Biomedical subjects

Torbjörn Bengtsson

Publications and source records attributed to Torbjörn Bengtsson.

9 recordsLinked to original sources

PubMed2005

Cross-talk between adenosine and the oxatriazole derivative GEA 3175 in platelets.

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.

Adenosine↗

PubMed2003

Oxygen radical production in neutrophils interacting with platelets and surface-immobilized plasma proteins: role of tyrosine phosphorylation.

The interaction between neutrophil granulocytes and platelets is considered to play an important role in the inflammatory process induced by an implanted foreign material. However, the cellular mechanisms involved remain incompletely understood. We used a luminol-dependent chemiluminescence (CL) technique to analyze the generation of reactive oxygen species (ROS) in human neutrophils interacting with different plasma protein-coated surfaces in the presence or absence of unstimulated or stimulated platelets. The role of tyrosine phosphorylation in the regulation of NADPH oxidase activity was evaluated with quantitative fluorescence microscopy and the specific tyrosine kinase inhibitor genistein. We found that the ROS-production is 2 to 3 times higher in neutrophils on immunoglobulin G (IgG)-coated surfaces than in cells interacting with albumin- or fibrinogen-coated surfaces. Incubation with superoxide dismutase and catalase revealed that about 45% of the ROS was released extracellularly on IgG surfaces whereas corresponding values were 90% and 85% in neutrophils interacting with albumin and fibrinogen, respectively. The presence of platelets markedly increased the extracellular generation of ROS, mainly in neutrophils interacting with IgG- or fibrinogen-coated surfaces whereas the intracellular production was only modestly affected. Quantitative fluorescence microscopy of neutrophils stained with FITC-conjugated anti-phosphotyrosine antibodies showed a correlation between tyrosine phosphorylation, cell spreading, and ROS production. Platelets markedly amplified the anti-phosphotyrosine staining on both fibrinogen- and IgG-coated surfaces whereas the low level of tyrosine phosphorylation in neutrophils on albumin-coated surfaces was not further elevated by platelets. Furthermore, the tyrosine kinase inhibitor genistein inhibited both extra- and intracellular ROS production in neutrophils regardless of the presence of platelets. We demonstrate that plasma protein coating and the presence of platelets are crucial for the inflammatory response of adhering neutrophils and that the oxidative response correlates with the extent of tyrosine phosphorylation of proteins in focal contacts.

Blood Platelets↗

PubMed2003

Chlamydia pneumoniae binds to platelets and triggers P-selectin expression and aggregation: a causal role in cardiovascular disease?

OBJECTIVE: Evidence linking Chlamydia pneumoniae to atherosclerotic cardiovascular disease is expanding. Platelets are considered to play an essential role in cardiovascular diseases; however, so far platelets have not been associated with an infectious cause of atherosclerosis. This study aims to clarify the interaction between C pneumoniae and platelets and possibly present a novel mechanism in the pathogenesis of atherosclerosis. METHODS AND RESULTS: The effects of C pneumoniae on platelet aggregation and secretion were assessed with lumiaggregometry, and the ability of C pneumoniae to bind to platelets and stimulate expression of P-selectin was analyzed with flow cytometry. We found that C pneumoniae, at a chlamydia:platelet ratio of 1:15, adheres to platelets and triggers P-selectin expression after 1 minute and causes an extensive aggregation and ATP secretion after 20 minutes of incubation. Inhibition of glycoprotein IIb/IIIa with Arg-Gly-Asp-Ser or abciximab markedly reduced C pneumoniae-induced platelet aggregation. Exposure of C pneumoniae to polymyxin B, but not elevated temperature, abolished the stimulatory effects on platelet activation, suggesting that chlamydial lipopolysaccharide has an active role. In contrast, other tested bacteria had no or only moderate effects on platelet functions. CONCLUSIONS: Our findings demonstrate a new concept of how C pneumoniae activates platelets and thereby may cause atherosclerosis and thrombotic vascular occlusion.

Bacterial Adhesion↗

PubMed2003

Interactions between surface-bound actin and complement, platelets, and neutrophils.

Actin exists as globular (G) monomers or polymeric filaments (F) in the cytoplasm of eukaryotic cells, mediating cell morphologic changes and motility. Large amounts of this protein may be released out to the extracellular compartment during tissue injury, but little is known about its role in biomaterial-related inflammation. We immobilized actin to methylated glass, methylated and aminated silicon, and gold model surfaces and studied the subsequent blood serum deposition and complement activation, generation of reactive oxygen species (ROS), and adhesion and aggregation of neutrophils and platelets. Null ellipsometry showed that approximately one monolayer of G-actin can be immobilized onto the model surfaces and that actin in buffer polymerized on top of this by the addition of K(+) and Mg(2+) ions to form a thicker layer of firmly bound F-actin. After serum incubation, F-actin bound low amounts of anti-complement factor 1q (anti-C1q). Cell responses upon contact with actin-coated surfaces were analyzed by luminol-amplified chemiluminescence, lumi-aggregometry, and fluorescence microscopy. It was shown that surface-triggered aggregation, spreading, and generation of ROS are down-regulated and comparable to the response by adsorbed albumin. However, F-actin on gold surfaces recruited platelets in a C1q-dependent manner. We conclude that in vitro adsorbed actin is a weak complement, platelet, and neutrophil activator, but that F-actin associates with both C1q and platelets.

Actins↗

PubMed2003

Platelets stimulated by IgG-coated surfaces bind and activate neutrophils through a selectin-dependent pathway.

Blood platelets bind rapidly to foreign surfaces and interact with adsorbed proteins and neutrophil granulocytes. We demonstrate by use of luminol-amplified chemiluminescence under stirred and non-stirred conditions that platelets at IgG-coated surfaces amplify the neutrophil extracellular release of reactive oxygen species (ROS). The neutrophil response involved tyrosine phosphorylation, but was only in part induced by neutrophil F(c gamma)-receptor stimulation. The platelet mediated effects were contact-dependent since the respiratory burst was inhibited when the IgG-stimulated platelets were removed by filtration, but not when they were fixed in paraformaldehyde. Bodipyphallacidin-staining of filamentous actin (F-actin) revealed that an actin-dependent platelet adhesion supported the subsequent adhesion and spreading of neutrophils. The neutrophil ROS-response was lowered when the interaction between platelet P-selectin (CD62P) and neutrophil P-selectin glycoprotein ligand-l (PSGL-1 or CD162) was inhibited. The blocking of L-selectin (CD62L) or blocking of the interaction between platelet glycoprotein (Gp) IIb/IIIa and neutrophil complement receptor 3 (CR3) showed no effect. We conclude that platelet activation on immobilized IgG trigger a contact-dependent "frustrated" phagocytosis by neutrophils, associated with a release of toxic ROS.

Blood Platelets↗

PubMed2003

Platelets induce reactive oxygen species-dependent growth of human skin fibroblasts.

A growing amount of evidence suggests that reactive oxygen species (ROS), such as hydrogen peroxide and superoxide anion, regulate intracellular signalling and have a role in cell proliferation. In the present study, we show that platelets increase the mitogenic rate in human fibroblasts and that this effect was inhibited by the intracellular antioxidant N-acetyl-L-cysteine (NAC) and the NADPH-oxidase inhibitor diphenyleneiodonium chloride (DPI). The mitogenic effects of platelets were mimicked by the platelet factors platelet-derived growth factor BB-isoform (PDGF-BB), transforming growth factor beta1 (TGF-beta1) and sphingosine-1-phosphate (S1P). The sphingosine kinase inhibitor DL-threo-dihydrosphingosine (DL-dihydro) abrogated the platelet-induced growth, while antibodies directed against PDGF or TGF-beta had modest effects. Exposure of fibroblasts to platelets, PDGF-BB, TGF-beta1 or S1P caused an extensive intracellular ROS production, measured as changes in dichlorofluorescein fluorescence. This ROS production was totally inhibited by NAC, pyrrolidinethiocarbamate (PDTC), DPI and apocynin. In conclusion, the results presented are indicative of a crucial role of ROS in the platelet-mediated regulation of fibroblast proliferation.

Acetophenones↗

PubMed2003

Comparison of plasma levels of cytokines and in vitro generation of reactive oxygen species after nicotine infusion in nicotine users with normal and impaired renal function.

Several in vitro and animal studies suggest effects of nicotine on the immune system, but little evidence exists regarding the in vivo immunomodulation of nicotine in humans. The increased use of nicotine replacement therapy to aid smoking cessation claims further understanding of how nicotine affects blood leukocytes. This is of particular importance when nicotine therapy is used in diseases associated with alterations of the immune system, such as chronic renal failure. The present study evaluates the acute effects of nicotine infusion (NI) on some immunoregulatory functions in seven healthy subjects and seven patients with renal failure. All subjects were nicotine users and had refrained from using nicotine for 36 h before NI. Blood was collected before, immediately after, and 2 h after NI. Plasma concentrations of intercellular adhesion molecule-1 (ICAM-1) and the cytokines interleukin-2 (IL-2), IL-4, IL-10, interferon-gamma and RANTES were measured using specific immunoassays. The generation of reactive oxygen species (ROS) induced by formyl-methionyl-leucyl-phenylalanine (fMLP), Ristocetin, adenosine 5'-diphosphate, or collagen was registered in whole blood as luminol-dependent chemiluminescence. Except for fMLP, these compounds induce leukocyte ROS generation by platelet mediated mechanisms. NI did not significantly affect the levels of the cytokines and ICAM-1 in any group. The peak and the persistent ROS production, induced by collagen and Ristocetin, was lower at some time points in patients with renal failure as compared to healthy subjects. Also in patients with renal failure, both peak height and persistent ROS generation induced by Ristocetin were reduced immediately after NI. Thus, nicotine inhibits some of the platelet-mediated activation of leukocyte ROS generation, and may be associated with platelet defects in renal failure.

Adjuvants, Immunologic↗

PubMed2002

On the binding of complement to solid artificial surfaces in vitro.

Since the realization of a complement activation capacity by artificial surfaces upon contact with blood, a common belief has evolved that charged nucleophilic surface groups such as amine (-NH2) and hydroxyl (-OH) react with and eventually bind to the internal thioester in complement factor 3 (C3). A covalent amide or ester linkage is thereby supposed to form between C3b and the surface itself. In this report, we present complement surface binding data by null-ellipsometry for two nucleophilic surfaces (-NH2 and -OH), for surfaces with immunoglobulin G (IgG) covalently bound, and for IgG spontaneously pre-adsorbed to hydrophobic silicon. The results reveal that the plasma proteins that were deposited during complement activation became eluted by sodium dodecyl sulfate. Hence the direct covalent binding between C3 and solid nucleophilic surfaces seems to be only of moderate importance, at least during shorter serum incubations. This strongly suggests that the prevalent covalent linkage model between solid artificial surfaces and C3b is not accurate. Instead we suggest a more pronounced role for C3 associations to other adsorbed proteins and or electrostatic and hydrophobic protein-surface interactions.

Adsorption↗

PubMed2002

The influence of plasma proteins and platelets on oxygen radical production and F-actin distribution in neutrophils adhering to polymer surfaces.

It is well known that blood cell interactions with artificial surfaces might have deleterious effects on host tissue, however, the mechanisms involved are far from understood. In this study, neutrophil-platelet interaction on uncoated or protein-coated polymer surfaces was investigated. Cell spreading, reorganization of actin filaments and release of oxygen metabolites (measured as luminol-amplified chemiluminescence) were used as criteria for cell activation on positively charged, hydrophilic 1,2-diaminocyclohexane, and negatively charged, hydrophobic hexamethylene-disiloxane. The model surfaces were made by radio frequency plasma discharge polymerization. Neutrophil contact with the uncoated polymers induced a prolonged generation of oxygen radicals. Precoating of the polymer surfaces with human serum albumin (HSA) or fibrinogen, markedly reduced neutrophil activation, whereas coating with human immunoglobulin G (IgG), a well-known opsonin, resulted in significantly higher levels of cell activation. Consequently, protein coating overruled the activating effects of the polymer surfaces. The presence of unstimulated or thrombin-stimulated platelets markedly increased the reactivity of neutrophils against fibrinogen- and IgG-coated surfaces. However, neutrophils remained relatively unreactive in the presence of platelets on HSA-treated surfaces. Comparison of the different types of surfaces used, reveals a correlation between the degree of cell spreading, reorganization of the actin cytoskeleton and the amount of oxygen radicals produced. Our results suggest that the acute inflammatory reaction on a biomaterial surface is highly dependent on the nature and composition of the first adsorbed protein layer and the extent of platelet activation.

Actins↗