Leukotriene B4 omega-oxidation by human polymorphonuclear leukocytes is inhibited by pyocyanin, a phenazine derivative produced by Pseudomonas aeruginosa.
Human polymorphonuclear leukocytes (PMNL) metabolize the potent chemotaxin leukotriene B4 (LTB4) by omega-oxidation to 20-hydroxyl-LTB4 and 20-carboxy-LTB4. The ability of unstimulated human PMNL to metabolize exogenous LTB4 was found to be inhibited by pyocyanin, a phenazine derivative produced by Pseudomonas aeruginosa, in a dose-dependent manner. 1-Hydroxyphenazine (1-OHP), a metabolite of pyocyanin, was not inhibitory under identical conditions. The initial enzymic step in the conversion of LTB4 is catalyzed by an NADPH-dependent cytochrome, P-450. Reduction of the phenazine derivatives by NADPH was measured spectrophotometrically. Pyocyanin was reduced by NADPH in vitro in a pH-dependent manner, while 1-OHP was poorly or negligibly reduced under similar conditions. Formation of NADP+ was 20.3 +/- 1.8 nmol min-1 for pyocyanin (10 microM) at pH 5.5, compared with 0.6 +/- 0.2 nmol min-1 for 1-OHP (10 microM), while at pH 7.5 a value of 2.2 +/- 1.3 nmol min-1 was obtained for pyocyanin, with no detectable activity for 1-OHP. This indicates that inhibition of LTB4 omega-hydroxylase activity by pyocyanin might be achieved by competition for NADPH. Incorporation of exogenous 5-hydroxyeicosatetraenoic acid by PMNL into lipid pools was not affected by either phenazine derivative. The ability of bacterial pyocyanin to limit the omega-oxidation of LTB4 may have important implications for PMNL LTB4 receptor status and chemotaxis in vivo.
Muller
M
M
Centre for Infectious Diseases and Microbiology, Westmead Hospital, University of Sydney, New South Wales, Australia.
Sorrell
T C
TC
D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism; D007975:Leukotriene B4 / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D010084:Oxidation-Reduction; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D011710:Pyocyanine / Q000494:pharmacology*; D013053:Spectrophotometry
D006893:Hydroxyeicosatetraenoic Acids; D007975:Leukotriene B4; C022022:5-hydroxy-6,8,11,14-eicosatetraenoic acid; D009249:NADP; D011710:Pyocyanine