. ; 109:2, s. 349-362
  • Journal article (peer-reviewed)abstract
    • In recent years, the concept of distinct subpopulations of human neutrophils has attracted much attention. One bona fide subset marker, exclusively expressed by a proportion of circulating neutrophils in a given individual, and therefore dividing neutrophils in two distinct subpopulations, is the glycoprotein CD177. CD177 is expressed on the plasma and granule membranes of 0-100% of circulating neutrophils depending on the donor. Several in vitro studies have linked CD177 to neutrophil transmigration, yet very few have looked at the role of CD177 for tissue recruitment in vivo. We investigate whether the CD177(+)and CD177(-)neutrophil subsets differ in their propensity to migrate to both aseptic- and microbe-triggered inflamed human tissues. Microbe-triggered neutrophil migration was evaluated in samples of gingival crevicular fluid (GCF) from patients with periodontitis, whereas neutrophil migration to aseptic inflammation was evaluated in synovial fluid from patients with inflammatory arthritis, as well as in exudate from experimental skin chambers applied on healthy donors. We found that the proportion of CD177(+)neutrophils was significantly higher in GCF from patients with periodontitis, as compared to blood from the same individuals. Such accumulation of CD177(+)neutrophils was not seen in the two models of aseptic inflammation. Moreover, the proportion of CD177(+)neutrophils in circulation was significantly higher in the periodontitis patient group, as compared to healthy donors. Our data indicate that the CD177(+)neutrophil subset is preferentially recruited to the gingival crevice of periodontitis patients, and may imply that this subtype is of particular importance for situations of microbe-driven inflammation.
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19.
  • Davidsson, Lisa, et al. (author)
  • A simple skin blister technique for the study of in vivo transmigration of human leukocytes.
  • 2013
  • In: Journal of immunological methods. - : Elsevier BV. - 1872-7905 .- 0022-1759. ; 393:1-2, s. 8-17
  • Journal article (peer-reviewed)abstract
    • The study of human leukocytes is almost exclusively conducted using cells isolated from peripheral blood. This is especially true for neutrophils, despite the fact that these cells are of main (pathological) importance in extravascular tissues upon e.g., infection and/or tissue damage. The journey from circulation to tissue is typically associated with a number of cellular changes, making the cells primed, or hyper-responsive, and in many aspects distinct from the cells present in circulation. Models to obtain in vivo transmigrated leukocytes from human tissue are available, but not widely used. We describe here an easy-to-use model for the study of local inflammation, stemming from limited tissue damage, which can be used to isolate viable and functional leukocytes. The model is based on the generation of aseptic skin blisters, formed by the application of negative pressure, and allows for investigations of the cellular infiltrate as well as of soluble mediators present in the exudate. We believe that this method, combined with modern analysis equipment suitable for small volumes and cell numbers, could be of great use for increasing our understanding of the nature and function of leukocytes that have left circulation and transmigrated to inflamed tissues.
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20.
  • Davidsson, Lisa, et al. (author)
  • In Vivo Transmigrated Human Neutrophils Are Highly Primed for Intracellular Radical Production Induced by Monosodium Urate Crystals.
  • 2020
  • In: International journal of molecular sciences. - : MDPI AG. - 1422-0067. ; 21:11
  • Journal article (peer-reviewed)abstract
    • Gout is an inflammatory disease caused by monosodium urate (MSU) crystals. The role of neutrophils in gout is less clear, although several studies have shown neutrophil extracellular trap (NET) formation in acutely inflamed joints of gout patients. MSU crystals are known to induce the production of reactive oxygen species (ROS) and NET formation in neutrophils isolated from blood, but there is inconclusive knowledge on the localization of ROS production as well as whether the ROS are required for NET formation. In this report we demonstrate that MSU crystals activate human neutrophils to produce ROS exclusively in intracellular compartments. Additionally, in vivo transmigrated neutrophils derived from experimental skin chambers displayed markedly increased ROS production as compared to resting blood neutrophils. We also confirmed that MSU stimulation potently induced NET formation, but this response was not primed in in vivo transmigrated neutrophils. In line with this we found that MSU-triggered NET formation was independent of ROS production and proceeded normally in neutrophils from patients with dysfunctional respiratory burst (chronic granulomatous disease (CGD) and complete myeloperoxidase (MPO) deficiency). Our data indicate that in vivo transmigrated neutrophils are markedly primed for oxidative responses to MSU crystals and that MSU triggered NET formation is independent of ROS production.
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21.
  • Evengård, Birgitta, 1952-, et al. (author)
  • Healthy ecosystems for human and animal health : Science diplomacy for responsible development in the Arctic
  • 2021
  • In: Polar Record. - : Cambridges Institutes Press. - 0032-2474 .- 1475-3057. ; 57
  • Journal article (peer-reviewed)abstract
    • Climate warming is occurring most rapidly in the Arctic, which is both a sentinel and a driver of further global change. Ecosystems and human societies are already affected by warming. Permafrost thaws and species are on the move, bringing pathogens and vectors to virgin areas. During a five-year project, the CLINF - a Nordic Center of Excellence, funded by the Nordic Council of Ministers, has worked with the One Health concept, integrating environmental data with human and animal disease data in predictive models and creating maps of dynamic processes affecting the spread of infectious diseases. It is shown that tularemia outbreaks can be predicted even at a regional level with a manageable level of uncertainty. To decrease uncertainty, rapid development of new and harmonised technologies and databases is needed from currently highly heterogeneous data sources. A major source of uncertainty for the future of contaminants and infectious diseases in the Arctic, however, is associated with which paths the majority of the globe chooses to follow in the future. Diplomacy is one of the most powerful tools Arctic nations have to influence these choices of other nations, supported by Arctic science and One Health approaches that recognise the interconnection between people, animals, plants and their shared environment at the local, regional, national and global levels as essential for achieving a sustainable development for both the Arctic and the globe.
  •  
22.
  • Flowers, Sarah A., et al. (author)
  • Decrease of core 2 O-glycans on synovial lubricin in osteoarthritis reduces galectin-3 mediated crosslinking
  • 2020
  • In: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 295:47, s. 16023-16036
  • Journal article (peer-reviewed)abstract
    • The synovial fluid glycoprotein lubricin (also known as proteoglycan 4) is a mucin-type O-linked glycosylated biological lubricant implicated to be involved in osteoarthritis (OA) development. Lubricin's ability to reduce friction is related to its glycosylation consisting of sialylated and unsialylated Tn-antigens and core 1 and core 2 structures. The glycans on lubricin have also been suggested to be involved in crosslinking and stabilization of the lubricating superficial layer of cartilage by mediating interaction between lubricin and galectin-3. However, with the spectrum of glycans being found on lubricin, the glycan candidates involved in this interaction were unknown. Here, we confirm that the core 2 O-linked glycans mediate this lubricin-galectin-3 interaction, shown by surface plasmon resonance data indicating that recombinant lubricin (rhPRG4) devoid of core 2 structures did not bind to recombinant galectin-3. Conversely, transfection of Chinese hamster ovary cells with the core 2 GlcNAc transferase acting on a mucin-type O-glycoprotein displayed increased galectin-3 binding. Both the level of galectin-3 and the galectin-3 interactions with synovial lubricin were found to be decreased in late-stage OA patients, coinciding with an increase in unsialylated core 1 O-glycans (T-antigens) and Tn-antigens. These data suggest a defect in crosslinking of surface-active molecules in OA and provide novel insights into OA molecular pathology.
  •  
23.
  • Flowers, Sarah A., et al. (author)
  • Lubricin binds cartilage proteins, cartilage oligomeric matrix protein, fibronectin and collagen II at the cartilage surface
  • 2017
  • In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
  • Journal article (peer-reviewed)abstract
    • Lubricin, a heavily O-glycosylated protein, is essential for boundary lubrication of articular cartilage. Strong surface adherence of lubricin is required given the extreme force it must withstand. Disulfide bound complexes of lubricin and cartilage oligomeric matrix protein (COMP) have recently been identified in arthritic synovial fluid suggesting they may be lost from the cartilage surface in osteoarthritis and inflammatory arthritis. This investigation was undertaken to localise COMP-lubricin complexes within cartilage and investigate if other cartilage proteins are involved in anchoring lubricin to the joint. Immunohistochemical analysis of human cartilage biopsies showed lubricin and COMP co-localise to the cartilage surface. COMP knockout mice, however, presented with a lubricin layer on the articular cartilage leading to the further investigation of additional lubricin binding mechanisms. Proximity ligation assays (PLA) on human cartilage biopsies was used to localise additional lubricin binding partners and demonstrated that lubricin bound COMP, but also fibronectin and collagen II on the cartilage surface. Fibronectin and collagen II binding to lubricin was confirmed and characterised by solid phase binding assays with recombinant lubricin fragments. Overall, COMP, fibronectin and collagen II bind lubricin, exposed on the articular cartilage surface suggesting they may be involved in maintaining essential boundary lubrication.
  •  
24.
  • Forsman, Huamei, et al. (author)
  • AZ2158 is a more potent formyl peptide receptor 1 inhibitor than the commonly used peptide antagonists in abolishing neutrophil chemotaxis.
  • 2023
  • In: Biochemical pharmacology. - : Elsevier BV. - 1873-2968 .- 0006-2952. ; 211
  • Journal article (peer-reviewed)abstract
    • Formyl peptide receptor 1 (FPR1), a G protein-coupled receptor expressed in phagocytes, recognizes short N-formylated peptides originating from proteins synthesized by bacteria and mitochondria. Such FPR1 agonists are important regulators of neutrophil functions and by that, determinants of inflammatory reactions. As FPR1 is implicated in promoting both pro-inflammatory and pro-resolving responses associated with inflammatory diseases, characterization of ligands that potently and selectively modulate FPR1 induced functions might be of high relevance. Accordingly, a number of FPR1 specific antagonists have been identified and shown to inhibit agonist binding or receptor down-stream signaling as well as neutrophil functions such as granule secretion and NADPH oxidase activity. The inhibitory effect on neutrophil chemotaxis induced by FPR1 agonists has generally not been part of basic antagonist characterization. In this study we show that the inhibitory effects on neutrophil chemotaxis of established FPR1 antagonists (i.e., cyclosporin H, BOC1 and BOC2) are limited. Our data demonstrate that the recently described small molecule AZ2158 is a potent and selective FPR1 antagonist in human neutrophils. In contrast to the already established FPR1 antagonists, AZ2158 also potently inhibits chemotaxis. Whereas the cyclosporin H inhibition was agonist selective, AZ2158 inhibited the FPR1 response induced by both a balanced and a biased FPR1 agonist equally well. In accordance with the species specificity described for many FPR1 ligands, AZ2158 was not recognized by the mouse orthologue of FPR1. Our data demonstrate that AZ2158 may serve as an excellent tool compound for further mechanistic studies of human FPR1 mediated activities.
  •  
25.
  • Forsman, Huamei, et al. (author)
  • Function and regulation of GPR84 in human neutrophils
  • 2024
  • In: British Journal of Pharmacology. - : Wiley. - 0007-1188 .- 1476-5381. ; 181:10, s. 1536-1549
  • Research review (peer-reviewed)abstract
    • Human neutrophils are components of the innate immune system and are the most abundant white blood cells in the circulation. They are professional phagocytes and express several G protein-coupled receptors (GPCRs), which are essential for proper neutrophil functions. So far, the two formyl peptide receptors, FPR1 and FPR2, have been the most extensively studied group of neutrophil GPCRs, but recently, a new group, the free fatty acid (FFA) receptors, has attracted growing attention. Neutrophils express two FFA receptors, GPR84 and FFA2, which sense medium- and short-chain fatty acids respectively, and display similar activation profiles. The exact pathophysiological role of GPR84 is not yet fully understood, but it is generally regarded as a pro-inflammatory receptor that mediates neutrophil activation. In this review, we summarize current knowledge of how GPR84 affects human neutrophil functions and discuss the regulatory mechanisms that control these responses, focusing on the similarities and differences in comparison to the two FPRs and FFA2.
  •  
26.
  • Fredriksson, Johanna, et al. (author)
  • GRK2 selectively attenuates the neutrophil NADPH-oxidase response triggered by beta-arrestin recruiting GPR84 agonists
  • 2022
  • In: Biochimica Et Biophysica Acta-Molecular Cell Research. - : Elsevier BV. - 0167-4889. ; 1869:7
  • Journal article (peer-reviewed)abstract
    • In order to avoid a prolonged pro-inflammatory neutrophil response, signaling downstream of an agonist-activated G protein-coupled receptor (GPCR) has to be rapidly terminated. Among the family of GPCR kinases (GRKs) that regulate receptor phosphorylation and signaling termination, GRK2, which is highly expressed by immune cells, plays an important role. The medium chain fatty acid receptor GPR84 as well as formyl peptide receptor 2 (FPR2), receptors expressed in neutrophils, play a key role in regulating inflammation. In this study, we investigated the effects of GRK2 inhibitors on neutrophil functions induced by GPR84 and FPR2 agonists. GRK2 was shown to be expressed in human neutrophils and analysis of subcellular fractions revealed a cytosolic localization. The GRK2 inhibitors enhanced and prolonged neutrophil production of reactive oxygen species (ROS) induced by GPR84-but not FPR2-agonists, suggesting a receptor selective function of GRK2. This suggestion was supported by beta-arrestin recruitment data. The ROS production induced by a non beta-arrestin recruiting GPR84 agonist was not affected by the GRK2 inhibitor. Termination of this beta-arrestin independent response relied, similar to the response induced by FPR2 agonists, primarily on the actin cytoskeleton. In summary, we show that GPR84 utilizes GRK2 in concert with beta-arrestin and actin cytoskeleton dependent processes to fine-tune the activity of the ROS generating NADPH-oxidase in neutrophils.
  •  
27.
  • Fu, Huamei, 1979, et al. (author)
  • The two neutrophil members of the formylpeptide receptor family activate the NADPH-oxidase through signals that differ in sensitivity to a gelsolin derived phosphoinositide-binding peptide
  • 2004
  • In: BMC cell biology. - : Springer Science and Business Media LLC. - 1471-2121. ; 5:1
  • Journal article (peer-reviewed)abstract
    • BACKGROUND: The formylpeptide receptor family members FPR and FPRL1, expressed in myeloid phagocytes, belong to the G-protein coupled seven transmembrane receptor family (GPCRs). They share a high degree of sequence similarity, particularly in the cytoplasmic domains involved in intracellular signaling. The established model of cell activation through GPCRs states that the receptors isomerize from an inactive to an active state upon ligand binding, and this receptor transformation subsequently activates the signal transducing G-protein. Accordingly, the activation of human neutrophil FPR and FPRL1 induces identical, pertussis toxin-sensitive functional responses and a transient increase in intracellular calcium is followed by a secretory response leading to mobilization of receptors from intracellular stores, as well as a release of reactive oxygen metabolites. RESULTS: We report that a cell permeable ten amino acid peptide (PBP10) derived from the phosphatidylinositol 4,5-bisphosphate (PIP2) binding region of gelsolin (an uncapper of actin filaments) blocks granule mobilization as well as secretion of oxygen radicals. The inhibitory effect of PBP10 is, however, receptor specific and affects the FPRL1-, but not the FPR-, induced cellular response. The transient rise in intracellular calcium induced by the active receptors is not affected by PBP10, suggesting that the blockage occurs in a parallel, novel signaling pathway used by FPRL1 to induce oxygen radical production and secretion. Also the FPR can activate neutrophils through a PBP10-sensitive signaling pathway, but this signal is normally blocked by the cytoskeleton. CONCLUSIONS: This study demonstrates that the two very closely related chemoattractant receptors, FPR and FPRL1, use distinct signaling pathways in activation of human neutrophils. The PIP2-binding peptide PBP10 selectively inhibits FPRL1-mediated superoxide production and granule mobilization. Furthermore, the activity of this novel PBP10 sensitive pathway in neutrophils is modulated by the actin cytoskeleton network.
  •  
28.
  • Huang, Shan, et al. (author)
  • Cathepsin g Degrades Both Glycosylated and Unglycosylated Regions of Lubricin, a Synovial Mucin
  • 2020
  • In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
  • Journal article (peer-reviewed)abstract
    • Lubricin (PRG4) is a mucin type protein that plays an important role in maintaining normal joint function by providing lubrication and chondroprotection. Improper lubricin modification and degradation has been observed in idiopathic osteoarthritis (OA), while the detailed mechanism still remains unknown. We hypothesized that the protease cathepsin G (CG) may participate in degrading lubricin in synovial fluid (SF). The presence of endogenous CG in SF was confirmed in 16 patients with knee OA. Recombinant human lubricin (rhPRG4) and native lubricin purified from the SF of patients were incubated with exogenous CG and lubricin degradation was monitored using western blot, staining by Coomassie or Periodic Acid-Schiff base in gels, and with proteomics. Full length lubricin (∼300 kDa), was efficiently digested with CG generating a 25-kDa protein fragment, originating from the densely glycosylated mucin domain (∼250 kDa). The 25-kDa fragment was present in the SF from OA patients, and the amount was increased after incubation with CG. A CG digest of rhPRG4 revealed 135 peptides and 72 glycopeptides, and confirmed that the protease could cleave in all domains of lubricin, including the mucin domain. Our results suggest that synovial CG may take part in the degradation of lubricin, which could affect the pathological decrease of the lubrication in degenerative joint disease. © 2020, The Author(s).
  •  
29.
  • Jin, Chunsheng, et al. (author)
  • Human Synovial Lubricin Expresses Sialyl Lewis x Determinant and Has L-selectin Ligand Activity
  • 2012
  • In: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 287:43, s. 35922-35933
  • Journal article (peer-reviewed)abstract
    • Lubricin (or proteoglycan 4 (PRG4)) is an abundant mucin-like glycoprotein in synovial fluid (SF) and a major component responsible for joint lubrication. In this study, it was shown that O-linked core 2 oligosaccharides (Gal beta 1-3(GlcNAc beta 1-6)GalNAc alpha 1-Thr/Ser) on lubricin isolated from rheumatoid arthritis SF contained both sulfate and fucose residues, and SF lubricin was capable of binding to recombinant L-selectin in a glycosylation-dependent manner. Using resting human polymorphonuclear granulocytes (PMN) from peripheral blood, confocal microscopy showed that lubricin coated circulating PMN and that it partly co-localized with L-selectin expressed by these cells. In agreement with this, activation-induced shedding of L-selectin also mediated decreased lubricin binding to PMN. It was also found that PMN recruited to inflamed synovial area and fluid in rheumatoid arthritis patients kept a coat of lubricin. These observations suggest that lubricin is able to bind to PMN via an L-selectin-dependent and -independent manner and may play a role in PMN-mediated inflammation.
  •  
30.
  • Karlsson, Jennie, 1979, et al. (author)
  • A methodological approach to studies of desensitization of the formyl peptide receptor: Role of the read out system, reactive oxygen species and the specific agonist used to trigger neutrophils.
  • 2010
  • In: Journal of immunological methods. - : Elsevier BV. - 1872-7905 .- 0022-1759. ; 352:1-2, s. 45-53
  • Journal article (peer-reviewed)abstract
    • Neutrophil accumulation at an inflammatory site or an infected tissue is dependent on the recognition of chemotactic peptides that bind to G-protein coupled receptors (GPCRs) exposed on the surface of the inflammatory cells. A GPCR activated by a chemoattractant quickly becomes refractory to further stimulation by ligands using the same receptor. This desensitization phenomenon has been used frequently to characterize new receptor agonists and to determine receptor hierarchies. In this study we show that desensitization patterns differ depending on what read out systems are used to follow neutrophil activity. When monitoring release of superoxide, neutrophils were readily desensitized against repeated stimulations with the prototypical agonist formylmethionyl-leucyl-phenylalanine (fMLF). In contrast, neutrophils were not desensitized for fMLF when cell activity was determined by intracellular calcium ([Ca(2+)](i)). The difference observed was dependent on inactivation of the agonist in one read out system but not in the other, and we suggest several different solutions to the problem. Agonist inactivation occurs through a myeloperoxidase (MPO)/hydrogen peroxide catalyzed reaction, and the problem could be avoided by using a FACS based technique to measure the change in [Ca(2+)](i), by the use of an agonist insensitive to the MPO/hydrogen peroxide-system or, by adding an MPO inhibitor or a scavenger that removes either superoxide/hydrogen peroxide or the MPO-derived metabolites.
  •  
31.
  • Kattge, Jens, et al. (author)
  • TRY plant trait database - enhanced coverage and open access
  • 2020
  • In: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
  • Journal article (peer-reviewed)abstract
    • Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
  •  
32.
  • Kouri, V. P., et al. (author)
  • Neutrophils produce interleukin-17B in rheumatoid synovial tissue
  • 2014
  • In: Rheumatology. - : Oxford University Press (OUP). - 1462-0324 .- 1462-0332. ; 53:1, s. 39-47
  • Journal article (peer-reviewed)abstract
    • Objective: T helper 17 (Th17) and mast cells produce IL-17A in RA and critically contribute to the pathogenesis of RA. However, the complete IL-17 cytokine profile in RA is unknown. The aim of the study was to systematically study the expression of IL-17 family cytokines in RA. Methods: The expression of all IL-17 cytokines in RA synovium and pannus as well as in the synovium of OA was determined using quantitative RT-PCR (qRT-PCR). IL-17A and IL-17B were immunostained. Peripheral blood neutrophils were analysed for IL-17B. The effect of IL-17B alone or in combination with TNF-α was tested in vitro on fibroblasts and endothelial cells. Results: In all tissues IL-17B was the most expressed IL-17 family cytokine, found in lining but most strongly expressed in human neutrophil elastase containing polymorphonuclear cells. This pattern was distinct from that of IL-17A, which was found in mast cell tryptase immunoreactive cells. Circulating neutrophils contained IL-17B, verifying the in vivo results. Fibroblasts up-regulated the expression of IL-17RB, a putative receptor of IL-17B, after TNF-α stimulation. IL-17B significantly enhanced TNF-α-induced production of G-CSF and IL-6 in fibroblasts. Conclusion: IL-17B, which is present in synovium, may contribute to the pathogenesis of RA. IL-17B can enhance the effects of TNF-α on the production of cytokines and chemokines that control immune cell trafficking and neutrophil homeostasis in the inflamed tissues. © The Author 2013. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved.
  •  
33.
  • Landgren, Anton J., 1989, et al. (author)
  • Incidence of and risk factors for nephrolithiasis in patients with gout and the general population, a cohort study
  • 2017
  • In: Arthritis Research & Therapy. - : Springer Science and Business Media LLC. - 1478-6354 .- 1478-6362. ; 19
  • Journal article (peer-reviewed)abstract
    • Background: Nephrolithiasis (NL) is known to be associated with gout, although there are few comparative studies on risk and risk factors for NL in gout compared to population cohorts. In this cohort study we investigated: (1) overall incidence of NL in gout (cases) and general population controls; (2) risk and risk factors (common comorbidities and medications) for first-time NL in cases and controls separately. Methods: Cases (n = 29,968) and age-matched and sex-matched controls (n = 138,678) were identified from the regional healthcare database in western Sweden (VEGA). The analyzed risk factors (comorbidities and current medication use) for first-time NL, and socioeconomic factors were retrieved from VEGA and other national Swedish registers. For cases, follow up began on 1 January 2006 or on the first diagnosis of gout if this occurred later, and for controls on their index patient's first diagnosis of gout. Follow up ended on death, emigration or 31 December 2012. Incidence rates (IR) per 1000 person-years and hazard ratios (HR) were calculated. The incidence calculations were performed for cases (regardless of prior NL) and their controls. HRs with first occurrence of NL as outcome were calculated only in those without previous NL. Results: In cases there were 678 NL events (IR: 6.16 events per 1000 person-years (95% CI: 5.70-6.64) and in controls 2125 NL events (IR 3.85 events per 1000 person-years (95% CI: 3.69-4.02), resulting in an age-sex-adjusted incidence rate ratio of 1.60 (95% CI: 1.47-1.74). Point estimates for predictive factors were similar in cases and controls, except for a significant interaction for losartan which increased the risk of NL only in controls (HR = 1.49 (95% CI: 1.03-2.14). Loop diuretics significantly decreased the risk of NL by 30-34% in both cases and controls. Further significant predictors of NL in gout cases were male sex, diabetes and obesity and in controls male sex and kidney disease. Conclusions: The risk (age and sex adjusted) of NL was increased by 60% in cases compared to controls. None of the commonly used medications increased the risk of NL in gout patients.
  •  
34.
  • Lind, Simon, 1993, et al. (author)
  • Functional selective ATP receptor signaling controlled by the free fatty acid receptor 2 through a novel allosteric modulation mechanism.
  • 2019
  • In: FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - 1530-6860. ; 33:6
  • Journal article (peer-reviewed)abstract
    • A nonactivating allosteric modulator of free fatty acid receptor 2 (FFA2R, also called GPCR 43) turns both propionate (an orthosteric FFA2R agonist) and ATP (an agonist for the purinergic P2Y2 receptor), into potent activating ligands that trigger an assembly of the superoxide-generating neutrophil NADPH oxidase. The ATP-induced activation requires the participation of FFA2R, and the signaling is biased toward oxidase activation, leaving the ATP-induced rise in intracellular Ca2+ unaffected. No NADPH oxidase activity was induced by ATP when propionate replaced the allosteric modulator. Signaling downstream of propionate-activated FFA2Rs was insensitive to Gαq inhibition, but the crosstalk activation involving both FFA2R and P2Y2R relied on Gαq signaling. The receptor crosstalk, by which allosterically modulated FFA2Rs communicate with P2Y2Rs and generate NADPH oxidase activating signals downstream of Gαq, represent a novel mechanism by which GPCR activities can be regulated from inside the plasma membrane. Further, the finding that an allosteric FFA2R modulator sensitizes not only the response induced by orthosteric FFA2R agonists, but also the response induced by ATP (P2Y2R-specific agonist) and formyl peptide receptor-specific agonists, violates the receptor restriction characteristics normally defining the selectivity of allosteric GPCR modulators.-Lind, S., Holdfeldt, A., Mårtensson, J., Sundqvist, M., Björkman, L., Forsman, H., Dahlgren, C. Functional selective ATP receptor signaling controlled by the free fatty acid receptor 2 through a novel allosteric modulation mechanism.
  •  
35.
  • Lind, Simon, 1993, et al. (author)
  • Interdependent allosteric free fatty acid receptor 2 modulators synergistically induce functional selective activation and desensitization in neutrophils
  • 2020
  • In: Biochimica Et Biophysica Acta-Molecular Cell Research. - : Elsevier BV. - 0167-4889. ; 1867:6
  • Journal article (peer-reviewed)abstract
    • The non-activating allosteric modulator AZ1729, specific for free fatty acid receptor 2 (FFAR2), transfers the orthosteric FFAR2 agonists propionate and the P2Y(2)R specific agonist ATP into activating ligands that trigger an assembly of the neutrophil superoxide generating NADPH-oxidase. The homologous priming effect on the propionate response and the heterologous receptor cross-talk sensitized ATP response mediated by AZ1729 are functional characteristics shared with Cmp58, another non-activating allosteric FFAR2 modulator. In addition, AZ1729 also turned Cmp58 into a potent activator of the superoxide generating neutrophil NADPH-oxidase, and in agreement with the allosteric modulation concept, the effect was reciprocal in that Cmp58 turned AZ1729 into a potent activating allosteric agonist. The activation signals down-stream of FFAR2 when stimulated by the two interdependent allosteric modulators were biased in that, unlike for orthosteric agonists, the two complementary modulators together triggered an activation of the NADPH-oxidase, but not any transient rise in the cytosolic concentration of free calcium ions (Ca2+). Furthermore, following AZ1729/Cmp58 activation, the signaling by the desensitized FFAR2s was functionally selective in that the orthosteric agonist propionate could still induce a transient rise in intracellular Ca2+. The novel neutrophil activation and receptor down-stream signaling pattern mediated by the two cross-sensitizing allosteric FFAR2 modulators represent a new regulatory mechanism that controls receptor signaling.
  •  
36.
  • Liu, Q., et al. (author)
  • Functional characteristics of circulating granulocytes in severe congenital neutropenia caused by ELANE mutations
  • 2019
  • In: Bmc Pediatrics. - : Springer Science and Business Media LLC. - 1471-2431. ; 19
  • Journal article (peer-reviewed)abstract
    • BackgroundNeutrophils and eosinophils are multifunctional granulocytes derived from common myelocytic-committed progenitor cells. Severe congenital neutropenia 1 (SCN1) caused by ELANE mutations is a rare disease characterized by very low numbers of circulating neutrophils. Little is known about the functional characteristics of the SCN1 granulocytes, except that eosinophilia has been noticed in both bone marrow and peripheral blood. In this study, we profiled the number and function of granulocytes in patients suffering from SCN1.MethodsNine patients diagnosed with SCN1 were enrolled in this study and absolute counts of eosinophils and neutrophils from bone marrow aspirates and peripheral blood samples were analysed. In addition, Ficoll-Paque enriched granulocytes from patients and healthy controls were analysed for specific eosinophil and neutrophil markers using flow cytometry and for NADPH-oxidase activity-profile by chemiluminescence.ResultsOur data demonstrate a skewed granulocyte population in SCN1 patients dominated by eosinophils in both bone marrow and peripheral blood. The latter was detected only by blood smear examination, but not by automated blood analysers. Furthermore, we show that the SCN1 eosinophils exerted normal production of reactive oxygen species generated by the NADPH-oxidase, however the response was profoundly different from that of healthy control neutrophils.ConclusionsSCN1 patients with ELANE mutations suffer from neutropenia yet display eosinophilia in the bone marrow and blood, as revealed by smear examination but not by automatic blood analysers. The SCN1 eosinophils are functionally normal regarding production of reactive oxygen species (ROS). However, the ROS profile produced by eosinophils differs drastically from that of neutrophils isolated from the same blood donor, implying that the eosinophilia in SCN1 cannot compensate forthe loss of neutrophils regarding ROS-mediated functions.
  •  
37.
  • Mårtensson, Jonas, et al. (author)
  • Neutrophil priming that turns natural FFA2R agonists into potent activators of the superoxide generating NADPH-oxidase
  • 2018
  • In: Journal of leukocyte biology. - : Oxford University Press (OUP). - 0741-5400 .- 1938-3673. ; 104:6, s. 1117-1132
  • Journal article (peer-reviewed)abstract
    • Acetate, an agonist for the free fatty acid receptor 2 (FFA2R/GPR43), triggers an increase in the cytosolic concentration of free Ca2+ in neutrophils without any assembly of the superoxide generating NADPH-oxidase. We show that the phenylacetamide compound 58 (Cmp 58; (S)-2-(4-chlorophenyl)-3,3-dimethyl-N-(5-phenylthiazol-2-yl)butanamide), lacking a direct activating effect on neutrophils, acts as a positive FFA2R modulator that turns acetate into a potent activating agonist that triggers an assembly of the NADPH-oxidase. The NADPH-oxidase activity could be further increased in neutrophils treated with the pro-inflammatory cytokine TNF-alpha. Many neutrophil chemoattractant receptors are stored in secretory organelles but no FFA2R mobilization was induced in neutrophils treated with TNF-alpha. The receptor selectivity was demonstrated through the inhibition of the neutrophil response induced by the combined action of acetate and Cmp 58 by the FFA2R antagonist CATPB. Receptor modulators that positively co-operate with natural FFA2R agonists and prime neutrophils in their response to such agonists, may serve as good tools for further unraveling the physiological functions of FFA2R and its involvement in various diseases. In this study, we show that neutrophils primed with a presumed allosteric FFA2R modulator produce increased amounts of reactive oxygen species when activated by receptor specific agonists.
  •  
38.
  • Mårtensson, Jonas, et al. (author)
  • The ketone body acetoacetate activates human neutrophils through FFAR2.
  • 2023
  • In: Journal of leukocyte biology. - : Oxford University Press (OUP). - 1938-3673. ; 113:6, s. 577-587
  • Journal article (peer-reviewed)abstract
    • Neutrophils express many surface receptors that sense environmental changes. One such sensor is FFAR2 (free fatty acid receptor 2), a receptor that detects gut microbiota-derived short chain fatty acids. As such, FFAR2 has been regarded as a molecular link between metabolism and inflammation. Our recent studies on FFAR2, using its endogenous agonist propionate in combination with allosteric modulators, have identified several novel aspects of FFAR2 regulation. A recent study has also identified the ketone body acetoacetate as an endogenous ligand for mouse FFAR2. Whether human FFAR2 also recognizes acetoacetate and how this recognition modulates human neutrophil functions has not been earlier investigated. In this study, we found that acetoacetate can induce a decrease of cAMP and translocation of β-arrestin in cells overexpressing FFAR2. In addition, we show that similar to propionate, FFAR2 specific allosteric modulators enhance acetoacetate-induced transient rise in cytosolic calcium, production of reactive oxygen species and cell migration in human neutrophils. In summary, we demonstrate that human neutrophils recognize the ketone body acetoacetate through FFAR2. Thus, our data further highlight the key role of FFAR2 in inflammation and metabolism.
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39.
  • Mårtensson, Jonas, et al. (author)
  • The Two Formyl Peptide Receptors Differently Regulate GPR84-Mediated Neutrophil NADPH Oxidase Activity
  • 2021
  • In: Journal of Innate Immunity. - : S. Karger AG. - 1662-811X .- 1662-8128. ; 13:4, s. 242-256
  • Journal article (peer-reviewed)abstract
    • Neutrophils express the two formyl peptide receptors (FPR1 and FPR2) and the medium-chain fatty acid receptor GPR84. The FPRs are known to define a hierarchy among neutrophil G protein-coupled receptors (GPCRs), that is, the activated FPRs can either suppress or amplify GPCR responses. In this study, we investigated the position of GPR84 in the FPR-defined hierarchy regarding the activation of neutrophil nicotine adenine dinucleotide phosphate (NADPH) oxidase, an enzyme system designed to generate reactive oxygen species (ROS), which are important regulators in cell signaling and immune regulation. When resting neutrophils were activated by GPR84 agonists, a modest ROS release was induced. However, vast amounts of ROS were induced by these GPR84 agonists in FPR2-desensitized neutrophils, and the response was inhibited not only by a GPR84-specific antagonist but also by an FPR2-specific antagonist. This suggests that the amplified GPR84 agonist response is achieved through a reactivation of desensitized FPR2s. In addition, the GPR84-mediated FPR2 reactivation was independent of beta-arrestin recruitment and sensitive to a protein phosphatase inhibitor. In contrast to FPR2-desensitized cells, FPR1 desensitization primarily resulted in a suppressed GPR84 agonist-induced ROS response, indicating a receptor hierarchical desensitization of GPR84 by FPR1-generated signals. In summary, our data show that the two FPRs in human neutrophils control the NADPH oxidase activity with concomitant ROS production by communicating with GPR84 through different mechanisms. While FPR1 desensitizes GPR84 and by that suppresses the release of ROS induced by GPR84 agonists, amplified ROS release is achieved by GPR84 agonists through reactivation of the desensitized FPR2.
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40.
  • Saevarsdottir, S., et al. (author)
  • Multiomics analysis of rheumatoid arthritis yields sequence variants that have large effects on risk of the seropositive subset
  • 2022
  • In: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 81:8
  • Journal article (peer-reviewed)abstract
    • Objectives To find causal genes for rheumatoid arthritis (RA) and its seropositive (RF and/or ACPA positive) and seronegative subsets. Methods We performed a genome-wide association study (GWAS) of 31 313 RA cases (68% seropositive) and similar to 1 million controls from Northwestern Europe. We searched for causal genes outside the HLA-locus through effect on coding, mRNA expression in several tissues and/or levels of plasma proteins (SomaScan) and did network analysis (Qiagen). Results We found 25 sequence variants for RA overall, 33 for seropositive and 2 for seronegative RA, altogether 37 sequence variants at 34 non-HLA loci, of which 15 are novel. Genomic, transcriptomic and proteomic analysis of these yielded 25 causal genes in seropositive RA and additional two overall. Most encode proteins in the network of interferon-alpha/beta and IL-12/23 that signal through the JAK/STAT-pathway. Highlighting those with largest effect on seropositive RA, a rare missense variant in STAT4 (rs140675301-A) that is independent of reported non-coding STAT4-variants, increases the risk of seropositive RA 2.27-fold (p=2.1x10(-9)), more than the rs2476601-A missense variant in PTPN22 (OR=1.59, p=1.3x10(-160)). STAT4 rs140675301-A replaces hydrophilic glutamic acid with hydrophobic valine (Glu128Val) in a conserved, surface-exposed loop. A stop-mutation (rs76428106-C) in FLT3 increases seropositive RA risk (OR=1.35, p=6.6x10(-11)). Independent missense variants in TYK2 (rs34536443-C, rs12720356-C, rs35018800-A, latter two novel) associate with decreased risk of seropositive RA (ORs=0.63-0.87, p=10(-9)-10(-27)) and decreased plasma levels of interferon-alpha/beta receptor 1 that signals through TYK2/JAK1/STAT4. Conclusion Sequence variants pointing to causal genes in the JAK/STAT pathway have largest effect on seropositive RA, while associations with seronegative RA remain scarce.
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41.
  • Stockfelt, Marit, et al. (author)
  • Increased CD11b and Decreased CD62L in Blood and Airway Neutrophils from Long-Term Smokers with and without COPD
  • 2020
  • In: Journal of innate immunity. - : S. Karger AG. - 1662-8128 .- 1662-811X. ; 12:6, s. 480-489
  • Journal article (peer-reviewed)abstract
    • There is incomplete mechanistic understanding of the mobilization of neutrophils in the systemic and local compartment in smokers with chronic obstructive pulmonary disease (COPD). In this pilot study, we characterized how the adhesion molecules CD11b and CD62L, surface markers indicative of priming, are altered as neutrophils extravasate, and whether surface density of CD11b and CD62L differs between long-term tobacco smokers (LTS) with and without COPD compared with healthy never-smokers (HNS). Unstimulated blood neutrophils from LTS with (<i>n</i> = 5) and without (<i>n</i> = 9) COPD displayed lower surface density of CD62L compared with HNS (<i>n</i> = 8). In addition, surface density of CD11b was higher in bronchoalveolar lavage (BAL) neutrophils from LTS without COPD compared with those with COPD and HNS. Moreover, in BAL neutrophils from all study groups, CD62L was lower compared with matched blood neutrophils. In addition, BAL neutrophils responded with a further decrease in CD62L to ex vivo TNF stimulation. Thus, neutrophils in the airway lumen display a higher state of priming than systemic neutrophils and bear the potential to be further primed by local cytokines even with no smoking or the presence of COPD, findings that may represent a universal host defense mechanism against local bacteria. Moreover, systemic neutrophils are primed in LTS regardless of COPD. Further studies in larger materials are warranted to determine whether the priming of neutrophils is protective against COPD or merely preceding it.
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42.
  • Sundqvist, Martina, et al. (author)
  • Severe chronic non-bacterial osteomyelitis in combination with total MPO deficiency and responsiveness to TNFα inhibition
  • 2023
  • In: Frontiers in Immunology. - : FRONTIERS MEDIA SA. - 1664-3224. ; 14
  • Journal article (peer-reviewed)abstract
    • We describe a female patient suffering from severe chronic non-bacterial osteomyelitis (CNO) with systemic inflammation and advanced malnutrition and complete deficiency of myeloperoxidase (MPO). CNO is a rare autoinflammatory bone disorder associated with dysregulation of the innate immune system. MPO deficiency is a genetic disorder with partial or complete absence of the phagocyte peroxidase MPO. MPO deficiency has no established clinical phenotype but reports indicate increased susceptibility to infection and chronic inflammation. The patient’s symptoms began at 10 years of age with pain in the thighs, systemic inflammation and malnutrition. She was diagnosed with CNO at 14 years of age. Treatment with nonsteroidal anti-inflammatory drugs, corticosteroids, bisphosphonates or IL1-receptor antagonists (anakinra) did not relieve the symptoms. However, the patient responded instantly and recovered from her clinical symptoms when treated with TNFα blockade (adalimumab). Three years after treatment initiation adalimumab was withdrawn, resulting in rapid symptom recurrence. When reintroducing adalimumab, the patient promptly responded and went into remission. In addition to clinical and laboratory profiles, neutrophil functions (reactive oxygen species, ROS; neutrophil extracellular traps, NETs; degranulation; apoptosis; elastase activity) were investigated both in a highly inflammatory state (without treatment) and in remission (on treatment). At diagnosis, neither IL1β, IL6, nor TNFα was significantly elevated in serum, but since TNFα blockade terminated the inflammatory symptoms, the disease was likely TNFα-driven. All neutrophil parameters were normal both during treatment and treatment withdrawal, except for MPO-dependent intracellular ROS- and NET formation. The role of total MPO deficiency for disease etiology and severity is discussed.
  •  
43.
  • Sundqvist, Martina, et al. (author)
  • Similarities and differences between the responses induced in human phagocytes through activation of the medium chain fatty acid receptor GPR84 and the short chain fatty acid receptor FFA2R.
  • 2018
  • In: Biochimica et biophysica acta. - : Elsevier BV. - 0006-3002. ; 1865:5, s. 695-708
  • Journal article (peer-reviewed)abstract
    • GPR84 is a recently de-orphanized member of the G-protein coupled receptor (GPCR) family recognizing medium chain fatty acids, and has been suggested to play important roles in inflammation. Due to the lack of potent and selective GPR84 ligands, the basic knowledge related to GPR84 functions is very limited. In this study, we have characterized the GPR84 activation profile and regulation mechanism in human phagocytes, using two recently developed small molecules that specifically target GPR84 agonistically (ZQ16) and antagonistically (GLPG1205), respectively. Compared to our earlier characterization of the short chain fatty acid receptor FFA2R which is functionally expressed in neutrophils but not in monocytes, GPR84 is expressed in both cell types and in monocyte-derived macrophages. In neutrophils, the GPR84 agonist had an activation profile very similar to that of FFA2R. The GPR84-mediated superoxide release was low in naïve cells, but the response could be significantly primed by TNFα and by the actin cytoskeleton disrupting agent Latrunculin A. Similar to that of FFA2R, a desensitization mechanism bypassing the actin cytoskeleton was utilized by GPR84. All ZQ16-mediated cellular responses were sensitive to GLPG1205, confirming the GPR84-dependency. Finally, our data of in vivo transmigrated tissue neutrophils indicate that both GPR84 and FFA2R are involved in neutrophil recruitment processes in vivo. In summary, we show functional similarities but also some important differences between GPR84 and FFA2R in human phagocytes, thus providing some mechanistic insights into GPR84 regulation in blood neutrophils and cells recruited to an aseptic inflammatory site in vivo.
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44.
  •  
45.
  • Welin, Amanda, 1983, et al. (author)
  • The Human Neutrophil Subsets Defined by the Presence or Absence of OLFM4 Both Transmigrate into Tissue In Vivo and Give Rise to Distinct NETs In Vitro.
  • 2013
  • In: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 8:7
  • Journal article (peer-reviewed)abstract
    • Neutrophil heterogeneity was described decades ago, but it could not be elucidated at the time whether the existence of different neutrophil subsets had any biological relevance. It has been corroborated in recent years that neutrophil subsets, defined by differential expression of various markers, are indeed present in human blood, calling for renewed attention to this question. The expression of the granule protein olfactomedin 4 (OLFM4) has been suggested to define two such neutrophil subsets. We confirm the simultaneous presence of one OLFM4-positive and one OLFM4-negative neutrophil subpopulation as well as the localization of the protein to specific granules. In vitro, these neutrophil subsets displayed equal tendency to undergo apoptosis and phagocytose bacteria. In addition, the subpopulations were recruited equally to inflammatory sites in vivo, and this was true both in an experimental model of acute inflammation and in naturally occurring pathological joint inflammation. In line with its subcellular localization, only limited OLFM4 release was seen upon in vivo transmigration, and release through conventional degranulation required strong secretagogues. However, extracellular release of OLFM4 could be achieved upon formation of neutrophil extracellular traps (NETs) where it was detected only in a subset of the NETs. Although we were unable to demonstrate any functional differences between the OLFM4-defined subsets, our data show that different neutrophil subsets are present in inflamed tissue in vivo. Furthermore, we demonstrate NETs characterized by different markers for the first time, and our results open up for functions of OLFM4 itself in the extracellular space through exposure in NETs.
  •  
46.
  • Öberg Sysojev, Anton, et al. (author)
  • Genome-wide investigation of persistence with methotrexate treatment in early rheumatoid arthritis
  • 2024
  • In: Rheumatology. - : Oxford University Press. - 1462-0324 .- 1462-0332. ; 63:5, s. 1221-1229
  • Journal article (peer-reviewed)abstract
    • Objectives: To investigate the influence of genetic factors on persistence to treatment of early rheumatoid arthritis (RA) with methotrexate (MTX) monotherapy.Methods: We conducted a genome-wide association study (GWAS) in a sample of 3902 Swedish early RA patients initiating MTX in DMARD-monotherapy as their first ever DMARD. The outcome, short- and long-term persistence to this treatment, was defined as remaining on MTX at one and at three years, respectively, with no additional DMARDs added. As genetic predictors, we investigated individual SNPs, and a polygenic risk score (PRS) based on SNPs associated with RA risk. The SNP-based heritability of persistence was estimated overall and by RA serostatus.Results: No individual SNP reached genome-wide significance (p < 5e-8), neither for persistence at one nor at three years. The RA PRS was not significantly associated with persistence at one (RR = 0.98 (0.96-1.01)) nor three years (RR = 0.96 (0.93-1.00)). The heritability for persistence was estimated to be 0.45 (0.15-0.75) at one year and 0.14 (0-0.40) at three years. Results in seropositive RA were comparable to those in the analysis of RA overall, while heritability estimates and PRS RRs were attenuated towards the null in seronegative RA.Conclusions: Despite being the largest GWAS on an MTX treatment outcome to date, no genome-wide significant associations were detected. The modest heritability observed, coupled with the broad spread of suggestively associated loci, indicate that genetic influence is of polygenic nature. Nevertheless, persistence to MTX monotherapy was lower in patients with a greater genetic disposition, per the PRS, towards RA.
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