5-Aminosalicylic acid inhibits leukotriene B4 omega-hydroxylase activity in human polymorphonuclear leukocytes

omega-Oxidation is regarded as the major pathway for the metabolism and inactivation of leukotriene B4 (LTB4). To investigate the action of 5-aminosalicylic acid (5-ASA) on LTB4 omega-hydroxylase activity, we incubated human polymorphonuclear leukocytes (PMNLs) with 3H-labeled LTB4 after pre-incubation with various concentrations of 5-ASA. omega-oxidation metabolites were separated by high performance liquid chromatography and each radioactivity was measured by a liquid scintilation counter. LTB4 omega-hydroxylase activity was inhibited by 5-ASA in a concentration-dependent fashion. The 50% inhibitory dose was about 50 mumol/l, which is within the concentration range found in the colonic mucosa. Our findings may be valuable in elucidating the potentially critical aspect of 5-ASA treatment in ulcerative colitis (UC).