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  • 1.
    Kälvegren, Hanna
    et al.
    Örebro University, School of Health and Medical Sciences. Fac Hlth Sci, Dept Med & Hlth Sci, Div Cardiovasc Med, Linköping Univ, Linköping, Sweden.
    Fridfeldt, Jonna
    Fac Hlth Sci, Dept Med & Hlth Sci, Div Drug Res, Linköping Univ, Linköping, Sweden.
    Bengtsson, Torbjörn
    Örebro University, School of Health and Medical Sciences. Fac Hlth Sci, Dept Med & Hlth Sci, Div Drug Res, Linköping Univ, Linköping, Sweden.
    The role of plasma adenosine deaminase in chemoattractant-stimulated oxygen radical production in neutrophils2010In: European Journal of Cell Biology, ISSN 0171-9335, E-ISSN 1618-1298, Vol. 89, no 6, p. 462-467Article in journal (Refereed)
    Abstract [en]

    Objectives: Adenosine deaminase (ADA) has a role in many immunity mediated disorders, such as asthma, tuberculosis and coronary artery disease. This study aims to investigate the ability of plasma ADA to modulate reactive oxygen species (ROS) production in neutrophils, and examine the involvement of adenosine and the cyclic AMP signaling pathway in this process. Methods: Neutrophils were stimulated, in the absence or presence of plasma, with the chemotactic peptide fMLP (formyl-methionyl-leucyl-phenylalanine), and the ROS production was determined with luminol-enhanced chemiluminescence. Activity of ADA was measured spectrophotometrically. Results: Plasma dose-dependently amplified the ROS generation in fMLP-stimulated neutrophils. In parallel, incubation of neutrophils in plasma elevated the total ADA-activity approximately 10 times from 1.3 U/ml to 12 U/ml. Inhibition of ADA, or type IV phosphodiesterases, significantly lowered the plasma-mediated ROS production. Furthermore, the high-affinity adenosine A(1) receptor antagonists DPCPX and 8-phenyltheophylline markedly inhibited the plasma-induced respiratory burst in neutrophils, suggesting an AI receptor-mediated mechanism. Conclusions: This study suggests that plasma ADA amplifies the release of toxic oxygen radicals from neutrophils through a downregulation of the inhibitory adenosine/cAMP-system and an enhanced activation of the stimulatory adenosine A(1)-receptor. This mechanism has probably a crucial role in regulating neutrophil function and in the defence against microbial infections. However, a sustained neutrophil activation could also contribute to inflammatory disorders such as atherosclerosis. (C) 2010 Elsevier GmbH. All rights reserved.

  • 2.
    Kälvegren, Hanna
    et al.
    Örebro University, School of Health and Medical Sciences.
    Jonsson, Simon
    Örebro University, School of Health and Medical Sciences.
    Jonasson, Lena
    Örebro University, School of Health and Medical Sciences.
    Release of matrix metalloproteinases-1 and-2, but not-9, from activated platelets measured by enzyme-linked immunosorbent assay2011In: Platelets, ISSN 0953-7104, E-ISSN 1369-1635, Vol. 22, no 8, p. 572-578Article in journal (Refereed)
    Abstract [en]

    Matrix metalloproteinases (MMPs), in particular MMP-9, have been introduced as novel biomarkers in coronary artery disease. Activated platelets are considered to be a major source of the highly elevated levels of MMPs that are detected in serum compared to plasma. The aim of this study was to clarify if activated platelets release MMPs-1, -2 and -9 as measured by enzyme-linked immunosorbent assays (ELISA). Isolated platelets (separated by several procedures) or platelet-rich plasma (PRP) were stimulated by collagen, thrombin or the TLR2 agonist Pam(3)CSK(4). The concentrations of MMPs-1,-2 and -9 in supernatants were determined by ELISA. In addition, a MMP-9 enzyme activity assay was used as well as immunofluorescent staining of MMPs-1,-2 and 9 in platelets. Isolated platelets stimulated by collagen, thrombin or Pam(3)CSK(4) released significant amounts of MMP-1 to the supernatant measured as either pro- or total-MMP-1. However, there was no detectable release of MMP-2 or -9 from isolated platelets. Collagen-stimulated platelets in PRP released MMP-2, but not -9. Before stimulation; platelets were positive for MMPs-1 and -2, but not -9, as assessed by immunofluorescence. Acting as positive controls, neutrophils were found to release significant amounts of MMP-9. Our findings indicate that activated platelets may be a major source of MMP-1 and to a minor extent MMP-2, in peripheral blood. However, in contrast to what has been argued in previous literature, platelets appear to be only negligible contributors to circulating MMP-9.

  • 3.
    Kälvegren, Hanna
    et al.
    Örebro University, School of Health and Medical Sciences. Fac Hlth Sci, Linkoping Univ, Linkoping, Sweden.
    Skoglund, Caroline
    Fac Hlth Sci, Linkoping Univ, Linkoping, Sweden.
    Helldahl, Christian
    Fac Hlth Sci, Linkoping Univ, Linkoping, Sweden.
    Lerm, Maria
    Fac Hlth Sci, Linkoping Univ, Linkoping, Sweden.
    Grenegård, Magnus
    Fac Hlth Sci, Linkoping Univ, Linkoping, Sweden.
    Bengtsson, Torbjörn
    Örebro University, School of Health and Medical Sciences. Fac Hlth Sci, Linkoping Univ, Linkoping, Sweden.
    Toll-like receptor 2 stimulation of platelets is mediated by purinergic P2X(1)-dependent Ca2+ mobilisation, cyclooxygenase and purinergic P2Y(1) and P2Y(12) receptor activation2010In: Thrombosis and Haemostasis, ISSN 0340-6245, Vol. 103, no 2, p. 398-407Article in journal (Refereed)
    Abstract [en]

    Toll-like receptor 2 (TLR2), which recognise and respond to conserved microbial pathogen-associated molecular patterns, is expressed on the platelet surface. Furthermore, it has recently been shown that the TLR2/1 agonist Pam(3)CSK(4) stimulates platelet activation. The aim of the present study was to clarify important signalling events in Pam(3)CSK(4)-induced platelet aggregation and secretion. Platelet interaction with Pam(3)CSK(4) and the TLR2/6 agonist MALP-2 was studied by analysing aggregation, ATP-secretion, [Ca2+](i) mobilisation and thromboxane B2 (TxB(2)) production. The results show that Pam(3)CSK(4) but not MALP-2 induces [Ca2+](i) increase, TxB(2) production, dense granule secretion and platelet aggregation. Preincubation of platelets with MALP-2 inhibited the Pam(3)CSK(4)-induced responses. The ATP-secretion and aggregation in Pam(3)CSK(4)-stimulated platelets was impeded by the purinergic P2X(1) inhibitor MRS 2159, the purinergic P2Y(1) and P2Y(12) antagonists MRS 2179 and cangrelor, the phospholipase C inhibitor U73122, the calcium chelator BAPT-AM and aspirin. The calcium mobilisation was lowered by MRS 2159, aspirin and U73122 whereas the TxB(2) production was antagonised by MRS 2159, aspirin and BAPT-AM. When investigating the involvement of the myeloid differentiation factor-88 (MyD88) -dependent pathway, we found that platelets express MyD88 and interleukin 1 receptor-associated kinase (IRAK-1), which are proteins important in TLR signalling. However, Pam(3)CSK(4) did not stimulate a rapid (within 10 minutes) phosphorylation of IRAK-1 in platelets. In conclusion, the results show that Pam(3)CSK(4)-induced platelet aggregation and secretion depends on a P2X(1)-mediated Ca2+ mobilisation, production of TxA(2) and ADP receptor activation. The findings in this study further support a role for platelets in sensing bacterial components.

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