Molecular pharmacological profile of a novel thiazolinone‐based direct and selective 5‐lipoxygenase inhibitor

BACKGROUND AND PURPOSE The potency of many 5‐lipoxygenase (5‐LOX) inhibitors depends on the cellular peroxide tone and the mechanism of 5‐LOX enzyme activation. Therefore, new inhibitors that act regardless of the mode of enzyme activation need to be developed. Recently, we identified a novel class of thiazolinone‐based compounds as potent 5‐LOX inhibitors. Here, we present the molecular pharmacological profile of ( Z )‐5‐(4‐methoxybenzylidene)‐2‐( p ‐tolyl)‐ 5H ‐thiazol‐4‐one, compound C06. EXPERIMENTAL APPROACH Inhibition of 5‐LOX product formation was determined in intact cells [polymorphonuclear leukocytes (PMNL), rat basophilic leukaemia‐1, RAW264.7] and in cell‐free assays [homogenates, 100 000× g supernatant (S100), partially purified 5‐LOX] applying different stimuli for 5‐LOX activation. Inhibition of peroxisome proliferator‐activated receptor (PPAR), cytosolic phospholipase A 2 (cPLA 2 ), 12‐LOX, 15‐LOX‐1 and 15‐LOX‐2 as well as cyclooxygenase‐2 (COX‐2) were measured in vitro . KEY RESULTS C06 induced non‐cytotoxic, direct 5‐LOX inhibition with IC 50 values about 0.66 µM (intact PMNL, PMNL homogenates) and approximately 0.3 µM (cell‐free PMNL S100, partially purified 5‐LOX). Action of C06 was independent of the stimulus used for 5‐LOX activation and cellular redox tone and was selective for 5‐LOX compared with other arachidonic acid binding proteins (PPAR, cPLA 2 , 12‐LOX, 15‐LOX‐1, 15‐LOX‐2, COX‐2). Experimental results suggest an allosteric binding distinct from the active site and the C2‐like domain of 5‐LOX. CONCLUSIONS AND IMPLICATIONS C06 was identified as a potent selective direct 5‐LOX inhibitor exhibiting a novel and unique mode of action, different from other established 5‐LOX inhibitors. This thiazolinone may possess potential for intervention with inflammatory and allergic diseases and certain types of cancer.