thromboxane-a2 and bepafant

Platelet-leukocyte interactions represent an important determinant of the inflammatory response. Although mechanisms of platelet-neutrophil adhesion were studied extensively, little is known on the mechanisms of platelet-eosinophil interactions. The aim of the present study was to analyze the involvement of adhesion molecules and lipid mediators in platelet-eosinophil adhesion as compared to platelet-neutrophil adhesion. For that purpose human platelets, eosinophils and neutrophils were isolated and platelet-eosinophil and platelet-neutrophil adhesion induced by thrombin (30 mU/ml), LPS (0.01 microg/ml) and fMLP (1 microM) was quantified using the "rosettes" assay. The involvement of adhesion molecules such as selectin P, glycoprotein IIb/IIIa (GPIIb/IIIa) and lipid mediators such as of thromboxane A2 (TXA2), platelet activating factor (PAF) and cysteinyl leukotrienes (cysLTs) were studied using monoclonal antibodies and pharmacological inhibitors, respectively. Thrombin (30 mU/ml), LPS (0.01 microg/ml) and fMLP (1 microM) each of them induced platelet-eosinophil adhesion that was even more pronounced as compared with platelet-neutrophil adhesion induced by the same stimulus. Anti-CD62P antibody (1 microg/ml) and anti-GP IIb/IIIa antibody (abciximab-3 microg/ml) strongly inhibited platelet-eosinophil as well as platelet-neutrophil adhesion. Aspirin inhibited platelet-eosinophil adhesion, while MK 886-a FLAP inhibitor (10 microM), or WEB 2170-a PAF receptor antagonist (100 microM) were less active. On the other hand aspirin, MK 886 and WEB 2170 all three of them inhibited platelet-neutrophil adhesion. In summary, platelets adhered avidly to eosinophils both after activation of platelets by thrombin, eosinophils by fMLP or simultaneous activation of platelets and eosinophils by LPS. Similarly to platelet-neutrophil interaction adhesion of platelets to eosinophils involved not only adhesion molecules (selectin P, GPIIb/IIIa), but also lipid mediators such as TXA2. The involvement of PAF and cysteinyl leukotrienes in platelet-eosinophil adhesion was less pronounced as compared to platelet-neutrophil adhesion.

Topics: Abciximab; Antibodies, Monoclonal; Aspirin; Azepines; Blood Platelets; Cell Adhesion Molecules; Cyclooxygenase Inhibitors; Eosinophils; Humans; Immunoglobulin Fab Fragments; In Vitro Techniques; Indoles; Inflammation Mediators; L-Selectin; Lipoxygenase Inhibitors; Neutrophils; P-Selectin; Platelet Adhesiveness; Platelet Glycoprotein GPIIb-IIIa Complex; Platelet Membrane Glycoproteins; Polysaccharides; Receptors, G-Protein-Coupled; Thromboxane A2; Triazoles

The mechanism of early pulmonary and systemic haemodynamic response to intravenous infusion of LPS from Escherichia coli was investigated in anesthetised Wistar rats. 10 mg of LPS given at a rate of 4 mg/kg/min but not at a rate of 1 mg/kg/min induced an increase in pulmonary arterial pressure (PAP) and a fall in systemic arterial pressure (SAP). Pretreatment with a PAF receptor antagonist; WEB 2170 (5 and 25 mg/kg) inhibited both PAP and SAP responses to LPS (4 mg/kg/min) while an inhibitor of thromboxane synthesis; Camonagrel (10 and 20 mg/kg) abolished PAP response without a major effect on SAP response to LPS. In conclusion, both PAF and TXA2 mediate LPS induced rise in pulmonary arterial pressure while LPS-induced fall in systemic arterial pressure is mediated by PAF.

Topics: Animals; Azepines; Blood Pressure; Enzyme Inhibitors; Escherichia coli; Indans; Lipopolysaccharides; Male; Platelet Activating Factor; Platelet Aggregation Inhibitors; Rats; Rats, Wistar; Thromboxane A2; Triazoles

The involvement of PAF, TXA2 and NO in LPS-induced pulmonary neutrophil sequestration an hyperlactataemia was studied in conscious rats. As pharmacological tools WEB 2170 (PAF receptor antagonist, 20 mg/kg), camongarel (inhibitor of TXA2 synthase, 30 mg/kg), N(G)-nitro L-arginine methyl ester (L-NAME -- non-selective nitric oxide synthase inhibitor, 30 mg/kg) were used.. Plasma lactate and NO2-/NO3- levels as well as myeloperoxidase (MPO) activity in lung tissue were measured one and five hours after administration of LPS (4 mg/kg(-1)).. LPS induced a twofold increase in plasma lactate levels and nearly 10-fold increase in plasma NO2-/NO3- levels five but not one hour after LPS administration. However, LPS-induced increase in pulmonary MPO activity was seen at both time intervals. Neither WEB 2170 nor camonagrel changed one or five hours responses to LPS (lactate, NO2-/NO3-, MPO). L-NAME potentiated LPS-induced rise in MPO activity in the lung and this potentiation was not affected by WEB 2170 or camonagrel. L-NAME supressed plasma NO2-/NO3- response and substantially potentiated plasma lactate response to LPS and both effects were partially reversed by WEB 2170 or camonagrel.. In summary, we demonstrated that PAF and TXA 2 play a role in overproduction of lactate during endotoxaemia in NO-deficient rats. However, these lipids do not mediate endotoxin-induced sequestration of neutrophils in the lung.

Topics: Animals; Azepines; Cell Movement; Endotoxemia; Indans; Lactic Acid; Lipopolysaccharides; Lung; Male; Neutrophils; NG-Nitroarginine Methyl Ester; Nitric Oxide; Platelet Activating Factor; Platelet Membrane Glycoproteins; Rats; Rats, Wistar; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Thromboxane A2; Triazoles

The effect of systemic endotoxin (lipopolysaccharide from Escherichia coli 0111:B4) on prostaglandin I2 (PGI2) and thromboxane A2 (TXA2) production by rat dental pulp was investigated. Intravenous injection of endotoxin increased ex vivo production of both PGI2 and TXA2 by the pulp tissue, when determined by radioimmunoassay. A significant effect on PGI2 and TXA2 production was observed with endotoxin doses of greater than 2 and 0.4 mg/kg, respectively. A significant increase was also observed at 30 min after injection of 10 mg/kg endotoxin, reaching a maximum after 60 min for both PG and TX production. Endotoxin (10 mg/kg for 60 min) also increased TXA2 but not PGI2 production in lung tissue, but had no effect in jejunal tissue. Indomethacin (10 microM) completely inhibited PGI2 and TXA2 production by the pulp of physiological saline- and endotoxin-treated rats. Further, arachidonic acids (10 microM) significantly increased PG and TX production by the pulp of saline- but not of endotoxin-treated rats. Endotoxin (100 micrograms/ml) had no in vitro effect on PG or TX production when incubated with isolated pulp, lung and jejunal tissues, suggesting that the endotoxin-induced increases in PG and TX production are an indirect effect. The endotoxin-induced increase in TXA2 production, but not in PGI2 production, by the pulp tissue was significantly suppressed by WEB 2170, a platelet-activating factor (PAF) antagonist. These results indicate that arachidonate metabolism in pulp tissue is susceptible to endotoxaemia in comparison with the lung and jejunum, and further suggest that the endotoxin-induced increase in, at least, TXA2 production by the pulp is mediated by PAF.

Topics: Animals; Arachidonic Acid; Azepines; Dental Pulp; Endotoxins; Epoprostenol; Escherichia coli; Indomethacin; Injections, Intravenous; Jejunum; Lung; Male; Platelet Activating Factor; Rats; Rats, Wistar; Thromboxane A2; Time Factors; Triazoles