The 5-lipoxygenase inhibitor, zileuton, suppresses prostaglandin biosynthesis by inhibition of arachidonic acid release in macrophages.
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Rossi
A
A
Department of Experimental Pharmacology, University of Naples Federico II, Naples, Italy.
Pergola
C
C
Koeberle
A
A
Hoffmann
M
M
Dehm
F
F
Bramanti
P
P
Cuzzocrea
S
S
Werz
O
O
Sautebin
L
L
D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000235:genetics; D016718:Arachidonic Acid / Q000378:metabolism*; D002351:Carrageenan; D051546:Cyclooxygenase 2 / Q000378:metabolism; D015232:Dinoprostone / Q000096:biosynthesis* / Q000097:blood; D004195:Disease Models, Animal; D006801:Humans; D006918:Hydroxyurea / Q000031:analogs & derivatives* / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology; D019746:Intramolecular Oxidoreductases / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains; D010998:Pleurisy / Q000139:chemically induced / Q000378:metabolism; D000071876:Prostaglandin-E Synthases; D011460:Prostaglandins F / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015054:Zymosan
D008070:Lipopolysaccharides; D016859:Lipoxygenase Inhibitors; D011460:Prostaglandins F; D016718:Arachidonic Acid; D007371:Interferon-gamma; D002351:Carrageenan; D015054:Zymosan; D001094:Arachidonate 5-Lipoxygenase; D051546:Cyclooxygenase 2; D019746:Intramolecular Oxidoreductases; D000071876:Prostaglandin-E Synthases; D015232:Dinoprostone; C063449:zileuton; C100006:prostaglandin F1; D006918:Hydroxyurea