Oxidative stress suppresses cysteinyl leukotriene generation by mouse bone marrow-derived mast cells

Abstract

Cysteinyl leukotrienes and oxidative stress have both been implicated in bronchial asthma; however, there is no previous study that focused on the ability of oxidative stress to alter cysteinyl leukotriene generation. In this study, treatment of bone marrow-derived mast cells with prostaglandin D 2 reduced their ability to generate leukotriene (LT) C4 upon calcium ionophore stimulation but had little effect on LTB4 generation. This effect could be reproduced by a selective agonist of the DP2 receptor, 15R-methyl prostaglandin D2 (15R-D 2). 15R-D2 dose-dependently inhibited LTC4 generation with an IC50 of 2 μM, and the effect was not altered by a DP2/thromboxane antagonist or by a peroxisome proliferator- activated receptor-γ antagonist. 15R-D2 exerted its suppressive effect via a reduction in intracellular GSH, a mechanism that involved the conjugation of its non-enzymatic breakdown product to GSH. At 10 μM, 15R-D2 reduced LTC4 generation to 10%, intracellular GSH to 50%, and LTC4 synthase (LTC4S) activity to 33.5% of untreated cells without altering immunoreactive LTC4S protein expression or 5-lipoxygenase activity. The effects of 15R-D2 on LTC4S activity could be partially reversed by reducing reagent. The sulfhydrylreactive oxidative agent diamide suppressed LTC4S activity and induced a reversible formation of covalent dimer LTC4S. LTC 4S bearing a C56S mutation was resistant to the effect of diamide. Covalent dimer LTC4S was observed in nasal polyp biopsies, indicating that dimerization and inactivation of LTC4S can occur at the site of inflammation. These results suggest a cellular redox regulation of LTC 4S function through a post-translational mechanism. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc.