interleukin-8 and 2-5-bis(3-4-5-trimethoxyphenyl)tetrahydrofuran

1. The role of platelet activating factor (PAF) in neutrophil infiltration in air pouch type allergic inflammation in rats was investigated. 2. Neutrophil infiltration into the pouch fluid 8 h after injection of the antigen (azobenzenearsonate-conjugated acetyl bovine serum albumin) solution into the air pouch of immunized rats was inhibited dose-dependently by treatment with PAF antagonists (CV-3988, L-652,731 and Y-24,180) in parallel with the decrease in neutrophil chemotactic activity in the pouch fluid. 3. Four hours after injection of the antigen solution into the air pouch of immunized and non-immunized rats, there was no significant difference between the two groups in the number of total leucocytes, neutrophils, mononuclear cells and eosinophils in the pouch fluid. However, when the infiltrated leucocytes were incubated in medium, chemotactic factor production by leucocytes from immunized rats was greater than that from non-immunized rats. 4. When leucocytes from non-immunized rats were preincubated for various periods in the medium containing 10 or 50 nM of PAF, washed, and further incubated in the medium containing no PAF, chemotactic factor production was not stimulated. 5. The increase in the chemotactic activity in the conditioned medium was not suppressed by the 5-lipoxygenase inhibitor, AA861. In addition, the chemotactic activity in the conditioned medium was not inhibited by the PAF antagonists. 6. Incubation of the infiltrated leucocytes in the medium containing the protein synthesis inhibitor, cycloheximide, inhibited chemotactic factor production in a concentration-dependent manner in parallel with the decrease in uptake of [3H]-leucine into the acid-insoluble fraction of leucocytes. 7. Separation of the chemotactic activity in the conditioned medium by isoelectric focusing revealed that the leucocyte infiltrated into the pouch fluid produce two kinds of factors, viz. leucocyte-derived neutrophil chemotactic factor-i (LDNCF-1) and LDNCF-2 of which pI values are 4-5 and above 8,respectively.8. The results indicate that PAF has no significant role in leucocyte activation to produce chemotactic factors, and that neutrophil chemotactic factors produced by infiltrated leucocytes are not PAF or leukotriene B4 but are produced through a protein synthesis mechanism.9. The mechanism of action of PAF antagonists on neutrophil infiltration into the inflammatory locus is discussed.

Topics: Animals; Azepines; Benzoquinones; Cells, Cultured; Culture Media, Conditioned; Dose-Response Relationship, Drug; Furans; Hypersensitivity; Immunization; Interleukin-8; Isoelectric Focusing; Leukocytes; Lipoxygenase Inhibitors; Phospholipid Ethers; Platelet Activating Factor; Rats; Triazoles

In a previous study we observed that neutrophils respond with a rapid rise in [Ca2+]i during adherence to cytokine-activated endothelial cells (EC), caused by EC membrane-associated platelet-activating factor (PAF). In the present study, we investigated whether this form of PAF was important in neutrophil adherence and migration across monolayers of rIL-1 beta- or rTNF alpha-prestimulated EC. PAF receptor antagonists prevented neutrophil migration across cytokine-pretreated EC by approximately 60% (P less than 0.005) without interfering with the process of adherence. The antagonists WEB 2086 and L-652,731 had no effect on neutrophil migration across resting EC induced by formylmethionyl-leucyl-phenylalanine (FMLP). A murine anti-IL-8 antiserum was found to also partially inhibit the neutrophil transmigration across cytokine-activated EC. When the anti-IL-8 antiserum was used in combination with a PAF receptor antagonist, neutrophil migration across cytokine-pretreated monolayers of EC was completely prevented. During transmigration, LAM-1 and CD44 on the neutrophils were down-modulated; both WEB 2086 and anti-IL-8 antiserum partially prevented this down-modulation caused by cytokine-prestimulated EC. Our results indicate that human neutrophils are activated and guided by EC-associated PAF and EC-derived IL-8 during the in vitro diapedesis in between cytokine-stimulated EC.

Topics: Antigens, Surface; Azepines; Cell Adhesion; Cell Movement; Cells, Cultured; Endothelium, Vascular; Female; Furans; Humans; Interleukin-8; Neutrophils; Platelet Activating Factor; Platelet Membrane Glycoproteins; Pregnancy; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Stimulation, Chemical; Triazoles; Tumor Necrosis Factor-alpha; Umbilical Veins