| 1. |
- Fu, Huamei, 1979, et al.
(författare)
-
Changes in the ratio between FPR and FPRL1 triggered superoxide production in human neutrophils-a tool in analysing receptor specific events
- 2008
-
Ingår i: Journal of Immunological Methods. - : Elsevier BV. - 0022-1759. ; 331:1-2, s. 50-8
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 2. |
- Aspberg, A., et al.
(författare)
-
Cartilage oligomeric matrix protein forms protein complexes with synovial lubricin via non-covalent and covalent interactions
- 2017
-
Ingår i: Osteoarthritis and Cartilage. - : Elsevier BV. - 1063-4584. ; 25:9, s. 1496-1504
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 3. |
- Björkman, Lena, 1965, et al.
(författare)
-
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
-
Ingår i: Data in brief. - : Elsevier BV. - 2352-3409. ; 10, s. 349-353
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 4. |
- Björkman, Lena, 1965, et al.
(författare)
-
Larixol is not an inhibitor of Gαi containing G proteins and lacks effect on signaling mediated by human neutrophil expressed formyl peptide receptors
- 2024
-
Ingår i: Biochemical Pharmacology. - 0006-2952 .- 1873-2968. ; 220
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 5. |
- Björkman, Lena, 1965, et al.
(författare)
-
Neutrophil recruitment to inflamed joints can occur without cellular priming.
- 2019
-
Ingår i: Journal of leukocyte biology. - 1938-3673. ; 105:6, s. 1123-1130
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 6. |
|
|
| 7. |
- Björkman, Lena, 1965, et al.
(författare)
-
Serum amyloid A mediates human neutrophil production of reactive oxygen species through a receptor independent of formyl peptide receptor like-1
- 2008
-
Ingår i: Journal of Leukocyte Biology. - : Oxford University Press (OUP). - 0741-5400 .- 1938-3673. ; 83:2, s. 245-53
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 8. |
- Björkman, Lena, 1965, et al.
(författare)
-
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
-
Ingår i: Molecular and Cellular Biology. - : Informa UK Limited. - 0270-7306 .- 1098-5549. ; 36:20, s. 2583-2595
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 9. |
- Björkman, Lena, 1965, et al.
(författare)
-
The proinflammatory activity of recombinant serum amyloid A is not shared by the endogenous protein in the circulation.
- 2010
-
Ingår i: Arthritis and rheumatism. - : Wiley. - 1529-0131 .- 0004-3591. ; 62:6, s. 1660-5
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 10. |
- Björkman, Lena, 1965
(författare)
-
The Role Of Serum Amyloid A In Inflammatory Disease - Proinflammatory Mediator Or Inert Biomarker?
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)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
|
|
