Inhibitory effect of 4-acylaminophenol derivatives (T-0799 and T-0757), novel lipoxygenase inhibitors, on arachidonic acid-induced infiltration of polymorphonuclear leukocytes in rat skin.

Effects of 4-acylaminophenol derivatives, novel 5-lipoxygenase inhibitors, on the neutrophil infiltration in arachidonic acid (AA) (10 mg/site)-induced skin inflammation in rats were examined. Myeloperoxidase (MPO) activity in the skin lesion, used as an indicator of neutrophil infiltration, was significantly increased after intradermal injection of AA. Dual inhibitors of cyclooxygenase and 5-lipoxygenase, phenidone (100 mg/kg x 2, i.p. and p.o.) and BW-755C (50 mg/kg x 2, p.o.), and 5-lipoxygenase inhibitors, AA-861 (100 mg/kg x 2, i.p.) and the 4-acylaminophenol derivatives T-0799 and T-0757 (10-100 mg/kg x 2, p.o.), inhibited the increase in MPO activity 5 hr after AA-injection, but the cyclooxygenase inhibitor indomethacin (5 mg/kg, i.p.) showed no effect. These results suggest that products of lipoxygenase, but not of cyclooxygenase, are involved in the MPO activity increase (i.e., neutrophil infiltration), and that this model is useful for in vivo evaluation of 5-lipoxygenase inhibitors. It is suggested that the 4-acylaminophenol derivatives may be useful as orally active drugs for treatment of some leukotriene-mediated diseases.