| 1. |
- Björnsdottir, Halla, et al.
(author)
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Neutrophil NET formation is regulated from the inside by myeloperoxidase-processed reactive oxygen species.
- 2015
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In: Free radical biology & medicine. - : Elsevier BV. - 1873-4596 .- 0891-5849. ; 89, s. 1024-1035
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Journal article (peer-reviewed)abstract
- Neutrophil extracellular traps (NETs) are mesh-like DNA fibers clad with intracellular proteins that are cast out from neutrophils in response to certain stimuli. The process is thought to depend on reactive oxygen species (ROS) generated by the phagocyte NADPH-oxidase and the ROS-modulating granule enzyme myeloperoxidase (MPO), but when, how, and where these factors contribute is so far uncertain. The neutrophil NADPH-oxidase can be activated at different cellular sites and ROS may be produced and processed by MPO within intracellular granules, even in situations where a phagosome is not formed, e.g., upon stimulation with phorbol myristate acetate (PMA).
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| 2. |
- Brown, Kelly, 1973, et al.
(author)
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Profile of blood cells and inflammatory mediators in periodic fever, aphthous stomatitis, pharyngitis and adenitis (PFAPA) syndrome.
- 2010
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In: BMC pediatrics. - : Springer Science and Business Media LLC. - 1471-2431. ; 10
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Journal article (peer-reviewed)abstract
- ABSTRACT: BACKGROUND: This study aimed to profile levels of blood cells and serum cytokines during afebrile and febrile phases of periodic fever, aphthous stomatitis, pharyngitis and adenitis (PFAPA) syndrome to advance pathophysiological understanding of this pediatric disease. METHODS: A cohort of patients with a median age of 4.9 years experiencing 'typical PFAPA' episodes participated in this study. Blood cells and serum cytokines were analyzed by CBC analysis and multiplex ELISA. RESULTS: Oscillations in the concentration of blood cells during the afebrile and febrile phases of typical PFAPA syndrome were observed; novel findings include increased monocytes and decreased eosinophils during a febrile episode and increased thrombocytes in the afebrile interval. Relatively modest levels of pro-inflammatory cytokines were present in sera. IFNγ-induced cytokine IP10/CXCL10 was increased after the onset of fever while T cell-associated cytokines IL7 and IL17 were suppressed during afebrile and febrile periods. CONCLUSIONS: Identification of dysregulated blood cells and serum cytokines is an initial step towards the identification of biomarkers of PFAPA disease and/or players in disease pathogenesis. Future investigations are required to conclusively discern which mediators are associated specifically with PFAPA syndrome.
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| 3. |
- Elmwall, Jonas, et al.
(author)
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Galectin-3 Is a Target for Proteases Involved in the Virulence of Staphylococcus aureus
- 2017
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In: Infection and Immunity. - : American Society for Microbiology. - 0019-9567 .- 1098-5522. ; 85:7
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Journal article (peer-reviewed)abstract
- Staphylococcus aureus is a major cause of skin and soft tissue infection. The bacterium expresses four major proteases that are emerging as virulence factors: aureolysin (Aur), V8 protease (SspA), staphopain A (ScpA), and staphopain B (SspB). We hypothesized that human galectin-3, a beta-galactoside-binding lectin involved in immune regulation and antimicrobial defense, is a target for these proteases and that proteolysis of galectin-3 is a novel immune evasion mechanism. Indeed, supernatants from laboratory strains and clinical isolates of S. aureus caused galectin-3 degradation. Similar proteolytic capacities were found in Staphylococcus epidermidis isolates but not in Staphylococcus saprophyticus. Galectin-3-induced activation of the neutrophil NADPH oxidase was abrogated by bacterium-derived proteolysis of galectin-3, and SspB was identified as the major protease responsible. The impact of galectin-3 and protease expression on S. aureus virulence was studied in a murine skin infection model. In galectin-3 (+)/(+) mice, SspB-expressing S. aureus caused larger lesions and resulted in higher bacterial loads than protease-lacking bacteria. No such difference in bacterial load or lesion size was detected in galectin-3 (+)/(+) mice, which overall showed smaller lesion sizes than the galectin-3 (+)/(+) animals. In conclusion, the staphylococcal protease SspB inactivates galectin-3, abrogating its stimulation of oxygen radical production in human neutrophils and increasing tissue damage during skin infection.
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| 4. |
- Salomonsson, Emma, et al.
(author)
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Mutational tuning of galectin-3 specificity and biological function.
- 2010
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In: The Journal of biological chemistry. - 1083-351X. ; 285, s. 35079-35091
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Journal article (peer-reviewed)abstract
- Galectins are defined by a conserved beta-galactoside binding site, which has been linked to many of their important functions in e.g. cell adhesion, signaling and intracellular trafficking. Weak adjacent sites may enhance or decrease affinity for natural beta-galactoside containing glycoconjugates, but little is known about the biological role of this modulation of affinity (fine specificity). We have now produced 10 mutants of human galectin-3, with changes in these adjacent sites, which have altered carbohydrate-binding fine specificity but which retain the basic beta-galactoside binding activity as show by glycan-array binding and a solution-based fluorescence anisotropy assay. Each mutant was also tested in two biological assays to provide a correlation between fine specificity and function. Galectin-3 R186S, which has selectively lost affinity for LacNAc, a disaccharide moiety commonly found on glycoprotein glycans, has lost the ability to activate neutrophil leukocytes and intracellular targeting into vesicles. K176L has increased affinity for beta-galactosides substituted with GlcNAcbeta1-3 as found in poly-N-acetyllactosaminoglycans, and increased potency to activate neutrophil leukocytes, even though it has lost other aspects of galectin-3 fine specificity. G182A has altered carbohydrate-binding fine specificity and altered intracellular targeting into vesicles, a possible link to the intracellular galectin-3-mediated anti-apoptotic effect known to be lost by this mutant. Finally, the mutants have helped to define the differences in fine specificity shown by Xenopus, mouse and human galectin-3 and as such, evidence for adaptive change during evolution.
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| 5. |
- Sundqvist, Martina, et al.
(author)
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Cord blood neutrophils display a galectin-3 responsive phenotype accentuated by vaginal delivery.
- 2013
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In: BMC pediatrics. - : Springer Science and Business Media LLC. - 1471-2431. ; 13
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Journal article (peer-reviewed)abstract
- Term neonates are at increased risk of infections due to undeveloped immune mechanisms, and proper neutrophil function is important for perinatal immune defence. Galectin-3, an endogenous β-galactoside-binding lectin, is emerging as an inflammatory mediator and we have previously shown that primed/activated, but not resting, adult neutrophils respond to this lectin by production of reactive oxygen species (ROS). We investigated if galectin-3 is of importance in perinatal immune defence, focusing on plasma levels and neutrophil responsiveness.
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| 6. |
- Sundqvist, Martina, et al.
(author)
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Elevated Mitochondrial Reactive Oxygen Species and Cellular Redox Imbalance in Human NADPH-Oxidase-Deficient Phagocytes
- 2017
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In: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 8
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Journal article (peer-reviewed)abstract
- Chronic granulomatous disease (CGD) is caused by mutations in genes that encode the NADPH-oxidase and result in a failure of phagocytic cells to produce reactive oxygen species (ROS) via this enzyme system. Patients with CGD are highly susceptible to infections and often suffer from inflammatory disorders; the latter occurs in the absence of infection and correlates with the spontaneous production of inflammatory cytokines. This clinical feature suggests that NADPH-oxidase-derived ROS are not required for, or may even suppress, inflammatory processes. Experimental evidence, however, implies that ROS are in fact required for inflammatory cytokine production. By using a myeloid cell line devoid of a functional NADPH-oxidase and primary CGD cells, we analyzed intracellular oxidants, signs of oxidative stress, and inflammatory cytokine production. Herein, we demonstrate that phagocytes lacking a functional NADPH-oxidase, namely primary CGD phagocytes and a gp91phox-deficient cell line, display elevated levels of ROS derived from mitochondria. Accordingly, these cells, despite lacking the major source of cellular ROS, display clear signs of oxidative stress, including an induced expression of antioxidants and altered oxidation of cell surface thiols. These observed changes in redox state were not due to abnormalities in mitochondrial mass or membrane integrity. Finally, we demonstrate that increased mitochondrial ROS enhanced phosphorylation of ERK1/2, and induced production of IL8, findings that correlate with previous observations of increased MAPK activation and inflammatory cytokine production in CGD cells. Our data show that elevated baseline levels of mitochondria-derived oxidants lead to the counter-intuitive observation that CGD phagocytes are under oxidative stress and have enhanced MAPK signaling, which may contribute to the elevated basal production of inflammatory cytokines and the sterile inflammatory manifestations in CGD.
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| 7. |
- Sundqvist, Martina, et al.
(author)
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Galectin-3 type-C self-association on neutrophil surfaces; The carbohydrate recognition domain regulates cell function
- 2018
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In: Journal of Leukocyte Biology. - 0741-5400. ; 103:2, s. 341-353
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Journal article (peer-reviewed)abstract
- Galectin-3 is an endogenous β-galactoside-binding lectin comprising a carbohydrate recognition domain (CRD) linked to a collagen-like N-domain. Both domains are required for galectin-3 to induce cellular effects; a C-terminal fragment of galectin-3, galectin-3C, containing the CRD but lacking the N-domain, binds cell surface glycoconjugates but does not induce cellular effects since cross-linking promoted by the N-domain is thought to be required. Instead, galectin-3C is proposed to antagonize the effects of galectin-3 by competing for binding sites. The aim of this study was to investigate the effects of galectin-3C on galectin-3 interactions with human neutrophils. Recombinant galectin-3C inhibited galectin-3-induced production of reactive oxygen species in primed neutrophils. Surprisingly, this inhibition was not due to competitive inhibition of galectin-3 binding to the cells. In contrast, galectin-3C potentiated galectin-3 binding, in line with emerging evidence that galectin-3 can aggregate not only through the N-domain but also through the CRD. The cell surface interaction between galectin-3C and galectin-3 was corroborated by colocalization of fluorescently labeled galectin-3 and galectin-3C. Galectin-3C can be generated in vivo through cleavage of galectin-3 by proteases. Indeed, in circulation, galectin-3 and galectin-3C were both attached to the cell surface of neutrophils, which displayed great capacity to bind additional galectin-3 and galectin-3C. In conclusion, galectin-3C enhances galectin-3 binding to neutrophils by nonactivating type-C self-association, in parallel to inhibiting neutrophil activation by galectin-3 (induced by type-N self-association). This implicates type-C self-association as a termination system for galectin-3-induced cell activation, with the purpose of avoiding oxidant-dependent tissue damage. ©2018 Society for Leukocyte Biology
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| 8. |
- Sundqvist, Martina, et al.
(author)
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Increased intracellular oxygen radical production in neutrophils during febrile episodes of PFAPA syndrome.
- 2013
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In: Arthritis and rheumatism. - : Wiley. - 1529-0131 .- 0004-3591. ; 65:11, s. 2971-2983
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Journal article (peer-reviewed)abstract
- Objective: Periodic Fever, Aphthous stomatitis, Pharyngitis, and cervical Adenitis (PFAPA) syndrome is an autoinflammatory disease of unknown etiology that primarily affects preschool children. PFAPA is characterized by recurrent attacks of fever and inflammatory symptoms consistent with the disease acronym. Since autoinflammatory diseases by definition are mediated by cells of the innate immune system, we aimed at evaluating functional features of neutrophils, the most abundant innate immune cell in circulation, in PFAPA syndrome. Methods: Blood neutrophils, obtained from PFAPA patients during both febrile and asymptomatic afebrile phases of disease, as well as from healthy children (afebrile controls) and children with fever and abdominal pain (febrile controls) were analysed for three key neutrophil characteristics: (i) apoptosis (measured by Annexin V/7AAD staining), (ii) production of reactive oxygen species (ROS; by luminol/isoluminol-amplified chemiluminescence), and (iii) priming status (as responsiveness to galectin-3 and upregulation of CD11b). Results: Compared to neutrophils from both PFAPA patients in an afebrile interval and from febrile controls, neutrophils obtained during a PFAPA flare produced elevated levels of intracellular NADPH-oxidase-derived ROS, had significantly diminished rates of spontaneous apoptosis, and displayed signatures of priming. In contrast, neutrophils from afebrile PFAPA patients had a significantly elevated rate of spontaneous apoptosis compared to neutrophils from afebrile controls. Conclusions: We demonstrate that three key aspects of neutrophil innate immune function, namely apoptosis, priming, and generation of an intracellular oxidative burst are altered, most prominently during febrile attacks in PFAPA syndrome. © 2013 American College of Rheumatology.
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| 9. |
- Svahn, Sara L, et al.
(author)
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Dietary Polyunsaturated Fatty Acids Promote Neutrophil Accumulation in the Spleen by Altering Chemotaxis and Delaying Cell Death
- 2019
-
In: Infection and Immunity. - : American Society for Microbiology. - 0019-9567 .- 1098-5522. ; 87:8
-
Journal article (peer-reviewed)abstract
- Neutrophils are the most abundant circulating leukocytes in humans and are essential for the defense against invading pathogens. Like many other cells of an organism, neutrophils can be highly influenced by the diet. We have previously described that mice fed a high-fat diet rich in polyunsaturated fatty acids (HFD-P) present a higher frequency of neutrophils in bone marrow than mice fed a high-fat diet rich in saturated fatty acids (HFD-S). Interestingly, such an increase correlated with improved survival against bacterium-induced sepsis. In this study, we aimed to investigate the effects of dietary polyunsaturated and saturated fatty acids on neutrophil homeostasis. We found that HFD-P specifically induced the accumulation of neutrophils in the marginal pools of the spleen and liver. The accumulation of neutrophils in the spleen was a result of a dual effect of polyunsaturated fatty acids on neutrophil homeostasis. First, polyunsaturated fatty acids enhanced the recruitment of neutrophils from the circulation into the spleen via chemokine secretion. Second, they delayed neutrophil cell death in the spleen. Interestingly, these effects were not observed in mice fed a diet rich in saturated fatty acids, suggesting that the type of fat rather than the amount of fat mediates the alterations in neutrophil homeostasis. In conclusion, our results show that dietary polyunsaturated fatty acids have a strong modulatory effect on neutrophil homeostasis that may have future clinical applications.
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| 10. |
- Svahn, Sara L., et al.
(author)
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Dietary Polyunsaturated Fatty Acids Promote Neutrophil Accumulation in the Spleen by Altering Chemotaxis and Delaying Cell Death
- 2019
-
In: Infection and Immunity. - 1098-5522 .- 0019-9567. ; 87:8
-
Journal article (peer-reviewed)abstract
- Neutrophils are the most abundant circulating leukocytes in humans and are essential for the defense against invading pathogens. Like many other cells of an organism, neutrophils can be highly influenced by the diet. We have previously described that mice fed a high-fat diet rich in polyunsaturated fatty acids (HFD-P) present a higher frequency of neutrophils in bone marrow than mice fed a high-fat diet rich in saturated fatty acids (HFD-S). Interestingly, such an increase correlated with improved survival against bacterium-induced sepsis. In this study, we aimed to investigate the effects of dietary polyunsaturated and saturated fatty acids on neutrophil homeostasis. We found that HFD-P specifically induced the accumulation of neutrophils in the marginal pools of the spleen and liver. The accumulation of neutrophils in the spleen was a result of a dual effect of polyunsaturated fatty acids on neutrophil homeostasis. First, polyunsaturated fatty acids enhanced the recruitment of neutrophils from the circulation into the spleen via chemokine secretion. Second, they delayed neutrophil cell death in the spleen. Interestingly, these effects were not observed in mice fed a diet rich in saturated fatty acids, suggesting that the type of fat rather than the amount of fat mediates the alterations in neutrophil homeostasis. In conclusion, our results show that dietary polyunsaturated fatty acids have a strong modulatory effect on neutrophil homeostasis that may have future clinical applications.
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