| 1. |
- Asplund Persson, Anna, 1966-, et al.
(författare)
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Cross-talk between adenosine and the oxatriazole derivative GEA 3175 in platelets
- 2005
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Ingår i: European Journal of Pharmacology. - : Elsevier BV. - 0014-2999 .- 1879-0712. ; 517:3, s. 149-157
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Tidskriftsartikel (refereegranskat)abstract
- We examined the interplay between adenosine and the nitric oxide (NO)-containing oxatriazole derivative GEA 3175 in human platelets. The importance of cyclic guanosine 3′5′-monophosphate (cGMP)-inhibited phosphodiesterases (PDEs) was elucidated by treating the platelets with adenosine combined with either GEA 3175 or the PDE3-inhibitor milrinone. The drug combinations provoked similar cyclic adenosine 3′5′-monophosphate (cAMP) responses. On the contrary, cGMP levels were increased only in GEA 3175-treated platelets. Both drug combinations reduced P-selectin exposure, platelet adhesion and fibrinogen-binding. However, adenosine together with GEA 3175 was more effective in inhibiting platelet aggregation and ATP release. Thrombin-induced rises in cytosolic Ca2+ were suppressed by the two drug combinations. Adenosine administered with GEA 3175 was, however, more effective in reducing Ca2+ influx.In conclusion, the interaction between adenosine and GEA 3175 involves cGMP-mediated inhibition of PDE3. The results also imply that inhibition of Ca2+ influx represent another cGMP-specific mechanism that enhances the effect of adenosine.
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| 2. |
- Bengtsson, Torbjörn, 1955-, et al.
(författare)
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Role of the actin cytoskeleton during respiratory burst in chemoattractant-stimulated neutrophils
- 2006
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Ingår i: Cell Biology International. - : Wiley. - 1065-6995 .- 1095-8355. ; 30:2, s. 154-163
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to clarify the role of the actin cytoskeleton during chemotactic peptide fMet-Leu-Phe (fMLF)-stimulated respiratory burst in human neutrophil granulocytes. Reactive oxygen species (ROS) was measured as luminol-amplified chemiluminescence (CL) and F-actin content as bodipy phallacidin fluorescence in neutrophils treated with latrunculin B or jasplakinolide, an inhibitor and activator of actin polymerization, respectively. Latrunculin B markedly decreased, whereas jasplakinolide increased, the F-actin content in neutrophils, unstimulated or stimulated with fMLF. Latrunculin B enhanced the fMLF-triggered ROS-production more than tenfold. Jasplakinolide initially inhibited the fMLF-induced CL-response, however, caused a potent second sustained phase (>400% of control). Both actin drugs triggered a substantial CL-response when added 5-25 min after fMLF. This was also valid for chemotactic doses of fMLF, where latrunculin B and jasplakinolide amplified the ROS-production 5-10 times. By using specific signal transduction inhibitors, we found that the NADPH oxidase activation triggered by destabilization of the actin cytoskeleton occurs downstream of phospholipase C and protein kinase C but is mediated by Rho GTPases and tyrosine phosphorylation. In conclusion, rearrangements of the actin cytoskeleton are a prerequisite in connecting ligand/receptor activation, generation of second messengers and assembly of the NADPH oxidase in neutrophil granulocytes. © 2005 International Federation for Cell Biology. Published by Elsevier Ltd. All rights reserved.
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| 3. |
- Berg, Cecilia, 1976-, et al.
(författare)
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Platelet-induced growth of human fibroblasts is associated with an increased expression of 5-lipoxygenase
- 2006
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Ingår i: Thrombosis and Haemostasis. - 0340-6245 .- 2567-689X. ; 96:5, s. 652-659
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Tidskriftsartikel (refereegranskat)abstract
- Proliferation of fibroblasts is vital for adequate wound healing but is probably also involved in different hyperproliferative disorders such as atherosclerosis and cancer. The regeneration of tissue usually starts with coagulation, involving release of mitogenic and inflammatory factors from activated platelets. This study focuses on the role of eicosanoids in the proliferative effects of platelets on human fibroblasts. We show that the phospholipase A2 inhibitor 7,7-dimethyl-5,8-eicosadienoic acid (DMDA), the combined cyclooxygenase (COX) and lipoxygenase (LOX) inhibitor 5,8,11,14-eicosatetraynoic acid (ETYA) and the LOX inhibitor 5,8,11-eicosatriynoic acid (ETI) block the platelet-induced proliferation of serum starved subconfluent human fibroblasts. Anti-proliferative effects were also obtained by specific inhibition of 5-LOX with 5,6-dehydro arachidonic acid (5,6-dAA), whereas the 12-LOX inhibitor cinnamyl-3,4-dihydroxy-α-cyanocinnamate (CDC) did not affect the platelet-stimulated growth of fibroblasts. The expression of 5-LOX was analyzed by reverse-transcriptase-mediated PCR (RT-PCR), Western blotting and HPLC. 5-LOX message and protein was detected in fibroblasts but not in platelets. Incubation with platelets markedly increased, already after one hour, the expression of 5-LOX in the fibroblast culture. The increased 5-LOX activity was associated with an elevated level of the 5-LOX metabolite 5-hydroxyeicosatetraenoic acid (5-HETE) reaching its maximum after 1-2 hours of co-incubation of fibroblasts and platelets. The 5-HETE production was reduced by the inhibitors DMDA, ETYA and ETI. In conclusion, this study suggests that platelet-stimulated proliferation of fibroblasts is mediated by an increased 5-LOX activity, which supports recent findings indicating a crucial role for this enzyme in proliferative disorders such as atherosclerosis. © 2006 Schattauer GmbH, Stuttgart.
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| 4. |
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| 5. |
- Sjöwall, Christoffer, et al.
(författare)
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Solid-phase classical complement activation by C-reactive protein (CRP) is inhibited by fluid-phase CRP-C1q interaction.
- 2007
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Ingår i: Biochemical and biophysical research communications. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 352:1, s. 251-8
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Tidskriftsartikel (refereegranskat)abstract
- C-reactive protein (CRP) interacts with phosphorylcholine (PC), Fcgamma receptors, complement factor C1q and cell nuclear constituents, yet its biological roles are insufficiently understood. The aim was to characterize CRP-induced complement activation by ellipsometry. PC conjugated with keyhole limpet hemocyanin (PC-KLH) was immobilized to cross-linked fibrinogen. A low-CRP serum with different amounts of added CRP was exposed to the PC-surfaces. The total serum protein deposition was quantified and deposition of IgG, C1q, C3c, C4, factor H, and CRP detected with polyclonal antibodies. The binding of serum CRP to PC-KLH dose-dependently triggered activation of the classical pathway. Unexpectedly, the activation was efficiently down-regulated at CRP levels > 150 mg/L. Using radial immunodiffusion, CRP-C1q interaction was observed in serum samples with high CRP concentrations. We propose that the underlying mechanism depends on fluid-phase interaction between C1q and CRP. This might constitute another level of complement regulation, which has implications for systemic lupus erythematosus where CRP is often low despite flare-ups.
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| 6. |
- Skoglund, Caroline, 1981-, et al.
(författare)
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C-reactive protein and C1q regulate platelet adhesion and activation on adsorbed immunoglobulin G and albumin.
- 2008
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Ingår i: Immunology and cell biology. - : Wiley. - 0818-9641 .- 1440-1711. ; 86:5, s. 466-74
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Tidskriftsartikel (refereegranskat)abstract
- Blood platelets and C-reactive protein (CRP) are both used clinically as markers of ongoing inflammation, and both participate actively in inflammatory responses, although the biological effects are still incompletely understood. Rapidly adhering platelets express receptors for complement factor 1q (C1q) and the Fc part of immunoglobulin G (IgG), and CRP is known to activate/regulate complement via C1q binding, and to ligate FcgammaRs. In the present study, we used normal human IgG pre-adsorbed to a well-characterized methylated surface as a model solid-phase immune complex when investigating the effects of CRP and C1q on platelet adhesion and activation. Protein adsorption was characterized using ellipsometry and polyclonal antibodies, and human serum albumin (HSA) and non-coated surfaces were used as reference surfaces. Platelet adhesion to IgG and HSA was inhibited by both C1q and CRP. Furthermore, CRP (moderately) and C1q (markedly) decreased the spreading of adhering platelets. The combination of C1q and CRP was slightly more potent in reducing cell adhesion to IgG, and also impaired the adhesion to HSA and non-coated surfaces. Platelet production of thromboxane B2 (TXB(2)) was also reduced by C1q both in the presence and absence of CRP, whereas CRP alone had no effect on TXB(2) production. We conclude that CRP and C1q regulate the behaviour of platelets, and that this may be an important immunoregulatory mechanism during inflammatory conditions.
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| 7. |
- Skoglund, Caroline, 1981-, et al.
(författare)
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C-reactive protein inhibit complement-mediated platelet activation suggesting a protective role in atherogenesis
- 2006
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Ingår i: Atherosclerosis Supplements. - Clare, Ireland : Elsevier. - 1567-5688 .- 1878-5050. ; 7:3, s. 284-284
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Objective: C-reactive protein (CRP) represents a powerful predictor of coro- nary artery disease. However, its physiological role is not fully understood. The binding of CRP to its ligand phosphorylcholine (PC) activates the com- plement system via the classical pathway, although limited to the initial stages, i.e. no membrane attack complex is formed. The aim of this study was to chaxacterize CRP-induced complement activation on PC-coated surfaces, and to investigate the regulatory effects of PC-bound crp on complement induced platelet activation.Methods: PC conjugated to keyhole limpet hemocyanin was immobilized to cross-linked fibrinogen on silica particles. Ellipsometry and polyclonal anti- bodies were used to quantify deposition of serum proteins, complement factors and CRP on the surfaces. Washed platelets as well as serum were prepared according to standard protocols. CRP concentrations were measured with a high sensitivity assay. Lumi-aggregometry was used to evaluate the effects of PC-coated particles and CRP on complement-induced platelet aggregation and secretion.Results: Serum (5%) induced platelet aggregation and secretion through complement-dependent mechanisms. PC-coated particles antagonized the complement-mediated platelet activation but only if CRP was present. Inter- estingly, we found that a minor elevation of CRR below 5 rag/1 was sufficient to inhibit platelet activation.Conclusions: We suggest that CRP bound to PC-expressing ligands, e.g. bacteria or modified low-density lipoproteins in an atherosclerotic lesion, modulate complement activation and thereby prevent a harmful platelet activation.
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