In vitro activity: Zileuton suppresses PG biosynthesis by interference with arachidonic acid (AA) release in macrophages. Zileuton significantly reduces PGE2 and 6-keto prostaglandin F1α (PGF1α) levels in activated mouse peritoneal macrophages and in J774 macrophages. Zileuton inhibits PGE2 production in LPS-stimulated human whole blood and suppresses PGE2 and 6-keto PGF1α pleural levels in rat carrageenan-induced pleurisy.

Kinase Assay: Zileuton inhibited 5-hydroxyeicosatetraenoic aicd synthesis in rat basophilic leukemia cell and polymorphonuclear leukocytes (IC50 = 0.5 and 0.3 μM), respectively.

Cell Assay: Treatment of H9c2 cells with zileuton efficiently induced COX-2 expression and PGE2 biosynthesis in a time- and dose-dependent manner. Zileuton also exerted a profound protective effect against H2O2-induced oxidative stress, a mimic of reperfusion damage in vitro, and this protective effect was abolished by COX-2-selective inhibitor. Furthermore, zileuton-stimulated ERK1/2 and Akt phosphorylation was attenuated by rottlerin, indicating that PKCδ might act upstream of ERK1/2 and Akt. These results suggest that zileuton-induced COX-2 expression is sequentially mediated through PKCδ-dependent activation of ERK1/2 and Akt. Based on these findings, we propose that zileuton might provide a new therapeutic strategy for ischemia/reperfusion injury of the heart.

Zileuton significantly reduces macroscopic damage score after four weeks of treatment in rats. Zileuton administration significantly increases the intracolonic release of both thromboxane B2 at week 1 and prostaglandin E2 at weeks 2 and 4 in rats. Zileuton reduces the spinal cord inflammation and tissue injury, neutrophil infiltration, TNF-alpha, COX-2 and pERK1/2 expression, PGE(2) and LTB(4) production, and apoptosis in mice. Zileuton significantly improves the recovery of limb function over 10 days in mice. Zileuton administrated before I/R significantly reduces the degree of renal dysfunction (urea, creatinine) and injury (AST, histology) in 5-lipoxygenase knockout mice. Zileuton reduces the expression of ICAM-1 and the associated PMN infiltration caused by I/R of the mouse kidney in 5-lipoxygenase knockout mice. Zileuton inhibits LTB(4) production in the peritonitis model more effectively than the LTA(4)H inhibitor, but the influx of neutrophils into the peritoneum after 1 and 2 hours is significantly higher in Zileuton- versus JNJ-26993135-treated mice.

To investigate the mechanism underlying zileuton's neuroprotection, SD rats underwent permanent middle cerebral artery occlusion (MCAO), then received treatment with zileuton or vehicle after the onset of ischemia. Zileuton was found to significantly reduce neurological deficit scores, cerebral infarct volume, MPO activity, and the lipid peroxidation levels. It also inhibited the expression of NF-kappaB and decreased the expression and activity of iNOS in rat brain. In addition, zileuton attenuated the release of TNF-alpha and IL-1beta in serum. These results suggested that zileuton reduces inflammatory reaction and brain damage in a rat model of permanent focal cerebral ischemia. The neuroprotective effect of zileuton in cerebral ischemia might be associated with the inhibition of inflammatory reaction.

Br J Pharmacol. 2010 Oct;161(3):555-70; Gut. 1996 Jun;38(6):899-904; Br J Pharmacol. 2008 Feb;153(3):568-82.