prostaglandin-f1 and Pleurisy

Zileuton is the only 5-lipoxygenase (5-LOX) inhibitor marketed as a treatment for asthma, and is often utilized as a selective tool to evaluate the role of 5-LOX and leukotrienes. The aim of this study was to investigate the effect of zileuton on prostaglandin (PG) production in vitro and in vivo.. Peritoneal macrophages activated with lipopolysaccharide (LPS)/interferon γ (LPS/IFNγ), J774 macrophages and human whole blood stimulated with LPS were used as in vitro models and rat carrageenan-induced pleurisy as an in vivo model.. Zileuton suppressed PG biosynthesis by interference with arachidonic acid (AA) release in macrophages. We found that zileuton significantly reduced PGE2 and 6-keto prostaglandin F1α (PGF1α) levels in activated mouse peritoneal macrophages and in J774 macrophages. This effect was not related to 5-LOX inhibition, because it was also observed in macrophages from 5-LOX knockout mice. Notably, zileuton inhibited PGE2 production in LPS-stimulated human whole blood and suppressed PGE2 and 6-keto PGF1α pleural levels in rat carrageenan-induced pleurisy. Interestingly, zileuton failed to inhibit the activity of microsomal PGE2 synthase1 and of cyclooxygenase (COX)-2 and did not affect COX-2 expression. However, zileuton significantly decreased AA release in macrophages accompanied by inhibition of phospholipase A2 translocation to cellular membranes.. Zileuton inhibited PG production by interfering at the level of AA release. Its mechanism of action, as well as its use as a pharmacological tool, in experimental models of inflammation should be reassessed.

Topics: Animals; Arachidonate 5-Lipoxygenase; Arachidonic Acid; Carrageenan; Cyclooxygenase 2; Dinoprostone; Disease Models, Animal; Humans; Hydroxyurea; Interferon-gamma; Intramolecular Oxidoreductases; Lipopolysaccharides; Lipoxygenase Inhibitors; Macrophages; Mice; Mice, Inbred Strains; Pleurisy; Prostaglandin-E Synthases; Prostaglandins F; Rats; Rats, Wistar; Zymosan

In the present study we used IL-6 knockout mice (IL-6KO) to evaluate the role of IL-6 in the inflammatory response caused by injection of carrageenan into the pleural space. Compared with carrageenan-treated IL-6 wild-type (IL-6WT) mice, carrageenan-treated IL-6KO mice exhibited a reduced degree of pleural exudation and polymorphonuclear cell migration. Lung myeloperoxidase activity and lipid peroxidation were significantly reduced in IL-6KO mice compared with those in IL-6WT mice treated with carrageenan. Immunohistochemical analysis for nitrotyrosine and poly(A)DP-ribose polymerase revealed a positive staining in lungs from carrageenan-treated IL-6WT mice. No positive staining for nitrotyrosine or PARS was found in the lungs of the carrageenan-treated IL-6KO mice. Staining of lung tissue sections obtained from carrageenan-treated IL-6WT mice with an anti-cyclo-oxygenase-2 Ab showed a diffuse staining of the inflamed tissue. Furthermore, expression of inducible nitric oxide synthase was found mainly in the macrophages of the inflamed lungs from carrageenan-treated IL-6WT mice. The intensity and degree of the staining for cyclo-oxygenase-2 and inducible nitric oxide synthase were markedly reduced in tissue sections obtained from carrageenan-treated IL-6KO mice. Most notably, the degree of lung injury caused by carrageenan was also reduced in IL-6KO mice. Treatment of IL-6WT mice with anti-IL-6 (5 microg/day/mouse at 24 and 1 h before carrageenan treatment) also significantly attenuated all the above indicators of lung inflammation. Taken together, our results clearly demonstrate that IL-6KO mice are more resistant to the acute inflammation of the lung caused by carrageenan injection into the pleural space than the corresponding WT mice.

Topics: Animals; Carrageenan; Cells, Cultured; Cytokines; Dinoprostone; DNA Damage; Enzyme Induction; Interleukin-6; Leukotriene B4; Lung; Macrophages; Male; Malondialdehyde; Mice; Mice, Knockout; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Peroxidase; Pleura; Pleurisy; Poly(ADP-ribose) Polymerases; Prostaglandin-Endoperoxide Synthases; Prostaglandins F; Tyrosine

During the development of an acute inflammatory reaction induced in the rat pleural cavity by dextran, calcium pyrophosphate, saline or phosphate buffered saline, macrophages present at a distant site (peritoneal cavity) display an increased capacity to release prostanoids: prostaglandins, prostacyclin and thromboxane. Enhanced levels of 6-keto-PGF1 alpha were observed both in peritoneal lavages (experiments in vivo) and in macrophage supernatants after 24-h culture (experiments in vitro). TXB2 levels were mainly increased in peritoneal lavages and PGE2 in culture supernatants. In vivo, levels of prostanoids in the peritoneal cavity reached a maximum 24 h after the induction of pleurisy whatever the injected substance. In vitro, amounts of arachidonic acid metabolites were highest in supernatants of cultured peritoneal macrophages harvested 72 h after the pleural injection of dextran or CaPP. These results show that the regulation of macrophage functions is closely related to prostanoid production, especially the release of PGE2 and PGI2.

Topics: Animals; Dinoprost; Dinoprostone; Macrophages; Male; Peritoneal Cavity; Pleurisy; Prostaglandins; Prostaglandins F; Rats; Rats, Inbred Strains; Thromboxane B2; Time Factors